AMA | December 2022

AMA December 2022

Roo Phillips
You, Colin Wright, and Jerry Coyne commented on a Twitter thread regarding the spectrum of sex. You appear to come down on the side that science says sex is a spectrum (not talking about gender here). Coyne and Wright claim that science says sex is binary with abnormalities. They seem to feel that this distinction is more than just semantics. Coyne says, "if sex is a spectrum and not binary, then people of different genders can somehow feel that they are in harmony with biological reality. But that’s an example of the 'appeal to nature.' The rights of people of different genders, including transsexual people, do not depend on the developmental biology of sex, or of any observations in nature about sex dichotomies." With this context, can you please elaborate on your views of how you think we should be talking about biological sex in public forums?

Henry Jacobs
The Margeret Levy interview was dope! In the previous AMA i pitched lottery voting as an alternative election system. I'd sum up your critique as "I get it... but we can't elect nazi's %3 of the time." Agreed. Here is a modified version I'll call "diet lottery voting":
Sample 100 citizens and have them vote in a plurality election. Use carrots and sticks to ensure that the sampled citizens cast a vote. Sadly, this system is non-proportionate, but the the fringes are regularized.
I think a diet lottery system could improve the tone of politics because it would be a waste of time for a candidate to rally her base and "get out the vote" under this system. This is because the voting population (the random sample) will exhibit %100 voter-turnout, and so "getting out the vote" is just not a thing. Instead the candidate should spend time talking to open minded non-partisans. Anyway, that's the theory. Is it convincing?

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Ulf Hlobil
What does it mean to be a naturalist?

Leo Behe
Although I call myself a naturalist for practical purposes, I'm unsure how we could even define something outside of the natural world. If we were to discover some other "stuff" that behaved very differently from our current understanding of how the world behaves, there would still have to be some way in which that stuff would interact with everyday things like protons, electrons, etc. To whatever extent this other stuff interacted with everyday matter, we would simply model those interactions as best we could with experiment and theory. Given that, do you think that it would even be possible in principle to discover anything that wouldn't fall under the category of natural?
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Paul Hess
If a particle has a 50/50 chance of being spin left or spin right, and then I measure it to be spin left, does that change its overall momentum? Is there any sort of conservation that is no longer true because of this?

Andrew K
I really enjoyed The Biggest Ideas In The Universe. I think you clearly covered the encoding of the curvature side of Einstein's equation but I'm still unsure about the stress-energy side, especially the off diagonal parts. How do we know it covers all possible forms of energy? Is there a good resource where I can learn more about it?

Kyle Stephens
In your recent podcast with Raphael Bousso, you seemed to object to his idea that the cosmological constant may not be constant as he believes it would lead to the Boltzmann Brain problem. Could you explain why you disagree with this (if you do disagree at all)?

Bruno Teixeira
Could we get an explanation of the hierarchy problem? I believe it has something to do with the predicted mass of the Higgs vs. the actual mass but, when We discovered it, did it match the prediction? Is there a naive prediction and a more informed/fine tuned prediction? Thanks

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Jay Peters
A deep tension within your views: you are open to the idea that time (and space) will turn out not to be aspects of the universe when described at the most fundamental level, yet you also claim to be a long time 76ers fan -- meaning that you Trust the Process, where a process is a series of events that unfold IN TIME. Perhaps you should jump onto the GSW dynasty train.

Keith
Do you have a second team that you root for? Afterall, GSW were originally the Philadelphia Warriors and had Wilt Chamberlain!
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Mike Briggs
PRIORITY QUESTION
THE SPHERICAL COW
I never assumed a spherical cow;
I hope to never do that.
But I can tell you here and now:
I'd rathe do than boo that.

With many thanks to Gelett Burgess
Surely this is not an original thought. But I haven't heard it on an AMA, so … let's go.

Paul Conti
I do realise that you don’t particularly like questions of the “Is it possible” variety.
However, do you think it likely - given the expansion of the Universe and the structure of the “Cosmic Web” - there may be entire galaxies or clusters of galaxies, that are made exclusively of Anti-matter ?

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Rad Antonov
What was the question Bousso was begging at the 1:09 mark that you left for an in person discussion?

Sid Huff
I enjoyed your recent podcast with Raphael Bousso. I gathered that you and he disagree on certain aspects of QM, among other things. At one point you commented that you would “table that discussion” for a later time. Could you highlight for us the two or three issues that you and he hold substantially different views on, and why you think that is.

Mickle Pickle
In the episode with Raphael Bousso you pressed a bit to get an answer to your question regarding whether we are more likely to live in a 3+1 dimensional world or a lower dimensional world. The basis for the question seemed to be that there are differences in the way one or the other reality would appear to us. I have thought that the equivalence of the two models means that they would appear the same to us--that if we were beings living in ADS or CFT the appearance of the world around us would be the same. Am I looking at that the wrong way?
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Murray Dunn
Is there anything than can absorb, reflect, or refract gravitational waves, or do they propagate undisturbed until end of time?

Igor Vilotic
When you discussed earlier the Boltzmann Brain problem, you mentioned the issue of the random fluctuation of the laws of logic and reasoning.
Given that you are not a Boltzmann Brain, how would you generally justify the use of logic, the way you use it? Could you do it without using some kind of "logic"?

Nate Waddoups
Do you think that wider adoption of ranked-choice voting, or approval voting, could mitigate the polarization that plagues politics and discourse in the United States these days?

Gregory Kusnick
Mobsters and tyrants know that the most effective deterrent is to punish the families of miscreants, but civilized folks of all ethical persuasions reject that option, which suggests that some notion of desert is still in play even for free-will skeptics. Attempts to frame this rejection as consequentialism -- it would be bad to live in a society that embraced punishment of the innocent -- seem like question-begging: it's our intuitions about desert that make it seem bad. What's your take on this conundrum?

Richard King
This is a priority question: Is it true that all life forms are survival driven converters and responders of varying complexity? Hint, the answer is yes.

Sam Hartzog
In your opinion, what role should government play in regulating "illicit drugs", "controlled substances", and "dietary supplements" in general? Is it possible, even in principle, to ground drug prohibitions / scheduling decisions on objective research given the nature of the questions involved?

Tarun
David Hume challenged the primacy of pure logical thinking when he said that “reason is, and ought only to be the slave of the passions”. To what extent do you agree with this view?

Bart Connelly
ONCE PER LIFETIME QUESTION!! As i enjoyed your podcast with Alan Lightman, i am wondering if you have any further thoughts on
how conscious beings can best persue "spiritual" interests in the material world.
Should we just regard them as something to outgrow or perhaps should we find ways using disciplines like meditation AND technology (everything from mediation devices to
neural engineering etc) to persue this goal much as we use science and technology to help with physical health?

David Maxwell
Your breadth of interests makes me tune in but it's your ability to simply communicate complex ideas across a range of topics that makes you unique to me. An interviewee can speak for ten minutes and you'll distil it in a way that crystallises my understanding and that your guests often want to borrow.
How do you do it? Do you think things through and come up with simple ways to understand? Do you ever pre-write your amazing reductive statements? Or is it just the way you think, perhaps a product of your fields (physics particularly, with a mind to complexity)?

Jim Watson
Understanding that models generally have a domain of applicability for accuracy or at least efficient calculation, I am curious how useful our lowest level quantum models are for explaining things at level of chemistry or materials science. For example, can one start with electron wave equations or electromagnetic force calculations and derive how covalent bonding of shared electrons across atoms works, or that the carbon lattice would be super hard, or the stress vs. strain and elasticity (Young's modulus) of iron, etc, etc.

James M MacKrell
This is a priority question: I have read many articles and listened to many discusssions that lead me to wonder what is meant by "The Cosmos is a Hologram or.a computer program made by some master programmer. Please decipher, are those describing actual processes or is all of this talk an attempt to describe the Comos in understandable term.

Schleyer
I read and enjoyed The Biggest Ideas in the Universe, Vol. I, so thank you. I followed the math, laboriously, but one problem I have is that when dealing with formulas my mind goes into “symbol manipulation” mode, which I find can’t coexist with “understanding the significance” mode. Are you able to do the math while keeping the big picture in mind, or is it normal to kind of toggle back and forth?

benjamin cowger
priority question
I've personally always struggled with the general 2D diagram of gravity, the standard bowling ball on a trampoline image engrained in everyone's minds and in most schoolbooks and online. It seems most folks I've talked with think of gravity this way, as a ball on rubber sheet, and it's been tough to explain gravity as a force acting on and curving 3D space. If you layer in 4D spacetime and how gravity acts upon it, it gets even harder to explain in words.
Why is the "ball on a sheet" the standard "go-to" image in most all articles, books, documentaries, etc? These depictions have always felt very deceiving to me.

Seth Holoweiko
(pronounced hollow-WEEK-oh)
I know that you loved Knives Out. There's a semi-sequel out, and I just went to see it. What are your thoughts on movie franchises versus one-off, original movies? And if you've see the new Knives Out movie (Glass Onion), what did you think? Rian Johnson is so darn clever, and I wish that more directors were being so creative.

Phil Hamilton
If it turns out that a non-material essence ("god") created the universe from nothing, how would scientists be able to differentiate that from the universe having spontaneously appeared from nothing? It seems that evidence of these two possible origins of the universe would appear the same to scientists.

Nick C.
When you take a class in Physics, you might learn about Newtonian mechanics, electromagnetism, relatively, quantum mechanics, etc., but you generally don't read the original writing of Newton, Maxwell, Einstein, Heisenberg, and the like; you usually read modern texts. By contrast, when I took philosophy classes in college, we generally read the original historical works of great philosophers. Especially in light of your new academic position, I'd be curious to hear your thoughts on whether this distinction between the approaches of physics and philosophy is generally true, why it's true, and whether either discipline should emulate the approach of the other more.

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Redman
Has the FTX debacle affected your view of effective altruism?

Nick B
Can one person define/destroy a philosophical position?
Unfortunately for Will MacAskill, Effective Altruism has a new face: Sam Bankman-Fried. He has made it world famous. What had been presented as a logical and potent approach for doing the most good for the most people - now and in the future - is currently being criticized as “utilitarianism with a god complex” and “bunk”.
Does its rapid fall from grace demonstrate an inherently flawed perspective, or is Effective Altruism robust enough to withstand the collapse of FTX?
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P Walder
Can you explain the difference between relativistic and constructivist foundations for morality?

James Alan
In The Biggest Ideas, you talk a lot about the value of “Spherical Cow” thinking. Do you think the reason this kind of thinking is so effective historically and practically is a surprising feature of our universe? Or is it just a necessary feature of anything that could reasonably be called “laws of physics”?

Shubhendu Harsh
The current system of peer-reviewed papers to get to objective truth, is this the best/quickest way to establish scientific truths?

Sandro Stucki
Your discussion with Raphael Bousso made me think about what we actually mean by the area of the event horizon of a black hole and the volume inside it. After a bit of googling, I found claims that the volume of a black hole is, respectively, zero, infinity or "large and increasing towards the future". Which of these is right (if any) and why?

Paul Hardie
What are your 2 or 3 best arguments to discount all the claims that astrology makes. I want to use them on people who are immune to science and evidence.

Suraj Rajan
In EP 200 Solo on manyworlds, you allude to the manyworlds "literally come into being when you do an experiment; and they are not located anywhere, they just exist simultaneously". Assuming space is emergent, do these parallel universes that come into existence have their own emergent space, all self-contained in them? Is that aspect also a prerequisite for these "descendant" universes not influencing each other?

Mark Scheuern
I’m curious as to how classes are assigned to faculty at Hopkins and Cal Tech. As an adjunct, I just take whatever my institutions give me. I’m guessing you get more of a say and that your interests and preferences are taken into account, including letting you design your own courses.

Jimi
I recently learned that Hawking Radiation isn't actually virtual particle separation, but something more like spacetime abhorring horizons and the curvature gradients they create, and reducing its curvature (via Hawking Radiation) to rid itself of them. At least that was my understanding of it. Can you explain the real story of black hole evaporation, and why evaporation only occurs when horizons are involved? For example, if a planet existed forever, would it eventually evaporate as well to eliminate the curvature it causes?

Chris Murray
It occurred to me that if it's possible for there to be, in the future, a time machine configured to immediately travel back to the present, then there should be infinitely many such machines in the far future, a la Boltzmann brains. I thought the fact that our world is not densely packed with such time machines could be evidence that backward time machines are impossible.

Jonathan Byrd
Why would abiogenesis ever stop? Shouldn’t molecules still be coming together to form tiny living things somewhere on Earth? What are the chances that there were some initial conditions that no longer exist anywhere on earth?

joey
Has teaching philosophy changed the way you view physics?

Kevin James
For all of the people in NA and Europe who are not in favour of strong (or any) action on climate change, do you think they could be convinced by considering the massive number of migrants that WILL be created once the "big middle" of the world becomes less hospitable due to worsening weather events and less food security? After all, where else will they have to go?

Jordan Dansby
Multiple popular science media (Nova, Scientific American, etc) have asked their readers and viewers to debate whether math is “invented” or “discovered”. The answer seems obvious to me - it is a human invention to describe the world. Is this a real debate among professional philosophers of science or relegated to the mass consumption media?

Joshua Hillerup
Are there any (non-physics or otherwise related to your day job) topics that you find really interesting, but don't think you would interview someone about it on Mindscape?

Eliot Specht
Mindscape has had many interesting episodes on subjects which are right in your core area of expertise, like cosmology, along with equally interesting episodes in far-off subjects like history and biology. Then there's a gap: few episodes have discussed areas of physics which aren't your specialty, like condensed matter or plasma. Is this because these fields are less interesting or because they are better covered by other podcasts?

Colleen Edwards
I’m new here, but have been fan of your writing and work for a while. Your book, “The Big Picture”, was eloquently positive and personally influential! You mentioned at the end of the book that you used to go to church as a child and you also went to Villanova U which I know is a religious university. I’m curious how your own family and loved ones responded to you going from a “believer” to an atheist and if you have any advice to help those of us who are going through that now?

Jeffrey Segall
The talk with Raphael Bousso was very interesting. I had not appreciated that even though black holes have incredibly high entropy, the fact that they evaporate implies that photons in empty space have even higher entropy. Is that correct? Do we have to go through black holes to get to the highest entropy state or could the universe have gone from big bang directly to photons in space? Actually, is photons in empty space even the highest possible entropy state of the universe, or could the development of new universes increase it even more?

Andrea Sperini
Priority question: could you explain why an airborne aircraft doesn’t loose the rotational velocity it had when in contact with the ground? I understand the atmosphere is still rotating with the Earth but somehow that doesn’t sound fully convincing.

Richard
In the last year or so what books did you read for the podcast that you would not have ordinarily been interested in reading? Were there any that particularly surprised you by being more interesting than you thought they’d be?

PSYBACK
I had the heartbreaking experience of falling in love with one of my closest friends who does not share the sentiment. Assuming 'many worlds' is correct, do you think there could be a real 'world' out there where she and I are living happily ever after together?

john wellborn
When it comes to studying science (including physics and space), is there an end-game you can imagine that makes this pursuit worth the time/money/energy spent? Or do you not look at it in those terms? I understand that we may discover things along the way that can help us here on Earth. But is there a purpose beyond that? If so, what is it? Why should we pursue anything more in life than making sure the people on earth are safe, healthy and happy?

Jim Murphy
I'm curious what it's like to be a public personality as well as a professor. Do you have any star struck students? Do other professors treat you differently?

Teo C Alexander
Let’s assume panpsychism or panexperientialism is the case. And for the sake of argument, let’s also assume that it is an emergent phenomenon but at a very fundamental level - not as fundamental as an electron or a proton, but still quite small and ubiquitous. Wouldn’t that then necessitate the constant collapsing of wave functions at every point where the consciousness “particles” exist? Follow up: Could that be one possible explanation for why all of us macroscopic humans more or less experience the same Universe?

bitsplusatoms
When I came across a passage about conservation of information while reading "The Biggest Ideas", I wondered what symmetry is associated with this conserved quantity. I understand Noether's theory to be: "For each symmetry of the Lagrangian, there is a conserved quantity". Does information fit into this framework?

Michael Ehling
To explain the uniformity of the CMB, has anyone proposed an alternative to thermal equilibrium? Could some other physical process have led to it all being the same temperature in an expanding universe without the need for inflation?

Ed
In the Futurama episode "Crimes of the Hot" (S5E1), the problem of global warming is solved by moving the earth farther from the sun. Leaving aside the engineering challenges of such a course (the method proposed in the episode is not practical), do you have an opinion or comment on the longer term possibility of controlling the earths temperature by adjusting the earth's orbit? As a bonus question, do you think it would be easier to physically move the entire earth, or to "fix" global capitalism such that carbon emissions can be reduced quickly?

Benjamin Barbrel
Priority question:
Do all the branches of the many worlds' multiverse look like our own familiar universe (homogeneous at large scales, clustered galaxies, gas clouds, stars, planets etc...), or would some of them appear somewhat exotic to our eyes?
Is our branch typical, if that means anything?

Danny Avidan
1d
Would you mind sharing your thoughts about morality and meat eating? I don’t mean it antagonistically - it’s just that as a public intellectual and a figure of high moral and intellectual standing - I wanted to hear your thoughts on the matter, especially given your love of cats.
Of course we all fall short of our moral aspirations, and contain contradictions - but how does a cow or pig fall short of the confines of your circle of empathy if a similar mammal doesn’t?

Justin Wolcott
In the Big Picture, you say:
>> We can’t pick out one moment, or a particular aspect of any one moment, and identify it as “the cause.” Different moments in time in the history of the universe follow each other, according to some pattern, but no one moment causes any other.
I'm trying to understand why its illegal to say "The Cat caused the ball to fall on the floor" but legal to say "The ball is on the floor because the prior state of the universe, plus the laws of physics".
Is there any way to restate this in a way that involves a cat?

Felix Dare
PRIORITY QUESTION
Since reading your book I am left with the inescapable idea that for each decision I take there is another universe, identical to this one up until that point, but in which I took the other decision. My understanding, if the multiverse theory is correct, is that this is happening constantly, driven by ongoing quantum-level events in my brain such that there is a different universe with a different version of me for every possible decision that I could ever have taken. I am struggling to reconcile this with any meaningful sense of agency or free will, so would be grateful for any explanation as to what I have got wrong?

Tim Gianitsos
You mentioned in another podcast that there is a theorem which seems to indicate that if the hidden variable interpretation of quantum mechanics is true, then any prediction it comes up with will always be the same as the many worlds interpretation. However, you were skeptical that this implication of the theorem was true. Have you found a resolution to this since making that statement?

Owe
I've recently been reading 'General Relativity for Babies' to my 16 month old son. I don't think he gets it, but maybe in time. One of pages talks about how a spinning mass 'drags' space with it, similar to how rest mass warps space time. I believe that an object spinning in space will continue to spin indefinitely absent an external force, due to angular momentum being conserved. Yet changes to spacetime require energy to create. How can a spinning mass 'drag' spacetime without expending energy to do so?

David Dubrow
Is the concept of (weak) emergence related to entropy in this way or am I missing something. Both seem to be a way to measuring our lack of complete information about the structure and dynamics of entities at lower levels when observed from higher levels. Entropy seems to be measuring our inability to detect the difference in micro states when observed from a macro point of view. Emergence seems to be a way of characterizing the exact same thing as far as I’m seeing. Namely, that there are larger patterns composed of lower level entities and we don’t need to know the exact happenings at the lower levels to see the patterns at the higher levels.

Douglas De Young
Is the concept of true randomness sensical? It seems like something from nothing, or information from nowhere. I appreciate that “many worlds” avoids the random outcomes of measurement by positing a larger deterministic possibility space.

Kevin O'Toole
3d
In the October AMA, you said there was “No experiment you can do” to prove the past hypothesis. However, it seems any universe where the laws of thermodynamics are true and the past hypothesis is false should makes some very strong, very falsifiable predictions! The theory in that universe would say with that, with overwhelming probability, our experiences are explained by a *small* world fluctuating from equilibrium, and by illusory stuff outside that world, just enough to make us think the universe is bigger and explain what we’ve observed so far.

Brent Meeker
You've written a paper with Jackie Lodman about violation of conservation laws in quantum measurements. You said that energy was only conserved on average but not in a single measurement. If I understood it correctly it would also apply to the measurement of any conserved quantity...not just energy. Does this provide any test of MWI vs. say QBism or the Transactional interpretation? Do all interpretations of QM imply non-conservation in measurements?

Qubit
Liouville's theorem tells us, that for a classical (hamiltonian) system the phase space volume stays constant. How is that possible for a chaotic system where neighbouring trajectories move away from each other exponentially?

Moshe Feder
With the World Cup in progress, I'm curious how you, as a fan of basketball, a game with lots of scoring, feel about soccer, a game with very little scoring. Personally, I think soccer is a very poorly-designed sport that is only so globally popular because it’s much more fun to play than it is to watch. Do you agree that soccer could be improved to be more entertaining and if so, what changes would you suggest?

Shambles
Do you get any sense that life, as in the origin of life, is/was inevitable?

