Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 35: Exomoons, black holes and math!

Transcript

Listener Questions 35: Exomoons, black holes and math! · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, do people still write us with questions? You know,
0:11
Speaker 1: the inboxes overflowing like usual, overflowing? Don't you answer them?
0:15
Speaker 1: I do, but every time I send a response, it
0:17
Speaker 1: just seems to generate more questions. You're not giving them
0:20
Speaker 1: a good answer. Maybe, but even when they say, oh,
0:23
Speaker 1: now I get it, they always come back with but
0:26
Speaker 1: that makes me wonder about something else. You should try
0:29
Speaker 1: asking them a question you stopped them that might give
0:32
Speaker 1: them something to think about, A question like would you
0:34
Speaker 1: fund my research? Oh? Nobody will ride you back? Then
0:40
Speaker 1: the question to end all questions? Literally, Hi am or
0:59
Speaker 1: handmad cartoonist and the creator of PhD comments. Hi, I'm Daniel.
1:02
Speaker 1: I'm a particle physicist and a professor at U c Irvine,
1:06
Speaker 1: and I refuse to limit my chuckles. Are people trying
1:09
Speaker 1: to limit your chuckles? Are you under the oppressive rule
1:12
Speaker 1: of an anti chuckler? Well, we did have one person
1:14
Speaker 1: who wrote in and complain about how much time I
1:16
Speaker 1: spent chuckling on the podcast, and then we talked about
1:18
Speaker 1: it on a recent episode, and then I got an
1:20
Speaker 1: avalanche of emails from people who say, never stopped chuckling.
1:23
Speaker 1: All right, there you go. You got some support from
1:26
Speaker 1: the internet to keep chuckling. Somebody literally wrote to me
1:29
Speaker 1: this morning and said, chuckle to your heart's content, sir.
1:32
Speaker 1: So here I am chuckling away. It seems like a
1:35
Speaker 1: bit of an overreaction over one comment from the internet.
1:38
Speaker 1: It's suddenly turned into a social cause. Here free Daniel's chuckles. Now,
1:43
Speaker 1: I'm self conscious about it. I don't know if I'm
1:45
Speaker 1: chuckling on purpose, or chuckling to chuckle, or what's going on.
1:48
Speaker 1: I got to get out of my own head. Oh man,
1:50
Speaker 1: So they are being limited, they are shackled. Now. I
1:53
Speaker 1: think maybe it's like a quantum thing. We just shouldn't
1:55
Speaker 1: look at it so much and just let it be itself.
1:57
Speaker 1: Let it be both annoying and endearing at this same time.
2:00
Speaker 1: Stop trying to measure the chuckle and let it be
2:03
Speaker 1: uncertain but welcome. For a podcast, Daniel and Jorge Explain
2:06
Speaker 1: the Universe, a production of I Heart Radio in which
2:08
Speaker 1: we do try to measure the universe, or at least
2:11
Speaker 1: our understanding of it. Our goal is to use our
2:15
Speaker 1: minds to try to nail down everything that's happening out
2:18
Speaker 1: there in the universe from the tiniest little vibrating strings
2:21
Speaker 1: that might make up the very fabric of reality, all
2:24
Speaker 1: the way up to cosmic black holes that are swallowing
2:27
Speaker 1: the centers of galaxies. We think it's a worthwhile way
2:31
Speaker 1: to spend your time to try to understand the universe,
2:34
Speaker 1: and we exult in the joy of our curiosity and
2:36
Speaker 1: the chuckles that we find along the way. Yeah, because
2:39
Speaker 1: it is a wonderful universe. It's huge, it's amazing, it's fascinating.
2:44
Speaker 1: It gives us a lot to think about, and, as
2:46
Speaker 1: you said, sometimes a lot to chuckle about. It's kind
2:48
Speaker 1: of a funny universe. Funny smelling, funny looking, or funny weird.
2:54
Speaker 1: It's got all the funnies. It's quantum in that way
2:56
Speaker 1: as well. It's both funny ha ha and funny uh
3:00
Speaker 1: at the same time. It's a superposition of funnies. It
3:03
Speaker 1: is pretty funny weird, that's for sure. So many things
3:06
Speaker 1: we have discovered about the universe that make us go,
3:08
Speaker 1: what that can't possibly be true, And then we do
3:11
Speaker 1: the experiment and the universe says, oh, yeah, that's exactly
3:14
Speaker 1: what's going on, and it makes us reformulate the way
3:17
Speaker 1: we think about the whole universe. For me, those are
3:20
Speaker 1: the best moments in science, when the universe tells us
3:23
Speaker 1: that we've been thinking about things the wrong way the
3:25
Speaker 1: whole time. And science is how we explore the universe
3:29
Speaker 1: and find out how things work and why they are
3:31
Speaker 1: the way they are. And the way we do that
3:33
Speaker 1: is with questions, right. Science is all based on questions.
3:36
Speaker 1: Science is basically just people asking questions. You might imagine
3:41
Speaker 1: that science is like some big building with columns where
3:44
Speaker 1: information gets turned out on like a ticker tape or something,
3:47
Speaker 1: But it's just a bunch of people being curious about
3:49
Speaker 1: the universe. Every time you spend like nineteen seconds reading
3:53
Speaker 1: about the life cycle of some guinea pig, it's because
3:56
Speaker 1: some person has decided to devote their life to studying
3:59
Speaker 1: that mee pig and how it spends its time. But
4:02
Speaker 1: what you mean every time I spend nineteen seconds reading
4:04
Speaker 1: about a guinea pig? Often do you spend nineteen seconds
4:06
Speaker 1: reading about guinea pigs? Do I need to answer that question?
4:10
Speaker 1: That's a question I don't want to answer to. I'm
4:13
Speaker 1: not sure we want to go there. It's just a
4:14
Speaker 1: hypothetical example. I want people to appreciate the time and
4:18
Speaker 1: devotion that goes into every single scientific bit of knowledge
4:22
Speaker 1: we have. Each one comes from some individual needing to
4:26
Speaker 1: know the answer to that question. So science is in
4:29
Speaker 1: the end, just a bunch of people asking questions and
4:32
Speaker 1: deciding they got to know the answer, and then Daniel
4:35
Speaker 1: deciding he's only going to spend nineteen seconds reading about
4:37
Speaker 1: their lives work. Well, there is this amazing asymmetry right
4:40
Speaker 1: in the same way you can spend decades doing research
4:43
Speaker 1: and somebody can just like skim it on their phone
4:45
Speaker 1: while they're in the bathroom and they go, oh, that's cool,
4:47
Speaker 1: and then they move on with their lives. Right, But
4:49
Speaker 1: think about the millions of people that could be reading
4:51
Speaker 1: this on their phones. If you multiply I guess those
4:54
Speaker 1: nineteen seconds of bathroom reading, you get, you know, millions
4:58
Speaker 1: of seconds of bathroom reading. It's my goal as a
5:00
Speaker 1: scientist is just to get maximum number of seconds of
5:03
Speaker 1: bathroom or aim low, you know, just aim somewhere. Who
5:10
Speaker 1: cares about Nobel prizes or citation counts or fancy awards
5:15
Speaker 1: seconds of bathroom phone scrolling. That's my new metric. All right,
5:19
Speaker 1: do you think academis should be based on that? Just
5:21
Speaker 1: forget about you know, impact factors and h Indices and
5:25
Speaker 1: Nobel Prices have a new award called the Toilets to Release.
5:31
Speaker 1: I do think it's important that we reach everybody out there.
5:34
Speaker 1: It's not important that they're on their toilet while we
5:37
Speaker 1: reach them, But I do think it's vital that science
5:40
Speaker 1: communicates outside of just academia and the rest of us scientists,
5:44
Speaker 1: to everybody out there who's curious about the world and
5:46
Speaker 1: who's helping to pay for our studies and pay our salaries.
5:50
Speaker 1: This knowledge and this curiosity belongs to everyone, which is
5:53
Speaker 1: why we did these episodes where we talk about questions
5:56
Speaker 1: from not just from cutting edge scientists, but from people
5:59
Speaker 1: out there like you. That's right, because science effects everybody,
6:02
Speaker 1: and in fact, everybody has questions about the universe, maybe
6:05
Speaker 1: not necessarily about guinea pigs or I'm sure people don't
6:08
Speaker 1: think they have questions about guinea pig, but maybe they do,
6:11
Speaker 1: and maybe they do have an ultimately question about how
6:13
Speaker 1: life on nurse is here, why we're here, why is
6:15
Speaker 1: the earth here, or what would it be like to
6:17
Speaker 1: live in other planets? Are you saying there are people
6:19
Speaker 1: out there who don't have questions about guinea pigs? Are
6:22
Speaker 1: you serious? How many people do you know? Have you
6:25
Speaker 1: met people outside of your little bubble there? It's just
6:27
Speaker 1: so easy for your brain to generate guinea pig questions,
6:30
Speaker 1: for example, how long would a guinea pig last on
6:32
Speaker 1: the surface of the moon, or on guinea meat or
6:35
Speaker 1: in outer space? Now you're sounding like a super villain.
