Speaker 1: Hey, Daniel, have you been watching the latest Marvel movies
Speaker 1: and TV shows?
Speaker 2: Hmmm, I hope you're not going to ask me about
Speaker 2: the physics of it. Oh.
Speaker 1: I wasn't going to ask you about time travel and Loki. Mm.
Speaker 2: But now you're not well.
Speaker 1: Here in your reaction. I think I have to travel
Speaker 1: back in time now and maybe think of another question.
Speaker 2: See, that's the problem. If you had done that, we'd
Speaker 2: never be having this conversation.
Speaker 1: Oh well, maybe it depends on which branch of the
Speaker 1: timeline we're on.
Speaker 2: No, my god, there are no branches too timelines. Oh
Speaker 2: my gosh.
Speaker 1: Or maybe I did go back in time and this
Speaker 1: is a better outcome than the one that I originally
Speaker 1: pitched to you. This might be the best timeline where
Speaker 1: that could be.
Speaker 2: Then I'm disappointed in the multiverse.
Speaker 1: Maybe you just don't know how much worse it could be.
Speaker 2: If this is the best it gets, then it must
Speaker 2: get pretty bad.
Speaker 1: It's like you maybe need to switch to the DC universe.
Speaker 3: Hi.
Speaker 1: I'm Jorge Made, cartoonist and the author of Oliver's Great
Speaker 1: Big Universe.
Speaker 2: Hi I'm Daniel. I'm a particle physicist and a professor
Speaker 2: at UC Irvine and I can mostly read science fiction
Speaker 2: without being grumpy mostly.
Speaker 1: What percentage would you say is your grumpiness level when
Speaker 1: you're reading science fiction.
Speaker 2: There is a spot on the wall across the bedroom
Speaker 2: where the books usually land when I throw them in frustration.
Speaker 1: I'll just say that there's a dent there, more like.
Speaker 2: A mark, but yeah, there's a physical impression left.
Speaker 1: Have you actually thrown a book?
Speaker 2: Oh many?
Speaker 1: Yes, no way. Wow, that's a strong reaction.
Speaker 2: It's just so disappointing when they set you up for something,
Speaker 2: they have some interesting ideas, and then they can't even
Speaker 2: be consistent, or they just write stuff that doesn't make sense.
Speaker 2: It's just frustrating because it makes me think about what
Speaker 2: it could have been.
Speaker 1: Oh man, But you're not angry at the physics, because
Speaker 1: I imagine the physics is all made up in science
Speaker 1: fiction to some degree. You're more frustrated with the storytelling
Speaker 1: or the logic of the story.
Speaker 2: Well, it's all tied together, right, of course, the physics
Speaker 2: is made up. It's science fiction. After all. They can
Speaker 2: have fictional science, but it's still science. They got to
Speaker 2: stick to it. If they're going to tell a story,
Speaker 2: they got to follow the rules. Otherwise, if there are
Speaker 2: no rules. It's hardly an interesting story.
Speaker 1: Now, after you throw the book, do you go and
Speaker 1: pick it up and finish it anyways or do you
Speaker 1: leave it there on the pile?
Speaker 2: It depends on what's on the top of the two
Speaker 2: read pile.
Speaker 1: I suppose you're not like a complete is like some
Speaker 1: people when they start a book, they have to finish it.
Speaker 2: Oh no, I don't finish most books.
Speaker 1: Oh interesting. Have you ever thrown a podcast at the wall?
Speaker 2: No, I've never thrown podcasts at the wall. I've just
Speaker 2: paused them.
Speaker 1: Although it does feel like this podcast is just us
Speaker 1: throwing things in the wall to see what sticks.
Speaker 2: No, this is us trying to explain physics to everybody
Speaker 2: out there listening.
Speaker 1: Well anyways, Welcome to our podcast, Daniel and Jorge Explain
Speaker 1: the Universe, a production of iHeartRadio.
Speaker 2: Where we do our best not to frustrate you into
Speaker 2: throwing your phone or computer or car across the wall,
Speaker 2: whatever device you're using to listen to us. We want
Speaker 2: to take you on a tour of everything that we
Speaker 2: understand in the universe and everything that we don't. We
Speaker 2: want to explain to you our vision of how the
Speaker 2: universe works from the tiniest little, itty bitty bits, all
Speaker 2: the way up to the biggest monster black holes. We
Speaker 2: think the universe does make sense, can be made sense of,
Speaker 2: and we want desperately to explain all of it to you.
Speaker 1: That's right. The universe we live in is not science fiction.
Speaker 1: It is science period science reality, and so we all
Speaker 1: have questions about how it works while we're here and
Speaker 1: what happens when you throw a bunch of books at
Speaker 1: a wall.
Speaker 2: Science reality. I like how you just renamed the whole
Speaker 2: nonfiction job. It's a better name, though.
Speaker 1: Yeah, science reality. There you go. Well, they have like
Speaker 1: reality TV, why not have reality science?
Speaker 2: Yeah? I don't want to be lumped in with reality TV. Actually, hey,
Speaker 2: the problem with nonfiction is you're defining it by what
Speaker 2: it isn't instead of what it is. Right.
Speaker 1: Oh yeah, yeah, nobody wants to be a non anything.
Speaker 2: I don't not want to be that.
Speaker 1: You don't want to be a nonconformist. Science trail blazing,
Speaker 1: that's your job, basically. How about reality trail blazing.
Speaker 2: Exploring the dense underbrush of reality, hacking our way through
Speaker 2: the jungles of truth.
Speaker 1: Yeah, that could be a nice show, like on Netflix,
Speaker 1: like Big science where you put a bunch of physicists
Speaker 1: in one house with a large particle collider and you
Speaker 1: see what happens every week They have to vote a
Speaker 1: physicists off.
Speaker 2: Or maybe they have to vote a physicist into the collider.
Speaker 1: Oh my goodness. That is both good and horrifying.
Speaker 2: Probably good TV. Yeah, yeah, yeah.
Speaker 1: It's like squid games exactly, h squid physics games, science game,
Speaker 1: science games. Yeah, there you go, particle games.
Speaker 2: But science isn't just a game. It's a serious effort
Speaker 2: to understand the universe, and that's what we try to
Speaker 2: do in our jobs. We try to do on this podcast,
Speaker 2: and we also encourage you to do because you can
Speaker 2: also pick up a machete and help us hack through
Speaker 2: the jungles of truth to understand the universe just by
Speaker 2: thinking like a physicist, which means just being curious and
Speaker 2: not settling for not understanding. There's too many knots there, huh.
Speaker 2: I should define it in terms of positives demanding sufficient explanations.
Speaker 2: And when you don't understand something about the universe, we
Speaker 2: want you to write into us share your question because
Speaker 2: probably somebody else out there has the same thought.
Speaker 1: I don't know if that was better. I'm a little
Speaker 1: nonplussed about it.
Speaker 2: I'm pretty plussed.
Speaker 1: Well, let's plus it, let's plus it some more.
Speaker 2: I might even be multiplied it. But I don't want
Speaker 2: to divide us over it.
Speaker 1: But yeah, science is a game, and it all starts
Speaker 1: with questions. The whole journey of sign starts with looking
Speaker 1: at the world around as I'm wondering, why is it
Speaker 1: like that? How does it work? And what would happen
Speaker 1: if I throw this at the wall.
Speaker 2: So you can either throw that thing at the wall,
Speaker 2: or you can just write to us with your question
Speaker 2: and we'll do our best to answer it. We answer
Speaker 2: every question we get from listeners. Just write to us
Speaker 2: to questions at Danielandjorge dot com. And some of the
Speaker 2: questions we think other people might want to hear the
Speaker 2: answers to, and so we select them to answer on
Speaker 2: the podcast.
