For many people, the phenomenon of consciousness is the best evidence we have that there must be something important missing in our basic physical description of the world. According to this worry, a bunch of atoms and particles, mindlessly obeying the laws of physics, can’t actually experience the way a conscious creature does. There’s no such thing as “what it is to be like” a collection of purely physical atoms; it would lack qualia, the irreducibly subjective components of our experience of the world. One argument for this conclusion is that we can conceive of collections of atoms that behave physically in exactly the same way as ordinary humans, but don’t have those inner experiences — philosophical zombies. (If you think about it carefully, I would claim, you would realize that zombies are harder to conceive of than you might originally have guessed — but that’s an argument for another time.)
The folks who find this line of reasoning compelling are not necessarily traditional Cartesian dualists who think that there is an immaterial soul distinct from the body. On the contrary, they often appreciate the arguments against “substance dualism,” and have a high degree of respect for the laws of physics (which don’t seem to need or provide evidence for any non-physical influences on our atoms). But still, they insist, there’s no way to just throw a bunch of mindless physical matter together and expect it to experience true consciousness.
People who want to dance this tricky two-step — respect for the laws of physics, but an insistence that consciousness can’t reduce to the physical — are forced to face up to a certain problem, which we might call the causal box argument. It goes like this. (Feel free to replace “physical particles” with “quantum fields” if you want to be fastidious.)
- Consciousness cannot be accounted for by physical particles obeying mindless equations.
- Human beings seem to be made up — even if not exclusively — of physical particles.
- To the best of our knowledge, those particles obey mindless equations, without exception.
- Therefore, consciousness does not exist.
Nobody actually believes this argument, let us hasten to add — they typically just deny one of the premises.
But there is a tiny sliver of wiggle room that might allow us to salvage something special about consciousness without giving up on the laws of physics — the concept of downward causation. Here we’re invoking the idea that there are different levels at which we can describe reality, as I discussed in The Big Picture at great length. We say that “higher” (more coarse-grained) levels are emergent, but that word means different things to different people. So-called “weak” emergence just says the obvious thing, that higher-level notions like the fluidity or solidity of a material substance emerge out of the properties of its microscopic constituents. In principle, if not in practice, the microscopic description is absolutely complete and comprehensive. A “strong” form of emergence would suggest that something truly new comes into being at the higher levels, something that just isn’t there in the microscopic description.
Downward causation is one manifestation of this strong-emergentist attitude. It’s the idea that what happens at lower levels can be directly influenced (causally acted upon) by what is happening at the higher levels. The idea, in other words, that you can’t really understand the microscopic behavior without knowing something about the macroscopic.
There is no reason to think that anything like downward causation really happens in the world, at least not down to the level of particles and forces. While I was writing The Big Picture, I grumbled on Twitter about how people kept talking about it but how I didn’t want to discuss it in the book; naturally, I was hectored into writing something about it.
But you can see why the concept of downward causation might be attractive to someone who doesn’t think that consciousness can be accounted for by the fields and equations of the Core Theory. Sure, the idea would be, maybe electrons and nuclei act according to the laws of physics, but those laws need to include feedback from higher levels onto that microscopic behavior — including whether or not those particles are part of a conscious creature. In that way, consciousness can play a decisive, causal role in the universe, without actually violating any physical laws.
One person who thinks that way is John Searle, the extremely distinguished philosopher from Berkeley (and originator of the Chinese Room argument). I recently received an email from Henrik Røed Sherling, who took a class with Searle and came across this very issue. He sent me this email, which he was kind enough to allow me to reproduce here:
Hi Professor Carroll,
I read your book and was at the same time awestruck and angered, because I thought your entire section on the mind was both well-written and awfully wrong — until I started thinking about it, that is. Now I genuinely don’t know what to think anymore, but I’m trying to work through it by writing a paper on the topic.
I took Philosophy of Mind with John Searle last semester at UC Berkeley. He convinced me of a lot of ideas of which your book has now disabused me. But despite your occasionally effective jabs at Searle, you never explicitly refute his own theory of the mind, Biological Naturalism. I want to do that, using an argument from your book, but I first need to make sure that I properly understand it.
