Cosmic Queries: Mysterious Cosmology, with Sean Carroll

String theory, the fabric of spacetime, the multiverse, quantum mechanics, and much more – explore the cosmological mysteries of the universe with Neil deGrasse Tyson, comic co-host Chuck Nice, and theoretical physicist Sean Carroll. NOTE: StarTalk All-Access subscribers can watch or listen to this entire episode commercial-free: https://www.startalkradio.net/all-access/cosmic-queries-mysterious-cosmology-with-sean-carroll/

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:21Neil deGrasse Tyson?

  This is StarTalk, and I'm your host Neil deGrasse Tyson, your personal astrophysicist, and I also serve as the director of New York City's Hayden Planetarium at the American Museum of Natural History, and my co-host today Chuck Nice. Hey Neil. Baby. How are you buddy? Tweeting at ChuckNiceComic. Yes sir, thank you. Well there, I love your tweets. Yeah, well, thank you. They're good? Love yours too. Uh, this is a Cosmic Queries edition. Yes it is. Of StarTalk, and we've subtitled it "Mysterious Cosmology." Ooh. I know a little bit of cosmology, but not enough to handle this. Just a little bit. Right, cuz we had Stephen Hawking's show. Right. And all manner of questions were... Bandied about and flying around like crazy. Flying, get hurt with some of those questions.

• 1:06Neil deGrasse Tyson?

  Exactly, right. Slapped upside the head. And so we just put them all in one spot, and into this Cosmic Queries. And so I've got with me, helping me out here, is a friend and colleague Sean Carroll, theoretical physicist. Sean, welcome to StarTalk.

• 1:22Sean Carroll?

  Thanks, great to be here.

• 1:23Neil deGrasse Tyson?

  Yeah, so you are a research scientist at Caltech, and you specialize in quantum physics and the fabric of spacetime, and that's kinda like exactly what we need, what kinda expertise we need in this moment.

• 1:36Sean Carroll?

  I'm here to lay down the expertise.

• 1:38Neil deGrasse Tyson?

  Nice. And most recently, you're author of "The Big Picture." You know, that takes some gonads, you know.

• 1:44Sean Carroll?

  Let me tell ya, that's right. I'm supposed to show it, here you go.

• 1:49Neil deGrasse Tyson?

  Oh, there you go.

• 1:50Sean Carroll?

  There it is. There it is. You can buy it right now from your phone on Amazon.

• 1:54Neil deGrasse Tyson?

  And it's subtitled "On the Origins of Life, Meaning, and the Universe Itself."

• 2:00Sean Carroll?

  Wow.

• 2:01Neil deGrasse Tyson?

  See, that's what I'm saying, that take gonads.

• 2:02Sean Carroll?

  That's a big, that's a big statement.

• 2:04Neil deGrasse Tyson?

  Just claiming that you got it.

• 2:05Sean Carroll?

  That's serious, yeah.

• 2:06Neil deGrasse Tyson?

  Okay, and so Sean, so what we have are questions solicited from our fanbase, and Chuck will read them, and you and I will tackle these, mostly you.

• 2:16Neil deGrasse Tyson?

  And answering these. Alright, so, so let's get right in.

• 2:19Chuck Nice?

  Yeah, let's get right into it. Uh, we always start with the Patreon patron. It's uh, someone who supports us uh, monetarily uh, on Patreon and in doing so, they get certain perks. One of which is that we will read their question before anyone else's.

• 2:35Neil deGrasse Tyson?

  Don't even pretend like, it's just.

• 2:38Chuck Nice?

  Straight up. Here's what we're saying. We're whores.

• 2:41Neil deGrasse Tyson?

  Yeah, yeah. Buy your way into the Cosmic Query List.

• 2:44Chuck Nice?

  We can be bought.

• 2:46Neil deGrasse Tyson?

  Okay.

• 2:46Chuck Nice?

  And uh, and so that's it. So Chris, uh, Ryu.

• 2:50Neil deGrasse Tyson?

  Just to be clear, just to be clear, um, uh, Patreon is a source of income to StarTalk, has enabled StarTalk to experiment with, by branching out into other places. So playing with science.

• 3:02Chuck Nice?

  That's right.

• 3:02Neil deGrasse Tyson?

  Which your co-host of, the intersection of.

• 3:04Chuck Nice?

  With Gary O'Reilly, who is.

• 3:05Neil deGrasse Tyson?

  Gary O'Reilly's, uh, intersection of sports and science.

• 3:08Chuck Nice?

  That's correct.

• 3:08Neil deGrasse Tyson?

  That's, um, you know, that, it helped birth that entire, uh, concept.

• 3:12Chuck Nice?

  Yeah, cause it gives us the opportunity and the uh, resources more importantly, to do different things. That along with uh, StarTalkAllAccess.com, which is another way that you can support us, so that we're doing our, you know, we'll get to do more. And it's all for you, baby. It's all for you.

• 3:27Neil deGrasse Tyson?

  Baby. Alright, what do you have now?

• 3:29Chuck Nice?

  So Chris Ryu says this, um.

• 3:32Neil deGrasse Tyson?

  What's the name again?

• 3:33Chuck Nice?

  Ryu or Ryu? Or?

• 3:36Neil deGrasse Tyson?

  Chuck, Chuck.

• 3:37Chuck Nice?

  Listen, I am going to butcher every name and you know it.

• 3:39Neil deGrasse Tyson?

  Alright.

• 3:40Chuck Nice?

  You know I'm gonna butcher these names.

• 3:41Neil deGrasse Tyson?

  We should say, when Chuck is doing Cosmic Queries, only John Smith should, should write in.

• 3:45Chuck Nice?

  And you know what? That'd be funny. It's like, look at this, another John Smith? Another John Smith. Who would've thought about it? Oh my God, John Smith. And look at this. Uh, but.

• 3:56Neil deGrasse Tyson?

  So what do you have?

• 3:56Chuck Nice?

  Says this, uh, Dear Sean, what is the meaning of life?

• 4:01Chuck Nice?

  Nah, I'm joking, man. I've just made that up. Uh, he says this. I love this question. Uh, hey, this is one of my favorite questions that has never been answered. Uh, so here you are, Chris. It is widely accepted that the further a star is from us, the faster it is moving away. But can we really assume that during a 13 billion year journey, that light would not have passed through anything else that could slow it down? Seems like an unlikely journey to me. Uh, sign Chris Ryu. Uh, P S Chuck, it's pronounced rye like the bread and you like the guy who's gonna butcher my name. Okay.

• 4:47Neil deGrasse Tyson?

  Is that really in there?

• 4:48Chuck Nice?

  No, I just put that in. I just, I just put that in there. Um, and he's coming to us from the UK.

• 4:53Neil deGrasse Tyson?

  Start with the football and I'll throw it to Sean. Okay. First of all, he probably, he's probably referring, Chris, we don't know if it's male or female, actually.

• 4:59Chuck Nice?

  Not.

• 4:59Neil deGrasse Tyson?

  Um, uh, so, uh, he referred to stars, uh, Chris referred to stars being, uh, uh, in the universe shifted, uh, in their spectrums, probably referring to galaxies. Right, cause stars in our own galaxy, uh, that we all orbit the center of the galaxy together. And there's no, nothing cosmological about that. But when you go out beyond our galaxy, you get to other galaxies and we speak of the light from galaxies that are shifted because of the expansion of the universe. Okay, so I just wanna correct that up front. Now I throw the football to Sean. Sean, where do you wanna take this?

• 5:31Sean Carroll?

