Cosmic Queries – The Fabric of Spacetime

Is it time to rethink string theory? Neil deGrasse Tyson and comedian Chuck Nice explore a mix of questions about the fundamental properties of the universe, particles, the speed of light and more!

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

• 0:00Chuck Nice?

  I just love that the neutrino is like Tom Cruise in The Mission Impossible. It leaves the sun and then it gets to Earth and it's just like, pulls his face off like, "It was me all along."

• 0:14Neil deGrasse Tyson?

  You can't detect me.

• 0:18Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. Today, we're gonna do a Cosmic Queries Grab Bag Edition. So Chuck, what does that even mean?

• 0:43Chuck Nice?

  Well, you know what it means. It means that anything that people wanna know, we just throw it in a bag and they get a chance to do it. We used to call it Galactic Gumbo.

• 0:57Neil deGrasse Tyson?

  I haven't had gumbo in a while, but last I had it, yeah, it kinda have pretty much everything in it.

• 1:01Chuck Nice?

  Yeah, man.

• 1:02Neil deGrasse Tyson?

  Whatever might have been left in the fridge overnight. But, okay, well, let's do it. You got 'em.

• 1:07Chuck Nice?

  Yep, we got the questions right here.

• 1:08Neil deGrasse Tyson?

  My co-host, yes.

• 1:09Chuck Nice?

  Thank you. So let's jump right into it. Let's go to Chris Hampton, who says, "Easy name here, Chuck." Hey, thanks, Chris. What the hell? I should really read these before the show.

• 1:24Chuck Nice?

  Thanks, Chris. Anyway, "Do you think future scientist Neil will look back at our particle colliders and think that they were somewhat barbaric? I.e. smash, smash, smash, which would also imply that they found a better way to observe particles and parts of atoms while they're still intact? What do you think is better?"

• 1:46Neil deGrasse Tyson?

  I like that question.

• 1:47Chuck Nice?

  Yeah, it's really...

• 1:48Neil deGrasse Tyson?

  That's a very, you know, peace-loving question.

• 1:53Chuck Nice?

  It is.

• 1:55Neil deGrasse Tyson?

  Yeah, because atom smashers and particle accelerators, they're entirely designed to smash particles. I don't think particles have feelings, so to be worried about them.

• 2:05Chuck Nice?

  Right.

• 2:05Neil deGrasse Tyson?

  And to think that we're committing violence upon them.

• 2:08Chuck Nice?

  Right.

• 2:09Neil deGrasse Tyson?

  I don't, I'm not, I'm big. So here's how to think about it.

• 2:13Chuck Nice?

  Yeah, rest, rest easy, you little particle pacifist.

• 2:16Neil deGrasse Tyson?

  Particle pacifist. If you, if you smashed a particle and then it was destroyed.

• 2:22Chuck Nice?

  Right.

• 2:23Neil deGrasse Tyson?

  And it would never, then, okay. But what, when you smash a particle, what you're doing is you're putting energy into the system, empowering it to make other particles.

• 2:33Chuck Nice?

  Oh.

• 2:34Neil deGrasse Tyson?

  So, so atom smashers, particle accelerators, they, they're means of infusing a system with high levels of energy to see what pops out the other side. Because some particles exist only under those conditions. So what we'd have to say is, is there a way to observe those conditions without being barbaric to arrive at them? Yes, there is. You know what that would be? Go back to the Big Bang.

• 3:00Chuck Nice?

  Ah.

• 3:02Neil deGrasse Tyson?

  Okay, there you go, with your microscope or with your telescope, go back to the Big Bang, because those are the conditions we are trying to duplicate in the laboratory. The, the conditions of density and temperature and pressure. These are the conditions of the Big Bang, and this, this is what started the field of astroparticle physics. Astroparticle physics deals with what happened in the early universe when the universe was small and very hot, and you couldn't have matter as we know it, you know, physical objects. Everything was a particle soup, seething back and forth between energy and matter. And this is what we're trying to create in the laboratory.

• 3:43Neil deGrasse Tyson?

  So these laboratories are actually, um, portals back to the origin of time itself.

• 3:51Chuck Nice?

  Look at that. So basically, they're giant replicators is what they're doing.

• 3:55Neil deGrasse Tyson?

  Exactly, exactly. And really, he shouldn't have to be, we're not going to one day find out that particles have feelings. I'm pretty sure about that one.

• 4:02Chuck Nice?

  Yeah, exactly.

• 4:03Neil deGrasse Tyson?

  Yeah.

• 4:03Chuck Nice?

  No, no need to have a protest for particles, you know? No justice, no peace. Yeah, we don't, we don't, it's gonna be all right.

• 4:13Neil deGrasse Tyson?

  All right, keep it coming.

• 4:14Chuck Nice?

  Very cool. All right, let's keep going here. Uh-oh. Wal Quira, Wal Quira Fontanes. There you go. That's, I think that's it.

• 4:28Neil deGrasse Tyson?

  That's it, no matter what.

• 4:29Chuck Nice?

  It is what it is now. That's what it is now.

• 4:33Neil deGrasse Tyson?

  Whatever it should be, that's what it is.

• 4:35Chuck Nice?

  That's what it is. Okay, okay, so, uh, so, uh, Wal Quira says, "Hello, my people. This is Wal Quira from Georgia, originally from the Bronx, Neil."

• 4:48Neil deGrasse Tyson?

  Bronx in the house.

• 4:49Chuck Nice?

  There you go. "If gravity pulls everything down, then how do clouds defy gravity? And how do clouds stay up?"

• 4:56Neil deGrasse Tyson?

  Oh, I love that.

• 4:58Chuck Nice?

  Yeah.

• 4:58Neil deGrasse Tyson?

  I love that. So let me, let me ask a different question that's exactly the same. If gravity pulls everything down, why do helium balloons go up?

• 5:06Chuck Nice?

  Oh, there you go.

• 5:07Neil deGrasse Tyson?

  So you can ask the question, "What does a helium balloon weigh?"

• 5:11Chuck Nice?

  Uh huh.

• 5:12Neil deGrasse Tyson?

  What does a cloud weigh?

• 5:14Chuck Nice?

  Right.

• 5:14Neil deGrasse Tyson?

  It does, it have negative weight? Do you have to take a scale and put it upside down above it? And have it press upwards? Does it have negative weight? Okay, that's the question. It's the same question, alright?

• 5:24Chuck Nice?

  Yeah, and it's weight relative to something, right?

• 5:27Neil deGrasse Tyson?

  Exactly, exactly. So...

• 5:31Neil deGrasse Tyson?

  So we, as physical objects called humans, are so much denser than air.

• 5:39Chuck Nice?

  Mm-hmm. Yeah, and you mean that as, uh, as in a physical sense?

• 5:43Neil deGrasse Tyson?

  Yeah.

• 5:44Chuck Nice?

  Cause you know, the other, the other part is true too.

