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What's the fastest event ever measured? · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Hey, or do you think our podcast episodes are getting
• 0:10
  Speaker 1: like a little too long?
• 0:12
  Speaker 2: Are they longer than it used to be?
• 0:13
  Speaker 1: You know, we used to start out around forty ish minutes,
• 0:16
  Speaker 1: and some of the recent ones been hitting an hour.
• 0:19
  Speaker 2: But not the ones with me in it. Right, I'll
• 0:22
  Speaker 2: just try to keep it short.
• 0:24
  Speaker 1: You ask a lot of questions, and sometimes it takes
• 0:27
  Speaker 1: an hour to explain them all.
• 0:28
  Speaker 2: I guess we are trying to explain the whole universe,
• 0:30
  Speaker 2: so that's supposed to take a while.
• 0:33
  Speaker 1: Yeah, it's actually amazing if you can explain like a
• 0:36
  Speaker 1: whole year's worth of physics in like sixty minutes.
• 0:39
  Speaker 2: Yeah. And the funny thing is that I usually forget
• 0:42
  Speaker 2: it within sixty seconds.
• 0:45
  Speaker 1: That's where you got to listen to it sixty times.
• 0:47
  Speaker 2: But then I'll give it when sixty of the attention
• 0:49
  Speaker 2: it needs. So, hey, we're done after an hour, right.
• 0:54
  Speaker 1: I think the math works out?
• 0:55
  Speaker 3: Yeah?
• 0:55
  Speaker 2: Yeah, I do pay attention to math. Hi. I'm poor
• 1:13
  Speaker 2: Hee Make cartoonist and the author of Oliver It's Great,
• 1:16
  Speaker 2: Big Universe.
• 1:16
  Speaker 1: Hi. I'm Daniel. I'm a particle physicist and a professor
• 1:19
  Speaker 1: at UC Irvine, and I'm very conscious of our finite
• 1:23
  Speaker 1: amounts of time.
• 1:24
  Speaker 2: You mean, like here on Earth or on the air.
• 1:27
  Speaker 1: Yeah, both, Absolutely, we're spending a non trivial amount of
• 1:31
  Speaker 1: time on Earth on the air now that we've done
• 1:34
  Speaker 1: so many episodes, you know, it's like a non zero
• 1:36
  Speaker 1: fraction of our lives we spent doing this podcast.
• 1:39
  Speaker 2: Yeah, I know.
• 1:42
  Speaker 1: But you know, more existentially, my kids are growing up.
• 1:45
  Speaker 1: I'm going to leave home soon, and so yeah, I'm
• 1:48
  Speaker 1: valuing every hour I have with them.
• 1:50
  Speaker 2: Yeah, they grow up pretty fast, sometimes too fast.
• 1:53
  Speaker 1: Do you believe in parental time dilation? Everybody says, oh,
• 1:56
  Speaker 1: those years go by so fast, but you know, when
• 1:59
  Speaker 1: you have a screaming top and it's two in the morning,
• 2:01
  Speaker 1: it feels like about a million hours before they go
• 2:04
  Speaker 1: down for their nap.
• 2:06
  Speaker 2: Definitely, times needs to go by faster. But I feel
• 2:09
  Speaker 2: like I've paid attention pretty good. There's definitely a lot
• 2:12
  Speaker 2: of video records of our children, so we always go back.
• 2:18
  Speaker 1: Down memory lean Yeah, that's true.
• 2:21
  Speaker 2: But anyways, welcome to our podcast, Daniel and Jorge Explain
• 2:23
  Speaker 2: the Universe, a production of iHeartRadio in.
• 2:25
  Speaker 1: Which we try to take an hour to slow down
• 2:28
  Speaker 1: and really understand something. We think it's worthwhile to update
• 2:32
  Speaker 1: the mental model in your mind that's explaining the way
• 2:35
  Speaker 1: the universe works out there. We wanted to correspond as
• 2:39
  Speaker 1: much as possible so to the way the universe actually works,
• 2:41
  Speaker 1: the weird rules that quantum particles follow, the incredible powerful
• 2:45
  Speaker 1: forces swirling in the hearts of black holes. We want
• 2:49
  Speaker 1: your brain to be aligned with the universe, even if
• 2:52
  Speaker 1: it does take a little bit of time.
• 2:54
  Speaker 2: Yeah, we do like to take our time to make
• 2:56
  Speaker 2: the most of your time when it's time to understand
• 2:59
  Speaker 2: the universe.
• 3:00
  Speaker 1: And the universe operates on so many amazingly different time scales.
• 3:04
  Speaker 1: We think about our lives and you know, tens of years,
• 3:07
  Speaker 1: maybe one hundred if we're lucky, but that's just the
• 3:09
  Speaker 1: blink of an eye. In the history of the universe
• 3:11
  Speaker 1: that is billions of years old. And then also between
• 3:15
  Speaker 1: every second, there's an incredible number of quantum operations happening,
• 3:19
  Speaker 1: electrons buzzing and tuing and throwing, and particles appearing and disappearing.
• 3:24
  Speaker 1: Things happen in the universe from the tiniest fractions of
• 3:26
  Speaker 1: a second all the way out to billions and maybe
• 3:29
  Speaker 1: even trillions of years.
• 3:31
  Speaker 2: Yeah, there's a lot going on in the universe, and
• 3:33
  Speaker 2: times seems to be underneath it all, dictating at what
• 3:36
  Speaker 2: rate things happen and in what order things happen.
• 3:40
  Speaker 1: And I wonder sometimes whether the deepest answers to the
• 3:42
  Speaker 1: nature of the universe are at the shortest time scales,
• 3:46
  Speaker 1: Like what is the real fabric of reality the smallest
• 3:49
  Speaker 1: bits in the smallest pieces of time, dictating how everything
• 3:52
  Speaker 1: else works somehow bubbling up to form our universe, or
• 3:55
  Speaker 1: whether the real story is of the longest time periods.
• 3:59
  Speaker 1: What's happening to the universe? How does it form? What
• 4:02
  Speaker 1: is its future? Over billions or maybe trillions of years?
• 4:05
  Speaker 1: You know, the billions of years that our universe has
• 4:08
  Speaker 1: existed could just be the first few moments of a
• 4:11
  Speaker 1: much longer, impossibly to imagine deep time future.
• 4:17
  Speaker 2: Do you feel like maybe you have a little bit
• 4:18
  Speaker 2: of a fear of missing out in the universe? You know,
• 4:21
  Speaker 2: but maybe things are happening too fast for you to
• 4:24
  Speaker 2: notice or too long for you to live through.
• 4:26
  Speaker 1: Yeah, I have FOMU. I have fear of missing the
• 4:28
  Speaker 1: universe for sure.
• 4:30
  Speaker 2: Yeah, physical fear of missing the universe f FOMU.
• 4:35
  Speaker 1: Yeah. Some of the most interesting things that happen in
• 4:37
  Speaker 1: the universe are not the tiniest rules of the little particles,
• 4:41
  Speaker 1: but how things come together over time. You know, galaxies
• 4:44
  Speaker 1: took hundreds of millions of years to form. Imagine you
• 4:48
  Speaker 1: were an intelligent species that existed somehow in the first
• 4:51
  Speaker 1: one hundred million years of the universe. You would never
• 4:53
  Speaker 1: even see a galaxy, which to us now is like
• 4:56
  Speaker 1: the basic building block of what's out there in space.
• 4:59
  Speaker 1: What if the most basic building block of the future
• 5:02
  Speaker 1: hasn't yet formed, and intelligent species that evolve in a
• 5:06
  Speaker 1: trillion years will wonder about what it was like to
• 5:08
  Speaker 1: be us, never even seeing the most basic thing that
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  Speaker 1: exists in their universe.
• 5:14
  Speaker 2: Or even if the future is set at all.
• 5:16
  Speaker 1: Yeah.
• 5:17
  Speaker 2: Right, they're a big question of whether the universe is deterministic,
• 5:21
  Speaker 2: meaning you can sort of know what's going to happen
• 5:23
  Speaker 2: in the future or at least in one of the futures,
• 5:26
  Speaker 2: or whether it's totally random.
• 5:28
  Speaker 1: That's right, And we're hoping to push ourselves into a
• 5:30
  Speaker 1: future where we understand the universe a little bit better
• 5:34
  Speaker 1: from the largest time scales to the shortest time scales.
• 5:37
  Speaker 2: Yeah, and when it's time to do that, we will
• 5:39
  Speaker 2: take a little bit of time to explain it to
• 5:41
  Speaker 2: you in hopefully more or less an hour, because time
• 5:44
  Speaker 2: seems to be one of the most fundamental things in
• 5:46
  Speaker 2: the universe, but sometimes you have to ask questions about
• 5:49
  Speaker 2: time itself.
• 5:50
  Speaker 1: And while we can't see the deep future yet, we
• 5:53
  Speaker 1: can do our best to try to understand the shortest
• 5:55
  Speaker 1: time scales to zoom in on how fast things are
• 5:58
  Speaker 1: happening in the universe.
• 6:00
  Speaker 2: So today on the podcast, we'll be tackling what's the
• 6:07
  Speaker 2: fastest event ever measured?
• 6:10
  Speaker 1: You know, when people run simulations like the Hearts of
• 6:13
  Speaker 1: Neutron stars or like weather or whatever, they always have
• 6:16
  Speaker 1: to choose like a minimum time step. Now you have
• 6:19
  Speaker 1: your universe, and then you evolve it forward in time,
• 6:21
  Speaker 1: one step in time, and then again and again and again,
• 6:24
  Speaker 1: and eventually you describe something longer. But there's that minimum
• 6:28
  Speaker 1: time on the computer, right, Yeah, on the computer when
• 6:30
  Speaker 1: you run simulations, and so in our real universe, I
• 6:33
  Speaker 1: think it's fascinating to think about, like, well, what is
• 6:35
  Speaker 1: the shortest time step? How far have we zoomed in
• 6:38
  Speaker 1: to see like the fastest thing ever happened?
• 6:41
  Speaker 2: Yeah, or possibly we are living in the simulation, right.
• 6:45
  Speaker 2: Isn't that something that even smart people think about, not
• 6:47
  Speaker 2: just conspiracy theorists.
• 6:50
  Speaker 1: I think it's definitely true that smart people think about it.
• 6:52
  Speaker 1: I don't know how true it is that smart people
• 6:54
  Speaker 1: believe in it or think that it's realistic. I know
• 6:57
  Speaker 1: there's a lot of talk out there about it, and
• 6:58
  Speaker 1: it's a lot of fun to think about, but if
• 7:01
  Speaker 1: you have to ask people like whether they really believed it,
• 7:03
  Speaker 1: I mean, I think it's unlikely we're living in a simulation.
• 7:06
  Speaker 1: For example, you.
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  Speaker 2: Mean it's fun to simulate in your head that maybe
• 7:11
  Speaker 2: we're living in a simulation.
• 7:13
  Speaker 1: Yeah, it's a really clever sort of meta idea. Like
• 7:16
  Speaker 1: we think about simulations, as you say, we run simulations
• 7:18
  Speaker 1: in our head. We use simulations for our science. We
• 7:20
  Speaker 1: had a whole fun podcast episode about the importance of
• 7:23
  Speaker 1: doing simulations in science. It's really a whole new branch
• 7:27
  Speaker 1: of science, sort of different from experimental and theoretical physics.
