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Speaker 1: Hey, or hey, do you like a surprise candy center?

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Speaker 1: It depends. Does it depend on what the surprise is? Absolutely,

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Speaker 1: you know if it do leg yes, sign me up.

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Speaker 1: If it's like marshmallow, I know. Thanks, Well, I guess

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Speaker 1: that makes sense. Yeah. Also it depends on what is

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Speaker 1: it surrounded by, Like what is it the center of?

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Speaker 1: Like I don't want to surprise candy center in my

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Speaker 1: taco or pizza. How about a surprise guacamole center in

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Speaker 1: your taco? You mean like candy guacamole. I'm not so

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Speaker 1: sure about that. How about candy guacamole in your dessert taco?

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Speaker 1: Dessert taco? Now you're talking, can we put bananas in it?

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Speaker 1: Banana avocado flavored ice cream? I'm not so sure. This

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Speaker 1: was a great idea. Yeah, we went too far. Hi

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Speaker 1: am r Hanmay, cartoonist and the creator of PhD comics. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 1: U c Irvine, and I will always try a weird

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Speaker 1: flavor of ice cream. Really, have you tried a garlic

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Speaker 1: ice cream? I have I tried garlic ice cream. I

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Speaker 1: even tried pasta Fa Julie flavored ice cream. I've tried

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Speaker 1: licorice ice cream. I've tried all the ice cream. Man,

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Speaker 1: there's a lot happening in your laboratory there. I'm married

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Speaker 1: to a biochemist. You know. She can really cook up

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Speaker 1: some crazy stuff. That's long. She doesn't put a gut

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Speaker 1: bacteria in your ice cream. That's what she researches, right,

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Speaker 1: that's true. Well, there's that famous Nathan for You episode

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Speaker 1: about poop flavored ice cream. What somebody made that? Or

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Speaker 1: somebody made that accidentally. No, there's a company apparently which

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Speaker 1: will create any flavor for you. So they created artificial

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Speaker 1: poof flavored ice cream and just to see if people

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Speaker 1: would try. Oh boy, let me try to are in

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Speaker 1: flavored ice cream. No, I haven't been able to find

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Speaker 1: that yet. Well, there you go. That's not too far

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Speaker 1: from from some of these extreme flavors. But welcome to

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Speaker 1: our podcast Daniel and Jorge Explain the Universe, a production

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Speaker 1: of I Heart Radio in which we take a deep

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Speaker 1: bite of the universe, hoping to enjoy its flavor. Whether

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Speaker 1: it tastes like black holes or neutron stars, or swirling

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Speaker 1: masses or tiny little particles, we are here to savor

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Speaker 1: it with you. Because we want to know what the

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Speaker 1: truth is out there in the universe, regardless of how

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Speaker 1: it tastes, and so we don't shy away from taking

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Speaker 1: a bite of any of the biggest questions in the universe.

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Speaker 1: Where does the universe come from? What does it all mean,

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Speaker 1: what's really going on on the tiny quantum scale, what's

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Speaker 1: swirling around in the center of our galaxy? How does

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Speaker 1: it all fit together? We talked about any end all

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Speaker 1: of those questions and explain them to you. Yeah, because

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Speaker 1: it is a wonderful and tasty universe. Now, Daniel, do

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Speaker 1: you think we were taking bites out of the universe

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Speaker 1: or are we just licking it before it melts? What

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Speaker 1: is the neiver is going to drip onto in this analogy?

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Speaker 1: That's my question. You know, a universe cone obviously hopefully

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Speaker 1: a waffle cone. Maybe physics is like the napkin because

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Speaker 1: we're trying to wipe up the messes. I see you're

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Speaker 1: not trying to create the messes. I thought I thought

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Speaker 1: physics was like the tongue doing the licking. I don't know,

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Speaker 1: this is getting very strange. We are definitely mixing our

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Speaker 1: metaphors here. But you know, the universe is delicious. The

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Speaker 1: thing that I love about physics is that every time

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Speaker 1: we do take a bite out of the universe, we

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Speaker 1: find something amazing. It's pretty rare that you uncover some

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Speaker 1: mystery and then go yawn, that was boring, And the

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Speaker 1: universe has lots of impressive surprises for us. Yeah, even

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Speaker 1: I hear it. It has Higgs boson flavored ice cream

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Speaker 1: and also some cork ice cream as well. Or is

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Speaker 1: all ice cream cork ice cream? Everything is cork flavor.

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Speaker 1: That's right. In the end. The corks are the fundamental

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Speaker 1: basis of flavor. And of course we do have flavor physics,

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Speaker 1: which talks about different kinds of corks, but totally ignores

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Speaker 1: the question of what they taste. Like, oh boy, we're

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Speaker 1: getting inception here. We're like going down a few levels.

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Speaker 1: It deploring the flavor of the particles that makeup flavor.

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Speaker 1: That's right. And you know it's not just stuff here

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Speaker 1: on Earth that you can taste. Astronauts report that space

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Speaker 1: itself has a flavor. What what do you mean? It

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Speaker 1: tastes like a vacuum. We talked about one time on

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Speaker 1: the podcast here when you come back in from a

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Speaker 1: spacewalk there are little volatile molecules from space that have

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Speaker 1: stuck to your space suit, and when you enter the

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Speaker 1: atmosphere they boil off and smell like barbecue. And sometimes

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Speaker 1: people say, like a raspberry? Whoa really? Like? I guess

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Speaker 1: there's like little tiny particles floating in space of raspberry

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Speaker 1: and possibly barbecue. Yeah, and some of the gas clouds

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Speaker 1: near the center of our galaxy are supposed to smell

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Speaker 1: a little bit like cranberry, though nobody's ever been there.

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Speaker 1: It's not raisins. Now, are you sure when they came

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Speaker 1: in from the spacewalk the barbecue they're smelling is not

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Speaker 1: themselves from being out out in the sun too long. Geez,

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Speaker 1: smells like my hair is on fire. What's going on?

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Speaker 1: It smells a cosmic ray fire. But anyway, it is

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Speaker 1: a pretty interesting and amazing universe, and there's still a

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Speaker 1: lot we don't know about it, even in our own neighborhood.

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Speaker 1: There are big mysteries in our solar system and especially

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Speaker 1: in our galaxy. Our galaxy is called the Milky Way,

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Speaker 1: and it's big and it's amazing, has millions of stars,

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Speaker 1: but there is a big mystery at the center of it.

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Speaker 1: Because remember that everything we know about the universe and

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Speaker 1: our galaxy comes from observations we have just made from

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Speaker 1: here on Earth. Yeah, we've sent a few probes, maybe

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Speaker 1: to the edge of our solar system, but mostly we

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Speaker 1: have one eyeball trapped here in one spot in the galaxy,

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Speaker 1: and we're trying to do something very difficult, which is

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Speaker 1: make a map of the whole galaxy, of the whole universe,

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Speaker 1: having seen it from just one spot. Imagine standing on

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Speaker 1: the top of a mountain and then trying to make

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Speaker 1: a map of the Earth. Some things are obscured from

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Speaker 1: your view. Other things you have to just sort of

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Speaker 1: sketch because you can't quite make them out. That's the

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Speaker 1: challenge we face in trying to map out the cosmos

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Speaker 1: around us. Yeah, it's pretty amazing how well we've done,

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Speaker 1: you know, just from standing in that mount ten with

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Speaker 1: a telescope, we've been able to basically figure out most

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Speaker 1: of what the universe looks like, and how it's structured together,

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Speaker 1: and how many stars there are out there, how many galaxies.

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Speaker 1: But there are things that we can quite see from

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Speaker 1: our point of view. Yes, sometimes we can be very

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Speaker 1: direct and say, look, we see that thing. We know

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Speaker 1: exactly what it is and where it is. Other times

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Speaker 1: we have to sort of infer what we think is

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Speaker 1: going on based on more indirect evidence, and that's how

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Speaker 1: we've leveraged our powers of observation to tell us about

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Speaker 1: how things look in places that we can't see. We

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Speaker 1: have to make these indirect conclusions. But sometimes we might

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Speaker 1: make mistakes because we might be folding in incorrect assumptions

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Speaker 1: or guesses about what might be there. And people can

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Speaker 1: come along with new ideas that give us new perspectives

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Speaker 1: on what's going on. Yeah, you could be linking the

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Speaker 1: wrong ice cream where all we know right there is

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Speaker 1: no wrong ice cream. Man, We'll wait until you taste

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Speaker 1: during ice cream or that poop ice cream that sounds

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Speaker 1: like the wrong kind of ice cream. But yeah, it's

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Speaker 1: a pretty mysterious galaxy that we live in. And so

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Speaker 1: today we'll be tackling a question related to what's at

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Speaker 1: the core of it. So on the podcast today we'll

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Speaker 1: be asking the question, could our galaxy have a dark

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Speaker 1: matter center? Mm? Hmm? Could our galaxy have a dark

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Speaker 1: matter center? Now? Isn't dark matter all over the galaxy

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Speaker 1: like it's in most of our galaxy made of dark matter. Yes,

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Speaker 1: most of the mass in the galaxy is dark matter,

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Speaker 1: and there is definitely dark matter hanging out at the

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Speaker 1: center of the galaxy. But conventional wisdom is that the

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Speaker 1: center of the galaxy also has a supermassive black hole

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Speaker 1: as a like gravitational anchor something that's really holding the

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Speaker 1: whole galaxy together, this incredibly massive object four million times

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Speaker 1: the mass of the Sun. But we've never seen that

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Speaker 1: black hole directly, and so some people wonder if it's

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Speaker 1: really there or if instead it's dark matter doing the work.

