Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions #5

Transcript

Listener Questions #5 · Daniel and Kelly’s Extraordinary Universe

• 0:06
  Speaker 1: Are black holes actually black? Is life always built on
• 0:10
  Speaker 1: a carbon stack?
• 0:11
  Speaker 2: Can one star make another explode? What happens if you
• 0:14
  Speaker 2: lick an electrode?
• 0:15
  Speaker 1: Would biology beat physics in a fair fight? Why is
• 0:19
  Speaker 1: dark chocolate better than white?
• 0:20
  Speaker 2: Hawking predicted that black holes glow? What makes a supernova blow?
• 0:25
  Speaker 1: Biology, physics, archaeology, forestry, really anything other than chemistry?
• 0:31
  Speaker 2: What diseases do you get from your cat? Well, we'll
• 0:34
  Speaker 2: find the answers to all that.
• 0:36
  Speaker 1: Whatever questions keep you up at night, Daniel and Kelly's
• 0:39
  Speaker 1: answer will make it right. Welcome to another Listener Questions
• 0:42
  Speaker 1: episode on Daniel and Kelly's Extraordinary Universe. Hello, Kelly Weener
• 1:00
  Speaker 1: Spin I'm a parasitologist, and today we're talking about chemistry.
• 1:05
  Speaker 2: Hi, I'm Daniel. I'm a particle physicist because I don't
• 1:09
  Speaker 2: like chemistry. So what am I even doing here today?
• 1:12
  Speaker 1: Well, so, Daniel, my question for you today is why
• 1:14
  Speaker 1: is chemistry the worst science?
• 1:17
  Speaker 2: How much time do you have, Kelly.
• 1:20
  Speaker 1: I've did, We've got an hour.
• 1:22
  Speaker 2: No, chemistry is amazing because it's the closest thing we
• 1:26
  Speaker 2: have to explaining magic, like the things that you can
• 1:29
  Speaker 2: see happen with your own eyes. You know, seeing a
• 1:33
  Speaker 2: solid turn into a liquid turn into a gas is
• 1:35
  Speaker 2: kind of incredible, and the fact that we can take
• 1:37
  Speaker 2: that apart and understand it microscopically is amazing. And it's
• 1:41
  Speaker 2: so much more concrete than particle physics or even astrophysics sometimes.
• 1:45
  Speaker 2: So I have a lot of respect for the relevance
• 1:47
  Speaker 2: of chemistry, but I really struggle with the complexity of it,
• 1:52
  Speaker 2: Like there's so many different rules to apply in different
• 1:55
  Speaker 2: situations and a weeks to remember all the exceptions, and
• 1:58
  Speaker 2: this electron and that electron, and it doesn't have the
• 2:01
  Speaker 2: simplicity that I like in particle physics. But you know, hey,
• 2:04
  Speaker 2: that's purely a subjective preference, right, And I'm really glad
• 2:08
  Speaker 2: that there's different kinds of science for different kinds of folks,
• 2:10
  Speaker 2: so we get all the fun different kinds of sciences
• 2:12
  Speaker 2: happening here on our planet.
• 2:14
  Speaker 1: Yeah, no, I agree, and I'm joking. My senior honors
• 2:17
  Speaker 1: research project was in organic chemistry. I'm minored in chemistry,
• 2:20
  Speaker 1: but man, it was hard taking oakem over the summer
• 2:23
  Speaker 1: because I'm not good at visualizing things in three D
• 2:26
  Speaker 1: and seeing those reactions happen in my head is really hard.
• 2:29
  Speaker 1: But I got lucky, so I took it over the summer,
• 2:31
  Speaker 1: and it was like four hours of lecture and then
• 2:33
  Speaker 1: two hours of lab like every day of the week.
• 2:36
  Speaker 1: It was intense. I had a group of friends. I
• 2:39
  Speaker 1: was one of six, and we called ourselves the Benzene
• 2:41
  Speaker 1: Ring because there's six carbons and a benzene ring.
• 2:44
  Speaker 2: I got a chemistry joke look at that.
• 2:47
  Speaker 1: And we would pull all nighters on Thursday nights to
• 2:49
  Speaker 1: study for the Friday exams. And I will always think
• 2:52
  Speaker 1: fondly of those people who got me through like the
• 2:54
  Speaker 1: hardest summer of my life. But anyway, I like it.
• 2:57
  Speaker 1: I just find it way harder than just about anything
• 3:01
  Speaker 1: else I have to think of. But you know, I
• 3:03
  Speaker 1: take a lot of medications that I'm sure would not
• 3:06
  Speaker 1: be around but for the miracle of chemistry.
• 3:08
  Speaker 2: Exactly. I'm ever so grateful for chemistry. And though I
• 3:11
  Speaker 2: take every opportunity to make fun of chemistry, I also
• 3:14
  Speaker 2: want to make sure people out there understand that I
• 3:16
  Speaker 2: have a lot of respect for it, of course as
• 3:17
  Speaker 2: a science. And I will say that there are a
• 3:19
  Speaker 2: few listeners who are chemistry professors who write in and say,
• 3:23
  Speaker 2: don't worry keep joking about chemistry.
• 3:25
  Speaker 1: It makes me laugh so good. Yes, I joke about
• 3:29
  Speaker 1: it the same way I joke about a sibling, where
• 3:31
  Speaker 1: it's like you love them, you're picking fun at them.
• 3:33
  Speaker 1: If somebody else does it, you get a little defensive.
• 3:35
  Speaker 1: But yes, no, I love chemistry. It's just man, My
• 3:38
  Speaker 1: brain was not made for chemistry, but I'm so glad
• 3:40
  Speaker 1: other people's brains are.
• 3:41
  Speaker 2: And chemistry, like all kinds of science, inspire people to
• 3:44
  Speaker 2: ask questions, to wonder like how does this work? How
• 3:47
  Speaker 2: does this fit together? What are the rules for this?
• 3:50
  Speaker 2: And if you have questions about physics, or biology or
• 3:53
  Speaker 2: even chemistry, please write to us and ask your questions.
• 3:57
  Speaker 2: We would love to dig into it to understand the
• 4:00
  Speaker 2: benzene rings and everything else about the universe.
• 4:03
  Speaker 1: Well, bring another expert on to explain.
• 4:05
  Speaker 2: That, And today on the podcast we'll be doing just that,
• 4:09
  Speaker 2: answering questions from listeners. We have a lot of fun questions,
• 4:12
  Speaker 2: including questions about chain reactions in space, which is sort
• 4:17
  Speaker 2: of like superspace chemistry, a question about the chemistry of life,
• 4:21
  Speaker 2: and a question about what it all means and how
• 4:23
  Speaker 2: we know when to accept a scientific theory.
• 4:26
  Speaker 1: An amazing set of questions. Let's get started by hearing
• 4:29
  Speaker 1: what Tim wanted to know about.
• 4:32
  Speaker 3: I was just listening to your podcast about the brightest
• 4:35
  Speaker 3: thing ever seen in the universe, and it got me thinking,
• 4:40
  Speaker 3: is there's such a thing as an event where maybe
• 4:45
  Speaker 3: a chain reaction explosion in space? Maybe it's a binary
• 4:50
  Speaker 3: system supernova, would the other stargo nova as well? Or
• 4:56
  Speaker 3: instead of maybe just disintegrating planets, is it possible for
• 4:59
  Speaker 3: like the core of a planet to heat up so
• 5:01
  Speaker 3: that it explodes. Just piqued by curiosity and thought I'd
• 5:04
  Speaker 3: ask the question.
• 5:05
  Speaker 1: Thanks, WHOA all right? So I could imagine like looking
• 5:08
  Speaker 1: out at the stars at night and seeing like things
• 5:11
  Speaker 1: starting to explode in a chain reaction, and being like
• 5:14
  Speaker 1: I should have put my kids to bed before this
• 5:16
  Speaker 1: happened so they couldn't see it.
• 5:18
  Speaker 4: Yeah.
• 5:18
  Speaker 2: I was wondering what inspired this question. Maybe Tim was
• 5:21
  Speaker 2: worried that, like, if something goes wrong in one star
• 5:24
  Speaker 2: and ends cataclysmically, if you could set off a chain
• 5:27
  Speaker 2: reaction that like destroys the whole universe or something, or
• 5:30
  Speaker 2: if we're safe because every star is so far from
• 5:32
  Speaker 2: the other stars that their fates are all independent.
• 5:35
  Speaker 1: Sounds like Tim and I would have a good time
• 5:37
  Speaker 1: catastrophizing together out of Friday Night.
• 5:40
  Speaker 2: But it's a great question because it makes us think
• 5:42
  Speaker 2: about the relationship between one star and another and also
• 5:45
  Speaker 2: what it takes to like send a star to explode
• 5:48
  Speaker 2: or to disintegrate a planet. It is a fun question.
