- YouTubeiverse, Tyson
here, StarTalk next, Summer School is in session. (upbeat music) 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. (laughs) - [Charles] Yeah. - Who said yeah? - The professor. (laughs) - Friend and colleague, Charles Liu. Charles, welcome. - Thank you so much for having
me, I love Summer School. - [Neil] You love Summer school. - Absolutely. - [Neil] And I got my cohost
for this episode, Matt Kirshen. Matt. - Hey.
- Welcome back. - Thank you so much. - All right, host of
Probably, Maybe Science. - Probably Science. - Could be Science? - Nearly Science. - Not Sure if it's Science? - Almost there. - (laughs) Almost the-- - I Can't Believe it's Not Science/ (laughs) Noisy Science. - Probably Science. A weekly review of science current events. - That's exactly it. - [Neil] Excellent, excellent. - That's the podcast. - [Neil] Keep that goin', keep that goin'. - [Neil] Charles, professor. - Yes. - [Neil] At City University of New York-- - So we're kind of equals here. (laughs) - Absolutely. No, we are. Peas in a pod. - This is a Cosmic Queries version, but it's called Summer School. People just tryin' to catch up-- - That's right. - [Neil] With stuff they might've missed. - Or get ahead. - Or get ahead. I forgot, summer school's
for gettin' ahead, too. For motivated students. - And with that in mind, I think, let's start off with a quite an academically advanced question. - Let's do it. - Ooh. - Cooper Holland on Instagram asks, "How hard would I have to fart to "knock Earth into escape velocity. "Also, wouldn't sunrise
be a good time to try it?" Mmm. That's Cooper Holland from Arizona State. - From ASU, huh. - 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? - No, he wants to escape from the Earth. - Oh, he wants to escape from the Earth. I thought he wanted the
Earth to escape from the Sun. - Oh, that's different.
- Now that is a massive-- - Yeah, it says to knock
Earth into escape velocity. - That's harder than just
if he wanted to escape. - Right, right. If he wanted to escape, that's easy. (laughs) - Just a few cans of beans-- - [Charles] There you go. - We put him on a gantry. (laughs) - No, Earth would be a lot harder. Because Earth's orbital velocity-- - Now I can't get that
picture out of my head. He's positioned on a
gantry at Cape Canavaral. - Three, two, one--
- Last two cup of beans, he goes-- (laughs) - Launch aborted for weather. - Ascends. - But is that solid fuel
or a liquid fuel rocket? - Oh, yeah, no-- - Yeah, see, see? - That would be, no that's
just air pressure fuel. - That's just the yeah-- - That's just pressure fuel. - It's really a bottle rocket. (laughs) - Pneumatic rocket. - Pneumatic. - Or like a, the CO2 pellet rifle-- - Yeah, right, like a, yeah, wow. No, see, Earth's orbital velocity is about 30 kilometers per second, right? - Per second, correct. - Around the Sun. You have to take the
square root of two of that, and so that makes 1.4 times 30, so about 42 kilometers a second. Earth's mass is about six-- - 'Cause 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. - [Charles] Yeah. - That's a very cool fact. - It is, it's neat. It's nice coincidence in math. And the Earth's mass of-- - Square root of two is about 1.4, yeah. - Earth's mass is six
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. - 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. - 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. - You can drag the Earth with you. - Right. - But otherwise you would just
fly off at a tangent, right. - [Charles] So I think-- - Ideally you'd want to get
all humans involved in this. - [Charles] Right. - You'd need every--
- you'd wanna be holding onto a tree or something. - You'd also need every
cow in the world, too. - [Neil] Yeah, the cows. - You gotta put 'em all together, I think that's a very
summer school problem calculation to do, yes. Cooper, good luck with that. (laughs) That's great. - But in principle, yes. So in other words, if you are in space, the various ways you can actually
set yourself into motion, but to do so you have to
lose mass from your body. Either through gas, liquid, or solid. - 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. - So you can build to the speed that the Earth has itself, yes. - Right. Okay. - By the way, but all that methane, that could be pretty dangerous situation. - It's true, one match
and you've got yeah-- - Then you have a bomb. - That's a flare. - That's a bomb. - And also that's a greenhouse gas. - [Neil] Yes it is. - Oh yeah, yeah, yeah, yeah. - Yeah, very potent, more potent than CO2. - True. So you really have to light that thing. Yeah. (laughs) You would fly out into space. (crosstalk) - Now wait a minute. Wait, if you leave Earth, you need the greenhouse gases to retain-- - To stay warm.