  Yeah, I mean, it's a very natural question, right? What we actually observe is light from distant galaxies with what we call a spectrum. That is to say, is the light blue, is it red, yellow, you know, what's the wavelength of it? And we can compare that to what the wavelength was when it left. Because different atomic processes give us very, very different, very, very specific colors that the light had. And what you almost always see is a red shift. The light moves from some short wavelength blue light to some longer wavelength red light.

• 6:02Sean Carroll?

  One obvious explanation for that is the Doppler effect. When something is moving away from you, it gets redshifted. If a sound moves away from you, it's a lower pitch, right?

• 6:12Neil deGrasse Tyson?

  Longer wavelength stretched out, yeah.

• 6:13Sean Carroll?

  Longer wavelengths, yeah. And we can interpret that in general relativity in Einstein's theory of space and time as space itself is expanding and stretching these wavelengths. So that idea fits perfectly. It fits all the data we have. We have not only distant galaxies, we also have the leftover light from the big bang. We have the leftover elements from the days when the early universe was a nuclear reactor.

• 6:38Neil deGrasse Tyson?

  You're telling me we're all just leftovers here today?

• 6:41Sean Carroll?

  We're all leftovers. We're all the, you know, what leftovers have been doing, stewing in our own juices for the last 14 billion years. Uh, but of course, as a scientist, you should consider alternative possibilities. Maybe the light is redshifted because it slowed down, like the, like the questioner said. Or maybe there's what we call a tired light hypothesis. Maybe light just gets worn out.

• 7:03Chuck Nice?

  Wait a minute, wait a minute.

• 7:04Sean Carroll?

  Traveling for all these billions of years.

• 7:05Chuck Nice?

  Yeah, can we please talk about the tired light?

• 7:09Sean Carroll?

  Yeah, the light is tired.

• 7:10Chuck Nice?

  Cause I just love the idea of light just going, ah, God, what a, God, this has been a rough billion years.

• 7:18Neil deGrasse Tyson?

  These light years.

• 7:19Chuck Nice?

  These light years are just taking it out of me, I'm telling you right now. Oh, what a day.

• 7:24Neil deGrasse Tyson?

  It was officially called the tired light hypothesis to try to compete with the redshift hypothesis.

• 7:29Chuck Nice?

  Okay. So what, what is the tired light? And I'm sorry, cause this is the first, and listen.

• 7:34Neil deGrasse Tyson?

  Never heard of this.

• 7:34Chuck Nice?

  You and I have been together for a very, very long time.

• 7:37Neil deGrasse Tyson?

  I never told you about tired light.

• 7:38Chuck Nice?

  You have never told me about tired light?

• 7:39Neil deGrasse Tyson?

  It's a whole thing for like decades. Oh, yeah.

• 7:41Chuck Nice?

  Aw, man.

• 7:42Sean Carroll?

  Hang out with better cosmologists.

• 7:46Neil deGrasse Tyson?

  Whoa, I got him on the east coast here with all your palm trees out the window in your, in your California home.

• 7:52Chuck Nice?

  Yeah, and so what was the idea behind the tired light? And has it been debunked?

• 7:56Neil deGrasse Tyson?

  Go ahead, Sean, you started it.

• 7:57Chuck Nice?

  Can you please?

• 7:58Sean Carroll?

  Yeah, I know. So it's wrong, the tired light hypothesis. But it was, you know, when you see something amazing, like almost all galaxies have this redshift, you try to come up with all the different ideas you can. And one is just that we don't understand light very well. It sort of leaks out energy as it travels through space, maybe by literally bumping into things, or maybe just that's how the laws of physics work. Turns out it's wrong for many reasons. One reason is this really fun thing. If you look at a supernova in a very distant galaxy, it gives off light, we can measure its redshift to figure out how far away it is. But it also takes time for the supernova to get bright and then to get dim again.

• 8:38Chuck Nice?

  Mm-hmm.

• 8:39Sean Carroll?

  If tired light were right, the time it takes for a supernova to go up and down in brightness would be the same no matter how far away it is. It would just be redder and redder the far further away it was. But if space is expanding, then it takes longer for the light to get to us that started out later. So not only is the light redder, but it takes longer for that supernova to go up and down in brightness. That's the prediction of general relativity of the expansion of space theory. And then you look at it, and it's bang on, that's exactly what we observe in the universe.

• 9:13Chuck Nice?

  Oh, that's very, very cool. So because of the time in that, in that small process, that we're able to know that tired light is wrong.

• 9:23Neil deGrasse Tyson?

  Well, so, so by the way, that, uh, may I announce here and now?

• 9:27Chuck Nice?

  Okay.

• 9:28Neil deGrasse Tyson?

  Okay? That the very first paper.

• 9:30Chuck Nice?

  Yes.

• 9:31Neil deGrasse Tyson?

  Show this stretching of the light curve of a supernova, I am co-author on.

• 9:36Chuck Nice?

  Get, yes! Oh! Yes! I'm, I'm sorry, so maybe I'm hanging out with the right cosmologist.

• 9:43Sean Carroll?

  You think I didn't know? I was setting him up, I was giving him a little small follow there.

• 9:47Neil deGrasse Tyson?

  So, uh, no, I was, it was, I was not the first author on that paper. I participated and contributed data to it. But the first author was Brian Schmidt, who would later, you know, collect all of his supernova data.

• 10:00Chuck Nice?

  Uh-huh.

• 10:01Neil deGrasse Tyson?

  And show that in fact, there's this acceleration of the expanding universe, and then go to Stockholm for the Nobel Prize.

• 10:06Chuck Nice?

  Nice. I don't know why, but I'm, I'm like fricking proud of you right now.

• 10:10Sean Carroll?

  So I gotta say, Brian got his start as my office mate in graduate school.

• 10:14Chuck Nice?

  Oh! What? Oh my God. Oh my God. Okay, so, um...

• 10:20Neil deGrasse Tyson?

  We each got a piece of Brian.

• 10:21Chuck Nice?

  I was gonna say, I, I gotta find out a way that I can be associated with Brian right now.

• 10:26Sean Carroll?

  Right, cool guy, yeah, have him on the show.

• 10:28Chuck Nice?

  There you go. Oh man, well that is super cool. That is, hey, Chris, thank you so much for that question, cuz that was great, I actually learned something. That's fantastic. All right, let's move on. Uh, next question here comes from, um... Mara00725, I believe it's a, it's probably in an artificial life form.

• 10:48Neil deGrasse Tyson?

  That's right.

• 10:49Chuck Nice?

  This is Mara00725 from Instagram.

• 10:52Neil deGrasse Tyson?

  It's an intelligent bacterium.

• 10:53Chuck Nice?

  Yes, exactly. We have a sentient bacterium who just writes in and says, hello there. What makes scientists think that there could possibly be parallel universes other than dimensions? And what kind of evidence would we find in order to confirm that such a thing actually exists? That's a small question with a hell of a lot of stuff in it.

• 11:18Neil deGrasse Tyson?

  Yeah, yeah, so Sean, let's assume this person is referring to the multiverse rather than just, because parallel universe has a formal meaning.

• 11:25Chuck Nice?

  Right.

• 11:25Neil deGrasse Tyson?

  But yes, Sean, I could do this, but we'll let you take this.

• 11:30Sean Carroll?

  All right, thanks. Giving me the softballs.

• 11:32Chuck Nice?

  Sean, Sean, I'm gonna go out and get some coffee. You handle this one, all right?

• 11:39Sean Carroll?

  No, no, you don't want to miss this, because this is good, because there are, as Neil says, there's more than one way to have parallel universes or a multiverse. Let me just at least mention two because they're both quite realistic. There's lots of ways that are kind of fun to think about, but there are two that scientists take very seriously.

• 11:55Neil deGrasse Tyson?