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Speaker 1: Interesting and yeah, because I guess we can't sort of

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Speaker 1: look directly to the center of our galaxy. I mean,

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Speaker 1: we can sort of look in the direction of the

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Speaker 1: center of the galaxy, but it's so far away maybe,

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Speaker 1: and there's so many things in between that it's hard

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Speaker 1: to kind of see in there. It is, in fact

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Speaker 1: completely obscured because the center of the galaxy is a

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Speaker 1: busy place. There are a lot of stars between us

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Speaker 1: and it, and there's also a lot of gas and dust,

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Speaker 1: so it's not something that's very easy to look at

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Speaker 1: directly in the visible light. And so we'll get into

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Speaker 1: details of what we know about what's going on in

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Speaker 1: the center of the galaxy. Why most astronomers think that

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Speaker 1: there is a black hole there, and some new evidence

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Speaker 1: that's casting doubt on that assumption. M I see. So

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Speaker 1: the prevailing thought is that there is a supermassive black

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Speaker 1: hole in the middle of our galaxy. But now the

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Speaker 1: question is maybe there's not. Maybe it's just a whole

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Speaker 1: bunch of super compact dark matter. Maybe. Yeah. In line

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Speaker 1: with our podcast about dark stars, we are casting doubt

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Speaker 1: on the existence of black holes everywhere. We are throwing

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Speaker 1: shade on black holes because in the end, they are

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Speaker 1: very difficult to see directly. It's always an inference. You're

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Speaker 1: always jumping to a conclusion, saying there's a certain amount

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Speaker 1: of mass and the certain amount of area, therefore it

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Speaker 1: must be a black hole. But you know, that's not

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Speaker 1: like finding the body in a murder. It's all circumstantial evidence. Yeah,

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Speaker 1: And the problem with throwing shade at a black hole

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Speaker 1: is that it never comes out. It just eats your

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Speaker 1: shade and says, thank you, Can I have another. It's

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Speaker 1: a pretty interesting question. What is at the center of

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Speaker 1: our galaxy? Is it a supermassive black hole or is

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Speaker 1: it dark matter? And so, as usual We were wondering

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Speaker 1: how many people out there have thought about this question

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Speaker 1: and think that maybe it could be dark matter. So

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Speaker 1: Daniel went out there into the internet to ask people

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Speaker 1: could our galaxy have a dark matter center instead of

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Speaker 1: a black hole? So thank you very much to our

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Speaker 1: cadre of volunteers. If you'd like to join them, please

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Speaker 1: don't be shy, just email me two questions at Daniel

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Speaker 1: and Jorge dot com. You know you want to, so

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

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Speaker 1: galaxy has a dark matter center? Here's what people had

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Speaker 1: to say. There is lots of evidence for a black

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Speaker 1: hole from a high concentration of mass at the center

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Speaker 1: of our galaxy because of the orbit of several star

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Speaker 1: ours that are have been whipping around something very very small,

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Speaker 1: very very fast. So that implies a density of matter

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Speaker 1: foreign excess what we normally would predict for dark matter,

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Speaker 1: and if the dark matter were to concentrate to that extent,

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Speaker 1: it would then just become a black hole, since it

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Speaker 1: is only gravity that matters. Anyway, I don't know why

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Speaker 1: our galaxy would have a dark matter center instead of

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Speaker 1: a black hole. I know that most galaxies do have

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Speaker 1: a black hole at their center, as do most spots

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Speaker 1: wear enough mass has just gotten together and hung out

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Speaker 1: for long enough. Maybe it could be both. Could our

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Speaker 1: galaxy have dark matter center instead of black hole? And

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Speaker 1: I think we have a super massive black hole center

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Speaker 1: of our galaxy, not dark matter. I don't really see

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Speaker 1: how we could have a dark matter only center of

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Speaker 1: our galaxy because would mean that all the regular matters

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Speaker 1: being pulled into it, which in my head, would make

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Speaker 1: it a black hole. Whether or not the dark matter

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Speaker 1: falls into the black hole, it's kind of irrelevant because

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Speaker 1: you've got a black hole there anyway, pulling in any

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Speaker 1: barrionic matter. I do think that the galaxy can have

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Speaker 1: the dark matter center because dark matter experiences gravity, it

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Speaker 1: has it has mass, and it definitely experiences gravity. It

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Speaker 1: accounts for like a very large amount of matter that

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Speaker 1: we know, so we only know that normal matter is

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Speaker 1: very less. And yeah, there is a possibility that there

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Speaker 1: is a huge quantity of dark matter at the center

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Speaker 1: of our galaxy instead of having a black hole. Turcky, Turcky.

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Speaker 1: I have no idea, but it reminds me of something

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Speaker 1: in in a video game I used to play. I'm

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Speaker 1: just gonna leave this one as a shrug. All right,

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Speaker 1: it seems that people are skeptical. Yeah, there's some great

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Speaker 1: answers here. People thinking about what would happen to the

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Speaker 1: dark matter if it got concentrated at the center of

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Speaker 1: the galaxy. Really some great stuff. Yeah. I like the

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Speaker 1: people who say it could be both, Like, yeah, why

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Speaker 1: can't it have both both a super massive black hole

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Speaker 1: and dark matter in it? Or how about a how

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Speaker 1: about a dark matter black hole? A dark matter black

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Speaker 1: hole be super awesome, Although you know, once material falls

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Speaker 1: into the black hole, it's not really clear what its

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Speaker 1: nature is anymore. Is it's still dark matter? Is it

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Speaker 1: gotten converted into energy? Has got turned into something else?

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Speaker 1: So once you're inside the black hole, it's just stuff. Man?

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Speaker 1: WHOA yeah, because I guess dark matter could technically turn

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Speaker 1: into regular stuff. Do you think it's made out of

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Speaker 1: the same kind of like energy. We don't know, right,

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Speaker 1: there might be some way for dark matter to turn

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Speaker 1: into normal matter. We do know that there was a

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Speaker 1: lot more dark matter in the early universe than there

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Speaker 1: is today, and so we hypothesize that there's some mechanism

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Speaker 1: by which dark matter can very slowly turn into normal matter.

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Speaker 1: But it needs a lot of energy density for that

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Speaker 1: to happen. So we think it might have happened in

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Speaker 1: the early universe and then frozen out, and it might

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Speaker 1: then again and have an inside black holes. Who knows,

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Speaker 1: maybe threw a lot of shade to the black holes

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Speaker 1: and lost some of its energy. All right, Well, let's

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Speaker 1: tackle this question. Could it be dark matter at the

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Speaker 1: center of our galaxy and not a supermassive black hole? Now,

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Speaker 1: first of all, I guess why did we think or

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Speaker 1: do we think that the center of our galaxy has

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Speaker 1: a supermassive black hole. Well, let's not be too click baity. Definitely,

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Speaker 1: the mainstream astronomy community is convinced that there's a supermassive

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Speaker 1: black hole at the heart of our galaxy. I mean,

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Speaker 1: they gave the twenty twenty Nobel Prize to two folks,

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Speaker 1: Reinhard Genzel and Andrea Guz from u c l A,

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Speaker 1: who've been observing the center of the galaxy for decades

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Speaker 1: and trying to figure out what's going on there. But

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Speaker 1: we've had a hint that there's something going on at

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Speaker 1: the center of the galaxy for decades, since people sent

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Speaker 1: up rockets into the upper atmosphere and heard this radio

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Speaker 1: signal from the center of the galaxy. And then it

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Speaker 1: was in the sixties and seventies that people figured out,

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Speaker 1: oh wow, maybe this could be a black hole, and

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Speaker 1: it was one of the first things identified as a

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Speaker 1: black hole at the center of our galaxy. Mmmm. That's

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Speaker 1: interesting because I think we talked about this in another

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Speaker 1: episode where you know, we talked about how do we

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Speaker 1: know there's maybe a black hole at the center of

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Speaker 1: our galaxy? And I remember one of the ways is

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Speaker 1: that you can tell from like how the stars around

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Speaker 1: the center of the galaxy are moving, like they're moving faster,

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Speaker 1: or their tighter orbits than you wouldn't have you didn't

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Speaker 1: have a black hole. You can never see a black

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Speaker 1: hole directly, right, It's just black. It's essentially invisible. So

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Speaker 1: what you need to do to identify a black hole

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Speaker 1: is to see its gravitational effect on stuff around it.

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Speaker 1: And so the argument that something is a black hole

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Speaker 1: is that you measure its mass by looking at how

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Speaker 1: hard it pulls on things gravitationally nearby. But then the

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Speaker 1: second crucial element is that you need to measure it's radius.

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Speaker 1: Because not everything with gravity has a black hole, or

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Speaker 1: the Earth has gravity. You can measure it's pull on

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Speaker 1: the Moon doesn't make the Earth of the black hole.

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Speaker 1: But if you can measure something's mass and it's radius

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Speaker 1: and the radius is really really small, that means that

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Speaker 1: the object is really dense, it's very compact, and below

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Speaker 1: a certain radius, an object of that mass has to

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Speaker 1: be a black hole as far as we know. Well,

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Speaker 1: I so you're saying that we know that there is

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Speaker 1: something really heavy at the center of our galaxy, is

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Speaker 1: super duper heavy, but we don't know if it's actually

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Speaker 1: a black hole. Like it could just be a giant

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Speaker 1: ball of ice cream, right, it could be all that

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Speaker 1: during and ice cream that people have been rejecting for

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Speaker 1: all of those years. Yeah, nobody wants to lick yet.

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Speaker 1: And so the tricky thing is the radius. And as

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Speaker 1: you say, a great way to study this is to

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Speaker 1: look at the effect on very close by stars, because

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Speaker 1: they're mostly affected by the gravitational pull of this thing.

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Speaker 1: And also as they pass close by, you can get

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Speaker 1: a sense for how big the black hole is, because

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Speaker 1: if something passes within one AU, for example, and survives,

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Speaker 1: then you know that whatever is there has to have

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Speaker 1: a radius of less than one AU, where a U

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Speaker 1: is an astronomical unit, the distance from the Earth to

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Speaker 1: the Sun. And that's exactly what they do, is they

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Speaker 1: look at all the nearby stars. Is it's like a

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Speaker 1: few stars that hang out really close to whatever this

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Speaker 1: is at the center of the galaxy and they zip

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Speaker 1: around it. So people look at the motion of those

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Speaker 1: stars to try to measure the mass of this object,

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Speaker 1: and they also look at the distance of closest approach

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Speaker 1: to try to get a sense for what the radius

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Speaker 1: of this thing might be. M So what you're saying

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Speaker 1: that we can sort of look at the center of

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Speaker 1: the galaxy, we can't see these stars orbiting around the

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Speaker 1: very center of the Milky Way. Well, it's not easy

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Speaker 1: and you can't see them invisible light, but infrared light

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Speaker 1: can pass through a lot of the gas and the dust.

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Speaker 1: So if you use filters on your telescope to only

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Speaker 1: look through the infrared, you can see these stars. And

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Speaker 1: in that way you can see what's going on in

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Speaker 1: the center of the galaxy. And if you google you

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Speaker 1: can watch these cool movies of these stars. And the

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Speaker 1: movies take like more than a decade to make because

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Speaker 1: these stars have like an orbital period of like sixteen years.

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Speaker 1: But you can see them whooshing around this blank spot

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Speaker 1: at the center of the galaxy, so it's really obvious

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Speaker 1: that there's something very massive. They're interesting. So we do

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Speaker 1: have sort of pictures of the center of the galaxy.

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Speaker 1: You can s to c through that gas and dust,

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Speaker 1: and it does show something pretty dense in the middle

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Speaker 1: of it. That's right, So we can measure the mass

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Speaker 1: pretty accurately to be about four million times the mass

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Speaker 1: of our Sun. It's very very heavy. It's an incredible

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Speaker 1: gravitational source. But the tricky thing is that we don't

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Speaker 1: have a great measurement for the radius of this thing,

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Speaker 1: because in order to measure the radius, something has to

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Speaker 1: pass really really close and then survive, right, it has

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Speaker 1: to like not fall into the black hole. There's a

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Speaker 1: star that's called S two that goes really close to it.