- There you go. - The warmth.
- That's right. So, it's the balance,
it's the balance of, yeah. Wow, that is very exciting. You know what, I think I'm
gonna have to assign that to my astrophysics class next year. - And then the Dean will call you, (laughs) to the office and say-- - Well, maybe Cooper will
help me out with that. - Well, while we are doing calculations, Tom Foreman on Facebook asks, "Is math a discovery or an invention?" - Beautiful, beautiful. - Don't get me started. I wanna hear Charles first. - Okay, well, remember that
my wife is a mathematician. - [Neil] Yes, she is. - Right. - And my wife has a PhD
in Mathematical Physics. - [Charles] That's right. - Yeah. - Twinsies! (laughs) - So we got math goin' in the family here. - Yeah, 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. - I'm sorry. - Yeah, I know, I know. - Such a disappointment. - When did you know? Were the signs always there? (laughs) - When he was a little kid,
putting refrigerator magnets in strange shapes, I knew
that something was up. - You just knew something-- - Something was up. - He was hiding something. - Something was up. - In the closet, okay. - (sighs) 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. 'Cause 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've stood anyway, if we had put them together
and not known the equations. 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've 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. - I'm okay with that. - [Charles] Okay. - 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. - Oh. - And would that word be a
discovery or an invention? (laughs) - It's the word between
the two that we don't have. - Disco-vention. - It's why we argue-- - (singing) Mathematics, math math. Oh yeah, yeah, ya math. - Is it a particle or is it a wave in-- 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, I just don't-- - Sounds like some sort of
branding exercise from the 80s. (laughs) It's wavical. - 70s, discovention, okay? - The fact that math works at all, as a tool to decode the universe, is evidence that the universe, at least the parts that have revealed itself to us, follows logical repeatable patterns. And math is simply a
way to code for logical, repeatable patterns. 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 'em together, of course, it's a marriage made in heaven. - Very much like music, right? Math, music, that kind of connection, and the BeeGees understood that well, with their song (singing) Calculus, calculus,
yeah yeah yeah calculus! - I thought Calculus
was an emperor of Rome. (laughs) That's a old joke, I heard that long ago. - I'm gonna-- - [Neil] Calculus, the brother of Clavius. (laughs) Matt. - Well, while we're talking about things-- - Get us off this topic really fast. - I will. Well I'm gonna combine two
different questions together. So Eric Hanson 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." - Yep, that's about right. - "How, then, can anyone
adequately explain "how the entire mass of
the observable universe "was at once a point only microns wide?" And then, I'm gonna combine this with this other question from-- - You're gonna combine that? - That's a beautiful question on its own. - How you gonna add somethin' to that? - Yeah, yeah, yeah, yeah. - Well, this is a little coda question, I could've 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. 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?" So those two together, or
separate as you choose. - Okay, so this is basically
a cosmology question. - Sure.
