Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions #28

Transcript

Listener Questions #28 · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: How can massless photons add to a black hole's might?
• 0:11
  Speaker 1: Can you really make a singularity out of light?
• 0:15
  Speaker 2: Organs that come in twos include the long hand, kidney, foot,
• 0:19
  Speaker 2: and eye? But why do I only have one of
• 0:23
  Speaker 2: some things? And what's the plural of venus?
• 0:26
  Speaker 1: Ain't I could drifting bubble universes collide to end our
• 0:30
  Speaker 1: cosmic show my gravity in other dimensions?
• 0:34
  Speaker 3: Ever?
• 0:34
  Speaker 2: Let us know whatever questions keep you up at night.
• 0:38
  Speaker 2: Daniel and Kelly's answers will make it right.
• 0:41
  Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe.
• 0:44
  Speaker 4: We've done twenty eight of these. Hello, Kelly, we or Smith.
• 1:01
  Speaker 2: I study parasites and space and whatever it is that
• 1:04
  Speaker 2: y'all ask me when you send us emails.
• 1:07
  Speaker 3: Hi, I'm Daniel.
• 1:08
  Speaker 1: I'm a particle physicist, and I've answered a lot of
• 1:11
  Speaker 1: questions from listeners, but never any about ANI.
• 1:14
  Speaker 2: Oh no, that's Daniel. You'd be taking my questions. I
• 1:17
  Speaker 2: am the ANI experts in this group. Thank you very much.
• 1:21
  Speaker 2: You stick to the black holes and I stick to
• 1:24
  Speaker 2: the biology black holes.
• 1:25
  Speaker 1: Isn't there an obvious connection exactly? Aren't black holes a
• 1:28
  Speaker 1: sort of physics anus?
• 1:30
  Speaker 4: Yeah?
• 1:31
  Speaker 3: Yes, yes, And I of the universe.
• 1:34
  Speaker 2: All right, you stick to the ani of the cosmos.
• 1:37
  Speaker 2: I stick to the ani of the Earth.
• 1:39
  Speaker 1: But wait now I'm realizing it. We have it all wrong,
• 1:41
  Speaker 1: don't we. Black holes are more like mouths, and white
• 1:44
  Speaker 1: holes would be more like anus'es. Why because things don't
• 1:47
  Speaker 1: come out of black holes?
• 1:48
  Speaker 4: Oh, they go in and things go out of white holes.
• 1:51
  Speaker 2: Well, you know yet another instance where the physicists did
• 1:54
  Speaker 2: a poor job of naming things.
• 1:56
  Speaker 4: Yes, there you go again.
• 1:57
  Speaker 1: It is hard to keep the inns in the out
• 1:59
  Speaker 1: streets and time.
• 2:00
  Speaker 2: Yes, okay, well we have started by going off track,
• 2:04
  Speaker 2: so let's work on getting back on track. So we
• 2:07
  Speaker 2: are very lucky to have an audience that has so
• 2:11
  Speaker 2: many absolutely fascinating questions, and you all send them to us.
• 2:15
  Speaker 2: You send them to us at Questions at danieland Kelly
• 2:18
  Speaker 2: dot org.
• 2:18
  Speaker 1: And it's our job to break down the ins and
• 2:20
  Speaker 1: the outs of the universe, to explain to you how
• 2:23
  Speaker 1: it all works, to inject the whole universe into your brain.
• 2:27
  Speaker 1: And that's what we're going to do. On today's episode.
• 2:29
  Speaker 1: We have three warrantful questions from listeners. People who are
• 2:32
  Speaker 1: curious about the universe, people who've been listening and thinking
• 2:36
  Speaker 1: and there's something that doesn't quite click in their minds.
• 2:39
  Speaker 1: We want to make that click happen for you. So
• 2:42
  Speaker 1: if you are sitting on a question something you've never
• 2:45
  Speaker 1: really had satisfactory explained, please don't be shy. Write to
• 2:48
  Speaker 1: us questions at danieland Kelly dot org. We really do
• 2:52
  Speaker 1: right back to everybody.
• 2:54
  Speaker 2: Daniel worries back to everybody within a day. I am
• 2:58
  Speaker 2: not quite as punk as Daniel. You'll get an answer
• 3:01
  Speaker 2: from me in less than a week, for sure. But yeah,
• 3:04
  Speaker 2: we write back to everybody. Some of the questions even
• 3:07
  Speaker 2: end up on the show.
• 3:08
  Speaker 1: I promise you that email address is not a black hole.
• 3:11
  Speaker 1: It's more like a white hole because answers come out
• 3:13
  Speaker 1: of it.
• 3:13
  Speaker 2: That's right, that's right, and we are going to stretch
• 3:15
  Speaker 2: this metaphor as far as we can, and so stick
• 3:18
  Speaker 2: with us till the end of the show to see
• 3:19
  Speaker 2: where we go with it. So let's start with our
• 3:22
  Speaker 2: first question with Stephen from British Columbia.
• 3:26
  Speaker 5: Hi, Daniel and Kelly, it's Stephen from BC Canada again
• 3:29
  Speaker 5: with another question about our universe. In one of your
• 3:32
  Speaker 5: past episodes, you glaze over a fact that photons can
• 3:35
  Speaker 5: collapse into tiny black holes. My question today is about
• 3:39
  Speaker 5: those tiny black holes. What is really going on inside
• 3:42
  Speaker 5: a tiny black hole? How can something with no mass
• 3:46
  Speaker 5: be able to collapse, never mind collapse into one of
• 3:48
  Speaker 5: the most densest objects known in the universe. How can
• 3:52
  Speaker 5: a black hole be tiny? Is there a singularity in them?
• 3:56
  Speaker 3: How can a.
• 3:56
  Speaker 5: Photon become a singularity inside a tiny black hole? I
• 4:01
  Speaker 5: look forward to your answers.
• 4:02
  Speaker 1: All right, I love this question because he's really thinking
• 4:06
  Speaker 1: about the extremes. You know, we talk on this show
• 4:08
  Speaker 1: about general relativity and energy density and stuff, and he's
• 4:12
  Speaker 1: pushing it to the edge, which is what you have
• 4:14
  Speaker 1: to do to really understand physics, to say, does this
• 4:17
  Speaker 1: really connect in my brain? Do I understand every scenario?
• 4:20
  Speaker 1: What about this? What about that? What about this other thing?
• 4:22
  Speaker 1: What about this thing?
• 4:23
  Speaker 3: I heard?
• 4:24
  Speaker 1: So stevens out there doing physics in his mind. Congrats Steven,
• 4:28
  Speaker 1: and I'm very excited to answer this question for you.
• 4:31
  Speaker 2: And usually when we need to answer a physics question,
• 4:34
  Speaker 2: it makes sense to go way back to the beginning
• 4:37
  Speaker 2: to terms that you've heard since you were in kindergarten,
• 4:40
  Speaker 2: because there's probably something basic about them that you don't
• 4:42
  Speaker 2: quite understand. So Daniel, let's start with gravity. What remind
• 4:48
  Speaker 2: us what is gravity?
• 4:50
  Speaker 1: Yes, so Newton told us that gravity was a force
• 4:53
  Speaker 1: between masses, but then Einstein revealed that it's actually the
• 4:56
  Speaker 1: curvature of space time. That what we think think of
• 5:00
  Speaker 1: its gravity is actually a pseudo force because we can't
• 5:03
  Speaker 1: see the curvature of space time and its effect on
• 5:06
  Speaker 1: the motion of objects, and because we can't see its effect,
• 5:09
  Speaker 1: we attribute some mysterious force to doing that, sort of
• 5:13
  Speaker 1: like if you're on a merry go Round and you
• 5:16
  Speaker 1: throw a ball at somebody across the merry go round
• 5:18
  Speaker 1: from you. It won't reach them, it'll curl to the side,
• 5:21
  Speaker 1: and you'll think, why is that I didn't throw it
• 5:23
  Speaker 1: to the side. So you'll come up with some pseudo
• 5:26
  Speaker 1: force that accounts for the motion of that object, the
• 5:29
  Speaker 1: acceleration of that object. In the same way, if you're
• 5:31
  Speaker 1: standing on the surface of the Earth and you let
• 5:33
  Speaker 1: go of an apple, it seems like something accelerates it
• 5:37
  Speaker 1: towards the Earth. Really the apple is just following the
• 5:40
  Speaker 1: curvature of space time, and you're the one accelerating against
• 5:43
  Speaker 1: space time. So general relativity reformulates gravity as the curvature
• 5:48
  Speaker 1: of space time that affects the motion of objects in
• 5:52
  Speaker 1: a way that makes us think there's a force we
• 5:54
  Speaker 1: would call gravity.
