Latest / Daniel and Kelly’s Extraordinary Universe / Frequently Asked Listener Questions About the Universe!

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Frequently Asked Listener Questions About the Universe! · Daniel and Kelly’s Extraordinary Universe

0:01
Speaker 1: Hey, it Jorhan Daniel here, and we want to tell
0:03
Speaker 1: you about our new book. It's called Frequently Asked Questions
0:06
Speaker 1: about the Universe because you have questions about the universe,
0:09
Speaker 1: and so we decided to write a book all about them.
0:12
Speaker 1: We talk about your questions, we give some answers, we
0:14
Speaker 1: make a bunch of silly jokes as usual, and we
0:17
Speaker 1: tackle all kinds of questions, including what happens if I
0:20
Speaker 1: fall into a black hole? Or is there another version
0:22
Speaker 1: of you out there that's right? Like usual, we tackle
0:25
Speaker 1: the deepest, darkest, biggest, craziest questions about this incredible cosmos.
0:29
Speaker 1: If you want to support the podcast, please get the
0:31
Speaker 1: book and get a copy not just for yourself, but
0:34
Speaker 1: you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,
0:39
Speaker 1: and for the aliens. So get your copy of Frequently
0:42
Speaker 1: Asked Questions about the Universe is available for pre order now,
0:46
Speaker 1: coming out November two. You can find more details at
0:49
Speaker 1: the book's website, Universe f a Q dot com. Thanks
0:53
Speaker 1: for your support, and if you have a hamster that
0:55
Speaker 1: can read, please let us know. We'd love to have
0:57
Speaker 1: them on the podcast. And Daniel, do you ever get
1:11
Speaker 1: questions from listeners that aren't about physics. Oh yeah, sure,
1:14
Speaker 1: Sometimes I get questions asking for life advice or books
1:18
Speaker 1: to recommend that kind of stuff. Really, people ask you
1:21
Speaker 1: for life advice and overworked academic like, how do I
1:25
Speaker 1: avoid making the same mistakes? I mean, yeah, exactly. Well,
1:29
Speaker 1: my life advice is actually mostly like my book advice.
1:33
Speaker 1: What do you mean, well, my life advice and generally
1:36
Speaker 1: read more books. There you go, that's good advice. What
1:39
Speaker 1: kinds of books do you usually recommend? Well, it just
1:42
Speaker 1: so happens that there's a great new book coming out
1:44
Speaker 1: today that I highly recommend. Is it about banana recipes?
1:49
Speaker 1: You know, I got plenty of those, I mean our
1:52
Speaker 1: book frequently asked questions about the universe. Oh right, yeah,
1:57
Speaker 1: I should get a copy or maybe three for my
2:00
Speaker 1: friends too. And I think it has been in a
2:03
Speaker 1: recipe to right, That was a frequently a question nobody
2:05
Speaker 1: asks for bed in recipes. I am more handmad cartoonist
2:24
Speaker 1: and the creator of PhD comics. Hi, I'm Daniel. I'm
2:27
Speaker 1: a particle physicist, and I'm the proud co author of
2:30
Speaker 1: the book. Frequently asked questions about all the incredible things
2:34
Speaker 1: that we want to understand about the universe. That's right,
2:37
Speaker 1: Daniel and I wrote another book and follow up to
2:40
Speaker 1: our first book, We Have No Idea, And this one
2:42
Speaker 1: is kind of about you, the listener, that's right. This
2:45
Speaker 1: one is literally inspired by listeners. It's about all the
2:48
Speaker 1: big questions that people ask over and over again. It's
2:51
Speaker 1: about those topics that resonate with everybody that everybody wants
2:55
Speaker 1: to know the answer to. Yeah, big questions like will
2:58
Speaker 1: time ever stop? And why haven't aliens visited us? Yeah?
3:02
Speaker 1: Or where is the center of the universe? And can
3:05
Speaker 1: I get Google Map to give me directions there? Yeah.
3:07
Speaker 1: We even tackle kind of philosophical questions, right, Daniel, like
3:11
Speaker 1: is there an afterlife? Or is there free will in
3:14
Speaker 1: our brains? Yeah? We talk about those things from a
3:17
Speaker 1: physics point of view, like what do we know about
3:19
Speaker 1: the universe and what can that tell us about these
3:22
Speaker 1: deep questions about life, happiness and everything. Yeah, and I
3:26
Speaker 1: think it came out pretty good. I really like this book.
3:28
Speaker 1: I feel like it's fun, it has short chapters, It
3:31
Speaker 1: tackles really interesting kind of existential questions, and I think
3:35
Speaker 1: we do a pretty good job of answering each question,
3:37
Speaker 1: you know, Like from a physics perspective and what people
3:40
Speaker 1: know when people don't know. It certainly was fun to
3:42
Speaker 1: work on and fun to write, and I hope that
3:44
Speaker 1: means that it's fun to read. And some of these
3:47
Speaker 1: topics in here are near and dear to my heart,
3:49
Speaker 1: and some of them were a little far afield for me,
3:51
Speaker 1: so I have to go off and do some research
3:53
Speaker 1: talk to experts. But that was always a lot of fun.
3:55
Speaker 1: There's a lot of Wikipedia reading, I think, is what
3:58
Speaker 1: you're saying, but not all at all story from Wikipedia.
4:01
Speaker 1: We do talk to experts, like we have a chapter
4:03
Speaker 1: about meteors coming to Earth, and we talked to people
4:06
Speaker 1: on NASA, Like we went to NASA and talked to
4:07
Speaker 1: somebody there. Yeah, we talked to the folks at NASA
4:10
Speaker 1: whose job it is to protect us from huge rocks
4:12
Speaker 1: from space. There are people out there whose job actually
4:15
Speaker 1: is planetary protection officer, and we went and talk to them.
4:19
Speaker 1: So you don't have to, yeah, because I think another
4:21
Speaker 1: big question we usually get is people ask how can
4:24
Speaker 1: we support the podcast or how can we help you guys,
4:26
Speaker 1: And so this is kind of a pretty good way
4:28
Speaker 1: to do it. To get the book and not just
4:30
Speaker 1: maybe get a copy for yourself, but get one for
4:32
Speaker 1: your friends, for your family members. You know that person
4:34
Speaker 1: you always wanted to convince them to listen to our podcast,
4:37
Speaker 1: but maybe it hasn't yet. I think this book is
4:39
Speaker 1: a really sort of nice introduction to these topics, to
4:42
Speaker 1: the universe, to you know, asking fun questions and getting
4:46
Speaker 1: fun answers about these great mysteries. Yeah, we hope that
4:49
Speaker 1: it strikes a balance. There are really interesting, deep nuggets
4:52
Speaker 1: of physics in there for those heavy duty nerds that
4:55
Speaker 1: really want to understand the details about something, but also
4:57
Speaker 1: a lot of just general approachable stuff about the universe.
5:01
Speaker 1: Then I'm pretty sure everybody wants to know. I mean,
5:03
Speaker 1: I feel tested on my kids, who are definitely not
5:06
Speaker 1: fans of science. Are they heavy duty or light duty nerds? Neither?
5:10
Speaker 1: They're like, oh, man, dad is talking about science again.
5:13
Speaker 1: My daughter's favorite phrase is I didn't ask for a
5:16
Speaker 1: physical lecture. Okay, oh my goodness. That is some high
5:20
Speaker 1: level sass there, exactly. That's what it's going to make
5:22
Speaker 1: her a TikTok star one day. It sounds like you
5:24
Speaker 1: need to buy our book. Well, my favorite thing is
5:26
Speaker 1: sometimes they ask me questions which come up in the book,
5:29
Speaker 1: and I'm like, oh, you should read my book. I
5:31
Speaker 1: answered that question and then they're like, my book. But yeah,
5:35
Speaker 1: if you want to support this, please check out the
5:37
Speaker 1: book and pre order it now, Daniel. It comes out
5:39
Speaker 1: in November. What It comes out November two, and you
5:42
Speaker 1: can pre order it now, which we'd be very grateful
5:44
Speaker 1: for your support. You can find it everywhere good books
5:47
Speaker 1: and bad books are sold, and you can also find
5:49
Speaker 1: it online at universe f a Q dot com. Yeah,
5:53
Speaker 1: and if we time things right, actually today is the
5:55
Speaker 1: day that it comes out, right, today is November two,
5:59
Speaker 1: that's right. We're recording this in September, but we're tying
6:02
Speaker 1: in this episode to release on the day of our
6:04
Speaker 1: book launch. So today should be the day that the
6:06
Speaker 1: book is physically existing in stories. You can drive to
6:09
Speaker 1: your local bookstore and buy one. Yeah, we promised it. It
6:12
Speaker 1: It has a ton of cartoons. I had to draw
6:14
Speaker 1: hundreds of cartoons for this one, which was a ton
6:16
Speaker 1: of fun. But also it was a sprint at the
6:18
Speaker 1: ant finish. Isn't every project you do a sprint to
6:21
Speaker 1: finish at the end. I like sprinting, you know, I
6:25
Speaker 1: feel like that's when you're really living. No, but I
6:27
Speaker 1: gotta say, the cartoons really add another voice to the book.
