Latest / Daniel and Kelly’s Extraordinary Universe / Winter solstice listener questions

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Winter solstice listener questions · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: So, Daniel, you do a lot of cooking. What is
• 0:10
  Speaker 1: the biggest kitchen implement that you have?
• 0:15
  Speaker 2: Do We measure kitchen implements by size. Now is the
• 0:18
  Speaker 2: biggest one? The most important?
• 0:21
  Speaker 1: It is to me, I got one giant ladle and
• 0:24
  Speaker 1: that is the most important. What is let's talk about
• 0:27
  Speaker 1: sheer volume? What takes up the most space for you?
• 0:31
  Speaker 2: Well, actually, we went out and bought a huge soup pot.
• 0:34
  Speaker 2: Last time, we made soup for about one hundred people.
• 0:37
  Speaker 1: One hundred people for dinner. That's a lot.
• 0:41
  Speaker 2: Yeah. Well, you know, we were out celebrating solstice and
• 0:44
  Speaker 2: you got to go a little crazy on the solstice.
• 0:46
  Speaker 2: So we had one hundred people over for sit down
• 0:48
  Speaker 2: dinner and we made a lot of soup.
• 0:50
  Speaker 1: I would rather burn my kitchen down in a ritualistic
• 0:54
  Speaker 1: bonfire than do one hundred sets of dishes after that.
• 1:00
  Speaker 2: That sounds like a great way to celebrate the solstice. Actually,
• 1:02
  Speaker 2: kitchen bonfire.
• 1:04
  Speaker 1: Kitchen effigy. There we go, No more washing dishes.
• 1:07
  Speaker 2: Hooray, it's the solstice magic.
• 1:27
  Speaker 1: Hi.
• 1:27
  Speaker 2: I'm Daniel. I'm a particle physicist and a professor a
• 1:30
  Speaker 2: uc irvine and I'm not into astrology, but I do
• 1:33
  Speaker 2: love the Solstice.
• 1:34
  Speaker 1: I am Katie Golden. I host podcast on animal behavior
• 1:39
  Speaker 1: called Creature Feature, and I am super duper into Solstice
• 1:46
  Speaker 1: magics such as logs in the house and putting stones
• 1:54
  Speaker 1: up such that they make interesting shapes and the light
• 1:59
  Speaker 1: hits them in just such a way. M.
• 2:02
  Speaker 2: I see you're building Katie hinge.
• 2:04
  Speaker 1: Katie hinge. You know, Okay for the summer Solstice one,
• 2:07
  Speaker 1: I actually did talk about Britta Boyne, but I also
• 2:11
  Speaker 1: want to talk about how there's a wood hinge as
• 2:15
  Speaker 1: well as the stone hinge. And the word hinge it
• 2:19
  Speaker 1: actually comes from the idea of a thing hanging like
• 2:24
  Speaker 1: a hinge hanging. So stone hinge is like hanging rocks,
• 2:28
  Speaker 1: and wood hinge is another ancient people's way of creating
• 2:34
  Speaker 1: basically a annual sun dial, and that was made out
• 2:39
  Speaker 1: of wooden timber.
• 2:41
  Speaker 2: M I just always thought they were trying to hinge
• 2:43
  Speaker 2: their bets. I was thinking about starting a hinge.
• 2:46
  Speaker 1: Fund, you know, Oh my god, Well we do need
• 2:49
  Speaker 1: to teach Daniel about the difference between a hinge and
• 2:52
  Speaker 1: a hedge.
• 2:56
  Speaker 2: Well could you have a hedge hinge?
• 2:57
  Speaker 1: Uh? You know what, It's never been done as far
• 3:01
  Speaker 1: as I know in gardening science, but that never doesn't
• 3:04
  Speaker 1: mean never.
• 3:05
  Speaker 2: Well, okay, how about a biology one that a hedgehog
• 3:07
  Speaker 2: hinge hedgehog hinge.
• 3:09
  Speaker 1: Well, you know, maybe there's a hedgehog hinge for hedgehogs
• 3:12
  Speaker 1: looking for love.
• 3:15
  Speaker 2: All right, we'll hedge our bets until we get there.
