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Speaker 1: Hey, Daniel, I think we've been using too much toilet humor.

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Speaker 2: You mean, all those obvious dark matter jokes we make.

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Speaker 1: Yeah, you know, I'm sure it makes all the nine

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Speaker 1: year old to google in the audience. But I don't

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Speaker 1: think we want to undercut our educational message.

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Speaker 2: All right, that's a good point. Let's try that. All right.

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Speaker 1: Well, so what are we talking about today today?

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Speaker 2: We're talking about hot gas.

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Speaker 1: Well, that didn't last very long. Hi. I am joeham Mack,

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Speaker 1: cartoonists and the author of Oliver's Great Big Universe. Hi.

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Speaker 2: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 2: UC Irvine, and I'm often full of hot air.

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Speaker 1: Are an all physicists full of hot air?

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Speaker 2: I'm just talking about the weather here in southern California.

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Speaker 2: I don't know what you mean.

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Speaker 1: What do you mean the weather is inside of you.

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Speaker 2: I'm breathing in the atmosphere literally.

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Speaker 1: I guess if you were breathing out cold there, that

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Speaker 1: would be bad news, because we all know physicists aren't

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Speaker 1: very cool.

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Speaker 2: I'm trying to make physics hot, is what I'm doing.

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Speaker 1: But anyways, welcome to our podcast. Daniel and Jorge explain

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Speaker 1: the Universe, a production of iHeartRadio.

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Speaker 2: In which we try to marinate in all of the

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Speaker 2: wonders and mysteries of the universe. We think that everything

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Speaker 2: that's out there should make sense to you, can make

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Speaker 2: sense to you, will make sense to you if you

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Speaker 2: just think about it, ask enough questions and listen to

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Speaker 2: this podcast long enough.

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Speaker 1: That's why we try to breathe in the universe and

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Speaker 1: breathe it out and think about all of the hot

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Speaker 1: and cold stuff out there in the universe, even the

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Speaker 1: things in toilets.

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Speaker 2: I thought we're avoiding the toilet jokes.

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Speaker 1: Well that was in the joke. I mean, there is

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Speaker 1: physics in toilets, isn't there.

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Speaker 2: That's true. You once challenged our listeners to record their

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Speaker 2: toilet spinning to see if they flush differently in Australia.

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Speaker 1: Oh did they do it.

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Speaker 2: I haven't gotten any didy yet, so we're still waiting

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Speaker 2: for the rest to those experiments. But that is serious

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Speaker 2: toilet science.

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Speaker 1: Yeah, there you go.

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Speaker 2: But in the non toilet realm of the universe, we

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Speaker 2: are very curious about how everything works out there, and

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Speaker 2: more specifically, what's out there and where is it all?

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Speaker 2: Can we figure out what in the end the universe

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Speaker 2: is made out of and where it's all distributed.

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Speaker 1: Yeah, because that is a fundamental human quest to figure

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Speaker 1: out what's going on out there. What is this universe

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Speaker 1: we're in, what's in it? Who else is in it?

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Speaker 1: And what is it made out of?

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Speaker 2: And where have they been dropping all their trash?

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Speaker 1: Wait?

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Speaker 2: What well you mentioned who else is in it? Makes

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Speaker 2: it sound like, you know, we're trying to figure out

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Speaker 2: where all their stuff is, Like did they lose their keys?

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Speaker 2: Where did that box go? This kind of stuff?

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Speaker 1: I was just wondering, you know, so we could say, hi,

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Speaker 1: not find their keys.

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Speaker 2: The first thing we want to do when we talk

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Speaker 2: to the aliens is ask them where they left their stuff.

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Speaker 2: Is this your trash? Did you leave this over here?

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Speaker 2: Please pick that up?

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Speaker 1: Although if they leave their keys to their spaceship line around,

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Speaker 1: I'm not really going to return that one. No one's

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Speaker 1: staying with me.

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Speaker 2: Well. On this podcast, we are often talking about one

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Speaker 2: of the deepest mysteries in modern physics, which is where

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Speaker 2: the dark matter is. We know that most of the

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Speaker 2: stuff in the universe is an invisible kind of matter

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Speaker 2: We've only recently discovered and have very little concrete information

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Speaker 2: about what it is. So we're used to the concept

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Speaker 2: of not understanding everything that's out there in the universe.

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Speaker 2: But it might surprise you to learn that even the

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Speaker 2: kind of stuff that we're used to, the hydrogen, the helium,

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Speaker 2: the kind of matter where made out of, is still

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Speaker 2: something of a mystery.

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Speaker 1: Wait what so then, how do we know how much

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Speaker 1: of it there is out there?

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Speaker 2: We have a bunch of really clever ways of figuring

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Speaker 2: out how much normal matter there should be out there

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Speaker 2: in the universe, but it's tricky to actually find all

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Speaker 2: of it.

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Speaker 1: I see, we know how much of there should be,

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Speaker 1: but we just haven't found it.

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Speaker 2: Is that what you're saying, that's basically it episode done?

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Speaker 1: All right, Well, thank you for joining us. I can

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Speaker 1: go do something else now.

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Speaker 2: Well, maybe the aliens have stolen all that missing matter.

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Speaker 1: WHOA, that's a pretty serious allegation or just you know,

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Speaker 1: impugning the goodwill of the aliens and their legality.

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Speaker 2: Well maybe instead of making a big mess, they've been

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Speaker 2: a little bit too aggressive about cleaning up after themselves.

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Speaker 1: Maybe it's the physicist mmm who stole all the matter

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Speaker 1: on the planet Earth with the wrench.

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Speaker 2: In the end, it's not about understanding the universe. It's

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Speaker 2: about figuring out who to blame for it.

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Speaker 1: Or who do thank for it? Right? Also, right, maybe

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Speaker 1: it's good that we live in this universe. I would

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Speaker 1: think so. But anyways, it is a big question about

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Speaker 1: where all the matter in the universe is that we

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Speaker 1: think should be there, and where it all went. So

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Speaker 1: today end the podcast, we'll be asking the question where

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Speaker 1: is all the missing matter? I guess this is kind

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Speaker 1: of a surprising question because because I didn't know there

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Speaker 1: was missing matter? Did this happen recently or a long

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Speaker 1: time ago?

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Speaker 2: I mean, you're making it sound like an Agatha Christie novel,

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Speaker 2: like the Case of the Missing Matter, Like we put

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Speaker 2: all this hydrogen over here and we came back and

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Speaker 2: it was gone.

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Speaker 1: Yeah. Yeah, there was a blackout, the lights went out,

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Speaker 1: there were some screens, and suddenly there was a missing

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Speaker 1: matter and we're all trapped on an island with a

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Speaker 1: limited number of suspects.

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Speaker 2: That's right. No, it's been a long standing mystery. It's

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Speaker 2: gotten a little bit less play and a less attention

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Speaker 2: than the grander mystery of dark matter, but it's still

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Speaker 2: a very important question in understanding how galaxies form and

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Speaker 2: how the universe looks the way that it does, and

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Speaker 2: where all this stuff is.

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Speaker 1: Now you're saying that this is actually called, or it's

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Speaker 1: called physics, the missing baryon problem.

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Speaker 2: Yeah, that's right, because the kind of matter that we

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Speaker 2: are made out of is made of protons and neutrons,

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Speaker 2: and those are things called baryons. A baryon is anything

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Speaker 2: made out of three quarks, and protons and neutrons are

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Speaker 2: made out of three quarks. So the kind of matter

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Speaker 2: that we are made out of, me and you, and

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Speaker 2: stars and galaxies and all the dust, all the visible

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Speaker 2: matter that's out there, we call that baryonic matter. And

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Speaker 2: so scientists have been trying to understand, like, where are

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Speaker 2: all the baryons in the universe? Are there as many

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Speaker 2: as we think there should be, And when they couldn't

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Speaker 2: find them, they call it the missing baryon problem.

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Speaker 1: M sounds very mysterious, and you also kind of make

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Speaker 1: it sound like it's somebody else's problem.

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Speaker 2: Hey, it's all about pre assignment to blame, right.

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Speaker 1: Right, Yeah, Like if you say like, yeah, it's a problem,

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Speaker 1: I think you're basically saying it's somebody else's problem.

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Speaker 2: Mistakes were made, right.

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Speaker 1: That's right, Yeah, things went missing.

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Speaker 2: Grand funding misallocated, I don't know.

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Speaker 1: So as usual, we were wondering how many people out

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Speaker 1: there knew or know that there is missing baryonic matter

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Speaker 1: out there in the universe.

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Speaker 2: So thanks very much to everybody who participates in this

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Speaker 2: segment of the podcast. We would love to hear your

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Speaker 2: voice among the coorse of listeners, so please don't be

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Speaker 2: shy write to me to questions at Danielandjorge dot com.

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Speaker 1: So think about it for a second. Do you know

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Speaker 1: where the missing baryonic matter in the universe could be?

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Speaker 1: What is the missing baryon problem?

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Speaker 3: I have never heard of the missing baryon problem, but

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Speaker 3: it might be something like the way that we had

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Speaker 3: predicted that the Higgs boson exists and we hadn't experimentally

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Speaker 3: verified it. So maybe there is a baryon, some form

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Speaker 3: of Bearyon particle that we mathematically know must exist, but

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Speaker 3: have it found.

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Speaker 1: I don't know what the missing baryon is, but I

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Speaker 1: hope someone finds it.

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Speaker 4: This is the term I've actually heard of before, if

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Speaker 4: I remember correctly. It has to do with the fact

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Speaker 4: that there is unexplained difference between the matter that existed

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Speaker 4: right after the Big Bang and the matter that exists today.

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Speaker 5: The baryon sounds like some sort of barrier to a atom,

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Speaker 5: So I suppose if it's missing, then it would be

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Speaker 5: some sort of other force that we cannot explain, that

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Speaker 5: it is holding something like an atom together.

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Speaker 1: All right, or interviews here didn't give us a lot

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Speaker 1: of clues.

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Speaker 2: This has not gotten a lot of press compared to

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Speaker 2: dark matter, out of which they've been like dozens and

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Speaker 2: dozens of books written, and it's all sorts of podcasts.

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Speaker 2: Whatever it's name is problem in physics, but the missing

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Speaker 2: baryon problem is sort of like its second cousin that

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Speaker 2: doesn't get top building.

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Speaker 1: It sounds like maybe it's a branding problem, you know,

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Speaker 1: like dark matter. Where's the dark matter in the universe?

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Speaker 1: That sounds mysterious and intriguing. Where's the baryonic matter in

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Speaker 1: the universe. It's like, I'm not a fan of Barry.

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Speaker 2: What they should have called it the dark baryons or something.

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Speaker 1: M yeah, or some other name, right, shining matter, super matter.

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Speaker 2: Well, you know, dark means a lot of different things.

