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Speaker 1: Hey, Kelly, do you ever wish that our night, Skuy was?

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Speaker 1: I don't know, a little bit more dramatic.

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Speaker 4: More dramatic. We've got a huge moon, planets, stars and

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Speaker 4: all of the Milky Way. You've got pretty high standards

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Speaker 4: for the night sky. What did you have in mind?

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Speaker 1: I don't know. Sometimes I think it's boring to have

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Speaker 1: just that one huge moon. It seems like it might

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Speaker 1: be more exciting to have lots of little moons up there.

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Speaker 4: Okay, all right, that's true. It's kind of like having

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Speaker 4: an only child.

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Speaker 1: Yeah, and not just an only child, like a single

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Speaker 1: mega child.

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Speaker 4: You want drama. What's more dramatic than the Earth's mega

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Speaker 4: child hovering above you in the sky.

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Speaker 1: Yeah, I guess I wanted drama. But now I'm worried

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Speaker 1: that the idea of a mega child is going to

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Speaker 1: give me nightmares.

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Speaker 4: Yeah, me too. I like my two little ones.

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

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Speaker 1: happy to have two normal sized children instead of one

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Speaker 1: mega child.

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Speaker 4: And I'm Kelly. I'm a parasitologist, and I also have

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Speaker 4: two normal sized children, and that works well for me.

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Speaker 1: You haven't considered the concept of like combining them together

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Speaker 1: into one child, unification of the children.

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Speaker 4: You know, Zach likes to joke that they stack when

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Speaker 4: he stacks them. They don't seem very happy about it,

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Speaker 4: and so, you know, I haven't thought too hard about

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Speaker 4: trying to combine them. I don't think they'd be big

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Speaker 4: fans of that.

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Speaker 1: I'm pretty sure my kids wouldn't be into that either. Well,

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

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Speaker 1: in which we ask the hard questions of the universe.

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Speaker 1: We talk about the crazy stuff that's out there deep

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Speaker 1: in the cosmos, and we talk about the tiny little

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Speaker 1: particles that are whiggling around inside my children, your children,

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Speaker 1: and everybody's children. We try to explore the entire universe

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Speaker 1: and explain all of it to you. Normally we have

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Speaker 1: my friend and co host Jorge cham here on the podcast,

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Speaker 1: but he's unavailable today, so we have our wonderful, hilarious

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Speaker 1: guest host, Kelly Wienersmith.

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Speaker 4: Hello, I'm excited to be back.

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Speaker 1: Thanks very much for joining us and for talking to

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Speaker 1: us about crazy stuff in the universe. So on the podcast,

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Speaker 1: we sometimes like to dig into stuff that's really complicated,

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Speaker 1: like how does quantum field theory work? And what is

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Speaker 1: the real charging the electron? Or what is it like

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Speaker 1: to go inside a black hole? These are deep and

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Speaker 1: complicated questions about the universe that we try to take

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Speaker 1: apart and explain to you. But sometimes we also like

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Speaker 1: to dive into simpler seeming questions, questions that might seem

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Speaker 1: like they have an obvious answer, but then have some

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Speaker 1: interesting little wrinkles.

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Speaker 4: It's good to have diversity, yeah.

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Speaker 1: Because questions are at the heart of science, and they're

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Speaker 1: not just the questions that scientists ask when they're doing

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Speaker 1: their research, but we're also interested in the questions that

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Speaker 1: everybody asks. And sometimes the best questions are the questions

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Speaker 1: that children ask, the most obvious questions which sometimes have

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Speaker 1: a tricky answer. And I remember looking up at the

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Speaker 1: night sky with my kids, who are now twelve and fourteen,

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Speaker 1: but earlier ask very simple, basic, fun questions about the universe,

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Speaker 1: like why do we only have one moon? Or do

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Speaker 1: we own only have one moon? Kelly, what kind of

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Speaker 1: questions do your kids ask when they look at the

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Speaker 1: night sky?

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Speaker 4: I was just trying to think of a good example

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Speaker 4: of a like, my daughter is seven, and she's always

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Speaker 4: asking me questions that I don't know the answer to,

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Speaker 4: some of them super fundamental, which make me think, how

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Speaker 4: is it that I'm walking around not knowing the answer

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Speaker 4: to all of these fundamental things, but yet I still

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Speaker 4: managed to survive. But no good example is coming to

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Speaker 4: mind right now. But we've got one of those apps

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Speaker 4: on our phone where you can sort of point it

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Speaker 4: at whatever in the night sky and it tells you

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Speaker 4: what it is. And we spend a lot of time

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Speaker 4: sitting on our car at night looking up at stuff,

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Speaker 4: and it's a lot of fun. She asks lots of questions,

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Speaker 4: but nothing's coming to mind right now that I did

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Speaker 4: not know the answer to. What's your favorite question your

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Speaker 4: kids have asked you?

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Speaker 1: One of my favorite questions my kids have asked me

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Speaker 1: are questions like where are we in the universe. You know,

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Speaker 1: they're just getting used to the idea of like our

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Speaker 1: house is in a neighborhood, and that neighborhood is in

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Speaker 1: a city, and that city is in a state somewhere

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Speaker 1: we have like a location and address, and so they

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Speaker 1: wanted to know, like, where are we in the universe?

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Speaker 1: What our like universe address? And of course, you know,

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Speaker 1: the hardcore physics answer is that every place in the

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Speaker 1: universe is the same, and physics doesn't care about location

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Speaker 1: and translationally invariant and stuff. But that answer is not

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Speaker 1: very satisfying for a four year old.

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Speaker 4: Yeah, that's why it's a bummer to have a physicist

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Speaker 4: for a dad.

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Speaker 1: But instead I try to describe to them, you know,

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Speaker 1: what the galaxy looks like, and how the galaxy fits

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Speaker 1: in with other galaxies, and what we know about sort

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Speaker 1: of our cosmic neighborhood. And the thing I love about

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Speaker 1: their questions is that they are both easy and hard.

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Speaker 1: They're like easy to ask, but sometimes hard to answer.

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Speaker 1: And they're the obvious questions, as you said, that you

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Speaker 1: don't always think about when you're walking around the world.

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Speaker 1: But that's why I think that children really are sometimes

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Speaker 1: the most natural scientists, because they don't just accept things

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Speaker 1: as they are. They ask questions about them and say

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Speaker 1: why is it this way or is it that way?

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Speaker 1: After all?

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Speaker 4: Totally? And what I love about Ada is that she'll

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Speaker 4: tell me that I'm wrong. I wish I had that confidence. So,

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Speaker 4: you know, not only do they ask good questions, but

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Speaker 4: they still have the confidence of children to be like, no,

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Speaker 4: I don't think so.

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Speaker 1: And so today in the podcast, we'll be talking about

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Speaker 1: a question which seems to have an obvious answer. So

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Speaker 1: on today's program, we'll be answering the question how many

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Speaker 1: moons does the Earth have? So Kelly, tell me what

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Speaker 1: you thought when you saw that we would be talking

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Speaker 1: about this today.

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Speaker 4: Yeah, so you sent me a list of topics we

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Speaker 4: could talk about, and when I read this one, I thought, well,

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Speaker 4: the answer seems obvious. The answer is one. And if

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Speaker 4: the answer seems obvious, then either Daniel needs to be

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Speaker 4: fired because he's not asking good questions anymore, or there's

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Speaker 4: something fundamental that I'm missing, And it's probably the second.

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Speaker 4: And so I suggested that we talk about this one

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Speaker 4: because I figured this was a question that would teach

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Speaker 4: me something new.

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Speaker 1: Awesome. This is a fun question to dig into. We

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Speaker 1: get to hear about like what exactly is a moon,

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Speaker 1: what counts as a moon, evens a little bit about

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Speaker 1: the etymology of the word moon and when he came

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Speaker 1: into use, and what else is out there or reading

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Speaker 1: around the earth, and could you call it a moon? So,

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Speaker 1: as usual, before I dug into this, I wanted to

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Speaker 1: know what everybody else out there thought. Sometimes I used

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Speaker 1: to walk around the campus and you see Irvine and

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Speaker 1: ask students there these questions to see what the general

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Speaker 1: level of knowledge was or confusion. These days, of course,

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Speaker 1: because of the pandemic, I'm sending emails out into the

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Speaker 1: Internet asking listeners to speculate baselessly without the chance to

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Speaker 1: do any research on these difficult physics questions.

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Speaker 4: Did you actually stop students on the campus and ask

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Speaker 4: them how many moons does the Earth have?

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Speaker 1: No, I haven't because this question is too recent, But

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Speaker 1: I wonder what they would say. I've noticed that our

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Speaker 1: listeners tend to give better informed answers than the random

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Speaker 1: you see Irvine student. Nothing against you see Irvine. Of course,

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Speaker 1: our listeners may just be like a subset of the

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Speaker 1: universe that's more interested in understanding the universe. But I

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Speaker 1: hope one day to get back to campus and getting

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Speaker 1: to ask the students those questions. It was fun to

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Speaker 1: sort of see their faces when I ask them these questions.

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Speaker 4: I bet you have a reputation as being one of

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Speaker 4: the like super weird professors.

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Speaker 1: Well, you know, I don't dress very fancy, so maybe

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Speaker 1: they just think I'm some random, homeless person asking them

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Speaker 1: hard physics questions.

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Speaker 4: Every college has.

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Speaker 1: Homeless person or physics professor. It can be hard to

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Speaker 1: tell the.

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Speaker 4: Difference physics professor. You can't tell the difference between Yeah.

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Speaker 1: Anyway, thank you to everybody who volunteered to answer these questions.

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Speaker 1: If you'd like to participate for a future episode of

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Speaker 1: the podcast. Please write me to questions at Daniel and

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Speaker 1: Jorge dot com. Here's what some of our listeners had

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Speaker 1: to say. The obvious answer that pops into my head

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Speaker 1: immediately would be one.

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Speaker 4: So I'm pretty sure that answer is wrong.

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Speaker 1: Well, we have.

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Speaker 5: Our celebrity moon, the moon, and I don't know, maybe

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Speaker 5: we might have caught off some small objects there probably

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Speaker 5: a testlock car dot ilon, musk scent, who knows.

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Speaker 1: I don't know exactly. I'm one hundred percent sure that

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Speaker 1: the Earth has two moons, the classic moon that we

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Speaker 1: see in the sky and Keith Moon.

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Speaker 4: I would say the Earth has one moon.

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Speaker 1: I don't know if you would consider satellites or the

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Speaker 1: space station a moon because they orbit the Earth, but

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Speaker 1: I would probably just consider one moon.

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Speaker 6: Well, I guess this depends on your definition of moon

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Speaker 6: the natural moons. It has the one large natural moon,

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Speaker 6: and I believe they've discovered a couple of asteroids that

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Speaker 6: have been captured in loose enough orbits that they're probably temporary.

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Speaker 6: If you're going to call any artificial satellite a moon,

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Speaker 6: which they've been called artificial moons, then the number goes

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Speaker 6: into the millions. Depending on how small a particle you

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Speaker 6: want to count. There's nuts and bolts and pieces of

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Speaker 6: rocket and larger things, dead satellites, fragments of satellites that

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Speaker 6: have collided with each other, a whole lot of.

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Speaker 1: Them, all right, Kelly, So what do you think about

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Speaker 1: our listener's responses here?

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Speaker 4: I thought there were some very insightful responses, you know.

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Speaker 4: One of them was essentially asking questions about maybe how

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Speaker 4: do we define moons. I thought somebody had a clever

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Speaker 4: thought that the Tesla car might now be sort of orbiting,

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Speaker 4: although I think the Tesla car was shot Mars word

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Speaker 4: instead of moonword. But it was clear that people sort

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Speaker 4: of thought through their answers, and yeah, they had some

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Speaker 4: clever answers. What do you think?

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Speaker 1: Yeah, I was impressed as well. In the end, of course,

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Speaker 1: is going to come down to the definition. I hope

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Speaker 1: that we end up with the definition of moon that

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Speaker 1: doesn't allow Elon Musk to have created his own personal moon.

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Speaker 1: So that seems sort of unsatisfied.

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Speaker 4: That would be too much power for one person.

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Speaker 1: The dude's already a billionaire and owns three like really

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Speaker 1: valuable companies, like it doesn't need to create astronomical objects

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Speaker 1: on top of all of it.

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Speaker 4: Although he wants to create a Mars colony, which is

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Speaker 4: maybe even more powerful than creating a moon. So I

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Speaker 4: guess we'll have to see what the future holds.

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Speaker 1: Do you think that's because he wants to be dictator

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Speaker 1: of Mars?

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Speaker 4: I like joking about that with Zach. Yes, he claims

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Speaker 4: he wants a representative not a direct democracy, So we'll

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Speaker 4: see what happens when the time comes.

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Speaker 1: Well, if you guess to pick who goes to Mars,

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Speaker 1: then they're probably going to elect him president anyway. But

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Speaker 1: let's get back to the topic. We're not talking about

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Speaker 1: Elon Musk's plan to colonize Mars. We're talking about moons

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Speaker 1: and how many moons the Earth has and what exactly

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Speaker 1: is a moon. So let's dig into that first and

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Speaker 1: talk about what qualifies as a moon. So, without doing

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Speaker 1: any research, Kelly, what would you use to define a moon?

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Speaker 4: So I would have guessed that a moon is a

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Speaker 4: big thing that isn't bigger than the planet that it orbits.

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Speaker 4: So a big thing that orbits around a planet, and

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Speaker 4: it has to be big, but it can't be bigger

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Speaker 4: than the thing that it's orbiting around. That's how I

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Speaker 4: would have defined it, but probably that's wrong.

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Speaker 1: And then your definition would it have to be natural

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Speaker 1: or could be man made that could we build an

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Speaker 1: artificial mood?

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Speaker 4: Oh uh no, No, I've always thought of it as

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Speaker 4: being natural. Yeah, what about you?

