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Have you ever wanted to travel to a distant star or to a planet orbiting another sun.

Have you ever wanted to travel to a distant star or to a planet orbiting another sun.

All the time? However I've heard that it's impossible.

All the time? However I've heard that it's impossible.

Yeah. The problem is that the universe is just so big and it comes with its built in speed limit makes it pretty tough.

Yeah. The problem is that the universe is just so big and it comes with its built in speed limit makes it pretty tough.

So that means that we'll never build a spaceship that will get us to another star within the span of a human lifetime.

So that means that we'll never build a spaceship that will get us to another star within the span of a human lifetime.

That's almost true. It's almost a hard and fast rule. It turns out there's one or two exceptions to that, immortality.

That's almost true. It's almost a hard and fast rule. It turns out there's one or two exceptions to that, immortality.

Being frozen like an ice cube.

Being frozen like an ice cube.

Hello.

Hello.

I'm Jorge and I'm Daniel, and this is our podcast.

I'm Jorge and I'm Daniel, and this is our podcast.

Daniel and Jorgey explain the universe.

Daniel and Jorgey explain the universe.

Where we're going to take the whole universe, break it into little bits that are bite size, and feed them to you one at a time.

Where we're going to take the whole universe, break it into little bits that are bite size, and feed them to you one at a time.

Today on the program, we are going to ask the question, will we ever be able to travel faster than the speed of light?

Today on the program, we are going to ask the question, will we ever be able to travel faster than the speed of light?

Zoom.

Zoom.

That's the sound it would make if we travel faster than the speed of light.

That's the sound it would make if we travel faster than the speed of light.

Right there, we're going full throttle on this episode.

Right there, we're going full throttle on this episode.

Pedal to the metal, that's right, Pedal to the podcast, that's right. And I love this question because not only do people like traveling fast, but it gives us a sense for like, will we ever be able to I feel like the subtext to the question is will we ever travel to other stars and get to other places in the universe? Because the universe is so darn big that it's hard to get places, right. So if we could travel fast than the speed of light, we can actually see some cool.

Pedal to the metal, that's right, Pedal to the podcast, that's right. And I love this question because not only do people like traveling fast, but it gives us a sense for like, will we ever be able to I feel like the subtext to the question is will we ever travel to other stars and get to other places in the universe? Because the universe is so darn big that it's hard to get places, right. So if we could travel fast than the speed of light, we can actually see some cool.

Stuff, Like what's the nearest star to us?

Stuff, Like what's the nearest star to us?

Oh, man, I should ask Siri, but I think it's about four light years away.

Oh, man, I should ask Siri, but I think it's about four light years away.

Okay, so even if we're able to go at the speed of light, you still have to sit in a spaceship for four years to get there.

Okay, so even if we're able to go at the speed of light, you still have to sit in a spaceship for four years to get there.

That's if you could travel at the speed of light. Yeah, but this is also the question of accelerating to the speed of light, Like if you could, if you had a spaceship which could get up to the speed of light, it would take a long time to get going that fast.

That's if you could travel at the speed of light. Yeah, but this is also the question of accelerating to the speed of light, Like if you could, if you had a spaceship which could get up to the speed of light, it would take a long time to get going that fast.

Because oh, just to get to the speed of light, Yeah.

Because oh, just to get to the speed of light, Yeah.

You can't tolerate a huge amount of acceleration, you know, like fighter pilots can take like eight or nine g's. Right, that eight or nine times the acceleration you feel on Earth. But squishy people like me and you get into a jet, we can't tolerate, tolerate more than a couple of g's. You know. It'd be like being on the craziest roller coaster ride for like a year.

You can't tolerate a huge amount of acceleration, you know, like fighter pilots can take like eight or nine g's. Right, that eight or nine times the acceleration you feel on Earth. But squishy people like me and you get into a jet, we can't tolerate, tolerate more than a couple of g's. You know. It'd be like being on the craziest roller coaster ride for like a year.

Year is just to get to the speed of light.

Year is just to get to the speed of light.

Just to get to the speed of light.

Just to get to the speed of light.

Yeah, and if you accelerate faster, you would just get smushed against the sea.

Yeah, and if you accelerate faster, you would just get smushed against the sea.

Yeah, exactly. You'd arrive as a puddler goo. And don't forget, you have to decelerate also because you don't want to arrive someplace going the speed of light.

Yeah, exactly. You'd arrive as a puddler goo. And don't forget, you have to decelerate also because you don't want to arrive someplace going the speed of light.

I see. So you'd be traveling as a puddle of goo and you would arrive as a splatter of goo on the front windshield.

I see. So you'd be traveling as a puddle of goo and you would arrive as a splatter of goo on the front windshield.

That's right. But hey, if your a puddle of goo doesn't really matter when you arrive, does it. You're not feeling or if or if you arrive. Yeah, that's why in a lot of these awesome science fiction books I've been reading, you spend half the trip accelerating, and then you turn the ship turns around and spends the second half the ship decelerating, slowing down because you know, if you arrive at your destination going a gazillion miles an hour, you just blow right through their solar system. You can't even stop or you know, get as smoothie or anything.

That's right. But hey, if your a puddle of goo doesn't really matter when you arrive, does it. You're not feeling or if or if you arrive. Yeah, that's why in a lot of these awesome science fiction books I've been reading, you spend half the trip accelerating, and then you turn the ship turns around and spends the second half the ship decelerating, slowing down because you know, if you arrive at your destination going a gazillion miles an hour, you just blow right through their solar system. You can't even stop or you know, get as smoothie or anything.

Okay, So the question is, is there hope of us ever getting to other stars or planets out there in the universe? Can we ever go faster than the speed of light?

Okay, So the question is, is there hope of us ever getting to other stars or planets out there in the universe? Can we ever go faster than the speed of light?

That's right, So we went around and we asked people on the street. Here's what they had to say. I do believe that one day we'll be able to travel faster than the speed light potentially.

That's right, So we went around and we asked people on the street. Here's what they had to say. I do believe that one day we'll be able to travel faster than the speed light potentially.

Yes, I don't think so, because it's you know, Einstein's theory something based on nothing coin fester speed of lights.