Searle says this of consciousness: it is caused by neuronal processes and realized in neuronal systems, but is not ontologically reducible to these; consciousness is not just a word we have for something else that is more fundamental. He uses the following analogy to visualize his description: consciousness is to the mind like fluidity is to water. It’s a higher-level feature caused by lower-level features and realized in a system of said lower-level features. Of course, for his version of consciousness to escape the charge of epiphenomenalism, he needs the higher-level feature in this analogy to act causally on the lower-level features — he needs downward causation. In typical fashion he says that “no one in their right mind” can say that solidity does not act causally when a hammer strikes a nail, but it appears to me that this is what you are saying.
So to my questions. Is it right to say that your argument against the existence of downward causation boils down to the incompatible vocabularies of lower-level and higher-level theories? I.e. that there is no such thing as a gluon in Fluid Dynamics, nor anything such as a fluid in the Standard Model, so a cause in one theory cannot have an effect in the other simply because causes and effects are different things in the different theories; gluons don’t affect fluidity, temperaturs and pressures do; fluids don’t affect gluons, quarks and fields do. If I have understood you right, then there couldn’t be any upward causation either. In which case Searle’s theory is not only epiphenomenal, it’s plain inaccurate from the get-go; he wants consciousness to both be a higher-level feature of neuronal processes and to be caused by them. Did I get this right?
Best regards,
Henrik Røed Sherling
Here was my reply:
Dear Henrik–
Thanks for writing. Genuinely not knowing what to think is always an acceptable stance!
I think your summary of my views are pretty accurate. As I say on p. 375, poetic naturalists tend not to be impressed by downward causation, but not by upward causation either! At least, not if your theory of each individual level is complete and consistent.
Part of the issue is, as often happens, an inconsistent use of a natural-language word, in this case “cause.” The kinds of dynamical, explain-this-occurrence causes that we’re talking about here are a different beast than inter-level implications (that one might be tempted to sloppily refer to as “causes”). Features of a lower level, like conservation of energy, can certainly imply or entail features of higher-level descriptions; and indeed the converse is also possible. But saying that such implications are “causes” is to mean something completely different than when we say “swinging my elbow caused the glass of wine to fall to the floor.”
So, I like to think I’m in my right mind, and I’m happy to admit that solidity acts causally when a hammer strikes a nail. But I don’t describe that nail as a collection of particles obeying the Core Theory *and* additionally as a solid object that a hammer can hit; we should use one language or the other. At the level of elementary particles, there’s no such concept as “solidity,” and it doesn’t act causally.
To be perfectly careful — all this is how we currently see things according to modern physics. An electron responds to the other fields precisely at its location, in quantitatively well-understood ways that make no reference to whether it’s in a nail, in a brain, or in interstellar space. We can of course imagine that this understanding is wrong, and that future investigations will reveal the electron really does care about those things. That would be the greatest discovery in physics since quantum mechanics itself, perhaps of all time; but I’m not holding my breath.
I really do think that enormous confusion is caused in many areas — not just consciousness, but free will and even more purely physical phenomena — by the simple mistake of starting sentences in one language or layer of description (“I thought about summoning up the will power to resist that extra slice of pizza…”) but then ending them in a completely different vocabulary (“… but my atoms obeyed the laws of the Standard Model, so what could I do?”) The dynamical rules of the Core Theory aren’t just vague suggestions; they are absolutely precise statements about how the quantum fields making up you and me behave under any circumstances (within the “everyday life” domain of validity). And those rules say that the behavior of, say, an electron is determined by the local values of other quantum fields at the position of the electron — and by nothing else. (That’s “locality” or “microcausality” in quantum field theory.) In particular, as long as the quantum fields at the precise position of the electron are the same, the larger context in which it is embedded is utterly irrelevant.
It’s possible that the real world is different, and there is such inter-level feedback. That’s an experimentally testable question! As I mentioned to Henrik, it would be the greatest scientific discovery of our lifetimes. And there’s basically no evidence that it’s true. But it’s possible.
