Pod Insights StarTalk Podcast The Smallest Ideas in the Universe with Sean Carroll About this episode What is the nature of quantum physics? Neil deGrasse Tyson and comedian Chuck Nice get quantum, exploring Schrodinger’s Cat, electrons, Hilbert Space, and the biggest ideas in the universe (in the smallest particles) with theoretical physicist Sean Carroll.
Transcript Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Neil deGrasse Tyson? Chuck, my brain is exhausted.
0:01 Chuck Nice? Yeah, I gotta tell you, first of all, I don't even know if I'm here right now. I'm not sure what field I'm in. I don't know if I exist.
0:09 Neil deGrasse Tyson? This is what happens when you spend time with theoretical physicist Sean Carroll, and we just did.
0:14 Chuck Nice? Yes, we did.
0:14 Neil deGrasse Tyson? He took us into the quantum realm.
0:16 Chuck Nice? Yeah.
0:17 Neil deGrasse Tyson? Which apparently was not even, barely contained in the universe itself.
0:20 Chuck Nice? Exactly, right. So, when you do this, don't even think.
0:24 Neil deGrasse Tyson? It's not real.
0:25 Chuck Nice? You don't even know. You don't even know what you're doing there, okay?
0:29 Neil deGrasse Tyson? Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.
0:42 Neil deGrasse Tyson? This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. Got with me Chuck, nice Chuck.
0:50 Chuck Nice? Hey, Neil.
0:50 Neil deGrasse Tyson? Hey.
0:51 Chuck Nice? What's happening?
0:51 Neil deGrasse Tyson? All right, what are you holding in your hand here?
0:53 Chuck Nice? Holding a book.
0:54 Neil deGrasse Tyson? Oh, okay.
0:54 Chuck Nice? A book that I, you know, that I picked up off of the coffee table.
1:01 Neil deGrasse Tyson? The biggest ideas in the universe. Well, that's what this episode is gonna be about.
1:05 Chuck Nice? Yes.
1:05 Neil deGrasse Tyson? But I know some big ideas.
1:08 Chuck Nice? Right.
1:08 Neil deGrasse Tyson? But I don't know the biggest ideas. There's a "the" in the front of this title.
1:12 Chuck Nice? Right.
1:12 Neil deGrasse Tyson? And...
1:13 Chuck Nice? Like the qualifier.
1:14 Neil deGrasse Tyson? Yeah, so...
1:18 Neil deGrasse Tyson? This is written by the one and only Sean Carroll. Sean, welcome to my office.
1:22 Sean Carroll? Thank you so much. New York, your office, these are the best places, most exciting places.
1:27 Neil deGrasse Tyson? We have corresponded and emailed and talked, and we have never been in the same space.
1:33 Sean Carroll? No, I think we did in LA once, right? I think so. I think briefly, very, very briefly. But yeah, many phone calls, many emails.
1:40 Neil deGrasse Tyson? Delighted to have a meaningful exchange with you at this point.
1:43 Sean Carroll? Right, with microphones in front of us. Cameras trained. Meaningful.
1:47 Chuck Nice? Exactly.
1:48 Neil deGrasse Tyson? Okay, so just before we delve in... Which Sean Carroll are you?
1:53 Sean Carroll? I'm the physicist one.
1:54 Neil deGrasse Tyson? The physicist Sean Carroll?
1:56 Sean Carroll? Yes.
1:56 Neil deGrasse Tyson? And the other Sean Carroll is who?
1:58 Sean Carroll? My evil twin. He has beards. You know which one is the evil twin.
2:02 Neil deGrasse Tyson? But is it like that? Is it a?
2:04 Sean Carroll? It's not quite as evil. It's more like bushy Santa Claus. It doesn't really look like, but he's a very accomplished biologist, also writes books. You should buy those too.
2:13 Neil deGrasse Tyson? Okay, nice. All right. Very good. So Sean Carroll, let me get your bio going here. The Homewood Professor of Natural Philosophy.
2:21 Sean Carroll? Ooh.
2:21 Neil deGrasse Tyson? That's very retro.
2:22 Sean Carroll? It is.
2:23 Neil deGrasse Tyson? Oh man, just like Newton.
2:25 Sean Carroll? I was gonna say, yeah.
2:26 Neil deGrasse Tyson? Good bike had some title like that. Natural Philosophy at the Johns Hopkins University down in Baltimore, which is the home of the headquarters of the Hubble Space Telescope.
2:36 Sean Carroll? Oh.
2:37 Neil deGrasse Tyson? The Space Telescope Science Institute is right there.
2:39 Sean Carroll? Cool.
2:40 Neil deGrasse Tyson? And you're also on the faculty at the Santa Fe Institute, but you're only on a visiting faculty. So they got really cute here fractal faculty.
2:49 Sean Carroll? Yeah, pretty cute.
2:49 Neil deGrasse Tyson? And you get cuter than, you can't get cuter than that.
2:52 Sean Carroll? No, you can't. I mean, unless there are a bunch of Sean Carrolls who are tinier and look exactly like Sean Carroll.
2:58 Neil deGrasse Tyson? Oh, to continue the fractal. Right. Move on in.
3:03 Sean Carroll? Sean Carroll at all scales. Right, exactly. Frightening.
3:06 Neil deGrasse Tyson? And your research area is quantum physics, spacetime, cosmology, emergence. I love emergence. Maybe we can hit on that. Entropy. I've seen a lot of that lately. Can you do something about entropy? If you can't do anything about it, I have nothing for us.
3:21 Sean Carroll? I can increase it.
3:24 Neil deGrasse Tyson? We can do that without you.
3:27 Neil deGrasse Tyson? Dark energy, symmetry and origins of the universe. You're all in. You got a podcast of your own. Mindscape. I think I've been on that. Have I been on that podcast?
3:37 Sean Carroll? Oh, not yet.
3:38 Neil deGrasse Tyson? Not yet. Okay.
3:39 Sean Carroll? We'll see.
3:41 Neil deGrasse Tyson? It's in my inbox. Maybe I haven't gotten to it yet.
3:45 Neil deGrasse Tyson? And this latest book of the biggest ideas in the universe, the second in a trilogy. This one, Quanta and Fields.
3:53 Chuck Nice? Quanta, wouldn't that be the smallest idea in the universe? Oh.
3:58 Sean Carroll? Smallest thing can be the biggest idea.
4:00 Chuck Nice? Oh, oh, oh, dear. Oh, snap.
4:07 Neil deGrasse Tyson? You gotta put Chuck in his place early, otherwise he'll just run red circles all over you. Yeah, he got you on that one.
4:14 Chuck Nice? Yeah, that's true.
4:15 Neil deGrasse Tyson? He got you. So if this is a trilogy, the first big ideas book was what?
4:19 Sean Carroll? It was called Space, Time and Motion, which is like publisher speak for classical physics.
4:24 Neil deGrasse Tyson? Regular, ordinary armchair physics.
4:26 Sean Carroll? Isaac Newton physics.