Yes, I don't think so, because it's you know, Einstein's theory something based on nothing coin fester speed of lights.

Someone say no, honestly, with like the way technology is going, I do think eventually we'll reach that point.

Someone say no, honestly, with like the way technology is going, I do think eventually we'll reach that point.

Yeah, optimistic.

Yeah, optimistic.

Okay. So the first thing I find interesting about the responses is that everyone has an opinion, you know, like it's like no evidence, no theoretical background. They're like I think so, or they're like no, I don't think so.

Okay. So the first thing I find interesting about the responses is that everyone has an opinion, you know, like it's like no evidence, no theoretical background. They're like I think so, or they're like no, I don't think so.

That's everybody feels like technological progress is inevitable, Like you can set whatever bar you want and eventually we'll get there. Science will figure it out. I love that optimism and enthusiasm that like, yeah, scientists can do anything.

That's everybody feels like technological progress is inevitable, Like you can set whatever bar you want and eventually we'll get there. Science will figure it out. I love that optimism and enthusiasm that like, yeah, scientists can do anything.

Yeah, well, think about all the crazy things we have been doing, right.

Yeah, well, think about all the crazy things we have been doing, right.

Yeah, absolutely, you know, like downloading pictures of cats from the internet.

Yeah, absolutely, you know, like downloading pictures of cats from the internet.

Yeah, and son, you'll be able to like change your genome using your cell phone or something like that.

Yeah, and son, you'll be able to like change your genome using your cell phone or something like that.

You want to be a ginger, there's an app for that. You want to be taller, dial it on your phone that pretty.

You want to be a ginger, there's an app for that. You want to be taller, dial it on your phone that pretty.

Oh man, swipe right for redhead, Swipe breath to be a taller.

Oh man, swipe right for redhead, Swipe breath to be a taller.

Well, I think we're spinning off ideas for science fiction novels here, But I love that optimism. And you know, frankly, I'm surprised because these days a lot of people aren't really believing in science, and like people aren't accepting global warming, and people aren't accepting this and that and the other. But everybody seems to believe that technological advancements will just be continue to be delivered on pace, right, And you know, people, you want technological deliverance, if you want technological marvels, you gotta fund science. So if you want a fancy new iPhone or to travel fast in the speed of light, you better call your congress person and tell them to fund basic science, all right, and Brandt.

Well, I think we're spinning off ideas for science fiction novels here, But I love that optimism. And you know, frankly, I'm surprised because these days a lot of people aren't really believing in science, and like people aren't accepting global warming, and people aren't accepting this and that and the other. But everybody seems to believe that technological advancements will just be continue to be delivered on pace, right, And you know, people, you want technological deliverance, if you want technological marvels, you gotta fund science. So if you want a fancy new iPhone or to travel fast in the speed of light, you better call your congress person and tell them to fund basic science, all right, and Brandt.

It's so permeated in science fiction and movies and things, right, Like, without faster than light travel, most science fiction stories that involve other planets would be super boring.

It's so permeated in science fiction and movies and things, right, Like, without faster than light travel, most science fiction stories that involve other planets would be super boring.

Right, that's right exactly, because it tells us something about the scale of the universe, right, Like, the universe is really big. Now, the speed of light is super fast. Like, let's remind people, it's three times ten to be eight meters per second or one hundred and eighty six thousand miles per second. It's like blindingly fast, right, It's not like any kind of speed we're used to.

Right, that's right exactly, because it tells us something about the scale of the universe, right, Like, the universe is really big. Now, the speed of light is super fast. Like, let's remind people, it's three times ten to be eight meters per second or one hundred and eighty six thousand miles per second. It's like blindingly fast, right, It's not like any kind of speed we're used to.

It's like, in one second, a ray of light can go around the Earth six times. Is that about it?

It's like, in one second, a ray of light can go around the Earth six times. Is that about it?

Six or seven times? Yeah, in a single second. It's incredible.

Six or seven times? Yeah, in a single second. It's incredible.

Like one that's it. It went around the world six times.

Like one that's it. It went around the world six times.

That's right. It brought us postcards and trinkets, exactly, And so it's incredibly fast. But the amazing thing is that even though the speed of light is so fast, the universe is ridiculously big. So even going at the speed of light, it takes you forever to get anywhere, right, right, thousands of years to get somewhere, even if you're traveling as a light beam.

That's right. It brought us postcards and trinkets, exactly, And so it's incredibly fast. But the amazing thing is that even though the speed of light is so fast, the universe is ridiculously big. So even going at the speed of light, it takes you forever to get anywhere, right, right, thousands of years to get somewhere, even if you're traveling as a light beam.

Well, so let's just ask the question, Daniel, can we go faster than the speed of light?

Well, so let's just ask the question, Daniel, can we go faster than the speed of light?

No? Boom, end of podcast.

No? Boom, end of podcast.

So we're done. That's right, we're done. It's a hard you're saying, it's a hard cannot go faster than the speed of light.

So we're done. That's right, we're done. It's a hard you're saying, it's a hard cannot go faster than the speed of light.

It's a hard note with a couple of asterisks and loopholes, which maybe we'll get to later.

It's a hard note with a couple of asterisks and loopholes, which maybe we'll get to later.

Okay, well, let's talk about first, like what kind of speed limit is it? Right, Like, if you go faster than the speed of light, does the intergalactic police like pull you over and say and give you the intergalactic ticket?

Okay, well, let's talk about first, like what kind of speed limit is it? Right, Like, if you go faster than the speed of light, does the intergalactic police like pull you over and say and give you the intergalactic ticket?

No, it's actually they're snipers, so they don't even bother the ticket to take you out. Right there, you loake you out. They don't mess around. This is the lots of physics we're talking about here, dude.

No, it's actually they're snipers, so they don't even bother the ticket to take you out. Right there, you loake you out. They don't mess around. This is the lots of physics we're talking about here, dude.

Okay, so it's embedded in the laws of physics.

Okay, so it's embedded in the laws of physics.

Yeah, And the right way to say it is that you can't travel through space faster than light can travel through space.

