I love that there is more than 1 guest. Robinson is a great interviewer but sometimes it feels like the answers to his questions are standard answers to such questions. Still good questions but not really a challenge for the guest. When the guests start to ask questions to each other you see that the guests have to think a bit more about the answer. Great episode!
I'm really enjoying these episodes on the foundations of physics -- who knew there was so much interesting stuff that I haven't thought about yet:D Greatful for the time from everyone participating:) Also I appreciate the both the clarity and the charitability in these discussions;)
Craig’s comments at 14:02 are really enlightening. In my opinion it’s a pretty damning criticism of a discipline and it’s methods when it can carry on for decades ‘investigating’ pseudo-problems like this…
Thanks for getting these two absolute legends of the current literature of time in here! I identify as an amateur philosopher dropping my few cents over here 23:35 Tim doing a lot of mental gymnastics. "There are facts, there are facts about the past, therefore there is a past." But the point is, is it manifest? Can you travel there? Indeed, mathematically or in your imagination presentism and eternalism should portray the same manifest reality, but which is more accurate concerning the word 'is'? You can travel left and right in space, therefore space 'is'. But you can't travel back into the past. Therefore the past 'isn't'. It all determines on what you put as a 'first coordinate' (or origin) in your theory or ontology, and for me that is our conciousness or existence in this moment. And not the mathematics and predictability conjured up, no matter how truthfull, by our minds. Therefore presentism is more relevant than eternalism in my opinion ------- I guess my next point is imagination has to be taken into account: both presentism and eternalism are visually imagined by our brain in the visual cortex. Which one is more 'real' though? Which one 'is'? Then you need to make a division between imagination and the external world, and as such we get into Kantian area.. -------- I feel it's fair to say eternalism is like the Everettian interpretation of reality, taking the unitary wavefunction seriously, while presentism is like Bohmian mechanics that takes reality's side seriously. --------- 33:00 the timelike area of the spacetime diagram (the light cone) supervenes on the spacelike area according to entanglement! Where there is time, there is also space in this diagram! Timelike doesn't equate to time, but to time + space! Therefore time is not different than a mathematical algorithm on the space dimension, which sounds like an indication for presentism. Proof of this is if you hypothetically decrease the lightspeed, the current timelike area will become spacelike. And for other reasons this is true: the null lines moves through space, thus the intermediate timelike area must also be in space. -------- Also I think again time travel is an important distinction between what can be counted as reality. If we can travel to the past, making the past the future, then eternalism makes sense. If however you can't travel to the past, a.k.a. make your past the future, then presentism makes sense. It means time is mostly current, the present, which can oscillate backwards and forwards with its internal energy but is restricted to a future move due to statistical mechanics. Otherwise the past could be the future according to this logic (Huw Price). --------- 1:17:00 David Wallace speaks of recurrent systems and irreversible systems with attractors, in deterministic classical mechanics. This is a better physical explanation then "causes precede effects", because this presumes human categorization of causes and effects (David Hume). In my opinion in classical mechanics the Hamiltonian is conserved, which means energy is conserved. Yet time is still deterministic with due to the first law of Newton, which is due to the conservation of energy. Therefore I feel there is something like a cosmic Hamiltonian, of potential and kinetic energy, starting with the big bang to now, in which potential energy gets turned into kinetic energy according and equalling the second law of thermodynamica, increasing entropy and with that causing the arrow of time. So spacetime has a local Hamiltonian which is conserved and called classical mechanics; and on top of that there is a global Hamiltonian of the expanding universe which causes a forward time direction due to entropy. So basically my thesis is that the potential for (literally!) thermodynamics is caused by the expansion of the spacetime of the universe...maybe similar to prof. Richard Muller's idea from Berkeley? Haven't read his book yet
The trick to superluminal signaling is that the ability to verify the results of measurements requires signaling that obeys relativity. The correlations are not communicable via light signals. There is a distinction between the signals that verify the results of the measurements and the correlations themselves.
@@robinsonerhardt It was a compromise between not wanting to measure success or worth in numbers and wanting your podcast to reach as many people as possible. ;)
When Craig started talking about the speed of light my first thought was “I wonder if Tim is going to say there’s no such thing as the speed of light” which is what he says in his Philosophy of Physics: Space and Time book, since relativisically speaking there are no speeds, the universe lacks the affine structure to talk about absolute speeds (but there are absolute accelerations). Tim understands talk of the speed of light as derivative, since reference frames are not part of the fundamental geometry of the world, they are mere representations of how we choose to assign coordinates. All there is to “the speed of light” talk is the law of light, the fact that the geometry of the world does include a light-cone structure and all worldlines of material particles are confined to the time-like regions of light-cone geometry.
