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What Is Time Dilation? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Hey, Daniel, do you somebody's feel when you're bored time
• 0:10
  Speaker 1: slows down? That never happens to me when I'm talking
• 0:13
  Speaker 1: to you, or Hey, every conversation with you is riveting,
• 0:16
  Speaker 1: It goes back super fast. That's right. Time just flies by,
• 0:21
  Speaker 1: you know, and call you up, and then all of
• 0:22
  Speaker 1: a sudden it's hours later. Do you know what I mean? Like,
• 0:24
  Speaker 1: it's the idea that maybe time is relative in our heads. No,
• 0:29
  Speaker 1: I think that's true. When you're waiting for something, time
• 0:31
  Speaker 1: feels like it goes really slow. When you're listening to
• 0:34
  Speaker 1: your favorite podcast hosts, it just whizzes right by. We're
• 0:38
  Speaker 1: pretty bad at measuring time as a species, are we really?
• 0:41
  Speaker 1: Like our brains are not good at estimating time? Oh yeah,
• 0:44
  Speaker 1: they do all these experiments where they ask people to
• 0:46
  Speaker 1: estimate how long something has been, and they always over underestimated.
• 0:50
  Speaker 1: So psychologically time can be relative. That's proven. But what
• 0:54
  Speaker 1: about physics can that actually happen? Yeah? It turns out
• 0:58
  Speaker 1: that physics also doesn't provide a bedrock layer of truth
• 1:02
  Speaker 1: that time can slow down. Huh, So there's no universal clock, like,
• 1:07
  Speaker 1: there's no impartial, godlike measure of time. That's right. So
• 1:12
  Speaker 1: if next time you're late for a meeting, you can
• 1:14
  Speaker 1: just say, hey, I got my own clock and my
• 1:16
  Speaker 1: observer says I was on time. Physics gives you an
• 1:20
  Speaker 1: excuse to be late for your meeting. And I'm Daniel.
• 1:40
  Speaker 1: Welcome to our podcast Daniel and Jorgey explain the universe,
• 1:43
  Speaker 1: in which we take plenty of time to explain to
• 1:45
  Speaker 1: you how time works in the universe. Hey, yeah, we're
• 1:48
  Speaker 1: here to help you. Whatever it is you're doing, communing
• 1:51
  Speaker 1: to work on a subway, going out for a jog.
• 1:54
  Speaker 1: We're here to help the time move a little bit
• 1:56
  Speaker 1: faster for you. That's right. We're here to kill some
• 1:58
  Speaker 1: time for you, and out's time to get on with it.
• 2:01
  Speaker 1: So today's topic is why do clocks run slower when
• 2:11
  Speaker 1: they are moving fast? That's right. This is a really
• 2:14
  Speaker 1: popular thing for people to get confused about in relativity.
• 2:18
  Speaker 1: It's technically called time dilation, the fact that clocks that
• 2:22
  Speaker 1: move fast run slow, and it's a topic that confuses
• 2:26
  Speaker 1: people from here to infinity. Yeah, it's the idea that
• 2:30
  Speaker 1: if you're going really fast, maybe it close up the
• 2:32
  Speaker 1: speed of light, then time slows down for you. That's right.
• 2:36
  Speaker 1: And the thing we want to understand today is not
• 2:38
  Speaker 1: just does it happen, but why does it happen? What
• 2:41
  Speaker 1: is it about the universe that makes that the way
• 2:43
  Speaker 1: it really works? And the thing that I love about
• 2:47
  Speaker 1: this is that it's one of the best examples of
• 2:49
  Speaker 1: how the universe doesn't work the way you think it does,
• 2:52
  Speaker 1: that it doesn't make sense to our sort of intuitive
• 2:56
  Speaker 1: understanding of the way the world should work, right, especially
• 2:59
  Speaker 1: at these extreme conditions. Right, that's right, because we're not
• 3:02
  Speaker 1: used to those extreme conditions. So we've like operated in
• 3:05
  Speaker 1: you know, on the surface of the Earth, which is
• 3:07
  Speaker 1: pretty slow speeds for thousands and thousands of years. We
• 3:10
  Speaker 1: build up these intuitive models for how we think the
• 3:13
  Speaker 1: universe behaves right, what the rules are, And one of
• 3:17
  Speaker 1: those rules is that we think that there is a
• 3:20
  Speaker 1: absolute history, right, We think that there is a reality
• 3:22
  Speaker 1: out there and that something actually happens and in the end,
• 3:26
  Speaker 1: everybody should agree if they're honest observers about what happened.
• 3:29
  Speaker 1: It turns out that's just not true. And hopefully this
• 3:33
  Speaker 1: is kind of a topic that a lot of people
• 3:35
  Speaker 1: have hopefully I think maybe have heard about. It's sort
• 3:37
  Speaker 1: of permeated out into popular culture a little bit, right, like,
• 3:40
  Speaker 1: it's the basis of the movie Interstellar. I knew you
• 3:43
  Speaker 1: were going to talk about Interstellar Interstellar reference, but it's
• 3:48
  Speaker 1: it's a big example of it in pop culture, right,
• 3:51
  Speaker 1: Like I think, really Interstellar was a pretty big movie
• 3:55
  Speaker 1: regardless of what your physicists thinks of it, and my
• 3:58
  Speaker 1: year and my year physicist is that how used to
• 4:00
  Speaker 1: refer to me? No, Interstellar actually did a pretty good
• 4:03
  Speaker 1: job of modeling the relativity portion. My issues with the
• 4:06
  Speaker 1: Interstellar are more about the time travel and going inside
• 4:08
  Speaker 1: a black hole. But from the point of view of relativity,
• 4:11
  Speaker 1: that made a lot of sense. I mean, I thought
• 4:12
  Speaker 1: it was good that they actually built into the plot
• 4:15
  Speaker 1: what would happen to various people's clocks. And that's the
• 4:17
  Speaker 1: key thing, is that relativity is all about comparing clocks.
• 4:21
  Speaker 1: How fast is my clock going to your compared to
• 4:23
  Speaker 1: your clock? So we're going to assume that you have
• 4:26
  Speaker 1: heard of this concept that if you are in a
• 4:28
  Speaker 1: spaceship going really fast and time will slow down for you.
• 4:32
  Speaker 1: But we were wondering how many people out there know why?
• 4:36
  Speaker 1: So as usual, I tortured the undergraduates of you see
• 4:39
  Speaker 1: Irvine by walking around and asking them random questions without
• 4:42
  Speaker 1: any preparation. And remember, for those of you who think
• 4:45
  Speaker 1: that these answers are silly, these are hard questions to
• 4:48
  Speaker 1: answer on the top of your head, so give them
• 4:50
  Speaker 1: some slack. It's tortured. This called the physics boarding, enhanced
• 4:55
  Speaker 1: physics exactly, physics boarding, you know, exactly. I'm gonna cover
• 5:00
  Speaker 1: your face with a towel and poor physics on your face. Um. Eventually,
• 5:05
  Speaker 1: I think the undergrads are gonna recognize me, and they're
• 5:07
  Speaker 1: gonna be like, don't let that guy talk to you.