Stewart Hayne
I have a question about the CMB. When I think of a supernova, I think of a flash of light being emitted and then travelling past us. If we are not looking, we may not see it. However, the CMB appears to be ever-present even though it originated from the surface of last scattering. Is that because the CMB effused all of space and was moving in all directions and therefore it will be ever-present?

Rob Patro
The recent "drama" surrounding Twitter has renewed the debate over the optimal bounds on speech in online platforms.
As someone who seems deeply dedicated to debate and free speech, but also cognizant of the shortcomings of absolutism and aware of the importance of practical solutions, I'm curious about your thoughts on this topic. How do you think that we, as a society, should balance the necessity of open and free debate with the dangers posed by speech that incites violence and constitutes harassment, particularly in the context of private platforms like Twitter that start to border the space of a "public utility"?

Bert Rich
When it comes to the "great filter", scenarios like climate change, wars and pandemics are being discussed. But my personal candidate is missing: a failed physics experiment, maybe always the same one. For example: some new particle being created that results in a cascading, all planetary matter pulverizing effect. As an insider, is this completely out of question or something that keeps you up at night?
Most other scenarios are in my opinion too slow and not devastating enough. I'm confident that we could fix or survive as a technological species just about all of them.

Kevadin
The political climate in the U.S. has grown increasingly tense and partisan in recent years with several unpresented events occurring (i.e. overturning of roe v wade, Jan 6th riots, etc). What is it about our current time that is causing such a tense political climate? And, do you see any positive way out of this and into a more "normal" political climate.

Anders Hektor
Is it possible to calculate the contribution to entropy of a human life? And how would a welder and a cleaner fare in comparison to e.g. Albert Einstein, or an ant, or a tree? Who contribute more to reducing entropy and what can I do to reduce the liability-side of my net-footprint on entropy?

Paul Duffield
When are infinities bugs, and when are they features? Sometimes physicists treat them as an indicator that the maths behind a theory no longer applies to reality in some way, and sometimes they're treated as a possible outcome (eg infinite dimensional Hilbert Space). Is there a consistent difference here, are these different types of infinity, or is it more of a case-by-case thing?

Cooper
I'm going to be a father next year, and it has had me thinking about my moral responsibility to my children compared to my community and country. We're moving to a nicer house in a better school district, which I'm very aware is a privilege that many other children in this country don't have. How do you think about your moral responsibility to those close to you compared to the broader world? I don't want to further contribute to inequality, but at the same time I want to give my children the best life I have the power to give.

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0:00:00.5 Sean Carroll: Hello everyone, welcome to the December 2022 Ask Me Anything edition of the Mindscape Podcast. I'm your host Sean Carroll. I wanted to start off, I can't believe it's December, this has been a long year for me, I'm sure for you as well. Had a book out, changed jobs, moved across the country, even the move is not completely done yet. We haven't actually moved into our official house. That's coming in a couple weeks. So things are been very hectic anyway all this year. It's been a very good year for Mindscape. I wanted to just share one very heartwarming story. If you remember a year ago, last December, we had Joshua Green from Harvard on the podcast, who is a psychologist and philosopher, moral psychologist, thinks about how deontology and consequentialism play out literally in the brain. But he also is one of the brains behind Giving Multiplier, which is a way to leverage two different facts. One fact is that certain charities are more effective than others in changing lives and saving lives and making people healthy. And the other fact is that we have certain emotional connections to certain charities. The local cat shelter is going to be an important one to me.

0:01:12.6 SC: So Giving Multiplier makes it possible to do both. You can give money and you can give some to your favorite local specific charities, and they will also spread some love to high impact charities that spend money on whatever the data says is the most effective way to do it. So Giving Multiplier, when Josh came on the show, had a special deal for Mindscape listeners, you can go, still true, by the way, you can go to https: //givingmultiplier.org/invite/mindscape, and you can donate and they will extra match. So there's a little bit of extra oomph to your donations. And this was a year ago and wait for it. We got $165,000 in donations from Mindscape listeners to Giving Multiplier. And Josh sent me the list of places that have been benefiting from this, clean air task force, Johns Hopkins Center for Health Security, nothing to do with the fact that I'm at Johns Hopkins, they're just health security is important thing anyway, Helen Keller International, etc. So Mindscape listeners have provided enough for over 5000 deworming treatments, over 3500 vitamin A supplements, 400 malaria nets, a whole bunch of other things. So it warms my heart that the Mindscape listeners have been that great.

0:02:34.2 SC: Also, of course, in parallel, we have the Mindscape Big Picture Scholarship at bold.org, which we're going to be giving out college scholarships this year to people studying these big questions. And it makes me feel good that we're doing something good. When I started this podcast, four years ago now, it was an experiment, didn't know whether I was going to keep doing it didn't know whether anyone would come on things that, didn't know whether we could build an audience. But it's been great. And I'm just super duper thankful and appreciative to all of the people out there who listen. Some of you contribute on Patreon. That's something you can do, you can go to patreon.com. Wait, is it patreon.org? I should know, I should be better at this, right?

0:03:19.1 SC: It's patreon.com/sean/carroll. And if you contribute there, you can ask questions at the monthly Ask Me Anything episodes like this one we have right now. But that's a tiny fraction of the total listenership. That's fine. I'm very, very happy just to people listen to it at all. Talk about the ideas. I've been super happy with the quality and the diversity and the amazing inspiration we get from the guests. The people have been very, very generous with their time. And it's completely 100% fulfilled my hopes of helping me learn about things that I just didn't seem to have time to learn about just by reading books and things like that. So now I force myself to read the books when the guests come on. So Mindscape listeners have been great, and I appreciate them very much. And it's been a good year, been a good four years.

0:04:16.2 SC: So let me remind you again, if you're on Patreon, you can ask questions. I'll apologize once again. I know I always do this, but I didn't get to do nearly all the questions. There were just so many questions. It's kind of charming. People are asking very technical questions in areas of physics that are not my area. And I'm warmed to think that you think I can answer those questions, but I can't. I have specific knowledge within physics, but there's other things I don't really know a lot about. So if I don't answer your question about that, sorry about that. And the final reminder is that at every year I take a week or two off over Christmas over the holidays. So there will not be any episode, nearest to Christmas, and there will be no Ask Me Anything episode in early January, right? So the next Ask Me Anything episode is going to be in early February. We do 11 of these every year. And so this is one of them. And with that, let's go.

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0:05:29.3 SC: Our first question is from Rue Phillips, who says, you, Colin Wright, and Jerry Coyne commented on a Twitter thread regarding the spectrum of sex. You appear to come down to the side that says science says sex is a spectrum, not talking about gender here. Coyne and Wright claim that science says sex is binary with abnormalities. They seem to feel this distinction is more than just semantics. Coyne says, "If sex is a spectrum and not binary, then people of different genders can somehow feel that they are in harmony with biological reality." But that's an example of the appeal to nature.

0:06:00.0 SC: The rights of people of different genders, including transsexual people, do not depend on the developmental biology of sex or of any observations in nature about sex dichotomies. With this context, can you please elaborate on your views of how you think we should be talking about biological sex in public forums? Yes, I figure I will get this one out of the way right away. For those of you who saw on Twitter a while back, there was a tweet by Colin Wright that just said, "Biological sex is real, immutable and binary." And I replied with or quote tweeted rather with a link to a Scientific American article. And I said, "Actual science would a word." And the Scientific American article was beyond XX and XY. And it was about all the different ways that biological sex is complicated. And the first thing is, the actual tweet that I wrote, the wording of it was terrible.

0:06:50.9 SC: And I do apologize for that actual science would like a word. It's snarky, it's dismissive, it lowers the tone of the debate. And I try to do better. I want to do better. This is sincerely true that I don't think that people should just be so glib and snarky and sarcastic on social media. But there's an enormous push to do that. And I am not immune to that. So I should have just said something like it's more complicated than that. But okay, the actual substance of what I'm saying, I think is 100% correct. So I thought I would take the opportunity to elaborate here because Twitter is a terrible medium for elaborating on subtle arguments at all. By the way, I waited into this an offhand moment and lots of people chimed in and not very productive ways, right? It's like opening the sewage spigot when you start writing about these things. There's lots of comments, not from my followers, but various dark corners of the internet found this and linked to it. So you got a lot of comments that you really don't want to spend a lot of time reading.

0:08:01.1 SC: And these people are very devoted to it, right? It's not just the comments on that tweet, but then they leave comments on other tweets calling me brain damaged and insane and things like that and worse kinds of insults. And then they look for me on other social media. So my Facebook page or my Instagram or whatever, I just get comments with the same kinds of insults. It's not my style. I'm not really into this name calling invective combat. But there you go. I entered into it. My feeling is that here on mindscape, there are many listeners who would be interested in my thought process, whichever side you are on, right? And I think that there's valuable, reasonable arguments on both sides. And maybe you've already made up your mind. But you're interested in why I think what I think, therefore, I'm going to talk about it.

0:08:52.4 SC: The idea is the following. Human sexuality is complicated. It just is complicated. Of course, we all know from high school biology that there are chromosomes, x, x, or x, y, in general, for what we typically identify as women and men. But there's other combinations, there can be different sort of people can be x, x, y, and things like that. And then it's not just your genes, there's development, there's hormones, there's the final product, there's the primary sexual characteristics, there's the secondary sexual characteristics, there are characteristics of people that are weakly but nevertheless definitely correlated with biological sex, like how tall you are, or the depth of your voice or things like that.

0:09:37.0 SC: And of course, inevitably, there are psychological, sociological, cultural, political aspects of sex, who you think of yourself as, how you are treated by other people, what bathrooms you can use, what rights you have, how you dress, there's a million different aspects to sexuality that are all complex and absolutely there. There are intersex people who are even biologically, physiologically, rather, not completely, clearly male or female in the traditional sense. The second podcast I ever did, or maybe third podcast I ever did was with Alice Drager, who talks all about this. And so you can go back to that podcast to hear some of the science there.

0:10:21.3 SC: And okay, so I think that basically, every reasonable person recognizes those complications. The question is how to talk about those complications. So I think that there are issues here that are not purely semantic, but there are absolutely semantic issues here. There are biological issues here, but there are absolutely also philosophical issues and language issues here. There's the facts that science tells us is what happens in the world, but then how we conceptualize them, how we divide them up, how we label them, how we talk about them is a more complicated question. So just like in a very different context, the question of free speech, the thing that I will not back off on is the point of view that says this is complicated. If you think it's simple, you're just not paying attention, or you have some other agenda. Of course, many people do have another agenda one way or the other.

0:11:15.6 SC: So in the face of this complication, why would you think that sex is binary and clearly immutably binary? Well, it's not completely surprising or out of the blue, right? To a good approximation, most people, many people, human beings are pretty regularly easily classified as male or female, into one of those two categories. That there are other possibilities that are complicating the picture, but approximately that they exist. So as a scientist, as a biologist, you might say, well, is there something clear and biologically definite that maps on to this informal, casual human scale association of people as either male or female? So you can look into it and you can do the science. And the answer is to some extent, yes, there are aspects of biology that really are binary.

0:12:12.6 SC: Okay. And the one that is most often people disagree about what they want to say, but the one that is most often brought up is the size of your gametes, your gametes, the sexual cells, the reproductive cells, I should say, sperm and ova, roughly speaking, right? So there is more or less a binary where some human beings produce ova, big sessile gametes, some human beings produce sperm, tiny mobile motile gametes, and that's more or less a binary. There's not a lot of in between in that. And therefore, as a biologist, you can say, "Okay, that's what I mean when I say biological sex, I mean that." And that's 100% fine as a term of art in biology, you're very welcome to do that. You've learned something very, very good. It does make for a weird dating profile. If you say, 5 feet 10 inches, 28 years old, sandy blonde hair, small motile gametes. Nobody ever says that, right? Why not? What is the point of me bringing this up?

0:13:20.4 SC: Well, somehow, for hundreds and thousands of years, human beings have been able to have this concept of human sexuality without knowing anything about the size of their gametes. The reason why is because, of course, there is not a unique one-to-one map between the size of your gametes and the other aspects of human sexuality. And it's a complicated picture. That's why we have intersex people and transgender people and all these things. It doesn't begin and end with the statement about the size of your gametes. So if you want, if you want to use that terminology, that's fine. You can go ahead and do that speaking as a biologist, speaking as someone who is just talking about certain biological aspects of human beings. But then you could choose to be clear if really what you mean is that and then you want to put up a tweet. You could just choose to be honest and straightforward and say human beings either have large sessile gametes or small mobile gametes. And guess what? No one would argue with you. It would not be a thing.

0:14:33.2 SC: The reason why people go on and translate that into biological sex is real, immutable and binary in a way that doesn't make clear that they are referring to this term of art within the context of biology is precisely because they want to claim more than that. Because I agree with Jerry Coyne very, very much that the... I agree with the contra positive of what he is saying. I don't know whether it's true that people of different genders want to feel their harmony with biological reality or not that I don't judge one way or the other. But the claim that the rights of people of different genders, including transsexual people, do not depend on the developmental biology of sex that I agree with.

0:15:18.6 SC: So why would people be on the internet, shouting about sex being a binary? Why would people get invited on the Tucker Carlson show to talk about the size of gametes? It's not because Tucker Carlson has an especially important, strong interest in biology one way or the other. It is precisely because they want to cheat. They want to equivocate between the biological definition and the human scale definitions. They want to use the language and deploy it in such a way that you can say, sex is only binary. Therefore, we should not believe that trans women are women, for example.

0:16:01.0 SC: Personally, I think that I'm less invested in these language battles than a lot of people are, I'm invested in them as an intellectual, as a philosopher and scientist, I'm interested in how the language works and trying to get it right. But on the political level, I'm less convinced that this is a crucially important thing. And this is a both sides thing. There are people who want to argue sex is only binary. And the reason why they want that linguistic move to be reified is so they can say, therefore, you should not be allowed in this bathroom, right? They want to make that leap, which is, at the level of philosophy or science, whatever, completely wrong, but they want to be able to make that, they think that if they can just get the language right, then the moral and cultural implications will follow. And on the other side, you have people who say trans women are women.

0:16:55.6 SC: And I think that's true, I would agree with that statement. But I'm not that invested in it. Because I think that the reason why people care about a motto like that so much is they think, if we can just get that language accepted, then trans women's rights will be respected. And I just don't think that that's necessarily true. I think that the people who want to discriminate against transgender people will do so regardless of what the language says, they would be very, very happy to accept a compromise that says, okay, trans women are women, and we're going to discriminate against that subset of women, they would take that compromise. And likewise, I think that people who want to protect the rights of trans women would be... If I were them, I would say, and I am one of them, but I'm one of the people who want to protect the rights, not one of the people who is actually trans. So I don't want to speak for them. But I'd be happy to give up on the language if I got the rights. That's my personal take on it.

0:17:50.5 SC: So I do think that that's what needs to be resisted here. If you wanted to just say, we have a term of art in biology that reflects a true binary in the size of gametes, that's fine, go ahead, say that. But it is very, very intentional that people have other agendas here other than just getting the biology right. And I think that speaking out against those agendas, calling out the move that is being made there is perfectly appropriate. But it's not the only strategy going on here. There's another strategy, which is to say, okay, there are two basically normal kinds of people, right? There are people who are men and people who are women, and the other people have a disease, or a deformity or some deviation from the norm. And so we're not going to count that, it remains even though there are intersex people and trans people, etc, that's because those people are deformed somehow. And it remains true that really, the essence of things is that there are either just men or women.

0:18:55.6 SC: That's a an old, not very valorous move to make in human history where you say, well, some people are normal, and other people are deviant. And we're going to define that deviance as a disorder. This has been done to people who are black, this has been done to people who are gay, this has been done to people who are left handed. It's a standard human move to say that people who I think are icky and not normal, are somehow deformed and diseased. And this is why you see in the medical literature, the definition of what is a disease or a deformity or whatever changes over time as we try to get over our biases and actually get down to the medical reality of it all. And you don't want to throw away the idea of disease and deformity entirely, those exists. Those are useful concepts out there in the world. But I certainly don't think that it's right to just put everyone who is not absolutely traditionally male or female in the stereotypical way into that bucket.

0:20:00.0 SC: One thing you can do is ask them, ask these people whether they think that they're suffering from some deformity. And I think in a lot of cases, they think that they're fine. There is something called gender dysphoria, right? That is a disease, that is a condition that it is better to try to get over where you think that your self image is different from your presentation, your body in some way, right? A mismatch between biological sex and gender identity. But that doesn't mean that transgender ism is a disease, recognizing that you are trans is the solution to gender dysphoria. And people are generally much happier when they can live in a world which accepts their trans identity.

0:20:53.0 SC: And so I think that we should be working hard to make that the world we actually live in. So I'm not at all convinced by people who want to get over this issue by classifying certain people as just a disorder.

0:21:08.5 SC: Finally, there's one other strategy that people use which is basically to count and say, well, so many people are just ordinary, regular, normal, it's a very normative language that is used here, right? But so many people are just obviously male or female, that who cares that there are other people who is a tiny minority that that doesn't change the idea that I can talk about sex as being immutable and binary, etc.

0:21:34.8 SC: And there's a one example that is used over and over again, I don't know, it must come from somewhere, there's not a million people who separately hit on this. But the example is, it's like saying human beings are bipedal, right? Or human beings have two legs. Sure, there are people who don't have two legs. But nevertheless, it's so true, and so very often true that we can say it anyway.

0:21:56.8 SC: I love this example, because it completely proves my point. The point being that I would get it if you said human beings are bipedal, I would understand if I were a person who had gone through amputation and didn't have both legs that I would be annoyed by this particular formulation. But still, if you're simply and clearly within some context, trying to be casual and approximate, and quick and not too careful, then you can say things like that, yeah, human beings have two legs, I get it.

0:22:30.8 SC: But what if you say human beings necessarily always and exclusively have two legs? The content of your statement is the same, right? Human beings are bipedal, and human beings always necessarily uniquely have two legs, you just added some adjectives there. But your statement has become false because all those little signalling words are precisely doing the work of saying, I'm not just trying to be casual, right? I'm trying to be very, very definitive about this. And then you're wrong, because that's just not true that human beings uniquely definitively have two legs.

0:23:08.3 SC: If you want to say, there are men and there are women, just as if you're talking about, I don't know, you're writing stories, and you want to say, is this character male or female, and you're not particularly in tune to issues of trans identity or whatever, fine, I'm not going to give you a hard time. But if you go out of your way to demand that biological sex is real, immutable and binary, you're exactly saying, human beings must only ever have two legs, and that is it.

0:23:36.0 SC: And that's just wrong. You're specifically going outside the domain of where you could be taken seriously there. So I don't think... I think that whether or not the percentages are relevant or not, actually depends on the precision with which you're trying to talk. And if you want to say, "Oh, is your child a boy or a girl?" That's fine, I'm not going to give you trouble about that. But if you say your child must be a boy or a girl, there's no other choices, which one is it, then I'm going to give you trouble because you're just trying to make some political point.

0:24:06.5 SC: That is, of course, the point, right? These people have a political agenda, lots of people have political agendas on all sides, right? And that's what makes it difficult to have reasonable conversations about these things. So I hope that whether or not you agree with with my perspective here, the people listening here are at least willing to think through the difficulties of these kinds of issues. Like I said, I'm not that devoted, I'm not interested, I don't care that much about this particular issue. I care a huge amount about whether we treat human beings with dignity and respect, including people who are intersex, including people who are trans. I think that in the world we live in, we do not do that right now. These people suffer, they are subject to depression and suicide and bullying. And it's an embarrassment, it's something that as a culture, we should be embarrassed about. It's one of the very clear ways in which we fall short of giving all human beings equal dignity, right?

0:25:08.5 SC: And I don't get it. I'm not going to give you points for making a big deal about the sex binary if you don't also make a big deal about the fact that there's a whole bunch of human beings that we treat like shit here in the world. That's what I would think is a much more important point.

0:25:28.8 SC: Henry Jacobs says, "The Margaret Levy interview was dope. In a previous AMA, I pitched lottery voting as an alternative election system. I'd sum up your critique is, I get it, but we can't elect Nazis 3% of the time." And I agree. Here's a modified version I'll call diet lottery voting. Sample 100 citizens and have them vote in a plurality election use carrots and sticks to ensure that sample citizens cast a vote. Sadly, the system is non-proportionate, but the fringes are de-regularized, or sorry, are regularized. I think that what Henry means is the 3% who end up in the 100 citizens are not going to have a big voice. He continues, "I think a diet lottery system could improve the tone of politics because it would be a waste of time for a candidate to rally her base and get out the vote under the system. This is because the voting population, the random sample, will exhibit 100% voter turnout. So getting out the vote is just not a thing. Instead, the candidate should spend time talking to open-minded non-partisans. Anyway, that's the theory. Is it convincing?"

0:26:27.6 SC: Even though this is against my usual response to this kind of thing, I like this idea. I think that it would... Well, there's zero chance it will ever be implemented, I think, as a political reality. But I do see advantages. It's similar in spirit to the idea of sortition, which I never heard of, but Astra Taylor introduced me to when we did her podcast a while back about democracy. Sortition is just when you have some issue that is very hot button, it was used in Ireland for talking about, I guess, birth control and abortion, something like that. You randomly collect a small group of people, put them in a room, and ask them to hammer it out.

