Latest / Daniel and Kelly’s Extraordinary Universe / Things that glow in the dark

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Things that glow in the dark · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, I heard you grew up in Los Alamos,
0:10
Speaker 1: New Mexico, home of the Manhattan Project. Oh yeah, that's true.
0:14
Speaker 1: But before you ask, our high school mascot was not
0:17
Speaker 1: the atomic bomb. It wasn't a Tommy or hydrogen. That
0:22
Speaker 1: would be in bad taste. No, but we did bomb
0:24
Speaker 1: at all of our home football games. Oh that's a
0:28
Speaker 1: radioactive topic. But I do have a question for you.
0:31
Speaker 1: All right, The people in Los Alamos glow in the dark,
0:34
Speaker 1: you know, because of all that radiation. No, though that
0:37
Speaker 1: would be useful at night. But I do have an
0:39
Speaker 1: extra eyeball that I try to keep closed in the public.
0:43
Speaker 1: Does that give you extra death perceptive or lets you
0:45
Speaker 1: keep an eye on your kids more easily? Lets me
0:48
Speaker 1: see the world in three D? Cool? But I guess
0:50
Speaker 1: that makes getting glasses kind of paine. Hi'm more handmade
1:09
Speaker 1: cartoonist and the creator of PhD comments. Hi, I'm Daniel.
1:12
Speaker 1: I'm a particle physicist, and I don't really glow in
1:15
Speaker 1: the dark. Really what spectrum? Though? Don't you glow in
1:18
Speaker 1: the darkness certain spectrums of light? No, I absolutely do.
1:21
Speaker 1: I should have said I'm a particle physicist and I
1:23
Speaker 1: do actually glow in the dark, just the way I
1:25
Speaker 1: do and you do and everybody does. We all glow
1:28
Speaker 1: in the infrared. Yes, if we all had I guess
1:32
Speaker 1: special night goggles, we would all see each other glow
1:34
Speaker 1: in at night. Yeah. Or if we had evolved eyeballs
1:37
Speaker 1: that could see in the infrared. Oh, that would be cool. Yeah,
1:40
Speaker 1: we would be able to tell when people are sick
1:41
Speaker 1: and everything, right, kind of, they have a fever, that's right,
1:44
Speaker 1: we could spot the virus with our naked eyes. Are
1:46
Speaker 1: you saying everybody has an aura about them kind of
1:48
Speaker 1: in some frequencies of light. The physics of aura's exactly.
1:52
Speaker 1: Welcome to our podcast. Daniel and Jorge explain the university
1:55
Speaker 1: production of I Heart Radio, in which we'd like to
1:57
Speaker 1: talk about the physics of the crazy, the insane, in
2:00
Speaker 1: the quantum mechanical, the black holes, the neutron stars, the
2:03
Speaker 1: centers of galaxies. But we also like to talk about
2:06
Speaker 1: the physics of the every day. Doing physics about the
2:09
Speaker 1: universe means understanding everything we see around us, Understanding the
2:13
Speaker 1: microscopic mechanisms that determine everything that happens inside our bodies
2:17
Speaker 1: and outside our bodies. Yeah, because physics is all around us.
2:20
Speaker 1: It's not just out there in space and the farthest
2:23
Speaker 1: reaches of the cosmos and black holes and stars and planets.
2:26
Speaker 1: It's also right here all around us, and the things
2:29
Speaker 1: that you touch every day, and the things that you
2:31
Speaker 1: play with and activate every day, and like you said,
2:34
Speaker 1: in our own bodies as well. Yeah, I think it's
2:36
Speaker 1: sort of amazing and beautiful. How physics. Let's just like
2:40
Speaker 1: peel back a layer of reality and see the tiny
2:43
Speaker 1: little microscopic things that are causing that behavior. You know,
2:46
Speaker 1: the reasons that metals are shiny, or that liquids flow,
2:49
Speaker 1: or that gases burn. All of its physics at the
2:52
Speaker 1: lowest level, the rules that govern those tiny little particles
2:55
Speaker 1: eventually bubble up and determine basically everything about the universe.
2:59
Speaker 1: And it's cool to go in both directions to see
3:02
Speaker 1: something you don't understand and take it apart into its
3:04
Speaker 1: microscopic little components, and to go to the other direction
3:07
Speaker 1: and to understand from the bottom up how the rules
3:10
Speaker 1: of the universe determine our experience. Did you say physics
3:13
Speaker 1: is at the lowest levels or at the glowest levels?
3:17
Speaker 1: Was that a little unintentional slip there, that's right? Halloween
3:21
Speaker 1: is coming, and so I have glow in the dark
3:23
Speaker 1: things in my mind. Your kids have those, like glowing
3:25
Speaker 1: the dark stars up in their ceilings. They do, but
3:28
Speaker 1: they're getting fainter and fainter every year, maybe because of
3:31
Speaker 1: dark energy. Oh, interesting, I don't think that's the thing
3:35
Speaker 1: is Oh? I see? Are you saying that the room
3:39
Speaker 1: is getting bigger and bigger and so therefore the stars
3:42
Speaker 1: are getting fainter and fainter. No, the universe is getting
3:45
Speaker 1: darker and darker because galaxies are accelerating away from us
3:48
Speaker 1: faster and faster every year, and so our actual night
3:51
Speaker 1: sky is getting darker and darker. And my kids cheap
3:55
Speaker 1: o glow in the dark stars are also fading, but
3:57
Speaker 1: for a different reason. So they are acci dentally, scientifically accurate. Well,
4:02
Speaker 1: that is something that is in our everyday lives, especially
4:04
Speaker 1: around this time of Halloween. Glow in the dark things,
4:08
Speaker 1: things that glow into dark that people make, little like
4:10
Speaker 1: ghosts and decorations that glow in the dark. That's right.
4:13
Speaker 1: And if you have physics on the brain and then
4:15
Speaker 1: you look at that and you wonder, how does that happen?
4:17
Speaker 1: And I got a lot of questions from listeners who
4:19
Speaker 1: want to understand the very basics of how light works,
4:22
Speaker 1: how photons bounce off of things and sometimes reflect and
4:25
Speaker 1: sometimes absorb, and how you get mirrors, and why things
4:28
Speaker 1: look like different colors. And this is a very basic
4:30
Speaker 1: question I remember wondering about as a kid, you know,
4:32
Speaker 1: like how light travels and why things are various colors
4:36
Speaker 1: and how that all works. Yeah. I do remember in
4:38
Speaker 1: the mid eighties, like getting my first glow in the
4:41
Speaker 1: dark thing. I think it was a frisbee maybe or
4:43
Speaker 1: something in a T shirt, and I just remember thinking like, Wow,
4:46
Speaker 1: that's amazing, that's like magic. How does that work? That's right?
4:49
Speaker 1: And the answer is always physics. Well, I have to say,
4:52
Speaker 1: when I grew up, I stop wondering about it because
4:55
Speaker 1: I just look at that and think, oh, that's just chemistry.
4:58
Speaker 1: Just chemistry, right, all you chemists out there, you just
5:01
Speaker 1: got like totally dissed ambating YouTube. No, it's the wonderful
5:06
Speaker 1: world of chemistry, the magnificent questions answered by chemistry. No,
5:11
Speaker 1: chemistry is too complicated for me. I can't think about
5:13
Speaker 1: all those particles at the same time. I see you
5:16
Speaker 1: like to drill down to the individual party. I have
5:19
Speaker 1: utmost respect for chemists and biologists who can think about
5:22
Speaker 1: such complex systems. I like to take things apart and
5:25
Speaker 1: think about a single particle interacting with one other particle. Well,
5:28
Speaker 1: that is a pretty interesting question. How did glow in
5:31
Speaker 1: the dark? Things glow? And I wish we could we
5:33
Speaker 1: could go back in time and tell my eighties kid
5:36
Speaker 1: self about it. So it's on the podcast. We'll be
5:38
Speaker 1: talking about why do things glow in the dark? And
5:47
Speaker 1: I guess you mean, like certain things? Why do all
5:49
Speaker 1: things glow in the dark? Or why do you like
5:51
Speaker 1: glow in the dark? Things glow in the dark? Yeah, well,
5:53
Speaker 1: some things glow in the visible, other things glow in
5:55
Speaker 1: the invisible. And it turns out almost everything in the
5:58
Speaker 1: universe glows in some way or another. And there's a
6:02
Speaker 1: lot of really subtle physics going on about how things
6:05
Speaker 1: absorbed light when they decide to give it off, what's
6:08
Speaker 1: going on in between, and whether or not we could
6:10
Speaker 1: use that to understand things like black holes. Mm. Interesting,
6:14
Speaker 1: I guess all things glow in the dark, or at
6:16
Speaker 1: least all things that have a temperature other than zero kelvin, right,
6:20
Speaker 1: technically they glow in the dark. Almost almost all things
6:23
Speaker 1: that have a temperature things interesting. But I guess what
6:27
Speaker 1: we mean today is how do things that glow in
6:30
Speaker 1: the visible light spectrum? Those things that glow without any
6:33
Speaker 1: electricity or any kind of a battery source, How did
6:35
Speaker 1: those glow in the dark? Exactly? What is the physics
6:39
Speaker 1: of that? So it's usually we'll be were wondering how
6:40
Speaker 1: many people out there have thought about this question looking
6:43
Speaker 1: at their star stickies in their ceiling or a Halloween
6:46
Speaker 1: decorations and wondered what makes something glow in the dark.
