Cosmic Queries – Quantum & Aliens with Charles Liu

Are we thinking about the fundamentals of the universe wrong? Neil deGrasse Tyson and co-hosts Chuck Nice and Gary O’Reilly answer grab bag questions about aliens, gravitons, and the big unknowns with astrophysicist Charles Liu.

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

• 0:00Neil deGrasse Tyson?

  Up next, StarTalk Special Edition. I've got Chuck Nice, I've got Gary O'Reilly, and our Geek in Chief, Charles Liu, to help us decode some of the deepest questions asked by our Patreon members. Including, for example, are there any questions that astrophysicists think about that we don't have an answer to yet? What's up with that? Also, where are the terrestrials, extraterrestrials having conversations with each other? Can we decode it? Is there some special encryption that they're using that we will never know how to break into it? We're gonna learn about that. Also, a little bit about quantum field theory. What is it? Why does it matter?

• 0:44Neil deGrasse Tyson?

  Coming up on StarTalk.

• 0:48Neil deGrasse Tyson?

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

• 1:02Neil deGrasse Tyson?

  This is StarTalk Special Edition. And you know what that means? We got Chuck Nice. Yes. Hey, hey. Got Gary O'Reilly? Hi, Neil. All right, and we're doing Cosmic Queries Grab Bag. And I think I'm OK with a grab bag, but generally, we need bigger guns than that. So we went into the silo, typed in the launch codes, and out came Chuck Liu, Charles Liu. How you doing, dude? Hi, Neil. Hi, everybody. Welcome back to StarTalk. Thank you. You know, I'm unworthy. I can get them to the, get them near the edge. You could take us off the edge and take us into orbit. And that's what we need you for in these situations.

• 1:45Neil deGrasse Tyson?

  We got questions from our Patreon members. So, so this is Grab Bag. So what do you guys have? What did you bring to the table?

• 1:51Gary O'Reilly?

  All right, let me jump in first. Thomas Cochrane from Kansas City. Are we thinking about the fundamental slash basic components of the universe incorrectly?

• 2:03Gary O'Reilly?

  Perhaps the universe's most basic building blocks are fields instead of particles. What merit does quantum field theory have? And there's already a "thank you" tagged on the end.

• 2:14Charles Liu?

  Oh, that's so nice. Well, the bottom line is, you're both right. Whether you're thinking in particles or in a field. In fact, quantum field theory is in fact trying to knit together quantum mechanics, special relativity, and classical field theory.

• 2:31Gary O'Reilly?

  Oh.

• 2:32Charles Liu?

  Field theory is what? It's pretty straightforward. We, as particles, interact with fields, such as a gravitational potential field of the Earth, or some electromagnetic field, something like that. So different kinds of object, depending on their properties, interact in different ways with different fields. Now, if you think instead that we, as particles, are actually not static things, solid things or whatever, but are rather waves or fields, but in sort of strange, unusual concept, then

• 3:10Charles Liu?

  you can just mathematically express every particle in our bodies as a field, interacting with a larger field, or with other kinds of fields, maybe the Higgs field, the thing that provides mass. So, we're not looking at it wrong, so much as we're looking at it in an incomplete fashion. Right? One of the big things about the universe, right, Neil, is that we still can't knit general relativity and quantum mechanics together. So people are using different approaches to try to get at the same answer, and it's totally okay if you're not able to address everything with your theory, as long as somebody else is addressing the other stuff with another theory, maybe we can bring them all together.

• 3:50Neil deGrasse Tyson?

  Yeah, I would add a nuance to that, that it's not that there are fields and there are particles and never the twain may meet. It is the very interaction of fields and particles that is the universe. That is what, that is the operations of the universe. So one of those would not be more fundamental than the other. When they need each other to manifest the universe as we have come to know and love. Now, we might say something else, we might say, is there something more fundamental than both the field and the particle? And, and Charles, would string theorists jump into this at this point?

• 4:23Charles Liu?

  They might claim.

• 4:24Neil deGrasse Tyson?

  Yeah, they, they want to claim that.

• 4:27Charles Liu?

  If the claim is that a particle is just a manifestation in our spacetime of what we see of a more complex object. And the interactions of strings to some extent might either supplant or supersede interactions between fields or interactions between particles.

• 4:46Neil deGrasse Tyson?

  Right, right, right. So that would be a deeper understanding. But we're not choosing particles versus fields, right? No, they're both working together very nicely.

• 4:54Charles Liu?

  That's right.

• 4:55Neil deGrasse Tyson?

  Worlds are colliding.

• 4:58Neil deGrasse Tyson?

  Think cats and dogs are sleeping together.

• 5:02Charles Liu?

  Yeah, that does happen.

• 5:04Neil deGrasse Tyson?

  That is a Bible verse, isn't it? That's one of the signs of the apocalypse, right? So who's next up?

• 5:09Chuck Nice?

  All right, how, how, how about Brandon Cortazar? Oh, look at that. And Brandon says, hello Neil, hello Charles. This is Brandon from Scranton, PA. My question to both of you.

• 5:23Charles Liu?

  Hi, Brandon from Scranton.

• 5:24Chuck Nice?

  Yeah. Say hello to the people of Dunder Mifflin. My question to you both is, what is the one thing that is currently unknown in the science and astronomy world? That you wish to find the answer to before your time on this earth comes to an end?

• 5:41Charles Liu?

  Oh, oh, why so, why so ominous?

• 5:47Chuck Nice?

  Yeah. The way that I, I, I had no other choice.

• 5:50Charles Liu?

  You changed that voice to make it sound like to an end.

• 5:54Neil deGrasse Tyson?

  The words required him to say it exactly the way he did.

• 5:58Chuck Nice?

  They did, you know? I mean, we, we are speaking of your ultimate demise.

• 6:06Chuck Nice?

  No, Chuck, it's your ultimate demise.

• 6:11Neil deGrasse Tyson?

  Doesn't weigh the same, I guess.

• 6:12Chuck Nice?

  Right, exactly.

• 6:15Charles Liu?

