Things You Thought You Knew – Faster Than Light

0:00Coming up on StarTalk, we've got another Things You Thought You Knew episode. This time, we talk about dimensions, isotopes, and tachyons. Check it out. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

0:29So Chuck, here's a topic I don't think we talk enough about, dimensions. Dementia, huh? No, no. I can say to you, Chuck, I'll meet you tomorrow at Starbucks. Right. And what's your reply to me? I'll be there all day waiting, man, because I got nothing to do. I got nothing to do. So I'll just be at Starbucks. I'll start off in the morning with some breakfast, maybe a little muffin, and then I'll just stay there until you get there. Okay, sorry. I'll meet you at Starbucks at 12 noon. Okay. Oh, thanks. Thanks. Thanks. Appreciate that. I gave you a location in space, and you had to wait until I gave you a location in time.

1:07Time. And that intersection of space and time is called your world line. Whoa, love it. It's called a world line. World line. So for our world lines to intersect, we have to be at the same place at the same time. See, now, fellas, if you're smart and you're single, you will hold this one in the back, put it away in your back pocket. Okay. Know what you mean? Girl, I just need you as a part of my world line. You know what I'm saying? It's rap lines from relativity. Exactly. Okay. And let's reverse that. I'll say, Chuck, I'll meet you tomorrow at noon. North America, good for you. Thank you, Earth.

1:45Is that all right? Yeah. So we know intuitively you need both the time and the space coordinates conjoined in order to actually meet. Absurd variance in that would be you cross the street and 10 minutes later, a truck barrels through in that same location. Right. So you were in the same location as the truck, but not at the same time. You wouldn't say, oh, man, I almost died today. You wouldn't because your world lines missed each other. Right. And you can do that another way. You exist at the same time as the truck, but you know we're near each other in location. Right. So what made Zoom and other video conferencing so useful during COVID is that you only had to be at the same time.

2:41Right. You didn't have to be at the same place. So you take away one of the components of the world lines, and then many more people can participate. But you are converging at the same place virtually or digitally.

2:59Okay, well, your image is on. I mean, I have my image of you on my computer, but it's not you. So let's keep talking about dimensions. Ready? So we have one dimension, which is just a line. The measure of the line is the length. There's no other measurement you can make of it that has any meaning. Right. It does not have a width. Now you can add another dimension. We call that X. We add a Y. And now you have a surface. A plane. A plane. And then it's two dimensions, X and Y. Okay? So you can make a square out of that, couldn't you? Yeah. Two-dimensional beings who live in that surface to everyone else in that surface, they only have an outer perimeter.

3:47Right. You can't see inside their bodies. They're all inside the flat plane. They're inside the flat plane. That's all they can see. All you see is the edge of them. Right, the edge. So medical surgery in a two-dimensional universe, they'd have to cut you open, part you, and then reach in and do what they need to, come out, and then stitch you up again. Okay? Right. If we live in three dimensions, you get to look down on that flat world and see all the inner guts of every living creature in that universe. Because there is no boundary above and below. It's only within the plane itself. You can see the heart beating.

4:36You can see the spleen, the liver, the pancreas, the lungs. You can see it all. In fact, if you wanted to be a surgeon for that world, you could go in, cut out the appendix if they needed appendectomy, and never have to cut through their outer boundary. You'd be like magically going into their body. Dimensional surgery. Dimensional surgery. They would have no access or even awareness that that was even possible. But you do. Right. And you can go in and rectify that. So now we are in three dimensions. We reveal our skin in all directions to the other people. Right. Our skin is the boundary between our innards and a medical doctor.

5:25If they want to get inside you, they got to cut you open. Right. A four-dimensional creature can just look inside our bodies. Oh, I feel violated. I know. Oh. I hope no one's watching right now. God. Anyone from the fourth spatial dimension has full access to your entire body's innards. Oh. They could pull stuff out, put stuff in, operate, whatever. We are the game operation to anybody in the fourth dimension. what i'm saying is if you had what you beautifully refer to as dimensional surgery you would be able to operate without ever cutting someone open provided you come from a higher dimension inward right and it is completely analogous to be a four-dimensional surgeon operating on us without cutting us open to be we as three-dimensional surgeons operating on two-dimensional creatures because you could just see all their organs just sitting there.

