Latest / Daniel and Kelly’s Extraordinary Universe / What color is the Sun?

Transcript

What color is the Sun? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Katie, I have a funny question. What color are
• 0:12
  Speaker 1: your eyes?
• 0:13
  Speaker 2: Daniel? How do you not know this?
• 0:15
  Speaker 1: How would I possibly know? We've never actually met in person.
• 0:19
  Speaker 1: I don't even know that you actually have eyes.
• 0:22
  Speaker 2: Well, I could tell you any color and you would.
• 0:24
  Speaker 1: Believe me, Right, I suppose I mean any color within reason.
• 0:28
  Speaker 2: Well, my husband says that they're like two sunsets on Mars.
• 0:34
  Speaker 1: All right, Now, I'm not very sure I should believe
• 0:37
  Speaker 1: you or your husband.
• 0:38
  Speaker 2: Well, my parents say that they are infinite pools of starlight.
• 0:44
  Speaker 1: All right, And when you look in the mirror, what
• 0:46
  Speaker 1: do you see staring back at you?
• 0:48
  Speaker 2: Really good podcasting eyes.
• 0:53
  Speaker 1: And we'll just leave you all with that mystery. Hi,
• 1:11
  Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
• 1:14
  Speaker 1: uc Erine, and I have brown eyes, but both of
• 1:17
  Speaker 1: my kids have blue or green eyes.
• 1:19
  Speaker 2: My name is Katie Golden. I host an evolutionary biology
• 1:23
  Speaker 2: podcast called Creature Feature, and I have lots of eyes
• 1:28
  Speaker 2: of many different colors. One could say their compact eyes.
• 1:34
  Speaker 1: The eyes have it It sounds like, Well, I have
• 1:38
  Speaker 1: a evolutionary biologist question for you, which is that my
• 1:41
  Speaker 1: wife is Scandinavian. She has blonde hair and blue eyes,
• 1:44
  Speaker 1: and I have dark hair and dark eyes, and both
• 1:47
  Speaker 1: of our kids have blonde hair and light eyes, and
• 1:50
  Speaker 1: I thought that dark colors were dominant. Is there a
• 1:54
  Speaker 1: nefarious explanation here or is there biology?
• 1:58
  Speaker 2: No? No, this is what's so and is Yes, dark
• 2:01
  Speaker 2: hair is dominant. But actually that makes it likely that
• 2:05
  Speaker 2: you can pass on recessive traits to your kids, especially
• 2:10
  Speaker 2: because your wife seems to have double recessives. So if
• 2:14
  Speaker 2: you have brown eyes, right, and brown eyes are a
• 2:18
  Speaker 2: dominant trait, so you could have just one dominant allele
• 2:23
  Speaker 2: of brown eyes. So you can absolutely, as a brown eye,
• 2:27
  Speaker 2: brown haired person, have a child who has blue eyes,
• 2:30
  Speaker 2: blonde hair, red hair, whatever.
• 2:32
  Speaker 1: So you're saying, I must have some blue eyes and
• 2:34
  Speaker 1: blonde hair jeens, they just don't show up in me.
• 2:37
  Speaker 2: Yeah, exactly. I think a lot of marriages would be
• 2:40
  Speaker 2: saved if people understood genetics.
• 2:44
  Speaker 1: Well, not for this reason, but we did do DNA
• 2:46
  Speaker 1: testing for our kids, and so welcome to the podcast
• 2:49
  Speaker 1: Daniel and Jorge Explain the Universe, a production of via
• 2:53
  Speaker 1: Heart Radio in which we talk about all of the
• 2:55
  Speaker 1: mysteries in the universe, not just Daniel's kids.
• 2:58
  Speaker 2: DNA We're not going.
• 3:04
  Speaker 1: To do any live DNA testing on the show. Today.
• 3:06
  Speaker 1: We speculate and wonder about everything in the universe. We
• 3:10
  Speaker 1: scratch our heads and wonder how things work, why things
• 3:13
  Speaker 1: look the way they do, and how the whole universe
• 3:16
  Speaker 1: came to be. From the tiniest quantum particles to those
• 3:19
  Speaker 1: colors in your eyeballs, to the very size and age
• 3:23
  Speaker 1: of the universe. We think all of these questions are fascinating.
• 3:27
  Speaker 1: My usual co host and friend, Jorge, can't be here today,
• 3:30
  Speaker 1: but we're very happy to have the spectacularly eyeballed Katie
• 3:34
  Speaker 1: along for our ride today.
• 3:35
  Speaker 2: And maybe Jorge's eyeballs are along for the ride. I
• 3:39
  Speaker 2: didn't steal them.
• 3:41
  Speaker 1: I don't have his eyeballs in like a glass jar
• 3:43
  Speaker 1: over here.
• 3:45
  Speaker 2: It's so he can see what's going on when he
• 3:47
  Speaker 2: can't be here for the recording.
• 3:50
  Speaker 1: One of my favorite things about asking questions about the
• 3:53
  Speaker 1: universe is that it's so easy to quickly get into
• 3:57
  Speaker 1: deep territory. You know, even if you are not an
• 3:59
  Speaker 1: academic physicist. You wonder about the nature of the universe,
• 4:03
  Speaker 1: how things work, and that comes just from looking at
• 4:06
  Speaker 1: the world around you and wondering why is it this
• 4:09
  Speaker 1: way and not some other way. Why do my kids
• 4:11
  Speaker 1: have this color eyeballs? Why is water transparent? Why is
• 4:15
  Speaker 1: the sky blue? Really basic questions of the very nature
• 4:18
  Speaker 1: of our environment can lead often to fascinating science puzzles
• 4:23
  Speaker 1: that help you understand the way the world works.
• 4:26
  Speaker 2: I love all kinds of science, and I think that
• 4:30
  Speaker 2: it is interesting because you can go from a relatively
• 4:34
  Speaker 2: simple question something that doesn't seem that deep on the surface.
• 4:38
  Speaker 2: In fact, the simpler the question, usually the more complex
• 4:42
  Speaker 2: the answer, the deeper you have to go. Many other
• 4:45
  Speaker 2: questions branch off from some of the more simple questions,
• 4:49
  Speaker 2: and I love how many rabbit holes you can go down.
• 4:52
  Speaker 1: Absolutely, And when I'm giving a public talk, like I
• 4:55
  Speaker 1: did in Aspen last week, my favorite questions are the
• 4:57
  Speaker 1: ones that start with, well, this is probably a really
• 5:00
  Speaker 1: easy question, but and then they ask a really deep,
• 5:04
  Speaker 1: very simple sounding question, but one that has huge ramifications
• 5:07
  Speaker 1: and requires you to understand all sorts of fascinating things.
• 5:11
  Speaker 1: And the thing to know about science is that it's
• 5:13
  Speaker 1: all just people being curious. The whole reason we're trying
• 5:17
  Speaker 1: to understand the cosmos is that the Sumerians and the
• 5:20
  Speaker 1: Mayans and the Chinese and the Greeks. We're looking up
• 5:22
  Speaker 1: at the sky and wondering like, hmm, why do the
• 5:25
  Speaker 1: planets sometimes go the other way? And why do things
• 5:27
  Speaker 1: rotate around the pole stars? And all these things come
• 5:30
  Speaker 1: from our very human, very ancient curiosity about the nature
• 5:34
  Speaker 1: of the world around us. It drives everything we do
• 5:37
  Speaker 1: in science, from people who study blind mole rats to
• 5:40
  Speaker 1: those people trying to understand why supernova explode.
• 5:43
  Speaker 2: I think one of the interesting kind of misconceptions people
• 5:47
  Speaker 2: have is that a basic question is one that's not
• 5:51
  Speaker 2: worth asking, or it's a dumb question, whereas like you
• 5:55
  Speaker 2: should be asking something like, oh, what is this specific
• 5:57
  Speaker 2: coefficient for this specific formula? But when you ask that
• 6:01
  Speaker 2: kind of question, the answer could be as simple as
• 6:03
  Speaker 2: like a decimal. So when you're asking a really basic question,
• 6:08
  Speaker 2: you may think it's basic, But the fact is, like
• 6:12
  Speaker 2: so many of the more complex science, the things that
• 6:16
  Speaker 2: Daniel studies and takes years and years to understand, are
• 6:20
  Speaker 2: things that have come from these really basic questions that
• 6:23
  Speaker 2: we may still not even really know the objective answer
• 6:26
  Speaker 2: to exactly.
• 6:27
  Speaker 1: And those questions come from within us. You know, they
• 6:30
  Speaker 1: are not objective questions. There's no way to like rank
• 6:33
  Speaker 1: what are the most important questions in the universe. They
• 6:36
  Speaker 1: just come from our burning desire to know, and everybody's
• 6:40
  Speaker 1: different that way. The questions that I ask are different
• 6:43
  Speaker 1: from the questions other people asking. Hey, that's cool. And
• 6:46
  Speaker 1: before we dig into the topic of today's podcast, I
• 6:49
  Speaker 1: think we need to do a little bit of house
• 6:50
  Speaker 1: cleaning from the last time you and I met, because
• 6:54
  Speaker 1: we were talking about the fantastic and amazing Greek ancient
• 6:57
  Speaker 1: astronomical computer, the anti kit Theram mechanism, and we got
• 7:00
  Speaker 1: into a little tangent and made some jokes about chemistry.
• 7:03
  Speaker 1: Maybe you remember Katie comparing chemistry to torture. I think.