Speaker 1: So today on the podcast, we'll be tackling listener questions
Speaker 1: number fifty one, Oh boy, listener questions in that over
Speaker 1: middle eight.
Speaker 2: That's right, we're rounding up to one hundred now it's
Speaker 2: fifty plus. We're going to get senior citizen discounts pretty soon,
Speaker 2: starting dinner at three pm that's right.
Speaker 1: Yeah, yeah, the discounts oh man, does that mean we
Speaker 1: have to give shorter answers.
Speaker 2: I'm not going to offend our senior listeners by suggesting
Speaker 2: that they can't comprehend long complex answers.
Speaker 1: No, I'm just saying, you know, your appetite goes down
Speaker 1: as you age.
Speaker 2: Oh, I see smaller meals. I don't know what I'm saying,
Speaker 2: more top us, maybe more top us.
Speaker 1: Yeah, there you go, more variety, because let's face it,
Speaker 1: the time is running out for those of us.
Speaker 2: Over fifty, unless you live near the vicinity of a
Speaker 2: black hole, in which case time is slowing down for
Speaker 2: others but not for you. Yeah, but relatively for you.
Speaker 2: You see everybody else living really fast.
Speaker 1: Well, let's try to get through these questions as fast
Speaker 1: as we can then.
Speaker 2: And the first one is actually about time. Yeah.
Speaker 1: Yeah, we have some awesome questions here today about the
Speaker 1: speed of light near a black hole, about quantum entanglement,
Speaker 1: and also about possible time travel. Pretty awesome questions from people, Daniel.
Speaker 1: Do these questions make you smile when you get them?
Speaker 2: All the questions make me smile. I love that ding
Speaker 2: when I get a question in the listener inbox and
Speaker 2: lets me take a break from whatever else I'm doing
Speaker 2: and think about physics.
Speaker 1: But way you were thinking about physics before, So your
Speaker 1: break from physics is to think about physics.
Speaker 2: Mostly I was thinking about spreadsheets and email every job spreadsheets, email.
Speaker 1: And grants and grand proposals, budgets. Oh I see. So
Speaker 1: then do you actually get to think about physics?
Speaker 2: Yeah, exactly. Yeah.
Speaker 1: What if your grand students send you a question about physics,
Speaker 1: is that the flatter or the former situation? No comment
Speaker 1: depends on the student. Actually is it an involved spreadsheet
Speaker 1: or a budget question?
Speaker 2: Depends Maybe their question is, hey, are you funding me
Speaker 2: next quarter? Or their question is like, how do we
Speaker 2: do anomally detection in this space of multiple tracks? You know,
Speaker 2: depends on and they're asking.
Speaker 1: I see, and one of those is good and the
Speaker 1: other one is bad. Is that they're different, they're different different.
Speaker 1: I see.
Speaker 4: You are.
Speaker 1: All right? Well, we have some awesome questions here to
Speaker 1: the answer. Let's just jump right in. Our first question
Speaker 1: comes from Nathan from Seattle.
Speaker 3: Hey, Danieline Horay, my name is Nathan Ramon from Seattle, Washington,
Speaker 3: and I have a question for y'all. I was watching
Speaker 3: ant Man last week, and it occurred to me that
Speaker 3: they are so small in that movie, right, that the
Speaker 3: speed of light might actually act a little bit differently.
Speaker 3: They're so small at that point that if the universe
Speaker 3: is still reacting, like still has the speed of light
Speaker 3: at the same rate, which it might not necessarily. They
Speaker 3: do talk a lot about how they're outside of space and.
Speaker 5: Time, but if it has that same speed limit, if
Speaker 5: you're so much smaller, it would make it feel to
Speaker 5: me like White was going way way faster. Sorry from
Speaker 5: my ramblem, let me know if you need clarification on that,
Speaker 5: and thanks for all you guys. Do I love your podcast?
Speaker 1: All right? Awesome question from Nathan, a Marvel fan. It
Speaker 1: seems well he didn't say whether he liked those movies.
Speaker 1: He just as he watched them and he had a
Speaker 1: small opinion about at Man.
Speaker 2: Well, the cool thing is he was watching it and
Speaker 2: he was thinking about the physics of it, like, does
Speaker 2: this make sense? How would this work? What would it
Speaker 2: actually be like to be that small? Would the experience
Speaker 2: of it be based on the phil principles of the universe?
Speaker 1: Have we done an episode on the physics of the
Speaker 1: Marvel movies? I feel like we talk about them all
Speaker 1: the time, but have we done like a whole dedicated
Speaker 1: episode to it.
Speaker 2: M Is there any physics of the Marvel movies or is.
Speaker 1: It always it's science fiction?
Speaker 2: Daniel, It's fiction, for sure.
Speaker 1: But the an Men movies are pretty good. The first
Speaker 1: one was really good, the second one was maybe not
Speaker 1: as good, and the there one was not as good,
Speaker 1: but overall it's sort of a charming character.
Speaker 2: Yeah. And I saw the first one. I enjoyed it.
Speaker 2: And the visit to the quantum Realm I thought was
Speaker 2: visually very creative. I thought the way they displayed it
Speaker 2: was very cool, very different from your standard depictions. So
Speaker 2: it was a lot of fun. I enjoyed it.
Speaker 1: Did I tell you I know the guy who came
Speaker 1: up with the term the quantum realm?
Speaker 2: Oh wow?
Speaker 1: Yeah, my friend Spiris mcglaucus. He's a physicist and he
Speaker 1: consulted for Marvel, and one day he was giving them
Speaker 1: a little spiel in the conference room and he's like,
Speaker 1: things are very different in the quantum realm, and they're like,
Speaker 1: we like that, that's in the script.
Speaker 2: Oh quantum reil.
Speaker 1: Yeah, he kind of has mixed feelings about what they've
Speaker 1: done with the ter and the whole idea of quantum physics.
Speaker 1: But it's pretty cool that he had that contribution.
Speaker 2: The lesson is be careful what you say around writers.
Speaker 1: That's right. Yes, we cannot be trusted with the innermost
Speaker 1: secrets or emotions or physics. But yeah, Nathan has an
Speaker 1: interesting question. His question is does the speed of light
Speaker 1: seem faster if you're smaller? So, if you were small,
Speaker 1: I guess at the level of ant man, does it
Speaker 1: mean that you see light move faster for you?
Speaker 2: Yeah? I think this is a really interesting question because
Speaker 2: it makes us think about the speed of light and
Speaker 2: the impact on physics, sort of the big and the small,
Speaker 2: and the way that I think about the speed of light,
Speaker 2: I think the way most physicists do, is that it's
Speaker 2: like a ratio between space and time. It's like a
Speaker 2: conversion between meters and seconds. Like meters is a measurement
Speaker 2: of distance, seconds is the measurement of time. And the
Speaker 2: fact that the universe has this number, this maximum speed
Speaker 2: tells you a relationship between space and time and tells
Speaker 2: you how to convert a huge distance into a time,
Speaker 2: and we're often doing that. Like the phrase a light
Speaker 2: year tells you how far light will go in a year.
Speaker 2: It sounds kind of like a unit of time, but
Speaker 2: it's actually distance. You've taken time, you're multiplied by the
Speaker 2: speed of light, and you've gotten a distance.