• 5:46Neil deGrasse Tyson?

  The other kind of dense.

• 5:47Chuck Nice?

  The other kind of dense is also true.

• 5:49Neil deGrasse Tyson?

  When did dense become, like, you can't learn anything? Dense, to me, means you have a lot of information in there. It's a density of enlightenment.

• 5:57Chuck Nice?

  See, and that, it lets you know who you are, okay? Because you look at dense as a good thing as in, um...

• 6:05Neil deGrasse Tyson?

  Pack it in.

• 6:06Chuck Nice?

  A great deal of information compacted.

• 6:08Neil deGrasse Tyson?

  Pack it in, pack it in.

• 6:10Chuck Nice?

  Whereas dense as in thick-headed, it's about getting it in there.

• 6:15Neil deGrasse Tyson?

  Oh, the barrier.

• 6:17Chuck Nice?

  The density is the barrier, the density of the barrier. You're a thick-headed dolt.

• 6:21Neil deGrasse Tyson?

  Okay, so it's a thick-skulled dolt.

• 6:23Chuck Nice?

  It's a thick skull, right?

• 6:24Neil deGrasse Tyson?

  Don't implicate the whole head here.

• 6:28Neil deGrasse Tyson?

  It's, okay, I didn't, I swear to you, I did not know that.

• 6:32Chuck Nice?

  Yeah, yeah.

• 6:33Neil deGrasse Tyson?

  The density of the barrier of entry of information into your mind, alright?

• 6:38Chuck Nice?

  There you go.

• 6:38Neil deGrasse Tyson?

  So, so you can ask what, so we are so much denser, physically denser than air. We don't think about...

• 6:47Neil deGrasse Tyson?

  How much less we weigh in air.

• 6:50Chuck Nice?

  Right.

• 6:51Neil deGrasse Tyson?

  Air has a buoyant force that makes you weigh a little bit less, but we don't care about it. We don't even think about it.

• 7:00Neil deGrasse Tyson?

  How about water? Okay, we are almost the same density as water. So some people float.

• 7:10Chuck Nice?

  Right.

• 7:10Neil deGrasse Tyson?

  And those who sink, they don't sink very fast.

• 7:13Chuck Nice?

  Right.

• 7:14Neil deGrasse Tyson?

  So how much do you weigh in water? Well, if you're floating, do you weigh zero? So what's happening here is everything has weight unless you're floating in something. Okay, so the helium balloon is lighter than air. If you started evacuating all the air of the earth, then all the helium balloons, however many are still up there, the Chinese balloon,

• 7:41Neil deGrasse Tyson?

  whatever, whatever balloon is up there, it will come to earth. And then you can stick a scale under it and figure out how much it actually weighs with no buoyant force assisting it.

• 7:55Chuck Nice?

  There you go.

• 7:55Neil deGrasse Tyson?

  Now you filter, now you pour air back into our atmosphere and things lighter than air will float above it, but that doesn't mean they're weightless.

• 8:04Chuck Nice?

  Look at that.

• 8:05Neil deGrasse Tyson?

  Yeah.

• 8:06Chuck Nice?

  That's awesome. And by the way, there's a lot of videos on social media right now circulating that speak to this questioning gravity because of things that float. And the fact that there are things that are on parts of the earth that they say are upside down. So it's keeping you upside down, but yet at the same time, the same so-called supposed force is allowing these other things to float around, so.

• 8:35Neil deGrasse Tyson?

  Okay, so, so this is a case of a person who thinks they know about enough about a subject to believe they're right. But they don't know enough about the subject to know that they're wrong.

• 8:48Chuck Nice?

  There you go. Look at that. Damn.

• 8:51Neil deGrasse Tyson?

  No, so here's the, in the, in all the lands down under, you know, that's because like civilization and to the dominant forces of cultures have all been like in the northern hemisphere, right?

• 9:02Chuck Nice?

  Right.

• 9:03Neil deGrasse Tyson?

  So, so we have northern hemisphere bias on southern hemisphere resonance. And we say that they're upside down.

• 9:11Chuck Nice?

  Right.

• 9:12Neil deGrasse Tyson?

  Any of us, if we saw a map with south up, we'd say that's upside down.

• 9:17Chuck Nice?

  Right.

• 9:17Neil deGrasse Tyson?

  Look how deep that bias is because space don't give a shit.

• 9:20Chuck Nice?

  And that's what I was about to say. In, in the, in the blackness of space, when you're floating in a void, right? Is there really any up or down?

• 9:29Neil deGrasse Tyson?

  Right, no, there's no up or down, correct.

• 9:30Chuck Nice?

  Right.

• 9:30Neil deGrasse Tyson?

  It's, it's correct. Uh, and so, well, you can point to places that locally will have an up or down where they are.

• 9:38Chuck Nice?

  Okay.

• 9:38Neil deGrasse Tyson?

  But where you are, no. So up and down is relative.

• 9:41Chuck Nice?

  There you go.

• 9:41Neil deGrasse Tyson?

  It's relative to where the center of gravity is of your closest object. So anyhow, all I'm saying is if you're floating, it's because there's a buoyant force. That's all.

• 9:50Chuck Nice?

  Right.

• 9:50Neil deGrasse Tyson?

  And I did, I once did this calculation for 150 pound person. Uh, what would that be in, in kilos? That would be, you know, something like 70, 75 kilos. Okay.

• 10:01Chuck Nice?

  Okay.

• 10:01Neil deGrasse Tyson?

  It's 2.2.

• 10:02Chuck Nice?

  2.2.

• 10:03Neil deGrasse Tyson?

  Pounds per.

• 10:03Chuck Nice?

  Pounds.

• 10:04Neil deGrasse Tyson?

  So, uh, that person, you know, there's a few, I mean, it's, it's a, it's a measurable amount, but no one cares. You know, is it 100 grams less because of the buoyant force of air? Like I said, we don't typically think about that because it doesn't really matter to us. That's all.

• 10:20Chuck Nice?

  Okay.

• 10:21Neil deGrasse Tyson?

  All right.

• 10:22Chuck Nice?

  There you go.

• 10:22Neil deGrasse Tyson?

  Next one.

• 10:23Chuck Nice?

  Fantastic. Let's move on to Michael Ranger. Cool name, Michael Ranger. Uh, is particle a placeholder word for things that are so small? We don't know what they are yet.

• 10:38Neil deGrasse Tyson?

  Ooh, is, is particle a placeholder? Yes, but only for one particle.

• 10:43Chuck Nice?

  Uh huh.

• 10:44Neil deGrasse Tyson?

  The electron.

• 10:46Chuck Nice?

  Uh huh.

• 10:47Neil deGrasse Tyson?

  Every other particle, well, every other particle we play with in the, in the, in the laboratory.

• 10:52Chuck Nice?

  Mm hmm.

• 10:52Neil deGrasse Tyson?

  Uh, every other particle that we control and play with has a measured size.