6:30
Speaker 1: You know, just like on our podcast you have like
6:32
Speaker 1: the voice of a scientist, and then you have the
6:34
Speaker 1: voice of our cartoonists. In the book, we also try
6:36
Speaker 1: to capture that you have the text which tells you
6:38
Speaker 1: about the physics, and then you have the cartoons which
6:40
Speaker 1: are sort of an interplay and liven it up and
6:43
Speaker 1: also really help clarify. You know, sometimes you really need
6:46
Speaker 1: a visual and on the podcast we can't communicate with
6:48
Speaker 1: you in visual medium, but in the book we can.
6:51
Speaker 1: And in addition, you also get to see Jorge's great art,
6:53
Speaker 1: which is really lively and clever. Yeah. So the book
6:56
Speaker 1: comes out today, please check it out, and to celebrate,
6:58
Speaker 1: we are having a special of our podcast today, we
7:02
Speaker 1: are doing kind of a dedicated oh to listener questions.
7:05
Speaker 1: That's right. We love questions from listeners that inspired our book.
7:08
Speaker 1: It powers the podcast, and it inspires me every day
7:11
Speaker 1: because every day that I get emails from listeners asking questions,
7:14
Speaker 1: I'm reminded that everybody out there wants to understand the universe.
7:18
Speaker 1: That it's not just me sitting in my office trying
7:20
Speaker 1: to puzzle away the deep secrets of the universe. But
7:22
Speaker 1: it's something that touches everybody in a really human way,
7:26
Speaker 1: that we have this desire to understand the world and
7:29
Speaker 1: the universe around us. It's an itch that will never
7:32
Speaker 1: be scratched, but we have to keep picking at it. Yeah,
7:34
Speaker 1: and that's why we ask questions. I mean, you do
7:36
Speaker 1: it professionally, kind of for living, Daniel. I guess you
7:38
Speaker 1: get paid, right, I haven't checked recently. I'm not getting
7:44
Speaker 1: any money, but I hope somebody. I think what you're
7:48
Speaker 1: saying is that all humans really ask these questions, right,
7:51
Speaker 1: you know, everyone you can't help, but wonder. It's kind
7:54
Speaker 1: of part of human nature to kind of ask questions
7:56
Speaker 1: and wonder what the answers are. Absolutely, it is part
7:59
Speaker 1: of human nature. And something I'm curious about is whether
8:01
Speaker 1: it's part of intelligence or whether it's just human. You know,
8:04
Speaker 1: if we meet aliens, I wonder will they be curious
8:07
Speaker 1: about the universe or will they be bored by that
8:09
Speaker 1: question and focused on something else which we find totally
8:12
Speaker 1: dull interesting, Like could you be an intelligent being but
8:16
Speaker 1: not curious? Who knows if science is a human endeavor
8:19
Speaker 1: or not? Maybe you need to be curious to develop
8:22
Speaker 1: intelligence from an evolutionary perspective. Yeah, it could go hand
8:25
Speaker 1: in hand. So lots of things will learn about the
8:28
Speaker 1: universe and the human perspective on it when we finally
8:30
Speaker 1: do meet those aliens, or maybe aliens will order a
8:33
Speaker 1: book and then write to us and tell us we
8:35
Speaker 1: got it all wrong. Well, we do have a chapter
8:38
Speaker 1: on why haven't we heard from aliens? So maybe deliverply
8:41
Speaker 1: would be like, we just don't like you. Maybe we
8:43
Speaker 1: were waiting for this book to come out. Now the moment,
8:47
Speaker 1: now that we read it in a book, will contact you.
8:49
Speaker 1: So to be on the podcast, we'll be tackling listener questions.
8:58
Speaker 1: Frequently asked questions about the Universe released edition. There was
9:01
Speaker 1: a lot of questions in the title of the episode. Well,
9:03
Speaker 1: that's the theme of the whole podcast, so we've got
9:05
Speaker 1: to underscore it with questions. Yeah, and so we're not
9:08
Speaker 1: going to be answering questions from the book, because you know,
9:10
Speaker 1: we don't want to give away any spoilers. But we
9:12
Speaker 1: do have some questions from actual listeners who are pretty
9:16
Speaker 1: good too. They're pretty interesting. Our questions here about gravity,
9:19
Speaker 1: about the relative velocity of stars, and also about the
9:24
Speaker 1: sound of the universe. That's right, the music of the
9:27
Speaker 1: early universe. Can't wait to talk about that one, the
9:29
Speaker 1: wailing cry of a newborn baby universe who doesn't want
9:33
Speaker 1: to hear that? If the universe screams alone in the forest,
9:36
Speaker 1: does anybody listen? And where is that forest anyway? All right? Well,
9:39
Speaker 1: our first question today comes from Lily, and she has
9:42
Speaker 1: a question about what would happen if gravity suddenly took
9:46
Speaker 1: a vacation. Hi, I'm Lily. What would happen if gravity
9:50
Speaker 1: just stopped? What would happen to the oceans, the trees,
9:53
Speaker 1: the houses, the Earth, the solar system, the universe? And
9:57
Speaker 1: what would happen if gravity never existed? I needs know? Thanks,
10:01
Speaker 1: Lily needs to Know. I should have been the title
10:03
Speaker 1: of our podcast. This sounds like a good kids show.
10:07
Speaker 1: Perhaps Eleanor wonders why Lily needs to know? But great question, Lily,
10:11
Speaker 1: Thank you so much for sending this question. It's a
10:13
Speaker 1: great question, like what if gravity suddenly like turned off
10:17
Speaker 1: or like quit? Yeah? Do you think this is in
10:19
Speaker 1: the vein of supervillain's planning take over the world? Kind
10:22
Speaker 1: of questions like do you think Lily is building a
10:24
Speaker 1: gravity destroyer? And wondering if you're gonna have enough impact.
10:28
Speaker 1: Oh man, you just turned Lily into a super villain. Boy.
10:32
Speaker 1: I thought she was really sweet and intelligent, but now
10:35
Speaker 1: you just put a dark spin on it. She's using
10:38
Speaker 1: that sweet intelligence just to fool you. Man. I'm sure
10:41
Speaker 1: Lately just needs to know because she's curious, right, I hope, yes, absolutely,
10:45
Speaker 1: But yeah, I guess you know, let's not maybe talk
10:47
Speaker 1: about how you would do that, like, you know, let's
10:50
Speaker 1: avoid that. But I think it's more of a hypothetical question.
10:53
Speaker 1: What would happen if gravity just stop one day? Yeah?
10:56
Speaker 1: That is a really fascinating question because gravity is so
11:00
Speaker 1: hortoned to shaping the structure of our universe and the
11:03
Speaker 1: very environment that we live in. So if it went away,
11:05
Speaker 1: we would definitely notice pretty quickly. Yeah, And it's also
11:08
Speaker 1: important because it keeps us grounding, you know, it's important
11:11
Speaker 1: not to keep your head in the clouds. It allows
11:13
Speaker 1: for some pretty massive puns. Yeah, some heavy duty Nearth.
11:16
Speaker 1: But yeah, So Daniel, what would happen if there was
11:18
Speaker 1: a switch in front of you that says gravity on
11:21
Speaker 1: off and you flipped it to off. How bad would
11:23
Speaker 1: it be? It would be pretty bad, pretty fast. And
11:25
Speaker 1: the reason, at least locally, like here on Earth, is
11:28
Speaker 1: that the Earth is spinning, which means that you need
11:30
Speaker 1: something to pull you down. You need gravity to keep
11:34
Speaker 1: you on the surface of the Earth. Like if you're
11:37
Speaker 1: on a rock and gravity is holding you on the surface,
11:39
Speaker 1: but the rock is not spinning, and then gravity turns off,
11:43
Speaker 1: then you don't necessarily go anywhere, right, you can just
11:45
Speaker 1: stay in the same place. You only move if there's
11:48
Speaker 1: a force on you. But if the rock is spinning,
11:50
Speaker 1: if you're on the Earth and it's spinning and gravity
11:52
Speaker 1: goes away, well you were relying on gravity to keep
11:55
Speaker 1: you on the Earth as it was spinning. Otherwise you
11:58
Speaker 1: would fly off pretty quickly, and without gravity to hold
12:01
Speaker 1: you on the Earth, pretty soon you're gonna be floating
12:04
Speaker 1: up into the sky. You know. I never maybe we
12:05
Speaker 1: thought about it this way, but I guess the Earth
12:07
Speaker 1: is spinning, right, It's spinning in space. But I'm not
12:10
Speaker 1: necessarily spinning in space, right, It's like I'm only spinning
12:13
Speaker 1: in space because I'm stuck to the Earth. That's right. Well,
12:15
Speaker 1: you are a part of the Earth, and so every
12:17
Speaker 1: element to the Earth is spinning in the same way.
