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Speaker 1: Hey, Daniel, is particle physics actually useful for anything?

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Speaker 2: I mean it's good for like understanding the universe for sure.

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Speaker 1: Yeah, But what can I use particles for? Can I

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Speaker 1: use a charm quark charm my way into a better life?

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Speaker 2: I think you're plenty charming already without any charm quarks.

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Speaker 2: But we might be able to, like use muons to

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Speaker 2: help us get to the moon.

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Speaker 1: What just because they start with an M, because there

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Speaker 1: are one letter off from moon and muon?

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Speaker 2: I'm just reaching here. Man.

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Speaker 1: Do you use a muans to feed cows?

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Speaker 3: You know?

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Speaker 1: Or grow more corn?

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Speaker 3: More?

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Speaker 2: Meuse less corn? I mean, nothing is certain in science,

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Speaker 2: but that's probably a no.

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Speaker 1: Why not? Don't cows eat muans? Don't they eat muuons?

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Speaker 2: I think muons actually cause cows to mutate and make

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Speaker 2: new kinds of cows.

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Speaker 1: Oh well, maybe we'll get a taste of cout of it,

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Speaker 1: In which case particles would be useful.

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Speaker 2: Better steaks through physics, that's.

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Speaker 1: Right, better particle burgers. Hi am jorg Im, cartoonist and

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

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Speaker 4: Hi.

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

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Speaker 2: UC Irvine, and I like believing that physics raises the steaks.

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Speaker 1: The steaks like the cow steaks. Yeah, we've got to

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Speaker 1: raise some steaks or the burgers maybe.

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Speaker 2: I mean you're always talking about setting the steaks and stories.

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Speaker 1: Right, Yeah, that's always important, but usually makes the emotional steaks,

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Speaker 1: not the raw or well done kind.

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Speaker 2: Well, I like to get my stakes at the restaurant

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Speaker 2: called mcguffins.

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Speaker 1: So do you like them rare or well done?

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Speaker 2: I rarely eat steaks. Actually, it's the truth.

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Speaker 1: He eats steaks rarely or rarely eat steaks.

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Speaker 2: Yeah, I almost never eat steaks. My son is a

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Speaker 2: big fan of protein, but he prefers chicken and turkey.

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Speaker 2: He's the poultry man.

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Speaker 1: Oh I see, he likes it lean.

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Speaker 2: He likes it with wings.

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Speaker 1: Nice's nice to stay lean and flighty as well. But anyways,

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Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,

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Speaker 1: a production of our Heart Radio in.

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Speaker 2: Which we help your brain to take flight and trim

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Speaker 2: all the fat from your understanding of the universe. We

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Speaker 2: think it's possible to zoom out there with our minds

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Speaker 2: and understand everything that happens in the universe from the

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Speaker 2: tiniest little particles to the biggest, most massive black holes,

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Speaker 2: and our goal is to break it all down and

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Speaker 2: explain it to you.

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Speaker 1: That's right. We try to prevent your brain from having

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Speaker 1: a cow thinking about the amazing and vast universe we

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Speaker 1: live in, with all the complete physics and mechanics that

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Speaker 1: are happening. We try to boil it all down to

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Speaker 1: make it digestible and lean. We trim all the fat

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Speaker 1: out of science communication while trying to keep it still

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Speaker 1: plenty juice. And it's all one hundred percent organic, right,

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Speaker 1: These no chemicals in this podcast.

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Speaker 2: I mean, I guess everything's a chemical.

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Speaker 1: So yeah, I mean I did use growth horribones to

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Speaker 1: inflate my intelligence a little bit.

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Speaker 2: But one of the reasons we're talking about such practical

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Speaker 2: matters is because one of the criticisms of particle physics

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Speaker 2: is that it can be kind of abstract, Like, are

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Speaker 2: the questions of particle physics really useful to you on

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Speaker 2: an everyday basis or is it more of a philosophical

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Speaker 2: search for understanding of the nature of the universe.

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Speaker 1: Yeah, you got to kind of wonder what is smashing

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Speaker 1: all those particles together, spending billions of dollars. What it

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Speaker 1: is that all useful for? How is that helping humanity

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Speaker 1: move forward and maybe eat better as well?

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Speaker 2: And of course there are lots of indirect benefits, just

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Speaker 2: understan in the nature of the universe is its own

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Speaker 2: prize and is priceless. But every dollar we invest in

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Speaker 2: basic research comes back to us in terms of technological

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Speaker 2: advancements and economic output and education and employment. So it's

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Speaker 2: definitely a worthy way to spend money, I say, with

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Speaker 2: absolutely no conflict of interest whatsoever.

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Speaker 1: I was gonna say it definitely means employment for certain

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Speaker 1: people like physicists.

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Speaker 2: Perhaps it certainly does, but it benefits everybody because investment

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Speaker 2: in basic research always leads to revolutions and our understanding

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Speaker 2: and in technology and all sorts of stuff.

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Speaker 1: Yeah. I guess without physics there wouldn't be this podcast,

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Speaker 1: which sort of employs us right.

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Speaker 2: And improves the lives of everybody on Earth.

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Speaker 1: I guess if physics wasn't around, we'd have to talk

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Speaker 1: about something else or explain the universe using other things.

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Speaker 2: Absolutely, but sometimes particle physics can be more directly useful.

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Speaker 2: Things we learned about weird particles exotic matter can actually

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Speaker 2: be put to use to help us solve everyday earthly mysteries.

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Speaker 1: It might actually also help us have X ray vision

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Speaker 1: in a way. So today on the podcast, we'll be

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Speaker 1: taxing the question can we use muons to see inside

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Speaker 1: of things? What kinds of things are we talking about?

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Speaker 1: Daniel m all kinds of boxes?

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Speaker 2: Yes, absolutely, escape rooms, people's pockets, safes and banks.

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Speaker 1: Yeah, oh boy? What's inside the burgers at McDonald's.

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Speaker 2: Perhaps nobody wants to know that for real, that's not

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Speaker 2: why you go to McDonald's.

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Speaker 1: I don't think we'll get grand funding for that question.

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Speaker 2: Now that's a situation where knowledge can ruin something.

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Speaker 1: Yeah, yeah, but it is an interesting question whether we

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Speaker 1: can use meons to see inside of things? You mean,

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Speaker 1: is this sort of like using muons as X rays?

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Speaker 2: Kind of Yeah, it's a similar idea. Can we use

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Speaker 2: penetrating radiation to reveal something that is hidden from us?

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Speaker 2: Can we look inside something without opening it up?

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Speaker 1: Can we just use X ray? I thought that was

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Speaker 1: already invented.

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Speaker 2: We can use X rays, but X rays also have

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Speaker 2: their limits, and some muons might open up the possibility

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Speaker 2: to see inside things that are otherwise still close to us.

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Speaker 2: Even with X rays hmm.

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Speaker 1: Interesting. All right, we'll dig into it, but first, as usual,

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Speaker 1: we were wondering how many people out there had thought

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Speaker 1: about using muons to see inside of things and how

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Speaker 1: we might be able to do that.

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Speaker 2: Thanks very much to everybody who plays the game for

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Speaker 2: this section of the podcast. We love hearing your voice,

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Speaker 2: and if you would like to participate, it's very easy.

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Speaker 2: It all happens over email. Just write to me too

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Speaker 2: questions at Danielandjorge dot com.

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

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Speaker 1: we can use muons to see inside of things? Here's

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Speaker 1: what people had to say.

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Speaker 4: No idea, absolutely, But I know that there's some talk

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Speaker 4: of making a Muon's collider or something like that. I

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Speaker 4: read about that in some news reports. So I'm gonna say, yeah, ah,

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Speaker 4: why not. You know, if you can accelerate them enough

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Speaker 4: and they don't dissipate energy like electrons, there should be

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Speaker 4: a way to create collisions.

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Speaker 3: I'm going to say, yes, I listened to your whole

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Speaker 3: podcast about muons, but I've completely forgotten what they are.

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Speaker 3: So I am going to take a kiss and say, yes,

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Speaker 3: you can use mulons to see inside something.

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Speaker 5: I would imagine using muons to look inside things would

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Speaker 5: be what the same principle is using an electron microscope.

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Speaker 5: I suspect muons are smaller than electrons, so for them

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Speaker 5: to bounce off something and give an image to be

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Speaker 5: bouncing off very small sub atomic particles.

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Speaker 2: I don't know what a mion is.

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Speaker 1: So I don't know, all right. I imagine a lot of

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Speaker 1: people are like that person who said they don't know

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Speaker 1: what a muon is. They don't know, but it sounds

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Speaker 1: like a reasonable question. A lot of people will seem

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Speaker 1: pretty optimistic about this.

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Speaker 2: Yeah, if a muone is some new kind of particle,

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Speaker 2: maybe it's got some new kind of powers or abilities

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Speaker 2: or properties that lets you do new kinds of stuff.

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Speaker 2: That's the optimism.

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Speaker 1: All right, Well, let's put a steak through this question,

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Speaker 1: and they started the basics, Daniel, What is exactly a muon?

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Speaker 1: A lot of people seem to have heard us talk

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Speaker 1: about it, but maybe forgotten. What it is.

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Speaker 2: A muon can best be understood is like a heavier version,

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Speaker 2: a more massive version of the electron. It's very very

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Speaker 2: similar to the electron, has a lot of the same properties,

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Speaker 2: same kinds of relationships as the electron, but it's more massive.

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Speaker 1: I see, So it's a particle, And I guess maybe

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Speaker 1: we should mention that the universe has particles, or at

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Speaker 1: least the potential to create particles or further to exist particles,

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Speaker 1: and a muon is one of these particles.

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Speaker 2: Yeah, there are lots of particles that make up me

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Speaker 2: and you and all the normal matter that's out there.

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Speaker 2: If you drill inside of us, you find molecules and atoms,

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Speaker 2: and those atoms are made of protons and neutrons and electrons.

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Speaker 2: The protons and neutrons are made out of quarks. So

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Speaker 2: at the most fundamental level, everything that you and I

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Speaker 2: are made out of, and everything that you and I eat,

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Speaker 2: including steaks and cows, are made up of upquarks and

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Speaker 2: down quarks and electrons. So those are the three basic

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Speaker 2: building blocks of normal matter. But there are other kinds

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Speaker 2: of particles out there that the universe can make. They're

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Speaker 2: sort of on the menu, but they're not stable and

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Speaker 2: they're not involved in building normal, everyday atomic matter. So

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Speaker 2: there's sort of various categories of particles out there. Ones

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Speaker 2: it can be made and exist all over the universe,

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Speaker 2: and ones it can be made but only exist briefly.

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Speaker 1: Or at least in the current universe that we have, right,

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Speaker 1: I think we talked about maybe before, Like maybe in

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Speaker 1: the early universe, the particles like nuons were common and

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Speaker 1: they would hang out.

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Speaker 2: Yeah, the frequency of which you find these particles definitely

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Speaker 2: depends on the temperature of the universe because the unstable

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Speaker 2: particles muons, charm corks, top quarks are a lot more

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Speaker 2: massive than the other particles that take more energy. These days,

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Speaker 2: it's rarer to create that kind of energy because the

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Speaker 2: universe is more spread out and colder. Back in the

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Speaker 2: early days of the universe, it wasn't as hard to

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Speaker 2: get enough energy together to make a muon or a

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Speaker 2: top quark. They always have a short lifetime, though they

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Speaker 2: still don't last very long, but they're made much more

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Speaker 2: often in the early universe. These days, it takes more

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Speaker 2: specialized conditions like humans smashing particles together or cosmic rays

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Speaker 2: hitting the atmosphere to create the conditions to make these

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Speaker 2: weird particles. They still don't last for very long.

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Speaker 1: So like the meon you said only lives for a

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Speaker 1: few microseconds, right.

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Speaker 2: Yeah, the muon lives for two point two microseconds before

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Speaker 2: it decays into an electron and a couple of neutrinos,

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Speaker 2: and we call the muon like a cousin of the

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Speaker 2: electron because it has a lot of the similar properties.

