AMA | September 2022

AMA Sept 2022 questions

Liam McCarty
What is complexity? 😉

Christian Wiegand
Regarding ep. 168 with Anil Seth:
What do you think is the most promising/helpful/interesting/fun approach towards a formal definition of (weak) emergence?
E.g. Dynamical independence as proposed by Barnett and Seth
or something like a ratio of macroscopic and microscopic systems' complexities
or some notion of computational irreducability?

Maggie Liu
how important do you think intelligence is for a career in physics?

Preston Justice
Immanuel Kant said in his “Critique of Pure Reason” that “Whatever the process and the means may be by which knowledge refers to its objects, intuition is that through which it refers to them immediately, and at which all thought aims as a means. But intuition takes place only insofar as objects are given to us.”
In what ways do you think Kant’s definition of intuition would change if he knew everything we know about the physical “world” today? Also, how would you describe intuition?

Paul Cousin
I am curious about what many worlds implies for the Big Bang. Is there something special about its version of the beginning of the universe? Were there a lot of branches created then and to which extent could they differ? Thanks.

Terrible Turnip
Would you be able to describe the way in which spatial locality arises from just a wave function, or is it too technical?

Mikolaj Szabo
How is the simulation hypothesis/argument/whatever a thing, that people take seriously? To me it always felt like it's just the repackaging of good old anthropocentrism and teleology and those urges of humanity. It's sneaking god in back again, exactly as creationism had tried a few decades earlier, by pretending to be scientific and by not mentioning god per se. Also, it's a bombastic claim so the press loves it. Also, you can explain it using a popular Hollywood movie that everybody saw, so anyone can get it, and it's as mindblowing as anything when you're high. Also, silicon valley people love it, because it's simulation, it's techy etc. But how can scientists and philosophers take this whole hype seriously and discuss it, argue about it?

Peter A Bamber
Is there any difference *that matters to you*, between thinking that we live in a simulation determined by rules chosen by the simulation’s commissioner/creator, and thinking that we live in a reality determined by rules/forces/mathematics that are part of nature?

Gregory Kusnick
I share your fondness for Heinlein's "The Moon is a Harsh Mistress" and am curious about your opinion of "Starship Troopers". In particular, do you think there's merit to the idea that citizens should have to earn the right to vote through some sort of public service (not necessarily military service)?

Brendan
Do you have a preference on how to be addressed? Doctor? Professor? Sean?

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Eric Dovigi
The possibility of "unperceived existence" is weird. Can we conceive of a universe with *no* lifeforms? In what sense would this universe exist? "To whom" would it exist? Suns, galaxies, dust---they don't know they exist. Or do they?

Gary Upshaw
Can nothing exist?
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Jeff B
I'm still a bit confused about interactions and particles in QFT. From your Biggest Ideas videos, I understand that there is a wavefunction of field configurations. So when two of these fields interact, does the wavefunction branch into "interacted" and "not interacted", and is there a precise way to tell where in the field this interaction will take place? As a sub question, is the interaction location what we think of as a "particle"?

Casey Mahone
While I agree with you that some things in the world may just be "brute facts", is it really useful to think that way? It strikes me as similar to invoking the anthropic principle. Rather than trying to determine why things are one way rather than another, you have an easy fallback option.

Keith
I am here to report that if all 7.9 billion people on Earth request their once in lifetime Priority Question, even with easy Yes/No questions, answerable at the rate of 1 question/second, it would take you just over 250 years.
Given that these conceivable future Patrons would be acting while honoring the unofficial AMA contract Priority Question section, should there be a caveat amended to the original contract?

Chris DiRubio
What is your credence that octonions, which I understand are an 8 dimensional analog to complex numbers, will give us deep insights into the fundamental laws of particle physics?

David McBurney
I recently listened to a podcast with Marcia Rieke on the James Webb Space Telescope. She mentioned that the two leading candidates for the next generation of space telescope (determined by Astro2020) were focused on studying exoplanets. Is that because we don't think we can do better than JWST for looking back closer to the big bang or because exoplanets and the potential for finding evidence of life is where astronomy is heading?

Anonymous
Suppose Alice commits a crime. Before Alice can be held accountable for the crime, she dies. Alice lived in a world of highly advanced technology, so a scientist is able to create a clone of Alice so accurate that the clone has all of her memories. Is it ethical to hold this new being accountable for the crimes of someone she's never met, solely on the basis of having memories that the scientist purposefully forced her to have?

Allistar Melville
What does it mean for a dimension to be "small" or "curled up"? Aren't dimensions effectively endless in two directions? Is this a concept that falls out of the maths and doesn't (yet) have any real world evidence?

Jake Kornegay
A black hole made of elements from a dead star would look different inside the event horizon than a black hole made of cats and people who happened to fall inside a black hole while studying it, at least briefly, right? So when we speak of black holes only having the characteristics of mass, spin and electric charge, isn’t that shorthand for what they look like OUTSIDE the event horizon, while very different interiors must exist across spacetime?

Daniel C
I would appreciate if you could speak in a bit more detail as to the argument against strong emergence in the form you refer to it. You mentioned on a recent AMA that strong emergence would violate locality, which sounded like a reason to reduce your prior for it. Is this violation of locality your biggest qualm with strong emergence? Does the fact that locality is not fundamental and seems to break down when gravity is strong enough (ie in black holes) open the possibility that there is in fact other nonlocal behavior in lower gravity conditions, but it is just not as easily visible to us, particularly when we try to resolve the universe at the scale of individual particles?

Ariel Assaf
To what extent do you think we are capable of understanding the universe? We clearly are able to make extraordinary predictions, but on the other hand.... Even if we are turing complete, we implicitly accept occam's razor, we rely on counterfactuals in our reasoning, tec... what confidence should we have that we can grasp the laws of nature?

Charles Haught
In an early AMA you said something along the lines of “If you believe in science and want to push naturalism forward then you should also listen to the science of convincing people.” With this in mind, how do you feel about the effects of so-called “militant” atheists/naturalists such as Christopher Hitchens, Ricky Gervais, and Richard Dawkins? Do you think that by being more debate-driven rather than empathetic they are doing more harm than good in this area?

Eike Pierstorff
Some scientific theories capture the public imagination in ways that other's don't. Recently, Constructor theory has been hailed as a new approach to doing science, yet the only people I hear talking about it are the inventors thereof. There is no sitcom and no flurry of popular science books about constructor theory. What do you think is the difference between a scientific theory that is a mainstay of public excitement, and one that is more or less ignored, even if within its own domain it might be just as important?

Qubit
Can you tell us your thoughts on quantum darwinism proposed by Wojciech Zurek? My impression is, that this concept tries to solve the measurement problem using only the Schrödinger equation. I don't see any difference to the many worlds theory. However, I have the impression, that Zurek doesn't like to talk about other worlds. What are your thoughts?

keefekg
If sending particles through a stern-gerlach device measures their spin, how does one go about aligning the spin of two particles without measuring them? Or is this just a non-practical idea that only gets proposed in thought experiments?

Jeffrey Segall
Regarding the Simon Conway Morris podcast, I was confused in that he starts off saying that the combinatorial immensity of biological space is “stupidly large” but then he seemed to imply that evolution could find optimal solutions, arguing that mammals were always going to win out over the dinosaurs and that convergent evolution was to be expected. It seems to me that in the limited time scales over which species evolve, it would be highly unlikely that the optimal solution in biological space would be found.

alexandra bates
What do you think of the Effective Altriusm movement? Have they changed your personal actions or views on anything? Do you think their method of improving the world is effective?

Tarun
PRIORITY QUESTION:
You identified my strategy on your last AMA - I have been going through my list of most burning questions each month, and now I am asking one of the questions that you didn't answer previously, as a priority question:
Much is made of the laws of physics relating to motion, whether deterministic or random, ruling out libertarian free will. Doesn't Einstein's block universe give us an equally good reason to not believe in libertarian free will given the future is fixed? I would be very interested to get your thoughts on this perspective. Thank you!

Nalita S
I was wondering what your thoughts are in terms of the first law of thermodynamics and understanding us humans as quantum systems… what happens to our “energy” after death? Does it die with us? Does it evaporate like a black hole? Does it “transform” into another form like dirt?

Brian Keating
Do you see any place for NFTs or blockchain technology in science and or publishing (e.g. proof of stake vs embargoes etc)?

Kyle Stephens
I am curious to learn more about the logistics of your podcasts. Do you record many in a short period of time, or are they recorded once per week? Are the length of your podcasts limited by your time availability or the availability of the guests, or have you just found the current length to be the best?

Seth Holoweiko
Can you think of any meaningful differences that might exist in science and society if we decided tomorrow that North was actually *down* rather than up and the earth and other planets actually rotated clockwise around the sun, etc.? It seems like "North" has an arbitrary positive value assigned to it that makes references to North (as opposed to South) the "right" way. I can't help but think that as a resident of the northern hemisphere who can literally see the North Star and grew up in a northern state I have some kind of minor implicit bias or privilege that is wholly unwarranted.

Chris Murray
How do you reconcile the Bekenstein bound with the fact that even a single real number requires an infinite amount of information to describe? Our world seems to have real numbers all over the place, so what is the right way to think about this?

Bill Warner
Normally, the hotter a thing is, the higher the entropy, but I often hear that the early universe was very hot and very low in entropy. Can you help me understand this?

Jesse Rimler
Effective Altruists recommend giving to charity and career selection as the best ways for 'ordinary people' to Do Good. What about Effective Organizing? Civil Rights and Labor laws came about not through donations and people taking career quizzes. Rather, ordinary people built complex networks, worked in solidarity, tried various tactics, and often put their bodies on the line to accomplish long lasting change. Do you think the EA movement focuses less on this because these actions are harder to quantify?

Frank Lehman
What, for you, was the peak era of the internet? In terms of feeling of promise, excitement, usefulness, uniqueness, not-horribleness, etc.

Josh Charles
If it's possible that space is an emergent property out of entanglement, is it possible that we'll find "spooky action at a distance" is not really "distant" at all, since locally it would seem like it was spatially close?

Sandy McDonald
My handle on mathematics stopped at high school level. Recently I’ve been feeling I might get more from your and other authors works if I pushed this further (by going for an open learning/distance learning course). How much further do you think I need to go to make it worthwhile? For context I left school in 1997!

Sid Huff
No one would reasonably deny that Einstein was right about a lot of things. What is your credence that he will eventually be shown to be right about quantum theory, i.e., that it is somehow incomplete, and when the “missing pieces” are found, it will consign both the Copenhagen interpretation as well as de Broglie-Bohm pilot wave theory, the Everettian many-worlds interpretation (sorry!), QBism, and all the other interpretations of quantum mechanics that are on offer today, to the dustbin of scientific history?

Richard Graff
In the August AMA you discussed a controversy in naming of the Webb telescope given allegations that Webb participated in anti-LGBT activities in the 1950-60s. A point not made was the amount of time and cultural shift between his alleged activity and now. But there is a more complex argument around how much we should project our current values on actions so long ago both chronologically and culturally. What is your perspective on this latter argument for both the Webb controversy and in general?

Rob Patro
This is a bit out of the blue, but I've not heard you talk much about this subject, and I'm quite curious about your take given your background (and prior collaborations with Scott Aaronson). What do you think about the P vs. NP problem? For example, do you think P != NP, what evidence for / against do you find most compelling (including evidence from the physical world), and do you think we'll see a proof (or counterexample) soon-ish?

Sandra Pagliani
When the math says that a black hole's store of information is measured by its surface area, does that mean that the black holes surface is where the information is stored? At the horizon?

Brent Meeker
In your conversation with William Macaskill you switch back and forth referring to ethics and morality as though they were interchangeable. I think that it was one of the advances of the Enlightenment that they were distinguished. That there is a domain of private virtue distinct from public virtue. The latter is dominated by rule utilitarianism because society must be persuaded that the rules are good for them. But private virtue was separated by the wall between church and state. The Church had never admitted this separation. So do you agree to this distinction and if so where is the line drawn.

Kunal Menda
Testimonies of near death experiences describe them as almost psychedelic. Why do you think humans have near death experiences? Is there a way evolution by natural selection could have had a mechanism to select for them?

David Maxwell
In the sub-fields closer to your heart, who do you think might win Nobel prizes for Physics in the coming years? And are there particular people or theories you think should win if experimental verification were not so important?

Tim Gianitsos
You argued in last month's AMA that it makes just as much causal sense to say the past is responsible for the present as it does to say the present is responsible for the past.
I wonder if similar reasoning can be applied to bottom-up empiricism vs top-down. Scientists are generally bottom-up. We think what's "really" going on is quantum phenomena, and so all macro phenomena could be reduced to complicated particle interactions. But isn't it equally legitimate to say that what's "really" going on is personal agency, fluid dynamics, & the economy, and that the quantum world must be the way it is because of THEM?

Jon
I'm wondering about the possible amplitudes of gravity waves. Is it possible to create a gravity wave so strong that its troughs are temporarily black holes or conversely to have a crest so high that light could escape a black hole?

Vladimir Belykh
How will higher education evolve over the next few decades, in your estimation? Nowadays, in the Information Age, more and more people choose to self study instead of going to college, because they are able to learn those same skills on the Internet practically for free, for instance.

Brendan Hall
An annoyed Asher Peres once said at a conference in response to a quantum interpretations poll 'And who here believes the laws of physics are decided by a democratic vote?'. Being a many worlder myself, this made me sad and angry that this very smart physicist could be opposed to discussion of interpretations, but especially his opposition to a simple pole of opinions. How can this attitude still be so strong in physics?

Oleg Ruvinsky
The great Polish Sci Fi writer Stanislav Lem devoted a lot of his works to the problem of contact between human and a truly alien intelligence. Even when both sides recognize each other as such he claimed that the different evolutionary paths that each taked makes any kind of meanigful contact or comprehension almost impossible.
Have you read some of his later works like "Fiasco" and what do you think about the idea in general ?

P Walder
Can abstract ideas have a causal effect on the material world ?

Paul Hess
The Higgs Boson seems unique among all other particles as having no charge and no spin value. Is there some deeper significance to this uniqueness?

Wells Burrell
Do you have any major ethical concerns about the gene editing revolution--other than germ line editing of human embryos--and if so what are they? On the whole, do you believe that gene editing is a positive technology which will deliver on the hype? what kind of future do you think is realistic here?

Shred Cadmium
Temperature is defined as the mean kinetic energy of a system. In my view this concept doesn’t have a direct equivalent in quantum theory because the ‘mean’ & ‘system’ bits, whilst representing something entirely real, are only appropriate to a macro-level of description.
My friend thinks I’m wrong. Is he right?

Andrew Goldstein
Any thoughts as to why human vision is limited to EM wavelengths of roughly 400 - 700 nanometers? I've read that insects can see ultraviolet light and birds can sense magnetic fields.

Sandro Stucki
Your discussion with Will MacAskill on Long-term-ism made me think about how one can increase one's confidence in predictions about the long-term future. I remembered that climate scientists evaluate their models by running them in the past and comparing the results against historical data. But this seems really hard when it comes to predictions about the impact of human choices. I'm struggling to come up with examples of historical decisions for which we can say with certainty that they improved or worsened the present. E.g. we probably needed the industrial revolution to get to today's high standard of living but it also resulted in climate change, etc. Are there historical decisions that impact us today and that you wish had been taken earlier or had not been taken at all?

Maxine
I have recently heard that a good way for a layperson to understand gravity in general relativity is that gravitational time dilation is what "causes" the gravity we experience here on Earth. The explanation is that one can imagine a falling person with a clock on its head and a clock on its feet ticking at different rates.
This "time gradient" is said to rotate the objects motion arrow (a.k.a. 4-velocity) more and more towards the Earth and this is what we experience as gravity. It seems pretty amazing and at least an apparent sense of being intuitive! Is this a good way for a lay person to understand the fascinating, but intimidating, inner workings of General Relativity??

Anthony Famularo
I'm afraid you triggered a touch of PTSD in me with your Bigfoot story in the last AMA. I'm a couple of years younger than you, and when I was a child, the documentary I believe you were talking about was heavily advertised on TV. Every time the ad appeared, I ran screaming from the room, and was terrified for hours afterward. Just to verify that it was the same documentary, do you remember whether there was a scene in which a someone was sitting calmly on a couch, only to have Bigfoot's huge arm crash through the window next to him and violently grab a table lamp? I'm afraid that just Googling it would be too much for my heart.

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Eric Stromquist
I’m interested in any comments you have on why the truth of the “past hypothesis” is taken to be surprising or unexpected.
I understand that if the initial microstate of the universe was drawn from some probability distribution of microstates in phase space, then that state would likely correspond to a high-entropy macrostate because higher entropy macrostates occupy most of phase space by definition. But why do we assume (if we do) that there should be such a random distribution, meaning that the big bang shouldn’t produce some especially simple, symmetrical or unique state, which may correspond to a low-entropy macro description: the big bang is, after all, a pretty special event.

Mike Brock
It often hear it said that the Big Bang did not happen at a point in space, and that it is a moment in time. It is also said that the Big Bang happened everywhere at once. I conceptually get this. But one question I have, is at the instant of the Big Bang, did the universe have spacial extent at all?
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Bruno Teixeira
Congratulations on the episode with William MacAskill, it was one of my favorites. It was too bad you couldn't dig into "Averages and Utilitarianism" so I'll ask here: isn't MacAskill's ranking alternative to scoring happiness, combined with Henry Sidgwick's idea of maximizing "number of people x average happiness", the perfect solution to your worries about Utilitarianism?

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Eric Speckhard
What exactly do constructivists and nihilists disagree about? What do nihilists deny that constructivists accept?

Jimi
Without moral realism, how can we ever justify intervening in other people's affairs to impose our own morality? I feel like there needs to be a way to help people without being hypocritical.
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David Wright
I have to ask your take on the controversy over whether recent JWST images showed evidence that cosmic inflation theory is mistaken. How do these images somehow contradict the red shift data that results from an expanding Universe?

Dušan Stojanović
Here is the gist of an often-made argument which I think is flawed, and which you’ve also used on occasion, most recently in the July AMA:
“Several of the most recent presidential elections would’ve gone Democrat, had the competition been for popular vote instead of for the electoral college.”
In my opinion, better political campaigns are the ones that are responsible for close election victories, and thus the better of the campaigns would’ve just campaigned differently - say, targeting California, New York, Illinois, Massachusetts, etc. - had the popular vote been the goal. Saying that Donald Trump won the electoral vote, but Hillary Clinton won the popular vote, is akin to saying that Team A won the basketball game against Team B on points, but Team B won on rebounds. The definition of the verb “to win” assumes the existence of a particular competition or contest. Please comment.

Igor Vilotic
What do you think about David Deutsch criticism of Bayesianism as philosophy of science or epistemology? With some examples like that when an experiment refutes a highly believed theory you don't know if "credence" for the theory or for the quality of an experiment should go down. Or the conjunction (T₁ & T₂) of two mutually inconsistent explanatory theories T₁ and T₂ (such as quantum theory and relativity) is provably false, and therefore has zero probability. Yet it embodies some understanding of the world and is definitely better than nothing.
As opposed to that he thinks that what science really seeks to ‘maximise’ is explanatory power, and that although all our best theories of fundamental physics are going to be superseded eventually, and we therefore believe their negations, it is still those false theories, not their true negations, that constitute all our deepest knowledge of physics.

Roo Phillips
How do you navigate interactions with professional colleagues that strongly disagree with the science you focus on? For example, Sabine Hossenfelder is someone you respect as a physicist and yet she calls people that do many worlds science "confused". Do you avoid interacting with credible professional scientists that can be somewhat hostile toward people like you and string theorists, or do you just avoid that topic when you chat, or something else? I'm curious about the interpersonal dynamics here.

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0:00:00.3 Sean Carroll: Hello everyone, welcome to the September 2022 Ask Me Anything Edition of the Mindscape Podcast. I'm your host, Sean Carroll. And coincidentally, the day that this AMA Podcast gets released into the wild, which will be Monday, August 29, is the first day that I will be teaching at Johns Hopkins. So I'm very excited about this. At 10:30 AM, the Physics of Democracy will meet, and then on Wednesday, I'll be teaching that class again as well as topics in the philosophy of physics. So very exciting, also very tedious in some ways, like I have to worry about learning how to use Canvas, which is what the universities these days use, is their app that interfaces between professors and students and stuff like that. Nobody likes Canvas as far as I can tell, but there it is, everyone's got to use it.

0:00:49.4 SC: I gotta figure out the room that we're in. Remember all that that I needed to worry about back many years ago, I gotta worry about it again. I looked at the rooms that we're in and they're okay, but they're not perfect, and I have to decide whether or not to try to make them more perfect. Very, very exciting. There's also substantive things about democracy in physics and philosophy that I need to worry about. That's the fun part. I'm very much looking forward to that.

0:01:12.4 SC: I'm very much looking forward to meeting the students and getting excited about what they're interested in and how we can learn about it during the upcoming semester. But also thinking about students and teaching them has reminded me of what it's like to be a student, all the issues there, and that's part of why we have the Mindscape big picture scholarship. So let me give you a very brief update on that. Remember, this is a scholarship that will give $10,000 to someone who wants to study the Fundamental Mysteries of the Universe as an undergraduate college/university student, with some preference for first generation students, people who are from underrepresented groups within Physics, Philosophy, Biology, Computer Science, whatever the area is that they are going to be studying. And what is the good news is we have enough donations from the Mindscape listenership to fund a scholarship this year, so someone is gonna get it. So I also wanted to send the word out there to potential students that you should apply if you are going to be a college undergraduate this upcoming year. I've already gotten requests from people who are not gonna quite be that.

0:02:24.7 SC: No, it's gotta be people who are going to be college undergraduates this year. Maybe you're entering, maybe you're already there, but that's who it's for. So you go to bold.org/scholarships/mindscape, and check it out. Also, if you are not going to be a college undergraduate, but you want to contribute to the scholarship, you can certainly still do that. We have enough to fund one scholarship, we're hoping to get enough to fund another one, so we're just a couple of thousand dollars away from being able to fund two scholarships this year. If we don't make it, no big deal, that money will roll over and we'll use it next year. So feel free to either donate or spread the word to people who might want to do that either as applicants or as donors. Bold.org/scholarships/mindscape. Occasional reminder, this is the Ask Me Anything edition of Mindscape, which means it is funded by Patreon supporters. I feel like I'm just asking for money all the time here. That's not any good. But on Patreon, you can go to patreon.com/seanmcarroll to become a Patreon supporter of Mindscape for a dollar per episode or something like that, whatever you want to donate.

