Celebrating 100 Years of Quantum Physics with Brian Greene, Hasan Minhaj & Janna Levin

0:00 we discover an expanding universe. If we're expanding, it is vast in every metric we've ever established for it. There are things that are vast in size, in temperature, in speed. Just to get a feel for that, take a tree and expand it to be the size of the observable universe. Then the plank scale would expand roughly to the size of an atom. So the plank scale is to an atom as a tree is to the universe. This very quickly leads you to have even greater existential dread because if you run the movie backwards, it gets to a point which seems quite catastrophic where these galaxies are literally on top of each other and eventually you're kind of imagining something that's so dense that

0:45 you have to start thinking of it as hot, soupy and and and chaotic. The reason why you can't put quantum mechanics into it, it already seems to have quantum mechanics embedded in a deep and subtle way that Einstein himself didn't recognize. Oh, please tell cuz my edible just kicked in. And this is fascinating. You can't put something into something there. We just don't know where it is inside of that thing. But once we find it in there, we're going to be like, "Yo, that's where it is." And be like, "I told you not to put it in there. It was already in there. That's simple. It's elegant. It's profound. It's amazing. I agree.

1:33 [Music] So maybe it's not the photon being pulled, maybe the space itself is being warped and the photon is like surfing on the space. And so it's just like, "Yeah, man. This wave is awesome. And so you see it curve, right? But if that's the case, um why can't it escape a black hole? Because does that mean that the space inside of a black hole is being folded in so that even the photons can't get out? Yeah, essentially. Sparkly, but but I want to be Morpheus, he says. You can't be Morpheus. I said why not?

2:21 He said because I'm Morphe. It's a stupid conversation. You ever hear those guys that sing in that really really low voice like Profundo Profundo. Profundo. It's like you can almost see the vocal cords vibrating. Oh my god. That's pretty good. Oh, look. I'm live. [Music] Hi J. Nice. Hey Richie number one. Hey man, the crowd is ready for it. I got you. I got you.

3:07 No, I don't do the back. Then I sit on it and I got a butt sticking out like this. I So this is where in 1920 we didn't know if there were other galaxies. Oh wow. Yeah. I mean we thought we were the main character the whole what the Milky Way was the universe. Oh yeah. Yeah. Emanuel Khan even in the 1700s imagined that some of these fuzzy things were island universes. I can't hear his name without so Stop saying it. Stop. Okay. Island universes. You think so? I have uncommonly fast. I was wondering maybe uncommonly found.

3:57 What do you What do you see? Yeah. Okay. I I want to double check it now. He's getting a little He's getting a knuckle there. So, you're pretty fast. Let me see. He was like [Music] Oh man, that's right. Okay. Damn. Nice. That was nice. But you got it, too. [Music] So before we begin, I just want I didn't know this until today that the two of you are actually current collaborators on some research. Could you just just highlight what that is? What are you

4:43 doing? I mean, Brian and I have been working together for years, but mostly we've been thinking about extra spatial dimensions and different cosmological implications implications for theoretical physics. You know, hiding some dark energy and some extra dimensions as one does. As one does. Yes. You're you're thinking about higher dimensions. Yes. Because the the three plus time dimensions are not enough for you. Well, you know, even Einstein when he started working wondered why three. I mean, it's a curious question. Once you start Well, it's a magic number. Yeah. Is it your favorite number? Wait. Those are schoolhouse rock people right there. They count to three. They They got it right away.

5:30 Okay. But how many dimensions are there really? Uh, we don't know. But certain theories tell us that it could be much more than the ones that meet the eye. So it could be as many as 10 or 11. Oh, like gender. [Laughter] But you I said it and now I'm getting arrested. You just make up other dimensions. I mean, it sounds like you're pulling it out of your ass. I mean, sorry. Yeah, it it it's all you didn't deny that immediately. That was worried about this. Okay. Well, partly it is, but it is also deep mathematical reasons that lead us to these ideas. Yeah. And you know, we figure if nature uh can try some experiments, she will. So, every

6:18 possibility might actually happen. Okay. So, we're just exploring. All right. How much weed do you guys smoke? All right. So, complete silence. The microscope and telescope were invented 400 years ago. And like I said, they take us to the grandest visions of our understanding of our place in the universe and the tiniest visions that also give us an understanding of our place in the universe. And so this those first steps were magnified at the dawn of the 20th century, especially through the 1920s. And so let let's start out

7:03 with the large and we'll end with the small. Okay. So let's go back to the roaring 20s. Let's just do that. And here's something that it's hard to even believe that just 105 years ago, we didn't know if there were other galaxies. We just thought all the stars in the night sky, the Milky Way was the entire universe. There was no, we weren't given reason to think anything of there were these fuzzy things in the sky. Okay, they're just fuzz. We call them nebula which is Latin for for fuzz. Yes. Thank you. So So we just thought it was just space lint. Yeah. Yeah. Yeah. And and but some fuzz

7:49 lint space now you mess nebula. Some nebula were spiral-shaped and others were irregular. And the irregular ones were found in the plane of the galaxy. Whereas the spiral ones were in every direction you looked. Interesting. So that was odd. It was a first thing. Well, maybe we can unpack this and figure out what's going on. So there was a famous debate took place in 1920 at the national hosted by the National Academy of Sciences between Heber D. Curtis. Yes. Unfortunate name. He had that name. and Harlo Chappley

8:36 soon to become the director of the Harvard College Observatory and Heber Curtis was director of the Alagany Observatory. Two very different Yeah, I'm going to say one of those sounds more expensive. All right. So they debated whether these spiral things were other galaxies with a term coined by Emanuel Kant in the 1700s who thought about this philosopher. Yes, Chuck. No, Brian Brian is did it to me, man. I'm sorry. What did Brian do to you? because he knows I can't hear the name Emanuel Kunt without being 12 years old. Okay, I'm so sorry.

