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Speaker 1: Hey, it Jorhan Daniel here, and we want to tell

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Speaker 1: you about our new book. It's called Frequently Asked Questions

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Speaker 1: about the Universe because you have questions about the universe,

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Speaker 1: and so we decided to write a book all about them.

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Speaker 1: We talk about your questions, we give some answers, we

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Speaker 1: make a bunch of silly jokes as usual, and we

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Speaker 1: tackle all kinds of questions, including what happens if I

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Speaker 1: fall into a black hole? Or is there another version

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Speaker 1: of you out there that's right? Like usual, we tackle

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Speaker 1: the deepest, darkest, biggest, craziest questions about this incredible cosmos.

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Speaker 1: If you want to support the podcast, please get the

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Speaker 1: book and get a copy not just for yourself, but

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Speaker 1: you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,

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Speaker 1: and for the aliens. So get your copy of Frequently

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Speaker 1: Asked Questions about the Universe is available for pre order now,

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Speaker 1: coming out November two. You can find more details at

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Speaker 1: the book's website, Universe f a Q dot com. Thanks

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Speaker 1: for your support, and if you have a hamster that

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Speaker 1: can read, please let us know. We'd love to have

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Speaker 1: them on the podcast. And Daniel, do you ever get

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Speaker 1: questions from listeners that aren't about physics. Oh yeah, sure,

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Speaker 1: Sometimes I get questions asking for life advice or books

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Speaker 1: to recommend that kind of stuff. Really, people ask you

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Speaker 1: for life advice and overworked academic like, how do I

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Speaker 1: avoid making the same mistakes? I mean, yeah, exactly. Well,

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Speaker 1: my life advice is actually mostly like my book advice.

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Speaker 1: What do you mean, well, my life advice and generally

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Speaker 1: read more books. There you go, that's good advice. What

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Speaker 1: kinds of books do you usually recommend? Well, it just

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Speaker 1: so happens that there's a great new book coming out

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Speaker 1: today that I highly recommend. Is it about banana recipes?

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Speaker 1: You know, I got plenty of those, I mean our

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Speaker 1: book frequently asked questions about the universe. Oh right, yeah,

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Speaker 1: I should get a copy or maybe three for my

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Speaker 1: friends too. And I think it has been in a

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Speaker 1: recipe to right, That was a frequently a question nobody

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Speaker 1: asks for bed in recipes. I am more handmad cartoonist

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Speaker 1: and the creator of PhD comics. Hi, I'm Daniel. I'm

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Speaker 1: a particle physicist, and I'm the proud co author of

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Speaker 1: the book. Frequently asked questions about all the incredible things

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Speaker 1: that we want to understand about the universe. That's right,

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Speaker 1: Daniel and I wrote another book and follow up to

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Speaker 1: our first book, We Have No Idea, And this one

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Speaker 1: is kind of about you, the listener, that's right. This

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Speaker 1: one is literally inspired by listeners. It's about all the

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Speaker 1: big questions that people ask over and over again. It's

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Speaker 1: about those topics that resonate with everybody that everybody wants

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Speaker 1: to know the answer to. Yeah, big questions like will

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Speaker 1: time ever stop? And why haven't aliens visited us? Yeah?

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Speaker 1: Or where is the center of the universe? And can

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Speaker 1: I get Google Map to give me directions there? Yeah.

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Speaker 1: We even tackle kind of philosophical questions, right, Daniel, like

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Speaker 1: is there an afterlife? Or is there free will in

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Speaker 1: our brains? Yeah? We talk about those things from a

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Speaker 1: physics point of view, like what do we know about

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Speaker 1: the universe and what can that tell us about these

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Speaker 1: deep questions about life, happiness and everything. Yeah, and I

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Speaker 1: think it came out pretty good. I really like this book.

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Speaker 1: I feel like it's fun, it has short chapters, It

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Speaker 1: tackles really interesting kind of existential questions, and I think

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Speaker 1: we do a pretty good job of answering each question,

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Speaker 1: you know, Like from a physics perspective and what people

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Speaker 1: know when people don't know. It certainly was fun to

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Speaker 1: work on and fun to write, and I hope that

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Speaker 1: means that it's fun to read. And some of these

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Speaker 1: topics in here are near and dear to my heart,

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Speaker 1: and some of them were a little far afield for me,

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Speaker 1: so I have to go off and do some research

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Speaker 1: talk to experts. But that was always a lot of fun.

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Speaker 1: There's a lot of Wikipedia reading, I think, is what

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Speaker 1: you're saying, but not all at all story from Wikipedia.

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Speaker 1: We do talk to experts, like we have a chapter

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Speaker 1: about meteors coming to Earth, and we talked to people

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Speaker 1: on NASA, Like we went to NASA and talked to

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Speaker 1: somebody there. Yeah, we talked to the folks at NASA

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Speaker 1: whose job it is to protect us from huge rocks

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Speaker 1: from space. There are people out there whose job actually

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Speaker 1: is planetary protection officer, and we went and talk to them.

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Speaker 1: So you don't have to, yeah, because I think another

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Speaker 1: big question we usually get is people ask how can

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Speaker 1: we support the podcast or how can we help you guys,

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Speaker 1: And so this is kind of a pretty good way

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Speaker 1: to do it. To get the book and not just

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Speaker 1: maybe get a copy for yourself, but get one for

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Speaker 1: your friends, for your family members. You know that person

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Speaker 1: you always wanted to convince them to listen to our podcast,

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Speaker 1: but maybe it hasn't yet. I think this book is

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Speaker 1: a really sort of nice introduction to these topics, to

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Speaker 1: the universe, to you know, asking fun questions and getting

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Speaker 1: fun answers about these great mysteries. Yeah, we hope that

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Speaker 1: it strikes a balance. There are really interesting, deep nuggets

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Speaker 1: of physics in there for those heavy duty nerds that

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Speaker 1: really want to understand the details about something, but also

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Speaker 1: a lot of just general approachable stuff about the universe.

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Speaker 1: Then I'm pretty sure everybody wants to know. I mean,

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Speaker 1: I feel tested on my kids, who are definitely not

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Speaker 1: fans of science. Are they heavy duty or light duty nerds? Neither?

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Speaker 1: They're like, oh, man, dad is talking about science again.

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Speaker 1: My daughter's favorite phrase is I didn't ask for a

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Speaker 1: physical lecture. Okay, oh my goodness. That is some high

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Speaker 1: level sass there, exactly. That's what it's going to make

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Speaker 1: her a TikTok star one day. It sounds like you

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Speaker 1: need to buy our book. Well, my favorite thing is

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Speaker 1: sometimes they ask me questions which come up in the book,

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Speaker 1: and I'm like, oh, you should read my book. I

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Speaker 1: answered that question and then they're like, my book. But yeah,

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Speaker 1: if you want to support this, please check out the

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Speaker 1: book and pre order it now, Daniel. It comes out

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Speaker 1: in November. What It comes out November two, and you

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Speaker 1: can pre order it now, which we'd be very grateful

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Speaker 1: for your support. You can find it everywhere good books

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Speaker 1: and bad books are sold, and you can also find

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Speaker 1: it online at universe f a Q dot com. Yeah,

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Speaker 1: and if we time things right, actually today is the

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Speaker 1: day that it comes out, right, today is November two,

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Speaker 1: that's right. We're recording this in September, but we're tying

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Speaker 1: in this episode to release on the day of our

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Speaker 1: book launch. So today should be the day that the

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Speaker 1: book is physically existing in stories. You can drive to

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Speaker 1: your local bookstore and buy one. Yeah, we promised it. It

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Speaker 1: It has a ton of cartoons. I had to draw

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Speaker 1: hundreds of cartoons for this one, which was a ton

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Speaker 1: of fun. But also it was a sprint at the

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Speaker 1: ant finish. Isn't every project you do a sprint to

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Speaker 1: finish at the end. I like sprinting, you know, I

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Speaker 1: feel like that's when you're really living. No, but I

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Speaker 1: gotta say, the cartoons really add another voice to the book.

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Speaker 1: You know, just like on our podcast you have like

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Speaker 1: the voice of a scientist, and then you have the

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Speaker 1: voice of our cartoonists. In the book, we also try

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Speaker 1: to capture that you have the text which tells you

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Speaker 1: about the physics, and then you have the cartoons which

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Speaker 1: are sort of an interplay and liven it up and

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Speaker 1: also really help clarify. You know, sometimes you really need

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Speaker 1: a visual and on the podcast we can't communicate with

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Speaker 1: you in visual medium, but in the book we can.

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Speaker 1: And in addition, you also get to see Jorge's great art,

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Speaker 1: which is really lively and clever. Yeah. So the book

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Speaker 1: comes out today, please check it out, and to celebrate,

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Speaker 1: we are having a special of our podcast today, we

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Speaker 1: are doing kind of a dedicated oh to listener questions.

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Speaker 1: That's right. We love questions from listeners that inspired our book.

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Speaker 1: It powers the podcast, and it inspires me every day

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Speaker 1: because every day that I get emails from listeners asking questions,

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Speaker 1: I'm reminded that everybody out there wants to understand the universe.

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Speaker 1: That it's not just me sitting in my office trying

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Speaker 1: to puzzle away the deep secrets of the universe. But

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Speaker 1: it's something that touches everybody in a really human way,

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Speaker 1: that we have this desire to understand the world and

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Speaker 1: the universe around us. It's an itch that will never

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Speaker 1: be scratched, but we have to keep picking at it. Yeah,

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Speaker 1: and that's why we ask questions. I mean, you do

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Speaker 1: it professionally, kind of for living, Daniel. I guess you

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Speaker 1: get paid, right, I haven't checked recently. I'm not getting

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Speaker 1: any money, but I hope somebody. I think what you're

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Speaker 1: saying is that all humans really ask these questions, right,

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Speaker 1: you know, everyone you can't help, but wonder. It's kind

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Speaker 1: of part of human nature to kind of ask questions

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Speaker 1: and wonder what the answers are. Absolutely, it is part

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Speaker 1: of human nature. And something I'm curious about is whether

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Speaker 1: it's part of intelligence or whether it's just human. You know,

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Speaker 1: if we meet aliens, I wonder will they be curious

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Speaker 1: about the universe or will they be bored by that

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Speaker 1: question and focused on something else which we find totally

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Speaker 1: dull interesting, Like could you be an intelligent being but

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Speaker 1: not curious? Who knows if science is a human endeavor

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Speaker 1: or not? Maybe you need to be curious to develop

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Speaker 1: intelligence from an evolutionary perspective. Yeah, it could go hand

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Speaker 1: in hand. So lots of things will learn about the

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Speaker 1: universe and the human perspective on it when we finally

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Speaker 1: do meet those aliens, or maybe aliens will order a

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Speaker 1: book and then write to us and tell us we

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Speaker 1: got it all wrong. Well, we do have a chapter

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Speaker 1: on why haven't we heard from aliens? So maybe deliverply

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Speaker 1: would be like, we just don't like you. Maybe we

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Speaker 1: were waiting for this book to come out. Now the moment,

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Speaker 1: now that we read it in a book, will contact you.

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Speaker 1: So to be on the podcast, we'll be tackling listener questions.