0:27:08.6 SC: The act of being randomly selected really makes people devoted to the cause. It's interesting how that works. They take it seriously, for the most part, and they come up with a pretty good compromise. So basically, what Henry is suggesting is sortition, but for voting, for actually choosing our representatives who will do the day-to-day work of governing the country. And I like the idea that getting out the vote becomes less important. That's also achieved, of course, just by making voting mandatory, like they do in Australia and some other places.

0:27:44.2 SC: The other thing that this thing would do would be to change how money infects politics. Right? Getting out the vote is one thing, but there's a whole way that money distorts everything in politics because you have to get out the vote and you have to campaign, and that costs a lot of money. And so the people who can give you money get outsized influence. Whereas if it's just randomly selected people every year, it's harder to see how spending millions of dollars to win their affections would work. Presumably, you could just try to buy their votes, but maybe you could put some legislation in there, some rules to prevent that.

0:28:19.8 SC: So I don't know. I haven't thought about it very much, but I like the outside-the-box thinking. I think that we have a terrible system right now, and we're paying the price for having a terrible system. I don't like the plurality voting aspect of Henry's idea. I think we can do better. One thing that teaching the physics of democracy course has impressed upon me is the difficulty, but also the importance of having a representation system that takes lots of people's opinions into account. The whole problem with plurality or first-past-the-post voting is that the majority wins and that's it, and the minority voices just don't get in there in any way.

0:29:00.4 SC: And if you have some more... So the typical example being if there's one candidate that is loved by a majority but hated by 49%, they will win, whereas someone who could more or less have been acceptable to everyone will lose, and maybe that's not the right choice. But anyway, that's tweaking around the edges. I like the idea of thinking outside the box in this way. I don't know if anyone else has suggested it, but I'll think about it some more.

0:29:25.2 SC: I'm going to group two questions together. Ulf Hallabiel says simply, "What does it mean to be a naturalist?" And Leo Behe says, "Although I call myself a naturalist for practical purposes, I'm unsure how we could even define something outside of the natural world. If we were to discover some other stuff that behave very differently from our current understanding of how the world behaves, there would still have to be some way in which that stuff would interact with everyday things like protons, electrons, etc." To whatever extent this other stuff interact with everyday matter, we would simply model those interactions as best we could with experiment and theory.

0:30:00.3 SC: Given that, do you think it would ever be possible, even be possible in principle, to discover anything that wouldn't fall under the category of natural? So both of these questions are, this is a classic question, how would you ever know whether something was not natural or not? I think that, naturalists define what they do in terms of a distinction between the natural world and natural phenomena and non-natural world and non-natural phenomena. And implicitly, although sometimes they don't spell it out, I think that the distinction has to do with regularity and predictability and law-based behavior.

0:30:35.5 SC: If you have a harmonic oscillator, you know exactly what it's going to do. It's not making choices that are unpredictable in some way. Whereas there is some idea that something supernatural or whatever would be a mind or an intelligence or in some ways not beholden to the laws of nature or to any laws at all in principle.

0:30:57.4 SC: But honestly, I don't worry about this question that much because I think that this is not a problem for naturalists. This is a problem for non-naturalists. I think that naturalists have a pretty good idea what they mean. There's a world, it's the natural world, it obeys rules, we can discover what those rules are by doing science, by proposing hypotheses and testing them empirically.

0:31:17.9 SC: If you want to say something else, then be my guest. But it's your job in that case to specify exactly what it is what you're saying. I think naturalism is perfectly obvious. The problem here is defining supernaturalism and that's not really my job.

0:31:32.9 SC: Paul Hess says, "If a particle has a 50-50 chance of being spin left or spin right and then I measure it to be spin left, does that change its overall momentum? Is there any conservation that is no longer true because of this?" It changes the momentum in the world that you're in, but typically in a way that you're going to measure this thing, the momentum goes somewhere else. So you have interacted physically when you measure with some apparatus and that interaction involves the spin or the angular momentum of the apparatus as well and everything is conserved. There's a subtlety there, I didn't group them together, but there's a subtlety there when it comes to energy which is a little bit different than these other things, but it certainly can and probably is the case that overall momentum or angular momentum in particular is conserved in these kinds of interactions.

0:32:23.3 SC: Andrew Kay says, "I really enjoyed the biggest ideas in the universe. I think you clearly covered the encoding of the curvature side of Einstein's equation, the left-hand side, but I'm still unsure about the stress energy side, especially the off diagonal parts. How do we know it covers all possible forms of energy? Is there a good resource where I can learn more about it?" Well, there's always something you can't get into when you write a book like that. There's always some level of technical detail that it's hard to cover. In this case, there is something called the stress energy tensor, the right-hand side of Einstein's equation, and it was invented long ago in some form or another. And then of course, we come to understand it better and better as time goes on. I think that the best way of thinking about the stress energy tensor is basically the tiny variation of the matter action with respect to changes in the metric. Now those words might mean nothing at all to you, and that's why I didn't go into explaining it. But the point is that mathematically, there is a very specific, very well-posed definition of the stress energy tensor.

0:33:29.2 SC: It's not just that we take all forms of energy and throw them in there, okay? We know exactly what we mean by that. Now, having said that, there are still debates. There are people who go back and forth about, can you modify? What do you mean by the stress energy tensor? Can you improve it in quantum field theory? These debates go back quite a ways, and they're all subtle and interesting and so forth. But I think you should be confident that the basic picture is pretty solid. As far as a good resource where you can learn more about it, I don't know. Obviously, if you want all the technical details, I wrote a textbook in general relativity, and the technical details are all in there, space, time, and geometry. I'm not sure if anyone covers that at the non-technical level. It might be... There is a book by Bernard Schutz, I think, which tries to do gravity at the semi-technical level that I did in The Biggest Ideas. But I'm not actually familiar with the book. I've seen it on Amazon, but I've never actually leafed through it. But that might be a place where you could look.

0:34:25.3 SC: Kyle Stevens says, "In your recent podcast with Raphael Bousso, you seem to object to his idea that the cosmological constant may not be constant, as he believes it would lead to the Boltzmann rain problem. Could you explain why you disagree with this if you disagree at all?" So look, I'm going to confess, I do not remember exactly what I said in the conversation with Raphael. But more importantly, I will try to tell you true things that I actually believe. The cosmological constant, there's three possibilities here. One is that the cosmological constant that we observe today is just it, once and for all, forever. The universe will continue to expand, ordinary matter and radiation will dilute away, we will come close to something like de Sitter space, which is empty space with nothing but a tiny positive cosmological constant. Another possibility is that the cosmological constant is constant at the moment, but will undergo a phase transition, a sudden change to some other number sometime in the future. And the third possibility is that even though it looks pretty constant, the cosmological constant is not quite the answer, not quite what the dark energy is, the dark energy is almost constant. But in fact, it's somehow slowly changing. It's a dynamical dark energy.

0:35:37.9 SC: I think that that last option, even though it's extremely popular, is also very, very hard to make work. Because if you have some thing that is slowly changing, that's a dynamical entity, that's a field and that field can interact with other things in the universe. And we should have seen those interactions already. And we haven't yet. There are loopholes there. If you go back to, I did, I think a holiday message podcast about the screwy universe some time ago, I talked about that possibility there, but I just don't think it's a natural solution. The temporary changes or rather the temporary constancy of the cosmological constant, punctuated by phase transition changes, that is possible, but also, it's hard to make it work because if those changes, if that phase transition could happen at all, it might very well have happened already. Chances are, I would say that it should have happened already. You need to, really very carefully tune it so that it will happen in the future, but it hasn't happened yet. So I think both of those options are a little bit dicey. And it's just more natural to stick with the constant cosmological constant.

0:36:51.2 SC: Now, the Boltzmann brain problem is a separate thing. There are separate issues there. The Boltzmann brain problem has been mentioned as something that would be a problem for the real world if we approached to de Sitter space. As I pointed out in a paper with Kim Boddy and Jason Pollock a while ago, that depends on your opinions about quantum gravity and quantum field theory and curved space time. In fact, it is very, very natural to imagine that we do approach to de Sitter space, but we do not get dynamical fluctuations into Boltzmann brains. That's a technical point about how the fluctuations work. But it depends on certain assumptions. And if the assumptions go the other way, things would be different. So there was absolutely an idea that one way of escaping the Boltzmann brain problem would be for the cosmological constant to go away before too long. Don Page, among other people, has suggested this. I think maybe Andre Linde did also.

0:37:47.9 SC: And in fact, that's how I stumbled across this idea with Jason and Kim because Kim and I wrote a paper asking whether or not the Higgs boson could lead to a change in the cosmological constant that would help us escape from the Boltzmann brain problem. And then in thinking about it more and more, we realized that maybe there's an easier escape. It just wasn't a problem if you took the quantum field theory seriously. So I forget exactly what Raphael said, but that's how I see the situation right now.

0:38:17.8 SC: Bruno Teixeira says, "Could we get an explanation of the hierarchy problem? I believe it has something to do with the predicted mass of the Higgs versus the actual mass. But when we discovered it, did it match the prediction. Is there a naive prediction and a more informed, fine-tuned prediction?" Well, yeah, so when you talk about a prediction for the Higgs mass, what are you allowing yourself to know ahead of time? So when we found the Higgs boson, we already knew a lot about low-energy physics, right? We know a lot about the W bosons and the top quarks and how they interact and things like that. And the Higgs boson, even before you directly detect it, feeds into those predictions. So you could indirectly say the Higgs boson mass had better be more or less here, and it was more or less there where we found it.

0:39:05.0 SC: But there's also the attitude you can take, well, what if I didn't know about the mass of the W boson and the mass of the top quark? Because after all, those depend on the Higgs boson. So if I just said, well, in the world of all possibilities, what is the most likely place for the Higgs boson mass to be? That's where you get the hierarchy problem. Because then it's a little bit dicey, and I don't like it. And I think the hierarchy problem is less well understood than people claim it to be. But the general idea is that you can take things like the mass of the Higgs boson, or maybe arguably be better to talk about the expectation value of the Higgs field in empty space, the value that the Higgs field has. And you can calculate that value as a sum of what you might think of as the classical value, the value that would exist if there were no such thing as quantum mechanics, and then quantum corrections to that classical value. And the reason why this is dicey is because nature certainly doesn't do that.

0:40:07.8 SC: Nature doesn't start with the classical value and add corrections to it. It just has a value, okay? But nevertheless, if you do take that attitude, what you find is that even if you make the classical value very small, the quantum corrections should be enormously big. If you don't add in new physics to squelch them somehow, the quantum contribution to the mass of the Higgs or the expectation value of the Higgs diverge, as we say. So they grow bigger and bigger, maybe up to the Planck scale or something like that. So that's the hierarchy problem.

0:40:39.2 SC: The hierarchy problem is that our natural expectation for the magnitude of the Higgs expectation value or mass is way bigger than the actual empirical value that we find it at. It's very, very, very much like the cosmological constant problem with one big important difference. The cosmological constant problem says all of the same things, classical value plus quantum corrections, quantum corrections diverge, and they're big, but the actual number is small. The really big difference is in the case of the hierarchy problem, there was at least the possibility that we would discover new physics at the right energy scale to explain the hierarchy problem, whether it was supersymmetry or extra dimensions of space or strong dynamics or whatever you want it to be.

0:41:24.5 SC: Whereas with the cosmological constant, the energy scale associated with the cosmological constant is so incredibly low, way less than an electron volt, that there's no room for new physics there. We would have seen any physics that is really relevant there. And so that was always thought to be more of a puzzle. Now, we've looked now in the Large Hadron Collider to try to find new particles that might be relevant for the hierarchy problem, and we have not found them. So maybe going forward, they will be thought of as similar kinds of problems.

0:41:54.8 SC: All right, I'm going to group two questions together. One is from Jay Peters, who said, "A deep tension within your views. You're open to the idea that time and space will turn out not to be aspects of the universe when described at the most fundamental level, yet you also claim to be a longtime 76ers fan, meaning that you trust the process where a process is a series of events that unfold in time. Perhaps you should jump onto the Golden State Warriors dynasty train." And then Keith says, "Do you have a second team that you root for? After all, the Golden State Warriors were originally the Philadelphia Warriors and had Wilt Chamberlain."

0:42:31.0 SC: So Jay, I'm sorry that is not a tension within my views, because for two reasons. Number one, I'm actually much less definitive about time not being fundamental than I am about space. I think space is not fundamental, almost certainly. I think that time is a much dicier proposition, and we just don't know. I'm pretty open. Maybe it's emergent. Maybe it's just fundamental. I'm not decided about that yet. But even if it is emergent, I'm still allowed to trust the process. I trust an emergent process. That makes perfect sense.

0:43:02.6 SC: So I have no incompatibilities inside my soul as far as that one is concerned. As far as rooting for the Golden State Warriors, I did root for the Golden State Warriors back in the day. So for two reasons. Number one, as you say, Keith, they used to be the Philadelphia Warriors. They were Wilt Chamberlain's first team back in the early 60s before they moved to San Francisco and the Syracuse Nationals moved to Philadelphia to become the 76ers. But also because some years ago, the Golden State Warriors were plucky underdogs. And one of their last pieces of the puzzle for them was signing Andre Iguodala, who had started his NBA career with the 76ers and was always a great player, someone who was very easy to root for. And he played a big role in those championship Golden State Warrior teams.

0:43:51.9 SC: So before they had even come close to winning a championship, I was rooting for them because they were plucky underdogs and had one of my favorite players on there. Steph Curry was always a lot of fun. Now it's a lot less fun to root for them as your second team., they're doing too well. What's the excitement there? My heart is always with the 76ers, even though this year it's been, let us generously say, an up and down year so far. I'm hoping that they will find their groove, get over the injuries before too long.

0:44:18.2 SC: Mike Briggs asks a priority question in the form of a poem. The poem is entitled, The Spherical Cow and it says, "I never assumed a spherical cow. I hope to never do that. But I can tell you here and now I'd rather do than boo that. With many thanks to Gillett Burgess, who wrote a similar piece of dog roll a while back." And Mike says, "Surely, this is not an original thought, but I haven't heard it on an AMA. So let's go." I perceive no questions in here. So I'm not sure exactly how to respond to it. I think the point of Mike's priority question was just to get me to read the poem out loud. Now I have done that. So I think that my job here is done. Paul Conti says, "I do realize that you don't particularly like questions of the, is it possible variety. However, do you think it likely, given the expansion of the universe and the structure of the cosmic web, that there may be entire galaxies or clusters of galaxies that are made exclusively of antimatter?"

0:45:15.6 SC: So I think I've actually answered a question like this before, but I wanted to answer it because, Paul, you're so close to doing what I hope people do. So you're right. I do not like questions of the, is it possible variety, but then you didn't ask a question that. What you asked was, "Do you think it's likely?" Now that's a much better question to ask. So just forget about asking, is it possible? Ask about the likelihood. Ask how reasonable certain things are, not whether they're possible or not. That's not the point. I think that people make a mistake like if something's possible, then there's at least a 10% chance that it's true. And I want to get over that particular option.

0:45:50.0 SC: In the case of antimatter galaxies, there's way, way, way less likelihood than 10%. Because, as you know, when antimatter comes into contact with ordinary matter, it annihilates and gives off an enormous amount of high energy radiation. Now you might say, these galaxies are very far away. We're not in contact with them. That's less true than you might think. There are high energy cosmic rays going back and forth between galaxies that actually you can calculate would be pretty visible if certain galaxies were spitting out high energy antimatter cosmic rays and other galaxies matter cosmic rays. But much more relevantly, the universe used to be a lot smaller. The galaxies didn't used to be that far away. In fact, they used to be a more or less smooth, homogeneous plasma. And if half of that plasma or even 10% of it were antimatter, you would know it would annihilate away very quickly into super high energy radiation and the microwave background would look like a very, very different place. So there's no realistic possibility that there's large collections of antimatter here in our universe today.

0:46:53.1 SC: Now I think I'm going to group these three together. Yeah, Red Antonov says, "What was the question Raphael Bousso was begging at the 109 mark that you left for an in-person discussion?" Sid Huff says, "I enjoyed your recent podcast with Raphael Bousso. I gather that you and he disagree on certain aspects of quantum mechanics, among other things. At one point, you commented that you would table that discussion for a later time. Can you highlight for us the two or three issues that you and he hold substantively different views on and why you think that is?" And Mikkel Pickel says, "In the episode with Raphael Bousso, you pressed a bit to get an answer to your question regarding whether we are more likely to live in a three plus one dimensional world or a lower dimensional world. The basis for the question seemed to be that there are differences in the way one or the other reality would appear to us. I have thought that the equivalence of the two models means that they would appear the same to us, that if we were beings living in ADS or CFT, the appearance of the world around us would stay the same. Am I looking at that the wrong way?"

0:47:48.8 SC: So for future reference, I like Mikkel's version of this the best, followed by Rad's, followed by Sid's, not because the questions are any different in substance, but because you can't expect me to remember a certain comment that I made in a podcast weeks ago, especially when we recorded that podcast with Raphael, I think in July or something like that. I've just been having to delay posting it because there were other people who had books coming out, etc. So if you want me to... I love it when people ask, talk about this specific point of this specific podcast, but you have to remind me of exactly what was being talked about. I'm not just going to remember.

0:48:26.1 SC: Raphael and I agree on lots of things. I hope people don't get the wrong impression here because the research that we do is so similar to each other's, we can get into very, very specific kinds of disagreements in ways that, Margaret Levy and I or Danny Bassett or Perry Zurn and I are just not going to get into because I'm an outsider in their research. But with Raphael, we've both been thinking about this for decades now and we can get down into the weeds a little bit. So even though we do disagree about things, probably our overall level agreement is substantially higher than those of two randomly chosen people in this sub field. So I don't even think that we were disagreeing about this except for maybe the significance of the question.

0:49:09.8 SC: And the question was, if you believe in dualities, okay, which you should. So a duality is basically two different classical descriptions of the same underlying single quantum mechanical theory. In the case of ADS-CFT, there's a single theory that looked at in a certain way, looks like a quantum field theory without gravity, the CFT, and looked at in a different way, the same exact theory looks like a theory with gravity in anti-de Sitter space. And mathematically, they're the same. But if you think that something like that is supposed to apply to the real world, then you realize that, we've gone thousands of years thinking that the world looks a certain way.

0:49:52.8 SC: And if we now discover that you can think of it in a different way, there's a question, which is, why didn't we think of that of it in the different way from the start? Why did we find ourselves very naturally in a role with gravity if there's another description of ourselves in a world without gravity? And I think that this is a tricky question. And I think there's different aspects coming into it. And the ADS-CFT version of the question is pretty darn well defined, there's two theories, there's a theory of ADS with gravity, theory on the boundary with one less dimension, no gravity. If there were people... If there were living beings in that world, they would almost, to answer Mikkel's question, they would not see both any more than we see both in our universe, because people think that we have holographic duels that are mathematical descriptions.

0:50:42.5 SC: But there is a first way that you obviously just using your nose, perceive around you that the world is. And I think that complex living beings in this universe would either think they were living in anti-de Sitter space or in a flat space conformal field theory. So why? What are the criteria that picks out one over the other? And I think there's two things going on. Raphael didn't answer it, but here's my half-baked answer, which I don't think is quite complete. Part of it is, comes down to what we call strong coupling. Famously in the world in which we live in the standard model of particle physics, we're very, very lucky that the fine structure constant of electromagnetism is 1 divided by 137, which is a small number, it's less than 1%. Because what that means is that we can accurately model the world to first order in that parameter alpha, the fine structure constant.

0:51:38.1 SC: So in quantum mechanics, in Feynman diagram language, there are electromagnetic interactions that are proportional to alpha, the fine structure constant, 1 over 137. Then there are corrections to those interactions that are proportional to alpha squared, alpha cubed, etc. But because alpha is small, those higher order corrections are very small and we can get pretty far ignoring them. So there's a natural language that we can use.

0:52:01.1 SC: And very often in these dualities, if you're weakly coupled like that, that's a weak coupling, small coupling constant. If you're weakly coupled on one side of the duality, you're strongly coupled on the other. In this strong coupling world, it's just harder to make sense of the world, you can use a classical approximation in a very easy way and therefore, it's harder to know what any beings would say about the world. And so maybe it's just easier to live on the weak coupling side of the duality. But there's another aspect to that, which is a little bit more murky, which is classicality depends on decoherence, right?

0:52:36.0 SC: Classicality is the emergence of a limit of quantum mechanics. And it's a limit that depends on things like the arrow of time, right? If there was no arrow of time, if in thermal equilibrium, things would not look classical at all. So that's much more murky to me. I think there's work to be done there. It's one of the things that I'm personally I'm interested in thinking about more. What role does decoherence and branching of the wave function have in what we call classical and therefore, in which side of a duality would we find ourselves living on? Because maybe the ability to think of our world as classical plays a really important role and their decoherence is important.