9:22 Okay, so he he's a philosopher, deep thinking philosopher. He looked up and he saw these spiral objects and he he thought of them as possible island universes. Oh, that's that's pretty cool. An island universe. That's beautiful. That is. But we didn't have evidence to say that to to support it. But it was a deep idea at the time. So there they are. They debated this and but based on what evidence? Just hot taken. They're scientists. Okay. All right. Which means sometimes we have rosecolored glasses towards the past. Yes. I get it. I get it. So here's how it works. Two scientists argue there's a pact implicitly signed before they even begin, which is either

10:08 you're right and she's wrong, you're right and he's wrong, or you're both wrong. They know this going into the conversation. It's nerd Thunderdog. So, two scientists enter. Two scientists leave, but one's a little embarrassed. Pay-per-view Saturday nights. Yeah. So, so here's this was their This is their Tyson, Jake Paul. Real kind of throwdown. So, let's go to the Harvard fellow. Yeah. Cuz you can always tell a Harvard man, but you can't tell them much. Oh, got it. Got it. So, they they were insufferable back then as well. Got it.

10:54 Were they also like I went to school in Boston? you. Just say it. Just say it. So say it, you know. I don't know. All right. So back to the here's what happened. Let's merch. Uh Shappley was heavily invested in the entire night sky being part of the being the whole universe and the Milky Way. and he had evidence at the time from a fellow astronomer who had looked at the spiral nebula and claimed that he found them having moved on the sky. Now, if you're really really far away, that's essentially impossible to measure. But if you're close up and

11:39 you're moving, you can see that movement. Okay? Things that are close to you. So the example here is if I see a plane moving across the sky and then I see a bird moving at the same angle. I don't conclude that the bird is going 600 mph the bird is much closer. So at much lower speeds I can see it cross my field of view. So because it's closer that evidence suggested that the spiral nebula were nearby and he he bet on that horse but it was the wrong horse. He he was he he was doing what a good scientist will do. He took the data put his confidence in the data. It was later shown that the data he was basing his

12:26 argument on was false. It could not be verified by the work of other scientists. In fact, no, the spiral nebula had no motion across the sky. And so, Shappley was just wrong. Later, we would later show that he's wrong. And what puts the nail in the coffin? 1923, Edwin Hubble. Oh, the man. Hubble was a person before he was a telescope. Yeah. I thought I thought he he was born a telescope. Born a telescope. Yeah. Just like when you're a kid, you're like, "Of course you there was Ninja Turtles and they were birthed and Yeah, there it is. There it is. So, you had an idea based on evidence and it

13:13 turned out to be wrong because the evidence was flawed. So, this there's some lessons there. All right. And if one scientist has one bit of evidence, you don't alert the authorities yet until there's confirming other experiments to do so. That is uh what the peer review is all about. That's the peer review is all about. And by the way, for anybody who wants to know, uh scientists are haters. Okay? That is what they do. You come up with something and somebody goes, I call And then it's on. Then it's just on. Wait, wait. So Neil, so Neil, a peer review to to us non-scientists is is basically it's scientific group chat where you present your takeer information and the

13:59 17 other friends that are in the group chat get to be like like and Sapply had a had a green bubble in in the chat. That's Oh godamn. God damn. What a horrible what a horrible life to live. He was the one green. He was the one green surrounded by blues. Yeah. And if you have an idea and it's and it's shown to be wrong, Yeah. then it's just wrong. In fact, Einstein after his relativity, which we'll get into in a couple of minutes, uh that was hard to accept by people, right? There was, you know, it was it was hard. It was very counterintuitive. Someone came up with a work saying 100 against Einstein. 100 against Einstein. And then he's rumored to say what after that? See, I I

14:45 I just learned this anecdote, but he's rumored to have said, "Why 100?" If I'm wrong, one would have been enough. Wow. Yeah. It's pretty great. Yeah. And believe me, I I've been married for 27 years. That is right. Good enough. Okay. So, here's what happened. So Edwin Hubble is curious about these spiral nebula and he finds a star in them that matches a kind of star that's not in a nebula that's just sort of nearer by than that star and it's it's a very specific kind of variable star uh named after the very first of its kind sephiid variable uh the first of its kind was

15:31 found in the constellation Sephiius and so that's how we categorize types of variable stars. The first one in a constellation. All the others, no matter where you find them, are that variety. Found a sephiid variable there. And what was tell us what's special about the sephiid variables. Well, they have a very predictable property where their luminosity, how bright they shine, is related to a sort of oscillation. And you so you can tell uh that you're looking at precisely one of those. It's it's very easily identifiable if you get the luminosity out of it. Yeah. Then you can say I can see the the period vary, right? Based on that period, I know how bright it should be. How bright it should be. So it's as though you knew your light bulb, right? You can tell if you have a very bright light bulb far away or a very dim light bulb up close,

16:17 right? But how can you distinguish the two? And how do you distinguish the two if you know nothing about the light bulb? But if you know everything about your light bulb, yes, you know exactly what it is. Then you can say, "Oh, I know this light bulb, so I know exactly how far away it So he says this star is of this particular luminosity and the only way it can be that dim Mhm. is if it is far out far away. You know everything happens in space and space is happening in spaceime. In the four dimensions of spacetime there can never be a time without a place and vice versa. If I say meet me, you will need to know where and what time to make that happen regardless of the place throughout the entire universe. Well, how would you like to give the gift of spacetime? Suppose I told you you could

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18:38 your life. That's underluckystars.com. And now back to the spaceime that is the show. But it's important to know what he actually meant by that because Hubble himself never was convinced that these were actually other galaxies. He proved that there was something beyond the outskirts of our galaxy. We knew our galaxy about 100,000 lighty years across. He his analysis showed this to be 900,000 lighty years. We now update it to 2 million lighty years. But Hubble was so conservative that he was unwilling to then say this is an island universe. This is a galaxy in its own right. What an idiot.