Speaker 1: It's like a measurement that you get by dividing distance
Speaker 1: divided by time. But does it really tie those two
Speaker 1: concepts together, like at a fundamental you know, physics level,
Speaker 1: because like, you know, you can talk about the speed
Speaker 1: of whorehet down the track that, like my speed is
Speaker 1: a speed that you can measure and compute, but it
Speaker 1: doesn't really tell you anything except how out of shape
Speaker 1: I am.
Speaker 2: Yeah, Also, the speed of foregete probably changes as a
Speaker 2: function of time in the universe.
Speaker 1: And how much chocolate you have, yeah, how many bananas
Speaker 1: of eaten?
Speaker 2: But the speed of light really does play a deep
Speaker 2: role in physics, and it really serves that purpose of
Speaker 2: converting between space and time. You know, we often talk
Speaker 2: about like space time being a four dimensional object with
Speaker 2: the original three dimensions of space and this worth dimension
Speaker 2: of time. But there's a subtle thing there we don't
Speaker 2: often talk about, which is that when we include times
Speaker 2: fourth dimension, we usually multiply it by the speed of light.
Speaker 2: So the four dimensions are actually like xyz and then ct,
Speaker 2: not just time because we want to convert it to
Speaker 2: effectively a distance.
Speaker 1: Right, Well, you do have to keep the units consistent.
Speaker 1: But like, for example, if we had a different speed
Speaker 1: of light in our universe, you know, things would be different.
Speaker 1: The physics of the universe would be different, but would
Speaker 1: space itself and would time itself be different.
Speaker 2: They would be the same, but their relationship would be different.
Speaker 2: That's what the speed of light is. It's a ratio
Speaker 2: a relationship between these two different kinds of measurements. Yeah, fundamentally,
Speaker 2: it really is telling you how these two things relate.
Speaker 1: H all right, Well, to answer Nathan's questions, let's say
Speaker 1: I shrink down. Let's say I'm at man or the
Speaker 1: wasp and I shrink down. Is the speed of lighting?
Speaker 1: It seemed faster for me? Like if I measure the
Speaker 1: speed of light, that's scale isn't going to seem faster.
Speaker 1: Or like if I shine a flashlight will do somehow
Speaker 1: the flash light seem quicker or brighter or something.
Speaker 2: Yeah, the speed of light is going to be the
Speaker 2: same because it's the same ratio between distances and times. Right,
Speaker 2: So you measure the speed of light. Using a tiny
Speaker 2: little experiment or a huge experiment, you're going to get
Speaker 2: the same answer. But if you think of the speed
Speaker 2: of light as a ratio between distance and time, what
Speaker 2: it means is that everything seems faster when you're small.
Speaker 2: Like basically, shorter distances mean shorter times. Things that are
Speaker 2: smaller can happen faster than things that are bigger.
Speaker 1: So like, for example, if you not just shrink me,
Speaker 1: but I use shrink the whole Earth, then for example,
Speaker 1: light can go around the Earth many more times per second.
Speaker 2: Yeah, exactly. Or if let's say you build a machine
Speaker 2: like a computer or even a mechanical device to do something,
Speaker 2: if it's smaller, it can finish faster than if it's huge.
Speaker 2: The bigger it is, the longer it'll take to finish,
Speaker 2: because there's this maximum speed limit. And that's why, like
Speaker 2: the speed of light seems really really fast to us
Speaker 2: here on Earth, is this crazy high number. It's basically
Speaker 2: irrelevant to our experience. It's because things that are almost instantaneous.
Speaker 2: But imagine if you are a brain made of like stars,
Speaker 2: you're like a galaxy size brain, it would take like
Speaker 2: one hundred thousand years to even have a thought.
Speaker 1: But then your thinking would be slower, so your cognition
Speaker 1: or your perception of time would be slower. So I
Speaker 1: think maybe Nathan's question I wonder is whether time will
Speaker 1: seem to be going faster or maybe it will seem
Speaker 1: to be the same, right, Because like, if I'm the
Speaker 1: size of a galaxy, my thoughts are going to be
Speaker 1: super slow. And so even though any effect I'm in
Speaker 1: the sea is going to be super slow because with
Speaker 1: the distances, my thoughts are going to be slow. And
Speaker 1: so therefore the experience of being that person is going
Speaker 1: to be the same as our experience here on Earth.
Speaker 2: Yeah. I think there's a few things there to disentangle,
Speaker 2: but basically you're right. Number one, if you measure the
Speaker 2: speed of light, you're going to get the same number.
Speaker 2: It doesn't matter if you're a galaxy brain or an
Speaker 2: ant brain, right, as long as you do it correctly,
Speaker 2: you're going to get this same number. Number two, things
Speaker 2: do seem to happen faster when you're smaller because you're
Speaker 2: just not as limited by this speed of light. Things
Speaker 2: have shorter distances to cross in order to accomplish some
Speaker 2: thinking or some task or whatever. Number three, Finally, we
Speaker 2: don't really know what it would be like to experience
Speaker 2: that what it seemed like time goes faster. We don't
Speaker 2: understand our experience of time or why we seem to
Speaker 2: experience it at you know, one second per second. So
Speaker 2: I don't know what it would be like to be
Speaker 2: a galaxy brain. They might have the same kind of
Speaker 2: subjective experience we do.
Speaker 1: Yeah, Or like thinking about the shrinking case, like if
Speaker 1: I shrink down to enman size, now my brain is smaller,
Speaker 1: Like the distances between my neurons are smaller, and so
Speaker 1: maybe my thinking will be sort of like hypercharge. Yeah,
Speaker 1: like I'll have a million of thoughts in the same
Speaker 1: amount of time that it used to take me to
Speaker 1: have one thought, and so I'll be sort of super
Speaker 1: bored looking at the bigger world, but looking at the
Speaker 1: small world, maybe it'll just seem like the same regular
Speaker 1: because things are moving faster. But I'm also like having
Speaker 1: a bazillion more cycles in my brain than I did before.
Speaker 2: Yeah, exactly, So we don't know what the experience would
Speaker 2: be like. This is an interesting wrinkle of evolutionary biology.
Speaker 2: There also which is wondering, like could humans be smarter?
Speaker 2: You can imagine being smarter by having like a bigger
Speaker 2: brain more neurons, but then it's harder to get that
Speaker 2: brain through the birth canal. You could also imagine getting
Speaker 2: smarter by having more neurons by making the neurons smaller.
Speaker 2: But I was reading a paper that said that if
Speaker 2: neurons got any smaller, they would be noisier, like more
Speaker 2: randomness and fuzz so it might not actually add computing power,
Speaker 2: So we might be at like the sweet spot of
Speaker 2: like the densest neuronal systems.
Speaker 1: Well, the other thing to consider is that neurons work
Speaker 1: by bioelectricity, right, biochemistry, not necessarily by like transmitting electrons. Right.
Speaker 1: It all depends on sort of reactions and electric fields
Speaker 1: and like molecules moving in and out of the little
Speaker 1: cell walls.
Speaker 2: Yeah, exactly, if you could actually shrink all that stuff,
Speaker 2: it would happen faster. Of course, you know, the physics
Speaker 2: wouldn't work if you shrink all that stuff because all
Speaker 2: the numbers would change. So the fundamental physics of ant
Speaker 2: Man is silly because you know, if he's shrunk down
Speaker 2: the size of an electron, then how big are his electrons? Right?
Speaker 1: Right, So basically we get into the fuzzy area of
Speaker 1: like perception and the subjective experience. But generally speaking, I
Speaker 1: think from a physics point of view, if you were
Speaker 1: down to the size of ant man, the light would
Speaker 1: sort of seem to travel faster, right, Like it would
Speaker 1: go one body length in a much shorter amount of
Speaker 1: time than it would go at our size.
