276 - Craig Callender: Lab-Grown Meat, De-Extinction, and the Tolman-Ehrenfest Effect

39:58Maybe. Okay. I'll take one. I mean, yeah, it would be kind of fun to have one maybe. But I mean, it would just be a wolf, really. But I mean, some people, there are an astounding number of Americans who have wolf or near wolf pets. And certainly for a substantial portion of my childhood, I wanted a wolf. But a vichla is enough at this point. Yeah. Somebody in the neighborhood had a wolf. It was, I guess it was some kind of very, very close to a wolf. and, you know, see, I would be walking my dog and they'd be walking theirs. And they had their dog on a leash and then they had another rope around the neck attached to their waist as a kind of safety.

40:51And then you would look at the, I mean, to really look at the wolf like right in the eyes and see those eyes, it can send like a shiver. I think there's like a kind of evolutionarily based, primordial shiver that goes up your spine when you actually look a wolf right in the eyes. Two animals, one you mentioned and one I'm not sure if you mentioned, the dodo and the woolly mammoth. Where do those currently fit into the de-extinction landscape? Yeah, so they both get mentioned and then as does the passenger pigeon um and then you can see you know maybe the passenger pigeon's a good one to where you can see my point which is that um the passenger pigeon you know i mean so there was no animal that would have been voted least likely to go extinct in the 1800s in america than that because there were flocks of just billions and there's all these contemporary reports of people's watching uh so like mirror talks about the this the the sun being blacked out for three days over an area as the plot goes by i mean it's just incredible but then the last one her name was martha i think she was up died at the university of cincinnati zoo in like 1913 or So this is amazing, you know.

42:19But as I understand it, part of their breeding strategy had to do with the numbers. You know, so they would, zillions of them go into these trees and that they needed somehow the large numbers. And so then the population collapsed once they got, you know, hunted so much below our threshold. and so the idea of bringing them back you're never going to put them in the wild you know so at best they're going to be some kind of curiosity in the zoo and so that's sort of my thing is it ever going to go back into the wild is it ever going to be you know part of nature ever again or not and so Schiavowski's horse hopefully yes there are other cases too which are really nice which is there's the black-footed ferret had very uh had some kind of inbreeding depression because the genetic diversity was very low and you can go in and do a kind of genetic rescue where you mix into the population some stuff that you know had been clone you know had been frozen from before and so if you can grab You know, it's like at the San Diego Frozen Zoo, they've got material from, you know, in some cases, the 70s and 80s of different animals when the populations are bigger and often more diversity.

43:48And then you can inject that diversity into current populations. Seems like a great idea. and then i contrast that with just having some kind of grotesque creature that has been kind of like painted white in a at best in a zoo and so to me there's a big difference yeah so it sounds kind of like there's a two-factor analysis or questioning that goes in here like one could the creature be de-extincted and two could it be successfully reintroduced in the environment And I'm wondering if for the dodo and the woolly mammoth, this is feasible or not. Oh, yeah. Yeah, I think, you know, so, you know, for the woolly mammoth, you know, I mean, my guess is no and no.

44:40You know, so you have, I mean, you could make some modifications and maybe make an elephant that's hairy. that maybe it could change things, that maybe its hemoglobin is better suited to the North. And so people talk about the elephant. You know, the North needs its elephant, and people talk about putting it in the kind of tundra in Siberia.

45:09But, you know, you already have enough trouble keeping the existing elephant populations alive. and so you know if you're you're gonna have I mean then you're gonna have another population that's gonna be under threat although it seems kind of like madness and then the thing is it's just gonna be it's not gonna be a woolly mammoth in any way it's just gonna be a few tweaks to it so you don't think that they will be able to find or find genetic material that's been frozen and preserved no i mean you you you've got well we've got they've got tons and tons of dna fragments uh but we you know to get like uh something really good though you need often like the the living the living cells that are that are frozen got it um and so actually like when you say the living cells that are frozen you mean they haven't died that's right they're frozen, so they're still viable.