• 5:09
  Speaker 1: He'll embarrass you. Run away. We're not trying to embarrass
• 5:12
  Speaker 1: these people. No, it's great. I think I would be
• 5:14
  Speaker 1: totally flabbergasted if you asked me these questions out of
• 5:17
  Speaker 1: the street. All right, I'll plan the ambush you one day.
• 5:19
  Speaker 1: So before you listen to these answers, think for yourself.
• 5:22
  Speaker 1: Do you know what time dilation is? Can you explain
• 5:25
  Speaker 1: why moving clocks run more slowly? Here's what people had
• 5:29
  Speaker 1: to say. Have you heard of time dilation? Do you
• 5:33
  Speaker 1: know that clocks that move really fast go slower? This
• 5:37
  Speaker 1: is trying your information to me. Yes, do you know
• 5:40
  Speaker 1: why that is? No? I don't know the real reason.
• 5:44
  Speaker 1: I'm sorry, No, no, there is no time, thanks very much.
• 5:52
  Speaker 1: All right, So maybe I was a little wrong. Not
• 5:53
  Speaker 1: a lot of people have heard about this concept. That's right,
• 5:56
  Speaker 1: and there are even people out there that deny the
• 5:57
  Speaker 1: time exists. Right, there is no time, there is no
• 6:03
  Speaker 1: concept of time, or that there was not enough time
• 6:05
  Speaker 1: to explain it to you. You know, I was so
• 6:07
  Speaker 1: flabbergasted by the response. I couldn't even formulate a follow
• 6:10
  Speaker 1: up question. I was like still processing, like, what does
• 6:13
  Speaker 1: that even mean? Wow? Did he did he just dropped
• 6:16
  Speaker 1: or she dropped the bike? There is no time? Great phase.
• 6:20
  Speaker 1: She said it with a lot of finality. Yeah, So
• 6:23
  Speaker 1: there wasn't a whole lot of opening there for interrogation
• 6:26
  Speaker 1: or follow up questions. It was like, this is a
• 6:28
  Speaker 1: clearly known fact, there is no time. Well, I mean
• 6:31
  Speaker 1: she was just going to rush and she's like, I
• 6:32
  Speaker 1: have no time for this. No. I think it was
• 6:35
  Speaker 1: definitely more of the time and time is an illusion.
• 6:38
  Speaker 1: So an answer, Yeah, I've heard of that time is
• 6:40
  Speaker 1: an illusion. Yeah, Well, I think we have to do
• 6:42
  Speaker 1: a whole other podcast episode about what is time and
• 6:44
  Speaker 1: how does it work? And why does it only go
• 6:46
  Speaker 1: forward and all that kind of stuff. But this is
• 6:48
  Speaker 1: kind of related. This topic is related to that idea
• 6:51
  Speaker 1: that time is not what we think it is. That's right.
• 6:55
  Speaker 1: We've met a lot of progress in the last hundred
• 6:57
  Speaker 1: years in understanding time, and we've connected it to space.
• 7:00
  Speaker 1: You've probably heard the concept of space time, right. We
• 7:02
  Speaker 1: have three dimensions at least of space and one dimension
• 7:06
  Speaker 1: of time, and Einstein's relativity tied them together and showed
• 7:08
  Speaker 1: us how time and space are connected. But that doesn't
• 7:11
  Speaker 1: mean that time can be simply understood as a fourth
• 7:14
  Speaker 1: dimension of space. It's much more complicated. It's different from
• 7:16
  Speaker 1: the other dimensions of space. Yeah, they're all tied together, time, speed, space,
• 7:22
  Speaker 1: It's all one big molasses of a universe. It's all
• 7:26
  Speaker 1: one big tangle. The amazing thing is that it actually
• 7:28
  Speaker 1: all does work. You know. We have this new version
• 7:31
  Speaker 1: of our understanding of the universe, not that new anymore
• 7:33
  Speaker 1: as a hundred years old, but this revised version of
• 7:37
  Speaker 1: our understanding the universe, and it actually hangs together. I mean,
• 7:40
  Speaker 1: the answers that gives you don't make any sense to
• 7:42
  Speaker 1: your intuition, Like they fly in the face of what
• 7:44
  Speaker 1: you think should happen. They require you to like throw
• 7:47
  Speaker 1: out the way you think the universe works, but they
• 7:50
  Speaker 1: actually do hang together mathematically and they are correct. Like
• 7:54
  Speaker 1: every time we make a ridiculous prediction from relativity and
• 7:57
  Speaker 1: God and check it, the universe is like, yep, that
• 8:00
  Speaker 1: ridiculous thing actually happens. Well, let's bring it down for people.
• 8:04
  Speaker 1: So what does it mean for clocks to run slower
• 8:07
  Speaker 1: when they move fast? So that's that's what we're exploring,
• 8:11
  Speaker 1: and that's what we're trying to explain, is why when
• 8:14
  Speaker 1: you're moving really fast, your clock is going to actually
• 8:17
  Speaker 1: slow down. Right, And so let's be very careful and
• 8:20
  Speaker 1: how we say this, because a lot of people get confused.
• 8:22
  Speaker 1: People think that if you are moving fast, that your
• 8:25
  Speaker 1: clock slows down. That like, if you're looking at your
• 8:27
  Speaker 1: watch and running that you can see the seconds tick slower.