19:23 Wait, what's the difference just from a space real estate standpoint? What's the difference between an island universe and a galaxy? What are we talking? They're poetically identical. They're the same. They're the same. Poetically identical. Got it. Yeah. Okay. Yeah. Because if our galaxy is our universe and there's another galaxy, then you get to call that a universe. Except once we see the full breadth of it all, we got to reallocate how we use the word universe. Cuz it's universe, one in one verse, right? But we're in we're in the we're in the the multiverse Spider-Man. We're in the We'll get to that. Okay. Yeah. Yeah. Yeah. We'll get to that. All right. Minus the Spider-Man, but we'll we'll we'll we'll

20:11 You didn't like the second one. I thought it was great. So So Jana, how did we're reeling from the fact that we are not the universe. We're just a part of a universe. And then a few years later, Hubble discovers that these spiral nebula are in motion, body and soul. So what's going on there? Yeah. So once he's starting to be able to use these sephiid variables and these standard candles to get a strong sense of how far away things are, he can start do that. He can start to do that kind of mapping out the local environment, what what we have right nearby and then also galaxies further away, these little smudges on the sky. And he begins to catalog not

20:57 only that there are other galaxies around us at great distances but there also seem to be receding away from us largely predominantly. Yeah. And so he makes a plot of makes a plot. So this is very strange. I mean you're looking at all of these enormous galaxies. So, a galaxy is a collection of hundreds of billions of stars and they're pretty localized and maybe they're spirals and uh blobs and they're very far away and they're also moving away from us in every direction which is very peculiar. So, he makes this plat. It's completely freaky but it gets freakier because the further away they are the faster they're expanding away from us and they're calculating this all without computers. Well, hundreds of billions people were called computers back then. Sure. Yeah. If you look at old

21:42 dictionaries, look at the word computer. A person who makes the person who computes. Yes. So, wait. Uh, and there's a room full of Yes. But they're doing it without the machines. The a room full of computers at Harvard at the time. Yes. So, he actually uses the work of one of the Harvard computers, which was a woman named Henrietta Levit. And um she was part of a group of women who worked at the Harvard Observatory that were called up like this. Well, they were called Pickering's Harum because Charles Pickering at one point was so frustrated with his male computers that he fired them all and he said, "My maid could do a better job." And he hired his maid who was Willamina Fleming and she did a great job. Um, and she hired all these other women and one of whom was Henrietta Levit and

22:28 she made 30 cents an hour. Go ahead. Are we applauding her or her pay? That was weird. 30 cents an hour. That's She should be making iPhones. Okay, so I said it. I said it. All right, so but mixed in here, we've got simultaneous things going on. Einstein's general theory of relativity is already at the races. Okay, so that came in in 1915. 15. Okay, that gave us a mechanism to understand what the whole universe could be doing. Just catch us up on that. Well, Einstein writes down

23:14 his equations in 1915 and initially he applies them to things like the motion of the earth around the sun and terrestrial and nearby motion, local things. But then some other very creative thinkers, one in particular was a Belgian priest named George Lamemetra. He decides to apply the mathematics not to something in the universe but to the entirety of the universe and find from the equations that the universe should be expanding over time. It should be just to be clear, he was able to do that not based on his training as a priest. He was a priest physicist. He was a priest physicist. But no doubt

24:01 his interest in applying these ideas to the entirety of the universe was not distinct from his focus on the big questions of existence. So they weren't that separate. Although he in his own mind was very clear. He said there are two ways to have deep insight about the world. There's mathematics and there's salvation. And he said, "Let me follow both." And that's what he did. But not intermingled. He was very clear not to. There was a line in the sand. Absolutely. Yeah. Wait. So what? So So matra, I'll let I'll let you guys figure out the pronunciation. So he takes the equations. We We have an expanding universe, but he So Lamatra before

24:47 before Lumatra predicts an expanding universe using Einstein's equations. Yes. So Einstein could have made the prediction and he didn't. Yeah. In fact, in 1917, Einstein actually got there first and when he applied the equations to the entirety of space was very disturbed that he couldn't get a universe that met his own philosophical prejudice which was that the universe is fixed, eternal, static and unchanging. Why would anybody think the universe could be anything other than that? Well, I mean there is this book called Genesis which seems to suggest a beginning. Okay. So, there are some people who think perhaps that that vision is not correct. But Einstein and many others at the time very firmly believed that the universe could not change on the largest of scales. And that's just a

25:32 philosophical bias. Totally. And in fact, heat changes. Wait, wait, wait, wait. How could he how could he get away with that? If all the galaxies have gravity and if they all feel each other's gravity, they would all collapse down into one point. Yeah. So this was an argument that Isaac Newton actually gave hundreds of years earlier. But if the universe is infinitely big and if the galaxies are spread across an infinity of space then there is no center for them to collapse toward. So you can envision a static universe. Now, if it's infinite, if it's infinite, if and only. But even more than that, Einstein then in his own general relativity recognized basically the issue that you're raising in a finite universe. And he said, "Let me introduce a repulsive push to counter the

26:19 attractive pull of gravity." And anti-gravity, an anti-gravity force field called the cosmological constant. So he introduces this into the math in 1917. It was not in the 1915 equations. He introduces it just to have a static universe that will allow him to breathe easy and to fulfill his philosophical bias. Then the mantra says we can have an expanding universe. And so how did Einstein react to that? Einstein learns of this from lametra in 1927 and he says to lamera your calculations are correct but your physics is abominable. Oh them fighting words. They were fighting words. Wait, by which he was saying you can't trust that every mathematical calculation tells you something real about reality. Some math

27:06 should be in math textbooks and it's interesting but it's nothing more than a mathematical curiosity. And he says, Lmetra, your idea of an expanding universe, that's a mathematical curiosity. It's not real. Okay. So then 1929, Hubble discovers an expanding universe. Now what? What happens next? Well, so it's interesting because the way I originally described it is kind of confusing. You might think it makes it seem like we're at the center of this expansion and everything's receding away from us. But the way the Hubble law is specifically, it's much more like the space between every galaxy is actually stretching. So from their point of view, if you were on one of those other galaxies, it would also look like everything, right? Everything's receding away from. And if you imagine that it's not the galaxies literally moving on spacetime,

27:51 but actually the distance between the galaxies that's stretching, then something further away is actually moving away from you faster. There's more space stretching. And this was really closer to Latra's description. Not even closer. It simply wasn't static. So, so just so I'm clear, at that time they believe there's only one galaxy in approximately 1925. Just so I'm following I feel like I'm in a Chris Nolan right now. I'm watching Tenant. Let me just let's pause real quick. No, no. Up until 23, 24, one galaxy. One galaxy. It wasn't. It was one universe. One universe. Copy. Yes. Here we are 2025 from what I understand. Yes. Now there's How many How many universes are we in now? But are you talking island universes or are you talking universe? Universe. I'm talking about the whole Oh, good God. There's one universe that