  Well, Neil, you have one. I, I, I think I know one. I got lots. You want a second? Okay. The one I want to know, I would like to know, is, does life exist outside of our solar system, outside of our Earth, that's based on DNA? I imagine, based on all the scientific knowledge, there is life out there. And when people ask me, do you think there are aliens? I say, yes. But the question is, will we recognize them if we see them? Would they have developed the same way that we did? So my question is pretty specific, because, because Brandon asked about being scientific, right? I gotta narrow it down as to just saying, is there alien life? But is there alien life based on DNA? That's what I would like to know.

• 7:00Chuck Nice?

  How, how Prometheus of you.

• 7:03Neil deGrasse Tyson?

  It is, it is. But wait, Charles, what you really mean is, not is it based on DNA, you, you have, the broader question is, because that's just a yes, no. The question is, if there is alien life, on what system of chemistry does it base its identity? Be it DNA or anything else?

• 7:22Charles Liu?

  Sure. That, that would be the extension of my question.

• 7:26Neil deGrasse Tyson?

  Yes, yeah, okay.

• 7:28Chuck Nice?

  Right, but if, if it is based on the DNA which we find in all human life, and, sorry, in all life on this planet, all life on this planet, okay, we share that DNA, then that would mean, most likely, that we came from someplace else.

• 7:46Neil deGrasse Tyson?

  It could mean that, but it wouldn't have to. I'll tell you why.

• 7:48Chuck Nice?

  It wouldn't have to.

• 7:49Charles Liu?

  A common ancestor.

• 7:50Chuck Nice?

  But, but, but it'd be a very likely scenario that we came.

• 7:56Neil deGrasse Tyson?

  No, no. All you have to do is look at the strand, look deep in the strand of DNA, see if it matches anything here. If it doesn't match anything, it's a complete separate genesis.

• 8:04Chuck Nice?

  Completely separate.

• 8:04Neil deGrasse Tyson?

  Correct, correct.

• 8:05Chuck Nice?

  Right. But if there are markers that match.

• 8:08Neil deGrasse Tyson?

  No, then we got it.

• 8:09Chuck Nice?

  That means that we share something that's out there.

• 8:12Neil deGrasse Tyson?

  And, and Charles, isn't it true in Star Trek, that they finally fessed up?

• 8:16Charles Liu?

  Season seven. Season seven, Star Trek: The Next Generation, the episode called The Chase. Yes.

• 8:22Chuck Nice?

  Damn.

• 8:23Gary O'Reilly?

  That's why he's always.

• 8:24Charles Liu?

  Jean-Luc Picard's old anthropology professor figures out that there's something really cool, but unfortunately, he dies before he can find the answer. So the card takes the Enterprise all around and they find out indeed that the reason all the Klingons and all the Romulans and all the Lurkans and all the humans have two arms, two legs and one head is because they share a common genetic ancestor.

• 8:44Chuck Nice?

  A common ancestor. Right.

• 8:47Gary O'Reilly?

  So what if, what if this isn't a DNA commonality here? And you know, you end up with Fermi's paradox and we're, we're, where are they all? That we're just not looking in the right way. They've turned up and they're all gas-based. And it's.

• 9:03Charles Liu?

  And this is why I think that Neil's extension of my question makes sense.

• 9:09Gary O'Reilly?

  Yeah.

• 9:10Charles Liu?

  If we are wise enough or insightful enough to look for life in ways that we don't have it here on Earth, we may find it much more quickly than you think. Or you can take sort of the Edward Snowden idea and think that any intelligent species out there will do its best to hide its presence from anybody else so as to protect their privacy.

• 9:32Chuck Nice?

  Oh, their size. Okay.

• 9:35Charles Liu?

  And there's a Star Trek: Next Generation episode about that too, where the Enterprise goes into an environment for a bunch of very shy aliens. And they usually find a way to sort of push the, anyone who comes in away. But the Enterprise is too good. They show up and so they wind up having to interact with the aliens and then they have to. Yeah.

• 9:53Chuck Nice?

  Well, there's one where they literally pushed the Enterprise away with a repulsor beam.

• 9:57Charles Liu?

  Oh, yeah.

• 9:57Chuck Nice?

  As they approached the planet. But yeah.

• 9:59Neil deGrasse Tyson?

  Well, actually, there's a branch of the military that concerns itself with this. There's an interesting phenomenon. So if I send you a signal and you decode it, I don't want you to decode it, right? So the fact that you know it's a signal is because it looks different from everything else that you're otherwise coming to your detector. So what I want to do is encode it so that you can't figure out what's in it. And the perfect encoding of my signal is where when you receive the signal, it looks completely like noise. Because if there's any lingering structure to it, then you hand it over to the cryptographers.

• 10:42Neil deGrasse Tyson?

  And then they decode the structure and they'll find the message within it. But if I have a key that will turn my message into something that's statistical noise to you,

• 10:55Neil deGrasse Tyson?

  then all- Then my recipient already knows to go ahead and decode that. No, no, you would have to have the key. No, I'm saying the recipient has to- Has the key. That's why you're sending it to them. But here's my point. The argument then is the most sophisticated forms of communication will be indistinguishable from noise. From just- And the civilization will just disappear into the din of the background. And you will never know what anybody's saying ever again. That's a limiting case of encrypted messaging. Just put it out there. Just blast it with a bunch of static. Why waste your time doing that? Well, because your signal would still be visible within it.

• 11:36Neil deGrasse Tyson?

  Unless your signal was encrypted to look like static. Correct. Yeah, it is. No, so my answer to that question is I want to know if, it's a two-part question. I want to know if we are smart enough to even answer the questions we have posed. Hmm. Or better yet, are we smart enough to even know what questions to ask?

• 12:06Neil deGrasse Tyson?

  That's the, I want the answers to those two questions. Hmm.

• 12:12Neil deGrasse Tyson?

  We're still asking that answer.

• 12:13Gary O'Reilly?

  But isn't this where AI comes in, Neil? Where we set it up to ask for the things that we haven't thought to ask for, to look for the things we haven't yet thought to look for. And analyze their presence.