Yeah, And the right way to say it is that you can't travel through space faster than light can travel through space.

Oh, that sounds like a loophole for later.

Oh, that sounds like a loophole for later.

Yeah, there's some lawyerly caveats I'm setting up for later.

Yeah, there's some lawyerly caveats I'm setting up for later.

Some intergalactic law firms salivating, They're like, I found a loophole.

Some intergalactic law firms salivating, They're like, I found a loophole.

That's right. I'm on retainer for some Androman lawyers exactly.

That's right. I'm on retainer for some Androman lawyers exactly.

Well, so what does happen? Like if I'm in spaceship and I let's say I live forever and I have infinite energy, and I just hit the accelerator on my spaceship and I just wait pedal to the metal for as long as it takes. What's going to happen?

Well, so what does happen? Like if I'm in spaceship and I let's say I live forever and I have infinite energy, and I just hit the accelerator on my spaceship and I just wait pedal to the metal for as long as it takes. What's going to happen?

So in this scenario, you're an infinitely rich alien with who lives forever, and this is how you're going to spend your time.

So in this scenario, you're an infinitely rich alien with who lives forever, and this is how you're going to spend your time.

Wow, Well, first of all, you don't know that I'm not an infinitely richy.

Wow, Well, first of all, you don't know that I'm not an infinitely richy.

It's true. Okay, So you're an infinitely rich alien and you're doing a podcast. Me, you know, I think even more perplexing.

It's true. Okay, So you're an infinitely rich alien and you're doing a podcast. Me, you know, I think even more perplexing.

I've lived forever, so you know, I get my kicks this way.

I've lived forever, so you know, I get my kicks this way.

All right, So you're getting down to item number three thousand, four hundred and two on your bucket list and this is it?

All right, So you're getting down to item number three thousand, four hundred and two on your bucket list and this is it?

So what, yeah, like, do you hit us like you hit a wall. Do you know what I mean? Like, at some point I can't go faster that do I crash? Does my engine burn out? At some point? What happens if I try to go faster than this speed of line?

So what, yeah, like, do you hit us like you hit a wall. Do you know what I mean? Like, at some point I can't go faster that do I crash? Does my engine burn out? At some point? What happens if I try to go faster than this speed of line?

Yeah? Well, people have intuition about this kind of stuff because they're used to balls and airplanes and cars and stuff, and they think that if you put in twice as much energy, you should go twice as fast. And that is true if you're on the surface of the Earth or you're going pretty slowly.

Yeah? Well, people have intuition about this kind of stuff because they're used to balls and airplanes and cars and stuff, and they think that if you put in twice as much energy, you should go twice as fast. And that is true if you're on the surface of the Earth or you're going pretty slowly.

Meaning like if you burn a certain amount of fuel you should get you should accelerate a certain amount, you should go faster a little bit, that's right, And if you burn the same amount of fuel again, you should go twice as fast.

Meaning like if you burn a certain amount of fuel you should get you should accelerate a certain amount, you should go faster a little bit, that's right, And if you burn the same amount of fuel again, you should go twice as fast.

Yeah, there's a linear relationship. There, doesn't matter what your speed is. If you add energy, you add speed. That's the people's intuition. But that's not true. That's not the way the universe actually works. So what happens in your scenario is you keep pouring on energy, but your speed, the increase in your speed starts to slow down. So at first you speed up a lot. When you when you're burning rocket fuel, but then you just can't get faster very quickly, and you start to approach the speed of light slower and slower and slower, so that every pile of energy or bottle of fuel you burn gives you a smaller increase in your speed.

Yeah, there's a linear relationship. There, doesn't matter what your speed is. If you add energy, you add speed. That's the people's intuition. But that's not true. That's not the way the universe actually works. So what happens in your scenario is you keep pouring on energy, but your speed, the increase in your speed starts to slow down. So at first you speed up a lot. When you when you're burning rocket fuel, but then you just can't get faster very quickly, and you start to approach the speed of light slower and slower and slower, so that every pile of energy or bottle of fuel you burn gives you a smaller increase in your speed.

So somebody watching you do this, like from the outside of your spaceship, they're going to see you take offerly fast, but at some point they're not going to see you go faster and faster. They're just going to see you peak in velocity.

So somebody watching you do this, like from the outside of your spaceship, they're going to see you take offerly fast, but at some point they're not going to see you go faster and faster. They're just going to see you peak in velocity.

Yeah, your legions of screaming fans are just going to watch. It's going to get kind of boring because you're going to get faster and faster and approach the speed of light, but never actually get there.

Yeah, your legions of screaming fans are just going to watch. It's going to get kind of boring because you're going to get faster and faster and approach the speed of light, but never actually get there.

Right, But what's happening to me inside the spaceship? Do I think I'm going faster than the speed of light or.

Right, But what's happening to me inside the spaceship? Do I think I'm going faster than the speed of light or.

Nope, no, you don't. You are aware of your speed, and you are aware of the fact that you're not going faster than the speed of light, and you're very frustrated, and you're screaming at your agent to get your better ship or whatever whatever infinitely rich alien Jorge does. But you just never get there.

Nope, no, you don't. You are aware of your speed, and you are aware of the fact that you're not going faster than the speed of light, and you're very frustrated, and you're screaming at your agent to get your better ship or whatever whatever infinitely rich alien Jorge does. But you just never get there.

But doesn't times slow down for me too. I've heard the time slows down for me, so that I think I'm going faster, but I'm actually times slowing down for me. This and that how it works, or am I just infinitely wrong here?

But doesn't times slow down for me too. I've heard the time slows down for me, so that I think I'm going faster, but I'm actually times slowing down for me. This and that how it works, or am I just infinitely wrong here?

Well, you on the spaceship, time always moves for you at one second per second, but other people looking at you will think the time is slowing down for you. So people watching you will see if they're like watching a clock that's in your ship, they'll see it slowing down. And that's one of the really bizarre things about relativity is that not only does it tell us that there's a speed limit, which is hard to understand, but it also tells us that the time is not the same for everybody. Time is a local thing. Like how I feel time depends on where I am and how fast I'm going.