• 7:30
  Speaker 1: You know, we describe things like in vivo or in
• 7:33
  Speaker 1: vitro and now sometimes we call them in silico. But
• 7:36
  Speaker 1: I don't know that we actually are living in a simulation,
• 7:39
  Speaker 1: or you know how we would actually prove that. But
• 7:41
  Speaker 1: we have a whole episode about that. So folks interested
• 7:43
  Speaker 1: in that go check out that episode.
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  Speaker 2: Right, right, But whether it's a simulation or not, there's
• 7:48
  Speaker 2: definitely time in it. And as you said, when we
• 7:50
  Speaker 2: create little universes in our computers, you have to pick
• 7:53
  Speaker 2: a timestep to do your simulation, and so you can
• 7:56
  Speaker 2: kind of ask the question, does that happen in the
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  Speaker 2: real universe?
• 8:00
  Speaker 1: Well, yeah, And when we do it in our simulations,
• 8:03
  Speaker 1: we pick a timestep short enough that we're not ignoring
• 8:06
  Speaker 1: anything important, So we try to figure out, like, what
• 8:08
  Speaker 1: is the shortest time step we're interested in. You know,
• 8:11
  Speaker 1: if you're simulating like a evolution of a galaxy, nothing
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  Speaker 1: really exciting happens in a year or one hundred years,
• 8:16
  Speaker 1: so you might take like thousand year time steps. But
• 8:19
  Speaker 1: if you're simulating like a nuclear explosion underground, you might
• 8:22
  Speaker 1: take time steps of like a millionth of a second
• 8:25
  Speaker 1: to make sure you're capturing all of the dynamics.
• 8:27
  Speaker 2: Yeah, and as you said, there's lots of things happening
• 8:29
  Speaker 2: in the universe, and the idea of a timestep is
• 8:33
  Speaker 2: also important when you try to measure things, right, Yeah,
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  Speaker 2: Like if you're trying to measure an explosion, you don't
• 8:37
  Speaker 2: want to sample the explosion every three minutes because it's
• 8:40
  Speaker 2: going to be gone and over and when you're sampling,
• 8:43
  Speaker 2: you know had the motion of a start. You don't
• 8:45
  Speaker 2: want to do it every femtosecond because you're going to
• 8:47
  Speaker 2: have too much data.
• 8:48
  Speaker 1: Yeah, exactly. So things happen on different timescales, and the
• 8:52
  Speaker 1: question is like, what's the fastest thing we've ever measured?
• 8:54
  Speaker 1: And what's the actual minimum time slice of the universe?
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  Speaker 2: Two big questions about very small things. Hopefully we can
• 9:03
  Speaker 2: do it in the short amount of time that we have. Well,
• 9:07
  Speaker 2: as usually, we were wondering how many people out there
• 9:08
  Speaker 2: had thought about the question of what is the fastest
• 9:11
  Speaker 2: event ever measured? So Daniel went out there once again
• 9:14
  Speaker 2: to ask people, what do you think is the most
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  Speaker 2: fleeting or fastest physical event ever measured?
• 9:21
  Speaker 1: Thanks very much to our listeners who answer these questions
• 9:23
  Speaker 1: very very quickly. I'm very grateful for your contributions. It
• 9:26
  Speaker 1: helps me understand what people are thinking about. And I
• 9:29
  Speaker 1: hope you enjoy hearing your voice on the air. And
• 9:32
  Speaker 1: if you are out there listening and would like to
• 9:34
  Speaker 1: hear your voice answering these questions, please don't be shy
• 9:37
  Speaker 1: write to me to questions at Danielandjorgey dot com.
• 9:40
  Speaker 2: So think about it for a second. What do you
• 9:41
  Speaker 2: think is the fastest thing humans have ever detected. Here's
• 9:46
  Speaker 2: what people had to say.
• 9:48
  Speaker 4: I don't know what the smallest time slice ever measured. Here,
• 9:53
  Speaker 4: I'm going to assume that it's somehow around fempto seconds.
• 9:58
  Speaker 4: I don't know why that number sticks my brain. I'm
• 10:00
  Speaker 4: gonna say thempto seconds. The smallest amount of space ever measured,
• 10:04
  Speaker 4: I think is the plank space.
• 10:07
  Speaker 1: Gonna go with plank time.
• 10:10
  Speaker 3: That's easy. It's the time between when butter goes from
• 10:13
  Speaker 3: being soft to being soup. But actually it probably tend
• 10:17
  Speaker 3: to the negative twenty something, at which point I guess
• 10:22
  Speaker 3: doesn't even show that time makes any sense anymore.
• 10:25
  Speaker 2: All Right, we got some cooking answers here.
• 10:29
  Speaker 1: You know, some people listen to our podcast while they're
• 10:31
  Speaker 1: making dinner, and that might have influenced this answer.
• 10:35
  Speaker 2: Well, I'm very interested in this recipe that where you
• 10:38
  Speaker 2: make soup out of butter.
• 10:40
  Speaker 1: You've never had butter soup. Oh man, that.
• 10:45
  Speaker 2: Sounds so healthy, so healthy.
• 10:47
  Speaker 1: Yeah, I'll have butter soup low fat version. Please.
• 10:51
  Speaker 2: Yeah, that'll definitely shorten your time on Earth for sure.
• 10:54
  Speaker 2: I mean, expand your space, but short in your time.
• 10:57
  Speaker 2: I mean that seems like the wrong proportion.
• 11:01
  Speaker 1: With well. Buttered chicken is a very popular recipe, so
• 11:04
  Speaker 1: I'm sure butter soup is a thing people can make.
• 11:06
  Speaker 2: M but buttered chicken soup. Oh my goodness.
• 11:10
  Speaker 1: What's better than.
• 11:12
  Speaker 2: The physics of that? How does it even work?
• 11:15
  Speaker 1: It definitely adds mass.
• 11:17
  Speaker 2: But yeah, it's definitely an interesting question, and so let's
• 11:20
  Speaker 2: jump into it. Daniel. First of all, I guess let's
• 11:23
  Speaker 2: talk about time in general and the idea that maybe
• 11:27
  Speaker 2: time is pixelated or there's a minimum amount of time
• 11:30
  Speaker 2: in the universe. What if physicists think about that.
• 11:33
  Speaker 1: Physicists really have no idea how time works.
• 11:36
  Speaker 2: All right, we're done.
• 11:37
  Speaker 1: Yeah, so it's about time we gave up.
• 11:40
  Speaker 2: No, Yeah, the shortest episode Ever's the shortest podcast about
• 11:44
  Speaker 2: physics ever recorded? Today's episode?
• 11:47
  Speaker 1: Yeah, every podcast is just we don't know. Done.
• 11:50
  Speaker 4: No.
• 11:51
  Speaker 1: It is really an enduring mystery, And it's weird because
• 11:53
  Speaker 1: time is something we sort of feel like we understand.
• 11:56
  Speaker 1: It's part of our everyday lives. We talk about all
• 11:58
  Speaker 1: the time. We all have complicated schedule, We rely on time,
• 12:01
  Speaker 1: we do time zones, we mess them up and miss meetings.
• 12:04
  Speaker 1: Time is both familiar and also mysterious because we don't
• 12:08
  Speaker 1: understand like what it is. Special relativity tells us that
• 12:11
  Speaker 1: it's deeply connected to space, and it makes actually much
• 12:15
  Speaker 1: more sense to think about time and space together as
• 12:18
  Speaker 1: one unit space time. And that makes sense because some
• 12:22
  Speaker 1: of the things in special relativity show us that space
• 12:24
  Speaker 1: and time are mixed. That you know, moving quickly through
• 12:28
  Speaker 1: space can affect your measurement of time. All these sorts
• 12:31
  Speaker 1: of things sort of the same way that like electricity
• 12:33
  Speaker 1: and magnetism make more sense when stuck together into one idea.
• 12:37
  Speaker 1: It doesn't tell you that electricity and magnetism are the
• 12:39
  Speaker 1: same thing, just that they're connected in the same way
• 12:42
  Speaker 1: space and time are connected. They're not the same, but
• 12:45
  Speaker 1: they're related to each other in special relativity.
• 12:48
  Speaker 2: Right, because I guess we grow up, you know, not
• 12:51
  Speaker 2: just as kids, but also like sort of through elementary
• 12:54
  Speaker 2: high school, thinking that space and time are sort of immovable, right,
• 12:57
  Speaker 2: like fixed in the universe. But really then eventually you
• 12:59
  Speaker 2: learn that space and time are both kind of squishy, right, envirorable,
• 13:04
  Speaker 2: and time can slow down, time can speed up, space
• 13:06
  Speaker 2: can contract, space can expand they can both wiggle. But
• 13:10
  Speaker 2: where did this idea that maybe time is pixelated? Where
• 13:13
  Speaker 2: did it come from or what would make physicists think
• 13:16
  Speaker 2: that it might be.
• 13:17
  Speaker 1: Yeah, it's fascinating you. You sort of trace the evolution of
• 13:21
  Speaker 1: the ideas and we all sort of have that same experience.
• 13:23
  Speaker 1: Like Newton thought of space and time as absolute and fixed,
• 13:26
  Speaker 1: as you say, sort of immutable. They're like the backdrop
• 13:29
  Speaker 1: of the universe. But then Einstein should us that they're not.
• 13:33
  Speaker 1: Actually they're flexible, they're interconnected. But most importantly, Einstein's theory
• 13:38
  Speaker 1: of general relativity and special relativity still suggests that time
• 13:43
  Speaker 1: is continuous, it's smooth, it's infinitely divisible, that it's not
• 13:48
  Speaker 1: discrete or pixelated. It's not like there are steps in time.
• 13:52
  Speaker 1: In Einstein's theory of the universe, you can take any
• 13:55
  Speaker 1: two moments and there's always another moment in between, right,
• 13:58
  Speaker 1: there's no minimum times that in Einstein's universe and general
• 14:01
  Speaker 1: relativity describes the universe very very well. It describes the
• 14:05
  Speaker 1: expansion of the universe and the motion of galaxies and
• 14:09
  Speaker 1: everything we've ever been able to test about general relativity
• 14:12
  Speaker 1: has always been bang on, exactly correct, with astonishing accuracy.
• 14:16
  Speaker 2: Now when you say the astin theories suggest that what
• 14:19
  Speaker 2: does that mean? Does that mean that it only works
• 14:21
  Speaker 2: but continuous time, or that is just always used continuous
• 14:24
  Speaker 2: time and nobody has thought about applying it to the
• 14:28
  Speaker 2: pixelated time.
• 14:30
  Speaker 1: Yeah, great question. It works assuming that space is continuous.
• 14:34
  Speaker 1: So you're like, let's start from that assumption and then
• 14:36
  Speaker 1: build on top of that. And then you could ask, well,
• 14:39
  Speaker 1: could you have a different theory that didn't make that assumption.
• 14:41
  Speaker 1: What if you assumed instead that space was pixelated? And
• 14:45
  Speaker 1: then you run into all sorts of mathematical problems that
• 14:47
  Speaker 1: nobody has been able to solve before. The motivation for
• 14:50
  Speaker 1: that comes from quantum mechanics, Like you might ask, well,
• 14:53
  Speaker 1: why would you wake time pixelated? It feels pretty smooth
• 14:55
  Speaker 1: to me. I mean we measure it in seconds, but
• 14:57
  Speaker 1: we know there's always milliseconds below those and microseconds those.
• 15:00
  Speaker 1: Why would you ever imagine there would be pixels? And
• 15:03
  Speaker 1: that comes from the idea of quantum mechanics, which tells
• 15:06
  Speaker 1: us that the nature of reality is a sort of discrete.