0:03:38.9 SC: Those are the folks who get to ask questions every month, and it is through those donations that we can afford to get the transcripts, things like that, and send these AMAs out into the world. But hopefully everyone enjoys listening to the questions and the answers, whether or not you are a Patreon supporter. The AMAs are for everyone, just like the rest of Mindscape. So with that, let's go.

[music]

0:04:19.0 SC: Ian McCarthy says, what is complexity? I love this question. It's a famous question, where we've been debating the definition of complexity for decades now. And there's two things that I will say, neither one of which will directly answer the question. Ian puts a little smiley face after his question. So I think that he knows that he's trying to stir the pot a little bit here.

0:04:40.1 SC: The one thing I will say is that I don't think that there is a single definition of complexity, I think that there are aspects of complexity that are important. One aspect is there is sort of structure going on on various different scales. Another aspect is that there is some number of steps that it takes for a process to happen. Yet another aspect is that the configuration or the image of something is hard to capture in a short definition, and so forth. There's many different aspects, and these are related to each other, but they're not the same.

0:05:13.8 SC: It's very analogous, I think, to the discussion we had about the nature of life with Stewart Bartlett on the podcast some time ago, and Stewart and his collaborator proposed that rather than trying to write down the definition of life, we would write down all of the different aspects that we took seriously when we talk about life, metabolism, reproduction and so forth, and we can even imagine that there are different things out there that you may or may not wanna call life, but that they have some subset of the different aspects that life has, and that's very interesting because it helps us plan out what to look for. I think complexity is the same way, rather than saying, this is what complexity is, that is not what complexity is, let's appreciate the different aspects and put them into context.

0:06:01.1 SC: But the other thing I will say is that if I were forced to come up with a definition, I would do it sort of negatively, I would define complexity in terms of what it is not, but this is, I will admit before I say it, I'm very much thinking like a physicist here, and as someone who has interest in computer science or something like that might have a very different way of thinking about complexity. But my definition is the following. In physics, we have situations where sometimes you have a small number of moving parts, where you're just doing the planets moving around the sun or the hydrogen atom, or even the uranium atom doesn't have that many moving parts, double-digit numbers of moving parts.

0:06:43.6 SC: And therefore it's helpful and useful and possible to look at the system in terms of just specifying what every part is doing, okay? And that's sort of the simple side of physics. Then there's another aspect where you have many, many, many moving parts, like gas in a box. Okay? And if you were back in the 1800s and you were helping to invent statistical mechanics and fluid mechanics and things like that, you would realise that you can average over the properties of these different tiny little pieces, atoms, molecules, etcetera, to define collective variables, like temperature, and pressure, and velocity, and so forth. And then in terms of these collective variables, emergent variables, you might want to say, you get a different description that is nonetheless simple, fluid mechanics and thermodynamics are still simple in their own ways, because the individual idiosyncrasies of the constituents don't matter, they can be averaged over, smoothed out. So that's a different kind of simplicity in collective behaviour.

0:07:48.1 SC: So you can define complexity, and I think in a fairly useful way by saying it's when neither of those two things happen, when you neither have just a small number of particles nor do you have a large number for which all of the individual idiosyncrasies smooth out and can be averaged over, still giving you something interesting. In complex systems, you have a large number of things going on and the individual things still matter in some sense. What exactly that sense is is difficult to pinpoint, but that's what makes the system complex because it gives rise to unpredictability, or at least maybe at the best, statistical predictability and things like that, it gives rise to power law behaviours rather than a naive application of the central limit theorem or something, it's not like all quantities home in on some average, but rather you have a distribution that is non-trivial and spread out, so that's where complexity comes in, where neither of those two versions of simplicity are working, everything that falls into the not fitting bucket then gets called complexity.

0:09:00.5 SC: Christian Wigont or Vigont says, "Regarding Episode 168 with Niel Seth, what do you think is the most promising, helpful, interesting, fun approach towards a formal definition of weak emergence? For example, dynamical independence as proposed by Barnett and Seth, or something like a ratio of macroscopic and microscopic systems complexities or some notion of computational irreducibility." So I don't think it's any of those, to be honest.

0:09:27.4 SC: I think that what we talked about with Niel Seth is a version of emergence that is very useful, but it's very much in the particular context of these stochastic unpredictable systems, where information about the state of the system or what the system is going to do can be correlated from moment to moment, and that's very helpful in those situations, but I think you might want a definition of emergence that is broader than that. Certainly the paradigm that I have in mind is pretty clear, but I will confess that the details are not completely clear, at least to me. I think this is one of the things I would like to do, is to offer up to the world yet another definition of emergence that is as broad as possible. And so to me, the definition is just that there exists some macro theory, that is to say some theory, which is a way of talking about, let's say, the dynamics of the system or something like that, that gives some predictions for how the system evolves, and those predictions are reliable, even if they are sometimes probabilistic in nature, flipping a coin, 50-50 chance, it's heads or tails, that's a theory of the coin, even though it doesn't tell you deterministically what the coin is going to do. Okay?

0:10:48.4 SC: And so the existence of emergence is when you have such a macro description that is a useful theory. That's it. And a macro description, of course, is one where many particular configurations of the microscopic system get mapped onto a single macroscopic description, so you're throwing away some information. That's the existence of what Daniel Dennett would call a real pattern. If you go back to the podcast we did with Dan Dennett, we talked about real patterns existing hidden in the full comprehensive description of the system. So if you think once again about fluid mechanics, okay, what you're saying is that you don't need to know where all the atoms are, what all of their momenta are to say something interesting and true about the system.

0:11:34.7 SC: There is an extra pattern over and above the comprehensive pattern. And the comprehensive pattern is given all the atoms and molecules, they obey Newton's laws or whatever, if you're doing quantum mechanics, etcetera. But there's an extra pattern, there's a pattern over and above that, a real pattern that says, you don't need to know all of the information that Newton's laws need. You can throw away almost all the information if you throw away the right information. Okay? And so there is... One way of thinking about it, the most naive way is there is a commuting diagram, maybe this is not exactly the most naive way, but this is how mathematicians think about it. Okay?

0:12:12.4 SC: So there is a diagram in the space of configurations of the system and the theories describing the system, so you have the initial configuration of the system and there is an arrow that points you to the later configuration of the system. So the system evolves for some time. But then there's another arrow pointing off in a perpendicular direction that says, I coarse-grain my system, I map that micro state of the system to a macro state that it's in, and then I can do a third arrow that maps the macro state forward in time under the new theory, and a fourth arrow that takes the evolved micro state to the evolved macro state. So I started from the micro-state and I can either evolve it forward in time and then coarse-grain it, or I can coarse-grain it and then evolve it forward in time.

0:13:00.8 SC: And the point is that the diagram commutes, you get to the same place by either one of those two routes, coarse-graining commutes with time evolution. Okay? I think that's the most important aspect of emergence. But there's a lot of details there that I'm glossing over to make it sound more clear than it is, but I think that's the heart of the matter. And one reason why the topic is confusing is because what I'm increasingly realising is that... Well, it's perfectly obvious the word "emergence" means different things to different people, even when you try to define it, they're gonna insist on using their own definition, and that's fine, but what I'm realising is that there are some people who have definitions of emergence that, by construction, leave out all of the examples that we understand, [chuckle] so they only want emergence to count when it's mysterious, when it's something that is hard to actually write down the equations for, etcetera.

0:14:06.1 SC: All of my inclination is going the other way, that if we have a definition, we should look for one that works for both simple situations and for complicated situations, because then our understanding of the simple situations will help us gain insight about the complex ones that we don't fully understand. So anyway, I think it's work in progress, to be honest, people have given very good definitions. The original... There's a classic paper by Mark Bedau about weak emergence and the difference between strong emergence that is well worth reading and has many, many citations. It's a pretty good definition if you want that. His definition is basically, I could put it on a computer, which I think is the same as my commuting diagram, macro state definition, but there's little details that do end up mattering.

0:14:51.8 SC: Maggie Liu says, how important do you think intelligence is for a career in physics? This is a bit of a loaded question. The simple question, the simple answer is, it does matter, it's pretty important, but there are much more nuanced and sophisticated answers here because two things, number one, I don't think that intelligence is a single thing that is easy to pinpoint or define, and number two, there are many, many ways to have a successful career in physics involving different skills, different skill sets, different career trajectories, and the whole bit. Being an atomic physics experimentalist is a very different lifestyle than being a string theorist, it requires very different skills. Of course, in both cases you need skills. [laughter]

0:15:38.6 SC: But I think that a lot of people over-simplify the definition of intelligence and they sort of mix it up with some particular aspect of intelligence that is related to solving complicated math puzzles, and that is actually pretty highly correlated with your success as a string theorist or other kinds of theoretical physics, but it's not perfectly correlated. Within the fields that I know very well of theoretical physics, some people are much better at math than others, and it's not a perfect correlation with how good you are at the physics side of things. Some people have physical insight that is pretty amazing. Albert Einstein was not as good at math as Henri Poincaré, but he did better at understanding relativity 'cause his physical insight was completely unmatched.

0:16:28.0 SC: So I think that I actually just wanna ignore the question, I wanna say, who cares how important intelligence is? What matters is, are you good at doing physics? That's what matters for a career in physics. And there are many different ways of being good at doing physics. Preston Justice says, Immanuel Kant said in his Critique of Pure Reason that whatever the process and the means may be by which knowledge refers to its objects, intuition is that through which it refers to them immediately, and at which all thought aims as a means, but intuition takes place only in so far as objects are given to us. In what ways do you think Kant's description of intuition would change if he knew everything we knew about the physical world today? Also, how would you describe intuition?

0:17:10.8 SC: I admire Immanuel Kant as a brilliant philosopher, a very important guy, but I'm not very Kantian in my own ways of thinking about these things. And sentences like this are part of the reason why. When Kant says, intuition takes place only in so far as objects are given to us, I'm not sure what he means. I think that he probably has something very clear in his head, but what does it mean for an object to be given to us? Does that mean that it's as I look at it and sort of experience the coffee mug right in front of me right now, or is it sort of some a priori notion of extent in space or something like that?

0:17:52.2 SC: I really don't know exactly what he's referring to, maybe a Kant scholar would know, 'cause they are more familiar with his linguistic stylings than I am. But anyway, I think that... Again, I'm not a Kant scholar, so maybe this is wrong, but I think that Kant also takes intuition much more seriously and fixedly than I would. I'm someone who believes in intuition, but I don't believe that intuition is just something that appears instantly when we're born and never changes, I think that intuitions can be developed.

0:18:26.8 SC: I mean, certainly, I think, in fact, it's kind of hilariously obvious that intuitions can be developed. In some sense, whenever you play a sport, whenever you do any physical activity, you notice that you sort of get better at it in ways that are not amenable to being described in words, or put into cognitive terms, in your body, how to hit the baseball, or how to hammer the nail, or whatever it is, how to cook a meal, how to drive to work. There's a whole bunch of things that we do in the world that are system one, as Daniel Kahneman would say, not system two, the conscious cognitive part of our brains. And we can train that, we can get better at it, and there's a version of that in science where you get to know the scientific insights better, whether it's relativity or quantum mechanics or DNA or biology or whatever, and you develop an intuition for it.

0:19:22.1 SC: So I don't think that it... I don't know what it means, it doesn't seem very helpful to me to say intuition takes place only in so far as objects are given to us, unless you really define "given to us" in such an incredibly broad way that it includes all of the different things we learn by doing science, which is given to us because we've worked really, really hard to get it, in some sense. But anyway, this is just my incredibly under-informed take on that really tiny excerpt from Kant's enormous corpus of writings.

0:19:58.4 SC: Paul Cousin says, "I'm curious about what many-worlds implies for the Big Bang. Is there something special about its version of the beginning of the universe. Were there a lot of branches created then? And to which extent could they differ?" Well, I think that we don't know what happened at the Big Bang, right? So that's... It's not clear. Is a very short answer. I think that many worlds is a theory... What many-worlds really matters for is the process of quantum measurement in something more like Copenhagen interpretation, quantum measurement is fundamental, it's an important part of the dynamics, the Wave Function collapses under measurement and so forth, whereas in many-worlds, measurement is nothing special, it's just a special case of decoherence and branching and so forth, is much more mechanistic and crisp. And what happens at the Big Bang is not really very highly influenced by your opinions about quantum measurement, I think. So I don't think that there is a straightforward good answer to what many-worlds implies for the Big Bang, if there's some quantum state of the universe near the Big Bang, that will be just as true in many-worlds or Copenhagen or whatever.

0:21:15.8 SC: The converse might be interesting. What does the Big Bang imply for many-worlds? Many-worlds is a story of time evolution that is irreversible. Many-worlds involves a very strong arrow of time. The fundamental ontology does not involve that, it's just a quantum state moving in a Hilbert space, but the way that it shows up in our actual world is very highly reliant on the arrow of time, branching happens toward the future, not toward the past. And so what you need to set up the whole theory and make it work is a quantum state near the Big Bang where there weren't that many branches, it was a small number of branches in the way that we would normally think of them, and branching happens toward the future.

0:21:57.3 SC: Again, I think that that's not saying anything about the quantum state of the universe that wouldn't be said in other formulations of quantum mechanics, but it is a specific, very, very important thing to say in many-worlds that we need to understand. Now, you know that the arrow of time depends on the low entropy of the Big Bang, and so there's clearly... Even if you do know about quantum mechanics, even if you're just being classical, even if you're Ludwig Boltzmann, you would be able to say, "Yes, the entropy of the early universe was very, very low, and also many-worlds require some particular features of the Wave Function of the universe at early times, clearly those are related, in fact, they're probably exactly the same thing. The reality is that there was one particular state of the universe at the Big Bang, and it was a small number of branches and low entropy, which are related statements, but not exactly the same statement. And then once you get that, whether you get it from Stephen Hawking or some other way of understanding the Wave Function, you're off to the races, then you just like quantum mechanics do its work.

0:23:01.1 SC: Terrible Turnip says, "Would you be able to describe the way in which spatial locality arises from just a Wave Function, or is it too technical?" Well, [chuckle] that would presume that we know the way in which spatial locality arises from just a Wave Function. But I don't think it's too technical, we have ideas, I certainly have ideas about how that happens. So when I thought about, when I read this question, there is a technical way of saying it, but I think that you're implying that you don't want the technical way of saying it, so let me say it in a different way, almost by way of analogy. Think of, again, particles in Newtonian physics interacting, let's say, through gravity. Okay?

0:23:44.5 SC: Or even... Yeah, even forget gravity. Let's say they interact as billiard balls, so they're hard spheres, so they bump into each other, but they're in outer space, a box of billiard balls. So a big box with bouncy walls with lots of billiard balls bumping into each other. And also there's no air in the box, so there's not a lot of air resistance or anything like that. And you could observe all these particles in the box, right? And of course, if they hit each other, they will bounce off and scatter at some angle, and if they don't, then they just keep going in straight directions, that's why it's better to ignore gravity for this, let's just have them bounce into each other.

0:24:20.1 SC: So hard sphere, contact interactions. Okay? So, if you have N such particles and we're in three-dimensional space, then Newtonian mechanics says you can describe these, you can do a weakly emergent mapping, 'cause you don't need to know where all of the atoms in the billiard balls are, you just need to know the locations of the billiard balls themselves to predict what is going to happen. So you have N points in three-dimensional space, and you actually also need the momento or the velocity of the particles, so you have another N points in three-dimensional space, but three-dimensional velocity space instead.

0:25:00.4 SC: So in total you have 6N dimensions to completely describe the state of such a system, billiard balls bouncing around. Okay? And what you can do is abstract yourself, be like a mathematician and say, well, that's equivalent mathematically to one point in a 6N dimensional space, and that 6N dimensional space, of course, is just the phase space, the space of initial conditions for that system of billiard balls bouncing around in the box. And the nice thing is you can write down Newton's laws of physics for the evolution of that single point in 6N-dimensional phase space. Right? And you don't need to know, if someone says that 6N equals, I don't know, 60, and you and I know that that means there's 10 particles, but it's a 60 dimensional space. And so you have a point in a 60 dimensional space, and you have some equations to tell you how the point evolves with time. And you don't need to know that it's 10 particles in three-dimensional space, you just need to know that it's one point in a 60-dimensional space in order to, in principle, tell you how the system evolves. Okay?

0:26:23.6 SC: So you could ask yourself, well, how do I know that it really is just a highly abstract mathematical level? How do I know it really is points in three-dimensional space with velocities? Where did the three-dimensional space come from if I could think of it as one point in 60-dimensional phase space? And the answer is, if you look at the laws of physics, and for that one point in 60-dimensional phase space, they look weird, [chuckle] they look like the point in 60-dimensional phase space just sort of moves on a straight line for a while, and then at some weird time it sort of moves into a different direction.

0:27:07.2 SC: And you and I know that it moves into a different direction because two of the balls hit each other, or one of the balls hit the wall. So the point is that there are two completely equivalent ways of describing it, one way is this abstract single point in 60 dimensional phase space, another is 10 balls moving in three-dimensional space with velocities, but the latter description, even though these two descriptions are mathematically completely equivalent, that latter description gives you way more intuition, as we were just talking about it, about what happened, so more understanding. You can say, "Oh yes, the two balls scattered. I saw it happen right in front of me, right there."

0:27:46.1 SC: Okay, that makes sense. So even if... So you can imagine some really weird counterfactual physics where you had just been handed that 60 dimensional system and you could do experiments, you could put a point down and watch it evolve and see what happens and say like, What are you looking at? What is this 60 dimensional system? And eventually you would work out that, Oh, you know what, it's actually better to think of it as a bunch of balls moving around in three-dimensional space with also three-dimensional velocities. And so that is a kind of emergence of locality. The idea of locality is there in the balls moving in three-dimensional space description, but it's not there, it's implicit, but it's not written down in the 60 dimensional phase space description. Okay?

0:28:38.9 SC: So locality is a simplification that gives you some handle on what happens and also some counterfactual reasoning abilities, you could easily know if you understand the local description in three dimensions of space and someone says, okay, I change the initial conditions by a little bit, what will be the difference in the evolution if the initial conditions to you looking at the three-dimensional space are, "Oh, I moved that billiard ball just before it was gonna hit another one," then you know instantly what's going on. Whereas if you're just given this abstract description in 60-dimensional space, you're going, "I don't know, I just have to run the simulation, I don't know what to say about it."

0:29:18.5 SC: So that is morally the way that spatial locality arises from the Wave Function, because the Wave Function is like that point in 60 dimensional phase space, right? It's the complete description of everything in the simplest possible form, but it's not giving you some intuition, the down and dirty level that you can easily extend to counterfactual situations or anything like that. But you can take that Wave Function, written abstractly, and say, "Well, let me chop it up into pieces in interesting ways. And what are the ways I can chop it up into sub-systems interacting with each other that give me some intuition?" Just like the billiard balls in the original example.

0:30:02.5 SC: And the answer is, if there is a spatial locality, then you're gonna be able to chop up your Wave Function into different subsets that interact with their nearest neighbours, as you interpret it after the fact, and not interact with regions far away. And so that's a technical exercise to go through to make that happen, but that's basically what you're doing when you're talking about spatial locality arising from the Wave Function. A footnote, it doesn't arise from just the Wave Function, it needs to also arise from the evolution of the Wave Function, so either The Schrödinger Equation or the Hamiltonian, or however you want to put it, a Wave Function sitting there statically gives you no information about spatial locality at all.

0:30:47.6 SC: Nikolas Sabo says, "How is the simulation hypothesis/argument/whatever a thing that people take seriously? To me, it's always felt like it's just the repackaging of good-old anthropocentrism, and teleology, and those urges of humanity, it's sneaking God in back again, exactly as creationism had tried a few decades earlier by pretending to be scientific and not mentioning God per se. Also, it's a bombastic claim, so the press loves it. Also, you can explain it using a popular Hollywood movie that everybody saw. Also, Silicon Valley people love it. But how can scientists and philosophers take this whole hype seriously and discuss it, argue about it?"

0:31:25.8 SC: Well, I notice in reading the question, clearly there is... It's what we call a leading question. [laughter] It's not just like, how can philosophers take this seriously or scientists take this seriously? It's like, and they certainly shouldn't, right? But you didn't actually give any reason why they shouldn't, you just indicated that you don't like it. There is something called the simulation argument, and it's not just there's the simulation hypothesis. Okay? That's one thing, but there's a simulation argument which is an argument that says, "Here's why I take it seriously." And the argument is that we can easily imagine building computers that simulate other conscious minds, and we can easily imagine building many such computers with many such simulations, so that there are many more conscious minds in our simulations than not in our simulations, and therefore in the set of all possible conscious observers that might exist in the near future, most of them are gonna live in simulations, and if that's the case, probably we live in a simulation.

0:32:36.9 SC: I don't necessarily buy that argument, but that is an argument, and if you want to disagree with an argument, you're welcome to do so, but you disagree with it by offering counter arguments or pointing out logical flaws in it, etcetera, you don't disagree with it by saying, "Yeah, it sounds like God to me," that is not really an argument for anything.

0:32:54.6 SC: Finally, God is a perfectly good thing to consider. I think it's very much like the simulation argument in that a thousand years ago, if I could completely implausibly imagining, transiting my current state of awareness back to a thousand years ago and removing all of the modern knowledge from myself, God would have made perfect sense, it would have been a leading candidate for understanding the world in the absence of science and things like that. It's not like God shouldn't be considered as a hypothesis at all, you should consider it, you should be a good Bayesian and predict what the world would look like if God really were the right thing, if theism were the correct ontology, compare it to naturalism, etcetera.