• 10:58Neil deGrasse Tyson?

  We can give the dimensions of an electron. We have never measured how big an electron is. And as far as we know, it's infinitesimally small. This is a profound point of mystery in particle physics.

• 11:10Chuck Nice?

  I did not know.

• 11:12Neil deGrasse Tyson?

  We don't dwell on it because we can still invoke it. We still make current and electricity. We can still do all manner of things with an electron, this thing we call an electron. But it is a spot in spacetime that we have never measured. We measured its charge, that's it. And its mass, we can measure its mass, but what the, have we ever seen it?

• 11:36Chuck Nice?

  Mass is not size.

• 11:37Neil deGrasse Tyson?

  It's not size, we've never seen it.

• 11:39Chuck Nice?

  Mass is not size. Wow.

• 11:40Neil deGrasse Tyson?

  Yeah.

• 11:41Chuck Nice?

  I just learned something. I did not know this.

• 11:43Neil deGrasse Tyson?

  You didn't know that about electrons?

• 11:44Chuck Nice?

  I did not know this about electrons.

• 11:46Neil deGrasse Tyson?

  I have an entire video course with The Great Courses. So I gave a series of lectures. What I do in each lecture is I take you to the frontier of our ignorance. And then I just drop you there and I say, here it is.

• 11:59Chuck Nice?

  Nice.

• 12:01Neil deGrasse Tyson?

  Peer out and your guess is as good as mine, okay? What's going on out there? So I take the viewer to the edge of the unknown in astronomy and physics. It's in The Great Courses series, check it out. If you're interested, in there I talk about the fact that we have no idea how big an electron is.

• 12:20Chuck Nice?

  That is fascinating. I mean, wow.

• 12:23Neil deGrasse Tyson?

  Neutrinos are pretty elusive as well, and we do manipulate them. And I don't know the latest on those and what size we have ascribed them. Maybe they're equally as intractable in our ability to measure their dimensions. But we do know the size of protons and they're composed of quarks. Three quarks, protons and neutrons. And how big is a quark? I don't know what our latest thinking is on that. But the fun one is electrons, because we've all heard of electrons.

• 12:50Chuck Nice?

  Right, we all know what they are. They're the satellites of the nucleus.

• 12:55Neil deGrasse Tyson?

  Yeah, yeah, that's right. Well, yeah, they quote orbit the nucleus.

• 12:59Chuck Nice?

  Right.

• 12:59Neil deGrasse Tyson?

  But we didn't want to use the word orbit because that applies to planets. And so we invented a new word orbital. So they have orbitals, right? Put a little distance between it and astronomy, yeah.

• 13:14Chuck Nice?

  Wow, look at that. Dude, what a great little question you had there, Michael Ranger. Thanks for that, man. Yeah, all right, here we go. This is Michelle Star Girl. Watch out.

• 13:27Chuck Nice?

  Watch out now. It's Michelle Star Girl.

• 13:30Neil deGrasse Tyson?

  Star Girl. That's her name?

• 13:31Chuck Nice?

  That's, that's what she wrote.

• 13:33Neil deGrasse Tyson?

  That's what she wrote.

• 13:34Chuck Nice?

  That's what she wrote. Now, I'm not, I'm not gonna judge her because that's what she wrote. Uh, she goes, greetings. This is Michelle from NYC. Now that the James Webb Space Telescope has seen mature galaxies not long after the Big Bang, that under current knowledge shouldn't exist, could these galaxies possibly be a window into another universe?

• 14:00Neil deGrasse Tyson?

  Ooh, I like that.

• 14:01Chuck Nice?

  Oh, what a lovely conjecture.

• 14:04Neil deGrasse Tyson?

  Thank you, Star Girl.

• 14:05Chuck Nice?

  Star Girl.

• 14:06Neil deGrasse Tyson?

  So, um, you know, when I was a kid, one of my favorite cartoons was Astro Boy.

• 14:11Chuck Nice?

  Oh, God. You know they brought Astro Boy back, man?

• 14:14Neil deGrasse Tyson?

  They did. I didn't know that.

• 14:15Chuck Nice?

  Yeah. Astro Boy bombs away. On a mission today. Rocket high to the sky. Okay, anyway.

• 14:24Neil deGrasse Tyson?

  So let's back up. So after the Big Bang, where there was this particles, matter soup, uh, everything was too hot to make stars. And so, but then there's a point where things cooled so that the universe became, because the universe was glowing back then. It cooled and became transparent, but it still was not in a, ready to make stars. So it would have to wait. I, I, I forgot how long, but long enough so that we have a word for this era, and it's called the Dark Ages. Where, you know, there's no, there's no stars, no galaxies.

• 15:00Chuck Nice?

  Right.

• 15:00Neil deGrasse Tyson?

  James Webb Space Telescope is exquisitely tuned to observe the birth of galaxies. So we turn on the telescope, look back to this era, and we find red-blooded galaxies doing the backstroke in the Dark Ages.

• 15:14Chuck Nice?

  Wow.

• 15:15Neil deGrasse Tyson?

  So that freaks us all out, because it's like, okay, who ordered that?

• 15:17Chuck Nice?

  Right.

• 15:18Neil deGrasse Tyson?

  Nobody ordered that. Okay? So either our entire understanding of the Big Bang and the expansion and cooling of the universe is wrong, or these are varieties of galaxies that we haven't seen before.

• 15:34Neil deGrasse Tyson?

  And we're mistakenly putting them in a place where an ordinary galaxy would have been with those same properties. But could there be a different kind of galaxy with those same properties that is otherwise unfamiliar to us? This happens all the time, by the way. So you say, "Oh, I know who you are because you're standing there and you're doing X, Y, Z." Because I'm using information that I think should describe fully who you are. Turns out, you're not that. You're something completely different. So all my understanding of you being there is wrong, is completely wrong.

• 16:11Chuck Nice?

  Right.

• 16:11Neil deGrasse Tyson?

  So, so if you're a betting person, I would not bet against the Big Bang.

• 16:18Chuck Nice?

  Exactly. I see what you're saying. So it's kind of basically like when you're looking back, because you're looking back in time, but you're looking back in time through different wavelengths.

• 16:29Neil deGrasse Tyson?

  Correct. Yeah, correct. And we have our catalogs of everything that we understand.

• 16:34Chuck Nice?

  Right.

• 16:34Neil deGrasse Tyson?

  And we're looking to a place we've never looked before in wavelengths that we've never received from that part of the universe. And we see objects, "Hey, these look like our galaxies that don't belong there."

• 16:45Chuck Nice?

  Right.

• 16:46Neil deGrasse Tyson?

  Maybe they're not our galaxies.

• 16:47Chuck Nice?

  Maybe they're not our galaxies.

• 16:48Neil deGrasse Tyson?

  Maybe there's nothing in this catalog that we have created of everything nearby to us. Maybe there's a whole new early universe catalog.