• 12:25Neil deGrasse Tyson?

  We put it, put it to work immediately. Because I can tell you this, a chimp will not know to ask the question, for example. Uh, can the rotation rate of Earth slow? Because an earthquake changed the moment of inertia of the rotating sphere. Not even Bubbles could ask that? No. I don't know, Neil. I mean, probably not. That is so removed that they don't even know that's a question. So I want to know, are there those kinds of questions we could be asking about the universe? And we're not even there yet. And even if we're there, will we know to ask the question? That's the question I want answered. Let's ask Bubbles at Chimp.

• 13:07Neil deGrasse Tyson?

  All right, next question. Keep it coming.

• 13:08Charles Liu?

  Those are great answers. Go ahead, Gary.

• 13:11Gary O'Reilly?

  Bill Whistle, or Wesale, Wesale, there's a number of ways you can pronounce this. Uh, he's from Texas Hill country.

• 13:18Neil deGrasse Tyson?

  There's probably only one.

• 13:19Gary O'Reilly?

  I know, but he even admits he'll probably get it wrong. Since time travel causes mass to disappear in one space-time and appear in another, wouldn't that require a mass-to-energy conversion in the scene, in the original space-time, and an energy-to-mass conversion in the destination? And wouldn't that essentially be a huge nuclear bomb, or reverse?

• 13:43Charles Liu?

  Hmm. Hmm. Okay. Well, let me see if I understand the correction correctly. I'm, I'm going to answer. Cause I, I was, I was about to say, I don't get what he's asking. I'm gonna answer the question.

• 13:53Neil deGrasse Tyson?

  And before, and before you answer, Charles, so, so Gary, look me in the eye, okay? Repeat after me. Nuclear.

• 14:01Gary O'Reilly?

  Nuclear.

• 14:02Neil deGrasse Tyson?

  Thank you. Not nuclear.

• 14:04Gary O'Reilly?

  Nuclear. Thank you for, thank you for the correction.

• 14:09Neil deGrasse Tyson?

  Nuclear. You're not George W. Bush.

• 14:12Gary O'Reilly?

  Okay. Thank you for that, thank you for that distinction.

• 14:16Neil deGrasse Tyson?

  Okay. On this show, it's nuclear. Okay, go.

• 14:21Charles Liu?

  Okay. So to avoid a nuclear explosion, the way that we would solve this problem is?

• 14:29Gary O'Reilly?

  Much appreciated.

• 14:33Neil deGrasse Tyson?

  That's the worst kind of explosion.

• 14:34Charles Liu?

  Gary, you pronounce nuclear however you want.

• 14:36Gary O'Reilly?

  I know.

• 14:37Charles Liu?

  You'll still be part of the nuclear family of StarTalks.

• 14:39Gary O'Reilly?

  Thank you.

• 14:40Neil deGrasse Tyson?

  Okay.

• 14:40Charles Liu?

  Oh, hilarious. All right, here's the story. I am assuming that what the question is asking him is time travel backwards. And in a large jump, like say from here now to Jurassic times, or to the sinking of a Titanic, or something like that, right? Because we are always moving through time anyway. When I am here, and then an hour from now, I move down the street, you know, to get an ice cream cone or something like that. Uh, then what'll happen is that... I have just moved in space and time. And there was no nuclear explosion.

• 15:21Charles Liu?

  So the question I think is being asked is, is there a scenario where if you're moving not the way we ordinarily move through spacetime, would that cause a contradiction and some sort of huge energy release because mass has been displaced and there's E equals mc squared, things like that?

• 15:37Neil deGrasse Tyson?

  Wait, wait, are you sure the question isn't really your mass changes as you move fast? So are you getting that mass from some other place? Is that getting converted out of some form of energy or vice versa?

• 15:51Charles Liu?

  That could be the question too. Maybe, I don't know. That could be the question too.

• 15:54Neil deGrasse Tyson?

  I'm not sure.

• 15:55Charles Liu?

  So anyway, yeah, the bottom line is it's a great question, but we're not exactly sure what the answer is because there are ways to interpret that question. Bottom line is, I would say that generally speaking, time travel forwards, you know, which was what we do, and occasionally backwards, like what antimatter particles do, does not necessarily have to cause an E equals mc squared like release of energy. You can do it in other ways.

• 16:19Neil deGrasse Tyson?

  Joel, did you just say antimatter moves backwards in time? You just said that, didn't you?

• 16:22Charles Liu?

  I did say that you could think of antimatter as backwards traveling.

• 16:26Neil deGrasse Tyson?

  Oh, okay. He's doing a, he's doing the Enrico Fermi thing on us here.

• 16:29Charles Liu?

  Am I correct? No, correct me if I'm wrong.

• 16:31Neil deGrasse Tyson?

  You're correct. Yeah, you're correct. You're correct.

• 16:33Charles Liu?

  Okay.

• 16:34Neil deGrasse Tyson?

  It was, it was discovered, part of the discovery thinking that led to the prediction for antimatter was antimatter would be indistinguishable from regular matter, but moving backwards through time. And then they figure, well, everything's moving forward through time, so maybe it's a new kind of matter called antimatter. So that's how that came about. Pretty wild.

• 17:05Neil deGrasse Tyson?

  Okay, give me some more.

• 17:06Chuck Nice?

  This is anthropoc cosmic Dylan. He says, Neil, in cosmic queries, you make the distinction between intelligence and life. Other than the common ways we transmit messages like radio and light, could we be bombarded with measurable or tangible transmissions and just not know it? Thanks, Dylan from San Diego.

• 17:25Neil deGrasse Tyson?

  Yeah, that relates to what we just said a moment ago.

• 17:27Chuck Nice?

  We just said that, yeah.

• 17:28Neil deGrasse Tyson?