Finally I am so glad to hear what Tim said about spacetime. Spacetime is not a 4D object where D standing for space like dimensions. Spacetime should be thought of as 3SD+1TD composite object where SD stands for space like dimensions which use the unit of distance and no intrinsic direction and TD stands for time like dimensions with a unit of time and intrinsic directional property and moving like a infinite, exorably moving treadmill belt undergirding the reality (only a vague metaphor). The rate of the time dimension is a relative notion and makes sense if we have clocks, which could be thought of as some cyclical subpart of the universe. If there were no cyclical subpart of the universe we will not be able to meaningfully talk about the rate of flow of time. In other words we can only measure the rate using some cyclic subpart if the universe. Without it, time will be reduced to a concept of change only. And if there is no change of state at all - time effectively seizes to exist. I think scientists know this but I blame their sloppy language/talk of spacetime as a 4D object to mislead people into conjuring up 4 spatial dimensional thingy. But one part I disagree with Tim is about is about the notion of global now - that global now is not from the perspective of a specific point in space, but from the point of view of each point's own perspective - in other words the proper time of each point itself. Think of the statement - the universe is thought of as being 13.7 years old no matter which spatial location you are in the universe. Why is that? Or think of the hypersurface of the end of every point's world line (worm). And if at the big bang the universe was at a point then long distances do no cause the issue of time needed to travel those distances. The light cones at that point are very very short (in height) with narrow base (spatial extent) and effectively touch each other for their full extent (from tip to the base) and then we follow the proper time of each point to get the global now. Hope this makes sense. The light cone structure tells us that the "now" that we visually perceive (fastest) is the very surface of the past light cone from our vantage point and not the global now. The auditory perception cone is a much narrower past sound cone which is obviously in the bulk of the past light cone. Also people should appreciate the fact that in terms of the day to day units we use for distance and time, the surfaces of the past and future light cones almost touch each other. Think this (crudely): --------- _____________________ ________________--------------- ==========================================*========================================== ______---------------------------------- --------------------------___________ i.e. the future and past light cone surfaces almost touching each other (for all practical, perceivable purposes) and only starting to sperate out vast distances away from our vantage point. Don't think this: . . . . . . . . * . . . . . . . . Agree with Tim that time intrinsically has a direction which is hinted at by the light cone structure and the fact that spacetime follows Minkowski hyperbolic geometry/metric (s^2 = t ^2 - x^2 - y^2 -z^2) i.e. the minus sign (i.e. the difference in SD and TD I talked about above) and not Euclidean geometry (d^2=x^2+y^2+z^2) and.
The way the universe works is b comes after a unless it comes before a in a changed timeline, then the universe will adjust and turn a into b and vise versa 👈
Your shirt is epic ….. tell Schrodinger that I AM 🐈 Such an interesting vid ! Love this ! Bell Institute sounds like a must donate to. Thanks Robinson and pod 🐈
I thought the discussion of the reality of the future was a bit fuzzy. It wasn’t clear to me that Tim was saying the future will be real or in some sense already is real. If there are two or more possible futures, the sense in which the undetermined future already is real seems like a nonobvious and interesting question.
I enjoyed this podcast. I'm glad foliations were discussed. I wonder how it may fit in with QFT or Bohemian Mechanics. The time of flight thing he talked about is pretty cool too that conceptually it is an interpretation of quantum mechanics which may answer certain questions that can't be explained by the other interpretations. I sorta felt left wanting about the A and B series discussion. I think it's more than that some A and B people can see compatibility between the 2 views but rather what makes them distinct. On the A view, there's something privileged about the present that the past and future aren't. There's tensed facts, the past has happened and the future has yet to come, temporal becoming is a real thing things go through. Time as we experience it isn't an illusion of our subconscious. Just because the past can't be changed, or what will happen will happen is a tautology, I think one would need more than the fact that light cones or a Minkowski space time is a useful way of understanding relativity to accept the B-view space time block. A nice book I read that introduced the A and B series to me was Time and Eternity.
Could we think of The Block consist of all possible interactions between quantum systems? Spatial separation and duration relations between the events are represented in Light cone structures.
as a presentist i need elements of reality now to be a transformation of elements of reality in the past and future, as an eternalist i need the same thing for continuity. if it's missing i can't make any sense of the continuity in the block or how the present turns into the future or got turned into by the past.
There is one thing about c -- the speed of causality -- which I find intriguing. The rate at which physics happens is the same everywhere because everywhere there is a local clock operating at the local speed of causality. Time can be seen as a kind of white-hole, emerging everywhere expanding each point's past light cone -- expanding the observable universe.
I sure wish that someone would have brought up Feynman's claim that the electron that emits the photon is in "agreement" with the electron that absorbs the photon. He was talking about quantum physics at the time, but i don't recall the specific context. It's always just kinda stuck in my head.
Proponents of pilot wave/ Bohmian mechanics ( like T. Maudlin) need an absolute reference frame, otherwise their quantum mechanics alternative doesn't work. But, in both Special and General Relativity there's no such thing as a preferred foliation. If your spacetime ( in GR) is "globally hyperbolic", you can choose any suitable spacelike hypersurface as a Cauchy surface, there's not a specific choice that is the "right" one. All such hypersurfaces are equally "good".
@@dimitrispapadimitriou5622 So on your understanding, GR is consistent with (but does not imply) a preferred foliation, right? ("Preferred," that is, on some basis not supplied by GR itself.)
@@snowpants2212 Well, no, I wouldn't say so: Starting from special relativity, if there's a need for a preferred foliation ( for fundamental reasons, as in pilot wave theories) then one cannot explain the usual well confirmed relativistic effects (like time dilation) in a simple kinematical way. One has to go back to the more complicated and contrived ether -related explanations ( see Larmor, Fitzgerald et al..). That's not strictly prohibited of course, but it's not Special Relativity. In GR things are getting even more complicated. Alternative theories of gravity with preferred foliation cannot compete the ( relative) simplicity, observational success and explanatory power of the standard GR. People are trying, though...
@@snowpants2212 There's no absolute simultaneity in Relativity, nor a definite temporal order between distant, space-like separated events, contrary to what is needed for non local hidden variable theories.
Time must be defined in relation to the size of now the observer experiences. For example, a newborn and a very elderly person may have very large, even vast sized perception of ‘now’, vs. a 40 year old with 4 kids, 2 jobs, and aging in parents may perceive a tiny, tiny ‘now’ as time flies by…. As if the amount of neurological physical change inside the brain - organized growth (newborn) vs. growing disorder (very elderly) vs. neural stasis of a middle ager forces.a dilation -or- contraction (dilation at the ends of the life cycle, contraction mid cycle) of the perception of ‘now’. Perhaps pre-post life/death - ‘now’ is ‘eternal - always- all time’. This is a theory I developed in college. Please reference me if you quote this.
