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Speaker 1: Hey, Daniel, what do you think about when you look

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Speaker 1: at the night Scott. Well, it's just staggeringly gorgeous, of course.

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Speaker 1: But what I'm most amazed at is the depth of

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Speaker 1: the view. What do you mean, Well, it's just incredible,

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Speaker 1: Like how far we can see from the Moon that's

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Speaker 1: kind of close by, all the way to the Sun

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Speaker 1: two stars that are like billions of light years away. Yeah,

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Speaker 1: that is pretty deep. That's like the deepest view. Yeah,

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Speaker 1: it makes you feel lucky, right, What do you mean lucky?

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Speaker 1: Are you imagining that space could have been foggy? Yeah?

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Speaker 1: In fact, the universe didn't always offer such crystal clear

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Speaker 1: views of crystals. The yell Per views from the early

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Speaker 1: universe had fewer stars. I am Orgemmaye, cartoonists and the

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Speaker 1: creator of PhD comics. Hi, I'm Daniel, I'm a particle physicist,

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Speaker 1: and on Yelp, I give our universe five stars. Do

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Speaker 1: physicists have Yelp reviews? No? I wish we did, though.

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Speaker 1: I wish we could just review parts of physics and

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Speaker 1: be like, Wow, this part is awesome, or this part

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Speaker 1: is kind of sticky, and go in and look at that.

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Speaker 1: When I got terrible service, when I try to order

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Speaker 1: a black hole. This collider works great, but this one

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Speaker 1: is usually down. My collider accidentally destroyed the universe. Down

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Speaker 1: zero stars and Welcome to our podcast Daniel and Jorge

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Speaker 1: Explain the Universe, a production of I Heart Radio in

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Speaker 1: which we explore all the amazing and wonderful star filled

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Speaker 1: the universe, all the things that are incredible and visible

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Speaker 1: that are out there that we can see from Earth,

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Speaker 1: all the things that we can't see that we have

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Speaker 1: to use our imagination, all the things that are happening

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Speaker 1: right now, and things that happened in the deep dark past. Yeah,

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Speaker 1: because it is a huge universe and we can see

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Speaker 1: a lot of it out there. There's a billions and

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Speaker 1: trimons of stars that we can see in galaxies, and

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Speaker 1: there's a lot that we can't see as well. That's right.

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Speaker 1: It's amazing to me. It sort of feels like you're

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Speaker 1: standing on the top of a mountain and you're looking

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Speaker 1: out and you can see things that are like billions

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Speaker 1: of light years away. It's like looking across a vast,

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Speaker 1: vast ocean of space, and those photons, you know, they

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Speaker 1: had to travel so far and for so long just

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Speaker 1: to get to your eyeball. It's amazing that nothing stopped

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Speaker 1: them along the way. Yeah, it seems like we just

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Speaker 1: happened to be looking at the universe on a clear day.

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Speaker 1: You know, it could have been an overcast day, or

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Speaker 1: a foggy day, or a hazy day, or you know,

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Speaker 1: there could have been small from all those aliens. But

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Speaker 1: somehow it's a pretty clear view of really far away stuff.

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Speaker 1: And imagine what life would be like if we didn't

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Speaker 1: have which a clear view, if the universe was foggy,

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Speaker 1: if you looked out into space and it was just

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Speaker 1: sort of like a gray blob. You couldn't see the

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Speaker 1: stars and the galaxies. We couldn't learn about the shape

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Speaker 1: of the universe and its structure and its history. We

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Speaker 1: would be so clueless if we couldn't see as far

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Speaker 1: as we do. Yeah, we would probably still think that

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Speaker 1: we are like the center of the universe and that

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Speaker 1: just the things we see around is all there is

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Speaker 1: to it. Yeah. Absolutely, And we can see pretty far

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Speaker 1: in the universe in the wavelengths were familiar with, you know,

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Speaker 1: in the wavelengths of visible light, but there are lots

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Speaker 1: of different wavelengths of light, and in some wavelengths the

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Speaker 1: universe is more or less transparent, and so these days

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Speaker 1: we've opened up lots of new kinds of eyeballs onto

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Speaker 1: the universe, infrared light and UV light and X ray

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Speaker 1: telescopes to be able to see different parts of the

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Speaker 1: universe at different depths. Yeah, it's a clear day in

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Speaker 1: the universe. But it sort of makes you wonder if

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Speaker 1: it was always this clear, where you always able in

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Speaker 1: the universe to look so far away and to see

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Speaker 1: so many stars and galaxies. Yeah, and there's actually a

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Speaker 1: really fascinating period at the beginning of the universe. You know,

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Speaker 1: people think about the universe starting the big bang boom,

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Speaker 1: huge explosion, lots of stuff rushing out, dot dot dot

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Speaker 1: galaxies are formed and we have stars and stuff. But

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Speaker 1: there's a lot of interesting stuff happening in that dot

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Speaker 1: dot dot period where stars get formed, before we actually

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Speaker 1: have the structure of the universe that we're familiar with today,

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Speaker 1: before we can see as far as we can out

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Speaker 1: into the deep reaches of the universe. That a lot

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Speaker 1: of YadA YadA happened, I imagine in those dot dot

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Speaker 1: dot moments. But yeah, the big bank does get a

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Speaker 1: lot of attention, and you sort of assume that it's

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Speaker 1: really bright the Big Bang, I guess, because it's a

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Speaker 1: big expansion and a big explosion. But uh, there happens

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Speaker 1: to be a period right after it in which you

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Speaker 1: couldn't see a lot of stuff. Yeah, it's fascinating to

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Speaker 1: imagine why the universe is bright at all. You know,

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Speaker 1: we only have light in the universe because it's created

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Speaker 1: by these pin pricks of stars. If we didn't have those,

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Speaker 1: the universe wouldn't be super dark. And so there was

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Speaker 1: this period after the Big Bang and before the first

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Speaker 1: stars when we didn't have light in the universe, another

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Speaker 1: really fascinating period after we had stars or the universe

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Speaker 1: cleared up. And so it doesn't usually get as much

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Speaker 1: attention as I think it should, but it's a really

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Speaker 1: interesting period of the universe and helps us understand like

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Speaker 1: how stars and galaxies actually came together. Yeah, so to

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Speaker 1: the other podcast, we'll be asking the question what happened

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Speaker 1: during the dark ages of the universe before the Renaissance

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Speaker 1: for the cosmic Renaissance, I guess, yeah, And there actually

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Speaker 1: is something of a cosmic renaissance. It's a fascinating parallel

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Speaker 1: to sort of human intellectual history. Was a universe full

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Speaker 1: of like feudal societies and everyone wore armor and you sword. Yeah,

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Speaker 1: it makes for really great like television epic dramas. Yeah,

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Speaker 1: so there was a long period and where the universe

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Speaker 1: wasn't as bright as it is now. In fact that

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Speaker 1: it was hundreds of millions of years of darkness and fog, right, Yeah,

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Speaker 1: exactly before the universe looked the way that it did today.

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Speaker 1: There's a lot of work that had to happen between

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Speaker 1: the Big Bang and molecules form and you get this hot,

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Speaker 1: dense gas and then for stars to actually pull together

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Speaker 1: and to light up. Yeah, it's kind of interesting to

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Speaker 1: think because you know, you don't usually assume that there

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Speaker 1: was a dark age. You just assumed that, you know,

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Speaker 1: the real dark age happened before the Big Bang. But

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Speaker 1: I guess we don't know what happened before the Big

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Speaker 1: Bang really, Yeah, we have no idea if that was

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Speaker 1: dark or it was crazy bright, or if it was

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Speaker 1: part of the meta universe or space didn't even exist.

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Speaker 1: Those are the kind of questions we can't even really ask.

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Speaker 1: We don't even know how to probe those questions. But

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Speaker 1: this is a part of the universe when things actually

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Speaker 1: had formed when the rules of physics as we know

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Speaker 1: them were in charge, and so we could ask these questions.

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Speaker 1: But it's a period that's also very difficult to study

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Speaker 1: because it was so dark, and so this happened right

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Speaker 1: after the Big Bang, and maybe a lot of people

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Speaker 1: don't know that we had a dark age at all

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Speaker 1: in the universe. I imagine most people just assumed that

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Speaker 1: there was a big bang and then thanks got brighter

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Speaker 1: from there. And so as usual, Daniel went out there

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Speaker 1: into the wild to the Internet to ask listeners what

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Speaker 1: they thought happened during the Dark Ages of the universe.

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Speaker 1: Thank you to everybody who participated in this exercise. And

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Speaker 1: if you would like to stand answers to questions for

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Speaker 1: which you are totally unprepared to give responses to, please

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Speaker 1: write to us two questions at Daniel and Jorge dot com.

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Speaker 1: Think about it for a second. Have you heard or

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Speaker 1: know what are the Dark Ages of the universe. It's

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Speaker 1: what people had to say, something to do with the

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Speaker 1: point in time where the universe was so hot and

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Speaker 1: tense that no light could escape. My guess is that

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Speaker 1: the dark Ages of the universe was when you know

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Speaker 1: there was no light so you couldn't see what else

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Speaker 1: is in the universe. I would put this dark ages

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Speaker 1: before being a big bank. That's it. I think it's

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Speaker 1: a time before the universe schooled down enough to be

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Speaker 1: transparent to photons. That's the photons emitted in that time

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Speaker 1: are stuck in that time and not detectable by us.