- Right? So I'll take the cosmology
question, number one, you can take cosmology
question number two. - I like both of 'em. - All right-- - No, I'm just kidding. (laughs) - I'll answer each one half way. - Okay, you answer each half. Leave me a little room at the end, go. - 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 the moment of the Big Bang, at the plank time, we call it, was approximately 10 to the
97 kilograms per cubic meter. - That's pretty dense. - Yeah. And even if we took-- - Heavy, man. - All of humanity-- (laughs) We're back in the 60s now. We went from the 70s to the 60s-- - Heavy. - Absolutely, you said it. We have a circumstance where
the matter of that density is so removed from
anything we can think of, 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. - So there was just
another state of matter, or the matter itself-- - Wait, wait Charles, I thought it's not even
that complicated, okay? - Okay. - If it stays as solid matter, just taking out all the
space between the particles, yeah, you're not gonna 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 kinda small volume you want. So-- - That's the right way to say it. - Is that a fair way to-- - It's 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. - Wait, wait, I have to tighten that. It's not that it went from that to now, it went from then to a
little bit after then, because we know what happened a little bit after then until now. We got that. - That's fair.
- That's good physics. - And by little bit after, Neil, I think you're referring
to 10 to the minus - 30th seconds, yeah.
- 30th seconds, right? 0.000000000. - A gazillionth of a second. (laughs) - So we've managed to trace
it back a very long way. - Yes, but that last little bit-- - Just that last
gazillionth of a second is the really confusing bit. - And that segues into that
second part of the question. - [Neil] It does, right. - 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. What could've 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. 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. - And let me just say, do you think we're happy about a Big Bang? - [Charles] Yeah. (laughs) That's a great point. - 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? - I think that's a great point, yeah. 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. - But what you don't know is whether the addition is just an add-on, or whether you have to
throw out everything and come up with a new idea. - Do you think that last
gazillionth of a second will be explained, or
is it even explainable? - We've got top people
working on it right now. They're called string theorists. Top people. - And cosmologists in general, yeah. - [Neil] Top people. - String theorists is just one group of promising paths, but all of cosmology is really about trying to get that last little tiny bit. - Chris Carlton on Facebook asks, "Why aren't we expanding with the universe if we are part of the universe?" - Ah. - Ooh. - I get asked that question
a lot by my students. - And I'm gonna add a coda to that, will I ever break six foot? (laughs) - Oh, you're still growing? - Well, I'm hopefully still expanding. - That can help you there. We will get to the answer
to that when we return for a second segment of Summer School. StarTalk. We're back in our second segment
of StarTalk Summer School. When you have to go to summer school, you have to bring in the big guns. Charles Liu, (laughs) professor. - Thank you Neil. - Professor Charles Liu. CUNY Staten Island. Matt Kirshen, - The little gun. (laughs) The littlest gun. - Wait, so how tall are
you, how tall are you? - Like five five. - Five five and 120 pounds. - Yep. - Eight and a half stone. Let's be specific. - Excuse me, eight and a half stone? - Yeah, 'cause Britain really doesn't know what units to use. (laughs) We're metric sometimes, sometimes we're-- - Which stone, you know? - In some cases we're ahead of you, we do fruit and vegemetric, we normally do Celsius for temperature, but then we'll do stones-- - Yeah, you have issues. You have metric issues. - We're comparing things to
the size of animals, it's-- (laughs) - So that's where the stones come from. - I don't even know-- - No, that's for the hands, you have hands for the height of horses. - We have hands and-- - Whose hands? Whose feet? So, we left off at the first segment, a question-- - About, yes, if the universe is expanding and we're part of the universe, why are we not expanding? - 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-- - Literally, the atoms and molecules in his pinky that he's pulling. As he picks his fingers on his hands, yes. - 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. - Way stronger forces. - In the shorts. - In the short distance. - Yeah, in the short distances. 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. - Even the solar system is not expanding. - That, okay, 'cause I always, I've been given the analogy in the past of blowing up the balloon and watching the dots get further apart. - On the surface-- - That's right. - But 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 in one clump-- - That is a correct,
better assessment to-- - And they become further
apart as the globe expands. - Yeah, on a balloon, if
you drew a galaxy on it, that galaxy would actually get bigger. But that's not what happens. - Put like little sticky
notes on the balloon and that would work. - Right, sticky notes that sort of have the ability to slide. - Lifesavers, you glue
'em on and they'll just stay in one shape-- - Yeah, you can do that, too. - So the sticky notes
themselves or the lifesavers would become further apart, but within themselves they
would stay the same size. - Correct. - You got it. - Okay. - [Neil] Yeah. - It's a very good question. - I understand something a lot better now. - We got good question
people out there, man. - What an excellent audience StarTalk has. - This is an excellent audience. Unless they just culled from-- (laughs) - No, no, no, no. I'm sure these are-- - We'll check with our
researcher and find out. All right, Matt, next. - All right, from Ben Rattner
at Ben Makes TV on Twitter-- - Oh, that guy. - I've heard of that guy before. - Ben says, "Please describe
the laws of physics." It sounds like we're doing Ben's homework. - Oh.
