Cosmic Queries – Summer School

The sun is out, the weather is warm, and summer school is in session! Neil deGrasse Tyson, co-host Matt Kirshen, and astrophysicist Charles Liu answer fan-submitted questions on mathematics, the Big Bang, the laws of physics, neutrinos, relativity, Pluto, the smell of the Milky Way, and more. NOTE: StarTalk All-Access subscribers can watch or listen to this entire episode commercial-free here: https://www.startalkradio.net/all-access/cosmic-queries-summer-school/ Photo Credit: LassenNPS [Public domain]

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

• 0:00Neil deGrasse Tyson?

  From the American Museum of Natural History in New York City, and beaming out across all of space and time, this is StarTalk, where science and pop culture collide.

• 0:33Neil deGrasse Tyson?

  This is StarTalk. I'm your host, Neil deGrasse Tyson, your personal astrophysicist, and we're coming to you from my office at the Hayden Planetarium of the American Museum of Natural History, right here in New York City. And this edition of StarTalk, we're calling "Summer School."

• 0:52Charles Liu?

  Yeah.

• 0:54Neil deGrasse Tyson?

  Who said yeah?

• 0:55Charles Liu?

  The professor.

• 0:56Neil deGrasse Tyson?

  Friend and colleague, Charles Liu. Charles, welcome.

• 0:59Charles Liu?

  Thank you so much for having me. I love summer school.

• 1:01Neil deGrasse Tyson?

  You love summer school.

• 1:02Charles Liu?

  Absolutely.

• 1:03Neil deGrasse Tyson?

  And I got my co-host for this episode, Matt Gershon. Matt?

• 1:06Matt Kirshen?

  Hey.

• 1:07Neil deGrasse Tyson?

  Welcome back.

• 1:08Matt Kirshen?

  Thank you so much.

• 1:09Neil deGrasse Tyson?

  All right. Host of Probably, Maybe Science?

• 1:12Matt Kirshen?

  Probably Science.

• 1:13Neil deGrasse Tyson?

  Or Could Be Science?

• 1:15Matt Kirshen?

  Nearly Science.

• 1:15Neil deGrasse Tyson?

  Not sure if it's Science?

• 1:16Matt Kirshen?

  Almost there. I can't believe it's not Science. I know it's a Science.

• 1:20Neil deGrasse Tyson?

  Probably Science. Weekly review of science current events.

• 1:26Matt Kirshen?

  That's exactly it.

• 1:27Neil deGrasse Tyson?

  Excellent, excellent.

• 1:28Matt Kirshen?

  That's the podcast.

• 1:29Neil deGrasse Tyson?

  Keep that going, keep that going. Charles, professor?

• 1:32Charles Liu?

  Yes.

• 1:32Neil deGrasse Tyson?

  At City University of New York.

• 1:34Matt Kirshen?

  So we're kind of equals here.

• 1:36Charles Liu?

  Absolutely. No, we are.

• 1:38Neil deGrasse Tyson?

  So this is a-

• 1:38Charles Liu?

  Peas in a pot.

• 1:39Neil deGrasse Tyson?

  This is a Cosmic Queries version, but it's called "Summer School." People just trying to catch up.

• 1:45Matt Kirshen?

  That's right.

• 1:45Neil deGrasse Tyson?

  With stuff they might have missed.

• 1:47Charles Liu?

  Or get ahead.

• 1:48Neil deGrasse Tyson?

  Or get ahead. I forgot. Summer School's for getting ahead, too.

• 1:51Matt Kirshen?

  Right.

• 1:51Neil deGrasse Tyson?

  For motivated students.

• 1:52Matt Kirshen?

  That's right. And with that in mind, I think let's start off with a quite academically advanced question.

• 1:58Neil deGrasse Tyson?

  Let's do it.

• 2:00Matt Kirshen?

  I think Cooper Holland on Instagram asks, "How hard would I have to fart to knock Earth into a skate velocity? Also, wouldn't sunrise be a good time to try it?" Mmm. That's Cooper Holland from Arizona State.

• 2:14Neil deGrasse Tyson?

  From ASU.

• 2:15Matt Kirshen?

  Oh, good.

• 2:17Charles Liu?

  I'm coughing because I'm imagining how much gas needs to be used to make that happen. But the reality is, first, I assume you have an escape velocity from the sun, right?

• 2:28Neil deGrasse Tyson?

  No, he wants to escape from the earth.

• 2:30Charles Liu?

  Oh, he wants to escape from the earth? I thought he wanted the earth to escape from the sun.

• 2:33Neil deGrasse Tyson?

  Oh.

• 2:34Charles Liu?

  Now that is a massive.

• 2:35Neil deGrasse Tyson?

  Yeah, it says to lock earth into escape velocity. That's harder than just if he wanted to escape.

• 2:40Charles Liu?

  If he's gonna escape, that's easy.

• 2:42Neil deGrasse Tyson?

  Just a few cans of beans.

• 2:43Charles Liu?

  There you go.

• 2:44Neil deGrasse Tyson?

  Put him on a gantry.

• 2:47Charles Liu?

  No, earth would be a lot harder, because earth's orbital velocity is about...

• 2:51Neil deGrasse Tyson?

  I just now can't get that picture out of my head. He's positioned on a gantry in Cape Canaveral.

• 2:56Charles Liu?

  Three.

• 2:56Neil deGrasse Tyson?

  Last two cup of beans.

• 2:58Charles Liu?

  One.

• 3:00Neil deGrasse Tyson?

  Launchable tip for weather.

• 3:03Charles Liu?

  But is that solid fuel or a liquid fuel rocket?

• 3:05Neil deGrasse Tyson?

  Oh, yeah, no, that would be... No, that's just air pressure fuel. That's just pressure fuel. That's really a bottle rocket. A bottle rocket, pneumatic rocket. Or like a CO2 pellet rifle. It's pneumatic.

• 3:21Charles Liu?

  Wow. No, see, earth's orbital velocity is about 30 kilometers per second.

• 3:26Neil deGrasse Tyson?

  Per second, correct.

• 3:27Charles Liu?

  Around the sun. You have to take the square root of two of that, and so that makes time 1.4 times 30, so about 42 kilometers per second. Earth's mass is about 6.

• 3:37Neil deGrasse Tyson?

  Because it's a cute little fact, that whatever is your orbital velocity around what you're orbiting, if you multiply that by the square root of two, that's the speed to escape that object.

• 3:47Charles Liu?

  Yeah.

• 3:47Neil deGrasse Tyson?

  It's a very cool fact.

• 3:48Charles Liu?

  It is. It's neat. It's a nice coincidence in math. And the earth's mass of course is...

• 3:53Neil deGrasse Tyson?

  Square root is about 1.4, yeah.

• 3:55Charles Liu?

  Yeah. Earth's mass is 6 billion trillion tons, right? So to generate the amount of impulse necessary to get earth that much mass up to that velocity, that's a lot of cans of beans.

• 4:11Neil deGrasse Tyson?

  Yeah, because you, it's a momentum thing. So you need enough expelled gas so that the recoil of your planet can be meaningful and significant.

• 4:23Matt Kirshen?

  Right, and correct me if I'm wrong, but you'd also have to make sure you're in some way tethered to the earth so you're not just blasting yourself.

• 4:28Neil deGrasse Tyson?

  You can drag the earth with you.

• 4:29Matt Kirshen?

  Right.

• 4:30Neil deGrasse Tyson?

  Otherwise you would just fly off at a tangent, right?

• 4:32Charles Liu?

  Yes.

• 4:33Neil deGrasse Tyson?

  Right.

• 4:33Charles Liu?

  So I think.

• 4:34Neil deGrasse Tyson?

  Ideally, you'd want all humans involved in this.

• 4:36Matt Kirshen?

  Right, you'd want to be holding on to a tree or something.

• 4:38Charles Liu?

  You'd also need every cow in the world.

• 4:40Neil deGrasse Tyson?

  Yeah, the cows.

• 4:41Charles Liu?

  Gotta put them all together.

• 4:42Neil deGrasse Tyson?

  Yeah.

• 4:43Charles Liu?

  Um, I think that's a very good summer school problem calculation to do, yes. Cooper, good luck with that. That's great.

• 4:51Neil deGrasse Tyson?

  But in principle, yes.

• 4:52Charles Liu?

  Yeah.

• 4:53Neil deGrasse Tyson?

  So in other words, if you are in space, there are various ways you can actually set yourself into motion. But to do so, you have to lose mass from your body. Either gas, through gas, liquid, or solid.

• 5:05Charles Liu?

  Yep, and if you're at sunrise, that would be a good time because the best way to inject that extra velocity, the delta V, is in the direction of the orbit, the tangent to the orbit. So not straight out, as some people might think, but actually out at a 90-degree angle.

