Listener Questions 4

Daniel and Jorge answer questions from listeners, like you!

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Episode Transcript

Speaker 1 (00:08):
Hey, Daniel, what's been in our inbox lately? Well, we
get the usual stuff, people with minor corrections, people with
you know, cosmic questions, people asking me for to send
them special stuff for Father's Day. So you said people
are asking about Father's Day. Yes, some people right in
I like this because they're not actually fans of our show,
but their dad or their mom is a fan of
the show, and they want us to send a special

(00:30):
Father's Day or Mother's Day message to their parents who listens.
So it's like young, cool, hip people saying, Hey, my
dad likes your show, and I have no ideas for
any Father's Day's gifts. So do we charge for these
or we don't charge for these because we're nice guys
and we like helping people, and we're also fathers, and
so I want to give a special shout out to

(00:50):
Paul truth Low, whose daughter Caitlin asked us to give
you a special Father's Day message. So happy Father's Day, Paul,
and uh roll Tide, I'm supposed to say. Also, Hi,

(01:15):
I'm Poor Hay, I'm a cartoonists and the creator of
PhD Comics. Hi I'm Daniel Whitson, I'm a particle physicist
by day and a podcaster by any other time I know.
Welcome to our podcast Daniel and Jorge Explain at Universe,
a production of I Heart Radio in which we really do,
honestly try to answer questions about physics, Questions that we have,
questions that you have, Questions that we just randomly float

(01:38):
into our minds some days. Yeah, and if you actually
send us a question, either at questions at Daniel and
Jorge dot com or any one of our social media
channels like Instagram or Twitter or Facebook, we will actually
get to your question and maybe even talk about it
on the podcast. That's right, because when you have a question,
probably other people have the same question. And that's the

(02:01):
wonderful thing about having people suggest questions, because sometimes there's
an angle to something that we haven't thought of because
we come at it from a scientific perspective, and seeing
it from the point of view of the audience helps
us really explain these things, really get down and untangle
all those mysteries that you have in your mind, because
our goal is at the end of this that you
have a crystal clear picture what's going on in this universe.

(02:24):
And if you send us a question that stumps Daniel,
you actually get a prize, right, Daniel, Yeah, banana cake.
I don't know. It's a podcast has to be audio,
So the sound of Jorgey eating a banana cake that
Daniel made. How about that? Some Rader shows give you
your phone message, they'll record your your voicemail message. We
will record one of the hosts eating bananas. What could

(02:44):
be better than that? Yeah? Well, hey, that could be
a good ring tone, right, that could be a good ringtowne. Hey,
I got a call coming and how do you know
it sounds like something's eating in your pocket. Yeah, that's right.
If you're really kind of personally doesn't like peop believing
your voicemails, this is this is the contest for you
right here. That's right, that's right. No, seriously, I would
love to get a question that stumps me. Um. I

(03:07):
do get questions A lot of times. I get questions
I've never heard before, and that's a wonderful experience because
you know, there's a standard as the questions people ask.
But then there's a question I'd never even thought to
ask before, and that's wonderful because it gives me a
little view into the mind of the question er. I
have to think what did they understand or what was
going on in their head that inspired this question, so

(03:27):
that I can then figure out how to guide them
from there to a clear picture of what's actually happening.
And that's the challenge of teaching, and that's what I
really love about that. So these are questions you hadn't
even thought anyone could ask or would ask. Yeah, I'll
give you an example. Um, I give demonstrations at elementary
school sometimes and we use like liquid nitrogen and all
sorts of stuff too, you know. Um, one time we

(03:49):
froze bananas and shattered it on the ground and the
kids thought that was cool, and afterwards were open for questions.
Wait wait, wait, you shattered bananas. That's right, some bananas
were harmed in the making of this pod cast. I
have to oh, man, my heart is bleeding, Daniel. But
afterwards we were open for questions, and some kid raised
his hand and he says, if lightsabers were real, would

(04:11):
they be made of liquid nitrogen? And I thought, I
have no idea how to answer that question, you know, like,
where do you even begin. You rolled your eye, You're like,
obviously they're made out of hyper crystal. Wikid do your research.
I had not done my research on fictional universes and
how science might work in that fictional universe. But I
love that he connected two things he found amazing liquid

(04:34):
nitrogen and lightsabers, and thought maybe these are the same things.
And actually we get a lot of emails like that.
They're like, hey, today you guys talked about the mystery
of you know, dark matter. Maybe that's the same thing
as this other mystery. Like after our time episode, a
lot of people wrote in and said, maybe dark energy
is just a mistake of how we observe time, and

(04:56):
time doesn't just move forward constantly. It's sort of stutter steps,
and that's dark energy. People love to connect to mysteries
and try to solve them at once. So you know
that little boy in the class, he really exemplified the
kinds of questions that that listeners ask. We're all just
little Star Wars fans inside. That's right, that's right. Yeah,
Well today we are answering your questions on the podcast.

