WEBVTT - Listener Questions #11

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<v Speaker 1>Black holes make a gravitational wave. White chocolate is Daniel's save.

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<v Speaker 2>What controls colors on our furry friends? It's biology, so.

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<v Speaker 1>It depends particle colliders make mini booms. The big Bang

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<v Speaker 1>filled the whole room.

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<v Speaker 2>Biology, physics, archaeology, and forestry. Thank you for not asking

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<v Speaker 2>about chemistry.

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<v Speaker 1>What diseases you get from your cats? We'll find answers

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<v Speaker 1>to all of that.

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<v Speaker 2>Whatever questions keep you up at night, Daniel and Kelly's

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<v Speaker 2>answers will make it all right.

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<v Speaker 1>Welcome to another Listener Questions episode on Daniel and Kelly's

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<v Speaker 1>Extraordinary Universe. Hello, I'm Kelly Wadersmith. I study parasites and space,

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<v Speaker 1>and I'm excited to learn more about black holes today.

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<v Speaker 2>Hi. I'm Daniel. I'm a particle physicist and I love cats,

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<v Speaker 2>though I don't have nearly as many pets as exist

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<v Speaker 2>on the Wienersmith Farm.

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<v Speaker 1>Well, I mean that's hard to beat. So you're a

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<v Speaker 1>cat person rather than a dog person, Is that what

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<v Speaker 1>I'm hearing?

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<v Speaker 2>Well, I grew up with cats, always loved cats, but

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<v Speaker 2>my daughter is allergic cats. So now we have a

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<v Speaker 2>dog and love my dog of course, and so kind

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<v Speaker 2>of a dog person now but my daughter is getting

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<v Speaker 2>shots so that she can tolerate cats, and we're hoping

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<v Speaker 2>to get a cat soon.

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<v Speaker 1>Oh exciting. Now are you going to adopt that cat?

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<v Speaker 1>Where are you going to get the cat from?

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<v Speaker 2>It? Was that? Or create the cat in collisions at

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<v Speaker 2>the large hadron collider? So probably going to adopt it.

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<v Speaker 1>Yeah, excellent. Well, we have a growing number of cats

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<v Speaker 1>because we live on a farm in the woods and

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<v Speaker 1>they find us and then they move in and I

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<v Speaker 1>can never kick them out. We almost ended up with

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<v Speaker 1>three beagles because they were also like dropped on the

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<v Speaker 1>property and well saying no more animals. I am like

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<v Speaker 1>simultaneously dumping pile of food in front of them. I

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<v Speaker 1>can't help myself.

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<v Speaker 2>Oh I see that was the other option. The option

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<v Speaker 2>is adopt cats or have them adopt you, which is

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<v Speaker 2>what you're doing on the farm.

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<v Speaker 1>Yep, yep, although the goats I think I will be

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<v Speaker 1>purchasing directly.

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<v Speaker 2>Well, there's some sort of gravitational cat hole effect there,

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<v Speaker 2>I think, because the more cats you get, the more

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<v Speaker 2>they attract more cats, and then cats hear about your

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<v Speaker 2>farm they're like, oh wow, it's a cat haven, and

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<v Speaker 2>pretty soon you're gonna be a cat lady.

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<v Speaker 1>Yeah, it's true. And we're also getting into chicken math.

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<v Speaker 1>Have you heard about chicken math?

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<v Speaker 2>Tell me about chicken math.

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<v Speaker 1>It's when you decide you're going to get four chickens

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<v Speaker 1>because it's not really that much work. So you actually

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<v Speaker 1>get ten chickens, and then before you know what, the

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<v Speaker 1>order you put in actually had a four in the front,

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<v Speaker 1>and now you've got forty chickens. And anyway, I did

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<v Speaker 1>duck math recently, and so now we have five ducks

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<v Speaker 1>and two geese coming. My husband's not excited about the geese.

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<v Speaker 1>We decided we were gonna name the geese Jacques Gusta

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<v Speaker 1>and franc Scene Gusto. I think Jacques had two wives.

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<v Speaker 1>One of them was Franccene. Anyway, we're very excited.

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<v Speaker 2>Well, at least you have control over the names of

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<v Speaker 2>the pets, even if not the species or number of them.

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<v Speaker 2>Gives you a little bit of illusion of control.

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<v Speaker 1>That's right. All that matters is that they let me

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<v Speaker 1>snuggle them.

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<v Speaker 2>And in this crazy universe that can sometimes feel out

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<v Speaker 2>of our control, one way we can sort of establish

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<v Speaker 2>a little bit of a finger hold on sanity is

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<v Speaker 2>to think about the universe and try to understand it,

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<v Speaker 2>try to grapple with the mysteries of the cosmos, and

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<v Speaker 2>the best way to do that is to start by

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<v Speaker 2>asking questions. Questions we have and questions that you have.

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<v Speaker 1>Chicken math might not make sense, but Daniel and Kelly's

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<v Speaker 1>answers do. So if you would like to submit your

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<v Speaker 1>questions about the universe, write us at questions at danielands

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<v Speaker 1>Kelly dot org. And it might take us a little

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<v Speaker 1>while before your answer airs, because we are actually fairly

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<v Speaker 1>well organized and we're about two months ahead of schedule,

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<v Speaker 1>and we've got a bit of a list of questions.

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<v Speaker 1>But you will get an answer from us, for sure.

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<v Speaker 1>We respond to everyone that's.

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<v Speaker 2>Right right to us with your questions at questions at

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<v Speaker 2>Daniel and Kelly dot org. Everyone gets an answer, and

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<v Speaker 2>some people get on the podcast. And today we have

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<v Speaker 2>questions from three listeners about black holes, about furry pets,

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<v Speaker 2>and about tiny little bangs. Our first question comes from

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<v Speaker 2>Mark from Ireland about black holes. Here's Mark's question.

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<v Speaker 3>Hi, Daniel and Kelly, this is Mark from Ireland and

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<v Speaker 3>I have a question about merging black holes. When two

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<v Speaker 3>black holes spiral towards each other to merge, they lose

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<v Speaker 3>mass and in doing so, generates gravitational waves. The newly

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<v Speaker 3>formed black hole will have a mass less than the

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<v Speaker 3>sum of the two original black holes. My question is

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<v Speaker 3>what actual mass is converted into gravitational waves and how

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<v Speaker 3>does this happen? In trying to get my head around

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<v Speaker 3>this phenomenon, I see there are lots of other interesting

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<v Speaker 3>questions that might arise. Maybe you can explain the merging

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<v Speaker 3>process and detail. I really enjoy the podcast and look

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<v Speaker 3>forward to new episodes. Thank you and keep up the

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<v Speaker 3>good work.

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<v Speaker 1>Whoa great question. Okay, so I'm going to assume that

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<v Speaker 1>we've never actually seen black holes collide and we are

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<v Speaker 1>guessing what happens, or have we seen black.

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<v Speaker 2>Holes Colyde, depends what you mean by seeing and black holes.

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<v Speaker 2>But yes, we actually have seen black holes collide. We've

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<v Speaker 2>observed these ingravitational waves collisions of dozens and dozens of

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<v Speaker 2>pairs of black holes. Now it seems sort of fantastical

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<v Speaker 2>and science fiction y, but it's our reality.

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<v Speaker 1>Okay, So then what did you mean when you said

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<v Speaker 1>it depends what you mean by black holes and observe,

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<v Speaker 1>because it sounds like we have seen black holes collide.

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<v Speaker 2>Yeah, I think most people in astronomy would say that

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<v Speaker 2>we have seen black holes collide. Okay, but you know,

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<v Speaker 2>we don't technically know that they are black holes. We've

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<v Speaker 2>seen very dense, compact, dark objects which are consistent with

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<v Speaker 2>black holes collide, that we've never really observed the event

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<v Speaker 2>horizon directly, So there's an asterisk there on do we

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<v Speaker 2>really know black holes are black holes? And in terms

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<v Speaker 2>of seeing, we've observed the radiation generated by that collision,

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<v Speaker 2>and that's what today's question is all about, how those

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<v Speaker 2>black holes merge and the radiation they give off. So

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<v Speaker 2>we've observed that gravitational radiation and it looks exactly like

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<v Speaker 2>you would expect from black holes colliding. But I don't

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<v Speaker 2>know if that counts as seeing it because it's not

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<v Speaker 2>like visible light.

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<v Speaker 1>Okay, all right, I got it. So let's start from

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<v Speaker 1>the basics. What's a black hole?

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<v Speaker 2>Right? So black hole famous prediction from classical general relativity. Right,

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<v Speaker 2>This is Einstein's theory that space is curved. Gravity is

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<v Speaker 2>not really a force. So what you think is gravity

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<v Speaker 2>is actually just the effect of space time being curved.

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<v Speaker 2>If you don't notice that space time is curved, it

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<v Speaker 2>looks like something is bending the light or changing the

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<v Speaker 2>path of the Earth. But it's actually just the curvature

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<v Speaker 2>of space time. Space time curves in response to mass,

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<v Speaker 2>and if you get enough mass in a small area,

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<v Speaker 2>it curves space time so much that things get trapped.

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<v Speaker 2>Space time is curved so that like light can't even escape.

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<v Speaker 2>It's not like there's so much gravity it even pulls

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<v Speaker 2>on photon. It's that space itself is bent so that

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<v Speaker 2>inside a black hole, space only points towards the center.

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<v Speaker 2>And so this creates the phenomenon we call the event horizon,

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<v Speaker 2>beyond which anything that falls in is trapped. It will

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<v Speaker 2>only move towards the center of the black hole. And

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<v Speaker 2>so this is the defining feature of a black hole,

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<v Speaker 2>the event horizon. This is the thing we haven't actually

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<v Speaker 2>literally technically observed. We've seen lots of indirect evidence for

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<v Speaker 2>black holes, but never actually observe the event horizon. And

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<v Speaker 2>beyond the event horizon, we can't tell anything that happens.

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<v Speaker 2>We can know the mass of the black hole, we

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<v Speaker 2>can know if it has electric charge, we can know

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<v Speaker 2>if it's spinning, but everything else is shrouded in mystery.

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<v Speaker 1>We've done eleven of these listener questions episodes so far.

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<v Speaker 1>In thinking back, I feel like most of them have

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<v Speaker 1>had at least a question about a black hole. What

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<v Speaker 1>do you think it is about black holes that keep

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<v Speaker 1>people up at night?