• 3:16
  Speaker 2: But anyway, welcome to the podcast Daniel and Jorge Explain
• 3:20
  Speaker 2: the Universe, a production of iHeartRadio in which we do
• 3:23
  Speaker 2: not hedge our bets. We go all in on trying
• 3:25
  Speaker 2: to understand how the universe works and explain it all
• 3:29
  Speaker 2: to you. We tackle the biggest questions, from the very
• 3:31
  Speaker 2: nature of the universe to the smallest questions about quantum
• 3:34
  Speaker 2: particles and the fundamental nature of space and time and
• 3:38
  Speaker 2: everything in between, including how to get your hedgehogs out
• 3:41
  Speaker 2: of your hinge.
• 3:42
  Speaker 1: So there is a question I always get about hedgehogs,
• 3:46
  Speaker 1: and it is how do they reproduce? And my answer
• 3:49
  Speaker 1: is very carefully, that's a.
• 3:54
  Speaker 2: Very pointed answer, Katie. And people have questions about the universe.
• 3:59
  Speaker 2: They want about hedgehogs, they want about quantum particles, they
• 4:02
  Speaker 2: wonder about quantum hedgehogs, they wonder about hinges, and what
• 4:05
  Speaker 2: ancient people saw on them. They wonder what the solstice means,
• 4:08
  Speaker 2: and they wonder what's going on between us and distant stars.
• 4:12
  Speaker 2: And that's all part of doing physics. You don't have
• 4:14
  Speaker 2: to be a professional academic to be a physicist. You
• 4:17
  Speaker 2: just have to wonder about the nature of the universe
• 4:20
  Speaker 2: and then share that curiosity with everybody else, and we
• 4:23
  Speaker 2: hope you share it with us. If you have a
• 4:26
  Speaker 2: question about how the universe works, and you can find
• 4:28
  Speaker 2: an answer on Google or chat, GPT or your friendly
• 4:31
  Speaker 2: neighborhood physicists, please write to me to questions at Daniel
• 4:35
  Speaker 2: Andjorge dot com. We will answer it. Everybody gets an
• 4:38
  Speaker 2: answer in their inbox, and sometimes we take an answer
• 4:41
  Speaker 2: and put it right here on the podcast, also because
• 4:44
  Speaker 2: we've been missing you and we wanted to hear from
• 4:45
  Speaker 2: you again.
• 4:47
  Speaker 1: So ninety nine percent of a part of coul physicist's
• 4:51
  Speaker 1: job is asking the right questions, and one percent is
• 4:55
  Speaker 1: you know, math or whatever.
• 4:58
  Speaker 2: And there's also got to be rooting there for now.
• 5:00
  Speaker 1: Napping is crucial, right right, And like a little bit
• 5:03
  Speaker 1: of grant.
• 5:03
  Speaker 2: Writing occasionally, and so on today's episode, we'll be answering
• 5:14
  Speaker 2: listener questions. Winter Solstice Edition Happy holidays and New Year
• 5:19
  Speaker 2: and Solstice to everybody out there who celebrates whatever it
• 5:22
  Speaker 2: is you celebrate. Today, we're going to be celebrating my
• 5:25
  Speaker 2: answering a really fun question from a listener, a question
• 5:29
  Speaker 2: he thought of while he was in his backyard shed,
• 5:32
  Speaker 2: maybe building his own hinge. Here's the question from Alex.
• 5:37
  Speaker 3: Hi, guys, I was working in my backyard on my shed,
• 5:42
  Speaker 3: and I was using a metal crowbar to help out
• 5:46
  Speaker 3: one day when I just realized holding it how strong
• 5:49
  Speaker 3: it was. So my question that came to me was,
• 5:53
  Speaker 3: what is actually the longest physical possible crowbar made of
• 5:57
  Speaker 3: metal that that could exist in space? Is it possible
• 6:05
  Speaker 3: that you could build one? One could exist that's long
• 6:09
  Speaker 3: enough to stretch between stars, especially if you didn't have
• 6:12
  Speaker 3: to worry about adding to its length with unlimited supplies,
• 6:17
  Speaker 3: and if it was nowhere near any other gravitational objects.
• 6:20
  Speaker 3: What would the ramifications be of having it like a
• 6:23
  Speaker 3: crowbar where one end was light hours away from the other,
• 6:26
  Speaker 3: or even light years away from the other. It seems
• 6:29
  Speaker 3: a bit weird to travel light speed and not get
• 6:32
  Speaker 3: from one end to the other on one particular object.