(05:18):
Today's episode is about listener questions Part four, right or
are we up to part pie? Are we sort of
this version? Pie? I think our podcasts are integer numbered, Yeah,
so this would be number four. It would be awesome

(05:38):
to have a point one four of a podcast, but
I'm not sure how do you pull that off? All right,
So today we have three interesting questions from listeners from
all across the world, right or at least the United States. Oh,
I think some of them are international. They don't always
tell us where they come from, but based on the accent,
I don't think all of these come from the Southwest
the United States, which seems to be are a big

(06:00):
hotbed for fans over our show. No, it was just random.
Last time I happened to pick three questions which all
like came from the south I was totally just random.
But today we have three pretty cool questions from listeners.
One is about gravity, another one about dark matter, and
the other one is about the nuclei of Adam, Like
how do they stay together? And why don't we all

(06:22):
just explode into balls of nuclear explosions? Maybe we will.
You'll find out on today's episode. I think people um
might already know the answer. But teaser, you're you're okay
for the next couple of seconds. You'll survive long enough
to hear the end of this episode at the very least,
and then you can you can then explode view like
from knowledge? Do you think anybody has ever perished while

(06:44):
listening to our episode? That just dark thoughts just entered
my head. Oh my god, let's let's cut that out.
Can you imagine being the last thing anybody ever heard
in their life for making a joke about bananas? It
blew their minds, banded their idea of what a joke
could be, and it's just overwhelmed their neural network. Yeah.

(07:07):
I don't know if that means the joke was amazing
so good that they couldn't take it, or they're just like,
you know what, I'm done after that. I can't take
anymore people get paid to say those kinds of jokes.
Then I'm out of here. There's no amazing to go on.
That's right, goodbye, cool, unfunny world. Well help, neither of
these things happen to you, our dear listeners. But our

(07:29):
first question comes from Florence from Texas, and she has
a question about how gravity could um keep the Earth
in orbit. Here's what you had to say. I have
a question about gravity. You've described it before as the
weakest force, and you said in fact that it's so
weak that when you're picking up an object with a magnet,

(07:50):
you're overpowering the entire Earth's gravity, So that's pretty weak.
My problem is when I start thinking about the objects
and the Kuiper Belt, they're thirty two fifty astronomer gold
units away and that's billions and billions of miles, and
yet the Sun's gravity is still able to keep them
in orbit. And that just gives me the impression that
gravity is really strong, not weak. So those two thoughts

(08:13):
really don't go together. Um, would you help me with that?
All right? Thank you, Florence from Texas. So that's a
pretty interesting question, right, Daniel. Is that we often mentioned
on the show that gravity is the weakest force, and
it's actually super duper duper weak. But at the same time,
I think maybe a lot of listeners are thinking, but
weight of gravity is a weak how is it keeping

(08:34):
the Earth going around in orbit and other planets in Jupiter?
And how is it such an amazing, an incredible force
in the universe. It is an amazing, incredible force in
the universe, And you're right to wonder about that, because
as you look out into the night sky, you think about,
like all the structures in the universe, the Solar system
with the planets going around the Sun, and even the
galaxy and the structures of galaxies and the superclusters, all

(08:58):
of that is determined by gravity, right, So gravity seems
to have a huge role in organizing the way the
universe works, right, And and the way we discovered dark
matters through gravity. And so if you just looked at it,
you say, well, gravity is one of the most important
forces because it shapes the whole universe. So then to
hear somebody say actually, gravity is the weakest force in

(09:18):
the universe, it does seem like a strong contradiction, right,
it It doesn't make sense in your mind, because how
can it be the weakest force and also be the
thing that shapes everything else? Right, It's kind of like
the organizing force in the universe, right, It organizes planets
into solar systems, and solar systems into galaxies and galaxies
in two clusters. Like if we didn't have gravity, everything

(09:40):
which is a fly fly away and fly apart. Yeah,
that's right, we wouldn't have any of the good stuff
that we have without gravity. So we own a big
thanks to gravity. And I like the way you said
it's I sort of organized these things. I think that's
one of the big ideas to understand how gravity can
play such a big role and be so weak. It's
sort of like the way you make a big mess
in your house and then you come back home and