6:49
Speaker 1: So Daniel went out there into the wilds of the
6:51
Speaker 1: internet to ask people this question. So thanks everybody who volunteered.
6:55
Speaker 1: And if you would like to participate and hear your
6:57
Speaker 1: voice on the podcast and you think you have some
6:59
Speaker 1: good is there is, please write to us two questions
7:02
Speaker 1: at Daniel and Jorge dot com. Everybody is very welcome.
7:05
Speaker 1: So think about it for a second. Did you owe
7:08
Speaker 1: a glow worm when you were a kid, and ever
7:11
Speaker 1: wonder how it works. Here's what people had to say.
7:15
Speaker 1: I'm inclined to say temperature is what makes the things
7:19
Speaker 1: glow in the dark, but in case of bioluminouscence in
7:24
Speaker 1: like fireflies or something, it's probably something else. It might
7:26
Speaker 1: be something involving some biological compound combined with electricity. I'm
7:32
Speaker 1: not sure how that works, really, but I'd say temperature
7:36
Speaker 1: is the usual suspect. The first thing that comes to
7:39
Speaker 1: mind is bioluminouscence. I'm sorry if I'm saying that wrong.
7:43
Speaker 1: I don't know how to pronounce that in English correctly.
7:46
Speaker 1: But it's like some fish in the deep water, they
7:50
Speaker 1: create kind of their own light. We also see that
7:53
Speaker 1: sometimes with algae in the ocean, but I don't know
7:57
Speaker 1: how that works. I'm guessing it's a mixture of chemicals.
8:02
Speaker 1: I've never thought about that. I know that there are
8:05
Speaker 1: certain chemical processes that can excite electrons in the correct way,
8:12
Speaker 1: and there's also bioluminescence that some organisms have. I think
8:17
Speaker 1: to glow in the dark, you have to be able
8:20
Speaker 1: to generate your own form of energy and admit that
8:26
Speaker 1: in some way. But I'm not sure of any other specifics.
8:29
Speaker 1: Interesting a lot of answers here the point to biology.
8:32
Speaker 1: They skip right over chemistry and went to bioluminescence. Man,
8:37
Speaker 1: that's a double insult there. No, it's all part of
8:41
Speaker 1: the same wonderful spectrum of science. But does make you
8:43
Speaker 1: realize that there are lots of ways that things glow
8:46
Speaker 1: in the dark. You know, they're like algae that glow
8:48
Speaker 1: in the ocean and their fish. And then there's also
8:50
Speaker 1: you know those watches that have like glow in the
8:52
Speaker 1: dark hands, And I remember as a kid thinking that
8:55
Speaker 1: those were amazing and wondering why they faded as the
8:57
Speaker 1: night went on. It was sort of like they captured
9:00
Speaker 1: sunlight and they were like slowly releasing it later, Like
9:03
Speaker 1: how do you capture photons? It's like I always imagined,
9:06
Speaker 1: like are their photons running around in circles inside those
9:08
Speaker 1: little watch hands? And there's also those glow sticks, right,
9:11
Speaker 1: I mean I don't go to a lot of raves,
9:13
Speaker 1: but I've heard that they use sticks a lot in those,
9:16
Speaker 1: and they're used a lot in like, you know, the
9:18
Speaker 1: Halloween too, right, Yeah, absolutely, we always deck our kids
9:21
Speaker 1: out with glowing stuff so they don't get run over.
9:23
Speaker 1: So there's lots of ways that you can emit light.
9:26
Speaker 1: You know, I think we should distinguish between things that
9:28
Speaker 1: like just reflect light and things that actually give off
9:31
Speaker 1: their own light, right because I guess, you know, like
9:34
Speaker 1: the moon doesn't midlight by itself, we only see it
9:37
Speaker 1: at night because it's reflecting light from the sun. That's right.
9:41
Speaker 1: Most of the light that you see is actually reflected, right,
9:44
Speaker 1: all the light from the sun. When you look at
9:46
Speaker 1: the ground, you're looking at reflected light from the sun.
9:49
Speaker 1: The ground is not like glowing in the visible light.
9:51
Speaker 1: And if you turned off the sun, the ground would
9:53
Speaker 1: be dark, right. And the same thing with the moon.
9:55
Speaker 1: The moon has a dark side and a light side,
9:57
Speaker 1: and you only see the light side because you were
9:59
Speaker 1: see light reflected off the moon from the sun in
10:03
Speaker 1: the visible light spectrum. Again, right in the visible light spectrum. Yeah,
10:06
Speaker 1: so you know moonlight is actually just sunlight, right, that's
10:09
Speaker 1: been reflected off of the moon. Which makes me wonder
10:12
Speaker 1: about all those creatures that you know, like only can
10:14
Speaker 1: live in the moonlight or whatever, like vampires. Wait, what
10:18
Speaker 1: are creatures we can only live in the moonlight on
10:21
Speaker 1: the moon or here on earth, nodological creatures. Don't vampires
10:25
Speaker 1: turn to stone in sunlight or something? Oh boy, you're
10:29
Speaker 1: really confusing me here today with chemistry and biology and
10:33
Speaker 1: mythical creatures and visible light, we're doing the plasics of
10:37
Speaker 1: vampires today from Daniel takes apart The science of vampires
10:41
Speaker 1: and you know, the Sun itself is actually glowing, it's
10:44
Speaker 1: actually emitting light. But the Earth and the Moon and
10:47
Speaker 1: all the planets, like when you look at Jupiter, right,
10:49
Speaker 1: that is reflected light from the Sun. Those photons have
10:52
Speaker 1: all shot out from the Sun, hit Jupiter and then
10:54
Speaker 1: come back to your eyeball. Right, Yeah, that's pretty cool
10:58
Speaker 1: to think about it. But then do the photons became
11:00
Speaker 1: um Jupiter photons? You know, like technically right, it's not
11:03
Speaker 1: the same photons that came from the Sun, Like Jupiter
11:06
Speaker 1: absorbed those photons from the Sun, did some something that
11:09
Speaker 1: we might talk about later, and then emitted its own photons. Yeah,
11:13
Speaker 1: it's complicated actually, Um, what happens when a photon hits
11:16
Speaker 1: the surface, it can either get absorbed and then later
11:20
Speaker 1: re emitted, but that you would really call emission, or
11:22
Speaker 1: can actually get reflected right and quantum mechanically to understand
11:27
Speaker 1: what happens during reflection is a whole other rabbit hole,
11:30
Speaker 1: which would take a whole other podcast, which we're planning
11:32
Speaker 1: to do in a few weeks actually. But so those
11:34
Speaker 1: photons are sort of really just still like stellar photons
11:38
Speaker 1: that have been reflected off of Jupiter. If something absorbs
11:42
Speaker 1: the photons and then like gets hotter and emits it.
11:44
Speaker 1: That's really a different kind of process. They are pretty
11:47
Speaker 1: stellar photons. They're fantastic, fantastic. But you know, like you
11:52
Speaker 1: see from stars, that's actually emitted from that star, right,
11:55
Speaker 1: those stars are glowing. And so when we say something
11:58
Speaker 1: is glowing, you really mean it's emitting its own photons.
12:00
Speaker 1: It's not just like reflecting somebody else's photons. But today
12:03
Speaker 1: we're sort of talking about things here on Earth that
12:06
Speaker 1: sort of glow into visible light spectrum sort of on
12:08
Speaker 1: their own, without any kind of battery or any light
12:10
Speaker 1: reflecting on them. And so we're going to start with
12:12
Speaker 1: things in chemistry and biology because we love chemistry and biology.
12:17
Speaker 1: We do love chemistry and biology and chemists and biologists, right,
12:20
Speaker 1: they're wonderful people. It's funny how we have to say
12:25
Speaker 1: that physics. I'm not overcompensate anying at all. You know,
12:30
Speaker 1: they're lovely people. But yes, there are things in biology
12:33
Speaker 1: that glow in the dark, like algae, right, and and
12:35
Speaker 1: some fungi absolutely, And so this is what we call bioluminescence.
12:40
Speaker 1: And this is essentially just like some critter that has
12:43
Speaker 1: energy stored inside of it and then releasing that energy
12:46
Speaker 1: in terms of a photon. All right. Photons are just
12:49
Speaker 1: like little units of energy, and when a chemical reaction
12:52
Speaker 1: happens and energy is released, it can be released in
12:55
Speaker 1: lots of ways. It can like heat up you know,
12:58
Speaker 1: other molecules, or you can actually also just emit a photon.
13:01
Speaker 1: And so that's what's happening in most cases inside these
13:05
Speaker 1: bioluminescent properties, and they have a chemical reaction. Actually it's happening,
13:09
Speaker 1: so it's biochemistry, and usually it's like oxygen reacting with
13:13
Speaker 1: this thing called lucifering. It's the enzyme, and there's lucifer
13:17
Speaker 1: in and lucifer aise and these things interact with oxygen
13:21
Speaker 1: and then release a photon and form some new chemical compounds, well,
13:25
Speaker 1: like lucifer like the fallen angel, or like lucid like light.
