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Speaker 1: Hey, or hey, do you think that our podcast exists

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Speaker 1: out there in the multiverse?

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Speaker 2: Like if I think there are other versions of us

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Speaker 2: doing this podcast?

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Speaker 1: Yeah? You know. Do you think in other universes there

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Speaker 1: are people puzzling over how the universe works and podcasts

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Speaker 1: trying to explain it to them.

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Speaker 2: I guess if they live in a universe, then there

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Speaker 2: are probably people wondering about the universe. And there might

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Speaker 2: be a cartoonist and a physicist also wondering about deniers,

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Speaker 2: and they might have also met and started a podcast.

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Speaker 2: That's technically possible.

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Speaker 1: I wonder if they also make the same chocolate and

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Speaker 1: banana jokes.

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Speaker 2: Ooh, maybe they make chocolate covered banana jokes.

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Speaker 1: Ooh, I think we're in danger of crossing over into

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Speaker 1: the multiverse.

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Speaker 2: What if they're making white chocolate and strawberry jokes, which

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Speaker 2: I'm allergic to? That'd be like the diversion of this podcast.

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Speaker 1: Then we would annihilate if we ever met.

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Speaker 2: Well, it's like the anti Daniel Horra explains the universe.

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Speaker 2: But would they still explain the universe if it's an

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Speaker 2: anti podcast.

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Speaker 1: Hmm, maybe they'd be explaining the anti universe.

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Speaker 2: They'll be not explaining the universe, So they're like, how

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Speaker 2: we do here most weeks?

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Speaker 1: I just want to taste their exotic chocolate.

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Speaker 2: What if we're the anti version of their podcast?

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Speaker 1: It's all relative, man, Does.

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Speaker 2: That mean our listeners are anti listeners.

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Speaker 1: As long as they're not anti listening?

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Speaker 2: Hi am hoe May, cartoonist and the author of Oliver's

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Speaker 2: Great Big Universe.

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

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Speaker 1: at UC Irvine, and I definitely listen rather than anti

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Speaker 1: listen to all the questions from our listeners.

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Speaker 2: But do you anti answer them or do you actually

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Speaker 2: answer them?

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Speaker 1: I think of my answers are sort of like anti

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Speaker 1: questions because they annihilate the question when they receive them.

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Speaker 2: Wait what oh I see? And then they become pure

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Speaker 2: energy and they disappear into the air. So really there's

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Speaker 2: no subsustenance or matter to them. Is that what you're saying?

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Speaker 2: The whole interaction just goes up in a flash of light.

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Speaker 1: I'm hoping that my answer turns their question into pure

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Speaker 1: mental energy illuminating the inside of their mind.

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Speaker 2: WHOA sounds a little dangerous and hippieb a little bit cunchy. Yeah,

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Speaker 2: but anyways, Welcome to our podcast, Daniel and Jorge Explain

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Speaker 2: the Universe, a black Chin of iHeartRadio.

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Speaker 1: Where we try to light up the inside of your

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Speaker 1: mind with our understanding of the universe. We tackle the

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Speaker 1: biggest questions out there, from the smallest particles to the

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Speaker 1: most vast astrophysical objects that humanity has ever observed. We

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Speaker 1: don't stop at the deep questions. We go for the

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Speaker 1: deepest questions. We don't stop at the big questions. We

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Speaker 1: try to answer the biggest questions because we think all

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Speaker 1: of those questions deserve our best answers.

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Speaker 2: That's right. This is the podcast where we're anti itching

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Speaker 2: and pro asking questions about the universe and learning how

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Speaker 2: everything works and why we are here specifically in this

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Speaker 2: part of the universe.

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Speaker 1: That's right. And we are pros some kinds of chocolate

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Speaker 1: and some kinds of bananas at certain times of the day.

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Speaker 2: Actually, you can't be pro against other kinds of bananas

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Speaker 2: because most of the bananas out there are the same kind.

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Speaker 2: Did you do that?

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Speaker 1: That's true? Isn't it like a monoculture?

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Speaker 2: Yeah? Yeah, Like they found one banana that tasted really

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Speaker 2: good and then they're like, everybody make the same banana.

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Speaker 2: So they've just been cloning the same banana for all

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Speaker 2: over the world basically.

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Speaker 1: But I've had like little red bananas sometimes in Mexico.

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Speaker 1: Aren't those different?

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Speaker 2: Yeah? Yeah, there are other kinds of bananas, but most

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Speaker 2: of the ones that you see, like the yellow ones

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Speaker 2: that you see in most supermarkets everywhere pretty much around

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Speaker 2: the world, they're the same bananas.

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Speaker 1: And welcome to our podcast, The Science of Bananas.

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Speaker 2: Ooh, hey, we did a podcast about chocolate. I challenged you,

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Speaker 2: Daniel uh huh, to do a podcast about the physics

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Speaker 2: of bananas.

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Speaker 1: We're doing.

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Speaker 2: It's a slippery subject.

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Speaker 1: I think it's quite appealing.

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Speaker 2: Actually yeah, I'll put a big yellow smile on your face.

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Speaker 1: All right. If you're a professor of banana physics, please

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Speaker 1: write to me. I want to talk to you about

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Speaker 1: the physics of bananas. If you are the chief banana

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Speaker 1: Officer of Chikita, also please reach out to me.

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Speaker 2: Aren't all physicists technically banana physicists.

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Speaker 1: We're all a little bit bananas, that's true.

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Speaker 2: Yeah, yeah, yeah, yeah. I mean you're discovering banana facts

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Speaker 2: about the universe.

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Speaker 1: The universe is bananas, that's for sure.

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Speaker 2: But Anyways, we do like to try to answer questions

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Speaker 2: here on the podcast because everybody has questions.

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Speaker 1: That's right, and we think that everybody's questions deserve answers,

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Speaker 1: not just professional physicists who've been spending their whole lives

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Speaker 1: working their ways to the forefront of human knowledge. Turns out,

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Speaker 1: everybody has questions that are tricky to answer that bring

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Speaker 1: us right into the abyss of human ignorance.

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Speaker 2: Yeah, because as much as we've learned about the universe

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Speaker 2: and discovered its laws and how it all works, there

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Speaker 2: are still a whole lot that we don't know about

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Speaker 2: how it's all put together, and there are still lots

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Speaker 2: of mysteries out there.

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Speaker 1: And one of our goals on this podcast is to

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Speaker 1: teach you to think about the universe like a physicist,

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Speaker 1: to try to make in your mind a minu the

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Speaker 1: model for how it all works, and then look for inconsistencies.

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Speaker 1: Try to figure out, if you really understand how it works,

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Speaker 1: does that mental model work in this scenario or that scenario,

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Speaker 1: How does it explain this thing or that thing, or

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Speaker 1: do you have a new idea for how we can

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Speaker 1: understand something. We want you to flex your brain in

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Speaker 1: that direction. And when it doesn't quite work, reach out

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Speaker 1: to us and ask us about it. You might be

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Speaker 1: surprised that lots of other people out there have the

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Speaker 1: same questions you do.

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Speaker 2: Does that mean you're trying to convert people to dark chocolate?

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Speaker 2: This is starting to feel like a little cult here,

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Speaker 2: like a physics cult.

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Speaker 1: I think if becoming educated and thinking clearly about the

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Speaker 1: universe leads people to eating dark chocolate, that tells you

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Speaker 1: something about chocolate.

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Speaker 2: Yeah, you're saying that's like a win win.

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Speaker 1: I think the universe has a dark chocolate bias.

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Speaker 2: Yes, well, we do like to answer questions. Answer Today

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Speaker 2: on the podcast, we'll be tackling listener questions number fifty. Well,

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Speaker 2: should this be kind of a celebration the fiftieth question episode?

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Speaker 1: Yeah? Congratulations us, and congratulations are listeners for asking so

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Speaker 1: many awesome questions?

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Speaker 2: Now? Did you have a rule that only people over

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Speaker 2: fifty can ask questions in this episode?

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Speaker 1: Oh? Definitely not. I think one of our listeners is

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Speaker 1: quite young, but I try not to ask them because

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Speaker 1: some people are sensitive.

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Speaker 2: But yeah, fifty is kind of a big number. Are

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Speaker 2: we supposed to have a midlife crisis here at some point?

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Speaker 1: No, a mid life celebration. I'm turning fifteen a couple

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Speaker 1: of years and I'm looking forward to it. I'm embracing it.

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Speaker 2: Nice. Do you have any big plans Sit in the

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Speaker 2: couch and eat dark chocolate. It's the big five zero

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Speaker 2: party for you.

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Speaker 1: Yeah. I was going to say that, but that sounds

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Speaker 1: like every day around here, So I'm not sure how

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Speaker 1: I'm going to distinguish that one day from the other days.

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Speaker 2: Oh well, you have to spend it the right way.

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Speaker 2: It means you you celebrate life every day, Danna. There

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Speaker 2: you go by sitting in your couch and eating dark

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Speaker 2: to embrace it.

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Speaker 1: And if you celebrate life and celebrate understanding the universe

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Speaker 1: and you have questions about how it all works, you

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Speaker 1: could have your question answered here on the podcast. Just

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Speaker 1: to write to us questions at Danielandjorge dot com. Definitely

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Speaker 1: get an answer to your question and you might even

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Speaker 1: have it played on the podcast.

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Speaker 2: Yes, so we like to answer listener questions here on

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Speaker 2: the podcast, And so today we have three great questions

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Speaker 2: from people all over the world, and they are about

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Speaker 2: dark matter, about rainbows and the wavelength of light. Daniels

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Speaker 2: your a theme to these questions.

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Speaker 1: These are all questions that arrived on the same day.

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Speaker 2: Are they like in the top fifty questions we've ever gotten?

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Speaker 1: They're in the top one hundred and fifty questions. Yes,

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Speaker 1: because we answer three purposes.

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Speaker 2: See, I see there's a special selection process here because

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Speaker 2: straight from the inbox into the microphone.

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Speaker 1: That's right, that's the pipeline right now.

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Speaker 2: But we do have some pretty cool questions here today,

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Speaker 2: and so we'll start with this one from Johnny from Sweden.

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Speaker 3: Hi, Daniel and Jorge, this is Johnny from Sweden. I

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Speaker 3: have a question about dark matter and that I have

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Speaker 3: thought about for a long time and haven't found an

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Speaker 3: answer to. If you can shed some light on this question,

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Speaker 3: I would be very grateful. Could dark matter actually be

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Speaker 3: the gravity from matter that exists in a higher dimension.

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Speaker 3: Thank you for the best podcast in the whole universe.

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Speaker 2: All right, great question from Johnny here, kind of a

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Speaker 2: trippy question. There's a lot going on here higher dimensions,

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Speaker 2: dark matter gravity hmmmm hmm.

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Speaker 1: I think Johnny is trying to find an out of

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Speaker 1: the box solution to the question of dark matter.

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Speaker 2: It's a heavy question.

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Speaker 1: It is a heavy question, one that physicists have been

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Speaker 1: struggling with I know that there's a lot of dissatisfaction

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Speaker 1: out there with the concept of dark matter being this

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Speaker 1: weird invisible matter that nobody ever noticed before but actually

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Speaker 1: dominates the universe. Sounds like a conspiracy theory, but we

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Speaker 1: think it's real. Of course, we're open to other ideas

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Speaker 1: and other theories and other explanations because in the history

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Speaker 1: of physics, sometimes the craziest ideas turn out to be true.

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Speaker 2: Yeah, even the banana ones, right.

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Speaker 1: Dark matter could just be bananas?

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Speaker 2: Yeah, okay, So the question here is kind of interesting.