• 8:31
  Speaker 1: That's not true. If you're holding a clock and the
• 8:34
  Speaker 1: clock is not moving relative to you, you'll always see
• 8:37
  Speaker 1: it moving at one second per second. Okay, no matter
• 8:39
  Speaker 1: how fast you're going relative to anything else, your clock
• 8:42
  Speaker 1: always runs the same way. It's not like I get
• 8:44
  Speaker 1: on a spaceship hit the warp speed and then that's
• 8:49
  Speaker 1: not what I experienced. That's right. You never notice your
• 8:52
  Speaker 1: own time changing, right, you experienced time at one second
• 8:55
  Speaker 1: per second, no matter what. Okay, the thing that does
• 9:00
  Speaker 1: happen is that clock's moving relative to you. Right. So,
• 9:03
  Speaker 1: if I'm standing still and Horge has a clock and
• 9:06
  Speaker 1: he runs because he's a pretty zippy guy, if he
• 9:08
  Speaker 1: runs a half speed of light because I'm running late,
• 9:11
  Speaker 1: probably if I notice that he's moving really fast, then
• 9:16
  Speaker 1: I will see his clock running more slowly. Right. So,
• 9:19
  Speaker 1: now from his point of view, he will see his
• 9:21
  Speaker 1: clock running normally, but I will see his clock running
• 9:24
  Speaker 1: more slowly. If I'm zooming past you and you just
• 9:26
  Speaker 1: look at my clock as I'm zooing by, it's not
• 9:30
  Speaker 1: going to be running at the same speed as your clock,
• 9:32
  Speaker 1: that's right. If I'm watching you as you go by,
• 9:34
  Speaker 1: and I'm watching your clock's hands tick forward, right, then
• 9:37
  Speaker 1: they don't agree with mine. Yours mark the seconds more
• 9:41
  Speaker 1: slowly than my clock does. And that's the key thing
• 9:44
  Speaker 1: is that the observation of time depends on your relative
• 9:48
  Speaker 1: velocity to the clock. So it's not that it actually
• 9:52
  Speaker 1: slowed down for me at least, it just you saw
• 9:55
  Speaker 1: it run slower. Right. I love how you try to
• 9:58
  Speaker 1: use the word actually right because you're in your imagining,
• 10:01
  Speaker 1: there's some true version of the effect of the effect, right,
• 10:04
  Speaker 1: I'm just this is an illusion or it looks this way,
• 10:07
  Speaker 1: but it's not actually happening. The problem is there is
• 10:10
  Speaker 1: no what actually happened. Okay, I observe one thing, you
• 10:14
  Speaker 1: observe something else. We can both be right even if
• 10:18
  Speaker 1: those accounts disagree. WHOA Okay, So then I'm running past
• 10:22
  Speaker 1: you really fast with a clock and you see it
• 10:25
  Speaker 1: run slower than I do, or it's running slower than
• 10:28
  Speaker 1: your clock. Then what happens if I stopped, like if
• 10:30
  Speaker 1: I stopped a few paces after you, Does that mean
• 10:33
  Speaker 1: our clocks are going to be out of sync? Yes,
• 10:35
  Speaker 1: our clocks will definitely be out of sync, exactly, And
• 10:38
  Speaker 1: there's a lot of interesting effects there. Right. So I'm
• 10:41
  Speaker 1: a I'm standing still from my point of view, right,
• 10:43
  Speaker 1: and you're running past me. I see your clock moving
• 10:45
  Speaker 1: more slowly. I see my clock running normally. Right, what
• 10:49
  Speaker 1: do you see? Well, you see your clock running normally, right,
• 10:52
  Speaker 1: because everybody sees their own clock running normally. But you
• 10:55
  Speaker 1: also see my clock running slowly because even though you're
• 10:59
  Speaker 1: doing doing the running, I'm moving relative to you and
• 11:03
  Speaker 1: your clock. So then what happens if I stopped, Because
• 11:05
  Speaker 1: I'm gonna think time moved normally, But when when I
• 11:08
  Speaker 1: compare my clock to your clock, your clock will have
• 11:10
  Speaker 1: skipped ahead because right or no, we'll have skip back.
• 11:15
  Speaker 1: This is really tricky, okay, and we should probably avoid
• 11:19
  Speaker 1: this topic. Well maybe we won't. Let's dig into it.
• 11:26
  Speaker 1: This is called the twin paradox, right, This is people say, well,
• 11:30
  Speaker 1: how do you reconcile this? Right? So the classic framing
• 11:33
  Speaker 1: of this is, say we're twins, right, and I stay
• 11:36
  Speaker 1: on We draw straws for Hugas to go to Alpha Centauri,
• 11:39
  Speaker 1: and you lose. So you have to go to Alpha
• 11:41
  Speaker 1: Centauri or you win. You have to go to Alpha Centauri.
• 11:44
  Speaker 1: I stand on Earth and you take a rocket shipped
• 11:46
  Speaker 1: Alpha Centauri, and I see your clock running more slowly. Okay,
• 11:48
  Speaker 1: well we sink First of all, we sink clocks like
• 11:51
  Speaker 1: before I take off. Yes, we're just going to sink clocks.
• 11:53
  Speaker 1: Time zero start go now, that's right, and I see
• 11:57
  Speaker 1: your clock running more slowly. Meanwhile, you have telescope. You're
• 12:00
  Speaker 1: looking at my clock. You see mine running more slowly. Right,
• 12:03
  Speaker 1: so we both see the other person as aging more slowly. Right.
• 12:07
  Speaker 1: So now after a hundred years, you see me as
• 12:10
  Speaker 1: only being ten years older, and I see you as
• 12:12
  Speaker 1: only being ten years older, right, right, So then I
• 12:14
  Speaker 1: come back and then what happened? Who's older? All right,
• 12:18
  Speaker 1: let's break this down really carefully because it is tricky.
• 12:21
  Speaker 1: So when the Earth twin is watching the ship twins clock,
• 12:25
  Speaker 1: he of course sees time moving more slowly on the ship, right,
• 12:28
  Speaker 1: that's relativity. The same way when the ship twin watches
• 12:31
  Speaker 1: the Earth twins clock, he also sees time moving more
• 12:34
  Speaker 1: slowly on Earth. So far everything is symmetric, right, and
• 12:37
  Speaker 1: that's why we like it. Because you could be in ship,
• 12:40
  Speaker 1: you could be in the Earth. That shouldn't really matter,
• 12:42
  Speaker 1: right now. If they just kept going this way, nothing
• 12:44
  Speaker 1: would change. Of course, they would have conflicting views of
• 12:48
  Speaker 1: whose clock is moving slower, right, But that's okay. In relativity,
• 12:51
  Speaker 1: you can have two people with conflicting but both correct
• 12:54
  Speaker 1: views of the same situation, right, Because there is no
• 12:57
  Speaker 1: ultimate truth, right, your answer is depend on your speed
• 13:00
  Speaker 1: and your location. So what happens to break the symmetry?
• 13:04
  Speaker 1: The symmetry is broken when the space twin turns around.
• 13:07
  Speaker 1: That's an acceleration, right, That changes everything. Well, only the
• 13:11
  Speaker 1: space twin does any acceleration, so that makes his case different, right,
• 13:15
  Speaker 1: And during that acceleration, the time on Earth seems to
• 13:19
  Speaker 1: zoom forward really fast from the point of view of
• 13:21
  Speaker 1: the space twin. So on the way back, yeah, he
• 13:24
  Speaker 1: sees Earth moving fast and Earth clock going slowly. But
• 13:27
  Speaker 1: during that acceleration Earth time has leapt forward really far,
• 13:32
  Speaker 1: so that when the space twin gets back to Earth,
• 13:34
  Speaker 1: he's younger than his twin on Earth. Right, And the
• 13:37
  Speaker 1: reason they're no longer symmetric is that only the space
• 13:40
  Speaker 1: twin has done any acceleration, so you shouldn't expect them
• 13:43
  Speaker 1: to be the same from each point of view. It's
• 13:46
  Speaker 1: the coming back that then lets me stay younger. Yeah, exactly. Okay,
• 13:51
  Speaker 1: let's let's dig into it even more. But let's take
• 13:55
  Speaker 1: a quick break, all right. So this idea that time
• 14:10
  Speaker 1: moves slower when you're going fast, it's what's cool is
• 14:13
  Speaker 1: that it's always happening, right. It doesn't just happen when
• 14:16
  Speaker 1: you're going at the speed of light or close to
• 14:18
  Speaker 1: the speed of light. It's it happens like on your
• 14:21
  Speaker 1: on a daily basis, That's right. It applies all the time.