• 5:20Neil deGrasse Tyson?

  So you can build with, to the speed that the earth has itself, yes.

• 5:23Matt Kirshen?

  Right. Okay.

• 5:26Neil deGrasse Tyson?

  Oh, by the way, but all that methane, that could be a pretty dangerous situation.

• 5:30Charles Liu?

  It's true, one match.

• 5:32Neil deGrasse Tyson?

  That's it.

• 5:32Charles Liu?

  And you've got, yeah.

• 5:33Neil deGrasse Tyson?

  Then you have a bomb.

• 5:34Charles Liu?

  That's a flare.

• 5:35Neil deGrasse Tyson?

  That's a bomb.

• 5:36Matt Kirshen?

  Also, that's a greenhouse gas.

• 5:38Neil deGrasse Tyson?

  Yes, it is.

• 5:38Charles Liu?

  Oh, yeah, yeah, yeah, yeah.

• 5:39Neil deGrasse Tyson?

  Yeah, very potent, more potent than CO2.

• 5:41Charles Liu?

  True, so you really have to light that thing, yeah, so.

• 5:46Matt Kirshen?

  But then light, would then lighting it.

• 5:48Charles Liu?

  Fly out into space.

• 5:48Matt Kirshen?

  If you could control that lighting.

• 5:49Neil deGrasse Tyson?

  No, wait a minute.

• 5:50Matt Kirshen?

  If that was a thrust.

• 5:51Neil deGrasse Tyson?

  Wait, if you leave earth, you need the greenhouse gases to retain the warmth.

• 5:56Charles Liu?

  That's right.

• 5:56Neil deGrasse Tyson?

  Yeah.

• 5:57Charles Liu?

  So it's the balance, it's the balance, yeah.

• 5:59Matt Kirshen?

  Wow.

• 6:00Charles Liu?

  That's very exciting. You know what, I think I'm gonna have to assign that to my astrophysics class next year.

• 6:06Neil deGrasse Tyson?

  And then the dean will call you.

• 6:10Charles Liu?

  Well, maybe Cooper will help me out with that.

• 6:12Neil deGrasse Tyson?

  Mm-hmm.

• 6:13Matt Kirshen?

  Well, while we are doing calculations, Tom Forman on Facebook asks, is math a discovery or an invention?

• 6:21Charles Liu?

  Beautiful, beautiful.

• 6:23Neil deGrasse Tyson?

  Don't get me started, I want to hear Charles first.

• 6:25Charles Liu?

  Okay, well, remember that my wife is a mathematician.

• 6:28Neil deGrasse Tyson?

  Yes, she is.

• 6:28Charles Liu?

  Right, and so.

• 6:30Neil deGrasse Tyson?

  My wife has a PhD in mathematical physics.

• 6:33Charles Liu?

  That's right. Twinsies.

• 6:36Neil deGrasse Tyson?

  So we got math going in the family here.

• 6:38Charles Liu?

  And my son also, given a choice of either studying math or astrophysics in college, has chosen math. Anyway, that's okay. We still love you.

• 6:49Neil deGrasse Tyson?

  Sorry.

• 6:49Charles Liu?

  Yeah, I know. I know.

• 6:53Neil deGrasse Tyson?

  Such a disappointment.

• 6:54Charles Liu?

  When did you know? Were the signs always there?

• 6:59Charles Liu?

  When he was a little kid, putting refrigerator magnets in strange shapes, I knew that something was up.

• 7:05Neil deGrasse Tyson?

  Something.

• 7:05Charles Liu?

  Something was up.

• 7:06Neil deGrasse Tyson?

  He was hiding something in the closet. Okay.

• 7:10Charles Liu?

  Anyway, math is something that exists by itself. But mathematics, as we use it and formulate it today, is an invention of humans. This is a clear reality of the universe. Because things will do what they're doing whether we understand them or not. And we created math in order to try to understand and reproduce and utilize those things that nature provides for us. So for example, when the ancients were building pyramids, they invented geometry, right? Those pyramids would have stood anyway if we had put them together and not known the equations.

• 7:55Charles Liu?

  But with the equations, the ancients were able to build them properly. The same is true with, say, rocket equations that allow us to send things out into space. We could have sent things into space without knowing how to do the calculations, but we wouldn't have had much control over it. So, bottom line, the math you see in textbooks today or in papers, we humans have invented that following a set of rules that nature has provided for us as a template. Neil.

• 8:24Neil deGrasse Tyson?

  I'm okay with that.

• 8:25Charles Liu?

  Okay.

• 8:25Neil deGrasse Tyson?

  I'm okay. I don't like debates about whether one word or another word best describes it. I'd rather say that maybe our language needs yet a third word that perfectly accounts for it, and then we get rid of the argument altogether.

• 8:41Matt Kirshen?

  And would that would be a discovery or an invention?

• 8:45Neil deGrasse Tyson?

  It's the word between the two that we don't have.

• 8:47Charles Liu?

  Discovention.

• 8:48Neil deGrasse Tyson?

  It's why we argue.

• 8:49Charles Liu?

  Math, the math, math, math. Oh, yeah, yeah, you're math.

• 8:53Neil deGrasse Tyson?

  Is it a particle or is it a wave in quantum? Why are we arguing that? It's both. We just don't have a word. We tried. We tried wavicle, but it didn't catch on. A wave and a particle. So, so I, I, I just don't.

• 9:05Matt Kirshen?

  Sounds like some sort of branding exercise from the eighties.

• 9:08Charles Liu?

  Seventies, seventies, discovention, okay?

• 9:13Neil deGrasse Tyson?

  The fact that math works at all as a tool to decode the universe is evidence

• 9:20Neil deGrasse Tyson?

  that the universe, at least the parts that have revealed itself to us,

• 9:27Neil deGrasse Tyson?

  follows logical, repeatable, repeatable patterns. And math is simply a way to code for logical, repeatable patterns. And if...

• 9:42Neil deGrasse Tyson?

  So, it's remarkable that math can describe the universe at all, except that math is a perfectly logical system, and so is the universe. Put them together, of course. It's a marriage made in heaven.

• 9:54Charles Liu?

  Very much like music, right? Math, music, that kind of connection. And the Bee Gees understood that well with their song. Calculus, calculus. Yeah, yeah, yeah, calculus.

• 10:06Neil deGrasse Tyson?

  And I thought calculus was an emperor of Rome.

• 10:12Neil deGrasse Tyson?

  That's an old joke. I heard that longer ago.

• 10:15Matt Kirshen?

  Um, I'm gonna.

• 10:17Neil deGrasse Tyson?

  Calculus, the brother of Clavius.

• 10:20Neil deGrasse Tyson?

  Matt.

• 10:21Matt Kirshen?

  Why are we talking about things between things?

• 10:22Neil deGrasse Tyson?

  Get us off this topic really fast.

• 10:23Matt Kirshen?

  I will. Well, I'm gonna combine two different questions together. So Eric Hansen on Facebook asks, "I recently read that if all of the space were taken out of every human on Earth, the resulting mass would be about the size of a cube of sugar."

• 10:38Charles Liu?

  Yep.

• 10:39Matt Kirshen?

  "How then can anyone adequately explain how the entire mass of the observable universe was once a point only microns wide?" And then I'm gonna combine this with this other question from...

• 10:51Neil deGrasse Tyson?

  You're gonna combine that?

• 10:51Matt Kirshen?

  Yeah.

• 10:52Charles Liu?

  That's a beautiful question on its own.

• 10:54Neil deGrasse Tyson?

  How are you gonna add something to that?

• 10:55Charles Liu?

  Yeah, yeah, yeah, yeah, yeah.

• 10:56Matt Kirshen?

  Well, this is a little coda question. I could have thrown it out afterwards, but I thought I'm gonna leave this just in your subconscious to bubble over while you're answering that one.

• 11:03Neil deGrasse Tyson?

  Gotcha.

• 11:03Matt Kirshen?

  From Ashton Norton, also on Facebook, "Other than the Big Bang, are there any other scientific theories that have been discussed as possible explanations for where we came from?" Well, so those two together or separate, as you choose.

• 11:20Charles Liu?

  Okay, so this is basically a cosmology question.

• 11:22Neil deGrasse Tyson?

  Sure.

• 11:23Charles Liu?

  Right? So I'll take the cosmology question number one. You can take cosmology question number two.

• 11:29Neil deGrasse Tyson?

  I like both of them.

• 11:30Charles Liu?

  All right.

• 11:30Neil deGrasse Tyson?

  No, I'm just kidding.

• 11:31Charles Liu?

  I'll answer each one halfway.

• 11:33Neil deGrasse Tyson?

