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Kids questions about the Universe! · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Any Daniel, do you think kids think about the world differently? Oh,
• 0:11
  Speaker 1: I'm sure they do because they aren't tied down by
• 0:14
  Speaker 1: all of our crazy misconceptions. Actually, I meant because they
• 0:17
  Speaker 1: have smaller brains. But I think you're right about the misconceptions.
• 0:21
  Speaker 1: Do you think that makes them smarter than us? I
• 0:24
  Speaker 1: don't know, but I think there's a reason that it's
• 0:26
  Speaker 1: rare to have, like a brilliant insight or crazy new
• 0:30
  Speaker 1: idea after your thirty Mm. So just because I'm older
• 0:34
  Speaker 1: than thirty, that means I'm never gonna win the Nobel
• 0:36
  Speaker 1: Prize in physics. Oh no, No, you might still, but
• 0:39
  Speaker 1: it would be for an idea you had when you
• 0:41
  Speaker 1: were twenty nine. You mean, like when I decided to
• 0:45
  Speaker 1: leave academia and become a cartoonist. Yeah, maybe the best
• 0:47
  Speaker 1: idea you ever had. Do they give Nobel prices in
• 0:50
  Speaker 1: bad career choices? Hi? I am more handmade cartoonist and
• 1:09
  Speaker 1: the creator of PhD comics. Hi, I'm Daniel. I'm a
• 1:12
  Speaker 1: particle physicist and a professor UC Irvine. And I was
• 1:15
  Speaker 1: once stumped by a question from a six year old. Really,
• 1:20
  Speaker 1: was it a question about physics or just about life?
• 1:23
  Speaker 1: It sort of was. I was doing demonstrations and the
• 1:26
  Speaker 1: elementary school about how cool liquid nitrogen is, and some
• 1:29
  Speaker 1: kid asked me if lightsabers were real, would they be
• 1:32
  Speaker 1: made of liquid nitrogen? Interesting question. It's like it's blending
• 1:37
  Speaker 1: fiction and reality and some imagination there. Yeah. I was
• 1:42
  Speaker 1: literally stumped. I had no idea how to that question
• 1:46
  Speaker 1: in the universe in which lightsabers like, is a khyber
• 1:49
  Speaker 1: crystal made out of liquid nitrogen? Really? It could be, right, Yeah,
• 1:53
  Speaker 1: I suppose it could. Can you make a crystal out
• 1:54
  Speaker 1: of liquid nitrogen? Somehow? I guess that would be crystal nitrogen? Yeah.
• 1:58
  Speaker 1: But welcome to our podcast Annual and Jorge Explain the Universe,
• 2:01
  Speaker 1: a production of I Heart Radio in which we try
• 2:04
  Speaker 1: to summon that curiosity we all had when we were
• 2:06
  Speaker 1: children about the way the world worked and extend that
• 2:09
  Speaker 1: to everything in the universe and wonder about the nature
• 2:12
  Speaker 1: of the universe, the origin of the universe, explanations for
• 2:15
  Speaker 1: how everything works, and dig into the mysteries for the
• 2:18
  Speaker 1: things that we still don't understand. We apply our innate
• 2:21
  Speaker 1: curiosity to everything in the universe because we think that
• 2:24
  Speaker 1: everything is understandable and that if we bang away at
• 2:28
  Speaker 1: it long enough, we eventually we will figure things out. Yeah,
• 2:31
  Speaker 1: because it is a big universe and there are enough
• 2:33
  Speaker 1: questions in it for all kinds of people are young
• 2:35
  Speaker 1: and old. He might be eight years old and still
• 2:39
  Speaker 1: have questions about the universe, or he might be ninety
• 2:41
  Speaker 1: nine and also have questions about the university. Universe seems
• 2:44
  Speaker 1: to never run out of questions. That's right, And some
• 2:47
  Speaker 1: of the questions that we are asking suggests that, like
• 2:50
  Speaker 1: we as a species are quite young. End of the way,
• 2:53
  Speaker 1: the kids ask very basic questions, you know, like where
• 2:56
  Speaker 1: does the sun go at night? Stuff like that. We
• 2:58
  Speaker 1: are still asking really basic questions. How old is the universe,
• 3:02
  Speaker 1: what happened before it? How big is it? What's past?
• 3:05
  Speaker 1: What we can see? Really, just like novice initial questions
• 3:09
  Speaker 1: do you ask as a species coming into these universe
• 3:12
  Speaker 1: and wondering about our place in it? Are you saying
• 3:15
  Speaker 1: our species is like in the teenage years you think
• 3:17
  Speaker 1: or are we tweens? No? I think we're basically six
• 3:20
  Speaker 1: year old intellectually as a species. I think we're six
• 3:23
  Speaker 1: years old. We're asking really basic questions. We're still in
• 3:26
  Speaker 1: the kindergarten of the galaxy exactly. We're asking questions that
• 3:30
  Speaker 1: reveal the way we think about the universe rather than
• 3:33
  Speaker 1: the way the universe works. You know, we're asking the
• 3:36
  Speaker 1: questions we think are important and that reveal our misunderstandings
• 3:40
  Speaker 1: about how the universe works. Well, we definitely don't have
• 3:42
  Speaker 1: our wisdom teeth yet. As a species, we're definitely lacking
• 3:46
  Speaker 1: any wisdom, it seems these days. But there is a
• 3:48
  Speaker 1: lot of that you can ask about the universe, and
• 3:51
  Speaker 1: it's for all kinds of ages. Yeah, and sometimes it's
• 3:54
  Speaker 1: fun to dig back into that. You know, as a researcher,
• 3:56
  Speaker 1: I'm working at like the very edge of knowledge, asking
• 3:59
  Speaker 1: very pacific questions what's inside a cork? Or are electrons
• 4:03
  Speaker 1: made of something smaller? But it's fun to go back
• 4:06
  Speaker 1: to the questions at five year old, six year old,
• 4:08
  Speaker 1: ten year olds ask and remember that we still don't
• 4:10
  Speaker 1: have answers to those big questions. And like, the whole
• 4:13
  Speaker 1: context of our exploration is that we're trying to answer
• 4:16
  Speaker 1: these really big, basic, deep questions, and that all the
• 4:19
  Speaker 1: specific work we're doing at the edge of knowledge and
• 4:21
  Speaker 1: the end is motivated by trying to get back to
• 4:23
  Speaker 1: those basic questions. I think trying to make a lightsaber
• 4:26
  Speaker 1: is at the edge of knowledge, thank you. I mean,
• 4:28
  Speaker 1: have you seen those YouTube videos where people try to
• 4:30
  Speaker 1: recreate lightsabers? It's hard, it's really impossible almost what motivated
• 4:35
  Speaker 1: you to walk to those who Hey, when you're trying
• 4:36
  Speaker 1: to build one yourself. I was curious as a kid, Yes,
• 4:42
  Speaker 1: to watch YouTube videos. You're gonna slice your way out
• 4:45
  Speaker 1: of your childhood situation. No, I've not gone down that
• 4:47
  Speaker 1: particular rabbit hole. But yeah, there's a lot of really
• 4:50
  Speaker 1: fun questions we asked there. Yeah, and sometimes we get
• 4:52
  Speaker 1: those questions here and our inbox, and specifically we get
• 4:55
  Speaker 1: questions from little kids, not just adults or young people
• 4:58
  Speaker 1: like like the people listening to this podcast right now,
• 5:01
  Speaker 1: But we got questions from a little little kids, that's right.
• 5:04
  Speaker 1: Sometimes folks have their seven year old or their ten
• 5:06
  Speaker 1: year olds listening with them and a podcast will inspire
• 5:09
  Speaker 1: a question, and then they'll write to us and say, Hey,
• 5:12
  Speaker 1: my kid asked me this question. I don't know the answer.
• 5:14
  Speaker 1: Maybe you guys can help out, which makes me glad
• 5:16
  Speaker 1: about all the jokes we don't say in this podcast,
• 5:20
  Speaker 1: all those jokes about dark matter, and that's right, all
• 5:22
  Speaker 1: those racy browser histories that we don't like to talk
• 5:25
  Speaker 1: about but exactly because we hope that you are out
• 5:27
  Speaker 1: there listening with your kids and that inspires conversations. I'm
• 5:30
  Speaker 1: always really happy to hear when somebody writes it and says,
• 5:32
  Speaker 1: how was listening to your podcast with my eleven year
• 5:35
  Speaker 1: old and then we spent an hour talking about what's
• 5:37
  Speaker 1: inside a black hole or just on the way to school,
• 5:39
  Speaker 1: wondering about the nature of the universe. Our whole goal
• 5:42
  Speaker 1: here is to share our joy of our ignorance and
• 5:44
  Speaker 1: wondering about what's in the universe and helping you talk
• 5:47
  Speaker 1: to everybody in your life about it. Yes, so if
• 5:49
  Speaker 1: you're a kid listening to this podcast right now, we
• 5:51
  Speaker 1: want to thank you for listening. We're glad that you're here,
• 5:54
  Speaker 1: and I'm sure you have a lot of questions as
• 5:55
  Speaker 1: well as well as a lot of other kids. And
• 5:58
  Speaker 1: we have a whole box full of questions from kids,
• 6:01
  Speaker 1: that's right, So don't be shy to ask your parents
• 6:03
  Speaker 1: questions or to send your questions to us. We'd love
• 6:06
  Speaker 1: to tackle them. So to be on the podcast, we'll
• 6:08
  Speaker 1: be tackling kid questions about the universe. At least are
• 6:17
  Speaker 1: questions about kids or buy kids. These are the biggest
• 6:21
  Speaker 1: questions from the littlest people. These are questions about the
• 6:24
  Speaker 1: whole universe, about black holes, and about how things work,
• 6:28
  Speaker 1: you know, the kind of things that go through the
• 6:29
  Speaker 1: vines of an eight year old. And these are all
• 6:31
  Speaker 1: spontaneously generated, right like kids just sent this question in
• 6:35
  Speaker 1: with their parents, that's right. I don't know if the
• 6:36
  Speaker 1: parents put the kids up to it, or these are
• 6:38
  Speaker 1: actually child actors. I can't vouch for the veracity of these,
• 6:41
  Speaker 1: but they are good questions, and so I thought they'd
• 6:44
  Speaker 1: be fun to talk about on the podcast. Yes, so
• 6:45
  Speaker 1: long as you didn't go around soliciting little kids or
• 6:49
  Speaker 1: things on the internet, I think we're safe. No, I
• 6:51
  Speaker 1: try to stay as far away as I can from
• 6:53
  Speaker 1: the child acting industry down here in southern California. Yeah.