• 7:09
  Speaker 2: I haven't slept a wink since that episode. I've been
• 7:11
  Speaker 2: filled with remorse. Chemistry is not torture. I was merely
• 7:16
  Speaker 2: joking at my sort of own expense in terms of
• 7:20
  Speaker 2: my limited ability to do chemistry or figure out chemistry equations,
• 7:25
  Speaker 2: because it takes a very specialized knowledge and it can
• 7:30
  Speaker 2: be quite complex. But I mean, without chemistry, my two
• 7:34
  Speaker 2: favorite sciences, astrophysics and evolutionary biology, would not exist exactly.
• 7:41
  Speaker 1: And I was commenting about how my son, who's in
• 7:44
  Speaker 1: tenth grade and taking tenth grade, chemistry was asking me
• 7:46
  Speaker 1: questions that I couldn't answer, and that was complaining. Chemistry
• 7:50
  Speaker 1: didn't seem like to me the funnest science man. We
• 7:52
  Speaker 1: got a bunch of feedback from chemistry loving folks about
• 7:55
  Speaker 1: our comments, and so I just want to address them
• 7:57
  Speaker 1: really quickly. You know. On one hand, I think it's
• 7:59
  Speaker 1: good that people understand that science is personal. The kind
• 8:02
  Speaker 1: of science that I do, which involves a lot of programming,
• 8:05
  Speaker 1: would bore a lot of other people. And there's lots
• 8:08
  Speaker 1: of science I think is valuable, but I could never
• 8:10
  Speaker 1: spend my days like pipetting or working at an optical table.
• 8:13
  Speaker 1: The point is that we all have different tastes, and
• 8:16
  Speaker 1: that works out because we don't want everyone to be
• 8:19
  Speaker 1: doing the same kind of science. But I do think
• 8:21
  Speaker 1: that we went too far and hurt joking, because while
• 8:24
  Speaker 1: it's good to have different preferences, we shouldn't be negative
• 8:26
  Speaker 1: about the science that gets other people excited. I'm very
• 8:30
  Speaker 1: glad that chemistry is a thing and that people love
• 8:32
  Speaker 1: it because it helps us all understand the world better.
• 8:35
  Speaker 1: So chemists and fans of chemistry with respect, my apologies,
• 8:39
  Speaker 1: and please keep chemistrying.
• 8:41
  Speaker 2: Yes, I think chemistry is amazing. For an example, I
• 8:46
  Speaker 2: one summer was helping out with some oceanographic research just
• 8:51
  Speaker 2: by calibrating this instrument that would look at diatoms, these
• 8:55
  Speaker 2: very very teeny tiny microscopic organisms, And so I spend
• 8:58
  Speaker 2: a lot of time on a microscope just counting diatoms.
• 9:02
  Speaker 2: And every time I would tell people about it, they're like, oh,
• 9:05
  Speaker 2: that sounds awful, And I actually really liked it because
• 9:08
  Speaker 2: it was, I don't know, it was fun to see
• 9:10
  Speaker 2: the little guys going and also really fun to try
• 9:13
  Speaker 2: to calibrate this machine to do the work that I
• 9:16
  Speaker 2: was doing counting these little microscopic organisms. And so for
• 9:21
  Speaker 2: one person's you know, kind of tedious activity is another
• 9:26
  Speaker 2: person's fascinating fun activities. So yes, I really do not
• 9:32
  Speaker 2: have any native attitudes towards chemistry. Perhaps one might even
• 9:36
  Speaker 2: say I'm jealous of people who understand chemistry better than
• 9:39
  Speaker 2: I do.
• 9:39
  Speaker 1: That's what it is. And if you're curious how people
• 9:42
  Speaker 1: ended up in their particular subfield, everybody's got a fascinating
• 9:45
  Speaker 1: story about what they tried, what they were excited about,
• 9:47
  Speaker 1: how they ended up having their passion stimulated. It's a
• 9:50
  Speaker 1: really fun podcast called The people behind the science, where
• 9:54
  Speaker 1: you can go and hear people tell their stories about
• 9:56
  Speaker 1: how they got to do the kind of science they're doing.
• 9:58
  Speaker 1: There's even one featuring me, if you're curious. But let's
• 10:01
  Speaker 1: move on and talk about the topic of the day,
• 10:04
  Speaker 1: because today we are talking about a really fun question,
• 10:06
  Speaker 1: one that sounds really simple but reveals a lot of
• 10:09
  Speaker 1: fascinating physics and might even teach you something about the
• 10:13
  Speaker 1: way we see the world.
• 10:15
  Speaker 2: I am so excited, Daniel hit me with it. What
• 10:18
  Speaker 2: are we exploring?
• 10:19
  Speaker 1: So today in the podcast, we are asking the very simple,
• 10:22
  Speaker 1: the very amazing, the very revealing question, what color is
• 10:31
  Speaker 1: the sun yellow?
• 10:32
  Speaker 2: Podcast over roll credits No, No, it can't be that easy.
• 10:38
  Speaker 1: It in fact isn't that easy. And in finding the answer,
• 10:40
  Speaker 1: we're going to learn a lot about what it means
• 10:42
  Speaker 1: to be color, where color comes from, why different things
• 10:45
  Speaker 1: emit different colors, and why we see things in different colors,
• 10:49
  Speaker 1: and how most of the popular descriptions about the color
• 10:52
  Speaker 1: of the sun aren't exactly quite right. But before we
• 10:55
  Speaker 1: do that, let's hear what our listeners had to say
• 10:57
  Speaker 1: about the color of the sun. I love hearing what
• 11:00
  Speaker 1: people out there are thinking about a topic. Before we
• 11:03
  Speaker 1: dig into it, and I have a cadre of volunteers
• 11:05
  Speaker 1: who answer our questions so that you can understand what
• 11:08
  Speaker 1: people out there are thinking. And if you would like
• 11:10
  Speaker 1: to participate for future episodes of the podcast, please everybody's
• 11:14
  Speaker 1: welcome right to me to questions at Danielandjorge dot com.
• 11:18
  Speaker 1: So before you hear these answers, think about it for
• 11:20
  Speaker 1: a moment yourself. What color do you think the sun is?
• 11:24
  Speaker 1: Here's what people had to say in space.
• 11:26
  Speaker 2: I think it's really really really bright yellow.
• 11:29
  Speaker 3: I think because of the fusion inside the sun. It
• 11:32
  Speaker 3: gives off all type of photons and the reason it
• 11:34
  Speaker 3: looks a little bit more yellow is maybe how much
• 11:36
  Speaker 3: fusion is going on inside.
• 11:38
  Speaker 4: My guess is that the Sun is emitting radiation on
• 11:43
  Speaker 4: every wavelength and also in the visible spectrum. But when
• 11:46
  Speaker 4: we look at the Sun, we are seeing it's light
• 11:49
  Speaker 4: filtered by the atmosphere, and I believe that the atmosphere
• 11:53
  Speaker 4: scatters the blue wavelengths, So when we look at the Sun,
• 11:56
  Speaker 4: we see it yellow because it's missing that blue wavelength.
• 12:00
  Speaker 3: Yes, maybe there's like a wavelength that it's uh, you know,
• 12:04
  Speaker 3: spin out more light of that wavelength. I feel like
• 12:07
  Speaker 3: it's got to be some sort of yellowish white, or
• 12:11
  Speaker 3: maybe it's like all the colors that'd be cool.
• 12:14
  Speaker 2: I'm surprised nobody said it's the color of ouch, because
• 12:18
  Speaker 2: when I look at the sun it hurts, and I
• 12:21
  Speaker 2: have heard that one is not supposed to do that.
• 12:24
  Speaker 1: Yes, we probably should have put a disclaimer like, please
• 12:27
  Speaker 1: do not pause the podcast and go out and stare
• 12:29
  Speaker 1: at the sun. Not a good idea.
• 12:31
  Speaker 2: No, the sun is very powerful, lots of energy coming
• 12:34
  Speaker 2: from it. It's why it feels so warm, and you
• 12:36
  Speaker 2: might not want to stare at it.
• 12:39
  Speaker 1: Well, most of these answers basically say that it's yellow,
• 12:41
  Speaker 1: and some even specifically comment about where you are looking
• 12:45
  Speaker 1: at it from. Somebody says in space, it's really right yellow,
• 12:48
  Speaker 1: And that's a really insightful comment, because things do look
• 12:52
  Speaker 1: different down here on the surface of the Earth than
• 12:54
  Speaker 1: they do in space.
• 12:55
  Speaker 2: So why is that. I know we've got this atmosphere
• 12:58
  Speaker 2: around us, but what exactly does the atmosphere do to
• 13:01
  Speaker 2: make things look different here versus space? Because I know,
• 13:04
  Speaker 2: like down here, you look at the sky and it
• 13:06
  Speaker 2: can be blue, it can be gray, it can be pink.
• 13:08
  Speaker 2: I mean at night, it can be black. But when
• 13:10
  Speaker 2: you're in space, usually the sky is sort of black.
• 13:14
  Speaker 2: I guess it's not even a sky at that point.
• 13:16
  Speaker 2: It's sort of a void and then stuff is scattered
• 13:18
  Speaker 2: in it.