Well, you on the spaceship, time always moves for you at one second per second, but other people looking at you will think the time is slowing down for you. So people watching you will see if they're like watching a clock that's in your ship, they'll see it slowing down. And that's one of the really bizarre things about relativity is that not only does it tell us that there's a speed limit, which is hard to understand, but it also tells us that the time is not the same for everybody. Time is a local thing. Like how I feel time depends on where I am and how fast I'm going.

So it's kind of an incremental slowing down of you. Like I was thinking, like it's really cool because we think of the speed limit as like a hard stop, but it really kind of affects us all the way to the speed of light. Right, that's right, Like even now, if I burn hat twice the amount of fuel I'm not gonna go twice as fast with my car. I'm actually gonna go a little bit less than twice as fast.

So it's kind of an incremental slowing down of you. Like I was thinking, like it's really cool because we think of the speed limit as like a hard stop, but it really kind of affects us all the way to the speed of light. Right, that's right, Like even now, if I burn hat twice the amount of fuel I'm not gonna go twice as fast with my car. I'm actually gonna go a little bit less than twice as fast.

Right, Yeah, but it's a really tiny effect until you get anywhere close to the speed of light. You can get up to like half the speed of light without really noticing the limits of relativity. It's not because and then it starts to get very very strong the closer you get to the speed of light. So unless you have a really snippy car, you won't notice.

Right, Yeah, but it's a really tiny effect until you get anywhere close to the speed of light. You can get up to like half the speed of light without really noticing the limits of relativity. It's not because and then it starts to get very very strong the closer you get to the speed of light. So unless you have a really snippy car, you won't notice.

Yeah, but I think people are used to thinking of it as like this thing that happens in spaceships or like physics experiments, but really it's happening all around. It's like if I move my arm back and forth here in my studio, I'm being affected by relativity, like it's slowing me down somehow.

Yeah, but I think people are used to thinking of it as like this thing that happens in spaceships or like physics experiments, but really it's happening all around. It's like if I move my arm back and forth here in my studio, I'm being affected by relativity, like it's slowing me down somehow.

That's right. Yeah. And the fact that you're looking at your arm means you're using light to see it, and so relativity is everywhere. It's deeply woven into the very fabric of our understanding of physics. Now, it's amazing that we went so long without understanding this really basic concept that space and time are different from what we thought they were.

That's right. Yeah. And the fact that you're looking at your arm means you're using light to see it, and so relativity is everywhere. It's deeply woven into the very fabric of our understanding of physics. Now, it's amazing that we went so long without understanding this really basic concept that space and time are different from what we thought they were.

Hm.

Hm.

So I guess the question then, is why should there be a speed limit? Like, why does relativity have this weird limit baked into it?

So I guess the question then, is why should there be a speed limit? Like, why does relativity have this weird limit baked into it?

Yeah, it's a really bizarre feature, and it comes from the observation that light always travels at the speed of light, no matter what you're doing or how fast you're going relative to the thing that's shooting out the light. Light is always traveling at the speed of light.

Yeah, it's a really bizarre feature, and it comes from the observation that light always travels at the speed of light, no matter what you're doing or how fast you're going relative to the thing that's shooting out the light. Light is always traveling at the speed of light.

That's like saying, Jorge is always traveling at the speed of Jorge.

That's like saying, Jorge is always traveling at the speed of Jorge.

That's right, Jorge is always at maximal humor, right, pores always the same funny.

That's right, Jorge is always at maximal humor, right, pores always the same funny.

Well, I mean it's kind of a weird statement. It's like saying I'm always going as fast as I'm going.

Well, I mean it's kind of a weird statement. It's like saying I'm always going as fast as I'm going.

That's right. So think about it like this. You're you know, if you have a ball, you can throw it at ten miles an hour.

That's right. So think about it like this. You're you know, if you have a ball, you can throw it at ten miles an hour.

Cool.

Cool.

Now, what if you're sitting in a car that's moving at ten miles an hour and then you throw the ball. Somebody on the ground is going to see the balls going at twenty miles an hour. Right, that's cool.

Now, what if you're sitting in a car that's moving at ten miles an hour and then you throw the ball. Somebody on the ground is going to see the balls going at twenty miles an hour. Right, that's cool.

Right, It's like the velocities add.

Right, It's like the velocities add.

Yeah, velocities add.

Yeah, velocities add.

They're supposed to add.

They're supposed to add.

You feel like they should add it makes sense. It's an intuitive thing for us, right, right. What if the person in the car, instead of having a ball, has a flashlight. Uh huh, Well, they shine their flashlight. How fast is the light going from their flashlight.

You feel like they should add it makes sense. It's an intuitive thing for us, right, right. What if the person in the car, instead of having a ball, has a flashlight. Uh huh, Well, they shine their flashlight. How fast is the light going from their flashlight.

At the speed of light?

At the speed of light?

Duh? Right, speed of light? Okay, But if they're in the car and they're moving at ten miles an hour and I'm on the ground, how fast do I measure the speed of light? Well, your intuition would say a speed of light plus ten miles an hour, right, because they add right, And that's where it breaks. You measure those photons is leaving your flashlight at the speed of light, and I'm outside the car on the ground, I still measure those photons as moving the same speed.

Duh? Right, speed of light? Okay, But if they're in the car and they're moving at ten miles an hour and I'm on the ground, how fast do I measure the speed of light? Well, your intuition would say a speed of light plus ten miles an hour, right, because they add right, And that's where it breaks. You measure those photons is leaving your flashlight at the speed of light, and I'm outside the car on the ground, I still measure those photons as moving the same speed.

WHOA So like if I put a rocket on a flashlight and the flashlight is going super fast. Let's say the flashlight is going at the speed of light or close to the speed of light, and then it shoots a pope photon or a beam of light. That light coming out of the flashlight is not going to go faster than the speed of light either.

WHOA So like if I put a rocket on a flashlight and the flashlight is going super fast. Let's say the flashlight is going at the speed of light or close to the speed of light, and then it shoots a pope photon or a beam of light. That light coming out of the flashlight is not going to go faster than the speed of light either.