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Speaker 1: The universe is for ten billion years old, give or

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Speaker 1: take a few, so maybe it was at a time

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Speaker 1: when the universe had had had time to cool off

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Speaker 1: and not be so intensely hot. So maybe five six

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Speaker 1: billion years ago. I think that was after the universe

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Speaker 1: was cool enough such that um the gas was not

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Speaker 1: emitting light anymore, at least not in a visible spectrum,

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Speaker 1: but before the first stars formed. All Right, a lot

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Speaker 1: of interesting answers here. Some of them sort of band

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Speaker 1: your brain a little bit, like the universe is so

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Speaker 1: bright that you couldn't see light or something like that,

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Speaker 1: or there was no light so you couldn't see anything, yeah,

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Speaker 1: or somebody else suggesting that it was pretty big bang

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Speaker 1: like you were. That's a fun idea. Yeah, And so

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Speaker 1: it's pretty tricky, I guess, because you know, the big

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Speaker 1: band was such a chaotic mess and it's hard to

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Speaker 1: tell when light could go around and when it could

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Speaker 1: not go around, or when it was created, or when

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Speaker 1: even light was created itself, because light didn't always exist, right, Yeah, exactly.

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Speaker 1: And there are a lot of these answers that thought

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Speaker 1: that the Dark Ages were somehow before the cosmic microwave background,

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Speaker 1: and so I think there's a bit of confusion out

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Speaker 1: there about the order of events. So it's a good idea,

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Speaker 1: I think, for us to clear it up and walk

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Speaker 1: through what happened before, during, and after the Dark Ages

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Speaker 1: of the universe. And I guess nobody gets that it

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Speaker 1: involved armor and castles and shields and feudal societies and

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Speaker 1: epic love poems, probably with loot Alright, So step us

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Speaker 1: through here, Daniel, let's go all the way back. I guess,

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Speaker 1: so before there was even a dark age in the universe.

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Speaker 1: What happened. Step us through from the moment of birth

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Speaker 1: of the universe to the first Dark Age. Yeah. So

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Speaker 1: it's pretty fascinating. And it always amazes me that we

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Speaker 1: know as much as we do about these first few

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Speaker 1: moments of the universe, you know, the big bang happens.

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Speaker 1: We don't really understand that at all. But we think

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Speaker 1: that it happened. There's some moment of singularity there, and

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Speaker 1: then the universe is filled with this very high density

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Speaker 1: of energy and very bidly things start to stretch. In

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Speaker 1: this period we call inflation, when the universe grew very

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Speaker 1: very quickly in a very short amount of time. So

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Speaker 1: you have a universe that's really hot and dense and

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Speaker 1: filled with stuff gets stretched out to a much cooler,

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Speaker 1: more dilute universe by a factor of ten to the

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Speaker 1: thirty and about ten to the minus thirty seconds. So

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Speaker 1: that's the very beginning of the universe. And after, you know,

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Speaker 1: like tend the minus five micro seconds, you have things happening,

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Speaker 1: like quarks are forming, particles are coming into existence. Before that,

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Speaker 1: you have this really dense soup of energy, but you

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Speaker 1: can't really think of it as particles. It's more like

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Speaker 1: thinking about an ocean of droplets rather than thinking about

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Speaker 1: an individual drop on its own. Yeah, and you can't

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Speaker 1: even think about forces like it. It was a point

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Speaker 1: right after the Big Bang or during inflation in which

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Speaker 1: you couldn't even say, hey there's gravity, Hey there's electromaniatism.

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Speaker 1: It was all just part of the same soup. Yeah,

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Speaker 1: that bit's a bit more speculative, but we think that

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Speaker 1: when you have really high energy, really high density of stuff,

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Speaker 1: that all the forces are the same, that they have

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Speaker 1: the same strength, and as you cool down, they sort

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Speaker 1: of break out into different strengths, which is why we

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Speaker 1: have the strong force is the strongest force, and gravity

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Speaker 1: is the weakest one, and they all have sort of

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Speaker 1: different characteristics. We think that only happens when things sort

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Speaker 1: of get cold and separate, But when things were hot

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Speaker 1: and dense in the early universe, we think they unified

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Speaker 1: into one force. And so as you go forwards in

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Speaker 1: time and the universe cools, we think of those things

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Speaker 1: that sort of breaking out. So the forces separated into

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Speaker 1: the forces we know now, and then particles formed and

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Speaker 1: you get like corks and gluons, But things are still

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Speaker 1: super duper hot, and so those corks and gluons they

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Speaker 1: don't like break off and make little particles like we

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Speaker 1: know now like protons and neutrons. They were in this

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Speaker 1: state called a cork gluon plasma, which is sort of

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Speaker 1: like the way we think about a plasma like hydrogen gas,

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Speaker 1: where the electrons have so much energy that they just

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Speaker 1: fly around. You don't get little bound states here for

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Speaker 1: cork flu on plasma. There's so much that you don't get,

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Speaker 1: like bound states of quarks, like protons and masons and

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Speaker 1: other kinds of stuff. It's just a big sea of

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Speaker 1: quarks and gluons all mixing around together. Really, they don't

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Speaker 1: snap together. I thought you couldn't have quarks by themselves. Yeah,

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Speaker 1: you can't have them by themselves, but you can have

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Speaker 1: them in a super dense ocean of quarks and gluons.

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Speaker 1: So they're not on their own. They're just sort of

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Speaker 1: like enmeshed in this soup. Or you can think about

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Speaker 1: like the whole universe is one big quark particle, you know,

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Speaker 1: fields with quarks and gluons all mixing around, sort of

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Speaker 1: like the interior of a proton, right, is a bunch

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Speaker 1: of quarks and luons flying around together. Think about like

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Speaker 1: the whole universe in that state. So the universe is

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Speaker 1: like a giant proton exactly. It's like a giant proton.

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Speaker 1: The proton universe was a proton, but then it continued

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Speaker 1: to expand and to cool, and then it sort of

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Speaker 1: broke up. Right, instead of being one massive quirk gluon plasma,

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Speaker 1: we have these hadrons forming, so you get things like

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Speaker 1: kaons and pons and protons and neutrons. Things that are

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Speaker 1: combinating should have corks is sort of like snap out

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Speaker 1: into their own little lego pieces. And that happened about

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Speaker 1: a second after the Big Bang. We think, so we're

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Speaker 1: a second into the universe and we already have particles

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Speaker 1: made out of corks. Okay, so now it's starting to

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Speaker 1: look more familiar to what we know, like protons and neutrons,

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Speaker 1: and so that universe is like a sea of them,

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Speaker 1: like still a hot soup and not as hot. Yeah,

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Speaker 1: still a hot soup. And you also had particles like

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Speaker 1: electrons flying around um and then the next twenty minutes

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Speaker 1: or so, the universe spent some time building atoms, and

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Speaker 1: so you get protons and electrons that come together and

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Speaker 1: make hydrogen. For example. Wait, how did the electrons form?

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Speaker 1: They just formed out of the energy and the hanging around.

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Speaker 1: They just popped into existence the same way the corks did.

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Speaker 1: You have this sort of raw energy that was in

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Speaker 1: all of these matter fields, slashing around between them, using

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Speaker 1: the forces to interact, and then it sort of crystallized

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Speaker 1: out into the various matter fields. You get quarks, you

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Speaker 1: can electrons, you get heavier stuff probably also, which then decayed.

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Speaker 1: All right, so now we're starting to form nuclei and atoms,

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Speaker 1: and that's where the most of the I guess hydrogen

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Speaker 1: came from. Yeah, And so then it crystallizes out and

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Speaker 1: you get hydrogen. You get some helium also, but mostly hydrogen.

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Speaker 1: You get very small amounts of lithium. But things are

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Speaker 1: still very very hot and dense, like you would want

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Speaker 1: to be in this situation. That temperature is very very high.

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Speaker 1: It's sort of like the interior of the sun. You know,

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Speaker 1: it's still a hot soup. I mean, we spent twenty

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Speaker 1: minutes already expanding and cooling in the universe from the

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Speaker 1: much hotter initial state. But it's still very hot. It's

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Speaker 1: still emitting photons, it's still sort of glowing and absorbing

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Speaker 1: that light. It's still a hot mess. It's still hot.

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Speaker 1: You don't you want no part of that? Yeah, exactly.

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Speaker 1: And at this point we still have about fifteen percent

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Speaker 1: of the matter in the universe is the kind of

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Speaker 1: matter we're familiar with. It's made out of baryons. You know,

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Speaker 1: it's going to be atomic matter eventually, but dark matter

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Speaker 1: is also formed right, you don't just make corks and electrons.

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Speaker 1: We don't know the particle nature of dark matter, but

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Speaker 1: we think it was created. We're pretty sure it was

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Speaker 1: created back in those same moments when you made your

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Speaker 1: quarks and electrons. So whatever dark matter is made out of,

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Speaker 1: it was already present back then in the early universe.

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Speaker 1: It was created just out of thin air. It just

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Speaker 1: like the corks and electrons too. Yeah, it was just

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Speaker 1: the energy in those fields collapsed into the matter fields,

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Speaker 1: and that's what making particles is. And so all that

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Speaker 1: stuff was made. And then you know, that soup sort

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Speaker 1: of sat around, you know, oscillating and glowing it itself

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Speaker 1: for like a hundred thousand years or so until you

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Speaker 1: get to the moment when it cools enough that the

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Speaker 1: electrons like to hang out around the nuclei, that the

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Speaker 1: nuclei could sort of grab their own electrons and become neutral.

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Speaker 1: So before, I mean before you had hydrogen and maybe helium,

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Speaker 1: but maybe the electrons weren't sticking around to the nuclear

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Speaker 1: to form like a regular hydrogen atom. Yeah, it was

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Speaker 1: more like a plasma. Right. You have electrons and they're

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Speaker 1: flying around. You have protons and they're flying around but

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Speaker 1: they haven't like cooled off together where they're going to

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Speaker 1: pair off and become neutral. And so you have helium

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Speaker 1: nuclei and hydrogen nuclei and electrons all flying around in

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Speaker 1: this big, messy plasma. But sort of an analogy to

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Speaker 1: the way we were talking about cork luon plasma before.

