Latest / Daniel and Kelly’s Extraordinary Universe / Daniel answers Listener Questions about the smell of space, the electroweak force and spotting distant aliens.

Transcript

Daniel answers Listener Questions about the smell of space, the electroweak force and spotting distant aliens. · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Why do we care so much about understanding the universe,
• 0:12
  Speaker 1: about revealing its deep truths? Why aren't we just happy
• 0:16
  Speaker 1: to live in it? I mean, does it change your
• 0:19
  Speaker 1: life to understand the Higgs Boson? Does it matter to
• 0:23
  Speaker 1: your day whether there's intelligent life on the other side
• 0:27
  Speaker 1: of the galaxy? Not practically, but it matters. It doesn't
• 0:32
  Speaker 1: matter to build spaceships or death stars, or to become
• 0:35
  Speaker 1: masters of the universe, but it matters to us to
• 0:38
  Speaker 1: know to understand it's just who we are as human beings.
• 0:59
  Speaker 1: I'm Daniel, I'm a particle physicist, and welcome to the
• 1:03
  Speaker 1: podcast Daniel and Jorge Explain the Universe, a production of
• 1:07
  Speaker 1: I Heart Radio in which we marinate in our desire
• 1:11
  Speaker 1: to understand everything in the universe. We cast our minds
• 1:14
  Speaker 1: out in the furthest reaches of space and hope to
• 1:17
  Speaker 1: understand what's going on out there. We turn our mental
• 1:21
  Speaker 1: eye down to the very smallest particles in our universe
• 1:24
  Speaker 1: and ask does this make sense to us? Can this
• 1:27
  Speaker 1: possibly make sense to us? Is there a mathematical way
• 1:31
  Speaker 1: that we could understand it? We talked about all of
• 1:33
  Speaker 1: these things on the podcast, and we try to make
• 1:36
  Speaker 1: sure they make sense to you, because we think that
• 1:39
  Speaker 1: everybody deserves to understand the universe. Because we know that
• 1:43
  Speaker 1: everybody wants to understand the universe. It's part of being
• 1:46
  Speaker 1: human to look around you and to try to understand.
• 1:50
  Speaker 1: And I don't know if there's an evolutionary reason to
• 1:53
  Speaker 1: want to understand our universe. May be fundamentally deriving the
• 1:57
  Speaker 1: laws of physics helps us plan the hunt for a
• 1:59
  Speaker 1: mammoth or chase down an antelope on the savannah. I'm
• 2:02
  Speaker 1: not sure, but here we are. We are curious creatures
• 2:06
  Speaker 1: and we have this desire inside us to make sure
• 2:09
  Speaker 1: that the world around us makes sense, to sort of
• 2:12
  Speaker 1: pull all of our observations together inside our mind into
• 2:16
  Speaker 1: a mental model that we can manipulate, that we can
• 2:18
  Speaker 1: probe and then we can use to predict what's going
• 2:21
  Speaker 1: to happen to us in the future and to make plans.
• 2:24
  Speaker 1: But also just to appreciate. There's a lot of talking
• 2:27
  Speaker 1: science these days about whether science and weather physics should
• 2:31
  Speaker 1: be searching for beauty. And I don't know if we
• 2:33
  Speaker 1: should be searching for it or whether we should prefer it,
• 2:36
  Speaker 1: but we can definitely appreciate it. There's a lot of
• 2:39
  Speaker 1: gorgeous beautiful results in physics that when we do reveal
• 2:43
  Speaker 1: something new and true about the universe, we are amazed.
• 2:46
  Speaker 1: We stand a gog and think, wow, there is some
• 2:49
  Speaker 1: real beauty and elegance to our universe. And so typically
• 2:53
  Speaker 1: on the podcast it's me and Jorge and we are
• 2:55
  Speaker 1: talking about some difficult to understand thing about physics and
• 2:58
  Speaker 1: explaining it to you or hey is not here today,
• 3:01
  Speaker 1: So I'm going to take the opportunity to catch up
• 3:04
  Speaker 1: not on the questions that science is asking, but on
• 3:06
  Speaker 1: the questions that listeners are asking you, specifically you. That's right,
• 3:10
  Speaker 1: I'm talking about you. You are sitting there or standing
• 3:13
  Speaker 1: there or driving around listening to our podcast because you
• 3:16
  Speaker 1: have questions about the universe, and I want to hear
• 3:19
  Speaker 1: those questions. I want to know what is it you'd
• 3:22
  Speaker 1: like explained, and so send us your questions to questions
• 3:26
  Speaker 1: at Daniel and Jorge dot com. If you're thinking that
• 3:29
  Speaker 1: physicists will never answer my email, you're wrong. I answer
• 3:32
  Speaker 1: all of our emails, and sometimes I put those questions
• 3:35
  Speaker 1: up on the podcast when I think somebody else might
• 3:38
  Speaker 1: want to hear the answer. When I think, oh, that's
• 3:40
  Speaker 1: a particularly interesting question that I bet a lot of
• 3:44
  Speaker 1: our listeners would like to hear about. So that's what
• 3:46
  Speaker 1: we're gonna do today. On today's program will be answering
• 3:54
  Speaker 1: real questions from listeners. And I love answering your questions
• 3:59
  Speaker 1: because they give me a sense for what people are
• 4:01
  Speaker 1: thinking about. What do people know about physics, what makes
• 4:04
  Speaker 1: sense to them? Because I've been doing physics for decades
• 4:06
  Speaker 1: and my brain is fully marinated in physics is a
• 4:09
  Speaker 1: language and is a way of thinking, So it's very
• 4:11
  Speaker 1: helpful to me to hear about the way people ask
• 4:14
  Speaker 1: about it when they're on the outside. So it's very
• 4:16
  Speaker 1: helpful to me to hear about what your questions are,
• 4:19
  Speaker 1: the way that you think about the universe and the
• 4:22
  Speaker 1: things that don't make sense to you. And also, because
• 4:24
  Speaker 1: while most podcasts are one directional is just a couple
• 4:28
  Speaker 1: of voices sending information and audio out there into your brain,
• 4:32
  Speaker 1: this podcast is interactive. That's right. We want to hear
• 4:35
  Speaker 1: from you. We want to know what you need to understand,
• 4:39
  Speaker 1: so please don't be shy. Send us your questions to
• 4:42
  Speaker 1: questions at Daniel and Jorge dot com. And if you
• 4:46
  Speaker 1: don't like writing emails or don't want to interact with
• 4:49
  Speaker 1: us on Twitter at Daniel and Jorge. Then hey, just
• 4:52
  Speaker 1: come to my free public office hours. I hang out
• 4:56
  Speaker 1: once a month for an hour on Zoom and answer
• 4:58
  Speaker 1: questions from all all commerce. It's an opportunity to have
• 5:01
  Speaker 1: a little bit more interactivity. You can ask a question,
• 5:05
  Speaker 1: you can ask a follow up question. I'll make sure
• 5:07
  Speaker 1: you go away with some understanding of the universe. So,
• 5:11
  Speaker 1: without further ado, let's dig into today's awesome pile of
• 5:14
  Speaker 1: listener questions. And thanks again to everybody who writes in,
• 5:17
  Speaker 1: and please don't be shy. So today's first question is
• 5:21
  Speaker 1: a rather stinky one from Bob Buyer. All right, Daniel,
• 5:25
  Speaker 1: this is Bob from Edmonds, Washington. Uh. Say, I have
• 5:29
  Speaker 1: always wondered, um if space might smell like something, or
• 5:34
  Speaker 1: even if it has a smell. I was thinking maybe
• 5:38
  Speaker 1: astronauts reported a smell after returning to the space station
• 5:44
  Speaker 1: when they're inside their decompression chamber and they take off
• 5:47
  Speaker 1: their helmets, or maybe Apollo mission astronauts after walking on
• 5:52
  Speaker 1: the Moon surface and returned back to their landing craft
• 5:55
  Speaker 1: and they take off their helmets inside there my be
• 6:00
  Speaker 1: residual smell from outdoors, and what would that smell like?