• 5:55
  Speaker 4: Feels like that doesn't make any sense.
• 5:57
  Speaker 2: But if Newton got it wrong, I don't feel so
• 5:59
  Speaker 2: bad about getting it wrong too.
• 6:03
  Speaker 1: And the crucial thing to understand in the context of
• 6:05
  Speaker 1: this question is that the curvature of space time comes
• 6:08
  Speaker 1: from energy density. We often think about it as mass
• 6:12
  Speaker 1: tells space time how to bend, but it's not just mass.
• 6:16
  Speaker 1: General relativity generalizes from beyond just mass to any kind
• 6:20
  Speaker 1: of energy density. So, for example, if you have a
• 6:23
  Speaker 1: bunch of photons that contribute to the energy density, and
• 6:27
  Speaker 1: it can make it easier to have a black hole
• 6:29
  Speaker 1: because photons have energy.
• 6:31
  Speaker 2: Of course, okay, photons have energy. That is not a
• 6:37
  Speaker 2: controversial statement, right.
• 6:38
  Speaker 1: Yeah, exactly. And so like the canonical way to make
• 6:41
  Speaker 1: a black hole is to take a big bunch of
• 6:43
  Speaker 1: mass and squeeze it down into a tiny area. Like
• 6:46
  Speaker 1: if you took the mass of the Earth and you
• 6:48
  Speaker 1: squeezed it down to the volume of about a peanut,
• 6:51
  Speaker 1: then it would become a black hole. So black holes
• 6:54
  Speaker 1: are about energy density. Or if you took the Sun
• 6:57
  Speaker 1: and you squeezed it down to a few kilometers, it
• 6:59
  Speaker 1: would become a black hole. But you can also do
• 7:02
  Speaker 1: that with just energy if you took enough light, if
• 7:05
  Speaker 1: you focused a lot of photons in a tiny region,
• 7:09
  Speaker 1: like you had a bunch of lasers overlapping where you
• 7:12
  Speaker 1: had a big spherical mirror, so all the photons were
• 7:14
  Speaker 1: in the same place. If you got enough energy density
• 7:17
  Speaker 1: in one location at the same moment, it would curve
• 7:21
  Speaker 1: space time enough to give you a black hole.
• 7:23
  Speaker 2: Ooh, all right, So isn't there that there's a facility
• 7:26
  Speaker 2: in California that's working on fusion and they're shooting a
• 7:30
  Speaker 2: bunch of lasers at a little bit of fusion fuel.
• 7:32
  Speaker 4: Are they going to kill us all with a black hole?
• 7:36
  Speaker 1: That's the National Ignition Facility, and they're working on inertial
• 7:40
  Speaker 1: confinement fusion. They take little pellets of fuel and they
• 7:43
  Speaker 1: zap them with like one hundred and ninety six lasers.
• 7:46
  Speaker 1: I think they are in order to implode it. Like
• 7:49
  Speaker 1: the explosion of the shell creates an implosion which compresses
• 7:52
  Speaker 1: the core and then ignites fusion for that little pellet.
• 7:56
  Speaker 1: Super awesome, really cool project, but not nearly enough energy
• 8:00
  Speaker 1: to create a black hole. In order to create this
• 8:03
  Speaker 1: kind of energy, you'd need very high energy density, something
• 8:07
  Speaker 1: like ten to the thirty five jewels in a region
• 8:11
  Speaker 1: like ten to the negative fifteen meters across. You need
• 8:14
  Speaker 1: like more energy than is put out by the Sun
• 8:17
  Speaker 1: every second concentrated into a tiny little region. So it's
• 8:22
  Speaker 1: a pretty big engineering problem. In principle, it's possible, which
• 8:27
  Speaker 1: I think is the source of Stephen's question. In practice,
• 8:29
  Speaker 1: you don't have to worry about black holes being made
• 8:31
  Speaker 1: on the Earth by tiny, little dinky.
• 8:34
  Speaker 3: Men made lasers.
• 8:35
  Speaker 4: That's comforting.
• 8:39
  Speaker 1: And so Steven's asking how can something with no mass
• 8:42
  Speaker 1: collapse into one of the densest objects in the universe.
• 8:45
  Speaker 1: So remember it's energy density that's collapsing here, that's creating
• 8:49
  Speaker 1: that surface. And when you think about, like, well, what
• 8:52
  Speaker 1: is that black hole made out of? Is there a
• 8:53
  Speaker 1: singularity inside of it? Remember that the black hole is
• 8:56
  Speaker 1: not made of the original matter that you put into it.
• 9:00
  Speaker 1: Like if you drop a bunch of electrons into a
• 9:02
  Speaker 1: tiny region to make a black hole, you don't know
• 9:05
  Speaker 1: what the form of the matter is inside the black hole.
• 9:08
  Speaker 1: It's not like there are a bunch of electrons still
• 9:10
  Speaker 1: in there. The only thing you can know about the
• 9:13
  Speaker 1: black hole is its total mass, which represents the energy
• 9:16
  Speaker 1: that's captured inside of it, it's total charge, and it's spin.
• 9:21
  Speaker 1: No original nature of the objects is preserved as far
• 9:24
  Speaker 1: as we know, So if you make a black hole
• 9:27
  Speaker 1: out of photons, it looks exactly the same as a
• 9:30
  Speaker 1: black hole made out of neutrons or anything else that
• 9:33
  Speaker 1: has the same total energy, charge and spin.
• 9:36
  Speaker 2: So what happened to the electrons? Did they just get
• 9:38
  Speaker 2: like smoohed into something unrecognizable?
• 9:40
  Speaker 1: We don't know, right, Like general relativity tells us that
• 9:43
  Speaker 1: they form a singularity, but that ignores all the quantum
• 9:45
  Speaker 1: mechanical stuff we know about electrons and how they don't
• 9:48
  Speaker 1: like to be on top of each other, and who
• 9:50
  Speaker 1: knows what happens when you squish them down. Maybe there's
• 9:52
  Speaker 1: things inside the electrons. Maybe the electron is a composite particle.
• 9:56
  Speaker 1: When you smush them together that tightly, they break open
• 9:58
  Speaker 1: and form some sort of plast of their intermediate states.
• 10:01
  Speaker 4: Who knows, Right, we might finally know.
• 10:04
  Speaker 1: We might finally know, but it would be hidden behind
• 10:06
  Speaker 1: the event horizon. So the point is that, like, yes,
• 10:10
  Speaker 1: general relativity predicts a singularity at the heart of a
• 10:12
  Speaker 1: black hole made out of pure photons. But you can't
• 10:15
  Speaker 1: really know, and the singularity itself is a prediction of
• 10:19
  Speaker 1: general relativity, which ignores quantum mechanics anyway, so we think
• 10:22
  Speaker 1: it's probably wrong. So the answer is, we have no
• 10:26
  Speaker 1: idea what's going on inside that black hole. But in principle,
• 10:29
  Speaker 1: that black hole is no different from a black hole
• 10:32
  Speaker 1: you made out of electrons or cheese, or you know,
• 10:35
  Speaker 1: the anuses of your lab.
• 10:37
  Speaker 3: Rats or whatever.
• 10:38
  Speaker 4: Oh great, would you pick lab rats? I feel like
• 10:40
  Speaker 4: blue whales.
• 10:41
  Speaker 2: Like there's if you're gonna make a black hole out
• 10:43
  Speaker 2: of something, you gotta go go big or go home.
• 10:46
  Speaker 1: Well, I mean, if you add up the biomass of
• 10:48
  Speaker 1: the anuses of rats on Earth versus blue whales, what
• 10:51
  Speaker 1: do you think is larger?