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Speaker 2: It's negatively charged like the electron is. It's paired with

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Speaker 2: the neutrino the way an electron is. So in our

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Speaker 2: sort of table of particles, we put the quarks in

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Speaker 2: one category and these other particles we call leptons in

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Speaker 2: another category because the muon, and like the electron, also

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Speaker 2: doesn't feel the strong nuclear force that the quarks do.

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Speaker 1: I see. So it's basically an electron, but somehow it

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Speaker 1: just has a more mass to it. Like the label

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Speaker 1: that says this is this is how much an electronic way,

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Speaker 1: it just happens to be more for the muon, But

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Speaker 1: other than that, it's almost exactly the same, Like it

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Speaker 1: has the same electrical charge and all the other quantum values.

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Speaker 2: Right, Yeah, it's about two hundred times more massive than

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Speaker 2: the electron. And nobody knows why that is, Like why

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Speaker 2: does the electron have this mass and the muon have

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Speaker 2: that mass? These are just numbers that we've discovered in

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Speaker 2: the universe without any explanation. You might think that the

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Speaker 2: Higgs gives an explanation for why some particles have more

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Speaker 2: mass than some have less. And it's true that the

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Speaker 2: muon has more mass than the electron because the Higgs

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Speaker 2: interacts with it more, giving it more mass, but that

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Speaker 2: doesn't explain why there's a difference. It just kicks the

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Speaker 2: can down the road. Instead of asking why does the

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Speaker 2: muon have more mass than the electron, we now ask

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Speaker 2: why does the muon interact with the Higgs more than

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Speaker 2: the electron does. The Higgs explains what mass is, but

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Speaker 2: not why some particles have more or less of it.

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Speaker 2: It's still just two numbers without an explanation. Now there's

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Speaker 2: two are interaction strength instead of mass. And there's a

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Speaker 2: third version of the electron called the tao, which is

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Speaker 2: even more massive. And this is the general pattern of

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Speaker 2: the particles. Each of the particles we talked about, the electron,

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Speaker 2: the upcork, the down cork has two copies of it

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Speaker 2: which are more massive. So this is some deep symmetry,

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Speaker 2: some structure to the universe that we've observed. We've organized,

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Speaker 2: we've seen the pattern, we've laid it out of the table,

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Speaker 2: but we've not understood it. And the mew one was

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Speaker 2: like one of the first clues we had that there

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Speaker 2: was more out there to the universe than just the

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Speaker 2: particles that made up our matter.

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Speaker 1: But I guess, you know, what does it mean that

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Speaker 1: it only lists for two point two microseconds? Like does

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Speaker 1: that even count as existing? You know, like why I

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Speaker 1: didn't call it a thing if it's only around for

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Speaker 1: two point two microseconds? You know, like can it move

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Speaker 1: around that much? Or or is this one of these

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Speaker 1: like relativistic things where to us it lists or two

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Speaker 1: point two microseconds, but maybe it's going really fast it

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Speaker 1: lives for a really really long time.

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Speaker 2: I think yes to all of that, although you know,

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Speaker 2: the timescale is always relative, like we only live for

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Speaker 2: one hundred years on the time scale the universe, that's

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Speaker 2: basically nothing. Do we even count as existing? I would

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Speaker 2: say yes, right, because time scales are relative relative to

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Speaker 2: some other particles, like the top quark lives for ten

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Speaker 2: to the money twenty three seconds, But we still think

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Speaker 2: that it's a thing. Like the neutron lasts for I

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Speaker 2: think eleven minutes before it decays, So these timescales are

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Speaker 2: all relative. What we actually mean by two point two

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Speaker 2: microseconds is in the muon's rest frame, like if you

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Speaker 2: had a muon in front of you at rest, and

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Speaker 2: you started a clock when it was created, and you

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Speaker 2: waited until a decayed, that would be two point two microseconds.

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Speaker 2: But you're right, relativity plays a big role. Muons are

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Speaker 2: often moving really really fast, especially when they're created in

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Speaker 2: the atmosphere, So if they're moving near the speed of light,

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Speaker 2: then a clock that's moving with them is slowed down.

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Speaker 2: And so the reason muons can actually survive from the

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Speaker 2: top of the atmosphere where they're made to hit us

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Speaker 2: on the ground is because their time is slowed. So

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Speaker 2: from our perspective, they can last for much much longer

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Speaker 2: than two point two microseconds, long enough to make it

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Speaker 2: to the surface of the Earth.

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Speaker 1: And what is it mean that it decays or does

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Speaker 1: it disintegrade? Does it like the energy just diffuses or

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Speaker 1: transforms it through something else? What does that actually mean?

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Speaker 2: Yeah, sometimes we think about decay as like something breaks

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Speaker 2: up and you get the component bits. It's like cracking

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Speaker 2: something open, breaking it into its basic legos, like an

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Speaker 2: atom broken up into its protons and neutrons. That's not

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Speaker 2: what's happening here, because when a muon decays, it turns

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Speaker 2: into an electron and two neutrinos. But it's not like

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Speaker 2: the electron and those neutrinos were inside the muon. It's

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Speaker 2: not like the muon is made of the electron and

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Speaker 2: the two neutrinos. Instead, think of that energy as passing

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Speaker 2: from the muon field to the electron field and the

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Speaker 2: neutrino fields. Remember that all these particles are really just

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Speaker 2: ripples in universe spanning fields that feel all of space.

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Speaker 2: Every part of space has a muon field, an electron field,

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Speaker 2: and the three different neutrino fields. So it's happening here

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Speaker 2: is that those fields are coming into contact, they're interacting,

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Speaker 2: and the muon field oscillations in that field are not stable.

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Speaker 2: They like to decay down into the electron field and

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Speaker 2: the neutrino fields. So that's what's happening here.

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Speaker 1: But maybe a question is like why is it so unstable,

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Speaker 1: Like what makes the muon field which makes muons prone

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Speaker 1: to be to basically dissipating or disappearing, and not, for example,

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Speaker 1: the electron field, which seems super duper stable.

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Speaker 2: The electron would like to decay, but there's nothing for

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Speaker 2: it to decay into because it's the lowest mass particle

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Speaker 2: in this chain, it's the lightest charged particle, and so

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Speaker 2: the muon can decay to an electron, which is a

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Speaker 2: lower mass particle, and so it does because in doing so,

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Speaker 2: it spreads out the energy. The universe doesn't like to

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Speaker 2: have a lot of energy concentrated in one place, likes

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Speaker 2: to spread it out. It's like entropy at a most

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Speaker 2: basic level. And so a high mass particle will tend

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Speaker 2: to decay into lower mass particles if it can, because

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Speaker 2: that provides more arrangements of that energy. Instead of having

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Speaker 2: all of it just in mass, now you have it

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Speaker 2: in a lower mass particle, plus lots of different possible

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Speaker 2: momentum states. So the quantum mechanical probabilities are just much

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Speaker 2: more for lower mass particles, and so they're more likely

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Speaker 2: to happen.

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Speaker 1: But I guess, maybe why doesn't Why can't the electron

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Speaker 1: break into something smaller? Is it just like we just

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Speaker 1: haven't seen it do that, or maybe it's impossible.

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Speaker 2: Well, we haven't seen an electron decay. We think electrons

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Speaker 2: are stable. Though it's possible that electrons live for like

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Speaker 2: a trillion years, we just never seen one decay because

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Speaker 2: they just last for a long, long time, right, it's

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Speaker 2: the same with the proton. We think the proton is stable,

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Speaker 2: but we don't know. We've never seen one decay, so

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Speaker 2: we think it might be stable or very very very

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Speaker 2: long lived. But for the electron to decay, there would

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Speaker 2: have to be something for it to decay into that

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Speaker 2: also has electric charge. Because electric charge is conserved, it

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Speaker 2: can't just go away. We don't know if any lower

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Speaker 2: mass charged particle than the electron, So it's sort of

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Speaker 2: like the bottom rung of the ladder, which is why

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Speaker 2: energy sort of gets stuck there.

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Speaker 1: I see, okay, so well, then the muon decays because

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Speaker 1: it can decay to other particles. Does it get triggered

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Speaker 1: by something, or if you just leave a meuon there,

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Speaker 1: it'll be like okay, I'm done, and then it breaks apart.

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Speaker 2: If you just leave a muon in the vacuum, it

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Speaker 2: will decay. Mwan flying through space will decay on their own.

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Speaker 2: They can also interact with stuff because they have charge.

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Speaker 2: They can interact with electrons, and they can interact with

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Speaker 2: protons and all sorts of stuff. So if you slam

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Speaker 2: them into a block of lead, for example, they will

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Speaker 2: interact and that can also trigger the decay, but muons

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Speaker 2: on their own will also just decay.

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Speaker 1: Can they appear out of nowhere? Like, what does it

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Speaker 1: take to make a muon? Or how are they made

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Speaker 1: if they're a thing in the universe. Is it just

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Speaker 1: whenever you have enough energy concentrated into one spot or

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Speaker 1: what's the origin story of a muon?

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Speaker 2: So the origin stories that you get enough energy into

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Speaker 2: sort of a higher mass field to feel that can

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Speaker 2: decay into muons. Energy likes to flow down the lower

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Speaker 2: mass fields like rungs down the ladder, So you got

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Speaker 2: to get enough energy into a higher mass field and

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Speaker 2: then it can decay into muons. So the typical way

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Speaker 2: that muons are made naturally in our environment is they

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Speaker 2: have a cosmic ray, which is like a proton slimming

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Speaker 2: into some particle in the atmosphere, which creates a lot

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Speaker 2: of energy density in one space, and then you create

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Speaker 2: some very massive, unstable particle, and a lot of particles

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Speaker 2: decay into muons, So you might create like a pion

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Speaker 2: or a chaon. These are more massive particles that like

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Speaker 2: to decay into muons, and then those decay in the atmosphere,

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Speaker 2: giving you a muon which flies down to the surface.

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Speaker 2: Of the Earth.

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Speaker 1: But don't you need where does the charge come from?

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Speaker 2: Protons are charged, right, so the charge comes from the

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Speaker 2: cosmic ray, and also there's loss of charge in the

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Speaker 2: upper atmosphere. Even a neutron slamming into a particle in

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Speaker 2: the upper atmosphere, and like disintegrating an oxygen molecule can

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Speaker 2: create showers of charged particles.

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Speaker 1: M where does the negative charge come from? Isn't a

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Speaker 1: photon neutral?

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Speaker 2: Well, first of all, we have two flavors of muons.

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Speaker 2: We have negative muons, which are the normal ones, and

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Speaker 2: then anti muons, which are positively charged. In particle physics

381
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Speaker 2: we don't really care so much about it, and both

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Speaker 2: of them are created in the upper atmospherees, So we

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Speaker 2: have anti muons and muons created in the upper atmosphere.

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Speaker 2: But your question is a good one. If you start

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Speaker 2: from a positively charged proton, how you end up making

386
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Speaker 2: like a negatively charged muon. The answer is that there's

387
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Speaker 2: just a lot more stuff in in this interaction then

388
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Speaker 2: we're describing, Because a proton is a big complicated bag

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Speaker 2: of quarks and it slams into something else in the atmosphere,

390
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Speaker 2: which is a big complicated bag of other protons and neutrons,

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Speaker 2: so there's plenty of charges around to create something which

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Speaker 2: decays into a negatively charged particle and balance it out

393
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Speaker 2: with all the rest of the stuff. So a proton

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Speaker 2: can turn into a huge shower of negative and positive

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Speaker 2: particles with a total charge of plus one. So you

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Speaker 2: can have lots of muons and anti muons created in

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Speaker 2: these showers.

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Speaker 1: All right, Well, whether you're pro or anti muon maybe

399
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Speaker 1: is the question of the episodes. Can we use a

400
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Speaker 1: muon to see inside of things and maybe put these

401
00:19:39,000 --> 00:19:43,199
Speaker 1: giant particles to use that's the question. Let's dig into that,

402
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Speaker 1: But first let's take a quick break. All right, we're

403
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Speaker 1: talking about the electrons, cousin, more massive cousin, the muon,

404
00:20:03,800 --> 00:20:05,800
Speaker 1: and whether it can be used to see inside of

405
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Speaker 1: things like steaks and cows perhaps.

