David Albert: A Masterclass on Time’s Arrow
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- เผยแพร่เมื่อ 3 ม.ค. 2025
- David Albert is the Frederick E. Woodbridge Professor of Philosophy at Columbia University, director of the Philosophical Foundations of Physics program at Columbia, and a faculty member of the John Bell Institute for the Foundations of Physics. This is David’s ninth appearance on Robinson’s Podcast. He last appeared on episode 221 to discuss the measurement problem of quantum mechanics. In this episode, David gives a pedagogical and introductory overview of the problem of time’s arrow, which is one of the most enduring of all physical and philosophical puzzles. David’s most recent book is A Guess at the Riddle (2023). If you’re interested in the foundations of physics, then please check out the JBI, which is devoted to providing a home for research and education in this important area. Any donations are immensely helpful at this early stage in the institute’s life.
A Guess at the Riddle: a.co/d/6qcsidl
The John Bell Institute: www.johnbellin...
OUTLINE
00:58 The Tension Between Past and Future in Physics
8:56 The Arrow of Time in Life and Physics
12:26 The Three Arrows of Time
18:12 Entropy and the Direction of Time
29:12 Thermodynamics and the Problem of the Past
38:26 Why Do We Remember the Past But Not the Future?
48:46 Two Ways to Understand the Past
1:04:21 Why Can We Affect the Future But Not the Past
1:17:51 Why Can Agents Control the Future but not the Past?
1:26:57 Can the Laws of Quantum Physics Be Run Backward?
1:33:11 The Connection Between the Foundations of Quantum Physics and Statistical Mechanics
1:41:53 Cosmology and the Past Hypothesis
1:44:25 Why are Left and Right Different from Past and Future?
1:49:28 The Difference Between Space and Time
1:57:14 Is Time a Fundamental Part of Reality?
1:59:14 Future Work
Robinson’s Website: robinsonerhardt...
Robinson Erhardt researches symbolic logic and the foundations of mathematics at Stanford University
Yes!!! I love your interviews with Professor Albert. What a wonderful mind. Thank you for another great interview, Robinson.
Me when I see Robinson has dropped yet another banger with Dr. Albert: "okay... good"
Hahahahaha
Damn, got me, dying over here
I really felt that
Another banger, and so on and so forth!
“Um…um…good.”
Can a mere thank you describe my sense of overwhelming gratitude to Dr Albert ... to guide us to the dazzling ocean of ontology ... can I be thankful enough to Robinson for his both most sincere and amiable service to the cause of education. I hope you will continue to gratify us in 2025. You already hinted about it and one look forward to such a discussion about the mystry of space. And please, Dr... dont wait for someone to implore you to take a water-break. Wish you both healthy 2025.
His vodka-breaks are essential.
Such a fascinating topic of discussion. Every time I try to contemplate the true nature of time I feel like I spiral just a little bit closer to madness.
I'm always amazed at how many words David Albert can use to get something said.
He's back! Very nice. Thank you Robinson.
I could listen to David Albert all day long. Thanks
Good.
Who couldn't. He just keeps talking. He needs to start contributing to physics.
@@TimoBlacks Ouch
Me too! Its like Popeye reruns
It feels like I did.
Such a unique and wonderful teaching style.
My favourite topic. Thank you, Robinson and David!
This was another level 👍🏽
Thank you both.
🙏❤️🌎🌏🌍🌿🕊🎵🎶🎵💫✨️💫
Outstanding
😊🏴☠️
The billiard balls must collide on a frictionless surface to look undistinguishable in forward or reverse , otherwise they'd experience deceleration, which would look like 'acceleration' if played backward.
also they emit thermal radiation and gravitational waves, undetectable by our instruments but in principle they are and it also is different if time is reversed or not
Prof. Albert seems to be explaining, with absolute certainty, that if you are not confused you don't understand the situation!
Yeah. Which is a whole bunch of hot air. Sam Harris of physics? Or did I miss something actually useful and interesting?