• 10:52
  Speaker 6: Oh?
• 10:52
  Speaker 4: Probably rats?
• 10:53
  Speaker 2: Yeah, But what do you think the greatest anus biomass
• 10:57
  Speaker 2: on the planet is.
• 10:58
  Speaker 4: I bet it's could be humans, might be humans.
• 11:02
  Speaker 1: I can't believe you're a biologist and you don't know
• 11:04
  Speaker 1: the answer to this question off the top of your head.
• 11:06
  Speaker 4: I'm a little embarrassed. I'm a little embarrassed.
• 11:10
  Speaker 1: And you know, while it's out of the reach of
• 11:12
  Speaker 1: our technology to create black holes out of photons. Currently
• 11:17
  Speaker 1: in the future, you know, maybe if we become like
• 11:19
  Speaker 1: a Kardashev type two civilization or whatever, we build a
• 11:22
  Speaker 1: dice in sphere that captures all of the energy of
• 11:24
  Speaker 1: the Sun. It is possible in the future we might
• 11:27
  Speaker 1: be able to do it. Or maybe aliens are out
• 11:30
  Speaker 1: there doing it right now and we could watch them
• 11:32
  Speaker 1: doing it from afar. That could be the way that
• 11:34
  Speaker 1: we discover the existence of aliens. Amazing, awesome, would be
• 11:39
  Speaker 1: super cool. Please don't point those beams at us. But
• 11:42
  Speaker 1: there's another way. It's possible that we could create these
• 11:45
  Speaker 1: black holes. It's possible they could also exist naturally. Now
• 11:50
  Speaker 1: there's no like natural huge laser focusing light beams. But
• 11:54
  Speaker 1: in the very early universe, things were very hot and
• 11:57
  Speaker 1: very dense, and there's the theory that black holes could
• 12:01
  Speaker 1: have formed even before, like protons formed and electrons formed
• 12:05
  Speaker 1: in that primordial soup, there was great energy density. Now,
• 12:10
  Speaker 1: the whole universe didn't collapse quickly into a black hole
• 12:13
  Speaker 1: because to get a black hole you need relative energy density.
• 12:16
  Speaker 1: You need one region to be denser than another. So
• 12:19
  Speaker 1: if the whole universe is filled with energy density, you
• 12:22
  Speaker 1: don't get a black hole. But we also know there
• 12:25
  Speaker 1: were little quantum fluctuations, some pockets that were more dense
• 12:28
  Speaker 1: than others, and so this is the theory of primordial
• 12:32
  Speaker 1: black holes, that maybe there were some regions that fluctuated
• 12:36
  Speaker 1: enough to have enough energy density to create black holes
• 12:39
  Speaker 1: before there was even particles made. Now we've never seen
• 12:43
  Speaker 1: any of these, but in principle, back in the early universe,
• 12:46
  Speaker 1: when it was radiation dominated, when most of the energy
• 12:50
  Speaker 1: in the universe was in things like photons, then it's
• 12:53
  Speaker 1: possible you had a pocketive space that had enough energy
• 12:56
  Speaker 1: density just in photons to make a primordial black hole
• 13:00
  Speaker 1: out of light. So it's possible it does exist in
• 13:03
  Speaker 1: the universe.
• 13:05
  Speaker 2: No, you're looking at me because it's my turn to
• 13:08
  Speaker 2: say something. But I am still trying to figure out
• 13:10
  Speaker 2: the anus thing.
• 13:11
  Speaker 4: I'm so sorry. I mostly was listening, but I can't.
• 13:16
  Speaker 1: Oh boy, all right, Well, then, since Kelly's since Kelly's
• 13:19
  Speaker 1: been distracted, let's see if Steven's been paying attention. Steven,
• 13:23
  Speaker 1: let us know if that answered your question or if
• 13:26
  Speaker 1: you're just gonna file it away in the white hole
• 13:28
  Speaker 1: in your mind.
• 13:31
  Speaker 3: I don't know if that made any sense.
• 13:32
  Speaker 4: I don't think so.
• 13:34
  Speaker 5: Hi, Daniel and Kelly, it's Stephen from British Columbia. Again,
• 13:39
  Speaker 5: thanks again for answering my question about what is going
• 13:42
  Speaker 5: on inside tiny black holes. That explanation was super helpful.
• 14:06
  Speaker 1: Okay, we're back and we're answering questions from listeners about
• 14:10
  Speaker 1: black holes, about white holes, about ins and outs, about
• 14:12
  Speaker 1: everything in the universe. We want to answer your questions
• 14:16
  Speaker 1: because science is for everybody in the universe deserves to
• 14:20
  Speaker 1: be understood. Up next, we have an amazing question about
• 14:23
  Speaker 1: the human body, and it's symmetry and asymmetry from Jerry.
• 14:28
  Speaker 7: Hey, Daniel and Kelly love the show.
• 14:30
  Speaker 8: My left brain learns so much, but then my right
• 14:34
  Speaker 8: brain has a question. How come there are two parts
• 14:38
  Speaker 8: to a lot of our body. We have two eyes,
• 14:41
  Speaker 8: we have two ears, We have two lungs, we have
• 14:44
  Speaker 8: two kidneys, but those kidneys only lead to one bladder,
• 14:48
  Speaker 8: and there's only one stomach, and there's only one spleen.
• 14:51
  Speaker 8: You probably could live with one lung or one kidney,
• 14:55
  Speaker 8: and maybe you could live with half a brain and
• 14:57
  Speaker 8: be a politician. But why are we built this way?
• 15:00
  Speaker 8: We have two of some things and only one of another.
• 15:03
  Speaker 8: Love the show.
• 15:04
  Speaker 4: Thanks, Well, I gotta be honest with you.
• 15:07
  Speaker 2: I have had this question sitting on my stack for
• 15:10
  Speaker 2: a few months because I just kind of wasn't really
• 15:13
  Speaker 2: sure how how to answer this one, Like what is
• 15:16
  Speaker 2: the answer why sometimes a human body just is the
• 15:20
  Speaker 2: way it is? And uh and so all right, So
• 15:23
  Speaker 2: here's what I came up with, because it is a
• 15:24
  Speaker 2: great a good question. It's a great question.
• 15:27
  Speaker 1: Well, let's start with the meta answer, like is there
• 15:29
  Speaker 1: always an answer? What kind of answer do you think
• 15:32
  Speaker 1: Jerry's looking for? Is he looking for an answer where
• 15:35
  Speaker 1: it's like this works better than the opposite, Like there's
• 15:38
  Speaker 1: a reason we don't have two brains and there's a
• 15:41
  Speaker 1: reason we don't have two mouths because it would be better.
• 15:44
  Speaker 1: Or is it satisfying just to say we don't know,
• 15:46
  Speaker 1: this seems to work and we can't ever trace back
• 15:49
  Speaker 1: all the details of our evolutionary history to understand why.
• 15:52
  Speaker 2: Yes, So I tried to find an evolutionary answer, and
• 15:55
  Speaker 2: I tried to find a mechanistic answer, and I tried
• 15:58
  Speaker 2: to find a like stories that kind of make this
• 16:01
  Speaker 2: make sense sort of answer.
• 16:03
  Speaker 1: You didn't go for an Aristotilian answer. It isn't the
• 16:06
  Speaker 1: way of humanity, to have one mouth.
• 16:08
  Speaker 4: To have one butt, one butt but with two cheeks.
• 16:12
  Speaker 1: What was Aristotle's theory of the anis? Was he the
• 16:15
  Speaker 1: first one to think about the anis?
• 16:16
  Speaker 4: You know, I didn't get as far back as Aristotle.
• 16:19
  Speaker 3: Actually, you always got to go back to Aristotle, Kelly.
• 16:22
  Speaker 1: He's like the original, you know, paper out of the
• 16:25
  Speaker 1: Soviet Union that you didn't read and that came out
• 16:27
  Speaker 1: in the nineteen seventies that totally scoops your thesis.
• 16:29
  Speaker 3: He was the original dude to do that.
• 16:31
  Speaker 2: Well, yes, yes, well I'm really I hope that I
• 16:34
  Speaker 2: can still give a satisfactory answer having not read Aristotle's.