Speaker 2: Yeah, your body would be shorter, so light would go
Speaker 2: across you faster, and I think a lot of things
Speaker 2: would happen faster. I don't know how he can say
Speaker 2: what it would be like though, to experience it.
Speaker 1: I wonder if it would be even that different, Like
Speaker 1: what's the difference between almost intustanious and almost almost instaneous.
Speaker 1: Maybe the difference is not that great, or maybe he's
Speaker 1: thinking about it, like when admin goes down to like
Speaker 1: the quantum size.
Speaker 2: Yeah, but as you say, distances are already so small
Speaker 2: compared to the speed of light, then our experience is
Speaker 2: very difficult to even tell that it's not instantaneous. It
Speaker 2: took people a long time to be able to devise
Speaker 2: experiments to measure the speed of light. That to be
Speaker 2: very very clever, because it's so blazingly fast compared to
Speaker 2: the distances in which we live. If you realize galaxy
Speaker 2: brain and then you got shrunk down to ant man,
Speaker 2: that might be more dramatic.
Speaker 1: Yeah, Or I wondered maybe the equivalent conversion is like,
Speaker 1: let's say you and I are living in our everyday
Speaker 1: lives here, but suddenly the speed of light goes up
Speaker 1: by a factor of ten. Let's say it was now
Speaker 1: three million kilometers per second. Would we even notice a difference.
Speaker 2: We wouldn't notice the difference here on Earth, but suddenly
Speaker 2: the rest of the universe would effectively be closer to us.
Speaker 2: You know, we could see things happening faster, We could
Speaker 2: get places faster. The size of a galaxy would effectively
Speaker 2: seem smaller.
Speaker 1: Well, seem smaller, No, it'll still be the same distance.
Speaker 1: We would just see it sooner.
Speaker 2: Yeah, like our information bubble would be larger. The distance
Speaker 2: over which things appear to happen instantaneously would be bigger.
Speaker 1: Maybe see further out or or I guess what we
Speaker 1: see would be more up to date, Yeah.
Speaker 2: More recent exactly. The time lag would no longer be
Speaker 2: noticeable for things that are close to us. Is to
Speaker 2: look even further out to notice that time lag?
Speaker 1: Well, I feel like they're not even noticeable. Now, like
Speaker 1: I can tell the difference between a billion year old
Speaker 1: star and a million year.
Speaker 2: Old star, astronomers can All.
Speaker 1: Right, well, I think that answer is a question, which
Speaker 1: is that the speed of light would not be different,
Speaker 1: but maybe your experience of it would be different. All right, Well,
Speaker 1: thanks for that question, Nathan. Let's get to our other questions.
Speaker 1: We have one here about quantum entanglement and time travel,
Speaker 1: so we'll get to those, but first let's take a
Speaker 1: quick break. All right, we're answering listener questions here today,
Speaker 1: and our next question is about quantum entanglement.
Speaker 4: How to Daniel question for you? Assume we know particle
Speaker 4: A and the particle B are entangled, and for simplicity's sake,
Speaker 4: let's say the states are positive or negative, and there's
Speaker 4: a fifty to fifty chance. Now, what would happen if
Speaker 4: two independent observers we can call them A and B
Speaker 4: for their respective particles, observed these two particles at the
Speaker 4: exact same time. This question really breaks my brain. The
Speaker 4: more I think about it, the less I feel like
Speaker 4: I understand special relativity, and the less I feel like
Speaker 4: I understand quantum mechanics. And adding to their question, is
Speaker 4: it even possible to make two observations with two observers
Speaker 4: at the same time. I really appreciate it. Thanks for
Speaker 4: helping me understand.
Speaker 1: All right, Well, that's quite a mindful of a question here.
Speaker 1: And Daniel, I notice he asked a question of you,
Speaker 1: not me, So I think I can just sit this
Speaker 1: one out because honestly, I don't understand the question. I'm
Speaker 1: a bit entangled in the whole flurry of words.
Speaker 2: You felt like some of the other physics questions were
Speaker 2: aimed towards you.
Speaker 1: The last one did say Daniel and Jorge, I think
Speaker 1: I was one of the targets. And sometimes they say hey,
Speaker 1: guys plural, so it does mean the two of us.
Speaker 2: Well, I think he's also counting on you to help
Speaker 2: me translate my understanding into something.
Speaker 1: Ever, no, no, no, I feel snubbed, So I'm not
Speaker 1: even gonna chime in.
Speaker 2: I'm gonna do my best, but I'm pretty sure you're
Speaker 2: going to have a hard time not interrupting.
Speaker 1: What are you trying to say?
Speaker 2: What are you trying to say? It's your job and
Speaker 2: you do it beautifully, man.
Speaker 1: What are you trying to say? Daniel? Did I interrupt you?
Speaker 2: Yes, exactly.
Speaker 1: All right, So what is the question? I know it's
Speaker 1: about quantum entanglement, but it didn't quite get the gist
Speaker 1: of it.
Speaker 2: Yeah, so the question is about quantum entanglement and special
Speaker 2: relativity and how these two things come together. But let's
Speaker 2: start just with the basic issue of quantum entanglement, which
Speaker 2: is weird enough, right. Quantum entanglement says what happens if
Speaker 2: you have two particles that are like the output of
Speaker 2: a single process. Something makes two particles, and so their
Speaker 2: fate is connected. Like let's say you have two electrons created,
Speaker 2: and one has to be spin up and one has
Speaker 2: to be spinned down because of the way they're made.
Speaker 2: The universe doesn't care which one is spin up and
Speaker 2: which one is spin down as long as they point opposite. Now,
Speaker 2: if you take those two particles and you send them
Speaker 2: different directions, they're now far apart. Quantum entanglement says that
Speaker 2: they're still somehow connected, that their fates are joined, And
Speaker 2: so if you measure one to be spin up, you
Speaker 2: now know the other one is spin down. But it's
Speaker 2: more than just like knowing that they have to be opposite.
Speaker 2: Quantum entanglement tells us that they're actually not determined that
Speaker 2: neither one is spin up or spin down. They both
Speaker 2: have that possibility, and that as soon as you measure one,
Speaker 2: then the fate of the other one is determined. That's
Speaker 2: a weird bit about quantum entanglement.
Speaker 1: Oh wait, you want me to jump in now you're
Speaker 1: going to interrupt. Yeah, So that's the basic of entanglement, right,
Speaker 1: Like you have two quantum things, like a particle or
Speaker 1: an atom or some sort of quantum object, and it's fuzzy,
Speaker 1: you don't know what it actually is inside. But if
Speaker 1: two of them have some sort of shared history, some
Speaker 1: sort of shared origin that ties them together, that's what
Speaker 1: quantum intalgent and guildment is.
Speaker 2: That's right, there's some correlation between them that's created locally
Speaker 2: when they're like both made and sent apart, but then
Speaker 2: the correlation persists as they get further and further apart.
Speaker 2: And again, this is not a scenario where one of
Speaker 2: them actually is spin up and the other one actually
Speaker 2: is spin down and we just don't know. We've proven
Speaker 2: through a whole complicated series of experiments suggested by John Bell,
Speaker 2: that they actually are undetermined until you measure. So the
Speaker 2: weird bit and the thing that makes it hard to
Speaker 2: reconcile with special relativity is that, apparently this happens instantaneously.
Speaker 2: You have these two particles that have a shared face,
Speaker 2: but they're both undetermined. Now you send them like five
Speaker 2: kilometers apart, you measure one of them, you get to
Speaker 2: spin up instantly. The other one has to be spinned down.