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Speaker 1: Well, I really wasn't sure, because it seems like in

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Speaker 1: lots of directions there are arbitrary distinctions you have to make,

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Speaker 1: And that's the problem often in astronomy is that the

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Speaker 1: categories between things get blurred, and you always find something

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Speaker 1: right on the edge between the different categories, and in

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Speaker 1: the end, you know, we're just we're looking at the

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Speaker 1: universe and we're trying to categorize it to understand it

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Speaker 1: so we can talk about it together. That doesn't mean

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Speaker 1: that those categories actually reflect something deep and true about

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Speaker 1: the universe. There's sometimes just the words we've used to

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Speaker 1: describe stuff, and so as we see more stuff out

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Speaker 1: there in the universe, we're going to find things that

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Speaker 1: break those categories. But the definition that I found for

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Speaker 1: Moon is that it has to be a quote natural body, right,

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Speaker 1: So it needs to be a natural body that's orbiting

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Speaker 1: a planet. And to me, already this is problematic like

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Speaker 1: a natural body means not like a human made satellite.

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Speaker 1: So if we built a death star, for example, officially,

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Speaker 1: that wouldn't qualify as a moon.

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Speaker 4: Sorry elon.

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Speaker 1: But what if we just like you know, pulled out

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Speaker 1: a huge chunk of Earth and threw it out into

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Speaker 1: space and then it went into orbit around the Earth?

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Speaker 1: Is that a natural body? It's like made of rock, right,

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Speaker 1: It's essentially the same process that created our moon as

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Speaker 1: we understand it. But I think according to this definition,

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Speaker 1: it wouldn't be a moon because you know, it would

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Speaker 1: have been like as the result of a human process.

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Speaker 4: It really does seem like if you just took a

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Speaker 4: chunk of Earth and you put it up there, it

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Speaker 4: should count. But I suppose satellites are just chunks of

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Speaker 4: Earth that we've done things too, that we send up

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Speaker 4: into space, and so maybe it shouldn't count.

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Speaker 1: Yeah, exactly, That's where I was going. What is a

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Speaker 1: satellite other than like an ultra refined piece of Earth

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Speaker 1: that you've somehow, you know, manipulated into a complex technological object.

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Speaker 1: But in the end, it's a piece of the Earth

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Speaker 1: that we've launched into space. And you know, for those

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Speaker 1: of you who don't know the history of our moon.

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Speaker 1: We think that our moon is basically a big chunk

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Speaker 1: of Earth that was vaulted out into space when another

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Speaker 1: proto planet hit Earth when it was very very young,

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Speaker 1: and this collision led to this enormous blob of stuff

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Speaker 1: getting tossed out there, which eventually coalesced into the Moon.

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Speaker 1: And when we've studied the surface of the Moon, we

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Speaker 1: found elements of it which would look exactly the same

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Speaker 1: as elements of the surface of the Earth. Would suggests

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Speaker 1: that they really do have sort of a common origin.

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Speaker 1: So this definition of a moon being a natural body

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Speaker 1: not a human made object is a little tricky, and

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Speaker 1: I don't think the definition there is very clear.

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Speaker 4: Can I ask a sort of tangential question? Of course,

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Speaker 4: So well, Zach and I were reading about the Moon,

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Speaker 4: we came across this fact that the Moon is sort

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Speaker 4: of carbon pore, like, maybe there's some carbon up there,

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Speaker 4: but you're going to have trouble growing plants and stuff

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Speaker 4: because there's not a lot of carbon. If the Moon

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Speaker 4: is just a chunk of Earth that got expelled, why

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Speaker 4: do we have so much carbon and they have so little.

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Speaker 4: Is that the result of natural processes that happened after

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Speaker 4: the Moon got cut off partly.

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Speaker 1: Yeah, Mostly the Earth and the Moon are made up

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Speaker 1: of very similar stuff. It's mostly oxygen and silicon and

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Speaker 1: calcium and iron and that kind of stuff. That's because

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Speaker 1: we think that the Moon and the Earth are made

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Speaker 1: up of the remnants of a huge collision between the

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Speaker 1: proto Earth and a Mars size planet, like fifty million

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Speaker 1: years after the Solar System formed, and the remnants of

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Speaker 1: that huge collision coalesced into the Earth and into the Moon.

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Speaker 1: But you're right that there is very little carbon on

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Speaker 1: the Moon, but there is carbon on the Earth's surface,

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Speaker 1: and we're not one hundred percent sure why. One theory

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Speaker 1: is that carbon tends to form very volatile compounds, things

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Speaker 1: that would end up in an atmosphere if the Moon

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Speaker 1: could keep one. So the Earth hangs on to some

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Speaker 1: of these things, some of this carbon, because it's big

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Speaker 1: enough to keep hold of its atmosphere it has more gravity,

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Speaker 1: but the Moon can't. Anything like an atmosphere on the

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Speaker 1: Moon just boils away.

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Speaker 4: Interesting.

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Speaker 1: Okay, thanks, So the definition of a moon is that

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Speaker 1: it needs to be a natural body in orbit around

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Speaker 1: a planet, and you said that it needs to be

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Speaker 1: big officially, technically there's no minimum size to a moon.

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Speaker 1: A moon could be like huge like our moon, or

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Speaker 1: you know, according to astronomers, it's okay to have a

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Speaker 1: moon that's like a kilometer in size.

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Speaker 4: I find that very unsatisfying. Like to me, a moon

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Speaker 4: is something that you should be able to, like put

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Speaker 4: a settlement on one day, and you can't really do

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Speaker 4: that with a one kilometer sized quote unquote moon. I

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Speaker 4: don't know. I don't want to buy that, but apparently

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Speaker 4: it's part of the definition.

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Speaker 1: It'd be like the little prints right walking around this

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Speaker 1: tiny little planet. But I think that comes from our experience, right,

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Speaker 1: just because we have this one big moon, we tend

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Speaker 1: to think that's what you got to have in a moon.

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Speaker 1: But as we'll talk about later, so many planets in

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Speaker 1: the Solar System don't have a huge moon, that have

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Speaker 1: a lot of smaller moons, And so part of the

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Speaker 1: joy of astronomy and of exploring the universe is discovering

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Speaker 1: that our corner of the universe is weird, is unusual,

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Speaker 1: is not representative, and we got to sort of like

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Speaker 1: stretch our minds and get used to a different way

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Speaker 1: of thinking about what a moon is.

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Speaker 4: Yeah, it is really hard to wrap your mind around

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Speaker 4: just how different it is. And yeah, I'm very earth centric.

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Speaker 4: I guess I would like moons to all sort of

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Speaker 4: fix in a nice little mold that matches the moon

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Speaker 4: that I have.

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Speaker 1: And you touch it on really all the important issues.

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Speaker 1: I think that was really tremendous. The other thing you

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Speaker 1: mentioned is that it shouldn't be bigger than the planet, right,

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Speaker 1: And in the definition of a moon, officially the upper

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Speaker 1: limit on the size of the moon is pretty vague,

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Speaker 1: Like what happens when the moon approaches the size of

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Speaker 1: the planet. Then you might ask, like, well, which one's

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Speaker 1: the planet and which one's the moon?

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Speaker 7: Right?

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Speaker 1: Or if they're exactly equal size, could you consider them

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Speaker 1: to be like a binary planet system?

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Speaker 4: So where does our moon fall relative? And they'll like

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Speaker 4: Earth to Moon ratio side like, is our moon big

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Speaker 4: for a moon? Is it the biggest relative to the

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Speaker 4: size of the planet in orbits?

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Speaker 8: Is?

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Speaker 7: So?

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Speaker 4: Is our moon weird relative to the other moons?

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Speaker 1: Our moon is very weird. Our moon is basically that megachild.

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Speaker 1: The diameter of the Moon is more than a quarter

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Speaker 1: of the diameter of the Earth, and that's the biggest

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Speaker 1: moon to planet ratio in the Solar System by like

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Speaker 1: a factor of five. There's no other planet out there

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Speaker 1: that has such a big moon relative to the planet. Like,

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Speaker 1: there are moons of Jupiter that are roughly the same

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Speaker 1: size as our moon, but of course Jupiter is huge,

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Speaker 1: and so relative to the size of Jupiter, those moons

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Speaker 1: are very very small, So we have a really weird

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Speaker 1: big moon.

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Speaker 4: You know, it's kind of amazing that we've managed to

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Speaker 4: figure out anything, which is sort of a phrase that,

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Speaker 4: if I'm remembering correctly, I've said in almost every single

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Speaker 4: one of these episodes we've done together. But it seems like,

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Speaker 4: you know, our Solar system is so weird, and our

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Speaker 4: planet and the moon is so weird. It gives us

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Speaker 4: such a weird frame of reference. But I don't know,

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Speaker 4: it's exciting that we can still figure stuff out.

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Speaker 1: Yeah, And it's a real journey to peel away these

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Speaker 1: preconceptions and understand that things we thought were fundamental, things

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Speaker 1: we thought were obvious or universal, are really just unusual.

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Speaker 1: You know. It's just like when you go traveling and

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Speaker 1: you discover like, oh, not everybody drinks coffee for breakfast.

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Speaker 1: You know, it turns out there are other ways to

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Speaker 1: live and that's the joy of exploring the universe, you know,

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Speaker 1: discovering the tea is also acceptable at breakfast times.

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Speaker 4: No, no, no, no, no, no, that's just wrong. One

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Speaker 4: fact that I really liked while I was reading through

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Speaker 4: here was that those like one kilometer size moons are

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Speaker 4: sometimes called moonlits, and I thought that was super cute.

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Speaker 4: So I asked my seven year old today. I was like,

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Speaker 4: how many moons does the Earth have? So she, being

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Speaker 4: a very clever kid, was like, well, I thought it

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Speaker 4: was one, but you're asking me this, so what does

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Speaker 4: that mean? And so I told her, like, well, you know,

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Speaker 4: you can have these little things called moonlits. And she said, well,

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Speaker 4: what does that mean? And so I tried to explain

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Speaker 4: that lets means little things and she was like, well,

440
00:20:27,200 --> 00:20:30,760
Speaker 4: when else does it mean that? And I had a like, uh,

441
00:20:30,920 --> 00:20:32,480
Speaker 4: you know, like a moment of not being able to

442
00:20:32,520 --> 00:20:34,600
Speaker 4: figure it out. But I came up with piglets and owlets,

443
00:20:34,600 --> 00:20:36,520
Speaker 4: and I was very proud of myself. So anyway, that

444
00:20:36,560 --> 00:20:38,439
Speaker 4: was a fun moment with the seven year old today.

445
00:20:38,560 --> 00:20:41,480
Speaker 1: Yeah, I love those little endings lits and like, it's

446
00:20:41,520 --> 00:20:45,000
Speaker 1: just like the diminutive in Spanish, you know, eto or

447
00:20:45,200 --> 00:20:47,439
Speaker 1: eno or these kind of things in romance languages, so

448
00:20:47,520 --> 00:20:49,359
Speaker 1: I'm glad that we have those in English. Also, you

449
00:20:49,359 --> 00:20:51,560
Speaker 1: could really stick them on anything, you know, like I'm

450
00:20:51,560 --> 00:20:53,600
Speaker 1: not having dessert, I'm having dessert lits.

451
00:20:54,920 --> 00:20:57,280
Speaker 4: It makes everything cuter, it really does.

452
00:20:57,600 --> 00:20:59,480
Speaker 1: So where are we with the moons? Moons have to

453
00:20:59,480 --> 00:21:02,920
Speaker 1: be a natural body orbiting a planet, no minimum size.

454
00:21:03,080 --> 00:21:06,000
Speaker 1: The upper limit is kind of vague. One thing I

455
00:21:06,040 --> 00:21:09,040
Speaker 1: read suggested that you could effectively describe an upper limit

456
00:21:09,119 --> 00:21:12,480
Speaker 1: on the Moon by requiring that the center of mass

457
00:21:12,720 --> 00:21:16,600
Speaker 1: of the planet and moon together should be inside the

458
00:21:16,600 --> 00:21:19,280
Speaker 1: diameter of the planet. Right, So the center of mass

459
00:21:19,280 --> 00:21:22,000
Speaker 1: of two objects, it's sort of like the weighted average

460
00:21:22,320 --> 00:21:24,600
Speaker 1: of all of their stuff. If you've got more stuff

461
00:21:24,640 --> 00:21:26,520
Speaker 1: in the planet than in the moon, it's going to

462
00:21:26,520 --> 00:21:29,359
Speaker 1: be closer to the planet. Mathematically and physically. It's actually

463
00:21:29,440 --> 00:21:31,560
Speaker 1: the location that the two things are orbiting.

464
00:21:31,840 --> 00:21:32,000
Speaker 9: Right.

465
00:21:32,040 --> 00:21:34,520
Speaker 1: We say that the Moon, for example, orbits the Earth,

466
00:21:34,800 --> 00:21:37,399
Speaker 1: but actually the two things are orbiting each other, or

467
00:21:37,400 --> 00:21:40,800
Speaker 1: more precisely, they are both orbiting the center of mass

468
00:21:40,800 --> 00:21:42,920
Speaker 1: of the two things. And if you have two things

469
00:21:42,920 --> 00:21:45,080
Speaker 1: that are equal mass, then the center of mass is

470
00:21:45,160 --> 00:21:47,920
Speaker 1: right between them. If one of them is infinitely massive,

471
00:21:48,080 --> 00:21:49,879
Speaker 1: then the center of mass is at the center of

472
00:21:49,880 --> 00:21:52,880
Speaker 1: that very massive object. In a more realistic scenario, where

473
00:21:52,880 --> 00:21:55,600
Speaker 1: one thing is very massive and one thing is much smaller,

474
00:21:55,720 --> 00:21:57,880
Speaker 1: you can have the center of mass of the system

475
00:21:57,920 --> 00:22:01,040
Speaker 1: of the two things be close to the center of

476
00:22:01,200 --> 00:22:04,040
Speaker 1: the larger object. And so here the definition is like,

477
00:22:04,480 --> 00:22:07,439
Speaker 1: is the center of mass of the two objects underneath

478
00:22:07,480 --> 00:22:11,320
Speaker 1: the ground within the radius of the larger object. That's

479
00:22:11,320 --> 00:22:12,400
Speaker 1: sort of a cool definition.

480
00:22:12,600 --> 00:22:14,080
Speaker 4: That is a cool So I have a couple questions

481
00:22:14,080 --> 00:22:17,679
Speaker 4: to see if I understand. So one, does it depend

482
00:22:17,720 --> 00:22:20,880
Speaker 4: on how far apart the things are or is it

483
00:22:21,000 --> 00:22:23,399
Speaker 4: like you just when you make this comparison, you you know,

484
00:22:23,440 --> 00:22:25,280
Speaker 4: sort of mentally put these things right next to each

485
00:22:25,320 --> 00:22:27,119
Speaker 4: other and then compare the center of mass.