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<v Speaker 2>I think it's an incredible prediction of physics, something so

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<v Speaker 2>strange and beyond our intuition. But macroscopic, right, like quantum

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<v Speaker 2>mechanics makes all sorts of weirds about electrons, what they're

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<v Speaker 2>secretly doing while you're asleep, whatever, But we'll never see

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<v Speaker 2>those because they're microscopic. You can never observe them. Black

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<v Speaker 2>holes are a prediction that are like technically you could

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<v Speaker 2>see you could be near a black hole and observe

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<v Speaker 2>it and see all this strange effects. So it feels

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<v Speaker 2>sort of like magic, I think. And yeah, you're right,

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<v Speaker 2>people are fascinated by black holes. It's a significant fraction

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<v Speaker 2>of the questions that we get are about black holes.

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<v Speaker 2>So yeah, absolutely, it's fantastic. It's wonderful. It's incredible that

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<v Speaker 2>we've actually seen them, and we've seen these collisions. I

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<v Speaker 2>remember in the late nineties deciding where to go to

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<v Speaker 2>graduate school and what to work on, and I had

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<v Speaker 2>an opportunity to work on this project Lego the gravitational

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<v Speaker 2>wave observatory, and they were looking to see these black

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<v Speaker 2>holes merging and the gravitational waves generated by them. And

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<v Speaker 2>I remember thinking, they're never going to make that work.

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<v Speaker 2>It's crazy, and so I decided not to work on that.

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<v Speaker 2>And then of course they won the Nobel Prize. But

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<v Speaker 2>you know, hey, maybe if I had worked on it,

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<v Speaker 2>it wouldn't have worked out, and they wouldn't have won

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<v Speaker 2>a Nobel Prize. So maybe they won the Nobel Prize

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<v Speaker 2>because I didn't work on it.

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<v Speaker 1>Anyway, hard to say, do you ever regret not going

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<v Speaker 1>into black holes? Or are you totally happy with the

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<v Speaker 1>path your life took?

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<v Speaker 2>You know, there are always other options you could consider,

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<v Speaker 2>but I'm pretty happy with how everything worked out, and

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<v Speaker 2>so yeah, I don't worry too much about the counterfactuals.

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<v Speaker 2>But it is amazing that humanity has figured out a

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<v Speaker 2>way to observe these collisions. Einstein predicted this decades and

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<v Speaker 2>decades ago, but he thought it was going to be

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<v Speaker 2>impossible to observe because gravitational radiation is very, very weak,

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<v Speaker 2>because gravity itself is not very powerful, and so you

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<v Speaker 2>need an extraordinarily sensitive instrument to see this stretching and

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<v Speaker 2>squeezing of space time, this gravitational radiation, unless, of course,

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<v Speaker 2>you're right next to the black holes colliding, in which

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<v Speaker 2>case the signal is very powerful and you're probably dead.

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<v Speaker 1>I feel like that's another thing that gets people interested

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<v Speaker 1>in the idea that observing this could kill you, but

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<v Speaker 1>if you could survive what's on the other side, I

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<v Speaker 1>just feel like it's amazing. But Okay, so we have

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<v Speaker 1>observed collisions, and you said that we've observed a lot

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<v Speaker 1>of them, and.

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<v Speaker 2>It was a little bit of a surprise when we

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<v Speaker 2>saw the first one. You know, we didn't know how

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<v Speaker 2>often does this happen in the universe. We're building our

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<v Speaker 2>first eyeball for gravitational waves, and how long it takes

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<v Speaker 2>the sea one depends on how often they happen, and

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<v Speaker 2>there were lots of predictions. Some people predicted that it

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<v Speaker 2>would take decades to see one, but they saw one

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<v Speaker 2>almost immediately after turning the thing on, and everyone's like,

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<v Speaker 2>oh my gosh. Wow. So it turns out these collisions

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<v Speaker 2>happen more often than people suspected.

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<v Speaker 1>So does that mean we were totally off in our

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<v Speaker 1>predictions for how many black holes there are or how

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<v Speaker 1>much they're moving? Around what were we wrong about in particular.

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<v Speaker 2>So we're not sure. Black hole formation is still kind

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<v Speaker 2>of mystery. Super massive black holes or things we don't

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<v Speaker 2>really understand, so something we're still trying to understand and

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<v Speaker 2>we don't understand. Also the distribution of black hole masses.

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<v Speaker 2>There seem to be some smaller ones, some bigger ones,

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<v Speaker 2>but there aren't intermediate sized ones. So there's a lot

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<v Speaker 2>we don't understand about black hole formation, how often it happens,

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<v Speaker 2>how often they're close to each other, right, this kind

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<v Speaker 2>of stuff, So a lot of really interesting astrophysics is

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<v Speaker 2>being opened up by this study.

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<v Speaker 1>No gold locks black holes, and Mark.

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<v Speaker 2>Is interested in what happens when these two black holes

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<v Speaker 2>form and where the mass goes, because you know, there's

0:11:08.400 --> 0:11:11.319
<v Speaker 2>nothing free in the universe. If two black holes collide

0:11:11.360 --> 0:11:15.160
<v Speaker 2>and produce gravitational waves, gravitational waves carry energy. They're stretching

0:11:15.200 --> 0:11:18.320
<v Speaker 2>and squeezing of space time, and that energy has to

0:11:18.360 --> 0:11:21.560
<v Speaker 2>come from somewhere, and it comes from the internal energy

0:11:21.600 --> 0:11:24.040
<v Speaker 2>of the black hole system. These two things are orbiting

0:11:24.040 --> 0:11:26.360
<v Speaker 2>each other and for them to collapse down into one,

0:11:26.400 --> 0:11:29.440
<v Speaker 2>they have to lose that angular momentum, so they radiate

0:11:29.480 --> 0:11:32.719
<v Speaker 2>it away in gravitational waves and Marx's questions trying to

0:11:32.800 --> 0:11:35.920
<v Speaker 2>understand where the mass goes, because the mass of the

0:11:35.960 --> 0:11:39.280
<v Speaker 2>resulting black hole is not just the sum of the

0:11:39.320 --> 0:11:41.600
<v Speaker 2>masses of the two black holes that go in. It's

0:11:41.800 --> 0:11:45.360
<v Speaker 2>smaller than that because energy is lost to gravitational waves.

0:11:45.679 --> 0:11:48.760
<v Speaker 1>And we have talked in other episodes about how energy

0:11:48.840 --> 0:11:51.400
<v Speaker 1>is mass, but maybe not. It's complicated, is that, right?

0:11:53.480 --> 0:11:57.319
<v Speaker 2>Yeah, Mass is a measure of internal stored energy. Right,

0:11:57.360 --> 0:11:59.480
<v Speaker 2>So like a proton's mass, it's not just the mass

0:11:59.480 --> 0:12:01.559
<v Speaker 2>of the stuff that makes it up. It's the mass

0:12:01.559 --> 0:12:03.120
<v Speaker 2>of the stuff that makes it up, plus the energy

0:12:03.120 --> 0:12:05.240
<v Speaker 2>they have relative to each other. In fact, most of

0:12:05.280 --> 0:12:07.520
<v Speaker 2>the mass of the proton comes from that energy, the

0:12:07.559 --> 0:12:11.520
<v Speaker 2>binding energy of the quarks together. So if you have

0:12:11.600 --> 0:12:14.400
<v Speaker 2>a black hole black hole system, two black holes orbiting

0:12:14.440 --> 0:12:17.320
<v Speaker 2>each other, the mass of the whole system is the

0:12:17.320 --> 0:12:19.640
<v Speaker 2>massive black hole one plus the massive black hole two

0:12:20.000 --> 0:12:23.160
<v Speaker 2>plus their relative energy, and that's a lot. There's a

0:12:23.200 --> 0:12:26.880
<v Speaker 2>lot of gravitational energy between those two black holes. Let's

0:12:26.920 --> 0:12:29.560
<v Speaker 2>say black hole one is forty masses of the Sun,

0:12:29.640 --> 0:12:32.000
<v Speaker 2>for example, and black hole two is thirty masses of

0:12:32.000 --> 0:12:34.559
<v Speaker 2>the Sun. These are typical numbers. Then the energy of

0:12:34.600 --> 0:12:38.240
<v Speaker 2>the whole system would be forty plus thirty plus whatever

0:12:38.440 --> 0:12:41.280
<v Speaker 2>energy they have in their relative rotation, and that could

0:12:41.320 --> 0:12:43.680
<v Speaker 2>be like thirty or forty or fifty, right, it depends

0:12:43.720 --> 0:12:46.680
<v Speaker 2>on the configuration. So the total energy of the system

0:12:46.920 --> 0:12:48.920
<v Speaker 2>could be much more than seventy. You could be one hundred,

0:12:48.920 --> 0:12:51.440
<v Speaker 2>one hundred and twenty, this kind of thing. But a

0:12:51.440 --> 0:12:54.200
<v Speaker 2>lot of that energy is lost when the two radiated

0:12:54.280 --> 0:12:57.040
<v Speaker 2>away in order to combine. They have to radiate away

0:12:57.080 --> 0:12:59.880
<v Speaker 2>some energy in order to combine, otherwise they would just

0:13:00.080 --> 0:13:00.720
<v Speaker 2>or bit forever.

0:13:01.000 --> 0:13:04.240
<v Speaker 1>And are they losing the energy of the black holes

0:13:04.360 --> 0:13:06.600
<v Speaker 1>or are they losing the energy that surrounds the black

0:13:06.640 --> 0:13:07.800
<v Speaker 1>holes or a little bit of both.

0:13:08.080 --> 0:13:09.719
<v Speaker 2>Yeah, So this is a great question. And this is

0:13:09.760 --> 0:13:11.760
<v Speaker 2>what Mark is asking, is like he wants to do

0:13:11.800 --> 0:13:14.520
<v Speaker 2>some accounting. Is their mass actually lost? And I think

0:13:14.520 --> 0:13:17.199
<v Speaker 2>he's interested in this because people think of black holes

0:13:17.200 --> 0:13:19.800
<v Speaker 2>as something that can never lose mass, right at least

0:13:19.800 --> 0:13:22.920
<v Speaker 2>in classical general relativity, And so he's wondering, like, is

0:13:22.960 --> 0:13:26.199
<v Speaker 2>this a way for mass to escape somehow the black holes?

0:13:26.640 --> 0:13:28.520
<v Speaker 2>And it's a little bit tricky. There's a couple of

0:13:28.520 --> 0:13:30.959
<v Speaker 2>things to keep in mind. So the final black hole

0:13:31.200 --> 0:13:34.440
<v Speaker 2>is smaller than the sum of the two original black holes,

0:13:34.600 --> 0:13:38.600
<v Speaker 2>but always larger than either of them. So neither black

0:13:38.600 --> 0:13:41.360
<v Speaker 2>hole shrinks. Both black holes grow.

0:13:41.720 --> 0:13:44.680
<v Speaker 1>Nope, no, no, no, You've lost me. Don't they become

0:13:44.720 --> 0:13:46.240
<v Speaker 1>one black hole when they merge.

