What came first matter or energy?

Daniel and Jorge answer listener questions about the solar system and the early Universe.

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:02):
Y Daniel, I have a deep philosophical question for you. Awesome,
let me just get some Banan appeals ready over here.
It is a slippery question, so watch out all right.
So which came first? Physics or math? Oh, tough one.
I'm inclined to say math because people have been doing

(00:25):
that since there was like money. I think there are
cuneiform tablets they have found with receipts for like cows
that somebody bought in two thousand BC. So economics came first? Well,
you know, economics is doing math to describe the physical
world like cows. So in a way they're secretly physicists,
aren't they. I see, you're just trying to point it
all back to physics. So even if I buy a Hamburger,

(00:48):
I'm being a physicist. Well, you know, if you spend
money doing it, then I guess you're like a Mathematterian.
We're already saying that I eat math or I eat mathematicians.
That depends on your ethical framework. Man, what came first?
Ethics or physics? Philosophy came first? Would you get a
doctorate in those? I think podcasts definitely didn't come first, Hi,

(01:23):
am or Hammay cartoonists and the creator of PhD comics. Hi,
I'm Daniel. I'm a particle physicist and a professor UC Irvine,
and I definitely liked math before I liked physics. Really,
math is your first love or just your first experience
with the academics. Well, you know, you learn math in
elementary school, but they don't really teach you a lot

(01:43):
of physics in elementary school. I mean maybe you do
a little bit of like this is what it's inside
of rock, but you definitely don't talk a lot about
astrophysics in elementary school. I see, so Daniel Whiteson was
a mathematician before he was a physicist. Yeah, my dad
was really into math, and so I learned a lot
of math at home and I really enjoyed math and
elementary school. I was definitely a math nerd before I

(02:04):
was a physics nerd. That kind of makes me a
little sad. I feel like that's like learning that Michael
Jordans really wanted to be a baseball player and not
a basketball player. I think that's true, actually, isn't it.
It is true? Yeah, his first love was baseball. But
I'm pleased with any analogy that puts me in the
same phrase as Michael Jordan. I'd like to be the

(02:24):
Michael Jordan of anything. You are full of air hot
air sometimes. But you know, don't they say that all
babies are kind of physicists when they're born. You know,
they're trying to explore the physical world around them, and
they're trying to, you know, learn the laws of physics
in a way. Yeah, it sounds to me like you're
saying everybody who's curious about the world is a physicist,
not just curious about the physics of the world. You know,

(02:45):
like how do I stand up? Or what happens if
I dropped this ball? Or how do I get more food?
Although babies come from biology, so made biology came first?
Now I'm confused. It's all philosophy in the end. But anyways,
Welcome for a podcast. Daniel and Jorge explain the university
production of I Heart Radio, in which we treat the
entire universe as one grand physics question. We ask how
does it work? Why does it work this way and

(03:07):
not some other way? And how will it work in
the future? And most of all, we ask is it
possible for our tiny little mathematical biology? Economics philosophy, loving
brains to understand it. Yeah, it is an amazing universe,
and it makes me wonder if we are still just
kind of babies in it trying to figure out the
basics of how it works, or are we PhD holders

(03:28):
who pretty much are going to understand everything there is
to know about the universe right now. It is fun
to look back at that sort of history of physics
and how it developed, people stumbling forward, having silly ideas,
having to backtrack, having new ideas, and then bursts of progress.
It really is similar to the way kids develop. I mean,
physics are just like banging blocks together, you know what,

(03:49):
You know what, that's kind of what you're doing, just
banging particles together seeing what happens. Yeah, well, there definitely
are false leads and stumbling blocks, you know. I was
reading some history of physics yesterday, and even after are
like the Michaelson Morley experiment that light travels at the
same speed no matter who measures it. Most physicists still
believed in the ether for years and years afterwards. It

(04:10):
takes physics a long time sometimes to change direction and
figure out a new course, the same way it takes
kids time to break old habits. Yeah, tell me about it.
We tried telling a kid what to do or try
to instill the habit of cleaning up the room. Impossible, impossible.
And so I hope that we are still babies when
it comes to the physics of the universe, because that

(04:31):
suggests we're going to grow up into some new, deeper
understanding of the way the cosmos works. That in our
future are some revelations. Yeah, we're gonna get PhDs in
PhDs or something, But there is still plenty to understand
about the universe and all the mysteries of the cosmos,
how it works, how things swirl around each other, how

(04:51):
things form, how they burn, how they die, generate questions,
not just in the minds of academic physicists, but in
children and in everybody out there. Yeah. Maybe in a
way before math or before physics or biology or philosophy
came just asking questions like that's kind of how everything
starts by a human asking a question about how something works. Yeah,

(05:12):
proto humans asking questions like how fast do I have
to throw my spear to get that mammoth? Yeah, that
it sounds like more of an engineering problem, Daniel, We're
all proto engineers. Is that what you're saying before asking questions?
We're engineers. We ask questions and the answers lead to
engineering problems, like all right, I need a spear this long,

(05:32):
somebody build me one. Yeah, well, I'm regardless of who
came first. What's important is that we ask questions. That
seems to be a very common human trait that everyone doesn't,
no matter how old you are or where you come from,
because we all look at the universe and we wonder like,
what's going on, how does it all fit together? And
what's going to happen next? And if you're listening to
this podcast, probably you're the kind of person who desperately

(05:54):
wants to know the answer to these questions. Feels like
there is a truth out there about how the universe
works and how it began and what its future holds,
and we want to know it because we believe that
if we apply our minds, we can understand the universe. Yeah,
and it's not just physicists asking these questions. It's people
like you asking these questions. And sometimes listeners like you

(06:15):
send their questions to us, and we invite you to
send your questions as well. If there's something about the
universe you don't understand, or you'd like to hear us
talk about and make silly jokes about. Please write to
us two questions at Daniel and Jorge dot com. Yeah,
Daniel answers every physics questions he gets, even if they
are crazy out there, right, that's right, And not just

(06:36):
physics questions. AHI answer every message I get from our listener,
even funding requests. He takes that funding requests. I guess
you can always answer it. No, I'd always answer no.
Sometimes people ride in with life advice questions like I'm
forty years old and I'm a computer programmer, but I
always wanted to be a physicist, and is there a
way for me to get there? Cool life advice, career

(07:00):
advice from a physicist, Life advice from somebody who doesn't
really know how the real world works. Yeah. So sometimes
we get these questions, and sometimes they're so interesting Daniel
puts them up to answer on the podcast live in
front of a studio audience. Who's the studio audience exactly
by the laugh track, Now it's the studio in my head.