Around 59:00 : This "simplicity" of adopting a preferred foliation is only superficial. As far as you're trying to just replace standard QM with an alternative theory like Bohm's it might seem quite easy and simple. But when you're trying to move to some other serious physics ( QFT, Gravity) things won't be so nice anymore...
The future, from my point of view, is a location (or a sequence of contiguous locations) in spacetime. We can't know the future with certainty, until we arrive at "that" particular location along our path or world line though spacetime. Once we arrive at or pass though a particular location in spacetime, "that point" immediately becomes the past-inaccessible, inalterable. So "time" or "when", is all about "where" we are at any "moment", and the future is a place where we are always traveling towards, from our birth to death.
There is a huge difference between "weak" non locality ( non separability) and "strong" non locality ( that implies causality violation). The former is well confirmed experimentally and does not contradict Relativity ( this is the kind of non locality that is associated with QM), while the latter belongs only to fiction, as far as we know ( and it could open Pandora's box if it was a real thing).
Scientist cannot predict the return of Haley's Comet, because of uncertainty. Haley's Comet may have been destroyed or deflected on its course in a collision with some object in the distant solar system. It's always possible, that Haley's Comet will never return.
find me a solution of a person where they are gaining knowledge while spitting out food and absorbing heat to do it. the direction of the formation of memories for example is known to always map onto a solution of a person eating food, getting hot, and then taking a shit, while forming memories, the direction of the formation of memories is always the same as the increase in entropy involved with driving the human physiology. i haven't found any counterexamples at least. if there is a gradient in entropy it is easy to explain the arrow of time in most systems in that context, but then when you get to equilibrium, processes in both directions sort of has to be equally likely. so either you admit defeat and say the initial conditions are always low entropy and then the directional of time survives for a while until you are just as likely to see a process happen in one direction as another direction. or you can say there is an eternal distinction by saying that entropy is a ball that is rolling down a hill with no bottom, always increasing because there are no stable equilibrium, and so when a system reaches equilibrium it can decay further into what is considered even higher entropy, and then you can have an arrow of time that is eternal, only having local fluctuations going the other direction. if you flip this things time derivatives, it will be like playing a movie backward, and if you don't like playing a movie the right way round. in contrast to a movie that is either finite between low entropy and equilibrium, or infinite with fluctuations on both directions when played both backward and forward. i don't think there is any other way to get around it fundamentally than saying there is no equilibrium, and the way entropy of approximate descriptions increase mostly in one direction and decrease mostly in the other direction, is related to that in the same way it is directed when you are not at equilibrium. essentially saying there is proper time derivative for entropy that is always directed. if i take a random low entropy state where all the time derivatives are related to position, then i don't know whether it increases or decreases in either time direction, but i know its more likely to increase in both directions. if increase in entropy is involved in all the time derivatives, then i know that in one direction it is more likely to increase and not decrease, this doesn't really make that much sense if you try to think about it with finite systems, but it can make sense, imagine for example that infinite stuff is happening everywhere all the time, and every approximate description at local scales involves some tendency for entropy to increase for some description, then my approximate solution might say that the initial conditions says that i will have a local decrease in entropy, but if you were to look very carefully at the subsystem you would see that the material properties, the scale of the characteristic elements or whatever else that has time derivatives associated with it, relies on gradients in entropy that point the same way, and each only have local dips in entropy, then you would still say that the subsystem has an increasing entropy even if at some level of description it seems to have a decreasing entropy, such things are possible in infinitely detailed systems, and then you can avoid all the problems with having to conjure up a permanently asymmetric arrow of time. the movie can still be played both ways, but there would be a difference between a Boltzmann brain thinking backwards and most brains, and it would be impossible for Boltzmann brains to be more likely than brains embedded in an environment with free energy to be had.
Problem is that it's a nonsense idea. If it's a block consisting of slices, but it contains all of time and space, in what way is it a block consisting of slices? If it is a metaphor, the metaphor is stretched way too thin.
Around 53:00 : Well, if you try to adopt the Lorentzian point of view, instead of Einstein's, then you can't explain kinematically the usual ( and well confirmed by any observation/ experiment) relativistic effects, like time dilation etc. You 'll need to go back to ( Larmor et al ) ether stuff, and their contrived "explanations". And then, what about Quantum Field Theories and so on and so forth...
We remember the future by statistics. Time is ultimately superpositioned portals in our consciencness. Disabled humans have different dimensions. Genetically enhanced humans access more positions. Evolution travels both toward the future, but can be repeated by our consciencness to resist entropy.
Another banger - but I don’t get all of this talk of “superluminal signaling”. If true, it violates special/general relativity and causality, which Maudlin holds up as fundamental at like 1:15. (Can’t believe I’m now a guy citing Wikipedia in UA-cam comments) “Causality is a fundamental principle of physics. If tachyons can transmit information faster than light, then, according to relativity, they violate causality, leading to logical paradoxes of the "kill your own grandfather" type.” en.m.wikipedia.org/wiki/Tachyon
Maudlin's explanation of the arrow of time (cause precedes effect) sounds particularly shallow. Once you accept, as Callender mentions, that you can calculate an earlier state based on a later state, you realize that there's nothing particularly binding about what is the cause and what is the effect, and in fact our familiar sense of direction can well be reversed.
A compressed spring no longer constrained is likely to expand. Spontaneous compression does not seem to be as likely. The configuration will undergo a predictable series of changes in a predictable order. How can we make causation run in reverse starting from the compressed state?