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Speaker 1: Frequently asked questions about the Universe released edition. There was

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Speaker 1: a lot of questions in the title of the episode. Well,

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Speaker 1: that's the theme of the whole podcast, so we've got

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Speaker 1: to underscore it with questions. Yeah, and so we're not

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Speaker 1: going to be answering questions from the book, because you know,

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Speaker 1: we don't want to give away any spoilers. But we

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Speaker 1: do have some questions from actual listeners who are pretty

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Speaker 1: good too. They're pretty interesting. Our questions here about gravity,

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Speaker 1: about the relative velocity of stars, and also about the

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Speaker 1: sound of the universe. That's right, the music of the

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Speaker 1: early universe. Can't wait to talk about that one, the

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Speaker 1: wailing cry of a newborn baby universe who doesn't want

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Speaker 1: to hear that? If the universe screams alone in the forest,

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Speaker 1: does anybody listen? And where is that forest anyway? All right? Well,

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Speaker 1: our first question today comes from Lily, and she has

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Speaker 1: a question about what would happen if gravity suddenly took

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Speaker 1: a vacation. Hi, I'm Lily. What would happen if gravity

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Speaker 1: just stopped? What would happen to the oceans, the trees,

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Speaker 1: the houses, the Earth, the solar system, the universe? And

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Speaker 1: what would happen if gravity never existed? I needs know? Thanks,

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Speaker 1: Lily needs to Know. I should have been the title

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Speaker 1: of our podcast. This sounds like a good kids show.

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Speaker 1: Perhaps Eleanor wonders why Lily needs to know? But great question, Lily,

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Speaker 1: Thank you so much for sending this question. It's a

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Speaker 1: great question, like what if gravity suddenly like turned off

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Speaker 1: or like quit? Yeah? Do you think this is in

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Speaker 1: the vein of supervillain's planning take over the world? Kind

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Speaker 1: of questions like do you think Lily is building a

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Speaker 1: gravity destroyer? And wondering if you're gonna have enough impact.

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Speaker 1: Oh man, you just turned Lily into a super villain. Boy.

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Speaker 1: I thought she was really sweet and intelligent, but now

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Speaker 1: you just put a dark spin on it. She's using

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Speaker 1: that sweet intelligence just to fool you. Man. I'm sure

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Speaker 1: Lately just needs to know because she's curious, right, I hope, yes, absolutely,

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Speaker 1: But yeah, I guess you know, let's not maybe talk

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Speaker 1: about how you would do that, like, you know, let's

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Speaker 1: avoid that. But I think it's more of a hypothetical question.

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Speaker 1: What would happen if gravity just stop one day? Yeah?

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Speaker 1: That is a really fascinating question because gravity is so

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Speaker 1: we would definitely notice pretty quickly. Yeah, And it's also

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Speaker 1: important because it keeps us grounding, you know, it's important

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Speaker 1: for some pretty massive puns. Yeah, some heavy duty Nearth.

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Speaker 1: But yeah, So Daniel, what would happen if there was

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Speaker 1: it be? It would be pretty bad, pretty fast. And

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Speaker 1: the reason, at least locally, like here on Earth, is

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Speaker 1: but the rock is not spinning, and then gravity turns off,

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Speaker 1: then you don't necessarily go anywhere, right, you can just

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Speaker 1: stay in the same place. You only move if there's

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Speaker 1: if you're on the Earth and it's spinning and gravity

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Speaker 1: goes away, well you were relying on gravity to keep

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Speaker 1: you on the Earth, pretty soon you're gonna be floating

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Speaker 1: up into the sky. You know. I never maybe we

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Speaker 1: thought about it this way, but I guess the Earth

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Speaker 1: is spinning, right, It's spinning in space. But I'm not

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Speaker 1: necessarily spinning in space, right, It's like I'm only spinning

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Speaker 1: in space because I'm stuck to the Earth. That's right. Well,

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Speaker 1: you are a part of the Earth, and so every

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Speaker 1: element to the Earth is spinning in the same way.

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Speaker 1: The Earth is, But you're right, the Earth can spin

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Speaker 1: without you, and in order to spin with the Earth,

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Speaker 1: you need gravity or something to pull you down. Like

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Speaker 1: for example, if you had a satellite going around the

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Speaker 1: Earth in orbit, right, and then the Earth disappeared, it's

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Speaker 1: gravity disappeared. What would happen to the satellite? It wouldn't

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Speaker 1: keep moving in a circle, right, It would just fly

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Speaker 1: The only reason that satellite moves around the Earth in

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Speaker 1: a circle is because of the gravity of the Earth,

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Speaker 1: and the same thing applies to you. The only thing

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Speaker 1: that keeps you moving with the surface of the Earth

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Speaker 1: is the gravity that bends your path down. Yeah, because

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Speaker 1: I guess you know, like you just said, if you

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Speaker 1: turn off gravity, the Earth would still keep on spinning.

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Speaker 1: It had us this angular romentous and would just keep

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Speaker 1: on spinning. But the thing is that you would sort

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Speaker 1: be sort of attached to it, and so you would

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Speaker 1: fly off. Yeah. It's sort of like you know a

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Speaker 1: picture does a big wind up spins his arm around

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Speaker 1: and then let's go of the ball. And when he

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Speaker 1: circle like his arm is anymore, moves in a straight line, right,

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Speaker 1: And so that's sort of like what the Earth was

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Speaker 1: doing there at the spinning and it's holding onto you,

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Speaker 1: so you're the ball, and then if gravity turns off,

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Speaker 1: it's no longer holding onto you, and boom, you fly

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Speaker 1: out into space at the speed of a fastball. Well

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Speaker 1: you just throw me a curveball there, But that's a

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Speaker 1: different episode. I guess physics is a bit of a

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Speaker 1: knuckleball to the brain. Sometimes it's a hit or miss.

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Speaker 1: So that's kind of what would happen if you turn

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Speaker 1: up gravity, Like everything would just fly off, everything that

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Speaker 1: wasn't bolted down to the Earth. Do you think the

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Speaker 1: Earth would break apart though, like with earth crust also

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Speaker 1: detached from the Earth and fly off into space. Well

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Speaker 1: that's a great question. You know, the Earth is held

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Speaker 1: together by forces much stronger than gravity, right, you know,

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Speaker 1: like electromagnetic forces and all those bonds that hold matter together.

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Speaker 1: But the Earth, sort of like the Sun, etcetera, is

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Speaker 1: a balance somewhat between pressure and gravity. Like the Earth

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Speaker 1: is the size that it is because that's where gravity

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Speaker 1: and the pressure from those bonds balance, right, if gravity

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Speaker 1: was stronger, it would compact the Earth even farther. If

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Speaker 1: the material the Earth was made of was tougher, it

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Speaker 1: was harder to compress. The Earth would be bigger, right,

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Speaker 1: gravity wouldn't have been able to squeeze it as far.

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Speaker 1: So if gravity goes away, then the Earth will eventually

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Speaker 1: just sort of like fluff up a little bit, like

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Speaker 1: bits of the Earth will fall off. Also, because gravity

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Speaker 1: isn't there sort of like compressing it and keeping things down.

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Speaker 1: It would sort of like trying into lose gravel kind

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Speaker 1: of floating space. Yeah, I guess, because like mountains would

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Speaker 1: just float off into space. Everything that isn't tied down

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Speaker 1: would break off. And even things that are tied down

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Speaker 1: now would effectively feel a force throwing them off the Earth.

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Speaker 1: You know, there's no actual force there, sort of a

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Speaker 1: product of having a rotating frame of motion, but the

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Speaker 1: effect is the same. It's like if you're on a

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Speaker 1: merry go round and somebody spins it. If you're not

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Speaker 1: holding on, then you're gonna feel the forced trying to

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Speaker 1: throw you off. And so if the Earth keeps spinning

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Speaker 1: with no gravity, then it's going to be testing all

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Speaker 1: the bonds between things and anything that gets a little

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Speaker 1: bit weakened is eventually going to fly off into space. Right.

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Speaker 1: And I'm also thinking, like, isn't that the center of

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Speaker 1: the Earth sort of liquid? Right, it's molten, it's liquid.

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Speaker 1: Wouldn't that also just kind of blob away, or would

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Speaker 1: like surface tension and liquid tension keep it all held in. Yeah,

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Speaker 1: that's a great question. I think gravity is essentially one

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Speaker 1: of the reasons why the center of the Earth is liquid.

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Speaker 1: All that pressure creates all this heat which keeps it liquid,

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Speaker 1: and so it would hasten the cooling of the Earth. Also,

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Speaker 1: we once talked about how long it would take the

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Speaker 1: Earth's core to cool under normal conditions, and it was

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Speaker 1: something like ninety billion years. But if gravity is no

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Speaker 1: longer around compressing the Earth keeping the center hot, then

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Speaker 1: the center will cool much faster. And it's not just

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Speaker 1: the Earth that would sort of cool and unravel, it's

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Speaker 1: also the Solar system and the galaxy to right, like

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Speaker 1: our galaxy would fall apart too, Yeah, our Solar system

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Speaker 1: almost immediately, right, because the only thing keeping the Earth

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Speaker 1: in orbit around this one is the gravity, and so

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Speaker 1: the Earth would just become like a fastball shooting out

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Speaker 1: into the galaxy, and the same thing with the Sun.

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Speaker 1: The Sun is orbiting the center of the galaxy. It's

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Speaker 1: not just like happens to be here in space near

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Speaker 1: other stars. It's moving in a coordinated swirl with a

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Speaker 1: bunch of other stars orbiting this incredible mass at the

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Speaker 1: center of the galaxy. And that's because of gravity. No

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Speaker 1: other force is capable of doing that. And so if

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Speaker 1: that disappeared, then the Sun would just continue moving in

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Speaker 1: the direction it was moving when Lily turned off the

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Speaker 1: universe's gravity, and it would just go in that direction

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Speaker 1: wherever it was and it but it certainly wouldn't be

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Speaker 1: a curve around the center of the galaxy would just

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Speaker 1: fly off, you know, like ping pong balls on a

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Speaker 1: Merry go round. The other stars in the galaxy would

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Speaker 1: do the same thing, right, like everything would just fly

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Speaker 1: off into space. Yeah. So these galaxies are almost all spinning,

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Speaker 1: and so they would all break apart. The stars would

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Speaker 1: spread out into the universe. And even more than that,

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Speaker 1: galaxies feel gravity on each other like we feel the

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Speaker 1: gravity of Andromeda, even though with millions of light years away,

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Speaker 1: all the galaxies and our local cluster are sort of

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Speaker 1: orbiting each other. They're orbiting the common center of mass.

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Speaker 1: So there's something not just keeping our galaxy together, but

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Speaker 1: keeping our galaxy cluster together, and that's gravity. So without that,

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Speaker 1: the galaxies themselves, even as they explode and their stars

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Speaker 1: go everywhere, the galaxies themselves would spread out further rather

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Speaker 1: than being clustered together into a cluster. The universe withold

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Speaker 1: de cluster. But even more interesting, I think is to

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Speaker 1: think about what would happen to black holes, Like would

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Speaker 1: they no longer be black holes? Would they no longer

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Speaker 1: be holes if you turned off gravity. Yeah, that's incredible

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Speaker 1: to think about. We just don't know because we don't

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Speaker 1: know what's inside the black holes. If you take general

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Speaker 1: relativity to be the truth, then there's a singularity in there.

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Speaker 1: But the singularity is overcoming incredible pressure, right Like matter

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Speaker 1: does not like to be squeezed down to a singularity.

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Speaker 1: It takes incredible gravity to do that. If you then

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Speaker 1: just turn that gravity off, then you know the quantum

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Speaker 1: mechanical pressure and the electron de generously pressure and all

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Speaker 1: that stuff. Those things are going to explode rapidly. So

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Speaker 1: every black cole basically turns into a massive bomb, including

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Speaker 1: the huge supermassive black hole of the center of our galaxy.