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Speaker 2: So dark matter is this thing out there in the

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Speaker 2: universe that we don't know much about, but we feel

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Speaker 2: its presence, but we can't see it, and it's pretty big.

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Speaker 2: It's like a quarter of the mass and energy of

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Speaker 2: the universe, right.

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Speaker 1: That's right, it's like eighty percent of the stuff in

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Speaker 1: the universe and like a quarter of all the energy

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Speaker 1: in the universe. Is this invisible source of gravity.

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Speaker 2: And it's super mysterious because we know it's there from

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Speaker 2: its gravity, like we can feel its pull, or at

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Speaker 2: least we can see the effects of its gravitational pull,

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Speaker 2: but we've never actually seen it or have any idea

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Speaker 2: what it could be like it's it's super weird, right,

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Speaker 2: Like it's there, but we can't see it or touch it.

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Speaker 1: Yeah, that's right. What we actually know, what we really observe,

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Speaker 1: is gravity. So in the most pure sense, the mystery

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Speaker 1: is what's the source of this unexplained gravity. There's no

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Speaker 1: matter out there in the universe we could see that

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Speaker 1: explains all the gravity that we measure, that's holding the

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Speaker 1: universe together, that's keeping galaxies from spinning apart, that shape

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Speaker 1: the structure of the whole universe. So there's unexplained gravity

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Speaker 1: out there, and dark matter is our best explanation for it,

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Speaker 1: to say, there must be some new kind of matter

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Speaker 1: that's invisible and probably intangible, and that's creating all of

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Speaker 1: this gravity, which seems.

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Speaker 2: Kind of bonkers if you really think about it, because

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Speaker 2: most of the matter that we know about that we've

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Speaker 2: known for one, hundreds or thousands of years. You can

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Speaker 2: see it and touch it. But this kind of matter,

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Speaker 2: it's like you're almost inventing a new kind of matter

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Speaker 2: to explain this gravitational phenomenon. But we don't really know

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Speaker 2: if that's true or not.

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Speaker 1: Right, it's true that it's kind of bonkers, but maybe

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Speaker 1: it's less bonkers than extrapolating from our kind of matter

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Speaker 1: to the whole universe. It's true that everything we've ever

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Speaker 1: experienced is made of atoms, but that doesn't mean that

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Speaker 1: everything has to be made out of atoms. The history

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Speaker 1: of physics tells us we should be really careful about

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Speaker 1: extrapolating from our little corner of the universe and our

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Speaker 1: kind of experience to the whole universe. The revolutions of

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Speaker 1: quantum mechanics and of relativity were moments when we realize

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Speaker 1: we've been looking too narrowly at only our own experience.

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Speaker 1: So to say that the rest of the universe should

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Speaker 1: also be made out of atoms because we are and

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Speaker 1: the Earth is seems like a pretty big leap. What

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Speaker 1: we're doing here is saying, well, maybe there are other

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Speaker 1: kinds of matter out there, ones that are not made

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Speaker 1: out of atoms and so don't interact in the same

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Speaker 1: way that atoms do.

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Speaker 2: Well, that's one possible explanation, and that seems to be

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Speaker 2: where most of physics is leaning. But Johnny here has

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Speaker 2: an alternate theory for what causes dark matter exactly.

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Speaker 1: He's asking me if this gravity could instead be coming

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Speaker 1: from matter that exists in a higher dimension rather than

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Speaker 1: like a new invisible kind of matter in our three

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Speaker 1: D space.

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Speaker 2: M Yeah, fascinating idea. If he's right, he would get

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Speaker 2: like all the Nobel prizes. Right.

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Speaker 1: If he's right and we can test it and prove it,

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Speaker 1: then yeah, Johnny has changed the world and history.

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Speaker 2: All right, Well, let's dig into his idea. He's saying

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Speaker 2: that maybe a dark matter what we experience or feel

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Speaker 2: is dark matter, is maybe actually matter that is not

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Speaker 2: in the dimensions we're in, but they're in other dimensions.

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Speaker 1: Yeah. I wasn't exactly sure what he meant by matter

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Speaker 1: that exists in a higher dimension, because the word dimension

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Speaker 1: is a little bit fuzzy, like in physics is a

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Speaker 1: crisp definition of it, But in popular science and in

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Speaker 1: science fiction and a normal everyday conversation, I think dimension

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Speaker 1: means something else. Like often I think people say dimension

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Speaker 1: when they mean like a parallel universe, you know, like

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Speaker 1: people talk about interdimensional aliens visiting the Earth, Right, I

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Speaker 1: think what they mean there are aliens from like a

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Speaker 1: parallel universe, from like another copy of the universe, like

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Speaker 1: a different set of space.

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Speaker 2: Right. And we've talked about this in our books and

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Speaker 2: in previous episodes. And I know that you're sort of

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Speaker 2: against this sci fi idea of the dimension as being

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Speaker 2: like in a separate universe that you go into, but

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Speaker 2: it sort of kind of is right. It is sort

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Speaker 2: of a the idea of a separate part of space

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Speaker 2: than the one we're sitting on.

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Speaker 1: I'm not against it. I mean, the idea of a

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Speaker 1: parallel universe is certainly possible. This concept of the multiverse,

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Speaker 1: that we could have multiple universes, maybe with different starting

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Speaker 1: conditions or different even laws of physics. Who knows, right,

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Speaker 1: I think that's totally plausible scientifically. I'm just pointing out

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Speaker 1: that that's not what we mean by dimension when we

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Speaker 1: talk talk about mathematically or physically. But you know, that's

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Speaker 1: just semantics. So let's assume first that this is what

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Speaker 1: he means by dimension, Like, is dark matter actually gravity

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Speaker 1: from a parallel universe? Like maybe in another universe there's

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Speaker 1: a huge blob of normal matter and we're feeling it's

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Speaker 1: gravity somehow leak out into our universe, and that's what

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Speaker 1: we're calling dark matter.

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Speaker 2: That's how you're interpreting his question, his scenario.

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Speaker 1: Yeah, that's one possibility. We could also talk about the

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Speaker 1: other definition, Well, let's do it one aount of time.

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Speaker 1: So in this scenario where a dimension means a parallel

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Speaker 1: universe and you're wondering if dark matter is actually like

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Speaker 1: some blob of stuff in another universe that's creating gravity

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Speaker 1: in our universe, I don't think that can work because

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Speaker 1: you know, gravity is the bending of space and time,

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Speaker 1: and so if matter is bending our space and time,

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Speaker 1: then it's in our space time. Like that's sort of

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Speaker 1: what it means to be in our space time. If

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Speaker 1: we have a shared space time like that matter can

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Speaker 1: bend our space time, then it's part of our universe.

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Speaker 1: So you can't both be in another universe and affect

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Speaker 1: things in this universe.

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Speaker 2: Well, well, I think you're sort of arguing semantics now.

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Speaker 2: It's like you're saying, like, if there is sort of

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Speaker 2: this whole part of this whole universe basically that you

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Speaker 2: can exist in but that we don't have a lot

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Speaker 2: of access to, but if it's somehow connected to our universe,

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Speaker 2: you're saying that means both the universes are really just

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Speaker 2: one universe exactly.

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Speaker 1: I'm saying it's one universe, and then it's really the

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Speaker 1: same idea right, then it's just some kind of matter

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Speaker 1: that we can't interact with for some reason, but is

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Speaker 1: able to bend our space time therefore cause gravity. That's

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Speaker 1: just the same idea as dark matter.

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Speaker 2: Well, you sort of sound like my daughter because she's

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Speaker 2: always saying like, if the multiverse exists, wouldn't it all

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Speaker 2: just be the universe? So I mean, like physicists do

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Speaker 2: have a name for like a universe, and something bigger

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Speaker 2: than a universe, which is a multiverse.

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Speaker 1: Yeah, I think this is a tiny bit different from

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Speaker 1: your daughter's point, and though she has a good one.

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Speaker 1: You know, the idea of a multiverse is that these

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Speaker 1: universes don't interact. They really are separate universes. But if

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Speaker 1: they do interact, why would you call them separate universe

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Speaker 1: versus how are these higher dimensions? If we're able to

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Speaker 1: interact with this kind of matter, and if we can

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Speaker 1: interact with it, why can't we see it? Well, the

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Speaker 1: answer has to be you with some other new kind

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Speaker 1: of matter, which basically we're back at dark matter, right right.

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Speaker 2: Well, I feel like it's kind of like, you know,

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Speaker 2: if I dig a tunnel from my house to your house,

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Speaker 2: I mean a pretty long tunnel, but if we do that,

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Speaker 2: would that mean that we all live in one house

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Speaker 2: or could you still say that we live in separate houses,

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Speaker 2: which is the tunnel connecting?

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Speaker 1: You know, I think if I can go from my

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Speaker 1: house to your house without going outside, then yeah, it's

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Speaker 1: probably just one house.

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Speaker 2: What if I put a door in the tunnel and

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Speaker 2: I lock it?

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Speaker 1: Interesting? I'm sure there's some California legal statute that defines

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Speaker 1: what is a residence and what is not, And I'm

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Speaker 1: not qualified to a pine on that question.

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Speaker 2: All right, all right, all right, So you're shooting down

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Speaker 2: this idea that his question actually means that dark matter

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Speaker 2: is matter in a separate universe, because then it would

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Speaker 2: just be the same.

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Speaker 1: Yeah, exactly, Then it would just be dark matter.

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Speaker 2: I think maybe Johnny's trying to get at the idea

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Speaker 2: that we can sort of feel it, but sort of

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Speaker 2: not feel dark matter. So like, maybe this is matter

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Speaker 2: that exists in another universe or another huge chunk of

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Speaker 2: the universe, but that is not fully connected to our universe.

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Speaker 2: Like it maybe it's only connected to tunnel, which in

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Speaker 2: this case would be gravity.

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Speaker 1: Yeah, potentially, But then you have to ask, like why

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Speaker 1: we can't interact with that other kind of matter, and

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Speaker 1: then you have to make it another kind of matter.

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Speaker 1: If it's sharing our space, bending our space time, it

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Speaker 1: doesn't interact with us, then you have to ask, you know,

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Speaker 1: why not what makes our matter our matter and that

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Speaker 1: matter that matter, and so you have to make it

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Speaker 1: another kind of matter, and then it becomes dark matter

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Speaker 1: all over again.

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Speaker 2: All right, now, say that quickly seven times in a row.

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Speaker 1: But there is another way to interpret his question, which

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Speaker 1: I think is much more interesting, which is the physics

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Speaker 1: definition of dimension. Because he doesn't say another dimension. He

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Speaker 1: says a higher dimension, which I think might be a

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Speaker 1: useful clue because in physics we think of dimensions not

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Speaker 1: as you know it came from another dimension, but as

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Speaker 1: directions of motion, like we describe our space as three

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Speaker 1: dimensional space or four dimensional space time because we say

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Speaker 1: there are three direct of motion, Like if you draw

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Speaker 1: axis out in space, you get x, y, and z.

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Speaker 1: There's three directions you can move. You don't need four

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Speaker 1: directions to describe our space. And so I think he

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Speaker 1: maybe he's asking, like, what if our space actually is

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Speaker 1: higher dimensional? What if there are four or five, six,

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Speaker 1: ten dimensions of space and we're only seeing a slice

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Speaker 1: of it and dark matter somehow exists in those higher

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Speaker 1: dimensions and is influencing us.

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Speaker 2: Interesting, Okay, So and I think maybe this is what

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Speaker 2: he means because he uses the word higher dimension, right,

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Speaker 2: Like if he meant like an alternate dimension, he wouldn't

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Speaker 2: say the word higher.