0:53:17.5 SC: Again, I don't know, but that's what I'm wondering about and asking questions of my podcast guests. Murray Dunn says, "Is there anything that can absorb, reflect or refract gravitational waves? Or do they propagate undisturbed until the end of time?" Well, gravitational waves interact with matter, they do, just like electromagnetic waves do, I shouldn't say just like, but not exactly just like.

0:53:41.2 SC: The crucially, crucially important difference, and I've emphasized this in many different contexts is that in electromagnetism, you have positive charges and negative charges. And by subtly mixing up the configuration of the positive charges and negative charges, you can basically create or cancel out any electromagnetic field you want. In particular, you can absorb or reflect, okay? Whereas gravitational charges are just the masses of the particles that you're making up your system from, and those are always positive. Gravity is always attractive, there's no repulsive gravitational force between two ordinary particles.

0:54:17.2 SC: And so it is enormously harder to manipulate gravitational waves, that plus, of course, the fact that gravity is just a really weak force, so that also makes it very, very hard. So therefore, to a really good approximation, gravitational waves just propagate undisturbed until the end of time. They will, of course, be deflected by other gravitational fields. There's gravitational lensing of gravitational waves, but reflecting them is almost impossible to do because they will lose energy. As a gravitational wave passes through a cloud of gas or whatever, it exerts energy on the cloud and therefore loses energy itself, but that effect is super duper really tiny. It's not one that you really have to take into account as a working astronomer.

0:55:02.0 SC: Igor Vlotic says, "When you discussed earlier the Boltzmann brain problem, you mentioned the issue with the random fluctuation of the laws of logic and reasoning. Given that you are not a Boltzmann brain, how would you generally justify the use of logic the way you use it? Could you do it without using some kind of logic?" So I'm not sure if this is mostly a question about logic or mostly a question about Boltzmann brains. I'm not sure, and I'm also not sure what you mean by the word justify. It's not your fault. There's a perfectly well-formed question, but I think that this is an example where being really, really specific about the meaning of those kinds of words matters.

0:55:39.1 SC: I don't necessarily justify the use of logic other than by saying that it works. In other words, look, maybe I am a Boltzmann brain. Maybe I am a brain in a vat, or maybe I live in a simulation and the whole world was created last Thursday. All of these are logically possible, but they're no way to go on living, right? There's no way to go through life. If they're true, then there's certain things that are just out of my control and I can't do anything about them. So there's a very down-to-earth pragmatic question. How do we model our world? And what we mean by that is what are the useful ways to model the world that we can imagine? And part of those useful ways are, we want our model of the world to be compatible with the data and to be simple and useful and fruitful and understandable and all of those things. But it's more than that, right?

0:56:26.6 SC: So there might be multiple models of the world that are compatible with the data that have very different levels of usefulness if they are true. So the thing about logic and the thing about not being a Boltzmann brain is if they're not true, if logic is false, if I am just a Boltzmann brain, then things are hopeless. I don't know what's going to happen next. I have no reason to trust any of my thoughts, etc. Whereas if I hypothesize that my impressions of the world are roughly correct, my knowledge of logic is roughly on the right track, then I can make progress. Maybe it's true, maybe it's not, but that's how I'm going to act.

0:57:07.4 SC: Nate Wadoops says, "Do you think that wider adoption of ranked choice voting or approval voting could mitigate the polarization that plagues politics and discourse in the United States these days?" Well, I don't have a favorite theory, honestly. I don't have a favorite solution. I think that ranked choice voting has its issues, as we've discussed before. Some approval voting or range voting, score voting might be the right way to go, but I'm very open to the possibility that there's simply practical worries about that. Asking everyone to carry through that more complicated voting procedure in a big country, heterogeneous country like the United States, might be very, very difficult to do. So there might just be practical questions of implementation that I don't know about. So right now I'm very much in the stage of thinking about different possibilities and being open to different possibilities rather than having settled on the one true answer to these difficult questions.

0:58:05.9 SC: Gregory Kuznik says, "Mobsters and tyrants know that the most effective deterrent is to punish the families of miscreants, but civilized folks of all ethical persuasions reject that option, which suggests that some notion of desert, I.e. What people deserve, is still in play even for free will skeptics. Attempts to frame this rejection as consequentialism, it would be bad to live in a society that embraced punishment of the innocent, seems question begging. It's our intuitions about desert that make it seem bad. What's your take on this conundrum?"

0:58:38.0 SC: Well, I'm not a free will skeptic and I'm not 100% a consequentialist either. So I think that there is free will and I'm not completely a consequentialist in the extent that I want to live in a world where people have rights, okay? And certain rights shouldn't be trampled on even if you could make an argument that it would be better for the rest of society. Again, I don't think this is easy. I don't have a simple way of talking about this or a final answer that I want to push on everybody else except to emphasize that it's not easy, that it is complicated, that it is subtle. We have to think through the subtleties here. We can't just glom on to some easy answer because it gives us clarity. So yeah, I don't want to live in a world where you deter bad behavior by punishing innocent people and even if that gives you the best consequentialist answer.

0:59:28.4 SC: And of course, someone like Josh Green who we talked to a year ago and I mentioned it in the introduction, what he would say is really if you work through it, the true consequences of a policy like that are actually not so good because people would rise up against the dictator or whatever and you could make some argument. I'm a little bit skeptical about that. I don't know. I think they might be wanting to get a certain answer and then convincing yourself that it's right. But then again, I haven't thought of it carefully enough to know for sure.

1:00:00.1 SC: So my short answer would be free will is fine. It's real. It's emergent, higher level, compatibilist version of free will, but I think it's there. And consequentialism is not the final answer. There are reasons to treat people with dignity and respect over and above simple consequentialist calculus. Richard King asks a priority question. "Is it true that all life forms are survival driven converters and responders of varying complexity?" Hint, the answer is yes. Well, I don't know is my answer because number one, I'm not quite sure what converters and responders mean.

1:00:37.5 SC: Varying complexity, yes. Life forms have varying complexity. Do they convert things? I guess, maybe, usually. I don't know. I want to know if that's an absolute part of being a life form. I would be willing to think that it is, but I don't have a very strong opinion about it. Responders is a more difficult question. It depends on your definition of response. Survival driven, I think, is pretty dubious. You first have to posit that there are drives, that there is what Dandana would call the intentional stance that you can attribute to something like a bacterium, and then that these drives are oriented in the direction of survival, which is going to largely be true, but not all the time. There's plenty of times when people do things that are counter to their individual survival. So again, I think that it's complicated, and I think we should embrace the complexity in situations like this.

1:01:30.6 SC: Sam Hartzog says, "In your opinion, what role should government play in regulating illicit drugs, controlled substances, and dietary supplements in general? Is it possible, even in principle, to ground drug prohibitions, scheduling decisions on objective research, given the nature of the questions involved?"

1:01:47.0 SC: Sure. Yes, I do think it is possible, in principle, to ground these things on objective research. Now, the reason one would ask a question like that is because, traditionally, they've not always been grounded on objective research. There's been a lot of fear mongering and bad policy about drugs in general, and that has held back scientific research, no doubt. So we could be a lot closer to grounding things on objective research. But we should also mention that it's never always objective research, objective research tells us scientific facts. It doesn't give us ought, right? We're not going to derive an ought from these iss. So what are you going to do with your objective research? You need some goals. How much freedom should you give individual people to ruin their own lives? I think, once again, that's a perfectly legitimate, difficult question. I think that it makes sense to regulate drugs, substances, dietary supplements that might be legitimately unhealthy, and people might not recognize it. There's a losing weight pill that, five months after you take it, has a 100% fatality rate.

1:02:49.7 SC: I think it's okay for the government to ban something like that, right? These are subtle questions. I think that I'm in favor of legalization of a lot more controlled substances than are legalized right now, but I recognize the difficulties involved. Taran says, "David Hume challenged the primacy of pure logical thinking when he says reason is and ought only to be the slave of the passions. To what extent do you agree with this view?" Well, I'm not sure if it's the primacy of pure logical thinking that he was challenging. I think he's just pointing out it's not the only thing. So, David Hume famously tried his best in a charming way to be a gripping writer and never quite succeeded. So, it actually worked against him because he was sometimes colorful and cute in ways that got in the way of what he was saying. So, slave of the passions is an example of that. I think what he's saying is you can logic your way into any conclusion you want or any true conclusion. It does say that you're doing it correctly. Okay, you're doing logic correctly.

1:03:56.3 SC: It still doesn't tell you how to act. Why? Because you can't derive ought from is as was pointed out by David Hume. This is the angle that he's trying to get at here. You still need to have some motivation, some goals, some values, okay? And those values are not derivable in any direct unique way from objective facts about the world. You can change your values, even though the objective facts of the world don't change. And so that's what he means by the passions in this case. Basically, what he's saying is we have passions that tell us what we want. Logic is going to tell us how to get it. Okay.

1:04:33.2 SC: So it's not really slavery as the actual relationship here, but we put logic to work to get what we want. Logic does not tell us what we want. And I do agree with that view. Bart Connolly says, "Once per lifetime question. As I enjoyed your podcast with Alan Lightman, I'm wondering if you have any further thoughts on how conscious beings can best pursue spiritual interests in the material world. Should we just regard them as something to outgrow? Or perhaps should we find ways using disciplines like meditation and technology to pursue this goal, much as we use science and technology to help with physical health?"

1:05:10.3 SC: I think this is another subtle question because I think that it's going to depend a lot on what you mean by the word spiritual, which Bart put in quotes in his question quite correctly. I personally don't ever like to use the word spiritual in this context because you have to really contort yourself into a weird definition of spiritual in order to make sense. I am going to be someone who says that when you use the word spiritual, people are going to think of spirits. They're going to think of these spirits as non-physical, non-natural manifestations. And if you don't want them to think about that, if you want to be purely naturalist in your inclinations, don't use the word spiritual. Okay? Use some other word. What word should you use? Sadly, I don't know. I don't have an opinion about that. But I take that what the important point of Alan Lightman's discussion was is that there are experiences that we have, there are feelings that we have, there are values that we have as human beings that we human beings struggle to put into clear, crisp, naturalistic language. And so we can group them into a bucket that if you want to label it spiritual, I'm not happy with it, but go ahead. I can't stop you from doing that.

1:06:27.9 SC: And these feelings of oneness with the universe, transcendence or whatever, on the one hand, have zero incompatibility with nature or the laws of nature. There's no evidence that there is a world beyond physics just because on a certain starlit night when I'm looking at the sky, I feel one with the universe. Okay? That's not actual refutation of naturalism. But on the other hand, they can still be important. You can still value them. You can still think that people will be better off if they spend time commuting with nature and becoming one with the universe rather than insulting people on Twitter or something like that. So I think that, yeah, this is part of the reason why I do things like organize that beyond or moving naturalism forward workshop that I organized way back when, 2012, something like that. Because I do think that our vocabulary isn't up to the task. We inherit this vocabulary from how we were thinking about things a thousand years ago. And we know better now, but the words and language hasn't caught up yet. And so I don't know what the right words to use would be, but I don't think the right answer is just to use the old words and with a wink and a nudge and say, but you know what I mean. I don't really mean that. I think we should be able to do better than that.

1:07:49.1 SC: David Maxwell says, "Your breadth of interests makes me tune in, but it's your ability to simply communicate complex ideas across a range of topics that makes you unique to me. An interviewee can speak for 10 minutes and you'll distill it in a way that crystallizes my understanding and that your guests often want to borrow. How do you do it? Do you think things through and through or come up with simple ways to understand? Do you ever pre-write your amazing reductive statements or is it just the way you think perhaps a product of your fields, physics particularly with a mind to complexity?"

1:08:17.9 SC: So thank you for the very nice words, David. I usually actually don't like to read questions with the compliments embedded in the beginning. That's not why we're here in the AMAs, but in this case, there is an interesting question here and I don't completely know the answer to, but I don't think it's any super-duper special ability on my own. I think there's two things going on. One very down to earth thing is Mindscape Enterprises worldwide is still very much a one-person shop. It's just me. And what that means is that, I'm not a radio host or even many podcasters who have a producer or a booker who is getting guests on the show. The guests I get are all invited by me personally and they're invited by me because I'm interested in what they have to say. So I don't need to pretend to be interested in what they have to say.

1:09:07.3 SC: Every single person who comes on has some knowledge that I want to get to. And so I'm motivated to try to understand it better myself. And the other aspect is, yeah, whether it's physics or complexity or just being in academia and... Well, at the intersection of being in academia doing research and also public discussion and communication, it trains you to distill things down, right? You can understand something. Well, number one, it's hard to understand things. You have to work at it. Number two, you can understand things and still fail in the attempt to communicate those things to other people. And I've been trying to do both of those things for a very long time. I'm old now. I've been around the block, not my first rodeo, didn't just fall off the turnip truck.

1:09:54.3 SC: And so I've had practice doing exactly this and not to... I should emphasize something very importantly. Other people have also done that, but I care about doing it well. So I try. So I think about how I do it. And, I think about how to distill these difficult ideas down. I do not pre-write anything as one page of little bullet point notes generally going into a podcast, but certainly no phrases or anything like that are pre-planned. But as the person is talking, I'm trying very hard to understand what they say and to distill it down and put it into my own words based on a lifetime of trying to take difficult concepts and put them into words that other people can understand.

1:10:39.8 SC: And very often, and this happens vice versa to other people say things about my work that I go, oh yeah, that's a good way of putting it. If you're in the weeds, if you're doing something every day and thinking about it, you can get into ruts. You can think about things using a certain set of words, using a certain set of moves, if you will. And they're just so useful to you that you can jump out and put things in another way. And talking to someone else who really cares about the ideas can help you put things in a different way because they haven't been in those ruts the whole time.

1:11:10.5 SC: Jim Watson says, "Understanding that models generally have a domain of applicability for accuracy or at least efficient calculation. I'm curious how useful our lowest level quantum models are for explaining things at the level of chemistry or material science. For example, can one start with the electron wave equations or electromagnetic force calculations and derive how covalent bonding of shared electrons across atoms works? Or that the carbon lattice would be super hard or stress versus strain of iron, etc.?" Yeah, actually, again, this is an example of something that is not precisely my domain of expertise. But yes, these are the kinds of things that you can actually derive using the principles of atomic physics and quantum mechanics.

1:11:57.0 SC: There's a whole field of density functional theory that tries to make these calculations easier. The problem is that quantum mechanics lives in Hilbert space. Hilbert space is very, very big. Even when you have a small number of particles, the calculational difficulty of following the quantum equations becomes very, very difficult. So that's okay. You derive approximation methods. Density functional theory is one such thing. But also you have higher level models that glue onto the lower level models. So things like BCS superconductivity and like things that are higher level versions of nevertheless manifestations of the quantum phenomena from the lower level. So it's generally not true that you try to derive detailed things about, why spaghetti splits into three pieces when you break it rather than just two, starting with the standard model of particle physics. But you build your way up, right? And actually, you can build your way up surprisingly far just from the fundamental quantum description.

1:12:57.5 SC: The calculational complexity of doing that is, of course, one of the major reasons why we're interested in building quantum computers. People talk about quantum computers in terms of cryptography, or teleportation or whatever. The real obvious killer app for quantum computers is simulating quantum systems. Probably difficult chemistry is an obvious thing to aim at, but material science and things like that will also be looked at.

1:13:25.3 SC: James McCrell says, "Priority question. I've read many articles and listened to many discussions that lead me to wonder what is meant by the cosmos is a hologram, or a computer program made by some master programmer. Please decipher, are those describing actual processes, or is all of this talk an attempt to describe the cosmos in understandable terms?"

1:13:44.8 SC: Well, the two things that you mentioned there are very, very different. The cosmos is a hologram, and the cosmos is a computer programmer made by some master programmer. The latter bit, the idea that we're a computer programmer, is supposed to be, a serious suggestion for the fundamental nature of reality, the simulation argument, it's usually called. One that we have no evidence is correct, but it's possible. People differ on whether how plausible it is. The cosmos as a hologram is an entirely different idea, we might have in mind the kinds of holograms we can buy in a toy store or whatever, that were clearly constructed by somebody, but this is not trying to say that the hologram is in any sense built by some higher intelligence or anything like that.

1:14:28.8 SC: It's just the idea that there's an alternative description of reality that encodes all the information about our world in a space that has one fewer dimension than the space that we seem to live in ourselves. That's what we were talking about when we were talking about Raphael Bousso's discussion and ADS-CFT. Again, we don't know that that's true or not either, but there's evidence for that one, at least. There's very good reasons to believe that some holographic behavior is part of our best understanding of quantum gravity, but it's all very mechanistic and it's just talking about a different way of describing the same fundamental stuff.

1:15:13.5 SC: Schleyer says, "I read and enjoyed the biggest ideas in the universe volume one, so I followed the math laboriously, but one problem I have is that when dealing with formulas, my mind goes into symbol manipulation mode, which I find can't coexist with understanding the significance mode. Are you able to do the math while keeping the big picture in mind or is it normal to toggle back and forth?"

1:15:37.7 SC: So I'm not exactly sure what you mean. There's certainly a mode where you're just pushing around symbols. That is absolutely true, but it doesn't seem, to me at least, to be exclusive with the mode where you're understanding what's going on. In fact, I think that at some point when you become practiced enough with the equations and with the symbols, you become frustrated when there are no equations. I know that this is often a frustration I have in reading some philosophy papers that, I think the ideas are right, but I would like to see some equations so that I'm sure that I'm following the argument as clearly as I am.

1:16:16.5 SC: So I don't think that it's a matter of toggling back and forth. I do think that, again, you can solve equations, when you're halfway through calculating the Riemann tensor, you can't point to one term and say, I know the significance of this. It doesn't have any significance. It's just part of a decomposition. It's like when you have the number 10 and someone says, well, I'm going to think of that as four plus six. They're welcome to do this, but it's 10 that matters. It's not the fact that one person has four plus six is the way they got there, right? Likewise, when you're in the middle of a calculation, very often the intermediate steps don't have any physical significance, but you should be able to attach some meaning to the final answer as well as to the starting point. I think that's just something you get better at with time.

1:16:58.3 SC: Benjamin Cowger asks a priority question. "I personally always struggle with the general two-dimensional diagram of gravity, the standard bowling ball and a trampoline image ingrained in everyone's minds and in most school books and online. It seems most folks I've talked with think of gravity this way as a ball on a rubber sheet, and it's been tough to explain gravity as a force acting on and curving 3D space. If you layer in 4D space time and how gravity acts upon it, it gets even harder to explain in words. Why is the ball on the sheet the standard go-to image in most all articles, books, documentaries, etc?" Well, it's hard to explain the curvature of four-dimensional space time in terms that would be familiar to people. Most people have a difficult time visualizing curved four-dimensional space time.

1:17:47.3 SC: So we reach for analogies and metaphors and visualizations and things like that, and that's perfectly okay as long as you are clear about what the limitations of the analogy are. There's a famous XKCD cartoon by former Mindscape guest, Randall Munroe, where someone, a professor, uses the rubber sheet analogy to explain gravity, and then someone raises their hand in the audience and says, "That's not possible because the bowl is embedded in a three-dimensional space, and it's only the two-dimensional space that is moving." The professor says, "Okay, well, what we really mean is there's something called the Riemann tensor, and we can track that to get the Einstein tensor," and the audience is like, no, no, we didn't want that either.

1:18:25.7 SC: You have to work your way from the picturesque metaphors to the exact equations, and different metaphors and visualizations and analogies are going to be useful to different people. So I'm always of the opinion that you should use all of them and be very, very clear about what the limitations are. So I'm on record as to really not liking the expanding balloon analogy for the universe, but I see why you would want to use it as long as you're super clear about its limitations. I feel likewise about the ball on a sheet. It's trying to illustrate the fact that a massive object can warp the space around it, right? And it's only doing it metaphorically, not directly. You have to both trust the audience to be able to see that distinction and help them see it by explaining why you're doing this. You don't just say, here's the ball on the sheet, space time is like that, trust me.

1:19:21.9 SC: Seth Hallowiko says, "I know that you loved Knives Out. There's a semi-sequel out and I just went to see it. What are your thoughts on movie franchises versus one off original movies? And if you've seen the new Knives Out movie, Glass Onion, what did you think? Rian Johnson is so darn clever and I wish that more directors were being so creative." Yeah, I almost never admit to this kind of thing, but I did ask the publicity people at Netflix whether Rian Johnson could come on the Mindscape Podcast and they never wrote back to me. So I didn't ask, I don't know Rian Johnson personally, I didn't ask himself, but Rian, if you're out there listening to the AMA, we'd love to have you on the show anytime.

1:20:01.4 SC: Someone pointed out, by the way, that in the very first episode zero of Mindscape, I extended an invitation to Lady Gaga to come on the Mindscape Podcast. And that also continues to be true. Lady Gaga, if you want to come on the podcast, we'd love to talk to you. But yeah, for anyone who doesn't know, Rian Johnson, who has directed a lot of movies spanning quite a space, has a sequel out to the original Knives Out from a couple of years ago. The new one is called Glass Onion. They're both murder mysteries starring Daniel Craig as Benoit Branc, who is a Kentucky detective. So it did take me a while, I will admit, to adjust to hearing Daniel Craig talk in a ridiculously over-the-top Kentucky accent during the movie. But you get into it very quickly and it's clearly, easily, no question, Daniel Craig's best roles ever.