(10:00):
your mom is organized the living room or whatever. Right,
some mysterious forces organized it while while you were gone.
Your mom still cleans your house. That's pretty good. Know what,
your mom cleans my house where hey, she doesn't. She
doesn't clean yours. She flies from Panama every every week
and clean your house and she doesn't even call me.
Oh my god, Maybe because I didn't celebrate Mother's Day. Yeah, exactly,

(10:24):
Well you should have sent her banana cake. Um No.
But the point I wanted to make, the actual physics point,
not a joke, is that gravity is a force that's
sort of left over like all the other forces in
the universe. Electromagnetism, the strong force, the weak force. All
these forces are so powerful that they get kind of
naturally balanced. Like there's no electrostatic force or electromagnetic force

(10:45):
between the Earth and the Sun. Why because if there were,
it would be incredibly powerful and it would balance itself
the way like lightning is a balancing of the electrons
between the Earth and the sky. Right, anytime there's any
imbalance June, there's a huge bolt of lightning to balance
these things out. And so as a result, there is
no electromagnetic force between these huge celestial objects, and so

(11:09):
it's gravity. Gravity can't be balanced though. It's the one
force that cannot be neutralized because it only has mass.
There's no negative mass to balance it out. So after
all the other forces have made their big mess, gravity
sort of left to pick up the pieces. It's the
only thing left on the playing field, right. Well, I
think it's important to maybe mention that when we say
it's the weakest force, it's a relative assessment, right, Like

(11:32):
we're we're not saying gravity is weak, it's just weak
relative to the electromagnetic force. Well I'm saying it. No,
I'm saying gravity is super weak. It's embarrassing. It's puny's pathetic,
but only only because you know other forces that are stronger.
But if you didn't know the other forces, you'd be like,
oh my god. Gravity is what keeps the Earth from
going around the Sun, and the Earth is pretty big,

(11:53):
so it's like a huge force. You just know that
in comparison, it's kind of wimpy. I guess, so, I mean,
I think in comparison is really the only metric we have.
It's also important to recognize how much weaker it is.
Like if you took electrons, for example, and you asked, like,
what is the force of their electrostatic repulsion compared to
their gravitational um attraction, then the difference is like ten,

(12:18):
with thirty three zeros after it. So you know, millions, billions, trillions, quadrillions.
You run out of numbers really quick. It's a huge difference.
It's like a completely different scale, right, So you're saying,
if I have an electron and maybe a proton, they're
both being attracted by two forces, gravity and electromagnetism. But
you're saying the electromagnetism is thirty two orders of magnetudes

(12:42):
stronger than the gravitational force between them. Yeah, exactly, They're
totally different scales, exactly. Electromagnetism, I mean, it's jatillion. What
what's the word for thirty zeros? It's an alien you
go be a zillion um. It's so much bigger. If
you don't even really want to describe them in the

(13:02):
same level. It's like, you know, the mass of the
Earth versus the math of mass of a penny or something.
You know, you don't you don't call a penny a
celestial object because it isn't right so tiny, you just
sort of round it up into the earth um. Anyway,
the reason that gravity can still play on the field
at all is that these other forces are so strong
that they balance each other out, and gravity you can't

(13:24):
do that, right, Like we were talking about one electron
another electron, they repel each other, whereas an electron or
a proton they attract each other. Right, Gravity only makes
attractive forces. Everything with mass feels gravity and it attracts itself.
There's no way to have repulsive gravity. And we did
a whole podcast episode about anti gravity. As far as
we know, it's not possible. So there's no way to

(13:45):
balance gravity out. After everybody else has done their stuff
and and been neutralized, gravity is left over, and so
then it gets to organize the universe. Yeah, I was thinking,
like maybe an interesting picture is to imagine a proton
in the Sun and then imagine a proton and an
electron on Earth. It's not that there's no electromagnetic force

(14:06):
between that proton and this proton and electron. It's just
that that the proton in the sun's pulling the electron
towards the Sun, but it's also pushing the proton away
from the Sun with the exact same force. So our
pair of proton and electron here on Earth just doesn't
feel any electro metnetic force with that proton in the Sun,
but it does feel gravity, yeah, exactly. And you know,

(14:28):
there's lots of protons and electrons in the Sun, and
so they all work, they all arrange themselves in such
a way that there's effectively no net force, and there's
no way to arrange the protons electrons to get no
net gravitational force. There's just no way to do that.
But I think it's interesting to think about. It's not
that there's no force, it's just that there's no net force,
you know, like it is pushing and pulling as electromagnetically