So I don’t think downward causation is of any help to attempts to free the phenomenon of consciousness from arising in a completely conventional way from the collective behavior of microscopic physical constituents of matter. We’re allowed to talk about consciousness as a real, causally efficacious phenomenon — as long as we stick to the appropriate human-scale level of description. But electrons get along just fine without it.
@Logicophilosophicus
“Hilbert spaces – vector spaces – are mathematical, not physical. We need a way to make sense of physics plus mathematics plus consciousness. Axiomatically claiming that physics achieves this – creating the Hilbert space? thinking about it? etc – doesn’t cut the mustard.”
Exactly so! In fact, with quantum wave functions (which seem real but can’t possibly be in physical space), I think we are seeing clear evidence of ‘pure information’ (non-physical computation) busting through to the physical level, strongly suggesting that computation is indeed more fundamental than physical reality (all the puzzles of QM can easily be explained by treating physical reality as a ‘leaky abstraction’).
John Merryman,
You seem to think that there is a fixed ruler somewhere, there is not. Perhaps it will be clearer to you when we talk about traveling distances at high speed.
Suppose a manned spaceship leaves earth the travel to the other side of the milky way galaxy, about 100,000 light years away. Many people, knowing that you can’t go faster than light, would tell you that it would take at least 100,000 years, and so the people would die, and the spaceship would be very old when it arrived, etc.
However, this is not true at all. Even if the spaceship had a constant acceleration of only 1g per year, the people onboard would arrive to their destination in only about 12 years, in their own reference frame.
While time will have seemed the flow at the same rate for them along the trip, they would notice nothing strange, the distance traveled will have appeared to be much shorter than 100,000 light years. In their view, it turned out that the diameter of the milky way, in the direction they were moving, was only about 10 light years.
And remember, if they did an experiment onboard the ship, using meter sticks they brought from earth, the speed of light would still come out to be ~299,792,458 m/sec in all directions, at all times, even using ancient light from the oldest stars in the universe. But, the color of the light, the wavelength, would be red shifted when coming from a star in the direction they came away from (and blue shifted the other direction). In this way, they could definitely say that they were moving at high speed away from the earth and sun.
What about the point of view of the generations of observers on earth, watching the spaceship along it’s journey, instead of them seeing generations of people dying and having children on the spaceship, they see the same people the entire time. They appear to move and age extremely slowly and send red-shifted messages and images (that still arrive at the speed of light from the viewpoint of people on earth).
Hopefully this will help you understand the connection between time, space, and red-shift from the perspective of moving massive observers.
Space is not fixed. Time is not fixed. The wavelength of light is not fixed. The speed of light is not fixed.
However, nearly everyone has agreed to say that we should just agree that the speed of light is the thing that is taken as a rule to never be changing. It makes all of the calculations much simpler, because our own physiology works like a physical clock. Our minds work like a physical clock. We are limited in the types of experiments we can perform.
As a different (but just as real and valid) way of thinking, you can imagine how experiments and measurements would be ‘experienced’ by a massless object moving at light speed, such as a photon. To a photon, length is contracted to nothing. Travel is instantaneous. So… not all spacetime locations are possible to reach. Most spacetime locations are absolutely impossible to reach. A massive object can adjust it’s velocity, and could arrive at ‘a space location’ at ‘different times’. This is not an option for photons.
@Ben
“An additional note: the very idea of a “fundamental” level of reality is itself as incoherent as “the largest number.” ”
But we can in theory still find out whether a given level of reality is ‘more or less fundamental’ than another one. What gives the game away is what is known as ‘leaky abstractions’. Effects from the lower levels of reality always ‘leak through’ to the higher ones.
Now, if ‘computation’ was more fundamental than physical reality, then we should see the ‘leaks’ from this postulated lower-level ….what we would see are strange effects where ‘pure information’ seems to be influencing things, but we can’t locate it in physical space.
Guess what….that’s exactly what we do see with quantum mechanics effects! Scott Aaronson has carefully analyzed the ‘wave-functions’ and he says they are exactly equivalent to ‘pure information’. And this ‘ non-physical information’ shows exactly the strange effects we would expect if physical reality was a ‘leaky abstraction’!
