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

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

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Speaker 1: It depends particle colliders make mini booms. The big Bang

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Speaker 1: filled the whole room.

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Speaker 2: Biology, physics, archaeology, and forestry. Thank you for not asking

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Speaker 2: about chemistry.

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Speaker 1: What diseases you get from your cats? We'll find answers

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Speaker 1: to all of that.

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Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's

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Speaker 2: answers will make it all right.

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Speaker 1: Welcome to another Listener Questions episode on Daniel and Kelly's

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

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Speaker 1: and I'm excited to learn more about black holes today.

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Speaker 2: Hi. I'm Daniel. I'm a particle physicist and I love cats,

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Speaker 2: though I don't have nearly as many pets as exist

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Speaker 2: on the Wienersmith Farm.

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

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Speaker 1: cat person rather than a dog person, Is that what

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Speaker 1: I'm hearing?

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Speaker 2: Well, I grew up with cats, always loved cats, but

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Speaker 2: my daughter is allergic cats. So now we have a

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Speaker 2: dog and love my dog of course, and so kind

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Speaker 2: of a dog person now but my daughter is getting

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Speaker 2: shots so that she can tolerate cats, and we're hoping

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Speaker 2: to get a cat soon.

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Speaker 1: Oh exciting. Now are you going to adopt that cat?

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Speaker 1: Where are you going to get the cat from?

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Speaker 2: It? Was that? Or create the cat in collisions at

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Speaker 2: the large hadron collider? So probably going to adopt it.

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Speaker 1: Yeah, excellent. Well, we have a growing number of cats

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Speaker 1: because we live on a farm in the woods and

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Speaker 1: they find us and then they move in and I

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Speaker 1: can never kick them out. We almost ended up with

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Speaker 1: three beagles because they were also like dropped on the

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Speaker 1: property and well saying no more animals. I am like

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Speaker 1: simultaneously dumping pile of food in front of them. I

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Speaker 1: can't help myself.

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Speaker 2: Oh I see that was the other option. The option

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Speaker 2: is adopt cats or have them adopt you, which is

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Speaker 2: what you're doing on the farm.

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Speaker 1: Yep, yep, although the goats I think I will be

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Speaker 1: purchasing directly.

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Speaker 2: Well, there's some sort of gravitational cat hole effect there,

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Speaker 2: I think, because the more cats you get, the more

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Speaker 2: they attract more cats, and then cats hear about your

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

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Speaker 2: pretty soon you're gonna be a cat lady.

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

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Speaker 1: Have you heard about chicken math?

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Speaker 2: Tell me about chicken math.

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Speaker 1: It's when you decide you're going to get four chickens

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Speaker 1: because it's not really that much work. So you actually

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Speaker 1: get ten chickens, and then before you know what, the

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Speaker 1: order you put in actually had a four in the front,

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

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Speaker 1: duck math recently, and so now we have five ducks

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Speaker 1: and two geese coming. My husband's not excited about the geese.

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Speaker 1: We decided we were gonna name the geese Jacques Gusta

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Speaker 1: and franc Scene Gusto. I think Jacques had two wives.

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Speaker 1: One of them was Franccene. Anyway, we're very excited.

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Speaker 2: Well, at least you have control over the names of

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Speaker 2: the pets, even if not the species or number of them.

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Speaker 2: Gives you a little bit of illusion of control.

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Speaker 1: That's right. All that matters is that they let me

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Speaker 1: snuggle them.

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Speaker 2: And in this crazy universe that can sometimes feel out

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Speaker 2: of our control, one way we can sort of establish

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Speaker 2: a little bit of a finger hold on sanity is

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Speaker 2: to think about the universe and try to understand it,

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Speaker 2: try to grapple with the mysteries of the cosmos, and

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Speaker 2: the best way to do that is to start by

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Speaker 2: asking questions. Questions we have and questions that you have.

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Speaker 1: Chicken math might not make sense, but Daniel and Kelly's

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Speaker 1: answers do. So if you would like to submit your

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Speaker 1: questions about the universe, write us at questions at danielands

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Speaker 1: Kelly dot org. And it might take us a little

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Speaker 1: while before your answer airs, because we are actually fairly

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Speaker 1: well organized and we're about two months ahead of schedule,

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Speaker 1: and we've got a bit of a list of questions.

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Speaker 1: But you will get an answer from us, for sure.

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Speaker 1: We respond to everyone that's.

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Speaker 2: Right right to us with your questions at questions at

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Speaker 2: Daniel and Kelly dot org. Everyone gets an answer, and

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Speaker 2: some people get on the podcast. And today we have

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Speaker 2: questions from three listeners about black holes, about furry pets,

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Speaker 2: and about tiny little bangs. Our first question comes from

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Speaker 2: Mark from Ireland about black holes. Here's Mark's question.

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Speaker 3: Hi, Daniel and Kelly, this is Mark from Ireland and

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Speaker 3: I have a question about merging black holes. When two

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Speaker 3: black holes spiral towards each other to merge, they lose

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Speaker 3: mass and in doing so, generates gravitational waves. The newly

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Speaker 3: formed black hole will have a mass less than the

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Speaker 3: sum of the two original black holes. My question is

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Speaker 3: what actual mass is converted into gravitational waves and how

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Speaker 3: does this happen? In trying to get my head around

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Speaker 3: this phenomenon, I see there are lots of other interesting

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Speaker 3: questions that might arise. Maybe you can explain the merging

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Speaker 3: process and detail. I really enjoy the podcast and look

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Speaker 3: forward to new episodes. Thank you and keep up the

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Speaker 3: good work.

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

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Speaker 1: we've never actually seen black holes collide and we are

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Speaker 1: guessing what happens, or have we seen black.

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Speaker 2: Holes Colyde, depends what you mean by seeing and black holes.

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

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Speaker 2: observed these ingravitational waves collisions of dozens and dozens of

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Speaker 2: pairs of black holes. Now it seems sort of fantastical

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Speaker 2: and science fiction y, but it's our reality.

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Speaker 1: Okay, So then what did you mean when you said

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Speaker 1: it depends what you mean by black holes and observe,

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Speaker 1: because it sounds like we have seen black holes collide.

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Speaker 2: Yeah, I think most people in astronomy would say that

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Speaker 2: we have seen black holes collide. Okay, but you know,

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

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Speaker 2: seen very dense, compact, dark objects which are consistent with

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Speaker 2: black holes collide, that we've never really observed the event

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Speaker 2: horizon directly, So there's an asterisk there on do we

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Speaker 2: really know black holes are black holes? And in terms

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Speaker 2: of seeing, we've observed the radiation generated by that collision,

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Speaker 2: and that's what today's question is all about, how those

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Speaker 2: black holes merge and the radiation they give off. So

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Speaker 2: we've observed that gravitational radiation and it looks exactly like

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Speaker 2: you would expect from black holes colliding. But I don't

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Speaker 2: know if that counts as seeing it because it's not

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Speaker 2: like visible light.

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

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Speaker 1: the basics. What's a black hole?

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Speaker 2: Right? So black hole famous prediction from classical general relativity. Right,

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Speaker 2: This is Einstein's theory that space is curved. Gravity is

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Speaker 2: not really a force. So what you think is gravity

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Speaker 2: is actually just the effect of space time being curved.

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Speaker 2: If you don't notice that space time is curved, it

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Speaker 2: looks like something is bending the light or changing the

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Speaker 2: path of the Earth. But it's actually just the curvature

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Speaker 2: of space time. Space time curves in response to mass,

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Speaker 2: and if you get enough mass in a small area,

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Speaker 2: it curves space time so much that things get trapped.

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

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Speaker 2: It's not like there's so much gravity it even pulls

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Speaker 2: on photon. It's that space itself is bent so that

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Speaker 2: inside a black hole, space only points towards the center.

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Speaker 2: And so this creates the phenomenon we call the event horizon,

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Speaker 2: beyond which anything that falls in is trapped. It will

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Speaker 2: only move towards the center of the black hole. And

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Speaker 2: so this is the defining feature of a black hole,

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Speaker 2: the event horizon. This is the thing we haven't actually

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Speaker 2: literally technically observed. We've seen lots of indirect evidence for

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Speaker 2: black holes, but never actually observe the event horizon. And

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

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Speaker 2: We can know the mass of the black hole, we

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Speaker 2: can know if it has electric charge, we can know

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

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Speaker 1: We've done eleven of these listener questions episodes so far.

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Speaker 1: In thinking back, I feel like most of them have

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Speaker 1: had at least a question about a black hole. What

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Speaker 1: do you think it is about black holes that keep

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Speaker 1: people up at night?

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Speaker 2: I think it's an incredible prediction of physics, something so

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Speaker 2: strange and beyond our intuition. But macroscopic, right, like quantum

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Speaker 2: mechanics makes all sorts of weirds about electrons, what they're

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

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Speaker 2: those because they're microscopic. You can never observe them. Black

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Speaker 2: holes are a prediction that are like technically you could

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Speaker 2: see you could be near a black hole and observe

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Speaker 2: it and see all this strange effects. So it feels

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

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Speaker 2: people are fascinated by black holes. It's a significant fraction

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Speaker 2: of the questions that we get are about black holes.