(14:51):
the Sun, it all just sort of cancels out. Yeah, yeah,
like it's pushing on a proton and it's pushing on
an electron the opposite direction, right, But because our proton
and the electron are holding on together, they're they're not
going anywhere. Yeah, that's that's a fine way to think
about it. Um. And I think the other thing to
recognize is that gravity is really really weak, but the
Sun is really really big, like really really really really big,

(15:15):
so it can have a pretty strong gravitational effect on
the Earth even though gravity is weak, because it just
has so much mass, right, And so yeah, gravity is weak,
but the Sun is so big that those two factors
kind of cancel each other out and it becomes an
important force. Yeah, the weakness accumulates exactly. You have like
a billion people all whispering your name, it's going to

(15:36):
add up to a huge scream, right, And that's the
way it is with gravity. All those protons in the
Sun are giving a tiny little tug on the protons
and electrons on Earth gravitationally. But there's so many protons
in the Sun that it's enough to pull a whole
planet around in a circle. Right. It's not a small
amount of force to keep the Earth in orbit, right,
It's a huge force that keeps the Earth in orbit.

(15:58):
Oh man, you just gave me a new nightmare. To
imagine a billion people whispering my name. That is so bizarre.
That is kind of creepy. Actually, yes, that doesn't where
that came from. Hey, let's all whisper Paul's name for
for father's sake, for father's days, didn't heal sense of

(16:20):
disturbance in the force when that happens. Everybody listened to
me to this right now, go Paul, Paul, Happy Father's Day, Paul,
your daughter is awesome. Cool. All right, that's um Florence's
question about gravity, and so the answer Florence is that

(16:44):
gravity is weak, but it's also happening on such a
large scale that it does. It is enough to pool
planets and keep galaxies together, that's right. And after all
the other forces have done their business, gravity is left
over to organize the universe because it can't be balanced out.
All right, Well, that's one question, and we'll get to

(17:05):
the two other questions we have today about dark matter
and atomic nuclei. But first let's take a quick break.
Our second question of the day comes from Margie, who

(17:27):
has a question about dark matter. Hey, Daniel and Jorge,
this is Marchie. My question is how does dark matter
influence the movement of the planets in the Solar System?
Does it make them all orbit at the same speed
and if so, all right, that's a pretty interesting question. Um,
we talked, we've talked a lot about dark matter in
this podcast and how it's there. It's all around us,

(17:49):
it's in the center of galaxies, right all over the galaxy,
and it's constantly pulling on everything and helping galaxy stay together. Yeah,
this is a wonderful question. And because this is a
kind of question that shows me that people are doing
physics in their mind, right, they says, you've learned how
dark matter influences how galaxies rotate, Like we discovered dark

(18:10):
matter because we saw the galaxies were spinning too fast
and they need more gravity to hold them together. So
that means that dark matter makes enough gravity to be
like noticeable about how things spin. Right, So that the
natural physics thing to do is to say, okay, I
have my new understanding, let me apply it to something else.
Does that make sense? And this listener obviously thought, well,

(18:30):
if there's dark matter enough to affect the galaxy spinning,
why can't we notice it here on Earth? Like, why
can't we do that same measurement and see like, hey,
the Earth is going around the Sun too fast? Can't
we detect the dark matter in our Solar system by
looking at how the Earth orbits the Sun the same
way we look at how the Sun orbits the center
of the galaxy. So it's really a genius question. Oh,

(18:52):
I see. The question is is the Earth going around
the Sun faster than it should be if dark matter
didn't exist? Because imagine, for example, that there wasn't just
the Sun in the center of the Solar system. Imagine
there were five sons, but you can only see the
one of them, right, and the other ones were made
of dark matter. What would happen in that case. In
that case, there'd be a much stronger gravitational force than

(19:14):
you would expect from one Sun, and for the Earth
to stay in its orbit, it would have to go
much much faster, and so you would see a discrepancy.
You'd measure the speed at which the Earth was orbiting
the Sun, and you'd say, huh, it's going way too fast.
What's what's um, what's keeping it together, what's keeping it
in the Solar system? Why isn't it just flying off?
And then you would deduce the presence of all those

(19:36):
dark suns. Right, So this listener is like, well, can
we see the dark matter? Because We've said on this
podcast several times, a dark matter is everywhere. It's not
just out there, it's here, It's in this room, it's
on your planet, it's hanging out in that bunch of
bananas you just ate. It's everywhere. So why can't we
see it in our solar system? Right? Well, I guess
question number one is is there dark matter in our
solar system? And then question number two is is does