• 6:36
  Speaker 1: Thank you, So you know I have a similar question.
• 6:40
  Speaker 1: But once I just saw a crow bar on the ground,
• 6:44
  Speaker 1: I think there were some people working on something like
• 6:47
  Speaker 1: a manhole or something sort of nearby. But also I
• 6:51
  Speaker 1: wondered if the world operates by video game rules, which is,
• 6:55
  Speaker 1: if you find a crowbar, is that yours now? Do
• 6:57
  Speaker 1: you pick it up and put it in your inventory?
• 6:59
  Speaker 1: Or is that that's still stealing?
• 7:02
  Speaker 2: I don't know. Maybe the world operates by checkof rules.
• 7:04
  Speaker 2: If you find a crowbar in act one, then you're
• 7:06
  Speaker 2: gonna have about to break into something with it in
• 7:08
  Speaker 2: Act three.
• 7:10
  Speaker 1: I mean that is just video game rules.
• 7:12
  Speaker 2: Also exactly exactly. I used to play like King's Quest
• 7:16
  Speaker 2: back in the day, and every time you found like
• 7:18
  Speaker 2: a weird magic rap mushroom, you put it in your
• 7:20
  Speaker 2: back pocket because you knew you were gonna need it
• 7:22
  Speaker 2: to solve some puzzle later on.
• 7:24
  Speaker 1: Get ye bucket. You're gonna need that bucket for the
• 7:27
  Speaker 1: dragon at the end of the game.
• 7:29
  Speaker 2: Exactly, and you can't go back, so get the bucket now.
• 7:32
  Speaker 2: And Alex is wondering about like the practical limits of
• 7:35
  Speaker 2: how big we could build something like, could you build
• 7:38
  Speaker 2: a crowbar that's long enough that you can use it
• 7:40
  Speaker 2: to like poke people on other planets that that's pretty crazy,
• 7:44
  Speaker 2: thought Alex.
• 7:45
  Speaker 1: It's interesting, right, because sure you could have like a
• 7:49
  Speaker 1: large object, but the bigger it gets. Like, there's a
• 7:52
  Speaker 1: lot of questions here, right, we need to know about
• 7:55
  Speaker 1: a what are crowbars made out of? Steel? Iron?
• 8:00
  Speaker 2: Feeling?
• 8:00
  Speaker 1: Steal? And so it's like, I guess a lot of
• 8:04
  Speaker 1: it is basically the strength, like the steal, you know,
• 8:08
  Speaker 1: the the what steals made out of? How that would work?
• 8:12
  Speaker 1: But also you know how even if it's made out
• 8:16
  Speaker 1: of any material, right, Like let's say crowbar made out
• 8:19
  Speaker 1: of whatever material, the strongest, hardest material you could get, Like,
• 8:24
  Speaker 1: is there a limit to the size of physical objects
• 8:28
  Speaker 1: in the universe before some wacky starts happening?
• 8:31
  Speaker 2: Yeah, this is really fun, And there's a really important
• 8:34
  Speaker 2: lesson here about how we do physics anyway, because an
• 8:38
  Speaker 2: important sort of often implicit step that we don't talk
• 8:41
  Speaker 2: about when we do physics is building a simplified model
• 8:45
  Speaker 2: of the universe. Like you want to answer a physics question,
• 8:48
  Speaker 2: you know, like a piano is falling from a window.
• 8:52
  Speaker 2: Is it going to squish that little doggie?
• 8:54
  Speaker 1: No?
• 8:55
  Speaker 2: Oh no, hopefully answer is no. But to answer that
• 8:58
  Speaker 2: physics question, which you have to do is simplify at first.
• 9:01
  Speaker 2: Because you don't care about a lot of the details.
• 9:03
  Speaker 2: You don't care about the color of the piano, you
• 9:05
  Speaker 2: can probably ignore the crosswinds. You build a simplified model
• 9:08
  Speaker 2: that just contains the information necessary to.
• 9:11
  Speaker 1: Answer the question, like the breed of the dog for.