Philosophers love to confuse subjectivism with contextualism, i.e. they think that if something changes depending on context, then it cannot be objectively real but must be subject-dependent. This comes up all the time with quantum contextuality which is falsely interpreted as observer-dependence, so-called "subjective experience" which is not subjective at all, and we see the language employed here as well: saying there cannot be an objective "now" just because what is considered "now" depends upon frame of reference, i.e. context. Yet, again, this is confusing the two categories. There is indeed an objective "now," it is just that "now" is context-dependent, i.e. it changes depending on the context and there is no universally consistent one. But it is a mistake to treat something that changes depending on context frame as equivalent to something that is subjectivist and observer-dependent, as if physics says this relative "now" is defined only in relation to subjects, when it's not. The relativity of simultaneity is an objective fact about the natural world, and it is objectively true what is "now" from a particular frame of reference.
Maybe the real problem is that our Languages do not have modalities that account for distinctions of local time. We seem to have the Newtonian idea of "absolute" time order built into the way we talk, thus talking about time in a different modality is very difficult at best.
The language should be able to take us as far as the way that we are able to think about it, even though it will fall short of the way that a mathematical theory can describe it. If we need to "understand" it mathematically, we probably can only show that the math works. That it's predictive, etc... Anyways, I totally agree.
Believing that only the present exists does not imply in any way that there's no fact of the matter about Socrates' blood type. We just don't know his blood type. That's a surprising view for a Bohmian. We don't know the initial position or momentum of a particle in Bohmian mechanics but that doesn't mean that there's no fact of the matter about its position and momentum. And I would go as far as saying that existence presentism does not imply that there's absolutely no way of knowing his blood type. A rare moment where I disagree with Tim.
Great content but I couldn't watch it. Too many adds. You might make more money turning down the adds and getting more viewers. This stuff is too heady to be interrupted every 3 to 5 minutes.
If you claim presentism is incoherent because it supposedly says facts about the past that are true but can’t be derived from the present are in fact not real, and then go on to say that the future is equally real, even though we clearly don’t have any way to access truth values about it even in principle as a result of indeterminacy, then that seems pretty incoherent to me
Presentism could be thought of in two different ways - Point Presentism and Global Presentism. Point Presentism - is how most people think of Presentism is from the vantage point of a single event and how the signals reach it from rest of the universe and thus is limited by the past light cone surface of that event and depends of different reference frames moving relative to each other. Sure. In that sense the Point Presentism may not be universal (by definition I guess) and thus does not hold be correct. Global Presentism - is the surface of leading points of the worms or world lines of all existing entitles in the universe since the big bang. And this definition, by definition, follows the frame independent proper time of each worm/world line, and thus one can imagine that such surface can exist. This is somewhat like Tim's point that there infinite A series embedded in the B series depending on where put the pin for a particular A series. Similarly there are infinite Point Presentisms in the Global Presentism depending on which event you put the pin on for it's point presentism.
When somebody says that they're compatibalists they kind of lose scientific credibility in my eyes because compatibilism doesn't make any sense logically. Sorry Tim.
Nope. I don't see why the lack of understanding of how information from the past is contained in the present proves that presenteeism is incoherent. They do not seem to notice that the concept of "interaction" greatly limits the reality of model B.
Tim correctly objects to the use of word "static" wrt block universe. Should he also not object to use of the word "exists" (not "existed" but "exists") wrt to past events. I mean I can understand the past event like landing on the moon "existed" then (and was "real"), but do not understand what it means to say that event "exists".
Time is both a human sense and an illusion. Time is our "present" location in space-time and it's how we sense or perceive our motion, i.e., relative direction and speed on our path or world line through space-time. Time is thus not fundamental or real. It is emergent or evolved in our lives as a tool to organize and coordinate with others.
Tim seems to always defend his position first by restating the position and then says that other positions are incredulous....just give the argument for Christ's sake
I love that Tim maudlin is doing a lot of podcasts. Thanks professor!
My Hosts Tim and Craig thank you for attending unto our OWN! Thank you!
I love that there is more than 1 guest. Robinson is a great interviewer but sometimes it feels like the answers to his questions are standard answers to such questions. Still good questions but not really a challenge for the guest. When the guests start to ask questions to each other you see that the guests have to think a bit more about the answer.
Great episode!
I'm really enjoying these episodes on the foundations of physics -- who knew there was so much interesting stuff that I haven't thought about yet:D Greatful for the time from everyone participating:) Also I appreciate the both the clarity and the charitability in these discussions;)
Glad you enjoy it!
Very good. Has both cleared things up for me and introduced new topics.
My Host Robinson keep the sincere conversations going =
Professor Tim Maudlin has opened my eyes. I'm a Physics graduate (1994) and I thought I understood it.. no, I don't. Fantastic!
Craig’s comments at 14:02 are really enlightening. In my opinion it’s a pretty damning criticism of a discipline and it’s methods when it can carry on for decades ‘investigating’ pseudo-problems like this…
Thanks for getting these two absolute legends of the current literature of time in here! I identify as an amateur philosopher dropping my few cents over here
23:35 Tim doing a lot of mental gymnastics. "There are facts, there are facts about the past, therefore there is a past." But the point is, is it manifest? Can you travel there? Indeed, mathematically or in your imagination presentism and eternalism should portray the same manifest reality, but which is more accurate concerning the word 'is'? You can travel left and right in space, therefore space 'is'. But you can't travel back into the past. Therefore the past 'isn't'.
It all determines on what you put as a 'first coordinate' (or origin) in your theory or ontology, and for me that is our conciousness or existence in this moment. And not the mathematics and predictability conjured up, no matter how truthfull, by our minds.
Therefore presentism is more relevant than eternalism in my opinion
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I guess my next point is imagination has to be taken into account: both presentism and eternalism are visually imagined by our brain in the visual cortex. Which one is more 'real' though? Which one 'is'? Then you need to make a division between imagination and the external world, and as such we get into Kantian area..