• 5:50
  Speaker 2: It sort of thinks about the whole universe as if
• 5:53
  Speaker 2: there were elements of a chemical reaction.
• 5:55
  Speaker 1: Right, that's true. But let's start with what's happening inside
• 5:58
  Speaker 1: of one star, and then we'll scale up to multiple stars.
• 6:01
  Speaker 1: You do have chain reactions happening in each star, right,
• 6:04
  Speaker 1: that's right.
• 6:05
  Speaker 2: Yeah, And a chain reaction essentially is a reaction which
• 6:08
  Speaker 2: sets the stage for itself, you know, which makes it
• 6:11
  Speaker 2: more likely for it to happen. And so like a
• 6:14
  Speaker 2: fire is a chain reaction because the combustion produces heat,
• 6:17
  Speaker 2: and that heat triggers more combustion, and so there's a
• 6:21
  Speaker 2: loop there, right, or a chain where one's link leads
• 6:25
  Speaker 2: to the next link. And as you say, inside a
• 6:27
  Speaker 2: star is a sort of a chain reaction because we
• 6:29
  Speaker 2: have fusion happening inside a star. You have gravity squeezing
• 6:33
  Speaker 2: this hot ball of hydrogen and maybe a little bit
• 6:35
  Speaker 2: of helium together, and it creates the conditions necessary for fusion,
• 6:40
  Speaker 2: heat and density, and then fusion itself produces more heat
• 6:44
  Speaker 2: and that increases the chances of fusion. The odds of
• 6:47
  Speaker 2: getting fusion grow very steeply with temperature. So the hotter
• 6:50
  Speaker 2: it is, you mean, the faster those particles are whizzing around,
• 6:54
  Speaker 2: the more likely you are to have fusion. So heat
• 6:56
  Speaker 2: makes fusion more possible.
• 6:58
  Speaker 1: Now we have to get to the really exciting part,
• 7:00
  Speaker 1: which is the explosions are explosions the results of all
• 7:03
  Speaker 1: of the fusion getting out of control. No, when do
• 7:07
  Speaker 1: we get the explosions?
• 7:08
  Speaker 4: Yeah?
• 7:08
  Speaker 2: Essentially you can think of a star during its normal lifetime,
• 7:12
  Speaker 2: during the millions or billions of years that it's burning
• 7:14
  Speaker 2: stably before it explodes, as in something of a balance.
• 7:18
  Speaker 4: Right.
• 7:18
  Speaker 2: You have gravity squeezing in, right, making things hot and dense,
• 7:22
  Speaker 2: and what it would like to do if it wasn't constrained,
• 7:24
  Speaker 2: is turned that into a black hole. Right. Gravity is
• 7:26
  Speaker 2: always just pushing and pushing and pushing, and if there's
• 7:29
  Speaker 2: nothing else but gravity, everything would collapse into a black hole.
• 7:33
  Speaker 2: But in the star you have lots of forces resisting gravity,
• 7:37
  Speaker 2: and when the star is burning, the primary force at
• 7:39
  Speaker 2: the frontier resistant gravity is fusion itself, which is pushing
• 7:43
  Speaker 2: out with radiation, right it produces all this heat, this energy,
• 7:47
  Speaker 2: it's pushing the star out. So fusion is pushing the
• 7:49
  Speaker 2: star out. Gravity is pushing the star back in, and
• 7:52
  Speaker 2: there's a balance there, and if you upset that balance,
• 7:55
  Speaker 2: then yes, the star can go kaboom. And there's basically
• 7:59
  Speaker 2: two ways for the star to go supernova. There's the
• 8:02
  Speaker 2: core collapse supernova and then there's the special fancy type
• 8:06
  Speaker 2: one A supernova, and the core collapse is the one
• 8:09
  Speaker 2: that we mostly think about. This is like the sort
• 8:11
  Speaker 2: of vanilla supernova. What happens is the fusion is doing
• 8:15
  Speaker 2: its job. It's turning hydrogen into helium, and then if
• 8:18
  Speaker 2: it's hot enough, it's turning helium into carbon, and if
• 8:20
  Speaker 2: it's hot enough, it's turning that carbon into neon and
• 8:23
  Speaker 2: oxygen and all sorts of heavier stuff all the way
• 8:26
  Speaker 2: up to iron. But fusing those heavier elements requires more temperature,
• 8:30
  Speaker 2: so a star might not be hot enough to fuse
• 8:33
  Speaker 2: a certain element. For example, right now, our star confuse hydrogen,
• 8:37
  Speaker 2: but it can't fuse helium. So what happens to the
• 8:39
  Speaker 2: helium or the core of our star it just sits
• 8:41
  Speaker 2: there and kind of gets in the way. It's like ash,
• 8:45
  Speaker 2: it's like the product of a fire. And if you
• 8:47
  Speaker 2: have too much of that without climbing over that temperature
• 8:51
  Speaker 2: threshold where you can burn it, also it starts to
• 8:54
  Speaker 2: put the fire out. So smaller stars reach their hotest
• 8:57
  Speaker 2: temperature and can't burn something. So, for example, our star
• 8:59
  Speaker 2: can't burn helium. If the star was larger, it would
• 9:02
  Speaker 2: get hotter at its core and it would burn a
• 9:04
  Speaker 2: heavier element, or a heavier element, or an even heavier
• 9:06
  Speaker 2: element all the way up to iron. When you get
• 9:09
  Speaker 2: up to iron, no star can burn iron and produce
• 9:12
  Speaker 2: energy because when you fuse iron together, it actually costs energy.
• 9:16
  Speaker 2: It cools the star. So the short version of the
• 9:20
  Speaker 2: story is, at some point you've done so much fusion
• 9:23
  Speaker 2: and you've made something that you can no longer burn
• 9:26
  Speaker 2: that's interfering with your fusion, and so fusion is failing
• 9:29
  Speaker 2: and gravity starts to win, and the star starts to
• 9:32
  Speaker 2: collapse because remember the reason it wasn't collapsing was fusion
• 9:35
  Speaker 2: pushing out against gravity, and now you've knocked out those supports,
• 9:40
  Speaker 2: gravity wins, the star implodes, and that implosion then triggers
• 9:45
  Speaker 2: a moment when the star is hot enough to do
• 9:48
  Speaker 2: stuff like burn iron and make super heavy elements, and
• 9:51
  Speaker 2: that triggers the explosion, which is the supernova. So the
• 9:54
  Speaker 2: core collapse supernova comes when the core is not hot
• 9:58
  Speaker 2: enough to burn the ash that's left over, which then
• 10:01
  Speaker 2: triggers the collapse and then an explosion.
• 10:03
  Speaker 1: That was a great explanation. Okay, so you said our
• 10:06
  Speaker 1: sun is not hot enough to make iron, so we've
• 10:08
  Speaker 1: got a bunch of helium. Does it matter what form
• 10:11
  Speaker 1: the ash takes, they all explode no matter what kind
• 10:15
  Speaker 1: of ash is made, or do you get a different
• 10:16
  Speaker 1: result if the ash is helium versus if the ash
• 10:19
  Speaker 1: gets to the iron fase.
• 10:20
  Speaker 2: Yes, So not every star is going to go supernova, Like,
• 10:23
  Speaker 2: for example, our star is not going to go supernova.
• 10:25
  Speaker 2: It's not big enough. It's going to accumulate a lot
• 10:27
  Speaker 2: of helium in its core, and then near the very
• 10:30
  Speaker 2: end it's gonna have a brief moment like maybe minutes
• 10:33
  Speaker 2: in the billions year long life cycle of the star
• 10:36
  Speaker 2: where it can burn that helium and a helium flash
• 10:40
  Speaker 2: and make a little bit of heavier stuff, but it
• 10:42
  Speaker 2: doesn't have enough gravity to actually collapse. Fusion is gonna
• 10:46
  Speaker 2: happen in the outer layers because the core is going
• 10:48
  Speaker 2: to be cold helium, and then you're gonna have this
• 10:50
  Speaker 2: helium flash and it's gonna blow off those outer layers
• 10:53
  Speaker 2: and you're gonna be left with a white dwarf, which
• 10:54
  Speaker 2: is just a hot blob of stuff. It's not fusing anymore.
• 10:58
  Speaker 2: It's just like a big rock sitting there in space glowing,
• 11:01
  Speaker 2: just a white dwarf. If it were bigger, then it
• 11:04
  Speaker 2: would have enough gravity to actually collapse and cause a supernova.
• 11:08
  Speaker 2: So our star is not going to become a supernova
• 11:10
  Speaker 2: unless there is a route for white dwarfs to become supernova's.
• 11:15
  Speaker 2: White dwarfs are just hot stuff sitting there in space,
• 11:18
  Speaker 2: not fusing. Gravity's trying to squeeze them, but it's resisting
• 11:22
  Speaker 2: because of the chemical strength of the stuff. The same
• 11:24
  Speaker 2: reason why like the Earth doesn't collapse into a black hole.