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Speaker 1: That doesn't sound good. What do you mean it would explode,

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Speaker 1: like just because it has so much of pressure. Yeah,

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Speaker 1: it would explode because, like stars, black holes are an

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Speaker 1: equilibrium between gravity and pressure. And in the case of

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Speaker 1: black holes, what's happened is gravity has one has overcome

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Speaker 1: all of that pressure. But if you release gravity, you know,

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Speaker 1: it's like you took a bunch of springs and you

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Speaker 1: squeeze them down to a tiny, tiny point and you're

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Speaker 1: holding them really really tight, and all of a sudden

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Speaker 1: you just let go. Like what happens. Well, you know,

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Speaker 1: it's like a bunch of snakes jumping out of a can.

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Speaker 1: Like it's going to be crazy. No snakes on a

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Speaker 1: black hole. That's a nice movie from Marvel. Yeah, and

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Speaker 1: you know the same thing will happen to stars. Right.

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Speaker 1: Why is the Sun not just a huge explosion because

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Speaker 1: it has fusion going on at its heart? Right, Fusion

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Speaker 1: is what powers nuclear bomb. So why isn't the Sun

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Speaker 1: just exploding? It's because of gravity. It's a delicate balance

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Speaker 1: of gravity keeping everything in and fusion pressure keeping it

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Speaker 1: from collapsing further. But you take gravity away and the

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Speaker 1: Sun just becomes an enormous hydrogen bomb. Oh my god,

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Speaker 1: would it even matter what happens here on Earth? Think

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Speaker 1: if we're just gonna the Sun is gonna explode and

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Speaker 1: we'll be fried in eight minutes. We'll be fried in

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Speaker 1: a little less than eight minutes because the Earth will

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Speaker 1: be free from its orbit, so we'll be flying onto

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Speaker 1: interstellar space with this incredible explosion behind us. We a

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Speaker 1: great scene for the next Jerry Brooke Connor movie. Yeah,

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Speaker 1: just we're floating away slow motion, are shure? It's open

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Speaker 1: and our hair tossing in the wind, and somehow we

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Speaker 1: have to survive that explosion though I don't think our

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Speaker 1: odds are very good. Wow. So basically the whole universe

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Speaker 1: everything would explode and fall apart, is what you're saying.

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Speaker 1: At the same time, Yeah, exactly, bad idea, not recommended. Yeah,

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Speaker 1: but literally had another part of her questions, which is

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Speaker 1: really interesting too, is what would happen if gravity never

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Speaker 1: even existed in the first place? And so let's get

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Speaker 1: into that part of her question. But first let's take

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Speaker 1: a quick Great all right, we're celebrating questions from listeners,

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Speaker 1: and like the kinds of questions that inspired our new book,

416
00:20:10,119 --> 00:20:13,400
Speaker 1: frequently asked questions about the Universe, which is out now today.

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Speaker 1: Even so, please go check out the website Universe f

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Speaker 1: a Q dot com and maybe get a copy or

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00:20:19,040 --> 00:20:22,119
Speaker 1: ten copies or ten. Well, geez boy, I feel like

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Speaker 1: that that's a little greedy, Daniel. I was gonna say

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Speaker 1: like two or three, but alright, five copies. That's my

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Speaker 1: final offer. I guess if you had ten nieces and

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00:20:29,720 --> 00:20:33,280
Speaker 1: nephews and cousins and uncles, that could add up to ten. No,

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Speaker 1: if you're curious about this kind of stuff and you

425
00:20:35,160 --> 00:20:37,320
Speaker 1: would enjoy a bunch of jokes in a bunch of physics,

426
00:20:37,320 --> 00:20:39,800
Speaker 1: please check out the book. So today we're asking questions

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Speaker 1: from listeners to celebrate, and we we have this great

428
00:20:42,080 --> 00:20:45,120
Speaker 1: question from Lily who asked what would happen if gravity stopped?

429
00:20:45,720 --> 00:20:48,800
Speaker 1: And she also asked what would happen if gravity never existed?

430
00:20:49,040 --> 00:20:51,560
Speaker 1: Like if we had a universe from the beginning with

431
00:20:51,680 --> 00:20:55,600
Speaker 1: the gravity setting set off. What a crazy question, Not

432
00:20:55,760 --> 00:20:59,440
Speaker 1: something I've ever thought about, and all the weird hypotheticals

433
00:20:59,440 --> 00:21:01,760
Speaker 1: I've considered, and all the questions people have asked, nobody's

434
00:21:01,760 --> 00:21:04,320
Speaker 1: ever asked the question what would happen if we never

435
00:21:04,440 --> 00:21:08,440
Speaker 1: had gravity in our universe. Awesome question, Lily, Yeah, kudos Lily.

436
00:21:08,560 --> 00:21:12,240
Speaker 1: I'm guessing also the answer is not good. It depends

437
00:21:12,240 --> 00:21:14,359
Speaker 1: on the kind of universe you like, but it would

438
00:21:14,400 --> 00:21:17,960
Speaker 1: definitely be very, very different from our universe because gravity

439
00:21:17,960 --> 00:21:21,520
Speaker 1: played a really, really critical role in shaping the universe

440
00:21:21,560 --> 00:21:24,480
Speaker 1: that we see today. You know, after the Big Bang

441
00:21:24,560 --> 00:21:26,840
Speaker 1: and everything happened, which we of course don't understand and

442
00:21:26,960 --> 00:21:29,160
Speaker 1: we don't even know if gravity was essential for all

443
00:21:29,200 --> 00:21:31,159
Speaker 1: that to happen. But assume that the Big Bang and

444
00:21:31,200 --> 00:21:33,800
Speaker 1: the inflation at the beginning of the universe happened the

445
00:21:33,840 --> 00:21:36,479
Speaker 1: same way, because that wasn't really dominated by gravity as

446
00:21:36,520 --> 00:21:38,920
Speaker 1: we understand it. Then you know what happened was that

447
00:21:38,960 --> 00:21:41,520
Speaker 1: we have a bunch of hydrogen gas. You know, the

448
00:21:41,600 --> 00:21:45,119
Speaker 1: universe creates particles, and those particles cool and then eventually

449
00:21:45,119 --> 00:21:47,320
Speaker 1: you get hydrogen to form, and then the universe is

450
00:21:47,320 --> 00:21:50,920
Speaker 1: basically this huge floating cloud of gas. And it's very

451
00:21:51,000 --> 00:21:53,760
Speaker 1: dark back then because hydrogen, when it's just like hanging

452
00:21:53,760 --> 00:21:56,800
Speaker 1: out and cold, doesn't glow very much. So we call

453
00:21:56,920 --> 00:21:59,639
Speaker 1: this the universe dark ages. When there was basically just

454
00:21:59,680 --> 00:22:01,919
Speaker 1: a big blob of gas and the next thing that

455
00:22:02,000 --> 00:22:05,280
Speaker 1: happened was that stars were formed as stars were only

456
00:22:05,320 --> 00:22:09,360
Speaker 1: formed though because of gravity, Like it's gravity that pulled

457
00:22:09,440 --> 00:22:12,800
Speaker 1: over dense clumps of hydrogen together to get enough together

458
00:22:12,880 --> 00:22:16,000
Speaker 1: to spark fusion and to create light. So without gravity,

459
00:22:16,040 --> 00:22:19,119
Speaker 1: the universe would still be in those dark ages. Oh wow,

460
00:22:19,280 --> 00:22:22,479
Speaker 1: I guess nothing would have ever come together. Kind of yeah, exactly,

461
00:22:22,520 --> 00:22:24,240
Speaker 1: things would just sort of like be happy to hang

462
00:22:24,280 --> 00:22:26,240
Speaker 1: out in a big cloud. And you know, it would

463
00:22:26,280 --> 00:22:29,520
Speaker 1: be like overwhelmingly all hydrogen. There's like a tiny bit

464
00:22:29,560 --> 00:22:32,600
Speaker 1: of helium and the tiniest bits of heavier stuff created

465
00:22:32,600 --> 00:22:35,280
Speaker 1: in the Big Bang, but almost all hydrogen. Everything else

466
00:22:35,280 --> 00:22:36,600
Speaker 1: that you and I are made of, you know, the

467
00:22:36,600 --> 00:22:40,160
Speaker 1: heavier metals, those were all born in stars. But stars

468
00:22:40,200 --> 00:22:42,879
Speaker 1: don't form without gravity, and so the universe is just

469
00:22:42,960 --> 00:22:46,160
Speaker 1: a big boring cloud without gravity. Wow, So things would

470
00:22:46,160 --> 00:22:50,359
Speaker 1: be gassy gravity there from the beginning, gassy and not

471
00:22:50,440 --> 00:22:53,080
Speaker 1: in an exciting way. I guess. Maybe one question is

472
00:22:53,080 --> 00:22:54,760
Speaker 1: what would happen to the Big Bang? Like with the

473
00:22:54,800 --> 00:22:58,080
Speaker 1: Big Bang happened the same way, would you have still

474
00:22:58,160 --> 00:23:00,679
Speaker 1: had had a Big Bang without gravity? Is it just

475
00:23:00,760 --> 00:23:02,840
Speaker 1: that the outcome would be different? We really just don't

476
00:23:02,840 --> 00:23:05,080
Speaker 1: know the answer to that question because we don't understand

477
00:23:05,160 --> 00:23:08,240
Speaker 1: the mechanism of inflation or the Big Bang, like we

478
00:23:08,240 --> 00:23:10,760
Speaker 1: don't know what caused it and what made it happen

479
00:23:10,760 --> 00:23:13,840
Speaker 1: in a certain way. It might be that the reason

480
00:23:13,880 --> 00:23:17,119
Speaker 1: inflation happened a certain way is a necessary product of

481
00:23:17,160 --> 00:23:19,840
Speaker 1: the structure of space and time, like you know, it's

482
00:23:19,960 --> 00:23:23,560
Speaker 1: negative pressure from quantum zero point energy or the cosmological

483
00:23:23,640 --> 00:23:26,280
Speaker 1: constant that's we've talked about, and that that has to happen,

484
00:23:26,560 --> 00:23:28,840
Speaker 1: and it just comes from the structure of space and time.

485
00:23:28,960 --> 00:23:31,399
Speaker 1: You know. Gravity is the same way. Gravity comes from

486
00:23:31,440 --> 00:23:34,040
Speaker 1: the structure of space and time, how it bends around

487
00:23:34,160 --> 00:23:36,399
Speaker 1: mass and energy. So it might be that if you

488
00:23:36,440 --> 00:23:39,280
Speaker 1: don't have gravity, it means that you can't like bend

489
00:23:39,359 --> 00:23:41,919
Speaker 1: space and time. And it might also mean that you

490
00:23:41,960 --> 00:23:44,639
Speaker 1: couldn't have inflation, that you couldn't have the Big Bang,

491
00:23:44,880 --> 00:23:47,439
Speaker 1: that the universe might have never gotten started. But we

492
00:23:47,520 --> 00:23:50,399
Speaker 1: just don't really know because we don't understand how inflation

493
00:23:50,480 --> 00:23:53,560
Speaker 1: and gravity work together, or if they're really two sides

494
00:23:53,600 --> 00:23:56,040
Speaker 1: of the same coin. Interesting, Yeah, I guess it depends

495
00:23:56,040 --> 00:23:59,000
Speaker 1: on whether you can have bending of space without gravity,

496
00:23:59,080 --> 00:24:01,960
Speaker 1: or whether gravity is the bending of space. Yeah, in

497
00:24:02,040 --> 00:24:04,879
Speaker 1: some sense, inflation is just like an expansion of space,

498
00:24:05,119 --> 00:24:08,480
Speaker 1: which is very similar to gravity, sort of like repulsive gravity.

