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Is Time Travel Possible? · Daniel and Kelly’s Extraordinary Universe

• 0:05
  Speaker 1: Hi, I'm Daniel and I'm Jrrie, and we're here to
• 0:09
  Speaker 1: explain the universe. Dude came in so late there. Oh,
• 0:14
  Speaker 1: I'm sorry. I travel back in time and get that right.
• 0:17
  Speaker 1: I guess I was out of time. Hi. I'm Daniel
• 0:23
  Speaker 1: and I'm Jrrie, and we're here to explain the universe.
• 0:42
  Speaker 1: I'm Horri. I'm a cartoonist the creator of PhD Comics.
• 0:45
  Speaker 1: And I'm Daniel. I'm a particle physicist, and together were
• 0:49
  Speaker 1: the authors of the book We Have No Idea, which
• 0:51
  Speaker 1: tries to tackle some of the biggest questions of the
• 0:54
  Speaker 1: universe and doesn't answer any of them. That's right. Like,
• 0:57
  Speaker 1: for example, today's topic, which is which movies get time travel? Right?
• 1:07
  Speaker 1: Are there any science fiction movies that actually get time
• 1:10
  Speaker 1: travel scientifically correct? Any that could really plausibly happen given
• 1:15
  Speaker 1: some technology in the future that we could invent. That's
• 1:18
  Speaker 1: the question we're going to tackle today. We went out
• 1:20
  Speaker 1: in the street and we asked people what they thought.
• 1:22
  Speaker 1: What do you think? Here's what people in the street
• 1:24
  Speaker 1: had to say. Do you think time travel is possible? Um?
• 1:33
  Speaker 1: I think theoretically yes, like based on math and everything,
• 1:39
  Speaker 1: but I don't think we as humans will be able
• 1:41
  Speaker 1: to I hope so, but I don't know if it is,
• 1:45
  Speaker 1: because everyone in movies always says you need infinite energy,
• 1:49
  Speaker 1: and I don't think that's possible. Probably. I mean, there's
• 1:54
  Speaker 1: so much out there that we don't know about that
• 1:56
  Speaker 1: I don't think I could really rule it out. What's
• 1:59
  Speaker 1: your favorite time of a movie, Daniel Man, I gotta
• 2:02
  Speaker 1: tell you, I don't think I like any time travel movies.
• 2:05
  Speaker 1: What do you mean you can't enjoy any of them? Right?
• 2:08
  Speaker 1: The problem for me is that when I watched science fiction,
• 2:11
  Speaker 1: I really wanted to make sense. I mean, you can
• 2:13
  Speaker 1: invent whatever rules you want, you come up with your
• 2:15
  Speaker 1: own universe, with your own physics, whatever, but then it
• 2:18
  Speaker 1: has to follow those rules, because if you don't follow
• 2:21
  Speaker 1: the rules, then anything can happen, and then you're not
• 2:23
  Speaker 1: really invested because at any point the plot could just
• 2:26
  Speaker 1: shift and twist and spike, and you know, you could
• 2:29
  Speaker 1: save the universe with crazy glowing bananas or something. So
• 2:32
  Speaker 1: you have to have some rules. What do you think
• 2:34
  Speaker 1: it's it's so appealing about time travel, right, there's so
• 2:37
  Speaker 1: many movies about it books. Why do you think humans
• 2:43
  Speaker 1: love to think about time travel? Or wish they could
• 2:45
  Speaker 1: do it. I think there's a lot of reasons. I
• 2:47
  Speaker 1: think one is just fascination, Like I'd like to go
• 2:50
  Speaker 1: back and see what dinosaurs really look like, or I'd
• 2:53
  Speaker 1: like to know who really killed JFK. Or I'd like
• 2:56
  Speaker 1: to travel to the future and like learn the secrets
• 2:58
  Speaker 1: of the universe that humans will one day reveal. Right,
• 3:01
  Speaker 1: this feeling that we're like trapped in the present. We
• 3:05
  Speaker 1: could travel somewhere else, We could we could see and
• 3:08
  Speaker 1: learn something new. And some of these things are facts,
• 3:10
  Speaker 1: like there is a real story about how the dinosaurs died,
• 3:14
  Speaker 1: or how the moon was made or all this kind
• 3:16
  Speaker 1: of stuff. It really happened, and in some cases the
• 3:19
  Speaker 1: clues for it are just gone. And if you could
• 3:20
  Speaker 1: travel back in time, you could you could learn those
• 3:23
  Speaker 1: things for real. The other big thing is that people
• 3:26
  Speaker 1: wish they could change things they've done in the past. Right,
• 3:29
  Speaker 1: of course, who doesn't try. Yeah, like regret, you have
• 3:32
  Speaker 1: regret about things you did. You wish you could go
• 3:34
  Speaker 1: back and like, um, I don't know, we'd been more
• 3:38
  Speaker 1: bold with a certain person or been more said something
• 3:42
  Speaker 1: differently than before. So that feeling of regret, like oh,
• 3:44
  Speaker 1: I can't go back, that's right, and we're trained like
• 3:47
  Speaker 1: in video games, you know you have another life, or
• 3:49
  Speaker 1: you can save the game and go back and try
• 3:51
  Speaker 1: it again. Right, it's a really tempting idea. Or you
• 3:54
  Speaker 1: remember an argument you had and then you wish you
• 3:56
  Speaker 1: had gone back and said something different, like when you've
• 3:58
  Speaker 1: had time later to come up with a really juicy
• 4:01
  Speaker 1: zinger and you could go back and deliver it and
• 4:03
  Speaker 1: embarrass somebody. We've all fantasized about that. And then in
• 4:07
  Speaker 1: the future, we worry about the future. Right, it's like
• 4:10
  Speaker 1: an unknown that makes us concern, so we somebody's wish
• 4:13
  Speaker 1: we could see what would happen, what's going to happen? Yeah, yeah,
• 4:16
  Speaker 1: Or even steal secrets from the future. Right. Imagine you
• 4:19
  Speaker 1: could go forward in a hundred years, scoop up a
• 4:21
  Speaker 1: bunch of inventions, bring them back, and then you know,
• 4:23
  Speaker 1: get rich and famous. Rights steal steal ideas from from
• 4:27
  Speaker 1: people who haven't even been born yet. Right, it's like
• 4:29
  Speaker 1: almost a victimless crime because the victims are not even yet.