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Speaker 2: So yeah, absolutely, it's fantastic. It's wonderful. It's incredible that

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Speaker 2: we've actually seen them, and we've seen these collisions. I

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Speaker 2: remember in the late nineties deciding where to go to

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Speaker 2: graduate school and what to work on, and I had

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Speaker 2: an opportunity to work on this project Lego the gravitational

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Speaker 2: wave observatory, and they were looking to see these black

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Speaker 2: holes merging and the gravitational waves generated by them. And

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

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

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Speaker 2: And then of course they won the Nobel Prize. But

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Speaker 2: you know, hey, maybe if I had worked on it,

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Speaker 2: it wouldn't have worked out, and they wouldn't have won

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Speaker 2: a Nobel Prize. So maybe they won the Nobel Prize

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Speaker 2: because I didn't work on it.

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Speaker 1: Anyway, hard to say, do you ever regret not going

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Speaker 1: into black holes? Or are you totally happy with the

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Speaker 1: path your life took?

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Speaker 2: You know, there are always other options you could consider,

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Speaker 2: but I'm pretty happy with how everything worked out, and

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

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Speaker 2: But it is amazing that humanity has figured out a

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Speaker 2: way to observe these collisions. Einstein predicted this decades and

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Speaker 2: decades ago, but he thought it was going to be

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Speaker 2: impossible to observe because gravitational radiation is very, very weak,

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Speaker 2: because gravity itself is not very powerful, and so you

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Speaker 2: need an extraordinarily sensitive instrument to see this stretching and

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Speaker 2: squeezing of space time, this gravitational radiation, unless, of course,

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Speaker 2: you're right next to the black holes colliding, in which

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Speaker 2: case the signal is very powerful and you're probably dead.

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Speaker 1: I feel like that's another thing that gets people interested

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Speaker 1: in the idea that observing this could kill you, but

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Speaker 1: if you could survive what's on the other side, I

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

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Speaker 1: observed collisions, and you said that we've observed a lot

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Speaker 1: of them, and.

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Speaker 2: It was a little bit of a surprise when we

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Speaker 2: saw the first one. You know, we didn't know how

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Speaker 2: often does this happen in the universe. We're building our

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Speaker 2: first eyeball for gravitational waves, and how long it takes

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Speaker 2: the sea one depends on how often they happen, and

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Speaker 2: there were lots of predictions. Some people predicted that it

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Speaker 2: would take decades to see one, but they saw one

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Speaker 2: almost immediately after turning the thing on, and everyone's like,

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Speaker 2: oh my gosh. Wow. So it turns out these collisions

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Speaker 2: happen more often than people suspected.

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Speaker 1: So does that mean we were totally off in our

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Speaker 1: predictions for how many black holes there are or how

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

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Speaker 2: So we're not sure. Black hole formation is still kind

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Speaker 2: of mystery. Super massive black holes or things we don't

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Speaker 2: really understand, so something we're still trying to understand and

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Speaker 2: we don't understand. Also the distribution of black hole masses.

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Speaker 2: There seem to be some smaller ones, some bigger ones,

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Speaker 2: but there aren't intermediate sized ones. So there's a lot

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

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Speaker 2: how often they're close to each other, right, this kind

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Speaker 2: of stuff, So a lot of really interesting astrophysics is

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Speaker 2: being opened up by this study.

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Speaker 1: No gold locks black holes, and Mark.

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Speaker 2: Is interested in what happens when these two black holes

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Speaker 2: form and where the mass goes, because you know, there's

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Speaker 2: nothing free in the universe. If two black holes collide

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Speaker 2: and produce gravitational waves, gravitational waves carry energy. They're stretching

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Speaker 2: and squeezing of space time, and that energy has to

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Speaker 2: come from somewhere, and it comes from the internal energy

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Speaker 2: of the black hole system. These two things are orbiting

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Speaker 2: each other and for them to collapse down into one,

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Speaker 2: they have to lose that angular momentum, so they radiate

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Speaker 2: it away in gravitational waves and Marx's questions trying to

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Speaker 2: understand where the mass goes, because the mass of the

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Speaker 2: resulting black hole is not just the sum of the

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Speaker 2: masses of the two black holes that go in. It's

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Speaker 2: smaller than that because energy is lost to gravitational waves.

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Speaker 1: And we have talked in other episodes about how energy

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Speaker 1: is mass, but maybe not. It's complicated, is that, right?

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Speaker 2: Yeah, Mass is a measure of internal stored energy. Right,

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Speaker 2: So like a proton's mass, it's not just the mass

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Speaker 2: of the stuff that makes it up. It's the mass

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Speaker 2: of the stuff that makes it up, plus the energy

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Speaker 2: they have relative to each other. In fact, most of

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Speaker 2: the mass of the proton comes from that energy, the

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Speaker 2: binding energy of the quarks together. So if you have

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Speaker 2: a black hole black hole system, two black holes orbiting

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Speaker 2: each other, the mass of the whole system is the

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Speaker 2: massive black hole one plus the massive black hole two

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Speaker 2: plus their relative energy, and that's a lot. There's a

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Speaker 2: lot of gravitational energy between those two black holes. Let's

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Speaker 2: say black hole one is forty masses of the Sun,

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Speaker 2: for example, and black hole two is thirty masses of

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Speaker 2: the Sun. These are typical numbers. Then the energy of

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Speaker 2: the whole system would be forty plus thirty plus whatever

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Speaker 2: energy they have in their relative rotation, and that could

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Speaker 2: be like thirty or forty or fifty, right, it depends

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Speaker 2: on the configuration. So the total energy of the system

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Speaker 2: could be much more than seventy. You could be one hundred,

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Speaker 2: one hundred and twenty, this kind of thing. But a

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Speaker 2: lot of that energy is lost when the two radiated

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Speaker 2: away in order to combine. They have to radiate away

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Speaker 2: some energy in order to combine, otherwise they would just

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Speaker 2: or bit forever.

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Speaker 1: And are they losing the energy of the black holes

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Speaker 1: or are they losing the energy that surrounds the black

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Speaker 1: holes or a little bit of both.

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Speaker 2: Yeah, So this is a great question. And this is

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Speaker 2: what Mark is asking, is like he wants to do

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Speaker 2: some accounting. Is their mass actually lost? And I think

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Speaker 2: he's interested in this because people think of black holes

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Speaker 2: as something that can never lose mass, right at least

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Speaker 2: in classical general relativity, And so he's wondering, like, is

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Speaker 2: this a way for mass to escape somehow the black holes?

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Speaker 2: And it's a little bit tricky. There's a couple of

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Speaker 2: things to keep in mind. So the final black hole

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Speaker 2: is smaller than the sum of the two original black holes,

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Speaker 2: but always larger than either of them. So neither black

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Speaker 2: hole shrinks. Both black holes grow.

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Speaker 1: Nope, no, no, no, You've lost me. Don't they become

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Speaker 1: one black hole when they merge.

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Speaker 2: Yes, they become one black hole exactly, And so there's

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Speaker 2: no shrinking of the event horizon. Like the final event

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Speaker 2: horizon is bigger than either of the incoming event horizons. Okay,

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Speaker 2: so no event horizon is shrinking. It's not like you're

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Speaker 2: seeing behind the event horizon of either black hole. Both

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Speaker 2: of them are growing, right, but the final is smaller

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Speaker 2: than the sum of the two parts. It feels trickier.

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Speaker 2: It feels like I'm cheating.

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Speaker 1: Yes, so I guess what I'm not following is Okay,

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Speaker 1: when they merge, I no longer think of them as

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Speaker 1: two separate parts. They're just one part. But it sounds

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Speaker 1: like you are still trying to keep accounting on two parts,

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Speaker 1: but now they've become one. So what am I missing?

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Speaker 2: Yeah? I think think about it from the point of

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Speaker 2: view of black hole one. Okay, black Hole one has

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Speaker 2: an event horizon, and it has a certain mass, and

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Speaker 2: you could just be in its reference frame and it

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Speaker 2: has another black hole orbiting it, right, and then that

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Speaker 2: black hole radiates some energy and falls in and it

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Speaker 2: gets gobbled up. Black Hole one grows. Right, So we

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Speaker 2: followed all the rules of general relativity. The event horizon

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Speaker 2: is not shrunk because it can never shrink, because if

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Speaker 2: it did, you'd see things inside the event horizon. It

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Speaker 2: has grown. Its mass has gone up. Right, in classical

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Speaker 2: general relativity, black hole masses can only go up. So

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Speaker 2: from the point of view of black hole one, the

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Speaker 2: fact that black hole two is a black hole is

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Speaker 2: kind of irrelevant. It's eaten some energy and it's grown.

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Speaker 2: You can play the same game from the point of

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Speaker 2: view a black hole two. Right, The thing is symmetric.

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Speaker 2: Black Hole two grows, it gains mass, it's eating black

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Speaker 2: hole one. The two merge. The final result is bigger

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Speaker 2: than black hole two. Everything is happy from a general

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Speaker 2: relativity point of view.

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Speaker 1: Okay, so at the end you still have just one

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Speaker 1: black hole, but that one black hole is bigger than

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Speaker 1: black hole one or black hole two were originally.