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Speaker 1: Here we have a nuclei electron plasma. So it's very

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Speaker 1: hot and it's emitting a lot of light, but it's

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Speaker 1: also absorbing that light, and so it's opaque. It glows

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Speaker 1: giving off light, but it also absorbs that same light,

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Speaker 1: so it's kind of like the sun. It's hot and

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Speaker 1: it's glowy, but it's not see through yet. And then

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Speaker 1: there's this moment when it cools enough that the protons

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Speaker 1: and electrons come together to make neutral hydrogen and it

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Speaker 1: doesn't absorb that light anymore, and so it becomes transparent. Right,

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Speaker 1: But at this stage they say that still the universe

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Speaker 1: was transparent because like a light could still move around

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Speaker 1: almost unimpeded, right, Like nothing really absorbed light. That's why

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Speaker 1: they say it was transparent. Yeah, Well, there's this threshold

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Speaker 1: here about three d and eighty thousand years after the

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Speaker 1: Big Bay when the universe becomes transparent, and so before

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Speaker 1: that it was like a big, hot, glowing mess, and

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Speaker 1: photons were being created, but they were also being absorbed

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Speaker 1: because any particle that's making photons can also absorb those photons,

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Speaker 1: so the photons can always go very far. But there's

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Speaker 1: this moment when the universe cooled sort of crystallized, literally

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Speaker 1: around three thousand years after the Big Bang. That's the

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Speaker 1: moment when things became neutral. And so now the photons

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Speaker 1: that had been created at that moment there was no

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Speaker 1: longer anything around that could absorb them as well, so

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Speaker 1: those started just flying through the universe. Because neutral atoms

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Speaker 1: don't absorb light. They do absorb light, but not at

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Speaker 1: the same wavelengths right. Free electrons and free protons can

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Speaker 1: absorb stuff at lots of different wavelengths, but neutral atoms

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Speaker 1: they're much more constrained into what wavelengths of light they

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Speaker 1: can create and they can absorb because of the quantization effects.

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Speaker 1: Like electrons have layers of energies that they can be in,

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Speaker 1: they can't just be at any energy that's different. For

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Speaker 1: a free electron that's just wandering around the universe, they

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Speaker 1: can admit a huge spec room of light and it

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Speaker 1: can absorb it a huge spectrum. Alright, So then the

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Speaker 1: universe went from transparent to non transparent, and that's ironically

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Speaker 1: sort of like when things when dark. Yeah, Actually the

349
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Speaker 1: universe went from opaque too transparent, and that light emitted

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Speaker 1: at that moment was sort of the last light emitted

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Speaker 1: before the universe went dark. Right. It was hot and

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Speaker 1: glowing but opaque, and then it switched to being transparent

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Speaker 1: but not really creating any more light like any light

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Speaker 1: that was there, it just flew away. Yes, And that light,

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Speaker 1: of course is famously still flying around. The cosmic microwave

356
00:18:36,880 --> 00:18:39,879
Speaker 1: background light that was created at that moment is the

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Speaker 1: stuff we see in the sky. You know. People write

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Speaker 1: in and they ask questions like, how can we can

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Speaker 1: still see the cosmic microway background radiation? It was just

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Speaker 1: created at one moment, right, hasn't it washed over us already?

361
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Speaker 1: Why can we still see it in the sky, Which

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Speaker 1: is a cool question, And the answer is it because

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Speaker 1: remember that it sort of happened everywhere, like the universe

364
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Speaker 1: was a big, hot, glowing plasma. It was emitting this

365
00:19:04,160 --> 00:19:07,679
Speaker 1: cosmic market wave background radiation everywhere at the same moment,

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Speaker 1: and so we're still seeing it because it's coming to

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Speaker 1: us from different parts of the universe, from further and

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00:19:12,520 --> 00:19:16,359
Speaker 1: further away, all right, And so that's when the Dark

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Speaker 1: Ages of the Universe started. And so let's get into

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Speaker 1: what actually happened during those Dark ages and how we

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Speaker 1: know about what happened then. But first let's take a

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Speaker 1: quick break. All right, we're talking about the Dark Ages

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Speaker 1: of the universe, so that there was a point in

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Speaker 1: the universe's childhood teenage years, Yeah, exactly when you couldn't

375
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Speaker 1: see anything. I mean, it was really bright the universe.

376
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Speaker 1: It was dance and bright, and then suddenly it became

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00:19:55,119 --> 00:19:59,240
Speaker 1: transparent and not bright. And that's kind of when things

378
00:19:59,320 --> 00:20:02,399
Speaker 1: went yeah, because two things happen at once, right at

379
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Speaker 1: the universe goes from being opaque to being transparent, and

380
00:20:06,160 --> 00:20:09,640
Speaker 1: everything that was creating light sort of switched off. The

381
00:20:09,680 --> 00:20:13,879
Speaker 1: ionized particles are no longer glowing because they became mostly

382
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Speaker 1: neutral hydrogen. So now you have the universe is just

383
00:20:16,840 --> 00:20:21,160
Speaker 1: filled with neutral hydrogen but not creating any light, and

384
00:20:21,200 --> 00:20:24,840
Speaker 1: so light can pass through that universe, but there's not

385
00:20:24,880 --> 00:20:28,119
Speaker 1: anything really glowing. The only thing that's left is the

386
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Speaker 1: light from the cosmic market way background radiation, which is

387
00:20:31,080 --> 00:20:35,080
Speaker 1: gradually getting redder and redder as the universe expands. It's

388
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Speaker 1: kind of like the party ended, or you know, like

389
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Speaker 1: the club suddenly turn off the music and so everyone's like,

390
00:20:41,480 --> 00:20:44,600
Speaker 1: all right, I'll conserve my energy, I'll stop dancing. Yeah, exactly.

391
00:20:44,640 --> 00:20:47,399
Speaker 1: And so the stuff is still there, right, the stuff

392
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Speaker 1: that made the hot plasma of the CNB is still around.

393
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Speaker 1: It's just a little cooler, which is why it sort

394
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Speaker 1: of fell into these neutral atoms, and it's not glowing

395
00:20:56,040 --> 00:20:59,040
Speaker 1: as much anymore. It's a little bit of glow because

396
00:20:59,119 --> 00:21:02,479
Speaker 1: neutral hydrogen and which is still pretty hot, can glow

397
00:21:02,560 --> 00:21:06,200
Speaker 1: at one wavelength, a one centimeter wavelength, but it doesn't

398
00:21:06,240 --> 00:21:09,720
Speaker 1: give this broad spectrum of light that you get from

399
00:21:09,760 --> 00:21:12,560
Speaker 1: the hot plasma. So the only light you have in

400
00:21:12,600 --> 00:21:16,200
Speaker 1: the universe at this point is this gentle cosmic microwave

401
00:21:16,200 --> 00:21:19,640
Speaker 1: background radiation left over from the hot plasma that was there,

402
00:21:20,000 --> 00:21:23,160
Speaker 1: and then the very very light glow of neutral hydrogen.

403
00:21:23,359 --> 00:21:26,280
Speaker 1: So it's basically just all black in the universe. Interesting,

404
00:21:26,400 --> 00:21:28,800
Speaker 1: so I guess the universe it's just full of hot

405
00:21:28,920 --> 00:21:31,560
Speaker 1: hydrogen and that glows a little bit, but not like

406
00:21:31,600 --> 00:21:34,720
Speaker 1: a regular light. Yeah. And also it glows at a

407
00:21:34,720 --> 00:21:38,199
Speaker 1: certain frequency, and it also absorbs at that frequency, so

408
00:21:38,280 --> 00:21:40,880
Speaker 1: that light doesn't really go very far. So if you're

409
00:21:40,920 --> 00:21:43,760
Speaker 1: in the universe at that point, you basically really don't

410
00:21:43,760 --> 00:21:47,280
Speaker 1: see anything except for the CMB if you can detect it.

411
00:21:47,800 --> 00:21:50,160
Speaker 1: And so, you know, if you were transported in your

412
00:21:50,200 --> 00:21:52,480
Speaker 1: time machine back to the dark age of the universe

413
00:21:52,760 --> 00:21:55,280
Speaker 1: and you unroll the window or whatever, you look out,

414
00:21:55,359 --> 00:21:58,520
Speaker 1: it's just black. There no stars, there's no galaxies, there's

415
00:21:58,600 --> 00:22:01,520
Speaker 1: no nebula. There is really nothing to see in that view.

416
00:22:02,400 --> 00:22:04,520
Speaker 1: And also you get a lot of hot hydgroen hitting

417
00:22:04,560 --> 00:22:08,000
Speaker 1: you in the face if you roll down the window. Yeah, exactly,

418
00:22:08,280 --> 00:22:10,240
Speaker 1: make sure to put your space suit on before you

419
00:22:10,400 --> 00:22:12,160
Speaker 1: roll down the way. Just crack it open a little

420
00:22:12,160 --> 00:22:15,760
Speaker 1: bit first, just to check. Because the universe was pretty hot.

421
00:22:15,800 --> 00:22:18,520
Speaker 1: I mean it's not it's not like warm hydrogen. It's

422
00:22:18,560 --> 00:22:22,560
Speaker 1: like four thousand degrees hydrogen. Yeah, exactly. It's cool relative

423
00:22:22,600 --> 00:22:26,240
Speaker 1: to the early Universe, but it's still pretty hot relative

424
00:22:26,359 --> 00:22:30,159
Speaker 1: to where we are today. And so the early universe

425
00:22:30,200 --> 00:22:33,080
Speaker 1: is like four thousand degrees and then it gradually cools

426
00:22:33,160 --> 00:22:36,200
Speaker 1: down to you know, like sixty degrees kelvin and it's

427
00:22:36,240 --> 00:22:39,800
Speaker 1: cooling just because the universe is expanding or you know,

428
00:22:39,920 --> 00:22:41,959
Speaker 1: things are bumping into each other. Words, that all that

429
00:22:42,080 --> 00:22:45,000
Speaker 1: energy going it's just cooling because the universe is expanding.