• 6:56
  Speaker 1: So we have all kinds of awesome questions here from
• 6:58
  Speaker 1: kids about black hole, about diamond cores, about the expanding universe,
• 7:03
  Speaker 1: and we have a whole bunch of him. So let's
• 7:05
  Speaker 1: dig into him. Daniel, what's our first question? Our first
• 7:08
  Speaker 1: question comes from Joey. He's seven years old. What are
• 7:11
  Speaker 1: the newest than the oldest black holes in the universe? Mmmm?
• 7:16
  Speaker 1: Appropriately A question about youngest and oldest something in the universe.
• 7:21
  Speaker 1: I wonder if there's a relationship there with like Grandpa
• 7:24
  Speaker 1: black holes and grandkid black holes. Yeah, like maybe the
• 7:27
  Speaker 1: younger black holes and more attitude, maybe they think they
• 7:30
  Speaker 1: had they know everything in the universe. I was thinking
• 7:33
  Speaker 1: the other direction, like maybe the little black holes look
• 7:35
  Speaker 1: up to the supermassive black holes and they're like, that's
• 7:38
  Speaker 1: gonna be me. One day. I'm gonna have my own
• 7:40
  Speaker 1: galaxy of stars swirling around me. I'm gonna devour millions
• 7:44
  Speaker 1: of stars and planets and potentially a civilizations and then
• 7:48
  Speaker 1: get bigger something. I'm gonna be huge and round. One day,
• 7:52
  Speaker 1: I'm gonna have a whole galaxy for bowling around me.
• 7:55
  Speaker 1: Just me. Yeah. So it's a great question because the
• 7:58
  Speaker 1: black holes weren't all made at this time. I guess
• 8:01
  Speaker 1: it's one thing that people may not know that black
• 8:04
  Speaker 1: holes are not all the same age. That's right, and
• 8:07
  Speaker 1: part of the reason is that we have several different
• 8:10
  Speaker 1: categories of black holes. We have different ways that black
• 8:13
  Speaker 1: holes could be made, so different processes that are capable
• 8:17
  Speaker 1: of creating this crazy density that you need to create
• 8:20
  Speaker 1: this craziest and most mysterious of universal objects. Yeah, so
• 8:24
  Speaker 1: there are black holes being born right now, and there
• 8:26
  Speaker 1: were maybe black holes that were made in the Big Bang.
• 8:29
  Speaker 1: So let's get into what we know, Daniel, What is
• 8:32
  Speaker 1: the youngest black hole that we know about? So we think,
• 8:36
  Speaker 1: as you say, that black holes are being made all
• 8:38
  Speaker 1: the time, right, because black holes come from collapsing stars,
• 8:41
  Speaker 1: at least one category do so. At the end of
• 8:43
  Speaker 1: the life of a star. We think that they collapse
• 8:45
  Speaker 1: and they form a black hole if they have enough mass,
• 8:48
  Speaker 1: and that should be happening basically all the time around
• 8:50
  Speaker 1: the universe. I mean, not like ten thousand every second
• 8:53
  Speaker 1: per cubic light year, but at a certain rate all
• 8:56
  Speaker 1: over the universe. So there should be a black hole
• 8:58
  Speaker 1: being made right now on another one right now, another
• 9:00
  Speaker 1: one right now. Every ten seconds, the black hole is born. Yeah,
• 9:03
  Speaker 1: it's like asking who is the youngest person on Earth.
• 9:05
  Speaker 1: It's a constantly changing answer because new babies are constantly
• 9:08
  Speaker 1: being born. But as you say, we can ask the question,
• 9:11
  Speaker 1: what is the youngest black hole that we have seen? Right?
• 9:15
  Speaker 1: And then there's another twist there, because you know, the
• 9:18
  Speaker 1: things that are further away from us are a little older.
• 9:21
  Speaker 1: So we're naturally going to have seen things that are younger,
• 9:24
  Speaker 1: that are closer to us, just because the light has
• 9:27
  Speaker 1: had a chance to reach us. Oh I see. So
• 9:30
  Speaker 1: there's kind of a delay between when something happens and
• 9:32
  Speaker 1: when we find out about it. So what we think
• 9:34
  Speaker 1: might be the youngest might not be the youngest. It's
• 9:36
  Speaker 1: just the youngest that we know about that the news
• 9:39
  Speaker 1: of which has gotten to us. Yeah, precisely. And so
• 9:44
  Speaker 1: the youngest black hole that we know about is about
• 9:47
  Speaker 1: twenty six thousand light years from Earth. It's called wt
• 9:52
  Speaker 1: B because astronomers are so creative with names, and we
• 9:54
  Speaker 1: think it's about a thousand years old. We think that
• 9:58
  Speaker 1: it was formed in a supernova that happened about a
• 10:00
  Speaker 1: thousand years ago. Supernova black hole. Now, not all stars
• 10:05
  Speaker 1: go supernova and become black holes, right, Like, there's lots
• 10:07
  Speaker 1: of stars that never become a black hole. Like, our
• 10:10
  Speaker 1: star is not going to become a black hole, that's right.
• 10:12
  Speaker 1: And our star won't even go supernova. And the whole
• 10:14
  Speaker 1: thing is determined just by how much stuff there is
• 10:17
  Speaker 1: in the original star. The more stuff there is, the
• 10:20
  Speaker 1: more likely that it's gonna have a supernova collapse. And
• 10:22
  Speaker 1: then only the heaviest of stars have enough mass to
• 10:25
  Speaker 1: create a black hole, because remember, to create a black hole,
• 10:28
  Speaker 1: you have to have gravity overcome all of the things
• 10:31
  Speaker 1: that are pushing back against gravity's pressure. Gravity is trying
• 10:34
  Speaker 1: to push everything into the smallest space possible because it's
• 10:37
  Speaker 1: just attracting mass to other mass. But things prevent that,
• 10:41
  Speaker 1: like our star is burning and shooting out radiation, which
• 10:43
  Speaker 1: prevents it from collapse. When that burning stops, then there
• 10:46
  Speaker 1: are other things that will prevent it from collapsing, like
• 10:48
  Speaker 1: just the atoms pushing against each other, or eventually just
• 10:51
  Speaker 1: like quantum mechanical effects. But if you have enough stuff,
• 10:54
  Speaker 1: you have a big enough scoop of original hydrogen serving,
• 10:57
  Speaker 1: then you can overcome that if you're above a minimum threshold.
• 11:00
  Speaker 1: So you're right, not every supernova becomes a black hole.
• 11:03
  Speaker 1: And so the youngest supernova and that that became a
• 11:06
  Speaker 1: black hole that we know about happened. We think a
• 11:08
  Speaker 1: thousand years ago, twenty six light years from Earth. Twenty
• 11:11
  Speaker 1: six thousand light years from twenty six thousands are light
• 11:15
  Speaker 1: years from Earth. What did I say? Twenty six thousand
• 11:17
  Speaker 1: miles light years? But hey, what's three years in magnitude
• 11:20
  Speaker 1: between friends? Yeah? It's right here, but really it must
• 11:23
  Speaker 1: have been then that it was maybe born twenty five
• 11:27
  Speaker 1: thousand light years or something like that years ago, Like
• 11:31
  Speaker 1: it can be a thousand years old, but then it's
• 11:33
  Speaker 1: twenty six thousand light years away, because it would take
• 11:35
  Speaker 1: twenty six thousand years for the light to get to us.
• 11:38
  Speaker 1: That's right. What we mean by that is the supernova
• 11:40
  Speaker 1: should have been visible here on Earth a thousand years ago, right,
• 11:44
  Speaker 1: And so a thousand years ago we should have seen
• 11:46
  Speaker 1: a supernova indicating the formation of the black hole. But
• 11:49
  Speaker 1: of course that would have happened twenty seven thousand years ago.
