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Speaker 1: Hey or he. Are you a fan of boba tea?

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Speaker 2: You mean like bubble tea?

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Speaker 1: Yeah? Is that what the kids are calling it?

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Speaker 2: I think they call it boba, but I think maybe

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Speaker 2: most people might not know what that is. But yeah,

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Speaker 2: I'm a fan. My kids are really into it, so

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Speaker 2: I've grown to like it.

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Speaker 1: Well, my daughter loves it, but personally, I can't get

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Speaker 1: over the fear of being choked by a floating blob

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Speaker 1: every time they take a sip.

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Speaker 2: Oh. Well, first of all, they don't float, which tells

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Speaker 2: me maybe you don't drink boba very often, Busty. The

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Speaker 2: other thing is they're not that big. I think they're

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Speaker 2: pretty much smaller than your throat.

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Speaker 1: I think maybe these new trends are just not for

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Speaker 1: the faint of heart.

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Speaker 2: So do you not like bubbles in general?

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Speaker 1: No, I'm pro bubbles in the universe, just not in

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Speaker 1: my tea, not as a choking hazard.

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Speaker 2: I see what about economic bubbles? Those are bad news?

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Speaker 3: Mmm.

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Speaker 1: I'm hoping to ride the podcast bubble until it pops.

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Speaker 2: Yeah, there you go. Not all bubbles are bad. Hi

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Speaker 2: am Jorge Mack, cartoonist and the author of All Ours

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Speaker 2: Great Big Universe.

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Speaker 1: Hi, I am Daniel, I'm a particle physicist and a

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Speaker 1: professor at UC Irvine, and I'm actually fascinated by the

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Speaker 1: mathematics of bubbles.

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Speaker 2: Oh yeah, it is, and it just a sphere.

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Speaker 1: Some bubbles are spheres, but you can also get bubbles

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Speaker 1: of all sorts of different shapes, which solve really complicated

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Speaker 1: sets of mathematical equations to like minimize surface area.

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Speaker 2: Now is that math or is that physics.

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Speaker 1: It's using physics to solve math. It's like using the

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Speaker 1: universe as a computer. Whoa bubble computers?

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Speaker 4: Man?

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Speaker 2: That sounds like an awesome topic for a podcast episode,

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Speaker 2: but I'm guessing that's not what we're talking about today.

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Speaker 1: We are not talking about my new Bubble Computers startup,

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Speaker 1: which will be serving bubble tea in the lobby, but

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Speaker 1: we are talking about bubbles.

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Speaker 2: You're going to ride that tech bubble. But anyways, welcome

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Speaker 2: to a podcast Daniel and Jorge Explain the Universe, a

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Speaker 2: production of iHeartRadio in.

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Speaker 1: Which we want you to ride the bubble of understanding.

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Speaker 1: As human thought expands further and further into the universe,

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Speaker 1: we understand more and more about this incredible and crazy cosmos.

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Speaker 1: We decode the messages that come to us from all

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Speaker 1: these distant places and try to piece them together into

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Speaker 1: a fragile bubble of understanding.

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Speaker 2: Because it is an awesome universe inflating every day with

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Speaker 2: more and more awesomeness. We like to inflate your brain

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Speaker 2: here on the podcast until it pops with an epiphany

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Speaker 2: about how the universe works.

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Speaker 1: I don't want anybody to bring the pop man. We

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Speaker 1: want to very gently inflate it.

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Speaker 2: I said, with an epiphany.

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Speaker 1: Oh, that sounds terrifying, but you're right. We do want

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Speaker 1: listeners to have that moment of understanding where suddenly things

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Speaker 1: click into place and you go, oh, I get it.

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Speaker 1: This thing I used to hear in that bit, I

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Speaker 1: thought I understood. Those actually fit together into a holistic

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Speaker 1: idea about how the universe works, and that, in the end,

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Speaker 1: is the goal of this podcast.

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Speaker 2: Yeah, we like to taggle the bit mysteries about the

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Speaker 2: universe from its large scale and what kinds of amazing

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Speaker 2: things you can find out there in the reaches of space,

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Speaker 2: but also in the smallest of scales done at the

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Speaker 2: atomic and particle sizes, from the beginning of the universe

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Speaker 2: to the end of the universe.

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Speaker 1: Exactly, and those little bubbles at the particle level in

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Speaker 1: the early universe turn out to have a ripple effect

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Speaker 1: that create bubbles in our universe billions of years later

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Speaker 1: and millions of light years across. It turns out that

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Speaker 1: bubbles are not just the core idea between my future

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Speaker 1: billion dollar bubble computing startup or the drinks that my

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Speaker 1: daughter enjoys. They are also fundamental to understanding the early

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Speaker 1: universe and the structure of the universe today.

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Speaker 2: But you mean you can tie the Big Band to boba.

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Speaker 1: The Big Bang was basically just a bobba bubble.

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Speaker 2: Big bubba bubble bang boom. Yes, Daniel said, a lot

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Speaker 2: of things that happened at the beginning of the universe,

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Speaker 2: even small, microscopic things that were going on, have a

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Speaker 2: huge impact in what the universe looks like today, and

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Speaker 2: maybe even might have tip things in our favor for

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Speaker 2: to be creative and for our galaxy to be the

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Speaker 2: way it is now.

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Speaker 1: One of my favorite things in physics is figuring out

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Speaker 1: a way to sift through the clues that are left

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Speaker 1: to us about what happened in deep time, what happened

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Speaker 1: in the very early universe. If we can figure out

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Speaker 1: the signs and signals, but those early events left for us.

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Speaker 1: We can actually reconstruct a complete history of what happened

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Speaker 1: in the universe. It's like the biggest detective game ever.

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Speaker 2: I don't think they can even trace how boba was invented,

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Speaker 2: so that would be an amazing feed if we can,

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Speaker 2: you know, trace our origin back to the Big Bang.

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Speaker 1: Are you saying it just organically bubbled up from nothing?

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Speaker 2: I don't know, that's the mystery. Maybe it was aliens.

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Speaker 2: I knew that NASA had secret alien technology. I just

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Speaker 2: didn't realize it was Boba technology. Well not NASA, and

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Speaker 2: NASA's is from Earth. Am saying the conspiracy runs deeper?

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Speaker 1: Oh my gosh, wow, intergalactic Boba bubble conspiracy.

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Speaker 2: There you go. That's what the world needs, more conspiracy theories.

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Speaker 1: But we are here on this podcast breaking down conspiratorial

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Speaker 1: nons sense and telling you the truth about what we

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Speaker 1: do and do not know, how we trace back to

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Speaker 1: the history of the early universe and how it affects

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Speaker 1: our lives today.

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Speaker 2: So today on the podcast, we'll be tackling the question

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Speaker 2: what did the early universe sound like? Interesting questions about

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Speaker 2: the sound of the early universe.

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Speaker 1: Yeah, did it sound like somebody choking onbah?

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Speaker 2: Maybe that is the origin of the universe. Maybe they're

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Speaker 2: all here because some intergalactic god choking a giant boba.

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Speaker 1: Exactly. He took his daughter out for intergalactic boba and

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Speaker 1: the rest is history.

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Speaker 2: Yeah, maybe black holes are like the boba of you know,

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Speaker 2: the higher beings.

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Speaker 1: Black hole boba. I will definitely sell that in the

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Speaker 1: cafe of my bubble computing startup.

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Speaker 4: Yeah.

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Speaker 2: They are pretty dense right in drink, They're like thing

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Speaker 2: in the drink.

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Speaker 1: They're terrifying.

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Speaker 2: Oh my gosh, you're really afraid of boba.

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Speaker 1: When I take sip of a I want to enjoy

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Speaker 1: a fresh liquid and not worry that something is going

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Speaker 1: to shoot down my throat. Yeah.

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Speaker 2: I think we've established the bow is not for you.

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Speaker 1: But I am a big fan of bubbles, including sound

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Speaker 1: bubbles in the early universe. People don't usually think about

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Speaker 1: what the universe sounds like because they think about space

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Speaker 1: is being mostly empty and so diffuse that sound waves

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Speaker 1: can't effectively travel through it. But that wasn't always the case.

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Speaker 2: Yeah, so this is an interesting question, and it sounds

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Speaker 2: like the early universe sounds are related to bubbles, like

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Speaker 2: bubbles popping or bubbles forming, bubbles.

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Speaker 1: Forming and slashing around, and even oscillating. In physics, this

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Speaker 1: whole field goes by the fancy name of baryon acoustic

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Speaker 1: oscillation b AO or bow.

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Speaker 2: Mm oh, well we should be talking about bows then, buba.

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Speaker 1: Bubble bow.

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Speaker 2: Those you can't probably choke on if you try to

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Speaker 2: eat a whole one at once.

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Speaker 1: Don't put those in your drinks, folks.

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Speaker 2: Yeah, that that's an interesting idea, Daniel. You might have

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Speaker 2: invented the newest trend.

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Speaker 1: Is that going to start a whole new universe?

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Speaker 2: Maybe? Yeah, maybe somebody will struggle to swelling one and

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Speaker 2: originate a whole new universe of lawsuits, I'm guessing. But anyways,

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Speaker 2: it's an interesting question. What did the early universe sound like?

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Speaker 2: And it sounds like it's related to something called the

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Speaker 2: baryon acoustic oscillation, and so, as usual, we were wondering

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Speaker 2: how many people had heard of this concept? Do they

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Speaker 2: know what it is? Do they want to know.

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Speaker 1: What it is? How could they live so long without

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Speaker 1: hearing about it? So thanks very much to everybody who

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Speaker 1: answers these questions for the podcast. If you'd like to

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Speaker 1: join the crew. Please don't be shy. Write to me

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Speaker 1: two questions at Danielandjorge dot com, or contact us on

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Speaker 1: Twitter or join our discord. We'd be happy to send

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Speaker 1: you these questions.

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Speaker 2: So think about it for a second. Do you know

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Speaker 2: what baryon acoustic oscillations are? Here's what people have to say.

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Speaker 3: I have no idea, but it reminds me of something

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Speaker 3: in a video game I used to play. Oscillation is

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Speaker 3: kind of like a ring of something I because in

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Speaker 3: my video game there's like a big circle ring the

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Speaker 3: boss called the ausciliator. Acoustic is like kind of like antiqueish.

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Speaker 1: I think, I'm sorry, I'll pass. Never heard about it.

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Speaker 4: I believe this is pressure waves in the cosmic background

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Speaker 4: radiation that is caused. We can see the slight changes

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Speaker 4: in temperature caused by pressure waves, and because the pressure

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Speaker 4: waves cannot propagate at greater than the speed of light,

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Speaker 4: the size of the acoustic variations gives an excellent estimate

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Speaker 4: of the distance to the cosmic background radiation source, and

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Speaker 4: therefore that, in conjunction with the red shift that we observe,

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Speaker 4: gives us a very good indication of the hubble constant

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Speaker 4: at that one point in time approximately four hundred thousand

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Speaker 4: years after the Big Bang.