• 16:38
  Speaker 4: Opinion on this, but you know, I will.
• 16:42
  Speaker 2: I'll note that having things like two eyes and two
• 16:45
  Speaker 2: lungs but only one heart and one brain is a
• 16:48
  Speaker 2: sort of ancient state. You know, pretty much all land
• 16:51
  Speaker 2: vertebrates have this, and land vertebrates have been around for
• 16:54
  Speaker 2: over a three hundred million years. When you go into like,
• 16:59
  Speaker 2: you know, the water, you find cephalopods that have three hearts.
• 17:02
  Speaker 2: So it is possible to have three hearts. It doesn't
• 17:06
  Speaker 2: have to be the case that you only have one heart.
• 17:08
  Speaker 2: And on land there are worms that have multiple heart
• 17:12
  Speaker 2: like things, but we only have one heart. It does
• 17:16
  Speaker 2: kind of start as like two hearts and it sort
• 17:18
  Speaker 2: of fuses together into one heart that's like symmetrical with
• 17:23
  Speaker 2: you know, two sets of chambers on each side. So
• 17:26
  Speaker 2: one answer is that it's ancient. This has been around
• 17:29
  Speaker 2: for a long time. So maybe this is the best
• 17:32
  Speaker 2: solution and that's why we've had it for three hundred
• 17:35
  Speaker 2: million years, or maybe we're just kind of locked in
• 17:37
  Speaker 2: at this point, and the fact that we've had it
• 17:39
  Speaker 2: for three hundred million years just shows that this arrangement
• 17:42
  Speaker 2: of things is sort of hard to get out of.
• 17:44
  Speaker 1: Well, what do you mean by three hundred million years?
• 17:46
  Speaker 1: What happened three hundred million years ago? Was that the
• 17:49
  Speaker 1: Cambrian explosion.
• 17:50
  Speaker 2: Well, this is when we started to get land vertebrates.
• 17:53
  Speaker 2: So it's when like vertebrates started coming up out of
• 17:55
  Speaker 2: the water and sort of walking around on land and
• 17:58
  Speaker 2: breathing air as opposed to using gills to extract oxygen
• 18:00
  Speaker 2: from the water.
• 18:01
  Speaker 1: Okay, because fish, for example, I have two eyes and
• 18:04
  Speaker 1: two ears and one mouth, and there's a lot of
• 18:05
  Speaker 1: similarities there, right, so it must go back even further.
• 18:08
  Speaker 2: There are a lot of similarities I mean, they don't
• 18:10
  Speaker 2: have like two lungs, for example, but they do have,
• 18:12
  Speaker 2: you know, like two gills. But yeah, so there are
• 18:15
  Speaker 2: a lot of things that are similar. But I was
• 18:17
  Speaker 2: trying to look for I had lungs on the brain
• 18:19
  Speaker 2: when I was starting this, and so I was looking
• 18:21
  Speaker 2: for things with two lungs. So I mean symmetry. If
• 18:23
  Speaker 2: you just want to ask about symmetry, symmetry goes back
• 18:26
  Speaker 2: even farging, Like, there's a lot of organisms that weren't
• 18:29
  Speaker 2: necessarily symmetrical the way we are. So if you were
• 18:32
  Speaker 2: to draw a line, you know, straight through our head
• 18:35
  Speaker 2: that goes down like through our butts, and you fold
• 18:38
  Speaker 2: us over more symmetrical that way. I think that's called
• 18:40
  Speaker 2: bilateral symmetry. But there are other organisms that are radially symmetrical.
• 18:45
  Speaker 4: I think that's what it's called.
• 18:46
  Speaker 2: I didn't necessarily plan on going this far back, so
• 18:48
  Speaker 2: I'm pulling this out of my uh Aristatilian hole Aristotelian hole.
• 18:53
  Speaker 2: So being symmetrical is a thing that has been around
• 18:56
  Speaker 2: for a long time. And there's a couple of different
• 18:58
  Speaker 2: hypotheses for why symmetry tree is good. A couple hypotheses
• 19:02
  Speaker 2: I came across were that, like, you know, one in
• 19:03
  Speaker 2: our very ancient history, when we were like tubes that
• 19:07
  Speaker 2: were symmetrical, the idea was that it was easier for
• 19:10
  Speaker 2: us to like pull food through our tube and like
• 19:14
  Speaker 2: extract resources from it when we were roughly symmetrical, and
• 19:17
  Speaker 2: then when we became bilaterally symmetrical. So like imagine you
• 19:21
  Speaker 2: have flippers, it's easier to move in a controlled manner
• 19:25
  Speaker 2: when you're symmetrical on both sides.
• 19:26
  Speaker 4: So it was for like locomotory purposes. Does that make sense?
• 19:29
  Speaker 1: Yeah, some things that can totally understand why two makes
• 19:32
  Speaker 1: sense and one doesn't. You know, like two eyes, one
• 19:35
  Speaker 1: on each side of your head to see in both
• 19:37
  Speaker 1: directions or to get binocular vision. Same thing for ears,
• 19:40
  Speaker 1: same thing for flippers, same thing for legs. Right, two
• 19:43
  Speaker 1: legs definitely seem to work better than one leg. But
• 19:47
  Speaker 1: I guess I wonder why then you don't have two
• 19:50
  Speaker 1: of everything? Right, Like, isn't it always better to have
• 19:53
  Speaker 1: to Is there a sort of cost benefit analysis going
• 19:56
  Speaker 1: on here where having two things means more to maintain.
• 19:59
  Speaker 3: More to go?
• 20:00
  Speaker 2: Yeah, So I started thinking about it on like an
• 20:04
  Speaker 2: organ by organ basis, and so you're right, it does
• 20:06
  Speaker 2: feel like from a survival standpoint, having a backup of
• 20:10
  Speaker 2: the organs might be helpful. So, for example, if one
• 20:12
  Speaker 2: of your kidneys goes, it would be helpful to have
• 20:15
  Speaker 2: another kidney, although that other kidney has to work really
• 20:17
  Speaker 2: hard if there's just one left, and there's some evidence
• 20:20
  Speaker 2: to suggest that that other kidney's going to fall apart
• 20:23
  Speaker 2: faster if it's doing essentially twice the work.
• 20:26
  Speaker 1: Yeah, obviously having a second kidney working as backup for
• 20:29
  Speaker 1: both isn't perfect, but it does extend your life if
• 20:32
  Speaker 1: one kidney fails.
• 20:33
  Speaker 2: Right, Oh, yeah, absolutely absolutely, But sometimes having two organs
• 20:36
  Speaker 2: isn't just a redundancy thing. So you mentioned that eyes,
• 20:40
  Speaker 2: having two of them gives you depth perception ears, having
• 20:44
  Speaker 2: two of them allows you to do a better job
• 20:45
  Speaker 2: of localizing where sounds are coming from. Nostrils, actually having
• 20:50
  Speaker 2: two of them is helpful. Your nostrils actually switch off.
• 20:53
  Speaker 2: There's this thing called nasal dominance, where one nostril is
• 20:58
  Speaker 2: the one that is doing the bulk of the breathing
• 21:02
  Speaker 2: while the other one is like moving air a little
• 21:04
  Speaker 2: bit more slowly. And it looks like there's a couple
• 21:07
  Speaker 2: different functions here. One of them is a little bit
• 21:09
  Speaker 2: more important for smelling, Like the air is moving more
• 21:13
  Speaker 2: slowly over that nostril, and it seems like there's some
• 21:17
  Speaker 2: sense that are better understood when part of it passes
• 21:21
  Speaker 2: over our scent receptors quickly and some part of it
• 21:25
  Speaker 2: passes over our scent receptors slowly.
• 21:28
  Speaker 3: Wow.
• 21:28
  Speaker 2: And so each of our nostrils are not doing the
• 21:30
  Speaker 2: exact same thing. Our nostrils are alternating. And sometimes when
• 21:34
  Speaker 2: you have a cold, I don't know if you can tell,
• 21:36
  Speaker 2: like you'll be like, ah, I can breathe on one
• 21:38
  Speaker 2: of my nose but not the other. And it's because
• 21:41
  Speaker 2: your nasal passages take turns, with one of them being
• 21:43
  Speaker 2: a little bit more swelled up to like make that
• 21:45
  Speaker 2: be the nostril that passes air a little bit more slowly.