• 11:53
  Speaker 1: I guess, how do we know that it's there or
• 11:55
  Speaker 1: how do we know it's age? Like black holes are black,
• 11:57
  Speaker 1: so they're kind of hard to see in space. How
• 12:00
  Speaker 1: do we know it's there? And how do we know
• 12:01
  Speaker 1: how old it is? So these are tricky to identify. Right,
• 12:04
  Speaker 1: every time you see a supernova, you don't necessarily get
• 12:06
  Speaker 1: a black hole, and so you can't actually see these
• 12:09
  Speaker 1: black holes directly. You always have to infer it indirectly,
• 12:13
  Speaker 1: and so you see for example, in acretion disc forming,
• 12:15
  Speaker 1: but you don't see any object there at the core,
• 12:18
  Speaker 1: or perhaps you can measure the mass because there's something
• 12:20
  Speaker 1: else nearby, and you can measure the radios because things
• 12:23
  Speaker 1: are passing near it, and so you can tell what
• 12:25
  Speaker 1: the density of the object is. And it's denser than
• 12:28
  Speaker 1: a neutron star could be. And so, as we talked
• 12:30
  Speaker 1: about on a recent episode about black holes, we're never
• 12:33
  Speaker 1: a hundred sure about a black hole. Were always inferring
• 12:36
  Speaker 1: in the argument is usually something like this is denser
• 12:39
  Speaker 1: than a neutron star could be or anything we know,
• 12:41
  Speaker 1: therefore it must be a black hole. There's always a
• 12:43
  Speaker 1: bit of a leap there, like we don't know anything
• 12:46
  Speaker 1: other than a black hole that could be this small
• 12:49
  Speaker 1: and this dense, So therefore we think it's a black hole.
• 12:51
  Speaker 1: And that's sort of the argument we make when we
• 12:53
  Speaker 1: look at these nebula, right you sort of look at
• 12:55
  Speaker 1: it black spot in the in space and you see
• 12:57
  Speaker 1: things moving around it in an orbit, and so you
• 12:59
  Speaker 1: mustn't for that there's something like a black holder. But
• 13:02
  Speaker 1: I guess, how do you know it's a thousand years old?
• 13:04
  Speaker 1: Like how do you know when it happened? Like we
• 13:05
  Speaker 1: weren't looking a thousand years ago? That's right, But these
• 13:08
  Speaker 1: things have clouds, right, The supernova is an active process,
• 13:12
  Speaker 1: and so there's a big explosion and a lot of
• 13:14
  Speaker 1: the stuff gets thrown out to form this nebula and
• 13:17
  Speaker 1: some of it collapses into the black hole. But we
• 13:19
  Speaker 1: can watch the process of this nebula and it's going
• 13:21
  Speaker 1: to like create new planets and have all sorts of dynamics,
• 13:24
  Speaker 1: and so that's sort of a thing that we can
• 13:26
  Speaker 1: watch and we can look at and we can say, well,
• 13:27
  Speaker 1: this nebula looks like it's about a thousand years old,
• 13:30
  Speaker 1: because we think it looks like about a thousand years
• 13:32
  Speaker 1: worth of like gravitational reformation has happened. You can see
• 13:35
  Speaker 1: the wrinkles. You don't have to check the idea. You
• 13:39
  Speaker 1: can just guess by looking at it. You can measure
• 13:42
  Speaker 1: the velocity of things in the nebula by seeing the
• 13:45
  Speaker 1: red shift, and so you can sort of tell where
• 13:47
  Speaker 1: it is in this process of having exploded and then
• 13:50
  Speaker 1: reforming something. Sometimes you'll get like new planets forming around
• 13:53
  Speaker 1: the neutron star or the black hole at the core.
• 13:56
  Speaker 1: Well that's cool. So then that's the youngest black hole
• 13:59
  Speaker 1: we've ever seen, Like we haven't seen one in the
• 14:01
  Speaker 1: last thousand years, or we don't think one has come
• 14:04
  Speaker 1: into existence in the last thousand years. Isn't that weird?
• 14:07
  Speaker 1: Given how many stars there are in the galaxy and
• 14:09
  Speaker 1: in the universe. It is kind of weird. And there's
• 14:11
  Speaker 1: a couple of things going on there. One is that
• 14:13
  Speaker 1: there aren't that many supernova in our galaxy, Like there's
• 14:17
  Speaker 1: a lot of stars in our galaxy, and we expect
• 14:19
  Speaker 1: only like a few supernova per century because not many
• 14:23
  Speaker 1: stars actually end up turning into supernova. And one of
• 14:26
  Speaker 1: the weird things is that we haven't seen a supernova
• 14:29
  Speaker 1: in more than four hundred years, like the last supernova
• 14:32
  Speaker 1: in the Milky Way that we saw. We see lots
• 14:34
  Speaker 1: of them in other galaxies constantly, hundreds every year, but
• 14:37
  Speaker 1: the last one that we saw in our galaxy was
• 14:39
  Speaker 1: in sixteen o four. Kepler saw the last supernova any
• 14:43
  Speaker 1: human has ever observed in our galaxy. Whoa really, how
• 14:48
  Speaker 1: do you know we didn't miss it? Like in the
• 14:50
  Speaker 1: eighteen hundreds for everyone with everyone looking, was everyone looking diligently,
• 14:54
  Speaker 1: Like what if we kind of like one happened and
• 14:56
  Speaker 1: we were looking the other way, or you know, the
• 14:58
  Speaker 1: French Revolution was happening that the we were a little busy,
• 15:01
  Speaker 1: or World War two is happening, and so there are
• 15:04
  Speaker 1: other things we were attending to do. Yeah, there are.
• 15:06
  Speaker 1: There are a couple of candidates where we see in Nebula,
• 15:08
  Speaker 1: were like, Hm, this looks like it should have been
• 15:10
  Speaker 1: a supernova about a hundred years ago. We should have
• 15:12
  Speaker 1: seen it. Why didn't anybody notice it? There are a
• 15:14
  Speaker 1: couple of candidates, but even still is kind of weird
• 15:16
  Speaker 1: because we expect a few per century and we haven't
• 15:19
  Speaker 1: seen a single one in four hundred years. We're actually
• 15:21
  Speaker 1: gonna dig into that in a whole podcast episode about
• 15:24
  Speaker 1: the formation of supernov and why we haven't seen any
• 15:26
  Speaker 1: in the Milky Way pretty soon. But basically, we haven't
• 15:29
  Speaker 1: seen a lot of supernova in the Milky Way recently,
• 15:32
  Speaker 1: and you need a supernova to form these black holes,
• 15:34
  Speaker 1: all right, So then the answer is stay tuned. But
• 15:36
  Speaker 1: that is the youngest black hole we've seen. It's a
• 15:38
  Speaker 1: thousand years old, twenty six thousand light years from Earth,
• 15:42
  Speaker 1: and so what's the oldest black hole we know about?
• 15:44
  Speaker 1: The oldest black holes we know about are ones that
• 15:46
  Speaker 1: formed at the hearts of galaxies the very beginning of
• 15:50
  Speaker 1: the universe. Remember that after the Big Bang stuff flew
• 15:53
  Speaker 1: out and then gravity started doing its job and made
• 15:56
  Speaker 1: stars and galaxies, and that took about a billion years
• 16:00
  Speaker 1: for the universe to look familiar, you know, eight hundred million,
• 16:04
  Speaker 1: maybe a billion years before we had the first galaxies.
• 16:07
  Speaker 1: And the interesting thing is that we already have supermassive
• 16:10
  Speaker 1: black holes at the hearts of those galaxies. Now, those
• 16:13
  Speaker 1: galaxies are billions of years old, which means we can
• 16:15
  Speaker 1: only see them if they're very very far away, because
• 16:18
  Speaker 1: the light from those far away galaxies is just now
• 16:20
  Speaker 1: hitting Earth. So if you look deep out into space,
• 16:23
  Speaker 1: you're looking back in time and you're looking at the
• 16:25
  Speaker 1: very very early galaxies. And the crazy thing is at
• 16:29
  Speaker 1: the heart of those galaxies there are these very bright emissions,
• 16:32
  Speaker 1: these things we called quaisars, which are light from the
• 16:35
  Speaker 1: gas that's surrounding those huge black holes in the very
• 16:38
  Speaker 1: early universe. So we think that black holes were formed
• 16:42
  Speaker 1: at the heart of these early galaxies, you know, just
• 16:44
  Speaker 1: a few hundred million years after the Big Bang. M interesting,
• 16:48
  Speaker 1: so we can see these black holes because they're actually
• 16:51
  Speaker 1: really shiny, or at least what's around them is really shiny.
• 16:54
  Speaker 1: In fact, super shiny. Right, It's like it's brighter than
• 16:56
  Speaker 1: the whole galaxy that it's in. That's right. They are
• 16:58
  Speaker 1: crazy shiny. These things are called quasars, and when they
• 17:02
  Speaker 1: were first discovered, people didn't really understand. They didn't believe
• 17:05
  Speaker 1: them if there must be something wrong because you're looking
• 17:07
  Speaker 1: at something super distant and yet super bright, which means
• 17:10
  Speaker 1: that added source, it must be like riduculously bright. And
• 17:13
  Speaker 1: people thought that just must be wrong. What could power that.