(19:57):
it influence the orbit of planets? So that Daniels, is
there a dark matter here in our solar system? We
think so. Now we don't know for sure, and the
reason is that gravity is pretty weak, right, as we
talked about recently, and so it's hard to get a
sense for exactly where dark matter is because the only
way that we can see it is is through its
gravitational effects, and so we can see its effects sort

(20:18):
of like on a galaxy sized scale, but it's really
hard to get a very clear map of where the
dark matter is. But we think it probably is. We
think it's probably distributed pretty evenly through the galaxy. There's
a blob in the very center and it sort of
just falls off gradually. So we suspect, like we would
see it as a haze just permeating everything exactly. And

(20:38):
you know what a deep question about dark matter is,
like is it just a smooth haze or are there structures?
It's a stuff happening. Is there like life forms in
dark matter? We really don't know because we haven't been
able to see it with enough resolution, because the only
way we've ever been able to probe it is through gravity.
And that's a it's you know, real frustration for us
as scientists. It's like most of the matter in the
universe is there, it's in front of us. We can't

(21:01):
see it. We can't tell if it's doing anything interesting
or just sort of a smooth haze. Right, And so
the question is if we are kind of in a
bath of dark matter right now, which we could be
or could not be. Maybe we're like in a bubble
of non dark matter. Is that possible? We might be
in a little gap, It's possible, right, But I think
the most sensible and the simplest assumption is just that
dark matter is smooth, and as you say, we're in

(21:23):
a bath of dark matter. I think that makes the
most sense. It's it's the most likely explanation. Okay, So
in that case, if we are bathing in dark matter,
would it affect the orbit of the planets. So the
short answer is yes, but not in a noticeable way.
And the reason is that the Solar System is not
big enough, right Like, if you take the density of

(21:43):
dark matter, and we expected, it's about like one protons
worth of dark matter about every three cubic centimeters, So
there's not actually that much dark matter spread out over
the universe, right Like, if you sort of look at
your thumb, there's probably only one proton's worth of dark
matter in it. Yeah. If you take all the dark
matter and you spread it out evenly through space, then

(22:04):
you end up with about one proton per per thumb.
I Like, the thumb is a unit of volume. Yeah,
one dark matter proton per thumb thumbs up. Yeah, And
you might and you might be thinking, hold on, isn't
there supposed to be more dark matter than normal matter?
And there is, but there's five times as much. But
here we're sort of spreading it evenly through space, so
we can imagine how it might affect the Solar System,

(22:25):
but we we actually don't sort of know that, right Like,
it could be all concentrated in my thumb, or it
could just be kind of this haze that's covering everything. Yes,
it could all be concentrated in your thumb. Now there's
some limits. I mean, if dark matter was really really
clumpy and it was all concentrated in your thumb, that
would be a huge amount of mass and we would
definitely notice that, Like your thumb would be attracting stuff

(22:45):
to it all the time, like a crazy weird magnet.
My thumb is pretty attractive. Well do you hitch high
a lot? Did your thumb stop a lot of cars? Uh? Yeah, No,
I get I get compliments from about my thumb all
the time. I'm gonna believe that for a second. I
don't believe that for a second. You're like, I've seen
your thumb. It's nothing special. Next time we're in a

(23:07):
random situation, I'm gonna ask somebody to come in on
your thumb and we'll just see what they say. All right,
let's do it. If you take one protons worth of
dark matter per thumb and you add that all up
inside the Solar system, it adds up to a lot.
It's like ten to the ten kms of dark matter
in the Solar system, and that might seem like, oh

(23:28):
my gosh, that's a huge amount, ten to the ten,
but it's small compared to the Sun, which is like
ten to the thirty. So dark matter, if you spread
it out evenly, there's not enough of it in our
solar system to influence the gravity on top of what
the Sun is already doing. So you're saying, like, our
solar system is a it's kind of a concentrated part
of the universe where there's a lot of mass here

(23:50):
as opposed to like in the empty gas between solar systems,
And so you're saying, like, here in our neighborhood, there
is just a lot more of the regular stuff than
there is dark matter. So dark matter is kind of
negligible right here where we are, exactly. Dark matter is
negligible for the for the gravitational effects of the Earth
and the Sun, exactly right, because mostly the Sun is

