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