• 11:26
  Speaker 2: It's got chemical strength supporting it. But if something comes
• 11:30
  Speaker 2: along and pours extra material onto the white dwarf, then
• 11:34
  Speaker 2: it can increase its gravity, and gravity can overcome that
• 11:37
  Speaker 2: strength and cause it to collapse and make a special
• 11:40
  Speaker 2: type one a supernova. This happens if you have a
• 11:43
  Speaker 2: white dwarf that has like a sister star nearby, and
• 11:46
  Speaker 2: it eats some of that sister star and then it
• 11:48
  Speaker 2: gets triggered into a supernova. So that's the second kind
• 11:52
  Speaker 2: of supernova. So our star could eventually have a Type
• 11:55
  Speaker 2: one a supernova, but it's not going to have a
• 11:57
  Speaker 2: core collapse supernova.
• 11:59
  Speaker 1: So already got into part of the answer then for
• 12:02
  Speaker 1: why you don't get chain reactions because some of the
• 12:05
  Speaker 1: stars in between can't explode. They're just not the right kind.
• 12:09
  Speaker 1: They're little, they don't have sisters they can eat. Why
• 12:12
  Speaker 1: do we always get to annibalism. I don't know, we do.
• 12:15
  Speaker 1: And so you can't get the chain reaction because there's
• 12:17
  Speaker 1: a lot of stars, you know, in the line that
• 12:19
  Speaker 1: are just not capable of exploding.
• 12:21
  Speaker 2: Yeah, you need the right kind of star. And so
• 12:23
  Speaker 2: the answer to this question is that it's very unlikely
• 12:25
  Speaker 2: to have lots of chain reactions, but it could be
• 12:28
  Speaker 2: possible if you set up the conditions just perfectly. And
• 12:31
  Speaker 2: I'm a big science fiction reader, and so when I
• 12:33
  Speaker 2: got this question from Tama, was reminded of this snippet
• 12:37
  Speaker 2: from a Laring Niven novel Ring World, And there's a
• 12:40
  Speaker 2: scene where they talk about how in the center of
• 12:42
  Speaker 2: the galaxy the stars are all packed together really really close.
• 12:45
  Speaker 2: One star goes nova, it releases a lot of heat
• 12:48
  Speaker 2: and gamma rays, and that heats of the neighboring stars
• 12:51
  Speaker 2: with then blow and it sets off a chain reaction.
• 12:53
  Speaker 2: So it's super cool idea that you could like have
• 12:56
  Speaker 2: this like set of fireworks going off in the galaxy.
• 13:00
  Speaker 2: In order to make this work, you really need exactly
• 13:01
  Speaker 2: the right conditions, and what he describes in Ring World
• 13:05
  Speaker 2: probably wouldn't happen the way he described it, because adding
• 13:08
  Speaker 2: heat to a star doesn't actually cause it to explode.
• 13:12
  Speaker 2: Remember we talked about core collapse supernova. The reason they
• 13:15
  Speaker 2: collapse is because they're not hot enough. They can no
• 13:18
  Speaker 2: longer do fusion to burn the ash that's at their core.
• 13:22
  Speaker 2: So adding heat to a star actually supports it actually
• 13:25
  Speaker 2: makes it more likely to live longer. It prevents its collapse.
• 13:28
  Speaker 2: It doesn't trigger its collapse. Right, These stars explode because
• 13:33
  Speaker 2: they no longer have fusion happening at their core.
• 13:36
  Speaker 1: Is that true? Even if the ash is iron like
• 13:38
  Speaker 1: the end of the process, even adding more heat won't help.
• 13:42
  Speaker 2: Yeah, exactly, because the process of fusing iron SAPs heat
• 13:44
  Speaker 2: from the core. So you have a bunch of iron
• 13:46
  Speaker 2: there and the stars trying to fuse it, but that
• 13:49
  Speaker 2: fusion process is gobbling the energy instead of creating energy.
• 13:52
  Speaker 2: It's like the opposite of a chain reaction. And if
• 13:55
  Speaker 2: you have an external source of heat that's fueling that,
• 13:58
  Speaker 2: that's providing that energy, then you can sustain the star longer.
• 14:02
  Speaker 2: So a core collapse supernova isn't triggered by external heat
• 14:06
  Speaker 2: like radiation from another star. But the other kind of supernova,
• 14:10
  Speaker 2: the type one A supernova, is triggered externally. Right, you
• 14:13
  Speaker 2: have a white dwarf which otherwise wasn't going to go supernova,
• 14:17
  Speaker 2: and you get a deposition of new material from some
• 14:20
  Speaker 2: neighboring star that does trigger it to go over this
• 14:23
  Speaker 2: threshold and then go supernova. And so I asked a
• 14:26
  Speaker 2: friend of mine, David Vartagnan, he's a scientist who studies
• 14:29
  Speaker 2: supernova's he's a Hubbele Einstein fellow at the Carnegie Observatories,
• 14:32
  Speaker 2: and he said, quote, this may be possible for thermonuclear supernova,
• 14:36
  Speaker 2: which requires some version of runaway nuclear chain reactions on
• 14:39
  Speaker 2: the stellar surface. It's possible to change this if situations
• 14:43
  Speaker 2: are just right. So the idea is that you have
• 14:46
  Speaker 2: like a series of these white dwarfs, and you add
• 14:49
  Speaker 2: material to one of them, it goes supernova and then
• 14:52
  Speaker 2: deposits material on the next nearby white dwarf, which causes
• 14:56
  Speaker 2: that to go supernova. Dot dot dot. You have a
• 14:58
  Speaker 2: chain reaction.
• 15:00
  Speaker 1: Do my kids have anything to worry about?
• 15:02
  Speaker 2: You know, your kids do not have anything to worry about.
• 15:05
  Speaker 2: But if you are designing a universe and you want
• 15:07
  Speaker 2: to see this happen, you might be able to arrange it.
• 15:10
  Speaker 2: So if your kids grow up to be god or
• 15:12
  Speaker 2: masters of their own domain, they could set up a
• 15:15
  Speaker 2: supernova chain reaction if they so desire.
• 15:18
  Speaker 1: Malevolent guns, not the nice ones. Also, d'Artagnan super cool
• 15:22
  Speaker 1: last name, like the polar opposite of Wiersmith. I guess
• 15:25
  Speaker 1: maybe it reminds me of d'Artagnan like the Three Musketeers. Okay,
• 15:29
  Speaker 1: on that note, let's get back in touch with Tim
• 15:32
  Speaker 1: and see if he feels like his question was answered.
• 15:34
  Speaker 2: Answer the awesome question, Tim, hope you like the answer.
• 15:37
  Speaker 3: Oh, thanks for answering my question. Danielle and Kelly, Yeah,
• 15:41
  Speaker 3: you answered it. I'm pretty excited to know that under
• 15:45
  Speaker 3: the right circumstances, it can happen, so that it's possible,
• 15:49
  Speaker 3: But it doesn't sound like we're going to have a
• 15:50
  Speaker 3: spectacular fireworks show up exploding stars in our night sky
• 15:55
  Speaker 3: anytime soon. So glad your kids are safe and thanks
• 16:00
  Speaker 3: to answering my question.
• 16:17
  Speaker 1: All right. So next we have a question from Julian
• 16:20
  Speaker 1: from our discord, Daniel, if somebody wants to play with
• 16:24
  Speaker 1: us on discord, where do they find the link to
• 16:26
  Speaker 1: our discord?
• 16:27
  Speaker 2: Go to our website www dot danieland Kelly dot org
• 16:31
  Speaker 2: and you'll see an invitation there to the discorder. You
• 16:33
  Speaker 2: can come and talk and ask questions and make silly
• 16:36
  Speaker 2: jokes and.
• 16:36
  Speaker 1: Be our friends. All right, So let's listen to a
• 16:40
  Speaker 1: question from a New Zealander.
• 16:42
  Speaker 5: Hi, Daniel and Kelly. I'm Julian from New Zealand, a
• 16:45
  Speaker 5: longtime fan of the pod. What I'm interested in hearing
• 16:48
  Speaker 5: is your opinion on the possibility of non carbon based life.
• 16:52
  Speaker 5: Given the practically infinite size of the universe, it seems
• 16:56
  Speaker 5: to me that we should consider other life chemistries as
• 16:58
  Speaker 5: probable rather than But I'm interested to hear your thoughts
• 17:02
  Speaker 5: on this and whether they would be any practical wife
• 17:04
  Speaker 5: for us to search for barmakers from other platforms. Thanks,
• 17:09
  Speaker 5: and keep up the great work. Bye.
• 17:11
  Speaker 2: I love this kind of question because it takes us
• 17:13
  Speaker 2: like out of the mindset that life on Earth is
• 17:16
  Speaker 2: the only way life can be. So I'm dying to
• 17:18
  Speaker 2: hear your thoughts about this, Kelly.