4:28 Neil deGrasse Tyson? Yeah, Isaac Newton physics.
4:29 Sean Carroll? And Albert Einstein for that, man. He was the star.
4:31 Chuck Nice? Isn't it funny? At this point, Albert Einstein is the old physics. Classical physics.
4:36 Neil deGrasse Tyson? Now we're going Quanta and Fields, two very big ideas.
4:39 Chuck Nice? Yeah.
4:39 Neil deGrasse Tyson? And can we get a hint in what?
4:42 Sean Carroll? You'll be happy to hear it's Complexity and Emergence is volume three. That's gonna be, it's basically appetizer main course dessert here. So the third one's gonna be fun.
4:51 Neil deGrasse Tyson? Okay, very good. You're an active research scientist, you publish books, you're active on social media. So this is great just to see kindred soul out there.
5:01 Sean Carroll? It's very tiring, isn't it? Why do we do this? Close idea was this.
5:07 Neil deGrasse Tyson? Let's go out and have a drink, we'll talk about it.
5:09 Chuck Nice? In service to the universe.
5:11 Neil deGrasse Tyson? We are servants of cosmic curiosity that permeates within us all. We know that the idea of fields as my memory of the history of physics began with Michael Faraday. Is that correct? Or does it go farther back than that?
5:24 Sean Carroll? That would be fine if you gave it to Faraday. I mean, he certainly played a huge role in figuring out that.
5:29 Neil deGrasse Tyson? Mid 19th century.
5:30 Sean Carroll? Mid 19th century, electricity, magnetism, both had fields associated with them. Technically, no one ever mentions this, but our old friend Pierre-Simon Laplace, circa 1800, realized that, you know, Isaac Newton had this idea of gravity, the inverse square law, and Newton was very puzzled, like you have the earth here, you have the moon over there, there's a gravitational force, how does the moon know? What the gravitational force is.
5:58 Neil deGrasse Tyson? It is nothing between them.
5:59 Sean Carroll? Nothing between them, action at a distance, right? And Laplace figured out you could rewrite Newton's theory of gravity in terms of a gravitational field. So I kind of give him credit. Wow, look at that.
6:12 Neil deGrasse Tyson? So in my high school, I had a friend who, his name was Frank Larisse. We just learned about some of these great French physicists, mathematicians, Lagrange, Laplace. And then over lunch, one day says, there will be the Larisse equation. This was just a fun little dream state that we all occupied in high school. Okay, so fields, why are fields real or are they just a convenience? Because by the way, you are partially in the department of philosophy there.
6:47 Sean Carroll? Yeah.
6:48 Neil deGrasse Tyson? So I get to ask you philosophically leaning questions.
6:51 Sean Carroll? I'm not allowed to say that's a philosophy question and ignore it. I actually have to answer those questions.
6:55 Neil deGrasse Tyson? You actually have to answer it.
6:56 Sean Carroll? That's my job.
6:56 Neil deGrasse Tyson? Good, all right.
6:57 Sean Carroll? Yeah, so the story that we tell in the book is if you were 1895, right? If you were just before the turn to the 20th century, you would have thought that matter, tables and chairs, was made of particles.
7:10 Neil deGrasse Tyson? Right.
7:10 Sean Carroll? Stuff. We knew about electrons, you knew about atoms. And you would have thought that the forces between the atom were mediated by fields, spatial field, the electric field, the magnetic field. And one of the great triumphs of quantum physics in the 20s and 30s was it said, it's all fields. Electricity, magnetism are fields, but so are electrons and quarks and neutrinos. And they vibrate in different ways and through the miracle of quantum mechanics, when you look at those vibrating fields, they appear to us as particles. The particles come out of the field.
7:42 Neil deGrasse Tyson? Is this an early variant of what would later be string theory? Where they're saying particles are vibrations in the strings?
7:49 Sean Carroll? Well, particles are vibrations in the fields, and that's absolutely accurate in the regimes we're talking about here. Is there something deeper that they could be vibrations of, strings, et cetera? That's a speculative idea, very, very promising.
8:01 Neil deGrasse Tyson? On a much smaller scale.
8:03 Sean Carroll? Yeah, much smaller. We don't need to know for predicting what's going to come out of the Large Hadron Collider.
8:07 Neil deGrasse Tyson? Okay, so let me ask you a blunt question, which sounds stupid, but I think it's a meaningful question. Do electrons exist?
8:16 Neil deGrasse Tyson? As, as, as.
8:17 Chuck Nice? Now wait, is that, is that a science or a philosophical question?
8:21 Neil deGrasse Tyson? Well, well, because.
8:22 Sean Carroll? Natural philosophy.
8:24 Neil deGrasse Tyson? As I understand it, we have never measured the size of the electron. It is smaller than the smallest capacity we have ever conjured to measure its size.
8:34 Sean Carroll? Okay, I gotta ask you a preliminary question. How truthful do you want me to be?
8:40 Chuck Nice? I love it.
8:42 Neil deGrasse Tyson? Okay, give me, give me what you say in the back room, in, in the back room with the cigars.
8:46 Chuck Nice? No, first lie to me.
8:50 Chuck Nice? Then tell me the truth.
8:52 Sean Carroll? The lie is.
8:53 Neil deGrasse Tyson? Yes.
8:54 Sean Carroll? What is real is the electron field. And little vibrations in those electron fields show up in our detectors as particles. So it's not that we haven't measured the size of the electron, it's that there is no such thing as the size of the electron. The electron is a vibration in a field. It can have different vibrational wavelengths.
9:12 Chuck Nice? But so, and it shows up as the particle?
9:15 Sean Carroll? Yes, that's right.
9:16 Chuck Nice? Oh my god.
9:17 Sean Carroll? Yeah, that's right.
9:17 Neil deGrasse Tyson? I mean, it comes to the party that way, but otherwise it's not.
9:20 Sean Carroll? Yeah, yeah.
9:21 Chuck Nice? Okay, that is so trippy. That is so freaky, man.
9:25 Neil deGrasse Tyson? Wait, wait, wait, wait.
9:26 Sean Carroll? Well, you and Einstein both were bothered by this.
9:28 Chuck Nice? I am very bothered by this.
9:30 Neil deGrasse Tyson? So you cannot measure the electron in its wave state to be a particle? Because the act of measuring it turns it into the particle.
9:40 Sean Carroll? The way that we usually measure things, you say, where is it? And you get a little track in your particle detector, because you keep asking where it is, and you always get a definite answer to the question, where is it? But when you're not asking that question, it's spread out all over the place.
9:55 Neil deGrasse Tyson? Okay, is that a lie or the truth?
9:56 Sean Carroll? That's really a lie. I haven't even gotten to the truth yet.
9:58 Neil deGrasse Tyson? Okay, okay, now, now give me the truth.
9:59 Sean Carroll? Okay, when quantum mechanics came along in the 1920s, we realized that instead of an electron.
10:04 Neil deGrasse Tyson? Let us celebrate, we're in the centennial.