• 4:32
  Speaker 1: Fetus is right, so you could again, but again it's
• 4:35
  Speaker 1: I guess it's also again this idea of um the
• 4:38
  Speaker 1: past and the future being inaccessible to us. Like you said,
• 4:41
  Speaker 1: we're trapped in the present, and the president itself is
• 4:44
  Speaker 1: a weird idea, like what is the present? You know,
• 4:46
  Speaker 1: if you imagine like time is like a line, the
• 4:49
  Speaker 1: president is like a moment an instant along that line.
• 4:53
  Speaker 1: But weirdly, it's not static, right, It's not a place
• 4:56
  Speaker 1: like in space. It like moves forward at one second
• 4:59
  Speaker 1: per secon And we could spend a whole podcast diving
• 5:02
  Speaker 1: into the mysteries and the science of time, and probably
• 5:05
  Speaker 1: we should. We don't have time time today, but I
• 5:08
  Speaker 1: think it's it's worth thinking about what time is so
• 5:11
  Speaker 1: we can understand what aspects of time travel are scientifically problematic, um,
• 5:15
  Speaker 1: so that we're prepared when we dig into all these
• 5:18
  Speaker 1: deeply flawed time travel movies. Yeah, well then that makes
• 5:21
  Speaker 1: sense why there's so many movies and and and stories
• 5:25
  Speaker 1: about it. It's like it's a great fantasy to be
• 5:29
  Speaker 1: able to travel through time. Absolutely, I'd love to be
• 5:31
  Speaker 1: able to do it. I mean, if somebody built a
• 5:33
  Speaker 1: real working time machine, I would be first in line
• 5:36
  Speaker 1: to use it to answer deep questions about the universe
• 5:38
  Speaker 1: and go forwards and backwards and you know, buy different
• 5:41
  Speaker 1: pair of socks and all sorts of stuff. We just
• 5:43
  Speaker 1: wrote down a little sentence here that I think I
• 5:46
  Speaker 1: will help us, uh drive home the point of what
• 5:49
  Speaker 1: time is, which is by saying what time is not? Right? Absolutely,
• 5:54
  Speaker 1: that's a great way to find a long list of
• 5:57
  Speaker 1: what time isn't time, it's not rather berries, I'm clouds. Yeah. Well,
• 6:03
  Speaker 1: but an interesting one we wrote down was time is
• 6:05
  Speaker 1: not like space? Right? What does that mean? Well, we're
• 6:10
  Speaker 1: all fascinated with space, right, And the idea of space
• 6:12
  Speaker 1: travel is fun, and even just in terms of space,
• 6:15
  Speaker 1: like is in your environment, like where you are on Earth.
• 6:18
  Speaker 1: We get in our car, we drive somewhere. We have
• 6:20
  Speaker 1: this agency, right, we can go where we want. We
• 6:23
  Speaker 1: can move forward and backwards, we can move up and
• 6:25
  Speaker 1: down a little bit, we can move side to side.