406
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Speaker 2: And also may be solving mysteries of archaeology.

407
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Speaker 1: Ooh, you mean like ancient buried cows.

408
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Speaker 2: Yes, maybe ancient buried cows? Literally?

409
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Speaker 1: Did early man eat steak or not? Or were they

410
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Speaker 1: v in?

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Speaker 2: Can you age a steak for thousands of years and

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Speaker 2: still have it be tasty?

413
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Speaker 1: Did Paleoman actually follow the paleodiet? We might use meons

414
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Speaker 1: for that all right, So we talked about what the

415
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Speaker 1: meon is. It's the more massive cousin of the electron,

416
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Speaker 1: and that it rarely lasts more than two point two

417
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Speaker 1: microseconds in nature in the universe. So if it's so

418
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Speaker 1: elusive and unstable, how did we discover this heavy particle.

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Speaker 2: Well, it turns out that muons are everywhere because cosmic

420
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Speaker 2: rays are constantly slamming into the upper atmosphere, creating showers

421
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Speaker 2: of particles, a lot of which turned into muons. So

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Speaker 2: there are ten thousand muons per square meter per minute

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Speaker 2: at the surface of the Earth.

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Speaker 1: By cosmic rays, you mean like just other particles going

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Speaker 1: really really fast somehow hitting the Earth exactly.

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Speaker 2: Sometimes people think that space is a vacuum. It's emptiness,

427
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Speaker 2: there's nothing out there, but the Sun is pumping out

428
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Speaker 2: protons and electrons and all sorts of stuff, and the

429
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Speaker 2: galaxy has lots of sources of high energy particles. So

430
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Speaker 2: we're really flying through a wind of particles, meaning that

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Speaker 2: you can think of them as like tiny little meteors

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Speaker 2: hitting the upper atmosphere one proton at a time, or

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Speaker 2: maybe an iron and nucleus at a time in creating

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Speaker 2: a little shower of energy, just the same way that

435
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Speaker 2: a meteor hitting the atmosphere will interact with the atmosphere

436
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Speaker 2: and get friction and break up and slow down. A

437
00:21:39,040 --> 00:21:41,720
Speaker 2: tiny particle like a proton, with enough energy will create

438
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Speaker 2: a shower of particles which eventually reaches the surface of

439
00:21:45,280 --> 00:21:48,119
Speaker 2: the Earth, and a lot of those are muons. There

440
00:21:48,160 --> 00:21:50,920
Speaker 2: are also photons and electrons and other stuff in there,

441
00:21:50,960 --> 00:21:53,760
Speaker 2: but muons are the most penetrating. They tend to pass

442
00:21:53,840 --> 00:21:56,360
Speaker 2: through matter without interacting, so a lot of them make

443
00:21:56,400 --> 00:21:57,240
Speaker 2: it to the surface of.

444
00:21:57,240 --> 00:22:00,520
Speaker 1: The Earth's sort of a good thing, right, we didn't

445
00:22:00,560 --> 00:22:03,119
Speaker 1: have the atmosphere and we were getting hit directly by

446
00:22:03,160 --> 00:22:05,840
Speaker 1: cosmic grays, we might not be around today, right. These

447
00:22:05,840 --> 00:22:07,920
Speaker 1: costomic grays are very harmful, so it's a good thing

448
00:22:07,960 --> 00:22:10,080
Speaker 1: they're being kind of broken up into muons.

449
00:22:10,200 --> 00:22:12,439
Speaker 2: Yeah. The atmosphere is like a big blanket that protects

450
00:22:12,480 --> 00:22:15,240
Speaker 2: you from the radiation of outer space. When astronauts go

451
00:22:15,320 --> 00:22:18,159
Speaker 2: up into space, they have to take special precautions to

452
00:22:18,240 --> 00:22:21,439
Speaker 2: avoid being slammed into by all of this radiation. When

453
00:22:21,480 --> 00:22:23,679
Speaker 2: there's like a solar storm, the astronauts have like a

454
00:22:23,720 --> 00:22:26,359
Speaker 2: panic room that can go into with extra shielding to

455
00:22:26,440 --> 00:22:29,080
Speaker 2: protect themselves from all that radiation. But the higher up

456
00:22:29,080 --> 00:22:31,480
Speaker 2: you go in the atmosphere, the more radiation you're exposed

457
00:22:31,480 --> 00:22:34,480
Speaker 2: to because more these particles survive. So every time you

458
00:22:34,480 --> 00:22:37,360
Speaker 2: take a flight, for example, you're exposing yourself to more radiation.

459
00:22:37,760 --> 00:22:40,400
Speaker 2: This is one reason why like flight attendants and pilots

460
00:22:40,400 --> 00:22:42,720
Speaker 2: are limited to how many days a month they can work.

461
00:22:42,840 --> 00:22:45,440
Speaker 1: All right, So then the atmosphere breaks up the cosmic

462
00:22:45,440 --> 00:22:48,320
Speaker 1: grays and you said, turns them mostly into muons or

463
00:22:48,600 --> 00:22:51,840
Speaker 1: rarely into meons. How often are muons created by these

464
00:22:51,880 --> 00:22:52,520
Speaker 1: cosmic rays.

465
00:22:52,720 --> 00:22:54,879
Speaker 2: It's sort of like a chain. The proton creates a

466
00:22:54,920 --> 00:22:57,359
Speaker 2: bunch of particles, which then decaynees is something, which then

467
00:22:57,400 --> 00:23:00,000
Speaker 2: decaynes something, and the muon is like an end product.

468
00:23:00,080 --> 00:23:02,480
Speaker 2: Then it tends to last the longest. So saw like

469
00:23:02,480 --> 00:23:06,200
Speaker 2: the muon dominates the production of particles. You also make electrons,

470
00:23:06,200 --> 00:23:09,440
Speaker 2: and you make neutrinos, and you make photons. The neutrinos

471
00:23:09,480 --> 00:23:11,040
Speaker 2: and the muons are the ones that make it through

472
00:23:11,040 --> 00:23:13,399
Speaker 2: the rest of the atmosphere. They tend to interact a

473
00:23:13,440 --> 00:23:17,040
Speaker 2: little bit less than electrons and photons, so you see

474
00:23:17,040 --> 00:23:19,000
Speaker 2: them on the surface of the Earth more often.

475
00:23:19,200 --> 00:23:21,679
Speaker 1: Oh, I see you're also making a lot of electrons

476
00:23:21,680 --> 00:23:24,560
Speaker 1: and other particles. But maybe like the electrons get stopped

477
00:23:24,560 --> 00:23:27,160
Speaker 1: by all the remaining air in the atmosphere.

478
00:23:27,240 --> 00:23:30,359
Speaker 2: Exactly. Electrons like to interact with stuff. The electrons passing

479
00:23:30,359 --> 00:23:33,560
Speaker 2: through air will interact with those molecules much more often

480
00:23:33,600 --> 00:23:36,960
Speaker 2: than muons do. Muons are more penetrating.

481
00:23:36,760 --> 00:23:39,359
Speaker 1: And why is that? Are they just more antisocial?

482
00:23:40,960 --> 00:23:43,240
Speaker 2: It actually has a really fascinating explanation that has to

483
00:23:43,280 --> 00:23:45,919
Speaker 2: do with special relativity, and this is the power that

484
00:23:46,000 --> 00:23:48,679
Speaker 2: muons have to let us see through things. Muons are

485
00:23:48,720 --> 00:23:52,320
Speaker 2: more penetrating because they have more mass, so they're two

486
00:23:52,400 --> 00:23:55,840
Speaker 2: hundred times more massive than the electron. Otherwise, from a

487
00:23:55,840 --> 00:23:59,280
Speaker 2: particle physics perspective, they're very similar. They feel the weak force,

488
00:23:59,520 --> 00:24:02,480
Speaker 2: they feel electromagnetism, they don't feel the strong force. But

489
00:24:02,520 --> 00:24:04,560
Speaker 2: if you shoot a beam of muons into like a

490
00:24:04,600 --> 00:24:06,879
Speaker 2: block of lead, you'll get a lot more out on

491
00:24:06,920 --> 00:24:09,199
Speaker 2: the other side than if you did with electrons. And

492
00:24:09,280 --> 00:24:10,880
Speaker 2: the reason is their mass.

493
00:24:11,280 --> 00:24:13,199
Speaker 1: Is it like to have more inertia? Is that kind

494
00:24:13,240 --> 00:24:14,800
Speaker 1: of what you're getting at? Just like you know, if

495
00:24:14,800 --> 00:24:17,560
Speaker 1: I shoot a small pebble into a pool or something,

496
00:24:17,640 --> 00:24:19,919
Speaker 1: or if you throw shoot a bulling ball through it,

497
00:24:20,000 --> 00:24:23,000
Speaker 1: like the bowling ball will get through the pool further.

498
00:24:23,280 --> 00:24:25,080
Speaker 1: Or is it some other kind of mechanism.

499
00:24:25,240 --> 00:24:28,040
Speaker 2: It's another mechanism. It's actually because they are interacting less

500
00:24:28,280 --> 00:24:31,240
Speaker 2: because they see less of the material. It's a special

501
00:24:31,280 --> 00:24:33,919
Speaker 2: relativity effect. If you have an electron and a muon

502
00:24:33,960 --> 00:24:37,440
Speaker 2: at the same energy, the muon is actually going slower

503
00:24:37,480 --> 00:24:40,280
Speaker 2: because it's more massive, like more of the energy is

504
00:24:40,359 --> 00:24:43,040
Speaker 2: taken up creating a mass of the muon. So if

505
00:24:43,080 --> 00:24:45,200
Speaker 2: you give them the same energy, the muon is moving

506
00:24:45,240 --> 00:24:48,199
Speaker 2: slower as a lower velocity than the electron at the

507
00:24:48,240 --> 00:24:50,600
Speaker 2: same energy because it has more mass.

508
00:24:51,040 --> 00:24:53,600
Speaker 1: So then you're sort of constraining things to be all

509
00:24:53,640 --> 00:24:54,359
Speaker 1: the same energy.

510
00:24:54,560 --> 00:24:57,280
Speaker 2: Yeah, exactly, because it's the typical energy that these particles

511
00:24:57,320 --> 00:24:59,840
Speaker 2: are produced at in these showers. So if you have

512
00:24:59,880 --> 00:25:02,240
Speaker 2: an electron and muon of the same energy, the muon

513
00:25:02,320 --> 00:25:05,359
Speaker 2: is going slower and that affects how it interacts because

514
00:25:05,359 --> 00:25:08,200
Speaker 2: it sees less of the material. To an electron moving

515
00:25:08,400 --> 00:25:11,040
Speaker 2: nearly the speed of light, everything in front of it

516
00:25:11,119 --> 00:25:14,480
Speaker 2: is squeezed by special relativity. Remember we talked about how

517
00:25:14,520 --> 00:25:17,640
Speaker 2: things moving near the speed of light look shorter. That's

518
00:25:17,680 --> 00:25:20,840
Speaker 2: also true from their perspective. An electron whizzing through the

519
00:25:20,840 --> 00:25:23,200
Speaker 2: atmosphere sees the distance to the surface of the Earth

520
00:25:23,240 --> 00:25:26,480
Speaker 2: as closer than we see it because it's moving fast

521
00:25:26,520 --> 00:25:29,280
Speaker 2: relative to the surface of the Earth, so things are squeezed.

522
00:25:29,400 --> 00:25:31,880
Speaker 2: As a result, it can interact with more the atmosphere.

523
00:25:32,160 --> 00:25:33,760
Speaker 2: Or another way to think about it is like the

524
00:25:33,800 --> 00:25:36,280
Speaker 2: atmosphere is denser because all that gas is like the

525
00:25:36,320 --> 00:25:39,080
Speaker 2: Lorentz contracted in front of it into something a little

526
00:25:39,080 --> 00:25:41,159
Speaker 2: more dense. So it can interact with more of the

527
00:25:41,200 --> 00:25:44,520
Speaker 2: atmosphere because it's moving at a higher speed and has

528
00:25:44,640 --> 00:25:46,840
Speaker 2: more of this special relativity enhancement.