• 17:20
  Speaker 1: Yeah, well, so I was really excited when I got
• 17:22
  Speaker 1: this question because it had the word life in it,
• 17:24
  Speaker 1: and then as I dug a little farther in, I
• 17:27
  Speaker 1: realized this was a chemistry question, and I remain excited.
• 17:31
  Speaker 1: But here we go. Let's do this, all right. So
• 17:33
  Speaker 1: there's about ninety four naturally occurring elements on the periodic table,
• 17:37
  Speaker 1: but the scaffold for life seems to be made of
• 17:41
  Speaker 1: carbon in every case that we've ever looked at, So
• 17:44
  Speaker 1: why carbon and why not something else?
• 17:47
  Speaker 2: So there's ninety four naturally occurring elements. So you're talking
• 17:49
  Speaker 2: about basically the building blocks of life out there in
• 17:52
  Speaker 2: the universe. But if we're starting on a rocky planet,
• 17:56
  Speaker 2: I guess we're assuming that there's like a good chunk
• 17:58
  Speaker 2: of silica and carbon and this kind of stuff, because
• 18:01
  Speaker 2: that's what you need to make a rocky planet, right, yep,
• 18:03
  Speaker 2: all right, cool?
• 18:04
  Speaker 1: You said that the sun makes everything up to iron.
• 18:07
  Speaker 1: Is that right? Yeah, that's right, So we would expect
• 18:10
  Speaker 1: everything up to iron to be fairly plentiful in the universe,
• 18:13
  Speaker 1: Is that fair to say?
• 18:14
  Speaker 2: Yeah, although there's a fascinating distribution of which elements are
• 18:17
  Speaker 2: more common and which ones are less common, which involves
• 18:19
  Speaker 2: a lot of chemistry, but we'll dig into it one day.
• 18:23
  Speaker 1: So the three criteria to sort of like enter us
• 18:25
  Speaker 1: in here is one abundance. So you wouldn't expect nobellium
• 18:30
  Speaker 1: to be the backbone for life because there's not a
• 18:32
  Speaker 1: lot of it out there, But the more common things,
• 18:35
  Speaker 1: you know, they'd be easier for organic organisms to find
• 18:37
  Speaker 1: and incorporate into their bodies. And so what are some
• 18:39
  Speaker 1: of these common atoms?
• 18:41
  Speaker 2: So the universe is mostly hydrogen, you know, because we
• 18:44
  Speaker 2: started with hydrogen and stars have been making heavier stuff
• 18:47
  Speaker 2: for a while, but we're pretty early on in the
• 18:49
  Speaker 2: history of the universe, So mostly hydrogen. Like seventy four
• 18:53
  Speaker 2: percent of the universe by mass fraction is hydrogen, and
• 18:57
  Speaker 2: then a big chunk of it is helium, So like
• 18:59
  Speaker 2: twenty four percent, which is already like most of the universe,
• 19:03
  Speaker 2: you got seventy four percent plus twenty four percent leaves
• 19:06
  Speaker 2: only two percent of the universe is left. But the
• 19:09
  Speaker 2: next one is kind of a surprise. It's oxygen, right,
• 19:11
  Speaker 2: Oxygen is much more common than anything else that's not
• 19:14
  Speaker 2: hydrogen or helium. And then you got carbon and neon
• 19:18
  Speaker 2: and then iron, so those are the most common building
• 19:22
  Speaker 2: blocks in the universe.
• 19:23
  Speaker 1: Okay, all right, so let's go from there. So all right,
• 19:25
  Speaker 1: so abundance is criteria one. Yeah, so you need stuff
• 19:28
  Speaker 1: that's abundant, so we're not surprised to find out that
• 19:30
  Speaker 1: it's carbon, although carbon, as you're noted, is not as
• 19:32
  Speaker 1: abundant as things like hydrogen, but there's still plenty of
• 19:34
  Speaker 1: it on Earth for example. And then the next criteria
• 19:38
  Speaker 1: is that it needs to be versatile and able to
• 19:40
  Speaker 1: make a lot of complex molecules. So the proteins that
• 19:44
  Speaker 1: we have these are very complex, they fold up in
• 19:47
  Speaker 1: different ways, they're made up of lots of different kinds
• 19:49
  Speaker 1: of elements, and the signaling molecules that bacteria make, like
• 19:53
  Speaker 1: every biological organism has lots and lots of super complex
• 19:58
  Speaker 1: molecules that it uses to carry out all of its
• 20:00
  Speaker 1: various functions. So it's thought that ideally you would end
• 20:03
  Speaker 1: up with atoms that are able to bind with the
• 20:06
  Speaker 1: most stuff. And as we move our way across the
• 20:09
  Speaker 1: periodic table, moving across the columns, when you get to
• 20:12
  Speaker 1: the column that carbon is at the top of the
• 20:16
  Speaker 1: stuff in that column are able to bond with four
• 20:19
  Speaker 1: other things. And the reason for that is that they've
• 20:22
  Speaker 1: got Now we're getting into electron shells, and I totally
• 20:26
  Speaker 1: went down a like mental rabbit hole, being like, oh,
• 20:28
  Speaker 1: but electrons, they're not really like particles. Does it make
• 20:31
  Speaker 1: sense to think of them this way in shells anymore?
• 20:33
  Speaker 1: Because maybe their entire functions and let's not go down
• 20:35
  Speaker 1: that rabbit hole for today, or maybe we should.
• 20:39
  Speaker 2: No, In terms of bonds, I think it's totally reasonable
• 20:42
  Speaker 2: to count the number of electrons because even if electrons
• 20:45
  Speaker 2: are waves or particles or something else alien, they follow
• 20:49
  Speaker 2: the rules of quantum mechanics, which dictate how many you
• 20:51
  Speaker 2: can have in each energy level, and that's what determines
• 20:54
  Speaker 2: the whole structure of the periodic table. Right The reason
• 20:56
  Speaker 2: we put carbon and silicon and germanium and tin and
• 21:00
  Speaker 2: lead in the same column is that they all need
• 21:03
  Speaker 2: four electrons to complete a shell. And if all the
• 21:06
  Speaker 2: electrons are filled in the shell, then the atom doesn't
• 21:08
  Speaker 2: like to interact very much, is very happy. And so
• 21:11
  Speaker 2: carbon and silicon both need four electrons to complete their shell.
• 21:14
  Speaker 2: And so I think you're saying that's why they like
• 21:16
  Speaker 2: to interact with four things.
• 21:18
  Speaker 1: So they can interact with as many as four things,
• 21:21
  Speaker 1: or they can interact with fewer and have like double
• 21:23
  Speaker 1: bonds with one of those things, for example. But their
• 21:25
  Speaker 1: ability to interact with the maximum number of things that
• 21:29
  Speaker 1: you can get interactions with on the periodic table allows
• 21:32
  Speaker 1: them to form these super complicated molecules that are necessary
• 21:38
  Speaker 1: for complex life.
• 21:39
  Speaker 2: So can I ask you a naive chemistry question, like
• 21:41
  Speaker 2: I don't understand why carbon is in this situation where
• 21:44
  Speaker 2: it can make the most bonds. Like I get that
• 21:46
  Speaker 2: it has four valence electrons out of the octet and
• 21:50
  Speaker 2: so it needs four more. But then you got nitrogen,
• 21:54
  Speaker 2: it's got five. Why can't they use its five electrons?
• 21:56
  Speaker 2: Or you got boron it's only got three. It could
• 21:58
  Speaker 2: take five more electrons, So why can nothing make five bonds?
• 22:02
  Speaker 1: Well, good start, Okay, Nitrogen tends to bond with three
• 22:07
  Speaker 1: other things to fill its aid to get to eat,
• 22:10
  Speaker 1: whereas boron tends to donate it's three to other things
• 22:13
  Speaker 1: as opposed to bonding with five things. I see.
• 22:16
  Speaker 2: So carbon sits right there in the sweet spot out
• 22:18
  Speaker 2: of the octet. It's got four so it can make
• 22:21
  Speaker 2: four bonds. That's pretty cool.
• 22:23
  Speaker 1: Yes, And so it's in the position to be the
• 22:25
  Speaker 1: backbone four the most complicated kinds of molecules that you
• 22:28
  Speaker 1: can make.
• 22:28
  Speaker 2: I have another basic question, which is like why do
• 22:30
  Speaker 2: we call life carbon based? Like I get carbon is useful,
• 22:34
  Speaker 2: but like, why can't we just have a big mix
• 22:35
  Speaker 2: of different kinds of chemistries. Why does carbon have to
• 22:38
  Speaker 2: be in everything, in every part of life.