28:36 we know about filled with 100 billion galaxies, each of which has on the order of 100 billion stars. There are theoretical ideas that Neil is suggesting we might get to tomorrow uh that that speak to the possibility there might be other universes. So the answer is we don't know for sure, but the data seems to suggest that there's one universe. Well, we we were talking about this backstage. If the del the delta is that big between those two numbers which is one and you just basically said a gajillion, how do we know how do we know that the what we're living in right now, the data that we know right now isn't going to be wildly off and 50 years from now or 100 years from now they'll be like look at those dumb dums in 2025. We hope we hope that that's what will happen. That's

29:22 what we live for. We live to be stupid. We live to be wrong. We're scientists. Oh, got it. So, we lived in Iran. We're scientists. Got it. Okay. Well, so let's let's follow through this reasoning. We discover an expanding universe. If we're expanding, that means we're bigger today than we were yesterday and bigger yesterday than we were the day before. So, logically, where does that take us? Bigger. No, no. going back in time. What is that? Oh, I'm sorry. So, yeah. So, if you're already disturbed about the lack of permanence to the universe, then this very quickly leads you to have even greater existential dread because if you

30:08 run the movie backwards, then everything was once closer together. And if you keep running the movie backwards, it gets to a point which seems quite catastrophic where these galaxies are literally on top of each other. And eventually you're kind of imagining something that's so dense that you have to start thinking of it as hot and uh soupy and and and chaotic and then what what did Lamontra call this? Yeah. So Latra basically said look if the math is saying that the universe is expanding today and if then Hubble's data shows that the universe is expanding today just wind the cosmic film in reverse. You run the film backwards and things get closer and closer together and there suggests that there's a point in the distant past when

30:53 everything was on top of everything else and he calls this the primeval atom. This is the beginning according to his description. Okay. I happen to know there was an astronomer active at the time, brilliant guy named Fred Hy who was not into a universe that would be changing. Yeah. He knew the universe was expanding. He couldn't reason that away. He accepted that. Yeah. accepted that. But if you're expanding, but you're always the same, that must mean matter is being spontaneously created in the void to create new galaxies. So that statistically the universe always looks the same. Yeah. You know, but here's the thing. If the universe is expanding, that in itself is a change. So why would you not accept a changing universe? Cuz

31:40 he wanted to always look the same for all of time, for all eternity, in the past and in the future. Again, it's a philosophical bias, but I think the idea of a beginning was particularly disturbing. Wow. The idea. So, so this primeval atom, the literatur scientists, but not for religious people where God made the universe. They're perfectly happy with the beginning. Look, Pope Pius I 12th, perhaps the nerdiest pope in history who love science. Wait, wait, why do you know this? He I don't know. He took he took Lmetra's work and he said, "There is the scientific evidence for Genesis." That's what he said. And and when Lmetra heard this, he threw a fit. Belgian priest Lmetra, the pope is talking to him d not directly, but yes, when he catches wind that this is what

32:26 the pope is saying. And one of his students who was in the class that Lmetra had to teach that afternoon after learning said that Lamemetra who normally was very quiet and mildmannered. He came in and ranted for 45 minutes because his whole point was I am not blending my religious life and my scientific life. And here the pope is taking my scientific work and he's turning into religion. But notice he said all that to a student and not the pope. You don't want to know the Galileo situation. Exactly. Yeah. So, I have a a tamer version of that quote. It's, "As far as I see, such a theory of the primeval atom remains entirely outside any metaphysical or religious question."

33:12 Yeah. That's after I had a couple drinks and chill. Okay. So, so then it got called the Big Bang by by Fred Hoy. By Fred Hy. Yeah. So Fred Hoy was in a 1948 BBC radio interview. Why do you know this level of detail about Okay. And so he is describing his own approach which as you mentioned is a steadystate approach where matter is created spontaneously and fills in the gaps in space. And so they ask him about this other approach not his. And he says oh that theory in which all matter must be created in one big bang. And that's where the idea of big bang theory comes from. Now people have interpreted that as a derogatory description. His own way of recounting

34:00 the story is he was simply trying to draw a distinction between a theory in which in his steady state only a little bit of matter is created here in the air cross space versus this other theory like one hydrogen atom per century per cubic lightyear. I mean there's some small rate not not quite that small. So it's it is one atom per century per Olympic size swimming pool. Oh, okay. I thought it was bigger than that. And that's all that you need. And so it's kind of an in the whole universe. Yeah. Yeah. Yeah. Because what's more believable that one little atom forms in a cubic, you know, in a swimming pool size arena of space per century or that there's this moment where everything is created all at once. Framing it that way, his theory sounds perhaps a little bit more believable, less less crazy.

34:45 Yeah. Yeah. So what do we have to assume if there is a big bang? So we got to assume that the expansion has been uniform the whole time. Not it doesn't have to be uniform. Yeah. It can change over time. Well, that's been always expanding. It's always expanding. Okay. And unless there's extra dimensions, those might All right. Well, so it could expand differently enough. Brian and I are talking about this later. Well, yeah, you can squeeze the other dimensions there. There could have been chaotic mixing of the expansion and contraction but overall the overall volume of the universe was expanding. But the way you get this is looking at the rate at which the universe is expanding. Yes. And that is a slope on a graph. And Hubble first derived that and it's there's a slope. He called it the

35:32 letter C which is for constant. But since then we swapped that out with a capital H for Hubble and we call it the Hubble constant. very famous Hubble constant. So it's constant over space. I mean it's important over time. It's really the Hubble parameter we should call it because it does change in time. It was it could have been faster in the early universe, faster in the future. All right. So Hubble I he had the wrong turned out uh the sephiid variable he used he didn't know at the time there were two varieties of sephiid variables. The one that's near us and the one that you can see from far far away. and he presumed they were the same. No reason to think otherwise. So he got the wrong distance, the wrong expansion rate of the universe. So Sephias is like