• 6:27
  Speaker 1: We have this freedom to move in space. And I
• 6:30
  Speaker 1: think that's where this notion of travel comes from. And
• 6:32
  Speaker 1: we'd love to apply that same notion to time. And
• 6:36
  Speaker 1: in fact, it's very scientifically titilating to think of time
• 6:40
  Speaker 1: as a fourth dimension of space. And it's true that
• 6:43
  Speaker 1: in Einstein's relativity he binds time and space together into
• 6:47
  Speaker 1: this one concept called space time. The two things get
• 6:50
  Speaker 1: part of the same kind of space, right, All kinds
• 6:54
  Speaker 1: of all part of the same mathematical construct. It's a
• 6:59
  Speaker 1: four dimensional mathematical construct that has three dimensions of space
• 7:02
  Speaker 1: and one dimension of time. And we kind of wish
• 7:05
  Speaker 1: we could travel through time the way we travel around
• 7:08
  Speaker 1: in space, like skipping around or doing loops or going
• 7:11
  Speaker 1: back to the same spot, but we can't do that
• 7:14
  Speaker 1: with time. It's like it's a one directional and it's
• 7:16
  Speaker 1: always moving forward. That's right. And in any science fiction universe,
• 7:21
  Speaker 1: you're gonna have a theory of physics. You're gonna have
• 7:23
  Speaker 1: some science in that universe, and that theory is going
• 7:25
  Speaker 1: to have time in it. Right. If it's a story
• 7:27
  Speaker 1: where something happens, right, and if it has time and
• 7:30
  Speaker 1: it then it has to have cause and effect, and
• 7:33
  Speaker 1: that's causality. Right, A happens then be if a cause
• 7:36
  Speaker 1: to B, then A have to happen before B. In
• 7:39
  Speaker 1: science fiction, we typically give people free reign to come
• 7:41
  Speaker 1: up with their own new laws of physics and then
• 7:44
  Speaker 1: create a story in that universe. Right, that's the creative
• 7:47
  Speaker 1: element of it. But they have to come up with
• 7:49
  Speaker 1: a consistent set and for it to be consistent, it
• 7:52
  Speaker 1: has to follow causality and causality rules out of time travel, right,
• 7:56
  Speaker 1: So that's basically screwed. That's the big bummer. That's the
• 8:00
  Speaker 1: big bummer then, because everything has to be linked from
• 8:04
  Speaker 1: A to B, B two s by the laws of physics.
• 8:06
  Speaker 1: You can't just kind of jump around, that's right. And
• 8:09
  Speaker 1: you also can't even really avoid it by trying to
• 8:13
  Speaker 1: make little changes. You know. There's this famous story, uh
• 8:17
  Speaker 1: one of the earlier time travel stories. Ray Bradberry think
• 8:20
  Speaker 1: that the story is called the Butterfly Effect. Guy goes
• 8:23
  Speaker 1: back in time and he goes he's like hunting t
• 8:26
  Speaker 1: rex is or something pretty awesome. There's some company and
• 8:29
  Speaker 1: they tell them you can't touch anything but the t
• 8:32
  Speaker 1: rex They find t rexes which were already gonna die,
• 8:34
  Speaker 1: so it doesn't affect anything else in the future. But
• 8:37
  Speaker 1: he accidentally steps on a butterfly and he kills that butterfly,
• 8:41
  Speaker 1: and killing that butterfly has some effect. You know, some
• 8:44
  Speaker 1: lizard which was going to eat that butterfly now doesn't
• 8:46
  Speaker 1: and then dies, and then the thing that was going
• 8:48
  Speaker 1: to eat that lizard dies, and then the thing that
• 8:50
  Speaker 1: was going to eat that right, and then dot dot
• 8:52
  Speaker 1: dot fifty million years later. Who knows how big the
• 8:55
  Speaker 1: effects are. The world is a chaotic system. Any tiny
• 8:58
  Speaker 1: little change that crushing a butterfly could lead to enormous changes,
• 9:02
  Speaker 1: like humans don't evolve, you know, or the world is
• 9:06
  Speaker 1: completely different. So any change to the past can have
• 9:10
  Speaker 1: enormous cataclysmic effects in the future, which might affect the
• 9:15
  Speaker 1: human going back in time in the first place, right exactly.
• 9:18
  Speaker 1: Think about it, like everything that happened in the past
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  Speaker 1: is a partial cause of you, because the system is
• 9:24
  Speaker 1: so complicated and interconnected that anything in the past can
• 9:28
  Speaker 1: conceivably play a role in your creation. So if you're
• 9:31
  Speaker 1: the time traveler and you go back and do anything,
• 9:34
  Speaker 1: even just breathe air molecules and warm them up a
• 9:37
  Speaker 1: little bit, you're changing some of the things that caused you.
• 9:41
  Speaker 1: And so then you as a physical object and the
• 9:44
  Speaker 1: science based universe no longer really exist. Right, So it's
• 9:47
  Speaker 1: an immediate paradox. Even if you just go back in
• 9:49
  Speaker 1: time and take a breath, right, and it's like going
• 9:53
  Speaker 1: around molecules that might have somehow is in influence to
• 9:59
  Speaker 1: you being there, that's right. Yeah, Okay, so causing effect
• 10:03
  Speaker 1: is a big bummer. It means that you can't mess
• 10:06
  Speaker 1: around with the ordering of things. You can't miss with
• 10:08
  Speaker 1: logic and that and even small changes will snowball into
• 10:13
  Speaker 1: large effects. I remember now the name of that story
• 10:15
  Speaker 1: is the Sound of Thunder. It's a Ray Bradberry story.
• 10:18
  Speaker 1: It's a really awesome story. Cool alright. So, um, so
• 10:21
  Speaker 1: you're saying time travel is impossible. Now we should clarify
• 10:24
  Speaker 1: time travel backwards backwards, right, That would reorder causing effect. Right,
• 10:29
  Speaker 1: because we're always travling forward, we're always traveling forward to time.
