Mindscape 158 | David Wallace on The Arrow of Time

[@ddavidjeremy]

David Wallace speaks so fast I literally had to drink some coffee so that my brain could keep up. I can only imagine how quickly he must think. On another level he is clearly brilliant. Great great guest. Thanks Professor Carroll.

[@bruce1437]

David is a breath of fresh air. His ability to communicate is excellent, he's not prone to hand waving and glossing over ideas, rather he gets into the detail and information

[@vt6653]

I was suffocated. He needs to slow down and stop going down circular rabbit holes.

[@devanairemccallister4194]

@@vt6653 yeah all he did was talk about the same thing over and over. It's like he's a physics book just talking paragraphs

[@riggmeister]

I love how both Sean and David occasionally go into teacher mode and say "Good ..." before answering as if they approve of the question!

[@logosworld2492]

The day has finally come. David Wallace episode! Thank you so much Sean and David!

[@martinds4895]

This has been one of my favourite episodes of this podcast. Everytime ENTROPY is mentioned in Mindscape my day is improved exponentially, I wish more episodes like this one. Thanks Sean and David!

[@kevinmccarthy8746]

I am a 64 year old beginner in physics as a result of the Clovid 19 lock down. I have not read up on the arrow of time yet. I am excited to heard Mr David. To me when I started reading things about Quantum entanglement, and super symmetry, I was just amazed and even called my brothers about all this duality of the Quarks? Incredibly fascinating. I wish I never played sports and wish I just studied Math. Thank you. Kevin from sunny Mexico.

[@VermontStrolls]

Cat poop ad in the middle of time arrow discussion is phenomenal !!

[@popevimtoripkeefhappysackXXX]

Was it alive or dead ?

[@UHFStation1]

Its poop was healthy anyway.

[@martinds4895]

Lol

[@zakh9463]

Sean, I've listened to all your episodes. If you see this I just want you to know how great this is as a break from the day to day of life. Wallace is one of my favorites to listen to

[@mitchelle4322]

I'm finding Prof Wallace more than a bit esoteric...thank goodness Sean is explaining after each answer.

[@aaron2709]

This is so great. I hope you will have Wallace back many times to discuss any and all subjects in physics.

[@terrywbreedlove]

I listened to this on the Pod Cast app yesterday on a long drive. This man is brilliant with a very open and quisitive mind.

[@stephenmacartney]

Ironically, David Wallace is a lot easier to understand when you slow the arrow of time down to 0.75x

[@stephenmacartney]

(Really enjoyed this episode btw)

[@quantisz4416]

His voice has an arrow of time really fast

[@devanairemccallister4194]

Thanks!

[@LeeLightfoot]

1 hour 9 minutes. Hell yes!! Thank you David Wallace for voicing this.

[@martinds4895]

I wish it was longer.

[@MarvinMonroe]

@@martinds4895 that's what she said

[@davy-jonesdevil-fruit7606]

@marvinmonroe fuck yes bro! Fuck yes

[@haysgoodman8068]

“Although it also shows why Everett is, ah...” (Sean, sotto voce) “Better?” LOL! I saw that one coming.

[@fallingintofilm]

David Deutsch next please!

[@exploringeclecticism]

This is beyond truly incredible. Thank you guys!

[@UHFStation1]

I can understand Sean at 2X speed and David at 0.75X speed. Any solutions towards a common arrow of time?

[@quantisz4416]

I thought the same😄

[@davegrundgeiger9063]

In this arrow of time interview, I find it somehow satisfying that when Sean makes his introductory comments, he does in fact remember the upcoming interview. 😆

[@Xen2288]

This is one of my favourite episodes! David is so insightful and really opens my mind to different ways of thinking

[@rumidude]

For whatever reason, I find David Wallace easy to follow unlike many other philosophers of physics/science.

[@Jay-xh9dl]

I think it's because he very deeply (and impressively) understands what is talking about and thus is able to articulate it near flawlessly. Carroll is also this way as Feynman was, so it's no surprise he occupies his old desk at Caltech. However, I still needed to listen to this twice to grasp it all!