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Speaker 2: As you know, dark can mean mysterious, unknown, not yet understood.

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Speaker 2: It can mean literally dark light does not emit light.

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Speaker 2: And it's confusing because there are things out there that

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Speaker 2: are dark and are made of matter, but are not

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Speaker 2: dark matter, right, Like a lump of charcoal is pretty dark,

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Speaker 2: but it's not dark matter.

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Speaker 1: You might think that physicists name thinks, very confusingly.

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Speaker 2: The missing Physics name committee.

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Speaker 1: So there's a bunch of matter that's missing that we

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Speaker 1: think should be there, but it's missing. That's what we'll

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Speaker 1: be talking about here today. And so let's break it down, Daniel.

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Speaker 1: What is baryonic matter?

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Speaker 2: So baryonic matter is our kind of matter, hydrogen, helium,

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Speaker 2: all of the elements are built out of baryons, because again,

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Speaker 2: a baryon is a particle made of three quarks. Number.

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Speaker 2: Quarks are these little particles that we think are probably fundamental,

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Speaker 2: maybe fundamental, but they interact with the strong nuclear force.

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Speaker 2: And the way they form stable objects is either you

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Speaker 2: get a pair of quarks like quark antiquark that can

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Speaker 2: make a pion, or you can get three of them

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Speaker 2: together to cancel out a red quark, a green cork,

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Speaker 2: and a blue quark, and that gives you a color

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Speaker 2: neutral object like a proton or a neutron that has

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Speaker 2: no overall strong force.

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Speaker 1: Okay, So a baryotic matter is matter made out of

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Speaker 1: quarks basically, right, that's the basic definition of it, like

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Speaker 1: the things that we're made out of, which are protons

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Speaker 1: and neutrons. But it sounds like there are other things

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Speaker 1: besides protons and neutrons you can make out of quarks.

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Speaker 2: Yeah, you can make all kinds of things out of quarks.

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Speaker 2: You can make other hadrons. There's other combinations of quarks

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Speaker 2: that you can use to make other hadrons, like you

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Speaker 2: put three strange quarks together, or you can make an

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Speaker 2: up and down and a strange etc. There's lots of

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Speaker 2: different baryons you can make out of three quarks. You

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Speaker 2: can also make combinations out of pairs of quarks. It's

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Speaker 2: a huge zoo of particles made out of quark pairs.

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Speaker 2: The only stable one is the proton. The proton by

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Speaker 2: itself we think will last for a long long time,

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Speaker 2: and the neutron is stable when combined with the proton

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Speaker 2: inside of nucleus. So that's why protons and neutrons are

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Speaker 2: the most common kind of baryon out there.

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Speaker 1: So today we're talking about which kind specifically all of

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Speaker 1: them or mostly protons and neutrons.

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Speaker 2: Mostly protons and neutrons, because that's what we expect the

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Speaker 2: baryons out there to be made out of. If you

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Speaker 2: have other baryons out there, they typically decay down to

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Speaker 2: protons and neutrons. Really, though, we're trying to account for

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Speaker 2: all the quarks. In the end, we don't really care

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Speaker 2: if they're in protons or in neutrons, or in helium

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Speaker 2: or in hydrogen. We just want to know how much

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Speaker 2: of our kind of matter, quark based matter, is there,

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Speaker 2: and how much of the other stuff is there, and

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Speaker 2: can we figure out where all the quarks.

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Speaker 1: Went saying baryon matter, barry on which kind of matter

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Speaker 1: it settles in.

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Speaker 2: Yeah, that's right, And it's a fascinating situation to be

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Speaker 2: in because we have all these really clever ways of

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Speaker 2: knowing how many quarks there should be in the universe.

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Speaker 2: That seems sort of crazy, like, how could you possibly

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Speaker 2: have an idea of how many quarks they're on the universe.

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Speaker 2: They're here, they're there, they're everywhere. How could you possibly

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Speaker 2: count them?

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Speaker 1: Well, I mean that's kind of basically what you're asking, right,

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Speaker 1: is you're asking where are all the quarks in the universe?

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Speaker 2: Right, exactly. We are asking that, but we're asking in

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Speaker 2: two ways. One way is using information from the very

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Speaker 2: early universe, which tells us how many quarks there should be,

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Speaker 2: and then another way is more direct, is going out

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Speaker 2: there and actually looking for them and saying, can we

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Speaker 2: find all the quarks that our early universe theories predict

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Speaker 2: are out there? And that's where the discrepancy comes from.

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Speaker 1: Hmmm, So I think you're saying that we could have

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Speaker 1: just titled the episode where are all the Missing quarks?

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Speaker 2: Yeah, where are all the missing quarks? Exactly? But in

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Speaker 2: physics it's called the missing barrier problem, and it makes

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Speaker 2: up the kind of matter that we're familiar with. Right,

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Speaker 2: we think that dark matter is not made of quarks,

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Speaker 2: that's made of something else entirely. So this little sliver

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Speaker 2: of the universe that we think is about five percent

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Speaker 2: of all the energy density of the universe, baryonic matter

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Speaker 2: stuff made out of quarks. That's the thing we're still

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Speaker 2: trying to understand after all these years.

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Speaker 1: Is there an important distinction between asking where all the

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Speaker 1: baryonic matter is and asking where all the quarks are? Like,

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Speaker 1: are there quarks that are not in baryonic matter? Or

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Speaker 1: is it all the same term.

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Speaker 2: There are no quarks that are not in some kind

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Speaker 2: of particle because quarks can't be by themselves, so they

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Speaker 2: always form either masons, which are quark quark pairs, or baryons,

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Speaker 2: which are triplets of quarks. Baryonic matter technically probably also

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Speaker 2: includes the electrons. So if you have, for example, a

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Speaker 2: hydrogen atom that's a proton and an electron that you

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Speaker 2: could call baryonic matter because it's based on the baryon

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Speaker 2: the proton, that technically includes the electron. So baryonic matter

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Speaker 2: is probably more accurate description because it includes the electrons.

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Speaker 2: Also they bind with the protons.

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Speaker 1: Wait, so what there's electrons missing too?

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Speaker 2: Well, electrons are part of the five percent of the

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Speaker 2: universe made out of normal matter, basically quarks and leptons.

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Speaker 1: Okay, so then there's a certain amount of quarks and

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Speaker 1: electrons in the universe that we think should be there.

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Speaker 1: And you're saying, we have an idea of how much

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Speaker 1: there should be there based on our measurements of the

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Speaker 1: origin of the universe.

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Speaker 2: Yeah, we have all these really clever ways of looking

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Speaker 2: at details from their early universe and using that to

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Speaker 2: figure out essentially how many quarks there should be today.

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Speaker 2: In order to build stuff up, we should be able

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Speaker 2: to predict how much hydrogen and how much helium and

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Speaker 2: all sorts of stuff there are from our pictures of

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Speaker 2: the early universe. And there's two totally separate ways to

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Speaker 2: predict how much baryonic matter there should be left over today.

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Speaker 2: One of them comes from the cosmic microwave background radiation,

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Speaker 2: this very early light from about three hundred and eighty

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Speaker 2: thousand years after the Big Bang, and another comes from

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Speaker 2: the ratio of the elements, how much hydrogen, how much helium,

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Speaker 2: how much detery there is in the universe. Both of

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Speaker 2: those are very sensitive to the quark density in the

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Speaker 2: early universe and so can tell us how many quarks

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Speaker 2: there should be.

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Speaker 1: Meaning like, we maybe start with a guess and see

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Speaker 1: if that makes the universe make sense as we see

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Speaker 1: it today, and then you adjust that until you get

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Speaker 1: an amount that do you think makes what we see

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Speaker 1: in the cosmic microwave background and in the amount of

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Speaker 1: stuff we see makes sense.

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Speaker 2: Yeah, I don't know that we have to start with

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Speaker 2: a guess. It's more like there's information in the cosmic

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Speaker 2: microwave background radiation that tells us exactly how many baryons

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Speaker 2: there should be. And also by measuring the ratios of

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Speaker 2: the elements how much hydrogen, how much helium, we can

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Speaker 2: use that to make a calculation of how many baryons

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Speaker 2: there should be, so we don't have to guess. We

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Speaker 2: can just like extract it directly from these measurements.

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Speaker 1: Well, maybe break it down for people. How does the

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Speaker 1: ratio of hydrogen and helium tells how many quarts the

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Speaker 1: universe started with?

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Speaker 2: So in the very early universe, things were super duper

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Speaker 2: dense and hot, right, the basic story of the universe,

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Speaker 2: things were very very hot and dense. We don't know

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Speaker 2: how we got to that state, that's sort of a

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Speaker 2: big question mark, but we're very certain that things were

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Speaker 2: very hot and dense and very compressed. And then the

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Speaker 2: universe expanded, and as it expands, it cools. So you

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Speaker 2: start out with like crazy high energy, and then things

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Speaker 2: cool further and those quarks form protons and neutrons, et cetera.

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Speaker 2: And then as things cool even further, those protons and

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Speaker 2: neutrons start to form bonds, so you make for example, deuterium,

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Speaker 2: which is a combination of protons and neutrons the deuterium

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Speaker 2: can then fuse into helium. So what's happening is the

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Speaker 2: universe is cooling and things are sort of like settling

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Speaker 2: into place. You're like baking bits and pieces of the universe.

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Speaker 2: After about twenty minutes, things are then too cold to

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Speaker 2: make any more helium or make any more deuterium, so

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Speaker 2: you sort of ran out of time to make deterium.

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Speaker 2: So in the very early universe you had this little

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Speaker 2: window to make deterium and to make helium, and the

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Speaker 2: rest of everything is just hydrogen. And the amount of

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Speaker 2: deuterium and helium you get depends very very sensitively on

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Speaker 2: the density of quarks, Like you have more we're exploding

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Speaker 2: around in that window, you get more deterium, you have

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Speaker 2: fewer quarks, you get less deterium. So if you measure

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Speaker 2: the hydrogen deterium helium ratios, now you can tell the

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Speaker 2: quark density back in that first little window in the

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Speaker 2: first twenty minutes of the universe.

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Speaker 1: And how do you measure that ratio right now? Like

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Speaker 1: we can we go out there into space and gather

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Speaker 1: hydrogen and helium. How do we determine it?

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Speaker 2: Yeah, you can actually just fill up a glass of

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Speaker 2: water from your tap, because one out of like every

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Speaker 2: six thousand atoms of hydrogen is actually an isotope of

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Speaker 2: hydrogen called deuterium, has a little neutron stuck to it,

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Speaker 2: and that deuterium is pretty stable. So the amount we

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Speaker 2: made back then is still the amount we make now.