499
00:24:08,520 --> 00:24:11,639
Speaker 1: Of a new theory, Daniel, Maybe this universe was born

500
00:24:11,800 --> 00:24:15,000
Speaker 1: because the previous universe is Lily turned off. Flip the

501
00:24:15,040 --> 00:24:17,800
Speaker 1: switch on gravity and it blew everything up. Lily prime

502
00:24:19,280 --> 00:24:22,240
Speaker 1: the first Lily, All right, well it sounds like gravity.

503
00:24:22,320 --> 00:24:24,280
Speaker 1: It's kind of important you turn it off now. I

504
00:24:24,280 --> 00:24:26,600
Speaker 1: think everything would would blow up and fall apart. And

505
00:24:26,600 --> 00:24:28,560
Speaker 1: if we never had it, then nothing would have ever

506
00:24:28,640 --> 00:24:31,040
Speaker 1: happened in the universe. Yeah, although you know, maybe after

507
00:24:31,119 --> 00:24:34,880
Speaker 1: trillions of years, some other weird phenomenon would emerge. Everything

508
00:24:34,920 --> 00:24:38,000
Speaker 1: that happens in our universe is a strange emergent phenomena

509
00:24:38,040 --> 00:24:40,320
Speaker 1: from all the crazy balance of all the forces and

510
00:24:40,359 --> 00:24:42,320
Speaker 1: the objects in it. If you have a different mix

511
00:24:42,320 --> 00:24:44,359
Speaker 1: of stuff, you might end up with a different, weird,

512
00:24:44,440 --> 00:24:47,399
Speaker 1: complex universe. It might have just taken trillions of years

513
00:24:47,480 --> 00:24:50,800
Speaker 1: or quadrillions of years. Who knows. I see you're saying

514
00:24:50,800 --> 00:24:54,720
Speaker 1: like maybe gravity is evil. Twin would have come up gravity.

515
00:24:54,760 --> 00:24:56,800
Speaker 1: But thank you, Lily, that's such a great question. Thanks

516
00:24:56,800 --> 00:24:59,640
Speaker 1: for sending your question, and thanks for asking questions in general.

517
00:24:59,680 --> 00:25:03,320
Speaker 1: It's to see you and other people out there being curious. Yeah,

518
00:25:03,320 --> 00:25:05,400
Speaker 1: Lily had to know, and I hope now she knows,

519
00:25:05,640 --> 00:25:07,879
Speaker 1: and I hope she needs to know more in the future.

520
00:25:08,080 --> 00:25:09,959
Speaker 1: All Right, well, let's get to our next question. This

521
00:25:10,000 --> 00:25:12,600
Speaker 1: one is from Peter and he has a question about

522
00:25:13,200 --> 00:25:16,640
Speaker 1: visiting other stars. Hello, Daniel and Jorrgey. This is Peter

523
00:25:16,720 --> 00:25:20,320
Speaker 1: from Colorado Springs, Colorado. My question is that we always

524
00:25:20,320 --> 00:25:23,240
Speaker 1: say that to travel to a distant star efficiently, we

525
00:25:23,280 --> 00:25:25,399
Speaker 1: need to accelerate to a high fraction of the speed

526
00:25:25,400 --> 00:25:27,840
Speaker 1: of light. Why don't we assume that we're starting from

527
00:25:27,840 --> 00:25:30,639
Speaker 1: a velocity of zero? Aren't we moving relative to the

528
00:25:30,720 --> 00:25:33,760
Speaker 1: distant stars already based on the speed of our solar

529
00:25:33,760 --> 00:25:36,000
Speaker 1: system as the circles around the galaxy, or based on

530
00:25:36,040 --> 00:25:38,840
Speaker 1: the speed of our galaxy as it moves around the universe.

531
00:25:39,200 --> 00:25:41,440
Speaker 1: Couldn't we just pick a star that we're already aimed

532
00:25:41,440 --> 00:25:44,400
Speaker 1: towards at a high relative velocity and let our existing

533
00:25:44,440 --> 00:25:46,880
Speaker 1: momentum do most of the work. Anyway, Thank you. Love

534
00:25:46,920 --> 00:25:49,120
Speaker 1: the show. Listen to what every day when it comes out. Awesome,

535
00:25:49,320 --> 00:25:52,280
Speaker 1: great question, Thank you, Peter. I think Daniel Peter is

536
00:25:52,320 --> 00:25:54,480
Speaker 1: asking why do we have to go to other stars.

537
00:25:54,560 --> 00:25:56,520
Speaker 1: Why can other stars come to us? Why are we

538
00:25:56,600 --> 00:25:59,560
Speaker 1: doing all the work? Right? I think somebody else never drives.

539
00:25:59,640 --> 00:26:02,080
Speaker 1: If it can go to the stars, maybe the stars

540
00:26:02,080 --> 00:26:04,879
Speaker 1: can come to mommed. I wonder if Peter is always

541
00:26:04,920 --> 00:26:06,960
Speaker 1: doing the driving when he visits his friends, or if

542
00:26:07,040 --> 00:26:08,840
Speaker 1: he's like, why don't you ever come in my house?

543
00:26:10,640 --> 00:26:12,040
Speaker 1: He's like, when I have to take my kids to

544
00:26:12,080 --> 00:26:14,840
Speaker 1: school every morning, why can't the school come to my house?

545
00:26:14,920 --> 00:26:18,920
Speaker 1: And then the pandemic happens and everyone regrets nobody is

546
00:26:18,960 --> 00:26:22,560
Speaker 1: a great question, and he's tackling a really important topic, right,

547
00:26:22,600 --> 00:26:25,520
Speaker 1: which is how do we efficiently get to visit other

548
00:26:25,520 --> 00:26:27,720
Speaker 1: solar systems? Because that's what we want to do. We

549
00:26:27,760 --> 00:26:29,359
Speaker 1: want to see other planets. We want to see if

550
00:26:29,359 --> 00:26:31,639
Speaker 1: they're aliens there. We want to learn if other solar

551
00:26:31,680 --> 00:26:34,199
Speaker 1: systems are really different from hours. We would learn so

552
00:26:34,400 --> 00:26:36,760
Speaker 1: much about the University if we could just visit other

553
00:26:36,800 --> 00:26:40,360
Speaker 1: solar systems. But they are frustratingly hard to get to. Yeah,

554
00:26:40,440 --> 00:26:42,960
Speaker 1: they're super duper far away. Like how close is the

555
00:26:43,040 --> 00:26:46,400
Speaker 1: near star? I think it's like four light years away? Right, Yeah,

556
00:26:46,520 --> 00:26:50,240
Speaker 1: Proximus Centaire is almost four light years away with four

557
00:26:50,359 --> 00:26:52,320
Speaker 1: sounds like a small number, but that's just because the

558
00:26:52,400 --> 00:26:55,360
Speaker 1: unit of light year is just like ridiculously long, So

559
00:26:55,640 --> 00:26:57,800
Speaker 1: four light years would take a long time to visit,

560
00:26:58,040 --> 00:27:01,120
Speaker 1: like millions and millions of miles, a lot of zeros

561
00:27:01,359 --> 00:27:03,320
Speaker 1: if you do do in terms of miles, even if

562
00:27:03,320 --> 00:27:06,480
Speaker 1: you do in terms of kilometers or centimeters. But I

563
00:27:06,520 --> 00:27:08,879
Speaker 1: think Peter's question is, like, you know, we're used to

564
00:27:08,920 --> 00:27:11,240
Speaker 1: thinking of this problem. Is like we're here and that

565
00:27:11,480 --> 00:27:13,800
Speaker 1: the other star is there, but actually everything is kind

566
00:27:13,800 --> 00:27:16,320
Speaker 1: of moving around in the universe. You know, why can't

567
00:27:16,320 --> 00:27:18,840
Speaker 1: we pick a star that's maybe moving towards is really

568
00:27:18,880 --> 00:27:21,760
Speaker 1: fast or at least you know it's going to be

569
00:27:21,800 --> 00:27:24,399
Speaker 1: flying by really fast at some point in the future,

570
00:27:24,440 --> 00:27:26,640
Speaker 1: and aim for that star because it's sort of coming

571
00:27:26,640 --> 00:27:29,000
Speaker 1: our way anyways. Yeah, that's what he's asking, and it's

572
00:27:29,000 --> 00:27:31,639
Speaker 1: a great idea, And if there was a star headed

573
00:27:31,640 --> 00:27:34,240
Speaker 1: our away, it would be cool to check it out

574
00:27:34,280 --> 00:27:37,000
Speaker 1: before it totally disrupts our solar system and throws the

575
00:27:37,000 --> 00:27:40,760
Speaker 1: Earth into interstellar space. I see, let's hope there's no

576
00:27:40,800 --> 00:27:43,000
Speaker 1: start coming our ways. What you're saying, Yeah, it's a

577
00:27:43,000 --> 00:27:45,320
Speaker 1: great idea, but it would be quite dangerous because another

578
00:27:45,320 --> 00:27:48,920
Speaker 1: star we totally gravitationally perturb our solar system and make

579
00:27:48,920 --> 00:27:51,879
Speaker 1: a big mess. Really, I guess like even if it

580
00:27:51,880 --> 00:27:55,040
Speaker 1: goes like if it passes you know, not through our

581
00:27:55,040 --> 00:27:57,520
Speaker 1: solar system, but you know, like adjacent to our solarism,

582
00:27:57,560 --> 00:28:00,000
Speaker 1: it would still disrupt us. It would still disrupt us. Yeah,

583
00:28:00,280 --> 00:28:01,840
Speaker 1: we might lose things in the outer part of the

584
00:28:01,880 --> 00:28:04,000
Speaker 1: solar system. It's a balance. The closer it gets, the

585
00:28:04,000 --> 00:28:06,240
Speaker 1: easier it would be to visit, but also the more

586
00:28:06,320 --> 00:28:08,919
Speaker 1: dangerous it would be for our solar system. Interesting, but

587
00:28:09,000 --> 00:28:11,080
Speaker 1: you know, we would only lose like you know, Pluto

588
00:28:11,200 --> 00:28:13,880
Speaker 1: and Neptune, Like, wouldn't that be worth it to visit

589
00:28:13,920 --> 00:28:16,159
Speaker 1: another star? Not just that. You know, we have the

590
00:28:16,240 --> 00:28:18,960
Speaker 1: or cloud, which is like a huge group of potential comets,

591
00:28:19,400 --> 00:28:21,719
Speaker 1: and if another star comes too close, it can perturb

592
00:28:21,800 --> 00:28:23,879
Speaker 1: those things and then they can all fall towards the

593
00:28:23,920 --> 00:28:26,199
Speaker 1: inner Solar system. We could have like you know, a

594
00:28:26,359 --> 00:28:29,240
Speaker 1: rain of comets on the inner Solar system, which would

595
00:28:29,280 --> 00:28:32,160
Speaker 1: be bad. That doesn't sound good. It does not sound good.