• 22:41
  Speaker 1: So I think part of why we end up with
• 22:43
  Speaker 1: a lot of carbon as the backbone to a lot
• 22:46
  Speaker 1: of this stuff is because carbon not only combined with
• 22:50
  Speaker 1: a lot of things, but it also forms really strong bonds,
• 22:53
  Speaker 1: so it's stable. The kind of molecules that it makes
• 22:55
  Speaker 1: are stable. So, for example, if you moved down the
• 22:58
  Speaker 1: column that has carbon to other things that are also
• 23:00
  Speaker 1: able to bond for things, silicon can also bond four things,
• 23:05
  Speaker 1: but that bonding is happening in an even farther out shell,
• 23:10
  Speaker 1: and because it's farther away from the nucleus, the bonds
• 23:12
  Speaker 1: that it forms are less strong.
• 23:13
  Speaker 2: You're saying that silicon is like carbon in the outermost
• 23:17
  Speaker 2: electron orbitals, but it's a more complex, heavier nucleus, so
• 23:20
  Speaker 2: it's got more electrons. So this outermost electron orbitals are
• 23:24
  Speaker 2: further from the core and they're not as tightly bound,
• 23:27
  Speaker 2: and so things are a little more loosey goosey.
• 23:29
  Speaker 1: Yeah. So carbon has two shells, an inner shell with
• 23:32
  Speaker 1: two electrons and then this outer shell with four and
• 23:34
  Speaker 1: then the ability to bond to four other things. And
• 23:36
  Speaker 1: then silicon has three shells, and so it's got you
• 23:39
  Speaker 1: two in the center, eight the one out from that,
• 23:42
  Speaker 1: and then it's got four in the outer one and
• 23:43
  Speaker 1: the ability to bind with four other things. But because
• 23:47
  Speaker 1: that shell where the binding is happening is farther away
• 23:49
  Speaker 1: from the nucleus, the bonds that it produces are weaker.
• 23:55
  Speaker 1: And so the thought is that when chemical reactions happen
• 23:58
  Speaker 1: a lot of times, what's happening is that one of
• 24:00
  Speaker 1: the things that bonds to for example, like a carbon backbone,
• 24:05
  Speaker 1: you know, gets sort of like pulled off when a
• 24:06
  Speaker 1: reaction happens. And when something gets pulled off, carbon is
• 24:10
  Speaker 1: strong enough that the backbone stays together and that molecule
• 24:13
  Speaker 1: stays complete. But when you've got silicone as the backbone,
• 24:16
  Speaker 1: when something breaks off as part of reaction, that process
• 24:21
  Speaker 1: of breaking off could also break the backbone of the silicon.
• 24:25
  Speaker 1: And so the idea is that carbon is not only
• 24:28
  Speaker 1: something that allows you to make super complex molecules, but
• 24:31
  Speaker 1: it's also strong enough to allow reactions to happen. I
• 24:34
  Speaker 1: think if you had anything else that was like creating
• 24:37
  Speaker 1: the backbone for these complicated molecules, the thought is they
• 24:41
  Speaker 1: wouldn't be complex enough or they wouldn't be strong enough
• 24:43
  Speaker 1: to survive reactions.
• 24:45
  Speaker 2: So you need some sort of backbone to hold things
• 24:48
  Speaker 2: together while you have this sort of interaction, these chemistry
• 24:51
  Speaker 2: of life happening.
• 24:52
  Speaker 1: Yes. Yes, And so through this conversation we've hit on
• 24:54
  Speaker 1: the three criteria the abundance, versatility, and complexity, which is
• 24:59
  Speaker 1: those bonding sites, and then the stability when reactions are happening.
• 25:03
  Speaker 1: So those are the three things that we think are
• 25:05
  Speaker 1: most important. We've talked about why silicon is thought to
• 25:09
  Speaker 1: maybe not be ideal for these reactions, so you'll often
• 25:12
  Speaker 1: hear discussions about like, well, could life be silicon based?
• 25:15
  Speaker 1: And one reason we think that's unlikely is because you
• 25:18
  Speaker 1: might get a lot more breakdown of chemical structures when
• 25:20
  Speaker 1: reactions happen. But another thought, water is really important for
• 25:24
  Speaker 1: a lot of biological processes. In fact, when we look
• 25:27
  Speaker 1: to see where we think life is in the universe,
• 25:29
  Speaker 1: one of the criteria we use is whether or not
• 25:31
  Speaker 1: there's water there. Water is a helpful solvent, which means
• 25:34
  Speaker 1: it helps move around like nutrients and molecules and stuff
• 25:37
  Speaker 1: like that. But when carbon binds with water, you make
• 25:43
  Speaker 1: carbon dioxide, which is like a gas that we can
• 25:46
  Speaker 1: breathe out. But when silicon binds with water, you make
• 25:50
  Speaker 1: silicon dioxide, which is sand. And so it's thought that
• 25:54
  Speaker 1: sand is probably not something that's like conducive to the
• 25:57
  Speaker 1: creation of life, And so that is another proposed reason
• 26:02
  Speaker 1: why we don't see silicon based life forms, although some
• 26:05
  Speaker 1: labs have managed to do like directed evolution studies to
• 26:07
  Speaker 1: get more silicon into molecules. But I feel like that's
• 26:11
  Speaker 1: very different than a molecule as part of a living
• 26:15
  Speaker 1: being that has no carbon at all.
• 26:17
  Speaker 2: So that all does make sense to me as an
• 26:19
  Speaker 2: explanation for like why the kind of life that we
• 26:22
  Speaker 2: have needs carbon and why having even silicon wouldn't make
• 26:28
  Speaker 2: the kind of life we have possible, But doesn't convince
• 26:31
  Speaker 2: me that a totally different kind of life wouldn't be possible.
• 26:34
  Speaker 2: I mean, if we sat here before there was any life,
• 26:36
  Speaker 2: and we were just like looking at atoms and speculating, like, hey,
• 26:39
  Speaker 2: what could be complicated enough to have weird things like
• 26:42
  Speaker 2: life arise? I don't know that we would have been
• 26:44
  Speaker 2: able to predict like carbon is useful. There's a lot
• 26:47
  Speaker 2: of complexity in the universe that we failed to predict.
• 26:50
  Speaker 2: So isn't it possible that silicon is complex enough to
• 26:53
  Speaker 2: do something else which could be the basis of life,
• 26:56
  Speaker 2: even if it's like very different and maybe even pretty sandy?
• 27:00
  Speaker 1: Yeah, I think maybe. And also, you know, if you
• 27:02
  Speaker 1: move over to nitrogen where you've got three binding sites
• 27:06
  Speaker 1: instead of four, it's not immediately obvious to me that
• 27:10
  Speaker 1: you couldn't have simple life with a little bit less complexity,
• 27:14
  Speaker 1: and that you need four and nitrogen wouldn't be enough.
• 27:16
  Speaker 1: And so I did find myself while I was reading
• 27:18
  Speaker 1: through these explanations wondering if we are to some extent
• 27:22
  Speaker 1: a little bit too constrained in our thinking based on
• 27:24
  Speaker 1: the life that we observe here. But you know, on
• 27:26
  Speaker 1: the other hand, you know, maybe you would have expected
• 27:29
  Speaker 1: to have seen a couple examples of like nitrogenous life
• 27:33
  Speaker 1: on this planet.
• 27:34
  Speaker 2: Here on Earth.
• 27:34
  Speaker 1: You mean, yeah, yeah, here on Earth, but we don't
• 27:37
  Speaker 1: see that. Yeah, so I don't know, but different temperature
• 27:39
  Speaker 1: or pressure conditions might make nitrogen or silicon based life
• 27:42
  Speaker 1: a little bit more likely to exist. But this is
• 27:46
  Speaker 1: their current I think best understanding of why it's carbon
• 27:49
  Speaker 1: based based on our end of one of life forms
• 27:52
  Speaker 1: that happen to have carbon backbones.
• 27:54
  Speaker 2: Well, why do you think it is that we have
• 27:56
  Speaker 2: one kind of life here on Earth? Like all life
• 27:59
  Speaker 2: shares the same basic biochemistry and we think there's probably
• 28:02
  Speaker 2: a single common ancestor why don't we live on a
• 28:04
  Speaker 2: planet where life arose independently multiple times and coexists. Is
• 28:09
  Speaker 2: if for the same reason that we have like one
• 28:11
  Speaker 2: species of humans because we kill all the other ones
• 28:14
  Speaker 2: and we can't tolerate it, or do you think it
• 28:17
  Speaker 2: just arose once?
• 28:18
  Speaker 1: I really don't know.
• 28:19
  Speaker 2: I need answers, Kelly, I need answers.
• 28:21
  Speaker 1: I don't think anyone knows. Calm down, Daniel, You know
• 28:24
  Speaker 1: that on this podcast we usually don't have the answers.
• 28:26
  Speaker 2: I know, but it's so frustrating.