• 10:33
  Speaker 1: That's not a problem. We're all time travelers. We're all
• 10:36
  Speaker 1: time travelers. It's not a very exciting ride, but you're
• 10:39
  Speaker 1: on it. And some, I mean technicate, some could even
• 10:42
  Speaker 1: travel forwards faster than others, right, like if I cop
• 10:44
  Speaker 1: in a spaceship, because with speed of light come back,
• 10:48
  Speaker 1: I traveled uh through time differently than you. That's right.
• 10:52
  Speaker 1: Now that we're done with the bummer part that time
• 10:54
  Speaker 1: travel backwards is not possible, let's talk about the exciting part,
• 10:57
  Speaker 1: which is you're absolutely right time travel forward. There's no
• 11:00
  Speaker 1: thing preventing that. And and you could build a machine,
• 11:03
  Speaker 1: which you know just I mean, it's very simple actually technologically,
• 11:06
  Speaker 1: you just like cryogenics. If I freeze you, the h
• 11:10
  Speaker 1: popsicle stays in place for a million years, as long
• 11:13
  Speaker 1: as we have technology, as long as we have technology
• 11:16
  Speaker 1: to dethaw you and revive you in five million years,
• 11:19
  Speaker 1: then you have traveled forward five million years and the
• 11:22
  Speaker 1: reason will have taken a break popped out in a
• 11:26
  Speaker 1: future time. That's right, Yeah, And I mean there's lots
• 11:30
  Speaker 1: of moral and biological problems with that, but from a
• 11:33
  Speaker 1: physics point of view, you're just stretching cause and effect.
• 11:36
  Speaker 1: You're not breaking it. May if that's later it okay. Yeah.
• 11:41
  Speaker 1: Backwards potentorial backwards is I'm possible, And that's kind of
• 11:43
  Speaker 1: the basis of most fun movies. Right, It's like going
• 11:45
  Speaker 1: back and changing something. And I want to talk about
• 11:48
  Speaker 1: that some more, but first let's take a quick break. So,
• 12:01
  Speaker 1: time travel backwards and possible, that's the basis of most
• 12:04
  Speaker 1: fun movies. And so, um, how do most movies get
• 12:07
  Speaker 1: around is like impossibility of breaking calosality and logic? Yeah,
• 12:14
  Speaker 1: so I think that most movies are just banking on
• 12:16
  Speaker 1: the fact that nobody's really paying super close attention and
• 12:19
  Speaker 1: it's just there for the ride and doesn't care as
• 12:22
  Speaker 1: much as I do about movies being logically they assume
• 12:25
  Speaker 1: most people are not trained physicists. That's right, And I
• 12:30
  Speaker 1: think a lot of science fiction fans probably more relaxed
• 12:34
  Speaker 1: about whether the universe follows its rules. And so if
• 12:36
  Speaker 1: you're willing to break the rules, then you know you
• 12:38
  Speaker 1: can do anything you like. Um, but they at least
• 12:41
  Speaker 1: put up the appearance usually of trying to follow some rules.
• 12:44
  Speaker 1: And so how do they do it? Well? One classic
• 12:47
  Speaker 1: way is the split universe. They say, okay, you go
• 12:50
  Speaker 1: back in time to see your grandfather, for example, and
• 12:54
  Speaker 1: then when you arrive back in time, you split the
• 12:57
  Speaker 1: universe is the original universe in which you didn't go
• 13:00
  Speaker 1: back in time, and this is new universe where you've
• 13:02
  Speaker 1: gone back in time. To talk about timelines, right, yeah,
• 13:08
  Speaker 1: and so you're a product of the original timeline called
• 13:10
  Speaker 1: timeline zero, and that you have inserted yourself into another
• 13:14
  Speaker 1: universe called timeline one. And if you make changes in
• 13:17
  Speaker 1: timeline one, it doesn't affect timeline zero, which is what
• 13:20
  Speaker 1: caused you, what created you, where you came from. That
• 13:23
  Speaker 1: you're freedom uck up timeline one. You can kill your grandfather,
• 13:26
  Speaker 1: for example, and he can be dead, and in timeline
• 13:29
  Speaker 1: one you're never even born. Right. Well, there's a famous scene,
• 13:32
  Speaker 1: that famous scene and Back to the Future where Doc
• 13:36
  Speaker 1: Brown played by Christopher Lloyd explains basically like he whips
• 13:40
  Speaker 1: out of chalkboard and explains time travel to Marty and
• 13:43
  Speaker 1: so he like draws online. It says like, this is
• 13:46
  Speaker 1: the time that you're in and then you travel back
• 13:48
  Speaker 1: in time and you split off a different timeline. Man,
• 13:53
  Speaker 1: that movie has so many problems because, yeah, they try
• 13:57
  Speaker 1: to go in that movie, they try to go for
• 13:59
  Speaker 1: the altar a timeline right right theory, right, But it
• 14:02
  Speaker 1: doesn't even really make sense because in that movie, he
• 14:05
  Speaker 1: has what broken up his parents, so his parents won't
• 14:08
  Speaker 1: get together, so they won't make him right, so he
• 14:10
  Speaker 1: won't exist anymore. So problem number one is if they're
• 14:13
  Speaker 1: in this split timeline theory, then it shouldn't matter. Right,
• 14:17
  Speaker 1: he's in a new timeline, but he's disappearing, you know,
• 14:21
  Speaker 1: just like fading from the photographs and his hand is
• 14:24
  Speaker 1: becoming transparent. Why is that happening If he's from the
• 14:27
  Speaker 1: original and changed timeline, the new timeline can affect the
• 14:31
  Speaker 1: old timeline, Yeah, which in which case you're not really
• 14:34
  Speaker 1: in a split timeline at all. The other. The other thing,
• 14:38
  Speaker 1: this is the thing that really irks me about that
• 14:39
  Speaker 1: whole approach, is that why does he fade slowly? Right?