- Oh. - No, here's what I'm doing. I'm gonna pull rank here, you ready? - Go ahead.
- Okay. In one of my books I have a chapter called On Earth as in the Heavens. - Ooh. - 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. And it's not a given that
that should be the case. - [Charles] Okay, okay. - It might've 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. - What I would be interested in is not necessarily the laws of physics, 'cause that's what I
live with all my life. - Do you? - [Charles] Yes. - Do you have a choice? - But. What are the laws of psychics? - I don't understand. - Well, laws of physics,
right, natural stuff, predictable, whatever. But the laws of psychics, like people who make
predictions about the future, people who cast themselves as those who understand things that are beyond nature, what are the laws of psychics? - Maybe there are no laws. - Well then why is there a
major in psychic studies? - Not in any university I know of, unless it's in Arizona. - Astrology. Yeah, I think it's in Arizona, yeah. - Yeah, other than Arizona, I don't think any accredited university has a major in astrology or psychics. - Yeah, but surely if
such a major does exist then there must be some
laws that they must follow. - Okay. I've never been curious about that. Maybe I should be. - [Charles] I don't know. - Yeah. Here's the thing, the
headline you've never seen, Psychic Predicts Winning the
Lottery Number a Second Time. (laughs) - That's true, that's true. - You don't get that. - That's true. Well, we'll have to ask this questioner yeah, what Ben Makes TV thinks about the laws of psychics. - But otherwise, the laws
of physics are very simple. I mean, they fit, you know, I remember I was in school, and somebody was taking
an accounting class, and I saw the book that
they were carrying, it had like a million pages in the book. 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 as fat just to be able to do somebody's taxes. - Fair enough. - 'Cause you can't deduce
the tax code from-- (laughs) - Thank you, that's the difference. The good thing about physics is, you learn some rules and then
all the rest derive from them. - [Charles] Pretty much. - Very powerful. - And then every so often
someone comes along goes, "Actually, those rules
are all slightly wrong." (laughs) - Yeah. - What we have, we have
Newton's F equals MA, you got E equals MC squared, you got Maxwell's equations, we're done. - Practically.
- pretty much, yeah. Yeah, yeah, yeah. - Throw in a few quantum
physics equations-- - Years worth of-- - Schrodinger's equation. - Yeah, years worth of physics studied is just F on 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 from that springs forth physics. - Unfolds for free. - Yeah, absolutely, absolutely. - Yeah, it's beautiful. - Great question. - I really enjoy this question, because apart from everything else it came from a four-year-old. - Ooh! - The four-year-old son-- - You should tell us
after, when we're stumped. - Yeah, yeah yeah yeah. - The four-year-old son
of Pinty from Laos asks-- - Laos, ooh. - Nice. - "Why do punctured balloons
fly around chaotically? "Why doesn't it fly on a straight line?" - Wonderful question. When you have a rocket, actually, you know how they travel
in straight lines, and we're 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. 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 linear way compared with whether it's just rushing out all at once. - Well also, you'd want
the movement of the air to line up with the center
of mass of the balloon, okay? So if that lines up, then the balloon will just get 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. Plus, a balloon is not symmetric. The bottom of it where you got the knot-- - [Charles] The knot, yeah, the knot. - So the balloon's
weight is not symmetric. - And the center of
the mass of the balloon would also move around
as the balloon deflates. - Yes! Yes! - That's right. - So, what you have to do
is configure something, like get a straw, maybe, to
guide the air a little better, have some stabilizers, and then you can make a balloon rocket. - That would be a lot of fun. - But I love that question. - It's a great question. - That sounds like a kid that's
tearin' up birthday parties. (laughs) - I want that kid on my research staff. (laughs) - By the way, most of the time
when you pin prick a balloon, it blows up. - [Matt] Right. - Right, so you have to do this carefully. - 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, then you can have it-- - So you've done this before. - Of course, hasn't everybody? - Okay, no, I haven't put tape
on a balloon to puncture it. - Ooh, give it a try sometime-- - But it's way more fun to just pop them. - It's too fast. - It is too fast. - It's too fast.