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Speaker 2: Yes, exactly, Okay, and so it feels like mass has

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Speaker 2: been lost and we're playing some sort of shell game here.

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Speaker 2: I think there's another thing to understand that might help people,

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Speaker 2: which is, the mass of the black hole doesn't just

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Speaker 2: depend on what's beyond the event horizon. You can make

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Speaker 2: a black hole more massive without crossing the event horizon. So,

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Speaker 2: for example, say I shoot Kelly into orbit around a

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Speaker 2: black hole, hypothetically speaking, or Zach. Should we talk about Zaz? Yeah, yes,

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Speaker 2: of course Zach is in orbit around a black hole. Okay,

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Speaker 2: Now that black hole's mass grows even before Zach goes

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Speaker 2: over the event horizon. Right, you tend to think like, oh,

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Speaker 2: it's has to eat Zach before it grows to add

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Speaker 2: to its mass. But the mass is a measure of

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Speaker 2: the energy of the system, right, So the black hole's

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Speaker 2: mass actually grows before Zach falls over the event horizon.

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Speaker 1: So at what point does Zach become part of the

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Speaker 1: system mm.

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Speaker 2: Hmm, Well when he has a relationship to it, like

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Speaker 2: it's a gravitationally bound to it, than to an external

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Speaker 2: observer who's like a little bit further away, like it's

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Speaker 2: a black hole, Zach's system. The whole thing has more

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Speaker 2: mass than the black hole or than Zach does, and

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Speaker 2: so you don't have to like add stuff to the

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Speaker 2: black hole over the event horizon in order for the

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Speaker 2: black hole to gain in mass. This is actually crucial

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Speaker 2: for the way that black holes actually grow in the universe.

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Speaker 2: You might have heard, for example, if you do throw

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Speaker 2: your husband into a black hole, you'll never actually see

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Speaker 2: him cross the event horizon because time slows down. And

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Speaker 2: a lot of people write it and say, all right,

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Speaker 2: but then how do black holes actually grow if nothing

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Speaker 2: can cross the event horizon because time slows down. But

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Speaker 2: the answer is that the event horizon grows before Zack

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Speaker 2: reaches it. It grows out to meet him. He and

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Speaker 2: the event horizon approach each other. And so if Zach

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Speaker 2: was the last thing you ever threw into a black hole,

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Speaker 2: it's true that he would never cross it, you'd never

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Speaker 2: see him. But if after you throw Zach into a

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Speaker 2: black hole, you feel bad and you throw him a sandwich,

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Speaker 2: and that sandwich approaches the black hole, and as it

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Speaker 2: approaches the black hole, it pulls the event horizon over Zack, right,

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Speaker 2: because the event horizon comes out to meet the thing

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Speaker 2: that's approaching it. Because again, the mass of the black

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Speaker 2: hole depends on the stored energy, which includes the gravitational

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Speaker 2: energy it has with things around it. So you shouldn't

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Speaker 2: think of these things as just like boxes, right, Remember,

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Speaker 2: mass it's not just like a measure of how much

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Speaker 2: stuff is inside the black hole. It's a more comprehensive

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Speaker 2: measure of the energy of that whole system. You don't

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Speaker 2: have to be over the event horizon in order to

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Speaker 2: be part of that system.

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Speaker 1: So one, the next time you say biology is complicated,

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Speaker 1: I'm going to just start laughing right away. But okay. Two,

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Speaker 1: So if you threw Zach ten thousand sandwiches because you

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Speaker 1: are like you're going to be there for a while,

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Speaker 1: would the event horizon pass Zach faster than if you

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Speaker 1: just threw him one sandwich because you don't really care

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Speaker 1: about what happens in the long run.

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Speaker 2: Mm hmm, yeah, absolutely, okay. And if you threw them

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Speaker 2: in a series, then chicken sandwich number one would pass first,

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Speaker 2: chicken sandwich number two, then chicken number three, and the

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Speaker 2: last chicken sandwich would not cross the event horizon. So

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Speaker 2: it's true, you can't see something cross the event horizon

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Speaker 2: if it's the last thing that you throw. But in

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Speaker 2: our universe there's never a last thing. There's always like

388
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Speaker 2: more gas and more particles. And that's how black holes

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Speaker 2: in the universe actually grow, all right, But back to

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Speaker 2: Mark's question, what's going on here is that the mass

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Speaker 2: of the whole system. Right, Let's say we start with

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Speaker 2: our example of a forty and a thirty black hole,

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Speaker 2: and together they have a mass of like one hundred

394
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Speaker 2: and twenty, right, including all gravitational energy and rotational energy.

395
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Speaker 2: As they inspirle, they radiate away a bunch of that energy.

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Speaker 2: So the mass of the system was one twenty. It's

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Speaker 2: radiated away I don't know sixty. So now the final

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Speaker 2: black hole is sixty instead of one twenty. So sixty

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Speaker 2: is bigger than forty and bigger than thirty, but smaller

400
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Speaker 2: than forty plus thirty. But all that's happened is that

401
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Speaker 2: some of that rotational gravitational energy has been radiated away.

402
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Speaker 2: So even though the whole system started out with mass

403
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Speaker 2: of one twenty, now it's down to sixty because it's

404
00:19:30,960 --> 00:19:33,919
Speaker 2: radiated away half of its energy. I'm just making up

405
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Speaker 2: these numbers. They're roughly correct in the order of magnitude,

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Speaker 2: but I haven't done like any calculations. But that's the

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00:19:38,800 --> 00:19:40,159
Speaker 2: right way to think about it as the energy of

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Speaker 2: the whole system.

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Speaker 1: All right, Well, I think I understand black holes better now,

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Speaker 1: although I say that after every explanation and then I

411
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Speaker 1: get things wrong the next time we talk about it.

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Speaker 1: But let's see what Mark from Ireland thinks of that explanation.

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Speaker 3: Hi, Daniel and Kelly, thank you very much for that

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Speaker 3: very informative answer to mike question. I think black holes

415
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Speaker 3: are really amazing, and merging black holes are even more amazing.

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Speaker 3: It's incredible that during the final fifth of a second

417
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Speaker 3: of their inward spiral, that they are flying around one

418
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Speaker 3: another at near relativistic speeds, often up to a rate

419
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Speaker 3: of two hundred and fifty orbits a second, and radiate

420
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Speaker 3: the equivalent of multiple solar masses of energy in the

421
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Speaker 3: former gravitational waves. It really is crazy, crazy physics. Well,

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Speaker 3: you've answered my questions very well, and thank you both

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Speaker 3: for taking the time to do so. I'm sure you'll

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Speaker 3: hear from me again at some stage in the future,

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Speaker 3: and in the meantime, I'm going to keep listening in.

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Speaker 1: All right, So now we are onto by all, from

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Speaker 1: black holes to black spots. We are talking about patterns

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Speaker 1: on our furry friends. Let's hear what Simon from Germany

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Speaker 1: wanted to know about.

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Speaker 4: Hi, Daniel N. Kelly Simon here from Germany. Thanks for

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Speaker 4: a great podcast. They're a fine background to my daily

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Speaker 4: run in the woods. I have a question here for Kelly,

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Speaker 4: one that has puzzled me for quite some time, and

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Speaker 4: it's in relation to the coloration of our furry friends.

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Speaker 4: So if we take a dog, for example, who is

436
00:21:29,400 --> 00:21:33,280
Speaker 4: black and white, and we zoom into the border between

437
00:21:33,320 --> 00:21:37,000
Speaker 4: the two colors, presumably we have one skin cell or

438
00:21:37,119 --> 00:21:41,640
Speaker 4: hair cell with black pigmentation and the neighboring cell as

439
00:21:41,680 --> 00:21:46,440
Speaker 4: a white pigmentation. The question is how is this information

440
00:21:46,640 --> 00:21:51,680
Speaker 4: passed down? Presumably the information is contained in a precursor cell,

441
00:21:51,720 --> 00:21:54,160
Speaker 4: one splitting into a black and one into a white.

442
00:21:54,400 --> 00:21:57,800
Speaker 4: The question is what is the mechanism for this? Thanks

443
00:21:57,840 --> 00:21:59,960
Speaker 4: for a great podcast, guys, Keep up the good work,

444
00:22:00,040 --> 00:22:03,359
Speaker 4: and I look forward to hearing some insight into this question.

445
00:22:03,960 --> 00:22:07,160
Speaker 2: See biology also has really massively important questions.

446
00:22:07,520 --> 00:22:08,719
Speaker 1: Are you being facetious?

447
00:22:08,760 --> 00:22:11,880
Speaker 2: I can't tell no, I'm trying to make a gravitational pun.

448
00:22:12,080 --> 00:22:15,000
Speaker 1: Oh good, excellent? Okay, sorry, went right over my head.

449
00:22:15,440 --> 00:22:19,000
Speaker 1: All right, So this was actually a fairly difficult question

450
00:22:19,240 --> 00:22:22,240
Speaker 1: to read about and to try to understand. And it's biology.

451
00:22:22,320 --> 00:22:23,720
Speaker 1: So it depends.