46:16Typically, I think of frozen things as being dead. I don't know. I don't know what dead or alive really mean here, but I mean like frozen sperm, frozen eggs. But you don't think that there are frozen woolly mammoth eggs or sperm out there? No, no. It's too long ago. Okay. It would have just degraded, even if it remained at that temperature. Yeah. And then even the DNA is degraded, so that's why you just have fragments. Okay. You get some idea of different things by, you know, all these very sophisticated ways of comparing DNA. And so you can maybe figure out that such and such codes for hair or things like that.

47:01And would it be the same then with the dodo? Because the dodo doesn't have the cold to rely on, even in the first place. yeah i know less about the dodo case um yeah so i yeah i i shouldn't even say really i don't know okay i can also i should say it's not that i even have a kind of thing that you know only the thing produced by you know like real egg and real sperm is the real thing and only the real thing could be useful in nature and so if you made some kind of grotesque you know creature that never existed before and you threw it out there and the idea was to actually throw it out there and you could show that it was expected that was going to do a lot of good for the ecosystem then even if it never existed i wouldn't actually have a problem with it of course that did exist gives you information that it could exist but okay that i really enjoyed that but let's uh now shift to something completely different in philosophy of physics and you told me that this topic is one that's somehow to you perplexingly not received any real philosophical attention.

48:12And that's the Tolman-Erinfest effect. So before we talk about the philosophy of it, can you just give a brief or as brief as you want, just tell the story of it and why it's interesting in the first place. Sure. Yeah, when I came across the Toll and Ehrenfest effect, I mean, it's a kind of common thing in cosmology, but somehow it doesn't get discussed much. And when people are thinking about philosophical foundations of statistical mechanics or thermodynamics, you know, really my jaw dropped really because I knew the history, which this is against. And, you know, so the history suggests this shouldn't exist, really.

48:58And so then when it does exist, you know, I was really surprised. But let me explain what the effect is.

49:08So if you had like a column of gas, so I suppose we took, so the example I've been using is just suppose we took like the, you know, really, really tall column of gas, just, it could be a tiny one, but just to make the fact that gravity is relevant, you know, more salient. So suppose you took like the Empire State Building and you took the elevator shaft in it. And then you, you know, thermally sealed it all like a kind of thermos inside. And so you had air in there and it's thermally sealed. And now you ask, is the temperature at the top colder, hotter or the same as the temperature at the bottom?

49:55um the tolman-ehrinfest effect sorry and i let the system go to equilibrium and then i asked the question you know is it the same temperature or is there a temperature gradient and the official answer after a hundred years of debate and thermodynamics and statistical mechanics is that the temperature damn well better be the same uh the tolman-ehrinfest So if it's in equilibrium, like by definition, it ought to be the same? Yeah. Okay. And the Toman-Erafest effect is that there's a temperature gradient, that it's colder at the top than at the bottom if this gas was on Earth. And this is just surprising because it seems to very much go against almost what we're stipulating.

50:46Well, not even just what we're stipulating, but what seemed to have to be. And I can describe, if you want, the sort of prehistory, which I think is a lot of fun. Okay, so you've got, you know, a system, you know, maybe it's a gas, and then you have, let's suppose we went back to the early 1800s, and then we asked this question, you know, when a system's in a gravitational field, should the temperature be the same when it's in equilibrium or not. Basically, a background assumption was sort of the assumption that most people would have had. So like if you climb a mountain at the top, what temperature is it?

51:31Colder. Yeah. And so people thought, well, I know the mountain is not a closed system or anything, but it's presumably colder at the top. and they already knew that the pressure was greater down at the bottom. They already knew that there were more particles, atoms or whatever they were, molecules down at the bottom. And so then it seemed natural then that the temperature, which is connected to the energy, would be different down at the bottom than at the top. And so the thought would be that it would be hotter down at the bottom. All these atoms are moving, and more of them are moving down there, and so there's more energy down there, and so there's more temperature, so it's hotter.