6:39
Speaker 1: I'm not suggesting we do these experiments, but I would
6:42
Speaker 1: like to know the answer that people do have questions,
6:45
Speaker 1: and sometimes we answer them here on the podcast. That's right.
6:48
Speaker 1: If you have a question about something that doesn't make
6:50
Speaker 1: sense to you, or maybe you heard us talk about
6:52
Speaker 1: something on the podcast and it doesn't quite click in
6:55
Speaker 1: your brain, or you were just line in your back
6:57
Speaker 1: staring up at the stars and wondering what's going on
7:01
Speaker 1: at the heart of them? Right to us two questions.
7:03
Speaker 1: At Daniel and Jorge dot com, we answer every single
7:06
Speaker 1: email and tweet, and we will answer your question as well. Wait, Daniel,
7:10
Speaker 1: you don't answer all of my emails answer all emails
7:15
Speaker 1: from listeners. Absolutely, do you listen to our podcast? I
7:18
Speaker 1: do listen to the podcast. Maybe I just need to
7:20
Speaker 1: frame it in the form of a physics question. There
7:22
Speaker 1: you go. But people do send questions to us and
7:25
Speaker 1: we answer them here. And so today we have three
7:27
Speaker 1: great questions from listeners about exciting topics like what's it
7:31
Speaker 1: like to live in a moon of Jupiter? Question about
7:34
Speaker 1: black holes and whether they have a surface, and also
7:37
Speaker 1: a question about math, which I guess maybe it's not
7:40
Speaker 1: as exciting as the first two. What if it's about
7:42
Speaker 1: guinea pig math? Would that make you more or less interested?
7:45
Speaker 1: Does that mean like a trial math for the universe? No,
7:49
Speaker 1: it is an exciting question. Also, it's about the very
7:52
Speaker 1: nature of reality and whether reality is based on that,
7:55
Speaker 1: And so it's tackled this first question first, and this
7:57
Speaker 1: one comes from Billy. Hey, guys, I'm wondering what life
8:01
Speaker 1: would be like for humans on the moon of a
8:03
Speaker 1: gas giant. So suppose we find a Jupiter like system
8:06
Speaker 1: within what we currently understand as the habitable zone of
8:09
Speaker 1: a star. In this system is a moon that could
8:11
Speaker 1: sustain human life. What would the day night cycle look
8:15
Speaker 1: like with the planet or other moons blocking the Sun?
8:18
Speaker 1: What kind of seasons would you go through with the
8:21
Speaker 1: passing of more or less massive moons disrupt gravity? And
8:24
Speaker 1: interesting ways could one of those moons support smaller satellites
8:28
Speaker 1: like Phobos and demos. M Thanks and I look forward
8:31
Speaker 1: to hearing your answer. Awesome, Thank you, Billie. That's a
8:34
Speaker 1: great question, like what's it like? Because we often hear
8:37
Speaker 1: about how the moons of other planets are maybe habitable,
8:41
Speaker 1: and there are maybe like the size of the of Earth,
8:43
Speaker 1: and sometimes they even have water, and so diggussion is like,
8:46
Speaker 1: what would it be like to live in a moon
8:48
Speaker 1: of another planet? It's a great question to put yourself
8:50
Speaker 1: on the surface of one of those moons and think about,
8:52
Speaker 1: like what would this guy look like? How long would
8:55
Speaker 1: the day be, what would you see in this sky?
8:57
Speaker 1: How many eclipses would there be, what would the seasons
8:59
Speaker 1: be like. It's a really fun question, especially for example,
9:02
Speaker 1: if you're writing a science fiction novel that's set on
9:05
Speaker 1: one of those planets, as I suspect Billy might be, Well,
9:08
Speaker 1: you're really suspicious here. Do you think Billy just has
9:10
Speaker 1: an ulterior motive here? Can't you be asking out of
9:13
Speaker 1: cheer curiosity? Absolutely, maybe he is and maybe he isn't.
9:16
Speaker 1: But after we give our answer, I think he'll be
9:18
Speaker 1: well set up to write that novel, and I'm looking
9:20
Speaker 1: forward to reading it him and tens of thousands of
9:23
Speaker 1: people where you get typing fast billy. But it is
9:26
Speaker 1: an interesting question. What would it be like to live,
9:28
Speaker 1: for example, in a moon like Europa, which is a
9:30
Speaker 1: moon of Jupiter here in our solar system, which has
9:33
Speaker 1: water and it's it's sort of inhabitable soon, right, Yeah,
9:36
Speaker 1: and these moons are huge. Remember that Jupiter is much
9:40
Speaker 1: much bigger than Earth, and so a moon of Jupiter
9:43
Speaker 1: can be basically the size of a planet. Yeah. And
9:46
Speaker 1: Europe in particular has liquid water in it, right, Europa
9:49
Speaker 1: has an icy crust and we think oceans of liquid
9:52
Speaker 1: water underneath. We're sending probes up there to sample those
9:55
Speaker 1: oceans because sometimes they crack and shoot geysers of crystallized
9:59
Speaker 1: water own into space, and we're gonna try to send
10:02
Speaker 1: something through one of those plumes and see like is
10:05
Speaker 1: their organic material in there, maybe little frozen microbes. It's
10:08
Speaker 1: going to be pretty exciting. Yeah, And I think people
10:10
Speaker 1: have also talked about Titan, right, which is another moon
10:13
Speaker 1: in here in our solar system that might be livable. Yeah.
10:15
Speaker 1: A lot of these moons are pretty big and pretty
10:18
Speaker 1: rocky and might have liquid under the surface, so they
10:20
Speaker 1: might like naturally have their own life. It's a great
10:23
Speaker 1: way to ask the question like how likely is life
10:25
Speaker 1: to evolve? Because it's like an independent way to sample
10:29
Speaker 1: whether life emerges from similar conditions to what we have
10:33
Speaker 1: on Earth. And there's another question, which is like, what
10:35
Speaker 1: would it be like for us if we try to
10:37
Speaker 1: colonize these places and actually established bases there. What would
10:41
Speaker 1: your daily life be like on those surfaces? Yeah, and
10:44
Speaker 1: I guess that's the question Billy had because I guess
10:46
Speaker 1: if you're in a moon, then you're orbiting another planet,
10:49
Speaker 1: and then that planet is presumably orbiting the Sun of
10:52
Speaker 1: its solar system. And so the question is would that
10:55
Speaker 1: make your days and nights super wonky and unpredictable or
11:00
Speaker 1: would they make them maybe more predictable, or would you
11:03
Speaker 1: even have seasons? Things like seasons. Yeah, it wouldn't make
11:06
Speaker 1: it less predictable, but it would make it very, very
11:09
Speaker 1: different from our experience. Earth. For example, currently just orbits
11:12
Speaker 1: the Sun and we have a day night cycle because
11:15
Speaker 1: of the Earth's spin. If your moon around Jupiter, for example,
11:18
Speaker 1: then what determines whether you're seeing the Sun or not.
11:21
Speaker 1: It's not your spin, but how long it takes you
11:23
Speaker 1: to go around Jupiter. Wait, what do you mean Why
11:26
Speaker 1: is it determined by your orbit around Jupiter. Wouldn't it
11:28
Speaker 1: also depend on your inherent spin of the moon. There's
11:32
Speaker 1: a couple of reasons. One the reason is Jupiter is huge,
11:34
Speaker 1: and so it's going to eclipse the Sun pretty often.
11:37
Speaker 1: Right half the time, You're gonna have Jupiter between you
11:40
Speaker 1: and the Sun, and so because Jupiter is so big
11:43
Speaker 1: in your sky, you can have like hours long eclipses
11:47
Speaker 1: every day. Okay, maybe, um, let's get down to specifics,
11:50
Speaker 1: like if I was in a moon of Jupiter, what
11:53
Speaker 1: should I expect to see in terms of day and night?
11:56
Speaker 1: How often would I see the Sun? One key thing
11:57
Speaker 1: to understand is that these moons tend to be tidally locked,
12:01
Speaker 1: meaning that one side of them faces Jupiter and one
12:04
Speaker 1: side of them doesn't, just the way that like our
12:06
Speaker 1: moon faces the Earth. So there's the near side of
12:08
Speaker 1: the Moon and the far side of the Moon. We
12:10
Speaker 1: always see the same side of the Moon from Earth.
