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Speaker 1: Hey, Katie, I have a funny question. What color are

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Speaker 1: your eyes?

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Speaker 2: Daniel? How do you not know this?

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Speaker 1: How would I possibly know? We've never actually met in person.

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Speaker 1: I don't even know that you actually have eyes.

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Speaker 2: Well, I could tell you any color and you would.

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Speaker 1: Believe me, Right, I suppose I mean any color within reason.

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Speaker 2: Well, my husband says that they're like two sunsets on Mars.

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Speaker 1: All right, Now, I'm not very sure I should believe

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Speaker 1: you or your husband.

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Speaker 2: Well, my parents say that they are infinite pools of starlight.

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Speaker 1: All right, And when you look in the mirror, what

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Speaker 1: do you see staring back at you?

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Speaker 2: Really good podcasting eyes.

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Speaker 1: And we'll just leave you all with that mystery. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 1: uc Erine, and I have brown eyes, but both of

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Speaker 1: my kids have blue or green eyes.

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Speaker 2: My name is Katie Golden. I host an evolutionary biology

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Speaker 2: podcast called Creature Feature, and I have lots of eyes

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Speaker 2: of many different colors. One could say their compact eyes.

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Speaker 1: The eyes have it It sounds like, Well, I have

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Speaker 1: a evolutionary biologist question for you, which is that my

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Speaker 1: wife is Scandinavian. She has blonde hair and blue eyes,

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Speaker 1: and I have dark hair and dark eyes, and both

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Speaker 1: of our kids have blonde hair and light eyes, and

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Speaker 1: I thought that dark colors were dominant. Is there a

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Speaker 1: nefarious explanation here or is there biology?

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Speaker 2: No? No, this is what's so and is Yes, dark

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Speaker 2: hair is dominant. But actually that makes it likely that

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Speaker 2: you can pass on recessive traits to your kids, especially

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Speaker 2: because your wife seems to have double recessives. So if

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Speaker 2: you have brown eyes, right, and brown eyes are a

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Speaker 2: dominant trait, so you could have just one dominant allele

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Speaker 2: of brown eyes. So you can absolutely, as a brown eye,

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Speaker 2: brown haired person, have a child who has blue eyes,

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Speaker 2: blonde hair, red hair, whatever.

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Speaker 1: So you're saying, I must have some blue eyes and

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Speaker 1: blonde hair jeens, they just don't show up in me.

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Speaker 2: Yeah, exactly. I think a lot of marriages would be

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Speaker 2: saved if people understood genetics.

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Speaker 1: Well, not for this reason, but we did do DNA

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Speaker 1: testing for our kids, and so welcome to the podcast

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Speaker 1: Daniel and Jorge Explain the Universe, a production of via

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Speaker 1: Heart Radio in which we talk about all of the

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Speaker 1: mysteries in the universe, not just Daniel's kids.

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Speaker 2: DNA We're not going.

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Speaker 1: To do any live DNA testing on the show. Today.

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Speaker 1: We speculate and wonder about everything in the universe. We

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Speaker 1: scratch our heads and wonder how things work, why things

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Speaker 1: look the way they do, and how the whole universe

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Speaker 1: came to be. From the tiniest quantum particles to those

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Speaker 1: colors in your eyeballs, to the very size and age

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Speaker 1: of the universe. We think all of these questions are fascinating.

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Speaker 1: My usual co host and friend, Jorge, can't be here today,

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Speaker 1: but we're very happy to have the spectacularly eyeballed Katie

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Speaker 1: along for our ride today.

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Speaker 2: And maybe Jorge's eyeballs are along for the ride. I

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Speaker 2: didn't steal them.

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Speaker 1: I don't have his eyeballs in like a glass jar

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Speaker 1: over here.

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Speaker 2: It's so he can see what's going on when he

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Speaker 2: can't be here for the recording.

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Speaker 1: One of my favorite things about asking questions about the

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Speaker 1: universe is that it's so easy to quickly get into

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Speaker 1: deep territory. You know, even if you are not an

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Speaker 1: academic physicist. You wonder about the nature of the universe,

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Speaker 1: how things work, and that comes just from looking at

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Speaker 1: the world around you and wondering why is it this

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Speaker 1: way and not some other way. Why do my kids

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Speaker 1: have this color eyeballs? Why is water transparent? Why is

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Speaker 1: the sky blue? Really basic questions of the very nature

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Speaker 1: of our environment can lead often to fascinating science puzzles

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Speaker 1: that help you understand the way the world works.

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Speaker 2: I love all kinds of science, and I think that

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Speaker 2: it is interesting because you can go from a relatively

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Speaker 2: simple question something that doesn't seem that deep on the surface.

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Speaker 2: In fact, the simpler the question, usually the more complex

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Speaker 2: the answer, the deeper you have to go. Many other

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Speaker 2: questions branch off from some of the more simple questions,

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Speaker 2: and I love how many rabbit holes you can go down.

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Speaker 1: Absolutely, And when I'm giving a public talk, like I

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Speaker 1: did in Aspen last week, my favorite questions are the

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Speaker 1: ones that start with, well, this is probably a really

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Speaker 1: easy question, but and then they ask a really deep,

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Speaker 1: very simple sounding question, but one that has huge ramifications

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Speaker 1: and requires you to understand all sorts of fascinating things.

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Speaker 1: And the thing to know about science is that it's

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Speaker 1: all just people being curious. The whole reason we're trying

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Speaker 1: to understand the cosmos is that the Sumerians and the

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Speaker 1: Mayans and the Chinese and the Greeks. We're looking up

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Speaker 1: at the sky and wondering like, hmm, why do the

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Speaker 1: planets sometimes go the other way? And why do things

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Speaker 1: rotate around the pole stars? And all these things come

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Speaker 1: from our very human, very ancient curiosity about the nature

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Speaker 1: of the world around us. It drives everything we do

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Speaker 1: in science, from people who study blind mole rats to

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Speaker 1: those people trying to understand why supernova explode.

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Speaker 2: I think one of the interesting kind of misconceptions people

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Speaker 2: have is that a basic question is one that's not

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Speaker 2: worth asking, or it's a dumb question, whereas like you

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Speaker 2: should be asking something like, oh, what is this specific

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Speaker 2: coefficient for this specific formula? But when you ask that

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Speaker 2: kind of question, the answer could be as simple as

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Speaker 2: like a decimal. So when you're asking a really basic question,

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Speaker 2: you may think it's basic, But the fact is, like

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Speaker 2: so many of the more complex science, the things that

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Speaker 2: Daniel studies and takes years and years to understand, are

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Speaker 2: things that have come from these really basic questions that

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Speaker 2: we may still not even really know the objective answer

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Speaker 2: to exactly.

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Speaker 1: And those questions come from within us. You know, they

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Speaker 1: are not objective questions. There's no way to like rank

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Speaker 1: what are the most important questions in the universe. They

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Speaker 1: just come from our burning desire to know, and everybody's

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Speaker 1: different that way. The questions that I ask are different

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Speaker 1: from the questions other people asking. Hey, that's cool. And

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Speaker 1: before we dig into the topic of today's podcast, I

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Speaker 1: think we need to do a little bit of house

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Speaker 1: cleaning from the last time you and I met, because

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Speaker 1: we were talking about the fantastic and amazing Greek ancient

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Speaker 1: astronomical computer, the anti kit Theram mechanism, and we got

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Speaker 1: into a little tangent and made some jokes about chemistry.

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Speaker 1: Maybe you remember Katie comparing chemistry to torture. I think.

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Speaker 2: I haven't slept a wink since that episode. I've been

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Speaker 2: filled with remorse. Chemistry is not torture. I was merely

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Speaker 2: joking at my sort of own expense in terms of

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Speaker 2: my limited ability to do chemistry or figure out chemistry equations,

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Speaker 2: because it takes a very specialized knowledge and it can

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Speaker 2: be quite complex. But I mean, without chemistry, my two

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Speaker 2: favorite sciences, astrophysics and evolutionary biology, would not exist exactly.

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Speaker 1: And I was commenting about how my son, who's in

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Speaker 1: tenth grade and taking tenth grade, chemistry was asking me

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Speaker 1: questions that I couldn't answer, and that was complaining. Chemistry

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Speaker 1: didn't seem like to me the funnest science man. We

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Speaker 1: got a bunch of feedback from chemistry loving folks about

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Speaker 1: our comments, and so I just want to address them

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Speaker 1: really quickly. You know. On one hand, I think it's

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Speaker 1: good that people understand that science is personal. The kind

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Speaker 1: of science that I do, which involves a lot of programming,

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Speaker 1: would bore a lot of other people. And there's lots

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Speaker 1: of science I think is valuable, but I could never

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Speaker 1: spend my days like pipetting or working at an optical table.

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Speaker 1: The point is that we all have different tastes, and

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Speaker 1: that works out because we don't want everyone to be

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Speaker 1: doing the same kind of science. But I do think

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Speaker 1: that we went too far and hurt joking, because while

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Speaker 1: it's good to have different preferences, we shouldn't be negative

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Speaker 1: about the science that gets other people excited. I'm very

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Speaker 1: glad that chemistry is a thing and that people love

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Speaker 1: it because it helps us all understand the world better.

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Speaker 1: So chemists and fans of chemistry with respect, my apologies,

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Speaker 1: and please keep chemistrying.

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Speaker 2: Yes, I think chemistry is amazing. For an example, I

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Speaker 2: one summer was helping out with some oceanographic research just

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Speaker 2: by calibrating this instrument that would look at diatoms, these

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Speaker 2: very very teeny tiny microscopic organisms, And so I spend

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Speaker 2: a lot of time on a microscope just counting diatoms.

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Speaker 2: And every time I would tell people about it, they're like, oh,

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Speaker 2: that sounds awful, And I actually really liked it because

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Speaker 2: it was, I don't know, it was fun to see

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Speaker 2: the little guys going and also really fun to try

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Speaker 2: to calibrate this machine to do the work that I

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Speaker 2: was doing counting these little microscopic organisms. And so for

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Speaker 2: one person's you know, kind of tedious activity is another

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Speaker 2: person's fascinating fun activities. So yes, I really do not

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Speaker 2: have any native attitudes towards chemistry. Perhaps one might even

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Speaker 2: say I'm jealous of people who understand chemistry better than

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Speaker 2: I do.

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Speaker 1: That's what it is. And if you're curious how people

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Speaker 1: ended up in their particular subfield, everybody's got a fascinating

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Speaker 1: story about what they tried, what they were excited about,

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Speaker 1: how they ended up having their passion stimulated. It's a

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Speaker 1: really fun podcast called The people behind the science, where

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Speaker 1: you can go and hear people tell their stories about

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Speaker 1: how they got to do the kind of science they're doing.

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Speaker 1: There's even one featuring me, if you're curious. But let's

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Speaker 1: move on and talk about the topic of the day,

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Speaker 1: because today we are talking about a really fun question,

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Speaker 1: one that sounds really simple but reveals a lot of

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Speaker 1: fascinating physics and might even teach you something about the

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Speaker 1: way we see the world.