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I feel it's fair to say eternalism is like the Everettian interpretation of reality, taking the unitary wavefunction seriously, while presentism is like Bohmian mechanics that takes reality's side seriously.
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33:00 the timelike area of the spacetime diagram (the light cone) supervenes on the spacelike area according to entanglement! Where there is time, there is also space in this diagram! Timelike doesn't equate to time, but to time + space! Therefore time is not different than a mathematical algorithm on the space dimension, which sounds like an indication for presentism.
Proof of this is if you hypothetically decrease the lightspeed, the current timelike area will become spacelike. And for other reasons this is true: the null lines moves through space, thus the intermediate timelike area must also be in space.
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Also I think again time travel is an important distinction between what can be counted as reality. If we can travel to the past, making the past the future, then eternalism makes sense. If however you can't travel to the past, a.k.a. make your past the future, then presentism makes sense. It means time is mostly current, the present, which can oscillate backwards and forwards with its internal energy but is restricted to a future move due to statistical mechanics. Otherwise the past could be the future according to this logic (Huw Price).
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1:17:00 David Wallace speaks of recurrent systems and irreversible systems with attractors, in deterministic classical mechanics. This is a better physical explanation then "causes precede effects", because this presumes human categorization of causes and effects (David Hume).
In my opinion in classical mechanics the Hamiltonian is conserved, which means energy is conserved. Yet time is still deterministic with due to the first law of Newton, which is due to the conservation of energy.
Therefore I feel there is something like a cosmic Hamiltonian, of potential and kinetic energy, starting with the big bang to now, in which potential energy gets turned into kinetic energy according and equalling the second law of thermodynamica, increasing entropy and with that causing the arrow of time. So spacetime has a local Hamiltonian which is conserved and called classical mechanics; and on top of that there is a global Hamiltonian of the expanding universe which causes a forward time direction due to entropy. So basically my thesis is that the potential for (literally!) thermodynamics is caused by the expansion of the spacetime of the universe...maybe similar to prof. Richard Muller's idea from Berkeley? Haven't read his book yet
The trick to superluminal signaling is that the ability to verify the results of measurements requires signaling that obeys relativity. The correlations are not communicable via light signals. There is a distinction between the signals that verify the results of the measurements and the correlations themselves.
Yes! Love Craig and Tim :)
me too.
Lord with the "NEW DAY"! GRATITUDE AND HONOR
Amazing conversation! You're putting all these dream crossovers together that probably would have never happened otherwise.
Haha that's awesome I'm glad you see it that way.
This is SO good. You deserve 100x more followers.
Thanks! But why stop at 100?! 🙃
@@robinsonerhardt It was a compromise between not wanting to measure success or worth in numbers and wanting your podcast to reach as many people as possible. ;)
When Craig started talking about the speed of light my first thought was “I wonder if Tim is going to say there’s no such thing as the speed of light” which is what he says in his Philosophy of Physics: Space and Time book, since relativisically speaking there are no speeds, the universe lacks the affine structure to talk about absolute speeds (but there are absolute accelerations). Tim understands talk of the speed of light as derivative, since reference frames are not part of the fundamental geometry of the world, they are mere representations of how we choose to assign coordinates. All there is to “the speed of light” talk is the law of light, the fact that the geometry of the world does include a light-cone structure and all worldlines of material particles are confined to the time-like regions of light-cone geometry.
Finally I am so glad to hear what Tim said about spacetime. Spacetime is not a 4D object where D standing for space like dimensions. Spacetime should be thought of as 3SD+1TD composite object where SD stands for space like dimensions which use the unit of distance and no intrinsic direction and TD stands for time like dimensions with a unit of time and intrinsic directional property and moving like a infinite, exorably moving treadmill belt undergirding the reality (only a vague metaphor). The rate of the time dimension is a relative notion and makes sense if we have clocks, which could be thought of as some cyclical subpart of the universe. If there were no cyclical subpart of the universe we will not be able to meaningfully talk about the rate of flow of time. In other words we can only measure the rate using some cyclic subpart if the universe. Without it, time will be reduced to a concept of change only. And if there is no change of state at all - time effectively seizes to exist. I think scientists know this but I blame their sloppy language/talk of spacetime as a 4D object to mislead people into conjuring up 4 spatial dimensional thingy.
But one part I disagree with Tim is about is about the notion of global now - that global now is not from the perspective of a specific point in space, but from the point of view of each point's own perspective - in other words the proper time of each point itself. Think of the statement - the universe is thought of as being 13.7 years old no matter which spatial location you are in the universe. Why is that? Or think of the hypersurface of the end of every point's world line (worm). And if at the big bang the universe was at a point then long distances do no cause the issue of time needed to travel those distances. The light cones at that point are very very short (in height) with narrow base (spatial extent) and effectively touch each other for their full extent (from tip to the base) and then we follow the proper time of each point to get the global now. Hope this makes sense.
The light cone structure tells us that the "now" that we visually perceive (fastest) is the very surface of the past light cone from our vantage point and not the global now. The auditory perception cone is a much narrower past sound cone which is obviously in the bulk of the past light cone.
Also people should appreciate the fact that in terms of the day to day units we use for distance and time, the surfaces of the past and future light cones almost touch each other.
Think this (crudely):
--------- _____________________ ________________---------------
==========================================*==========================================
______---------------------------------- --------------------------___________
i.e. the future and past light cone surfaces almost touching each other (for all practical, perceivable purposes) and only starting to sperate out vast distances away from our vantage point.
Don't think this:
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. .
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*
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. .
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Agree with Tim that time intrinsically has a direction which is hinted at by the light cone structure and the fact that spacetime follows Minkowski hyperbolic geometry/metric (s^2 = t ^2 - x^2 - y^2 -z^2) i.e. the minus sign (i.e. the difference in SD and TD I talked about above) and not Euclidean geometry (d^2=x^2+y^2+z^2) and.
