What is the densest thing in the universe?

EXTREME UNIVERSE! What has the most stuff stuffed into it?

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Episode Transcript

Speaker 1 (00:08):
Hey, or Hey. You know how sometimes everybody thinks they
know the answer to a question, but they're actually all wrong.
You mean, like how you think everything weird in space
is because of aliens. Well, that's not a good example.
I think it probably is because of aliens. Or you mean, like,
what why people think this guy is blue? Yeah, a
lot of people think this guy is blue because of
the ocean. Wait, it's not because of the ocean. Do

(00:30):
you even listen to our podcast? We did a whole
episode about that. I don't listen to our podcast. I'm
too busy looking out for aliens. Well, if you did
pay attention, sometimes you'd realize that sometimes there's a question
in science that everybody assumes they know the answer to,
but it turns out they don't. Hi. I'm or Hey.

(01:02):
I'm a cartoonists and the creator of PhD comics. Hi
I'm Daniel. I'm a podcast host and part time particle physicist.
Have you been downgraded to part time? Now? I decided
let's make this podcast thing my primary activity. That's right,
it's two hours a week, but it's the most important
and valuable two hours of my week. Two hours of work.
Isn't that too much? For a physicist. Well, you know,

(01:25):
you've got your naps in, you've got your coffee breaks,
you got your scribbling nonsense on the board to look busy.
So it's a pretty full day after a while, you
mean a pretty full week, pretty for a week. Yeah,
you know. But I modeled my work day after my
um my cartooning role models. You know. Yeah, sleep in,
never change out of your pajamas, this kind of stuff. Yeah, No,

(01:46):
we should all look up to cartoonists as a nation.
We would all be more productive if we follow the
cartooning work week. We'd all be a lot more funny,
that's right. We would do the low way to prosperity.
But you are listeners are listening to our podcast, Daniel
and Jorge Explain the Universe, a production of I Heart Radio,

(02:06):
in which we take weird and funny and amazing and
crazy things about the universe and try to doodle them
into your brain with silly analogies and bad jokes. That's right.
We try to take you to the corners, the far
reaching corners of the universe, and to explore the heaviest things,
the biggest things, the brightest things, the smallest things that

(02:26):
are out there for us to discover that's right, And
so we have this series of podcasts we've been really
enjoying about the extreme Universe, Extreme Extreme, in which we
look at all the weirdest, nastiest, hottest, wettest, craziest things
in the universe, and we have actually done some of those.
We did the hottest, we did the brightest, we did
the biggest. What else did we do? You Ma, you

(02:47):
make our podcast sound a little not safe for work there, Daniel.
That's all in the minds of the listener. Okay, well,
that's that's kind of the universe totally. The universe is
not safe for work. Oh I thought you meant the
universe is in the minds of the listener, which is
also sort of true from a philosophical point of view.
So today we're continuing our series of extreme Things in
the universe, and in this episode we are going to

(03:10):
explore what is the dnsest thing in the universe, the
densest thing in the universe, that's right, Not the heaviest,
not the biggest, not the smallest, but the most compact,
the thing with the most stuffed stuffed into it, that's right,
Not the sharpest thing, the densest thing, that's right, Not

(03:33):
the brightest thing, but the densest things, right, Not the
smartest thing in the universe, the dances, that's right. Yeah,
the smartest thing in the universe. That would be an
interesting discussion. I wonder what is the smartest thing in
the universe. Do you think it's a human? Who? You
think it's some super intelligent alien race? I think the
universe is the smartest thing in the universe. Oh snap,
we are the universe thinking? Is that what you're thinking?

(03:55):
Where you're going? We are the brain of the universe.
The universe is us. It's very holistic of you. I
gotta get some of those banana peals you must have
been smoking for today's episode. I am one with the universe,
and the universe is me, and I am thinking the
thoughts of the universe. Well, I but I don't. I
don't smoke banana peals. I just I just eat them. Wrong,
You eat them, you eat the flesh, and I smoked
the peels. So we're a perfect team. Well, so, yeah,

(04:17):
what is the densest thing you meaning? Like, what is
the most compact crunched up think? Is you know, craziest
most amount of stuff in a small amount of space.
Thing that exists out there in the universe, that's right.
And the point of this series, the Extreme Universe series,
is to remind you that our little corner of the
universe is fairly ho hum. It's not very fast, it's

(04:40):
not very big, it's not very hot, it's not very cold.
It's sort of just right. And what that means is
that there is crazy stuff out there, this stuff out
there that's bigger you than you can imagine, that's hotter
than you can imagine, that's emptier than you can imagine.
And one of my funniest extremes is density. To imagine
how much stuff you can cram into the tiniest spot,

(05:00):
get those atoms all crowded up into each other. Because
when that happens, really weird things happen. Matter does all
sorts of strange stuff when you squeeze it together. And
so a lot of our listeners, a lot of you
listening out there, might be thinking, Oh, I know the
answer to this question. It's obviously a black hole. Hint,
it's not a black hole. It's not a black hole.

