Speaker 1: Hey, Daniel, what's been in our inbox lately? Well, we
Speaker 1: get the usual stuff, people with minor corrections, people with
Speaker 1: you know, cosmic questions, people asking me for to send
Speaker 1: them special stuff for Father's Day. So you said people
Speaker 1: are asking about Father's Day. Yes, some people right in
Speaker 1: I like this because they're not actually fans of our show,
Speaker 1: but their dad or their mom is a fan of
Speaker 1: the show, and they want us to send a special
Speaker 1: Father's Day or Mother's Day message to their parents who listens.
Speaker 1: So it's like young, cool, hip people saying, Hey, my
Speaker 1: dad likes your show, and I have no ideas for
Speaker 1: any Father's Day's gifts. So do we charge for these
Speaker 1: or we don't charge for these because we're nice guys
Speaker 1: and we like helping people, and we're also fathers, and
Speaker 1: so I want to give a special shout out to
Speaker 1: Paul truth Low, whose daughter Caitlin asked us to give
Speaker 1: you a special Father's Day message. So happy Father's Day, Paul,
Speaker 1: and uh roll Tide, I'm supposed to say. Also, Hi,
Speaker 1: I'm Poor Hay, I'm a cartoonists and the creator of
Speaker 1: PhD Comics. Hi I'm Daniel Whitson, I'm a particle physicist
Speaker 1: by day and a podcaster by any other time I know.
Speaker 1: Welcome to our podcast Daniel and Jorge Explain at Universe,
Speaker 1: a production of I Heart Radio in which we really do,
Speaker 1: honestly try to answer questions about physics, Questions that we have,
Speaker 1: questions that you have, Questions that we just randomly float
Speaker 1: into our minds some days. Yeah, and if you actually
Speaker 1: send us a question, either at questions at Daniel and
Speaker 1: Jorge dot com or any one of our social media
Speaker 1: channels like Instagram or Twitter or Facebook, we will actually
Speaker 1: get to your question and maybe even talk about it
Speaker 1: on the podcast. That's right, because when you have a question,
Speaker 1: probably other people have the same question. And that's the
Speaker 1: wonderful thing about having people suggest questions, because sometimes there's
Speaker 1: an angle to something that we haven't thought of because
Speaker 1: we come at it from a scientific perspective, and seeing
Speaker 1: it from the point of view of the audience helps
Speaker 1: us really explain these things, really get down and untangle
Speaker 1: all those mysteries that you have in your mind, because
Speaker 1: our goal is at the end of this that you
Speaker 1: have a crystal clear picture what's going on in this universe.
Speaker 1: And if you send us a question that stumps Daniel,
Speaker 1: you actually get a prize, right, Daniel, Yeah, banana cake.
Speaker 1: I don't know. It's a podcast has to be audio,
Speaker 1: So the sound of Jorgey eating a banana cake that
Speaker 1: Daniel made. How about that? Some Rader shows give you
Speaker 1: your phone message, they'll record your your voicemail message. We
Speaker 1: will record one of the hosts eating bananas. What could
Speaker 1: be better than that? Yeah? Well, hey, that could be
Speaker 1: a good ring tone, right, that could be a good ringtowne. Hey,
Speaker 1: I got a call coming and how do you know
Speaker 1: it sounds like something's eating in your pocket. Yeah, that's right.
Speaker 1: If you're really kind of personally doesn't like peop believing
Speaker 1: your voicemails, this is this is the contest for you
Speaker 1: right here. That's right, that's right. No, seriously, I would
Speaker 1: love to get a question that stumps me. Um. I
Speaker 1: do get questions A lot of times. I get questions
Speaker 1: I've never heard before, and that's a wonderful experience because
Speaker 1: you know, there's a standard as the questions people ask.
Speaker 1: But then there's a question I'd never even thought to
Speaker 1: ask before, and that's wonderful because it gives me a
Speaker 1: little view into the mind of the question er. I
Speaker 1: have to think what did they understand or what was
Speaker 1: going on in their head that inspired this question, so
Speaker 1: that I can then figure out how to guide them
Speaker 1: from there to a clear picture of what's actually happening.
Speaker 1: And that's the challenge of teaching, and that's what I
Speaker 1: really love about that. So these are questions you hadn't
Speaker 1: even thought anyone could ask or would ask. Yeah, I'll
Speaker 1: give you an example. Um, I give demonstrations at elementary
Speaker 1: school sometimes and we use like liquid nitrogen and all
Speaker 1: sorts of stuff too, you know. Um, one time we
Speaker 1: froze bananas and shattered it on the ground and the
Speaker 1: kids thought that was cool, and afterwards were open for questions.
Speaker 1: Wait wait, wait, you shattered bananas. That's right, some bananas
Speaker 1: were harmed in the making of this pod cast. I
Speaker 1: have to oh, man, my heart is bleeding, Daniel. But
Speaker 1: afterwards we were open for questions, and some kid raised
Speaker 1: his hand and he says, if lightsabers were real, would
Speaker 1: they be made of liquid nitrogen? And I thought, I
Speaker 1: have no idea how to answer that question, you know, like,
Speaker 1: where do you even begin. You rolled your eye, You're like,
Speaker 1: obviously they're made out of hyper crystal. Wikid do your research.
Speaker 1: I had not done my research on fictional universes and
Speaker 1: how science might work in that fictional universe. But I
Speaker 1: love that he connected two things he found amazing liquid
Speaker 1: nitrogen and lightsabers, and thought maybe these are the same things.
Speaker 1: And actually we get a lot of emails like that.
Speaker 1: They're like, hey, today you guys talked about the mystery
Speaker 1: of you know, dark matter. Maybe that's the same thing
Speaker 1: as this other mystery. Like after our time episode, a
Speaker 1: lot of people wrote in and said, maybe dark energy
Speaker 1: is just a mistake of how we observe time, and
Speaker 1: time doesn't just move forward constantly. It's sort of stutter steps,
Speaker 1: and that's dark energy. People love to connect to mysteries
Speaker 1: and try to solve them at once. So you know
Speaker 1: that little boy in the class, he really exemplified the
Speaker 1: kinds of questions that that listeners ask. We're all just
Speaker 1: little Star Wars fans inside. That's right, that's right. Yeah,
Speaker 1: Well today we are answering your questions on the podcast.