486
00:22:27,200 --> 00:22:29,920
Speaker 1: It definitely depends on how far apart they are, right

487
00:22:29,960 --> 00:22:32,800
Speaker 1: because for example, if they're equally massive, you'd be right

488
00:22:32,840 --> 00:22:35,520
Speaker 1: between them. And that definitely depends on the distance between

489
00:22:35,520 --> 00:22:36,159
Speaker 1: the two objects.

490
00:22:36,280 --> 00:22:38,360
Speaker 4: Yes, and so that would mean you have two planets

491
00:22:38,400 --> 00:22:40,439
Speaker 4: as opposed to a moon and a planet.

492
00:22:40,600 --> 00:22:41,680
Speaker 1: Yeah, in that definition.

493
00:22:41,800 --> 00:22:44,640
Speaker 4: And so say you have two things that are like

494
00:22:44,800 --> 00:22:47,360
Speaker 4: one is just a little bit smaller than the other

495
00:22:47,480 --> 00:22:50,880
Speaker 4: and one is bigger but the smaller one is made

496
00:22:51,000 --> 00:22:55,960
Speaker 4: out of something much more massive or dense or I'm

497
00:22:56,000 --> 00:22:57,960
Speaker 4: not quite sure what word I'm looking for here. Could

498
00:22:57,960 --> 00:23:01,480
Speaker 4: the smaller thing end up being the planet that gets

499
00:23:01,560 --> 00:23:03,800
Speaker 4: orbited by a bigger thing because it has more like

500
00:23:03,960 --> 00:23:05,040
Speaker 4: gravitational pull?

501
00:23:05,240 --> 00:23:09,000
Speaker 1: Absolutely? Yeah. For example, if you had something orbiting a

502
00:23:09,000 --> 00:23:12,240
Speaker 1: black hole, right, a super duper dense object, then the

503
00:23:12,320 --> 00:23:14,240
Speaker 1: center of mass and the system is definitely going to

504
00:23:14,280 --> 00:23:16,600
Speaker 1: be within the event horizon, even if though the black

505
00:23:16,600 --> 00:23:19,440
Speaker 1: hole could be smaller. Right, black holes are very very compact.

506
00:23:19,480 --> 00:23:21,399
Speaker 1: They don't have to be very very large, but they

507
00:23:21,400 --> 00:23:23,959
Speaker 1: are super massive, so that's awesome. You're really like pushing

508
00:23:24,000 --> 00:23:26,480
Speaker 1: the boundaries of this definition. But I don't know. I

509
00:23:26,520 --> 00:23:28,879
Speaker 1: guess a black hole could have a planet orbiting it.

510
00:23:28,920 --> 00:23:30,479
Speaker 1: I'm not sure if you would call that a planet

511
00:23:30,560 --> 00:23:33,000
Speaker 1: or a moon, right, if you're orbiting a black hole.

512
00:23:32,920 --> 00:23:36,840
Speaker 4: Yeah, it's trippy. I guess, I, as a not physicist,

513
00:23:37,240 --> 00:23:40,520
Speaker 4: find it sort of unsatisfying that if the moon is

514
00:23:40,640 --> 00:23:43,320
Speaker 4: too far away, it might or if something that feels

515
00:23:43,320 --> 00:23:45,480
Speaker 4: sort of moon like is too far away, it wouldn't

516
00:23:45,560 --> 00:23:48,399
Speaker 4: count as a moon because the center of mass is

517
00:23:48,440 --> 00:23:51,480
Speaker 4: not within the bigger body or something it feels like

518
00:23:51,560 --> 00:23:55,119
Speaker 4: distance shouldn't matter for the definition, but that's a biologist

519
00:23:55,200 --> 00:23:55,600
Speaker 4: take on it.

520
00:23:55,640 --> 00:23:57,639
Speaker 1: Well, it definitely has to be in orbit. And I

521
00:23:57,680 --> 00:24:01,080
Speaker 1: think one problem with this whole categoryzation is that there's

522
00:24:01,160 --> 00:24:03,800
Speaker 1: like a natural hierarchy. I mean, you have the Sun,

523
00:24:04,080 --> 00:24:06,800
Speaker 1: and there's stuff orbiting around the Sun, and then you

524
00:24:06,840 --> 00:24:09,280
Speaker 1: call those planets, but that's sort of arbitrary because they're

525
00:24:09,359 --> 00:24:12,200
Speaker 1: orbiting around the Sun. And then there's things orbiting around

526
00:24:12,200 --> 00:24:15,200
Speaker 1: the planets, right, and you call those moons. In the end,

527
00:24:15,200 --> 00:24:17,719
Speaker 1: it's just sort of a natural hierarchy of stuff orbiting

528
00:24:17,760 --> 00:24:21,280
Speaker 1: stuff that's orbiting other stuff, and our categorization of it

529
00:24:21,320 --> 00:24:23,480
Speaker 1: is you're really going to try to draw lines there

530
00:24:23,520 --> 00:24:24,879
Speaker 1: where there really aren't lines.

531
00:24:25,119 --> 00:24:28,080
Speaker 4: Yeah, but that's like a fundamental problem with science. You know,

532
00:24:28,160 --> 00:24:31,800
Speaker 4: in biology, we categorize things, and constantly nature does not

533
00:24:31,880 --> 00:24:34,199
Speaker 4: care how we categorize it. She moves way outside of

534
00:24:34,200 --> 00:24:36,320
Speaker 4: our categories. Yeah. I guess it's tough just finding a

535
00:24:36,320 --> 00:24:37,800
Speaker 4: definition that is useful.

536
00:24:37,880 --> 00:24:40,119
Speaker 1: I guess in biology there was a huge revolution a

537
00:24:40,119 --> 00:24:42,320
Speaker 1: couple hundred years ago, right because you guys had been

538
00:24:42,359 --> 00:24:45,160
Speaker 1: categorizing stuff based on how it looked and what it did,

539
00:24:45,520 --> 00:24:49,800
Speaker 1: and then discovered the genetic relationships between everything, and that

540
00:24:49,880 --> 00:24:52,640
Speaker 1: there was actually a real, true organization to all these

541
00:24:52,680 --> 00:24:56,280
Speaker 1: animals that didn't necessarily respect how they looked or how

542
00:24:56,280 --> 00:24:57,399
Speaker 1: we observe them well.

543
00:24:57,440 --> 00:24:59,080
Speaker 4: And then it turns out that, you know, how do

544
00:24:59,119 --> 00:25:01,800
Speaker 4: you define species? That's actually a pretty difficult question. The

545
00:25:01,840 --> 00:25:04,040
Speaker 4: tree of life doesn't just branch, It sort of comes,

546
00:25:04,119 --> 00:25:07,680
Speaker 4: the branches come back together, and you get horizontal gene transfer,

547
00:25:07,720 --> 00:25:10,760
Speaker 4: And how do you categorize species of bacteria when they're

548
00:25:10,760 --> 00:25:13,600
Speaker 4: swapping genes all the time, and it gets complicated fast.

549
00:25:13,680 --> 00:25:16,280
Speaker 1: Well, in physics, it's interesting they think about how these

550
00:25:16,280 --> 00:25:18,960
Speaker 1: words were used for a long time. People use the

551
00:25:18,960 --> 00:25:22,440
Speaker 1: word satellite to also refer to moons, and this is

552
00:25:22,480 --> 00:25:26,160
Speaker 1: before we had things in space like GPS and telecommunications,

553
00:25:26,200 --> 00:25:28,919
Speaker 1: satellites and you know, laser weapons and all that kind

554
00:25:28,920 --> 00:25:31,159
Speaker 1: of stuff. Now, when you say satellite, you think of

555
00:25:31,200 --> 00:25:34,159
Speaker 1: something people built, made of electronics and launched into space.

556
00:25:34,280 --> 00:25:38,560
Speaker 1: But before Sputnik, before nineteen fifty seven, astronomers use the

557
00:25:38,560 --> 00:25:42,800
Speaker 1: word satellite to talk about anything orbiting another object, and

558
00:25:42,880 --> 00:25:46,320
Speaker 1: so they didn't really use the word moon scientifically. They

559
00:25:46,400 --> 00:25:50,760
Speaker 1: referred to Luna, for example, as Earth's satellite. Then when

560
00:25:50,800 --> 00:25:53,119
Speaker 1: they launched Sputnik, they realized a whole on a second,

561
00:25:53,160 --> 00:25:54,840
Speaker 1: what are we going to call that? And so they

562
00:25:54,880 --> 00:25:57,280
Speaker 1: started to use the word artificial satellite, but that was

563
00:25:57,320 --> 00:25:59,639
Speaker 1: a little bit too cumbersome, and so now we just

564
00:25:59,640 --> 00:26:04,080
Speaker 1: say when we mean artificial satellite. And then moon, which

565
00:26:04,280 --> 00:26:07,000
Speaker 1: was a word mostly used like in science fiction and

566
00:26:07,160 --> 00:26:11,000
Speaker 1: sort of popular culture, became a more official scientific word.

567
00:26:11,200 --> 00:26:13,800
Speaker 1: I think that's sort of cool that the scientists adopted

568
00:26:13,840 --> 00:26:16,040
Speaker 1: a word from sort of common usage.

569
00:26:16,080 --> 00:26:18,560
Speaker 4: That's totally fascinating. And I've been reading about the space

570
00:26:18,640 --> 00:26:21,280
Speaker 4: race and I didn't know this history of the word satellite.

571
00:26:21,359 --> 00:26:25,040
Speaker 4: And when I saw that they named Sputnik an artificial satellite,

572
00:26:25,080 --> 00:26:26,879
Speaker 4: I was like, well, that's sort of clunk. Why not

573
00:26:26,960 --> 00:26:29,280
Speaker 4: just call it satellite? But it makes sense now. A

574
00:26:29,320 --> 00:26:32,720
Speaker 4: lot of the fathers of rocket science or whatever were

575
00:26:32,880 --> 00:26:35,800
Speaker 4: really into sci fi. I think almost all of the

576
00:26:35,840 --> 00:26:38,440
Speaker 4: fathers of rocket science claimed that they were inspired by

577
00:26:38,520 --> 00:26:41,399
Speaker 4: Jules Vern's what is it Called to the Moon? I

578
00:26:41,440 --> 00:26:43,280
Speaker 4: wonder if the fact that they were all super into

579
00:26:43,280 --> 00:26:46,360
Speaker 4: sci fi sort of helped get the word moon into

580
00:26:46,400 --> 00:26:47,399
Speaker 4: the scientific literature.

581
00:26:47,480 --> 00:26:49,800
Speaker 1: Yeah, it makes me wonder what else, like will in

582
00:26:49,840 --> 00:26:52,280
Speaker 1: the future be part of science. You know things that

583
00:26:52,320 --> 00:26:54,359
Speaker 1: we say but you wouldn't hear a scientists say, you know,

584
00:26:54,440 --> 00:26:57,399
Speaker 1: like a shooting star is our word for a meteor,

585
00:26:57,520 --> 00:26:59,240
Speaker 1: but you never see that in the science paper. But

586
00:26:59,320 --> 00:27:02,040
Speaker 1: maybe someday in the future, you know, the language will

587
00:27:02,240 --> 00:27:07,040
Speaker 1: transmography itself into official scientific physics speak. Could be all right,

588
00:27:07,119 --> 00:27:09,360
Speaker 1: So we have our definition of a moon. It has

589
00:27:09,400 --> 00:27:13,360
Speaker 1: to be a natural body, right, not something engineered by

590
00:27:13,440 --> 00:27:16,680
Speaker 1: humanity or elon musk that has to orbit a planet.

591
00:27:17,119 --> 00:27:20,600
Speaker 1: But there's really no minimum size to it, though there

592
00:27:20,640 --> 00:27:22,680
Speaker 1: seems to be some sort of sense of an upper

593
00:27:22,720 --> 00:27:25,280
Speaker 1: limit that you shouldn't have your moon being larger than

594
00:27:25,320 --> 00:27:25,880
Speaker 1: your planet.

595
00:27:25,920 --> 00:27:28,480
Speaker 4: All right, So now that we have our definition, or

596
00:27:28,480 --> 00:27:30,159
Speaker 4: at least a definition we're going to work with for

597
00:27:30,200 --> 00:27:32,560
Speaker 4: the rest of this episode, let's take a break before

598
00:27:32,560 --> 00:27:34,879
Speaker 4: we move back to figuring out exactly how many moons

599
00:27:34,960 --> 00:27:39,120
Speaker 4: Earth has.

600
00:27:40,280 --> 00:27:43,239
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00:30:40,000 --> 00:30:43,120
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659
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660
00:30:46,800 --> 00:30:49,760
Speaker 1: Many farms use anaerobic digestors that turn the methane from

661
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Speaker 1: maneuver into renewable energy that can power farms, towns, and

662
00:30:53,240 --> 00:30:55,480
Speaker 1: electric cars. So the next time you grab a slice

663
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Speaker 1: of pizza or lick an ice cream, cone. Know that

664
00:30:57,480 --> 00:31:00,160
Speaker 1: dairy farmers and processors around the country are using the

665
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666
00:31:03,960 --> 00:31:06,640
Speaker 1: products we love with less of an impact. Visit us

667
00:31:06,720 --> 00:31:09,240
Speaker 1: dairy dot com slash sustainability to learn more.

668
00:31:17,040 --> 00:31:20,880
Speaker 4: So we have a definition. Now, how many moons do

669
00:31:20,920 --> 00:31:21,200
Speaker 4: we have?

670
00:31:21,360 --> 00:31:24,680
Speaker 1: Daniel, So let's count them first. Of course, we have

671
00:31:24,800 --> 00:31:27,240
Speaker 1: the number one candidate, the classic moon, the one you're

672
00:31:27,240 --> 00:31:30,400
Speaker 1: familiar with, the one we all grew up loving. Right,

673
00:31:30,720 --> 00:31:33,400
Speaker 1: this is the moon we call the moon, which is

674
00:31:33,520 --> 00:31:35,640
Speaker 1: sort of a silly name, right, calling the moon the moon.