0:13:46.520 --> 0:13:49.800
<v Speaker 2>Yes, they become one black hole exactly, And so there's

0:13:49.840 --> 0:13:52.080
<v Speaker 2>no shrinking of the event horizon. Like the final event

0:13:52.080 --> 0:13:56.200
<v Speaker 2>horizon is bigger than either of the incoming event horizons. Okay,

0:13:56.320 --> 0:13:58.720
<v Speaker 2>so no event horizon is shrinking. It's not like you're

0:13:58.760 --> 0:14:02.080
<v Speaker 2>seeing behind the event horizon of either black hole. Both

0:14:02.120 --> 0:14:05.440
<v Speaker 2>of them are growing, right, but the final is smaller

0:14:05.440 --> 0:14:07.640
<v Speaker 2>than the sum of the two parts. It feels trickier.

0:14:07.800 --> 0:14:08.760
<v Speaker 2>It feels like I'm cheating.

0:14:09.120 --> 0:14:11.400
<v Speaker 1>Yes, so I guess what I'm not following is Okay,

0:14:11.600 --> 0:14:13.720
<v Speaker 1>when they merge, I no longer think of them as

0:14:13.720 --> 0:14:16.400
<v Speaker 1>two separate parts. They're just one part. But it sounds

0:14:16.440 --> 0:14:20.240
<v Speaker 1>like you are still trying to keep accounting on two parts,

0:14:20.640 --> 0:14:24.040
<v Speaker 1>but now they've become one. So what am I missing?

0:14:24.640 --> 0:14:26.440
<v Speaker 2>Yeah? I think think about it from the point of

0:14:26.520 --> 0:14:29.080
<v Speaker 2>view of black hole one. Okay, black Hole one has

0:14:29.120 --> 0:14:32.040
<v Speaker 2>an event horizon, and it has a certain mass, and

0:14:32.080 --> 0:14:33.960
<v Speaker 2>you could just be in its reference frame and it

0:14:34.000 --> 0:14:37.360
<v Speaker 2>has another black hole orbiting it, right, and then that

0:14:37.400 --> 0:14:40.280
<v Speaker 2>black hole radiates some energy and falls in and it

0:14:40.280 --> 0:14:43.920
<v Speaker 2>gets gobbled up. Black Hole one grows. Right, So we

0:14:44.040 --> 0:14:46.400
<v Speaker 2>followed all the rules of general relativity. The event horizon

0:14:46.480 --> 0:14:49.040
<v Speaker 2>is not shrunk because it can never shrink, because if

0:14:49.080 --> 0:14:52.200
<v Speaker 2>it did, you'd see things inside the event horizon. It

0:14:52.240 --> 0:14:55.720
<v Speaker 2>has grown. Its mass has gone up. Right, in classical

0:14:55.760 --> 0:14:58.760
<v Speaker 2>general relativity, black hole masses can only go up. So

0:14:58.840 --> 0:15:00.800
<v Speaker 2>from the point of view of black hole one, the

0:15:00.840 --> 0:15:02.720
<v Speaker 2>fact that black hole two is a black hole is

0:15:02.800 --> 0:15:06.200
<v Speaker 2>kind of irrelevant. It's eaten some energy and it's grown.

0:15:06.640 --> 0:15:08.200
<v Speaker 2>You can play the same game from the point of

0:15:08.280 --> 0:15:10.320
<v Speaker 2>view a black hole two. Right, The thing is symmetric.

0:15:10.520 --> 0:15:14.160
<v Speaker 2>Black Hole two grows, it gains mass, it's eating black

0:15:14.200 --> 0:15:17.680
<v Speaker 2>hole one. The two merge. The final result is bigger

0:15:17.720 --> 0:15:20.160
<v Speaker 2>than black hole two. Everything is happy from a general

0:15:20.200 --> 0:15:21.280
<v Speaker 2>relativity point of view.

0:15:21.560 --> 0:15:23.960
<v Speaker 1>Okay, so at the end you still have just one

0:15:24.000 --> 0:15:28.160
<v Speaker 1>black hole, but that one black hole is bigger than

0:15:28.200 --> 0:15:32.360
<v Speaker 1>black hole one or black hole two were originally.

0:15:32.120 --> 0:15:35.560
<v Speaker 2>Yes, exactly, Okay, and so it feels like mass has

0:15:35.640 --> 0:15:38.040
<v Speaker 2>been lost and we're playing some sort of shell game here.

0:15:38.400 --> 0:15:41.280
<v Speaker 2>I think there's another thing to understand that might help people,

0:15:41.280 --> 0:15:44.400
<v Speaker 2>which is, the mass of the black hole doesn't just

0:15:44.480 --> 0:15:48.280
<v Speaker 2>depend on what's beyond the event horizon. You can make

0:15:48.320 --> 0:15:51.400
<v Speaker 2>a black hole more massive without crossing the event horizon. So,

0:15:51.440 --> 0:15:54.520
<v Speaker 2>for example, say I shoot Kelly into orbit around a

0:15:54.520 --> 0:16:00.400
<v Speaker 2>black hole, hypothetically speaking, or Zach. Should we talk about Zaz? Yeah, yes,

0:16:00.480 --> 0:16:03.280
<v Speaker 2>of course Zach is in orbit around a black hole. Okay,

0:16:03.440 --> 0:16:07.240
<v Speaker 2>Now that black hole's mass grows even before Zach goes

0:16:07.280 --> 0:16:10.120
<v Speaker 2>over the event horizon. Right, you tend to think like, oh,

0:16:10.120 --> 0:16:12.800
<v Speaker 2>it's has to eat Zach before it grows to add

0:16:12.840 --> 0:16:15.280
<v Speaker 2>to its mass. But the mass is a measure of

0:16:15.400 --> 0:16:18.760
<v Speaker 2>the energy of the system, right, So the black hole's

0:16:18.840 --> 0:16:22.720
<v Speaker 2>mass actually grows before Zach falls over the event horizon.

0:16:23.200 --> 0:16:25.400
<v Speaker 1>So at what point does Zach become part of the

0:16:25.440 --> 0:16:26.480
<v Speaker 1>system mm.

0:16:26.440 --> 0:16:28.840
<v Speaker 2>Hmm, Well when he has a relationship to it, like

0:16:28.880 --> 0:16:31.880
<v Speaker 2>it's a gravitationally bound to it, than to an external

0:16:31.880 --> 0:16:34.920
<v Speaker 2>observer who's like a little bit further away, like it's

0:16:34.960 --> 0:16:37.840
<v Speaker 2>a black hole, Zach's system. The whole thing has more

0:16:37.960 --> 0:16:41.120
<v Speaker 2>mass than the black hole or than Zach does, and

0:16:41.200 --> 0:16:44.160
<v Speaker 2>so you don't have to like add stuff to the

0:16:44.200 --> 0:16:46.920
<v Speaker 2>black hole over the event horizon in order for the

0:16:46.920 --> 0:16:49.960
<v Speaker 2>black hole to gain in mass. This is actually crucial

0:16:50.040 --> 0:16:52.800
<v Speaker 2>for the way that black holes actually grow in the universe.

0:16:52.880 --> 0:16:54.520
<v Speaker 2>You might have heard, for example, if you do throw

0:16:54.560 --> 0:16:56.920
<v Speaker 2>your husband into a black hole, you'll never actually see

0:16:57.000 --> 0:17:00.880
<v Speaker 2>him cross the event horizon because time slows down. And

0:17:00.880 --> 0:17:02.280
<v Speaker 2>a lot of people write it and say, all right,

0:17:02.320 --> 0:17:04.560
<v Speaker 2>but then how do black holes actually grow if nothing

0:17:04.680 --> 0:17:07.639
<v Speaker 2>can cross the event horizon because time slows down. But

0:17:07.760 --> 0:17:10.720
<v Speaker 2>the answer is that the event horizon grows before Zack

0:17:10.880 --> 0:17:13.840
<v Speaker 2>reaches it. It grows out to meet him. He and

0:17:13.880 --> 0:17:17.160
<v Speaker 2>the event horizon approach each other. And so if Zach

0:17:17.320 --> 0:17:19.480
<v Speaker 2>was the last thing you ever threw into a black hole,

0:17:19.800 --> 0:17:21.680
<v Speaker 2>it's true that he would never cross it, you'd never

0:17:21.680 --> 0:17:24.200
<v Speaker 2>see him. But if after you throw Zach into a

0:17:24.200 --> 0:17:26.520
<v Speaker 2>black hole, you feel bad and you throw him a sandwich,

0:17:26.960 --> 0:17:29.720
<v Speaker 2>and that sandwich approaches the black hole, and as it

0:17:29.760 --> 0:17:33.320
<v Speaker 2>approaches the black hole, it pulls the event horizon over Zack, right,

0:17:33.359 --> 0:17:36.240
<v Speaker 2>because the event horizon comes out to meet the thing

0:17:36.960 --> 0:17:39.040
<v Speaker 2>that's approaching it. Because again, the mass of the black

0:17:39.040 --> 0:17:42.280
<v Speaker 2>hole depends on the stored energy, which includes the gravitational

0:17:42.400 --> 0:17:45.360
<v Speaker 2>energy it has with things around it. So you shouldn't

0:17:45.359 --> 0:17:47.560
<v Speaker 2>think of these things as just like boxes, right, Remember,

0:17:47.680 --> 0:17:49.840
<v Speaker 2>mass it's not just like a measure of how much

0:17:49.920 --> 0:17:53.080
<v Speaker 2>stuff is inside the black hole. It's a more comprehensive

0:17:53.080 --> 0:17:56.000
<v Speaker 2>measure of the energy of that whole system. You don't

0:17:56.000 --> 0:17:58.199
<v Speaker 2>have to be over the event horizon in order to

0:17:58.240 --> 0:17:59.400
<v Speaker 2>be part of that system.

0:18:00.160 --> 0:18:03.480
<v Speaker 1>So one, the next time you say biology is complicated,

0:18:04.200 --> 0:18:06.760
<v Speaker 1>I'm going to just start laughing right away. But okay. Two,

0:18:06.920 --> 0:18:10.919
<v Speaker 1>So if you threw Zach ten thousand sandwiches because you

0:18:10.960 --> 0:18:12.399
<v Speaker 1>are like you're going to be there for a while,

0:18:12.840 --> 0:18:16.800
<v Speaker 1>would the event horizon pass Zach faster than if you

0:18:16.960 --> 0:18:19.560
<v Speaker 1>just threw him one sandwich because you don't really care

0:18:19.600 --> 0:18:20.880
<v Speaker 1>about what happens in the long run.