• 14:24
  Speaker 1: It always applies to things that have velocity relative to you.
• 14:28
  Speaker 1: But it's a really tiny effect if you're not going
• 14:31
  Speaker 1: really really fast. So when you're driving sixty in the freeway, yeah,
• 14:35
  Speaker 1: your clock is running a little bit slower, but you'll
• 14:38
  Speaker 1: never notice it. Wow, but it's there. Like if we're
• 14:41
  Speaker 1: all feeling relativity and time dilation all the time everywhere,
• 14:45
  Speaker 1: there's no way to escape relativity. It is everywhere. It's
• 14:49
  Speaker 1: relatively everywhere. It's absolutely every Absolutely thing about relativity is
• 14:54
  Speaker 1: that it's everywhere. Okay, so it only happens when you
• 14:58
  Speaker 1: get it's only noticeable. You're saying, when you're going to
• 15:01
  Speaker 1: close the speed up. But I heard it happens to
• 15:04
  Speaker 1: astronauts here on Earth, like the Space Shuttle. The clocks
• 15:08
  Speaker 1: get out of sync with the clocks on Earth. That's right,
• 15:10
  Speaker 1: though it takes a lot of precision to measure it.
• 15:12
  Speaker 1: It's something like every six months or so they lose
• 15:15
  Speaker 1: like less than a hundredth of a second. So it's
• 15:18
  Speaker 1: something we can measure, and they have really precise clocks
• 15:20
  Speaker 1: precisely to measure this to verify these predictions, but it's
• 15:24
  Speaker 1: not something that people have really like qualitatively experienced. We
• 15:28
  Speaker 1: haven't had an astronaut come back, you know, deep into
• 15:30
  Speaker 1: the future and still feel young. And it goes really nonlinear, right,
• 15:34
  Speaker 1: as you get faster and faster, the effect gets stronger
• 15:36
  Speaker 1: and stronger. But they did do the twin experiment with astronauts, right, Like,
• 15:40
  Speaker 1: they sent to one twin into space for a whole year,
• 15:43
  Speaker 1: and then he came back and technically he was point
• 15:46
  Speaker 1: oh one seconds younger. That's right. I wonder if he
• 15:49
  Speaker 1: was the one who was originally born first or the
• 15:51
  Speaker 1: one who's ovisually born second, because it be interesting and
• 15:53
  Speaker 1: be like, well you used to be the older twin,
• 15:55
  Speaker 1: but now I'm the older twin. A should have stayed
• 15:58
  Speaker 1: up there for ten more years. Do you think growing
• 16:02
  Speaker 1: up twins still argue by that kind of stuff. Well,
• 16:04
  Speaker 1: I'm the older brother, so you have to listen to me.
• 16:06
  Speaker 1: What do you think they're both austers. They're probably trying
• 16:09
  Speaker 1: to one up each other. Well, yeah, I'm an engineer.
• 16:12
  Speaker 1: Oh yeah, I'm a pilot. Oh yeah, I'm a I'm
• 16:14
  Speaker 1: an auster. Not me too, yeah, probably it never ends, right,
• 16:19
  Speaker 1: but technically that's true. He went out into space, went
• 16:22
  Speaker 1: around the Earth for a whole year. When he came back. Technically,
• 16:25
  Speaker 1: time for him moved one hundred of a second slower. Yeah,
• 16:29
  Speaker 1: I wonder what he's gonna do with all that extra time,
• 16:31
  Speaker 1: you know, scratches nose or something. Right, it's gone, he
• 16:35
  Speaker 1: lost it. He used it up. Yeah, But as you
• 16:37
  Speaker 1: go faster and faster, the effect gets stronger and stronger,
• 16:40
  Speaker 1: and as you approached the speed of light, time gets
• 16:43
  Speaker 1: so slow that we can say that if you go
• 16:46
  Speaker 1: the speed of light, time would actually stop. So if
• 16:50
  Speaker 1: I'm zooming running past you at the speed of light,
• 16:53
  Speaker 1: you would see my clock totally frozen, exactly. Now, caveats
• 16:57
  Speaker 1: are important here. Nothing that has mass actually go the
• 17:00
  Speaker 1: speed of light, right, and only massless things can go
• 17:03
  Speaker 1: the speed of light, So you can never go the
• 17:05
  Speaker 1: speed of lights. Are saying I have much mass, Daniel.
• 17:09
  Speaker 1: You're pretty massive, dude, Yeah, by which I mean you're funny,
• 17:12
  Speaker 1: and you're massively awesome thanking, and you have a massively
• 17:17
  Speaker 1: excellent podcast, and you are brilliant. But you're not entirely
• 17:20
  Speaker 1: made of light. But that all right, Yeah, I was
• 17:23
  Speaker 1: just fishing for relative compliments. You're absolutely wonderful. So if
• 17:28
  Speaker 1: you have somebody in a spaceship and they're going super
• 17:30
  Speaker 1: duper fast and they're approaching the speed of light, and
• 17:33
  Speaker 1: time slows down further and further, to the point where
• 17:35
  Speaker 1: it almost stops. But remember, for them, time doesn't slow down.
• 17:39
  Speaker 1: It's not like they're living in molasses. It's just our
• 17:41
  Speaker 1: observation of their time. So if somehow a photon had
• 17:45
  Speaker 1: a clock, yeah, our view of the photons clock would
• 17:48
  Speaker 1: be that it was frozen. Right for us, Photons don't
• 17:51
  Speaker 1: move forward in time. They are frozen in time. But
• 17:53
  Speaker 1: if you were a photon, what would your experience be. Well,
• 17:57
  Speaker 1: it's hard to answer that because you're not a photon,
• 17:59
  Speaker 1: and you have to have that concept of like ascension photon,
• 18:01
  Speaker 1: which seems impossible, but it's always basically an impossible question
• 18:06
  Speaker 1: to answer. But they remember, your time always moves forward
• 18:10
  Speaker 1: um at one second per second. Okay, so that's the
• 18:16
  Speaker 1: effect of time dilation. Time moves seems to move slower
• 18:20
  Speaker 1: when you're going faster. So let's get into why it happens.
• 18:24
  Speaker 1: Do we know why this happens. We do know why,
• 18:28
  Speaker 1: and it's a consequence of another really strange, counterintuitive thing
• 18:32
  Speaker 1: that we've observed about the universe that makes very little sense.