52:21And so that was sort of the... But people didn't really have a good theory about this, and so then people started to come up with these theories that were known as kinetic theories of matter, And so they started thinking about little particles and molecules banging around and trying to explain, you know, who explained pressure, temperature, entropy and heat and all that in terms of particles. and you know one of the first theories was by herapath in like the 1830s and he had this crazy model where he thought that the temperature up above was going to be um colder because he thought gravity got weaker uh up there and so he had this idea that from looking at the solar system that the colder plants moves slower um so that's all wrong but it shows you how much things were like up for grabs um also i mean i mentioned the hair path just really so i can mention a completely irrelevant detail but that's kind of amusing which is hair path he sent in his first kinetic theory to public to get published in the proceedings of the royal academy it got rejected and so then what her path did over the next year was he wrote uh about he wrote these challenges to the head of the royal academy uh in the times of london unlike page three daring him to challenge you know calling him out mano a mano can you solve such and such a problem i'll give you 30 days and 500 whatever quid if you could solve it and then he would do And so imagine being challenged in like the New York Times every month by somebody.

54:18And so he did this. And then he started to work for a railroad. He ended up publishing his kinetic theory of gas in Railway Magazine, which is weird.

54:35Anyway, if you get really back to the story, which is so Maxwell was the, you know, I think James Clerk Maxwell is founder of electromagnetism, but also was really big in statistical mechanics and thermodynamics. And so he puts out his massive book, and he notes that what he's trying to do is figure out what is the distribution of all the molecular speeds associated with being in equilibrium. And so he finds this, and it's called the Maxwell Distribution, and he points out, gosh, this is weird, but it says that the temperature is going to be the same than the bottom and the top of this gas that we're talking about.

55:23Anyway, so he publishes this, and then Guthrie from South Africa, who allegedly had drawings for a solar-powered plane, and this is like in the 1860s, and also came up with the four-color theorem, So there's no slouch. He says, but Maxwell, he writes in Nature, he says, but Maxwell, this can't be right. Because, you know, when these particles are bouncing around, so imagine inside this chamber, inside the elevator shaft of the Empire State Building, when these particles are bouncing around, the ones that are falling in the gravitational field are picking up energy. and the ones that are going up are losing energy.

56:09And if temperature is just a function of the energy, then it should be colder up at the top and hotter at the bottom. And then Maxwell says, oh, you have no idea what the trouble I've gone through on this thing. Because he said, that thought occurred to me. And he said, it almost upset my belief in calculation, this problem. And so if you've got Maxwell, the father of electromagnetism and all this saying that it upset his belief in calculation, you know, you know, you're like, it's a tricky, tricky issue. But he says, look, Guthrie, you're wrong, though, because, you know, the gas is in equilibrium.

56:53So each layer stays the same. And we know the density is higher, lower. and so more of them are coming up to the next stratum hitting it and then returning down and the ones that are making it through are the ones that were initially faster right and so you have it's true you have you know so we have all the fast ones up here and the slow ones down there and so and then he shows how with the maxwell distribution you can show that uh the factorization of the energy into kinetic potential leads to a factorization in his thing that makes the temperature independent of the height in the gravitational field.

57:41And so mathematically, it just falls out of this distribution. And so that's, you know, the accepted correct answer. Boltzmann then comes around. So Boltzmann is then the father of statistical mechanics and all of that. And then he says, yeah, Maxwell, he's right. And he said, because if he wasn't right, then the thing would move out of equilibrium. And so he's happy with that. But then Boltzmann's former teacher, Lachmitt, whom some viewers would know from Lachmitt's attack on Boltzmann's H-theorem, but most people wouldn't know Lashmitt's attack on Boltzmann on this question and Lashmitt says I know that Maxwell argument and I just don't believe it he challenges a bunch of the assumptions and then he points out the kind of Guthrie point that as things are falling they'll pick up energy he then calculates a difference which I then calculated for this Empire State Building where he thinks there would be a 15 degrees Fahrenheit difference between the top and the bottom Oh, that's a big gradient.

