Cosmic Queries – The Big Stretch

0:01Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. this is star talk neil degrasse tyson here your personal astrophysicist we're doing cosmic queries today grab bag yeah and i look to my left i don't see chuck nice chuck what did you do we look a little different harrison greenbaum welcome back to star talk yes it's so nice to be here thank Thank you for having me. Yeah, last time it was B.C., before COVID. That's right. When you last made an appearance here. We had a whole pandemic in between. A whole pandemic in between. And also you had like a Las Vegas residency in there.

0:50I went across the country and back at that time. And back. So just congratulations on where your talents have taken you. Thank you. And now you're right here in my office at the American Museum of Natural History. As much going on here as the circus, I will say. No, well, the universe is a circus unto itself. Absolutely. And it's many more than three rings going on there. Yes. Saturn's got rings. Multiple ring circus in the cosmos. So this is a grab bag. Fantastic. And you've got the questions. I haven't seen them. And because it's a grab bag, it's a grab bag without an expert that we bring in.

1:24So I'm your expert. Fantastic. I'll do my best. If I don't know an answer, I'll just say, I don't know. Okay? Okay. But you have to - We have Siri. we do have we have tools at our disposal you've got you yeah the ways to bail me out is what you're saying okay all right we don't know it might be known okay all right so what do you have first all right so we have lana mcgrath she writes hello neil i'm lana from orlando where do photons come from for instance are they already inside my birthday candles or are they created from the fire. Oh, I love that. Does not specify what birthday she is on. Does not.

2:05Okay. Does not. But the fact that she still uses candles. Yeah. What age would you say you stopped using candles? Once the cake is too full. Yeah. I think I stopped at 30. Oh wow. That's longer than I lasted. I made it high in there. I think after high school I was candle free. So it's a great question. It's reminiscent of a famous essay from the 19th century written by Michael Faraday. And it's called, What is Fire? Ooh. Because what is it? It's an emoji I use too often. Oh, okay. I've seen the emoji. Can you touch it? Can you grab it? Can you hold it? Not really. So what is it? So there's a famous essay from the 19th century.

2:46So a photon is a packet of energy, a pure energy. And it moves at the speed of light. It's the only thing it knows how to do, is move at the speed of light. And so if, by the way, energy can manifest in a dozen, many different ways, okay? You can have potential energy. Now, why is it that you can harm yourself by jumping out of a window, okay? There's a reason for it. because when you hit the ground, energy killed you. I thought it was the sidewalk. Okay, you had energy in your body while you were falling. One red bull right before the show. And the energy kept accumulating as you fell faster and faster.

3:33Right. Then you hit the sidewalk. All the energy that was in you from your motion, kinetic energy, goes back into you as mechanical energy. And the only way your body can accommodate mechanical energy is to break stuff. Because it takes energy to break your bones. Sure. Energy can manifest in different ways. And the higher you take the elevator before you jump out the window, the more energy you have to break your bones upon hitting the sidewalk. That's why jumps from higher altitudes will do more damage than from lower altitudes. But if you're watching this and thinking about it, don't do it.

4:11Do not try this at home. Don't do it. Above a certain height, there's an air resistance. You hit what's called a terminal velocity, where the air is absorbing away some of that energy. I am about to terminate. Be terminated. Terminal velocity to be terminated. So there are other ways that energy can be stored, like inside of an atom. An electron can sit in many different energy levels. The atom has energy levels within it. It's not a continuous placement of energies. if there's an electron at a higher energy level and something happens to make a drop to a lower energy level, it just lost energy.

4:50Where did it go? Actually, it can go in one of two places. If another atom hits it, some of the energy of that electron can go to the kinetic energy of the other atom as it careens off. This happens a lot. So it's a kinetic energy. A mudging. A fly-by looting of its energy. All right. So, but occasionally it just sort of jostles it. The electron de-excites, goes to a lower energy level. Where does that energy go? Bada-bing. A photon is released from the atom of exactly the same energy as the difference between the energy levels of the electron. All the energy is accounted for. And so, and the photon goes in a random direction at the speed of light.