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Speaker 2: I am so excited, Daniel hit me with it. What

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Speaker 2: are we exploring?

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Speaker 1: So today in the podcast, we are asking the very simple,

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Speaker 1: the very amazing, the very revealing question, what color is

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Speaker 1: the sun yellow?

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Speaker 2: Podcast over roll credits No, No, it can't be that easy.

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Speaker 1: It in fact isn't that easy. And in finding the answer,

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Speaker 1: we're going to learn a lot about what it means

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Speaker 1: to be color, where color comes from, why different things

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Speaker 1: emit different colors, and why we see things in different colors,

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Speaker 1: and how most of the popular descriptions about the color

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Speaker 1: of the sun aren't exactly quite right. But before we

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Speaker 1: do that, let's hear what our listeners had to say

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Speaker 1: about the color of the sun. I love hearing what

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Speaker 1: people out there are thinking about a topic. Before we

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Speaker 1: dig into it, and I have a cadre of volunteers

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Speaker 1: who answer our questions so that you can understand what

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Speaker 1: people out there are thinking. And if you would like

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Speaker 1: to participate for future episodes of the podcast, please everybody's

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Speaker 1: welcome right to me to questions at Danielandjorge dot com.

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Speaker 1: So before you hear these answers, think about it for

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Speaker 1: a moment yourself. What color do you think the sun is?

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Speaker 1: Here's what people had to say in space.

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Speaker 2: I think it's really really really bright yellow.

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Speaker 3: I think because of the fusion inside the sun. It

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Speaker 3: gives off all type of photons and the reason it

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Speaker 3: looks a little bit more yellow is maybe how much

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Speaker 3: fusion is going on inside.

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Speaker 4: My guess is that the Sun is emitting radiation on

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Speaker 4: every wavelength and also in the visible spectrum. But when

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Speaker 4: we look at the Sun, we are seeing it's light

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Speaker 4: filtered by the atmosphere, and I believe that the atmosphere

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Speaker 4: scatters the blue wavelengths, So when we look at the Sun,

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Speaker 4: we see it yellow because it's missing that blue wavelength.

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Speaker 3: Yes, maybe there's like a wavelength that it's uh, you know,

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Speaker 3: spin out more light of that wavelength. I feel like

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Speaker 3: it's got to be some sort of yellowish white, or

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Speaker 3: maybe it's like all the colors that'd be cool.

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Speaker 2: I'm surprised nobody said it's the color of ouch, because

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Speaker 2: when I look at the sun it hurts, and I

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Speaker 2: have heard that one is not supposed to do that.

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Speaker 1: Yes, we probably should have put a disclaimer like, please

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Speaker 1: do not pause the podcast and go out and stare

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Speaker 1: at the sun. Not a good idea.

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Speaker 2: No, the sun is very powerful, lots of energy coming

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Speaker 2: from it. It's why it feels so warm, and you

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Speaker 2: might not want to stare at it.

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Speaker 1: Well, most of these answers basically say that it's yellow,

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Speaker 1: and some even specifically comment about where you are looking

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Speaker 1: at it from. Somebody says in space, it's really right yellow,

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Speaker 1: And that's a really insightful comment, because things do look

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Speaker 1: different down here on the surface of the Earth than

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Speaker 1: they do in space.

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Speaker 2: So why is that. I know we've got this atmosphere

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Speaker 2: around us, but what exactly does the atmosphere do to

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Speaker 2: make things look different here versus space? Because I know,

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Speaker 2: like down here, you look at the sky and it

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Speaker 2: can be blue, it can be gray, it can be pink.

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Speaker 2: I mean at night, it can be black. But when

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Speaker 2: you're in space, usually the sky is sort of black.

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Speaker 2: I guess it's not even a sky at that point.

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Speaker 2: It's sort of a void and then stuff is scattered

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Speaker 2: in it.

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Speaker 1: Yeah, that's really fun. If you are standing on the Moon,

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Speaker 1: what color is the sky? The sky on the Moon

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Speaker 1: is black because there's no atmosphere. We did a podcast

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Speaker 1: episode actually about the atmosphere of the Moon, which is

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Speaker 1: really fun. But the reason the sky is blue here

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Speaker 1: on Earth is that not all wavelengths, not all frequencies,

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Speaker 1: not all colors of light move through the atmosphere equally,

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Speaker 1: blue light gets bounced around more, and so if you're

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Speaker 1: on the surface of the Earth, some of the light

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Speaker 1: that otherwise wouldn't have hit your eye gets bounced down

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Speaker 1: to your eye, and it's mostly the blue light that

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Speaker 1: gets bounced around and ends up at your eyeball. So

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Speaker 1: on the Earth during the day we see the sun,

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Speaker 1: of course, very brightly, and all around it we see

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Speaker 1: blue light from the Sun that's been scattered off off

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Speaker 1: the atmosphere to our eyeballs. Now, if you're on the

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Speaker 1: Moon during the daytime, you see a very bright sun

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Speaker 1: and you see a black sky. So even during the day.

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Speaker 1: The sky is black on the Moon because there's almost

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Speaker 1: no atmosphere there to scatter the light down to your eyeballs.

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Speaker 1: So that tells you that when you're on Earth, you're

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Speaker 1: not seeing all the frequencies of light from the sun

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Speaker 1: the same way because the atmosphere doesn't treat them all equally.

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Speaker 2: So why is blue so special? Why isn't our sky

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Speaker 2: always red or green?

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Speaker 1: Yeah, it depends on the composition of our atmosphere, And

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Speaker 1: in fact, on Mars, the sky is red most because

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Speaker 1: the dust in the atmosphere which reflects that red light.

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Speaker 1: So on Mars during the daytime, the sky is red

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Speaker 1: and sunsets are actually blue.

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Speaker 2: Wow, that sounds pretty although I associate red skies with wildfires,

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Speaker 2: so I'd be mildly panicking when I'm on Mars. I'd

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Speaker 2: actually probably be mildly panicking on Mars for many different reasons.

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Speaker 1: But before we talk about why exactly that is, I

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Speaker 1: think we need to get down to the basics and understand,

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Speaker 1: like what it is we're talking about when we say

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Speaker 1: color and frequency and wavelength and why that even exists.

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Speaker 2: Color comes from paint cans, right, podcast over roll.

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Speaker 1: Credits Exactly did somebody paint you.

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Speaker 2: They must have when I was a baby.

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Speaker 1: Light in color is really actually super fascinating to understand

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Speaker 1: from a physics point of view. Fundamentally, you see color

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Speaker 1: when photons hit your eyeball. Right, so we're talking about

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Speaker 1: light hitting your eyeball somehow carrying that information about color.

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Speaker 1: So to understand color, you really have to understand what

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Speaker 1: is light and light We can think about either classically

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Speaker 1: as like wiggling electromagnetic fields, or we can think about

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Speaker 1: it from a quantum mechanical point of view, where there

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Speaker 1: are individual photons moving through a quantum field. But in

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Speaker 1: either way it's wiggling fields. And this can be hard

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Speaker 1: for people to visualize sometimes, but you know, just imagine

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Speaker 1: like an electron in space. Around that electron is an

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Speaker 1: electric field. That's what the electron uses to like push

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Speaker 1: on other electrons. If there's another electron somewhere far away,

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Speaker 1: the electric field from the first one pushes on the

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Speaker 1: other electron. That's how two electrons talk to each other. Now,

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Speaker 1: if you take that first electron and you wiggle it,

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Speaker 1: then the field wiggles with it. Right, It's sort of

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Speaker 1: like if you put your hand on the bathtub surface.

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Speaker 1: And you tap it, you generate a series of waves. Right,

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Speaker 1: the whole surface of the bathtub doesn't move down with

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Speaker 1: you instantly. In the same way, when you wiggle an electron,

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Speaker 1: the electric field doesn't move instantly. The part nearby moves

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Speaker 1: down first, then the next part, and the next part

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Speaker 1: in the next part. So the motion of the field

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Speaker 1: moves like a wave through the field as you wiggle

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Speaker 1: the electron.

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Speaker 2: So you're saying that light waves are sort of like

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Speaker 2: lazy rivers with a bunch of electrons and inner tubes,

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Speaker 2: wiggling the water around while they affect other electrons and

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Speaker 2: inner two.

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Speaker 1: Yeah, exactly. It's a little bit more energetic than that,

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Speaker 1: but exactly. So you can think about electrons generating ste

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Speaker 1: electric fields that don't change, and then when the electric

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Speaker 1: field needs to change. That's what a photon is. A

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Speaker 1: photon is a wiggle in the electromagnetic field. That's what

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Speaker 1: we mean when we say that that's what a photon is. Anyway,

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Speaker 1: light is oscillating electric fields, and you can oscillate it

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Speaker 1: different frequencies. You can move that electron really slowly and

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Speaker 1: have long wavelengths and low frequencies, or you can wiggle

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Speaker 1: it super duper fast, and you can get high frequencies

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Speaker 1: and short wavelengths. It just depends on how fast you're

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Speaker 1: wiggling the source of the field to generate those photons.

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Speaker 1: And this is like how antennas work. They have a

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Speaker 1: bunch of electrons in them and they wiggle them up

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Speaker 1: and down. They generate radio waves or cell phone towers

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Speaker 1: or whatever. The antenda on your phone receives that electromagnetic

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Speaker 1: radiation because it has electrons in it which get wiggled

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Speaker 1: by that radiation, those oscillating fields, and you receive those messages.

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Speaker 1: So in the end, light is just wiggling electromagnetic fields,

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Speaker 1: and every wiggle has a different frequency.

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Speaker 2: I think most of our senses are wiggly things that

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Speaker 2: end up hitting some kind of sensory cell like hearing site.

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Speaker 2: Maybe not touch, but sometimes I don't know. Electrons are

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Speaker 2: still wiggly, even like if I'm touching my table. Those

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Speaker 2: electrons aren't completely static, are they.

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Speaker 1: Yeah. That's a really interesting and insightful point that sight

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Speaker 1: and sound are both just oscillations in something. There are vibrations, right,

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Speaker 1: and that actually makes it easier to do things like

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Speaker 1: digitize them. You can take any song and break it

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Speaker 1: down into all the different frequencies that are involved in it,

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Speaker 1: and then you can record those frequencies and recreate it later.

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Speaker 1: You can do the same thing with images. You can say, oh,

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Speaker 1: what frequencies of light arrived, record those and regenerate them.

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Speaker 1: So it's sort of like a recipe for breaking down

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Speaker 1: your experience and recreating it. But taste and smell, as

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Speaker 1: you well know, Katie, are not like that. You have

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Speaker 1: like so many thousands of different receptors to different molecules,

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Speaker 1: and that's one reason why we haven't been able to

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Speaker 1: like digitize smell. You can't like email a smell to

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Speaker 1: some or a taste to somebody, or have like a

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Speaker 1: digital smell creator or taste creator on the other side

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Speaker 1: for you to receive it.

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Speaker 2: I mean, someday, maybe if we can figure out how

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Speaker 2: to like have a sort of tongue VR experience where

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Speaker 2: you use small electrical impulses to sort of trigger the

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Speaker 2: receptors on your tongue. Maybe, but we're not there yet.