529
00:25:47,080 --> 00:25:49,359
Speaker 1: Wait, that doesn't make a whole lot of sense to me.

530
00:25:49,960 --> 00:25:52,240
Speaker 1: Like you're saying, like the rest of the atmosphere to

531
00:25:52,280 --> 00:25:55,640
Speaker 1: an electron, because it's moving fast, the atmosphere looks thinner

532
00:25:55,880 --> 00:25:59,439
Speaker 1: and more dense, and so it's harder to get through it.

533
00:25:59,480 --> 00:26:02,680
Speaker 1: But it's still the same length to us. Isn't it

534
00:26:03,680 --> 00:26:06,200
Speaker 1: like it's squeezed, but it's still the same It's going

535
00:26:06,240 --> 00:26:09,320
Speaker 1: through the same amount of stuff as the slower nuon.

536
00:26:09,640 --> 00:26:09,720
Speaker 5: No.

537
00:26:10,040 --> 00:26:12,440
Speaker 2: Yeah, but it sees more of the material at once.

538
00:26:12,600 --> 00:26:16,240
Speaker 2: It's like it has more atoms to interact with so

539
00:26:16,359 --> 00:26:18,560
Speaker 2: this is a quantum mechanical process, and it has like

540
00:26:18,600 --> 00:26:21,480
Speaker 2: a probability to interact with an atom. An electron flies

541
00:26:21,520 --> 00:26:23,320
Speaker 2: by an atom, there's a chance it's going to interact

542
00:26:23,320 --> 00:26:25,480
Speaker 2: and a chance that it's not. The more atoms it

543
00:26:25,480 --> 00:26:28,040
Speaker 2: flies by, the more likely it's going to interact and

544
00:26:28,080 --> 00:26:30,520
Speaker 2: lose some of its energy. So if you squeeze more

545
00:26:30,560 --> 00:26:33,200
Speaker 2: atoms into the same space, then it's got a higher

546
00:26:33,280 --> 00:26:36,600
Speaker 2: chance of interacting. And what special relativity does is because

547
00:26:36,600 --> 00:26:39,840
Speaker 2: the electron is moving faster, it Lorentz contracts the stuff

548
00:26:39,880 --> 00:26:42,840
Speaker 2: in front of it basically squeezes in more atoms at once.

549
00:26:43,640 --> 00:26:46,360
Speaker 1: I see, you sort of have to change the way

550
00:26:46,359 --> 00:26:49,119
Speaker 1: you're thinking about how these particles interact. Like you're saying,

551
00:26:49,119 --> 00:26:51,920
Speaker 1: like you know, an electron when it hits a wall,

552
00:26:53,080 --> 00:26:55,679
Speaker 1: it's not actually touching the wall. It just gets close

553
00:26:55,800 --> 00:26:58,240
Speaker 1: enough to it that there's some sort of quantum mechanical

554
00:26:58,440 --> 00:27:02,200
Speaker 1: transmission between the two that makes them technically interact.

555
00:27:02,280 --> 00:27:05,760
Speaker 2: Right, Yeah, exactly. And that's why, for example, neutrinos can

556
00:27:05,800 --> 00:27:08,239
Speaker 2: pass through a light year of lead. They're passing through

557
00:27:08,280 --> 00:27:11,679
Speaker 2: the same material and they're not like dodging around those particles.

558
00:27:11,680 --> 00:27:15,440
Speaker 2: It's not a mechanical physical interaction of things touching. It's

559
00:27:15,440 --> 00:27:19,600
Speaker 2: a quantum mechanical interaction of forces. The neutrino just doesn't

560
00:27:19,640 --> 00:27:22,240
Speaker 2: interact with those particles at all, like phases right through

561
00:27:22,280 --> 00:27:25,480
Speaker 2: that stuff, because it doesn't feel electromagnetism. It only has

562
00:27:25,480 --> 00:27:29,080
Speaker 2: a smaller chance to interact with every single particle. So

563
00:27:29,080 --> 00:27:31,760
Speaker 2: that's why neutrinos pass through almost everything, and that's why

564
00:27:31,840 --> 00:27:35,920
Speaker 2: there's a difference between the penetrating power of muons and electrons. Muons,

565
00:27:35,960 --> 00:27:39,600
Speaker 2: being more massive at the same energy, are effectively moving slower,

566
00:27:39,880 --> 00:27:42,720
Speaker 2: so they have less of this special relativity boost where

567
00:27:42,720 --> 00:27:46,480
Speaker 2: they can interact with otherwise further away atoms that now

568
00:27:46,520 --> 00:27:49,600
Speaker 2: look closer to them, and so they can feel their fields.

569
00:27:50,880 --> 00:27:53,600
Speaker 1: So as thee electron is a showering down coming down

570
00:27:53,600 --> 00:27:56,679
Speaker 1: the atmosphere, you're saying it sees the bottom of the

571
00:27:56,760 --> 00:27:59,800
Speaker 1: atmosphere as closer, which might make it more likely to

572
00:28:00,280 --> 00:28:02,760
Speaker 1: But I guess the weird thing is that, you know,

573
00:28:02,760 --> 00:28:05,280
Speaker 1: if it does interact with the bottom of the atmosphere,

574
00:28:05,600 --> 00:28:07,760
Speaker 1: what didn't it mean it made it through the atmosphere,

575
00:28:08,040 --> 00:28:10,280
Speaker 1: And so it's really, isn't it sort of the same

576
00:28:10,720 --> 00:28:11,720
Speaker 1: thing probability?

577
00:28:11,800 --> 00:28:13,359
Speaker 2: It's a cool way to look at it. But it

578
00:28:13,400 --> 00:28:15,920
Speaker 2: can interact with the bottom of the atmosphere while still

579
00:28:15,960 --> 00:28:18,320
Speaker 2: not being that far through the atmosphere because to it,

580
00:28:18,359 --> 00:28:20,320
Speaker 2: the bottom of the atmosphere is not that far away,

581
00:28:20,400 --> 00:28:23,080
Speaker 2: so it can still feel those fields right right, it

582
00:28:23,119 --> 00:28:24,040
Speaker 2: feels it closer.

583
00:28:24,080 --> 00:28:26,240
Speaker 1: But if it interacts with the bottom of the atmosphere,

584
00:28:26,320 --> 00:28:28,720
Speaker 1: isn't it the same as making it through the atmosphere,

585
00:28:28,880 --> 00:28:31,399
Speaker 1: Like it's kipped everything above and it made it to

586
00:28:31,440 --> 00:28:33,000
Speaker 1: the bottom of the atmosphere. That means it made it

587
00:28:33,000 --> 00:28:33,880
Speaker 1: through the atmosphere.

588
00:28:33,920 --> 00:28:35,840
Speaker 2: It doesn't have to make it to the bottom of

589
00:28:35,880 --> 00:28:38,200
Speaker 2: the atmosphere in order to interact with things at the

590
00:28:38,200 --> 00:28:40,880
Speaker 2: bottom of the atmosphere. Remember, all of these things are

591
00:28:40,920 --> 00:28:44,200
Speaker 2: action at a distance. You're feeling the fields of things.

592
00:28:44,240 --> 00:28:46,200
Speaker 2: Two electrons don't have to touch each other in order

593
00:28:46,200 --> 00:28:48,320
Speaker 2: to interact. They just have to feel their.

594
00:28:48,200 --> 00:28:50,200
Speaker 1: Field or I guess maybe, But I mean it's like,

595
00:28:50,240 --> 00:28:53,640
Speaker 1: what's the difference between an electron that makes it through

596
00:28:53,680 --> 00:28:56,200
Speaker 1: the atmosphere and interacts with the bottom of the atmosphere

597
00:28:56,280 --> 00:28:59,400
Speaker 1: and an electron that sees the bottom of the atmosphere

598
00:28:59,440 --> 00:29:01,640
Speaker 1: is closer and interacts with it. Aren't they both the

599
00:29:01,680 --> 00:29:03,880
Speaker 1: same result, and that don't both mean that they made

600
00:29:03,920 --> 00:29:04,880
Speaker 1: it through the atmosphere.

601
00:29:04,920 --> 00:29:08,000
Speaker 2: So higher speed electron is more likely to interact because

602
00:29:08,040 --> 00:29:10,640
Speaker 2: it sees more of the atmosphere, and it's going to

603
00:29:10,680 --> 00:29:14,600
Speaker 2: interact at a higher altitude than a lower velocity electron,

604
00:29:15,000 --> 00:29:17,120
Speaker 2: which doesn't see as much of the atmosphere because a

605
00:29:17,200 --> 00:29:20,480
Speaker 2: special relativity boost. And so even if you're interacting with

606
00:29:20,520 --> 00:29:23,400
Speaker 2: things that are lower down, your actual location is still

607
00:29:23,480 --> 00:29:24,080
Speaker 2: higher up.

608
00:29:24,320 --> 00:29:27,040
Speaker 1: Oh, I see you're talking about it might decay before

609
00:29:27,040 --> 00:29:30,000
Speaker 1: it reaches the bottom of the atmosphere. It's not necessarily

610
00:29:30,080 --> 00:29:32,520
Speaker 1: interacting with the bottom of the atmosphere. Like if it

611
00:29:32,560 --> 00:29:34,800
Speaker 1: touches the bottom of the atmosphere, it means it made

612
00:29:34,800 --> 00:29:36,040
Speaker 1: it through the atmosphere, doesn't it.

613
00:29:36,120 --> 00:29:39,040
Speaker 2: Well, electrons don't decay, right, All they can do is interact.

614
00:29:39,080 --> 00:29:40,920
Speaker 2: But again, you can interact with something at the bottom

615
00:29:40,920 --> 00:29:43,720
Speaker 2: of the atmosphere without being there, right the same way

616
00:29:43,800 --> 00:29:46,600
Speaker 2: like the Earth is interacting with the Sun without touching

617
00:29:46,640 --> 00:29:49,080
Speaker 2: the Sun, because if you can feel its gravity at

618
00:29:49,080 --> 00:29:49,640
Speaker 2: a distance.

619
00:29:49,760 --> 00:29:52,120
Speaker 1: All right, well, let's assume that then that that's the case.

620
00:29:52,200 --> 00:29:55,320
Speaker 1: And so you're saying neuons can make it through more

621
00:29:55,320 --> 00:29:58,160
Speaker 1: of the atmosphere or anything in particular, just because they're moving,

622
00:29:58,480 --> 00:30:00,880
Speaker 1: they tend to be moving slower, although if you had

623
00:30:00,880 --> 00:30:02,480
Speaker 1: a fast moving meuon, that wouldn't be.

624
00:30:02,400 --> 00:30:04,520
Speaker 2: The case exactly, And we actually see those at the

625
00:30:04,600 --> 00:30:07,840
Speaker 2: Large Hadron Collider. We can make muons with enough energy

626
00:30:07,920 --> 00:30:11,400
Speaker 2: that they're moving at very relativistic speeds and they interact

627
00:30:11,400 --> 00:30:13,760
Speaker 2: with matter like electrons do, so we can see like

628
00:30:14,080 --> 00:30:17,000
Speaker 2: muon created showers when we happen to make a really

629
00:30:17,040 --> 00:30:19,640
Speaker 2: really high velocity muon. It's just a feature of muons

630
00:30:19,640 --> 00:30:22,040
Speaker 2: and electrons at the energies that they tend to be

631
00:30:22,080 --> 00:30:25,600
Speaker 2: produced at in our cosmic rays here on Earth because

632
00:30:25,640 --> 00:30:27,000
Speaker 2: of the ratio of their masses.

633
00:30:28,600 --> 00:30:32,000
Speaker 1: I guess, couldn't you just use a slower moving electron.

634
00:30:32,640 --> 00:30:35,400
Speaker 1: Wouldn't that be the equivalent of a slow moving muon?