• 28:29
  Speaker 1: It is surprising to me that like in one ocean,
• 28:32
  Speaker 1: we didn't end up with, you know, in one puddle
• 28:35
  Speaker 1: life arose, and then in another puddle on the other
• 28:37
  Speaker 1: side of the planet, life arose, and we still see
• 28:41
  Speaker 1: signs of both of those. I don't know. I don't know.
• 28:44
  Speaker 1: I'd love to know the answer, but I don't.
• 28:45
  Speaker 2: It's so frustrating to only have this one example and
• 28:47
  Speaker 2: to not know how to generalize and what's typical and
• 28:50
  Speaker 2: what's weird. So it'd be fun to find even just
• 28:54
  Speaker 2: one more example of life somewhere else, and maybe on
• 28:57
  Speaker 2: that planet there's several different kinds of life and several
• 28:59
  Speaker 2: different kinds of chemistries of that life would be amazing.
• 29:03
  Speaker 1: That would be absolutely amazing, And it would blow my
• 29:06
  Speaker 1: mind if we found, like, for example, bacteria in the
• 29:08
  Speaker 1: lava tubes or underground on Mars, and if it ended
• 29:11
  Speaker 1: up that that was like an independent evolution of life.
• 29:14
  Speaker 1: I feel like that would be the coolest discovery of
• 29:17
  Speaker 1: my lifetime for sure.
• 29:18
  Speaker 2: Yeah, And I think this is a really healthy way
• 29:20
  Speaker 2: to think, Like, let's look at the example we have,
• 29:23
  Speaker 2: and let's wonder which of these things might be different.
• 29:26
  Speaker 2: It's a good way to like try to think outside
• 29:28
  Speaker 2: the box, even though it's really hard for us to
• 29:30
  Speaker 2: imagine what else could be out there. And I'm sure
• 29:32
  Speaker 2: that we're failing to describe the complexity of non Earth life,
• 29:36
  Speaker 2: but at least we're making the effort right where like
• 29:38
  Speaker 2: trying to understand what could be outside the box of
• 29:41
  Speaker 2: our thinking. How you mentioned briefly how water is super
• 29:44
  Speaker 2: important for life on Earth, but then I think you
• 29:47
  Speaker 2: said something about how it's maybe not necessary, how you
• 29:49
  Speaker 2: could have life without water, what could replace water.
• 29:52
  Speaker 1: So there's lakes of liquid ethane and methane on Titan,
• 29:56
  Speaker 1: which is a moon of Saturn, and it's possible that
• 29:59
  Speaker 1: these could be used as solvents to sort of move
• 30:01
  Speaker 1: stuff around a living organism instead of water if you
• 30:05
  Speaker 1: don't have water present, And maybe this could create different
• 30:08
  Speaker 1: kinds of life forms or create the sort of conditions
• 30:10
  Speaker 1: necessary for something else to become the backbone of life
• 30:14
  Speaker 1: instead of carbon. But I think we're a little bit
• 30:16
  Speaker 1: far away from sending probes out there to deliver samples back.
• 30:20
  Speaker 2: But fun NASA, that's right, We're doing as much as
• 30:25
  Speaker 2: we can to try to think our way outside the box.
• 30:27
  Speaker 2: But really what we got to do is actually climb
• 30:29
  Speaker 2: outside the box, go to these crazy places in our
• 30:32
  Speaker 2: own backyard where there could be other examples of life
• 30:36
  Speaker 2: right there waiting for us to discover them. And the
• 30:39
  Speaker 2: crazy thing is that all it does is cost money, right,
• 30:42
  Speaker 2: and we spend more money on an aircraft carrier than
• 30:45
  Speaker 2: it would cost to discover life on Titan. So let's
• 30:48
  Speaker 2: go do it, people, Let's go buy some knowledge.
• 30:50
  Speaker 1: That's like a good investment to me to ching. All right, Julian,
• 30:55
  Speaker 1: I did my best with the chemistry question, but if
• 31:00
  Speaker 1: you don't feel like you've got a sufficient answer, let
• 31:02
  Speaker 1: us know, and maybe we'll have to pull in a
• 31:05
  Speaker 1: chemist to help us answer this question. But I'm looking
• 31:07
  Speaker 1: forward to hearing what you had to.
• 31:09
  Speaker 5: Say, Danielle and Kelly fist Off. I was a little
• 31:12
  Speaker 5: bit worried that I might get kicked off the Discord
• 31:14
  Speaker 5: channel for asking such a chemistry heavy question, but it
• 31:18
  Speaker 5: was really inspiring to you guys looking at it and
• 31:22
  Speaker 5: tackling a subject where you're not necessarily the most comfortable,
• 31:25
  Speaker 5: and so thanks very much, and that does definitely answer
• 31:28
  Speaker 5: my question. Thanks again, Yes, bye.
• 31:47
  Speaker 1: All right, Now for something a little more philosophical.
• 31:50
  Speaker 4: I was listening to your episode about thinking like a physicist.
• 31:53
  Speaker 4: It got me thinking about different theories that I've been
• 31:55
  Speaker 4: proposed over the last few decades, which led me to
• 31:57
  Speaker 4: Hawking radiation. There isn't any observation or experimental data confirm
• 32:01
  Speaker 4: Hawking radiation, yet the physics community seems to have accepted it.
• 32:06
  Speaker 4: My question is why do some theories get accepted and
• 32:09
  Speaker 4: others don't. Please help me figure out where my thought
• 32:11
  Speaker 4: process might be wrong. Thank you for all you do.
• 32:14
  Speaker 2: All right, great question, Eric, I love this because it
• 32:17
  Speaker 2: dives into the process of science itself. Not as much
• 32:20
  Speaker 2: as the science questions we're asking, but how as a
• 32:23
  Speaker 2: community we decide that something is part of the canon
• 32:27
  Speaker 2: or something is not. It's a great question.
• 32:30
  Speaker 1: It's a great question. Let's start, though, with what is
• 32:33
  Speaker 1: Hawking radiation so we can then, you know, compare other
• 32:36
  Speaker 1: theories to it.
• 32:37
  Speaker 2: Hawking radiation is an amazing little bit of science. We
• 32:41
  Speaker 2: talked in the podcast a lot about the biggest question
• 32:44
  Speaker 2: in modern physics is how to reconcile gravity with quantum mechanics.
• 32:49
  Speaker 2: Nobody knows how to do it. This program of quantum
• 32:51
  Speaker 2: gravity we've talked about string theory, we've talked about post
• 32:53
  Speaker 2: quantum gravity, this loop quantum gravity, all sorts of efforts,
• 32:56
  Speaker 2: nobody knows how to do it, nobody's had any success.
• 33:00
  Speaker 2: Accept Stephen Hawking figured out like one little corner of it.
• 33:05
  Speaker 2: He used a really clever mathematical trick to understand what
• 33:09
  Speaker 2: happens to quantum fields when they're near a black hole.
• 33:13
  Speaker 2: So he doesn't have like the big answer to how
• 33:16
  Speaker 2: to unify these things or what is the gravity of particles,
• 33:20
  Speaker 2: or to do all the calculations. He just was able
• 33:23
  Speaker 2: to figure out what happens to quantum fields when they're
• 33:26
  Speaker 2: near a black hole using a really clever little mathematical trick.
• 33:30
  Speaker 1: And how did he do that.
• 33:33
  Speaker 2: It's totally worth digging into it for a minute because
• 33:35
  Speaker 2: the story of Hawking radiation, as it's often told in
• 33:38
  Speaker 2: popular science accounts, is pretty much totally wrong and doesn't
• 33:42
  Speaker 2: describe what was actually done and what Hawking actually figured out.
• 33:46
  Speaker 2: The popular story is a story of what happens to particles.
• 33:49
  Speaker 2: Do you have fields near an event horizon and they
• 33:52
  Speaker 2: fluctuate and create like a particle antiparticle pair. One particle
• 33:56
  Speaker 2: falls into the black hole and the other one doesn't,
• 33:59
  Speaker 2: and so escapes and that's your Hawking radiation. And the
• 34:02
  Speaker 2: problem with that account is that that's not at all
• 34:04
  Speaker 2: what we think happens. We don't know how to describe that.
• 34:06
  Speaker 2: That would require understanding like how gravity affects particles and
• 34:11
  Speaker 2: are those particles real anyway. Really, what Hawking did was
• 34:14
  Speaker 2: he thought about the mathematical solutions to the quantum wave equations,
• 34:19
  Speaker 2: like quantum fields have waves in them. Those waves are
• 34:21
  Speaker 2: particles or other kinds of ripples, and they slash around
• 34:24
  Speaker 2: and they follow rules. Those are wave equations, just like
• 34:27
  Speaker 2: the mathematics that describes waves in the ocean or waves
• 34:31
  Speaker 2: in traffic. Waves are everywhere, and the equations that describe
• 34:34
  Speaker 2: quantum fields are also wave equations. And when you solve
• 34:37
  Speaker 2: wave equations, you have to make sure that they line
• 34:40
  Speaker 2: up on top of each other and they match what
• 34:42
  Speaker 2: you see at boundaries and stuff like this. This is
• 34:45
  Speaker 2: how we figure out like reflection and refraction of light,
• 34:48
  Speaker 2: all sorts of wave equation stuff. And he figured out
• 34:51
  Speaker 2: what happens to those waves if you have a weird
• 34:54
  Speaker 2: barrier and event horizon. You add that to your quantum fields.