Speaker 2: It went from I don't know, maybe up or down
Speaker 2: to has to be down instantaneously across space and.
Speaker 1: Time, right, which that first glance seems to violate the
Speaker 1: speed of light. Right, because something changed in one part
Speaker 1: of the universe, and then it suddenly costs something else
Speaker 1: to change in another part, seemingly instantaneously.
Speaker 2: Exactly what you said is important. You said it violates
Speaker 2: the speed of light, and that's correct. This is something
Speaker 2: that happens faster than the speed of light. Speed of
Speaker 2: light says is a limit to how fast things can
Speaker 2: happen across the universe. This is instantaneous, but doesn't actually
Speaker 2: break special relativity because you're not sending information faster than
Speaker 2: the speed of light. Like the quantum state is non local,
Speaker 2: It stretches over space and collapses instantaneously. The whole thing
Speaker 2: at the same time, but you can't actually use that
Speaker 2: to send information. Are often writing in and saying, well,
Speaker 2: can't I send information by making a measurement and the
Speaker 2: other person's going to see that theirs is now collapsed.
Speaker 2: You can't actually tell when your probabilities have collapsed. All
Speaker 2: you can do is measure or not measure. When you
Speaker 2: measure your particle, you don't know if it was already
Speaker 2: collapsed or if you're collapsing it by measuring it.
Speaker 1: Right. Also, when you collapse one of them, it's not
Speaker 1: like you're sending that information to the other person. Like
Speaker 1: let's say we entangle to particles. I have one, and
Speaker 1: when we split up a part I have one, you
Speaker 1: have one. If I open mind, I measure it and
Speaker 1: I see it that for example, it's up, and I
Speaker 1: know that yours is down. Like I know something about
Speaker 1: your particle, But that doesn't mean you know that about
Speaker 1: your particle. Like to you over there in Irvine, your
Speaker 1: particle is still this quantum object that could be fifty
Speaker 1: percent up or down. So like, no information is actually
Speaker 1: traveled unless I send you an email, which would then
Speaker 1: be limited by the speed of light exactly, and or
Speaker 1: my sale signal exactly. And if I still have my
Speaker 1: particle in the box, you measure yours. I can't tell,
Speaker 1: well if you've measured yours, like mine doesn't look any
Speaker 1: different if I'm not measuring it, I'm just waiting to
Speaker 1: measure it. I don't know if you've measured yours or not.
Speaker 1: I can't tell that you have measured it. So it's
Speaker 1: like information about something far away has been revealed to
Speaker 1: me instantaneously, But that doesn't mean that information actually got
Speaker 1: transmitted from one place to the other.
Speaker 2: Yeah, exactly.
Speaker 1: So then what's the actual question here?
Speaker 2: So the question is what happens we measure them at
Speaker 2: the same time. Who collapses the wave function? Mmmm?
Speaker 1: So we each have a particle that's been entangled the
Speaker 1: other and we open it at the same time, nothing happens.
Speaker 2: Right, Well, this is a really interesting question.
Speaker 1: Like you'll find that you'll find yours up and I'll
Speaker 1: find my down, or I'll find mine up and you'll
Speaker 1: find yours. Now that's all that really happens, is it.
Speaker 2: Yeah? I love your answer, and you're right from the
Speaker 2: point of view of like what we experience. You open
Speaker 2: your box, you measure it up or you measure it down.
Speaker 2: But I think what he's asking is, like, what's happening
Speaker 2: behind the scenes? You know, what is the wave function doing?
Speaker 2: Even if we can't observe it and can't measure it
Speaker 2: and can't ever know what in theory is the explanation
Speaker 2: for how this happens. And I think there's touching on
Speaker 2: a deeper question, which is about simultaneity. We talked on
Speaker 2: the podcast how special relativity tells us that at the
Speaker 2: same time is a fuzzy concept. Two events could occur
Speaker 2: at the same time for one person, but not for
Speaker 2: somebody else if they have a different velocity or different
Speaker 2: location in space. And so this seems very fuzzy all
Speaker 2: of a sudden, like two people measure the wave function
Speaker 2: at the same time, what happens to that wave function?
Speaker 2: And what happens according to somebody flying by in a
Speaker 2: spaceship at nearly the speed of light?
Speaker 1: So then what's the answer for our question? Asker?
Speaker 2: So the best answer to the way you just gave,
Speaker 2: which is this is not a physical problem.
Speaker 1: This is only I answered the question even though he
Speaker 1: didn't ask me, I'm the one who ended up answering.
Speaker 2: You answered it. In the classical dismissive way, which is like,
Speaker 2: it doesn't matter. It's just a philosophy question about what's
Speaker 2: happening to the wave function. It's not a question.
Speaker 1: I mean, I was being pejorative maybe.
Speaker 2: But it's true though it's an important distinction. We know
Speaker 2: what would happen. I measure mine, you measure yours done,
Speaker 2: it doesn't really matter, right, But the question is what's
Speaker 2: happening behind the scenes, which is a philosophical question about
Speaker 2: something we may never be able to know, like what
Speaker 2: is the wave function really? And there's whole philosophical debates
Speaker 2: about whether the wave function is just a mathematical tool
Speaker 2: we use to make these calculations, or if it's a
Speaker 2: real physical thing in the universe. And so there's long
Speaker 2: answer is it depends on what you think the wave
Speaker 2: function is. It depends on your philosophical interpretation of quantum mechanics.
Speaker 2: And we can walk through a few of those examples.
Speaker 1: Like is there a wave function that physically connects my
Speaker 1: particle to your particle or is the wave function just
Speaker 1: some mathematical tool we used to explain things when things
Speaker 1: are not far apart. Yeah, and then when you split them,
Speaker 1: maybe actually you get two wave functions or maybe there's
Speaker 1: no such thing as a physical common wave.
Speaker 2: Function, or maybe there are many wave functions, or maybe
Speaker 2: the wave function never collapses. Now in the standard interpretation
Speaker 2: of quantum mechanics, which I'll say up front is nonsense,
Speaker 2: the Copenhague interpretation, which doesn't work and is deeply flawed,
Speaker 2: but it's still the one most people think about and
Speaker 2: is most often taught. In that interpretation, the wave function
Speaker 2: is a thing, and it's real, and before you measure something,
Speaker 2: it allows for multiple possibilities, like the wave function says
Speaker 2: you might be up and you might be down. And
Speaker 2: then when you make a measurement with a classical object
Speaker 2: where classical object is not defined, just something big, then
Speaker 2: it collapses and it chooses one of these options. And
Speaker 2: I think it's in that scenario that the question is asking,
Speaker 2: like number one, what happens if two people make the
Speaker 2: measurement at the same time, who collapses it? And then
Speaker 2: what happens to an observer flying by the speed of light?
Speaker 2: The answer is sort of nonsense. Like number one, if
Speaker 2: two people make your measurement at the same time, well,
Speaker 2: you can't do that in Copenhagen interpretation because you can
Speaker 2: only make one measurement on a wave function at a time.
Speaker 2: It's just not allowed because making a measurement changes the
Speaker 2: wave function, and you have to do them in sequence.
Speaker 2: That's why it's like important whether you're measuring position or
Speaker 2: momentum first, or momentum and then position, because every measurement
Speaker 2: change is a wave function. There's no way to even
Speaker 2: describe making two measurements at the same time.
Speaker 1: I see, well, if there is sort of like a
Speaker 1: physical wave function connecting my particle to your particle, then
Speaker 1: you do sort of get the sense of that there
Speaker 1: is a shared now.