• 9:13
  Speaker 2: Example, Yeah we don't care, I mean we care, but
• 9:16
  Speaker 2: doesn't change the answer. And so the trick there is
• 9:19
  Speaker 2: to make a model that's simple enough that you can
• 9:21
  Speaker 2: actually answer it because you've included all the details of
• 9:23
  Speaker 2: all the quantum particles and be intractable, but is sophisticated
• 9:27
  Speaker 2: enough that it still provides a realistic answer. That's the
• 9:30
  Speaker 2: sweet spot for doing physics. And the interesting thing is
• 9:34
  Speaker 2: that that's a different model in every scenario. You can
• 9:37
  Speaker 2: ignore the winds in this case, but if you're solving
• 9:39
  Speaker 2: a different problem like what's going to happen to this
• 9:41
  Speaker 2: leaf and a tornado, you can't ignore the winds. So
• 9:44
  Speaker 2: every time you solve a physics problem, you need to
• 9:46
  Speaker 2: ask yourself, am I including the right assumptions or the
• 9:49
  Speaker 2: assumptions I'm making going to ruin it? And so I
• 9:52
  Speaker 2: run into this all the time with these very long
• 9:55
  Speaker 2: space rods. Al It turns out Alex is not the
• 9:57
  Speaker 2: only person to think about really long rods. It comes
• 10:00
  Speaker 2: up a lot because people have this idea that a
• 10:02
  Speaker 2: rod is sort of like infinitely rigid. Like if I'm
• 10:06
  Speaker 2: across the room from you and I have a dowel
• 10:08
  Speaker 2: like a wooden stick, if I push it, then you're
• 10:11
  Speaker 2: gonna feel me pushing it. You're holding the other end,
• 10:13
  Speaker 2: you're gonna feel it. And people imagine that sort of
• 10:15
  Speaker 2: happens instantaneously, that if I push on the stick on
• 10:18
  Speaker 2: one side, you feel it instantly. And that's mostly true,
• 10:21
  Speaker 2: and for basically every problem you're going to solve here
• 10:23
  Speaker 2: on Earth, that's basically the case, because the information travels
• 10:27
  Speaker 2: very very fast. But then people wonder, all right, what
• 10:29
  Speaker 2: if I take a rod and I build it so
• 10:31
  Speaker 2: it's like four light years long, and I stretch it
• 10:35
  Speaker 2: from here to Alpha Centauri and some alien is holding
• 10:37
  Speaker 2: the other side. Can I tap on my side and
• 10:41
  Speaker 2: use that to communicate faster than the speed of light.
• 10:43
  Speaker 2: That's a very common question I get, And the answer
• 10:46
  Speaker 2: is obviously no. You can't break special relativity with a
• 10:50
  Speaker 2: dowel that's four light years long.
• 10:52
  Speaker 1: Even dowels have their limits.
• 10:54
  Speaker 2: I guess, yeah, and the reason is that you've broken
• 10:57
  Speaker 2: the assumptions. Down here on Earth, it works to a boom. Yeah,
• 11:00
  Speaker 2: the information travels instantly. That when you push one side
• 11:03
  Speaker 2: of the dowel, the other side moves instantly. But that
• 11:06
  Speaker 2: doesn't work anymore when the dowel's really really long, because
• 11:09
  Speaker 2: the time it takes now matters, because a dowel, even
• 11:13
  Speaker 2: here on Earth, doesn't transmit information instantly. What happens when
• 11:16
  Speaker 2: you push on one side of the dowel is that
• 11:19
  Speaker 2: you don't immediately move the other side. You push on
• 11:21
  Speaker 2: one side, and it moves the layer of molecules that
• 11:24
  Speaker 2: are next to the edge, which you mean the next layer,
• 11:27
  Speaker 2: which moved the next layer, which moved the next layer.
• 11:29
  Speaker 2: Because a dowel is not infinitely rigid, it's like a
• 11:32
  Speaker 2: very stiff version of a tube of water or like
• 11:34
  Speaker 2: a string. You're pushing on it and there's a wave
• 11:37
  Speaker 2: of information that travels down the dowel. So here on Earth,
• 11:41
  Speaker 2: you push on one side of the dowel, the other
• 11:42
  Speaker 2: side moves very shortly afterwards, but not instantly. It takes
• 11:46
  Speaker 2: time for that information and move down the dowel. Now,
• 11:50
  Speaker 2: when your Dowel is four light years long. That time
• 11:52
  Speaker 2: is no longer something you can ignore. It plays a
• 11:54
  Speaker 2: big part in how long it takes for the information
• 11:57
  Speaker 2: to get there. And if you ignore that, you're violating
• 12:00
  Speaker 2: special relativity. And it seems like you could send information
• 12:03
  Speaker 2: to the stars faster than the speed of light, which
• 12:05
  Speaker 2: of course you can't.