@@catejames6453 I hope you never lecture to a lay audience.
You are so deep into your formalisms that you can no longer distinguish the solution space (your powerful formalisms) from the problem space (why anyone bothered to invent those formalisms in the first place).
Or at least, I'm entirely entitled to assume that from the cavalier way you throw around the term "useful", a concept which can only be anchored to a specific purpose, which I (rightfully) presume that you didn't bother to do (until you demonstrate otherwise), because in your mind the only viable purpose remaining is to polish your formalisms, and thus such purpose can be satisfactorily left unstated.
Thank you Robinson!
wow, i don't know what to say. i'm in awe. I'm filled with a sense of excitement and wonderment. what a brilliant speaker/video/channel you have here. please keep it coming Mr Erhardt.
Thanks Podcat and crew!
Is it just me or does Prof David have the perfect "I don't say many wrong things" kinda face?!!!
The abundant "ok" seems to confirm that (and annoy me a bit).
I watched every second of this and was high as hell.
This is good stuff😂
Maybe I missed it, but where was this recorded. What a beautiful setting.
Good presentation, glad you pulled in the measurement/collapse issue.
Would have enjoyed some comments about:
1. CPT Theorem - we know CP is violated, so T must also be violated for CPT to be preserved.
2. Information flow and (possibly non-) conservation...
How do physical states encode information; how does it relate to entropy;
how does it transform/grow/shrink - for various different measures of information?
Yes -- I was puzzled by their failure to discuss CP violation.
Dude is a lot of fun. Thanks for doing this. I love the drum video intro. We think it's true.
Great episode!!
There is no such thing as time-reversal symmetry, at least as long as matter, energy and fields are involved! In this example with billiard balls collision you may think it may exist, but then it disappears as soon as you start measuring ball temperatures or speeds before and after. Even with such near-perfect objects there will be an energy loss causing some mechanical energy conversing to heat. Entropy will absolutely increase over time and that that is not time-reversal symmetric. I also strongly suspect that there is no time-reversal symmetry on a quantum level: atoms, elemental particles and photons will not be coming together to create unstable isotopes. I guess elemental particle collisions are even less symmetrical than for billiard balls! So physicists are very well aware of that! Mathematicians may entertain the idea and even believe it has some true-life meaning. But on another hand they may even consider themselves "physicists", so what: it is all math theories that may be fun to play with but you take them one step too far and they lose any physical meaning!
Philosophy is awesome.
So funny, David used to bug me but over time he really grew on me. I really appreciate how you manage to look after your guests with prompts to take a drink/breath.
About half way through this excellent discussion, my mental picture is going towards the idea that we are stuck moving through the time dimension at the speed of light. This leads to the notion that when considering 4 dimensional time space, there is a direction we can't stop moving in, so that creates a non uniformity. As with gravity, going up is a very different proposition than coming down. With time it's like infinitely strong gravity.
The first couple minutes seems wrong to me. You may see a billiard ball leaving the one that hit it but beyond the human eyes capabilities you might have seen in say infrared heat dispersion when they hit and if run Back wards heat being added which would give it away. The force is not perfectly transferred from one ball to the next. Some leaves by transforming to another energy like heat
Love ye all and GRATITUDE AND HONOR!
Thank you.
For thy perseverance to have sincere conversations. Will draws many
David Albert has the New Balance shoes of a man who knows about Physics, and I say that with full reverence.
Students shared "i" Am remember with thee dwelling within thee and walking with thee! If takes to carry thee! 1 footprint! Just know I have loved thee!
There is a speculative physics theory that solves this problem, and it is about expansions of the universe where it involves negative energy and negative mass.
It is not a collapse of the wave function. It is a phase change. It is part of a critical point phenomenon, like in super cooled water that can freeze at the just the right level of perturbation.
To me all that is being done (which is typical in physics) is to replace "time has an arrow for some reason" with "entropy increases with time for some reason."