John Merryman,
I will try to explain it another way. Hopefully this is very clear.
You could accurately say that red-shift has nothing to do with how much space there is between the points of emission and absorption of a photon. You could also say that it has nothing to do with the amount of space changing. That would also be an accurate thing to say.
As you can see from my relativistic speed space ship story, red-shift has only to do with relative velocities of the source of emission and absorption of the photon. We today are moving at very high velocity away from all of the sources of ancient emission of photons. Because of this relative velocity, the light that was emitted from well known reactions is red shifted compared to the same reactions happening in places like our local solar system, where the relative velocities of everything is much smaller.
So, to answer the question of why everything that is far away is moving rapidly away from us, we say that space is expanding.
The wavelength of light is how we measure it’s momentum. But, momentum is a relative quantity between two objects, not an absolute property of one object. It can only be measured as a transfer of energy, which comes in different interchangable forms (these forms of energy appear different based on your own reference frame). Mass in one reference frame is seen as velocity in another reference frame.
We can be sitting in our broken spaceship in empty space, and believe that we are totally at rest and still, so our mass is low and we have little kinetic energy. But, a different broken spaceship may pass by us at 99% of the speed of light, with an enormous mass and kinetic energy. From their point of view, it is we who are massive and moving rapidly, and they are at rest. We are both correct, and no matter who calculates the total amount of momentum, we will come out with the same answer.
This is the same with light. The momentum carried by a photon emitted by an object (which we see as it’s wavelength), is relative to our motion to the emitting object. It we are both moving apart from each other rapidly, the photon will appear to have less momentum (and be more red), just as a mass like a baseball will not be able to transfer as much momentum if the thrower and catcher are moving rapidly apart from each other.
John
In an expanding universe, it appears at every point in space that it is the center of the expansion. The explanation can be found in lots of places, including Sean’s book. That is no mystery.
Moe,
I understand about the dilation of space and time. To repeat for the nth time, this is not about absolute metrics. This is about one metric, based on the spectrum of intergalactic light, that expands, because it is redshifted, compared to another metric, based on the speed of the very. same. exact. light, that doesn’t expand, because it is assumed the light will take longer to cross between the same points, so there are more units, not expanded units.
So I ask you, do you understand about numerators and denominators? Because in this relationship, the speed of light is assumed to be the denominator.
Neil,
Yet something so basic as the vacuum through which light travels at C doesn’t expand, because it presumably takes light longer to cross, as the universe expands. Do any of those books explain why the speed of light doesn’t remain CONSTANT to this expanding space?
Since you showed some willingness to think it through, keep in mind the reason Einstein added the Cosmological Constant was to balance gravity, from collapsing the universe. Now where is there the most gravity? Galaxies maybe? So where would we logically look for a Cosmological Constant? Between galaxies, maybe? If gravity is a contraction of space, then logically the CC would express as an expansion of space. Logical?
Yet overall, these balance. Space expands between galaxies and collapses into them, in some big cosmic convection cycle. Radiation expands, mass collapses. What do we measure with redshift? Radiation. What do we measure with gravity? Mass.
John Merryman:
First, Moe and Neil have been giving you a great crash course in Relativity.
I highlight the above because it’s indicative that you’re still thinking of light as being waves within a medium. It’s a very seductive mode of thought because of its intuitiveness, such that it can be so difficult to see how and why you’re making that incorrect assumption. But it really, truly, honestly does continue to lie at the heart of your confusion.
Because there’s no medium in which light is propagating, it doesn’t make any difference to the light if it’s getting red- or blueshifted because of the relative velocities of the observers or because space itself is expanding or contracting, and it similarly doesn’t matter if the distortions of space are from gravity or inflationary expansion. That universality is the fundamental concept at the core of Relativity.
Leave aside for a moment the discussion about galactic redshift and instead spend a bit contemplating time and space from the perspective of a photon, as Moe described. Length doesn’t exist because Lorenztian contraction shrinks it all the way to zero. Time doesn’t exist, either, because there’s no length to traverse. For the photon, it experiences all time instantaneously, and the entire Universe is exactly 0.0±0 cm wide. Always, for every photon, in all circumstances, including both the photons coming off your computer display as you’re reading these words as well as the photons of the CMB that were created a few hundred thousand years after the Big Bang and, from our perspective (but not the photon’s!) have been “in flight” (covering zero distance as far as the photon is concerned) for the past baker’s dozen billion years.