• 15:09
  Speaker 1: It's like made out of chunks. It's not smooth, you know,
• 15:12
  Speaker 1: like when we look at a beam of life from
• 15:14
  Speaker 1: a flashlight. Einstein's actual discovery from the photoelectric effect tells
• 15:18
  Speaker 1: us that it's not just like smooth beams of light
• 15:21
  Speaker 1: that you could like chop up infinitely small, that there's
• 15:24
  Speaker 1: like a minimum brightness because light comes in packets, these
• 15:27
  Speaker 1: little things called photons, right, And so quantum mechanics suggests
• 15:32
  Speaker 1: that even though the universe seems continuous and smooth when
• 15:35
  Speaker 1: you zoom in, it really is kind of pixelated. It's
• 15:38
  Speaker 1: just like when you look at your computer screen and
• 15:40
  Speaker 1: you zoom in, it seems smooth, right, but actually there's
• 15:43
  Speaker 1: little dots there. There are little basic units.
• 15:46
  Speaker 2: So that's the motivation, right, Like, even this podcast is pixelated, right,
• 15:50
  Speaker 2: Like we're recording into a digital device. It's recording it
• 15:54
  Speaker 2: with a time sample with a minimum time sampling rate,
• 15:56
  Speaker 2: and then it gets transmitted as bits and then it
• 16:00
  Speaker 2: plays out there where you're listening to this as those
• 16:03
  Speaker 2: little bits.
• 16:04
  Speaker 1: Yeah, you're exactly right. Digitization is creating some pixelization, right,
• 16:09
  Speaker 1: You're creating these units and exactly the sort of way
• 16:12
  Speaker 1: quantum mechanics works. Fascinatingly though, even analog measurements have a resolution,
• 16:16
  Speaker 1: right like a photograph. You think of it as like, oh,
• 16:19
  Speaker 1: it's photons. It's not like pixels like a digital camera
• 16:23
  Speaker 1: or a analog recording on like vinyl or on a tape.
• 16:27
  Speaker 1: It's not using digits. It's analog. It's using some sort
• 16:30
  Speaker 1: of like magnetic technology to record it, or like physical
• 16:33
  Speaker 1: bumps on the vinyl. Still that is discrete, right, because
• 16:36
  Speaker 1: in the end, there's a finite resolution. Like for photographs,
• 16:40
  Speaker 1: there's a resolution of a photon or the molecule of
• 16:43
  Speaker 1: the chemical atoms that are you know, recording the light,
• 16:47
  Speaker 1: or on the tape, there's still the resolution of like
• 16:49
  Speaker 1: the little magnets that are aligned to record your information,
• 16:52
  Speaker 1: or on the vinyl there's still like the chemistry of
• 16:54
  Speaker 1: the vinyl itself. So analog is higher resolution, but it's
• 16:58
  Speaker 1: not infinite resolution, right.
• 17:00
  Speaker 2: And so the idea is that maybe time is also pixelated.
• 17:03
  Speaker 1: Yeah, because it's weird to think about time as infinite.
• 17:06
  Speaker 1: You know, we don't see infinities in reality. Everywhere we
• 17:10
  Speaker 1: see infinities in our theory, always something acts to prevent
• 17:13
  Speaker 1: it from happening in reality. And this is what quantum
• 17:16
  Speaker 1: mechanics tells us, that there are new infinities. You can't
• 17:19
  Speaker 1: divide things infinitely small, and maybe space itself and time
• 17:24
  Speaker 1: are pixelated. Maybe there's a minimum unit of space and
• 17:28
  Speaker 1: a minimum unit of time. This would be very natural
• 17:31
  Speaker 1: from a quantum mechanical point of view. You asked earlier, like, well,
• 17:34
  Speaker 1: has anybody tried that? What if you built general relativity
• 17:37
  Speaker 1: out of discrete units of space and time, you know,
• 17:40
  Speaker 1: pixelated the universe. And people are trying to do that,
• 17:42
  Speaker 1: but bringing together the ideas of general relativity and the
• 17:45
  Speaker 1: ideas of quantum mechanics to make that new concept, like
• 17:48
  Speaker 1: a theory of gravity and space and time that's built
• 17:50
  Speaker 1: on discrete units has so far not been successful. People
• 17:53
  Speaker 1: have been trying for decades. You run into all sorts
• 17:55
  Speaker 1: of mathematical problems doing so. So we don't have a
• 17:59
  Speaker 1: theory of general relativity that's built on discrete time. So
• 18:02
  Speaker 1: we have this theory of general relativity. It tells us
• 18:04
  Speaker 1: about space and gravity but assumes continuous time. And then
• 18:07
  Speaker 1: this idea that the universe is quantum mechanical and time
• 18:10
  Speaker 1: and space are probably discrete. But we can't bring these
• 18:13
  Speaker 1: two things together.
• 18:14
  Speaker 2: Right. But this theory, even though it comes from Einstein,
• 18:17
  Speaker 2: does have its problems, right, Like it sort of breaks down,
• 18:19
  Speaker 2: especially when you get down to the smallest levels of
• 18:22
  Speaker 2: particles in quantum physics.
• 18:24
  Speaker 1: Yeah, exactly. General relativity is very, very accurate. But everything
• 18:29
  Speaker 1: we think in physics has its limitations, Like every theory
• 18:32
  Speaker 1: you describe is applicable only in certain situations, situations where
• 18:37
  Speaker 1: you've derived it, you know, under the assumptions that are valid,
• 18:41
  Speaker 1: and so as you mentioned, like general relativity we think
• 18:43
  Speaker 1: breaks down in certain situations Like number one, It can't
• 18:46
  Speaker 1: describe particles, like what is the gravity of a particle?
• 18:50
  Speaker 1: We don't know because particles have uncertainty. General relativity can
• 18:54
  Speaker 1: only tell you about how space is bent when you
• 18:57
  Speaker 1: know where a mass is, Well, what if you don't
• 18:59
  Speaker 1: know where it is is? What if it only has
• 19:00
  Speaker 1: a probability to be here and a probability to be there,
• 19:03
  Speaker 1: is space probably bent or space bent on average? We
• 19:07
  Speaker 1: don't know the answers to these questions, So we don't
• 19:09
  Speaker 1: know how to do general relativity for quantum particles, and
• 19:13
  Speaker 1: it makes weird predictions.
• 19:14
  Speaker 2: Are we ever going to find out? Like how are
• 19:16
  Speaker 2: we going to tell if the universe is pixelated in time? Ever?
• 19:21
  Speaker 1: Yeah, those are two great questions. Will we ever find
• 19:24
  Speaker 1: out how general relativity or how space is bent by
• 19:27
  Speaker 1: quantum particles. There's a bunch of really cool, clever experiments. Well,
• 19:30
  Speaker 1: one way to do it is to try to come
• 19:31
  Speaker 1: up with a theory of quantum gravity that mirrors these
• 19:34
  Speaker 1: things together and tells us sort of like conceptually how
• 19:36
  Speaker 1: time might work. Another is to try to like make
• 19:39
  Speaker 1: approximate calculations and guess even without the theory of quantum gravity.
• 19:43
  Speaker 1: And you heard one of the listeners talk about the
• 19:44
  Speaker 1: plank time. And another is to try to make fast
• 19:47
  Speaker 1: measurements and see, like, can we zoom in on stuff
• 19:50
  Speaker 1: in the universe and see if we can measure these
• 19:53
  Speaker 1: pixels if we can notice some like discrete unit of
• 19:56
  Speaker 1: time happening in our experiments.
• 19:58
  Speaker 2: Like we might measure some in an experiment and actually
• 20:01
  Speaker 2: see the pixels of time.
• 20:03
  Speaker 1: Yeah, exactly, the way you can zoom in on a
• 20:05
  Speaker 1: screen and see the pixels are there, right, Or you
• 20:08
  Speaker 1: could slow down a movie and notice, oh, it's not
• 20:11
  Speaker 1: actually a continuous motion, it's just a bunch of still frames.
• 20:15
  Speaker 1: If you could zoom in on the physical universe in time,
• 20:19
  Speaker 1: then you might notice those time pixels if they're there.
• 20:22
  Speaker 2: Yeah, Well, I guess the question is how fast are
• 20:25
  Speaker 2: things in nature? And the second question you can ask
• 20:28
  Speaker 2: is what's the fastest thing that we can measure or
• 20:31
  Speaker 2: that we have been able to measure? Yeah, so far,
• 20:33
  Speaker 2: So let's dig into both of those small questions. I
• 20:36
  Speaker 2: guess short questions. Probably not, But unfortunately it's time to
• 20:41
  Speaker 2: take a quick break. All right, very quickly, Daniel, what
• 20:56
  Speaker 2: are we talking about today?
• 20:58
  Speaker 1: We're talking about the fastest thing that ever happened.
• 21:02
  Speaker 2: Not the fastest podcast episode. I think we're we're already
• 21:06
  Speaker 2: passed that point.
• 21:07
  Speaker 1: Maybe somebody out there is playing our podcast at like
• 21:09
  Speaker 1: ten x, so they're understanding the universe's so much faster
• 21:12
  Speaker 1: than us.
• 21:12
  Speaker 2: Well, do we sound like chipmunks now?
• 21:14
  Speaker 1: Then to them we should talk really slowly for those people.
• 21:21
  Speaker 2: Maybe we shouldn't like figure out how to encode secret
• 21:23
  Speaker 2: messages by talking backwards. Like if you play the podcast backwards.
• 21:28
  Speaker 1: If you only listen to every twenty fifth word, I say,
• 21:31
  Speaker 1: I've been talking in secret messages the whole time. It's
• 21:34
  Speaker 1: for the special audience.
• 21:35
  Speaker 2: It's like you and Tater Swift hiding secret messages.
• 21:40
  Speaker 1: Yeah, it's like those books where if you read only
• 21:42
  Speaker 1: the words along the left side of the page, it's
• 21:44
  Speaker 1: a whole second message.
• 21:45
  Speaker 2: There all right, if you take every twenty fifth word
• 21:47
  Speaker 2: Daniel has ever said in all five hundred plus episodes,
• 21:50
  Speaker 2: and you take every thirteenth word that I ever said
• 21:53
  Speaker 2: in all five hundred episodes, and you put them in
• 21:55
  Speaker 2: the right order, you'll get the answer to the origin
• 21:58
  Speaker 2: of the universe, like the.
• 22:00
  Speaker 1: Universe and everything. Yeah, that's exactly. It is the big
• 22:03
  Speaker 1: reveal of folks plot twist at the end.
• 22:05
  Speaker 2: Today's a day where we announce it.
• 22:06
  Speaker 1: Yes, absolutely, But we.
• 22:09
  Speaker 2: Are talking about how fast things are in the universe.
• 22:12
  Speaker 2: And I guess two sort of basic questions. What's the
• 22:15
  Speaker 2: fastest thing that we know about in the universe and
• 22:17
  Speaker 2: what's the fastest thing we've ever measured in the universe. Yeah,
• 22:21
  Speaker 2: so talk to us about how fast things are in
• 22:23
  Speaker 2: the universe, Like what are the different scales that we
• 22:26
  Speaker 2: know about.
• 22:27
  Speaker 1: Yeah. So, first of all, there's the unit of the second, right,
• 22:30
  Speaker 1: The second is like our natural unit of time, but
• 22:32
  Speaker 1: it's totally arbitrary. We just made it up. It's not
• 22:35
  Speaker 1: like a physical thing. You know, light travels a certain
• 22:38
  Speaker 1: distance in a second. There's some caesium atom that oscillates
• 22:41
  Speaker 1: billions of times in a second. But a second tells
• 22:44
  Speaker 1: us something about ourselves and our relationship with time, because
• 22:47
  Speaker 1: it's what we feel like is the minimum unit of
• 22:50
  Speaker 1: time that sort of makes sense to talk about between people.