- It's too fast. - Yeah, yeah, yeah. - You are correct. (laughs) Okay, I will try this from now on. Any kind of, masking tape, or-- - I used, like, plastic invisible tape-- - Okay, Scotch tape. - Scotch tape, yeah. - Wait wait, now you put it
on both sides of the balloon-- - There you go. - And open it up, the balloon
won't know where to go. - It won't know where to
go, it'll start spinning. (laughs) That would be fun. All right, four year
old balloon experiments. - 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?" - Okay, okay, first-- - And the question, it doesn't make clear whether they themselves
are the dumb teenager or are trying to-- - It's a friend, a friend, I
want to explain to a friend. - 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 pretend to be dumb, they may think they're dumb-- - 'Cause it's cool. - Yeah, but they're not actually dumb. I want people always to
feel like 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, sorry,
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-- - [Neil] Nuclear interactions. - In nuclear interactions
energy is properly balanced. Both in the motion and in the amount. I think that's really what a simple way of describing a neutrino is. - Yeah, it's a pretty weird particle. 'Cause 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 who said, "There's gotta be a particle carrying "away this momentum, there has to." We look and we don't find-- Gotta keep looking. It's gotta be. What properties should it have? Well it can't have any charge, so it's gotta be neutral, and it's gotta be really
low mass and little. So it's gotta be little and neutral. And-- - Well, the funny thing is, of course-- - So in Italian, neutrino. Like bambino, neutrino. - So it's just the diminutive
version of neutral. - Of neutral, or of a neutron, right. - But the funny thing is
when this was first proposed the neutron had not yet been discovered. So when the neutron was discovered, people are like, "Oh, is this it?" And did more calculations
said, "Nope, still not it." There's something that's even
smaller that the neutron. - That has no charge, right, right right. So yeah, 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? - Many trillions. - Trillions. - Many, many trillions. - Can you feel it? - Matt, can you feel it?
- Can't feel it. - I mean, I can a bit. (laughs) It could be the air
conditioning, I don't know, it's hard to tell. So how do we-- - 'Cause they don't
interact and that's why they were so hard to detect. - But they do interact
very minimally, right? We can detect them. - 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 dry cleaning fluid, very pure. Put it down more than
mile below the surface in South Dakota, and surrounded it-- - I think it was just a
pre-existing salt mine, wasn't it? - It was a gold mine. - Oh, gold mine. - The Homestake Gold Mine. - Gold mine, not a salt mine, okay. - 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 awhile. 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 (mumbles). - Why cleaning fluid? - Turns out that that particular molecule, perchlorate-- - Yeah, I think it needed
the chlorine in it. - Yeah, had a special, nice property that it would, when hit by a neutrino, with that interaction, very
rare, occasional interaction would cause a flash of light. - How long ago did that experiment happen? Was it recent? - Couple of decades, yeah. - Several decades ago. - 70s, 80s. - Ray Davis, Jr. was the experimentalist, John Bacall was the theorist that was-- - And Ray Davis got the Nobel
Prize, I think, for that, but not John Bacall. - Yes, yes. - 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. - 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. - Scary prospect. - Yes, scary prospect. Turned out, though, that it
was just something happening in our upper atmosphere,
called neutrino oscillations. Another amazing discovery. - Yeah, so it'd be I
throw you a basketball, but you catch a football. - Right. - So the experiment was
designed to detect basketballs, and what you were actually
receiving footballs. - And what it is is someone in between us is swapping them out. - That's right. (laughs) And it was amazing, that
was what was happening. These neutrinos come in
different flavors, it turns out. Who knew? - Who knew at the time? - Oh okay, so there isn't
just one neutrino particle, there's three. - Yeah.