675
00:31:35,680 --> 00:31:38,120
Speaker 1: It reminds me. Actually, when I was a kid, we

676
00:31:38,240 --> 00:31:40,360
Speaker 1: had a cat and nobody could agree on what to

677
00:31:40,440 --> 00:31:43,560
Speaker 1: call the cat, so we just called it the cat,

678
00:31:43,640 --> 00:31:46,640
Speaker 1: and that just became its name. And for a while

679
00:31:46,640 --> 00:31:49,000
Speaker 1: it felt sad, for like, oh, poor cat doesn't get

680
00:31:49,000 --> 00:31:52,120
Speaker 1: a name, but he didn't care. It got fed, it

681
00:31:52,120 --> 00:31:53,960
Speaker 1: got pet. Well, it doesn't need a name.

682
00:31:54,240 --> 00:31:56,400
Speaker 4: I think it's good that you became more creative as

683
00:31:56,400 --> 00:31:59,480
Speaker 4: you got. I can't tell if calling it the moon

684
00:31:59,640 --> 00:32:02,600
Speaker 4: is very egocentric, like that is our moon, so it

685
00:32:02,680 --> 00:32:05,560
Speaker 4: is the moon, or if it just represents a lack

686
00:32:05,600 --> 00:32:07,080
Speaker 4: of creativity hard to say.

687
00:32:07,240 --> 00:32:09,680
Speaker 1: Well, as we were saying earlier, it's really weird, Like

688
00:32:09,760 --> 00:32:12,320
Speaker 1: it's huge. It's more than a quarter of the diameter

689
00:32:12,360 --> 00:32:15,280
Speaker 1: of the Earth in the Solar System. The next largest

690
00:32:15,280 --> 00:32:17,600
Speaker 1: moon relative to his planet is one of the moons

691
00:32:17,640 --> 00:32:20,080
Speaker 1: of Neptune, which is almost six percent of the diameter

692
00:32:20,160 --> 00:32:23,720
Speaker 1: of Neptune. So that's a pretty big gap. Like, mostly

693
00:32:23,840 --> 00:32:26,800
Speaker 1: moons are small compared to their planet. The moon is

694
00:32:26,880 --> 00:32:28,880
Speaker 1: really very weird. And or hey, and I did a

695
00:32:28,880 --> 00:32:31,400
Speaker 1: whole episode about how the Earth got its moon and

696
00:32:31,440 --> 00:32:34,320
Speaker 1: the various theories and how people are testing those, and

697
00:32:34,360 --> 00:32:36,479
Speaker 1: so if you're interested in the details and the history

698
00:32:36,520 --> 00:32:39,959
Speaker 1: of the moon, then go check out that episode. But

699
00:32:40,000 --> 00:32:42,120
Speaker 1: it's interesting that, you know, in the sort of the

700
00:32:42,200 --> 00:32:45,480
Speaker 1: history of astronomy I was reading about this, people didn't

701
00:32:45,520 --> 00:32:49,760
Speaker 1: really think about the Moon as a moon until they

702
00:32:49,840 --> 00:32:53,440
Speaker 1: discovered Jupiter's moons. Like people were looking up in the

703
00:32:53,480 --> 00:32:55,880
Speaker 1: sky and they saw, of course stars, and they saw

704
00:32:55,960 --> 00:32:58,080
Speaker 1: the moon, but they just thought of it as like

705
00:32:58,160 --> 00:32:59,840
Speaker 1: another celestial object.

706
00:33:00,120 --> 00:33:01,000
Speaker 4: Well they were wrong.

707
00:33:01,640 --> 00:33:04,560
Speaker 1: They were wrong. And then you know when Galileo and

708
00:33:04,680 --> 00:33:07,120
Speaker 1: other folks saw the moons of Jupiter and they're like, hey,

709
00:33:07,160 --> 00:33:10,160
Speaker 1: look at that. There are things orbiting Jupiter. That's when

710
00:33:10,160 --> 00:33:12,000
Speaker 1: it clicked into place and they're like, wait a second,

711
00:33:12,440 --> 00:33:14,760
Speaker 1: what Jupiter's got over there is the same thing that

712
00:33:14,800 --> 00:33:17,720
Speaker 1: we've got over here. And that's when they realized that

713
00:33:17,760 --> 00:33:20,719
Speaker 1: this was a whole new kind of thing in space.

714
00:33:20,880 --> 00:33:23,200
Speaker 4: That's so interesting. That's why it's so important to you know,

715
00:33:23,280 --> 00:33:25,200
Speaker 4: to learn more and to step outside your comfort zone

716
00:33:25,240 --> 00:33:27,240
Speaker 4: because there's so many things that become obvious when you

717
00:33:27,400 --> 00:33:28,920
Speaker 4: see how other things are done.

718
00:33:29,040 --> 00:33:31,360
Speaker 1: Yeah, and the moon was actually considered a planet for

719
00:33:31,400 --> 00:33:34,680
Speaker 1: a while, though the definition of a planet has also changed.

720
00:33:34,880 --> 00:33:38,400
Speaker 1: Back then, a planet was just like another astronomical object.

721
00:33:38,400 --> 00:33:41,440
Speaker 1: People didn't really understand the relationship between the planets and

722
00:33:41,480 --> 00:33:43,360
Speaker 1: the stars and all this kind of stuff. So if

723
00:33:43,360 --> 00:33:46,040
Speaker 1: you go back to like very early astronomy, what these

724
00:33:46,080 --> 00:33:48,960
Speaker 1: words mean is totally different from what they mean today.

725
00:33:49,280 --> 00:33:52,040
Speaker 1: So it's pretty tricky to read, like, you know, early

726
00:33:52,080 --> 00:33:53,200
Speaker 1: astronomical texts.

727
00:33:53,280 --> 00:33:55,680
Speaker 4: That sounds super confusing. So it makes me wonder, So

728
00:33:55,800 --> 00:33:58,400
Speaker 4: if you can be changing what the definition of a

729
00:33:58,440 --> 00:34:02,120
Speaker 4: planet is, can you have things that are not planets

730
00:34:02,680 --> 00:34:03,760
Speaker 4: that have moons?

731
00:34:04,280 --> 00:34:07,520
Speaker 1: You can definitely have things that are not planets that

732
00:34:07,640 --> 00:34:10,759
Speaker 1: have stuff orbiting them and We will talk about that

733
00:34:10,840 --> 00:34:13,400
Speaker 1: later in the episode. There are things in the Solar

734
00:34:13,400 --> 00:34:15,800
Speaker 1: System orbiting other things that are not planets.

735
00:34:15,840 --> 00:34:17,240
Speaker 4: For sure, Sorry I got excited.

736
00:34:18,000 --> 00:34:20,600
Speaker 1: It's very cool. And for example, you know, just as

737
00:34:20,640 --> 00:34:25,040
Speaker 1: a teaser, Pluto no longer considered a planet, but it

738
00:34:25,160 --> 00:34:28,360
Speaker 1: does have things orbiting it, right, Pluto has something which

739
00:34:28,600 --> 00:34:31,560
Speaker 1: you would call a moon, Sharon, which is half the

740
00:34:31,640 --> 00:34:34,879
Speaker 1: diameter of Pluto. So that's pretty fuzzy, like which one

741
00:34:34,920 --> 00:34:37,160
Speaker 1: is a planet, which one's the moon. Pluto's only twice

742
00:34:37,200 --> 00:34:38,520
Speaker 1: as big as its moon.

743
00:34:38,800 --> 00:34:41,920
Speaker 4: So if Sharon or Charon, however you say, it ends

744
00:34:42,040 --> 00:34:44,120
Speaker 4: up being called a moon, that makes our moon a

745
00:34:44,160 --> 00:34:46,000
Speaker 4: little bit less exciting.

746
00:34:46,239 --> 00:34:49,080
Speaker 1: Yeah, Or if Pluto gets repromoted back into it being

747
00:34:49,120 --> 00:34:52,400
Speaker 1: a planet, then Charon would be the largest moon relative

748
00:34:52,440 --> 00:34:54,880
Speaker 1: to a planet in the Solar System. But because Pluto's

749
00:34:55,120 --> 00:35:00,400
Speaker 1: no longer technically a planet, Sharon loses that distinction. For Sharon, Sharon,

750
00:35:00,640 --> 00:35:03,080
Speaker 1: all right, So everybody knows about the moon. That's not

751
00:35:03,080 --> 00:35:05,680
Speaker 1: what people want to hear about. Are there other things

752
00:35:05,800 --> 00:35:09,319
Speaker 1: orbiting the Earth that could also be considered moons? And so,

753
00:35:09,800 --> 00:35:12,440
Speaker 1: in fact there are, but they're sort of on the

754
00:35:12,600 --> 00:35:16,280
Speaker 1: borderline of whether you would really technically call them a moon.

755
00:35:16,440 --> 00:35:18,200
Speaker 1: One of my favorites is this object, which I won't

756
00:35:18,200 --> 00:35:20,080
Speaker 1: even try to pronounce. You're gonna have to look it up.

757
00:35:20,080 --> 00:35:22,360
Speaker 1: But it goes by the name of the space bean,

758
00:35:23,120 --> 00:35:27,560
Speaker 1: and it's this object like five kilometers in diameter that's

759
00:35:27,680 --> 00:35:30,280
Speaker 1: orbiting the Sun in the vicinity of the Earth.

760
00:35:30,400 --> 00:35:32,080
Speaker 4: But it seems like we've got to try to pronounce

761
00:35:32,080 --> 00:35:36,320
Speaker 4: it right, So I'm gonna try what krwyne krewythne kerwythni.

762
00:35:36,400 --> 00:35:38,960
Speaker 1: Yeah, that sounds about right. If I had no idea

763
00:35:38,960 --> 00:35:40,920
Speaker 1: how to pronounce it, I would guess that was correct, And.

764
00:35:40,880 --> 00:35:42,719
Speaker 4: I have no idea how to pronounce it, so I

765
00:35:42,719 --> 00:35:43,600
Speaker 4: guess that's correct.

766
00:35:44,440 --> 00:35:46,719
Speaker 1: I don't even know what the like origin of that,

767
00:35:46,760 --> 00:35:48,040
Speaker 1: what language that comes from.

768
00:35:48,160 --> 00:35:50,800
Speaker 4: It looks Irish to me, and I have no reason.

769
00:35:51,280 --> 00:35:53,200
Speaker 4: I don't actually know anything about the Irish language, So

770
00:35:53,719 --> 00:35:54,600
Speaker 4: maybe I should stop.

771
00:35:54,719 --> 00:35:57,239
Speaker 1: Maybe it's Gaelic for space bean. Somebody out there who

772
00:35:57,320 --> 00:35:59,640
Speaker 1: speaks Gaelic, let us know how to say space being

773
00:35:59,800 --> 00:36:03,719
Speaker 1: in Gamic. So this is a fun object because it's

774
00:36:03,840 --> 00:36:08,160
Speaker 1: in orbit technically around the Sun, but it's in resonance

775
00:36:08,200 --> 00:36:11,120
Speaker 1: with the Earth. This is something maybe people haven't realized that,

776
00:36:11,280 --> 00:36:14,200
Speaker 1: like things that are orbiting the Sun are also interacting

777
00:36:14,239 --> 00:36:16,799
Speaker 1: with each other. Right, our orbit around the Sun is

778
00:36:16,800 --> 00:36:19,080
Speaker 1: mostly a big ellipse, and it's dominated by the Sun.

779
00:36:19,120 --> 00:36:21,799
Speaker 1: The shape of that ellipse is mostly controlled by the

780
00:36:21,800 --> 00:36:25,280
Speaker 1: gravitational power of the Sun. But there are other things

781
00:36:25,320 --> 00:36:27,879
Speaker 1: also orbiting with us, and they tug on us, they

782
00:36:27,920 --> 00:36:30,960
Speaker 1: pull on us, and they can change our orbit. And

783
00:36:31,000 --> 00:36:33,760
Speaker 1: sometimes you get two objects and what you call a resonance,

784
00:36:33,760 --> 00:36:36,680
Speaker 1: which means that they are very regularly tugging on each

785
00:36:36,680 --> 00:36:39,279
Speaker 1: other in a systematic way that changes both of their

786
00:36:39,360 --> 00:36:41,880
Speaker 1: orbits and makes it stable, so that for example, they

787
00:36:41,880 --> 00:36:45,120
Speaker 1: will like meet two or four times while going around

788
00:36:45,160 --> 00:36:47,719
Speaker 1: the Sun, depending on their relative speed, and nudge each

789
00:36:47,719 --> 00:36:50,440
Speaker 1: other in just the right way. So, for example, Saturn

790
00:36:50,480 --> 00:36:53,400
Speaker 1: and Jupiter are both really really powerful and they're in

791
00:36:53,440 --> 00:36:55,880
Speaker 1: an orbital resonance with each other. So this is an

792
00:36:55,920 --> 00:36:58,960
Speaker 1: object that's moving around the Sun, but it's in resonance

793
00:36:59,080 --> 00:37:03,200
Speaker 1: with the Earth, so it's strongly influenced by the Earth's gravity.

794
00:37:03,400 --> 00:37:06,240
Speaker 4: But does it orbit in the same shape the Moon does?

795
00:37:06,520 --> 00:37:09,240
Speaker 4: So how is an orbit in a resonance different?

796
00:37:09,440 --> 00:37:12,040
Speaker 1: So this thing moves around the Sun, you know, but

797
00:37:12,280 --> 00:37:14,680
Speaker 1: so does the Moon. Right, if you tracked the moon,

798
00:37:14,760 --> 00:37:17,240
Speaker 1: the Moon goes around the Sun, the Earth goes around

799
00:37:17,239 --> 00:37:20,759
Speaker 1: the Sun. But the Moon is gravitationally mostly bound to

800
00:37:20,880 --> 00:37:24,560
Speaker 1: the Earth. This thing is primarily mostly bound to the Sun,

801
00:37:25,320 --> 00:37:28,640
Speaker 1: but because of the influence of the Earth, if you

802
00:37:28,719 --> 00:37:30,920
Speaker 1: look at its orbit from the Earth, it looks like

803
00:37:30,960 --> 00:37:35,239
Speaker 1: it makes a bean shaped motion around the Earth. Like

804
00:37:35,320 --> 00:37:36,960
Speaker 1: if you put the Earth, if you're the center of

805
00:37:36,960 --> 00:37:39,359
Speaker 1: your reference frame, and you plot where the space bean

806
00:37:39,480 --> 00:37:41,719
Speaker 1: is and you like take data points from day to

807
00:37:41,800 --> 00:37:44,320
Speaker 1: day and imagine where it is, it makes a bean

808
00:37:44,600 --> 00:37:46,360
Speaker 1: shape all the way around the Earth.