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Speaker 1: We're not there yet, and maybe the chemistry folks can

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Speaker 1: help us with that. Right that seems like definitely a

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Speaker 1: chemistry based experience rather than a physics based sensation.

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Speaker 2: I will phosphate myself before the chemists if they can

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Speaker 2: bring us smell a vision.

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Speaker 1: But back to normal vision. We have all these different

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Speaker 1: frequencies of light. So when you get a beam of light,

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Speaker 1: for example, like a laser pulse, it has photons of

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Speaker 1: a specific frequency in it, right, and so one photon

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Speaker 1: can have that frequency, another photon can have the other frequency.

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Speaker 1: Here's where we start to talk about the quantum mechanical

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Speaker 1: nature of light. So far, we've just been saying it's

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Speaker 1: ripples and the electromagnet field. That's like the classical view.

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Speaker 1: That's what Maxwell thought one hundred and fifty years ago.

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Speaker 1: Then we realize that you have to actually quantize you

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Speaker 1: and break it into pieces. You don't just get like

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Speaker 1: a whole massive wave in the field. It's broken into

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Speaker 1: these little packets, and each one has a different frequency,

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Speaker 1: but you can still think of them as like little ripples.

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Speaker 1: It's just ripples in a quantum field instead of a

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Speaker 1: classical field.

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Speaker 2: So these different frequencies will basically be different colors that

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Speaker 2: we see, right exactly.

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Speaker 1: Each frequency means a different energy in the photon, which

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Speaker 1: we perceive as different colors. And it's important to understand

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Speaker 1: that photons are quantized in the number of photons you

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Speaker 1: can receive. You can receive one photon or seven photons,

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Speaker 1: but not three point two photons. But they're not quantized

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Speaker 1: in the energy. There's like an infinite spectrum of possible energies.

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Speaker 1: Any number you can imagine for a wavelength of light,

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Speaker 1: you could have a photon of that wavelength. There's no

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Speaker 1: frequencies that are not allowed. There's an infinite number of

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Speaker 1: frequencies between like five hundred and six hundred nanometers, right,

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Speaker 1: So they're quantized only in the number of photons you

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Speaker 1: can receive, not in the frequencies, which means is an

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Speaker 1: infinite number of different kinds of photons that you can see.

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Speaker 1: But that doesn't mean that there's an infinite number of

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Speaker 1: colors that you can see. Right. While color is connected

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Speaker 1: to frequency, it's actually subtly different. Concept is a little

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Speaker 1: bit more biological and philosophical.

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Speaker 2: Yeah, it is interesting because when you look even at

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Speaker 2: just life on Earth, right, so many different animals have

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Speaker 2: so many different ways to perceive color, and they will

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Speaker 2: perceive the world differently just in terms of color. And

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Speaker 2: that's because the eye and the brain is very different

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Speaker 2: for many different species, and so humans we see color

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Speaker 2: a certain way, our brains interpreted a certain way. But

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Speaker 2: even among humans we have variation in how people perceive color.

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Speaker 2: But before we dive too deep inside of the eyeball,

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Speaker 2: let's take a quick break, rest our eyes, and when

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Speaker 2: we get back we'll talk about how color is a

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Speaker 2: product of both biology, are psychology, and philosophy, And don't

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Speaker 2: forget chemistry and chemistry. Don't you dare forget chemistry? And

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Speaker 2: we are back, and I have been closing my eyes

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Speaker 2: and trying to think of a new color that I've

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Speaker 2: never seen before, and I can't do it.

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Speaker 1: That's a really fascinating sort of philosophy question, and it

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Speaker 1: really gets to the heart of like what color is

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Speaker 1: because a lot of people imagine that photons are colored.

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Speaker 1: They're like a photon flying through space is either a

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Speaker 1: red photon or a green photon or a blue photon.

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Speaker 1: And in shorthand that's fine. We can attach labels to

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Speaker 1: photons and say they're a color that's connected to their frequency,

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Speaker 1: But the photons themselves don't have color, right, Like different

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Speaker 1: animals will see the same photon and have a different experience.

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Speaker 1: The color is actually your experience of the photon, right

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Speaker 1: the way, like your experience of sugar or your experience

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Speaker 1: of fats are not a characteristic of that molecule. They're

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Speaker 1: characteristic of your experience of your brain chemistry giving you

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Speaker 1: a sensation.

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Speaker 2: Yeah, two people can taste the same dish and one

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Speaker 2: person can love it and the other person can think

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Speaker 2: it tastes disgusting, and it's the same food. And you know,

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Speaker 2: we were essentially quite similar in terms of our biology.

437
00:23:34,960 --> 00:23:39,480
Speaker 2: We have tongues and eyes generally, but both the structure

438
00:23:39,480 --> 00:23:42,480
Speaker 2: of the eye and the structure of the brain can

439
00:23:42,560 --> 00:23:46,159
Speaker 2: be different, as can things like our sort of lived

440
00:23:46,200 --> 00:23:50,040
Speaker 2: experience and how that influences how we see things or

441
00:23:50,080 --> 00:23:57,240
Speaker 2: taste things. So even among humans, when you look at green, Daniel,

442
00:23:57,320 --> 00:24:01,800
Speaker 2: and I look at green, we may have different experiences

443
00:24:01,840 --> 00:24:04,600
Speaker 2: of what green is, and it's so hard to know

444
00:24:05,080 --> 00:24:08,080
Speaker 2: whether it's the same green or a different green because

445
00:24:08,119 --> 00:24:10,240
Speaker 2: if I'm like, well, yeah, it's green like an apple,

446
00:24:10,600 --> 00:24:13,720
Speaker 2: and You're like, yeah, we haven't gotten any closer to

447
00:24:13,760 --> 00:24:16,480
Speaker 2: answering the question of whether it's the same green because

448
00:24:16,840 --> 00:24:19,439
Speaker 2: we may just have different perceptions of what an apple

449
00:24:19,520 --> 00:24:20,000
Speaker 2: looks like.

450
00:24:20,359 --> 00:24:23,480
Speaker 1: Right, And before we dig into like the deep brain philosophy.

451
00:24:23,800 --> 00:24:26,000
Speaker 1: Let's take one step back and trace the path of

452
00:24:26,040 --> 00:24:28,960
Speaker 1: the information. Like the photon hits my eyeball and it

453
00:24:29,000 --> 00:24:32,280
Speaker 1: has a certain frequency. Do you know the biology of

454
00:24:32,359 --> 00:24:35,840
Speaker 1: how it then generates like a signal in the nerve, Like,

455
00:24:35,920 --> 00:24:38,439
Speaker 1: how do you go from the photon to the signal

456
00:24:38,480 --> 00:24:39,920
Speaker 1: of the optical nerve to your brain.

457
00:24:40,240 --> 00:24:44,399
Speaker 2: Yeah. So we have sensory cells at the back of

458
00:24:44,400 --> 00:24:51,120
Speaker 2: our eyes called rods and cones, and the rods generally

459
00:24:51,160 --> 00:24:55,320
Speaker 2: help us see light or not light, so they really

460
00:24:55,359 --> 00:24:58,560
Speaker 2: help us see at night in low levels of light.

461
00:24:58,920 --> 00:25:04,199
Speaker 2: But the cones are responsive to those light photons. And

462
00:25:04,240 --> 00:25:07,760
Speaker 2: so what actually happens on the very very teeny tiny

463
00:25:07,800 --> 00:25:12,360
Speaker 2: microscopic level is a protein structure in the cone will

464
00:25:12,400 --> 00:25:16,119
Speaker 2: actually kind of snap when it is attacked with a

465
00:25:16,200 --> 00:25:20,080
Speaker 2: sort of certain level of energy from this photon, and

466
00:25:20,480 --> 00:25:24,480
Speaker 2: it will trigger a neural cell that is connected to

467
00:25:24,800 --> 00:25:28,000
Speaker 2: that photoreceptive cell, and then there is a whole sort

468
00:25:28,000 --> 00:25:32,320
Speaker 2: of chain reaction to the bundle of nerves that go

469
00:25:32,480 --> 00:25:35,240
Speaker 2: from the back of the eye and then go to

470
00:25:35,440 --> 00:25:38,880
Speaker 2: your brain. So that is sort of how each individual

471
00:25:39,000 --> 00:25:42,560
Speaker 2: cone works. Like you have that like snapping action of

472
00:25:42,560 --> 00:25:48,080
Speaker 2: that protein once it is activated by specific frequencies of

473
00:25:48,160 --> 00:25:52,440
Speaker 2: these photons, and then the color you see isn't from

474
00:25:52,440 --> 00:25:55,720
Speaker 2: that one individual sensory cell, it is from sort of

475
00:25:55,760 --> 00:26:00,560
Speaker 2: the average of these the level of activations these have

476
00:26:00,800 --> 00:26:05,080
Speaker 2: in combination, and all of that information goes through your

477
00:26:05,119 --> 00:26:08,920
Speaker 2: nerve from the eye to your occipital lobe and it's

478
00:26:08,960 --> 00:26:12,560
Speaker 2: interpreted in your occipital lobe. And so you have this

479
00:26:12,800 --> 00:26:16,800
Speaker 2: interface between the kind of structure of your eye and

480
00:26:16,840 --> 00:26:20,640
Speaker 2: the cones and your brain to then interpret what that

481
00:26:20,720 --> 00:26:23,159
Speaker 2: color is. And that's why we don't just see like

482
00:26:23,600 --> 00:26:27,879
Speaker 2: blue or red or green. We see a spectrum of color.

483
00:26:28,240 --> 00:26:32,440
Speaker 2: We see different shades, different darknesses, different depths and qualities

484
00:26:32,480 --> 00:26:32,960
Speaker 2: of color.

485
00:26:33,119 --> 00:26:35,040
Speaker 1: Yeah, I think it's really interesting. I used to think

486
00:26:35,080 --> 00:26:38,320
Speaker 1: about it working like a TV screen or a computer screen.

487
00:26:38,400 --> 00:26:41,360
Speaker 1: We had like RGB and you had a certain number

488
00:26:41,359 --> 00:26:43,000
Speaker 1: of photons in each one and you could mix them

489
00:26:43,040 --> 00:26:44,959
Speaker 1: to get any color. But it is a little bit

490
00:26:45,000 --> 00:26:46,959
Speaker 1: more sull than that. If you look at like the

491
00:26:47,000 --> 00:26:49,840
Speaker 1: wavelength of visible wavelength, it starts at like four hundred

492
00:26:49,920 --> 00:26:52,320
Speaker 1: and goes up to like seven hundred nanometers. Each kind

493
00:26:52,359 --> 00:26:55,080
Speaker 1: of cone responds better to a different frequency, Like there's

494
00:26:55,080 --> 00:26:57,080
Speaker 1: one kind of cone that peaks at like four point fifty,

495
00:26:57,280 --> 00:26:59,720
Speaker 1: but it can still see photons up to like five hundred.

496
00:27:00,080 --> 00:27:03,000
Speaker 2: Yeah, there's overlap, a good amount of overlap.