(24:10):
a concentrated blob of normal matter, and we don't think
the dark matter has been concentrated in that same way.
Not only is it negligible, but it's also going to
spread out evenly all around us, right, So it wouldn't
it would be sort of maybe tugging us in all
directions at the same time and maybe not really affecting
the orbit. It would be tugging us in all directions.
But um physics says that if you're moving in an orbit,

(24:32):
you're affected by the mass of all the stuff that's
the smaller radius than your orbit, and you actually it
doesn't matter how that's distributed inside that radius. If it's
like you know, like if the Sun was a point particle,
or the Sun was its normal size or twice its size,
if it doesn't change its mass, the physics says that
it doesn't affect how you're how the force of gravity
acts on that body. It all integrates out to be

(24:53):
the same thing. So the dark matter outside of our
orbit is just cannot affect our orbit. That's right. It's
sort of like that episode we talked about where you
jump into the center of the Earth. You're only affected
by the mass of the Earth has a smaller radius
than you do. Everything else outside of you cancels out
because there's always one bit tugging you here and another
bit tugging you the other direction, and the stuff with

(25:15):
a smaller orbit adds up to give you an overall tug.
That's the same as if you just put a particle
with the mass of that stuff at the center of
mass of it, which would be the center of the Earth.
So in this case you would still be affected by
dark matter, and we are, like the orbit of the
Earth is affected by the dark matter in the Solar system,
but it's you know, one part in tend of the twenty,

(25:35):
so it's not measurable. So you're saying that we do
sort of have like an equivalent of a dark Sun
in the middle of our Solar system affecting our orbit.
It's just very small, that's right. Dark matter is changing
our lives. It makes our years shorter by one part
and tend to the twenty because it speeds up the
Earth because of its additional gravity. But it's you know,
it's not something we can measure on the galaxy scale,

(25:56):
though you can. And the reason it affects things on
the galaxy scale, the reason that you can detect it
at all, is that galaxies are just so much bigger
than solar systems, and so they add up to a
huge amount of dark matter um compared to the mass
of the Sun. Like the stuff in between solar systems
adds up. But maybe the stuff within a Solar System
doesn't add up to much exactly. So when you're calculating

(26:18):
the force of gravity on the Sun as it rotates
around the center of the galaxy, it's influenced by everything
that has a radius smaller than it's compared to the
center of the galaxy, and that's a huge amount of
dark matter. Well, I think that's probably why I was
late to the recording of this podcast. It's it was,
you know, dark matter shortening my ear. That's right, Well,

(26:38):
you used up your one you know, one ten, one
in ten of the twenty a year, so you need
another excuse next, no build over my entire life and
leading up to me being late to this podcast, it's
not that you were finishing that one last piece of
banana cream cake. No, no, I finished that, Yester. Al Right.
So that's Marki's question about whether dark matter affects the

(27:01):
orbits of the planets in our Solar system, and the
answer is yes, we kind of do have a dark
matter sun in our dark dark matter mass in our
Solar system, making everything just a little bit faster, go
faster around the Solar System, but it's really not measurable,
and without seeing how galaxy spin, I don't think we

(27:22):
ever would have discovered dark matter just by looking at
the orbit of the Earth. All right, thank you, Margie,
And so we'll get to our last question from Prita
when we get back from a quick break. Alright, our

(27:46):
last question of this episode comes from Preda, and she
has a question about why the nucleus is stable. I
imagine the nucleus of an atom, right, what else could
it be about the nucleus of what the cell, the
nucleus of a banana? At This is a physics podcast, man,
So here's a Prettius question. My name is Pritto, and

(28:07):
my question is why is the nucleus of an atom
even stable? The nucleus of atom has protons which are
positively charged. They're supposed to reple each other and they're
not supposed to stay to Please explain why does this happen? Right?
So Preta wants to know how a nucleus can be
stable like because then the nuclei of atoms are made

(28:29):
up of protons mostly right, and nucle and neutrons but
mostly but a lot of protons, and all the protons
are positively charged, so they should be repelling each other
with the electro magnetic force. Yeah, So how how do
how can they all stay together? How? How is it
that you and I are here? Daniel? Yeah, I love

(28:50):
that we're talking about forces and force, bouncing and all
these questions today. This is a great question, right, And
they all are positive and they are pushing away from
from each other. So what holds it together? There? Um?
I don't know, that's a really positive thing, I think, yeah,
and kind of negative to well. I'm kind of neutral
on the topic. But I was wondering whether people knew