(05:20):
Maybe it is, maybe it isn't. There's a bit of
a philosophical argument there at the end teaser, there's a
plot twist. It is it isn't It is it isn't.
Some people say it is, some people say it isn't.
Those other people throw the other first people into a
black hole, and the argument and at all just becomes
a black hole of a mess exactly, it becomes a

(05:42):
mental black hole. We all get a little denser. So
hopefully that sucked you in into the topic of this podcast,
and so stay tuned to see if it is or
if it's not a black hole. Daniel says, maybe it
is not, Maybe it is, maybe it's not. Exactly, But
before we dive into that, I went around and I
asked folks on campus that you see Irvine. I said,
what do you think is the densest thing in the universe?

(06:04):
Because I was curious, is everybody just going to say
it's a black hole? To people have other ideas? Have
people done the careful reading about the fundamental issues in
the corners and the centers black holes? Or maybe people
knew what the densest thing in the universe is. Maybe
there it's it's something else and people knew about it. Yeah,
that's right. Maybe it's the center of some weird kind
of candy and you know, famously dance or something else

(06:26):
weird people have read about. So I walked around I
asked people. I said, what do you think is the
densest thing in the universe? So think about it for
a second, and if somebody asked you on the street,
what is the denist thing in the universe, would you
answer that it's a black hole. Here's what people had
to say. A black hole. Oh, man, I hope it's
chocolate black hole. Probably a black hole, a black hole,

(06:48):
neutron stars, something like that. Black holes gets the anti
matter black hole. I think I want to say the core,
the core core of the Earth, okay, okay, or actually,
so you know universe, probably the sun in the star, right, yeah,
I would say a star al right. So most people
answered black hole. A lot of people said it's a

(07:09):
black hole. It's a good go to thing. I think
people think what's the densest thing in the universe and
their mind goes straight to a black hole because they
imagine a black hole has a lot of stuff stuffed
into it. But it wasn't the only answer. There was
some pretty interesting ones here. I like the one that
said it's chocolate exactly. I'm not sure that was a
serious answer. Somebody out there really had a hanker and
for some dark, dark chocolate. Right. The thing that interested

(07:32):
me about these answers maybe they were thinking like richest,
Like what's the richest thing you've ever tasted? Most? What's
the most calorie dense thing in the universe? Maybe that's
what they're thinking. There you go, is it still a
black hole? Like what if you eat a black hole?
That's a lot of calories technically, right, what if you
ate a black hole? I think that's a physics question
nobody has ever asked me before. While we are breaking

(07:55):
new ground today. One of the things I liked about
these answers is in contrast to someone the other extreme
universe questions, where you you might have noticed people tended
to answer in their local environment. They're like, thought about
what is the brightest thing in our solar system? Or
what is the biggest thing nearby here? People really went
s at a universal They really cast their minds into
the entire universe to find something really really dense. I

(08:18):
mean like the person who said it was the core
of the earth exactly, not that person, everybody, but that
person yeah, all right, Well there were other answers here.
Some people said neutron stars, other people said antimatter. Those
are pretty a space physics the answers yeah, yeah, I
think antimatters a would have stabbed there. You know, Um,
antimatter is not anymore or less than the normal matter, right,

(08:40):
it's just another kind of matter. It's at the opposite
kind of matter. But a neutron star is a good answer. Um.
I like the people who said, you know, I don't
know something strange out there in space like that, you know,
just conveys the whole idea we're trying to get across here,
which is that space is filled with weird stuff, something
crazy and strange and you probably can't even imagine. Well,

(09:01):
that needs to be the answer to every single one
of these extreme universe episodes. It's like, what's the brightest
thing in the universe, some weird thing out there in space,
something in space. I've noticed this trend that you seem
to be trying to assemble a sort of universal list
of answers to physics questions, Like how many physics questions
can you just answer with the with the phrase the

(09:23):
Big bang or space or you know, physics. Um, it's
like you're trying to find shortcuts or something. Well, you know,
I want to be ready when that physicist approaches me
on the street wearing sandals and asking me strange questions
about the universe. I want to be ready. You know,
you want to be ready. I think we should do
that someday. We should just flip your answers in and

(09:43):
see if any listeners even noticed. Right, do I get
to Google first? Nobody gets to Google first. There's no
googling allowed in these questions. It's just what do you know? Now?
What's in your mind? What answer can you construct? All right, well,
let's launch into this discussion, Daniel. Let's figure out what
is the dancest thing in the universe. But first let's
maybe talk about what is density. I think we all

(10:04):
have an intuitive sense of what density is, but you know,
maybe there's a it's different from the physics definition. Yeah,
and we talk a lot in this podcast about sort
of the difference between technical physical definitions and sort of
cultural definitions, and in this one case, I think they're
pretty well aligned. But let's just go through the basics.
Being people up to speed in case they haven't thought
about density. Since you know high school chemistry or something

(10:27):
um And so density is not a fundamental unit, it's
a derived unit, which means it's a ratio of two
other things. It's mass over volume. So mass is just
like how much stuff is there. It's different from weight. Right, Wait,
is how much force is there on you from from
Earth's gravity. Mass is just like how much stuff is
there in you? Right, And remember we talked about that
another time. What is mass? And it comes from inertia