10:06 Chuck Nice? We're very close.
10:07 Neil deGrasse Tyson? Of this, of the, of the discovery of quantum physics. The centennial decade.
10:11 Sean Carroll? The quantum year, yeah.
10:12 Neil deGrasse Tyson? Yeah, yeah, the centennial decade, and, and that was a watershed decade. Where Hubble discovers that the Milky Way is not alone among galaxies in the universe, and he discovers the universe is expanding. And I'm just saying, we gotta tip our hat to the 1920s.
10:27 Chuck Nice? Yeah.
10:28 Neil deGrasse Tyson? The roaring 20s.
10:29 Sean Carroll? We live in shame that we can't live up to that anymore.
10:31 Neil deGrasse Tyson? I know. I think about that all the time.
10:33 Sean Carroll? Yeah, it was too bad.
10:34 Chuck Nice? Yeah, well, I mean, let's be honest, they weren't working with much to start with.
10:38 Sean Carroll? Low hanging fruit.
10:40 Chuck Nice? Yeah, low hanging. You guys are building on top of everything that they've actually discovered, you know.
10:44 Sean Carroll? Oh, yeah, absolutely. Yeah. All right, we're building up to the truth here. So you realize in the 1920s that you thought the electron was a little particle. In fact, you should describe it in quantum mechanics by a wave function. If you ever took chemistry, if you ever saw those pictures of the orbitals of electrons, et cetera, that's the wave function of the electron.
11:02 Chuck Nice? Mm-hmm.
11:03 Sean Carroll? Soon thereafter, you realize, no, actually, you should be doing field theory, quantum field theory. And so there is a field that the electron is a vibration in. And you're asking what really exists? Well, there's a wave function of that field. So there's like fieldiness on top of fieldiness. And finally, you say that, okay, what if you have like different fields, different particles? Do they each have a wave function? No. There is one wave function for the whole kit and caboodle of them, the wave function of the universe. That's what's real, the wave function of the universe.
11:37 Neil deGrasse Tyson? You know, he's been smoking something.
11:39 Chuck Nice? That's crazy.
11:40 Neil deGrasse Tyson? You know, where was he before this? Where were they? Are you just talking this? Or is this hypothesized, soon to be experimentally verified?
11:51 Sean Carroll? I encourage all of the listeners out there to check out my paper entitled Reality-
11:56 Neil deGrasse Tyson? This would be your research paper.
11:57 Sean Carroll? Research paper called Reality as a Vector in Hilbert Space.
12:01 Neil deGrasse Tyson? Okay.
12:02 Sean Carroll? That's what reality is. So, look, first, let me explain. Not everyone agrees with the true thing I just said. So there's disagreement because of this fact that physicists-
12:12 Neil deGrasse Tyson? It's your personal truth.
12:13 Sean Carroll? Can't agree on what quantum mechanics really said. So we have this idea that everyone uses in quantum mechanics, Hilbert space, which is the space of all possible imaginable quantum states of the universe. And someone like me, who is a purist and extremist about this, says, we have all possible quantum states, the actual universe is one of them, and it changes with time. Other people will say, "No, that's not reality. That's just a tool we use to describe predictions, to make predictions for experiments." Other people will say, "That's part of reality, but there's other parts as well." We don't have a consensus on this.
12:50 Neil deGrasse Tyson? Okay, I like the absence of consensus. Yeah, exactly. It wakes you up in the morning.
12:56 Neil deGrasse Tyson? All things sounds very political.
13:02 Neil deGrasse Tyson? All right, so how do you square all the successful predictions of quantum physics with any intuitive understanding of what's going on? Because I've said many times, and I'm happy to say it again, the universe is under no obligation to make sense to us. So, once you accept that, why try to make sense of it? And jump through hoops and brain twists just to say, "Well, it's gotta be this, or it's gotta be that." But it calculates and it works. Move on.
13:32 Sean Carroll? The universe is under no obligation to make sense, but remarkably, it keeps making sense. Once we really let ourselves listen to what the universe is trying to tell us, the universe seems to be intelligible. It's not deeply ineffably mysterious. And it's a give and take. It's not like our intuition just maps on to reality. Reality is like, "Nope, your intuition was a little bit off there. Try to update." And if you're open-minded about it, and you buy the right books, very updatable. You can absolutely get there, is what I'm saying.
14:19 Speaker 03 I'm Ali Khan Hemraj, and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.
14:34 Neil deGrasse Tyson? I'm reminded of the charming illustrated book series by George Gamow. Mr. Tompkins in, I guess, Wonderland, or, and what he would do is, he's a physicist, famous physicist, mid 20th century. Lived only, died only 20 years ago or so, but he, yeah, George Gamow, he was one of the original predictors of the temperature of the universe.
15:02 Sean Carroll? I hear the Big Bang Theory.
15:03 Neil deGrasse Tyson? Yeah, if the universe began as an explosion with the Big Bang, could you measure that? And then he was on a paper that, okay, so what temperature did he get for it? It was like, uh...
15:13 Sean Carroll? He was in a factor of 10, yeah.
15:15 Neil deGrasse Tyson? No, was it a factor of 10?
15:17 Sean Carroll? Within a factor of 10.
15:19 Neil deGrasse Tyson? I think it was like 5 degrees. He said, "The universe is 5 degrees," and the universe turned out to be 3 degrees.
15:26 Sean Carroll? Oh, okay.
15:27 Neil deGrasse Tyson? Okay, so Rich Gott, okay, friend of the show, has said, "That's like predicting that a 50-foot flying saucer will land on the White House lawn, but a 30-foot flying saucer..."
15:41 Sean Carroll? That's pretty wild, yeah.
15:43 Neil deGrasse Tyson? Right? Yeah, it's not even that the numbers are different, it's that it's a prediction at all that would come true.
15:50 Sean Carroll? But the story you're telling right here is exactly why this crazy talk about Hilbert spaces and quantum fields has some plausibility, because we have some data in front of us, we try to explain it, we invent an equation that explains it, and then we extrapolate that equation to wild places that it's never been before, and it comes back telling us, "Yeah, that's what I said, that's what I said was gonna happen, and the Big Bang is an example, quantum field theory is another example."
16:17 Neil deGrasse Tyson? But Mark Twain did this first, you know, the Mark Twain-ism?
16:20 Sean Carroll? Yeah.
16:21 Neil deGrasse Tyson? Yeah, so he had read that there was some research paper about the rate at which the Mississippi River is depositing silt in the Delta, and so it's growing in this direction, and then he says, "Oh, that means, you know, 30 million years ago, the Mississippi River ended in Canada." And then he says, "The great thing about science, there's such wholesale conclusions drawn from a trifling investment of fact."
16:51 Sean Carroll? Ooh.
16:53 Sean Carroll? And that's brilliant.
16:54 Neil deGrasse Tyson? Yeah, that's Mark Twain.
16:55 Sean Carroll? Beautiful.