12:19
Speaker 1: The Earth is, But you're right, the Earth can spin
12:21
Speaker 1: without you, and in order to spin with the Earth,
12:24
Speaker 1: you need gravity or something to pull you down. Like
12:28
Speaker 1: for example, if you had a satellite going around the
12:30
Speaker 1: Earth in orbit, right, and then the Earth disappeared, it's
12:33
Speaker 1: gravity disappeared. What would happen to the satellite? It wouldn't
12:36
Speaker 1: keep moving in a circle, right, It would just fly
12:39
Speaker 1: off in a straight line in the direction it was going.
12:41
Speaker 1: The only reason that satellite moves around the Earth in
12:44
Speaker 1: a circle is because of the gravity of the Earth,
12:47
Speaker 1: and the same thing applies to you. The only thing
12:49
Speaker 1: that keeps you moving with the surface of the Earth
12:51
Speaker 1: is the gravity that bends your path down. Yeah, because
12:55
Speaker 1: I guess you know, like you just said, if you
12:57
Speaker 1: turn off gravity, the Earth would still keep on spinning.
12:59
Speaker 1: It had us this angular romentous and would just keep
13:01
Speaker 1: on spinning. But the thing is that you would sort
13:03
Speaker 1: of quit the Earth, and so you would no longer
13:06
Speaker 1: be sort of attached to it, and so you would
13:07
Speaker 1: fly off. Yeah. It's sort of like you know a
13:09
Speaker 1: picture does a big wind up spins his arm around
13:12
Speaker 1: and then let's go of the ball. And when he
13:14
Speaker 1: let's go to the ball, it's not moving in a
13:16
Speaker 1: circle like his arm is anymore, moves in a straight line, right,
13:19
Speaker 1: And so that's sort of like what the Earth was
13:21
Speaker 1: doing there at the spinning and it's holding onto you,
13:23
Speaker 1: so you're the ball, and then if gravity turns off,
13:26
Speaker 1: it's no longer holding onto you, and boom, you fly
13:28
Speaker 1: out into space at the speed of a fastball. Well
13:31
Speaker 1: you just throw me a curveball there, But that's a
13:33
Speaker 1: different episode. I guess physics is a bit of a
13:36
Speaker 1: knuckleball to the brain. Sometimes it's a hit or miss.
13:38
Speaker 1: So that's kind of what would happen if you turn
13:40
Speaker 1: up gravity, Like everything would just fly off, everything that
13:42
Speaker 1: wasn't bolted down to the Earth. Do you think the
13:44
Speaker 1: Earth would break apart though, like with earth crust also
13:47
Speaker 1: detached from the Earth and fly off into space. Well
13:50
Speaker 1: that's a great question. You know, the Earth is held
13:52
Speaker 1: together by forces much stronger than gravity, right, you know,
13:56
Speaker 1: like electromagnetic forces and all those bonds that hold matter together.
13:59
Speaker 1: But the Earth, sort of like the Sun, etcetera, is
14:01
Speaker 1: a balance somewhat between pressure and gravity. Like the Earth
14:05
Speaker 1: is the size that it is because that's where gravity
14:08
Speaker 1: and the pressure from those bonds balance, right, if gravity
14:11
Speaker 1: was stronger, it would compact the Earth even farther. If
14:14
Speaker 1: the material the Earth was made of was tougher, it
14:17
Speaker 1: was harder to compress. The Earth would be bigger, right,
14:20
Speaker 1: gravity wouldn't have been able to squeeze it as far.
14:22
Speaker 1: So if gravity goes away, then the Earth will eventually
14:25
Speaker 1: just sort of like fluff up a little bit, like
14:27
Speaker 1: bits of the Earth will fall off. Also, because gravity
14:30
Speaker 1: isn't there sort of like compressing it and keeping things down.
14:33
Speaker 1: It would sort of like trying into lose gravel kind
14:35
Speaker 1: of floating space. Yeah, I guess, because like mountains would
14:38
Speaker 1: just float off into space. Everything that isn't tied down
14:41
Speaker 1: would break off. And even things that are tied down
14:44
Speaker 1: now would effectively feel a force throwing them off the Earth.
14:47
Speaker 1: You know, there's no actual force there, sort of a
14:50
Speaker 1: product of having a rotating frame of motion, but the
14:53
Speaker 1: effect is the same. It's like if you're on a
14:55
Speaker 1: merry go round and somebody spins it. If you're not
14:57
Speaker 1: holding on, then you're gonna feel the forced trying to
15:00
Speaker 1: throw you off. And so if the Earth keeps spinning
15:03
Speaker 1: with no gravity, then it's going to be testing all
15:06
Speaker 1: the bonds between things and anything that gets a little
15:08
Speaker 1: bit weakened is eventually going to fly off into space. Right.
15:11
Speaker 1: And I'm also thinking, like, isn't that the center of
15:14
Speaker 1: the Earth sort of liquid? Right, it's molten, it's liquid.
15:16
Speaker 1: Wouldn't that also just kind of blob away, or would
15:20
Speaker 1: like surface tension and liquid tension keep it all held in. Yeah,
15:23
Speaker 1: that's a great question. I think gravity is essentially one
15:26
Speaker 1: of the reasons why the center of the Earth is liquid.
15:29
Speaker 1: All that pressure creates all this heat which keeps it liquid,
15:32
Speaker 1: and so it would hasten the cooling of the Earth. Also,
15:35
Speaker 1: we once talked about how long it would take the
15:37
Speaker 1: Earth's core to cool under normal conditions, and it was
15:39
Speaker 1: something like ninety billion years. But if gravity is no
15:42
Speaker 1: longer around compressing the Earth keeping the center hot, then
15:45
Speaker 1: the center will cool much faster. And it's not just
15:48
Speaker 1: the Earth that would sort of cool and unravel, it's
15:50
Speaker 1: also the Solar system and the galaxy to right, like
15:53
Speaker 1: our galaxy would fall apart too, Yeah, our Solar system
15:56
Speaker 1: almost immediately, right, because the only thing keeping the Earth
15:59
Speaker 1: in orbit around this one is the gravity, and so
16:01
Speaker 1: the Earth would just become like a fastball shooting out
16:04
Speaker 1: into the galaxy, and the same thing with the Sun.
16:06
Speaker 1: The Sun is orbiting the center of the galaxy. It's
16:09
Speaker 1: not just like happens to be here in space near
16:12
Speaker 1: other stars. It's moving in a coordinated swirl with a
16:15
Speaker 1: bunch of other stars orbiting this incredible mass at the
16:18
Speaker 1: center of the galaxy. And that's because of gravity. No
16:21
Speaker 1: other force is capable of doing that. And so if
16:23
Speaker 1: that disappeared, then the Sun would just continue moving in
16:26
Speaker 1: the direction it was moving when Lily turned off the
16:29
Speaker 1: universe's gravity, and it would just go in that direction
16:32
Speaker 1: wherever it was and it but it certainly wouldn't be
16:35
Speaker 1: a curve around the center of the galaxy would just
16:37
Speaker 1: fly off, you know, like ping pong balls on a
16:39
Speaker 1: Merry go round. The other stars in the galaxy would
16:41
Speaker 1: do the same thing, right, like everything would just fly
16:43
Speaker 1: off into space. Yeah. So these galaxies are almost all spinning,
16:46
Speaker 1: and so they would all break apart. The stars would
16:48
Speaker 1: spread out into the universe. And even more than that,
16:52
Speaker 1: galaxies feel gravity on each other like we feel the
16:55
Speaker 1: gravity of Andromeda, even though with millions of light years away,
16:59
Speaker 1: all the galaxies and our local cluster are sort of
17:02
Speaker 1: orbiting each other. They're orbiting the common center of mass.
17:05
Speaker 1: So there's something not just keeping our galaxy together, but
17:08
Speaker 1: keeping our galaxy cluster together, and that's gravity. So without that,
17:12
Speaker 1: the galaxies themselves, even as they explode and their stars
17:15
Speaker 1: go everywhere, the galaxies themselves would spread out further rather
17:19
Speaker 1: than being clustered together into a cluster. The universe withold
17:22
Speaker 1: de cluster. But even more interesting, I think is to
17:25
Speaker 1: think about what would happen to black holes, Like would
17:27
Speaker 1: they no longer be black holes? Would they no longer
17:31
Speaker 1: be holes if you turned off gravity. Yeah, that's incredible
17:34
Speaker 1: to think about. We just don't know because we don't
17:36
Speaker 1: know what's inside the black holes. If you take general
17:39
Speaker 1: relativity to be the truth, then there's a singularity in there.
17:42
Speaker 1: But the singularity is overcoming incredible pressure, right Like matter
17:46
Speaker 1: does not like to be squeezed down to a singularity.
17:48
Speaker 1: It takes incredible gravity to do that. If you then
17:50
Speaker 1: just turn that gravity off, then you know the quantum
17:53
Speaker 1: mechanical pressure and the electron de generously pressure and all
17:56
Speaker 1: that stuff. Those things are going to explode rapidly. So
17:59
Speaker 1: every black cole basically turns into a massive bomb, including
18:03
Speaker 1: the huge supermassive black hole of the center of our galaxy.