(10:49):
and it's the property of an object to resist changes
in its motion. Right, So that's what mass is. All
the particles inside you and all their energy addupt to
give you a certain amount of mass. And then on
the bottom of that volume, right, So it's mass over
a volume. And volume is just how much space do
you take up? Right? How big are you? So something
can be really dense if it has a lot of
mass and not very much volume, or not very much

(11:11):
mass but even less volume. Right. So it's not about
being extremes in mass or extremes in volume. It's all
about the ratio. It's having a lot of mass in
a small space. I see. It's not about being the
biggest thing or about having the most mass. It's about
having the most mass in the smallest amount of space. Yeah,
because you can think of things that are really really
big and really really massive, but not very dense, like

(11:35):
a blimp. Right. You know, a blimp is not that
dense because it can float in the air. Right, It's
filled with a gas that's less dense than air, even
though it's really big and uh and and it has
a huge amount of mass to it. A blimp is
not actually that dense. But if the blimp was made
out of rocks, that would be really really dense. That's right.
That would be a terrible design for a blimp exactly. Um,

(11:57):
I don't recommend you buy any stocks and your friends
rock blimp startup. Well, it depends on what you're trying
to float in, right, If you're trying to float into
something that is denser than rock, then they would work. Yeah,
that's true. I'm not sure where that exists, so you know,
he's lava denser than rock, probably not right, So I'm
not sure where your rock blimp would even work, but

(12:18):
sure yeah, maybe you know, on the surface sid maybe
in the liquid nitrogen oceans of Jupiter. There you go, there,
there you go. There's a great reason to invest in
your in that startup now. Yeah. But the point is,
things can be really big and really massive without being
very dense. Right. Dense requires a huge amount of mass
compacted into a small space. So the densest thing in

(12:40):
the universe doesn't have to be something big. It can
be something small, that's right. And things can be very
very dense without being that big. Right. You can have
a really really small amount of something that's very dense
as long as there's a huge amount of stuff crammed
into it. But it could also be a really big thing,
like you could you know, the densest thing in the
universe could be like a star or a neutron star.

(13:01):
It could be something that big. Yeah, exactly, it could
be big, it could be small. It could be massive,
it could be not that massive. The key is the
ratio again between the mass and the volume, how much
stuff is cramped into a certain amount of space exactly.
And you know, that's physics density, And I think that
matches pretty well with what people's intuition is for density.
I don't think we have a pretty big disconnect like

(13:22):
we usually do. So congratulation Physics Naming team. You picked
a good one this time. Well, I guess intuitively, you know,
it's kind of like, um, holding something in your hand.
You know, like if you're holding a little rock that's
dense and you know it's dnse because it feels heavy,
but it still fits in your hand. But if you
have you have like a ball of cotton in your hand,

(13:42):
that's not very dense, that's right. And so one way
to compare densities is to say, I'm going to compare
different kinds of stuff and have the same volume, so
the same amount of its same like physical space full
of it, and then just compare the mass because it's
the ratio of mass to volume. And if you fix
the volume, then you can just compare the mass us.
So you can compare like a handful of rock to

(14:03):
a handful of cotton, to a handful of air to
a handful of you know, hot lava or whatever. And
don't actually try to get a handful of hot lava,
but hand full of lava sounds like it sounds like
a you know, a high school band name or something
up next an extreme universe handful of lava. Anyway, Um, yeah,

(14:23):
you if you fix the volume, then you can compare
the mass. Okay, so you have a couple of great
interesting numbers here for us, and they're all based on
a fixed volume, which is a one teaspoon, right, that's right.
I thought a teaspoon is like a macroscopic quantity. You know,
you can imagine it's just like a normal kitchen spoonful
of stuff. And then we can think about how heavy,
how much mass is there in a teaspoon of this

(14:46):
versus a teaspoon of that versus the teaspoon of something else.
So if we fix the volume, then we can just
think about how much mass there is, how much a
teaspoon of something would Wait, that's right now. Wait, of
course is slightly different from mass, but you know they're connected.
And here Earth, something that has more mass has more weight. Um,
you know, far away from the Earth, then you can
still have mass even if you don't have weight. But

(15:07):
they're the same if we're if we're doing this experiment
on the surface of the Earth, then it's equivalent. So
step us through here, Daniel. All right, so I thought
we'd start really really light, all right, just sort of
for scale, and imagine if you had, for example, um,
a teaspoon of space right. I mean, I don't know
how you would get that, but so you like scooped
up a teaspoon of space, so you had, you know,
stuff that had the same density of space. Like what

(15:29):
do you mean space, like average space or like if
you win out into space, grabbed the scoop of it
and brought it back to Earth. Is that what you mean? Yeah?
The average amount the average amount of stuff in space.
And remember we did a whole podcast episode about how
space he is space and it turns out that the
answer is pretty different depending on where you get your
scoop of space. But in all cases, as long as

(15:51):
you're far away from the Earth's atmosphere, the answer is
pretty pretty low. You know, you're gonna get less than
one proton in your tea spoon. Okay, so this is
like the average teaspoon of the universe. Yeah, exactly. The
average density of a teaspoon in the universe is one
times ten to the negative twenty seven kilograms, So that's
zero point twenties seven. Zero's one. That's how much a proton. Ways,