58:53Yeah, it's really big. And like in mountains or area, you know, stuff, it actually isn't a bad, it's not that far off. But then he says...

59:11We're now freed from the terroristic nimbus of the second law. And then it goes on and says, well, no, mankind is no longer going to be dependent just on the sun and oil. We can just use gravity and it will get us out of this, which, of course, would be awesome. But then, you know, Boltzmann sort of beats on him a little bit for his arguments there. the English physicist Burberry comes in he's like Boltzmann, Gibbs sorry, Boltzmann, Maxwell, they're right Gibbs, the American father of more modern statistical mechanics he comes in, says Maxwell, Boltzmann, they're right he produces the same thing within his own system and so over this long period you know there was all this fighting back and forth but then um well i should say the historian of physics stephen brush is great on this he has a uh paper called uh geniuses and gadflies and then it's like each genius is paired with a gadfly who's some help you know birth birth a new theory um and then uh you know so now this is accepted so this is this is what it has to be But anyway, we just momentarily go back to Maxwell.

1:00:36Maxwell said, I've proved it in the ideal case that it has to be no gradient. And then he says, but that implies all gases, all systems, not just gases, everything has to be the same temperature in a gravitational field when in equilibrium. And why? Because just take my system, you know, the Empire State Building. if I put it on a thermally conducting plate with something else, I could then bring a rod from the top of the other one. And then if they're different substances, they would have different temperatures at the different heights. So I should be able to get a heat pump and then break and get a perpetual motion machine.

1:01:23And so Maxwell says... Got a lot of physicists. This is, you know, so you would be able to get all this work for free and you can't. And so that's why everybody has to have the same temperature, the top and the bottom when you turn on gravity. So that all seemed right to most people. That was then the, you know, accepted wisdom. Do you say that was Maxwell? Yeah. Okay. Yeah, it's really beautiful. I mean, Maxwell writes beautifully, and the explanations are beautiful. It's really wonderful.

1:02:02Anyway, so then you can see then when I saw the Tolman-Erenfest effect in 1930 that said that there is a difference, I was like, what the heck? How could there be a difference? Because then I could do the Maxwell fit. Why can't I break the second law, get a perpetual motion machine? What is going on here with this effect? So Tolman and Narenfest prove it in relativistic cosmology with a very kind of special system. How robust is it? You know, what the heck is going on there? And so then I wrote a paper with my PhD student, and now he's a professor at NTU in Singapore, Eugene Chua. and so we have this paper coming out which it doesn't include all the cool prehistory looking at this effect and you know what happens is that in general relativity you do have this sort of modification due to the gravitational field and you'll predict so it's very super super tiny so in that same system the empire state building it predicts something like to the order of you know 10 to the minus 11 of of of one degree fahrenheit difference between the two so it's super super tiny relativistic effect it's actually like almost exact can be written almost exactly the same formula as loschmidt had except that the loschmidt formula you would need to divide by C squared, and then you get the same effect.

1:03:48So anyway, and you can't break the second law with it because if you think of in general relativity, since the system's in equilibrium, as you're moving your heat, as you're moving things through the system, it's going to equilibrium at every moment. And so when you then try to transport something down, it's gradually changing temperature ever so slightly. And then when you go to send it back to the other system, you're just sending it back at the same temperature as what it is in that other system. And so it's kind of weird that you then can't break the second law, but you can't. But you still have this difference.

1:04:35And it does violate then the, it violates the zeroth law of thermodynamics, violates one of the Clausius versions of the second law. In some sense, it kind of technically violates the first law. and anyway what is going on? Where did this effect come from? Do you need general relativity? And so there's a great paper by the great general relativist Visser and then he had a PhD student named Santiago and she wrote her PhD on this effect and they suggest a counterfactual history where the effect was discovered before general relativity. And then Eugenia and I show that the counterfactual history is actual because Einstein actually discovered the effect in 1911.