• 13:19
  Speaker 1: Yeah, that's really fun. If you are standing on the Moon,
• 13:22
  Speaker 1: what color is the sky? The sky on the Moon
• 13:25
  Speaker 1: is black because there's no atmosphere. We did a podcast
• 13:28
  Speaker 1: episode actually about the atmosphere of the Moon, which is
• 13:30
  Speaker 1: really fun. But the reason the sky is blue here
• 13:32
  Speaker 1: on Earth is that not all wavelengths, not all frequencies,
• 13:36
  Speaker 1: not all colors of light move through the atmosphere equally,
• 13:40
  Speaker 1: blue light gets bounced around more, and so if you're
• 13:42
  Speaker 1: on the surface of the Earth, some of the light
• 13:44
  Speaker 1: that otherwise wouldn't have hit your eye gets bounced down
• 13:47
  Speaker 1: to your eye, and it's mostly the blue light that
• 13:50
  Speaker 1: gets bounced around and ends up at your eyeball. So
• 13:52
  Speaker 1: on the Earth during the day we see the sun,
• 13:54
  Speaker 1: of course, very brightly, and all around it we see
• 13:57
  Speaker 1: blue light from the Sun that's been scattered off off
• 14:00
  Speaker 1: the atmosphere to our eyeballs. Now, if you're on the
• 14:03
  Speaker 1: Moon during the daytime, you see a very bright sun
• 14:06
  Speaker 1: and you see a black sky. So even during the day.
• 14:09
  Speaker 1: The sky is black on the Moon because there's almost
• 14:12
  Speaker 1: no atmosphere there to scatter the light down to your eyeballs.
• 14:15
  Speaker 1: So that tells you that when you're on Earth, you're
• 14:17
  Speaker 1: not seeing all the frequencies of light from the sun
• 14:19
  Speaker 1: the same way because the atmosphere doesn't treat them all equally.
• 14:22
  Speaker 2: So why is blue so special? Why isn't our sky
• 14:26
  Speaker 2: always red or green?
• 14:28
  Speaker 1: Yeah, it depends on the composition of our atmosphere, And
• 14:31
  Speaker 1: in fact, on Mars, the sky is red most because
• 14:34
  Speaker 1: the dust in the atmosphere which reflects that red light.
• 14:37
  Speaker 1: So on Mars during the daytime, the sky is red
• 14:40
  Speaker 1: and sunsets are actually blue.
• 14:43
  Speaker 2: Wow, that sounds pretty although I associate red skies with wildfires,
• 14:48
  Speaker 2: so I'd be mildly panicking when I'm on Mars. I'd
• 14:52
  Speaker 2: actually probably be mildly panicking on Mars for many different reasons.
• 14:57
  Speaker 1: But before we talk about why exactly that is, I
• 14:59
  Speaker 1: think we need to get down to the basics and understand,
• 15:01
  Speaker 1: like what it is we're talking about when we say
• 15:03
  Speaker 1: color and frequency and wavelength and why that even exists.
• 15:07
  Speaker 2: Color comes from paint cans, right, podcast over roll.
• 15:10
  Speaker 1: Credits Exactly did somebody paint you.
• 15:14
  Speaker 2: They must have when I was a baby.
• 15:17
  Speaker 1: Light in color is really actually super fascinating to understand
• 15:21
  Speaker 1: from a physics point of view. Fundamentally, you see color
• 15:24
  Speaker 1: when photons hit your eyeball. Right, so we're talking about
• 15:26
  Speaker 1: light hitting your eyeball somehow carrying that information about color.
• 15:32
  Speaker 1: So to understand color, you really have to understand what
• 15:34
  Speaker 1: is light and light We can think about either classically
• 15:38
  Speaker 1: as like wiggling electromagnetic fields, or we can think about
• 15:41
  Speaker 1: it from a quantum mechanical point of view, where there
• 15:43
  Speaker 1: are individual photons moving through a quantum field. But in
• 15:48
  Speaker 1: either way it's wiggling fields. And this can be hard
• 15:51
  Speaker 1: for people to visualize sometimes, but you know, just imagine
• 15:54
  Speaker 1: like an electron in space. Around that electron is an
• 15:58
  Speaker 1: electric field. That's what the electron uses to like push
• 16:02
  Speaker 1: on other electrons. If there's another electron somewhere far away,
• 16:06
  Speaker 1: the electric field from the first one pushes on the
• 16:08
  Speaker 1: other electron. That's how two electrons talk to each other. Now,
• 16:12
  Speaker 1: if you take that first electron and you wiggle it,
• 16:14
  Speaker 1: then the field wiggles with it. Right, It's sort of
• 16:17
  Speaker 1: like if you put your hand on the bathtub surface.
• 16:20
  Speaker 1: And you tap it, you generate a series of waves. Right,
• 16:23
  Speaker 1: the whole surface of the bathtub doesn't move down with
• 16:25
  Speaker 1: you instantly. In the same way, when you wiggle an electron,
• 16:29
  Speaker 1: the electric field doesn't move instantly. The part nearby moves
• 16:32
  Speaker 1: down first, then the next part, and the next part
• 16:34
  Speaker 1: in the next part. So the motion of the field
• 16:37
  Speaker 1: moves like a wave through the field as you wiggle
• 16:40
  Speaker 1: the electron.
• 16:41
  Speaker 2: So you're saying that light waves are sort of like
• 16:45
  Speaker 2: lazy rivers with a bunch of electrons and inner tubes,
• 16:49
  Speaker 2: wiggling the water around while they affect other electrons and
• 16:53
  Speaker 2: inner two.
• 16:54
  Speaker 1: Yeah, exactly. It's a little bit more energetic than that,
• 16:56
  Speaker 1: but exactly. So you can think about electrons generating ste
• 17:00
  Speaker 1: electric fields that don't change, and then when the electric
• 17:02
  Speaker 1: field needs to change. That's what a photon is. A
• 17:05
  Speaker 1: photon is a wiggle in the electromagnetic field. That's what
• 17:09
  Speaker 1: we mean when we say that that's what a photon is. Anyway,
• 17:12
  Speaker 1: light is oscillating electric fields, and you can oscillate it
• 17:16
  Speaker 1: different frequencies. You can move that electron really slowly and
• 17:20
  Speaker 1: have long wavelengths and low frequencies, or you can wiggle
• 17:24
  Speaker 1: it super duper fast, and you can get high frequencies
• 17:27
  Speaker 1: and short wavelengths. It just depends on how fast you're
• 17:30
  Speaker 1: wiggling the source of the field to generate those photons.
• 17:34
  Speaker 1: And this is like how antennas work. They have a
• 17:36
  Speaker 1: bunch of electrons in them and they wiggle them up
• 17:38
  Speaker 1: and down. They generate radio waves or cell phone towers
• 17:41
  Speaker 1: or whatever. The antenda on your phone receives that electromagnetic
• 17:44
  Speaker 1: radiation because it has electrons in it which get wiggled
• 17:47
  Speaker 1: by that radiation, those oscillating fields, and you receive those messages.
• 17:51
  Speaker 1: So in the end, light is just wiggling electromagnetic fields,
• 17:55
  Speaker 1: and every wiggle has a different frequency.
• 17:57
  Speaker 2: I think most of our senses are wiggly things that
• 18:01
  Speaker 2: end up hitting some kind of sensory cell like hearing site.
• 18:07
  Speaker 2: Maybe not touch, but sometimes I don't know. Electrons are
• 18:10
  Speaker 2: still wiggly, even like if I'm touching my table. Those
• 18:13
  Speaker 2: electrons aren't completely static, are they.
• 18:15
  Speaker 1: Yeah. That's a really interesting and insightful point that sight
• 18:19
  Speaker 1: and sound are both just oscillations in something. There are vibrations, right,
• 18:24
  Speaker 1: and that actually makes it easier to do things like
• 18:26
  Speaker 1: digitize them. You can take any song and break it
• 18:30
  Speaker 1: down into all the different frequencies that are involved in it,
• 18:33
  Speaker 1: and then you can record those frequencies and recreate it later.
• 18:36
  Speaker 1: You can do the same thing with images. You can say, oh,
• 18:39
  Speaker 1: what frequencies of light arrived, record those and regenerate them.
• 18:43
  Speaker 1: So it's sort of like a recipe for breaking down
• 18:46
  Speaker 1: your experience and recreating it. But taste and smell, as
• 18:48
  Speaker 1: you well know, Katie, are not like that. You have
• 18:50
  Speaker 1: like so many thousands of different receptors to different molecules,
• 18:54
  Speaker 1: and that's one reason why we haven't been able to
• 18:56
  Speaker 1: like digitize smell. You can't like email a smell to
• 18:59
  Speaker 1: some or a taste to somebody, or have like a
• 19:02
  Speaker 1: digital smell creator or taste creator on the other side
• 19:06
  Speaker 1: for you to receive it.
• 19:07
  Speaker 2: I mean, someday, maybe if we can figure out how
• 19:10
  Speaker 2: to like have a sort of tongue VR experience where
• 19:16
  Speaker 2: you use small electrical impulses to sort of trigger the
• 19:22
  Speaker 2: receptors on your tongue. Maybe, but we're not there yet.
• 19:25
  Speaker 1: We're not there yet, and maybe the chemistry folks can
• 19:28
  Speaker 1: help us with that. Right that seems like definitely a
• 19:30
  Speaker 1: chemistry based experience rather than a physics based sensation.
• 19:33
  Speaker 2: I will phosphate myself before the chemists if they can
• 19:37
  Speaker 2: bring us smell a vision.
• 19:39
  Speaker 1: But back to normal vision. We have all these different
• 19:41
  Speaker 1: frequencies of light. So when you get a beam of light,
• 19:43
  Speaker 1: for example, like a laser pulse, it has photons of
• 19:47
  Speaker 1: a specific frequency in it, right, and so one photon
• 19:50
  Speaker 1: can have that frequency, another photon can have the other frequency.