12:13
Speaker 1: But that doesn't necessarily mean that you're sort of going
12:16
Speaker 1: around the Earth at the same rate that the Earth
12:18
Speaker 1: is spinning, Like the Moon has a certain period around
12:21
Speaker 1: the Earth, but the Earth is also spinning. So it
12:23
Speaker 1: gets kind of complicated right, that's right. The Moon sees
12:26
Speaker 1: different parts of the Earth, right, but the Earth always
12:28
Speaker 1: sees the same side of the Moon. But now put
12:31
Speaker 1: yourself on the Earth sized moon around Jupiter. It takes
12:33
Speaker 1: like eighty five hours for Europa, for example, to go
12:36
Speaker 1: around Jupiter. So now your day night cycle is determined
12:39
Speaker 1: by how long it takes you to go around Jupiter. Okay,
12:42
Speaker 1: so like if Jupiter was standing still, Europa would take
12:45
Speaker 1: eighty five hours to go around to orbit around Jupiter.
12:48
Speaker 1: That's what you're saying, Yeah, exactly. And so at any
12:51
Speaker 1: given time, if it's on the side of Jupiter that's
12:55
Speaker 1: facing the Sun, and the outward facing side of the
12:58
Speaker 1: moon of Jupiter would see the sun, but the inner
13:01
Speaker 1: part of this, the part of the moon that's facing Jupiter,
13:05
Speaker 1: would not see the sun. Yeah, so you have like
13:07
Speaker 1: two important hemispheres. You have the far side of Europa,
13:09
Speaker 1: the one that's facing away from Jupiter, and the inner
13:12
Speaker 1: side of the one that's facing towards Jupiter on the
13:14
Speaker 1: far side, the outer side, that part never sees Jupiter.
13:17
Speaker 1: Jupiter never appears in the sky on the far side
13:20
Speaker 1: of Europa. But you do have eighty five hour long
13:22
Speaker 1: day night cycles. So you have like forty two hours
13:25
Speaker 1: of sunlight and then forty two hours of darkness. And
13:28
Speaker 1: that's a big difference from what we have here. Right,
13:30
Speaker 1: we have twenty four hour long periods which are determined
13:32
Speaker 1: by the spin of the Earth. On Europa, the day
13:34
Speaker 1: night cycles to term by how long it takes to
13:36
Speaker 1: go around Jupiter. And a longer day night cycle means
13:39
Speaker 1: higher temperatures during the day and colder temperatures at night. Yeah,
13:43
Speaker 1: you gotta pack a heavier sweater. I guess, But I
13:45
Speaker 1: guess if you're on the outside of the outward facing
13:48
Speaker 1: side of the Moon, then life would be pretty regular, right,
13:51
Speaker 1: and be sort of like here, except just longer days. Yeah,
13:54
Speaker 1: it would be here, just longer days. And it depends
13:56
Speaker 1: on how close in your orbit. For example, gannymed it's
13:59
Speaker 1: pure it is like a hundred and seventy hours, and
14:02
Speaker 1: I owe its period is forty two hours. So it
14:04
Speaker 1: depends how close you are to the gas giant. You
14:08
Speaker 1: can have a much longer or a shorter day night cycle.
14:11
Speaker 1: It depends on how long it takes to go around
14:13
Speaker 1: the gas giant instead of how fast you spin. And
14:16
Speaker 1: all of those moons are tidally locked to Jupiter, Like
14:18
Speaker 1: they're all always facing the same way towards Jupiter. Yeah,
14:22
Speaker 1: they are. Okay, So like half of the world or
14:25
Speaker 1: half of Europa just sees the regular day night cycle,
14:29
Speaker 1: and I guess also regular seasons, right, because then the
14:31
Speaker 1: season is kind of depend on whether Jupiter is farther
14:34
Speaker 1: or closer to the Sun. Yeah, the seasons depend on
14:36
Speaker 1: the tilt of the planet, right, And so Earth's axis
14:38
Speaker 1: of rotation is tilted relative to the Sun's for example,
14:41
Speaker 1: so part of the year the northern hemisphere is closer
14:43
Speaker 1: to the Sun, and the other part of the year
14:44
Speaker 1: the southern hemisphere is closer to the Sun. If you
14:46
Speaker 1: have no tilt, then you don't have seasons. Every part
14:49
Speaker 1: of the year is the same. If you're on a
14:51
Speaker 1: moon of a planet that's tidally locked to that planet,
14:54
Speaker 1: then the moon's tilt is connected to the planet's tilt.
14:56
Speaker 1: In the case of Jupiter, for example, the tilt is
14:59
Speaker 1: actually pretty all It's only three degrees, much less than
15:02
Speaker 1: Earth's tilt. So on Jupiter the seasons are more mild.
15:06
Speaker 1: The winter and summer are not as dramatic. So if
15:09
Speaker 1: you're on the XO moon of a planet that isn't
15:11
Speaker 1: tilted very much, then you're not going to have seasons.
15:13
Speaker 1: You could also imagine being on the moon of a
15:15
Speaker 1: planet that it tilted more. I see, so the seasons,
15:18
Speaker 1: for example in Europe, at least in our case where
15:21
Speaker 1: there isn't a lot of tilt, the seasons would be
15:23
Speaker 1: pretty mild or like not a lot of variations in
15:26
Speaker 1: the seasons like we have here on Earth. But maybe
15:28
Speaker 1: that you're saying that day and night cycle would be
15:30
Speaker 1: pretty dramatic, like the days would be super hot and
15:32
Speaker 1: the nights would be super cool. And if you're on
15:35
Speaker 1: the inside surface of the Moon, the one that's always
15:37
Speaker 1: facing Jupiter, then things are pretty dramatic because Jupiter would
15:41
Speaker 1: be huge in your sky. For example, you're on Europa,
15:44
Speaker 1: then Jupiter would be like twenty times as big in
15:47
Speaker 1: the sky as our moon is here on Earth. It
15:50
Speaker 1: would be a huge thing. You'd see it all the time.
15:52
Speaker 1: Would be like a giant thing blocking your your view. Right,
15:55
Speaker 1: you see Jupiter like a huge thing in the sky. Yeah,
15:58
Speaker 1: And you would see eclipses basically every day, right, because
16:01
Speaker 1: Jupiter would get between you and the Sun every single day,
16:05
Speaker 1: and every time you get that eclipse, it will it
16:07
Speaker 1: will look like night, right, because Jupiter castle sich a
16:10
Speaker 1: huge shadow. Yeah, so you have this day night cycle,
16:13
Speaker 1: but then on the inside surface of the Moon you
16:15
Speaker 1: also have a daily eclipse, which is like a mini
16:18
Speaker 1: night in the middle of your day. So like everybody
16:21
Speaker 1: takes a siesta, sounds great, let's move to open And
16:25
Speaker 1: if you think about it, also, how much you see
16:27
Speaker 1: of Jupiter depends on its relationship to the Sun, the
16:30
Speaker 1: same way that like our moon, either looks full in
16:33
Speaker 1: the sky if the sun is shining straight on it,
16:35
Speaker 1: or it can look dark if the sun is shining
16:37
Speaker 1: on the other side of it. The same thing will
16:39
Speaker 1: happen to Jupiter. You could have like a crescent Jupiter
16:42
Speaker 1: or a full Jupiter. Right, it would be pretty dramatic.
16:45
Speaker 1: And also probably Jupiter would be spinning, so you would
16:48
Speaker 1: see different sides of it as well, like sometimes you
16:51
Speaker 1: see the red eye, sometimes you wouldn't. It would be
16:53
Speaker 1: pretty beautiful actually, because Jupiter is a gorgeous planet. It's
16:56
Speaker 1: got so much texture on it. It's frankly a lot
16:58
Speaker 1: better looking than our moon. Well, it depends on your taste,
17:01
Speaker 1: I guess, But I guess we're saying that if you're
17:03
Speaker 1: on the side of the Moon and Jupiter that's facing Jupiter.
17:07
Speaker 1: Then you would basically like your day would be split
17:09
Speaker 1: into too many days, kind of like you would see
17:12
Speaker 1: the sunrise above your horizon, but then it would dip
17:15
Speaker 1: behind Jupiter then when it come out of Jupiter, and
17:17
Speaker 1: then it would sunset back to the horizon on the
17:20
Speaker 1: other side, right, and the sunset could be pretty dramatic
17:23
Speaker 1: as well. Right, you have like light bending around Jupiter.