596
00:28:32,240 --> 00:28:34,239
Speaker 1: That's not hope for a start to come here. But

597
00:28:34,359 --> 00:28:37,160
Speaker 1: I think let's maybe think about the less dangerous case

598
00:28:37,240 --> 00:28:39,120
Speaker 1: that he might be asking about, which is like, what

599
00:28:39,200 --> 00:28:41,640
Speaker 1: if there's a star, you know, not coming near us,

600
00:28:41,640 --> 00:28:43,560
Speaker 1: but you know at least sort of towards us a

601
00:28:43,600 --> 00:28:46,840
Speaker 1: little bit, or you know, in our neighborhood. Can we

602
00:28:47,120 --> 00:28:49,200
Speaker 1: aim for that star. Yeah, it's a good idea. The

603
00:28:49,200 --> 00:28:51,280
Speaker 1: issue is that most of the stars are sort of

604
00:28:51,320 --> 00:28:54,160
Speaker 1: moving together. Like we were just talking about, the galaxy

605
00:28:54,280 --> 00:28:56,840
Speaker 1: is a big swirl of stars, but they are rotating

606
00:28:56,880 --> 00:29:00,160
Speaker 1: around the center of the galaxy and mostly together there.

607
00:29:00,440 --> 00:29:02,800
Speaker 1: You know, it's like a huge crowd, all running in

608
00:29:02,840 --> 00:29:05,920
Speaker 1: the same direction. So their velocity relative to the center

609
00:29:05,920 --> 00:29:07,960
Speaker 1: of the galaxy is really high. Like the Sun is

610
00:29:07,960 --> 00:29:10,480
Speaker 1: moving really fast relative to the center of the galaxy,

611
00:29:10,600 --> 00:29:13,320
Speaker 1: but it's sort of moving together with all the other stars.

612
00:29:13,520 --> 00:29:15,720
Speaker 1: Not in parallel because it's moving in a circle, but

613
00:29:15,800 --> 00:29:17,800
Speaker 1: you know, there's all sort of moving with very small

614
00:29:17,920 --> 00:29:20,560
Speaker 1: velocity relative to each other. I see. It's like we're

615
00:29:20,600 --> 00:29:23,840
Speaker 1: all in a lazy river. We're all kind of in

616
00:29:23,880 --> 00:29:26,640
Speaker 1: the same flow of stars. We're all in the same

617
00:29:26,640 --> 00:29:29,840
Speaker 1: flow exactly. And astronomers talk about this. They measure like

618
00:29:29,880 --> 00:29:32,680
Speaker 1: the local standard of rest where they take all those

619
00:29:32,720 --> 00:29:35,960
Speaker 1: stars nearby and they take their average velocity. They say,

620
00:29:36,040 --> 00:29:38,080
Speaker 1: all right, let's define that to be like the rest

621
00:29:38,160 --> 00:29:41,480
Speaker 1: frame of the neighborhood, and then they measure the velocity

622
00:29:41,520 --> 00:29:43,720
Speaker 1: of stars relative to that, so you know, you can

623
00:29:43,720 --> 00:29:46,040
Speaker 1: ask the question, like, you know, not relative to the

624
00:29:46,040 --> 00:29:48,800
Speaker 1: center of the galaxy, but relative to the other stars

625
00:29:48,840 --> 00:29:51,719
Speaker 1: in the lazy river near me, how fast am I going?

626
00:29:52,240 --> 00:29:53,960
Speaker 1: And so they actually do that, and they measure the

627
00:29:54,080 --> 00:29:57,520
Speaker 1: relative velocity of all the stars nearby, but it's pretty small,

628
00:29:57,640 --> 00:30:00,880
Speaker 1: like stars are mostly in a stable configure duration. Isn't

629
00:30:00,880 --> 00:30:03,040
Speaker 1: that weird? Like you're saying there's no cross traffic of

630
00:30:03,080 --> 00:30:06,440
Speaker 1: stars kind of like, why aren't stars kind of flying

631
00:30:06,440 --> 00:30:08,000
Speaker 1: all over the place? Well, they're moving in the same

632
00:30:08,000 --> 00:30:11,120
Speaker 1: direction for the same reason, right, They're all rotating around

633
00:30:11,120 --> 00:30:13,600
Speaker 1: the center of the galaxy because of its gravity and

634
00:30:13,640 --> 00:30:15,800
Speaker 1: the galaxy form because you have this big blob of

635
00:30:15,840 --> 00:30:19,600
Speaker 1: stuff which compactified to form stars. But originally it was

636
00:30:19,640 --> 00:30:22,960
Speaker 1: sort of spinning, and so that spinning motion is still there.

637
00:30:23,080 --> 00:30:26,600
Speaker 1: So it's sort of angular momentum that started things spinning

638
00:30:26,640 --> 00:30:29,200
Speaker 1: and it's keeping things spinning. And so, you know, if

639
00:30:29,240 --> 00:30:31,680
Speaker 1: you think about the lazy river analogy, it's like, why

640
00:30:31,720 --> 00:30:33,480
Speaker 1: do a bunch of inner tubes in a lazy river

641
00:30:33,600 --> 00:30:35,560
Speaker 1: mostly go at the same speed Because they're in the

642
00:30:35,600 --> 00:30:38,240
Speaker 1: same river, right, Interesting, But I guess maybe a question

643
00:30:38,360 --> 00:30:40,240
Speaker 1: is sort of like in our Solar system. You know,

644
00:30:40,280 --> 00:30:43,040
Speaker 1: we're all in the same many lazy river around the Sun,

645
00:30:43,280 --> 00:30:45,840
Speaker 1: but there are planets to sort of spin around the

646
00:30:45,880 --> 00:30:48,200
Speaker 1: Sun faster than others. And you know, you can play

647
00:30:48,200 --> 00:30:50,240
Speaker 1: all these games, like you know, to get to Mars,

648
00:30:50,280 --> 00:30:53,240
Speaker 1: you give your time the orbit, right, it's a shorter

649
00:30:53,360 --> 00:30:55,840
Speaker 1: or longer trip. You know, why why aren't the stars

650
00:30:56,000 --> 00:30:58,560
Speaker 1: moving at different speeds? Yeah, you're right that the planets

651
00:30:58,560 --> 00:31:01,160
Speaker 1: are moving at different speed, but that's because they are

652
00:31:01,200 --> 00:31:05,040
Speaker 1: at very different distances from the Sun. The closer planets

653
00:31:05,040 --> 00:31:07,680
Speaker 1: moved faster and the further ones moved more slowly. The

654
00:31:07,720 --> 00:31:10,920
Speaker 1: same thing is true for stars in the galaxy. Stars

655
00:31:11,080 --> 00:31:13,880
Speaker 1: much closer into the center are moving faster, but they

656
00:31:13,880 --> 00:31:17,000
Speaker 1: are very very far away from us. Stars much farther

657
00:31:17,160 --> 00:31:20,000
Speaker 1: out from the center are moving more slowly, but they're

658
00:31:20,000 --> 00:31:22,640
Speaker 1: also much further away than we are. All the stars

659
00:31:22,720 --> 00:31:26,320
Speaker 1: in our neighborhood are basically the same distance from the center,

660
00:31:26,360 --> 00:31:29,200
Speaker 1: and so they're moving at roughly the same speed. You

661
00:31:29,320 --> 00:31:31,520
Speaker 1: notice the speed difference is more in the Solar system

662
00:31:31,520 --> 00:31:34,720
Speaker 1: because things here are closer together, so the Milky Way

663
00:31:34,800 --> 00:31:36,840
Speaker 1: is sort of like a lazy river. I mean, it's

664
00:31:36,840 --> 00:31:39,200
Speaker 1: not a rapid thrill, right, it's it's you know, it's

665
00:31:39,200 --> 00:31:42,520
Speaker 1: a chill galaxy. Well, we're actually all moving pretty fast

666
00:31:42,600 --> 00:31:45,000
Speaker 1: relative to the center of the galaxy, but relative to

667
00:31:45,040 --> 00:31:48,000
Speaker 1: each other, we're not moving that fast. Like our Sun

668
00:31:48,200 --> 00:31:51,800
Speaker 1: is only moving at like twenty kilometers per second through

669
00:31:51,880 --> 00:31:54,320
Speaker 1: the local standard rest our Son is actually a bit

670
00:31:54,400 --> 00:31:57,160
Speaker 1: zippier than the other stars in our lazy river, but

671
00:31:57,200 --> 00:31:59,640
Speaker 1: not by that much. You know, twenty kilometers per second

672
00:31:59,720 --> 00:32:02,720
Speaker 1: is nothing on the scale of the galaxy, right, it's

673
00:32:02,720 --> 00:32:06,120
Speaker 1: super fast twenty kilometers in one second, but in the

674
00:32:06,160 --> 00:32:09,560
Speaker 1: scale of Giant's Son, it's like it's just crawling along.

675
00:32:10,040 --> 00:32:11,920
Speaker 1: And if you look at all the stars in our neighborhood,

676
00:32:12,160 --> 00:32:14,800
Speaker 1: most of them have like a relative velocity to the

677
00:32:14,840 --> 00:32:18,400
Speaker 1: Sun of less than thirty kilometers per second, which is

678
00:32:18,440 --> 00:32:22,160
Speaker 1: really pretty small and not really enough to use Peter's idea.

679
00:32:22,200 --> 00:32:23,960
Speaker 1: None of them are really going fast enough to make

680
00:32:24,000 --> 00:32:26,360
Speaker 1: it easier to get to them. So it is sort

681
00:32:26,360 --> 00:32:28,560
Speaker 1: of like that you know, kindergarten group of kids that

682
00:32:28,640 --> 00:32:31,680
Speaker 1: everyone's staying together. Yeah, there is one star, Bernard's Star,

683
00:32:31,720 --> 00:32:33,560
Speaker 1: which is six light years away. This is the one

684
00:32:33,600 --> 00:32:36,080
Speaker 1: that has the highest velocity relative to the Sun, like

685
00:32:36,360 --> 00:32:39,320
Speaker 1: coming closer to us. It's moving at us at about

686
00:32:39,360 --> 00:32:43,720
Speaker 1: a hundred and ten kilometers per second. That's the fastest one, right,

687
00:32:43,760 --> 00:32:46,520
Speaker 1: But it's like millions of kilometers way, so it's not

688
00:32:46,600 --> 00:32:48,560
Speaker 1: coming near us anytime soon. Even if it was going

689
00:32:48,560 --> 00:32:52,360
Speaker 1: a thousand kilometers per second, that's still one three hundreds

690
00:32:52,400 --> 00:32:54,760
Speaker 1: of the speed of light. So, you know, I think

691
00:32:54,800 --> 00:32:57,080
Speaker 1: Peter was hoping that some stars are approaching us at

692
00:32:57,120 --> 00:32:59,240
Speaker 1: like half the speed of light, so they wouldn't take

693
00:32:59,280 --> 00:33:01,440
Speaker 1: that long to get there. So even if you pick

694
00:33:01,480 --> 00:33:04,280
Speaker 1: a star moving towards us that a thousand kilometers per

695
00:33:04,320 --> 00:33:07,240
Speaker 1: second and there aren't any nearby, you wouldn't automatically have

696
00:33:07,360 --> 00:33:09,640
Speaker 1: a fast speed relative to the star. It's still a

697
00:33:09,680 --> 00:33:12,240
Speaker 1: tiny fraction of the speed of light. So things are

698
00:33:12,320 --> 00:33:14,360
Speaker 1: sort of moving relative to each other, but not in

699
00:33:14,400 --> 00:33:17,000
Speaker 1: any you know way that it can help us, really

700
00:33:17,040 --> 00:33:19,840
Speaker 1: because the distances are so big. But there are some

701
00:33:19,920 --> 00:33:22,040
Speaker 1: crazy stars in the Milky Way. They are these stars

702
00:33:22,080 --> 00:33:26,040
Speaker 1: called hyper velocity stars that are moving really really fast,

703
00:33:26,400 --> 00:33:29,720
Speaker 1: more than a thousand kilometers per second relative to their neighborhood.