(07:22):
We have a live audience in my head in front
of the studio audience of nobody know. Sometimes I get
a question that I think we'll be fun to talk about,
or I suspect other people will want to hear the
answer to, and so then we get audio from that
listener so we can talk about it here on the podcast.
Yes to the On the program, we'll be tackling listener questions.

(07:45):
Remember that's the six episode in which we answer questions
from listeners. That's right, and last time we did this,
or hey, you had so much fun, you said we
should do this more often, And so here we are again,
just a couple of weeks later, doing it more often.
Oh man, I didn't know I had that kind of
influence in the universe. Should I wish for more things?
Oh man, Daniel, I wish I had a bazillion dollars.

(08:06):
You can submit a request to the Daniel Science Foundation,
but they usually say now do they ever say yes?
What's their track record? Zero percent? We responded to all requests.
I see response rate zero percent, affirmative response. We have
issued of our foundation of bank account, have issued knows

(08:29):
in your operations. That's right. But anyways, we're so we're
answering questions from listeners today and we have some awesome
questions here today, some from kids about the Solar system
and the planets in the Sun and the moons around us,
and also some interesting questions about asteroids that may or
may not kill us, and also about matter and energy
at the Big Bang. We're going all the way back

(08:51):
to the beginning. That's right. We want to understand everything
about the universe from the way it is today to
the way it started. Yeah. So we have awesome questions here,
and the first few are from a couple of kids
who listen to the podcast, and they have questions about
kind of our immediate neighborhood. So the first one is
from Kendall, who is seven years old. Hi, my name
is Kendall. I'm seven years old. I would like to

(09:13):
know why our stars so hot? Or hey you're a star,
why are you so hot? I don't know. You know,
I work out, I eat well, a mom cartoonists. I
think that adds to that air of you know, attractiveness. Yeah,
so great, another piece of life advice from somebody who
doesn't live a typical life. That's right, someone who doesn't
leave their house very much. But thank you Kendall for

(09:35):
sending in this question. That's awesome. That you're curious about
the Sun, about stars, about what's out there in space.
That's amazing And it's a great question because it sounds
like a simple question on the surface but actually gets
into a lot of really interesting physics. And it's not
that simple a question to answer. WHOA see, Kendall, you
just dumped the footy seven year old physicists. So Kendall's

(09:56):
question is why our stars so hot? I guess star
are pretty hot? Right, They're not cold. Stars are pretty hot.
The reason we can see them is because they're so hot. Remember,
everything in the universe glows, and the frequency at which
it glows depends on its temperature. So the Sun is
hot enough to glow in the visible spectrum, which is

(10:17):
pretty cool or pretty hot. Well, it's interesting because I
guess you know, maybe people your age and mind associate
light and something bright is something being hot, right, because
light bulbs are hot. You don't want to touch a
light bulb from from when we came from. But nowadays,
you know, with LED lights you can have like cool lights, right,
you can have a cold light bulb. Yeah, because the
light generated by an LED is not like black body radiation,

(10:40):
the way light from like a tungsten filament is it
comes from a quantum mechanical process, which is pretty super cool.
But one of the interesting things about stars is that
they are hot, but in order for them to even
get formed, they have to actually start out very, very cold.
So they have a really interesting sort of thermal history
to them, right, right, because I guess all star us
out there in space in the universe started off as

(11:04):
cold clouds of gas, right, That's how they all started. Like,
the gas isn't hot, it's just like it's just floating
out there in space, and space is really cold, so
really it comes from cold gas. It comes from cold gas.
And if you have a big cloud of gas, if
it starts out too hot, it can't form stars because
remember stars are formed by gravity pulling together all these

(11:24):
little bits of stuff. But gravity is super duper weak.
So for gravity to succeed pulling together a big cloud
of gas, it can't be too hot. If it's too hot,
it'll just ignore the gravity. So cloud has to cool
down enough for gravity to be able to take over
and compress it. And so if a cloud is more
than like ten or twenty degrees kelvin, it just can't
form stars. So a star starts off as cold gas,

(11:48):
and then gravity makes it all sort of clump together
into one kind of smaller ball of super hot gas exactly,
And it's that gravitational pressure that provides the heat. A
lot of people think that stars are hot because they
have fusion going on, because they are burning, but it's
the other way around. Stars get hot from gravity and

(12:08):
that temperature allows fusion to happen, and then the fusion
sustains them. But the reason that they're hot is that
gravity takes the gas and squeezes it into a smaller
space and that heats up the gas. Just maybe step
us through a little bit, because that's kind of a
tricky step. Like when you start off with a big
cold cloud of gas, well, why does crunching it together
make it hotter. It's an interesting bit of chemistry, right,

(12:30):
If you compress something, you make it hotter. And that
feels weird because you're like, hold on a second, it's
the same amount of stuff. I'm not doing anything. I'm
just squeezing it down. You're just like storing it closer together. Yeah,
it feels counterintuitive to think about it getting hotter, and
it's helpful to think about the temperature of that gas
as like the speed of the molecules of gas flying

(12:51):
around in it. Temperatures are really complicated topping. We have
a whole podcast about just that. But a simple way
to think about it is that a temperature is like
a spedometer of the particles in a gas. So a
hotter gas means particles moving faster, and a colder gas
means particles moving more slowly. So when when you take
a big cloud of gas and you squeeze it together,
somehow that makes the molecules, the little gas particles inside