635
00:30:35,520 --> 00:30:37,440
Speaker 1: Then then the electron could penetrate things more.

636
00:30:37,640 --> 00:30:40,360
Speaker 2: Yeah, it's a good question. You can slow down electrons,

637
00:30:40,680 --> 00:30:42,320
Speaker 2: but then there are other effects that are going to

638
00:30:42,360 --> 00:30:44,320
Speaker 2: come into play that are going to make it interact more.

639
00:30:44,640 --> 00:30:47,440
Speaker 2: So there isn't a window there for electrons to do

640
00:30:47,480 --> 00:30:49,120
Speaker 2: the same trick that muons can do.

641
00:30:49,520 --> 00:30:52,040
Speaker 1: I think what you're really saying is like you're trying

642
00:30:52,040 --> 00:30:56,040
Speaker 1: to use muons, not as a general concept, but neuons

643
00:30:56,080 --> 00:30:59,040
Speaker 1: that are particularly created in the cosmic rays when they interact,

644
00:30:59,200 --> 00:31:01,920
Speaker 1: when they slam into the atmosphere. You're trying to put

645
00:31:02,080 --> 00:31:04,600
Speaker 1: forward the idea of using these meons that are showering

646
00:31:04,640 --> 00:31:07,640
Speaker 1: as as maybe like an X ray machine.

647
00:31:07,720 --> 00:31:10,720
Speaker 2: Yeah, exactly. Muons have this window of energy in which

648
00:31:10,760 --> 00:31:13,800
Speaker 2: they can penetrate really really deeply. If they move more slowly,

649
00:31:13,840 --> 00:31:16,280
Speaker 2: then they run into the same atomic physics that electrons have.

650
00:31:16,320 --> 00:31:18,840
Speaker 2: They can get captured. They move faster, then they get

651
00:31:18,840 --> 00:31:21,600
Speaker 2: the realtivistic effects, and they interact just like electrons. But

652
00:31:21,680 --> 00:31:24,920
Speaker 2: muons have this special window, this energy range in which

653
00:31:24,960 --> 00:31:27,600
Speaker 2: they can pass through a lot of matter, much more

654
00:31:27,640 --> 00:31:29,680
Speaker 2: than X rays can. X rays can pass through some

655
00:31:29,760 --> 00:31:31,680
Speaker 2: kinds of matter, which is why you can use them

656
00:31:31,680 --> 00:31:34,240
Speaker 2: to see your bones and inside your body, but muons

657
00:31:34,240 --> 00:31:37,040
Speaker 2: can pass through a lot more matter than X rays can.

658
00:31:37,320 --> 00:31:41,640
Speaker 2: X rays, for example, cannot pass through huge blocks of granite.

659
00:31:42,320 --> 00:31:46,080
Speaker 1: But you sort of skip through something, which is you said, electrons,

660
00:31:46,160 --> 00:31:48,080
Speaker 1: even if you slow them down, are not as good

661
00:31:48,120 --> 00:31:51,440
Speaker 1: as muons for X rays applications.

662
00:31:51,640 --> 00:31:53,800
Speaker 2: And why is that, Well, they'll get captured by atoms

663
00:31:53,800 --> 00:31:56,560
Speaker 2: like electrons moving slowly will just get captured, but not

664
00:31:56,640 --> 00:31:59,760
Speaker 2: a muon. A muon moving really slowly also will get captured. Yeah,

665
00:32:00,080 --> 00:32:02,600
Speaker 2: muon has a window. It's got a minimum energies do

666
00:32:02,680 --> 00:32:05,400
Speaker 2: this and a maximum energy in order to do this

667
00:32:05,480 --> 00:32:06,360
Speaker 2: penetrating trick.

668
00:32:06,680 --> 00:32:09,840
Speaker 1: So then you were saying, how were these muons discovered?

669
00:32:09,920 --> 00:32:12,959
Speaker 2: So these muons were discovered in cosmic rays. People were

670
00:32:12,960 --> 00:32:17,040
Speaker 2: studying electrons and somebody had even discovered the anti electron,

671
00:32:17,440 --> 00:32:19,920
Speaker 2: and they're studying these particles by watching them move in

672
00:32:20,000 --> 00:32:23,440
Speaker 2: magnetic fields and seeing how they curve, and they saw

673
00:32:23,480 --> 00:32:25,920
Speaker 2: something which looked kind of like an electron and had

674
00:32:25,920 --> 00:32:28,920
Speaker 2: a charge like an electron. They curved in a magnetic

675
00:32:28,920 --> 00:32:31,560
Speaker 2: field the same direction as an electron, but they didn't

676
00:32:31,600 --> 00:32:34,520
Speaker 2: curve as much, and it penetrated much more deeply, like

677
00:32:34,560 --> 00:32:36,200
Speaker 2: you could put slabs of lead in front of your

678
00:32:36,200 --> 00:32:39,600
Speaker 2: detector and you would still see it. So nineteen thirty

679
00:32:39,640 --> 00:32:42,240
Speaker 2: six physicistic Caltech first discovered.

680
00:32:41,800 --> 00:32:45,160
Speaker 1: These things and they bend less in a magnetic field

681
00:32:45,200 --> 00:32:48,480
Speaker 1: because of their mass, right, basically their innership or is

682
00:32:48,520 --> 00:32:50,600
Speaker 1: it also some weird quantum interaction.

683
00:32:51,000 --> 00:32:53,040
Speaker 2: No, it's no, it's a very classical thing. It's just

684
00:32:53,120 --> 00:32:55,600
Speaker 2: because of their mass. Yeah, mmmmm, I see.

685
00:32:56,680 --> 00:32:59,120
Speaker 1: All right, Well let's get into how you might use

686
00:32:59,240 --> 00:33:02,680
Speaker 1: muons to penetrate things, see inside of things, maybe discover

687
00:33:02,880 --> 00:33:08,400
Speaker 1: ancient artifacts inside of pyramids. So let's dig into that.

688
00:33:08,440 --> 00:33:23,480
Speaker 1: But first let's take another quick break. Or we're talking

689
00:33:23,520 --> 00:33:25,440
Speaker 1: about neons and how you can use them to see

690
00:33:25,480 --> 00:33:29,120
Speaker 1: inside of things, and we talked about how meons sort

691
00:33:29,120 --> 00:33:32,560
Speaker 1: of have an extra penetrating effects more than its cousin,

692
00:33:32,680 --> 00:33:37,280
Speaker 1: the electron, because it's heavier. And so the idea is

693
00:33:37,760 --> 00:33:39,960
Speaker 1: then to use this like an X ray basically, like

694
00:33:39,960 --> 00:33:43,800
Speaker 1: shoot it at something and if it gets through, then

695
00:33:43,840 --> 00:33:45,280
Speaker 1: that tells you what's inside of the thing.

696
00:33:45,480 --> 00:33:47,120
Speaker 2: Yeah, you can sort of use it as a way

697
00:33:47,120 --> 00:33:49,840
Speaker 2: to measure the density of something. If you have an

698
00:33:49,840 --> 00:33:52,280
Speaker 2: object and you don't know if inside of it is

699
00:33:52,440 --> 00:33:55,520
Speaker 2: nothing like a vacuum or a huge block of super

700
00:33:55,560 --> 00:33:58,320
Speaker 2: dense uranium, you can try to shoot it with a

701
00:33:58,320 --> 00:34:01,040
Speaker 2: bunch of muons and count how any come out. By

702
00:34:01,040 --> 00:34:02,920
Speaker 2: figuring out how many make it through, you can tell

703
00:34:02,920 --> 00:34:05,360
Speaker 2: what the density of something is. This only works if

704
00:34:05,400 --> 00:34:08,319
Speaker 2: you have something which has a chance to make it through, Right,

705
00:34:08,360 --> 00:34:10,640
Speaker 2: If you just shoot photons at a block then none

706
00:34:10,680 --> 00:34:11,960
Speaker 2: of them are going to make it through. They're all

707
00:34:12,000 --> 00:34:15,160
Speaker 2: going to get absorbed. Doesn't tell you anything about what's inside.

708
00:34:15,280 --> 00:34:17,200
Speaker 2: But if you have a particle which has a chance

709
00:34:17,239 --> 00:34:20,399
Speaker 2: to make it through for some densities, then you can

710
00:34:20,440 --> 00:34:22,520
Speaker 2: measure the rate at which does make it through and

711
00:34:22,560 --> 00:34:25,640
Speaker 2: figure out what the density of that stuff was, right.

712
00:34:25,560 --> 00:34:28,000
Speaker 1: Right, I guess it's sort of like X rays. Like

713
00:34:28,239 --> 00:34:32,080
Speaker 1: X rays, if I just shine of flashlight onto my body,

714
00:34:32,160 --> 00:34:33,879
Speaker 1: it's going to bounce off the skin, or at least

715
00:34:33,880 --> 00:34:35,800
Speaker 1: most of the photons, because the light is at a

716
00:34:35,800 --> 00:34:38,160
Speaker 1: certain wavelength. But if I change the wavelength to that

717
00:34:38,200 --> 00:34:40,200
Speaker 1: of an X ray, it will go through my body.

718
00:34:40,280 --> 00:34:42,520
Speaker 2: Sort of, yeah, exactly, some of the X rays will

719
00:34:42,520 --> 00:34:44,480
Speaker 2: make it through. And if you have an X ray

720
00:34:44,480 --> 00:34:46,560
Speaker 2: detector on the other side, you can pick that up

721
00:34:46,840 --> 00:34:48,640
Speaker 2: and by looking at the pattern of where the X

722
00:34:48,760 --> 00:34:50,799
Speaker 2: rays made it through and didn't make it through, you

723
00:34:50,800 --> 00:34:52,640
Speaker 2: can tell what the density of stuff is. And that's

724
00:34:52,680 --> 00:34:55,319
Speaker 2: how you can tell the difference between like bone or

725
00:34:55,440 --> 00:34:59,080
Speaker 2: metal and soft tissues, which have different densities and therefore

726
00:34:59,120 --> 00:35:01,799
Speaker 2: different absorption for the X rays. So it's exactly the

727
00:35:01,840 --> 00:35:04,440
Speaker 2: same principle for muons, except that muons will make it

728
00:35:04,480 --> 00:35:07,880
Speaker 2: through things that X rays will not survive, which allows

729
00:35:07,920 --> 00:35:12,080
Speaker 2: you to effectively X ray or muon ray other kinds

730
00:35:12,120 --> 00:35:14,360
Speaker 2: of things that you couldn't otherwise see inside.

731
00:35:14,440 --> 00:35:16,400
Speaker 1: So in the case of an X ray and actually

732
00:35:16,520 --> 00:35:19,239
Speaker 1: can go through my body because it's a different wavelength,

733
00:35:19,280 --> 00:35:21,279
Speaker 1: which what makes it go through my body more than

734
00:35:21,440 --> 00:35:22,759
Speaker 1: say the life from a flashlight.

735
00:35:22,920 --> 00:35:26,200
Speaker 2: So X rays have more energy their higher frequency, right,

736
00:35:26,239 --> 00:35:28,560
Speaker 2: And the interaction with a photon with the materials in

737
00:35:28,600 --> 00:35:31,560
Speaker 2: your body depends on the energy. But a whole episode

738
00:35:31,600 --> 00:35:34,480
Speaker 2: about transparency. Why photons can go through some things and

739
00:35:34,520 --> 00:35:36,919
Speaker 2: can't go through other things, and it's all about whether

740
00:35:36,960 --> 00:35:40,200
Speaker 2: they will interact. Photons can interact with matter depending on

741
00:35:40,239 --> 00:35:42,840
Speaker 2: their energy. They can get absorbed if there are atoms

742
00:35:42,840 --> 00:35:44,360
Speaker 2: out there that can eat them.

743
00:35:44,239 --> 00:35:46,800
Speaker 1: Because atoms only like to eat photons that are a

744
00:35:47,040 --> 00:35:50,480
Speaker 1: particular frequency, right, Yeah, exactly, Like they don't just like

745
00:35:50,520 --> 00:35:53,840
Speaker 1: any photon. They have to be a special frequency because

746
00:35:53,880 --> 00:35:55,640
Speaker 1: of quantum mechanics.