• 6:05
  Speaker 1: So anyway, I hope you can shed some light on
• 6:09
  Speaker 1: that question. Thanks a lot. All right, that's a super
• 6:11
  Speaker 1: fun question. Thank you so much Bob for sending that in.
• 6:14
  Speaker 1: I'm excited to talk about the smells of space or
• 6:17
  Speaker 1: the stinks of space, But first I want to think
• 6:19
  Speaker 1: for a minute about the motivation for this question. I
• 6:22
  Speaker 1: think it's super fun to look up at the night
• 6:25
  Speaker 1: sky and wonder about it and want to understand it.
• 6:29
  Speaker 1: And what does understanding mean. It means somehow transforming that
• 6:33
  Speaker 1: knowledge into something that makes sense to us, something that
• 6:37
  Speaker 1: relates to our everyday experience. And you know, how do
• 6:41
  Speaker 1: we interact with the world. We taste it, we touch it,
• 6:43
  Speaker 1: we smell it, and so there's a little bit there
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  Speaker 1: about like trying to hook in the sky and bring
• 6:49
  Speaker 1: it down to Earth and wonder like what would it
• 6:51
  Speaker 1: be like to interact with the sky using our earth
• 6:55
  Speaker 1: based senses. So I totally applaud this idea. I think
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  Speaker 1: it's wonderful, and frankly, it follows in the footsteps of
• 7:01
  Speaker 1: geniuses like Isaac Newton. He's the guy who thought, if
• 7:04
  Speaker 1: I have a theory of gravity that describes how an
• 7:07
  Speaker 1: apple falls from a tree, can I also use it
• 7:10
  Speaker 1: to describe the motion of the stars. There was this
• 7:13
  Speaker 1: idea that you could unify our understanding of what happens
• 7:16
  Speaker 1: here on Earth with what happens out there, the idea
• 7:20
  Speaker 1: that the Earth is not a special place, and the
• 7:22
  Speaker 1: laws of physics that we find should apply equally everywhere.
• 7:25
  Speaker 1: And so flip that around and think, well, if I
• 7:27
  Speaker 1: can smell stuff down here on Earth, could I smell
• 7:30
  Speaker 1: stuff out there in space? And what would it smell like?
• 7:33
  Speaker 1: So super fun, wonderful question. Now, of course, the easy
• 7:38
  Speaker 1: answer is that if you opened your helmet in space,
• 7:42
  Speaker 1: you wouldn't smell anything, because you're a news would freeze. Right.
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  Speaker 1: Space is mostly a vacuum. It's very cold and very
• 7:49
  Speaker 1: low pressure, and so if you exposed yourself to the
• 7:53
  Speaker 1: vacuum of space, then of course you wouldn't smell anything.
• 7:55
  Speaker 1: But that's not the only way to smell space, right,
• 7:58
  Speaker 1: because space is not actually empty. We talked on this
• 8:02
  Speaker 1: podcast a lot about how space is actually filled with stuff.
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  Speaker 1: And we're not talking here about like quantum fields and
• 8:08
  Speaker 1: other crazy low energy phenomena. I'm talking about actual particles.
• 8:13
  Speaker 1: There's a whole podcast episode we did about where is
• 8:15
  Speaker 1: the Emptiest Place? In space, and as you leave the Earth,
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  Speaker 1: of course, the atmosphere gets thinner and thinner and thinner.
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  Speaker 1: And then when you're out there in sort of interplanetary space,
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  Speaker 1: it's not like there's nothing there. There are a lot
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  Speaker 1: of particles out there, from big rocks which are pretty
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  Speaker 1: rare and down to tiny grains of space dust which
• 8:35
  Speaker 1: are frankly everywhere. Space is not really empty at all.
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  Speaker 1: Add to that, of course the solar wind, which is
• 8:41
  Speaker 1: pumping out huge numbers of particles all the time, protons
• 8:45
  Speaker 1: and electrons and other kinds of small particles mostly, But
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  Speaker 1: there's a lot of stuff bumping around up there. So
• 8:51
  Speaker 1: it's a really fair question to ask, what would those
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  Speaker 1: things smell like if you could somehow use your nose
• 8:57
  Speaker 1: to probe them, Because remember, the human nose is amazing.
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  Speaker 1: It's a very sensitive, basically molecular detector. The way your
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  Speaker 1: nose works is that you suck in air and has
• 9:08
  Speaker 1: a bunch of molecules in it, and those molecules hit
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  Speaker 1: various sensors. These sensors are all sort of differently shaped
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  Speaker 1: and they can lock into different molecules to detect it,
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  Speaker 1: so they can detect lots of different molecules, and it's
• 9:21
  Speaker 1: very related to this sense of taste. You know, the
• 9:24
  Speaker 1: taste buds on your tongue, for example, are receptive to
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  Speaker 1: sugar molecules or other kinds of molecules or salt, and
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  Speaker 1: you have a handful of different sensors on your tongue
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  Speaker 1: that can taste different kinds of molecules just the same way.
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  Speaker 1: Your eyeballs, for example, have different cones and rods inside them,
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  Speaker 1: and they use that to build up a picture of
• 9:42
  Speaker 1: what you're seeing. But there again, there's only a few
• 9:45
  Speaker 1: rods and cones. There's only really three different kinds of
• 9:48
  Speaker 1: colors that you can see, and the rest is interpretated
• 9:51
  Speaker 1: by your brain. But when it comes to your nose,
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  Speaker 1: it's actually much much more powerful than those other senses.
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  Speaker 1: Your nose can sense hundreds of individual different molecules. You
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  Speaker 1: can identify them, It can pick them out even if
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  Speaker 1: they're very, very faint. You ever smell something just a
• 10:09
  Speaker 1: tiny little bit that your nose picking out the tiniest
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  Speaker 1: little serving of whatever it is that you're smelling. So
• 10:16
  Speaker 1: your nose is actually a pretty good way to explore
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  Speaker 1: what's going on out there, and there really is plenty
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  Speaker 1: of stuff out there to smell. Space is not just
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  Speaker 1: filled with hydrogen gas. There are complex organic molecules out there.
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  Speaker 1: We know because when we sample comments or get bits
• 10:34
  Speaker 1: of asteroids or meteors, we see these things. We see
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  Speaker 1: the molecular composition, and there's fascinating stuff out there. You
• 10:41
  Speaker 1: know that, Like moons of Jupiter and Saturn have really
• 10:44
  Speaker 1: interesting organic molecules on them. Not signs of life we're
• 10:48
  Speaker 1: talking about here, like molecular precursors of life, like the
• 10:51
  Speaker 1: amino acids you might need to build life. And it's
• 10:55
  Speaker 1: very reasonable to expect that those molecules might smell like something.