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Speaker 1: Yeah, I think so, although maybe he's smoking something and

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Speaker 1: he's higher you never.

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Speaker 2: Know, yeah, or maybe he's more elevated or enlightened exactly.

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Speaker 1: And this can be hard to visualize what is higher

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Speaker 1: dimensional space because three D space sort of fills up

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Speaker 1: your mind because we're so used to thinking in three

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Speaker 1: D space because we live in three D space, So

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Speaker 1: it's easier to take a step from two D space

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Speaker 1: to three D space to like take a step back

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Speaker 1: and imagine what if our universe was two D. What

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Speaker 1: would it be like to have a three dimensional universe

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Speaker 1: rather than trying to go from three to four. So imagine,

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Speaker 1: for example, we're living on the surface of the ocean.

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Speaker 1: You know, our universe is just the two D surface

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Speaker 1: of the ocean. But what if the universe actually has

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Speaker 1: another dimension that can influence us, like the depth of

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Speaker 1: the ocean.

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Speaker 2: And so then Johnny's ideas and maybe there's matter in

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Speaker 2: our universe that maybe only exists in these other dimensions

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Speaker 2: that are not our regular three D dimensions. Mm hmm,

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Speaker 2: Now is that possible? Like can matter exists in some

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Speaker 2: dimensions and not others? If there is maybe a fourth

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Speaker 2: or fifth dimension to our universe? Am I moving around

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Speaker 2: in it? Or do I have to be moving around

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Speaker 2: in it? Or do you know what I mean?

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Speaker 1: I do know what you mean, and I think there's

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Speaker 1: an important but maybe subtle distinction here. Matter has to

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Speaker 1: exist in all of the dimensions of space time. You

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Speaker 1: have to have a location in all those directions. But

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Speaker 1: it could be that there's matter that has a different

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Speaker 1: location in this new dimension. Like say, for example, our

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Speaker 1: universe is the two D surface of the ocean, so

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Speaker 1: we have a location in the depth dimension. But you

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Speaker 1: could imagine having matter that exists deeper in the ocean,

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Speaker 1: so it doesn't intersect our two D surface at all.

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Speaker 1: It's in the universe. It exists in all three dimensions

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Speaker 1: of that three D universe, but now part of it

427
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Speaker 1: overlaps in our two D slice of the universe. But

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Speaker 1: it could still influence us.

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Speaker 2: It could still influence it because it's connected to us

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Speaker 2: three dimension exactly.

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Speaker 1: It's part of our space time, right, And so then

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Speaker 1: Johnny's question is, like, well, what if there's matter that's

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Speaker 1: part of a four dimensional space, but its location in

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Speaker 1: that four D space means we can't see it. It's

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Speaker 1: like in a different location along that new fourth dimension

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Speaker 1: than we are, Like we're on the three D surface

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Speaker 1: of that four D ocean, and it's like deeper down

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Speaker 1: along that fourth dimension. If gravity is the curvature of

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Speaker 1: space time, and there's matter in that part of the universe,

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Speaker 1: the deeper ocean of the universe, wouldn't it also affect

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Speaker 1: our space time and therefore look like dark matter?

442
00:20:04,760 --> 00:20:07,760
Speaker 2: Right? It might affect us gravitationally, because let's say, like

443
00:20:07,800 --> 00:20:09,840
Speaker 2: we're on the surface of the ocean, as you're saying,

444
00:20:09,880 --> 00:20:13,960
Speaker 2: and this other matter is right below us. We might

445
00:20:14,000 --> 00:20:16,320
Speaker 2: feel its gravity might pull us in a certain direction,

446
00:20:16,560 --> 00:20:19,639
Speaker 2: but when we try to look around and feel for

447
00:20:19,680 --> 00:20:22,160
Speaker 2: it and touch it and see it, we can't because

448
00:20:22,200 --> 00:20:24,200
Speaker 2: it's actually underneath this exactly.

449
00:20:24,240 --> 00:20:26,399
Speaker 1: And this is a really compelling idea. There's sort of

450
00:20:26,440 --> 00:20:29,480
Speaker 1: two problems with it. One is you need an explanation

451
00:20:29,600 --> 00:20:31,720
Speaker 1: for why we can't touch it, Like why are we

452
00:20:31,800 --> 00:20:34,960
Speaker 1: restricted to the surface of this four dimensional ocean. Why

453
00:20:34,960 --> 00:20:36,760
Speaker 1: can't this kind of matter exist and move in four

454
00:20:36,800 --> 00:20:39,479
Speaker 1: dimensions and we're stuck at this one location in that

455
00:20:39,520 --> 00:20:41,840
Speaker 1: fourth dimension? Like why are we on the surface of

456
00:20:41,880 --> 00:20:44,119
Speaker 1: this ocean and this other matter can like sink or

457
00:20:44,160 --> 00:20:45,640
Speaker 1: swim or whatever.

458
00:20:45,440 --> 00:20:47,480
Speaker 2: You mean, Like, why are we stuck in two dimensions?

459
00:20:47,520 --> 00:20:49,280
Speaker 2: Why can't we go down into the ocean?

460
00:20:49,320 --> 00:20:52,760
Speaker 1: Exactly? Yeah? And why does that matter never surface? Right?

461
00:20:52,800 --> 00:20:55,760
Speaker 1: How can we never see it? But the real problem

462
00:20:55,840 --> 00:20:59,480
Speaker 1: is mathematical, which is that we know how many dimensions

463
00:20:59,520 --> 00:21:02,680
Speaker 1: there are to space time. We can measure how many

464
00:21:02,680 --> 00:21:05,879
Speaker 1: dimensions there are to space time because the dimensionality of

465
00:21:05,920 --> 00:21:09,040
Speaker 1: space time, like how many ways you can move changes

466
00:21:09,119 --> 00:21:10,359
Speaker 1: how gravity works.

467
00:21:11,119 --> 00:21:14,919
Speaker 2: But isn't higher dimensions or other dimensions part of things

468
00:21:14,960 --> 00:21:18,159
Speaker 2: like string theory, Like isn't this an active possibility that

469
00:21:18,200 --> 00:21:19,520
Speaker 2: physicists are considering?

470
00:21:19,720 --> 00:21:22,760
Speaker 1: Yeah, you're exactly right. People do look for extra dimensions.

471
00:21:22,880 --> 00:21:25,159
Speaker 1: But one of the big challenges to those ideas like

472
00:21:25,200 --> 00:21:27,879
Speaker 1: string theory that requires the universe has ten or twenty

473
00:21:27,920 --> 00:21:31,520
Speaker 1: six dimensions or other crazy theories that look for additional

474
00:21:31,520 --> 00:21:34,240
Speaker 1: dimensions of space time is that we're not seeing them.

475
00:21:34,560 --> 00:21:36,000
Speaker 1: We can go out in the universe and we can

476
00:21:36,040 --> 00:21:39,520
Speaker 1: pretty easily look for extra dimensions and we don't see them.

477
00:21:39,760 --> 00:21:41,800
Speaker 1: You know, for example, the number of dimensions of space

478
00:21:41,840 --> 00:21:45,000
Speaker 1: time changes how gravity varies with distance. We know in

479
00:21:45,040 --> 00:21:48,000
Speaker 1: the Newtonian description that gravity gets weaker as you get

480
00:21:48,000 --> 00:21:50,800
Speaker 1: further away, But it doesn't just fall off linearly. It's

481
00:21:50,800 --> 00:21:53,160
Speaker 1: not like twice as far away gravity as twice as weak.

482
00:21:53,400 --> 00:21:56,080
Speaker 1: Twice as far away gravity is four times this week.

483
00:21:56,280 --> 00:21:59,120
Speaker 1: It goes like one over the distance squared. And that

484
00:21:59,240 --> 00:22:03,000
Speaker 1: number of the where tells you the dimensionality of space time.

485
00:22:03,400 --> 00:22:05,720
Speaker 1: If we lived in four dimensional universe, that would be

486
00:22:05,800 --> 00:22:08,280
Speaker 1: one over the distance cubed. If we lived in a

487
00:22:08,359 --> 00:22:10,880
Speaker 1: nineteen dimensional universe, it would be one over the distance

488
00:22:10,960 --> 00:22:12,320
Speaker 1: to the eighteenth power.

489
00:22:12,480 --> 00:22:15,040
Speaker 2: But isn't that only if you assume that gravity works

490
00:22:15,080 --> 00:22:17,040
Speaker 2: a certain way? Like what if the gravity doesn't work

491
00:22:17,040 --> 00:22:17,760
Speaker 2: the way you think it does.

492
00:22:17,920 --> 00:22:20,800
Speaker 1: Yeah, if you want to also overthrow general relativity, then

493
00:22:20,800 --> 00:22:22,119
Speaker 1: you've got a lot more work ahead of you.

494
00:22:22,200 --> 00:22:24,160
Speaker 2: Yeah, I'm not afraid of work. I got on there.

495
00:22:24,320 --> 00:22:26,040
Speaker 1: You and Johnny should get to that higher dimension and

496
00:22:26,080 --> 00:22:27,880
Speaker 1: get to work on it. But you know, if we're

497
00:22:27,880 --> 00:22:30,360
Speaker 1: not changing gravity, if we're not changing how gravity works,

498
00:22:30,400 --> 00:22:33,479
Speaker 1: we're just asking does the universe have additional dimensions? And

499
00:22:33,520 --> 00:22:36,280
Speaker 1: could there be matter hiding those dimensions that creates gravity

500
00:22:36,320 --> 00:22:39,119
Speaker 1: that we see that could be explaining what we're seeing

501
00:22:39,160 --> 00:22:42,000
Speaker 1: instead of dark matter. Then if we're sticking with our

502
00:22:42,040 --> 00:22:44,560
Speaker 1: theory of gravity, that's pretty hard to make it happen.

503
00:22:44,760 --> 00:22:47,600
Speaker 2: Isn't your assumption here that this theory of gravity that

504
00:22:47,640 --> 00:22:50,399
Speaker 2: you're saying that you're sticking by, isn't that a theory

505
00:22:50,440 --> 00:22:53,600
Speaker 2: of gravity that we've gotten by doing experiments then the

506
00:22:53,600 --> 00:22:54,440
Speaker 2: dimensions that we have.

507
00:22:54,440 --> 00:22:57,480
Speaker 1: Access to hmm, yeah, absolutely, could.

508
00:22:57,320 --> 00:23:00,320
Speaker 2: Maybe gravity be actually more powerful than you think and

509
00:23:00,320 --> 00:23:03,400
Speaker 2: those so therefore when you try to measure it, there

510
00:23:03,440 --> 00:23:05,640
Speaker 2: are other dimensions, but it drops off as one over

511
00:23:05,680 --> 00:23:06,119
Speaker 2: our square.