452
00:22:24,040 --> 00:22:25,720
Speaker 2: Let me see if I can interpret the question to

453
00:22:25,720 --> 00:22:28,120
Speaker 2: make sure I understand what he's asking. Okay, I think

454
00:22:28,119 --> 00:22:30,439
Speaker 2: he's basically trying to do some physics here, which is

455
00:22:30,480 --> 00:22:33,879
Speaker 2: to like zoom in on the microprocesses involved. He's like

456
00:22:34,240 --> 00:22:37,040
Speaker 2: looking at his dog and seeing there's white patches and

457
00:22:37,080 --> 00:22:40,560
Speaker 2: black patches and wondering like what makes one bit white

458
00:22:40,560 --> 00:22:42,359
Speaker 2: and one black? And he's trying to understand it by

459
00:22:42,400 --> 00:22:44,680
Speaker 2: zooming in on the boundary and saying like, there's got

460
00:22:44,720 --> 00:22:47,320
Speaker 2: to be a point where there's one cell that's white

461
00:22:47,359 --> 00:22:50,240
Speaker 2: and one cell that's black, and that's where the difference is.

462
00:22:50,280 --> 00:22:53,000
Speaker 2: And he wants to highlight like what's going on between

463
00:22:53,040 --> 00:22:56,320
Speaker 2: those cells to understand why one turns white and black,

464
00:22:56,520 --> 00:22:59,080
Speaker 2: but also obviously to zoom out and understand, like how

465
00:22:59,080 --> 00:23:00,200
Speaker 2: do you get these patterns?

466
00:23:00,600 --> 00:23:02,800
Speaker 1: Yes, And that's how I interpreted the question as well.

467
00:23:03,400 --> 00:23:06,679
Speaker 1: And the answer is that if you are looking at

468
00:23:06,680 --> 00:23:10,199
Speaker 1: animal patterns in general, it depends on the colors, it

469
00:23:10,240 --> 00:23:12,800
Speaker 1: depends on the pattern shape, it depends on the animal.

470
00:23:13,280 --> 00:23:18,479
Speaker 1: But Simon in particular referenced dogs and referenced white and black,

471
00:23:18,960 --> 00:23:21,000
Speaker 1: and so I decided that I was going to hone

472
00:23:21,040 --> 00:23:23,720
Speaker 1: in on that in particular, all right, because I needed

473
00:23:23,760 --> 00:23:27,560
Speaker 1: a foothold for this question. And so in dogs, there

474
00:23:27,560 --> 00:23:32,560
Speaker 1: are hair follicles or fur follicles that produce either black

475
00:23:32,680 --> 00:23:36,320
Speaker 1: or brown colors, or yellow or white colors. So one

476
00:23:36,440 --> 00:23:40,000
Speaker 1: follicle can produce either of those colors depending on the

477
00:23:40,000 --> 00:23:42,920
Speaker 1: instructions that it's given. So it's not like you have

478
00:23:43,080 --> 00:23:46,400
Speaker 1: different kinds of cells next to each other. It's all

479
00:23:46,480 --> 00:23:49,880
Speaker 1: the same cell, but it just is following different sets

480
00:23:49,880 --> 00:23:50,640
Speaker 1: of instructions.

481
00:23:51,040 --> 00:23:52,960
Speaker 2: So they're just like printers, and they can get an

482
00:23:52,960 --> 00:23:55,320
Speaker 2: instruction for a black hair or a white hair and

483
00:23:55,320 --> 00:23:56,119
Speaker 2: they're happy to do it.

484
00:23:56,400 --> 00:23:57,920
Speaker 1: That's right, Yes, exactly.

485
00:23:57,920 --> 00:23:59,679
Speaker 2: Interesting, So who sends the instructions?

486
00:24:00,119 --> 00:24:05,399
Speaker 1: So the instructions are encoded in a gene called a gooty,

487
00:24:05,800 --> 00:24:08,680
Speaker 1: and this gene is important for coloration in a lot

488
00:24:08,680 --> 00:24:13,760
Speaker 1: of different species, and the gene produces a hormone. The

489
00:24:13,800 --> 00:24:15,640
Speaker 1: hormone gets released from the cell.

490
00:24:15,800 --> 00:24:18,440
Speaker 2: I'm a little confused because a gene is part of

491
00:24:18,480 --> 00:24:21,200
Speaker 2: your DNA, and so when you're saying the gene produces

492
00:24:21,200 --> 00:24:24,120
Speaker 2: a hormone, do you mean the gene when it's transcribed

493
00:24:24,160 --> 00:24:27,560
Speaker 2: into a protein is that hormone or the gene when

494
00:24:27,560 --> 00:24:30,040
Speaker 2: transcribed into a protein. Is some little machine that makes

495
00:24:30,040 --> 00:24:32,920
Speaker 2: the hormone or excuse my naive biologic question.

496
00:24:33,000 --> 00:24:34,600
Speaker 1: No, No, that's a great question. I skipped a bunch

497
00:24:34,600 --> 00:24:37,880
Speaker 1: of steps. So, as I understand it, the gene encodes

498
00:24:37,920 --> 00:24:40,560
Speaker 1: for a hormone, and so when that gene is essentially

499
00:24:40,600 --> 00:24:44,080
Speaker 1: read and turned into a protein, that protein is a

500
00:24:44,119 --> 00:24:47,359
Speaker 1: hormone that subsequently gets released from the cell.

501
00:24:47,359 --> 00:24:49,440
Speaker 2: The hair follicle cell, or some other kind of cell

502
00:24:49,440 --> 00:24:51,320
Speaker 2: that's controlling the hair follicle cells.

503
00:24:51,760 --> 00:24:53,640
Speaker 1: What I think is happening here is that hair follicle

504
00:24:53,720 --> 00:24:56,560
Speaker 1: cells are producing this message and then also sharing it

505
00:24:56,560 --> 00:24:57,560
Speaker 1: with nearby cells.

506
00:24:57,760 --> 00:25:00,280
Speaker 2: Oh interesting, Okay, one.

507
00:25:00,240 --> 00:25:03,720
Speaker 1: Gets released and it talks to the nearby cells. If

508
00:25:03,720 --> 00:25:06,800
Speaker 1: you are a hair follicle next to a cell that

509
00:25:06,880 --> 00:25:11,000
Speaker 1: has just released this hormone, then you produce white.

510
00:25:11,440 --> 00:25:11,960
Speaker 2: Interesting.

511
00:25:12,680 --> 00:25:16,639
Speaker 1: If you don't get that hormone message, you default to

512
00:25:16,720 --> 00:25:18,240
Speaker 1: making black or brown?

513
00:25:18,359 --> 00:25:19,800
Speaker 2: Wow? Fascinating right.

514
00:25:19,840 --> 00:25:23,280
Speaker 1: So cells can do either, and so the question is

515
00:25:24,359 --> 00:25:28,560
Speaker 1: why are some cells making the signal that say turn

516
00:25:28,600 --> 00:25:31,560
Speaker 1: on white and why are some cells not making that

517
00:25:31,640 --> 00:25:35,600
Speaker 1: signal and telling nearby cells to default to brown or black?

518
00:25:35,760 --> 00:25:38,280
Speaker 2: I loveI we like follow the chain of logic here like,

519
00:25:38,480 --> 00:25:40,359
Speaker 2: this is happening because of that, because of that, because

520
00:25:40,359 --> 00:25:42,800
Speaker 2: of that, because of that, and now we're like detectives

521
00:25:42,800 --> 00:25:44,399
Speaker 2: following the clues all the way back to the source.

522
00:25:44,480 --> 00:25:46,080
Speaker 2: So are you going to tell us who the killer is?

523
00:25:46,400 --> 00:25:49,440
Speaker 2: Who is making these decisions about whether to produce this hormone?

524
00:25:49,480 --> 00:25:51,680
Speaker 1: You know, it's biology, so that the answer is never,

525
00:25:51,760 --> 00:25:55,440
Speaker 1: you know, kernel mustard. It's much more complicated. So you've

526
00:25:55,480 --> 00:25:58,280
Speaker 1: got this a gooty gene, And what determines whether or

527
00:25:58,280 --> 00:26:00,760
Speaker 1: not genes are turned on or off is that there

528
00:26:00,760 --> 00:26:03,480
Speaker 1: are these regions called promoters, and when something binds to

529
00:26:03,520 --> 00:26:06,159
Speaker 1: the promoter, that can turn the gene on. And so

530
00:26:06,680 --> 00:26:08,920
Speaker 1: it seems that whether or not this hormone is made

531
00:26:09,000 --> 00:26:11,760
Speaker 1: or not has to do with some complicated interactions happening

532
00:26:11,800 --> 00:26:14,840
Speaker 1: with the promoter for the genes. And so some cells

533
00:26:14,880 --> 00:26:18,000
Speaker 1: have these promoters turned on, so they're making this make

534
00:26:18,080 --> 00:26:21,439
Speaker 1: white message, and some genes don't get this promoter turned on,

535
00:26:21,600 --> 00:26:23,960
Speaker 1: so they are not giving a message, and nearby cells

536
00:26:24,000 --> 00:26:26,840
Speaker 1: make black or brown. Part of why I didn't get

537
00:26:26,840 --> 00:26:29,520
Speaker 1: into the details is because it might help you understand

538
00:26:29,560 --> 00:26:33,040
Speaker 1: exactly what's happening in this very particular instance. But to

539
00:26:33,119 --> 00:26:37,000
Speaker 1: understand coloration in general, that's more a story about promoters

540
00:26:37,000 --> 00:26:38,439
Speaker 1: getting turned on or off.