• 19:54
  Speaker 1: Here's where we start to talk about the quantum mechanical
• 19:56
  Speaker 1: nature of light. So far, we've just been saying it's
• 19:58
  Speaker 1: ripples and the electromagnet field. That's like the classical view.
• 20:02
  Speaker 1: That's what Maxwell thought one hundred and fifty years ago.
• 20:04
  Speaker 1: Then we realize that you have to actually quantize you
• 20:06
  Speaker 1: and break it into pieces. You don't just get like
• 20:09
  Speaker 1: a whole massive wave in the field. It's broken into
• 20:12
  Speaker 1: these little packets, and each one has a different frequency,
• 20:15
  Speaker 1: but you can still think of them as like little ripples.
• 20:17
  Speaker 1: It's just ripples in a quantum field instead of a
• 20:20
  Speaker 1: classical field.
• 20:21
  Speaker 2: So these different frequencies will basically be different colors that
• 20:27
  Speaker 2: we see, right exactly.
• 20:29
  Speaker 1: Each frequency means a different energy in the photon, which
• 20:32
  Speaker 1: we perceive as different colors. And it's important to understand
• 20:36
  Speaker 1: that photons are quantized in the number of photons you
• 20:39
  Speaker 1: can receive. You can receive one photon or seven photons,
• 20:42
  Speaker 1: but not three point two photons. But they're not quantized
• 20:45
  Speaker 1: in the energy. There's like an infinite spectrum of possible energies.
• 20:49
  Speaker 1: Any number you can imagine for a wavelength of light,
• 20:51
  Speaker 1: you could have a photon of that wavelength. There's no
• 20:54
  Speaker 1: frequencies that are not allowed. There's an infinite number of
• 20:56
  Speaker 1: frequencies between like five hundred and six hundred nanometers, right,
• 21:00
  Speaker 1: So they're quantized only in the number of photons you
• 21:02
  Speaker 1: can receive, not in the frequencies, which means is an
• 21:05
  Speaker 1: infinite number of different kinds of photons that you can see.
• 21:09
  Speaker 1: But that doesn't mean that there's an infinite number of
• 21:11
  Speaker 1: colors that you can see. Right. While color is connected
• 21:15
  Speaker 1: to frequency, it's actually subtly different. Concept is a little
• 21:19
  Speaker 1: bit more biological and philosophical.
• 21:22
  Speaker 2: Yeah, it is interesting because when you look even at
• 21:26
  Speaker 2: just life on Earth, right, so many different animals have
• 21:29
  Speaker 2: so many different ways to perceive color, and they will
• 21:33
  Speaker 2: perceive the world differently just in terms of color. And
• 21:37
  Speaker 2: that's because the eye and the brain is very different
• 21:41
  Speaker 2: for many different species, and so humans we see color
• 21:46
  Speaker 2: a certain way, our brains interpreted a certain way. But
• 21:48
  Speaker 2: even among humans we have variation in how people perceive color.
• 21:53
  Speaker 2: But before we dive too deep inside of the eyeball,
• 21:56
  Speaker 2: let's take a quick break, rest our eyes, and when
• 22:00
  Speaker 2: we get back we'll talk about how color is a
• 22:03
  Speaker 2: product of both biology, are psychology, and philosophy, And don't
• 22:09
  Speaker 2: forget chemistry and chemistry. Don't you dare forget chemistry? And
• 22:26
  Speaker 2: we are back, and I have been closing my eyes
• 22:30
  Speaker 2: and trying to think of a new color that I've
• 22:33
  Speaker 2: never seen before, and I can't do it.
• 22:36
  Speaker 1: That's a really fascinating sort of philosophy question, and it
• 22:39
  Speaker 1: really gets to the heart of like what color is
• 22:42
  Speaker 1: because a lot of people imagine that photons are colored.
• 22:46
  Speaker 1: They're like a photon flying through space is either a
• 22:48
  Speaker 1: red photon or a green photon or a blue photon.
• 22:51
  Speaker 1: And in shorthand that's fine. We can attach labels to
• 22:54
  Speaker 1: photons and say they're a color that's connected to their frequency,
• 22:57
  Speaker 1: But the photons themselves don't have color, right, Like different
• 23:01
  Speaker 1: animals will see the same photon and have a different experience.
• 23:04
  Speaker 1: The color is actually your experience of the photon, right
• 23:09
  Speaker 1: the way, like your experience of sugar or your experience
• 23:12
  Speaker 1: of fats are not a characteristic of that molecule. They're
• 23:16
  Speaker 1: characteristic of your experience of your brain chemistry giving you
• 23:19
  Speaker 1: a sensation.
• 23:20
  Speaker 2: Yeah, two people can taste the same dish and one
• 23:23
  Speaker 2: person can love it and the other person can think
• 23:26
  Speaker 2: it tastes disgusting, and it's the same food. And you know,
• 23:30
  Speaker 2: we were essentially quite similar in terms of our biology.
• 23:34
  Speaker 2: We have tongues and eyes generally, but both the structure
• 23:39
  Speaker 2: of the eye and the structure of the brain can
• 23:42
  Speaker 2: be different, as can things like our sort of lived
• 23:46
  Speaker 2: experience and how that influences how we see things or
• 23:50
  Speaker 2: taste things. So even among humans, when you look at green, Daniel,
• 23:57
  Speaker 2: and I look at green, we may have different experiences
• 24:01
  Speaker 2: of what green is, and it's so hard to know
• 24:05
  Speaker 2: whether it's the same green or a different green because
• 24:08
  Speaker 2: if I'm like, well, yeah, it's green like an apple,
• 24:10
  Speaker 2: and You're like, yeah, we haven't gotten any closer to
• 24:13
  Speaker 2: answering the question of whether it's the same green because
• 24:16
  Speaker 2: we may just have different perceptions of what an apple
• 24:19
  Speaker 2: looks like.
• 24:20
  Speaker 1: Right, And before we dig into like the deep brain philosophy.
• 24:23
  Speaker 1: Let's take one step back and trace the path of
• 24:26
  Speaker 1: the information. Like the photon hits my eyeball and it
• 24:29
  Speaker 1: has a certain frequency. Do you know the biology of
• 24:32
  Speaker 1: how it then generates like a signal in the nerve, Like,
• 24:35
  Speaker 1: how do you go from the photon to the signal
• 24:38
  Speaker 1: of the optical nerve to your brain.
• 24:40
  Speaker 2: Yeah. So we have sensory cells at the back of
• 24:44
  Speaker 2: our eyes called rods and cones, and the rods generally
• 24:51
  Speaker 2: help us see light or not light, so they really
• 24:55
  Speaker 2: help us see at night in low levels of light.
• 24:58
  Speaker 2: But the cones are responsive to those light photons. And
• 25:04
  Speaker 2: so what actually happens on the very very teeny tiny
• 25:07
  Speaker 2: microscopic level is a protein structure in the cone will
• 25:12
  Speaker 2: actually kind of snap when it is attacked with a
• 25:16
  Speaker 2: sort of certain level of energy from this photon, and
• 25:20
  Speaker 2: it will trigger a neural cell that is connected to
• 25:24
  Speaker 2: that photoreceptive cell, and then there is a whole sort
• 25:28
  Speaker 2: of chain reaction to the bundle of nerves that go
• 25:32
  Speaker 2: from the back of the eye and then go to
• 25:35
  Speaker 2: your brain. So that is sort of how each individual
• 25:39
  Speaker 2: cone works. Like you have that like snapping action of
• 25:42
  Speaker 2: that protein once it is activated by specific frequencies of
• 25:48
  Speaker 2: these photons, and then the color you see isn't from
• 25:52
  Speaker 2: that one individual sensory cell, it is from sort of
• 25:55
  Speaker 2: the average of these the level of activations these have
• 26:00
  Speaker 2: in combination, and all of that information goes through your
• 26:05
  Speaker 2: nerve from the eye to your occipital lobe and it's
• 26:08
  Speaker 2: interpreted in your occipital lobe. And so you have this
• 26:12
  Speaker 2: interface between the kind of structure of your eye and
• 26:16
  Speaker 2: the cones and your brain to then interpret what that
• 26:20
  Speaker 2: color is. And that's why we don't just see like
• 26:23
  Speaker 2: blue or red or green. We see a spectrum of color.
• 26:28
  Speaker 2: We see different shades, different darknesses, different depths and qualities
• 26:32
  Speaker 2: of color.
• 26:33
  Speaker 1: Yeah, I think it's really interesting. I used to think
• 26:35
  Speaker 1: about it working like a TV screen or a computer screen.
• 26:38
  Speaker 1: We had like RGB and you had a certain number
• 26:41
  Speaker 1: of photons in each one and you could mix them
• 26:43
  Speaker 1: to get any color. But it is a little bit
• 26:45
  Speaker 1: more sull than that. If you look at like the
• 26:47
  Speaker 1: wavelength of visible wavelength, it starts at like four hundred
• 26:49
  Speaker 1: and goes up to like seven hundred nanometers. Each kind
• 26:52
  Speaker 1: of cone responds better to a different frequency, Like there's
• 26:55
  Speaker 1: one kind of cone that peaks at like four point fifty,
• 26:57
  Speaker 1: but it can still see photons up to like five hundred.
• 27:00
  Speaker 2: Yeah, there's overlap, a good amount of overlap.