Speaker 2: But even though it's quantum mechanical, unless you're gonna pixelate time,
Speaker 2: time itself is infinitely divisible, So saying you're making two
Speaker 2: measurements at the same time would mean you're like exactly
Speaker 2: matching those two moments.
Speaker 1: Meaning like maybe there's no way to know who collapsed
Speaker 1: it first unless we somehow sink clocks or something beforehand
Speaker 1: and then we compare clocks afterwards.
Speaker 2: But you'd have to sink them exactly perfectly to like
Speaker 2: an infinite number of digits, which seems impossible, right, And
Speaker 2: it gets even weirder if you ask, like what happens
Speaker 2: according to other observers, Like, what if I make my
Speaker 2: measurement and then ten seconds later you make your measurement,
Speaker 2: and now, in our frame of reference, I was first
Speaker 2: and you were second. But somebody flying by at the
Speaker 2: speed of light, they could your measurement happen first before
Speaker 2: mine because the order events is not guaranteed in special
Speaker 2: relativity depends on the observer.
Speaker 1: Interesting, So I think what you're saying is that in
Speaker 1: the quantum realm, at man would not know what time
Speaker 1: it is.
Speaker 2: I'm saying that this picture of the wave function collapsing
Speaker 2: and happening instantly across space in time, that picture itself
Speaker 2: doesn't really work in the Coponhagd interpretation. Imagine a more
Speaker 2: complex situation, for example, like an observer flying by and
Speaker 2: then changing directions and going the other way. As they
Speaker 2: change directions, their concept of what happens first when happens
Speaker 2: second changes, So you could arrange a trajectory where they're
Speaker 2: seeing me make my measurement first, and then later they
Speaker 2: see you make your measurement first because their velocity is changing.
Speaker 2: And in that scenario, the wave function collapses in one
Speaker 2: way and then uncollapses and recollapses in a different way,
Speaker 2: so like the whole picture becomes very confusing and it's
Speaker 2: kind of nonsensical, but it doesn't change anything physical. This
Speaker 2: is just philosophical and there are other philosophical approaches to
Speaker 2: quantum mechanics that don't have these issues that the Copenhagen
Speaker 2: interpretation has, and Copenhagen is already known to be nonsense
Speaker 2: because this division between like what is quantum and what
Speaker 2: is classical is not even defined or described.
Speaker 1: Well, it seems like kind of the main problem is
Speaker 1: that you're basically trying to put together general relativity and
Speaker 1: quantum mechanics, which, as we've talked about a million times
Speaker 1: in this podcast, like they don't really play well with
Speaker 1: each other, right, Like, quantum mechanics is kind of a
Speaker 1: local effect and general relativity things that happen over maybe
Speaker 1: big distances or big amounts of time, and it involves
Speaker 1: curature time and space, and so we don't really know
Speaker 1: how to marry those two.
Speaker 2: Well, I'm not sure we're getting into general relativity here.
Speaker 2: Really all these questions are about special relativity, and we
Speaker 2: do know how to marry special relativity and quantum mechanics
Speaker 2: into a theory. We have relativistic quantum mechanics, and we
Speaker 2: have quantum field theories, and those make predictions about all
Speaker 2: the measurements, and those all work. The philosophical underpinnings of
Speaker 2: what happens when you try to bring these two together
Speaker 2: is more complicated, and there people have a lot of disagreements.
Speaker 2: But what's going on behind the scenes.
Speaker 1: Well, I think maybe the basic conclusion is that I
Speaker 1: answered this question and even though I wasn't asked for you.
Speaker 1: All right, Well, let's get to our last question, which
Speaker 1: is about time travel, and the question people should think
Speaker 1: about during this break is do we already answer this
Speaker 1: question or are we going to answer it in the future.
Speaker 2: Or have we already answered it in the future?
Speaker 1: Yeah, or have we already asked this question about answering
Speaker 1: the question in the past?
Speaker 2: Have we already made every possible time travel check?
Speaker 1: Let's go back in time and make some more but
Speaker 1: first let's take a quick break. Or are we're answering
Speaker 1: listening to questions here today? And our last question of
Speaker 1: the day is about the past, the present, the future
Speaker 1: and whether we can move between them.
Speaker 6: Hey, guys, this is Trevor. I was recently listening to
Speaker 6: an episode of the podcast in which Daniel mentions that
Speaker 6: we have never observed anything that was moving backwards in time.
Speaker 6: My question is, how would we be able to identify
Speaker 6: whether an object we're observing was moving backwards in time?
Speaker 6: What characteristics would make backwards motion in time distinguishable to us?
Speaker 6: Are we sure we would even be able to observe
Speaker 6: a reverse time object while we are moving forward in time.
Speaker 6: I love what you guys do, and I sincerely appreciate
Speaker 6: you taking my.
Speaker 1: Question interesting question. I feel like this question relates to
Speaker 1: the movie Tenet. Have you seen that movie?
Speaker 2: I've seen that movie and I saw that. Christopher Nolan
Speaker 2: was like, people who try to understand Tenant are not
Speaker 2: really getting what I was after. Like, the movie just
Speaker 2: doesn't make sense.
Speaker 1: He's like, why are people throwing my movie at the wall?
Speaker 1: It's signs fiction people, It's.
Speaker 2: Not supposed to make sense, he says, as he presents
Speaker 2: and asks you to solve it.
Speaker 1: Like what, Yeah, It's all about the experience of the mystery, right.
Speaker 2: I'm not being a physicist. I'm just like experiencing the universe. Man,
Speaker 2: I'm not trying to fit it all together in my
Speaker 2: head in the way that makes sense. Yeah.
Speaker 1: Yeah, maybe your wall would be intact if he took
Speaker 1: that attitude more. But yeah, in the movie Tenet, they
Speaker 1: sort of figure out how to make something move backwards
Speaker 1: in time, Like they can make a bullet move backwards
Speaker 1: in time, and so even though we're moving forwards in time,
Speaker 1: the bullet is moving backwards in time. And at some
Speaker 1: point they make people move backwards in time.
Speaker 2: Right, I don't know. I went back in time and
Speaker 2: erased that movie from them, Right.
Speaker 1: I think that's the basic question that Trevor has here,
Speaker 1: which is like, could something move backwards in time? And
Speaker 1: would we know it's moving backwards in time?
Speaker 2: Yeah, it's a really cool question with a lot of
Speaker 2: interesting subtlety, depending exactly what you mean by move backwards
Speaker 2: in time, because there's a fundamental question we have about time,
Speaker 2: which is like why does it flow forward? If you
Speaker 2: look at the equations of physics, they seem to work
Speaker 2: just as well forwards and backwards. You know, for most things.
Speaker 2: If you took a video of them, and then you
Speaker 2: play the video forwards and you play the video backwards,
Speaker 2: the laws of physics would work just as well for
Speaker 2: both scenarios Like you're playing pool and you hit a
Speaker 2: ball and they bounce off each other. You could play
Speaker 2: that whole reaction backwards and the same thing would work
Speaker 2: according to the laws of momentum and all that kind
Speaker 2: of stuff.
Speaker 1: In like a perfect world, in a perfect bouncy ball
Speaker 1: that doesn't lose energy each time it bounces, like a
Speaker 1: bouncing ball moving forwards in time looked exactly like a
Speaker 1: bouncing ball moving backwards sometimes.
Speaker 2: Yeah, and we could start with the individual particles, so
Speaker 2: we're not thinking about like ten to the twenty nine
Speaker 2: objects and thermodynamics yet for like the individual particles, these
Speaker 2: rules work just as well forwards and backwards in time.