• 17:16
  Speaker 1: Then they discover that, oh, it's the energy from these
• 17:19
  Speaker 1: black holes that's like squeezing and pushing on all this
• 17:22
  Speaker 1: gas around it that creates this very intense radiation. Again
• 17:26
  Speaker 1: not from the black hole, as you say, but from
• 17:28
  Speaker 1: the gas that's around it. And so you're saying that
• 17:30
  Speaker 1: we see these quasars, these super bright black holes in
• 17:33
  Speaker 1: galaxies that are really really far away, which means that
• 17:37
  Speaker 1: they're really really old, which puts their age at around
• 17:40
  Speaker 1: thirteen billion years old. We think the black hole is
• 17:44
  Speaker 1: thirteen billion years old. Yeah, we think the black hole
• 17:46
  Speaker 1: is thirteen billion years old. Now we haven't seen them recently, right,
• 17:49
  Speaker 1: we are looking at very outdated information. So we're looking
• 17:53
  Speaker 1: at a black hole which is fairly young, maybe a
• 17:56
  Speaker 1: few hundred million years, but thirteen billion years ago. So
• 18:00
  Speaker 1: now we're assuming that those black holes are still around
• 18:03
  Speaker 1: because we don't know of any mechanism for super massive
• 18:06
  Speaker 1: black holes to disappear. The only way a black hole
• 18:09
  Speaker 1: can shrink is through hawking radiation, but that happens very
• 18:12
  Speaker 1: very gradually for very large black holes, and these things
• 18:15
  Speaker 1: are probably still eating, so they're probably even bigger now
• 18:18
  Speaker 1: than we are seeing them from thirteen billion years ago. Well,
• 18:21
  Speaker 1: it's like getting a photograph of someone from the nineteen twenties,
• 18:24
  Speaker 1: and you know, assuming they're still alive, that would make
• 18:26
  Speaker 1: them really old, just because you have a photo of
• 18:28
  Speaker 1: them when they were young, but the photo is really old. Yeah, exactly.
• 18:32
  Speaker 1: So these things been around basically the entire history of
• 18:35
  Speaker 1: the universe, right, almost though almost by like what a
• 18:38
  Speaker 1: hundred thousand years you said, a few hundred million years
• 18:44
  Speaker 1: order between a podcast hook covers. That's right, exactly, So
• 18:49
  Speaker 1: those are pretty old. Thirteen billion years old is pretty old.
• 18:51
  Speaker 1: But there might be even older black holes, that's right.
• 18:54
  Speaker 1: We don't know, but it's possible that there were black
• 18:57
  Speaker 1: holes made before there was even matter, for the universe
• 19:01
  Speaker 1: cooled down so that the energy in the quantum fields
• 19:04
  Speaker 1: could even be described as like particles as you know,
• 19:07
  Speaker 1: like corks and electrons flying around when the universe is
• 19:10
  Speaker 1: still so crazy dense and intense that you couldn't even
• 19:13
  Speaker 1: describe things as particles. We think there might have been
• 19:16
  Speaker 1: black holes made in that state of matter, and those
• 19:19
  Speaker 1: we call primordial black holes. I see, because you don't
• 19:23
  Speaker 1: necessarily need matter to make a black hole, right, you
• 19:25
  Speaker 1: could also make one out of pure energy. That's right,
• 19:28
  Speaker 1: because general relativity treats matters just another form of energy,
• 19:32
  Speaker 1: and it's really energy density that curves space, and so
• 19:35
  Speaker 1: you can accomplish that with matter, of course, but you
• 19:37
  Speaker 1: could also accomplish that with energy. Like if you take
• 19:39
  Speaker 1: powerful enough lasers and overlap them, you can create a
• 19:42
  Speaker 1: black hole out of light. How about liquid niitrogen lightsabers?
• 19:46
  Speaker 1: What if you cross those beams? Can you cut a
• 19:50
  Speaker 1: black hole in half with a lightsaber? There's a physics
• 19:53
  Speaker 1: question I don't have the answer to. Only here, Yoda,
• 19:57
  Speaker 1: only after nine engineers of training. So least primordial black
• 20:01
  Speaker 1: holes would be the oldest black holes in the universe.
• 20:03
  Speaker 1: But we don't really know if they exist, right, We
• 20:06
  Speaker 1: definitely do not know if they exist. If they did exist,
• 20:09
  Speaker 1: we should be seeing them, because they should have been
• 20:12
  Speaker 1: created all sorts of different sizes, really large ones, really
• 20:15
  Speaker 1: small ones. It's nice to imagine that they might exist
• 20:18
  Speaker 1: because they might explain how supermassive black holes got so
• 20:21
  Speaker 1: massive so young, Like you might ask, how do you
• 20:23
  Speaker 1: get such a big black hole after only a few
• 20:26
  Speaker 1: hundred million years? While they could have been seeded by
• 20:28
  Speaker 1: primordial black holes, they could also explain what the dark
• 20:31
  Speaker 1: matter is. Maybe dark matter is just a bunch of
• 20:33
  Speaker 1: these primordial black holes floating around in the universe. But
• 20:38
  Speaker 1: if they were creating all sorts of different sizes, then
• 20:40
  Speaker 1: some of them should be just the right size to
• 20:43
  Speaker 1: live around fourteen billion years and then evaporate to disappear.
• 20:47
  Speaker 1: And when black holes evaporate, they're giving off their light.
• 20:50
  Speaker 1: It happens more rapidly. They get brighter and brighter as
• 20:53
  Speaker 1: they're about to disappear, so we should be able to
• 20:56
  Speaker 1: see them sort of like flashing out of existence. But
• 20:58
  Speaker 1: we've never seen that happen, and so it's sort of
• 21:00
  Speaker 1: hard to understand how you can have primordial black holes.
• 21:04
  Speaker 1: Maybe they feel out, you know, kind of silent. Maybe
• 21:07
  Speaker 1: they don't feel a lot with a bang. Is that
• 21:09
  Speaker 1: possible it's possible, but our current theory of black hole
• 21:12
  Speaker 1: evaporation suggests that when they evaporate they turn into photons
• 21:16
  Speaker 1: and also to other crazy particles, and we should definitely
• 21:18
  Speaker 1: be seeing those, like at the edges of the galaxy
• 21:21
  Speaker 1: or something. But we've been looking and we haven't seen
• 21:22
  Speaker 1: a single one. We've never seen a black hole evaporation,
• 21:26
  Speaker 1: and so that suggests that probably they're either just not
• 21:29
  Speaker 1: formed in the right sizes, like maybe their only form
• 21:31
  Speaker 1: really really small and really really big. That's possible, or
• 21:34
  Speaker 1: they just weren't made. But if they were made, then
• 21:37
  Speaker 1: they'd be essentially as old as the universe. They would
• 21:40
  Speaker 1: be made like less than a second after the Big Bang. Interesting,
• 21:44
  Speaker 1: But isn't it a theory that some of those super
• 21:46
  Speaker 1: massive black holes in the middle of galaxies maybe we're
• 21:49
  Speaker 1: made by primordial black holes. It could be, yeah, because
• 21:52
  Speaker 1: as we said, we don't understand how those black holes
• 21:55
  Speaker 1: got so big so fast. If you try to model
• 21:57
  Speaker 1: the formation of galaxies in the early universe, stars coming
• 22:00
  Speaker 1: together forming a black hole, cetera, you can't get black
• 22:03
  Speaker 1: holes that are like billions of solar masses so quickly.
• 22:07
  Speaker 1: So we just don't understand how that happened. And as
• 22:08
  Speaker 1: you say, one idea is maybe they got a jump
• 22:11
  Speaker 1: start because they were seeded by a really big primordial
• 22:14
  Speaker 1: black hole. So that's a possibility. So it sounds like
• 22:17
  Speaker 1: the oldest black holes in the universe are thirteen billion
• 22:20
  Speaker 1: years old at least at least it might be older.
• 22:23
  Speaker 1: All right, Well, thank you Joy for a great question.
• 22:25
  Speaker 1: I think that's your answer. The youngest and the oldest
• 22:28
  Speaker 1: black holes in the universe are both still older than
• 22:31
  Speaker 1: your parents apparently, but maybe billions of years or at
• 22:34
  Speaker 1: least a thousand years and maybe billions of years. That's right.
• 22:37
  Speaker 1: These black holes make your parents seem like children. All right,
• 22:40
  Speaker 1: Thank you, Joey. And so let's get into more questions
• 22:42
  Speaker 1: from kids. But first let's take a quick break. All right,
• 22:58
  Speaker 1: we are answering kids questions about the universe on today's episode,
• 23:02
  Speaker 1: and we have some pretty cool questions here, Daniel, or
• 23:06
  Speaker 1: any of these questions from your own kids. None of
• 23:08
  Speaker 1: these questions are from my kids. These are questions that
• 23:10
  Speaker 1: people didn't have the answers too, so they wanted me
• 23:13
  Speaker 1: to answer them. If my kids ask me questions, I
• 23:15
  Speaker 1: just answered them, or if I don't know the answer,
• 23:18
  Speaker 1: I try to look it up, but I don't send
• 23:19
  Speaker 1: them to the podcast. I see you're like a pinch
• 23:22
  Speaker 1: hit hitter for parents when it comes to physics questions. Yeah,
• 23:25
  Speaker 1: I try to be. I think that's a lot of fun.