6:27Now, we can move forward and back, left and right, up and down, okay? Those are the three spatial dimensions. But the time dimension, you don't have access to the past or the future. We are prisoners of the present, forever transitioning between our inaccessible past and our unknowable future. But let's think this through. How would you imprison a two-dimensional creature draw a line what kind of line a square a square just draw a square that's its prison cell yeah but we say wait just step up out of it and then you escape good to go i don't know what you're talking about i'm fully locked in fully locked in how do we put us in a cell we have six walls right a ceiling floor four walls around us right we think we are completely contained within it a higher dimensional creatures just step out and then step back in and you're outside the cell we said i don't know what you're talking about right wait a minute i said a four-dimensional creature if if we had access to the fourth dimension which for us is what time time but wait we're prisoners of time so suppose we weren't prisoners of time suppose you could move through time the way we move through space could you then escape the prison yeah just move to a time when i'm not in prison exactly just say let me get out of these six walls here you just go back to a time before you got put into prison or go to the future where you would let go from the prison right each of those counts as escaping the prison without ever breaking down the wall right so time can't serve that same role if you had access to the past and to the future that's pretty cool man of course we go higher this fifth dimension, six dimensions, this sort of thing.

8:20And mathematically, you can calculate what all the properties are. And it's fascinating to watch. Another quick one. You ready? Go ahead. Knots in strings only exist in three dimensions.

8:37Okay. In other words, in a fourth dimension, you hand them a knot in the fourth dimension and say, Wait, wait, just pull the ends. Right. And it unravels itself. That's the same thing as we three-dimensional people looking at two-dimensional people, and they have a string that just has this loop in it. One loop. Right. And they say, how do I untie this? I can't untie. Say, dude, pick up the two ends and stretch. They can't do that. Right. They can't do that. So knots are different things in higher dimensions. The way to do it is you have to make a knot out of a two-dimensional ribbon. And there are ways to do that, I think, rather than just out of a string.

9:19So a lot of interesting things change and are mind-boggling for ascending to a higher dimension. Sweet. One last quick thing. Why does anyone want a flying car? So you can get up and over traffic. So you only really think about flying cars in cities where you're plugged with traffic. And what a flying car gets you is another dimension of travel. True. You know, when I'm talking a one-lane road, because that's bad, all right? But even if you go two dimensions and you have multiple lanes, and now you're in a plane, that can get cloggy too. Right. So get a third dimension is wide open. But wait a minute.

10:02That means we already have flying cars. It's called the subway. Oh. Instead of being in the air, it's underground, bypassing the traffic you're in. It still invoked the third dimension. But also, it means overpasses, where the freeway goes right through and the overpass goes, oh, that's a flying car right there. You invoked another dimension. You have a very low bar for what's called a flying car.

10:45I'm Joel Cherico and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

11:02Chuck. Yeah. Have you ever wanted to travel faster than light? Sure. I mean, who doesn't? I mean, I spent countless hours just sitting around saying to myself, I wish I could go to like Proxima B and just float above it and be there. You may know that Voyager 1 is the fastest thing we've ever sent out of the solar system. Right. If we had aimed that towards Alpha Centauri, the star system that contains Proxima, this very closest star to the sun. Right. You would get there in plus or minus a few months, 70 ,000 years. But even if you went there at the speed of light, we would watch you take four years.

11:47Your time would stop. Right. So you would get there instantly. But you want to cross the galaxy, that's 100 ,000 years. Earth time for you to do that. So we need other ways to travel. Experimentally and theoretically, that you cannot travel faster than light. Right. Through space. Right. However, some decades ago, someone hypothesized, suppose you don't increase your speed to try to get to the speed of light. Suppose you exist on the other side of that boundary. You just start life on the other side of that boundary. What would that be? What does that even mean? Okay? So if you look at the equations of relativity, there are three things that happen as you travel faster.