16:55 Neil deGrasse Tyson? Doing it. In Mr. Tompkins and Wonderland, what made it entertaining, especially if you're a budding scientist, is it changes the values of the physical constants in an ordinary world.
17:06 Sean Carroll? Okay.
17:06 Neil deGrasse Tyson? So, and then you get to see what happens in an ordinary way. Otherwise, these phenomena are inaccessible to us. And one of them, he said, all right, 60 miles an hour is the speed of light. And now you're driving down the street, what do you see? And then another one, I think he changed Planck's constant.
17:23 Sean Carroll? Yeah, sure.
17:23 Neil deGrasse Tyson? And so, could you just give me a handle?
17:27 Sean Carroll? Oh, cool.
17:28 Neil deGrasse Tyson? On things that would happen if Planck's constant were macroscopic. Like, if I walked through the doorway, I would like diffract, right? Wouldn't I?
17:38 Sean Carroll? Yeah, you would diffract, and we wouldn't be able to know exactly that you had a position and velocity at the same time, right? You know, the old joke about Werner Heisenberg being pulled over, and the cop says, you know how fast you were going? And Heisenberg says, no, but I know exactly where I am. Because you can't know, according to the Heisenberg uncertainty principle, both your velocity and position at the same time.
17:58 Neil deGrasse Tyson? That's your rock at physics, constantly.
18:03 Neil deGrasse Tyson? I was gonna say, who wrote that? Can I try that out? I don't know.
18:08 Sean Carroll? That's the uncertainty principle. No one would pin you down. In quantum mechanics, you're fundamentally not a set of particles. You're a set of waves. If the Planck constant, which sort of sets the scale for quantum physics, were much bigger, macroscopic, then we would all be these kind of undulating waves moving through the universe, interfering with each other, and becoming entangled, and then measuring things. And you don't want to live there. It's not, no place to be, really.
18:34 Neil deGrasse Tyson? And so, you mentioned entangled. That's been a buzz phrase.
18:38 Sean Carroll? Everybody loves it.
18:39 Neil deGrasse Tyson? Everybody loves.
18:39 Sean Carroll? It's one of the biggest hits.
18:41 Neil deGrasse Tyson? Hearing about.
18:42 Sean Carroll? It's one of the biggest hits right now. Entanglement.
18:44 Neil deGrasse Tyson? Entanglement. So, one of the goals is, what's the farthest particle?
18:53 Neil deGrasse Tyson? That you can entangle on the premise that maybe that'll be useful one day. And from all the news articles, I've seen China leads the world
19:00 Chuck Nice? Uh oh.
19:00 Neil deGrasse Tyson? In entangled particle distances. So, so what do you have to do?
19:06 Chuck Nice? Oh, no, no, I'm sorry, uh, cause I'm, I'm just losing something right here. I'm missing something. If something is entangled, what difference would it make about the distance? I'm missing that.
19:18 Neil deGrasse Tyson? Who knows? I'm saying in science, you just push the envelope if you've never pushed it before.
19:23 Chuck Nice? I got you.
19:23 Neil deGrasse Tyson? One day are they, we heard in Congress, it just, did you hear in Congress? China is, is going to land something on the far side of the moon and Congress wants to know why? How come we're not landing something on the far side of it? This is an entire conversation in Congress.
19:38 Chuck Nice? Right, right.
19:39 Sean Carroll? Now, but Chuck is completely right about entanglement. It doesn't matter how far away things are, but the problem with two entangled particles, which we haven't even defined what that means, but you have a very sophisticated audience. So they know what this means is that as soon as you measure one of them, the entanglement breaks. So it's not that they get further apart, it's just that as you bring them further apart, the chances that one of them bumps into something gets bigger and bigger.
20:01 Neil deGrasse Tyson? And so therefore, so that's what makes this distance record meaningful
20:06 Chuck Nice? I got you.
20:07 Neil deGrasse Tyson? As a, as a record. So one of them was they entangled particles between orbit and earth's surface. And another one was they entangled particles inside a fiber optic, uh, uh, network.
20:20 Chuck Nice? Okay.
20:21 Neil deGrasse Tyson? Fifty kilometers, which was about, which is about city size. And so then the suspicion is with entangled particles, you might be able to make a secure internet, undecodable, un, un-
20:34 Chuck Nice? Unhackable, unhackable. You can't, you can't, it doesn't, encryption wouldn't make a difference at that point.
20:39 Neil deGrasse Tyson? Right. Cause it's instantly, so is this, is this a pipe dream?
20:43 Sean Carroll? Well, it's very hard because once you get beyond a few particles, it becomes harder and harder and harder to remain all of them being entangled with each other. And that's ultimately what you need. But it's a technology problem. It's not like you're violating the laws of physics. So we're setting our best engineers on it, trying to build quantum computers, etc.
21:01 Neil deGrasse Tyson? Get a bridge, engineers, you fix it.
21:02 Sean Carroll? Yeah, you do that. Yeah, we've shown it's conceivable. What do you want from us?
21:07 Neil deGrasse Tyson? Yeah, what more do you need?
21:08 Chuck Nice? The math works.
21:09 Neil deGrasse Tyson? Yeah.
21:10 Chuck Nice? All right, Johnson?
21:10 Neil deGrasse Tyson? There's no law of physics against it.
21:12 Sean Carroll? Exactly.
21:14 Neil deGrasse Tyson? You know, the engineers who said we will never fly faster than sound did not get that from a physicist.
21:19 Sean Carroll? That's right.
21:20 Neil deGrasse Tyson? Okay. Because we, rifle bullets went faster than sound. The crack of a whip is faster than sound. You know, we had that. So, but, so back to this. Can you foresee a value with 50-kilometer quantum entangled network? The size of a city?
21:39 Sean Carroll? You know, mostly that's just showing off. I think it's much more important technologically to have a thousand or a million quantum entangled things very close to each other. Then you can manipulate them, build a computer doo there.
21:53 Neil deGrasse Tyson? Isn't that what goes on in a quantum chip? Isn't there a lot of entangled?
21:57 Sean Carroll? We would like it to be. We don't, it's very, very hard because literally any photon that bumps into them messes things up. That's why you need to push it down to absolute zero or very, very close.
22:08 Neil deGrasse Tyson? Oh, I had not fully appreciated that.
22:10 Sean Carroll? Yeah.
22:10 Neil deGrasse Tyson? The photos I saw, most of that was just
22:12 Sean Carroll? Refrigerators.
22:13 Neil deGrasse Tyson? The door. Yeah, the freezer compartment. Just to have the little bitty thing in the middle.
22:19 Sean Carroll? Otherwise, because like you and I radiating our infrared all over the place would totally decohere those quantum bits.
22:26 Neil deGrasse Tyson? That would be the opposite of coherent.
22:28 Chuck Nice? Which, which is what this conversation makes me feel like.
22:31 Neil deGrasse Tyson? Are you decoherent?
22:33 Chuck Nice? I'm decoherent.