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Speaker 1: But the closest approach we've ever seen to this object

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Speaker 1: is about twelve a U twelve times the distance between

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Speaker 1: the Earth and the Sun. Wow, that that seems really

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Speaker 1: small to me, right kind of right, like it's smaller

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Speaker 1: than our solar system. Like this thing, whatever it is,

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Speaker 1: the super dense thing at the center of the galaxy

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Speaker 1: is smaller than our solar system. It is smaller than

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Speaker 1: our solar system. But but it's four million times of

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Speaker 1: the mass or sun. Four million times the mass of

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Speaker 1: the Sun. But if you calculate how big should a

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Speaker 1: black hole b, if it's four million times the mass

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Speaker 1: of the Sun, then you can answer of like point

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Speaker 1: one a U, like a tenth of an a U.

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Speaker 1: So whatever this thing is, it's much smaller than sort

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Speaker 1: of the radius we've been able to probe. Right, it

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Speaker 1: might be a black hole that's really dense and at

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Speaker 1: the heart of this sphere we haven't been able to

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Speaker 1: see inside of yet. But that's the uncertainty. We don't

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Speaker 1: really know if whatever this stuff is that has massive

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Speaker 1: four million times the Sun is actually compactified enough to

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Speaker 1: make a black hole, or if it's something else, something

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Speaker 1: sort of larger and fluffier. Right, Like you could take

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Speaker 1: four million times the mass of our sun in ice

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Speaker 1: cream and put it in a giant ball, and probably

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Speaker 1: would it be about that, you know, smaller than the

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Speaker 1: size that we're observing. That could it be like you know,

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Speaker 1: for a U, Yeah, twelve a U is a really

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Speaker 1: large radius, and so it makes a huge volume. And

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Speaker 1: so even though four million times the mass of the

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Speaker 1: Sun is a lot of mass. If you spread it

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Speaker 1: out through a sphere that's like twelve a U and radius,

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Speaker 1: it's not actually that dense, So yeah, you don't have

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Speaker 1: to be nearly as dense as a black hole. It's

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Speaker 1: still a little bit denser than dury and ice cream,

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Speaker 1: but you know, it's pretty close dense and flavor at least,

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Speaker 1: all right, So that's kind of the mystery. We know

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Speaker 1: there's something super heavy, four million times the mass of

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Speaker 1: the Sun and in the center of our galaxy, but

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Speaker 1: we don't know how dense it is, whether it's dense

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Speaker 1: enough to be a black hole, or maybe it's just

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Speaker 1: dense enough to be a big ball of ice cream

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Speaker 1: or dust or cloud or who knows. So let's get

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Speaker 1: into why would not be a black hole and what

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Speaker 1: evidence we have for either answer. But first let's take

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Speaker 1: a quick break, right, Daniel, we're asking the question what

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Speaker 1: is at the center of our galaxy? And it could

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Speaker 1: be a super massive black hole or it could be

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Speaker 1: something else. All we know is that it's super heavy.

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Speaker 1: It's four million times the mass of our Sun, and

396
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Speaker 1: it's pretty small and smaller than our solar system, but

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Speaker 1: maybe not small enough to be a black hole. So

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Speaker 1: how did not be a black hole? Like, if you

399
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Speaker 1: have that much mass four million times the mass of

400
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Speaker 1: our Sun in that space, when it eventually collapse into

401
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Speaker 1: a black hole anyways, Well, it depends a little bit

402
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Speaker 1: on what it is. Right, Things don't always collapse into

403
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Speaker 1: a black hole because they have ways of resisting that collapse.

404
00:20:14,840 --> 00:20:18,360
Speaker 1: Like why doesn't this Sun collapse into a black hole immediately? Well,

405
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Speaker 1: because it has fusion. That energy is pushing out and

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Speaker 1: keeping the Sun fluffy. Why doesn't the Earth collapse into

407
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Speaker 1: a black hole? Because of the strength of the materials, Right,

408
00:20:26,800 --> 00:20:30,440
Speaker 1: they have this actual tensile strength to resist being crushed

409
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Speaker 1: by gravity. And as things get denser and denser, they're

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Speaker 1: all these thresholds to overcome. Like even neutron stars, which

411
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Speaker 1: are crazy dense, are resisting collapse into a black hole

412
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Speaker 1: because of the quantum degeneracy pressure. Like all these corks

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Speaker 1: don't want to be on top of each other. And

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Speaker 1: so in order to become a black hole, you have

415
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Speaker 1: to have enough mass and already be compact enough to

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Speaker 1: collapse to overcome all of these sort of thresholds. So

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Speaker 1: it's possible to arrange this much mass in that small

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Speaker 1: space that doesn't collapse into a black hole. Mmmmm, but

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Speaker 1: I guess you know, if you had four million times

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Speaker 1: the mass of our Sun in it, and if it

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Speaker 1: was just gas or does wouldn't you know? Don't we

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Speaker 1: have models that say what would happen to something like that,

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Speaker 1: Like if it had fusion keeping it from collapsing to

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Speaker 1: a black hole, we it would be shining and we

425
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Speaker 1: would see it, right m m yeah, So clearly it's

426
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Speaker 1: not shining. But there's also questions about like velocity. If

427
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Speaker 1: something is swirling really really fast, then it's hard for

428
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Speaker 1: it to collapse. That's why, for example, dark matter doesn't

429
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Speaker 1: collapse into a black hole because dark matter has a

430
00:21:29,840 --> 00:21:33,119
Speaker 1: lot of rotational energy. It's swirling around the center of

431
00:21:33,119 --> 00:21:35,960
Speaker 1: the galaxy, and in order for it to collapse into

432
00:21:35,960 --> 00:21:38,320
Speaker 1: a tiny point, it needs to lose some of that

433
00:21:38,440 --> 00:21:42,040
Speaker 1: angular momentum, right, and angler momentum is conserved in our universe,

434
00:21:42,320 --> 00:21:44,320
Speaker 1: So the only way to lose angular momentum is to

435
00:21:44,359 --> 00:21:47,520
Speaker 1: like bump into something else and give your angular momentum away.

436
00:21:47,880 --> 00:21:50,439
Speaker 1: And that's really difficult for dark matters to do because,

437
00:21:50,480 --> 00:21:53,320
Speaker 1: as we've talked about before, it's not sticky, So it's

438
00:21:53,320 --> 00:21:55,600
Speaker 1: possible that whatever is there is just swirling around for

439
00:21:55,640 --> 00:21:58,040
Speaker 1: a while. But there are also other explanations, and people

440
00:21:58,080 --> 00:22:01,040
Speaker 1: have a very specific theory for what could be at

441
00:22:01,040 --> 00:22:04,240
Speaker 1: the center of the galaxy that's resisting this collapse and

442
00:22:04,359 --> 00:22:07,840
Speaker 1: has the same mass. Well, again, maybe let's take a

443
00:22:07,840 --> 00:22:10,199
Speaker 1: step back. You said the prevailing theory is that it

444
00:22:10,320 --> 00:22:12,600
Speaker 1: is a black hole. So what makes people think that

445
00:22:12,680 --> 00:22:14,480
Speaker 1: it is a black hole if we don't really have

446
00:22:14,600 --> 00:22:17,240
Speaker 1: direct evidence of it. I guess it's just the leading candidate,

447
00:22:17,359 --> 00:22:19,840
Speaker 1: you know, of the things that could have that mass

448
00:22:19,880 --> 00:22:22,680
Speaker 1: and that radius and not give off any direct light,

449
00:22:22,960 --> 00:22:25,480
Speaker 1: a black hole is sort of the least exotic. You

450
00:22:25,520 --> 00:22:27,960
Speaker 1: can't come up with other things, but usually they require

451
00:22:28,040 --> 00:22:31,439
Speaker 1: inventing new particles, things that we haven't discovered yet. So

452
00:22:31,480 --> 00:22:34,440
Speaker 1: there's no way to arrange like normal matter as far

453
00:22:34,480 --> 00:22:36,960
Speaker 1: as we know, into a configuration like that that's going

454
00:22:37,040 --> 00:22:39,320
Speaker 1: to be stable and last a long time and not

455
00:22:39,440 --> 00:22:41,840
Speaker 1: collapse into a black hole. Like even a big swirling

456
00:22:41,880 --> 00:22:44,760
Speaker 1: cloud of gas that's spinning and resisting falling into a

457
00:22:44,760 --> 00:22:48,119
Speaker 1: black hole eventually will collapse into a black hole because

458
00:22:48,320 --> 00:22:51,439
Speaker 1: they'll bump against itself and lose its angular momentum. So

459
00:22:51,480 --> 00:22:53,440
Speaker 1: you need some sort of like new kind of particle.

460
00:22:53,680 --> 00:22:55,280
Speaker 1: I see. So, as far as we know, if you

461
00:22:55,320 --> 00:22:57,240
Speaker 1: did have a giant ball of ice froam that big,

462
00:22:57,560 --> 00:23:00,520
Speaker 1: it would sort of collapse into a black hole eventually, Yes, exactly,

463
00:23:00,560 --> 00:23:03,840
Speaker 1: would be a Durian flavored black hole. Yeah, and that

464
00:23:03,880 --> 00:23:06,359
Speaker 1: one you don't want to lick. I feel like we're

465
00:23:06,359 --> 00:23:08,959
Speaker 1: going to get so much hate mail from Duryan lovers

466
00:23:09,040 --> 00:23:12,240
Speaker 1: out there. Don't write his hate mail until you've actually

467
00:23:12,280 --> 00:23:15,880
Speaker 1: tasted during an ice cream and can vouch for its deliciousness.

468
00:23:16,040 --> 00:23:18,680
Speaker 1: All right, So then that's the leading candidate, because any

469
00:23:18,720 --> 00:23:21,520
Speaker 1: other explanation requires a new theory or a new particle

470
00:23:21,640 --> 00:23:23,760
Speaker 1: or something super exotic. You know, as far as we know,

471
00:23:23,840 --> 00:23:27,120
Speaker 1: the universe dictates that something that big would fall into

472
00:23:27,160 --> 00:23:29,080
Speaker 1: a black hole. So that's kind of why we think

473
00:23:29,080 --> 00:23:30,959
Speaker 1: there is a black hole. It is, and it was

474
00:23:31,240 --> 00:23:34,919
Speaker 1: very widely accepted until recently. What happened, Well, there's this

475
00:23:35,000 --> 00:23:38,760
Speaker 1: really cool astronomical experiment. You know, astronomers don't get to

476
00:23:38,800 --> 00:23:42,080
Speaker 1: do what particle physicists do, which is like design collisions.

477
00:23:42,359 --> 00:23:43,919
Speaker 1: I get to like, say, I'm going to smash a

478
00:23:43,960 --> 00:23:47,160
Speaker 1: proton into an electron or let's try shooting muans at

479
00:23:47,160 --> 00:23:49,879
Speaker 1: this thing and see what happens. Astronomers don't get to

480
00:23:49,880 --> 00:23:52,240
Speaker 1: do that. They don't get to build colliders and smash

481
00:23:52,280 --> 00:23:54,560
Speaker 1: two black holes together. They just have to wait for

482
00:23:54,600 --> 00:23:56,800
Speaker 1: stuff to happen in the universe in a place that

483
00:23:56,840 --> 00:23:58,840
Speaker 1: they can observe it. So they have to get lucky.