• 12:06
  Speaker 1: This is actually the same problem from a biological perspective
• 12:10
  Speaker 1: of having like a giant brain, right, could you have
• 12:14
  Speaker 1: an enormous brain that could like communicate instantly, right, like
• 12:20
  Speaker 1: some galaxy sized brain. And the problem is that the
• 12:24
  Speaker 1: way our brains work in the same way that you
• 12:26
  Speaker 1: talked about, how like the molecules have to push on
• 12:29
  Speaker 1: the other molecules, Like our brain is all physics based.
• 12:32
  Speaker 1: Our whole bodies are basically a big rub Goldberg machine
• 12:35
  Speaker 1: of molecules bonking into other molecules, which creates things like thought.
• 12:41
  Speaker 1: And so if you have a say, a giant enough brain,
• 12:45
  Speaker 1: the time it would take to like have a single
• 12:48
  Speaker 1: thought would be incredibly slow. So the bigger the brain,
• 12:53
  Speaker 1: the more galaxy size the brain, actually the slower it
• 12:57
  Speaker 1: would take to have it.
• 12:58
  Speaker 2: Not yeah, exactly. And so if you're ignoring that, when
• 13:01
  Speaker 2: you're just thinking about a small brain. You can no
• 13:03
  Speaker 2: longer ignore that in a large brain. So the lesson is,
• 13:06
  Speaker 2: when you're doing physics, you have to always think about
• 13:08
  Speaker 2: what are the assumptions we're making and are those assumptions
• 13:11
  Speaker 2: still valid for this scenario. In the case of the
• 13:14
  Speaker 2: like five light year long rod, if you assume instantaneous
• 13:19
  Speaker 2: motion from one side to the other, then you're assuming
• 13:21
  Speaker 2: special relativity is broken. So you can't then go and say, oh, look,
• 13:24
  Speaker 2: this rod breaks special relativity. Well, you assume to it
• 13:26
  Speaker 2: is broken, and that's why you broke it. And so
• 13:29
  Speaker 2: there's a lot of unpacking of those assumptions in these questions.
• 13:33
  Speaker 2: But Alex's question is a little bit different. He's not
• 13:35
  Speaker 2: trying to communicate with aliens. He's just trying to build
• 13:37
  Speaker 2: a really long rod, and he's wondering, like how big
• 13:39
  Speaker 2: could you make it? Anyway? And I think that's exactly
• 13:42
  Speaker 2: what he's digging into, like what would break down? What
• 13:45
  Speaker 2: assumptions we make about building long rods would break down
• 13:48
  Speaker 2: if we try to make one that's like a light
• 13:50
  Speaker 2: year long, Which is a really cool question.
• 13:52
  Speaker 1: Yeah, because I mean there's a lot of things that
• 13:55
  Speaker 1: we could say, like on Earth, right, Like, we could
• 13:57
  Speaker 1: try to build a really long crow bar and at
• 14:00
  Speaker 1: a certain point it could collapse under its own weight.
• 14:03
  Speaker 1: But if something's in space, we'd have to figure out
• 14:07
  Speaker 1: what kinds of forces or how gravity would be acting
• 14:11
  Speaker 1: on something in a way that's different from Earth, right, Like, yes,
• 14:15
  Speaker 1: you can. You know, it's like have you ever you
• 14:18
  Speaker 1: know whiteboard pins? Like you create a big old lightsaber
• 14:21
  Speaker 1: out of whiteboard pins and at a certain point there's
• 14:25
  Speaker 1: too many and it collapses. But that's all using Earth physics.
• 14:29
  Speaker 1: So you could make a much longer whiteboard pin lightsaber
• 14:35
  Speaker 1: out in space because gravity is not impacting it in
• 14:39
  Speaker 1: the same way that it is on Earth. But then
• 14:41
  Speaker 1: once you get big enough, right with this pin dowel
• 14:45
  Speaker 1: or iron crowbar or whatever it is, something's happening. And
• 14:49
  Speaker 1: this is where I would like you to talk.