497
00:27:03,119 --> 00:27:05,040
Speaker 1: Yeah, they do overlap, and all of them have a

498
00:27:05,080 --> 00:27:07,360
Speaker 1: width to them, And so what your brain is doing

499
00:27:07,440 --> 00:27:09,720
Speaker 1: is some kind of interpolation. It's like, well, I saw

500
00:27:09,840 --> 00:27:12,960
Speaker 1: this kind respondibily brightly and that kind very dimly, So

501
00:27:13,000 --> 00:27:15,960
Speaker 1: it must be a lower frequency photon, or must be

502
00:27:15,960 --> 00:27:18,160
Speaker 1: a higher frequency photon. And as you say, it does

503
00:27:18,160 --> 00:27:21,520
Speaker 1: some calculation in there, and like then gives you an experience,

504
00:27:21,920 --> 00:27:25,920
Speaker 1: and that experience comes from its calculation, its interpretation. Right,

505
00:27:25,960 --> 00:27:29,680
Speaker 1: that color is in your mind, it's not in the photon.

506
00:27:30,000 --> 00:27:35,000
Speaker 2: Yeah, it's really interesting because difference in color perception and humans, say,

507
00:27:35,040 --> 00:27:38,200
Speaker 2: for people who have color blindness, it can be due

508
00:27:38,280 --> 00:27:42,480
Speaker 2: to basically the range of frequencies that those cones pick

509
00:27:42,560 --> 00:27:46,760
Speaker 2: up can either overlap more, which makes it harder to

510
00:27:46,840 --> 00:27:50,080
Speaker 2: distinguish between two different colors because you have more overlap

511
00:27:50,119 --> 00:27:53,560
Speaker 2: of these cones, or they can kind of be shifted

512
00:27:53,640 --> 00:27:55,760
Speaker 2: on the spectrum of where you are picking it up,

513
00:27:55,840 --> 00:27:59,280
Speaker 2: so you don't pick up certain frequencies as well. So

514
00:27:59,560 --> 00:28:04,280
Speaker 2: it's not so simple as like an operator switchboard for

515
00:28:04,640 --> 00:28:10,160
Speaker 2: turning selecting colors. It is a spectrum experience, but it's

516
00:28:10,200 --> 00:28:14,239
Speaker 2: also one that differs from person to person and is

517
00:28:14,480 --> 00:28:17,240
Speaker 2: very observable in cases of say like color blindness.

518
00:28:17,359 --> 00:28:19,239
Speaker 1: And there are even people out there who have a

519
00:28:19,359 --> 00:28:24,040
Speaker 1: fourth kind of cone. They're called tetrachromats, so instead of

520
00:28:24,080 --> 00:28:26,680
Speaker 1: having three cones in their eye, they have four. When

521
00:28:26,680 --> 00:28:28,639
Speaker 1: I first learned about this, I thought, oh, my gosh,

522
00:28:28,680 --> 00:28:32,560
Speaker 1: that's amazing. Is there like a fourth primary color that

523
00:28:32,600 --> 00:28:35,240
Speaker 1: they can see that we can't, some color out there

524
00:28:35,280 --> 00:28:38,120
Speaker 1: that they experience that we never do. It's actually a

525
00:28:38,160 --> 00:28:41,600
Speaker 1: little bit more complicated and less exciting than that. They

526
00:28:41,680 --> 00:28:43,880
Speaker 1: have four kinds of cones, so they sort of sample

527
00:28:43,960 --> 00:28:47,000
Speaker 1: the spectrum four ways instead of three, and that just

528
00:28:47,080 --> 00:28:49,760
Speaker 1: lets them interpolate better. There's not like a new primary

529
00:28:49,800 --> 00:28:52,080
Speaker 1: color that they can see that we can't. It's just

530
00:28:52,120 --> 00:28:54,960
Speaker 1: like they have like more resolution on their ruler, and

531
00:28:55,040 --> 00:28:58,320
Speaker 1: so they're better able to distinguish colors. Like you put

532
00:28:58,360 --> 00:29:00,800
Speaker 1: two very close shades of green in front of people.

533
00:29:00,880 --> 00:29:03,000
Speaker 1: Some people can't tell the difference and some people can.

534
00:29:03,400 --> 00:29:07,080
Speaker 1: And tetrachromats, these people with four cones are especially good

535
00:29:07,120 --> 00:29:07,320
Speaker 1: at that.

536
00:29:07,720 --> 00:29:10,840
Speaker 2: Yeah, it's more granular. All throughout the animal kingdom, we

537
00:29:10,920 --> 00:29:16,880
Speaker 2: have monochromats, die chromats, trichromats, which is generally humans, and

538
00:29:16,920 --> 00:29:21,320
Speaker 2: then tetrachromats, which is some animals and some humans too.

539
00:29:21,920 --> 00:29:24,840
Speaker 2: And so it is really interesting because we think of

540
00:29:25,080 --> 00:29:28,240
Speaker 2: vision like in this sense of like, oh, a monochromat

541
00:29:28,320 --> 00:29:32,240
Speaker 2: must have a very boring kind of visual experience because

542
00:29:32,320 --> 00:29:35,640
Speaker 2: they're really only seeing you know, this very limited range.

543
00:29:35,720 --> 00:29:38,800
Speaker 2: They're not seeing color like we do. But that's not

544
00:29:38,880 --> 00:29:41,680
Speaker 2: necessarily true. So a monochromat has only one kind of

545
00:29:41,680 --> 00:29:45,880
Speaker 2: photoreceptive cell to generally like a rod, something like an

546
00:29:45,920 --> 00:29:51,680
Speaker 2: octopus is actually a monochromat, and so we think that, oh, well,

547
00:29:51,720 --> 00:29:54,280
Speaker 2: it just kind of season black and white. It must be,

548
00:29:54,600 --> 00:29:57,120
Speaker 2: you know, not exciting to be an octopus and have

549
00:29:57,160 --> 00:30:02,520
Speaker 2: octopus vision. But there's also some speculation that the octopus's

550
00:30:02,680 --> 00:30:05,360
Speaker 2: unique eye shape. Have you noticed how that like pupil

551
00:30:05,360 --> 00:30:08,360
Speaker 2: is sort of stretched and elongated. It might be that

552
00:30:08,440 --> 00:30:13,680
Speaker 2: way so that it actually measures the focal length of

553
00:30:13,720 --> 00:30:16,400
Speaker 2: an object as it hits the eye. It creates this

554
00:30:16,520 --> 00:30:19,640
Speaker 2: sort of blurriness or an out of focus from different

555
00:30:19,920 --> 00:30:23,640
Speaker 2: sort of like wavelengths of light. And so it could

556
00:30:23,680 --> 00:30:27,200
Speaker 2: be that with only rods, they are still able to

557
00:30:27,320 --> 00:30:31,520
Speaker 2: have a brain's response to color because they are actually

558
00:30:31,560 --> 00:30:34,840
Speaker 2: seeing the wavelengths hitting at different sort of angles on

559
00:30:35,000 --> 00:30:37,760
Speaker 2: the eye based on its shape, could actually be interpreted

560
00:30:37,800 --> 00:30:40,360
Speaker 2: as colors. We don't know. We have never been able

561
00:30:40,360 --> 00:30:42,719
Speaker 2: to figure out how to ask an octopus whether it's

562
00:30:42,720 --> 00:30:45,880
Speaker 2: season color. I'm sure there will be studies to see

563
00:30:46,240 --> 00:30:51,080
Speaker 2: whether octopuses can detect color, but it's very complicated. The

564
00:30:51,760 --> 00:30:55,680
Speaker 2: power of the brain is in being able to interpret

565
00:30:55,720 --> 00:30:58,280
Speaker 2: sensory information. So as long as you're getting that information

566
00:30:58,400 --> 00:31:01,080
Speaker 2: to the brain somehow, even if it is a different

567
00:31:01,080 --> 00:31:04,080
Speaker 2: way than say, like humans do, you could still be

568
00:31:04,200 --> 00:31:07,320
Speaker 2: perceiving color, but just using very different hardware.

569
00:31:07,560 --> 00:31:10,280
Speaker 1: Yeah, and the hardware and software is sort of important.

570
00:31:10,320 --> 00:31:12,640
Speaker 1: I was reading the mantis strip has an incredible number

571
00:31:12,640 --> 00:31:16,280
Speaker 1: of different kinds of cones, like maybe even up to twenty,

572
00:31:16,680 --> 00:31:19,280
Speaker 1: but it has no like processing power behind it. The

573
00:31:19,320 --> 00:31:22,160
Speaker 1: brain behind it is very simple, and so even though

574
00:31:22,160 --> 00:31:24,600
Speaker 1: it has so many different kinds of cones, its experience

575
00:31:24,600 --> 00:31:27,120
Speaker 1: of color might just be that it can only see

576
00:31:27,160 --> 00:31:29,640
Speaker 1: one color per cone. It's just like an on off

577
00:31:30,080 --> 00:31:33,360
Speaker 1: because it doesn't have the interpolation power that our brain does.

578
00:31:33,640 --> 00:31:36,640
Speaker 2: And this may work for the mantistrim because it gives

579
00:31:36,680 --> 00:31:40,520
Speaker 2: it really really lightning fast reflexes and the ability to

580
00:31:40,600 --> 00:31:43,800
Speaker 2: detect something that is in its perfhery really easily and

581
00:31:43,840 --> 00:31:47,800
Speaker 2: really quickly. So it's going for speed over say the

582
00:31:47,840 --> 00:31:50,800
Speaker 2: definition of its vision. But that works for the mantistrimp

583
00:31:50,800 --> 00:31:52,760
Speaker 2: because that's what it needs, whereas.

584
00:31:52,400 --> 00:31:54,480
Speaker 1: We humans are slow and we like to think, hmmm,

585
00:31:54,600 --> 00:31:57,000
Speaker 1: what is that really? Is that a red or is

586
00:31:57,040 --> 00:31:59,600
Speaker 1: that a maroon? I have all these arguments with my daughter,

587
00:31:59,720 --> 00:32:01,680
Speaker 1: but like what is blue and what is green? And

588
00:32:01,760 --> 00:32:04,640
Speaker 1: I think we see colors differently. At leads to really

589
00:32:04,680 --> 00:32:09,120
Speaker 1: fascinating philosophy questions about how people's experiences might be different.

590
00:32:09,320 --> 00:32:11,960
Speaker 1: And this is famous thought experiment about the color red.

591
00:32:12,320 --> 00:32:14,360
Speaker 1: You know, if you put somebody in a box and

592
00:32:14,520 --> 00:32:17,560
Speaker 1: never give them the experience of red, could you then

593
00:32:17,640 --> 00:32:20,080
Speaker 1: describe red to them in a way that when they

594
00:32:20,120 --> 00:32:21,880
Speaker 1: came out of the box they would see a rose

595
00:32:21,920 --> 00:32:23,640
Speaker 1: and be like, oh, that's what you meant? You know?

596
00:32:23,720 --> 00:32:26,600
Speaker 1: Is there a way to capture redness other than the

597
00:32:26,640 --> 00:32:30,040
Speaker 1: actual experience of red? Anyway, it's a whole fun question

598
00:32:30,080 --> 00:32:31,880
Speaker 1: in philosophy that we don't have time to dig into.