Time is an illusion. Lunchtime, doubly so. The arrow of time, most of all.
Good!
Some will say, why HE calls many HIS POPS? Like thank you pop David for attending unto our own!
Everything is gr8 , David, the topic the explanation... But i just want to see an ANGRY ROBINSON. How can someone be so monotonous / singular/ calm. Just love the guy. Any tips would help of how can one be calm, when the mind is racing at the speed of light
Hey Robinson, if you are talking to Tim I was wondering if you could ask him a question about time. I have heard him talk about it before and I have wondered if he views time like an update function for the universe? Like time is what steps the universe forward so interactions can occur. From what he says this is how I understand his conception of time but I am not sure.
It is a common misunderstanding about time reversibility of microphysics, and especially bad is the example David gave of perfectly elastic billiard balls. There are other forces like gravitation (which always attract) and eletrostatic ( where same charges repel and opposite charges attract) in the real world. It is obvious that even if the time was assumed to be OK to be reversed , that will not change the nature of the laws of gravitation and electrostatic force. Even in the example of billiard balls, the film is supposed to be run in reverse, i.e., velocity reversal, not time reversal. SO the example of billiard balls could be thought of as velocity reversal invariant physics - not time reversal invariant physics. The correct way to then say is that microphysics is velocity reversible - in the idealized condition of perfectly elastic billiard balls - not time reversal invariant. And even in that example, the billiard balls, they will be warmer after the collision than before the collision.
I think it has been a prime mistake to assign a notion of "forward" with the direction of the flow time - which misleads us to imagine a reversed time - why? because reverse is opposite of forward. But time simply flows from before to after event - causing to cased event direction. It should not be called forward. It is just like - it is OK to think of up and down on the surface of the earth, but in deep space, these are meaningless ideas. Time simply flows, i.e. if there is successively different configuration of the universe, the time can be thought of as flowing. The notion of reverse flow of time is absurd and contradicts the definition. Even when an eventual equilibrium is reached, i.e., not change in entropy - if there is a change in configuration of parts of the universe , then time could be thought of as flowing. Tim Maudlin has it right. Time is not like the other 3 space dimensions and has intrinsic property of flowing in only one direction - that of causation.
Why we can perceive/remember the past events - Well - only if the effects of the past events on the universe are recoverable at the present moment. If someone walks on a wet beach leaving the foot prints - and the tide washes them away - it is as if no one walked on the beach. It is trivial why we remember the past.
It is true that entropy increases in the direction of the flow of time. But increasing entropy is not the cause of that direction of flow of time.
Good common sense idea, I also felt super physicist discussing about the reverse time just for the sake of high end fancy concept. I cannot digest reverse time. As I feel every event in this universe has a cause. Effect can never cause a cause. Time cannot reverse. As you rightly pointed out, as entropy always increase with time, it doesnt mean decrease in entropy is reversal of time, it may be a problem with our understanding of entropy, not reversal of time.
I would only add that there's no point to even talk about "time" or "flow of time", because time doesn't exist, it's just a tool we use. Physical objects are doing all the interactions and "time" is not involved in any shape or form. And past and future never exist, obviously. So I have no idea why people like the professor in the video are talking about non-existent problems with non-existent phenomena, that only exist when they play with math in their minds.