(16:17):
so you can have like a whole teaspoon with just
a proton in it. That's about the average density of
stuff out there, and a proton is pretty small, right,
I mean it's it's pretty much. Uh, it's it's tiny.
It's almost nothing, right, it's almost a fundamental unit of
of mass. Right. Yeah, it's amazing because it's almost nothing.
But then it makes up everything, right, And it's incredible

(16:38):
how you can get big macroscopic stuff made out of
super tiny stuff. Right. It boggles the mind how small
a proton is, and then how many protons you need
to make, Like you know, a cookie or whatever. There's
so many protons in your cookie and you don't even
think about them as you eat it. Wow. So that's
the average density of the universe really, right, it's it's
about one proton per teaspoon. And the reason is, you know,

(17:01):
there's a lot of stuff out there in the universe,
a lot of stars and they're big, and a lot
of galaxies, but most of the universe is pretty empty,
you know, the stuff between stars and between galaxies. There's
not that much stuff there. And the biggest volume of
the universe are these super voids, you know, between the
sheets of superclusters. But there's really basically almost nothing. And
so because density is mass over volume, and the volume

(17:23):
of the universe is unbelievably gigantic. Then that's why the
density is so small. I mean, it's amazing that it's
even anywhere close to a proton. Frankly, Wow, that's pretty
incredible to think that if you sort of, like if
you shrank the entire universe into a teaspoon, like everything
that's stuff, stars as planets, would just be about the
size of a proton exactly. But but the next I thought,

(17:45):
let's let's look at something sort of around here on
the Earth, and and a good sort of normalization for
like a standard for what density is is water, because
water is one um gram per cubic centimeter, right, and
a teaspoon is five cubic centimeters, So water is five
grams per cubic centimeter. So you have a teaspoon of water,

(18:06):
it weighs five grams, which is a whole lot more
than a proton. What about a teaspoon of tea? A
teaspoon of tea, that's a good question. It must be
a little bit more dense, right because you put something
into it, but it's about the same, Okay, So that's um.
I think that's a pretty good anchor for people, maybe,

(18:28):
you know, because we're all sort of familiar with how
water feels and how much it wasgs. That's right, And
if you're holding a teaspoon, you can tell the difference
between having a full teaspoon and an empty teaspoon. Right,
somebody pours water into your teaspoon with your eyes closed,
you can tell the difference. Whereas if I put a
single proton in your teaspoon, you're not gonna notice. So
you can feel it, right, you can feel five grams.

(18:49):
It's not it's not a lot, but it's also not nothing.
That really kind of tells you how empty the universe is, right, Like,
if our average experience of matter is a teaspoon of water,
compare that to a teaspoon with one proton in it.
That's that's really kind of the difference between our everyday
experience and the actual whole other rest of the universe,

(19:09):
exactly at the low extreme, most of the universe is
really not very dense at all, So we live in
a pretty dense place compared to most of the universe.
But then again, as you'll hear, our surroundings are not
very dense at all compared to the densest places in
the universe, So The craziest thing about the universe is
that it has this enormous range. Most of it's not
very dense at all, and then there's these incredible pockets

(19:31):
of total density. Well, let's keep scooping up more and
more dens for things. But first let's take a quick break.
All right, we're scooping things up indiscriminately here and measuring

(19:54):
their density to find out the densest thing in the universe.
And we we just scipped up some water. So some
water is about five grams that's right, five grams per
tea spoon. And then people, um, a lot of people said, oh,
maybe the sun or a star. That seems like a
dense thing, right, because it seems like it's trapped by
gravity and the reason it's burning is that it's all
this gasp and compressed. So people figure, well, it must

(20:17):
be pretty dense, right, Well, it is dense, but it's
surprisingly not that dense. I mean, the density of the
sun is about seven grams per teaspoon, so only a
little bit denser than water. Are you serious? Yeah, the
sun is not that much denser than water. Yeah, the
Sun is not that much denser than the water. Now,
the sun is really big, and the Sun is really hot,

(20:38):
but it's not actually that dense. So this is the
average density of the Sun, because I imagine the Sun
is dens or at the middle in the middle unless
dense at the edges. Right, the Sun really doesn't like
when you talk about its middle that way. It's been
working on it for a few billion years um. But yes,
the the density of the Sun does vary. So this
is the average density exactly. And I think the reason

(21:00):
that it's not more dense is that there's more than
just gravity going on. Right. Gravity is the thing that
made the Sun. It pulled all that stuff together, it
starts that fire. But once you have that fire happening,
it's like a constant explosion, and that explosion is making
the Sun less dense. So the Sun is this constant balance, right,
It's a trapped, ongoing nuclear explosion. The explosions are pushing

(21:22):
things out and gravity is pulling things in. And so
if it was just gravity, then you know, the Sun
would collapse into a very very dense state. But the
reason it doesn't collapse is because it's exploding, so that
keeps it, you know, a little fluffy, So you're really
only kind of measuring the density of the fuel of
the sun, Like once it turns into fire and photons
once it turns into light, you don't really count that