What do we measure with Clocks? Rates of Change. The change in one system relative to the other in an interaction, for example.
favorite podcast right now :)
I LOVE to hear this
Little LIGHT (LOVE) with the "NEW DAY"!
The way the universe works is b comes after a unless it comes before a in a changed timeline, then the universe will adjust and turn a into b and vise versa 👈
Your shirt is epic ….. tell Schrodinger that I AM 🐈 Such an interesting vid ! Love this ! Bell Institute sounds like a must donate to. Thanks Robinson and pod 🐈
Thanks so much, Bernardo!
The present is real. The past was real. The future will be real. There. Settled it for ya'll!
I thought the discussion of the reality of the future was a bit fuzzy. It wasn’t clear to me that Tim was saying the future will be real or in some sense already is real. If there are two or more possible futures, the sense in which the undetermined future already is real seems like a nonobvious and interesting question.
I am always so astouned that great minds like that just can't see that there is no such thing as time flowing
Remember what is Life without came with sincere conversations given just for thee? Love you too!
Given new eyes to see!
Likewise give Gratitude and Honor unto my Hosts shared "i" AM and my Beautiful molded and form the Sea of glass.
Beautiful will say, from HIS SIDE!
I enjoyed this podcast. I'm glad foliations were discussed. I wonder how it may fit in with QFT or Bohemian Mechanics. The time of flight thing he talked about is pretty cool too that conceptually it is an interpretation of quantum mechanics which may answer certain questions that can't be explained by the other interpretations.
I sorta felt left wanting about the A and B series discussion. I think it's more than that some A and B people can see compatibility between the 2 views but rather what makes them distinct.
On the A view, there's something privileged about the present that the past and future aren't. There's tensed facts, the past has happened and the future has yet to come, temporal becoming is a real thing things go through. Time as we experience it isn't an illusion of our subconscious. Just because the past can't be changed, or what will happen will happen is a tautology, I think one would need more than the fact that light cones or a Minkowski space time is a useful way of understanding relativity to accept the B-view space time block.
A nice book I read that introduced the A and B series to me was Time and Eternity.
Their books are great! Go get 'What makes time special?' and 'Philosophy of physics: space and time'!
Yes, I totally agree! Links happen to be in the description.
Interesting discussion. With one hell of a fine silent participant - A. Cat! Most excellent ears. Looks almost Egyptian.
She says thanks!
Could we think of The Block consist of all possible interactions between quantum systems? Spatial separation and duration relations between the events are represented in Light cone structures.
Interesting conversation, despite some major disagreements.
Beloved!
as a presentist i need elements of reality now to be a transformation of elements of reality in the past and future, as an eternalist i need the same thing for continuity. if it's missing i can't make any sense of the continuity in the block or how the present turns into the future or got turned into by the past.
There is one thing about c -- the speed of causality -- which I find intriguing. The rate at which physics happens is the same everywhere because everywhere there is a local clock operating at the local speed of causality. Time can be seen as a kind of white-hole, emerging everywhere expanding each point's past light cone -- expanding the observable universe.
yay!
Great vid but you’re tripping w the amount of ads you put….
Have Comforted US! LIKEWISE Lord will be Comforter in front of thee! Thank you!
How do you influence the past without changing the past?
I sure wish that someone would have brought up Feynman's claim that the electron that emits the photon is in "agreement" with the electron that absorbs the photon.
He was talking about quantum physics at the time, but i don't recall the specific context.
It's always just kinda stuck in my head.
I was under the (mis)impression that general relativity precluded a foliation; Maudlin and Callender suggest GR merely doesn't require one.
Agreed - isn’t GR “there is no preferred reference frame?”
Proponents of pilot wave/ Bohmian mechanics ( like T. Maudlin) need an absolute reference frame, otherwise their quantum mechanics alternative doesn't work.
But, in both Special and General Relativity there's no such thing as a preferred foliation.
If your spacetime ( in GR) is "globally hyperbolic", you can choose any suitable spacelike hypersurface as a Cauchy surface, there's not a specific choice that is the "right" one.
All such hypersurfaces are equally "good".
@@dimitrispapadimitriou5622 So on your understanding, GR is consistent with (but does not imply) a preferred foliation, right? ("Preferred," that is, on some basis not supplied by GR itself.)
@@snowpants2212 Well, no, I wouldn't say so:
Starting from special relativity, if there's a need for a preferred foliation ( for fundamental reasons, as in pilot wave theories) then one cannot explain the usual well confirmed relativistic effects (like time dilation) in a simple kinematical way.
One has to go back to the more complicated and contrived ether -related explanations ( see Larmor, Fitzgerald et al..).
That's not strictly prohibited of course, but it's not Special Relativity.
In GR things are getting even more complicated.
Alternative theories of gravity with preferred foliation cannot compete the ( relative) simplicity, observational success and explanatory power of the standard GR. People are trying, though...
@@snowpants2212 There's no absolute simultaneity in Relativity, nor a definite temporal order between distant, space-like separated events, contrary to what is needed for non local hidden variable theories.
Little LIGHT came with a Candy as an offering to comfort the COMFORTER! Remembering not to flood my Footstool!
Sickness!
Looking for dry grounds in front!
Unfamiliar ways of speaking unto many but yet is clear as water unto Whom BELONGS?
Banger pod! Why not more views? Mind boggling...
My mind is also boggled.