[@dwaynepeters4520]

It seems like the arrow of time is a strong argument against the Everettian hypothesis. I've always thought the most appealing part of Everett is that you just need Schrodinger's equation and nothing else to make the universe work. There's no mysterious collapse that happens at measurement time. But if we're trying to account for the arrow of time, and Schrodinger's equation is time symmetric while wavefunction collapse is not, doesn't that mean Copenhagen has an easier time explaining the arrow of time than Everett?

[@davy-jonesdevil-fruit7606]

Couldn't one propose that the cumulative collapse of every "branch" or "possible" course of events besides the one to which we belong, in fact may hold the information some perceive as the measurement issue?

[@seionne85]

This was a joy to listen to thank you both

[@SpaceExplorer]

love david wallace. infinite jest is my favorite book. I have bought it three times and plan on reading it at some point

[@camspiers]

That’s a different David Wallace who unfortunately is dead 😞

[@SandipChitale]

Great podcast Sean. Thanks Sean and David. I am thankful to modern technologies which allows general public, access to very interesting and deep topics being discussed by great minds of our time, which were only discussed in the corridors of universities, conferences and published technical papers. The podcast format lends it self very well to avoid very mathematical discussion and instead have the discussion in common, colloquial language and keep it conceptual. Two points: Past leaves chain of traces that are available at present moment, future does not. If foot imprints on the beach get washed away, we will not know someone walked on the beach in the past even though entropy increased. So is it as simple as past is different from the future not because entropy increases but because past events tend to leave traces that can be accessed (remembered) in the present? It is generally said that microscopic physics is time reversible. However is it more correct to say that the microscopic physics is velocity reversible? Velocity is a vector so it has direction and opposite velocity is reverse of for forward velocity. And that opposite direction provides the negative sign not the time. I say this because even in the classic, intuitive example of time reversibility of microphysics that is given i.e. running the film of billiard balls bouncing off of each other backwards, watching it one is not able to tell the difference that film is running backwards or forwards. Well, we are running the film in reverse direction still in forward time. It is just that we ran the film playing mechanism backwards which for mechanical projector could be the motor running in reverse direction or digital projector sampling the digital data in reverse order relative to the order it was written into memory? interestingly in the same example if we run the film very fast or very slow we will be able to tell even though we did not slow down our time itself. In the simple example of billiard balls, we have single mechanism to run the film in reverse. However to practically make that happen a daemon will have to reverse the velocity of all particles everywhere at the same time (simultaneously?) which I guess a daemon can do, even though simulteneity is not supported by GR.

[@bendavis2234]

Yes I totally agree that podcasts are an amazing result of modern tech advances. I personally wasn’t interested in science until hearing people like Sean Carroll, Brian Greene, Sir Rodger Penrose, Brian Cox, and other inspirational physicists on various podcasts. I wonder how many people will be influenced by these podcasts in a way that changes their future life and careers. And all for free too! Imagine if these podcasts existed 100 years ago and that you could hear conversations from Einstein, Gördel, Bohr and colleagues. Or a little later with Feynman. The internet is a godsend to us! I’m glad to live in this time.

[@myu4039]

Wow! Excellent! Thanks Dr. Carroll :)

[@cagatayacuner670]

Based on their research, James Crutchfield (Szilard's engine, Demonology), David Wolpert (non equilibrium thermodynamics, physical limits of inference), Sussane Still (non equilibrium thermodynamics), Jeremy England (non equilibrium thermodynamics), Sharon Glotzer (entropy/complexity), Paul Davies (state dependent laws and physical universality), Scott Aaronson/Dominik Janzing (physical universality), Matthew Leifer (retrocausality), Rob Spekkens (disentangling influence and inference) and David Deutsch (initial conditions and dynamical laws vs constructor theory) might also have interesting things to say on that topic...

[@doublegone]

Way out of my depth with this one, even after several attempts. Almost every sentence David uttered when he let loose, went straight over my head.

[@vancouverpuppet]

Play it @0,75 speed. Helped me :)

[@dreed7312]

I couldn't tell what he was saying. Weird voice, delivery, and phrasing. Not his best podcast.

[@zipperpillow]

Get taller.