That's right. Two people always measure light traveling at the same speed, no matter how fast they're going relative to each other, which is really weird. That's the core nugget of the counterintuitive bits of relativity, and everything follows from that. Okay, So you can ask why does light always travel at the speed of light? And let's get to that in a minute. But first, that's connected back to what we were saying earlier. So if light always travels at the speed of light, that's the thing that makes it impossible to go faster than light.

That's right. Two people always measure light traveling at the same speed, no matter how fast they're going relative to each other, which is really weird. That's the core nugget of the counterintuitive bits of relativity, and everything follows from that. Okay, So you can ask why does light always travel at the speed of light? And let's get to that in a minute. But first, that's connected back to what we were saying earlier. So if light always travels at the speed of light, that's the thing that makes it impossible to go faster than light.

Okay, because it's this observation that light can go faster than the speed of light or never does that then limits our ability to go faster than the speed of light? Is that what you're saying.

Okay, because it's this observation that light can go faster than the speed of light or never does that then limits our ability to go faster than the speed of light? Is that what you're saying.

Yeah, because velocity and time are connected in relativity. If you're moving really fast past the Earth, you see time on the Earth passing more slowly. If you were moving the speed of light, you would see time and earth as frozen. If you were moving faster than the speed of light, you would see time and earth moving backwards, which is totally impossible and breaks causality. I mean, trains would arrive at the station before they left. It'd be crazy.

Yeah, because velocity and time are connected in relativity. If you're moving really fast past the Earth, you see time on the Earth passing more slowly. If you were moving the speed of light, you would see time and earth as frozen. If you were moving faster than the speed of light, you would see time and earth moving backwards, which is totally impossible and breaks causality. I mean, trains would arrive at the station before they left. It'd be crazy.

I have so many questions for you, But before we dive in, let's take a short break.

I have so many questions for you, But before we dive in, let's take a short break.

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So we can go faster than the speed of light, because light can't go faster than the speed of light. And if we were to go faster than the speed of light, things just like they'll make me east.

So we can go faster than the speed of light, because light can't go faster than the speed of light. And if we were to go faster than the speed of light, things just like they'll make me east.

Yeah, time would be reversed and crazy stuff like that. And to understand that in great detail you have to have a few moving bits and some sort of thought experiments. We actually go into that in some fun detail in our book. We have no idea. There's a whole chapter outlining that and dotting all the logic lines from the statement that light's always traveling at the same speed to nothing can go faster than the speed of light. So that's pretty solid. Yeah, yeah, And so that all comes from this one observation that light travels at the same speed no matter what. And people discover that about one hundred and twenty hundred and thirty years ago, and that blew people's minds. It didn't make any sense at all. I mean, people did this experiment, it's called the Michaelson Morley experiment, and they shot beams of light in two different directions and then measured how fast they went and came back. And the idea is, well, the Earth is moving, and so if the Earth is moving through space, it has some speed, right, and so we should be able to measure that speed by seeing how fast light is moving in one direction versus another direction. But no matter when they did it or how they did it, they always got the answer that light is traveling at the same speed, which shocked everybody. Was like, it's the kind of a result I always fantasize about, you know, the kind of physics experiment where you get the result and people say, no, that doesn't make any sense. You must have done something wrong. But instead it requires unraveling like the whole foundation of physics.

Yeah, time would be reversed and crazy stuff like that. And to understand that in great detail you have to have a few moving bits and some sort of thought experiments. We actually go into that in some fun detail in our book. We have no idea. There's a whole chapter outlining that and dotting all the logic lines from the statement that light's always traveling at the same speed to nothing can go faster than the speed of light. So that's pretty solid. Yeah, yeah, And so that all comes from this one observation that light travels at the same speed no matter what. And people discover that about one hundred and twenty hundred and thirty years ago, and that blew people's minds. It didn't make any sense at all. I mean, people did this experiment, it's called the Michaelson Morley experiment, and they shot beams of light in two different directions and then measured how fast they went and came back. And the idea is, well, the Earth is moving, and so if the Earth is moving through space, it has some speed, right, and so we should be able to measure that speed by seeing how fast light is moving in one direction versus another direction. But no matter when they did it or how they did it, they always got the answer that light is traveling at the same speed, which shocked everybody. Was like, it's the kind of a result I always fantasize about, you know, the kind of physics experiment where you get the result and people say, no, that doesn't make any sense. You must have done something wrong. But instead it requires unraveling like the whole foundation of physics.

Well, I think it's weird. For people, because you can't imagine light going faster than light. You can imagine a little photon, little wave moving faster and fast and faster, Like, why should this little photon be limited in speed? Like why can't it just keep going faster?

Well, I think it's weird. For people, because you can't imagine light going faster than light. You can imagine a little photon, little wave moving faster and fast and faster, Like, why should this little photon be limited in speed? Like why can't it just keep going faster?

Yeah? Why should there be a maximum speed limit at all? Right?

Yeah? Why should there be a maximum speed limit at all? Right?

Yeah, even for light?

Yeah, even for light?

Right? Yeah, it's total.

Right? Yeah, it's total.

But you saying like that's not how like the universe doesn't like things to go faster than that? Like, I know there was an idea of then either at some point in physics history, like maybe we're swimming in some kind of goo that just doesn't let things travel very fast through it.

But you saying like that's not how like the universe doesn't like things to go faster than that? Like, I know there was an idea of then either at some point in physics history, like maybe we're swimming in some kind of goo that just doesn't let things travel very fast through it.

Right, Well, the idea of ether was trying to explain what light is wiggling through, right, I mean, light is a wave, and most waves, like sound waves or pressure waves, are waves through something like sound waves are pressure waves in air. Right, So people were wondering what is light moving through? Because if light's a wave, it has to be the wiggling of something. And that's why they invented the ether. They thought, well, light must be wiggles in this invisible thing we've never seen before called the ether. And it was not a terrible idea it just turned out to be wrong, you know, And so that was the origin of this experiment. People thought, let's measure the velocity of the Earth through the ether, and then we'll be able to tell how fast light is going relative to the ether. M But it turns out it wasn't. Light is not wiggling through ether. Light is an electromagnetic radiation that moves through vacuum on its own. It's a really bizarre thing. It doesn't have to wiggle something.