599
00:32:32,000 --> 00:32:34,880
Speaker 1: Today we're thinking about the color of the sun, and

600
00:32:34,920 --> 00:32:37,960
Speaker 1: now we understand that color is an experience in our mind,

601
00:32:38,040 --> 00:32:41,560
Speaker 1: but it's linked to this physical property that photons have

602
00:32:41,600 --> 00:32:45,280
Speaker 1: different frequencies and we experience those frequencies in different ways.

603
00:32:45,320 --> 00:32:47,960
Speaker 1: So really we need to think about, like why photons

604
00:32:48,000 --> 00:32:51,719
Speaker 1: have different frequencies so that we can understand what frequency

605
00:32:51,760 --> 00:32:53,440
Speaker 1: of light the sun generates.

606
00:32:53,760 --> 00:32:56,320
Speaker 2: Yeah, like this kind of gets back to my question

607
00:32:56,440 --> 00:32:59,320
Speaker 2: earlier of like why is blue so special when we

608
00:32:59,360 --> 00:33:02,160
Speaker 2: see like why why does that interact with our atmosphere,

609
00:33:02,280 --> 00:33:04,560
Speaker 2: not say red or green? Why do they have these

610
00:33:04,600 --> 00:33:06,680
Speaker 2: different wavelengths? What is going on?

611
00:33:07,080 --> 00:33:09,120
Speaker 1: Yeah, you might wonder like why are some things blue

612
00:33:09,200 --> 00:33:11,600
Speaker 1: and other things green? And there's really a couple of

613
00:33:11,600 --> 00:33:14,640
Speaker 1: different reasons, and they're both actually due to quantum mechanics,

614
00:33:14,760 --> 00:33:17,520
Speaker 1: which is super awesome. And the first is that there

615
00:33:17,560 --> 00:33:22,240
Speaker 1: are certain energy levels allowed to electrons. Like electrons flying

616
00:33:22,280 --> 00:33:25,200
Speaker 1: through space, we call them free particles. They can have

617
00:33:25,280 --> 00:33:28,000
Speaker 1: any energy they want, they can have super high energy,

618
00:33:28,000 --> 00:33:30,320
Speaker 1: they can have no energy. They can do whatever they like.

619
00:33:30,560 --> 00:33:33,080
Speaker 1: They are not bound by anything. But when you put

620
00:33:33,080 --> 00:33:36,480
Speaker 1: an electron into an atom, there are only certain solutions

621
00:33:36,480 --> 00:33:39,200
Speaker 1: to the Shorteninger equation to the quantum mechanical equation that

622
00:33:39,280 --> 00:33:42,360
Speaker 1: tells an electron what it can and cannot do. And

623
00:33:42,400 --> 00:33:44,800
Speaker 1: because you are binding the electron, you're like putting it

624
00:33:44,840 --> 00:33:48,400
Speaker 1: in a little well, only certain solutions work, and that's

625
00:33:48,400 --> 00:33:52,240
Speaker 1: where quantization comes from. It comes from confining the electron

626
00:33:52,400 --> 00:33:54,640
Speaker 1: to the atom, and you end up with this like

627
00:33:54,840 --> 00:33:58,640
Speaker 1: ladder of possible energy levels. So if you've studied some chemistry,

628
00:33:58,680 --> 00:34:02,200
Speaker 1: for example, and extremely important and valuable science, then you've

629
00:34:02,400 --> 00:34:05,400
Speaker 1: understood that, like around an atom, an electron can have

630
00:34:05,480 --> 00:34:07,880
Speaker 1: a certain energy level or the next one or the

631
00:34:07,920 --> 00:34:10,640
Speaker 1: next one, but it can't be in between. So there's

632
00:34:10,680 --> 00:34:13,440
Speaker 1: this ladder of energy levels for an electron.

633
00:34:13,600 --> 00:34:15,560
Speaker 2: Maybe this is why I'm so jealous of people who

634
00:34:15,640 --> 00:34:20,080
Speaker 2: can understand chemistry well, because I've always been confused why

635
00:34:20,160 --> 00:34:24,680
Speaker 2: there are these different ladder stages for the electron to

636
00:34:24,719 --> 00:34:27,640
Speaker 2: sort of jump into, and why can't it go in between.

637
00:34:27,920 --> 00:34:30,520
Speaker 1: The technical answer is that those are the only solutions

638
00:34:30,520 --> 00:34:33,719
Speaker 1: to the Shorting air equation. The intuitive answer is like,

639
00:34:33,840 --> 00:34:36,400
Speaker 1: why are those the only solutions to the Shorting air equation?

640
00:34:36,920 --> 00:34:39,360
Speaker 1: And there's like sort of a cartoon picture, which is helpful,

641
00:34:39,440 --> 00:34:43,160
Speaker 1: it's not technically accurate, which is like imagine electrons wave

642
00:34:43,200 --> 00:34:45,800
Speaker 1: wiggling around the central proton. It like wiggles up and

643
00:34:45,840 --> 00:34:48,400
Speaker 1: wiggles down, and wiggles up and wiggles down. Energy levels

644
00:34:48,440 --> 00:34:51,960
Speaker 1: the electron have are those where it completes an integer

645
00:34:52,120 --> 00:34:54,680
Speaker 1: number of half wavelengths, so that when it gets back

646
00:34:54,719 --> 00:34:57,360
Speaker 1: to where it was, it sort of matches up to

647
00:34:57,440 --> 00:35:00,359
Speaker 1: its previous wiggle. It's sort of like a standing it

648
00:35:00,360 --> 00:35:04,680
Speaker 1: reinforces itself. Anything else it ends up canceling itself out.

649
00:35:04,840 --> 00:35:06,960
Speaker 1: And so you can sort of like fit a certain

650
00:35:07,080 --> 00:35:09,719
Speaker 1: number of half wavelengths sort of the same way when

651
00:35:09,760 --> 00:35:12,400
Speaker 1: you pluck a guitar string right, it can oscillate in

652
00:35:12,440 --> 00:35:14,799
Speaker 1: different modes and like the whole thing can move up

653
00:35:14,840 --> 00:35:16,640
Speaker 1: and down, or you can have a node in the

654
00:35:16,680 --> 00:35:18,400
Speaker 1: middle where one side is moving up and the other

655
00:35:18,440 --> 00:35:20,520
Speaker 1: side is moving down. Or you can have two nodes,

656
00:35:20,760 --> 00:35:23,839
Speaker 1: so you have like three half wavelengths. There's into your

657
00:35:23,920 --> 00:35:27,160
Speaker 1: number of ways to fit them into your fixed length

658
00:35:27,239 --> 00:35:29,879
Speaker 1: guitar string. And that's actually a pretty good example because

659
00:35:30,040 --> 00:35:32,320
Speaker 1: you're confining the wiggle of the string because you've nailed

660
00:35:32,360 --> 00:35:34,400
Speaker 1: the string down on the two sides of the guitar.

661
00:35:34,800 --> 00:35:37,640
Speaker 1: And here we're confining the electron to the atom and

662
00:35:37,680 --> 00:35:41,480
Speaker 1: restricting it to certain states, and that has important consequences

663
00:35:41,520 --> 00:35:44,360
Speaker 1: for the color of that atom, because the light generated

664
00:35:44,360 --> 00:35:48,400
Speaker 1: by that atom comes from electrons moving down energy levels.

665
00:35:48,400 --> 00:35:51,200
Speaker 1: An electron gets excited and it absorbs some energy, and

666
00:35:51,200 --> 00:35:53,399
Speaker 1: it jumps up a few energy levels. A moment later,

667
00:35:53,440 --> 00:35:55,320
Speaker 1: it's going to relax and come back down to the

668
00:35:55,360 --> 00:35:57,839
Speaker 1: lowest energy level, because that's what nature likes to do,

669
00:35:57,920 --> 00:36:00,839
Speaker 1: is relax down to lower energy levels spread things out.

670
00:36:00,880 --> 00:36:02,319
Speaker 1: When it does that, it gives up some of that

671
00:36:02,440 --> 00:36:04,919
Speaker 1: energy in the form of a photon and emits light.

672
00:36:05,560 --> 00:36:08,680
Speaker 1: So that light has a certain energy, which is due

673
00:36:08,680 --> 00:36:11,320
Speaker 1: to the difference in its higher energy level and the

674
00:36:11,360 --> 00:36:14,200
Speaker 1: lower energy level. Jumps down the ladder and it gets

675
00:36:14,239 --> 00:36:16,799
Speaker 1: a certain amount of energy, and that's always going to

676
00:36:16,800 --> 00:36:19,480
Speaker 1: be the same frequency. Every time it makes a certain jump,

677
00:36:19,520 --> 00:36:22,000
Speaker 1: from like three to two or from three to one,

678
00:36:22,280 --> 00:36:25,239
Speaker 1: it's always going to have exactly the same energy and

679
00:36:25,640 --> 00:36:27,960
Speaker 1: exactly the same frequency of photons.

680
00:36:28,000 --> 00:36:32,960
Speaker 2: So you'll have photons that are sort of imbued with

681
00:36:33,120 --> 00:36:37,759
Speaker 2: different energy based on the way that this electron has

682
00:36:37,840 --> 00:36:40,840
Speaker 2: jumped down from the ladder exactly.

683
00:36:41,200 --> 00:36:44,680
Speaker 1: And every atom has a different ladder, So the spacings

684
00:36:44,680 --> 00:36:47,759
Speaker 1: of the ladder for hydrogen are different than the spacings

685
00:36:47,800 --> 00:36:50,960
Speaker 1: of the ladder for zinc, for example, or for copper.

686
00:36:51,280 --> 00:36:55,120
Speaker 1: So copper will emit photons of different frequency than zinc will,

687
00:36:55,200 --> 00:36:58,160
Speaker 1: or hydrogen will, or oxygen will. And this is actually

688
00:36:58,239 --> 00:37:01,440
Speaker 1: super valuable and important because when you're looking, for example,

689
00:37:01,440 --> 00:37:04,319
Speaker 1: at light from a distant star and you're wondering, Hm,

690
00:37:04,840 --> 00:37:07,640
Speaker 1: what's that star made out of, what's in its atmosphere,

691
00:37:08,080 --> 00:37:11,040
Speaker 1: what is burning in its core? You can tell without

692
00:37:11,040 --> 00:37:13,560
Speaker 1: ever going to that star, just by looking at the

693
00:37:13,640 --> 00:37:17,000
Speaker 1: light that it emits. There's a fingerprint for hydrogen, and

694
00:37:17,040 --> 00:37:20,080
Speaker 1: a fingerprint for zinc, and a fingerprint for oxygen, and

695
00:37:20,120 --> 00:37:22,880
Speaker 1: you can see those fingerprints in its spectrum. If you

696
00:37:22,920 --> 00:37:25,600
Speaker 1: count up the number of photons you get at different frequencies,

697
00:37:25,640 --> 00:37:28,120
Speaker 1: you'll be like, oh, to get these peaks, to get

698
00:37:28,200 --> 00:37:30,719
Speaker 1: light at these frequencies, you have to have copper. And

699
00:37:30,760 --> 00:37:33,799
Speaker 1: so we can tell what distant stars and distant planetary

700
00:37:33,840 --> 00:37:36,919
Speaker 1: atmospheres are made out of just by looking at the

701
00:37:36,960 --> 00:37:39,279
Speaker 1: color of the light, the frequency of the light that

702
00:37:39,320 --> 00:37:39,800
Speaker 1: they emit.