(21:44):
as part of the density. That's right, we're measuring the
matter density of the sun. But you know a lot
of the photons produced in the sun never leave it
because they're reabsorbed. You make a photon somewhere in the
middle of the sun, it's going to get reabsorbed before
it leaves the sun. But I think they did is
that if you scooped up a teaspoon of the sun,
it would it would sort of feel the same as
this teaspoon of water. It might be a lot brighter, right,

(22:07):
and hotter, but exactly. Yeah, that's the idea, right, Somebody
out there is imagining being blindfolded, and you're saying, I'm
either going to pour a teaspoon of water into your
teaspoon or a teaspoon of the sun, and you won't
be able to tell which. And you're thinking, yeah, I
think I'll be able to tell. But you're right, you
won't be able to tell from the from the heaviness
of it, because it's not that much heavier than water,

(22:29):
all right, And in fact, it seems like things are
even denser here on Earth. Yeah, exactly. And you might
be thinking, well, water is not that dense, and you're right,
And if you just like bent down and scooped up
a teaspoon of rocks, you know of like gravel or whatever,
then you would have something denser. In fact, the density
of the Earth, again averaging over everything in the Earth,
is thirty grams per teaspoon. Remember waters five grams, the

(22:52):
sun is seven grams. The Earth is thirty grams per teaspoon.
That's a lot denser than the Sun. So the Sun
is actually kind of fluffy, right, Yeah, it's like a
big cozy pillow on fire. Yeah. And the reason is right,
the Earth is not on fire. Right. If the Earth
was more massive so that there was more gravity so

(23:12):
we can press it more infusion would get started, then
it would actually get bigger, right, and then it would
be more fluffy. So Earth is more dense because we
only have gravity going on. We have no outward pressure
from fusion to make us fluffy. We're not living in
an explosion. We are pretty compact. So but that's kind
of the average density of the Earth. But there must

(23:33):
be things on Earth that are denser than the average density.
Big variation in density. You know, the core of the
Earth is more dense than the rocks under your feet,
for example. So there's a lot of variation. But if
you look around on Earth, for like, what is the
densest thing that occurs on Earth? There's this one element
it's called osmy um, and osmium weighs a hundred ten

(23:53):
grams per teaspoon a hundred and ten grams, so like, um,
that's a lot. That's like, how much is that like
fifteen scoops of the sun compressed down? Is how much
osm that's right? Um, If you had a teaspoon of osmium,
it would feel like you had like a half a
cup of water in your teaspoon. The stuff is pretty dense.

(24:16):
I've never seen ausman. I don't even know what it
looks like or if you can pour it, if it's
liquided room temperature or whatever. But it's the densest stuff
on Earth. But that's at the on the surface of
the Earth. Like maybe down in the center of the Earth,
things are more compact because there's more pressure. Yeah, and
you're right, the core of the Earth is more dense
than the rest of the Earth or the Earth's crust
for example, or the average density of the Earth, which

(24:38):
is what we mentioned earlier. But sort of surprisingly, it's
not that much more dense, Like it's twice as dense
at the core of the Earth than it is at
the Earth's crust, which is most of the Earth. But
so it's not crazy. It's not like a jillion times
denser or anything. I mean, twice as dance is a lot,
but it's not. It's not shocking. Okay, So now take
us out into space, Daniel, what are some of the
densest things out there in space? Well, so, as we

(25:00):
talked about, stars that are normally burning, are not actually
that dense, right, and so in our solar they're pretty fluffy.
In our Solar system, one of the densest things is
just the Earth, right, It's a pretty concentrated blob of rock.
So what you gotta do if you want something really
dense is something I think one of our listeners on
the street or one of our interviewees on the street
actually mentioned what you need is a failed star or

(25:22):
a star that has gone supernova and then collapsed, right.
And sometimes when a star blows its load, and it's
finished burning all of its fuel and it's expended all
of its energy, and that it no longer has that
radiation pressure to keep it fluffy. It collapses into a
neutron star. It's called a neutron star because the the

(25:43):
gravity is so intense that it forces all the protons
to give off an electron and become neutrons. And it's
just like a big ball of neutrons and they are
really scrunched in together, right, because there's so many of
them that the gravity really compresses things and makes it really,
really really dense. That's it. It's ridiculously dense because again
there's no process going on to counteract is, so all

(26:05):
you have is gravity. Is just like packing these little
neutrons and imagine like a huge bag of ping pong balls, right,
and you squeeze it so that they find like every
little gap of space gets squeezed out, and they all
find exactly the tightest way they can all fit together.
And the density of this thing is incredible. I mean,
it's even hard to understand. You know, we're talking about
a teaspoon. If you had a teaspoon of a neutron star,

(26:27):
it would be fifty times ten to the eleven kilograms.
That's a lot of eleven Yeah, exactly. I think that's
five thousand billion kilograms per teaspoon. And you rode here,
it's about seven hundred thousand Eiffel towers in a single
tea spoon. Yeah. I was trying to find an understandable
unit of of mass, like you know, what is comparable