The time problem does not even arise if you just take seriously what time is. It is this activity we engage in of relating events by simultaneity. Eg, the co-existence of events. And when they don't co-exist, it's not that one happened "at a later time", but that it happened along with that (now other) event, regardless of time. If there is no such other with respect an event happened, the event did NOT happen (meaningless to say it happened). It's like a mass having a position, OFF the presence of some other. If that other was not present, this mass's position meaningless. Time is like that. Like space. Time is merely this approach to the world, whereby we relate events in 'pairs', or by simultaneity. The flower had reached its full height WHEN he finished playing his long guitar song. "I'll see you at the Mall RIGHT WHEN this thing on my wrist points to my knuckles... don't ask me what determines when it does!, I just know I'll be there when it does!" (a watch). "How many times did the sun revolve during your fasting?" (same as saying where was the sun simultaneous with the end of fasting, only it adds the complication of lapping, because the range of sun positions does not contain a unique position for the end of fasting point). That's all time is. It's this activity we (strange creatures) engage in, of pairing events like that. Relating them BY simultaneity. Time is that, and is Nothing else. Einstein knew it, and several knew it before him. And today, every thoughtful physicist who knows GR knows it. And yes, time can be made to go backward and forward. Get in a rocket, or go stand on a dense planet for a while. Then come back. You've gone to our future, and we've gone to your past. Had you brought a planet with you, we've gone to that whole planet's past, including every organism on it. Not complicated. Also clear, that us going to your past that happened prior the moment you left here is not capable, because prior to that moment is prior to your accelerating = prior to dilation. No problems. Easy peasy. The trouble comes from people stuck still in presumptive Newtonian way of thinking, where they project this "time" thing into the universe so that it ticks up there and everywhere, and since they have it there ticking, they have the automatic thought of its having a direction of ticking, and so, they also have the automatic thought of that direction possibly reversing. I see how you approached the issue of how they came to the idea of reverse. You stated that it's due to the notion forward. I like that. But I prefer one step deeper, by looking at what has caused that notion forward. And again, what has caused it, is a failure to accept what time is, and an insistent to make friends with Newton even in 2024. Drop the bad habit. You're just wasting the time you have left. Spend it in good habits instead. Who wants to die believing in total BS? I don't. That's robbery of life on top of that cold robbery of it. To believe in false things while living, is almost as bad as being unable to believe anything while not living Life should not be a place to be robbed, only its end be that place. PS, saying "time simply flows" is not right. You should not be talking of a flow. THAT TOO gives rise to the impression "direction" (then forward, etc etc). Stay away from what Time is not. Study physics closely, and you'll see what it is.
@@autopilot3176 Last sentence you wrote. Because that is what it MEANS to be a philosopher. It means to get lost in the ways that words can be strung. They think as if the ways that words can be strung gives rise to legitimate things to be made sense of, just by virtue that the words _can_ be strung in so and so way. They are basically hazards onto themselves. Like drunks with untied shoe laces, walking through a forest of sticks. They snag on every single thing, and spend their lives untying the inevitable knots at their feet. The only philosopher I respect and admire, and admired so much he caused me to drop my studies in Philosophy after 4 years in, and go into Physics, is the one that felt in similar ways about Philosophers (and philosophy). He was the most brilliant I had ever read. His name was Wittgenstein. His mind was so pure and beautiful, in the way that Einstein's was. Perhaps even more abstract, and obsessive over exactness and essence. Totally obsessed with those. His ideas were so detached from 'common' sense that he perpetually doubted himself, wondered if he was nuts. I agree with what you have said. If you are a philosopher, I apologise. But I am sure you will be able to decipher that of them all I do not speak. But of many. Too many for me. This Albert guy included. A good communicator though. Buckles you in very tight and proper, but totally lost is his train in the woods. A philosopher.
@@premkumarrn6674 To me time is the moment of now. What we remember is a lot of "now's".
The measuring of time is some thing different. It is the counting of a number of occurrences (or now's).
The thing we can measure are cycles. We count days. We count years - and then we divide it up and make hours, minute's and seconds etc.
I believe that in every particle (so called) there is a small clock. I believe these clocks are like electric oscillations in every electron, every atom and so on. That will account for that if one thing is moved in regards to another thing it will experience a different time. A fast moving thing will have a slower oscillation and as such have slower time (time dilation).