0:33:39.2 SC: And then in my view, it doesn't come out very well. And likewise for the simulation argument, by all means, you should consider it, and then you should make predictions on the basis of it, you should compare them to the world that we observe and you should compare the mechanistic reality-based version to the simulated version. In my mind, one, when doing that, I find no evidence that there's anything gained by imagining that we're living in a simulation, and in fact, I think I could easily argue that if we did live in a simulation, the world would look different, and so as a good Bayesian, I count that against the argument, but you have to do the work, you have to do the logic, you have to do the reasoning, you can't just say, "Yeah, I don't like it".

0:34:20.2 SC: Peter Bamber says, "Is there any difference that matters to you between thinking that we live in a simulation determined by rules chosen by the simulations commissioners last creator, and thinking that we live in a reality determined by rules, forces, mathematics that are part of nature?" Clearly a related question, but I didn't wanna group them together because they're a little bit different in directionality, I suppose, in thrust. I'm not sure Peter went to the effort of putting "is there any difference that matters to you" in emphasis, but I'm not sure what exactly you mean by that. Do you mean like matters to me living my life, in terms of ethics or morality or anything like that, or do you mean my vision of the world, my scientific curiosity, trying to understand the world? So certainly, I care about whether or not we live in a simulation or whether or not it's just physical reality, because I care about the ultimate nature of reality, otherwise, I wouldn't be doing what I do for a living. This is a goal of mine, to understand correctly the fundamental nature of reality, and that fundamental nature of reality is certainly very different if we live in a simulation than if we don't.

0:35:30.3 SC: So that matters to me in that sense. If you mean, do I live my life differently, then no, I don't really have strong feelings about how to live your life if you do live in a simulation, but it's clearly one of those things... It is... This is a similarity, I think, between the simulation argument and theism, which is that the world that we find ourselves in is really very well described by naturalism, physicalism, and taking the world that we see as base reality. So I could easily imagine either theistic universes or simulated universes in which the nature of those universes as simulated or created by God was perfectly obvious, like God just made his reality known, or the simulators made it very clear, or even if the simulators didn't make it very clear, there was various features of our world that were very simulation-like, right?

0:36:29.3 SC: So we see none of those, and this is why I'm not a fan of either theism or the simulation argument, because you have to buy into versions of those arguments where for whatever reason, the world ends up looking perfectly physical and naturalistic. And so once you get to there, I don't have any differences in my every day life for how I live whether or not I live in a simulation. Gregory Casnic says, "I share your fondness for Robert Heinlein's The Moon Is a Harsh Mistress, and I'm curious about your opinion of Starship Troopers. In particular, do you think there's a merit to the idea that citizens should have to earn the right to vote through some sort of public service, not necessarily military service?"

0:37:10.9 SC: So for those of who don't know, Robert Heinlein's book, Starship Troopers, which won the Hugo Award for best science fiction novel of the year, imagines a society where you can vote, it's a democracy, but the right to vote is earned rather than just given to all citizens when they reach a certain age, and it's earned by doing some government service. The particular government service that is focused on the novel is military service, thus the name Starship Troopers, but it's made clear in the novel that many other kinds of public service still get you the right to vote, so gets you the franchise. The movie that was made with the same title is very, very loosely based on the book, completely different in spirit from the book. The movie has its own charms, but it's not the book, so don't mix up the two of them.

0:38:02.2 SC: Look, and I think that as a book, Starship Troopers, for me just isn't nearly as interesting and deep and fascinating as The Moon Is a Harsh Mistress is, it's a fine book, but also I don't take too seriously these thought-experiment societies that are investigated in these books. I don't think of Starship Troopers as an advertisement for the idea that we should earn the right to vote by public service. It's a thought experiment. It inspires you to think about that idea. So I don't think that just because Heinlein proposes that idea in that book means that he was trying to say that it should be done, maybe he did think that, but I don't think the existence of that book does it. After all, there's plenty of other books he wrote where you don't have that system.

0:38:54.6 SC: And also, I don't think it's a good system, no, very roughly speaking, I don't think it's a good system. I think that I get it. And I remember there was a question either last month or a couple of months ago about, given my support and concern for modern democracy, what are the flaws and worries that I have about democracy? And a possible worry that you might have is that you're giving the control authority over the country, over your nation, to every random person, not necessarily to people who have any expertise, much less a vested interest in some form.

0:39:29.1 SC: And I get that worry, I appreciate that. That is a worry, and I think that the virtues of democracy are enough to overcome that worry, and I think that the same thing is true for investment in the country as they are for expertise in running the country, namely that to me, the real reason to have a democracy is not because it is the best decision-making process. We did talk with Henry Farrell on the podcast about how democracy can be a very, very good decision-making process for very various reasons. But to me that's not the real sales pitch. The real sales pitch is people who live in a country have an interest in it, they have desires, they have values, they have things that they want to be their own interest to be protected, and so therefore they have a right to vote.

0:40:19.0 SC: That's the argument for me, it's not that they're smarter or better educated or have done more work for the country, it's just that we're trying to reflect their interests in the most fair way possible. That's the moral argument for democracy. You would also, to really be convincing and making an argument for democracy, you'd also need to give a sort of more practical argument for democracy, saying that the system actually works to protect those interests in an effective way, that I think is a harder argument to make, but I do think that they're, as far as I currently believe, it's one of those, it's not a great system, but it's better than all the alternatives kind of things.

0:41:03.7 SC: So I actually think everyone should get the right to vote, everyone above a certain age. I think that it does make sense in any society to draw a distinction between people who are responsible and people who are not, and by responsible, I don't mean like you don't lie to people or whatever, or you do what you promised to do, I just mean you're an adult, you're in sound mind or whatever, whatever criteria you have for saying, okay, you are a fully credentialed member of society, and I think that every such member of society should have the right to vote. That's my own personal belief. Brendan says, "Do you have a preference on how to be addressed; Doctor, Professor, Sean?" So, for podcast purposes, if you're a Patreon of the podcast or any other listener for that matter, you're perfectly allowed to call me Sean, that's fine.

0:41:57.3 SC: In my personal goings from day to day, it's almost always people calling me Sean, not doctor or professor. Of course, this is a timely question because in a couple of days, a couple of minutes, I'm gonna be teaching again undergraduates, and when I was an undergraduate, the system was pretty much that you refer to your professors as either professor or doctor, I see no difference whatsoever between those two things, and I suspect that is what my students will do.

0:42:24.8 SC: When I got to graduate school, then it flips. And in graduate school, at least in the sciences, we referred to all the professors by their first name. Okay. Then, you know, you've made the transition. You've graduated from being a student to being a colleague. Once you're in graduate school. Of course there were some professors that I had as undergraduates that were the cool professors who wanted to be addressed by their first names. And that was great. You know, it was very good when it worked. I have since been influenced by an argument that it's a, there are hidden subtleties unanticipated consequences of being the cool professor who asks to be referred to by their first name, namely, that there are power differentials and hierarchies and expectations and amounts of respect that are differential given to different kinds of professors, maybe depending on your age or your looks or your race or your gender or whatever.

0:43:23.5 SC: And the point is that some people need to work harder to get the respect they deserve as professors than others do. And aging, white dudes like myself, need to work the least hard, so it's easy for me to say, Oh yeah, I'm gonna be the cool professor. Just call me by my first name. But for other people, they need to like establish, you know, look, I am credentialed. I am the boss of the class. I am going to be addressed by doctor accordingly. And I agree with that perspective and I get it. And so I think it's just better for everyone to address their undergraduate professors as either doctor or professor. Having said that if someone calls me by my first name, I'm not gonna complain, it's not a big deal, there are more important issues out there to worry about.

0:44:13.4 SC: Eric Dovigi. I'm combining two questions together, I'm gonna group them together here, Eric Dovigi says, "The possibility of unperceived existence is weird. Can we conceive of a universe with no life forms? In what sense could this universe exist, to whom would it exist? Suns, galaxies, dust, they don't know they exist or do they?" and then Gary Upshaw says, "Can nothing exist?" So I think these are related questions, but they're importantly different questions. Let's do Gary's question first. Can nothing exist? No, because I think that there's a difference between saying, it depends on what you mean by the question. Okay. There's two different parsings of that three word question. Can nothing exist? One would be, can there be something that exists and that something that exists is usefully labeled as nothingness. Okay. That's what I'm answering no to like, I think that's a little bit of a contradiction in terms, if it exists, then it's not nothing.

0:45:15.2 SC: But then there's a, maybe more profound version of the question that says, Could there be nothing that exists, right? Could there be no existing things labeled as nothingness or anything else? There, I don't want to give a firm answer 'cause I don't know, because I worry that it's an ill formed question, because you're, the, it's not because of the word "nothingness", "nothing" or the word "exists", but the word "can". Can there be nothing that exists? What do you mean by can? Okay. And then this is where we need to hire the professional philosophers to chime in here. I think that traditionally sneakily implicitly, when you say like, Can we build a skyscraper a kilometer tall, or can the universe be infinite or something like that. We're thinking about possible actual worlds, right? Whether we believe, you know, we're asking questions within the realm of plausible things, feasible things, or just things that obey the laws of physics or even things that would obey laws of physics in different worlds, with different laws of physics, we're comparing different alternative realities.

0:46:30.8 SC: So the reality in which nothing exists, isn't maybe a reality, right? 'Cause nothing exists in it. It's not there. So I am tempted to say no even to that, but that sounds like I'm saying that we had to exist. The universe had to exist. Something had to exist. I think this is just Tomfoolery caused by a failure of our ability to linguistically construct the question accurately rather than some deep insight into nature of reality. But I don't know, like I did in my paper, Why is there something rather than nothing. I did float the idea that maybe the idea of nothing is just incoherent, right? Like that we're just not dealing with it in a sensible way. And I honestly don't know. I don't have firm feelings about that. To Eric's question, which is, I think is a more straightforward one, what about a universe that existed, but had no life in it?

0:47:24.7 SC: Sure. That can exist. No problem. I mean, after all, there's plenty of places in our universe that exist that have no life forms in them, plenty of places that exist in our universe that no life form will ever witness, the center of the sun will never be looked at up close and personal, but it still exists. Right. It's an extrapolation that we think is there because we look at the outside of the sun and we know how physics works. Okay. So I don't think that existence needs any sort of observation or measurement to be there personally, that's that's my take. Jeff B says, "I'm still a bit confused about interactions and particles in quantum field theory. From your biggest ideas videos I understand that there is a wave function of field configurations. So when two of these fields interacts does the wave function branch into interacted and non interacted?

0:48:15.7 SC: And is there a precise way to tell where in the field, this interaction will take place? As a sub-question, Is the interaction location what we think of as a particle?" So last question first, 'cause that's the easiest one. No, the interaction location is not what we think of as a particle. The way it works is when you take a field and you quantize it, so imagine that you have in the back of your mind, some kind of visualisation of a classical field, you know, some wave that is moving through space. It's actually much harder to visualise than you think, because inevitably you visualise waves in a two dimensional space, but we live in three dimensional space and you have to visualise something going on at every point in space. Okay. So that's actually hard to do, but you could do it. The quantum version of that says that now you're obeying the Schrödinger equation for the quantum fields and you solve that equation for the different energy levels.

0:49:13.4 SC: And it turns out that there is a single energy level called the vacuum, no energy, the lowest energy state of the quantum field theory. And then there is a set of states with a little bit higher energy and I'm hesitating because the energies of these states can be different numbers, but also there's different momenta. Okay. So what I'm getting at, I should just reveal the answer. The point is that there are states of a quantum field theory that to you and me look exactly like one particle and why I'm talking slowly and hesitating here is because of course the energy of a particle can be different, but the energy of a particle in its rest frame is a fixed thing. So there's a set of states that have both a momentum and an energy and have the property that if you measure the energy in the rest frame, then you will get a fixed number for all of these different states.

0:50:07.1 SC: And we call that the mass of the particle being described by this quantum field. And then there's another set of states that have more energy that have at least twice as much energy as those first set of states. And we call those two particle states, et cetera. So the single quantum field describes simultaneously the possibility of zero particles, one particle, two particles all the way up, and then we have different kinds of quantum field. So the particle is not an interaction location. It's a state of the field. And now the state of the field might be all spread out. In which case the particle doesn't look very particle like, but if you were to measure it somehow you would always see it at a location. And that's just a feature that you don't measure the whole wave function, you measure, there's only certain measurement outcomes you can possibly get.

0:50:56.4 SC: So when you're asking about the wave function field configurations, when the, you, the question is so I can repeat it for clarity. When two of these fields interact, does the wave function branch into interacted and not interacted? Almost. So it's a little bit trickier than that. Let's say I have two fields, an electron field and a photon field, right? And they can interact, the electron can scatter off the photon or they cannot interact. They can just go their separate ways. And so there's smooth evolution, according to the Schrödinger equation that takes the wave functions for the two fields and entangles them. And there's going to be part where it looks like the electron and the photon interacted and part where it looks like it didn't, just as you say, but the only reason I'm hesitating is you say, does the wave function branch?

0:51:47.0 SC: But remember branching happens when decoherence happens. And that means entanglement between the system and the environment and the whole rest of the world. So a single electron and a single photon interacting with each other and entangling doesn't count as branching of the wave function. If we then measured the position or the location or the velocity or whatever of the photon or the electron then decoherence would happen because measuring in that sense means I've detected it in a macroscopic detector that has a lot of moving parts. That's the environment and therefore decoherence and branching did in fact happen. So once we measure it, the branching actually happens. But of course, as we said before, measurement is just a fancy way in Many Worlds of saying decoherence.

0:52:37.5 SC: Casey Mahone says, "While I agree with you that some things in the world may just be brute facts, Is it really useful to think that way? It strikes me as similar to invoking the anthropic principle rather than trying to determine why things are one way rather than another, we have an easy fallback option." Well, I would put it very differently. If we admit that some things may be brute facts, it's not that we just say, and therefore they are, that's not being a good Bayesian, right. That's one of the propositions in front of us. So when we have something like the initial conditions for the universe, okay. The conditions that we see near the Big Bang, there is one proposition that says, why is it like that? It just is, it's a brute fact. That's just a feature of the world. There is no more further explanation to be given. There are other propositions that say, Yes, I can explain that in terms of the wave function of the universe or inflation or what, whatever different things you have.

0:53:32.8 SC: And you're gonna have a long list of different claims, different theories that have different ways of explaining or not explaining the initial conditions of the universe. And the good Bayesian says, they're all considerable. They're all there. They should all have some non-zero credence. And as we investigate, it may be that we think for various reasons that probably there is an explanation, even though we don't know what it is, or there might be reasons why we start thinking, no, it's probably just a brute fact. Okay. So it's not giving up. It's just correctly recognizing that sometimes that is the most plausible looking thing.

0:54:10.4 SC: For the initial conditions of the universe, I don't think that attributing them to brute facts is the most plausible thing. I think there's probably better explanations, but for the existence of the universe, I do think that it's most plausible to just attribute it to a brute fact. I could be wrong about that. I don't give it 100% credence. There's certainly other possibilities, even if I can't articulate what they are. So it's, I don't think it's any different than any other option that's on the table. Keith says, "I'm here to report that if all 7.9 billion people on earth request their once in a lifetime priority question, even with easy yes/no questions, answerable at the rate of one question per second, It would take you just over 250 years, given that these conceivable future Patreons would be acting while honoring the unofficial AMA contract priority question section, should there be a caveat amended to the original contract?"

0:55:02.7 SC: So when I first read this question, I was like, you know what? I'd be willing to try. I'd be willing to have 7.9 billion Patreon supporters. That sounds pretty awesome, me making a lot of money. Of course, yes. There would be problems answering all the priority questions. If you do look carefully at what I say about the priority questions, it doesn't actually say I will succeed in answering them. It says, I will try. Right. So I could fail to actually succeed. But it is as Keith points out a little unrealistic to imagine spending 250 years. So I decided to wonder, what could be the most realistic thing that could happen, right? Like how much money could I make at this operation here? And if I had a 100,000 Patreon supporters, little bit more realistic than 7.9 billion, but still not very realistic.

0:55:50.4 SC: And they all asked questions and I gave one second per question. It would take me a little over a day of talking to answer them. So that's quasi realistic, 'cause I wouldn't do it in a row. It wouldn't just be a day out of my life. It would be a day scattered over a week or whatever and so what kind of dreams of filthy lucre would this actually correspond to? Would I be the richest person on earth? And at 100,000 people giving a dollar per podcast episode, that's $100,000 per week, except it's more like $50,000 'cause there's taxes and there's Patreon taking out a cut and all these kinds of dissipation that we have in our financial system. And at that rate, even if I did it, every week with that many with 100,000 Patreon supporters, I figured that it would take me, pardon me if my math isn't working out here, but it would take me about 400 years to become a billionaire. So this is not the way to become a billionaire, to have a podcast here and support it by Patreon, just so you know, but it also, it just pinpoints how much money a billion dollars really is and how we don't make it by the sweat of our hands and our brow all by itself. There needs to be a system in place to funnel money, as we've said before. And there are systems in place that funnel lots of money to single people but Patreon support is not the way to do it.

0:57:11.9 SC: So not that I again, would be against having a 100,000 supporters. That'd be great, but I would try to give them more than one second answers also. So there's a trade off there in addition. Okay. Chris DiRubio says, "What is your credence that octonions which I understand are an eight dimensional analog to complex numbers, will give us deep insights into the fundamental law as of particle physics?" And there were a couple of other octonion questions this month. So I'm just grouping them all together in yeah, in that particular question. So the very short answer is I have no idea. I'm not an octonion expert. You know, I know the basic idea of, ah, maybe I don't even know the basic idea, division algebras, associative division algebras, I forget exactly what the technical math term is for these generalisations of the complex numbers.

0:58:00.2 SC: You have the real numbers, you have the complex numbers, you have the quaternions invented by William Rowan Hamilton, and then you have the octonions. So one dimensional, two dimensional, four dimensional, and eight dimensional. And that's it in this particular classification of things. And of course, complex numbers and real numbers for that matter have been all over physics. Very, very, very important for physics, quaternions haven't had a lot of success in physics. You know, there's a relationship there, but most working physicists wouldn't know a quaternion if it bit them in the nose and octonions have had almost no success in physics, there's been some relationship to exceptional lead groups and things like that, but it's definitely not a major thing. So I can give you my rough guess as to the answer, which is, so the real answer is, I don't know, the slightly more firm answer is, probably not.

0:58:52.0 SC: I don't think it'll give us any deep insights into the fundamental laws of particle physics. Now I could be wrong. That's not proposition on which we have credences and I will update my credence appropriately. But I think that that kind of hope is a little bit backwards compared to the actual historical progress of physics. You know, there's a long tradition in physics of people falling in love with mathematical constructions and operations and trying to shoehorn them into physics. And as far as I know, it literally never works. Like it's never led to anything really important. The important things that we have are almost always the other way around, you start with physics and you are forced into using some higher level math to describe it. You know, Einstein didn't want to use differential geometry in his theory of gravity, he was forced to it by thinking about the principle of equivalence and the, what he knew about special relativity. Heisenberg didn't want to use matrices.

0:59:48.9 SC: He basically invented something that was the equivalent of matrices. And it was later pointed out to him by Max Born that he just reinvented matrices when he invented matrix mechanics. Later on in gauge theories of quantum field theory we realised, Oh, look, there's topological configurations of these gauge fields. We're gonna have to learn a little bit about homotopy theory and so forth. That's almost always the way that real progress is made. So, there are plenty of mathematical constructions that are very, very beautiful in their own right. And maybe they very well will find use in fundamental physics someday, but it almost never happens that just because the thing is pretty or compelling in some ways, in some mystical ways that mathematical constructions can be that it will somehow probably find usefulness in the fundamental laws of physics. If you have a more specific reason why this particular thing would find use, then that's great.

1:00:46.6 SC: But as I said, even quaternions, which are simpler than octonions, haven't found that much use, there are quaternion enthusiasts out there who like to compare them, or, you know, say it's the right way to think about spin in quantum mechanics, et cetera, but there are better ways. There are more useful ways to think about spin in quantum mechanics, just using Pauli matrices and so forth that don't directly rely on calling them quaternions or using those relations that William Rowan Hamilton scribbled on a bridge in Ireland many years ago. David McBurney says, "I recently listened to a podcast with Marcia Rieke." I don't know how to pronounce Marcia's name. "On the James Webb space telescope. She mentioned that the two leading candidates for the next generation of space telescope determined by Astro 2020, were focused on studying exoplanets. Is that because we don't think we can do better than JWST for looking back closer to the Big Bang or because exoplanets and the potential for finding evidence of life is where astronomy is heading?"

1:01:42.5 SC: Well, it's a little bit of both, but let me talk about this idea of looking back closer to the Big Bang. So I think, and I said this before in previous podcasts, but I wanna keep saying it, 'cause I worry that people get the wrong idea about the James Webb space telescope. It's not looking very close to the Big Bang. Okay. We have evidence of what happened 380,000 years after the Big Bang from the cosmic microwave background, we have very, very detailed evidence. We have somewhat cruder, but still very informative evidence from primordial nucleosynthesis about what was going on a few seconds or a few minutes after the Big Bang. In contrast, JWST is looking at things maybe that were happening a billion years after the Big Bang. Okay. Maybe we can go to hundreds of millions of years if we're really, really lucky, but anyway, nowhere close to the Big Bang, right?

1:02:33.5 SC: It's long after the actual Big Bang, it's early in the days of galaxy formation. And I think that was the original selling point for JWST, that it would help us understand galaxy formation at early times in the history of the universe. And that's great, but nothing to do with the Big Bang. I know that David, your question didn't imply that it was telling us about the Big Bang. Just that it was closer to the Big Bang, but it's still never gonna get that close, there's... They were, these are called the dark ages, the years in between the cosmic microwave background formation and recombination and the lighting up of the first stars. It's very, very hard to get any information of what was going on there because not that much was going on and what was going on wasn't given off light, right? That's always a little bit of a hindrance when it comes to building a telescope to look at it. On the exoplanets idea, exoplanets are a very, very high priority target for modern astronomy, right?