36:18 diabetes is type one and type two. Yes, there's a type one and type two. Exactly. I think [Music] maybe not exactly. Yes, there's literally type one sephiid and type two sephiate. And you got to use apples and apples when you're doing this exercise. So, so he got an age of the universe of two billion years. We would later refine these numbers. Uh, when I was in graduate school many moons ago, the uncertainty in the Hubble constant was a factor of two. It there was a 10. So, with the with the Hubble constant, you run the film backwards. Ask how much time at this expansion rate looking backwards, when do we get to time zero? Mhm. That makes sense. Well,

37:04 yeah. Just just when is everybody in the same place at the same time? That's a perfectly sensible question. And we got two number. There are two camps. Okay. A 10 billionyear camp and a 20 billion year camp. A fac a whole factor of two. And everyone is, you know, fighting for their and we know they both can't be right. And so we need better data. One of the goals of Wait, isn't isn't being off by 10 billion quite a bit? That's a lot. But I again comedian and I only took physics one in undergrad. I did not advance not I don't want the smoke but I am saying being off by 10 billion is a lot. Here's the thing like if you go out to dinner and we split it and I'm off

37:49 by that like that big of a delta. If I'm if I'm Yeah. If I'm 100% off. Yes. Yes. Aren't you like you lose your science little thing? No. So you know what I mean? like could have been disbarred. Yeah. Here's the thing. But you know, you just get to talk your Here's the thing. You are off by 10 billion. You get to talk your still. Here's the thing. Like my dad in the living room when he's giving his opinions about politics. He just gets to run his mouth continuously. I got this. Go ahead. No, this is me and my This is a me and my dad thing, but I'm just a little mad that that that a capital S scientist was this off. Okay. Go ahead. Uh and I have a second question, but go ahead. The universe is vast. Yes. In time. Yeah. And in space.

38:39 It is vast in every metric we've ever established for it. There are things that are vast in size, in temperature, in speed, in gravity. And so if I'm off by a factor of two, between 10 billion and 20 billion, yeah, I could have been off by a factor of 10, by a factor of a thousand, by a factor of a million. We were quite happy. We were in the same sandbox having that conversation. So it's kind it's kind of like being Jeff Bezos, you know, if I'm off by 10 billion, eh, not so bad.

39:24 So, so can I also ask you the second philosophical question which is which is no no this is this is for real when when you were like it's either 10 billion or 20 billion and I was asking you this backstage which was if when the number is that big is it almost like the United States's debt where they're like the the deficit is at 28 trillion and you're like what does it even matter now it's at a gajillion manilion like what does it matter why does the Cuz I feel like a freshman When I'm done, it's going to matter an awful lot. [Laughter] I would I would say that actually 10 billion is actually quite good. 10 to 20 is very much in the ballpark because you should run the Federal Reserve. You should Yeah. Yeah. This stage, you

40:11 know, who knows who has a good way to think about it. You could have been off by a trillion. Well, but the future is going to be much much longer than the past. So, it's not as though the universe kind of will expire within another 10 billion years like we're confined to this number. The future could be just a huge number. We could be living in a time where it's not 10 billion. But can I give you perhaps one these are all very very good answers but perhaps one other way of looking at it. You're saying it was a bad question. Bad question. These are great answers. Bad question. We don't care whether it's 10 billion or 20 billion. The number doesn't matter. What does matter is That's the most American answer by the way. That's the most American answer. Yeah, the truth is we don't care. But we want our theories to work. We want our theories to make predictions that match with observations. That's the only thing

40:56 that matters to us. The actual answer that comes out, whether it's 10 billion or 50 billion or 42 like you're saying, it just doesn't matter. But we need to have a consistent description so that we have evidence that we know what we're doing because evidence matters. And both sides could not be right. Right. And so when the Hubble telescope was launched, okay, I'm just getting out of graduate school, it is launched. The number one goal set for that telescope was to resolve that discrepancy. The telescope's named after the guy who gave us the Hubble constant in the first place. Within two or three years, we nailed it. And the Hubble constant, its value would give us an age of the universe at about 14 billion years, which is comfortably between those two extremes. And that's science working at

41:42 its best. It was there's a limit to how much we can keep beating each other over the head. Let let's get more data. Let's build a telescope that'll solve this. And in fact, today there is a similar argument happening. It's not between 20 billion and 10 billion, which as you say is a factor of two or 100% difference. Now we're down to the 5% difference. We understand things that well that we have two groups that are 5% apart describing a number of years billions of years into the past and that's the precision with which we can do it within 5%. People will kill each other. So again, we don't care the exact number. We care that we can describe it

42:29 with that level of precision when we're talking about events that happened billions of years ago. That's the mindbending. And and here's the issue. When it was 10 and 20 billion, you always have to report your uncertainties for a number in science. And those uncertainties had a little bit of overlap in the middle. And it landed where you expected it to land. Now that we have two other waring factions on the value of the Hubble constant, those two numbers are within 5% of each other, but the uncertainties are tight. Yeah. So the uncertainties don't overlap. And if you look at go Google search on Hubble tension and that's what will come up. Adam Ree is coming to Pioneer Works in October. I just planted an ad coming to Adam Ree who's a Nobel Prize one of the

43:15 Nobel Prize winners who discovered that the universe is not just expanding. The expansion is getting over faster. It's accelerating. Who is part of this Hubble tension debate uh will be speaking at Pioneerics on the H without without waxing without waxing philosophical. I just don't want to miss this point that we're not actually saying which is what makes science so incredibly great is exactly what you all just uh demonstrated. It is this pursuit of the truth based upon the best available information at the time. So it's okay if it's wrong because when it's right, we're going to get there. Yes,

44:06 you got it. All right. So, we're turning the clock back and we get to the big bang and but now the universe large scale universe described by general relativity is now small. It is so small you extend the equations go back. The universe is the size of an atom. Does quantum physics apply to the entire universe or only to atoms. What where does that where where are you on that both of you? Well, at this point we feel we have to invoke quantum mechanics to understand what was happening in the big bang at the energy scales are so dramatic and um that we're really probing quantum physics. high energies,