  Okay, you answer each half.

• 11:34Charles Liu?

  All right.

• 11:34Neil deGrasse Tyson?

  Leave me a little room at the end. Go.

• 11:36Charles Liu?

  All right. So the reason the universe is so different now than it was back then is simply because there was some kind of physics that happened between the moment of the Big Bang and the present day that we still don't yet understand. It is completely true that the universe back then, the density of the universe right around that moment of the Big Bang, at the Planck time we call it, was approximately 10 to the 97 kilograms per cubic meter. All right?

• 12:06Matt Kirshen?

  That's pretty dense.

• 12:07Charles Liu?

  Yeah, and even if we took all of humanity... We're back in the 60s now. We went from the 70s to the 60s.

• 12:15Neil deGrasse Tyson?

  It's heavy.

• 12:15Charles Liu?

  Yeah, that's absolutely, you said it. We have a circumstance where the matter of that density is so removed from anything we can think of that that human beings the size of a cube of sugar analogy, when you move all the space, that density is still only about 10 to the 15 kilograms per cubic meter.

• 12:37Matt Kirshen?

  So there was just another state of matter or the matter itself.

• 12:41Neil deGrasse Tyson?

  Wait, Charles, I thought it's not even that complicated, okay?

• 12:45Charles Liu?

  Okay.

• 12:45Neil deGrasse Tyson?

  If it stays as solid matter, just taking out all the space between the particles, yeah, you're not going to get much smaller than that. But at the temperatures of the early universe, matter is not stable as solid matter. It's energy and you can pack energy into any kind of small volume you want. So is that a fair way to characterize?

• 13:07Charles Liu?

  It is a completely fair way to say it. And so as a result, the laws of physics that were governing that behavior produced something that eventually evolved into our universe today. And we have yet to decipher scientifically the processes that went from that to now.

• 13:26Neil deGrasse Tyson?

  Wait, I have to tighten that. It's not that went from then to a little bit after then. Because we know what happened a little bit after then until now.

• 13:34Charles Liu?

  Yeah, that's fair.

• 13:35Neil deGrasse Tyson?

  That's good physics.

• 13:36Charles Liu?

  Yeah, yeah. And by little bit after, Neil, I think you're referring to 10 to the minus 30 seconds, right?

• 13:42Neil deGrasse Tyson?

  Yeah, yeah, yeah.

• 13:44Charles Liu?

  So 0.000000.

• 13:45Neil deGrasse Tyson?

  A gazillionth of a second.

• 13:47Matt Kirshen?

  So we've managed to trace it back a very long way.

• 13:50Charles Liu?

  Yes, but that last little bit.

• 13:52Matt Kirshen?

  But just that last gazillionth of a second is the really confusing bit.

• 13:55Charles Liu?

  And that segues into that second part of the question.

• 13:59Neil deGrasse Tyson?

  It does.

• 14:00Charles Liu?

  Where what is going on in that tiny, tiny fraction of a second? That is so different from what we know today in our universe. And so that's where the speculation can lie, right? What could have happened other than a big bang as we understand it today? Could something else have generated the kinds of energies and effects that have led to the way the universe expands today? There's lots of speculation. It was really, really hard to be able to decipher or to pinpoint the physics involved. It's we're adding extra dimensions. We're adding extra particles. We're adding all kinds of extra crazy ideas. And none of them have yet panned out in a scientifically verifiable way.

• 14:43Neil deGrasse Tyson?

  And let me just say, do you think we're happy about a big bang?

• 14:46Charles Liu?

  Yeah, that's a great point.

• 14:48Neil deGrasse Tyson?

  This is like weird stuff, all right? But evidence points to that. The universe we now occupy can be described by what happens if you had a big bang as accounted for with a small, dense, hot, early beginning. And it gives us the amount of hydrogen and helium and neutrinos and the age and the density and the distribution. All of this comes out of that. If you have a better idea, fine, we'll take it. But until then, we're stuck with the big bang. How's that, is that another way to think about it?

• 15:27Charles Liu?

  I think that's a great point.

• 15:28Neil deGrasse Tyson?

  Okay.

• 15:28Charles Liu?

  The imperfections of a scientific theory drive people nuts. We want theories to be perfect, but they're not. And that's where the science and the learning happens.

• 15:39Neil deGrasse Tyson?

  But what you don't know is whether the addition is just an add on or whether you have to throw out everything to come up with a new idea.

• 15:46Matt Kirshen?

  Do you think that last gazillionth of a second will be explained? Or is it even explainable?

• 15:52Neil deGrasse Tyson?

  We've got top people working on it right now. They're called string theorists.

• 15:56Charles Liu?

  Yeah.

• 15:57Neil deGrasse Tyson?

  Top people.

• 15:58Charles Liu?

  And cosmologists in general, yeah.

• 16:00Neil deGrasse Tyson?

  Top people.

• 16:01Charles Liu?

  String theorists is just one group of promising paths. But all of cosmology is really about trying to get that last little tiny bit.

• 16:13Matt Kirshen?

  Question, this is, I'm gonna stay on this theme for one more question. Because Chris Colton on Facebook asks, why aren't we expanding with the universe if we are part of the universe?

• 16:25Charles Liu?

  Ah, I get asked that question a lot by my students.

• 16:28Matt Kirshen?

  And I'm gonna add a coder to that, will I ever break six foot?

• 16:34Neil deGrasse Tyson?

  Are you still growing? We're still wearing- Well, I'm hopefully still expanding. The machines that can help you there. We will get to the answer to that when we return for our second segment of Summer School StarTalk.

• 17:09Speaker 03

  The future of space and the secrets of our planet revealed.

• 17:18Speaker 03

  This is StarTalk.

• 17:32Neil deGrasse Tyson?

  We're back in our second segment of StarTalk Summer School. When you have to go to summer school, you gotta bring in the big guns. Charles Lu. Professor. Thank you, Neil. Professor Charles Lu, Cuny, Staten Island. Matt Kirshen.

• 17:47Matt Kirshen?

  The little gun.

• 17:50Matt Kirshen?

  The littlest gun.

• 17:51Neil deGrasse Tyson?

  Wait, so how tall are you? How tall are you?

• 17:53Matt Kirshen?

  Like 5'5".

• 17:53Neil deGrasse Tyson?

  5'5" and 120 pounds.

• 17:55Matt Kirshen?

  Yep.

• 17:57Neil deGrasse Tyson?

  Eight and a half stone, let's be specific. Excuse me, excuse me. Eight and a half stone?

• 18:01Matt Kirshen?

  Yeah, because Britain really doesn't know what units to use. We're metric sometimes.

• 18:06Neil deGrasse Tyson?

  Which stone, you know?

• 18:09Matt Kirshen?

  In some cases, we're ahead of you. We do fruit and veg in metric. We normally do Celsius for temperature, but then we'll do stones.

• 18:15Neil deGrasse Tyson?

  Yeah, you have issues. You have metric issues.

• 18:18Matt Kirshen?

  We're comparing things to the size of animals.

• 18:22Neil deGrasse Tyson?

  Oh, that's where the stones come from.

• 18:23Matt Kirshen?

  I don't even know what the stone originally is.

• 18:24Neil deGrasse Tyson?

  Well, you have hands.

• 18:25Matt Kirshen?

  Their hands, yeah.

• 18:27Neil deGrasse Tyson?

  Whose hands? Whose feet?

• 18:30Neil deGrasse Tyson?

  So, we left off at the first segment, a question.

• 18:33Matt Kirshen?

  About, yes, if the universe is expanding and we are part of the universe, why are we not expanding?

• 18:39Charles Liu?

  And the answer is electromagnetic forces. See, the expansion of the universe is its own thing, but it does not counteract on small scales. Things like atoms and molecules pulling one another, or electrons and protons, or even.

• 18:56Neil deGrasse Tyson?

  In fact, literally the atoms and molecules in his pinky that he was pulling.

• 18:59Charles Liu?

  Right, right. So.

• 19:00Neil deGrasse Tyson?

  As he picks, his fingers on his hand.

• 19:02Charles Liu?

  That's an excellent point, yeah. So, the reason my pinky nail is not expanding away from my pinky finger is because they're being held together by other kinds of forces.

• 19:12Neil deGrasse Tyson?

  Way stronger forces.

• 19:14Charles Liu?

  In the shorts.

• 19:15Neil deGrasse Tyson?

  In the short distance.

• 19:16Charles Liu?

  Yeah, in the short distances.

• 19:17Neil deGrasse Tyson?

  Yeah.

• 19:18Charles Liu?

  So, out at the distances of millions or billions of light years, the expansion of the universe dominates. Even galaxies are carried along for the ride. But, on scales of humans, or even planets, really, those other forces are much stronger.