• 22:53
  Speaker 1: It's like the natural rhythm of our thoughts. One second,
• 22:56
  Speaker 1: is it? I think that's why we pick the second,
• 22:59
  Speaker 1: you know, because it's a reason, like you pick a
• 23:01
  Speaker 1: unit so that you're usually talking about small numbers. I mean,
• 23:04
  Speaker 1: we could live our lives with clocks that go down
• 23:07
  Speaker 1: to the microseconds, but it would be pretty exhausting, you know,
• 23:09
  Speaker 1: if you had to tell your kid, like, okay, you
• 23:11
  Speaker 1: can watch TV for six billion milliseconds or six billion nanoseconds,
• 23:16
  Speaker 1: that'd be confusing all the time. So we tend to
• 23:18
  Speaker 1: pick units so you can say small numbers.
• 23:20
  Speaker 2: I think you're talking about like the scale of a second,
• 23:22
  Speaker 2: not exactly like the second, Like why is in the
• 23:24
  Speaker 2: second one point one seconds? Nobody knows, right.
• 23:27
  Speaker 1: Yeah, nobody knows. It's totally arbitrary, But why is this
• 23:30
  Speaker 1: second not like one hundred times longer or one hundred
• 23:33
  Speaker 1: times shorter? That tells us something about like the scale
• 23:35
  Speaker 1: in which we live.
• 23:36
  Speaker 2: We also talk about like minutes and hours. Those are
• 23:39
  Speaker 2: really important too, But I think you're saying like the
• 23:41
  Speaker 2: second is maybe the minimum amount of time that sort
• 23:44
  Speaker 2: of our brains can grow or understand or grasp.
• 23:48
  Speaker 1: Yeah, exactly, we have no smaller time unit that's not
• 23:51
  Speaker 1: just like a fraction of a second.
• 23:53
  Speaker 2: That makes sense, right, Like nobody worries about things that
• 23:55
  Speaker 2: happen in the millisecond level on an everyday basis.
• 23:58
  Speaker 1: Yeah, exactly. And if you think, but by the way
• 24:00
  Speaker 1: your body works, you know, like roughly your heart beats
• 24:03
  Speaker 1: once a second ish, depending on whether you're an athlete
• 24:06
  Speaker 1: or not. And your eyes, for example, blink in like
• 24:09
  Speaker 1: a tenth of a second, and your eyes can only
• 24:12
  Speaker 1: see things that happen, you know, to like one thirtieth
• 24:15
  Speaker 1: of a second, which is why you can play a
• 24:16
  Speaker 1: movie with like thirty frames per second and it looks continuous.
• 24:20
  Speaker 1: Your eye can't tell the difference between that and actual
• 24:23
  Speaker 1: continuous motion.
• 24:25
  Speaker 2: So maybe more it's more like the one tenth of
• 24:26
  Speaker 2: a second is really kind of the minimum unit that
• 24:29
  Speaker 2: we were used to thinking about, right, But we are
• 24:31
  Speaker 2: used to thinking about things that happen in the blink
• 24:32
  Speaker 2: of an eye.
• 24:33
  Speaker 1: And I think that's why you choose a unit to
• 24:35
  Speaker 1: be like a second, and you can think about small
• 24:37
  Speaker 1: numbers of it, you know, a tenth of a second
• 24:38
  Speaker 1: or ten seconds. It encapsulates the typical range of human activity.
• 24:43
  Speaker 1: But of course the physical universe things happen much faster,
• 24:46
  Speaker 1: you know, like even inside your brain, neurons fire. You know,
• 24:50
  Speaker 1: we think like about a thousand times a second, so
• 24:53
  Speaker 1: the processing speed of your brain is like a thousand
• 24:55
  Speaker 1: times faster than a second. And you know, tiny particles
• 24:58
  Speaker 1: out there can interact and live for much shorter times,
• 25:02
  Speaker 1: like do you create a muon in the upper atmosphere
• 25:04
  Speaker 1: because the cosmic rays smashed into a particle, that muon
• 25:07
  Speaker 1: lives for ten to the minus six seconds a millionth
• 25:10
  Speaker 1: of a second. Whoa, And you can zoom in much faster,
• 25:14
  Speaker 1: of course, and think about like what happens in a
• 25:16
  Speaker 1: billionth of a second. Well, in a billionth of a second,
• 25:19
  Speaker 1: light travels about a foot.
• 25:21
  Speaker 2: Yeah, light is fast.
• 25:23
  Speaker 1: Light is pretty fast. But it's amazing to think about,
• 25:25
  Speaker 1: like slowing time down enough to see light move right,
• 25:28
  Speaker 1: for light to travel at a small distance. Usually we
• 25:31
  Speaker 1: think about light as going like around the Earth lots
• 25:34
  Speaker 1: of times, but in a billionth of a second, it
• 25:36
  Speaker 1: only goes afoot, which is cool. There are other tiny
• 25:38
  Speaker 1: particles that live much shorter than the muon. For example,
• 25:41
  Speaker 1: if you create a bottom cork, it lives about a
• 25:43
  Speaker 1: billionth of a second before flying off to something else.
• 25:47
  Speaker 1: This is a slice of time it's hard to even
• 25:49
  Speaker 1: really think about, Like does that really exist? Is there
• 25:51
  Speaker 1: like a moment when the bottom cork is like there
• 25:54
  Speaker 1: and doing its thing before it decays? It feels almost
• 25:57
  Speaker 1: like zero time already.
• 25:59
  Speaker 2: Well, I wonder if it feels like zero time to
• 26:01
  Speaker 2: us because we're so slow, you know, in our thinking.
• 26:04
  Speaker 2: But maybe if you have like you know, microscopic creatures
• 26:08
  Speaker 2: or you know, really tiny beings that probably think a
• 26:12
  Speaker 2: lot faster, I wonder if that will seem slow to them.
• 26:14
  Speaker 1: Yeah, exactly. It's all relative, right, this choice of a second.
• 26:18
  Speaker 1: It tells us about like how we live our lives.
• 26:20
  Speaker 1: It's relative to the length of our lives and the
• 26:21
  Speaker 1: operating of our brain, but it's arbitrary. Time extends on
• 26:25
  Speaker 1: this enormous spectrum from the many, many, many billions of
• 26:28
  Speaker 1: years down to the tiniest slice, and we're operating on
• 26:31
  Speaker 1: a tiny little bit of it. It's sort of like
• 26:33
  Speaker 1: the way we can see a little slice of the
• 26:35
  Speaker 1: visual spectrum, but there's light with much higher frequencies and
• 26:38
  Speaker 1: lower frequencies in the universe is a wash in that
• 26:40
  Speaker 1: kind of light that we don't normally see. It's just
• 26:43
  Speaker 1: it's like our human perspective, but the universe operates on
• 26:47
  Speaker 1: even shorter time scales. You know, if you go down
• 26:48
  Speaker 1: to like ten to the minus fifteen seconds, this is
• 26:51
  Speaker 1: now a themto second.
• 26:53
  Speaker 2: I wonder if because we also know time is sort
• 26:55
  Speaker 2: of relative, right, So I wonder, like, if you create
• 26:57
  Speaker 2: a bottom cored near a black hole hole or in
• 27:00
  Speaker 2: a space ship going at near the speed of light,
• 27:03
  Speaker 2: is that we're going to seem longer lived to us
• 27:06
  Speaker 2: from our perspective.
• 27:08
  Speaker 1: Absolutely? Yeah. And like these muons, for example, that we
• 27:11
  Speaker 1: create in the upper atmosphere, they only live for a
• 27:14
  Speaker 1: millionth of a second, and so you might wonder like, well,
• 27:16
  Speaker 1: would they ever get down to the surface of the Earth.
• 27:18
  Speaker 1: And the answer is yes. And the only reason they
• 27:21
  Speaker 1: do make it to the surface is because they're going
• 27:23
  Speaker 1: very very fast relative to us, so their clocks are
• 27:26
  Speaker 1: running slow. So even though they live for a millionth
• 27:29
  Speaker 1: of a second, that's enough time for them to make
• 27:32
  Speaker 1: it to the surface because that million of a second
• 27:35
  Speaker 1: clicks very very slowly as we're watching them.
• 27:38
  Speaker 2: Essentially, to them, so are you saying it, they live
• 27:41
  Speaker 2: a million of a second if you're the muon, But
• 27:43
  Speaker 2: to us they actually live longer.
• 27:45
  Speaker 1: To us they live longer. Yet they travel much further
• 27:48
  Speaker 1: than otherwise because they're going fast, and so their time
• 27:50
  Speaker 1: ticks slowly. From our point of view. If you had
• 27:53
  Speaker 1: like a little clock traveling with a muon, you would
• 27:56
  Speaker 1: see its ticks going very very slowly, and it would
• 27:58
  Speaker 1: fly very far before a millionth of a second ticked over,
• 28:01
  Speaker 1: and then that muon decayed. From its point of view,
• 28:04
  Speaker 1: it only lives for a millionth of a second, but
• 28:07
  Speaker 1: it sees the atmosphere is compressed because when you're moving
• 28:09
  Speaker 1: fast relative to something you see, it's shortened. So for
• 28:12
  Speaker 1: the muon's point of view, it sees the atmosphere is compressed.
• 28:16
  Speaker 1: In short, it can make it to the bottom of
• 28:18
  Speaker 1: the atmosphere to the surface in a millionth of a second.
• 28:21
  Speaker 1: So that's an example of how special relativity is cool,
• 28:23
  Speaker 1: because from one point of view, it's time dilation, from
• 28:26
  Speaker 1: another point of view, it's length contraction. It's really the
• 28:28
  Speaker 1: same physics. But yeah, time is.
• 28:30
  Speaker 2: Relative, okay, So what else is fast in the universe.
• 28:33
  Speaker 1: So if you go down to like a femtosecond, how
• 28:36
  Speaker 1: far can light travel and like ten to the minus
• 28:38
  Speaker 1: fifteen seconds. Now we're talking about short distances. We're talking
• 28:42
  Speaker 1: about like less than a micrometer, and you can go
• 28:45
  Speaker 1: down even further to attoseconds. This is ten to the
• 28:48
  Speaker 1: mince eighteen seconds. This is a hard number to think about.
• 28:52
  Speaker 1: It's so short that the number of atoseconds in a
• 28:55
  Speaker 1: single second is the same as the number of seconds
• 28:58
  Speaker 1: that have elapsed in the whole history three of the universe. Like,
• 29:01
  Speaker 1: there's been about ten to the eighteen seconds since the
• 29:05
  Speaker 1: beginning of the universe, and an autosecond is one in
• 29:08
  Speaker 1: ten to the eighteenth of a second. So it's really
• 29:11
  Speaker 1: an incredible slice. WHOA.
• 29:12
  Speaker 2: That's like if you take a second and you split
• 29:15
  Speaker 2: it into a million, and then take each of those
• 29:17
  Speaker 2: and split it it into a million, and then take
• 29:19
  Speaker 2: each of those and split it it into a million timesteps.
• 29:22
  Speaker 2: That's what an atosecond is.
• 29:23
  Speaker 1: Yeah, exactly, it's a millionth of a millionth of a millionth.