512
00:23:06,160 --> 00:23:09,040
Speaker 1: As you're saying, there are some really cool theories that

513
00:23:09,080 --> 00:23:11,639
Speaker 1: there are these other dimensions, but those dimensions are not

514
00:23:11,880 --> 00:23:14,480
Speaker 1: like our dimensions. They don't go out to negative and

515
00:23:14,560 --> 00:23:18,400
Speaker 1: positive infinity like ours, but they're like curled up little rings,

516
00:23:18,640 --> 00:23:20,600
Speaker 1: so that you can really have like two centimeters or

517
00:23:20,640 --> 00:23:23,640
Speaker 1: one centimeter, and that would solve this problem with gravity

518
00:23:23,640 --> 00:23:26,520
Speaker 1: getting stronger or weaker. It actually would solve the problem

519
00:23:26,520 --> 00:23:29,280
Speaker 1: in a really fascinating way, because if you get really

520
00:23:29,320 --> 00:23:32,120
Speaker 1: close to something, then gravity would get very very powerful,

521
00:23:32,119 --> 00:23:34,560
Speaker 1: and that would actually help us understand why gravity is

522
00:23:34,560 --> 00:23:37,159
Speaker 1: so weirdly weak. But go check out our podcast on

523
00:23:37,320 --> 00:23:40,000
Speaker 1: extra dimensions. But you got to assume something, right, And

524
00:23:40,080 --> 00:23:42,600
Speaker 1: so if you're assuming our theory of gravity that I

525
00:23:42,640 --> 00:23:46,760
Speaker 1: don't think this quite works because if those extra dimensions exist,

526
00:23:46,840 --> 00:23:48,800
Speaker 1: they would have to be super duper tiny and they

527
00:23:48,840 --> 00:23:51,600
Speaker 1: wouldn't be mass in them. But if we're also getting

528
00:23:51,640 --> 00:23:54,600
Speaker 1: rid of our theory of gravity, than they anything's possible.

529
00:23:55,400 --> 00:23:56,919
Speaker 2: Well, it sounds like you kind of have to have

530
00:23:57,119 --> 00:23:59,600
Speaker 2: that open mind right when you explore.

531
00:24:00,440 --> 00:24:02,840
Speaker 1: Yeah, absolutely you do, And we do think that there

532
00:24:02,880 --> 00:24:05,320
Speaker 1: are problems with our theory of gravity. We think that

533
00:24:05,359 --> 00:24:07,880
Speaker 1: general relativity is probably not the final answer to how

534
00:24:07,880 --> 00:24:10,520
Speaker 1: space time works because it ignores the quantum nature of it.

535
00:24:10,840 --> 00:24:13,600
Speaker 1: So we're definitely open to modification of those ideas.

536
00:24:13,680 --> 00:24:17,120
Speaker 2: Yeah, all right, well, then what's the final answer for

537
00:24:17,240 --> 00:24:17,800
Speaker 2: Johnny Here?

538
00:24:17,840 --> 00:24:20,040
Speaker 1: I would say that it's possible that there are additional

539
00:24:20,040 --> 00:24:23,520
Speaker 1: dimensions with matter in them that doesn't appear in our

540
00:24:23,800 --> 00:24:26,200
Speaker 1: three D slice of space, But it would be pretty

541
00:24:26,200 --> 00:24:29,120
Speaker 1: hard to explain all of the dark matter using that

542
00:24:29,160 --> 00:24:31,840
Speaker 1: because those dimensions would be tiny and would be curled up.

543
00:24:32,359 --> 00:24:35,520
Speaker 1: I think it's much more likely that dark matter really

544
00:24:35,640 --> 00:24:38,560
Speaker 1: is a new kind of matter that exists in our.

545
00:24:38,520 --> 00:24:41,280
Speaker 2: Universe, unless, of course, our whole theory of gravity is.

546
00:24:41,280 --> 00:24:44,359
Speaker 1: Wrong, right, yeah, absolutely, all.

547
00:24:44,320 --> 00:24:46,840
Speaker 2: Right, Well, great question, Johnny, Thanks for sending that in.

548
00:24:47,040 --> 00:24:49,000
Speaker 2: Now let's get to our other questions. We have a

549
00:24:49,080 --> 00:24:54,120
Speaker 2: question here about rainbows and one about the wavelength of light,

550
00:24:54,480 --> 00:24:56,639
Speaker 2: so let's dig into those. But first let's take a

551
00:24:56,720 --> 00:24:57,240
Speaker 2: quick break.

552
00:25:09,600 --> 00:25:09,920
Speaker 1: All right.

553
00:25:09,920 --> 00:25:13,000
Speaker 2: We're answering listener questions here today, and our next question

554
00:25:13,119 --> 00:25:17,119
Speaker 2: comes from Sonia. Hi, Daniel, and Jorge. My name is Sonia,

555
00:25:17,160 --> 00:25:19,680
Speaker 2: and I was wondering if there was a minimum and

556
00:25:19,840 --> 00:25:24,840
Speaker 2: or maximum wavelength for light. Thank you, all right, great question, Sonya.

557
00:25:25,240 --> 00:25:27,320
Speaker 2: I wonder what made her think about the nature of light.

558
00:25:27,640 --> 00:25:29,760
Speaker 1: I get this question all the time, which is one

559
00:25:29,800 --> 00:25:31,359
Speaker 1: of the reasons why I wanted to answer it on

560
00:25:31,440 --> 00:25:33,720
Speaker 1: the podcast. It's something that a lot of people seem

561
00:25:33,720 --> 00:25:37,400
Speaker 1: to wonder about because you learn that light is described

562
00:25:37,400 --> 00:25:39,919
Speaker 1: by this wavelength, and the wavelength is connected to the color,

563
00:25:40,280 --> 00:25:42,080
Speaker 1: and then I think it just makes people wonder about

564
00:25:42,119 --> 00:25:44,480
Speaker 1: the extremes, Like we talk about the extreme nature of

565
00:25:44,480 --> 00:25:46,439
Speaker 1: the universe all the time. What is the beginning what

566
00:25:46,560 --> 00:25:48,720
Speaker 1: is the end, what is the biggest, what is the smallest.

567
00:25:48,920 --> 00:25:51,480
Speaker 1: People's curiosity make them want to push to the extreme

568
00:25:51,640 --> 00:25:52,480
Speaker 1: edges of knowledge.

569
00:25:53,880 --> 00:25:56,439
Speaker 2: All right, Well, her question is whether light has a

570
00:25:56,480 --> 00:26:00,720
Speaker 2: minimum or maximum wavelength. So, Daniel, how do you describe

571
00:26:00,720 --> 00:26:02,119
Speaker 2: what the wavelength of light is?

572
00:26:02,280 --> 00:26:06,600
Speaker 1: So we understand light to be electromagnetic oscillations. That just

573
00:26:06,680 --> 00:26:11,400
Speaker 1: means waves in electrical and magnetic fields. Like electrical fields

574
00:26:11,480 --> 00:26:14,400
Speaker 1: are things that we're very familiar with. You have charged particles,

575
00:26:14,440 --> 00:26:18,080
Speaker 1: they make electric fields. Magnetic fields something we're familiar with.

576
00:26:18,400 --> 00:26:21,800
Speaker 1: You have magnets moving electric charges can make magnetic fields.

577
00:26:22,320 --> 00:26:26,080
Speaker 1: And so light is this particular configuration of electromagnetic fields

578
00:26:26,080 --> 00:26:28,680
Speaker 1: where the electric field creates a magnetic field, which creates

579
00:26:28,680 --> 00:26:32,400
Speaker 1: an electric field slashes back and forth. But it's fundamentally

580
00:26:32,480 --> 00:26:35,520
Speaker 1: a wave. It's a wave in these fields that fill space,

581
00:26:36,280 --> 00:26:38,840
Speaker 1: and those waves are described, like all waves, by a

582
00:26:38,880 --> 00:26:41,679
Speaker 1: wave length, which is like how long it takes in

583
00:26:41,800 --> 00:26:45,720
Speaker 1: distance as the light travels before it repeats the same configuration.

584
00:26:46,040 --> 00:26:48,479
Speaker 1: So the electric field's going up and down, the magnetic

585
00:26:48,560 --> 00:26:51,240
Speaker 1: fields going up and down. How far does the light

586
00:26:51,280 --> 00:26:54,600
Speaker 1: travel before the electric field is back into its original configuration.

587
00:26:54,920 --> 00:26:56,280
Speaker 1: That's the wavelength of the.

588
00:26:56,320 --> 00:26:58,800
Speaker 2: Light sort of like a wave in the ocean, right.

589
00:26:58,840 --> 00:27:02,000
Speaker 1: Yeah, exactly. Something that I understand about these waves is

590
00:27:02,200 --> 00:27:05,760
Speaker 1: people see visualizations of light traveling and they see it

591
00:27:05,760 --> 00:27:08,439
Speaker 1: as like a sinusoidal wave moving through space, and they

592
00:27:08,480 --> 00:27:11,720
Speaker 1: get the impression that the light is like wiggling sideways

593
00:27:12,119 --> 00:27:14,520
Speaker 1: that has like a width to it. But light moves

594
00:27:14,560 --> 00:27:17,760
Speaker 1: along a line, and what's changing is the magnitude of

595
00:27:17,760 --> 00:27:20,480
Speaker 1: the electric and magnetic field to draw like little arrows

596
00:27:20,640 --> 00:27:23,879
Speaker 1: that are pegged to that line. Sometimes those arrows are

597
00:27:23,920 --> 00:27:26,680
Speaker 1: drawn like with their base pointing in some direction and

598
00:27:26,720 --> 00:27:28,959
Speaker 1: their tip away from the line. That's just telling you

599
00:27:29,240 --> 00:27:32,320
Speaker 1: the magnitude of the electric field. The electric field doesn't

600
00:27:32,320 --> 00:27:35,679
Speaker 1: like reach out sideways. It's a vector field, and so

601
00:27:35,720 --> 00:27:37,359
Speaker 1: it can point in different directions.

602
00:27:38,080 --> 00:27:41,879
Speaker 2: Okay, So it's an oscillation of these fields. And so

603
00:27:41,960 --> 00:27:44,879
Speaker 2: things can have a wavelength, which, as far as we know,

604
00:27:45,000 --> 00:27:47,360
Speaker 2: can vary, right Like, that's how we get different colors

605
00:27:47,440 --> 00:27:48,320
Speaker 2: when we look at things.

606
00:27:48,440 --> 00:27:51,320
Speaker 1: Exactly. Light comes in all kinds of different wavelengths, and

607
00:27:51,359 --> 00:27:54,440
Speaker 1: different wavelengths are interpreted by our eye as different colors.

608
00:27:54,520 --> 00:27:57,159
Speaker 1: So there's a very narrow set of those wavelengths that

609
00:27:57,160 --> 00:28:00,280
Speaker 1: we can actually see. You call that the visible spectrum.

610
00:28:00,520 --> 00:28:02,720
Speaker 1: It goes, you know, from the reddest colors we can

611
00:28:02,760 --> 00:28:05,440
Speaker 1: see up to the most violet colors we can see.

612
00:28:05,720 --> 00:28:09,040
Speaker 1: But light extends its spectrum well above that and well

613
00:28:09,080 --> 00:28:14,040
Speaker 1: below that the ultraviolet, the infrared, X rays, gamma rays,

614
00:28:14,160 --> 00:28:17,680
Speaker 1: radio waves, all these are just light with different wavelengths.

615
00:28:17,920 --> 00:28:20,760
Speaker 2: Yeah, I think that's basically Sonia's question is, like, light

616
00:28:21,000 --> 00:28:22,800
Speaker 2: can go up in frequency from what we can see,

617
00:28:22,840 --> 00:28:25,320
Speaker 2: and can go down in frequency, and their question is

618
00:28:25,440 --> 00:28:26,440
Speaker 2: how far can that go?