• 14:44
  Speaker 1: It takes him, like, you know, two hours of movie
• 14:47
  Speaker 1: time for his hand to gradually disappear and then bloated
• 14:52
  Speaker 1: right away. No, if he doesn't exist anymore, then boom,
• 14:55
  Speaker 1: he just doesn't exist. It makes no sense. You're you're
• 14:58
  Speaker 1: killing it. A childhood favorite movie here, it's a great movie. Everybody,
• 15:02
  Speaker 1: I love the movie, Go and watch it. I showed
• 15:04
  Speaker 1: it to my kids. They loved it. But from a
• 15:07
  Speaker 1: time perspective, it just makes no sense. And that's the
• 15:09
  Speaker 1: part that that drives me bonkers. And then like I
• 15:13
  Speaker 1: can imagine you jointed your kids. Okay the movie ended,
• 15:16
  Speaker 1: then you whip out a chalkburn and then launch it
• 15:18
  Speaker 1: to it when I would like your how this movie
• 15:20
  Speaker 1: was bunking? Right? All right? Kids, I hope you enjoyed
• 15:23
  Speaker 1: that it's all wrong. Well, in comparison, let's compare this
• 15:27
  Speaker 1: out to other ways in which other movies have sort
• 15:29
  Speaker 1: of trying to get around this impossibility of time trouble.
• 15:32
  Speaker 1: So what are other ways movies try it? So? Other
• 15:34
  Speaker 1: ways people do it? Is to imagine one consistent universe
• 15:38
  Speaker 1: where you go back in time and then do you
• 15:41
  Speaker 1: change the future, but the future has already been affected
• 15:45
  Speaker 1: by your going back in time, which just like you
• 15:48
  Speaker 1: can't change the future future, well you can't. The past
• 15:52
  Speaker 1: always can change the future. Right, that's the way it works, right,
• 15:55
  Speaker 1: causality A causes B. You change A, it changes B.
• 15:59
  Speaker 1: But in the these stories, they try to make us
• 16:02
  Speaker 1: so that the future comes back to affect the past,
• 16:05
  Speaker 1: and that that past has already even taken new account
• 16:08
  Speaker 1: into the future. So an example of that is the
• 16:10
  Speaker 1: movie like Looper or Primer is sort of similar where
• 16:14
  Speaker 1: the Harry Potter is one of my favorite time termin movies,
• 16:17
  Speaker 1: the third Harry Potters. Have you seen Harry Potter movies. Yeah,
• 16:20
  Speaker 1: he goes back in time and tries to change thing,
• 16:24
  Speaker 1: but it turns out he was there all along. That's right.
• 16:27
  Speaker 1: He was there all along, and that's right. And so
• 16:31
  Speaker 1: they avoid the split universe thing right where it happens
• 16:35
  Speaker 1: one way once then happens another way later, Like that
• 16:37
  Speaker 1: makes any sense for it happen later. We're talking about
• 16:39
  Speaker 1: time travel, right, um, And so in the Harry Potter example,
• 16:43
  Speaker 1: he loops back and he's there there's sort of two
• 16:45
  Speaker 1: of him for a while, right, is the one that's
• 16:48
  Speaker 1: come back to to change this, and the one the
• 16:50
  Speaker 1: original one um, so the A version in the B
• 16:53
  Speaker 1: version UM. And so the way they try to avoid
• 16:56
  Speaker 1: that any inconsistencies there is that the second time through,
• 17:01
  Speaker 1: when he's looped back and he's observing the same events
• 17:04
  Speaker 1: from now, having already seen it once, he somehow feels
• 17:08
  Speaker 1: obligated to follow the rules, right because he could break them.
• 17:13
  Speaker 1: If Harry goes back in time and doesn't save his life,
• 17:17
  Speaker 1: what would happen, Well, we don't know, right, because then
• 17:21
  Speaker 1: he would die, and then he wouldn't be there in
• 17:22
  Speaker 1: the future to come back, and and and he wouldn't
• 17:26
  Speaker 1: be there anymore, right, he would he would blow up
• 17:28
  Speaker 1: the universe. It suddenly wouldn't make sense logically. So if
• 17:31
  Speaker 1: he saves him, if future Harry saves him and then
• 17:34
  Speaker 1: he becomes future Harry and doesn't save himself, is a
• 17:37
  Speaker 1: logically inconsistency. But I mean that's the separate question of like,
• 17:41
  Speaker 1: is there free will in the universe and all that?