• 29:26
  Speaker 2: Is there anything that happens at the at a second
• 29:28
  Speaker 2: level that we know about?
• 29:29
  Speaker 1: Absolutely? There are lots of particles that decay in an autosecond,
• 29:32
  Speaker 1: and as we'll talk about a minute, we've actually measured
• 29:34
  Speaker 1: things down to the autosecond. It's sort of incredible. But
• 29:37
  Speaker 1: the universe happens even faster. So we can think about
• 29:40
  Speaker 1: like a zepto second, which is ten to the minus
• 29:42
  Speaker 1: twenty one seconds. This is how long it takes a
• 29:46
  Speaker 1: photon to go from one side of the hydrogen atom
• 29:49
  Speaker 1: to the other side of the hydrogen atom. Like super
• 29:52
  Speaker 1: fast photon moving a very short distance, only takes a
• 29:56
  Speaker 1: zepto second. Pretty zipty, pretty zipty. But you know, down
• 30:00
  Speaker 1: in the realm of fundamental particles, even a zepto second
• 30:03
  Speaker 1: can feel like a long time. If we create a
• 30:05
  Speaker 1: Higgs boson in the Large Hadron Collider, for example, that
• 30:08
  Speaker 1: lasts for a thousandths of a zepto second, it's ten
• 30:11
  Speaker 1: to the minus twenty four seconds.
• 30:14
  Speaker 2: Well, meaning like you create a Higgs boson, but in
• 30:17
  Speaker 2: less than one thousands of a zept to second, it's
• 30:19
  Speaker 2: gone yeah, or probably gone.
• 30:21
  Speaker 1: It's probably gone yeah. Each one has a distribution, they're
• 30:24
  Speaker 1: pretty tighty. It's sort of like radioactive decay. It's not
• 30:26
  Speaker 1: an exact measurement doesn't disappear when its time is up.
• 30:29
  Speaker 1: There's an average there, but yeah, they live much much
• 30:32
  Speaker 1: shorter than muons. Muons live forever compared to a higgs boson.
• 30:37
  Speaker 1: You know, higgs boson can be born and died ten
• 30:40
  Speaker 1: to eighteen times before a muon decays. Whoa digging down
• 30:44
  Speaker 1: even deeper. Some of the shortest lived particles we know
• 30:47
  Speaker 1: about are things like the W boson, the z boson
• 30:49
  Speaker 1: on the top quark. These last for like ten to
• 30:52
  Speaker 1: the minus twenty seven seconds. And that's about as far
• 30:56
  Speaker 1: as we can go in terms of like theoretical stuff
• 30:58
  Speaker 1: that we can describe. And this is just probing theoretically,
• 31:01
  Speaker 1: like what can we describe in our theories of quantum
• 31:04
  Speaker 1: particles that takes this short amount of time. That's about
• 31:07
  Speaker 1: the bottom of.
• 31:08
  Speaker 2: It, meaning like of all the things that we have
• 31:11
  Speaker 2: names for physically in the universe, that's about the shortest
• 31:15
  Speaker 2: scale that the operating.
• 31:16
  Speaker 1: Yeah, exactly, And you could postulate something that happens short.
• 31:19
  Speaker 1: There's no limitation there, Like we think about other particles
• 31:23
  Speaker 1: that are really really heavy that might decay much much faster.
• 31:26
  Speaker 1: There's nothing that's stopping you from thinking about that. But
• 31:28
  Speaker 1: we don't know of any particles in the universe that
• 31:30
  Speaker 1: operate on a shorter timescale.
• 31:32
  Speaker 2: You can always talk about how fast things go right
• 31:35
  Speaker 2: or light goes right, like like, can't you say, well,
• 31:39
  Speaker 2: light travels one zipto fento minisecond in less amount of
• 31:45
  Speaker 2: time than that?
• 31:46
  Speaker 1: Mm hmm, yeah, exactly. You can always divide time further
• 31:49
  Speaker 1: according to general relativity. You can just keep slicing it
• 31:52
  Speaker 1: and you could measure it the way you describe, like
• 31:54
  Speaker 1: how far does light go? And if space is continuous
• 31:57
  Speaker 1: and time is continuous, you could just keep doing that forever. Right,
• 32:00
  Speaker 1: you go down to ten to the minus a million,
• 32:02
  Speaker 1: you know, zero point zero with a million zeros and
• 32:05
  Speaker 1: then a one of seconds, and think about how far
• 32:08
  Speaker 1: light goes there. But at some point you're beyond the
• 32:12
  Speaker 1: extrapolation the same way that we talked about like genm
• 32:14
  Speaker 1: relativity breaking down. You know, when we go to the
• 32:18
  Speaker 1: heart of black holes and having infinite density. We're not
• 32:21
  Speaker 1: really comfortable thinking about things theoretically smaller than a certain
• 32:25
  Speaker 1: time called the Plank time, which is ten to the
• 32:27
  Speaker 1: minus forty four seconds. We think that our theory of
• 32:31
  Speaker 1: quantum particles and quantum field theory and the standard model
• 32:34
  Speaker 1: works very very well down to about that resolution, and
• 32:37
  Speaker 1: beyond that we don't trust it.
• 32:39
  Speaker 2: I know we had an episode about the plank time,
• 32:41
  Speaker 2: but it was too much time ago I don't remember.
• 32:45
  Speaker 2: So maybe for our listeners, what is the plank time?
• 32:48
  Speaker 2: But make it quick.
• 32:50
  Speaker 1: The plank time is sort of two things. It's on
• 32:52
  Speaker 1: one hand, just like you put together a bunch of
• 32:55
  Speaker 1: physical constants of the universe until you get something that
• 32:58
  Speaker 1: has units of time, and then you ask, okay, what's
• 33:01
  Speaker 1: the number. So you take like the speed of light
• 33:04
  Speaker 1: and the gravitational constant and planks constant, and those all
• 33:07
  Speaker 1: have units on them, you know, energy or meters or
• 33:09
  Speaker 1: seconds whatever, but you can put them together in a
• 33:11
  Speaker 1: way that cancels and you get a number, and that
• 33:13
  Speaker 1: number is ten to the minus forty four seconds, and
• 33:16
  Speaker 1: then you can ask, well, what does that number mean?
• 33:18
  Speaker 1: And you know the number doesn't mean anything very precisely.
• 33:21
  Speaker 1: You hear a lot in popular science that it's like,
• 33:23
  Speaker 1: definitively the minimum resolution of time. It's definitely not that.
• 33:26
  Speaker 1: It's just like, this is what we can do to
• 33:29
  Speaker 1: say roughly where things start to be different because at
• 33:32
  Speaker 1: the plank time, or if you rearrange it to the
• 33:35
  Speaker 1: plank distance, or you rearrange it differently to like the
• 33:37
  Speaker 1: plank energy. That's where we think our theories break down,
• 33:40
  Speaker 1: where we need to have some contribution from gravity and
• 33:44
  Speaker 1: some contribution from quant mechanics, and again we don't know
• 33:47
  Speaker 1: how to put those two things together. So we can
• 33:49
  Speaker 1: extrapolate our theories up to about the plank energy or
• 33:52
  Speaker 1: down to the plank time it's equivalent, but beyond that
• 33:55
  Speaker 1: is basically a question mark. Theoretically, we don't know how
• 33:58
  Speaker 1: to do calculations that we trust and rely on shorter
• 34:01
  Speaker 1: than the plank time.
• 34:02
  Speaker 2: Maybe another way to look at it is that it's
• 34:04
  Speaker 2: sort of like when the things that we know about
• 34:07
  Speaker 2: that happen physically in the universe sort of end, right,
• 34:09
  Speaker 2: Like we don't know of anything that's smaller than the
• 34:11
  Speaker 2: plank distance, or we don't know of anything that happens
• 34:15
  Speaker 2: shorter than the plank time to scale, and so it's
• 34:17
  Speaker 2: like unknown territory.
• 34:19
  Speaker 1: Yeah, it's unknown territory, and it's unknown territory. We can't
• 34:22
  Speaker 1: even like really think coherently past it, like we've never
• 34:26
  Speaker 1: seen anything at ten to the minus forty four seconds.
• 34:29
  Speaker 1: But we can talk about it, and we can calculate it,
• 34:31
  Speaker 1: we can imagine it, we can use our theories, but
• 34:34
  Speaker 1: beyond that, we don't even really know how to think
• 34:36
  Speaker 1: about it carefully. Like you could think about it not carefully.
• 34:39
  Speaker 1: You could say, well, I'm just going to use general
• 34:41
  Speaker 1: relativity and assume it is correct and talk about infinite
• 34:44
  Speaker 1: slices of time and infinitely short distances like travel. You
• 34:46
  Speaker 1: could do that, but nobody believes that that describes reality,
• 34:50
  Speaker 1: the same way nobody believes that there's a singularity the
• 34:53
  Speaker 1: heart of a black hole. It's a naive extrapolation of
• 34:56
  Speaker 1: general relativity beyond what we think is reasonable, and so
• 34:59
  Speaker 1: we can't even really think coherently about it, sort of
• 35:02
  Speaker 1: the way we can't think coherently about what happened before
• 35:04
  Speaker 1: the Big Bang, because for the same reason our theories
• 35:07
  Speaker 1: break down there. We need a theory of quantum gravity
• 35:09
  Speaker 1: to take us further back. So we don't even have
• 35:12
  Speaker 1: like mental theoretical pictures that we can trust.
• 35:15
  Speaker 2: Right right, all right, Well, that's kind of a picture
• 35:17
  Speaker 2: of how fast things move in the universe, now, Daniel,
• 35:19
  Speaker 2: how fast do kids grow up? Faster than that? Or flow?
• 35:23
  Speaker 1: It feels like a million years every hour when you're
• 35:27
  Speaker 1: in it and then it feels like a million of
• 35:29
  Speaker 1: a second, and when you're looking back on.
• 35:30
  Speaker 2: It as their physical effect. A name for that. It's
• 35:35
  Speaker 2: called the theory of relations, theory of relatives. Yeah, that's
• 35:40
  Speaker 2: what I was gonna say, the relatives. Yeah, the relative
• 35:43
  Speaker 2: theory of relatives.
• 35:45
  Speaker 1: Parental time dilation in the theory of relatives. But no,
• 35:48
  Speaker 1: we have been doing our best to try to understand
• 35:51
  Speaker 1: how fast things actually happen in our universe, not just
• 35:53
  Speaker 1: think about them theoretically, and lots of really cool, amazing
• 35:57
  Speaker 1: techniques out there to measure really really short of time.
• 36:02
  Speaker 2: I guess what we've been talking about are things that
• 36:05
  Speaker 2: we know happen in super short time scales. But then
• 36:07
  Speaker 2: there's the other question, the flip side, which is which
• 36:10
  Speaker 2: of these events can we actually measure and see for
• 36:14
  Speaker 2: ourselves that they happen at that timescale. Yeah, so let's
• 36:17
  Speaker 2: get into that technology. But first let's take another quick break.
• 36:33
  Speaker 2: All right, we're talking about the fastest things in the universe,
• 36:37
  Speaker 2: or I guess, the fastest events in the universe, the
• 36:39
  Speaker 2: things that happened in at the shortest time scales.
• 36:42
  Speaker 1: Yeah, exactly, the most fleeting things in the universe.
• 36:45
  Speaker 2: Yeah, yeah, and this podcast is I think at it
• 36:48
  Speaker 2: for maybe the longest event in the universe. But let's
• 36:53
  Speaker 2: get to it because we're gonna get a run short
• 36:54
  Speaker 2: of time soon.