17:26
Speaker 1: You have like sunsetting behind Jupiter, which would be pretty
17:28
Speaker 1: dramatic because then the sun is being filtered through the
17:30
Speaker 1: Jovian atmosphere, which would be pretty cool. And at night
17:34
Speaker 1: you might have a really dramatic auroras like the northern
17:36
Speaker 1: lights and the Southern lights. Cool. So you would have
17:39
Speaker 1: to sunsets and in two sunrises every day, yeah, exactly,
17:43
Speaker 1: you'd have one over the horizon of your own moon
17:46
Speaker 1: and one over the horizon of Jupiter. All right, Now,
17:49
Speaker 1: this sort of depends a lot on like you said,
17:52
Speaker 1: the tilt, but it is maybe a pretty typical example
17:54
Speaker 1: if you have like a big gas giant and with moons, right, like,
17:57
Speaker 1: if that was somewhere other in another solar system, the
18:00
Speaker 1: like the probability is that the Moon will be tidally
18:04
Speaker 1: locked to the giant planet. Right. Yeah, it depends a
18:06
Speaker 1: little bit on how close it is. The closer moon
18:09
Speaker 1: gas planet, the stronger this effect is. You can also
18:12
Speaker 1: have more complex tidal relationships, like, for example, Mercury is
18:16
Speaker 1: technically tidally locked to the Sun, but the same side
18:18
Speaker 1: of Mercury doesn't face the Sun all the time. It's
18:20
Speaker 1: a complicated three to spin orbit resonance where it does
18:24
Speaker 1: like three flips every two times around the Sun. So
18:27
Speaker 1: you can get even more complex relationships. But we do
18:30
Speaker 1: expect in other solar systems to see gas giants near
18:34
Speaker 1: the habitable zone. Like in our solar system we have
18:36
Speaker 1: Jupiter and Saturn kind of far out compared to the Earth.
18:40
Speaker 1: But in many other solar systems we see in telescopes
18:43
Speaker 1: we see what we call hot Jupiter's big gas giants
18:46
Speaker 1: much closer to the Sun than our gas giants. So
18:49
Speaker 1: it's possible they have moons inhabitable zone. Yeah, and those
18:53
Speaker 1: moons would see a pretty regular day and night pycho,
18:56
Speaker 1: which might be an ingredient for life. Right, Like it's
18:58
Speaker 1: things were totally chiotic. If your days and nights were
19:01
Speaker 1: totally unpredictable. Maybe life wouldn't be able to thrive in
19:04
Speaker 1: a place like that. Yeah, it would be really amazing
19:06
Speaker 1: to see life develop in other cycles, Like what would
19:09
Speaker 1: it be like to have a big night and a
19:11
Speaker 1: mini night and how would that affect the development of
19:14
Speaker 1: life and reproductive cycles. Be really amazing to see those
19:17
Speaker 1: experiments play out in reality. Yeah, everyone would be like
19:20
Speaker 1: the Spanish were like, what you don't take siesta? Everybody
19:23
Speaker 1: takes siesta, even the plants, even the guinea pigs or
19:26
Speaker 1: I guess exo guinea pigs on that planet. Would they
19:29
Speaker 1: still be called guinea pigs? Well, I think that answer
19:31
Speaker 1: is a question. For Billy, life on an extra moon
19:34
Speaker 1: of a gas giant in another solar system would be
19:37
Speaker 1: most likely pretty regular. Now let's get to our next question,
19:40
Speaker 1: and this one is about black holes and whether they
19:43
Speaker 1: have a surface. So we'll get to that question, but
19:46
Speaker 1: first let's take a quick break. Alright, we were answering
20:01
Speaker 1: listener questions and we just answered one about what it's
20:05
Speaker 1: like to live on a moon of a gas giant
20:07
Speaker 1: in another solar system. This one has asked kind of
20:10
Speaker 1: a similar question, almost and it comes from Bobby Pelod
20:14
Speaker 1: annual Horge. My name is Bobby from Arizona. This question
20:17
Speaker 1: comes to you is kind of a two part Could
20:18
Speaker 1: a black hole have a surface in that if you
20:22
Speaker 1: gathered enough materials, let's say iron at a thousand or
20:25
Speaker 1: billions of times the mass of the sun, and it
20:28
Speaker 1: became a black hole, would you be able to fall
20:31
Speaker 1: in that hole hypothetically and stand on the surface of
20:34
Speaker 1: that solid iron. Additionally, could this same black hole potentially
20:39
Speaker 1: gather enough materials around it to spark fusion again within
20:45
Speaker 1: the black hole? All right, A little bit of a
20:47
Speaker 1: mind bending question here is can a black hole have
20:50
Speaker 1: a surface inside of its event horizon? And could you
20:55
Speaker 1: maybe like spark a sun inside of the hole? Man?
20:58
Speaker 1: I love that image of a sun hidden inside a
21:01
Speaker 1: black hole, like fusion burning away furiously pumping out photons
21:05
Speaker 1: which are forever trapped by the black hole. So thank
21:08
Speaker 1: you Bobby for this question. What do you think Bobby
21:10
Speaker 1: was thinking? I think Bobby, like many people, is wondering
21:13
Speaker 1: what's going on inside a black hole? When stuff falls
21:17
Speaker 1: inside a black hole, what happens to it, what does
21:19
Speaker 1: it do? What is the structure of matter in there?
21:22
Speaker 1: What kind of weird stuff does it form. I think
21:25
Speaker 1: that's sort of the heart of his question, and that's
21:27
Speaker 1: a question that many people have, including black hole experts
21:31
Speaker 1: and cosmologists and astronomers. Basically everybody wants to know what's
21:36
Speaker 1: going on inside a black hole. All right, well, let
21:39
Speaker 1: maybe let's dig into this and let's be maybe clear,
21:41
Speaker 1: because black holes do kind of have a surface to them, right,
21:44
Speaker 1: They have an edge to them, which is kind of
21:46
Speaker 1: like the where the black starts. Basically, there's definitely like
21:48
Speaker 1: an edge to a black hole in the sense that
21:51
Speaker 1: we can say there's a point of no return. If
21:53
Speaker 1: you get closer to the black hole than this, then
21:56
Speaker 1: all paths lead towards the center. There's no escape, right.
22:00
Speaker 1: That's what we call the event horizon. It's like a threshold,
22:03
Speaker 1: but it's not a surface in the sense that it's
22:05
Speaker 1: like a physical boundary. If you're falling into the black hole,
22:09
Speaker 1: you don't necessarily even notice when you pass the event horizon.
22:12
Speaker 1: There's no like gatekeeper there or force field or anything.
22:16
Speaker 1: You can't even necessarily know whether you're past the event horizon.
22:20
Speaker 1: The only way to know if you're past the event
22:21
Speaker 1: horizon is to do the calculations and see if there's
22:24
Speaker 1: any path out for any particle, even into the infinite future.
22:28
Speaker 1: So there is this distance from the center of the
22:30
Speaker 1: black hole we call the event horizon. That doesn't necessarily
22:33
Speaker 1: mean that that is a surface. It's a surface only
22:35
Speaker 1: in sort of a mathematical sense, right. It's it's kind
22:38
Speaker 1: of like you say, a boundary, but it is a
22:40
Speaker 1: three dimensional boundary, which kind of makes it a fear. Technically, yes,
22:45
Speaker 1: and that one that's the mathematical event horizon, but that's
22:48
Speaker 1: not necessarily what we see when we look at pictures
22:50
Speaker 1: of a black hole. That's not necessarily like the black
22:53
Speaker 1: that we see in those pictures, right, That one's bigger
22:56
Speaker 1: than this event horizon, But that is that does sort
22:58
Speaker 1: of look like a surface. Yeah, you're used to looking
23:01
Speaker 1: at something and seeing it the way it is because
23:04
Speaker 1: your mind is used to reconstructing objects in front of you,
23:07
Speaker 1: assuming that light travels in straight lines, which is why
23:10
Speaker 1: your mind gets confused. If you're looking at like a
23:12
Speaker 1: bendy mirror or through some lenses, things look distorted, right,
23:16
Speaker 1: in the same way, space itself is distorted even outside
23:21
Speaker 1: the black hole, and light doesn't travel in straight lines.
23:24
Speaker 1: It gets all twisted and bent. So what you see
23:26
Speaker 1: when you look at a black hole is not the
23:29
Speaker 1: actual physical extent of the black hole, but an image
23:32
Speaker 1: of the black hole that's been distorted by these weird
23:35
Speaker 1: paths that light follows. So specifically, you see a black
23:38
Speaker 1: circle that's actually larger than the event horizon and includes
23:42
Speaker 1: not just the part of the event horizon that's facing you,
23:44
Speaker 1: but also the part from behind. Like photons that leave
23:47
Speaker 1: the event horizon from behind the black hole get bent
23:50
Speaker 1: around by the gravity and then back towards your eye,
23:52
Speaker 1: so you can see the entire surface of the black
23:55
Speaker 1: hole from any side of it, right, So, and that
23:57
Speaker 1: sort of counts as a surface, right. You said the
24:00
Speaker 1: word surface in the sense that maybe you wouldn't be
24:02
Speaker 1: able to tell us you're falling in, but maybe somebody
24:04
Speaker 1: from the outside would see you sort of fall into
24:06
Speaker 1: that surface, right where they would see a surface relative
24:09
Speaker 1: to somebody falling in. Yeah, it's definitely a boundary. It's
24:12
Speaker 1: a surface mathematically, it's not a surface in the sense
24:14
Speaker 1: that you could like stand on it. There's nothing there
24:16
Speaker 1: to support you. You can't like walk around on the
24:19
Speaker 1: event horizon. Right. So, I think Bobby's question now here
24:23
Speaker 1: is whether or not a black hole has a surface
24:25
Speaker 1: in the sense of like having a physical hard surface
24:29
Speaker 1: on which you can actually like stand or into which
24:31
Speaker 1: you would crash if you fell into a black hole.