619
00:28:26,960 --> 00:28:29,320
Speaker 1: Yeah, exactly, And there's a few different concepts there. Right now,

620
00:28:29,320 --> 00:28:33,119
Speaker 1: we're just talking about wavelength, right, long wavelengths or like

621
00:28:33,240 --> 00:28:37,280
Speaker 1: radio waves short wavelengths, or like ultraviolet gamma rays. You

622
00:28:37,320 --> 00:28:41,120
Speaker 1: can also talk about frequency. Frequency is the inverse of

623
00:28:41,160 --> 00:28:44,959
Speaker 1: wavelength because light always has the same velocity. So short

624
00:28:45,000 --> 00:28:49,360
Speaker 1: wavelengths means high frequency radio waves that have long wavelengths

625
00:28:49,440 --> 00:28:52,000
Speaker 1: have very low frequency. It's all the same thing. You

626
00:28:52,000 --> 00:28:54,880
Speaker 1: can just express it in different ways. But the frequency

627
00:28:54,960 --> 00:28:58,000
Speaker 1: is useful because it's connected to the energy, like the

628
00:28:58,160 --> 00:29:02,280
Speaker 1: energy of light is connected to its frequency. Higher frequency

629
00:29:02,360 --> 00:29:06,360
Speaker 1: light ultraviolet X rays have more energy than lower frequency

630
00:29:06,440 --> 00:29:08,080
Speaker 1: light like radio waves.

631
00:29:07,840 --> 00:29:10,280
Speaker 2: But it's all the same thing, right, Like for light,

632
00:29:10,400 --> 00:29:12,320
Speaker 2: it's all tied to the speed of light, and so

633
00:29:12,760 --> 00:29:14,600
Speaker 2: you can also say that the energy of a light

634
00:29:14,680 --> 00:29:16,440
Speaker 2: wave is tied to its wavelength as well.

635
00:29:16,480 --> 00:29:19,360
Speaker 1: Yeah, absolutely has an inverse relationship to its wavelength, and

636
00:29:19,400 --> 00:29:21,440
Speaker 1: it's linearly proportional to its frequency.

637
00:29:21,600 --> 00:29:23,080
Speaker 2: Right, it's the same thing. So you can also say

638
00:29:23,080 --> 00:29:24,880
Speaker 2: that the energy or something is tied to its wavelength.

639
00:29:24,920 --> 00:29:28,080
Speaker 2: The higher the wavelength, the lower the energy of light.

640
00:29:28,160 --> 00:29:29,160
Speaker 1: Yeah, that's exactly right.

641
00:29:29,240 --> 00:29:31,880
Speaker 2: Okay, So her question is how far up and down

642
00:29:31,960 --> 00:29:34,800
Speaker 2: the frequency spectrum or the wavelength spectrum can you go

643
00:29:35,200 --> 00:29:35,680
Speaker 2: with light?

644
00:29:36,200 --> 00:29:39,680
Speaker 1: Yeah, and so in theory there's no limit, Like, as

645
00:29:39,680 --> 00:29:41,840
Speaker 1: you say, it's just controlled by the energy. Is there

646
00:29:41,880 --> 00:29:44,680
Speaker 1: any limit to how much energy a photon can have?

647
00:29:45,040 --> 00:29:47,680
Speaker 1: Is there any minimum to how much energy a photon

648
00:29:47,720 --> 00:29:50,600
Speaker 1: can have? The only limit there is zero. Theoretically, it

649
00:29:50,640 --> 00:29:53,120
Speaker 1: can't have zero energy, but it could have any tiny

650
00:29:53,200 --> 00:29:56,479
Speaker 1: amount of energy, any number you want, zero points zero zero,

651
00:29:56,560 --> 00:29:58,960
Speaker 1: zero zero zero zero, one hundred zeros and then a

652
00:29:59,000 --> 00:30:02,200
Speaker 1: one uels or whatever. You could have a photon with

653
00:30:02,240 --> 00:30:03,120
Speaker 1: that energy.

654
00:30:02,840 --> 00:30:04,560
Speaker 2: Could you, though? Are you sure about that? Like what

655
00:30:04,600 --> 00:30:06,480
Speaker 2: if the electromagnetic fields are quantized?

656
00:30:06,560 --> 00:30:10,120
Speaker 1: So if we're still just talking theoretically, then electromagnetic fields

657
00:30:10,160 --> 00:30:13,960
Speaker 1: are quantized, but they're quantized in number of photons, not

658
00:30:14,200 --> 00:30:17,080
Speaker 1: in energy of those photons. And so if we're just

659
00:30:17,120 --> 00:30:19,800
Speaker 1: talking about like photons out in free space, they're not

660
00:30:19,880 --> 00:30:22,800
Speaker 1: confined or anything, then they can have any wavelength and

661
00:30:22,840 --> 00:30:25,800
Speaker 1: therefore any energy. This is just in theory. There are

662
00:30:25,880 --> 00:30:29,360
Speaker 1: some maybe practical limits to how long a wavelength of

663
00:30:29,400 --> 00:30:32,480
Speaker 1: photon might have or how short a wavelength of photon

664
00:30:32,560 --> 00:30:35,880
Speaker 1: might have, But according to like theoretical quantum field theory

665
00:30:35,880 --> 00:30:39,000
Speaker 1: of electromagnetism, there are no limits there except for zero.

666
00:30:39,160 --> 00:30:41,520
Speaker 1: You can't have a photon with zero energy.

667
00:30:42,680 --> 00:30:43,840
Speaker 2: According to the theory.

668
00:30:43,680 --> 00:30:45,680
Speaker 1: Right, Yeah, according to the theory.

669
00:30:45,520 --> 00:30:48,240
Speaker 2: Is it possible that maybe they'll turn out later that

670
00:30:48,360 --> 00:30:51,880
Speaker 2: these magnetic fields are quantized or to have a minimum

671
00:30:51,920 --> 00:30:52,760
Speaker 2: wavelength to them.

672
00:30:52,920 --> 00:30:56,200
Speaker 1: Yeah, it's possible, Like we might extend our theory to

673
00:30:56,360 --> 00:31:00,080
Speaker 1: understand the universe differently. For example, this theory assumes that

674
00:31:00,080 --> 00:31:03,160
Speaker 1: that space is continuous, that it's smooth, that there's no

675
00:31:03,200 --> 00:31:07,000
Speaker 1: shortest possible distance in space, and therefore no minimum wavelength,

676
00:31:07,480 --> 00:31:09,800
Speaker 1: that you can keep getting smaller and smaller and smaller

677
00:31:09,800 --> 00:31:12,960
Speaker 1: distances than those things are meaningful but that might be wrong.

678
00:31:13,320 --> 00:31:16,680
Speaker 1: It might be that space is not smooth and continuous,

679
00:31:16,840 --> 00:31:21,520
Speaker 1: but it's pixelated, that there's a minimum meaningful distance to space,

680
00:31:21,800 --> 00:31:24,840
Speaker 1: in which case there would be a minimal possible wavelength

681
00:31:25,080 --> 00:31:25,840
Speaker 1: to light.

682
00:31:26,960 --> 00:31:30,120
Speaker 2: Or at least one meaningful minimum wavelength, right like, maybe

683
00:31:30,120 --> 00:31:33,360
Speaker 2: you could still have minimum wavelengths, smaller wavelengths which you

684
00:31:33,360 --> 00:31:35,720
Speaker 2: just wouldn't be able to see them, or are you

685
00:31:35,760 --> 00:31:37,120
Speaker 2: saying they might not exist at all?

686
00:31:37,160 --> 00:31:39,920
Speaker 1: In this scenario, they wouldn't exist at all because remember

687
00:31:40,280 --> 00:31:43,320
Speaker 1: that light is an oscillation of the electromagnetic field, which

688
00:31:43,360 --> 00:31:46,200
Speaker 1: is part of space. And so if you have like

689
00:31:46,240 --> 00:31:49,720
Speaker 1: a fundamental unit of space, like a space pixel, then

690
00:31:49,760 --> 00:31:53,240
Speaker 1: you can't have anything very inside that pixel. The electromagnetic

691
00:31:53,320 --> 00:31:56,000
Speaker 1: field can only have like one value in that pixel,

692
00:31:56,240 --> 00:31:59,080
Speaker 1: which means you couldn't have an oscillation with a wavelength

693
00:31:59,200 --> 00:32:02,000
Speaker 1: smaller than a pixel, sort of like on your screen,

694
00:32:02,360 --> 00:32:04,680
Speaker 1: each pixel can only have one color, right, It's like

695
00:32:04,720 --> 00:32:06,840
Speaker 1: it's green, or it's blue, or it's pumpkin or whatever

696
00:32:06,880 --> 00:32:09,600
Speaker 1: the color is, but it can't be two colors at

697
00:32:09,600 --> 00:32:12,040
Speaker 1: the same time. That's what a pixel is. And so

698
00:32:12,120 --> 00:32:15,239
Speaker 1: if space is quantized, then every unit of space can

699
00:32:15,320 --> 00:32:18,400
Speaker 1: only have one value of the electromagnetic field, and therefore

700
00:32:18,400 --> 00:32:21,360
Speaker 1: you couldn't have oscillations smaller than the size of that pixel.

701
00:32:22,320 --> 00:32:25,560
Speaker 2: I see, all right, Well that's only if space is pixelated.

702
00:32:26,120 --> 00:32:28,640
Speaker 2: Can you imagine other scenarios, like maybe inside of a

703
00:32:28,640 --> 00:32:33,520
Speaker 2: black hole at this singularity, could maybe the wavelength of light?

704
00:32:33,600 --> 00:32:34,440
Speaker 2: Good is zero? There?

705
00:32:34,680 --> 00:32:37,440
Speaker 1: Yeah, that's a really cool question. But singularities are a

706
00:32:37,440 --> 00:32:41,040
Speaker 1: feature of general relativity, and general relativity assumes that space

707
00:32:41,120 --> 00:32:44,200
Speaker 1: is smooth and continuous. The whole idea of having a

708
00:32:44,200 --> 00:32:47,280
Speaker 1: singularity is having a bunch of mass in an infinitely

709
00:32:47,440 --> 00:32:50,760
Speaker 1: small space. So you can't both have a bunch of

710
00:32:50,800 --> 00:32:54,240
Speaker 1: stuff in an infinitely small space and a minimum wavelength

711
00:32:54,280 --> 00:32:57,200
Speaker 1: of light because having stuff in an infinitely small space

712
00:32:57,240 --> 00:32:59,760
Speaker 1: assumes that there's no limit to how small stuff can get,

713
00:33:00,160 --> 00:33:03,440
Speaker 1: so near singularities or near the event horizon of black holes,

714
00:33:03,880 --> 00:33:07,240
Speaker 1: light can go to very extremely long or short wavelengths.

715
00:33:07,360 --> 00:33:10,440
Speaker 2: I see, But what about the singularity? Then? Would light

716
00:33:10,680 --> 00:33:13,840
Speaker 2: have a zero wavelength if a singularity exists?

717
00:33:13,920 --> 00:33:18,160
Speaker 1: What is the wavelength of light inside a singularity? Yeah,

718
00:33:18,160 --> 00:33:19,200
Speaker 1: that's a cool question.

719
00:33:20,000 --> 00:33:21,280
Speaker 2: That's why they pay me the big books.

720
00:33:21,280 --> 00:33:24,480
Speaker 1: Then that's a really cool question. I don't think it

721
00:33:24,520 --> 00:33:28,080
Speaker 1: could have zero wavelength, because that would imply infinite energy,

722
00:33:28,360 --> 00:33:31,920
Speaker 1: and a singularity is infinite density. But it's not infinite energy,

723
00:33:31,960 --> 00:33:35,120
Speaker 1: it's finite energy. And so in principle, you can like

724
00:33:35,320 --> 00:33:38,520
Speaker 1: make a black hole and singularities just piling up a

725
00:33:38,520 --> 00:33:41,520
Speaker 1: bunch of high energy photons in a small space. You

726
00:33:41,560 --> 00:33:43,520
Speaker 1: don't need infinite energy to do that.