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Speaker 2: There's like basically no other natural, significant sources of deuterium,

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Speaker 2: So the universe is kind of like locked into this

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Speaker 2: deterium ratio. When you fill a glass of water at

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Speaker 2: the tap, one out of six thousand atoms of those

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Speaker 2: waters has a hydrogen in it that's actually deuterium. How

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Speaker 2: do you measure that? You can just put it through

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Speaker 2: like a mass spectrometer to measure the weight of the

368
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Speaker 2: at and you'll see this little peak of some water

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Speaker 2: that's a little heavier.

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Speaker 1: But how do I know that's just not the water

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Speaker 1: in my town that has that level of deuterium, or

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Speaker 1: even like in our solar system or even galactic neighborhood.

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Speaker 1: How do you do you extrapolate my tap water to

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Speaker 1: the entire universe?

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Speaker 2: You're right, You've unraveled this entire science. No, we obviously

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Speaker 2: don't just base it on the top water in your

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Speaker 2: house or in anybody else's house. We make measurements all

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Speaker 2: over the place. We can make measurements in the rest

379
00:17:26,920 --> 00:17:29,439
Speaker 2: of the Solar system by looking at like vibrational modes,

380
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Speaker 2: because deuterium has slightly different energy levels than normal hydrogen,

381
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Speaker 2: so you can see evidence for this all over the universe.

382
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Speaker 2: And so we see a pretty well known mixture of

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Speaker 2: deuterium inside hydrogen.

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Speaker 1: All right, So then that tell us how much quark

385
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Speaker 1: matter there should be in the universe, and how much

386
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Speaker 1: is that amount?

387
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Speaker 2: That's about five percent of the energy density of the universe.

388
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Speaker 2: And this is a number that's easy to misunderstand. What

389
00:17:52,240 --> 00:17:54,080
Speaker 2: we mean by that is like, take a big chunk

390
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Speaker 2: of the universe, like a cubic light year, and out

391
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Speaker 2: of all the energy inside of it, all the photons,

392
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Speaker 2: all the dark matter, all the normal matter, all the

393
00:18:02,080 --> 00:18:05,440
Speaker 2: dark energy, all of that stuff, and the normal matter

394
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Speaker 2: should account for five percent of the energy density of

395
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Speaker 2: that chunk. So we're not saying anything about the size

396
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Speaker 2: of the universe or the total number. We're just saying, like,

397
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Speaker 2: what's the ratio five percent of all the energy in

398
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Speaker 2: any given chunk of space should be due to buryonic matter.

399
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Speaker 1: According to what we know of the Big Bang and

400
00:18:23,040 --> 00:18:26,800
Speaker 1: the cosmic microwave background. But it seems that some of

401
00:18:26,800 --> 00:18:30,199
Speaker 1: that matter is missing. Somebody took it or destroyed it,

402
00:18:30,359 --> 00:18:33,400
Speaker 1: or I don't know, hate it. And so let's get

403
00:18:33,400 --> 00:18:36,880
Speaker 1: into that mystery and who we can blame for that

404
00:18:37,000 --> 00:18:39,600
Speaker 1: in more detail. But first let's take a quick break.

405
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Speaker 1: All right, we're talking about some missing matter in the universe.

406
00:18:55,000 --> 00:18:58,439
Speaker 1: There's a certain amount of quark matter in the universe

407
00:18:58,440 --> 00:19:01,520
Speaker 1: that we think should be there. Five percent of the

408
00:19:01,640 --> 00:19:03,760
Speaker 1: energy and matter in the universe should be quark matter.

409
00:19:03,920 --> 00:19:06,439
Speaker 1: But Daniel, it sounds like that's not what we're seeing.

410
00:19:06,560 --> 00:19:08,800
Speaker 2: Yeah, that's right. We have not yet figured out where

411
00:19:08,840 --> 00:19:11,360
Speaker 2: that five percent of matter is. And if you're skeptical

412
00:19:11,400 --> 00:19:14,280
Speaker 2: about that five percent calculation, know that we have other

413
00:19:14,320 --> 00:19:17,320
Speaker 2: ways to calculate this number that are totally independent. Right.

414
00:19:17,320 --> 00:19:19,600
Speaker 2: The description we gave you about the deterium fraction of

415
00:19:19,600 --> 00:19:23,840
Speaker 2: the universe, that's called Big Bang nucleosynthesis. It's understanding how

416
00:19:23,960 --> 00:19:26,800
Speaker 2: much of various elements were made in the very early universe.

417
00:19:26,920 --> 00:19:30,000
Speaker 2: We have other measurements from the cosmic microwave background radiation

418
00:19:30,160 --> 00:19:32,160
Speaker 2: which come from much later in the universe, like three

419
00:19:32,280 --> 00:19:36,480
Speaker 2: hundred and eighty thousand years that are completely independent, totally

420
00:19:36,520 --> 00:19:39,840
Speaker 2: separate measurements. There, we see the early universe plasma sloshing

421
00:19:39,920 --> 00:19:42,760
Speaker 2: around in a way that's sensitive to the number of

422
00:19:42,920 --> 00:19:44,960
Speaker 2: baryons and the amount of dark matter and the number

423
00:19:45,000 --> 00:19:48,200
Speaker 2: of photons. And that's a very very precise measurement, much

424
00:19:48,240 --> 00:19:51,840
Speaker 2: more precise even than the Big Bang nucleosynthesis, and it degrees.

425
00:19:51,880 --> 00:19:55,520
Speaker 2: It's about five percent of the energy density should be baryons.

426
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Speaker 1: But I wonder are they really that independent? I mean,

427
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Speaker 1: don't they both depend on our model of the universe

428
00:20:02,000 --> 00:20:04,160
Speaker 1: and or at least our model of the Big Bang.

429
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Speaker 2: Absolutely, yeah, there are a lot of assumptions in common,

430
00:20:06,600 --> 00:20:09,640
Speaker 2: but there are independent measurements. Like they have different sources.

431
00:20:09,680 --> 00:20:12,399
Speaker 2: You know, one is measuring the fraction of deterium in

432
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Speaker 2: the universe. The other one is like looking at these

433
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Speaker 2: very cold photons in the night sky. They also come

434
00:20:18,359 --> 00:20:20,919
Speaker 2: from a different age in the universe. So they're absolutely

435
00:20:20,920 --> 00:20:24,360
Speaker 2: they're not completely independent, but they're very useful cross checks. Right,

436
00:20:24,640 --> 00:20:27,200
Speaker 2: we would be surprised and confused if those two numbers

437
00:20:27,200 --> 00:20:28,480
Speaker 2: didn't agree with each other.

438
00:20:28,680 --> 00:20:30,960
Speaker 1: Right, all right, So then those measurements are telling us

439
00:20:31,000 --> 00:20:33,840
Speaker 1: there's missing matter, how much quark matter in the universe

440
00:20:33,960 --> 00:20:37,879
Speaker 1: is missing, so like most of it, five percent of

441
00:20:37,880 --> 00:20:39,160
Speaker 1: the universe is missing.

442
00:20:39,960 --> 00:20:42,440
Speaker 2: More like eighty percent of the universe. If you look

443
00:20:42,440 --> 00:20:44,560
Speaker 2: around for quark matter, you can find loss of it. Right,

444
00:20:44,600 --> 00:20:47,520
Speaker 2: Like I'm made a cork matter, You're made of cork matter, right,

445
00:20:47,760 --> 00:20:49,919
Speaker 2: your lunch is made of cork matter. The Earth, the

446
00:20:50,080 --> 00:20:52,520
Speaker 2: Sun is made out of quark matter. All this stuff

447
00:20:52,560 --> 00:20:55,400
Speaker 2: is pretty easy out of all the galaxies and the

448
00:20:55,440 --> 00:20:58,679
Speaker 2: stars and the gas that glows in the universe, and

449
00:20:58,720 --> 00:21:00,879
Speaker 2: then add the harder bits. Right, Some of the stuff

450
00:21:00,880 --> 00:21:02,360
Speaker 2: that's out there in the universe, like we were talking

451
00:21:02,359 --> 00:21:05,720
Speaker 2: about earlier, is matter that is dark, but it's not

452
00:21:05,880 --> 00:21:09,560
Speaker 2: dark matter. You know, things like black holes or things

453
00:21:09,600 --> 00:21:12,760
Speaker 2: like big massive planets that are not glowing. These things

454
00:21:12,800 --> 00:21:16,200
Speaker 2: are harder to spot and harder to account for. But

455
00:21:16,240 --> 00:21:18,040
Speaker 2: people have done a sort of census of all of

456
00:21:18,040 --> 00:21:20,919
Speaker 2: this stuff. Where is all the stuff that we know about,

457
00:21:21,240 --> 00:21:23,399
Speaker 2: how much is there, and how does it add up?

458
00:21:23,440 --> 00:21:26,240
Speaker 2: And together it comes to, you know, about fifteen twenty

459
00:21:26,400 --> 00:21:27,720
Speaker 2: percent of what we.

460
00:21:27,680 --> 00:21:30,679
Speaker 1: Expect, fifteen to twenty percent of the five percent that

461
00:21:30,760 --> 00:21:31,600
Speaker 1: we think should be there.

462
00:21:31,720 --> 00:21:34,359
Speaker 2: Mm hmm exactly. So most of the buryonic matter in

463
00:21:34,359 --> 00:21:36,520
Speaker 2: the universe is not in the stars and in the

464
00:21:36,560 --> 00:21:39,399
Speaker 2: galaxies and in the gas, or in black holes, or

465
00:21:39,440 --> 00:21:42,000
Speaker 2: in planets, or we think in big chunks of rock

466
00:21:42,080 --> 00:21:44,479
Speaker 2: floating out there in the universe. And again we're not

467
00:21:44,520 --> 00:21:46,879
Speaker 2: talking about dark matter, right. We know dark matter is

468
00:21:46,880 --> 00:21:49,560
Speaker 2: out there and it's another mysterious thing. We're just talking

469
00:21:49,560 --> 00:21:52,040
Speaker 2: about the missing quarks. We just can't find as many

470
00:21:52,119 --> 00:21:53,280
Speaker 2: quarks as we expect.

471
00:21:54,840 --> 00:21:56,679
Speaker 1: I wonder if then you just need to lure your

472
00:21:56,720 --> 00:22:03,200
Speaker 1: expectations anyway, like mactation is wrong. Maybe that's the real problem.

473
00:22:03,560 --> 00:22:06,800
Speaker 2: Yeah, but we have these two fairly independent measurements that

474
00:22:06,880 --> 00:22:09,639
Speaker 2: tell us that the universe should be five percent. And

475
00:22:09,680 --> 00:22:12,080
Speaker 2: this all fits in very nicely with our model of

476
00:22:12,119 --> 00:22:15,200
Speaker 2: the universe, how it expands and how structure has formed.