809
00:37:46,480 --> 00:37:48,960
Speaker 4: So does that mean it doesn't quite fit the definition,

810
00:37:49,080 --> 00:37:52,640
Speaker 4: because like do orbits need to be elliptical and not

811
00:37:53,080 --> 00:37:53,800
Speaker 4: bean shaped?

812
00:37:54,000 --> 00:37:56,480
Speaker 1: It means that there's not really a clear distinction. We

813
00:37:56,560 --> 00:37:59,360
Speaker 1: have a three body system. We have the Sun, we

814
00:37:59,440 --> 00:38:01,680
Speaker 1: have the Earth, and we have the space bean, and

815
00:38:01,719 --> 00:38:04,759
Speaker 1: they're all tugging on each other. And so to ask

816
00:38:04,800 --> 00:38:07,759
Speaker 1: the question like what is the space being orbiting? Is

817
00:38:07,800 --> 00:38:10,080
Speaker 1: it orbiting the Earth? Is it orbiting just the Sun,

818
00:38:10,560 --> 00:38:13,319
Speaker 1: doesn't have a clear precise answer unless you define an

819
00:38:13,400 --> 00:38:17,239
Speaker 1: arbitrary distinction. But there is no natural distinction between these

820
00:38:17,280 --> 00:38:20,440
Speaker 1: two scenarios. It's like a smooth continuum of being like

821
00:38:20,520 --> 00:38:22,880
Speaker 1: the Moon where you're very clearly just orbiting the Earth,

822
00:38:22,960 --> 00:38:26,440
Speaker 1: and being like Mercury, where you're very clearly just orbiting

823
00:38:26,440 --> 00:38:30,480
Speaker 1: the Sun. And then these quasi satellites of Earth that

824
00:38:30,560 --> 00:38:33,080
Speaker 1: are very clearly affected by Earth and sort of moving

825
00:38:33,160 --> 00:38:36,120
Speaker 1: around Earth as they move around the Sun. And that's

826
00:38:36,120 --> 00:38:39,520
Speaker 1: what the space bean is. It's a quasi satellite of

827
00:38:39,560 --> 00:38:40,440
Speaker 1: the Earth, all right.

828
00:38:40,480 --> 00:38:43,120
Speaker 4: So two things. One, every time you say space bean,

829
00:38:43,160 --> 00:38:45,080
Speaker 4: I'm going to continue to chuckle. I don't think I'm

830
00:38:45,120 --> 00:38:47,880
Speaker 4: going to stop doing that because it's just funny and cute.

831
00:38:48,160 --> 00:38:50,400
Speaker 4: And Two, you know, I feel like it would be

832
00:38:50,440 --> 00:38:54,680
Speaker 4: really nice in science classes if like how hard it

833
00:38:54,719 --> 00:38:57,200
Speaker 4: is to do these definitions and how so few things

834
00:38:57,280 --> 00:38:59,600
Speaker 4: fit into these definitions was sort of made more clear,

835
00:38:59,600 --> 00:39:01,760
Speaker 4: and maybe they do that in school today. It constantly

836
00:39:01,760 --> 00:39:03,759
Speaker 4: blows my mind how much I think that we have

837
00:39:03,960 --> 00:39:08,000
Speaker 4: the world bend nicely, but everything breaks the bins.

838
00:39:08,280 --> 00:39:11,399
Speaker 1: Everything breaks the bins because the world is continuous, right,

839
00:39:11,480 --> 00:39:13,920
Speaker 1: and it's huge, and so there's always going to be

840
00:39:13,960 --> 00:39:17,480
Speaker 1: an example of something in between. These crisp distinctions are

841
00:39:17,719 --> 00:39:21,080
Speaker 1: our artificial way to try to impose order on the universe,

842
00:39:21,400 --> 00:39:24,000
Speaker 1: and back when we hadn't seen so many things, those

843
00:39:24,000 --> 00:39:26,839
Speaker 1: gaps might have seen meaningful. But as we keep looking

844
00:39:26,880 --> 00:39:29,560
Speaker 1: at the universe, we find stuff that fills in those gaps.

845
00:39:29,800 --> 00:39:32,080
Speaker 1: And you know, the same must be true in biology, right,

846
00:39:32,200 --> 00:39:34,239
Speaker 1: that's what the duck billed platypus is. Right, It's like,

847
00:39:34,320 --> 00:39:36,759
Speaker 1: hold on a second, what do you mean mammals?

848
00:39:36,840 --> 00:39:37,040
Speaker 6: You know?

849
00:39:37,640 --> 00:39:39,840
Speaker 4: Right? Right? It's nature's way of being, like, you cannot

850
00:39:39,880 --> 00:39:40,760
Speaker 4: put me in a box.

851
00:39:41,760 --> 00:39:44,239
Speaker 1: Yeah, so that's the space bean. Also, I'm saying the

852
00:39:44,239 --> 00:39:46,120
Speaker 1: space bean because it is fun to say, and because

853
00:39:46,120 --> 00:39:48,319
Speaker 1: I'm trying to avoid having to pronounce the actual name

854
00:39:48,360 --> 00:39:48,759
Speaker 1: of the thing.

855
00:39:49,040 --> 00:39:51,520
Speaker 4: Yeah. No, sure, that makes sense. Okay, So here's what

856
00:39:51,560 --> 00:39:54,400
Speaker 4: I want to know. So we're not taught that the

857
00:39:54,480 --> 00:39:57,719
Speaker 4: space bean is a moon in school, or at least

858
00:39:57,760 --> 00:40:00,080
Speaker 4: I wasn't. So if you were to walk into a

859
00:40:00,160 --> 00:40:05,239
Speaker 4: random astronomer's office at some university and ask them does

860
00:40:05,280 --> 00:40:07,560
Speaker 4: the space being count as a moon? Are they going

861
00:40:07,640 --> 00:40:10,000
Speaker 4: to like roll their eyes and be like not this again.

862
00:40:10,200 --> 00:40:12,000
Speaker 4: Or are they going to be like, oh, that's a

863
00:40:12,040 --> 00:40:15,960
Speaker 4: really interesting question, Like how does the astronomy community view

864
00:40:16,040 --> 00:40:16,600
Speaker 4: this question?

865
00:40:17,800 --> 00:40:19,680
Speaker 1: That's a great question. I bet that half of them

866
00:40:19,680 --> 00:40:21,520
Speaker 1: would roll their eyes, and half of them would be like,

867
00:40:21,920 --> 00:40:24,600
Speaker 1: you know, I was on the committee that decided what

868
00:40:24,719 --> 00:40:26,920
Speaker 1: a quasi satellite is, and I have a very strong

869
00:40:26,960 --> 00:40:29,160
Speaker 1: opinion about it, because you know, they get hot headed

870
00:40:29,200 --> 00:40:30,279
Speaker 1: about this stuff.

871
00:40:30,080 --> 00:40:31,919
Speaker 4: Right, And you will now sit for three hours while

872
00:40:31,920 --> 00:40:35,560
Speaker 4: I explain the difference to you and you regret asking immediately.

873
00:40:35,760 --> 00:40:38,160
Speaker 1: Yeah, And sometimes I wonder, like, what does it matter?

874
00:40:38,480 --> 00:40:40,680
Speaker 1: You know, people argue about whether Pluto is a planet

875
00:40:40,800 --> 00:40:43,480
Speaker 1: or a dwarf planet, like what are the consequences? Why

876
00:40:43,480 --> 00:40:46,680
Speaker 1: does anybody really care? We're just making these names up.

877
00:40:46,719 --> 00:40:49,480
Speaker 1: It doesn't change what Pluto is. It's not like Pluto

878
00:40:49,719 --> 00:40:52,520
Speaker 1: shrinks if we call it a dwarf planet or grows

879
00:40:52,719 --> 00:40:55,239
Speaker 1: in importance if we call it a real planet. These

880
00:40:55,280 --> 00:40:58,440
Speaker 1: are just our arbitrary categorizations of the universe, so they

881
00:40:58,480 --> 00:41:00,640
Speaker 1: affect how we think and how we te but really

882
00:41:00,719 --> 00:41:02,040
Speaker 1: it's inconsequential.

883
00:41:02,120 --> 00:41:02,279
Speaker 9: You know.

884
00:41:02,280 --> 00:41:03,600
Speaker 4: I can see why it would matter to you if

885
00:41:03,600 --> 00:41:05,640
Speaker 4: you are an astronomer, because maybe it affects the way

886
00:41:05,680 --> 00:41:08,560
Speaker 4: you model things based on how these definitions fall out.

887
00:41:08,680 --> 00:41:10,759
Speaker 4: But I imagine to the lay public it's like, what

888
00:41:10,800 --> 00:41:12,040
Speaker 4: are we paying these people for.

889
00:41:13,400 --> 00:41:16,080
Speaker 1: That's a good point, that's a good point. And so

890
00:41:16,280 --> 00:41:18,840
Speaker 1: we have this thing, this second Moon's is a quasi satellite,

891
00:41:19,080 --> 00:41:21,040
Speaker 1: And that's just one example. You know, there are lots

892
00:41:21,080 --> 00:41:23,759
Speaker 1: of these things that are sort of loosely bound to

893
00:41:23,800 --> 00:41:27,280
Speaker 1: the Earth orbiting the Sun, and that can be fairly small,

894
00:41:27,320 --> 00:41:29,920
Speaker 1: like this thing is only five kilometers in diameter. As

895
00:41:29,960 --> 00:41:32,239
Speaker 1: you get smaller and smaller, there are many, many more

896
00:41:32,280 --> 00:41:34,560
Speaker 1: of these things, some of them are more loosely bound

897
00:41:34,640 --> 00:41:36,560
Speaker 1: to the Earth. But you know, if you're gonna call

898
00:41:36,600 --> 00:41:38,200
Speaker 1: this thing a moon, then you've got to call all

899
00:41:38,200 --> 00:41:41,239
Speaker 1: those other little things moons also. So if you're gonna

900
00:41:41,239 --> 00:41:43,400
Speaker 1: open the door that wide, then Earth is gonna have

901
00:41:43,520 --> 00:41:44,560
Speaker 1: a lot of little moons.

902
00:41:44,640 --> 00:41:47,160
Speaker 4: And high school astronomy becomes totally untenable.

903
00:41:48,800 --> 00:41:50,840
Speaker 1: And unfortunately, it doesn't change what it looks like in

904
00:41:50,880 --> 00:41:52,520
Speaker 1: the sky. Right, You can't look up in the sky

905
00:41:52,600 --> 00:41:55,360
Speaker 1: and see this thing. The closest that ever comes to

906
00:41:55,440 --> 00:41:58,759
Speaker 1: Earth is like seven and a half million miles away,

907
00:41:58,800 --> 00:42:02,319
Speaker 1: which is thirty times further away from the Earth than

908
00:42:02,400 --> 00:42:05,480
Speaker 1: our moon is. Plus, of course it's super tiny, so

909
00:42:05,560 --> 00:42:07,400
Speaker 1: you have almost no chance of spotting this thing. It

910
00:42:07,440 --> 00:42:10,360
Speaker 1: was difficult for astronomers to even see it in the

911
00:42:10,360 --> 00:42:12,720
Speaker 1: first place. It was only discovered in the last twenty years.

912
00:42:12,880 --> 00:42:14,760
Speaker 4: Is it safe to assume that its center of mass

913
00:42:14,800 --> 00:42:16,600
Speaker 4: is within the Earth or the center of mass for

914
00:42:16,680 --> 00:42:18,440
Speaker 4: the two bodies falls within Earth?

915
00:42:18,600 --> 00:42:21,440
Speaker 1: Absolutely? Yeah, because the Earth totally dominates this thing when

916
00:42:21,480 --> 00:42:23,800
Speaker 1: it comes to mass. This thing is only five kilometers

917
00:42:23,840 --> 00:42:25,520
Speaker 1: in diameter and it's just a big chunk of rock,

918
00:42:25,840 --> 00:42:27,319
Speaker 1: and so the Earth dwarfs this thing.

919
00:42:27,560 --> 00:42:30,200
Speaker 4: Okay, even though it's super far away, it still works. Okay,

920
00:42:30,320 --> 00:42:33,880
Speaker 4: that's our best candidates. Is there like a second best candidate.

921
00:42:34,040 --> 00:42:36,120
Speaker 1: There's something else which I think is super fun, which

922
00:42:36,280 --> 00:42:40,680
Speaker 1: astronomers and science communicators called a temporary moon for a while.

923
00:42:40,880 --> 00:42:43,480
Speaker 1: And this is a weird object which at the end

924
00:42:43,480 --> 00:42:46,800
Speaker 1: of last year sort of swooped in from deep space

925
00:42:46,880 --> 00:42:50,440
Speaker 1: and orbited the Earth a couple of times, and people

926
00:42:50,440 --> 00:42:52,120
Speaker 1: are like, oh, what is this thing? It was like

927
00:42:52,200 --> 00:42:55,120
Speaker 1: only forty feet long, and it has this strange cylindrical

928
00:42:55,160 --> 00:42:58,200
Speaker 1: shape and they spotted it on a telescope and they're like,

929
00:42:58,239 --> 00:43:00,680
Speaker 1: wait a second, what is this thing? And it looks

930
00:43:00,760 --> 00:43:02,560
Speaker 1: like a piece of a rocket.

931
00:43:02,760 --> 00:43:04,360
Speaker 4: What it's space debris.

932
00:43:04,480 --> 00:43:07,160
Speaker 1: It's space debris. And so it turns out this is

933
00:43:07,200 --> 00:43:10,040
Speaker 1: a long lost piece of an ill fated NASA mission.