703
00:37:40,160 --> 00:37:43,279
Speaker 2: Is this kind of how classic neon lights work. You

704
00:37:43,320 --> 00:37:46,160
Speaker 2: can fill a glass tube with sort of different chemicals

705
00:37:46,239 --> 00:37:49,400
Speaker 2: or different atoms, and then once you put some energy

706
00:37:49,400 --> 00:37:51,280
Speaker 2: into it, it produces a different color.

707
00:37:51,480 --> 00:37:53,959
Speaker 1: Exactly. A neon is an element that tends to glow

708
00:37:53,960 --> 00:37:56,880
Speaker 1: at certain colors, and so that's exactly right. You're filling

709
00:37:56,880 --> 00:37:59,680
Speaker 1: it with a hot plasma, a gas that's become excited

710
00:37:59,719 --> 00:38:02,799
Speaker 1: and glows at certain energies. And to get back to

711
00:38:02,800 --> 00:38:05,520
Speaker 1: your question of like why are something's blue and something's red,

712
00:38:05,560 --> 00:38:08,000
Speaker 1: Like your T shirt is not blue because it's glowing.

713
00:38:08,280 --> 00:38:11,719
Speaker 1: It's actually the opposite process happening there. It's absorbing. Like

714
00:38:11,760 --> 00:38:15,440
Speaker 1: when light hits your T shirt, the atoms in that

715
00:38:15,520 --> 00:38:18,680
Speaker 1: T shirt can absorb photons of certain energy. It's like

716
00:38:18,719 --> 00:38:21,640
Speaker 1: the reverse process of electrons jumping down the ladder and

717
00:38:21,680 --> 00:38:26,000
Speaker 1: giving off photons. The reverse process is them absorbing photons

718
00:38:26,040 --> 00:38:29,120
Speaker 1: of certain energy and jumping up the ladder. So when

719
00:38:29,200 --> 00:38:32,120
Speaker 1: light hits your T shirt, it can absorb only certain

720
00:38:32,160 --> 00:38:36,160
Speaker 1: frequencies of light, only ones that match the energy levels

721
00:38:36,160 --> 00:38:39,120
Speaker 1: of the electrons in your T shirt, and so those

722
00:38:39,120 --> 00:38:42,080
Speaker 1: things get absorbed. Anything else is not absorbed, and so

723
00:38:42,120 --> 00:38:43,279
Speaker 1: it can be reflected.

724
00:38:43,560 --> 00:38:47,200
Speaker 2: So my shirt is basically every color except blue.

725
00:38:47,440 --> 00:38:49,920
Speaker 1: Well, what it means to be blue is to reflect

726
00:38:50,000 --> 00:38:53,719
Speaker 1: blue light. Right, It's absorbing all the other photons and

727
00:38:53,800 --> 00:38:57,200
Speaker 1: reflecting blue light, and so you see it as blue.

728
00:38:57,280 --> 00:38:59,319
Speaker 1: When we call something blue, what we really mean is

729
00:38:59,600 --> 00:39:02,960
Speaker 1: that thing reflects blue light. It's counterintuitive. You'd like to think, oh,

730
00:39:02,960 --> 00:39:05,719
Speaker 1: it absorbs blue light and becomes blue, but then you

731
00:39:05,719 --> 00:39:08,440
Speaker 1: wouldn't see any blueness from it. You only see blue

732
00:39:08,600 --> 00:39:10,319
Speaker 1: if it's reflecting the blue light.

733
00:39:10,520 --> 00:39:13,400
Speaker 2: I mean, this is in nature. This is how we

734
00:39:13,480 --> 00:39:16,359
Speaker 2: see different colors. Usually you have some kind of like

735
00:39:16,400 --> 00:39:20,279
Speaker 2: pigment that absorbs every color except for the color that

736
00:39:20,320 --> 00:39:22,239
Speaker 2: you see, which is reflected back at you. But you

737
00:39:22,280 --> 00:39:26,800
Speaker 2: can also have things like tiny microscopic prisms that actually

738
00:39:26,880 --> 00:39:31,959
Speaker 2: scatter light structural coloration, and instead of absorbing the light,

739
00:39:32,080 --> 00:39:35,360
Speaker 2: it scatters it, and then that scattered light hits your eye.

740
00:39:35,480 --> 00:39:38,759
Speaker 1: Yeah. Really fun. So that's quantum mechanics process number one.

741
00:39:38,800 --> 00:39:42,280
Speaker 1: It's like energy levels of the atom determine what colors

742
00:39:42,320 --> 00:39:45,279
Speaker 1: it glows in and what colors it absorbs. There's a

743
00:39:45,320 --> 00:39:48,239
Speaker 1: second process, which is also due to quantum mechanics, which

744
00:39:48,320 --> 00:39:50,560
Speaker 1: is just that hot things tend to glow, and they

745
00:39:50,600 --> 00:39:53,720
Speaker 1: tend to glow at different frequencies. So like the sun

746
00:39:53,880 --> 00:39:56,920
Speaker 1: is really really hot and it's glowing, and part of

747
00:39:56,920 --> 00:39:59,040
Speaker 1: the light that it emits is due to these atoms

748
00:39:59,120 --> 00:40:01,439
Speaker 1: jumping up and down on the energy levels, but part

749
00:40:01,440 --> 00:40:03,640
Speaker 1: of it is also just due to having like a

750
00:40:03,680 --> 00:40:06,840
Speaker 1: big soup of electrons up there that are all zipping

751
00:40:06,880 --> 00:40:10,319
Speaker 1: around at certain temperatures and giving off photons. And the

752
00:40:10,440 --> 00:40:13,279
Speaker 1: hotter the thing is, the more these electrons that are

753
00:40:13,280 --> 00:40:15,880
Speaker 1: not bound to atoms are going to be wiggling around

754
00:40:15,960 --> 00:40:18,799
Speaker 1: and giving off photons. So things that are really really

755
00:40:18,840 --> 00:40:22,080
Speaker 1: hot have their freer electrons sort of wiggling around a

756
00:40:22,120 --> 00:40:25,680
Speaker 1: lot in giving off high frequency photons. Things that are

757
00:40:25,719 --> 00:40:28,800
Speaker 1: colder have their electrons not moving this fast and giving

758
00:40:28,840 --> 00:40:33,719
Speaker 1: off lower energy, lower frequency photons. So, for example, Katie,

759
00:40:33,960 --> 00:40:36,680
Speaker 1: you glow, and not just in a sort of intellectual

760
00:40:36,680 --> 00:40:39,800
Speaker 1: way or because of your brilliant personality. You are literally

761
00:40:39,960 --> 00:40:44,160
Speaker 1: emitting photons right now. They're just not photons in our

762
00:40:44,360 --> 00:40:47,480
Speaker 1: visible range. So when your husband looks at you, he

763
00:40:47,600 --> 00:40:50,319
Speaker 1: can't see that you are glowing in the infrared. You

764
00:40:50,360 --> 00:40:53,040
Speaker 1: are giving off light like in a dark room when

765
00:40:53,080 --> 00:40:55,920
Speaker 1: you imagine nobody could see me, you are glowing in

766
00:40:55,960 --> 00:40:59,240
Speaker 1: the infrared. And that's what for example, night vision goggles

767
00:40:59,320 --> 00:40:59,880
Speaker 1: can see.

768
00:41:00,160 --> 00:41:05,120
Speaker 2: M I see. Is that also called black body radiation?

769
00:41:05,480 --> 00:41:08,120
Speaker 1: Yeah, that's the physics name for it, black body radiation.

770
00:41:08,800 --> 00:41:11,279
Speaker 1: So we imagine if you have an object which does

771
00:41:11,320 --> 00:41:15,440
Speaker 1: not reflect any light, which absorbs everything and only emits

772
00:41:15,520 --> 00:41:18,520
Speaker 1: light through this process where your electrons inside you are

773
00:41:18,520 --> 00:41:21,120
Speaker 1: sort of zipping around and giving off photons. These are

774
00:41:21,160 --> 00:41:24,040
Speaker 1: the electrons that are again not totally bound to an atom,

775
00:41:24,120 --> 00:41:26,480
Speaker 1: and so they're freer to emit in sort of a

776
00:41:26,520 --> 00:41:29,799
Speaker 1: broader spectrum. Then we call this thing a black body. Now,

777
00:41:29,840 --> 00:41:32,840
Speaker 1: nothing in the universe is actually a black body. Everything

778
00:41:32,880 --> 00:41:35,520
Speaker 1: in the universe is sort of partially a black body

779
00:41:35,600 --> 00:41:38,799
Speaker 1: and partially emitting due to the energy levels of the

780
00:41:38,800 --> 00:41:41,759
Speaker 1: bound atoms. And so for example, our sun is like that.

781
00:41:41,840 --> 00:41:44,840
Speaker 1: Our sun can be described as a black body object

782
00:41:45,200 --> 00:41:48,319
Speaker 1: because it does emit at a certain frequency based on

783
00:41:48,360 --> 00:41:51,000
Speaker 1: its temperature. But also you can tell what's in the

784
00:41:51,040 --> 00:41:53,399
Speaker 1: sun because the atoms in it glow. So the Sun

785
00:41:53,480 --> 00:41:57,520
Speaker 1: is a complicated mixture of mostly black body radiation due

786
00:41:57,520 --> 00:41:59,640
Speaker 1: to its temperature, and also a lot of peaks and

787
00:41:59,719 --> 00:42:03,040
Speaker 1: dip because of the other quantum mechanical effect where electrons

788
00:42:03,160 --> 00:42:06,759
Speaker 1: around atoms are absorbing and emitting only at specific frequencies.

789
00:42:06,920 --> 00:42:10,560
Speaker 2: Well, it sounds like the Sun contains multitudes, kind of

790
00:42:10,840 --> 00:42:15,879
Speaker 2: literally and maybe very violently. So we are not going

791
00:42:15,920 --> 00:42:18,759
Speaker 2: to look at the Sun with our eyeballs, but with

792
00:42:18,920 --> 00:42:34,879
Speaker 2: our minds when we get back. So we are back,

793
00:42:34,920 --> 00:42:37,000
Speaker 2: and we are going to take a safe look at

794
00:42:37,040 --> 00:42:40,840
Speaker 2: the Sun, not by staring at it, but by thinking

795
00:42:40,880 --> 00:42:41,359
Speaker 2: about it.