13:29
Speaker 1: I think there's a connection there, Yeah, I think they
13:31
Speaker 1: have the same route. All right. Interesting, So, like all
13:35
Speaker 1: bioluminescences is evils what you're saying, or at least this
13:41
Speaker 1: ends I'm called lucifer Ese. This is a surprisingly HALLOWEENI
13:44
Speaker 1: themed episode, isn't it. Oh my goodness, are you in
13:46
Speaker 1: costume right now? I'm dressed up as a physicist today.
13:51
Speaker 1: Could let me get sandals, shorts, a T shirt or
13:55
Speaker 1: is a T shirt optional? No comment? But you know
13:57
Speaker 1: this happens in lots of different kinds of creature. You
14:00
Speaker 1: have like bacteria that can do it. You have bugs
14:03
Speaker 1: that can do it, like fireflies. You have fung gui
14:05
Speaker 1: that can do it. A deep sea squids can do it.
14:08
Speaker 1: You've probably seen pictures of those fish that have like
14:10
Speaker 1: a little lantern that they have in front of themselves
14:13
Speaker 1: to attract craters to eat. Yeah. Are you saying that
14:15
Speaker 1: those all work with the same mechanism, the same enzyme
14:19
Speaker 1: or like a similar enzyme. They're all very similar. There's
14:22
Speaker 1: like forty different ways that this has evolved independently, and
14:26
Speaker 1: they all use some variety of a lucifer in or
14:29
Speaker 1: a lucifer ase, though it varies pretty widely between the species. Well,
14:33
Speaker 1: it's pretty cool, and I think the point is that
14:35
Speaker 1: they're expending energy, right. There's like using oxygen and they're
14:38
Speaker 1: probably using some kind of sugar right to sort of
14:40
Speaker 1: make this chemical reaction work. Yeah, Usually it starts out
14:43
Speaker 1: with you know, your typical energy carrying molecule a t
14:46
Speaker 1: P in the body and then it just converts that
14:49
Speaker 1: energy into something else, which becomes a photon. And I
14:52
Speaker 1: guess a big question is kind of why they do
14:54
Speaker 1: those things. I guess just to sort of see things
14:56
Speaker 1: in the dark or be able to communicate in the dark.
14:59
Speaker 1: It's thing that the biologists speculate a lot. In some cases,
15:02
Speaker 1: they do it to communicate like toxicity, the way like
15:05
Speaker 1: a plant might be brightly colored or an insect might
15:08
Speaker 1: be brightly colored to say like hey, watch out, stay
15:10
Speaker 1: away from me. In other cases, they use it to
15:12
Speaker 1: attract prey, like the lantern fish, you know, use it
15:16
Speaker 1: to draw things to it because some microbes are attracted
15:18
Speaker 1: to light. And so there's lots of different reasons, you know,
15:21
Speaker 1: some of them to use this to communicate, like fireflies
15:24
Speaker 1: or you know, for mating dances. So there's a really
15:26
Speaker 1: wide variety of uses across the various creatures that do
15:29
Speaker 1: bioluminous Interesting and you're saying they all evolved this independently,
15:34
Speaker 1: like they all came up with the same solution, but
15:36
Speaker 1: they hadn't talked to each other about it. Yeah, they
15:38
Speaker 1: don't have a single common evolutionary history, which means that
15:41
Speaker 1: it's something that's not that hard to evolve or something
15:44
Speaker 1: that's pretty useful, And it's something I think biologists have
15:47
Speaker 1: sort of learned to hack to write, Like they can
15:50
Speaker 1: now like tweet the DNA of something or bacteria or
15:53
Speaker 1: something and make it glow right, Yeah, exactly. It's not
15:56
Speaker 1: that complicated a process, so they can sort of engineer
15:58
Speaker 1: it into something, which means in the future, you know,
16:01
Speaker 1: maybe you'll be able to bio hack your body into
16:03
Speaker 1: glowing in the dark if you'd want that, or your
16:06
Speaker 1: kids so you can keep on hall. That would be
16:10
Speaker 1: pretty useful, just like give him a quick drink thank
16:13
Speaker 1: you in the dark. Probably there's be an app on
16:14
Speaker 1: your phone you can like turn your kid various colors,
16:16
Speaker 1: you know, like where's my kid? Where is the playground
16:19
Speaker 1: or something? Yeah, and you can change their color on
16:22
Speaker 1: the app. That would be pretty handy. I know. Then
16:25
Speaker 1: hackers take over and everybody's kids are just like blinking constantly.
16:29
Speaker 1: That would be crazy. It seems like a bad idea,
16:31
Speaker 1: or you get a raise on everyone's like as these
16:33
Speaker 1: fun patterns in your skin, But there are actual technological applications.
16:38
Speaker 1: It turns out that miners knew that some fish had
16:41
Speaker 1: a very faint glow in them, and even after the
16:44
Speaker 1: fish were dead, this process continued in their skins, and
16:48
Speaker 1: so miners used to take dried fish skins down into
16:51
Speaker 1: the mines with them as a sort of very very
16:54
Speaker 1: faint lamp. And your eyeballs are so powerful that even
16:57
Speaker 1: a very small source of light and a deep dark
17:00
Speaker 1: is enough to sort of show you how to get around.
17:02
Speaker 1: And an advantage of course in the deep caves not
17:05
Speaker 1: to have like an open flame something that's consuming oxygen
17:08
Speaker 1: and making smoke. Oh interesting, Yeah, although I imagine, you know,
17:12
Speaker 1: taking dead fish into a very close and cramped quarter,
17:16
Speaker 1: probably it becomes a bad idea in a short while.
17:19
Speaker 1: There's always trade offs, all right. So that's bioluminescence, how
17:23
Speaker 1: living creatures make light in the dark. But there's also
17:25
Speaker 1: sort of the chemistry of it, right, Like we can
17:27
Speaker 1: have glowst eggs, and we can have those sticky things
17:31
Speaker 1: that glow in the dark and glow in the dark,
17:33
Speaker 1: skulls and that that Halloween. How do those work? There's
17:36
Speaker 1: a lot of ways that you can have chemo luminescence. Essentially,
17:39
Speaker 1: you just need any sort of reaction that releases energy,
17:43
Speaker 1: and sometimes it releases energy in terms of light and
17:45
Speaker 1: not just heat. And so these are pretty simple reactions.
17:48
Speaker 1: What's happening inside those things that you have like a
17:51
Speaker 1: little glass vial that's separating two different chemicals that when
17:55
Speaker 1: they come together, they react and they give off some
17:57
Speaker 1: of their energy. Typically it's like hydrogen peroxide and then
18:01
Speaker 1: some sort of activator chemical, and so you know how
18:03
Speaker 1: you have to like bend those things and snap them
18:06
Speaker 1: so that the two things then mix and form that
18:08
Speaker 1: chemical reaction. Interesting, and so what's happening, Like the molecules
18:11
Speaker 1: of one chemical are reacting with the other molecules, and
18:15
Speaker 1: then somehow that process, as they rearranged themselves somehow releases
18:19
Speaker 1: a photon. The end product requires less energy to build
18:23
Speaker 1: than the actual ingredients, and so you've left over energy. Right,
18:27
Speaker 1: It's like these two things have like fallen in together
18:29
Speaker 1: into like a little potential. Well, so there's leftover energy
18:32
Speaker 1: which is admitted in terms of a photon, and so
18:34
Speaker 1: that's chemo and bioluminescence. That's pretty cool, all right, So
18:37
Speaker 1: let's get into the things that glow in the dark
18:41
Speaker 1: in other ways using physics. But first let's take a
18:44
Speaker 1: quick break. All right, we're talking about things that glow
19:00
Speaker 1: in the dark in a fun, fun way, right, not
19:02
Speaker 1: in a scary way, that's right, and a sort of joyful,
19:06
Speaker 1: you're gonna eat chocolate at the end of this night,
19:07
Speaker 1: halloweeny sort of way. Yeah, probably too much. So we
19:11
Speaker 1: talked about animals and bacteria and fun guy that glow
19:14
Speaker 1: in the dark and how to do that with chemicals.
19:16
Speaker 1: But then there's also things that seem to glow in
19:18
Speaker 1: the dark without any kind of reactive reaction or any
19:21
Speaker 1: kind of consumption of sugars or energy. Which are you know,
19:25
Speaker 1: glow in the dark stickers and glow in the dark,
19:28
Speaker 1: you know, decals and T shirts and things like that.