[@devanairemccallister4194]

Yeah and plus he rambled the same shit over and over lol

[@Al-ji4gd]

Physics is difficult, philosophy is challenging. Putting them together makes it very hard lol.

[@davidfanning1600]

I didn't understand the kitty litter hypothesis ...

[@jellyicecream3324]

Time for Sean is his great escape from free will.

[@danlthorn]

Sort of classic for a Mindscape episode. Perfect guest, Sean’s favorite set of topics - any time there’s a chance to say Everetian many times is a win ! Still this fell short of my hope - not a criticism - just for a tough complex and nuanced issue I was hoping to leave with more of an incremental feeling of illumination on the topic Instead I felt there was a rehash, some good and helpful, and a heavy dose of parsing and precise restating what’s already been said. I liked the section on the arrow of time best- it was a good explanation for why something so obvious is a puzzle. The math and the models are the source of the puzzle - not the world around us. Fair enough, though it is more a puzzle how to do science than it is a puzzle about melting ice cubes not spontaneously freezing. Good solid episode and hopefully one day Everett himself will be on Surely time will treat him better than the rest of us and it will be no issue.

[@user-wu8yq1rb9t]

Hello professor Carroll I hope you have a plan in your schedule for making a podcast about the Legendary *Steven Weinberg*. Thank you professor

[@nickidaisydandelion4044]

I prefer to see a video conversation. I need the visual aspect very much. But anyway I very much appreciate conversations about infinity and non linearity.

[@udayh3284]

The guest speaks too fast! It was hard for me to grasp although the topic was exciting.

[@caiocesar275]

It's a nightmare to understand, for non-native english speakers like me

[@Liasisws]

If you stop focusing on his words, he sounds like he’s speaking at 5x faster. And I’m a native English speaker. 😔

[@miguelg4556]

Thank you for this!

[@spaceinyourface]

Excellent stuff 👏

[@royalbloodedledgend]

I love the episodes about time

[@JiveDadson]

"Time flies like an arrow. Fruit flies like a banana."

[@popevimtoripkeefhappysackXXX]

Arf !!!

[@babaranwar5462]

What species are time flies?

[@popevimtoripkeefhappysackXXX]

@@babaranwar5462 Blue-Boltzmanns

[@Staplegunner]

“David here it is, my philosophy is basically this, and this is something that I live by, and I always have, and I always will: Don’t ever, for any reason, do anything, to anyone, for any reason, ever, no matter what, no matter where, or who, or who you are with, or where you are going, or where you’ve been, ever, for any reason whatsoever” -Michael Scott to David Wallace Has david taken Michaels advice?

[@jellyicecream3324]

Here's mine "I awake again, I am again." The "I" can be misleading as in my interpretation it means my brain. I've just come all for the ride and by fuck this mind is driving it like it stole it.

[@rohanjagdale97]

Please invite Carlo rovelli on show one time. 🙂

[@patrickoneil3202]

Wondrous - thanks So much guys

[@jennydeepable]

love the show

[@Lance_Lough]

Wow. One of the great triumvirate, the three amazing Davids of Everettian quantum physics!

[@fallingintofilm]

Wallace, Deutsch and?

[@Lance_Lough]

@@fallingintofilm ...and David Z. Albert..

[@fallingintofilm]

@@Lance_Lough oh really. That’s interesting. Thanks!

[@justinshere]

@@Lance_Lough David Albert isn’t a proponent of Everettian quantum mechanics.

[@Al-ji4gd]

David Albert is not a proponent of the many-worlds interpretations. In fact, he's one of its biggest critics.

[@AlexanderKoryagin]

Thank you so much for this, as always!

[@DevilTigermoth]

time indicates the direction in which entropy increases. humans run around putting things into order. we try and undo entropy and increase cleanliness. ergo, that's why we feel we are constantly battling time. and the longer we battle it the longer we live. we want to live as long as possible because cleanliness is next to ..... careful, you can't say that when dealing with science.

[@riggmeister]

The assumption by David that there are an 'infinite' number of configurations in the box of gas struck me as a bit odd. Surely there are a finite number of configurations allowed if we are constrained to planck volumes? If the wave function for each particle extends to infinity (or even just to the edge of the box) then there are presumably a much larger number of configurations outside the current volume than inside. 🤔 - My assumption being that a truly continuous (and therefore infinitely precise) position of a particle is impossible/meaningless. And if so, I suppose this would necessarily be true for velocity and higher order derivatives of position wrt time if there is a similar planck time constraint too.