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  Speaker 1: So how would you actually go about smelling it. You
• 11:03
  Speaker 1: can't go out there into space and open your helmet
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  Speaker 1: and take a deep whiff, right, Well, what you can
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  Speaker 1: do is you can collect those molecules and then smell
• 11:11
  Speaker 1: them when you're back in an aerrated chamber. And one
• 11:14
  Speaker 1: way this has actually happened is by astronauts going out
• 11:17
  Speaker 1: into space and then coming back inside. Like if you
• 11:20
  Speaker 1: come back into the space station, then your suit and
• 11:24
  Speaker 1: your helmet have collected some of those particles that are
• 11:26
  Speaker 1: out there in space. They've stuck to you, and when
• 11:29
  Speaker 1: you go back inside into the airlock. Then the air
• 11:31
  Speaker 1: releases them and they swirled all around, and some of
• 11:34
  Speaker 1: them go up your nose and just smell them. The
• 11:37
  Speaker 1: most common thing that you're gonna be smelling if you
• 11:40
  Speaker 1: do take a whiff of space are these things called
• 11:43
  Speaker 1: aromatic hydrocarbons. These are molecules built out of carbon and hydrogen,
• 11:48
  Speaker 1: which is why they're called hydrocarbon, and they're aromatic, which
• 11:51
  Speaker 1: means you're gonna smell them. And most of these things
• 11:54
  Speaker 1: smells sort of like hot metal or like diesel gas,
• 11:57
  Speaker 1: or and some people have described them as like smell
• 12:00
  Speaker 1: thing like a barbecue, and that's because those are the
• 12:02
  Speaker 1: processes on Earth that generates similar kinds of molecules. So
• 12:07
  Speaker 1: it's not like somebody out there is have a barbecue
• 12:09
  Speaker 1: in space or or running a diesel engine. But those
• 12:12
  Speaker 1: things on Earth produce similar molecules which end up in
• 12:16
  Speaker 1: your nose on Earth, and you remember them, and so
• 12:19
  Speaker 1: when you smell them out there in space, or when
• 12:21
  Speaker 1: you just come back inside from space, then that's the
• 12:25
  Speaker 1: association you're going to get. But there are lots of
• 12:27
  Speaker 1: different possible smells of things in space. For example, there's
• 12:31
  Speaker 1: a vast dust cloud to the center of our galaxy
• 12:34
  Speaker 1: that's made of a chemical called ethyl formate, and evil
• 12:37
  Speaker 1: formate itself is something you can make here on Earth,
• 12:40
  Speaker 1: and it smells sort of like rum. That's right. It
• 12:43
  Speaker 1: smells like the pirate cloud of the galaxy. And if
• 12:46
  Speaker 1: you separated, then one part of it esther, among other things,
• 12:50
  Speaker 1: is the chemical responsible for the flavor of raspberries. So yeah,
• 12:54
  Speaker 1: we're talking about vast dust clouds that might smell like
• 12:58
  Speaker 1: raspberry rum. But you know, all the amino acids out
• 13:01
  Speaker 1: there have different smells. I was looking at a chart
• 13:04
  Speaker 1: yesterday and some of them have different smells. Some of
• 13:07
  Speaker 1: them would smell sour, some of them would smell sweet,
• 13:10
  Speaker 1: some of them would smell like, oh mommy. So it
• 13:12
  Speaker 1: really just sort of depends on the particular mixture of
• 13:16
  Speaker 1: stuff that you encounter, sort of like asking what does
• 13:19
  Speaker 1: Earth smell like? Well, it depends are you at the
• 13:21
  Speaker 1: center Manhattan or the top of a mountain or in
• 13:24
  Speaker 1: a wheat field in Kansas, Right, Different places have different
• 13:28
  Speaker 1: stuff floating around, and so lots of different smells. And
• 13:31
  Speaker 1: I think that's the most important answer is that space
• 13:34
  Speaker 1: does have a smell because it's filled with interesting stuff.
• 13:37
  Speaker 1: And those smells depend on where you are. So I
• 13:40
  Speaker 1: also looked up a bunch of reports from what astronauts
• 13:43
  Speaker 1: have said, what do they think it's smells like, because
• 13:46
  Speaker 1: there haven't been a lot of scientific studies because these
• 13:48
  Speaker 1: studies require people. You know, another really fascinating thing about
• 13:51
  Speaker 1: the nose is that it's something that's escaped digitization so far.
• 13:56
  Speaker 1: You know, we've been able to capture visual images and
• 14:00
  Speaker 1: store them digitally and recreate them with a screen. We've
• 14:03
  Speaker 1: been able to capture sounds right and store them digitally
• 14:06
  Speaker 1: as information and recreate them with a speaker. We haven't
• 14:09
  Speaker 1: yet been able to capture digital sense and store that
• 14:12
  Speaker 1: information electronically in a way so that some sort of
• 14:16
  Speaker 1: digital smell speaker would be able to recreate them so
• 14:19
  Speaker 1: you could experience them. That would be pretty awesome or
• 14:23
  Speaker 1: maybe pretty terrible. I'm not sure if you want your
• 14:25
  Speaker 1: like movie to necessarily have smells, do it. But one
• 14:29
  Speaker 1: reason that we haven't yet is that the nose is
• 14:31
  Speaker 1: much more complicated than the eye or the tongue in
• 14:35
  Speaker 1: terms of the complexity of sensors that it has, and
• 14:39
  Speaker 1: so the complexity of the information that needs to be
• 14:41
  Speaker 1: stored and then reproduced, so it's particularly difficult anyway. So
• 14:45
  Speaker 1: here are some reports from astronauts. Some report that it
• 14:49
  Speaker 1: smells like burned steak. Astronaut Tom Jones says that a
• 14:54
  Speaker 1: quote carries a distinct odor of ozone, a faint, accurate smell,
• 14:58
  Speaker 1: a little like gunpower, maybe sulfurous. Don Pettit said it
• 15:03
  Speaker 1: had a quote rather pleasant, sweet metallic sensation. Three times
• 15:08
  Speaker 1: Spacewalker Tom Jones says it quote carries a distinct odor
• 15:13
  Speaker 1: of ozone, a faint, acrid smell. There was even a
• 15:16
  Speaker 1: time when NASA was considering commissioning a perfume that smelled
• 15:21
  Speaker 1: like space to sort of get folks used to it
• 15:24
  Speaker 1: so they weren't sort of surprised and put off balance
• 15:27
  Speaker 1: by the smell of space when they came back inside
• 15:30
  Speaker 1: from their spacewalks. But I think they ditched that plan.
• 15:33
  Speaker 1: And there's also another side interesting question, which is what
• 15:36
  Speaker 1: does the space station smell like? Because the space station
• 15:39
  Speaker 1: is sort of like the inside of a tent, right,
• 15:42
  Speaker 1: These folks can't go outside. They're stuck inside there, living
• 15:44
  Speaker 1: together a lot, and so you might wonder, like, does
• 15:48
  Speaker 1: this smell good inside the space station? So here's one
• 15:50
  Speaker 1: report I found of what mirror smells like. They said, quote,
• 15:54
  Speaker 1: just imagine sweaty feet, stale body odor, and then mix
• 15:58
  Speaker 1: that odor with nail polish remover and gasoline. So that
• 16:02
  Speaker 1: doesn't sound particularly nice. I'd like to go after a
• 16:04
  Speaker 1: walk into space and smell the raspberry rum if I
• 16:08
  Speaker 1: was stuck inside with all those sweaty feet. All right,
• 16:10
  Speaker 1: so thanks very much Bob for that super fun question.
• 16:13
  Speaker 1: I'd like to dig into some more questions, but first
• 16:16
  Speaker 1: let's take a quick break. All right, we are back
• 16:31
  Speaker 1: and we were talking about the smells of space, but
• 16:34
  Speaker 1: now we're gonna turn our minds inwards and ask questions
• 16:37
  Speaker 1: about the tiniest little particles and how they work. So
• 16:41
  Speaker 1: here's a super fun question from Larry. Hello, it's my
• 16:45
  Speaker 1: favorite physicist and roboticist term cartoonist team. This is Larry
• 16:48
  Speaker 1: Garfield's Illinois We all, though there are four fundamental forces
• 16:52
  Speaker 1: in the universe, you've also said many times in previous
• 16:55
  Speaker 1: episodes that you've figured out that the week nuclear force
• 16:58
  Speaker 1: and electromagnetism are really the same thing, or different aspects
• 17:02
  Speaker 1: of the same thing, or linked or something. I don't
• 17:05
  Speaker 1: quite understand. It. Doesn't that mean there's only three forces.