• 36:56
  Speaker 1: Yeah. So when we try to see things happening in
• 36:58
  Speaker 1: the universe, we do something pretty basic. We take slow
• 37:01
  Speaker 1: motion footage. Like if you're taking a movie and you
• 37:04
  Speaker 1: measure thirty frames per second and then you play them
• 37:06
  Speaker 1: on the screen at thirty frames per second, then everything
• 37:09
  Speaker 1: plays like normal. But if instead you take like three
• 37:12
  Speaker 1: hundred frames per second and you play them on the
• 37:15
  Speaker 1: screen at thirty frames per second, then time looks slow.
• 37:18
  Speaker 1: In the movie, everything is slowed down. You can see
• 37:21
  Speaker 1: ussin Bolt running at a reasonable rate. You can see
• 37:24
  Speaker 1: fast things happening more slowly. So that's what we try
• 37:28
  Speaker 1: to do, is we try to develop cameras that can
• 37:30
  Speaker 1: basically take pictures or make measurements equivalently much faster than
• 37:35
  Speaker 1: thirty frames per second, so that we can watch them
• 37:37
  Speaker 1: slow down and try to understand what happens.
• 37:40
  Speaker 2: Right, And it sort of depends on what you're trying
• 37:42
  Speaker 2: to capture too, Right, Like the slow motion camera on
• 37:45
  Speaker 2: your phone can capture you know, your kids running, maybe
• 37:48
  Speaker 2: somebody jumping into a pool, pretty good. But if you're
• 37:51
  Speaker 2: trying to capture something faster, like a bullet or an explosion,
• 37:54
  Speaker 2: it's not going to be fast enough exactly.
• 37:56
  Speaker 1: And in the old days, people used shutters for this,
• 37:59
  Speaker 1: Like you had a camera and you open the shutter
• 38:01
  Speaker 1: and you let light in. And if you're trying to take,
• 38:03
  Speaker 1: for example, a picture of a sporting event, where when
• 38:06
  Speaker 1: things are moving really fast, you had a really fast
• 38:08
  Speaker 1: shutter setting right, your shutters open for a tiny fraction
• 38:10
  Speaker 1: of a second. Whereas if you're taking a picture of
• 38:13
  Speaker 1: something in the dark, like at night, I have a
• 38:15
  Speaker 1: really long exposure, so gather as much light maybe seconds
• 38:18
  Speaker 1: or even hours.
• 38:19
  Speaker 2: Now, what made you think of a camera? I wonder
• 38:22
  Speaker 2: if that, in the history of humanity, if cameras are
• 38:25
  Speaker 2: maybe the first time that we've had something like automated
• 38:28
  Speaker 2: recording instances of data about the world, because before that, I imagine,
• 38:34
  Speaker 2: you know, it was maybe people writing things down on
• 38:36
  Speaker 2: a piece of paper.
• 38:38
  Speaker 1: I think that before cameras, we probably had recordings of
• 38:41
  Speaker 1: sound also, right, which you could think about the same way,
• 38:45
  Speaker 1: you know, probably within decades of each other. I haven't
• 38:48
  Speaker 1: looked at the details.
• 38:49
  Speaker 2: But those were analogue probably right, Yeah.
• 38:51
  Speaker 1: Those were definitely analog. The first measurements were definitely analog.
• 38:54
  Speaker 1: It's a interesting question, like how far back do we
• 38:57
  Speaker 1: have like data things where we have recordings that are
• 38:59
  Speaker 1: not just eyewitness testimony, you know. I mean Gallet, for example,
• 39:03
  Speaker 1: has his drawings of the night sky, and in some
• 39:06
  Speaker 1: sense that's still data, right, it went into his eye
• 39:08
  Speaker 1: and out his arm, so he's sort of the recording
• 39:11
  Speaker 1: device there.
• 39:11
  Speaker 2: Yeah, well that's what I mean. Like I wonder for
• 39:13
  Speaker 2: most of the history of science, people will just writing
• 39:16
  Speaker 2: things down a piece of paper. But maybe the cameras,
• 39:18
  Speaker 2: where you expose a piece of film or played for
• 39:21
  Speaker 2: a certain amount of time, that's maybe some of the
• 39:23
  Speaker 2: first times that we had kind of this idea of
• 39:26
  Speaker 2: a mechanical recording of what's happening in the universe.
• 39:30
  Speaker 1: Yeah, very cool question. I'm not sure we'll dig into
• 39:33
  Speaker 1: the history that. Maybe I'll look into that for an episode.
• 39:36
  Speaker 1: But these days we use digital cameras, right, And these
• 39:39
  Speaker 1: digital cameras can be very very fast, and the technology
• 39:43
  Speaker 1: behind the digital camera actually limits how fast they can go.
• 39:47
  Speaker 1: The way a digital camera works is that a photon
• 39:49
  Speaker 1: comes in the lens the same way it does for
• 39:51
  Speaker 1: a normal camera. But instead of hitting a piece of
• 39:53
  Speaker 1: film which has like special chemicals on it that react
• 39:56
  Speaker 1: to the light, instead you hit a pixel, which is
• 39:59
  Speaker 1: a piece of phil and the photon hits an electron
• 40:01
  Speaker 1: inside that piece of silicon, and then the electron is
• 40:04
  Speaker 1: like free. It's like bumped out a little hole it
• 40:06
  Speaker 1: was stuck in. It can move along a little bit,
• 40:08
  Speaker 1: and then it drifts along to the edge of the
• 40:10
  Speaker 1: pixel and it gets picked up by some electronics and measured.
• 40:14
  Speaker 1: That's how individual pixel works inside your digital camera. It's
• 40:17
  Speaker 1: this interaction between the photon the electron. The electron causes
• 40:20
  Speaker 1: a little bit of current, and those can be really fast.
• 40:23
  Speaker 1: Like you can get CCDs or sea moss devices which
• 40:26
  Speaker 1: are more modern, which can take pictures down to millions
• 40:28
  Speaker 1: of frames per second.
• 40:30
  Speaker 2: Well, you mean, like the camera in my phone can
• 40:32
  Speaker 2: do that.
• 40:32
  Speaker 1: Not necessarily the camera in your phone, but like very
• 40:35
  Speaker 1: high tech sea moss and CCD devices can do this.
• 40:38
  Speaker 1: People who want to take pictures of lightning or like
• 40:40
  Speaker 1: fuel in a plasma dissolving, or very high speed scientific events,
• 40:45
  Speaker 1: they have specialized cameras that can get down to millions
• 40:47
  Speaker 1: of frames per second In order to be that fast,
• 40:50
  Speaker 1: you need like very small pixels with very fast electron
• 40:53
  Speaker 1: drift time. That's what in the end limits it how
• 40:55
  Speaker 1: long it takes the electron once it's been freed to
• 40:58
  Speaker 1: like slide over to the park to the PicTel where
• 41:00
  Speaker 1: it gets read out. If you went really really high
• 41:02
  Speaker 1: speed cameras, you're going to make some sacrifices in the
• 41:05
  Speaker 1: design to make it that fast. So then it's not
• 41:07
  Speaker 1: as good for like taking pictures of your kids, but
• 41:10
  Speaker 1: it's really good for measuring fast things.
• 41:12
  Speaker 2: You might be able to catch the exact point at
• 41:14
  Speaker 2: which they grew up and record it forever.
• 41:17
  Speaker 1: Yeah, exactly when they started rolling their eyes at you
• 41:20
  Speaker 1: instead of laughing at your jokes.
• 41:21
  Speaker 2: Yeah, there you go. That's slow roll their eyes. You
• 41:24
  Speaker 2: can have it at a million of a second resolution.
• 41:27
  Speaker 1: Yeah, and these are cool devices. Actually played with one
• 41:29
  Speaker 1: for one of my first science projects when I was
• 41:32
  Speaker 1: a summer student, using it to take pictures of lightning
• 41:36
  Speaker 1: in the skies in New Mexico at thousands of frames
• 41:38
  Speaker 1: per second, which is pretty cool. It's amazing to see
• 41:41
  Speaker 1: the world slow down.
• 41:42
  Speaker 2: But I wonder why you bring up cameras. I know
• 41:44
  Speaker 2: cameras are used in astronomy, right, like those big telescopes
• 41:48
  Speaker 2: they have basically camera sensors at the end of the telescope.
• 41:52
  Speaker 2: But how much are cameras used in like physics labs.
• 41:56
  Speaker 1: Well, it's a little bit philosophical.
• 41:57
  Speaker 3: You know.
• 41:57
  Speaker 1: You could think of our particle physics detectors kind of
• 42:00
  Speaker 1: a camera. You know, it's a bunch of pixels arranged
• 42:03
  Speaker 1: around a collision point, and it takes an image. In
• 42:06
  Speaker 1: some sense, a camera really is just an array of detectors.
• 42:09
  Speaker 1: You know, any kind of detector you have, just make
• 42:11
  Speaker 1: an array of them so you get some sort of
• 42:13
  Speaker 1: like spatial measurement as well as time. You know, that's
• 42:16
  Speaker 1: really what a picture is. It's just like a bunch
• 42:18
  Speaker 1: of measurements all in an array.
• 42:21
  Speaker 2: Are you saying that the large Hadron collider the eight
• 42:23
  Speaker 2: billion dollar machine there, and we could have just used
• 42:25
  Speaker 2: the cell phone camera.
• 42:28
  Speaker 1: Yeah, actually that's what we did. We just bought one
• 42:30
  Speaker 1: iPhone and we kept the rest of the month for ourselves.
• 42:32
  Speaker 2: It's just a whole bunch of iPhones, yes, arranged around
• 42:35
  Speaker 2: the collision point.
• 42:36
  Speaker 1: Your hard hitting investigative journalism right here has exposed the
• 42:39
  Speaker 1: scam today.
• 42:41
  Speaker 2: Yes, no, but seriously, like what's the difference between the
• 42:44
  Speaker 2: sensors that the large had and collider and like my
• 42:47
  Speaker 2: cell phone camera, do they work faster or are they
• 42:49
  Speaker 2: basically the same or.
• 42:51
  Speaker 1: They are basically the same. I mean, actually the devices
• 42:54
  Speaker 1: near the center of the collision, the fastest, smallest devices
• 42:57
  Speaker 1: we have are silicon devices, and we borrow the technology
• 43:01
  Speaker 1: from the semiconductor industry, which use them to develop chips
• 43:04
  Speaker 1: and cameras, so we're basically piggybacking off of that technology.
• 43:08
  Speaker 1: It's a little bit different because we apply higher voltage
• 43:11
  Speaker 1: across these pixels to make them read out a little
• 43:13
  Speaker 1: bit faster, but it's fundamentally the same thing. Yeah.
• 43:16
  Speaker 2: Wait wait, so then when you take a picture of
• 43:18
  Speaker 2: a Higgs boson, can you put it in portrait mode?
• 43:21
  Speaker 1: Also you can do the touch up? Yeah? Absolutely, I
• 43:26
  Speaker 1: like my Sepia Higgs boson only timey Higgs boson.
• 43:30
  Speaker 2: Or like the Higgs boson with bunny ears or something.
• 43:34
  Speaker 1: All the best scientific papers and bunny ears. Absolutely.
• 43:36
  Speaker 2: Yes, yeah, I know it'd be very popular in TikTok.
• 43:39
  Speaker 1: Yeah, but in the end, this is limited in time.