Speaker 1: Today's episode is about listener questions Part four, right or
Speaker 1: are we up to part pie? Are we sort of
Speaker 1: this version? Pie? I think our podcasts are integer numbered, Yeah,
Speaker 1: so this would be number four. It would be awesome
Speaker 1: to have a point one four of a podcast, but
Speaker 1: I'm not sure how do you pull that off? All right,
Speaker 1: So today we have three interesting questions from listeners from
Speaker 1: all across the world, right or at least the United States. Oh,
Speaker 1: I think some of them are international. They don't always
Speaker 1: tell us where they come from, but based on the accent,
Speaker 1: I don't think all of these come from the Southwest
Speaker 1: the United States, which seems to be are a big
Speaker 1: hotbed for fans over our show. No, it was just random.
Speaker 1: Last time I happened to pick three questions which all
Speaker 1: like came from the south I was totally just random.
Speaker 1: But today we have three pretty cool questions from listeners.
Speaker 1: One is about gravity, another one about dark matter, and
Speaker 1: the other one is about the nuclei of Adam, Like
Speaker 1: how do they stay together? And why don't we all
Speaker 1: just explode into balls of nuclear explosions? Maybe we will.
Speaker 1: You'll find out on today's episode. I think people um
Speaker 1: might already know the answer. But teaser, you're you're okay
Speaker 1: for the next couple of seconds. You'll survive long enough
Speaker 1: to hear the end of this episode at the very least,
Speaker 1: and then you can you can then explode view like
Speaker 1: from knowledge? Do you think anybody has ever perished while
Speaker 1: listening to our episode? That just dark thoughts just entered
Speaker 1: my head. Oh my god, let's let's cut that out.
Speaker 1: Can you imagine being the last thing anybody ever heard
Speaker 1: in their life for making a joke about bananas? It
Speaker 1: blew their minds, banded their idea of what a joke
Speaker 1: could be, and it's just overwhelmed their neural network. Yeah.
Speaker 1: I don't know if that means the joke was amazing
Speaker 1: so good that they couldn't take it, or they're just like,
Speaker 1: you know what, I'm done after that. I can't take
Speaker 1: anymore people get paid to say those kinds of jokes.
Speaker 1: Then I'm out of here. There's no amazing to go on.
Speaker 1: That's right, goodbye, cool, unfunny world. Well help, neither of
Speaker 1: these things happen to you, our dear listeners. But our
Speaker 1: first question comes from Florence from Texas, and she has
Speaker 1: a question about how gravity could um keep the Earth
Speaker 1: in orbit. Here's what you had to say. I have
Speaker 1: a question about gravity. You've described it before as the
Speaker 1: weakest force, and you said in fact that it's so
Speaker 1: weak that when you're picking up an object with a magnet,
Speaker 1: you're overpowering the entire Earth's gravity, So that's pretty weak.
Speaker 1: My problem is when I start thinking about the objects
Speaker 1: and the Kuiper Belt, they're thirty two fifty astronomer gold
Speaker 1: units away and that's billions and billions of miles, and
Speaker 1: yet the Sun's gravity is still able to keep them
Speaker 1: in orbit. And that just gives me the impression that
Speaker 1: gravity is really strong, not weak. So those two thoughts
Speaker 1: really don't go together. Um, would you help me with that?
Speaker 1: All right? Thank you, Florence from Texas. So that's a
Speaker 1: pretty interesting question, right, Daniel. Is that we often mentioned
Speaker 1: on the show that gravity is the weakest force, and
Speaker 1: it's actually super duper duper weak. But at the same time,
Speaker 1: I think maybe a lot of listeners are thinking, but
Speaker 1: weight of gravity is a weak how is it keeping
Speaker 1: the Earth going around in orbit and other planets in Jupiter?
Speaker 1: And how is it such an amazing, an incredible force
Speaker 1: in the universe. It is an amazing, incredible force in
Speaker 1: the universe, And you're right to wonder about that, because
Speaker 1: as you look out into the night sky, you think about,
Speaker 1: like all the structures in the universe, the Solar system
Speaker 1: with the planets going around the Sun, and even the
Speaker 1: galaxy and the structures of galaxies and the superclusters, all
Speaker 1: of that is determined by gravity, right, So gravity seems
Speaker 1: to have a huge role in organizing the way the
Speaker 1: universe works, right, And and the way we discovered dark
Speaker 1: matters through gravity. And so if you just looked at it,
Speaker 1: you say, well, gravity is one of the most important
Speaker 1: forces because it shapes the whole universe. So then to
Speaker 1: hear somebody say actually, gravity is the weakest force in
Speaker 1: the universe, it does seem like a strong contradiction, right,
Speaker 1: it It doesn't make sense in your mind, because how
Speaker 1: can it be the weakest force and also be the
Speaker 1: thing that shapes everything else? Right, It's kind of like
Speaker 1: the organizing force in the universe, right, It organizes planets
Speaker 1: into solar systems, and solar systems into galaxies and galaxies
Speaker 1: in two clusters. Like if we didn't have gravity, everything
Speaker 1: which is a fly fly away and fly apart. Yeah,
Speaker 1: that's right, we wouldn't have any of the good stuff
Speaker 1: that we have without gravity. So we own a big
Speaker 1: thanks to gravity. And I like the way you said
Speaker 1: it's I sort of organized these things. I think that's
Speaker 1: one of the big ideas to understand how gravity can
Speaker 1: play such a big role and be so weak. It's
Speaker 1: sort of like the way you make a big mess
Speaker 1: in your house and then you come back home and
Speaker 1: your mom is organized the living room or whatever. Right,
Speaker 1: some mysterious forces organized it while while you were gone.