19:30
Speaker 1: How did those work? Those are more physics, right, Yeah,
19:33
Speaker 1: these are more physicals. And these are really cool because
19:35
Speaker 1: they really are like little batteries. They're like storing the
19:38
Speaker 1: energy from the sun and then slowly emitting its slowly
19:42
Speaker 1: releasing it. So it really is sort of cool. Like
19:44
Speaker 1: you know how you can charge these up? Right? You
19:45
Speaker 1: put it in sunlight and then you rush into the
19:48
Speaker 1: closet and it seems to glow really brightly and then
19:50
Speaker 1: it fades very gradually, but it takes a long time,
19:53
Speaker 1: and so it's i think of it like delayed reflection,
19:56
Speaker 1: rather than just immediately reflecting all the light from the sun,
19:59
Speaker 1: like it gathers at holds it, and it sort of
20:01
Speaker 1: meters it out for you, the same way. You know
20:03
Speaker 1: on Halloween you get a huge bucket of candy, but
20:05
Speaker 1: your mom only lets you have one or two pieces
20:07
Speaker 1: every day. We have two very different moms. I guess
20:10
Speaker 1: my mom was not that concerned about my candy consumpt Yeah,
20:15
Speaker 1: did you just eat it all herself? We just had
20:17
Speaker 1: no rules, I think, Alis, I don't remember having any rules.
20:21
Speaker 1: And is that the way you're raising your kids? Eat
20:23
Speaker 1: as much candi as you like. Whenever you're like no,
20:25
Speaker 1: of course he turned into the worst of yourself as
20:28
Speaker 1: a parent. We we meet her up throughout the year.
20:30
Speaker 1: All right, well, there you go. That's a good model
20:32
Speaker 1: for the phosphorescence process which is happening and glow in
20:36
Speaker 1: the dark toys. So what's happening here is that the
20:38
Speaker 1: photon is hitting the object and it's in some low
20:41
Speaker 1: energy state and absorbs that photon. R It doesn't just reflected,
20:44
Speaker 1: it absorbs it, which means that like some electron in
20:47
Speaker 1: that material now has more energy than it did before.
20:50
Speaker 1: And that's not that unusual. But what happens here is
20:53
Speaker 1: that the electron doesn't just immediately then release that energy. Instead,
20:57
Speaker 1: it gets trapped. It's sort of like you've pushed the
20:59
Speaker 1: electro up a hill and then before it can roll
21:02
Speaker 1: back down, it gets caught on some ledge or something
21:05
Speaker 1: and it has to hang out there for a while,
21:06
Speaker 1: and it's very hard for it to get off that ledge.
21:09
Speaker 1: And so you have this like pile of electrons stuck
21:11
Speaker 1: up on that ledge, storing that energy, and occasionally one
21:14
Speaker 1: will drop down and give off a photon. Interesting, and now,
21:18
Speaker 1: is it like one photon per atom, or like one
21:21
Speaker 1: electron per atom, or can like an atom store multiple
21:25
Speaker 1: photon You can't really think about it in terms of
21:27
Speaker 1: atoms because these are objects. So it's really like a lattice,
21:30
Speaker 1: and the electrons are not really like held onto an
21:32
Speaker 1: individual atom. So these electrons are like flowing around this crystal,
21:36
Speaker 1: this lattice of whatever material it is that that you're
21:39
Speaker 1: thinking about. You know, when we think about crystal, you
21:41
Speaker 1: think of like a really hard firm object, but really
21:44
Speaker 1: any solid you can think about in terms of a
21:46
Speaker 1: crystal or a lattice. It's like a mesh of atoms
21:49
Speaker 1: that are all woven together, and the electrons jump happily around.
21:52
Speaker 1: And so what happens here is like an individual electron
21:55
Speaker 1: gets energy and then it's like flowing freely, but it
21:58
Speaker 1: can get stuck, like the is a defect in the lattice,
22:01
Speaker 1: or you know, whether bonds are not perfect, or there's
22:04
Speaker 1: like some doping materials some other kind of thing which
22:06
Speaker 1: sort of breaks the lattice, and electrons can get stuck
22:09
Speaker 1: in those little holes and then they have to wait
22:11
Speaker 1: for like a little bit of heat or something else
22:13
Speaker 1: to sort of knock them out of that hole and
22:15
Speaker 1: down to a lower energy so they can give off
22:17
Speaker 1: that light. And that's why the light is emitted over time. Interesting,
22:22
Speaker 1: But then what happens to the photons? Do they like disappear,
22:25
Speaker 1: they get transformed into a different kind of energy. What
22:28
Speaker 1: what happens to the actual photon? So the initial photon,
22:31
Speaker 1: it goes into the energy of the electron, right, and
22:33
Speaker 1: then the electron has more energy, is like whizzing around
22:36
Speaker 1: inside the lattice. When we say it's trapped, we don't
22:39
Speaker 1: mean it's like physically stuck in a particular physical state.
22:42
Speaker 1: We mean that it's like stuck in a higher energy state,
22:45
Speaker 1: like can't release its energy. It's a it's stuck in
22:48
Speaker 1: a state where it's very difficult to transition back down
22:51
Speaker 1: to the lower state. You know, you can think about
22:54
Speaker 1: these quantum states is sort of like a ladder, but
22:56
Speaker 1: really it's not always easy to go up or down
22:59
Speaker 1: the connections tween these two ladders. So weach require some
23:02
Speaker 1: kind of interaction, you know, some sort of forces involved
23:05
Speaker 1: in going from one part of the ladder to the
23:07
Speaker 1: other part of the ladder, and sometimes those things are
23:09
Speaker 1: difficult to happen, and so you can get stuck in
23:12
Speaker 1: an upper state and very slowly the electrons can leak
23:15
Speaker 1: down to the lower state. So that's what's happening here,
23:18
Speaker 1: is that the process that takes the electron, that lets
23:20
Speaker 1: it release its energy down to the lower state, is rare.
23:23
Speaker 1: It's not like it could happen all the time, and
23:25
Speaker 1: so a lot of the electrons are just like, you know,
23:28
Speaker 1: whizzing around really excited, like kids that have had too
23:30
Speaker 1: much candy, and they can't let that energy go. I see.
23:33
Speaker 1: It's like it captures electrons easily, but it sort of
23:36
Speaker 1: doles them out more rarely, and so that's why you
23:39
Speaker 1: can sort of store light in a way, like you
23:42
Speaker 1: charge in it in the sunlight and then you take
23:43
Speaker 1: it into the dark room and it slowly gives us
23:46
Speaker 1: those photons it absorbed. Yeah, Like imagine a huge bowl
23:50
Speaker 1: with a tiny little hole at the bottom and you
23:52
Speaker 1: fill it with ping pong balls. You're not gonna get
23:54
Speaker 1: all the ping pong balls out at once. They're all
23:56
Speaker 1: going to dribble out one at a time because the
23:58
Speaker 1: size of the hole is small. And so that's the said,
24:00
Speaker 1: see what's happening. And so that's how most glow in
24:02
Speaker 1: the dark toys and stickers work. They all use the
24:04
Speaker 1: same material or are there different materials that do this?
24:07
Speaker 1: There are lots of different materials that can do this.
24:09
Speaker 1: But the process in general is called phosphorescence. It's called
24:12
Speaker 1: fluorescence if you just absorb and immediately re emit. It's
24:16
Speaker 1: called phosphorescence if you absorb and you hang onto it
24:19
Speaker 1: for a little while and then you emit. And so
24:21
Speaker 1: it's phosphorescence that makes like the hands on your watch
24:24
Speaker 1: glow or your little plastic toy glow or whatever it is.
24:27
Speaker 1: Anything that needs to be charged by sunlight is phosphorescence. Interesting,
24:32
Speaker 1: is it related to phosphor. Yeah, well, confusingly, something which
24:35
Speaker 1: is a phosphor is anything which is either fluorescent or phosphorescent.
24:40
Speaker 1: So that's a confusing set of names there. But the
24:43
Speaker 1: phosphor is anything essentially that just glows. And I guess
24:47
Speaker 1: can it trap energy in other ways or only through sunlight? Like?
24:50
Speaker 1: Can I stick it in the microwave and then they'll glow,
24:53
Speaker 1: or rub it really hard or put it over a
24:55
Speaker 1: flame and they'll glow, you know what I mean? Or
24:57
Speaker 1: is it only able to store energy from sunlight? That's
25:00
Speaker 1: the most efficient way for it to happen, because what
25:02
Speaker 1: you want is for the electrons to get their energy.
25:05
Speaker 1: You don't want to break up the lattice itself. If
25:07
Speaker 1: you put this thing in the microwave, you're gonna melt it.
25:09
Speaker 1: You're gonna change the chemical composition. It's no longer going
25:12
Speaker 1: to be that lattice that can hold that energy in
25:15
Speaker 1: this particular state and admit it over time. So you
25:17
Speaker 1: can destroy by heating it up. Yes, you will be
25:20
Speaker 1: giving energy to those electrons, but the whole process relies
25:23
Speaker 1: on the electrons moving through this lattice, and if you
25:25
Speaker 1: destroy that lattice, then you've you've messed it up. I see.
25:28
Speaker 1: So don't stick your glow in the darks in the
25:30
Speaker 1: microwave is the main takeaway here today. That's right. Physics
25:34
Speaker 1: tells you don't mark or weave random stuff, all right.