Remember time sent forth as a messenger LORD increase in knowledge! Indeed
Time must be defined in relation to the size of now the observer experiences. For example, a newborn and a very elderly person may have very large, even vast sized perception of ‘now’, vs. a 40 year old with 4 kids, 2 jobs, and aging in parents may perceive a tiny, tiny ‘now’ as time flies by…. As if the amount of neurological physical change inside the brain - organized growth (newborn) vs. growing disorder (very elderly) vs. neural stasis of a middle ager forces.a dilation -or- contraction (dilation at the ends of the life cycle, contraction mid cycle) of the perception of ‘now’. Perhaps pre-post life/death - ‘now’ is ‘eternal - always- all time’. This is a theory I developed in college. Please reference me if you quote this.
Alan Watts would've been a great addition to this panel. If only Time weren't an arrow...
hahaha
time is the expansion of the univers
Digital come here in front and remind! What is Love?
Around 59:00 : This "simplicity" of adopting a preferred foliation is only superficial.
As far as you're trying to just replace standard QM with an alternative theory like Bohm's it might seem quite easy and simple.
But when you're trying to move to some other serious physics ( QFT, Gravity) things won't be so nice anymore...
A pilot that flys only toward the east, still follows the block even though the pilot never experiences the future.
The future, from my point of view, is a location (or a sequence of contiguous locations) in spacetime. We can't know the future with certainty, until we arrive at "that" particular location along our path or world line though spacetime. Once we arrive at or pass though a particular location in spacetime, "that point" immediately becomes the past-inaccessible, inalterable. So "time" or "when", is all about "where" we are at any "moment", and the future is a place where we are always traveling towards, from our birth to death.
There is a huge difference between "weak" non locality ( non separability) and "strong" non locality ( that implies causality violation).
The former is well confirmed experimentally and does not contradict Relativity ( this is the kind of non locality that is associated with QM), while the latter belongs only to fiction, as far as we know ( and it could open Pandora's box if it was a real thing).
Scientist cannot predict the return of Haley's Comet, because of uncertainty. Haley's Comet may have been destroyed or deflected on its course in a collision with some object in the distant solar system. It's always possible, that Haley's Comet will never return.
Beloved remember what is 80-100 years if luckily can live that long?
find me a solution of a person where they are gaining knowledge while spitting out food and absorbing heat to do it. the direction of the formation of memories for example is known to always map onto a solution of a person eating food, getting hot, and then taking a shit, while forming memories, the direction of the formation of memories is always the same as the increase in entropy involved with driving the human physiology. i haven't found any counterexamples at least. if there is a gradient in entropy it is easy to explain the arrow of time in most systems in that context, but then when you get to equilibrium, processes in both directions sort of has to be equally likely. so either you admit defeat and say the initial conditions are always low entropy and then the directional of time survives for a while until you are just as likely to see a process happen in one direction as another direction. or you can say there is an eternal distinction by saying that entropy is a ball that is rolling down a hill with no bottom, always increasing because there are no stable equilibrium, and so when a system reaches equilibrium it can decay further into what is considered even higher entropy, and then you can have an arrow of time that is eternal, only having local fluctuations going the other direction. if you flip this things time derivatives, it will be like playing a movie backward, and if you don't like playing a movie the right way round. in contrast to a movie that is either finite between low entropy and equilibrium, or infinite with fluctuations on both directions when played both backward and forward. i don't think there is any other way to get around it fundamentally than saying there is no equilibrium, and the way entropy of approximate descriptions increase mostly in one direction and decrease mostly in the other direction, is related to that in the same way it is directed when you are not at equilibrium. essentially saying there is proper time derivative for entropy that is always directed. if i take a random low entropy state where all the time derivatives are related to position, then i don't know whether it increases or decreases in either time direction, but i know its more likely to increase in both directions. if increase in entropy is involved in all the time derivatives, then i know that in one direction it is more likely to increase and not decrease, this doesn't really make that much sense if you try to think about it with finite systems, but it can make sense, imagine for example that infinite stuff is happening everywhere all the time, and every approximate description at local scales involves some tendency for entropy to increase for some description, then my approximate solution might say that the initial conditions says that i will have a local decrease in entropy, but if you were to look very carefully at the subsystem you would see that the material properties, the scale of the characteristic elements or whatever else that has time derivatives associated with it, relies on gradients in entropy that point the same way, and each only have local dips in entropy, then you would still say that the subsystem has an increasing entropy even if at some level of description it seems to have a decreasing entropy, such things are possible in infinitely detailed systems, and then you can avoid all the problems with having to conjure up a permanently asymmetric arrow of time. the movie can still be played both ways, but there would be a difference between a Boltzmann brain thinking backwards and most brains, and it would be impossible for Boltzmann brains to be more likely than brains embedded in an environment with free energy to be had.
Tim's description of slices running through the spacetime block sounds pretty static to me...
Problem is that it's a nonsense idea. If it's a block consisting of slices, but it contains all of time and space, in what way is it a block consisting of slices? If it is a metaphor, the metaphor is stretched way too thin.
A metaphor stretched so thin that it’s a single slice? Sounds like presentism to me.
Too many ads, I’m gonna listen to it elsewhere.
Likewise will visit the far generations! To visit for good!
Around 53:00 : Well, if you try to adopt the Lorentzian point of view, instead of Einstein's, then you can't explain kinematically the usual ( and well confirmed by any observation/ experiment) relativistic effects, like time dilation etc.
You 'll need to go back to ( Larmor et al ) ether stuff, and their contrived "explanations".
And then, what about Quantum Field Theories and so on and so forth...
Philosophy come here in front and remind!
Reason creation itself and all thy shared "i" AM in front!
We remember the future by statistics. Time is ultimately superpositioned portals in our consciencness. Disabled humans have different dimensions. Genetically enhanced humans access more positions. Evolution travels both toward the future, but can be repeated by our consciencness to resist entropy.
Beloved thy shared Feet upon the Sea of Glass and thy shared Feet resting upon my Footstool all dry grounds nor the world in front!
To see "WHO"?