• 17:09
  Speaker 1: More to the point, how can there be different representations
• 17:12
  Speaker 1: of the same thing if particles like neutrinos only interact
• 17:15
  Speaker 1: with the weak force. If the weak force and electromagnetism
• 17:18
  Speaker 1: are really the same thing, how can a particle only
• 17:21
  Speaker 1: interact with one of them? I'm very confused. All right,
• 17:24
  Speaker 1: super awesome, Western Larry, Thanks so much for asking this.
• 17:27
  Speaker 1: This is one of my favorite topics to think about,
• 17:30
  Speaker 1: not just to talk about and to explain the unification
• 17:33
  Speaker 1: of all the forces, trying to understand whether there are
• 17:36
  Speaker 1: connections and patterns between the forces and whether we can
• 17:39
  Speaker 1: pull them together into some sort of unified concept. And
• 17:43
  Speaker 1: you might wonder like, well, why would we want to
• 17:45
  Speaker 1: do that, Why do we think it's even possible. Well,
• 17:48
  Speaker 1: that's basically the goal of physics is to look around us,
• 17:51
  Speaker 1: observe what we see, and try to explain all of
• 17:54
  Speaker 1: it using a small set of ideas. It's not hard
• 17:58
  Speaker 1: to explain the universe if you need a different explanation
• 18:01
  Speaker 1: for every single event. Right If you say, well, that
• 18:04
  Speaker 1: apple falls down because that apple falls down, and this
• 18:06
  Speaker 1: apple falls down because this apple falls down, which you
• 18:09
  Speaker 1: want is a theory of apples that describes how every
• 18:12
  Speaker 1: apple works. So what we've done in physics is collect
• 18:15
  Speaker 1: all the weird effects that we've seen and try to
• 18:17
  Speaker 1: describe them in terms of a set of forces, and
• 18:20
  Speaker 1: then look at those and say, oh, look this is electricity.
• 18:22
  Speaker 1: That's electricity. Let's describe all of it using one theory.
• 18:26
  Speaker 1: Oh this is a magnet. That's a magnet. Let's have
• 18:28
  Speaker 1: a theory of magnetism. And then we slowly pull those
• 18:31
  Speaker 1: things together and look for relationships between the different forces
• 18:35
  Speaker 1: and see are these actually just two sides of the
• 18:37
  Speaker 1: same coin. So what we've accomplished so far is breaking
• 18:41
  Speaker 1: it down to a few fundamental forces. And how many
• 18:45
  Speaker 1: fundamental forces are there depends a little bit on how
• 18:48
  Speaker 1: you count. Some people are taught that there are five
• 18:51
  Speaker 1: fundamental forces. The strong nuclear force that's what holds the
• 18:55
  Speaker 1: nucleus together, gravity, electricity, magnetism, and then the weak nuclear force,
• 19:02
  Speaker 1: the one that's responsible for radioactive to k and all
• 19:04
  Speaker 1: sorts of cool neutrino effects. But about a hundred and
• 19:07
  Speaker 1: fifty years ago, physicists realized that electricity and magnetism are
• 19:12
  Speaker 1: not the same thing, but there are two parts of
• 19:15
  Speaker 1: a larger thing, and that's the essential concept. We're not
• 19:18
  Speaker 1: showing that two things are the same. We're showing that
• 19:21
  Speaker 1: there are two parts of something bigger, a more complete
• 19:25
  Speaker 1: idea that includes both of them, rather than just having
• 19:28
  Speaker 1: a list. Right, we don't want to explain the universe
• 19:30
  Speaker 1: in terms of just like, here's a big list of ideas.
• 19:33
  Speaker 1: We want a single concept that simplifies things, that pulls
• 19:37
  Speaker 1: back a layer of reality and shows us what's going
• 19:39
  Speaker 1: on underneath. So when we unified electricity and magnetism, we
• 19:43
  Speaker 1: didn't say, hey, magnets and lightning are the same thing.
• 19:48
  Speaker 1: We just showed that electricity and magnetism are so tightly connected.
• 19:52
  Speaker 1: That is that moving charges make magnetic field, and magnetic
• 19:56
  Speaker 1: fields can bend the path of charges. We showed that
• 19:59
  Speaker 1: it makes worse since mathematically and conceptually to think of
• 20:03
  Speaker 1: them as two parts of the same thing. And so
• 20:06
  Speaker 1: that's what's happened in the last fifty years with the
• 20:08
  Speaker 1: weak force. We've been able to integrate the weak force
• 20:12
  Speaker 1: into a theory of electromagnetism. We call this the electroweak theory,
• 20:17
  Speaker 1: which I always thought was weird because we basically just
• 20:19
  Speaker 1: ignore magnetism. Right. It's like when a law firm gets
• 20:23
  Speaker 1: a lot of partners, and they start dropping names from
• 20:25
  Speaker 1: the title of the law firm. Nobody was advocating for magnetism.
• 20:29
  Speaker 1: They should call it the electromagnetic weak force, but instead
• 20:32
  Speaker 1: they just call it electroweak. So let's dig in for
• 20:36
  Speaker 1: a moment about what that means. What does it mean
• 20:38
  Speaker 1: to have electroweak force. Well, first, let's remind ourselves what
• 20:41
  Speaker 1: electricity and magnetism and the weak force do. And the
• 20:45
  Speaker 1: question was specifically about why neutrinos only feel the weak
• 20:48
  Speaker 1: force if the weak force is connected to electricity and magnetism.
• 20:53
  Speaker 1: So let's talk about the interactions. What do we actually
• 20:56
  Speaker 1: mean by these forces. We mean that particles can interact, Right,
• 20:59
  Speaker 1: That's what a force is. It's a way for things
• 21:01
  Speaker 1: to push or pull on each other, including particles. So
• 21:05
  Speaker 1: electricity and magnetism that forces carried out by photons. Every
• 21:09
  Speaker 1: time there's an electromagnetic interaction, some lightning or magnetic field
• 21:14
  Speaker 1: or anything that's carried by photons. And you can think
• 21:18
  Speaker 1: about this in two different ways. You can think about
• 21:19
  Speaker 1: in terms of the fields they're like electromagnetic fields that
• 21:23
  Speaker 1: fill the universe, or you can think about in terms
• 21:25
  Speaker 1: of particles, little photons passing back and forth. It's really
• 21:28
  Speaker 1: the same thing. You can think alsose photons is little
• 21:32
  Speaker 1: ripples in those fields. They're two totally equivalent but different
• 21:35
  Speaker 1: conceptual ways of thinking about it. So what do photons
• 21:40
  Speaker 1: interact with? Well, photons fly around the universe and they
• 21:43
  Speaker 1: can interact with anything that has electric charge. So, for example,
• 21:47
  Speaker 1: electrons interact via photons. When you push two electrons together,
• 21:51
  Speaker 1: they exchange photons, or you can think about their electric
• 21:54
  Speaker 1: fields affecting each other. So photons only interact with things
• 21:59
  Speaker 1: that have electric charge. Right, If you put a neutral
• 22:02
  Speaker 1: particle in an electric field, it just ignores that. It
• 22:05
  Speaker 1: can't tell it's there, it's not affected at all. So
• 22:08
  Speaker 1: what does that mean, right, Why do photons only interact
• 22:12
  Speaker 1: with particles that have electric charge? We don't really know,
• 22:15
  Speaker 1: and you can kind of turn the question around. Electric
• 22:19
  Speaker 1: charge is sort of just like a description of the
• 22:21
  Speaker 1: fact that the particle does interact with an electric field.
• 22:24
  Speaker 1: We don't know what generates it, or where it comes from,
• 22:27
  Speaker 1: or why it's there. It's sort of like a label
• 22:30
  Speaker 1: that says whether or not the particle feels the electric field,
• 22:34
  Speaker 1: whether or not the particle can interact with photons. So
• 22:37
  Speaker 1: the picture we have of electromagnetism is that the photons
• 22:40
  Speaker 1: fly through the universe and they touch stuff that have
• 22:43
  Speaker 1: this special property we call electric charge either positive or negative.