477
00:22:15,840 --> 00:22:18,480
Speaker 2: We have all these ideas for how the universe comes

478
00:22:18,480 --> 00:22:21,240
Speaker 2: together from the hot gas to forming these very cold

479
00:22:21,320 --> 00:22:24,360
Speaker 2: galaxies later on, and all these things are very sensitive

480
00:22:24,400 --> 00:22:27,879
Speaker 2: to the dark energy, dark matter, and normal matter fraction

481
00:22:28,080 --> 00:22:30,800
Speaker 2: of the universe. So it's the number we feel pretty

482
00:22:30,800 --> 00:22:34,080
Speaker 2: confident in five percent, and it gives us enough confidence

483
00:22:34,119 --> 00:22:35,919
Speaker 2: that we want to go out there and look for

484
00:22:35,960 --> 00:22:38,600
Speaker 2: these missing burials. We're pretty sure they exist, we just

485
00:22:38,720 --> 00:22:39,760
Speaker 2: hadn't seen them yet.

486
00:22:40,480 --> 00:22:42,120
Speaker 1: We Well, just so you know, that is an option

487
00:22:42,200 --> 00:22:45,400
Speaker 1: in life. You can just lower your expectations and then

488
00:22:45,440 --> 00:22:46,360
Speaker 1: you can take a vacationion.

489
00:22:46,400 --> 00:22:48,159
Speaker 2: Well, I want to encourage all of our listeners in

490
00:22:48,200 --> 00:22:51,480
Speaker 2: the opposite direction to keep pushing forward until your questions

491
00:22:51,520 --> 00:22:52,879
Speaker 2: are answered. Don't give up.

492
00:22:52,920 --> 00:22:54,800
Speaker 1: All right, Well, let's keep going then. So, there is

493
00:22:55,000 --> 00:22:57,479
Speaker 1: a certain amount of cork matter in universe we think

494
00:22:57,520 --> 00:23:00,560
Speaker 1: should be there, but we can't seem to for it.

495
00:23:00,600 --> 00:23:02,560
Speaker 1: Like we do some accounting of what we can see

496
00:23:02,560 --> 00:23:04,880
Speaker 1: and what we think is there, and it's not enough

497
00:23:04,960 --> 00:23:06,520
Speaker 1: to where could it be and how are we going

498
00:23:06,600 --> 00:23:07,040
Speaker 1: to find it?

499
00:23:07,080 --> 00:23:10,520
Speaker 2: So one obvious place to look is between the galaxies.

500
00:23:11,080 --> 00:23:13,560
Speaker 2: Like we know there's a lot of quark matter in galaxies.

501
00:23:13,600 --> 00:23:15,960
Speaker 2: We can see it. There's gas, this dust, is stars,

502
00:23:16,040 --> 00:23:17,959
Speaker 2: is all that stuff. But we also know that there

503
00:23:17,960 --> 00:23:20,879
Speaker 2: should be a lot of matter between the galaxies, that

504
00:23:20,920 --> 00:23:24,120
Speaker 2: there should be these huge filaments of gas and dark

505
00:23:24,200 --> 00:23:27,439
Speaker 2: matter as well between the galaxies. Because remember, the universe

506
00:23:27,520 --> 00:23:29,880
Speaker 2: is not just like all these little dots of stars

507
00:23:29,920 --> 00:23:33,600
Speaker 2: and dots of galaxies. It's more like a big cosmic web.

508
00:23:34,240 --> 00:23:36,840
Speaker 2: Because as the universe cooled down. It was this hot,

509
00:23:36,920 --> 00:23:40,440
Speaker 2: dense plasma. You have these little dense spots that gather

510
00:23:40,600 --> 00:23:43,960
Speaker 2: together more stuff. The universe is expanding, and then those

511
00:23:43,960 --> 00:23:47,240
Speaker 2: dense spots see the formation of structure, right, they see

512
00:23:47,320 --> 00:23:50,560
Speaker 2: those galaxies, but they don't become isolated. You still have

513
00:23:50,600 --> 00:23:53,400
Speaker 2: these strands between them. And so the place to look,

514
00:23:53,480 --> 00:23:56,399
Speaker 2: the place that our simulations predict there should be a

515
00:23:56,480 --> 00:23:58,919
Speaker 2: lot of quark matter that's sort of hard to spot

516
00:23:59,080 --> 00:24:00,200
Speaker 2: is between the gas.

517
00:24:00,000 --> 00:24:04,320
Speaker 1: Galaxies because they can't be in the galaxies. Because you

518
00:24:04,359 --> 00:24:06,400
Speaker 1: think you can see everything in a galaxy.

519
00:24:06,520 --> 00:24:08,600
Speaker 2: We think we know how much matter there is in

520
00:24:08,640 --> 00:24:11,679
Speaker 2: a galaxy. Yeah, we can see all the luminous stuff

521
00:24:11,680 --> 00:24:14,679
Speaker 2: that's there, all the gas, and all the stars and

522
00:24:14,720 --> 00:24:17,040
Speaker 2: the dark matter, and the motion of those stars tells

523
00:24:17,080 --> 00:24:21,359
Speaker 2: us a lot about the gravitational profile of the galaxy. Remember,

524
00:24:21,400 --> 00:24:24,840
Speaker 2: as the galaxy spins, we can tell how much gravitational

525
00:24:24,880 --> 00:24:27,000
Speaker 2: force there is on those stars by looking at the

526
00:24:27,080 --> 00:24:30,280
Speaker 2: rotation velocity of the stars. That's how we deduce the

527
00:24:30,359 --> 00:24:33,240
Speaker 2: existence of dark matter in the first place. We're pretty

528
00:24:33,240 --> 00:24:36,760
Speaker 2: sure we understand the density profiles of galaxies, which is

529
00:24:36,800 --> 00:24:39,159
Speaker 2: why outside of galaxies is a good target.

530
00:24:39,359 --> 00:24:41,440
Speaker 1: So you're saying that maybe eighty to eighty five percent

531
00:24:41,480 --> 00:24:43,840
Speaker 1: of the missing quark matter in the universe might be

532
00:24:44,040 --> 00:24:48,119
Speaker 1: in between galaxies where we can't see them or what.

533
00:24:48,400 --> 00:24:50,680
Speaker 2: Yeah, that's exactly right. Most of the quarks in the

534
00:24:50,760 --> 00:24:54,600
Speaker 2: universe are not in galaxies. Like you might imagine that.

535
00:24:54,680 --> 00:24:56,800
Speaker 2: You know, matter forms in the Big Bang and then

536
00:24:56,840 --> 00:24:59,680
Speaker 2: things cool and clump together and form galaxies, and that's

537
00:24:59,720 --> 00:25:01,560
Speaker 2: part of the story. But it turns out it's not

538
00:25:01,800 --> 00:25:05,480
Speaker 2: most of the story, that this galaxy formation process is

539
00:25:05,600 --> 00:25:07,879
Speaker 2: kind of inefficient, that most of the normal matter in

540
00:25:07,920 --> 00:25:11,080
Speaker 2: the universe didn't participate it or hasn't.

541
00:25:10,800 --> 00:25:15,159
Speaker 1: Yet, because I guess the stuff that does come together

542
00:25:15,400 --> 00:25:18,040
Speaker 1: is kind of the fancy stuff that everyone pays attention to,

543
00:25:18,119 --> 00:25:19,560
Speaker 1: right the stars and the planets.

544
00:25:19,960 --> 00:25:22,879
Speaker 2: Yeah, it's got the most glitter and glam.

545
00:25:22,880 --> 00:25:25,320
Speaker 1: Okay, So then now is that confirmed? Like if you

546
00:25:25,480 --> 00:25:27,879
Speaker 1: look for things in between galaxies, do you find all

547
00:25:27,920 --> 00:25:29,120
Speaker 1: of this missing quark matter?

548
00:25:29,320 --> 00:25:31,560
Speaker 2: So there's several steps here. The first thing is to

549
00:25:31,600 --> 00:25:34,879
Speaker 2: look for hydrogen, so like, are there huge amounts of

550
00:25:35,000 --> 00:25:38,440
Speaker 2: hydrogen between the galaxies? And you can imagine the galaxies

551
00:25:38,480 --> 00:25:40,960
Speaker 2: is sort of like in these gravitational wells you have

552
00:25:40,960 --> 00:25:43,720
Speaker 2: a blob of dark matter which has gathered together the

553
00:25:43,760 --> 00:25:46,320
Speaker 2: normal matter to form stars and galaxies. And you can

554
00:25:46,359 --> 00:25:49,840
Speaker 2: think about like gravitational filaments like feeding into these wells,

555
00:25:49,840 --> 00:25:52,639
Speaker 2: sort of the way rivers feed into a lake, and

556
00:25:52,720 --> 00:25:56,160
Speaker 2: gas flowing into these galaxies. And we know that gas

557
00:25:56,200 --> 00:25:58,239
Speaker 2: is flowing into these galaxies, we can see like the

558
00:25:58,280 --> 00:26:01,440
Speaker 2: impact of gas flowing to these galaxies. Sometimes it even

559
00:26:01,440 --> 00:26:04,639
Speaker 2: affects star formation in those galaxies. But this gas can

560
00:26:04,640 --> 00:26:07,399
Speaker 2: be tricky to see because it's very, very dilute. Remember,

561
00:26:07,440 --> 00:26:12,119
Speaker 2: there huge space between galaxies, millions and millions of light years,

562
00:26:12,560 --> 00:26:14,960
Speaker 2: and so seeing these things is tricky. One way that

563
00:26:15,000 --> 00:26:17,320
Speaker 2: we have seen them though, is using quasars.

564
00:26:17,720 --> 00:26:19,879
Speaker 1: What do you mean? How do those help us see

565
00:26:20,040 --> 00:26:22,000
Speaker 1: the hydrogen between galaxies?

566
00:26:22,080 --> 00:26:24,240
Speaker 2: They basically light it up for us in this really

567
00:26:24,240 --> 00:26:27,320
Speaker 2: cool way. Remember, a quasar is like a black hole

568
00:26:27,440 --> 00:26:30,080
Speaker 2: at the center of a galaxy that's actively feeding. It's

569
00:26:30,080 --> 00:26:32,800
Speaker 2: like gobbling up a lot of stuff and emitting a

570
00:26:32,920 --> 00:26:36,000
Speaker 2: huge amount of radiation. Now it's confusing for people sometimes

571
00:26:36,000 --> 00:26:37,840
Speaker 2: when you say a black hole is emitting a lot

572
00:26:37,840 --> 00:26:41,000
Speaker 2: of radiation, the black hole itself is not emitting the radiation.

