This is some of the purest intellectual gold out there my friend. I could listen to David talk all day, he's not afraid to get into the weeds, his ideas are always very thorough and sprinkled with the sort of wit only he can conjure. Thank you endlessly for this, is there a patreon for your podcast?
@@robinsonerhardt Dude, stop! Keep going and you will make me readjust my deep anti-Stanford prejudices. Couldn't agree more with Epistemological Despair above. I got here by way of following Tim Maudlin and your (later) conversation with him AND David Albert. (Anybody who liked this one, go there NOW!) I am just an old man who can read (and still think semi-clearly occasionally) and who has tried to follow the elite and elusive (and, at times, maddeningly sloppy) debates around these issues for several decades. I can tell you, to hear conversations like this happening is far more than interesting. They satisfy on levels hard to describe. Maybe Epistemological Hope is on the way? If not for "truth" at least for honest clear conversations. Thank you, sir.
The Arrow of Energy: "In any system of energy, Control is what consumes energy the most. Time taken in stocking energy to build an energy system, adding to it the time taken in building the system will always be longer than the entire useful lifetime of the system. No energy store holds enough energy to extract an amount of energy equal to the total energy it stores. No system of energy can deliver sum useful energy in excess of the total energy put into constructing it. This universal truth applies to all systems. Energy, like time, flows from past to future".
Please have Tim Maudlin on the podcast. He will explain that thinking of the time dimension as being qualitatively the same as the other 3 space dimensions is a mistake in the first place. And the key difference is that the time dimension has the notion of direction built into it. And just because we call time the 4th dimension, does not therefore mean that qualitatively it has to be dimension like spatial dimensions. That is why, instead of thinking of the universe as 4 dimensional manifold, we should think of it as a 3+1 manifold. Remember the minus sign in the Mikowski spacetime distance between two events: s^2 = t^2 - (x^2 + y^2 + z^2) That minus sign tells us that the time dimension is different. Minkowsky space is not Euclidean 4-dimensional space.
That's certainly a good point. On the other hand, in Relativity there is no unique way to have spatial slices in some moment of coordinate time ( in other words we cannot uniquely separate 4d spacetime into 3+1 space and time, because there's no single preferred "coordinate Time" to choose). So, perhaps the best way is to use the "causal structure" and talking about " timelike " trajectories ( worldlines) or hypersurfaces, vs "spacelike " distances/or hypersurfaces etc.
To be honest, I don't know why we even refer to linear experience as a dimension, as, by definition, it is not a true degree of freedom. I think it is much more effectively described as being nothing more than simply a Pervasive quality of our experience. It only seems to exist as an artifact of the mechanism by which the universe facilitates spontaneous symmetry breaking, and the subsequent generation of mass,, through the Higgs mechanism: A continuous, pervasive, self-referential calculation that determines, according to a set of rules, which specific Configuration of masses the probabilities will collapse into. Interestingly enough, it seems to preferentially collapse the components of the system into states that embody the qualia that will generate the maximal amount of subsequent interactions with the other components of the system, which has the side effect (or intention, if such a thing is possible) of generating a maximal amount of information with each calculation. ( In my understanding, this is likely because the generation of information is only possible through the expenditure of energy, meaning that the resulting state in which the energy is the most uniformly spread out as novel information would be the most entropically favorable, but, honestly, I would be hard pressed to even call that explanation half-baked, as there doesn't seem to be a satisfactory description of exactly how entropy primarily interacts with our universe, especially on or beyond the cusp of the portion of reality that manifests within the confines of spacetime.) The aforementioned comoutation is outlined in the Wolfram Physics Project, and seems to me to be the best definition, as to the behaviors of reality we have thusfar cataloged, so I like to compare it with other models of reality as I come to understand the observed behaviors and their effects more completely, and I actively encourage any comments or criticisms. Honestly, Donald Hoffman's theory that conscious agents are the fundamental building blocks of existence has the very alluring benefit of making sense of why these computations even take place to begin with, As their nature of inherently collapsing probabilistic wave functions through I'm the only sensible reason why the universe would violate the law of conservation of energy, and create this otherwise meaningless physical reality. Regardless of what the fundamental nature of reality truly is, or if we can ever fully grasp it from within hour inherently limited perspectives in space time, I think that we are Going to have to swallow more than one quite seemingly large paradigm shift in our quest to uncovers it.