484
00:23:59,080 --> 00:24:02,320
Speaker 1: And about ten years ago, people realized that there was

485
00:24:02,359 --> 00:24:06,520
Speaker 1: this huge cloud of gas called G two which was

486
00:24:06,600 --> 00:24:09,200
Speaker 1: headed for the black hole. It was going to make

487
00:24:09,200 --> 00:24:12,640
Speaker 1: a really close approach in our galaxy or in another galaxy.

488
00:24:12,760 --> 00:24:15,679
Speaker 1: In our galaxy. It was heading right for the center

489
00:24:15,760 --> 00:24:18,280
Speaker 1: of our galaxy. It was gonna make a near miss

490
00:24:18,359 --> 00:24:20,480
Speaker 1: of the black hole. And they thought this would be

491
00:24:20,520 --> 00:24:22,840
Speaker 1: really cool because it allows them to really study the

492
00:24:22,880 --> 00:24:25,840
Speaker 1: black hole in a new way. Let's throw something at

493
00:24:25,880 --> 00:24:28,520
Speaker 1: it and see what happens, right, and let them test

494
00:24:28,760 --> 00:24:32,040
Speaker 1: the details of this encounter between the gas cloud in

495
00:24:32,040 --> 00:24:34,280
Speaker 1: the black hole. So you could see this gas cloud

496
00:24:34,359 --> 00:24:37,000
Speaker 1: like you can see it through the PLoud of gas

497
00:24:37,040 --> 00:24:38,720
Speaker 1: in the center of the galase. You can see it

498
00:24:39,040 --> 00:24:41,200
Speaker 1: like that. There was one nearby. Yeah, you can see

499
00:24:41,480 --> 00:24:43,399
Speaker 1: X rays coming out of this thing. And so you

500
00:24:43,400 --> 00:24:46,000
Speaker 1: can watch this cloud of gas and everybody got really

501
00:24:46,040 --> 00:24:48,960
Speaker 1: excited because they were not sure what's going to happen.

502
00:24:49,000 --> 00:24:51,760
Speaker 1: It sort of reminds me of when everybody saw that

503
00:24:51,840 --> 00:24:54,080
Speaker 1: comment that was going to smash into Jupiter, Like we

504
00:24:54,119 --> 00:24:55,919
Speaker 1: saw a comment coming into the Solar system, and then

505
00:24:55,920 --> 00:24:58,440
Speaker 1: people calculate its trajectory and they're like, oh, yeah, it's

506
00:24:58,480 --> 00:25:02,119
Speaker 1: gonna hit Jupiter like citing. Yeah, it's exciting unless you

507
00:25:02,119 --> 00:25:05,159
Speaker 1: live in Jupiter. If you just bought real estate and Jupiter,

508
00:25:05,240 --> 00:25:07,800
Speaker 1: I'm sorry your investment is a waste. But you know,

509
00:25:08,000 --> 00:25:11,280
Speaker 1: astronomical collisions are a great way to learn about stuff.

510
00:25:11,600 --> 00:25:14,320
Speaker 1: So people get really excited. And just like seven years

511
00:25:14,320 --> 00:25:17,159
Speaker 1: ago or so, and they had all these calculations for

512
00:25:17,280 --> 00:25:20,480
Speaker 1: what they expected to happen when this gas cloud passed

513
00:25:20,640 --> 00:25:24,040
Speaker 1: near the black hole. Interesting like sprinkling dust into a

514
00:25:24,119 --> 00:25:27,160
Speaker 1: swirling toilet bowl, right, kind of like what's gonna happen

515
00:25:27,200 --> 00:25:30,119
Speaker 1: to it? Is it gonna stay together or is it

516
00:25:30,119 --> 00:25:33,360
Speaker 1: gonna gonna get shredded apart? Yeah, And the calculation suggested

517
00:25:33,400 --> 00:25:35,560
Speaker 1: that this thing should be totally shredded. I mean, a

518
00:25:35,640 --> 00:25:38,399
Speaker 1: gas cloud is not really held together very tightly. It's

519
00:25:38,440 --> 00:25:41,399
Speaker 1: just a big loose cloud of gas. And what happens

520
00:25:41,400 --> 00:25:43,240
Speaker 1: when you get near a black hole is that there

521
00:25:43,280 --> 00:25:47,360
Speaker 1: are huge tidal forces. Right. Remember, tidal forces are gravity

522
00:25:47,400 --> 00:25:49,879
Speaker 1: trying to pull you apart, because if part of you

523
00:25:49,920 --> 00:25:52,639
Speaker 1: it's closer to the black hole than another part, then

524
00:25:52,680 --> 00:25:55,080
Speaker 1: the part that's closer is getting pulled on harder than

525
00:25:55,119 --> 00:25:57,399
Speaker 1: the rest of you, And so the gravity essentially is

526
00:25:57,440 --> 00:25:59,680
Speaker 1: trying to pull you apart because it's pulling on bits

527
00:25:59,720 --> 00:26:02,600
Speaker 1: of you with different forces. So they expected that when

528
00:26:02,600 --> 00:26:05,359
Speaker 1: this gas cloud came close to the black hole, it

529
00:26:05,359 --> 00:26:08,920
Speaker 1: would be totally shredded by these title forces. But wait,

530
00:26:08,960 --> 00:26:11,320
Speaker 1: how close did it get? Like I thought, we could

531
00:26:11,359 --> 00:26:14,120
Speaker 1: only see up to like twelve AU. That's the closest

532
00:26:14,160 --> 00:26:16,800
Speaker 1: that anything has ever come to the black hole. This

533
00:26:16,880 --> 00:26:19,399
Speaker 1: gas cloud wasn't going to get that close. It was

534
00:26:19,440 --> 00:26:22,399
Speaker 1: going to approach like a couple hundred a U, but

535
00:26:22,480 --> 00:26:25,119
Speaker 1: close enough that you could get some information about the

536
00:26:25,160 --> 00:26:27,600
Speaker 1: black hole. You know, you can get some like distant

537
00:26:27,640 --> 00:26:30,480
Speaker 1: information about the black hole just by measuring the gravitational

538
00:26:30,480 --> 00:26:33,679
Speaker 1: effect on nearby stuff. You can measure, for example, like

539
00:26:33,760 --> 00:26:36,600
Speaker 1: the slope with a gravitational field. Right, but at that

540
00:26:36,920 --> 00:26:39,640
Speaker 1: far away, wouldn't a black hole act the same way

541
00:26:39,680 --> 00:26:42,360
Speaker 1: as a giant ball of ice cream. Yeah. Absolutely. If

542
00:26:42,359 --> 00:26:44,960
Speaker 1: you stay outside of the heavy object at the center

543
00:26:44,960 --> 00:26:48,280
Speaker 1: of the galaxy, then you can't tell the difference gravitationally

544
00:26:48,600 --> 00:26:51,080
Speaker 1: between a black hole or a ball of ice cream

545
00:26:51,320 --> 00:26:53,640
Speaker 1: or a giant space taco. As long as it has

546
00:26:53,680 --> 00:26:56,560
Speaker 1: four million solar masses, they would all have the same

547
00:26:56,640 --> 00:26:59,800
Speaker 1: gravity from the outside. You're absolutely right. So you can't

548
00:27:00,080 --> 00:27:02,720
Speaker 1: use a gas cloud at like hundreds of AU to

549
00:27:02,800 --> 00:27:06,760
Speaker 1: help understand what's going on inside the twelve AU radius

550
00:27:06,760 --> 00:27:09,719
Speaker 1: where we think there's a black hole. But what if

551
00:27:09,720 --> 00:27:12,360
Speaker 1: it's not actually a black hole, and what if it's

552
00:27:12,400 --> 00:27:16,120
Speaker 1: not actually contained within the twelve AU What if it's

553
00:27:16,119 --> 00:27:20,600
Speaker 1: something else much larger and fluffier, bigger than the twelve AU.

554
00:27:20,720 --> 00:27:23,399
Speaker 1: If it's a big, fluffy mass that's hundreds of a

555
00:27:23,600 --> 00:27:26,159
Speaker 1: U yde with a very very dense core, then it

556
00:27:26,200 --> 00:27:29,080
Speaker 1: could still look like a black hole to the stars

557
00:27:29,200 --> 00:27:31,480
Speaker 1: orbiting at twelve AU, but it would have a very

558
00:27:31,560 --> 00:27:34,439
Speaker 1: different effect on the gas cloud. So I talked to

559
00:27:34,480 --> 00:27:37,399
Speaker 1: Grant Weldon. He's an astrophysics grad student at u c

560
00:27:37,520 --> 00:27:39,960
Speaker 1: l A who actually works in Professor Guests group. She's

561
00:27:40,000 --> 00:27:43,200
Speaker 1: the recent Nobel lawyer who studies the center of the galaxy.

562
00:27:43,400 --> 00:27:46,160
Speaker 1: He said, think of it like a fog that all

563
00:27:46,200 --> 00:27:49,199
Speaker 1: the objects in the galactic center sit in. The idea

564
00:27:49,359 --> 00:27:52,680
Speaker 1: is that if it's not a black hole concentrated within

565
00:27:52,760 --> 00:27:56,600
Speaker 1: that twelve AU, but instead some bigger, more extended mass

566
00:27:56,760 --> 00:27:59,520
Speaker 1: larger than the twelve AU, then it wouldn't have the

567
00:27:59,560 --> 00:28:02,040
Speaker 1: same time tidal force effect on the cloud because the

568
00:28:02,080 --> 00:28:06,080
Speaker 1: gas cloud G two would be passing partially inside this

569
00:28:06,240 --> 00:28:09,920
Speaker 1: new fluffy blob. So the title force calculations that assume

570
00:28:10,040 --> 00:28:12,560
Speaker 1: a big mass within the twelve au would be wrong.

571
00:28:12,840 --> 00:28:14,760
Speaker 1: But I guess the point is that this gas cloud

572
00:28:14,800 --> 00:28:17,120
Speaker 1: survived like it didn't get shredded as if it would

573
00:28:17,240 --> 00:28:19,000
Speaker 1: if there was a black hole in the middle of

574
00:28:19,040 --> 00:28:21,760
Speaker 1: the galaxy. Yeah, everybody was expecting this thing to get

575
00:28:21,800 --> 00:28:24,879
Speaker 1: totally torn apart by this black hole or whatever is there.