573
00:26:41,119 --> 00:26:44,080
Speaker 2: But if there's a very intense disk of matter near

574
00:26:44,160 --> 00:26:46,440
Speaker 2: the black hole. It's going to be very hot because

575
00:26:46,480 --> 00:26:49,320
Speaker 2: of all the gravitational tidal forces glowing, and a lot

576
00:26:49,359 --> 00:26:51,560
Speaker 2: of that radiation gets funneled up because of the magnetic

577
00:26:51,640 --> 00:26:54,560
Speaker 2: field of the black hole, and you get these extraordinarily

578
00:26:54,600 --> 00:26:57,480
Speaker 2: powerful beams of light that sort of like pencil raised

579
00:26:57,480 --> 00:27:00,600
Speaker 2: through the universe. Some of them hit the Earth. So

580
00:27:00,640 --> 00:27:03,160
Speaker 2: if there's this very powerful beam of light that passes

581
00:27:03,160 --> 00:27:05,159
Speaker 2: all the way through the universe, it's also going to

582
00:27:05,200 --> 00:27:07,680
Speaker 2: pass through some of these filaments of gas. And when

583
00:27:07,680 --> 00:27:10,760
Speaker 2: it does so, it changes the spectrum of light because

584
00:27:10,760 --> 00:27:13,000
Speaker 2: that gas likes to absorb some light. So if this

585
00:27:13,119 --> 00:27:15,520
Speaker 2: hydrogen there, it's going to absorb the light that likes

586
00:27:15,520 --> 00:27:19,119
Speaker 2: to interact with hydrogen, it's sort of deleted from the spectrum.

587
00:27:19,359 --> 00:27:22,440
Speaker 2: So by looking at the spectrum of light from these quasars,

588
00:27:22,680 --> 00:27:25,440
Speaker 2: we can tell how much hydrogen there is between us

589
00:27:25,720 --> 00:27:26,880
Speaker 2: and the source of the light.

590
00:27:27,160 --> 00:27:29,639
Speaker 1: You mean, like all of this quark matter that's floating

591
00:27:29,640 --> 00:27:32,320
Speaker 1: out there between galaxies X kind of like a filter.

592
00:27:32,840 --> 00:27:35,440
Speaker 1: So you have something bright like a quasar is shining

593
00:27:35,680 --> 00:27:38,760
Speaker 1: just directly at us and it filters through this gas.

594
00:27:38,840 --> 00:27:40,919
Speaker 1: You can sort of tell how much of the gas there.

595
00:27:40,800 --> 00:27:44,080
Speaker 2: Is exactly, and it's even more detailed and powerful than that,

596
00:27:44,480 --> 00:27:48,040
Speaker 2: because the hydrogen between us and this distant quasar is

597
00:27:48,119 --> 00:27:50,840
Speaker 2: all going to be moving at different velocities relative to us,

598
00:27:51,119 --> 00:27:53,359
Speaker 2: Like the further away it is, the faster it's going

599
00:27:53,400 --> 00:27:54,840
Speaker 2: to be moving away from us, it's going to be

600
00:27:54,840 --> 00:27:58,120
Speaker 2: red shifted, and that actually changes the frequency of light

601
00:27:58,160 --> 00:28:00,959
Speaker 2: that it interacts with. So if you look at the

602
00:28:01,000 --> 00:28:03,480
Speaker 2: spectrum of life from a quasar, you don't just see

603
00:28:03,520 --> 00:28:05,560
Speaker 2: one dip that tells you how much hydrogen there is.

604
00:28:05,800 --> 00:28:07,920
Speaker 2: You see a lot of dips. You see a forest

605
00:28:08,080 --> 00:28:11,920
Speaker 2: of these dips, each one corresponding to absorption of hydrogen

606
00:28:12,040 --> 00:28:15,080
Speaker 2: at a different red shift. And so not only does

607
00:28:15,119 --> 00:28:17,240
Speaker 2: it tell you how much hydrogen there is between you

608
00:28:17,280 --> 00:28:19,720
Speaker 2: and the quasar, it's like a one d map that

609
00:28:19,760 --> 00:28:23,160
Speaker 2: tells you where that hydrogen was between you and the quasar.

610
00:28:23,280 --> 00:28:24,919
Speaker 2: You can use these quasars to sort of like X

611
00:28:25,000 --> 00:28:27,919
Speaker 2: ray the universe and tell you where the hydrogen is.

612
00:28:28,200 --> 00:28:31,080
Speaker 1: WHOA, but how often do we get signals like this?

613
00:28:31,160 --> 00:28:33,439
Speaker 1: How many quasars are pointing directly at us?

614
00:28:33,520 --> 00:28:35,800
Speaker 2: Yeah, not as many as we'd like, of course, lots

615
00:28:35,800 --> 00:28:37,879
Speaker 2: of them, because there's lots of galaxies out there, and

616
00:28:38,320 --> 00:28:41,360
Speaker 2: in the early universe, quasars were very active. It's a

617
00:28:41,360 --> 00:28:44,280
Speaker 2: whole other mystery like why the quasars mostly get formed

618
00:28:44,320 --> 00:28:46,720
Speaker 2: in the early universe and not so much now. But

619
00:28:46,760 --> 00:28:49,320
Speaker 2: there are a lot of very distant, very bright quasars

620
00:28:49,320 --> 00:28:51,920
Speaker 2: that sort of like shine these lights through the universe,

621
00:28:51,960 --> 00:28:53,680
Speaker 2: and we'd like to see more of them. It's tricky,

622
00:28:53,840 --> 00:28:55,720
Speaker 2: but there's enough that we could have an estimate for

623
00:28:55,800 --> 00:28:59,960
Speaker 2: how much hydrogen gas there is in these filaments between galaxies.

624
00:28:59,560 --> 00:29:04,120
Speaker 1: And these quasars basically like illuminate the hidden matter between galaxies.

625
00:29:04,320 --> 00:29:06,920
Speaker 2: They do. They illuminate the hydrogen. Right. That's when you

626
00:29:06,920 --> 00:29:09,920
Speaker 2: have a proton and an electron together, because that's what's

627
00:29:09,960 --> 00:29:13,120
Speaker 2: going to interact with these photons. The neutral hydrogen will

628
00:29:13,120 --> 00:29:14,959
Speaker 2: do this. So when you look at this information from

629
00:29:15,000 --> 00:29:16,640
Speaker 2: the quasars, you can add it all up and you

630
00:29:16,680 --> 00:29:20,680
Speaker 2: can guess how much neutral hydrogen gas there is between galaxies,

631
00:29:21,000 --> 00:29:23,400
Speaker 2: and that brings you to about half of the five

632
00:29:23,480 --> 00:29:26,520
Speaker 2: percent that we expected. So just stars and galaxies and

633
00:29:26,560 --> 00:29:29,680
Speaker 2: all that stuff gives you like fifteen percent. Adding the

634
00:29:29,720 --> 00:29:32,920
Speaker 2: neutral hydrogen between galaxies and you're up to about fifty percent.

635
00:29:33,080 --> 00:29:34,320
Speaker 1: That we can account for.

636
00:29:34,480 --> 00:29:36,320
Speaker 2: That, we can account for exactly Well.

637
00:29:36,200 --> 00:29:38,160
Speaker 1: You're saying it's not missing, then that we know where

638
00:29:38,160 --> 00:29:38,440
Speaker 1: it is.

639
00:29:38,640 --> 00:29:41,000
Speaker 2: Well, even this very clever technique only brings us to

640
00:29:41,040 --> 00:29:44,280
Speaker 2: fifty percent. The other half is still not explained.

641
00:29:44,640 --> 00:29:47,760
Speaker 1: Mm so only half of that five percent is missing.

642
00:29:47,520 --> 00:29:50,320
Speaker 2: Then, Yeah, so like fifteen percent of it is stars

643
00:29:50,320 --> 00:29:53,400
Speaker 2: and galaxies and black holes and the obvious easy stuff.

644
00:29:53,640 --> 00:29:56,400
Speaker 2: Another like thirty five percent turns out to be this

645
00:29:56,560 --> 00:30:00,959
Speaker 2: neutral hydrogen between galaxies. Until very re we've had no

646
00:30:01,120 --> 00:30:04,840
Speaker 2: explanation for the other fifty percent that part was still missing.

647
00:30:05,040 --> 00:30:08,080
Speaker 1: Could it be some other kinds of gases in between galaxies?

648
00:30:08,360 --> 00:30:11,520
Speaker 2: So the crucial thing is that this quasar method will

649
00:30:11,560 --> 00:30:14,720
Speaker 2: tell us about neutral hydrogen, because you know, the photons

650
00:30:14,800 --> 00:30:18,200
Speaker 2: passing through these filaments will excite. Neutral hygrogen has these

651
00:30:18,280 --> 00:30:21,280
Speaker 2: very particular energy levels. The rest of a popular theory

652
00:30:21,680 --> 00:30:25,040
Speaker 2: is that it's a low density plasma that it's ionized.

653
00:30:25,320 --> 00:30:27,600
Speaker 2: It's not like a proton or electron hanging out in

654
00:30:27,600 --> 00:30:29,760
Speaker 2: a hydrogen atom. It might just be like a bunch

655
00:30:29,760 --> 00:30:32,120
Speaker 2: of protons and a bunch of electrons that are too

656
00:30:32,240 --> 00:30:34,480
Speaker 2: hot to settle down into a hygrogen atom. They're like

657
00:30:34,520 --> 00:30:37,840
Speaker 2: flying around free and they wouldn't interact with equasars in

658
00:30:37,880 --> 00:30:40,560
Speaker 2: the same way. And people argue about whether it's warm

659
00:30:40,720 --> 00:30:43,080
Speaker 2: or whether it's hot, and so they give this stuff

660
00:30:43,120 --> 00:30:48,160
Speaker 2: the name warm hot Intergalactic medium WHIM or.

661
00:30:48,240 --> 00:30:54,600
Speaker 1: WHIM interesting acronym there. So you're saying that light doesn't

662
00:30:54,960 --> 00:30:58,720
Speaker 1: interact with cork matter unless there's an electron attached to it,

663
00:30:58,800 --> 00:31:02,120
Speaker 1: and that's because light only interacts with electrons.

664
00:31:02,240 --> 00:31:05,280
Speaker 2: Light will interact with any charged particle. But this particular

665
00:31:05,320 --> 00:31:08,640
Speaker 2: signature that we can see relies on a feature of

666
00:31:08,840 --> 00:31:12,640
Speaker 2: neutral hydrogen. So photons will interact with protons when electrons

667
00:31:12,640 --> 00:31:15,080
Speaker 2: and scatter and do all sorts of stuff. But this

668
00:31:15,120 --> 00:31:17,800
Speaker 2: particular method only lets us see the neutral hydrogen.

669
00:31:17,880 --> 00:31:20,000
Speaker 1: Why doesn't it let us see the protons.