Speaker 1: Your mom still cleans your house. That's pretty good. Know what,
Speaker 1: your mom cleans my house where hey, she doesn't. She
Speaker 1: doesn't clean yours. She flies from Panama every every week
Speaker 1: and clean your house and she doesn't even call me.
Speaker 1: Oh my god, Maybe because I didn't celebrate Mother's Day. Yeah, exactly,
Speaker 1: Well you should have sent her banana cake. Um No.
Speaker 1: But the point I wanted to make, the actual physics point,
Speaker 1: not a joke, is that gravity is a force that's
Speaker 1: sort of left over like all the other forces in
Speaker 1: the universe. Electromagnetism, the strong force, the weak force. All
Speaker 1: these forces are so powerful that they get kind of
Speaker 1: naturally balanced. Like there's no electrostatic force or electromagnetic force
Speaker 1: between the Earth and the Sun. Why because if there were,
Speaker 1: it would be incredibly powerful and it would balance itself
Speaker 1: the way like lightning is a balancing of the electrons
Speaker 1: between the Earth and the sky. Right, anytime there's any
Speaker 1: imbalance June, there's a huge bolt of lightning to balance
Speaker 1: these things out. And so as a result, there is
Speaker 1: no electromagnetic force between these huge celestial objects, and so
Speaker 1: it's gravity. Gravity can't be balanced though. It's the one
Speaker 1: force that cannot be neutralized because it only has mass.
Speaker 1: There's no negative mass to balance it out. So after
Speaker 1: all the other forces have made their big mess, gravity
Speaker 1: sort of left to pick up the pieces. It's the
Speaker 1: only thing left on the playing field, right. Well, I
Speaker 1: think it's important to maybe mention that when we say
Speaker 1: it's the weakest force, it's a relative assessment, right, Like
Speaker 1: we're we're not saying gravity is weak, it's just weak
Speaker 1: relative to the electromagnetic force. Well I'm saying it. No,
Speaker 1: I'm saying gravity is super weak. It's embarrassing. It's puny's pathetic,
Speaker 1: but only only because you know other forces that are stronger.
Speaker 1: But if you didn't know the other forces, you'd be like,
Speaker 1: oh my god. Gravity is what keeps the Earth from
Speaker 1: going around the Sun, and the Earth is pretty big,
Speaker 1: so it's like a huge force. You just know that
Speaker 1: in comparison, it's kind of wimpy. I guess, so, I mean,
Speaker 1: I think in comparison is really the only metric we have.
Speaker 1: It's also important to recognize how much weaker it is.
Speaker 1: Like if you took electrons, for example, and you asked, like,
Speaker 1: what is the force of their electrostatic repulsion compared to
Speaker 1: their gravitational um attraction, then the difference is like ten,
Speaker 1: with thirty three zeros after it. So you know, millions, billions, trillions, quadrillions.
Speaker 1: You run out of numbers really quick. It's a huge difference.
Speaker 1: It's like a completely different scale, right, So you're saying,
Speaker 1: if I have an electron and maybe a proton, they're
Speaker 1: both being attracted by two forces, gravity and electromagnetism. But
Speaker 1: you're saying the electromagnetism is thirty two orders of magnetudes
Speaker 1: stronger than the gravitational force between them. Yeah, exactly, They're
Speaker 1: totally different scales, exactly. Electromagnetism, I mean, it's jatillion. What
Speaker 1: what's the word for thirty zeros? It's an alien you
Speaker 1: go be a zillion um. It's so much bigger. If
Speaker 1: you don't even really want to describe them in the
Speaker 1: same level. It's like, you know, the mass of the
Speaker 1: Earth versus the math of mass of a penny or something.
Speaker 1: You know, you don't you don't call a penny a
Speaker 1: celestial object because it isn't right so tiny, you just
Speaker 1: sort of round it up into the earth um. Anyway,
Speaker 1: the reason that gravity can still play on the field
Speaker 1: at all is that these other forces are so strong
Speaker 1: that they balance each other out, and gravity you can't
Speaker 1: do that, right, Like we were talking about one electron
Speaker 1: another electron, they repel each other, whereas an electron or
Speaker 1: a proton they attract each other. Right, Gravity only makes
Speaker 1: attractive forces. Everything with mass feels gravity and it attracts itself.
Speaker 1: There's no way to have repulsive gravity. And we did
Speaker 1: a whole podcast episode about anti gravity. As far as
Speaker 1: we know, it's not possible. So there's no way to
Speaker 1: balance gravity out. After everybody else has done their stuff
Speaker 1: and and been neutralized, gravity is left over, and so
Speaker 1: then it gets to organize the universe. Yeah, I was thinking,
Speaker 1: like maybe an interesting picture is to imagine a proton
Speaker 1: in the Sun and then imagine a proton and an
Speaker 1: electron on Earth. It's not that there's no electromagnetic force
Speaker 1: between that proton and this proton and electron. It's just
Speaker 1: that that the proton in the sun's pulling the electron
Speaker 1: towards the Sun, but it's also pushing the proton away
Speaker 1: from the Sun with the exact same force. So our
Speaker 1: pair of proton and electron here on Earth just doesn't
Speaker 1: feel any electro metnetic force with that proton in the Sun,
Speaker 1: but it does feel gravity, yeah, exactly. And you know,
Speaker 1: there's lots of protons and electrons in the Sun, and
Speaker 1: so they all work, they all arrange themselves in such
Speaker 1: a way that there's effectively no net force, and there's
Speaker 1: no way to arrange the protons electrons to get no
Speaker 1: net gravitational force. There's just no way to do that.