25:37
Speaker 1: So those are phosphorescent glow in the dark toys. But
25:39
Speaker 1: there are other ways in which physics can make you
25:41
Speaker 1: glow in the dark, right, And some of them are
25:43
Speaker 1: kind of intense, that's right. If you have like an
25:45
Speaker 1: old fashioned glow in the dark, watch it might have
25:49
Speaker 1: hands that glow in the dark all the time without
25:52
Speaker 1: needing to be charged by sunlight. And that's particular and
25:55
Speaker 1: kind of scary process because that's actually radioactive decay, you know.
25:59
Speaker 1: That's something Some elements are not stable, like uranium. For example.
26:04
Speaker 1: Uranium hangs out, but it doesn't hang out for the
26:06
Speaker 1: whole life of the universe. Eventually it falls apart, and
26:09
Speaker 1: it falls apart and gives off some energy. And in
26:12
Speaker 1: some cases when these things decay, they emit very high
26:15
Speaker 1: energy photons like cobalt sixty or nickel sixty. These are
26:20
Speaker 1: unstable isotopes and when they decay they give off gamma
26:24
Speaker 1: raise whoa. And they used to put this in like
26:26
Speaker 1: regular watches for people. Yeah, regular watches for people. And
26:30
Speaker 1: so you know, they wouldn't put like cobalt or nickel,
26:32
Speaker 1: but they would use things like radium, which is pretty prevalent,
26:35
Speaker 1: and a little bit of radium would give off essentially radiation,
26:39
Speaker 1: and you know, gamma rays you can't see with your eyes.
26:42
Speaker 1: These are photons, but they're very very high energy, which
26:45
Speaker 1: means they're small wavelengths, so you can't see them. So
26:47
Speaker 1: they would mix this with something else which can absorb
26:50
Speaker 1: gamma raise and then emits at a different frequency, So
26:53
Speaker 1: it's called wavelength shifting, like absorbs photon avoiding frequency, and
26:58
Speaker 1: then it gives off photons of a ower frequency, which
27:01
Speaker 1: you can see. It's like little physics batteries, right. You know,
27:04
Speaker 1: you have energy stored in this radium and it's slowly
27:06
Speaker 1: leaking out and gets transformed into visible light that your
27:09
Speaker 1: eyeballs can see. WHOA, but aren't these watches dangerous? Like
27:13
Speaker 1: doesn't the rada activity give you some sort of mutation
27:16
Speaker 1: in your genes and stuff like that? Yeah? Absolutely, And
27:19
Speaker 1: that's why they're not doing it so much anymore. You know,
27:21
Speaker 1: these things I've been phased out. But radium used to
27:24
Speaker 1: be treated a lot more casually. You know, the experiments
27:26
Speaker 1: that Marie Curie did decades and decades ago, and she
27:30
Speaker 1: worked in her lab for a long time, and now
27:32
Speaker 1: her lab is so radioactive that you can't even go
27:34
Speaker 1: inside it. So we're taking radiation much more seriously than
27:37
Speaker 1: people used to. And so yeah, now we don't just
27:39
Speaker 1: like casually paint things with radioactive paint because it's basically
27:43
Speaker 1: cancer paint, well, or cancer at least in other ways.
27:48
Speaker 1: There are still pretty dangerous chemicals and some paints. But
27:51
Speaker 1: I guess the question is, like is all radiation dangerous? Like,
27:54
Speaker 1: if it's just radiating photons, that's probably okay, right, It's
27:57
Speaker 1: like when they radiate other heavier particles that that's the problem.
28:01
Speaker 1: That's the part that gives you cancer. Right, Well, it
28:04
Speaker 1: depends on whether or not it has enough energy to
28:06
Speaker 1: penetrate your skin. Are various kinds of radiation. You can
28:09
Speaker 1: radiate electrons, or you can really like a helium nucleus,
28:12
Speaker 1: or you can radiate a photon. You might think how
28:15
Speaker 1: dangerous could a photon B? But if a photon is
28:18
Speaker 1: a gamma ray, which means it has a lot of energy,
28:20
Speaker 1: then you can really penetrate your body, just like X rays.
28:23
Speaker 1: X rays are also photons, but we're very careful with
28:26
Speaker 1: X rays because we know that they cause mutations and
28:29
Speaker 1: too many X rays will give you cancer, and so
28:32
Speaker 1: you wouldn't want like something on your wrist which emits
28:35
Speaker 1: X rays all the time. Gamma rays are in the
28:37
Speaker 1: same category. They're ionizing radiation that can penetrate your body
28:40
Speaker 1: and they can do damage right or like UV rays
28:42
Speaker 1: right from the sun. That's why you need sun block. You.
28:46
Speaker 1: V are a little bit lower energy than gamma rays,
28:48
Speaker 1: but still dangerous, all right. So that's another way to
28:50
Speaker 1: have something glow in the dark is they get radioactive
28:53
Speaker 1: and have that radio activity kind of work it so
28:55
Speaker 1: that it somehow emits visible light photons. Yeah, and there's
28:58
Speaker 1: lots of different ways you can take advantage of radioactivity.
29:00
Speaker 1: Remember that some of our awesome like robotic explorers around
29:04
Speaker 1: the Solar System take advantage of the same property. They
29:06
Speaker 1: have a chunk of radioactive material which is slowly decaying
29:09
Speaker 1: and giving off energy in terms of photons or other radiation,
29:13
Speaker 1: which is then captured and turned into electricity empowers those
29:16
Speaker 1: rovers and those satellites. So it's also kind of awesome.
29:19
Speaker 1: It's just not something you should have close to people, right,
29:21
Speaker 1: And those that don't glow in the dark, right, like
29:23
Speaker 1: they're in case in all this sort of material inside
29:26
Speaker 1: of the battery, that's right. I don't think that those
29:28
Speaker 1: things glow in the dark. That would be pretty cool
29:30
Speaker 1: to glow in the dark, Mars Rover. I think it
29:32
Speaker 1: has the flashlights, so it can't technically glow in the dark.
29:36
Speaker 1: All right, Well, what's another way in which physics can
29:39
Speaker 1: make things glow in the dark. As we were saying earlier,
29:41
Speaker 1: almost everything in the universe does already actually glow, It
29:46
Speaker 1: just might not be hot enough to glow in the
29:49
Speaker 1: visible light spectrum. This is something in physics we call
29:51
Speaker 1: black body radiation. By black body, we just mean something
29:55
Speaker 1: that doesn't reflect any light, which absorbs all of the
29:58
Speaker 1: energy of the light that hits it, and then amidst
30:00
Speaker 1: light based on its temperature. And you're saying, everything in
30:04
Speaker 1: the universe does this, right, Everything in the universe does
30:06
Speaker 1: this exactly, And it depends on your temperature. The hotter
30:09
Speaker 1: you are, the higher the frequency of the photons you emit.
30:13
Speaker 1: The colder you are, the lower the frequency of the
30:16
Speaker 1: photons you emit, and that's why, for example, the Earth glows,
30:19
Speaker 1: but it doesn't glow in the visible spectrum like the
30:21
Speaker 1: Sun does. The Sun very very hot on its surface
30:26
Speaker 1: and it glows in the visible light. The Earth also glows,
30:30
Speaker 1: but only in the infrareds. You need like special cameras
30:33
Speaker 1: to see the Earth's glow. And I glow like That's
30:36
Speaker 1: why you can see me in ninth vision, and I
30:38
Speaker 1: look different from things around me because I'm hotter and
30:41
Speaker 1: the spectrum that I emit has a higher frequency than
30:45
Speaker 1: like the table next to me or the ground beneath me. Mmmm.
30:48
Speaker 1: Just seeing like so like to an alien who could
30:50
Speaker 1: see in the infrared, Earth would look like a star
30:53
Speaker 1: kind of them one, but it would still glow in
30:55
Speaker 1: the sky exactly. And that's why we build the James
30:58
Speaker 1: web Space Telescope, which is gonna low very soon and
31:01
Speaker 1: can see in the infrared, because we want to see
31:03
Speaker 1: those planets. We don't just want to study things in
31:06
Speaker 1: the universe that glow in the visible. We want to
31:08
Speaker 1: see things that glow in infra red. So that's an
31:10
Speaker 1: awesome telescope that's kept very very very cold, so it
31:13
Speaker 1: can be sensitive to these very low energy photons coming
31:17
Speaker 1: from for example, exo planets, so we can see how
31:20
Speaker 1: hot those agians are, whether they're hot or not. That's right.
31:23
Speaker 1: And you know you know this already because you know
31:25
Speaker 1: that things glow different colors as they get hotter. Like
31:28
Speaker 1: you have a chunk of metal, it can get red
31:30
Speaker 1: hot and then it can get white hot. Right, so
31:33
Speaker 1: we have a very intuitive sense for how things glow
31:35
Speaker 1: differently as they get hot. And it just turns out
31:38
Speaker 1: that that continues. You know, something that's super duper hot,
31:41
Speaker 1: it starts to glow in the UV or starts to
31:43
Speaker 1: give off X rays. You know why does the gas
31:46
Speaker 1: around a black hole give off X rays because it's
31:49
Speaker 1: super duper crazy hot. Well, I guess the question is
31:52
Speaker 1: what's that mechanism? Like why is temperature related to the
31:55
Speaker 1: freuencular light that's emitted by something? Or I guess even
31:58
Speaker 1: a step further back, like why do things that are
32:01
Speaker 1: hot glow at all? Yeah, it's a great question. It's
32:04
Speaker 1: just basically entropy. You have a bunch of energy in
32:06
Speaker 1: a small space and you have stuff nearby that doesn't
32:09
Speaker 1: have as much energy, then that energy is going to transfer.