• 16:56Chuck Nice?

  Completely different. Yeah. It's like looking at an ultrasound and you see a baby, but the baby is like watching TV and smoking a cigar. Right? You're like, "Hey, something's wrong with this."

• 17:09Neil deGrasse Tyson?

  Something doesn't work.

• 17:09Chuck Nice?

  Something's up. But it doesn't necessarily mean that it's not a baby in there, you know?

• 17:13Neil deGrasse Tyson?

  Right. Yes. I don't know what the hell that would be, but if you...

• 17:19Chuck Nice?

  Dude, that's so great. All right.

• 17:21Neil deGrasse Tyson?

  All right. We gotta, let's close this out, this first segment. And when we come back, more Cosmic Queries Grab Bag when StarTalk returns.

• 17:37Speaker 02

  Hey, I'm Roy Hill Percival and I support StarTalk on Patreon. Bringing the universe down to earth. This is StarTalk with Neil deGrasse Tyson.

• 17:53Neil deGrasse Tyson?

  We're back, Cosmic Aquarius. Grab bag. These are fun. I like grab bags. Chuck? Yeah, exactly. I got Chuck nice with me. Oh Chuck, I have something to add to that question. How much does a cloud weigh? Okay. I'm gonna add something to that. So generally, if you look up whales in, you know, in a book or on a Wiki page, it'll say how much they weigh. Right. Okay. And there's a lot. They're the heaviest animals that ever existed. Mm-hmm. But is it really fair to say how much they weigh? Because you know what you're doing? You're taking them out of the water. Right. And putting them on land. Right. And measuring them on dry land immersed in air. Your big blubbery fat butt.

• 18:38Neil deGrasse Tyson?

  Tell that to its face. Exactly.

• 18:42Neil deGrasse Tyson?

  So the point is, the whale doesn't live on land. Right. It lives in the water. So what matters here is not the air buoyancy it gets, which would be irrelevant as it is for us. What matters is the water buoyancy. Right. So in water, a whale weighs zero. Okay? It can move up and down freely the way a perfectly neutrally buoyant balloon could move up and down freely in our air. So to a whale, a whale weighs nothing. Wow. That's kinda cool. Yeah. Because in the medium, it weighs nothing. Right. There you go. It is. That's very cool. Okay. All right. Here we go. Let's keep moving on with... Keep on moving.

• 19:24Neil deGrasse Tyson?

  We're gonna keep moving with... This is Rebecca. I'm gonna say, "Fuchs."

• 19:32Neil deGrasse Tyson?

  Okay.

• 19:32Chuck Nice?

  Yeah. Spelled could be a bunch of different things, but I'm gonna go with fukes.

• 19:37Neil deGrasse Tyson?

  Fine.

• 19:37Chuck Nice?

  All right. Uh, she says, hello, Dr. Tyson, Lord Nice, Rebecca from Connecticut here. Uh, could you please explain in the simplest terms possible, please? Why do we think that space and time are emergent and not fundamental?

• 19:56Neil deGrasse Tyson?

  Oh.

• 19:57Chuck Nice?

  I don't know what that means, Neil.

• 19:58Neil deGrasse Tyson?

  Oh, oh.

• 20:00Chuck Nice?

  Oh, I don't even know what she means by that.

• 20:02Neil deGrasse Tyson?

  Oh. Um, so there's been some murmurs about it being the consequence. Well, so I, I can tell you the little bit that I know. Okay.

• 20:14Chuck Nice?

  Okay.

• 20:14Neil deGrasse Tyson?

  Actually, I think that question might've come in when we had Stefan Alexander here, who was a sort of cosmologist particle physicsist dude. And maybe he would've been better equipped to answer that. But let me tell you what I just learned in a conversation with Brian Greene, who's right up the street from us in Columbia Universe.

• 20:35Chuck Nice?

  Our buddy Brian.

• 20:36Neil deGrasse Tyson?

  But our buddy Brian, author of the bestselling book, The Elegant Universe. And he followed it up with The Fabric of the Cosmos. Here's what he told me, and it's blew my mind. All right. So you gotta like hang with me for this.

• 20:49Chuck Nice?

  Okay.

• 20:49Neil deGrasse Tyson?

  So quantum physics tells us that there's no such thing as empty space.

• 20:57Chuck Nice?

  Okay.

• 20:58Neil deGrasse Tyson?

  That in empty space, where you would classically say there's zero energy because there's nothing there, quantum physics says, uh-uh, uh-uh. There's always a chance of there being some energy everywhere. Okay? And, and this is called the vacuum energy of the universe. This is where the source is called. Okay. So how is this manifested? So if you run through the quantum physics equations, you get particles.

• 21:30Neil deGrasse Tyson?

  Out of that energy popping into existence, matter, antimatter particle pairs that then rejoin and make energy again. Okay, so, energy is coming and going with particles, and it's a seething soup within the vacuum of space. Okay, these are called virtual particles. So, no one denies that they're there, even though we've never measured them. There's a very natural prediction of quantum physics, and what quantum physics, everything else quantum physics had predicted has turned out to be correct. So, we're sticking with this explanation. Now, it turns out, these particle pairs, since they were created together, know about each other. Ah.

• 22:12Neil deGrasse Tyson?

  They know about each other in a quantum entanglement sort of way. Okay. Okay. Well, if they know about each other because they're quantum entangled, and quantum entanglement means if something happens to one particle over here, the other one knows about it instantly. And the only way we can think about that is if there's some kind of wormhole between the two of them, where it doesn't have to then travel through the physicality of space. Some kind of wormhole, because then you can get to two places instantly, without, quote, violating the, the speed of light rule. So, here's what he told me, that there's some emergent thinking that suggests that the very fabric of spacetime

• 22:58Neil deGrasse Tyson?

  is the network of these wormholes created by the seething soup of virtual particles. So that those wormholes are themselves the fabric of the universe. They're weaving together the fabric of the universe. And that blew my mind. So, because we, we speak of the fabric as distorting, and it's sort of metaphor, right, and, you know, but is it literal? Is it a literal thing that could be true? So, so, there's that. Okay, so now about time.

• 23:36Neil deGrasse Tyson?

  What I do know is that we measure time by things that repeat. Okay.

• 23:40Chuck Nice?

  Right.

• 23:41Neil deGrasse Tyson?

  Cycles. If cycle, right. If nothing repeats, you could maybe know what happened before something or after something, but you wouldn't be able to measure the time between it. So I don't know about time as being emergent relative to what I just learned from Brian Greene, that the very fabric of spacetime might itself be emergent and a property of the vacuum. So I lost a few nights of sleep on that one.

• 24:06Chuck Nice?

  Nah, I don't blame you. Uh, jeez, I'm, I'm losing like just brain cells listening to it. That is fricking.

• 24:13Neil deGrasse Tyson?

  Okay, that's the best I could do in this situation. So.

• 24:16Chuck Nice?