1:03:26.9 SC: It's, I wouldn't say it's where astronomy is heading. 'Cause astronomy is not heading in any one direction. There's lots of different directions that astronomy and astronomers are interested in, but exoplanets are absolutely one of the big ones. And it's a perfect combination of both super duper interesting and potentially accessible. You know, whenever you do science, it's not enough to say this puzzle is interesting. You have to say, and I can make progress on it. And by building better telescopes, we can make huge progress on understanding exoplanets, which is a really interesting thing. So I think it's a pretty natural choice for a big next space telescope. Anonymous says, "Suppose Alice commits a crime before Alice can be held accountable for the crime she dies. Alice lived in a world of highly advanced technology. So a scientist is able to create a clone of Alice so accurate that the clone has all of her memories.

1:04:17.8 SC: Is it ethical to hold this new being accountable for the crimes of someone she's never met solely on the basis of having memories that the scientist purposefully forced her to have?" I love this question. This is an awesome question. Good for you, anonymous. Because it highlights something. I mean this, this could very easily be the basis for a philosophy paper, right? About the nature of personal identity and responsibility and blame and things like that. And here's the way I think about it. The short answer is yes. I do think that this, that she can be held responsible or accountable as you put it. I'm assuming that when you say she has the memories, I'm gonna go further than that and assuming that really this new version of Alice is essentially indistinguishable in every way from the old version of Alice, even though there was a gap in Alice's lifespan.

1:05:07.6 SC: So to me, there is no such thing metaphysically as the you-ness of your identity that persists through time and follows you from one moment to another. You, what we think of as you, is you are a pattern in the collection of atoms and molecules and stuff, right? And in fact, most of the particular atoms and molecules that are in you now, weren't in you when you were a baby or whatever, that's the pattern that persists over time. And this is a, the reason why I like the question is because it's a great example of how we get intuitions from the actual world in which we live. And then we use those intuitions to build them up into purported rules of behaviour, whether or not they're just physical rules, behavioural rules, or even moral, ethical, suggestions. And then we extend those rules to situations that we haven't experienced.

1:06:08.6 SC: This happens all the time. And it's not a bad thing. It's not a mistake that this is what we do, but then we can realise either through experience or through thought experiments that our extension of our experience doesn't work into these new situations because we were assuming something would always be true that really isn't. So our knowledge, our experience with moral accountability comes from actual people who do not die and then get reconstructed, right? That's not a thing that we had to worry about so far, but we can imagine what it would be. And so I know that this is a good intuition pump for thinking well, that new version of Alice isn't responsible for anything, she was put together by a scientist, right? She didn't do anything, but I don't think that's the right way of thinking about it because I think that the notion of personal identity has to be extended.

1:07:00.8 SC: When you can imagine these crazy thought experiments where people don't just persist in obviously identifiable ways from birth to death, right? Whether it's a Star Trek transporter machine or whatever. I think what matters is that pattern, is that process. And what you're saying here is that there's a temporal interruption in the pattern, but it's the same pattern, right? The new Alice is the same one as the old one, just with an interruption in their lifespan. So to me, that's just as much Alice as it ever was. There's no rule that says there has to be temporal continuity there and therefore, whatever ideas about accountability you would have had for the original Alice after she committed a crime, you should also have for her identical version that is later on. And it does conflict with our intuitions a little bit. And therefore our intuitions need a little bit of upgrading, I would think.

1:07:56.4 SC: This is not to, you know, this is separate from the question of what the accountability should consist of but whatever it is, I think it should be the same for the new Alice and the old one. Allister Melville says, "What does it mean for a dimension to be small or curled up, aren't dimensions effectively endless in two directions? Is this a concept that falls out of the maths or doesn't yet have any real world evidence?" Well there's no real world evidence. That's right. So, in the world in which we live, dimensions, as far as we know, go on as far as we can tell, dimensions of space, the three dimensions of space. Up down, left right, forward backward. But it's very, very easy to imagine dimensions that don't, right. Just draw a circle. A circle is a one dimensional mathematical structure, and it does not go on in all forever. Right? It's a finite size. So you can ask the question, hypothetically, can we imagine dimensions of space that are like that, that are curled up and don't go on forever? Or is it even possible that our dimensions that we do see are curled up? It's just that the they're still nevertheless big they're finite in size, but just very, very big, bigger than our observable universe?

1:09:03.7 SC: Yeah. These things are just all completely plausible. They could happen. So no, there's no evidence for them, but it's not at all difficult to imagine them happening. Jake Cornegy says, "A black hole made of elements from a dead star would look different inside the event horizon than a black hole made of cats and people who happen to fall inside of a black hole while studying it at least briefly. Right? So when we speak of black holes only having the characteristics of mass spin and electric charge, isn't that shorthand for what they look like outside the event horizon while very different interiors must exist across space time?" Short answer is yes, absolutely. But we often speak of black holes as what they look like from the outside. 'Cause once you go inside, you're dead or at least you can't talk to the people outside about what you're seeing.

1:09:48.2 SC: So yes, when we say the black holes are characterized by mass spin and electric charge, we do mean by as far as what they look like outside is concerned. Daniel C says, "I would appreciate if you could speak in a bit more detail as to this argument against strong emergence in the form you refer to it. You mentioned on a recent AMA that strong emergence would violate locality, which sounded like a reason to reduce your prior for it. Is this violation of locality, your biggest qualm with strong emergence? Does the fact that locality is not fundamental and seems to break down when gravity is strong enough open the possibility that there is in fact other non-local behaviour and lower gravity conditions, but it is just not as easily visible to us, particularly when we try to resolve the universe at the scale of individual particles.

1:10:32.6 SC: So yeah, there's a lot going on here in this question. And this is, you know, by the way, for those of you who are contemplating future AMA questions, this is about as long as the question should ever be. You know, despite my protestations people are just quite loquacious in their AMA questions sometimes. And some of the questions would be good if you just wrote them shorter, but you just can't resist. Can you? So anyway, Daniel's question is about the limit where I'm willing to read it out loud and then, and try to tackle it here. So the idea is that the, there's this idea of the laws of physics underlying our everyday lives. Okay. The core theory, and it is very, very, very, very, very, very well delineated as an ordinary quantum field theory, which implies the word local to it. And what that means is that all of the laws of the dynamical laws that tell us how the quantum fields evolve with time over the course of evolution can be derived from an expression, whether it's, it could be the Hamiltonian or Lagrangian or whatever.

1:11:34.8 SC: There's different ways of writing down the expression, but the expression takes the form, something specific happening individually at individual locations in space. Okay. So quantum fields only interact with each other at the same locations in space. The value of a quantum field at one location does not directly affect the value of the quantum field or the evolution of a quantum field at any other location in space. If you poke it, or if something happens to the fields, there can be ripples that spread out, but those spreading outs only happen at the speed of light or more slowly than that. So that's locality. Now that locality might be broken by gravitational effects, but those gravitational effects are completely 100% invisible in our everyday lives. You know, they're important for quantum gravity and for black holes, they do not affect us. And so I think that the people who care about strong emergence would not be able to lean on that particular potential violation of locality.

1:12:34.4 SC: I don't think locality is fundamental. I think locality is an emergent approximation, but my point is that in the world in which we live in our everyday lives, the lives of human beings, that approximation is super duper good. So you don't want to really rely at a deep level on violating that somehow. Now the relation to strong emergence is basically the idea that there's no, if you believe that that is true. If you believe that we have written down the laws of physics underlying everyday life, and it takes the form of locality or of a local quantum field theory, you know, there's two ways to say what is basically the same thing. One is that the fact that the laws of physics are local means that what is happening at one point in space, Like what does the electron do located at one point in space? It responds to what the other quantum yields are doing at the same point in space, period, full stop.

1:13:31.3 SC: Okay. So therefore all of the hopes of the strong emergentists that it basically come down to the idea that an electron would behave differently if it were in a rock or in a brain or in interstellar space, even if it's local conditions of the other fields at the same point in space were the same. Okay. And so that's just incompatible with locality full stop. You're done. Now maybe locality's wrong, so, okay, good for you. But that's an enormous kind of thing to break about fundamental physics. I predict that if you try to break it, you'll fail or you'll come up with some theory that is wrong for other reasons. The idea that you can just wave your hands and say, Ah, maybe it's broken is entirely unconvincing. You gotta show me exactly how it's broken, 'cause these things all depend on each other.

1:14:22.2 SC: But the other way to say basically the same thing is the core theory works. Okay. It's pretty good and you gotta violate it and you have to violate it by violating locality in this particular case. But more importantly, you have to violate it. So if you're gonna violate it, tell me how, that's my only claim. That's my only request of the strong emergentists. Don't just say, well, it'll be violated. You have to tell me exactly how. We have equations for the core theory that are enormously well tested. And if you're gonna violate them tell me what equations you're gonna use instead, tell me how to modify the equations that we have. That is not too much to ask when you're messing with our best understanding of the fundamental laws of physics.

1:15:03.6 SC: Ariella Soft says, "To what extent do you think we are capable of understanding the universe? We clearly are able to make extraordinary predictions, but on the other hand, even if we are Turing-complete, we implicitly accept Ockham's razor. We rely on counterfactuals in our reasoning, etcetera, what confidence should we have that we can grasp the laws of nature?" Well, you know, I think it's a back and forth, right? I think that we guess and hope that we can understand the laws of nature. And then we, on the basis of those guesses, try to do it and we either succeed or fail. And so far we've been doing extraordinarily well, right? I mean, like I just talked about with the core theory, our understanding of the laws of nature in the regimes where we really tested things is honestly way better than has any right to be. This is a good news, bad news situation. Good news for us in terms of the accomplishments that human beings have made throughout history, bad news for physicists, because it's hard to improve your theory when it works so well.

1:15:58.7 SC: Now that's not proof that we will definitely be able to understand all the laws of nature, but I see absolutely zero obstacle to doing that. So other than some vague thing that, anything could happen so who knows, which is always true, but not very persuasive. I'm not moved by arguments that maybe we cannot ultimately grasp the laws of nature. Charles Hut says, "In an early AMA you said something along the lines of, if you believe in science and want to push naturalism forward, then you should also listen to the science of convincing people. With this in mind, How do you feel about the effects of the so-called militant atheist/naturalists, such as Christopher Hitchens, Ricky Gervais and Richard Dawkins. Do you think that by being more debate driven rather than empathetic, they're doing more harm than good in this area?" Well, you know, I can't speak for them about what their goals were, right?

1:16:51.5 SC: Like sometimes you want to persuade people who are on the fence, but other times you just wanna say things that you think are true, you just wanna get something off your chest, right. And maybe tell some jokes or whatever it is. So I don't think you can criticise them as not following the best science about how to persuade people. Unless they've said my goal is to persuade people and this is what I'm trying to do, then you could persuade them. But I don't know of them actually saying that. Furthermore, I do think that there have been both good and bad repercussions of the whole sort of new atheist discussion that we had in the early 2000s. The good part is atheism is much more on the table these days than it ever was as a point of view that needs to be taken seriously and respected, you know, and in the '80s, people just wouldn't take atheism seriously at all.

1:17:41.8 SC: And now it is at least recognised even if you don't accept it, you have to confront it. You have to deal with it, right. It's just much more a place at the table kind of thing. At the same time there have undoubtedly been people who've been turned off by the debate derogatory kind of attitude of the conversations that were had back then. I have no way of knowing, of quantifying what the relative sizes of these effects are. What I know is that people who are sympathetic to one side or the other might cherry pick and say like, Oh, this thing I like, or this thing I don't like, and I don't see it any way to actually measure it. But, you know, it depends on what your goals are. So, I really don't know what the overall effect is, but I think that my guess is it's been good. I don't have any evidence for that, but there you go.

1:18:34.6 SC: Eike, Eike, E-I-K-E Purestoff says, "Some scientific theories capture the public imagination in ways that others don't. Recently Constructor theory has been hailed as a new approach to doing science yet the only people I hear talking about it are the inventors thereof. There's no sitcom, no flurry of popular science books about constructive theory. What do you think is the difference between a scientific theory that is a mainstay of public excitement and one that is more or less ignored, even if within its own domain, it might be just as important?" Well, I think there's two things going on here. One is the relative importance or attention being paid to new scientific theories within the realm of professional science. And the other is the relationship between that and how much attention is given to scientific theories outside the realm of professional science.

1:19:22.6 SC: So Constructor theory is not paid that much attention within professional science, maybe because it's brand new, maybe because there's not been any tangible results coming out of it, maybe because people just don't like it when they do hear about it, but for whatever reason, it's a minority pursuit. Like I kind of think that there's something interesting there, but I'm not dropping everything to do it myself. Just like I would say with Stephen Wolfram stuff, right? Like I'm glad other people are doing it, but I'm not gonna do it. I don't personally think it's the most promising way forward, but I'm happy if it turns out to be right. They should. I'm glad that some people are doing it. I would say if anything, the amount of attention being paid to Constructor theory in the public domain is quite a bit larger than the amount that is paid to it by professional scientists.

1:20:06.2 SC: I mean, you can walk through the physics departments of major universities throughout the world. You're not gonna find a lot of people working on Constructor theory, but you will find it discussed in popular magazines and on podcasts and things like that. Okay. So that's a more general question, you know, should the amount of attention given to scientific ideas in the popular domain be equal precisely to the same amount of attention that is given in the scientific domain? Well, no, I don't think it needs to be. I do think that we should be honest with the public. I think that we should try to be very clear when we talk about a scientific idea, to not only say what we think the arguments for and against it are, but recognizing that none of us is perfect and that other people are also smart and have their own reasons for believing things we should share how respectable or popular or influential it is within the realm of professional scientists.

1:21:02.9 SC: So, when I talk about Many Worlds, I'm always very quick to say there's plenty of other people who don't believe it. There's other options out there on the table. I'm gonna give you the arguments that I believe make Many Worlds very attractive. And those are the arguments that I think are right, but I'll say, but, you know, there are other people who disagree. So I see no problem with people who are enthusiasts about Constructor theory or whatever, both writing their scientific papers and talking about it to the wider world, but they should just be honest that it's a minority pursuit. That's fine. Right? And, I think that's more or less the way it works. You know, like people complain that String theory gets so much more hype than loop quantum gravity does. But again, the relative importance of String theory to loop quantum gravity is much greater among professional physicists than it is among the public. Loop quantum gravity gets way more play in the public than it does among professional physicists. It doesn't get zero among professional physicists, but is a very tiny minority pursuit compared to something like String theory.

1:22:07.4 SC: Qubit says, "Can you tell us your thoughts on quantum Darwinism proposed by Wojciech Zurek? My impression is that this concept tries to solve the measurement problem only using the Schrödinger equation. I don't see any difference to the Many Worlds theory. However, I have the impression that Zurich doesn't like to talk about other worlds. What are your thoughts?" You know, I don't like to imagine that myself in the mindset of somebody else. So I can't tell you what Zurek is thinking, or doesn't like to talk about. He did just this week, come out with a new comprehensive review article on quantum Darwinism, et cetera. So you can check that out. You just Google it or go to the archive and look for Zurek's papers.

1:22:43.8 SC: For those of you who don't know what we're talking about, Wojciech Zurek at Los Alamos is one of the leaders in understanding decoherence and has been for a very long time. Heinz-Dieter Zeh, who was really one of the biggest pioneers passed away recently and I think that this understanding of decoherence is crucially important to understanding quantum mechanics in the real world. So I'm a huge booster of this work. Zurek in particular has done more than anybody to help understand why when we do branch the wave function, or if you like, when we do observe a quantum system, we see certain states and not others, pointer states as they are called. Okay. I think this is again, crucially important insights into how reality works. I'd be very, very happy if Zurek shares a Nobel prize at some point for improving our understanding of how the classical world emerges from quantum mechanics.

1:23:36.5 SC: Quantum Darwinism in particular, is something that's sort of a more specific set of ideas within that program that I haven't personally found very useful yet, but that's just not a disagreement with the idea. It's just that, you know, some ideas are useful to your own research and some are not, okay. I do think that my favourite way of thinking about Zurek's work and the equations is, is squarely within the idea of the many-world's formulation. And now people slice and dice what they define to be Many-worlds. To me, as long as the fundamental ontology of your theory is a vector in Hilbert space and the fundamental dynamical equation is the Schrödinger equation, You're doing Many-worlds. Okay. That's the important thing to define. What do you mean by the theory, but different people have their different sub-versions of it. And that's fine. That's a healthy research program with people trying out different ideas. And so Zurek has his own set of ideas within what I would call many-worlds, but he would call it, you know, his own kind of interpretation, right? And so that's fine. And the proof of the pudding is in the tasting. We'll see which set of ideas and concepts is actually most useful moving forward. But I do think that his work is front and center in addressing some of the most important questions that there are to be asked out there.

1:24:56.7 SC: Keithec says, "If sending particles through a Stern-Gerlach device measures their spin, how does one go about aligning the spin of two particles without measuring them or is this just a non-practical idea that only gets proposed in thought experiments?"

1:25:11.0 SC: I'm not sure what you mean by aligning the spin of two particles, if you mean like creating a entangled EPR pair, like one particle's up and the other is down or vice versa. That's very easy to do, just let a particle with no spin decay into two particles with spin, and then the fact that momentum is conserved will tell you that the two spinning particles had anti-aligned spins. There you go, very easy to do, but it's also easy to take two electrons that are not created by the decay of a particle and align their spins, you just measure the spins of both of them. There you go. [laughter] If you measure the spins of both of them and they're both spin up, then they're aligned, right? I mean, maybe what you wanna do is put them into an entangled state, but that's also possible to do, you just let them interact in a certain way, or you take one particle and you just modulate it, like if you had two particles that are both spin up, you can do things to just one of the particles that flips its spin upside down and then they are anti-aligned, if you want it to be that way.

1:26:14.5 SC: So this is a very practical idea, I'm not the guy to ask about what is the most practical way to do it in some particular technological instantiation of this, but it is very, very doable. Jeffrey Segal says, "Regarding the Simon Conway Morris podcast, I was confused in that he starts off by saying that the combinatorial immensity of biological space is stupidly large, but then he seems to imply that evolution could find optimal solutions, arguing that mammals were always going to win out over the dinosaurs and that convergent evolution was to be expected, it seems to me that in limited time scales over which species evolved, it would be highly unlikely that the optimal solution in biological space would be found." So I'm very, very happy to talk about stuff that happened in recent and past podcasts, but we have to keep in mind, I am not the expert here on biology, right? I mean, this is a question for Conway Morris, not for me.

1:27:07.4 SC: Having said that, you're certainly correct that because the combinatorial immensity of biological space is stupidly large. We're never going to find the truly optimal solution in any exact sense, but on the other hand, who cares about that? It's not even clear that there is a sensible idea of the truly optimal solution in biology, because the conditions that we live in are always changing, it's a race against the changing environment and the changing competition from other species that real biological organisms live in. So it's not really a matter of the super-duper exact optimal solution, it's a matter of a pretty good solution, a good enough solution, which is a better sort of characterization than optimal. And I think that was the point, and again, I'm not gonna defend whether the point is true or not, but the point was that there is on the one hand, a lot of things that biology can do, but on the other hand, an especially small number of constraints is trying to satisfy, that it has enough freedom to find a more or less pretty good solution that could be found by a very different trajectories, right? That's the convergence of evolution, that even though the path that you take through the space of genomes and through the space of environments might be very different. At the end of the day, you end up with more or less the same morphology, the same shape and size and habits as a grown-up organism that you would have in either one of those two trajectories.

1:28:34.3 SC: So they're not gonna be exactly the same. It won't be a perfectly optimal solution, but will be good enough. I mean, more generally, I would say that I think a lot of questions in both philosophy and science suffer a lot of opinions or ideas, suffer from over-emphasising perfection and exactness, right? The world is not perfect or exact. And when you relax the demand for perfection or exactness a little bit, your impression about what is possible and what actually happens might change by a lot. That's an easy thing to say, very hand-wavy thing, but I do think that's a general impression that I have.

1:29:12.0 SC: Alexandra Bates says, "What do you think of the effective altruism movement? Have they changed your personal actions or views on anything, do you think their method of improving the world is effective?" Well, I think that there is sort of the strong or weak versions of being an effective altruist, and maybe the weak version is so weak that it's just common sense, but I think it's true, namely that if you're going to be altruistic at all, if you're gonna give money to charities, et cetera, because you think you're doing some good for the world, and maybe that's what you're telling yourself, that you're doing some good for the world, then I think it's pretty much true that it would be better to do more good for the world. [chuckle] I don't think it's a radical kind of idea, so in other words, being a little bit more conscious of what your altruism is actually doing and deploying it in ways that are most effective seems to be a very sensible thing to do, and maybe something that isn't always done, right?

1:30:13.3 SC: If you look at what money actually goes to, I don't think anyone could argue that we are trying to optimise for the effectiveness of it. Now, it can go too far, right? So there's a stronger version that says, yes, we should run our own personal lives as if our goal was to optimise the utility or happiness of the world. I don't think that's realistic, and I don't think it's what anyone actually does, I don't think that's what is ever going to happen, so I don't think it... I think that's too strong, but maybe it's some optimal point that we can keep in mind as we do our actual moves through the world. So I do think that it's kind of an idea that just the phrase and the general idea can work to push people in slightly better directions, but in the real world, of course, people don't become altruists, people don't give money. Let's just call it giving money to make keep things definite. People don't give money simply because they want to optimize the utility of the world, that's not the only reason why they give money, there might be some personal cause that they care about. They wanna give to the alma mater that they graduated from, or they want to donate within the sphere they care about. Here at Mindscape, we have a scholarship that we're giving, and I didn't sit down and carefully think about what is the scholarship I could give that would maximise the happiness of the world.

1:31:36.5 SC: I saw a need or usefulness for a particular kind of targeted scholarship that I thought would be useful to give. That's why I kinda like the version that was promulgated by Joshua Green when we had him on the podcast, where there's sort of a mixed strategy, where you allow people or you encourage people to both give money to their favourite charity to save their local kittens at the cat shelter, and also something that has been optimised for saving the most lives or something like that. That makes people happy and tickles their desire to focus on their personal favourite ideas. I think that's a perfectly legit. Tarun says, "Priority question." Remember, priority questions are the ones, as we've discussed, you get to label a question priority, and I will try my best to answer it with the caveat that you only get one priority question in your whole life, okay? And I'm counting on you to not abuse that privilege. So Tarun says, "You identified my strategy in the last AMA, I've been going through my list of most burning questions each month, and now I'm asking one of the questions you didn't answer previously as a priority question."