You’re hung up on rulers with measurements and denominators, and trying to apply them to light. But, as far as the light itself is concerned, the numerators and denominators are both zero. What sense does your intuition make of the concept of a ruler in that context?
Cheers,
b&
zarzuelazen:
Though a tempting question to ask, it’s the worng one.
What you really want is its inverse: is there anything computable that doesn’t exist?
Clearly, the answer to that is overwhelming. Lots of stuff computable that clearly don’t ever exist. Indeed, the set of things that’s computable that doesn’t exist is infinite.
So that tells us that we’ve got an effective language for communicating about reality, but the language itself is just the paper upon which we draw the map. The map itself, of course, is still not the territory.
Sean’s day job is making toy universes on his blackboard. One of his favorites that he uses in talks to the general public is an universe with a single particle that propagates through spacetime. The universe is infinite in space and eternal to both the past and future. Its laws of physics are complete. It is entirely computable.
You could propose computing it and thus instantiating it, making it real in at least some sense of the term…but, in reality, you’d need infinite resources to compute it. So, while it’s computable, it’s not something that you could actually compute and thus bring into existence.
Consider for a moment that you had the Schrödinger equation for our real Universe written on a chalkboard. That dust clearly isn’t the actual universe, but just a description of it. You’d face the same problem (on steroids!) attempting to compute it as for Sean’s toy universe. And you could change any of the terms of the equation on the chalkboard by the tiniest amount and get a completely map that clearly doesn’t exist.
To call reality a computation means you’ve got to have something actually doing the computing. I’ve repeatedly explained why the simulation argument doesn’t hold water; any attempts at building a computer with physics as we know it are doomed to failure, no matter how “big” the exterior universe. And if you’re going to propose physics not as we know it, there’s no sense left in anthropomorphizing the process by calling it computation; it’s just physics as Sean studies it.
So…it is entirely reasonable to describe the Universe as computable without implying that it is actually a computation. All that statement says is that we’ve got the right language to talk about the Universe. But going the other direction, as you are, is, simply, as religious as saying that Jesus Spoke the Word into Being. Maybe you like the poetic imagery it conjures, but it’s no more real than Harry Potter’s Platform 4 3/4 at Paddington Bear Station.
Cheers,
b&
Logicophilosophicus:
You’re actually very close to the right track; you simply didn’t take the final step.
We know that the concept of a creator god is incoherent for all the reasons that stem from asking who created the creator.
But the exact same logic applies to the concept of a fundamental reality. On what foundation does the fundament lie?
It can be demonstrated another way. Let’s assume that, per your example, Everett’s universal wave function is fundamental to reality as it applies to us. You would propose that that’s the bottom, the end of the line. It’s the bookend of the infinite regress.
But I would challenge you: how can you distinguish between a reality in which Everett is truly fundamental, and one in which the Red King from Alice in Wonderland is Dreaming of the full expansion of Everett’s waveform? And, even if you did manage to do so, how do you rule out the possibility that the Red King himself is but a subroutine of the Matrix in some universe with physics where computers don’t collapse into black holes due to density? And how do you know that the Matrix isn’t, after all, a school project of young Zeus in his classes on Olympus?
The practical answer is that these are all conspiracy theories and, by design, they are explicitly not subject to disconfirmation. They may well all be true, or something even more bizarre may be true. Or none of them may be true.
However, there’s no point in giving them or any other conspiracy theory any credence unless and until supportive evidence is produced.
But it really does mean that the “fundamental level of reality” is equally incoherent, whether couched in the language of theology or physics. After all, even the gods themselves couldn’t rule out the possibility that they themselves were being subjected to a conspiracy that tricked them into thinking they were all-powerful, so what makes us think we’re in any better position?