430
00:22:45,359 --> 00:22:48,480
Speaker 1: As you expand the volume of a gas, it's temperature

431
00:22:48,520 --> 00:22:52,439
Speaker 1: goes down, right, And so here we're expanding space. Space

432
00:22:52,520 --> 00:22:55,040
Speaker 1: is getting bigger and bigger, but we're not creating any

433
00:22:55,080 --> 00:22:57,600
Speaker 1: more matter, and so it's getting more dilute, and so

434
00:22:57,680 --> 00:22:59,760
Speaker 1: the temperature is just dropping. And you know that's still

435
00:23:00,000 --> 00:23:02,760
Speaker 1: happening today. I guess this is a little technical, but

436
00:23:02,800 --> 00:23:05,679
Speaker 1: I thought temperature was related to like the kinetic energy,

437
00:23:05,760 --> 00:23:08,439
Speaker 1: not really the density. Temperatures are really tricky quantity, as

438
00:23:08,440 --> 00:23:11,040
Speaker 1: we've dug into on the podcast before. But you know,

439
00:23:11,080 --> 00:23:14,440
Speaker 1: it's connected not just to the energy of the particles,

440
00:23:14,600 --> 00:23:17,200
Speaker 1: but it's the statistical quantity that you can only really

441
00:23:17,200 --> 00:23:20,360
Speaker 1: talk about for a large number of particles. And so

442
00:23:20,440 --> 00:23:23,479
Speaker 1: the temperature of a gas, for example, depends also on

443
00:23:23,520 --> 00:23:26,359
Speaker 1: the pressure. You know, there's the ideal gas formula that

444
00:23:26,440 --> 00:23:28,760
Speaker 1: tells you that as you lower the pressure, the temperature

445
00:23:28,760 --> 00:23:31,520
Speaker 1: will drop. All right, So the gas got more diluted,

446
00:23:31,640 --> 00:23:35,520
Speaker 1: so that cooled it down, and that's pretty much the

447
00:23:35,600 --> 00:23:37,760
Speaker 1: dark ages of the universe. Right, it's all you know,

448
00:23:37,920 --> 00:23:40,080
Speaker 1: no light out there when you look out, it's just

449
00:23:40,160 --> 00:23:45,160
Speaker 1: pitch black. And it lasts for hundreds of millions of years, right,

450
00:23:45,160 --> 00:23:47,200
Speaker 1: Like it wasn't just a short period, Like there were

451
00:23:47,720 --> 00:23:50,320
Speaker 1: hundreds of millions of years where you there was nothing

452
00:23:50,840 --> 00:23:52,880
Speaker 1: going on. You can't see anything. Yeah, and if you've

453
00:23:52,920 --> 00:23:55,200
Speaker 1: been around in the universe at this point, you might think, well,

454
00:23:55,440 --> 00:23:57,560
Speaker 1: I guess this is it. You know, we had a

455
00:23:57,600 --> 00:23:59,639
Speaker 1: moment of creation. Things were hot and dense for a

456
00:23:59,680 --> 00:24:02,040
Speaker 1: while and exciting and glowy, and I guess we're just

457
00:24:02,040 --> 00:24:05,240
Speaker 1: going to sort of settle in comfortably to this boring,

458
00:24:05,560 --> 00:24:09,160
Speaker 1: dark universe. And yeah, it lasted for a long long time.

459
00:24:09,440 --> 00:24:12,480
Speaker 1: But you know, things eventually happen, and there's this transition

460
00:24:12,560 --> 00:24:16,439
Speaker 1: between when the really powerful forces are in charge, you know,

461
00:24:16,520 --> 00:24:20,760
Speaker 1: like electromagnetism, which is what gives you the neutralization of

462
00:24:20,800 --> 00:24:24,439
Speaker 1: the hydrogena, pulls those protons and those electrons together, and

463
00:24:24,480 --> 00:24:26,680
Speaker 1: it's happy. Now, it's like, all right, I've done my job.

464
00:24:26,720 --> 00:24:29,520
Speaker 1: I've made a bunch of neutral stuff. And then finally

465
00:24:29,600 --> 00:24:32,600
Speaker 1: the weakest force in the universe, gravity, it wakes up

466
00:24:32,640 --> 00:24:35,280
Speaker 1: and it's time for gravity to be in charge, right,

467
00:24:35,280 --> 00:24:37,480
Speaker 1: But it's not like it just suddenly wakes up and

468
00:24:37,680 --> 00:24:41,240
Speaker 1: turns on. It's just that as things cool down, gravity

469
00:24:41,320 --> 00:24:45,840
Speaker 1: sort of becomes more significant, right, Like it's always been there,

470
00:24:46,000 --> 00:24:48,240
Speaker 1: it's always been acting. But you know, the party was

471
00:24:48,600 --> 00:24:51,320
Speaker 1: too crazy at the beginning for it to really be

472
00:24:51,400 --> 00:24:54,639
Speaker 1: able to control anything. Yeah, exactly, it was basically irrelevant.

473
00:24:54,880 --> 00:24:57,320
Speaker 1: I mean the very early universe, gravity play a little

474
00:24:57,359 --> 00:24:59,919
Speaker 1: bit of a role in how these things come together

475
00:25:00,160 --> 00:25:02,800
Speaker 1: and the over densities in the very very early universe,

476
00:25:03,080 --> 00:25:05,920
Speaker 1: but then it's electricity and magnetism and the strong force

477
00:25:06,000 --> 00:25:09,280
Speaker 1: that really dominate the formation of these particles and then

478
00:25:09,560 --> 00:25:14,040
Speaker 1: their neutralization into hydrogen gas and helium gas. And you're right,

479
00:25:14,040 --> 00:25:16,080
Speaker 1: gravity was around. It was doing its thing. It was

480
00:25:16,119 --> 00:25:19,160
Speaker 1: tugging on stuff. But remember that gravity is like ten

481
00:25:19,240 --> 00:25:22,800
Speaker 1: to the forty times weaker than the other forces, and

482
00:25:22,840 --> 00:25:25,879
Speaker 1: so until the other forces get neutralized, gravity really can't

483
00:25:25,920 --> 00:25:28,439
Speaker 1: do its thing, right, And so then that's what it

484
00:25:28,480 --> 00:25:31,160
Speaker 1: was doing. During all those hundreds of millions of years

485
00:25:31,160 --> 00:25:35,280
Speaker 1: of the Dark Ages, gravity was getting to work making stuff. Yeah,

486
00:25:35,640 --> 00:25:38,320
Speaker 1: and so you have these huge clouds of hydrogen and

487
00:25:38,400 --> 00:25:41,399
Speaker 1: just like we still have happening in our universe. Something

488
00:25:41,640 --> 00:25:45,040
Speaker 1: can see them, like a small spot of over density

489
00:25:45,119 --> 00:25:48,040
Speaker 1: where dark matter has clumped stuff together, or for some

490
00:25:48,160 --> 00:25:51,440
Speaker 1: random quantum fluctuation. In the early universe, you have more

491
00:25:51,520 --> 00:25:54,399
Speaker 1: stuff there than you know, one meter over, and that

492
00:25:54,480 --> 00:25:58,320
Speaker 1: can sde sort of gravitational runaway effect where it has

493
00:25:58,359 --> 00:26:00,320
Speaker 1: more stuff to it, so it has more grab so

494
00:26:00,359 --> 00:26:04,399
Speaker 1: it pulls other stuff nearby, which then gives it more mass,

495
00:26:04,400 --> 00:26:07,880
Speaker 1: which means it has more gravity. So gravity pulls stuff together,

496
00:26:08,160 --> 00:26:11,840
Speaker 1: and then eventually it can do things like make a star. Right,

497
00:26:11,920 --> 00:26:14,399
Speaker 1: And a lot of it had to do with dark matter, right,

498
00:26:14,480 --> 00:26:19,560
Speaker 1: Like I guess dark matter was important in the dark ages. Yeah,

499
00:26:19,680 --> 00:26:22,200
Speaker 1: the reason this happened at the speed that it did

500
00:26:22,400 --> 00:26:25,199
Speaker 1: was because of dark matter. Remember that most of the

501
00:26:25,240 --> 00:26:29,640
Speaker 1: matter in the universe is dark matter. Of the matter, right,

502
00:26:29,680 --> 00:26:31,800
Speaker 1: of all the stuff that's out there that has gravity

503
00:26:32,200 --> 00:26:35,760
Speaker 1: is dark matter, and so it dominates this early universe.

504
00:26:35,800 --> 00:26:38,200
Speaker 1: It dominates the structure. Like where are you going to

505
00:26:38,280 --> 00:26:40,159
Speaker 1: get a star? You're going to get a star in

506
00:26:40,200 --> 00:26:43,560
Speaker 1: a little gravity well determined by the dark matter. So

507
00:26:43,600 --> 00:26:45,800
Speaker 1: it doesn't really matter in the early universe how the

508
00:26:45,880 --> 00:26:48,840
Speaker 1: hydrogen is distributed. It's much more important how the dark

509
00:26:48,880 --> 00:26:51,840
Speaker 1: matter is distributed, and that's kind of cool because it

510
00:26:51,880 --> 00:26:54,960
Speaker 1: means that the normal matter, which turned into stars and galaxies,

511
00:26:55,200 --> 00:26:57,399
Speaker 1: is sort of like a tracer for the dark matter.

512
00:26:57,440 --> 00:27:00,160
Speaker 1: It tells you where the dark matter was because as

513
00:27:00,160 --> 00:27:02,000
Speaker 1: this sort of follows it because it has to because

514
00:27:02,040 --> 00:27:05,280
Speaker 1: it's gravity pulls it in. It's not a pioneer in

515
00:27:05,320 --> 00:27:08,480
Speaker 1: making stuff like it was just following what dark matter

516
00:27:08,560 --> 00:27:11,719
Speaker 1: was doing, which was clumped for some reason in the

517
00:27:11,720 --> 00:27:16,080
Speaker 1: early universe. Quantum fluctuations in dark matter led to small

518
00:27:16,119 --> 00:27:18,320
Speaker 1: amounts of clumping in dark matter, and then gravity did

519
00:27:18,320 --> 00:27:21,480
Speaker 1: his job, and then the normal matter sort of follows

520
00:27:21,520 --> 00:27:24,120
Speaker 1: along in that process. But you know, it doesn't dictate

521
00:27:24,160 --> 00:27:26,320
Speaker 1: what happens because it's only a small bit of it.