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Speaker 5: Based purely on the name, I would guess that baryon

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Speaker 5: acoustic castellation has something to do with either using sound

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Speaker 5: to cause beryons to bump each other or using sound

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Speaker 5: like properties to study how they behave.

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Speaker 6: I have it in my head that baryon acoustic ostellations

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Speaker 6: has something to do with the beginning of the universe

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Speaker 6: and tower. The original quantum fluctuations prior to inflation taking

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Speaker 6: place could be seen as being like waves through the

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Speaker 6: kind of plasmi y stuff at the beginning, and then

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Speaker 6: when that gets blown out by inflation, you can still

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Speaker 6: detect and see those acoustic ostellations today.

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Speaker 3: So Buryon's some atomic particle, and probably.

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Speaker 1: It has acoustic.

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Speaker 3: Oscillation to it, like having a pattern repeating over a

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Speaker 3: period of time.

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Speaker 6: Or something like that.

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Speaker 2: All right, and a lot of answers here. I like

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Speaker 2: the person who said, I'm sorry, I'll pass. What do

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Speaker 2: you say to that, okay next? Or do you try

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Speaker 2: to convince them that they want to know what burying

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Speaker 2: acoustic oscillations are.

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Speaker 1: I don't want to pressure anybody. I'm just impressed that

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Speaker 1: they decided to record their passing and send it in

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Speaker 1: rather than just not responding.

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Speaker 2: Oh, they actually like took the time to record this exactly.

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Speaker 1: They sat down and record their answers and sent it

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Speaker 1: in even though they were passing.

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Speaker 2: I love that, I see. Do you think what do

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Speaker 2: you think happened? Do you think they heard the question?

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Speaker 2: Were like, I don't want to say anything about burying

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Speaker 2: acoustic oscillation.

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Speaker 4: Yeah.

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Speaker 1: Well, the rules are no googling, no looking at the

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Speaker 1: questions ahead of time. I want people's real, spontaneous ideas

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Speaker 1: about what these topics are, because we want to get

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Speaker 1: a sense for what people out there know before they

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Speaker 1: look things up. And so this person was just reading

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Speaker 1: through the questions in real time and recording themselves, and

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Speaker 1: maybe their brain just had a bubble which popped and

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Speaker 1: they decided I got nothing.

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Speaker 2: Okay, I see, it's more like I got nothing not

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Speaker 2: so much A.

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Speaker 1: No, thanks, next question please.

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Speaker 2: Well, people seem to sort of into it or know

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Speaker 2: that it's somehow related to the beginning of the universe.

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Speaker 2: And also I guess to something related to waves, right

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Speaker 2: and sound and oscillations. Nobody gets bows or boba.

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Speaker 1: Nobody made the boba connection. That's just me, all.

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Speaker 2: Right, well, let's jump into it, Daniel. What are baryon

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Speaker 2: acoustic oscillations.

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Speaker 1: Yeah, baryon acoustic oscillations are really fascinating, sort of like

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Speaker 1: fossilized sound waves from very very early universe. You know,

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Speaker 1: like if somebody's playing an acoustic guitar or like an

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Speaker 1: acoustic recording. It refers to the quality and the fabrication

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Speaker 1: of the sound waves that you're hearing. So acoustic there

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Speaker 1: tells you that you're hearing sound waves, and the word

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Speaker 1: buryon tells you what you're hearing those sound waves in

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Speaker 1: that you're hearing it as baryons bump against each other.

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Speaker 2: But I guess maybe not to confuse folks in this case,

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Speaker 2: acoustic doesn't mean necessarily sounds your hearers at the air.

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Speaker 2: They can also mean like sound waves and you hear

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Speaker 2: in the ocean or maybe through even a solid right.

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Speaker 1: Yeah, exactly. Sound Waves can travel through air, but they

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Speaker 1: can also travel through water, or they can travel to steal,

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Speaker 1: they can travel through your body, They can travel through

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Speaker 1: any kind of gas or plasma. Sound Waves are just

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Speaker 1: pressure waves. If you have a bunch of molecules that

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Speaker 1: can interact with each other, that can push against each other,

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Speaker 1: then if you push on one side of that blog,

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Speaker 1: then it's going to push on the next layer, which

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Speaker 1: pushes on the next layer, which it pushes on the

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Speaker 1: next layer. That's what sound waves are. You're hearing us

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Speaker 1: right now because the speaker in your ear is making

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Speaker 1: sound waves that push on layers of air, which push

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Speaker 1: on the next layer of air, etc.

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Speaker 2: I see so an acoustic wave or acoustic oscillations. They're

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Speaker 2: just like when things propagate through material, because things are

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Speaker 2: bumping into each other basically through electromagnetic forces, or can

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Speaker 2: it be other force.

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Speaker 1: It's almost always electromagnetic forces. The crucial thing is that

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Speaker 1: they bump against each other. If they pass right through

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Speaker 1: each other, then they don't cause pressure waves. The crucial

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Speaker 1: thing is that they're bumping up against each other. That

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Speaker 1: one layer pushes the next layer, which pushes the next layer.

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Speaker 1: The microphysics of how that pushing happens is electromagnetic. You

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Speaker 1: have electrons in one atom are pushing up against the

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Speaker 1: electrons in another atom. They don't like to overlap, they

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Speaker 1: resist each other. It's the same reason why you don't

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Speaker 1: pass through your chair, or when you're leaning against the wall,

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Speaker 1: the wall pushes back or the Earth is pushing up

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Speaker 1: on you. Basically, anything structural is built with electromagnetic forces,

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Speaker 1: because that's the bond of chemistry.

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Speaker 2: Now, for those of us who are not particle physicists,

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Speaker 2: can you remind us what a baryon is.

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Speaker 1: Yeah, Baryons are anything made out of quarks, basically baryon

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Speaker 1: the shorthand for our kind of matter, stuff like protons

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Speaker 1: and neutrons, these are baryons. We call them baryons mostly

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Speaker 1: to distinguish them from the other kind of matter in

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Speaker 1: the universe, dark matter, which is some other kind of

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Speaker 1: stuff that's out there. It feels gravity, it has masks.

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Speaker 1: We think it's made of stuff. We don't know if

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Speaker 1: it's made of particles, but we're very sure that it's

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Speaker 1: not made of our kind of particles. And so when

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Speaker 1: we talk about the very early universe, we have a

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Speaker 1: few components to sort of like that very early universe smoothie.

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Speaker 1: There's baryons, there's photons, there's dark matter, and so we

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Speaker 1: talk about baryon acoustic oscillations because it's the sound waves

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Speaker 1: in those early universe protons mostly that we're thinking about.

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Speaker 2: Does that include electrons as well or electrons something else?

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Speaker 1: So electrons are not technically baryons because they're not made

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Speaker 1: out of quarks. Baryons are particles that are made out

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Speaker 1: of three quarks. Quarks are these incredible particles that feel

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Speaker 1: a strong force in order to have a neutral particle

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Speaker 1: and the strong force and that it doesn't have an

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Speaker 1: overall strong force charge the way, for example, a proton,

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Speaker 1: an electron can make a neutral atom with no overall

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Speaker 1: electric charge. In or for quarks to come together to

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Speaker 1: make an object that doesn't feel a strong force, it's

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Speaker 1: overall neutral. You need either three of them or two

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Speaker 1: of them, and if you put three of them together

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Speaker 1: you get a baryon like a proton or a neutron,

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Speaker 1: or there are other more exotic baryons. So technically an

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Speaker 1: electron is not a baryon, but it is included when

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Speaker 1: you talk about baryonic matter, which is like atoms made

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Speaker 1: out of a baryon and an electron.

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Speaker 2: I see that makes not a lot of sense.

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Speaker 1: Yeah. The short answer is you can lump electrons in

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Speaker 1: with baryonic matter even though technically they're not buryons.

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Speaker 2: Okay, I see, so it's really just regular matter. You're

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Speaker 2: using that shorthand for regular matter or at least the

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Speaker 2: matter that we're made out.

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Speaker 1: Of, exactly the matter that really matters.

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Speaker 2: So then we're talking about the Big Bang. This is

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Speaker 2: the early moments of the universe, and now what was

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Speaker 2: going on there.

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Speaker 1: When we talk about the Big Bang. It's also important

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Speaker 1: to clarify what we really mean by the Big Bang.

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Speaker 1: If you say that to a lot of people, they

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Speaker 1: imagine some very dense dot in space which then exploded

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Speaker 1: to make our universe. But when physicists talk about the

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Speaker 1: Big Bang, they really have a different idea in mind.

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Speaker 1: First of all, we don't go all the way back

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Speaker 1: to the creation of the universe. We don't know how

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Speaker 1: the universe was created, if it was created, if it

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Speaker 1: existed forever, how everything came to be. We only go

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Speaker 1: back as far as our theories can describe, which is

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Speaker 1: some moment around fourteen billion years ago when the universe

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Speaker 1: was filled with a very very hot and dense material.

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Speaker 1: Our theories go back that far, and our observations verify

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Speaker 1: that that happened. Where that stuff came from and how

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Speaker 1: it got there and all that stuff is all very speculative,

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Speaker 1: and we have theories about that inflation, et cetera. But

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Speaker 1: really the Big Bang, when physicists describe it, starts from

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Speaker 1: that very hot, dense state and then watches it expand

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Speaker 1: and form our universe. So the Big Bang is not

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Speaker 1: like a singularity at some point. It's a moment in

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Speaker 1: time when the universe was very hot and dense and

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Speaker 1: filled with plasma.

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Speaker 2: Well, part of it was that there was a lot

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Speaker 2: less space back then in that those early moments of

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Speaker 2: the universe, or at least what we call the early

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Speaker 2: moments of the universe. Like space expanded a lot since then,

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Speaker 2: from then to now, and so basically maybe a way

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Speaker 2: to think about it is just like all space was

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Speaker 2: more compressed, but it had the same amount of stuff

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Speaker 2: and it so everything was hot and dense.

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Speaker 1: Yeah, it's tricky if you think about size and use

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Speaker 1: words like smaller, because we don't know the size of

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Speaker 1: the universe. It might always have been infinite and might

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Speaker 1: still be infinite today. What we do know is about

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Speaker 1: the density. So as you say, it's more compressed, so

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Speaker 1: you should think about a universe, whether it's infinite or not,

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Speaker 1: just as filled with really hot, dense stuff and then

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Speaker 1: space expands. That's the Big Bang as we think about

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Speaker 1: it today, and makes everything more dilute. So things are

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Speaker 1: cooling down and getting more dilute. There's more space per

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Speaker 1: bit of stuff. That doesn't really tell you anything about

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Speaker 1: whether the universe was infinite or not. We obviously don't know.

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Speaker 2: And so I think the early universe went through a

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Speaker 2: lot of different phases, right Like, at some point there

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Speaker 2: weren't even maybe quantum fields or the quantum fields. We're

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Speaker 2: still trying to figure it out. And then things started

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Speaker 2: to change. But as you said, at some point in

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Speaker 2: that history, everything was basically a hot plasma exactly.

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Speaker 1: Things started out so hot and dense that we can't

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Speaker 1: even really use the physics of today to describe it.