42:00 the problem with the billiard balls example is that a careful detection of the "backwards" version of this procedure ( e.g measuring velocities/ directions of the balls) reveals the asymmetry, due to the heat loss during the collisions. This issue cannot be avoided for macroscopic objects although it is usually assumed that the losses can be - in principle - negligible. In all these considerations, the Elephant in the room is the "dividing line" between what is considered elementary and what "macroscopic". Such macroscopic objects with internal structure and non vanishing size are not test particles.
He’s referring to idealized billiard balls, and I think really it’s just meant as a more intuitive stand-in for a few elementary particles bouncing around. Of course real life macroscopic billiard balls still in principal reflect the arrow of time, as you suggested, although you might have to look very carefully to notice it
@@jordanbvids The Past Hypothesis is probably a significant part of the answer ( for the arrow of time in our fundamentally reversible currently known physical theories), but is it the whole answer?
I also think so; there is some tension between the mechanical description of the world and the thermodynamical description. Though this problem is known for more than a hundred years now, I have the feeling, this tension has never been fully resolved. The "proof" that both, the mechanical description and the thermodynamical description would not be in tension with one another (but could be smoothly blended into each other) came from Boltzmann and Paul and Tatjana Ehrenfest. But I tend to disagree because it is not clear, why and how there are macrostates at all in the mechanical world and why it would be okay to "lump together" (i.e. count) all microstates compatible with a given macrostate. In mechanics, at any given point in time, there is just one microstate - and that's it. The "pull" of entropy (i.e. the drift towards macrostates that can be realized via an increased number of microstates) is just not there. A microstate doesn't "know" of any other (similar) microstates, it just evolves according to the laws of motion of mechanics. I have the feeling that some intermediate theory is missing; a theory, which describes how the macro-behaviour arises from the underlying mechanics. I think, what is needed, is some sort of natural explanation, how information about the microstate *really* vanishes, when adding particles and going to the macro. I reckon that there must be some sort of self-sampling going on; and that self sampling goes along with a real loss of information.
I totally love him! He was also on 23 with Justin Clarke-Doane and 67 with Tim Maudlin. 67 is almost certainly the best episode of the show so far, so check it out if you haven't!
@@robinsonerhardt his discussion with maudlin and you lead me to this video! Seriously man! Thanks for cranking out the content. Insanely wonderful discussions. Brings me so much joy rn
Thanks for visiting the show Mr. Albert and spending such valuable “time?” Speaking on such amazing topics. I am following a lot of your work and it is so amazing how much I have learned this past year from your educational efforts.
❤thanks so much for podcast. Following David Albert since the release of film"What the bleep". His extended interview in CD, was just the grounding I needed in naturalism. Perhaps future questions might cover, Hawkin's initial claim the exisrence of black holes violate the conservation of info, matter and energy, rendering our models of physical laws not only incomplete, but wrong with respect to causes preceeding effects, the flow of time. Sure a mathemagical solution was proposed involving a holographic model, where three dimensions are preserved in two dimensions, the edge of the black hole. Seems lkke a gimmick to me. Math modeled by a former NY plummer. But it achieves the naturalist's goal and preserves the physical laws. Do we have a light horizon? This is by far the best podcasts I have seen. ❤
41:30 The fundamental microscopic laws of physics are not time symmetric, if we assume CPT invariance. We know CP symmetry is violated (1964), so T invariance must also be violated to preserve CPT invariance.
47:00 onwards: Semi-classical physics ( QFT in curved spacetime background) with the 50 years ongoing controversy about the fate of information/ retrodictability in the case of the evaporating black holes has risen doubts about the fundamental universality of time reversal invariance.