• 21:48
  Speaker 2: And you can really tell that that's the case when
• 21:50
  Speaker 2: you have a cold and you're congested.
• 21:52
  Speaker 3: Wait, so they switch.
• 21:53
  Speaker 1: I thought you were going to say, like one is
• 21:54
  Speaker 1: dominant for a lifetime, like you're a lefty or a righty.
• 21:57
  Speaker 3: News.
• 21:58
  Speaker 4: No, No, over the course of the day.
• 22:00
  Speaker 1: Switches the course of the day.
• 22:02
  Speaker 3: Yes, what Yeah, I had no idea.
• 22:04
  Speaker 4: I know, I know, there's like yes, so much you
• 22:06
  Speaker 4: don't even know about your own body. It's crazy.
• 22:09
  Speaker 3: Wow, noses are amazing.
• 22:11
  Speaker 2: Right, yes, okay, so your nostrils aren't just redundant, they're
• 22:14
  Speaker 2: actually like, you know, tag teaming each other. Maybe that
• 22:17
  Speaker 2: they're still redundant, but like they're working together to accomplish
• 22:19
  Speaker 2: a goal, and having two of them is helpful. But okay,
• 22:23
  Speaker 2: So say you wanted to have two mouths and two
• 22:26
  Speaker 2: digestive tracts and ani to complete the loop. One of
• 22:32
  Speaker 2: the reasons we have such long stretches of digestive tract
• 22:35
  Speaker 2: is that you have all of this surface area, and
• 22:37
  Speaker 2: across that surface area, nutrients and stuff are being absorbed
• 22:42
  Speaker 2: out of your digestive tract and into the rest of
• 22:44
  Speaker 2: your body. So the more surface area you have, the
• 22:46
  Speaker 2: better job your body can do of like processing the
• 22:49
  Speaker 2: food that you eat. So if you were to have
• 22:52
  Speaker 2: two separate digestive tracts, like maybe in the middle of
• 22:55
  Speaker 2: each one of your cheeks you had a mouth and
• 22:57
  Speaker 2: that sounds pretty freaky now, and you had you know,
• 23:01
  Speaker 2: two butts or something, each one of those tracks would
• 23:05
  Speaker 2: probably have to have less surface area in order for
• 23:07
  Speaker 2: you to have enough space to fit everything in there.
• 23:10
  Speaker 2: So that's probably not a more efficient system, and so
• 23:14
  Speaker 2: I don't think it would necessarily be a better system
• 23:16
  Speaker 2: to have two sets of digestive tracks. If you add
• 23:20
  Speaker 2: two hearts and they were connected to the same circulatory system,
• 23:24
  Speaker 2: you'd have to be very careful about coordinating because if
• 23:27
  Speaker 2: you weren't coordinating, you could end up having very high
• 23:30
  Speaker 2: blood pressure, or you could end up having, you know,
• 23:32
  Speaker 2: problems with blood like pooling in some areas, depending on
• 23:35
  Speaker 2: how the hearts are pumping together. And so, even though
• 23:38
  Speaker 2: it would be super cool to be kind of like
• 23:40
  Speaker 2: doctor who, you would have to worry about if your
• 23:43
  Speaker 2: hearts are coordinating well enough. And so in order for
• 23:46
  Speaker 2: that to work, you'd have to have completely separate vasculature,
• 23:49
  Speaker 2: and that might get complicated. And if one heart fails,
• 23:52
  Speaker 2: maybe you're still in as much trouble because now everything's
• 23:55
  Speaker 2: not getting enough blood, it's getting half as much blood
• 23:57
  Speaker 2: as it needed. So it's not necessarily clear that having
• 24:00
  Speaker 2: two of those organs would be beneficial when I think
• 24:03
  Speaker 2: through it.
• 24:04
  Speaker 1: But what do you think, Well, the thing I think
• 24:05
  Speaker 1: about is lungs. I feel like we're so susceptible to
• 24:09
  Speaker 1: choking on something. If you had like two different breeding tubes,
• 24:14
  Speaker 1: then it'd be like, no big deal if you had
• 24:15
  Speaker 1: a chunk of steaks stuck in one all right, it
• 24:17
  Speaker 1: wouldn't be like you're going to die within minutes. It
• 24:21
  Speaker 1: seems like it would relieve a lot of the emergency
• 24:23
  Speaker 1: status of breeding.
• 24:24
  Speaker 2: I don't have a good answer for that. That is
• 24:26
  Speaker 2: a good point. That does seem that's a choke point.
• 24:28
  Speaker 3: Yeah, there you go.
• 24:32
  Speaker 4: I'm done.
• 24:33
  Speaker 1: But maybe it's complicated and expensive and maybe it's not
• 24:36
  Speaker 1: enough of a benefit to make it worth it.
• 24:38
  Speaker 4: Yeah, yeah, I don't know.
• 24:39
  Speaker 2: I mean some of this stuff also might just be constraints,
• 24:41
  Speaker 2: like you know, there's not enough space, or it would
• 24:43
  Speaker 2: be difficult from an evolutionary perspective to get two of
• 24:46
  Speaker 2: them in there. I didn't come up with like a
• 24:49
  Speaker 2: super satisfactory answer for why. I mean, like, you know,
• 24:52
  Speaker 2: so many of us at this point die from like
• 24:55
  Speaker 2: heart issues when we get old. Yeah, maybe it would
• 24:57
  Speaker 2: be great if we had a backup or like one
• 24:59
  Speaker 2: we didn't use until we turn sixty and then that
• 25:01
  Speaker 2: one kicked in or something.
• 25:02
  Speaker 1: And well we do have like a whole second set
• 25:04
  Speaker 1: of teeth that come in after you know, fifteen years
• 25:06
  Speaker 1: or so, which is like super weird if you think
• 25:08
  Speaker 1: about it, it'd be amazing if we had like a
• 25:11
  Speaker 1: backup heart that came in when you were fifty. Yeah,
• 25:13
  Speaker 1: and it was like, all right, let's toss out the
• 25:15
  Speaker 1: old one and you know, get an upgrade.
• 25:17
  Speaker 3: That would be amazing. Let's do that now.
• 25:19
  Speaker 4: Yeah, let's let's talk to evolution about that.
• 25:21
  Speaker 2: But you know, I guess the problem is that by
• 25:22
  Speaker 2: the time most of us are sixty and our hearts
• 25:24
  Speaker 2: are starting to go, we are probably post reproduction or
• 25:29
  Speaker 2: you know, post reproductive age, and I guess evolutionary pressure
• 25:32
  Speaker 2: is probably not selecting for us to have new hearts
• 25:34
  Speaker 2: at that point. But anyway, I didn't really find a
• 25:38
  Speaker 2: super satisfactory answer, to be honest, But hopefully there's been
• 25:41
  Speaker 2: some interesting information here. And I can't find another good
• 25:47
  Speaker 2: connection to butts to end with here. I am so sorry.
• 25:51
  Speaker 1: Well, I think the challenge here with biology is that
• 25:54
  Speaker 1: we can never really know because it's sort of asking
• 25:58
  Speaker 1: a meta question, you know, it's asking like, hey, if
• 26:01
  Speaker 1: you ran the Earth as an experiment a million times,
• 26:04
  Speaker 1: how often would you end up with this configuration? Is
• 26:07
  Speaker 1: the result of like some random cosmic ray which ended
• 26:10
  Speaker 1: us down this path, which is unusual or is this
• 26:13
  Speaker 1: like really the only efficient way to do it? And
• 26:16
  Speaker 1: you're going to end up with this in most of
• 26:18
  Speaker 1: those Earth simulations, And that's definitely a question we can't
• 26:21
  Speaker 1: answer until, you know, we slip into the black hole,
• 26:25
  Speaker 1: come out the white hole on the other end, and
• 26:27
  Speaker 1: meet some aliens and discover, oh, look, they do have
• 26:30
  Speaker 1: seventeen butts, and it turns out that we are weird
• 26:33
  Speaker 1: being in the like unious part.