[@danielm5161]

Great chat

[@dougmarkham]

Perhaps the asymmetry of time arises from self-organised systems ie, where more complex units interact in such a way as to prevent time reversibility.

[@RobRoss]

No analogy is perfect; analogies simplify and remove characteristics of a new or unknown system to make it easier to understand by comparing it to a known system. With that disclaimer, I don’t think it’s *impossible* to think about what a superposition of states would look like if we could observe it directly. Two analogies come to mind - light and sound, both waves. With sound, a pure tone is a vibration in the atmosphere at a specific frequency. When this frequency is between about 2 Hz and 20 KHz, we call this “sound”, and we perceive it subjectively as a particular tone. But you can vibrate the atmosphere with multiple frequencies at the same time, and this superposition of frequencies can be experienced by us subjectively differently than if we experienced each frequency individually. Also, a light wave at a particular frequency in the spectrum of “visible light” will appear to us subjectively as a particular “color.” But you can excite the EM spectrum with multiple frequencies of light at the same time, and we will experience this as a new “color”, via the mix of pure frequencies. This is a different experience than if we observed each light wave separately. So, conceptually, a superposition of quantum states at the macro level is theoretically observable... by something something. Perhaps a brain with different sense organs could in fact “see” superposition, the way we normal humans can see and hear superpositions of light and sound waves.

[@gerrycrabtree3274]

I might need to shell out to be a Patreon. If time unfolded from future to past how could you process the unrembering of events ?

[@bentationfunkiloglio]

If a little knowledge is a dangerous thing, then I’m an incredibly dangerous person. Therefore, I can only hope the following question doesn’t inflict too much pain. Somewhere in the Universe, the rate of the Universe’s expansion has or will eventually exceed the speed of light, right? Shouldn’t a new “big bang” occur wherever this happens? Regions of space receding from each other at the speed of light effectively create an event horizon equivalent to the event horizon of a black hole. (At least, seems like this should be the case.) If so, the event horizon itself should expand (at the speed of light?) as well thereby generating an ever growing amount of Hawking radiation until, Boom! New Big Bang! If, by some miracle, the above is reasonable, then it would explain the arrow of time. Eventually, enough matter condenses to counter dark energy fueled expansion. Now, we have ourselves a baby low entropy, matter filled Universe derived from a high entropy parent. I hope reading the above didn’t cause too much retinal damage. :)

[@timberclip]

It's not whether time moves back or forth, it's about the brain's ability to perceive it. The brain is a predictive tool. The brain senses, learns and interprets patterns; therefore, we can predict and understand our world. If time flowed backward in a way that we could perceive, this would not be a predictable cause and effect world. Life would not exist as we know it. So, I think the question should be altered. How do we percieve backwards time without using the brain? (or at least screwing up our brain's view )

[@matthewrichmond4139]

You look for evidence of traces of energy - friction fór eg( high order energy creating disorder) which gives evidence of the past. Everything else is our perception.

[@SandipChitale]

The discussion on branching assumed the whole experiment in real time. But the podcast is listened to at many different times by different listeners who may have some other shared common experience in the intervening times. So does it mean the branches can merge and split over and over at different points in time? Is that merging related to Stephen Wolfram's merging in bracheal space? The shape of wave function is continuous and analog? So does it mean infinite branching happen into infinite branches? When the box is opened, cat may be fully alive, beginning to die, half dead and fully dead.

[@timeslips82]

You inspire me, Sean... I'll give you 20 dollars soon...

[@alexandersumer4295]

I didn't know David Wallace was also a philosopher of physics?? How can one be so talented? Infinite Jest is a phenomenal piece of literature.

[@ddavidjeremy]

Conclusion: physicists still don't care much for cats

[@sunroad7228]

The impossibility of branching more useful Energy from a parent total Energy, similar to the impossibility of injecting a spare extra hour between hours: "No energy system can produce sum useful energy in excess of the total energy put into constructing it. This universal truth applies to all energy systems. Energy, like time, flows from past to future. The Arrow of Energy, proposed 2017.