0:18:21.440 --> 0:18:24.119
<v Speaker 2>Mm hmm, yeah, absolutely, okay. And if you threw them

0:18:24.119 --> 0:18:28.480
<v Speaker 2>in a series, then chicken sandwich number one would pass first,

0:18:28.560 --> 0:18:31.320
<v Speaker 2>chicken sandwich number two, then chicken number three, and the

0:18:31.400 --> 0:18:34.439
<v Speaker 2>last chicken sandwich would not cross the event horizon. So

0:18:34.480 --> 0:18:37.240
<v Speaker 2>it's true, you can't see something cross the event horizon

0:18:37.240 --> 0:18:40.159
<v Speaker 2>if it's the last thing that you throw. But in

0:18:40.200 --> 0:18:42.320
<v Speaker 2>our universe there's never a last thing. There's always like

0:18:42.400 --> 0:18:44.800
<v Speaker 2>more gas and more particles. And that's how black holes

0:18:44.800 --> 0:18:47.560
<v Speaker 2>in the universe actually grow, all right, But back to

0:18:47.760 --> 0:18:51.240
<v Speaker 2>Mark's question, what's going on here is that the mass

0:18:51.280 --> 0:18:53.800
<v Speaker 2>of the whole system. Right, Let's say we start with

0:18:53.800 --> 0:18:56.160
<v Speaker 2>our example of a forty and a thirty black hole,

0:18:56.400 --> 0:18:58.359
<v Speaker 2>and together they have a mass of like one hundred

0:18:58.400 --> 0:19:02.200
<v Speaker 2>and twenty, right, including all gravitational energy and rotational energy.

0:19:02.640 --> 0:19:06.320
<v Speaker 2>As they inspirle, they radiate away a bunch of that energy.

0:19:06.359 --> 0:19:08.480
<v Speaker 2>So the mass of the system was one twenty. It's

0:19:08.600 --> 0:19:11.399
<v Speaker 2>radiated away I don't know sixty. So now the final

0:19:11.440 --> 0:19:15.280
<v Speaker 2>black hole is sixty instead of one twenty. So sixty

0:19:15.359 --> 0:19:18.440
<v Speaker 2>is bigger than forty and bigger than thirty, but smaller

0:19:18.480 --> 0:19:21.600
<v Speaker 2>than forty plus thirty. But all that's happened is that

0:19:21.640 --> 0:19:25.639
<v Speaker 2>some of that rotational gravitational energy has been radiated away.

0:19:25.720 --> 0:19:28.560
<v Speaker 2>So even though the whole system started out with mass

0:19:28.560 --> 0:19:30.879
<v Speaker 2>of one twenty, now it's down to sixty because it's

0:19:30.960 --> 0:19:33.919
<v Speaker 2>radiated away half of its energy. I'm just making up

0:19:33.960 --> 0:19:36.560
<v Speaker 2>these numbers. They're roughly correct in the order of magnitude,

0:19:36.560 --> 0:19:38.760
<v Speaker 2>but I haven't done like any calculations. But that's the

0:19:38.800 --> 0:19:40.159
<v Speaker 2>right way to think about it as the energy of

0:19:40.200 --> 0:19:41.200
<v Speaker 2>the whole system.

0:19:41.320 --> 0:19:45.480
<v Speaker 1>All right, Well, I think I understand black holes better now,

0:19:45.520 --> 0:19:49.280
<v Speaker 1>although I say that after every explanation and then I

0:19:49.320 --> 0:19:50.959
<v Speaker 1>get things wrong the next time we talk about it.

0:19:51.000 --> 0:19:54.639
<v Speaker 1>But let's see what Mark from Ireland thinks of that explanation.

0:19:55.400 --> 0:19:58.399
<v Speaker 3>Hi, Daniel and Kelly, thank you very much for that

0:19:58.560 --> 0:20:02.320
<v Speaker 3>very informative answer to mike question. I think black holes

0:20:02.440 --> 0:20:06.200
<v Speaker 3>are really amazing, and merging black holes are even more amazing.

0:20:07.000 --> 0:20:09.760
<v Speaker 3>It's incredible that during the final fifth of a second

0:20:09.800 --> 0:20:13.280
<v Speaker 3>of their inward spiral, that they are flying around one

0:20:13.280 --> 0:20:17.400
<v Speaker 3>another at near relativistic speeds, often up to a rate

0:20:17.440 --> 0:20:21.000
<v Speaker 3>of two hundred and fifty orbits a second, and radiate

0:20:21.280 --> 0:20:24.720
<v Speaker 3>the equivalent of multiple solar masses of energy in the

0:20:24.800 --> 0:20:29.520
<v Speaker 3>former gravitational waves. It really is crazy, crazy physics. Well,

0:20:29.720 --> 0:20:33.200
<v Speaker 3>you've answered my questions very well, and thank you both

0:20:33.240 --> 0:20:36.000
<v Speaker 3>for taking the time to do so. I'm sure you'll

0:20:36.000 --> 0:20:38.240
<v Speaker 3>hear from me again at some stage in the future,

0:20:38.359 --> 0:20:43.120
<v Speaker 3>and in the meantime, I'm going to keep listening in.

0:20:57.640 --> 0:21:00.600
<v Speaker 1>All right, So now we are onto by all, from

0:21:00.680 --> 0:21:03.760
<v Speaker 1>black holes to black spots. We are talking about patterns

0:21:03.760 --> 0:21:07.440
<v Speaker 1>on our furry friends. Let's hear what Simon from Germany

0:21:07.480 --> 0:21:08.720
<v Speaker 1>wanted to know about.

0:21:09.040 --> 0:21:12.720
<v Speaker 4>Hi, Daniel N. Kelly Simon here from Germany. Thanks for

0:21:12.760 --> 0:21:15.960
<v Speaker 4>a great podcast. They're a fine background to my daily

0:21:16.000 --> 0:21:18.760
<v Speaker 4>run in the woods. I have a question here for Kelly,

0:21:19.040 --> 0:21:22.640
<v Speaker 4>one that has puzzled me for quite some time, and

0:21:22.880 --> 0:21:26.639
<v Speaker 4>it's in relation to the coloration of our furry friends.

0:21:27.040 --> 0:21:29.399
<v Speaker 4>So if we take a dog, for example, who is

0:21:29.400 --> 0:21:33.280
<v Speaker 4>black and white, and we zoom into the border between

0:21:33.320 --> 0:21:37.000
<v Speaker 4>the two colors, presumably we have one skin cell or

0:21:37.119 --> 0:21:41.640
<v Speaker 4>hair cell with black pigmentation and the neighboring cell as

0:21:41.680 --> 0:21:46.440
<v Speaker 4>a white pigmentation. The question is how is this information

0:21:46.640 --> 0:21:51.680
<v Speaker 4>passed down? Presumably the information is contained in a precursor cell,

0:21:51.720 --> 0:21:54.160
<v Speaker 4>one splitting into a black and one into a white.

0:21:54.400 --> 0:21:57.800
<v Speaker 4>The question is what is the mechanism for this? Thanks

0:21:57.840 --> 0:21:59.960
<v Speaker 4>for a great podcast, guys, Keep up the good work,

0:22:00.040 --> 0:22:03.359
<v Speaker 4>and I look forward to hearing some insight into this question.

0:22:03.960 --> 0:22:07.160
<v Speaker 2>See biology also has really massively important questions.

0:22:07.520 --> 0:22:08.719
<v Speaker 1>Are you being facetious?

0:22:08.760 --> 0:22:11.880
<v Speaker 2>I can't tell no, I'm trying to make a gravitational pun.

0:22:12.080 --> 0:22:15.000
<v Speaker 1>Oh good, excellent? Okay, sorry, went right over my head.

0:22:15.440 --> 0:22:19.000
<v Speaker 1>All right, So this was actually a fairly difficult question

0:22:19.240 --> 0:22:22.240
<v Speaker 1>to read about and to try to understand. And it's biology.

0:22:22.320 --> 0:22:23.720
<v Speaker 1>So it depends.

0:22:24.040 --> 0:22:25.720
<v Speaker 2>Let me see if I can interpret the question to

0:22:25.720 --> 0:22:28.120
<v Speaker 2>make sure I understand what he's asking. Okay, I think

0:22:28.119 --> 0:22:30.439
<v Speaker 2>he's basically trying to do some physics here, which is

0:22:30.480 --> 0:22:33.879
<v Speaker 2>to like zoom in on the microprocesses involved. He's like

0:22:34.240 --> 0:22:37.040
<v Speaker 2>looking at his dog and seeing there's white patches and

0:22:37.080 --> 0:22:40.560
<v Speaker 2>black patches and wondering like what makes one bit white

0:22:40.560 --> 0:22:42.359
<v Speaker 2>and one black? And he's trying to understand it by

0:22:42.400 --> 0:22:44.680
<v Speaker 2>zooming in on the boundary and saying like, there's got

0:22:44.720 --> 0:22:47.320
<v Speaker 2>to be a point where there's one cell that's white

0:22:47.359 --> 0:22:50.240
<v Speaker 2>and one cell that's black, and that's where the difference is.

0:22:50.280 --> 0:22:53.000
<v Speaker 2>And he wants to highlight like what's going on between

0:22:53.040 --> 0:22:56.320
<v Speaker 2>those cells to understand why one turns white and black,

0:22:56.520 --> 0:22:59.080
<v Speaker 2>but also obviously to zoom out and understand, like how

0:22:59.080 --> 0:23:00.200
<v Speaker 2>do you get these patterns?

0:23:00.600 --> 0:23:02.800
<v Speaker 1>Yes, And that's how I interpreted the question as well.

0:23:03.400 --> 0:23:06.679
<v Speaker 1>And the answer is that if you are looking at

0:23:06.680 --> 0:23:10.199
<v Speaker 1>animal patterns in general, it depends on the colors, it

0:23:10.240 --> 0:23:12.800
<v Speaker 1>depends on the pattern shape, it depends on the animal.

0:23:13.280 --> 0:23:18.479
<v Speaker 1>But Simon in particular referenced dogs and referenced white and black,

0:23:18.960 --> 0:23:21.000
<v Speaker 1>and so I decided that I was going to hone

0:23:21.040 --> 0:23:23.720
<v Speaker 1>in on that in particular, all right, because I needed

0:23:23.760 --> 0:23:27.560
<v Speaker 1>a foothold for this question. And so in dogs, there

0:23:27.560 --> 0:23:32.560
<v Speaker 1>are hair follicles or fur follicles that produce either black

0:23:32.680 --> 0:23:36.320
<v Speaker 1>or brown colors, or yellow or white colors. So one

0:23:36.440 --> 0:23:40.000
<v Speaker 1>follicle can produce either of those colors depending on the

0:23:40.000 --> 0:23:42.920
<v Speaker 1>instructions that it's given. So it's not like you have

0:23:43.080 --> 0:23:46.400
<v Speaker 1>different kinds of cells next to each other. It's all

0:23:46.480 --> 0:23:49.880
<v Speaker 1>the same cell, but it just is following different sets

0:23:49.880 --> 0:23:50.640
<v Speaker 1>of instructions.