The discussion at 43:00 seems to be misleading. Even when the film of billiard balls is shown in reverse, the time itself is still moving in the forward direction. Only the film is moving in front of the projector lens in the reverse direction. Similarly, when it is said that microphysics is time reversible - is a misleading statement. The correct way to think about it is that it is velocity reversible. Remember velocity is a vector. So reverse velocity basically means the distance traversed in the opposite direction but time (denominator) is still moving in the forward direction. IMO reverse flowing time is a meaningless concept. Time can only flow in one direction - which we happen to call forward. Just because the word reverse is the opposite of forward, does not mean that it can be meaningfully applied to time or order of events. It is somewhat like -3 is the opposite of +3, but only +3 apples make sense. -3 apples are a meaningless concept. If microphysics is thought to be velocity reversible (not time-reversible) there is no confusion, because time does not have to flow in the reverse direction. Also in the billiards experiment, the balls would have heated up after the collision, therefore we would have been able to tell whether the film was running forward vs backward. And if we were disallowed access to the temperature change information then that loss of knowledge makes the experiment constrained and contrived.
I’m halfway through, but I wished to ask when “physics” became the study of atoms and galaxies rather than the original study of nature. When did the rest of natural philosophy become their own disciplines and why did the study of galaxies stayed in the category “physics” (I think it’s easier to see why atoms remained there)
An interesting discussion! Maybe I'm missing something but the talk about time directionality strikes me as confused and much ado about very little. I see both time reversal symmetry and the arrow of time argument from entropy as canards. Simply, when something changes it cannot unchange. It might be good fantasy to believe in time travel but the Law of Identity and the laws of logic tell us that is a contradiction and thus forbid it. You've got to look at reality. Then metaphysics trumps physics, full stop.
When we access (remember) the past in the present, we can do so only if we can access the traces left by the past events on the environment in the present. We do not access the past directly in the present. And why we do not remember the future in the present because the traces left by future events cannot be accessed in the present. What is the big deal? It is trivial.
The idea that the future, on into infinity, already exists is just nonsense. The only thing that exists is the present instant. You don't still exist in the past. There is no past, nor future, to access.
You have to specify what you're talking about: If you're referring to "proper time" , that is uniquely defined for each timelike trajectory ( worldline in Spacetime) then you have a point. But philosophers and physicists are usually referring to the non uniquely defined 'global ' notion of Time. There are arbitrarily many ways to slice spacetime into space and time, so there's no universal "present instant" as you seem to believe. On the other, the notion of a Block Universe as "already existing" is a category mistake, i could agree on that...
It's not nonsense. What perdurance/4 dimensionalism/block universe asserts is that the past, present, and future are all equally real, not that things in the past exist *now.* Words like "now," "still," "already," and other terms that invoke tense are treated as temporal indexicals in the block universe model, in the same way that words like "here" and "there" are spatial indexicals. To say that dinosaurs exist is not to say that dinosaurs exist at every point in time, any more than to say that London exists is to say that London exists at every location in space.
There is a problem with time , the problem arises when Homosapiens describe the world around them , a description with just events and an understanding of those processes gives a more than adequate description as you are describing all that is there , when we add time , time being an abstract idea that if we use gives us a false impression that those events take place within some frame work other than one of Quarks and Gluons and space , if you believe that space is a structure with physical properties and was in a state with few or no particles of mass and now we see lots of mass and if theories are correct will be in a different state with few or no particles as the processes goes through changes , then the notion of events being time reversible are false , if the universe we live in is a series of interactions and events that appear in a certain order then the events might lead back to a state they were in somewhere in that process before . which would look like time reversible , but which in fact are just the events and their order , i think personally , based on nothing more than my Homosapien intuition ( very unreliable ) that time will be seen as an add on and not a necessity built into the structure of space .
I have so much respect for David Albert. His willingness to explain things to us mortals is so appreciated.
I love David Albert. He speaks so clearly even a dumbo like me can understand him.
The cat was as excited to see David as Robinson was.
Tuning in now, happy to see David return !
He's the best.
This is some of the purest intellectual gold out there my friend. I could listen to David talk all day, he's not afraid to get into the weeds, his ideas are always very thorough and sprinkled with the sort of wit only he can conjure. Thank you endlessly for this, is there a patreon for your podcast?
I agree--I'm already excited to have him back again sometime soon. And I appreciate the thanks! There's no Patreon, but I appreciate your asking.