541
00:26:38,760 --> 00:26:41,719
Speaker 2: So in general, then how do promoters get turned on

542
00:26:42,080 --> 00:26:44,360
Speaker 2: or off? I mean, this is part of your DNA,

543
00:26:44,880 --> 00:26:47,640
Speaker 2: what determines whether or not that DNA is getting turned

544
00:26:47,640 --> 00:26:48,120
Speaker 2: on or off.

545
00:26:48,359 --> 00:26:51,800
Speaker 1: In general, we don't understand what's happening super well here,

546
00:26:51,960 --> 00:26:54,720
Speaker 1: and we understand this process a lot better in rodents

547
00:26:54,760 --> 00:26:57,280
Speaker 1: in birds, and in part that's because we feel much

548
00:26:57,320 --> 00:26:59,879
Speaker 1: more comfortable doing experiments on these animals in the lab.

549
00:27:00,240 --> 00:27:02,520
Speaker 2: All that's kind of sad, I know.

550
00:27:02,520 --> 00:27:04,119
Speaker 1: I know it is sad, But then you can also

551
00:27:04,160 --> 00:27:08,119
Speaker 1: pick animals that have much simpler color patterns and fewer

552
00:27:08,119 --> 00:27:10,840
Speaker 1: colors to boots, and that makes it easier to sort

553
00:27:10,880 --> 00:27:12,679
Speaker 1: of get a handle on these sorts of things, whereas

554
00:27:12,720 --> 00:27:16,440
Speaker 1: dogs have loads of different color patterns, and so trying

555
00:27:16,440 --> 00:27:18,359
Speaker 1: to get a handle on all of the different ways

556
00:27:18,359 --> 00:27:21,080
Speaker 1: these patterns can be made is much more complicated. The

557
00:27:21,119 --> 00:27:23,439
Speaker 1: manuscript that I read even had a sentence being like,

558
00:27:23,640 --> 00:27:26,440
Speaker 1: the situation in dogs is still unresolved, but they're doing

559
00:27:26,440 --> 00:27:27,560
Speaker 1: their best to figure it out.

560
00:27:27,760 --> 00:27:29,680
Speaker 2: Well, this is super interesting how we can go from

561
00:27:29,720 --> 00:27:33,479
Speaker 2: like totally clues about it to understanding, Oh, follicles can

562
00:27:33,520 --> 00:27:36,560
Speaker 2: print either color to understanding what controls what they print,

563
00:27:36,600 --> 00:27:38,840
Speaker 2: and then follow that up the chain, and we're still

564
00:27:38,880 --> 00:27:40,480
Speaker 2: crawling up the chain. It's incredible.

565
00:27:40,800 --> 00:27:42,440
Speaker 1: It is incredible, And like I said, we've got a

566
00:27:42,480 --> 00:27:45,560
Speaker 1: better handle on some species. And animal coloration in general

567
00:27:45,640 --> 00:27:48,080
Speaker 1: is sort of fascinating. Like sometimes there are some animals

568
00:27:48,080 --> 00:27:50,320
Speaker 1: that get it from their diet. For example, there are

569
00:27:50,320 --> 00:27:52,640
Speaker 1: some fish that have red coloration that they get from

570
00:27:52,680 --> 00:27:55,199
Speaker 1: the animals that they eat, and it just sort of

571
00:27:55,240 --> 00:27:56,720
Speaker 1: like accumulates in their skin.

572
00:27:57,240 --> 00:28:00,879
Speaker 2: That would be amazing if humans, for example, change color

573
00:28:00,960 --> 00:28:02,080
Speaker 2: based on what they ate.

574
00:28:02,880 --> 00:28:05,320
Speaker 1: Oh man, Yeah, there'd be very specific kinds of diets

575
00:28:05,359 --> 00:28:08,400
Speaker 1: I imagine, And around Halloween you'd eat like a lot

576
00:28:08,440 --> 00:28:10,080
Speaker 1: more carrots to get in the mood.

577
00:28:10,240 --> 00:28:15,280
Speaker 2: Would be great, well, amazing. You could get a tan

578
00:28:15,440 --> 00:28:16,280
Speaker 2: just by having lunch.

579
00:28:16,600 --> 00:28:18,879
Speaker 1: That would be incredible and probably a lot safer than

580
00:28:18,880 --> 00:28:20,000
Speaker 1: what we do now to get tans.

581
00:28:20,440 --> 00:28:22,439
Speaker 2: All Right, So it turns out that Simon's question is

582
00:28:22,520 --> 00:28:27,440
Speaker 2: cracked open a huge canyon of unresolved questions in biology.

583
00:28:28,000 --> 00:28:30,119
Speaker 2: And not only do we not understand dogs, but the

584
00:28:30,160 --> 00:28:33,560
Speaker 2: whole question of how animals get color is still an

585
00:28:33,560 --> 00:28:36,760
Speaker 2: active area of research. And maybe having different answers in

586
00:28:36,800 --> 00:28:38,320
Speaker 2: each species. Amazing.

587
00:28:38,720 --> 00:28:41,080
Speaker 1: That's right, And so let's see if Simon feels like

588
00:28:41,080 --> 00:28:42,480
Speaker 1: he learned anything from this answer.

589
00:28:44,120 --> 00:28:45,800
Speaker 2: It sounds like Kelly read a lot of papers and

590
00:28:45,880 --> 00:28:46,440
Speaker 2: learned a lot.

591
00:28:46,600 --> 00:28:48,320
Speaker 1: Kelly read a lot of papers, learned a lot, and

592
00:28:48,360 --> 00:28:50,000
Speaker 1: also learned that there's a lot that she doesn't know

593
00:28:50,040 --> 00:28:51,959
Speaker 1: about how this stuff works out. So it was a

594
00:28:52,080 --> 00:28:53,640
Speaker 1: learning experience for sure.

595
00:28:53,920 --> 00:28:56,280
Speaker 2: All right, let's hear from Simon. Uh huh.

596
00:28:56,360 --> 00:29:00,239
Speaker 4: Kelly definitely did learn something, and I think we as

597
00:29:00,280 --> 00:29:03,560
Speaker 4: the audience, I've definitely learned something too. Thanks Kelly for

598
00:29:03,920 --> 00:29:08,360
Speaker 4: the great insight into the invisible and incredibly complicated, it

599
00:29:08,400 --> 00:29:13,240
Speaker 4: seems biological mechanisms behind something as simple as the coloration

600
00:29:13,360 --> 00:29:16,840
Speaker 4: of our furry friends. I think understanding how it works

601
00:29:16,840 --> 00:29:19,920
Speaker 4: at this very last step perhaps gives us some insight

602
00:29:20,000 --> 00:29:22,239
Speaker 4: into how it works at the very first step. So

603
00:29:22,280 --> 00:29:25,280
Speaker 4: if I go back to the very first cell directly

604
00:29:25,320 --> 00:29:27,920
Speaker 4: after conceptions, say, where it splits into two, and then

605
00:29:27,960 --> 00:29:30,960
Speaker 4: to four, and then to eight and so on, eventually

606
00:29:31,000 --> 00:29:33,960
Speaker 4: giving rise to something that resembles a head, a torso,

607
00:29:34,120 --> 00:29:37,040
Speaker 4: and four legs, to understand the finer details of how

608
00:29:37,080 --> 00:29:40,320
Speaker 4: this information has passed down. How one cell knows to

609
00:29:40,360 --> 00:29:43,280
Speaker 4: be a torso while as a direct neighbor knows to

610
00:29:43,320 --> 00:29:47,120
Speaker 4: become a leg To understand how this transfer of information

611
00:29:47,200 --> 00:29:49,719
Speaker 4: works from one cell division to the next will be

612
00:29:50,080 --> 00:29:52,960
Speaker 4: fascinating to find out one day, But that's a question

613
00:29:53,200 --> 00:29:56,120
Speaker 4: for another day. Maybe. Thanks Kelly for taking the time

614
00:29:56,200 --> 00:29:59,440
Speaker 4: to look deeper into this mechanism and give us some

615
00:29:59,520 --> 00:30:03,440
Speaker 4: insight into this very last step of cell division. Gave

616
00:30:03,560 --> 00:30:04,440
Speaker 4: up the Great White cause.

617
00:30:21,520 --> 00:30:23,280
Speaker 2: All right, we're back and we're moving on from the

618
00:30:23,320 --> 00:30:27,040
Speaker 2: mysteries of biology to the mysteries of the very early universe?

619
00:30:27,600 --> 00:30:29,320
Speaker 2: Which one do we understand less?

620
00:30:30,480 --> 00:30:32,240
Speaker 1: Does it really need to be a competition? We don't

621
00:30:32,320 --> 00:30:33,480
Speaker 1: understand much about anything.

622
00:30:33,520 --> 00:30:36,560
Speaker 2: Some days it feels like Leonardo wanted to understand the

623
00:30:36,600 --> 00:30:40,480
Speaker 2: relationship between particle collisions and the Big Bang. Here's his question.