522
00:27:26,760 --> 00:27:28,920
Speaker 1: And you would still get even without dark matter. You

523
00:27:28,920 --> 00:27:32,720
Speaker 1: would still get formation of structure and stars and stuff

524
00:27:32,760 --> 00:27:34,840
Speaker 1: even if you just had normal matter, but it would

525
00:27:34,840 --> 00:27:38,440
Speaker 1: take a lot longer, Like the dark ages were only

526
00:27:38,480 --> 00:27:41,560
Speaker 1: as short as they were a brief few hundred million

527
00:27:41,640 --> 00:27:44,560
Speaker 1: years because of dark matter. Without dark matter, they could

528
00:27:44,600 --> 00:27:47,200
Speaker 1: have lasted billions of years, right, And so then that's

529
00:27:47,240 --> 00:27:51,600
Speaker 1: how the first stars were born. And these were huge, right,

530
00:27:51,640 --> 00:27:54,280
Speaker 1: These weren't like the stars we know today. Like the

531
00:27:54,320 --> 00:27:57,719
Speaker 1: first stars were much bigger than the ones we have,

532
00:27:58,080 --> 00:28:00,679
Speaker 1: for example, in our solar system. Yeah, weirdly, these are

533
00:28:00,680 --> 00:28:04,399
Speaker 1: called population three stars even though they're the first population

534
00:28:04,440 --> 00:28:09,120
Speaker 1: of stars. Why would you name something confusing because they're

535
00:28:09,119 --> 00:28:12,280
Speaker 1: not as smart as particle physicists astronomers. They have no

536
00:28:12,359 --> 00:28:15,480
Speaker 1: idea what they're doing when it comes to me, we

537
00:28:15,640 --> 00:28:19,920
Speaker 1: just lost a couple of astronomy listeners there. Obviously I'm

538
00:28:19,920 --> 00:28:22,119
Speaker 1: making fun of particle physics there, but I think they

539
00:28:22,200 --> 00:28:25,320
Speaker 1: count backwards. The stars we have the most recently creator

540
00:28:25,400 --> 00:28:28,760
Speaker 1: called population one, and the stars in the previous generation

541
00:28:28,800 --> 00:28:32,360
Speaker 1: are called population two, and then the previous generation, which

542
00:28:32,400 --> 00:28:34,880
Speaker 1: happens to be the first one ever made, are called

543
00:28:34,920 --> 00:28:39,240
Speaker 1: population three stars. That is kind of smart, actually, because

544
00:28:39,240 --> 00:28:43,040
Speaker 1: you don't know, maybe there are more populations than initially

545
00:28:43,040 --> 00:28:46,040
Speaker 1: thoughts it makes sense to go, you know, in the

546
00:28:46,120 --> 00:28:49,120
Speaker 1: negative direction. Yeah, maybe they should have called them population

547
00:28:49,200 --> 00:28:52,600
Speaker 1: minus three or something. Anyway, we don't actually know about

548
00:28:52,640 --> 00:28:56,480
Speaker 1: population three stars. They're still theoretical. We've never observed one

549
00:28:56,680 --> 00:28:59,920
Speaker 1: on its own because they existed for such a brief

550
00:29:00,080 --> 00:29:03,400
Speaker 1: period in the very early universe. They were brief because

551
00:29:03,440 --> 00:29:06,600
Speaker 1: they were so big. Remember that a star burns faster

552
00:29:06,760 --> 00:29:09,560
Speaker 1: and hotter if it's much bigger. And you're right, these

553
00:29:09,560 --> 00:29:11,680
Speaker 1: stars were much bigger than the stars we have in

554
00:29:11,720 --> 00:29:15,240
Speaker 1: our universe. They're like thirty to three hundred times the

555
00:29:15,280 --> 00:29:18,360
Speaker 1: mass of our sun and they're just hydrogen. And they

556
00:29:18,360 --> 00:29:21,800
Speaker 1: burned really quickly after a few million years and spewed

557
00:29:21,800 --> 00:29:24,480
Speaker 1: out their light. And so these are starting to form

558
00:29:24,720 --> 00:29:26,720
Speaker 1: in the Dark Ages. So that is this kind of

559
00:29:26,760 --> 00:29:30,640
Speaker 1: when the Dark ages and when you first have these stars, Like,

560
00:29:30,680 --> 00:29:32,920
Speaker 1: how long did it take for them to start forming? Well,

561
00:29:32,960 --> 00:29:34,920
Speaker 1: it didn't take that long for them to start forming,

562
00:29:35,280 --> 00:29:37,880
Speaker 1: but the Dark Ages didn't end as soon as you

563
00:29:38,000 --> 00:29:41,520
Speaker 1: got stars because these stars were burning, but they were

564
00:29:41,560 --> 00:29:45,160
Speaker 1: still surrounded by these shrouds of hydrogen. Like you didn't

565
00:29:45,160 --> 00:29:48,000
Speaker 1: get all the hydrogen and clumped together into stars. You

566
00:29:48,120 --> 00:29:51,160
Speaker 1: got these like little pockets that collapsed into a star,

567
00:29:51,560 --> 00:29:55,440
Speaker 1: but then they're still surrounded by huge cloud of hydrogen gas.

568
00:29:55,960 --> 00:29:58,840
Speaker 1: And the light that's created by these stars is mostly

569
00:29:58,840 --> 00:30:01,760
Speaker 1: the light that hydrogen makes when it glows, and that

570
00:30:01,840 --> 00:30:05,600
Speaker 1: light is also absorbed by hydrogen. So you have this

571
00:30:05,760 --> 00:30:08,680
Speaker 1: universe filled with hydrogen clouds and then pinpricks of it

572
00:30:08,760 --> 00:30:11,720
Speaker 1: start to glow, but that light can't really penetrate the

573
00:30:11,800 --> 00:30:14,920
Speaker 1: hydrogen cloud. Oh, I see, there's there is light. Light

574
00:30:15,040 --> 00:30:17,720
Speaker 1: is being created in these dark ages, but it's also

575
00:30:17,800 --> 00:30:20,240
Speaker 1: really foggy. So this is more like the foggy Ages.

576
00:30:20,440 --> 00:30:22,360
Speaker 1: I mean, you couldn't really call it the dark Ages.

577
00:30:22,720 --> 00:30:25,280
Speaker 1: It's more like the dark Ages became the foggy Ages. Yeah,

578
00:30:25,280 --> 00:30:27,040
Speaker 1: but if you were anywhere far away from any of

579
00:30:27,120 --> 00:30:29,040
Speaker 1: these stars, you couldn't see any of them. It wouldn't

580
00:30:29,040 --> 00:30:31,480
Speaker 1: look any different to you. You couldn't tell that these

581
00:30:31,520 --> 00:30:34,920
Speaker 1: stars had started to burn. It's like it's nighttime and

582
00:30:35,000 --> 00:30:37,640
Speaker 1: you're in deep, deep fog. And yes, somebody turns on

583
00:30:37,680 --> 00:30:39,960
Speaker 1: a light a mile away, but the light is totally

584
00:30:40,040 --> 00:30:42,760
Speaker 1: absorbed by the fog, so you can't see it. But

585
00:30:42,880 --> 00:30:47,240
Speaker 1: wouldn't there be likely a somebody turning on light near you,

586
00:30:47,360 --> 00:30:50,200
Speaker 1: because you know the stars are forming everywhere. Yeah, well,

587
00:30:50,240 --> 00:30:52,800
Speaker 1: in a random spot in the universe, you're probably not

588
00:30:52,840 --> 00:30:55,360
Speaker 1: that close to a star. Remember, space is much much

589
00:30:55,400 --> 00:30:58,240
Speaker 1: bigger than we can even possibly grasp in our minds,

590
00:30:58,400 --> 00:31:00,280
Speaker 1: even in our current space. Like, if you pick a

591
00:31:00,440 --> 00:31:03,760
Speaker 1: random cubic meter of space, you would be far away

592
00:31:03,800 --> 00:31:06,400
Speaker 1: from any supercluster, not to mention any galaxy you not

593
00:31:06,440 --> 00:31:09,840
Speaker 1: to mention any star. Space is really vast and these

594
00:31:09,840 --> 00:31:12,240
Speaker 1: stars are few and far between in comparison. I see,

595
00:31:12,240 --> 00:31:15,080
Speaker 1: So things were that foggy like I guess we're thinking

596
00:31:15,440 --> 00:31:17,640
Speaker 1: as separate as they are now, Like we're there big

597
00:31:18,080 --> 00:31:20,520
Speaker 1: patches of empty universe like there are now? Or was

598
00:31:20,560 --> 00:31:24,200
Speaker 1: it pretty, you know, foggy throughout? Oh that's a great question.

599
00:31:24,200 --> 00:31:26,600
Speaker 1: But we think structure forms sort of bottom up. So

600
00:31:26,640 --> 00:31:29,000
Speaker 1: what happens first is that these stars form, and then

601
00:31:29,080 --> 00:31:32,720
Speaker 1: later they gathered together into galaxies. So things are more

602
00:31:32,760 --> 00:31:35,720
Speaker 1: spread out in the early universe than they are today.

603
00:31:35,760 --> 00:31:38,520
Speaker 1: Like today we have these dense clusters of stars that

604
00:31:38,560 --> 00:31:41,200
Speaker 1: we call galaxies and superclusters and stuff, and then the

605
00:31:41,400 --> 00:31:44,840
Speaker 1: huge voids where there's basically nothing. Back in the early universe,

606
00:31:45,000 --> 00:31:47,840
Speaker 1: things were more evenly spread out, sort of sprinkled through

607
00:31:47,840 --> 00:31:51,440
Speaker 1: the universe because the stars hadn't pulled together to form galaxies.