One proof I believe that time can not go backwards is that if we shine a light on an atom at the right frequency the atom will absorb some of the light energy. It will cause the electrons to go outwards and there by absorb energy. Later these electrons may jump inwards again and give off light (a so called photon) but in random directions. Now if we reverse this and bombard the atom with light photons from random directions we will not get a light beam out in just one direction as we started with. It will just come out in other random directions. A video plaid in reverse would make a light beam come out from an atom.
GRW theory is merely a refinement of Vonnegut's Universal Will To Become, which now reads as Universal Will To Become Localized.
I'd love for you to do an episode with Robert Lawrence Kuhn - you both have interviewed similar people about similar topics, plus I don't think Robert is appreciated enough as an expert in his own right.
Yellowing of paper if it was merely oxidation would be a reversible phenomenon, although the additional breaking of chemical bonds in the lignin and cellulose makes this more difficult 🤔 20:13
Please consider putting back the videos of you playing the drums when you play the audio :)
if you watch the billiard balls but with a special camera you can see them radiating away because their temperature is above absolute zero. so you can decide by watching if time moves on or not. or can you?
Good.
Nothing is ever truly at rest in an expanding universe.
The question in my opinion is whether future can be predicted with certainty or not .
I doubt it, not with Bell’s theorem and non locality .
Yes and no. ;)
Just because microscopic processes appear temporally symmetrical does not mean they occurred both ways. The arrow of time is ambiguous unless observed in this case. Think of a camera recording two billard balls colliding, creating an ambiguous video, the camera person knew which came first.
the camera person is made of 'ambiguous' billiard balls so why is the camera man not ambiguous?
Students shared "i" Am will say, LORD ye have been so patience!
I believe that if an atom is illuminated with light from one direction of a correct frequency the electrons may jump inwards. They may later randomly jump outwards again and light will be emitted in a random direction.
If we illuminate the atom randomly (reverse of the above) and light is absorbed it will not come out in one direction if it is re emitted. This should prove that an occurrence can not be reversed like a video can.
I think we need to question in the first place that time flow is reversible is meaningful in any sense of the word.
I agree. It was an interesting talk and talented and engaging speaker etc BUT - as a non speciaist, its seems the science community is asking a lot for us to accept that because we could fiddle with our camera, and play the film of the billiard balls stiking backwards, and it would "look the same" - that time flow is assymetrical and can flow backwards and forwards just as easily. Is there a better example/illustration?
..... The billiard ball example doesn't do it for me. For example, I can watch a car crossing my horizon - and a large aeroplane flying above in the same direction. The speed they are travelling may " "look the same" - but we know that the speed is different, and the plane is much quicker. Our daily experience, dropping an egg on the floor etc suggest time flows in on direction.
If I placed a sugar cube on top of the stationary billiard ball, then the film reversal is obviously not the same.
What am I not understanding here ?
Time "flows" with the speed of light. It's the measure of change. Cause and effect, observer doesn't matter (if he can distinguish between past and future or not). Physical effect, which are all the bosons happen to move with the speed of light.
Great interview!
I suspect much confusion comes from the difficulty of accepting existence without time. Indeed, it is at first hard to imagine that something exists without it exists in time. But if time is, as some will argue, emerging, and maybe simply "change", existence will have to be possible without time, and duration as well as universal coordination of motion in accordance with the Lorentz transformations will need explanations other than those of being due to the existence of time.
Better than clickbait physics
What is hope? Nor what is less?
Things fall downwards. That tells me the sense of forwards time.
In think you’re missing the point. Newtonian mechanics is time reversible.
@pmcate2 Thank you for your comment. Perhaps I am missing the point. Are you saying that the fact that things fall downwards doesn't provide a sense of time? If so, please enlighten me as to why.
@pmcate2 Yes, Newtonian mechanics is time reversible. But it is a mechanics of point particles. That is an idealisation that allows point particles to have finite mass. It amounts to an assumption that force can propagate so fast that the diameter of a particle is negligible. That abolishes causal delay. Newton did not reckon on the finite speed of causation (aka speed of light). Causal delay is built into our world. It isn't reversible.