624
00:30:41,160 --> 00:30:44,479
Speaker 5: Hi, Kelly and Daniel loved the show. I heard particle

625
00:30:44,560 --> 00:30:47,920
Speaker 5: accelerators being described as tiny banks as in The Big

626
00:30:47,960 --> 00:30:51,400
Speaker 5: Bang but tiny in another podcast by doctor Katie Mack.

627
00:30:52,080 --> 00:30:54,640
Speaker 5: I also know we measure the energy of impacts in

628
00:30:54,720 --> 00:30:58,480
Speaker 5: giga electron votes, so can we also estimate the energy

629
00:30:58,520 --> 00:31:00,320
Speaker 5: of the Big Bang in electron votes?

630
00:31:00,960 --> 00:31:01,080
Speaker 6: And?

631
00:31:01,120 --> 00:31:04,680
Speaker 5: If so, why are we not classifying accelerators in Meli

632
00:31:04,840 --> 00:31:07,720
Speaker 5: or Fento banks and Easy because the number would be

633
00:31:07,800 --> 00:31:10,240
Speaker 5: too unsatisfying. Grains from Brazil.

634
00:31:10,760 --> 00:31:13,000
Speaker 1: All right, So, Daniel, I remember you telling me once

635
00:31:13,200 --> 00:31:15,760
Speaker 1: that when you all turned on the particle collider for

636
00:31:15,800 --> 00:31:17,440
Speaker 1: the first time, there was a little bit of a

637
00:31:17,480 --> 00:31:21,000
Speaker 1: concern that maybe you would destroy the universe? Is that

638
00:31:21,040 --> 00:31:22,640
Speaker 1: because you all thought you were going to kick off

639
00:31:22,680 --> 00:31:23,640
Speaker 1: a tiny, big bang.

640
00:31:25,800 --> 00:31:28,240
Speaker 2: Well, you know, anytime you do something that's never been

641
00:31:28,280 --> 00:31:30,240
Speaker 2: done before, you don't know what's going to happen. That's

642
00:31:30,280 --> 00:31:34,880
Speaker 2: the excitement of research, right, you know, you're exploring the unknown,

643
00:31:34,960 --> 00:31:39,320
Speaker 2: you're potentially unleashing something you didn't expect. And so yeah,

644
00:31:39,320 --> 00:31:43,280
Speaker 2: there's always a little frison of you know, enthusiasm and

645
00:31:43,320 --> 00:31:44,720
Speaker 2: fear when that happens.

646
00:31:44,920 --> 00:31:47,120
Speaker 1: But when I first infect a fish with a parasite,

647
00:31:47,120 --> 00:31:49,160
Speaker 1: I don't worry that it's the end of humanity. Like,

648
00:31:49,240 --> 00:31:51,240
Speaker 1: the scale feels very different here.

649
00:31:51,240 --> 00:31:53,680
Speaker 2: Maybe you should think bigger, Kelly. Yeah, okay, for those

650
00:31:53,720 --> 00:31:55,640
Speaker 2: of you worried at home, we didn't actually worry about

651
00:31:55,640 --> 00:31:57,640
Speaker 2: that too much because the collisions we'd do with the

652
00:31:57,640 --> 00:32:01,320
Speaker 2: particle colliders are not unusual in nature. They're very high

653
00:32:01,400 --> 00:32:04,560
Speaker 2: energy collisions from particles slamming into the Earth's atmosphere all

654
00:32:04,600 --> 00:32:07,320
Speaker 2: the time, much higher energy than what we achieve with

655
00:32:07,360 --> 00:32:09,720
Speaker 2: the large a drunk collider. We didn't worry that we'd

656
00:32:09,760 --> 00:32:12,720
Speaker 2: be collapsing the Higgs field or creating a black hole

657
00:32:12,840 --> 00:32:16,160
Speaker 2: or anything like that. But it is a fascinating experiment

658
00:32:16,200 --> 00:32:19,760
Speaker 2: because we are recreating conditions of the early universe. They're

659
00:32:19,760 --> 00:32:23,720
Speaker 2: also conditions of our current universe, just not as widespread.

660
00:32:24,320 --> 00:32:28,000
Speaker 2: And so it's often said that particle collisions recreate the

661
00:32:28,000 --> 00:32:30,960
Speaker 2: Big Bang, and that's true in some sense, but there's

662
00:32:30,960 --> 00:32:34,640
Speaker 2: also the potential there to sort of underscore misunderstandings about

663
00:32:34,640 --> 00:32:36,360
Speaker 2: the Big Bang that we should probably clear up.

664
00:32:36,600 --> 00:32:38,480
Speaker 1: Well, can we start with, like, what is the defining

665
00:32:38,560 --> 00:32:43,720
Speaker 1: characteristic of a bang of any size? Small, medium, or large?

666
00:32:44,520 --> 00:32:47,160
Speaker 2: Yeah, that's a good question. You know, in terms of

667
00:32:47,320 --> 00:32:51,080
Speaker 2: the Big Bang, the Big Bang is more of a

668
00:32:51,120 --> 00:32:54,920
Speaker 2: whiff than a bang, right, because the universe is expanding,

669
00:32:54,960 --> 00:32:59,040
Speaker 2: but it's really sort of cooling. It's becoming older and colder.

670
00:32:59,400 --> 00:33:01,640
Speaker 2: So the Big Bang is a description of how the

671
00:33:01,760 --> 00:33:05,160
Speaker 2: universe is decreasing in density as time goes on. It's

672
00:33:05,160 --> 00:33:08,320
Speaker 2: cooling down and getting more dilute. To run the clock backwards,

673
00:33:08,520 --> 00:33:11,760
Speaker 2: the universe gets hotter and denser, and we can run

674
00:33:11,840 --> 00:33:13,680
Speaker 2: backwards to a certain point what we call the plank

675
00:33:13,760 --> 00:33:16,640
Speaker 2: time beyond which we know our theories don't work, and

676
00:33:16,640 --> 00:33:18,800
Speaker 2: so everything is a question mark. And that's what we

677
00:33:18,840 --> 00:33:21,720
Speaker 2: call the Big Bang is expansion from that moment. So

678
00:33:21,760 --> 00:33:24,320
Speaker 2: it's a description of when the universe had very high

679
00:33:24,520 --> 00:33:28,560
Speaker 2: energy density. It's not a tiny dot in empty space.

680
00:33:28,800 --> 00:33:31,080
Speaker 2: The idea of a big bang, especially if you compare

681
00:33:31,160 --> 00:33:33,880
Speaker 2: to particle collisions, makes it sound like something happening at

682
00:33:33,960 --> 00:33:37,520
Speaker 2: one location, but the Big Bang was everywhere, and so

683
00:33:37,560 --> 00:33:40,400
Speaker 2: the similarity between particle collisions and the Big Bang is

684
00:33:40,440 --> 00:33:43,520
Speaker 2: that both have high energy density. Particle collisions of course,

685
00:33:43,560 --> 00:33:46,960
Speaker 2: though in just one spot, the Big Bang was everywhere.

686
00:33:46,960 --> 00:33:49,719
Speaker 1: Got it? Okay? And what kind of scale difference are

687
00:33:49,760 --> 00:33:52,080
Speaker 1: we talking about in terms of energy between big and

688
00:33:52,160 --> 00:33:52,880
Speaker 1: tiny bangs?

689
00:33:53,600 --> 00:33:56,520
Speaker 2: Yeah, so it's a pretty big difference. We compare these

690
00:33:56,520 --> 00:34:00,120
Speaker 2: things in a weird unit called electron volts, and it's

691
00:34:00,120 --> 00:34:02,520
Speaker 2: sort of a generic unit of energy. You can also

692
00:34:02,600 --> 00:34:04,720
Speaker 2: use it to measure mass, because we don't care about

693
00:34:04,760 --> 00:34:07,240
Speaker 2: things like the speed of light, and so an electron

694
00:34:07,320 --> 00:34:09,359
Speaker 2: volt is our unit, and to calibrate. For example, a

695
00:34:09,360 --> 00:34:13,080
Speaker 2: proton has a mass of one giga electron vault, so

696
00:34:13,200 --> 00:34:16,040
Speaker 2: a billion electron volts is the mass of a proton,

697
00:34:16,320 --> 00:34:19,279
Speaker 2: and collisions that we can achieve here on Earth are

698
00:34:19,320 --> 00:34:22,439
Speaker 2: in the scale of ten tarra electron vaults, so ten

699
00:34:22,560 --> 00:34:26,520
Speaker 2: thousand times the mass of a proton. And that sounds

700
00:34:26,520 --> 00:34:30,160
Speaker 2: pretty big, right, like ooh wow tarra Like that's a big.

701
00:34:30,040 --> 00:34:31,840
Speaker 1: Number, But protons are pretty small.

702
00:34:32,400 --> 00:34:36,120
Speaker 2: Protons are pretty small, exactly, And so the energy of

703
00:34:36,160 --> 00:34:38,400
Speaker 2: the Big Bang in the same units is ten to

704
00:34:38,440 --> 00:34:42,640
Speaker 2: the sixteen terra electron vaults, so ten to the fifteen

705
00:34:42,719 --> 00:34:46,560
Speaker 2: times more energy than the collisions we have at the LHC.