• 26:35
  Speaker 3: Of the universe.
• 26:37
  Speaker 2: You did such a nice job wrapping that up, and
• 26:38
  Speaker 2: I'm going to go ahead and mess it up by
• 26:40
  Speaker 2: continuing this conversation a little bit longer. And so, you know,
• 26:44
  Speaker 2: I feel like in so many depictions of aliens they're
• 26:46
  Speaker 2: kind of like octopuses, which made me wonder.
• 26:49
  Speaker 4: You know, octopuses have three hearts.
• 26:51
  Speaker 2: Maybe we would have three hearts if it was like
• 26:52
  Speaker 2: the octopus lineage that had moved on to land.
• 26:56
  Speaker 4: And what would that be like? I don't know.
• 26:58
  Speaker 2: And so anyway, now that I've gotten us off track
• 27:01
  Speaker 2: after Daniel's beautiful segue, let's go ahead and find out
• 27:05
  Speaker 2: if we answered the question.
• 27:07
  Speaker 7: Thanks for the answer, Daniel and Kelly appreciate it makes sense.
• 27:11
  Speaker 7: Body symmetry, efficiency of organs, and I guess with two
• 27:16
  Speaker 7: eyes two ears, you know, back in the planes of
• 27:19
  Speaker 7: Africa and where we came from, keeping away from predators
• 27:23
  Speaker 7: and finding prey. The stereolocation certainly held. I will now
• 27:27
  Speaker 7: run and check and see which one of my nostrils
• 27:30
  Speaker 7: is most dominant. Love the show, Thanks.
• 27:52
  Speaker 4: All right.
• 27:53
  Speaker 2: I always personally love it when we get questions, either
• 27:56
  Speaker 2: directly from kids or from kids through their parents. And
• 28:01
  Speaker 2: so today we have a question from Andy and jos
• 28:04
  Speaker 2: So let's go ahead and hear it.
• 28:06
  Speaker 6: Hi there, Daniel and Kelly. My son woke up the
• 28:09
  Speaker 6: other morning and he had a new theory about how
• 28:12
  Speaker 6: the universe might end. His theory is that there are
• 28:17
  Speaker 6: many different bubble universes and they're all moving around inside
• 28:23
  Speaker 6: one big, greater universe. They drew a lovely diagram showing
• 28:28
  Speaker 6: all the bubble universes with a little plus and minus
• 28:30
  Speaker 6: next to it to demonstrate we don't know how many
• 28:32
  Speaker 6: there are. The theory goes that the bubble universes are
• 28:37
  Speaker 6: drawn together by gravity and pushed apart by dark energy,
• 28:42
  Speaker 6: so they all perhaps come together at the edge of
• 28:45
  Speaker 6: the greater universe and then burst. The greater universes edge
• 28:51
  Speaker 6: and destroy the whole multiverse. Our questions are like this,
• 28:57
  Speaker 6: Could this be the nature of our universe? Could science
• 29:02
  Speaker 6: ever know? If this was the nature of our universe?
• 29:05
  Speaker 6: Could gravity interact with other universes outside our small bubble universes,
• 29:11
  Speaker 6: perhaps by traveling through extra dimensions? Thanks very much for
• 29:14
  Speaker 6: any time you can spend on this question on your podcast.
• 29:18
  Speaker 6: Look forward to hearing any thoughts you have.
• 29:21
  Speaker 1: It is wonderful to know that kids are out there
• 29:23
  Speaker 1: thinking about how the universe works and how it might work,
• 29:26
  Speaker 1: and crazy ideas about explaining it and understanding it. I
• 29:30
  Speaker 1: love that these kinds of topics tackle children, and to me,
• 29:34
  Speaker 1: that's why this science is so exciting. It's because it
• 29:37
  Speaker 1: connects with things we've always wanted to know, basic questions
• 29:41
  Speaker 1: we've been asking about the universe since we were kids
• 29:43
  Speaker 1: and since humans were humans.
• 29:45
  Speaker 2: Can I tell you a quick story, Yeah, yep. My
• 29:48
  Speaker 2: daughter the other day was like, hey, mom, can.
• 29:51
  Speaker 4: Animals communicate with each other?
• 29:52
  Speaker 2: Like we can't communicate to dogs, but can you know,
• 29:55
  Speaker 2: like one bird communicate to another bird?
• 29:57
  Speaker 4: And I was like, I don't know.
• 29:58
  Speaker 2: And then I was listening to this book and they
• 30:00
  Speaker 2: were explaining that actually birds and squirrels and a couple
• 30:04
  Speaker 2: other different kinds of species have calls that they can
• 30:07
  Speaker 2: recognize like across these species boundaries that tell each other, hey,
• 30:11
  Speaker 2: there's an aerial predator or there's a predatory snake on
• 30:15
  Speaker 2: the ground, and so they can like actually convey pretty
• 30:18
  Speaker 2: complicated information about not only there is a risk, but
• 30:21
  Speaker 2: what kind of risk it is from like you.
• 30:24
  Speaker 4: Know, birds to mammals.
• 30:26
  Speaker 2: And the answer was yes, And I think we only
• 30:28
  Speaker 2: figured this out, you know, like not yesterday, but like
• 30:31
  Speaker 2: not that recently, which makes me feel like, I don't know,
• 30:33
  Speaker 2: maybe we should bring kids into like ecology departments and
• 30:36
  Speaker 2: be like just like think thoughts at us and we'll
• 30:39
  Speaker 2: go check some of it out. You know, they should
• 30:40
  Speaker 2: do the same thing to physics departments and see what
• 30:42
  Speaker 2: we find out.
• 30:43
  Speaker 1: They definitely should, And that's exciting to think that like
• 30:46
  Speaker 1: squirrels and birds and dogs are talking to each other.
• 30:48
  Speaker 1: But it's also a bit of a bummer. I mean, basically,
• 30:51
  Speaker 1: there's like an Earth animal group chat and we are
• 30:54
  Speaker 1: not included.
• 30:54
  Speaker 2: Okay, but one we're starting to decipher it so we
• 30:58
  Speaker 2: know what they're talking about. And two, like some of
• 31:00
  Speaker 2: it is eavesdropping, Like I don't necessarily know that the
• 31:02
  Speaker 2: birds want the squirrels to know, and so that makes
• 31:06
  Speaker 2: it a little bit less exciting.
• 31:07
  Speaker 4: And the messages are pretty straightforward. It's not like.
• 31:11
  Speaker 1: Did you see what Kelly was wearing yesterday?
• 31:12
  Speaker 4: Ha ha?
• 31:13
  Speaker 3: What ad we You don't think they're roasting us on
• 31:16
  Speaker 3: the group chat?
• 31:17
  Speaker 2: I mean they might be or like, oh the acorn
• 31:20
  Speaker 2: cap on your head.
• 31:21
  Speaker 4: Listen, it's really cute. You look really nice in that
• 31:23
  Speaker 4: head Like. I don't think it's you know, it's like
• 31:26
  Speaker 4: survival things.
• 31:27
  Speaker 2: It's not too subtle, probably, but still it's awesome that
• 31:30
  Speaker 2: like they are sort of paying attention to each other
• 31:33
  Speaker 2: and communicating in that way.
• 31:35
  Speaker 1: All right, well, you know what, Kelly, there was no
• 31:36
  Speaker 1: contest already, but I think you just cinched yourself for
• 31:40
  Speaker 1: the award for twenty twenty five, getting us the most
• 31:42
  Speaker 1: Off Track Podcast award.
• 31:45
  Speaker 4: Yeah, well you know what, Daniel, we are.
• 31:49
  Speaker 2: We have one question left and we're only thirty four
• 31:52
  Speaker 2: minutes in, so I thought we could take a bit
• 31:55
  Speaker 2: of ad tour.