• 17:44
  Speaker 1: But you know that I feel like there's a separate conversation. No,
• 17:47
  Speaker 1: that's totally connected because it doesn't cause and effect. Right,
• 17:51
  Speaker 1: we have the freedom. We have the free will to
• 17:53
  Speaker 1: change causes. That's how we have an effect on the
• 17:55
  Speaker 1: future goods. We could launch the whole thing about free will,
• 17:59
  Speaker 1: but like as an idea of like a single timeline
• 18:02
  Speaker 1: in which the future in which the present already took
• 18:07
  Speaker 1: into account, you going back in time. What's wrong with
• 18:10
  Speaker 1: that idea? From a physics point of view, everybody has
• 18:12
  Speaker 1: to play nice, right, so everybody has to agree we're
• 18:15
  Speaker 1: going to follow this dance card and do exactly what
• 18:18
  Speaker 1: we know we have to do to to create the
• 18:20
  Speaker 1: future that we came from. It only works if there's
• 18:23
  Speaker 1: a very tightly constructed loop there where the things you
• 18:26
  Speaker 1: did in the past cause your future self exactly the
• 18:29
  Speaker 1: person who then came back to the past, right, right,
• 18:31
  Speaker 1: If that's happen, well do you said that it's the
• 18:34
  Speaker 1: way you said it has we finally constructed? Right, So
• 18:37
  Speaker 1: writer is really good and finally constructed. Then it's logically consistent,
• 18:41
  Speaker 1: isn't it all? Right? So there's two possibilities. Right, if
• 18:43
  Speaker 1: you believe in free will, this is all bunk because
• 18:46
  Speaker 1: there's no way to control what people do, and people
• 18:49
  Speaker 1: have the options to do whatever they like, including screwing
• 18:51
  Speaker 1: up the future. If you don't believe in free will,
• 18:54
  Speaker 1: if you think that people are just a product of
• 18:56
  Speaker 1: their experiences and their situations, and then there's still a problem.
• 19:00
  Speaker 1: Even if you're a brilliant writer, you're having to solve
• 19:02
  Speaker 1: an enormously chaotic problem, right, which is somehow cause a past,
• 19:07
  Speaker 1: a create a past which exquisitely causes the future, which
• 19:11
  Speaker 1: will then come back and cause that same past. Like
• 19:13
  Speaker 1: even in the Harry Potter example, he can't just decide
• 19:16
  Speaker 1: what he's gonna do. He's got to follow a dance
• 19:18
  Speaker 1: card and to be told exactly what to do, and
• 19:22
  Speaker 1: and other food. Other movies have the same idea. For example,
• 19:25
  Speaker 1: one of my favorites that I mentioned earlier, primer Um.
• 19:27
  Speaker 1: In primer they climb into a box and the box
• 19:31
  Speaker 1: moves them back in time um and then they get
• 19:34
  Speaker 1: out of the box right and they then there's two
• 19:37
  Speaker 1: of them, So there's two of them that that overlap
• 19:40
  Speaker 1: in the same time period. So but before they get
• 19:43
  Speaker 1: in the box, they have to isolate themselves. Because there's
• 19:45
  Speaker 1: two of them at the same time, one of them
• 19:47
  Speaker 1: has to isolate itself so that doesn't interact and doesn't
• 19:50
  Speaker 1: do anything to mess up the future. So the way
• 19:52
  Speaker 1: they've handled it there, as they've said, well, one of
• 19:54
  Speaker 1: them is going to be a good citizen. It's gonna
• 19:56
  Speaker 1: go sit in a basement and not interact, not create
• 19:59
  Speaker 1: any time and problems. Right. And you see this a
• 20:01
  Speaker 1: lot in time travel movies where they say they travel
• 20:04
  Speaker 1: back in time. They say, oh, don't touch that or
• 20:06
  Speaker 1: you can't kiss that girl because you'll cause a problem. Right,
• 20:10
  Speaker 1: But it's impossible because the world is so complicated and
• 20:13
  Speaker 1: so interconnected. As we were saying earlier, anything you do,
• 20:16
  Speaker 1: even just being there, is going to cause these problems.