@@robinsonerhardt Dude, stop! Keep going and you will make me readjust my deep anti-Stanford prejudices. Couldn't agree more with Epistemological Despair above. I got here by way of following Tim Maudlin and your (later) conversation with him AND David Albert. (Anybody who liked this one, go there NOW!) I am just an old man who can read (and still think semi-clearly occasionally) and who has tried to follow the elite and elusive (and, at times, maddeningly sloppy) debates around these issues for several decades. I can tell you, to hear conversations like this happening is far more than interesting. They satisfy on levels hard to describe. Maybe Epistemological Hope is on the way? If not for "truth" at least for honest clear conversations. Thank you, sir.
@@patrickirwin3662 Haha! This is one of the best comments I have gotten. Thanks so much :)
The Arrow of Energy:
"In any system of energy, Control is what consumes energy the most.
Time taken in stocking energy to build an energy system, adding to it the time taken in building the system will always be longer than the entire useful lifetime of the system.
No energy store holds enough energy to extract an amount of energy equal to the total energy it stores.
No system of energy can deliver sum useful energy in excess of the total energy put into constructing it.
This universal truth applies to all systems.
Energy, like time, flows from past to future".
Please have Tim Maudlin on the podcast. He will explain that thinking of the time dimension as being qualitatively the same as the other 3 space dimensions is a mistake in the first place. And the key difference is that the time dimension has the notion of direction built into it. And just because we call time the 4th dimension, does not therefore mean that qualitatively it has to be dimension like spatial dimensions. That is why, instead of thinking of the universe as 4 dimensional manifold, we should think of it as a 3+1 manifold.
Remember the minus sign in the Mikowski spacetime distance between two events:
s^2 = t^2 - (x^2 + y^2 + z^2)
That minus sign tells us that the time dimension is different. Minkowsky space is not Euclidean 4-dimensional space.
That's certainly a good point. On the other hand, in Relativity there is no unique way to have spatial slices in some moment of coordinate time ( in other words we cannot uniquely separate 4d spacetime into 3+1 space and time, because there's no single preferred "coordinate Time" to choose).
So, perhaps the best way is to use the "causal structure" and talking about " timelike " trajectories ( worldlines) or hypersurfaces, vs "spacelike " distances/or hypersurfaces etc.
To be honest, I don't know why we even refer to linear experience as a dimension, as, by definition, it is not a true degree of freedom. I think it is much more effectively described as being nothing more than simply a Pervasive quality of our experience.
It only seems to exist as an artifact of the mechanism by which the universe facilitates spontaneous symmetry breaking, and the subsequent generation of mass,, through the Higgs mechanism: A continuous, pervasive, self-referential calculation that determines, according to a set of rules, which specific Configuration of masses the probabilities will collapse into. Interestingly enough, it seems to preferentially collapse the components of the system into states that embody the qualia that will generate the maximal amount of subsequent interactions with the other components of the system, which has the side effect (or intention, if such a thing is possible) of generating a maximal amount of information with each calculation. ( In my understanding, this is likely because the generation of information is only possible through the expenditure of energy, meaning that the resulting state in which the energy is the most uniformly spread out as novel information would be the most entropically favorable, but, honestly, I would be hard pressed to even call that explanation half-baked, as there doesn't seem to be a satisfactory description of exactly how entropy primarily interacts with our universe, especially on or beyond the cusp of the portion of reality that manifests within the confines of spacetime.)
The aforementioned comoutation is outlined in the Wolfram Physics Project, and seems to me to be the best definition, as to the behaviors of reality we have thusfar cataloged, so I like to compare it with other models of reality as I come to understand the observed behaviors and their effects more completely, and I actively encourage any comments or criticisms.
Honestly, Donald Hoffman's theory that conscious agents are the fundamental building blocks of existence has the very alluring benefit of making sense of why these computations even take place to begin with, As their nature of inherently collapsing probabilistic wave functions through I'm the only sensible reason why the universe would violate the law of conservation of energy, and create this otherwise meaningless physical reality.
Regardless of what the fundamental nature of reality truly is, or if we can ever fully grasp it from within hour inherently limited perspectives in space time, I think that we are Going to have to swallow more than one quite seemingly large paradigm shift in our quest to uncovers it.