• 27:03
  Speaker 1: Yeah, they do overlap, and all of them have a
• 27:05
  Speaker 1: width to them, And so what your brain is doing
• 27:07
  Speaker 1: is some kind of interpolation. It's like, well, I saw
• 27:09
  Speaker 1: this kind respondibily brightly and that kind very dimly, So
• 27:13
  Speaker 1: it must be a lower frequency photon, or must be
• 27:15
  Speaker 1: a higher frequency photon. And as you say, it does
• 27:18
  Speaker 1: some calculation in there, and like then gives you an experience,
• 27:21
  Speaker 1: and that experience comes from its calculation, its interpretation. Right,
• 27:25
  Speaker 1: that color is in your mind, it's not in the photon.
• 27:30
  Speaker 2: Yeah, it's really interesting because difference in color perception and humans, say,
• 27:35
  Speaker 2: for people who have color blindness, it can be due
• 27:38
  Speaker 2: to basically the range of frequencies that those cones pick
• 27:42
  Speaker 2: up can either overlap more, which makes it harder to
• 27:46
  Speaker 2: distinguish between two different colors because you have more overlap
• 27:50
  Speaker 2: of these cones, or they can kind of be shifted
• 27:53
  Speaker 2: on the spectrum of where you are picking it up,
• 27:55
  Speaker 2: so you don't pick up certain frequencies as well. So
• 27:59
  Speaker 2: it's not so simple as like an operator switchboard for
• 28:04
  Speaker 2: turning selecting colors. It is a spectrum experience, but it's
• 28:10
  Speaker 2: also one that differs from person to person and is
• 28:14
  Speaker 2: very observable in cases of say like color blindness.
• 28:17
  Speaker 1: And there are even people out there who have a
• 28:19
  Speaker 1: fourth kind of cone. They're called tetrachromats, so instead of
• 28:24
  Speaker 1: having three cones in their eye, they have four. When
• 28:26
  Speaker 1: I first learned about this, I thought, oh, my gosh,
• 28:28
  Speaker 1: that's amazing. Is there like a fourth primary color that
• 28:32
  Speaker 1: they can see that we can't, some color out there
• 28:35
  Speaker 1: that they experience that we never do. It's actually a
• 28:38
  Speaker 1: little bit more complicated and less exciting than that. They
• 28:41
  Speaker 1: have four kinds of cones, so they sort of sample
• 28:43
  Speaker 1: the spectrum four ways instead of three, and that just
• 28:47
  Speaker 1: lets them interpolate better. There's not like a new primary
• 28:49
  Speaker 1: color that they can see that we can't. It's just
• 28:52
  Speaker 1: like they have like more resolution on their ruler, and
• 28:55
  Speaker 1: so they're better able to distinguish colors. Like you put
• 28:58
  Speaker 1: two very close shades of green in front of people.
• 29:00
  Speaker 1: Some people can't tell the difference and some people can.
• 29:03
  Speaker 1: And tetrachromats, these people with four cones are especially good
• 29:07
  Speaker 1: at that.
• 29:07
  Speaker 2: Yeah, it's more granular. All throughout the animal kingdom, we
• 29:10
  Speaker 2: have monochromats, die chromats, trichromats, which is generally humans, and
• 29:16
  Speaker 2: then tetrachromats, which is some animals and some humans too.
• 29:21
  Speaker 2: And so it is really interesting because we think of
• 29:25
  Speaker 2: vision like in this sense of like, oh, a monochromat
• 29:28
  Speaker 2: must have a very boring kind of visual experience because
• 29:32
  Speaker 2: they're really only seeing you know, this very limited range.
• 29:35
  Speaker 2: They're not seeing color like we do. But that's not
• 29:38
  Speaker 2: necessarily true. So a monochromat has only one kind of
• 29:41
  Speaker 2: photoreceptive cell to generally like a rod, something like an
• 29:45
  Speaker 2: octopus is actually a monochromat, and so we think that, oh, well,
• 29:51
  Speaker 2: it just kind of season black and white. It must be,
• 29:54
  Speaker 2: you know, not exciting to be an octopus and have
• 29:57
  Speaker 2: octopus vision. But there's also some speculation that the octopus's
• 30:02
  Speaker 2: unique eye shape. Have you noticed how that like pupil
• 30:05
  Speaker 2: is sort of stretched and elongated. It might be that
• 30:08
  Speaker 2: way so that it actually measures the focal length of
• 30:13
  Speaker 2: an object as it hits the eye. It creates this
• 30:16
  Speaker 2: sort of blurriness or an out of focus from different
• 30:19
  Speaker 2: sort of like wavelengths of light. And so it could
• 30:23
  Speaker 2: be that with only rods, they are still able to
• 30:27
  Speaker 2: have a brain's response to color because they are actually
• 30:31
  Speaker 2: seeing the wavelengths hitting at different sort of angles on
• 30:35
  Speaker 2: the eye based on its shape, could actually be interpreted
• 30:37
  Speaker 2: as colors. We don't know. We have never been able
• 30:40
  Speaker 2: to figure out how to ask an octopus whether it's
• 30:42
  Speaker 2: season color. I'm sure there will be studies to see
• 30:46
  Speaker 2: whether octopuses can detect color, but it's very complicated. The
• 30:51
  Speaker 2: power of the brain is in being able to interpret
• 30:55
  Speaker 2: sensory information. So as long as you're getting that information
• 30:58
  Speaker 2: to the brain somehow, even if it is a different
• 31:01
  Speaker 2: way than say, like humans do, you could still be
• 31:04
  Speaker 2: perceiving color, but just using very different hardware.
• 31:07
  Speaker 1: Yeah, and the hardware and software is sort of important.
• 31:10
  Speaker 1: I was reading the mantis strip has an incredible number
• 31:12
  Speaker 1: of different kinds of cones, like maybe even up to twenty,
• 31:16
  Speaker 1: but it has no like processing power behind it. The
• 31:19
  Speaker 1: brain behind it is very simple, and so even though
• 31:22
  Speaker 1: it has so many different kinds of cones, its experience
• 31:24
  Speaker 1: of color might just be that it can only see
• 31:27
  Speaker 1: one color per cone. It's just like an on off
• 31:30
  Speaker 1: because it doesn't have the interpolation power that our brain does.
• 31:33
  Speaker 2: And this may work for the mantistrim because it gives
• 31:36
  Speaker 2: it really really lightning fast reflexes and the ability to
• 31:40
  Speaker 2: detect something that is in its perfhery really easily and
• 31:43
  Speaker 2: really quickly. So it's going for speed over say the
• 31:47
  Speaker 2: definition of its vision. But that works for the mantistrimp
• 31:50
  Speaker 2: because that's what it needs, whereas.
• 31:52
  Speaker 1: We humans are slow and we like to think, hmmm,
• 31:54
  Speaker 1: what is that really? Is that a red or is
• 31:57
  Speaker 1: that a maroon? I have all these arguments with my daughter,
• 31:59
  Speaker 1: but like what is blue and what is green? And
• 32:01
  Speaker 1: I think we see colors differently. At leads to really
• 32:04
  Speaker 1: fascinating philosophy questions about how people's experiences might be different.
• 32:09
  Speaker 1: And this is famous thought experiment about the color red.
• 32:12
  Speaker 1: You know, if you put somebody in a box and
• 32:14
  Speaker 1: never give them the experience of red, could you then
• 32:17
  Speaker 1: describe red to them in a way that when they
• 32:20
  Speaker 1: came out of the box they would see a rose
• 32:21
  Speaker 1: and be like, oh, that's what you meant? You know?
• 32:23
  Speaker 1: Is there a way to capture redness other than the
• 32:26
  Speaker 1: actual experience of red? Anyway, it's a whole fun question
• 32:30
  Speaker 1: in philosophy that we don't have time to dig into.
• 32:32
  Speaker 1: Today we're thinking about the color of the sun, and
• 32:34
  Speaker 1: now we understand that color is an experience in our mind,
• 32:38
  Speaker 1: but it's linked to this physical property that photons have
• 32:41
  Speaker 1: different frequencies and we experience those frequencies in different ways.
• 32:45
  Speaker 1: So really we need to think about, like why photons
• 32:48
  Speaker 1: have different frequencies so that we can understand what frequency
• 32:51
  Speaker 1: of light the sun generates.
• 32:53
  Speaker 2: Yeah, like this kind of gets back to my question
• 32:56
  Speaker 2: earlier of like why is blue so special when we
• 32:59
  Speaker 2: see like why why does that interact with our atmosphere,
• 33:02
  Speaker 2: not say red or green? Why do they have these
• 33:04
  Speaker 2: different wavelengths? What is going on?
• 33:07
  Speaker 1: Yeah, you might wonder like why are some things blue
• 33:09
  Speaker 1: and other things green? And there's really a couple of
• 33:11
  Speaker 1: different reasons, and they're both actually due to quantum mechanics,
• 33:14
  Speaker 1: which is super awesome. And the first is that there
• 33:17
  Speaker 1: are certain energy levels allowed to electrons. Like electrons flying
• 33:22
  Speaker 1: through space, we call them free particles. They can have
• 33:25
  Speaker 1: any energy they want, they can have super high energy,
• 33:28
  Speaker 1: they can have no energy. They can do whatever they like.