934
00:43:10,400 --> 00:43:13,640
Speaker 1: There was this mission in nineteen sixty six called survey

935
00:43:13,760 --> 00:43:16,239
Speaker 1: Or two. It is a robotic spacecraft that was going

936
00:43:16,320 --> 00:43:18,200
Speaker 1: to go land on the Moon and it was going

937
00:43:18,239 --> 00:43:21,120
Speaker 1: to go explore the Moon, et cetera. But mid course,

938
00:43:21,200 --> 00:43:23,680
Speaker 1: there was a failure in the sort of ballistics and

939
00:43:23,719 --> 00:43:27,000
Speaker 1: the trajection and they lost contact with the craft and

940
00:43:27,040 --> 00:43:29,600
Speaker 1: one of the thrusters failed to ignite, and so basically

941
00:43:29,680 --> 00:43:31,719
Speaker 1: they lost this thing. Part of it crashed on the Moon,

942
00:43:31,960 --> 00:43:34,120
Speaker 1: and part of it just like tumbled out into deep

943
00:43:34,120 --> 00:43:37,279
Speaker 1: space sort of lost, they thought, forever. And so this

944
00:43:37,320 --> 00:43:40,480
Speaker 1: thing has been like out there in space for you

945
00:43:40,480 --> 00:43:45,440
Speaker 1: know what, seventy years, almost bouncing around, swoshing around, and

946
00:43:45,560 --> 00:43:48,480
Speaker 1: somehow it ended up coming back to Earth.

947
00:43:48,680 --> 00:43:50,640
Speaker 4: That's crazy, first of all, I think it's more like

948
00:43:50,680 --> 00:43:53,120
Speaker 4: fifty years though, right, But like it's amazing that we

949
00:43:53,280 --> 00:43:57,080
Speaker 4: have that much resolution that we could find it again.

950
00:43:57,160 --> 00:43:59,840
Speaker 1: It's really incredible. But you know, we are monitoring stuff

951
00:43:59,880 --> 00:44:02,200
Speaker 1: that comes close to Earth, and we're looking for stuff

952
00:44:02,200 --> 00:44:04,080
Speaker 1: that's sort of like tumbling towards the Earth. This is

953
00:44:04,120 --> 00:44:07,640
Speaker 1: a pretty small object though that it's also a weird shape, right,

954
00:44:07,760 --> 00:44:09,600
Speaker 1: if you're looking out into space and you see this

955
00:44:09,760 --> 00:44:12,360
Speaker 1: forty foot long cylindrical object, My first guess is going

956
00:44:12,440 --> 00:44:16,000
Speaker 1: to be like aliens, right, and so how disappointing to

957
00:44:16,040 --> 00:44:18,480
Speaker 1: look at it and then see like USA written down

958
00:44:18,480 --> 00:44:23,680
Speaker 1: the side. It's just our old trash, but it's fascinating.

959
00:44:23,680 --> 00:44:25,520
Speaker 1: People have done a study to figure out like what

960
00:44:25,680 --> 00:44:27,799
Speaker 1: happened to it, and it turns out that when it

961
00:44:27,840 --> 00:44:30,640
Speaker 1: tumbled out into space, it was very gently pushed further

962
00:44:30,800 --> 00:44:35,120
Speaker 1: into space by the pressure of sunlight. We've talked about

963
00:44:35,120 --> 00:44:37,440
Speaker 1: this on the podcast, that you could build a spaceship

964
00:44:37,480 --> 00:44:40,759
Speaker 1: that sails on light. It's called a solar sail. Just

965
00:44:40,800 --> 00:44:43,799
Speaker 1: have a huge sheet of material and the photons from

966
00:44:43,800 --> 00:44:45,760
Speaker 1: the sun when they hit it are going to transfer

967
00:44:45,840 --> 00:44:49,600
Speaker 1: their momentum to that, just like wind on Earth transfers

968
00:44:49,640 --> 00:44:52,040
Speaker 1: it to momentum to a sail on a sailboat. And

969
00:44:52,120 --> 00:44:54,960
Speaker 1: so that's like by design. But here, of course, it's

970
00:44:55,080 --> 00:44:57,839
Speaker 1: just a rocket tumbling in space was very gently, over

971
00:44:57,960 --> 00:45:00,840
Speaker 1: decades and decades pushed deeper into space.

972
00:45:00,960 --> 00:45:02,920
Speaker 4: Are you familiar with Project Westward?

973
00:45:03,320 --> 00:45:03,520
Speaker 6: No?

974
00:45:03,600 --> 00:45:05,840
Speaker 4: Tell me, Oh my gosh. So the idea here was

975
00:45:05,840 --> 00:45:07,960
Speaker 4: so this was like during the Cold War, and the

976
00:45:08,080 --> 00:45:10,200
Speaker 4: US was worried that they would lose their ability to

977
00:45:10,200 --> 00:45:14,239
Speaker 4: communicate with other nations if our undersea cables got cut

978
00:45:14,239 --> 00:45:17,239
Speaker 4: by the Soviets. And so in that case, we would

979
00:45:17,239 --> 00:45:19,840
Speaker 4: have to rely on sending radio waves up and we

980
00:45:19,880 --> 00:45:22,160
Speaker 4: would have to hope that they would bounce off the ionosphere.

981
00:45:22,360 --> 00:45:24,400
Speaker 4: But that's sort of a not super reliable way of

982
00:45:24,440 --> 00:45:27,800
Speaker 4: sending radio communications. And so I think it was MIT

983
00:45:28,080 --> 00:45:30,200
Speaker 4: came up with this solution where they were like, well,

984
00:45:30,440 --> 00:45:33,880
Speaker 4: we could be sure that the ionosphere would have stuff

985
00:45:34,480 --> 00:45:37,200
Speaker 4: that would bounce the radio waves back if we put

986
00:45:37,320 --> 00:45:42,840
Speaker 4: up over four hundred million copper needles. What that's a

987
00:45:42,880 --> 00:45:45,880
Speaker 4: great idea, right, And so the argument was that you

988
00:45:45,920 --> 00:45:48,200
Speaker 4: would put these needles up and it would give us

989
00:45:48,239 --> 00:45:50,160
Speaker 4: some information about how well this was going to work.

990
00:45:50,280 --> 00:45:52,680
Speaker 4: But in about two to three years, the combination of

991
00:45:52,760 --> 00:45:56,960
Speaker 4: gravity and the sun pushing these needles back into the

992
00:45:57,000 --> 00:45:59,320
Speaker 4: atmosphere would clear everything.

993
00:45:58,960 --> 00:46:02,359
Speaker 1: Out, everything out. Does that mean these copper needles come

994
00:46:02,480 --> 00:46:05,160
Speaker 1: raining back down to the surface to impale people.

995
00:46:05,040 --> 00:46:08,120
Speaker 4: Well, they do start raining back down towards Earth, but

996
00:46:08,160 --> 00:46:10,600
Speaker 4: they're like literally only a couple maybe centimeters long, like

997
00:46:10,600 --> 00:46:12,960
Speaker 4: maybe two centimeters or something. These aren't huge, and that's

998
00:46:12,960 --> 00:46:15,279
Speaker 4: why they needed four hundred million of them.

999
00:46:15,560 --> 00:46:18,640
Speaker 1: That sounds like approximately the size of a bullet. So

1000
00:46:18,680 --> 00:46:22,319
Speaker 1: you're talking about space bullets raining down on the Earth.

1001
00:46:22,080 --> 00:46:24,920
Speaker 4: But that would definitely burn up before it hits Earth, right.

1002
00:46:25,080 --> 00:46:27,880
Speaker 1: All right, yes, of course I think so, yeah woo.

1003
00:46:27,920 --> 00:46:29,879
Speaker 1: So our atmosphere is like a bulletproof vest.

1004
00:46:30,040 --> 00:46:32,480
Speaker 4: Yes, thank you atmosphere. But so the first one that

1005
00:46:32,480 --> 00:46:34,600
Speaker 4: they shot up there, it didn't deploy the right way,

1006
00:46:34,600 --> 00:46:37,120
Speaker 4: so a bunch of these needles clumped instead of spreading nicely,

1007
00:46:37,440 --> 00:46:40,359
Speaker 4: and so some of these clumps, fifty years later are

1008
00:46:40,400 --> 00:46:44,680
Speaker 4: still tracked as space debris because the clumps didn't deorbit

1009
00:46:44,719 --> 00:46:46,000
Speaker 4: the way that they thought they would. And then they

1010
00:46:46,040 --> 00:46:48,239
Speaker 4: did a second shot, and the second shot dispersed and

1011
00:46:48,239 --> 00:46:50,479
Speaker 4: they were able to confirm, yes, the radio waves bounce

1012
00:46:50,560 --> 00:46:53,839
Speaker 4: back more when we have supplemented the ionosphere with all

1013
00:46:53,880 --> 00:46:55,560
Speaker 4: of these needles. But then we had to go to

1014
00:46:55,600 --> 00:46:58,640
Speaker 4: the United Nations and promise we were gonna stop messing

1015
00:46:58,760 --> 00:47:00,920
Speaker 4: up the space environment and that we were going to

1016
00:47:00,920 --> 00:47:03,520
Speaker 4: consult people from here on out. And one of the

1017
00:47:03,600 --> 00:47:06,600
Speaker 4: articles of the Outer Space Treaty actually requires people to

1018
00:47:06,600 --> 00:47:10,320
Speaker 4: do consultations. And that was motivated by Project Westward because

1019
00:47:10,480 --> 00:47:13,440
Speaker 4: what the heck is the US doing so anyway, tangent

1020
00:47:13,520 --> 00:47:17,240
Speaker 4: related to the Sun pushing things back into orbits or sorry,

1021
00:47:17,280 --> 00:47:18,400
Speaker 4: back into the atmosphere.

1022
00:47:18,480 --> 00:47:20,600
Speaker 1: Yeah, and we have a whole fun podcast episode about

1023
00:47:20,719 --> 00:47:23,719
Speaker 1: space junk and how dangerous it is now it's all

1024
00:47:23,719 --> 00:47:26,000
Speaker 1: smashing into itself and if we don't get this stuff

1025
00:47:26,040 --> 00:47:28,799
Speaker 1: under control, all of space might be useless to us.

1026
00:47:28,880 --> 00:47:31,640
Speaker 1: We might be trapped down here on Earth because we'd

1027
00:47:31,680 --> 00:47:34,239
Speaker 1: be surrounded by our own garbage. So check out that

1028
00:47:34,280 --> 00:47:37,000
Speaker 1: episode if you're interested. But this is one particularly interesting

1029
00:47:37,320 --> 00:47:41,000
Speaker 1: object and it came in November twenty twenty and made

1030
00:47:41,120 --> 00:47:43,600
Speaker 1: a few large loops around the Earth. And so that's

1031
00:47:43,600 --> 00:47:45,879
Speaker 1: why they called this sort of like a temporary moon,

1032
00:47:46,160 --> 00:47:49,280
Speaker 1: because even though it was lost in deep space, somehow

1033
00:47:49,320 --> 00:47:51,280
Speaker 1: it ended up close enough for the Earth to grab

1034
00:47:51,320 --> 00:47:54,640
Speaker 1: it again and loop around. But it wasn't a stable orbit,

1035
00:47:54,680 --> 00:47:56,800
Speaker 1: which is really fascinating. It was like stable enough to

1036
00:47:56,840 --> 00:47:58,919
Speaker 1: loop around a few times and then get tossed back

1037
00:47:58,960 --> 00:48:01,920
Speaker 1: out into space. So in March twenty twenty one it

1038
00:48:01,960 --> 00:48:05,360
Speaker 1: continued his journey and is now back into deep space somewhere.

1039
00:48:05,520 --> 00:48:08,960
Speaker 4: WHOA. So was this like a ci calm angle for

1040
00:48:09,000 --> 00:48:11,720
Speaker 4: getting people interested in this? Because it seems like because

1041
00:48:11,719 --> 00:48:14,799
Speaker 4: it was artificial, it shouldn't count as a moon at all,

1042
00:48:15,160 --> 00:48:17,359
Speaker 4: not a temporary moon, it shouldn't be a moon. Or

1043
00:48:17,400 --> 00:48:19,560
Speaker 4: do different people use different definitions than the one that

1044
00:48:19,560 --> 00:48:21,480
Speaker 4: we settled upon at the beginning of the episode.

1045
00:48:21,640 --> 00:48:24,120
Speaker 1: Yeah, exactly. I think this was just a clickbait moon,

1046
00:48:24,440 --> 00:48:27,160
Speaker 1: not really a moon by any definition. If you're going

1047
00:48:27,200 --> 00:48:29,799
Speaker 1: to require that moons be natural, then they not be

1048
00:48:30,440 --> 00:48:33,480
Speaker 1: manufactured by humanity. Then this is definitely not a mood.

1049
00:48:33,600 --> 00:48:35,760
Speaker 1: But it's cool that we captured something from deep space

1050
00:48:35,800 --> 00:48:38,520
Speaker 1: and it orbited us a little while before going back

1051
00:48:38,560 --> 00:48:40,640
Speaker 1: out into the dark deep emptiness.

1052
00:48:40,719 --> 00:48:42,920
Speaker 4: Yeah no, that's super cool. All right, So let's take

1053
00:48:42,920 --> 00:48:44,919
Speaker 4: our second break before we start to talk a bit

1054
00:48:44,920 --> 00:48:47,640
Speaker 4: more about moons on planets other than our own.

1055
00:48:52,360 --> 00:48:54,160
Speaker 1: When you pop a piece of cheese into your mouth

1056
00:48:54,239 --> 00:48:57,400
Speaker 1: or enjoy a rich spoonful of greeky yogurt, you're probably

1057
00:48:57,440 --> 00:49:01,520
Speaker 1: not thinking about the environmental impact of each and every bite.