  Yeah, I mean, we just talked about that. If the civilization wants to be noticed? Their signal should look different from the background noise of the universe. Otherwise, how could they could expect us to pick it up? I would assume they're smart enough to arrive at that conclusion. But if they wanted to talk about us without us knowing, which would be the alien equivalent of pig Latin in front of children, okay? Or some, you know, way that you do that. They would, they would, as we said earlier, they would encode their message. You need a key and with that key,

• 18:09Neil deGrasse Tyson?

  it would be able to decode complete noise into the signal that you put there. But the real issue, because it's, there's an issue here. Real issue is how did they get the key in the first place?

• 18:21Charles Liu?

  X name on the EK.

• 18:24Chuck Nice?

  Yeah, I'm gonna say the key is pig Latin.

• 18:28Chuck Nice?

  Wouldn't it be funny if they just sent us a message in pig Latin? Al yay, ar yay, ooh yay.

• 18:35Charles Liu?

  Or Ubi dubby, Ubi dubby. There's a great one.

• 18:38Gary O'Reilly?

  So Neil, do we need AI to, to build us a 21st century Enigma machine?

• 18:45Neil deGrasse Tyson?

  Yes.

• 18:46Gary O'Reilly?

  Okay.

• 18:47Neil deGrasse Tyson?

  I think AI will do things that we don't know how to, we can't figure out how to do. By the way, Charles and I, as astrophysicists, have been invoking the brilliance of computers from the beginning and not just doing rote tasks, but have it do tasks where it's going to discover stuff that we would glaze over if we had to review that much data or just find things that are weird or wacky. So now we can get it to try to decode or to invent a code that could be sent? Sure, AI, you know, we don't fear AI the way everybody else is right now.

• 19:18Gary O'Reilly?

  Okay, it's not in charge just yet.

• 19:20Chuck Nice?

  You guys, you guys, you guys are gonna destroy us all. I see.

• 19:25Charles Liu?

  I already know the name of our robot overlords.

• 19:28Neil deGrasse Tyson?

  Yeah, but Charles, I don't want to speak for you, but I think we've been using the powers of computer ever from the beginning. And all of a sudden, a computer can now compose your term paper and everyone loses their shit because it stepped into the world of, of, of, of the liberal arts.

• 19:44Charles Liu?

  Those, those term papers are like C plus, E minus at best. I wouldn't worry.

• 19:48Neil deGrasse Tyson?

  I'd agree. If you really, if you really look at, they may get better.

• 19:51Charles Liu?

  In my most recent final exam, I had for my students the following question. Type the following question into an artificial intelligence language generator, and now tell me what the answer is wrong about.

• 20:07Chuck Nice?

  Interesting. So you trick these people into using AI. They're like, damn, this guy won't even let us cheat.

• 20:14Charles Liu?

  It's a matter of it's a matter of them understanding what you need to know today. Right. If we can't be better than some free app you can get on the internet, then what is your value to an organization or to a graduate program or to a company? Right. So you should learn how to use them, see their weaknesses, and use your education and your thought processes to make you more valuable. And that's how we must move forward in all of education. If we teach people exactly the same way we did in the 19th century, you know, which unfortunately, a lot of times we do, especially with math and science. Right. What are we giving them? What is the advantage that they're getting from their education?

• 20:53Neil deGrasse Tyson?

  Wait, Chuck, Gary, Gary, I think Charles Liu is the overlord.

• 21:00Neil deGrasse Tyson?

  All right. So keep going. What else? Who's next up?

• 21:03Gary O'Reilly?

  Okay, next up, Nathan Hill, right? Nathan Hill's from Austin, Texas, and he did go to your Cosmic Perspective talk, as was the Q and A when you were down there, Neil.

• 21:12Neil deGrasse Tyson?

  I was there, yes. Yes. I gave the talk, yes.

• 21:14Gary O'Reilly?

  My question is regarding gravitons. If gravity is an effect of mass warping spacetime, where does the need for a graviton fit into the relativistic model?

• 21:25Neil deGrasse Tyson?

  Ooh, I think I have an answer for this. But Charles, you got it or what?

• 21:29Charles Liu?

  Well.

• 21:30Neil deGrasse Tyson?

  I'll give my best answer. You fix it up, okay? So if you have a piece of mass sitting there in space, there's the distortion of space and time. Okay, there it is. It's a it's a it's the fabric responding to the existence of the mass. Now you poke the mass. You either collide two black holes, you jiggle it, you shake and bake it, and a ripple gets sent. That ripple moves at the speed of light, and the quantum analog to that ripple is a graviton moving at the speed of light. And so, but the fabric shape itself is not the graviton. That's my understanding of this, Charles.

• 22:12Charles Liu?

  I think you've said it exactly correct. Uh, the, another way to think about it is the following. The graviton is a particle that's been proposed but never been detected. And the reason it was proposed is because we want to try to fit gravity into quantum physics. Right? The theory of relativity that Einstein came up with did not have in it this idea that you had to had a particle transmitting gravity. But once we built quantum theory and quantum field theory and all those kinds of things, and we got the sense that in order for any one particle to interact with any other particle, a third particle has to mediate the transfer of something between those two.

• 22:57Neil deGrasse Tyson?

  This is the field theory.

• 22:58Charles Liu?

  That's right. And so people said, well, if gravity is indeed a field that generates force, then there must be a particle that transmits that force. Let's call it the graviton. But it doesn't fit well in the current standard model of particle physics. In fact, you don't need the graviton to do any of those things with quarks and fermions and bosons and, and all those kinds of neat things. So at the moment, gravitons remain a mystery and they're a placeholder for some more sophisticated physical theories that we don't have yet that will link quantum mechanics with general relativity.

• 23:38Neil deGrasse Tyson?

  We have nonetheless detected gravitational waves.

• 23:40Charles Liu?

  Yes.

• 23:41Neil deGrasse Tyson?

  So that's a very Nobel Prize all around for that.

• 23:44Charles Liu?

  That's right.

• 23:44Neil deGrasse Tyson?

  And so.

• 23:45Charles Liu?

  Good deal. Numerous people do think that the gravitational waves are essentially in direct confirmation of the existence of gravitons.

• 23:52Neil deGrasse Tyson?