Speaker 1: But I think it's interesting to think about. It's not
Speaker 1: that there's no force, it's just that there's no net force,
Speaker 1: you know, like it is pushing and pulling as electromagnetically
Speaker 1: the Sun, it all just sort of cancels out. Yeah, yeah,
Speaker 1: like it's pushing on a proton and it's pushing on
Speaker 1: an electron the opposite direction, right, But because our proton
Speaker 1: and the electron are holding on together, they're they're not
Speaker 1: going anywhere. Yeah, that's that's a fine way to think
Speaker 1: about it. Um. And I think the other thing to
Speaker 1: recognize is that gravity is really really weak, but the
Speaker 1: Sun is really really big, like really really really really big,
Speaker 1: so it can have a pretty strong gravitational effect on
Speaker 1: the Earth even though gravity is weak, because it just
Speaker 1: has so much mass, right, And so yeah, gravity is weak,
Speaker 1: but the Sun is so big that those two factors
Speaker 1: kind of cancel each other out and it becomes an
Speaker 1: important force. Yeah, the weakness accumulates exactly. You have like
Speaker 1: a billion people all whispering your name, it's going to
Speaker 1: add up to a huge scream, right, And that's the
Speaker 1: way it is with gravity. All those protons in the
Speaker 1: Sun are giving a tiny little tug on the protons
Speaker 1: and electrons on Earth gravitationally. But there's so many protons
Speaker 1: in the Sun that it's enough to pull a whole
Speaker 1: planet around in a circle. Right. It's not a small
Speaker 1: amount of force to keep the Earth in orbit, right,
Speaker 1: It's a huge force that keeps the Earth in orbit.
Speaker 1: Oh man, you just gave me a new nightmare. To
Speaker 1: imagine a billion people whispering my name. That is so bizarre.
Speaker 1: That is kind of creepy. Actually, yes, that doesn't where
Speaker 1: that came from. Hey, let's all whisper Paul's name for
Speaker 1: for father's sake, for father's days, didn't heal sense of
Speaker 1: disturbance in the force when that happens. Everybody listened to
Speaker 1: me to this right now, go Paul, Paul, Happy Father's Day, Paul,
Speaker 1: your daughter is awesome. Cool. All right, that's um Florence's
Speaker 1: question about gravity, and so the answer Florence is that
Speaker 1: gravity is weak, but it's also happening on such a
Speaker 1: large scale that it does. It is enough to pool
Speaker 1: planets and keep galaxies together, that's right. And after all
Speaker 1: the other forces have done their business, gravity is left
Speaker 1: over to organize the universe because it can't be balanced out.
Speaker 1: All right, Well, that's one question, and we'll get to
Speaker 1: the two other questions we have today about dark matter
Speaker 1: and atomic nuclei. But first let's take a quick break.
Speaker 1: Our second question of the day comes from Margie, who
Speaker 1: has a question about dark matter. Hey, Daniel and Jorge,
Speaker 1: this is Marchie. My question is how does dark matter
Speaker 1: influence the movement of the planets in the Solar System?
Speaker 1: Does it make them all orbit at the same speed
Speaker 1: and if so, all right, that's a pretty interesting question. Um,
Speaker 1: we talked, we've talked a lot about dark matter in
Speaker 1: this podcast and how it's there. It's all around us,
Speaker 1: it's in the center of galaxies, right all over the galaxy,
Speaker 1: and it's constantly pulling on everything and helping galaxy stay together. Yeah,
Speaker 1: this is a wonderful question. And because this is a
Speaker 1: kind of question that shows me that people are doing
Speaker 1: physics in their mind, right, they says, you've learned how
Speaker 1: dark matter influences how galaxies rotate, Like we discovered dark
Speaker 1: matter because we saw the galaxies were spinning too fast
Speaker 1: and they need more gravity to hold them together. So
Speaker 1: that means that dark matter makes enough gravity to be
Speaker 1: like noticeable about how things spin. Right, So that the
Speaker 1: natural physics thing to do is to say, okay, I
Speaker 1: have my new understanding, let me apply it to something else.
Speaker 1: Does that make sense? And this listener obviously thought, well,
Speaker 1: if there's dark matter enough to affect the galaxy spinning,
Speaker 1: why can't we notice it here on Earth? Like, why
Speaker 1: can't we do that same measurement and see like, hey,
Speaker 1: the Earth is going around the Sun too fast? Can't
Speaker 1: we detect the dark matter in our Solar system by
Speaker 1: looking at how the Earth orbits the Sun the same
Speaker 1: way we look at how the Sun orbits the center
Speaker 1: of the galaxy. So it's really a genius question. Oh,
Speaker 1: I see. The question is is the Earth going around
Speaker 1: the Sun faster than it should be if dark matter
Speaker 1: didn't exist? Because imagine, for example, that there wasn't just
Speaker 1: the Sun in the center of the Solar system. Imagine
Speaker 1: there were five sons, but you can only see the
Speaker 1: one of them, right, and the other ones were made
Speaker 1: of dark matter. What would happen in that case. In
Speaker 1: that case, there'd be a much stronger gravitational force than
Speaker 1: you would expect from one Sun, and for the Earth
Speaker 1: to stay in its orbit, it would have to go
Speaker 1: much much faster, and so you would see a discrepancy.
Speaker 1: You'd measure the speed at which the Earth was orbiting
Speaker 1: the Sun, and you'd say, huh, it's going way too fast.
Speaker 1: What's what's um, what's keeping it together, what's keeping it
Speaker 1: in the Solar system? Why isn't it just flying off?