24:34
Speaker 1: Because I imagine maybe he's thinking, like a regular hole
24:36
Speaker 1: here on the ground on Earth. It's a hole, and
24:38
Speaker 1: you would fall in, but eventually you would hit something.
24:40
Speaker 1: And if there's a whole bunch of stuff in the
24:42
Speaker 1: hole you or like like a trash or something, you
24:44
Speaker 1: would eventually fall into the hole, but then you would
24:47
Speaker 1: hit the pile of trash. And so I think maybe
24:49
Speaker 1: Bobby is wondering, like, you know, the black holes have
24:51
Speaker 1: all this stuff inside of him. If you fell into
24:53
Speaker 1: the black hole, wouldn't you eventually hit this stuff? Yeah,
24:56
Speaker 1: And it's a great question when you think about this
24:58
Speaker 1: is in terms of the forces. So gravity is very
25:01
Speaker 1: powerful when things get very massive and things get very close,
25:04
Speaker 1: but it's not all powerful, right, Like think about the
25:07
Speaker 1: huge ball of iron in the center of the Earth.
25:10
Speaker 1: Why isn't that a black hole. It's not a black
25:13
Speaker 1: hole because iron has internal structure, has enough internal structure
25:16
Speaker 1: to resist the gravitational collapse, like the atoms pushing against
25:20
Speaker 1: each other that form this ball of iron, they resist gravity.
25:24
Speaker 1: But inside a black hole, gravity is much much more powerful.
25:28
Speaker 1: It's more powerful than the structure of iron. It's more
25:30
Speaker 1: powerful than any sort of bond that we are aware of.
25:34
Speaker 1: We don't think there's anything that can overcome the power
25:36
Speaker 1: of gravity once you are inside the black hole. So
25:39
Speaker 1: if you take a big blob of iron, as he said,
25:41
Speaker 1: a huge mass of iron, like millions of times the
25:44
Speaker 1: mass of the Sun, and collapse it to a black hole.
25:46
Speaker 1: Once all that iron is inside the black hole, it
25:49
Speaker 1: doesn't have the strength to resist the gravitational collapse. And
25:53
Speaker 1: that's why general relativity predicts a singularity. It says that
25:56
Speaker 1: things just keep compressing and compressing and compressing until you
25:59
Speaker 1: get dot of infinite density. M hmmm. I think you're saying,
26:03
Speaker 1: like here on Earth and there's a bunch of stuff
26:05
Speaker 1: at the center, but it's not collapsing because other forces
26:08
Speaker 1: are keeping gravity from collapsing further, you know, like the
26:12
Speaker 1: electromagnetic force between all of the electrons and the protons
26:15
Speaker 1: and the corks inside of the atoms in Earth's core.
26:18
Speaker 1: But in a black hole, like we've sort of done
26:20
Speaker 1: something different. We've like accumulated so much stuff that gravity
26:23
Speaker 1: is so powerful it squishes even the electromagnetic force, like
26:27
Speaker 1: it just squeezes everything down theoretically into an infinite point. Exactly.
26:32
Speaker 1: You can have a certain mass of iron and you
26:34
Speaker 1: can hold itself up, but if you make it too massive,
26:37
Speaker 1: gravity gets too strong and then it collapses. And that's
26:40
Speaker 1: how black holes form. Right. Black holes form from stars
26:43
Speaker 1: that made too much heavy stuff at their core, so
26:46
Speaker 1: they're no longer able to resist gravity's collapse, and then
26:49
Speaker 1: it turns into a black hole. So all that iron,
26:52
Speaker 1: according to general relativity, forms a singularity, a dot at
26:56
Speaker 1: the center of the black hole where all of that
26:58
Speaker 1: mass has accumulated. And so unless you can walk around
27:01
Speaker 1: on an infinitesimal point, according to general relativity, there's not
27:04
Speaker 1: really a surface inside the black hole, and there's no
27:07
Speaker 1: chemistry going on and no fusion or no anything else. Right,
27:10
Speaker 1: are you saying, at the center of a black hole,
27:12
Speaker 1: there's no surface, there's no pile of trash or iron,
27:14
Speaker 1: there's just an infinite dot. But what about the stuff
27:18
Speaker 1: getting to the dot? Isn't that stuff accumulated? Maybe? Yeah,
27:22
Speaker 1: that's a good point. It takes a finite amount of
27:24
Speaker 1: time once you pass the event horizon to reach the singularity.
27:27
Speaker 1: And so if the black hole is actively feeding, then
27:30
Speaker 1: you have singularity surrounded by stuff that's still falling in,
27:34
Speaker 1: you know, sort of like a toilet bowl of stuff
27:36
Speaker 1: swirling around it. And remember this is according to general relativity.
27:39
Speaker 1: Einstein's equations predict this runaway effect that leads to a collapse,
27:44
Speaker 1: that leads to a point because in Einstein's theory, space
27:46
Speaker 1: is smooth and continuous, it can be chopped up into
27:49
Speaker 1: infinitely small slices, and you can also know where everything
27:53
Speaker 1: is at all times. These assumptions are in total contradiction
27:57
Speaker 1: to what we know about the universe being quantum mechanical,
28:00
Speaker 1: and so physicists don't take this prediction of singularity seriously.
28:03
Speaker 1: We don't see it as like an actual prediction of
28:05
Speaker 1: what's happening inside. It's sort of like an indication that
28:09
Speaker 1: the theory itself is breaking down because it predicts something
28:12
Speaker 1: kind of crazy, right, physicist, something that maybe general relativity
28:15
Speaker 1: is wrong, and you wouldn't get a singularity at the
28:18
Speaker 1: center of a black hole. You would maybe get like
28:20
Speaker 1: a quantum blob. Yeah, we think that something will prevent
28:23
Speaker 1: the singularity from happening, because you can't confine particles to
28:26
Speaker 1: an infinitely solved space without giving them effectively infinite energy
28:30
Speaker 1: because of the quantum uncertainty principle, and so there's a
28:32
Speaker 1: minimum quantum fuzz to the universe always. So when you
28:36
Speaker 1: try to compress matter really, really far, there must be
28:39
Speaker 1: some quantum mechanical way that they resist becoming a singularity,
28:43
Speaker 1: you know. I think of them as sort of like
28:44
Speaker 1: layers of defense. Matter has many ways to protect itself
28:48
Speaker 1: from collapsing. First, there's like the chemical internal structure like
28:51
Speaker 1: the Earth, or if you have a star, then it's fusion,
28:53
Speaker 1: which is pushing out and pumping out energy to prevent collapse.
28:56
Speaker 1: If you're like a neutron star, then there's like the
28:58
Speaker 1: neutron degeneracy. We don't know what's going on inside a
29:01
Speaker 1: black hole. There might be something else quantum mechanical that
29:04
Speaker 1: matter can do to resist being compressed into a singularity.
29:08
Speaker 1: To know how that works, we'd have to have a
29:10
Speaker 1: theory of quantum gravity, which we just don't have that.
29:13
Speaker 1: There's lots of fun ideas about what might be going
29:16
Speaker 1: on inside. Yeah, and so inside of a black hole
29:19
Speaker 1: there might not actually be a hole. I think it's
29:21
Speaker 1: what you're saying, or it would still be a hole.
29:23
Speaker 1: There just wouldn't be a pinpoint singularity in the middle.
29:26
Speaker 1: And it might be that the stuff inside of the
29:27
Speaker 1: hole is still holding together or you know, making a pile,
29:32
Speaker 1: due to some other quantum force. Yeah, and it's very
29:35
Speaker 1: unlikely that if you throw a bunch of iron into
29:38
Speaker 1: a black hole that it's going to stay iron. It's
29:41
Speaker 1: going to turn into some other completely different state of
29:44
Speaker 1: matter because the iron molecules are not going to be
29:46
Speaker 1: able to survive that intense experience. They're gonna get shredded
29:49
Speaker 1: apart to their basic constituents. Maybe even the protons will
29:52
Speaker 1: get pulled apart into their quarks. Maybe those quarks we
29:55
Speaker 1: have pulled apart into whatever they are made out of.
29:58
Speaker 1: We just don't know. From outside, it still just looks
30:01
Speaker 1: like a black hole. You can't see beyond the event horizon.