  Yeah.

• 23:53Charles Liu?

  I don't know.

• 23:54Neil deGrasse Tyson?

  Yeah.

• 23:54Gary O'Reilly?

  So basically what you're saying is we rebuilt the engine and we've got this other stuff left on the side. But we know it's important somewhere, but we can't quite work out where it has to go in the thing.

• 24:06Charles Liu?

  Yeah. Then you start the engine and then your car blows up and you know, oops, that should have gone there.

• 24:11Neil deGrasse Tyson?

  Yeah, but oddly that doesn't happen. That's the weird thing about it. Everybody I know is rebuilt in engines. There's always some parts. Yep.

• 24:19Chuck Nice?

  It's the, it's the universe's equivalent of an Ikea furniture.

• 24:24Charles Liu?

  That's right. Why do I have this extra Allen wrench?

• 24:27Chuck Nice?

  What the hell? What is that? Why is all this stuff left over? But you know, it works. The chair works. It works. It works. All right. This is Johnny, and that's all he says. Uh, but Johnny says, hello, Charles. Hello, Neil. In a prior episode, Neil mentioned that Hawking radiation process occurs due to the intense gravitational energy directly around the event horizon. It, is it really because of the curvature that it's so intense that it manifests into actual energy? Or is it just the energy of stuff it's sucking in? I have always thought that gravity was just merely potential energy.

• 25:07Charles Liu?

  So there's a lot to unpack in that question, Johnny.

• 25:09Neil deGrasse Tyson?

  So let me, let me rehand it to you, Charles.

• 25:11Charles Liu?

  Yeah.

• 25:11Neil deGrasse Tyson?

  So tell us the difference between just the gravitational field and, and what we think of as gravitational energy and then energy density. Just unpack all that, Charles.

• 25:24Charles Liu?

  It gets, it gets a little bit in the weeds, but fundamentally, if you have a field and you have a particle in that field that interacts with the field, there's a little bit of energy. When you move that particle in the field, it feels a force and some sort of energy gets released. Depending on where you are in the field, the amount of energy released varies. Hence the concept of energy density. Over here, you're going to have more energy per cubic centimeter or

• 25:57Neil deGrasse Tyson?

  Volume, yeah.

• 25:58Charles Liu?

  Something like that. Over there, you have fewer. Okay. So when you're talking about Hawking radiation in a black hole, there's actually a lot that still needs to be straightened out. All right. You know what Hawking was doing was doing a quantum slash thermodynamic argument about any object that's in the universe that's compact and it's got some sort of event horizon. Okay. But really, you can take those equations and extend them, and you can say that pretty much anything.

• 26:29Charles Liu?

  Exerts at pretty much anything emits something along the lines of Hawking radiation. It's just that for black holes, it's actually important because that amount of emission is the only stuff that's coming away from the event horizon of the black hole, right? The rest of the stuff is all outside the event horizon that's doing any kind of emission of energy. So that's why Hawking radiation is cool. At the moment, we don't know if it's because of, you know, some sort of, say, effect that you have antimatter-matter pairs near the event horizon. We don't know if it's quantum tunneling. We don't know if it's just some sort of basic thermodynamic effect that happens in all cases.

• 27:14Charles Liu?

  So there's still mystery there. So you put your finger on a good question that yet needs to be answered.

• 27:20Neil deGrasse Tyson?

  I tell you what Brian Greene told me recently. I had lunch with him. Brian Greene up the street here at Columbia University.

• 27:25Charles Liu?

  The Elegant Universe guy.

• 27:27Neil deGrasse Tyson?

  Author of The Elegant Universe and several other books to follow. So he told me that there's emergent thinking that this vacuum energy of virtual particles that pop in and out of existence, and these particles are matter and antimatter pairs that energy creates, and then they refine each other, and then they become energy again, which is a vacuum version of what Hawking radiation is right outside of a black hole. He was suggesting that when they are created and separated, they're quantum entangled. And while they are quantum entangled, the actual connection between them is a wormhole.

• 28:09Charles Liu?

  Oh.

• 28:10Neil deGrasse Tyson?

  Which is how you can have information move basically instantly, okay? Or the state be resolved instantly because it's an actual wormhole. And what he said was that the very stitches of spacetime might be this myriad network of wormholes created by virtual particles coming in and out of existence.

• 28:36Charles Liu?

  Hmm.

• 28:37Neil deGrasse Tyson?

  So it's not just metaphor that the spacetime is a fabric. It's like it is a fabric and the wormholes is the material that weaves the fabric of space and time. That freaked me out. I digest it.

• 28:53Charles Liu?

  That's really cool, man. Well, the virtual particles wink in and out of existence in tiny fractions of a second. So they have to keep replenishing themselves all the time. If that's the fabric of spacetime, otherwise the fabric of spacetime just falls apart. Like the tapestry that's been hanging for too long. Oh, oh dear.

• 29:11Neil deGrasse Tyson?

  Oh dear.

• 29:13Gary O'Reilly?

  A renovation in the castle.

• 29:15Neil deGrasse Tyson?

  The castle.

• 29:17Gary O'Reilly?

  You know, the end, the end of this guy's question, the end of Johnny's question, he says, and I always thought gravity was merely potential energy. But surely that can't be the case in space because there's no up, no down. It's not like I could take it up, so it drops down and I've got potential energy.

• 29:33Charles Liu?

  Gravity is not potential energy.

• 29:35Gary O'Reilly?

  Thank you.

• 29:35Charles Liu?

  Gravity, if you have a particle that's in a gravitational field and that particle has mass, it contains gravitational potential energy, which can then be released if it falls through the system.

• 29:48Gary O'Reilly?

  Okay.

• 29:49Charles Liu?

  And in that case, it's not a matter of going.

• 29:51Neil deGrasse Tyson?

  If the particle's not there, we still use the phrase, it's a gravitational potential.

• 29:55Gary O'Reilly?

  Okay.

• 29:56Neil deGrasse Tyson?

  Okay, potential well. You get put the particle here, then it has gravitational potential energy. I just want to finish that thought.