576
00:28:25,040 --> 00:28:27,880
Speaker 1: But instead it derived. It passed right by, and it

577
00:28:27,960 --> 00:28:30,240
Speaker 1: mostly held its shape. You know, it got a little

578
00:28:30,280 --> 00:28:33,199
Speaker 1: bit twisted up, but it was not totally pulled apart

579
00:28:33,280 --> 00:28:35,679
Speaker 1: the way that you would expect for a gas cloud

580
00:28:35,920 --> 00:28:39,560
Speaker 1: passing by this massive gravitational object. So that was a

581
00:28:39,600 --> 00:28:42,480
Speaker 1: real mystery. People were like, hold on a second, what's

582
00:28:42,480 --> 00:28:47,040
Speaker 1: going on. This isn't described at all by our calculations. Wow,

583
00:28:47,160 --> 00:28:49,640
Speaker 1: maybe the gas cloud was made out of drain and

584
00:28:49,680 --> 00:28:51,240
Speaker 1: the black hole was like, I don't want any I

585
00:28:51,280 --> 00:28:55,240
Speaker 1: don't want to lick. This thing totally explains it. Break

586
00:28:55,840 --> 00:28:58,240
Speaker 1: when you're getting rejected by clouds of gas, Wow, you

587
00:28:58,320 --> 00:29:02,280
Speaker 1: must really be stinky. So then that threw some shade

588
00:29:02,400 --> 00:29:04,520
Speaker 1: on the theory that maybe there's a black hole at

589
00:29:04,520 --> 00:29:06,160
Speaker 1: the center of the galaxy, like, maybe it's not a

590
00:29:06,160 --> 00:29:08,600
Speaker 1: black hole exactly. People start to think, maybe we should

591
00:29:08,600 --> 00:29:12,080
Speaker 1: consider some alternatives. Are there other ways we can explain

592
00:29:12,160 --> 00:29:15,200
Speaker 1: what happened to this gas cloud other than a black hole,

593
00:29:15,360 --> 00:29:18,680
Speaker 1: because that would be then consistent with all of our observations.

594
00:29:19,120 --> 00:29:21,400
Speaker 1: And that's when people started drilling into this question of

595
00:29:21,640 --> 00:29:24,800
Speaker 1: how well do we know the density of this object?

596
00:29:24,880 --> 00:29:28,160
Speaker 1: Is it possible that there's something actually much larger they're

597
00:29:28,240 --> 00:29:31,640
Speaker 1: not actually a black hole, but something really much more extended,

598
00:29:31,960 --> 00:29:36,680
Speaker 1: fluffier and broader and not actually a black hole. Interesting? Right, Yeah,

599
00:29:36,680 --> 00:29:38,760
Speaker 1: I guess everyone just assumed this was a black hole,

600
00:29:38,800 --> 00:29:41,080
Speaker 1: but now you have this evidence that maybe may people go,

601
00:29:41,120 --> 00:29:43,200
Speaker 1: await a minute, how do we actually know that? Yeah?

602
00:29:43,200 --> 00:29:45,600
Speaker 1: And so people have been creative and there's this really

603
00:29:45,680 --> 00:29:48,800
Speaker 1: fun theory of a new kind of dark matter. It's

604
00:29:48,840 --> 00:29:52,080
Speaker 1: called the dark nose. So this would be little particles

605
00:29:52,440 --> 00:29:54,960
Speaker 1: that make up dark matter. They call them darky nose,

606
00:29:55,360 --> 00:29:59,000
Speaker 1: and these are fermions, and fermions are a kind of

607
00:29:59,040 --> 00:30:02,680
Speaker 1: fundamental particle. They're sort of like electrons and quarks. They

608
00:30:02,720 --> 00:30:05,200
Speaker 1: have this really important property that they don't like to

609
00:30:05,240 --> 00:30:07,280
Speaker 1: be on top of each other. They don't like to

610
00:30:07,360 --> 00:30:10,160
Speaker 1: share the same state, you know how Electrons, for example,

611
00:30:10,160 --> 00:30:12,640
Speaker 1: if you put one around an atom, it fills up

612
00:30:12,640 --> 00:30:14,600
Speaker 1: a state, and you put another one there, it can't

613
00:30:14,640 --> 00:30:16,520
Speaker 1: go into the same energy level, has to go into

614
00:30:16,600 --> 00:30:19,160
Speaker 1: the next one. That's because their fermions, they don't like

615
00:30:19,240 --> 00:30:22,120
Speaker 1: to ever occupy the same quantum states. The idea is

616
00:30:22,160 --> 00:30:26,480
Speaker 1: that these dark matter particles, these dark enos, are fermions,

617
00:30:26,640 --> 00:30:30,840
Speaker 1: so they can coalesce gravitationally, but they resist collapsing into

618
00:30:30,840 --> 00:30:34,480
Speaker 1: a black hole because of this quantum degeneracy pressure, this

619
00:30:34,640 --> 00:30:37,760
Speaker 1: polity exclusion principle that keeps them from getting too dense.

620
00:30:37,960 --> 00:30:40,400
Speaker 1: WHOA wait a minute, you're saying, maybe it's not a

621
00:30:40,440 --> 00:30:43,640
Speaker 1: black hole, and so therefore your go to explanation is

622
00:30:43,680 --> 00:30:47,080
Speaker 1: to invent a totally new kind of matter. Another new

623
00:30:47,160 --> 00:30:49,760
Speaker 1: kind of matter, Like, are there other explanations using regular

624
00:30:49,760 --> 00:30:52,680
Speaker 1: matter that could explain this giant ball of stuff in

625
00:30:52,720 --> 00:30:54,640
Speaker 1: the middle of our galaxy. Well, we talked about a

626
00:30:54,640 --> 00:30:57,160
Speaker 1: few minutes ago. Any kind of normal matter is going

627
00:30:57,200 --> 00:31:00,520
Speaker 1: to eventually coalesced into a black hole, and whatever is

628
00:31:00,560 --> 00:31:02,480
Speaker 1: there has been there for a long long time, and

629
00:31:02,520 --> 00:31:05,200
Speaker 1: so it would have time to collapse into a black hole.

630
00:31:05,600 --> 00:31:08,360
Speaker 1: So you need something which has a new property of

631
00:31:08,440 --> 00:31:11,160
Speaker 1: not collapsing into a black hole. So you have to

632
00:31:11,200 --> 00:31:13,560
Speaker 1: give it this like you know, quantum de generously pressure

633
00:31:13,640 --> 00:31:17,760
Speaker 1: or something in order for it to survive this crushing gravity.

634
00:31:17,800 --> 00:31:20,280
Speaker 1: Didn't you mentioned like a neutron star maybe, or some

635
00:31:20,320 --> 00:31:23,120
Speaker 1: other kind of dense object. Neutron stars can only be

636
00:31:23,280 --> 00:31:25,880
Speaker 1: up to like two times the mass of the Sun.

637
00:31:26,280 --> 00:31:29,600
Speaker 1: If it gets any bigger than they collapse gravitationally. So

638
00:31:29,680 --> 00:31:32,520
Speaker 1: this thing is four million times the mass of the Sun.

639
00:31:32,720 --> 00:31:36,120
Speaker 1: Neutron stars are a really very special case of avoiding

640
00:31:36,160 --> 00:31:38,880
Speaker 1: a black hole. But if it's two million neutron stars

641
00:31:39,360 --> 00:31:43,120
Speaker 1: kind of orbiting around each other like a beehive, you know,

642
00:31:43,160 --> 00:31:46,200
Speaker 1: like I guess that would also eventually collapse to it

643
00:31:46,200 --> 00:31:49,280
Speaker 1: would also eventual collapse and neutron stars are not black, right,

644
00:31:49,520 --> 00:31:52,239
Speaker 1: they do emit. They're super hot and they glow. They

645
00:31:52,240 --> 00:31:55,239
Speaker 1: emit X rays and they spin also, and we can

646
00:31:55,280 --> 00:31:58,120
Speaker 1: actually see hot spots on the surface of neutron stars

647
00:31:58,160 --> 00:32:00,920
Speaker 1: because they emit X rays. Is a telescope on the

648
00:32:00,960 --> 00:32:04,440
Speaker 1: International Space Station called the Nicer Telescope, which looks just

649
00:32:04,560 --> 00:32:07,600
Speaker 1: at those kind of objects. So in order to explain

650
00:32:07,680 --> 00:32:11,600
Speaker 1: this like maybe new fuzzy fluffy stuff at the center

651
00:32:11,600 --> 00:32:14,160
Speaker 1: of the galaxy, they had to use these new particles

652
00:32:14,160 --> 00:32:17,120
Speaker 1: with this special property. Okay, So so then you're saying,

653
00:32:17,160 --> 00:32:20,680
Speaker 1: this possible explanation for this heavy mass that's maybe not

654
00:32:20,760 --> 00:32:22,640
Speaker 1: a black hole at the center of the galaxy. So

655
00:32:22,680 --> 00:32:24,720
Speaker 1: it's a dark matter. But now you're sort of positing

656
00:32:25,080 --> 00:32:27,360
Speaker 1: what dark matter is, and you're saying dark matter is

657
00:32:27,400 --> 00:32:30,600
Speaker 1: maybe made out of a certain particle called the dark keynote. Yeah,

658
00:32:30,680 --> 00:32:32,680
Speaker 1: and this would give dark matter the property that it

659
00:32:32,760 --> 00:32:36,040
Speaker 1: needs to avoid collapsing into a black hole once it's

660
00:32:36,080 --> 00:32:39,440
Speaker 1: already gotten into this little area of twelve a U

661
00:32:39,920 --> 00:32:42,960
Speaker 1: and having four million times in the mass of the Sun. Right,

662
00:32:43,040 --> 00:32:45,280
Speaker 1: because I think we talked about this in another episode,

663
00:32:45,280 --> 00:32:48,160
Speaker 1: that dark matter can itself turn into a black hole, Like,

664
00:32:48,200 --> 00:32:50,520
Speaker 1: if you get enough dark matter in a small enough space,

665
00:32:50,600 --> 00:32:53,440
Speaker 1: it will create a dark matter black hole exactly, because

666
00:32:53,480 --> 00:32:55,960
Speaker 1: anything can create a black hole that has mass. The

667
00:32:56,040 --> 00:32:58,280
Speaker 1: cool thing about black holes and the cool thing about

668
00:32:58,280 --> 00:33:01,280
Speaker 1: gravity is that they talked to anything that has mass,

669
00:33:01,320 --> 00:33:03,680
Speaker 1: anything that has energy. So there are a really cool

670
00:33:03,760 --> 00:33:06,520
Speaker 1: way to probe things in the universe that are otherwise

671
00:33:06,680 --> 00:33:10,080
Speaker 1: totally invisible to us, that we might otherwise have no

672
00:33:10,200 --> 00:33:12,840
Speaker 1: way to interact with. So if dark matter falls new

673
00:33:12,920 --> 00:33:14,800
Speaker 1: black hole, it just adds to the mass of the

674
00:33:14,800 --> 00:33:17,200
Speaker 1: black hole. It is challenging, however, to create a dark

675
00:33:17,200 --> 00:33:19,520
Speaker 1: matter black hole, because it's hard to get dark matter

676
00:33:19,840 --> 00:33:22,640
Speaker 1: that dense. Dark matter tends to be diffused, and it

677
00:33:22,680 --> 00:33:24,640
Speaker 1: tends to be sort of fluffy, and it's hard to

678
00:33:24,720 --> 00:33:27,680
Speaker 1: squeeze it down because there are no other interactions. It's