Speaker 1: And then you would deduce the presence of all those
Speaker 1: dark suns. Right, So this listener is like, well, can
Speaker 1: we see the dark matter? Because We've said on this
Speaker 1: podcast several times, a dark matter is everywhere. It's not
Speaker 1: just out there, it's here, It's in this room, it's
Speaker 1: on your planet, it's hanging out in that bunch of
Speaker 1: bananas you just ate. It's everywhere. So why can't we
Speaker 1: see it in our solar system? Right? Well, I guess
Speaker 1: question number one is is there dark matter in our
Speaker 1: solar system? And then question number two is is does
Speaker 1: it influence the orbit of planets? So that Daniels, is
Speaker 1: there a dark matter here in our solar system? We
Speaker 1: think so. Now we don't know for sure, and the
Speaker 1: reason is that gravity is pretty weak, right, as we
Speaker 1: talked about recently, and so it's hard to get a
Speaker 1: sense for exactly where dark matter is because the only
Speaker 1: way that we can see it is is through its
Speaker 1: gravitational effects, and so we can see its effects sort
Speaker 1: of like on a galaxy sized scale, but it's really
Speaker 1: hard to get a very clear map of where the
Speaker 1: dark matter is. But we think it probably is. We
Speaker 1: think it's probably distributed pretty evenly through the galaxy. There's
Speaker 1: a blob in the very center and it sort of
Speaker 1: just falls off gradually. So we suspect, like we would
Speaker 1: see it as a haze just permeating everything exactly. And
Speaker 1: you know what a deep question about dark matter is,
Speaker 1: like is it just a smooth haze or are there structures?
Speaker 1: It's a stuff happening. Is there like life forms in
Speaker 1: dark matter? We really don't know because we haven't been
Speaker 1: able to see it with enough resolution, because the only
Speaker 1: way we've ever been able to probe it is through gravity.
Speaker 1: And that's a it's you know, real frustration for us
Speaker 1: as scientists. It's like most of the matter in the
Speaker 1: universe is there, it's in front of us. We can't
Speaker 1: see it. We can't tell if it's doing anything interesting
Speaker 1: or just sort of a smooth haze. Right, And so
Speaker 1: the question is if we are kind of in a
Speaker 1: bath of dark matter right now, which we could be
Speaker 1: or could not be. Maybe we're like in a bubble
Speaker 1: of non dark matter. Is that possible? We might be
Speaker 1: in a little gap, It's possible, right, But I think
Speaker 1: the most sensible and the simplest assumption is just that
Speaker 1: dark matter is smooth, and as you say, we're in
Speaker 1: a bath of dark matter. I think that makes the
Speaker 1: most sense. It's it's the most likely explanation. Okay, So
Speaker 1: in that case, if we are bathing in dark matter,
Speaker 1: would it affect the orbit of the planets. So the
Speaker 1: short answer is yes, but not in a noticeable way.
Speaker 1: And the reason is that the Solar System is not
Speaker 1: big enough, right Like, if you take the density of
Speaker 1: dark matter, and we expected, it's about like one protons
Speaker 1: worth of dark matter about every three cubic centimeters, So
Speaker 1: there's not actually that much dark matter spread out over
Speaker 1: the universe, right Like, if you sort of look at
Speaker 1: your thumb, there's probably only one proton's worth of dark
Speaker 1: matter in it. Yeah. If you take all the dark
Speaker 1: matter and you spread it out evenly through space, then
Speaker 1: you end up with about one proton per per thumb.
Speaker 1: I Like, the thumb is a unit of volume. Yeah,
Speaker 1: one dark matter proton per thumb thumbs up. Yeah, And
Speaker 1: you might and you might be thinking, hold on, isn't
Speaker 1: there supposed to be more dark matter than normal matter?
Speaker 1: And there is, but there's five times as much. But
Speaker 1: here we're sort of spreading it evenly through space, so
Speaker 1: we can imagine how it might affect the Solar System,
Speaker 1: but we we actually don't sort of know that, right Like,
Speaker 1: it could be all concentrated in my thumb, or it
Speaker 1: could just be kind of this haze that's covering everything. Yes,
Speaker 1: it could all be concentrated in your thumb. Now there's
Speaker 1: some limits. I mean, if dark matter was really really
Speaker 1: clumpy and it was all concentrated in your thumb, that
Speaker 1: would be a huge amount of mass and we would
Speaker 1: definitely notice that, Like your thumb would be attracting stuff
Speaker 1: to it all the time, like a crazy weird magnet.
Speaker 1: My thumb is pretty attractive. Well do you hitch high
Speaker 1: a lot? Did your thumb stop a lot of cars? Uh? Yeah, No,
Speaker 1: I get I get compliments from about my thumb all
Speaker 1: the time. I'm gonna believe that for a second. I
Speaker 1: don't believe that for a second. You're like, I've seen
Speaker 1: your thumb. It's nothing special. Next time we're in a
Speaker 1: random situation, I'm gonna ask somebody to come in on
Speaker 1: your thumb and we'll just see what they say. All right,
Speaker 1: let's do it. If you take one protons worth of
Speaker 1: dark matter per thumb and you add that all up
Speaker 1: inside the Solar system, it adds up to a lot.
Speaker 1: It's like ten to the ten kms of dark matter
Speaker 1: in the Solar system, and that might seem like, oh
Speaker 1: my gosh, that's a huge amount, ten to the ten,
Speaker 1: but it's small compared to the Sun, which is like
Speaker 1: ten to the thirty. So dark matter, if you spread
Speaker 1: it out evenly, there's not enough of it in our
Speaker 1: solar system to influence the gravity on top of what
Speaker 1: the Sun is already doing. So you're saying, like, our
Speaker 1: solar system is a it's kind of a concentrated part
Speaker 1: of the universe where there's a lot of mass here
Speaker 1: as opposed to like in the empty gas between solar systems,
Speaker 1: And so you're saying, like, here in our neighborhood, there
Speaker 1: is just a lot more of the regular stuff than
Speaker 1: there is dark matter. So dark matter is kind of
Speaker 1: negligible right here where we are, exactly. Dark matter is
Speaker 1: negligible for the for the gravitational effects of the Earth
Speaker 1: and the Sun, exactly right, because mostly the Sun is
Speaker 1: a concentrated blob of normal matter, and we don't think
Speaker 1: the dark matter has been concentrated in that same way.
Speaker 1: Not only is it negligible, but it's also going to
Speaker 1: spread out evenly all around us, right, So it wouldn't
Speaker 1: it would be sort of maybe tugging us in all
Speaker 1: directions at the same time and maybe not really affecting
Speaker 1: the orbit. It would be tugging us in all directions.