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Speaker 1: You can't even really talk about particles because the fields

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Speaker 1: were so filled with energy. But eventually things cooled down

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Speaker 1: and particles formed, and you got quarks, and you've got electrons.

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Speaker 1: Those quarks then cooled down to make protons. And it's

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Speaker 1: really that moment that we want to zero in on today,

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Speaker 1: the moment when we had protons and electrons and photons

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Speaker 1: and also dark matter in this big hot plasma. But

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Speaker 1: that hot plasma is not uniform. It's not like everywhere

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Speaker 1: in space has exactly the same hot plasma, there's little

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Speaker 1: ripples in it. Some parts are denser than others, and

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Speaker 1: the baryon acoustic oscillation describes how the bears in that

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Speaker 1: hot plasma, we're sloshing around and ringing with sound waves.

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Speaker 2: Well, I think maybe a good way to think about

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Speaker 2: plasma is that it's basically just a gas. The only

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Speaker 2: difference between the plasma and a regular gas is that

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Speaker 2: the atoms are broken up, right Like in a regular gas,

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Speaker 2: like the air we're breathing, the electrons are tied together

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Speaker 2: with the protons and neutrons into atoms. But in the plasma,

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Speaker 2: it things are so heated up that they break apart.

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Speaker 2: But it's still basically a gas, right Like it's just

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Speaker 2: things flying around a space.

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Speaker 1: Yeah, exactly. It's a gas of charged particles, and it's

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Speaker 1: sort of a natural evolution of matter. You know, as

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Speaker 1: things get colder, they form more structure because they don't

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Speaker 1: have the energy to escape the power of those bonds.

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Speaker 1: So you think about an individual electron, if it has

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Speaker 1: a lot of energy, in other words, if it's in

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Speaker 1: a really hot gas, then it's going to have too

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Speaker 1: much energy to be captured by a proton. But as

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Speaker 1: things cool down, then those electrons are susceptible to being

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Speaker 1: captured by the proton, and then you get neutral hydrogen.

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Speaker 1: So as the universe cools, you go from having charged

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Speaker 1: plasma like you say, a charged gas, to having neutral gas.

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Speaker 1: And so, yeah, plasma is just a charged version of

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Speaker 1: a normal gas.

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Speaker 2: Right, It's a gas made out of ions, right, electrons

404
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Speaker 2: and programs lying around on their own, and so like

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Speaker 2: any gas, it would have sound waves.

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Speaker 1: In it exactly, so that hot plasma was not a

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Speaker 1: quiet place, right. It was also super dup or dense,

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Speaker 1: which means that sound propagated through it at shockingly high speeds.

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Speaker 2: All right, well, let's get a little bit more into

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Speaker 2: this hot plasma, how it works, and how those early

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Speaker 2: sound waves in that plasma led to the universe we

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Speaker 2: see today, Boba included. So let's dig into that. But

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Speaker 2: first let's take a quick break. All right, we're talking

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Speaker 2: about the early sounds of the universe. Now, Daniel, what

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Speaker 2: genre of music do you think the universe sounded like

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Speaker 2: at the beginning? Was it like elevator music? Was it

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Speaker 2: like rocking, banging music? What do you think k pop?

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Speaker 1: I think it sounded mostly like white noise and screams.

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Speaker 2: I see, that's right, that's right, because it was some

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Speaker 2: deity choking on a giant black hole wave exactly. It

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Speaker 2: was not a pleasant sound. But yeah, you were saying

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Speaker 2: that the universe was basically at some point it evolved

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Speaker 2: into basically all hot plasma in it, and there were

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Speaker 2: sound waves in it and ripples in it, because I

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Speaker 2: guess it's just the gas. And so even the air

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Speaker 2: we see around us is not perfectly totally completely uniform, right.

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Speaker 1: That's right. There are pressure waves everywhere as you talk,

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Speaker 1: and you're making pressure waves. As the wind blows and

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Speaker 1: makes pressure waves. As there are temperature variations, you've got

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Speaker 1: pressure waves, and so nothing around you is really totally uniform.

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Speaker 2: So then what made those waves in the early universe? Like,

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Speaker 2: if I just have a room here and I leave

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Speaker 2: it alone, the gas is gonna basically all equalize, isn't it.

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Speaker 1: Mm hmm exactly. So to get sound in the early universe,

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Speaker 1: you need a couple of things. First of all, you

436
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Speaker 1: need some initial over densities. You need some spots be

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Speaker 1: a little hot and a little denser than others. Then

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Speaker 1: you need a way for it to propagate or for

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Speaker 1: it to ring So what are those initial over densities

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Speaker 1: come from. Because if we're imagining the early universe just

441
00:21:08,520 --> 00:21:11,359
Speaker 1: this big hot plasma, and we say everywhere in the

442
00:21:11,440 --> 00:21:14,880
Speaker 1: universe is the same, there's no special location to the universe.

443
00:21:14,920 --> 00:21:17,000
Speaker 1: There's no reason why the universe would put more stuff

444
00:21:17,040 --> 00:21:19,240
Speaker 1: here and than there. Then it's hard to imagine like

445
00:21:19,320 --> 00:21:22,520
Speaker 1: where any sort of really initial ripple might come from.

446
00:21:22,560 --> 00:21:25,480
Speaker 1: And that comes just from quantum fluctuations in the very

447
00:21:25,600 --> 00:21:29,760
Speaker 1: very early universe. So way back before the plasma even formed,

448
00:21:30,119 --> 00:21:33,920
Speaker 1: much earlier on, you had just some quantum fluctuations, particles

449
00:21:33,960 --> 00:21:37,920
Speaker 1: popping in and out of the vacuum, just true quantum randomness.

450
00:21:38,000 --> 00:21:40,359
Speaker 1: It is true that everywhere in the universe follows the

451
00:21:40,359 --> 00:21:43,520
Speaker 1: same laws of physics, But if quantum mechanics really is random,

452
00:21:43,560 --> 00:21:46,000
Speaker 1: then it can do different things in different spots, and

453
00:21:46,040 --> 00:21:49,960
Speaker 1: that's how you get little, tiny fluctuations. But then inflation

454
00:21:50,080 --> 00:21:52,920
Speaker 1: or whatever caused the universe to expand dramatically blue those

455
00:21:52,960 --> 00:21:57,240
Speaker 1: tiny little quantum ripples up to tiny little macroscopic ripples

456
00:21:57,600 --> 00:21:59,920
Speaker 1: big enough that gravity could do something with them.

457
00:22:00,280 --> 00:22:03,800
Speaker 2: Well, you call them tiny microscopic quantum fluctuations. But I

458
00:22:03,880 --> 00:22:08,200
Speaker 2: wonder if back then, when the universe was a lot smaller, basically,

459
00:22:08,240 --> 00:22:11,240
Speaker 2: like all of the quantum particles and fields were basically

460
00:22:11,240 --> 00:22:13,359
Speaker 2: more on top of each other. And for example, the

461
00:22:13,359 --> 00:22:16,320
Speaker 2: size of an electron today it does seem huge back then.

462
00:22:17,320 --> 00:22:18,359
Speaker 2: Is that a good way to look at it.

463
00:22:18,359 --> 00:22:21,000
Speaker 1: It's definitely true that everything was much more compressed back then,

464
00:22:21,080 --> 00:22:23,440
Speaker 1: like you had the same amount of stuff with less

465
00:22:23,480 --> 00:22:26,120
Speaker 1: space between them. But those electrons probably weren't even born

466
00:22:26,200 --> 00:22:28,840
Speaker 1: yet when these ripples that were talking about were made.

467
00:22:28,960 --> 00:22:31,600
Speaker 1: Eventually that same energy did cool down and spread out

468
00:22:31,640 --> 00:22:34,800
Speaker 1: into specific particles. But the ripples we're talking about are

469
00:22:34,840 --> 00:22:38,280
Speaker 1: probably pre particle. They're just like ripples in the froth

470
00:22:38,320 --> 00:22:41,120
Speaker 1: and quantum fields before you can even really identify them

471
00:22:41,200 --> 00:22:42,639
Speaker 1: as particles.

472
00:22:42,280 --> 00:22:43,800
Speaker 2: Right right. I didn't mean to say that there were

473
00:22:43,840 --> 00:22:46,000
Speaker 2: electrons back then, but I just mean like the scale

474
00:22:46,040 --> 00:22:48,840
Speaker 2: things was very different back then. Like what we might

475
00:22:48,880 --> 00:22:51,520
Speaker 2: ignore today is a quantum fluctuation because it's so small.

476
00:22:51,640 --> 00:22:53,840
Speaker 2: Back then, maybe a quantum fluctuation was huge.

477
00:22:53,960 --> 00:22:56,280
Speaker 1: Right, Yeah, it's a really interesting comparison. I guess. Really

478
00:22:56,320 --> 00:22:58,960
Speaker 1: the only meterstick we have to compare today with back

479
00:22:59,000 --> 00:23:01,280
Speaker 1: then is the speed of light, And so you do

480
00:23:01,359 --> 00:23:04,400
Speaker 1: have this sense of like the horizon that an electron

481
00:23:04,440 --> 00:23:06,800
Speaker 1: could see, like what fraction of the universe an electron

482
00:23:06,840 --> 00:23:09,760
Speaker 1: could interact with, and then that did later get blown up.

483
00:23:09,840 --> 00:23:11,639
Speaker 1: And so back then the electron was sort of in

484
00:23:11,640 --> 00:23:13,800
Speaker 1: a smaller pond of the universe of sort of a

485
00:23:13,800 --> 00:23:14,399
Speaker 1: bigger deal.

486
00:23:14,680 --> 00:23:17,920
Speaker 2: Then, as you said, these small ripples kind of god

487
00:23:18,160 --> 00:23:20,760
Speaker 2: stretched out as the universe expanded. So maybe take us

488
00:23:20,800 --> 00:23:23,199
Speaker 2: through a little bit of what was happening as the

489
00:23:23,280 --> 00:23:25,600
Speaker 2: universe started to expand, like what was going on with

490
00:23:25,680 --> 00:23:26,080
Speaker 2: dark matter.