679
00:33:27,680 --> 00:33:31,080
Speaker 1: not sticky like other kinds of matter. I see. So

680
00:33:31,200 --> 00:33:33,760
Speaker 1: then you're saying the possible explanation is not really a

681
00:33:33,760 --> 00:33:35,960
Speaker 1: new kind of matter. It's just like, maybe it's helping

682
00:33:36,040 --> 00:33:39,040
Speaker 1: us pinpoint a specific property of dark matter that would

683
00:33:39,040 --> 00:33:42,240
Speaker 1: allow it to become a dense black hole object without

684
00:33:42,440 --> 00:33:45,280
Speaker 1: turning into a black hole. Sure, yeah, I think people

685
00:33:45,280 --> 00:33:47,080
Speaker 1: in the dark matter community would say that this is

686
00:33:47,120 --> 00:33:49,280
Speaker 1: a new kind of matter, and it's definitely not like

687
00:33:49,360 --> 00:33:53,360
Speaker 1: the number one candidate for dark matter otherwise. And these

688
00:33:53,560 --> 00:33:57,680
Speaker 1: particles are not like everybody's favorite dark matter theory, but

689
00:33:58,000 --> 00:34:00,080
Speaker 1: they do have the properties you need that if you

690
00:34:00,120 --> 00:34:02,840
Speaker 1: put them together and create this object of dark nose

691
00:34:02,920 --> 00:34:05,280
Speaker 1: at the center of the galaxy, it's fluffy enough that

692
00:34:05,320 --> 00:34:08,879
Speaker 1: it can explain why this gas cloud survived. I see,

693
00:34:08,880 --> 00:34:10,919
Speaker 1: And it doesn't collapse into a black hole. You're saying

694
00:34:10,960 --> 00:34:14,160
Speaker 1: because of its quantum properties, like it has this exclusion

695
00:34:14,280 --> 00:34:18,040
Speaker 1: principle that lets it not collapse. Yeah, precisely. And you

696
00:34:18,040 --> 00:34:20,800
Speaker 1: know it's a little bit cooked up, right. They created

697
00:34:20,880 --> 00:34:23,680
Speaker 1: this idea. They've cooked up these dark he nose just

698
00:34:23,880 --> 00:34:26,799
Speaker 1: to solve this problem. So it's not like something we

699
00:34:26,920 --> 00:34:30,479
Speaker 1: otherwise already thought existed. We have good evidence for. Oh look,

700
00:34:30,480 --> 00:34:33,759
Speaker 1: it also explains this, right, it's a little bit more descriptive.

701
00:34:33,960 --> 00:34:35,359
Speaker 1: So you've always got to be a little bit more

702
00:34:35,400 --> 00:34:37,920
Speaker 1: skeptical when somebody has cooked up a new idea just

703
00:34:38,000 --> 00:34:42,000
Speaker 1: to explain one particular observation. Really, you've got to test

704
00:34:42,000 --> 00:34:43,719
Speaker 1: it in other places. You've got to see like a

705
00:34:43,840 --> 00:34:47,480
Speaker 1: symphony of results that are all telling you the same story. Yeah,

706
00:34:47,520 --> 00:34:50,000
Speaker 1: I'm always skeptical when there's a physicist doing the cooking.

707
00:34:51,520 --> 00:34:54,080
Speaker 1: So that's a possible explanation for what could be inside

708
00:34:54,080 --> 00:34:56,560
Speaker 1: of the center of our galaxy. And let's get into

709
00:34:56,800 --> 00:34:58,840
Speaker 1: what the answer is. What does the evidence say, is

710
00:34:58,840 --> 00:35:00,600
Speaker 1: there a black hole at the center of our galaxy?

711
00:35:00,840 --> 00:35:03,600
Speaker 1: Or could it be a big ball of this dark

712
00:35:03,680 --> 00:35:06,880
Speaker 1: keno dark matter? But first, let's take another quick break.

713
00:35:18,719 --> 00:35:21,520
Speaker 1: All right, what's at the candy center of our galaxy?

714
00:35:21,880 --> 00:35:26,080
Speaker 1: Is it marshmallows? Is it? Is it guacamole? Or is

715
00:35:26,120 --> 00:35:28,359
Speaker 1: it a new kind of dark matter called a dark

716
00:35:28,400 --> 00:35:34,360
Speaker 1: keno which um ironically taste kind of like, how do

717
00:35:34,440 --> 00:35:38,920
Speaker 1: you know what darkness tas like? I've been there, you know,

718
00:35:39,960 --> 00:35:44,919
Speaker 1: they offer free samples. Alright, I'm packing my bags, let's go. So, yeah,

719
00:35:45,040 --> 00:35:46,359
Speaker 1: we thought for a long time it was a black

720
00:35:46,400 --> 00:35:49,120
Speaker 1: hole at the center of our galaxy, but maybe it's not.

721
00:35:49,520 --> 00:35:51,640
Speaker 1: And so the only other thing that could explain it

722
00:35:51,719 --> 00:35:53,920
Speaker 1: is something called dark keno, which is a kind of

723
00:35:54,000 --> 00:35:56,920
Speaker 1: dark matter that doesn't collapse when it gets that compacted

724
00:35:57,000 --> 00:35:59,319
Speaker 1: to What does the evidence say, Daniel, where's it thinking

725
00:35:59,360 --> 00:36:02,600
Speaker 1: in the physics community. I think the physics community reacts

726
00:36:02,600 --> 00:36:05,840
Speaker 1: to this idea like that's cute, but probably not. It

727
00:36:05,880 --> 00:36:09,040
Speaker 1: hasn't really persuaded a lot of astronomers, And one reason

728
00:36:09,239 --> 00:36:11,600
Speaker 1: is that it's not so easy to understand how you

729
00:36:11,640 --> 00:36:14,799
Speaker 1: would make such a big ball of dark matter. As

730
00:36:14,880 --> 00:36:17,200
Speaker 1: you've talked about a few times, dark matter is big,

731
00:36:17,239 --> 00:36:20,640
Speaker 1: it's fluffy, it's diffused, it's swirling around the center of

732
00:36:20,680 --> 00:36:23,440
Speaker 1: the galaxy, and so we don't know like how you

733
00:36:23,440 --> 00:36:25,480
Speaker 1: would get it to collapse. Like if I gave you

734
00:36:25,520 --> 00:36:27,360
Speaker 1: a serving of dark matter that had in the mass

735
00:36:27,360 --> 00:36:30,120
Speaker 1: of four million sons, it wouldn't be easy for you

736
00:36:30,560 --> 00:36:33,400
Speaker 1: to force it into that dense in area. So we

737
00:36:33,440 --> 00:36:36,759
Speaker 1: have no story for how this thing could have formed, right,

738
00:36:36,760 --> 00:36:39,080
Speaker 1: because as far as we know, dark matter is not

739
00:36:39,719 --> 00:36:41,839
Speaker 1: very sticky or not sticky at all. Right, Like, if

740
00:36:41,840 --> 00:36:43,719
Speaker 1: we have a bunch of dark matter in space, it's

741
00:36:43,760 --> 00:36:47,719
Speaker 1: not gonna come together in clumb naturally. It's gonna get

742
00:36:47,760 --> 00:36:50,440
Speaker 1: attracted to itself, but it's gonna keep flying past itself

743
00:36:50,480 --> 00:36:52,840
Speaker 1: and keep flying past itself to the point where it

744
00:36:52,880 --> 00:36:55,360
Speaker 1: would just be a fluffy cloud maybe forever. Yeah, And

745
00:36:55,400 --> 00:36:58,160
Speaker 1: people have done simulations to test this and say, well,

746
00:36:58,160 --> 00:37:01,319
Speaker 1: what if dark matter are these kind of dark eno fermions,

747
00:37:01,600 --> 00:37:03,560
Speaker 1: and you have a big galaxy sized blob of them.

748
00:37:03,600 --> 00:37:06,800
Speaker 1: What happens and you just don't get this kind of core.

749
00:37:06,880 --> 00:37:10,080
Speaker 1: You don't get this like really dense ball in the center.

750
00:37:10,160 --> 00:37:12,719
Speaker 1: That would explain the data. Now, if you happen to

751
00:37:12,880 --> 00:37:15,240
Speaker 1: have that dense ball in the center of the galaxy,

752
00:37:15,280 --> 00:37:18,319
Speaker 1: it can explain what happened to this gas cloud. But

753
00:37:18,400 --> 00:37:21,320
Speaker 1: nobody understands how you would make such a dense blob

754
00:37:21,400 --> 00:37:24,319
Speaker 1: of dark matter. It doesn't arise naturally in our simulations,

755
00:37:25,040 --> 00:37:27,239
Speaker 1: I see. But these simulations are based on what we

756
00:37:27,280 --> 00:37:29,880
Speaker 1: know about dark matter. But we don't really understand dark matter.

757
00:37:30,040 --> 00:37:32,200
Speaker 1: So could dark matter have some sort of property we

758
00:37:32,239 --> 00:37:34,239
Speaker 1: don't know about that would make it clump like that?

759
00:37:34,320 --> 00:37:36,600
Speaker 1: It would need to have some sort of other self

760
00:37:36,640 --> 00:37:39,480
Speaker 1: interaction right some way to get sticky, so that it

761
00:37:39,520 --> 00:37:42,440
Speaker 1: tends to clump someone to like bump into itself and

762
00:37:42,520 --> 00:37:45,520
Speaker 1: lose its angular momentum so it doesn't just orbit forever

763
00:37:45,920 --> 00:37:48,440
Speaker 1: and it falls into itself somehow. But nobody has a

764
00:37:48,520 --> 00:37:51,319
Speaker 1: theory of dark matter like that that's also consistent with

765
00:37:51,400 --> 00:37:54,160
Speaker 1: everything else. You know, we're pretty sure that dark matter

766
00:37:54,360 --> 00:37:57,680
Speaker 1: doesn't have a very strong interaction with itself. We've seen

767
00:37:57,840 --> 00:38:01,279
Speaker 1: huge clouds of dark matter pass through each other, you know.

768
00:38:01,320 --> 00:38:04,320
Speaker 1: The Bullet cluster, for example, was a collision of two

769
00:38:04,400 --> 00:38:07,400
Speaker 1: huge galaxy clusters, each of which had a lot of

770
00:38:07,480 --> 00:38:10,200
Speaker 1: dark matter, but the dark matter just passed right through

771
00:38:10,320 --> 00:38:12,799
Speaker 1: itself to the other side. Even though there is some

772
00:38:12,880 --> 00:38:15,960
Speaker 1: gravitational attraction between the two clouds of dark matter, that's

773
00:38:16,040 --> 00:38:18,479
Speaker 1: really pretty weak. So we're pretty sure that dark matter

774
00:38:18,560 --> 00:38:22,239
Speaker 1: does not have any very strong interactions with itself, and

775
00:38:22,280 --> 00:38:24,680
Speaker 1: so it's really hard to explain how you would get

776
00:38:24,680 --> 00:38:27,000
Speaker 1: a dense clump of dark matter at the center of

777
00:38:27,000 --> 00:38:29,759
Speaker 1: the galaxy. Just like, no way to get it there, right,

778
00:38:29,800 --> 00:38:32,560
Speaker 1: even if you give it these interesting quantum properties that

779
00:38:32,640 --> 00:38:35,000
Speaker 1: it doesn't work out like you said, simulated, it still

780
00:38:35,040 --> 00:38:38,600
Speaker 1: doesn't clump. But remember that also we have questions about

781
00:38:38,600 --> 00:38:41,160
Speaker 1: how black holes form, right. We have a pretty good

782
00:38:41,200 --> 00:38:44,320
Speaker 1: theory for why black holes conform at the center of galaxies,

783
00:38:44,360 --> 00:38:47,440
Speaker 1: but we don't really understand how they got so big.