22:37 Neil deGrasse Tyson? Catch us up on entangled particles.
22:39 Sean Carroll? Well, this is part of this fact that we said before that there's not a separate quantum wave function for every individual thing in the universe. There's only one wave function for all of them at once. And what the wave function tells us is the probability of observing something. So if you have two particles, and let's say they have positions, you don't know where it is. In fact, literally, when something like the Higgs boson decays. It goes into an electron and a positron, the anti-elect. And you say, well, what direction are they going in? And the answer is they're both going in all directions. Their wave functions are coming out sort of in a spherical pattern. But then when you observe one of them.
23:15 Chuck Nice? That's where it is.
23:16 Sean Carroll? That's where it is, and momentum is conserved. So now you know the other one is going in exactly. So you know where the other one is without having detected it yet. That's entanglement.
23:27 Neil deGrasse Tyson? So what entangles them?
23:28 Sean Carroll? The rules of physics.
23:30 Chuck Nice? Okay, that doesn't. That's not, stop it.
23:33 Neil deGrasse Tyson? That's just the end of the interview.
23:34 Chuck Nice? You can't do that.
23:38 Chuck Nice? That's my mother saying because I said so. That's what the, Mom, why can't I have ice cream for breakfast? Because I said so. That's why.
23:46 Neil deGrasse Tyson? What law of physics prescribes this?
23:48 Sean Carroll? Quantum mechanics. That's the nature of quantum mechanics. It's sort of that this is how science works. You sort of conjecture an idea, then you say, is that right or not? And so in quantum mechanics, the fundamental way things work is that the state of the universe is a vector in Hilbert space, which means that the combined state of every particle in the universe and every field and every everything is described by one single mathematical object. And in fact, I don't like the word entanglement because it kind of, it makes it hard to update your intuition. It makes it sound like what really exists are these two particles. And you measure one, then you're like, why did the other one change?
24:30 Sean Carroll? If you just accept that what exists is the combined quantum state of everything in the universe, then it's no surprise at all that when you look at a little bit of it, it affects the rest.
24:39 Neil deGrasse Tyson? Okay, but.
24:39 Chuck Nice? Interesting.
24:40 Neil deGrasse Tyson? Can I just take two random particles?
24:43 Chuck Nice? Okay, that's, I gotta admit, that makes a lot of sense.
24:48 Neil deGrasse Tyson? Can I take two random particles that were not born together and entangle them?
24:54 Sean Carroll? Sure.
24:54 Chuck Nice? Okay.
24:55 Sean Carroll? Yeah. Entanglement happens whenever you have two objects that are not entangled, but they interact with each other in different ways depending on different parts of their wave function. Let me just give you a down-to-earth example. Schrodinger's cat. You've heard about this, Schrödinger, who apparently didn't like cats, goes to a great amount of thought experiment effort to put a cat in a superposition.
25:19 Neil deGrasse Tyson? That would have never worked with Schrödinger's dog.
25:21 Sean Carroll? No.
25:22 Neil deGrasse Tyson? That would not have flown.
25:23 Sean Carroll? Schrödinger's daughter said that he didn't like cats.
25:26 Neil deGrasse Tyson? Right, okay.
25:26 Sean Carroll? That's why he picked the cat. So it's in a superposition of alive and dead. I'm a cat person, but in my version, they're a superposition of awake and asleep.
25:35 Neil deGrasse Tyson? Oh.
25:35 Sean Carroll? It's very sweet. You don't have to kill the cat.
25:37 Chuck Nice? You don't have to kill it.
25:38 Neil deGrasse Tyson? I didn't know you didn't have to kill the cat.
25:39 Sean Carroll? The point is, you don't have to kill the cat, but the point is there are different places in the box, okay? And what that means is that everything in the box, the air, the light, you know, everything moving around in the background interacts differently with the awake cat running around, trying to get out, and the asleep cat just snoring peacefully on the ground. And so the environment, as we say, entangles with the cat right away, because it interacts with it, but interacts with it differently depending on different parts of the wave function.
26:10 Neil deGrasse Tyson? I don't know that that's more clear to me. So you're asleep and awake cat. But we declared that without actually sticking asleep and awake cat in the box. I mean, we're just asserting that.
26:24 Chuck Nice? Could the cat just be drowsy?
26:27 Neil deGrasse Tyson? In between.
26:29 Sean Carroll? No, this is, this is.
26:30 Chuck Nice? I'm in and out.
26:31 Sean Carroll? This is Schrödinger's whole point. This is why he set up in the, in the experiment, there's a radioactive substance. Thought experiment? He didn't do it.
26:38 Neil deGrasse Tyson? Just to be clear.
26:39 Sean Carroll? So radioactivity, and there's a Geiger counter, and the Geiger counter will click when it detects a radioactive decay.
26:45 Neil deGrasse Tyson? And radioactivity, you have no idea which particle is going to decay.
26:50 Sean Carroll? Okay.
26:50 Neil deGrasse Tyson? Just statistically, you know very accurately what fraction of them will. But the fact that you don't know creates a brilliant, beautiful, random number, in a sense.
27:00 Sean Carroll? Yeah.
27:01 Neil deGrasse Tyson? Okay? So if you needed a random thing, you get a decaying set of particles, and you can build, you can draw randomness from that, that is, that's as good a random as we can produce.
27:12 Sean Carroll? Hundred percent random, as far as we know, right?
27:13 Neil deGrasse Tyson? Yeah, as far as we know, okay.
27:14 Sean Carroll? Nothing better. And this is, you know, the 1930s, when Schrödinger was very unhappy with the state of quantum mechanics. He was not bragging about quantum mechanics. He was saying, surely you don't believe this. And he says, when we say this particle has a probability of decaying, what quantum mechanics actually says is there's a wave function for the particle. And it is in a superposition of I have decayed and I have not decayed.
27:39 Chuck Nice? Uh huh.
27:40 Sean Carroll? And the part of it that has decayed sets off the Geiger counter. Now, the Geiger counter is in a superposition of I have clicked and I have not clicked. And the Geiger counter in the part that clicks knocks over a hammer, breaks a vial full of sleeping gas. And the cat goes to sleep. So the cat goes into a superposition of being awake and being asleep. That's the whole point of the sort of Rube Goldberg gizmo that Schrodinger builds in there.
28:09 Chuck Nice? But how does that help anything? Like?
28:12 Sean Carroll? Well, Schrodinger is trying to say, in the way that we thought of quantum mechanics back then, there was these giant debates between Bohr and Einstein about what quantum mechanics really means.
28:22 Chuck Nice? Niels Bohr.
28:22 Sean Carroll? And Niels Bohr would have said, look, when you open the box and look, the cat suddenly changes from being in a superposition of awake and asleep to being one or the other.
28:32 Chuck Nice? Okay.
28:32 Sean Carroll? And Schrodinger is like, come on.
28:34 Chuck Nice? Right.
28:35 Sean Carroll? You think that when I look at it, it changes like that?