(13:12):
in the in the cloud move faster exactly because what
you're doing when you squeeze it is that you're pushing
in on it. You're providing energy. You're actually putting energy
into that gas by squeezing it down. Think about, for example,
throwing a tennis ball against the wall. It comes back
at the same speed as you threw it. Cool, But
what if you threw a tennis ball against the front
of a train, Then when it comes back it would

(13:33):
be going faster. So if you're a tennis ball inside
a box and that box is shrinking, then every time
you hit the wall, you're gonna bounce off with more energy,
and so very gradually, as the box gets compressed, the
balls start moving faster and faster and they have a
higher temperature. Interesting. Now, just to be clear, candles seven
year old should not be throwing balls in front of
moving train. Right, that's a parenting question. I'm not going

(13:56):
to step in because I don't have realistic life advice.
That's right as your parents first, always for all things.
But that's interesting, and that's an interesting analogy. Like if
the walls are closing in on you, they're going to
be imparting some energy on the balls hitting the walls.
But I guess in space there's there are no walls.
It's just gravity moving things together. So where does that
extra energy come from? Right? Well, gravity is pulling stuff together,

(14:19):
and the way it creates more pressure is that it's
like pulling gas on the outside of you in you know,
So the wall is like the next layer of gas,
which is less and less pressure, but effectively it acts
like a wall. So gravity is pulling everything and it
creates this gravitational well which makes it harder for the
particles to leave. So each shell of gas is sort
of compressing the next shell of gas. Interesting, all right,

(14:41):
so then you have a big cold cloud of gas
that gets compressed. Then that gets hot, and at some
point it gets so hot it starts to explode in
the middle. Yeah, if when it reaches like twelve million
degrees kelvin internally, it can start to fuse hydrogen into
helium and that releases a bunch of energy, and that
helps us start stay hot and actually also EAPs the
star from collapsing further. If you just let gravity do

(15:03):
its thing, it would turn those particles into a black hole.
But fusion pushes back, and then you get this balance
between the energy released from fusion, the outward pressure and
the inward pressure of gravity, and the star burns for
a few million, billion or trillion years, depending on its size.
I see. So then I guess the answer to Kendall's
question is that stars are hot because they can't have

(15:23):
to be Otherwise you won't have a star, Like you
can't have a cold star, right, You can't have a
cold star unless you call it black dwarf, a star
which is a remnant from a white dwarf that has
cooled off. But yeah, you can't have a cold star.
So I guess by definition, right, a star is something
that is hot. But I think the most direct answer
to this question is that gravity is what makes a
star hot to begin with. It ignites the star and

(15:45):
then fusion keeps it hot. Yeah, because I guess you know,
once gravity crunches everything together, it will stay hot even
if there's no fusion, right, true, But if there was
no fusion, it would compress into a black hole. And
then you get me into questions of like what's the
temperature of a black hole? That that's the subject of
another podcast. That's a whole rabbit hole. All right, Well,

(16:06):
thank you Kendall. Hope that answered the question. And so
we have another question from Megan who's ten years old,
who is a question about the moon. How my name's Megan,
and I'm wondering why they are craters on the moon. Yeah,
why are there creators on the moon? Like if you
look at the moon, great question, Megan. By the way
you look at the moon, it's not like a perfect
little sephee or perfect circle. It's not just all one

(16:27):
color or one um, one smooth surfer that it has
a bunch of holes and pop marks in it. Right, Yeah,
there are a lot of craters on the moon. By
last count there are nine thousand, one d and thirties
seven recognized creators with names nine that's a lot. I
have a friend who did her PhD in like moon craters,
Like she was in a moon crater when she did
her PhD that time. Yeah, suddenly she became a lot cooler.

(16:52):
You're right, Yeah, Yeah, there are a lot of these craters,
and it's fascinating because you look at the Moon you're like, Wow,
the Moon is filled with creators, but the error there
is not. And so that's an interesting question. Yeah, we
don't have like giants holes here north, at least not
not that are visible. And it's not a question we
actually knew the answer to. Until we went to the Moon.

(17:14):
This was an open question about the source of these craters.
Some people thought maybe there was like volcanic activity on
the Moon and each crater was like a little mini volcano,
and other people thought they were impact from rocks from
space and there they were even crazier ideas. And until
we went to the Moon and got samples and studied
the age of the surface, we didn't know the answer
to Megan's question. Interesting, Yeah, they could have been like

(17:35):
holes on a piece of cheese. Was that your friend's
thesis topic on the lore of the moon cheese hypothesis. Well,
now we know that the surface of the Moon is
about as old as the surface of the Earth, about
four and a half billion years old. But the Moon,
unlike the Earth, doesn't have an atmosphere, right, doesn't have
like a cloud of gas surrounding it. And so the

(17:57):
short answer to Megan's question is that it's rocks from space.
Space is filled with rocks that are constantly hitting everything
in the Solar System. And if you have a shield
like the Earth does, and most of those don't hit
the ground, But the Moon doesn't have a shield, and
so it gets smacked by every rock that comes its way. Yeah,
and it's kind of interesting to think like that happened
or is happening all over the Solar System, right, Like

(18:18):
there are planets who also don't have an atmosphere who
are filled with craters too. Yeah, Basically every surface on
the Solar System will get impacted with craters, and so
you need some kind of protection if you're going to
live there, either an atmosphere or like a really strong umbrella.
All right, So to answer Megan's question, the Moon has
craters because it gets hit by a lot of rocks

(18:38):
from space and it doesn't have a coating of air
to kind of protect it. Yeah, and some of these
craters are like more than two billion years old. No
wind or water on the Moon, so if you form
a crater, it will last a very very long time.
There's one crater on the Moon that might even be
four billion years old, and scientists think that an asteroid

(18:58):
more than a hundred d miles across smashed into it
about four billion years ago, such a big explosion. It
probably rain did debris down on the surface of the Earth.
Interesting Also, I think another part of the answer is
that there's no lava on the Moon, right Like we
have lava here on Earth and that's kind of making
the surface move a lot, which kind of gets rid