18:06
Speaker 1: That doesn't sound good. What do you mean it would explode,
18:08
Speaker 1: like just because it has so much of pressure. Yeah,
18:10
Speaker 1: it would explode because, like stars, black holes are an
18:13
Speaker 1: equilibrium between gravity and pressure. And in the case of
18:16
Speaker 1: black holes, what's happened is gravity has one has overcome
18:19
Speaker 1: all of that pressure. But if you release gravity, you know,
18:22
Speaker 1: it's like you took a bunch of springs and you
18:24
Speaker 1: squeeze them down to a tiny, tiny point and you're
18:27
Speaker 1: holding them really really tight, and all of a sudden
18:29
Speaker 1: you just let go. Like what happens. Well, you know,
18:32
Speaker 1: it's like a bunch of snakes jumping out of a can.
18:34
Speaker 1: Like it's going to be crazy. No snakes on a
18:36
Speaker 1: black hole. That's a nice movie from Marvel. Yeah, and
18:39
Speaker 1: you know the same thing will happen to stars. Right.
18:42
Speaker 1: Why is the Sun not just a huge explosion because
18:45
Speaker 1: it has fusion going on at its heart? Right, Fusion
18:48
Speaker 1: is what powers nuclear bomb. So why isn't the Sun
18:51
Speaker 1: just exploding? It's because of gravity. It's a delicate balance
18:54
Speaker 1: of gravity keeping everything in and fusion pressure keeping it
18:58
Speaker 1: from collapsing further. But you take gravity away and the
19:01
Speaker 1: Sun just becomes an enormous hydrogen bomb. Oh my god,
19:05
Speaker 1: would it even matter what happens here on Earth? Think
19:07
Speaker 1: if we're just gonna the Sun is gonna explode and
19:09
Speaker 1: we'll be fried in eight minutes. We'll be fried in
19:11
Speaker 1: a little less than eight minutes because the Earth will
19:14
Speaker 1: be free from its orbit, so we'll be flying onto
19:16
Speaker 1: interstellar space with this incredible explosion behind us. We a
19:19
Speaker 1: great scene for the next Jerry Brooke Connor movie. Yeah,
19:22
Speaker 1: just we're floating away slow motion, are shure? It's open
19:26
Speaker 1: and our hair tossing in the wind, and somehow we
19:28
Speaker 1: have to survive that explosion though I don't think our
19:30
Speaker 1: odds are very good. Wow. So basically the whole universe
19:33
Speaker 1: everything would explode and fall apart, is what you're saying.
19:36
Speaker 1: At the same time, Yeah, exactly, bad idea, not recommended. Yeah,
19:41
Speaker 1: but literally had another part of her questions, which is
19:43
Speaker 1: really interesting too, is what would happen if gravity never
19:46
Speaker 1: even existed in the first place? And so let's get
19:48
Speaker 1: into that part of her question. But first let's take
19:51
Speaker 1: a quick Great all right, we're celebrating questions from listeners,
20:07
Speaker 1: and like the kinds of questions that inspired our new book,
20:10
Speaker 1: frequently asked questions about the Universe, which is out now today.
20:13
Speaker 1: Even so, please go check out the website Universe f
20:16
Speaker 1: a Q dot com and maybe get a copy or
20:19
Speaker 1: ten copies or ten. Well, geez boy, I feel like
20:22
Speaker 1: that that's a little greedy, Daniel. I was gonna say
20:24
Speaker 1: like two or three, but alright, five copies. That's my
20:27
Speaker 1: final offer. I guess if you had ten nieces and
20:29
Speaker 1: nephews and cousins and uncles, that could add up to ten. No,
20:33
Speaker 1: if you're curious about this kind of stuff and you
20:35
Speaker 1: would enjoy a bunch of jokes in a bunch of physics,
20:37
Speaker 1: please check out the book. So today we're asking questions
20:39
Speaker 1: from listeners to celebrate, and we we have this great
20:42
Speaker 1: question from Lily who asked what would happen if gravity stopped?
20:45
Speaker 1: And she also asked what would happen if gravity never existed?
20:49
Speaker 1: Like if we had a universe from the beginning with
20:51
Speaker 1: the gravity setting set off. What a crazy question, Not
20:55
Speaker 1: something I've ever thought about, and all the weird hypotheticals
20:59
Speaker 1: I've considered, and all the questions people have asked, nobody's
21:01
Speaker 1: ever asked the question what would happen if we never
21:04
Speaker 1: had gravity in our universe. Awesome question, Lily, Yeah, kudos Lily.
21:08
Speaker 1: I'm guessing also the answer is not good. It depends
21:12
Speaker 1: on the kind of universe you like, but it would
21:14
Speaker 1: definitely be very, very different from our universe because gravity
21:17
Speaker 1: played a really, really critical role in shaping the universe
21:21
Speaker 1: that we see today. You know, after the Big Bang
21:24
Speaker 1: and everything happened, which we of course don't understand and
21:26
Speaker 1: we don't even know if gravity was essential for all
21:29
Speaker 1: that to happen. But assume that the Big Bang and
21:31
Speaker 1: the inflation at the beginning of the universe happened the
21:33
Speaker 1: same way, because that wasn't really dominated by gravity as
21:36
Speaker 1: we understand it. Then you know what happened was that
21:38
Speaker 1: we have a bunch of hydrogen gas. You know, the
21:41
Speaker 1: universe creates particles, and those particles cool and then eventually
21:45
Speaker 1: you get hydrogen to form, and then the universe is
21:47
Speaker 1: basically this huge floating cloud of gas. And it's very
21:51
Speaker 1: dark back then because hydrogen, when it's just like hanging
21:53
Speaker 1: out and cold, doesn't glow very much. So we call
21:56
Speaker 1: this the universe dark ages. When there was basically just
21:59
Speaker 1: a big blob of gas and the next thing that
22:02
Speaker 1: happened was that stars were formed as stars were only
22:05
Speaker 1: formed though because of gravity, Like it's gravity that pulled
22:09
Speaker 1: over dense clumps of hydrogen together to get enough together
22:12
Speaker 1: to spark fusion and to create light. So without gravity,
22:16
Speaker 1: the universe would still be in those dark ages. Oh wow,
22:19
Speaker 1: I guess nothing would have ever come together. Kind of yeah, exactly,
22:22
Speaker 1: things would just sort of like be happy to hang
22:24
Speaker 1: out in a big cloud. And you know, it would
22:26
Speaker 1: be like overwhelmingly all hydrogen. There's like a tiny bit
22:29
Speaker 1: of helium and the tiniest bits of heavier stuff created
22:32
Speaker 1: in the Big Bang, but almost all hydrogen. Everything else
22:35
Speaker 1: that you and I are made of, you know, the
22:36
Speaker 1: heavier metals, those were all born in stars. But stars
22:40
Speaker 1: don't form without gravity, and so the universe is just
22:42
Speaker 1: a big boring cloud without gravity. Wow, So things would
22:46
Speaker 1: be gassy gravity there from the beginning, gassy and not
22:50
Speaker 1: in an exciting way. I guess. Maybe one question is
22:53
Speaker 1: what would happen to the Big Bang? Like with the
22:54
Speaker 1: Big Bang happened the same way, would you have still
22:58
Speaker 1: had had a Big Bang without gravity? Is it just
23:00
Speaker 1: that the outcome would be different? We really just don't
23:02
Speaker 1: know the answer to that question because we don't understand
23:05
Speaker 1: the mechanism of inflation or the Big Bang, like we
23:08
Speaker 1: don't know what caused it and what made it happen
23:10
Speaker 1: in a certain way. It might be that the reason
23:13
Speaker 1: inflation happened a certain way is a necessary product of
23:17
Speaker 1: the structure of space and time, like you know, it's
23:19
Speaker 1: negative pressure from quantum zero point energy or the cosmological
23:23
Speaker 1: constant that's we've talked about, and that that has to happen,
23:26
Speaker 1: and it just comes from the structure of space and time.
23:28
Speaker 1: You know. Gravity is the same way. Gravity comes from
23:31
Speaker 1: the structure of space and time, how it bends around
23:34
Speaker 1: mass and energy. So it might be that if you
23:36
Speaker 1: don't have gravity, it means that you can't like bend
23:39
Speaker 1: space and time. And it might also mean that you
23:41
Speaker 1: couldn't have inflation, that you couldn't have the Big Bang,
23:44
Speaker 1: that the universe might have never gotten started. But we
23:47
Speaker 1: just don't really know because we don't understand how inflation
23:50
Speaker 1: and gravity work together, or if they're really two sides
23:53
Speaker 1: of the same coin. Interesting, Yeah, I guess it depends
23:56
Speaker 1: on whether you can have bending of space without gravity,
23:59
Speaker 1: or whether gravity is the bending of space. Yeah, in
24:02
Speaker 1: some sense, inflation is just like an expansion of space,
24:05
Speaker 1: which is very similar to gravity, sort of like repulsive gravity.