• 18:36
  Speaker 1: So it's a conundrum built on a conundrum. It's a bizarre,
• 18:41
  Speaker 1: counterintuitive consequence of something really weird about the universe and
• 18:45
  Speaker 1: really weird about light. Actually, it's the fact that everybody
• 18:49
  Speaker 1: always observes light going at the same speed, no matter
• 18:53
  Speaker 1: how fast they're going relative to the source of the light. Okay,
• 18:57
  Speaker 1: let's break it down what that means. So light travels
• 19:00
  Speaker 1: through space, but nobody can see it move faster than
• 19:04
  Speaker 1: that speed that light losing. That's right. There's a certain
• 19:07
  Speaker 1: speed of light that goes through space three times ten
• 19:09
  Speaker 1: to the eights per second. And we'll call it the
• 19:11
  Speaker 1: speed of light. Of course. And if I'm standing on
• 19:14
  Speaker 1: a planet and I turn on a flashlight, then the
• 19:17
  Speaker 1: light leaves me and travels at three times tended them
• 19:21
  Speaker 1: per second away from me. Right, And if I'm and
• 19:25
  Speaker 1: if you're shooting it at me, then I see moving
• 19:27
  Speaker 1: towards me at three times ten to the eight meters
• 19:29
  Speaker 1: per second. Okay, that's right, even if you're even if
• 19:32
  Speaker 1: you're on a rocket ship and you're moving towards me, right,
• 19:34
  Speaker 1: say you're moving towards me at half the speed of light.
• 19:37
  Speaker 1: I shoot my laser beam at you're my flashlight at you,
• 19:40
  Speaker 1: you still see that flashlight, the light from it coming
• 19:42
  Speaker 1: at you at the speed of light, right, And that's
• 19:44
  Speaker 1: different from you know, sound waves or rocks or something,
• 19:48
  Speaker 1: or a baseball. Like that's weird. Right, Like, if you
• 19:51
  Speaker 1: throw a baseball at me and I'm running full speed
• 19:54
  Speaker 1: towards you, that baseball is going to be it's gonna
• 19:57
  Speaker 1: look like it's moving really fast towards me. That's right.
• 19:59
  Speaker 1: If I threw a baseball at you at a hundred
• 20:01
  Speaker 1: miles an hour, which I promise I can totally do,
• 20:03
  Speaker 1: this is very realistic, and you're running towards me at
• 20:06
  Speaker 1: fifty miles an hour, which I'm sure you're totally capable of. Um,
• 20:10
  Speaker 1: then obviously I see the baseball is moving away from
• 20:13
  Speaker 1: me at a hundred miles per hour, but you see
• 20:15
  Speaker 1: the baseball is coming towards you at a hundred fifty
• 20:17
  Speaker 1: miles per hour. Right. That's the way it works for
• 20:20
  Speaker 1: normal things. But you're saying that if that baseball instead
• 20:22
  Speaker 1: of a baseball, it was a beam of light, that
• 20:24
  Speaker 1: wouldn't happen. That's right. Light doesn't follow those rules. Everybody
• 20:28
  Speaker 1: who measures it measures it as traveling at that fixed
• 20:31
  Speaker 1: speed of light. No matter what. I mean, there are
• 20:33
  Speaker 1: caveats here, like it slows down and it travels through
• 20:36
  Speaker 1: air or water, whatever, But let's just talk about it
• 20:38
  Speaker 1: in a vacuum. The crazy thing is that doesn't matter
• 20:41
  Speaker 1: how fast you're going, everybody sees light is traveling at
• 20:43
  Speaker 1: this maximum speed of the universe, no matter what. And
• 20:47
  Speaker 1: that's crazy, right and right there is where your concept
• 20:51
  Speaker 1: that everybody sees the same thing the same way, or
• 20:54
  Speaker 1: that there is one absolute truth that we're all observing
• 20:57
  Speaker 1: in different ways breaks down because your description of events
• 21:00
  Speaker 1: and my description events are going to be very different.
• 21:02
  Speaker 1: If we see light moving at different speeds. It's the
• 21:05
  Speaker 1: weird It's like a weird rule of the universe. Not
• 21:08
  Speaker 1: that light something can't travel at this faster than the
• 21:11
  Speaker 1: speed of light. It's a weird rule that says nothing
• 21:13
  Speaker 1: can be seen to travel faster than the speed of light,
• 21:16
  Speaker 1: not even light. That's right. Light always travels at the
• 21:19
  Speaker 1: speed of light, and nothing can travel faster than the
• 21:21
  Speaker 1: speed of light. And these two things are connected, right,
• 21:23
  Speaker 1: because if light operated the same way as baseballs, then
• 21:27
  Speaker 1: you could see light moving as faster than the speed
• 21:29
  Speaker 1: of light just by moving towards me. When I'm shooting
• 21:31
  Speaker 1: a laser at you, right then that light would be
• 21:33
  Speaker 1: moving relative to you. It's faster than the speed of light.
• 21:36
  Speaker 1: But it doesn't right, you move towards me, and you
• 21:38
  Speaker 1: still measure light as moving at the same speed. It
• 21:41
  Speaker 1: doesn't matter if you're running away from me or towards me. Okay,
• 21:44
  Speaker 1: So if you shoot a light beam at me and
• 21:46
  Speaker 1: I'm running towards you really really, really fast, You're going
• 21:49
  Speaker 1: to measure the light moving at the speed of light.
• 21:51
  Speaker 1: And I should measure the light moving faster towards me.
• 21:54
  Speaker 1: But I'm also going to measure it moving at the
• 21:57
  Speaker 1: speed of light, even if I'm moving towards you or
• 22:00
  Speaker 1: away from you or to the side of you exactly,
• 22:02
  Speaker 1: no matter how fast and moving, I'm always going to
• 22:05
  Speaker 1: measure it and moving at the speed of light exactly.
• 22:07
  Speaker 1: And that's crazy, right, It's bonkers, doesn't make any sense.
• 22:11
  Speaker 1: And it's a famous experiment, Michael said. Morally, the experiment
• 22:13
  Speaker 1: that that did this, they shot beams of light in
• 22:15
  Speaker 1: two directions, and because the earth is moving, they figured, well,
• 22:19
  Speaker 1: one of them is going to go slower than the
• 22:20
  Speaker 1: other one because the earth is moving, right, So they
• 22:22
  Speaker 1: did the experiment different times of year, and the light
• 22:25
  Speaker 1: came back took the same amount of time to go
• 22:28
  Speaker 1: in these two perpendicular directions every single time. And that
• 22:31
  Speaker 1: told them that that the speed at which light travels
• 22:35
  Speaker 1: is not dependent on how fast you are moving the
• 22:38
  Speaker 1: observer is moving. It's always the same speed. It's crazy.
• 22:42
  Speaker 1: Is it like some kind of um just like fundamental
• 22:45
  Speaker 1: limit in this stuff of the universe itself? You know,
• 22:49
  Speaker 1: like nothing can propagate through this thing we call space
• 22:53
  Speaker 1: faster than the speed of light. Is that kind of
• 22:55
  Speaker 1: what it's related to. Yeah, definitely, But it's it's a
• 22:57
  Speaker 1: deep question and we don't have a solid answer to too.