(29:11):
about this, like is this a common question? Do people
have an idea? So actually, yesterday when my kids were
watching a movie, I walked around the mall here in
Irvine and I asked people, um if they knew what
kept the nucleus together? And I got some interesting answers. Cool.
So here's what people had to say. Do you know
why the nucleus stays together? Like what keeps it together
if it's all positive charges opposite course on the outside,

(29:34):
or what holds an atom together? Huh? Right, I'm sure
I learned that in physics long ago, but I can't remember.
I don't know about that one. I don't know more
electrons they stay together because the more protons there are,
the heavier the atomic weight. So what do you think
Now we're getting random people on the street to answer

(29:56):
listen to questions. Eventually we don't even need to be
here anymore, right, Yeah, I wish you just crowdsource this podcast,
just going the mom and be like, hey, here's the question.
We'll give you twenty bucks to talk about it for
forty minutes. Exactly. That's our retirement plan. Uh No, this
one was interesting enough, and I really was curious about
what people knew. So I thought, we don't often do
this for listening to questions, but I did the man

(30:17):
of the street interviews for this one. Well, I'm surprised
that people kind of I knew a little bit of
what you were talking about, right, because they they were like, oh,
you mean like the O an Adam, and they sort
of understood the question because it's not an easy question
to get your head around, right. No, it's not an
easy question. It's not a simple answer. But you're right,
people understood the question and that was cool. Um, so

(30:38):
I think it is a common question. And all these
people after I asked them, they're like, we tell me
what is the answer? You can't just walk away after
asking me that question. I have to know now it's
like inspire this burning desire and them to understand why
their nuclei were not flying apart. Do you try to
when you're roaming the malls looking for people? Do you
try to always hit like the you know, the dad
or the mom just waiting for their kids or their

(31:00):
spouse who's dropping. I try to ask people who are
on their phone board. Yeah. I don't interrupt people in
conversation or people who look like they're going somewhere. I
look for somebody who's like sitting there on their phone
obviously waiting for somebody to like try on pants or something,
so they don't they don't. I don't want to interrupt
somebody's day. You're going to the dressing room, You're like, hey,
I have a physics question for you, friendly neighborhood physicist.

(31:24):
Physicists arrested at local mall and then I ask people
in the next cell when I get arrested. All right,
so let's ask you the question. So how is it
that protons stick together inside the nuclei of atoms? Yeah, Well,
to answer this question, you need to understand a little
bit about how protons and neutrons are held together because
protons and neutrons, remember, are not fundamental particles, but they're

(31:46):
made of quarks. So there's up corks and down corks,
and those particles are held together by a different force
called the strong nuclear force, and it's called the strong
nuclear force because it's super duper strong. It's much much
stronger an electromagnetism, which of course puts gravity to shame.
So the strong nuclear force is the strongest, most powerful
force we've ever discovered, and that's what holds the protons together. Yeah,

(32:10):
it's the reason the protons and the neutrons their bound
states of this force, so that there's quarks inside the
proton and quirks inside the neutron, and they're exchanging gluons
all the time. There is this particle called a gluon
which holds the corks together into a proton and into
a neutron. So that's what holds the protons and neutrons together.

(32:30):
But what what keeps the protons from repelling each other? Yeah,
so the strong nuclear force which holds them together. It's
very short range, like it's super powerful, but it doesn't
go very far, but it extends a little bit of
ways past the edge of the proton, and so what
happens is that there's a little bit of the strong
nuclear force left over between the corks inside the proton

(32:50):
and neutron to attract the protons and neutrons to each other.
So even this little extra bit of the strong nuclear
force is enough to overcome the pulsion of the protons
because they have the same charge. Oh really, I never
thought about that? Is that? Is that? How you explain it?
Is that the force that's keeping the protons together is

(33:11):
also the force that keeps a proton stuck to another proton,
because it's sort of leaks outside of the proton. Yeah. Essentially,
it's like the quarks in one proton are talking a
little bit with the quirks in the neighboring proton or
the neighboring neutron, and to them, the fact that there's
like an overall positive charge in protons and um and
not a neutrons is irrelevant because those forces are so
weak compared to the strong nuclear force. The strong nuclear

(33:34):
force doesn't care about your electro magnetic charge, right, Yeah, exactly,
doesn't care at all. And the corks do have electromagnetic
charges and Actually they're really weird that like two thirds
charges and minus one thirds charge. They're pretty strange, but
they're the forces are much weaker than the strong nuclear force.
So the strong nuclear force sort of leaks out of
the proton and into the next neutron and into that

(33:56):
next neutron, and that's how they tie themselves together. There's
enough lefto or after you make the proton or the
neutron to tie it to the next one. How can
there be any leftover? I mean, if if the proton
is stable right like it likes being held together, how
can it have any leftover? You know, attraction, doesn't it