24:08
Speaker 1: Of a new theory, Daniel, Maybe this universe was born
24:11
Speaker 1: because the previous universe is Lily turned off. Flip the
24:15
Speaker 1: switch on gravity and it blew everything up. Lily prime
24:19
Speaker 1: the first Lily, All right, well it sounds like gravity.
24:22
Speaker 1: It's kind of important you turn it off now. I
24:24
Speaker 1: think everything would would blow up and fall apart. And
24:26
Speaker 1: if we never had it, then nothing would have ever
24:28
Speaker 1: happened in the universe. Yeah, although you know, maybe after
24:31
Speaker 1: trillions of years, some other weird phenomenon would emerge. Everything
24:34
Speaker 1: that happens in our universe is a strange emergent phenomena
24:38
Speaker 1: from all the crazy balance of all the forces and
24:40
Speaker 1: the objects in it. If you have a different mix
24:42
Speaker 1: of stuff, you might end up with a different, weird,
24:44
Speaker 1: complex universe. It might have just taken trillions of years
24:47
Speaker 1: or quadrillions of years. Who knows. I see you're saying
24:50
Speaker 1: like maybe gravity is evil. Twin would have come up gravity.
24:54
Speaker 1: But thank you, Lily, that's such a great question. Thanks
24:56
Speaker 1: for sending your question, and thanks for asking questions in general.
24:59
Speaker 1: It's to see you and other people out there being curious. Yeah,
25:03
Speaker 1: Lily had to know, and I hope now she knows,
25:05
Speaker 1: and I hope she needs to know more in the future.
25:08
Speaker 1: All Right, well, let's get to our next question. This
25:10
Speaker 1: one is from Peter and he has a question about
25:13
Speaker 1: visiting other stars. Hello, Daniel and Jorrgey. This is Peter
25:16
Speaker 1: from Colorado Springs, Colorado. My question is that we always
25:20
Speaker 1: say that to travel to a distant star efficiently, we
25:23
Speaker 1: need to accelerate to a high fraction of the speed
25:25
Speaker 1: of light. Why don't we assume that we're starting from
25:27
Speaker 1: a velocity of zero? Aren't we moving relative to the
25:30
Speaker 1: distant stars already based on the speed of our solar
25:33
Speaker 1: system as the circles around the galaxy, or based on
25:36
Speaker 1: the speed of our galaxy as it moves around the universe.
25:39
Speaker 1: Couldn't we just pick a star that we're already aimed
25:41
Speaker 1: towards at a high relative velocity and let our existing
25:44
Speaker 1: momentum do most of the work. Anyway, Thank you. Love
25:46
Speaker 1: the show. Listen to what every day when it comes out. Awesome,
25:49
Speaker 1: great question, Thank you, Peter. I think Daniel Peter is
25:52
Speaker 1: asking why do we have to go to other stars.
25:54
Speaker 1: Why can other stars come to us? Why are we
25:56
Speaker 1: doing all the work? Right? I think somebody else never drives.
25:59
Speaker 1: If it can go to the stars, maybe the stars
26:02
Speaker 1: can come to mommed. I wonder if Peter is always
26:04
Speaker 1: doing the driving when he visits his friends, or if
26:07
Speaker 1: he's like, why don't you ever come in my house?
26:10
Speaker 1: He's like, when I have to take my kids to
26:12
Speaker 1: school every morning, why can't the school come to my house?
26:14
Speaker 1: And then the pandemic happens and everyone regrets nobody is
26:18
Speaker 1: a great question, and he's tackling a really important topic, right,
26:22
Speaker 1: which is how do we efficiently get to visit other
26:25
Speaker 1: solar systems? Because that's what we want to do. We
26:27
Speaker 1: want to see other planets. We want to see if
26:29
Speaker 1: they're aliens there. We want to learn if other solar
26:31
Speaker 1: systems are really different from hours. We would learn so
26:34
Speaker 1: much about the University if we could just visit other
26:36
Speaker 1: solar systems. But they are frustratingly hard to get to. Yeah,
26:40
Speaker 1: they're super duper far away. Like how close is the
26:43
Speaker 1: near star? I think it's like four light years away? Right, Yeah,
26:46
Speaker 1: Proximus Centaire is almost four light years away with four
26:50
Speaker 1: sounds like a small number, but that's just because the
26:52
Speaker 1: unit of light year is just like ridiculously long, So
26:55
Speaker 1: four light years would take a long time to visit,
26:58
Speaker 1: like millions and millions of miles, a lot of zeros
27:01
Speaker 1: if you do do in terms of miles, even if
27:03
Speaker 1: you do in terms of kilometers or centimeters. But I
27:06
Speaker 1: think Peter's question is, like, you know, we're used to
27:08
Speaker 1: thinking of this problem. Is like we're here and that
27:11
Speaker 1: the other star is there, but actually everything is kind
27:13
Speaker 1: of moving around in the universe. You know, why can't
27:16
Speaker 1: we pick a star that's maybe moving towards is really
27:18
Speaker 1: fast or at least you know it's going to be
27:21
Speaker 1: flying by really fast at some point in the future,
27:24
Speaker 1: and aim for that star because it's sort of coming
27:26
Speaker 1: our way anyways. Yeah, that's what he's asking, and it's
27:29
Speaker 1: a great idea, And if there was a star headed
27:31
Speaker 1: our away, it would be cool to check it out
27:34
Speaker 1: before it totally disrupts our solar system and throws the
27:37
Speaker 1: Earth into interstellar space. I see, let's hope there's no
27:40
Speaker 1: start coming our ways. What you're saying, Yeah, it's a
27:43
Speaker 1: great idea, but it would be quite dangerous because another
27:45
Speaker 1: star we totally gravitationally perturb our solar system and make
27:48
Speaker 1: a big mess. Really, I guess like even if it
27:51
Speaker 1: goes like if it passes you know, not through our
27:55
Speaker 1: solar system, but you know, like adjacent to our solarism,
27:57
Speaker 1: it would still disrupt us. It would still disrupt us. Yeah,
28:00
Speaker 1: we might lose things in the outer part of the
28:01
Speaker 1: solar system. It's a balance. The closer it gets, the
28:04
Speaker 1: easier it would be to visit, but also the more
28:06
Speaker 1: dangerous it would be for our solar system. Interesting, but
28:09
Speaker 1: you know, we would only lose like you know, Pluto
28:11
Speaker 1: and Neptune, Like, wouldn't that be worth it to visit
28:13
Speaker 1: another star? Not just that. You know, we have the
28:16
Speaker 1: or cloud, which is like a huge group of potential comets,
28:19
Speaker 1: and if another star comes too close, it can perturb
28:21
Speaker 1: those things and then they can all fall towards the
28:23
Speaker 1: inner Solar system. We could have like you know, a
28:26
Speaker 1: rain of comets on the inner Solar system, which would
28:29
Speaker 1: be bad. That doesn't sound good. It does not sound good.
28:32
Speaker 1: That's not hope for a start to come here. But
28:34
Speaker 1: I think let's maybe think about the less dangerous case
28:37
Speaker 1: that he might be asking about, which is like, what
28:39
Speaker 1: if there's a star, you know, not coming near us,
28:41
Speaker 1: but you know at least sort of towards us a
28:43
Speaker 1: little bit, or you know, in our neighborhood. Can we
28:47
Speaker 1: aim for that star. Yeah, it's a good idea. The
28:49
Speaker 1: issue is that most of the stars are sort of
28:51
Speaker 1: moving together. Like we were just talking about, the galaxy
28:54
Speaker 1: is a big swirl of stars, but they are rotating
28:56
Speaker 1: around the center of the galaxy and mostly together there.
29:00
Speaker 1: You know, it's like a huge crowd, all running in
29:02
Speaker 1: the same direction. So their velocity relative to the center
29:05
Speaker 1: of the galaxy is really high. Like the Sun is
29:07
Speaker 1: moving really fast relative to the center of the galaxy,
29:10
Speaker 1: but it's sort of moving together with all the other stars.
29:13
Speaker 1: Not in parallel because it's moving in a circle, but
29:15
Speaker 1: you know, there's all sort of moving with very small
29:17
Speaker 1: velocity relative to each other. I see. It's like we're
29:20
Speaker 1: all in a lazy river. We're all kind of in
29:23
Speaker 1: the same flow of stars. We're all in the same
29:26
Speaker 1: flow exactly. And astronomers talk about this. They measure like
29:29
Speaker 1: the local standard of rest where they take all those
29:32
Speaker 1: stars nearby and they take their average velocity. They say,
29:36
Speaker 1: all right, let's define that to be like the rest
29:38
Speaker 1: frame of the neighborhood, and then they measure the velocity
29:41
Speaker 1: of stars relative to that, so you know, you can
29:43
Speaker 1: ask the question, like, you know, not relative to the
29:46
Speaker 1: center of the galaxy, but relative to the other stars
29:48
Speaker 1: in the lazy river near me, how fast am I going?