44:53 you're really looking somewhat surprisingly at small scales. Um, so we we are still trying to grapple with what the big bang is telling us about uh the potential to understand not just general relativity but a kind of quantum variant of that if there is such a thing. Yeah. So I got general relativity, I got quantum physics. Do they make nice in the sandbox? That's it's a deep and difficult question and one that I and many others have spent their lives trying to answer and we do not fully have the answer yet. Let me restate that. Yeah. That you and others have spent your lives failing to answer. Yes. Okay. I agree. But I think this guy you hear that ah take that. Okay. You got a fan over here. All right. Go. No,

45:38 it's exactly the case. So when you take Einstein's equations of the general theory of relativity and you try to invoke quantum mechanics within the same calculations which as you eloquently noted you'd have to do if you're talking about the whole universe when it's incredibly small. You need Einstein's general theory of relativity. It's the whole universe after all. But you also need quantum physics because it is so small and that's the theory that describes the small things. And when you try to simply put the equations together, you get one answer out from almost any calculation, which is infinity. And that might sound, oh, that's interesting, a big, deep, mystical number. No, it's nonsense. Infinity is nature's way of grabbing us by the lapel and slapping us around and

46:25 saying, "You're doing something wrong. You've got to figure this out." So, I've heard another one. That's where affinity is where God divides by zero. Yes. Yeah. Stephen Hawking. Yes. Yeah. Oh, Stephen Hawking said that. Well, at least that's what he's attributed to. Okay. Okay. So, but they you're saying they don't make nice in the sandbox. Yeah. So, so there's a limit. What's this plank length? What's going on there? Well, the the plank length is is the scale at which But named after who? After Mox Plunk, the the uh I love how you say Mox. I don't know. Is it? What do you think? Am I say Max Plank? Max. Okay. Uh well a hundred years ago in the early discoveries of quantum mechanics was was uh thinking about whether the universe

47:12 was discrete or if it really was a continuum and um and if I looked for instance at the air in this room if I look closer and closer do I find out it's actually made of individual molecules moving around and is not actually continuum and same with water and um was thinking about these things. So in other words, mortar is not infinitely divisible. You get to a molecule at some point. Eventually you get to an individual quanta, a little particulate, a discrete bundle. Um and in thinking about this, there was sort of a fundamental scale that that we would say is when we can definitely no longer think um in a way where we're ignoring this quantum scale where we're forced as Brian's describing beyond that we're definitely going to strike an

47:57 infinity but by the plunk length we're in trouble. We really should be um trying to understand the theory of gravity at a quantum level. Maybe that means that spaceime is coming in little individual bundles. I don't even know how to think about that. I'm just thinking about correlations between little tiny spaceime is coming. Yeah, that was that was wild. That was a wild sentence. That was Yeah, that was very Game of Thrones. Space time is coming. Well, I mean, if it came from the big bang, I mean, was it the moment that space and time was in fact created? Um, and are we thinking about things of a continuum of spaceime itself? Brian, how big is that smallest unit? Uh, the plank length is 10 the minus 33 cm. And again,

48:43 I know the question will be, well, you know, how do you think about something that so well, what does it matter was 10us 33 or 10us 31? And again, we don't care about the exact value, but that's where the mathematics takes us. And just to get a feel for that, if you were to take an atom and uh well, let's take a tree. Take a tree and expand it to be the size of the observable universe. A tree. Yes. Then the plank scale that 10us 33 centimeters would expand roughly to the size of an atom. So the plank scale is to an atom as a tree is to the universe. That's how tiny the distance we're talking about here. And why I'm going to channel So, you measure this, you measure this with a

49:28 ruler. What do you Yeah, I know. I'm going to channel her. Can I channel you right now? You can channel me. I'm I'm not going to even pretend like I understand what's happening right now. I'm going to be 100% honest. There's like 3,500 people here and I'm like, don't act like you know. No, I'm going to channel. I You lost me at FaceTime is coming. And by the way, you came in quite hot, Brian, and you're like, I know what you're thinking. And that's not what I was thinking. I was thinking I think it's really incredible. Let's just have a quick little tangent here. I think it's really incredible. It is almost 9:00 p.m. and this many people went on ticketmaster.com. Paid fees you way back there in the up there. Yes, way up there. Yeah, you guys paid tickets to learn about space nebuli. It really

50:14 it was very heartening that so that's what I was thinking about Brian. It was actually like you know when people say this country is going to and math and science is at an all-time low. I'm like, you know what? It's it's the math and science lovers, I feel theater on a, you know, of all things you could be doing at 9:00 p.m. Just so so I'm challening Hassan here. Sure. What? Why do you have any confidence at all that you know what's happening on a scale that small? We don't. We don't. Oh, okay. That's the answer. That's the end. Thank you. Oh, Chuck, come back. Thank you. You guys, we don't know anything and we could be off by a whole lot. Good night. Take care. Thank you, Beacon. No,

51:00 no. So, so let me see if I can unpack this. Yeah. Um, is it true We're going to figure it out right now. Do Okay, sure. Is it true that every prediction we've ever made with quantum physics when we've been able to test it has come true? Absolutely. Okay. Is it true that general relativity we already know what its boundaries are because there are calculations you cannot make because of this infinity problem. Absolutely. Therefore, if one of those is going to succumb to the other, it sounds like Einstein has to he's going to have to bow down to the quantum. He's gonna have bow down to the bend the knee to bend the knee to the quant. So either quantum will absorb Einstein or there's a higher

51:47 level understanding that'll absorb them both. I would say it's it's that's true but also quantum isn't in competition. We have theories of matter for instance nuclear forces that we understand they can be quantized right theory of electromagnetism can be quantized. So there are laws of physics and quantum mechanics is a regime in which we're understanding the highest energy attributes of those laws of physics. Now gravity Einstein's general relativity is replaced the theory of gravity with this theory of spaceime this theory of geometry replace Newton's theory of gravity replaces Newton's theory of gravity but it is one of those forces it should sit with the matter forces and have a classical regime meaning a regime in which we don't have to worry about quantum mechanics things look smooth we