1:20:56.1 SC: And I love the fact that there's sequels to this kind of thing. I think that whether or not you have sequels to movies or original movies as one-off standalone pictures depends an enormous amount on the material, right? There's plenty of things where, especially not just with movies, but with limited series TV shows, where there's a novel and they based a six or ten part TV show on the novel and they keep going. Because once you've set up everything, it's cheaper to just have a season two and a season three and it often doesn't work very well because it's not following the novel anymore. And that's a clear example where you should just stick with the original material. But Rian Johnson is clearly having enormous fun with the genre of mystery novels, which is also one of my favorite genres. And he does it in an updated, postmodern way.

1:21:46.8 SC: So he's not slavishly following the tropes of the mystery novel, he's playing with them. And it's just brilliantly creative and hilarious. I think I'd give a slight edge to Knives Out over Glass Onion, but I love them both enormously. I saw that and another movie called The Menu with Anya Taylor Joy and Nicholas Hoult and Ralph Fiennes. And that I won't spoil it for anyone, but that was also an amazingly good movie, just came out this week or last week.

1:22:18.9 SC: Unlike Glass Onion, I cannot recommend The Menu unreservedly because really, it was written for me, that movie. It's a dark comedy about upscale cuisine and various other jokes about race and class and things that. And it was all very, very well done and the acting was amazing and I loved it. But other people might not like it, whereas everyone will love Glass Onion, I think. Phil Hamilton says, "If it turns out that a non-material essence, God, created the universe from nothing, how would scientists be able to differentiate that from the universe having spontaneously appeared from nothing? It seems that evidence of these two possible origins of the universe would appear the same to scientists."

1:23:00.9 SC: Yeah, that's a perfectly reasonable question and I think that it depends on both our future good understanding of the laws of physics and maybe hopefully our future better understanding of God. The problem with God as a hypothesis to explain features of the physical world is, it's just way too ill-defined, you say, okay, God created the universe. Okay, what kind of universe would God create and why? And these are very, very hard questions to answer. Whereas with laws of physics, you can say, oh yes, according to these equations, the universe would be created this way rather than that way. So that's why I think that there's just a prior preference for purely naturalistic explanations when you can find them. But maybe in the course of your investigations, you just come up across a roadblock. You say, look, we've tried as hard as we can. We cannot come up with a set of laws of physics that both fit our universe as we currently understand it and allow for the universe to have an initial moment.

1:24:00.8 SC: By the way, parenthetically, created out of nothing is a terrible, terrible way of saying it. The universe is not created out of nothing. The question is, did it have an initial moment or did it last forever? That is the distinction. And if we cannot find reasonable equations or models or theories that explain the universe either eternally lasting all by itself or having an initial moment, then we might conclude that the best theory we have is that God did it. We might maintain some uncertainty about that, right? We might say, "Well, we don't know."

1:24:33.5 SC: The thing about God is it would be super duper easy for God to make perfectly clear to us that he exists. And he's chosen not to do that. So I'm going to count that as evidence against his existence. Nick C says, "When you take a class in physics, you might learn about Newtonian mechanics, electromagnetism, relativity, etc. But you don't generally read the original writings of Newton, Maxwell, Einstein, etc. You usually read modern texts. By contrast, when I took philosophy classes, we generally read the original historical works of great philosophers. Especially in light of your new academic position, I'd be curious to hear your thoughts on whether this distinction between the approaches of physics philosophy is generally true, why it's true, and whether either discipline should emulate the approach of the other more."

1:25:17.5 SC: Yeah, I think that I'm sympathetic with the general tone of your question, which I take to be that the reason why in physics we generally read modern textbooks rather than the original writings is because the ideas are there. They exist independently of the person who came up with them. And in fact, we generally understand the ideas better than the people who came up with them because we've had more time to think about it, to really dig into it, to get the notation right, all those things. As I've often said, I understand general relativity better than Einstein did, in some ways anyway, because I'm standing on the shoulders of other giants, not because I'm especially smart myself. Whereas philosophy, that's much less common. It is not at all absent.

1:26:01.3 SC: There's plenty of discussion of ideas in philosophy from secondary literature, etc. Plenty of people writing articles other than the greats of the history of philosophy. But you're right, we read the originals much more often in philosophy than in physics. And in part, that's because the... Well, it depends very much on the specific philosophy you're talking about. If you're doing mathematical logic, for example, you're more likely honestly to read a textbook in mathematical logic than you are to read Gödel's original papers on Gödel's theorem, or Russell and Whitehead's Principia Mathematica, etc.

1:26:35.9 SC: But in some kinds of philosophy, it's thought that it is hard to get it right by translating what someone said into one's own language, and therefore the original text really matters and is important. And I think that's done too much, honestly, a little bit, but not that much, because I get it. It depends on what philosophy you're talking about, as I said, but in some areas of philosophy, it is really hard to capture those ideas exactly, and different people can read the same text and get a slightly different opinion about what is going on in them.

1:27:13.1 SC: That is partly because not every philosopher is a great writer, just like not every physicist is, partly because the ideas are just very, very hard. So I would argue that both fields could learn a little bit from each other. I think that philosophers... Well, I'm less interested in the history of philosophy than the average philosopher is. I want to use philosophy to move forward, to improve our understanding, and not just to improve our understanding of past philosophers, but to improve our understanding of the fundamental nature of reality. That's my personal goal. But physicists, they could do a much better job at understanding their history. They butcher their history pretty badly, and it does lead to lingering misunderstandings that can last for a very long time. So maybe a little bit more of, if not the original writers, then at least the history of how they were thinking would be good for physics, I think.

1:28:06.4 SC: Grouping two questions together, Redmond says, "Has the FTX debacle affected your view of effective altruism?" And Nick B says, "Can one person define or destroy a philosophical position?" Unfortunately for Will MacAskill, effective altruism has a new face. Sam Bankman-Fried... I'm sorry, I don't know if it's Fried or Fryde that he pronounces his name. Fried, I think. He has made it world famous. What had been presented as a logical and potent approach for doing the most good for the most people now and in the future is currently being criticized as utilitarianism with a God complex and bunk. Does its rapid fall from grace demonstrate an inherently flawed perspective, or is effective altruism robust enough to withstand the collapse of FTX?

1:28:48.2 SC: So I think there's a lot going on here. These are perfectly good questions to ask, my own relationship to effective altruism has been cautious interest. I've never been part of what is called the effective altruism community. Effective altruism is an approach to altruism, which tries to make it effective. So you say, yes, it's good to give the charity, but some charities do more than others, as we talked about way in the introduction of this podcast.

1:29:16.7 SC: And I've talked about it with Will MacAskill recently, but also Josh Green and other people on the podcast. Look, starting from scratch, I would rather my altruism be effective than ineffective. So that's good. Now, there's a couple of caveats there. One is that you can go too far. You can... Much of effective altruism is based on a utilitarian perspective. And as I've said before, I'm not really a utilitarian. I have a utilitarian sympathies in certain directions, but I'm not a fully going utilitarian. I thought that hopefully that came out in the conversation with Will MacAskill, that I tried to bring up some of the possible objections here to long-termism and effective altruism.

1:29:58.9 SC: And the second aspect that is raised is that there is something called the effective altruism community. And I think it's very, very important to separate the ideas from the community. I'm not even sure it's healthy that there is a community, there's a certain ingroupiness, there's a certain us versus them, the in-crowd versus the normies vibe that comes into the game when you have a community, but also communities can do good and work together and have an effect on the world.

1:30:28.2 SC: Effective altruism has had much more of an effect on the world than I have, for better or for worse. Do I think that the malfeasance of Samuel Bankman-Fried has changed things? For those of you who don't know, Sam Bankman-Fried, aka SBF, is someone who made a lot of money in cryptocurrency exchange called FTX and was also very vocal proponent of effective altruism and turns out to be a huge fraudster and lost billions of dollars for himself and for other people. And so the question is, does this undermine effective altruism? Well, it doesn't undermine the idea of effective altruism in any possible way, I think.

1:31:08.1 SC: The fact that some bad actor holds an idea, in my view, doesn't affect whether the idea is right or wrong at all. It might undermine one's confidence in the judgment of people in the community, the effective altruism community, that they went along with such an obvious fraudster from the start. Yeah, I think that the psychology there, the story is very, very interesting. Michael Lewis, who wrote Moneyball and The Big Short and all those things, I don't know how he does it.

1:31:44.2 SC: I don't know how Michael Lewis does it. He has a nose for these things. He was literally embedded in FTX while it was collapsing and he's going to write about it. I'm sure what he writes will turn out to be fascinating reading. But that's a story about human psychology and how we can get caught up in wishful thinking and therefore be susceptible to frauds and liars more than it is a story about effective altruism. So, my personal feelings about effective altruism are entirely unchanged, namely that I'm sympathetic to some of its statements without being a full-fledged member of the community or complete believer in it. I think that things are a little bit more complicated than the typical effective altruist would have you believe. I guess I should mention what I take to be the most effective critique of effective altruism going all the way back to Peter Singer, who's the godfather of the whole movement, which is that there's just a lot of emphasis here on charitable giving.

1:32:44.2 SC: And charitable giving is good, but it in many ways doesn't change the world, sometimes we have systematic problems that need some systematic upheaval and giving money to this or that non-government organization that is doing good is not addressing the underlying systematic issues. That doesn't mean it's bad to do it. I think that, saving people from malaria is still important even if the systematic problems are still there. You just can't let it be a distraction from the fact that there are more systematic ways to change things that will ultimately have a bigger impact. P. Walder says, "Can you explain the difference between relativistic and constructivist foundations for morality?"

1:33:26.2 SC: I think, yeah, this is actually a case where more or less the words are accurate. When you talk about moral relativism, what you're saying is that morality is relative to the beliefs of some community or something like that, right? If a community decides that something is moral, then it's moral. That's what it means to be moral. And people who are outside the community have nothing to say about that, have no rights, no leverage, to critique it. Whereas constructivism is just saying that morality is constructed. In other words, it's not out there in the world to be discovered. It's something that human beings come together and individually and collectively construct on the basis of something.

1:34:06.6 SC: And there'll be a difference between human constructivists who think that different people might ultimately construct different, perfectly plausible, sensible versions of morality because their individual inclinations and their passions are different. Whereas a Kantian constructivist will say that there is one uniquely rational moral system that you could construct. But there's nothing in any of that that says that morality is relative to some community or that anything could be a decent formulation of morality as long as some community believes it, or that some person outside the community is not allowed to critique it. It's just admitting that morality is not objectively real out there in the world like scientific facts are out there in the world.

1:34:53.8 SC: Once I have my morality, I'm going to feel perfectly free to criticize other people who don't go along with it. The critique is not on the basis that those people are objectively making a mistake, that they're making a mistake if they say 2 plus 2 equals 5 or the universe is contracting or something like that. It's a different criticism. It's saying that according to my version of morality, they're doing something wrong. Here's why I think my version of morality is good. That's it. Okay? It's not objective and foundational, but I have no reason to say I'm not allowed to make that critique.

1:35:27.5 SC: James Allen says, "In The Biggest Ideas, you talk a lot about the value of spherical cow thinking. Do you think the reason this kind of thinking is so effective historically and practically is a surprising feature of our universe or is it just a necessary feature of anything that could be reasonably called laws of physics?"

1:35:44.2 SC: I think this is a great question. I don't know the answer. I think that there's two aspects going on here. One is that... Well, just to back up a little bit, I should say, what we mean by spherical cow thinking is the idea that you can take away many of the complications in a system, analyze a much simpler toy model system, and then put the complications back in when you want to compare to reality. This is a technique that works super duper well in many areas of physics. It doesn't always work well in other kinds of sciences, biology or sociology or whatever. So the aspects I was going to mention are, number one, certainly in those areas where spherical cow thinking works, it is a wonderful technique that lets you make a lot of progress.

1:36:29.9 SC: So when that works, you're going to feel like you're getting further in your quest to understand nature more because nature is making it easy for you. That's why physicists are able to go much further and develop a lot more elaborate model building in the world because the questions are fundamentally simpler than questions of biology or sociology, etc. But the other aspect is, did it have to be there? Did the universe have to be in such a way that there are some aspects with the property that they can be analyzed effectively in this way? And that's the second part of James's question. Is it a necessary feature of anything that could be called the laws of physics? I don't think that's true.

1:37:15.1 SC: I don't see why there must be a regime of the physical world which is amenable to that kind of, let's abstract away the complications and then let's add it back in later reasoning. But I don't know. I don't have a proof or anything like that. So I think that's an interesting question. I suspect that the answer is that it's not necessary. That's my suspicion. I think that there probably are alternative laws of physics that we would still call laws of physics, but they'd be much harder to discover what they are because everything is coupled to everything else and you can't abstract away certain complications. But then maybe there's always some change of variables that make things look simple. That's what I just don't know.

1:37:56.8 SC: So Ben-Drew Harsh says, "The current system of peer-reviewed papers to get to objective truth, is this the best or quickest way to establish scientific truths?" I always think it's a little bit dicey to talk about truths and objective truths in this matter because I do think there are truths and I do think there are objective truths, but science doesn't get them in any deterministic way. Science creeps up on them in a way that might not even be monotonic. Sometimes we have setbacks, right? Science tries to uncover them, but it's important to distinguish between the truths of nature and what is actually uncovered by science. So I wouldn't say that the system of peer-reviewed papers is trying to get to objective truth. It's just trying to improve our success rate, right?

1:38:45.1 SC: I make this point very often that there are plenty of papers that are not peer-reviewed and yet nevertheless are interesting and important and true. There are plenty of papers that are peer-reviewed and published and yet are completely false. But overall, the fraction of papers that are peer-reviewed and published that are worthwhile contributions is going to be higher than the fraction of those that are not peer-reviewed. If something really matters, if a certain claim and a certain piece of scientific literature is very, very important to you, then you should more or less not care whether it appears in a peer-reviewed journal. You should read it and understand it and judge whether or not it's likely to be true, right? And that can be work.

1:39:25.5 SC: The peer-reviewed system, like many other things, is a labor-saving device. It gives you a little bit more credence that the result is reliable and respectable, but it is not a substitute for your actual judgment. Among all the labor-saving devices, is it the best/quickest? That I don't know. I think that we're in a world now where technology at least enables us to think in other ways, maybe community or peer peer-review, right? Like put something on the web and let people critique it and publish those critiques or something like that. But I really haven't put any serious thought into what is, as a practical matter, the best way to get those things done.

1:40:06.4 SC: Sandra Stuckey says, "Your discussion with Raphael Bousso made me think about what we actually mean by the area of the event horizon of a black hole and the volume inside it. After a bit of googling, I found claims that the volume of a black hole is respectively zero, infinity, or large and increasing toward the future. Which of these is right, if any, and why?" I'm not sure, but I think those are all wrong. None of those sounds right to me. Certainly zero and infinity are wrong. But it depends, it's not actually a well-posed question. That's why you can get these different answers.

1:40:41.5 SC: So think about what you mean by area and volume. Area is pretty well-defined, right? Because we have the notion of the rest frame of a black hole. And in that rest frame, we have the event horizon, and that event horizon has an area, and we can measure it or we can determine what it is using features of the black hole. The volume inside, in the context of relativity, is going to depend on how you divide space-time up into space and time. Volume is a feature of space, not of space-time. There is something called space-time volume, but that's not usually what people have in mind when you talk about the volume of a black hole.

1:41:20.0 SC: And so how you slice space-time is going to matter a lot to this question of what the volume of the black hole is. I think that depending on what black hole you have, if a black hole is more or less old and stationary and you're ignoring Hawking radiation and things like that, there will be some constant number that you can attach to that, but it still will depend on how you do the slicing. It might not be unique. Certainly, it's not zero or infinity, and I don't even think it's large and increasing toward the future unless maybe they have an idea that the black hole is growing because matter is falling into it. Maybe that's what they have in mind. But really the answer is you should think about space-time rather than volumes of space.

1:42:01.2 SC: Paul Hardy says, "What are your two or three best arguments to discount all the claims that astrology makes? I want to use them on people who are immune to science and evidence." So I will first start by saying to Paul, you've probably already lost if you start by saying, I want to use them on people who are immune to science and evidence. Number one, I don't think anyone is immune to science and evidence. And number two, if you think of the people you're talking to in that way, you're not going to change their mind about anything, maybe they are immune to whatever you have to say, in which case why are you trying to use anything on them? Why are you bothering talking to them, right? The people who are immune to science and evidence, the people who are worth talking to in the world are those who are willing to listen and think and contemplate about what you're saying. Those people are not immune to science and evidence.

1:42:45.2 SC: So I think a little bit of humility is called for here. You should ask, what is it that causes this person to have a belief in astrology? Where did that belief come from? You can't just quote facts at them or science at them and expect them to go along with your superior knowledge. But personally, on the substantive level here, my objections to astrology are the same as my objections to telekinesis, etc, namely that it violates the laws of physics. There is no way for forces to pass between celestial objects and us here on earth, especially not in a way that is especially important at the moment of your birth, rather than the moment of your conception or the moment of your high school prom or anything like that. We know what the long range forces are, they're gravity and electromagnetism. And in both cases, nearby effects are enormously more important than the effects of other celestial bodies. So it is much easier for me to just believe the laws of physics as we currently understand them and discount the predictions that appear in newspaper astrology columns, then overthrow the laws of physics for such flimsy reasons.

1:43:54.7 SC: Siraj Rajan says, "In episode 200, the solo episode on many worlds, you allude to the many worlds literally coming into being when you do an experiment and they are not located anywhere, they just exist simultaneously. Assuming space is emergent, do these parallel universes that come into existence have their own emergent space, all self-contained in them? Is that aspect also a prerequisite for these descending universes not influencing each other?

1:44:20.4 SC: So the answers are yes, and not really. The motto is that the universes in many worlds do not exist within some space. Space exists within them. Each parallel world is a parallel world. It is a parallel copy of space-time and all the things in it. They're not contained inside space. That's not really the reason why these descendant universes are not influencing each other though, that's just a mathematical consequence of how decoherence works. If the quantum state of the environment that is entangled with the state of the system in your particular world is perpendicular to the relevant state in some other world, then there's just zero overlap between those two worlds and you cannot interfere from one to another. So it's not specifically about the emergence of space in any definite way.

1:45:13.1 SC: Mark Scheuern says, "I'm curious as to how classes are assigned to faculty at Hopkins and Caltech. As an adjunct, I just take whatever my institutions give me. I'm guessing that you get more of a say and that your interests and preferences are taken into account, including letting you design your own courses." Yes, you are correct in that, but I don't think it's anything special to Hopkins or Caltech. I think this is a tenured/senior faculty issue versus adjuncts. Adjuncts are treated very badly and, I think that if I were in charge of the world, there'd be fewer adjunct positions and more permanent positions among institutions of higher education here in the United States. I am still, as of yet, not in charge of the world, so I don't know how to bring that about. But basically, every year there is a negotiation between the faculty and the department.

1:46:01.1 SC: So the department might take the form of the department chair or some teaching committee, usually. And roughly speaking, the faculty have put in a request, I would like to teach these courses. The teaching committee looks at them and says, yes, that makes sense, or no, we don't need that this year. It's certainly not you just get to teach whatever you want. Someone's got to teach junior year electromagnetism. Someone's got to do that even if no one wants to, so you might get assigned that. But people will generally try to be good citizens and take some turns teaching their favorite courses, some turns teaching the more necessary ones, and you do get the chance to design your own courses.

1:46:40.7 SC: Since I have a... As usual with me, I have a weird unusual position here at Hopkins as a Homewood professor. I am not beholden to the demands of either the physics department or the philosophy department. So basically, I get to teach what I want with the caveat that if someone else is already teaching it, then I don't get to teach it, okay? But if I design it my own course, then they... I've only been here half a year, but the impression is more or less I get to do that. But that is not always the case everywhere. Jimmy says, "I recently learned that Hawking radiation isn't actually vertical particle separation, but something more like space-time abhorring horizons and the curvature gradients they create and reducing its curvature by Hawking radiation to rid itself of them. At least that was my understanding. Can you explain the real story of black hole evaporation and why evaporation only occurs when horizons are involved? For example, if the planet existed forever, would it eventually evaporate as well to eliminate the curvature it causes?"

1:47:41.5 SC: Well, this is a tricky thing because once again, the equations are perfectly clear, but the translation into words is imperfect, necessarily, okay? So when you say space-time abhors a horizon and the curvature gradient they create, nah, that's true to some extent, but I wouldn't necessarily take that too seriously. For example, in de Sitter space, if you have a cosmology with nothing but a positive cosmological constant, there are horizons around every location in space, but they're not abhorred and they don't go away. There is a thermal temperature associated with them, much as with a black hole, but it's a static state that can last forever, unlike a black hole.