0:23:51.040 --> 0:23:52.960
<v Speaker 2>So they're just like printers, and they can get an

0:23:52.960 --> 0:23:55.320
<v Speaker 2>instruction for a black hair or a white hair and

0:23:55.320 --> 0:23:56.119
<v Speaker 2>they're happy to do it.

0:23:56.400 --> 0:23:57.920
<v Speaker 1>That's right, Yes, exactly.

0:23:57.920 --> 0:23:59.679
<v Speaker 2>Interesting, So who sends the instructions?

0:24:00.119 --> 0:24:05.399
<v Speaker 1>So the instructions are encoded in a gene called a gooty,

0:24:05.800 --> 0:24:08.680
<v Speaker 1>and this gene is important for coloration in a lot

0:24:08.680 --> 0:24:13.760
<v Speaker 1>of different species, and the gene produces a hormone. The

0:24:13.800 --> 0:24:15.640
<v Speaker 1>hormone gets released from the cell.

0:24:15.800 --> 0:24:18.440
<v Speaker 2>I'm a little confused because a gene is part of

0:24:18.480 --> 0:24:21.200
<v Speaker 2>your DNA, and so when you're saying the gene produces

0:24:21.200 --> 0:24:24.120
<v Speaker 2>a hormone, do you mean the gene when it's transcribed

0:24:24.160 --> 0:24:27.560
<v Speaker 2>into a protein is that hormone or the gene when

0:24:27.560 --> 0:24:30.040
<v Speaker 2>transcribed into a protein. Is some little machine that makes

0:24:30.040 --> 0:24:32.920
<v Speaker 2>the hormone or excuse my naive biologic question.

0:24:33.000 --> 0:24:34.600
<v Speaker 1>No, No, that's a great question. I skipped a bunch

0:24:34.600 --> 0:24:37.880
<v Speaker 1>of steps. So, as I understand it, the gene encodes

0:24:37.920 --> 0:24:40.560
<v Speaker 1>for a hormone, and so when that gene is essentially

0:24:40.600 --> 0:24:44.080
<v Speaker 1>read and turned into a protein, that protein is a

0:24:44.119 --> 0:24:47.359
<v Speaker 1>hormone that subsequently gets released from the cell.

0:24:47.359 --> 0:24:49.440
<v Speaker 2>The hair follicle cell, or some other kind of cell

0:24:49.440 --> 0:24:51.320
<v Speaker 2>that's controlling the hair follicle cells.

0:24:51.760 --> 0:24:53.640
<v Speaker 1>What I think is happening here is that hair follicle

0:24:53.720 --> 0:24:56.560
<v Speaker 1>cells are producing this message and then also sharing it

0:24:56.560 --> 0:24:57.560
<v Speaker 1>with nearby cells.

0:24:57.760 --> 0:25:00.280
<v Speaker 2>Oh interesting, Okay, one.

0:25:00.240 --> 0:25:03.720
<v Speaker 1>Gets released and it talks to the nearby cells. If

0:25:03.720 --> 0:25:06.800
<v Speaker 1>you are a hair follicle next to a cell that

0:25:06.880 --> 0:25:11.000
<v Speaker 1>has just released this hormone, then you produce white.

0:25:11.440 --> 0:25:11.960
<v Speaker 2>Interesting.

0:25:12.680 --> 0:25:16.639
<v Speaker 1>If you don't get that hormone message, you default to

0:25:16.720 --> 0:25:18.240
<v Speaker 1>making black or brown?

0:25:18.359 --> 0:25:19.800
<v Speaker 2>Wow? Fascinating right.

0:25:19.840 --> 0:25:23.280
<v Speaker 1>So cells can do either, and so the question is

0:25:24.359 --> 0:25:28.560
<v Speaker 1>why are some cells making the signal that say turn

0:25:28.600 --> 0:25:31.560
<v Speaker 1>on white and why are some cells not making that

0:25:31.640 --> 0:25:35.600
<v Speaker 1>signal and telling nearby cells to default to brown or black?

0:25:35.760 --> 0:25:38.280
<v Speaker 2>I loveI we like follow the chain of logic here like,

0:25:38.480 --> 0:25:40.359
<v Speaker 2>this is happening because of that, because of that, because

0:25:40.359 --> 0:25:42.800
<v Speaker 2>of that, because of that, and now we're like detectives

0:25:42.800 --> 0:25:44.399
<v Speaker 2>following the clues all the way back to the source.

0:25:44.480 --> 0:25:46.080
<v Speaker 2>So are you going to tell us who the killer is?

0:25:46.400 --> 0:25:49.440
<v Speaker 2>Who is making these decisions about whether to produce this hormone?

0:25:49.480 --> 0:25:51.680
<v Speaker 1>You know, it's biology, so that the answer is never,

0:25:51.760 --> 0:25:55.440
<v Speaker 1>you know, kernel mustard. It's much more complicated. So you've

0:25:55.480 --> 0:25:58.280
<v Speaker 1>got this a gooty gene, And what determines whether or

0:25:58.280 --> 0:26:00.760
<v Speaker 1>not genes are turned on or off is that there

0:26:00.760 --> 0:26:03.480
<v Speaker 1>are these regions called promoters, and when something binds to

0:26:03.520 --> 0:26:06.159
<v Speaker 1>the promoter, that can turn the gene on. And so

0:26:06.680 --> 0:26:08.920
<v Speaker 1>it seems that whether or not this hormone is made

0:26:09.000 --> 0:26:11.760
<v Speaker 1>or not has to do with some complicated interactions happening

0:26:11.800 --> 0:26:14.840
<v Speaker 1>with the promoter for the genes. And so some cells

0:26:14.880 --> 0:26:18.000
<v Speaker 1>have these promoters turned on, so they're making this make

0:26:18.080 --> 0:26:21.439
<v Speaker 1>white message, and some genes don't get this promoter turned on,

0:26:21.600 --> 0:26:23.960
<v Speaker 1>so they are not giving a message, and nearby cells

0:26:24.000 --> 0:26:26.840
<v Speaker 1>make black or brown. Part of why I didn't get

0:26:26.840 --> 0:26:29.520
<v Speaker 1>into the details is because it might help you understand

0:26:29.560 --> 0:26:33.040
<v Speaker 1>exactly what's happening in this very particular instance. But to

0:26:33.119 --> 0:26:37.000
<v Speaker 1>understand coloration in general, that's more a story about promoters

0:26:37.000 --> 0:26:38.439
<v Speaker 1>getting turned on or off.

0:26:38.760 --> 0:26:41.719
<v Speaker 2>So in general, then how do promoters get turned on

0:26:42.080 --> 0:26:44.360
<v Speaker 2>or off? I mean, this is part of your DNA,

0:26:44.880 --> 0:26:47.640
<v Speaker 2>what determines whether or not that DNA is getting turned

0:26:47.640 --> 0:26:48.120
<v Speaker 2>on or off.

0:26:48.359 --> 0:26:51.800
<v Speaker 1>In general, we don't understand what's happening super well here,

0:26:51.960 --> 0:26:54.720
<v Speaker 1>and we understand this process a lot better in rodents

0:26:54.760 --> 0:26:57.280
<v Speaker 1>in birds, and in part that's because we feel much

0:26:57.320 --> 0:26:59.879
<v Speaker 1>more comfortable doing experiments on these animals in the lab.

0:27:00.240 --> 0:27:02.520
<v Speaker 2>All that's kind of sad, I know.

0:27:02.520 --> 0:27:04.119
<v Speaker 1>I know it is sad, But then you can also

0:27:04.160 --> 0:27:08.119
<v Speaker 1>pick animals that have much simpler color patterns and fewer

0:27:08.119 --> 0:27:10.840
<v Speaker 1>colors to boots, and that makes it easier to sort

0:27:10.880 --> 0:27:12.679
<v Speaker 1>of get a handle on these sorts of things, whereas

0:27:12.720 --> 0:27:16.440
<v Speaker 1>dogs have loads of different color patterns, and so trying

0:27:16.440 --> 0:27:18.359
<v Speaker 1>to get a handle on all of the different ways

0:27:18.359 --> 0:27:21.080
<v Speaker 1>these patterns can be made is much more complicated. The

0:27:21.119 --> 0:27:23.439
<v Speaker 1>manuscript that I read even had a sentence being like,

0:27:23.640 --> 0:27:26.440
<v Speaker 1>the situation in dogs is still unresolved, but they're doing

0:27:26.440 --> 0:27:27.560
<v Speaker 1>their best to figure it out.

0:27:27.760 --> 0:27:29.680
<v Speaker 2>Well, this is super interesting how we can go from

0:27:29.720 --> 0:27:33.479
<v Speaker 2>like totally clues about it to understanding, Oh, follicles can

0:27:33.520 --> 0:27:36.560
<v Speaker 2>print either color to understanding what controls what they print,

0:27:36.600 --> 0:27:38.840
<v Speaker 2>and then follow that up the chain, and we're still

0:27:38.880 --> 0:27:40.480
<v Speaker 2>crawling up the chain. It's incredible.

0:27:40.800 --> 0:27:42.440
<v Speaker 1>It is incredible, And like I said, we've got a

0:27:42.480 --> 0:27:45.560
<v Speaker 1>better handle on some species. And animal coloration in general

0:27:45.640 --> 0:27:48.080
<v Speaker 1>is sort of fascinating. Like sometimes there are some animals

0:27:48.080 --> 0:27:50.320
<v Speaker 1>that get it from their diet. For example, there are

0:27:50.320 --> 0:27:52.640
<v Speaker 1>some fish that have red coloration that they get from

0:27:52.680 --> 0:27:55.199
<v Speaker 1>the animals that they eat, and it just sort of

0:27:55.240 --> 0:27:56.720
<v Speaker 1>like accumulates in their skin.

0:27:57.240 --> 0:28:00.879
<v Speaker 2>That would be amazing if humans, for example, change color

0:28:00.960 --> 0:28:02.080
<v Speaker 2>based on what they ate.

0:28:02.880 --> 0:28:05.320
<v Speaker 1>Oh man, Yeah, there'd be very specific kinds of diets

0:28:05.359 --> 0:28:08.400
<v Speaker 1>I imagine, And around Halloween you'd eat like a lot

0:28:08.440 --> 0:28:10.080
<v Speaker 1>more carrots to get in the mood.

0:28:10.240 --> 0:28:15.280
<v Speaker 2>Would be great, well, amazing. You could get a tan

0:28:15.440 --> 0:28:16.280
<v Speaker 2>just by having lunch.