491
00:23:26,200 --> 00:23:29,320
Speaker 1: Yeah, so you have these initial ripples which create over densities,

492
00:23:29,640 --> 00:23:32,720
Speaker 1: mostly in the dark matter. Remember that there's more dark

493
00:23:32,800 --> 00:23:35,080
Speaker 1: matter than anything else. And so if your mental image

494
00:23:35,200 --> 00:23:38,760
Speaker 1: you're imagining some like hot bright plasma, add a layer

495
00:23:38,800 --> 00:23:41,679
Speaker 1: to that, an invisible layer of dark matter, which has

496
00:23:41,760 --> 00:23:44,000
Speaker 1: most of the mass of the matter in the universe

497
00:23:44,040 --> 00:23:45,879
Speaker 1: at the time, not most of the energy. Most of

498
00:23:45,880 --> 00:23:47,600
Speaker 1: the energy in the universe at this time is still

499
00:23:47,600 --> 00:23:50,919
Speaker 1: in photons. It's mostly radiation dominated. But most of the

500
00:23:50,960 --> 00:23:54,000
Speaker 1: stuff in the universe is dark matter. So now you

501
00:23:54,000 --> 00:23:55,719
Speaker 1: have these little ripples. You have like a little bit

502
00:23:55,720 --> 00:23:57,560
Speaker 1: more dark matter here and a little bit more dark

503
00:23:57,600 --> 00:24:00,600
Speaker 1: matter there, and dark matter has gravity of course, it

504
00:24:00,600 --> 00:24:02,800
Speaker 1: so it starts to pull things in. Because you have

505
00:24:02,840 --> 00:24:04,680
Speaker 1: a little bit more dark matter, it means it has

506
00:24:04,760 --> 00:24:07,240
Speaker 1: more gravity than everything around it. It's going to start

507
00:24:07,240 --> 00:24:09,560
Speaker 1: to pull stuff in, which gives it more density, which

508
00:24:09,600 --> 00:24:11,960
Speaker 1: gives it more gravity. So dark matter is starting to

509
00:24:12,000 --> 00:24:16,320
Speaker 1: form clusters, it's starting to amplify those initial quantum fluctuations.

510
00:24:16,400 --> 00:24:18,480
Speaker 2: Well, I guess the big question is what do we

511
00:24:18,520 --> 00:24:21,240
Speaker 2: know about dark matter in those early moments, Like we

512
00:24:21,280 --> 00:24:24,200
Speaker 2: know that regular matter, it started to dissociate into protons

513
00:24:24,200 --> 00:24:28,320
Speaker 2: and electrons, and before that they dissociated even more. Did

514
00:24:28,440 --> 00:24:32,480
Speaker 2: dark matter break down too, or did it also have

515
00:24:32,560 --> 00:24:36,000
Speaker 2: quantum fluctuations or does it even have quantumness to it?

516
00:24:36,200 --> 00:24:37,960
Speaker 1: Yeah? Wow, I wish I knew the answer to any

517
00:24:37,960 --> 00:24:40,960
Speaker 1: of those questions. We don't know, right because we don't

518
00:24:41,000 --> 00:24:43,600
Speaker 1: know what particles dark matter is made out of, if

519
00:24:43,600 --> 00:24:46,359
Speaker 1: it's even made out of particles in this theory. Instead,

520
00:24:46,359 --> 00:24:49,240
Speaker 1: we treat dark matter sort of as like a collisionless fluid,

521
00:24:49,640 --> 00:24:52,880
Speaker 1: some that has no interactions other than gravity. We think

522
00:24:52,960 --> 00:24:56,480
Speaker 1: just about its mass density and the gravitational impact of that.

523
00:24:56,760 --> 00:24:58,760
Speaker 1: We don't try to break it down into the microphysics

524
00:24:58,800 --> 00:25:01,400
Speaker 1: because we don't have that story at all. We don't

525
00:25:01,440 --> 00:25:03,520
Speaker 1: know if dark matter is ten different kinds of dark

526
00:25:03,520 --> 00:25:05,640
Speaker 1: particles that are all turning into each other and back

527
00:25:05,760 --> 00:25:09,320
Speaker 1: or not. But because it doesn't interact with the baryons

528
00:25:09,400 --> 00:25:12,680
Speaker 1: except for gravity, we don't really need to know those details.

529
00:25:12,720 --> 00:25:14,800
Speaker 1: I mean, we'd love to know, who wouldn't want to know,

530
00:25:15,000 --> 00:25:17,360
Speaker 1: But it doesn't change the story of the baryon acoustic

531
00:25:17,400 --> 00:25:19,200
Speaker 1: oscillations that we're focused on today.

532
00:25:19,320 --> 00:25:22,040
Speaker 2: I see at this point we're just squinting at dark matter.

533
00:25:22,119 --> 00:25:24,560
Speaker 2: We're sort of waving our hands. We're like, well, I

534
00:25:24,560 --> 00:25:29,000
Speaker 2: don't care what's happening at the small microscopic level of

535
00:25:29,040 --> 00:25:31,520
Speaker 2: dark matter. It could be anything, but you just sort

536
00:25:31,520 --> 00:25:34,119
Speaker 2: of treat it as, like you said, like a cloud

537
00:25:34,200 --> 00:25:35,280
Speaker 2: or liquid of stuff.

538
00:25:35,640 --> 00:25:38,040
Speaker 1: Yeah, it's not that we don't care. We deeply care,

539
00:25:38,160 --> 00:25:40,920
Speaker 1: and we'd love to know. But the game of physics

540
00:25:40,960 --> 00:25:43,280
Speaker 1: is trying to make progress even when you don't know things.

541
00:25:43,359 --> 00:25:45,520
Speaker 1: And so here's a question we can focus on even

542
00:25:45,560 --> 00:25:48,199
Speaker 1: without knowing what's going on with the dark matter. We

543
00:25:48,280 --> 00:25:50,720
Speaker 1: can still think clearly about what's going on with the

544
00:25:50,760 --> 00:25:53,840
Speaker 1: baryons because we think we do understand their interactions.

545
00:25:54,160 --> 00:25:56,159
Speaker 2: Right, So then you're saying that the dark matter was

546
00:25:56,359 --> 00:26:00,119
Speaker 2: influenced by the quantum fluctuations of the regular matter. But

547
00:26:00,160 --> 00:26:03,400
Speaker 2: could dark matter itself have had its own quantum fluctuations.

548
00:26:03,560 --> 00:26:06,000
Speaker 1: Now, they had their own quantum fluctuations for sure. Dark

549
00:26:06,040 --> 00:26:08,760
Speaker 1: matter and regular matter both come out of these initial

550
00:26:08,840 --> 00:26:11,240
Speaker 1: quantum fluctuations. So one spot in the universe we have

551
00:26:11,280 --> 00:26:13,280
Speaker 1: like an over density of energy that turns into more

552
00:26:13,359 --> 00:26:16,600
Speaker 1: dark matter and more normal matter. And it's mostly the

553
00:26:16,680 --> 00:26:20,959
Speaker 1: quantum fluctuations in the dark matter itself that spur everything

554
00:26:20,960 --> 00:26:23,240
Speaker 1: we're talking about, because it's the gravity of the dark

555
00:26:23,280 --> 00:26:25,000
Speaker 1: matter that triggers everything.

556
00:26:24,960 --> 00:26:27,359
Speaker 2: Right, because there's more dark matter than regular matter. But

557
00:26:27,400 --> 00:26:30,959
Speaker 2: then are you assuming that, like the dark matter fluctuations

558
00:26:31,000 --> 00:26:33,639
Speaker 2: and the regular matter fluctuation, we're somehow in sync in

559
00:26:33,680 --> 00:26:34,600
Speaker 2: the early universe.

560
00:26:34,920 --> 00:26:38,000
Speaker 1: The quantum fluctuations we're talking about again predate the formation

561
00:26:38,080 --> 00:26:40,640
Speaker 1: of the particles themselves, and this division of energy into

562
00:26:40,720 --> 00:26:43,480
Speaker 1: dark matter and normal matter, which frankly, we don't understand,

563
00:26:43,760 --> 00:26:45,320
Speaker 1: and to understand it, we'd have to have a better

564
00:26:45,359 --> 00:26:48,320
Speaker 1: idea of what particles there are and how the quantum

565
00:26:48,359 --> 00:26:50,679
Speaker 1: fields sort of filter out into the dark matter. So

566
00:26:50,720 --> 00:26:53,119
Speaker 1: we just say that there's an initial quantum fluctuation and

567
00:26:53,119 --> 00:26:54,960
Speaker 1: then at each point, if you have more stuff or

568
00:26:55,040 --> 00:26:57,640
Speaker 1: less stuff, you get about eighty percent of it into

569
00:26:57,720 --> 00:27:00,000
Speaker 1: dark matter and twenty percent of it into normal matter.

570
00:27:00,400 --> 00:27:02,359
Speaker 1: So from that point of view, they are correlated because

571
00:27:02,359 --> 00:27:05,439
Speaker 1: they come from the same initial quantum fluctuations, which are

572
00:27:05,480 --> 00:27:08,159
Speaker 1: independent from the dark matter or the normal matter nature.

573
00:27:08,760 --> 00:27:11,080
Speaker 2: I see, you are sort of imagining a point in

574
00:27:11,119 --> 00:27:14,639
Speaker 2: the universe when even dark matter was maybe dissociated or

575
00:27:14,840 --> 00:27:16,760
Speaker 2: didn't exist exactly.

576
00:27:17,000 --> 00:27:19,479
Speaker 1: Those are where the quantum fluctuations are happening before we

577
00:27:19,520 --> 00:27:22,240
Speaker 1: even have dark matter or normal matter, and then down

578
00:27:22,320 --> 00:27:25,080
Speaker 1: the road tiny fractions of a second later, when we

579
00:27:25,119 --> 00:27:27,840
Speaker 1: do have matter, some of that energy has gotten into

580
00:27:27,920 --> 00:27:29,760
Speaker 1: dark matter and some of it into normal matter.

581
00:27:29,920 --> 00:27:33,160
Speaker 2: Okay, So then both dark matter and regular matter are

582
00:27:33,280 --> 00:27:37,800
Speaker 2: kind of have these expanding fluctuations ripples, which, as you said,

583
00:27:37,840 --> 00:27:41,520
Speaker 2: create pockets of the higher density dark matter and regular matter,

584
00:27:41,680 --> 00:27:45,600
Speaker 2: which then I guess is what creates the sound ways, right,

585
00:27:45,640 --> 00:27:48,400
Speaker 2: because when you have something more dense in one side,

586
00:27:48,440 --> 00:27:50,320
Speaker 2: it tends to try to go to the other side.

587
00:27:50,119 --> 00:27:52,560
Speaker 1: Exactly, and sort of a push and a push back here.

588
00:27:52,920 --> 00:27:55,399
Speaker 1: So dark matter is creating these over densities. It's like

589
00:27:55,480 --> 00:27:58,880
Speaker 1: gravitationally collapsing things, and that's fine for dark matter. Dark

590
00:27:58,880 --> 00:28:01,280
Speaker 1: matter doesn't really care happy it gets pulled in by

591
00:28:01,320 --> 00:28:04,760
Speaker 1: gravity and overlap with itself whatever. But baryons are different.

592
00:28:05,160 --> 00:28:08,000
Speaker 1: Baryons and photons interact with each other, and so if

593
00:28:08,040 --> 00:28:11,080
Speaker 1: you squeeze them down, then they're going to push back.

594
00:28:11,400 --> 00:28:13,879
Speaker 1: Like you squeeze a bunch of baryons together, they push

595
00:28:13,960 --> 00:28:17,000
Speaker 1: against each other and they push back out. And remember

596
00:28:17,000 --> 00:28:19,199
Speaker 1: that there's a huge number of baryons but also an

597
00:28:19,320 --> 00:28:23,680
Speaker 1: enormous number of photons. So as you squeeze these protons together,

598
00:28:24,200 --> 00:28:28,560
Speaker 1: then they're effectively squeezing on the photons, which push back out.