[@DiegoRodriguez-vx6ys]

Te amo sean

[@cagatayacuner670]

If spacetime (locality) and quantum mechanics (unitarity) are emergent from more basic "objects" ("primitives") as Nima Arkani Hamed claims, then maybe the arrow of time explanation might get a different form. Who knows?

[@twonumber22]

Nice.

[@dannybrook3611]

David deutsch next please

[@LeeLightfoot]

on my third listen.

[@zazee6480]

So if the universe was shrinking would the arrow of time be reversed ???

[@Im-just-Stardust]

If Ariel was in a game, he would definitely be a final boss.

[@devanairemccallister4194]

David doesn't talk like a human being. He's a walking text book.

[@stephenkamenar]

he sounds like a balloon

[@SandipChitale]

In case of schrodingers cat experiment the box is closed and have to open the box to find out if the cat is dead after half life period of radioactive decay. However it is conceivable to to setup the experiment where acid sprays and dissolves opaque paint on the glass walls of the box. In that case when does the wave function collapses in Copenhagen interpretation of QM?

[@mikethek5494]

I can remember it for you wholesale...

[@Frohicky1]

The Emergent Multiverse is denser than a black hole.

[@frontech3271]

DANGER! "A Little Knowledge" Zone Premise : Time - Everything happening at once (or, absolutely nothing happening). No directionality. The Past is not "behind", it is "inside". Time is a thing absorbed. Sans Time, nothing is. Space - keeps everything from happening all at once. Multi-directional. In the world of a computer graphics, 3-D Modeling, Concepts of size, volume, area, etc., are relative. Computer does not deal with "size", it deals with point coordinates. 1mm, 1 kilometer, 1000 km - can appear the same size in relation to the screen. Two or more objects can occupy the same space simultaneously. This is an illusion. The perception matters not-so-much. The INFORMATION is the key. Is this Holographic? Goodnight.

[@babylongate]

18:58 get me a napkin, my mouth’s watering. Lol

[@DKamps]

Hey please talk about googles newly created successful time crystal.

[@zazee6480]

And also if the universe was infinite and shrunk to a singularity would it still be infinate

[@Albeit_Jordan]

Damn, this guy even vagely resembles DFW when he had long hair...

[@baleriontheblackdread4491]

What does the owner of a paper company know about time?

[@rajeevgangal542]

😁

[@treborheminway3814]

I wonder what the Sour scoop universe is like...

[@GrinninPig]

I liked infinite jest

[@helicalactual]

Only reason, for the “arrow of time” is the Higgs mechanism. Otherwise there’s parity. Your welcome

[@Mesohornet11]

hype!

[@Tiago-lw5bv]

Sean would you be my professor?

[@SandipChitale]

If at the time of big bang the universe was a single point with no structure then by definition does it not mean it had low entropy?

[@albirtarsha5370]

I think there is disagreement that the universe was a single point.

[@SandipChitale]

@@albirtarsha5370 I guess quantum mechanics. But how about very few degrees of freedom.

[@albirtarsha5370]

My understanding is that it is only the visible universe that was so extremely localized. The entire universe is [theoretically] infinite and always has been but was denser in the past.

[@SandipChitale]

@@albirtarsha5370 understand. But in the discussion they were talking about low entropy at the big bang of our visible universe right? If not then what is the point of talking about big bang and low entropy 😀

[@albirtarsha5370]

@@SandipChitale I am convinced that these things are related. Meanwhile physicists say that they can't understand the big bang without new physics like quantum gravity. So the early big bang is open for speculation IMO. Even the cosmic inflation is sometimes explained by theoretical particles: inflatons. So in spite of all they know there is still a great unknown.

[@JiveDadson]

Many Worlds is a copout.

[@fatmaramadan6928]

If the wave function does not collapse, it is a logical conclusion.

[@SandipChitale]

Can a local system be time reversed? What happens if there was other stuff at the same location where reversing may take particles of your system? In other words a local system cannot be time reversed for long before it starts running into other stuff that is going forward in time. In other words only full universe can only be velocity reversed?