32:12
Speaker 1: And one way for that to happen is for things
32:15
Speaker 1: to emit photons. So basically, everything that has charged particles
32:18
Speaker 1: inside of it, electrons or atoms or whatever, is constantly
32:22
Speaker 1: just giving off photons. And so if you have something
32:24
Speaker 1: nearby that isn't as hot, then it's going to be
32:27
Speaker 1: accepting those photons. So basically, you know, electrons as they
32:31
Speaker 1: move around are constantly just radiating away photons just because
32:36
Speaker 1: their decaying, like decays is it's sort of like a
32:38
Speaker 1: decaying process, like the electrons just suddenly like, hey, I
32:42
Speaker 1: give up, I'm done with this universe. I'll just chill
32:44
Speaker 1: out in a mid of photon sort of. It's sort
32:46
Speaker 1: of like, you know, like a bath. You know, electrons
32:49
Speaker 1: aren't just like flying around holding onto their energy. They're
32:52
Speaker 1: constantly like transferring it back and forth to each other
32:54
Speaker 1: and between themselves and the atoms nearby. And if you're
32:57
Speaker 1: at an edge of an object, then some of those photons,
33:00
Speaker 1: instead of getting like absorbed by another atom or absorbed
33:03
Speaker 1: by another electron, just fly out into the universe with
33:06
Speaker 1: the electron at the photon the photon. It's sort of
33:08
Speaker 1: like if you're you know, if there's a party, everybody's
33:10
Speaker 1: talking to each other everybody's sort of in the middle
33:12
Speaker 1: of this soup of conversation. If you're in the outside
33:15
Speaker 1: of the party, you're gonna hear some of that conversation
33:16
Speaker 1: because some of those voices are pointed in your direction Accidentally,
33:20
Speaker 1: it's not going to be as intense as if you're
33:21
Speaker 1: actually inside of it. But always leaks out. Energy, always
33:25
Speaker 1: spreads out through the universe, and this is just, you know,
33:27
Speaker 1: another way for that to happen. But yeah, I guess
33:29
Speaker 1: if you're at like at the edge of that party,
33:31
Speaker 1: not that many people are talking to you, so you
33:32
Speaker 1: might be like, yeah, I'll just go home and watch
33:34
Speaker 1: some Netflix, and so you leave the party and so
33:37
Speaker 1: like eventually the whole party sort of evaporates, Right, that's
33:40
Speaker 1: the idea. Everybody just goes home and eat their Halloween
33:42
Speaker 1: candy and silence eventually. Yeah, So that's kind of what's
33:45
Speaker 1: what's happening in your body right now, which is like,
33:47
Speaker 1: you know, some of the atoms and electrons at the surface,
33:50
Speaker 1: they're just like, you know, spontaneously giving off photons. Yeah,
33:54
Speaker 1: it's a spontaneous process of just like the radiative distribution
33:58
Speaker 1: of entropy. Why does hotter body correspond to a higher
34:02
Speaker 1: frequency of the light, did you emit Because higher frequency
34:04
Speaker 1: is higher energy. So as the body gets hotter, right, is,
34:08
Speaker 1: there's more energy stored inside of it than it's possible
34:10
Speaker 1: for it to admit photons at higher energy. So it's
34:13
Speaker 1: actually a whole spectrum. It's not like there's a single
34:15
Speaker 1: wavelength emitted by a certain object based on its temperature.
34:18
Speaker 1: It's a whole spectrum. Something it's really hot emits at
34:21
Speaker 1: low frequencies and at high frequencies. Something that's cold only
34:25
Speaker 1: emits the lower frequencies because it doesn't hap enough photons
34:28
Speaker 1: inside of it to emit at the higher frequencies. Interesting.
34:31
Speaker 1: So this is where it gets a little bit confusing too,
34:33
Speaker 1: because sometimes what people call a star is really just
34:36
Speaker 1: like a hot bodying space. Yeah, exactly. The future of
34:39
Speaker 1: our star is to become something called a white dwarf.
34:43
Speaker 1: When all the fusion has finished and it's blown out
34:46
Speaker 1: a huge amount of its mass into space, the core
34:48
Speaker 1: of it will collapse into a very heavy blov of
34:51
Speaker 1: stuff that's not capable of fusing anymore, but it will
34:54
Speaker 1: still be super duper hot. And this is what we
34:57
Speaker 1: call a white dwarf. And you know, we call it
34:59
Speaker 1: a star, or some people call it a stellar remnant.
35:01
Speaker 1: It's gonna be really hot, and it's called a white
35:04
Speaker 1: dwarf because it's gonna glow white hot. You know, I
35:06
Speaker 1: think it's gonna be tens of thousands of degrees and
35:10
Speaker 1: so it's going to be glowing into the universe and
35:12
Speaker 1: looking like a star. But no fusion is happening inside
35:15
Speaker 1: of it. It's just because it's hot, right, It's just
35:18
Speaker 1: glowing because it's hot, the same way that like, you know,
35:20
Speaker 1: metal that you've taken out of a forge glows because
35:23
Speaker 1: it's hot, or a light bulb glows because it's hot. Right,
35:26
Speaker 1: And but technically there is some sort of reaction going on, right,
35:28
Speaker 1: things are breaking down, and so that's why it's emitting light. Well,
35:32
Speaker 1: it's just sort of this spontaneous redistribution of energy. You know,
35:35
Speaker 1: anything that's hot is going to glow and give off
35:37
Speaker 1: its energy and cool down essentially, And the future of
35:40
Speaker 1: these white dwarves is not that they're going to chemically change, right,
35:43
Speaker 1: they have a lump of iron. It's gonna stay iron,
35:46
Speaker 1: but they will cool down and in trillions of years
35:48
Speaker 1: eventually become black dwarves. Well, so ironically, it'll still have
35:53
Speaker 1: the same meaning. It will literally become a black body eventually.
35:56
Speaker 1: All right, well, let's take it up a notch, Daniel,
35:58
Speaker 1: and let's talk about bigger and crazier things in the
36:01
Speaker 1: universe that glow in the dark, like black holes in
36:03
Speaker 1: dark matter. But first, let's take another quick break. All right,
36:19
Speaker 1: we're talking about things that glow in the dark, and ironically,
36:23
Speaker 1: in this universe, things that have the name black and
36:26
Speaker 1: dark also glow in the dark. That's right, it's weird
36:29
Speaker 1: to think about black body is something that glows in
36:31
Speaker 1: the dark, like the Sun is an almost perfect black body. Right.
36:35
Speaker 1: It's just another example of physics using words that we
36:38
Speaker 1: find familiar in ways that make no sense. What I mean,
36:41
Speaker 1: the sun is a black body. The sun is a
36:42
Speaker 1: black body. What they mean by that is that the
36:45
Speaker 1: Sun absorbs almost any light that hits it. It doesn't
36:47
Speaker 1: reflect any light. Black body just means no reflection. You
36:51
Speaker 1: can absorb light, and you can admit light because you're hot,
36:54
Speaker 1: but there's no reflection. So when you say we model
36:57
Speaker 1: this as a black body, we just mean that there's
36:59
Speaker 1: no selection and the Sun absorbs almost any light that
37:02
Speaker 1: hits it. The Sun is not a good mirror. Yeah,
37:04
Speaker 1: I guess any light that hits it just goes into
37:07
Speaker 1: that crazy plasma that is inside of it, right, Yeah,
37:10
Speaker 1: and heats it up and then it will emit again.