599
00:28:28,760 --> 00:28:30,479
Speaker 1: So it's sort of like a mini version of what

600
00:28:30,520 --> 00:28:33,760
Speaker 1: happens in a star where you collapse it gravitationally and

601
00:28:33,760 --> 00:28:36,800
Speaker 1: then it creates fusion, and that radiation pressure from the

602
00:28:36,880 --> 00:28:39,960
Speaker 1: fusion keeps the star from collapsing. Here you have dark

603
00:28:40,040 --> 00:28:43,840
Speaker 1: matter pulling blobs of baryons and photons together, and then

604
00:28:43,880 --> 00:28:46,920
Speaker 1: those photons and baryons interacting when they get squeezed to

605
00:28:46,960 --> 00:28:50,720
Speaker 1: push back out, and that's what creates these ripples in

606
00:28:50,760 --> 00:28:51,600
Speaker 1: the baryons.

607
00:28:52,920 --> 00:28:56,040
Speaker 2: Like it's like the dark matter collects all of the

608
00:28:56,080 --> 00:28:58,840
Speaker 2: other the regular matter tries to squeeze it down, but

609
00:28:58,880 --> 00:29:00,640
Speaker 2: then it bounces back exactly.

610
00:29:00,720 --> 00:29:03,280
Speaker 1: It bounces back sort of like a mini weaker version

611
00:29:03,320 --> 00:29:06,800
Speaker 1: of a supernova, you know, gravitational collapse, which then bounces

612
00:29:06,800 --> 00:29:10,040
Speaker 1: back out in impollusion, which leads to an explosion. Some

613
00:29:10,080 --> 00:29:11,760
Speaker 1: way I want to get clearing people's minds, which is

614
00:29:11,800 --> 00:29:15,680
Speaker 1: sort of crazy to imagine, is the ratio of different particles,

615
00:29:15,720 --> 00:29:19,120
Speaker 1: Like there's about a billion photons for every proton and

616
00:29:19,160 --> 00:29:21,480
Speaker 1: every electron at this point at the universe, Like the

617
00:29:21,600 --> 00:29:24,920
Speaker 1: universe is mostly light, so there's a huge number of

618
00:29:24,960 --> 00:29:27,400
Speaker 1: photons pushing against these baryons.

619
00:29:27,560 --> 00:29:32,280
Speaker 2: Now, are you sweeping electrons and protons into radiation here

620
00:29:32,360 --> 00:29:35,800
Speaker 2: or do you actually mean real photons that later got

621
00:29:35,880 --> 00:29:37,320
Speaker 2: transformed into electrons.

622
00:29:37,920 --> 00:29:41,120
Speaker 1: Totally fair question, because you're right that if things are

623
00:29:41,120 --> 00:29:43,280
Speaker 1: moving near the speed of light, we just call it radiation.

624
00:29:43,600 --> 00:29:45,840
Speaker 1: But here we're talking about real radiation. We're just talking

625
00:29:45,840 --> 00:29:50,000
Speaker 1: about photons. We're treating electrons, protons, and photons separately, and

626
00:29:50,040 --> 00:29:53,600
Speaker 1: it really is mostly photons. But those photons they push

627
00:29:53,680 --> 00:29:56,000
Speaker 1: on the baryons, they push on the protons, they push

628
00:29:56,040 --> 00:29:58,120
Speaker 1: on the electrons in a way that they of course

629
00:29:58,200 --> 00:30:01,040
Speaker 1: don't push on the dark matter. So the dark matter

630
00:30:01,080 --> 00:30:04,560
Speaker 1: is collapsing into the center and the baryons get pushed

631
00:30:04,600 --> 00:30:07,960
Speaker 1: back out because they have this electric interaction that dark

632
00:30:08,000 --> 00:30:08,800
Speaker 1: matter doesn't have.

633
00:30:09,040 --> 00:30:12,280
Speaker 2: But the photons are not being pulled together by gravity,

634
00:30:12,360 --> 00:30:12,720
Speaker 2: are they?

635
00:30:12,880 --> 00:30:16,440
Speaker 1: Photons are affected by gravity? Right, Photons bend around the Sun,

636
00:30:16,560 --> 00:30:18,520
Speaker 1: or can bend around a black hole. So as dark

637
00:30:18,520 --> 00:30:22,120
Speaker 1: matter curved space, photons are also gathered into that well

638
00:30:22,320 --> 00:30:25,120
Speaker 1: together with the protons. But then they push back and

639
00:30:25,160 --> 00:30:27,760
Speaker 1: there's so many protons, so many photons that you get

640
00:30:27,800 --> 00:30:30,640
Speaker 1: a sound, right, This is the sound of the early universe.

641
00:30:30,920 --> 00:30:34,239
Speaker 1: Is this pressure wave in the buryons created by the

642
00:30:34,240 --> 00:30:37,440
Speaker 1: baryons and the photons being squeezed down by dark matter.

643
00:30:37,600 --> 00:30:43,000
Speaker 2: M it's the sound of regular matter being uncomfortable, like whoa, whoa,

644
00:30:43,400 --> 00:30:45,080
Speaker 2: I don't want to be so close to my neighbors.

645
00:30:45,320 --> 00:30:49,760
Speaker 1: Exactly, it's here, Exactly. It's the sound on the subway

646
00:30:49,760 --> 00:30:52,320
Speaker 1: when another ten people get on and squeeze you into

647
00:30:52,400 --> 00:30:54,880
Speaker 1: the back and you're like, hell, I can't breathe back here.

648
00:30:54,960 --> 00:30:57,440
Speaker 2: It's the groan of a million introverts.

649
00:30:58,000 --> 00:31:00,760
Speaker 1: What you're saying, Yeah, Another one rides. That was the

650
00:31:00,800 --> 00:31:01,920
Speaker 1: sound of the early universe.

651
00:31:03,080 --> 00:31:07,160
Speaker 2: Another one gets gathered by dark matter against its well.

652
00:31:07,120 --> 00:31:10,240
Speaker 1: Exactly, and the density of the universe is really really high,

653
00:31:10,600 --> 00:31:14,280
Speaker 1: and the density controls the speed of sound. Like sound

654
00:31:14,320 --> 00:31:17,800
Speaker 1: travels faster through water than does through air because those

655
00:31:17,840 --> 00:31:21,280
Speaker 1: molecules are more tightly packed together, so the soundwave propagates

656
00:31:21,320 --> 00:31:24,040
Speaker 1: more quickly, and their bonds are more rigid because they're denser.

657
00:31:24,080 --> 00:31:28,400
Speaker 1: So the soundwave propagates faster through denser materials like steel

658
00:31:28,680 --> 00:31:31,280
Speaker 1: than it does through water, than does through air, than

659
00:31:31,320 --> 00:31:34,840
Speaker 1: it does through really diffuse gases like the upper atmosphere.

660
00:31:34,880 --> 00:31:38,320
Speaker 1: And in the early universe, things are super duper crazy dense,

661
00:31:38,480 --> 00:31:40,800
Speaker 1: So the speed of sound in the early universe is

662
00:31:40,920 --> 00:31:42,400
Speaker 1: like half the speed of light.

663
00:31:42,800 --> 00:31:45,760
Speaker 2: Whoa wouldn't you have to call it radiation wave?

664
00:31:48,680 --> 00:31:49,960
Speaker 1: Fair point? Fair point?

665
00:31:50,000 --> 00:31:54,000
Speaker 2: All right? So then there were these waves from the

666
00:31:54,040 --> 00:31:56,400
Speaker 2: material sort of bouncing back, and that means that like

667
00:31:56,440 --> 00:32:00,480
Speaker 2: those waves propagated at which made things more dents in

668
00:32:00,480 --> 00:32:03,160
Speaker 2: some places than others, right, because that's what a wave.

669
00:32:03,040 --> 00:32:05,840
Speaker 1: Is, yeah, exactly, So you have this dark matter core

670
00:32:06,240 --> 00:32:09,680
Speaker 1: and then you have this density wave of baryons propagating out.

671
00:32:10,080 --> 00:32:12,360
Speaker 1: But this doesn't last forever, right, Things in the universe

672
00:32:12,360 --> 00:32:15,800
Speaker 1: are happening fast, and the universe is expanding and it's cooling,

673
00:32:15,960 --> 00:32:18,520
Speaker 1: and at some point, around three hundred and eighty thousand

674
00:32:18,560 --> 00:32:21,160
Speaker 1: years after this first moment, we can describe what we

675
00:32:21,240 --> 00:32:22,960
Speaker 1: call the beginning of the universe, or at least the

676
00:32:22,960 --> 00:32:25,880
Speaker 1: Big Bang. Things cool down enough that the protons and

677
00:32:25,920 --> 00:32:29,040
Speaker 1: the electrons did bond together to make neutral hydrogen. The

678
00:32:29,040 --> 00:32:32,240
Speaker 1: electrons no longer had enough energy to escape the pull

679
00:32:32,280 --> 00:32:35,320
Speaker 1: of the protons, so the universe became transparent to photons

680
00:32:35,360 --> 00:32:38,280
Speaker 1: instead of opaque. So now when photons are flying through

681
00:32:38,280 --> 00:32:40,880
Speaker 1: the universe, instead of interacting with all the protons and

682
00:32:40,880 --> 00:32:43,720
Speaker 1: the electrons, they see now they just see neutral hydrogen.

683
00:32:43,920 --> 00:32:46,320
Speaker 1: So they no longer push on it. Now they just

684
00:32:46,440 --> 00:32:49,720
Speaker 1: fly through it. And so the universe can expand and cool,

685
00:32:49,760 --> 00:32:52,600
Speaker 1: and these photons can dissipate, and so the sound wave

686
00:32:52,640 --> 00:32:53,840
Speaker 1: basically got frozen.

687
00:32:54,160 --> 00:32:57,360
Speaker 2: It's sort of like if you suddenly frozy ocean, you

688
00:32:57,360 --> 00:33:00,880
Speaker 2: would see all these water molecules frozen in the shape

689
00:33:00,600 --> 00:33:01,400
Speaker 2: of a wave.

690
00:33:01,560 --> 00:33:03,680
Speaker 1: Yeah, that's right. Or say you slap your hand in

691
00:33:03,680 --> 00:33:06,320
Speaker 1: your bathtub and it creates a wave and then you

692
00:33:06,360 --> 00:33:09,080
Speaker 1: suddenly cool it to freeze it. You can come back later.

693
00:33:09,160 --> 00:33:11,360
Speaker 1: You can still see that water wave. Otherwise it would

694
00:33:11,360 --> 00:33:14,400
Speaker 1: have kept propagating and slashing around. But now it's frozen

695
00:33:14,480 --> 00:33:17,360
Speaker 1: because your bathtub, the water has cooled so it can

696
00:33:17,400 --> 00:33:20,240
Speaker 1: no longer propagate. And the same thing happened in the universe.