• 33:30
  Speaker 1: They are not bound by anything. But when you put
• 33:33
  Speaker 1: an electron into an atom, there are only certain solutions
• 33:36
  Speaker 1: to the Shorteninger equation to the quantum mechanical equation that
• 33:39
  Speaker 1: tells an electron what it can and cannot do. And
• 33:42
  Speaker 1: because you are binding the electron, you're like putting it
• 33:44
  Speaker 1: in a little well, only certain solutions work, and that's
• 33:48
  Speaker 1: where quantization comes from. It comes from confining the electron
• 33:52
  Speaker 1: to the atom, and you end up with this like
• 33:54
  Speaker 1: ladder of possible energy levels. So if you've studied some chemistry,
• 33:58
  Speaker 1: for example, and extremely important and valuable science, then you've
• 34:02
  Speaker 1: understood that, like around an atom, an electron can have
• 34:05
  Speaker 1: a certain energy level or the next one or the
• 34:07
  Speaker 1: next one, but it can't be in between. So there's
• 34:10
  Speaker 1: this ladder of energy levels for an electron.
• 34:13
  Speaker 2: Maybe this is why I'm so jealous of people who
• 34:15
  Speaker 2: can understand chemistry well, because I've always been confused why
• 34:20
  Speaker 2: there are these different ladder stages for the electron to
• 34:24
  Speaker 2: sort of jump into, and why can't it go in between.
• 34:27
  Speaker 1: The technical answer is that those are the only solutions
• 34:30
  Speaker 1: to the Shorting air equation. The intuitive answer is like,
• 34:33
  Speaker 1: why are those the only solutions to the Shorting air equation?
• 34:36
  Speaker 1: And there's like sort of a cartoon picture, which is helpful,
• 34:39
  Speaker 1: it's not technically accurate, which is like imagine electrons wave
• 34:43
  Speaker 1: wiggling around the central proton. It like wiggles up and
• 34:45
  Speaker 1: wiggles down, and wiggles up and wiggles down. Energy levels
• 34:48
  Speaker 1: the electron have are those where it completes an integer
• 34:52
  Speaker 1: number of half wavelengths, so that when it gets back
• 34:54
  Speaker 1: to where it was, it sort of matches up to
• 34:57
  Speaker 1: its previous wiggle. It's sort of like a standing it
• 35:00
  Speaker 1: reinforces itself. Anything else it ends up canceling itself out.
• 35:04
  Speaker 1: And so you can sort of like fit a certain
• 35:07
  Speaker 1: number of half wavelengths sort of the same way when
• 35:09
  Speaker 1: you pluck a guitar string right, it can oscillate in
• 35:12
  Speaker 1: different modes and like the whole thing can move up
• 35:14
  Speaker 1: and down, or you can have a node in the
• 35:16
  Speaker 1: middle where one side is moving up and the other
• 35:18
  Speaker 1: side is moving down. Or you can have two nodes,
• 35:20
  Speaker 1: so you have like three half wavelengths. There's into your
• 35:23
  Speaker 1: number of ways to fit them into your fixed length
• 35:27
  Speaker 1: guitar string. And that's actually a pretty good example because
• 35:30
  Speaker 1: you're confining the wiggle of the string because you've nailed
• 35:32
  Speaker 1: the string down on the two sides of the guitar.
• 35:34
  Speaker 1: And here we're confining the electron to the atom and
• 35:37
  Speaker 1: restricting it to certain states, and that has important consequences
• 35:41
  Speaker 1: for the color of that atom, because the light generated
• 35:44
  Speaker 1: by that atom comes from electrons moving down energy levels.
• 35:48
  Speaker 1: An electron gets excited and it absorbs some energy, and
• 35:51
  Speaker 1: it jumps up a few energy levels. A moment later,
• 35:53
  Speaker 1: it's going to relax and come back down to the
• 35:55
  Speaker 1: lowest energy level, because that's what nature likes to do,
• 35:57
  Speaker 1: is relax down to lower energy levels spread things out.
• 36:00
  Speaker 1: When it does that, it gives up some of that
• 36:02
  Speaker 1: energy in the form of a photon and emits light.
• 36:05
  Speaker 1: So that light has a certain energy, which is due
• 36:08
  Speaker 1: to the difference in its higher energy level and the
• 36:11
  Speaker 1: lower energy level. Jumps down the ladder and it gets
• 36:14
  Speaker 1: a certain amount of energy, and that's always going to
• 36:16
  Speaker 1: be the same frequency. Every time it makes a certain jump,
• 36:19
  Speaker 1: from like three to two or from three to one,
• 36:22
  Speaker 1: it's always going to have exactly the same energy and
• 36:25
  Speaker 1: exactly the same frequency of photons.
• 36:28
  Speaker 2: So you'll have photons that are sort of imbued with
• 36:33
  Speaker 2: different energy based on the way that this electron has
• 36:37
  Speaker 2: jumped down from the ladder exactly.
• 36:41
  Speaker 1: And every atom has a different ladder, So the spacings
• 36:44
  Speaker 1: of the ladder for hydrogen are different than the spacings
• 36:47
  Speaker 1: of the ladder for zinc, for example, or for copper.
• 36:51
  Speaker 1: So copper will emit photons of different frequency than zinc will,
• 36:55
  Speaker 1: or hydrogen will, or oxygen will. And this is actually
• 36:58
  Speaker 1: super valuable and important because when you're looking, for example,
• 37:01
  Speaker 1: at light from a distant star and you're wondering, Hm,
• 37:04
  Speaker 1: what's that star made out of, what's in its atmosphere,
• 37:08
  Speaker 1: what is burning in its core? You can tell without
• 37:11
  Speaker 1: ever going to that star, just by looking at the
• 37:13
  Speaker 1: light that it emits. There's a fingerprint for hydrogen, and
• 37:17
  Speaker 1: a fingerprint for zinc, and a fingerprint for oxygen, and
• 37:20
  Speaker 1: you can see those fingerprints in its spectrum. If you
• 37:22
  Speaker 1: count up the number of photons you get at different frequencies,
• 37:25
  Speaker 1: you'll be like, oh, to get these peaks, to get
• 37:28
  Speaker 1: light at these frequencies, you have to have copper. And
• 37:30
  Speaker 1: so we can tell what distant stars and distant planetary
• 37:33
  Speaker 1: atmospheres are made out of just by looking at the
• 37:36
  Speaker 1: color of the light, the frequency of the light that
• 37:39
  Speaker 1: they emit.
• 37:40
  Speaker 2: Is this kind of how classic neon lights work. You
• 37:43
  Speaker 2: can fill a glass tube with sort of different chemicals
• 37:46
  Speaker 2: or different atoms, and then once you put some energy
• 37:49
  Speaker 2: into it, it produces a different color.
• 37:51
  Speaker 1: Exactly. A neon is an element that tends to glow
• 37:53
  Speaker 1: at certain colors, and so that's exactly right. You're filling
• 37:56
  Speaker 1: it with a hot plasma, a gas that's become excited
• 37:59
  Speaker 1: and glows at certain energies. And to get back to
• 38:02
  Speaker 1: your question of like why are something's blue and something's red,
• 38:05
  Speaker 1: Like your T shirt is not blue because it's glowing.
• 38:08
  Speaker 1: It's actually the opposite process happening there. It's absorbing. Like
• 38:11
  Speaker 1: when light hits your T shirt, the atoms in that
• 38:15
  Speaker 1: T shirt can absorb photons of certain energy. It's like
• 38:18
  Speaker 1: the reverse process of electrons jumping down the ladder and
• 38:21
  Speaker 1: giving off photons. The reverse process is them absorbing photons
• 38:26
  Speaker 1: of certain energy and jumping up the ladder. So when
• 38:29
  Speaker 1: light hits your T shirt, it can absorb only certain
• 38:32
  Speaker 1: frequencies of light, only ones that match the energy levels
• 38:36
  Speaker 1: of the electrons in your T shirt, and so those
• 38:39
  Speaker 1: things get absorbed. Anything else is not absorbed, and so
• 38:42
  Speaker 1: it can be reflected.
• 38:43
  Speaker 2: So my shirt is basically every color except blue.
• 38:47
  Speaker 1: Well, what it means to be blue is to reflect
• 38:50
  Speaker 1: blue light. Right, It's absorbing all the other photons and
• 38:53
  Speaker 1: reflecting blue light, and so you see it as blue.
• 38:57
  Speaker 1: When we call something blue, what we really mean is
• 38:59
  Speaker 1: that thing reflects blue light. It's counterintuitive. You'd like to think, oh,
• 39:02
  Speaker 1: it absorbs blue light and becomes blue, but then you
• 39:05
  Speaker 1: wouldn't see any blueness from it. You only see blue
• 39:08
  Speaker 1: if it's reflecting the blue light.
• 39:10
  Speaker 2: I mean, this is in nature. This is how we
• 39:13
  Speaker 2: see different colors. Usually you have some kind of like
• 39:16
  Speaker 2: pigment that absorbs every color except for the color that
• 39:20
  Speaker 2: you see, which is reflected back at you. But you
• 39:22
  Speaker 2: can also have things like tiny microscopic prisms that actually
• 39:26
  Speaker 2: scatter light structural coloration, and instead of absorbing the light,
• 39:32
  Speaker 2: it scatters it, and then that scattered light hits your eye.
• 39:35
  Speaker 1: Yeah. Really fun. So that's quantum mechanics process number one.