• 20:18
  Speaker 1: Right over millions of years, though that's more likely, right, Yeah,
• 20:22
  Speaker 1: small changes over millions of years, that's a problem. But
• 20:25
  Speaker 1: you know, maybe like small changes over a couple of hours. Yeah,
• 20:28
  Speaker 1: you're right. If we destroy the universe in a million years,
• 20:30
  Speaker 1: who cares, right, as long as we get to make
• 20:32
  Speaker 1: money in the stock market. Okay, Yeah, I see where
• 20:34
  Speaker 1: you're going. Well, this is a perfect point to take
• 20:37
  Speaker 1: a break. Okay. So that those are two great devices,
• 20:52
  Speaker 1: multiple timelines, one exclusitely constructed, logically consistent timeline in which
• 20:57
  Speaker 1: there's no free will. Are there any other ways that
• 21:00
  Speaker 1: people do time travel. Well, there's a whole other approach
• 21:04
  Speaker 1: which is trying to think of time as a dimension
• 21:07
  Speaker 1: of space, right, And that's sort of the original idea
• 21:09
  Speaker 1: we had earlier, like why can't we move through time
• 21:12
  Speaker 1: the way we moved through space? Can you see this
• 21:14
  Speaker 1: in some movies, for example, very famously an Interstellar I
• 21:18
  Speaker 1: saw this movie. It involves a guy going into a
• 21:21
  Speaker 1: black hole, which has its own problems. We can talk
• 21:24
  Speaker 1: about in another episode, but I have a whole episode
• 21:27
  Speaker 1: just on how Interstellar um has has problems. And Interstellar
• 21:33
  Speaker 1: a great movie. Lots of the physics is correct, but
• 21:35
  Speaker 1: this part of it is is total is total gibberish.
• 21:38
  Speaker 1: He goes inside of a black hole, and inside the
• 21:40
  Speaker 1: black hole he can move through time as if it
• 21:43
  Speaker 1: was space, Like he could say, oh, I'm at this time.
• 21:46
  Speaker 1: I'm gonna walk over to the left by ten feet.
• 21:48
  Speaker 1: That's going to take me back twenty years. He needs
• 21:51
  Speaker 1: like right like this kind of like claytoscope type of
• 21:56
  Speaker 1: reality where like moving sideways moves you sideway backwards and
• 22:00
  Speaker 1: time or something exactly. And he uses that to talk
• 22:03
  Speaker 1: to his daughter and to send her a message and
• 22:04
  Speaker 1: give her the secret physics that a knowledge that means
• 22:07
  Speaker 1: that they can get off the planet, etcetera, ETCETERA. Problem
• 22:10
  Speaker 1: with that is he's moving through time as if it
• 22:14
  Speaker 1: was space, right, So like he's here and then he
• 22:17
  Speaker 1: was there, So they've they've created another dimension of time
• 22:21
  Speaker 1: on top of it. Right, what is moving through time mean?
• 22:24
  Speaker 1: Moving his motion over time? It just doesn't make any sense.
• 22:28
  Speaker 1: And and the reason is that stories have time, right.
• 22:31
  Speaker 1: Stories are a narrative. I'm sitting down, I'm telling you
• 22:34
  Speaker 1: a story by the fire where caveman. There's a narrative.
• 22:37
  Speaker 1: It starts and it finishes. It has to have time
• 22:39
  Speaker 1: through it. So if you're going to create this new
• 22:42
  Speaker 1: idea of time being able to move through time like
• 22:44
  Speaker 1: it was space, you can't tell that story without adding
• 22:47
  Speaker 1: another new dimension of time to it. So an interstellar
• 22:51
  Speaker 1: they create time as if it was a dimension of space.
• 22:53
  Speaker 1: But then they bolt on this new dimension of time
• 22:56
  Speaker 1: without telling extra which doesn't make extra time moving a
• 23:00
  Speaker 1: time time. Well, it's interesting that we can't like, uh,
• 23:05
  Speaker 1: And that's kind of the magic of movies, right, is
• 23:07
  Speaker 1: that you can make fantasies and story and books and
• 23:10
  Speaker 1: stories can like violate the laws of physics. And still
• 23:13
  Speaker 1: senhow come up with a fun story? Yeah? Absolutely absolutely,
• 23:18
  Speaker 1: and and you know that that's part of that movie
• 23:21
  Speaker 1: is forgiven. I personally liked Interstill a lot. I thought
• 23:23
  Speaker 1: it was a lot of fun. I rolled my eyes
• 23:25
  Speaker 1: and grin and did that one scene, you know, but
• 23:28
  Speaker 1: I like get the theater and he was like, you're
• 23:32
  Speaker 1: like grown. I try to grow quietly and I save
• 23:39
  Speaker 1: it for this, I save it for talking to you
• 23:41
  Speaker 1: or he that resentment. Remember, I remember I went to
• 23:45
  Speaker 1: see Contact. Remember the movie Contact, of course, one of
• 23:49
  Speaker 1: my favorite movies of all time. It's about this woman
• 23:52
  Speaker 1: who receives a signal from space and she it's her
• 23:56
  Speaker 1: search for like what the meaning of life? And it's
• 23:59
  Speaker 1: a main using movie, really great where the scientist is
• 24:03
  Speaker 1: the hero, right right people scientists not a bad sign,
• 24:06
  Speaker 1: just not a mad sign, just not a selfie crazy
• 24:08
  Speaker 1: selfish crazy scientists, but the hero. Yeah, awesome movie. Go
• 24:12
  Speaker 1: see if Robert Semeg has directed it. But I happened
• 24:16
  Speaker 1: to go to see that movie when it first came out.