670
00:31:20,160 --> 00:31:22,120
Speaker 2: Well, what happens when the life from the quasar hits

671
00:31:22,120 --> 00:31:24,240
Speaker 2: a proton or hits an electron is it just basically

672
00:31:24,240 --> 00:31:26,560
Speaker 2: gives it a boost. It makes it glow a little bit.

673
00:31:26,640 --> 00:31:28,360
Speaker 2: But it's hard to know how to interpret that. We

674
00:31:28,400 --> 00:31:30,720
Speaker 2: can't see very well the glow from these protons and

675
00:31:30,720 --> 00:31:34,120
Speaker 2: these electrons because they're very very hot, so we think

676
00:31:34,160 --> 00:31:37,640
Speaker 2: they might emit some X rays or some UV rays

677
00:31:37,760 --> 00:31:40,480
Speaker 2: but it's very hard to detect those here on Earth.

678
00:31:40,240 --> 00:31:43,160
Speaker 1: So we wouldn't see it in the signature from the quasars.

679
00:31:42,720 --> 00:31:45,360
Speaker 2: Exactly, because these free protons and these free electrons can

680
00:31:45,400 --> 00:31:48,040
Speaker 2: interact with any kind of photon, so they generally would

681
00:31:48,080 --> 00:31:51,280
Speaker 2: just like overall, reduce the signature from the quasars neutral

682
00:31:51,360 --> 00:31:53,480
Speaker 2: hydrogen because it's a bound state of the proton, and

683
00:31:53,520 --> 00:31:56,360
Speaker 2: the electron is very rigid about which photons it will

684
00:31:56,360 --> 00:31:59,000
Speaker 2: interact with, and so it makes this very particular measurable

685
00:31:59,040 --> 00:32:02,320
Speaker 2: signature on the quasars. A free proton or free electron

686
00:32:02,360 --> 00:32:04,720
Speaker 2: can interact with any kind of photon, and so it

687
00:32:04,760 --> 00:32:08,000
Speaker 2: doesn't create this like obvious signature in the quasar beam.

688
00:32:08,240 --> 00:32:11,400
Speaker 2: We need another method to see these protons and electrons.

689
00:32:11,800 --> 00:32:14,320
Speaker 1: I see the light from the quasar is maybe getting

690
00:32:14,360 --> 00:32:18,160
Speaker 1: absorbed by these free quarks floating out there, but it

691
00:32:18,200 --> 00:32:20,000
Speaker 1: would just look like it's a little dimmer to us,

692
00:32:20,040 --> 00:32:22,120
Speaker 1: which we can tell if it's because of that or

693
00:32:22,320 --> 00:32:24,320
Speaker 1: maybe because the quasar is not as bright as we

694
00:32:24,320 --> 00:32:26,520
Speaker 1: thought it is. All right, well, let's get into some

695
00:32:26,640 --> 00:32:29,320
Speaker 1: of the ways that we maybe could measure this missing

696
00:32:29,480 --> 00:32:32,680
Speaker 1: quark matter and what it all means about our understanding

697
00:32:32,760 --> 00:32:35,880
Speaker 1: of the universe. But first, let's take another quick break.

698
00:32:48,480 --> 00:32:52,360
Speaker 1: All right, we are slowly piecing together this problem, this

699
00:32:52,480 --> 00:32:55,280
Speaker 1: missing matter in the universe. Apparently there's a lot of

700
00:32:55,360 --> 00:32:57,400
Speaker 1: quark matter that we think should be there, but it's not.

701
00:32:57,640 --> 00:32:59,480
Speaker 1: Although I feel like we've already a kount of for

702
00:32:59,560 --> 00:33:01,960
Speaker 1: fifty percent of it. We started with only being able

703
00:33:01,960 --> 00:33:04,719
Speaker 1: to count fifteen percent of it, but now we're up

704
00:33:04,720 --> 00:33:05,640
Speaker 1: to fifty percent of it.

705
00:33:05,800 --> 00:33:07,680
Speaker 2: Yeah, and you know, I guess fifty percent is like

706
00:33:07,840 --> 00:33:10,320
Speaker 2: on the edge of a passing grade. So you might

707
00:33:10,360 --> 00:33:12,400
Speaker 2: be tempted to call it a day move on, But

708
00:33:12,640 --> 00:33:14,320
Speaker 2: you know, some of us are curious. We want to

709
00:33:14,360 --> 00:33:16,720
Speaker 2: know where is the other half of all the matter in.

710
00:33:16,680 --> 00:33:19,000
Speaker 1: The universe, don't Some of these measurements have like a

711
00:33:19,040 --> 00:33:23,480
Speaker 1: plus or minus fifty percent uncertainty or error bar on them.

712
00:33:23,480 --> 00:33:25,760
Speaker 2: Anyway, I guess that's one way to resolve the mystery.

713
00:33:25,920 --> 00:33:28,200
Speaker 2: Just be like, well, let's just inflate the aerror and

714
00:33:28,280 --> 00:33:29,680
Speaker 2: it's no longer a mystery.

715
00:33:29,880 --> 00:33:30,520
Speaker 1: There you go.

716
00:33:31,640 --> 00:33:34,120
Speaker 2: Yeah, there are big uncertainties on some of these measurements,

717
00:33:34,160 --> 00:33:36,560
Speaker 2: but they're smaller than the discrepancy. And that's how you

718
00:33:36,680 --> 00:33:39,040
Speaker 2: know when you have an interesting scientific puzzle that you

719
00:33:39,080 --> 00:33:41,280
Speaker 2: think you have measured things well and yet you still

720
00:33:41,360 --> 00:33:44,040
Speaker 2: can't explain it. Things are not adding up. The error

721
00:33:44,160 --> 00:33:46,720
Speaker 2: is smaller than the size of the effect you're looking for.

722
00:33:47,440 --> 00:33:49,680
Speaker 1: All right. So now we've accounted for fifty percent of

723
00:33:49,720 --> 00:33:52,720
Speaker 1: the quark matter in the universe. There's still fifty percent missing.

724
00:33:52,800 --> 00:33:53,720
Speaker 1: How are we looking for it?

725
00:33:53,840 --> 00:33:55,800
Speaker 2: So we're using all sorts of clever techniques to look

726
00:33:55,840 --> 00:33:58,280
Speaker 2: for this stuff the whim. And this stuff is hard

727
00:33:58,320 --> 00:34:00,720
Speaker 2: to see because even though it could be pretty hot,

728
00:34:00,760 --> 00:34:04,120
Speaker 2: we're talking about like a million calvin right ten to six,

729
00:34:04,240 --> 00:34:08,360
Speaker 2: ten to seven calvin, it's also very very dilute, you know,

730
00:34:08,400 --> 00:34:11,840
Speaker 2: it's like one atom per cubic meter. It's like a

731
00:34:11,920 --> 00:34:15,480
Speaker 2: billionth of a billionth of the density of our atmosphere.

732
00:34:15,719 --> 00:34:17,760
Speaker 2: So this stuff is not very easy to see, especially

733
00:34:17,760 --> 00:34:20,440
Speaker 2: if it's very far away. And so we're looking for

734
00:34:20,560 --> 00:34:22,480
Speaker 2: a way to excite it. We're looking for something that's

735
00:34:22,520 --> 00:34:24,960
Speaker 2: going to pass through it and get interacted with it

736
00:34:25,000 --> 00:34:27,480
Speaker 2: in a characteristic way that can tell us about the

737
00:34:27,480 --> 00:34:30,120
Speaker 2: density of this plasma. And one really cool way is

738
00:34:30,160 --> 00:34:34,960
Speaker 2: to use another cosmic mystery, these things called fast radio bursts.

739
00:34:35,520 --> 00:34:38,560
Speaker 2: Something out there in the universe is generating these very

740
00:34:38,600 --> 00:34:42,319
Speaker 2: intense pulses of radio waves. Remember, radio waves are just

741
00:34:42,360 --> 00:34:46,319
Speaker 2: photons with very very long frequency. We call it radio waves.

742
00:34:46,360 --> 00:34:48,279
Speaker 2: If it's in a certain frequency regime, we call them

743
00:34:48,400 --> 00:34:51,440
Speaker 2: X rays, and another frequency regime, and visible light in another.

744
00:34:51,800 --> 00:34:54,719
Speaker 2: It's all just photons of different energies. But these very

745
00:34:54,800 --> 00:34:58,000
Speaker 2: very bright pulses of radio waves are created somewhere out

746
00:34:58,000 --> 00:35:01,200
Speaker 2: there in the universe, passing through all the matter between

747
00:35:01,320 --> 00:35:03,720
Speaker 2: us and them, And as we study them here on Earth,

748
00:35:03,760 --> 00:35:05,920
Speaker 2: we can look at the details of those radio waves

749
00:35:06,120 --> 00:35:08,640
Speaker 2: as a way to sort of like X ray, this whim,

750
00:35:08,800 --> 00:35:10,800
Speaker 2: this warm, hot intergalactic medium.

751
00:35:10,960 --> 00:35:13,960
Speaker 1: So how do these bursts of radio waves tell us

752
00:35:14,000 --> 00:35:17,640
Speaker 1: about this plasma that might be hiding all of the

753
00:35:17,640 --> 00:35:18,480
Speaker 1: missing cord matter.

754
00:35:18,640 --> 00:35:21,160
Speaker 2: Yeah, so you had the basic idea earlier when you're saying, like,

755
00:35:21,520 --> 00:35:25,240
Speaker 2: wooden photons interact with this whim. The protons, they're electrons,

756
00:35:25,280 --> 00:35:27,799
Speaker 2: they're charged particles, and you're absolutely right they do. But

757
00:35:27,880 --> 00:35:30,040
Speaker 2: you need the right kind of photon in order to

758
00:35:30,080 --> 00:35:32,400
Speaker 2: tell you what you need to know. As light passes

759
00:35:32,440 --> 00:35:35,080
Speaker 2: through matter, it slows down like the speed of light

760
00:35:35,160 --> 00:35:37,520
Speaker 2: through a vacuum. Is the famous speed that we all know,

761
00:35:37,800 --> 00:35:40,359
Speaker 2: but light passing through glass or through air will move

762
00:35:40,440 --> 00:35:43,600
Speaker 2: slower than light through a vacuum, and that effect actually

763
00:35:43,600 --> 00:35:47,680
Speaker 2: depends on the energy of the photon. So longer wavelengths

764
00:35:47,680 --> 00:35:51,399
Speaker 2: of light are slowed more than shorter wavelengths of light.

765
00:35:51,480 --> 00:35:53,200
Speaker 2: So if you start with the pulsive light of several

766
00:35:53,239 --> 00:35:56,160
Speaker 2: frequencies and then you measure the arrival time of that

767
00:35:56,280 --> 00:35:59,200
Speaker 2: light here on Earth, you can actually measure the density

768
00:35:59,200 --> 00:36:03,120
Speaker 2: of stuff between you and the pulse, because the higher

769
00:36:03,120 --> 00:36:05,640
Speaker 2: the density, the more the difference in the arrival times

770
00:36:05,680 --> 00:36:08,240
Speaker 2: between the long wavelengths and the short wavelengths.