28:37 Chuck Nice? I got you. I got you. So his thing is that superposition exists at all times, everywhere, no matter what. It has nothing to do with the fact that I looked at it. It's in that superposition. You just gotta accept that.
28:52 Sean Carroll? Should have said that. He blinked. He lost courage at the last second.
28:56 Chuck Nice? Oh.
28:57 Sean Carroll? And it was a decade and a half later, or two decades later, a graduate student at Princeton named Hugh Everett said exactly those words. He said, just believe what the formula is telling you. And what the formula tells you is, when you look at it, guess what? You enter into a superposition.
29:14 Chuck Nice? Right.
29:15 Sean Carroll? There's a part of you that has seen the cat awake and a part of you that has seen the cat asleep. And Hugh Everett says, that's because both of those possibilities exist just in two separate worlds.
29:27 Chuck Nice? Because what we're dealing with is a probability in the first place. So that always exists. It doesn't change because you observed it. Exactly. It's still the same.
29:36 Neil deGrasse Tyson? Well, you just mentioned in that world, I have some memory that I haven't heard about lately, but that...
29:44 Neil deGrasse Tyson? It was a Copenhagen interpretation.
29:48 Sean Carroll? Yeah, that was Niels Bohr.
29:49 Neil deGrasse Tyson? Niels Bohr is Danish.
29:50 Sean Carroll? Okay.
29:51 Neil deGrasse Tyson? And so they credited, I guess, the city. But it was really a Bohr interpretation, not a Copenhagen.
29:58 Sean Carroll? Well, he had his people who would come into his institute and hang around and go out, you know, spreading the gospel of Bohr.
30:04 Neil deGrasse Tyson? Oh, gosh.
30:04 Sean Carroll? So this was the idea. Heisenberg, Pauli, there's a bunch.
30:09 Neil deGrasse Tyson? There's a bunch, okay. So can you catch us up on the many worlds interpretation?
30:14 Sean Carroll? Right, so the Copenhagen interpretation really frustrated people like Einstein and Schrodinger because it seemed to give up on arguably the single most crucial feature of science, which is realism about the physical world. You know, before quantum mechanics came along, you knew there was a real world out there, even if you didn't know exactly what it was doing.
30:35 Neil deGrasse Tyson? You could touch it, poke it, measure it.
30:36 Sean Carroll? And Bohr and his friends seemed to be saying that before you open the box and look at the cat, there is no fact of the matter about what the cat is. And Einstein and Schrodinger said, you know, even if you don't know what the fact of the matter is, there should be some. And so Everett sort of lives up to the dreams of Einstein and Schrodinger and says, yes, there is a reality there, but sadly for you, the reality is there's many different worlds and they don't interact with each other. So Everett is just saying that in this world of superposition that quantum mechanics always describe, you should just take them all seriously. They're all actually there. It's not just a mathematical trick.
31:18 Chuck Nice? That is really, really tough.
31:23 Sean Carroll? I get it.
31:23 Chuck Nice? That is rough.
31:24 Neil deGrasse Tyson? All right, you got the sleepy cat, you got the awake, the sleep cat, you got the awake cat. Is there a world where I open the box and I see the awake cat as a different world?
31:37 Neil deGrasse Tyson? From the one in which I opened the box and it's asleep?
31:40 Sean Carroll? There is, there are, there will be two worlds and it happens long before you open the box. Because as soon as the other stuff in the box, as soon as the photons and atoms and everything become entangled with the cat, boom, there's two worlds.
31:53 Neil deGrasse Tyson? So where are those two worlds? Or is that the wrong question?
31:56 Sean Carroll? That's the wrong question. I see that you quickly got it. As soon as you asked it, you knew.
31:59 Neil deGrasse Tyson? No, I knew, but...
32:00 Sean Carroll? The worlds are not located in space. Space is located in each world. He knows it, Chuck gets it. He gets it.
32:08 Neil deGrasse Tyson? Chuck, I need you, Chuck. Chuck, I need you for this.
32:11 Sean Carroll? I don't believe in anything anymore. It's over. No, there is no God. Oh, no. I mean, that's also true. But okay, that's a whole nother podcast.
32:22 Chuck Nice? Wow. That is so cool. I mean, that is really, really freaky trippy cool.
32:28 Sean Carroll? And many, many people believe this. Not everyone does, so it's a, it's a something we don't have a consensus on right now.
32:34 Neil deGrasse Tyson? Do the people who don't believe it have a better explanation?
32:35 Chuck Nice? Yeah, I was gonna say, if you don't believe that, then you gotta go back to what we were just talking about, which is the Niels Bohr. Now, you're actually, I'm sorry, that sounds more like magic. That doesn't, that sounds like magic to me. Like, I opened it up, or I looked at it, or because I looked at the electron, that's when it is where it is and became what it became. Why would that be? Why, I mean, why would that ever be?
33:02 Neil deGrasse Tyson? I have to clear something up here.
33:03 Chuck Nice? Go ahead, please.
33:04 Neil deGrasse Tyson? Just before...
33:04 Chuck Nice? Help me out.
33:05 Neil deGrasse Tyson? Okay. Let me just clear something up.
33:07 Chuck Nice? Go ahead.
33:08 Neil deGrasse Tyson? In physics, we talk about the observer.
33:11 Chuck Nice? Uh huh.
33:11 Neil deGrasse Tyson? Okay? On many levels.
33:14 Chuck Nice? Okay.
33:15 Neil deGrasse Tyson? In quantum physics, the observer is not simply some conscious entity looking at it.
33:20 Chuck Nice? Right, I understand that.
33:21 Neil deGrasse Tyson? If you wanna make a measurement, you have to like shine light on it. You have to interact with it in some way. And what happened over the years, over the decades, is like the, there was like a new age movement that was convinced, after hearing this kind of vocabulary, started saying, oh, it's our consciousness that's affecting the outcome.
33:42 Neil deGrasse Tyson? Look at it. It's your, your brain energy going into the thing. Yeah, that's like some quantum field of dreams stuff right there, man. That's crazy. That's crazy. So do you get a lot of this new age folks coming back to you?
33:56 Sean Carroll? Absolutely respectable physicists who said exactly things like that.
33:59 Neil deGrasse Tyson? No.
33:59 Sean Carroll? Who really, oh yeah.
34:00 Neil deGrasse Tyson? No.
34:01 Sean Carroll? Ignar, Howley, yeah, they actually, oh yeah. Oh yeah.
34:06 Neil deGrasse Tyson? Okay, but they're all dead now.
34:07 Sean Carroll? Quantum mechanics is forcing you to make some hard decisions about how reality works. And so they're all freaky one way or the other. Either there's many, many worlds, or you bring it into existence by looking at it, or there is no reality. And none of them are exactly what we grew up thinking.
34:39 Neil deGrasse Tyson? Quantum physics, uh, is, you'd agree, is the most successful idea of the universe we've ever had.
34:46 Sean Carroll? Yes.