• 14:52
  Speaker 2: Yeah, exactly. So let's take this question out into deep space.
• 14:57
  Speaker 2: And the first thing the wonder is like, well, what's
• 14:59
  Speaker 2: the biggest thing we built in space so far? And
• 15:02
  Speaker 2: that's the International Space Station. It's not that impressively long,
• 15:04
  Speaker 2: it's about thirty six meters long, but you know, it's
• 15:07
  Speaker 2: not very far out in space, and they're not trying
• 15:10
  Speaker 2: to build something super duper long. I think the longest
• 15:13
  Speaker 2: thing that's ever actually been in space, it's more like
• 15:15
  Speaker 2: a kilometer. They build a space tether, which is like
• 15:18
  Speaker 2: a really long wire that you dangle from a spaceship
• 15:21
  Speaker 2: to try to like generate electrical current or to learn
• 15:24
  Speaker 2: to steer using mechnetic fields. So like a kilometer long,
• 15:28
  Speaker 2: it's the biggest thing that we've ever put into space.
• 15:31
  Speaker 2: But again that's also just the near Earth orbit. So
• 15:34
  Speaker 2: let's go deeper out into space and try to build
• 15:37
  Speaker 2: something that's really long and think about the forces involved.
• 15:40
  Speaker 2: Like when you build a rod at a steel or
• 15:43
  Speaker 2: even a dowel out of wood or whatever, how are
• 15:46
  Speaker 2: you actually building that thing. Usually we ignore it and
• 15:48
  Speaker 2: just say, oh, it's some smooth, continuous substance. But if
• 15:51
  Speaker 2: you zoom in, the reason it takes time to propagate
• 15:54
  Speaker 2: information along it is the same thing that's holding it together,
• 15:57
  Speaker 2: which is the forces between those molecules. All of these
• 16:00
  Speaker 2: objects in the end are like a mesh of modules.
• 16:03
  Speaker 2: Yet you have these little bits of matter tied together
• 16:05
  Speaker 2: by forces to build something larger, and it's those forces
• 16:09
  Speaker 2: that transmit the information also limit how big something can
• 16:12
  Speaker 2: get right and so out into deep space. What is
• 16:16
  Speaker 2: the thing that's limiting us. Well, those forces can work.
• 16:19
  Speaker 2: They can tie something together basically infinitely. There's no limitation there.
• 16:22
  Speaker 2: You can just keep adding layers and layers and layers
• 16:25
  Speaker 2: to your rod. The thing that's going to keep you
• 16:27
  Speaker 2: from building that rod light years long or infinitely long
• 16:30
  Speaker 2: in the end, are going to be the gravitational effects,
• 16:33
  Speaker 2: residual as they are, and the nature of space and
• 16:37
  Speaker 2: time itself. But let's first talk about the gravitational effects.
• 16:40
  Speaker 2: So one effect are tidal forces. So you say, well,
• 16:44
  Speaker 2: let's be out between the stars. AX is actually talking
• 16:47
  Speaker 2: about something which stretches between the stars. You have like
• 16:49
  Speaker 2: one end at one star and the other end at
• 16:51
  Speaker 2: another star. And if you have something that's like five
• 16:54
  Speaker 2: light years long, you can't have it that far away
• 16:56
  Speaker 2: from stars because it's going to be big enough. There's
• 16:59
  Speaker 2: always going to be some star nearby. And remember that
• 17:02
  Speaker 2: gravity does more than just pull on things. It can
• 17:04
  Speaker 2: actually pull things apart. These are called tidal forces. And
• 17:07
  Speaker 2: for example, if you're near a black hole, then your
• 17:11
  Speaker 2: head can have a different gravitational tug on it than
• 17:14
  Speaker 2: your feet, and that can effectively tear you apart. Like,
• 17:17
  Speaker 2: if the black hole is pulling on your feet harder
• 17:19
  Speaker 2: than it's pulling on your head because your feet are
• 17:21
  Speaker 2: a little bit closer, then it's going to pull you
• 17:23
  Speaker 2: apart because its gravity is really really strong. But if
• 17:26
  Speaker 2: you're really really long, then you don't need strong gravity
• 17:30
  Speaker 2: to have tidal forces. Because if one end of this
• 17:32
  Speaker 2: rod is closer to the star then the other end,
• 17:35
  Speaker 2: and the rod is really really long, it's going to
• 17:37
  Speaker 2: be a very large difference in the gravitational force from
• 17:40
  Speaker 2: one end of the rod to the other, and that
• 17:42
  Speaker 2: star is going to tear it apart. Even if the
• 17:44
  Speaker 2: star doesn't have really powerful gravity like black holes, the
• 17:47
  Speaker 2: sheer length of the rod makes the title forces very significant.