  You mean plausible, when you say realistic, you actually mean plausible, right?

• 11:59Sean Carroll?

  Plausible, I would say, you know, there are people who think the chance is at least 50% that this is true.

• 12:04Neil deGrasse Tyson?

  There you go.

• 12:05Chuck Nice?

  Wow.

• 12:06Sean Carroll?

  Grown up people with jobs, as a professional scientist.

• 12:09Neil deGrasse Tyson?

  Not sci fi writers for Hollywood.

• 12:12Sean Carroll?

  Yeah, that's it. People who write papers. So, one way is what we call the cosmological multiverse, which is just the idea that really far away, there are regions of, frankly, what is our universe, but there are regions where things look so different that it might as well be another universe. The laws of physics could look different, different particles, different forces, maybe even more than three dimensions of space, right?

• 12:36Chuck Nice?

  Gotcha.

• 12:38Sean Carroll?

  That's something you're welcome to imagine, but in modern physics, it's actually a prediction of certain theories about the early universe. String theory, eternal inflation, all these crazy speculative ideas. It's not that we just sat around and said, "Hey dude, maybe like the universe is full of stuff, far away." It's that we started with a very simple theory, followed its predictions, and realized that it predicts the existence of this cosmological multiverse.

• 13:05Chuck Nice?

  Okay, alright.

• 13:07Sean Carroll?

  So that's one idea.

• 13:08Neil deGrasse Tyson?

  So that's one idea. Okay, wait, wait, but so, all you did was justify that the thoughts about a multiverse are authentic and genuine, but you didn't, I think the real part of that question is, if they do exist, how would we know they're there?

• 13:22Sean Carroll?

  Good, exactly. So, there's the good news and the bad news. The, of course, we don't have any direct evidence right now. The idea could be completely wrong. This is definitely in the realm of a speculation, not something that we have confirmed. We could, the good news is, actually find direct evidence for it. If there was another region of space that was far away but not too far away, these regions of space where things look different often appear in the form of bubbles of space which grow near the speed of light. And these bubbles can literally bump into each other, and we could have what is basically a bruise on our universe at early times that would appear as a circle, circular pattern

• 14:05Sean Carroll?

  in the cosmic microwave background, the leftover radiation from the Big Bang.

• 14:09Neil deGrasse Tyson?

  Just a sec, so you're gonna get a circle because two spheres, when they intersect, the intersecting membrane is a circle, right?

• 14:17Sean Carroll?

  Exactly right.

• 14:18Neil deGrasse Tyson?

  Yeah, okay.

• 14:19Chuck Nice?

  Okay, cool. So, so go ahead.

• 14:21Sean Carroll?

  So, we're looking for that, we haven't seen it, but maybe it's just too faint to be seen.

• 14:25Neil deGrasse Tyson?

  And there's collisions of universes. That's what you're talking about.

• 14:29Sean Carroll?

  Yeah, exactly.

• 14:31Chuck Nice?

  Now, is it, well, you know what, I'm getting ahead, I'm gonna let you finish, and then I'm gonna ask my question, so go ahead. So, we're looking for these collisions, and we would see them as the circles that would be an imprint on the cosmic background radiation that we observe as the universe.

• 14:44Neil deGrasse Tyson?

  As an example of how you might see it.

• 14:45Chuck Nice?

  That's how you might see it. Okay, go ahead. I'm still with you so far.

• 14:48Sean Carroll?

  The bad news is, you might not see it, even if the universes are there. Could be a scientist too. They might be too far away. In fact, it's kind of weird if they did bump into each other, but it was only barely noticeable, not really obvious. That seems like a little delicate balance there. So, chances are, even if the cosmological multiverse is true, we'll never know for sure. It'll be an idea that's on the table, and what we'll be asking ourselves is, is imagining the existence of such a multiverse helping us explain features of our universe, or is it just a waste of time? And that's what cosmologists will have to decide. Right. All right. So that's one kind of multiverse. The other one that I gotta mention, because I

• 15:32Sean Carroll?

  think it's actually 90% likely to be true, is the quant multiverse. The, what we call the many worlds interpretation of quantum mechanics. So, you may have heard that, depending on which street corners you hang out at, that uh... Physics street corners. I was gonna say, uh, we're getting into some dangerous territory right now. That's good. Having the extra coffee now. Exactly.

• 15:57Chuck Nice?

  Yo, man, I got that quantum physics.

• 16:00Sean Carroll?

  When you're talking about electron spin, right? They could be spinning either clockwise or counterclockwise. You observe it, and you see always that it's one way or the other, it's never in between. But when you describe the electron when you're not looking at it, it's in a superposition of both possibilities. And that's the, the miracle and the danger of quantum mechanics, is that what the electron is when we're not looking at it, is different than what you see when you look at it. And the important word here is superposition. There's a, both possibilities are there. It's not that we don't know, it's that really there's both at once. And if you believe that, if you believe that an electron could be in a superposition of spinning clockwise and spinning counterclockwise, then you should

• 16:43Sean Carroll?

  believe that a person who goes and looks at the electron... Could be in a superposition of I saw it spinning clockwise and a superposition of I saw it spinning counterclockwise. And if you believe that, you should be believe that the universe could be in a superposition of there were people who saw it spinning clockwise and there were some people. And so the it just falls out of the formalism of quantum mechanics, whether you like it or not, that the natural evolution of stuff is to go from one universe. Here is an electron in a superposition of two different spins. But then someone comes and look at it and the universe splits. Now there's a universe where you saw it spinning clockwise and a universe when you saw it spinning counterclockwise. Again, uh, this is not definitive.

• 17:27Sean Carroll?

  This is not absolutely proven. This is something that is speculative. I personally am a huge fan of the idea.

• 17:33Neil deGrasse Tyson?

  Well, wait. Why would the act of observing it have to be the moment when the universe splits? Why can't the universe just exist in both states at the same time? And then when you observe it, you figure out which one of those you happen to be in.

• 17:46Chuck Nice?

  Oh, good.

• 17:47Neil deGrasse Tyson?

  That's a good, damn good. You know what? You might want to look into the science thing. It's a really good question.

• 17:54Sean Carroll?

  You could do that professionally. Yeah, so that's the idea. This is invented by a guy named Hugh Everett back in the 1950s. His idea was, you know, everyone in quantum mechanics believes the electron can be in a superposition and when you look at it, you see it spinning one way or the other. His idea was just that, no, actually both alternatives remain real, but they separate, they branch. And you ask exactly the right question, you know, who says they branch? You know, why, why is that? And ultimately, we finally understand that, like Everett didn't really understand the answer to that question. But it's because you keep bumping into the rest of the universe. It's because of the quantum feature known as entanglement. The observer looks at the electron and becomes entangled with it.

• 18:39Sean Carroll?

  And then the observer becomes entangled with the rest of the universe and there's no going back. That's an irreversible process. So it is as if these two separate branches of reality have become separate worlds.

• 18:50Chuck Nice?

  Wow. Wow. So, doggone man, this is, this is just.

• 18:56Neil deGrasse Tyson?

  We gotta take a break after that.

• 18:57Chuck Nice?

  I know, I need a second just to digest that. And by that, I mean, we'll be back next Tuesday.

• 19:05Chuck Nice?

  Damn.

• 19:06Neil deGrasse Tyson?

  This is StarTalk. We're gonna take a break from our Cosmic Queries cosmology edition with Sean Carroll of Caltech. We'll be right back.

• 19:20Neil deGrasse Tyson?

  We're back on StarTalk, Cosmic Queries Edition, a cosmological excursion with the help of Sean Carroll, research scientist at Caltech Department of Physics, specializing in quantum physics, theoretical physics, and all the ways that touches the fabric of the spacetime continuum.