697
00:33:20,640 --> 00:33:24,520
Speaker 1: The universe became transparent, it became cooler, became less dense,

698
00:33:24,600 --> 00:33:27,280
Speaker 1: and the photons passed through this wave overcame it. So

699
00:33:27,400 --> 00:33:30,480
Speaker 1: now that single ring of sound is like frozen in

700
00:33:30,520 --> 00:33:32,200
Speaker 1: the structure of the early universe.

701
00:33:32,440 --> 00:33:34,640
Speaker 2: Right, But I guess maybe the confusing thing is is

702
00:33:34,640 --> 00:33:39,520
Speaker 2: that it's like a sound wave in the density of photons. Right.

703
00:33:39,600 --> 00:33:42,360
Speaker 2: It's like there were sound waves propagating because the regular

704
00:33:42,400 --> 00:33:44,880
Speaker 2: matter was interacting with photons and with itself. There were

705
00:33:44,920 --> 00:33:47,880
Speaker 2: waves in that slash. But then it's almost like you

706
00:33:47,920 --> 00:33:50,800
Speaker 2: took away the regular matter, you took all the protons

707
00:33:50,800 --> 00:33:53,920
Speaker 2: and electrons out of it, and now suddenly the light

708
00:33:54,960 --> 00:33:57,480
Speaker 2: was kind of stuck in these like oscillations of density.

709
00:33:57,520 --> 00:33:58,680
Speaker 2: And that's what we see today.

710
00:33:58,760 --> 00:34:01,120
Speaker 1: The light was really powering these oscillations. It's the thing

711
00:34:01,160 --> 00:34:04,480
Speaker 1: that was pushing the baryons and the electrons along. Once

712
00:34:04,520 --> 00:34:07,440
Speaker 1: the electrons and baryons cooled so they became neutral, they're

713
00:34:07,440 --> 00:34:10,000
Speaker 1: no longer like riding this wave of the light, so

714
00:34:10,040 --> 00:34:11,960
Speaker 1: they sort of jump off the train. They get frozen

715
00:34:11,960 --> 00:34:14,319
Speaker 1: where they are, and the light continues on and it

716
00:34:14,400 --> 00:34:17,319
Speaker 1: just passes right through and it diffuses around, and that

717
00:34:17,360 --> 00:34:20,720
Speaker 1: becomes the cosmic microwave background light that we still see today.

718
00:34:20,840 --> 00:34:22,759
Speaker 1: So we see the echoes and the ripples of that

719
00:34:22,840 --> 00:34:24,880
Speaker 1: light today and we can measure it. But the baryons

720
00:34:24,960 --> 00:34:27,640
Speaker 1: electrons got left behind after that moment when they could

721
00:34:27,680 --> 00:34:30,960
Speaker 1: no longer ride the light train, because they became neutral.

722
00:34:31,000 --> 00:34:32,879
Speaker 2: Right, Yeah, that's kind of what I mean is that

723
00:34:33,239 --> 00:34:36,520
Speaker 2: it's not like the photons continue to ripple with this sound.

724
00:34:36,520 --> 00:34:39,000
Speaker 2: It's more like you took out the regular matter and

725
00:34:39,040 --> 00:34:42,520
Speaker 2: so the photons that were creating those waves stayed in

726
00:34:42,560 --> 00:34:45,160
Speaker 2: those different layers of density, and.

727
00:34:45,200 --> 00:34:47,919
Speaker 1: The photons can keep propagating out and rippling, and they did.

728
00:34:48,040 --> 00:34:50,120
Speaker 1: In truth, it's a little bit more complicated, it's like

729
00:34:50,160 --> 00:34:53,080
Speaker 1: sloshing back and forth. But basically the picture you should

730
00:34:53,080 --> 00:34:55,279
Speaker 1: have in your head is like a core of dark

731
00:34:55,360 --> 00:34:59,000
Speaker 1: matter and then these rings of frozen sound waves. At

732
00:34:59,040 --> 00:35:02,200
Speaker 1: the time, we're talking about like five hundred thousand light

733
00:35:02,280 --> 00:35:05,319
Speaker 1: years across, where you should have like more baryons, like

734
00:35:05,320 --> 00:35:08,800
Speaker 1: a higher density of baryons, this baryons frozen sound wave

735
00:35:09,320 --> 00:35:11,840
Speaker 1: like five hundred thousand light years across, and then the

736
00:35:11,920 --> 00:35:14,440
Speaker 1: light continuing on and slashing through the whole universe.

737
00:35:14,800 --> 00:35:17,600
Speaker 2: Right, It's almost like the light the photons were holding

738
00:35:17,600 --> 00:35:20,160
Speaker 2: the regular matter in these wave patterns, and then you

739
00:35:20,200 --> 00:35:23,520
Speaker 2: took away the wave the water basically, and so you

740
00:35:23,600 --> 00:35:25,880
Speaker 2: have this light kind of stuck in that pattern.

741
00:35:25,960 --> 00:35:28,480
Speaker 1: And we think that basically this seated the structure of

742
00:35:28,520 --> 00:35:31,840
Speaker 1: the whole universe. After this point, gravity takes over. In

743
00:35:31,920 --> 00:35:34,640
Speaker 1: places that you have more dark matter and more baryons,

744
00:35:34,960 --> 00:35:37,080
Speaker 1: things are going to get clustered together more and more

745
00:35:37,120 --> 00:35:38,560
Speaker 1: and more, and that's where you're going to end up

746
00:35:38,560 --> 00:35:40,840
Speaker 1: getting galaxies, and that's where you're going to end up

747
00:35:40,840 --> 00:35:43,840
Speaker 1: getting gas clouds, and then stars and planets and people

748
00:35:43,880 --> 00:35:46,520
Speaker 1: and podcasts and eventually boba.

749
00:35:46,040 --> 00:35:50,000
Speaker 2: And bows as well. All right, well, let's dig into

750
00:35:50,080 --> 00:35:53,360
Speaker 2: how we can see this cosmic microwave background. Well, we

751
00:35:53,440 --> 00:35:55,719
Speaker 2: know about it and also what it means about how

752
00:35:55,719 --> 00:35:57,799
Speaker 2: we ended up here today, So let's dig into that.

753
00:35:57,840 --> 00:36:12,719
Speaker 2: But first let's take another quick break. All Right, we're

754
00:36:12,760 --> 00:36:15,719
Speaker 2: talking about the sound of the early universe, and it

755
00:36:15,800 --> 00:36:18,040
Speaker 2: sounds like. It sounded kind of uncomfortable. It was really

756
00:36:18,040 --> 00:36:21,640
Speaker 2: hot and crowded, and the regular matter in the universe

757
00:36:21,680 --> 00:36:22,840
Speaker 2: did not like it exactly.

758
00:36:23,080 --> 00:36:26,040
Speaker 1: Very loud but very short lived early universe scream.

759
00:36:26,280 --> 00:36:28,520
Speaker 2: And so you were saying that you had these ripples

760
00:36:28,560 --> 00:36:31,600
Speaker 2: of matter kind of bouncing back from being compressed. Things

761
00:36:31,600 --> 00:36:34,120
Speaker 2: were slashing around, things had sound waves in it. But

762
00:36:34,200 --> 00:36:37,120
Speaker 2: then at some point the regular matter kind of froze

763
00:36:37,160 --> 00:36:40,680
Speaker 2: into place. They got together into atoms, which then let

764
00:36:40,719 --> 00:36:43,400
Speaker 2: the light continue on. Does that mean that at that

765
00:36:43,520 --> 00:36:45,160
Speaker 2: point the universe went silent?

766
00:36:46,960 --> 00:36:49,680
Speaker 1: Yeah, basically that's when the universe quieted down and the

767
00:36:49,680 --> 00:36:53,200
Speaker 1: speed of sound dropped really really fast. Right, So things

768
00:36:53,239 --> 00:36:54,880
Speaker 1: couldn't propagate nearly as fast.

769
00:36:55,040 --> 00:36:58,440
Speaker 2: Why not, Like we wouldn't regular atoms carry those waves.

770
00:36:58,640 --> 00:37:00,840
Speaker 1: Well, regular atoms can still carry waves the way they

771
00:37:00,920 --> 00:37:03,000
Speaker 1: do today, Like the sound we hear today is mostly

772
00:37:03,040 --> 00:37:05,840
Speaker 1: in neutral atoms in the air. Right, So neutral atoms

773
00:37:05,960 --> 00:37:08,880
Speaker 1: certainly can bump into each other and can certainly carry

774
00:37:08,880 --> 00:37:11,160
Speaker 1: sound waves. But the pressure was just a lot lower

775
00:37:11,280 --> 00:37:14,239
Speaker 1: because the photons had decoupled, and so the density was

776
00:37:14,280 --> 00:37:16,239
Speaker 1: a lot lower, and so the speed of sound just

777
00:37:16,320 --> 00:37:19,319
Speaker 1: dropped very quickly, and so there still was sound, it

778
00:37:19,360 --> 00:37:22,080
Speaker 1: was just much slower moving. It's no longer anywhere close

779
00:37:22,160 --> 00:37:24,960
Speaker 1: to the speed of light, and so it's effectively frozen

780
00:37:25,000 --> 00:37:28,240
Speaker 1: because soundwaves can still propagate, but just very very slowly.

781
00:37:28,280 --> 00:37:30,080
Speaker 1: So things are not going to change very fast the

782
00:37:30,080 --> 00:37:31,040
Speaker 1: way they had initially.

783
00:37:31,200 --> 00:37:33,239
Speaker 2: I wonder if you can still measure those waves in

784
00:37:33,320 --> 00:37:35,319
Speaker 2: the regular matter, you know what I mean? Like, I

785
00:37:35,360 --> 00:37:38,160
Speaker 2: wonder if like collectively all the galaxies in the universe

786
00:37:38,200 --> 00:37:42,719
Speaker 2: still has ours kind of slashing around or being moved

787
00:37:42,719 --> 00:37:44,200
Speaker 2: around by those sound waves.

788
00:37:44,239 --> 00:37:46,440
Speaker 1: Absolutely you can, and we have looked for this and

789
00:37:46,480 --> 00:37:49,040
Speaker 1: we have actually seen it. We can see these waves

790
00:37:49,040 --> 00:37:51,920
Speaker 1: in two different ways. One, we can look back at

791
00:37:51,920 --> 00:37:55,240
Speaker 1: those photons from the early universe and see these ripples,

792
00:37:55,600 --> 00:37:58,000
Speaker 1: like there were more photons in some places than in others.

793
00:37:58,080 --> 00:38:00,439
Speaker 1: We can look back at those photons ones that we're

794
00:38:00,440 --> 00:38:03,600
Speaker 1: created when the universe just became transparent, that's the cosmic

795
00:38:03,680 --> 00:38:06,520
Speaker 1: microwave background radiation, and we see these ripples and we

796
00:38:06,520 --> 00:38:09,479
Speaker 1: see exactly what we expect. But we can also see

797
00:38:09,480 --> 00:38:12,640
Speaker 1: it in the structure of the universe today. Those rings

798
00:38:12,640 --> 00:38:15,239
Speaker 1: that were five hundred thousand light years across, they expanded

799
00:38:15,280 --> 00:38:18,000
Speaker 1: as the universe expands and now we expect them to

800
00:38:18,000 --> 00:38:21,279
Speaker 1: be about five hundred million light years across. So what

801
00:38:21,320 --> 00:38:23,560
Speaker 1: people have done is they've looked at the distribution of

802
00:38:23,600 --> 00:38:26,680
Speaker 1: galaxies and they say, hm, our galaxies just like sprinkled

803
00:38:26,760 --> 00:38:31,279
Speaker 1: randomly everywhere, or is there a typical distance between the galaxies?