Speaker 1: But um physics says that if you're moving in an orbit,
Speaker 1: you're affected by the mass of all the stuff that's
Speaker 1: the smaller radius than your orbit, and you actually it
Speaker 1: doesn't matter how that's distributed inside that radius. If it's
Speaker 1: like you know, like if the Sun was a point particle,
Speaker 1: or the Sun was its normal size or twice its size,
Speaker 1: if it doesn't change its mass, the physics says that
Speaker 1: it doesn't affect how you're how the force of gravity
Speaker 1: acts on that body. It all integrates out to be
Speaker 1: the same thing. So the dark matter outside of our
Speaker 1: orbit is just cannot affect our orbit. That's right. It's
Speaker 1: sort of like that episode we talked about where you
Speaker 1: jump into the center of the Earth. You're only affected
Speaker 1: by the mass of the Earth has a smaller radius
Speaker 1: than you do. Everything else outside of you cancels out
Speaker 1: because there's always one bit tugging you here and another
Speaker 1: bit tugging you the other direction, and the stuff with
Speaker 1: a smaller orbit adds up to give you an overall tug.
Speaker 1: That's the same as if you just put a particle
Speaker 1: with the mass of that stuff at the center of
Speaker 1: mass of it, which would be the center of the Earth.
Speaker 1: So in this case you would still be affected by
Speaker 1: dark matter, and we are, like the orbit of the
Speaker 1: Earth is affected by the dark matter in the Solar system,
Speaker 1: but it's you know, one part in tend of the twenty,
Speaker 1: so it's not measurable. So you're saying that we do
Speaker 1: sort of have like an equivalent of a dark Sun
Speaker 1: in the middle of our Solar system affecting our orbit.
Speaker 1: It's just very small, that's right. Dark matter is changing
Speaker 1: our lives. It makes our years shorter by one part
Speaker 1: and tend to the twenty because it speeds up the
Speaker 1: Earth because of its additional gravity. But it's you know,
Speaker 1: it's not something we can measure on the galaxy scale,
Speaker 1: though you can. And the reason it affects things on
Speaker 1: the galaxy scale, the reason that you can detect it
Speaker 1: at all, is that galaxies are just so much bigger
Speaker 1: than solar systems, and so they add up to a
Speaker 1: huge amount of dark matter um compared to the mass
Speaker 1: of the Sun. Like the stuff in between solar systems
Speaker 1: adds up. But maybe the stuff within a Solar System
Speaker 1: doesn't add up to much exactly. So when you're calculating
Speaker 1: the force of gravity on the Sun as it rotates
Speaker 1: around the center of the galaxy, it's influenced by everything
Speaker 1: that has a radius smaller than it's compared to the
Speaker 1: center of the galaxy, and that's a huge amount of
Speaker 1: dark matter. Well, I think that's probably why I was
Speaker 1: late to the recording of this podcast. It's it was,
Speaker 1: you know, dark matter shortening my ear. That's right, Well,
Speaker 1: you used up your one you know, one ten, one
Speaker 1: in ten of the twenty a year, so you need
Speaker 1: another excuse next, no build over my entire life and
Speaker 1: leading up to me being late to this podcast, it's
Speaker 1: not that you were finishing that one last piece of
Speaker 1: banana cream cake. No, no, I finished that, Yester. Al Right.
Speaker 1: So that's Marki's question about whether dark matter affects the
Speaker 1: orbits of the planets in our Solar system, and the
Speaker 1: answer is yes, we kind of do have a dark
Speaker 1: matter sun in our dark dark matter mass in our
Speaker 1: Solar system, making everything just a little bit faster, go
Speaker 1: faster around the Solar System, but it's really not measurable,
Speaker 1: and without seeing how galaxy spin, I don't think we
Speaker 1: ever would have discovered dark matter just by looking at
Speaker 1: the orbit of the Earth. All right, thank you, Margie,
Speaker 1: And so we'll get to our last question from Prita
Speaker 1: when we get back from a quick break. Alright, our
Speaker 1: last question of this episode comes from Preda, and she
Speaker 1: has a question about why the nucleus is stable. I
Speaker 1: imagine the nucleus of an atom, right, what else could
Speaker 1: it be about the nucleus of what the cell, the
Speaker 1: nucleus of a banana? At This is a physics podcast, man,
Speaker 1: So here's a Prettius question. My name is Pritto, and
Speaker 1: my question is why is the nucleus of an atom
Speaker 1: even stable? The nucleus of atom has protons which are
Speaker 1: positively charged. They're supposed to reple each other and they're
Speaker 1: not supposed to stay to Please explain why does this happen? Right?
Speaker 1: So Preta wants to know how a nucleus can be
Speaker 1: stable like because then the nuclei of atoms are made
Speaker 1: up of protons mostly right, and nucle and neutrons but
Speaker 1: mostly but a lot of protons, and all the protons
Speaker 1: are positively charged, so they should be repelling each other
Speaker 1: with the electro magnetic force. Yeah, So how how do
Speaker 1: how can they all stay together? How? How is it
Speaker 1: that you and I are here? Daniel? Yeah, I love
Speaker 1: that we're talking about forces and force, bouncing and all
Speaker 1: these questions today. This is a great question, right, And
Speaker 1: they all are positive and they are pushing away from
Speaker 1: from each other. So what holds it together? There? Um?
Speaker 1: I don't know, that's a really positive thing, I think, yeah,
Speaker 1: and kind of negative to well. I'm kind of neutral
Speaker 1: on the topic. But I was wondering whether people knew
Speaker 1: about this, like is this a common question? Do people
Speaker 1: have an idea? So actually, yesterday when my kids were
Speaker 1: watching a movie, I walked around the mall here in
Speaker 1: Irvine and I asked people, um if they knew what
Speaker 1: kept the nucleus together? And I got some interesting answers. Cool.