• 17:51
  Speaker 1: I see. So you can't span a dell from one
• 17:56
  Speaker 1: start to the other because of the same title forces
• 17:59
  Speaker 1: that spaghettifies you in a black hole. But what if
• 18:04
  Speaker 1: you took away the stars? Right? Like, could you get
• 18:08
  Speaker 1: a like infinity rod if you took away stars and
• 18:14
  Speaker 1: just had it existing on its own in space without
• 18:18
  Speaker 1: hitting anything?
• 18:19
  Speaker 2: Yeah? Right, So get rid of the other gravity, and
• 18:21
  Speaker 2: you still have the issue of the gravity of the
• 18:23
  Speaker 2: rod itself. Right, You can't build an infinitely massive rod,
• 18:28
  Speaker 2: because eventually that thing is going to have its own
• 18:30
  Speaker 2: self gravity, that it's going to collapse into a black hole. Like,
• 18:34
  Speaker 2: you can't just make a blob of metal and keep
• 18:36
  Speaker 2: adding blobs of metal to it and make it as
• 18:38
  Speaker 2: big as you want, because it's going to start collapsing.
• 18:41
  Speaker 2: This already happens for things like planets, like the Earth
• 18:44
  Speaker 2: is about the largest rocky planet you can make. You
• 18:47
  Speaker 2: can add more rock to it, but that's going to
• 18:49
  Speaker 2: mean more gravity, and it's just going to compress the
• 18:51
  Speaker 2: Earth further. So as you add more mass to the Earth,
• 18:54
  Speaker 2: it doesn't get any bigger, it just gets denser. And
• 18:57
  Speaker 2: eventually you keep adding mass, you're going to end up
• 19:00
  Speaker 2: with a black hole. And so there is a limit
• 19:02
  Speaker 2: to how large and how massive you can make something
• 19:06
  Speaker 2: before it collapses into a black hole. So something self
• 19:09
  Speaker 2: gravity will also limit how large you can make an
• 19:12
  Speaker 2: object out of practical stuff like steel or wood.
• 19:15
  Speaker 1: Okay, so what about a really thin rod. Now stay
• 19:19
  Speaker 1: with me. What if you have a rod that is
• 19:22
  Speaker 1: like one atom per unit, right, is like one atom thick,
• 19:27
  Speaker 1: and then you just stack a bunch of atoms into
• 19:30
  Speaker 1: this very long rod, would that still be something that
• 19:37
  Speaker 1: would at a certain point start to collapse in on
• 19:40
  Speaker 1: itself because of gravity, or am I already breaking some
• 19:44
  Speaker 1: laws of physics by trying to create a one atom
• 19:49
  Speaker 1: diameter rod.
• 19:50
  Speaker 2: Now you could probably make a carbon nanofiber. Eventually it's
• 19:53
  Speaker 2: like one atom thick and super duper long. I don't
• 19:55
  Speaker 2: think it's a technical problem there, But what you're going
• 19:58
  Speaker 2: to run into is a problem with a knee. You're
• 20:00
  Speaker 2: a space and time, and if you can get rid
• 20:02
  Speaker 2: of gravity then nearby stars and effectively get rid of
• 20:05
  Speaker 2: the self gravity by making this thing really really lightweight,
• 20:08
  Speaker 2: you're going to run into dark energy. So in short distances,
• 20:12
  Speaker 2: like the size of our Solar system of the size
• 20:14
  Speaker 2: of our galaxy, the dominant force is gravity. It holds
• 20:17
  Speaker 2: things together, it shapes things, it determines the nature of
• 20:20
  Speaker 2: our universe. But over very large distances, gravity gets weaker. Right,
• 20:24
  Speaker 2: the further you are away from something, the weaker it's
• 20:26
  Speaker 2: gravity is. And at those distances something else takes over,
• 20:30
  Speaker 2: which is dark energy, meaning the expansion of the universe itself.