1:05:35And so he didn't have general relativity in 1911. And he gets it later. There are various understandings of what you mean by general relativity, but more like 1915. And so Einstein had this kind of weird theory that few people have, unless you're a historian of physics, you know it, but otherwise you don't, called the scalar theory of gravity, which is going to sound so un-Einsteinian. So on this theory, Einstein thought that the speed of light changed in the gravitational field. So like on Earth, the speed of light would be different down near your feet than at your head. That seems so contrary to Einstein.

1:06:23Right. But what he was dealing with was he had had, from 1905, he had had, basically, to get the Tolman effect, you need two things. You need equals mc squared, and then you need what is called the principle of equivalence. and so equals mc squared says that you know the the amount of energy is you know connected to the amount of mass uh and uh so that is then uh connecting but that's the um inertial mass then but the principle of equivalence this is kind of weird you know whenever you look at Einstein it's always so amazing because so like 1907 he had he started working on gravity a little bit and then he gave up and then in like 1910 11 he returns to it because he sees some experiments are being done that maybe he could do some he that maybe some of his ideas could be testable in some day and so he starts working on this and it's so weird because he's just like knows in his heart that this principle of equivalence is true and so the principle of equivalence is this famous you know, thought experiment with the, that there's no, there's no observable difference between an accelerating locally, an accelerating frame of reference and falling in gravity.

1:07:48And so if you think of the elevator, it's such this, this famous elevator thought experiment, where if I'm being pulled up in an elevator, that's like being pulled down, that's like being pulled down by gravity. So Einstein just keeps doing this again and again where he takes a system, then accelerates it, you know, theoretically, and then says, well, that must be what it's like when gravity is turned on. And so in particular, like locally, in a kind of homogeneous gravitational field. so like near the surface of the earth and so with this with these two things he's able to get you know the far more famous gravitational redshift and the bending of the light around the sun but then this is another thing you know because heat is sort of well in some ways it's sort of like light and then this is this temperature gradient turns out to be like a kind of another big general relativistic effects that you get before general relativity just from equals mc squared and the principle of equivalence.

1:09:03And so his principle of equivalence is telling him that the gravitational mass and the inertial mass are the same, equals mc squared, giving you that with the energy. He is a form of energy. And so then he then sees that there's going to be some kind of effect, which sometimes people talk about the weight of heat, which I don't really like but you can see why people say it and then yeah this effect is real that would be way too hard to measure you could never measure that the empire state building thing but this could show up in cosmology maybe you're looking at some kind of extra solar planet and wondering, what phase is it in?

1:09:54Is it liquid or gas or that? And then you'd have to take into account this temperature gradient. On the other hand, wait, maybe I should say, is what I said clear so far? I think everything that you said is clear, but nonetheless, in case we lost anyone, it would probably be worthwhile to just summarize why if we let this empire state building size chamber of gas into equilibrium there is nonetheless this temperature gradient between the top and the bottom yeah so well it is yeah so it's a it's a general well sorry it's a pre general relativistic effect so you don't need all of germ relativity you just need some ingredients and it is a lot like the Guthrie sort of point, which is about falling in the gravitational field.

1:10:56But now we're looking at, you know, the extra energy that comes from equals MC squared and what's happening to that as it's falling. And so this is then what's giving this effect. And then this is shocking, but it's sort of like half shocking, I guess, because on the one hand, you can't get perpetual energy from it like Maxwell worried. On the other hand, it does obliterate most of what you think of when you think of thermodynamics. And so one thing you could do, so there is like an escape that already Einstein had mentioned in 1911 or 12. And he said, well you could just redefine the temperature and so he called it the VAR temperature the true temperature and so that true temperature you would then build in essentially the gravitational potential into the temperature now Tolman and Ehrenfest didn't like this they wanted to use the what they called the pocket temperature which Einstein named the pocket temperature now Ehrenfest named it the pocket temperature in like 1911 or 12.