34:46 Neil deGrasse Tyson? Yes. Nothing comes close. So I can exist in my macroscopic state because the quantum averages of me make me a physical object. That's fair, probably to say that, okay? I see what you're saying. I got you. So I can still be described by quantum physics, that's just not as convenient as Newtonian physics.
35:08 Sean Carroll? And all the light in the room is constantly measuring you and localizing you.
35:13 Neil deGrasse Tyson? Okay. Yes, exactly. Exactly. Okay. So now, are you here?
35:17 Sean Carroll? At the moment.
35:18 Neil deGrasse Tyson? You're here right now. Okay. So if all the quantum phenomenon average out into my macroscopic state, is there any quantum manifestation in the large-scale universe?
35:33 Sean Carroll? Oh yeah, sure. Um, our favorite has to be the microwave background, the cosmic microwave background, right? And we don't know this for sure, but you look at the relic radiation from the Big Bang, okay? Big Bang, 14 billion years ago, was hot and dense and glowing. About 300 and some hundred thousand, 380, I think, hundred thousand years after the Big Bang, it became transparent. And so we see the relic radiation from the Big Bang. And for reasons we don't completely understand, it's super duper smooth. It's almost exactly the same temperature of radiation from place to place. But it's not exactly the same.
36:12 Neil deGrasse Tyson? Direction, you can look in this direction.
36:14 Sean Carroll? Every.
36:14 Neil deGrasse Tyson? Opposite direction.
36:15 Sean Carroll? Coming to you everywhere.
36:16 Neil deGrasse Tyson? Two completely opposite directions.
36:18 Sean Carroll? Right. And we have.
36:19 Neil deGrasse Tyson? The temperature in this office is nowhere near that stable.
36:23 Sean Carroll? Right, right.
36:24 Neil deGrasse Tyson? In this corner, it's like two degrees higher, three, five degrees. And what's it's.
36:28 Sean Carroll? So you're saying for the. One part in a hundred thousand.
36:31 Neil deGrasse Tyson? One part in a hundred thousand difference in temperature from this side of the universe to that side of it.
36:36 Sean Carroll? And it's that uniform all the way across. Yeah, that's right. Insane.
36:39 Neil deGrasse Tyson? It's insane.
36:40 Sean Carroll? That's insane.
36:41 Neil deGrasse Tyson? And my office can't.
36:42 Sean Carroll? Wow, but that, that really does kind of say.
36:46 Neil deGrasse Tyson? Forces your hand.
36:46 Sean Carroll? That you know, that all of that, that the big bang happened and that, you know, it came from this one thing. It had to come from the one thing because that's how, that's the only way as it spreads out that you can get that kind of uniformity. Is that it comes from this one thing. That's right. And the best theory that we have for why it's so uniform is called inflation. Okay. You might have heard before, the universe expands at some super fast rate very, very early on. And it's very much like stretching your sheet on your bed and smoothing it out, right? It wants to smooth it out, but something gets in the way, quantum mechanics. So quantum mechanics says you're trying to smooth out the universe the best you can. But when you measure it, there'll be little ripple.
37:27 Sean Carroll? And we think that those tiny variations in temperature, one part in a hundred thousand, come from the quantum mechanical uncertainty in the state of the universe at early times. And of course, those grow into planets and stars and galaxies.
37:42 Neil deGrasse Tyson? The quantum is, it has left its paw print in the picture of the early universe.
37:48 Sean Carroll? Right. Oh, man.
37:50 Neil deGrasse Tyson? Another way is, am I right to say that had it been completely smooth, it's not clear that we would have made galaxies.
37:56 Sean Carroll? I was gonna say, would we even be here?
37:58 Neil deGrasse Tyson? Exactly.
37:58 Sean Carroll? Would we even be here?
37:59 Neil deGrasse Tyson? These fluctuations give us the seeds on which you collapse matter.
38:03 Sean Carroll? Yeah.
38:03 Neil deGrasse Tyson? All right.
38:04 Sean Carroll? That is so nutty. Let me bring up one other important manifestation of quantum mechanics.
38:09 Neil deGrasse Tyson? Understand it better.
38:10 Sean Carroll? Hopefully it will.
38:12 Neil deGrasse Tyson? Not if it regresses.
38:13 Sean Carroll? The chair is solid. That's all because of quantum mechanics. You know, you've seen the picture, the cartoon of an atom, right? Little nucleus in the middle, electrons orbiting around like it's a solar system. That can't be right because if you get a bunch of atoms together and they're all little solar systems, they would just squish together. It's not right, that picture, because the electrons are not little point particles moving in orbits. They're wave functions that have a size. They take up space. And the reason why the chair can be solid is because the wave functions of electrons in the atoms take up space and don't want to overlap, and therefore matter has extent.
38:52 Neil deGrasse Tyson? One of my favorite stories was, was it from the book Night Thoughts of a Classical Physicist?
38:57 Sean Carroll? Oh, yeah, Louis.
38:58 Neil deGrasse Tyson? But to be said.
38:59 Sean Carroll? Oh, no, that's not Louis.
39:00 Neil deGrasse Tyson? Or, no, no, maybe, no, I'm misremembering. Either it was fictionalized in that novel, or I'm remembering it as a memoir from Ernest Rutherford, who first showed how empty the atom is.
39:13 Sean Carroll? Mm-hmm.
39:13 Neil deGrasse Tyson? By passing, was it neutrons or?
39:17 Sean Carroll? Alpha particles.
39:17 Neil deGrasse Tyson? Alpha particles, okay. So he's got, he's got helium nuclei, and he has a very thin sheet of gold, because you can hammer gold very, very thin. And so he wants to get like the fewest width atoms of gold soil that he can possibly bit. And then he starts firing particles through it, and like nearly all of them just go straight through, untouched, undiverted, nothing. And then he alone, at that moment, realized how empty matter was.
39:48 Sean Carroll? Mm-hmm.
39:49 Neil deGrasse Tyson? And this is the story what I hear, that the next morning he woke up, he was afraid to step on the ground, out of fear he would fall through the floor. Is this just a Pocker full?
39:59 Sean Carroll? The last part you might have made up. I don't know about that one. But the story you can read about in my new book, Quantum and Fields, where I explain this. But the idea that it's empty, you know, I don't like it when people say that, because what Rutherford really figured out.
40:15 Neil deGrasse Tyson? It's because you're a field guy.
40:16 Sean Carroll? Is that, well, the fields are, they matter. But what he really figured out is that most of the mass is at the center in the nucleus, right? And so it's not just that they mostly pass through that's important. Also, very occasionally, one ricochets right back at you. So it's not just that the gold is sort of spread out and diffuse. There's some oomph there right at the middle in the nucleus of the atom.
40:37 Neil deGrasse Tyson? Just while we're like fired up here, what's, what's the latest thinking on dark matter, dark energy? Where we, where should we see future advances?
40:46 Sean Carroll? These are, you know, these are the-
40:47 Neil deGrasse Tyson? We're just looking for a dark matter particle. Is that, are you all in on the particle thing? You got some other exotic?