• 19:40Chuck Nice?

  Nice. That's good.

• 19:42Neil deGrasse Tyson?

  So Sean, what does your business card say? I just want to know how badass it is.

• 19:47Sean Carroll?

  Uh, it's not that badass. I just stick with theoretical physics. I have a little picture of, uh, uh, ink mixing into water to indicate the increase of entropy in the arrow of time.

• 19:58Neil deGrasse Tyson?

  Okay.

• 19:59Sean Carroll?

  That's a subtle little...

• 20:00Chuck Nice?

  Well, you might want to change that and go with "bad mother effer."

• 20:05Chuck Nice?

  You know what I mean? That's my card.

• 20:08Sean Carroll?

  You're probably right now that I think about.

• 20:11Neil deGrasse Tyson?

  Plus, the dude wrote a book called "The Big Picture"

• 20:13Chuck Nice?

  Right.

• 20:13Neil deGrasse Tyson?

  On the origins of life, meaning

• 20:16Chuck Nice?

  Meaning.

• 20:16Neil deGrasse Tyson?

  And the universe itself.

• 20:18Chuck Nice?

  Wow.

• 20:19Neil deGrasse Tyson?

  There are no other books to be written after that book.

• 20:21Chuck Nice?

  After that, it's all done, right? You know, and 'cause you kind of got me with the meaning.

• 20:25Neil deGrasse Tyson?

  Yeah.

• 20:26Chuck Nice?

  That's where everybody, that's where everybody wants to get into the thick of it.

• 20:28Neil deGrasse Tyson?

  That's right.

• 20:29Chuck Nice?

  You know?

• 20:29Sean Carroll?

  I'd be happy to have the books like in every hotel room around the world.

• 20:34Neil deGrasse Tyson?

  Top drawer.

• 20:36Chuck Nice?

  Oh, that's funny. You gotta change your name to Gideon.

• 20:42Neil deGrasse Tyson?

  So Chuck, what do you have for us?

• 20:43Chuck Nice?

  All right, let's jump right back into it. This is, ooh, Preston, I think it's Ch- Preston Chaw? Preston Chaw? Preston Shao?

• 20:56Neil deGrasse Tyson?

  Chuck, Preston?

• 20:57Chuck Nice?

  All right. All right, Preston, here you go, buddy. Here's your question. Uh, you'll know who you are when I read your question. If at absolute zero, particles have the minimal amount of energy, what is the, a maximum amount of energy a particle can have? Wow. Is that, can we even know that?

• 21:20Neil deGrasse Tyson?

  Well, so, so, so Sean, let me, let me again throw you the ball, um, after I, like, you know, touch it.

• 21:28Neil deGrasse Tyson?

  I'm gonna play center on this one. You give me an audible.

• 21:32Chuck Nice?

  Yeah, give me one.

• 21:32Sean Carroll?

  You're running a sleep slicker.

• 21:33Neil deGrasse Tyson?

  There you go. This is an audible, Sean. Uh, so I think we learned in quantum physics that this absolute zero temperature, uh, there's, there's still a probability that it is like not at that absolute lowest temperature. Sean will pick this up in a minute. Okay. Recently, Sean, I learned about discussions about there being a highest possible temperature. And then when I read into it a little further, I became less convinced of it. And I just want to hear what you, your reflections on these two extremes that we hear about in chemistry class. Okay. You know, a cold as possible temperature. Absolute zero. Is there a highest possible temperature? So where can you take us on that?

• 22:11Sean Carroll?

  Yeah, so the shortest possible correct answer is we don't know for sure. If you think about it.

• 22:16Neil deGrasse Tyson?

  I could be a scientist.

• 22:17Sean Carroll?

  High temperatures means, yeah, you gotta be honest about, you know, we know a lot. We don't know that.

• 22:22Neil deGrasse Tyson?

  Yeah.

• 22:23Sean Carroll?

  Uh, high temperatures means high energies means it's hard to make things that, uh, are actually at such temperatures. You know, for one particle, there's no such thing as what the energy is because of what we call relativity. It depends on what frame of reference you're looking at it in. It's the energy of one particle is its mass times the speed of light squared. If it's just sitting still, it's more if you're moving with respect to it. But when you have a bunch of particles, that's when you have, uh, what we call a temperature or a whole bunch of energy because they have a mutual velocity, right? If they're sitting still with respect to each other, they can be near or at absolute zero. If they're moving fast, they're bundling up and they're packed densely, then they can have a lot of energy.

• 23:03Neil deGrasse Tyson?

  Just to be clear, just because Sean said this very quickly and I think we should pause. Okay. Temperature as a concept exists only in an ensemble of particles. Okay. You can't say, what is the temperature of this one particle? It had, the question has no meaning because of the way temperature is defined. Right, okay. Right, so I just want to make that clear. Okay, okay. Yeah, yeah, okay. Sean, go for it. And is that because, is that because of energy? Is that the deal? Like the, it's sitting there by itself? It has to have something else? Well, Sean, unless there's some other way we think of temperature beyond the, sort of the average vibrational energy of particles in a. In a, in a package?

• 23:41Sean Carroll?

  No, that's plenty good enough. And temperature's the average energy of whatever's shaking around.

• 23:45Chuck Nice?

  Yeah, okay, I got you.

• 23:46Neil deGrasse Tyson?

  And it could be a solid object because the things are still wriggling in the solid object.

• 23:50Chuck Nice?

  Exactly. Okay, cool.

• 23:51Sean Carroll?

  That's right.

• 23:51Chuck Nice?

  Cool.

• 23:52Sean Carroll?

  And so you might think, well, you know, things can wriggle as fast as they can. Or maybe you say, well, oh, they can't move faster than the speed of light. But the energy of an individual particle, if you were just Albert Einstein's thinking about special relativity, the energy can go infinitely high. Here's the problem. If you have a bunch of particles moving with an enormous relative velocity, pack an enormous amount of energy into a small region, you hit a limit because you eventually make a black hole. A black hole is the maximum amount of energy you can have in a region of space. It's not really fair to assign a temperature to the black hole, a small black hole. Black holes have temperature. Stephen Hawking worked that out in the 1970s.

• 24:37Sean Carroll?

  But now we're beyond the realm where we can think of that temperature as the average velocity of shaking or energy of shaking of some individual atoms. It's the black hole itself.

• 24:45Chuck Nice?

  Is the black hole temperature, is it, is it comfortable? Is it like sweater weather? I mean.

• 24:50Sean Carroll?

  If it's a big astrophysical black hole, it is incredibly cold, the, the temperature. The temperature of a black hole is colder than the temperature of the desolate reaches of intergalactic space. A tiny little black hole has a high temperature. So they will actually just disappear, explode in a puff of radiation being given off. And there's a maximum temperature you can reach there called the Planck scale, the quantum gravity scale, this amount of energy that was invented back 100 years ago as sort of the most we can fit into a tiny little region of space.

• 25:24Chuck Nice?

  Cool.

• 25:25Neil deGrasse Tyson?

  So, so if small black holes are, are hot, that, that wouldn't be so bad. It's the humidity that.

• 25:31Chuck Nice?

  It's not a dry heat, and that's the problem.

• 25:36Neil deGrasse Tyson?

  It's a dry heat in this small black hole.

• 25:38Chuck Nice?

  Exactly, there you go, alright.

• 25:40Neil deGrasse Tyson?

  Next one.

• 25:40Chuck Nice?

  That was great.

• 25:41Neil deGrasse Tyson?

  That's McQuarries.

• 25:42Chuck Nice?

  Alright, here we go, um. Woo, Rick Henkel, yay Rick! What a freaking great name.