1058
00:49:01,520 --> 00:49:04,120
Speaker 1: But the people in the dairy industry are us. Dairy

1059
00:49:04,160 --> 00:49:08,480
Speaker 1: has set themselves some ambitious sustainability goals, including being greenhouse

1060
00:49:08,480 --> 00:49:11,080
Speaker 1: gas neutral by twenty to fifty That's why they're working

1061
00:49:11,120 --> 00:49:13,480
Speaker 1: hard every day to find new ways to reduce waste,

1062
00:49:13,520 --> 00:49:17,719
Speaker 1: conserve natural resources, and drive down greenhouse gas emissions. Take water,

1063
00:49:17,800 --> 00:49:20,839
Speaker 1: For example, most dairy farms reuse water up to four

1064
00:49:20,920 --> 00:49:24,400
Speaker 1: times the same water cools the milk, cleans equipment, washes

1065
00:49:24,440 --> 00:49:27,240
Speaker 1: the barn, and irrigates the crops. How is US dairy

1066
00:49:27,239 --> 00:49:31,000
Speaker 1: tackling greenhouse gases? Many farms use anaerobic digestors that turn

1067
00:49:31,040 --> 00:49:34,960
Speaker 1: the methane from maneure into renewable energy that can power farms, towns,

1068
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Speaker 1: and electric cars. So the next time you grab a

1069
00:49:37,080 --> 00:49:39,120
Speaker 1: slice of pizza or lick an ice cream cone, know

1070
00:49:39,160 --> 00:49:41,839
Speaker 1: that dairy farmers and processors around the country are using

1071
00:49:41,880 --> 00:49:45,399
Speaker 1: the latest practices and innovations to provide the nutrient dense

1072
00:49:45,520 --> 00:49:48,239
Speaker 1: dairy products we love with less of an impact. Visit

1073
00:49:48,320 --> 00:49:51,120
Speaker 1: usdairy dot com slash sustainability to learn more.

1074
00:49:52,160 --> 00:49:55,680
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00:50:00,360 --> 00:50:03,880
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1078
00:50:03,880 --> 00:50:06,200
Speaker 3: from the California Office of Traffic Safety and Caltrans.

1079
00:50:06,280 --> 00:50:08,640
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1100
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Speaker 4: Okay, so we talked a bit about how Earth has

1101
00:51:16,200 --> 00:51:19,960
Speaker 4: one for sure moon and a couple maybe.

1102
00:51:19,560 --> 00:51:22,280
Speaker 1: Moons, quasi moons, quasi moons.

1103
00:51:22,400 --> 00:51:24,160
Speaker 4: Right, tell me a bit more about what else is

1104
00:51:24,200 --> 00:51:26,360
Speaker 4: typical in the Solar System. How many moons do the

1105
00:51:26,400 --> 00:51:27,080
Speaker 4: other planets have.

1106
00:51:27,239 --> 00:51:30,200
Speaker 1: It's really interesting because the Earth, as we were saying,

1107
00:51:30,360 --> 00:51:34,240
Speaker 1: is really weird, Like having a really big moon is weird. Also,

1108
00:51:34,560 --> 00:51:37,880
Speaker 1: having just one moon is weird. So the eighth planets

1109
00:51:37,880 --> 00:51:39,919
Speaker 1: in the Solar System. Of course the Earth has one moon.

1110
00:51:40,160 --> 00:51:44,280
Speaker 1: Two of the planets have no moons, Mercury and Venus,

1111
00:51:44,320 --> 00:51:48,040
Speaker 1: and the other five planets have two hundred and four

1112
00:51:48,160 --> 00:51:51,880
Speaker 1: moons in between them. So that's really fascinating and you

1113
00:51:51,960 --> 00:51:54,799
Speaker 1: might wonder like, well, why do Mercury and Venus have

1114
00:51:54,920 --> 00:51:58,000
Speaker 1: no moons? And the reason is that they are so

1115
00:51:58,239 --> 00:52:02,680
Speaker 1: close to the Sun. Is this like really terrible overwhelming

1116
00:52:02,760 --> 00:52:06,560
Speaker 1: gravitational force and it tugs on things. We talked in

1117
00:52:06,560 --> 00:52:09,759
Speaker 1: the program before about tidal forces. The closer you are

1118
00:52:09,840 --> 00:52:12,160
Speaker 1: to the Sun, the more it tugs on you. So

1119
00:52:12,239 --> 00:52:14,160
Speaker 1: if you're an object that's not just like a point,

1120
00:52:14,320 --> 00:52:16,319
Speaker 1: if you have like an extent to you, then the

1121
00:52:16,360 --> 00:52:18,600
Speaker 1: Sun is going to tug harder on the bit that's

1122
00:52:18,640 --> 00:52:21,560
Speaker 1: closer and not as hard on the bit that's further away,

1123
00:52:21,800 --> 00:52:23,799
Speaker 1: and that's an effective force on you. So the Sun is,

1124
00:52:23,800 --> 00:52:26,960
Speaker 1: for example, squeezing Mercury and Venus all the time. It's

1125
00:52:27,000 --> 00:52:29,239
Speaker 1: pulling on them, and that makes it very hard for

1126
00:52:29,360 --> 00:52:33,000
Speaker 1: them to have anything in a stable orbit around them. Basically,

1127
00:52:33,000 --> 00:52:34,880
Speaker 1: if they have a moon, the Sun is going to

1128
00:52:34,960 --> 00:52:37,520
Speaker 1: steal it when it swoops around the planet on the

1129
00:52:37,560 --> 00:52:38,280
Speaker 1: close side.

1130
00:52:38,360 --> 00:52:40,319
Speaker 4: So here I'm finding that I want to ask you

1131
00:52:40,360 --> 00:52:43,160
Speaker 4: if that means in other Solar systems the close planets

1132
00:52:43,200 --> 00:52:45,320
Speaker 4: don't have moons. But I'm jumping if I do that, aren't.

1133
00:52:45,120 --> 00:52:47,480
Speaker 1: I We don't know the answer to that question yet.

1134
00:52:47,560 --> 00:52:49,600
Speaker 1: We'll talk about that in a minute, but yeah, it's

1135
00:52:49,600 --> 00:52:52,720
Speaker 1: a fascinating question. We know that in our Solar system,

1136
00:52:52,800 --> 00:52:56,279
Speaker 1: the innermost planets Mercury and Venus have no moons, and

1137
00:52:56,320 --> 00:52:58,799
Speaker 1: you know, that might be part of the answer of

1138
00:52:58,880 --> 00:53:01,320
Speaker 1: why the Earth only has one moon, and it's a

1139
00:53:01,360 --> 00:53:04,200
Speaker 1: really big one. It might be that anything else the

1140
00:53:04,280 --> 00:53:07,320
Speaker 1: Sun is basically gonna steal, and that we're only capable

1141
00:53:07,320 --> 00:53:10,600
Speaker 1: of having like either really big moons or quasi moons

1142
00:53:10,600 --> 00:53:13,399
Speaker 1: that we're sort of sharing with the Sun. That might

1143
00:53:13,480 --> 00:53:15,160
Speaker 1: be the partial answer to that question.

1144
00:53:15,400 --> 00:53:17,040
Speaker 4: Interesting, So we have the Sun to banks of a

1145
00:53:17,040 --> 00:53:17,560
Speaker 4: space being.

1146
00:53:17,800 --> 00:53:20,080
Speaker 1: Yeah, the Sun is toasting our space being for us.

1147
00:53:20,120 --> 00:53:22,160
Speaker 1: But then further out in the Solar System there are

1148
00:53:22,239 --> 00:53:25,120
Speaker 1: lots and lots of moons. You know, the other five

1149
00:53:25,160 --> 00:53:27,879
Speaker 1: planets with moons have two hundred and four of these

1150
00:53:27,920 --> 00:53:30,960
Speaker 1: things combined. You know, in Jupiter and Saturn have like

1151
00:53:31,040 --> 00:53:34,080
Speaker 1: dozens of them, and you know, Saturn has this crazy

1152
00:53:34,160 --> 00:53:37,600
Speaker 1: ring system, and inside those rings are rocks that are

1153
00:53:37,600 --> 00:53:41,839
Speaker 1: big enough to be considered moons. Sometimes they're called you know, moonlits.

1154
00:53:41,920 --> 00:53:44,960
Speaker 1: Sometimes they are called minor moons. But there are all

1155
00:53:45,000 --> 00:53:47,319
Speaker 1: sorts of things. And so the deeper you go out

1156
00:53:47,320 --> 00:53:50,200
Speaker 1: into our Solar system, the more you find these objects

1157
00:53:50,200 --> 00:53:52,400
Speaker 1: that have moons and lots and lots of moons.

1158
00:53:52,480 --> 00:53:54,920
Speaker 4: So do any of the moons have moons?

1159
00:53:55,160 --> 00:53:56,880
Speaker 1: I wish they did have moons? And what would you

1160
00:53:56,880 --> 00:53:58,879
Speaker 1: call that anyway? Would that be like a moon moon

1161
00:53:59,200 --> 00:54:05,279
Speaker 1: or a way section? That's a great question. And so

1162
00:54:05,400 --> 00:54:08,719
Speaker 1: far we haven't found any moons that have moons. And

1163
00:54:08,760 --> 00:54:12,240
Speaker 1: the reason is similar to why Mercury doesn't have moons.

1164
00:54:12,520 --> 00:54:14,439
Speaker 1: And if you're a moon, then you're near a big

1165
00:54:14,480 --> 00:54:17,239
Speaker 1: planet and That means that there are tidal forces, and

1166
00:54:17,280 --> 00:54:19,719
Speaker 1: so it's pretty hard to hold on to something and

1167
00:54:19,760 --> 00:54:22,280
Speaker 1: not have it gets slurfed up and just become another

1168
00:54:22,360 --> 00:54:25,399
Speaker 1: moon of the planet you're orbiting. Yeah, So if you're

1169
00:54:25,440 --> 00:54:28,480
Speaker 1: Io and you're orbiting Jupiter, right, Jupiter is an enormous

1170
00:54:28,520 --> 00:54:31,479
Speaker 1: gravitational pull it. The reason that Io is like hot

1171
00:54:31,520 --> 00:54:34,680
Speaker 1: inside is because of Jupiter's tidle forces, and so anything

1172
00:54:34,880 --> 00:54:37,560
Speaker 1: orbiting Io is just going to get pulled away. It's very,

1173
00:54:37,640 --> 00:54:41,080
Speaker 1: very hard to have a stable orbit. Although there's this

1174
00:54:41,280 --> 00:54:44,800
Speaker 1: really crazy moon of Saturn. This moon is called Rhea,

1175
00:54:45,160 --> 00:54:48,560
Speaker 1: and recently they've spotted some stuff in orbit around Ria,

1176
00:54:48,760 --> 00:54:52,160
Speaker 1: maybe sort of like these very small particles. It almost

1177
00:54:52,239 --> 00:54:56,440
Speaker 1: looks like this moon of Saturn has its own ring system.

1178
00:54:56,719 --> 00:54:59,719
Speaker 1: What I know, isn't that cool? I never thought about

1179
00:54:59,760 --> 00:55:02,800
Speaker 1: like a moon with rings around it is pretty cool.

1180
00:55:03,080 --> 00:55:06,000
Speaker 4: That's awesome. So how if it can't have moons, how

1181
00:55:06,040 --> 00:55:08,080
Speaker 4: does it manage to maintain its rings?

1182
00:55:08,440 --> 00:55:11,080
Speaker 1: Well, the reason you sometimes have rings instead of moons

1183
00:55:11,080 --> 00:55:14,239
Speaker 1: are because of tidal forces. Basically, rings are moons that

1184
00:55:14,280 --> 00:55:17,160
Speaker 1: have been torn apart by tidal forces, and so it

1185
00:55:17,280 --> 00:55:19,279
Speaker 1: might be that there was an object there and that

1186
00:55:19,360 --> 00:55:21,840
Speaker 1: it got sort of shredded by tidal forces, and what

1187
00:55:21,880 --> 00:55:24,600
Speaker 1: we're seeing is something transient that these rings might not

1188
00:55:24,719 --> 00:55:26,799
Speaker 1: last for very long. You know, by very long we

1189
00:55:26,880 --> 00:55:29,239
Speaker 1: mean on astrophysical timescale, So they might be there a

1190
00:55:29,239 --> 00:55:31,520
Speaker 1: million years or so, but if you leave the solar

1191
00:55:31,520 --> 00:55:33,759
Speaker 1: system and come back in five hundred million, you might

1192
00:55:33,760 --> 00:55:35,080
Speaker 1: find that they're not there anymore.

1193
00:55:35,480 --> 00:55:38,319
Speaker 4: Okay, so let's move out of our solar system? What

1194
00:55:38,360 --> 00:55:40,760
Speaker 4: does this look like in other solar systems? So, for example,

1195
00:55:40,840 --> 00:55:44,719
Speaker 4: do the mercury and venus equivalents and other solar systems

1196
00:55:44,840 --> 00:55:47,680
Speaker 4: lack moons like we see in our solar system.

1197
00:55:47,800 --> 00:55:50,120
Speaker 1: It's such a good question and one we just don't

1198
00:55:50,160 --> 00:55:53,320
Speaker 1: know the answer to yet because we have never seen

1199
00:55:53,600 --> 00:55:56,799
Speaker 1: a moon in another solar system, Like every moon that

1200
00:55:56,920 --> 00:55:59,719
Speaker 1: any human has ever seen has only ever been in

1201
00:55:59,800 --> 00:56:03,680
Speaker 1: our solar system. Isn't that like crazy and slightly frustrating?

1202
00:56:03,880 --> 00:56:06,239
Speaker 4: Yeah, it's both of those things. And it reveals to

1203
00:56:06,280 --> 00:56:08,400
Speaker 4: me like just how often I assume that science has

1204
00:56:08,440 --> 00:56:10,520
Speaker 4: figured out so many things that are much harder than

1205
00:56:10,719 --> 00:56:13,319
Speaker 4: I apparently understand. So why do we know that all

1206
00:56:13,320 --> 00:56:15,360
Speaker 4: these other solar systems have planets, but we don't know

1207
00:56:15,400 --> 00:56:16,280
Speaker 4: that they have moons.

1208
00:56:16,400 --> 00:56:18,520
Speaker 1: Well, moons are much smaller, and they're just harder to

1209
00:56:18,520 --> 00:56:20,799
Speaker 1: see than planets. You know. We now sort of take

1210
00:56:20,840 --> 00:56:23,800
Speaker 1: it for granted that we can see planets around other stars,

1211
00:56:23,880 --> 00:56:26,880
Speaker 1: but that's pretty recent. It was like ninety five that

1212
00:56:26,920 --> 00:56:28,759
Speaker 1: we started to be able to really do this and

1213
00:56:28,800 --> 00:56:32,120
Speaker 1: spot planets in other solar systems. Until then, we had

1214
00:56:32,160 --> 00:56:35,480
Speaker 1: never seen a planet around a star that wasn't our star.