• 23:00
  Speaker 1: Why does light always travel at this speed regardless of
• 23:03
  Speaker 1: the speed of the observer. We don't know the answer
• 23:05
  Speaker 1: to that. That's just like Einstein postulated that. He said, Okay,
• 23:09
  Speaker 1: let's start from this crazy assumption and build the math
• 23:12
  Speaker 1: up from there, and if everything then works, and we'll say, well,
• 23:15
  Speaker 1: that assumption must be true. And if you start from
• 23:17
  Speaker 1: that assumption, you get all sorts of crazy predictions which
• 23:20
  Speaker 1: all turn out to be true. Right, So that is
• 23:24
  Speaker 1: a deep truth of the universe. But the answer is,
• 23:26
  Speaker 1: we don't know why. We don't know why light always
• 23:28
  Speaker 1: travels at the same speed, or a light is always
• 23:31
  Speaker 1: observed at the same speed, no matter who is doing
• 23:33
  Speaker 1: the measuring and how fast they're going. It's a weird
• 23:37
  Speaker 1: rule about the universe. It's a weird, weird rule. And
• 23:39
  Speaker 1: when I meet the people who wrote the simulation, I'm
• 23:41
  Speaker 1: gonna ask them, why did you do that, man that
• 23:43
  Speaker 1: made everything so complicated about the universe? One star on
• 23:50
  Speaker 1: Yelp for that for that bit of load. No, I
• 23:53
  Speaker 1: think it's it's there's a fascinating angle there, you know,
• 23:56
  Speaker 1: because we grew up sort of as a species in
• 23:58
  Speaker 1: an environment where nothing was near the speed of light,
• 24:01
  Speaker 1: and so we never noticed this, and so we assume
• 24:04
  Speaker 1: things like everybody's clock runs at the same time because
• 24:07
  Speaker 1: we've always thought it did. And so they're not allowed
• 24:10
  Speaker 1: us to assume things like there must be some sort
• 24:12
  Speaker 1: of absolute sense of time and absolute history and there's
• 24:15
  Speaker 1: a really universe out there, and this is I mean,
• 24:18
  Speaker 1: this shakes the very foundations of how we even think
• 24:21
  Speaker 1: about the universe that's out there and whether it makes
• 24:23
  Speaker 1: sense at all. So it's it's pretty crazy stuff. I
• 24:26
  Speaker 1: feel like we're kepped with weirdness at both ends of
• 24:29
  Speaker 1: the specter. What I mean is like, if you move
• 24:33
  Speaker 1: it close to the speed of light, things get weird.
• 24:35
  Speaker 1: But also if you don't move at all, things good weird.
• 24:37
  Speaker 1: Right because of quantum physics and the uncertainty principle. Right,
• 24:41
  Speaker 1: Like if you try to discertain things that zero velocity,
• 24:44
  Speaker 1: things get weird too. Things always get weird. I think
• 24:46
  Speaker 1: that's the takeaway, right. The universe is weird, like I
• 24:49
  Speaker 1: think I said last week, is weirder and stranger and
• 24:52
  Speaker 1: hotter and nastier and wetter than you could ever even imagine.
• 24:55
  Speaker 1: And the I think the craziest surprises about the way
• 24:57
  Speaker 1: the universe work are still yet to come. You know,
• 25:00
  Speaker 1: we've made these discoveries that showed us to the universe
• 25:02
  Speaker 1: is so different from the way our ancestors have imagined.
• 25:06
  Speaker 1: There must be more of those discoveries coming. It's certainly
• 25:08
  Speaker 1: not the case that we figured them all out. There
• 25:10
  Speaker 1: are crazy revelations in our future. Well, that's good for
• 25:13
  Speaker 1: our podcast topics, that's right. Okay, let's so let's get
• 25:19
  Speaker 1: into how this affects time. But first let's take a
• 25:22
  Speaker 1: quick break. So we know that the speed of light,
• 25:37
  Speaker 1: you can observe going anything faster than the speed of light.
• 25:40
  Speaker 1: So how does this affect how we view time or
• 25:42
  Speaker 1: how we experience time? Right, So it comes directly the
• 25:46
  Speaker 1: fact that light can't travel at any other speed is
• 25:49
  Speaker 1: what directly affects how time passes and how we measure time.
• 25:53
  Speaker 1: And it can be a complicated topic, but I think
• 25:55
  Speaker 1: the best way to do is to think about maybe
• 25:57
  Speaker 1: how a simple clock operates. So let's build a simple
• 26:00
  Speaker 1: clock that uses light. You mean like an Apple watch? Er, No,
• 26:04
  Speaker 1: I mean let's imagine that you're you have to build
• 26:06
  Speaker 1: a clock, and all you have as a laser, right,
• 26:08
  Speaker 1: And so you know, for example, that light takes about
• 26:13
  Speaker 1: ten nanoseconds to go ten feet right, it goes about
• 26:17
  Speaker 1: one ft every nanosecond. So what you do is you
• 26:20
  Speaker 1: measure very precisely, you know, ten ft. You put a
• 26:24
  Speaker 1: mirror at the end, and then you shoot your laser.
• 26:26
  Speaker 1: You shoot a laser pulse, and you say, however long
• 26:29
  Speaker 1: it takes to go um there and back. That's two seconds, right,
• 26:34
  Speaker 1: ten feet there and ten feetback. And you set up
• 26:36
  Speaker 1: the mirrors in the floor and in the ceiling, right,
• 26:38
  Speaker 1: so that being is bouncing up and down right right,
• 26:42
  Speaker 1: So you you shoot the laser up towards the ceiling
• 26:45
  Speaker 1: and back, and you know how far it is to
• 26:48
  Speaker 1: your ceiling and how far it is back to your floor,
• 26:50
  Speaker 1: and so you say that's twenty ft, so that's two
• 26:52
  Speaker 1: seconds round trip. Oh I see. So then the way
• 26:55
  Speaker 1: you turn that into a clock is you count how
• 26:58
  Speaker 1: many times the light bounces up and down the ceiling,
• 27:01
  Speaker 1: and that sort of gives you a sense of how
• 27:04
  Speaker 1: time is moving. That's right. You want to say, well,
• 27:06
  Speaker 1: how long does it take my cat to finish his lunch?