29:52
Speaker 1: And so they actually do that, and they measure the
29:54
Speaker 1: relative velocity of all the stars nearby, but it's pretty small,
29:57
Speaker 1: like stars are mostly in a stable configure duration. Isn't
30:00
Speaker 1: that weird? Like you're saying there's no cross traffic of
30:03
Speaker 1: stars kind of like, why aren't stars kind of flying
30:06
Speaker 1: all over the place? Well, they're moving in the same
30:08
Speaker 1: direction for the same reason, right, They're all rotating around
30:11
Speaker 1: the center of the galaxy because of its gravity and
30:13
Speaker 1: the galaxy form because you have this big blob of
30:15
Speaker 1: stuff which compactified to form stars. But originally it was
30:19
Speaker 1: sort of spinning, and so that spinning motion is still there.
30:23
Speaker 1: So it's sort of angular momentum that started things spinning
30:26
Speaker 1: and it's keeping things spinning. And so, you know, if
30:29
Speaker 1: you think about the lazy river analogy, it's like, why
30:31
Speaker 1: do a bunch of inner tubes in a lazy river
30:33
Speaker 1: mostly go at the same speed Because they're in the
30:35
Speaker 1: same river, right, Interesting, But I guess maybe a question
30:38
Speaker 1: is sort of like in our Solar system. You know,
30:40
Speaker 1: we're all in the same many lazy river around the Sun,
30:43
Speaker 1: but there are planets to sort of spin around the
30:45
Speaker 1: Sun faster than others. And you know, you can play
30:48
Speaker 1: all these games, like you know, to get to Mars,
30:50
Speaker 1: you give your time the orbit, right, it's a shorter
30:53
Speaker 1: or longer trip. You know, why why aren't the stars
30:56
Speaker 1: moving at different speeds? Yeah, you're right that the planets
30:58
Speaker 1: are moving at different speed, but that's because they are
31:01
Speaker 1: at very different distances from the Sun. The closer planets
31:05
Speaker 1: moved faster and the further ones moved more slowly. The
31:07
Speaker 1: same thing is true for stars in the galaxy. Stars
31:11
Speaker 1: much closer into the center are moving faster, but they
31:13
Speaker 1: are very very far away from us. Stars much farther
31:17
Speaker 1: out from the center are moving more slowly, but they're
31:20
Speaker 1: also much further away than we are. All the stars
31:22
Speaker 1: in our neighborhood are basically the same distance from the center,
31:26
Speaker 1: and so they're moving at roughly the same speed. You
31:29
Speaker 1: notice the speed difference is more in the Solar system
31:31
Speaker 1: because things here are closer together, so the Milky Way
31:34
Speaker 1: is sort of like a lazy river. I mean, it's
31:36
Speaker 1: not a rapid thrill, right, it's it's you know, it's
31:39
Speaker 1: a chill galaxy. Well, we're actually all moving pretty fast
31:42
Speaker 1: relative to the center of the galaxy, but relative to
31:45
Speaker 1: each other, we're not moving that fast. Like our Sun
31:48
Speaker 1: is only moving at like twenty kilometers per second through
31:51
Speaker 1: the local standard rest our Son is actually a bit
31:54
Speaker 1: zippier than the other stars in our lazy river, but
31:57
Speaker 1: not by that much. You know, twenty kilometers per second
31:59
Speaker 1: is nothing on the scale of the galaxy, right, it's
32:02
Speaker 1: super fast twenty kilometers in one second, but in the
32:06
Speaker 1: scale of Giant's Son, it's like it's just crawling along.
32:10
Speaker 1: And if you look at all the stars in our neighborhood,
32:12
Speaker 1: most of them have like a relative velocity to the
32:14
Speaker 1: Sun of less than thirty kilometers per second, which is
32:18
Speaker 1: really pretty small and not really enough to use Peter's idea.
32:22
Speaker 1: None of them are really going fast enough to make
32:24
Speaker 1: it easier to get to them. So it is sort
32:26
Speaker 1: of like that you know, kindergarten group of kids that
32:28
Speaker 1: everyone's staying together. Yeah, there is one star, Bernard's Star,
32:31
Speaker 1: which is six light years away. This is the one
32:33
Speaker 1: that has the highest velocity relative to the Sun, like
32:36
Speaker 1: coming closer to us. It's moving at us at about
32:39
Speaker 1: a hundred and ten kilometers per second. That's the fastest one, right,
32:43
Speaker 1: But it's like millions of kilometers way, so it's not
32:46
Speaker 1: coming near us anytime soon. Even if it was going
32:48
Speaker 1: a thousand kilometers per second, that's still one three hundreds
32:52
Speaker 1: of the speed of light. So, you know, I think
32:54
Speaker 1: Peter was hoping that some stars are approaching us at
32:57
Speaker 1: like half the speed of light, so they wouldn't take
32:59
Speaker 1: that long to get there. So even if you pick
33:01
Speaker 1: a star moving towards us that a thousand kilometers per
33:04
Speaker 1: second and there aren't any nearby, you wouldn't automatically have
33:07
Speaker 1: a fast speed relative to the star. It's still a
33:09
Speaker 1: tiny fraction of the speed of light. So things are
33:12
Speaker 1: sort of moving relative to each other, but not in
33:14
Speaker 1: any you know way that it can help us, really
33:17
Speaker 1: because the distances are so big. But there are some
33:19
Speaker 1: crazy stars in the Milky Way. They are these stars
33:22
Speaker 1: called hyper velocity stars that are moving really really fast,
33:26
Speaker 1: more than a thousand kilometers per second relative to their neighborhood.
33:29
Speaker 1: So there are some sort of like out of control stars,
33:31
Speaker 1: but not very many. There's like a thousand of them
33:34
Speaker 1: spread out through the whole Milky Way. Of its hundreds
33:37
Speaker 1: of billions of stars. Wow, only a thousand. Interesting astronomers
33:40
Speaker 1: think that they probably had like a close encounter with
33:43
Speaker 1: the black hole at the center of the Milky Way
33:45
Speaker 1: and then just got like thrown out from the craziness
33:47
Speaker 1: of the action there and are now like on their
33:49
Speaker 1: way to escape the galaxy. I think they've measured the
33:52
Speaker 1: contents of the star and there's a lot of sugar
33:54
Speaker 1: in it. That's a myth man's myth, so maybe they
33:59
Speaker 1: like out to close to the center and then got
34:01
Speaker 1: spewed out or something. But for the most part, the
34:04
Speaker 1: galaxy is a pretty calm place, and we're not moving
34:07
Speaker 1: very fast relative to any of our nearby stars, and
34:09
Speaker 1: so unfortunately, while that's a great idea Pere, it doesn't
34:12
Speaker 1: actually work in our case. Sorry Peter, but it is
34:16
Speaker 1: I guess a good thing that the universe is kind
34:18
Speaker 1: of a chill place. Otherwise, who knows, we could have
34:20
Speaker 1: stars kind of zipping by and killing our orbits or
34:23
Speaker 1: causing comment storms. So it's kind of a good thing, right,
34:27
Speaker 1: that things are chill. Absolutely, it's a good thing. It's
34:29
Speaker 1: necessary for life to form and for civilizations to prosper.
34:33
Speaker 1: But great question. Thank you Peter for writing in. And
34:35
Speaker 1: so let's get to our last question of today, and
34:38
Speaker 1: that has to do with the sound of the universe.
34:41
Speaker 1: But first let's take another quick break. All right, we
34:56
Speaker 1: are celebrating the release of our new book frequently ask
34:59
Speaker 1: questions about the Diniverse, which is out now. You can
35:01
Speaker 1: get it at universe f a Q dot Calm. It's
35:04
Speaker 1: a pretty good book, right, Daniel. I think it's more
35:06
Speaker 1: than just pretty good. I think it's hilarious. It's insightful,
35:09
Speaker 1: it's clever, it's really fun tour of all the big
35:12
Speaker 1: questions about the universe answered in a way that makes
35:15
Speaker 1: sense to you. Yeah, we got some good reviews and
35:17
Speaker 1: publishers Weekly and Kirkis. People seem to like this book.
35:20
Speaker 1: Even my kids enjoyed reading it. Oh my goodness, that
35:22
Speaker 1: is the ultimate compliment. My kids don't even know what
35:26
Speaker 1: I do. To be honest, I wonder where your kids
35:28
Speaker 1: would say if I asked them. He wears pajamas for
35:30
Speaker 1: a living. He takes naps in the couch. They pay
35:35
Speaker 1: him for that right. No, I think they've lost track
35:37
Speaker 1: of all the things that I did my hands in.
35:39
Speaker 1: But we are celebrating today, and we're celebrating by answering
35:42
Speaker 1: listener questions. Instead. We've answered questions about gravity and about
35:46
Speaker 1: visiting other stars, and now we have a great question
35:49
Speaker 1: from Addison about whether the universe has a sound. Hey,
35:54
Speaker 1: Danieline Jorrie, I've got a question for you about the
35:57
Speaker 1: early universe and sound. It sounds like early universe was
36:01
Speaker 1: dense enough, add enough stuff close enough together to have sound,
36:05
Speaker 1: to have sound waves propagate through it. Is there a
36:08
Speaker 1: reason why we don't see the rippling effects of sound
36:10
Speaker 1: waves from the early universe when we look at it today.