• 30:02Charles Liu?

  You're exactly right. And so in space, we don't worry about up or down, Gary, as you rightly say. We worry about whether it's in or out. If it's close to or away from some sort of gravitational center. Yeah, yeah, yeah. All good.

• 30:19Gary O'Reilly?

  All right, Brian Ridge, doesn't say where he's from. Uh, instead of dark energy within the known universe, is there a chance something beyond? Is sucking to cause the expansion of the universe from beyond? If it was traveling away at the speed of light, we would never witness it. Right? Question mark. Hmm.

• 30:39Neil deGrasse Tyson?

  Again, so, so Charles, does the, does the universe suck?

• 30:42Chuck Nice?

  Hey.

• 30:45Charles Liu?

  The universe does not suck.

• 30:46Neil deGrasse Tyson?

  Okay, thank you, thank you.

• 30:48Charles Liu?

  And neither do black holes, but that's another conversation.

• 30:51Chuck Nice?

  I was gonna say, which universe doesn't suck?

• 30:52Neil deGrasse Tyson?

  Thank you, I said the other universe sucking.

• 30:54Chuck Nice?

  There's, yeah, there's so many of them, Charles, I mean, come on.

• 30:58Charles Liu?

  No, in order for-

• 30:59Neil deGrasse Tyson?

  The question is whether another universe is creating this anti-gravity suction.

• 31:03Charles Liu?

  Is, is somehow causing the expansion. Uh, in other, in order for that to happen, there are two assumptions you can make, and it depends, right? Assumption number one is, if that were the case, then that means that our observable universe is just a little bubble in a much larger universe. And something around the outside can therefore create that kind of expansion through suction. Right? But that, that hasn't been confirmed yet. There are ideas, for example, something called eternal inflation, which suggests that that might be a way that multiverse is created. But there's nothing that we know of, uh, in terms of the mechanics of the cosmology that we understand that could cause that, that scenario.

• 31:46Charles Liu?

  The other situation might be that if we, as a four-dimensional spacetime, were embedded in a five-dimensional membrane, then that fifth dimension, well, then you could imagine, although we again haven't figured out anything physical yet that could be this, you could imagine that our four-dimensional thing is expanding in the fifth-dimensional thing almost because of something, say, a surface tension. In the same way that, say, an oil slick expands across a pond-

• 32:17Chuck Nice?

  Right, across the surface of the water.

• 32:18Charles Liu?

  A surface of the water when the water is deep.

• 32:20Chuck Nice?

  And it just, cause it just keeps expanding no matter what.

• 32:22Charles Liu?

  That's right. And so you have a situation where we're trying to figure out the mathematical aspects of how you might connect, uh, four-dimensional spacetimes within five-dimensional membranes, but there's nothing physical yet that allows that to happen. So, uh, the answer, I guess, to the question is stay tuned.

• 32:40Neil deGrasse Tyson?

  Yeah.

• 32:40Gary O'Reilly?

  So if it's surface tension, Charles? Could we not use that to travel? Like a pond skater? Across the surface of a pond?

• 32:48Charles Liu?

  Well, if it is some kind of surface tension, that would be an awesome way to travel in the fifth dimension.

• 32:53Gary O'Reilly?

  There you go.

• 32:54Charles Liu?

  Right. But. And then you could violate the, you know, this faster than light. But that's because you're not. Yes, but that's because you're not in our four dimensional space time anymore. The laws of speed limits and physics or whatever mass, et cetera, could be completely different. Which is, for example, one of the tenets of something called Randall Sundrum theory. Where Dr. Randall and Dr. Sand. Randall Sundrum theory. Okay. Okay. Ballerah Sundrum and Lisa Randall. Uh, they came up with this idea some years ago, suggesting that if indeed our space time were connected to other four dimensional space time via membranes, that might explain things like why gravity is so much weaker

• 33:39Charles Liu?

  on same distance scales as the nuclear force. Right? Why is that the case? These are the things that we don't know yet, but they're, they're being thought about. And that's kind of funny.

• 33:48Neil deGrasse Tyson?

  Gravity is, is embarrassingly weak.

• 33:50Charles Liu?

  Right. And remember, well, yes, gravity is ridiculously weak. But because it can extend over long distances and because it does not have a negative that cancels out the positive, gravity in the universe on cosmic scales has no equal.

• 34:09Neil deGrasse Tyson?

  Yeah.

• 34:09Speaker 04

  I may be weak, but I'll beat your ass any day. Come on with it. What you wanna do? I'm gravity.

• 34:16Neil deGrasse Tyson?

  Yeah, that is the exact voice gravity would have, I'm sure.

• 34:19Speaker 04

  Try me, try me. You know who I am? You all know I'm gravity.

• 34:24Charles Liu?

  No, I'm gravity.

• 34:36Neil deGrasse Tyson?

  Who's, who's teed up next?

• 34:37Gary O'Reilly?

  Okay, let's jump straight in. Joe Stamps, that's with an S. If you move backwards from a giant ticking clock at the speed of light, what does it do? Stop ticking because of the relativity or because the light from the next second can never reach you? Thanks for all you do and respect from me and my family who keep looking up.

• 34:58Neil deGrasse Tyson?

  Oh.

• 34:58Chuck Nice?

  Oh, that's so cool.

• 35:00Charles Liu?

  Yeah. Well, yeah, the answer is actually, they're both right. Relativity allows you to think of time and space in different ways because they are relative to one another. They behave differently. So you do not see that clock tick because you are moving away from it at the speed of light. And so the sound or the information for the tick never reaches you. It will still tick in its own stationary frame of reference, but you will never know that it ever happened. So in that sense, you could say the clock ticks, but it doesn't tick for you.

• 35:38Chuck Nice?

  Oh.

• 35:39Charles Liu?

  Ask not for whom the clock ticks.

• 35:42Neil deGrasse Tyson?

  But for whom the clock tolls. Yeah, okay. So, but if there's another clock that you're headed towards.

• 35:48Chuck Nice?

  Right.