40:52 Sean Carroll? I'm happy for it to be a particle. You know, I've proposed theories where it's not a particle, but they're not very good, these theories. The dark matter is probably kind of a particle. We haven't found it yet, and I would say that, you know, we, we had a chance of having found it already. The experiments are pretty good, but it wasn't like a 99% chance. It was like a 50% chance it would have found it already. So the fact that we haven't found it already is not yet cause for concern.
41:16 Neil deGrasse Tyson? Okay.
41:17 Sean Carroll? Um, the dark energy is interesting. Again, I've written papers about different possibilities for that, but the simplest one is the best Einstein's idea, that there's energy in empty space. It's just a fact of the matter. Every cubic centimeter of space has 100 millionth of an erg of energy inherent in space itself.
41:37 Neil deGrasse Tyson? Erg is a unit of energy.
41:38 Sean Carroll? Pushing the universe apart. And so we don't know. In fact, there was a provocative recent result from the dark energy spectroscopic instrument, which claimed that maybe the dark energy is declining very slowly.
41:52 Neil deGrasse Tyson? A DESI, dark energy spectrum.
41:54 Sean Carroll? But there's like three different experiments whose nickname is DESI. So I actually like to use all the words.
41:59 Neil deGrasse Tyson? Okay.
41:59 Sean Carroll? This one says-
42:00 Neil deGrasse Tyson? DESI Lu, DESI Lu is a, that's a different one. Yeah, yeah.
42:04 Sean Carroll? So we don't know. That'll be very, very fascinating and exciting.
42:07 Neil deGrasse Tyson? That the, that the dark matter field is changing.
42:09 Sean Carroll? Dark energy field is slowly declining with time.
42:12 Neil deGrasse Tyson? Declining. Now, is that allowed if the Einstein's cosmological constant, which was our first indication that there might be this thing such as dark energy working opposite gravity? That is identically a constant, the way it comes out of the equation.
42:26 Sean Carroll? That's right. So if this is true, then the cosmological constant is not the dark energy. Dark energy is something else. The cosmological constant, the vacuum energy, uh, which are equivalent, that was a candidate. That's one possible thing the dark energy could be.
42:37 Neil deGrasse Tyson? Yeah.
42:38 Sean Carroll? The simplest, most basic thing.
42:39 Neil deGrasse Tyson? I didn't appreciate that.
42:40 Sean Carroll? Yeah.
42:40 Neil deGrasse Tyson? And it's a leading candidate because it comes out of the, we're using the equation anyway, and it was already there.
42:45 Sean Carroll? That's right.
42:45 Neil deGrasse Tyson? And, and then-
42:46 Sean Carroll? Everything else is, is a little bit more delicate, a little more fragile, hard to figure out, but cosmological constant is pretty easy to put in there.
42:55 Chuck Nice? This has been exhausting.
42:58 Neil deGrasse Tyson? One last thing, just as a teaser for your next book.
43:01 Sean Carroll? Yeah.
43:02 Neil deGrasse Tyson? When I think of emergence, I assume you mean it in the tree of life. There are life forms that have features that cannot be deduced from their biological form. Like flocking birds, right?
43:18 Sean Carroll? Yeah.
43:18 Neil deGrasse Tyson? You can't analyze anything about a bird that we know of that will tell you that they should flock with other birds.
43:24 Sean Carroll? Right. So you will not be surprised to learn that there's a lot of philosophical controversy about these concepts. But basically, yes. You know, the point is, we can, as you said before, we can get through the day talking about people and tables and chairs without knowing that they're made of atoms or quantum fields, right? So there's different levels of description that all seem to work. They have to be consistent with each other. But you don't need to know about your quantum fields to get through the day or balance your stock portfolio. Just go through, yeah. Emergence, there we are.
43:57 Chuck Nice? There you go.
43:57 Neil deGrasse Tyson? Emergence.
43:58 Sean Carroll? Consciousness, free will.
43:59 Chuck Nice? Yeah.
44:00 Sean Carroll? All part of that.
44:01 Chuck Nice? All part of emergence.
44:02 Neil deGrasse Tyson? Yeah, the more I think about free will, the less I think we have it. It's, I've not reversed in this vector direction I'm headed about.
44:13 Sean Carroll? That's some momentum.
44:14 Chuck Nice? Yeah, it makes sense. I mean, what if you stripped away everything? Would you then have free will? So if you don't have free will, then what you're talking about is there has to be an influence put upon you.
44:24 Neil deGrasse Tyson? No, no, I'm going to take whoever said it, you'll know. I don't think we have free will, but what choice do I have? Somebody said that, who said that?
44:34 Sean Carroll? That's funny. I don't know that one. There's a philosopher joke, like, you know, you walk into the restaurant and they say, what do you want? And I'll have whatever the universe says I'm going to have. Like, I have no choice about what it's going to be. But I don't think that's the right way to talk. I think I do have the ability to make choices.
44:48 Neil deGrasse Tyson? Well, I've heard you on other podcasts give, for me... What was most resonant account of free will that I can think of while others were spouting off all manner of things. So I felt very in your club. Good. I got your back on this one. Good. So we don't have time for that here, but I, other.
45:08 Sean Carroll? Oh man, you can't leave me hanging like that.
45:11 Neil deGrasse Tyson? There's another book coming out. Oh, okay.
45:13 Sean Carroll? We gotta bring him back.
45:14 Neil deGrasse Tyson? That'll be good. Bring him back. He used to be in California. He's now just down the street in Baltimore. A seller. Right, yeah.
45:20 Chuck Nice? We'll train right away.
45:21 Neil deGrasse Tyson? We can totally do that.
45:22 Chuck Nice? But are you gonna make that trip? I mean, seriously.
45:25 Neil deGrasse Tyson? I'm literally here right now.
45:28 Neil deGrasse Tyson? Where are you?
45:28 Sean Carroll? I was gonna say, how would I know?
45:31 Neil deGrasse Tyson? His vibrational energy is here. It's a probability. Otherwise, don't know. Sean, delight to have you in my office here at the Hayden Planetarium, the American Museum of Natural History. Thanks for making the trip. You're on a book tour right now. Yep. So good luck with that. Sometimes you need a little bit of that. Mm. And keep the physics coming. I will do that. Absolutely. Thanks for having me on. It's always great. There's surely an unlimited appetite for the cool stuff. Lots of cool stuff, big ideas. All right. Chuck, always gonna have you, man.
45:57 Chuck Nice? Always a pleasure.
45:58 Neil deGrasse Tyson? All right. This has been the latest update on the moving frontier of the universe through the lens of theoretical physicist Sean Carroll. I'm Neil deGrasse Tyson, your personal astrophysicist. As always, keep looking up.
Previous The Science of Flavor with Arielle Johnson Next Physics Freestylin’ with Charles Liu & More Page updated September 29, 2026 · transcript and summary are machine-generated