727
00:33:45,240 --> 00:33:48,200
Speaker 2: All right, Well, that's the minimum of light for a wavelength.

728
00:33:48,280 --> 00:33:52,120
Speaker 2: What about the maximum? Can light have a maximum wavelength.

729
00:33:51,680 --> 00:33:54,880
Speaker 1: In order to generate a photon? In order to generate light,

730
00:33:55,200 --> 00:33:57,920
Speaker 1: you usually need an antenna. You need something to oscillate

731
00:33:58,160 --> 00:34:01,080
Speaker 1: to make these electromagnetic fields. Like you want to make

732
00:34:01,080 --> 00:34:03,480
Speaker 1: a radio waves, you need to have an antenna that's

733
00:34:03,520 --> 00:34:06,120
Speaker 1: pretty big where the electrons can zoom up and down

734
00:34:06,160 --> 00:34:10,040
Speaker 1: that antenna to make wiggles in the electromagnetic field. So,

735
00:34:10,239 --> 00:34:12,479
Speaker 1: in principle, if you want to make a photon that's

736
00:34:12,560 --> 00:34:15,560
Speaker 1: like a galaxy wide, you need an antenna that's like

737
00:34:15,640 --> 00:34:19,960
Speaker 1: a galaxy wide. So, for example, if the universe is

738
00:34:20,040 --> 00:34:24,240
Speaker 1: not infinitely big, if it's a finite size, that limits

739
00:34:24,520 --> 00:34:28,440
Speaker 1: the practical size of a photon's wavelength because you couldn't

740
00:34:28,440 --> 00:34:31,279
Speaker 1: make an antenna bigger than the universe, and therefore you

741
00:34:31,320 --> 00:34:34,840
Speaker 1: couldn't make a photon with a wavelength bigger than the universe.

742
00:34:35,680 --> 00:34:38,400
Speaker 2: I feel like now you're sort of mixing practicality with theory.

743
00:34:38,440 --> 00:34:41,359
Speaker 2: Oh yeah, so if we stick with theory, is there

744
00:34:41,360 --> 00:34:43,920
Speaker 2: a theoretical maximum wavelength of light?

745
00:34:44,160 --> 00:34:47,080
Speaker 1: I don't think there is theoretically, even if the universe

746
00:34:47,239 --> 00:34:49,880
Speaker 1: is finite, because you could just have like a part

747
00:34:50,000 --> 00:34:53,359
Speaker 1: of the photon's wave. So theoretically, I don't think there's

748
00:34:53,400 --> 00:34:56,880
Speaker 1: any limit to the wavelength of a photon. You're talking

749
00:34:57,000 --> 00:35:01,120
Speaker 1: really really low energy photons with really long wavelengths, so

750
00:35:01,280 --> 00:35:03,840
Speaker 1: long that even if the universe is finite size, you

751
00:35:03,920 --> 00:35:05,839
Speaker 1: might only be able to fit a part of that

752
00:35:05,920 --> 00:35:09,719
Speaker 1: wave in it. Still technically would have that very low wavelength.

753
00:35:10,120 --> 00:35:12,160
Speaker 1: So I think there's only a practical limit, not a

754
00:35:12,200 --> 00:35:13,080
Speaker 1: theoretical limit.

755
00:35:13,160 --> 00:35:16,240
Speaker 2: So like, theoretically you could have a photon that's bigger

756
00:35:16,239 --> 00:35:18,920
Speaker 2: than the universe, Well.

757
00:35:18,800 --> 00:35:20,960
Speaker 1: You would have a photon whose wavelength is bigger than

758
00:35:20,960 --> 00:35:23,880
Speaker 1: the universe. You wouldn't have the full period of that

759
00:35:23,920 --> 00:35:27,880
Speaker 1: photon's oscillation inside the universe. Yeah.

760
00:35:27,920 --> 00:35:29,759
Speaker 2: Well, I mean, like, let's say the universe is much

761
00:35:29,760 --> 00:35:32,880
Speaker 2: bigger than what we can see than the observable universe. Technically,

762
00:35:32,920 --> 00:35:36,240
Speaker 2: the whole observable universe could right now be sitting inside

763
00:35:36,280 --> 00:35:36,880
Speaker 2: of a photon.

764
00:35:37,040 --> 00:35:38,920
Speaker 1: Yeah, it sounds like the cool title of a book,

765
00:35:39,000 --> 00:35:42,480
Speaker 1: the photon bigger than the universe, the.

766
00:35:42,480 --> 00:35:48,239
Speaker 2: Light that contains our universe. Oh my gosh, bestseller.

767
00:35:48,960 --> 00:35:52,200
Speaker 1: Boom. Let's get Anthony Door to write that one. All

768
00:35:52,239 --> 00:35:53,880
Speaker 1: the light we cannot fit in the universe.

769
00:35:53,920 --> 00:35:55,799
Speaker 2: Yeah, there you go, all the light It Waitedn't somebody

770
00:35:55,840 --> 00:35:56,480
Speaker 2: already write that?

771
00:35:56,840 --> 00:35:58,719
Speaker 1: I think you want a pultzer for it, but I'm

772
00:35:58,760 --> 00:35:59,719
Speaker 1: sure we can just copy it.

773
00:36:00,600 --> 00:36:03,760
Speaker 2: Yeah, we're changing a few words. You know. That counts

774
00:36:03,760 --> 00:36:06,759
Speaker 2: as fair game, fair use. Well, so you talked about

775
00:36:06,760 --> 00:36:08,799
Speaker 2: the theory of it. Now now you're sort of getting

776
00:36:08,800 --> 00:36:11,239
Speaker 2: into the practicality of it. And you said, there's maybe

777
00:36:11,280 --> 00:36:14,520
Speaker 2: a practical limitation to making a photon bigger than the

778
00:36:14,560 --> 00:36:17,279
Speaker 2: observable universe. What about is there a practical limitation to

779
00:36:17,320 --> 00:36:21,920
Speaker 2: making a minimum or smallest photon? Because isn't all lights

780
00:36:21,920 --> 00:36:25,839
Speaker 2: sort of generated by the motions or interactions of particles

781
00:36:26,640 --> 00:36:28,160
Speaker 2: which are quantized.

782
00:36:27,719 --> 00:36:30,480
Speaker 1: Which are quantized, but you only need one electron, like

783
00:36:30,520 --> 00:36:34,279
Speaker 1: a single electron wiggling can make a photon The only

784
00:36:34,320 --> 00:36:37,880
Speaker 1: practical limit to making a photon with a really short

785
00:36:37,920 --> 00:36:40,960
Speaker 1: wavelength is that it's really high energy. So you need

786
00:36:41,000 --> 00:36:43,320
Speaker 1: a lot of energy. So if you took like, for example,

787
00:36:43,400 --> 00:36:46,000
Speaker 1: all the light the Sun emitted in a year and

788
00:36:46,040 --> 00:36:50,239
Speaker 1: poured that into a single, like really powerful photon, that

789
00:36:50,280 --> 00:36:52,040
Speaker 1: would be very very short wavelength.

790
00:36:53,000 --> 00:36:55,160
Speaker 2: Well, there might be a limitation to like how much

791
00:36:55,360 --> 00:36:57,840
Speaker 2: energy there is in the universe, in which case that

792
00:36:57,840 --> 00:37:00,640
Speaker 2: would give you maybe limitation to how small of a

793
00:37:00,640 --> 00:37:01,480
Speaker 2: photon you can make.

794
00:37:01,640 --> 00:37:04,640
Speaker 1: Yeah, if you annihilated all of the particles in the

795
00:37:04,760 --> 00:37:08,279
Speaker 1: universe and converted all of their energy into a single photon,

796
00:37:09,040 --> 00:37:11,840
Speaker 1: then number one, you would no longer exist to observe

797
00:37:11,880 --> 00:37:15,720
Speaker 1: this amazing photon. But even then it would be finite,

798
00:37:15,719 --> 00:37:18,040
Speaker 1: because the amount of energy in the universe, the observable

799
00:37:18,120 --> 00:37:20,759
Speaker 1: universe at least, is finite. So, yeah, you're right, that's

800
00:37:20,800 --> 00:37:24,520
Speaker 1: a practical limit to how short wavelength photon you can make.

801
00:37:25,120 --> 00:37:27,560
Speaker 2: Yeah, that would be the sequel novel all the light

802
00:37:27,640 --> 00:37:29,200
Speaker 2: we cannot make in the universe.

803
00:37:29,880 --> 00:37:32,160
Speaker 1: The other limitation there is the black hole. Right, you

804
00:37:32,200 --> 00:37:35,239
Speaker 1: make a very short wavelength photon, you're going to make

805
00:37:35,239 --> 00:37:35,839
Speaker 1: a black hole.

806
00:37:35,880 --> 00:37:38,000
Speaker 2: Oh. Interesting, And so if you use all the energy

807
00:37:38,040 --> 00:37:40,239
Speaker 2: in the universe to make a photon, it would just

808
00:37:40,280 --> 00:37:42,440
Speaker 2: instantly turn into a giant black hole, or would it.

809
00:37:42,480 --> 00:37:44,839
Speaker 1: I don't know, No, it definitely would. I mean you're

810
00:37:44,840 --> 00:37:46,840
Speaker 1: talking about putting all the energy in the universe in

811
00:37:46,920 --> 00:37:49,160
Speaker 1: one spot. That's definitely a black hole for sure.

812
00:37:49,400 --> 00:37:51,719
Speaker 2: Oh so maybe that is maybe a limitation on the

813
00:37:51,719 --> 00:37:54,840
Speaker 2: minimum size of a photon, Like at some point a

814
00:37:54,840 --> 00:37:56,640
Speaker 2: photon would be so small it would turn into a

815
00:37:56,640 --> 00:37:57,040
Speaker 2: black hole.

816
00:37:57,120 --> 00:38:00,000
Speaker 1: Yeah, a photon with energy greater than the Plank energy

817
00:38:00,440 --> 00:38:02,560
Speaker 1: would turn into a black hole. That's basically how you

818
00:38:02,600 --> 00:38:03,840
Speaker 1: calculate the Plank energy.

819
00:38:04,000 --> 00:38:06,680
Speaker 2: So there is a limitation to a minimum wavelength of light.

820
00:38:06,560 --> 00:38:08,760
Speaker 1: Then, yeah, that's the practical limitation.

821
00:38:08,480 --> 00:38:10,040
Speaker 2: Because after that you get a black hole.

822
00:38:10,239 --> 00:38:12,359
Speaker 1: Unless that's what you wanted, right, that's sort of what

823
00:38:12,400 --> 00:38:14,000
Speaker 1: you were going for, like I want a black hole

824
00:38:14,080 --> 00:38:15,240
Speaker 1: singularity photon.

825
00:38:16,400 --> 00:38:20,120
Speaker 2: So there is a theoretical and practical minimum wavelength of light.

826
00:38:20,360 --> 00:38:22,719
Speaker 1: Yeah, the asterisk there is. We don't really know what

827
00:38:22,840 --> 00:38:25,320
Speaker 1: happens in that scenario. Like if you make a photon

828
00:38:25,600 --> 00:38:28,239
Speaker 1: with energy greater than the Plank energy, so it collapses

829
00:38:28,239 --> 00:38:31,080
Speaker 1: into a black hole, is it still a photon? Does

830
00:38:31,080 --> 00:38:33,520
Speaker 1: it turn into like singularity stuff. We don't know what

831
00:38:33,600 --> 00:38:35,680
Speaker 1: goes on inside a black hole, so I don't know

832
00:38:35,719 --> 00:38:38,120
Speaker 1: if that really is technically a limit. It might just

833
00:38:38,160 --> 00:38:39,839
Speaker 1: be like, Okay, you made a photon, but now it's

834
00:38:39,880 --> 00:38:42,160
Speaker 1: also a black hole at the same time, is it

835
00:38:42,200 --> 00:38:43,520
Speaker 1: still a photon? I don't know.