5:37That's where photons come from. They come from ways that used to be energy in an atom or the vibrations of atoms and molecules and other particles. And in those vibrations, it can lose energy by releasing a photon. And that's what's going on. And it happens in all kinds of ways. If you have an electric stove and you turn it on and eventually it glows. It goes like blue, orange, which are different colors. I hope your stove doesn't glow blue. go you can tell by the way how much i cook by my inability to answer this question you have no idea what a stove is you have no idea what you were right astrophysically but in a kitchen you're completely wrong okay so the hottest your stove is going to get is red hot gotcha but if you could if you had an infinite knob it will go it would go white hot and eventually blue hot doesn't mean my band name if i ever form a band infinite knob oh infinite knob blue hot's better but one of those Pick one.

6:37I'm good with you. I'll come see you. Okay, great. So the fact that the stove is glowing red is emitting light. Red light. So you have vibrating particles in the heating element of the stove, and those vibrations will actually release light. And that, in a way, is cooling the stove, except you keep pumping energy into the stove. Right. If you turn off the stove, it's still glowing red, but then it sort of fades away. Why? Because it's giving up all its energy without it being replaced. And if it's hot but not glowing red, it's still giving off photons but not red photons. If it's hot, generally, what is that?

7:17Do you remember? Don't touch it. Don't touch it. Still don't touch it until it's cool. So it would actually, if you put on infrared goggles, it would be glowing in the infrared. That's still a form of light. You can have infrared photons. So all these ways will generate photons. and stars are doing it every moment of their lives and photons are crisscrossing through the universe and it'll continue that way until the last star dies. So what does that have to do with birthday candles? Oh, good, very good. Okay, thank you for bringing it back on point. I feel like Lena is at home right now. She's celebrating her birthday.

7:55The candle's already melted down. It's ruined the cake. It's like, Neil, where's the answer? So you have to give energy to the candle from somewhere else, a lighter or a match, right? There's no free lunch here, right? The energy's got to come. So what that will do— Free cake. Okay, free cake. You will light the— The wick. You will light the wick of the candle, which is typically coated in wax because the candles are made of wax. so you ignite the wick that will use molten wax as a fuel source there you have it now why doesn't the whole candle burn up in one instant because the the wick is drawing the molten wax in and if you have too much of the wax it'll put out the flame you need just the right amount to feed it and keep it going.

8:51And candles are beautiful this way, okay? If the candle gets sort of, you know, if you, if you, if you tried this, who has candles anymore? But you have like a three inch candle, let's say, and it's got liquid there. If you sort of tip liquid towards the wick, you can extinguish the wick. Right. You say, well, why is that if it's using the wick to light? Have you ever questioned this? I have a couple of scented candles. Most of them smell like my apartment burning down when I fall asleep. Why does the liquid wax put out the wick when the wick needs the liquid wax to burn. Right. Because it's too much at a given time.

9:23It's too much. So the wick draws it at just the right amount that it could burn the little bitty drops that come in at the rate that you need. So the energy, the starter energy, comes from the match or from a lighter, and you hit the wick. Now the wick simply burns the wax. And wax is one of the great things that kept us lit for centuries. Wax candles, you know, 17th, 18th centuries. We didn't have light bulbs. So candles was a thing, wax candles. So wax is a fuel source. By the way, if you get wax hot enough where it goes molten and you just keep heating it, it can burn without a wick. What? So this happened to me at home.

10:14I ignited the entire surface of the liquid wax in the pot. I thought you told the police it was an accident. No, I used to make candles, okay? I'm just trying to picture this birthday party. No, no, no. I used to make candles. So you melt the candles and you can dip. What happens, you dip a wick in so it gets wet with wet wax. You put it in the air. Room temperature air will cool the wax and then it's a skinny candle. You dip it again and it keeps building layers and layers until there's the thickness you want, okay? That's one way to make it, as you make a dip candle. And normally you just pour it into a mold.

10:53Okay. So I melted this pot. I had all these candle shards, right? And you put them all in there. You pull out the dead wicks. And now I have liquid candle wax. And I left it on the stove too long. It ignited. You can't put water on it. Oh, no. It is hotter than boiling water. So if you put water in there, the water will be heated, start to boil, and then it'll boil fragments of flaming wax out of the... So there's only one way to put out that fire. Throw it out the window. Hope its potential energy is high enough. Yeah, now you're going to give it extra potential energy. Or kinetic energy. So, no, you got to take a lid and cover it, and that'll smother it.