36:13
Speaker 1: Did some sort of force erase that signature? Or were
36:16
Speaker 1: acoustic waves just not as impactful or powerful as you
36:20
Speaker 1: would think? Thank you all right? Sounds like a great question.
36:23
Speaker 1: It sounds like it's time to talk about it. I
36:25
Speaker 1: like the sound of that. Thank you, Addison. It's an
36:28
Speaker 1: interesting question. I think he's asking whether in the early universe,
36:33
Speaker 1: when it was you know, really compact, whether things were
36:35
Speaker 1: so dance that you could have sound waves traveling through
36:39
Speaker 1: that dense, you know, primordial stuff and he's asking if
36:43
Speaker 1: we can see those ripples, or why can't we see
36:45
Speaker 1: those ripples today? I guess maybe. You know, when most
36:48
Speaker 1: people think of sound, they think of sound through air,
36:51
Speaker 1: which is what we used to talk to each other
36:52
Speaker 1: and listen to music. But sound can travel through anything, right, water,
36:57
Speaker 1: even solid materials can have sound waves traveling through the Yeah,
37:00
Speaker 1: you can travel through almost anything. It's any material that
37:03
Speaker 1: has pressure, any material with like the particles bump into
37:06
Speaker 1: each other and push against each other. For example, we
37:09
Speaker 1: don't think that dark matter can feel sound because dark matter,
37:12
Speaker 1: if it's made of particles, we don't think they feel
37:14
Speaker 1: each other. They pass right through each other. So you
37:16
Speaker 1: can't have sound waves in dark matter. But in any
37:18
Speaker 1: other kind of matter, yeah, you can have sound waves.
37:21
Speaker 1: They're just like these compression waves. You push on the surface,
37:23
Speaker 1: for example, and it pushes on the next one, It
37:25
Speaker 1: pushes on the next one, it pushes on the next one,
37:27
Speaker 1: and that's the sound wave just traveling through. But the
37:30
Speaker 1: way it gets from one layer to the next is
37:32
Speaker 1: having some interaction between the particles. It's kind of like
37:34
Speaker 1: a crowded room. If people are crowded together, then you
37:37
Speaker 1: can have you know, kind of waves where people push
37:39
Speaker 1: each other, but it's a bad party and everyone's really
37:42
Speaker 1: far away from each other. You can't really kind of
37:44
Speaker 1: have that, right or you can see this in traffic also,
37:47
Speaker 1: like when somebody slams on the brakes, then the car
37:49
Speaker 1: behind them slams on the brakes, and then the sort
37:51
Speaker 1: of break slamming passes down the road all the way
37:54
Speaker 1: down right. You can see it in like the brake lights. Yeah,
37:56
Speaker 1: so that's the same sort of deal because the person
37:59
Speaker 1: is reacting to the car in front of them, and
38:00
Speaker 1: so that's the sort of the interaction. And so the
38:02
Speaker 1: universe right now is pretty empty and things are fairly
38:05
Speaker 1: far apart, so you don't you just don't see these
38:08
Speaker 1: kinds of sound waves going through the universe. But I
38:10
Speaker 1: think Addison is saying maybe in the early universe, when
38:12
Speaker 1: things really crunched together, you could have sound waves, and
38:16
Speaker 1: maybe they could you could still see them today or
38:18
Speaker 1: the effects of them. Yeah, you actually can still see
38:20
Speaker 1: them today. Like there are sound waves in the universe
38:23
Speaker 1: right now, like big clouds of gas running into each other,
38:26
Speaker 1: and you can see shock waves, and so that's really
38:28
Speaker 1: equivalent to sound waves. You know, we have pressure waves
38:31
Speaker 1: in these mammoth clouds of gas. Some of them probably
38:34
Speaker 1: are the reasons why stars form, you know, a cloud
38:37
Speaker 1: of gas, and what triggers the collapse into a star.
38:39
Speaker 1: It might be a shock wave from a nearby supernova,
38:43
Speaker 1: so that's also a sound wave. But yeah, the sound
38:46
Speaker 1: waves were definitely stronger in the early university, right, because
38:48
Speaker 1: the universe was much denser, right, we think in the
38:51
Speaker 1: very beginning, everything was sort of like it is today
38:54
Speaker 1: in the center of the sun. You know, it's hot,
38:56
Speaker 1: it's dense, it's crazy, and so they're definitely worse sound
39:00
Speaker 1: waves back then. Yeah. So I guess in the early
39:02
Speaker 1: universe before or during the Big Bang, things were compact
39:06
Speaker 1: enough for there to be sound. But how does that
39:08
Speaker 1: even work? Like things? It's like sound through ions through quarks.
39:12
Speaker 1: What does that mean? Yea, So imagine that this is
39:15
Speaker 1: after the Big Bang now, and which you have in
39:17
Speaker 1: the universe is a bunch of like protons and electrons
39:21
Speaker 1: and photons and then a bunch of dark matter. So
39:23
Speaker 1: you have this big soup and it's very very dense, right,
39:26
Speaker 1: and so sometimes you'll get like a bunch of dark
39:28
Speaker 1: matter clumped together an over density and it's incredible gravity
39:33
Speaker 1: will pull things together, you know, like pull everything together.
39:36
Speaker 1: But then those molecules will resist, like the protons don't
39:39
Speaker 1: like to be squeezed together, and all the photons bouncing
39:42
Speaker 1: around have a lot of energy, and so it'll sort
39:44
Speaker 1: of like bounce back and it will make these waves.
39:47
Speaker 1: And so because dark matter creates something of higher pressure,
39:50
Speaker 1: that higher pressure than propagates out. So you get this
39:53
Speaker 1: like sound wave of this like ringing through the plasma
39:55
Speaker 1: of the early universe in response to these momentary over
39:59
Speaker 1: density these Wait what you're saying that in the early
40:02
Speaker 1: universe it was dark matter that was making sounds. Absolutely
40:06
Speaker 1: dark matter triggers it, right, you know, imagine you have
40:08
Speaker 1: this big plasma and it's just sort of like hanging
40:11
Speaker 1: out and it's quiet. Well, how do you make like
40:13
Speaker 1: a ripple in it? You know, you need to like
40:15
Speaker 1: flick it, just like if you have a surface of water,
40:17
Speaker 1: how do you make waves through it? But you know
40:19
Speaker 1: you tap the surface. And so dark matter is still
40:22
Speaker 1: the overwhelming source of gravity in the universe, even back then.
40:25
Speaker 1: If you have a clump of over dense dark matter,
40:27
Speaker 1: it like pulls together the other stuff nearby effectively like
40:31
Speaker 1: tapping on the surface of the plasma and it creates
40:33
Speaker 1: this pressure wave in response that rings out from those
40:36
Speaker 1: dark matter centers. But what clump the dark matter in
40:39
Speaker 1: the first place, Well, that's just random fluctuations. Like we
40:42
Speaker 1: think that the early universe was not totally smooth. You
40:45
Speaker 1: think that there were just like a random quantum fluctuations
40:48
Speaker 1: from the very very beginning of the universe that got
40:50
Speaker 1: blown up by inflation to be macroscopic. So you have
40:54
Speaker 1: this dark matter that's like a little bit clumpy in
40:56
Speaker 1: some places due to quantum fluctuations. Then those he did
41:00
Speaker 1: these pressure centers, which led to sound wave propagating through
41:03
Speaker 1: this early universe plasma. Interesting, so like a little bit
41:06
Speaker 1: of dark matter clump tier Dad brought in a little
41:09
Speaker 1: bit of the plasma, and then that pulled pulled some
41:12
Speaker 1: of the plasma around it, and that creates kind of
41:14
Speaker 1: a wave. And then this wave travels out through the
41:17
Speaker 1: early universe and travels really really fast because the universe
41:21
Speaker 1: was very very dense, and dense materials have a very
41:24
Speaker 1: high speed of sound. Right, You know that sound travels
41:26
Speaker 1: faster through water or through steel, and it does through
41:29
Speaker 1: air because you have like more tightly packed particles they
41:32
Speaker 1: transmit the information faster from one to the other, and
41:34
Speaker 1: so the speed of sound back then was like half
41:37
Speaker 1: of the speed of light. What like sound and light
41:40
Speaker 1: or almost you know, in the same magnitude of speed. Yeah, exactly,
41:44
Speaker 1: Light traveled faster. Obviously, nothing can travel faster than light.
41:47
Speaker 1: But these sound waves were so fast because the early
41:49
Speaker 1: universe was so dense. But then what happens to these waves?