Cheers,
b&
Bottom up, top down, it’s all a matter of perspective. Emergence and reductionism are the key concepts. You can create a framework and work within a model. But there are many possible models. Most fields of science don’t require a philosophical theory of everything. And you don’t need to dwell on it for daily activities. But sometimes it’s fun to think about it.
zarzuelazen:
You’ve just proposed a zilbot particle. Especially within the domain you’re referring to, we can and should reject your proposal with extreme prejudice.
Cheers,
b&
Ben,
Again, how do you manage to interpret the word “vacuum” as “medium?”
Obviously there is no time at C, because there is no change at C. Time is a measure of change.
John Merryman:
Because all the properties you’re attributing to the vacuum are properties of media.
Or, by analogy…you’re pointing to a cat, using the word, “cat,” but you’re wanting us to tell you where its bill is, why it doesn’t quack, why it has clawed paws instead of webbed feet, how it’s supposed to fly without wings, and so on. And you’re wondering why I’m telling you that it’s a cat, not a duck.
b&
Ben G
“We know that the concept of a creator god is incoherent for all the reasons that stem from asking who created the creator.” No – Dawkins’s argument is actually based on a false premise. I just cited it as a familiar example of the method of arguing from the absurdity of infinite regression.
“But the exact same logic applies to the concept of a fundamental reality. On what foundation does the fundament lie?” I guess you have just asserted that the sequence 5, 6, 7, 8, 9… proves that there is no smallest integer. Many progressions have a starting point. In this example, the starting point, unity, is absolutely fundamental – all the other numbers rely on the axiomatic existence of unity.
“It can be demonstrated another way. Let’s assume that, per your example, Everett’s universal wave function is fundamental to reality as it applies to us… how can you distinguish between a reality in which Everett is truly fundamental, and one in which the Red King from Alice in Wonderland is Dreaming of the full expansion of Everett’s waveform? [etc ad infinitum]” Is this a wind-up? “Alice” is a work of fiction by Lewis Carroll (pseudonym – so probably no relation…) LC is part of the universe or the reality we are trying to explain. IFF Everett’s interpretation was fundamental (it isn’t) it would fully account in principle for that author and his work. Are you really saying not only that there is no fundamental theory (actually that there CAN’T be), but that any hypothesis however stupid is equally valid at any level?
“They may well all be true, or something even more bizarre may be true. Or none of them may be true. However, there’s no point in giving them or any other conspiracy theory any credence unless and until supportive evidence is produced.”
Well, replacing “conspiracy theory” with “hypothesis”, there is a lot of supporting evidence for the computational hypothesis. In particular, note that all the disparate “bits and pieces” which constitute present day physics/cosmology have only one thing in common, as regularly noted by scientists ever since Kant first pointed it out: mathematics. Wigner famously pondered “The Unreasonable Effectiveness of Mathematics in the Natural Sciences”. Also note that the physics does not generate the mathematics, but that minds regularly do so.
John
The speed of light is a universal constant because that is a central postulate of relativity and relativity has been tested extensively. So extensively, there is no reason to doubt. There have been some variable speed of light alternatives out there, but they have been refuted empirically.
Ben,
C=the speed of light in a vacuum. Explain to me how that is a medium?
A medium is stuff, like water, or air, or metal. A vacuum is empty space devoid of stuff.
You shine light into a medium and it just absorbs it and turns to heat.
Is this an act, or a diversion, or do you really not understand the difference?
Neil,
“The speed of light(in a vacuum) is a universal constant because that is a central postulate of relativity.”
Do you agree to my correction?
Logicophilosophicus:
Richard’s logic is impeccable. The theological arguments inevitably result in an infinite regression, and then switch to special pleading to escape the regression. That special pleading is a result of primitive superstitious abhorrence of the infinite, famously embedded in Western philosophy by Aristotle. But we now know how to deal with infinities, and sound logic demonstrates that the initial premise, that there’s always some sort of a singular explanation underlying everything, is invalid. Instead, there may or may not be such explanations, and there is no way to know “from the inside” whether or not you’ve arrived at such. That’s what lies at the heart of the famous works of Cantor and Turing and Gödel — and it applies just as well to the Universe as an whole as it does to the countability of real numbers.