11:47That's a less exciting answer than I thought. It's totally less exciting, but I knew enough. You just suffocate it. I knew enough about, yeah, you're suffocating it. I knew enough about thermodynamics that that's how you do that. So the candle doesn't all burn at once because it can only burn a little bit at a time, and it burns its way down. And there you have it. Nice. Well, happy birthday, Lena. Yes, however old you are.

12:18Hi, I'm Ernie Carducci from Columbus, Ohio. I'm here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

12:43oh by the way these are all our patreon supporters these are they pay amazing so you get to ask questions as a patreon supporter at our entry level amount which is like five dollars a month so go for it all right so we have alan rare he wrote hello everyone waving emoji cowboy emoji It's Alan from Lithuania. A lot of cowboys there. Always wondered about gravitational waves. Please explain how and what did they actually detect in 2015. Oh, very nice. Yeah, so that's the first detection of gravitational waves was then. Nice. Interestingly, it was the centennial, the near centennial. I think the prediction came out in 1916.

13:25But basically the centennial of Einstein's prediction that such a thing even exists. so it took a century to verify that what he predicted was correct so just to put that in context all right so the way this works is um according to einstein's general theory of relativity where you're here and you have we say you have a gravitational force i don't know if you knew that but you do right i like it okay and the more mass you have the more is your gravitational force i've had an increasing amount of gravitational force over the last few years Is that right? Okay. So it'll go up according to your mass, and we can measure that, more importantly.

14:05If you move through space and time, then your gravitational field needs to respond to that in some way, because it used to be over here, and now you're over there. Newton described gravity as just a force at a distance. Okay? Action at a distance. But he was still mystified. How could it gap the vacuum of space? What's going on? How do we know each other? How do we know about what? Why do we know? Why? He knew his equations worked, so he went with it. That's some confidence. It's still. He's like, I know these are right. I can't prove it, but I am 100 % sure. I can't demonstrate it? what's going on in the mystery of the vacuum of space but it's working so exhibit a trust me so it's working and einstein said gravity is not so much action at a distance gravity is a is a disturbance in the fabric of space and time so disturbance is too violent it is a shape of the fabric of space and time made by the existence of matter and energy wherever you might find it.

15:24Let's take a black hole, for example. A black hole is such a distortion of space and time that light cannot even escape. That's why we call it black. And you can't come out, it's a whole black hole. Best named thing there ever was, ever. So if you're just somebody wandering by a black hole, you'll feel your trajectory altered by it. Newton would say that's action at a distance. Einstein would say that is the shape of curved space-time. And you're just following where space and time wants to bring you. It's like in NASCAR. Are they actually turning left? No, because the track is banked. The bank turns them forth, turns the cars forth.

16:11I feel like the drivers would be very upset by this. Like, what are we training for? Yeah, so their steering is primarily maneuvering in the traffic rather than making a left turn as they go around the track. So the track is shaping their path in the same way space and time will shape the path of anything moving, but light is the best tracer of this. What happens when two black holes collide? OMG. Black holes collide. they are already a disturbance in the space-time continuum. Now they come together, it is such a disturbance that they will create a ripple in the fabric of space and time, emanating at the speed of light.

16:58A ripple, because as they come closer and closer, they spiral and faster and faster, and then they come together, and right at that instant, poof, there's a ripple. The first of these that was discovered have been traveling for 3 billion years. How do you detect it? We need special equipment. We call it LIGO, Laser Interferometer Gravitational Wave Observatory, sensibly abbreviated LIGO. So they have two, I forgot how long they are, kilometer long tunnels evacuated, no air. They have lasers that simultaneously go up the tunnel and back from a mirror that's at the other end. These two laser beams know about each other.

17:44They are coherent. They march to the beat of the same drummer when emitted. If on the up and back trip, something happened to the fabric of space-time, then one of those paths will be slightly different from the other. slightly longer or slightly shorter. And then the waves will no longer match up. And you can conclude that something happened here that didn't happen there. They're at right angles to each other. So this wave, this gravitational wave, as it washes over the observatory, depending on which angle was oriented relative to the wave, they will stretch or expand by different amounts from each other.