771
00:36:08,560 --> 00:36:10,840
Speaker 1: I see, But don't you need to know what that

772
00:36:10,920 --> 00:36:13,319
Speaker 1: bursts looked like before it went through the filter of

773
00:36:13,440 --> 00:36:16,560
Speaker 1: this plasma between galaxies? How do we know that if

774
00:36:16,600 --> 00:36:18,680
Speaker 1: these are of unknown origin?

775
00:36:18,760 --> 00:36:20,680
Speaker 2: You're right, we do need to know something, But essentially

776
00:36:20,719 --> 00:36:23,400
Speaker 2: all we need to know is that they're all produced

777
00:36:23,440 --> 00:36:25,600
Speaker 2: at the same moment, or very very close to the

778
00:36:25,600 --> 00:36:28,120
Speaker 2: same time. We don't need to know something about the

779
00:36:28,160 --> 00:36:30,560
Speaker 2: spectrum because we're looking for it's just the difference in

780
00:36:30,640 --> 00:36:32,960
Speaker 2: arrival times. If you shoot a long wavelength and a

781
00:36:33,000 --> 00:36:36,200
Speaker 2: short wavelength photon at me at the same time, then

782
00:36:36,239 --> 00:36:38,640
Speaker 2: I can tell you the density of matter between us

783
00:36:38,880 --> 00:36:41,200
Speaker 2: by looking at the difference in the arrival times between

784
00:36:41,239 --> 00:36:44,359
Speaker 2: the short and the long wavelength photon, because the long

785
00:36:44,400 --> 00:36:47,600
Speaker 2: wave looking photon will be slowed down more by higher

786
00:36:47,640 --> 00:36:49,879
Speaker 2: density material. So I don't need to know anything else.

787
00:36:49,920 --> 00:36:51,480
Speaker 2: I just need to know that there's like a pulse

788
00:36:51,560 --> 00:36:54,160
Speaker 2: created and these two photons were made of basically the

789
00:36:54,200 --> 00:36:56,920
Speaker 2: same moment. And that's what these fast radio bursts do.

790
00:36:57,040 --> 00:36:59,800
Speaker 2: We don't know what's actually making them. That's a big mystery,

791
00:37:00,360 --> 00:37:02,160
Speaker 2: but we suspect that they're being made in a very

792
00:37:02,200 --> 00:37:04,560
Speaker 2: short amount of time, like a one millisecond pulse.

793
00:37:05,320 --> 00:37:07,480
Speaker 1: But how do you know they weren't made at different times.

794
00:37:07,600 --> 00:37:09,680
Speaker 2: Yeah, we're not exactly sure. That's an assumption. When they

795
00:37:09,760 --> 00:37:11,680
Speaker 2: arrive here on Earth, they're spread out over a few

796
00:37:11,719 --> 00:37:14,040
Speaker 2: seconds or sometimes tens of seconds. But because of the

797
00:37:14,160 --> 00:37:17,160
Speaker 2: enormous amount of energy overall, we suspect that it was

798
00:37:17,200 --> 00:37:19,960
Speaker 2: a very fast event, though we still don't understand it.

799
00:37:20,000 --> 00:37:21,319
Speaker 1: I think I know what you're saying. You're saying like

800
00:37:21,640 --> 00:37:24,320
Speaker 1: there's a burst of radio waves, like a bright flash

801
00:37:24,360 --> 00:37:26,920
Speaker 1: of light that we see that was made out there

802
00:37:27,120 --> 00:37:30,239
Speaker 1: in the universe, and we measure that burst of light

803
00:37:30,280 --> 00:37:33,319
Speaker 1: when it gets here on Earth at different frequencies. You're saying, like,

804
00:37:33,480 --> 00:37:37,160
Speaker 1: the bursts at one frequency is going to arrive earlier

805
00:37:37,200 --> 00:37:40,440
Speaker 1: than the burst from another frequency, and that difference in

806
00:37:40,480 --> 00:37:42,560
Speaker 1: the arrival time tells you like, oh, there must have

807
00:37:42,600 --> 00:37:47,080
Speaker 1: been some quark matter in plasma form between us and

808
00:37:47,160 --> 00:37:51,239
Speaker 1: that burst that absorb or slowed down some of that

809
00:37:51,400 --> 00:37:53,320
Speaker 1: second frequency exactly.

810
00:37:53,440 --> 00:37:57,360
Speaker 2: This effect is called dispersion, you know, wavelength dependent effect

811
00:37:57,520 --> 00:37:59,640
Speaker 2: on the speed of light essentially, and by measuring this

812
00:37:59,680 --> 00:38:03,200
Speaker 2: dip you can infer the density of the plasma between

813
00:38:03,239 --> 00:38:05,600
Speaker 2: you and the source. But you're right, we're making some

814
00:38:05,680 --> 00:38:08,600
Speaker 2: assumptions about the nature of the source. We're assuming, essentially

815
00:38:08,920 --> 00:38:11,720
Speaker 2: that the length of time over which those radio waves

816
00:38:11,719 --> 00:38:14,239
Speaker 2: were produced is negligible compared to the length of time

817
00:38:14,280 --> 00:38:15,200
Speaker 2: over which they arrive.

818
00:38:15,560 --> 00:38:17,640
Speaker 1: You also have to know where that burst came from,

819
00:38:17,680 --> 00:38:18,080
Speaker 1: don't you.

820
00:38:18,160 --> 00:38:20,560
Speaker 2: Yeah, you do. You have to know the direction. And

821
00:38:20,600 --> 00:38:23,600
Speaker 2: so we've been seeing these fast radio bursts over the

822
00:38:23,680 --> 00:38:26,600
Speaker 2: last few decades. They were discovered sort of accidentally. We

823
00:38:26,680 --> 00:38:29,600
Speaker 2: have a whole fun podcast episode about that, but only

824
00:38:29,640 --> 00:38:32,000
Speaker 2: recently have we been able to locate them, to tell

825
00:38:32,040 --> 00:38:34,600
Speaker 2: where in the sky they come from, and to do

826
00:38:34,640 --> 00:38:37,400
Speaker 2: that you need like larger instruments, or you need coordination

827
00:38:37,520 --> 00:38:40,400
Speaker 2: between various instruments so you can tell about their arrival

828
00:38:40,440 --> 00:38:42,480
Speaker 2: time at various parts on Earth. But in the last

829
00:38:42,480 --> 00:38:44,360
Speaker 2: couple of decades they've been able to do that and

830
00:38:44,440 --> 00:38:47,920
Speaker 2: gather enough information to estimate the mass of the WHIM

831
00:38:48,120 --> 00:38:49,600
Speaker 2: from these fast radio.

832
00:38:49,360 --> 00:38:53,000
Speaker 1: Bursts, at least the part of that quark plasma that's

833
00:38:53,040 --> 00:38:56,320
Speaker 1: hiding that we can tell using this method.

834
00:38:56,440 --> 00:38:59,719
Speaker 2: Yeah, exactly. And you always want to have like multiple

835
00:38:59,719 --> 00:39:02,440
Speaker 2: ways to measure things, especially if it's very uncertain, and

836
00:39:02,520 --> 00:39:04,759
Speaker 2: if you're talking about half of all the stuff in

837
00:39:04,800 --> 00:39:07,719
Speaker 2: the universe or the normal matter. So there actually is

838
00:39:07,760 --> 00:39:12,080
Speaker 2: a second, completely independent way to measure this WIM to

839
00:39:12,120 --> 00:39:14,719
Speaker 2: see where it is and how much stuff there is.

840
00:39:15,160 --> 00:39:17,840
Speaker 2: And this one is more sensitive to the electrons in

841
00:39:17,840 --> 00:39:19,880
Speaker 2: the wim. Remember we think the WIM is a plasma.

842
00:39:19,880 --> 00:39:22,880
Speaker 2: It's protons and its electrons, and those are separated, and

843
00:39:22,880 --> 00:39:26,759
Speaker 2: the electrons themselves can get like jazzed up by interacting

844
00:39:26,800 --> 00:39:29,799
Speaker 2: with the old cosmic microwave background light in a way

845
00:39:29,840 --> 00:39:32,319
Speaker 2: that some people can see and can use that to

846
00:39:32,520 --> 00:39:34,759
Speaker 2: estimate where the WIM is and how much there is.

847
00:39:35,520 --> 00:39:38,520
Speaker 1: And so using these measurements what is our estimate of

848
00:39:38,640 --> 00:39:41,799
Speaker 1: orre all this missing quark matter up to.

849
00:39:41,920 --> 00:39:44,400
Speaker 2: So it comes out pretty close to one hundred percent.

850
00:39:44,840 --> 00:39:47,719
Speaker 2: So the current idea is that this WIM fills in

851
00:39:47,760 --> 00:39:50,040
Speaker 2: the gap that when you add in the WHIM and

852
00:39:50,080 --> 00:39:53,040
Speaker 2: the neutral hydrogen between galaxies and then all the stuff

853
00:39:53,040 --> 00:39:56,560
Speaker 2: inside the galaxies, it all adds up to explain the

854
00:39:56,600 --> 00:40:00,279
Speaker 2: amount of baryonic matter we predicted from the CMB and

855
00:40:00,320 --> 00:40:03,080
Speaker 2: from Big Bang nucleosynthesis. So it all sort of like

856
00:40:03,120 --> 00:40:04,520
Speaker 2: clicks into place amazingly.

857
00:40:04,680 --> 00:40:07,000
Speaker 1: So then we think we found all the missing matter.

858
00:40:07,040 --> 00:40:09,320
Speaker 2: Then we have cracked the case of the missing matter

859
00:40:09,400 --> 00:40:12,839
Speaker 2: in the universe, which is like sort of exciting and

860
00:40:12,880 --> 00:40:14,319
Speaker 2: also sort of disappointing.

861
00:40:14,480 --> 00:40:17,200
Speaker 1: So wait, using these radio burss, we think we've seen

862
00:40:17,560 --> 00:40:18,520
Speaker 1: all of the missing matter.

863
00:40:18,680 --> 00:40:20,799
Speaker 2: Yeah, the current thinking is that this WHIM is that

864
00:40:20,880 --> 00:40:23,680
Speaker 2: missing piece, that fifty percent that we couldn't account for

865
00:40:23,800 --> 00:40:26,560
Speaker 2: after we figured out the neutral hydrogen component is probably

866
00:40:26,600 --> 00:40:28,960
Speaker 2: all the WHIM, which means that like half of all

867
00:40:29,000 --> 00:40:31,840
Speaker 2: the quarks in the universe are in the WHIM.