• 35:48Neil deGrasse Tyson?

  Then you would see that clock go faster because you're catching up with every next tick, correct?

• 35:54Charles Liu?

  That's right. That's right. So it's the, the direction you're traveling.

• 35:58Chuck Nice?

  Frame of reference.

• 35:59Charles Liu?

  Speed, it's all about frame.

• 36:01Neil deGrasse Tyson?

  Yeah, okay.

• 36:01Chuck Nice?

  Frame of reference, that's what makes the whole thing work.

• 36:03Neil deGrasse Tyson?

  Nice, nice. All right, let's keep going.

• 36:05Chuck Nice?

  Super cool. Okay, how about Alexandria French? Alexandria French, she says, my husband and I listen while we cook dinner every night.

• 36:13Neil deGrasse Tyson?

  Nice, what are you cooking? What you cooking?

• 36:16Chuck Nice?

  Yeah, and, and thanks for sending us some.

• 36:18Neil deGrasse Tyson?

  No, no, right, right?

• 36:20Chuck Nice?

  Yeah.

• 36:21Charles Liu?

  It's your French food. It's French cooking, yeah.

• 36:23Neil deGrasse Tyson?

  Yeah. Okay.

• 36:24Chuck Nice?

  Yes, we'll have a little coq au saint Jacques, we'll take it. Uh, let's see, she says, uh, I have a burning question that came from, uh, that I came from Patreon to ask if we could.

• 36:35Neil deGrasse Tyson?

  But the question burns? But there's, there's an ointment for that, I think. Jesus.

• 36:41Charles Liu?

  Hope, hope it doesn't burn while you're cooking. Don't burn your food. Don't burn your food.

• 36:47Chuck Nice?

  Okay. If we could put a telescope on a galaxy, say 15 million light years away, with the depth of the observable universe change based on the changing the point of the observation.

• 37:02Neil deGrasse Tyson?

  Love it.

• 37:04Charles Liu?

  Well, uh, the answer.

• 37:07Charles Liu?

  Alexandria and husband, um, I would say is that no, it does not change. Because fifteen million light years away Alexandria is actually the center of that spot's observable universe. Fifteen million, fifteen billion, wherever you are away from us, that is the center of the observable universe. At that point, you see, uh, we are living in a universe that expanded from a single point. Which means that you can't actually point to one spot in our current universe and say that one is the center. Any more than you can point to any other place and say it's the center.

• 37:51Charles Liu?

  So every spot in the universe is expanding away from every other spot. And therefore, we have an infinite number of centers of observable universes. Because every single spot is a center in its own observable. Am I throwing it often enough in there?

• 38:09Neil deGrasse Tyson?

  But Charles, I gotta add, if there, if there's a galaxy at the edge of the universe.

• 38:13Charles Liu?

  Uh huh.

• 38:14Neil deGrasse Tyson?

  Which is on the edge of our observable universe and we go there.

• 38:17Charles Liu?

  Mm hmm.

• 38:18Neil deGrasse Tyson?

  That galaxy will see just as far on the other side.

• 38:22Charles Liu?

  Yes.

• 38:23Neil deGrasse Tyson?

  Of its location and it'll see half the universe that we cannot see.

• 38:29Charles Liu?

  Correct, so.

• 38:30Neil deGrasse Tyson?

  So it's in the center of its own horizon. So I, my thought, the question was, what will they see relative to us?

• 38:37Charles Liu?

  Oh.

• 38:38Neil deGrasse Tyson?

  If you go to the horizon, they'll see parts of the universe we can't see.

• 38:42Charles Liu?

  That will happen.

• 38:42Neil deGrasse Tyson?

  Think they're in the middle of the known universe.

• 38:44Charles Liu?

  Yes, that's exactly.

• 38:46Chuck Nice?

  It's like being out in the middle of the ocean and spotting an island.

• 38:49Charles Liu?

  Uh huh.

• 38:50Chuck Nice?

  You're like, you know, land ho, but from, from, on the other side of that island, they may be looking out at stuff that you won't be able to see as you look at that.

• 38:58Neil deGrasse Tyson?

  If the island was on your horizon, right.

• 39:00Chuck Nice?

  If the island was on your horizon, yes.

• 39:01Neil deGrasse Tyson?

  Right, right, right.

• 39:02Charles Liu?

  That's right.

• 39:02Neil deGrasse Tyson?

  I think that's where I was coming from, I think.

• 39:04Charles Liu?

  Sounds good, yeah.

• 39:05Neil deGrasse Tyson?

  Okay, but Gary, what do you got?

• 39:07Gary O'Reilly?

  Christopher Scott's next up. Given that energy is neither created nor destroyed. Does this mean that all of the fossil fuels that are in the ground as forms of stored energy have been around for eons already? If so, are we simply redistributing the location of the energy on our tiny little rock in space? We are not actually adding any more energy to the system, just moving where it is.

• 39:34Neil deGrasse Tyson?

  Can I take, can I answer this?

• 39:35Gary O'Reilly?

  Oh, please do.

• 39:36Charles Liu?

  Oh, yeah.

• 39:37Neil deGrasse Tyson?

  Double camera to answer this? Okay.

• 39:39Charles Liu?

  Mm-hmm.

• 39:39Neil deGrasse Tyson?

  Okay. You ready?

• 39:40Charles Liu?

  Mm-hmm.

• 39:40Neil deGrasse Tyson?

  Okay. Uh, all, so first of all, energy can be destroyed by turning it into matter. Okay, so the, it's so the, the concept of energy can neither be created or destroyed was modified after equals mc squared, and it's the sum of energy and matter that cannot be created or destroyed. It's the sum of those two. Okay. So now, the fossil fuels are solar energy.

• 40:10Charles Liu?

  Mm-hmm. Right.

• 40:12Neil deGrasse Tyson?

  All those life forms got their energy from the sun. If they were plant life, they got it directly. If they were animal life, they got it because they ate the plants that got the sunlight. So fossil fuels is solar power. Except that it's polluting the air and it's, we're not gonna be able to reproduce it because all that energy was, came and was sitting there for us for millions of years. It's been buried energy. Once we use it and it radiates out into space, it goes back into the universe. It's not still here on Earth. Charles, you take it over from there.