1:12:15And so then there's a question about like, which is the right temperature, this pocket temperature. So pocket temperature is like one, like if you just took your temperature, you know, with a thermometer, that would give the pocket temperature. So it's named pocket, like a pocket watch, one that goes around with you. And so when Einstein's doing all of this stuff about time, you know, he's imagining you're walking around with a pocket watch. now you can imagine walking around taking your temperature with your you know the thermometer that you just buy from CVS or something and as you're walking around taking that temperature but that temperature is now not if you say that that's not the the real temperature the the var temperature then that them that reading is not then the right one you would have to then multiply it by some gravitational factor and then you'd get the real one.

1:13:13But then the interesting thing is now, if I took that thermometer like you would, you know, you might like put under your tongue to take your temperature, if I stuck that into the bottom of the Empire State Building and I stick it into the top, it's going to read a difference. But now Einstein will come along and say, but the true temperature is this one that's modified. And then because there's a difference between the top and the bottom in terms of gravity, it's going to work out that they're exactly the same temperature. And so then the whole Maxwellian story is all correct again.

1:13:49And Tolman doesn't really like that because he thinks, you know, he's more an empiricist, wants the thermometer, the measured thermometer to be the temperature. To me, you know, I always think to get from the measured temperature to the actual temperature is already many, many assumptions and many, many things have to be assumed. One more, adding gravity to me isn't a big deal. And so although I don't really care which one is the temperature, you just define both and try to be clear. But on the other hand, I do think that this Einstein temperature is a better one because it's sort of, it's more the one, I've been putting it in different talks this way, I think of the Einstein one and the real temperature.

1:14:50It's like the boss temperature. So if I'm imagining where is heat flowing and I have to make a prediction, so I take a hot box and a cold box, I put them together, which way is heat going to flow? If by hot and cold, I mean the thermometer one, I can get systems where it's going from cold to hot, which then violates some forms of the second law. If I then insist on, but the one that really matters for not getting perpetual motion machines and stuff like that is the actual heat is really going to go from the hot one to the cold one. And so I prefer to use a definition of temperature where the hot one is the hot one and the cold one is the cold one.

1:15:41And that it would be the Einstein one. But I don't really get too excited about like, you know, arguing about definitions, but that definition is the more natural one, I think, because it is responding to the parameter that is better described as the boss when it comes to things that are important thermodynamically. And when you think about this puzzle as a philosopher, naturally it's very interesting to see the historical progression and how science, in particular with regard to this one problem, develops historically and sociologically. But what else is it that, as a philosopher, makes this episode and this puzzle so interesting to you?

1:16:35Yeah, to me, I've always had this sort of interest in these sort of laws of what philosophers often call the special sciences, the non-fundamental physics, so laws of biology, economics and stuff. Where do they come from and how do they arise and how can they be so robust when they seem kind of, from the point of view of, you know, down there at the lower level and you're, it all seems like accidents. You know, so I think Jerry Fodor had said in his special sciences paper, you know, like, how do the rabbits know to, you know, how do the electrons inside the rabbits know to, you know, make the laws of ecology true?

1:17:24And so then you have these laws of thermodynamics, which are like the ultimate special science laws. you know so eddington famously had said you know um you know well uh your theory could you know be you know be conflicted with evidence you know conflict with this conflict with that but if it conflicts with thermodynamics he says i can give you no hope but your your theory is going to collapse into deep with in deepest humiliation and then you know this you know it's like a very strong endorsement that these laws are like, you know, never to be, you know, exceptionless. And I mean, it makes it up all the way into the Simpsons, you know, so in one episode, you know, Lisa invents a perpetual motion machine and then Homer yells at her, you know, in this house, we obey the laws of thermodynamics.