836
00:38:44,960 --> 00:38:47,239
Speaker 2: All Right, Well, I guess that's all the answer that

837
00:38:47,280 --> 00:38:50,160
Speaker 2: we can fit in this universe podcast.

838
00:38:50,440 --> 00:38:53,040
Speaker 1: That was both the longest and shortest answer we could find.

839
00:38:53,239 --> 00:38:57,000
Speaker 2: Yeah, we reached the maximum in both directions. Here. We

840
00:38:57,040 --> 00:39:00,840
Speaker 2: need another dimension just to fully explore this question. That

841
00:39:00,920 --> 00:39:02,640
Speaker 2: was a great question. Thank you, Sonia. And so let's

842
00:39:02,640 --> 00:39:05,440
Speaker 2: get into our last question of the day, which is

843
00:39:05,480 --> 00:39:08,960
Speaker 2: about rainbows. Let's jump into that rainbow, but first let's

844
00:39:09,040 --> 00:39:24,120
Speaker 2: take another quick break. All right, we're answering listener questions

845
00:39:24,120 --> 00:39:27,359
Speaker 2: here today, and our last question comes from Clark, who

846
00:39:27,680 --> 00:39:28,920
Speaker 2: is seven years old.

847
00:39:29,040 --> 00:39:32,040
Speaker 1: And I love getting questions from kids. I love when

848
00:39:32,120 --> 00:39:34,239
Speaker 1: kids listen to our podcast. I love when kids listen

849
00:39:34,239 --> 00:39:36,440
Speaker 1: with our parents and talk about it. Thanks to all

850
00:39:36,440 --> 00:39:39,400
Speaker 1: of you parents who are raising the next generation of scientists.

851
00:39:39,880 --> 00:39:43,640
Speaker 2: Why do we always see rainbows bend the same way?

852
00:39:43,719 --> 00:39:48,600
Speaker 2: Why can't they bend sideways or upside down. All right,

853
00:39:48,640 --> 00:39:51,640
Speaker 2: great question from Clark. I guess basically the question is

854
00:39:51,800 --> 00:39:54,160
Speaker 2: why does a rainbow look like a rainbow? Like, why

855
00:39:54,200 --> 00:39:57,080
Speaker 2: does it look like an arc in an S shape

856
00:39:57,200 --> 00:40:00,560
Speaker 2: or any other shape? And specifically, why is always an

857
00:40:00,680 --> 00:40:04,680
Speaker 2: arch bending down? From what we can see? Could you

858
00:40:04,760 --> 00:40:08,640
Speaker 2: have a smiley face rainbow or a S shade rainbow

859
00:40:09,560 --> 00:40:10,560
Speaker 2: without turning your head?

860
00:40:10,840 --> 00:40:15,160
Speaker 1: Yeah, it is very cool. Rainbows actually do bend sideways

861
00:40:15,200 --> 00:40:18,239
Speaker 1: and upside down. Rainbows are actually circles, so you're only

862
00:40:18,280 --> 00:40:20,600
Speaker 1: seeing part of it because the earth is blocking the

863
00:40:20,640 --> 00:40:21,359
Speaker 1: rest of the view.

864
00:40:21,480 --> 00:40:24,240
Speaker 2: They're not actually circles, right, because they're not actually things.

865
00:40:24,400 --> 00:40:27,040
Speaker 1: Yeah, so rainbows are not physical objects. There are image

866
00:40:27,040 --> 00:40:29,919
Speaker 1: that you are seeing. Your brain reconstructs what it thinks

867
00:40:29,960 --> 00:40:31,880
Speaker 1: is going on out there based on the directions of

868
00:40:31,920 --> 00:40:34,520
Speaker 1: light that hit your eye, and so you can see

869
00:40:34,520 --> 00:40:36,480
Speaker 1: things that are like not there, the same way you

870
00:40:36,520 --> 00:40:39,040
Speaker 1: can see yourself in the mirror, but you're not actually

871
00:40:39,080 --> 00:40:41,560
Speaker 1: behind the mirror. It's just an image of yourself in

872
00:40:41,600 --> 00:40:42,080
Speaker 1: the mirror.

873
00:40:42,200 --> 00:40:44,560
Speaker 2: Right. A rainbow is like a mirage or like a

874
00:40:44,560 --> 00:40:45,920
Speaker 2: hologram basically, right.

875
00:40:45,960 --> 00:40:48,480
Speaker 1: Yeah, it's an image your brain has reconstructed. It says

876
00:40:48,560 --> 00:40:50,640
Speaker 1: all this light is coming in in this direction, so

877
00:40:50,680 --> 00:40:53,799
Speaker 1: it looks like there is something they are giving off

878
00:40:53,840 --> 00:40:55,880
Speaker 1: this light. But it doesn't have to be like just

879
00:40:55,920 --> 00:40:58,120
Speaker 1: like with a mirror, you don't have to have somebody

880
00:40:58,120 --> 00:41:01,440
Speaker 1: standing through a window to create that image. You can

881
00:41:01,520 --> 00:41:04,040
Speaker 1: just use a mirror and it looks exactly as if

882
00:41:04,040 --> 00:41:06,000
Speaker 1: there's an inverted copy of you standing on the other

883
00:41:06,040 --> 00:41:07,000
Speaker 1: side of the wall.

884
00:41:07,080 --> 00:41:09,600
Speaker 2: Right, Although I guess philosophical you could say that the

885
00:41:09,840 --> 00:41:13,120
Speaker 2: rainbow is a physical object, right, because it's the water

886
00:41:13,200 --> 00:41:16,400
Speaker 2: droplets that make up the rainbow that it is the rainbow.

887
00:41:16,800 --> 00:41:18,640
Speaker 1: Yeah, in the same way that the mirror is a

888
00:41:18,680 --> 00:41:21,280
Speaker 1: physical object and it's creating this image in your mind.

889
00:41:21,880 --> 00:41:24,440
Speaker 1: And you're right about the physical mechanism. Also, the reason

890
00:41:24,480 --> 00:41:27,600
Speaker 1: you see a rainbow is that the sunlight is hitting

891
00:41:27,680 --> 00:41:30,680
Speaker 1: the water droplets, and those water droplets are spreading out

892
00:41:30,760 --> 00:41:34,480
Speaker 1: the light. When light passes from air to water, different

893
00:41:34,480 --> 00:41:37,600
Speaker 1: colors of light bend a different amount as that happens,

894
00:41:38,080 --> 00:41:40,080
Speaker 1: and so when they go into the water droplet and

895
00:41:40,080 --> 00:41:44,320
Speaker 1: then back out of the water droplet, different colors green, red, blue, yellow,

896
00:41:44,560 --> 00:41:47,120
Speaker 1: all take a slightly different path, And that's why you

897
00:41:47,120 --> 00:41:49,440
Speaker 1: see a rainbow. It spreads the light out into those

898
00:41:49,480 --> 00:41:50,879
Speaker 1: different colors, right.

899
00:41:50,920 --> 00:41:52,680
Speaker 2: I wonder if it would help to sort of paint

900
00:41:52,680 --> 00:41:56,400
Speaker 2: the situation that leads to a rainbow, right, because we

901
00:41:56,440 --> 00:41:59,239
Speaker 2: don't see rainbows every day. You also don't see them

902
00:41:59,239 --> 00:42:00,799
Speaker 2: anywhere in the sky. They have to mean a certain

903
00:42:00,800 --> 00:42:03,440
Speaker 2: position in the sky relative to the sun for you

904
00:42:03,480 --> 00:42:05,680
Speaker 2: to see a rainbow, and there also has to be

905
00:42:05,760 --> 00:42:08,320
Speaker 2: a lot of rain or water in the air, right.

906
00:42:08,280 --> 00:42:10,640
Speaker 1: Yeah, exactly. So in order to make a rainbow, you

907
00:42:10,640 --> 00:42:13,080
Speaker 1: need to distribute a bunch of water droplets in the

908
00:42:13,160 --> 00:42:16,239
Speaker 1: air and have the sun behind you. Then the sun

909
00:42:16,280 --> 00:42:19,160
Speaker 1: will pass like over your head, it will enter those

910
00:42:19,200 --> 00:42:22,480
Speaker 1: water droplets, bounce off the back of the water droplet,

911
00:42:22,880 --> 00:42:25,920
Speaker 1: come back out, and then hit your eye. And so

912
00:42:25,960 --> 00:42:28,680
Speaker 1: if you imagine just like a single water droplet, it's

913
00:42:28,719 --> 00:42:33,760
Speaker 1: going to be spreading the light out in different colors green, red, orange, purple,

914
00:42:33,840 --> 00:42:36,359
Speaker 1: or whatever. And you will see one color of light

915
00:42:36,400 --> 00:42:39,040
Speaker 1: from each droplet. But if the droplet is a little

916
00:42:39,040 --> 00:42:41,160
Speaker 1: bit higher, you're going to be seeing red light from it.

917
00:42:41,200 --> 00:42:42,960
Speaker 1: If a droplet is a little bit lower, you're going

918
00:42:43,040 --> 00:42:45,480
Speaker 1: to be seeing purple light from it. Because those different

919
00:42:45,480 --> 00:42:47,960
Speaker 1: colors come out of the droplets at slightly different angles.

920
00:42:48,160 --> 00:42:50,600
Speaker 2: Right, you can have to imagine like a wall of

921
00:42:50,719 --> 00:42:53,279
Speaker 2: water drops floating in the air in front of you,

922
00:42:53,760 --> 00:42:55,719
Speaker 2: and the light the sun is right behind you. It's

923
00:42:55,719 --> 00:42:58,520
Speaker 2: shining in light sort of like a projector or a flashlight.

924
00:42:58,560 --> 00:43:01,160
Speaker 2: It's shining the light behind you over your head, and

925
00:43:01,200 --> 00:43:04,400
Speaker 2: it's hitting this giant wall of water drops. Some of

926
00:43:04,440 --> 00:43:07,600
Speaker 2: the light will just go through, right, Yeah, and you'll

927
00:43:07,600 --> 00:43:10,640
Speaker 2: never see that light again. But over the arch of

928
00:43:10,640 --> 00:43:13,960
Speaker 2: the rainbow, light actually gets reflected back to you in

929
00:43:14,000 --> 00:43:14,760
Speaker 2: different colors.

930
00:43:15,000 --> 00:43:18,320
Speaker 1: That's right, And every droplet there is sending every color

931
00:43:18,320 --> 00:43:21,320
Speaker 1: of light out, so it's like a big screen. Every

932
00:43:21,520 --> 00:43:26,040
Speaker 1: droplet is sending out a whole spectrum purple, blue, green, orange, red,

933
00:43:26,360 --> 00:43:29,319
Speaker 1: all in different directions. Where you're standing, You're seeing a

934
00:43:29,480 --> 00:43:32,480
Speaker 1: ring of droplets that are all sending you red light,

935
00:43:32,520 --> 00:43:34,520
Speaker 1: and then you see another ring of droplets that are

936
00:43:34,520 --> 00:43:36,719
Speaker 1: all sending you green light, and then another ones that

937
00:43:36,760 --> 00:43:39,319
Speaker 1: are all standing you purple light. And you see them

938
00:43:39,320 --> 00:43:41,480
Speaker 1: in a ring because they all have the same angle

939
00:43:41,560 --> 00:43:42,399
Speaker 1: relative to you.