Right, Well, the idea of ether was trying to explain what light is wiggling through, right, I mean, light is a wave, and most waves, like sound waves or pressure waves, are waves through something like sound waves are pressure waves in air. Right, So people were wondering what is light moving through? Because if light's a wave, it has to be the wiggling of something. And that's why they invented the ether. They thought, well, light must be wiggles in this invisible thing we've never seen before called the ether. And it was not a terrible idea it just turned out to be wrong, you know, And so that was the origin of this experiment. People thought, let's measure the velocity of the Earth through the ether, and then we'll be able to tell how fast light is going relative to the ether. M But it turns out it wasn't. Light is not wiggling through ether. Light is an electromagnetic radiation that moves through vacuum on its own. It's a really bizarre thing. It doesn't have to wiggle something.

Else, right, but it is limited in like speed, Like there's only so fast and this stuff we call space around this there's only there's a kind of a maximum propagation speed.

Else, right, but it is limited in like speed, Like there's only so fast and this stuff we call space around this there's only there's a kind of a maximum propagation speed.

Yeah, so light is this really bizarre thing that can only move at a certain maximum speed and nothing can move faster than that. And no matter how fast you're going, you always measure light moving at the same speed. And that always boggled my mind because it makes me feel like two people can observe the same things and get different answers and both be right. You know, Like if you shoot a flashlight and I'm traveling at half the speed of light to try to catch up with it, it's strange to me that you'll measure those photons that is going at the speed of light, and all also measure those photons that going at the speed of light. It feels like our observations disagree, but we're both correct, you know. We can have different views of the same events and both be right. That's the craziest thing about relativity.

Yeah, so light is this really bizarre thing that can only move at a certain maximum speed and nothing can move faster than that. And no matter how fast you're going, you always measure light moving at the same speed. And that always boggled my mind because it makes me feel like two people can observe the same things and get different answers and both be right. You know, Like if you shoot a flashlight and I'm traveling at half the speed of light to try to catch up with it, it's strange to me that you'll measure those photons that is going at the speed of light, and all also measure those photons that going at the speed of light. It feels like our observations disagree, but we're both correct, you know. We can have different views of the same events and both be right. That's the craziest thing about relativity.

I feel like a really great way to kind of visualize how things break down that you once told me about was this idea that like, if there's a ray of light going through the universe, and like you were able to catch up to it, like you could go as fast as that beam of light and you were standing next to it, going at the speed of light, it wouldn't make any sense for you to see a beam of light just standing there, do you know what I mean? Like, if I'm going down the highway and I catch up to a truck and I match its speed to me, the truck will seem like it's just standing there. But for ray of light like that just doesn't make any sense to see a light ray just standing there. Like that's where things would sort of break down.

I feel like a really great way to kind of visualize how things break down that you once told me about was this idea that like, if there's a ray of light going through the universe, and like you were able to catch up to it, like you could go as fast as that beam of light and you were standing next to it, going at the speed of light, it wouldn't make any sense for you to see a beam of light just standing there, do you know what I mean? Like, if I'm going down the highway and I catch up to a truck and I match its speed to me, the truck will seem like it's just standing there. But for ray of light like that just doesn't make any sense to see a light ray just standing there. Like that's where things would sort of break down.

Right, Yeah, Because not only did I no, No, that's totally right. Not only can you never go the speed of light because you have mass, and things that have mass to the speed of light and never get there. But things that are massless always go the speed of light. So not only photons but also gravitons and other things that have no mass always go the speed of light. And the reason is that exactly what you said, that if they weren't going the speed of light, then you could eventually catch up to them and be next to them. But what is a photon, right, Yeah, if it has no mass, there's no stuff to it. There's nothing there. It's just it's velocity. So if you catch up to it and it's not moving relative to you, then it doesn't really exist. So it actually makes more sense for light to always be zooming along at the speed of light relative to everybody who's measuring.

Right, Yeah, Because not only did I no, No, that's totally right. Not only can you never go the speed of light because you have mass, and things that have mass to the speed of light and never get there. But things that are massless always go the speed of light. So not only photons but also gravitons and other things that have no mass always go the speed of light. And the reason is that exactly what you said, that if they weren't going the speed of light, then you could eventually catch up to them and be next to them. But what is a photon, right, Yeah, if it has no mass, there's no stuff to it. There's nothing there. It's just it's velocity. So if you catch up to it and it's not moving relative to you, then it doesn't really exist. So it actually makes more sense for light to always be zooming along at the speed of light relative to everybody who's measuring.

It at the maximum speed.

It at the maximum speed.

At the maximum speed. Yeah, okay, And I think something you said earlier is really interesting. Why should there be a maximum speed? Right? And I think that's really cool, But it tells you something about our universe, right. We need there to be a maximum speed so that there's causality so the things make sense, so things don't happen out of order, so that cause happens before effect. Right, if you go faster than the speed of light, then cause and effect breaks.

At the maximum speed. Yeah, okay, And I think something you said earlier is really interesting. Why should there be a maximum speed? Right? And I think that's really cool, But it tells you something about our universe, right. We need there to be a maximum speed so that there's causality so the things make sense, so things don't happen out of order, so that cause happens before effect. Right, if you go faster than the speed of light, then cause and effect breaks.

Well, let's break it down, like I think maybe it breaks down to the question what would happen if we had no speed limit in the universe? Like, what if things could go faster than the speed of light? What would happen?

Well, let's break it down, like I think maybe it breaks down to the question what would happen if we had no speed limit in the universe? Like, what if things could go faster than the speed of light? What would happen?

Well, you'd have to have a totally different universe because the way our universe is set up, that's pretty much baked in at the ground level, and so the universe would be totally different if there was no maximum speed. I think one thing that's fun to think about is what if the maximum speed was different? Right, what if it was like twice as much, or ten times as much or a tenth as much. Because one deep question we have is why is the speed of light this speed and not some other speed?