608
00:31:52,440 --> 00:31:54,800
Speaker 1: All right, Well, let's get into what else happens in

609
00:31:54,840 --> 00:31:59,360
Speaker 1: this foggy, dark ages, and let's talk about how we

610
00:31:59,400 --> 00:32:01,200
Speaker 1: know any of the is because it happens so long

611
00:32:01,200 --> 00:32:03,640
Speaker 1: ago and it was dark, so how do we know

612
00:32:03,760 --> 00:32:06,640
Speaker 1: anything about it? But first, let's take another quick break.

613
00:32:18,920 --> 00:32:21,920
Speaker 1: All right, Daniel, I have my fog lights on now

614
00:32:22,000 --> 00:32:25,280
Speaker 1: because we're in the foggy part of the Dark Ages

615
00:32:25,720 --> 00:32:28,719
Speaker 1: and everything is a giant cloud of hydrogen. There are stars,

616
00:32:28,760 --> 00:32:31,120
Speaker 1: they're burning bright, but yeah, everything is so foggy you

617
00:32:31,120 --> 00:32:34,560
Speaker 1: can't really see anything. And so that is part of

618
00:32:34,560 --> 00:32:37,480
Speaker 1: the Dark Ages. There there is light, but it's foggy.

619
00:32:37,520 --> 00:32:40,680
Speaker 1: There is light, but it's foggy. And what happens next

620
00:32:41,080 --> 00:32:44,040
Speaker 1: is that that fog clears. And remember what happened to

621
00:32:44,240 --> 00:32:46,880
Speaker 1: make the universe go dark was that we went from

622
00:32:46,920 --> 00:32:51,080
Speaker 1: ions nuclei that didn't have electrons around them, to neutral

623
00:32:51,120 --> 00:32:54,120
Speaker 1: atoms like hydrogen mostly and then a little bit of helium.

624
00:32:54,160 --> 00:32:57,600
Speaker 1: So what happens next is called reionization, is when we

625
00:32:57,680 --> 00:33:01,760
Speaker 1: break that neutral hydrogen back up into the proton and

626
00:33:01,800 --> 00:33:05,560
Speaker 1: the electron so that it's transparent to light. So the

627
00:33:05,600 --> 00:33:08,520
Speaker 1: next thing that happens is that these stars or maybe

628
00:33:08,560 --> 00:33:11,400
Speaker 1: black holes or maybe we don't know what broke up

629
00:33:11,440 --> 00:33:14,160
Speaker 1: this fog. Yeah, it broke apart all of those hydrogen

630
00:33:14,200 --> 00:33:18,280
Speaker 1: atoms and that made it transparent again eventually. So you

631
00:33:18,360 --> 00:33:21,160
Speaker 1: have this picture of like, you know, a foggy universe

632
00:33:21,240 --> 00:33:23,320
Speaker 1: with these little dots of light in it. And then

633
00:33:23,360 --> 00:33:26,920
Speaker 1: we don't exactly understand how this happened. One theory is

634
00:33:26,960 --> 00:33:30,000
Speaker 1: that the light from these stars eventually started to ionize

635
00:33:30,000 --> 00:33:32,920
Speaker 1: that hydrogen because the stars emit light that's absorbed by

636
00:33:32,960 --> 00:33:36,080
Speaker 1: that hydrogen, but they also admit higher energy light, these

637
00:33:36,320 --> 00:33:39,720
Speaker 1: ultra violet waves that the hydrogen can't absorb. Instead of

638
00:33:39,840 --> 00:33:43,160
Speaker 1: breaks up those nuclei and knocks off those electrons sometimes,

639
00:33:43,520 --> 00:33:46,160
Speaker 1: and so you break them up and you reionize, and

640
00:33:46,200 --> 00:33:49,240
Speaker 1: then you've broken that up. It's become transparent and so

641
00:33:49,320 --> 00:33:51,880
Speaker 1: eventually sort of pushes through that cloud the way sort

642
00:33:51,880 --> 00:33:54,760
Speaker 1: of like the sun can burn the fog off on

643
00:33:54,800 --> 00:33:58,120
Speaker 1: a really sunny day. So you get these kind of

644
00:33:58,120 --> 00:34:03,200
Speaker 1: like bubbles of visibility forming in a giant, foggy universe. Yeah,

645
00:34:03,200 --> 00:34:05,520
Speaker 1: it's sort of like the universe is a huge Swiss

646
00:34:05,560 --> 00:34:07,800
Speaker 1: cheese with these bubbles in it, and the bubbles are

647
00:34:07,800 --> 00:34:10,640
Speaker 1: growing and growing and growing, and eventually they meet and

648
00:34:10,680 --> 00:34:14,120
Speaker 1: then the universe essentially is more clear than it is foggy.

649
00:34:14,960 --> 00:34:16,960
Speaker 1: That is a pretty good analogy. A little cheesy, but

650
00:34:17,719 --> 00:34:21,000
Speaker 1: pretty clear. Yeah, And it's sort of incredible to imagine,

651
00:34:21,040 --> 00:34:23,560
Speaker 1: like what it could have been like to be alive. Then,

652
00:34:23,680 --> 00:34:26,279
Speaker 1: you know, imagine that you are around one of these

653
00:34:26,280 --> 00:34:29,200
Speaker 1: stars and you're living there and you see this fog

654
00:34:29,280 --> 00:34:31,600
Speaker 1: sort of like blocking your view of the universe, and

655
00:34:31,600 --> 00:34:33,520
Speaker 1: then one day it just sort of like it breaks

656
00:34:33,560 --> 00:34:36,760
Speaker 1: and you can see another star or two other stars,

657
00:34:36,880 --> 00:34:39,000
Speaker 1: or you know, sometimes when the fog lifts, you can

658
00:34:39,040 --> 00:34:42,360
Speaker 1: see like enormous views and you can see lots and

659
00:34:42,400 --> 00:34:45,160
Speaker 1: lots of other stars, and you finally understand the context

660
00:34:45,200 --> 00:34:47,799
Speaker 1: you're living in. What an exciting moment that must have been. Yeah,

661
00:34:47,880 --> 00:34:49,719
Speaker 1: but was it a moment It probably took you know,

662
00:34:49,800 --> 00:34:52,680
Speaker 1: again millions of years in it, Yeah, absolutely, but you know,

663
00:34:52,760 --> 00:34:56,239
Speaker 1: from the cosmic time scales, it's basically a moment. And

664
00:34:56,239 --> 00:34:59,120
Speaker 1: of course there was nobody around then. There were no galaxies,

665
00:34:59,160 --> 00:35:01,719
Speaker 1: and it probably weren't even really planets, maybe not even

666
00:35:01,760 --> 00:35:04,239
Speaker 1: life and any of these early objects. And so it's

667
00:35:04,280 --> 00:35:06,640
Speaker 1: just sort of like a mental exercise to imagine what

668
00:35:06,760 --> 00:35:09,080
Speaker 1: that might look like if you had been around, or

669
00:35:09,080 --> 00:35:11,240
Speaker 1: if we could send a time machine back in time

670
00:35:11,280 --> 00:35:13,359
Speaker 1: to visualize it. To me, that's pretty cool to think

671
00:35:13,400 --> 00:35:15,480
Speaker 1: about and and press the fast forward one because you

672
00:35:15,480 --> 00:35:18,880
Speaker 1: don't want to wait around a few hundred million years.

673
00:35:19,160 --> 00:35:22,000
Speaker 1: It's like that video on YouTube of watching paint dry

674
00:35:22,040 --> 00:35:24,800
Speaker 1: that has like ten million views. People do like watching

675
00:35:24,880 --> 00:35:28,200
Speaker 1: stuff happen gradually, all right, And so is that the

676
00:35:28,320 --> 00:35:30,560
Speaker 1: end of the Dark Ages when now you have the

677
00:35:30,880 --> 00:35:34,080
Speaker 1: flog kind of burning away. Yeah, that's it. And we

678
00:35:34,160 --> 00:35:36,400
Speaker 1: have this one theory that maybe it was starlight, that

679
00:35:36,680 --> 00:35:39,959
Speaker 1: the ultra violet light from these stars eventually burned these

680
00:35:39,960 --> 00:35:42,279
Speaker 1: holes in the fog and clear things up, but we're

681
00:35:42,320 --> 00:35:45,200
Speaker 1: not a hundred percent sure because population three stars are

682
00:35:45,200 --> 00:35:48,160
Speaker 1: still sort of theoretical. We don't really understand it. Another

683
00:35:48,280 --> 00:35:52,279
Speaker 1: idea is that you've got supermassive black holes created early on,

684
00:35:52,840 --> 00:35:55,799
Speaker 1: maybe from primordial black holes from the Big Bang, that

685
00:35:55,920 --> 00:35:57,920
Speaker 1: then grow as they eat a lot of gas and

686
00:35:57,960 --> 00:36:00,400
Speaker 1: they can emit a lot of radiation which might helped

687
00:36:00,400 --> 00:36:04,040
Speaker 1: clear this fog. And so it's not something we totally understand.