As of right now, your fundamental computation is every bit as much fiction as the Red King. Both your fundamental computation and the Red King are logically consistent theories of everything. One is more colorful than the other, but neither can lay claim to even the hypothetical possibility of being ultimate than whatever the Internet Prime Search has most recently discovered can lay claim to being the largest possible prime number.
Math is simply language — though, granted, a very intelligently evolved language. The math of ancient Greece isn’t even remotely what we would consider effective today; they didn’t even have a zero! Yet it was still sufficient to describe Euclidean geometry — which has good reason to lay claim to the oldest rigorous theory of physics. Coming up with ineffective math is trivial — 2 + 2 = 5, for example. We only spend our time on the effective math, so of course all math is effective — the ineffective math gets weeded out long before it makes it to publication, usually.
A more perfect demonstration of the fact that math is mere language would be difficult to propose. Unless, of course, it is your position that minds are supernatural magical entities that merely share approximate spatiotemporal coordinates with our bodies….
Cheers,
b&
John:
Yes! Exactly!
…so why do you keep insisting that we must show you stuff like rulers and denominators and rubber bands in the nothingness devoid of stuff? We can’t show you stuff of any kind, including the kinds you want to see, in the vacuum, because the vacuum is — in your very own words — empty space devoid of stuff.
I’d also add that you’re not doing yourself any flavors if you’re thinking of light as propagating within the vacuum. Don’t even think of it that way. Instead, think of light as simply propagating, not within anything at all, but just propagating, period, full stop. Light propagates. It doesn’t propagate within the vacuum; it just propagates.
Cheers,
b&
John,
“This is about one metric, based on the spectrum of intergalactic light, that expands, because it is redshifted, compared to another metric, based on the speed of the very. same. exact. light, that doesn’t expand, because it is assumed the light will take longer to cross between the same points, so there are more units, not expanded units.”
So I suspect that you are just trying to be difficult here.
I already tried to explain that the red shift is from relative momentum. There is no need for any metrics at all. Just pick which measurement is your personal favorite to be fixed, and then plug it into the equations. There is no reason to be confused.
Ben,
Okay. I can work with this. So, light propagates. Around in circles? Across the universe? Give me some transmission/reception points of this light.
For interest sake, ones not propagating across a space, or vacuum, since you insist that is irrelevant.
Ps, Just out of curiosity, would you give me your definition of the word “vacuum?”
Moe,
“red shift is from relative momentum”
And would that “relative momentum” be C?
I’m still seeing something compared to something else. As in a numerator compared to a denominator.
Moe:
Yes! This is the essence of Relativity. Everything is relative to everything else, with nothing in any special frame of reference — not even spacetime itself. It is equally valid to say that the Universe has no center and that all points are at the center.
So, what we do, is we arbitrarily pick some frame of reference (typically centered around our skulls), declare it to be the center of all existence, and measure everything else RELATIVE to it. And somebody else can do similar measurements RELATIVE to their own entirely different center-of-existence frame-of-reference, get their own answers valid only for themselves…and yet it’s all consistent for everybody.
Relative to the Earth, some particular highly-redshifted galaxy is moving away from us at some insane fraction of the speed of light. The Earth, of course, isn’t going anywhere. But relative to that distant galaxy, we’re the ones moving away and they’re the ones standing still. And when they look around in all directions, they, too, see that, relative to themselves, everybody else is moving away at accelerating speeds.
Now, consider a third galaxy, midway between us. We see them moving away, too, but at a lower redshift. The same for the distant one, only opposite. And the one in the middle sees us other two moving in opposite directions with the lower redshift.
And — and this should really bake your noodle — all three of us will observe the cosmic microwave background as essentially the same. The same temperature, the same anisotropy, the works…though the actual distribution of the clumping might differ. And that’s because, for each of us, the CMB is the same relative distance / age. Go far enough away, and the CMB is still basically the same…only the Milky Way is now so redshifted that it appears as part of the CMB. (Or, rather, the matter that would eventually condense into the Milky Way, since the CMB long predates the formation of galaxies.)
John, does this help any?