Another banger - but I don’t get all of this talk of “superluminal signaling”. If true, it violates special/general relativity and causality, which Maudlin holds up as fundamental at like 1:15.
(Can’t believe I’m now a guy citing Wikipedia in UA-cam comments)
“Causality is a fundamental principle of physics. If tachyons can transmit information faster than light, then, according to relativity, they violate causality, leading to logical paradoxes of the "kill your own grandfather" type.” en.m.wikipedia.org/wiki/Tachyon
Nor why HE tilted?
Why say Sea of Glass?
Cute Kitty! 🐈
thanks :)
freewill x chaos
Some will say, How did the Bird survive?
yaaaaa bwaiiiiiiii
100%
❤
Maudlin's explanation of the arrow of time (cause precedes effect) sounds particularly shallow. Once you accept, as Callender mentions, that you can calculate an earlier state based on a later state, you realize that there's nothing particularly binding about what is the cause and what is the effect, and in fact our familiar sense of direction can well be reversed.
A compressed spring no longer constrained is likely to expand. Spontaneous compression does not seem to be as likely.
The configuration will undergo a predictable series of changes in a predictable order.
How can we make causation run in reverse starting from the compressed state?
Specially have persecuted my shared "i" AM own!
Lord Saul He have healed!
Lord from Phillipi!
Philosophers love to confuse subjectivism with contextualism, i.e. they think that if something changes depending on context, then it cannot be objectively real but must be subject-dependent. This comes up all the time with quantum contextuality which is falsely interpreted as observer-dependence, so-called "subjective experience" which is not subjective at all, and we see the language employed here as well: saying there cannot be an objective "now" just because what is considered "now" depends upon frame of reference, i.e. context. Yet, again, this is confusing the two categories. There is indeed an objective "now," it is just that "now" is context-dependent, i.e. it changes depending on the context and there is no universally consistent one. But it is a mistake to treat something that changes depending on context frame as equivalent to something that is subjectivist and observer-dependent, as if physics says this relative "now" is defined only in relation to subjects, when it's not. The relativity of simultaneity is an objective fact about the natural world, and it is objectively true what is "now" from a particular frame of reference.
Maybe the real problem is that our Languages do not have modalities that account for distinctions of local time. We seem to have the Newtonian idea of "absolute" time order built into the way we talk, thus talking about time in a different modality is very difficult at best.
And many times without noticing people shift between many different sense of the use of the word time.
The language should be able to take us as far as the way that we are able to think about it, even though it will fall short of the way that a mathematical theory can describe it.
If we need to "understand" it mathematically, we probably can only show that the math works. That it's predictive, etc...
Anyways, I totally agree.
I thought time was a dimension not really something that you could debate about. ????
Beloved Saul to Paul forgiveness, salvation, and the Redeemer "i" AM the WORD.
What happened?
Believing that only the present exists does not imply in any way that there's no fact of the matter about Socrates' blood type. We just don't know his blood type. That's a surprising view for a Bohmian. We don't know the initial position or momentum of a particle in Bohmian mechanics but that doesn't mean that there's no fact of the matter about its position and momentum. And I would go as far as saying that existence presentism does not imply that there's absolutely no way of knowing his blood type. A rare moment where I disagree with Tim.
Where else all thy given names came from?
Great content but I couldn't watch it. Too many adds. You might make more money turning down the adds and getting more viewers. This stuff is too heady to be interrupted every 3 to 5 minutes.
If you claim presentism is incoherent because it supposedly says facts about the past that are true but can’t be derived from the present are in fact not real, and then go on to say that the future is equally real, even though we clearly don’t have any way to access truth values about it even in principle as a result of indeterminacy, then that seems pretty incoherent to me
Very tip of time come here in front and remind! LORD thy messenger sent forth! Before thy visitation.
Nor some will say, who tilted?
Presentism could be thought of in two different ways - Point Presentism and Global Presentism.
Point Presentism - is how most people think of Presentism is from the vantage point of a single event and how the signals reach it from rest of the universe and thus is limited by the past light cone surface of that event and depends of different reference frames moving relative to each other. Sure. In that sense the Point Presentism may not be universal (by definition I guess) and thus does not hold be correct.
Global Presentism - is the surface of leading points of the worms or world lines of all existing entitles in the universe since the big bang. And this definition, by definition, follows the frame independent proper time of each worm/world line, and thus one can imagine that such surface can exist.
This is somewhat like Tim's point that there infinite A series embedded in the B series depending on where put the pin for a particular A series. Similarly there are infinite Point Presentisms in the Global Presentism depending on which event you put the pin on for it's point presentism.
When somebody says that they're compatibalists they kind of lose scientific credibility in my eyes because compatibilism doesn't make any sense logically. Sorry Tim.
Nope. I don't see why the lack of understanding of how information from the past is contained in the present proves that presenteeism is incoherent. They do not seem to notice that the concept of "interaction" greatly limits the reality of model B.
Tim correctly objects to the use of word "static" wrt block universe. Should he also not object to use of the word "exists" (not "existed" but "exists") wrt to past events. I mean I can understand the past event like landing on the moon "existed" then (and was "real"), but do not understand what it means to say that event "exists".
Time is both a human sense and an illusion. Time is our "present" location in space-time and it's how we sense or perceive our motion, i.e., relative direction and speed on our path or world line through space-time. Time is thus not fundamental or real. It is emergent or evolved in our lives as a tool to organize and coordinate with others.
Beloved many trying to reach?
Tim seems to always defend his position first by restating the position and then says that other positions are incredulous....just give the argument for Christ's sake
Lord Saul to Paul knows Thee?
The past we know is gone it is no more than the future. Nurturing time axis is far different from naturing time like evolutionary mythology treats it.
Anyone know what the goose/geese talk is all about?
just my affectionate name for my listeners