41:52
Speaker 1: Do they just keep propagating forever or did the universe
41:56
Speaker 1: when it finished expanding kind of killed these waves. Yeah,
41:59
Speaker 1: that's exactly what happened. The universe kept expanding, and then
42:02
Speaker 1: it cooled down, right, and then these protons and the
42:05
Speaker 1: electrons weren't flying free anymore. They lost some energy. They
42:09
Speaker 1: were cooler, so they fell into atoms. Than the universe neutralized, right,
42:13
Speaker 1: and it became these dark ages like we talked about,
42:15
Speaker 1: And so they're no longer like a lot of photons
42:17
Speaker 1: interacting with stuff, and things got a lot less dense,
42:20
Speaker 1: and so the speed of sound dropped a lot, right,
42:23
Speaker 1: all of a sudden, the speed of sound went from
42:25
Speaker 1: like half the speed of light too much much much
42:27
Speaker 1: much smaller, and it's sort of like froze. These ripples
42:31
Speaker 1: these ripples which were moving really really fast screaming out
42:34
Speaker 1: from these dark matter centers, all of a sudden, they
42:36
Speaker 1: couldn't move very fast anymore, so they got kind of
42:39
Speaker 1: frozen there because I guess they didn't have anything to
42:41
Speaker 1: push against, right, Yeah, exactly. There's no more pressure coming
42:44
Speaker 1: out because these photons are no longer coupled to the matter,
42:46
Speaker 1: and the photons were something that was really driving this.
42:49
Speaker 1: And then you have all these neutral atoms which aren't
42:51
Speaker 1: interacting as much as protons and electrons do, and so
42:55
Speaker 1: the speed of sound is much much lower, and so
42:57
Speaker 1: all of a sudden, that sound wave just sort of
42:59
Speaker 1: like boom it. It's the brakes and it's sort of
43:01
Speaker 1: stuck there. And the really cool thing is that we
43:03
Speaker 1: can still see those in the universe today, what the
43:08
Speaker 1: frozen sounds from the Big Bang caused by dark matter.
43:12
Speaker 1: You can see that absolutely because what you see out
43:15
Speaker 1: there in the universe are patterns in where galaxies are.
43:18
Speaker 1: See at the very center of these pressure centers, there
43:21
Speaker 1: was a lot of dark matter, as you expect a
43:22
Speaker 1: lot of matter to fall in and formed galaxies, and
43:25
Speaker 1: then also sort of on the edge of this frozen
43:27
Speaker 1: bubble where this wave was when it got frozen, you
43:31
Speaker 1: expect that to be denser than everything else. And so
43:33
Speaker 1: if you just look around the universe and you calculate
43:36
Speaker 1: like the average distance between galaxies, you find a lot
43:39
Speaker 1: of clumps, and then you also find these big bubbles
43:42
Speaker 1: of galaxies around the clumps, exactly the place you would
43:46
Speaker 1: expect to see from these frozen sound waves. Who so
43:50
Speaker 1: are you saying that this structure of the universe, because
43:52
Speaker 1: I know we're like organized in clusters of galaxies, superclusters,
43:57
Speaker 1: and then sheets and bubbles. Those bulls are b because
44:00
Speaker 1: of the initial shock wave of the universe. Absolutely, it's
44:04
Speaker 1: called barry On acoustic oscillation. And so you can see
44:08
Speaker 1: these bubbles in the universe today, like galaxies are organized
44:11
Speaker 1: more likely on the surface or on the centers of
44:14
Speaker 1: these bubbles than sort of in the middle of the bubbles.
44:17
Speaker 1: And there's all these overlapping bubbles. You get places where
44:20
Speaker 1: like the sheets cross each other and you get an
44:22
Speaker 1: over density. It's really pretty incredible. It's also a super
44:26
Speaker 1: cool way to measure the expansion of the universe because
44:29
Speaker 1: we can calculate how big those bubbles should have been
44:32
Speaker 1: when they were formed. Because it's just like calculations about plasma,
44:35
Speaker 1: and we know how to do those calculations, and then
44:37
Speaker 1: we can measure how big they are today, and that
44:39
Speaker 1: gives us a completely independent measurement of how much the
44:43
Speaker 1: universe has expanded. It's like a standard ruler. Oh. Interesting,
44:46
Speaker 1: you can see like how big the bubbles are, and
44:48
Speaker 1: that tells you how much the universe group. Yeah, and
44:50
Speaker 1: so we have all these piece of evidence that the
44:52
Speaker 1: universe expanded. This is a completely separate one from like
44:55
Speaker 1: looking at the stars and the supernova and all the
44:58
Speaker 1: other ways. And the cool thing is that it tells
45:00
Speaker 1: the same story, right, It tells us the same story
45:03
Speaker 1: about the expansion of the universe that all the other
45:05
Speaker 1: ones do. And I love when that happens. When you
45:07
Speaker 1: have completely different methods with totally different ways to make
45:10
Speaker 1: mistakes and they all tell you the same story. That's
45:12
Speaker 1: when you know you've really solved the detective mry, Like
45:15
Speaker 1: you found the murderer. You kind of red handed got
45:18
Speaker 1: the universe with its dark matter hand in the honey jar. Yeah.
45:22
Speaker 1: It's also cool to see these things in real life.
45:24
Speaker 1: You know, we have this picture in our minds of
45:26
Speaker 1: this thing happening in the early universe, and it feels
45:29
Speaker 1: kind of abstract because it's something that happened a long
45:31
Speaker 1: time ago, when the rules of the universe seemed really
45:34
Speaker 1: really different. But if you look out there in the
45:36
Speaker 1: night sky, they are still there. Those bubbles are there
45:39
Speaker 1: to see. It's really incredible to see it imprinted on
45:42
Speaker 1: the sky itself. But you kind of need a special telescope, right,
45:45
Speaker 1: You can't see it with the naked eye, but it's
45:47
Speaker 1: there for us to see it somehow. Yeah, that's right.
45:50
Speaker 1: You need telescopes. You need to look at a lot
45:51
Speaker 1: of galaxies and do some calculations, but it's definitely there.
45:54
Speaker 1: It's pretty cool that, you know, like the universe, you know,
45:58
Speaker 1: kind of rang out or cried as it was born
46:00
Speaker 1: and that got frozen in its structure. Yeah, but we
46:03
Speaker 1: could also make it positive. You could say it's like
46:05
Speaker 1: a singing of the universe, you know, its moment of
46:08
Speaker 1: joy of this creation, because that's how all babies come out,
46:13
Speaker 1: come out singing such pleasant sounds. Yeah, or you could
46:16
Speaker 1: consider it this screaming crying of the painful birth of
46:19
Speaker 1: the universe. Either way, it depends on your personality. That's
46:21
Speaker 1: a personality test for you, right, there. I guess if
46:24
Speaker 1: you have a sort of personality, yeah, you would find
46:26
Speaker 1: music in that it would ring sweetly in your ears.
46:29
Speaker 1: All right, well, that was our last question for today.
46:31
Speaker 1: Thank you, Addison. It sounds like the universe did have
46:35
Speaker 1: a sound early in the universe, and we can still
46:37
Speaker 1: see it today. We can still see it today, and
46:40
Speaker 1: the universe continues to make music. It's very dilute, and
46:43
Speaker 1: it's very thin, and the speed of sound is now
46:46
Speaker 1: very very slow, but things still do bump into each
46:48
Speaker 1: other and still do make noise. What do you think
46:50
Speaker 1: is the genre of the music of the universe cosmic chill,
46:54
Speaker 1: scream rock. I think dark matters, dark rock. There are
46:58
Speaker 1: a lot of rocks, so are a lot of rocks.
47:01
Speaker 1: All right, well, thanks for joining us in this podcast
47:04
Speaker 1: celebration of the release of our new book. If you're
47:06
Speaker 1: not tired of us plugging it, please check it out.
47:09
Speaker 1: It's The Universe f a q dot com. It has
47:11
Speaker 1: how many questions that we answering the book, Daniel, I
47:13
Speaker 1: don't know, that's a great question. I think it's something
47:16
Speaker 1: like sixteen sixteen seventeen questions, and we try to make
47:19
Speaker 1: them as good questions as possible. Yeah, So thank you
47:22
Speaker 1: everybody for your support for this project and for all
47:25
Speaker 1: of our projects. And we'd love if you checked out
47:27
Speaker 1: this book and if it strikes your fancy, buy a copy.
47:30
Speaker 1: Thanks for supporting us, and because we do all this
47:32
Speaker 1: for you, for our listeners, for our readers. This is
47:35
Speaker 1: all about connecting with you and having our sound sort
47:39
Speaker 1: of ripple out into the universe, creating, hopefully pressure ways
47:43
Speaker 1: of knowledge and understanding. Do you think when our collaboration
47:46
Speaker 1: was born that started with the screen. If we didn't scream,
47:49
Speaker 1: then it's screaming now all right, Well, thanks for joining us,
47:54
Speaker 1: Thanks again for your support, See you next time. Thanks
48:04
Speaker 1: for listening, and remember that Daniel and Jorge Explain the
48:07
Speaker 1: Universe is a production of I Heart Radio. Or more
48:10
Speaker 1: podcast from my Heart Radio visit the i heart Radio app,
48:14
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.