• 24:18
  Speaker 1: With a bunch of signal processing PhD s, like four
• 24:23
  Speaker 1: of them. These are like Stanford PhDs and like signal,
• 24:26
  Speaker 1: and they came out and I was like, that was amazing,
• 24:29
  Speaker 1: and they were just laughing at like all the ways
• 24:32
  Speaker 1: they try to boost the signal or like let's invert
• 24:35
  Speaker 1: the phase whatever, and they thought that was all bonkers.
• 24:39
  Speaker 1: It's probably like going to see It's like probably probably
• 24:41
  Speaker 1: like watching you know cs I with a bunch of
• 24:44
  Speaker 1: actual friends and scientists like enhanced that image, you know. So,
• 24:48
  Speaker 1: But I try to be a good citizen in the
• 24:50
  Speaker 1: movie theater, I grown internally and I'm trying to to
• 24:52
  Speaker 1: spoil everybody else's experience. You keep it in, bottle it
• 24:57
  Speaker 1: up U. Another one in that same category is the
• 25:02
  Speaker 1: movie Arrival, which is based on a short story called
• 25:05
  Speaker 1: The Story of Your Life. And it's a nice story. Yeah,
• 25:09
  Speaker 1: it's it's very well written. It's beautifully written. Um, and
• 25:12
  Speaker 1: it has the same idea. Aliens come, and these aliens
• 25:16
  Speaker 1: have a different perception of time. They can move through
• 25:18
  Speaker 1: time as if it was a dimension of space. And
• 25:21
  Speaker 1: the cool thing is that the author has thought about
• 25:23
  Speaker 1: what would that mean for their language. So in the
• 25:26
  Speaker 1: short story at least and a little bit in a movie,
• 25:29
  Speaker 1: it changes the linguistics of the aliens, which makes it
• 25:32
  Speaker 1: hard initially for humans to figure out what they're doing
• 25:35
  Speaker 1: because they write their sentences all at once, not like
• 25:38
  Speaker 1: we're starting now and I'm ending there. They have this
• 25:40
  Speaker 1: different kind of language where they I think it is
• 25:43
  Speaker 1: that the consciousness of the aliens are spread through time
• 25:48
  Speaker 1: like it like like their brains are spread through space,
• 25:51
  Speaker 1: their consciousness is spread through time, and so they can
• 25:53
  Speaker 1: reference facts from the future and from the present and
• 25:56
  Speaker 1: from the past. Um. And that's cool. But that the
• 26:00
  Speaker 1: canstality thing, right, like their consciousness in the future can't
• 26:03
  Speaker 1: possibly affect the consciousness in the past. Right, there's that problem.
• 26:08
  Speaker 1: But I don't even have to get into that to
• 26:09
  Speaker 1: take a part that movie, which is they have this
• 26:13
  Speaker 1: nice idea, but they don't even really follow through because,
• 26:15
  Speaker 1: for example, the aliens have a conversation with us back
• 26:18
  Speaker 1: and forth. I say this, you say that, I say this,
• 26:21
  Speaker 1: You say that. A conversation has time in it, right,
• 26:24
  Speaker 1: So if they were going to be consistent about it,
• 26:26
  Speaker 1: then there should just be one blob of a conversation.
• 26:28
  Speaker 1: Here's everything I'm going to ever say to you all
• 26:31
  Speaker 1: at once, right, there shouldn't be any back and forth
• 26:33
  Speaker 1: in their linguistic structure at all. The talk you down
• 26:36
  Speaker 1: to us. So that was the problem, right, They needed
• 26:38
  Speaker 1: to find out how to talk down to us humans
• 26:41
  Speaker 1: who only got it literally forwards. Yeah, we're too stupid
• 26:46
  Speaker 1: to understand their language, right, or were too stupid to
• 26:49
  Speaker 1: find the potholes in the story. It's the same idea
• 26:52
  Speaker 1: that they want to liberate us from time, because that's
• 26:54
  Speaker 1: a really appealing idea. But they need to tell a story,
• 26:57
  Speaker 1: and in the story, time has to move forward. There
• 26:59
  Speaker 1: has to be dramatic elements and something that we can't
• 27:02
  Speaker 1: really affect something in the past, like you can't reverse right.
• 27:07
  Speaker 1: All right, well, I think we're out of time. Daniel.
• 27:12
  Speaker 1: Let's time travel back to the beginning this podcast. You
• 27:15
  Speaker 1: do it all over again and start over. How do
• 27:17
  Speaker 1: you know he didn't? Maybe we did this time? Yeah, yeah,
• 27:23
  Speaker 1: the second thing. We went back and we made this
• 27:25
  Speaker 1: podcast so funny. You should have seen the first time
• 27:29
  Speaker 1: we have recorded with and the first time we listened
• 27:31
  Speaker 1: to this podcast. Oh my god, you're groaning out loud
• 27:35
  Speaker 1: like Daniel in the theater. Do you have a question
• 27:41
  Speaker 1: you wish we would cover. Send it to us. We'd
• 27:44
  Speaker 1: love to hear from you. You can find us on Facebook, Twitter,
• 27:47
  Speaker 1: and Instagram at Daniel and Jorge One word or email
• 27:51
  Speaker 1: us to feedback at Daniel and Jorge dot com.