18:28And they measure this. They measured it. They knew what two colliding black holes should look like in their experiment. Matched up. The announcement gets made. Nobel Prize is awarded. Now, just for context. You said with a tone of voice that it was later discovered that it was wrong. No, no, no. I have a follow-on to that. 2017, they took it back. Turns out one of them just jostled the machine a little bit. No, they only discovered it in 2015. Nobel Prize is later. Gotcha. Okay, all right. So many people don't know that Einstein wrote down the first equations that enabled the laser to be invented later on.

19:07This is crumbs on his plate. Right. Okay? When you're that brilliant, crumbs do great things because you're focusing on the main events, like the theory of relativity and other things. The back page of his notebook just said tunnel laser. So Einstein invents a new theory of the universe, the general theory of relativity, that predicts the existence of gravitational waves. Shortly after that, he writes down the equation that permits the invention of the laser. Decades later, people invent the laser. Decades after that, they use the laser to measure and discover the existence of gravitational waves.

19:48And entertain cats. Yes. Einstein's a badass. 100%. People are getting Nobel Prizes off of crumbs that fell off his plate. He should have had eight Nobel Prizes. Right. Did he get one? Yeah, he got one. He got one. Okay, okay, good. He got one. But for other stuff, I mean, not for his greatest work. For really important work, but not his greatest work. He demonstrated that atoms actually exist. That's pretty good. I would say. I would say, yeah. And he demonstrated that light comes in discrete packets called photons. Which we just talked about. We just talked about. So that's good. That's pretty good.

20:29That's pretty good. If you do that in a lifetime, you did good. But you did that and then just kept going. Yeah, but at the same time, I was learning magic and you were nearly burning your house down with the biggest wax candle. That's the backstory. and the lead scientist on this was Kip Thorne. Yeah. Kip Thorne. People who read movie credits will recognize Kip Thorne as one of the co-executive producers of the film Interstellar. Nice. That's how you knew if there's going to be any black holes in it, they're going to get it right. Yes. Okay? You don't have to double check that one. He's got it.

21:02Yeah. Yeah. I love that. All right. Give me some more. All right. Well, you were talking about the Fabrega space. So it makes sense to bring this question up because Matt D wrote, Greetings, Dr. Tyson. I'm Matt from Oklahoma and have a question about the fabric of space. In all caps, what is it? You tear it like cloth fiber and sew it back together. Take it easy, Matt. Okay. All right. So he has issues with the word fabric. Maybe. I mean, it sounds like he thinks it is a fabric. Well, it does stretch. Lycra style, right? So the universe stretches, but we don't know how much longer it will continue to stretch.

21:37Oh, it's like my pants eventually? It snaps. Been there, done that. I think we did a whole episode or a whole section of an episode on the future of the universe. One of the possible futures is it will expand so rapidly that the fabric of the universe cannot keep up with it and it will rip. And it's called the big rip. And I'm terrified by this because I finally grew accustomed to the stretching of space and time, whatever even that means, right? Now you're going to tell me it's stretching and it's going to rip? Oh my gosh. Do we know where it's going to rip? Are we near the rip site? Do we need to move a little bit?

22:22Put some pre-stitches in it to keep it going? It would rip at its very core. All places within the fabric would just disassemble. Rip and fabric go together as two words. but before we used the word rip and the fabric, we spoke of space as a rubber sheet that stretches. And maybe it can stretch forever. Like we don't know. We just don't know. So now the specifics of the question was what? It just said, what is it? What is the fabric? All we can say is space behaves as though it is a stretchy substance. pick any words you want to give it right maybe we should have called the lycra of the universe or the neoprene right i don't know call it anything but we try to find an analogy that can make it more understandable to you to anyone to ourselves so fabric of the universe seems to fit the bill very well, right on up to the rip.

23:30Right. So that's why. And that's when everything in the universe disassembles, including us. Oh, you're made of things in the universe. So yeah. I was trying to be optimistic. Yeah. All the electrons, protons, and neutrons, they're not all going to break apart, but you'll be intact. Okay. Exactly. That'll be. Do I feel it? Yeah. I'm terrified by it. if it happens at all it'll happen in 22 billion years oh so we're okay we're okay no I got it on my calendar so fabric is metaphor but it's a very apt metaphor for what the universe is because the universe can curve it can curve back on itself it can stretch if you're not happy with fabric come up with another term but I think we're good I think it's pretty good alright alright this question comes from Geezer Windbag greetings Dr.