• 34:57
  Speaker 2: And he showed that what happens is you have to
• 34:59
  Speaker 2: have have a wave coming out of that event horizon.
• 35:03
  Speaker 2: So the short version is that the mathematics of quantum
• 35:06
  Speaker 2: fields require some outgoing radiation from an event horizon if
• 35:11
  Speaker 2: the quantum fields are ever going to work. So you
• 35:13
  Speaker 2: don't have to know what the gravity is for particles,
• 35:15
  Speaker 2: or what's happening inside that event horizon, or even why
• 35:18
  Speaker 2: you have an event horizon, but very generally, anytime that's
• 35:22
  Speaker 2: an event horizon near a quantum field, that's going to
• 35:24
  Speaker 2: be outgoing radiation. So that's really what Hawking radiation is.
• 35:28
  Speaker 2: That's the prediction. And again we don't have a complete
• 35:31
  Speaker 2: description of quantum gravity or understand how gravity affects little particles,
• 35:35
  Speaker 2: but he predicts that there's this radiation that comes out
• 35:38
  Speaker 2: of event horizons just to make the wave equation work
• 35:41
  Speaker 2: for quantum fields.
• 35:42
  Speaker 1: Okay, so this is a prediction, but it hasn't been tested.
• 35:46
  Speaker 1: So for something that you can't test, you can still
• 35:48
  Speaker 1: feel pretty good about it if it predicts a lot
• 35:50
  Speaker 1: of other things. So like, how good in general is
• 35:53
  Speaker 1: the evidence even if we can't directly test it.
• 35:55
  Speaker 2: There's absolutely no evidence for Hawking radiation. Okay, but it's
• 35:59
  Speaker 2: very cool because it connects to other kinds of physics.
• 36:02
  Speaker 2: It also lets you think about black holes thermodynamically. It
• 36:06
  Speaker 2: lets you think about black holes as things that have temperature.
• 36:09
  Speaker 2: In our universe, everything that's made out of some kind
• 36:12
  Speaker 2: of matter has a temperature and glows. Like the Sun
• 36:16
  Speaker 2: obviously glows it's really hot, but the Earth also glows.
• 36:19
  Speaker 2: It just glows in a wavelength of light that we
• 36:21
  Speaker 2: can't see. Glows in the infrared, and you glow, which
• 36:25
  Speaker 2: is why if somebody puts on night vision goggles they
• 36:28
  Speaker 2: can see you because they're seeing you in the infrared.
• 36:30
  Speaker 2: The light that you glow in, and your temperature determines
• 36:33
  Speaker 2: what you glow in. So as you get hotter, you
• 36:35
  Speaker 2: glow in higher frequency light, which is why, for example,
• 36:38
  Speaker 2: metal when you heat it up, gets red hot and
• 36:41
  Speaker 2: then white hot. For example. That's all just black body radiation.
• 36:45
  Speaker 2: Everything that has a temperature glows. So now if black
• 36:48
  Speaker 2: holes glow, you can describe them as having a temperature,
• 36:52
  Speaker 2: which is pretty cool, haha. Thermodynamics joke, and it lets
• 36:56
  Speaker 2: you use a whole other branch of mathematics and physics
• 37:00
  Speaker 2: we've developed for hundreds of years and apply it to
• 37:02
  Speaker 2: black holes and think about their entropy and stuff like this.
• 37:05
  Speaker 2: So people have been having a lot of fun using
• 37:08
  Speaker 2: black holes as a concept and playing around with the
• 37:11
  Speaker 2: mathematics of it. There's absolutely no evidence for hawking radiation
• 37:14
  Speaker 2: because if hawking radiation does exist in the universe, black
• 37:18
  Speaker 2: holes are too far away and hawking radiation is too
• 37:21
  Speaker 2: dim for us to see it. So it's possible that
• 37:24
  Speaker 2: black holes are all out there emitting this hawking radiation,
• 37:27
  Speaker 2: but we've never seen it, and it's very hard to
• 37:30
  Speaker 2: imagine how we could in the near future unless we
• 37:33
  Speaker 2: made artificial black holes here on Earth to study their radiation.
• 37:38
  Speaker 1: All right, So Stephen Hawking is like the rock star physics.
• 37:42
  Speaker 1: A rock star, y'all have like three And so to
• 37:46
  Speaker 1: what extent do you think this theory has been like,
• 37:48
  Speaker 1: quote unquote accepted because he's a rock star.
• 37:52
  Speaker 2: Well, I think this theory helped make him a rock star, right,
• 37:54
  Speaker 2: So there's some cause and effect there. But Eric's question
• 37:58
  Speaker 2: is a good one, like why do people pick up
• 38:00
  Speaker 2: on this theory and run with it and build on
• 38:02
  Speaker 2: top of it and other stuff is sort of dismissed.
• 38:04
  Speaker 2: You know, we have, like Stephen Wolfram got a theory
• 38:07
  Speaker 2: of everything that not very many people are working on
• 38:10
  Speaker 2: has become accepted. Lots of fringe theories out there that
• 38:14
  Speaker 2: nobody's taking up. You know, you have to remember that,
• 38:16
  Speaker 2: like science is not some official institution where things get
• 38:21
  Speaker 2: graded and accepted or rejected.
• 38:23
  Speaker 1: It's just a.
• 38:24
  Speaker 2: Bunch of people, and people work on the things they're
• 38:26
  Speaker 2: excited about. And the reason hawking radiation has become kind
• 38:30
  Speaker 2: of mainstream is that because it opened the door to
• 38:33
  Speaker 2: working on other things. Thinking about black holes as thermodynamic
• 38:37
  Speaker 2: objects and calculating their temperature and thinking about information. It
• 38:40
  Speaker 2: sort of left things for people to do and to
• 38:42
  Speaker 2: work on and to build on top of them. But
• 38:45
  Speaker 2: you know, that's just personal judgment. People decided, hey, this
• 38:48
  Speaker 2: is fun and interesting, I'm going to go work on this,
• 38:51
  Speaker 2: and so people just sort of vote with their feet,
• 38:53
  Speaker 2: whereas other ideas that might be more valid or better
• 38:57
  Speaker 2: descriptions of nature are not getting as much a because
• 39:01
  Speaker 2: maybe there's not an obvious problem to work on, or
• 39:03
  Speaker 2: there's nothing to do there, or it just doesn't seem
• 39:06
  Speaker 2: as fun. People have a sort of a simplistic view
• 39:09
  Speaker 2: of how science works and what is science, and think
• 39:13
  Speaker 2: that like science has to be experimentally proven before is accepted,
• 39:17
  Speaker 2: but there's no official stamp of accepted science. It's just
• 39:20
  Speaker 2: what are people doing, what are people working on, what
• 39:22
  Speaker 2: are people thinking about? And so it's possible that we
• 39:25
  Speaker 2: could discover that Hawking was totally wrong, or it could
• 39:28
  Speaker 2: be that Hawking's ideas lead us to understand quantum gravity
• 39:31
  Speaker 2: in some way, or it could be that it's a
• 39:33
  Speaker 2: dead end that he was able to figure this one
• 39:35
  Speaker 2: thing out, but it doesn't give us an opportunity to
• 39:37
  Speaker 2: discover anything else.
• 39:39
  Speaker 1: Yeah, So ruminating a little bit more on the human
• 39:41
  Speaker 1: side of science. I imagine that when you pick a
• 39:44
  Speaker 1: theory that you want to spend your career on, you
• 39:47
  Speaker 1: probably want to pick a theory that you think is
• 39:49
  Speaker 1: one of the ones that has the highest chance of
• 39:51
  Speaker 1: being right. I know that people are okay with working
• 39:54
  Speaker 1: on theories and finding out that they're wrong, because that
• 39:57
  Speaker 1: is an answer and answers are important. But I think
• 39:59
  Speaker 1: that probably you pick the ones you want to be correct.
• 40:02
  Speaker 1: But I wonder if when you're picking these ideas, how
• 40:04
  Speaker 1: much does it also have to do with what is
• 40:06
  Speaker 1: testable and what's not. Like even if you think an
• 40:09
  Speaker 1: idea is correct, but you can't really test it directly,
• 40:12
  Speaker 1: and maybe that makes it hard to like get grants
• 40:14
  Speaker 1: to fund your lab or something like how do you
• 40:16
  Speaker 1: think these various human factors sort of all add up?