52:34 understand general relativity works beautifully regime sounds very political very it does it does dictator dictator It sounds very very USSR. It sounds very unfortunately everywhere. Okay, got it. Okay. But then we when we go to the early universe like the big bang or in the course of black holes where where things start to get very extreme, we want to be able to quantize that that law of as we have quantized other things. It's not going to replace grav. Exactly. It's not going to replace gravity. We want to quantize gravity. And that seemed like a perfectly reasonable request. Okay. Wait, so Einstein's equations are not quantized. They require a continuum. Yes. So how do you quantize gravity? Good. So Jan's describing the history is very

53:20 insightful and useful. So we had an equation for electricity and magnetism that came from Maxwell. We were able to blend that with quantum mechanics giving us quantum electronamics. It works. We had equations describing the strong and weak nuclear forces. We were able to embed quantum mechanics into those theories. works wonderfully well. When we try to play exactly the same game with Einstein's theory of gravity, general relativity, and try to put quantum mechanics in there to quantize it, it just doesn't work. So, what does that mean? It means you're not smart enough to Well, it's an interesting It could be that we're not smart enough, and I'm full well willing to take that as the ultimate answer, but there's a lot of evidence, if you allow me to come right up till today for just a moment. I

54:06 know you wanted to go to this is the centennial, but go ahead. Yeah. So, so there is evidence today that Einstein's general relativity, the reason why you can't quantize it, the reason why you can't put quantum mechanics into it, it already seems to have quantum mechanics embedded in a deep and subtle way that Einstein himself didn't recognize. Oh, please tell cuz my edible just kicked in and this is fascinating. I mean, what you're saying right now is revolutionary because what you're saying is you can't put something into something where the thing is there. We just don't know where it is inside of that thing. But once we find it in there, we're going to be like, "Yo, that's where it is." And be like, "I told you not to put it in there. It was

54:52 already in there." Okay. Amazing. Chuck just blew a gasket. We got to No, that is like that's like that's simple. It's elegant. It's profound. It's amazing. I agree. All right, so let me let's back up back to the roaring 20s and I just want to go down the list of completely freaky things that quantum physics prescribed that defied anybody's common sense and which is why it's still freaky. Mhm. I in fact what's that quote from was it Fineman about quantum physics? What did he say? Yeah, there are a few. But if you think about quantum mechanics without getting dizzy, you haven't understood a single single thing about it. Oh, and I understand it very well.

55:43 Okay. So 1923, the wave particle duality is proposed. Yeah. So that's kind of freaky. Mhm. that particles are also waves. Yeah. It was Prince Louisie De Bruy who basically he was a prince. Yeah. And so he said look in 1905 Einstein showed us that light which we had thought of as a wave actually needs to be described as a particle so-called photoelectric effect. That's how he went5 1905. And then in 1923 in his PhD thesis Louis de Bruy says let me do the reverse. Electrons we always think about them as particles. Maybe they need to be thought of as waves. Wow. And that is a key moment in his That was a prince who did that. A

56:29 prince. Prince. I don't believe it. I I I know current monarchy. Not that intelligent. Let's be honest. Harry or William, you're not cooking you're not cooking this up. There's there's too much incest. I mean, you know this. You understand science for you to be operating at that level. So, not buying it. Not he cheated off someone's paper. Not buying it. So, his PhD thesis, if I remember correctly, was like 12 pages long or something. Very short. Very short. Yeah. And he got a Nobel Prize for Nobel Prize. PF and he got a Nobel Prize for a 12page PhD. A PhD paper. Yeah. You should Okay, let me just say that's the smartest dude ever.

57:14 Well, that's how that's how you know he was royalty. He turned in a 12-page PhD paper. They're like, "Dr. Prince and he's Thank you. double space 12page PhD paper." Tighter, you know, margin. You entitled piece of A couple years later, Neil, you just I'm sorry, Neil. I shouldn't have shouldn't have uh spoken ill of the the monarchs there. No, no, that's this I got this America. We fought a war to get away from monarchs. Um, not for long. Just give it time. Okay.

58:01 So, so then Schroinger came around. Oh, we have a Schroer fan up. That was the cat. That was the cat. That That was the cat. Cat. So what does Schroinger do for us? Well, Schrodener begins to think more abstractly about what's real and what's not real. So we're used to thinking of particles. You've already described Deb Brogley and the electron. We we think of these little fundamental particles almost like billiard balls acting out their lives and they have some concrete existence. Schroinger starts to say, well, this wave particle duality, that's pretty profound, but maybe the only thing that's real is this thing called the wave function, which is the probability

58:46 for the particle to be in a certain state, to be in a certain location, to be moving with a certain speed. But the particle itself in some sense isn't real anymore. If you look for it, sometimes you'll find it in a concrete location. But what is really determined by equations, by the laws of physics, is the wave function, which is this probabilistic description. And the wave function occupies physical space, doesn't it? Yeah, the wave function occupies physical space for only for a single particle. So it's a kind of important subtlety. For one particle, you can think about this wave function as filling space. If there are two particles, it lives in sixdimensional space. If there are three particles, it's a nine dimensional space. So you really can't think of it in these

59:32 ordinary terms. Oh, I am high. Okay. So, so if the particle can be anywhere here and I have some barrier here, Mhm. it could show up on the other side of the barrier. Yeah. Right. But it doesn't actually travel through. So let's say your barrier is a concrete wall. There's some small probability that you would find the particle. Well, the wave function would describe the probability of finding the particle in this region of space, but it doesn't actually like a billiard ball travel through the cement wall. Okay, this might be the THC talking, but the way you guys are talking, there just might just be one particle. Like, there aren't bunch of particle. It's just one particle. I told you he

1:00:19 blew a gasket. Well, but but but but Richard Feineman had the idea that maybe there was one particle that circled around through time and cycled back over and over again, giving what appear to be many particles now, but there's only a single particle through this temporal cycle. So, you're right on target, moving forward and backwards through time. I can Oh my god. Okay. Okay. All right. So, but what I'm saying is if a particle can show up on the other side of the the barrier, then that's you guys came up with a word for that and it's tunneling. Quantum tunneling. It can quantum tunnel through the barrier. But that but that's the the point of shortinger saying what's real is just this probabilistic likelihood of finding the particle. The particle itself in