• 39:38
  Speaker 1: It's like energy levels of the atom determine what colors
• 39:42
  Speaker 1: it glows in and what colors it absorbs. There's a
• 39:45
  Speaker 1: second process, which is also due to quantum mechanics, which
• 39:48
  Speaker 1: is just that hot things tend to glow, and they
• 39:50
  Speaker 1: tend to glow at different frequencies. So like the sun
• 39:53
  Speaker 1: is really really hot and it's glowing, and part of
• 39:56
  Speaker 1: the light that it emits is due to these atoms
• 39:59
  Speaker 1: jumping up and down on the energy levels, but part
• 40:01
  Speaker 1: of it is also just due to having like a
• 40:03
  Speaker 1: big soup of electrons up there that are all zipping
• 40:06
  Speaker 1: around at certain temperatures and giving off photons. And the
• 40:10
  Speaker 1: hotter the thing is, the more these electrons that are
• 40:13
  Speaker 1: not bound to atoms are going to be wiggling around
• 40:15
  Speaker 1: and giving off photons. So things that are really really
• 40:18
  Speaker 1: hot have their freer electrons sort of wiggling around a
• 40:22
  Speaker 1: lot in giving off high frequency photons. Things that are
• 40:25
  Speaker 1: colder have their electrons not moving this fast and giving
• 40:28
  Speaker 1: off lower energy, lower frequency photons. So, for example, Katie,
• 40:33
  Speaker 1: you glow, and not just in a sort of intellectual
• 40:36
  Speaker 1: way or because of your brilliant personality. You are literally
• 40:39
  Speaker 1: emitting photons right now. They're just not photons in our
• 40:44
  Speaker 1: visible range. So when your husband looks at you, he
• 40:47
  Speaker 1: can't see that you are glowing in the infrared. You
• 40:50
  Speaker 1: are giving off light like in a dark room when
• 40:53
  Speaker 1: you imagine nobody could see me, you are glowing in
• 40:55
  Speaker 1: the infrared. And that's what for example, night vision goggles
• 40:59
  Speaker 1: can see.
• 41:00
  Speaker 2: M I see. Is that also called black body radiation?
• 41:05
  Speaker 1: Yeah, that's the physics name for it, black body radiation.
• 41:08
  Speaker 1: So we imagine if you have an object which does
• 41:11
  Speaker 1: not reflect any light, which absorbs everything and only emits
• 41:15
  Speaker 1: light through this process where your electrons inside you are
• 41:18
  Speaker 1: sort of zipping around and giving off photons. These are
• 41:21
  Speaker 1: the electrons that are again not totally bound to an atom,
• 41:24
  Speaker 1: and so they're freer to emit in sort of a
• 41:26
  Speaker 1: broader spectrum. Then we call this thing a black body. Now,
• 41:29
  Speaker 1: nothing in the universe is actually a black body. Everything
• 41:32
  Speaker 1: in the universe is sort of partially a black body
• 41:35
  Speaker 1: and partially emitting due to the energy levels of the
• 41:38
  Speaker 1: bound atoms. And so for example, our sun is like that.
• 41:41
  Speaker 1: Our sun can be described as a black body object
• 41:45
  Speaker 1: because it does emit at a certain frequency based on
• 41:48
  Speaker 1: its temperature. But also you can tell what's in the
• 41:51
  Speaker 1: sun because the atoms in it glow. So the Sun
• 41:53
  Speaker 1: is a complicated mixture of mostly black body radiation due
• 41:57
  Speaker 1: to its temperature, and also a lot of peaks and
• 41:59
  Speaker 1: dip because of the other quantum mechanical effect where electrons
• 42:03
  Speaker 1: around atoms are absorbing and emitting only at specific frequencies.
• 42:06
  Speaker 2: Well, it sounds like the Sun contains multitudes, kind of
• 42:10
  Speaker 2: literally and maybe very violently. So we are not going
• 42:15
  Speaker 2: to look at the Sun with our eyeballs, but with
• 42:18
  Speaker 2: our minds when we get back. So we are back,
• 42:34
  Speaker 2: and we are going to take a safe look at
• 42:37
  Speaker 2: the Sun, not by staring at it, but by thinking
• 42:40
  Speaker 2: about it.
• 42:42
  Speaker 1: Exactly. And so first we will think about the Sun
• 42:46
  Speaker 1: just as a black body object or as something which
• 42:49
  Speaker 1: glows due to its temperature. And as we said before,
• 42:52
  Speaker 1: the theory of black body radiation tells you that the
• 42:55
  Speaker 1: hotter you are, the shorter the wavelength of light, or
• 42:59
  Speaker 1: the higher the frequency of light, higher the energy of
• 43:02
  Speaker 1: photons that you emit. So if you are cooler like
• 43:05
  Speaker 1: you and me, then we glow in long wavelengths, low frequencies.
• 43:09
  Speaker 1: And if you are hotter, then you tend to glow
• 43:12
  Speaker 1: in higher energies or higher frequencies or shorter wavelengths. But
• 43:17
  Speaker 1: that simplifies it a little bit there. We're really just
• 43:19
  Speaker 1: describing the peak where most of the energy is emitted.
• 43:23
  Speaker 1: If you're an object like the sun at five thousand
• 43:25
  Speaker 1: degrees kelvin, you tend to emit mostly in the visible spectrum, right,
• 43:31
  Speaker 1: but you also emit at lower and higher frequencies. It's
• 43:34
  Speaker 1: a very broad range there. So the Sun isn't limited
• 43:37
  Speaker 1: to only emitting light at one frequency, but it does
• 43:40
  Speaker 1: tend to peak at exactly the kind of frequency that
• 43:43
  Speaker 1: our eyes are good at seeing.
• 43:45
  Speaker 2: It's kind of like how in our eyes, our cones
• 43:49
  Speaker 2: can see a whole range of frequencies. Things can also
• 43:53
  Speaker 2: emit a whole range of frequencies.
• 43:55
  Speaker 1: That's exactly right, And so the sun emits a very
• 43:58
  Speaker 1: very broad range. We can actually only see a little
• 44:00
  Speaker 1: slice of it. Like if you develop infrared telescopes or
• 44:04
  Speaker 1: UV telescopes, things that can see frequencies below and above
• 44:08
  Speaker 1: what our eyes can, you can still see the sun, right,
• 44:11
  Speaker 1: The sun is not black and higher frequencies. And it's
• 44:13
  Speaker 1: also not a coincidence that the Sun peaks in its
• 44:16
  Speaker 1: emission and exactly the frequency range that we can see.
• 44:19
  Speaker 2: The sun was made for us, clearly, Can I stop
• 44:24
  Speaker 2: you right there?
• 44:25
  Speaker 1: I think it might be the opposite, right, Our eyes
• 44:28
  Speaker 1: clearly evolved in an environment that's dominated by certain frequencies,
• 44:32
  Speaker 1: so those frequencies are more useful. And I think if
• 44:35
  Speaker 1: the sun had been hotter or colder and admitted at
• 44:38
  Speaker 1: different frequencies. If very likely we would see at different frequencies,
• 44:42
  Speaker 1: and like, I don't know what that experience would be like.
• 44:44
  Speaker 1: But you know, the reason that our eyeballs can see
• 44:47
  Speaker 1: exactly in the range where the sun peaks probably not
• 44:50
  Speaker 1: a coincidence.
• 44:51
  Speaker 2: Well, that's why certain animals, especially invertebrates and pollinators can
• 44:57
  Speaker 2: often see u V light is because it is something
• 45:01
  Speaker 2: that they've evolved to see that helps them pollinate, because
• 45:04
  Speaker 2: they can see light that is given off by flowers,
• 45:08
  Speaker 2: and the flowers have co evolved with them to emit
• 45:11
  Speaker 2: even more UV lights that they can see, and this
• 45:15
  Speaker 2: helps them, you know, I identify basically their target to
• 45:19
  Speaker 2: get nectar from flowers. And so birds and insects can
• 45:24
  Speaker 2: see UV light and we generally can't. And that's not
• 45:29
  Speaker 2: a failure of ours. That's just because it does not
• 45:32
  Speaker 2: generally have an evolutionary benefit for us to do.
• 45:35
  Speaker 1: So. Yeah, and it's a fascinating story. We told them the
• 45:37
  Speaker 1: podcast once about a kind of bird, kind of bird
• 45:39
  Speaker 1: called the blue tit, which actually looks spectacular in the ultraviolet.
• 45:44
  Speaker 1: But let's get back to the sun and start in
• 45:46
  Speaker 1: outer space before we think about the atmosphere. If you're
• 45:48
  Speaker 1: in outer space and you look at the Sun with
• 45:50
  Speaker 1: of course protection, what would you see. And you often
• 45:54
  Speaker 1: hear science communicators in popular science articles describing the Sun
• 45:57
  Speaker 1: as green, saying the Sun is actually green. The reason
• 46:01
  Speaker 1: is that if you just treat the Sun as a
• 46:02
  Speaker 1: black body object, and you know it's temperature, its peak
• 46:06
  Speaker 1: is in the green, it would emit more green photons
• 46:09
  Speaker 1: than orange photons or red photons or blue photons. So
• 46:13
  Speaker 1: that's why people say, sometimes, oh, the Sun is actually green.
• 46:16
  Speaker 1: What does that really mean though? I mean, if you're
• 46:18
  Speaker 1: in outer space and you look at the Sun, you
• 46:20
  Speaker 1: do not see it as green. You see it as white,
• 46:24
  Speaker 1: because it does peak in the green. But as we
• 46:26
  Speaker 1: said before, it emits in a very broad spectrum, and
• 46:29
  Speaker 1: it emits plenty of red photons and blue photons and
• 46:32
  Speaker 1: orange photons. So if you're in outer space, you're an astronaut,
• 46:35
  Speaker 1: you look at the Sun, you do not see it
• 46:37
  Speaker 1: as green. You see it as white because you see
• 46:40
  Speaker 1: a huge mixture of these colors. In order for you
• 46:43
  Speaker 1: to see it as green, it would have to be
• 46:44
  Speaker 1: like overwhelmingly only green photons and very very few other photons.