0:28:16.600 --> 0:28:18.879
<v Speaker 1>That would be incredible and probably a lot safer than

0:28:18.880 --> 0:28:20.000
<v Speaker 1>what we do now to get tans.

0:28:20.440 --> 0:28:22.439
<v Speaker 2>All Right, So it turns out that Simon's question is

0:28:22.520 --> 0:28:27.440
<v Speaker 2>cracked open a huge canyon of unresolved questions in biology.

0:28:28.000 --> 0:28:30.119
<v Speaker 2>And not only do we not understand dogs, but the

0:28:30.160 --> 0:28:33.560
<v Speaker 2>whole question of how animals get color is still an

0:28:33.560 --> 0:28:36.760
<v Speaker 2>active area of research. And maybe having different answers in

0:28:36.800 --> 0:28:38.320
<v Speaker 2>each species. Amazing.

0:28:38.720 --> 0:28:41.080
<v Speaker 1>That's right, And so let's see if Simon feels like

0:28:41.080 --> 0:28:42.480
<v Speaker 1>he learned anything from this answer.

0:28:44.120 --> 0:28:45.800
<v Speaker 2>It sounds like Kelly read a lot of papers and

0:28:45.880 --> 0:28:46.440
<v Speaker 2>learned a lot.

0:28:46.600 --> 0:28:48.320
<v Speaker 1>Kelly read a lot of papers, learned a lot, and

0:28:48.360 --> 0:28:50.000
<v Speaker 1>also learned that there's a lot that she doesn't know

0:28:50.040 --> 0:28:51.959
<v Speaker 1>about how this stuff works out. So it was a

0:28:52.080 --> 0:28:53.640
<v Speaker 1>learning experience for sure.

0:28:53.920 --> 0:28:56.280
<v Speaker 2>All right, let's hear from Simon. Uh huh.

0:28:56.360 --> 0:29:00.239
<v Speaker 4>Kelly definitely did learn something, and I think we as

0:29:00.280 --> 0:29:03.560
<v Speaker 4>the audience, I've definitely learned something too. Thanks Kelly for

0:29:03.920 --> 0:29:08.360
<v Speaker 4>the great insight into the invisible and incredibly complicated, it

0:29:08.400 --> 0:29:13.240
<v Speaker 4>seems biological mechanisms behind something as simple as the coloration

0:29:13.360 --> 0:29:16.840
<v Speaker 4>of our furry friends. I think understanding how it works

0:29:16.840 --> 0:29:19.920
<v Speaker 4>at this very last step perhaps gives us some insight

0:29:20.000 --> 0:29:22.239
<v Speaker 4>into how it works at the very first step. So

0:29:22.280 --> 0:29:25.280
<v Speaker 4>if I go back to the very first cell directly

0:29:25.320 --> 0:29:27.920
<v Speaker 4>after conceptions, say, where it splits into two, and then

0:29:27.960 --> 0:29:30.960
<v Speaker 4>to four, and then to eight and so on, eventually

0:29:31.000 --> 0:29:33.960
<v Speaker 4>giving rise to something that resembles a head, a torso,

0:29:34.120 --> 0:29:37.040
<v Speaker 4>and four legs, to understand the finer details of how

0:29:37.080 --> 0:29:40.320
<v Speaker 4>this information has passed down. How one cell knows to

0:29:40.360 --> 0:29:43.280
<v Speaker 4>be a torso while as a direct neighbor knows to

0:29:43.320 --> 0:29:47.120
<v Speaker 4>become a leg To understand how this transfer of information

0:29:47.200 --> 0:29:49.719
<v Speaker 4>works from one cell division to the next will be

0:29:50.080 --> 0:29:52.960
<v Speaker 4>fascinating to find out one day, But that's a question

0:29:53.200 --> 0:29:56.120
<v Speaker 4>for another day. Maybe. Thanks Kelly for taking the time

0:29:56.200 --> 0:29:59.440
<v Speaker 4>to look deeper into this mechanism and give us some

0:29:59.520 --> 0:30:03.440
<v Speaker 4>insight into this very last step of cell division. Gave

0:30:03.560 --> 0:30:04.440
<v Speaker 4>up the Great White cause.

0:30:21.520 --> 0:30:23.280
<v Speaker 2>All right, we're back and we're moving on from the

0:30:23.320 --> 0:30:27.040
<v Speaker 2>mysteries of biology to the mysteries of the very early universe?

0:30:27.600 --> 0:30:29.320
<v Speaker 2>Which one do we understand less?

0:30:30.480 --> 0:30:32.240
<v Speaker 1>Does it really need to be a competition? We don't

0:30:32.320 --> 0:30:33.480
<v Speaker 1>understand much about anything.

0:30:33.520 --> 0:30:36.560
<v Speaker 2>Some days it feels like Leonardo wanted to understand the

0:30:36.600 --> 0:30:40.480
<v Speaker 2>relationship between particle collisions and the Big Bang. Here's his question.

0:30:41.160 --> 0:30:44.479
<v Speaker 5>Hi, Kelly and Daniel loved the show. I heard particle

0:30:44.560 --> 0:30:47.920
<v Speaker 5>accelerators being described as tiny banks as in The Big

0:30:47.960 --> 0:30:51.400
<v Speaker 5>Bang but tiny in another podcast by doctor Katie Mack.

0:30:52.080 --> 0:30:54.640
<v Speaker 5>I also know we measure the energy of impacts in

0:30:54.720 --> 0:30:58.480
<v Speaker 5>giga electron votes, so can we also estimate the energy

0:30:58.520 --> 0:31:00.320
<v Speaker 5>of the Big Bang in electron votes?

0:31:00.960 --> 0:31:01.080
<v Speaker 6>And?

0:31:01.120 --> 0:31:04.680
<v Speaker 5>If so, why are we not classifying accelerators in Meli

0:31:04.840 --> 0:31:07.720
<v Speaker 5>or Fento banks and Easy because the number would be

0:31:07.800 --> 0:31:10.240
<v Speaker 5>too unsatisfying. Grains from Brazil.

0:31:10.760 --> 0:31:13.000
<v Speaker 1>All right, So, Daniel, I remember you telling me once

0:31:13.200 --> 0:31:15.760
<v Speaker 1>that when you all turned on the particle collider for

0:31:15.800 --> 0:31:17.440
<v Speaker 1>the first time, there was a little bit of a

0:31:17.480 --> 0:31:21.000
<v Speaker 1>concern that maybe you would destroy the universe? Is that

0:31:21.040 --> 0:31:22.640
<v Speaker 1>because you all thought you were going to kick off

0:31:22.680 --> 0:31:23.640
<v Speaker 1>a tiny, big bang.

0:31:25.800 --> 0:31:28.240
<v Speaker 2>Well, you know, anytime you do something that's never been

0:31:28.280 --> 0:31:30.240
<v Speaker 2>done before, you don't know what's going to happen. That's

0:31:30.280 --> 0:31:34.880
<v Speaker 2>the excitement of research, right, you know, you're exploring the unknown,

0:31:34.960 --> 0:31:39.320
<v Speaker 2>you're potentially unleashing something you didn't expect. And so yeah,

0:31:39.320 --> 0:31:43.280
<v Speaker 2>there's always a little frison of you know, enthusiasm and

0:31:43.320 --> 0:31:44.720
<v Speaker 2>fear when that happens.

0:31:44.920 --> 0:31:47.120
<v Speaker 1>But when I first infect a fish with a parasite,

0:31:47.120 --> 0:31:49.160
<v Speaker 1>I don't worry that it's the end of humanity. Like,

0:31:49.240 --> 0:31:51.240
<v Speaker 1>the scale feels very different here.

0:31:51.240 --> 0:31:53.680
<v Speaker 2>Maybe you should think bigger, Kelly. Yeah, okay, for those

0:31:53.720 --> 0:31:55.640
<v Speaker 2>of you worried at home, we didn't actually worry about

0:31:55.640 --> 0:31:57.640
<v Speaker 2>that too much because the collisions we'd do with the

0:31:57.640 --> 0:32:01.320
<v Speaker 2>particle colliders are not unusual in nature. They're very high

0:32:01.400 --> 0:32:04.560
<v Speaker 2>energy collisions from particles slamming into the Earth's atmosphere all

0:32:04.600 --> 0:32:07.320
<v Speaker 2>the time, much higher energy than what we achieve with

0:32:07.360 --> 0:32:09.720
<v Speaker 2>the large a drunk collider. We didn't worry that we'd

0:32:09.760 --> 0:32:12.720
<v Speaker 2>be collapsing the Higgs field or creating a black hole

0:32:12.840 --> 0:32:16.160
<v Speaker 2>or anything like that. But it is a fascinating experiment

0:32:16.200 --> 0:32:19.760
<v Speaker 2>because we are recreating conditions of the early universe. They're

0:32:19.760 --> 0:32:23.720
<v Speaker 2>also conditions of our current universe, just not as widespread.

0:32:24.320 --> 0:32:28.000
<v Speaker 2>And so it's often said that particle collisions recreate the

0:32:28.000 --> 0:32:30.960
<v Speaker 2>Big Bang, and that's true in some sense, but there's

0:32:30.960 --> 0:32:34.640
<v Speaker 2>also the potential there to sort of underscore misunderstandings about

0:32:34.640 --> 0:32:36.360
<v Speaker 2>the Big Bang that we should probably clear up.

0:32:36.600 --> 0:32:38.480
<v Speaker 1>Well, can we start with, like, what is the defining

0:32:38.560 --> 0:32:43.720
<v Speaker 1>characteristic of a bang of any size? Small, medium, or large?

0:32:44.520 --> 0:32:47.160
<v Speaker 2>Yeah, that's a good question. You know, in terms of

0:32:47.320 --> 0:32:51.080
<v Speaker 2>the Big Bang, the Big Bang is more of a

0:32:51.120 --> 0:32:54.920
<v Speaker 2>whiff than a bang, right, because the universe is expanding,

0:32:54.960 --> 0:32:59.040
<v Speaker 2>but it's really sort of cooling. It's becoming older and colder.

0:32:59.400 --> 0:33:01.640
<v Speaker 2>So the Big Bang is a description of how the

0:33:01.760 --> 0:33:05.160
<v Speaker 2>universe is decreasing in density as time goes on. It's

0:33:05.160 --> 0:33:08.320
<v Speaker 2>cooling down and getting more dilute. To run the clock backwards,

0:33:08.520 --> 0:33:11.760
<v Speaker 2>the universe gets hotter and denser, and we can run

0:33:11.840 --> 0:33:13.680
<v Speaker 2>backwards to a certain point what we call the plank

0:33:13.760 --> 0:33:16.640
<v Speaker 2>time beyond which we know our theories don't work, and

0:33:16.640 --> 0:33:18.800
<v Speaker 2>so everything is a question mark. And that's what we

0:33:18.840 --> 0:33:21.720
<v Speaker 2>call the Big Bang is expansion from that moment. So

0:33:21.760 --> 0:33:24.320
<v Speaker 2>it's a description of when the universe had very high

0:33:24.520 --> 0:33:28.560
<v Speaker 2>energy density. It's not a tiny dot in empty space.