940
00:43:42,760 --> 00:43:44,359
Speaker 2: Yeah. I think this is maybe where it gets kind

941
00:43:44,360 --> 00:43:48,480
Speaker 2: of hairy to describe in an audio podcast, But basically

942
00:43:48,480 --> 00:43:52,200
Speaker 2: the answer to Clark's question is geometry, right, Basically, the

943
00:43:52,200 --> 00:43:55,120
Speaker 2: reason it looks like an arch is that the physics,

944
00:43:55,120 --> 00:43:58,000
Speaker 2: the phenomenon that creates the illusion of a rainbow basically

945
00:43:58,080 --> 00:44:02,000
Speaker 2: depends on the geometry of you and your eyeball and

946
00:44:02,040 --> 00:44:04,920
Speaker 2: the sun, and that's why it looks like it's a semicircle.

947
00:44:05,120 --> 00:44:07,839
Speaker 1: Yeah, exactly. And if the ground wasn't in the way

948
00:44:07,880 --> 00:44:10,399
Speaker 1: and there was water down there as well, like if

949
00:44:10,400 --> 00:44:12,919
Speaker 1: you were floating up in the atmosphere and you're looking

950
00:44:12,920 --> 00:44:14,840
Speaker 1: at a sheet of water, you would see the rainbow

951
00:44:14,840 --> 00:44:16,120
Speaker 1: as a complete.

952
00:44:15,640 --> 00:44:18,080
Speaker 2: Circle, right, And so the reason it's not like an

953
00:44:18,200 --> 00:44:21,719
Speaker 2: arch bending upwards or to the side has to do

954
00:44:21,840 --> 00:44:25,400
Speaker 2: with the fact that the sun is a circle, or

955
00:44:25,640 --> 00:44:28,200
Speaker 2: because your eyeball is a circle or is it? Oh,

956
00:44:28,280 --> 00:44:31,160
Speaker 2: because the water drops are a circular, right, they're little spheres.

957
00:44:31,760 --> 00:44:34,440
Speaker 1: That's the real reason, right, Well, the water drop is

958
00:44:34,440 --> 00:44:36,320
Speaker 1: our little spheres, but they don't have to be spheres

959
00:44:36,360 --> 00:44:38,440
Speaker 1: for this to work. The reason that the rainbow is

960
00:44:38,440 --> 00:44:40,440
Speaker 1: an arch is because actually it's a circle, and you're

961
00:44:40,480 --> 00:44:43,840
Speaker 1: only seeing part of it circle, because any drop along

962
00:44:43,920 --> 00:44:47,160
Speaker 1: that circle has the same angle relative to your eye

963
00:44:47,400 --> 00:44:49,279
Speaker 1: of the same colored light coming out of it.

964
00:44:49,560 --> 00:44:51,480
Speaker 2: Now, but I think if the water drops for a

965
00:44:51,480 --> 00:44:54,799
Speaker 2: different shape, the rainbow would be a different shapeouldn't it.

966
00:44:54,960 --> 00:44:57,680
Speaker 2: Like let's say if the all the rain drops were

967
00:44:58,040 --> 00:45:02,080
Speaker 2: shaped like a cylinder vertically, then you wouldn't see maybe

968
00:45:02,320 --> 00:45:05,040
Speaker 2: an arch, or maybe they were all football shade pointing

969
00:45:05,040 --> 00:45:07,120
Speaker 2: in the same direction. Then the arch would be kind

970
00:45:07,120 --> 00:45:07,760
Speaker 2: of distorted.

971
00:45:07,840 --> 00:45:09,920
Speaker 1: Oh yeah, I see what you're saying. That's definitely true.

972
00:45:10,120 --> 00:45:13,200
Speaker 1: The reason it's a circle is that there's a symmetry

973
00:45:13,280 --> 00:45:15,839
Speaker 1: right that the water droplets can hit you from any

974
00:45:15,880 --> 00:45:18,799
Speaker 1: angle because there's spheres. Yeah, I get your point. So

975
00:45:18,840 --> 00:45:21,520
Speaker 1: if they all were distorted, that would definitely would distort

976
00:45:21,520 --> 00:45:23,640
Speaker 1: the rainbow. It wouldn't be a circle anymore. There's other

977
00:45:23,680 --> 00:45:26,360
Speaker 1: interesting things going on there with the geometry, like sometimes

978
00:45:26,400 --> 00:45:29,800
Speaker 1: you can see a second rainbow, and that happens because

979
00:45:29,800 --> 00:45:33,399
Speaker 1: the light bounces twice within the rain drop. Like it

980
00:45:33,440 --> 00:45:35,799
Speaker 1: goes into the rain drop, it bounces off the back

981
00:45:35,840 --> 00:45:37,919
Speaker 1: of the rain drop, and then bounces off again from

982
00:45:37,920 --> 00:45:40,000
Speaker 1: the back of the rain drop and then comes out

983
00:45:40,040 --> 00:45:41,520
Speaker 1: of the rain drop. So it comes out at a

984
00:45:41,560 --> 00:45:44,719
Speaker 1: different angle than the like primary beam, which is why

985
00:45:44,760 --> 00:45:47,680
Speaker 1: you see it in a different location. And because it

986
00:45:47,719 --> 00:45:51,360
Speaker 1: bounces twice, it actually flips the colors. So the normal

987
00:45:51,440 --> 00:45:53,520
Speaker 1: rainbow has like red on the top and purple on

988
00:45:53,560 --> 00:45:56,720
Speaker 1: the bottom. The double bow, the second one has purple

989
00:45:56,760 --> 00:45:59,920
Speaker 1: on the top and red on the bottom.

990
00:46:00,400 --> 00:46:02,440
Speaker 2: So maybe the real answer for Clark here is that

991
00:46:02,440 --> 00:46:04,839
Speaker 2: the reason it bends the same way is because you're

992
00:46:04,880 --> 00:46:07,360
Speaker 2: always looking at it the same way, and because the

993
00:46:07,360 --> 00:46:08,920
Speaker 2: ground is always beneath you.

994
00:46:09,239 --> 00:46:12,520
Speaker 1: Mm hmm. It's generated by the angle between the sun

995
00:46:12,600 --> 00:46:14,879
Speaker 1: and your eyeball and the rain drops, and so you're

996
00:46:14,880 --> 00:46:17,960
Speaker 1: going to see it wherever that relationship exists, which is

997
00:46:18,000 --> 00:46:19,719
Speaker 1: why it always looks the same, right.

998
00:46:19,800 --> 00:46:21,879
Speaker 2: But I think as you were saying, like, so, let's

999
00:46:21,880 --> 00:46:23,640
Speaker 2: say we were out there in space and there was

1000
00:46:23,680 --> 00:46:25,840
Speaker 2: a huge cloud of water drops in front of me

1001
00:46:25,920 --> 00:46:28,040
Speaker 2: and the sun was behind me, I would see a

1002
00:46:28,120 --> 00:46:32,880
Speaker 2: rainbow as a circle, yes, And if there was, you know,

1003
00:46:32,960 --> 00:46:35,719
Speaker 2: a planet blocking some of that water on top, then

1004
00:46:35,760 --> 00:46:39,960
Speaker 2: I would see the rainbow as an up pointing arch, yeah, exactly. Yeah,

1005
00:46:40,080 --> 00:46:42,319
Speaker 2: Or somehow the water drops that ended on the right

1006
00:46:42,360 --> 00:46:44,120
Speaker 2: side of this cloud, or there was a planet on

1007
00:46:44,160 --> 00:46:47,640
Speaker 2: my right, then the rainbow would look like a sea

1008
00:46:47,760 --> 00:46:48,520
Speaker 2: exactly exactly.

1009
00:46:48,560 --> 00:46:50,960
Speaker 1: And if you're an alien or a different species that

1010
00:46:51,040 --> 00:46:54,279
Speaker 1: could see different wavelengths of light. Then you would see

1011
00:46:54,280 --> 00:46:57,920
Speaker 1: the rainbow extend. Because rainbows have not just visible light

1012
00:46:58,000 --> 00:47:00,960
Speaker 1: but also U V and in for red light in them.

1013
00:47:01,400 --> 00:47:03,640
Speaker 1: They are invisible rings to the rainbow, so it would

1014
00:47:03,640 --> 00:47:06,799
Speaker 1: look like a thicker rainbow. There'd be more stripes to it,

1015
00:47:06,840 --> 00:47:10,720
Speaker 1: depending how your alien or manti shrimp brain interpreted it. Interesting.

1016
00:47:10,800 --> 00:47:14,000
Speaker 2: Okay, so here's the answer for Clark. The reason rainbows

1017
00:47:14,040 --> 00:47:17,040
Speaker 2: are circular is because the water drops our little spheres.

1018
00:47:17,400 --> 00:47:21,080
Speaker 2: There are also little circles, little balls of water. And

1019
00:47:21,160 --> 00:47:23,480
Speaker 2: the reason you only see the top arch of that

1020
00:47:23,560 --> 00:47:27,040
Speaker 2: circle is because usually the ground is blocking the bottom half.

1021
00:47:27,040 --> 00:47:29,440
Speaker 2: But if the ground was blocking the side half or

1022
00:47:29,440 --> 00:47:31,520
Speaker 2: the top half, then we would see rainbows as a

1023
00:47:31,520 --> 00:47:33,640
Speaker 2: different shape. Or if it just tilt your head.

1024
00:47:33,600 --> 00:47:36,040
Speaker 1: Yeah, exactly, if you stood next to a cliff, you

1025
00:47:36,040 --> 00:47:37,759
Speaker 1: could see a rainbow sideways.

1026
00:47:38,080 --> 00:47:40,480
Speaker 2: All right, Well, great question, Klark. Thanks for sending that in,

1027
00:47:40,840 --> 00:47:42,960
Speaker 2: and thanks to everyone who send the question in today,

1028
00:47:43,200 --> 00:47:43,680
Speaker 2: and thanks.

1029
00:47:43,560 --> 00:47:46,680
Speaker 1: To everybody who asks questions and thinks about the universe

1030
00:47:46,719 --> 00:47:50,360
Speaker 1: and joins this community of curious people wanting to understand.

1031
00:47:50,680 --> 00:47:52,600
Speaker 2: Yeah, and thank you for listening to this program and

1032
00:47:52,719 --> 00:47:55,239
Speaker 2: telling all your friends about it, and posting it on

1033
00:47:55,280 --> 00:48:00,200
Speaker 2: social media and reviewing us on the podcast apps, laying

1034
00:48:00,239 --> 00:48:05,040
Speaker 2: it for your children, and liking banana jokes. All right, well,

1035
00:48:05,040 --> 00:48:07,719
Speaker 2: we hope you enjoyed that. Thanks for joining us. See

1036
00:48:07,760 --> 00:48:08,279
Speaker 2: you next time.

1037
00:48:13,080 --> 00:48:16,280
Speaker 1: For more science and curiosity, come find us on social media,

1038
00:48:16,360 --> 00:48:20,880
Speaker 1: where we answer questions and post videos. We're on Twitter, Discorg, Insta,

1039
00:48:21,000 --> 00:48:24,720
Speaker 1: and now TikTok. Thanks for listening, and remember that Daniel

1040
00:48:24,719 --> 00:48:28,200
Speaker 1: and Jorge Explain the Universe is a production of iHeartRadio.

1041
00:48:28,480 --> 00:48:33,640
Speaker 1: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

1042
00:48:33,719 --> 00:48:36,080
Speaker 1: or wherever you listen to your favorite shows.