868
00:40:31,880 --> 00:40:34,680
Speaker 1: Are in hot gas in between in the middle of nowhere.

869
00:40:34,719 --> 00:40:38,360
Speaker 2: Basically, yeah, the universe is half hot gas.

870
00:40:38,480 --> 00:40:42,520
Speaker 1: It's incredible sort of like the US. I guess, so

871
00:40:42,600 --> 00:40:44,360
Speaker 1: the population lives in the middle of nowhere.

872
00:40:44,520 --> 00:40:46,920
Speaker 2: Yeah, exactly. And so if you want to like make

873
00:40:46,960 --> 00:40:48,640
Speaker 2: a ranked list of all the stuff that's out there

874
00:40:48,640 --> 00:40:50,920
Speaker 2: in the universe, it's mostly, you know, stuff that's very

875
00:40:50,920 --> 00:40:54,080
Speaker 2: susceptible to toilet humor. It's dark matter is a lot

876
00:40:54,120 --> 00:40:56,759
Speaker 2: of the universe, and then of the five percent that

877
00:40:56,800 --> 00:40:59,080
Speaker 2: makes up our kind of stuff, half of it is

878
00:40:59,160 --> 00:41:02,480
Speaker 2: hot gas floating out there in the universe between galaxies.

879
00:41:02,680 --> 00:41:04,960
Speaker 1: Well, it's only toilet humor if you like, if your

880
00:41:05,200 --> 00:41:06,399
Speaker 1: head is in the toilet.

881
00:41:08,760 --> 00:41:10,680
Speaker 2: Maybe it's good or humor then. But you know, it's

882
00:41:10,719 --> 00:41:13,239
Speaker 2: exciting to have these confirmation to be like, wow, we

883
00:41:13,280 --> 00:41:15,600
Speaker 2: do really understand what's going on out there in the universe.

884
00:41:15,719 --> 00:41:18,799
Speaker 2: These incredible calculations from the early universe that make these

885
00:41:18,800 --> 00:41:21,920
Speaker 2: predictions about how many baryons should be floating out there

886
00:41:21,960 --> 00:41:25,640
Speaker 2: billions of years later are kind of accurate. And we've

887
00:41:25,680 --> 00:41:28,160
Speaker 2: been able to like X ray and pinpoint the universe

888
00:41:28,239 --> 00:41:30,520
Speaker 2: using all these clever techniques to figure out where the

889
00:41:30,600 --> 00:41:33,920
Speaker 2: stuff actually is. And it tells us this amazing story

890
00:41:33,920 --> 00:41:36,840
Speaker 2: that galaxies are not the most important thing in the universe.

891
00:41:36,880 --> 00:41:39,520
Speaker 2: They're not even the most important part of the normal matter.

892
00:41:39,880 --> 00:41:43,440
Speaker 2: There are these massive halos of gas surrounding the galaxies

893
00:41:43,440 --> 00:41:47,279
Speaker 2: and then between the galaxies, So that's super exciting, but

894
00:41:47,360 --> 00:41:49,680
Speaker 2: it's also kind of a letdown because when you do

895
00:41:49,680 --> 00:41:52,560
Speaker 2: these kind of calculations, which you're hoping for is some

896
00:41:52,840 --> 00:41:55,760
Speaker 2: great new discovery. Right the way we discover dark matter

897
00:41:55,960 --> 00:41:58,920
Speaker 2: by finding a discrepancy in our calculations, this could have

898
00:41:58,960 --> 00:42:02,000
Speaker 2: been the discovery of something else, totally weird and new.

899
00:42:02,280 --> 00:42:05,000
Speaker 1: Well, you're disappointed that you solve the problem. You wanted

900
00:42:05,040 --> 00:42:05,760
Speaker 1: more problems.

901
00:42:05,840 --> 00:42:07,880
Speaker 2: Yes, I wanted more problems exactly.

902
00:42:07,920 --> 00:42:09,959
Speaker 1: You want it more, more of a job.

903
00:42:11,160 --> 00:42:13,200
Speaker 2: It would be fascinating, right, Like finding out that it's

904
00:42:13,200 --> 00:42:16,160
Speaker 2: the whim is cool, it makes sense, But it would

905
00:42:16,160 --> 00:42:18,479
Speaker 2: have been more exciting if it was some new kind

906
00:42:18,480 --> 00:42:21,320
Speaker 2: of matter, something else that we didn't expect, quarks forming

907
00:42:21,400 --> 00:42:24,680
Speaker 2: some new kind of stuff that we hadn't anticipated, or

908
00:42:24,719 --> 00:42:27,959
Speaker 2: maybe discovering something was wrong in our early universe calculations.

909
00:42:28,239 --> 00:42:30,759
Speaker 2: That would have been I think a bigger discovery because

910
00:42:30,800 --> 00:42:32,880
Speaker 2: we would have learned more about the universe.

911
00:42:33,120 --> 00:42:35,160
Speaker 1: Well, maybe that's why this problem didn't get a lot

912
00:42:35,160 --> 00:42:37,200
Speaker 1: of press, because you guys sold it as like, Eh,

913
00:42:37,480 --> 00:42:41,040
Speaker 1: we found it. Whatever, it's not that exciting. Now you're

914
00:42:41,040 --> 00:42:43,560
Speaker 1: complaining that it doesn't get any uh.

915
00:42:43,400 --> 00:42:45,600
Speaker 2: Press, Well, here we are trying to get it some

916
00:42:45,640 --> 00:42:48,319
Speaker 2: more attention. Right, So I'm out here trumpeting the case

917
00:42:48,360 --> 00:42:50,680
Speaker 2: of the missing matter and its whimsical solution.

918
00:42:50,960 --> 00:42:52,879
Speaker 1: Well, I think maybe the other reason is that it's

919
00:42:52,920 --> 00:42:54,480
Speaker 1: not really a problem anymore, exactly.

920
00:42:55,239 --> 00:42:58,480
Speaker 2: Yeah, Unfortunately we've mostly figured it out. I unfortunately or

921
00:42:58,560 --> 00:43:01,160
Speaker 2: unfortunately fortunately because it means our theories of physics are

922
00:43:01,160 --> 00:43:04,520
Speaker 2: mostly working and our techniques are clever and effective. Unfortunately,

923
00:43:04,560 --> 00:43:06,160
Speaker 2: because it means now we've got to move on to

924
00:43:06,239 --> 00:43:07,000
Speaker 2: something else.

925
00:43:07,480 --> 00:43:10,000
Speaker 1: So maybe you just need to rename it. Right, It's

926
00:43:10,000 --> 00:43:12,560
Speaker 1: no longer the missing baryon problem is just the found

927
00:43:12,600 --> 00:43:13,360
Speaker 1: barian flat.

928
00:43:16,200 --> 00:43:19,440
Speaker 2: Yeah, the once missing baryon. The Baryon's formerly known as

929
00:43:19,480 --> 00:43:20,399
Speaker 2: missing all right.

930
00:43:20,440 --> 00:43:24,640
Speaker 1: Well, another interesting reminder that the universe keeps surprising us,

931
00:43:24,719 --> 00:43:28,200
Speaker 1: even in I guess not so surprising ways. It's surprising

932
00:43:28,239 --> 00:43:31,360
Speaker 1: that you can sort of make these models and figure

933
00:43:31,360 --> 00:43:34,680
Speaker 1: out where everything should be and where it needs to be.

934
00:43:34,880 --> 00:43:37,759
Speaker 2: Yeah, asking questions in several different ways, trying to do

935
00:43:37,840 --> 00:43:40,720
Speaker 2: calculations from this and from that, piecing it all together

936
00:43:40,840 --> 00:43:42,759
Speaker 2: is a great way to figure out what's actually out

937
00:43:42,800 --> 00:43:45,480
Speaker 2: there in the universe, and sometimes actually leads you to

938
00:43:45,520 --> 00:43:46,000
Speaker 2: an answer.

939
00:43:46,080 --> 00:43:47,439
Speaker 1: Well, I kind of wish we had read the last

940
00:43:47,480 --> 00:43:49,960
Speaker 1: chapter of this mystery. I had to save this a

941
00:43:49,960 --> 00:43:50,759
Speaker 1: lot of time here.

942
00:43:50,960 --> 00:43:54,360
Speaker 2: This was decades of work and lots of careful energy,

943
00:43:54,480 --> 00:43:57,160
Speaker 2: and like lots of people's peachdtcs. You know, we're like

944
00:43:57,239 --> 00:44:00,840
Speaker 2: taking tiny steps in this direction. So you can summarize

945
00:44:00,840 --> 00:44:02,960
Speaker 2: it all in about five seconds, but you know, it

946
00:44:03,000 --> 00:44:03,239
Speaker 2: was a.

947
00:44:03,239 --> 00:44:06,439
Speaker 1: Journey, and also it's kind of a still a work

948
00:44:06,440 --> 00:44:08,919
Speaker 1: in progress, I imagine. I mean, you have some measurements,

949
00:44:08,960 --> 00:44:12,080
Speaker 1: but you can always refine those or somebody might find

950
00:44:12,120 --> 00:44:13,960
Speaker 1: something that disproved those measurements.

951
00:44:13,600 --> 00:44:16,480
Speaker 2: Right, yeah, precisely. Now we fold these things into our

952
00:44:16,480 --> 00:44:19,600
Speaker 2: models of galaxy formation. Because we have a better understanding

953
00:44:19,640 --> 00:44:22,440
Speaker 2: of the density and the temperature of this whim. We

954
00:44:22,480 --> 00:44:25,160
Speaker 2: can make sure that it describes the kinds of galaxies

955
00:44:25,160 --> 00:44:27,480
Speaker 2: that we see, the sizes of galaxies, the rate of

956
00:44:27,520 --> 00:44:31,400
Speaker 2: galaxy formation, how often galaxies merge. It all gets folded

957
00:44:31,440 --> 00:44:34,680
Speaker 2: into a more precise description of our universe, which we

958
00:44:34,760 --> 00:44:38,960
Speaker 2: hope will reveal more discrepancies and more surprises in the future.

959
00:44:39,160 --> 00:44:43,239
Speaker 1: And more toilet humor inevitable. All right, well it's time

960
00:44:43,280 --> 00:44:46,799
Speaker 1: to flush. I guess we hope you enjoyed that. Thanks

961
00:44:46,800 --> 00:44:49,080
Speaker 1: for joining us, see you next time.

962
00:44:57,000 --> 00:44:59,880
Speaker 2: Thanks for listening, and remember that. Daniel and Jorge Explaining

963
00:44:59,880 --> 00:45:03,879
Speaker 2: You Universe is a production of iHeartRadio. For more podcasts

964
00:45:03,880 --> 00:45:08,560
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

965
00:45:08,600 --> 00:45:10,320
Speaker 2: you listen to your favorite shows.