1:48:24.8 SC: So things are subtle here, okay? It is a feature of horizons. Hawking radiation definitely does depend on the existence of horizons. Planets and stars ordinary stars do not have any Hawking radiation at all. It's not that they only have a little, they have zero. And the point is that in all of these cases, you have quantum mechanics, you have equations of quantum mechanics, the equations of field theory, and the Schrodinger equation for whatever degrees of freedom you have, and you try to solve those equations in a certain background. So the background might be the gravitational field of a planet, or it might be the gravitational field of a black hole. And what you find is that for a planet or for a star, the quantum fields can settle into a vacuum state, which is just static, which just doesn't evolve in time, much like the wave function of electron in a hydrogen atom could just settle down there and stay there forever. But a black hole is more like an unstable nucleus, right? When you have the nucleus of a particle, of an atom rather, that is an unstable isotope, it can sit there for a long time, but its wave function isn't static.

1:49:33.0 SC: Its wave function is always leaking out a little bit. So the experience that we have of an unstable particle is, there it is, it's sitting there for a long time, and then at some random moment we observe it to have decayed. What's really going on is there's a wave function that is very gently evolving over time from, I have not decayed, to I have decayed, okay? And that's just a feature of the local physics of the protons and neutrons inside the nucleus, and what is stable and what is not stable. And black holes are like that.

1:50:06.6 SC: Black holes do not have solutions to the equations of quantum mechanics that are perfectly static around them, and so they change over time a little bit. And we observe that time evolution as particles being emitted from the black hole until it evaporates away completely. And as you might suspect, if that's the case, you might ask, "Well, okay, are there versions of black holes which do have stable solutions around them?" And the answer is not that many, but there are some, basically what we call extremal black holes have zero temperature and therefore do not radiate away, but we think that that's much like absolute zero temperature more generally, that you can't actually get there in any physical process. So we don't think that these extremal black holes actually exist. They're spherical cow thought experiments for physicists to play with.

1:51:00.0 SC: Chris Murray says, "It occurred to me that if it's possible for there to be in the future a time machine configured to immediately travel back to the present, there should be infinitely many such machines in the far future like Boltzmann brains. I thought the fact that our world is not densely packed with such time machines could be evidence that backward time machines are impossible." Well, logically, no, what you're saying doesn't quite follow for a couple of reasons. The most important reason is that the way the time machines would work in general relativity, if they worked at all, is that they would be connections between two different moments in time.

1:51:38.8 SC: So you can't start in the future and build the time machine that stretches into the past. You can't do that even in general relativity, even given you all of the weirdness of negative energies and wormholes and whatever craziness you want to make to use to make a time machine, you can't just start in the future and then send a tendril back and go to the past. What you could possibly in principle do is build a time machine in the present, which represents a wormhole attaching two different points in space time, and then let one of those ends of the wormhole stretch to the future. And now you have a connection between the present and the future. But if you haven't built that wormhole in the present, then it's not here. And therefore, no one can come back to the past.

1:52:26.6 SC: You can't use a time machine in general relativity to go back to a point before you built the time machine. That's one thing. The other thing is, there's no reason to suspect that even if time machines exist, that Boltzmann brain-like fluctuations would bring them into existence. Maybe that's something you could contemplate, but for that, the evidence is against it. But that doesn't mean that backward time machines are impossible. That just means that you can't build backward time machines. That just means that there aren't Boltzmann brain-like fluctuations that bring them into existence. It's certainly possible for certain things to be possible, and yet not fluctuating into existence. As I mentioned earlier in the podcast, Kim Boddy and Jason Pollack and I argue that there are not Boltzmann brain-like fluctuations in our actual future universe. So there you go. There'd be no evidence at all one way or another about these things.

1:53:20.4 SC: Jonathan Bird asks, "Why would abiogenesis ever stop?" Abiogenesis is the origin of life. "Shouldn't molecules still be coming together to form tiny living things somewhere on Earth? What are the chances that there were some initial conditions that no longer exist anywhere on Earth?"

1:53:35.3 SC: Well, there's a lot we don't know about this also, but there's a very simple counter-argument to the thought experiment that you're proposing here, namely that life already exists on Earth and has evolved for billions of years, and therefore the life that already exists is way better than any little protomolecule life at competing for the resources that we have here on Earth. In other words, even if a new life did come into existence, it's extremely plausible. I can't tell you what absolutely happened, but extremely plausible to imagine that it just dies out because it's being out-competed by the life that already exists. Living organisms need resources, energy and food and light and whatever, and the life that we have here on Earth is really good at hoovering up those resources. So I would not expect that even if life began again, it would flourish in any noticeable way.

1:54:30.9 SC: Joey asks, "Has teaching philosophy changed the way you view physics?" Well, largely no, I think because my teaching philosophy experience is literally one course this semester. My thinking about philosophy and doing philosophy over the last decade or so has absolutely changed the way I view physics. I have a much clearer idea of a lot of issues in the foundations of physics. I recently gave a talk at Hopkins to the physics department on why the foundations of physics is interesting. I shouldn't say this out loud because I'll obligate myself to do it, but at some point I would like to do a video along those lines trying to explain to people why there are issues in the foundations of physics that real physicists should be interested in. But I think that there are. I think that there are issues where physicists are trained to get the right answer in sometimes sloppy ways, and that is often fine, but some cases it is not fine. It can lead you astray, and I think that there are places in physics today where some more careful philosophical kinds of reasoning would be of use. So in that extent, yes, I have been changed.

1:55:46.6 SC: Kevin James says, "For all the people in North America and Europe who are not in favor of strong or any action on climate change, do you think they could be convinced by considering the massive number of migrants that will be created once the big middle of the world becomes less hospitable due to worsening weather events and less food security? After all, where else will they have to go?"

1:56:07.5 SC: Well, if what you're asking me is as a matter of empirical practical fact, will they be convinced by that? No, I think they will not be convinced by that, because I think that anyone in the modern world who pays any attention to what is going on and is not in favor of strong action on climate change is just deeply living in denial, right? They're clearly not wanting to accept that conclusion, and therefore they're not gonna. And therefore, if you say, well, here's another bad aspect of that conclusion, it's very easy for them to still not accept that conclusion. So I think it's fine to emphasize these problems, the problems are real. You should be honest about what they are.

1:56:44.9 SC: It's not a matter of scaremongering. Be honest. Just say, what is actually likely to happen. But again, it's not like there's some fact that we've not been telling people that if we just share with them, they will all change their minds. It's just not that simple or that straightforward. Jordan Dansby says, "Multiple popular science media have asked their readers and viewers to debate whether math is invented or discovered." The answer seems obvious to me. It is a human invention to describe the world. "Is this a real debate among professional philosophers of science or relegated to the mass consumption media?" Yeah, this is very much a real debate.

1:57:21.7 SC: In fact, we have had here on the podcast people with opposite points of view about this. Max Tegmark, who is a physicist, of course, not a philosopher, but he is a champion of thinking that mathematics is discovered, not invented, that mathematics is a real platonic existence out there in the world. And this is probably the majority point of view among professional mathematicians, at least. I'm not sure what the majority point of view is among professional physicists. But it's not a consensus point of view. There's plenty of people who disagree. So last year we began in January with Jodi Izzouni, who is a philosopher who's a champion of nominalism, which says that mathematics is invented. It's a way of talking about the world. The world exists, but mathematics is a language we use to describe it. The word nominalism comes from naming, giving words to things. And so nominalism as opposed to realism about mathematical truths. But it's very, very much not completely agreed upon. So that's a real debate, no doubt.

1:58:26.8 SC: Joshua Hillerup says, "Are there any non-physics or otherwise related to your day jobs, topics that you find really interesting but don't think you would interview someone about on Mindscape?" I try to think about this. This is a good question. There's two true things that I can say. One is that the overwhelming criterion for a Mindscape episode is that I am interested in it. So I'm not trying to be uniform or fair or comprehensive in my coverage. I try to do things that I think are interesting. Other people will think other things are interesting and they will do their own podcasts. And that's great. Let a thousand flowers bloom.

1:59:09.8 SC: Are there other topics that I do think are interesting and yet would not do an episode about? There probably are, but they're more practical or political or aesthetic things. The kinds of podcasts I listen to are not clones of Mindscape. I listen to comedians or crime podcasts or something like that on the off chance that I had time to listen to podcasts or political news podcasts or history podcasts or things like that. I think these things are very valuable and serve a purpose, but they're a different purpose than what we have here at Mindscape. So it will occasionally happen that something like that we talk about here on Mindscape overlaps with a question of current political interest, but only as a side effect.

2:00:02.0 SC: I want the questions we talk about here to be more or less universal, to be still interesting a hundred years from now or at least let's say 10 years from now. So there's no like, "Oh, here's the aftermath of the most recent election." I think that's really important and interesting. I think the politics is important and it matters. But if we're talking about politics here on Mindscape, we're probably talking about political theory and very, very big picture questions, not why did this person do better than another person in an election?

2:00:32.3 SC: I have a rough guideline that I don't want to have people who are currently in political office on the podcast. I always violate my own guidelines. We did have Andrew Lee from Australia. He's in the Australian parliament, but I think that politicians have things they need to do other than be scholars and intellectuals. So they're trying to get things done in the real world, which is good, but it's not what I want to talk about here on the podcast.

2:01:00.0 SC: Elliot Specht says, "Mindscape has had many interesting episodes on subjects which are right in your core area of expertise like cosmology, along with equally interesting episodes in far off subjects history and biology. Then there is a gap. Few episodes have discussed areas of physics which aren't your specialty like condensed matter or plasma. Is this because these fields are less interesting or because they are better covered by other podcasts? Again, I think that it's a complicated list of things. We do not reveal here on Mindscape the set of people who I've invited on, but didn't come on. Okay? But also, I do think that there are certain things that I will do a better job talking about than other things. So perhaps they are better left talked about by others. We have had condensed matter physicists on the podcast, Monika Schleier-Smith, Nigel Goldenfeld and others, but it's certainly not my expertise. And I do think that... I'm not trying to be comprehensive. I never ever promised that I will give fair coverage to every single field.

2:02:04.7 SC: This is not meant to be a judgment on the relative interestingness or importance of different fields. This is a very idiosyncratic personal decision on the basis of me thinking that things are interesting, me thinking that I can do a job talking to someone and the someone out there being willing to come on the podcast. So don't read too much into what fields do and do not appear here on Mindscape. Colleen Edwards says, "I'm new here but have been a fan of your writing and work for a while. Your book, The Big Picture was eloquently positive and personally influential. You mentioned at the end of the book that you used to go to church as a child and you also went to Villanova University, which I know is a religious university. I'm curious how your own family and loved ones responded to you going from a believer to an atheist and if you have any advice to help those of us who are going through that now."

2:02:57.4 SC: Well, giving advice like that is very, very difficult because it's always true that everyone's individual situation is different and that's especially true for something like talking to your family about your religious beliefs. My family was in some sense religious but honestly not that religious. It was more of a social thing than a deep-seated belief thing. They were never fundamentalist or especially devoted or anything like that and even Villanova, even though it was a Catholic university, wasn't all that demanding of its students in terms of being religious.

2:03:30.8 SC: In fact, there were zero demands in terms of being religious. The closest to a demand was something like you had to take religious studies courses. There were huge numbers of demands of how many courses you had to take but that's okay. I liked taking those courses. They were interesting, the presence and absence of God, death and dying, these are interesting topics that I had fun learning about. So, I never personally had any dramatic phase transition in my beliefs or confrontation with my family or anything like that. I know that other people are in a very different situation where it's very important to their families that they have beliefs and that they want everyone in the family to have a belief. So, I'm not really in a good position to offer advice based on experience about how to deal with a situation like that.

2:04:20.8 SC: I think that it's important to just emphasize to your family that you should love each other in the family regardless of your beliefs about the fundamental nature of reality. How you are as a person is what matters, how you treat other people. But that's just what an atheist would say. So, if they choose not to be convinced by that, then I don't know what to do. My only other marginally useful advice might be to make sure you're talking to other people who are on your side, who are not within your family and who appreciate where you're coming from, but are not overly judging about your family either. Your family members are human beings. They have their own pluses and minuses in terms of intellect and compassion and all those things. And look, there's a spectrum, okay?

2:05:07.2 SC: There are people... There are families that are super-duper religious but will nevertheless be supportive and understanding of children or whatever who become non-religious. There are other families that are just terrible people and will treat you badly because of your personal religious beliefs. And I think that you should deal very differently with those two circumstances. So, hang in there. There's plenty of people in the world who are not religious and plenty of people who have gone through these experiences, their whole ex-evangelical communities or ex-Mormon communities or ex-Muslim communities. Like I said, I never felt the need to engage with them because my transition as it were was extremely mild, but if something that you're going through is more difficult than that, then that might be a set of people to reach out to.

2:05:58.4 SC: Jeffrey Segal says, "The talk with Raphael Bousso was very interesting. I had not appreciated that even though black holes have incredibly high entropy, the fact that they evaporate implies that photons in empty space have even higher entropy. Is that correct? Do we have to go through black holes to get to the highest entropy state or could the universe have gone from Big Bang directly to photons in space? Actually, is photons in empty space even the highest possible entropy state of the universe or could the development of new universes increase it even more?"

2:06:30.3 SC: So, there's a couple questions there. You're only supposed to ask one question, but sometimes I let people get away with it. Yeah, it is absolutely correct that the state the black hole evaporates into, which is a set of photons and other particles moving away from the black hole and increasingly dilute gas, is higher entropy than the black hole itself was. And that makes sense. You could predict that because there's something called the second law of thermodynamics that says that entropy increases, right? So this is completely compatible with entropy increasing. There's no rule that says the universe has to go through any particular state, black holes included, to get to a higher entropy state.

2:07:12.1 SC: The specific paths that any physical system takes to go from low entropy to high entropy can in principle be very complex and hard to predict. That's not something that is subject to a simple rule like entropy increases. There's no rule that says entropy increases as fast as possible or in this particular way or anything like that. Those rules are all much more situation dependent and complicated. As far as what the highest entropy state is, it is empty space. It is not a gas of photons because we live in a world with gravity.

2:07:44.3 SC: Einstein's general relativity says that in a universe with energy in it, it's either going to be expanding or contracting. Our universe is expanding and that expansion relates to an increase of entropy of the universe. So, we're going to keep expanding and emptying out until we are as empty as can be in what we call de Sitter space as we've talked about before. Empty space with a positive vacuum energy. In fact, Aidan Chatwin Davies, who used to be a grad student at Caltech and I wrote a paper establishing this result using previous results from Raphael Bousso and O'Neda Engelhardt, two former Mindscape guests.

2:08:23.0 SC: So, O'Neda and I established that this fact that the universe expands and empties out can literally be thought of as a manifestation of the second law of thermodynamics. And why? What is the entropy? What are the degrees of freedom there? Well, I wish we knew better than we did. This comes into deep questions about quantum gravity and how to relate cosmology and curvature of space-time to more traditional thermodynamic notions, which is something that we don't have a really good handle on. So, I can't tell you really more about that.

2:08:55.3 SC: Andrea Sperini says, "Priority question. Could you explain why an airborne aircraft doesn't lose the rotational velocity it had when in contact with the ground? I understand the atmosphere is still rotating with the earth, but somehow that doesn't sound fully convincing." Yeah, I'm not quite sure what the lack of conviction here is. If an object is in empty space, it maintains its velocity, right? The velocity doesn't just get lost.

2:09:24.6 SC: In order to lose velocity, you need to somehow have friction or dissipation or something like that. Of course, the atmosphere of the earth is moving with the earth. So, if you have an airplane that is just sitting stationary above the ground, then it will not lose any energy, but of course it has no velocity, so it will just fall to the ground. But real aircrafts have engines, propellers, jet engines, whatever, and they push them forward. So, you're moving with respect to the motion of the earth and the atmosphere. If you're sitting stationary on the ground, you're really, from the point of view of the reference frame of the solar system, moving along with the surface of the earth, and so is the atmosphere moving along the surface of the earth.

2:10:10.7 SC: It's a little bit subtle because it's a rotating reference frame and things like that, but those subtleties don't matter. The right way to think about it is simply all of your motions are with respect to the earth, not with respect to some absolute reference frame out there in the universe because there is no such thing. When you take off in an airplane and the engine is pushing you in some direction, you are accelerating with respect to the earth, and that's the velocity that you continue to have.

2:10:36.0 SC: Richard says, "In the last year or so, what books did you read for the podcast that you would not have ordinarily been interested in reading? Were there any that particularly surprised you by being more interesting than you thought they'd be?"

2:10:47.6 SC: Well, again, the people I invite on the podcast are the ones whose books I want to read, no one's forcing me to do this, so there's really no books out there that I would not have been interested in reading. There's a lot of books written by Mindscape guests that I might not have found the time to read, okay? So therefore, that's why I have them on the podcast, both to talk to them and to nudge me to reading as much of the book as I can. So really, the question would be whose books are even more interesting than I thought they would be? And I always hesitate to answer questions like this because I think it's super-duper unfair to all the people who I'm not going to mention, again, the people who appear on the podcast I'm enormously grateful for. They're busy people. They take time out of their day to share some of these thoughts widely, and I don't want to rank previous podcasts or anything like that.

2:11:37.5 SC: But, if I were forced to, which I'm not, this is not a priority question, but okay, I'll pretend I'm being forced here. Again, there's a lot, and they're very different. Camilla Pang's book, The Instruction Manual for Being Humans, written by someone on the autism spectrum, was fascinating and very educational. Nick Lane's book on mitochondria, of all things and the Krebs cycle. Elizabeth Cohen's book on the political value of time. These are all really just interesting books that are all very much in my wheelhouse for being interested in. I'll also mention especially Brad DeLong's book on the economic history of the long 20th century. Again, something I am interested in, but Brad is an even better writer than I thought he would be. And his discursive style, which is a pleasure to listen to, although it makes it hard to get through as much stuff as you might want to get through in the course of the podcast, but it makes for great writing because, he illuminates all of these points with these wonderful examples, and it turns out to be a giant book, a massive tome, but well worth diving into if you haven't already read that one.

2:12:46.7 SC: CyBack says, "I had the heartbreaking experience of falling in love with one of my closest friends who does not share the sentiment. Assuming many worlds is correct, do you think there could be a real world out there where she and I are living happily ever after together?" Well, I'll give you the honest answer that I always give to questions like this, which is no, there is not a world where she and you are living happily ever after. There might be a world out there where other people who are kind of like you and her are living happily ever after together, but they're not you and they're not her.

2:13:22.8 SC: You're not the same person as copies of yourself that come through different quantum histories living in other worlds. You're you here on this earth, and that's the right way to conceptualize who you are. I feel bad. I'm sorry that you had this heartbreaking experience. This is one that often happens, but in the end, it's easy for me to say, but you're going to be way, way better off falling in love with people who do share the sentiment, and chances are good that if you keep looking around, that will eventually happen. So don't let one such event like this get you down. It's keeping you open for something much better to happen down the road.

2:14:07.6 SC: John Welborn says, "When it comes to studying science, including physics and space, is there an end game you can imagine that makes this pursuit worth the time, money, energy spent, or do you not look at it in those terms? I understand that we may discover things along the way that can help us here on earth, but is there a purpose beyond that? If so, what is it? Why should we pursue anything more in life than making sure the people on earth are safe, healthy, and happy?" Well, what I would answer in response is, why should we even pursue that? Who says that we should pursue making people safe, healthy, and happy?

2:14:42.6 SC: Not that I'm against doing that. I'm in favor of doing that, but why do you want to do that? Be serious about it. Think about what the motivation is. What is your philosophical justification for saying that that particular pursuit is worthwhile? And I think that there's plausible answers to that, but it's non-trivial to think about what they are and how best to put them. I don't think that purposes in life are given to us from outside, much like morality. I don't think it's objectively out there in the world. I talk about this at some length in the big picture, if you want to read more about it. I think that purposes are constructed by human beings, and we base our construction of purpose on preexisting inclinations and intuitions and passions that we have within ourselves.

2:15:28.4 SC: In the case of doing science, those inclinations come from curiosity, a desire to better understand our world. Some of that is very down-to-earth and survival-driven, right? The better picture we have of the world, the better we're going to do at living within it. But some of it is a little bit more lofty than that. Evolution is not very good at fine-tuning our existence and abilities as living beings to down-to-earth survival mechanisms. It does that, but there's all these spin-offs, all these extra things, the same capacities that help us as human beings conceptualize the world for purposes of survival and flourishing and reproduction. Go beyond those. I want to understand the world. I am curious about it. That's why it's worth spending, because I want it. That's why it's worth spending time on this. And that leaves completely open the idea that other people might not find it worthwhile, and that's fine.

2:16:27.5 SC: I don't judge them to be faulty because they don't share the same drives and desires and intuitions as I have. And it's completely compatible in my mind to want to understand the world better and to make people on earth safe, healthy, and happy. Maybe, not to be too insinuating about it, but maybe understanding the world better helps us make people safe, healthy, and happy.

2:16:52.9 SC: Jim Murphy says, "I'm curious what it's like to be a public personality as well as a professor. Do you have any star-struck students? Do other professors treat you differently?" Short answer is no. I don't have any star-struck students, and other professors don't treat me differently. There's different levels of being a public personality. I'm not the level of, I don't know, Dolly Parton or someone like that. I can easily walk down the street without being recognized. Of course, to people who listen to the Mindscape podcast, they are used to hearing my voice, but most of my students and very few of my colleagues are Mindscape listeners. I did have one student recently come up to me and say, hey, yeah, I was listening to someone else's podcast, and your name came up, and I forgot you're famous.