• 19:32Neil deGrasse Tyson?

  Even the solar system is not expanding.

• 19:34Matt Kirshen?

  That's, okay, because I always, I've been given the analogy in the past of the blowing up the balloon and watching the dots get further apart.

• 19:41Neil deGrasse Tyson?

  On the surface, yeah.

• 19:42Matt Kirshen?

  That's right. But is it, is it then almost more like sort of blowing up a globe that has like ice sheets floating on it, but the ice sheets stay, the ice sheets stay in one clump?

• 19:53Neil deGrasse Tyson?

  That is a correct, better

• 19:55Matt Kirshen?

  Yes.

• 19:55Neil deGrasse Tyson?

  assessment.

• 19:56Matt Kirshen?

  And they become further apart as the globe expands?

• 19:58Neil deGrasse Tyson?

  Yeah, on a balloon, if you drew a galaxy on it, that galaxy would actually get bigger.

• 20:01Charles Liu?

  Yeah, would actually get bigger, right.

• 20:02Neil deGrasse Tyson?

  That's not what happened.

• 20:03Charles Liu?

  So it should put like little sticky notes on the balloon and that would work?

• 20:05Matt Kirshen?

  Right, sticky notes that have the ability to slide.

• 20:07Neil deGrasse Tyson?

  Lifesavers, you glue them on and they'll just stay one shape.

• 20:10Charles Liu?

  Yeah, you can do that too.

• 20:11Matt Kirshen?

  So the sticky notes themselves, or the lifesavers, would become further apart, but within themselves, they would stay the same size?

• 20:16Charles Liu?

  Correct.

• 20:16Neil deGrasse Tyson?

  You got it.

• 20:17Matt Kirshen?

  Okay.

• 20:18Neil deGrasse Tyson?

  Yeah.

• 20:19Matt Kirshen?

  So I understand something a lot better now.

• 20:20Charles Liu?

  There you go.

• 20:21Neil deGrasse Tyson?

  We got good question people out there.

• 20:22Charles Liu?

  We do, we do. What an excellent audience StarTalk has.

• 20:25Neil deGrasse Tyson?

  This is an excellent audience, unless they just called from.

• 20:28Charles Liu?

  No, no, no, no. I'm sure these are.

• 20:31Neil deGrasse Tyson?

  We'll check with our researchers, find out. All right. Matt, next.

• 20:35Matt Kirshen?

  All right, from Ben Ratner, at Ben makes TV on Twitter.

• 20:39Charles Liu?

  Oh, that guy.

• 20:40Neil deGrasse Tyson?

  I've heard of that guy before.

• 20:41Charles Liu?

  Oh, yeah.

• 20:42Matt Kirshen?

  Ben says, please describe the laws of physics.

• 20:47Matt Kirshen?

  It sounds like we're doing Ben's homework.

• 20:48Neil deGrasse Tyson?

  Oh, no, no, here's what I'm doing. I'm gonna pull rank here. You ready?

• 20:51Matt Kirshen?

  Go ahead.

• 20:51Neil deGrasse Tyson?

  Okay.

• 20:54Neil deGrasse Tyson?

  In one of my books.

• 20:55Charles Liu?

  Yeah.

• 20:56Neil deGrasse Tyson?

  I have a chapter called Unearth As in the Heavens.

• 21:00Charles Liu?

  Ooh.

• 21:01Neil deGrasse Tyson?

  And it's all about the effort to discover laws of physics on Earth. And the question about whether they apply in places other than Earth.

• 21:09Charles Liu?

  Hmm.

• 21:09Neil deGrasse Tyson?

  And it's not a given that that should be the case.

• 21:12Charles Liu?

  Okay, okay.

• 21:12Neil deGrasse Tyson?

  It might have been that something you discover here on Earth is different on Mars or different on... But it turns out, it's not. It's the same.

• 21:20Charles Liu?

  What I would be interested in is not necessarily the laws of physics, because that's what I lived with all my life.

• 21:25Neil deGrasse Tyson?

  Do you?

• 21:26Charles Liu?

  Yes.

• 21:28Neil deGrasse Tyson?

  Do you have a choice?

• 21:29Charles Liu?

  What are the laws of psychics?

• 21:34Neil deGrasse Tyson?

  Okay, I've never been curious about that. Maybe I should be.

• 21:37Charles Liu?

  I don't know.

• 21:37Neil deGrasse Tyson?

  Yeah. Here's the thing.

• 21:40Charles Liu?

  Yeah, we can get...

• 21:41Neil deGrasse Tyson?

  The headline you've never seen.

• 21:43Charles Liu?

  Yeah, yeah.

• 21:44Neil deGrasse Tyson?

  Psychic predicts winning lottery number a second time.

• 21:50Charles Liu?

  That's true. That's true.

• 21:51Neil deGrasse Tyson?

  You don't get that.

• 21:52Charles Liu?

  That's true.

• 21:53Neil deGrasse Tyson?

  But otherwise, the laws of physics are very simple.

• 21:55Charles Liu?

  Yeah, yeah.

• 21:55Neil deGrasse Tyson?

  I mean, they fit, you know, if you...

• 21:58Charles Liu?

  Okay.

• 21:59Neil deGrasse Tyson?

  I remember I was in school and somebody was taking an accounting class.

• 22:01Charles Liu?

  Oh.

• 22:02Neil deGrasse Tyson?

  And I saw the book that they were carrying.

• 22:03Charles Liu?

  Uh huh, uh huh.

• 22:03Neil deGrasse Tyson?

  It had like a million pages in the book.

• 22:06Charles Liu?

  Yeah.

• 22:06Neil deGrasse Tyson?

  And my book, which was on like all of gravitational physics, had like a third that many pages. So I can understand the whole universe based on what's in my book, but they need a book four times the fat just to be able to do somebody's taxes.

• 22:18Charles Liu?

  Fair enough.

• 22:18Neil deGrasse Tyson?

  And I said...

• 22:19Matt Kirshen?

  Because you can't deduce the tax code.

• 22:21Neil deGrasse Tyson?

  Thank you. That's the difference.

• 22:23Charles Liu?

  Yeah.

• 22:23Neil deGrasse Tyson?

  The good thing about physics is you learn some rules and then all the rest derive from them.

• 22:27Charles Liu?

  Pretty much, yeah.

• 22:28Neil deGrasse Tyson?

  Very powerful.

• 22:29Matt Kirshen?

  And then every so often, a cop, someone comes along and goes, actually, those rules are all slightly wrong.

• 22:34Charles Liu?

  Yeah.

• 22:35Neil deGrasse Tyson?

  Well, we have Newton's F equals ma. You got equals mc squared. You got Maxwell's equations.

• 22:41Charles Liu?

  Yeah.

• 22:41Neil deGrasse Tyson?

  We're done practically.

• 22:42Charles Liu?

  Pretty much. Yeah, yeah, yeah, yeah.

• 22:44Neil deGrasse Tyson?

  Throw in a few quantum physics equations.

• 22:47Charles Liu?

  Years, years.

• 22:47Neil deGrasse Tyson?

  Schrodinger equation?

• 22:48Charles Liu?

  Yeah. Years worth of physics study is just F on one side, force, and then ma, mass times acceleration on the other side. And you just change F in a gazillion different ways. You change ma in a gazillion different ways. And that, that springs from that springs force for physics.

• 23:06Neil deGrasse Tyson?

  Unfolds for free.

• 23:07Charles Liu?

  Yeah, absolutely.

• 23:08Neil deGrasse Tyson?

  Yeah, it's beautiful. It's beautiful.

• 23:09Matt Kirshen?

  Great question.

• 23:10Neil deGrasse Tyson?

  All right.

• 23:11Matt Kirshen?

  I really enjoy this question because apart from anything else, it came from a four-year-old.

• 23:15Charles Liu?

  Oh.

• 23:16Matt Kirshen?

  The four-year-old son.

• 23:17Neil deGrasse Tyson?

  They should tell us after, when we're stumped.

• 23:19Charles Liu?

  Yeah, yeah, yeah, yeah.

• 23:20Matt Kirshen?

  The four-year-old son of Pinty from Laos asks.

• 23:23Charles Liu?

  Laos?

• 23:24Matt Kirshen?

  Mm-hmm.

• 23:24Charles Liu?

  Ooh.

• 23:25Neil deGrasse Tyson?

  Nice.

• 23:26Matt Kirshen?

  Why do punctured balloons fly around chaotically? Why doesn't it fly on a straight line?

• 23:33Charles Liu?

  Wonderful question.

• 23:37Charles Liu?