(26:49):
in mass to a teaspoon of a neutron star. And
it turns out, you know, it's almost a million Eiffel
towers boiled down into a tea spoon. Like, I mean,
it's ridiculous, Like you couldn't hold up a sing the
Eiffel Tower. I mean, I know you've been working out
and you're pretty strong and everything, but an Eiffel tower
weighs a lot. Now I take a million Eiffel towers
and then condense them down into a tiny teaspoon, It's

(27:10):
hard to even imagine what that kind of matter is. Like,
what you know I am stronger in France is that
because the Earth is not round, there's a difference in
like the difference from the distance from the center of
the Earth. It's probably just the French wines out there.
You feel stronger in France. Exactly, But I think I

(27:34):
see what you're saying is that, like a neutron start
is really just a star that went out right, or
that collapse, Yeah, exactly, it finished burning. And so you're
saying that, like our son would be that dense, except
that since it's exploding, it kind of keeps everything fluffy.
But if you were to suddenly turn it off, all
that stuff woulds crunched down into something like a neutron star. Right.

(27:55):
And so to take the bomb analogy, you know, a
nuclear bomb when it's exploded is not actually that dense.
It's a huge fireball, right, But the fireball itself is
not that dense. It's much more dense before it explodes, right,
when it has all that fuel compacted into a small place.
After it explodes, it's much less dense. So an exploding
bomb is less dense than a non exploding bomb. Right.

(28:15):
It's kind of like can candy. You know how can
candy is big and fluffy, but if you like crunch
it down, then you just get one really dense piece
of candy. Yeah, you're making, uh, the sun sound really
comfortable and cozy. It's like big and fluffy like cotton candy.
You know, every pink pink? What is in the air

(28:37):
over your house that you think the sun is pink? Well,
you know that it depends on your If you're wearing
a rose color glasses, you know, I'll give it to you.
That's your cartoonist license, you know, that's your art um. Yeah, exactly.
So a neutron star is actually one of the densest
things in the universe. It's it's unbelievably dense. You know,
I think isn't even denser than Thor's hammer. You're the

(29:00):
Marvel Universe guy. I think it is. It is made
from the heart of a dying neutron star. So I
don't know if it's heavier, but it sounds like it's
maybe in the same order of magnitude. Well, so then
do the calculation. You know, if a teaspoon of neutron
star is a million Eiffel towers, then Thor's hammer is what,

(29:21):
I don't know, a hundred teaspoons, a thousand teaspoons. You know,
you're talking a billion Eiffel towers. So every time Thorpe
picks up that hammer, he's lifting a billion Eiffel towers.
It's a calming book. Wait, we're doing the physics of
comic books here today, folks. Um. Yeah, but you know,
not only do you have to be strong, but you

(29:41):
have to be worthy right to pick up Thor's hammer.
So so that's pretty dense. If you scoop up some
neutron star in a teaspoon, you would be picking up
a million Eiffel towers. Yeah, so make sure you do
your stretches before you try that, or you're gonna hurt yourself.
Make sure you use a strong spoon. Boon made out
of osmium, or a spoon made out of a billion

(30:04):
Eiffel towers, that's right, or vibranium. You sort of give
it away. You said a neutron star is one of
the densest things in the universe. But maybe so you're
saying it's not the densest thing. Well, it's it's a
little bit unclear. Depends a little bit who's camp you're in.
Are you an Einstein kind of person or are you

(30:25):
a shorting Your kind of person, Because depending on what
you think is going on inside a black hole, black
holes are either the densest thing in the universe or
not very dense at all. All right time to pick
sides Einstein versus short Anger. But first let's take a
quick break. All right, we're talking about the densest thing

(30:57):
in the universe, and we got to we are now
at um black holes. That's right, and we are right
smack in the middle of the longest standing physics grudge match.
It's general relativity versus quantum mechanics, Albert Einstein versus Schrodinger
in Heisenberg and all those other smart folks. And so

(31:18):
you might be thinking that there are Let's tell me
how dance is a black hole, because a black hole
is also something that happens after a star collapses. Right,
Sometimes the star performs a neutron star. Sometimes it forms
a black hole. And a black hole seems like it
must be the densest thing in the universe because it
has the strongest gravity. Right. The problem with the black
hole is that how do you define the edge of

(31:38):
the black hole? Remember that to talk about density, we
have to talk about mass. Black holes have huge masses,
but we also have to talk about volume. So what's
the denominator? What's the edge of the black hole? And
one very reasonable thing to say is that the edge
of the black hole is the point of no return,
you know, the point where if you're closer to the
center of the black hole than that than light can't

(32:00):
escape and nothing can never leave. Right, So you're sort
of saying, how do you when what do you count
as the black hole? Is the question exactly, because if
you're gonna do density, you have to calculate mass over volume.
So what volume are you including? So you're saying, one
option is to use what they call the event horizon, right, right,
the point where not even light can escape the vicinity

(32:23):
of the black hole. That's right, And I think that's
a reasonable definition because we can't see inside the event horizons.
We have no idea what's going on inside the event horizon,
so all we really can do is average over it. Right,
we can say, well, we know how much mass there is,
and we know how big it is, what's going on inside?
You know, that's Einstein versus Shortinger. So if you don't
want to be dependent on which physics genius is right

(32:45):
about the universe, then you just need to calculate the
mass the black hole divided by the volume includes enclosed
by that event horizon. So I think you're saying that
a black hole should be measured by when it's when
it's black. Yeah, exactly when the black star like that
where the black star and the whole holiness. That's right.