Cheers,
b&
Ben
You wrote: “It is an objectively observable and independently verifiable (through multiple different approaches) fact that, within certain well-defined limits, all humans perceive color the same way. ”
That’s clearly not correct since there are significant numbers of people with red-green color blindness, others with yellow-blue blindness, and some people with no color perception whatsoever.
Apart from that, even for people with normal vision, we have no way to know they are perceiving color the same way just because they can differentiate colors the same. You can’t know what my “red” looks like.
There is a great book Visual Intelligence: How We Create What We See by Donald Hoffman on visual perception. One of the more interesting things mentioned in the book is an experiment with providing people with special glasses that actually turned everything upside down. After initial disorientation people eventually adapted and could operate normally. When they removed the glasses once again initial disorientation and then adaption.
So quite literally two people could actually have completely upside down views of the world and still function normally and we would never suspect any difference in their subjective view of the world.
John:
That’s still the language of a medium. You’re looking for the “stuff” that light is originating from and moving through — but the whole point of Michelson / Morley is that that’s not, contrary to all intuition, how light actually behaves.
…the next obvious question, of course, is how light does behave…and that’s where we have to pull out quantum field theory. Which, unfortunately, bears a certain superficial resemblance to the Luminiferous Aether even though it most emphatically is not, so please forgive me if I put that off until you’re ready to let go of any last remaining vestiges of your intuition about light propagating within a medium of some sort.
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Ben G
Ignoring the key parts of an argument is embarrassingly weak. You wanted evidence, you ignore it. Your claim that there can naver be fundamental explanations was answered, you ignore that too. I don’t even think you are defending any recognisable position – you have declared views which were expressed by Einstein, Heisenberg, Schrodinger, etc, etc, to be utterly emphatically rubbish. Enough said on that score.
I have a feeling that your repeated Cantor, Godel, Turing name-dropping is meant to catch me out somehow. You mention that they dealt with infinity. For Cantor, he is perhaps best remembered for his diagonalization proof, and for his work, in correspondence with Dedekind, on the continuum. Not everyone accepted his proofs at the time – I won’t bore you by bringinging up Kronecker’s famous remark – but nor did Wittgenstein, who returns to the issue again and again in the lectures on the foundations of mathematics reconstructed by Cora Diamond (and btw attended by Turing). Godel (in his most famous proof – from memory I think its the second proof) simply systematically replaced mathematical propositions by sequentially numbered labels, and could then apply the diagonalization proof. Likewise Tarski. Turing (and Church I think – I haven’t read Church) used the same trick, by systematically listing computations. I’m with Wittgenstein (I first studied him over 50 years ago). He complained that Cantor could never show anyone a completed infinite set, or point at an infinitesimal point, yet his proofs relied on these entities. It has become a slogan of mine: “Show me one. ” The halting problem is a really minor issue in Turing’s famous paper on computability – I reckon it was only the glamour attached to Hilbert’s challenges which motivated him. In practical terms the distinction between a computation which will take a trillion years and one which will never halt is irrelevant: every real computation halts because we program in a conditional instruction to make it so. They even do that systematically/theoretically in quantum physics – they call it renormalization, Feynman (who pioneered it) always believed it was unjustified (but pragmatic) “hocus pocus”, and it is therefore (in my view) one of the very best pieces of evidence that reality is computational.
For anyone interested, the side issue (Dawkins’s argument) is simply this. Dawkins claimed that anything which could create the complex (especially living) world we observe would have to be more complex; if that had been true, then it would also be true of the creator, etc… But it isn’t. If it were so, the universe we see would have to be less complex than the singularity at the Big Bang, and so forth. What has that to do with this argument? Not much – like my A-listers (Einstein, Heisenberg, and so on) I expect this horribly complex world to be accounted for by a vey simple underlying reality. Dawkins doesn’t see that, but then wasn’t it von Neumann who observed that there are only two kinds of science – physics and stamp collecting? (I must stop relying on my memory.)
“Show me one.”
Example: If you accept Turing’s proof then you accept the key result (from diagonalization) that there are non-computable numbers among the irrationals – according to Cantor there are infinitely more of them than of any other kind of number. Show me one.