Speaker 1: Meaning like if you records and particles having some interactions
Speaker 1: when you play it backwards, that's also a perfectly feasible
Speaker 1: thing for the particles to do, or what you observe
Speaker 1: on doing is also perfectly feasible.
Speaker 2: Yes, ninety nine point ninety nine percent. There's a little
Speaker 2: asterisk there about how some particle interactions do prefer one
Speaker 2: direction in time, but it's a really really tiny effect.
Speaker 1: So then what are you saying. Are you're saying like
Speaker 1: we are technically all moving backwards and forwards in time,
Speaker 1: or there's no meaning to something moving backwards in time.
Speaker 2: I think that implies something really interesting about the universe,
Speaker 2: about causality. It implies that, of course the past determines
Speaker 2: the future, right, things flow, the laws of physics determine things,
Speaker 2: but also that the future is unique because the future
Speaker 2: is determined by the past. But you could also flip
Speaker 2: it the other way around. You could say the future
Speaker 2: determines the past, right, Like if there's only one possible
Speaker 2: future for every past, and you can go from the
Speaker 2: future and predict the past if they're you know, connected
Speaker 2: by the laws of physics in the same way, then
Speaker 2: like what direction is causality anyway? And so that's what
Speaker 2: we mean when we say, like which direction does time flow?
Speaker 2: The laws of physics don't care. There's sort of like
Speaker 2: time independent.
Speaker 1: Right, Well, you sort of get into the idea of
Speaker 1: determinism and whether things move in a predictable way, but
Speaker 1: doesn't quantum mechanics sort of do away with that, Like,
Speaker 1: you know, I can't really predict the future because what
Speaker 1: absurdin particle is going to do is sort of random
Speaker 1: according to quantum physics. And if I have an outcome
Speaker 1: of a particle, I can't really trace back its history
Speaker 1: because there was a random process somewhere in the middle.
Speaker 2: Yeah, great question, and there's a couple directions there. Now,
Speaker 2: if you only have quantum interactions, then what you said
Speaker 2: is not technically correct because quantum information is preserved and
Speaker 2: you can go forwards and backwards, like if there's no
Speaker 2: wave function collapse, then the future is completely predicted by
Speaker 2: the past, and you can derive the past from the future.
Speaker 2: You know. Quantum information just flows through time like particles
Speaker 2: into react with each other. There may be randomness, but
Speaker 2: if there's no wave function collapse, so you don't force
Speaker 2: the universe to choose from those probability distributions, then all
Speaker 2: that information is preserved. So wave function collapse does break
Speaker 2: that deep rule of quantum mechanics, which is another reason
Speaker 2: why wave function collapse is kind of nonsense from a
Speaker 2: philosophical and a physics point of view and not something
Speaker 2: we understand.
Speaker 1: Wait, wait, we're having your crossover here with another question.
Speaker 1: The other question.
Speaker 2: Connected man in the quantum realm, there is a larger
Speaker 2: sense in which we think quantum mechanics does yield a
Speaker 2: definition of time because the randomness of quantum mechanics does
Speaker 2: affect like multiple particles, And we talked about an individual
Speaker 2: particle and what happens to it. Now, imagine like ten
Speaker 2: to the thirty particles. Instead of tracing each of them individually,
Speaker 2: you're thinking about the population of those particles. What are
Speaker 2: they more likely to do or less likely to do?
Speaker 2: And because they're governed by randomness.
Speaker 1: Let's stick to maybe one particle. Like The classic example
Speaker 1: of a of a quantum particle is like if I
Speaker 1: s an electron at a magnetic electric field, is it
Speaker 1: going to veer to the right or is it going
Speaker 1: to veer.
Speaker 2: To the left.
Speaker 1: Now, in the past, I don't know whether it's going
Speaker 1: to be veering to the right or to the left.
Speaker 1: But then I shoot it at the electric field and
Speaker 1: the particle goes right or left. Now I'm in the future,
Speaker 1: and the particle went right.
Speaker 2: Because you collapse the wave function by insisting on measuring
Speaker 2: it with a classical object. Let's change your experiment a
Speaker 2: little bit. Let's say you shoot the electron into the
Speaker 2: magnetic field, but you don't measure which direction it went
Speaker 2: With some big classical thing like a detector or an
Speaker 2: eyeball or a graduate student, you record whether it went
Speaker 2: left or right. Into some other quantum object. You know
Speaker 2: another particle or photon or something.
Speaker 1: But I reject your scenario, Daniel. I reject your scenario,
Speaker 1: and I want to stick to my scenario. In my scenario,
Speaker 1: there's a future which is the wind right that I
Speaker 1: couldn't know in the past.
Speaker 2: Yeah.
Speaker 1: And if I'm in the future and I saw that
Speaker 1: the particle went right, I can still sort of figure
Speaker 1: out where the particle came from. So it just sort
Speaker 1: of seems like there is a direction to time. In
Speaker 1: the past, I couldn't tell the future, but in the
Speaker 1: future I could tell the past.
Speaker 2: Yes, if there's wave function collapse.
Speaker 1: Which there was in this scenario.
Speaker 2: Which violates a basic principle quantum mechanics loss of information,
Speaker 2: then yes, the future is different from the past because
Speaker 2: the collapse makes the future different. If you don't believe
Speaker 2: in collapse, because it's fundamentally nonsense, then your whole premise,
Speaker 2: then the whole setup is flawed.
Speaker 1: But I have to believe in collapse because I live
Speaker 1: in a collapse world. Like when I'm talking to you,
Speaker 1: I'm collapsing things. You don't know that, man grab my
Speaker 1: steering wheel. My experience. Maybe there's a multiverse somebody else
Speaker 1: does something else But to me, in this multiverse version,
Speaker 1: there's collapse. It's a real thing. And so is there
Speaker 1: a direction of time in my universe?
Speaker 2: Well, if there's a multiverse, then the wave function doesn't collapse.
Speaker 2: It splits in the many pieces. They're all part of
Speaker 2: the same big universe wave function, but they can't interact
Speaker 2: with each other, and that preserves the flow of quantum information.
Speaker 2: All those things do happen, they're just sort of like
Speaker 2: happening on top of each other in a way that
Speaker 2: they can't interact with each other. It's the quantum multiverse.
Speaker 2: So there is a scenario in which there is no
Speaker 2: collapse and quantum information is not changed as time goes on.
Speaker 1: Sure, if you're like a mega entity, then you can
Speaker 1: see all the multiverse at the same time. But to me,
Speaker 1: to us right now talking to each other, we live
Speaker 1: in a collapse universe. This is our universe, and we
Speaker 1: don't even know if there are other universes. So does
Speaker 1: that mean that time does have a direction? Just make
Speaker 1: it about me, Daniel, not the watcher who's watching the
Speaker 1: multiverse from afar.
Speaker 2: I think portions of the universe no longer have access
Speaker 2: to the full information. That doesn't mean that time couldn't
Speaker 2: flow backwards, right, the same physical process could still go
Speaker 2: in the other direction.
Speaker 1: Well, it could, But to us, to our understanding and
Speaker 1: our experience of the universe, this is all the information
Speaker 1: that we have, and you don't know if there's actually
Speaker 1: other information.
Speaker 2: Yeah, we don't know that's true.
Speaker 1: So we have to assume that this is maybe all
Speaker 1: there is. This could be all that there is.
Speaker 2: We don't have to assume that.
Speaker 1: If you assume it is not all there is to
Speaker 1: our experience of the universe. In this universe we live in,
Speaker 1: there is a direction of time.