• 23:27
  Speaker 1: I just love hearing the kinds of questions that other
• 23:30
  Speaker 1: kids are asking because it tells you something about how
• 23:33
  Speaker 1: they see the universe. And you know, I feel like
• 23:35
  Speaker 1: my brain is sort of like stuck in the modern
• 23:38
  Speaker 1: physics view of how things work, and I'm sure to
• 23:41
  Speaker 1: have all sorts of like misconceptions that have sort of
• 23:44
  Speaker 1: fallen into and been thinking about for twenty years. So
• 23:46
  Speaker 1: a kid's question can really stop you in your tracks
• 23:48
  Speaker 1: and ask you like, how do we know this? Or
• 23:50
  Speaker 1: why do we think about it this way? It's really refreshing, alright.
• 23:54
  Speaker 1: Our next question comes from Anthony, who has a question
• 23:57
  Speaker 1: about diamond core Daniel and horror. Hey, my name is Anthony.
• 24:03
  Speaker 1: I am eight years old, and why does fifty king
• 24:07
  Speaker 1: trying eat have a diamond core? Looking forward to hear
• 24:12
  Speaker 1: your answer, pleasing, thank you, Hey, thanks Anthony. What a
• 24:15
  Speaker 1: polite little young person. I know they said please and
• 24:19
  Speaker 1: thank you. Some of our listeners apparently are teaching their
• 24:22
  Speaker 1: kids manners in addition to science, can Anthony talk to
• 24:25
  Speaker 1: my kids please and run a little etiquette class? That's right,
• 24:29
  Speaker 1: and we will trae you some physics answers for some
• 24:31
  Speaker 1: manner's lessons. Now, this is an interesting question because, to
• 24:35
  Speaker 1: be honest, I didn't quite understand it. It almost sounded
• 24:37
  Speaker 1: like a Star Wars reference, like does this kind of
• 24:39
  Speaker 1: lightsaber model have a crystal core? It's a great question.
• 24:43
  Speaker 1: It's about an exo planet. This is the planet around
• 24:47
  Speaker 1: another star that we're trying to understand because you know,
• 24:50
  Speaker 1: we are looking at our own Solar system and wondering
• 24:53
  Speaker 1: are these the only kinds of planets you can have
• 24:55
  Speaker 1: or are there other weird kinds of planets out there.
• 24:58
  Speaker 1: As always, when we venture out from our little corner
• 25:01
  Speaker 1: of the universe, we expect to be shocked. We look
• 25:03
  Speaker 1: forward to seeing things that we couldn't have imagined. And
• 25:06
  Speaker 1: so this is a planet around another star, and we're
• 25:08
  Speaker 1: trying to understand what it's made out of it, you know,
• 25:10
  Speaker 1: like what it's like to walk on its surface. And
• 25:13
  Speaker 1: so there was a recent paper suggesting that maybe the
• 25:16
  Speaker 1: entire core of this planet could be one huge diamond,
• 25:19
  Speaker 1: and that's what Anthony is asking about WHOA. Yeah, because
• 25:22
  Speaker 1: we've seen now thousands and thousands of planets in other
• 25:25
  Speaker 1: solar systems, right like, we've detected them, we've even sort
• 25:28
  Speaker 1: of sort of have pictures of them. We can tell
• 25:30
  Speaker 1: what's in their atmosphere. Are we down to the point
• 25:32
  Speaker 1: where you can tell what's inside these planets out there
• 25:35
  Speaker 1: in space? We sort of can. And you know, we
• 25:37
  Speaker 1: have very limited information about each one of these things,
• 25:40
  Speaker 1: and so we're trying to do as much science as
• 25:43
  Speaker 1: we can with a very basic information. And here, for example,
• 25:46
  Speaker 1: we have like some knowledge about the mass of the
• 25:49
  Speaker 1: planet and then some knowledge of the radius of the planet,
• 25:52
  Speaker 1: and that lets you do really basic stuff like ask
• 25:54
  Speaker 1: what's the density of the planet. And if you know
• 25:56
  Speaker 1: what the density is, then you can ask questions like, well,
• 25:58
  Speaker 1: what could make a plant of that density? What materials
• 26:01
  Speaker 1: are consistent with that? So now we can't like go
• 26:04
  Speaker 1: and drill into the planet and say, oh, look, we
• 26:06
  Speaker 1: found diamond, but we can ask questions about what it
• 26:09
  Speaker 1: might be met out of based on what we do know.
• 26:11
  Speaker 1: Interesting and athink it was asking about a specific planet
• 26:15
  Speaker 1: that has been found out there, and he had a
• 26:17
  Speaker 1: name for it. It was fifty five something. Yeah, the
• 26:20
  Speaker 1: official name of the planet is fifty five can create E,
• 26:23
  Speaker 1: and so sometimes abbreviated fifty five C E can create E.
• 26:27
  Speaker 1: That does sound like a star trek name. It's a
• 26:30
  Speaker 1: planet that's orbiting the star. Fifty five can create A
• 26:34
  Speaker 1: and so can create E. Is you know, like one
• 26:37
  Speaker 1: of the things around can create A. I see there's
• 26:40
  Speaker 1: a B S D N A D. But we're talking
• 26:42
  Speaker 1: about the thing around that star. That's right. This is
• 26:45
  Speaker 1: the one that's most interesting, and it's kind of really
• 26:47
  Speaker 1: interesting history to it because it was first discovered in
• 26:50
  Speaker 1: two thousand four using the Wiggle method. The Wiggle method
• 26:54
  Speaker 1: says that a planet moving around a star should tug
• 26:57
  Speaker 1: on the star. It's not just that the stars pulling
• 27:00
  Speaker 1: on the planet. The planet is pulling on the star.
• 27:03
  Speaker 1: And so if you have a planet moving around the star,
• 27:04
  Speaker 1: you should see the star moving also, and you can
• 27:07
  Speaker 1: measure that by measuring the velocity of the star by
• 27:10
  Speaker 1: seeing how much it changes the light that's coming to
• 27:13
  Speaker 1: us from the star. So these doppler shifts, right, just
• 27:16
  Speaker 1: like like the Earth is making the Sun wiggle a
• 27:19
  Speaker 1: little tiny bit. And if you were you know, smart
• 27:21
  Speaker 1: knife and had pretty good tascos in another galaxy or
• 27:24
  Speaker 1: another planet, you could tell that we were here, And
• 27:27
  Speaker 1: so you can tell if there's a planet there because
• 27:29
  Speaker 1: it's pulling on the star, and you can tell something
• 27:32
  Speaker 1: about the mass of the planet because you can tell
• 27:35
  Speaker 1: how much it's pulling on the star, and you can
• 27:37
  Speaker 1: tell something about its period because you can tell, like
• 27:40
  Speaker 1: how when the star wiggles one way and the other way.
• 27:42
  Speaker 1: But this wiggle method doesn't tell you anything about the
• 27:45
  Speaker 1: size of the planet because you know, you don't know
• 27:47
  Speaker 1: if it's like a big fluffy pile of styrofoam or
• 27:50
  Speaker 1: a tiny little black hole. They would have the same
• 27:53
  Speaker 1: gravitational effect on the star, right, they would wiggle the
• 27:56
  Speaker 1: star in the same way. And so that was two
• 27:58
  Speaker 1: thousand four. All we knew about this thing was how
• 28:01
  Speaker 1: long it took to go around its Sun and how
• 28:04
  Speaker 1: massive it was. But then like seven years later, we
• 28:07
  Speaker 1: got better telescopes and we trained them on the star
• 28:10
  Speaker 1: and we were able to measure the size of this
• 28:12
  Speaker 1: planet by seeing it eclipsing its star. Like you know,
• 28:15
  Speaker 1: if you go out and you watching eclipse, you see
• 28:17
  Speaker 1: the Moon passing in front of the Sun and it
• 28:18
  Speaker 1: blocks it out it's very dramatic. This is very different
• 28:21
  Speaker 1: because the planet is much much smaller than the star,
• 28:23
  Speaker 1: and so it's sort of like watching a moth lock
• 28:26
  Speaker 1: in front of a light bulb from like thousands of
• 28:28
  Speaker 1: miles away and then measuring how much the light bulb
• 28:30
  Speaker 1: dims because of the moth And you can use that
• 28:33
  Speaker 1: to measure the size of the planet, because the larger
• 28:35
  Speaker 1: planet would dim the star more than a smaller planet. Right.