0:33:28.800 --> 0:33:31.080
<v Speaker 2>The idea of a big bang, especially if you compare

0:33:31.160 --> 0:33:33.880
<v Speaker 2>to particle collisions, makes it sound like something happening at

0:33:33.960 --> 0:33:37.520
<v Speaker 2>one location, but the Big Bang was everywhere, and so

0:33:37.560 --> 0:33:40.400
<v Speaker 2>the similarity between particle collisions and the Big Bang is

0:33:40.440 --> 0:33:43.520
<v Speaker 2>that both have high energy density. Particle collisions of course,

0:33:43.560 --> 0:33:46.960
<v Speaker 2>though in just one spot, the Big Bang was everywhere.

0:33:46.960 --> 0:33:49.719
<v Speaker 1>Got it? Okay? And what kind of scale difference are

0:33:49.760 --> 0:33:52.080
<v Speaker 1>we talking about in terms of energy between big and

0:33:52.160 --> 0:33:52.880
<v Speaker 1>tiny bangs?

0:33:53.600 --> 0:33:56.520
<v Speaker 2>Yeah, so it's a pretty big difference. We compare these

0:33:56.520 --> 0:34:00.120
<v Speaker 2>things in a weird unit called electron volts, and it's

0:34:00.120 --> 0:34:02.520
<v Speaker 2>sort of a generic unit of energy. You can also

0:34:02.600 --> 0:34:04.720
<v Speaker 2>use it to measure mass, because we don't care about

0:34:04.760 --> 0:34:07.240
<v Speaker 2>things like the speed of light, and so an electron

0:34:07.320 --> 0:34:09.359
<v Speaker 2>volt is our unit, and to calibrate. For example, a

0:34:09.360 --> 0:34:13.080
<v Speaker 2>proton has a mass of one giga electron vault, so

0:34:13.200 --> 0:34:16.040
<v Speaker 2>a billion electron volts is the mass of a proton,

0:34:16.320 --> 0:34:19.279
<v Speaker 2>and collisions that we can achieve here on Earth are

0:34:19.320 --> 0:34:22.439
<v Speaker 2>in the scale of ten tarra electron vaults, so ten

0:34:22.560 --> 0:34:26.520
<v Speaker 2>thousand times the mass of a proton. And that sounds

0:34:26.520 --> 0:34:30.160
<v Speaker 2>pretty big, right, like ooh wow tarra Like that's a big.

0:34:30.040 --> 0:34:31.840
<v Speaker 1>Number, But protons are pretty small.

0:34:32.400 --> 0:34:36.120
<v Speaker 2>Protons are pretty small, exactly, And so the energy of

0:34:36.160 --> 0:34:38.400
<v Speaker 2>the Big Bang in the same units is ten to

0:34:38.440 --> 0:34:42.640
<v Speaker 2>the sixteen terra electron vaults, so ten to the fifteen

0:34:42.719 --> 0:34:46.560
<v Speaker 2>times more energy than the collisions we have at the LHC.

0:34:46.640 --> 0:34:49.040
<v Speaker 2>And ten of the fifteen is not a small number,

0:34:49.280 --> 0:34:52.719
<v Speaker 2>you know, it's not fifteen times. It's ten to fifteen

0:34:53.160 --> 0:34:57.080
<v Speaker 2>ten with fifteen zeros. If your bank account had one

0:34:57.160 --> 0:35:00.799
<v Speaker 2>with fifteen zeros in it, you'd be very very rich,

0:35:00.960 --> 0:35:03.800
<v Speaker 2>much much much richer than Elon Musk, probably like Elon

0:35:03.880 --> 0:35:07.560
<v Speaker 2>Musk squared. So it's very very high energy.

0:35:07.840 --> 0:35:11.080
<v Speaker 1>If particle physicists had enough money, would you guys try

0:35:11.120 --> 0:35:13.120
<v Speaker 1>to make a particle collider you could do the Big

0:35:13.160 --> 0:35:17.400
<v Speaker 1>Bang in because I'm not sure we can trust.

0:35:17.120 --> 0:35:19.520
<v Speaker 2>You, guys, No, I think we would. And you know,

0:35:19.680 --> 0:35:22.640
<v Speaker 2>the higher the energy collision, the more stuff you can make.

0:35:22.920 --> 0:35:24.920
<v Speaker 2>Right we don't know what's out there in the sort

0:35:24.920 --> 0:35:28.759
<v Speaker 2>of universe's menu of particles. And the incredible thing about

0:35:28.800 --> 0:35:31.399
<v Speaker 2>these collisions is that you pour energy in and there's

0:35:31.400 --> 0:35:35.320
<v Speaker 2>some sort of like quantum mechanical magic alchemy that happens,

0:35:35.440 --> 0:35:38.279
<v Speaker 2>and the universe decides what from its menu to make,

0:35:38.600 --> 0:35:40.560
<v Speaker 2>and it just sort of picks randomly from all the

0:35:40.560 --> 0:35:43.160
<v Speaker 2>things that it can make, which means that if you

0:35:43.160 --> 0:35:46.080
<v Speaker 2>pour enough energy into the collisions, you'll see everything the

0:35:46.239 --> 0:35:49.160
<v Speaker 2>universe is capable of making. If you do it often enough,

0:35:49.280 --> 0:35:51.440
<v Speaker 2>you don't even have to know what's out there. So

0:35:51.480 --> 0:35:54.360
<v Speaker 2>it's like a way to explore the capacity of the

0:35:54.480 --> 0:35:57.560
<v Speaker 2>universe without even knowing what it's capable of. You don't

0:35:57.560 --> 0:35:59.799
<v Speaker 2>have to leave your house. It's like, hey, make me

0:36:00.080 --> 0:36:03.560
<v Speaker 2>everything you can make right here. And as you turn

0:36:03.719 --> 0:36:06.600
<v Speaker 2>up that energy, you get to explore higher and higher

0:36:06.640 --> 0:36:09.640
<v Speaker 2>on nature's menu. And you could be just below the

0:36:09.680 --> 0:36:11.680
<v Speaker 2>threshold and not make the thing because they don't have

0:36:11.760 --> 0:36:13.799
<v Speaker 2>enough energy, and then you crank up the energy and

0:36:13.840 --> 0:36:16.160
<v Speaker 2>boom it starts to pop out. So Yeah, we'd love

0:36:16.320 --> 0:36:18.880
<v Speaker 2>to crank up the energy these things. We're still a

0:36:18.880 --> 0:36:21.560
<v Speaker 2>factor of ten to fifteen away from the Big Bang,

0:36:21.600 --> 0:36:24.160
<v Speaker 2>which means there could be particles that were made in

0:36:24.200 --> 0:36:28.080
<v Speaker 2>the early universe and they're super duper massive and we

0:36:28.160 --> 0:36:29.880
<v Speaker 2>haven't been able to make them yet. They could be

0:36:29.920 --> 0:36:32.480
<v Speaker 2>made in collisions of cosmic rays in the atmosphere, but

0:36:32.520 --> 0:36:34.680
<v Speaker 2>they're very short lived and we don't have detectors up

0:36:34.719 --> 0:36:35.720
<v Speaker 2>there to see them.

0:36:35.880 --> 0:36:38.359
<v Speaker 1>So check out Daniels go fundme for the next big

0:36:38.400 --> 0:36:39.280
<v Speaker 1>particle collider.

0:36:40.440 --> 0:36:43.360
<v Speaker 2>Leon artists question also asked, can we measure particle collisions

0:36:43.360 --> 0:36:46.240
<v Speaker 2>in terms of milli or fempto bangs? And the answer

0:36:46.280 --> 0:36:49.239
<v Speaker 2>is yes. So if you define one bang as ten

0:36:49.280 --> 0:36:52.560
<v Speaker 2>to the sixteen TeV, then the Large Hadron Collider has

0:36:52.560 --> 0:36:55.520
<v Speaker 2>collisions at about ten of the minus fifteen bangs or

0:36:55.640 --> 0:36:59.480
<v Speaker 2>one femto bang, which, yeah, doesn't sound very impressive and

0:37:00.160 --> 0:37:03.360
<v Speaker 2>not a great way to headline your science funding request.

0:37:03.680 --> 0:37:05.920
<v Speaker 1>I don't know. I think femto bang sounds pretty.

0:37:05.640 --> 0:37:08.640
<v Speaker 2>Cool, but it's also a way to sort of trace

0:37:08.719 --> 0:37:11.440
<v Speaker 2>back the history of the universe. Like as the energy

0:37:11.440 --> 0:37:13.759
<v Speaker 2>of your collisions goes up and up and up, you

0:37:13.840 --> 0:37:17.960
<v Speaker 2>recreate conditions that existed everywhere in the universe further and

0:37:18.040 --> 0:37:22.520
<v Speaker 2>further back in time and already ten TV one. Femto

0:37:22.560 --> 0:37:25.200
<v Speaker 2>bang is pretty high energy. It takes you all the

0:37:25.200 --> 0:37:28.719
<v Speaker 2>way back to like microseconds after the Big Bang because

0:37:28.719 --> 0:37:31.960
<v Speaker 2>the energy started to fall off really really quickly. It

0:37:32.000 --> 0:37:34.719
<v Speaker 2>becomes more gradual as time goes on. So we are

0:37:34.800 --> 0:37:39.320
<v Speaker 2>probing conditions in a very very early universe microseconds after

0:37:39.360 --> 0:37:39.960
<v Speaker 2>the Big Bang.

0:37:40.160 --> 0:37:43.520
<v Speaker 1>Well, let's see if Leonardo is impressed by femto bangs.

0:37:45.239 --> 0:37:48.399
<v Speaker 6>Hello, I'm also in teen Kelly, I'm also impressed by

0:37:48.600 --> 0:37:53.560
<v Speaker 6>fento bank. Also, thanks for clarifying the differences between a

0:37:53.680 --> 0:37:57.600
<v Speaker 6>particle collider and the early universe. I actually never considered

0:37:57.680 --> 0:38:00.360
<v Speaker 6>that there could have been particle so massive. If that

0:38:00.680 --> 0:38:04.040
<v Speaker 6>we will likely never be able to recreate. Thanks.