- Okay. - Three different kinds. Electron neutrinos, Tao
neutrinos, and Mu neutrinos. - And their antimatter counterparts. - And the antimatter counterparts. - There are really six. - Yeah. - Yeah, it's pretty cool. - Physics is amazing, isn't it? I love summer school. Great question. - Summer school, next question. - All right, Kyle Ryan
Toth on Patreon asks, "Ignoring the cold, could
a settlement survive "on the surface of Pluto? "What would radiation levels be like, "are their any useful resources "other than water-ice?" - Hold me back. (laughs) We'll get to that question
when we return on StarTalk. Matt, before the break
you had a Pluto question. - It is, yeah-- - You know me and Pluto have history. (laughs) But we buried the hatchet long ago. - Well, whether it's a planet or not, could a settlement survive on it? - Oh. Well you can ask why would
you want to do such a thing? - [Matt] Right. - Because, just take for example, Charles, is there a line of people
waiting to settle in Antarctica? - No. - And Antarctica is warmer and is balmier and wetter than Pluto. - And there's penguins. (laughs) To the best of my knowledge,
there are none on Pluto. - And in a pinch, we can
eat a penguin, right? - That's right. - So Pluto, in principle, we could just pitch a tent anywhere and just bring enough resources, right? - Yeah, yeah. This 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's
so low out at that distance. - And food, you need a
way to generate food. - Yeah, you need food. - 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-- - The flux is only about
one 1600th the amount of flux that we get from
the Sun here on Earth. - Is it only that much? I thought, I'm going on memory now, not on a calculation, that the Sun from Pluto is about like a full moon night here. Is it brighter than that? - Ooh, let me do that
quick calculation there. Well, absolute magnitude
negative 26 for the Sun, minus 15-- - No, 12, moon is 12. - So that's 14 magnitudes. - 14. - Soo that's a factor of-- - So seven-- - Yeah. - So seven, so 10 to the 14. - No, not quite that much. - Yeah, seven magnitudes. Oh no, I'm sorry, five, five. So it's a factor of 100,000. - Yeah, right. So it's a little bit-- - [Neil] And you said it's-- - I said 16,000 because, so 40 AU, right? - Oh, you just divide it out, yeah, okay. (man speaks inaudibly off-screen). 1600, yeah. - So, they're-- - You think we need HuffPo
to find out if we're-- (laughs) You're in the middle of an
active calculation here. You pull up a HuffPo page? - 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. - We are 40, Pluto is
40 times farther away from the Sun than Earth is, on average, and so it's one over that squared-- - That's right. So that's where you get the 1600. - One 1600th as bright. - That's right. But the idea that a person could-- - Inverse square law of light. Very cool. - 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 just not picking
Google specifically-- - Sounds like he doesn't wanna
be replaced with a robot. Matt, does that sound like that to you? - 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. - Charles for president,
Charles for president! (laughs) - We know that Charles is a
better singer than Google, so-- (laughs) - I think that was Charles's
stump speech right there. - Oh dear. - Well we are talking
about singing and the like, Marcus, and I'm gonna apologize
for butchering this name, but Goyamarez? 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 arts in general. - [Neil] (gasps) "I think that's not true," says Marcus. - Aaah! Excuse me while I go throw up. - "Dr. Tyson loves art, and he loves "the Starry Night by Van Gogh. "Could you please tell us
something about the subject?" - (coughs) - Charles, are you okay there? You seem put out somehow. - Science hates art? (retches) No way. - Yeah, I don't know, 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, one of the books behind you on a shelf is called Mathematics and Art, a book written by an art curator, who is fascinated by the role of science as it has influenced art, and I was privileged to be asked to write the forward to that book. And, as the writer knows, I'm
a big fan of the Starry Night, by Vincent Van Gogh, 1889. And so I, and I'm not
unusual in this regard. Our colleagues love music, love art, on levels that you might