• 28:39
  Speaker 1: Or if you're like looking at the Moon at night,
• 28:41
  Speaker 1: for example, and a little fly between you and the Moon,
• 28:45
  Speaker 1: you would sort of see the light from the Moon,
• 28:47
  Speaker 1: you know, get a little bit dimmer. But it's just
• 28:50
  Speaker 1: a little tiny bit, just a little tiny bit. But
• 28:53
  Speaker 1: if you watch, you can see it. And you can
• 28:54
  Speaker 1: see it happened periodically also, which really helps. It's not
• 28:58
  Speaker 1: just like one blip and you say, oh, is that
• 29:00
  Speaker 1: noise or mistake in my data. If it happens periodically
• 29:03
  Speaker 1: regularly and it matches up with the velocity measurements you're
• 29:06
  Speaker 1: making of the star, that you can be pretty confident
• 29:09
  Speaker 1: that that's what you're seeing, So then you know the
• 29:11
  Speaker 1: size of the planet. Also from that, you can make
• 29:13
  Speaker 1: measurements of its density and you can know like something
• 29:16
  Speaker 1: about what it's made out of. So you can tell
• 29:18
  Speaker 1: the mass from the wiggle, and you can tell the
• 29:21
  Speaker 1: size from the shadow it makes in front of the
• 29:23
  Speaker 1: that star. And so we have a measure of its density,
• 29:26
  Speaker 1: and I'm guessing it must be pretty dense if we're
• 29:28
  Speaker 1: thinking it might be made out of diamond core. Yeah,
• 29:30
  Speaker 1: this thing is like nine times the massive the Earth,
• 29:34
  Speaker 1: but its diameter is only twice the Earth, right, and
• 29:37
  Speaker 1: so it's definitely denser than the Earth is by how
• 29:40
  Speaker 1: much like three or four times? Yeah, Well, the diameter
• 29:42
  Speaker 1: of twice the Earth means that is volume is eight
• 29:46
  Speaker 1: times the Earth, right, and it's got a massive nine
• 29:49
  Speaker 1: times the Earth, So it's actually only a little bit
• 29:51
  Speaker 1: denser than the Earth is. So it must be like
• 29:53
  Speaker 1: a rocky planet or something, but it's just a little
• 29:56
  Speaker 1: bit more dense than the Earth. And the Earth is
• 29:58
  Speaker 1: pretty dense, right, Like the Earth is a rock you
• 30:00
  Speaker 1: planet with lava and rock, right, it's not. We're not
• 30:02
  Speaker 1: made out of a coun candy exactly. But this planet
• 30:05
  Speaker 1: is very different from the Earth because it's so close
• 30:07
  Speaker 1: to its son and it has an eighteen hour orbit,
• 30:11
  Speaker 1: like it takes eighteen hours for a year to pass
• 30:14
  Speaker 1: on this planet, like it goes around its son every
• 30:16
  Speaker 1: eighteen hours. Every eighteen hours there's a birthday party. It's
• 30:21
  Speaker 1: spent basically all of your time shopping for presents, an
• 30:24
  Speaker 1: opening presence, half the time shopping the o they have
• 30:27
  Speaker 1: opening them, that's right, and eating cake. And that makes
• 30:30
  Speaker 1: the surface of this planet very, very hot, like three thousand,
• 30:33
  Speaker 1: nine hundred degrees fahrenheit or c that's hot. That's pretty hot.
• 30:38
  Speaker 1: You don't need to lie your birthday candle. They're already
• 30:41
  Speaker 1: on fire, so I recommend a pool party. And that's
• 30:43
  Speaker 1: important to understand because when you're building models of these planets,
• 30:47
  Speaker 1: you have to understand like what state the materials that
• 30:50
  Speaker 1: you're putting into your model of the planet are. So
• 30:52
  Speaker 1: for example, they started off by assuming that this planet,
• 30:55
  Speaker 1: like Earth, has a lot of oxygen in it, Like
• 30:57
  Speaker 1: Earth is a lot of oxygen that doesn't have a
• 31:00
  Speaker 1: whole lot of carbon in it. And if you're going
• 31:02
  Speaker 1: to have a planet this size and with a lot
• 31:04
  Speaker 1: of oxygen in it, it should have a lot of
• 31:06
  Speaker 1: water on it. But it's sort of weird to have
• 31:09
  Speaker 1: all that water on the surface, like this planet would
• 31:11
  Speaker 1: be like ten water ten percent of the mass of
• 31:14
  Speaker 1: this planet would be watering to get the right size
• 31:16
  Speaker 1: and their identsity. But if you have that much water,
• 31:18
  Speaker 1: you're basically talking an ocean planet, but that much radiation
• 31:22
  Speaker 1: on the surface which split all the water and put
• 31:24
  Speaker 1: it in a supercritical state. So sort of a weird
• 31:27
  Speaker 1: idea to begin with. A right, it's not a good
• 31:29
  Speaker 1: assumption to think it's just like the Earth. Yeah, So
• 31:31
  Speaker 1: then what happened to convince them that maybe this planet
• 31:34
  Speaker 1: was different was that they learned something about the star.
• 31:36
  Speaker 1: They looked in more depth at what the star was
• 31:39
  Speaker 1: made out of, and they noticed that it had a
• 31:41
  Speaker 1: lot of carbon in it, a lot more carbon than
• 31:44
  Speaker 1: our star. For example, remember that these solar systems are
• 31:47
  Speaker 1: formed from leftover materials from other generations of solar systems,
• 31:51
  Speaker 1: So you have still mostly hydrogen, but like some of
• 31:54
  Speaker 1: them have more oxygen, some of them more carbon, some
• 31:56
  Speaker 1: of them have more of this, some of them have
• 31:58
  Speaker 1: more of that. This solar system seemed to have been
• 32:00
  Speaker 1: formed out of materials that were richer in carbon than
• 32:04
  Speaker 1: our solar system. So they think, Okay, that star has
• 32:07
  Speaker 1: a lot of carbon in it, Maybe the planet has
• 32:09
  Speaker 1: a lot of carbon also, maybe our assumption that this
• 32:12
  Speaker 1: planet was oxygen rich like the Earth was wrong. And
• 32:15
  Speaker 1: they said, well, what model could you build if you
• 32:17
  Speaker 1: started from carbon instead of from oxygen. I see, to
• 32:20
  Speaker 1: get the right sort of like size and mass, and
• 32:24
  Speaker 1: to make it sort of carbon ridge, you would have
• 32:26
  Speaker 1: to make the planet have a lot of carbon. Yeah,
• 32:29
  Speaker 1: so they said, well, maybe the planet is like one
• 32:31
  Speaker 1: third carbon, And then they started playing with models like
• 32:34
  Speaker 1: what would happen if you had a planet that was
• 32:36
  Speaker 1: one third carbon and this big right at this certain density.
• 32:40
  Speaker 1: They realized that would create an incredible pressure at its
• 32:43
  Speaker 1: core and that in some circumstances you would get an
• 32:46
  Speaker 1: enormous diamond, you know, like we're talking a diamond it's
• 32:49
  Speaker 1: like thousands of kilometers across because I guess you're assuming
• 32:52
  Speaker 1: all the carbon would sort default to the middle or
• 32:55
  Speaker 1: like it would push all the other stuff out as
• 32:57
  Speaker 1: it forms the diamond. And this incredible pressure, you know,
• 33:01
  Speaker 1: would essentially turn all of this carbon at the core
• 33:04
  Speaker 1: into a diamond. And obviously there would be impurities, right,
• 33:07
  Speaker 1: You'd have heavier metals like iron also, So wouldn't be
• 33:09
  Speaker 1: just like one pure perfect diamond, great triple A or anything,
• 33:14
  Speaker 1: but it would be like mostly diamond. Wow. And so
• 33:16
  Speaker 1: we're talking how big do you think this diamond is?
• 33:19
  Speaker 1: Like the size of Manhattan or the size of Australia.
• 33:22
  Speaker 1: How big do you think this diamond cores? You know,
• 33:24
  Speaker 1: this thing would be a third of the planet. So
• 33:27
  Speaker 1: it's huge. Yeah, I mean we're talking thousands of kilometers across. Wow,
• 33:31
  Speaker 1: Like bigger than the Moon, Bigger than much bigger, like
• 33:35
  Speaker 1: almost the size of Earth exactly. So what's kind of
• 33:37
  Speaker 1: ring would you need for a diamond bigger than the moon? Yeah,
• 33:40
  Speaker 1: so I guess if you like it, you better put
• 33:42
  Speaker 1: a rig on it, right exactly? There create a better
• 33:49
  Speaker 1: step up. All right, Well, thank you, Anthony. I that's
• 33:52
  Speaker 1: a great question, and I think that's the answer. We
• 33:54
  Speaker 1: think that this planet that's out there orbiting another star
• 33:58
  Speaker 1: has a lot of carbon in it. And if you
• 34:00
  Speaker 1: have that much carbon in a planet under that much
• 34:03
  Speaker 1: pressure inside it might form into a diamond. And so yes,
• 34:06
  Speaker 1: there might be a giant diamond inside of that planet.
• 34:09
  Speaker 1: That's right. But this, of course is all hypothetical. We
• 34:12
  Speaker 1: have a very few pieces of information. We're playing a
• 34:14
  Speaker 1: lot of games about what might be possible, and in
• 34:17
  Speaker 1: coming years we'll be able to image these planets and
• 34:19
  Speaker 1: see more about the light that's reflected from the surface
• 34:22
  Speaker 1: off of their stars and learning more about their atmospheres.
• 34:25
  Speaker 1: We'll get a lot more information about these planets, and
• 34:27
  Speaker 1: then we'll figure out what's out there, and probably what
• 34:30
  Speaker 1: we learned will be even more shocking than anything we hypothesized.
• 34:34
  Speaker 1: I guess the hard part would be mining this giant diamond, Like,
• 34:36
  Speaker 1: first of all, how do you like break it apart?