• 27:09
  Speaker 1: And so you count how many times it takes the
• 27:12
  Speaker 1: laser pults to go up to the ceiling and back,
• 27:14
  Speaker 1: and that's the number of two second intervals it takes
• 27:16
  Speaker 1: your cat to eat his lunch. Okay, so that's where
• 27:19
  Speaker 1: it seems like a pretty impractical clock. But hey, this
• 27:23
  Speaker 1: this is how we do things in physics. Man, be like,
• 27:26
  Speaker 1: can we build this thing using lasers? What's the most
• 27:31
  Speaker 1: inconvenient wristwatch we can build with lasers at home? The
• 27:35
  Speaker 1: way we toast bread for breakfast as we use lasers,
• 27:38
  Speaker 1: of course, and cats cats, I feel like it's a key. No,
• 27:42
  Speaker 1: that's just how we toast our cats. Man. Let's say
• 27:47
  Speaker 1: you cooked the food for the I want to I
• 27:48
  Speaker 1: want to officially distance myself from that joke, because nobody
• 27:51
  Speaker 1: should ever fire a laser at a cat. Well, you
• 27:54
  Speaker 1: can fire a laser near a cat to entertain it,
• 27:56
  Speaker 1: of course, but I don't actually hit your your cat
• 27:58
  Speaker 1: with a laser, please, oh man? All right, So now
• 28:00
  Speaker 1: we have our clock, right, that's the way a clock
• 28:02
  Speaker 1: that uses light. Okay, so this is a thought experiment.
• 28:05
  Speaker 1: We're going to build a clock where we measure time
• 28:07
  Speaker 1: by measuring counting how many times it bounces off the
• 28:09
  Speaker 1: ceiling up and down. That's right, And it doesn't have
• 28:12
  Speaker 1: to be a thought experiment. You've got mirrors, you've got lasers.
• 28:14
  Speaker 1: Go ahead, build your self o'clock. Um. But the interesting
• 28:17
  Speaker 1: thing is that what happens if you put that clock
• 28:20
  Speaker 1: on a spaceship right right on the train. Let's make
• 28:23
  Speaker 1: it even more inconvenient. Let's put this on a spaceship.
• 28:29
  Speaker 1: And so that's when things start to get interesting, right, Like,
• 28:31
  Speaker 1: that's when we start to see how time slows down. Yeah,
• 28:35
  Speaker 1: Or let's put the clock on the back of your cat, right,
• 28:37
  Speaker 1: and then see what happens when you're well, I guess
• 28:39
  Speaker 1: you need the ceiling on the back of the cap.
• 28:41
  Speaker 1: Maybe that doesn't. Actually, I feel like trying to get
• 28:43
  Speaker 1: a cat to do what you want is even more
• 28:46
  Speaker 1: difficult than getting on a spaceship. Einstein had no idea
• 28:49
  Speaker 1: how to get your cat to do what you want.
• 28:50
  Speaker 1: You can master. He was the master of the cosmos,
• 28:53
  Speaker 1: but not of cats. All right. So we have a
• 28:59
  Speaker 1: clock where you measure time by counting how many times
• 29:02
  Speaker 1: it bounced off the ceiling on the floor, and we
• 29:04
  Speaker 1: stick it in a spaceship, and then we start going.
• 29:07
  Speaker 1: What happens then, right, So if you're in the spaceship,
• 29:10
  Speaker 1: nothing changes. It doesn't matter that you're going at half
• 29:13
  Speaker 1: the speed of light or nine tenths of speed of light.
• 29:15
  Speaker 1: You're in the spaceship. You have no velocity relative to
• 29:17
  Speaker 1: the clock. So things work the same way on the
• 29:19
  Speaker 1: spaceship for you as they did when you tested your
• 29:21
  Speaker 1: clock in your living room. As you just see the
• 29:23
  Speaker 1: beam go up and down, bounce up and down, and
• 29:25
  Speaker 1: you count, and that's your time. That's right. And since
• 29:27
  Speaker 1: you brought your cat along, it takes your cat the
• 29:29
  Speaker 1: same amount of time to eat his lunch in your
• 29:31
  Speaker 1: spaceship as it does at home, assuming he's not wearing
• 29:35
  Speaker 1: a silly cat space suit. The interesting thing is that
• 29:38
  Speaker 1: when since you left me, Um, you left me on Earth,
• 29:40
  Speaker 1: you didn't invite me on your awesome spaceship. Thanks by
• 29:43
  Speaker 1: the way, that would have been too inconvenient. And I'm
• 29:47
  Speaker 1: so heartbroken that I'm spying on you. Have a massive
• 29:50
  Speaker 1: telescope and I'm watching your cat eat lunch on a spaceship. Um.
• 29:54
  Speaker 1: Now I'm looking at your clock, okay, and I'm wondering
• 29:56
  Speaker 1: how long does it take his cat to eat lunch, etcetera.
• 30:00
  Speaker 1: And I'm watching your clock. Okay, you're trying to count
• 30:03
  Speaker 1: how many times it bounces off the ceiling to exactly.
• 30:07
  Speaker 1: So I see the laser pulse go up, and I
• 30:09
  Speaker 1: see the laser pulse come down. Right. The problem is
• 30:12
  Speaker 1: that I don't see the laser pulse going ten feet
• 30:15
  Speaker 1: up and ten feet down. I see the laser pulse
• 30:18
  Speaker 1: as going further because you're moving, which means the laser
• 30:21
  Speaker 1: pulse is not just going up and down. It's also
• 30:23
  Speaker 1: going sideways in the direction of your motion. So you
• 30:26
  Speaker 1: have the up and down and the sideways. So the
• 30:29
  Speaker 1: light for me, the laser is going in a diagonal right,
• 30:31
  Speaker 1: diagonal up hit the ceiling, and diagonal back down to
• 30:35
  Speaker 1: hit the floor, because you see it hit the ceiling
• 30:38
  Speaker 1: and then on its way down, the spaceship is awesome moving,
• 30:41
  Speaker 1: so it's kind of moving diagonally to hit the floor
• 30:45
  Speaker 1: where it's going to be exactly. And so the mirrors
• 30:48
  Speaker 1: and the clock move with the laser. Obviously they're all
• 30:50
  Speaker 1: going at the same speed sideways, and so the laser
• 30:53
  Speaker 1: beam hits the mirror on the top and it hits
• 30:55
  Speaker 1: the receiver or whatever on the bottom. But I see
• 30:57
  Speaker 1: you traveling further than you do, right, And this is
• 31:00
  Speaker 1: where the the absolute speed of light kicks in because
• 31:03
  Speaker 1: you say, okay, travel ten feet, right. It traveled those
• 31:06
  Speaker 1: ten feet at the speed of light, So I know
• 31:08
  Speaker 1: it takes ten seconds, but I see it traveled further. Right,
• 31:11
  Speaker 1: Depending on how fast you're going, it could have traveled
• 31:13
  Speaker 1: like fourteen fifteen feet, right, because light always travels at
• 31:17
  Speaker 1: the same speed. Right, I see it taking longer because
• 31:21
  Speaker 1: it's gone further and it can go faster than the
• 31:24
  Speaker 1: speed of light. It can go faster than the speed
• 31:26
  Speaker 1: of light. So I see your clock running slower. It
• 31:28
  Speaker 1: literally takes longer to count off seconds for you because
• 31:33
  Speaker 1: the clock is built on the premise that it takes
• 31:35
  Speaker 1: light a certain time to go a certain distance. But
• 31:38
  Speaker 1: now that distance is further and the speed can't change
• 31:40
  Speaker 1: because it's going up and down. The light is going
• 31:42
  Speaker 1: up and down, and it's trying to go forward to exactly,
• 31:45
  Speaker 1: so it has to take longer exactly. Now, if you
• 31:48
  Speaker 1: built this same kind of clock using something else, like
• 31:51
  Speaker 1: sound waves, right, you had a speaker, then this wouldn't
• 31:54
  Speaker 1: happen because the sound waves don't have that same property
• 31:57
  Speaker 1: that they always travel at the speed at a certain
• 31:59
  Speaker 1: speed relative to observers. Right. Um, sound waves, as we
• 32:03
  Speaker 1: know from Doppler shifts, change their speed based on how
• 32:06
  Speaker 1: fast you're going. So if this is a sound wave,
• 32:08
  Speaker 1: if we use sound waves instead, then I would just
• 32:10
  Speaker 1: see the sound waves is traveling faster. But light can't
• 32:13
  Speaker 1: do that. Light always travels to the same speed no
• 32:15
  Speaker 1: matter who the observer is. So it slows your clock down.