• 25:52Neil deGrasse Tyson?

  Pronounceable last name.

• 25:52Chuck Nice?

  Rick Henkel from Facebook says this. "Is there any way to capture gravitational waves and use them as an energy source? Or are we limited to observational uses of gravity waves? Uh, by the way, love the show." And, uh, the reason I love this question is because there was an episode of Star Trek where, uh, they actually, um, used gravitational waves as a method of transport because somehow they were able to get the gravitational waves to allow you to fa- uh, travel faster than warp speed.

• 26:32Neil deGrasse Tyson?

  So they're surfing the waves.

• 26:33Chuck Nice?

  Surfing the wave, and so, and by the way, you did not need an energy source. Once you created the gravitational wave, you could surf it without the, without the means of an energy source, so, you know, uh, I'm sorry, that's-

• 26:46Neil deGrasse Tyson?

  And that was a movie.

• 26:46Chuck Nice?

  That was, by the way, I was about to say, I'm talking to two astrophysicists about a make-believe science fiction-

• 26:56Neil deGrasse Tyson?

  That's alright, that's alright.

• 26:57Chuck Nice?

  And I'm just like, "Yeah, man!"

• 27:00Neil deGrasse Tyson?

  So, so Sean, let me reshape that question in another way. So, uh, when we think of light waves, you know, we come from the stars and we can capture them and measure them and do what we want, and it's energy, and, and depending on how we detect them, they'll manifest as photons, and they can tri- trigger detections in a CCD.

• 27:19Chuck Nice?

  Right.

• 27:19Neil deGrasse Tyson?

  And so we get digital photography, is how that works. So, uh, with a gravity wave, they're still, we're still detecting it as waves, not as gravitons, right? Would there be a difference in our ability to exploit it if we detected them as gravitons as distinct from waves?

• 27:36Sean Carroll?

  Yeah, I think that, uh, yeah, all these questions are sort of bundled up into the same answer, which is no, because gravity is too weak. That's, that's the basic story here. There's an enormous amount of energy emitted in gravitational waves. When the, these events that we've been recently seeing in LIGO, the gravitational wave observatory, they're seeing two black holes spiral together and make one big black hole, right? And that emits gravitational waves and you can, you can count how much energy is emitted. And for that, you know, few seconds, that the black hole's emitting gravitational waves, its total energy output is greater than that of all the stars in the observable universe

• 28:17Sean Carroll?

  emitting light. So it's really bright in the sense of emitting gravitational waves, but utterly useless in the sense of transporting energy or anything like that, just because most of the, for the most part, the gravity waves just go right through us. You don't even notice them. You need a four kilometer long vacuum tube to notice the very, very, very tiny displacement of mirrors.

• 28:41Neil deGrasse Tyson?

  He didn't have enough varies there. He had four varies, it takes like nine varies.

• 28:45Sean Carroll?

  Nine varies. Very, very, very, very.

• 28:47Neil deGrasse Tyson?

  Very, very, very, very, very, very little.

• 28:49Sean Carroll?

  Anyway, if you wanna send energy, or you wanna observe something, or something like that, electromagnetism and light will always be more efficient. The traditional thing to do is to say, you know, look, I have an object here.

• 29:03Neil deGrasse Tyson?

  Randomly found on his office.

• 29:05Sean Carroll?

  And, and look, even though the entire Earth is pulling it down with all the gravitational strength it can muster, my little electromagnetic impulses in my arm can lift it up. I win. My electromagnetism is better than the Earth's gravity.

• 29:19Chuck Nice?

  Take that, gravity, you big [BLEEP].

• 29:22Sean Carroll?

  Exactly. And that's why we're not gonna see individual gravitons, individual particles of gravity. They're there.

• 29:30Chuck Nice?

  No, I, I was gonna say, when you say we're not gonna see them, is that because they don't exist? Or is there, is there a graviton? Is there a particle?

• 29:38Neil deGrasse Tyson?

  Here's a calculation we do in like... The second month of your first class in physics.

• 29:44Sean Carroll?

  Okay.

• 29:44Neil deGrasse Tyson?

  Uh, well, right when you get into electromagnetism. So maybe the second semester of your first class in physics. You, you ask the question, what is the relative strength between electromagnetic forces and gravitational forces?

• 29:56Sean Carroll?

  Mm-hmm.

• 29:57Neil deGrasse Tyson?

  How do they compare? Right?

• 29:59Sean Carroll?

  Right.

• 29:59Neil deGrasse Tyson?

  And you can calculate that.

• 30:00Sean Carroll?

  Okay.

• 30:00Neil deGrasse Tyson?

  Right, so you know what a factor of ten is.

• 30:03Sean Carroll?

  Excellent.

• 30:03Neil deGrasse Tyson?

  Right, one, one, okay. So, you can, so you can ask, how mu- so electromagnetism is stronger than gravity.

• 30:09Sean Carroll?

  Always.

• 30:10Neil deGrasse Tyson?

  How many factors of ten? Factor ten, ten, ten, ten, ten, ten, ten, ten. You do that forty times. Is it forty or forty-two? Which is it?

• 30:20Sean Carroll?

  Eh, I'm a cosmologist, what do I know?

• 30:21Neil deGrasse Tyson?

  Call it forty.

• 30:22Sean Carroll?

  Forty and forty-two, those are the same number.

• 30:23Neil deGrasse Tyson?

  No difference.

• 30:24Sean Carroll?

  Just count big.

• 30:26Neil deGrasse Tyson?

  Well, uh, how about, um, let's use forty-two, cause it shows up in, in sci-fi literature.

• 30:31Sean Carroll?

  Okay.

• 30:31Neil deGrasse Tyson?

  Um, so, there's like forty, forty-two orders of magnitude difference in strength.

• 30:36Sean Carroll?

  Right.

• 30:36Neil deGrasse Tyson?

  Between gravity and electromagnetism. So, I, I, all Sean, Sean is saying here is that these waves are out there, but relative to everything else that's holding us together, this is a non-thing.

• 30:46Sean Carroll?

  It's, it's an issue because it's so much weaker.

• 30:48Neil deGrasse Tyson?

  It's so much weaker, so it's not that it does not exist.

• 30:51Sean Carroll?

  Right.

• 30:51Neil deGrasse Tyson?

  It exists at a level so unusable to us.

• 30:54Sean Carroll?

  Right.

• 30:55Neil deGrasse Tyson?

  That it becomes more an intellectual exercise that we were able to detect it at all, not as some way, oh my gosh, now we have a new way to, you know, make a gravitational wave weapon, you know?

• 31:06Sean Carroll?

  Right, right, right.

• 31:07Neil deGrasse Tyson?

  But, but let me ask you that, Sean. So could you surf a gravity wave? If you are sort of low enough, um, size or energy or whatever?

• 31:14Sean Carroll?

  No.

• 31:16Neil deGrasse Tyson?

  This is like fifth no, you know, this is the last time we're asking you back.

• 31:19Sean Carroll?

  You know, again, it's just so.

• 31:20Neil deGrasse Tyson?

  You are not cooperative at all. Last time. We ask is no, I'm not asking this man back on the show.

• 31:27Sean Carroll?

  It's always no but, you gotta like follow up. Uh, there's something very, very similar to that idea. I mean, gravitational waves sadly, it's just gonna go right by you, it's not gonna be very good at pushing. But what you could imagine doing is hopping into your specially designed spaceship and constructing, uh, an amount of energy, both positive energy and negative energy distributed around the spaceship, to warp spacetime around you so much that from the point of view of someone outside, you seem to be going faster than the speed of light.

• 31:59Chuck Nice?

  But you're really not.