• 43:41
  Speaker 1: You know, in the large Hadron collider, we don't need
• 43:43
  Speaker 1: things much faster than that. We have millions of collisions
• 43:46
  Speaker 1: per second, and so that the fact that our devices
• 43:48
  Speaker 1: can read out millions of times per second is fast enough.
• 43:51
  Speaker 1: We don't need to go faster. But there are people
• 43:53
  Speaker 1: who are interested in things that happen in like a
• 43:56
  Speaker 1: trillionth of a second instead of a billionth or a millionth.
• 43:59
  Speaker 1: There are special vice some special cameras that can take
• 44:01
  Speaker 1: footage with trillions of frames per second.
• 44:04
  Speaker 2: Wait. Wait, so you're saying the large pattern collider. You
• 44:06
  Speaker 2: don't care about things or you can't measure things that
• 44:09
  Speaker 2: happen faster than a minute of a second.
• 44:11
  Speaker 1: We don't care about things that happen faster than that,
• 44:14
  Speaker 1: and we can't resolve it anyway. It would be much
• 44:17
  Speaker 1: more expensive to have our devices be able to do that.
• 44:19
  Speaker 1: But we only have one collision.
• 44:21
  Speaker 2: I know you need the latest iPhone.
• 44:22
  Speaker 1: Probably we're interested in one collision at a time, right,
• 44:26
  Speaker 1: So if we only looked at one collision, we wouldn't
• 44:30
  Speaker 1: need to be very fast. You just have a collision.
• 44:32
  Speaker 1: It sits in your detector, you read it out. It's
• 44:34
  Speaker 1: like a single picture. We're not taking movies of these interactions.
• 44:38
  Speaker 1: We only take one picture basically per interaction.
• 44:42
  Speaker 2: Oh I see, but could you would you learn more?
• 44:44
  Speaker 2: Ife you could take a slow motion movie of like
• 44:46
  Speaker 2: two protons hitting each other.
• 44:48
  Speaker 1: We can't actually instrument the collision itself, only the stuff
• 44:51
  Speaker 1: that flies out of it, and so in the end
• 44:53
  Speaker 1: we're just sort of looking at the debris. And sometimes
• 44:56
  Speaker 1: we are interested in like when bits arise, because it
• 44:59
  Speaker 1: tells us like how fast they're moving. So we do
• 45:01
  Speaker 1: have some specialized time of flight detectors people developed to
• 45:05
  Speaker 1: see like did this photon arrive before that electron in
• 45:08
  Speaker 1: the same collision or not, So we do sometimes dig
• 45:11
  Speaker 1: into that a little bit, but mostly we just care
• 45:13
  Speaker 1: about what flew out. We don't usually care about like
• 45:15
  Speaker 1: what the order was or the sequence of events doesn't
• 45:17
  Speaker 1: really tell us that much more. And it's really really
• 45:20
  Speaker 1: hard to do, especially that fast.
• 45:22
  Speaker 2: Interesting, but you're saying that there are, as we talked
• 45:24
  Speaker 2: about before, there are physical events that happen in a
• 45:27
  Speaker 2: much shorter timescale, and so for that you need even
• 45:30
  Speaker 2: better cameras.
• 45:31
  Speaker 1: Yeah, and these are called streak cameras. The idea of
• 45:33
  Speaker 1: a CCD or SEEMS device is a photon releases an
• 45:37
  Speaker 1: electron and then you pick up those electrons. But you
• 45:40
  Speaker 1: don't distinguish between an electron that arrived near the end
• 45:43
  Speaker 1: of your time cycle and near the beginning of it,
• 45:45
  Speaker 1: and within a single frame, you count those electrons the
• 45:47
  Speaker 1: same way, and that loses information. If there are things
• 45:49
  Speaker 1: happening faster than your time cycle than your frame, then
• 45:53
  Speaker 1: you're losing them. So a streak camera tries to take
• 45:56
  Speaker 1: advantage of that, and it applies a time varying electric feel.
• 46:00
  Speaker 1: So electrons that are released at one moment and electrons
• 46:02
  Speaker 1: are released another moment will end up in different directions,
• 46:05
  Speaker 1: so it sort of like sweeps a single frame across
• 46:10
  Speaker 1: something in space and like spreads it out. That's why
• 46:13
  Speaker 1: it's called a streak camera, like takes these electrons and
• 46:16
  Speaker 1: sprays them across something so you can tell when they arrived.
• 46:20
  Speaker 2: Well wait, wait, so this is like a sensor just
• 46:24
  Speaker 2: like the camera or is this a different kind of sensor.
• 46:26
  Speaker 1: It's fundamentally like a camera, right. A photon comes in
• 46:29
  Speaker 1: and releases an electron, but instead of just letting the
• 46:31
  Speaker 1: electrons drift across your pixel, you know, guiding these electrons
• 46:35
  Speaker 1: to different places like on a mini screen based on
• 46:38
  Speaker 1: when they arrived.
• 46:40
  Speaker 2: So sort of instead of catching the electrons in a bucket.
• 46:42
  Speaker 2: You sort of sweep the bucket so that you can
• 46:45
  Speaker 2: tell when the electrons were released, which tells you when
• 46:48
  Speaker 2: the photons arrived at your sensor.
• 46:50
  Speaker 1: Exactly. Yeah, So where the electron hits tells you when
• 46:54
  Speaker 1: it was created, which tells you when the photon arrived.
• 46:57
  Speaker 1: So then you could tell the difference between a photon
• 46:59
  Speaker 1: that arrived at the beginning or the end of your frame.
• 47:02
  Speaker 2: And this gets you more more time resolution.
• 47:05
  Speaker 1: Yes, exactly, And so street cameras go down to like
• 47:09
  Speaker 1: ten to the minus fourteen seconds. The fastest that I
• 47:11
  Speaker 1: found was one that can do seventy trillion frames per second.
• 47:16
  Speaker 1: That's like a lot of pictures of your kid picking
• 47:18
  Speaker 1: their nose.
• 47:22
  Speaker 2: Well, depends how quickly they do it. But what kinds
• 47:26
  Speaker 2: of things are being measured with this crazy camera? Like
• 47:29
  Speaker 2: what are they trying to do?
• 47:31
  Speaker 1: These things are used to understand like biochemistry and some
• 47:34
  Speaker 1: kind of interactions, you know, like proteins folding or bonds forming,
• 47:39
  Speaker 1: you know, basically chemicals interacting this kind of stuff. But
• 47:44
  Speaker 1: you know, lots of people are just curious and nobody
• 47:45
  Speaker 1: really knows. It's sort of like uncharted territory. There are
• 47:48
  Speaker 1: things we think happen in a certain way, and it
• 47:50
  Speaker 1: might be that if you slow them down they happen differently.
• 47:53
  Speaker 1: This weird stuff happening that nobody expected. So it's sort
• 47:56
  Speaker 1: of like exploring the unknown. So people are using street
• 47:59
  Speaker 1: cameras to or all sorts of things hoping to find
• 48:02
  Speaker 1: something new.
• 48:03
  Speaker 2: Now, this is if you're trying to capture photons, right.
• 48:06
  Speaker 1: Yeah, in order to like take a picture of something.
• 48:09
  Speaker 2: Right, right, But you can also just measure things in
• 48:12
  Speaker 2: other ways, right, like measure the voltage of something, or
• 48:14
  Speaker 2: measure I don't know, the magnetic field or something.
• 48:16
  Speaker 1: Hmm.
• 48:17
  Speaker 2: Would those be able to be measured faster?
• 48:20
  Speaker 1: Yeah? Absolutely, there's not a fundamental limitation there. You know.
• 48:23
  Speaker 1: The question is really like can you capture something which
• 48:26
  Speaker 1: varies that quickly? Can you isolate it? And in order
• 48:30
  Speaker 1: to do that you need to like probe it. You
• 48:32
  Speaker 1: need to like create something that happens at that fast
• 48:34
  Speaker 1: time slice so that you can take a picture of it.
• 48:37
  Speaker 1: You need like something that happens really quickly, and then
• 48:39
  Speaker 1: something that can respond very quickly, and then something that
• 48:42
  Speaker 1: can record that. And people are really pushing the forefront
• 48:46
  Speaker 1: of that technology. This is actually what won the Nobel
• 48:49
  Speaker 1: Prize in twenty twenty three is making super duper short
• 48:53
  Speaker 1: laser pulses down to the atto second, down to ten
• 48:56
  Speaker 1: to the minus eighteen seconds. And these were super short
• 49:00
  Speaker 1: laser pulses created by layering longer laser pulses on top
• 49:04
  Speaker 1: of each other to sort of like interfere with each
• 49:06
  Speaker 1: other to make a super short pulse. And you can
• 49:09
  Speaker 1: use this to like probe things that are happening inside
• 49:12
  Speaker 1: the nucleus or inside an atom. You can give it
• 49:15
  Speaker 1: a super short kick and see what happens.
• 49:17
  Speaker 2: Yeah, how does that help you measure of something fast
• 49:20
  Speaker 2: a short laser pulse.
• 49:22
  Speaker 1: They use this technique called pump probe measurements. Basically, you
• 49:25
  Speaker 1: shoot this laser pulse at the thing you're trying to
• 49:28
  Speaker 1: look at and you take one measurement of it, so
• 49:30
  Speaker 1: you have like one measurement of where your electron is
• 49:33
  Speaker 1: after you zap it with a laser. And what you're
• 49:35
  Speaker 1: really interested in is like a movie, So you want
• 49:37
  Speaker 1: to see, like how does the electron jumping from one
• 49:40
  Speaker 1: energy level to another or from one atom to another.
• 49:43
  Speaker 1: So you zap it with this laser pulse and you
• 49:45
  Speaker 1: take one measurement of your electron. That doesn't give you
• 49:47
  Speaker 1: a whole movie, but you can do it over and
• 49:49
  Speaker 1: over again. So if you can set up the same
• 49:51
  Speaker 1: system over and over again and zap it with a
• 49:54
  Speaker 1: laser pulse at slightly different times along the process, and
• 49:58
  Speaker 1: take a measurement each time, and you can put them
• 50:00
  Speaker 1: together into a movie. So it's like if you watch
• 50:04
  Speaker 1: your kid do a long jump, and you take a
• 50:06
  Speaker 1: really fast picture, but only one picture per long jump,
• 50:09
  Speaker 1: and then you stitch them together into a whole description
• 50:12
  Speaker 1: of the long jump. Because you're able to take really
• 50:14
  Speaker 1: fast pictures, you have a now very slow motion movie
• 50:17
  Speaker 1: of the long jump. It's really a movie of like
• 50:20
  Speaker 1: a thousand long jumps. So you took one picture from each,
• 50:22
  Speaker 1: so it's not exactly the same thing, but in principle,
• 50:25
  Speaker 1: they are very fast measurements of this event.
• 50:28
  Speaker 2: I think I see what you're saying that this is
• 50:30
  Speaker 2: like a flash basically, right, Yeah, you're basicallyating a super
• 50:33
  Speaker 2: fast flash, which lets you capture what's going on even
• 50:37
  Speaker 2: if that thing is going super super fast. By having
• 50:40
  Speaker 2: a really short flash, you can get a picture of
• 50:43
  Speaker 2: it because otherwise, like even the flash in your camera
• 50:46
  Speaker 2: takes a while. And so if anything happens faster than
• 50:48
  Speaker 2: that will just get streaked in your photo.