706
00:34:46,640 --> 00:34:49,040
Speaker 2: And ten of the fifteen is not a small number,

707
00:34:49,280 --> 00:34:52,719
Speaker 2: you know, it's not fifteen times. It's ten to fifteen

708
00:34:53,160 --> 00:34:57,080
Speaker 2: ten with fifteen zeros. If your bank account had one

709
00:34:57,160 --> 00:35:00,799
Speaker 2: with fifteen zeros in it, you'd be very very rich,

710
00:35:00,960 --> 00:35:03,800
Speaker 2: much much much richer than Elon Musk, probably like Elon

711
00:35:03,880 --> 00:35:07,560
Speaker 2: Musk squared. So it's very very high energy.

712
00:35:07,840 --> 00:35:11,080
Speaker 1: If particle physicists had enough money, would you guys try

713
00:35:11,120 --> 00:35:13,120
Speaker 1: to make a particle collider you could do the Big

714
00:35:13,160 --> 00:35:17,400
Speaker 1: Bang in because I'm not sure we can trust.

715
00:35:17,120 --> 00:35:19,520
Speaker 2: You, guys, No, I think we would. And you know,

716
00:35:19,680 --> 00:35:22,640
Speaker 2: the higher the energy collision, the more stuff you can make.

717
00:35:22,920 --> 00:35:24,920
Speaker 2: Right we don't know what's out there in the sort

718
00:35:24,920 --> 00:35:28,759
Speaker 2: of universe's menu of particles. And the incredible thing about

719
00:35:28,800 --> 00:35:31,399
Speaker 2: these collisions is that you pour energy in and there's

720
00:35:31,400 --> 00:35:35,320
Speaker 2: some sort of like quantum mechanical magic alchemy that happens,

721
00:35:35,440 --> 00:35:38,279
Speaker 2: and the universe decides what from its menu to make,

722
00:35:38,600 --> 00:35:40,560
Speaker 2: and it just sort of picks randomly from all the

723
00:35:40,560 --> 00:35:43,160
Speaker 2: things that it can make, which means that if you

724
00:35:43,160 --> 00:35:46,080
Speaker 2: pour enough energy into the collisions, you'll see everything the

725
00:35:46,239 --> 00:35:49,160
Speaker 2: universe is capable of making. If you do it often enough,

726
00:35:49,280 --> 00:35:51,440
Speaker 2: you don't even have to know what's out there. So

727
00:35:51,480 --> 00:35:54,360
Speaker 2: it's like a way to explore the capacity of the

728
00:35:54,480 --> 00:35:57,560
Speaker 2: universe without even knowing what it's capable of. You don't

729
00:35:57,560 --> 00:35:59,799
Speaker 2: have to leave your house. It's like, hey, make me

730
00:36:00,080 --> 00:36:03,560
Speaker 2: everything you can make right here. And as you turn

731
00:36:03,719 --> 00:36:06,600
Speaker 2: up that energy, you get to explore higher and higher

732
00:36:06,640 --> 00:36:09,640
Speaker 2: on nature's menu. And you could be just below the

733
00:36:09,680 --> 00:36:11,680
Speaker 2: threshold and not make the thing because they don't have

734
00:36:11,760 --> 00:36:13,799
Speaker 2: enough energy, and then you crank up the energy and

735
00:36:13,840 --> 00:36:16,160
Speaker 2: boom it starts to pop out. So Yeah, we'd love

736
00:36:16,320 --> 00:36:18,880
Speaker 2: to crank up the energy these things. We're still a

737
00:36:18,880 --> 00:36:21,560
Speaker 2: factor of ten to fifteen away from the Big Bang,

738
00:36:21,600 --> 00:36:24,160
Speaker 2: which means there could be particles that were made in

739
00:36:24,200 --> 00:36:28,080
Speaker 2: the early universe and they're super duper massive and we

740
00:36:28,160 --> 00:36:29,880
Speaker 2: haven't been able to make them yet. They could be

741
00:36:29,920 --> 00:36:32,480
Speaker 2: made in collisions of cosmic rays in the atmosphere, but

742
00:36:32,520 --> 00:36:34,680
Speaker 2: they're very short lived and we don't have detectors up

743
00:36:34,719 --> 00:36:35,720
Speaker 2: there to see them.

744
00:36:35,880 --> 00:36:38,359
Speaker 1: So check out Daniels go fundme for the next big

745
00:36:38,400 --> 00:36:39,280
Speaker 1: particle collider.

746
00:36:40,440 --> 00:36:43,360
Speaker 2: Leon artists question also asked, can we measure particle collisions

747
00:36:43,360 --> 00:36:46,240
Speaker 2: in terms of milli or fempto bangs? And the answer

748
00:36:46,280 --> 00:36:49,239
Speaker 2: is yes. So if you define one bang as ten

749
00:36:49,280 --> 00:36:52,560
Speaker 2: to the sixteen TeV, then the Large Hadron Collider has

750
00:36:52,560 --> 00:36:55,520
Speaker 2: collisions at about ten of the minus fifteen bangs or

751
00:36:55,640 --> 00:36:59,480
Speaker 2: one femto bang, which, yeah, doesn't sound very impressive and

752
00:37:00,160 --> 00:37:03,360
Speaker 2: not a great way to headline your science funding request.

753
00:37:03,680 --> 00:37:05,920
Speaker 1: I don't know. I think femto bang sounds pretty.

754
00:37:05,640 --> 00:37:08,640
Speaker 2: Cool, but it's also a way to sort of trace

755
00:37:08,719 --> 00:37:11,440
Speaker 2: back the history of the universe. Like as the energy

756
00:37:11,440 --> 00:37:13,759
Speaker 2: of your collisions goes up and up and up, you

757
00:37:13,840 --> 00:37:17,960
Speaker 2: recreate conditions that existed everywhere in the universe further and

758
00:37:18,040 --> 00:37:22,520
Speaker 2: further back in time and already ten TV one. Femto

759
00:37:22,560 --> 00:37:25,200
Speaker 2: bang is pretty high energy. It takes you all the

760
00:37:25,200 --> 00:37:28,719
Speaker 2: way back to like microseconds after the Big Bang because

761
00:37:28,719 --> 00:37:31,960
Speaker 2: the energy started to fall off really really quickly. It

762
00:37:32,000 --> 00:37:34,719
Speaker 2: becomes more gradual as time goes on. So we are

763
00:37:34,800 --> 00:37:39,320
Speaker 2: probing conditions in a very very early universe microseconds after

764
00:37:39,360 --> 00:37:39,960
Speaker 2: the Big Bang.

765
00:37:40,160 --> 00:37:43,520
Speaker 1: Well, let's see if Leonardo is impressed by femto bangs.

766
00:37:45,239 --> 00:37:48,399
Speaker 6: Hello, I'm also in teen Kelly, I'm also impressed by

767
00:37:48,600 --> 00:37:53,560
Speaker 6: fento bank. Also, thanks for clarifying the differences between a

768
00:37:53,680 --> 00:37:57,600
Speaker 6: particle collider and the early universe. I actually never considered

769
00:37:57,680 --> 00:38:00,360
Speaker 6: that there could have been particle so massive. If that

770
00:38:00,680 --> 00:38:04,040
Speaker 6: we will likely never be able to recreate. Thanks.

771
00:38:04,600 --> 00:38:07,680
Speaker 2: All right, and today we have a special bonus question

772
00:38:08,200 --> 00:38:12,799
Speaker 2: on gravitational and velocity based time dilation from ASTHMT. We

773
00:38:12,880 --> 00:38:15,800
Speaker 2: decided we could squeeze in a fourth question for y'all,

774
00:38:16,120 --> 00:38:19,080
Speaker 2: So here's Ozma's question about time dilation.

775
00:38:19,800 --> 00:38:22,920
Speaker 7: Hello, I'm a smith, and my question is what would

776
00:38:22,920 --> 00:38:26,160
Speaker 7: happen to time dialation if both high velocity and strong

777
00:38:26,200 --> 00:38:30,360
Speaker 7: magnetic feeling interacted simultaneously. Would this cost time to slow

778
00:38:30,400 --> 00:38:34,160
Speaker 7: down even more significantly or would there be no additional effect?

779
00:38:34,600 --> 00:38:34,960
Speaker 7: Thank you?

780
00:38:35,680 --> 00:38:38,600
Speaker 1: All right? So Daniel, I have been listening, well you talk,

781
00:38:38,719 --> 00:38:41,600
Speaker 1: and I remember you told me there's two kinds of

782
00:38:41,640 --> 00:38:46,680
Speaker 1: time dilation, gravity and velocity. But my brain is a sieve,

783
00:38:47,120 --> 00:38:49,759
Speaker 1: so remind me what the difference between those is.