• 20:34
  Speaker 2: Remember that everywhere in the universe is expanding. Take any
• 20:38
  Speaker 2: arbitrary chunk of space as time goes on, that space
• 20:41
  Speaker 2: is getting larger. It's making new space. So between the
• 20:45
  Speaker 2: Earth and the Sun, for example, new space is being made,
• 20:48
  Speaker 2: but the gravity of the Earth and the Sun overpowers it.
• 20:51
  Speaker 2: Between our galaxy and the neighboring galaxy, new space is
• 20:54
  Speaker 2: being made, but again the gravity overpowers it. But eventually,
• 20:58
  Speaker 2: between clusters of galonyes, dark energy becomes more powerful because
• 21:02
  Speaker 2: you have more of these cubes of space and each
• 21:05
  Speaker 2: one is expanding, so that adds up and gravity gets
• 21:08
  Speaker 2: very very weak. So take Alex's super duper long, infinitely
• 21:12
  Speaker 2: thin rod. Eventually it's going to be so long that
• 21:15
  Speaker 2: dark energy is going to tear it apart. It's going
• 21:18
  Speaker 2: to be creating new space between those atoms faster than
• 21:21
  Speaker 2: those atoms can recover and bind themselves together. So you
• 21:25
  Speaker 2: can get spaghettified by space and time.
• 21:28
  Speaker 1: All right, So we cannot make an infinity rod. Unfortunately,
• 21:33
  Speaker 1: do we know, like how big something can get before
• 21:37
  Speaker 1: the expansion of the universe starts to break it apart.
• 21:42
  Speaker 2: It's gonna be really really big. And remember that nearby
• 21:45
  Speaker 2: galaxies are millions of light years away, and dark energy
• 21:49
  Speaker 2: only really dominates between clusters of galaxies, So we're talking
• 21:54
  Speaker 2: hundreds of millions of light years. So if you can
• 21:57
  Speaker 2: overcome the gravity of nearby stars and overcome tidal forces
• 22:01
  Speaker 2: completely and overcome collapsing due to self gravity, then you
• 22:05
  Speaker 2: could still build something that's like hundreds of millions of
• 22:08
  Speaker 2: light years long. So that's pretty good.
• 22:10
  Speaker 1: You know what. That sounds great. I'm going to write
• 22:13
  Speaker 1: a grant for UH to get started building on the
• 22:18
  Speaker 1: biggest spaghetti that one.
• 22:20
  Speaker 2: Could make, exact spaghetti simo.
• 22:24
  Speaker 1: Yeah. I bet Italy's government would fun that.
• 22:27
  Speaker 2: It's going to write yes in honor of the winter solstice.
• 22:31
  Speaker 2: I think that's a great idea. All right, Well, thank
• 22:34
  Speaker 2: you very much Alex for thinking big and wondering about
• 22:37
  Speaker 2: how far we can push our concepts of distance and
• 22:40
  Speaker 2: structure and space and time. Really fun way to explore
• 22:44
  Speaker 2: all of those different factors, and really appreciate everybody out
• 22:47
  Speaker 2: there who's thinking about the universe and wondering about it,
• 22:50
  Speaker 2: and who's brave enough to write into their favorite Internet
• 22:52
  Speaker 2: physicists to look for some answers. If you'd like to
• 22:55
  Speaker 2: see my email in your inbox, write to me two
• 22:57
  Speaker 2: questions at Daniel and Jorge dot com. I'd sure love
• 23:00
  Speaker 2: to hear from you. Thanks very much, Katie for pushing
• 23:03
  Speaker 2: the boundaries of space and time and humor today.
• 23:06
  Speaker 1: And thank you for signing on to my petition for
• 23:10
  Speaker 1: universe's longest spaghetti.
• 23:14
  Speaker 2: Funded funded funded. All right, Thanks everyone for listening, and
• 23:17
  Speaker 2: tune in next time for more science and curiosity. Come
• 23:25
  Speaker 2: find us on social media, where we answer questions and
• 23:27
  Speaker 2: post videos. We're on Twitter, disc Org, Instant, and now TikTok.
• 23:32
  Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain
• 23:35
  Speaker 2: the Universe is a production of iHeartRadio. For more podcasts
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• 23:44
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