37:12
Speaker 1: But it's not a reflection. All right. Well, I think
37:14
Speaker 1: you're telling me earlier that black holes also glow in
37:17
Speaker 1: the dark. Black holes do glow, which is super awesome,
37:20
Speaker 1: And people might be familiar with this because the whole
37:22
Speaker 1: idea of Hawking radiation. But I think it's interesting to
37:25
Speaker 1: understand the origin of this idea, Like how did Hawking
37:28
Speaker 1: come up with the concept that black holes might give
37:31
Speaker 1: off radiation? And it came from thinking about the temperature
37:34
Speaker 1: of things and how things glow, this connection between how
37:38
Speaker 1: things that have temperature seemed to glow. So he and
37:41
Speaker 1: his student, whose named Bekenstein, we're thinking about this, like
37:45
Speaker 1: what is the thermodynamics of black holes? And so Hawkings
37:49
Speaker 1: contributions to physics and the black holes is much more
37:52
Speaker 1: than just like realizing that there might be some radiation
37:55
Speaker 1: leaking at the side, is from thinking about black holes
37:58
Speaker 1: in terms of thermodynamic quantities, like what is its temperature
38:02
Speaker 1: and what is its entropy? And very quickly they realize
38:06
Speaker 1: that black holes have to have some entropy because entropy
38:09
Speaker 1: is conservad entry always increases in the universe, and when
38:12
Speaker 1: something falls into a black hole, you can't just like
38:15
Speaker 1: delete its entropy, which means the black holes have to
38:18
Speaker 1: hold some entropy. And if they have an entropy, then
38:21
Speaker 1: they have to have temperature. You're using entropy sort of
38:23
Speaker 1: as a standing for like heat and energy. Well, they're
38:26
Speaker 1: definitely connected, right. Remember, entropy is like a measure of
38:30
Speaker 1: the disorder of a system sort of. It's like the
38:33
Speaker 1: number of ways you can rearrange the microscopic state of
38:36
Speaker 1: an object to be consistent with its macroscopic state. And
38:40
Speaker 1: so something that has a lot of temperature is going
38:42
Speaker 1: to have a lot of entropy because it'll be a
38:44
Speaker 1: lot of different ways you can rearrange it. And so
38:46
Speaker 1: if you have something and falls into a black hole,
38:49
Speaker 1: it carries with it some entropy. It's sort of like
38:52
Speaker 1: thinking about information, right, you know, where's the information for
38:55
Speaker 1: something that falls into a black hole? Goes into the
38:57
Speaker 1: black hole. So black holes have to have in formation,
39:00
Speaker 1: and the folks that work on the black hole information paradox,
39:03
Speaker 1: this question about what happens to information that falls inside
39:06
Speaker 1: the black hole. They tend to think about it in
39:08
Speaker 1: terms of entropy. Also basically talking said that, you know,
39:11
Speaker 1: black holes are not just like a spot of nothing.
39:13
Speaker 1: They have something to them, They have something to them,
39:16
Speaker 1: they have some entropy, They have to have some temperature,
39:19
Speaker 1: and if they have some temperature, they have to glow.
39:21
Speaker 1: Because everything in the universe that interacts electromagnetically, right, everything
39:26
Speaker 1: in the universe that has some energy localized into it
39:29
Speaker 1: tends to give off some of that tends to radiate
39:31
Speaker 1: that a way, just like a white dwarf, or just
39:34
Speaker 1: like the sun, or just like that piece of metal
39:37
Speaker 1: you stuck in a forge, or just like the Earth,
39:39
Speaker 1: everything should glow. And so to sort of makes sense
39:42
Speaker 1: of this, mathematically invented this whole field of black hole thermodynamics,
39:46
Speaker 1: and out of it came this concept of Hawking radiation,
39:49
Speaker 1: that even black holes give off radiation because they have
39:51
Speaker 1: a non zero temperature. Right. But I guess the problem
39:55
Speaker 1: is that, you know, black holes are supposed to be
39:57
Speaker 1: things out of which nothing can come out. So even
39:59
Speaker 1: if has you know, information or entroprety or energy inside
40:03
Speaker 1: of it, how does that energy get out If nothing
40:06
Speaker 1: can come out of a black hole? Right, and classically
40:09
Speaker 1: according to general relativity, which is a classical theory, meaning
40:12
Speaker 1: that ignores quantum mechanics. You're right, and classical black holes
40:16
Speaker 1: do not emit anything. They're just one way doors of
40:19
Speaker 1: information and objects. And so the way we usually talk
40:22
Speaker 1: about black holes on this podcast is in the realm
40:25
Speaker 1: of general relativity, because it's the only idea we have
40:28
Speaker 1: to describe black holes. But we know that general relativity
40:32
Speaker 1: isn't right because general relativity is not consistent with quantum mechanics,
40:36
Speaker 1: which are pretty sure is the law of the universe.
40:38
Speaker 1: And so what Hawking tried to do was like take
40:40
Speaker 1: first steps towards a theory of quantum gravity, a quantum
40:44
Speaker 1: mechanically consistent description of black holes. He wasn't able to
40:48
Speaker 1: do that. We don't have a theory of quantum gravity.
40:50
Speaker 1: What he did was sort of take general relativity and
40:52
Speaker 1: try to tweak a little bit to make it a
40:53
Speaker 1: little bit quantum mechanical. It's like semi classical now, and
40:57
Speaker 1: so he's got sort of like a patched up version
41:00
Speaker 1: of a theory of black holes that's not like general relativity,
41:05
Speaker 1: but also not fully consistent with quantum mechanics. He still
41:08
Speaker 1: has holes in his theory, that's what you're saying about
41:10
Speaker 1: black holes. Yeah, and that's why, for example, we don't
41:13
Speaker 1: have a good microscopic understanding of Hawking radiation. People talk about,
41:17
Speaker 1: you know, virtual particles being produced at the edge of
41:20
Speaker 1: a black hole, and there's some hand wavy stories which
41:23
Speaker 1: we've given sometimes on this podcast, But the truth is
41:25
Speaker 1: none of those are correct. They're sort of like hand
41:28
Speaker 1: wavy stories that give you a sense for what might
41:30
Speaker 1: be happening, but we don't have a good microscopic understanding
41:33
Speaker 1: of what's going on because we don't understand the gravity
41:36
Speaker 1: of quantum particles. So Hawking has sort of like a
41:39
Speaker 1: statistical argument for why black holes should emit radiation, which
41:43
Speaker 1: comes from them having temperature and therefore needing to radiate,
41:46
Speaker 1: but it doesn't have like a good quantum description of
41:49
Speaker 1: what's actually happened to these particles near the edge of
41:51
Speaker 1: the black hole. We don't have that because we don't
41:53
Speaker 1: have a theory of quantum gravity. He has sort of
41:55
Speaker 1: like a band aid on top of general relativity that
41:58
Speaker 1: lets him do a few character lations. But you know,
42:01
Speaker 1: later people are going to realize that it's like an
42:03
Speaker 1: approximation of the true theory. So he predicts that black
42:06
Speaker 1: holes will glow in the dark, but we don't know
42:09
Speaker 1: how they would fill in the dark. But have we
42:11
Speaker 1: actually seen a black hole glow in the dark or
42:13
Speaker 1: is this all still a prediction. We have not. Nobody's
42:16
Speaker 1: ever observed hawking radiation. Remember, it would be really really faint.
42:20
Speaker 1: Hawking radiation happens more dramatically for smaller black holes, so
42:24
Speaker 1: for large black holes, like the few that we have seen,
42:27
Speaker 1: it would be really really faint, and large black holes
42:30
Speaker 1: tend to be surrounded by other things that glow very brightly,
42:33
Speaker 1: like accretion disks a very very hot gas, so it
42:36
Speaker 1: would be very difficult to observe hawking radiation. The best
42:39
Speaker 1: way to do it would be to create a tiny
42:41
Speaker 1: black hole, like a really small one that we could
42:44
Speaker 1: study here in the laboratory before gob will up the earth,
42:47
Speaker 1: because it would evaporate rather quickly and it would give
42:50
Speaker 1: off a lot of Hawking radiation. So no, we have
42:52
Speaker 1: never seen hawking radiation. So it's still just a theory,
42:55
Speaker 1: but it's very convincing and it lets people do lots
42:57
Speaker 1: of other calculations about black hole holes, and so the
43:00
Speaker 1: whole theory built on top of it, all right. So
43:02
Speaker 1: that's one way in which black holes can technically glow
43:05
Speaker 1: in the dark. But they also sort of glow because
43:07
Speaker 1: they have all this gas around them, right that it's
43:09
Speaker 1: a lot of radiation, that's right, Yeah, And so that's
43:11
Speaker 1: sort of like the black hole system. The black hole itself,
43:14
Speaker 1: of course doesn't glow, but the stuff around it that's
43:16
Speaker 1: getting like squeezed by all the energy from the black
43:19
Speaker 1: hole does glow, all right. And so the other big
43:22
Speaker 1: universe thing that glows is dark matter. Dark matter itself
43:26
Speaker 1: also glows. You're saying, we don't know if dark matter glows.
43:29
Speaker 1: It's really a fascinating question because we say that everything
43:32
Speaker 1: in the universe that has the temperature glows, right, But
43:36
Speaker 1: the caveat there is that it has to have some
43:38
Speaker 1: sort of electromagnetic interaction. Like why do things glow, as
43:42
Speaker 1: we were saying before, because the electrons inside them are
43:44
Speaker 1: whizzing around and giving off photons. But if you're made
43:46
Speaker 1: of things that don't interact with photons, like dark matter,
43:49
Speaker 1: then you can't give off photons. So it might be
43:52
Speaker 1: the dark matter has a temperature, like we know it
43:55
Speaker 1: has a temperature, it moves it has a speed. But
43:58
Speaker 1: it might be that it doesn't glow. It could the
44:00
Speaker 1: only thing in the universe that has a temperature but
44:03
Speaker 1: doesn't glowing, right, because it doesn't know how to talk
44:07
Speaker 1: to the electromagnetic radiation. It doesn't interact with it or
44:10
Speaker 1: know how to talk in that language or give it off,
44:13
Speaker 1: and so it has all this energy, and so how
44:15
Speaker 1: can it be glowing in a sort of energy sense.
44:18
Speaker 1: It depends on how dark matter interacts. We know that
44:20
Speaker 1: dark matter feels gravity, can talk to things via gravity.