  The, when you have a rocket, actually, you know how they travel in straight lines and are always very impressed, right? But what we don't see is the amount of control mechanisms and structures within the rocket that make sure the exhaust comes out in a very orderly and a very directional fashion, right? When you puncture a balloon, the exhaust that's coming out is coming out in a way that's poorly controlled. It's not a pin-pricked hole, for example. Just, there's a difference. You can try this. You put a little tiny hole in a balloon as opposed to a large hole in the balloon. The larger the hole, the more chaotic the flow goes. So it's a matter of whether or not you can control the air coming out in a reasonable or a linear way

• 24:21Charles Liu?

  compared with whether it's just rushing out all at once.

• 24:23Neil deGrasse Tyson?

  Well, also, you'd want the movement of the air to line up with the center of mass of the balloon.

• 24:30Charles Liu?

  Yeah.

• 24:30Neil deGrasse Tyson?

  Okay? So if that lines up, then the balloon will just be pushed in one direction. If the jet's air is coming out. At an angle different from straight to the center of mass, you'll start rotating the balloon.

• 24:42Charles Liu?

  Right.

• 24:42Neil deGrasse Tyson?

  Plus, the balloon is not symmetric. There's that little, the bottom of it where you got the knot.

• 24:46Charles Liu?

  Yeah, the knot.

• 24:47Neil deGrasse Tyson?

  The knot. So the balloon's weight is not symmetric.

• 24:50Matt Kirshen?

  And the center of the mass of the balloon would also move around as the balloon deflates.

• 24:53Neil deGrasse Tyson?

  Yes! Yes!

• 24:56Charles Liu?

  That's right.

• 24:56Neil deGrasse Tyson?

  So what you'd have to do is configure something, like get a straw, maybe?

• 25:00Charles Liu?

  Yeah.

• 25:00Neil deGrasse Tyson?

  To guide the air a little better, have some stabilizers, and then you can make a balloon rocket.

• 25:06Charles Liu?

  Yeah. That would be a lot of fun.

• 25:08Neil deGrasse Tyson?

  But I love that question.

• 25:09Matt Kirshen?

  It's a great question.

• 25:10Neil deGrasse Tyson?

  That sounds like a kid that's tearing up birthday parties.

• 25:14Charles Liu?

  I want that kid on my research stack.

• 25:19Matt Kirshen?

  Okay.

• 25:20Neil deGrasse Tyson?

  By the way, most of the time when you pinprick a balloon, it blows up.

• 25:23Matt Kirshen?

  Right.

• 25:23Neil deGrasse Tyson?

  Right, so you have to do this carefully.

• 25:25Charles Liu?

  Yeah. I learned as a child, if you put a piece of tape on the balloon, then you poke the hole through the tape. Then the rubber or the outside, like, flexible stuff doesn't rupture in a rip, and you just get a little hole, and you can have it go around.

• 25:39Neil deGrasse Tyson?

  So you've done this before?

• 25:41Charles Liu?

  Of course, hasn't everybody?

• 25:42Neil deGrasse Tyson?

  Okay, no, I haven't put tape on a balloon to puncture it.

• 25:44Charles Liu?

  Oh, give it a try sometime.

• 25:44Neil deGrasse Tyson?

  But it's way more fun to just pop them.

• 25:47Charles Liu?

  It's too fast.

• 25:48Neil deGrasse Tyson?

  It is too fast.

• 25:49Charles Liu?

  It's too fast.

• 25:49Neil deGrasse Tyson?

  It's too fast.

• 25:50Charles Liu?

  Yeah.

• 25:51Neil deGrasse Tyson?

  You are correct. I will try this from now on. Any kind of masking tape or?

• 25:55Charles Liu?

  I used, like, plastic invisible tape.

• 25:57Neil deGrasse Tyson?

  Okay.

• 25:58Charles Liu?

  Scotch tape. Scotch tape, yeah.

• 26:00Matt Kirshen?

  So, pulsa priv on Instagram.

• 26:02Neil deGrasse Tyson?

  Now you put on both sides of the balloon.

• 26:04Charles Liu?

  There you go, that's it.

• 26:05Neil deGrasse Tyson?

  Then the balloon won't know where to go.

• 26:06Charles Liu?

  It'll start spinning.

• 26:09Charles Liu?

  That would be fun. All right, four-year-old balloon experiments.

• 26:12Matt Kirshen?

  Yeah, I like that. So pulsa priv on Instagram says, "Hi, quick question. How would you explain neutrinos to dumb teenagers who know nothing about astrophysics?"

• 26:21Charles Liu?

  Okay, okay.

• 26:22Matt Kirshen?

  And the question doesn't make clear whether they themselves are a dumb teenager or a trying to...

• 26:26Neil deGrasse Tyson?

  It's a friend, a friend, I would explain to a friend.

• 26:29Charles Liu?

  Let me jump in right now and say that there are no dumb teenagers. There just aren't. I'm an educator and maybe I'm showing my bias here, but I've never found an actual dumb teenager. They can be pretend to be dumb. They may think they're dumb.

• 26:43Neil deGrasse Tyson?

  Because it's cool.

• 26:43Charles Liu?

  Yeah, but they're not actually dumb. I want people always to feel like that they are smart, because they are, and not have to act dumb or pretend to be dumb to be cool. All right, so there's no such thing as a dumb teenager. That's just my opinion. I'm sorry I had to get it out there. Now, to answer the question. A neutrino is just a little tiny particle that comes out so that in atomic interactions.

• 27:08Neil deGrasse Tyson?

  Nuclear interactions.

• 27:09Charles Liu?

  In nuclear interactions, energy is properly balanced. Okay, both in the motion and in the amount. I think that's really what a simple way of describing a neutrino is.

• 27:22Neil deGrasse Tyson?

  It's a pretty weird particle, because no one knew they existed and there was an imbalance in the experiments that were being done in nuclear physics. And it was Enrico Fermi.

• 27:31Charles Liu?

  Yes.

• 27:31Neil deGrasse Tyson?

  Who said, "There's gotta be a particle carrying away this momentum. There has to. We're looking, we don't find it. It's gotta keep looking. It's gotta be. What properties would it have? It can't have any charge, so it's gotta be neutral and it's gotta be really low mass, a little. So it's gotta be a little and neutral. And...

• 27:51Charles Liu?

  Well, the funny thing is of course...

• 27:52Neil deGrasse Tyson?

  And so in Italian, neutrino.

• 27:54Charles Liu?

  Right.

• 27:55Neil deGrasse Tyson?

  Like bambino, neutrino.

• 27:56Matt Kirshen?

  So it's just the diminutive version of neutral.

• 27:58Neil deGrasse Tyson?

  Of neutron, or of a neutron, right, right.

• 28:00Charles Liu?

  But the funny thing is, when this was first proposed, the neutron had not yet been discovered.

• 28:04Neil deGrasse Tyson?

  Mmm.

• 28:04Charles Liu?

  So when the neutron was discovered, people were like, "Oh, is this it?" Did more calculations.

• 28:08Neil deGrasse Tyson?

  No.

• 28:09Charles Liu?

  Nope, still not it.

• 28:10Neil deGrasse Tyson?

  Yeah, too massive.

• 28:10Charles Liu?

  There's something that's even smaller than the neutron.

• 28:12Neil deGrasse Tyson?

  That has no charge, right, right, right. So yeah, it's got, it's necessary to what's going on in the universe, but it's very hard to stop. It plows through anything. What's the number of neutrinos that go through your thumb every second from the sun?

• 28:25Charles Liu?

  Many trillions.

• 28:26Neil deGrasse Tyson?

  Trillions.

• 28:26Charles Liu?

  Many, many trillions.

• 28:27Neil deGrasse Tyson?

  Can you feel it? Man, can you feel it?

• 28:29Matt Kirshen?

  I'm gonna kinda bet. It could be the air conditioning. I don't know. It's hard to tell. So how do, how do we...

• 28:35Neil deGrasse Tyson?

  Because they don't interact and that's why they were so hard to detect.

• 28:37Matt Kirshen?

  But they do interact very minimally, right? We can detect them.

• 28:41Charles Liu?

  And it was one of the great experiments in astrophysics that allowed us to find neutrinos coming out of the sun. What happened was that people took a very large vat of...

• 28:55Charles Liu?

  Dry cleaning fluid, very pure. Put it down more than a mile below the surface in South Dakota. And surrounded it-

• 29:05Neil deGrasse Tyson?

  I think it was just a pre-existing salt mine, wasn't it?

• 29:07Charles Liu?

  It was a gold mine.

• 29:07Neil deGrasse Tyson?

  Oh, gold mine.

• 29:08Charles Liu?

  The Homestead gold mine.

• 29:09Neil deGrasse Tyson?

  Gold mine, not a salt mine, okay.

• 29:10Charles Liu?