747
00:35:55,760 --> 00:35:58,240
Speaker 2: Yeah, they have various energy levels. They have these ladders

748
00:35:58,239 --> 00:36:01,000
Speaker 2: of energies, so they can absorb photons of like just

749
00:36:01,040 --> 00:36:03,959
Speaker 2: the right energy, and that affects what photons can pass

750
00:36:04,000 --> 00:36:07,200
Speaker 2: through your body or through glass. Or through metal or

751
00:36:07,239 --> 00:36:08,120
Speaker 2: any kind of stuff.

752
00:36:08,320 --> 00:36:10,399
Speaker 1: So that's why X rays can go through things more

753
00:36:10,400 --> 00:36:13,879
Speaker 1: than regular light. And we talked about how muons can

754
00:36:13,920 --> 00:36:18,200
Speaker 1: do that too. Why is that because they don't they

755
00:36:18,200 --> 00:36:21,640
Speaker 1: have a specific energy range that makes them go through

756
00:36:21,800 --> 00:36:24,320
Speaker 1: but not interact with the atoms, say inside my body.

757
00:36:24,640 --> 00:36:27,960
Speaker 2: Yeah, exactly. At certain energy range, they won't be captured

758
00:36:27,960 --> 00:36:30,440
Speaker 2: by atoms, and they're not quite going fast enough to

759
00:36:30,480 --> 00:36:33,840
Speaker 2: have a special relativistic boost where they interact with lots

760
00:36:33,880 --> 00:36:36,640
Speaker 2: more atoms than otherwise, and so they can make it

761
00:36:36,680 --> 00:36:38,799
Speaker 2: through a lot of this material. And so you can

762
00:36:38,840 --> 00:36:41,839
Speaker 2: see muons even if you're like deep underground, you put

763
00:36:41,840 --> 00:36:45,080
Speaker 2: a muon detector like meters and meters underground, those muons

764
00:36:45,080 --> 00:36:47,960
Speaker 2: will pass right through that solid rock and hit your

765
00:36:48,040 --> 00:36:48,800
Speaker 2: muon detector.

766
00:36:48,920 --> 00:36:51,840
Speaker 1: Now, is the idea that you're shooting these muons like

767
00:36:51,880 --> 00:36:54,080
Speaker 1: you're creating them and shooting them with like an X

768
00:36:54,200 --> 00:36:57,440
Speaker 1: ray gun or a mewray gun and then catching them

769
00:36:57,440 --> 00:36:59,560
Speaker 1: on the other side, or is the idea that you're

770
00:36:59,800 --> 00:37:02,520
Speaker 1: using the ones that are showering down on us from

771
00:37:02,560 --> 00:37:03,399
Speaker 1: the atmosphere.

772
00:37:03,400 --> 00:37:05,520
Speaker 2: In principle, you could do both. Right, If you have

773
00:37:05,680 --> 00:37:08,200
Speaker 2: a muon beam, then you could put stuff in the

774
00:37:08,280 --> 00:37:10,200
Speaker 2: muon beam in order to do these kind of tests.

775
00:37:10,360 --> 00:37:12,839
Speaker 2: There is a muon beam. It's cern and we've put

776
00:37:12,880 --> 00:37:15,000
Speaker 2: cell phones in it and stuff like that. It's a

777
00:37:15,040 --> 00:37:16,960
Speaker 2: lot of fun. But it's hard to build a muon beam.

778
00:37:17,000 --> 00:37:18,680
Speaker 2: It's hard to point a muon beam. It's hard to

779
00:37:18,680 --> 00:37:20,480
Speaker 2: bring stuff to a muon beam.

780
00:37:20,719 --> 00:37:21,480
Speaker 1: Why why is that?

781
00:37:21,760 --> 00:37:23,719
Speaker 2: Why is it hard to bring stuff to the muon beam?

782
00:37:23,840 --> 00:37:23,920
Speaker 5: Now?

783
00:37:24,040 --> 00:37:26,040
Speaker 1: Like, why is it hard to make a muon shoot

784
00:37:26,120 --> 00:37:26,560
Speaker 1: a gun?

785
00:37:26,719 --> 00:37:29,160
Speaker 2: Yeah? Great question. Muons are created from the decays of

786
00:37:29,200 --> 00:37:31,359
Speaker 2: other particles. So the way you make a muon beam

787
00:37:31,400 --> 00:37:34,759
Speaker 2: is actually you smash protons into like a block of

788
00:37:34,840 --> 00:37:38,160
Speaker 2: material like graphite, which creates a shower of other stuff.

789
00:37:38,200 --> 00:37:41,640
Speaker 2: It's basically stimulating what's happening in the upper atmosphere. Then

790
00:37:41,680 --> 00:37:44,239
Speaker 2: a lot of those things decay into muons. So you

791
00:37:44,280 --> 00:37:47,239
Speaker 2: need a proton accelerator of sufficient energy, and there just

792
00:37:47,400 --> 00:37:49,759
Speaker 2: aren't that many of those. They're not that portable. You

793
00:37:49,800 --> 00:37:52,560
Speaker 2: need like a linear accelerator. You need magnets to filter

794
00:37:52,680 --> 00:37:53,600
Speaker 2: some of this stuff out.

795
00:37:53,680 --> 00:37:55,920
Speaker 1: How big would it have to be? Like can you

796
00:37:55,960 --> 00:37:58,120
Speaker 1: make it a handheld version or do you need like

797
00:37:58,160 --> 00:38:01,080
Speaker 1: a building size anything to shoot muons.

798
00:38:01,200 --> 00:38:03,680
Speaker 2: Yeah, that's a great question. What's the smallest muon gun

799
00:38:03,719 --> 00:38:07,200
Speaker 2: in the world. Definitely the size of a large physics laboratory.

800
00:38:07,480 --> 00:38:09,640
Speaker 2: Not something you can pick up and carry, though you

801
00:38:09,760 --> 00:38:11,360
Speaker 2: might be able to put it in the back of

802
00:38:11,360 --> 00:38:15,520
Speaker 2: a flatbed truck. But mostly it's unnecessary because the world

803
00:38:15,600 --> 00:38:18,759
Speaker 2: is filled with muons from cosmic rays. Like there's a

804
00:38:18,840 --> 00:38:22,319
Speaker 2: constant stream of these things just naturally produced in the atmosphere,

805
00:38:22,520 --> 00:38:24,000
Speaker 2: and you can just use those.

806
00:38:24,120 --> 00:38:27,799
Speaker 1: M What do you mean, like there's we're surrounded or

807
00:38:27,880 --> 00:38:31,239
Speaker 1: being penetrated by muons from all directions all the time.

808
00:38:31,080 --> 00:38:33,640
Speaker 2: Not from all directions from above, right, these things are

809
00:38:33,680 --> 00:38:37,399
Speaker 2: made in the upper atmosphere and are streaming down to us. Again,

810
00:38:37,440 --> 00:38:41,319
Speaker 2: there's ten thousand muons per square meter per minute, so

811
00:38:41,360 --> 00:38:44,160
Speaker 2: there's not a small number of muons passing through us.

812
00:38:44,480 --> 00:38:47,480
Speaker 2: And so if you want to measure the density of something,

813
00:38:47,640 --> 00:38:50,480
Speaker 2: you just put like a muon detector underneath it and

814
00:38:50,640 --> 00:38:53,239
Speaker 2: count how many muons are making it, and then you

815
00:38:53,280 --> 00:38:56,120
Speaker 2: can tell how many were absorbed by the material, and

816
00:38:56,160 --> 00:38:57,840
Speaker 2: that tells you what the density of it was.

817
00:38:58,280 --> 00:39:01,560
Speaker 1: Mmm. But our neons coming at us from the sides

818
00:39:01,600 --> 00:39:04,920
Speaker 1: as well, Like, aren't their cosmic rays hitting us from

819
00:39:04,920 --> 00:39:05,560
Speaker 1: all directions.

820
00:39:05,600 --> 00:39:07,680
Speaker 2: There's definitely an angular dependence, but most of them come

821
00:39:07,719 --> 00:39:09,360
Speaker 2: straight down. It's the most likely.

822
00:39:09,239 --> 00:39:10,920
Speaker 1: Direction, all right. So then the idea is that if

823
00:39:10,920 --> 00:39:13,160
Speaker 1: I want to see through something, I just put a

824
00:39:13,280 --> 00:39:16,320
Speaker 1: meuon detector under it. And so what are these meon

825
00:39:16,360 --> 00:39:18,080
Speaker 1: detectors made out of? How do you make a muon

826
00:39:18,200 --> 00:39:20,960
Speaker 1: detector if muons go through things so easily.

827
00:39:21,040 --> 00:39:23,879
Speaker 2: The original sort of old school ones are these films. Now,

828
00:39:23,960 --> 00:39:27,080
Speaker 2: muons are hard to stop, but they're not that hard

829
00:39:27,120 --> 00:39:29,520
Speaker 2: to see like. They will leave a little trail of

830
00:39:29,560 --> 00:39:32,600
Speaker 2: evidence as they go. For example, you can build a

831
00:39:32,719 --> 00:39:35,920
Speaker 2: cloud chamber in your garage, which is just like a

832
00:39:35,960 --> 00:39:40,240
Speaker 2: transparent box filled with water vapor super saturated in the air,

833
00:39:40,600 --> 00:39:43,360
Speaker 2: and as muons fly through it, they won't be stopped,

834
00:39:43,400 --> 00:39:45,239
Speaker 2: they won't lose a lot of energy, but they will

835
00:39:45,280 --> 00:39:48,239
Speaker 2: interact with those things and create little a stream of droplets.

836
00:39:48,400 --> 00:39:50,719
Speaker 2: So you can actually build a muon detector like at

837
00:39:50,760 --> 00:39:54,400
Speaker 2: home with simple materials. There's all sorts of fun instructions

838
00:39:54,440 --> 00:39:56,640
Speaker 2: on YouTube that you can follow, so they'll leave like

839
00:39:56,719 --> 00:39:59,759
Speaker 2: breadcrumbs for where they were. The original ones were like

840
00:39:59,760 --> 00:40:02,760
Speaker 2: fit and moultion blocks. These days, we use like charged

841
00:40:02,800 --> 00:40:05,960
Speaker 2: gases or scintillating plastics in order to see these muons.

842
00:40:06,480 --> 00:40:08,879
Speaker 1: You see, you don't stop the muons, You just kind

843
00:40:08,880 --> 00:40:11,040
Speaker 1: of see the evidence of them going through.

844
00:40:11,320 --> 00:40:13,920
Speaker 2: Yeah, exactly, it's hard to stop the muon for them

845
00:40:13,920 --> 00:40:16,640
Speaker 2: to interact in a significant enough way to get slowed

846
00:40:16,680 --> 00:40:19,359
Speaker 2: down to deposit all of their energy. But they will

847
00:40:19,440 --> 00:40:21,799
Speaker 2: leave a little trace of energy as they go by

848
00:40:22,080 --> 00:40:24,319
Speaker 2: if you have the right setup. So it's not that

849
00:40:24,440 --> 00:40:25,760
Speaker 2: hard to detect muons.

850
00:40:26,239 --> 00:40:28,200
Speaker 1: Interesting, all right, So then what kinds of things have

851
00:40:28,280 --> 00:40:30,879
Speaker 1: we seen with a meon ray? Have we seen a

852
00:40:31,040 --> 00:40:35,800
Speaker 1: instead of a cow? I think Donald's hamburger.

853
00:40:37,320 --> 00:40:39,239
Speaker 2: I don't know that anybody's tried that, you know, put

854
00:40:39,280 --> 00:40:42,160
Speaker 2: a cloud chamber under a cow to see what is eaten.

855
00:40:42,320 --> 00:40:44,480
Speaker 2: I do not know if that experiment has been done,

856
00:40:44,920 --> 00:40:46,839
Speaker 2: So I don't know if we have muon ray to cow.

857
00:40:47,160 --> 00:40:48,680
Speaker 1: There's an instruction on YouTube to do that.