42:00 the problem with the billiard balls example is that a careful detection of the "backwards" version of this procedure ( e.g measuring velocities/ directions of the balls) reveals the asymmetry, due to the heat loss during the collisions. This issue cannot be avoided for macroscopic objects although it is usually assumed that the losses can be - in principle - negligible.
In all these considerations, the Elephant in the room is the "dividing line" between what is considered elementary and what "macroscopic".
Such macroscopic objects with internal structure and non vanishing size are not test particles.
He’s referring to idealized billiard balls, and I think really it’s just meant as a more intuitive stand-in for a few elementary particles bouncing around. Of course real life macroscopic billiard balls still in principal reflect the arrow of time, as you suggested, although you might have to look very carefully to notice it
@@jordanbvids The Past Hypothesis is probably a significant part of the answer ( for the arrow of time in our fundamentally reversible currently known physical theories), but is it the whole answer?
I also think so; there is some tension between the mechanical description of the world and the thermodynamical description. Though this problem is known for more than a hundred years now, I have the feeling, this tension has never been fully resolved. The "proof" that both, the mechanical description and the thermodynamical description would not be in tension with one another (but could be smoothly blended into each other) came from Boltzmann and Paul and Tatjana Ehrenfest. But I tend to disagree because it is not clear, why and how there are macrostates at all in the mechanical world and why it would be okay to "lump together" (i.e. count) all microstates compatible with a given macrostate. In mechanics, at any given point in time, there is just one microstate - and that's it. The "pull" of entropy (i.e. the drift towards macrostates that can be realized via an increased number of microstates) is just not there. A microstate doesn't "know" of any other (similar) microstates, it just evolves according to the laws of motion of mechanics. I have the feeling that some intermediate theory is missing; a theory, which describes how the macro-behaviour arises from the underlying mechanics. I think, what is needed, is some sort of natural explanation, how information about the microstate *really* vanishes, when adding particles and going to the macro. I reckon that there must be some sort of self-sampling going on; and that self sampling goes along with a real loss of information.
Albert is great! I read quantum mechanics and experience! Albert is great guest 🖤
I totally love him! He was also on 23 with Justin Clarke-Doane and 67 with Tim Maudlin. 67 is almost certainly the best episode of the show so far, so check it out if you haven't!
@@robinsonerhardt his discussion with maudlin and you lead me to this video! Seriously man! Thanks for cranking out the content. Insanely wonderful discussions. Brings me so much joy rn
Thanks for visiting the show Mr. Albert and spending such valuable “time?” Speaking on such amazing topics. I am following a lot of your work and it is so amazing how much I have learned this past year from your educational efforts.
❤thanks so much for podcast. Following David Albert since the release of film"What the bleep". His extended interview in CD, was just the grounding I needed in naturalism.
Perhaps future questions might cover, Hawkin's initial claim the exisrence of black holes violate the conservation of info, matter and energy, rendering our models of physical laws not only incomplete, but wrong with respect to causes preceeding effects, the flow of time.
Sure a mathemagical solution was proposed involving a holographic model, where three dimensions are preserved in two dimensions, the edge of the black hole.
Seems lkke a gimmick to me.
Math modeled by a former NY plummer.
But it achieves the naturalist's goal and preserves the physical laws.
Do we have a light horizon?
This is by far the best podcasts I have seen. ❤
I am so happy to hear this! He'll be back soon :)
the holographic principle is for anti De-sitter space and not our universe , there is empirical evidence for black holes now .
41:30 The fundamental microscopic laws of physics are not time symmetric, if we assume CPT invariance. We know CP symmetry is violated (1964), so T invariance must also be violated to preserve CPT invariance.
47:00 onwards: Semi-classical physics ( QFT in curved spacetime background) with the 50 years ongoing controversy about the fate of information/ retrodictability in the case of the evaporating black holes has risen doubts about the fundamental universality of time reversal invariance.
seems the cat really enjoys David's explanations :)
We all do!
State-vector collapse is time-asymmetric.