  And it was sunk all the way down to the bottom. They put it there and they surrounded it with a lot of cameras. And so they just watched this tank of very pure cleaning fluid. And when a neutrino hit, even though trillions and trillions pass through every second, they might only get one neutrino hit every long once in a while. And when that happened, there would be a flash of light. And so they'd watch it and make sure that the flash of light is not caused by anything other than a solar neutrino. And that's what they were. So it was an amazing discovery. Turns out that that particular molecule, perchlorate-

• 29:47Neil deGrasse Tyson?

  Yeah, but I think it needed the chlorine in it.

• 29:50Charles Liu?

  Had a special, nice property that it would, when hit by a neutrino and with that interaction, very rare occasional interaction, would cause a flash of light.

• 29:59Matt Kirshen?

  How long ago did that experiment happen? Was it recent?

• 30:01Neil deGrasse Tyson?

  Couple of decades.

• 30:02Charles Liu?

  That was several decades ago. The-

• 30:04Matt Kirshen?

  It was still-

• 30:04Neil deGrasse Tyson?

  Seventies, eighties.

• 30:05Charles Liu?

  Ray Davis Jr. was the experimentalist. John Bacall was the theorist that was involved with that.

• 30:09Neil deGrasse Tyson?

  Ray Davis got the Nobel Prize, I think, for that. But not John Bacall.

• 30:11Charles Liu?

  Yes, yes.

• 30:13Neil deGrasse Tyson?

  People didn't fully understand that. You have the theory and the experiment and the observations. They all have to come together to make that discovery.

• 30:20Charles Liu?

  That's correct. But that was a real triumph. And it led to a secondary discovery, actually, because it turned out that the number of neutrinos that were being detected from the sun were fewer than we expected. And so for a moment, people thought, wait a second, is the sun dead and we just don't know it yet? It was known as the solar neutrino problem. Because those neutrinos had to be produced in order for nuclear fusion to be going on. So if they were half as many as we expected, then maybe the sun itself was starting to run out of fuel.

• 30:52Neil deGrasse Tyson?

  Scary prospect.

• 30:53Charles Liu?

  Yeah, scary prospect. Turned out, though, that it was just something happening in our upper atmosphere, called neutrino oscillations. Another amazing discovery.

• 31:02Neil deGrasse Tyson?

  Yeah, so it'd be I throw you a basketball, but you catch a football.

• 31:07Matt Kirshen?

  Right.

• 31:07Neil deGrasse Tyson?

  So the experiment was designed to detect basketballs. And but you're actually receiving footballs.

• 31:14Matt Kirshen?

  And what it is, is someone in between us is swapping them out.

• 31:17Charles Liu?

  That's right. And it was amazing. That was what was happening. Yeah, these neutrinos come in different flavors, it turns out. Who knew?

• 31:22Neil deGrasse Tyson?

  Who knew at the time?

• 31:23Matt Kirshen?

  Oh, OK, so there isn't just one neutrino particle, there's...

• 31:26Charles Liu?

  Three.

• 31:27Matt Kirshen?

  OK.

• 31:28Charles Liu?

  Yeah, three different kinds. Electron neutrinos, tau neutrinos, and mu neutrinos.

• 31:33Neil deGrasse Tyson?

  And their antimatter counterparts.

• 31:34Charles Liu?

  And their antimatter counterparts.

• 31:35Neil deGrasse Tyson?

  Really six.

• 31:36Charles Liu?

  Yeah.

• 31:37Neil deGrasse Tyson?

  Yeah, it's pretty cool.

• 31:38Charles Liu?

  Physics is amazing, isn't it? I love summer school.

• 31:40Matt Kirshen?

  Great question.

• 31:41Neil deGrasse Tyson?

  Summer school, next question.

• 31:42Matt Kirshen?

  All right, Kyle Ryan Tull on Patreon asks, ignoring the cold, could a settlement survive on the surface of Pluto? What would radiation levels be like? Are there any useful resources other than water ice?

• 31:55Neil deGrasse Tyson?

  Hold me back. We'll get to that question when we return.

• 32:48Neil deGrasse Tyson?

  StarTalk Summer School. Matt, before the break, you you had a Pluto question.

• 32:53Matt Kirshen?

  It is, yeah.

• 32:54Neil deGrasse Tyson?

  You know, me and Pluto have have history. But we buried the hatchet long ago.

• 32:58Matt Kirshen?

  Well, whether it's a planet or not, could a settlement survive on it?

• 33:02Neil deGrasse Tyson?

  Oh. Well, you can ask, why would you want to do such a thing?

• 33:06Matt Kirshen?

  Right.

• 33:06Neil deGrasse Tyson?

  Because, but just take for example, Charles.

• 33:08Matt Kirshen?

  Yeah.

• 33:09Neil deGrasse Tyson?

  Is there a line of people waiting to settle in Antarctica?

• 33:13Charles Liu?

  No.

• 33:14Neil deGrasse Tyson?

  And Antarctica is warmer and is balmer and wetter than Pluto.

• 33:20Matt Kirshen?

  And there's penguins. So the best of my knowledge, there are.

• 33:23Neil deGrasse Tyson?

  In a pinch, we can eat a penguin, right?

• 33:26Matt Kirshen?

  That's right.

• 33:26Neil deGrasse Tyson?

  So Pluto, in principle, Charlie, in principle, we could just pitch tent anywhere. Just bring enough resources, right?

• 33:32Charles Liu?

  Yeah, yeah. The settlement could survive there as long as you could shield yourself from the cosmic rays that hit it. And as long as you can keep yourself warm because the temperature is so low out at that distance.

• 33:44Neil deGrasse Tyson?

  And food, you need no way to generate food.

• 33:46Charles Liu?

  You need food.

• 33:46Matt Kirshen?

  How faint is the sun? If I was standing on the surface of Pluto and staring straight at the sun, which I presume I would be safe to do.

• 33:53Charles Liu?

  The flux is only about one sixteen hundredth the amount of flux that we get from the sun here on Earth.

• 34:00Neil deGrasse Tyson?

  Is it only that much? I thought, I'm going on a memory now, not on a calculation, that the sun from Pluto is about like a full moon night here. Is it brighter than that?

• 34:13Charles Liu?

  Quick calculation there. Well, absolute magnitude negative twenty six for the sun, minus fifteen.

• 34:18Neil deGrasse Tyson?

  No, twelve.

• 34:19Charles Liu?

  Minus twelve for the most, so that's fourteen magnitudes.

• 34:21Neil deGrasse Tyson?

  Fourteen.

• 34:21Charles Liu?

  So that's a factor of ten.

• 34:23Neil deGrasse Tyson?

  So seven.

• 34:24Charles Liu?

  Yeah.

• 34:25Neil deGrasse Tyson?

  So ten of the four, it's ten to fourteen.

• 34:28Charles Liu?

  No, not quite that much.

• 34:29Neil deGrasse Tyson?

  Yeah, seven magnitudes. Oh, no, five, five. So, so two, yeah, so it's a factor of a hundred thousand.

• 34:37Charles Liu?

  Right, so it's a little bit.

• 34:39Neil deGrasse Tyson?

  And you said it's.

• 34:40Charles Liu?

  I said sixteen hundred because, so forty AU, right?

• 34:44Neil deGrasse Tyson?

  Oh, you just divided it out.

• 34:45Charles Liu?

  Yeah, okay. So.

• 34:49Charles Liu?

  So there, there may be.

• 34:50Neil deGrasse Tyson?

  You think we need HuffPo to find out if we're.

• 34:53Neil deGrasse Tyson?

  You're in the middle of an active calculation here. You pull up a HuffPo page?

• 34:58Charles Liu?

  No, no, this actually brings up a very good point, and I teach this to all my students. And since this is a summer school episode, it's quite appropriate.

• 35:03Neil deGrasse Tyson?

  We are forty, Pluto is forty times farther away from the sun than Earth is on average. And so it's one over that square.

• 35:09Charles Liu?

  That's right. So that's, that's where you get the sixteen hundred.

• 35:11Neil deGrasse Tyson?

  Sixteen hundredth as bright.

• 35:13Charles Liu?

  That's right. But, but the idea that a person.

• 35:15Neil deGrasse Tyson?

  Inverse square law of light, very cool.

• 35:17Charles Liu?

  The, the idea that a person can just pull up the answer on Google faster than we can do the calculation brings up a really important point about school in general and education in specific. You might agree with this, Neil. We can no longer think that we are educated if all we can do is memorize facts or calculate things that can already be calculated and sit on a database. We have the world's information at our fingertips. The only way that we can remain viable as a productive member of society or as a civilization is if we are better than Google. We have to do that, and I'm not picking Google specifically.