(19:20):
of all of the craters that we used to have.
But in the Moon there's no lava, so it does
nothing ever moved. And the surface of the Moon really
interestingly is covered in this like really fine grain soil.
If you look at the astronauts footsteps, for example, you
know that they were walking through like several centimeters of
what looks like dust, and this lunar dust. It basically
the shattered surface. There's been so many impacts on the

(19:41):
Moon that its surface is basically covered with shattered little
pieces of rock. I guess the question is, like, are
there still new craters being formed in the Moon? Like
does the Solar system now have fewer asteroids flying around
or are there still is the Moon still getting bombarded
by meteors. It's still getting bombarded. We actually we saw
one happen in two thousand and thirteen which was visible

(20:03):
to the naked eye. A nine pound meteoroid strike the
surface at like nine thousand kilometers per hour and left
a new crater. So it's still happening. Wow, But is
it happening faster or at the same rate as before
or has the Solar system sort of calmed down a
little bit? The Solar system definitely has calmed down. In
the very early part of the history of the Solar System,

(20:25):
there was the heavy bombardment period when the Solar System
was a huge mess. Since then, things have calmed down
and larger objects have pulled together to make fewer objects.
Since you have fewer rocks out there than you used
to see. Yeah, we've made it past purity, right, skin
is now going to clear up a little bit more.
All right, well, thank you Kendall and Megan for these

(20:46):
awesome questions. We hope you keep asking questions, and so
now let's get to our other questions about asteroids that
might kill us here on Earth and also about the
nature of matter and energy. But first let's take a
quick break. All right, we are answering questions from listeners,

(21:14):
and we've just answered some awesome questions about the stars
in our in the moon, and so now let's get
into some terior topics like the possible extinction of humankind. Hi,
Dani and Jorge, this is Shawn calling from Ottawa, Ontario, Canada.
We always hear about asteroids and comets hitting the Earth
at thousands of kilometers per second and wiping out life

(21:36):
as we know it. But I was wondering, is it
possible for a comet or an asteroid two come in
and slowly hit the Earth where it won't kill us all?
Maybe if we're both on the same trajectory and it
can come in and just gently land somewhere on Earth
and not destroy everything. Anyways, thanks for the great podcast.

(21:59):
All right, some question, thank you, Sean. It's an interesting question, Yeah,
because I guess when you think of asteroids hitting the Earth,
you usually think of them as coming in fast and
crashing on Earth. But he's asking, you know, could one
somehow sort of like creep up on us and kind
of shem me onto our planet and gently, you know,
land in the middle of the ocean or something. Yeah,

(22:21):
it's very Canadian. He's looking for like a friendly asteroid
that just comes and settles down gently. But yeah, maybe
the land in Canada and apologize for causing a disturbance.
It is an awesome question. Why do we always think
about asteroids? It's basically like bullets aimed at the Earth.
Can't we think about them like moving in parallel to

(22:42):
the Earth and very gently coming into the surface. It's
a really cool question. I guess, um, it maybe seems
unlikely that something would just come out of the blue
and then just happened to like fly right next to
us slowly, And that's the answer. It is possible, but
it's much less likely if you just pick like random
trajectories for rocks in space that are going to come

(23:03):
into contact with the Earth. It's just much easier for
those rocks to be going the opposite direction of the
Earth or to be going in opposite direction of the Earth.
At least at some level. It's possible for a rock
from the asteroid belt or the Kuiper Belt or even
the Orc Cloud to end up in like the Earth's orbit,
but it would take a very special circumstance. You mean,

(23:24):
like it is possible maybe for one of the asteroids
around us to like suddenly kind of jump into our orbit.
It is possible, But everything right now in the Solar
System hasn't orbit. The reason it's still around is that
it hasn't fallen into the Sun. It's in some orbit.
So even to come into contact with the Earth would
require it most likely to change its orbit. The collision
happens when the trajectory of one of those objects intersects

(23:44):
with the Earth right, which is very unlikely to happen
in parallel. In order for one of those things to
like jump into the Earth's orbit, it would need to
change its trajectory, which means like hitting something else and
bouncing off. So you need like two things to come
into contact and change each other orbits that one of
them happens to end up in Earth's orbit and kind
of going at the same speed. But I guess couldn't

(24:06):
it also happened that the Earth, you know, maybe passes
by close enough to a cloud of asteroids that maybe
like pulls one along with our gravity. Yeah, that is possible.
And in fact, there are some things out there that
have been sort of like captured by the Earth. They
haven't landed on the Earth when they came close enough
to the Earth that sort of now in orbit around
the Earth or sharing the Earth's orbit around the Sun.

(24:28):
At least one of these things is called the space
being because it traces out this weird path relative to
the Earth. It's this five kilometer diameter rock where there
is a rock like that that it has somehow fallen
into our orbit and it is kind of going along
with us. Yeah, officially, it's like a quasi satellite of
the Earth. It's got a fancy name which I can pronounce,
and it has its own elliptical orbit around the Sun

(24:49):
that's sort of in residence with the Earth's and so
from our perspective, it has this like weird being shaped
orbit around the Earth. But effectively it's been captured and
in a very similar or bit to the Earth. But
of course it's not landing on our surface, right right,
but it's interesting that it's possible, right, Like, what maybe
can happen again and we could pick up another bean. Well,
this one, the closest it ever comes is like seven

(25:11):
and a half million miles from the surface of the Earth,
which is like thirty times further than the Moon. I see,
I see, But maybe it eventually, could it somehow, you know,
creep into the Earth, Like maybe not now, maybe, but
maybe in a million years, could it somehow, you know,
start creeping in and maybe go into orbit around the
Earth at some point. It's certainly possible, right if it

(25:32):
impacts something or something else comes along and tugs on it,
it could change its orbit. And it is possible for
something to get even closer to the Earth and eventually
even come into the atmosphere. And in theory it could
come in slowly, could like gently approach the Earth's atmosphere. Interesting, Well,
you said it's not very likely because I guess we
have most asteroids out there kind of catalog, So I