858
00:40:50,239 --> 00:40:53,160
Speaker 2: One of the first applications of this was to measure

859
00:40:53,280 --> 00:40:55,719
Speaker 2: like how much rock and the density of rock over

860
00:40:55,760 --> 00:40:58,320
Speaker 2: a tunnel, Like you're building a tunnel through a mountain.

861
00:40:58,360 --> 00:41:00,640
Speaker 2: You can put a muon detector in the tunnel and

862
00:41:00,680 --> 00:41:03,120
Speaker 2: you can use it to measure the total mass of

863
00:41:03,160 --> 00:41:05,879
Speaker 2: the rock, or effectively the density of the rock that's

864
00:41:05,920 --> 00:41:09,680
Speaker 2: above you, to measure your overburden because you're basically shooting

865
00:41:09,719 --> 00:41:12,319
Speaker 2: through the rock with the muons, and you can tell

866
00:41:12,320 --> 00:41:15,000
Speaker 2: by counting how many muons make it to your tunnel

867
00:41:15,280 --> 00:41:16,479
Speaker 2: the density of the rock.

868
00:41:16,600 --> 00:41:18,960
Speaker 1: So for like construction projects.

869
00:41:18,800 --> 00:41:21,320
Speaker 2: That was the first application. But then in the sixties

870
00:41:21,440 --> 00:41:24,759
Speaker 2: a physicist thought, ooh, let's use this to basically X

871
00:41:24,880 --> 00:41:27,160
Speaker 2: ray the pyramids, because you know, a lot of people

872
00:41:27,200 --> 00:41:29,960
Speaker 2: wonder like if there's something in the pyramids, or are

873
00:41:29,960 --> 00:41:32,960
Speaker 2: there hidden chambers in the pyramids. Nobody wants to take

874
00:41:33,000 --> 00:41:37,080
Speaker 2: the pyramids apart because they're obviously treasures of humanity, but

875
00:41:37,120 --> 00:41:39,520
Speaker 2: we would like to see inside the pyramids in a

876
00:41:39,600 --> 00:41:43,799
Speaker 2: non invasive way. So in the sixties, Louis Alvarez thought, oh,

877
00:41:43,840 --> 00:41:47,200
Speaker 2: let's use muons to see inside the pyramids to see

878
00:41:47,239 --> 00:41:49,600
Speaker 2: if there's like an opening or a gap, or like

879
00:41:49,640 --> 00:41:51,840
Speaker 2: a big void somewhere that nobody's discovered.

880
00:41:52,080 --> 00:41:55,440
Speaker 1: Ooh, wouldn't that require you to put the mean detector

881
00:41:55,640 --> 00:41:56,480
Speaker 1: under the pyramid?

882
00:41:56,680 --> 00:42:00,000
Speaker 2: Yes, exactly, so you do need some access to the pyramid,

883
00:42:00,239 --> 00:42:02,400
Speaker 2: and there are some openings, but this is limiting factor.

884
00:42:02,640 --> 00:42:05,000
Speaker 2: You can't just like drill under the pyramid and put

885
00:42:05,000 --> 00:42:08,160
Speaker 2: a muon detectors everywhere. There are some shafts and some

886
00:42:08,239 --> 00:42:10,600
Speaker 2: chambers we know about. What you can do is put

887
00:42:10,600 --> 00:42:12,879
Speaker 2: the muon detector there in the bottom of the as

888
00:42:12,880 --> 00:42:15,480
Speaker 2: far below the pyramid as you can, and then measure

889
00:42:15,520 --> 00:42:18,680
Speaker 2: the rate of the muons and compare it to calculations

890
00:42:18,719 --> 00:42:21,319
Speaker 2: you do, like how many muons should I see if

891
00:42:21,360 --> 00:42:24,399
Speaker 2: there are no additional chambers, or how many muons going

892
00:42:24,440 --> 00:42:26,960
Speaker 2: in this direction versus that direction, if there's a chamber

893
00:42:26,960 --> 00:42:28,160
Speaker 2: here or a chamber there.

894
00:42:28,480 --> 00:42:31,000
Speaker 1: Wait, if I put a detector under a pyramid, let's

895
00:42:31,040 --> 00:42:33,759
Speaker 1: say it's like a tile the size of like a

896
00:42:33,840 --> 00:42:36,400
Speaker 1: one by one foot square, it can only detect the

897
00:42:36,440 --> 00:42:39,080
Speaker 1: muons that are coming from right above that one square

898
00:42:39,120 --> 00:42:42,440
Speaker 1: foot area, or can it detect muons from all directions?

899
00:42:42,520 --> 00:42:44,440
Speaker 2: If you have like a one foot tile, it'll detect

900
00:42:44,480 --> 00:42:47,520
Speaker 2: any muon that passes through that tile, you know, coming

901
00:42:47,520 --> 00:42:49,439
Speaker 2: from any direction. And so if you have a few

902
00:42:49,440 --> 00:42:52,160
Speaker 2: of those, then you can start to get directional information.

903
00:42:52,239 --> 00:42:54,200
Speaker 2: If there's like a difference in how many muons you

904
00:42:54,200 --> 00:42:57,000
Speaker 2: see in one place versus another, what do you mean, Well,

905
00:42:57,040 --> 00:42:58,960
Speaker 2: the way you can tell, like the difference between parts

906
00:42:59,000 --> 00:43:00,680
Speaker 2: of your body is a you have an X ray

907
00:43:00,680 --> 00:43:02,879
Speaker 2: detector that's not just a point, it's like a whole array,

908
00:43:02,960 --> 00:43:04,960
Speaker 2: or it takes an image. You can tell how many

909
00:43:05,080 --> 00:43:06,920
Speaker 2: X rays came through this part of your body versus

910
00:43:07,000 --> 00:43:09,239
Speaker 2: that other part of your body. So imagine if you

911
00:43:09,239 --> 00:43:12,160
Speaker 2: could put X rays all over the bottom of the pyramid,

912
00:43:12,400 --> 00:43:14,960
Speaker 2: then you could like muon X ray the whole pyramid.

913
00:43:15,160 --> 00:43:17,120
Speaker 2: You can't do that, but you can put a few

914
00:43:17,160 --> 00:43:19,440
Speaker 2: here and a few there based on what access points

915
00:43:19,440 --> 00:43:21,160
Speaker 2: you do have, and you can get like a very

916
00:43:21,320 --> 00:43:24,520
Speaker 2: rough image of what's going on inside the pyramid from

917
00:43:24,560 --> 00:43:25,640
Speaker 2: your various detectors.

918
00:43:26,239 --> 00:43:28,120
Speaker 1: But wouldn't that just give you like a couple of

919
00:43:28,200 --> 00:43:30,120
Speaker 1: pixels basically of an image.

920
00:43:30,200 --> 00:43:32,799
Speaker 2: Yeah, it's very rough, but it's better than nothing. Right

921
00:43:32,960 --> 00:43:35,680
Speaker 2: right now, we have basically no image, and so this

922
00:43:35,800 --> 00:43:37,560
Speaker 2: is like a way to crack it open a little

923
00:43:37,600 --> 00:43:39,839
Speaker 2: bit and give you some very rough idea of what

924
00:43:40,000 --> 00:43:40,600
Speaker 2: might be there.

925
00:43:40,800 --> 00:43:44,920
Speaker 1: Mmm. I guess alternately, you could create a mion ray

926
00:43:45,200 --> 00:43:47,440
Speaker 1: gun m hmm and shoot it from the side, right.

927
00:43:47,480 --> 00:43:48,719
Speaker 1: Wouldn't that be more convenient?

928
00:43:49,000 --> 00:43:50,960
Speaker 2: Yeah? Absolutely, you had a big meon detector on one

929
00:43:51,000 --> 00:43:53,040
Speaker 2: side and a big meuon gun on the other side,

930
00:43:53,360 --> 00:43:57,160
Speaker 2: then you could really muonograph the pyramids. That would be awesome.

931
00:43:57,640 --> 00:43:59,520
Speaker 1: Were you about to take a mea on the heck

932
00:43:59,560 --> 00:44:03,640
Speaker 1: out of it? Are these muons dangerous? Like if I

933
00:44:03,680 --> 00:44:06,400
Speaker 1: create a muone gun and I aim it at somebody,

934
00:44:06,960 --> 00:44:08,759
Speaker 1: is it going to harm them? Just like X rays

935
00:44:08,760 --> 00:44:11,200
Speaker 1: are sort of harmful if you take an X ray

936
00:44:11,200 --> 00:44:12,879
Speaker 1: gun and shoot it at a person for too long.

937
00:44:13,080 --> 00:44:17,040
Speaker 2: Absolutely, these are radiation and muons are responsible for mutations

938
00:44:17,080 --> 00:44:19,319
Speaker 2: in our DNA. They're part of the natural radiation of

939
00:44:19,320 --> 00:44:22,200
Speaker 2: our environment, and they do cause mutations. So yes, in

940
00:44:22,239 --> 00:44:25,920
Speaker 2: principle they can cause cancer. Right, So an intense dose

941
00:44:25,960 --> 00:44:28,920
Speaker 2: of muons from a beam could definitely give you cancer.

942
00:44:29,200 --> 00:44:30,480
Speaker 2: It's not something to play around with.

943
00:44:31,080 --> 00:44:32,959
Speaker 1: Does sound like a great idea to make a muon

944
00:44:32,960 --> 00:44:36,480
Speaker 1: gun or a good idea for certain applications, perhaps.

945
00:44:36,719 --> 00:44:39,040
Speaker 2: Yeah, exactly, And the difficult to shield. Right once you

946
00:44:39,040 --> 00:44:41,120
Speaker 2: start that muon beam, it's going to pass right through

947
00:44:41,120 --> 00:44:43,480
Speaker 2: your pyramid and then through your detector, and then it's

948
00:44:43,520 --> 00:44:46,319
Speaker 2: just going to keep going for kilometers and kilometers. So

949
00:44:46,360 --> 00:44:47,960
Speaker 2: it's not like you can have a beam dump or

950
00:44:47,960 --> 00:44:49,880
Speaker 2: something to protect people from the other side.

951
00:44:50,400 --> 00:44:52,240
Speaker 1: Well, I guess it would just shoot off into space,

952
00:44:52,280 --> 00:44:55,040
Speaker 1: right because the Earth is curved, or with gravity pull

953
00:44:55,080 --> 00:44:55,839
Speaker 1: them back down.

954
00:44:55,880 --> 00:44:57,480
Speaker 2: No, you're right there, showed off into space, So maybe

955
00:44:57,480 --> 00:44:59,239
Speaker 2: you just need to angle it up a little bit.

956
00:45:00,120 --> 00:45:02,200
Speaker 1: Interesting, But then you might be like shooting it. Maybe

957
00:45:02,200 --> 00:45:04,920
Speaker 1: an alien civilization out there they might take offense.

958
00:45:05,080 --> 00:45:07,520
Speaker 2: Yeah, you could accidentally be sending them a mewanograph of

959
00:45:07,520 --> 00:45:09,440
Speaker 2: our pyramids. I don't know how they would interpret that.

960
00:45:09,360 --> 00:45:12,520
Speaker 1: That's right, or a picture of cows. They'd be like, oh,

961
00:45:12,600 --> 00:45:14,520
Speaker 1: that look's tasty, let's go invade them.

962
00:45:14,560 --> 00:45:16,719
Speaker 2: But people have actually done this for the pyramids without

963
00:45:16,719 --> 00:45:19,520
Speaker 2: building me on gun. They've just used cosmic rays and

964
00:45:19,600 --> 00:45:21,880
Speaker 2: measured the rate at which the constant rays make it

965
00:45:21,920 --> 00:45:25,560
Speaker 2: through the pyramids to see are there new cavities.

966
00:45:25,000 --> 00:45:27,160
Speaker 1: Inside the pyramids and what have they found.