• 22:47
  Speaker 1: All right, So let's take that sort of framework for
• 22:49
  Speaker 1: understanding and turn it around and look at the weak force.
• 22:52
  Speaker 1: The weak force has different particles it uses to interact
• 22:55
  Speaker 1: or equivalently, different fields and uses to interact with. These
• 22:59
  Speaker 1: particles are the W and Z boson. There's three of them.
• 23:02
  Speaker 1: There's Z boson and to W particles. There's a W
• 23:05
  Speaker 1: plus that has a positive electric charge and a W
• 23:08
  Speaker 1: minus that has a minus electric charge. So the weak
• 23:11
  Speaker 1: force has these three particles. These particles fly around and
• 23:15
  Speaker 1: they interact with any particle that has the weak version
• 23:18
  Speaker 1: of electric charge. So every particle out there has either
• 23:22
  Speaker 1: a positive, negative, or zero charge that tells you whether
• 23:25
  Speaker 1: a photon interacts with it. There's a version of that
• 23:28
  Speaker 1: electric charge which operates for the weak force, and it
• 23:31
  Speaker 1: works the same way. If a particle has we call
• 23:34
  Speaker 1: it weak hypercharge, that means that it feels the W
• 23:38
  Speaker 1: and Z boson so it can interact with them. And
• 23:40
  Speaker 1: so now you can think about every particle is having
• 23:43
  Speaker 1: two kinds of charges. One that we used to just
• 23:45
  Speaker 1: call charge. Now we think about as electric charge because
• 23:48
  Speaker 1: it refers to whether it interacts with electromagnetism, and another
• 23:52
  Speaker 1: kind of charge that tells us whether it interacts with
• 23:56
  Speaker 1: the weak force. So we have electric charge and weak hypercharge,
• 23:59
  Speaker 1: and only particles that have weak hypercharge will interact with
• 24:03
  Speaker 1: the weak force, and every particle that we discovered so
• 24:06
  Speaker 1: far has weak hypercharge. For those of you super into
• 24:10
  Speaker 1: particle physics, you know that that's a little bit of
• 24:12
  Speaker 1: a lie, because for example, electrons have a left and
• 24:15
  Speaker 1: a right handed version, and only the left handed version
• 24:18
  Speaker 1: interacts with the weak force. The right handed version doesn't
• 24:21
  Speaker 1: have weak hypercharge. But anyway, everything out there has it,
• 24:25
  Speaker 1: including the Higgs boson. So what does it mean then,
• 24:28
  Speaker 1: to say that electromagnetism and the weak force are linked?
• 24:31
  Speaker 1: Are there the same thing? If they were the same thing,
• 24:34
  Speaker 1: they should do the same thing, and for example, the
• 24:36
  Speaker 1: photon should interact with neutrinos. Right, Well, they are not
• 24:40
  Speaker 1: the same thing. There are two parts of something larger.
• 24:43
  Speaker 1: It's like saying, oh, our heads and tails the same thing. No,
• 24:47
  Speaker 1: they're connected. There are two parts of the same coin.
• 24:50
  Speaker 1: It doesn't mean that they are the same thing, right,
• 24:53
  Speaker 1: But what it means that when you fit them together
• 24:55
  Speaker 1: you get an object which makes sense, which sort of
• 24:58
  Speaker 1: reflects a larger concept. And so what we do here
• 25:02
  Speaker 1: is we take these three week bosons, the two ws
• 25:05
  Speaker 1: and the Z and the single electromagnetic boson, the photon,
• 25:10
  Speaker 1: and we put them together and we have four bosons.
• 25:12
  Speaker 1: But there's something very cool that happens when you put
• 25:14
  Speaker 1: these four particles together, because they snap together mathematically and
• 25:19
  Speaker 1: they work together. And when you consider them all together
• 25:22
  Speaker 1: instead of individually, you notice something really cool happens, something physical,
• 25:26
  Speaker 1: which is there's a new conserved quantity. You know, for example,
• 25:30
  Speaker 1: how energy is usually conserved, but parts of energy are
• 25:33
  Speaker 1: not always conserved. You can go, for example, from having
• 25:36
  Speaker 1: kinetic energy to potential energy and back. So kinetic energy
• 25:40
  Speaker 1: by itself is not conserved. Potential energy by itself is
• 25:44
  Speaker 1: not conserved. But when you put those together, boom, you
• 25:47
  Speaker 1: get a larger concept energy which is conserved. So when
• 25:50
  Speaker 1: you put these three bosons from the weak force to
• 25:53
  Speaker 1: gather with this boson from electromagnetism, they operate together to
• 25:57
  Speaker 1: create a new symmetry, as symmetry that protects this property
• 26:01
  Speaker 1: called weak isospin that we don't have to get into.
• 26:04
  Speaker 1: But that's what tells us that we think they really
• 26:06
  Speaker 1: are related. We think they really are part of something larger.
• 26:10
  Speaker 1: There's a lot of really beautiful mathematics that tells us
• 26:13
  Speaker 1: that these things really do fit together. And you know,
• 26:16
  Speaker 1: these four particles we think have more in common than
• 26:20
  Speaker 1: you might think. Three of them operate for the weak force,
• 26:23
  Speaker 1: one of them operates for electricity magnetism, And while they
• 26:26
  Speaker 1: look different, they do have a lot in common. One
• 26:29
  Speaker 1: way that they look different is that the photon doesn't
• 26:31
  Speaker 1: have any mass, but the W and the z bosons
• 26:35
  Speaker 1: do have a lot of mass. And that's why the
• 26:37
  Speaker 1: weak force is weak. It's weak because those particles are
• 26:40
  Speaker 1: so massive that they don't last very long. The weak
• 26:43
  Speaker 1: force becomes a very weak and very short range force,
• 26:46
  Speaker 1: whereas photons that have no mask can fly all through
• 26:49
  Speaker 1: the universe and last for billions of years before they
• 26:51
  Speaker 1: get to your eyeball or hit another star or whatever. Well,
• 26:55
  Speaker 1: the reason that the W and the Z bosons half
• 26:57
  Speaker 1: mass and the photons don't is the higg field. The
• 27:01
  Speaker 1: Higgs field is an idea that came out of this question.
• 27:04
  Speaker 1: We saw that all these particles had a lot in common.
• 27:07
  Speaker 1: It made perfect sense to fit the photon in with
• 27:10
  Speaker 1: the weak bosons, except for this one puzzle, which is
• 27:14
  Speaker 1: why is the photon have no mass while the other
• 27:16
  Speaker 1: ones do and the Higgs field is the answer to that.
• 27:20
  Speaker 1: It breaks what we call electro weak symmetry, the symmetry
• 27:24
  Speaker 1: that protects weak isospin this way that these four particles
• 27:27
  Speaker 1: fit together. They fit together beautifully and perfectly if all
• 27:30
  Speaker 1: the particles have no mass. But then the Higgs field
• 27:33
  Speaker 1: comes along and it gives mass to three of those particles,
• 27:36
  Speaker 1: which become the weak force, and so the Higgs boson
• 27:40
  Speaker 1: sort of breaks that otherwise beautiful symmetry. So it's awesome,
• 27:44
  Speaker 1: and we think it's real because it led us to
• 27:46
  Speaker 1: discover the Higgs boson. It's like a fun, interesting mathematical
• 27:50
  Speaker 1: puzzle that told us something was going on and led
• 27:54
  Speaker 1: us to discover the Higgs boson. So we don't think
• 27:57
  Speaker 1: that the weak force and electricity and magnetism are exactly
• 28:00
  Speaker 1: the same thing. That we think they fit together to
• 28:03
  Speaker 1: make a larger hole. That sort of makes more conceptual
• 28:06
  Speaker 1: sense and reflects something physical about our universe. That doesn't
• 28:09
  Speaker 1: mean they always have to do the same thing. And so,
• 28:12
  Speaker 1: for example, why don't neutrinos feel the photon. It's because
• 28:16
  Speaker 1: they have no electric charge, and the photon only interacts
• 28:20
  Speaker 1: with things that have electric charge, and so that might
• 28:22
  Speaker 1: seem like a non answer, Like you might also ask
• 28:25
  Speaker 1: why do neutrinos have no electric charge? And that's a
• 28:28
  Speaker 1: great question and not a question we have an answer to.