784
00:38:47,600 --> 00:38:49,680
Speaker 1: So it's sort of a similar question. You know, if

785
00:38:49,719 --> 00:38:53,319
Speaker 1: you simulate black hole formation in galaxies, they get big,

786
00:38:53,320 --> 00:38:56,160
Speaker 1: but they don't get as big as the supermassive black

787
00:38:56,160 --> 00:38:59,080
Speaker 1: holes that we see, So that's also an open questions.

788
00:38:59,120 --> 00:39:01,440
Speaker 1: Just's just a lot we don't understand about how the

789
00:39:01,520 --> 00:39:05,240
Speaker 1: centers of galaxies form, So you can criticize this theory

790
00:39:05,280 --> 00:39:07,799
Speaker 1: for like, well, yeah, maybe that's what it's there, but

791
00:39:07,840 --> 00:39:10,080
Speaker 1: how can you explain how it got there. We can't

792
00:39:10,080 --> 00:39:12,319
Speaker 1: explain how black holes form at the center of these

793
00:39:12,360 --> 00:39:16,560
Speaker 1: galaxies either, WHOA I see. So just because you can't

794
00:39:16,560 --> 00:39:18,919
Speaker 1: explain how it got there doesn't mean it's not there.

795
00:39:19,320 --> 00:39:21,279
Speaker 1: Because we don't know how the black hole. Even if

796
00:39:21,320 --> 00:39:22,440
Speaker 1: it is a black hole, we don't know how the

797
00:39:22,440 --> 00:39:25,080
Speaker 1: black hole got there. That means it could still be

798
00:39:25,239 --> 00:39:27,279
Speaker 1: dark matter. It could still be dark matter. I think

799
00:39:27,280 --> 00:39:30,239
Speaker 1: prevailing wisdom is still that is probably a black hole.

800
00:39:30,320 --> 00:39:32,319
Speaker 1: And people have been creative and trying to find other

801
00:39:32,400 --> 00:39:35,440
Speaker 1: ways to explain why the gas cloud wasn't torn up

802
00:39:35,560 --> 00:39:37,960
Speaker 1: even if it is a black hole. Like Andrea Guez,

803
00:39:38,040 --> 00:39:39,640
Speaker 1: the u c l A professor who won the know

804
00:39:39,680 --> 00:39:42,680
Speaker 1: About prize, she suggested that maybe it's not actually just

805
00:39:42,760 --> 00:39:45,680
Speaker 1: a gas cloud. Maybe inside this gas cloud there's like

806
00:39:45,719 --> 00:39:49,320
Speaker 1: a string of stars that have the gravitational like strength

807
00:39:49,520 --> 00:39:52,399
Speaker 1: to hold the gas cloud together, and that's why when

808
00:39:52,400 --> 00:39:55,880
Speaker 1: it passed near this object. It wasn't actually torn to shreds.

809
00:39:55,880 --> 00:39:59,960
Speaker 1: It has like more gravitational self consistency than people imagine.

810
00:40:00,480 --> 00:40:02,840
Speaker 1: I see. Maybe that's why it didn't get treaded, Like

811
00:40:03,000 --> 00:40:05,640
Speaker 1: it wasn't just my gas in that cloud. Yeah, and

812
00:40:05,680 --> 00:40:08,160
Speaker 1: she has a very specific prediction for like a binary

813
00:40:08,239 --> 00:40:11,439
Speaker 1: star system inside this gas cloud that could really hold

814
00:40:11,440 --> 00:40:14,920
Speaker 1: it together so when it passes by, like keeps its consistency,

815
00:40:14,920 --> 00:40:18,439
Speaker 1: it doesn't get pulled apart by the black hole. I see. Now,

816
00:40:18,440 --> 00:40:20,880
Speaker 1: what about some of our listeners said that what if

817
00:40:20,920 --> 00:40:23,600
Speaker 1: it's both, Like what if there's dark batter and the

818
00:40:23,680 --> 00:40:25,960
Speaker 1: black hole in the center of our galaxy? Like, could

819
00:40:26,000 --> 00:40:28,200
Speaker 1: it be a mixture of the two things, like some

820
00:40:28,280 --> 00:40:30,960
Speaker 1: sort of super compact dark matter thing and maybe a

821
00:40:31,000 --> 00:40:33,000
Speaker 1: black hole or not a black hole, or a bunch

822
00:40:33,000 --> 00:40:35,160
Speaker 1: of intron stars or something like that. Yeah, it could

823
00:40:35,160 --> 00:40:37,960
Speaker 1: basically be you know, all of the above, right, And

824
00:40:37,960 --> 00:40:40,359
Speaker 1: remember the current theory, the prevailing wisdom is not just

825
00:40:40,440 --> 00:40:42,799
Speaker 1: that it's only a black hole. We do think that

826
00:40:42,840 --> 00:40:44,880
Speaker 1: there's a lot of dark matter at the center of

827
00:40:44,880 --> 00:40:47,960
Speaker 1: the galaxy. We think that's the densest place to find

828
00:40:48,080 --> 00:40:51,000
Speaker 1: dark matter in our galaxy is at the center. But

829
00:40:51,120 --> 00:40:53,600
Speaker 1: the current thinking about the density of dark matter is

830
00:40:53,640 --> 00:40:56,239
Speaker 1: that it's not that great, right, dark matter, there's a

831
00:40:56,239 --> 00:40:58,640
Speaker 1: lot of it in the galaxy, but it's also spread

832
00:40:58,719 --> 00:41:01,879
Speaker 1: out through space a lot more evenly than normal matter,

833
00:41:01,920 --> 00:41:04,880
Speaker 1: because again, it doesn't clump. And so for example, in

834
00:41:04,920 --> 00:41:07,239
Speaker 1: the volume of the Earth, we think there's like less

835
00:41:07,239 --> 00:41:09,920
Speaker 1: than a kilogram of dark matter, like with less than

836
00:41:10,000 --> 00:41:13,000
Speaker 1: one squirrels worth of dark matter. So there is almost

837
00:41:13,000 --> 00:41:15,880
Speaker 1: certainly some dark matter at the center of the galaxy,

838
00:41:15,920 --> 00:41:18,759
Speaker 1: and almost certainly some dark matter in that black hole

839
00:41:18,880 --> 00:41:21,920
Speaker 1: if it exists, but it's not contributing significantly because it's

840
00:41:21,960 --> 00:41:24,920
Speaker 1: not that dense. It's sort of spread out everywhere through

841
00:41:24,960 --> 00:41:27,600
Speaker 1: the center of the galaxy. M m. Yeah, dark matter

842
00:41:27,719 --> 00:41:30,600
Speaker 1: is pretty squirrely like that hard to catch. But we

843
00:41:30,640 --> 00:41:33,160
Speaker 1: also see dark matter sort of clumping in our galaxy, right,

844
00:41:33,200 --> 00:41:35,520
Speaker 1: Like dark matter is not a totally diffused cloud. It

845
00:41:35,560 --> 00:41:37,560
Speaker 1: does sort of clump in the middle, but you're saying

846
00:41:37,680 --> 00:41:40,480
Speaker 1: it doesn't clump enough to maybe explain what's going on. Yeah,

847
00:41:40,520 --> 00:41:43,200
Speaker 1: what we're talking about here is like an enormous spike

848
00:41:43,440 --> 00:41:46,640
Speaker 1: con density. Yes, dark matter is denser at the center

849
00:41:46,680 --> 00:41:49,200
Speaker 1: of our galaxy, but this object, whatever it is, with

850
00:41:49,320 --> 00:41:51,279
Speaker 1: four million times the mass of the Sun in a

851
00:41:51,440 --> 00:41:54,719
Speaker 1: very small area is much denser than the typical dark

852
00:41:54,760 --> 00:41:58,000
Speaker 1: matter density at the center. Yeah, it's four million sons

853
00:41:58,120 --> 00:42:00,600
Speaker 1: basically in the space of our sources them. Yeah, that's

854
00:42:00,600 --> 00:42:03,319
Speaker 1: a lot of ice cream. It's a big scoop. It's

855
00:42:03,320 --> 00:42:06,160
Speaker 1: a big scoop of stuff. All right. Well, it sounds

856
00:42:06,280 --> 00:42:08,600
Speaker 1: like a black hole is what most people think is

857
00:42:08,640 --> 00:42:10,560
Speaker 1: at the center of our galaxy, But there are still

858
00:42:10,640 --> 00:42:13,279
Speaker 1: a lot of questions about that, and there's even maybe

859
00:42:13,280 --> 00:42:15,439
Speaker 1: a little bit of uncertainty whether it is a black hole.