30:04
Speaker 1: So gravitationally speaking, a singularity or a quantum blob with
30:08
Speaker 1: the same mass all acts the same from the outside,
30:10
Speaker 1: So as you say, it still looks like a hole. Yeah,
30:13
Speaker 1: But to Bobby's question, then if there is a quantum
30:16
Speaker 1: flows ball in the middle, that means that the inside
30:19
Speaker 1: of a black hole there would be a surface, right,
30:21
Speaker 1: like a physical surface that you could maybe stand on,
30:24
Speaker 1: if you could somehow survive or even think inside of
30:27
Speaker 1: a black hole, right, Yeah, perhaps it depends a lot
30:30
Speaker 1: on that theory of quantum gravity. So what's going on
30:32
Speaker 1: inside it? You know, we talked to the podcast once
30:35
Speaker 1: about the dark star theory that black holes are not
30:38
Speaker 1: actually black holes. They're just very slowly collapsing stars that
30:42
Speaker 1: will reach a minimum point from quantum mechanics and then
30:45
Speaker 1: bounce back out and turn into like white holes eventually.
30:49
Speaker 1: And so that's also not the kind of thing you'll
30:51
Speaker 1: necessarily be able to walk around on a collapsing star
30:54
Speaker 1: unless you have like really good boots. Yeah you have
30:57
Speaker 1: dark Star shoes. But achnically it would have a surface, right,
31:01
Speaker 1: It would answer Bobby's question, And the answer would be yes,
31:04
Speaker 1: there would be like a physical blob inside of a
31:06
Speaker 1: black hole, and that has a surface that you could
31:09
Speaker 1: stand on or throw things at, and that they would
31:12
Speaker 1: splat you stand on in sense that you could like
31:14
Speaker 1: be there on top of it. I don't know if
31:16
Speaker 1: he would absorb you or pull you apart or melt
31:19
Speaker 1: you instantly, So I certainly wouldn't recommend it to anybody
31:21
Speaker 1: out there who's considering it, It It sounds like people maybe
31:23
Speaker 1: want to test it first, you know, by throwing like
31:26
Speaker 1: an animal at it. What what kind of animal the
31:28
Speaker 1: people usually do experiments with first? Is it bananas? Hamsters?
31:34
Speaker 1: I can't remember bananas animals on other planets. Maybe exo
31:39
Speaker 1: bananas might be in the animal category. Oh my goodness,
31:42
Speaker 1: he'll bring up all kinds of ethical issues for me there.
31:45
Speaker 1: Did I tell you, by the way, what my kids
31:47
Speaker 1: dressed up as for Halloween? Well, my son has become
31:50
Speaker 1: very long and lean, and so he dressed up as
31:52
Speaker 1: a banana. All right, He's aspiring to the greatest fruit
31:56
Speaker 1: on the planet. So we had a banana in the family.
31:59
Speaker 1: But I'm not throwing him into any black holes no
32:01
Speaker 1: matter what he wears on Halloween. Yeah, I might get
32:03
Speaker 1: a little slippery, but I think that answers Bobby's question.
32:06
Speaker 1: Could a black hole have a surface? The answer is yes.
32:09
Speaker 1: I mean it has kind of a threshold surface. It
32:12
Speaker 1: has a visual surface, which is the part that looks black,
32:16
Speaker 1: and it may if general relativity is wrong, and we
32:19
Speaker 1: think it most probably is, it does have maybe a
32:21
Speaker 1: physical surface inside of the hole. It certainly might It
32:24
Speaker 1: could be a dark star, it could be a fuzzball
32:27
Speaker 1: made of strings, it could be something else entirely we
32:30
Speaker 1: haven't yet imagined. If we could see inside a black hole,
32:33
Speaker 1: we could know what happens when you compress matter in
32:35
Speaker 1: these extreme circumstances, and we could learn something about the
32:38
Speaker 1: fundamental nature of reality. All right, well, thank you Bobby
32:41
Speaker 1: for that question, and now let's get to our last question.
32:44
Speaker 1: This one's about the very nature of the universe and
32:47
Speaker 1: whether or not it all adds up. So we'll tackle
32:49
Speaker 1: that question. But first let's take another quick break. All right,
33:05
Speaker 1: we were answering the listener questions, and our last question
33:08
Speaker 1: is about the nature of reality. It comes from Matthew. Hello, Daniel,
33:13
Speaker 1: and ho. I have a question about the math of
33:16
Speaker 1: the universe. What is it? Trigonometry, algebra, calculus, the math
33:23
Speaker 1: of space exploration. I was thinking about the James Web
33:27
Speaker 1: space telescope out there in Lagrange too. How the heck
33:34
Speaker 1: that was math? Right, Like somebody was like, oh, look,
33:38
Speaker 1: here's the math. We can put this thing there and
33:40
Speaker 1: it'll stay put because it's like circling the Sun with
33:45
Speaker 1: the Earth and the Moon. But then it's like doing
33:47
Speaker 1: little loop de loops in addition to the circling the sun.
33:51
Speaker 1: And another thing, how do they get it to stay
33:53
Speaker 1: focused on something a billion trillion miles away when it's
33:58
Speaker 1: doing all that motion? Are they kind like firing thrusters? Anyways?
34:02
Speaker 1: Tell me about the math of the universe, like from
34:06
Speaker 1: the olden days to now? What the heck trigonometry? What
34:09
Speaker 1: is it? Like that scene in Apollo thirteen where they'll
34:13
Speaker 1: check their math and oh, my gosh, I gotta know more.
34:17
Speaker 1: All right, thank you Matthew for that awesome question. Also,
34:20
Speaker 1: I think, uh, I think that's my reaction to a
34:22
Speaker 1: lot of these things about the universe. What the heck?
34:26
Speaker 1: I can't? I can't anymore. It is amazing how the
34:29
Speaker 1: universe works and how it seems to be so describable
34:32
Speaker 1: by math. It really is incredible. Yeah, And so that's
34:35
Speaker 1: Matthew's question, is that he's asking what is the math
34:38
Speaker 1: up the universe? Is it trigonometry, algebra, calculus, long division?
34:44
Speaker 1: It is really interesting to wonder which parts of math
34:47
Speaker 1: describe the universe, because you can imagine that we could
34:50
Speaker 1: invent a whole bunch of math that doesn't describe the universe,
34:53
Speaker 1: that isn't relevant necessarily. What do you mean, Like, you
34:56
Speaker 1: can have mathods as one plus one equals two of it,
34:58
Speaker 1: but but maybe you could have a neverse where one
35:00
Speaker 1: plus one doesn't equal to no. I mean that you
35:02
Speaker 1: can invent kinds of math that don't have to reflect
35:05
Speaker 1: the physical universe. For example, you can invent weird kinds
35:08
Speaker 1: of geometry, you know, surfaces that live in eight dimensions,
35:12
Speaker 1: but the universe might not be eight dimensionals. So you
35:14
Speaker 1: can spend your whole life thinking about the mathematics of
35:17
Speaker 1: eight dimensional objects, but that's not actually relevant to our
35:21
Speaker 1: universe if our universe is just three dimensional. But you know,
35:24
Speaker 1: we don't know how people spend, for example, decades developing
35:27
Speaker 1: ideas called group theory about how things relate to each other,
35:31
Speaker 1: then later it turns out to be totally relevant to
35:33
Speaker 1: particle physics. So you never know what math is going
35:36
Speaker 1: to be relevant. But it's definitely possible that there's kinds
35:39
Speaker 1: of math which are not relevant to the universe, right.
35:42
Speaker 1: But I guess it's kind of a tricky philosophical question
35:44
Speaker 1: because like, if you can come up with math that
35:47
Speaker 1: makes sense, doesn't technically mean that it exists in the universe.
35:51
Speaker 1: Even if you can find like a you know, a
35:53
Speaker 1: law of particles that follows that math. The maths is
35:57
Speaker 1: still there and it makes sense in this universe. Doesn't
35:59
Speaker 1: mean it it's part of the universe. Yeah, It's one
36:01
Speaker 1: of the deepest questions in the philosophy of math, like
36:05
Speaker 1: are those numbers real and the part of the universe?
36:08
Speaker 1: And then you get into weird things like well, what
36:10
Speaker 1: does it mean to be real? Because like those numbers,
36:13
Speaker 1: the number two, where is the number two? Right? Everything
36:15
Speaker 1: else that's real has like a location, it has behavior,
36:18
Speaker 1: can participate in experiments. You can talk about whether protons
36:22
Speaker 1: are real and you can do tests on them. You
36:24
Speaker 1: can't do that for the number two. There's no way
36:26
Speaker 1: the number two can like participate in experiments, can cause effects.