12:32your time slows down as you near the speed of light right your length shortens okay in the direction of your motion and your your mass increases okay if you try to get to the speed of light as a physical object your length shortens to zero your math mass goes to infinity and time stops. Okay, this is just insane. This is insane. Because the equations blow up there. That's the numbers, right. Okay, the numbers give you. All right. So, it was hypothesized, suppose you come at it from the other side. So you're not working your way towards the speed of light. You just exist with speeds that are already faster than the speed of light.

13:19So you don't have this violation of approaching the speed of light itself. Okay. When you do that, what comes out the other side is that you live backwards in time. Oh, that's a measurement button. Okay. So it's not just that, you know, time slows down. Time now goes backwards. A. B. The slowest you can travel is the speed of light. Right. And in fact, it would take infinite energy to slow you down to that speed. Right. In the same way, it would take infinite energy to speed you on this side of that universe. To speed you up to the speed of light. To speed you up to that speed. Right. So someone said, could anything exist there?

14:03And so we came up with it. We, people, decades ago, came up with the name tachyon. And that's because they dress poorly. Tachyon. They just mix in stripes and polka dots and all kinds of madness. But electrons and protons, they're badass. Electrons and protons, they GQ to the max. tachyons don't invite them to the park plus they'll come late or they'll come early they don't know they don't even know when to show up you know what do you want i'm on tachyon time brother tachyos from the greek is a word for speed okay so tachyons the slowest they can go is the speed of light and the fastest they can go is infinite speed right yeah so in that case you can go any distance you can go any distance in any amount of time right because you at that point you don't need a warp engine you need a tachyon engine you need a tachyon tachyon propulsion a tachyon chariot to carry you look at that well you made it very poetic and it's the vehicle of the greek gods here's an interesting fact uh that the early universe expanded faster than the speed of light right okay now the way that happened was the space itself is expanding right nothing is moving through space.

15:18Nothing's moving through space. Right. Space is no longer a medium. It's the actual vehicle. But medium to which you're moving, it is the thing itself. It's the thing that's moving. There's no violation of the speed of light there. And we learned that from the general theory of relativity, which generalizes all of the parameters for which there were very specific descriptions in the special theory of relativity. Right. In other words, the special theory of relativity involved a constant motion with no acceleration. So it was a simplified case. If we can call relativity simple at all, the simplified case, the general relativity involves accelerations and gravity and curve space time and all the rest of this.

15:58Right. When you learn about space and time as a fabric of the universe, it can stretch at any speed at all. And the early universe stretches faster than light. So that's where that's coming in. Right. In case there was a question about it. Yeah. But now, it turns out you can travel faster than light in a medium where light travels with a lower speed than it would in a vacuum. Okay. So, like, water going, like water? Light going through water, light going through glass, light going through diamond, all travel slower than light going through a vacuum. Gotcha. Those lower speeds, hey, we can go fast.

16:40We know how to send particles faster than those speeds. We do that all the time. When we accelerate electrons and protons in particle accelerator. So in a diamond, light travels 40 % as fast as it does in empty space. Wow. If light were 60 miles an hour, in a diamond, light's going 24 miles an hour. Right. So what happens now if we send a particle faster than light in the medium? We didn't know, and it was tested. And we found out that when that happens, the whole universe explodes. Everything disintegrates like a Thanos snap. So you have water. And so now you take a particle and accelerate it, not only to the speed of light in water, but exceeding it.

17:31And when that happens, there's a flash of light. It's called, in that case, Cherenkov radiation. Cherenkov radiation. The speed of light would be faster in air, but still slower than the vacuum of space. So air is less dense than water, water is less dense than diamond. Okay. So we're getting slow light when it hits our atmosphere and comes down to us. It's already slowed down. It's already slowed down. It's already slowed down. So it bends in the atmosphere and then it bends again going into the water. If you have a diamond ring underwater, it bends going into the diamond ring. So you got to, you know, get a four bend path on that.