• 35:52Neil deGrasse Tyson?

  Sounds like he doesn't want to be replaced with a robot. Matt, does that sound like that to you?

• 35:56Charles Liu?

  It is absolutely right. We all can easily be replaced by a search engine. Our education system, our learning, our interaction with nature and with the world and with other people must be better than a search engine.

• 36:10Matt Kirshen?

  We know already that-

• 36:10Neil deGrasse Tyson?

  Charles for president, Charles for president.

• 36:12Matt Kirshen?

  We know that Charles is a better singer than Google, so.

• 36:16Neil deGrasse Tyson?

  I think that was Charles's stump speech right there, wasn't it?

• 36:19Matt Kirshen?

  Oh dear. While we are talking about singing and the like, Marcus, and I'm going to apologize for butchering this name, Gui Maras, I apologize if that is way off, on Patreon asks, "I had a debate with a friend of mine where he said that scientists hate art in general. I think that's not true," says Marcus. "Doctor Tyson loves art and he loves The Starry Night by Van Gogh. Could you please tell us something about the subject?" Charles, are you okay there? You seem, you seem, uh, you seem put out somehow.

• 36:50Charles Liu?

  Science states art? No way, no way.

• 36:54Neil deGrasse Tyson?

  First, I don't know any scientist who hates art. A, B, many scientists I know not only just don't hate it, but love it. C, um, the, one of the books behind you on a shelf is called Mathematics and Art, a book written by an art curator who has fascinated by the role of science as it has influenced art, and I was privileged to be asked to write the foreword to that book. And as the writer knows, I'm a big fan of The Starry Night by Vincent van Gogh, 1889. And so, and I'm not unusual in this regard. There are colleagues love music, I love art, on levels that you might not even know or suspect.

• 37:39Neil deGrasse Tyson?

  Because generally if they're in the news, it's not because of that, it's because of the science they're doing. Oh, no, no, we're art-loving community, all the way back. And why do you think universities, they're called the schools of arts and sciences? We go way back.

• 37:54Charles Liu?

  Yeah, way back.

• 37:55Neil deGrasse Tyson?

  Two sides of a coin, each the pinnacle of human creativity and expression. One constrained by the universe, the other constrained by imagination itself. Science and art.

• 38:14Charles Liu?

  I could not say it better, Neil. It is absolutely true, science and art are inextricably intertwined. There is no scientist I know that doesn't like art.

• 38:23Neil deGrasse Tyson?

  Have him take up that question with Leonardo da Vinci.

• 38:25Charles Liu?

  Absolutely. And Albert Einstein himself wrote in 1930, "That the sense of the mysterious, the wish to be awed by things we don't know, is the root of all great art and science." And I agree with that statement.

• 38:44Matt Kirshen?

  Trina Jennings on Facebook asks, "If we can figure out the center of the Milky Way galaxy smells like raspberries, can we figure out what things would smell like elsewhere? Would the center of all galaxies smell like raspberries?"

• 38:58Neil deGrasse Tyson?

  Who said the center of the galaxy smelled like raspberries?

• 39:00Charles Liu?

  Oh, it's a cute press release about people who are looking at molecules in gas clouds. And it turned out that they detected certain aromatic compounds which are found in raspberries. So they said, "Oh, it smells like raspberries." Oh, it smells like raspberries because there are these volatile organic compounds that are in gas clouds near the Milky Way galaxy center.

• 39:24Neil deGrasse Tyson?

  There's also a lot of ethanol there, too.

• 39:26Charles Liu?

  Yes.

• 39:26Neil deGrasse Tyson?

  You sound like a drunkard.

• 39:27Charles Liu?

  Yeah, it would smell like a brewery.

• 39:29Neil deGrasse Tyson?

  Brewery.

• 39:30Charles Liu?

  And actually...

• 39:31Neil deGrasse Tyson?

  That'd be the yeast. I think the yeast is the predominant smell in a brewery.

• 39:34Charles Liu?

  That's right.

• 39:34Matt Kirshen?

  A distillery?

• 39:35Charles Liu?

  A distillery, yeah.

• 39:35Neil deGrasse Tyson?

  There's a lot of organic molecules in space, so...

• 39:39Charles Liu?

  And there's even a sunless tanning lotion, too. DHA in molecules over there, so you can not only get a great sun tan.

• 39:46Neil deGrasse Tyson?

  I've never looked.

• 39:47Charles Liu?

  You can also smell.

• 39:48Neil deGrasse Tyson?

  I didn't know such a thing existed.

• 39:49Charles Liu?

  Yeah, yeah, sorry.

• 39:51Neil deGrasse Tyson?

  Up in the hood, it's not even...

• 39:53Matt Kirshen?

  You guys don't tanning much?

• 39:54Neil deGrasse Tyson?

  Yeah, the CVS doesn't have that on the front counter.

• 39:56Matt Kirshen?

  You don't think it's very tan?

• 39:58Neil deGrasse Tyson?

  No, no, no, not in the hood.

• 40:00Charles Liu?

  So...

• 40:01Neil deGrasse Tyson?

  So, so it's a little deceptive to say that space smells like that.

• 40:05Charles Liu?

  Right.

• 40:06Neil deGrasse Tyson?

  Space smells like nothing, unless you put molecules where you're sniffing, and there are molecules everywhere, and so there it is. Then you're smelling molecules in space rather than space itself.

• 40:16Charles Liu?

  So to answer that question constructively, the answer is yes. As long as we can find the molecules that create certain smells in our brains through our noses in a location, we can tell you exactly what that person smells.

• 40:28Neil deGrasse Tyson?

  Precisely.

• 40:28Charles Liu?

  But there are a lot of particles out there, and they can smell like a lot of different things. Yeah.

• 40:34Neil deGrasse Tyson?

  Indeed.

• 40:34Matt Kirshen?

  Nice.

• 40:35Neil deGrasse Tyson?

  All right.

• 40:35Matt Kirshen?

  All right, who wants a relativity question?

• 40:37Neil deGrasse Tyson?

  Bring it on!

• 40:38Matt Kirshen?

  Yeah. Hussein Sajwani on Twitter says, "I am still having a hard time understanding the concept of how if your twin is on Earth and you travel at almost the speed of light, you will not age as much as them," or something like that. "Can you really try to dumb it down or using analogies?"

• 40:53Charles Liu?

  Again, before Neil says anything...

• 40:55Neil deGrasse Tyson?

  No, no, I'm not saying anything. I'm out of this one. Go.

• 40:58Charles Liu?

  Please don't use the term "dumb down." We are not dumbing things down. We are merely translating the concept into a language that everyone can understand.

• 41:06Matt Kirshen?

  In that case, can you smart it up?

• 41:08Charles Liu?

  That's right. Thank you, Matt. Okay, here's the basic point.

• 41:13Neil deGrasse Tyson?

  Smart it down.

• 41:14Matt Kirshen?

  Yeah.

• 41:14Neil deGrasse Tyson?

  Smart it down.

• 41:16Charles Liu?

  Time is experienced at different rates for people who are traveling at different rates of speed. That's a very, very complicated concept. If you're trying to lock it into our idea in our regular time that a second is a second is a second. But the moment you acknowledge the possibility that time is a dimension, like length, width, and height, and you can move through it at different speeds. Then the twin paradox that is described here or other paradoxes become not too difficult because what you're doing is measuring time intervals. Right? You're not measuring actually the amount of time at this very instant. But you're measuring the time from the time you experienced one minute ago to the time you experience a minute from now.

• 42:00Charles Liu?

  That person who is traveling at a different rate through time and space will simply experience a different interval.

• 42:08Neil deGrasse Tyson?

  And you'll both call it a minute.

• 42:09Charles Liu?

  Yeah.

• 42:10Neil deGrasse Tyson?

  But relative to each other, they're different lengths. So, yeah.

• 42:13Matt Kirshen?

  And you only realize that once you come back into contact with each other.

• 42:15Neil deGrasse Tyson?

  Correct. Yeah, that's right. That's right. And the way to know who will be younger, because both of them in motion will say that the other one is ticked their the opposite clock is ticking slower, is that the your twin who went out had to slow down, turn around, and come back.

• 42:34Charles Liu?

  Right.

• 42:35Neil deGrasse Tyson?

  And that breaks the symmetry. It's called a paradox. Because if I see you traveling and your time is ticking more slowly and motion is relative, and you see me, I'm actually standing still, but as far as you're concerned, you're standing still and I'm moving. You see my time ticking slowly. How is it that at the end of this exercise, one person is younger than the other?

• 42:55Matt Kirshen?

  Right. How do we not know like if, yeah, the train is going past the platform rather than the platform is going past the train?

• 43:01Neil deGrasse Tyson?