36:31
Speaker 1: So if it's real, it's real in a different way
36:33
Speaker 1: than other things that are real. But I think maybe
36:36
Speaker 1: Matthew's question is not so much about these big philosophical questions.
36:39
Speaker 1: I think maybe he's coming at it from a more
36:42
Speaker 1: intuitive point of view, which is like, you know, does
36:44
Speaker 1: the universe have a mathematical description? Can you describe the
36:50
Speaker 1: universe with math? And if you can, what kind of
36:53
Speaker 1: math is it? Is it trigonometry, algebra or is it
36:56
Speaker 1: just all addition all the way down. Um. I would
37:00
Speaker 1: say there's two parts of that answer. One is what
37:03
Speaker 1: kind of math do we use to describe the universe?
37:06
Speaker 1: And the other is whether we could boil that down
37:08
Speaker 1: to one sort of like basic kind of math. So
37:11
Speaker 1: on the first one, we tend to use calculus a lot.
37:14
Speaker 1: Like calculus is often described as the language of physics,
37:18
Speaker 1: it's really a very very powerful tool to describe what
37:21
Speaker 1: we see about the universe. That's because calculus is like
37:24
Speaker 1: the mathematics of change. If you have something flying through
37:27
Speaker 1: the air with a certain velocity, that's fine. But now
37:30
Speaker 1: if you want to change that's velocity and you want
37:32
Speaker 1: to understand where it's gonna go, you have to accumulate
37:35
Speaker 1: all those changes and figure out where it's going to land.
37:38
Speaker 1: That requires calculus. So the mathematics of change is really
37:42
Speaker 1: the mathematics of motion in our universe. So calculus is
37:46
Speaker 1: really fundamental, right because we have you saying because we
37:49
Speaker 1: have time and universe and time kind of implies change
37:51
Speaker 1: and we need calculus. But it's also I think a
37:53
Speaker 1: little bit maybe more fundamental, I wonder, because it calcula
37:57
Speaker 1: is also about how the rates of change the pend
38:00
Speaker 1: on each other, right, Like we seem to have found laws,
38:03
Speaker 1: for example, like F equals m A that says that,
38:05
Speaker 1: you know, the rate of change depends on this force
38:09
Speaker 1: or that force or this situation, and so it seems
38:12
Speaker 1: like the universe has laws that govern over the rate
38:16
Speaker 1: of changes of things, and that's why calculus is useful. Yeah,
38:20
Speaker 1: Calculus is useful because he gives us these tools, and
38:23
Speaker 1: we can express the laws of the universe that we
38:25
Speaker 1: discover in terms of those So you're right, almost all
38:28
Speaker 1: the laws of physics, like F equals m A, that's
38:31
Speaker 1: an expression in calculus, because a is a derivative. Acceleration
38:35
Speaker 1: is the rate of change of velocity. That's a differential
38:38
Speaker 1: that's part of calculus. Force is really change in momentum
38:42
Speaker 1: with respect to time, right, and so that's a differential.
38:46
Speaker 1: So you're absolutely right that most of the laws of
38:48
Speaker 1: physics can be expressed in terms of objects that were
38:51
Speaker 1: invented for calculus. But calculus also handles things that are
38:54
Speaker 1: not rate of change with time. You know, calculus lets
38:57
Speaker 1: you integrate over space. Also, if you have an object
39:00
Speaker 1: that has like a varying density and you want to
39:02
Speaker 1: know it's total mass. You can integrate over the object
39:06
Speaker 1: over space in order to get the total mass if
39:08
Speaker 1: the density is varying. So calculus is the math of
39:11
Speaker 1: change of time or of space. Yeah, and then what
39:14
Speaker 1: happens when you go down to the quantum level? First
39:16
Speaker 1: of all, does calculus still apply or does it get
39:19
Speaker 1: more into like quantum of waves and and functions and fields.
39:23
Speaker 1: Is calculus still useful there and maybe even appropriate because
39:26
Speaker 1: the world is quantized. It's absolutely still useful there. Like
39:29
Speaker 1: the shorting your equation, that's a differential equation. Absolutely, it's
39:33
Speaker 1: a wave equation which tells you how the wave changes
39:36
Speaker 1: in space and how that relates to how it changes
39:38
Speaker 1: in time. So calculus super fundamental, and the basic theory
39:43
Speaker 1: of the standard model, which we call quantum field theory,
39:46
Speaker 1: is full of calculus because calculus involves integrals, and integrals
39:49
Speaker 1: allow you to add up over many, many different things.
39:52
Speaker 1: You can add up slices in time or slices in
39:54
Speaker 1: space a quantum mechanically, it also leads you add up
39:57
Speaker 1: different probabilities. So, for example, one important formulation of quantum
40:01
Speaker 1: mechanics by Feinneman says, if you want to understand how
40:03
Speaker 1: a particle moves from A to B. You have to
40:06
Speaker 1: integrate over all possible paths of the particle. So calculus
40:10
Speaker 1: lest you consider multiple different possibilities simultaneously. So it's crucial
40:15
Speaker 1: to quantum field theory. Right, So calculus is pretty useful,
40:19
Speaker 1: So kids pay attention to that class when you when
40:21
Speaker 1: you get to calculus. But I guess maybe a question
40:24
Speaker 1: here is is calculus the theory to use for the university?
40:28
Speaker 1: Like it's useful and you definitely seem to be able
40:30
Speaker 1: to use it to describe a lot of the universe
40:32
Speaker 1: and even predict a lot of what happens in the universe.
40:34
Speaker 1: But maybe we're just kind of lucky, Like maybe calculus
40:37
Speaker 1: just sort of works most of the time, and so
40:39
Speaker 1: we think it's the way to go. But maybe there's
40:41
Speaker 1: a different math the here that would describe the universe
40:43
Speaker 1: in more detailed The more we learn about it, is
40:45
Speaker 1: that possible? It certainly is possible, and we're constantly improving
40:49
Speaker 1: on and developing new techniques in calculus. It's not like
40:52
Speaker 1: calculus is a finished thing. It's not like Newton enliven.
40:55
Speaker 1: It's invented a few and years ago and now it's done.
40:57
Speaker 1: People are still working on it, like today, figuring out
41:00
Speaker 1: ways to do complicated integrals and whole new techniques that
41:04
Speaker 1: that makes previously unsolvable problems now solvable. So it's definitely
41:08
Speaker 1: a developing field and it's improving, and so that means
41:11
Speaker 1: that in the future we will have more powerful math
41:13
Speaker 1: that describes the universe even better, because there's lots of
41:16
Speaker 1: things that we still don't know how to do, problems
41:19
Speaker 1: we can't solve, probably because we just don't have the
41:22
Speaker 1: mathematical tools for them. Yet you're saying is pretty good
41:25
Speaker 1: and we're going to stick with it, But maybe less
41:28
Speaker 1: you were saying, the deeper question is whether or not
41:31
Speaker 1: this is just in general, using math to describe the universe,
41:35
Speaker 1: if that is something fundamental about the universe, or it's
41:38
Speaker 1: just our way of understanding it. This is the question
41:40
Speaker 1: the philosophers of math debate and have been debating for
41:43
Speaker 1: thousands of years and probably will keep debating for thousands
41:47
Speaker 1: more years. I'm not sure it's something they can really
41:50
Speaker 1: make progress on that Really at the heart of it,
41:52
Speaker 1: we're asking whether math describes the universe or whether it
41:55
Speaker 1: controls the universe, Like is the universe itself mathematical. Is
42:00
Speaker 1: math part of the universe itself or is it just
42:02
Speaker 1: our description of it is the way that we organize
42:05
Speaker 1: our thoughts. Is it like a convenient way to think,
42:08
Speaker 1: or is it really the source code of the universe itself?
42:11
Speaker 1: And telling the difference between those things is pretty tricky.
42:15
Speaker 1: You mean, like the difference is kind of like whether
42:17
Speaker 1: the universe actually cares about math, right, because maybe, like
42:20
Speaker 1: in one scenario, the universe just does its thing and
42:23
Speaker 1: the universe doesn't even care about math or know what
42:25
Speaker 1: math is. The other scenario is that the universe is
42:28
Speaker 1: kind of beholden to math or somehow the universe is
42:32
Speaker 1: math at its core. That's the difference, right, Yeah, that's
42:35
Speaker 1: a good way to think about it. Sometimes the way
42:36
Speaker 1: I think about it is in terms of like a
42:38
Speaker 1: computer program. Say somebody writes a computer program and then
42:41
Speaker 1: you use it Microsoft Word for example, and you could
42:44
Speaker 1: try to like figure out how word works, and you
42:46
Speaker 1: could reverse engineering using some other programming language. Maybe it
42:50
Speaker 1: was written in Python and you figured out how to
42:53
Speaker 1: write it in C. Right now you have a description
42:55
Speaker 1: of this computer program in your own language. That doesn't
42:58
Speaker 1: necessarily mean that that's the per brand that's actually running
43:01
Speaker 1: inside of word. You might just have a description of it,
43:04
Speaker 1: or it might be that you've discovered the actual source
43:06
Speaker 1: code ForWord itself. In the same way, the math that
43:09
Speaker 1: we are building might be the actual code that the
43:12
Speaker 1: universe is following. Or it could just be a good
43:15
Speaker 1: description of it. And there might be other possible descriptions
43:18
Speaker 1: that are equally valid. We just don't know, all right, Well,
43:22
Speaker 1: which is it? Then? I guess I wish we knew.