• 32:01Neil deGrasse Tyson?

  Well, another way to say it is, isn't it true, Sean, that in general relativity, space is not constrained by the speed of light?

• 32:09Chuck Nice?

  Ooh.

• 32:09Neil deGrasse Tyson?

  Space itself.

• 32:10Chuck Nice?

  Oh, my God.

• 32:10Neil deGrasse Tyson?

  So if you move with the fabric of space.

• 32:13Chuck Nice?

  Right.

• 32:14Neil deGrasse Tyson?

  Then there's, sky's the limit.

• 32:16Chuck Nice?

  It's no telling how, how fast.

• 32:18Neil deGrasse Tyson?

  Is that, is that a fair way to characterize this, Sean?

• 32:20Sean Carroll?

  Well, I think, what I like to remember is the word relativity in, you know, general and special relativity. You shouldn't be talking about speeds at all unless you're talking about relative to what? And in relativity, in general relativity, like you say, there's a limit that says you can't move faster than the speed of light relative to something that is at the same location as you. If you're talking about the speed relative to something very, very far away, then it's a parent velocity, like you say, yeah, it can be well greater than the speed of light, but it's not really the same thing you're comparing.

• 32:51Neil deGrasse Tyson?

  Mm-hmm.

• 32:52Chuck Nice?

  Gotcha.

• 32:52Neil deGrasse Tyson?

  All right.

• 32:53Chuck Nice?

  By the way, I like, and not, not because, um, you know, that I've known him longer, Sean, but I like Neil's explanation better.

• 33:07Neil deGrasse Tyson?

  So Chuck knows who pays him.

• 33:10Sean Carroll?

  I was gonna say that, but okay, yeah.

• 33:14Chuck Nice?

  No, no, no, no, that, that.

• 33:15Sean Carroll?

  Whatever he's paying you, Chuck, I'll double it.

• 33:19Chuck Nice?

  And good night. Nah, nah.

• 33:22Neil deGrasse Tyson?

  So we gotta take another break?

• 33:23Chuck Nice?

  Okay.

• 33:23Neil deGrasse Tyson?

  And when we come back, more of Cosmic Queries with my co-host Chuck Nice and friend and colleague Sean Carroll when we return.

• 33:38Neil deGrasse Tyson?

  We're back on StarTalk. I'm your personal astrophysicist, Neil deGrasse Tyson. Chuck Nice.

• 33:43Chuck Nice?

  Yes, sir. How are you?

• 33:44Neil deGrasse Tyson?

  And we've, this is a Cosmic Queries edition.

• 33:47Chuck Nice?

  Yes, it is.

• 33:48Neil deGrasse Tyson?

  Specializing in sort of cosmological phenomena.

• 33:51Chuck Nice?

  Absolutely.

• 33:52Neil deGrasse Tyson?

  I can only take it so far. I had a few classes in it, but we've got Sean Carroll.

• 33:56Chuck Nice?

  Right.

• 33:57Neil deGrasse Tyson?

  From Caltech on video call, because he lives this.

• 34:00Chuck Nice?

  Yes.

• 34:01Neil deGrasse Tyson?

  Who you need in this, in this Cosmic Queries. And Sean, you, you tweet as well. What is your Twitter handle?

• 34:06Sean Carroll?

  I do. I'm on Twitter, Sean M. Carroll.

• 34:08Neil deGrasse Tyson?

  So Chuck, what questions you have?

• 34:09Chuck Nice?

  All right, let's jump right back into it. And I gotta get to this one early in our segment because I really, I want you guys to tackle this.

• 34:18Neil deGrasse Tyson?

  All right.

• 34:19Chuck Nice?

  Okay?

• 34:19Neil deGrasse Tyson?

  Bring it on.

• 34:20Chuck Nice?

  And this is beginner's mind at Dharma World on Twitter. And this is what he says, very simply. String theory, in your own words, please. Bang, that's it. And I love it. I love that. And, and, and so what I'm gonna ask is, uh, make pretend, which you really don't have to because I'm right here, that you're talking to Chuck Nice, and make me understand string theory. Okay, cuz now that is a challenge.

• 34:51Neil deGrasse Tyson?

  So Sean, go for it.

• 34:52Chuck Nice?

  We all know.

• 34:53Sean Carroll?

  The irony is.

• 34:54Neil deGrasse Tyson?

  Sean will do it, and then I'll tie a bow on it when he's done.

• 34:56Chuck Nice?

  Okay.

• 34:57Neil deGrasse Tyson?

  With that, alright.

• 34:57Chuck Nice?

  Alright, Sean.

• 34:58Neil deGrasse Tyson?

  For it, Sean.

• 34:58Sean Carroll?

  This is the easy question.

• 35:00Chuck Nice?

  Oh, really?

• 35:01Sean Carroll?

  That's, that's the weird thing, yeah.

• 35:03Chuck Nice?

  Okay.

• 35:03Sean Carroll?

  You know, if you think about what we know about atoms and, and molecules and things like that, they're made of particles, right? There's an electron, there's a proton. Inside the proton, there's quarks. And in quantum mechanics, these particles are just points. They're just infinitely tiny little points. So string theory is the following idea. What if, instead of points, the world was made of little loops of string? And you say, well, what is the string made of? And the answer is, no, no, no. The stringy stuff is what the world is made out of. This is the, the er stuff, the fundamental thing. And you might say, well, that's a silly, why would we ever even ask that question? Particles seem to work fairly well. If you take a string and you look at it, it's really, really tiny. It looks like a particle, so that's okay.

• 35:48Sean Carroll?

  And people invented this back in the sixties, early seventies, trying to explain the strong nuclear force, the forces that holds protons and neutrons and quarks and gluons together.

• 36:00Chuck Nice?

  Okay.

• 36:00Neil deGrasse Tyson?

  Now I'm gonna tie the bow on the thing, okay? So first of all, I, I'm gonna, I will lose this battle, but I wanna say to Sean here, standing flat footed, that I'm gonna start calling it not string theory, but string hypothesis.

• 36:14Chuck Nice?

  Ooh.

• 36:14Neil deGrasse Tyson?

  We have evolutionary theory, quantum theory, gravitational theory, string hypothesis, okay?

• 36:21Chuck Nice?

  Oh, well, you know what? He, I, I don't know if this has ever happened to you. You've just been downgraded.

• 36:28Neil deGrasse Tyson?

  I did it with Pluto. I've been down this road before.

• 36:31Chuck Nice?

  Sorry, Sean, but United is dragging you off of this flight.

• 36:39Neil deGrasse Tyson?

  So, so, and correct me if I'm wrong, Sean. If you have, if, if the universe is the strings, then depending on what the circumstances of a string is, it will manifest to us as one particle or another. So that's what, so that is what would make the string more fundamental than the particle itself.

• 36:59Chuck Nice?

  Okay, okay, yes, right, because it's the whole stuff, it's the stuff.

• 37:03Neil deGrasse Tyson?

  Kid and the kaboodle.

• 37:05Chuck Nice?

  It's everything.

• 37:06Neil deGrasse Tyson?

  Kaboodle especially.

• 37:07Chuck Nice?

  Right.

• 37:09Chuck Nice?

  Okay, I got you, yeah.

• 37:10Neil deGrasse Tyson?

  So, so, so the power of this is its capacity to explain everything. As, it's, because it's the fun, by the way, this good little historical philosophical, the word atom, proposed by the Greeks, you know what it means in Greek?

• 37:25Chuck Nice?

  Um, no.

• 37:27Neil deGrasse Tyson?

  Indivisible.

• 37:28Chuck Nice?

  Oh, wow, so it's supposedly the smallest thing that can't be cut.