not even know or suspect, 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 call the schools of Arts and Sciences? We go way back. - Yeah, way back. - To 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. - 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. - Have him take up that
question with Leonardo da Vinci. (laughs) - 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. - Trina Jennings on Facebook asks, "If we can figure out the center of "the Milky Way galaxy
smells like raspberries, (laughs) "can we figure out what things
would smell like elsewhere? "Would the center of all
galaxies smell like raspberries?" - Okay, who said the center of the galaxy smelled like raspberries? - 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." - There's also a lot
of ethanol there, too, you sound like a drunkard. - Yeah, it would smell
like a brewery, yeah. - But that'd be the yeast, I think the yeast is the
predominant smell in a brewery. - That's right. - A distillery. - A distillery, yeah. - There's a lot of organic
molecules in space, so-- - And there's even sunless
tanning lotion, too. DHA in molecules over there, so you can not only get a great suntan-- - I've never looked, I-- - You can also smell-- - I didn't know such a thing existed. - Yeah, yeah, sorry. - Up in the hood, it was not a-- (laughs) - You guys weren't tanning much? - Yeah, the CVS doesn't have
that on the front counter. - You don't do the spray tan? - No, no, no, no, not in the hood. So, it's a little deceptive to say that space smells like that, 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. - Right, 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-- - [Neil] What that would smell like. Precisely. - But there are a lot
of particles out there. And they can smell like a
lot of different things. - [Neil] Indeed. - Nice. Who wants a relativity question? - Bring it on. - Hussein Sagwani on Twitter says, "I'm 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?" - Again, before Neil says anything-- - No, no I'm not saying anything. I'm out of this one, go. - 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. - In that case, can you smart it up? (laughs) - That's right, thank you Matt. Okay, here's the basic point. - [Neil] Smart it down, smart it down. - 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 are 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, the the twin paradox
that is described here, or other paradoxes
become not too difficult. 'Cause what you're doing is measuring time in 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 experience one minute ago, to the time you experience
a minute from now. That person who is traveling
at a different rate through time and space will simply experience a different interval. - And you'll both call it a minute. - [Charles] Yeah. - But relative to each other,
they're different lengths. So, yeah. - And you only realize that once you come back into contact with each other. - 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, their opposite clock is ticking slower, is that the, the twin who went out had to slow down, turn
around, and come back. 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? - 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. - That's one of the great
jokes against Einstein, who said, "Hey Einstein, when
does Grand Central Station "arrive at the next train?" (laughs) Everyone was trying to
get their head around this back at the time. - So it's specifically
the acceleration of the one twin who goes out on the space ship and goes out and then turns
around and comes back. It's that-- - [Neil] That breaks the symmetry. - It's that acceleration
and then deceleration that-- - Yeah, the whole thing is either positive or negative acceleration, but it's just, it wouldn't matter, it's just an acceleration. - The one that leaves and comes back, that's the one that is the thing that appears to be wrong. - So it's an uncomfortable concept because we don't experience
that in everyday life. - [Charles] That's right. - As 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. - But it's absolutely
necessary in this day and age of atomic energy and
very very high speeds. - Matt, it's time for Lightning Round. - Oh yeah. - Okay.