• 28:32
  Speaker 1: This is the kind of thing that we observe, we discover,
• 28:34
  Speaker 1: we catalog and we wait for the future generations of
• 28:38
  Speaker 1: physicists to understand these patterns. There are lots of obvious,
• 28:42
  Speaker 1: apparent patterns in the sort of periodic table of the
• 28:45
  Speaker 1: fundamental particles, the quirks and the leptons, that are not
• 28:48
  Speaker 1: explained at all, and one of them are these weird charges,
• 28:53
  Speaker 1: you know. Another one is like why do the charges
• 28:55
  Speaker 1: of the proton and the electron exactly balance? The proton
• 28:59
  Speaker 1: gets it's electric charges from the corks that make it up,
• 29:02
  Speaker 1: but we don't have any relationship in the standard model
• 29:05
  Speaker 1: between those charges. They could have any value basically, and
• 29:08
  Speaker 1: yet they magically add up to the proton and the
• 29:11
  Speaker 1: electronic exactly the opposite charge, not like opposite by one
• 29:15
  Speaker 1: percent or by point one percent exactly opposite. So that
• 29:19
  Speaker 1: seems like a clue. So there are lots of really
• 29:22
  Speaker 1: deep mysteries remaining about why particles have charged, why some
• 29:25
  Speaker 1: don't have charge, why other ones, for example, feel the
• 29:28
  Speaker 1: strong force, and electrons and neutrinos don't feel a strong force.
• 29:32
  Speaker 1: Not something we understand at all, just something we are observing.
• 29:35
  Speaker 1: But we're noticing these patterns, and we're fitting them together
• 29:38
  Speaker 1: into larger ideas that we think reflects sort of deeper
• 29:42
  Speaker 1: understandings of how these forces are connected and might one
• 29:45
  Speaker 1: day lead us on a path to unify even more
• 29:48
  Speaker 1: forces and take steps towards our goal of having the
• 29:51
  Speaker 1: one force that rules them all. All right, super fun question,
• 29:55
  Speaker 1: Thanks very much. I want to answer another question, but
• 29:58
  Speaker 1: first let's take a second break. All right, we're back.
• 30:13
  Speaker 1: We've been talking about the smells of space and the
• 30:16
  Speaker 1: nature of fundamental particles, and so now I want to
• 30:19
  Speaker 1: turn our minds again out into the depth of space
• 30:22
  Speaker 1: and answer a super fun question from Matha about aliens. Hi, Daniel,
• 30:27
  Speaker 1: and Hore. This is Massa from Boston. I love your
• 30:30
  Speaker 1: podcasts and have listened to every episode so far. I
• 30:33
  Speaker 1: have a question that was inspired by a recent episode
• 30:35
  Speaker 1: about how we can detect exo galactic exo planets. If
• 30:39
  Speaker 1: there were a solar system identical to ours, where Alpha
• 30:42
  Speaker 1: Centauri is four light years away, complete with a copy
• 30:45
  Speaker 1: of our Sun as well as a copy of Earth
• 30:48
  Speaker 1: with over seven billion people, and there are f and
• 30:50
  Speaker 1: atmospheric output, would we be able to detect that planet's presence.
• 30:55
  Speaker 1: Would we be able to detect life? Would we be
• 30:58
  Speaker 1: able to detect intelligent life if it had to our
• 31:00
  Speaker 1: level of technology, and if not, at the rate of
• 31:03
  Speaker 1: which our detection and capabilities presently advantacy roughly one, might
• 31:07
  Speaker 1: we be able to detect human activity from a range
• 31:09
  Speaker 1: of four light years? Would it be ten years, fifty years?
• 31:14
  Speaker 1: For the sake of this hypothetical exercise, let's assume that
• 31:17
  Speaker 1: whatever alignment necessary to use the various detection methods is
• 31:19
  Speaker 1: in place. Keep up the good work, guys. All right,
• 31:22
  Speaker 1: thank you very much Maza for that really fun and
• 31:25
  Speaker 1: detailed question. I'm really looking forward of digging into how
• 31:29
  Speaker 1: we might detect life around our nearest star. Though. It's
• 31:32
  Speaker 1: a reasonable question, because you know now we are developing
• 31:36
  Speaker 1: this capability to see planets around other stars and to
• 31:39
  Speaker 1: study their atmospheres. And our technology is increasing, and so
• 31:42
  Speaker 1: you might ask, you know, is it likely that we
• 31:45
  Speaker 1: could find aliens around nearby stars? And you know, should
• 31:48
  Speaker 1: we be expecting this news any day? Or equivalently, the
• 31:52
  Speaker 1: fact that we haven't yet announced to discovery of aliens,
• 31:55
  Speaker 1: does that mean that we haven't found them or that
• 31:57
  Speaker 1: we're just not yet capable. So super fun question. Let's
• 32:01
  Speaker 1: break it up into three parts. First, he was just wondering,
• 32:04
  Speaker 1: could we tell if there was a planet around Alpha Centauri.
• 32:08
  Speaker 1: Alpha Centauri is a nearby star system. It's one of
• 32:11
  Speaker 1: the closest ones in our neighborhood in the Milky Way.
• 32:14
  Speaker 1: There just aren't that many stars. Is on average several
• 32:18
  Speaker 1: light years between stars, which means you want to get
• 32:21
  Speaker 1: from here to there, it's going to take you a
• 32:23
  Speaker 1: long long time. And so that's why I think massa
• 32:25
  Speaker 1: pick like the nearest solar system, one that we might
• 32:28
  Speaker 1: possibly be able to visit or at least talk to
• 32:32
  Speaker 1: or observe aliens. So let's remind ourselves how do we
• 32:36
  Speaker 1: find planets around other stars? Because mostly looking at them
• 32:41
  Speaker 1: is impossible. These planets are very close to their stars
• 32:44
  Speaker 1: compared to their distance from Earth, so basically right on
• 32:47
  Speaker 1: top of the star, which makes it very hard to
• 32:50
  Speaker 1: distinguish them from their star. You can't seem the reflected
• 32:53
  Speaker 1: light from a planet that's so far away and so
• 32:56
  Speaker 1: close to something else really really bright. So we have
• 32:59
  Speaker 1: a few methods of observing planets around other stars. The
• 33:02
  Speaker 1: first one is called the wobble method, is just using
• 33:05
  Speaker 1: the gravitational tug of the planet on the star. The planet,
• 33:10
  Speaker 1: of course, is also a big massive object. It has
• 33:12
  Speaker 1: its own gravity, and so it pulls on the star
• 33:15
  Speaker 1: and makes it wobble a little bit, and we can
• 33:17
  Speaker 1: use that to detect the existence of a planet. Another method,
• 33:21
  Speaker 1: which is even more powerful. It's called the transit method.