1:32:43.3 SC: The last AMA I mentioned that a good game theorist would say, like given that you only are able to ask a priority question once in your life, you wouldn't just answer... Use it on the first question that came to mind, you would try to get the questions answered anyway, and then when that didn't work, you would label them priority. Apparently that's what Tarun has been doing, so good for him. "The question is, much has been made of laws of physics relating to motion, whether deterministic or random ruling out Libertarian Free Will. Doesn't Einstein's Block Universe, give us an equally good reason, 'Do not believe in Libertarian Free Will, given that the future is fixed.' I'd be very interested to get your thoughts on this perspective." Well, yeah, but the idea is that the Block Universe is not actually real, not correct, because the laws of physics are not classical. The Block Universe has to be upgraded a little bit in quantum mechanics, and the way in which it gets upgraded might differ from formulation to formulation. In many-worlds, it gets upgraded to a block wave function, I guess you wanna call it, but that wave function describes multiple worlds, multiple blocks, multiple universes, and you cannot make predictions at any one moment of time, even if you were Laplace's Demon and knew everything about what any individual observer would find themselves observing later on in the universe, so it's just not deterministic in that way.

1:34:07.1 SC: The wave function of it as a whole evolves deterministically but that is utterly irrelevant for human experience, 'cause we don't live in the wave function as a whole, we live on a branch. And of course, in other versions of quantum mechanics, it is truly stochastic in which case, it is not a Block Universe that is determined by our present configuration. You can still think of it as a Block Universe, but not one that is fixed by present conditions. So I think that the Block Universe is kind of irrelevant to the question of free will, determinism or non-determinism or the laws of physics. I also think is irrelevant to free will as a compatibilist, but it's very relevant to the question of Libertarian Free Will. If the universe is deterministic within a single universe, then you can't have Libertarian Free Will, but that's prior to the question of whether or not there's a Block Universe, right? If the universe is not deterministic, then that simplistic notion of the Block Universe is incorrect, so it's not really helpful in figuring out whether it's Libertarian Free Will. NeLita S says, "I was wondering what your thoughts are in terms of the first law of thermodynamics and understanding us humans as quantum systems, what happens to our energy after death? Does it die with us? Does it evaporate like a black hole? Does it transform into another form like dirt?"

1:35:24.5 SC: This is an easy one, actually. Yeah, it doesn't go anywhere. It's like saying, "Where does the energy of a candle go when it stops burning?" The burning was a conversion of the energy that was in the candle from one form to another by a combustion oxidation, and the burning is a process that stops, and life in a living organism is exactly the same thing, the energy is in the organism. It's doing something, it's undergoing a process, it's living. And that process stops, but the energy doesn't go anywhere, it's still there, you have exactly the same amount of energy the moment after you die as the moment before.

1:35:58.3 SC: Brian Keating says, "Do you see any place for NFTs or blockchain technology in science and/or publishing, proof of stake versus embargoes, et cetera?" So Brian, by the way, is an astrophysicist, an observational cosmologist, UC San Diego, and host of his own podcast, Into The Impossible, where I've been known to appear. So you can check that out. But the short answer to this question for me is, no. I don't really see any special place, not in the sense that I see the lack of a place, like I'm predicting that there won't be any place, but I don't see any particular special need for NFT or blockchain technology in science or publishing right now.

1:36:40.4 SC: I think it's kind of the opposite. I mean, I think that in modern science, the way that you claim something is to make it public, it's a weird thing that back in the day, they used to get a result, Newton or Galileo or whatever, and they wouldn't wanna publish it and they would... But they wouldn't want to claim priority to it, so they would write it in a fake language or in a code, or backward or in an Anagram or something like that. I think we're beyond that now, and I think that we just put the result out there, and whoever puts the result out there first gets priority for it. I think it's a pretty good system actually, because it incentivizes sharing the scientific results as much as possible, which is good for science. Now, of course, I am only familiar with my own little kind of science and it might not work that well in other areas, like areas that are economically or politically meaningful unlike mine, so who knows, there might be other uses that I don't know about, but I don't see it in the areas that I'm familiar with.

1:37:44.3 SC: Kyle Steven says, "I'm curious to learn more about the logistics of your podcasts, do you record many in a short period of time, or are they recorded once per week? Are the length of your podcasts limited by your time availability or the availability of the guests, or have you just found the current length to be the best?" I think it's all very variable, I'm just not very systematic about these things. I think I might need to be more systematic, now that I'm teaching every week, and that's more of a weekly constraint on my time than I had before, but sometimes I'll do a bunch of podcasts in a row, other times, it's roughly once a week or whatever. It depends mostly on the availability of the guests and me at the same time, the usual coordination problem there. I don't wanna record too many, like I did record a bunch before I moved across the country 'cause I knew that that would be soaking up my time, so I'm still going through some of those, and I feel bad because people are getting delayed quite a bit. I did Rick Beato months ago, and I had people I haven't actually released yet because sometimes someone has a book coming out and I will try to organise the release of the podcast around the book coming out. Like for example, I have a book coming out on September 20th.

1:38:57.6 SC: We're releasing The Biggest Ideas in the Universe volume one. Did I not say that? Boy, I'm very bad at this. Yeah, we're releasing volume one of The Biggest Ideas in the Universe in book form, and so I... It will be clear to podcast listeners 'cause I will try anyway, I haven't done it yet, but I will try to put out a solo podcast talking about some of the themes in the book. Now, the book is not about new sexy physics, it's about good old established physics, and so it's not like it's going to be speculative or anything like that, but there's still things to be said about the ideas themselves and the best way to talk about them and think about them. So when that happens, when a book is coming out and therefore the podcast episode release date is scheduled accordingly, it might push back people who I've done on the podcast who I've recorded but who don't have a deadline or anything like that. So some people are still waiting for their episodes to be released. Sorry about that. People who are like that, but usually I don't like to record too far in advance for exactly that reason. I try to be really, really considerate of the guests, they're busy people, they're giving me their time, I don't wanna record something with them, and then release it six months later, that's a little bit annoying to them. And likewise, I don't wanna spend hours and hours of their time, which they rarely have, right?

1:40:15.8 SC: So I think about between an hour and an hour and a half is a good compromise between the idea of just rambling on for hours and hours and going too briefly to actually say anything substantive. So I think that roughly works, I don't know what it is about the time scale of an hour that is so compatible with this, I mean, maybe it's just because I'm used to giving talks or going to classes that last that long, I'm not really sure.

1:40:42.9 SC: Seth Hollowako says, "Can you think of any meaningful differences that might exist in science and society if we decided tomorrow that the North was actually down rather than up, and that the Earth and other planets actually rotated clockwise around the sun, et cetera? It seems like North has an arbitrary positive value assigned to it, that makes references to North as opposed to South, the right way. I can't help but think that as a resident of the northern hemisphere, who can literally see the Northern star and grew up in a northern state, I have some kind of minor implicit bias or privilege that is holy unwarranted." I think in a minor way, there could be. People have absolutely pointed out and even made maps reflecting the fact that we could very easily or arbitrarily choose to put what we know called the southern hemisphere at the top of our maps.

1:41:31.9 SC: Then again, up and down are also pretty arbitrary when it comes to maps and things like that, so these are all arbitrary choices, and it may be possible that our putting the northern hemisphere at the top privileges it in some way. On the other hand, a lot more people live in northern hemisphere of the Earth than the southern hemisphere of the Earth, so it's not a completely arbitrary choice. I think that among the many implicit biases and privileges that people have, that's one of the more minor ones, and you have to pick your battles. We're all finite creatures. I think I'm not gonna spend too much effort on that particular battle.

1:42:11.6 SC: Chris Murray says, "How do you reconcile the Bekenstein bound with the fact that even a single real number requires an infinite amount of information to describe, our world seems to have real numbers all over the place, so what is the right way to think about this?" The Bekenstein bound relates the information or entropy that we can squeeze into a certain region of the universe of a fixed size. I mean, basically, it's only so many things you can do in a region. If you try to do more than that, you make a black hole, right? And that has a finite amount of entropy. But sometimes this is casually described as a bound on the amount of information that could be put into a region, but there's a subtlety here, I mean, as you might expect, there's lots of subtleties here. When we have quantum mechanics, when we talk about the quantum state of a system, there's lots of subtleties going on, especially the fact that individual systems that are entangled with the outside world don't have wave functions of their own, and they need to be described, using density matrices. Okay? That's a complication, but one that isn't completely relevant here.

1:43:11.0 SC: Here's a more relevant one. When you have a quantum state even of just a single spin, right, you have on the one hand, just two states that you could measure the spin to be in, you measure the spin with respect to some axis, and if it's a spin one half object, then it's either spin up or spin down, just two states. But before you measured it, there is an infinite amount of information required to specify the state because it is a linear combination of spin up and spin down, there's an angle between the spin up access and the spin down access and that angle could be any real number. Right? In fact, in a single spin, it's described by a two-dimensional space of possibilities called the Block Sphere, and a sphere just like a real number has an infinite number of points. Okay?

1:43:58.4 SC: But we're not talking about that when we talk about the information or the number of states, that there can be inside a black hole, we're referring to the number of possible measurement outcomes, even if you're not measuring it. Well, we're really... What I'm trying to say is we're referring to the number of basis states that are going into the state, the dimensionality of the space, not the specific state that is within that N dimensional space. Okay? So it's not a real numbers worth of information that is required to tell you what quantum states formed the basis for the system we're looking at. To pick out the specific quantum state doesn't in fact require a continuum information. But we never do that. We never have that information. We don't have access to it. All of our measurements only have a finite resolution, right? So anyway, but the technical answer to this question is, the thing that is being limited by the Bekenstein bound is the number of basis states, not the amount of information required to fully specify the linear combination of such basis states that would make you an arbitrary quantum state or wave function.

1:45:11.1 SC: Bill Warner says, "Normally, the hotter a thing is the higher the entropy, but I often hear that the early universe was very hot and very low in entropy. Can you help me understand this?" Yes. The early universe is not normal in that sense. I mean, when you say normally, you mean like things you see around you in the everyday world. If you have a cup of liquid with a fixed volume of liquid, then the higher temperature state that that liquid is in, the higher entropy is in.

1:45:40.1 SC: That is true. And remember what entropy is really telling you is the number of micro states or micro arrangements that give you that macro state. So the reason why there's more entropy for a higher temperature thing is because the distribution of individual velocities, momenta of the molecule making it up is broader, right. In a higher temperature state, that like tells you the average kinetic energy, but there's a distribution of actual kinetic energies, and if the average is higher, that means there's sort of more individual ways for the specific velocities and momenta to be distributed and therefore higher entropy. But the world is not a liquid at fixed volume in a cup of coffee, so it's just more complicated than that. In the early universe, it is true that it is high temperature, and there's the sort of weird ill-defined discourse that cosmologists throw around where they say that, "The matter degrees of freedom are high entropy in the early universe, but the gravitational degrees of freedom are not."

1:46:44.0 SC: That's more or less ill-posed in every way, and that's not words that you should ever say out loud. For one thing, it's not degrees of freedom, gravitationally that are low entropy, because gravitational degrees of freedom or gravitational waves or Gravitons, okay, and those are not what is being referred to. What's being referred to is the configuration of the matter fields in the presence of strong gravitational fields or by strong, we just mean gravitational fields that matter, as far as entropy is concerned. They don't want the... In the presence of these gravitational self-interactions, higher entropy means lumpier, generally. The thing about the liquid in the cup of coffee or whatever, is that its self-gravitational interactions are completely irrelevant, the gravitational force from one coffee molecule to another doesn't affect its configuration very much. But in the early universe, the gravitational interaction between one part of the universe and another is crucially important, it could have been a black hole, right? [chuckle] Or it could have been at least very lumpy with lots of black holes scattered around or even strong concentrations of matter surrounded by empty spaces, even if they're not literally black holes. So when you just go through the details, the lumpy configuration of the early universe is much higher entropy than a smooth configuration would be regardless of what temperature it's at.

1:48:12.4 SC: Jesse Rimler says, "Effective altruists recommend giving to charity and career selection as the best ways for ordinary people to do good. What about effective organizing, civil rights and labour laws came about not through donations and people taking career quizzes rather, ordinary people build complex networks, worked in solidarity, tried various tactics, and often put their bodies on the line to accomplish long-lasting change. Do you think the EA movement focuses less on this because these actions are harder to quantify?" Well, I don't know why they do that. Again, I'm not trying to read people's minds, I do think that you could easily just try to make an argument rather than phrasing it in terms of rhetorical questions. You could say the actual best way to affect the world is not to earn a lot of money and then give it away, but to put in the same amount of effort into making the world a better place by organising or by fixing things or whatever it is. These are all very, very hard things to do, and so I don't think you should be... Or we should be too definitive in our statements about what would actually make the world a better place, I think we should think about it and talk about it and be open-minded about the possibilities.

1:49:19.2 SC: Certainly, if I did sort of stoop to psychoanalysis here, which is always dangerous and wrong, but maybe we can temporarily do that, I do think that when it comes to effective altruists, there sort of a crisp, rigorous, rational feeling about distributing our charitable dollars, right? That is something where it's kind of straightforward and sensible to say, "We're trying to do good for the world by giving money away, what's the best way to do that?" Whereas when it comes to organising or protesting or making the world a better place through demonstrations, things get very emotional very quickly, and it might be that the kind of people who are into effective altruism just are turned off by that kind of emotionality. Right?

1:50:07.8 SC: And I think that the correct balance to strike is a tricky question, I'm not gonna try to come down on it, I think that emotionality and passion are very, very important, they're not mistakes when it comes to making the world a better place. There's at any one point in our lives, there're literally an infinite number of things you can do. Like right now, sitting listening to the podcast, there're an infinite number of actions you could take within the next five minutes. Right? They might not be dramatically different from each other, you could walk to the left, you walk to the right, as we were just talking about, there's an infinite number of directions you can walk in, so it's not a very meaningful infinity.

1:50:44.1 SC: But the point is, we make decisions implicitly all the time about what actions to actually take, and emotions and passions are really important drivers of getting us up off our butts to do more difficult actions. The world is a certain way, and it's very often easy to just let the world go on being the way it is, and not worry ourselves too much about improving it, and sometimes getting worked up about the state of the world matters. It helps, it's important, and that's hard to analyse at a perfectly rational level sometimes. So again, it might be possible that the kind of psychological states that lend themselves to being an effective organiser are different than the kinds of psychological states that lend themselves to figuring out how best to allocate our charitable donations. Okay? I'm in the favour of both. I don't think it's a competition between them.

1:51:44.3 SC: Frank Layman says, "For you, what was the peak era of the internet in terms of feeling of promise, excitement, usefulness, uniqueness, not horribleness, et cetera." So I'll give you two answers to this. One is, that's probably not a good question to ask. I think it's probably very much like asking, what was the peak era of the automobile in 1925? Asking that question. You weren't at the peak era of the automobile, yet the automobile's still pretty new, I don't think we're anywhere near an equilibrium state for the internet right now. So asking what was its peak era is probably wildly premature.

1:52:22.9 SC: Having said that, I think that the obvious answer is right now. I mean, as terrible as the internet is in many ways, it's also really useful and really good in many ways, one of which is, wait for it. Letting podcasts out there in the world and letting us listen to podcasts, right? It's too easy to find terrible things on the internet, that's certainly true. And it's too easy to be terrible on the internet, responding to things thoughtlessly, spreading your not very considered opinions out there more widely than we could ever before, these are all things that can get us into trouble and can be irritating. But there's also genuine goodness out there, and I do think that the consumer needs to take some responsibility for going out and finding the good stuff on the internet, not being too focused on being annoyed at the bad stuff.

1:53:16.2 SC: Josh Charles said, "If it's possible that space is an emergent property out of an entanglement, is it possible that we'll find spooky action at a distance? Is not really distant at all, since locally it would seem like it was spatially close." Again, two answers to this. I think when I talk about, and I think when everyone talks about space being an emergent property out of entanglement, it does not follow that two entangled particles are close. That is not... I know that it sounds like it does, but it really doesn't, because when I talk about... In my scientific technical work, the ideas that we have been exploring about distance being related to entanglement, the entangled systems that we're talking about are empty space, not particles, okay? And that's because for a very good reason, there are far, far more quantum degrees of freedom in empty space in their vacuum states, than there are particles even at the center of a neutron star or something like that. Most of space is empty as far as quantum field theory is concerned, so when you're talking about the geometry of space, it's only the empty space degrees freedom that matter, not the particles. Now, one can be more bold as Maldacena and Susskind are with the ER equals EPR conjecture and suggest that even two entangled particles have in some sense a tiny quantum wormhole connecting them. It is still after some effort unclear to me what sense that is.

1:54:46.4 SC: The places where the ER equals EPR conjecture works very well are places where, or at least is very clear, are places where there's enormous amount of entanglement between what is basically different regions of empty space, making a big macroscopic wormhole when it comes to just a single particle at a time, it's not clear what that wormholes supposed to be telling us. Okay, so that's one sort of technical answer to the question. The other is that the phrase, "Is not really distant at all," might not be relevant in this context because... And again, in the way that I think about spatial locality arising from entanglement, the entanglement is absolutely more fundamental, the entanglement comes first, and you just define distances in a way that is a convenient way of talking about the entanglement structure of the system and predicting its future evolution, et cetera, et cetera. So my way of thinking is that the spooky action at a distance isn't that spooky because it's not really at a distance, it's just action. [chuckle] That's all it is. It's just a wave function evolving through space time or wave function evolving in time, I should say, and space emerging out of it.

1:56:00.5 SC: So in other words, let me back up and be more clear about this, almost everyone, including most modern physicists, thinks of things happening inside space time, even if they know about quantum gravity, not everyone, but a lot of people just think that way, deep down, and certainly Einstein thought that way, deep down. I think that we should be thinking about wave functions evolving in Hilbert space, not in space time at all. So to me, the spooky thing is not that action happens at a distance, the weird thing, the thing that needs to be explained, is that the idea of distance and locality makes sense at all, is a useful emerging concept, right? So it's completely backwards, it's not like, here is space, here's action at a distance in space, isn't that weird? The question to be answered is, why is there space at all, and why is there a such a good approximation to think that actions from one quantum system to another seem to be not at a distance in this emergent space? I think we have answers to that, these are not implacable questions or these are not impossible questions, but that's a very different way of framing the question than, oh my goodness, there are these actions at a distance, what are you gonna do about that?

1:57:13.7 SC: Sandy McDonald says, "My handle on mathematics stopped at high school level. Recently, I've been feeling that I might get more from your and other author's works, if I push this further by going for an open learning/distance learning course. How much further do you think I need to go to make it worthwhile? For context, I left school in 1997." I don't think the year that you left school is relevant, there's not up been such important developments in mathematics that you need them to understand most of modern physics, but I think this... I think that this question is equivalent to saying, what are the basic pieces of mathematics you really need to get more out of physics?

1:57:50.1 SC: It depends, of course, on the kind of physics you're talking about, like most physics goes very, very far with enough calculus to understand vectors and differential equations and complex numbers, those three things, right? Once you understand complex analysis, vector calculus, and solving differential equations, especially partial differential equations, then you can do the vast majority of modern physics, including much of quantum mechanics. There's little bits and pieces you need to know, so for quantum mechanics you might need a little bit more linear algebra and things like that, but still solving the differential equations, is the most important thing. And that's a subset of calculus, it's the kind of thing you might only begin to get to in your first year long Calculus course in undergraduate.

1:58:36.0 SC: So if you're an undergraduate physics major, you take a year of calculus when you get there, and you're just beginning to think about solving partial differential equations, and very often you will take other courses later on in your second or third year or whatever, that either are focused courses about solving differential equations one way or the other, or other courses like electromagnetism or quantum mechanics, where as part of the curriculum, you learn more about solving differential equations. So that's the single most important piece of mathematical technology for being a working physicist. And then if you wanna get more advanced, string theory or gravity or whatever, you might need to know more pieces, but then usually you learn them as part of the physics, because they're not shared among everyone, like many physicists don't need to know tensors because they just don't need them for the kind of physics they're doing. If you wanna do general relativity, you do need to know tensors, and everyone knows that.

1:59:34.0 SC: So every general relativity book teaches you tensors. They don't assume that you know tensors ahead of time, 'cause you probably don't. Likewise, string theory will teach you the right kinds of differential and algebraic geometry and topology that you need to know string theory. Statistical mechanics books will teach you about probability and so forth. So I don't think you need that much math, but it's like a year and a half of good, solid college level math will get you a very solid grounding for things.

2:00:01.1 SC: Sid Huff says, "No one would reasonably deny that Einstein was right about a lot of things. What is your credence that he will eventually be shown to be right about quantum theory. I.e, that it's somehow incomplete and when the missing pieces are found, it will consign both the Copenhagen interpretation as well as the de Broglie-Bohm pilot wave theory, the Everettian many-worlds interpretation, cubism to the dustbin of scientific history?"

2:00:27.1 SC: Well, I think that it's a little bit wrong to contrast Einstein with those things, with the de Broglie-Bohm pilot wave theory, Everett cubism, because Einstein wasn't around to see them, he didn't have opinions about them. Okay? So I think that Einstein was right to rail against Copenhagen and say that Copenhagen was incomplete. But Copenhagen is terrible, everyone knows that there are modern Copenhagenists, but they try to improve it, they try to fix it up to make it more respectable. But the other things you're mentioning, especially de Broglie-Bohm and Everett, those are well-posed scientific theories, they're different than the sort of slap dash set of incoherent rules that the Copenhagen interpretation gives you. More of them might be right, but I don't think you can say that Einstein was complaining about them 'cause he wouldn't have complained about them, he might have preferred one to the other, he might have liked some aspects of them and not others.

2:01:26.5 SC: So John Bell very famously, when he was talking about Bohmian mechanics, and he was a fan of Bohmian mechanics, and he knew that Bohmian mechanics was compatible with the Bell inequality rules that quantum mechanics has, and he points out that Einstein had this worry that he put forward in the EPR paper about spooky action at a distance, and Bohmian mechanics completely resolves that worry, as Bell says, but in the way that Einstein would have liked the least, by basically buying into non-locality, the way that the quantum particles respond to the wave function is non-local.