• 34:39
  Speaker 1: And the other part is how do you get it
• 34:41
  Speaker 1: out of the core of a giant planet? How do
• 34:43
  Speaker 1: you polish it right? You need to shine this thing
• 34:45
  Speaker 1: up if you're gonna sell it at market value. All right, well,
• 34:48
  Speaker 1: let's get into our last question from kids today, and
• 34:50
  Speaker 1: it's about the expanding the universe. But first let's take
• 34:53
  Speaker 1: another quick break. We are taking questions from kids today
• 35:09
  Speaker 1: and our last question comes from Addie, who is eight
• 35:12
  Speaker 1: years old. Hi, danieland my name is Abby and I
• 35:18
  Speaker 1: am eight years old. My question is, since the universe
• 35:23
  Speaker 1: is expanding faster than the speed of why can it
• 35:26
  Speaker 1: go back in time? Thank you? WHOA. This question just
• 35:31
  Speaker 1: blew my mind. Can the universe itself be traveling back
• 35:37
  Speaker 1: in time? That's crazy? But first, of all, I have
• 35:39
  Speaker 1: a question for you, Daniel, why do kids always identify
• 35:42
  Speaker 1: their age? Like, at what point do we as adults
• 35:44
  Speaker 1: stop saying how old we are? I think the point
• 35:46
  Speaker 1: where we stop remembering how old we are. I introduced
• 35:49
  Speaker 1: myself and I'm like, oh, I'm forty four. My kids
• 35:50
  Speaker 1: are like, no, you're forty six, dude. Yeah. Yeah, but
• 35:56
  Speaker 1: it's great to know. Thank you, Addie. This is a
• 35:58
  Speaker 1: great question. I think Audi is putting a couple of
• 36:01
  Speaker 1: ideas here together, right, Like we know, and we've talked
• 36:03
  Speaker 1: about the idea that the universe is expanding, and it's
• 36:06
  Speaker 1: expanding at its edges, or at least as far as
• 36:09
  Speaker 1: the furthest from us as you can faster than the
• 36:12
  Speaker 1: speed of light. And we've also talked about how like,
• 36:15
  Speaker 1: nothing can move this faster than the speed of light,
• 36:17
  Speaker 1: but if it does, it would mean it would sort
• 36:19
  Speaker 1: of go back in time or break the rules of time. Yeah,
• 36:21
  Speaker 1: these are two really fun ideas, and I love hearing
• 36:24
  Speaker 1: kids put these ideas together and your first you're like, no,
• 36:26
  Speaker 1: that's crazy, and you know, hold on a second, Maybe
• 36:28
  Speaker 1: that's a good point. Maybe he's right, maybe going back right,
• 36:31
  Speaker 1: it's not just kids I'm like, yeah, yeah, what's the
• 36:34
  Speaker 1: answer here is the edge of the universe going back
• 36:37
  Speaker 1: in time. It's a great question, and you know, he's
• 36:40
  Speaker 1: right that the universe is expanding faster than the speed
• 36:43
  Speaker 1: of light. But there's some important subtleties there, right, like
• 36:47
  Speaker 1: what is happening. It's not that things are flying out
• 36:51
  Speaker 1: through the universe and that they're traveling relative to each
• 36:54
  Speaker 1: other faster than the speed of light. You know, like
• 36:57
  Speaker 1: no object is looking at another object and saying your
• 37:00
  Speaker 1: velocity is greater than the speed of light. However, that
• 37:03
  Speaker 1: doesn't mean that distances can't increase faster than the speed
• 37:07
  Speaker 1: of light. Right, It all depends on sort of who's
• 37:10
  Speaker 1: asking the question. It's like, nobody is moving faster than
• 37:12
  Speaker 1: the speed of light, but things are. The space itself
• 37:16
  Speaker 1: is growing faster than the speed of light overall. That's right,
• 37:19
  Speaker 1: because new space is being created between galaxies, new spaces
• 37:24
  Speaker 1: being created, and there's no limit to how fast space
• 37:27
  Speaker 1: can be created. And you might ask, like a hold
• 37:29
  Speaker 1: on a second, who's creating new space and how does
• 37:31
  Speaker 1: it work? And surely there's somebody in charge of it
• 37:34
  Speaker 1: and there's limits, right, we don't know. The answer is
• 37:36
  Speaker 1: to any of those questions. We just see that space
• 37:39
  Speaker 1: is expanding. This is what we call dark energy, and
• 37:41
  Speaker 1: so we know that something out there is capable of
• 37:45
  Speaker 1: expanding the universe itself, of stretching space or making new space,
• 37:49
  Speaker 1: and that's happening everywhere Isotropically, the whole universe is expanding,
• 37:53
  Speaker 1: but it only happens a little bit over a short distance.
• 37:57
  Speaker 1: So between me and you, for example, wherever you are
• 37:59
  Speaker 1: in the Earth Earth, space is expanding a very very
• 38:02
  Speaker 1: tiny bit every year, but you know, the Earth holds
• 38:04
  Speaker 1: us together. Between us and the Sun, space is expanding
• 38:07
  Speaker 1: a little bit more every year, but the Sun holds
• 38:10
  Speaker 1: us together. But between us and other galaxies, there's a
• 38:13
  Speaker 1: lot of space there. So all the new little bits
• 38:15
  Speaker 1: of space add up and it becomes pretty significant. And
• 38:18
  Speaker 1: across the whole universe is huge amounts of space. So
• 38:21
  Speaker 1: you're add up all of those expansions and you actually
• 38:24
  Speaker 1: do get speeds that exceed the speed of light. It's
• 38:27
  Speaker 1: kind of like maybe for audi here it's almost like
• 38:29
  Speaker 1: you can't run faster than the speed of light in
• 38:31
  Speaker 1: your house, but your house is sort of growing a
• 38:34
  Speaker 1: little bit. So you stand on one end of the
• 38:36
  Speaker 1: house and you look at the other end of the house,
• 38:38
  Speaker 1: at the on the other side, you would see it
• 38:40
  Speaker 1: sort of growing faster than like could move. That's exactly right,
• 38:45
  Speaker 1: And so we can measure the distances to things we
• 38:48
  Speaker 1: see that those velocities do seem to add up to
• 38:50
  Speaker 1: be greater than the speed of light. But you know,
• 38:52
  Speaker 1: if you looked at any one thing and you asked,
• 38:54
  Speaker 1: how fast is this one thing moving relative to me,
• 38:57
  Speaker 1: you would never measure a velocity greater than the speed
• 39:00
  Speaker 1: of light, because remember, you can't measure velocity relative to space.
• 39:04
  Speaker 1: Space doesn't have like a reference frame. There's no absolute
• 39:07
  Speaker 1: frame there. You can only measure velocities relative to an object.
• 39:10
  Speaker 1: All right, So then the universe is expanding faster than
• 39:13
  Speaker 1: light can travel, but nothing is actually moving faster than light.
• 39:17
  Speaker 1: And so the other idea they put together is this
• 39:19
  Speaker 1: idea that going faster than light somehow breaks time or
• 39:22
  Speaker 1: makes you go backwards in time. Yeah, that's a really
• 39:24
  Speaker 1: fun conclusion, and it's sort of meant to tell you
• 39:28
  Speaker 1: that you can't go faster than the speed of light.
• 39:30
  Speaker 1: You know, we have these ideas of how the universe works,
• 39:33
  Speaker 1: of how information can propagate, and how there's a maximum
• 39:36
  Speaker 1: speed of information, that no information can move faster than
• 39:39
  Speaker 1: the speed of light. No object, and no information, no particle,
• 39:43
  Speaker 1: no wave can ripple faster than the speed of light.
• 39:45
  Speaker 1: And what happens if you ask, like, well, what happens
• 39:48
  Speaker 1: if an object does move faster than the speed of light, Well,
• 39:51
  Speaker 1: then you get a paradox, You get contradictions. You get
• 39:53
  Speaker 1: things like, well, if it could move fast in the
• 39:56
  Speaker 1: speed of light, that would be equivalent to it moving
• 39:58
  Speaker 1: backwards in time, which we know to be impossible. And
• 40:01
  Speaker 1: so it's sort of just like another way of saying
• 40:03
  Speaker 1: that you can't move fast in the speed of light.
• 40:05
  Speaker 1: Sometimes people interpret this saying like, oh, if you want
• 40:07
  Speaker 1: to go backwards in time, all you gotta do is
• 40:09
  Speaker 1: go fast in the speed of light. But it's sort
• 40:11
  Speaker 1: of like saying no, that's impossible, right, like Superman and Superman.
• 40:15
  Speaker 1: But I guess maybe I'm wondering if it's maybe a
• 40:17
  Speaker 1: little bit of a circular argument, Like you're sort of
• 40:19
  Speaker 1: assuming you can't go it faster than the speed of light,
• 40:21
  Speaker 1: and then you say, but if you can, then it
• 40:23
  Speaker 1: would break the rules. It's almost like you make an
• 40:26
  Speaker 1: assumption and then you say, if you break the assumption,
• 40:28
  Speaker 1: then it doesn't work. Yeah, absolutely, And you're right, And
• 40:31
  Speaker 1: we don't understand this limit at all. You know, we
• 40:33
  Speaker 1: observe this limit. We say the speed of light is constant.