0:38:04.600 --> 0:38:07.680
<v Speaker 2>All right, and today we have a special bonus question

0:38:08.200 --> 0:38:12.799
<v Speaker 2>on gravitational and velocity based time dilation from ASTHMT. We

0:38:12.880 --> 0:38:15.800
<v Speaker 2>decided we could squeeze in a fourth question for y'all,

0:38:16.120 --> 0:38:19.080
<v Speaker 2>So here's Ozma's question about time dilation.

0:38:19.800 --> 0:38:22.920
<v Speaker 7>Hello, I'm a smith, and my question is what would

0:38:22.920 --> 0:38:26.160
<v Speaker 7>happen to time dialation if both high velocity and strong

0:38:26.200 --> 0:38:30.360
<v Speaker 7>magnetic feeling interacted simultaneously. Would this cost time to slow

0:38:30.400 --> 0:38:34.160
<v Speaker 7>down even more significantly or would there be no additional effect?

0:38:34.600 --> 0:38:34.960
<v Speaker 7>Thank you?

0:38:35.680 --> 0:38:38.600
<v Speaker 1>All right? So Daniel, I have been listening, well you talk,

0:38:38.719 --> 0:38:41.600
<v Speaker 1>and I remember you told me there's two kinds of

0:38:41.640 --> 0:38:46.680
<v Speaker 1>time dilation, gravity and velocity. But my brain is a sieve,

0:38:47.120 --> 0:38:49.759
<v Speaker 1>so remind me what the difference between those is.

0:38:50.480 --> 0:38:53.719
<v Speaker 2>Right, So there are two ways that clocks can appear slow. Now,

0:38:53.800 --> 0:38:57.200
<v Speaker 2>clocks that you hold, that you have with you always

0:38:57.280 --> 0:39:01.040
<v Speaker 2>run the same speed. But if Kelly gives Zach clock

0:39:01.160 --> 0:39:02.920
<v Speaker 2>and then shoots them out of a cannon a very

0:39:03.000 --> 0:39:06.160
<v Speaker 2>high speed relative to her, she will see Zach's clock

0:39:06.280 --> 0:39:12.520
<v Speaker 2>running slow because velocity time dilation says moving clocks run slow. Now, Zach,

0:39:12.600 --> 0:39:14.920
<v Speaker 2>with this telescope looking back at Kelly's clock, will disagree.

0:39:14.960 --> 0:39:17.719
<v Speaker 2>He'll say, no, no, Kelly's clock is running slow. So that

0:39:17.840 --> 0:39:22.320
<v Speaker 2>kind of time dilation is symmetric, meaning both wiener Smith's

0:39:22.480 --> 0:39:25.359
<v Speaker 2>see the other one's clock running slow. And at least

0:39:25.400 --> 0:39:27.600
<v Speaker 2>to this sort of confusion like whose clock is really

0:39:27.640 --> 0:39:30.360
<v Speaker 2>slower and the answer is there is no really slower,

0:39:30.360 --> 0:39:33.279
<v Speaker 2>they can argue forever and both be right. So it's

0:39:33.320 --> 0:39:35.239
<v Speaker 2>sort of a marital trap for the two of them.

0:39:35.400 --> 0:39:36.200
<v Speaker 1>Yeah, that's not great.

0:39:37.840 --> 0:39:41.640
<v Speaker 2>But the other kind of time dilation, gravitational time dilation,

0:39:42.280 --> 0:39:45.520
<v Speaker 2>is asymmetric, which means everybody can agree on it. So,

0:39:45.600 --> 0:39:48.680
<v Speaker 2>for example, if Kelly does drop Zach near a black hole,

0:39:49.000 --> 0:39:51.759
<v Speaker 2>she'll see his clock running slower, but he will see

0:39:51.760 --> 0:39:55.600
<v Speaker 2>her clock running faster. They agree in this scenario, but

0:39:55.680 --> 0:39:58.239
<v Speaker 2>whose clock is running slower or faster? Both of them

0:39:58.280 --> 0:40:01.160
<v Speaker 2>see their own clocks running at normal speed. And so

0:40:01.200 --> 0:40:03.799
<v Speaker 2>the cool thing here, and this is Ozma's question, is like,

0:40:03.840 --> 0:40:07.400
<v Speaker 2>what happens when you have both? Do they constructively interfered,

0:40:07.400 --> 0:40:10.360
<v Speaker 2>destructively interfered to his universe? Explode? What happens?

0:40:10.840 --> 0:40:13.160
<v Speaker 1>I hope The answer is Kelly is right. Whatever time

0:40:13.280 --> 0:40:15.359
<v Speaker 1>Kelly says is the correct time.

0:40:18.080 --> 0:40:22.520
<v Speaker 2>The answer is they both contribute. So let's say, for example,

0:40:22.760 --> 0:40:26.719
<v Speaker 2>that Kelly launches Zach into orbit. Right now, Zach is

0:40:26.760 --> 0:40:30.520
<v Speaker 2>going really, really fast, and so his velocity means that

0:40:30.600 --> 0:40:34.080
<v Speaker 2>his clock runs slower than clocks we have here on

0:40:34.160 --> 0:40:37.759
<v Speaker 2>Earth from our point of view. Okay, but he's also

0:40:38.080 --> 0:40:41.440
<v Speaker 2>further from the gravitational well of the Earth, so his

0:40:41.520 --> 0:40:45.799
<v Speaker 2>clocks will run faster than ours. Because of the gravitational

0:40:45.840 --> 0:40:49.000
<v Speaker 2>time dilation is less so we have actually gravitational time

0:40:49.000 --> 0:40:51.640
<v Speaker 2>dilation right here on the surface of the Earth. Because

0:40:51.719 --> 0:40:54.240
<v Speaker 2>of the Earth, we're all experiencing it all the time.

0:40:54.560 --> 0:40:57.480
<v Speaker 2>Clocks out in deep space run faster. So from Kelly's

0:40:57.520 --> 0:41:01.040
<v Speaker 2>point of view, Zach's clock runs slower because of velocity

0:41:01.440 --> 0:41:05.280
<v Speaker 2>and faster because of gravity, and the gravity actually wins out.

0:41:05.560 --> 0:41:08.879
<v Speaker 2>So the velocity time delation is like seven microseconds per

0:41:09.000 --> 0:41:12.919
<v Speaker 2>day if he's up with GPS satellites, and forty five

0:41:13.080 --> 0:41:17.080
<v Speaker 2>microseconds per day the other direction due to gravity. So

0:41:17.360 --> 0:41:19.000
<v Speaker 2>overall gravity wins.

0:41:19.239 --> 0:41:22.400
<v Speaker 1>So when I shoot him into orbit, because gravity is

0:41:22.440 --> 0:41:25.319
<v Speaker 1>winning and it makes things faster, he should still be

0:41:25.400 --> 0:41:27.480
<v Speaker 1>on time or early to the meetings. I let no

0:41:27.560 --> 0:41:29.040
<v Speaker 1>excuse for being late, Is that right?

0:41:30.400 --> 0:41:32.200
<v Speaker 2>I really feel like I don't want to get in

0:41:32.200 --> 0:41:35.279
<v Speaker 2>the middle of here. Physics is not going to solve

0:41:35.320 --> 0:41:36.080
<v Speaker 2>your marital.

0:41:35.800 --> 0:41:39.120
<v Speaker 1>Problems, all right, all right, but baby sandwiches, well.

0:41:40.520 --> 0:41:44.040
<v Speaker 2>Sandwiches yet well exactly now, from Zach's point of view,

0:41:44.560 --> 0:41:48.120
<v Speaker 2>both of the effects make Earth's clocks slower. It's fascinating

0:41:48.160 --> 0:41:49.800
<v Speaker 2>because from the Earth's point of view, we see the

0:41:49.840 --> 0:41:53.160
<v Speaker 2>effects having different directions. But from Zach's point of view,

0:41:53.200 --> 0:41:56.040
<v Speaker 2>he sees both effects having the same direction. He sees

0:41:56.120 --> 0:41:59.080
<v Speaker 2>us moving quickly, which means our clocks run slow, and

0:41:59.239 --> 0:42:02.800
<v Speaker 2>he sees a closer to a gravitational well of the earth,

0:42:03.000 --> 0:42:05.000
<v Speaker 2>which means our clocks run slow.

0:42:05.280 --> 0:42:06.919
<v Speaker 1>Oh see, now, I feel like you're citing with zech.

0:42:10.120 --> 0:42:11.040
<v Speaker 1>This is no excuse.

0:42:11.120 --> 0:42:12.640
<v Speaker 2>I feel like I need my lawyer present.

0:42:15.360 --> 0:42:17.759
<v Speaker 1>All right, everybody, thanks for playing. Just a reminder that

0:42:17.800 --> 0:42:21.200
<v Speaker 1>you too can send us questions at questions at danielant

0:42:21.280 --> 0:42:24.000
<v Speaker 1>Kelly dot org. We answer every question, some of them

0:42:24.080 --> 0:42:25.680
<v Speaker 1>end up on the show and we can't wait to

0:42:25.680 --> 0:42:26.120
<v Speaker 1>hear from you.

0:42:26.400 --> 0:42:29.400
<v Speaker 2>And some of our questions come from conversations on the discord.

0:42:29.440 --> 0:42:32.399
<v Speaker 2>We encourage you to join our discord, where people ask

0:42:32.480 --> 0:42:34.840
<v Speaker 2>and answer questions and make a bunch of nerdy jokes.

0:42:35.040 --> 0:42:37.360
<v Speaker 2>You can find the invitation on our website Daniel and

0:42:37.480 --> 0:42:38.480
<v Speaker 2>Kelly dot org.

0:42:45.719 --> 0:42:49.560
<v Speaker 1>Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We

0:42:49.600 --> 0:42:52.000
<v Speaker 1>would love to hear from you, We really would.

0:42:52.160 --> 0:42:54.920
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0:42:55.120 --> 0:42:56.800
<v Speaker 2>Extraordinary Universe.

0:42:56.920 --> 0:42:59.799
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0:42:59.840 --> 0:43:02.879
<v Speaker 1>for future shows. If you contact us, we will get

0:43:02.920 --> 0:43:03.319
<v Speaker 1>back to you.

0:43:03.560 --> 0:43:07.040
<v Speaker 2>We really mean it. We answer every message, email us

0:43:07.080 --> 0:43:09.920
<v Speaker 2>at Questions at Danielankelly dot.

0:43:09.719 --> 0:43:11.560
<v Speaker 1>Org, or you can find us on social media. We

0:43:11.640 --> 0:43:15.520
<v Speaker 1>have accounts on x, Instagram, Blue Sky and on all

0:43:15.560 --> 0:43:17.840
<v Speaker 1>of those platforms. You can find us at D and

0:43:18.280 --> 0:43:19.320
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0:43:19.440 --> 0:43:20.960
<v Speaker 2>Oh be shy right to us