(33:06):
And the issue with black holes then is that they
are really really massive, right, which means it's a huge
amount of gravity, which means the event horizon is really
really big. So you say, you don't know what's going
on inside a black hole, but there's a huge amount
of mass in there. The event horizon grows linearly with mass.
So for example, you have twice as much mass, the
event horizon is twice as big. It's it's it's linear.

(33:29):
It's like a it's like a one to one increase.
I give you double the mass exactly. You double the
radius of the of the black area exactly. You double
the radius of the event horizon. Now, for those of
you you know something about geometry, think about that sphere
right now. If you double the radius of the sphere,
how much does the volume go up? Well, it goes

(33:50):
up like the radius cubed. Right. So, so you have
some black hole and you double its mass somehow, then
you've increased its mass by two, but you've increased its
volume by eight. Right, two cubed, so the density actually
goes down. So you double the mass of a black hole,
it's density goes down by a factor of four, which

(34:11):
means really really massive according to your definition of the
of the black holes, if you count the black part
as the black hole exactly, which seems like a reasonable
definition though you know, we'll talk about another definition in
a moment. And so what that means is that the
bigger your black hole is, sorry, the more massive your
black hole is, the less dense it actually is. But
you know, I guess it's a your I see what

(34:33):
you're saying, like that you should count the black as
the black hole. But that's it's not like a physical boundary,
you know, And it's not like it's not like a surface,
do you know what I mean. It's just where the
effect of the gravity starts to get crazy, but it's
not really sort of like you can't really touch the
surface of the black part, right. I wouldn't recommend it, um,

(34:54):
but you know, it is a real physical boundary. You know,
if you're a photon and you are pro do that
and you don't turn, you're gonna fall in. You know.
It's like saying, how big is the Grand Canyon. While
you start the definition at the edge of the Grand Canyon, right,
not at the not at the river at the bottom
of it. That made that Grand canyon. Right, you fall
in the Grand Canyon, you still fell in the Grand Canyon.
It doesn't matter if you fall into the edge or

(35:15):
if you jump out of a helicopter in the middle.
So I think it's a pretty reasonable definition that you're
you're putting the emphasis on the whole part. Well, that's
what makes the black hole so cool, right, is the
whole part, not the black part. So if you just
think of it the black hole as a whole, then
you have to measure where the whole starts. Yeah, so
you're saying them the density of the black hole, not

(35:36):
determined by how much mass is inside of the black hole,
is just kind of like how big the hole is,
which when it grows, it doesn't help the density, that's right,
because it's a connection there. Right. The more mass, the
bigger the hole, and the bigger the whole, the less dense, right,
So you sort of trapped there. In fact, to get
a really dense black hole, what you need to do
is is have um a smaller black hole. Right, If

(36:00):
you take half of the mass away from the black hole,
which of course you can't do, right, Then the mass
goes down by two, but the volume goes down by eight.
And so now the density increases by a factor of four. Okay,
so then the smaller the black hole, the denser it is. Yes, exactly,
So start with like a really big black hole, right.
I did some some calculations here. If you have a

(36:21):
supermassive black hole that has like the mass of four
billion sons, right, four billion times the mass of our Sun,
would be really really big black hole. It's event horizon
would be so big that the density of the black
hole would be the same as water, be five grams
per teaspoon of black hole. Oh, I see, because all
the masses just concentrated inside of this really really big hole. Exactly.

(36:46):
And again we're saying we don't know where stuff is
inside the hole. You know, we'll talk about that in
a moment. But if you have a really really dense
blob of matter that forms a black hole, then it's
event horizing is so big that it's really on average
on it's not denser than the water. Do you see
them unsatisfied by that? Well, I'm just confused a little bit.

(37:06):
So you're saying it's it's you need a billion sons
for this, right, four billion sons. Four billion sons. So
if you stuck four billion sons inside of a sphere
that big, it would be a black hole. It would
be a black hole. It doesn't matter how those sons
are arranged inside. It could be in a little point
in the middle, or it could be in a you know,
the form of unicorns spread all over the whole. It

(37:28):
would still create the same black hole. They could spell
out your name absolutely. So you're saying that we don't
know what the mass, how the mass is distributed inside
of that black sphere. It could be anything that's right,
and we don't because we can't see inside black holes.
So we don't know what the distribution of mass is.
Is it all in one little point in the center.
Is it a little fuzzier because the quantum mechanics is

(37:51):
it's some broader distribution. We don't know because we can't see.
That's why it's a reasonable definition to say, you know
everything inside this sphere, because we can't see any deeper anyway.
Anything beyond that requires speculation. I always thought black holes
had to be like a point. Everything had to be
inside of a little point. But you're saying that they don't.
They could. They could really be like like a fluffy