  Hey Rebecca.

• 24:17Neil deGrasse Tyson?

  And so Chuck, this word emergence, of course, has its own meaning in biology, in biological circles in evolution. Right? Because you could look at a bird like pecking away on the ground. And you can study every atom and molecule of that bird. And you probably would not know that a group of birds will flock together by analyzing a single bird.

• 24:39Chuck Nice?

  Right.

• 24:39Neil deGrasse Tyson?

  So that flocking is sort of an emergent feature of a group of birds that you would never learn by studying one bird. We don't, as far as we can tell, you wouldn't learn it. So, so emergent property, maybe consciousness is emergent. Which is one, they're worried about AI. You keep programming up AI. Bada bing.

• 24:58Chuck Nice?

  If you get enough data points coming together with enough computing power, then all of a sudden, it's not that you made it intelligent enough to become sentient. It just becomes that because of those things.

• 25:13Neil deGrasse Tyson?

  And I just saw the, the preview again for that movie Megan.

• 25:18Chuck Nice?

  Oh my God, I love that movie.

• 25:20Neil deGrasse Tyson?

  Oh no, I don't, I can't see the movie after that preview. That's a little freak, it'll scoop me forever.

• 25:24Chuck Nice?

  So much.

• 25:25Neil deGrasse Tyson?

  So, so that's an emergence, but here in, in the universe, the emergent would be something that was not there from the beginning. Right? It'll show up later because something else happened. So, so this is, this is how we're using the term in physics, which is a bit different from how it's been commonly used in biology. That's all.

• 25:45Chuck Nice?

  Cool. Cool, man.

• 25:47Neil deGrasse Tyson?

  Yeah, all right.

• 25:47Chuck Nice?

  Well Rebecca, what a great question. Look at you. That was very cool. All right, let's go on to Catherine B here and Catherine B says, "Good day all. My name is Catherine and I'm from a small insignificant town near Ottawa, Canada."

• 26:04Chuck Nice?

  Don't sell yourself short there, Cap.

• 26:05Neil deGrasse Tyson?

  I know, right? Let us be the judge of whether it's significant.

• 26:08Chuck Nice?

  We can tell you, you don't matter. You don't have to lead with that.

• 26:13Neil deGrasse Tyson?

  Let other people tell you.

• 26:14Chuck Nice?

  Let other people put you down. That's what, that's how you know you're Canada and not American. Right? Yeah, cuz we, other people around the world gotta put us down. We're like, we're number one. All right. She says, I have a question that I have not been able to find the answer to, and I know you can answer it, Neil, or at least you'll have a theory about it. If time speeds as we leave Earth's gravity and slows with velocity, how will astronauts traveling to Mars be affected once they leave Earth's gravity? Does it no longer slow? So they will only be impacted by the speeding up of time

• 26:58Chuck Nice?

  because of their velocity? If that's so, how long will a three-year Earth journey be for them? I hope I'm making sense right now.

• 27:08Neil deGrasse Tyson?

  Completely, completely. So, so this is a combination of a bunch of things. We know that the closer you get to a source of gravity, the slower time ticks for you. And the farther away, the faster it ticks. The faster you move, the slower time ticks for you. And this, okay, sorry. So, if you are not only moving farther away from Earth's gravity,

• 27:30Chuck Nice?

  Right.

• 27:31Neil deGrasse Tyson?

  which would speed up time, but now you are traveling fast, that would slow down time. You gotta run the equations and see which equations win.

• 27:40Chuck Nice?

  Right, which is greater. Which is a greater pull.

• 27:42Neil deGrasse Tyson?

  Which is a greater, and I can't do that in my head. I could do that on paper, I can do it. But here's one I did do already, and that's for GPS satellites. So GPS satellites orbit the Earth at very high speeds. So relative to us, their time is slowing down. Okay? If you only factor in their high speeds, but they're also much farther away from Earth's surface than we are.

• 28:08Chuck Nice?

  Right.

• 28:08Neil deGrasse Tyson?

  So their time is speeding up. And the speed up time is about twice what the slowdown time is.

• 28:17Chuck Nice?

  Mm-hmm.

• 28:17Neil deGrasse Tyson?

  So the speeding up wins

• 28:20Chuck Nice?

  Gotcha.

• 28:21Neil deGrasse Tyson?

  against the, the speeding up of the time wins against the slowing down of the time for its orbital speed. Which means the GPS satellites do not keep the same time we do. And they have to be pre-corrected before you get the time signal from your phone company.

• 28:39Chuck Nice?

  Wow.

• 28:40Neil deGrasse Tyson?

  Yeah.

• 28:41Chuck Nice?

  So these factors are all in work, working in either conjunction or against one another at all times.

• 28:49Neil deGrasse Tyson?

  At all times.

• 28:50Chuck Nice?

  At all times.

• 28:51Neil deGrasse Tyson?

  And it's cumulative. It's cumulative. So.

• 28:53Chuck Nice?

  Okay.

• 28:54Neil deGrasse Tyson?

  So if you're gonna, if you're on a mission for three, by the way, it's very tiny. It's cumulative but tiny. So you wanna know how much younger or older is your twin astronaut sibling who went to Mars? It would be fractions of a second.

• 29:09Chuck Nice?

  Gotcha.

• 29:10Neil deGrasse Tyson?

  Yeah.

• 29:11Chuck Nice?

  There you go.

• 29:11Neil deGrasse Tyson?

  Just off the top of my head.

• 29:13Chuck Nice?

  Wow. It's still fascinating because it's not a perception of time.

• 29:18Neil deGrasse Tyson?

  Correct.

• 29:18Chuck Nice?

  Speeding up or slowing down. It is actual time itself.

• 29:22Neil deGrasse Tyson?

  Yes. Timekeeping devices, your heartbeat, your brain thoughts, everything.

• 29:26Chuck Nice?

  Everything.

• 29:26Neil deGrasse Tyson?

  Slow down.

• 29:27Chuck Nice?

  Mm-hmm.

• 29:28Neil deGrasse Tyson?

  So crazy.

• 29:30Chuck Nice?

  All right. Hey, Catherine B. Thanks for that. That's very cool. Look forward to some more information forthcoming about your trip to Mars, Catherine, because I know that's why you asked.

• 29:39Neil deGrasse Tyson?

  Ah, I actually got a plan.

• 29:41Chuck Nice?

  I know. You're like.

• 29:41Neil deGrasse Tyson?

  You got a plan.

• 29:42Chuck Nice?

  I'm from nowhere, Ottawa, but I'm going to Mars. So how about that?

• 29:50Neil deGrasse Tyson?

  Okay.

• 29:51Chuck Nice?

  All right, here we go. Let's move on to, okay, man, you just messing with me. This is Keti Kukunasvili. Kukunasvili.

• 30:01Neil deGrasse Tyson?

  Don't pretend like you knew that.

• 30:06Neil deGrasse Tyson?