(25:55):
imagine if any do sort of surprises, it's they're going
to be coming in pretty fast. But maybe, just for fun,
let's assumed that um Seawan scenario here comes through in
which is like make an asteroid appear right next to Earth,
we would it kills or would it's just kind of
gently bump us. Yeah, I just want to make one
more comment and the likelihood of it. Another way to
think about why it's unlikely is that these objects are

(26:16):
moving typically faster than the Earth. You know, the Earth
moves like thirty kilos per second around the Sun, and
these asteroids moved like fortify or even faster if their
comments from the outer Solar System. And if you think
about like two velocity vectors, in order for one of
these to catch the Earth, they basically have to be
perfectly aligned with the Earth. Otherwise to impact they could

(26:36):
have at any angle. So it's just unlikely for these
things to be perfectly aligned with the Earth's direction. But
you ask a great question, like what would happen if
this thing like gently came up to the Earth's atmosphere?
Would that actually hurt us? And I like Shaun's fantasy
that this thing would like gently sink down to the
surface of the Earth so we could like you know,
touch it and build a monument to it or whatever,
But actually I don't think that's likely either. I guess

(26:58):
maybe let's paint the picture a little it better. So
the Earth is moving through space, We're spinning, and somehow
like another an esteroid kind of like chemis up to us,
going at the same speed, in the same direction, maybe
in the same orbit, and then just a little by little,
just kind of bumps into the Earth. Is that possible.
It's possible for it to get close to the Earth
and like join our orbit, but then it's going to
be captured by the Earth and it's going to fall

(27:20):
into the Earth's gravitational Well, remember the Earth itself has
a lot of gravity. So if you just like dropped
a big rock at zero velocity at the top of
the atmosphere, what would happen, Well, the Earth would pull
on it. By the time it reached the surface, it
would have a lot of kinetic energy. Imagine what would
happen if you drop like a penny from the top
of the atmosphere. It would be going super duper fast

(27:43):
by the time I hit the ground. Oh, I see
you're seeing. Like, even if I parked this esteroid close
to us, just the earth gravity is gonna pull it
in and make it go faster towards us. Yeah, the
escape velocity of the Earth he's like eleven kilometers per second,
And so that means if you're going at like zero
kilometers per second at the top of the atmosphere, then
by the time you get to the bottom, you're gonna

(28:04):
be going in eleven kilometers per second. So it's a
lot of kinetic energy, right. But I guess maybe Shawn's
point was that, you know, even if it's going at
eleven kilometers per second, that's still not as fast as
most asteroids that hit Earth are going. And so maybe
it would he's saying it would. Would it might survive
the atmosphere, right, not get burned up by all the
friction from the error, and maybe it might it will

(28:27):
crash onto Earth, Yeah, and I think that's likely that
it would make it to the surface of the Earth.
You know, it wouldn't actually get to eleven kilometers per
second by the time it hits the Earth because of
the resistance from the air. It would heat up and
parts of it would blow off. But probably it would survive,
but it might make a crater when it lands because
it would be going pretty fast. But even asteroids that
do hit the Earth at high speed, some of them
make it to the surface. If they're big enough to

(28:49):
survive the trip through the atmosphere. Interesting, I guess maybe
then the real answer to Shaun's question of couldn't asteroid
hits slowly without killing us? The answer is not, because
and a story can hit its slowly. Any asteroid that
hits is going to be coming in pretty fast because
the Earth's gravity pulls it in and it's going to
pick up speed. You might imagine another scenario where a

(29:11):
rock comes in near the Earth and it has like
negative velocity, like the Earth is catching up to it,
but it's running away in the atmosphere gradually slows it
down so it lands on Earth. But that's even more unlikely.
The Earth would have to like sneak up on this rock, right.
It's it's less likely, but much cooler to think about.
So you're saying that there could be an asteroids flying

(29:32):
through space sort of in our orbit, and so Earth
sort of sneak like we sneak up behind it, and
we're in such a trajectory, and it's in such a
trajectory that it really just kind of slowly touches us.
So what you're saying, Yeah, I think that's probably possible.
I haven't run the simulation, but you'd have to have
a lot of factors exactly a line to make that work.

(29:53):
Like what's the slowest it could hit Earth? You know
what I mean? Like would it still pick up eleven
kilombers per second? Or is there a snario in which
it literally like just slowly kind of touches the Earth. Well,
there's some things you have to balance there, because in
order for it to be going slower when it hits
the Earth, you wanted to start with like negative velocity
velocity away from the Earth at the top of the atmosphere.

(30:15):
But then you know, how is it getting to the
top of the atmosphere. It has velocity away from the Earth,
so it can't be going too fast away from the Earth.
The Earth has like sneak up behind it while it's
moving fast away from the Earth, and then the atmosphere
somehow slows it down and pulls it in. So it's
a pretty tricky set of circumstances. But I bet it's
technically possible, and you know, if the solar systems around

(30:36):
for long enough, maybe it will happen. Right right, just
got to the mass, right, Anything is possible with them,
But are you envisioning that this could like literally just
like touch down like a spaceship or would it crash
land anyways, just because you know the guy is big
and it's going to fall. Well, the slower you wanted
to hit the Earth's surface, the less likely this scenario
is because the faster it has to be going away

(30:58):
from us at the top of the atmosphere. And I
think technically it might be possible for it to like
gradually sink into the Earth's atmosphere if it has enough
initial velocity away from us and the atmosphere just sort
of like slurps it in gradually. Interesting. That was pretty
cool to see a giant rock slowly land on Earth.
I don't expect that to happen. And after this, I'm

(31:19):
gonna have to go write some code to simulate this
too but actually work. But that's my instinct. All right,
let's stay tuned. Well that Daniel writes in a scientific
paper about it, and when it comes out, we'll we'll
let you know. That's right, and Sean will make you
a co author. Wow. Nice, See what can happened when
you write questions to us? You might become a physicist
for real? All right, Well, let's get into our last

(31:40):
question about the nature of matter and energy at the
Big Bank. But first let's take another quick break. All right,
we're answering listener questions, and we've answered questions from kids

(32:03):
about the sun and the moon, and also a question
about an asteroid slowly killing us slowly with its song
that with its a space song. I guess it's telling
our whole life with its trajectory. I guess that's that's
kind of a philosophical question. If an asteroid is going
to come and kills do you want it to be
fast or do you do you want it to be

(32:23):
slow and you want to see it coming. I definitely
want to see it coming so we can potentially divert
it so it doesn't come and kill us. What if,
like you do, see it's coming, but there's nothing we
can do about it. We always have Bruce willis Man,
did you see that latest movie with the Leonardo DiCaprio
and the asteroid don't look up? Yeah? Yeah, I did.