18:06So my point is going faster than light triggers this reaction between the charged particle, electron or proton, and the medium and flashes of blue light come out. And it's called Cherenkov radiation. Which is a Cherenkov light, just to be simple. All light is radiation. Exactly. So it scares people. It was radiation. Oh my God. But, um, yeah, you're being bombarded with radiation every single day, all day. Correct. It's just low energy radiation. Your arms don't fall off. Right. Okay. High energy radiation that is ionizing. That's bad for you. Low energy radiation. It makes no difference to your body.

18:45Body doesn't care. Exactly. So this thing about going faster than light and then emitting this energy is kind of like a sonic boom, right? I mean, it's, it's conceptually similar. You go faster than sound in the medium, then there's this shockwave that comes out upon doing so. So think of it as kind of a light shockwave. Oh, that's pretty cool. You know what will just bypass tachyons? What's that? Wormholes. Of course, yes. Yeah, wormholes, you don't need rockets. You don't need transporters like what they have on Star Trek. Right. Just open a portal, step through, you're there. There you go. You don't have to be dematerialized, beamed, and then rematerialized on the other side.

19:27All right. And not only that, that material, I think, only goes at the speed of light. You're still limited by the speed of light, even when they do beam. Right. All right. That's all I got for you. All right. This is the most time we've ever spent about talking about something that we don't know exists. That we don't know exists. That's pretty cool. There it is.

20:07There's a word, a subject, a topic of interest that I think people don't know as much about as they should. Okay. It's all about isotopes. There's a sequence of elements beginning with hydrogen, and they get sort of heavier and heavier and heavier. Right. And they each have a number. So hydrogen is number one. Helium is number two. So we're not just numbering them. That is the count of protons in their nucleus. Who's got 12 protons? Who's got six protons? There is an element, and only one element, that has that many protons in the nucleus. There you go. Some famous ones. Carbon has six protons.

20:48Six protons. Oxygen has eight protons. I left one out. Nitrogen has seven protons. Okay. Uranium has 92 protons. Okay. When the periodic table of elements was being discovered, there were gaps. So you knew exactly what to look for if you were missing an element. Look for the one with 39 protons. Go back to the lab. It's like a chemical Lego set. You just put it in a slot, clicks right in, and you move on. And so we have found 92, quote, natural elements in the universe, one through 92. Hydrogen right on up through uranium. And we have another, how many, up to 118 now going beyond uranium. We made those in the laboratory.

21:44You think you can play God, sir? Is that so? You're just making elements now? The answer is, frankly, yes. There you go. So these are the protons and they're immutable. What I mean is if you take away a proton, it's no longer that element. It's the other element. Right. If you add a proton, it's now a different element. Wait a minute. Protons all have the same charge. They all have positive charge. So what does it mean to cram them into the nucleus of an atom if left to their own devices, they would what? Oh man, they'd be the real housewives of New Jersey. That's what they'd be. Get out of it.

22:31Get out of it. What's your heart of a house? Flip the table. So what holds them together? Well, there's a whole other force of nature called the strong force. Fundamental force of nature? Fundamental force of nature. And it's propagated by a particle called the gluon. Right. Aptly named, I might add. And this happens by the presence of neutrons in the nucleus. Right. So neutrons tamp down the resistive forces, and they act as a sort of a glue for the nucleus. Unless you're Martha Stewart atom, in which case it's a hot glue on. That was terrible. They all can't be winners, like you said. Exactly.

23:15You know, I would say Martha should not have gone to prison for that. I should have. So hydrogen in its native state only has one proton. Right. It doesn't need a neutron. Right. To hold anything together. So native hydrogen is just one proton and then one electron on the outer side. Oh, by the way, in a red-blooded atom, they have as many electrons as protons. So they're electrically neutral. Right. Okay. So uranium would have how many electrons? As many as it has neutrons. No, no. As many as it has protons. I mean, protons. Protons. How many is that? I don't know. You don't remember? I said it.

23:5192. 92. Exactly. So matter is generally neutral for this reason. Okay. Hydrogen is happy. Let's go to helium. Right. Helium has two protons. Right. Its native state has two neutrons. Okay. Suppose I force hydrogen to accept a neutron and I cram it in there. Okay. I can do that. Now I have what's called heavy hydrogen. Heavy hydrogen. It has a whole word that we have for it. It's called deuterium. Oh. You might've heard the word deuterium. Deutel. What does deuterium do? You can make a water molecule out of deuterium. H2O. If one of those hydrogens is a deuterium, then it's DHO. Is that heavy water?