(38:11):
cloud of four billion sons. That's right. And another cool
thing is that any amount of matter can become a
black hole as long as you put it in the
right density. Right. You take your teaspoon of earth or
a teaspoon of water, you can make that into a
black hole if you candense it down to a small
enough area. Right, however small that event horizon has to be.
But if you have enough mass, right then then it

(38:33):
doesn't have to be that dense. That's the point. Right,
So you take four billion sons, you can distribute them
in a really big area and it will still be
a black hole, a really huge black hole. So I
don't recommend that if you are distributing sons around, please
be careful not to make a black hole. It's easier
than you think can be careful handling those sons. Yeah,
So the point is for huge masses, it's easier to

(38:55):
make a black hole because they don't have to be
as dense for small masses, like you want to turn
your teaspoon of water or tea into. A black hole
has to be really dense to become a black hole.
There is a number, right, you can calculate how small
you have to compress that into. But it has to
be really dense, all right. So then, so a super
massive black hole that's a four billion times the mass

(39:15):
of our Sun would actually not be that dense. It
would be about us dance as a tea spoon of water,
that's right. But if you made a black hole out
of just one sun, right, then it would be really
pretty dense. It would be about as dense as a
neutron star. Oh, I see, huh about us dance, But
but it could be denser. Well, smaller black holes in
that could be denser than neutron stars. Yes, but the

(39:37):
smallest black hole we've ever seen is about six times
the mass of the Sun. So in terms of actual
stuff we've we've observed in the universe, then the densest
black hole we've observed is not as dense as neutron
stars because we've never seen one smaller than six solar
masses and I have to be smaller than that to
be denser. But so why haven't we seen one? Could

(40:00):
one exist? They certainly could exist. Yeah, there's no minimum
size to a black hole. Remember, at the large Hadron Collider,
we think we might create black holes and those black
holes would be like particle sized, So there's no minimum
size to a black hole. So they certainly could exist.
There could be black holes out there that are the
mass of the Sun, or half the mass of the Sun,
or the mass of one Horge for example. They could exist,

(40:21):
but they're harder to see, right. Smaller black holes are
harder to see. So the densest thing in any of
the universe is probably a black hole, but it would
have to a be a small black hole less massive
than our sun and be we haven't seen what. So
technically the densest thing we've seen is a neutron star.

(40:43):
But the densest thing that could exist is a small
black hole unless you're willing to pierce the veil of
the event horizon and talk about what's going on inside
the black hole. What's inside a hole? Right, Well, then
that's the thing we don't know right now. Originally, Einstein
and general Relative they say, in the center of a
black hole is a singularity is a point, and a

(41:04):
singularity means a point of infinite density, right, at a
point where there is a huge amount of mass in
zero volume, which is pretty hard to get your mind around,
like how do you have stuff in no space? But
black holes are hard to get your mind around anyway,
So that's what Einstein would say. I would say, Oh,
the answer this question is obvious, it's the singularity inside
a black hole. But but que quantum mechanics, and he

(41:26):
wouldn't say that. His spokesperson would say that, I guess
um Foundation, that's right, the estate of Albert Einstein Um.
But the quantum mechanics folks would say, look, we know
the universe is quantum mechanical, and quantum mechanics says, you
can't have that much stuff in a well defined location, right.
Quantum mechanics says, we know there can't be a singularity

(41:48):
at the center of black holes. We don't know what's there,
we don't know how it works, we don't know what's
going on. And at that point gravity gets so strong
that our theories of quantum mechanics don't work, and we
don't have a theory of quantum mechanics that work when
gravity is really really powerful um, So it's a big mess.
We don't know what's going on inside a black hole.
If it's if general relativity is correct, which we're pretty

(42:09):
sure it's not, then there's an infinite density singularity. If
quantum mechanics is correct, which we think it is, but
it doesn't work inside a black hole, then we don't know.
So what's the densest thing in the universe? Apparently it's
the ignorance of physicists. We don't really know i'near these things.
We have no idea, that's the answer. We have no

(42:30):
idea what the densest thing in the universe is. It
could be a neutron star. It could be a small
black hole, It could be a singularity at the center
of a black hole. It could be something else weird
and quantum mechanical that's going on inside a black hole.
We just don't know, all right. So that so that's
the answer to what is the dnist thing at the
universe is? We don't know exactly, and it kind of
depends on what we've observed and what the true theory

(42:53):
of physics is at these extreme situations. That's right. But
the densest thing we've ever found is a neutrons are,
which is plenty dance to impress you about extreme densities
in the universe, right, it goes from like a proton
in a teaspoon up to a million Eiffel towers in
the teaspoon. So there's an enormous range of densities. You know.

(43:14):
The universe is not just like uniform and spread out right,
it's like mostly empty with these incrediblely tight packed pockets.
And that works even in France. That works email in France,
exactly all right. Thanks for joining us and another one
of our Extreme Universe series. We hope you enjoyed that.
Thanks for tuning in, and hey, if you have a
question about the universe or or want us to talk

(43:36):
about another extreme thing in the universe, let us know.
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,
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(43:58):
email us at Feedback Daniel and Jorge dot com. Thanks
for listening and remember that Daniel and Jorge Explain the
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