  Oops.

• 30:09Neil deGrasse Tyson?

  That's a good act there.

• 30:10Chuck Nice?

  Yeah.

• 30:10Neil deGrasse Tyson?

  Okay.

• 30:12Chuck Nice?

  Keti Kukunasvili.

• 30:13Neil deGrasse Tyson?

  Yeah, all right. That could, that sounds like it could be it.

• 30:15Chuck Nice?

  Kukunasvili.

• 30:16Neil deGrasse Tyson?

  All right, go ahead.

• 30:17Chuck Nice?

  Hey, Neil. Hey, Chuck. I'm new to Patreon, but a longstanding fan of StarTalk.

• 30:24Chuck Nice?

  I have a very basic question. Why is string theory so unprovable? And if so, why are we still trying to prove it?

• 30:33Neil deGrasse Tyson?

  You know, every time I see Brian Greene, I slap him upside the head and say, Brian, why haven't you string theorists solved this problem yet? And his answer is, well, it's a very hard problem. Well, so was general relativity and Einstein did it all by himself. And he took 10 years, which was a long time for an Einstein brain, but he solved it. And here all y'all, that's the plural of y'all.

• 30:59Chuck Nice?

  Right.

• 30:59Neil deGrasse Tyson?

  It's all y'all.

• 31:00Chuck Nice?

  All y'all.

• 31:00Neil deGrasse Tyson?

  Okay, here's all y'all string theorists, there's dozens of them, probably not much more than that, but I'd say dozens of them in the world, working on it for 40 years. And so I, why don't you all, so I said, why don't you just confess to yourselves, you are collectively too stupid to figure it out?

• 31:16Chuck Nice?

  Oh, no.

• 31:17Neil deGrasse Tyson?

  Or, I said this to his face, or that the, or, or that it's not the problem that you should be solving and the actual solution is something else that nobody's thought of yet.

• 31:30Chuck Nice?

  Ooh.

• 31:31Neil deGrasse Tyson?

  Yeah, I was in his face.

• 31:32Chuck Nice?

  Oh, my goodness. Yo, that's, that's hardcore, bro.

• 31:36Neil deGrasse Tyson?

  It was, now I'm bigger than him, so I knew I could.

• 31:38Chuck Nice?

  I was gonna say.

• 31:40Chuck Nice?

  You kind of called him to question the, you know, the veracity of his entire life's work.

• 31:48Chuck Nice?

  That's a little rough, man.

• 31:49Neil deGrasse Tyson?

  It's a little rough. It's, it's a little rough. Uh, yeah, I did it to be, of course, purposely antagonistic.

• 31:54Chuck Nice?

  Of course, you're joking.

• 31:55Neil deGrasse Tyson?

  But it was, um, how long are you gonna say the problem is just hard? Rather than we are barking up the wrong tree.

• 32:03Chuck Nice?

  Ooh.

• 32:03Neil deGrasse Tyson?

  So that's, so that's kind of how I think about it. Plus, it assumes that there can be one coherent theoretical understanding of all phenomena in the universe. It assumes that. And you're putting your philosophical mission statement on the universe that you're investigating. And the history of that exercise has never proven to be successful. I'll give an example. Uh, Copernicus says, you know, I think the sun is in the middle of the universe and not Earth. And so let me create a, a, a, a, a sun-centered universe. So he does it and he puts the sun in the middle and Mercury, the orbits of Mercury, Venus,

• 32:46Neil deGrasse Tyson?

  Mars, Jupiter, Saturn, asteroid belt wasn't discovered yet, but on out, he does this, okay.

• 32:53Neil deGrasse Tyson?

  Do you realize it was still wrong? Because he assumed that the universe is per- God made the universe, the universe is perfect, because God is perfect. So clearly, God made orbits that are perfect circles, because a circle is a perfect shape.

• 33:09Chuck Nice?

  Concentrated circles, right.

• 33:11Neil deGrasse Tyson?

  So that was a theoretical expectation placed upon his ideas about what the uni- how the universe is put together. And it was just wrong. The orbits are squashed circles. And they're all squashed differently. And the most squashed circle among objects known as planets, or formerly known as planets, is Pluto. Pluto's orbit is so squashed, it crosses the orbit of Neptune.

• 33:39Chuck Nice?

  Right.

• 33:40Neil deGrasse Tyson?

  This is hardly the handiwork of someone who really cares about perfect circles. All right? So, so I'd just like to take a step back and stay open to the possibility that there's a whole other idea that could supplant everything they're doing, that wouldn't take thirty people forty years to try to figure it out. Because that's a lot of brain power going in there. In all fairness to them, they made certain progress with their string theory in interpreting, using it to interpret things that we now understand more deeply. Okay, so that works. And by the way, how close are we to proving it experimentally? Some predictions cannot, forever in the future will never, no.

• 34:24Chuck Nice?

  No matter what.

• 34:24Neil deGrasse Tyson?

  But-

• 34:25Chuck Nice?

  Some of it is interdimensional.

• 34:31Neil deGrasse Tyson?

  Like, yeah, I'm gonna go there too. You're holding your chin like you're contemplating. Interdimensional, yeah, a higher dimension, I got this one, all right. The point is, you can have a hypothesis that is untestable in its core, but if the hypothesis is true, some other things might be true that you can then test. So you can test the edges of it, all right? And that can still make progress on the thing that you're waiting to test if you can't do it today.

• 35:07Chuck Nice?

  I got you. I mean, that makes perfect sense. And what you're saying is they're not even close to that.

• 35:16Chuck Nice?

  That's rough, man.

• 35:17Neil deGrasse Tyson?

  Yeah, so Einstein said, so here's what Einstein said. Einstein said, um, he has something called the equivalence principle, deep and profound statement that, that the mass that gravity sees when it pulls on you is identically equal to the mass that a force sees when it accelerates it

• 35:45Neil deGrasse Tyson?

  through space.

• 35:46Chuck Nice?

  Ooh.

• 35:47Neil deGrasse Tyson?

  Okay, these are, these two masses, there's no reason in heaven and earth why these two masses have to be the same.

• 35:56Chuck Nice?

  Right.

• 35:57Neil deGrasse Tyson?

  But they sort of seem to be the same. And Einstein said, let us declare them to be the same. And if they are the same, here's something that would be true. And what is that? If I'm in an elevator and you cut the cable and I let go of a ball.

• 36:16Chuck Nice?

  Right.

• 36:17Neil deGrasse Tyson?

  I will fall, the elevator's falling, the ball is falling and it'll stay

• 36:21Chuck Nice?

  Stay.

• 36:21Neil deGrasse Tyson?

  stationary in front of my face.

• 36:23Chuck Nice?

  Right. You'll be falling at the same rate. And then also Einstein will have to face murder charges.

• 36:30Neil deGrasse Tyson?

  What, at the end of the?

• 36:31Chuck Nice?

  At the end of that experiment.