2:02:04.6 SC: There you go. What are you gonna do? The Everettian version, of course, is deterministic and it's local within worlds, et cetera, but non-local more generally, but it denies the primacy of space time, space time exists within the world's not world's existing within Space Time, so Einstein would not have liked that either. But who knows what he actually would have done when... If actually faced with these theories, 'cause we do not have that actual historical event to look at.

2:02:31.6 SC: Richard Graff says, "In the August AMA, you discussed a controversy in naming of the Webb telescope, given allegations that Webb participated in anti-LGBT activities in the 1950, '60s. A point not made was that the amount of time and cultural shift between his alleged activity and the now, but there is a more complex argument around how much we should project our current values on actions so long ago, both chronologically and culturally. What is your perspective on this latter argument for both the Webb controversy and in general?" I think there's a lot of complicated questions here, one is, don't go too far in the other direction in pretending that people in the 1950s and '60s were all terrible bigots, there were plenty of people in 1950s and '60s who tried very hard to campaign for LGBT rights, and there was people against them, it was like an ongoing conversation, so it's not like everyone had that kind of feeling. And the other thing is that some people might have had private feelings but didn't act on them, and maybe their private feelings are ones that we wouldn't have agreed with now, but it's an entirely other level to go out there and make an effort to make life worse for LGBT people and others, and so I think that kind of thing is worth condemning.

2:03:52.1 SC: I think that slave owners at a time when slave ownership was common, still are worthy of condemnation, 'cause that was wrong, and there were still people in the Abolitionist Movement, even hundreds of years ago who were pointing out the opposite. And again, as I said in last month's AMA, the choice of attaching someone's name to a telescope is entirely to honour them, that's what it's for, it's not to remember something historically or whatever, it is a reward in some sense, and if that is a big part of your legacy then, I completely get that the argument that that's not someone we should be honouring and rewarding, and again and again, again, as I said last month, I don't have an informed opinion about how involved James Webb was with those controversies, to the extent that I've seen arguments for and against them, it seems to me that he was, but I'm not an expert historian. I have not read the original documents, et cetera, I think that should be in the hands of other people to do that carefully, you know, universities like both Caltech and Johns Hopkins in recent years have done that. They have sat down and said, Look, we have a lot of things named after a lot of people who maybe did some bad things, should we change the names of things and...

2:05:11.5 SC: It's not that hard. Yeah, just do it. If they turn out to be terrible people. Change the names, right? Caltech's tallest building is the library building right in the center of campus, and it was named after Robert Millikan, a very famous, very accomplished physicist, turns out... It's not turns out, it's been known for a long time, he was a huge eugenicist and racist, like being a eugenicist and trying to depress the reproductive rate of other races and people he considered inferior was a really big part of his life. And so they decided that that was not the kind of person they wanted to honour naming the library after him anymore, and they changed the name of the library. Not a big deal, and I think it's a perfectly sensible thing to do.

2:05:54.0 SC: Rob Petro says, "This is a bit out of the blue, but I've not heard you talk much about the subject, and I'm quite curious about your take, given your background. What do you think about P versus NP? For example, do you think the P is not equal to NP? What evidence for or against it do you find most compelling? And do you think we'll see a proof?" So P versus NP is the question of complexity classes of computational problems, P is the set of problems that you can solve in a relatively short period of time, and NP problems are those that... Whose solutions, you can check if you're given the solution to them, you can check that it's the right solution in a short period of time. All sensible people think that these are not the same complexity classes, that P does not equal NP, in other words, to think that P is not equal to NP is to say, I think there are some problems that are hard to solve, but it's easy to check the solution for... To say that they are equal as complexity classes is to say that there are no problems that are hard to solve, for which we can also check the solution easily, and most problems when you're given the solution, you can check it whether it's a good solution or not, right. But we haven't proven it yet.

2:07:05.7 SC: So people worry whenever we think something is true, but we haven't proven it, this is why this is the charm and beauty of mathematics, that it's not going to settle for our fuzzy intuition, it says, You've gotta prove things. And so as long as we haven't proven it, then it's still an open question, and you shouldn't be super duper sure.

2:07:26.0 SC: But there are good reasons to think things are true, even if we haven't proven them yet. Scott is a... Scott Aaronson is a much better person than I am to go on about this. And you can read his blog writings about it, all of the things that would be very easy to do in a world where P equals NP that we think are hard to do. [chuckle] Right? Axiomatizing creativity and things like that. Again, maybe that's all possible, but it just seems very wrong to us. And so I have no reason whatsoever to think that P is equal to NP. I see lots of reasons to think it's not. So I'm gonna go with that until there's good evidence otherwise. As far as when we'll see a proof, I have no idea whatsoever. Might take a long while, there's no deadline on this. There's no ticking clock. It takes how long, however long it takes.

2:08:18.0 SC: Sandra Polliani says, "When the math says that a black hole's store of information is measured by its surface area, does that mean that the black hole's surface is where the information is stored? At the horizon?" Yeah. Good question. So no, it doesn't mean that necessarily. So it doesn't mean that logically, it doesn't follow as an implication. That just because that's how much information it's stored in the black hole means that that's where it's stored. Right? You can certainly imagine alternatives. But on the other hand, it certainly provocative, certainly suggested maybe something like that is true. And so the modern view of holography and complementary is that there are different ways of thinking about where the information is in the black hole. And there's no fundamental answer to the question where the information is stored. From the perspective of a far away observer outside the black hole it is as if the information is stored at the horizon. From the perspective of someone falling into the black hole, it is as if the information is spread across the volume inside because different observers see different things. That's a very common thing in quantum mechanical setups. We did talk about this a little bit with Lenny Susskind when he was on the podcast and without being too revealing, we'll have another podcast talking about similar things very soon.

2:09:37.7 SC: Brent Meeker says, "In your conversation with William MacAskill, you switched back and forth referring to ethics and morality as though they were interchangeable. I think that it is one of the advances of the enlightenment that they were distinguished, that there is a domain of private virtue distinct from public virtue. The latter is dominated by rural utilitarianism because society must be persuaded that the rules are good for them, but private virtue was separated by the wall between church and state. The church has never admitted this separation. So do you agree to this distinction? If so, where is the line drawn?" Well, I agree that there are plenty of distinctions one can draw. I do not agree that it maps on immediately and universally to the words, ethics and morality. If you talk to people who are philosophers specialising in ethics and morality, you know, if you put a couple of drinks into them and they will admit that usually these words are used interchangeably. There is maybe a slight difference of connotation in the sense that ethics kind of refers to rules and morality might be more private. Sure. But very, very often these are used completely interchangeably. And so in that podcast, we were just not being very careful, we were using them interchangeably.

2:10:49.1 SC: Kunal Minda says, "Testimonies of near-death experiences describe them as almost psychedelic. Why do you think humans have near-death experiences? Is there a way evolution by natural selection could have had a mechanism to select for them?" Well, I don't know if evolution plays a role here except in the most tangential way, but I'm not gonna speculate on that because I think that the answer to the prior question is pretty easy. Near-death experiences are almost by definition, pretty stressful. [chuckle] They are experiences where things are not going well for the organism undergoing those experiences. Right? Our guard is down. Our resources are failing us. Our systems are breaking down. Okay? And psychedelic experiences are, you know, as I did in a blog post long ago, I talked about the fact that you can actually, when it comes to geometric hallucinations, like certain kinds of hallucinations that we see on psychedelic substances have geometries and they even classified what kinds, you know, some of them look like tunnels.

2:11:56.6 SC: Some of them look like spider webs or whatever, and you can actually reproduce the classification of these geometric hallucinations just by solving equations representing vibrations in the visual cortex. Okay? And of course the question is not, why do these appear when we do psychedelics or when we're near death, but why don't they appear all the time if they're just sort of fundamental vibrations in the visual cortex? And the answer as people who have studied psychedelics have established, and as far as I understand it, I did a podcast with Robin Carhart-Harris. You can go back and check. He is an actual psychedelic researcher. You know, the vibrations and lots of things are going on in our brains all the time, but they don't bubble up to our conscious perceptions. And in part that's because they get filtered out. So the reasons why you hallucinate when you're on psychedelics and so forth, and probably also when you're having a near-death experience is not because there is some new visual thing that pops up, but that the barriers between your conscious perception and the existing visual things churning around in the background of your brain come down. Okay? The barriers are lowered. And so you can experience these things. So it is literally the least surprising thing to think that near-death experiences resemble psychedelic experiences. In both cases, our guards are down and we're seeing things that are going on naturally in our brains.

2:13:26.4 SC: David Maxwell says, "In the sub-fields closer to your heart, who do you think might win Nobel prizes for physics in the coming years? And are there particular people or theories you think should win if experimental verification were not so important?" So first I should say, I don't care. Really. I don't care who's gonna win the Nobel Prize. I would love to win it myself, except I would be pretty embarrassed. 'Cause I clearly have not done any work deserving of the Nobel Prize. So when I say I would like to win it myself, what I mean is I would like to do some work deserving of the Nobel Prize. But if that happens, honestly, and maybe this is just me blowing smoke, but I think it's true doing the work is more important than winning the prize. Like if you, I don't know if you wrote down the theory of general relativity, which by the way, never won the Nobel Prize.

2:14:11.6 SC: But if you are the person who wrote down the theory of general relativity, that matters more than winning some prize that people vote on. I mean, come on. [chuckle] That's just something no one can take away from you if you're the person who figured that out. Okay. So I don't really care who wins it. Having said that, I think there's two areas close to my heart where there's sort of good cases to be made for prizes. One is in the foundations of quantum mechanics, right? The last time anyone won a Nobel Prize for the foundations of quantum mechanics was in the 1950s when Max Born won it for the probabilistic interpretation, years after he actually did the probabilistic interpretation. But there are stories there. And I think we've made progress, especially in the last few decades. I mean, I guess few is becoming a larger number now, but we talked already in this AMA about decoherence.

2:15:02.4 SC: And the fact that we understand the phenomenon of entanglement and the technological ramifications and how to use it much better than we used to. And that could be involved in a Nobel Prize given to all sorts of different people. Zurek might be one of them. I don't feel any groundswell for that. So I'm not gonna vote. I'm not gonna bet, place bets that that's gonna happen, but I'd be very happy if it did, a Nobel Prize for decoherence or pointer states. Also in the quantum realm, quantum computing, quantum algorithms, Peter Shor, Charles Bennett, people like that, right? A whole new wonderful field that has opened up over the last few years. And other fundamental quantum things like the Aharonov-Bohm effect, right? Yakir Aharonov is still around and would be a very worthy Nobel Prize winner.

2:15:52.5 SC: The other area that's obvious is we did discover the Higgs boson and we immediately gave prizes to the theorists who helped invent the idea, which is good, which is fine, which is great, but the experimentalists deserve some credit there too. They are the ones who put their lives to the effort of actually finding it. Of course, we all know what the problem there is. So the Nobel committee has made up a rule where it can only be given to three people at a time. And thousands of people worked on finding the Higgs boson. There were specific individuals who gave the talks, but that's not because they were necessarily the most important people in the actual discoveries. They were the spokespeople for the collaborations at that moment in time, and they're world-class great physicists. So I wouldn't complain if they won the Nobel Prize, but it's hard to reconcile giving it to them without giving it to all their colleagues.

2:16:47.6 SC: I would be very much in favour of changing the rules so that big collaborations can win the prize. But no one's asking me about that. The other thing to do is to give it to people who built the LHC, right? That's an enormous technological achievement, and I think that Lyn Evans, for example, whose story I talk about in my book, The Particle at the End of the Universe, arguably the single person who did more than anyone else to guide the LHC to its eventual successful status, would be a wonderful choice of Nobel Prize winner. Tim Zianitos says, "You argued in last month's AMA that it takes just as much causal sense," I just had to check that it wasn't casual sense, "causal sense to say the past is responsible for the present as it does to say the present is responsible for the past. I wonder if some similar reasoning can be applied to bottom-up empiricism versus top-down. Scientists are generally bottom-up. We think what's really going on is quantum phenomena, and so all macro phenomena could be reduced to complicated particle interactions. But isn't it equally legitimate to say that what's really going on is personal agency, fluid dynamics in the economy and that the quantum world must be the way it is because of them?

2:17:55.8 SC: So, first, I think I wanna clarify the beginning of the question, 'cause you say that I said it makes as much causal sense to say the past is responsible for the present, as it does to say the present is responsible for the past. That's not true. That's not true without qualification. The qualification needs to put on is that's true in the context of reversible micro physical dynamics. Okay? So if we're really working at the level of classical Newtonian mechanics or the Schrodinger equation or any other purportedly exact fundamental description that has reversible dynamics in it, then it makes just as much sense to say past is responsible for the future or the present as it does vice versa, because everything's reversible. Information is conserved from moment to moment.

2:18:42.5 SC: But very often we are not working at that level. At the everyday level where we course-grain and have macro states and things are not reversible, it does not make just as much sense to say that causes come after effects as before them. That would not make any sense. There are good reasons why in the everyday world causes precede effects. So that's one thing to say. Then to your actual question about top-down versus bottom-up, no. [chuckle] I do not agree that similar reasoning can be applied to bottom-up empiricism versus top-down, because the relationship between the microscopic theories we're talking about and the macroscopic theories is very much one way. It's a relationship of throwing away information. If I give you the positions and velocities of all of the atoms in a planet, I can calculate its center of mass and its center of mass momentum.

2:19:41.8 SC: But if I give you the center of mass, location and the center of mass momentum, I cannot calculate the positions and velocities of all those particles, right? It's a irreversible mapping. It's a very, very one way process. In fact, there is what we call multiple realizability. Given any set of macroscopic phenomena, we can imagine all sorts of different microscopic phenomena that could give rise to them. So it is not equally legitimate to say that what's really going on is personal agency, et cetera, and the quantum world must be the way it is because of them. I mean, for many thousands of years, we talked about personal agency and fluid dynamics without knowing there was such a thing as quantum mechanics, right? You cannot derive quantum mechanics from human agency or anything like that.

2:20:28.2 SC: Jon, J-O-N, says, "I'm wondering about the possible amplitudes of gravity waves. Is it possible to create a gravity wave so strong that it's troughs are temporarily black holes or conversely to have a crest so high that light could escape a black hole?" So, yes, except with, for a footnote and no. So it is possible to make a gravity wave so strong that it forms a black hole, but it's not going to be temporary. Black holes are not temporary. I mean, of course they eventually evaporate away, but putting aside that completely separate effect in the context of classical general relativity, once you make a black hole it's forever, and that's true in gravitational waves also. Of course, if a single gravitational wave is just propagating along then it either is, or is not a black hole. But if you have two gravitational waves with strong amplitudes and they intersect each other, then maybe you get enough stretching of space time that you make a black hole, that's completely plausible. Could it have a crest so high that light could escape a black hole? No. Light cannot escape black holes. Otherwise, we would've told you about that. Sorry.

2:21:35.1 SC: Vladimir Balik says, "How will higher education evolve over the next few decades in your estimation? Nowadays in the information age, more and more people choose to self-study instead of going to college, because they're able to learn those same skills in the internet practically for free, for instance." You know, I don't know, like people are asking me a lot of these questions, I apologize to people who ask me questions about my idea of what the future will hold. You know, I try, I don't always succeed, but I try to limit things that I say, even in these AMAs to things that either I believe are strongly true or things that I, you know, know as much as anyone else does. And therefore at least have an informed opinion. But something like this, I don't know. You know, it's certainly the case that things are changing. The internet has made lots of things accessible that were not accessible before. But I don't think that there's any simple replacement of online education for in-person education.

2:22:35.3 SC: I'm a huge believer in online education. I love online courses. I think more people should take them. I love the fact that it's made high level knowledge, much more accessible than it ever has been. And I predict that it will continue to grow in importance. On the other hand, it's not a replacement. There are other things that ordinary in-person education does that online education doesn't. Many of the interactions, many of the important roles played by going to college are socialisation roles, you know, meeting people from different environments, talking to them, getting to know different ways of being in the world or different backgrounds or whatever. The informal conversations you have at breakfast before going to class can be crucially, crucially important, sitting down with friends to do problem sets or whatever, just going out and socialising, dating, you know. There's many, many roles that are played in those crucial years from when you're 18-22 years old, that really happen in-person on a campus in ways, is not the only way to make them happen, of course, there are plenty of ways to grow up and mature as a person that do not involve going to college, but it's not the same going to campus and being on campus as just taking some online courses.

2:23:51.3 SC: The other thing, of course, is that the, there's a credentialing aspect, right? So you can do this online or in person, but a college education is more than just learning things. For me, learning things is the most important thing, but let's not fool ourselves. There's also being able to say, I have gotten some skills and I can now use those skills in the real world, and that is important for being hired and going on forward in your life. So learning things will always be important, but also being able to say, "I got a degree," will always matter. Therefore, I don't know how it will all play out going forward. Hopefully it will make things more flexible and more accessible to a wider set of people. But I don't see any end to the existing system where people, to a large extent, go to college for four years and take classes at a physical location.

2:24:50.1 SC: Brendan Hall says, "An annoyed Asher Peres once said at a conference in response to a quantum interpretation poll, 'who here believes that the laws of physics are decided by a democratic vote?' Being a many-worlder myself, this made me sad and angry that this very smart physicist could be opposed to discussion of interpretations, but especially his opposition to a simple poll of opinions. How can this attitude still be so strong in physics?" Well, there's two different attitudes being mixed up here. One, both of which I think are bad. So I'm on your side. One is just being against the idea of discussing quantum interpretations or foundations of quantum mechanics or different approaches to quantum foundations. I think, I mean, I'm not gonna spend a lot of time amplifying that, if you listen to this podcast, you know what I think about that. I wrote a book, I've done many podcasts about it. I think it's important. It is still a very strong attitude in physics, but I think it's gradually declining. I think things are getting better to be honest. The other is this attitude that, you know, we shouldn't take an opinion poll because that's not how the laws of physics are decided. No, duh, that's not how laws of physics are decided.

2:25:56.1 SC: Guess what? When we do an opinion poll about, you know, who should win the election, the result of that opinion poll does not actually decide the election. We actually have to go out and vote. So even in the most heavily polled things, we all know there's a distinction between deciding and polling people. I think it's interesting to poll people and to ask them questions and to get their opinions about things. It's, there's even something, a recent concept that I learn, from Kevin Zollman who's a philosopher. The concept is called Pluralistic Ignorance and it's basically the Emperor's New Clothes or the Emperor has no clothes. Yeah, the emperor's new groove is what I'm thinking of. The emperor has no clothes, right? The story where everyone is reluctant to point out that the emperor is not wearing any clothes. And one reason is because they think all of their friends see the clothes, right? And pluralistic ignorance is when you are reluctant to say what you actually believe, because you believe everyone else believes something different and will think badly about you, but it's not true.

2:26:58.9 SC: They actually all think the same thing, and they themselves are not saying it out loud because they think that everyone disagrees with them. This is a real phenomenon and it can cause harm. And so I think that talking to people, getting rough ideas about how many people believe different things, this is a hugely useful thing. Philosophers are much less fussy about this, right? I mean, they have the wonderful project by David Chalmers and David Borge, I think his name is, on what philosophers believe. And if you are a professional philosopher and you sign up for philpeople.org. So it's just a list of all the philosophers. Right? And what one wonderful charming thing about this site is that mostly it's a way to link to your papers and your website, but they also ask you to tell them what your philosophical views are. So you can say like, I'm a naturalist, I'm a compatibilist about free will. I'm a determinist or whatever. Right? And they, and then you can list them, and you can say, I don't have any opinion about things you don't have any opinions about, but it's a nice way to get a general feeling for where people land, nothing wrong with that in the real world of human beings.

2:28:02.9 SC: Ole Grovinsky says, "The great Polish sci-fi writer, Stanislaw Lem devoted a lot of his works to the problem of contact between human and alien intelligence. Even when both sides recognise each other as such, he claimed that the different evolutionary paths that each took makes any kind of meaningful contact or comprehension almost impossible. Have you read some of his later works like Fiasco and what do you think about the idea in general?" I've read some of his works, not Fiasco. I'm certainly not an expert. I really don't have any idea about this very important question. You know, we've had a few podcasts lately about evolutionary biology here on earth and the question of convergence versus divergence, the role of contingency and randomness as would be championed by my namesake, Sean B. Carroll, versus the role of convergence as other people who've been on more recently would talk about. But that's number one, here on earth. And number two, mostly about biological morphology, not about cognitive capacities or ways of thinking. So to be very honest, I can absolutely see both sides to this one.

2:29:13.0 SC: I can see that, you know, the way that different species develop intelligence, let's imagine the following argument. The way that different species develop intelligence is more or less in response to similar problems and more or less in the presence of similar resources to solve them. Right? So therefore it would not be surprising if they developed more or less similar strategies and tools for doing it. And therefore, maybe the kinds of thinking and cognition and consciousness that alien creatures have is even if it's different in details, still recognisable and familiar to us and something that we could meaningfully communicate with. That's a perfectly legitimate argument. Here's another argument. We only know one way to be advanced technological, highly intelligent creatures, mainly the way that we do it here on earth, right? In principle, there could be a huge number of different ways to be those kinds of creatures. We don't know, we've only literally have one data point.

2:30:16.3 SC: So we should be humble and recognise that there could be many other ways that we haven't thought of 'cause we're not that smart to be intelligent and to communicate with each other. And therefore, when we meet an alien the smart money says we probably will have enormous difficulty understanding them. I don't know. I think both of those are very reasonable arguments, honestly. So I would love to, I would love to hear better arguments for and against it. And, you know, one of the things is this is an area where, for reasons I don't understand when I do talk to people who have strong opinions about these things, about the nature of aliens, and alien life and civilisations, they always seem really biased one way or the other. Like they seem to have reasons why they believe what they're saying is likely to be true about alien organisms or beings for reasons other than a cold, rational discussion of the scientific possibilities.