• 32:19
  Speaker 1: So let's let's go back a step. Um. Okay, So
• 32:21
  Speaker 1: so I'm gonna be in my spaceship counting how many
• 32:24
  Speaker 1: times it bounces off the ceiling, and for me, it's
• 32:26
  Speaker 1: going to be like bounce, bounce, bounce, bounce, bounds. But
• 32:29
  Speaker 1: for you, you're saying because it has to travel up
• 32:33
  Speaker 1: and down and forward. You're going to count it slower,
• 32:35
  Speaker 1: right like for you, it's going to be bounds, bounds, bounds,
• 32:40
  Speaker 1: And so that's kind of the definition of time. Yeah, exactly, exactly,
• 32:45
  Speaker 1: and any clock. And you're thinking, okay, well, that's just
• 32:47
  Speaker 1: one example, right, But the same argument holds for if
• 32:51
  Speaker 1: you're going in another direction, right, you don't have just
• 32:53
  Speaker 1: be going sideways. If you're shooting in the direction of
• 32:56
  Speaker 1: the mirror, right, then the light has longer to go
• 32:58
  Speaker 1: in one direction, but it can't make up the time.
• 33:01
  Speaker 1: And if you're going at an angle, the same thing happens.
• 33:04
  Speaker 1: And also for any clock. This is just one example.
• 33:07
  Speaker 1: It's the clearest example because we've built it out of
• 33:10
  Speaker 1: something that only uses light, but the true the same
• 33:13
  Speaker 1: happens for every physical process, for any kind of clock. Okay.
• 33:17
  Speaker 1: So that's kind of the explanation is that time, the
• 33:21
  Speaker 1: definition of time is sort of tied to the speed
• 33:24
  Speaker 1: of light, and the universe has this weird rule about
• 33:28
  Speaker 1: the speed of light, which is that nobody can never
• 33:30
  Speaker 1: see it move faster than the speed of light. That's right,
• 33:33
  Speaker 1: And the other important thing to understand is that your
• 33:35
  Speaker 1: definition of time and your definition of what happens depends
• 33:39
  Speaker 1: on how fast you are going. There is no absolute
• 33:41
  Speaker 1: sense of time. It's not like the universe has a
• 33:44
  Speaker 1: big clock out there and it's keeping track of what's
• 33:46
  Speaker 1: going on, and we're trying to make measures of measurements
• 33:48
  Speaker 1: of it, and they're kind of sloppy sometimes when we
• 33:50
  Speaker 1: get them wrong, Like there is no absolute sense of time, right,
• 33:54
  Speaker 1: And you can do crazy experiments where you know, depending
• 33:57
  Speaker 1: on how fast people are going relative to experiment, they
• 34:00
  Speaker 1: can see the order of events changing, like I can
• 34:03
  Speaker 1: see A happen before B, and you can see B
• 34:06
  Speaker 1: happen before A because you're zooming in the other direction.
• 34:09
  Speaker 1: And you might think, well, that's impossible either A happened
• 34:12
  Speaker 1: before B or BE happened before A. There is a
• 34:14
  Speaker 1: real truth, right, answer is there is no truth. The
• 34:17
  Speaker 1: truth is not out there. X Files was a lie.
• 34:21
  Speaker 1: So I feel like we should get into that in
• 34:22
  Speaker 1: another episode. But I think the conclusion we're reaching here
• 34:25
  Speaker 1: is that basically there is no time. After all, there's
• 34:30
  Speaker 1: no time to talk about this anymore. And that's true. No,
• 34:32
  Speaker 1: there is time, but time is a different thing that
• 34:34
  Speaker 1: you than you thought it was, right, It's something weirder
• 34:37
  Speaker 1: and more malleable now in our safe, little slow worlds,
• 34:40
  Speaker 1: it doesn't. You can pretend that time is the way
• 34:43
  Speaker 1: you thought it was right and you'll get by just fine.
• 34:46
  Speaker 1: But in reality, if you want to understand the way
• 34:48
  Speaker 1: that that physics works at its deepest level, whether universe
• 34:51
  Speaker 1: is actually put together, what the real rules are, that
• 34:53
  Speaker 1: it turns out time is really different than you thought
• 34:56
  Speaker 1: it was. So that person who answered there is no
• 34:59
  Speaker 1: time sort of, I feel like she skipped ahead to
• 35:02
  Speaker 1: the end of this count. She's probably a physicist visiting
• 35:05
  Speaker 1: from the future from Alpha centri. Is it her? Or
• 35:10
  Speaker 1: she's your cat evolved for thousands of years into a
• 35:14
  Speaker 1: future physicist and then traveled back in time to deliver
• 35:16
  Speaker 1: that message. I think she's your twin Danny. Maybe she is,
• 35:22
  Speaker 1: maybe she is. Well, speaking of time, I think we're
• 35:25
  Speaker 1: out of time for this episode, so it's time to
• 35:27
  Speaker 1: wrap it up. Thank you everyone for your patients and
• 35:29
  Speaker 1: for listening, And if you have questions about how things
• 35:32
  Speaker 1: work in the universe or anything else crazy, please send
• 35:35
  Speaker 1: them to us on Twitter or email us at feedback
• 35:38
  Speaker 1: at Daniel and Jorge dot com. We love listener questions. Yeah,
• 35:42
  Speaker 1: hopefully We made time move a little bit faster for you,
• 35:45
  Speaker 1: whatever it is you're doing, unless you were bored, which
• 35:49
  Speaker 1: is probably canceled out. If you still have a question
• 36:01
  Speaker 1: after listening to all these explanations, please drop us a line.
• 36:04
  Speaker 1: We'd love to hear from you. You can find us
• 36:07
  Speaker 1: at Facebook, Twitter, and Instagram at Daniel and Jorge That's
• 36:10
  Speaker 1: one word, or email us at Feedback at Daniel and
• 36:14
  Speaker 1: Orge dot com.