804
00:38:31,320 --> 00:38:33,839
Speaker 1: How are they clustered? So they gathered a bunch of

805
00:38:33,880 --> 00:38:37,680
Speaker 1: galaxies together, they did these redshift measurements to see how

806
00:38:37,719 --> 00:38:39,839
Speaker 1: far away they are, so we can have a three

807
00:38:39,920 --> 00:38:42,120
Speaker 1: D map of the galaxies in the universe. And then

808
00:38:42,160 --> 00:38:44,640
Speaker 1: they just like counted up what is the distance between

809
00:38:44,640 --> 00:38:48,080
Speaker 1: all the pairs of galaxies? Is there any preferred distance?

810
00:38:49,000 --> 00:38:50,640
Speaker 2: And what did they find? Did they find that there's

811
00:38:51,120 --> 00:38:54,240
Speaker 2: so even or did they find that this distance varied

812
00:38:54,320 --> 00:38:55,640
Speaker 2: according to leg a soundwave?

813
00:38:55,920 --> 00:38:57,960
Speaker 1: So they found that it was not smooth, that there

814
00:38:58,000 --> 00:39:00,160
Speaker 1: was a bump there, that you were more like you

815
00:39:00,320 --> 00:39:03,759
Speaker 1: have galaxies about five hundred million light years apart than

816
00:39:03,760 --> 00:39:06,200
Speaker 1: you were other distances. And this is exactly what they

817
00:39:06,239 --> 00:39:09,640
Speaker 1: expected to see because those rings the sound horizon from

818
00:39:09,680 --> 00:39:13,080
Speaker 1: the early universe was five hundred thousand light years across

819
00:39:13,120 --> 00:39:16,040
Speaker 1: at that time. But the universe has expanded since right

820
00:39:16,080 --> 00:39:19,400
Speaker 1: We've had deceleration and acceleration. We know the expansion history

821
00:39:19,440 --> 00:39:22,040
Speaker 1: of the universe, and we expect those rings to now

822
00:39:22,120 --> 00:39:24,640
Speaker 1: be five hundred million light years across. And when you

823
00:39:24,680 --> 00:39:27,120
Speaker 1: look at the distribution of galaxies, you see many more

824
00:39:27,120 --> 00:39:28,920
Speaker 1: at that distance apart than you do at like four

825
00:39:29,000 --> 00:39:31,560
Speaker 1: hundred million or six hundred million. So this is like

826
00:39:31,600 --> 00:39:33,680
Speaker 1: twenty years ago. In two thousand and five, they saw

827
00:39:33,719 --> 00:39:38,000
Speaker 1: this statistical evidence for the Bury on acoustic ostellations that

828
00:39:38,080 --> 00:39:40,719
Speaker 1: when you add up all these galaxies and compare their distances,

829
00:39:40,960 --> 00:39:43,840
Speaker 1: you tend to see the more at exactly the size

830
00:39:43,920 --> 00:39:45,040
Speaker 1: of this sound ring.

831
00:39:46,080 --> 00:39:49,439
Speaker 2: No wait, are you saying that somehow this early sound

832
00:39:49,480 --> 00:39:53,080
Speaker 2: wave got frozen and the distances between galaxies and the

833
00:39:53,120 --> 00:39:55,799
Speaker 2: structure of the universe, or are you saying this sound

834
00:39:55,840 --> 00:39:58,680
Speaker 2: wave is still rippling through the structure of the universe.

835
00:39:58,800 --> 00:40:01,640
Speaker 1: They got frozen in the early universe and then gravity

836
00:40:01,680 --> 00:40:04,440
Speaker 1: took over it like seeded the structure. It's like if

837
00:40:04,440 --> 00:40:06,800
Speaker 1: somebody sprinkled a bunch of seeds in a circle and

838
00:40:06,960 --> 00:40:08,640
Speaker 1: you came back one hundred years later and you found

839
00:40:08,640 --> 00:40:10,480
Speaker 1: a bunch of oak trees and you wondered, like, why

840
00:40:10,520 --> 00:40:12,799
Speaker 1: are there oak trees in a circle? It comes from

841
00:40:12,880 --> 00:40:15,919
Speaker 1: the initial distribution of seeds. And so here we're talking

842
00:40:15,960 --> 00:40:18,839
Speaker 1: about slashing around the very early universe when things were

843
00:40:18,880 --> 00:40:22,680
Speaker 1: still very chaotic, left this over density of baryons in

844
00:40:22,719 --> 00:40:26,000
Speaker 1: these sound rings which no longer were able to ripple

845
00:40:26,000 --> 00:40:28,880
Speaker 1: as fast because the photons the decoupled and weren't pushing

846
00:40:28,880 --> 00:40:31,640
Speaker 1: them anymore, and things got cooler and less dense. And

847
00:40:31,640 --> 00:40:35,120
Speaker 1: those are likely initial seeds which formed galaxies, which grew

848
00:40:35,200 --> 00:40:36,279
Speaker 1: up to be galaxies.

849
00:40:37,200 --> 00:40:40,200
Speaker 2: I see. So we also see these frozen sound waves

850
00:40:40,280 --> 00:40:41,200
Speaker 2: out there exactly.

851
00:40:41,239 --> 00:40:43,960
Speaker 1: And so about twenty years ago people saw the statistical evidence.

852
00:40:44,000 --> 00:40:46,239
Speaker 1: They're like, oh, the galaxies tend to be more far

853
00:40:46,280 --> 00:40:49,120
Speaker 1: apart at this particular distance than other distances. And that

854
00:40:49,239 --> 00:40:52,360
Speaker 1: was evidence that the baryon acoustic ostellations were real, that

855
00:40:52,400 --> 00:40:54,840
Speaker 1: we were seeing them in the universe. But very excitingly,

856
00:40:54,920 --> 00:40:58,240
Speaker 1: just a few weeks ago, people see an actual single bubble.

857
00:40:58,640 --> 00:41:01,080
Speaker 1: When you look out into the unit, you can actually

858
00:41:01,120 --> 00:41:04,640
Speaker 1: see like a ring, a huge structure, ring of galaxies

859
00:41:04,680 --> 00:41:08,960
Speaker 1: and superclusters lined up into a massive bubble. How big

860
00:41:09,080 --> 00:41:11,520
Speaker 1: this thing is, a ring structure about two hundred and

861
00:41:11,520 --> 00:41:15,160
Speaker 1: fifty mega parsecs around, And we're sort of near the

862
00:41:15,200 --> 00:41:17,640
Speaker 1: center of it, and at the actual center of it

863
00:41:17,680 --> 00:41:21,239
Speaker 1: is this huge supercluster called the Buches supercluster, which we

864
00:41:21,280 --> 00:41:23,839
Speaker 1: think was gathered together because there's a huge dark matter

865
00:41:23,880 --> 00:41:26,480
Speaker 1: blob at the center of this ripple. And then along

866
00:41:26,520 --> 00:41:29,840
Speaker 1: the edges are other superclusters that we found, like the

867
00:41:29,920 --> 00:41:33,080
Speaker 1: Slow and Great Wall and other pieces that we've been

868
00:41:33,120 --> 00:41:36,120
Speaker 1: discovering of structure here and there in the universe. Turns

869
00:41:36,120 --> 00:41:40,520
Speaker 1: out they assemble themselves into this incredible, enormous ring two

870
00:41:40,640 --> 00:41:42,719
Speaker 1: hundred and fifty mega parsex across.

871
00:41:43,200 --> 00:41:45,560
Speaker 2: Now it's a bubble because, as you said, the early

872
00:41:45,680 --> 00:41:49,240
Speaker 2: universe dark matter brought together this barren matter, the barrion

873
00:41:49,320 --> 00:41:52,120
Speaker 2: matter bounce back, and when it bounced back, I guess

874
00:41:52,120 --> 00:41:54,200
Speaker 2: it looked like a bubble, right, that's what you're saying.

875
00:41:54,239 --> 00:41:56,920
Speaker 2: And then the universe expanded, things froze, and we still

876
00:41:56,920 --> 00:41:58,840
Speaker 2: see that bubble today exactly.

877
00:41:58,880 --> 00:42:00,600
Speaker 1: And you can look at this paper. You can see

878
00:42:00,640 --> 00:42:03,439
Speaker 1: in this distribution of galaxies this sort of faint ring.

879
00:42:03,800 --> 00:42:05,000
Speaker 1: It's not crisp and clear.

880
00:42:05,040 --> 00:42:07,160
Speaker 2: It's not like there're no legs a ring or a bubble.

881
00:42:07,239 --> 00:42:09,000
Speaker 1: It's definitely a bubble. It's a sphere. But you know

882
00:42:09,040 --> 00:42:11,760
Speaker 1: this is a physics paper, which means it's two dimensional slices.

883
00:42:12,080 --> 00:42:13,920
Speaker 1: So if you look at the slices, you know, we

884
00:42:13,960 --> 00:42:15,799
Speaker 1: don't publish in three D yet, we're not three D

885
00:42:15,840 --> 00:42:18,839
Speaker 1: printing our papers. But actually, if you look online, they

886
00:42:18,880 --> 00:42:21,000
Speaker 1: have a really cool animation of which you can see

887
00:42:21,000 --> 00:42:22,839
Speaker 1: the three D version, So it definitely has a three

888
00:42:22,880 --> 00:42:25,520
Speaker 1: D structure. But in two D slices you see rings.

889
00:42:25,760 --> 00:42:28,040
Speaker 2: I see. But was the analysis done in rings or

890
00:42:28,120 --> 00:42:29,680
Speaker 2: was it done in a bubble? Or were you saying

891
00:42:29,719 --> 00:42:31,680
Speaker 2: ring because that's how you read it in the paper.

892
00:42:31,800 --> 00:42:33,960
Speaker 1: Well, originally they spotted it as a ring. They were

893
00:42:33,960 --> 00:42:36,480
Speaker 1: just like, hold on, is that a huge ring? And

894
00:42:36,520 --> 00:42:38,400
Speaker 1: then they started looking in three D They're like, wow,

895
00:42:38,440 --> 00:42:39,960
Speaker 1: look at that. It really is kind of a bubble.

896
00:42:39,960 --> 00:42:41,719
Speaker 1: And then they calculated the size of it and they

897
00:42:41,760 --> 00:42:43,759
Speaker 1: were like, huh, this is exactly the size you would

898
00:42:43,800 --> 00:42:47,400
Speaker 1: expect from a single baryon acoustic ostellation bubble, which nobody

899
00:42:47,400 --> 00:42:49,879
Speaker 1: had ever seen before. And these folks, they weren't looking

900
00:42:49,960 --> 00:42:52,520
Speaker 1: for this. They were doing some other studies of galaxies

901
00:42:52,560 --> 00:42:55,080
Speaker 1: and their distributions, and they just like spotted this visual

902
00:42:55,160 --> 00:42:57,759
Speaker 1: and they were like, hold on a second, this is

903
00:42:57,960 --> 00:43:00,840
Speaker 1: literally a frozen scream from the early universe.