• 40:37
  Speaker 1: It doesn't depend on who is sending the message or
• 40:40
  Speaker 1: their velocity. It's always the same speed. And if you
• 40:42
  Speaker 1: start from that, then you get to consequences like you
• 40:45
  Speaker 1: can't move faster than the speed of light, and all
• 40:47
  Speaker 1: sorts of things about how time varies, all of special
• 40:50
  Speaker 1: relativity is based on that one observation. We don't know
• 40:52
  Speaker 1: why that thing is true, but everything flows from that
• 40:56
  Speaker 1: thing that the speed of light is constant for all observers,
• 40:59
  Speaker 1: and so that's what limits you to going faster than
• 41:02
  Speaker 1: the speed of light. And so you're right. If we
• 41:04
  Speaker 1: observe the scenario in which that wasn't true anymore, then
• 41:07
  Speaker 1: maybe you would, you know, change all these other rules,
• 41:09
  Speaker 1: or maybe that's wrong and we just don't understand. So
• 41:12
  Speaker 1: if you see somebody going fast in the speed of
• 41:13
  Speaker 1: light or going backwards in time, that suggests that the
• 41:17
  Speaker 1: speed of light is not constant for all observers. Interesting,
• 41:21
  Speaker 1: I see. It's like from what we can see about
• 41:22
  Speaker 1: the universe, we came up with the speed limit of
• 41:25
  Speaker 1: the universe, and then breaking that speed limit suddenly breaks
• 41:28
  Speaker 1: everything we know about time and everything else. But it is,
• 41:31
  Speaker 1: I guess, technically possible that you could would like go
• 41:33
  Speaker 1: faster than light. It's technically possible in the sense that,
• 41:36
  Speaker 1: you know, we've never observed it, and everything we have
• 41:38
  Speaker 1: observed suggests that it is impossible. But you know, that's
• 41:41
  Speaker 1: just physics. These are theories. We make an observation here,
• 41:44
  Speaker 1: we infer about the universe. From it, we draw conclusions.
• 41:47
  Speaker 1: If those conclusions are wrong, then either our inference was
• 41:50
  Speaker 1: wrong or the observations we made were wrong, And hey,
• 41:53
  Speaker 1: that would be awesome because that would be you know,
• 41:56
  Speaker 1: a childlike dream to overthrow something so basic. Is like
• 41:59
  Speaker 1: the fact that the speed of light is the same
• 42:01
  Speaker 1: as measured by everybody. But you know, it's something it's
• 42:03
  Speaker 1: experiments we've been doing for more than a hundred years,
• 42:05
  Speaker 1: and we've seen it very concretely and very stable for
• 42:09
  Speaker 1: a long time. So we're pretty confident in this observation
• 42:12
  Speaker 1: that the speed of light is always the same no
• 42:14
  Speaker 1: matter who measures it, and the implication of that that
• 42:16
  Speaker 1: it means that you can't go faster than the speed
• 42:18
  Speaker 1: of light is also pretty solid, so I think it's
• 42:21
  Speaker 1: pretty air tight. But yeah, we have made mistakes before, right,
• 42:24
  Speaker 1: And so where there's this idea that going faster than
• 42:27
  Speaker 1: the speed of light would make time go backwards somehow, Well,
• 42:30
  Speaker 1: it comes from the idea that time is sort of fungible,
• 42:33
  Speaker 1: that like the order of events that happen depends on
• 42:36
  Speaker 1: your speed. Like if you're watching two things happen, like
• 42:39
  Speaker 1: Alice eats a pie and then Bob eats a pie,
• 42:43
  Speaker 1: and you're sitting there with them and you're watching, maybe
• 42:45
  Speaker 1: you think Alice finishes first. But if I'm going at
• 42:47
  Speaker 1: really high speed, I can find some scenario in which
• 42:51
  Speaker 1: I see the order of events happening differently. Right, So,
• 42:54
  Speaker 1: like Alice finishing before Bob is not like a universal truth.
• 42:58
  Speaker 1: It depends on who's asking and how fast they're going.
• 43:01
  Speaker 1: And so this idea that you know you can change
• 43:03
  Speaker 1: the order of events depends on your velocity tells you
• 43:07
  Speaker 1: that you can sort of play with time, and that
• 43:09
  Speaker 1: the velocity and time are connected. But it's not necessarily
• 43:13
  Speaker 1: the case that if you are going faster than the
• 43:15
  Speaker 1: speed flight. Let's say it was possible that some out
• 43:18
  Speaker 1: time would flow backwards or like your clocks would certainly
• 43:22
  Speaker 1: start going the other way, or you know, you would
• 43:24
  Speaker 1: travel to a different time. And that's sort of so
• 43:27
  Speaker 1: far kind of not really establishing the math. Well, what
• 43:30
  Speaker 1: the math suggests is that if you go faster than
• 43:32
  Speaker 1: the speed of light, then you can invert the order
• 43:35
  Speaker 1: of things that you otherwise shouldn't be able to, Like
• 43:37
  Speaker 1: you can switch who wins the pie eating contest, Alice
• 43:40
  Speaker 1: or Bob by going faster or slower, going in some
• 43:42
  Speaker 1: direction because those things aren't like caustically connected, doesn't really
• 43:45
  Speaker 1: matter which one happens first. But if you go faster
• 43:48
  Speaker 1: than the speed of light, then you might see weird
• 43:50
  Speaker 1: things like Alice arrives in the pie eating contest before
• 43:53
  Speaker 1: she leaves her house. You know, you can switch the
• 43:56
  Speaker 1: order of things so they're like reversed in time. So
• 43:59
  Speaker 1: in that sense, you're sort of like going backwards. You
• 44:01
  Speaker 1: would maybe experience things backwards, is what you're saying, which
• 44:05
  Speaker 1: is sort of like and if the whole universe is
• 44:07
  Speaker 1: going backwards, and it's sort of like you're going back
• 44:09
  Speaker 1: in time, is what you're saying. And we have a
• 44:11
  Speaker 1: whole interesting episode about this theoretical particle called a tachion,
• 44:16
  Speaker 1: which in principle moves faster than the speed of light.
• 44:18
  Speaker 1: But you know, if it exists, it would break all
• 44:20
  Speaker 1: sorts of special relativity, but has really weird properties, like
• 44:24
  Speaker 1: you see it as if it's leaving, even if it's arriving,
• 44:27
  Speaker 1: because the later light arrives first, because it's moving faster
• 44:30
  Speaker 1: than light. I see. So if this particle is really
• 44:33
  Speaker 1: would be very tacky. It would be breaking everything in
• 44:37
  Speaker 1: the universe, and that's just not cool. That's right. You'd
• 44:39
  Speaker 1: invited your birthday party and it would look like it's
• 44:41
  Speaker 1: leaving your birthday party, and you're like, hey man, yeah,
• 44:44
  Speaker 1: hey man. All right. Well it's a great question from Audi,
• 44:47
  Speaker 1: is if the universe expanding faster than light, can I
• 44:50
  Speaker 1: go back in time? And the answer is kind of
• 44:53
  Speaker 1: yes and no, Like, yes, the universe is expanding faster
• 44:56
  Speaker 1: than light, but for you to sort of break the
• 44:58
  Speaker 1: laws of time, you kind of have to travel faster
• 45:01
  Speaker 1: than light, which is not what the universe is doing.
• 45:03
  Speaker 1: The universe is expanding faster than light, but it's not
• 45:06
  Speaker 1: traveling faster than light. That's right. Nothing is moving faster
• 45:09
  Speaker 1: than light relative to any other thing, and so that
• 45:12
  Speaker 1: doesn't break the laws of special relativity. Well, things are
• 45:15
  Speaker 1: growing in distance from one edge of the universe to
• 45:17
  Speaker 1: the other. It's faster than light, but nothing's actually you
• 45:20
  Speaker 1: could say, is traveling through that space faster than than light? Yeah,
• 45:23
  Speaker 1: that's right, all right. Well those were three awesome questions
• 45:26
  Speaker 1: from kids. Thank you kids for sending in your questions,
• 45:29
  Speaker 1: and thank you parents for encouraging your kids to think
• 45:32
  Speaker 1: about the universe and ask the deep questions, because it's
• 45:35
  Speaker 1: those kids that we hope are going to one day
• 45:37
  Speaker 1: figure out the answers to these questions. They're not so
• 45:40
  Speaker 1: entrenched in today's ideas about how the universe work, and
• 45:43
  Speaker 1: they might have crazy new ideas about how to use
• 45:46
  Speaker 1: lightsabers to cut open black holes and solve the mysteries
• 45:48
  Speaker 1: of quantum gravity. I don't think we need to think
• 45:50
  Speaker 1: the parents, Daniel. Everyone knows it's a thankless job you
• 45:54
  Speaker 1: don't really get. But thank you to all of our listeners,
• 45:58
  Speaker 1: young and old for having question us about the universe.
• 46:00
  Speaker 1: I've been curious for wandering about this amazing and mysterious
• 46:05
  Speaker 1: cosmos that we live in. And if you have questions,
• 46:07
  Speaker 1: please feel free to send them to us. We hope
• 46:10
  Speaker 1: you enjoyed that. Thanks for listening, See you next time.
• 46:21
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge explained.
• 46:24
  Speaker 1: The Universe is a production of I heart Radio. For
• 46:27
  Speaker 1: more podcast for my heart Radio, visit the i heart
• 46:30
  Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your
• 46:33
  Speaker 1: favorite shows. Ye