• 31:57
  Speaker 1: So let's veer back from what Dogs and Square are
• 32:00
  Speaker 1: saying about us and think about Joss's question about bubble
• 32:05
  Speaker 1: universes that could be moving around and drawn together by
• 32:08
  Speaker 1: gravity and pushed apart, and what's going on there. So
• 32:11
  Speaker 1: these are fascinating ideas, Jos, and they connect with real
• 32:14
  Speaker 1: ideas in cosmology. I mean, the concept of a bubble
• 32:18
  Speaker 1: universe is something we have in real physics cosmology. It's
• 32:22
  Speaker 1: a sort of proto idea that's not improven but is
• 32:26
  Speaker 1: taken pretty seriously. And the idea is to try to
• 32:29
  Speaker 1: explain where the Big Bang came from. You know, the
• 32:32
  Speaker 1: Big Bang says we had a hot, dense state about
• 32:35
  Speaker 1: thirteen point eight billion years ago which expanded and cooled.
• 32:39
  Speaker 1: It wasn't a dot of matter exploding into empty space.
• 32:42
  Speaker 1: But the Big Bang doesn't tell us where that hot
• 32:44
  Speaker 1: dance matter came from. It doesn't explain it at all.
• 32:47
  Speaker 1: And there's lots of different theories, and one of them
• 32:50
  Speaker 1: is that that matter came from some earlier kind of stuff,
• 32:54
  Speaker 1: something we call inflationary matter. So imagine now a universe
• 32:57
  Speaker 1: filled with some weird inflationary matter, and this stuff expands
• 33:02
  Speaker 1: super duper rapidly, you know, like my factors of ten
• 33:05
  Speaker 1: to the thirty every ten to the minus twenty seconds.
• 33:09
  Speaker 1: Crazy expansion. But occasionally some of it decays. The way
• 33:13
  Speaker 1: like some particles can turn into other particles. This inflationary
• 33:17
  Speaker 1: matter turned into normal matter and created like a little
• 33:21
  Speaker 1: bubble of hot dense stuff. Now this doesn't really answer
• 33:24
  Speaker 1: the question of where did that hot dense matter come from.
• 33:27
  Speaker 1: It just sort of kicks it down the road and says,
• 33:29
  Speaker 1: maybe it came from some weird inflationary matter. Where did
• 33:31
  Speaker 1: that come from? We don't know. But in this picture,
• 33:35
  Speaker 1: you have like a universe filled with this inflationary matter,
• 33:38
  Speaker 1: and then these little bubbles of normal matter, these little pockets.
• 33:42
  Speaker 1: So our universe could be like one little bubble among
• 33:45
  Speaker 1: this vast landscape of bubbles.
• 33:48
  Speaker 2: Okay, so you've got these ever growing bubbles that are giant,
• 33:51
  Speaker 2: and then you've got some bubbles. They get big, and
• 33:53
  Speaker 2: then they stop getting big, but they get really hot,
• 33:55
  Speaker 2: and so then wouldn't they eventually get like swallowed up
• 33:57
  Speaker 2: by the other bubbles.
• 33:58
  Speaker 3: No, the bubbles are our universe.
• 34:00
  Speaker 1: So you have like a landscape that's just filled with
• 34:02
  Speaker 1: this inflationary matter that's expanding. Its not bubbles, just like
• 34:05
  Speaker 1: the whole universe is expanding and filled with this stuff,
• 34:09
  Speaker 1: and then some pockets of it turn into normal matter.
• 34:12
  Speaker 1: So instead of having a universe just filled with inflationary matter.
• 34:15
  Speaker 1: You have these little pockets of normal matter, but between
• 34:18
  Speaker 1: them is still inflationary matter expanding super rapidly. So like
• 34:22
  Speaker 1: we are in one of those little bubbles and there's
• 34:25
  Speaker 1: another one over there, but between us and that other
• 34:27
  Speaker 1: universe is more of this inflationary matter that's expanding like crazy,
• 34:32
  Speaker 1: and so that other bubble gets further and further away
• 34:34
  Speaker 1: from us every nanosecond.
• 34:36
  Speaker 4: Okay, so the bubbles are filled with little things inside
• 34:42
  Speaker 4: of them.
• 34:43
  Speaker 3: Yeah, our universe is one of those bubbles.
• 34:45
  Speaker 4: Oka, Yeah, got it.
• 34:46
  Speaker 1: So this is an attempt to explain some things about
• 34:49
  Speaker 1: the early universe we don't understand, and there's a whole
• 34:51
  Speaker 1: theory about this inflation. But it creates the idea of
• 34:55
  Speaker 1: bubble universes. And it's true that the bubble universes might
• 34:59
  Speaker 1: be pulled together by gravity, Like we have stuff. The
• 35:02
  Speaker 1: other bubble universe has stuff, but it's going to be
• 35:06
  Speaker 1: totally overwhelmed, totally dominated by the inflation between them. Like
• 35:11
  Speaker 1: the inflation is so quick it's hard to even really
• 35:13
  Speaker 1: wrap your mind around the scale here, Like blowing up
• 35:16
  Speaker 1: by a factor of ten to the thirty means like
• 35:20
  Speaker 1: taking a grain of sand and turning it into a
• 35:22
  Speaker 1: star and doing that every ten to the minus twenty seconds.
• 35:27
  Speaker 1: It's just the numbers are incredible and so gravity is
• 35:30
  Speaker 1: going to be definitely overwhelmed by that. So you do
• 35:33
  Speaker 1: have these bubbles, but they're just getting further and further
• 35:36
  Speaker 1: apart from each other because of this incredible, intense, constant inflation.
• 35:40
  Speaker 2: Okay, so we know that the universe is expanding, and
• 35:43
  Speaker 2: that would be would that be consistent with what is
• 35:46
  Speaker 2: happening with the bubbles.
• 35:47
  Speaker 1: Yeah, So there's lots of different kinds of expansion going
• 35:50
  Speaker 1: on here, which is a little hard to keep track of.
• 35:52
  Speaker 1: There's the expansion we call the Big Bang, where you
• 35:54
  Speaker 1: have a hot, dense state and then the universe got
• 35:57
  Speaker 1: bigger and colder and more dilute. And it's something we
• 36:00
  Speaker 1: know and very well established and we've measured and we've
• 36:02
  Speaker 1: seen and we've studied. Of course, there's still questions about it.
• 36:06
  Speaker 1: And that's one kind of expansion, and that's even accelerating
• 36:08
  Speaker 1: because of dark energy. So that's our bubble getting bigger
• 36:12
  Speaker 1: and more dilute. Then there's the inflationary expansion which is
• 36:15
  Speaker 1: happening between the bubbles, which is much more dramatic and
• 36:18
  Speaker 1: much more powerful, and so Josh was asking about whether
• 36:22
  Speaker 1: these bubble universes could be drawn together by gravity and
• 36:25
  Speaker 1: pushed apart by dark energy until they come to the
• 36:28
  Speaker 1: edge of a greater universe and destroy the whole multiverse.
• 36:31
  Speaker 1: Love the dramatic ending to Jos's story. So we don't
• 36:35
  Speaker 1: know if there is an edge to the greater universe.
• 36:37
  Speaker 1: It could be that this landscape filled with inflationary matter
• 36:41
  Speaker 1: then dotted with these bubble universes. It could be that
• 36:44
  Speaker 1: that goes on forever, that it's infinite, right, that there
• 36:48
  Speaker 1: is no.
• 36:48
  Speaker 3: Edge to it at all. We don't know.