• 33:24
  Speaker 1: This allows us to find a planet when it passes
• 33:27
  Speaker 1: in front of the star, effectively blocking some of the
• 33:31
  Speaker 1: life from the starts like a many planetary eclipse. Of course,
• 33:34
  Speaker 1: it doesn't completely block the star because the star is
• 33:37
  Speaker 1: much much bigger than the planet, but by the fraction
• 33:40
  Speaker 1: of the star's light that dips, we can tell how
• 33:43
  Speaker 1: big that planet is. So that's pretty awesome because it
• 33:46
  Speaker 1: lets us measure the radius of that planet, and by
• 33:50
  Speaker 1: the orbital period we can tell the mass of the planet,
• 33:53
  Speaker 1: so then we can get a pretty good sense of
• 33:56
  Speaker 1: how big and how large, and therefore how dense that
• 34:00
  Speaker 1: and it is, and therefore what it's made out of.
• 34:03
  Speaker 1: Is it big and fluffy like cotton candy or does
• 34:05
  Speaker 1: it have the density of Jubiter or like the density
• 34:08
  Speaker 1: of Earth. So we can get a pretty good sense
• 34:10
  Speaker 1: for what's going on with these planets, and these methods
• 34:13
  Speaker 1: work for really distant planets. We have studied planets across
• 34:16
  Speaker 1: a big swath the Milky Way. The Milky Way remembers
• 34:19
  Speaker 1: about a hundred thousand light years across, and we've detected
• 34:23
  Speaker 1: planets as far away as about twenty five thousand light
• 34:26
  Speaker 1: years away. That's because some of these methods are pretty
• 34:29
  Speaker 1: insensitive to the distance of the star. If you're looking
• 34:33
  Speaker 1: at the wobble method, for example, we get that information
• 34:35
  Speaker 1: by how the light from the star is shifting as
• 34:38
  Speaker 1: the star is wobbling, and that information doesn't fade as
• 34:41
  Speaker 1: the star gets further and further away, so we can
• 34:44
  Speaker 1: detect planets around stars that are much further away than
• 34:47
  Speaker 1: Alpha Centauri. Typically, though, it's easier to detect really big
• 34:51
  Speaker 1: planets like Jupiter size planets, because they're bigger, they block
• 34:55
  Speaker 1: more light, and they have more mass, they tug on
• 34:57
  Speaker 1: their star and they block their star more dramatically. But
• 35:00
  Speaker 1: for a nearby star like Alpha Centauri, it's really no problem.
• 35:04
  Speaker 1: And in fact, there's even a star that's a tiny
• 35:07
  Speaker 1: bit closer. It's called Proxima Centauri, and we have found
• 35:11
  Speaker 1: an earth like planet around Proxima Centauri. It's about the
• 35:14
  Speaker 1: same size of Earth's about bigger, and it has about
• 35:18
  Speaker 1: the right density to be a rocky planet. So we
• 35:20
  Speaker 1: think that there is an Earth like rocky planet in
• 35:24
  Speaker 1: ahabitable zone around a nearby star. So that one we
• 35:28
  Speaker 1: can definitely check off the answer to be yes, we
• 35:31
  Speaker 1: can detect nearby planets in nearby solar systems, So that
• 35:35
  Speaker 1: we have done. The next question is much harder. Could
• 35:39
  Speaker 1: we detect life on that planet? How could we do it?
• 35:42
  Speaker 1: This is really chicky because before you even get started
• 35:44
  Speaker 1: you have to ask a definitional question. Right if Jorgey
• 35:47
  Speaker 1: would hear, he would say, hold on a second, what
• 35:49
  Speaker 1: do you even mean by life? Do we mean animals,
• 35:52
  Speaker 1: do we mean plants? Do we just mean microbes? Are
• 35:55
  Speaker 1: we open to something which is completely different from life
• 35:58
  Speaker 1: on Earth? And it sort of gets to what question
• 36:02
  Speaker 1: are you asking? What do you want to discover, And
• 36:05
  Speaker 1: for me, I'd like to discover life on other planets
• 36:08
  Speaker 1: just because it gives me a sense that there might
• 36:10
  Speaker 1: be life all over the universe, which tells me there
• 36:12
  Speaker 1: might be intelligent life, there might be an incredible diversity
• 36:15
  Speaker 1: of things to learn from. And so I don't want
• 36:17
  Speaker 1: to discover life as we know it. I don't want
• 36:20
  Speaker 1: to find an alien planet with trees and slugs and
• 36:23
  Speaker 1: all sorts of other familiar things on it, because that
• 36:26
  Speaker 1: would be kind of boring. I want to see other
• 36:28
  Speaker 1: examples of life, things I couldn't have imagined myself. That's
• 36:34
  Speaker 1: the joy of doing science in this universe is being surprised,
• 36:38
  Speaker 1: is finding things you couldn't have imagined that even science
• 36:41
  Speaker 1: fiction writers hadn't considered. Those are the best moments in science.
• 36:45
  Speaker 1: Those are also the hardest discoveries to make, because you
• 36:48
  Speaker 1: somehow have to be open to them. The only ways
• 36:51
  Speaker 1: we know to look for life are the ways we
• 36:53
  Speaker 1: have thought to look for life, which are limited to
• 36:56
  Speaker 1: the kinds of life we have thought of. So let's
• 36:59
  Speaker 1: focus on that. Even though I prefer to discover something
• 37:02
  Speaker 1: super weird and something super surprising, But could we detect
• 37:05
  Speaker 1: life as we know a massa was imagining, You know,
• 37:08
  Speaker 1: a bunch of people around a planet a few light
• 37:10
  Speaker 1: years away, could we tell they were there? So, the
• 37:13
  Speaker 1: only way we can really study distant planets and ask
• 37:16
  Speaker 1: the question about whether there's life on them is looking
• 37:19
  Speaker 1: at their atmosphere. And you might think a whole lot
• 37:21
  Speaker 1: of second, we only recently figured out how to detect
• 37:23
  Speaker 1: the existence of those planets. How are we going to
• 37:26
  Speaker 1: possibly sample their atmosphere. We can sample their atmosphere using
• 37:30
  Speaker 1: light from their star when that planet eclipses the star.
• 37:34
  Speaker 1: The light passes through the atmosphere of the planet before
• 37:38
  Speaker 1: coming to Earth, and we can tell We can tell
• 37:40
  Speaker 1: when the planet starts to eclipse the star, and we
• 37:42
  Speaker 1: can try to study just that light that sort of
• 37:45
  Speaker 1: skimmed the surface of the planet went through that atmosphere
• 37:49
  Speaker 1: and came to us. And that light will be changed
• 37:51
  Speaker 1: by what's in the atmosphere because the atmosphere, based on
• 37:55
  Speaker 1: its chemistry, will absorb different things. If there's water in
• 37:58
  Speaker 1: that atmosphere, it will absorb light at the right energy
• 38:02
  Speaker 1: levels for water to absorb it, and then we will
• 38:04
  Speaker 1: notice some frequencies missing in the light that comes from
• 38:08
  Speaker 1: the atmosphere. Or if there's methane in the atmosphere, or
• 38:11
  Speaker 1: if there's phosphing, for example, in that atmosphere, and so
• 38:14
  Speaker 1: we can use that technique to sort of probe the
• 38:16
  Speaker 1: atmosphere of that alien planet. It's not great, it's not
• 38:20
  Speaker 1: super high precision, but we're getting much much better at it,
• 38:23
  Speaker 1: and it's very promising. On the other hand, it's not
• 38:26
  Speaker 1: always conclusive. Right, So we see methane around Mars, does
• 38:30
  Speaker 1: that mean that there's life on Mars. We don't really know.
• 38:33
  Speaker 1: Nobody really believes that there's life on Mars until we
• 38:36
  Speaker 1: see those criters wriggling around. We know that there's methane
• 38:39
  Speaker 1: production on Mars. We even know that it's seasonal. It
• 38:43
  Speaker 1: seems like maybe something is waking up on Mars and
• 38:45
  Speaker 1: farting and during the summer and then in the winter
• 38:48
  Speaker 1: less cell. But there are other explanations you could come
• 38:51
  Speaker 1: up with, like geological explanations for the production of methane
• 38:54
  Speaker 1: on Mars. And we recently saw the signal on Venus
• 38:58
  Speaker 1: of phosphing production. Phosphing is something people imagine could only
• 39:01
  Speaker 1: be produced by processes we understand to be life, but
• 39:06
  Speaker 1: it's a difficult thing to see in there's a lot
• 39:08
  Speaker 1: of background, and recently those discoveries have been kind of debunked.