1215
00:56:35,960 --> 00:56:38,839
Speaker 1: We didn't know until then, if, for example, our star

1216
00:56:39,000 --> 00:56:41,279
Speaker 1: was the only one that had planets, we could have

1217
00:56:41,320 --> 00:56:44,400
Speaker 1: been like the weirdest star in the universe. Now, of

1218
00:56:44,400 --> 00:56:46,640
Speaker 1: course we know because we've looked and we've seen that

1219
00:56:46,719 --> 00:56:48,520
Speaker 1: lots and lots and lots of stars have lots and

1220
00:56:48,520 --> 00:56:50,560
Speaker 1: lots of planets. We're also learning, of course, that our

1221
00:56:50,560 --> 00:56:52,880
Speaker 1: Solar system is weird in all sorts of interesting ways.

1222
00:56:53,000 --> 00:56:55,800
Speaker 1: But the problem is that the techniques we use to

1223
00:56:55,840 --> 00:56:59,160
Speaker 1: see those planets are better when the planets are large

1224
00:56:59,200 --> 00:57:01,640
Speaker 1: and when they're close to the Sun, and that makes

1225
00:57:01,680 --> 00:57:04,160
Speaker 1: it pretty hard to see moons, which tend to be

1226
00:57:04,239 --> 00:57:06,239
Speaker 1: small and further from the star.

1227
00:57:06,400 --> 00:57:09,840
Speaker 4: We haven't found any instances of a moon that's like huge,

1228
00:57:10,000 --> 00:57:11,880
Speaker 4: or one of those instances where it's hard to determine

1229
00:57:11,880 --> 00:57:13,640
Speaker 4: which one is the planet and which one's the moon,

1230
00:57:13,680 --> 00:57:16,720
Speaker 4: because they're both pretty big and so there's no big

1231
00:57:16,760 --> 00:57:20,240
Speaker 4: things that break this rule. We haven't confirmed any moons

1232
00:57:20,240 --> 00:57:21,200
Speaker 4: and other solar systems.

1233
00:57:21,640 --> 00:57:23,960
Speaker 1: You're looking for the duck built platypus of moons out

1234
00:57:23,960 --> 00:57:26,520
Speaker 1: there somewhere. No so far as zero. There have been

1235
00:57:26,600 --> 00:57:29,880
Speaker 1: some candidates. People have some really clever ideas for how

1236
00:57:29,920 --> 00:57:33,720
Speaker 1: you might see moons around planets in other solar systems.

1237
00:57:34,200 --> 00:57:36,480
Speaker 1: Like one way that we see the planet is that

1238
00:57:36,520 --> 00:57:39,160
Speaker 1: the planet passes in front of the star, makes like

1239
00:57:39,160 --> 00:57:41,760
Speaker 1: a little eclipse, It like dims the star a little bit,

1240
00:57:42,080 --> 00:57:43,760
Speaker 1: And if it does that several times, you can see

1241
00:57:43,760 --> 00:57:45,640
Speaker 1: a pattern, so you can get a sense for like, oh,

1242
00:57:45,640 --> 00:57:47,760
Speaker 1: this is really something that's passing in front of the star.

1243
00:57:47,760 --> 00:57:49,840
Speaker 1: It must be a planet. Now, if there's a moon

1244
00:57:49,920 --> 00:57:52,760
Speaker 1: around that planet and it's orbiting that planet as it

1245
00:57:53,040 --> 00:57:55,960
Speaker 1: passes around the planet, it might add to that eclipse

1246
00:57:56,000 --> 00:57:58,760
Speaker 1: a little bit and then pass behind the planet and

1247
00:57:58,760 --> 00:58:01,960
Speaker 1: dip again. And if you have really refined measurements, you

1248
00:58:02,040 --> 00:58:05,760
Speaker 1: might see these like wiggles on the wiggles that tell

1249
00:58:05,800 --> 00:58:08,960
Speaker 1: you that there's something going around that planet and there

1250
00:58:09,000 --> 00:58:11,200
Speaker 1: are some cases where people look at the data and

1251
00:58:11,200 --> 00:58:13,200
Speaker 1: they're like, yeah, I think those are wiggles and wiggles,

1252
00:58:13,400 --> 00:58:15,720
Speaker 1: but other people analyze the same data and they're like, no,

1253
00:58:15,960 --> 00:58:18,200
Speaker 1: there's no evidence for that. So we're really at the

1254
00:58:18,360 --> 00:58:21,400
Speaker 1: edge of being able to detect exo moons. We haven't

1255
00:58:21,400 --> 00:58:22,240
Speaker 1: seen any yet.

1256
00:58:22,320 --> 00:58:24,960
Speaker 4: Well that's exciting, Like, hopefully in our lifetime we figure

1257
00:58:24,960 --> 00:58:25,600
Speaker 4: out how to do that.

1258
00:58:25,640 --> 00:58:28,240
Speaker 1: Well, yeah, hopefully in our lifetime. I mean, we were

1259
00:58:28,240 --> 00:58:30,000
Speaker 1: on the edge of learning so much about these other

1260
00:58:30,040 --> 00:58:33,400
Speaker 1: solar systems, like figuring out what's any atmosphere of those planets,

1261
00:58:33,440 --> 00:58:35,640
Speaker 1: seeing what moons there are. There was also a lot

1262
00:58:35,640 --> 00:58:37,440
Speaker 1: of excitement. I don't know if you remember about this

1263
00:58:37,440 --> 00:58:41,400
Speaker 1: one particular star called Tabby Star, which dimmed really weirdly

1264
00:58:41,880 --> 00:58:44,160
Speaker 1: all of a sudden, and people thought, like, wait a second,

1265
00:58:44,200 --> 00:58:46,400
Speaker 1: what's blocking this star? Is this evidence of like an

1266
00:58:46,440 --> 00:58:49,640
Speaker 1: alien mega structure. Is somebody out there building a dice

1267
00:58:49,680 --> 00:58:52,080
Speaker 1: and sphere around this star? Which was really fun and

1268
00:58:52,160 --> 00:58:54,480
Speaker 1: you know, inspired I'm sure a lot of science fiction novels.

1269
00:58:54,920 --> 00:58:56,560
Speaker 1: But it turns out that it was just like a

1270
00:58:56,560 --> 00:59:00,800
Speaker 1: big cloud of dust and debris. But it might be that, like,

1271
00:59:01,160 --> 00:59:03,320
Speaker 1: you know, there was a planet out there and it

1272
00:59:03,360 --> 00:59:06,480
Speaker 1: had a moon, and that moon got like tidally disrupted

1273
00:59:06,520 --> 00:59:09,280
Speaker 1: and torn up and ended up being this big cloud

1274
00:59:09,320 --> 00:59:12,120
Speaker 1: of stuff that partially blocked the star. So that might

1275
00:59:12,160 --> 00:59:14,880
Speaker 1: have been like, you know, evidence of the destruction of

1276
00:59:14,920 --> 00:59:15,720
Speaker 1: an excellent moon.

1277
00:59:16,000 --> 00:59:17,440
Speaker 4: WHOA, that's pretty cool.

1278
00:59:17,600 --> 00:59:20,560
Speaker 1: That's pretty cool. Yeah, But I'm looking forward to scientists

1279
00:59:20,600 --> 00:59:22,400
Speaker 1: figuring that out and so we can get a sense

1280
00:59:22,400 --> 00:59:25,720
Speaker 1: for like, how unusual is it to have just like

1281
00:59:25,800 --> 00:59:29,120
Speaker 1: one big moon, How unusual is it to have inner

1282
00:59:29,200 --> 00:59:31,600
Speaker 1: planets with no moons? How weird is it to have

1283
00:59:31,720 --> 00:59:34,680
Speaker 1: huge gas giants with like a dozen moons. We ask

1284
00:59:34,800 --> 00:59:37,200
Speaker 1: these basic questions because we just don't know the answers,

1285
00:59:37,200 --> 00:59:38,800
Speaker 1: and really the only way to figure it out is

1286
00:59:38,840 --> 00:59:41,240
Speaker 1: to go out there and explore the universe and to

1287
00:59:41,360 --> 00:59:44,400
Speaker 1: like actually look with our eyeballs and our telescopes and

1288
00:59:44,480 --> 00:59:45,240
Speaker 1: get the answers.

1289
00:59:45,480 --> 00:59:46,720
Speaker 4: It's a cool time to be alive.

1290
00:59:47,000 --> 00:59:49,120
Speaker 1: It is a cool time to be alive. So, Kelly,

1291
00:59:49,160 --> 00:59:50,600
Speaker 1: what are you going to go back and tell your

1292
00:59:50,600 --> 00:59:52,800
Speaker 1: seven year old about how many moons the Earth has?

1293
00:59:53,560 --> 00:59:55,760
Speaker 4: Well, I think she's going to be super excited. She

1294
00:59:55,960 --> 00:59:58,280
Speaker 4: We've been talking to her about Apollo and the space

1295
00:59:58,360 --> 00:59:59,960
Speaker 4: race and I think she'll be super excited to hear

1296
01:00:00,280 --> 01:00:02,640
Speaker 4: that one of those you know, boosters came back around

1297
01:00:02,640 --> 01:00:04,920
Speaker 4: again and is still floating in deep space. So I'll

1298
01:00:04,920 --> 01:00:07,440
Speaker 4: tell her about that, and I definitely think she's going

1299
01:00:07,600 --> 01:00:10,600
Speaker 4: to love that there's something called a space bean or

1300
01:00:10,960 --> 01:00:12,760
Speaker 4: something we referred to as the space bean because we

1301
01:00:12,800 --> 01:00:15,000
Speaker 4: can't pronounce its real name. I think she's going to

1302
01:00:15,080 --> 01:00:17,400
Speaker 4: get a total kick out of that information. What about you,

1303
01:00:17,400 --> 01:00:18,480
Speaker 4: What are you going to tell your kids?

1304
01:00:18,640 --> 01:00:20,919
Speaker 1: Yeah, my kids also, I'll tell them that there's weird

1305
01:00:21,000 --> 01:00:23,640
Speaker 1: stuff floating out there and that in the end, it's

1306
01:00:23,680 --> 01:00:25,840
Speaker 1: all just sort of arbitrary. What we call a moon

1307
01:00:26,040 --> 01:00:28,960
Speaker 1: and what we call a quasi satellite is really just

1308
01:00:29,000 --> 01:00:32,800
Speaker 1: an arbitrary distinction, but that their questions are valuable questions,

1309
01:00:32,840 --> 01:00:35,760
Speaker 1: and these really simple, basic questions about the universe are

1310
01:00:35,800 --> 01:00:39,440
Speaker 1: sometimes the most interesting, the hardest to answer and reveal

1311
01:00:39,560 --> 01:00:42,400
Speaker 1: something about. You know, what we've thought about our place

1312
01:00:42,440 --> 01:00:44,720
Speaker 1: in the universe, what we think is natural, what we

1313
01:00:44,760 --> 01:00:47,240
Speaker 1: think is normal, what we think is typical, and it

1314
01:00:47,440 --> 01:00:50,840
Speaker 1: probably is really unusual. And that's somewhere out there, there's

1315
01:00:50,880 --> 01:00:53,840
Speaker 1: an alien kid looking up at the sky and asking

1316
01:00:54,000 --> 01:00:56,880
Speaker 1: the alien mom, like, why do we have five moons.

1317
01:00:57,160 --> 01:00:59,280
Speaker 1: You know, it's just every planet to have five moons.

1318
01:00:59,400 --> 01:01:02,240
Speaker 4: I love that I that we're all asking the same questions,

1319
01:01:02,440 --> 01:01:04,240
Speaker 4: but just very much separated, all.

1320
01:01:04,280 --> 01:01:06,880
Speaker 1: Right, So thank you very much everybody for going on

1321
01:01:06,920 --> 01:01:09,760
Speaker 1: this curiosity journey with us and listening to us talk

1322
01:01:09,840 --> 01:01:12,640
Speaker 1: about the number of moons around the Earth. If you

1323
01:01:12,680 --> 01:01:14,600
Speaker 1: have stuff you'd like to hear us talk about, please

1324
01:01:14,880 --> 01:01:18,560
Speaker 1: send them to us to questions at Danielandjorge dot com.

1325
01:01:18,560 --> 01:01:20,720
Speaker 1: Thanks again, Kelly for joining us today, and thanks to

1326
01:01:20,720 --> 01:01:21,840
Speaker 1: all of you for tuning in.

1327
01:01:21,920 --> 01:01:23,280
Speaker 4: Thanks for having me. It was a lot of fun.

1328
01:01:31,160 --> 01:01:33,960
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

1329
01:01:34,040 --> 01:01:38,040
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts

1330
01:01:38,040 --> 01:01:42,680
Speaker 1: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

1331
01:01:42,760 --> 01:01:44,480
Speaker 1: you listen to your favorite shows.

1332
01:01:55,800 --> 01:01:58,240
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Speaker 1: When you pop a piece of cheese into your mouth,

1341
01:02:27,760 --> 01:02:31,080
Speaker 1: you're probably not thinking about the environmental impact. But the

1342
01:02:31,080 --> 01:02:33,960
Speaker 1: people in the dairy industry are. That's why they're working

1343
01:02:34,000 --> 01:02:36,640
Speaker 1: hard every day to find new ways to reduce waste,

1344
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Speaker 1: conserve natural resources, and drive down greenhouse gas emissions. How

1345
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Speaker 1: is us dairy tackling greenhouse gases? Many farms use anaerobic

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Speaker 1: digestors to turn the methane from manure into renewable energy

1347
01:02:48,680 --> 01:02:52,280
Speaker 1: that can power farms, towns, and electric cars. Visit you

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Speaker 1: as dairy dot COM's Last Sustainability to learn more.

1349
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Speaker 3: There are children, friends, and families walking riding paths and

1350
01:03:00,480 --> 01:03:02,960
Speaker 3: roads every day. Remember they're real people with loved ones

1351
01:03:02,960 --> 01:03:05,480
Speaker 3: who need them to get home safely. Protect our cyclists

1352
01:03:05,480 --> 01:03:07,120
Speaker 3: and pedestrians because they're people too.

1353
01:03:07,400 --> 01:03:07,920
Speaker 1: Go safely.

1354
01:03:08,000 --> 01:03:10,840
Speaker 3: California From the California Office of Traffic Safety and Caltrans