(34:16):
all just cancel out within the proton? How can you
have some left over to attract more protons? Now, you're right,
and it would if all the corks inside the proton
were like right on top of each other, but they're not.
They're like all slashing around. So if you're like on
one side of the proton, you're a little bit closer
to one of the corks than the other two, and
so the force from that one little cork is enough

(34:37):
to have like a little bit of leftover charge. So
actually maybe two protons being stuck together makes them weaker inside, right,
each one is maybe just a little bit weaker because
they're stuck to each other. You can think of it
sort of the way you know atoms for molecules, right,
and atom is electrically neutral, right, because the protons and

(34:58):
the electrons right are balanced. But how do atoms form
molecules their bonds between the electrons because the electrons, you know,
they talk to each other and one like jumps from
here to there, and they exchange photons and stuff and
so um, this is like protons getting stuck together by
those extra little bits of leftover forces. So it's a
strong nuclear force that's so much more powerful than electromagnetism

(35:20):
that even the little extra leftover bits can overpower the
protons pushing away from each other. This strikes me as
a little bit as a nuclear infidelity. You know, like
you've got three quarts being perfectly happy in a bond
to make a proton, but then one of them is like, hey,
look at that. There's some other quartz over there, and
that other trio mana protons um a little bit attracted

(35:45):
to them too, and so that's what brings the two
things together. Right. Yeah, quarks feel a lot of love, right,
They they're happy to to share their love with quarks
even inside other protons and neutrons, and and and you know,
the sort of a limit how much you can do
this because these forces are very short range, and so
the bigger the nucleus gets, then the weaker the sort

(36:06):
of the stability of the nucleus. If you try to
make a nucleus that's too big, then like the protons
on the opposite sides of the nucleus, they'll feel the
electrostatic repulsion, but they won't be close enough to feel
the strong nuclear force anymore. And that's why like heavier
elements are less stable and more likely like decay radioactively.
That's why we use uranium and like uranium two thirty

(36:27):
five to do radioactive fission, and not like helium or lithium.
Put enough protons together, they bunch up, and at some
point the nuclear force, the strong force, isn't enough. They
start to repel each other exactly because the strong force
drops very quickly with distance, right, And so if you're
far enough away from the proton, then you don't feel
it then all. Then it's like all the corks are

(36:48):
on top of each other, and so that's why there's
like a maximum size you can make to a nucleus
because the strong force which holds it together it's a
very short range. And when the nucleus gets sort of
bigger than that range, then it can't do the job anymore.
It's like, you know, you trying to hold a bunch
of balloons, right, Imagine trying to hold a huge pile
of balloons. Is a maximum number you can hold until
somebody You need somebody else to come over and grab

(37:10):
a bunch of them. So then the nucleus splits into two.
And that's what happens in a radioactive decay. Alright, So
then that's the answer to the question. The nucleus stays
together even though the protons are are repelling each other,
they're trying to push each other apart. There is another
force that leaks out from inside of each proton that

(37:31):
then sort of links up the two protons together, and
that force is stronger than the electric magnetic repulsion exactly.
That's what holds them together, and that's what holds us
together with you, listeners, the force of these questions. You guys,
have all these questions bouncing around your head, and you
send them to us, and we love thinking about them,
we love talking about them, and we love trying to
explain them to you. And really it's this love of

(37:53):
the universe and this desire to ask questions and this
hunger to get the answers that brings us all together.
All right, Well, thank you so much to Florence, Margie
and Pritta for sending in their questions, and thanks to
all of you who are sending us questions as well.
We enjoy reading them and it kind of makes our
day to hear from you. Guys. Absolutely, please don't stop

(38:13):
sending questions questions at Daniel and Jorge dot com. All right,
and that's our podcast. We hope you enjoyed those questions,
and stay tuned for more amazing facts and questions and
interesting perspectives about the universe. And stay tuned for the
sound of Jorge enjoying a banana cake. That's right, one
of you lucky people will win this prize. Lucky unlucky.

(38:35):
We're not sure, but somebody's gonna win it. Positive and negative.
See you next time. If you still have a question
after listening to all these explanations, please drop us a line.
We'd love to hear from you. You can find us
at Facebook, Twitter, and Instagram at Daniel and Jorge That's

(38:58):
one Word, or e fail us at feedback at Daniel
and Jorge dot com. Thanks for listening and remember that
Daniel and Jorge Explain the Universe is a production of
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