Well, you'd have to have a totally different universe because the way our universe is set up, that's pretty much baked in at the ground level, and so the universe would be totally different if there was no maximum speed. I think one thing that's fun to think about is what if the maximum speed was different? Right, what if it was like twice as much, or ten times as much or a tenth as much. Because one deep question we have is why is the speed of light this speed and not some other speed?

Right, that's an interesting idea, the idea that that's just how our universe is put together, Like that's just baked into the rules. And maybe there's another universe where the speed of light is different or there's no speed of light. Is that kind of what you're saying, Like it's possible maybe to construct the universe without a speed limit.

Right, that's an interesting idea, the idea that that's just how our universe is put together, Like that's just baked into the rules. And maybe there's another universe where the speed of light is different or there's no speed of light. Is that kind of what you're saying, Like it's possible maybe to construct the universe without a speed limit.

I'm not sure if it's possible to construct the universe with no speed limit, but it's definitely possible to construct the universe with a different speed limit, one that's much higher or one that's much lower. I mean, as far as we know. You know, if you're like at the control panel of the universe, this is just a parameter that you can set, and if you change the speed of light to something else, physics still works. So we don't know why the speed limit is what it is. We can't construct the universes that don't have speed limits, where things travel instantaneously across time and space. Those things don't work because they break causality. Things can arrive before they leave and stuff like that. But we can make universes where the speed of light is different, and that's fun to think about because it changes your relationship, like we were talking about earlier, with far away things. You know, the fact that stars are really far away really tells you about how far away they are relative to the speed of light.

I'm not sure if it's possible to construct the universe with no speed limit, but it's definitely possible to construct the universe with a different speed limit, one that's much higher or one that's much lower. I mean, as far as we know. You know, if you're like at the control panel of the universe, this is just a parameter that you can set, and if you change the speed of light to something else, physics still works. So we don't know why the speed limit is what it is. We can't construct the universes that don't have speed limits, where things travel instantaneously across time and space. Those things don't work because they break causality. Things can arrive before they leave and stuff like that. But we can make universes where the speed of light is different, and that's fun to think about because it changes your relationship, like we were talking about earlier, with far away things. You know, the fact that stars are really far away really tells you about how far away they are relative to the speed of light.

Yeah, let's talk about that, but first, let's take a quick break.

Yeah, let's talk about that, but first, let's take a quick break.

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How would break this speed of light break the fundamental like logic of the universe.

How would break this speed of light break the fundamental like logic of the universe.

It would break the universe because it would break causality and by that I mean that things could happen out of order. Relativity tells us that things happen differently depending on your velocity, right, and so, and time works differently depending on your velocity. As you go faster, you can see the order of events the time of events change, and if you go faster than the speed of light, some things flip so that the effect happens before the cause.

It would break the universe because it would break causality and by that I mean that things could happen out of order. Relativity tells us that things happen differently depending on your velocity, right, and so, and time works differently depending on your velocity. As you go faster, you can see the order of events the time of events change, and if you go faster than the speed of light, some things flip so that the effect happens before the cause.

Like the equation is just no longer make any sense.

Like the equation is just no longer make any sense.

It just no longer make sense, like it just breaks. And it comes from this fact that how you see time changes based on how fast you're going, which again is totally connected to the fact that everybody sees the speed of light always moving at the same speed no matter what.

It just no longer make sense, like it just breaks. And it comes from this fact that how you see time changes based on how fast you're going, which again is totally connected to the fact that everybody sees the speed of light always moving at the same speed no matter what.

Wow.

Wow.

But the basic idea is just that it's just baked into the equations that nothing can go faster than the speed of light. That's right, it's just big. If you try to go faster, it will just break the equations by which the universe is put together.

But the basic idea is just that it's just baked into the equations that nothing can go faster than the speed of light. That's right, it's just big. If you try to go faster, it will just break the equations by which the universe is put together.

Yep. And we have tested it a zillion ways from here to Sunday, and relativity is very solid. This part of relativity is called special relativity that describes how light moves and time is affected, is totally well tested, and we really believe it, okay, and it's the underpinnings of everything we've built. So if it's wrong, then we're going to throw everything away. Now I'm not saying that doesn't mean it's wrong, right, It could be wrong, And it could be that we discover that is replaced by a different theory and everything is wrong. That would be frankly kind of awesome. I love these revolutions at physics, but so far it seems to be pretty solid.

Yep. And we have tested it a zillion ways from here to Sunday, and relativity is very solid. This part of relativity is called special relativity that describes how light moves and time is affected, is totally well tested, and we really believe it, okay, and it's the underpinnings of everything we've built. So if it's wrong, then we're going to throw everything away. Now I'm not saying that doesn't mean it's wrong, right, It could be wrong, And it could be that we discover that is replaced by a different theory and everything is wrong. That would be frankly kind of awesome. I love these revolutions at physics, but so far it seems to be pretty solid.

Like maybe like your kids or some kid out there right now, future physicists might figure it out that it's a real special where relativity is wrong.

Like maybe like your kids or some kid out there right now, future physicists might figure it out that it's a real special where relativity is wrong.

Yeah. And in fact, there was a result a few years ago where people thought they had figured that out. There was this result from the Opera experiment it's cerned that sent neutrinos zooming through Italy, and they thought they measured some neutrinos going faster than the speed of light, right, and they put out this big paper and then it turned out to be wrong and.

Yeah. And in fact, there was a result a few years ago where people thought they had figured that out. There was this result from the Opera experiment it's cerned that sent neutrinos zooming through Italy, and they thought they measured some neutrinos going faster than the speed of light, right, and they put out this big paper and then it turned out to be wrong and.

Turned out to be an operatic traveler.

Turned out to be an operatic traveler.

That's right. It was actually quite embarrassing. One of the cables they were using to measure the timing had come loose and there's a little bit of jiggle in it, and that was the source of the whole mistake, and they had to pull it back and the spokespeople resigned and it was embarrassing. So, if you're going to try to disprove all of modern physics, check your cables, make sure they're right.

That's right. It was actually quite embarrassing. One of the cables they were using to measure the timing had come loose and there's a little bit of jiggle in it, and that was the source of the whole mistake, and they had to pull it back and the spokespeople resigned and it was embarrassing. So, if you're going to try to disprove all of modern physics, check your cables, make sure they're right.