44:24
Speaker 1: It might be that it has some other force, like
44:25
Speaker 1: there's some weird new dark electromagnetic force we had never
44:29
Speaker 1: heard before, and maybe it can glow using dark photons, right,
44:32
Speaker 1: But that's all speculations, so put that aside for now.
44:35
Speaker 1: We do know that it feels gravity, and so it
44:38
Speaker 1: might be that dark matter can glow gravitationally. Right. For example,
44:42
Speaker 1: black holes that interact with each other and combine, they
44:45
Speaker 1: give off gravitational radiation that's gravitational waves, and so dark
44:50
Speaker 1: matter might be able to give off like very faint
44:53
Speaker 1: gravitational waves as it's just sort of sitting around, slashing
44:56
Speaker 1: around the universe. That's sort of like a faint glow,
44:59
Speaker 1: not info tons in terms of other kinds of radiation. Right,
45:02
Speaker 1: and interesting because I think we can detect gravitational waves,
45:06
Speaker 1: but only from like these incredible events like two black
45:09
Speaker 1: holes colliding, because that's how faint gravitational waves are. Are
45:13
Speaker 1: you saying that dark matter might be giving off also
45:15
Speaker 1: gravitational waves, but they would be so small and indetectable
45:19
Speaker 1: that we would maybe never see them. You and I
45:22
Speaker 1: are giving off gravitational waves. Anybody in the universe that
45:25
Speaker 1: has mass and accelerates gives off gravitational waves. But as
45:29
Speaker 1: you say, because gravity is so weak, that's undetectable. You
45:31
Speaker 1: have to be an incredible mass undergoing incredible acceleration to
45:36
Speaker 1: feel those gravitational waves. Wait, you and I are are
45:38
Speaker 1: glowing in the gravitationals feel but only if we move
45:42
Speaker 1: though if we stay still, we don't, Or do we
45:44
Speaker 1: Or are you saying our atoms are emitting gravitational waves
45:47
Speaker 1: all of those Yet if we accelerate in any way,
45:50
Speaker 1: then we are giving off gravitational waves. So as we
45:52
Speaker 1: move around the Sun, that's circular motion, that's acceleration. As
45:55
Speaker 1: the Sun moves around the center of the galaxy, it's
45:58
Speaker 1: glowing gravitationally. But these things are very faint, and even
46:01
Speaker 1: the atoms in our body which do that, which accelerated
46:04
Speaker 1: in any way, they give out gravitational radiation. We have
46:07
Speaker 1: a podcast episode you might remember about the cosmic gravitational background.
46:11
Speaker 1: That's like the sum of all these little gravitational waves
46:14
Speaker 1: that you can't really discern because they're all so dim.
46:17
Speaker 1: They just add up to like a general hum. But
46:19
Speaker 1: I guess what you're saying is, like, you know, the
46:21
Speaker 1: fact that we have a temperature means that our molecules
46:24
Speaker 1: are vibrating. In that vibration, they are emitting gravitational waves. Yes, absolutely,
46:29
Speaker 1: they are very very faint, probably never detectable, but technically, yes, whoa,
46:34
Speaker 1: that's pretty cool. So we're all hot and glowy in
46:38
Speaker 1: some sense exactly, and so even dark matter, which we
46:41
Speaker 1: can see with photons, might be glowing gravitationally. And this
46:44
Speaker 1: also gets into quantum mechanics, right, there's something called the
46:47
Speaker 1: ultra violet catastrophe. Yes, the ultra violet catastrophe was one
46:51
Speaker 1: of the first clues that told us about quantum mechanics.
46:55
Speaker 1: When we people first calculated how black bodies might radiate
46:58
Speaker 1: like at what equency should an object radiate given its temperature.
47:03
Speaker 1: They did some basic calculations using electromagneticism, and they got
47:07
Speaker 1: these crazy predictions. You know. They predicted, for example, that
47:10
Speaker 1: an object at a thousand degrees kelvin should emit an
47:13
Speaker 1: infinite amount of energy because there's an infinite number of
47:16
Speaker 1: ways for a photon to glow. There's an infinite number
47:19
Speaker 1: of like different wavelengths of photon could have. They fought,
47:22
Speaker 1: and so they got all these crazy numbers, which obviously
47:25
Speaker 1: didn't agree with their experiments. You know, you put something
47:27
Speaker 1: in the toaster, it doesn't like explode with infinite energy, right,
47:32
Speaker 1: the Sun is not exploding with infinite energy. It depends
47:35
Speaker 1: on what you put into that the toaster oven. Put
47:38
Speaker 1: in too much Halloween candy and pop rocks, it might
47:40
Speaker 1: explode with energy. Yeah, some mento, some coke, who knows.
47:43
Speaker 1: But this was known as the ultra violet catastrophe like
47:46
Speaker 1: a twenty years ago because people didn't understand why this
47:49
Speaker 1: wasn't happening. The calculations suggested it should. Obviously it wasn't,
47:52
Speaker 1: And it wasn't until a young physicist named Max Plunk
47:56
Speaker 1: realized that if you made this weird assumption that photons
48:00
Speaker 1: couldn't have just any arbitrary energy, but that they came
48:03
Speaker 1: in steps, that they were like quantized units of energy.
48:06
Speaker 1: Then that killed the problem because it meant that there
48:08
Speaker 1: weren't an infinite number of modes for photons to have.
48:11
Speaker 1: They're just a finite ladder. And the way the math
48:13
Speaker 1: worked out, that meant that it solved the problem and
48:15
Speaker 1: it predicted perfectly the experiments, and so Plank was like, oh, well,
48:19
Speaker 1: maybe things are quantized. Interesting. So actually quantum mechanics sort
48:23
Speaker 1: of limits how things glow in the dark, like things
48:26
Speaker 1: would glow in the dark more if it wasn't for
48:28
Speaker 1: quantum mechanics. Yes, exactly, quantum mechanics limits how things glow.
48:31
Speaker 1: And things glowing in the dark was one of our
48:33
Speaker 1: very first clues that the universe is quantum mechanical. And
48:36
Speaker 1: it was Einstein actually who recognized this. Plank just said like,
48:39
Speaker 1: I don't know what this means, but if you make
48:41
Speaker 1: this assumption, the math all works out, and Einstein is thinking,
48:45
Speaker 1: and he read about the photo electric effect. Check out
48:47
Speaker 1: a whole podcast about the discovery the photon. It was
48:50
Speaker 1: Einstein who put it all together and said, oh, maybe
48:52
Speaker 1: photons travel in chunks that they are quantized in units.
48:56
Speaker 1: I guess it's all that. This ties it all back.
48:58
Speaker 1: Things glow in the dark at the end of the day.
49:00
Speaker 1: It is a very fundamental and quantum mechanical process. Yeah,
49:04
Speaker 1: And asking questions about why things glow and why they
49:06
Speaker 1: don't glow and why they don't explode when you put
49:08
Speaker 1: them in toaster can sometimes reveal crazy secrets about the
49:12
Speaker 1: nature of the universe, like quantum mechanics, and so asking
49:15
Speaker 1: questions about like dark matter glowing and black holes glowing
49:18
Speaker 1: might help us in our struggles to understand the big
49:21
Speaker 1: questions of today's physics. What's the universe made out of?
49:24
Speaker 1: And what is the quantum mechanical description of space and time? Yeah,
49:27
Speaker 1: and so I guess it reminds you a little bit
49:29
Speaker 1: that the universe is kind of speaking to us all
49:32
Speaker 1: the time, even in the dark. You know, even in
49:34
Speaker 1: the dark. You know, animals and bacteria and and creatures glow,
49:38
Speaker 1: and you can mix chemicals to glow as well. And
49:42
Speaker 1: things that they're in space are glowing all the time.
49:44
Speaker 1: And even yourself within you are glowing, that's right, And
49:47
Speaker 1: all those stars out there in the universe that are
49:50
Speaker 1: sending you photons, They're telling you about themselves. They're telling
49:52
Speaker 1: you stories about what they are burning and what they
49:55
Speaker 1: are made out of. The University is like screaming information
49:58
Speaker 1: at us. And to me, the frustrating thing is that
50:00
Speaker 1: most of the time we aren't listening. Yeah, except they're saying,
50:03
Speaker 1: eat more candy, eat more candy. So maybe it's good
50:07
Speaker 1: that we don't listen to them all the time. I
50:10
Speaker 1: think you should give your kids an extra piece of
50:12
Speaker 1: candy for this podcast. Oh yeah, I'm sure they sneak
50:14
Speaker 1: some anyways. All right, Well, we hope you enjoyed that,
50:17
Speaker 1: and maybe this Halloween or in general, look at things
50:20
Speaker 1: in the dark a little bit differently because everything is
50:23
Speaker 1: glowing in the dark and trying to tell you answers
50:27
Speaker 1: to the secrets of the universe. Thanks for joining us,
50:30
Speaker 1: See you next time. Thanks for listening, and remember that
50:40
Speaker 1: Daniel and Jorge Explain the Universe is a production of
50:43
Speaker 1: I Heart Radio or more podcast for my Heart Radio,
50:46
Speaker 1: visit the I Heart Radio app, Apple Podcasts, or wherever
50:50
Speaker 1: you listen to your favorite shows.