@@christophergame7977 I don't think that reasoning is correct. Newtonian mechanics is based on differential equations and so is general relativity. In other words, both theories are built on infinitesimals. Both mechanics can model point particles or objects with non-zero volume, so I don't think the issue comes from point-particles. I will back track slightly on what I said before: Newtonian mechanics is time reversible if the force is conservative, which is the case for gravity. As for your original comment, I guess it is correct in a rough sense. But what if you were in a spaceship in intergalactic space? You couldn't use your test to establish a sense of time. That comes from something else. It's more than just objects falling to the surfaces of planets. That was my point.
@pmcate2 Thank you for your response.
Yes, Newtonian mechanics is formulated in differential equations. But what makes it mechanics is its ability to refer to point particles. (Yes, one can construct continuum mechanics from it.) I still say that point particles are abstractions that rely on infinitely fast propagation of force, which wrecks the idea of causal delay. As for infinitesimals, calculus can do without them. A topic for another place.
As for my space ship. Was it Cavendish who in 1798 showed gravitational attraction by putting suspended barbells half beside, half at length? Mine is a big spaceship with a big lead floor. I think that deals with that question?
I am a little surprised to see you say that you guess that my comment is, in a rough sense, 'correct'. I was open to your insisting it is nonsense. I don't recall seeing it advanced as a way of defining the sense of time. I think it is such, but again, many people seem to insist that the time symmetry of Newtonian mechanics by itself leaves us without a touchstone for the sense of time.
I have recently seen an argument that there is a problem with the time reversibility of Newtonian mechanics. One can let a particle be carried by its momentum to rest at the top of an ideal windless hill, where it will stay ever after.
I think that time occurs in finite stretches. A point in time is only an abstraction, not an actual process.
Actually if the film of billiard balls is of very very high quality you can compute the slight loss of kinetic energy after the collision due to a small transfer of kinetic energy into heat and therefore determine the time arrow
But Oswald did miss Kennedy…
Thanks!
All this masterclass was mindblowing to me. If this is true, could we argue for telepathy, or exchange of information at a distance? There is this TikTok game where a couple plays, counts to three, and says the first word that comes to mind. Then they count to 3 again and say another word, repeat until you reach the same word. Could we argue that information was exchanged by doing the word repetition because what I do now affects the future? I am not a physicist or scientist, just a guy with questions
David Albert: "Good."
Inego Montoya: "You keep using that word. I do not think it means what you think it means."
The arrow of time is the accumulation of causal event data. You cannot rationalize times arrow looking at an isolated physical process hypothetically, you have to look at the same process occurring in reality as a product of a causal event and it becomes self-evident.
Even the deceiver imitating HIM! Can't hold this book! Without being crushed nor consumed in front of HIM!
Thank you Algorithm.
And many upon all dry grounds!
And thank you for visiting to comfort thy Son for many have NOT KNOWN HIM?
Need link to video on "measurement problem".
Good
That's the listener tax on Albert talks.
Beat me to it.
Time is the entropy of spacetime, how difficult can this be, lets get past this endless back and forth.
its difficult because evolving forward in time gets you less ordered states but evolving backwards in time also gets you less ordered states. except we don't observe that in systems. where is the arrow coming from?
another conceptual problem with entropy is what is a valid coarse graining? different definitions of a macro state give different definitions of entropy. entropy is always measured relative to an observer (macro state). you can have situations where one observer will say its increasing another will say its decreasing.
getting past things that aren't understood isn't a good idea
What is Nostradamus' predictions or premonitions, of records of the future.?
Where are they?
Is Prof DaveAlb going down in history ? Bet ?
For thy Lord to see! My shared "i" Am Host Robinson will do concerning have drawn near!