Speaker 1: So here's what people had to say. Do you know
Speaker 1: why the nucleus stays together? Like what keeps it together
Speaker 1: if it's all positive charges opposite course on the outside,
Speaker 1: or what holds an atom together? Huh? Right, I'm sure
Speaker 1: I learned that in physics long ago, but I can't remember.
Speaker 1: I don't know about that one. I don't know more
Speaker 1: electrons they stay together because the more protons there are,
Speaker 1: the heavier the atomic weight. So what do you think
Speaker 1: Now we're getting random people on the street to answer
Speaker 1: listen to questions. Eventually we don't even need to be
Speaker 1: here anymore, right, Yeah, I wish you just crowdsource this podcast,
Speaker 1: just going the mom and be like, hey, here's the question.
Speaker 1: We'll give you twenty bucks to talk about it for
Speaker 1: forty minutes. Exactly. That's our retirement plan. Uh No, this
Speaker 1: one was interesting enough, and I really was curious about
Speaker 1: what people knew. So I thought, we don't often do
Speaker 1: this for listening to questions, but I did the man
Speaker 1: of the street interviews for this one. Well, I'm surprised
Speaker 1: that people kind of I knew a little bit of
Speaker 1: what you were talking about, right, because they they were like, oh,
Speaker 1: you mean like the O an Adam, and they sort
Speaker 1: of understood the question because it's not an easy question
Speaker 1: to get your head around, right. No, it's not an
Speaker 1: easy question. It's not a simple answer. But you're right,
Speaker 1: people understood the question and that was cool. Um, so
Speaker 1: I think it is a common question. And all these
Speaker 1: people after I asked them, they're like, we tell me
Speaker 1: what is the answer? You can't just walk away after
Speaker 1: asking me that question. I have to know now it's
Speaker 1: like inspire this burning desire and them to understand why
Speaker 1: their nuclei were not flying apart. Do you try to
Speaker 1: when you're roaming the malls looking for people? Do you
Speaker 1: try to always hit like the you know, the dad
Speaker 1: or the mom just waiting for their kids or their
Speaker 1: spouse who's dropping. I try to ask people who are
Speaker 1: on their phone board. Yeah. I don't interrupt people in
Speaker 1: conversation or people who look like they're going somewhere. I
Speaker 1: look for somebody who's like sitting there on their phone
Speaker 1: obviously waiting for somebody to like try on pants or something,
Speaker 1: so they don't they don't. I don't want to interrupt
Speaker 1: somebody's day. You're going to the dressing room, You're like, hey,
Speaker 1: I have a physics question for you, friendly neighborhood physicist.
Speaker 1: Physicists arrested at local mall and then I ask people
Speaker 1: in the next cell when I get arrested. All right,
Speaker 1: so let's ask you the question. So how is it
Speaker 1: that protons stick together inside the nuclei of atoms? Yeah, Well,
Speaker 1: to answer this question, you need to understand a little
Speaker 1: bit about how protons and neutrons are held together because
Speaker 1: protons and neutrons, remember, are not fundamental particles, but they're
Speaker 1: made of quarks. So there's up corks and down corks,
Speaker 1: and those particles are held together by a different force
Speaker 1: called the strong nuclear force, and it's called the strong
Speaker 1: nuclear force because it's super duper strong. It's much much
Speaker 1: stronger an electromagnetism, which of course puts gravity to shame.
Speaker 1: So the strong nuclear force is the strongest, most powerful
Speaker 1: force we've ever discovered, and that's what holds the protons together. Yeah,
Speaker 1: it's the reason the protons and the neutrons their bound
Speaker 1: states of this force, so that there's quarks inside the
Speaker 1: proton and quirks inside the neutron, and they're exchanging gluons
Speaker 1: all the time. There is this particle called a gluon
Speaker 1: which holds the corks together into a proton and into
Speaker 1: a neutron. So that's what holds the protons and neutrons together.
Speaker 1: But what what keeps the protons from repelling each other? Yeah,
Speaker 1: so the strong nuclear force which holds them together. It's
Speaker 1: very short range, like it's super powerful, but it doesn't
Speaker 1: go very far, but it extends a little bit of
Speaker 1: ways past the edge of the proton, and so what
Speaker 1: happens is that there's a little bit of the strong
Speaker 1: nuclear force left over between the corks inside the proton
Speaker 1: and neutron to attract the protons and neutrons to each other.
Speaker 1: So even this little extra bit of the strong nuclear
Speaker 1: force is enough to overcome the pulsion of the protons
Speaker 1: because they have the same charge. Oh really, I never
Speaker 1: thought about that? Is that? Is that? How you explain it?
Speaker 1: Is that the force that's keeping the protons together is
Speaker 1: also the force that keeps a proton stuck to another proton,
Speaker 1: because it's sort of leaks outside of the proton. Yeah. Essentially,
Speaker 1: it's like the quarks in one proton are talking a
Speaker 1: little bit with the quirks in the neighboring proton or
Speaker 1: the neighboring neutron, and to them, the fact that there's
Speaker 1: like an overall positive charge in protons and um and
Speaker 1: not a neutrons is irrelevant because those forces are so
Speaker 1: weak compared to the strong nuclear force. The strong nuclear
Speaker 1: force doesn't care about your electro magnetic charge, right, Yeah, exactly,
Speaker 1: doesn't care at all. And the corks do have electromagnetic
Speaker 1: charges and Actually they're really weird that like two thirds
Speaker 1: charges and minus one thirds charge. They're pretty strange, but
Speaker 1: they're the forces are much weaker than the strong nuclear force.
Speaker 1: So the strong nuclear force sort of leaks out of
Speaker 1: the proton and into the next neutron and into that
Speaker 1: next neutron, and that's how they tie themselves together. There's
Speaker 1: enough lefto or after you make the proton or the
Speaker 1: neutron to tie it to the next one. How can
Speaker 1: there be any leftover? I mean, if if the proton
Speaker 1: is stable right like it likes being held together, how
Speaker 1: can it have any leftover? You know, attraction, doesn't it
Speaker 1: all just cancel out within the proton? How can you
Speaker 1: have some left over to attract more protons? Now, you're right,
Speaker 1: and it would if all the corks inside the proton
Speaker 1: were like right on top of each other, but they're not.