688
00:36:04,040 --> 00:36:06,440
Speaker 1: There's like a few ideas for how the fog lifted,

689
00:36:06,680 --> 00:36:09,279
Speaker 1: but again not something we totally understand because it's very

690
00:36:09,280 --> 00:36:12,080
Speaker 1: difficult to study, right, all right, So then we get

691
00:36:12,160 --> 00:36:15,000
Speaker 1: the universe as we know it. Then you get galaxies

692
00:36:15,040 --> 00:36:19,640
Speaker 1: and galaxies clusters and superstructures, and everything's clear the way

693
00:36:19,680 --> 00:36:21,719
Speaker 1: it is now. Yeah, and it's about after like a

694
00:36:21,800 --> 00:36:25,399
Speaker 1: billion years that the universe starts to look familiar, things

695
00:36:25,400 --> 00:36:28,640
Speaker 1: that you would recognize, as you say, stars and galaxies

696
00:36:28,640 --> 00:36:31,760
Speaker 1: and structures of galaxies and black holes at the center

697
00:36:31,800 --> 00:36:34,719
Speaker 1: of those galaxies and all that familiar stuff. But it

698
00:36:34,719 --> 00:36:37,759
Speaker 1: took about a billion years, you know, between three d

699
00:36:37,960 --> 00:36:40,840
Speaker 1: eighty thousand years after the Big Bang when the universe

700
00:36:40,880 --> 00:36:45,400
Speaker 1: went transparent, to a billion years later when structure formed

701
00:36:45,400 --> 00:36:48,000
Speaker 1: and the stars were created and the fog lifted. So

702
00:36:48,040 --> 00:36:50,480
Speaker 1: that's a long period between the Big Bang and when

703
00:36:50,520 --> 00:36:53,279
Speaker 1: the universe started to look familiar. It's kind of like

704
00:36:53,320 --> 00:36:56,319
Speaker 1: the adolescence of the universe. You know, you're in a

705
00:36:56,360 --> 00:37:00,560
Speaker 1: bad mood, you're feeling dark, you can't feel foggy the

706
00:37:00,560 --> 00:37:03,520
Speaker 1: whole time, but then suddenly things clear up and you

707
00:37:03,600 --> 00:37:05,560
Speaker 1: sort of come into your own Maybe you're not happy

708
00:37:05,560 --> 00:37:07,480
Speaker 1: with your complexion, so you prefer to spend some time

709
00:37:07,520 --> 00:37:09,280
Speaker 1: in the dark rather than go out into the sunlight.

710
00:37:09,360 --> 00:37:12,560
Speaker 1: So yeah, exactly the awkward teenage moments of the universe,

711
00:37:12,600 --> 00:37:15,400
Speaker 1: and then finally it grows up into the beautiful, gorgeous

712
00:37:15,480 --> 00:37:18,399
Speaker 1: views that we know and love today. All Right, Well,

713
00:37:18,440 --> 00:37:20,719
Speaker 1: maybe a big question that a lot of people might

714
00:37:20,719 --> 00:37:22,840
Speaker 1: have is how do we know any of the information

715
00:37:22,880 --> 00:37:25,759
Speaker 1: about the dark ages or that even that there was

716
00:37:25,840 --> 00:37:28,640
Speaker 1: a dark age in the universe. I mean, it happened

717
00:37:28,680 --> 00:37:32,120
Speaker 1: so long ago, fourteen billion years ago. How can we

718
00:37:32,160 --> 00:37:35,879
Speaker 1: look back and know with so much detail what happened. Well,

719
00:37:35,920 --> 00:37:38,680
Speaker 1: a lot of this is speculation because we don't have

720
00:37:38,800 --> 00:37:41,000
Speaker 1: data about this stuff. You know, we can see the

721
00:37:41,080 --> 00:37:45,320
Speaker 1: cosmic microwave background radiation that's the last light created before

722
00:37:45,640 --> 00:37:49,120
Speaker 1: the universe became transparent and neutral, and we can still

723
00:37:49,160 --> 00:37:51,680
Speaker 1: see that, and then we can see things start to

724
00:37:51,719 --> 00:37:54,360
Speaker 1: form later, you know, hundreds of millions of years or

725
00:37:54,400 --> 00:37:57,440
Speaker 1: billions of years later, and we see this gap, right,

726
00:37:57,719 --> 00:38:00,840
Speaker 1: we know when the constic microway background aready happened. We

727
00:38:00,880 --> 00:38:03,359
Speaker 1: can look back further and further in time and try

728
00:38:03,400 --> 00:38:06,480
Speaker 1: to see these early galaxies and these early stars, but

729
00:38:06,560 --> 00:38:09,319
Speaker 1: we just sort of don't see anything further. There's just

730
00:38:09,400 --> 00:38:12,399
Speaker 1: nothing there to see. I see. So you're saying you're

731
00:38:12,440 --> 00:38:17,680
Speaker 1: just guessing, and uh, well, also there's so you're saying

732
00:38:17,680 --> 00:38:19,439
Speaker 1: there's a gap and what we can see like there's

733
00:38:19,440 --> 00:38:21,960
Speaker 1: a missing spot in the our picture of the universe.

734
00:38:22,040 --> 00:38:24,880
Speaker 1: You know, we don't see stars and galaxies from before

735
00:38:24,920 --> 00:38:27,839
Speaker 1: that time because we think that there weren't there, and

736
00:38:27,880 --> 00:38:29,759
Speaker 1: so it's sort of like, how do you see the

737
00:38:29,840 --> 00:38:33,160
Speaker 1: dark ages? You're seeing the lack of something, right. The

738
00:38:33,239 --> 00:38:35,920
Speaker 1: dark ages are the lack of stars and light and

739
00:38:36,000 --> 00:38:38,839
Speaker 1: all sorts of fancy emissions that we could study, and

740
00:38:38,880 --> 00:38:40,520
Speaker 1: so we don't see them because we don't think that

741
00:38:40,600 --> 00:38:43,560
Speaker 1: information was being created there because there weren't stars and

742
00:38:43,600 --> 00:38:46,080
Speaker 1: galaxies and stuff to create pictures for us to see.

743
00:38:46,840 --> 00:38:48,839
Speaker 1: But I guess you're not just guessing. I mean you're

744
00:38:49,480 --> 00:38:51,839
Speaker 1: piecing together what makes sense from what we know now,

745
00:38:51,960 --> 00:38:54,960
Speaker 1: Like if you run a simulation of the universe backwards,

746
00:38:55,000 --> 00:38:57,000
Speaker 1: this is kind of what makes sense for things to

747
00:38:57,040 --> 00:38:59,360
Speaker 1: be the way they are now exactly. We're trying to

748
00:38:59,400 --> 00:39:03,320
Speaker 1: put together a holistic, coherent explanation for how the universe

749
00:39:03,360 --> 00:39:05,680
Speaker 1: came to be, and it makes sense for it to

750
00:39:05,680 --> 00:39:08,239
Speaker 1: have a dark age, like the physics suggests that it should.

751
00:39:08,280 --> 00:39:12,040
Speaker 1: You shouldn't get stars immediately after the universe gets filled

752
00:39:12,040 --> 00:39:14,680
Speaker 1: with nutral hydrogen. Should take a while for gravity to

753
00:39:14,680 --> 00:39:17,919
Speaker 1: pull it together, And our simulations, which now include dark matter,

754
00:39:17,960 --> 00:39:20,799
Speaker 1: explained pretty well how long that should happen and what

755
00:39:20,840 --> 00:39:23,960
Speaker 1: it should look like and even the nature of the structure.

756
00:39:24,360 --> 00:39:26,279
Speaker 1: You know, if you didn't have dark matter, or dark

757
00:39:26,320 --> 00:39:29,000
Speaker 1: matter had a different temperature even or a different distribution,

758
00:39:29,280 --> 00:39:31,560
Speaker 1: you would get a whole different shape of the universe.

759
00:39:31,880 --> 00:39:33,840
Speaker 1: We talked about that on a podcast once, about the

760
00:39:33,840 --> 00:39:36,799
Speaker 1: temperature of dark matter and how the speed of those

761
00:39:36,880 --> 00:39:40,279
Speaker 1: dark matter particles changes how things clump together. So we

762
00:39:40,320 --> 00:39:43,560
Speaker 1: actually have a really detailed picture of that period, but

763
00:39:43,719 --> 00:39:46,600
Speaker 1: we're lacking a sort of direct evidence. But we can

764
00:39:46,640 --> 00:39:48,839
Speaker 1: do something pretty cool, which is we make this whole

765
00:39:48,920 --> 00:39:51,520
Speaker 1: coherent view of how the universe should have worked the

766
00:39:51,560 --> 00:39:53,880
Speaker 1: history of the universe, and then we try to identify

767
00:39:54,000 --> 00:39:55,880
Speaker 1: things we can do to test that. We're like, well,

768
00:39:56,280 --> 00:39:59,640
Speaker 1: if this picture is true, what could we see, And

769
00:39:59,640 --> 00:40:02,320
Speaker 1: there's a few opportunities there to maybe get some hints

770
00:40:02,320 --> 00:40:04,960
Speaker 1: about what was going on in those dark ages? Right,

771
00:40:05,520 --> 00:40:07,560
Speaker 1: And I guess if we're looking out into the universe

772
00:40:07,600 --> 00:40:10,520
Speaker 1: and we're looking backwards some time, you can maybe literally

773
00:40:10,719 --> 00:40:13,440
Speaker 1: see this dark age, right, you could see the fog

774
00:40:13,560 --> 00:40:17,680
Speaker 1: almost or at least the first few stars that formed

775
00:40:18,280 --> 00:40:21,080
Speaker 1: that broke through the fog, right, because I mean at

776
00:40:21,120 --> 00:40:22,759
Speaker 1: some point and when you look out into space, you

777
00:40:22,760 --> 00:40:25,000
Speaker 1: would see those, right, Yeah, exactly, the ones that were

778
00:40:25,000 --> 00:40:27,040
Speaker 1: happening really far away. Yeah, And so those are the

779
00:40:27,080 --> 00:40:30,200
Speaker 1: two primary areas of investigation, where it's like, let's see

780
00:40:30,239 --> 00:40:33,200
Speaker 1: the oldest things we can and see when they formed

781
00:40:33,200 --> 00:40:35,600
Speaker 1: and what was going on. And you know, the oldest

782
00:40:35,600 --> 00:40:38,120
Speaker 1: things we see are like three hundred seventy to four

783
00:40:38,239 --> 00:40:40,799
Speaker 1: hundred million years after the Big Bang, and we see,

784
00:40:40,800 --> 00:40:44,000
Speaker 1: for example, clumps of stars that were all created at

785
00:40:44,000 --> 00:40:47,319
Speaker 1: the same time. We think, we don't really understand why,

786
00:40:47,400 --> 00:40:50,040
Speaker 1: and you know, we can't study these stars individually. These

787
00:40:50,040 --> 00:40:53,520
Speaker 1: things are so far away that they're just like blobs

788
00:40:53,680 --> 00:40:57,320
Speaker 1: of many, many, many stars that we can study all together.