[@fatmaramadan6928]

Maybe inside a black hole. We know light cannot escape the pull of a black hole . So If matter is drawn into a black hole ,is there a possibility movement of anything past the event horizon is faster than the speed of light ? If so, what can we deduce or conclude from this?

[@crunchy3546]

Dunder mifflin?

[@DiegoRodriguez-vx6ys]

you see he isn't working there anymore hahaha

[@origins7298]

Why doesn't Sean debate some of the critics like physicist Sabine hossenfelder would be cool to have a bunch of physicist on at once discussing quantum mechanics and the interpretations of it! At the end of the day there will never be mathematical rigor with linguistic expression and there will always be a gray area where people get into making statements that are somewhat vague and the accuracy cannot really be determined I think the two important points that don't get emphasized enough for the fact that when you put a numerical value on any physical system there is always a degree of error or error bars attached... and these error bars can have huge implications for both past and future predictions of the system Also the fact that at some point you have to use photons to measure photons... you come up against the fundamental limit that there is imprecision in the fact that you have to use a physical Force to gain empirical knowledge about other physical systems. In such interactions there is always turbulence, waste Heat, and imprecision These basic facts make it impossible to build a linguistic representation of the Universe in any fundamental level. Anyway I still think would be cool to have continued dialogue between some of the leading public intellectuals kind of surprised Sean doesn't do this as he's pretty Progressive

[@Albeit_Jordan]

Oh... So not _that_ David Wallace...

[@doublesandtrips]

Is there something I can do in the future that will affect the production of this podcast-episode, if not, I don't care to listen to it.

[@websurfer352]

To study the nature of the arrow of time we first need to define time itself more precisely!! What is time?? Is time merely a degree of freedom, a definition that would be in keeping with defining time as a dimension!! A degree of freedom per se does not have an arrow unless in extreme conditions like inside a black hole where space acquires an arrow with time. Does the arrow of time pertain to time as a degree of freedom or does it rather pertain to the second law of thermodynamics which is coupled into time, is married to time fooling us into ascribing the arrow to time itself?? Non of the three Euclidean dimensions have an arrow, might time not have an arrow as well?? Imagine a long road with a one way rule imposed on all vehicles traveling on the road?? In this case it’s not the road itself that has an arrow but the one way rule imposed on all vehicles traveling on that road?? That is how I see the arrow of time!!! If it was time itself that was directional then I would suppose that the laws of physics would prohibit time reversals?? But they do not!!

[@albirtarsha5370]

I have never heard the arrow of time being defined as more than an asymmetry. I think this narrow definition works well for physicists because it is testable.

[@SandipChitale]

A one good definition of fundamental time I have heard is succession of different configuration of universe however small. In this you can note that there is no notion of rate of progression of time as the configuration may change after arbitrary gap which we have no way to detect. In this model we use day to day time based on some local system's repeating approximately configuration e.g. clock hand aligning with number on dial, sun rising, number of vibrations of atom etc.

[@SandipChitale]

In you example it is not only that the road is one way but has moving forward slice where all vehicle have to be. Think of a diorama of present moment stuck on a conveyor belt. The vehicles move in space in that diorama.

[@albirtarsha5370]

@@SandipChitaleTime is what clocks measure. Time t progresses in relation to tau [proper time]. So the definition of time is circular but relatively consistent.

[@calvingrondahl1011]

😺❤

[@OBGynKenobi]

Too bad it wasn't David Foster Wallace

[@joelsacrafamilia9833]

I thought it was for a sec. Then I realised he is no more.

[@onlyonetoserve]

Shawn can we offer you anser to big questons riddel planit erth?

[@HarryNicNicholas]

yoo kan gess end make suggests.

[@wrongtimeweeder1076]

Latte for worc? Latte for diner? Only thyme wheel Tel.

[@onlyonetoserve]

@@HarryNicNicholas Reed buk for anser

[@twonumber22]

get rekt Sean

[@Method5440]

First

[@HarryNicNicholas]

i second that first.

[@devanairemccallister4194]

If i hear the word Entropy one more time..

[@devanairemccallister4194]

David just talks in circles really. Sean was trying to get him to not do that.