704
00:33:29,880 --> 00:33:31,920
Speaker 1: So there are some sort of like out of control stars,

705
00:33:31,920 --> 00:33:34,240
Speaker 1: but not very many. There's like a thousand of them

706
00:33:34,320 --> 00:33:36,959
Speaker 1: spread out through the whole Milky Way. Of its hundreds

707
00:33:37,000 --> 00:33:40,920
Speaker 1: of billions of stars. Wow, only a thousand. Interesting astronomers

708
00:33:40,960 --> 00:33:43,120
Speaker 1: think that they probably had like a close encounter with

709
00:33:43,200 --> 00:33:45,120
Speaker 1: the black hole at the center of the Milky Way

710
00:33:45,120 --> 00:33:47,800
Speaker 1: and then just got like thrown out from the craziness

711
00:33:47,840 --> 00:33:49,920
Speaker 1: of the action there and are now like on their

712
00:33:49,960 --> 00:33:52,560
Speaker 1: way to escape the galaxy. I think they've measured the

713
00:33:52,600 --> 00:33:54,360
Speaker 1: contents of the star and there's a lot of sugar

714
00:33:54,400 --> 00:33:59,560
Speaker 1: in it. That's a myth man's myth, so maybe they

715
00:33:59,640 --> 00:34:01,520
Speaker 1: like out to close to the center and then got

716
00:34:01,560 --> 00:34:04,200
Speaker 1: spewed out or something. But for the most part, the

717
00:34:04,480 --> 00:34:07,040
Speaker 1: galaxy is a pretty calm place, and we're not moving

718
00:34:07,120 --> 00:34:09,680
Speaker 1: very fast relative to any of our nearby stars, and

719
00:34:09,719 --> 00:34:12,720
Speaker 1: so unfortunately, while that's a great idea Pere, it doesn't

720
00:34:12,719 --> 00:34:16,200
Speaker 1: actually work in our case. Sorry Peter, but it is

721
00:34:16,280 --> 00:34:18,080
Speaker 1: I guess a good thing that the universe is kind

722
00:34:18,120 --> 00:34:20,520
Speaker 1: of a chill place. Otherwise, who knows, we could have

723
00:34:20,600 --> 00:34:23,839
Speaker 1: stars kind of zipping by and killing our orbits or

724
00:34:23,960 --> 00:34:27,239
Speaker 1: causing comment storms. So it's kind of a good thing, right,

725
00:34:27,239 --> 00:34:29,640
Speaker 1: that things are chill. Absolutely, it's a good thing. It's

726
00:34:29,760 --> 00:34:33,080
Speaker 1: necessary for life to form and for civilizations to prosper.

727
00:34:33,200 --> 00:34:35,759
Speaker 1: But great question. Thank you Peter for writing in. And

728
00:34:35,800 --> 00:34:38,200
Speaker 1: so let's get to our last question of today, and

729
00:34:38,320 --> 00:34:41,040
Speaker 1: that has to do with the sound of the universe.

730
00:34:41,800 --> 00:34:56,680
Speaker 1: But first let's take another quick break. All right, we

731
00:34:56,680 --> 00:34:59,080
Speaker 1: are celebrating the release of our new book frequently ask

732
00:34:59,200 --> 00:35:01,359
Speaker 1: questions about the Diniverse, which is out now. You can

733
00:35:01,400 --> 00:35:04,319
Speaker 1: get it at universe f a Q dot Calm. It's

734
00:35:04,320 --> 00:35:06,640
Speaker 1: a pretty good book, right, Daniel. I think it's more

735
00:35:06,680 --> 00:35:09,440
Speaker 1: than just pretty good. I think it's hilarious. It's insightful,

736
00:35:09,760 --> 00:35:12,439
Speaker 1: it's clever, it's really fun tour of all the big

737
00:35:12,520 --> 00:35:15,279
Speaker 1: questions about the universe answered in a way that makes

738
00:35:15,280 --> 00:35:17,440
Speaker 1: sense to you. Yeah, we got some good reviews and

739
00:35:17,480 --> 00:35:20,160
Speaker 1: publishers Weekly and Kirkis. People seem to like this book.

740
00:35:20,200 --> 00:35:22,680
Speaker 1: Even my kids enjoyed reading it. Oh my goodness, that

741
00:35:22,760 --> 00:35:25,960
Speaker 1: is the ultimate compliment. My kids don't even know what

742
00:35:26,000 --> 00:35:28,600
Speaker 1: I do. To be honest, I wonder where your kids

743
00:35:28,640 --> 00:35:30,800
Speaker 1: would say if I asked them. He wears pajamas for

744
00:35:30,840 --> 00:35:34,960
Speaker 1: a living. He takes naps in the couch. They pay

745
00:35:35,040 --> 00:35:37,319
Speaker 1: him for that right. No, I think they've lost track

746
00:35:37,360 --> 00:35:39,080
Speaker 1: of all the things that I did my hands in.

747
00:35:39,440 --> 00:35:42,400
Speaker 1: But we are celebrating today, and we're celebrating by answering

748
00:35:42,480 --> 00:35:46,800
Speaker 1: listener questions. Instead. We've answered questions about gravity and about

749
00:35:46,960 --> 00:35:49,200
Speaker 1: visiting other stars, and now we have a great question

750
00:35:49,320 --> 00:35:53,919
Speaker 1: from Addison about whether the universe has a sound. Hey,

751
00:35:54,040 --> 00:35:57,480
Speaker 1: Danieline Jorrie, I've got a question for you about the

752
00:35:57,560 --> 00:36:01,040
Speaker 1: early universe and sound. It sounds like early universe was

753
00:36:01,160 --> 00:36:05,480
Speaker 1: dense enough, add enough stuff close enough together to have sound,

754
00:36:05,520 --> 00:36:08,560
Speaker 1: to have sound waves propagate through it. Is there a

755
00:36:08,600 --> 00:36:10,759
Speaker 1: reason why we don't see the rippling effects of sound

756
00:36:10,800 --> 00:36:13,280
Speaker 1: waves from the early universe when we look at it today.

757
00:36:13,480 --> 00:36:16,480
Speaker 1: Did some sort of force erase that signature? Or were

758
00:36:16,520 --> 00:36:20,120
Speaker 1: acoustic waves just not as impactful or powerful as you

759
00:36:20,160 --> 00:36:23,640
Speaker 1: would think? Thank you all right? Sounds like a great question.

760
00:36:23,800 --> 00:36:25,759
Speaker 1: It sounds like it's time to talk about it. I

761
00:36:25,840 --> 00:36:28,839
Speaker 1: like the sound of that. Thank you, Addison. It's an

762
00:36:28,840 --> 00:36:33,160
Speaker 1: interesting question. I think he's asking whether in the early universe,

763
00:36:33,239 --> 00:36:35,759
Speaker 1: when it was you know, really compact, whether things were

764
00:36:35,800 --> 00:36:39,279
Speaker 1: so dance that you could have sound waves traveling through

765
00:36:39,320 --> 00:36:43,160
Speaker 1: that dense, you know, primordial stuff and he's asking if

766
00:36:43,200 --> 00:36:45,479
Speaker 1: we can see those ripples, or why can't we see

767
00:36:45,480 --> 00:36:48,160
Speaker 1: those ripples today? I guess maybe. You know, when most

768
00:36:48,200 --> 00:36:50,919
Speaker 1: people think of sound, they think of sound through air,

769
00:36:51,080 --> 00:36:52,919
Speaker 1: which is what we used to talk to each other

770
00:36:52,960 --> 00:36:56,880
Speaker 1: and listen to music. But sound can travel through anything, right, water,

771
00:36:57,200 --> 00:37:00,359
Speaker 1: even solid materials can have sound waves traveling through the Yeah,

772
00:37:00,360 --> 00:37:03,200
Speaker 1: you can travel through almost anything. It's any material that

773
00:37:03,280 --> 00:37:06,120
Speaker 1: has pressure, any material with like the particles bump into

774
00:37:06,160 --> 00:37:08,920
Speaker 1: each other and push against each other. For example, we

775
00:37:09,000 --> 00:37:12,239
Speaker 1: don't think that dark matter can feel sound because dark matter,

776
00:37:12,239 --> 00:37:14,440
Speaker 1: if it's made of particles, we don't think they feel

777
00:37:14,440 --> 00:37:16,480
Speaker 1: each other. They pass right through each other. So you

778
00:37:16,480 --> 00:37:18,879
Speaker 1: can't have sound waves in dark matter. But in any

779
00:37:18,920 --> 00:37:21,000
Speaker 1: other kind of matter, yeah, you can have sound waves.

780
00:37:21,040 --> 00:37:23,640
Speaker 1: They're just like these compression waves. You push on the surface,

781
00:37:23,680 --> 00:37:25,320
Speaker 1: for example, and it pushes on the next one, It

782
00:37:25,360 --> 00:37:27,120
Speaker 1: pushes on the next one, it pushes on the next one,

783
00:37:27,360 --> 00:37:30,160
Speaker 1: and that's the sound wave just traveling through. But the

784
00:37:30,160 --> 00:37:32,080
Speaker 1: way it gets from one layer to the next is

785
00:37:32,239 --> 00:37:34,840
Speaker 1: having some interaction between the particles. It's kind of like

786
00:37:34,840 --> 00:37:37,160
Speaker 1: a crowded room. If people are crowded together, then you

787
00:37:37,200 --> 00:37:39,759
Speaker 1: can have you know, kind of waves where people push

788
00:37:39,760 --> 00:37:42,520
Speaker 1: each other, but it's a bad party and everyone's really

789
00:37:42,520 --> 00:37:44,880
Speaker 1: far away from each other. You can't really kind of

790
00:37:44,880 --> 00:37:47,200
Speaker 1: have that, right or you can see this in traffic also,

791
00:37:47,280 --> 00:37:49,560
Speaker 1: like when somebody slams on the brakes, then the car

792
00:37:49,640 --> 00:37:51,239
Speaker 1: behind them slams on the brakes, and then the sort

793
00:37:51,280 --> 00:37:54,439
Speaker 1: of break slamming passes down the road all the way

794
00:37:54,440 --> 00:37:56,840
Speaker 1: down right. You can see it in like the brake lights. Yeah,

795
00:37:56,960 --> 00:37:58,920
Speaker 1: so that's the same sort of deal because the person

796
00:37:59,040 --> 00:38:00,840
Speaker 1: is reacting to the car in front of them, and

797
00:38:00,880 --> 00:38:02,759
Speaker 1: so that's the sort of the interaction. And so the

798
00:38:02,880 --> 00:38:05,400
Speaker 1: universe right now is pretty empty and things are fairly

799
00:38:05,440 --> 00:38:08,000
Speaker 1: far apart, so you don't you just don't see these

800
00:38:08,120 --> 00:38:10,480
Speaker 1: kinds of sound waves going through the universe. But I

801
00:38:10,520 --> 00:38:12,920
Speaker 1: think Addison is saying maybe in the early universe, when

802
00:38:12,960 --> 00:38:16,719
Speaker 1: things really crunched together, you could have sound waves, and

803
00:38:16,760 --> 00:38:18,560
Speaker 1: maybe they could you could still see them today or

804
00:38:18,600 --> 00:38:20,880
Speaker 1: the effects of them. Yeah, you actually can still see

805
00:38:20,920 --> 00:38:23,320
Speaker 1: them today. Like there are sound waves in the universe

806
00:38:23,520 --> 00:38:26,600
Speaker 1: right now, like big clouds of gas running into each other,

807
00:38:26,640 --> 00:38:28,919
Speaker 1: and you can see shock waves, and so that's really

808
00:38:28,960 --> 00:38:31,640
Speaker 1: equivalent to sound waves. You know, we have pressure waves

809
00:38:31,640 --> 00:38:34,760
Speaker 1: in these mammoth clouds of gas. Some of them probably

810
00:38:34,800 --> 00:38:37,280
Speaker 1: are the reasons why stars form, you know, a cloud

811
00:38:37,280 --> 00:38:39,759
Speaker 1: of gas, and what triggers the collapse into a star.