2:17:40.5 SC: I think that you're just like my professor. And I think that's basically what people have as the attitude. The number of Mindscape listeners, sadly, still very tiny compared to the number of people in the world or even the number of people who buy my books or et cetera. So no, not a lot of celebrity treatment just within the academic environment.

2:18:02.3 SC: TO Alexander says, "Let's assume panpsychism or pan-experientialism is the case. And for the sake of argument, let's also assume that it is an emergent phenomenon but at a very fundamental level, not as fundamental as an electron or proton, but still quite small and ubiquitous. Wouldn't that then necessitate the constant collapsing of wave functions at every point where the consciousness particles exist?" Follow up, "Could that be one possible explanation for why all of us macroscopic humans more or less experience the same universe?"

2:18:34.0 SC: So I'm not at all sure that the assumptions of the question fit together nicely. If you're literally panpsychist or pan-experientialist, then I don't think you can say it's an emergent phenomenon. I think that the whole idea of panpsychism is to say that consciousness is absolutely fundamental. So when you say panpsychism but not emergent or only emergent, not fundamental, not existing electrons and protons, I don't know what that means or how that would work.

2:19:03.3 SC: To the other part of the question, I don't know what the answer to that one is either, but here it's facing the very real issues that all of these kinds of proposals face when they try to reconcile themselves with reality. That you can't just add things like consciousness or minds to the laws of physics and not have serious consequences there. What do you mean by consciousness particles? Are there consciousness degrees of freedom? Can you have consciousness decoherence? I don't know the answer to those questions. I suspect there are no answers to those questions because all of these ideas are fundamentally ill-defined. They're just not that specific enough to provide answers and if they were, they would probably be ruled out by experiment. So in terms of could this be an explanation for why we all experience the same universe? No, you don't need an explanation for that. The explanation for that is that there is a universe and we're in it. That's the explanation.

2:20:02.6 SC: Bits Plus Adams says, "When I came across a passage about conservation of information while reading the Biggest Ideas, I wondered what symmetry is associated with this conserved quantity. I understand Noether's theory to be for each symmetry of the Lagrangian there is a conserved quantity. Does information fit into this framework?" I think the answer is no, it doesn't because you're pointing out something that is very true about Noether's theorem. For each symmetry of the Lagrangian there is a conserved quantity. It's not the other way around. It's not true that for everything conserved there must be a symmetry. The fact that information is conserved is a basic feature of the setup that has Lagrangians in it in the first place, information would be conserved even if there was not a symmetry of the Lagrangian. As long as you have a Lagrangian, this is a particular way of formulating dynamical laws of physics, information will be conserved. There's other non-Lagrangian based laws of physics where information is not conserved, but our universe, at least for we many worlds people, the Lagrangian picture seems to be pretty good and therefore information does seem to be conserved in the wave function of the universe.

2:21:10.2 SC: Michael Ayling says, "To explain the uniformity of the CMV, has anyone proposed an alternative to thermal equilibrium? Could some other physical process have led to it all being the same temperature and expanding universe without the need for inflation?" So you have to be careful here because of course thermal equilibrium does not explain the uniformity of the CMV. We live in a universe with gravity and in a universe with gravity thermal equilibrium does not look smooth. You get lumpy regions with black holes, empty regions elsewhere. So the CMV is smooth and the temperature spectrum, the spectrum of the radiation, is that of a black body in equilibrium, but it's the spectrum of an object in equilibrium without gravity. But it is not an object without gravity. That's the mystery. Why does it have that particular spectrum even though it is not that kind of thing?

2:22:06.0 SC: So inflation provides one way to do that, a way for the matter degrees of freedom to thermalize even though the gravitational configuration of matter is very very much out of equilibrium. Are there other ways to do it other than inflation? Well, the only real good way of doing it other than inflation is just to posit that this is some initial condition, right? Maybe the wave function of the universe just is that way or maybe God just made it that way. That's not to say there's not some other theory that is not inflation that will be good but we haven't come up with it yet.

2:22:38.3 SC: Ed says, "In the Futurama episode, Crimes of the Hot, the problem of global warming is solved by moving the earth farther from the sun. Leaving aside the engineering challenges of such a course, do you have an opinion or comment on the long-term possibility of controlling the earth's temperature by adjusting the earth's orbit? As a bonus question, do you think it would be easier to physically move the entire earth or to fix global capitalism such that carbon emissions can be reduced quickly?" So yeah, I think it's easier to fix global capitalism. The idea of moving the earth physically farther from the sun is very very very very far away from being practically feasible. It is much much easier to imagine fixing the earth's atmosphere one way or the other. Even if you go to very science fiction-y scenarios like inventing little microorganisms that will eat all of the greenhouse gases etc.

2:23:34.7 SC: That's not completely science fictional. Maybe we'll be able to do that someday. Maybe we'll be able to geo-engineer or that's not really the right way to do it, right? Terraform the earth itself, okay? That's very very difficult. Still way easier than moving the earth around its orbit. Fixing capitalism is actually even easier than that. Is it easy? No. But you have to be a little bit realistic about the different levels of complexity involved here. At least if nothing else, it's a good reminder of how difficult it would be to terraform another planet like Mars or Venus or whatever. We can't even get our act together to fix the earth's atmosphere. Even though it's already pretty good, we're just breaking it. We can't prevent ourselves from breaking it. Just imagine how difficult it would be to completely alter a whole other planet's atmosphere.

2:24:25.1 SC: Benjamin Barbrel says, "Priority question. Do all of the branches in many worlds multiverse look our own familiar universe, homogeneous at large scales etc, or would some of them appear somewhat exotic to our eyes? Is our branch typical, if that means anything?" Well, again, we don't know. We can't visit these other universes, but it is completely plausible that other branches look very very different. You would like to think that our branch is typical in some sense, but this is just, yeah, maybe I even shouldn't... It is a priority question, so I have to answer it, but my answer is we don't know nearly enough about the wave function of the overall universe, including other branches of the wave function, to answer a question like this. I'm not sure whether we ever will, but we can ask it. We can think about it. I just don't have any informed basis for speculation.

2:25:17.6 SC: Danny Avidin says, "Would you mind sharing your thoughts about morality and meat eating? I don't mean it antagonistically. It's just that as a public intellectual and a figure of high moral intellectual standing, I wanted to hear your thoughts on the matter, especially given your love of cats. Of course, we all fall short of our moral aspirations and contain contradictions, but how does a cow or pig fall short of the confines of your circle of empathy if a similar mammal doesn't?" So I have talked about this before, so I can just say, Danny, you might not have heard it, but I'll try to put it as clearly as possible.

2:25:53.2 SC: I'm not sure what the love of cats has to do with it. I don't have any moral objection against other people eating cats. I don't want them to eat my cats. I will prevent that from happening because I have bonded with my cats, but I do think that human beings are different than other kinds of animals, including mammals. I'm very open to the idea that there are other species that are not human and yet nevertheless should be protected and not eaten, but I don't think that cows and pigs or even cats and dogs fall into those categories. And my reasoning is that I don't attach any metaphysical essence of worthiness to lives. I'm a pragmatist about this. I think that I don't like it when people or even animals suffer or have pain. And so I don't want any animals to needlessly suffer, whether or not they're used for food or not. That is definitely a place where I guess if you want to talk about it in terms of a circle of empathy, I'm very empathetic about those kinds of things. But I think that there's an important difference between human beings and cows about how we live in the world and how we conceptualize death.

2:27:10.3 SC: I don't think that cows really have a picture of what it would like to not be not existing, to visualize hypothetical counterfactual futures in which they have died and to fret about them. And I think that the relationship of human beings with respect to past, present and future is different than those in other animals. And we've talked about this on the podcast before. We'll talk about it again. But I think that's a crucial difference. And I think that that ability to fear death, to fear not just to instinctively fear that you're in danger, which certainly cows can do and other animals can do, but to mentally visualize the hypothetical prospect of being in danger just for abstract intellectual reasons. Like if someone tells you using words that they are going to kill you, okay, or that you're in danger of dying for something, you are afraid already, right?

2:28:10.6 SC: Just because of words entering your ears and listening to them. And that's the thing that other animals just don't have. They don't have that capacity to abstractly reason the same way. To me, that's a difference. There's no intrinsic value to life. All lives end. We live in a world where lives are finite. My life will end. Ariel and Caliban's lives will end. Ariel and Caliban, by the way, certainly not vegetarians. They have no problem at all. Cycle of life. They will eat. They will be predators. And they will eat other animals with no qualms. And that happens in the world. And I don't think that you can object to that reality. You can try to make a world in which there is less suffering and there is less needless pain. And that is a world that I am in favor of trying to make.

2:29:04.2 SC: Justin Wolcott says, "In the big picture, you say we can't pick out one moment or a particular aspect of any one moment and identify it as the cause. Different moments in time in the history of the universe follow each other according to some pattern, but no one moment causes any other. And then Justin says, I'm trying to understand why it is illegal to say the cat caused the ball to fall on the floor, but legal to say the ball is on the floor because of the prior state of the universe plus the laws of physics. Is there any way to restate this in a way that involves a cat?'

2:29:36.0 SC: So I'm trying to understand why you are asking this question, because I would never say it is illegal to say the cat caused the ball to fall on the floor. And I would not emphasize that you should instead say the ball is on the floor because of the prior state of the universe plus the laws of physics. What I was saying in the quote is you cannot pick out one moment, including the prior state of the universe, identify it as the cause. The important thing here is that there is a crucial difference between the fundamental laws of physics and the emergent higher level description that we use to go through our everyday lives.

2:30:13.7 SC: At the fundamental level, there are patterns, there are laws of physics that relate the configuration of the universe at one moment in time to the configuration at other moments in time. It is not useful to think about those patterns as a series of cause and effect relations at the fundamental level. Rather, think about them as the laws of physics. That's what they are, whether it's the Schrodinger equation or F equals MA or whatever. A web of cause and effect relationships becomes a relevant and important way to think about the universe at the higher emergent level, precisely when you have cats and balls falling on the floor. It makes 100% sense to say the cat caused the ball to fall on the floor.

2:30:58.1 SC: It does not make sense to say that is a deep down feature of the fundamental nature of reality. It is an emergent higher level description because we live in a world with macro states and an arrow of time from which you can sensibly ex post facto define cause and effect relationships.

2:31:19.4 SC: Felix Dare asks a priority question. "Since reading your book, I'm left with the inescapable idea that for each decision I make, there's another universe identical to this one up until that point, but in which I took the other decision. My understanding, if the multiverse theory is correct, is that this is happening constantly driven by ongoing quantum level events in my brain, such that there is a different universe with a different version of me for every possible decision that I ever could have taken. I'm struggling to reconcile this with any meaningful sense of agency or free will, so I would be grateful to any explanation as to what I have got wrong."

2:31:54.6 SC: So there's two things to say about this. One is, I tried in the book to very carefully separate the idea of branches of the wave function coming into existence from the idea of human beings making decisions. Human beings making decisions do not cause different universes to come into existence. Now if you're trying to be careful about it, which I was trying to be, you might say the different quantum mechanical processes that do cause different universes to come into existence might be interpreted at the macroscopic level as human beings making decisions. Okay?

2:32:34.6 SC: So I'm not sure whether that distinction came through in your reading, but I hope to emphasize it here. As far as free will is concerned, there's literally no difference in the discussion of free will between this universe with a deterministic equation the Schrodinger equation and many worlds versus a classical universe with a deterministic equation Newton's equation. In both equations, in both universes, you follow the laws of physics. That's what you do. Whether or not you would like to speak about those universes in terms of free will, has nothing to do with the nature of the fundamental laws of physics.

2:33:12.7 SC: What it has to do with is, is there a notion of free will that is useful to us, that is compatible with us being physical systems following the fundamental laws of physics? I think there is. I do not talk about that in great detail in Something Deeply Hidden, the book that you're talking about, but I do talk about it in some detail in The Big Picture and elsewhere. We talked about it here on the podcast with Jinen Ismael and other people. This is called compatibilism. Free will has nothing to do with the fundamental laws of physics. It has to do with how we talk about human beings at the higher emergent level and therefore is completely compatible with whatever the fundamental laws of physics happen to be.

2:33:56.3 SC: Tim Giannitsos says, "You mentioned in another podcast that there is a theorem which seems to indicate that if the hidden variable interpretation of quantum mechanics is true, any prediction it comes up with will always be the same as in the many worlds interpretation. However, you were skeptical of this implication of the theorem was true. Have you found a resolution to this since making that statement?" No, I have not. I don't suspect to do so anytime soon. That's just something that is percolating in the back of my mind, not something that I am putting a lot of effort into at the present moment. Just to fill out what is going on here, in Bohmian mechanics, which is one particular version of hidden variable theories, AKA the pilot wave theory, there is a notion called equivariance. So you have both the wave function and you have variables that represent the positions of particles or what have you.

2:34:45.0 SC: And the equivariance idea says that if you start the distribution of particle positions in a random selection that follows the probability distribution given by the wave function squared, then it will continue to follow the distribution given by the wave function squared. So there is an extra big leap you need to make in these hidden variable theories that the extra variables that you have invented line up with the Born rule of quantum mechanics. You can prove that or you can claim to prove that if they do initially line up, they stay lining up. And then there are arguments that maybe even if they don't, they will evolve into that, but those arguments are a lot more dicey. So I would to better understand both the equilibration aspect as opposed to equivariance, which is if you start out of that distribution, do you truly evolve to it? I worry about how that fits in with Liouville's theorem or something that, but it's not classical mechanics, so you can't just invoke Liouville's theorem in a simple way.

2:35:51.9 SC: But the other is any theorem always involves assumptions and famously in physics, there's a whole bunch of theorems that have turned out to be irrelevant because the assumptions behind them are not physically true. So I just don't know exactly what the assumptions of this theorem are or whether or not you can wriggle out of them in some other situation or whatever. I'm curious about it, but I just don't know. Probably not, but I'm just curious.

2:36:18.8 SC: Owe, O-W-E says, "I've recently been reading general relativity for babies to my 16-month-old son. I don't think he gets it, but maybe in time. One page talks about how a spinning mass drags space with it, similar to how rest mass warps spacetime. I believe that an object spinning in space will continue to spin indefinitely, absent an external force due to angular momentum being conserved, yet changes to spacetime require energy to create. How can a spinning mass drag spacetime without expending energy to do so?"

2:36:52.4 SC: Yeah, this is a very good question and perhaps disappointingly, the answer is that the word drag is not really completely appropriate here. You've almost put your finger on the right answer here. It is similar to how a rest mass warps spacetime. So if you have a mass at rest that is not rotating, it will have around it a gravitational field, a warping of the geometry of spacetime. And if the mass is just sitting there not doing anything, the warping of spacetime around it will also sit there and not do anything. It will be static.

2:37:25.5 SC: Now if the object is rotating, then the configuration of spacetime around it will also bend in a way that is related to that rotation. But it doesn't get dragged in the sense that there is some force that is dragging it back, okay? It's not really like friction on a floor or something like that. The statement is simply that the static eternal configuration of the spacetime reflects the angular momentum of the body in it that is spinning. There is no energy being transferred from the spinning mass to spacetime. It's just that the solution to Einstein's equation for the spinning metric has a fixed angular momentum and that's it. So your intuition is correct but this is precisely a case where the attempt to translate things into the English language has led your intuition astray.

2:38:27.0 SC: David Dubrow says, "Is the concept of weak emergence related to entropy in this way or am I missing something? Both seem to be a way of measuring our lack of complete information about the structure and dynamics of entities at lower levels when observed from higher levels. Entropy seems to be measuring our inability to detect the difference in microstates when observed from a macro point of view. Emergence seems to be a way of characterizing the exact same thing as far as I'm seeing, namely that there are larger patterns composed of lower level entities and we don't need to know the exact happenings of the lower levels to see the patterns at the higher levels."

2:39:01.7 SC: Well, they're related but they're not the same thing. So they're both related to the fact that in the world in which we live, there are macro states. So I would say in some sense emergence is prior to entropy because the reason why entropy is a useful interesting concept is because we can take a system that is made of many microscopic constituents and coarse grain it into macro states made of potentially many different possible micro states corresponding to the same macro state. So that is a feature of emergence and then we use that feature to define entropy in the emergent higher level description where you have the macro states. The entropy is the logarithm of the number of micro states that would have looked like that macro state.

2:39:47.6 SC: But the point of it is a little bit different, right? Emergence is useful when we can take those coarse grained macroscopic descriptions and from them make a theory, use those macro descriptions and observable macroscopic properties to predict what will happen next to get some handle on how the universe behaves even in the absence of the microscopic information. Whereas the entropy is keeping track of something more thermodynamic.

2:40:19.6 S2: Again, it's very closely related but you know as the origin of entropy was from thermodynamics in the 19th century where entropy was reflecting the fact that certain processes happen in one direction of time and not in the other direction of time. So you could have emergence even without that, right? With the earth going around the sun being followed by just its center of mass position and momentum is an example of emergence. You don't need to keep track of all the microscopic atoms and molecules in the earth to keep track of its motion around the sun, but no entropy is being generated or anything like that. So I would say that entropy is a special case of the usefulness of coarse graining and emergence.

2:41:04.2 SC: Douglas de Young says, "Is the concept of true randomness sensical? It seems like something from nothing or information from nowhere. I appreciate that many worlds avoids the random outcomes of measurement by positing a larger deterministic possibility space. Well, I'm not going to give you a definitive answer here. It depends on what you mean by true randomness. There's different kinds of randomness and there's different kinds of truth. So the way that we usually talk about it in philosophy of sciences is probability objective or subjective. In other words, is there some sense in which when you say that something is a probability of happening, you're really just reflecting the fact that there's something that will definitely happen but you just don't know, right?

2:41:47.9 SC: It's your knowledge, your epistemic state, in which case you would classify that probability notion as being subjective at the bottom level because it's relative to your knowledge versus there's no possible thing you could know that would prevent this from being a probability, okay? A true objective chance. And you might say that in objective collapse models of quantum mechanics, there is just a true objective probability there. Even there, I'm much more of a subjectivist about probability myself. I think that if it is true, that in the fundamental laws of physics, I don't think this is true, but if it were true, that given the complete state of the universe now, we could not deterministically say what the future holds, but we could say on the basis of past frequencies that there is a probability of something happening this way versus that way.

2:42:42.5 SC: I would still want to say that there is a possibility of something happening in the future. I would still want to say that's not an objective probability, that's just something we don't know, namely the future of the universe. So this goes hand in hand with me being an eternalist about time. If you think that what exists is all moments of time, but you just don't know what is going to happen in the future, then you can be someone who believes in truly stochastic laws of physics but still treats probability as fundamentally subjective. If you're a presentist about time and you think that the fundamental laws of physics are stochastic or chancy, then you're going to be more likely to be an objectivist about probability.

2:43:21.8 SC: Kevin O'Toole says, "In the October AMA, you said there was no experiment you can do to prove the past hypothesis. However, it seems that any universe where the laws of thermodynamics are true and the past hypothesis is false should make some very strong, very falsifiable predictions. The theory in that universe would say that with overwhelming probability, our experiences are explained by a small world fluctuating from equilibrium and by illusory stuff outside that world just enough to make us think that the universe is bigger and explain what we've observed so far.

2:43:52.8 SC: All that's true, but it does not get you the result, Kevin, that you want to get because you have to distinguish between asking, given this universe, in other words a universe where there really just are random fluctuations and we don't have the past hypothesis, what would you expect to see next? That is a question you can ask and that is what you're talking about. But the theory choice question about doing an experiment to prove the past hypothesis is not that question. That's just calculating the likelihood function in Bayes' theorem. To choose between the theories, you have to multiply that likelihood function by the prior. So the question is not given this theory, what do you expect to see next? But given what you see, what is the most likely theory?

2:44:41.8 SC: And given a universe that is randomly fluctuating, it is true that given what we see now, the next thing we should see is just some thermal equilibrium random fluctuations. But given that the next thing we see is not thermal equilibrium random fluctuations, if that universe were real, it would still be overwhelmingly likely that all that stuff had just fluctuated into existence, okay? So that's why you need to assume the past hypothesis. You can't actually be a good Bayesian and rule it out by data because under that set of assumptions that all configurations of stuff in the universe are equally likely, the prior probability that you're seeing things randomly fluctuate into existence is so overwhelmingly large that you can't beat it down just by likelihood functions and collecting new data.

2:45:32.9 SC: Brent Meeker says, "You've written a paper with Jackie Kaufman about violation of conservation laws and quantum measurements. You said that energy was only conserved on average but not in a single measurement. If I understood it correctly, it would also apply to the measurement of any conserved quantity, not just energy. Does this provide any test of many worlds versus a cubism or the transactional interpretation? Do all interpretations of quantum mechanics imply non-conservation in measurements?" So a couple of clarifications here. I did write such a paper. We did not say that energy is conserved on average. Energy is not conserved on average. It fluctuates up and down but it fluctuates up and down by sizes that will generally decrease with time. The fluctuations in energy go down over time so that by now, in the late universe, energy looks pretty darn conserved to us. You might think that this should apply to the measurement of any conserved quantity, but there is a loophole there. You can be in a universe that has a definite value of other conserved quantities, that has a definite value of momentum or angular momentum or electrical charge or whatever. And in that case, there are zero fluctuations whatsoever.