A+
good
You should bring Tim Maudlin too since he has a very different perspective, since he doesn't think time's arrow is reducible to entropic assymetries
oh just reached the end of you guys discussed that you will be bringing Tim Maudlin lol
We don't remember and have record of the future because it hasn't happened yet.
The billiards is interesting, because it is elastic, but lets say there is a slight faliure, a slight breakdown of elasticity, then after the collision entropy will have increased because there is no heat in the balls that was purely kinetic energy in one ball before the collision and in the frame of 0 momentum the individual momenta of the two balls must be slightly reduced in their respective directions of motion. Therefore there is a clear distinction between past and future that is encoded in the microstates of the two balls, it is not a fundamental irreversibility, but a statement about the configurations that lead ti elastic breakdown. And so will it be with all such distinctions between past and future, and an eternal directionality will then require the world to be a system with no ground state.
What is mountains nor the highest mountains before HIM? Melted as wax in front of HIM!
Yes, but time is also the framework within which meaningful human development occurs. That is in fact its primary purpose.
Holography is the representation of reality of moment of time reversal. Large BH has low temperature, thus low entropy. Penrose's CCC predicts such BH can be seen in CMB of the next aeon, like in our universe, where holography of the surface of the BH of the next cycle will show the entire time traversed.
Yeah and BC id CMB which is AA. The point is we are inside a giant black hole where time looks upon itself.
If it’s just an illusion then we can go back in time?
We have good precognition
Fun fun fun!
Fun my ass billiard ball crack
To every action there is an equal and opposite reaction. Undisputable law of the universe.
Yet, taking ownership!'
What about thermodynamics?
Time is a compact dimension one single Planck second in size.
And you can travel almost nowhere in that Planck second, if you stand at a pole, or you can move one full Planck length! Though outwardly because of texture of space it looks like a reduced Planck
Arrow Time's on Masterclass A. 😵💫 ( Minutes five taken have should this.)
There is effectively not even an infinitesimally tiny reference point where the future meets the past. The present is both eternally in motion and utterly in stasis.
That's why we have ideas like the specious present
1:27:10 Why does he always leave off the relational interpretation?
The only thing I took away from this is that I need to play with more billiard balls in the future
Robinson: This whole episode will be about the mirror of time.
David: Good.
Robinson: Before we go on the air, do you want to consult the mirror in my bathroom?
David: Huh? You have a mirror in your bathroom? Whatever for?
I shouldn't laugh. I'm still (mostly) that person myself. I also galumph into normal-sized chairs in exactly the same way.
While entropy provides a statistical explanation for irreversibility, quantum randomness adds a fundamental, non-deterministic layer:
Even if we could hypothetically reverse all classical motions (e.g., all gas molecules or heat particles), quantum randomness would still prevent an exact restoration of the initial state.
Quantum processes are not strictly time-symmetric because of the probabilistic nature of quantum events (e.g., particle decays proceed forward but not backward).
Yes, Michel Bitbol and Francois-Igor Pris have talked about this. There is a clear arrow of time at least from a pragmatic standpoint even in classical mechanics, because we are always passing from prediction into the realization of the properties of a system. Prediction always contains errors and thus many possible properties can be realized, yet in practice only a single outcome is realized, which closes the door to all other possibilities, ultimately making it asymmetrical.
In classical mechanics, you can interpret this as, again, purely pragmatic, that it is just due to the ignorance of the observer and that at a fundamental level there was really genuinely only a single possible option, so it remains symmetrical in some god-like frame of reference. This does not work in quantum mechanics, however, if there are genuinely random events, because evolving the state's system into the future would not be the same as evolving it into the past. This pragmatic asymmetry becomes an ontological asymmetry.
The future is genuinely "open" as opposed to the past which is "closed."
Showering with riches to approach thy Lord!
It's an illuuuuuuuusion!
I love David Albert but I prefer Wolfram's explanation of time as the progression of a computation, not an illusion.
every which way is forward. there is no causality but something similar, every particle is moving with laws of physics, in a determined dance.