(32:45):
That was a lot of fun. I heard that he
couldn't write the equations himself on the board, so they
had to have a hand double doing the math close
ups for those shots. Whoa that could have been you, Daniel.
Now I have a new life, the real Leonard of
the Caprio's hand physics hand model. It's like being a
stuntman basically, it's just that dangerous, right right, Yeah, you

(33:08):
could get carpal tunnel from or I could become a
movie star and then I could brag and say I
do my own math. Well, let's see what happens first.
It's more likely that a huge rock will slowly touchdown
the atmosphere than at that any of that happens. Yeah,
I guess if you become a movie star that there

(33:28):
would be the end of the world. That's one of
the signs of the apocalypse, right there, Frogs falling from
this guy Daniel co starring in a movie with Leonardo DiCaprio,
although Neil de grass Tyson has been in big movies, right,
So it's possible there are physics out there that have
broken into Hollywood. Oh man, it is the end of
the world then. But anyways, we're answering listener questions and

(33:51):
our last question of the day comes from Jeels, who
has a question about which came first in the universe. Hello,
Danny on Jorge, how are you guys? My name's chill,
and I was curious about the following. I know that
matter and energy are intimately connected, but I was wondering

(34:15):
what came first matter or energy. I would appreciate if
you guys can address this in your podcast. Thanks a lot,
Bye bye. Alright, awesome question. I feel like this is
getting back to like elementary school philosophy, you know, like
which came first, the chicken or the egg. It's a
deep question about the early history of the universe. I

(34:35):
love this stuff. Yeah, so gals Um kind of acknowledges,
first of all, that matter and energy are really closely related.
And I always thought that matter is energy, right, isn't
that what E mc squares says That they're the same
thing sort of, But it's not entirely symmetric. The way
I would explain it is that mass is a form
of energy. Right. The reason things have mass, it's because

(34:56):
they have internal stored energy. And so you can think
about mass is like a form of energy, or you
can think about mass is like a little dial that
tells you how much stored energy is inside this thing.
But you can turn mass into other kinds of energy,
like velocity, or you can turn velocity into mass and
so you can think about mass it's like a form
of energy. But energy is not a form of mass,

(35:18):
so they're not entirely symmetric. Oh I see, it's not
really an equivalence. E equals mc square. It just says
that mass is energy, but it doesn't say that energy
is mass. Yeah, equals mc squared tells you how much
energy is stored in an object at rest with mass.
M I see, So I guess you're saying that matter
is a subset of energy, and therefore therefore it can

(35:41):
be first, can it. Yeah, that's right. Matter is a
kind of energy, so it can't really predate energy. You
can't imagine a scenario where you have matter in the
universe without energy because matter is a kind of energy.
It's like saying an egg is really a baby chicken,
so therefore the chicken can first. Not a biologist not
going to weigh in on that one. But it sounded good.

(36:03):
That sounded good. The mass funded, right, we'll go with that.
I'll have to do a simulation later, but yeah, it
sounded another paper. Oh man, we are cracking out the
assigns here. So I think it's pretty clear that energy
came first, because you can't have matter without energy. But
it's interesting to think about sort of what forms of
energy were created in the universe at what time, When

(36:24):
did matter come about, When did we get radiation, what
came first, How did that all happen because the history
is quite complicated and really nuanced. Oh, interesting because you're
saying that, you know, in the Big Bang, maybe there
was sort of an opportunity for matter to be more dominant. Yeah.
The way we think about it in the very early
universe is that you have very high energy density. Right,
the universe used to be much more dense, it used

(36:46):
to be much more compact, it used to be higher temperature,
so things were flying around, they were crazy, and there
were such high energy that all the quantum fields were
buzzing with so much energy that doesn't even really make
sense to talk about particle in the way we think
about it. There was a moment very early on in
the universe when there's a lot of energy, but there
weren't even really particles flying around in the universe had

(37:08):
to like cooled down a little bit before you can
even start to talk about the quantum fields buzzing in
the way that we think about it today is like
these little discrete pockets of energy flying around the universe.
It was just more like a huge ocean of energy,
like pure like everything was just pure energy. I guess
the question now that I have is which came first,

(37:28):
energy or quantum fields. Yeah, that's a great question, and
we don't know the answer. We have a description of
the universe in terms of quantum fields. For certain energies,
like for the energies that exist today in the universe,
which are very very cold, we know that we can
describe the universe in terms of quantum fields, and for
higher energies like what happens inside the Large Hadron Collider

(37:49):
and going back to the early moments of the universe,
we can describe that in terms of quantum fields. Beyond that,
we don't know, Like we have quantum fields, and we
suspect that those theories and the disc oricteen to the
universe in terms of quantum fields probably works at very
very high temperatures very early on in the universe. But
the truth is that we just don't know. One of
the reasons we don't know is that we don't understand

(38:10):
how gravity works in a quantum sense. So what you're
really asking about is like can you give a quantum
field description of the universe when gravity was just as
important as all these other forces? And we don't know
because we don't have a theory of quantum gravity. So
we're really pretty clueless about a sort of a quantum
picture of the universe when gravity was very important early on. Interesting,

(38:32):
I guess you're saying, you know that in the beginning
of the universe, at the Big Bang, things were so crazy,
so crunched together and so high energy density. Did we
really don't know what was going on at that moment? Yeah,
in the same way that we don't know today what's
going on inside a black hole for the same reasons.
Like you send a particle inside a black hole, we