24:23Tyson I'm curious why we say the universe exploded in the Big Bang. It seems to me more likely that the singularity expanded and fragmented and the universe we see is still all within the singularity. An observer outside the original singularity would still see a singularity, though from our perspective, the universe is incredibly huge. Thoughts? Okay, so a couple of things. If he doesn't like the word explosion, I'm okay with that because the singularity that birthed the universe was the rapid stretching of space-time. There we go. See what I did there? So the rapid stretching, you can say, was there an explosion?

25:00You know what an explosion is? It is a rapidly moving shockwave within a medium. That's what blows out windows and blows down doors. It's a shockwave moving through the air. Well, the Big Bang is not a thing moving through something else. It is the expansion of space and time. So it's more accurate to say it's the big stretch rather than the Big Bang. The Big Bang was used pejoratively by, now I'm going back 70 years, by an opponent of the Big Bang who couldn't imagine the universe would begin this way. He wanted the universe to be in a steady state at all times. And so he used the term Big Bang as an insult to the ideas that people were having.

25:48He came and he said, you know what? This theory is a big stretch. And they're like, you have no idea how right you are. That's exactly right. This is a stretch. So yeah, it's metaphor, but we're good with it. All right, cool. Well, thank you, geezer windbag. No, no, but he asked something else about it. Well, he said, is it more likely that the singularity expanded and fragmented and the universe we see is still all within the singularity? We are no longer the singularity. So anyone observing us will not say they look like a singularity. the interesting question is if you look at the math of our universe out to the horizon the density of matter within it the size of the horizon if you run the math we have all the same properties of an authentic black hole and black holes have singularities in their center so are we some mondo black hole?

26:38is there a point where the similarities end? we don't know We could all be in a black hole? Yes. Yes. Yes. I have a book on my shelf that describes the new space-time that opens up after you fall into a black hole. Time changes for you. It ticks more slowly relative to everybody outside the black hole. So as you fall in, you will see the entire future history of the universe unfold before your very eyes and a new space-time continuum open up. That sounds awesome. A whole... Minus the being ripped apart. Minus the being ripped apart part. Yeah. So if the black hole's big enough, the tidal forces won't rip you apart.

27:21You can survive the fall. Oh, that's cool. Yeah, yeah, yeah. Yeah, it's good. It kind of feels like a way to go. I totally want to go that way. You know, rather than get hit by a bus or laid up in the hospital, launch me into a black hole. I'll give all my reports until I can't. All right, so we have Eliezer Vega. Hello, Dr. Tyson. This is Elie Iser from Puerto Rico. Puerto Rico. I love that place. Is that your best way you could pronounce it? Puerto Rico. All right. I'll give you a B plus. All right. Puerto Rico. I have a last gap to fill with gravity. If gravity is the effect of the mass bending space, then why when a star goes supernova, space still bent for a black hole to form instead of immediately unbending, it is as matter is blown apart.

28:03Or better said, what makes space remember what was there before? so when it blows and matter is dispersed, space won't recover back but stay bent as a black hole. Did you get all of that? Wow. Stars above a certain mass, when they die, will go a supernova and they'll leave behind a neutron star. Stars of even higher mass, we're not entirely certain of the boundary of this, but stars of a higher mass can go supernova and make a black hole. Stars of even higher mass, the supernova never gets out. Black hole all the way. So only in that last case is all the mass of the entire system part of the black hole.

28:43And the space-time curvature at the end was the same as it was in the beginning. Whereas the one where some gets blown out and others become a black hole, yeah, that black hole does not have the full gravity that the whole system had before because half of it got blown away. It's that simple. So he's right to think about this, but the answer is not that deep. That's pretty good, yeah. Matthew Jury wrote, Hello, everyone. How can a gravitational singularity exist if infinite curvature means infinite time? We do not have a good way to talk about the singularity. Would you say the jury is out? What I would say is, that's why we have string theorists.