1:01:04 some sense does not have concrete existence anymore. It challenges the whole nature of reality. No, but concretely there is a probability that we could calculate Yes. for the likelihood of you tunneling through the stage and being underneath the floor. And it's a nonzero probability. It's kind of small, so it's unlikely to happen, but that's what quantum mechanics tells us. But the smaller I get, the more likely it will happen. Exactly. It can happen in the laboratory. Yeah. Okay. So, just for context here. Wow. That is we were trying to understand how the sun made energy and we did the calculation. Once we determined the sun is mostly hydrogen and it's hottest in the center, we said it must be undergoing fusion. And what you run the math to undergo fusion, a proton, y the nucleus of a hydrogen atom

1:01:51 has to merge with another proton, the nucleus of another hydrogen atom. Protons have the same charge. Electrostatically like charges repel. So they have to be moving fast enough so that before they have a chance to repel, they stick together and form a new nucleus. Okay, we calculated what temperature that was necessary because high temperatures give you higher speeds. We calculated that temperature and it was 100 million degrees and there was no way the center of the sun was going to give us 100 million degrees because you can calculate through sensible laws of thermodynamics what that should be. And we were scratching our heads. And then quantum physics comes around and then you invent this

1:02:36 spooky magical thing called tunneling. And we discover in our calculations that at a mere 10 million degrees, see these this matters 10 million, 100 million, at a mere 10 million degrees, they would otherwise not hit, but some of them tunnel through and connect. Tunneling makes the sun's energy production even possible. Yeah. And I was like, because it's not just some some thing that particle physicists worry about in their laboratory. I had to worry about it as an astrophysicist. Why Why are you worried about this? It's okay. Okay. I The sun's going to sun, you know.

1:03:23 Robbins, let them let the sun let the sun do that. Thank you. It's okay. Okay. Thank you, Neil. Don't Don't blow that. That's very very okay. So tunneling more there's a lot tunneling and Yeah. So now what about the Heisenberg uncertainty principle? That's that seems like the biggest thing of them all. Talk me through that real fast. Yeah, I would say so that's the real moment when the old ways of looking at the world are shown they have to be jettisoned because the old way of looking at the world, what is reality? Reality is stuff that's at a location moving with a certain speed. That's the way we describe the world. And Heisenberg with the armature of quantum mechanics says you can't actually do that. You can't specify the location and the speed simultaneously of

1:04:10 any object. You can't do it according to the quantum equation. So the very language of reality that we used to use no longer applies. No longer applies. Why can't you measure both at the same time? Well, if you have a particle described as a wave, right, and you want that particle to have a definite location, that wave has to be highly spiked. So that you can say, ah, almost 100% likelihood it's at this location. But when you see how the notion of velocity comes into quantum mechanics, it has to do with the wavelength of the wave. And so if you want something to have a definite speed, it has to have a definite wavelength. That's not spiky. So to have definite location, you need spike. To have definite speed, you need

1:04:56 wave. Those are different shapes. And you can't have them at the same time. Can't have them at the same time. Can I try analogy? Nowhere near as precise as what Brian just said, but sometimes I like this musical analogy. If you play a chord, which is a whole bunch of notes together, you can play chords, but you can't simultaneously be playing a single note. So the chord is like a superposition of the notes. And how this relates is that when you're in a precise location, what Brian's describing as a sharp spike, you're sort of in a superp position of velocities or momenta. So it's like it's like the the location is the note, the the velocities are the chords. Or vice versa, if I know the velocity exactly and I'm playing chords, I'm no longer playing individual. I'm I'm playing I can't isolate a single

1:05:42 individual note. I'm in a superp position of notes. So what is so how does all this connect to the what they call the observer effect where you I want to measure the particle right there I I got to look at it so I shine light on it and the light sends it somewhere else so I can't actually ever know what the particle is doing right and and so there's two things in there one is as you're saying to look is to interact and when you interact say by bouncing a photon off a particle you affect the particle because I need the photon to take the picture that that's right so that's one key point that emerges from these ideas. But the other point that we can never know anything on that on that. That's the crazy thing. Y'all went on this crazy I'm sorry. I'm

1:06:28 sorry. I got that. That is just not right. Okay. Quantum mechanics tells us that the things that you thought you could know are not the things that you can know. But with quantum mechanics, we've made predictions of the anomalous magnetic moment of the electron to 14 decimal places using a theoretical calculation. And we've measured it and it agrees decimal by decimal by decimal on all of those numbers. And that's why we love these numbers. They show us that we understand what we're doing. [Applause] Okay, Brian just blew a gasket. So you can know without knowing is what you're saying. We can know. Let me just say this, Brian. The type of energy you're bringing.

1:07:15 All right. Wait, wait. Oh, man. You are built for CNN. This type of panel smoke. Oh, fantastic. Yeah. All right. So, this is so be one of those Street Fighter squares. The decimal to the decimal to the Yeah. Oh, it's great. This is great. This is good stuff. This is good television. So, so go ahead Neil. So, this this observe effect bring us home with certain has been widely mis applied by people thinking my consciousness is affecting the measurement. Look, there is a big mystery at the heart of quantum mechanics. Even with our capacity to make calculations that agree with observations to the level of precision that I just emphasized, perhaps with unnecessary theatricality, there is

1:08:00 there is a question that we don't know how to answer, which is what you're asking. When you observe, you seem to be able to coax one result, one answer. Even though the quantum description embodies many possibilities, we don't understand how that happens. Is this the many worlds hypothesis? It's it's one answer. But the shinger equation is so beautiful and it does not actually include in it uh a way to understand how measurements are made. Yes, that's the key point. And and so if you really take the shortage of equation very seriously, it simply says there are all of these possibilities and they're all because we don't have a theory of measurement to get us through where we are in this in the physics. Just you know there are proposals people have put down mathematical equations that do answer

1:08:46 this question. What is the many worlds hypothesis? The many worlds hypothesis is if you have a description of a quantum system like a particle and the quantum wave says 30% chance here, 20% chance here, 50% chance over here, when you measure it, you don't get only one result. There's one of you that finds it over here. There's another one of you that finds it over here. And there's a third one of you that finds it over here. But these are all in different

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