Speaker 2: If you don't have the full information, you might not
Speaker 2: have enough information to reconstruct the past.
Speaker 1: Yeah, okay, so then is that what do you think
Speaker 1: Trevor means by things moving backwards in time? Like, could
Speaker 1: there be something moving in the opposite direction of this
Speaker 1: direction of time?
Speaker 2: I don't think that's what Trevor is asking about at all,
Speaker 2: and he's probably wondering, like why these guys talking about
Speaker 2: quantum mechanics I was thinking about. So let's get to time.
Speaker 1: Okay, Well, let's get to this question. The question is
Speaker 1: can something move backwards in time?
Speaker 2: Yeah?
Speaker 1: And would we notice you're the one who went into
Speaker 1: quantum mechanics. I mean, or are we not answering the
Speaker 1: question with quantum mechanics or are we no, we're not,
Speaker 1: We're not so okay.
Speaker 2: That was a stepping stone towards the concept of thermodynamics,
Speaker 2: which builds up from the microscopic picture of quantum mechanics.
Speaker 2: It says, zoom out from the tiny particles. Our experience
Speaker 2: is not of tiny particles. It's of big things with
Speaker 2: ten to the twenty nine or ten to the thirty particles.
Speaker 2: And on that scale something else emerges, and it's called entropy.
Speaker 2: You have lots of quantum particles interacting. You notice that
Speaker 2: they tend to spread out over the possibilities, which is
Speaker 2: another way basically saying entropy increases as time goes on.
Speaker 2: And that's where our experience of time comes from. What
Speaker 2: you were alluding to earlier. Like a bouncing ball bouncing
Speaker 2: up and down, that's a lot of particles interacting. What
Speaker 2: happens there is that energy tends to spread out, and
Speaker 2: the ball loses some energy and it bounces lower and
Speaker 2: lower as time goes on. So that video you could
Speaker 2: definitely tell if something going forwards or backwards in time.
Speaker 1: I see you're saying, let's not think about quantity physics.
Speaker 1: Let's start think about a bouncing ball. And so maybe
Speaker 1: in Trevor's question, something moving backwards in time is maybe
Speaker 1: like a ball whose entropy to us seems to be decreasing.
Speaker 2: Yes, exactly, there's a sort of a subtlety hear like,
Speaker 2: take that ball that's bouncing and entropy is increasing. You
Speaker 2: could all say, well, how do we know that ball
Speaker 2: is not going backwards in time with decreasing entropy. You're like, well,
Speaker 2: that's just sort of like definitional. Is it moving forwards
Speaker 2: in time with its entropy increasing, or is it moving
Speaker 2: backwards in time with its enterpy decreasing. It's basically the
Speaker 2: same thing. I think what he's asking about. And the
Speaker 2: original comment that inspired this is that we don't see
Speaker 2: things moving forwards in time with their entropy decreasing, Like
Speaker 2: we don't see coffee cups reassembling themselves, we don't see
Speaker 2: ice freezing on the countertop. All these things would have
Speaker 2: entropy decreasing, and that's what it would look like. It's
Speaker 2: to see something moving backwards in time, because we would
Speaker 2: be moving backwards in time with its entropy increasing. Backwards
Speaker 2: in time, which to us would look like it's moving
Speaker 2: forwards in time with its entropy decreasing.
Speaker 1: So then the answer to the question is that if
Speaker 1: something was moving backwards in time in our world, which
Speaker 1: is moving forwards that you're saying, we would be able
Speaker 1: to notice that it is moving backwards in time because
Speaker 1: its entropy would be decreasing.
Speaker 2: Yeah, and I don't remember, but that probably happened in Tenant, right,
Speaker 2: somebody moved backwards in time and dropped a coffee cup,
Speaker 2: and to the people moving forwards in time, it looked
Speaker 2: really weird because they saw a broken coffee cup jump
Speaker 2: up off the floor and reassemble itself.
Speaker 1: Yeah. No, no, no, that's exactly. That's the trippy thing
Speaker 1: about the movies that you see things sort of moving
Speaker 1: in unnatural ways. Yes, which really to our brain is
Speaker 1: like you're seeing entropy decrease, which we're not used to.
Speaker 2: Right, Yeah, exactly, that's what it would look like to
Speaker 2: see something move backwards in time.
Speaker 1: Well, I feel like we answered the question, which is like,
Speaker 1: you know, it's all about entropy, but entropy is not
Speaker 1: really kind of like a fundamental thing in the universe, right,
Speaker 1: isn't it sort of like something that emerges from the
Speaker 1: interaction of lots of things. Like at the quantum level,
Speaker 1: do you still have entropy and does it play a role?
Speaker 1: Like let's say we go back to the idea of
Speaker 1: looking at an electron, could you tell if an electron
Speaker 1: was moving backwards in time?
Speaker 2: Yeah, great question. We don't really understand how the air
Speaker 2: of time emerges. But you're right, it's not something that's
Speaker 2: fundamental to the universe. It's emergent. But you know, we
Speaker 2: don't really understand emergence either, like why do laws ever emerge?
Speaker 2: Why isn't everything just controlled by the tiny little objects
Speaker 2: and chaos rules? On top of that, we don't understand emergence.
Speaker 2: We don't understand how time emerges from quantum mechanics. We
Speaker 2: don't understand the importance of emergent things. There are some
Speaker 2: hints there and some clues maybe in particle physics, but
Speaker 2: fundamentally that's not an understood question. You can't even really ask,
Speaker 2: like what is entropy in quantum mechanics because entropy is
Speaker 2: about differences and how things are arranged in the macroscopic
Speaker 2: and the microscopic. You have to like define two levels
Speaker 2: of information even be talking about entropy.
Speaker 1: I wonder if then the answer to Trevor's question is, like,
Speaker 1: you can't do something's moving back to in time unless
Speaker 1: it's really small, or unless it's only one particle.
Speaker 2: No, from the one particle, you can't tell at all. Right,
Speaker 2: there is no sense of entropy for a single particle.
Speaker 1: That's what I mean. You can't tell. Like a ball,
Speaker 1: you could tell if it was moving backwards in time,
Speaker 1: but an individual electron you cannot.
Speaker 2: Yeah, that's exactly right.
Speaker 1: So that's what you're saying, unless the multiverse doesn't exist.
Speaker 2: Yeah, that's right.
Speaker 1: All right. Well, do you think you need to go
Speaker 1: back in time and re answer this question?
Speaker 2: I think I want to go back in time and
Speaker 2: not bring up quantum mechanics.
Speaker 1: No, but it totally changes the answer, right, Like if
Speaker 1: you ignore quantum mechanics, and yes, you can tell something
Speaker 1: wing backwards in time. If you do things about quantum mechanics,
Speaker 1: then you can.
Speaker 4: No.
Speaker 2: I'm very glad we got into qutum mechanics. That's just you.
Speaker 1: I think you're always glad to get into quantum mechanics.
Speaker 1: He has a particle physics. I think the problem sometimes
Speaker 1: is giving you off of quantum mechanics.
Speaker 2: Yeah, totally agree.
Speaker 1: It's a little interesting reversal here. It's like we went
Speaker 1: backwards in time. All right, Well, thanks to all of
Speaker 1: our questions askers today, really interesting questions.
Speaker 2: And if you have questions about how the universe works,
Speaker 2: please don't be shy right to me to questions at
Speaker 2: Daniel and Jorge dot com. You can address your questions
Speaker 2: to me, or to me and Jorge, or to anybody
Speaker 2: you like. You'll still get an answer from me.
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