• 40:51Charles Liu?

  What else can I add? What a beautiful explanation. Completely correct.

• 40:54Chuck Nice?

  Uh, you can add the fact that the energy that it is creating is a perturbation of the atmosphere, conditions that create global warming.

• 41:04Charles Liu?

  Oh, that is a great thing to add.

• 41:06Chuck Nice?

  And that creates more energy or actually intensifies energy and

• 41:12Neil deGrasse Tyson?

  Interesting part of that cycle.

• 41:13Chuck Nice?

  It's gonna destroy us all.

• 41:15Neil deGrasse Tyson?

  Well, we trap more sunlight.

• 41:16Chuck Nice?

  Yeah, right. We trap more sunlight.

• 41:18Gary O'Reilly?

  It becomes a giant magnifying glass.

• 41:19Charles Liu?

  Right. Releasing the solar energy, precisely, Gary, releasing the solar energy that was stored in these microorganisms which were turned into coal and oil and natural gas or whatever these fossil fuels are, uh, also releases at the same time. How it got bound down underneath the earth, which in this case is carbon. And the carbon comes out in the form of carbon dioxide. And it is adding something new to our atmosphere. Atmosphere, right. That we haven't seen in hundreds of thousands of years. So the answer is that if you define the system as the universe, including the sun and down in the earth and out in space, the energy has not been created or destroyed. Good point. It's been redistributed.

• 42:04Charles Liu?

  But if you're thinking about the system as our earth's atmosphere, our biosphere, the environment that humans live in. Oh, yes, we are injecting a lot of energy. Lot of energy. We are adding a huge amount and it's not just a balance change. It's an actual increase. And by all the different features that everybody here has said so far. So, yes.

• 42:26Neil deGrasse Tyson?

  And of course, the difference is the original source of energy was the sun. It came to earth, was stored and locked underground. Now we have re-released that energy. Uh, we're after we've created civilization on a stable, relatively stable climate. And now we are altering the climate by re-releasing this Pandora's box of energy.

• 42:49Charles Liu?

  Right.

• 42:50Neil deGrasse Tyson?

  Well, primarily because of the byproduct of it, which is the burning of fossil fuels, which is where you get your CO2. There you go.

• 42:56Charles Liu?

  There you go.

• 42:57Neil deGrasse Tyson?

  Yeah.

• 42:57Charles Liu?

  There you go.

• 42:58Neil deGrasse Tyson?

  Guys, we've got time for one more question. Give it to me.

• 43:00Gary O'Reilly?

  All right, okay. Gavin Bamber from North Vancouver says, please visit, maybe, maybe not, we'll see.

• 43:05Charles Liu?

  Sure.

• 43:07Gary O'Reilly?

  I ask, what is the largest object in the universe?

• 43:13Charles Liu?

  The universe.

• 43:14Neil deGrasse Tyson?

  The universe itself.

• 43:16Charles Liu?

  The universe. Okay, now that's.

• 43:20Gary O'Reilly?

  I'm guessing Gavin was looking for a slightly different answer.

• 43:23Charles Liu?

  How come we are so unified in that ridiculous joke? I know, we said that too many times.

• 43:29Neil deGrasse Tyson?

  It depends, I think it depends what they mean by object. Like, are we an object? So there are forces that hold together our.

• 43:37Charles Liu?

  Right.

• 43:37Neil deGrasse Tyson?

  Molecules, but you can separate the molecules. So what is the object? You or the molecules?

• 43:43Charles Liu?

  Right.

• 43:43Neil deGrasse Tyson?

  Right? Is the galaxy an object? Even though it's composed of things? That we're stars and planets.

• 43:51Charles Liu?

  Right, right.

• 43:52Neil deGrasse Tyson?

  You know, so on that scale, what would you say, Charles?

• 43:54Charles Liu?

  Well, if I were to say that an object is defined as something that is being held together in some recognizable way by some kind of force.

• 44:04Neil deGrasse Tyson?

  I'd go with that.

• 44:05Charles Liu?

  Okay, then the largest objects are these superclusters of galaxies out in space. They contain huge amounts of matter. Our Milky Way, you guys know, has about hundreds of billions of stars in it, right? But these superclusters contain thousands, sometimes hundreds of thousands of galaxies. And so you add all that together, and then there's all that cosmological dark matter in between them. And so you've got a huge chunk of material that all is bound together by gravity. So that would probably be the object.

• 44:40Neil deGrasse Tyson?

  If it's bound together, we think of that as a coherent object.

• 44:42Charles Liu?

  Yeah.

• 44:43Neil deGrasse Tyson?

  In that sense, the cluster as an object.

• 44:46Charles Liu?

  Right.

• 44:47Speaker 04

  And what makes it work? Gravity, man. It's me, man, gravity. What you messing with? What you wanna do?

• 44:55Neil deGrasse Tyson?

  Okay, so an illustrator is gonna come hear us and then have gravity, personify gravity, it's gonna be Chuck's voice.

• 45:03Charles Liu?

  I'm gravity. I'm gravity.

• 45:06Neil deGrasse Tyson?

  Oh, you wanna be Batman? That's Batman, that's not gravity.

• 45:08Charles Liu?

  Well, actually, what's gonna work is teamwork.

• 45:13Neil deGrasse Tyson?

  Oh, yeah, okay.

• 45:14Charles Liu?

  Okay.

• 45:14Neil deGrasse Tyson?

  Gravity.

• 45:18Neil deGrasse Tyson?

  But Chuck, we've concluded in this episode, you are AI's overlord. That's what we just did.

• 45:23Charles Liu?

  Yes, right, Chuck. Thank you for being all my cringing underlings.

• 45:30Neil deGrasse Tyson?

  All right, that's all we got here. Guys, thanks for doing this once again. StarTalk Special Edition. Neil deGrasse Tyson here, looking out.