967
00:45:27,320 --> 00:45:29,160
Speaker 2: So the first time they looked, they looked in one pyramid,

968
00:45:29,200 --> 00:45:31,760
Speaker 2: they didn't find anything unusual. But then later on, actually

969
00:45:31,760 --> 00:45:34,760
Speaker 2: in twenty fifteen, they did this for the Great Pyramid

970
00:45:35,080 --> 00:45:37,400
Speaker 2: and they found what they called the Big Void, and

971
00:45:37,480 --> 00:45:40,440
Speaker 2: then another opening they labeled maybe a corridor. What they're

972
00:45:40,440 --> 00:45:42,600
Speaker 2: seeing is a region of the pyramid that seems to

973
00:45:42,640 --> 00:45:45,279
Speaker 2: have lower density than the rest of the pyramid. So

974
00:45:45,320 --> 00:45:48,000
Speaker 2: this could be like a big opening, maybe a treasure

975
00:45:48,080 --> 00:45:51,560
Speaker 2: chamber filled with all sorts of jewels and fascinating information

976
00:45:51,600 --> 00:45:53,680
Speaker 2: about ancient Egypt. Or maybe it's just like a gap

977
00:45:53,719 --> 00:45:56,080
Speaker 2: they left in the pyramid to reduce the pressure on

978
00:45:56,160 --> 00:45:57,719
Speaker 2: the rest of it. You know, it could just be

979
00:45:57,800 --> 00:46:00,359
Speaker 2: like a construction trick. We don't exactly know, but there's

980
00:46:00,360 --> 00:46:03,320
Speaker 2: some sort of large cavity within the Great Pyramid.

981
00:46:03,600 --> 00:46:05,720
Speaker 1: Interesting. I guess what you're saying is making me feel

982
00:46:05,719 --> 00:46:09,000
Speaker 1: a little skeptical just because you needed like a lot

983
00:46:09,160 --> 00:46:12,680
Speaker 1: of space underneath the pyramid to create these to be

984
00:46:13,080 --> 00:46:16,200
Speaker 1: certain that there's something there, right, you need to basically

985
00:46:16,200 --> 00:46:18,960
Speaker 1: put a lot of these neon detectors under a pyramid,

986
00:46:19,239 --> 00:46:21,239
Speaker 1: Like just putting like a couple doesn't seem like you'd

987
00:46:21,239 --> 00:46:25,320
Speaker 1: be able to find or resolve any kind of real details,

988
00:46:25,480 --> 00:46:25,759
Speaker 1: can you.

989
00:46:25,880 --> 00:46:30,000
Speaker 2: Yeah, your resolving power definitely improves as you have more detectors.

990
00:46:29,640 --> 00:46:31,600
Speaker 1: Or just more space to put these detectors.

991
00:46:31,719 --> 00:46:33,480
Speaker 2: But you'd be surprised what you can accomplish with a

992
00:46:33,520 --> 00:46:36,360
Speaker 2: few detectors, the same way that like a radio array

993
00:46:36,600 --> 00:46:39,879
Speaker 2: is just a few detectors scattered over kilometers and kilometers.

994
00:46:39,920 --> 00:46:43,120
Speaker 2: By measuring the difference between signals received by one antenna

995
00:46:43,160 --> 00:46:45,760
Speaker 2: and another, you can get a lot of directional information

996
00:46:45,800 --> 00:46:49,240
Speaker 2: and resolving power, almost as if you had the detector

997
00:46:49,320 --> 00:46:52,279
Speaker 2: the same size as a full array. Not quite, but

998
00:46:52,400 --> 00:46:54,920
Speaker 2: almost as if. So you do some complex data analysis

999
00:46:54,960 --> 00:46:57,040
Speaker 2: and you can recover a lot of information with just

1000
00:46:57,080 --> 00:46:58,440
Speaker 2: a few measurements.

1001
00:46:58,239 --> 00:47:00,960
Speaker 1: Right, right, But those arrays the antennas right which you

1002
00:47:00,960 --> 00:47:04,000
Speaker 1: can focus and point in the certain directions to kind

1003
00:47:04,000 --> 00:47:07,360
Speaker 1: of get the equivalent of a giant lens. This feels like,

1004
00:47:07,400 --> 00:47:11,120
Speaker 1: you know, laying out a bunch of photographic negatives a

1005
00:47:11,120 --> 00:47:13,719
Speaker 1: film out on the ground and trying to get an

1006
00:47:13,760 --> 00:47:14,279
Speaker 1: image from that.

1007
00:47:14,520 --> 00:47:16,759
Speaker 2: Yeah, it's difficult. And if you look at the reconstruction

1008
00:47:16,840 --> 00:47:18,719
Speaker 2: of the void, you see it's very fuzzy. They're very

1009
00:47:18,840 --> 00:47:21,600
Speaker 2: uncertain but exactly where it is, how big it is.

1010
00:47:21,600 --> 00:47:23,480
Speaker 2: They have no idea what shape it is. This is

1011
00:47:23,480 --> 00:47:25,600
Speaker 2: not like a crystal clear image the way an X

1012
00:47:25,719 --> 00:47:28,200
Speaker 2: ray is at all. This is just like a hint

1013
00:47:28,400 --> 00:47:31,360
Speaker 2: that there's an under density somewhere inside this pyramid.

1014
00:47:31,560 --> 00:47:33,800
Speaker 1: All right, Well, it seems like a pretty cool application

1015
00:47:33,920 --> 00:47:36,759
Speaker 1: that maybe let's us see through mountains and tonaments and

1016
00:47:37,480 --> 00:47:40,279
Speaker 1: potential of bovine animals.

1017
00:47:40,760 --> 00:47:43,640
Speaker 2: Especially if they're the size of pyramids or mountains.

1018
00:47:43,719 --> 00:47:47,760
Speaker 1: What else can you use these meon rays for to detect.

1019
00:47:47,480 --> 00:47:50,920
Speaker 2: People have used it actually to see inside mountains like Vesuvius,

1020
00:47:50,920 --> 00:47:53,919
Speaker 2: for example, the famous volcano. They've used muans to try

1021
00:47:53,920 --> 00:47:57,360
Speaker 2: to understand what's going on inside Vesuvius to maybe do

1022
00:47:57,360 --> 00:47:59,480
Speaker 2: a better job predicting of when it's going to blow.

1023
00:48:00,080 --> 00:48:01,719
Speaker 1: Need to get under Vesuvius to do this.

1024
00:48:02,080 --> 00:48:03,759
Speaker 2: The best case scenario is to have a bunch of

1025
00:48:03,840 --> 00:48:06,200
Speaker 2: mealon detectors under Vesuvius. But if you put a bunch

1026
00:48:06,239 --> 00:48:08,759
Speaker 2: around it, then you can get muons which shoot through

1027
00:48:08,840 --> 00:48:11,200
Speaker 2: sort of at an angle. Especially if you can measure

1028
00:48:11,200 --> 00:48:13,520
Speaker 2: the angle of the muon, so you can tell whether

1029
00:48:13,560 --> 00:48:15,839
Speaker 2: they came through the mountain or whether they came from

1030
00:48:15,880 --> 00:48:18,360
Speaker 2: the other side, then you can get some good information.

1031
00:48:18,560 --> 00:48:20,239
Speaker 1: Wait, you can angle these detectors.

1032
00:48:20,480 --> 00:48:20,640
Speaker 5: Yeah.

1033
00:48:20,680 --> 00:48:23,040
Speaker 2: Absolutely. The detectors are not just like a flat sheet.

1034
00:48:23,280 --> 00:48:24,600
Speaker 2: They can be thick and so you can see a

1035
00:48:24,640 --> 00:48:26,880
Speaker 2: whole track of a muon. You can tell which direction

1036
00:48:27,000 --> 00:48:29,200
Speaker 2: it was going, not just that a muon was there,

1037
00:48:29,400 --> 00:48:30,719
Speaker 2: but the direction of its motion.

1038
00:48:31,320 --> 00:48:34,960
Speaker 1: Hmmm. Interesting. So you can angle these then kind of

1039
00:48:35,000 --> 00:48:35,600
Speaker 1: like an antenna.

1040
00:48:35,800 --> 00:48:37,360
Speaker 2: Yeah, kind of like an antenna exactly.

1041
00:48:37,480 --> 00:48:39,320
Speaker 1: Okay, it seemed like maybe you're saying you can't.

1042
00:48:39,560 --> 00:48:41,840
Speaker 2: No, you can. The thicker they are, the better angle

1043
00:48:41,840 --> 00:48:44,120
Speaker 2: measurement you can make like a cloud chamber that you

1044
00:48:44,120 --> 00:48:45,680
Speaker 2: can build in your garage. You can see the whole

1045
00:48:45,719 --> 00:48:48,520
Speaker 2: track of the muon flying through. It's really pretty cool.

1046
00:48:48,640 --> 00:48:52,560
Speaker 1: All right, So geology and archeology, those are pretty cool

1047
00:48:52,800 --> 00:48:54,319
Speaker 1: uses for particle physics.

1048
00:48:54,160 --> 00:48:57,200
Speaker 2: Yeah, exactly. So maybe particles will not just teach us

1049
00:48:57,200 --> 00:48:59,319
Speaker 2: about the nature of the universe. They might teach us

1050
00:48:59,440 --> 00:49:02,400
Speaker 2: about what's going on inside mountains and what humans have

1051
00:49:02,480 --> 00:49:04,160
Speaker 2: hidden away inside pyramids.

1052
00:49:04,320 --> 00:49:08,640
Speaker 1: All right, Well, another great justification for Daniel's job at

1053
00:49:08,640 --> 00:49:09,320
Speaker 1: the university.

1054
00:49:10,920 --> 00:49:13,880
Speaker 2: I'm not mute anything, but I'm definitely a favor of it.

1055
00:49:13,920 --> 00:49:15,520
Speaker 1: I feel like half of these episodes are just a

1056
00:49:15,560 --> 00:49:19,719
Speaker 1: commercial for your job in particle physics.

1057
00:49:19,920 --> 00:49:22,640
Speaker 2: They're a commercial for particle physics and for physics in

1058
00:49:22,680 --> 00:49:25,000
Speaker 2: general and trying to understand the nature of the universe,

1059
00:49:25,080 --> 00:49:26,280
Speaker 2: and yeah, why it matters?

1060
00:49:26,400 --> 00:49:28,240
Speaker 1: Should we have a disclaimer here at the bottom?

1061
00:49:28,480 --> 00:49:32,879
Speaker 2: Every episode is indirectly Daniel's self promotion. Yes, yeah, there

1062
00:49:32,920 --> 00:49:35,640
Speaker 2: you go. Yeah, absolutely, I'm totally transparent about that?

1063
00:49:35,719 --> 00:49:38,319
Speaker 1: All right, well, engineers, please clip that and put it

1064
00:49:38,360 --> 00:49:41,719
Speaker 1: at the bottom of every episode. It'll be like the

1065
00:49:41,760 --> 00:49:42,600
Speaker 1: fine print.

1066
00:49:42,480 --> 00:49:45,520
Speaker 2: And every conversation I have basically with everybody.

1067
00:49:47,360 --> 00:49:48,919
Speaker 1: Unless you're talking about something else.

1068
00:49:48,960 --> 00:49:51,760
Speaker 2: Perhaps it's all particles, man, everything is made of particles.

1069
00:49:51,880 --> 00:49:58,080
Speaker 1: Oh interesting, even non particles. All right, well, we hope

1070
00:49:58,080 --> 00:50:01,239
Speaker 1: you enjoyed that. Thanks for joining us, See you next time.

1071
00:50:05,719 --> 00:50:08,920
Speaker 2: For more science and curiosity, come find us on social media,

1072
00:50:09,000 --> 00:50:13,520
Speaker 2: where we answer questions and post videos. We're on Twitter, Discorg, Insta,

1073
00:50:13,640 --> 00:50:17,360
Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel

1074
00:50:17,400 --> 00:50:20,840
Speaker 2: and Jorge Explain the Universe is a production of iHeartRadio.

1075
00:50:21,120 --> 00:50:26,279
Speaker 2: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

1076
00:50:26,400 --> 00:50:28,760
Speaker 2: or wherever you listen to your favorite shows.