[chuckle]

2:31:18.3 SC: So I haven't heard a lot of discussion about this kind of thing that is persuasive to me. I mean, to be persuasive to me would both have to be informed and, you know, thinking carefully about both of those sides of the argument that I both, that I just put forward, and to really sort of go through the details. Right? I mean, when I say out loud, "Oh, there's many ways of thinking," what does that mean? How many ways of thinking are there? You know, [chuckle] I don't know what that means exactly. To be much more careful about it would be required or on the other side, if you saying, well, you're gonna converge to the same thing, well, prove it. Or at least give me an argument for it. Like show me this convergence in thought space, and the necessity of it. I don't know. It's very hard. So I'm not surprised that no one has a very, very strong convincing answer, even though some people think they do. But I think it's a good question to think about.

2:32:11.9 SC: P Walder says, "Can abstract ideas have a causal effect on the material world?" Well, guess what? That depends. [chuckle] It depends on what you mean by having a causal effect. So, if I needed to give a one word answer, the answer would be yes. But I need to explain what that means. When you talk about causal effects, you need to have a theory of causality, right? You have a theory of what that means. And so I, in my personal way of thinking about cause and effect relations, I don't talk about them at all at the micro physical reversible level. I don't think that cause effect relations are the right way of thinking about Newtonian mechanics or the Schrodinger equation or anything like that. I think that cause effect relations are emergent phenomena at a higher level of description where you have irreversible dynamics, an arrow of time, randomness and unpredictability et cetera. Okay? And so in that world, in the higher level emergent world, can abstract ideas have a causal effect means, when you're trying to successfully describe the behaviour of the things in that higher level emergent description, is it important and useful and relevant to include abstract ideas in the set of things that, in the set of degrees of freedom, if you wanna put it that way?

2:33:37.5 SC: So not only do I say, here is a set of people with certain body types and ages and locations in space and they're interacting in the following room, but also some of the people have the following abstract ideas in their head and other people have different abstract ideas in their head. Well, guess what? Yes, those abstract ideas are gonna have a hugely important causal effect. They help understand what's going on. You know, like this person sacrificed himself because of a feeling of patriotism. Is that a meaningful sentence? Yeah, I think it is. Or motherhood or, you know, whatever, different reasons why you might think that there's certain moral obligations or ethical rules or whatever.

2:34:23.0 SC: These are all abstract ideas and they absolutely play a crucial role in our best understanding of the macroscopic human scale world. This is basically exactly the argument I give for believing in compatibilist free will. Our best understanding, our best theory, our best way of describing actual human beings is as agents making choices. I don't see any way around that. If you had a better theory than good. Tell me what that theory is. Tell me a way of predicting when human beings can do that does not involve them making choices. Then that would be great, and then good for you. But I haven't seen that theory. Likewise, I think that our best theory of talking about the actions of human beings includes abstract ideas in their head as some of the degrees of freedom that you need to include.

2:35:11.9 SC: Paul Hess says, "The Higgs boson seems unique among all other particles as having no charge and no spin. Is there some deeper significance to this uniqueness?" Maybe, [chuckle] but I think it sort of goes the other way around. So here's what the, I think that most modern field theorists would say. There's no problem whatsoever in inventing fields and corresponding particles that have no charge and no spin, neutral spinless bosons. It's easy to write those down. I mean, cosmologists make a living doing this. The inflaton field is one that is supposed to have no charge and no spin, for example. But the Higgs boson is the only one that we found and you notice it was hard to find, [chuckle] right? We didn't find it first. We knew about electrons and photons long before we do about the Higgs boson. Why is that? Anyway, the rough answer is that there is kind of a natural scale in known physics in the core theory, given by the Planck scale; the scale at which quantum gravitational effects might become important. And that scale is very, very high, very, very energetic compared to the masses of particles that we know about.

2:36:24.4 SC: But the way you think about that in modern physics is not, "Oh my goodness, the Planck scale is so big," but, "Oh my goodness, the masses and energies of most of physics are so tiny compared to the Planck scale." How can we make sense of that? And the answer is, for almost every particle, there are symmetries that keep the masses of these particles low. Gauge in variants in electromagnetism keeps the mass of the photon zero. Similarly, something very similar for the gluon of QCD and the graviton of gravity, there are what are called Chiral symmetries that help keep the masses of the fermions low. So the mass of the electron, the mass of the quarks, et cetera, are kept low. And both of those symmetries, the existence of both of those symmetries depend on the spin of the particles. Okay? Not the charge, really. The charge is, it plays a semi-related role, but the spin is really, really important. So the spin one-half fermions and the spin one-gauge bosons both have a natural way to keep their masses lower than the Planck scale. The Higgs boson, since it's a scalar particle does not have any known symmetry that keeps its mass low.

2:37:37.1 SC: So there is a mystery. Why is the mass of the Higgs boson so low? Okay? So the question is, you know, why is there only one particle that has no charge and no spin? The real question is, why is there even one particle that we've been able to discover? I mean, maybe there's lots of particles up near, near the Planck scale, but they have masses up near the Planck scale. That's the natural thing. The fact that the mass of the Higgs boson is so low compared to the Planck scale is a famous problem. It's called the hierarchy problem in particle physics. And we don't know the answer to it. We have many suggestions on the table, and this was the there's sort of a general version and a specific version of what we expected to see at the Large Hadron Collider, the LHC. Like you'll often read that people were very optimistic about finding super symmetry at the LHC. And I'm speaking in the past tense, but it's still possible we do, however, it's absolutely, it could have been possible we would've already, and we didn't yet.

2:38:34.7 SC: And the reason why is because super symmetry offers an explanation for why the mass of the Higgs boson is so small. Super symmetry can be that symmetry that protects the Higgs boson from getting a mass. And even if it wasn't super symmetry, we really thought there would be something else near the electroweak scale where the Higgs mass is located, that would explain why it's not more massive, and there isn't anything. So we would, we thought that the hierarchy problem gave us a good reason to think that we would discover new particles at the LHC. And, of course, again, maybe we will tomorrow, but we haven't yet, and that's a big puzzle. So that's the deep significance that there is a puzzle we don't know the answer to, which is why is the Higgs boson mass so low that we actually have a chance of seeing it in particle accelerators.

2:39:26.9 SC: Wells Burrell says, "Do you have any major ethical concerns about the gene editing revolution other than germline editing of human embryos? And if so, what are they? Do you believe that gene editing is a positive technology, which will deliver on the hype? What kind of future do you think is realistic here?" So again, a what kind of future thing going on here about in an area where I have no expertise whatsoever, except for, you know, the ethical things. I have a little bit of expertise there, after all I am now a philosopher officially credentialed. So I think I have fewer ethical concerns than the average person. I think that a lot of people's ethical concerns about gene editing arise from a feeling of ickiness, [chuckle] that, you know, that genes, that we go in there and alter are somehow less legitimate or natural, or okay, than ones that randomly bump into each other during the ordinary course of sexual reproduction. I think that's kind of a false distinction. So I don't feel that very much. I think the more important thing to say is, I think it's gonna happen.

2:40:29.9 SC: I'm not someone who thinks like, there seems to be a bunch of people who think we can just write down rules and stop gene editing from happening in human beings. I think that's just hopelessly unrealistic. It's gonna happen. Somebody's gonna do it. It's actually not that hard. Remember the podcast we did with Fyodor Urnov who says, "Oh yeah, you know, it's gonna happen in people's garages." [chuckle] So not only are other countries gonna do it, who might not feel the same way as us, but even individuals in any one country will be able to do it. And there's a lot of obvious good things to do. You know, if you can prevent babies from having diseases or whatever, ahead of time, knowing that stop them from suffering, I think that's just good. I think we should just do it. And then if you could also make them smarter and stronger and healthier, I think, you know, why not? I don't see the problem with that. I don't think that necessarily leads to any Gattaca, Stepford Wives. I don't know what the worry that you might have is.

2:41:31.7 SC: So I think it's gonna happen. I think it's probably less bad than a lot of people worry about. Having said all that there are obvious problems that you can go into. Maybe people start editing genes to be something other than simply making babies healthier and stronger or whatever. Maybe they make them worse rather than better. Maybe they want to eliminate certain kinds of human beings that exist now in the world. Oh, that would be very, very bad. So I kind of think that the current, that in some sense, maybe it's a little bit unfair, but my rough untutored feeling is that the current state of discourse about these things is pretty primitive and not really taking the problems and the potentials nearly seriously enough. It's just sort of acting on the basis of ickiness, and let's not change anything because natural behaviours are better. I don't think that's realistic or good, but I do think that there are concerns and worries that are important. And so we should be taking those concerns and worries more carefully, even if I am not enough of an expert to tell you what the biggest concerns and worries actually are.

2:42:40.7 SC: Shred Cadmium says, "Temperature is defined as the mean kinetic energy of a system. In my view, this concept doesn't have a direct equivalent in quantum theory because the mean, and system bits, while representing something entirely real are only appropriate to a macro level of description. My friend thinks I'm wrong, is he right?" So I do think you're wrong, but I think you're wrong for a subtle reason that I'm getting from reading in between the lines of your question. And I could be completely misreading here. So sorry if I'm misinterpreting, but you seem to be contrasting quantum theory versus macro level of description. And I think that's an inappropriate distinction to draw. The difference is between quantum and classical, and micro and macro, but those are two different sets of distinction. Quantum systems can be macroscopic. There's no problem with that. Or let's say there can be macroscopic systems that we choose to describe using the rules of quantum mechanics. No problem at all. So if you go back to the podcast I recently did with Nicole Yunger Halpern, the whole subject she studies is quantum thermodynamics.

2:43:48.0 SC: You need to have a temperature to talk about thermodynamics, at least in equilibrium, you have a temperature, in non-equilibrium situations things get more complicated, but there is absolutely no problem in defining the temperature of a quantum system in equilibrium. I mean, there are explicit formulas for it. So it's very, very common and very, very frequent that we talk about quantum many body systems that are macroscopic, you know, depends on your definition of macroscopic, but have enough particles or whatever in them that we find it useful to not describe them particle by particle, but collectively, and in those cases, temperature is a 100% useful quantum parameter.

2:44:30.2 SC: Andrew Goldstein says, "Any thoughts as to why human vision is limited to electromagnetic wavelengths of roughly 400-700 nanometers? I've read that insects can see ultraviolet light and birds can sense magnetic fields." Well, yes, I hope that you not only read that, but heard it discussed in the recent podcast with Ed Yong, that's exactly what he was talking about. The fact that many different animal species have many different sensory capacities that we human beings don't. So I don't know specifically the reason why that's the range of human vision. Obviously, it is the most obviously useful range because it is the visibility, the transparency of the atmosphere. So it is the part of the sun's light that gets to us here on earth. But you can imagine it would also be useful even if perhaps not as directly useful to see infrared light, 'cause that's sort of the thing that living beings give off through their heat radiation and maybe even ultraviolet light, I don't know. But what you have to keep in mind is all these capacities have costs associated with them, right? So, you know, evolution happens as a very delicate balancing act between many different constraints. We take an energy, we put that energy to use. One of the reasons why humans are so different than other animals is that we have a much greater percentage of our energy budget devoted to our brains. Human brain is a tremendous energy eater up. That's not the best word, consumer.

2:46:01.2 SC: And so why would you ever do that? Why would you waste so much energy that could be used for running and jumping away from your prey or whatever, I guess, toward your prey, away from your predators, rather than just using it for thinking, right? And the answer is there turns out to be some usefulness in being able to think, but you need to have the kind of niche ecologically, where it is more useful to put that energy into thinking than it was to putting that energy into running and jumping, and maybe those niches are kind of rare. I can imagine that similar considerations work for vision. So, you know, it's, again, it's not just some solid state apparatus where you program into the human eye what it's sensitive to. You build the human eye out of chemicals and out of specific configurations of biochemical processes that happen when the photons of light hit the rods and cones in your eyes. Maybe in order to see other wavelengths, you would need to add on more chemical super structure into your eyes, and that would cost resources and either energy or just sort of chemical instructions or whatever. And it turns out not to be worth it. Right? All of evolution and all of biological design is a set of compromises. So you can't just say, why don't we have this ability? You have to say, what would it cost to get that ability? And is it really worth it?

2:47:26.8 SC: Sandro Stuckey says, "Your discussion with Will MacAskill on longtermism made me think about how one can increase one's confidence in predictions about the long-term future. I remember that climate scientists evaluate their models by running them in the past and comparing their results against historical data. But this seems really hard when it comes to predictions about the impact of human choices. I'm struggling to come up with examples of historical decisions for which we can say with certainty that they improved or worsened the present, e.g., we probably needed the industrial revolution to go to today's high standard of living, but it also resulted in climate change, et cetera. Are there historical decisions that impact us today and that you wish had been taken earlier or not been taken at all?" So I guess Sandro you're, that was a twisty question that ended up in a different place than I thought you were going. [chuckle] I mean, so let me say what I wanted to respond to at the beginning of the question, which is, I agree. It is difficult to have high confidence and predictions about the long-term future.

2:48:26.5 SC: There are too many variables, you know, society and life and the Earth's ecosystem are all highly non-linear systems with lots of possibilities for unanticipated consequences. At the same time, we need to have opinions about what is likely, we need to have credences. Okay? You can't just have a no nothing attitude that says, "Well, it's hard. Therefore I don't care." You have to do your best, even if your best is not very, very good. So that's where I thought you were going with the question, but where you're actually going is, are there historical decisions that you wish had been taken earlier and not been taken at all? I mean, sure, [chuckle] in retrospect, I wish we had put tight controls on spewing fossil fuels into the... Fossil fuel remnants, relics, gases, into the air a lot longer ago. 'Cause climate change is a big problem. I wish we hadn't done the Holocaust, right? That was a bad decision. [chuckle] I don't wanna, you know, make light of all the terrible historical tragedies that occurred that I wish hadn't happened, but some of them were human decisions. Right?

2:49:27.8 SC: So I think it's easy to say like the industrial revolution had both good consequences and bad consequences. When you go at that grand scope of event, they will always have both good advances and bad advances. Religion, science these have had both positive consequences and negative consequences. I think we nevertheless need to weigh them, right? I mean, maybe you could say that between the year zero and the year 1500 religion had mostly good consequences or maybe not. I don't know. And maybe you could also say after 1500 had mostly bad consequences, but you have to try, right? I mean, you have to, I don't have a list of historical decisions that are tricky and that I have a different opinion about than other people, but I do think that you can't duck the question.

2:50:19.3 SC: You do have to sit down and think about it, going forward. For history, you can duck the question, you can ignore that question if you wanted to. But going forward, even if you're talking about things which will have both positive and negative consequences, you either do that thing or you don't, and so you have to decide the best you can, whether it's gonna be net positive or net negative, to the best of your ability.

2:50:44.7 SC: Maxine says, "I've recently heard that a good way for a lay person to understand gravity and general relativity is that gravitational time dilation is what causes the gravity we experience here on Earth. The explanation is, that one can imagine a falling person with a clock on its head and a clock on its feet ticking at different rates. This time gradient is said to rotate the objects motion arrow, aka fall velocity more and more toward the Earth, and this is what we experience as gravity. It seems pretty amazing, and at least in apparent sense of being intuitive. Is this a good way for a lay person to understand the fascinating but intimidating inner workings of general relativity? Well, I'm gonna take a wishy-washy stance toward this question.

2:51:27.8 SC: I think it's a good question, it's a good question to think about and ask. Here is what I worry about. So actually, I don't know, is the short... I don't even know if this explanation is correct. [chuckle] It sounds like the kind of thing that could very well be correct and probably was come up... Come up with by someone who knew what they were talking about. But I haven't sat down and thought about it, I know the equations, the geodesic equation that we use, that we actually solve to show what the motion of particles is in a curved spacetime, or people for that matter, and then what you can try to do is say that rather than just telling people, Don't worry, things move on geodesics, you can try to be a little bit more clear about the physical-ness behind why the geodesics take the form they do. Having said that, there's also a huge worry in purported explanations of this form, which is that they give the illusion of understanding, that they put together a bunch of words that sound kind of right and give you the right answer, and therefore you accept them. But if you dig into them more deeply, maybe they don't work as much for the specific scenario that you just outlined, even if I have a single point particle, that doesn't have a head and a foot, and it's just of zero dimensionality or really, really tiny.

2:52:47.1 SC: It still falls in a gravitational field. I don't see how I can relate the clock on its head and the clock on its feet to that kind of motion because its head and its foot are in the same place. It's just a particle. So I'm not sure that that explanation is really capturing everything. The example I know even better is in cosmology, when we talk about dark energy and the cosmological constant. You will sometimes hear the following kind of thing, that the cosmological constant has negative pressure. So, a negative pressure is like a tension, so if you had a box of cosmological constant and zero cosmological constant outside, you can't do that, but if you could, the cosmological constant would pull in on the box and cause it to squeeze rather than pushing it out like air in a balloon. Negative pressure, okay? And this is supposed to be what causes the universe to accelerate rather than to expand ever more slowly, because what we're told is the thing that counts for making the universe accelerate or decelerate is the energy density plus three times the pressure, and so if the pressure is large and negative, you get an effectively negative amount to push.

2:54:02.3 SC: All of those words are individually correct. But a miracle occurred. I don't know if you noticed this, but who says that the thing that matters for the expansion of the universe is pressure plus... Is energy density plus three times the pressure? I mean that just came out of nowhere, right? And in fact, it's not even really true, if you look at the Friedmann equation for the expansion of the universe, it's H squared where H is the Hubble constant is proportional to rho, the energy density. There's no mention of the pressure in that equation. There's another equation for the second derivative that does involve the pressure, but I don't need that second equation to solve for to get the entire accelerating history of the universe. And I think it's just a wrong explanation, I think a better explanation relies on the fact that dark energy is persistent, that it does not dilute away as the universe expands. I think the negative pressure thing sort of plays on your intuition, that pressure pushes things and... Well, sorry, I should say the other way around. The negative pressure explanation is really bad because people can start thinking about it, and they realise that a negative pressure is a tension that pulls things together.

2:55:17.9 SC: So why isn't the negative pressure pulling galaxies together rather than pushing them apart? And the answer is, that the negative pressure isn't doing anything at all by itself, it's the gravitational effect of the negative pressure on the curvature of spacetime that is doing something. But anyway, this is what happens when I start talking about my [2:55:36.4] ____, my own hot button issues here. You didn't care about that, what you cared about is this completely different attempts to understand why objects fall in general relativity. So the short answer is, I don't know whether this is a good explanation or not, but I would be aware and cautious about purported explanations that make you feel good without actually making you completely understand what is going on.

2:56:02.9 SC: Anthony Famularo says, "I'm afraid you triggered a touch of PTSD in me with your Bigfoot story in the last AMA. I'm a couple of years younger than you, and when I was a child, the documentary, I believe you were talking about, was heavily advertised on TV, every time the ad appeared, I ran screaming from the room and was terrified for hours afterward, just to verify that it was the same documentary, do you remember whether there was a scene in which someone was sitting calmly on a couch only to have Bigfoot's huge arm crash through the window next to him and violently grab a table lamp? I'm afraid that just Googling it would be too much for my heart."

2:56:37.9 SC: So I don't know. Probably, yes. What you're describing is completely consistent with my memories, but I do not actually remember that particular scene. I do remember the documentary was scary, and so it's completely compatible, like I said, that that scene was there, but no, I don't wanna Google it either, honestly, like time is short, I don't wanna relive my childhood traumas. I'm not afraid of Bigfoot anymore, by the way, but who knows? Maybe Googling would change that. Alright, I'm gonna group together two questions about the past hypothesis and the Big Bang.

2:57:14.9 SC: Eric Stromquist says, "I'm interested in any comments you have on why the truth of the past hypothesis is taken to be surprising or unexpected. I understand if the initial micro-state of the universe was drawn from some probability distribution of micro-states and phase space, then that state would likely correspond to a higher entropy macro-state because higher entropy macro-states occupy most of the phase space by definition. But why do we assume if we do that there should be such a random distribution, meaning that the Big Bang shouldn't produce some especially simple symmetrical or unique state, which may correspond to a low entropy macro description."

2:57:52.3 SC: The Big Bang is after all a pretty special event. And then Mike Brock says, "I often heard it said that the Big Bang did not happen at a point in space and that it is a moment in time. It is also said that the Big Bang happened everywhere at once. I conceptually get this, but one question I have is that at the incident of the Big Bang, did the universe had a spatial extent at all?" So these questions are about different things, but they feed into each other, and as usual, I will go for the second question first here. What we say is that the Big Bang is a moment in time. That's a correct thing to say, but we should also say the Big Bang doesn't exist. It's a feature of classical general relativity in a regime where classical general relativity doesn't apply. So it's just a warning sign that says, Don't believe classical general relativity here, that's all it is. We don't know what actually happened in the real world, we talk about the time since the Big Bang, but that's just a way of approximating the time since spacetime became classical enough that we could talk about such things, and since we think that that time is really, really really short.

2:59:00.4 SC: If the time between the actual beginning of the universe, whenever and whatever that was, and the time when everything became classical and well-described by classical general relativity was 10 to the minus 30 seconds, then talking about one second after the Big Bang makes perfect sense even if the Big Bang itself does not, okay. So you ask the question, Did the universe have any spatial extent at all? I can answer that in the context of classical general relativity, which is, there's no such thing as the incident of the Big Bang. So that's a simple cop out, what I can talk about is any time after the Big Bang in classical general relativity. And then, yes, the universe had a spatial extent, in fact, it could have been infinite. There are absolutely solutions to Einstein's equations where space was infinite extent arbitrarily close to the singularity of the Big Bang, that's just a feature of general relativity because it is a moment of time after all. But then again, we don't know for sure.

2:59:55.8 SC: So we don't know is the short answer. What this has to do with the previous question is, saying the Big Bang is a pretty special event. Yes, it is a unique event in the history of the universe, as far as we know, and certainly in the history of our observable universe, but the question being asked is, How do we know that the universe was taken from a random distribution? So of course, we don't know that. No one thinks that the universe was taken from a random distribution, people think the universe had some particular beginning state. The point of arguing about the past hypothesis and the initial conditions near the Big Bang is...