  It's one of the great jokes against Einstein who said, hey Einstein, when does Grand Central Station arrive at the next train?

• 43:07Neil deGrasse Tyson?

  People, you, everyone was trying to get their head around this back at the time.

• 43:10Matt Kirshen?

  So it's specifically the acceleration of the the one twin who goes out on the spaceship and goes out and then turns around and comes back.

• 43:17Neil deGrasse Tyson?

  That breaks the symmetry.

• 43:18Matt Kirshen?

  Is that acceleration and then deceleration?

• 43:20Neil deGrasse Tyson?

  Right. Yeah, the whole thing is either positive or negative acceleration, but it's just it wouldn't matter. It's an acceleration.

• 43:26Charles Liu?

  The one that leaves and comes back, that's the one that is the Thing that appears to be wrong.

• 43:33Neil deGrasse Tyson?

  So it's it's it's an uncomfortable concept because we don't experience that in everyday life.

• 43:39Charles Liu?

  That's right.

• 43:39Neil deGrasse Tyson?

  As our active senses do, it was not necessary to know this on the plains of the Serengeti. To avoid getting eaten by a lion, you didn't need to know relativity.

• 43:49Charles Liu?

  But it's absolutely necessary in this day and age of atomic energy and very, very high speeds.

• 43:57Neil deGrasse Tyson?

  Yeah.

• 43:59Neil deGrasse Tyson?

  Matt, it's time for lightning round.

• 44:02Charles Liu?

  Oh, yeah.

• 44:02Neil deGrasse Tyson?

  Okay.

• 44:03Matt Kirshen?

  Nice.

• 44:04Neil deGrasse Tyson?

  See if the bell works. It does. So Charles and I will try to answer in sound bites.

• 44:09Matt Kirshen?

  All right. Well, we're going to jump back from Einstein to Newton. DJ Melky on Instagram says, I read a few years back that the Earth is technically falling into the sun, but doesn't actually go into the sun. Is that true?

• 44:20Charles Liu?

  Yes, and the reason it doesn't go in is because it's traveling at orbital velocity around the sun.

• 44:25Neil deGrasse Tyson?

  Yeah, if we if we travel any slower sideways, we would fall towards get closer to the sun. So we are falling towards the sun, but we're being held up, if you will, by our very high sideways speed. So, yeah, we got this. And Isaac Newton first demonstrated this in

• 44:41Matt Kirshen?

  Principia.

• 44:42Neil deGrasse Tyson?

  Principia and first drew it in The System of the World. That was his Cliff Notes for his Principia.

• 44:50Charles Liu?

  Terrific.

• 44:50Neil deGrasse Tyson?

  Written in English. Very cool. All right, you got it.

• 44:53Matt Kirshen?

  All right. CodeMonkeyIA on Instagram says, what causes the Earth's magnetic poles to move and what would cause the magnetic north and south to flip?

• 45:03Charles Liu?

  Ah, very good question. Our magnetic field is created by the dynamic motion of ferromagnetic materials inside our Earth.

• 45:12Neil deGrasse Tyson?

  Iron.

• 45:13Charles Liu?

  Yeah, almost all iron.

• 45:14Neil deGrasse Tyson?

  It's almost entirely iron.

• 45:15Charles Liu?

  Almost all iron. And because of that, because it's fluid and it moves, that's why our poles move. It's as if you had a dancing magnet inside, but it's kind of somewhat semi-solid, somewhat liquid.

• 45:26Neil deGrasse Tyson?

  And it rotates, but not exactly the same rate that Earth does. So all these dynamics influence which direction on Earth's surface you find the north and south pole and whether the north is up or down relative to it. And history has shown that the poles have flipped multiple times in the past. Yeah, next. Oh, by the way, if our, if Earth cools completely and the core becomes solid, the magnetic field shuts off.

• 45:48Charles Liu?

  It's frozen. Yeah, it's done.

• 45:49Neil deGrasse Tyson?

  Good, good.

• 45:51Charles Liu?

  All right.

• 45:52Neil deGrasse Tyson?

  It wouldn't shut off the magnetic field, it just changed the movement of the magnetic field. Good, good, okay.

• 45:56Matt Kirshen?

  Evan Howington on Facebook says, "If the universe is infinite, then how could time exist other than the meaning we give it?"

• 46:03Charles Liu?

  Um, "If the universe is infinite" is the key point. We don't know necessarily yet that the universe is infinite.

• 46:09Neil deGrasse Tyson?

  He's saying if it's infinite, let's, let's, let's change the question. Suppose the universe had no beginning and no known end, is infinite in time and space, what does it even mean to have a calendar?

• 46:20Charles Liu?

  Hmm, great point.

• 46:21Neil deGrasse Tyson?

  What are you measuring? Is that kind of the paraphrase of that question?

• 46:24Charles Liu?

  I think so, yes. That's a good way to put it. And, and what we would be measuring in time is the various atomic processes going on in our bodies. And a clock, like the definition of a second, is just a way to macroscopically allow us to know whether we're getting older or whether we're not.

• 46:40Neil deGrasse Tyson?

  So you need vibrating, repeating phenomenon to measure time accurately at all? So in a universe where nothing repeats, there can be no measurement of time?

• 46:51Charles Liu?

  Well.

• 46:52Neil deGrasse Tyson?

  What do you think of that?

• 46:53Charles Liu?

  If you can measure the passage of time, or define the passage of time as the expansion of the universe, then you don't have to have a vibration, you can just have the change that's going in a single direction from smaller to larger.

• 47:05Neil deGrasse Tyson?

  Okay, so time then gets measured by size?

• 47:07Charles Liu?

  Yeah.

• 47:08Neil deGrasse Tyson?

  Size of things, interesting.

• 47:09Charles Liu?

  Rather than repetition.

• 47:10Neil deGrasse Tyson?

  Matt, last question, go for it.

• 47:12Matt Kirshen?

  All right, I'm gonna go with this one then. Uh, Billy from Queens here, out of Hunter College.

• 47:17Neil deGrasse Tyson?

  Give me some Billy.

• 47:17Matt Kirshen?

  Hunter College, City University of New York, oh yeah. Cosmically curious on Instagram says, "What are some tips for an everyday astrophysics student who wants to become an extremely successful science educator?"

• 47:29Charles Liu?

  Oh, uh, read Neil's books.

• 47:33Charles Liu?

  I don't know. I really love it when educators express their knowledge in the language of the people who are listening. In other words, a really good science educator is essentially a very good interpreter, a very good translator. Not someone that just dumbs things down, not just someone that turns things into sound bites, but someone that can really take a concept that's sort of described by math and science and turned into English or French or whatever language that the person is fluent in. That is the mark of a true science educator, thinking about the audience and not necessarily about the source.

• 48:11Neil deGrasse Tyson?

  Ooh. I can't, I can't touch that. I can't touch it. Other than to add punctuation and say that Galileo, an academic fluent in Latin, when he decided to write about the whether Earth was in the center of the known universe or it orbiting the sun, he wrote that in Italian.

• 48:33Charles Liu?

  Yes.

• 48:33Neil deGrasse Tyson?

  Knowing that the common folk would be able to then embrace and appreciate the discoveries he was making. And so that was quite a striking fact. That's like Carl Sagan appearing on The Tonight Show.

• 48:46Charles Liu?

  Yeah, yeah.

• 48:47Neil deGrasse Tyson?

  That's, you're crossing-

• 48:48Charles Liu?

  A pivotal moment.

• 48:49Neil deGrasse Tyson?

  You're crossing boundaries there. And then he became a regular guest on The Tonight Show, coming to the people. Where the people, where the people are.

• 48:58Charles Liu?

  Right. And, and never like claiming that he was somehow smarter or better than they were.

• 49:04Neil deGrasse Tyson?

  Empowering people to think even more highly of their own intellect that maybe they only just discovered for the first time.

• 49:15Charles Liu?

  Well said, sir.

• 49:16Neil deGrasse Tyson?

  We gotta end it there. Charles.

• 49:19Charles Liu?

  Neil.

• 49:20Neil deGrasse Tyson?

  Dude.

• 49:21Charles Liu?

  Dude.

• 49:21Neil deGrasse Tyson?

  Love you, man.

• 49:22Charles Liu?

  Love you too, man.

• 49:22Neil deGrasse Tyson?

  Family, everybody's okay?

• 49:24Charles Liu?

  Everybody's good, last I checked.

• 49:25Neil deGrasse Tyson?

  Excellent, excellent. Matt? It's been a joy. Probably science is going strong. That is the podcast, yeah. We look for that on the podcast. And you've been watching, more likely perhaps, listening to this episode of StarTalk, our edition called Summer School. I've been your host, Neil deGrasse Tyson, and as always.