784
00:38:50,480 --> 00:38:53,719
Speaker 2: Right, So there are two ways that clocks can appear slow. Now,

785
00:38:53,800 --> 00:38:57,200
Speaker 2: clocks that you hold, that you have with you always

786
00:38:57,280 --> 00:39:01,040
Speaker 2: run the same speed. But if Kelly gives Zach clock

787
00:39:01,160 --> 00:39:02,920
Speaker 2: and then shoots them out of a cannon a very

788
00:39:03,000 --> 00:39:06,160
Speaker 2: high speed relative to her, she will see Zach's clock

789
00:39:06,280 --> 00:39:12,520
Speaker 2: running slow because velocity time dilation says moving clocks run slow. Now, Zach,

790
00:39:12,600 --> 00:39:14,920
Speaker 2: with this telescope looking back at Kelly's clock, will disagree.

791
00:39:14,960 --> 00:39:17,719
Speaker 2: He'll say, no, no, Kelly's clock is running slow. So that

792
00:39:17,840 --> 00:39:22,320
Speaker 2: kind of time dilation is symmetric, meaning both wiener Smith's

793
00:39:22,480 --> 00:39:25,359
Speaker 2: see the other one's clock running slow. And at least

794
00:39:25,400 --> 00:39:27,600
Speaker 2: to this sort of confusion like whose clock is really

795
00:39:27,640 --> 00:39:30,360
Speaker 2: slower and the answer is there is no really slower,

796
00:39:30,360 --> 00:39:33,279
Speaker 2: they can argue forever and both be right. So it's

797
00:39:33,320 --> 00:39:35,239
Speaker 2: sort of a marital trap for the two of them.

798
00:39:35,400 --> 00:39:36,200
Speaker 1: Yeah, that's not great.

799
00:39:37,840 --> 00:39:41,640
Speaker 2: But the other kind of time dilation, gravitational time dilation,

800
00:39:42,280 --> 00:39:45,520
Speaker 2: is asymmetric, which means everybody can agree on it. So,

801
00:39:45,600 --> 00:39:48,680
Speaker 2: for example, if Kelly does drop Zach near a black hole,

802
00:39:49,000 --> 00:39:51,759
Speaker 2: she'll see his clock running slower, but he will see

803
00:39:51,760 --> 00:39:55,600
Speaker 2: her clock running faster. They agree in this scenario, but

804
00:39:55,680 --> 00:39:58,239
Speaker 2: whose clock is running slower or faster? Both of them

805
00:39:58,280 --> 00:40:01,160
Speaker 2: see their own clocks running at normal speed. And so

806
00:40:01,200 --> 00:40:03,799
Speaker 2: the cool thing here, and this is Ozma's question, is like,

807
00:40:03,840 --> 00:40:07,400
Speaker 2: what happens when you have both? Do they constructively interfered,

808
00:40:07,400 --> 00:40:10,360
Speaker 2: destructively interfered to his universe? Explode? What happens?

809
00:40:10,840 --> 00:40:13,160
Speaker 1: I hope The answer is Kelly is right. Whatever time

810
00:40:13,280 --> 00:40:15,359
Speaker 1: Kelly says is the correct time.

811
00:40:18,080 --> 00:40:22,520
Speaker 2: The answer is they both contribute. So let's say, for example,

812
00:40:22,760 --> 00:40:26,719
Speaker 2: that Kelly launches Zach into orbit. Right now, Zach is

813
00:40:26,760 --> 00:40:30,520
Speaker 2: going really, really fast, and so his velocity means that

814
00:40:30,600 --> 00:40:34,080
Speaker 2: his clock runs slower than clocks we have here on

815
00:40:34,160 --> 00:40:37,759
Speaker 2: Earth from our point of view. Okay, but he's also

816
00:40:38,080 --> 00:40:41,440
Speaker 2: further from the gravitational well of the Earth, so his

817
00:40:41,520 --> 00:40:45,799
Speaker 2: clocks will run faster than ours. Because of the gravitational

818
00:40:45,840 --> 00:40:49,000
Speaker 2: time dilation is less so we have actually gravitational time

819
00:40:49,000 --> 00:40:51,640
Speaker 2: dilation right here on the surface of the Earth. Because

820
00:40:51,719 --> 00:40:54,240
Speaker 2: of the Earth, we're all experiencing it all the time.

821
00:40:54,560 --> 00:40:57,480
Speaker 2: Clocks out in deep space run faster. So from Kelly's

822
00:40:57,520 --> 00:41:01,040
Speaker 2: point of view, Zach's clock runs slower because of velocity

823
00:41:01,440 --> 00:41:05,280
Speaker 2: and faster because of gravity, and the gravity actually wins out.

824
00:41:05,560 --> 00:41:08,879
Speaker 2: So the velocity time delation is like seven microseconds per

825
00:41:09,000 --> 00:41:12,919
Speaker 2: day if he's up with GPS satellites, and forty five

826
00:41:13,080 --> 00:41:17,080
Speaker 2: microseconds per day the other direction due to gravity. So

827
00:41:17,360 --> 00:41:19,000
Speaker 2: overall gravity wins.

828
00:41:19,239 --> 00:41:22,400
Speaker 1: So when I shoot him into orbit, because gravity is

829
00:41:22,440 --> 00:41:25,319
Speaker 1: winning and it makes things faster, he should still be

830
00:41:25,400 --> 00:41:27,480
Speaker 1: on time or early to the meetings. I let no

831
00:41:27,560 --> 00:41:29,040
Speaker 1: excuse for being late, Is that right?

832
00:41:30,400 --> 00:41:32,200
Speaker 2: I really feel like I don't want to get in

833
00:41:32,200 --> 00:41:35,279
Speaker 2: the middle of here. Physics is not going to solve

834
00:41:35,320 --> 00:41:36,080
Speaker 2: your marital.

835
00:41:35,800 --> 00:41:39,120
Speaker 1: Problems, all right, all right, but baby sandwiches, well.

836
00:41:40,520 --> 00:41:44,040
Speaker 2: Sandwiches yet well exactly now, from Zach's point of view,

837
00:41:44,560 --> 00:41:48,120
Speaker 2: both of the effects make Earth's clocks slower. It's fascinating

838
00:41:48,160 --> 00:41:49,800
Speaker 2: because from the Earth's point of view, we see the

839
00:41:49,840 --> 00:41:53,160
Speaker 2: effects having different directions. But from Zach's point of view,

840
00:41:53,200 --> 00:41:56,040
Speaker 2: he sees both effects having the same direction. He sees

841
00:41:56,120 --> 00:41:59,080
Speaker 2: us moving quickly, which means our clocks run slow, and

842
00:41:59,239 --> 00:42:02,800
Speaker 2: he sees a closer to a gravitational well of the earth,

843
00:42:03,000 --> 00:42:05,000
Speaker 2: which means our clocks run slow.

844
00:42:05,280 --> 00:42:06,919
Speaker 1: Oh see, now, I feel like you're citing with zech.

845
00:42:10,120 --> 00:42:11,040
Speaker 1: This is no excuse.

846
00:42:11,120 --> 00:42:12,640
Speaker 2: I feel like I need my lawyer present.

847
00:42:15,360 --> 00:42:17,759
Speaker 1: All right, everybody, thanks for playing. Just a reminder that

848
00:42:17,800 --> 00:42:21,200
Speaker 1: you too can send us questions at questions at danielant

849
00:42:21,280 --> 00:42:24,000
Speaker 1: Kelly dot org. We answer every question, some of them

850
00:42:24,080 --> 00:42:25,680
Speaker 1: end up on the show and we can't wait to

851
00:42:25,680 --> 00:42:26,120
Speaker 1: hear from you.

852
00:42:26,400 --> 00:42:29,400
Speaker 2: And some of our questions come from conversations on the discord.

853
00:42:29,440 --> 00:42:32,399
Speaker 2: We encourage you to join our discord, where people ask

854
00:42:32,480 --> 00:42:34,840
Speaker 2: and answer questions and make a bunch of nerdy jokes.

855
00:42:35,040 --> 00:42:37,360
Speaker 2: You can find the invitation on our website Daniel and

856
00:42:37,480 --> 00:42:38,480
Speaker 2: Kelly dot org.

857
00:42:45,719 --> 00:42:49,560
Speaker 1: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We

858
00:42:49,600 --> 00:42:52,000
Speaker 1: would love to hear from you, We really would.

859
00:42:52,160 --> 00:42:54,920
Speaker 2: We want to know what questions you have about this

860
00:42:55,120 --> 00:42:56,800
Speaker 2: Extraordinary Universe.

861
00:42:56,920 --> 00:42:59,799
Speaker 1: We want to know your thoughts on recent shows, suggestions

862
00:42:59,840 --> 00:43:02,879
Speaker 1: for future shows. If you contact us, we will get

863
00:43:02,920 --> 00:43:03,319
Speaker 1: back to you.

864
00:43:03,560 --> 00:43:07,040
Speaker 2: We really mean it. We answer every message, email us

865
00:43:07,080 --> 00:43:09,920
Speaker 2: at Questions at Danielankelly dot.

866
00:43:09,719 --> 00:43:11,560
Speaker 1: Org, or you can find us on social media. We

867
00:43:11,640 --> 00:43:15,520
Speaker 1: have accounts on x, Instagram, Blue Sky and on all

868
00:43:15,560 --> 00:43:17,840
Speaker 1: of those platforms. You can find us at D and

869
00:43:18,280 --> 00:43:19,320
Speaker 1: K Universe.

870
00:43:19,440 --> 00:43:20,960
Speaker 2: Oh be shy right to us