3:00:32.7 SC: When you see features of that initial state that are unusual in some course-grained macroscopic human point of view sense, then maybe that is a clue to a better understanding, because after all, we don't know what happened at the Big Bang. So as referencing back the previous statements about brute facts versus explanations, you can always say, the Big Bang just happened in a certain way, or whatever did happen at the Big Bang happened at a certain way, and that's it. Stop asking questions. You're allowed to do that, and that might even be right. But since we don't know what happened at the Big Bang, you can also say, maybe what we think of as the Big Bang is a process that happens in a more general context and the reasons why it looks so smooth and low entropy. And that's a natural thing to ask because, even though the Big Bang is a pretty special event, as far as we understand it, it very easily could have been otherwise. There's nothing that we know currently in our understanding of early universe, cosmology, or the Big Bang that would've prevented the Big Bang from being highly inhomogeneous and much higher entropy other than the fact that it doesn't look that way.

3:01:48.4 SC: So to me, this is a very, very precious clue for theoretical cosmologists, to try to work on better understandings of what happened at the beginning of the universe, and I don't wanna give that up.

3:02:00.4 SC: Bruno Toshera says, "Congratulations on the episode with William MacAskill. It was one of my favourites. It was too bad you didn't... You couldn't dig into averages and utilitarianism. So I'll ask here, isn't MacAskill's ranking alternative to scoring happiness combined with Henry Sidgwick's idea of maximising number of people times average happiness, the perfect solution to your worries about utilitarianism?" So I almost didn't answer this question because I'm really not familiar... I couldn't even tell you exactly what MacAskill's ranking alternative to scoring happiness is, or Sidgwick's idea of maximising number of people, times average happiness. So I cannot tell you that those are perfect solutions to my worries. But I don't think that they are because my worries aren't of that form. My worries, my real worries are not... Well, there's two kinds of worries that one might have about any ethical theory, and that I, in particular, have about utilitarianism.

3:02:56.6 SC: As a moral constructivist, I think what we mean by our... The way that we get to moral principles via meta ethical considerations is we start with some moral intuitions. There are things that we just feel are better. People should be happy. They should be nice to each other, whatever your moral intuitions are, people should play fair. People should be treated equally, all else being equal. And then we try to systematize that, and this is what we do. As moral philosophers, we sit down and say, "Okay, I have these very rough incoherent, sometimes incompatible kind of messy moral intuitions. Let's work them up into a logical system that is internally consistent at the very least." And then put that forward. And then the hard part starts. That was the easy part. The hard part is, you realise that your system, that is nice and logical and pristine, only captures some of your moral intuitions, but then, other times, conflicts with them. What do you do? And that's the situation you're in with arguments like the repugnant conclusion of Parfit, and things like that, where, basically, what you're saying is, "I thought that my moral intuitions, when I tried to systematize them, I systematized them into utilitarianism, but it led me to this conclusion I really don't like."

3:04:20.8 SC: Other more naive versions of utilitarianism will say, if you can save one person by killing them and cutting out their organs and distributing them to needy people who need organs, then you should do that. You're saving five lives by only killing one. But then someone says, "No, no, no. That was not my moral intuitions at all." And so then you conclude either one of two things. Either that you don't have the right system, because you did not successfully systematize your moral intuitions, or one of your moral intuitions has gotta go. And either one of those is a perfectly legitimate move, a priori. Maybe you thought something was right, and then by thinking about it more carefully, you realise it wasn't. That's okay. That's fine. You're allowed to do that. But also, you're allowed to say, and people like Peter Singer, the world's most famous utilitarian, is just the best in the world at accepting the implications of his system, [chuckle] as unpalatable as they may be. That's not the way I generally will go. Because I am a constructivist, I want the system that I invent to do absolutely the best it can to systematize my actual moral intuitions. And if I find that it doesn't, my first move is to fix the system, not to change my moral intuitions.

3:05:44.3 SC: Sometimes I will, but that's not the first move. And so that is why I object to utilitarianism at that technical level, because it does not fulfill my moral intuitions. But there's also a different objection that I have, which, and this is where I'm more skeptical of the particular moves that Bruno is suggesting are going to help. I just don't think it makes sense, utilitarianism. I don't think that the very idea of utility makes sense, the idea that there is some number that we can attack... Well, let's be very, very careful because I could be wrong about this and this deserves to be carefully considered, not to be casually dismissed. If you have any rules at all, whenever you have rules, when you have a decision, procedure, an algorithm or whatever, you can always, after the fact, phrase that rule as maximising some number. Basically, if I have a rule that says, "Do A and not B," I attach the number one to the doing of A and the number zero to the doing of B, and then I say, maximise that number. It's equivalent. It's just a mathematically formally equivalent way of stating your rules. So it's always possible to define something that you maximise and call that your moral rule, even if you're the world's biggest deontologist or virtue ethicist.

3:07:06.8 SC: But the specific feature of utility that worries me is the idea that we must add it up among people. That the idea that somehow people have different amounts of utility and we add them up, and that's what we maximise. It's the way of defining utility as a sum over sub utilities of individuals. That just seems to make no sense whatsoever to me. I don't see why that should be true. I don't see how to do it. I don't see how to compare the utilities of different people. It just doesn't seem like a good starting point for anything. So maybe there's some clever kind of construal that still calls itself utilitarianism, but doesn't do that, but I don't know about it. I mean it, when I say maybe, I don't mean that in a sort of sarcastic way. I mean, maybe there is such a way, but I haven't seen it, so I'm not, and I haven't been really very motivated to look for it. It just doesn't seem very promising to me.

3:07:57.2 SC: I'm gonna group together two questions here. And again, this is about morality. So this is Eric Speckhard asking, "What exactly do constructivist and nihilists disagree about? What do nihilists deny that constructivists accept?" And Jimi, J-I-M-I, says, "Without moral realism, how can we ever justify intervening in other people's affairs to impose our own morality? I feel like there needs to be a way to help people without being hypocritical." So I like these two questions, obviously they're about similar topics, but also they sort of, if I'm reading them correctly, which is always possible that I'm not, but they seem to have opposing implicit beliefs in them. Okay? Which is I kind of like that, 'cause it illustrates that the implicit beliefs need not be universal. Eric is saying, you know, why should constructivist and nihilists ever disagree? Where we take nihilism to be, you know, just the statement, there are no moral truths. There's really no such thing as morality, anything goes.

3:08:55.5 SC: I'm sure a real card carrying nihilist would be more careful than that, but that's roughly what we have in mind. Whereas a constructivist says there's no objective moral reality, grounding moral truths out there, but we can construct our morality and we do construct it. And when we construct it, it exists and it gives us guidance as to how to behave. Okay? And then different kinds of constructivists disagree on the basis on which we do the constructing. Humean constructivist are more like what I said just now where you have your moral intuitions and you try to systematize them. They're also Kantian constructivist who try to say that there, we can just rationally think our way into the correct constructed rules. And so the hidden idea there seems to be that that constructing step doesn't really mean much. It's just kind of a fake, because, I mean, the way that I stated it, the disagreement is pretty obvious. Like nihilists don't think that there are moral rules and constructivist do. And the constructivist doesn't think that they're objective. They think that they're constructed. And so the implication seems to be, that's just meaningless, fluffery. Right?

3:10:06.4 SC: And I don't think it is. I think it's just correctly describing what real human beings actually do and the best that they possibly can do. So what do they disagree about? They disagree about the existence of morals and ethics which is kind of a pretty big thing to disagree about. Whereas Jimi, on the other hand is, has basically the implicit idea that unless your morals are objectively grounded in real stuff out there in the world, then they're meaningless, right? I mean, maybe this is the same implicit idea. I'm not quite sure. But the constructivist is gonna say, yeah, I have morals right? Here they are. I can tell you what they are. I can tell you that killing innocent babies for no good reason is wrong. That's a moral thing. I constructed it. I didn't find it by doing experiment with electrons or whatever, but it is nevertheless a good moral way of being, and I will try to convince other people to live in the same way. And Jimi is saying, well, how could I ever justify intervening in other people's affairs 'cause they might disagree with me? Well, I think that's the difference between relativism and constructivism. The relativists say individuals or groups of individuals more typically construct their own moral codes. And that's all there is ever to be said. Morality is only relative to that society or that community that you're a member of.

3:11:26.4 SC: That's not what constructivists are saying. They're saying I construct moral rules, and I think that they're right. I don't think that they're objectively right, I think that they're subjectively right. But I have every justification for intervening to stop other people from violating them. Why shouldn't I? So the implicit thing here is that the only real justification for intervening in other people's affairs is moral realism, right? Is that there's some objective reason we can all agree on. And if people disagree with me, I have no right to interfere in their affairs. Well, wait a minute. What do you mean you have no right? Like where do these rights come from that we're talking about here? I wasn't talking about rights. If you don't have moral realism, then where is this right supposed to be coming from? I as a moral constructivist, think that murdering innocent babies for no good reason is wrong, and if I see a person murdering innocent babies for no good reason, I will stop them. I will intervene in their affairs. I see no problem with that. I just think I'm being way more honest and candid about where my moral feelings come from, than the moral realist who is pretending that they're really out there in the world.

3:12:36.8 SC: David Wright says, "I have to ask your take on the controversy over whether recent JWST images, show evidence that cosmic inflation theory is mistaken. How do these images somehow contradict the Red Shift data, that results from an expanding universe?" So they obviously don't. The universe is expanding. Don't let anyone tell you any differently. JWST is not conflicting with the expanding universe idea. Now there was a claim, there is a claim that, you know, the JWST, remember that it's one of its things is to look at the earliest galaxies, hundreds of millions of years after the Big Bang. And we're learning more about them. We have a better telescope now, we're seeing galaxies younger than we used to see. Okay? And the claim is that we are seeing galaxies, even though they're just a couple pixels in size, they are too young and too compact and well formed to be what is predicted by the conventional cosmological model. They're forming too early. So...

3:13:37.2 SC: Of course, it may be that we don't know a lot about galaxy formation. Right? This is exactly the kind of thing that is involving a lot more ideas than just the basic idea of the Big Bang Theory in the expanding universe, forming a galaxy is kind of a mess, it is exactly the kind of complex system gastro physically intimidating problem that we poor human beings are not very good at solving, so if you find data that is not an immediate fit to your current best theory of galaxy formation, you don't throw out the big bang, you throw out your current best theory of galaxy formation or you even maybe probably just update it a little bit. I don't know how easy it is to update it.

3:14:23.3 SC: But there's absolutely zero reason in anything that the James Webb has seen or anything else, to doubt the basic Big Bang model of the universe expanding from an initial hot dense state. Now, cosmic inflation theory is not part of the standard big bang model, it's an addition to it, that says what happened in the first 10th of the minus 30th of a second, right? And that may or may not be true, that's much less settled than the Big Bang theory overall, and maybe the inflation theory makes specific predictions that are hard to accommodate with the galaxy data. I think that's not true by the way, but it is a conceivable thing that could be true once we understand both the theory and the data better.

3:15:05.0 SC: But nothing the data for the broad parameters of what we call the Big Bang model, not the Big Bang event, right, which is this mysterious thing that didn't happen. That is just the place where classical general relativity breaks down, but the Big Bang model is what cosmologists use to refer to the whole general story of a universe expanding and cooling from an initially hot, dense state. That is just true. That is just solid. You should always be a good Bayesian and have a tiny credence in alternatives, but as I've said before, you should... There reaches a point where credence is so small that it's not worth worrying about, and this is such an example, Big Bang nucleosynthesis, the cosmic microwave background, structure formation, the very basic predictions of general relativity all offer overwhelming evidence in the basic Big Bang model.

3:15:58.9 SC: Deshaun Stoyanovich says, "Here is the gist of an often made argument, which I think is flawed, in which you've also used on occasion most recently in the July AMA. Several of the most recent presidential elections would have gone Democrat had the competition been for the popular vote instead of for the Electoral College. In my opinion, better political campaigns are ones that are responsible for close election victories, and thus the better of the campaigns would have just campaigned differently had the popular vote been the goal. Saying that Donald Trump won the electoral vote, but Hillary Clinton won the popular vote is akin to saying that team A won the basketball game against team B on points, but team B won on rebounds. The definition of the verb to win assumes the existence of a particular competition or contest. Please comment."

3:16:44.9 SC: So a couple of nitpicky comments first before getting to the bigger picture, you say the quote is several of the most recent presidential elections would have gone Democrat dot dot dot, which you call an often made argument, but it's not an argument. That wasn't an argument there, that's just a statement. It's a hypothetical statement, which could be true or false, but presumably one has in mind some argument for the truth or falsity of that statement, and that would be the actual argument. The second nitpicky thing is the basketball game analogy.

3:17:17.1 SC: Sure. No one is... At least I'm not denying that Donald Trump did win the election against Hillary Clinton, the claim that if it had been a popular vote rather than the electoral college, Clinton would have won is not the same that saying that she did win just on some weird thing, right. Trump won the election. That's perfectly unassailable. The purported claim is that under a different electoral system, the outcome would have been different, and I think that's entirely plausible. I think that politics is more than just who had the best political team. The argument here is not about whose political team was doing better, it is how best to coarse-grain the will of the people into choosing its representation and it may very well be possible that Donald Trump's political team was just so savvy that had the goal been to win the popular vote instead of the electoral vote he would have done that too.

3:18:15.9 SC: I see zero evidence for that claim. I see no reason to think that it's true and also it's not the point. The point is, I don't think that the current electoral college is the best way of aggregating the will of the people into picking a winner, if it had been the case that we had a system where it was the popular vote that chose the President and Donald Trump's political team was just so smart, they would have won in that condition also, then good for them.

3:18:47.3 SC: I still think it would be the better thing. My goal here is not to change the rules so that Clinton wins the game. My goal here is to get the best political system to pick our representatives and the reason why we have the Electoral College in its current form are very antiquated reasons that just don't apply anymore, even if they were good to start, which probably they weren't. So I think there's more important things you can do to fix the political system than have the popular vote for the presidency, but I do think it would be one step forward.

3:19:19.6 SC: Igor Vellotage says, "What do you think about David Deutsch criticism of Bayesianism as a philosophy of science or epistemology? With some examples like that, when an experiment refutes a highly believed theory, you don't know if the credence for the theory or for the quality of an experiment should go down, or the conjunction T1 and T2 are two mutually inconsistent explanatory theories, T1 and T2, such as quantum theory and relativity is provably false, and therefore has zero probability, yet it embodies some understanding of the world and is definitely better than nothing, as opposed to that what he thinks, that what scientists, science really seeks to maximise is explanatory power, and that although all our best theories of fundamental physics are going to be superseded eventually and therefore we believe their negations, it is still those false theories, not their true negations that constitute all of our deepest knowledge of physics."

3:20:11.1 SC: So I'm not an expert on Deustch's criticisms of Bayesianism, so whatever I say here should not be taken as a refutation of David Deutsch, 'cause I'm reading Igor's question, not David's statements about these things, but I can explain to you how a good bayesian would deal with the situations which you mentioned, which are perfectly legitimate situations to worry about. So there's two different examples here. One is, experiment refutes a highly believed theory, so let's make it specific. Someone claims they have measured the travel velocity of some neutrinos and they go faster than the speed of light, okay. So you have an experimental result, neutrinos going faster than light, and you have a highly believed theory, special relativity, and the idea and the standard model that neutrinos do not go faster than the speed of light. So what you say is, you don't know if credence for the theory or for the quality of an experiment should go down. Well, I think it's both. I think you just take these seriously with all of the different possibilities on the table.

3:21:15.4 SC: It's not that we have to look at them separately. They're coupled to each other in interesting ways. So we have the credence that the theory is wrong, we have the credence that the experiment is wrong, we have the credence that both of them are wrong or that we're missing something entirely, and we're allowed to take all of our information and our other priors into consideration. If the prior for our theory is really, really good and our prior that these experimenters could have made a mistake is non-trivially large, then the credence that we have in our theory is not going to change very much on the basis of that experiment. You just run through the math, you just run through the equations, and you find in that situation that you end up believing it's probably true that the experiment was a mistake, and then you can go up and get more data with more experiments, as you always do in science. So I don't see this as any kind of critique of Bayesianism at all.

3:22:11.3 SC: The other example, when you have two mutually inconsistent explanatory theories, like quantum theory and relativity, and I imagine what you mean is general relativity, Einstein's theory of gravity. So the point is, you know that these theories both can't be right and therefore have zero probability, but they do embody some understanding of the world. I think that's just missing what the theories are. I think that theories have domains of applicability. Neither quantum mechanics as we currently understand it, nor general relativity, especially general relativity, are purported to be true in every domain. Quantum mechanics might be and it has a chance of being, at least, but general relativity, certainly not. So, when you say general relativity is true, I would agree that it captures something true about nature in a certain limit, and quantum mechanics also captures something true about nature. They can't both be extended to fully comprehensive theories of nature at the same time. That I agree with, but who cares? No one ever thought they should be. General relativity is a classical theory, there's no more claim that it needs to be extended to every domain of explanation any more than any other classical theory. It's supposed to be true in the classical limit.

3:23:28.3 SC: So there's no problem for a good bayesian in saying both the general relativity does a really good job of fitting the data in its domain of applicability and the quantum mechanics does a really good job of fitting the experiments in its domain of applicability, so there I don't even know what the worry is supposed to be, honestly. It's just, once again, I think that not really thinking carefully enough about what you think the labels T1 and T2 are really supposed to refer to. Rue Phillips says... This is the last question, we're ending up for the day, thanks for your indulgence here once again... Rue says, "How do you navigate interactions with professional colleagues that strongly disagree with the science you focus on? For example, Sabine Hossenfelder is someone you respect as a physicist, and yet she calls people that do many-worlds science confused. Do you avoid interacting with credible professional scientists that can be somewhat hostile toward people like you and string theorists or do you just avoid the topic when you chat or something else? I'm curious about the interpersonal dynamics here." Well, I think it is a very good question. That is why I picked it for the last question here.

3:24:37.5 SC: I think that there could be better understanding of how scientists or academics, more generally, doesn't need to be scientists, interact with each other, because two things are simultaneously true. One is, there are plenty of academics who are just jerks, who are just bad people, and it's unpleasant to interact with them. I'm not... This is not Sabine I'm talking about, but there exists out there in the world of academia, people who are unpleasant. Again, not very surprising. Academics are people just like everybody else, and so you deal with them the same way you deal with other people, you just try to avoid them the best you can.

3:25:14.3 SC: I'm someone who believes, probably more stronger than average, that obnoxious people are not worth having around even if they're brilliant. Like, if you say you're trying to hire someone as a post-doc or faculty member or whatever, and you say, "Well, they're a really terrible person and I don't wanna talk with them, but they're really brilliant and do good work," I don't wanna work with that person, I don't wanna hire that person. There are other brilliant people there who are not unpleasant to talk to, so I would like to hire those people and hang out with them. But the more interesting question is, what about people who are not obnoxious or not intrinsically obnoxious? We can all be obnoxious sometimes, that's why I'm hesitating, there's no such thing as a completely non-obnoxious person, maybe there is, but most people have moments for and against, but what I'm thinking of is people who are basically good people and easy to talk to, but who strongly disagree with you about something. That's the interesting case to interact with, and I think... I would like to understand this better, even though I've been immersed in it for decades, for much of my life.

3:26:19.2 SC: I think academics do pretty well at being friends and interacting and yet disagreeing really strongly about things. It's kind of a weird thing. You can get out of control, and that's why I'm talking slowly and hesitating here, 'cause I can think of examples where people have taken the paradigm too far, but roughly speaking, I have seen people including... And I could be on one side of this interaction myself, I can see people in seminars or in discussions over coffee saying like, "Oh my God, you're completely insane. You completely lost the plot. That is an idiotic thing to say, like How dare you... Like What happened to you? You used to be smarter than that." Right?

3:27:04.0 SC: And at the end then you go out and have fun at dinner, or have a beer or whatever... Right, because it's about the material, it's about the subject matter, it's not a personal attack. It could become personal, and this is what I'm sort of getting at, that it can slip into overly personal attacks and that's bad. There are absolutely examples where two people who used to be friends have come to disagree about something scientific and the friendship has deteriorated because of that, and that's too bad. So I want to acknowledge two things simultaneously, one is that scientists are people and that they can get out of control, both in being a little thoughtless and in reacting against that thoughtless-ness, and there is a possibility that is often a reality of strong, strong disagreements that do not become personal or unfriendly, and so that should happen more often than it does, but it does happen.

3:28:02.1 SC: Some of my best friends, I think, are just completely crazy pants when it comes to certain of their scientific beliefs, and we joke about it like they'll say like, "Oh yeah, you know, I'm a Bohmian" and I say, "Oh my goodness. Look, I didn't know. You've kept that dirty laundry hidden for so long, how could you do that? How could you say this to me?" But it's a joke 'cause it's not personal, it doesn't insult me.

3:28:24.1 SC: We don't know the final answers to a lot of these questions, Like Carlo Rovelli, who is a friend of mine, has on more than one occasion, in more than one context said like, "How can you be so smart and yet believe the string theory is still reasonable?" or, "Pretty good for a string theorist", kind of thing. And by the way, I'm not a string theorist. I just think that it is, for good reason, the most promising route to quantum gravity we have on the table right now. But anyway, these are things that I think are just part of being a good academic. It's a part of being a good intellectual, a good scholar, separating out your opinions, your credences on questions of substance from your personal opinions about other people and their opinions, and part of it is you can't help but know people who you respect otherwise, who have some crazy ideas in their heads, that's just how life is, so anyway.

3:29:17.8 SC: I don't know, whether that's a very helpful answer to the question, but I think that there are both things going on, people are getting a little too touchy, a little too personal, attack-y sometimes, but a pretty remarkable ability to have cordial, respectful relations without getting that personal sometimes. I think that's crucial to being an academic, and I think that more people outside of academia should develop that capacity. Anyway, thanks for listening. Thanks for supporting Mindscape, and thanks for listening to another AMA. Great gratitude always goes out from me to all of you who support Mindscape by being patrons, and any of you who listen to it for any reason whatsoever, I hope that it gives you something to think about and maybe sparks an idea here or there. Bye-bye.

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