• 37:31Neil deGrasse Tyson?

  Right, exactly, so you.

• 37:32Chuck Nice?

  Now we know that's not right, because we split atoms.

• 37:34Neil deGrasse Tyson?

  That's what I'm saying, so you keep dividing things, it gets smaller and smaller, and there'll be some point, we can't divide it anymore, and that was known as the atom.

• 37:41Chuck Nice?

  Right.

• 37:41Neil deGrasse Tyson?

  Okay, and then the alchemist said, wait a minute, if this is a lead atom, but I like gold atoms.

• 37:49Chuck Nice?

  I can actually rearrange this thing and make gold.

• 37:53Neil deGrasse Tyson?

  Let me, let me stir the lead to get gold, but all they're doing is stirring atoms, and if you want to make gold, you gotta get into the nucleus, but no one knew about the nucleus.

• 38:03Chuck Nice?

  Right.

• 38:03Neil deGrasse Tyson?

  So now you find that you can split atoms, and people freaked out. Atom smashers and splitters, and oh, that's where God is, that's why people freaked out. A hundred years ago, they said, oh, my gosh, what are you doing? And then we found, now you split that, now we have the fundamental particles, we have protons and neutrons and electrons, that's the fundamental particles. Then we, no, we, then we poke inside the neutron and the proton, and then you get quarks.

• 38:25Chuck Nice?

  Right.

• 38:26Neil deGrasse Tyson?

  So, Sean, what's inside a quark?

• 38:28Chuck Nice?

  Ooh, yeah, maybe the strings, that's what we don't know.

• 38:33Neil deGrasse Tyson?

  Piece of string.

• 38:34Chuck Nice?

  A piece of string.

• 38:35Neil deGrasse Tyson?

  I would be so pissed off if it's just a little bit of string.

• 38:37Chuck Nice?

  Something like string cheese. Matter of fact, I'm gonna, I'm gonna start a company called Quark String Cheese. Wow, okay, so.

• 38:47Neil deGrasse Tyson?

  So, Sean, I just, a, a, just a physics question. I can think of these strings of, of energy, can we call them that, is that fair? String, okay.

• 38:56Chuck Nice?

  Yeah.

• 38:56Neil deGrasse Tyson?

  I can, I can think of them in configuring such that one would look like a quark, one would look like an electron, I get that. How do they configure so that they would have different charges? Electrical charges.

• 39:08Chuck Nice?

  Okay, uh, now.

• 39:09Neil deGrasse Tyson?

  How do you do that?

• 39:11Chuck Nice?

  I'm, uh, listen, this is, this is outside my pay rate, my pay grade.

• 39:17Neil deGrasse Tyson?

  Cause how do you just wiggle a string?

• 39:18Sean Carroll?

  That's not the simple question. You know, the simple question is why, what is string theory? Why they have different charges? The, the simple version of the answer is because they're vibrating differently.

• 39:29Neil deGrasse Tyson?

  So what are you saying? It can, it can vibrate in a negative way and in a positive way. And then you get.

• 39:34Sean Carroll?

  Yeah, or you know, you can imagine going around the string clockwise or counterclockwise. There's different things that can happen. Uh, different ways, the strings can be either loops.

• 39:43Chuck Nice?

  There's different loops to the string? Is that what it is? Is like different little loops?

• 39:46Neil deGrasse Tyson?

  So what are you saying? So as you configure the string in different modes, it manifests to us as different particles and different charges. This is what you're saying.

• 39:54Chuck Nice?

  Okay, okay.

• 39:55Sean Carroll?

  That's what I'm saying.

• 39:56Neil deGrasse Tyson?

  Yeah, yeah.

• 39:57Chuck Nice?

  Man, this is.

• 39:57Sean Carroll?

  Now you're a professional string theorist. This is awesome.

• 40:01Neil deGrasse Tyson?

  No, it's cool and it's hugely promising and powerful.

• 40:03Chuck Nice?

  Right.

• 40:04Neil deGrasse Tyson?

  But it, it's not without its critics is my point. Because of the, can you predict this experimental, uh, you make, can you experimentally verify the predictions made? Is it beyond our reach? Is it, you know, so the whole book's criticizing string theory for this reason. But I, but it's cool. It doesn't make it any less cool. Is my, is my point.

• 40:25Chuck Nice?

  Super cool. All right. Man, that was a, hey, uh, what a great, great question, uh, beginner's mind.

• 40:31Neil deGrasse Tyson?

  We're coming up on the lightning round.

• 40:32Chuck Nice?

  Lightning round. All right, guys. Here we go.

• 40:35Neil deGrasse Tyson?

  Give it to us. Go.

• 40:36Chuck Nice?

  Time for the lightning round. Uh, Mark Eric Sevenson says, or Svenson says this from Facebook. Are gravitational waves significant enough to affect experiments in particle accelerators? Ooh, good question.

• 40:51Neil deGrasse Tyson?

  All right, Sean, what do you have?

• 40:52Sean Carroll?

  No.

• 40:53Neil deGrasse Tyson?

  Good answer. All right.

• 40:54Chuck Nice?

  And we are off to our flying start. Oh, there we go.

• 40:59Neil deGrasse Tyson?

  Okay.

• 41:01Chuck Nice?

  All right, Dee Saltzman from 1983 from Instagram says this. Uh, there is no way that this is the first big bang. So why do all of our theories have the universe ending in nothingness with no matter? Ooh.

• 41:15Neil deGrasse Tyson?

  Ooh. Let me, let me reword that a little bit.

• 41:19Chuck Nice?

  Okay.

• 41:19Neil deGrasse Tyson?

  So Sean, Sean, how is it that we could be in the only one universe that had one beginning and one ending? How's that even possible? Why aren't there others of these out there? And why, if there are, why don't we know about it? And what's up with all of that?

• 41:34Sean Carroll?

  I think there could be a lot of others. I wrote a whole book about it. You can buy that one too, From Eternity to Here. But we don't know.

• 41:40Neil deGrasse Tyson?

  Oh, snap. Read the book. But what'd you say? I missed your last bit.

• 41:45Sean Carroll?

  But we don't know is the final answer. That's it's, maybe this is the only universe. We gotta be humble about what we do and don't know.

• 41:51Neil deGrasse Tyson?

  But we agree experimentally that this universe in its only ever existence is on a one-way trip.

• 41:57Chuck Nice?

  A one-way trip.

• 41:58Neil deGrasse Tyson?

  One birth and a, and a.

• 41:59Chuck Nice?

  Nothing.

• 42:01Sean Carroll?

  I can't promise you that in the future, our universe will not give birth to other baby universes.

• 42:05Neil deGrasse Tyson?

  Oh.

• 42:06Chuck Nice?

  Oh, there you go.

• 42:07Neil deGrasse Tyson?

  Ooh.

• 42:07Chuck Nice?

  Right on.

• 42:08Neil deGrasse Tyson?

  Okay.

• 42:09Chuck Nice?

  I'm the baby daddy of the universe.

• 42:11Neil deGrasse Tyson?

  Baby. Come be baby daddy.

• 42:13Chuck Nice?

  The baby daddy happening. Right, here we go.

• 42:17Neil deGrasse Tyson?

  So Sean, this would be, there'd be some, uh, uh, sector of the universe that, that spawns another one. Uh, within the one that we currently enjoy.

• 42:26Sean Carroll?

  Not within, in addition to, we would really get something that pinches off and goes its own way. It's a separate universe.

• 42:31Neil deGrasse Tyson?

  Okay, all right.

• 42:32Chuck Nice?

  There you go.

• 42:32Neil deGrasse Tyson?

  I'll give you that.