• 36:50
  Speaker 1: Another possibility is that it's finite, that it's like wraps
• 36:54
  Speaker 1: around on itself, the way like the surface of a
• 36:56
  Speaker 1: sphere does. If the universe has two dimensions, but universe
• 37:00
  Speaker 1: has more than two dimensions, you have to imagine like
• 37:02
  Speaker 1: the three D surface of a four dimensional sphere being
• 37:06
  Speaker 1: closed on itself. So we don't know if that larger
• 37:09
  Speaker 1: space is finite or infinite, and it's possible that we
• 37:13
  Speaker 1: might never know because it's so big and it's so
• 37:17
  Speaker 1: rapidly accelerating and expanding, that information just leaves our cosmic horizon,
• 37:23
  Speaker 1: you know, the way that even inside our universe, the
• 37:25
  Speaker 1: expansion is happening so fast that there are parts of
• 37:28
  Speaker 1: it we will never see, because the expansion between us
• 37:31
  Speaker 1: and those parts of the universe is happening so fast
• 37:34
  Speaker 1: that light from that part of the universe will never
• 37:37
  Speaker 1: reach us, like a photon shot out by some of
• 37:40
  Speaker 1: the most distant galaxies will never get here because space
• 37:44
  Speaker 1: between us and it is expanding so fast. And so
• 37:47
  Speaker 1: in the same way, if there is an edge to
• 37:50
  Speaker 1: the inflationary eternal universe, we might not ever know, because
• 37:54
  Speaker 1: it's sort of beyond our ability to probe. The speed
• 37:57
  Speaker 1: of light really limits what fraction of the universe we
• 38:00
  Speaker 1: can ever study. So we don't know if there's an
• 38:03
  Speaker 1: edge to this larger universe, and we don't know if
• 38:06
  Speaker 1: we could ever know. What we can do is look
• 38:09
  Speaker 1: to see if these bubbles ever collide, like we think
• 38:12
  Speaker 1: in principle they shouldn't because the material between them is
• 38:16
  Speaker 1: expanding so fast. But you could occasionally, if there are
• 38:19
  Speaker 1: lots of these things, get them bumping into each other
• 38:22
  Speaker 1: sort of by chance, and people have looked for this.
• 38:25
  Speaker 1: If that happened, you would expect to see like an
• 38:27
  Speaker 1: imprint in the sky and the pattern of stars, it
• 38:30
  Speaker 1: wouldn't look quite as random and smooth out as it does.
• 38:34
  Speaker 1: You would see like basically a big dent somewhere, and
• 38:37
  Speaker 1: we've looked for that and we haven't seen it. So
• 38:39
  Speaker 1: there's no evidence that our bubble universe has collided with
• 38:42
  Speaker 1: any other bubble universes so far.
• 38:45
  Speaker 2: So if you had to like put a probability on
• 38:47
  Speaker 2: your thoughts that the bubble universe theory is a valid theory,
• 38:53
  Speaker 2: a valid explanation, how likely do you think the bubble
• 38:56
  Speaker 2: universe thing is is a good explanation.
• 38:58
  Speaker 1: I mean, it's a good word hypothesis. It's like an
• 39:02
  Speaker 1: exploration of what might be going on out there. We
• 39:06
  Speaker 1: can't really evaluate it without having any data, you know,
• 39:09
  Speaker 1: because there could always just be a better idea somebody had.
• 39:12
  Speaker 1: This is the problem with thinking about things that you
• 39:15
  Speaker 1: can't check in the universe. And I don't mean to
• 39:19
  Speaker 1: say that it's not scientific. I'm not a big fan
• 39:21
  Speaker 1: of like drawing arbitrary dotted lines and saying this is science.
• 39:24
  Speaker 3: That's not science.
• 39:26
  Speaker 1: Lots of things that you can't immediately test are still
• 39:28
  Speaker 1: science because they eventually contribute to our understanding of the
• 39:32
  Speaker 1: universe somehow, like all of mathematics. For example, you know
• 39:37
  Speaker 1: euclid developed his geometry and that it was crucial to
• 39:40
  Speaker 1: understanding a lot of the universe, and other folks developed
• 39:44
  Speaker 1: non Euclidean geometry not because they cared about the universe.
• 39:47
  Speaker 1: They were just nerds thinking about stuff, and that turned
• 39:49
  Speaker 1: out to also be crucial. So I think all of
• 39:52
  Speaker 1: it is scientific, but I don't think we can assign
• 39:54
  Speaker 1: numbers to like the probability that we're in a bubble universe,
• 39:58
  Speaker 1: because there's a gazillion other ideas out there and we
• 40:01
  Speaker 1: don't know how to weigh them against each other without
• 40:04
  Speaker 1: being able to take some measurements the universe. Nature is
• 40:07
  Speaker 1: the ultimate arbiter of these theories, right. Your theory can
• 40:10
  Speaker 1: be beautiful, it can be elegant, it can be amazing.
• 40:13
  Speaker 1: It can also just be wrong, and so we need
• 40:16
  Speaker 1: to sort of consult with nature, and we don't have
• 40:18
  Speaker 1: a method to do that because we can't see outside
• 40:20
  Speaker 1: our universe. So it might be that somebody in the
• 40:23
  Speaker 1: future comes up with a really clever way to test
• 40:26
  Speaker 1: these ideas. Never rule out future smart people like the
• 40:29
  Speaker 1: young Joss, But it might be that we never know,
• 40:33
  Speaker 1: and that's sort of frustrating.
• 40:34
  Speaker 2: Well, maybe it's comforting because it means we're unlikely to
• 40:37
  Speaker 2: be destroyed by these bubble universes. But I guess just
• 40:39
  Speaker 2: because we can't measure it doesn't mean it's not going
• 40:42
  Speaker 2: to result in our impending dual.
• 40:44
  Speaker 1: But there are ways that bubbles could destroy our universe,
• 40:48
  Speaker 1: not from other bubbles interacting with it or bouncing in it,
• 40:52
  Speaker 1: but from our universe changing state. You know, the state
• 40:56
  Speaker 1: of our universe where we have all of these fields
• 40:58
  Speaker 1: and some of them, like the Higgs field, have energy
• 41:01
  Speaker 1: stuck in them.
• 41:02
  Speaker 3: We don't know how stable.
• 41:03
  Speaker 1: That is, and it's possible that like some arrant particle
• 41:07
  Speaker 1: physicists doing an experiment sort of pushes the universe out
• 41:11
  Speaker 1: of its unstable state and collapses the Higgs field down
• 41:14
  Speaker 1: to lower energy, which would change like the masses of
• 41:17
  Speaker 1: all the particles and chemistry would be totally different in
• 41:20
  Speaker 1: life as we know. It would be impossible, and all
• 41:22
  Speaker 1: atoms would fly apart because electrons would lose their mass.
• 41:26
  Speaker 1: And if this happened, it would happen at one location
• 41:28
  Speaker 1: and then in a bubble moving outwards at the speed
• 41:31
  Speaker 1: of light, and so that eventually would take over the
• 41:34
  Speaker 1: whole universe and convert everything into this sort of new
• 41:38
  Speaker 1: kind of physics. This is the Higgs field collapse. So
• 41:41
  Speaker 1: that's the opposite of bubbles like bumping into each other
• 41:44
  Speaker 1: and destroying the universe. But it is a bubble from
• 41:47
  Speaker 1: within our universe, which wouldn't destroy it, but it would
• 41:50
  Speaker 1: change life fundamentally.
• 41:52
  Speaker 2: You are such a ray of sunshine. Do you think
• 41:56
  Speaker 2: physicists is the field that would be like most likely
• 41:59
  Speaker 2: to accidentally just story humanity?
• 42:02
  Speaker 3: Wow?
• 42:05
  Speaker 1: I think physicists are probably most likely to destroy the planet,
• 42:08
  Speaker 1: But I think destroy humanity. You got viruses, and you've
• 42:11
  Speaker 1: got pollution, and you got all sorts of stuff. So
• 42:13
  Speaker 1: I think chemists and biologists are in the running for,
• 42:16
  Speaker 1: you know, killing off humanity. Yea, all right, Well, I
• 42:22
  Speaker 1: hope that Joss is out there thinking about ways to
• 42:25
  Speaker 1: save humanity from the ravages of physics and biology and chemistry,
• 42:29
  Speaker 1: and that everything we've taught him contributes to the positive,
• 42:32
  Speaker 1: harmonious future of humanity. Thanks to the question, Andy and Joss,
• 42:36
  Speaker 1: and let us know if we answered it. Follow up
• 42:38
  Speaker 1: questions always welcome.
• 42:40
  Speaker 9: Thank you for taking the science and twerk questions. I
• 42:43
  Speaker 9: was exciting to hear you talking about my ideas on
• 42:45
  Speaker 9: the pollodcast. Assuming the Higgs serials get us first, I've said,
• 42:49
  Speaker 9: did any things as I think of them?
• 42:51
  Speaker 3: Thank you Daniel and Kelly all right?
• 42:53
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• 42:56
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• 42:58
  Speaker 1: cat pictures we got week.
• 43:00
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• 43:01
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