1:18:17So we have to always obey them. They're super strong. But then from my point of view, looking at this episode, you know, it's really interesting because it shows how much work goes into making the laws of thermodynamics hold. So the way I was thinking about it was, so you've got this temperature gradients. You can barely notice them. Well, you can't really observe them, but we know they're there. but then the assumptions behind the tolman effect are such that we can only derive it in these circumstances where the gravitational field is is is really pretty um well there's all these technical terms you know you need a time-like killing field it needs to be a stationary metric and all this but basically you know really sort of nicely behaved gravitational fields that uniform homogeneous um and so why and i thought why you know i could just can i get tolman like effects all over the place because you know the real world is the space-time curvature is variably curved you know you're curving space-time near you differently than the picture behind you and things like that and so it's all a kind of big variable mess and so what i have to do is, so shouldn't there be these Tommen gradients all over?

1:19:45And I thought, well, couldn't there even be really weird ones, like ones where not just spatial gradients, but temporal gradients? So could there be a thing where the temperature of a gas in equilibrium is different at one time than another time? I thought, well, that would be awesome because that's really weird. but then equilibrium is tied to time and so no you can't have that but you can't but you have those gradients all over the place it's just that they don't you know equilibrium isn't doesn't apply because you to find equilibrium to be you know kind of stationary observables in time and so then you have to go around the universe looking for these little patches where you find things that are nicely enough have behaved so that you can say ah, I can define equilibrium and then I define equilibrium and then I find a gradient and so I'm doing like a lot of work to get thermodynamics you know, off the ground to begin with and this kind of fits in with some earlier thoughts I've had where I just you know, like if you think about the gravitational force um so here we've just been talking about the gravitational force as an external field but you can imagine turning on self-interactions where you have you know all the different particles are feeling the mass of each other and then what happens so suppose you thought of like all the stars as like the particles in the gaps but then those things are interacting primarily by gravity.

1:21:30Now, what will happen when I then model that thermodynamically? Well, then, you know, we'll fire the gas in a box and gas in another box. Now the gas in this box is feeling the gas in that box. You know, do they all clump on there? Or that would cause trouble with thermodynamics as well. What if I had like, what if I drew my boxes so that they were so tiny and so small and so weird in these little sawtooth pattern that they could feel the electromagnetic force between the particles from the one gas and the one box and the other. That would screw up with things. If I go really, really, really, really, really, really small, things start to look a little bit thermodynamic still, but not as much.

1:22:21And so I'm always interested in these kind of like fringe phenomena for thermodynamics. And so then you kind of see, get a kind of good picture that's hard to get for some of the other special sciences of just like, instead of, so sort of the opposite of the Eddington. So Eddington is saying it's super robust. Anything that conflicts with it is going to be humiliated. And then I'm looking at how fragile those special sciences are and how much, and a lot of it is actually like not entirely constructed because there are the fundamental probability flows of all these particles and stuff at the bottom.

1:23:03But there is some element of construction in what we call thermodynamics. I'm really glad that we took the time to talk about that because it's certainly nothing that's ever come up on the podcast before. So even though I've done a number of thermodynamics episodes. So very, very cool. We've run the gamut, but there's one other topic that I wanted to ask you about, just because I've done over the years, many episodes on quantum mechanics. But it's always great for me, at least, to hear different people describe the problem and how they look at it. Because, I mean, everybody just does it very, like if you ask Tim, you'll get a very different answer from what you'll get from David Albert.

1:23:56You'll get a different answer from what you get from Jacob Brandes, who I've been speaking with lately. So just at a high level, what is the problem with quantum mechanics or how we perceive of quantum mechanics that results in or has resulted in these debates over the quote unquote interpretations of quantum mechanics or theories of quantum mechanics? yeah i think you know what from my point of view what the the problem is you know so you've got this mathematical formalism and then you've got a kind of some measurement practices connected to that um that then you know yield a an amazing amazingly successful theory with great predictions but you really just don't have any kind of um you know model of what the physical reality is and so then you know people had all these different interpretations of what what's really going on and you know some of them are just hideous uh they're just terrible and they didn't really uh they would have they would manifest a lot of the sort of uh vices i mean if you think of like theoretical virtues then the opposite i guess like a theoretical vice and so there'd be inconsistent or incomplete or absurd or just vague and fuzzy and hard to understand.