812
00:38:39,880 --> 00:38:42,920
Speaker 1: It might be a shock wave from a nearby supernova,

813
00:38:43,000 --> 00:38:46,120
Speaker 1: so that's also a sound wave. But yeah, the sound

814
00:38:46,120 --> 00:38:48,919
Speaker 1: waves were definitely stronger in the early university, right, because

815
00:38:48,920 --> 00:38:51,360
Speaker 1: the universe was much denser, right, we think in the

816
00:38:51,480 --> 00:38:54,360
Speaker 1: very beginning, everything was sort of like it is today

817
00:38:54,400 --> 00:38:56,560
Speaker 1: in the center of the sun. You know, it's hot,

818
00:38:56,640 --> 00:39:00,239
Speaker 1: it's dense, it's crazy, and so they're definitely worse sound

819
00:39:00,239 --> 00:39:02,800
Speaker 1: waves back then. Yeah. So I guess in the early

820
00:39:02,880 --> 00:39:06,200
Speaker 1: universe before or during the Big Bang, things were compact

821
00:39:06,320 --> 00:39:08,200
Speaker 1: enough for there to be sound. But how does that

822
00:39:08,280 --> 00:39:12,800
Speaker 1: even work? Like things? It's like sound through ions through quarks.

823
00:39:12,880 --> 00:39:15,040
Speaker 1: What does that mean? Yea, So imagine that this is

824
00:39:15,080 --> 00:39:17,239
Speaker 1: after the Big Bang now, and which you have in

825
00:39:17,239 --> 00:39:21,160
Speaker 1: the universe is a bunch of like protons and electrons

826
00:39:21,320 --> 00:39:23,759
Speaker 1: and photons and then a bunch of dark matter. So

827
00:39:23,800 --> 00:39:26,200
Speaker 1: you have this big soup and it's very very dense, right,

828
00:39:26,280 --> 00:39:28,719
Speaker 1: and so sometimes you'll get like a bunch of dark

829
00:39:28,760 --> 00:39:33,040
Speaker 1: matter clumped together an over density and it's incredible gravity

830
00:39:33,120 --> 00:39:36,160
Speaker 1: will pull things together, you know, like pull everything together.

831
00:39:36,320 --> 00:39:39,200
Speaker 1: But then those molecules will resist, like the protons don't

832
00:39:39,200 --> 00:39:42,080
Speaker 1: like to be squeezed together, and all the photons bouncing

833
00:39:42,120 --> 00:39:44,560
Speaker 1: around have a lot of energy, and so it'll sort

834
00:39:44,560 --> 00:39:47,080
Speaker 1: of like bounce back and it will make these waves.

835
00:39:47,480 --> 00:39:50,120
Speaker 1: And so because dark matter creates something of higher pressure,

836
00:39:50,239 --> 00:39:52,920
Speaker 1: that higher pressure than propagates out. So you get this

837
00:39:53,000 --> 00:39:55,880
Speaker 1: like sound wave of this like ringing through the plasma

838
00:39:55,960 --> 00:39:59,600
Speaker 1: of the early universe in response to these momentary over

839
00:39:59,640 --> 00:40:02,840
Speaker 1: density these Wait what you're saying that in the early

840
00:40:02,920 --> 00:40:06,120
Speaker 1: universe it was dark matter that was making sounds. Absolutely

841
00:40:06,160 --> 00:40:08,680
Speaker 1: dark matter triggers it, right, you know, imagine you have

842
00:40:08,760 --> 00:40:11,000
Speaker 1: this big plasma and it's just sort of like hanging

843
00:40:11,040 --> 00:40:13,200
Speaker 1: out and it's quiet. Well, how do you make like

844
00:40:13,239 --> 00:40:15,040
Speaker 1: a ripple in it? You know, you need to like

845
00:40:15,120 --> 00:40:17,440
Speaker 1: flick it, just like if you have a surface of water,

846
00:40:17,680 --> 00:40:19,279
Speaker 1: how do you make waves through it? But you know

847
00:40:19,360 --> 00:40:22,160
Speaker 1: you tap the surface. And so dark matter is still

848
00:40:22,160 --> 00:40:25,279
Speaker 1: the overwhelming source of gravity in the universe, even back then.

849
00:40:25,520 --> 00:40:27,439
Speaker 1: If you have a clump of over dense dark matter,

850
00:40:27,480 --> 00:40:31,120
Speaker 1: it like pulls together the other stuff nearby effectively like

851
00:40:31,160 --> 00:40:33,800
Speaker 1: tapping on the surface of the plasma and it creates

852
00:40:33,840 --> 00:40:36,879
Speaker 1: this pressure wave in response that rings out from those

853
00:40:36,960 --> 00:40:39,560
Speaker 1: dark matter centers. But what clump the dark matter in

854
00:40:39,600 --> 00:40:42,160
Speaker 1: the first place, Well, that's just random fluctuations. Like we

855
00:40:42,200 --> 00:40:45,759
Speaker 1: think that the early universe was not totally smooth. You

856
00:40:45,920 --> 00:40:48,400
Speaker 1: think that there were just like a random quantum fluctuations

857
00:40:48,440 --> 00:40:50,640
Speaker 1: from the very very beginning of the universe that got

858
00:40:50,680 --> 00:40:54,319
Speaker 1: blown up by inflation to be macroscopic. So you have

859
00:40:54,440 --> 00:40:56,839
Speaker 1: this dark matter that's like a little bit clumpy in

860
00:40:56,880 --> 00:41:00,279
Speaker 1: some places due to quantum fluctuations. Then those he did

861
00:41:00,320 --> 00:41:03,719
Speaker 1: these pressure centers, which led to sound wave propagating through

862
00:41:03,760 --> 00:41:06,560
Speaker 1: this early universe plasma. Interesting, so like a little bit

863
00:41:06,600 --> 00:41:09,520
Speaker 1: of dark matter clump tier Dad brought in a little

864
00:41:09,520 --> 00:41:12,360
Speaker 1: bit of the plasma, and then that pulled pulled some

865
00:41:12,480 --> 00:41:14,799
Speaker 1: of the plasma around it, and that creates kind of

866
00:41:14,840 --> 00:41:17,920
Speaker 1: a wave. And then this wave travels out through the

867
00:41:17,960 --> 00:41:20,920
Speaker 1: early universe and travels really really fast because the universe

868
00:41:21,000 --> 00:41:23,920
Speaker 1: was very very dense, and dense materials have a very

869
00:41:24,080 --> 00:41:26,920
Speaker 1: high speed of sound. Right, You know that sound travels

870
00:41:26,960 --> 00:41:29,560
Speaker 1: faster through water or through steel, and it does through

871
00:41:29,600 --> 00:41:32,279
Speaker 1: air because you have like more tightly packed particles they

872
00:41:32,280 --> 00:41:34,920
Speaker 1: transmit the information faster from one to the other, and

873
00:41:34,960 --> 00:41:37,240
Speaker 1: so the speed of sound back then was like half

874
00:41:37,239 --> 00:41:40,680
Speaker 1: of the speed of light. What like sound and light

875
00:41:40,920 --> 00:41:44,080
Speaker 1: or almost you know, in the same magnitude of speed. Yeah, exactly,

876
00:41:44,160 --> 00:41:47,000
Speaker 1: Light traveled faster. Obviously, nothing can travel faster than light.

877
00:41:47,200 --> 00:41:49,719
Speaker 1: But these sound waves were so fast because the early

878
00:41:49,800 --> 00:41:52,840
Speaker 1: universe was so dense. But then what happens to these waves?

879
00:41:52,960 --> 00:41:56,040
Speaker 1: Do they just keep propagating forever or did the universe

880
00:41:56,120 --> 00:41:59,520
Speaker 1: when it finished expanding kind of killed these waves. Yeah,

881
00:41:59,520 --> 00:42:02,480
Speaker 1: that's exactly what happened. The universe kept expanding, and then

882
00:42:02,480 --> 00:42:05,600
Speaker 1: it cooled down, right, and then these protons and the

883
00:42:05,840 --> 00:42:09,239
Speaker 1: electrons weren't flying free anymore. They lost some energy. They

884
00:42:09,239 --> 00:42:12,640
Speaker 1: were cooler, so they fell into atoms. Than the universe neutralized, right,

885
00:42:13,040 --> 00:42:15,360
Speaker 1: and it became these dark ages like we talked about,

886
00:42:15,719 --> 00:42:17,719
Speaker 1: And so they're no longer like a lot of photons

887
00:42:17,760 --> 00:42:20,600
Speaker 1: interacting with stuff, and things got a lot less dense,

888
00:42:20,920 --> 00:42:23,560
Speaker 1: and so the speed of sound dropped a lot, right,

889
00:42:23,640 --> 00:42:25,160
Speaker 1: all of a sudden, the speed of sound went from

890
00:42:25,200 --> 00:42:27,520
Speaker 1: like half the speed of light too much much much

891
00:42:27,600 --> 00:42:31,320
Speaker 1: much smaller, and it's sort of like froze. These ripples

892
00:42:31,440 --> 00:42:34,600
Speaker 1: these ripples which were moving really really fast screaming out

893
00:42:34,640 --> 00:42:36,640
Speaker 1: from these dark matter centers, all of a sudden, they

894
00:42:36,640 --> 00:42:39,000
Speaker 1: couldn't move very fast anymore, so they got kind of

895
00:42:39,000 --> 00:42:41,200
Speaker 1: frozen there because I guess they didn't have anything to

896
00:42:41,239 --> 00:42:44,319
Speaker 1: push against, right, Yeah, exactly. There's no more pressure coming

897
00:42:44,320 --> 00:42:46,879
Speaker 1: out because these photons are no longer coupled to the matter,

898
00:42:46,920 --> 00:42:49,200
Speaker 1: and the photons were something that was really driving this.

899
00:42:49,680 --> 00:42:51,680
Speaker 1: And then you have all these neutral atoms which aren't

900
00:42:51,680 --> 00:42:55,239
Speaker 1: interacting as much as protons and electrons do, and so

901
00:42:55,280 --> 00:42:57,080
Speaker 1: the speed of sound is much much lower, and so

902
00:42:57,160 --> 00:42:59,040
Speaker 1: all of a sudden, that sound wave just sort of

903
00:42:59,080 --> 00:43:01,480
Speaker 1: like boom it. It's the brakes and it's sort of

904
00:43:01,520 --> 00:43:03,880
Speaker 1: stuck there. And the really cool thing is that we

905
00:43:03,920 --> 00:43:08,120
Speaker 1: can still see those in the universe today, what the

906
00:43:08,280 --> 00:43:12,520
Speaker 1: frozen sounds from the Big Bang caused by dark matter.