• 36:33Neil deGrasse Tyson?

  It's only if he cut the cable.

• 36:34Chuck Nice?

  Yeah, oh, that's true.

• 36:37Chuck Nice?

  He's probably too smart to cut the cables himself, to be honest, right?

• 36:41Neil deGrasse Tyson?

  Okay, so the, the point there is, I am in free fall. Okay?

• 36:46Chuck Nice?

  Right.

• 36:47Neil deGrasse Tyson?

  Fine. But if I had, so I'm zero G, but if I'm standing on Earth, watch this, I'm standing on Earth and I let go of the ball, it falls. I'm in one G. Okay, so now watch, now I have rockets on the back of your ship and I accelerate you through the universe at one G. And you, holding a ball, you let go of the ball, it'll fall down to the ground. You cannot distinguish whether you were in a rocket accelerating through empty space or standing on a planet. Under that same 1G force.

• 37:20Chuck Nice?

  That is such a like elegant little thought experiment.

• 37:25Neil deGrasse Tyson?

  Elegant and profound and you could do these experiments. It's a thought experiment, you could do the experiment.

• 37:30Chuck Nice?

  You can actually do it.

• 37:31Neil deGrasse Tyson?

  Right, on the edges of it.

• 37:32Chuck Nice?

  On a train or I think that's what they did though, yeah. That's so cool.

• 37:36Neil deGrasse Tyson?

  Okay, gotta take another break. When we come back, more Cosmic Queries, the grab bag edition.

• 37:55Neil deGrasse Tyson?

  We're back, StarTalk Cosmic Queries, grab bag edition. Chuck, why did we stop calling it Galactic Gumbo? Because that was fun.

• 38:03Chuck Nice?

  I think maybe people got tired of me imitating.

• 38:08Neil deGrasse Tyson?

  Paul Puddin.

• 38:09Chuck Nice?

  Yeah, Paul Puddin, that old Galactic Gumbo.

• 38:13Neil deGrasse Tyson?

  But is he the one that spoke like that?

• 38:14Chuck Nice?

  I don't know if it was him. I just know that that guy was on PBS and he was amazing. Because he'd be like, now, now, now, here we're going to do it. Bring that on there and put that.

• 38:25Neil deGrasse Tyson?

  Whoever that guy was, that's the guy.

• 38:26Chuck Nice?

  Yeah, we're going to add some cay on pepper.

• 38:34Chuck Nice?

  That was amazing, that dude. He was awesome.

• 38:37Neil deGrasse Tyson?

  So, all right, so we've got some more questions. Bring it on.

• 38:40Chuck Nice?

  All right, here we go. Here, this is Captain James Riley.

• 38:46Neil deGrasse Tyson?

  Okay.

• 38:47Chuck Nice?

  Captain Riley says, if a photon is a particle.

• 38:53Neil deGrasse Tyson?

  Which it is.

• 38:54Chuck Nice?

  Can't it just sit still? Why does it always have to be moving at the speed of light?

• 39:02Neil deGrasse Tyson?

  Oh.

• 39:03Chuck Nice?

  Wow, look at that.

• 39:04Neil deGrasse Tyson?

  Okay, so here's what we have concluded. And this might sound like a cop out answer.

• 39:09Chuck Nice?

  Okay.

• 39:11Neil deGrasse Tyson?

  Objects that have mass.

• 39:15Chuck Nice?

  Right?

• 39:16Neil deGrasse Tyson?

  Can never attain the speed of light.

• 39:20Chuck Nice?

  Oh.

• 39:21Neil deGrasse Tyson?

  And objects that do not have mass.

• 39:23Chuck Nice?

  Right.

• 39:24Neil deGrasse Tyson?

  Only exist at the speed of light.

• 39:28Neil deGrasse Tyson?

  That is how, that is the hand we're dealt in this universe.

• 39:32Chuck Nice?

  Wow, so it's a massless particle that ceases to exist when it stops traveling at the speed of light?

• 39:38Neil deGrasse Tyson?

  Well, it can't not.

• 39:39Chuck Nice?

  It can't not?

• 39:40Neil deGrasse Tyson?

  Right, yeah, right. So what will happen is?

• 39:42Chuck Nice?

  So it has to hit something?

• 39:43Neil deGrasse Tyson?

  If, exactly. So if it's gonna, if that, if the energy of that particle is gonna become matter.

• 39:48Chuck Nice?

  Right.

• 39:49Neil deGrasse Tyson?

  Then the matter has to be moving slower than the speed of light. But the energy budget remains the same. We're fine in the energy budget.

• 39:56Chuck Nice?

  Exactly, cuz you got a little exchange going on there.

• 39:58Neil deGrasse Tyson?

  Exchange going on.

• 39:58Chuck Nice?

  Wow!

• 39:59Neil deGrasse Tyson?

  Mc squared. Yeah, so I, I'm not, I'm not answering it with a why. I'm just declaring that that is the universe we live in. Now. Now, you wanna hear something profound? I think, okay? This, this is profound. Um, you may know that time slows down as you go faster and faster and stops at the speed of light.

• 40:24Chuck Nice?

  Exactly.

• 40:25Neil deGrasse Tyson?

  Okay, okay. Well, neutrinos, there was something called the solar neutrino problem. Where everything we understood about thermonuclear fusion in the core of the sun told us how many neutrinos it should be making. We build detectors on Earth and we were detecting only a fraction of the predicted neutrinos.

• 40:45Chuck Nice?

  Okay.

• 40:46Neil deGrasse Tyson?

  And this was, this went on for decades. And people say, maybe we don't understand fusion. But it worked out. We're getting the energy budget for the sun. That seemed to work. Maybe there's something wrong with the detector. No, we got the detector thing. So what's going on? Okay, here's what we found. Well, plus, we didn't quite know how fast do neutrinos move? Could they be moving the speed of light? Okay, we don't know. Here's what we found. There's more than one species of neutrino.

• 41:16Chuck Nice?

  Oh.

• 41:17Neil deGrasse Tyson?

  And the neutrinos emitted by the sun change species en route to Earth.

• 41:24Chuck Nice?

  What?

• 41:24Neil deGrasse Tyson?

  So the detectors we built were detected to find only the kind of neutrinos that the sun made, not the kind of neutrinos that ended up landing and arriving here on Earth. It'd be as though I tossed you a basketball.

• 41:39Chuck Nice?

  Right.

• 41:39Neil deGrasse Tyson?

  And you received a football.

• 41:41Chuck Nice?

  Look at that.

• 41:42Neil deGrasse Tyson?

  But you set up detectors only for basketball.

• 41:44Chuck Nice?

  Right.

• 41:45Neil deGrasse Tyson?

  Okay, so now watch, wait, wait. So, basically, it decays into another species, okay?

• 41:51Chuck Nice?

  Gotcha.

• 41:51Neil deGrasse Tyson?

  Okay.

• 41:53Neil deGrasse Tyson?