860
00:42:15,560 --> 00:42:17,360
Speaker 1: So what are we doing about it? How? How are

861
00:42:17,400 --> 00:42:19,000
Speaker 1: we going to answer this question? Well, we have an

862
00:42:19,040 --> 00:42:23,120
Speaker 1: awesome new telescope, this event horizon telescope, which is actually

863
00:42:23,160 --> 00:42:25,359
Speaker 1: you know, like a collection of telescopes that all work

864
00:42:25,440 --> 00:42:28,040
Speaker 1: together to make an effective telescope like the size of

865
00:42:28,080 --> 00:42:30,080
Speaker 1: the Earth. And it recently took a picture of a

866
00:42:30,120 --> 00:42:32,680
Speaker 1: black hole, right M A D seven, this black hole

867
00:42:32,760 --> 00:42:35,160
Speaker 1: the center of a distant galaxy. And that was really

868
00:42:35,200 --> 00:42:37,600
Speaker 1: cool because you could see essentially the size of the

869
00:42:37,719 --> 00:42:40,040
Speaker 1: event horizon. You could see a black circle at the

870
00:42:40,120 --> 00:42:43,640
Speaker 1: center surrounded by gas and dust that was emitting a

871
00:42:43,680 --> 00:42:46,360
Speaker 1: lot of light, and that told you essentially the radius

872
00:42:46,480 --> 00:42:48,560
Speaker 1: of the event horizon because you can see where the

873
00:42:48,680 --> 00:42:51,520
Speaker 1: lights stopped. That's what's really awesome about that picture. So

874
00:42:51,719 --> 00:42:54,120
Speaker 1: if you could train the same telescope at the center

875
00:42:54,160 --> 00:42:57,160
Speaker 1: of our galaxy, you get a much better measurement of

876
00:42:57,280 --> 00:43:00,040
Speaker 1: the radius of the event horizon if there isn't a

877
00:43:00,320 --> 00:43:02,359
Speaker 1: black hole there, and then we could get a clear

878
00:43:02,520 --> 00:43:05,239
Speaker 1: idea for what's really going on, because that's the thing

879
00:43:05,320 --> 00:43:07,400
Speaker 1: we don't understand very well. It's like, what is the

880
00:43:07,560 --> 00:43:09,960
Speaker 1: radius of this thing, whatever it is. Is it big

881
00:43:10,000 --> 00:43:12,400
Speaker 1: and fluffy like a blob of dark matter or ice cream,

882
00:43:12,560 --> 00:43:15,080
Speaker 1: or is it really compact less than a tenth of

883
00:43:15,120 --> 00:43:18,680
Speaker 1: an au like a black hole would be. I see, yeah,

884
00:43:18,800 --> 00:43:21,120
Speaker 1: I guess having a picture of another black hole at

885
00:43:21,120 --> 00:43:23,920
Speaker 1: the center of another galaxy basically says like, hey, this

886
00:43:24,080 --> 00:43:26,200
Speaker 1: is normal, Like, look, there are black holes at the

887
00:43:26,239 --> 00:43:29,640
Speaker 1: center of galaxy, so probably ours has one to probably

888
00:43:29,880 --> 00:43:33,000
Speaker 1: And this is challenging though, because it's very difficult to

889
00:43:33,080 --> 00:43:35,120
Speaker 1: take these pictures, and it's harder in fact, to get

890
00:43:35,160 --> 00:43:37,160
Speaker 1: the picture of the center of our galaxy than this

891
00:43:37,320 --> 00:43:40,040
Speaker 1: other distant galaxy m A D seven. We could just

892
00:43:40,040 --> 00:43:42,160
Speaker 1: sort of look at the center of it we're not

893
00:43:42,560 --> 00:43:45,680
Speaker 1: buried in the galaxy having to look through most of it.

894
00:43:45,960 --> 00:43:47,800
Speaker 1: We could look at it sort of from the side,

895
00:43:48,320 --> 00:43:51,040
Speaker 1: from the top, you know, whereas our galaxy like we're

896
00:43:51,160 --> 00:43:52,520
Speaker 1: right in the middle of it, so we have to

897
00:43:52,640 --> 00:43:55,640
Speaker 1: look through all of this gas and dust to see

898
00:43:55,719 --> 00:43:58,320
Speaker 1: the center of the galaxy. Right, And m AT seven

899
00:43:58,480 --> 00:44:02,000
Speaker 1: also is targeted because it's like huge monster black holes,

900
00:44:02,080 --> 00:44:04,520
Speaker 1: like really enormous. Where's the black hole the center of

901
00:44:04,560 --> 00:44:07,520
Speaker 1: our galaxy? It's big, but it's sort of smaller on

902
00:44:07,600 --> 00:44:11,320
Speaker 1: the scale of supermassive black holes. Right, Yeah, it is

903
00:44:11,400 --> 00:44:14,200
Speaker 1: that I guess, closer than this other galaxy, but it's

904
00:44:14,200 --> 00:44:17,160
Speaker 1: still you know, like fifty thousand light years away, right, Yeah,

905
00:44:17,200 --> 00:44:19,799
Speaker 1: we're about twenty six thousand light years from the center

906
00:44:19,800 --> 00:44:22,560
Speaker 1: of the galaxy, which seems like a lot, right, but

907
00:44:22,680 --> 00:44:26,040
Speaker 1: astronomically speaking, it's really not that big. A number other

908
00:44:26,160 --> 00:44:30,279
Speaker 1: galaxies are millions of light years away. Oh yeah, I

909
00:44:30,360 --> 00:44:33,040
Speaker 1: guess it's just it's closer, but it's smaller and it's

910
00:44:33,120 --> 00:44:35,960
Speaker 1: a dustier and it's also a dimmer black hole. Right,

911
00:44:36,080 --> 00:44:38,839
Speaker 1: it's a dimmer black hole, and there's a more variability,

912
00:44:39,320 --> 00:44:41,879
Speaker 1: Like the fact that it's smaller means that there's much

913
00:44:41,920 --> 00:44:44,799
Speaker 1: more like variation in the brightness of this black hole,

914
00:44:44,960 --> 00:44:46,719
Speaker 1: so it's not as easy to look at it to

915
00:44:46,760 --> 00:44:49,160
Speaker 1: stitch this picture together. Now they've taken the data, like

916
00:44:49,239 --> 00:44:52,400
Speaker 1: they turned the telescope towards the black hole effectively in

917
00:44:52,440 --> 00:44:55,440
Speaker 1: two thousand and seventeen, and since then they've been crunching

918
00:44:55,480 --> 00:44:57,720
Speaker 1: it through the computers to try to make this picture.

919
00:44:57,880 --> 00:44:59,960
Speaker 1: So the only thing standing between us and a picture

920
00:45:00,360 --> 00:45:02,440
Speaker 1: of the black hole the center of our galaxy is

921
00:45:02,480 --> 00:45:05,480
Speaker 1: you know, enough computers, right, Yeah, we need more computers,

922
00:45:06,120 --> 00:45:08,120
Speaker 1: but I think even if they we do get a picture,

923
00:45:08,280 --> 00:45:10,799
Speaker 1: sometimes we're not sure if it's a black hole either, right,

924
00:45:10,880 --> 00:45:13,400
Speaker 1: Like you were saying before, even the picture of the

925
00:45:13,440 --> 00:45:15,560
Speaker 1: black hole we have in the other galaxy, it might

926
00:45:15,640 --> 00:45:17,759
Speaker 1: not be a black hole, right, Yeah, there are other

927
00:45:17,920 --> 00:45:22,840
Speaker 1: ideas for what could be that dense and that gravitationally powerful.

928
00:45:23,040 --> 00:45:25,440
Speaker 1: You know. In the end, black hole observations are always

929
00:45:25,520 --> 00:45:28,360
Speaker 1: a little bit indirect because you can't actually tell if

930
00:45:28,440 --> 00:45:31,120
Speaker 1: there's an event horizon there or if it's just something

931
00:45:31,239 --> 00:45:34,400
Speaker 1: that's not emitting and is very very dense. You know.

932
00:45:34,560 --> 00:45:36,239
Speaker 1: It's sort of like we have a list of things

933
00:45:36,320 --> 00:45:38,640
Speaker 1: that can do that, and black holes are the only

934
00:45:38,760 --> 00:45:41,400
Speaker 1: thing on the list, So we assume that whenever we

935
00:45:41,480 --> 00:45:44,719
Speaker 1: see something that dense, that gravitationally powerful, it must be

936
00:45:44,800 --> 00:45:46,680
Speaker 1: a black hole. But then people come up with other

937
00:45:46,760 --> 00:45:51,400
Speaker 1: ideas like dark stars, these very time dilated collapsing stars

938
00:45:51,600 --> 00:45:53,600
Speaker 1: that could also do that. We don't know that's a

939
00:45:53,680 --> 00:45:56,040
Speaker 1: thing in our universe or not. But in the end,

940
00:45:56,120 --> 00:45:58,319
Speaker 1: until we go and visit the black hole, we won't

941
00:45:58,360 --> 00:46:02,000
Speaker 1: know for sure if there really is an event horizon there. Yeah,

942
00:46:02,200 --> 00:46:05,680
Speaker 1: so back your bags, Daniel, we're sending you all right.

943
00:46:05,680 --> 00:46:08,239
Speaker 1: I'll bring my ice cream spoons. Yeah, make it a

944
00:46:08,280 --> 00:46:11,120
Speaker 1: big scoop, all right. Well, it's a big mystery at

945
00:46:11,160 --> 00:46:13,480
Speaker 1: the center of our galaxy, and it sounds like scientists are,

946
00:46:13,920 --> 00:46:16,320
Speaker 1: you know, licking away at the data to get to

947
00:46:16,400 --> 00:46:19,480
Speaker 1: the juicy candy center to find out the flavor of

948
00:46:19,560 --> 00:46:23,040
Speaker 1: truth hopefully tastes like butter scotch or do legit. It

949
00:46:23,120 --> 00:46:27,640
Speaker 1: tastes like hard work and a lot of GPUs. Let's

950
00:46:27,640 --> 00:46:30,600
Speaker 1: be honest, it just tastes like coffee. That's what physics

951
00:46:30,680 --> 00:46:33,759
Speaker 1: tastes like. Yeah, from all the coffee consumed to do it,

952
00:46:33,920 --> 00:46:38,239
Speaker 1: chalkboard dust and coffee. That's the flavor of physics right there. Hey,

953
00:46:38,239 --> 00:46:39,640
Speaker 1: you should come up with a candy for that and

954
00:46:39,680 --> 00:46:42,879
Speaker 1: sell it chalk and coffee choffee. Yeah, it'll be good

955
00:46:42,880 --> 00:46:45,400
Speaker 1: for your bones. Alright, Well, it's stay tuned. Well. We

956
00:46:45,520 --> 00:46:48,719
Speaker 1: are slowly but surely looking closer at the center of

957
00:46:48,800 --> 00:46:51,120
Speaker 1: our galaxy to find out what's at the center of

958
00:46:51,200 --> 00:46:53,320
Speaker 1: it and what's inside could tell us a lot about

959
00:46:53,360 --> 00:46:55,840
Speaker 1: how the galaxy got formed and even how the universe

960
00:46:56,040 --> 00:46:58,720
Speaker 1: got structured and got to the shape it is today.

961
00:46:58,880 --> 00:47:00,520
Speaker 1: And we're doing everything we can and to try to

962
00:47:00,640 --> 00:47:03,480
Speaker 1: understand what's out there in the universe from this tiny

963
00:47:03,560 --> 00:47:06,040
Speaker 1: little rock floating out in space. And every time we

964
00:47:06,160 --> 00:47:08,080
Speaker 1: build a new kind of eyeball or figure out a

965
00:47:08,120 --> 00:47:10,399
Speaker 1: new way to look out into the universe, we learned

966
00:47:10,480 --> 00:47:12,919
Speaker 1: something new about what's out there. Yeah. I just hope

967
00:47:12,920 --> 00:47:15,000
Speaker 1: we do it before it belt, but we hope you

968
00:47:15,080 --> 00:47:17,520
Speaker 1: enjoyed that. Thanks for joining us, See you next night.

969
00:47:25,400 --> 00:47:28,280
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explained.

970
00:47:28,280 --> 00:47:31,120
Speaker 1: The Universe is a production of I Heart Radio. For

971
00:47:31,320 --> 00:47:34,239
Speaker 1: more podcast from my Heart Radio, visit the I heart

972
00:47:34,320 --> 00:47:37,880
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your

973
00:47:37,960 --> 00:47:44,280
Speaker 1: favorite shows. Ye