907
00:43:12,960 --> 00:43:15,319
Speaker 1: You can see that absolutely because what you see out

908
00:43:15,320 --> 00:43:18,080
Speaker 1: there in the universe are patterns in where galaxies are.

909
00:43:18,280 --> 00:43:21,120
Speaker 1: See at the very center of these pressure centers, there

910
00:43:21,160 --> 00:43:22,799
Speaker 1: was a lot of dark matter, as you expect a

911
00:43:22,840 --> 00:43:25,360
Speaker 1: lot of matter to fall in and formed galaxies, and

912
00:43:25,360 --> 00:43:27,719
Speaker 1: then also sort of on the edge of this frozen

913
00:43:27,800 --> 00:43:31,040
Speaker 1: bubble where this wave was when it got frozen, you

914
00:43:31,120 --> 00:43:33,759
Speaker 1: expect that to be denser than everything else. And so

915
00:43:33,800 --> 00:43:36,400
Speaker 1: if you just look around the universe and you calculate

916
00:43:36,440 --> 00:43:39,319
Speaker 1: like the average distance between galaxies, you find a lot

917
00:43:39,360 --> 00:43:42,879
Speaker 1: of clumps, and then you also find these big bubbles

918
00:43:42,960 --> 00:43:46,239
Speaker 1: of galaxies around the clumps, exactly the place you would

919
00:43:46,239 --> 00:43:50,160
Speaker 1: expect to see from these frozen sound waves. Who so

920
00:43:50,280 --> 00:43:52,879
Speaker 1: are you saying that this structure of the universe, because

921
00:43:52,920 --> 00:43:57,200
Speaker 1: I know we're like organized in clusters of galaxies, superclusters,

922
00:43:57,239 --> 00:44:00,360
Speaker 1: and then sheets and bubbles. Those bulls are b because

923
00:44:00,440 --> 00:44:04,359
Speaker 1: of the initial shock wave of the universe. Absolutely, it's

924
00:44:04,360 --> 00:44:08,040
Speaker 1: called barry On acoustic oscillation. And so you can see

925
00:44:08,080 --> 00:44:11,600
Speaker 1: these bubbles in the universe today, like galaxies are organized

926
00:44:11,920 --> 00:44:14,680
Speaker 1: more likely on the surface or on the centers of

927
00:44:14,719 --> 00:44:17,400
Speaker 1: these bubbles than sort of in the middle of the bubbles.

928
00:44:17,520 --> 00:44:20,080
Speaker 1: And there's all these overlapping bubbles. You get places where

929
00:44:20,080 --> 00:44:22,319
Speaker 1: like the sheets cross each other and you get an

930
00:44:22,320 --> 00:44:26,320
Speaker 1: over density. It's really pretty incredible. It's also a super

931
00:44:26,320 --> 00:44:29,600
Speaker 1: cool way to measure the expansion of the universe because

932
00:44:29,680 --> 00:44:32,160
Speaker 1: we can calculate how big those bubbles should have been

933
00:44:32,200 --> 00:44:35,640
Speaker 1: when they were formed. Because it's just like calculations about plasma,

934
00:44:35,640 --> 00:44:37,560
Speaker 1: and we know how to do those calculations, and then

935
00:44:37,560 --> 00:44:39,759
Speaker 1: we can measure how big they are today, and that

936
00:44:39,800 --> 00:44:43,000
Speaker 1: gives us a completely independent measurement of how much the

937
00:44:43,080 --> 00:44:46,400
Speaker 1: universe has expanded. It's like a standard ruler. Oh. Interesting,

938
00:44:46,440 --> 00:44:48,359
Speaker 1: you can see like how big the bubbles are, and

939
00:44:48,400 --> 00:44:50,920
Speaker 1: that tells you how much the universe group. Yeah, and

940
00:44:50,920 --> 00:44:52,400
Speaker 1: so we have all these piece of evidence that the

941
00:44:52,480 --> 00:44:55,400
Speaker 1: universe expanded. This is a completely separate one from like

942
00:44:55,760 --> 00:44:58,200
Speaker 1: looking at the stars and the supernova and all the

943
00:44:58,239 --> 00:45:00,400
Speaker 1: other ways. And the cool thing is that it tells

944
00:45:00,400 --> 00:45:03,040
Speaker 1: the same story, right, It tells us the same story

945
00:45:03,080 --> 00:45:05,000
Speaker 1: about the expansion of the universe that all the other

946
00:45:05,040 --> 00:45:07,080
Speaker 1: ones do. And I love when that happens. When you

947
00:45:07,080 --> 00:45:10,319
Speaker 1: have completely different methods with totally different ways to make

948
00:45:10,360 --> 00:45:12,719
Speaker 1: mistakes and they all tell you the same story. That's

949
00:45:12,719 --> 00:45:15,480
Speaker 1: when you know you've really solved the detective mry, Like

950
00:45:15,560 --> 00:45:18,200
Speaker 1: you found the murderer. You kind of red handed got

951
00:45:18,200 --> 00:45:22,120
Speaker 1: the universe with its dark matter hand in the honey jar. Yeah.

952
00:45:22,160 --> 00:45:24,640
Speaker 1: It's also cool to see these things in real life.

953
00:45:24,640 --> 00:45:26,920
Speaker 1: You know, we have this picture in our minds of

954
00:45:26,960 --> 00:45:29,240
Speaker 1: this thing happening in the early universe, and it feels

955
00:45:29,280 --> 00:45:31,719
Speaker 1: kind of abstract because it's something that happened a long

956
00:45:31,760 --> 00:45:34,160
Speaker 1: time ago, when the rules of the universe seemed really

957
00:45:34,160 --> 00:45:36,400
Speaker 1: really different. But if you look out there in the

958
00:45:36,520 --> 00:45:39,560
Speaker 1: night sky, they are still there. Those bubbles are there

959
00:45:39,600 --> 00:45:42,560
Speaker 1: to see. It's really incredible to see it imprinted on

960
00:45:42,600 --> 00:45:45,719
Speaker 1: the sky itself. But you kind of need a special telescope, right,

961
00:45:45,760 --> 00:45:47,640
Speaker 1: You can't see it with the naked eye, but it's

962
00:45:47,680 --> 00:45:50,239
Speaker 1: there for us to see it somehow. Yeah, that's right.

963
00:45:50,239 --> 00:45:51,799
Speaker 1: You need telescopes. You need to look at a lot

964
00:45:51,840 --> 00:45:54,919
Speaker 1: of galaxies and do some calculations, but it's definitely there.

965
00:45:54,960 --> 00:45:58,040
Speaker 1: It's pretty cool that, you know, like the universe, you know,

966
00:45:58,120 --> 00:46:00,760
Speaker 1: kind of rang out or cried as it was born

967
00:46:00,920 --> 00:46:03,759
Speaker 1: and that got frozen in its structure. Yeah, but we

968
00:46:03,800 --> 00:46:05,600
Speaker 1: could also make it positive. You could say it's like

969
00:46:05,800 --> 00:46:08,719
Speaker 1: a singing of the universe, you know, its moment of

970
00:46:08,840 --> 00:46:13,160
Speaker 1: joy of this creation, because that's how all babies come out,

971
00:46:13,640 --> 00:46:16,319
Speaker 1: come out singing such pleasant sounds. Yeah, or you could

972
00:46:16,440 --> 00:46:19,400
Speaker 1: consider it this screaming crying of the painful birth of

973
00:46:19,440 --> 00:46:21,759
Speaker 1: the universe. Either way, it depends on your personality. That's

974
00:46:21,760 --> 00:46:24,000
Speaker 1: a personality test for you, right, there. I guess if

975
00:46:24,040 --> 00:46:26,280
Speaker 1: you have a sort of personality, yeah, you would find

976
00:46:26,640 --> 00:46:29,120
Speaker 1: music in that it would ring sweetly in your ears.

977
00:46:29,480 --> 00:46:31,720
Speaker 1: All right, well, that was our last question for today.

978
00:46:31,760 --> 00:46:35,080
Speaker 1: Thank you, Addison. It sounds like the universe did have

979
00:46:35,160 --> 00:46:37,759
Speaker 1: a sound early in the universe, and we can still

980
00:46:37,800 --> 00:46:40,000
Speaker 1: see it today. We can still see it today, and

981
00:46:40,040 --> 00:46:43,799
Speaker 1: the universe continues to make music. It's very dilute, and

982
00:46:43,840 --> 00:46:46,040
Speaker 1: it's very thin, and the speed of sound is now

983
00:46:46,160 --> 00:46:48,600
Speaker 1: very very slow, but things still do bump into each

984
00:46:48,640 --> 00:46:50,719
Speaker 1: other and still do make noise. What do you think

985
00:46:50,800 --> 00:46:53,439
Speaker 1: is the genre of the music of the universe cosmic chill,

986
00:46:54,360 --> 00:46:58,600
Speaker 1: scream rock. I think dark matters, dark rock. There are

987
00:46:58,640 --> 00:47:01,160
Speaker 1: a lot of rocks, so are a lot of rocks.

988
00:47:01,480 --> 00:47:04,840
Speaker 1: All right, well, thanks for joining us in this podcast

989
00:47:04,840 --> 00:47:06,920
Speaker 1: celebration of the release of our new book. If you're

990
00:47:06,920 --> 00:47:09,359
Speaker 1: not tired of us plugging it, please check it out.

991
00:47:09,400 --> 00:47:11,799
Speaker 1: It's The Universe f a q dot com. It has

992
00:47:11,840 --> 00:47:13,840
Speaker 1: how many questions that we answering the book, Daniel, I

993
00:47:13,880 --> 00:47:16,239
Speaker 1: don't know, that's a great question. I think it's something

994
00:47:16,280 --> 00:47:19,719
Speaker 1: like sixteen sixteen seventeen questions, and we try to make

995
00:47:19,719 --> 00:47:22,440
Speaker 1: them as good questions as possible. Yeah, So thank you

996
00:47:22,440 --> 00:47:25,200
Speaker 1: everybody for your support for this project and for all

997
00:47:25,239 --> 00:47:27,839
Speaker 1: of our projects. And we'd love if you checked out

998
00:47:27,840 --> 00:47:30,320
Speaker 1: this book and if it strikes your fancy, buy a copy.

999
00:47:30,480 --> 00:47:32,759
Speaker 1: Thanks for supporting us, and because we do all this

1000
00:47:32,840 --> 00:47:35,080
Speaker 1: for you, for our listeners, for our readers. This is

1001
00:47:35,120 --> 00:47:39,160
Speaker 1: all about connecting with you and having our sound sort

1002
00:47:39,160 --> 00:47:43,080
Speaker 1: of ripple out into the universe, creating, hopefully pressure ways

1003
00:47:43,120 --> 00:47:46,000
Speaker 1: of knowledge and understanding. Do you think when our collaboration

1004
00:47:46,080 --> 00:47:49,600
Speaker 1: was born that started with the screen. If we didn't scream,

1005
00:47:49,640 --> 00:47:54,080
Speaker 1: then it's screaming now all right, Well, thanks for joining us,

1006
00:47:54,160 --> 00:48:04,560
Speaker 1: Thanks again for your support, See you next time. Thanks

1007
00:48:04,560 --> 00:48:07,239
Speaker 1: for listening, and remember that Daniel and Jorge Explain the

1008
00:48:07,280 --> 00:48:10,399
Speaker 1: Universe is a production of I Heart Radio. Or more

1009
00:48:10,480 --> 00:48:13,840
Speaker 1: podcast from my Heart Radio visit the i heart Radio app,

1010
00:48:14,120 --> 00:48:17,560
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.