(38:53):
think of it like a little wiggle in a quantum field.
What happens when it goes inside a black hole? Well,
now it's under very strong gravitational pressure. Is it's still
a quantum wiggle? Is it turned into something else a
new kind of matter? Are there gravitational quantum fields? We
just don't know. In the same way we don't know
what was the state of the universe when gravity was
really strong and very important early on. So it might

(39:14):
be that we can describe in terms of wiggles and
quantum fields. But it might be that we can't. But
we do have a pretty nice picture of what happens,
like after the universe drops in temperature to a point
where it turns into particles, and we can then think about,
like how much of the energy in the universe is
in terms of these particles or in terms of the
photons that go between them and that kind of stuff. Oh,
I see, but I guess before that it starts to

(39:37):
cool off. Does it even make sense to talk about
energy as we know it? Like inside of a black hole?
Does it makes sense to talk about energy? Or can
you still, you know, define energy in a such a scenario.
We can define energy, but you're right, we don't know
if it's the most important quantity. Like people think about energy,
it's fundamental to the universe and a really insightful way
to think about the state of the universe. Remember that

(39:58):
we discovered recently that energy is not even conserved in
the universe. Right, It turns out it's something we can measure,
and it seems to be conserved in most of our experiments.
But we know that in an expanding space, if the
universe is growing. If space itself is changing, the amount
of energy in the universe is also changing, so energy
might not be the right way to think about the

(40:20):
nature of the universe. We talked a few weeks ago
about what happened in those first few moments of the universe,
this inflation theory, and you know, we have some like
pictures of what that means. Maybe there was this insulaton
field with these influcton particles which decayed into normal matter.
So you can possibly think about it in terms of
like weird new quantum fields. But we just don't know
if any of those theories are at all accurate. They're

(40:42):
just more like sketches of ideas that we're using to
try to think about it in terms of stuff we
already know. But but there's no guarantee that the kinds
of ideas we have are the right ideas. Well. I
feel like you're saying, like we almost don't even know
if math worked at the beginning of he never you know,
like maybe one those one was three back then, you know,
because energy and things were just popping out of nothingness.

(41:02):
It's definitely a very weird situation, and I'm pretty sure
there's going to be mind blowing surprises when we figure
out how that worked and how to even think about
it and how to talk about it. And that's one
reason why we do crazy collisions is super high energy,
because we want to probe the most extreme situations to
see when do our theories break down? When do we
need a new kind of structure. You know, quantum field

(41:22):
theories themselves are only a few decades old, and they
came into play to explain collisions at high energy that
we couldn't otherwise understand. And so maybe that a crazier
high energies we need a whole new kind of idea
about what's going on in the universe, or maybe quantum
fields will describe everything up to the playing scale. We
just don't know. Yeah, I think that's how I would

(41:43):
describe my childhood as well. It's a lot of weird
things happen and I'm still trying to understand it. Did
you break mathematics? I probably thought I could. Yeah, that
broke a lot of things when I was a kid.
But I think I think your main point, though, is
that we maybe don't know what happened during the Big Bang,
were before the Big Bang, were right after the Big Bang?

(42:04):
We do have kind of a clear picture of how
much of the universe was matter and how much of
it was kind of like flying energy, which you call radiation. Yeah,
so some mysterious thing happens, the universe exists, and then
some other mysterious thing happens. The universe inflates and expands
and cools down rapidly, and just after that we can
start to talk more concretely about quantum fields. And in

(42:25):
that situation, when the universe is still very very hot,
but we can talk about it in terms of quantum fields.
It's a really interesting situation because every particle back then
was massless. This is before the Higgs boson even came
into play, and so every particle, the electron, the w,
the z, all these particles had zero mass. Whoa, whoa,
Yeah that's wild. Yeah, at some point the universe had

(42:47):
nothing had mass because the Higgs field hadn't come into being. Yeah,
none of these initial particles had mass. You could still
have mass by combining particles into some like object, the
same way like if you put a bunch of photons
into a rage box, it actually gains mass because any
stored energy turns into mass. But the particles themselves. None
of them had mass in the very early universe until

(43:09):
the Higgs boson sort of settled into this weird state
that it's in today that gives them that mass. So
if it's nothing had mass, that means nothing what not,
Nothing mattered kind of in a way like you didn't
have matter. Particle physicists talk about the difference between matter
and radiation, and it's sort of a fuzzy line because
you know, when we talk about radiation chemically, we say, like, oh,

(43:30):
electrons are alpha particles, that's radiation, even though they have mass.
So we have all sorts of totally inconsistent definitions of radiation.
But in terms of like early universe physics, we divide
things into matter and radiation. Things that are radiation or
things that are traveling at light speed, and things that
are matter things that are traveling not at light speed.
But in the very early universe everything was massless, so

(43:52):
everything was moving at light speed, so it was just
a d radiation. Oh interesting, So we don't know which
can first, matter or energy, but we know which game second,
which is a radiation which is really energy, right yea.
So in the first moments of the universe that we
can really talk about we have all these buzzing quantum
fields with massless particles flying everywhere. The whole universe was radiation.

(44:14):
Then the Higgs field broke that symmetry between electromagnetism and
the weak force, made the W and the Z massive
and also made a bunch of other particles massive, and
then you have matter, and then the electron has mass.
You know, the corks have mass, and so that happened
very early on in the universe. But still most of
the energy in the universe was in terms of radiation

(44:35):
photons and other massless particles, meaning like it was in particles,
but it wasn't. It was in particles moving at the
speed of light. And so the first like fifty thousand
years of the universe was a radiation dominated era. Most
of the energy in the universe was in terms of
massless speed of light particles for the first fifty thousand years,
which sounds like a lot in human years, but in

(44:59):
the terms of the age of the universe, it's like
it's like just the first blink. Yeah, exactly, it's just
like a blip. Like if you ruled for fifty years,
that sounds pretty impressive, But if the universe is fourteen
billion years, then it's almost forgettable, all right. So then
at first it was all radiation and then what happened?
When did it change? Things are expanding and things are
cooling down, and that expansion affects matter and radiation differently