789
00:40:57,360 --> 00:41:01,000
Speaker 1: We don't have the resolving power to identify one individual

790
00:41:01,120 --> 00:41:04,480
Speaker 1: population three star, but people are looking for that. And

791
00:41:04,480 --> 00:41:06,799
Speaker 1: then the second area of investigation is, as you say,

792
00:41:06,920 --> 00:41:08,919
Speaker 1: to look for that fog, like we should be able

793
00:41:08,960 --> 00:41:11,320
Speaker 1: to see it. It did admit some light. It was

794
00:41:11,400 --> 00:41:15,160
Speaker 1: neutral hydrogen, and neutral hydrogen when it's hot, does emit

795
00:41:15,320 --> 00:41:19,200
Speaker 1: light at one particular wavelength, this twenty one centimeter wavelength,

796
00:41:19,600 --> 00:41:21,320
Speaker 1: and so we can look for that. But that's a

797
00:41:21,400 --> 00:41:23,759
Speaker 1: radio signal, which means it's really hard to listen to

798
00:41:23,920 --> 00:41:27,440
Speaker 1: because frankly, our society makes a lot of radio noise,

799
00:41:27,840 --> 00:41:30,000
Speaker 1: and so it's very difficult to listen for this very

800
00:41:30,120 --> 00:41:34,200
Speaker 1: faint signal of the early universe hydrogen. Well, maybe in

801
00:41:34,200 --> 00:41:36,480
Speaker 1: the future will be making less great a waste, right,

802
00:41:36,520 --> 00:41:43,399
Speaker 1: I mean nobody watches broadcast TV now, it's all Netflix. Yeah,

803
00:41:43,480 --> 00:41:46,720
Speaker 1: that's true. We still use a lot of wireless communication, however,

804
00:41:47,040 --> 00:41:49,320
Speaker 1: which makes a lot of noise. All of your WiFi

805
00:41:49,400 --> 00:41:51,239
Speaker 1: out there, in your cell phone signals and all that

806
00:41:51,480 --> 00:41:54,640
Speaker 1: contributes to noise roughly in this spectrum. But we do

807
00:41:54,760 --> 00:41:57,840
Speaker 1: have some fun ideas for how to find quiet spots

808
00:41:58,040 --> 00:42:00,960
Speaker 1: that we can use to listen for the radio signal

809
00:42:01,000 --> 00:42:03,600
Speaker 1: from the early universe, and one of them involves building

810
00:42:03,640 --> 00:42:07,560
Speaker 1: something on the far side of the moon. Cool because

811
00:42:07,600 --> 00:42:09,759
Speaker 1: it's quiet there. Yeah, because it's quiet there. It's like

812
00:42:09,920 --> 00:42:12,719
Speaker 1: the quietest spot in the Solar system if you don't

813
00:42:12,800 --> 00:42:15,799
Speaker 1: want to listen to all of humanity's noise. And so

814
00:42:15,920 --> 00:42:18,200
Speaker 1: the idea is to build something which actually orbits the

815
00:42:18,200 --> 00:42:20,520
Speaker 1: Moon and it goes around the Moon. Is called the

816
00:42:20,600 --> 00:42:25,279
Speaker 1: Dark Ages Radio Explorer DARE, and it goes around the

817
00:42:25,320 --> 00:42:27,440
Speaker 1: Moon and when it's on the quiet side, the far side,

818
00:42:27,480 --> 00:42:30,600
Speaker 1: it listens for this hydrogen signal. And then when it's

819
00:42:30,640 --> 00:42:32,399
Speaker 1: on the four side, the side that we can see

820
00:42:32,440 --> 00:42:35,080
Speaker 1: it sends back us information and so that's a pretty

821
00:42:35,120 --> 00:42:37,080
Speaker 1: cool idea. I like that. Right, It goes to the

822
00:42:37,160 --> 00:42:39,480
Speaker 1: dark side of the moon to study the dark ages

823
00:42:39,960 --> 00:42:44,440
Speaker 1: that had dark matter in them exactly, and hopefully it

824
00:42:44,480 --> 00:42:47,600
Speaker 1: will brighten our day with some illuminations about the nature

825
00:42:47,640 --> 00:42:50,320
Speaker 1: of the universe. There you go, lift the fog, you know,

826
00:42:50,360 --> 00:42:53,480
Speaker 1: our understanding of the universe. Al right, well, that's the

827
00:42:53,560 --> 00:42:55,960
Speaker 1: dark ages of the universe. It sort of makes you

828
00:42:56,000 --> 00:42:58,840
Speaker 1: think when a roller coaster, Right, this whole universe is,

829
00:42:58,880 --> 00:43:01,319
Speaker 1: you know, first it was really bright and and explosive,

830
00:43:01,400 --> 00:43:04,560
Speaker 1: and then it was dark and quiet and foggy, and

831
00:43:04,640 --> 00:43:07,840
Speaker 1: now it's pretty bright and pretty. But maybe someday it

832
00:43:08,040 --> 00:43:11,080
Speaker 1: will go back to being dark and and quiet again. Right, Yeah,

833
00:43:11,120 --> 00:43:13,480
Speaker 1: I think that's the lesson. You know that one period

834
00:43:13,480 --> 00:43:15,640
Speaker 1: of the universe can seem sort of final, like it's

835
00:43:15,640 --> 00:43:18,719
Speaker 1: sort of settled into its final form, and it could

836
00:43:18,800 --> 00:43:21,640
Speaker 1: last for hundreds of millions of years, and then it

837
00:43:21,680 --> 00:43:25,439
Speaker 1: can change to something totally different. Right, And so even

838
00:43:25,440 --> 00:43:28,239
Speaker 1: though the universe is now fourteen billion years old and

839
00:43:28,239 --> 00:43:30,680
Speaker 1: it seems like to have mostly settled into this whole

840
00:43:30,719 --> 00:43:33,920
Speaker 1: structure of stars and galaxies and whatever. Who knows in

841
00:43:33,960 --> 00:43:36,799
Speaker 1: another hundred billion years, if something else will happen, if

842
00:43:36,800 --> 00:43:39,080
Speaker 1: we'd be in a totally new form, and people will

843
00:43:39,080 --> 00:43:41,640
Speaker 1: look back at this as like the bright period of

844
00:43:41,640 --> 00:43:44,600
Speaker 1: the universe, or the light ages of the universe, like

845
00:43:44,760 --> 00:43:48,200
Speaker 1: the prime of the universe, the middle age of the universe,

846
00:43:48,440 --> 00:43:52,560
Speaker 1: that's right, or going into the not so active part

847
00:43:52,560 --> 00:43:55,520
Speaker 1: of the universe. Yeah, or maybe the universe will continue

848
00:43:55,560 --> 00:43:58,239
Speaker 1: like this forever, or you know, it's one possibility is

849
00:43:58,280 --> 00:44:00,600
Speaker 1: that things will keep getting pulled upon art and the

850
00:44:00,680 --> 00:44:03,239
Speaker 1: universe will get dark. Not because things will turn off,

851
00:44:03,400 --> 00:44:05,520
Speaker 1: but because things will just be so distant that we

852
00:44:05,560 --> 00:44:08,279
Speaker 1: can't see each other, that all the other galaxies will

853
00:44:08,280 --> 00:44:11,160
Speaker 1: be yanked away from us due to dark energy, and

854
00:44:11,239 --> 00:44:14,040
Speaker 1: so the night sky will get darker and darker again,

855
00:44:14,080 --> 00:44:17,200
Speaker 1: not because stuff is disappearing, but because it becomes invisible.

856
00:44:17,239 --> 00:44:20,680
Speaker 1: It goes beyond our event horizon because it's just so

857
00:44:20,760 --> 00:44:23,560
Speaker 1: far away. Yeah, So I guess people should go out

858
00:44:23,640 --> 00:44:27,480
Speaker 1: there at night and hopefully somewhere where you can see

859
00:44:27,520 --> 00:44:30,880
Speaker 1: stars and appreciate the view because it's not gonna last forever.

860
00:44:32,280 --> 00:44:34,680
Speaker 1: You've got a few billion years, but still make some plans.

861
00:44:34,680 --> 00:44:38,160
Speaker 1: I guess appreciate it on a cosmic scalpe. Al Right, well,

862
00:44:38,480 --> 00:44:41,439
Speaker 1: we hope you enjoyed that little trip down memory lane

863
00:44:41,480 --> 00:44:44,840
Speaker 1: for the universe and enjoyed spending some time in the

864
00:44:45,000 --> 00:44:48,919
Speaker 1: dark and quiet period of the universe awkward teenage years

865
00:44:48,960 --> 00:44:52,560
Speaker 1: but also nice and quiet. Thanks for joining us, See

866
00:44:52,560 --> 00:45:02,360
Speaker 1: you next time. Hmm. Thanks for listening, and remember that

867
00:45:02,480 --> 00:45:05,200
Speaker 1: Daniel and Jorge explain the Universe is a production of

868
00:45:05,320 --> 00:45:08,680
Speaker 1: I Heart Radio or more podcast from my heart Radio.

869
00:45:08,840 --> 00:45:12,400
Speaker 1: Visit the I Heart Radio Apple Apple Podcasts, or wherever

870
00:45:12,520 --> 00:45:14,200
Speaker 1: you listen to your favorite shows.