796
00:42:42,960 --> 00:42:45,760
Speaker 1: Exactly. And so first we will think about the Sun

797
00:42:46,080 --> 00:42:48,920
Speaker 1: just as a black body object or as something which

798
00:42:49,040 --> 00:42:52,080
Speaker 1: glows due to its temperature. And as we said before,

799
00:42:52,120 --> 00:42:55,080
Speaker 1: the theory of black body radiation tells you that the

800
00:42:55,160 --> 00:42:59,200
Speaker 1: hotter you are, the shorter the wavelength of light, or

801
00:42:59,239 --> 00:43:02,440
Speaker 1: the higher the frequency of light, higher the energy of

802
00:43:02,480 --> 00:43:05,839
Speaker 1: photons that you emit. So if you are cooler like

803
00:43:05,880 --> 00:43:09,879
Speaker 1: you and me, then we glow in long wavelengths, low frequencies.

804
00:43:09,920 --> 00:43:12,320
Speaker 1: And if you are hotter, then you tend to glow

805
00:43:12,520 --> 00:43:17,040
Speaker 1: in higher energies or higher frequencies or shorter wavelengths. But

806
00:43:17,160 --> 00:43:19,400
Speaker 1: that simplifies it a little bit there. We're really just

807
00:43:19,440 --> 00:43:23,400
Speaker 1: describing the peak where most of the energy is emitted.

808
00:43:23,640 --> 00:43:25,760
Speaker 1: If you're an object like the sun at five thousand

809
00:43:25,840 --> 00:43:30,839
Speaker 1: degrees kelvin, you tend to emit mostly in the visible spectrum, right,

810
00:43:31,200 --> 00:43:34,200
Speaker 1: but you also emit at lower and higher frequencies. It's

811
00:43:34,200 --> 00:43:37,800
Speaker 1: a very broad range there. So the Sun isn't limited

812
00:43:37,800 --> 00:43:40,279
Speaker 1: to only emitting light at one frequency, but it does

813
00:43:40,320 --> 00:43:43,200
Speaker 1: tend to peak at exactly the kind of frequency that

814
00:43:43,360 --> 00:43:45,080
Speaker 1: our eyes are good at seeing.

815
00:43:45,320 --> 00:43:49,520
Speaker 2: It's kind of like how in our eyes, our cones

816
00:43:49,600 --> 00:43:53,200
Speaker 2: can see a whole range of frequencies. Things can also

817
00:43:53,440 --> 00:43:55,600
Speaker 2: emit a whole range of frequencies.

818
00:43:55,880 --> 00:43:58,080
Speaker 1: That's exactly right, And so the sun emits a very

819
00:43:58,200 --> 00:44:00,920
Speaker 1: very broad range. We can actually only see a little

820
00:44:00,920 --> 00:44:04,319
Speaker 1: slice of it. Like if you develop infrared telescopes or

821
00:44:04,520 --> 00:44:08,480
Speaker 1: UV telescopes, things that can see frequencies below and above

822
00:44:08,480 --> 00:44:11,000
Speaker 1: what our eyes can, you can still see the sun, right,

823
00:44:11,000 --> 00:44:13,799
Speaker 1: The sun is not black and higher frequencies. And it's

824
00:44:13,800 --> 00:44:16,399
Speaker 1: also not a coincidence that the Sun peaks in its

825
00:44:16,400 --> 00:44:19,800
Speaker 1: emission and exactly the frequency range that we can see.

826
00:44:19,920 --> 00:44:24,480
Speaker 2: The sun was made for us, clearly, Can I stop

827
00:44:24,520 --> 00:44:25,120
Speaker 2: you right there?

828
00:44:25,719 --> 00:44:28,360
Speaker 1: I think it might be the opposite, right, Our eyes

829
00:44:28,440 --> 00:44:32,600
Speaker 1: clearly evolved in an environment that's dominated by certain frequencies,

830
00:44:32,880 --> 00:44:35,839
Speaker 1: so those frequencies are more useful. And I think if

831
00:44:35,880 --> 00:44:38,680
Speaker 1: the sun had been hotter or colder and admitted at

832
00:44:38,719 --> 00:44:42,120
Speaker 1: different frequencies. If very likely we would see at different frequencies,

833
00:44:42,160 --> 00:44:44,440
Speaker 1: and like, I don't know what that experience would be like.

834
00:44:44,640 --> 00:44:46,880
Speaker 1: But you know, the reason that our eyeballs can see

835
00:44:47,360 --> 00:44:50,200
Speaker 1: exactly in the range where the sun peaks probably not

836
00:44:50,280 --> 00:44:51,080
Speaker 1: a coincidence.

837
00:44:51,239 --> 00:44:57,000
Speaker 2: Well, that's why certain animals, especially invertebrates and pollinators can

838
00:44:57,120 --> 00:45:01,040
Speaker 2: often see u V light is because it is something

839
00:45:01,080 --> 00:45:04,080
Speaker 2: that they've evolved to see that helps them pollinate, because

840
00:45:04,120 --> 00:45:08,520
Speaker 2: they can see light that is given off by flowers,

841
00:45:08,560 --> 00:45:11,120
Speaker 2: and the flowers have co evolved with them to emit

842
00:45:11,200 --> 00:45:15,279
Speaker 2: even more UV lights that they can see, and this

843
00:45:15,400 --> 00:45:18,880
Speaker 2: helps them, you know, I identify basically their target to

844
00:45:19,080 --> 00:45:24,040
Speaker 2: get nectar from flowers. And so birds and insects can

845
00:45:24,080 --> 00:45:28,680
Speaker 2: see UV light and we generally can't. And that's not

846
00:45:29,120 --> 00:45:31,840
Speaker 2: a failure of ours. That's just because it does not

847
00:45:32,120 --> 00:45:35,520
Speaker 2: generally have an evolutionary benefit for us to do.

848
00:45:35,560 --> 00:45:37,759
Speaker 1: So. Yeah, and it's a fascinating story. We told them the

849
00:45:37,760 --> 00:45:39,799
Speaker 1: podcast once about a kind of bird, kind of bird

850
00:45:39,840 --> 00:45:43,919
Speaker 1: called the blue tit, which actually looks spectacular in the ultraviolet.

851
00:45:44,000 --> 00:45:46,200
Speaker 1: But let's get back to the sun and start in

852
00:45:46,280 --> 00:45:48,799
Speaker 1: outer space before we think about the atmosphere. If you're

853
00:45:48,840 --> 00:45:50,719
Speaker 1: in outer space and you look at the Sun with

854
00:45:50,760 --> 00:45:54,360
Speaker 1: of course protection, what would you see. And you often

855
00:45:54,400 --> 00:45:57,879
Speaker 1: hear science communicators in popular science articles describing the Sun

856
00:45:57,920 --> 00:46:01,160
Speaker 1: as green, saying the Sun is actually green. The reason

857
00:46:01,280 --> 00:46:02,920
Speaker 1: is that if you just treat the Sun as a

858
00:46:02,960 --> 00:46:06,280
Speaker 1: black body object, and you know it's temperature, its peak

859
00:46:06,480 --> 00:46:09,520
Speaker 1: is in the green, it would emit more green photons

860
00:46:09,920 --> 00:46:13,400
Speaker 1: than orange photons or red photons or blue photons. So

861
00:46:13,440 --> 00:46:16,520
Speaker 1: that's why people say, sometimes, oh, the Sun is actually green.

862
00:46:16,680 --> 00:46:18,319
Speaker 1: What does that really mean though? I mean, if you're

863
00:46:18,360 --> 00:46:20,480
Speaker 1: in outer space and you look at the Sun, you

864
00:46:20,560 --> 00:46:24,080
Speaker 1: do not see it as green. You see it as white,

865
00:46:24,400 --> 00:46:26,880
Speaker 1: because it does peak in the green. But as we

866
00:46:26,920 --> 00:46:29,440
Speaker 1: said before, it emits in a very broad spectrum, and

867
00:46:29,440 --> 00:46:32,520
Speaker 1: it emits plenty of red photons and blue photons and

868
00:46:32,560 --> 00:46:35,240
Speaker 1: orange photons. So if you're in outer space, you're an astronaut,

869
00:46:35,320 --> 00:46:37,200
Speaker 1: you look at the Sun, you do not see it

870
00:46:37,200 --> 00:46:40,239
Speaker 1: as green. You see it as white because you see

871
00:46:40,280 --> 00:46:43,080
Speaker 1: a huge mixture of these colors. In order for you

872
00:46:43,160 --> 00:46:44,839
Speaker 1: to see it as green, it would have to be

873
00:46:44,880 --> 00:46:49,799
Speaker 1: like overwhelmingly only green photons and very very few other photons.

874
00:46:50,160 --> 00:46:52,200
Speaker 2: This is a trick you kind of can do with

875
00:46:52,400 --> 00:46:56,240
Speaker 2: lights here on Earth. If you mix light, not pigment,

876
00:46:56,360 --> 00:47:00,000
Speaker 2: but light together, you get white. When you mix pigments together,

877
00:47:00,120 --> 00:47:02,759
Speaker 2: you often get brown, because that's a different sort of

878
00:47:03,200 --> 00:47:05,200
Speaker 2: thing going on with pigments. But yeah, when you mix

879
00:47:05,239 --> 00:47:07,120
Speaker 2: a bunch of different lights, you'll get white light.

880
00:47:07,440 --> 00:47:10,680
Speaker 1: You get white light exactly. The second problem with saying

881
00:47:10,719 --> 00:47:14,360
Speaker 1: that the Sun is green is that that's only true

882
00:47:14,400 --> 00:47:16,839
Speaker 1: if the Sun was a perfect black body, if all

883
00:47:16,880 --> 00:47:19,759
Speaker 1: of its radiation only came from its temperature. But the

884
00:47:19,800 --> 00:47:22,080
Speaker 1: Sun is not a black body. It emits light not

885
00:47:22,200 --> 00:47:24,600
Speaker 1: just because it's hot, but because the atoms in it

886
00:47:24,680 --> 00:47:27,520
Speaker 1: are doing other quantum mechanical things. Electrons are jumping up

887
00:47:27,520 --> 00:47:30,640
Speaker 1: and down energy levels. It emits in many complicated ways,

888
00:47:30,640 --> 00:47:32,719
Speaker 1: as you say, it contains multitudes.

889
00:47:32,880 --> 00:47:36,040
Speaker 2: It's got electron shoots and electron ladders.

890
00:47:36,520 --> 00:47:38,960
Speaker 1: So if you actually go out into space and you

891
00:47:39,040 --> 00:47:42,120
Speaker 1: measure the photons coming from the Sun, you find that

892
00:47:42,200 --> 00:47:44,600
Speaker 1: it doesn't peak in the green the way it would

893
00:47:44,680 --> 00:47:47,400
Speaker 1: if it was a perfect black body object. It actually

894
00:47:47,480 --> 00:47:51,400
Speaker 1: peaks in the violet, right, And so the most common

895
00:47:51,600 --> 00:47:53,960
Speaker 1: frequency of light coming from the Sun if you're in

896
00:47:54,040 --> 00:47:57,640
Speaker 1: outer space is not green, or it's not yellow, it's violet.

897
00:47:57,920 --> 00:48:01,239
Speaker 2: That must be a very interesting experience for animals on

898
00:48:01,280 --> 00:48:05,840
Speaker 2: Earth who can see more in the ultraviolet frequencies. They

899
00:48:05,880 --> 00:48:08,680
Speaker 2: must see the sun differently, at least from space.