904
00:43:01,400 --> 00:43:03,840
Speaker 2: Whoa They were like, that's a big boba.

905
00:43:04,360 --> 00:43:06,799
Speaker 1: It's a big that's when you would choke on for sure.

906
00:43:07,000 --> 00:43:09,040
Speaker 2: Yeah, they choke Maybe they were drinking boba at the time.

907
00:43:09,080 --> 00:43:11,000
Speaker 2: They're like, well, what what is that?

908
00:43:12,320 --> 00:43:14,560
Speaker 1: And I think it's super cool because it gives us

909
00:43:14,560 --> 00:43:17,799
Speaker 1: a way to understand not just how our universe was

910
00:43:17,840 --> 00:43:19,839
Speaker 1: formed and why we have galaxies over here and why

911
00:43:19,880 --> 00:43:23,640
Speaker 1: we have galaxies over there, but also how the universe expanded,

912
00:43:24,040 --> 00:43:26,200
Speaker 1: Like we know how big that sound wave when it

913
00:43:26,239 --> 00:43:28,239
Speaker 1: was created, because it just comes down to like the

914
00:43:28,239 --> 00:43:31,160
Speaker 1: physics of protons and photons and dark matter, how they

915
00:43:31,160 --> 00:43:33,319
Speaker 1: push on each other, and we know how big they are.

916
00:43:33,400 --> 00:43:35,880
Speaker 1: Now we can measure them, and so that gives us

917
00:43:35,920 --> 00:43:39,280
Speaker 1: like an independent way to measure the expansion of the universe,

918
00:43:39,320 --> 00:43:41,600
Speaker 1: which of course is a big question and a deep mystery,

919
00:43:41,640 --> 00:43:43,800
Speaker 1: like the source of dark energy and how that all works.

920
00:43:44,080 --> 00:43:46,560
Speaker 2: I guess maybe a question is why do we see

921
00:43:46,600 --> 00:43:49,239
Speaker 2: more of these bubbles, Like wasn't the universe filled with

922
00:43:49,280 --> 00:43:52,240
Speaker 2: these sound ways and these screams of the early universe.

923
00:43:52,320 --> 00:43:53,840
Speaker 2: We aren't these bubbles more obvious?

924
00:43:54,040 --> 00:43:57,280
Speaker 1: Yeah, great question. We haven't seen that much of the universe.

925
00:43:57,320 --> 00:44:00,560
Speaker 1: You know, our precision maps of the locations of galaxies

926
00:44:00,600 --> 00:44:03,680
Speaker 1: basically are just big enough to include one of these.

927
00:44:03,840 --> 00:44:06,040
Speaker 1: If you look online and check this thing out, you

928
00:44:06,080 --> 00:44:09,600
Speaker 1: see that this one bubble occupies a huge fraction of

929
00:44:09,640 --> 00:44:12,440
Speaker 1: the known galaxies we've seen. We just haven't looked out

930
00:44:12,480 --> 00:44:14,320
Speaker 1: far enough to see one of these things before.

931
00:44:14,600 --> 00:44:16,759
Speaker 2: Oh wow, it's that big of a bubble, Like it's

932
00:44:16,800 --> 00:44:18,600
Speaker 2: almost the size of the observable universe.

933
00:44:18,600 --> 00:44:20,400
Speaker 1: You're saying, it's almost the size of the set of

934
00:44:20,440 --> 00:44:23,600
Speaker 1: galaxies that we have mapped. Well, yeah, as things get

935
00:44:23,640 --> 00:44:25,960
Speaker 1: further out, it's harder and harder to map these things.

936
00:44:26,000 --> 00:44:29,000
Speaker 1: You need more and more precise measurements. Like if we

937
00:44:29,080 --> 00:44:31,840
Speaker 1: could use a James Webspace telescope and pointed in every

938
00:44:31,880 --> 00:44:34,520
Speaker 1: direction for a month, we would get an awesome map

939
00:44:34,560 --> 00:44:36,960
Speaker 1: of the galaxies in the universe. But the map we

940
00:44:37,000 --> 00:44:39,560
Speaker 1: have is really sporadic, and in some places it goes

941
00:44:39,560 --> 00:44:41,840
Speaker 1: really far. In some places it doesn't because we just

942
00:44:41,880 --> 00:44:45,040
Speaker 1: don't have enough telescopes and enough telescope time to do

943
00:44:45,080 --> 00:44:46,200
Speaker 1: these careful surveys.

944
00:44:46,320 --> 00:44:48,000
Speaker 2: Well, as you said, it sort of gives us sort

945
00:44:48,040 --> 00:44:50,400
Speaker 2: of like a marker in the history of the universe

946
00:44:50,680 --> 00:44:53,120
Speaker 2: and how it expanded. And now what's the connection to

947
00:44:53,239 --> 00:44:53,840
Speaker 2: dark energy.

948
00:44:53,880 --> 00:44:56,560
Speaker 1: Well, dark energy is our word for how the universe

949
00:44:56,600 --> 00:44:59,799
Speaker 1: expanded and how that expansion has accelerated. The picture we

950
00:44:59,800 --> 00:45:02,280
Speaker 1: have is that the early universe was dominated by matter

951
00:45:02,320 --> 00:45:05,960
Speaker 1: and radiation early on and expanded and things cooled. But

952
00:45:06,000 --> 00:45:09,000
Speaker 1: then that matter radiation starts to decelerate the expansion of

953
00:45:09,000 --> 00:45:11,440
Speaker 1: the universe, start to slow it down, because that's what

954
00:45:11,560 --> 00:45:14,680
Speaker 1: energy density does. It curves space and pulls things back together.

955
00:45:14,920 --> 00:45:17,560
Speaker 1: But at the same time, some new force was waking up,

956
00:45:17,600 --> 00:45:20,240
Speaker 1: something we call dark energy, was pushing the other direction

957
00:45:20,360 --> 00:45:23,400
Speaker 1: and accelerated the expansion of the universe. And this is

958
00:45:23,440 --> 00:45:25,640
Speaker 1: something we'd like to understand the detail because we don't

959
00:45:25,719 --> 00:45:28,360
Speaker 1: understand the mechanism for it, but we want to understand

960
00:45:28,400 --> 00:45:30,040
Speaker 1: the history so we can get a better sense for

961
00:45:30,160 --> 00:45:33,440
Speaker 1: what might have been causing this. So measuring the precise

962
00:45:33,560 --> 00:45:36,040
Speaker 1: rate of the expansion and how the universe has grown

963
00:45:36,080 --> 00:45:37,960
Speaker 1: over time is very, very valuable.

964
00:45:38,360 --> 00:45:40,839
Speaker 2: I see, because I guess these bubbles can't just come

965
00:45:40,920 --> 00:45:41,920
Speaker 2: up randomly, right.

966
00:45:41,840 --> 00:45:44,600
Speaker 1: Yeah, these bubbles have a fixed size in the early universe,

967
00:45:44,800 --> 00:45:47,839
Speaker 1: just determined by like the physics of acoustic oscillations which

968
00:45:47,840 --> 00:45:50,520
Speaker 1: we think we understand, and then they're stretched by dark

969
00:45:50,640 --> 00:45:53,080
Speaker 1: energy to a new size which we can measure. So

970
00:45:53,200 --> 00:45:56,239
Speaker 1: measuring the size of these bubbles now and comparing them

971
00:45:56,280 --> 00:45:58,200
Speaker 1: to the size we knew they had in the early

972
00:45:58,280 --> 00:46:00,799
Speaker 1: universe gives us a way to say how much has

973
00:46:00,840 --> 00:46:03,439
Speaker 1: the universe been stretched, which, of course is something we're

974
00:46:03,520 --> 00:46:04,200
Speaker 1: very interested in.

975
00:46:04,440 --> 00:46:08,120
Speaker 2: All right, Well, another interesting exploration into our origins and

976
00:46:08,200 --> 00:46:10,759
Speaker 2: how much we can and how much we still don't

977
00:46:10,800 --> 00:46:11,920
Speaker 2: know about what was happening.

978
00:46:12,160 --> 00:46:14,759
Speaker 1: To me, it's amazing how cosmology has gone from a

979
00:46:14,800 --> 00:46:17,960
Speaker 1: field where it's like mostly hand wavy stories with rough

980
00:46:18,080 --> 00:46:20,640
Speaker 1: numbers to a field where we can measure things and

981
00:46:20,680 --> 00:46:24,239
Speaker 1: do precise calculations and compare this and that and know

982
00:46:24,400 --> 00:46:27,880
Speaker 1: things about the early universe from these calculations. We have

983
00:46:27,960 --> 00:46:31,520
Speaker 1: filtered through crazy data to get these stories of the universe,

984
00:46:31,560 --> 00:46:34,960
Speaker 1: to find these clues to build back this history of

985
00:46:35,040 --> 00:46:36,920
Speaker 1: what happened and how we all got here.

986
00:46:37,600 --> 00:46:40,480
Speaker 2: I see it's now precision handwaiting.

987
00:46:42,200 --> 00:46:44,400
Speaker 1: Baby steps, man, baby steps, Boba steps.

988
00:46:44,880 --> 00:46:46,200
Speaker 2: You need a thicker straw.

989
00:46:47,440 --> 00:46:49,759
Speaker 1: Well, we need are more smart people thinking hard about

990
00:46:49,760 --> 00:46:53,040
Speaker 1: how the universe works and asking questions and listening to podcasts.

991
00:46:53,239 --> 00:46:55,600
Speaker 2: All right, Well, the next time you're in a crowded subway,

992
00:46:55,640 --> 00:46:58,520
Speaker 2: think about how the universe felt back then, how it's

993
00:46:58,520 --> 00:47:01,359
Speaker 2: screamed out in a discomfort, and how we still see

994
00:47:01,400 --> 00:47:05,840
Speaker 2: those screams today in the shape and the distribution of

995
00:47:05,880 --> 00:47:07,359
Speaker 2: galaxies and also light.

996
00:47:07,719 --> 00:47:10,560
Speaker 1: And please continue to enjoy your boba at your own risk.

997
00:47:10,840 --> 00:47:12,879
Speaker 2: Well, we hope you enjoyed that. Thanks for joining us,

998
00:47:13,640 --> 00:47:14,359
Speaker 2: see you next time.

999
00:47:22,239 --> 00:47:25,040
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

1000
00:47:25,080 --> 00:47:29,080
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts

1001
00:47:29,080 --> 00:47:33,760
Speaker 1: from iHeartRadio, visit the iHeartRadio Apple Apple Podcasts, or wherever

1002
00:47:33,800 --> 00:47:35,600
Speaker 1: you listen to your favorite shows.