24:40That's heavy water. Heavy water. You might have heard of heavy water. Yeah. You can add two neutrons to it. Okay. We have a word for that. Obese water. It's called tritium. Tritium. Point is, when you do this to an atom, adding neutrons or possibly subtracting neutrons, If it has stuff, it won't miss. You made an isotope. Aha. So deuterium and tritium are isotopes of hydrogen. Of hydrogen. Let's go to carbon. Carbon has six protons in the nucleus. Right. So red-blooded carbon would have how many neutrons? Six. Six. And it'll have six electrons. Carbon. What do you do? Bada-bing. Okay. Oh, wait a minute.

25:28I can add two neutrons to it. Ooh. So now it has six protons and now eight neutrons. Add those two numbers to get. What do you got? 14. 14. Carbon 14. Carbon 14. As in carbon 14 dating. Yes. Yes. You know, someone should make a carbon 14 app, a dating app. That'd be kind of cool. That'd be kind of cool. So that's an isotope of carbon. All right. It turns out carbon 12 is stable. 12 is six protons, six neutrons. It's stable. Right. You add two neutrons, it's not stable. Right. It will decay. In a half-life. In a half-life. And the half-life of carbon-14, if I remember correctly, it's around 5 ,000 years, which means after that amount of time, half of the carbon-14 is no longer there.

26:23Right. It has decayed. And then you wait another 5 ,700 years, half is gone again. Right. You ate another 5 ,700, it's half a half of a half is an eighth. So you keep doing this and you know what it does? It gives you access to dates across all of recent human history. From when we were in caves up through recorded history, right on up back through a thousand years ago, 500 years ago. So it's very useful for dating life on earth. Some carbon that's in your body is carbon-14. So how do we end up with the carbon-14 in our bodies? So carbon in nature, add carbon-13 in there too. So carbon-12, stable.

27:13Carbon-13, stable. There's not much of that. Carbon-14, unstable. Unstable. Okay. So in the environment, carbon-14 would normally just disappear, except there are sources of carbon-14 from cosmic rays from space. Space rays? Space rays. Space rays. Space rays. We got space rays. Okay. You know what else? Boosted carbon 14 levels? What? Nuclear tests that went on in the 1950s and 60s. Ah. So here's what happens. When you are alive, you uptake that native amount of carbon 12, 13, and 14 into your body. Okay. And it stays at that level, okay, until you die because then you stop ingesting more carbon.

27:59There's carbon in all food you eat, basically. Right. All food that has any nutritional value has carbon in it. Okay? The moment you die, you're no longer refreshing the carbon. And the carbon-14 then decays. And then that's when we can figure out the timing. Correct. The nuclear tests have interfered with some of the baseline measurements of what's going on in our environment. So you have to sort of get the nuclear tables together with the tables of nature in order to figure out what the starting levels were for life forms that were exposed to it. We've actually put the finger on the scale. The thumb on the scale.

28:38The thumb on the scale with the nuclear test. Yeah, with the nuclear test. Anyhow, I was just, you know, chewing the fat here with isotopes. I love it. And, you know, they're a fun other part of what's going on on the periodic table of elements. Yes. And one other thing, hydrogen has one proton and helium, remember, has two. And helium in its native state has a total of four nucleons, two protons, two neutrons. Right. And it's stable. Okay. It turns out that's called helium four because it's got four particles in its nucleus, two protons, two neutrons. Helium four. If you take away one of the neutrons, guess what you have?

29:17Helium three? Yes. helium 3 now here's what's cool about helium 3 helium 3 is one of the particles ejected by the sun and it gets embedded into the lunar surface we might have talked about this in another show so helium 3 is yet another isotope but now that's one with one fewer neutrons instead of more neutrons that was another installment of things you thought you knew Neil deGrasse Tyson here as always keep looking up Thank you.