2:46:47.5 SC: Why can't you be in a universe with a definite value of energy? Because energy is special in quantum mechanics. Energy is the thing that tells you how the wave function evolves with time. Remember the Schrodinger equation says the Hamiltonian operates on the wave function to tell you the time derivative of the wave function. The Hamiltonian is just the energy.

2:47:10.3 SC: So if you are in a state with definite well-defined energy and nothing ever changes, literally nothing happens in such a universe. This is a subtle and tricky set of issues that people debate about but that is the basic reason why we don't want to say that we live in a universe that has a definite energy. We have an average value of energy, an expectation value. At least that's the way you would talk in many worlds. So when you compare many worlds to other versions of the story, the shortcut is to say that in any theory of quantum mechanics where the energy of a quantum state is well-defined as the expectation value of the Hamiltonian in that state, then energy is not conserved, whether it's MWI or anything else.

2:47:58.8 SC: But there are other formulations of quantum mechanics. In something like cubism, you don't even say that the quantum state is not physical. It's just a state of your brain. So you don't assign an energy to that thing. Therefore, there's nothing there to be conserved. Likewise, in hidden variable theories, you might want to talk about what the other variables are doing when you talk about the energy, but you don't know what the other variables are. So you just never know what the energy is. So that's why it's a tricky fun thing. And I hope that other people dive into this in their own favorite interpretations of quantum mechanics.

2:48:33.2 SC: Qubit says, "Liouville's theorem tells us that for a classical Hamiltonian system, the phase space volume stays constant. How is that possible for a chaotic system where neighboring trajectories move away from each other exponentially?" Well, there's two aspects here. One is that you have some area or some volume in phase space. And in a chaotic system, usually its volume does stay constant. That is what the theorem tells you. But it gets stretched and pulled into taffy with long little tendrils while keeping the overall volume constant. Why can that happen yet it's hard to visualize it? Well, it's because phase space has a much higher dimensionality than you can visualize very well.

2:49:19.2 SC: So I know what you're thinking. You're thinking of something that is just two-dimensional phase space. And it's hard to get a two-dimensional phase space with truly chaotic dynamics to it. You usually have a bigger phase space than that. And so in the real world, in a higher dimensional phase space, that original blob of volume in phase space will be distorted, but its volume will stay constant, even if the system is chaotic.

2:49:44.6 SC: Moshe Fader says, "With the World Cup in progress, I'm curious how you as a fan of basketball, a game with lots of scoring, feel about soccer, a game with very little scoring. Personally, I think soccer is a very poorly designed sport that is only so globally popular because it's so much more fun to play than it is to watch. Do you agree that soccer could be improved, be more entertaining? And if so, what changes would you suggest?"

2:50:07.7 SC: I'm a pluralist about appreciating sports. I think that there's different ways to appreciate sports. One of the reasons why I like basketball is because there is a lot of scoring, not because scoring is intrinsically exciting, although that is arguably true, but because I think it averages out over fluctuations, right? Over the course of a basketball game, you can always hit a lucky shot here or there, but the chances that single lucky shot will be decisive are very small because there's an integrated effect of the whole effort that both teams are putting in over time. Whereas in not just soccer, but any other sport where the number of scores per game is much lower, random fluctuations will generally play a much larger role. They're not definitive, they're not, the whole story by any stretch, but they will be more important than in a game where you have lots of chances to average over those fluctuations.

2:51:03.8 SC: But I get it if people like to see the chess match of teams fighting for every little advantage in able to be... In order to be able to score at all, right? You can easily say that you the fact that scoring is precious. I'm not going to say that people are wrong to like that. You should whatever sports you like. Having said that, there is one way in which soccer or football, as they call it in the rest of the world could obviously be improved in the World Cup, which is those penalty kick shootouts at the end. Those are terrible. That is absolutely just saying, okay, we're going to flip a coin and you can do better than that. You can do... I haven't watched the World Cup this year. Maybe they haven't been doing better than that this year. I'm not sure. But that's always annoyed me by the World Cup, which otherwise I quite enjoy.

2:51:53.0 SC: Shambles asks, "Do you get any sense that life as in the origin of life is or was inevitable?" Well, no, I get no such sense. My sense is that life was hard to get started. Otherwise, it would be much more ubiquitous in the universe around us. But guess what? Nobody cares about my personal sense. I think that these are issues where our data is very, very, very meager. And we can have impressions or get answers and we can have impressions or guesses or priors, but we shouldn't be too wedded to them. We'll be able to collect a lot better data going forward.

2:52:25.0 SC: Stuart Hain says, "I have a question about the cosmic microwave background. When I think of a supernova, I think of a flash of light being emitted and then traveling past us. If we're not looking, we may not see it. However, the CMB appears to be ever present, even though it originated from the surface of last scattering. CMB effused all of space and was moving in all directions and therefore it will be ever present?" Yes, this is the question I in AMAs. The answer is yes. You asked the question and you also answered it. We talk about the surface of last scattering, but it's better to think about a moment of last scattering throughout all the universe.

2:53:02.0 SC: Think of the early universe. It's more or less homogeneous, more or less the same everywhere. It's evolving in time because space is expanding and matter is diluting away, cooling off. At some moment, things recombine, the electrons come back with the protons and you get atoms. That's what we call the moment of last scattering. The surface of last scattering is just the intersection of that moment with our personal past light cone.

2:53:27.9 SC: And as time goes on for us, our light cone moves out just a little bit. As we look at the microwave background from moment to moment, we're not looking at the same place in the microwave background. It looks the same place because the microwave background is very, very smooth. If you look at the microwave background once and then a year later, the photons that you see came from one light year further away. That's almost no difference as far as the CMB is concerned. It looks more or less static and fixed, but in fact, you're looking at slightly different places.

2:54:05.1 SC: Rob Patro says, "The recent drama surrounding Twitter has renewed debate over the optimal bounds of speech on online platforms. As someone who seems deeply dedicated to debate and free speech, but also cognizant of the shortcomings of absolutism and aware of the importance of practical solutions, I'm curious about your thoughts on this topic. How do you think that we as a society should balance the necessity of open and free debate with the dangers posed by speech that incites violence and constitutes harassment, particularly in the context of private platforms like Twitter that start to border the space of a public utility?"

2:54:37.9 SC: I don't think I can give an answer that is any better than all the implications here in the question that Rob asked. I think that there is a lot of drama surrounding Twitter. I'm contemplating just decreasing my use of Twitter, honestly. Twitter has been great to me, and I get a lot of value out of it. But both with Elon Musk buying it and letting a lot of more disreputable people back onto the platform and generally lowering the tone overall, plus the fact that everyone else is just talking about drama on Twitter rather than talking about substantive things, it's become less enjoyable for me to go on there. And so I don't know what I will do. I'm still there, and I might just stay there or I might leave or I really don't know.

2:55:23.8 SC: I think there's a lot of interesting questions here. Everyone knows, everyone who's thought about these in detail and with care knows that you have to moderate social media. You can't just let everyone yap about whatever they want. Or if you do, that's fine, but no one is going to join you because there's a lot of hate-filled, terrible voices out there and who no one wants to listen to.

2:55:46.3 SC: So moderation is important and necessary, if only to obey the law, but also just to create a space that is pleasant and people want to be in. You can't just let anyone say anything they want. That is no way to run a social media network. You see that with Elon Musk inviting a bunch of people on and then kicking them back off again or changing a rule and then changing it back again. There are reasons why these rules are there. What should the rules be? I think that's an honest, difficult question. I would, ideally, in the utopia, we would have different social media platforms that maybe could even talk to each other, but people would have an ability to choose what content they were exposed to.

2:56:29.3 SC: So people could, in some sense, choose among a menu of possible moderation strategies or something like that. But you have to do some moderation. You have to balance different considerations. You have to balance the considerations of open and free debate with considerations of peaceful coexistence and harassment and various kinds of things. Now, the very end of the question becomes super interesting and difficult where Rob brings up the idea that Twitter starts to border the space of a public utility. Twitter is a private company and to some extent, let the private company do whatever it wants as long as it's not actively harming other people. But if it does become almost like a monopoly or a special shared public space, then is there a motivation for government to become involved and to curate it or to regulate it?

2:57:24.9 SC: I would want to keep that to a minimum because we've seen in history that cyberspace, the internet moves very quickly. It wasn't that long ago. In my lifetime anyway, people thought that Microsoft and Microsoft Explorer were a monopoly on the internet and that didn't last very long, right? I think Twitter could easily go away. I don't think that Twitter is in any sense necessary. So Twitter could just die, in fact, might be dying in front of our eyes right now. I don't know. Maybe it's not. Again, I hope it's not. I would much rather live in a world where Twitter were flourishing and pleasant to be on. But it could go away. It could be replaced by something else. Look, if Google came along and just did more or less exactly a clone of Twitter with more or less reasonable content moderation and an edit button, everyone would move there.

2:58:15.0 SC: I don't see why... It is hard to do. Of course, there's enormous infrastructure and things like that. That's why I said Google rather than someone in their garage. But there's no inevitability to these giant social media platforms. Their assets are rather intangible, right? The asset of Twitter is the user base. It's not some factory or something like this. This is what we talked about with John Quiggin when we talk about interest rates and the new disconnect between interest rates and company valuations, because Twitter is the people and the people could easily move tomorrow.

2:58:56.9 SC: So Twitter better get its act in gear. Otherwise, everyone will just go somewhere else. That's why I don't want government to regulate it too much. Because it's not inevitable. If it becomes inevitable, if it becomes something as necessary and important and unique as roads or airways or electromagnetic radio frequencies, then maybe there should be more government intervention. Bert Rich says, when it comes to the great filter, scenarios like climate change wars and pandemics are being discussed. But my personal candidate is missing. A failed physics experiment may be always the same one. For example, some new particle being created that results in a cascading all planetary matter pulverizing effect. As an insider, is this completely out of the question or something that keeps you up at night? Most other scenarios are, in my opinion, too slow and not devastating enough. I'm confident that we could fix or survive as a technological species just about all of them.

2:59:55.5 SC: So look, I've said it before, my very straightforward solution to the great filter is that technological civilizations are just super duper rare, either because life is rare or because complex eukaryotic/multicellular life is super duper rare. Because you're right, most of these other things about climate change wars, pandemics or whatever, maybe they'll happen some of the time, but they're not inevitable if this happens thousands of times or millions of times across the galaxy, but maybe life just never forms or evolved life, super advanced life never forms, that's much easier to believe.

3:00:28.8 SC: As far as the new particle being created, there's a very strong argument against that possibility, namely that everything we do here on Earth is done at much higher energies and much more often out there in the universe. High energy cosmic rays bump into each other, bump into the Earth. They do all the physical processes that we try to reproduce with all of our particle accelerators, etc, here on Earth. People can and have tried to wriggle out of that very strong bound on what can possibly happen to try to cleverly invent some scenario where something could uniquely happen in a particle accelerator, but the smart money is that's just not going to happen. So that is not something that keeps me up at night or does it keep up as far as I know any other particle physicists that I know about.

3:01:18.1 SC: Kevydin says, "The political climate in the US has grown increasingly tense and partisan in recent years with several unprecedented events occurring, Roe v. Wade overturning, January 6th riots, etc. What is it about our current time that is causing such a tense political climate and do you see any positive way out of this and into a more normal political climate?" Yeah, I think it's, I hate to say this, it's complicated, this seems to be the theme of this month's AMA. This is a real issue, there's a real question. This is not, oh, there's some simple answer that has been overlooked. Part of it is at the level of politics, as we discussed with people like Will Wilkinson and Ezra Klein, there is more polarization.

3:01:58.0 SC: Politicians have done the game theory calculation that if what they want to maximize is their chance of getting reelected rather than what is best for the country, then stoking dislike of the other political party is the way to go. It makes it harder to compromise and get things done, but if you don't care about compromising and getting things done, all you care about is getting out your vote, then that's the way to go. And this has been creeping up on us for a while, but at least since the 90s it's become very vivid and very obvious. But there's other things going on. I do think that modernity, the modern world, modern technological industrial society gives people the impression that they are left behind and they feel bad about it.

3:02:46.0 SC: There's a lot of people out there who feel powerless, who do not feel that the democratic institutions are on their side, who do not feel supported, that don't have either jobs at all or don't have good jobs. They have jobs that are not very meaningful, not very high paying, not very secure, etc. We don't have good health care and things like that in the United States anyway. And this builds up resentment, it builds up dislike of the system, and people don't always react rationally to that feeling of feeling powerless. And so they're more likely to overthrow the institutions or not to respect the institutions that they have. And then other people take advantage of that, right? They inflame those sentiments and use them to get power. It goes back to the podcast that I did long ago with Edward Watts about the end of the Roman Republic, where the Gronkowski brothers, who with the best of intentions, maybe, they wanted to be populists and they wanted to share the land and distribute it from small nations to large nations, and they wanted to share the land and distribute it from a small number of very rich people to a larger number of citizens.

3:03:56.6 SC: But the way that they did it was to assemble a mob and to pressure the Senate to go along with them. And then once you open that Pandora's box and you realize, oh, the way to get my political goals reached is not to pass a bill, but to assemble a mob, that becomes a way of operating, that becomes something you can do. And maybe we're getting there in the United States right now. Do I see a positive way out of this?

3:04:26.6 SC: I'm honestly not sure. Again, I don't mean to weasel out of this. To me, this is absolutely uncertainty. I think that we could very well get out of this. We could calm down and go back to a world where there's political disagreement but it's not always end of the world level stuff. But we might not. The United States, here in the United States, which is where I'm thinking about, is what the question is about, but there's similar things you could say about other countries. Our constitutional system has lasted a long time, historically speaking, over two centuries.

3:05:02.6 SC: There's no guarantee it lasts another two centuries. It might not last another 10 years. Who knows? We're going to have another election in 2024. I could easily see people just go online. People have laid out the failure modes. If there's an election in which one candidate, I'll pretend not to know which candidate it would be or for which political party it would be, but you can all fill in the blanks. If one candidate wins most of the state elections and therefore wins the electoral college, but the other candidate has supporters that are on the state legislatures or are the secretary of state in the states where they lost, and those states choose to not respect the will of their voters and to hand in a list of electors that is different than what people actually voted for, you could absolutely overthrow the actual democratic decision of our system.

3:06:00.6 SC: And guess what? People would not like that. People would object to that, and who knows what happens next? It is not at all difficult to see a future where democracy in the US comes crashing down in a very short time scale. I'm not going to assign a probability to it because I really, truly don't know, but it is conceivable and plausible in a way that 10 or 20 years ago it just wasn't, and so that's a scary thought.

3:06:26.1 SC: Anders Hector says, "Is it possible to calculate the contribution to entropy of a human life and how a welder or a cleaner fare in comparison to, for example, Albert Einstein or an Ant or a tree who contributes more to reducing entropy, and what can I do to reduce the liability side of my net footprint on entropy?" I would not worry about reducing the liability side of your net entropy input. There's many, many, many things in the universe that are making way more entropy than you are like the sun. The sun radiating out into space does enormously more to increase the entropy of the universe than every human being who ever existed in total. Human beings are mostly themselves at a more or less constant entropy.

3:07:18.5 SC: It's not that we ourselves increase in entropy. It's that we increase the entropy of the world around us by eating and sweating and making noise and making podcasts and all this stuff, all of these irreversible processes increase the entropy of the universe. I don't think there's a huge difference. I don't know how to calculate the difference between Albert Einstein and an Ant. I don't. Einstein is bigger. He ate more food, so he probably creates more entropy, but again, it's nothing compared to very natural processes out there in the universe, so I just wouldn't worry about it.

3:07:53.0 SC: Paul Duffield says, "When are infinities bugs and when are they features? Sometimes physicists treat them as an indicator that the maths behind a theory no longer applies to reality in some way, and sometimes they're treated as a possible outcome. Is there a consistent difference here? Are these different types of infinity, or is it more of a case-by-case thing?" I think it's largely a case-by-case thing, but there's a rough guide. When you're talking about the setup, the physical space of possibilities or Hilbert space or phase space or the size of the universe, the whole arena in which things play out, there's no principled reason for that thing not to be infinite. We have no evidence that that's finite or conceptual evidence that it should be finite, etc. Maybe it's infinite.

3:08:44.9 SC: The kinds of infinities we tend to worry about are when a quantity within the universe that is usually finite is predicted to become infinite because of some prediction of an equation, right? Like the infinite curvature at a singularity in general relativity or the infinity of a renormalized Feynman diagram or unrenormalized Feynman diagram. We don't have experience within nature, within our experience, of seeing infinite things in any ways. So it's those kinds of infinities within the physical universe that we worry about as predictions of our theories, but the universe itself being infinite is not something that we treat as a big problem.

3:09:26.6 SC: Okay, the last question comes from Cooper who says, "I'm going to be a father next year and it has had me thinking about my moral responsibility to my children compared to my community and country. We're moving to a nicer house in a better school district, which I'm very aware is a privilege that many other children in this country don't have. How do you think about your moral responsibility to those close to you compared to the broader world? I don't want to further contribute to inequality, but at the same time I want to give my children the best life I have the power to give.' I put this question last because it's a whopper. It's another super-duper complicated important question. Again, going back to the very beginning of the podcast, I value these conversations. I don't just do the AMAs out of a sense of obligation, although there is that, but I actually really do get something out of some of the good questions that are being asked here.

3:10:20.5 SC: This is one of the reasons why I'm not a pure utilitarian consequentialist, a la Peter Singer, because I think it's okay to put more effort into caring about your children than to caring about people elsewhere in the world or in other times that you don't know and have never met. Okay? I think that it is perfectly natural. Again, I'm a moral constructivist, so people are going to invent, construct their versions of morality based on their inclinations, and their inclinations are to pay more attention to people close to them than to people far away.

3:10:55.6 SC: I think that's okay. I don't... I remember when we had the Moving Naturalism Forward get together, Steven Weinberg wanted to talk about morality. That was his request. He didn't want to talk about physics. Of course, everyone's like, yeah, you just talk about whatever you want, but he gave a very unconvincing talk about morality because he said, "I think morality is overrated." The example he gave was that he will make an effort to recruit a hot young physicist to the University of Texas where he was because he wants the University of Texas to do well, even if the larger community of physicists does not necessarily benefit from that. The rest of us are like, that's not immoral. That's just pointing out that your version of morality puts some extra emphasis on your local environment, and that's okay. That is a version of morality. It might not be everyone's. Peter Singer wants to convince you to care about everyone equally. I think it's almost inhumanly difficult to actually do that. I don't think you should not care about other people.

3:12:01.1 SC: That's the balance that comes in. Whether or not we are thinking about sending our children to school or whether or not we're thinking about regulating free speech on Twitter or whether we're thinking about talking about gender and sexuality, it's okay to admit there are different considerations that need to be balanced rather than saying, oh, here's the simple, clear, once and for all answer. There's a problem of inequality in the United States, in the world. I think we should make an effort to make the world better for people who are not having a good time, for people who are the lesser off people in the world. I think it's also okay to play by the rules. Whatever the rules are, if you're not actively hurting other people, to try to make the world better for your children is fine. To try to make their environment better is fine.

3:12:52.7 SC: Also, try to make the world better for other people's children. You can do those at the same time. This is where effective altruism gets into trouble. There are people who take it so seriously that they become miserable. They think the only good thing that I can do in the world is to give away everything I own because I'm going to save some lives somewhere else and then they become miserable and it's not a good long-term strategy.

3:13:17.8 SC: I think you should care about everybody and it's okay to care about people who are near to you more. The exact balance is really, really difficult to strike and honestly, probably we err on the side of caring about people near to us too much and people far away not enough. That I would absolutely buy. But that's complicated. It's difficult to exactly balance that. I certainly wouldn't feel guilty about doing what is best for your own children. I do think that we can also do more to change the world, to get rid of inequality, etc. But don't make that feel guilty. That's a trap. I think that's wrong. It shouldn't be thought of as a competition between you and other people and the rest of the world.

3:14:09.8 SC: There's a zero-sum game between what you do for your children or your family and what you do for the rest of the world. It's not a zero-sum game. We can all work to make everyone better off. Probably most of us, including myself, can do more to help the rest of the world. That's a much better argument. If someone wants to argue that I'm not doing enough to help the rest of the world, I might have to agree with that.

3:14:35.4 SC: But I would not agree that I am doing too much to help the people near and dear to me. I think that's okay. We can do both. We should try to do both as well as we can. That's who we are as human beings. And with that, have a good rest of the year. Have a good rest of 2022. Of course, we have a couple more podcasts the end of the year, but the next AMA will be end of January. So have good holidays and things like that. Thanks again for the support of Mindscape. It means a lot to me. Take care and talk to you later.

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