• 46:50
  Speaker 2: This is a trick you kind of can do with
• 46:52
  Speaker 2: lights here on Earth. If you mix light, not pigment,
• 46:56
  Speaker 2: but light together, you get white. When you mix pigments together,
• 47:00
  Speaker 2: you often get brown, because that's a different sort of
• 47:03
  Speaker 2: thing going on with pigments. But yeah, when you mix
• 47:05
  Speaker 2: a bunch of different lights, you'll get white light.
• 47:07
  Speaker 1: You get white light exactly. The second problem with saying
• 47:10
  Speaker 1: that the Sun is green is that that's only true
• 47:14
  Speaker 1: if the Sun was a perfect black body, if all
• 47:16
  Speaker 1: of its radiation only came from its temperature. But the
• 47:19
  Speaker 1: Sun is not a black body. It emits light not
• 47:22
  Speaker 1: just because it's hot, but because the atoms in it
• 47:24
  Speaker 1: are doing other quantum mechanical things. Electrons are jumping up
• 47:27
  Speaker 1: and down energy levels. It emits in many complicated ways,
• 47:30
  Speaker 1: as you say, it contains multitudes.
• 47:32
  Speaker 2: It's got electron shoots and electron ladders.
• 47:36
  Speaker 1: So if you actually go out into space and you
• 47:39
  Speaker 1: measure the photons coming from the Sun, you find that
• 47:42
  Speaker 1: it doesn't peak in the green the way it would
• 47:44
  Speaker 1: if it was a perfect black body object. It actually
• 47:47
  Speaker 1: peaks in the violet, right, And so the most common
• 47:51
  Speaker 1: frequency of light coming from the Sun if you're in
• 47:54
  Speaker 1: outer space is not green, or it's not yellow, it's violet.
• 47:57
  Speaker 2: That must be a very interesting experience for animals on
• 48:01
  Speaker 2: Earth who can see more in the ultraviolet frequencies. They
• 48:05
  Speaker 2: must see the sun differently, at least from space.
• 48:08
  Speaker 1: Yeah, yeah, well, I hope they're also not looking up
• 48:10
  Speaker 1: at the sun. So any animal or insect listeners be careful.
• 48:14
  Speaker 2: But if we put birds in space and gave them
• 48:16
  Speaker 2: eye protection and then ask them put a pairrot up
• 48:20
  Speaker 2: there so it can talk to us.
• 48:21
  Speaker 1: I'm glad that we're thinking about these details. Now. That's
• 48:24
  Speaker 1: definely the most important thing. So if you're in outer space,
• 48:28
  Speaker 1: the photons you get from the Sun are most often violet.
• 48:32
  Speaker 1: Green is also very common, but you still see the
• 48:35
  Speaker 1: sun as white. If you look at pictures of the
• 48:37
  Speaker 1: Sun from space, then it's definitely white. But here on Earth,
• 48:41
  Speaker 1: if you look up at the sun safely, of course
• 48:43
  Speaker 1: you don't see it white. Right, You do not see
• 48:46
  Speaker 1: a white sun. And the reason is the one that
• 48:48
  Speaker 1: we talked about before, that the atmosphere is not democratic
• 48:52
  Speaker 1: when it comes to letting light through that the very
• 48:55
  Speaker 1: high frequencies of light, the blue gets scattered and so
• 48:58
  Speaker 1: all the photons that are zooming towards your eyeball. When
• 49:01
  Speaker 1: they come from the sun through the atmosphere, they don't
• 49:04
  Speaker 1: all make it, so the blue ones get scattered sideways
• 49:07
  Speaker 1: and make somebody else's blue sky. If you're standing next
• 49:10
  Speaker 1: to me, Katie, then those blue photons which originally were
• 49:13
  Speaker 1: pointed towards my eyeball might end up at your eyeball,
• 49:17
  Speaker 1: and so you will see the sky as blue, whereas
• 49:20
  Speaker 1: I will see the sun as having less blue than
• 49:22
  Speaker 1: it actually does. And that's why we see the sun
• 49:25
  Speaker 1: as yellow. It's like originally white but then distorted by
• 49:30
  Speaker 1: the atmosphere to look yellow.
• 49:31
  Speaker 2: And is that why the sun changes color as it
• 49:35
  Speaker 2: rises and as it sets, because it is hitting the
• 49:38
  Speaker 2: atmosphere at a different angle relative to our eyes.
• 49:41
  Speaker 1: Exactly during sunrise and during sunset, you're going through more
• 49:45
  Speaker 1: atmosphere than usual, And so the higher frequencies of light
• 49:48
  Speaker 1: get scattered more, and you get even more bias towards
• 49:51
  Speaker 1: the low frequency red light. So the scattering the atmosphere
• 49:55
  Speaker 1: depends on the frequency to the fourth power. Actually, so
• 49:58
  Speaker 1: high frequency light like blue oh get scattered much more
• 50:01
  Speaker 1: than red light. And if you go through more atmosphere,
• 50:04
  Speaker 1: you get more scattering and that's why sunrises and sunsets
• 50:07
  Speaker 1: are red.
• 50:08
  Speaker 2: This might be a topic for a different episode, but
• 50:11
  Speaker 2: I do have a question. Do you have an opinion
• 50:14
  Speaker 2: on whether the green flash exists? Have you heard of
• 50:17
  Speaker 2: that in terms of like as the sunsets, people claim
• 50:20
  Speaker 2: that there's a green flash just as it goes beyond
• 50:23
  Speaker 2: the horizon.
• 50:24
  Speaker 1: There is a green flash, and I've seen it.
• 50:28
  Speaker 2: I feel like I've seen it too, but I didn't
• 50:30
  Speaker 2: know if it was just sort of psychosomatic.
• 50:32
  Speaker 1: But yes, that is a topic for another day. But
• 50:35
  Speaker 1: it's also fascinating to think about the colors of everything
• 50:38
  Speaker 1: else out there in the Solar System. You probably have
• 50:40
  Speaker 1: mental images of what various planets look like from pictures
• 50:44
  Speaker 1: you've seen online, but they're not always representative. Mars usually
• 50:48
  Speaker 1: looks red because of the red rocks on Mars, but Venus,
• 50:52
  Speaker 1: for example, looks different than you might imagine. The images
• 50:55
  Speaker 1: we have of Venus are mostly from UV telescopes, where
• 50:59
  Speaker 1: the pictures they've taken have been shifted down into the
• 51:02
  Speaker 1: visible spectrum so that we can see them. If you
• 51:04
  Speaker 1: were to fly by Venus, it would look just kind
• 51:06
  Speaker 1: of like a big gray blob with almost no features
• 51:09
  Speaker 1: to it. At all in the visible spectrum.
• 51:12
  Speaker 2: Well, that's too bad, because I was really planning a
• 51:14
  Speaker 2: road trip to go sight see Venus.
• 51:19
  Speaker 1: Bring your acid proof goggles because I think you're going
• 51:22
  Speaker 1: to need them on the surface of Venus, all right.
• 51:25
  Speaker 1: And so to recap photons our wiggles in the electromagnetic
• 51:29
  Speaker 1: spectrum that come at all different frequencies, and objects can
• 51:32
  Speaker 1: emit and absorb photons based on their energy levels or
• 51:35
  Speaker 1: also just based on their temperature. The sun out in
• 51:38
  Speaker 1: space is white, even though it peaks in the violet.
• 51:40
  Speaker 1: You would see it as white with your eyeballs, but
• 51:43
  Speaker 1: here on Earth we see it as yellow because of
• 51:46
  Speaker 1: atmospheric effects.
• 51:47
  Speaker 2: And all of that depends on our eyeballs, biology and
• 51:51
  Speaker 2: our brains and.
• 51:52
  Speaker 1: The chemistry that makes it all work.
• 51:54
  Speaker 2: We owe everything to chemistry, and I am extremely remorseful
• 51:58
  Speaker 2: to make it sound like anything else.
• 52:01
  Speaker 1: And in the end, everybody should be out there following
• 52:03
  Speaker 1: their personal curiosity. You can love a kind of science
• 52:07
  Speaker 1: that I would find super boring, and I can find
• 52:09
  Speaker 1: it super interesting even if it makes you yawn. That
• 52:12
  Speaker 1: diversity of interest is why we have such a beautiful
• 52:14
  Speaker 1: diversity of scientists and such a beautiful diversity of discoveries
• 52:18
  Speaker 1: about the universe. It's that widely varying curiosity and enjoyment
• 52:22
  Speaker 1: of different kinds of puzzles that powers our broad spectrum
• 52:25
  Speaker 1: human curiosity about the universe.
• 52:28
  Speaker 2: It's not a competition except for the Universal Scientist Decathlon.
• 52:34
  Speaker 1: That's right. So thanks very much everybody for going on
• 52:36
  Speaker 1: this journey with us, following photons from the sun all
• 52:39
  Speaker 1: the way to your eyeball, and following these phonons from
• 52:43
  Speaker 1: our mouths all the way to your earballs. And thank
• 52:45
  Speaker 1: you very much Katie for joining us today. Yeah, of course,
• 52:48
  Speaker 1: thanks for listening. Tune in next time. Thanks for listening,
• 52:59
  Speaker 1: and remember that Dniel and Jorge Explain the Universe is
• 53:01
  Speaker 1: a production of iHeartRadio. For more podcasts from iHeartRadio, visit
• 53:06
  Speaker 1: the iHeartRadio app, Apple Podcasts, or wherever you listen to
• 53:10
  Speaker 1: your favorite shows.