Speaker 1: They're like all slashing around. So if you're like on
Speaker 1: one side of the proton, you're a little bit closer
Speaker 1: to one of the corks than the other two, and
Speaker 1: so the force from that one little cork is enough
Speaker 1: to have like a little bit of leftover charge. So
Speaker 1: actually maybe two protons being stuck together makes them weaker inside, right,
Speaker 1: each one is maybe just a little bit weaker because
Speaker 1: they're stuck to each other. You can think of it
Speaker 1: sort of the way you know atoms for molecules, right,
Speaker 1: and atom is electrically neutral, right, because the protons and
Speaker 1: the electrons right are balanced. But how do atoms form
Speaker 1: molecules their bonds between the electrons because the electrons, you know,
Speaker 1: they talk to each other and one like jumps from
Speaker 1: here to there, and they exchange photons and stuff and
Speaker 1: so um, this is like protons getting stuck together by
Speaker 1: those extra little bits of leftover forces. So it's a
Speaker 1: strong nuclear force that's so much more powerful than electromagnetism
Speaker 1: that even the little extra leftover bits can overpower the
Speaker 1: protons pushing away from each other. This strikes me as
Speaker 1: a little bit as a nuclear infidelity. You know, like
Speaker 1: you've got three quarts being perfectly happy in a bond
Speaker 1: to make a proton, but then one of them is like, hey,
Speaker 1: look at that. There's some other quartz over there, and
Speaker 1: that other trio mana protons um a little bit attracted
Speaker 1: to them too, and so that's what brings the two
Speaker 1: things together. Right. Yeah, quarks feel a lot of love, right,
Speaker 1: They they're happy to to share their love with quarks
Speaker 1: even inside other protons and neutrons, and and and you know,
Speaker 1: the sort of a limit how much you can do
Speaker 1: this because these forces are very short range, and so
Speaker 1: the bigger the nucleus gets, then the weaker the sort
Speaker 1: of the stability of the nucleus. If you try to
Speaker 1: make a nucleus that's too big, then like the protons
Speaker 1: on the opposite sides of the nucleus, they'll feel the
Speaker 1: electrostatic repulsion, but they won't be close enough to feel
Speaker 1: the strong nuclear force anymore. And that's why like heavier
Speaker 1: elements are less stable and more likely like decay radioactively.
Speaker 1: That's why we use uranium and like uranium two thirty
Speaker 1: five to do radioactive fission, and not like helium or lithium.
Speaker 1: Put enough protons together, they bunch up, and at some
Speaker 1: point the nuclear force, the strong force, isn't enough. They
Speaker 1: start to repel each other exactly because the strong force
Speaker 1: drops very quickly with distance, right, And so if you're
Speaker 1: far enough away from the proton, then you don't feel
Speaker 1: it then all. Then it's like all the corks are
Speaker 1: on top of each other, and so that's why there's
Speaker 1: like a maximum size you can make to a nucleus
Speaker 1: because the strong force which holds it together it's a
Speaker 1: very short range. And when the nucleus gets sort of
Speaker 1: bigger than that range, then it can't do the job anymore.
Speaker 1: It's like, you know, you trying to hold a bunch
Speaker 1: of balloons, right, Imagine trying to hold a huge pile
Speaker 1: of balloons. Is a maximum number you can hold until
Speaker 1: somebody You need somebody else to come over and grab
Speaker 1: a bunch of them. So then the nucleus splits into two.
Speaker 1: And that's what happens in a radioactive decay. Alright, So
Speaker 1: then that's the answer to the question. The nucleus stays
Speaker 1: together even though the protons are are repelling each other,
Speaker 1: they're trying to push each other apart. There is another
Speaker 1: force that leaks out from inside of each proton that
Speaker 1: then sort of links up the two protons together, and
Speaker 1: that force is stronger than the electric magnetic repulsion exactly.
Speaker 1: That's what holds them together, and that's what holds us
Speaker 1: together with you, listeners, the force of these questions. You guys,
Speaker 1: have all these questions bouncing around your head, and you
Speaker 1: send them to us, and we love thinking about them,
Speaker 1: we love talking about them, and we love trying to
Speaker 1: explain them to you. And really it's this love of
Speaker 1: the universe and this desire to ask questions and this
Speaker 1: hunger to get the answers that brings us all together.
Speaker 1: All right, Well, thank you so much to Florence, Margie
Speaker 1: and Pritta for sending in their questions, and thanks to
Speaker 1: all of you who are sending us questions as well.
Speaker 1: We enjoy reading them and it kind of makes our
Speaker 1: day to hear from you. Guys. Absolutely, please don't stop
Speaker 1: sending questions questions at Daniel and Jorge dot com. All right,
Speaker 1: and that's our podcast. We hope you enjoyed those questions,
Speaker 1: and stay tuned for more amazing facts and questions and
Speaker 1: interesting perspectives about the universe. And stay tuned for the
Speaker 1: sound of Jorge enjoying a banana cake. That's right, one
Speaker 1: of you lucky people will win this prize. Lucky unlucky.
Speaker 1: We're not sure, but somebody's gonna win it. Positive and negative.
Speaker 1: See you next time. If you still have a question
Speaker 1: after listening to all these explanations, please drop us a line.
Speaker 1: We'd love to hear from you. You can find us
Speaker 1: at Facebook, Twitter, and Instagram at Daniel and Jorge That's
Speaker 1: one Word, or e fail us at feedback at Daniel
Speaker 1: and Jorge dot com. Thanks for listening and remember that
Speaker 1: Daniel and Jorge Explain the Universe is a production of
Speaker 1: I Heart Radio. For more podcast from My Heart Radio,
Speaker 1: visit the I heart Radio app, Apple Podcasts, or wherever
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