• 50:51
  Speaker 1: Yeah, exactly. Like remember those Strobe photographs. People develop really
• 50:55
  Speaker 1: fast flashes and they took pictures like a bullet them
• 50:57
  Speaker 1: through an apple. You don't need a really fast camera
• 50:59
  Speaker 1: if you have a really fast flash and everything is
• 51:01
  Speaker 1: dark otherwise, because then you're only illuminating it during one
• 51:04
  Speaker 1: very brief moment. Now imagine you did that same experiment
• 51:08
  Speaker 1: a million times, and you turn the flash on a
• 51:10
  Speaker 1: slightly different time each time. You'd have a whole movie,
• 51:13
  Speaker 1: a whole slow motion movie. It'd be from different bullets
• 51:16
  Speaker 1: hitting different apples, but in principle you'd put together the
• 51:19
  Speaker 1: dynamics of what's happening.
• 51:21
  Speaker 2: All right, So that's a camera then that can take
• 51:23
  Speaker 2: pictures as essentially sort of every at a second.
• 51:27
  Speaker 1: Yeah. The limitation so far as forty three auto seconds.
• 51:31
  Speaker 1: So this is really getting to the edge of what
• 51:33
  Speaker 1: we can do. But the fastest thing ever measured actually
• 51:38
  Speaker 1: does get down to the zepdo second. This is a
• 51:42
  Speaker 1: really cool technique where they shoot a photon and a
• 51:45
  Speaker 1: molecule that has two electrons. So say, for example, you
• 51:48
  Speaker 1: have like H two, which is two protons and two electrons, right,
• 51:53
  Speaker 1: two atoms of hydrogen bonded together. You shoot a photon
• 51:56
  Speaker 1: at it, and it actually interacts with both electrons. Okay,
• 52:00
  Speaker 1: So this single photon like hits one electron and then
• 52:02
  Speaker 1: it hits another electrons and those electrons react, right, both
• 52:07
  Speaker 1: of them generate some signal, and those signals interfere. And
• 52:10
  Speaker 1: by looking at the interference between the light generated from
• 52:14
  Speaker 1: those two electrons, you can see this time difference. So
• 52:18
  Speaker 1: you can tell that the photon hit one and then
• 52:20
  Speaker 1: later it hit the other one, and the time difference
• 52:23
  Speaker 1: between those two things is about two hundred and fifty
• 52:26
  Speaker 1: zepto seconds.
• 52:27
  Speaker 2: WHOA, now, what does this help you measure? When you
• 52:31
  Speaker 2: use this to take a photograph.
• 52:32
  Speaker 1: Of it, lets you declare yourself the king of time. Man.
• 52:35
  Speaker 1: This is the fastest thing ever measured. So, in one sense,
• 52:38
  Speaker 1: this is just like engineers being awesome and like trying
• 52:42
  Speaker 1: to make things as fast as possible, just for the
• 52:44
  Speaker 1: purpose of making things as fast as possible.
• 52:46
  Speaker 2: Well, first of all, Daniel, engineers are awesome, yes, just
• 52:49
  Speaker 2: by being engineeredselves.
• 52:50
  Speaker 1: Yes, even when they sleep in and sit around in
• 52:52
  Speaker 1: their pajamas and doodle cartoons all day. Engineers are exactly.
• 52:55
  Speaker 2: I mean, that's even more awesome. Let's face it, absolutely,
• 52:58
  Speaker 2: that's the pinnacle of awesome obviously, right, Like who wouldn't
• 53:01
  Speaker 2: go on that job.
• 53:03
  Speaker 1: Without doubt, without doubt. But you know, if you're interested
• 53:07
  Speaker 1: in how H two works and how electrons interfere with
• 53:10
  Speaker 1: each other, you know, and understanding the system and all
• 53:13
  Speaker 1: is full glory. Usually we think about like an individual
• 53:16
  Speaker 1: electron one at a time, but really it's a complicated
• 53:18
  Speaker 1: system where the electrons can interact and affect each other.
• 53:21
  Speaker 1: If you want to understand the finite gradations of energy
• 53:25
  Speaker 1: levels in H two, then this can help you understand that.
• 53:28
  Speaker 1: By poking one electron and poking another.
• 53:30
  Speaker 2: So what is it actually measuring, like the difference in
• 53:33
  Speaker 2: time between when the electrons came out of the atom
• 53:36
  Speaker 2: or just when the photons hit each of the atoms
• 53:39
  Speaker 2: or what.
• 53:39
  Speaker 1: Yeah, it's measuring those two electrons. So you're knocking both
• 53:42
  Speaker 1: electrons out of the atom, and then you're making measurements
• 53:45
  Speaker 1: of those electrons, and because they're sort of almost on
• 53:48
  Speaker 1: top of each other, those two electrons can interfere, and
• 53:50
  Speaker 1: the interference pattern lets you recover that there's a time
• 53:54
  Speaker 1: difference between the two electrons when they get knocked out.
• 53:57
  Speaker 2: And the normal measurement you think, oh, both electrons can
• 54:00
  Speaker 2: not at the same time. But yeah, now you're saying
• 54:01
  Speaker 2: we can actually tell like, oh, this one, the right
• 54:03
  Speaker 2: one came out first, then the black one exactly.
• 54:06
  Speaker 1: And the difference in time is really minute. It's two
• 54:09
  Speaker 1: times ten of the negative nineteen seconds. And that is
• 54:12
  Speaker 1: the fastest thing ever measured.
• 54:15
  Speaker 2: Wha, that's even faster than the Higgs boson.
• 54:18
  Speaker 1: It's not faster than the Higgs boson, but we've never
• 54:21
  Speaker 1: measured the lifetime of a Higgs boson. The Higgs boson
• 54:24
  Speaker 1: lifetime ten of the minus twenty four seconds. That's theoretical, Like,
• 54:28
  Speaker 1: we don't know how long the Higgs boson lasts. We'd
• 54:31
  Speaker 1: haven't measured it.
• 54:32
  Speaker 2: Actually, maybe if you install the new iOS on your
• 54:36
  Speaker 2: large hydron collider phones here, yeah, a particle physics portrait mode.
• 54:42
  Speaker 2: Mm hmm.
• 54:43
  Speaker 1: There's a way indirectly to understand the lifetime of the
• 54:45
  Speaker 1: Higgs boson because it's connected to its mass and how
• 54:48
  Speaker 1: different Higgs bosons have different masses, And there's a bunch
• 54:51
  Speaker 1: of theory that lets you say, if you measure the
• 54:53
  Speaker 1: mass of the Higgs boson. You can then extrapolate to
• 54:55
  Speaker 1: know what its lifetime is, but that's not the same
• 54:57
  Speaker 1: as actually measuring its lifetime. That theory and be wrong.
• 55:01
  Speaker 1: So we haven't been able to resolve the lifetime of
• 55:03
  Speaker 1: a Higgs boson, like the time between when it's created
• 55:06
  Speaker 1: and it decays. And even this zep doo second measuring
• 55:10
  Speaker 1: device is like a factor of ten thousand too slow
• 55:14
  Speaker 1: to observe a Higgs boson.
• 55:16
  Speaker 2: Well, I guess maybe what you mean, like, this is
• 55:18
  Speaker 2: the fastest physical event we've seen. Yeah, with like a
• 55:22
  Speaker 2: camera basically.
• 55:23
  Speaker 1: Yeah, with a camera, we're like the definition of a
• 55:26
  Speaker 1: camera is kind of loose here because we're not like
• 55:28
  Speaker 1: getting pixels or images here. We're just sort of making
• 55:30
  Speaker 1: measurements after illuminating it, right, we flash it with an
• 55:33
  Speaker 1: X ray, maybe take some measurements.
• 55:35
  Speaker 2: Right, So this is the fastest event that we have
• 55:38
  Speaker 2: a pick for. So definitely it happened exactly, because otherwise
• 55:42
  Speaker 2: it didn't happen.
• 55:44
  Speaker 1: Pigs, or it didn't happen, and this is the fastest.
• 55:46
  Speaker 2: Pigs it didn't happen, Yeah, exactly, And.
• 55:48
  Speaker 1: We think probably the universe is operating on a much
• 55:51
  Speaker 1: shorter timescale we do these calculations. We're pretty confident in
• 55:55
  Speaker 1: our theory about Higgs bosons and Wz's bosons. We think
• 55:59
  Speaker 1: it's happening, but it's not the same as actually seeing it.
• 56:02
  Speaker 2: M all right, Well, it's kind of this interesting convergence
• 56:07
  Speaker 2: of technology and theory, right, It's like this is where
• 56:09
  Speaker 2: rubber meets throat basically, right, Like you have these theories,
• 56:12
  Speaker 2: but then you need actual measurements to prove that these
• 56:14
  Speaker 2: things are happening at those time scales, and that's where
• 56:17
  Speaker 2: the technology is right now, that's right.
• 56:19
  Speaker 1: And the experimental technology actually taking these pictures is still
• 56:22
  Speaker 1: like twenty five orders of magnitude away from the theory.
• 56:26
  Speaker 1: Like the theory will work down to ten of the
• 56:28
  Speaker 1: mist forty four seconds. We've only measured down to ten
• 56:31
  Speaker 1: of the mist nineteen seconds. So there's a long way
• 56:34
  Speaker 1: to go.
• 56:35
  Speaker 2: Oh so we're halfway there. Sure, Sure, we've done that
• 56:39
  Speaker 2: in what twenty years?
• 56:40
  Speaker 1: So yeah, the same way that like getting one thousand
• 56:43
  Speaker 1: dollars is like halfway to a million dollars, right, it's
• 56:45
  Speaker 1: just ten to the three insteah exactly.
• 56:47
  Speaker 2: If you think logarithms scale actually or the way inflation
• 56:53
  Speaker 2: is going right now for much to say, totally fair.
• 56:58
  Speaker 1: Anyway, we're making progress. We're illuminating the universe. It's smaller
• 57:01
  Speaker 1: and smaller time slices. Maybe eventually, one day we'll see
• 57:05
  Speaker 1: it at its smallest time slice and discover the granularity
• 57:09
  Speaker 1: of the universe itself.
• 57:10
  Speaker 2: Yeah, and we can measure the progress of human eyes
• 57:13
  Speaker 2: to see the fast things in the universe. Daniel, when
• 57:16
  Speaker 2: should be the next podcast episode where we sample how
• 57:19
  Speaker 2: fast things can be measured?
• 57:22
  Speaker 1: You know, things are happening pretty rapidly, so maybe in
• 57:24
  Speaker 1: the next couple of years so we will break this record.
• 57:28
  Speaker 2: In which case we might set a new record for
• 57:30
  Speaker 2: what's the fastest change in how fast we can measure
• 57:33
  Speaker 2: things measured by a podcast in portrait mode.
• 57:37
  Speaker 1: Yeah, and maybe by then we'll be making millions of
• 57:39
  Speaker 1: dollars instead of thousands.
• 57:41
  Speaker 2: Yeah, by then we're halfway there. Yeah, hopefully hopefully, we
• 57:44
  Speaker 2: can only hope so and maybe by then I'll actually
• 57:48
  Speaker 2: remember what we talked about in the episodes. Sounds like
• 57:51
  Speaker 2: a plan, All right, Well, we hope you enjoyed that.
• 57:53
  Speaker 2: Thanks for joining us, See you next time.
• 58:01
  Speaker 1: For more science and curiosity, come find us on social media,
• 58:04
  Speaker 1: where we answer questions and post videos. We're on Twitter, Discorg,
• 58:08
  Speaker 1: Insta and now TikTok. Thanks for listening and remember that
• 58:12
  Speaker 1: Daniel and Jorge Explain the Universe is a production of iHeartRadio.
• 58:16
  Speaker 1: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,
• 58:21
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