900
00:48:08,760 --> 00:48:10,759
Speaker 1: Yeah, yeah, well, I hope they're also not looking up

901
00:48:10,760 --> 00:48:13,840
Speaker 1: at the sun. So any animal or insect listeners be careful.

902
00:48:14,200 --> 00:48:16,719
Speaker 2: But if we put birds in space and gave them

903
00:48:16,760 --> 00:48:20,040
Speaker 2: eye protection and then ask them put a pairrot up

904
00:48:20,080 --> 00:48:21,600
Speaker 2: there so it can talk to us.

905
00:48:21,719 --> 00:48:23,960
Speaker 1: I'm glad that we're thinking about these details. Now. That's

906
00:48:24,000 --> 00:48:28,240
Speaker 1: definely the most important thing. So if you're in outer space,

907
00:48:28,440 --> 00:48:31,920
Speaker 1: the photons you get from the Sun are most often violet.

908
00:48:32,360 --> 00:48:35,279
Speaker 1: Green is also very common, but you still see the

909
00:48:35,280 --> 00:48:37,239
Speaker 1: sun as white. If you look at pictures of the

910
00:48:37,280 --> 00:48:41,680
Speaker 1: Sun from space, then it's definitely white. But here on Earth,

911
00:48:41,760 --> 00:48:43,760
Speaker 1: if you look up at the sun safely, of course

912
00:48:43,960 --> 00:48:46,360
Speaker 1: you don't see it white. Right, You do not see

913
00:48:46,400 --> 00:48:48,520
Speaker 1: a white sun. And the reason is the one that

914
00:48:48,560 --> 00:48:51,879
Speaker 1: we talked about before, that the atmosphere is not democratic

915
00:48:52,000 --> 00:48:54,919
Speaker 1: when it comes to letting light through that the very

916
00:48:55,000 --> 00:48:58,319
Speaker 1: high frequencies of light, the blue gets scattered and so

917
00:48:58,520 --> 00:49:01,680
Speaker 1: all the photons that are zooming towards your eyeball. When

918
00:49:01,680 --> 00:49:04,279
Speaker 1: they come from the sun through the atmosphere, they don't

919
00:49:04,280 --> 00:49:07,200
Speaker 1: all make it, so the blue ones get scattered sideways

920
00:49:07,440 --> 00:49:10,440
Speaker 1: and make somebody else's blue sky. If you're standing next

921
00:49:10,440 --> 00:49:13,359
Speaker 1: to me, Katie, then those blue photons which originally were

922
00:49:13,400 --> 00:49:16,960
Speaker 1: pointed towards my eyeball might end up at your eyeball,

923
00:49:17,200 --> 00:49:20,080
Speaker 1: and so you will see the sky as blue, whereas

924
00:49:20,080 --> 00:49:22,640
Speaker 1: I will see the sun as having less blue than

925
00:49:22,640 --> 00:49:25,640
Speaker 1: it actually does. And that's why we see the sun

926
00:49:25,880 --> 00:49:30,200
Speaker 1: as yellow. It's like originally white but then distorted by

927
00:49:30,239 --> 00:49:31,880
Speaker 1: the atmosphere to look yellow.

928
00:49:31,960 --> 00:49:35,360
Speaker 2: And is that why the sun changes color as it

929
00:49:35,520 --> 00:49:38,360
Speaker 2: rises and as it sets, because it is hitting the

930
00:49:38,400 --> 00:49:41,080
Speaker 2: atmosphere at a different angle relative to our eyes.

931
00:49:41,239 --> 00:49:45,000
Speaker 1: Exactly during sunrise and during sunset, you're going through more

932
00:49:45,080 --> 00:49:48,600
Speaker 1: atmosphere than usual, And so the higher frequencies of light

933
00:49:48,640 --> 00:49:51,160
Speaker 1: get scattered more, and you get even more bias towards

934
00:49:51,280 --> 00:49:55,040
Speaker 1: the low frequency red light. So the scattering the atmosphere

935
00:49:55,080 --> 00:49:58,279
Speaker 1: depends on the frequency to the fourth power. Actually, so

936
00:49:58,560 --> 00:50:01,600
Speaker 1: high frequency light like blue oh get scattered much more

937
00:50:01,680 --> 00:50:04,120
Speaker 1: than red light. And if you go through more atmosphere,

938
00:50:04,200 --> 00:50:07,360
Speaker 1: you get more scattering and that's why sunrises and sunsets

939
00:50:07,760 --> 00:50:08,480
Speaker 1: are red.

940
00:50:08,840 --> 00:50:11,520
Speaker 2: This might be a topic for a different episode, but

941
00:50:11,680 --> 00:50:14,120
Speaker 2: I do have a question. Do you have an opinion

942
00:50:14,280 --> 00:50:17,160
Speaker 2: on whether the green flash exists? Have you heard of

943
00:50:17,200 --> 00:50:20,360
Speaker 2: that in terms of like as the sunsets, people claim

944
00:50:20,360 --> 00:50:23,280
Speaker 2: that there's a green flash just as it goes beyond

945
00:50:23,320 --> 00:50:24,640
Speaker 2: the horizon.

946
00:50:24,280 --> 00:50:26,239
Speaker 1: There is a green flash, and I've seen it.

947
00:50:28,040 --> 00:50:30,359
Speaker 2: I feel like I've seen it too, but I didn't

948
00:50:30,400 --> 00:50:32,440
Speaker 2: know if it was just sort of psychosomatic.

949
00:50:32,600 --> 00:50:35,120
Speaker 1: But yes, that is a topic for another day. But

950
00:50:35,160 --> 00:50:38,360
Speaker 1: it's also fascinating to think about the colors of everything

951
00:50:38,360 --> 00:50:40,640
Speaker 1: else out there in the Solar System. You probably have

952
00:50:40,800 --> 00:50:44,080
Speaker 1: mental images of what various planets look like from pictures

953
00:50:44,120 --> 00:50:48,480
Speaker 1: you've seen online, but they're not always representative. Mars usually

954
00:50:48,480 --> 00:50:52,000
Speaker 1: looks red because of the red rocks on Mars, but Venus,

955
00:50:52,040 --> 00:50:55,200
Speaker 1: for example, looks different than you might imagine. The images

956
00:50:55,239 --> 00:50:59,120
Speaker 1: we have of Venus are mostly from UV telescopes, where

957
00:50:59,160 --> 00:51:01,920
Speaker 1: the pictures they've taken have been shifted down into the

958
00:51:02,000 --> 00:51:04,440
Speaker 1: visible spectrum so that we can see them. If you

959
00:51:04,480 --> 00:51:06,719
Speaker 1: were to fly by Venus, it would look just kind

960
00:51:06,760 --> 00:51:09,760
Speaker 1: of like a big gray blob with almost no features

961
00:51:09,840 --> 00:51:12,360
Speaker 1: to it. At all in the visible spectrum.

962
00:51:12,480 --> 00:51:14,759
Speaker 2: Well, that's too bad, because I was really planning a

963
00:51:14,840 --> 00:51:17,760
Speaker 2: road trip to go sight see Venus.

964
00:51:19,600 --> 00:51:22,360
Speaker 1: Bring your acid proof goggles because I think you're going

965
00:51:22,440 --> 00:51:25,200
Speaker 1: to need them on the surface of Venus, all right.

966
00:51:25,239 --> 00:51:28,960
Speaker 1: And so to recap photons our wiggles in the electromagnetic

967
00:51:29,040 --> 00:51:32,080
Speaker 1: spectrum that come at all different frequencies, and objects can

968
00:51:32,120 --> 00:51:35,239
Speaker 1: emit and absorb photons based on their energy levels or

969
00:51:35,280 --> 00:51:37,960
Speaker 1: also just based on their temperature. The sun out in

970
00:51:38,040 --> 00:51:40,880
Speaker 1: space is white, even though it peaks in the violet.

971
00:51:40,960 --> 00:51:43,600
Speaker 1: You would see it as white with your eyeballs, but

972
00:51:43,760 --> 00:51:46,000
Speaker 1: here on Earth we see it as yellow because of

973
00:51:46,080 --> 00:51:47,440
Speaker 1: atmospheric effects.

974
00:51:47,840 --> 00:51:51,520
Speaker 2: And all of that depends on our eyeballs, biology and

975
00:51:51,640 --> 00:51:52,719
Speaker 2: our brains and.

976
00:51:52,640 --> 00:51:54,480
Speaker 1: The chemistry that makes it all work.

977
00:51:54,840 --> 00:51:58,600
Speaker 2: We owe everything to chemistry, and I am extremely remorseful

978
00:51:58,640 --> 00:52:01,200
Speaker 2: to make it sound like anything else.

979
00:52:01,600 --> 00:52:03,880
Speaker 1: And in the end, everybody should be out there following

980
00:52:03,920 --> 00:52:07,040
Speaker 1: their personal curiosity. You can love a kind of science

981
00:52:07,080 --> 00:52:09,439
Speaker 1: that I would find super boring, and I can find

982
00:52:09,440 --> 00:52:12,040
Speaker 1: it super interesting even if it makes you yawn. That

983
00:52:12,160 --> 00:52:14,840
Speaker 1: diversity of interest is why we have such a beautiful

984
00:52:14,840 --> 00:52:18,680
Speaker 1: diversity of scientists and such a beautiful diversity of discoveries

985
00:52:18,719 --> 00:52:22,680
Speaker 1: about the universe. It's that widely varying curiosity and enjoyment

986
00:52:22,719 --> 00:52:25,840
Speaker 1: of different kinds of puzzles that powers our broad spectrum

987
00:52:25,880 --> 00:52:27,760
Speaker 1: human curiosity about the universe.

988
00:52:28,000 --> 00:52:33,880
Speaker 2: It's not a competition except for the Universal Scientist Decathlon.

989
00:52:34,239 --> 00:52:36,839
Speaker 1: That's right. So thanks very much everybody for going on

990
00:52:36,880 --> 00:52:39,920
Speaker 1: this journey with us, following photons from the sun all

991
00:52:39,960 --> 00:52:43,080
Speaker 1: the way to your eyeball, and following these phonons from

992
00:52:43,080 --> 00:52:45,799
Speaker 1: our mouths all the way to your earballs. And thank

993
00:52:45,840 --> 00:52:48,320
Speaker 1: you very much Katie for joining us today. Yeah, of course,

994
00:52:48,560 --> 00:52:59,040
Speaker 1: thanks for listening. Tune in next time. Thanks for listening,

995
00:52:59,040 --> 00:53:01,759
Speaker 1: and remember that Dniel and Jorge Explain the Universe is

996
00:53:01,800 --> 00:53:06,399
Speaker 1: a production of iHeartRadio. For more podcasts from iHeartRadio, visit

997
00:53:06,440 --> 00:53:10,520
Speaker 1: the iHeartRadio app, Apple Podcasts, or wherever you listen to

998
00:53:10,560 --> 00:53:11,560
Speaker 1: your favorite shows.