  Wait a minute. If it knows to do that after a certain amount of time, then it can't be traveling at the speed of light. Because if it was at the speed of light, it would have no concept of time and would not know when to change.

• 42:07Chuck Nice?

  When to transition.

• 42:09Neil deGrasse Tyson?

  Exactly.

• 42:09Chuck Nice?

  It could not know because traveling at the speed of light means that it can only exist as it is.

• 42:17Neil deGrasse Tyson?

  As it.

• 42:18Chuck Nice?

  While it's traveling at the speed of light.

• 42:19Neil deGrasse Tyson?

  Correct. Because there's no time clock to tell it to do anything else.

• 42:23Chuck Nice?

  There's no time to tell it what to do.

• 42:24Neil deGrasse Tyson?

  Correct.

• 42:25Chuck Nice?

  Yeah.

• 42:25Neil deGrasse Tyson?

  So in one swell foop, we had, we learned that we're looking for the wrong neutrino, and the neutrino does not travel at the speed of light. It travels very close to it.

• 42:39Chuck Nice?

  Close, close, but not the same.

• 42:41Neil deGrasse Tyson?

  But not the same.

• 42:42Chuck Nice?

  That is fascinating.

• 42:44Neil deGrasse Tyson?

  Yes, this is science, dude. This is crazy fun.

• 42:49Chuck Nice?

  Interesting phenomenon. It really is.

• 42:51Neil deGrasse Tyson?

  Yeah.

• 42:51Chuck Nice?

  I just love that the neutrino is like Tom Cruise in The Mission Impossible.

• 42:56Neil deGrasse Tyson?

  Oh.

• 42:56Chuck Nice?

  It leaves the sun and then it gets to Earth and it's just like, pulls his face off like, "It was me all along." You can't detect me.

• 43:09Neil deGrasse Tyson?

  All right, so you got another question.

• 43:12Chuck Nice?

  All right, wow, that was really good stuff.

• 43:14Neil deGrasse Tyson?

  So when neutrinos change species, they go neutrino oscillations, we call them.

• 43:20Chuck Nice?

  Neutrino oscillations, that is so cool.

• 43:22Neil deGrasse Tyson?

  But it will only know to oscillate from one species to another if there's an internal clock. And it can only have it until a clock, if it's going slower than the speed of light. It's that simple.

• 43:31Chuck Nice?

  All right, here we go. This is, um, Walker Folland. And Walker says, gentlemen, this is Walker from West Branch, Michigan. I don't know why I think he sounds like that.

• 43:49Chuck Nice?

  He goes, if two objects travel parallel on a sphere, three dimensional sphere, they will eventually converge at a point.

• 43:59Neil deGrasse Tyson?

  Yes.

• 44:01Chuck Nice?

  If we extrapolate that the fourth dimension, does that roughly explain behavior of gravity in our universe? So if we extrapolate that to the fourth dimension, does that roughly explain the behavior of gravity in our universe?

• 44:21Neil deGrasse Tyson?

  Yeah, so for us, the fourth dimension is time. And so I'm not quite getting where that would land. But let me just remind people that how we learned in grade school, perhaps, certainly by middle school, that parallel lines, parallel lines never intersect. That's only if the space in which they're embedded is completely flat.

• 44:42Chuck Nice?

  Right.

• 44:43Neil deGrasse Tyson?

  But if it's curved, like on a surface, parallel lines, and a line is very rigidly defined, as if you cut through that line, that cut will go through the center of your sphere. Okay, that assures you that that's a proper line, a geodesic, it's called, or great circle if you're taking an airplane. Okay, so two lines that are parallel will ultimately intersect in two places on a sphere.

• 45:14Neil deGrasse Tyson?

  Okay, which is odd, not odd, which is interesting because we refer colloquially to lines of latitude as parallels.

• 45:28Neil deGrasse Tyson?

  Lines of latitude do not intersect. And we're borrowing the concept of not intersecting lines being parallel and applying it to the surface of the earth and calling latitude lines parallel. But they're not parallel because they're not authentic lines. There's only one authentic latitude line in the world. And what line is that?

• 45:52Chuck Nice?

  The equator.

• 45:52Neil deGrasse Tyson?

  The equator. Because even cut through the equator, that goes to the center of the earth. All the other cuts do not go through the center. They're not legitimate lines. And that's why airplanes don't go along latitude lines. Because it's not the shortest distance between two points.

• 46:07Chuck Nice?

  Wow.

• 46:08Neil deGrasse Tyson?

  Yeah, you ever see the airplane trajectories? It's always, well, why are you looping up like that? Why don't you just go along this straight line here on your Mercator map, which completely distorts, you know, what you might think is how you got to get from one place to another.

• 46:24Chuck Nice?

  Wow. Look at that.

• 46:26Neil deGrasse Tyson?

  Yeah.

• 46:26Chuck Nice?

  That's very cool.

• 46:28Neil deGrasse Tyson?

  Yeah. So, but I don't think I answered the question. What was the question?

• 46:31Chuck Nice?

  Well, because he's saying that if we were to extrapolate that out to the fourth dimension, which is time, would that explain gravity in our universe?

• 46:39Neil deGrasse Tyson?

  Yeah, I don't, I don't feel that. I don't feel that. What I do know is that as you go back in time, the universe was smaller. So if you take, imagine our universe has the surface of a sphere that is expanding. We're all just on a surface, okay? So I lost a dimension just for the sake of this explanation.

• 46:59Chuck Nice?

  Right.

• 47:00Neil deGrasse Tyson?

  So if you go back in time, the universe was smaller and smaller and smaller. So you can follow a time arc backwards and all time arcs will meet at the center of the balloon.

• 47:19Neil deGrasse Tyson?

  So if you ask, "On the surface of balloon, where's the center?" I say, "It is nowhere on this balloon." The center of our universe exists in time 14 billion years ago. Let's find that center. And now you go back in time as the balloon shrinks, and there it is, infinitesimally small. That is the center of everything. That is the center of the universe.

• 47:47Chuck Nice?

  Wow, that's fascinating.

• 47:49Neil deGrasse Tyson?

  So time has a center, in a way.

• 47:50Chuck Nice?

  Right, exactly. Right, right, right.

• 47:53Neil deGrasse Tyson?

  Dude, that was a mind-blowing... I'm exhausted.

• 47:57Chuck Nice?

  Oh, man. These people came with it today, boy.

• 48:00Neil deGrasse Tyson?

  They came out of the bushes for that one.

• 48:02Chuck Nice?

  Yeah, they really did. It was good stuff.

• 48:04Neil deGrasse Tyson?

  All right, thanks, everyone, for those questions. Great to have a new Patreon member coming in on the Q and A. All right, that's all the time we have. Chuck, always great to have you there. This has been StarTalk Cosmic Queries, the grab-bag edition. I am Neil deGrasse Tyson, as always, wishing you keep looking up.