• 42:33Chuck Nice?

  Right. Night.

• 42:34Neil deGrasse Tyson?

  All right, let's move on. Next one.

• 42:35Chuck Nice?

  Okay, O Galanis wants to know this. People keep asking why there is something instead of nothing. Why is nothing normal or expected while something needs a special explanation? It's a little existential, but I know what he's saying.

• 42:49Neil deGrasse Tyson?

  Yes, we go. Sean, do it.

• 42:51Sean Carroll?

  Yeah, I think the answer is why not have something rather than nothing? The, the subtext of that question is exactly right. Something is just as natural and expected as nothing would be. There's not that much to be explained.

• 43:01Chuck Nice?

  Okay, that was a, that, listen, it's the lightning round, people.

• 43:04Neil deGrasse Tyson?

  That's it.

• 43:04Sean Carroll?

  Lightning round.

• 43:05Chuck Nice?

  It's a lightning round.

• 43:06Sean Carroll?

  I could go off.

• 43:07Chuck Nice?

  Nope, that was it.

• 43:08Neil deGrasse Tyson?

  He's doing good, too.

• 43:09Chuck Nice?

  He is, he's killing it, he's killing it. Caleb Bingham from Facebook wants to know this. Do you think that dark matter might be regular matter from a parallel universe that doesn't react to light or in our universe? Making it possible for us to see it? Thank you, Caleb from Bingham.

• 43:25Neil deGrasse Tyson?

  My answer to that is yes. Sean, what's your answer?

• 43:29Sean Carroll?

  My answer is no, because it's not just that it's dark, it's that it behaves differently. Dark matter doesn't dissipate and clump together like ordinary matter does.

• 43:37Neil deGrasse Tyson?

  No, no, but wait, Sean, if this is, if this is gravity leaking from an adjacent universe, because as I understand, uh, I don't claim full understanding of, of the limits of field theory, but as I understand it, gravity is not contained within the spacetime in which it's found, isn't that correct? It can leak out. Okay, okay. If that's the case, there could be an adjacent universe whose gravity we feel made by ordinary matter in that universe, but here we mysteriously. And that's why it doesn't behave the same way. And then we're looking at, we're, how come it's not clumping? Because it ain't your matter. Right. It's somebody else's matter. Okay, Sean, I love this gravity smackdown.

• 44:16Sean Carroll?

  It would clump with itself in its universe.

• 44:19Neil deGrasse Tyson?

  Yes.

• 44:19Sean Carroll?

  It would still be clumping.

• 44:20Neil deGrasse Tyson?

  Yes, in its universe, but in our universe it wouldn't, because all we're feeling is the gravity of it.

• 44:25Sean Carroll?

  But we would feel the gla- gravity of clumpy stuff.

• 44:28Neil deGrasse Tyson?

  Yes.

• 44:28Sean Carroll?

  Not of stuff that is all spread out, and it is spread out.

• 44:31Neil deGrasse Tyson?

  Caleb, here's your answer.

• 44:32Chuck Nice?

  We don't know.

• 44:33Neil deGrasse Tyson?

  No.

• 44:35Neil deGrasse Tyson?

  I'm gonna think about Sean's point there. Next one. Next one. Like, one more question.

• 44:39Chuck Nice?

  One more, one more. Um, this person is trying to mess with me. I'm a human boy.

• 44:45Neil deGrasse Tyson?

  Human boy, okay.

• 44:46Chuck Nice?

  I'm a human boy, that's the, the, what does the general theory of relatively tell us about the fabric of spacetime itself?

• 44:54Sean Carroll?

  Yeah, it tells us that the fabric of spacetime has a life of its own, that it's dynamical, that it moves and stretches and warps in response to the stuff that we see in the universe.

• 45:05Neil deGrasse Tyson?

  That was a damn good question. I mean, damn good answer, Sean. So I'm gonna, I'm gonna quote, was it Einstein or John Wheeler who said, uh, "Space tells matter how to move, and matter tells space how to curve." Ooh.

• 45:20Sean Carroll?

  That was Wheeler, exactly right.

• 45:21Neil deGrasse Tyson?

  John Wheeler.

• 45:22Sean Carroll?

  He's a fifty guy. He would have been a good on lightning rounds, too bad.

• 45:26Neil deGrasse Tyson?

  Actually had him for relativity in physics in graduate school. And I met my wife in relativity class.

• 45:32Chuck Nice?

  Ah, well, that's the, that's the only thing that's relative that means something.

• 45:37Sean Carroll?

  He became your relative.

• 45:39Neil deGrasse Tyson?

  Thank you, Mr. Wheeler. Just a quick question here before we take it out. I'll give my own question to Sean.

• 45:45Sean Carroll?

  Okay.

• 45:46Neil deGrasse Tyson?

  And I'm not always on video call with the, with the dude.

• 45:48Sean Carroll?

  Alright.

• 45:48Neil deGrasse Tyson?

  So Sean, what is the chances that we are in sort of a false vacuum and could possibly tunnel to a, a more stable state in the universe, changing all the known laws of physics and we all die?

• 46:03Sean Carroll?

  Yeah, the chances are depressingly large.

• 46:06Chuck Nice?

  What a happy question, thank you.

• 46:07Sean Carroll?

  Very large.

• 46:08Neil deGrasse Tyson?

  Just to clarify, so you can imagine me at the bottom of a, of a well, okay? And if you displace a, a ball up the side of the well, it'll roll back to the bottom. So it's kind of stable, okay? But suppose there's a deeper well adjacent to this one that is lower. If this ball ever saw that, it would go there. It would have to go there. It would have to go there, right? So if you sort of pushed it up the hill, it'll roll down, it'll never come back to that high state. But quantum physics says you can actually tunnel through the walls that could separate two states. And tunnel, just. Right. Just burrow right through. Then you're here. You're right. And if you show up here, you, you sink to a whole other thing. And Sean, you're, you're a betting man, you're saying, oh my gosh, this could really be true.

• 46:54Sean Carroll?

  Yeah, it could really be true. Again, a bad news, good news situation. The bad news is, uh, it's very plausibly true. And in fact, there's a little bit of a hint, right? Because for good reasons, you might imagine that the true vacuum, the vacuum that is the most stable and wouldn't decay, would have exactly zero energy in empty space. It would have exactly zero vacuum energy or cosmological constant. A false vacuum that was temporary and will eventually decay would have a non-zero, positive energy in empty space. Our universe has a positive energy in empty space. That's exactly the kind. That's the bad news. The good news is, we wouldn't know it, because we would be instantly dead if we did underwent this transition. No time to worry.

• 47:39Neil deGrasse Tyson?

  It doesn't even happen at the speed of light, it happens instantly.

• 47:43Sean Carroll?

  Instantly. It's essentially the speed of light, but you don't see it coming, because the doom comes just as fast as the warning of the doom coming. That's the good news.

• 47:52Chuck Nice?

  Oh, God, I'm gonna sleep so well.

• 47:55Sean Carroll?

  It's cosmically reassuring.

• 47:58Neil deGrasse Tyson?

  Sean, it's been great to have you on the show. Your latest book, The Big Picture, with the audacious subtitle, "On the Origins of Life, Meaning, and the Universe Itself." Sean, always great to chat with you. Thanks for keeping up the fight over on the West Coast. And we'll try to maybe get you back on the show a couple more times, if we can.

• 48:18Sean Carroll?

  Happy to be on, thanks so much for having me.

• 48:19Neil deGrasse Tyson?

  Excellent, dude. Chuck, always good to have you. This was fun. On StarTalk. Great show. I'm Neil deGrasse Tyson, I've been your host. This has been StarTalk, and as always, I bid you looking up.