• 40:20
  Speaker 4: Yeah.
• 40:20
  Speaker 2: I think in theoretical physics, whether it's immediately testable is
• 40:24
  Speaker 2: not always one of the top considerations. I think one
• 40:27
  Speaker 2: of the top considerations is can I make progress in
• 40:30
  Speaker 2: a reasonable amount of time? Like, personally, as a scientist,
• 40:34
  Speaker 2: when I choose projects, I could choose to work on
• 40:37
  Speaker 2: really big questions like hey, what came before the Big Bang?
• 40:40
  Speaker 2: But I have no way to make progress on that
• 40:42
  Speaker 2: in a reasonable amount of time. And as a scientist,
• 40:44
  Speaker 2: I have to produce science regularly, so I have to
• 40:46
  Speaker 2: choose projects where I can make some progress. And I
• 40:50
  Speaker 2: think this is a really important thing for young scientists
• 40:52
  Speaker 2: to learn, is to spot opportunities like, hey, here's something
• 40:56
  Speaker 2: where if we spend a couple of years on this,
• 40:58
  Speaker 2: we could actually learn something given the resources and the
• 41:01
  Speaker 2: skills that we have. Right, So it's sort of like
• 41:05
  Speaker 2: spotting a business opportunity. Oh, there's a market for this,
• 41:08
  Speaker 2: and we know how to do it, so let's jump
• 41:10
  Speaker 2: on that. And so in my research, for example, you
• 41:13
  Speaker 2: know we use machine learning, we're always like looking for
• 41:16
  Speaker 2: ways machine learning can solve problems that weren't solved before,
• 41:19
  Speaker 2: but again in a reasonable amount of time. So on
• 41:22
  Speaker 2: the theoretical physics side, people looking for problems where they
• 41:24
  Speaker 2: can make some progress, where there's an opening, but they're
• 41:27
  Speaker 2: not always concerned about like is this immediately going to
• 41:30
  Speaker 2: be testable, because science isn't just about experiments, you know.
• 41:34
  Speaker 2: Science is a big, complex dance that eventually leads to answers.
• 41:38
  Speaker 2: We hear a lot of criticism of string theory, for example, saying, oh,
• 41:41
  Speaker 2: it's not science because you can't test it, but you know,
• 41:44
  Speaker 2: it's a precursor to testing. Sometimes it takes something fifty years,
• 41:47
  Speaker 2: one hundred years before it bubbles up and produces something
• 41:50
  Speaker 2: that you can test. Doesn't mean that it wasn't science
• 41:53
  Speaker 2: until then that you retroactively go back and say, okay,
• 41:55
  Speaker 2: now we can test it. So the last one hundred
• 41:57
  Speaker 2: years count to science, whereas if it never to something
• 42:00
  Speaker 2: you can test that you say it never was science.
• 42:03
  Speaker 2: I think that's a little bit overly simplistic.
• 42:05
  Speaker 1: All right, Well, so continuing to think out loud here,
• 42:07
  Speaker 1: So you said that you don't work on questions related
• 42:09
  Speaker 1: to the Big Bang, because you can't produce science regularly
• 42:12
  Speaker 1: by doing that. So how do we get questions to
• 42:16
  Speaker 1: these really important problems that take a long time? Is
• 42:20
  Speaker 1: our system just not set up to answer those questions?
• 42:22
  Speaker 1: Or is it something so you know, for example, Darwin,
• 42:25
  Speaker 1: he came up with the idea of natural selection, but
• 42:27
  Speaker 1: it was like an idea that was the accumulated result
• 42:30
  Speaker 1: of observations that happened over like maybe decades. But he
• 42:33
  Speaker 1: was publishing a lot of like mollusk papers along the way,
• 42:36
  Speaker 1: or like, you know, observations on other things. So are
• 42:39
  Speaker 1: people working on the really big questions but just sort
• 42:42
  Speaker 1: of slowly in the background while producing something to keep
• 42:44
  Speaker 1: their jobs, or like, is it harder and harder to
• 42:47
  Speaker 1: get answers to those big questions that take a long
• 42:50
  Speaker 1: time today because of the way our funding system is
• 42:51
  Speaker 1: set up.
• 42:52
  Speaker 2: Yeah, there are people working on big questions. A great
• 42:54
  Speaker 2: example are things we call quantum foundations, like which of
• 42:58
  Speaker 2: the quantum mechanical interpretations of reality are real? The Copenhagen interpretation,
• 43:02
  Speaker 2: the Many World's interpretation. How do we grapple with all that?
• 43:05
  Speaker 2: Everybody thinks that's a big problem. A lot of people
• 43:08
  Speaker 2: have no idea how to make progress on it, and
• 43:11
  Speaker 2: so it's sort of a bit of a dangerous thing
• 43:13
  Speaker 2: to dig into for like a young scientist, because you
• 43:15
  Speaker 2: could jump into it, work for a couple of years,
• 43:18
  Speaker 2: make no progress, and then what do you have to
• 43:19
  Speaker 2: show for yourself. So it's the kind of thing that
• 43:21
  Speaker 2: people who are well established with like tangent positions i e.
• 43:24
  Speaker 2: Like Sean Carroll can dig into and try to make
• 43:27
  Speaker 2: some progress on and everybody understands it's really important, but yeah,
• 43:31
  Speaker 2: it's hard to know if you're going to make any progress,
• 43:33
  Speaker 2: and so a lot of people don't work on that.
• 43:35
  Speaker 2: There are also some places that specifically fund this kind
• 43:38
  Speaker 2: of work because they realize, hey, it's really important for
• 43:41
  Speaker 2: people to be thinking about these big questions or we're
• 43:44
  Speaker 2: never going to make any progress on them. And so
• 43:46
  Speaker 2: there's some places that specifically right grants just to support
• 43:50
  Speaker 2: that kind of research, but they're pretty few and far
• 43:53
  Speaker 2: in between. The bigger picture tendency and science I think
• 43:56
  Speaker 2: is towards short term promises. A lot of grants that
• 43:59
  Speaker 2: you right require you to know what you're going to
• 44:02
  Speaker 2: learn in advance and to have a lot of preliminary
• 44:05
  Speaker 2: data because this is arms race and science. You know,
• 44:08
  Speaker 2: this lab is already set up to do that. That
• 44:10
  Speaker 2: lab is already set up.
• 44:11
  Speaker 1: To do that.
• 44:12
  Speaker 2: And so a lot of science is more about these
• 44:14
  Speaker 2: sort of short term results, which I think is a
• 44:16
  Speaker 2: shame because we should be doing science as exploratory research. Say, hey,
• 44:20
  Speaker 2: let's see what happens if we give a bunch of
• 44:23
  Speaker 2: smart people money and time and see what they figure out.
• 44:26
  Speaker 1: Agreed, that's a big complaint of mind for the system.
• 44:30
  Speaker 1: All right, Well, have we said everything that we want
• 44:34
  Speaker 1: to say about Eric's question?
• 44:35
  Speaker 2: I think so. If I had to sum it up,
• 44:37
  Speaker 2: I would say to Eric that there is no such
• 44:39
  Speaker 2: thing as accepted science or not accepted science. It's just
• 44:42
  Speaker 2: the kind of things people are working on right now
• 44:45
  Speaker 2: that people are excited about, and it's a personal decision,
• 44:48
  Speaker 2: not some like institutional label we put on ideas.
• 44:51
  Speaker 1: And let's see what Eric has to say about that answer.
• 44:54
  Speaker 4: Hi, Danielle Kelly, this does help me understand better how
• 44:57
  Speaker 4: science works. I tend to make the mistake of thinking
• 44:59
  Speaker 4: looks science is monolithic with nothing but cold heart facts,
• 45:03
  Speaker 4: and I forget that behind the science are human beings.
• 45:06
  Speaker 4: My idea of the scientific method comes from high school,
• 45:08
  Speaker 4: which took a more simplistic approach. I think it's more
• 45:12
  Speaker 4: accurate to say science is more the art of human
• 45:15
  Speaker 4: curiosity than just cold, hard facts.
• 45:19
  Speaker 3: It is, after all.
• 45:20
  Speaker 4: Human beings and all their complexities that ultimately strive to
• 45:25
  Speaker 4: unravel the mysteries of the universe through a blend of
• 45:28
  Speaker 4: creativity and skepticism, and ultimately, if it is a good
• 45:32
  Speaker 4: idea that can stand scrutiny, it will become accepted. Hockey
• 45:38
  Speaker 4: radiation is a prime example of this. Thank you, Daniel
• 45:42
  Speaker 4: and Kelly for taking the time to help me understand
• 45:45
  Speaker 4: the process of science a bit more, and I certainly
• 45:47
  Speaker 4: appreciate everything you do. Take care.
• 45:57
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