- Nice. - See if the bell works,
(bell dings) it does. So Charles and I will try
to answer in sound bytes. - All right, well we're gonna jump back from Einstein to Newton. DJ Milky 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?" - Yes, and the reason it
doesn't go in is because it's traveling at orbital
velocity around the Sun. - Yeah, if we traveled
any slower sideways, we would fall towards,
get closer to the Sun. So we are falling towards the Sun, but we are being held up, if you will, by our very high sideways speed. So yeah, we got this. And Isaac Newton first demonstrated this-- - [Charles] In Principia. - In Principia. And first drew it in
The System of the World. That was his Cliff
Notes for his Principia. - [Charles] Terrific. - Written in English, very cool. All right (bell dings) you got it. - All right, Code Monkey
IA on Instagram says, "What causes the Earth's
magnetic poles to move, "and what would cause the
magnetic North and South to flip?" - Ah, very good question. Our magnetic field is
created by the dynamic motion of ferro-magnetic
materials inside our Earth. - Iron. - [Charles] Yeah, almost all iron. - (laughs) It's almost entirely iron. - 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. - 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 (bell dings), oh, by the way, if our Earth cools completely,
and the core becomes solid, (snaps) the magnet field shuts off. - It's frozen, yeah, yeah, it's done. - Good, (bell dings) good. - All right-- - Sorry, it wouldn't shut
off the magnetic field, it just changes the movement
of the magnetic field. - [Charles] Right. - Good, (bell dings) good, okay. - Evan Harrington on Facebook says, "If the universe is infinite, "then how could time exist other "than the meaning we give it?" - If the universe is
infinite is the key point. We don't know necessarily yet
that the universe is infinite. - He's saying if it's infinite, 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? - [Charles] Hmm, great point. - What are you measuring? Is that kinda the
paraphrase of that question? - I think so, yes.
- I think so, yeah. - That's a good way to put it. - Yeah, yeah. - 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. - 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. - Well-- - What do you think of that? - 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. - Okay, so time, then,
gets measured by size. - [Charles] Yeah. - Size of things, interesting. - [Charles] Rather than repetition. - Matt, last question, go for it. (bell dings) - All right, I'm gonna
go with this one, then. Billy from Queens here
out of Hunter College. - Give me some Billy. - 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?" - Oh, read Neil's books. (laughs) 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 who just dumbs things down, not just someone that turns
things into sound bytes, but someone that can really take a concept that's sort of it's
ascribed by math and science and turn it 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. - Ooh. I can't touch that. (laughs) I can't touch that. Other than to add punctuation and say that Galileo, an
academic, fluent in Latin, when he decided to write about whether Earth was in the
center of the known universe or it orbiting the Sun, he wrote that in Italian. 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 thing. That's like Carl Sagan
appearing on the Tonight Show. - Yeah, yeah. - That's, you're crossing-- - A pivotal moment. - You're crossing boundaries there. And then he became a regular
guest on the Tonight Show. Coming to the people. Where the people are. - Right, right, and never, like, claiming that he was somehow smarter or better than they were. - Empowering people to
think even more highly of their own intellect that maybe they only just discovered
for the first time. - Well said, sir. - We gotta end it there. Charles. - Neil. - Dude.
- Dude. - Love you, man. - Love you, too, man. - Family, everybody's okay? - Everybody's good last I checked. - Excellent, excellent. Matt. - It's been a joy. - When you come back, can you weigh like 10 pounds more or something? (laughs) - All right, I'll put stones
in my pocket or something. (laughs) - Growing taller, we don't expect that, but there's a gym somewhere,
just put on some-- - I'll stretch myself out. (laughs) See if I can weaken those
electromagnetic bonds. (laughs) - There you go. - Do I need to rub magnets on myself? - Yeah, and they'll stretch him out, and then you'll get it. But Matt, always good to have you. - It's always good to be here, thank you. - Probably Science is goin' strong. - That is the podcast,
yeah, please check it out. - We look for that on the podcast. You've been listening to,
and possibly even watching, this episode of StarTalk. Our edition called Summer School. I've been your host, Neil DeGrasse Tyson, and, as always, I bid
you to keep looking up. (upbeat music)