1:25:34And so you had all of these problems. And now I think you do have some interpretations that are satisfactory. But the fundamental problem is just that you didn't really have a good a good interpretation of what all this math was. That's a really nice and useful way of putting it, that on the one hand, you have the mathematical formalism that enables you to make very accurate predictions, but then on the other, you don't have a clear, understandable picture of the world in which all of this is happening. and then let me ask you the only follow-up i had is what interpretation or theory do you find most promising at this point or comprehensible and why is that yeah so i'm in the minority because you know i've always been you know clear that you know i've always liked the the bohm interpretation of quantum mechanics So you and Tim are buddies on this?

1:26:50Yeah. And I studied under Tim, so there's probably a... But yeah, there were a bunch of Bohmians there. And I think, well, I like to think even if I had grown up differently intellectually, I still would have liked the Bohm interpretation. To me, you know, so the Bohm interpretation says, you know, there are particles or fields. There's some stuff. and the stuff is guided by the quantum wave function. And then there's all these differences between different Bohmians and different Bohm theories and different, especially in quantum field theory. But the core thought is that there's some stuff and it's guided by the wave function.

1:27:36And so David Bohm came up with this idea in 1952. De Broglie had come up with it in 27. to me John Bell endorsed it to me as the most again maybe it's just I've been at it too long or that but to me it just seems like the most obvious thing to do in the world because when I look at the Schrodinger equation it's like the most obvious thing for me is to choose the Bohmian interpretation Yeah, because I think when I have, you know, so in all these other areas of physics, if I have this thing mathematically that's, you know, the probability current, and then I have, assume there's some stuff that moves with some velocity.

1:28:30If I, if it's probabilistic theory, then the velocity is just given by the probability current divided by the probability density. so I've got a whole lot of stuff moving with a current there's a bunch of things in there divide by the density boom pops out the velocity that's what the bomb theory is it just says there's a bunch of particles with that velocity and then it's empirically adequate and you would do that with the velocity everywhere else um on youtube I should advertise it's like 20 years old maybe But on YouTube, there's the quick derivation of the bone theory. And I don't even know who does it, but it's super funny.

1:29:17It's only a few seconds long. It says, step one, grab off your bookshelf a good book, any textbook in quantum mechanics. And so then they grab a book. And then they go to a page. and there's a page which has v, the velocity, and then scare quotes equals j over rho, the current over the probability density. And then it says, cut the bullshit, and you cross out the scare quotes. That's the derivation. So every textbook has this formula, it but they all put like scare quotes in it uh some i saw square quotes over the whole thing i saw square quotes over all over the v yeah over the v over the equals so over anyway yeah just get rid of those scare quotes just assume that there's some stuff and it's you know it's still a weird theory but it's a heck of a less a lot less weird actually having some stuff out there no many worlds no collapses no observer consciousness doesn't matter to what's going on and all that it's a beautiful theory I think and I think it's still a scandal that it's not taught in textbooks I still think that history is

1:30:56not not um how should i put it yeah so it has this dramatic history where bohm was basically you know he was brought before the house for un-american activities committee and then he was basically thrown out of the country and he never really was you know he never worked in the country again and people actively try like uh oppenheimer actively tried to suppress it and so i think it's not all the people were anti-Bohm for his politics, but I think that that still would have, the story of how we understand quantum mechanics would have went very differently had that episode not happened. Interesting.

1:31:38Well, thanks for humoring me on that digression. And as with our last conversations on the show, I really enjoyed this, And I look forward to hearing what's coming next in there, or what comes next in the disinformation landscape in particular. So thanks so much for having this conversation with me. Thanks so much, Robinson. It's always so much fun.