The discussion at 43:00 seems to be misleading. Even when the film of billiard balls is shown in reverse, the time itself is still moving in the forward direction. Only the film is moving in front of the projector lens in the reverse direction. Similarly, when it is said that microphysics is time reversible - is a misleading statement. The correct way to think about it is that it is velocity reversible. Remember velocity is a vector. So reverse velocity basically means the distance traversed in the opposite direction but time (denominator) is still moving in the forward direction. IMO reverse flowing time is a meaningless concept. Time can only flow in one direction - which we happen to call forward. Just because the word reverse is the opposite of forward, does not mean that it can be meaningfully applied to time or order of events. It is somewhat like -3 is the opposite of +3, but only +3 apples make sense. -3 apples are a meaningless concept.
If microphysics is thought to be velocity reversible (not time-reversible) there is no confusion, because time does not have to flow in the reverse direction. Also in the billiards experiment, the balls would have heated up after the collision, therefore we would have been able to tell whether the film was running forward vs backward. And if we were disallowed access to the temperature change information then that loss of knowledge makes the experiment constrained and contrived.
I’m halfway through, but I wished to ask when “physics” became the study of atoms and galaxies rather than the original study of nature. When did the rest of natural philosophy become their own disciplines and why did the study of galaxies stayed in the category “physics” (I think it’s easier to see why atoms remained there)
Yes, that's a great question!
An interesting discussion! Maybe I'm missing something but the talk about time directionality strikes me as confused and much ado about very little. I see both time reversal symmetry and the arrow of time argument from entropy as canards.
Simply, when something changes it cannot unchange. It might be good fantasy to believe in time travel but the Law of Identity and the laws of logic tell us that is a contradiction and thus forbid it. You've got to look at reality.
Then metaphysics trumps physics, full stop.
When we access (remember) the past in the present, we can do so only if we can access the traces left by the past events on the environment in the present. We do not access the past directly in the present. And why we do not remember the future in the present because the traces left by future events cannot be accessed in the present. What is the big deal? It is trivial.
Only 5500 views
This is David Albert FFS
Everyone should see this at least 3 times. That's 21 billion views give or take.
great podcast. some timestamps would be useful.
Thanks. I have started including outlines in more recent episodes.
Ads every five mins
The idea that the future, on into infinity, already exists is just nonsense. The only thing that exists is the present instant. You don't still exist in the past. There is no past, nor future, to access.
non-intuitive perhaps, but not nonsense
You have to specify what you're talking about:
If you're referring to "proper time" , that is uniquely defined for each timelike trajectory ( worldline in Spacetime) then you have a point.
But philosophers and physicists are usually referring to the non uniquely defined 'global ' notion of Time.
There are arbitrarily many ways to slice spacetime into space and time, so there's no universal "present instant" as you seem to believe.
On the other, the notion of a Block Universe as "already existing" is a category mistake, i could agree on that...
It's not nonsense. What perdurance/4 dimensionalism/block universe asserts is that the past, present, and future are all equally real, not that things in the past exist *now.* Words like "now," "still," "already," and other terms that invoke tense are treated as temporal indexicals in the block universe model, in the same way that words like "here" and "there" are spatial indexicals. To say that dinosaurs exist is not to say that dinosaurs exist at every point in time, any more than to say that London exists is to say that London exists at every location in space.
There is a kind of madness amongst some with higher intellect. So much junk spoken at the outer fringes of science.
There is a problem with time , the problem arises when Homosapiens describe the world around them , a description with just events and an understanding of those processes gives a more than adequate description as you are describing all that is there , when we add time , time being an abstract idea that if we use gives us a false impression that those events take place within some frame work other than one of Quarks and Gluons and space , if you believe that space is a structure with physical properties and was in a state with few or no particles of mass and now we see lots of mass and if theories are correct will be in a different state with few or no particles as the processes goes through changes , then the notion of events being time reversible are false , if the universe we live in is a series of interactions and events that appear in a certain order then the events might lead back to a state they were in somewhere in that process before . which would look like time reversible , but which in fact are just the events and their order , i think personally , based on nothing more than my Homosapien intuition ( very unreliable ) that time will be seen as an add on and not a necessity built into the structure of space .