43:24
Speaker 1: One of my favorite philosophical attempts to answer this question
43:26
Speaker 1: came from hartree Field. He said, let's see if it's
43:29
Speaker 1: possible to do science and physics specifically without any math,
43:34
Speaker 1: without any numbers at all, Like, can you devise laws
43:38
Speaker 1: of physics that don't have numbers in them? Wait, numbers
43:42
Speaker 1: or even like variables and symbols or none of that,
43:45
Speaker 1: none of that at all, he writes in his book,
43:48
Speaker 1: like I denied that numbers exist. He wrote this whole
43:52
Speaker 1: book called Science Without Numbers where he was admitting that
43:56
Speaker 1: math is useful, but he was trying to prove that
43:58
Speaker 1: it's not necessary by building up a new version of
44:01
Speaker 1: these theories that didn't use any numbers. What what would
44:05
Speaker 1: that even look like if you wrote it down, that
44:07
Speaker 1: you have to write down something. While on page forty
44:10
Speaker 1: seven of his book without Numbers, for example, he talks
44:14
Speaker 1: about how to do this. It's pretty philosophically intricate. He
44:17
Speaker 1: like abuse points of space with certain kind of properties
44:22
Speaker 1: so that you don't ever have to do any calculations.
44:24
Speaker 1: Like most specifically he thinks about gravity and how gravity work,
44:29
Speaker 1: and when we do gravitational calculations, we create all sort
44:31
Speaker 1: of abstract intermediate ideas, like the gravitational field that we
44:35
Speaker 1: say that the Earth is pulled on the Sun because
44:37
Speaker 1: of the gravitational field of the Sun. And he's like,
44:40
Speaker 1: you need numbers to describe that field, but what if
44:42
Speaker 1: that field wasn't there. You don't ever observe the field directly,
44:46
Speaker 1: You just observe the Sun pulling on the Earth. What
44:48
Speaker 1: if that's just something that space does and there is
44:51
Speaker 1: no field at all. That's an example of how he's
44:53
Speaker 1: trying trying to rid the calculation of intermediate steps that
44:57
Speaker 1: need numbers to describe them, but all tim redly would
45:00
Speaker 1: and you have to write it down, And what do
45:02
Speaker 1: you eventually have to you know, have an equation or
45:06
Speaker 1: something you know in his formulation of Newton's gravity, there
45:10
Speaker 1: are new equations, there are no numbers, there is no mathematics.
45:13
Speaker 1: It's hard to imagine because we think that math is
45:16
Speaker 1: the answer, right, Like you do a calculation, you get
45:18
Speaker 1: a result, it says, oh, the force on the earth.
45:20
Speaker 1: Is this for us? Math is the language itself. But
45:23
Speaker 1: he developed a way to perform these calculations to think
45:25
Speaker 1: about it that doesn't have math as the internal steps
45:28
Speaker 1: or either as the answer. And is this credible? Does
45:31
Speaker 1: this seem suspect or is this like an actual valid
45:35
Speaker 1: possibility for the universe. I think that most philosophers see
45:38
Speaker 1: its like a heroic effort to make the point that
45:41
Speaker 1: maybe math isn't necessary. But there's a lot of steps
45:44
Speaker 1: he took along the way which people quipple with. And
45:46
Speaker 1: people don't think that this effort could be applied to
45:49
Speaker 1: like everything in physics. And so it's like, hey, cool point, man,
45:53
Speaker 1: But it doesn't really work. It doesn't really convince anybody
45:56
Speaker 1: that you don't need math to do science. I see
45:59
Speaker 1: people are like, hey, there are a number of errors
46:01
Speaker 1: in your theory, and then he's like, wait, but there
46:02
Speaker 1: are no numbers exactly. I think that most people, most
46:06
Speaker 1: mathematicians and most physicists think that math is an inherent
46:09
Speaker 1: part of the universe, right, But then I guess the
46:12
Speaker 1: larger question I was kind of alluding to is whether
46:15
Speaker 1: the universe cares if there's math or not, or like
46:17
Speaker 1: which came first, math or physics. I don't know what
46:21
Speaker 1: it means for the universe to care about something, but
46:24
Speaker 1: I think there is another interesting aspect to Matthew's question,
46:26
Speaker 1: which is, like which math is essential? Trigonometry, algebra, calculus.
46:31
Speaker 1: And that's interesting because you're like slicing up math now
46:34
Speaker 1: into different categories which are a little bit arbitrary, right,
46:37
Speaker 1: Like calculus uses trigonometry and algebra and all of these things.
46:41
Speaker 1: But there actually is a really interesting effort inside of
46:44
Speaker 1: math to try to like boil all of math down
46:47
Speaker 1: into the shortest list of rules you would need to
46:49
Speaker 1: build up all the rest of math, like to find
46:52
Speaker 1: the core axioms at the heart of it all. Oh, yeah,
46:55
Speaker 1: where is that coming from? From the math fields or
46:57
Speaker 1: from the physics fields? That comes from mathematics? Like a
47:00
Speaker 1: hundred fifty years ago, people have been doing math for
47:02
Speaker 1: thousands of years. About a hundred and fifty years ago,
47:04
Speaker 1: people were like, hold on a second, what are the
47:07
Speaker 1: basic rules of math? Anyway? And so there was a
47:09
Speaker 1: guy named Piano who showed that almost all of arithmetic
47:13
Speaker 1: can be boiled down to just a basic fuel rules,
47:15
Speaker 1: and then people who came after him showed that most
47:18
Speaker 1: of math could be boiled down to arithmetic, and then
47:20
Speaker 1: later people showed that most arithmetic can be boiled down
47:23
Speaker 1: to something called set theory, which is math about like
47:26
Speaker 1: groups and what's in a group, what's out of a group?
47:29
Speaker 1: How do you combine groups? How do you overlap groups?
47:31
Speaker 1: So the current like idea about the very foundation of
47:34
Speaker 1: math is that in the end, it's all about sets.
47:36
Speaker 1: It's all about like what's in a group, what's out
47:38
Speaker 1: of group? From that you can build arithmetic, and from
47:41
Speaker 1: that you can build calculus. So fundamentally, we think that
47:44
Speaker 1: the description of the universe is mathematical and it's all
47:47
Speaker 1: set theory all the way down. That's kind of what
47:49
Speaker 1: I was saying, Right, there's addition. Basically, it's just a
47:53
Speaker 1: group exactly. It's addition and its popularity. It's all clicks
48:00
Speaker 1: versus very elitist or it's all about clickbait. All right, Well,
48:03
Speaker 1: I think that answers Matthew's question, what is the math
48:06
Speaker 1: of the universe? Well, the answer is, so far calculus
48:09
Speaker 1: has been really useful in describing the universe, but um
48:12
Speaker 1: physicists are not sure if maybe even calculus is the
48:15
Speaker 1: fundamental way to describe the universe, or even the most
48:18
Speaker 1: fundamental um way to describe math itself. That's right, but
48:22
Speaker 1: that doesn't mean we don't like thinking about these questions
48:25
Speaker 1: and wondering about what's going on in the heart of
48:27
Speaker 1: the universe and why it is even possible to describe
48:29
Speaker 1: it mathematically or to make sense of it with our
48:32
Speaker 1: little primate brains. So you're gonna keep going until it
48:35
Speaker 1: all adds up, or until you ask what the heck?
48:37
Speaker 1: I can't even until we're part of the in group
48:40
Speaker 1: that actually knows some answers, until we're all guinea pigs,
48:43
Speaker 1: we're all test subjects in this universe living on the
48:45
Speaker 1: surface of some crazy exo moon or black hole. All right, Well,
48:49
Speaker 1: thank you to everyone who sent in their questions. We
48:53
Speaker 1: love answering questions. We hope you enjoyed that. Thanks for
48:56
Speaker 1: joining us. See you next time. Ye, thanks for listening,
49:07
Speaker 1: and remember that Daniel and Jorge Explain the Universe is
49:09
Speaker 1: a production of I Heart Radio. For more podcast for
49:13
Speaker 1: my heart Radio, visit the I heart Radio app, Apple Podcasts,
49:17
Speaker 1: or wherever you listen to your favorite shows. Yeah.