• 39:12
  Speaker 1: It looks like the signal isn't really there. That sort
• 39:15
  Speaker 1: of a data analysis problem, but the takeaway messages it's hard.
• 39:19
  Speaker 1: You might be able to detect specific gases in the
• 39:22
  Speaker 1: atmospheres on planets around other stars, but having like a
• 39:26
  Speaker 1: really smoking guns signal for life just from atmosphere composition
• 39:31
  Speaker 1: is pretty difficult. So what we really need is a
• 39:34
  Speaker 1: much clear signal that there's intelligent life. Massa is asking
• 39:38
  Speaker 1: if there are folks on that planet broadcasting the golden
• 39:40
  Speaker 1: age of television, would we be able to see it?
• 39:44
  Speaker 1: And so this again is more like life as we
• 39:47
  Speaker 1: know it, except it's intelligent life as we know it. Questions,
• 39:50
  Speaker 1: you know, could there be intelligent life that's out there
• 39:53
  Speaker 1: that's broadcasting messages that we are missing because we don't
• 39:56
  Speaker 1: know to look for them, or we haven't imagined the
• 39:59
  Speaker 1: format it could exist in. Absolutely, there could be life
• 40:02
  Speaker 1: that exists on very long time scales and their message
• 40:06
  Speaker 1: takes a hundred years even just to listen to, or
• 40:09
  Speaker 1: life that lives on short time skills, or life that's
• 40:11
  Speaker 1: communicating in some medium we haven't even imagined maybe they've
• 40:15
  Speaker 1: discovered axions and they are the best way to communicate
• 40:17
  Speaker 1: in the universe, and we don't even know the exist
• 40:20
  Speaker 1: and so we're missing all the information. Think about how
• 40:23
  Speaker 1: many thousands of years humans lived on Earth and didn't
• 40:27
  Speaker 1: understand all the information around us before we even knew
• 40:30
  Speaker 1: new trinos existed, and the wealth of information they encode
• 40:33
  Speaker 1: about the nature of the universe and what's going on
• 40:35
  Speaker 1: in supernova So it's certainly very possible that there's a
• 40:39
  Speaker 1: huge amount of information, maybe even about alien life that's
• 40:42
  Speaker 1: just washing over us now because we do not know
• 40:45
  Speaker 1: how to recognize it. But that's again, that's sort of
• 40:48
  Speaker 1: an unprobable question. It's potentially infinite. It's the unknown unknowns.
• 40:52
  Speaker 1: So let's focus on the known knowns. If there was
• 40:55
  Speaker 1: a civilization on this planet around Proxima Centauri, would we
• 40:59
  Speaker 1: be able to pick up their signals. Well, if they're
• 41:02
  Speaker 1: not broadcasting to us, then probably not. The reason is
• 41:06
  Speaker 1: that they are still pretty far away. Remember that signals
• 41:10
  Speaker 1: fade with distance and not a little bit. They fade
• 41:13
  Speaker 1: with distance squared. If you shine a flashlight, for example,
• 41:17
  Speaker 1: then the photons you're sending out from your flashlights spread out,
• 41:20
  Speaker 1: and as the area that they cover gets bigger and bigger,
• 41:23
  Speaker 1: the density of photons per area falls. And so, for example,
• 41:27
  Speaker 1: if you broadcast a signal in every direction, then it
• 41:31
  Speaker 1: gets spread across the inside of a sphere, and as
• 41:33
  Speaker 1: the radius of that sphere grows, the area of that
• 41:36
  Speaker 1: sphere grows with the radius squared. So that's why signals
• 41:40
  Speaker 1: fall by one over the distance squared. The same thing
• 41:43
  Speaker 1: for the law of gravity and electromagnetism. It's all very geometrical.
• 41:47
  Speaker 1: But the problem is if you're not beaming us a signal,
• 41:50
  Speaker 1: then your signal has to be really powerful at the
• 41:53
  Speaker 1: source for it to still be detectable by the time
• 41:56
  Speaker 1: it lasts four light years. The reason we can see
• 41:59
  Speaker 1: those stars is because they are incredibly bright. If you
• 42:03
  Speaker 1: were close to the Centauri, of course, it would blind you.
• 42:06
  Speaker 1: The reason that we can see the light from the
• 42:08
  Speaker 1: star is because that sun is so luminous. So a
• 42:11
  Speaker 1: message from a planet around Proximus Centauri would have to
• 42:15
  Speaker 1: be extraordinarily strong. We are not yet capable as the
• 42:18
  Speaker 1: species of generating a signal that strong if it's beamed
• 42:22
  Speaker 1: in all directions. For example, our most powerful radio telescope
• 42:26
  Speaker 1: until recently was Arecibo. Aricibo could detect a message from
• 42:32
  Speaker 1: a similar telescope to Aricibo if it was within one
• 42:36
  Speaker 1: light year, but of course there are no other stars
• 42:39
  Speaker 1: within one light year, and even the closest star is
• 42:41
  Speaker 1: four light years away, so we couldn't detect omnidirectional messages
• 42:46
  Speaker 1: sent in every direction from a technology similar to ours.
• 42:49
  Speaker 1: They would have to be beaming it to us, which
• 42:52
  Speaker 1: is totally possible. If you knew we were here, you
• 42:54
  Speaker 1: could send a message directly to us from that planet,
• 42:58
  Speaker 1: But they would somehow have to know we were here
• 43:00
  Speaker 1: and then send us a message, and that we could
• 43:03
  Speaker 1: definitely hear. If we detected somehow aliens existing on that planet,
• 43:07
  Speaker 1: we could definitely beam them a message that they would
• 43:09
  Speaker 1: be able to pick up. Now, remember that conversation would last,
• 43:13
  Speaker 1: you know, decades, because it takes five years almost just
• 43:16
  Speaker 1: for our message to arrive. Then they have to argue
• 43:19
  Speaker 1: about how to respond and then send us a reply,
• 43:21
  Speaker 1: so it's like ten years between responses, and you know
• 43:24
  Speaker 1: how we're going to figure out how to even talk
• 43:26
  Speaker 1: to them. It takes ten minutes even just to start
• 43:29
  Speaker 1: a Skype conversation these days, and make sure everybody can
• 43:32
  Speaker 1: hear you. Imagine how many back and force it takes
• 43:34
  Speaker 1: to establish like the basis for communication and learn each
• 43:38
  Speaker 1: other's languages and understand what a language even is and
• 43:41
  Speaker 1: do they use mathematics, and like, we would have a
• 43:43
  Speaker 1: lot to learn and taking ten years between questions and answers.
• 43:46
  Speaker 1: It would take a long time, but I hope that
• 43:49
  Speaker 1: it happens, and I look forward to one day listening
• 43:51
  Speaker 1: to that message from Proximus Centauri. Alright, so thank you
• 43:55
  Speaker 1: everybody for sending in your questions and for coming along
• 43:58
  Speaker 1: with us on this ride and curiosity and wondering about
• 44:01
  Speaker 1: the universe. I want to make sure your questions are answered.
• 44:04
  Speaker 1: That's right, I'm talking to you specifically. You've got a
• 44:08
  Speaker 1: question in there you haven't asked. Please send it to
• 44:10
  Speaker 1: us to questions at Daniel and Jorge dot com. I
• 44:13
  Speaker 1: promise you you'll get an answer. Thanks for listening, and
• 44:24
  Speaker 1: remember that Daniel and Jorge explained. The Universe is a
• 44:26
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• 44:30
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