That's right. If you're going up against Einstein, double check the boxes.

That's right. If you're going up against Einstein, double check the boxes.

That's right. If you're going to shoot for the king, you better kill him.

That's right. If you're going to shoot for the king, you better kill him.

So I guess the last question is, like, does that mean that we can never reach these like far away planets in a decent amount of time without turning into puddles of ooze? Like does that mean, like, you know, like you and me will never get to step on another solar system and things like that, Or you know, if we can go faster the speed of light, does that mean that interstellar travel is impossible?

So I guess the last question is, like, does that mean that we can never reach these like far away planets in a decent amount of time without turning into puddles of ooze? Like does that mean, like, you know, like you and me will never get to step on another solar system and things like that, Or you know, if we can go faster the speed of light, does that mean that interstellar travel is impossible?

Right? So it's time to return to those caveats we talked about. Yeah, traveling through space faster than the speed of light is impossible, and as far as we can tell, will never be possible. It's not like there's some technological breakthrough we're waiting for. It's like just difficult or expensive or something or complicated. Right, it seems totally impossible to move through space faster than the speed of light. Now, I say through space, because that's the caveat. We've recently learned the last couple of decades that space is not this fixed thing that you move through. It's not like this empty backdrop. It's squishy, it's dynamical. It can do things, and we can squeeze it and expand it and ripple in it. So instead, so the caveat is, instead of trying to move through space faster than the speed of light, let's change the space we're moving through. So you want to go from here to Alpha Centauri, can we squeeze that space to make the distance shorter, right than breaking the rules of physics to go through it.

Right? So it's time to return to those caveats we talked about. Yeah, traveling through space faster than the speed of light is impossible, and as far as we can tell, will never be possible. It's not like there's some technological breakthrough we're waiting for. It's like just difficult or expensive or something or complicated. Right, it seems totally impossible to move through space faster than the speed of light. Now, I say through space, because that's the caveat. We've recently learned the last couple of decades that space is not this fixed thing that you move through. It's not like this empty backdrop. It's squishy, it's dynamical. It can do things, and we can squeeze it and expand it and ripple in it. So instead, so the caveat is, instead of trying to move through space faster than the speed of light, let's change the space we're moving through. So you want to go from here to Alpha Centauri, can we squeeze that space to make the distance shorter, right than breaking the rules of physics to go through it.

So it's kind of like we're we're not. Space is not an empty and emptiness, right, It's like maybe we are in some kind of like a sponge or some kind of liquid as if, you know, just as an analogy, and you can't move through this sponge faster than the speed of light, but you could maybe like bend the sponge or squish the sponge to get from one side of the sponge to the other side. You could do tricks like that.

So it's kind of like we're we're not. Space is not an empty and emptiness, right, It's like maybe we are in some kind of like a sponge or some kind of liquid as if, you know, just as an analogy, and you can't move through this sponge faster than the speed of light, but you could maybe like bend the sponge or squish the sponge to get from one side of the sponge to the other side. You could do tricks like that.

That's exactly what I mean, and that is theoretically totally possible, though experimentally very very difficult. It's not like we've achieved this or we're like on the edge of being able to do this or whatever. But you know, the first step in a project like this is go from impossible to possible, and then the rest is engineering to go from possible to practical. Right, So I leave that for the engineers. The physicist job is to go from impossible to possible.

That's exactly what I mean, and that is theoretically totally possible, though experimentally very very difficult. It's not like we've achieved this or we're like on the edge of being able to do this or whatever. But you know, the first step in a project like this is go from impossible to possible, and then the rest is engineering to go from possible to practical. Right, So I leave that for the engineers. The physicist job is to go from impossible to possible.

Next week it'll be a feature on your Tesla, you.

Next week it'll be a feature on your Tesla, you.

Know, autopilot to Alpha Centauri.

Know, autopilot to Alpha Centauri.

Anyways.

Anyways.

Yeah, so you might be wondering, well, how is it possible? Yeah, well, you know that space can bend, right, I mean with the Earth goes around the Sun because Sun has bent space, so that Earth moves around it, right, because this is bent, right, and gravitational waves show us that, like colliding black holes can make ripples in space. So how did you actually get from here to there? You'd have to squeeze the space, which takes a huge amount of energy.

Yeah, so you might be wondering, well, how is it possible? Yeah, well, you know that space can bend, right, I mean with the Earth goes around the Sun because Sun has bent space, so that Earth moves around it, right, because this is bent, right, and gravitational waves show us that, like colliding black holes can make ripples in space. So how did you actually get from here to there? You'd have to squeeze the space, which takes a huge amount of energy.

So just like a gravitational wave can propagate, you could maybe like create a giant wave that somehow compresses space from here to Offha Centauri so that it's just really close.

So just like a gravitational wave can propagate, you could maybe like create a giant wave that somehow compresses space from here to Offha Centauri so that it's just really close.

Yeah, or some sort of standing wave that is always compressing the space right in front of you so that you can move through it rapidly.

Yeah, or some sort of standing wave that is always compressing the space right in front of you so that you can move through it rapidly.

Oh yeah, like you're surfing a gravitational wave exactly.

Oh yeah, like you're surfing a gravitational wave exactly.

Surfing a gravitational wave exactly. But remember the gravitational wave caused by like colliding black holes squeezes space by like one part in ten to the twenty.

Surfing a gravitational wave exactly. But remember the gravitational wave caused by like colliding black holes squeezes space by like one part in ten to the twenty.

Oh.

Oh.

I see, so you need an even bigger source of gravitational energy than colliding black holes. So that's a tall order.

I see, so you need an even bigger source of gravitational energy than colliding black holes. So that's a tall order.

Well, in the movies like Star Wars and Star Trek, whenever they go into warp speed, you see, kind of they always show it as this kind of like distortion of space, right, like the stars stretch out or like the spaceships stretches out before it disappears. But maybe there's something, I mean, they got something right about that, right, Like maybe that's whether we're thinking that we're thinking like you're actually like stretching space or you're like compressing space. That's how you're moving faster than.