(45:22):
because as the universe expands, matter gets dilute. Right, the
same amount of matter exists, we have more volume, so
the density of matter drops. That makes sense, But radiation
is effected in another way. As space expands, radiation gets dilute.
It also gets red shifted. Like if you have a
photon in space and that space expands, it doesn't just

(45:42):
make the photon have fewer neighbors, It makes the photon
have a longer wavelength, which means less energy. So this
red shifting of radiation means that radiation loses energy faster
than matter does as the universe expands. Whoa interesting, It's
like it slows down light. But you can't slow down light,
but it just it makes it kind of less energetic. Yeah,

(46:04):
it steals away energy from light and we know that happens.
We see it all the time. Like the cosmic background
radiation was generated actually really high energies like three thousand
degrees kelvin. We see it now like three degrees kelvin
really long wavelengths because the universe has expanded and red
shifted all of that, and so radiation sort of lost
out after about fifty thousand years, and then for a

(46:26):
long time the universe was matter dominated. Most of the
energy in the universe was in the form of matter,
and a lot of that came because matter kind of
transformed from that early energy, right, like things, things kind
of clumped together and then they became matter. Yeah, the
Higgs boson gave math to a lot of those particles
and shifted them from the radiation category into the matter

(46:49):
category because now they had mass. And so then there
was this huge universe filled with particles, you know, electrons
and protons, and stars were formed and galaxies were formed,
and I was most of the energy budget of the
universe for billions of years was in terms of stuff,
mostly dark matter actually, but in terms of like things
we would think of today as stuff. It was the

(47:10):
stuff dominated era of the universe. WHOA, well, you just
blew my mind a little bit here, uh, either in
the dark matter here as a surprise twist here, so
like we know where dark matter came from, is that
what you're saying, Like, we traced the history of dark matter,
we know that dark matter was made at the same
time as all those other particles. When the energy in
the early universe coalesced into the different fields, electrons, and quirks.

(47:31):
That happened equally across all of the fields. And so
if dark matter is a particle and it's described by
a quantum field, then it was also made in the
early universe and it's been around since then. We're pretty
sure about that because it's changed the way the universe
has evolved. Like the reason we have stars and galaxies
is because of the gravity of dark matter early on

(47:52):
in the universe. So it had to have been around
for a long time. So when you say that the
universe became matter dominated, really you mean dark matter are dominated,
because there's like, even since the beginning of time and
or those early moments, there's been you know, five times
more dark matter than regular matter. Yeah, although the ratio
between dark matter and regular matter does change through the

(48:13):
history of the universe, we think there was even more
dark matter early on and some of it converted into
normal matter. That's a whole other podcast episode. We talked
about the whimp miracle ones about how we think dark
matter converted into normal matter. But yes, there's been dark
matter since the very beginning. Well, and so when really
in this period of matter domination, really you're saying it's

(48:33):
dark matter domination. Dark matter ruled for about nine billion
years long lived dark matter, but then something happened, the
dark energy revolution. Yes, dark energy took over. I remember
that the universe is expanding, and so as the universe
gets bigger and bigger, every new chunk of space that's
created comes with its own dark energy. So, unlike matter

(48:55):
and radiation, which get more and more dilute as space expands,
dark energy doesn't get diluted because a new chunk of
space comes with its own fresh dark matter. So as
the universe expands, dark energy starts to climb, and eventually,
at some point it crosses over and there's more dark
energy in the universe than there is energy in the
dark matter. And that happened about four or five billion

(49:17):
years ago. I see, yeah, And we're still in that period, right,
We're still in the dark energy dynasty. We're still in
that period, and this period is gonna last for a
long long time. Maybe forever, because once dark energy is dominant,
it accelerates the expansion of the universe, which makes more
dark energy more rapidly. And so now dark energy is
like completely dominant sev of the energy of the universe,

(49:38):
and the future suggests it's going to get higher and higher,
and it might even expand the universe to almost nothingness
right into my dad expanded into that there's nothing left. Yeah.
Although remember, dark energy is something we observe, we see
it happening. We have these ideas about how it works,
but we're really not very confident in it, which makes
it very difficult to make solid predictions for the future
of dark energy. You could turn out the dark energy

(50:01):
is much more complicated than we imagine. It has some
weird oscillations in it, for example, and maybe it's going
to turn around and cause a big crunch. We really
just can't say for sure because we don't understand it
like at all. But I guess we go back to
Jews question. He kind of just wanted to know which
came first, matter or energy. I think what you're saying
is that the picture is kind of complicated. It's not
just kind of about the sequence of things it's you know,

(50:22):
two physicists. It's kind of like which is more dominant,
and that that question has changed over the Big Bang
and the history of the universe. It's a really fascinating
history and nuanced and one that we've only really picked
apart in the last couple of decades. So we're just
at the very beginning of understanding the whole history of
the universe in terms of its energy budget, how it formed,

(50:42):
and how that evolved. N see. But I guess to
answer the question the question, the answer is that energy
came first, that's kind of for sure you sort of
have high confidence in. But in terms of what came second,
and third and four, that's been changing and it's a
more complex picture. And can we described the early moments
of the universe in turn energy? That is an open question. Yeah,
math otherians, I think people who ate math. That's a

(51:06):
question for people to chew on. I'm sure we'll have
a very filling answer. All right. Well, thank you Jeels
for that great question, and thank you to everyone who
sent in their questions. We really enjoy answering them on
the podcast. We absolutely do. We love your messages with
or with out questions, so please don't be shy if
it's something you've been thinking about, don't hesitate right to us.
Do questions at Daniel and Jorne dot com. Yeah, we

(51:27):
look forward to your awesome questions. Until then, keep being
curious about the universe. Come up with questions and look
at the things you're on you and think about what
might have come first for a second or third, or
whether or not you can get a PhD. Of a
PhD because science is just people asking questions and that
includes you. We hope you enjoyed that. Thanks for joining us,

(51:49):
See you next time. Thanks for listening, and remember that
Anniel and Jorge Explain the Universe is a production of
I Heart Radio. Or more podcast from my Heart Radio
visit the I heart Radio app, Apple Podcasts, or wherever

(52:09):
you listen to your favorite shows. Ye