Kids questions about the Universe!

Daniel and Jorge answer questions from kids about black holes, diamond planets and faster-than-light travel!

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Episode Transcript

Speaker 1 (00:08):
Any Daniel, do you think kids think about the world differently? Oh,
I'm sure they do because they aren't tied down by
all of our crazy misconceptions. Actually, I meant because they
have smaller brains. But I think you're right about the misconceptions.
Do you think that makes them smarter than us? I
don't know, but I think there's a reason that it's
rare to have, like a brilliant insight or crazy new

(00:30):
idea after your thirty Mm. So just because I'm older
than thirty, that means I'm never gonna win the Nobel
Prize in physics. Oh no, No, you might still, but
it would be for an idea you had when you
were twenty nine. You mean, like when I decided to
leave academia and become a cartoonist. Yeah, maybe the best
idea you ever had. Do they give Nobel prices in

(00:50):
bad career choices? Hi? I am more handmade cartoonist and
the creator of PhD comics. Hi, I'm Daniel. I'm a

(01:12):
particle physicist and a professor UC Irvine. And I was
once stumped by a question from a six year old. Really,
was it a question about physics or just about life?
It sort of was. I was doing demonstrations and the
elementary school about how cool liquid nitrogen is, and some
kid asked me if lightsabers were real, would they be

(01:32):
made of liquid nitrogen? Interesting question. It's like it's blending
fiction and reality and some imagination there. Yeah. I was
literally stumped. I had no idea how to that question
in the universe in which lightsabers like, is a khyber
crystal made out of liquid nitrogen? Really? It could be, right, Yeah,

(01:53):
I suppose it could. Can you make a crystal out
of liquid nitrogen? Somehow? I guess that would be crystal nitrogen? Yeah.
But welcome to our podcast Annual and Jorge Explain the Universe,
a production of I Heart Radio in which we try
to summon that curiosity we all had when we were
children about the way the world worked and extend that
to everything in the universe and wonder about the nature
of the universe, the origin of the universe, explanations for

(02:15):
how everything works, and dig into the mysteries for the
things that we still don't understand. We apply our innate
curiosity to everything in the universe because we think that
everything is understandable and that if we bang away at
it long enough, we eventually we will figure things out. Yeah,
because it is a big universe and there are enough
questions in it for all kinds of people are young

(02:35):
and old. He might be eight years old and still
have questions about the universe, or he might be ninety
nine and also have questions about the university. Universe seems
to never run out of questions. That's right, And some
of the questions that we are asking suggests that, like
we as a species are quite young. End of the way,
the kids ask very basic questions, you know, like where

(02:56):
does the sun go at night? Stuff like that. We
are still asking really basic questions. How old is the universe,
what happened before it? How big is it? What's past?
What we can see? Really, just like novice initial questions
do you ask as a species coming into these universe
and wondering about our place in it? Are you saying
our species is like in the teenage years you think

(03:17):
or are we tweens? No? I think we're basically six
year old intellectually as a species. I think we're six
years old. We're asking really basic questions. We're still in
the kindergarten of the galaxy exactly. We're asking questions that
reveal the way we think about the universe rather than
the way the universe works. You know, we're asking the
questions we think are important and that reveal our misunderstandings

(03:40):
about how the universe works. Well, we definitely don't have
our wisdom teeth yet. As a species, we're definitely lacking
any wisdom, it seems these days. But there is a
lot of that you can ask about the universe, and
it's for all kinds of ages. Yeah, and sometimes it's
fun to dig back into that. You know, as a researcher,
I'm working at like the very edge of knowledge, asking
very pacific questions what's inside a cork? Or are electrons

(04:03):
made of something smaller? But it's fun to go back
to the questions at five year old, six year old,
ten year olds ask and remember that we still don't
have answers to those big questions. And like, the whole
context of our exploration is that we're trying to answer
these really big, basic, deep questions, and that all the
specific work we're doing at the edge of knowledge and
the end is motivated by trying to get back to

(04:23):
those basic questions. I think trying to make a lightsaber
is at the edge of knowledge, thank you. I mean,
have you seen those YouTube videos where people try to
recreate lightsabers? It's hard, it's really impossible almost what motivated
you to walk to those who Hey, when you're trying
to build one yourself. I was curious as a kid, Yes,
to watch YouTube videos. You're gonna slice your way out

(04:45):
of your childhood situation. No, I've not gone down that
particular rabbit hole. But yeah, there's a lot of really
fun questions we asked there. Yeah, and sometimes we get
those questions here and our inbox, and specifically we get
questions from little kids, not just adults or young people
like like the people listening to this podcast right now,
But we got questions from a little little kids, that's right.
Sometimes folks have their seven year old or their ten

(05:06):
year olds listening with them and a podcast will inspire
a question, and then they'll write to us and say, Hey,
my kid asked me this question. I don't know the answer.
Maybe you guys can help out, which makes me glad
about all the jokes we don't say in this podcast,
all those jokes about dark matter, and that's right, all
those racy browser histories that we don't like to talk
about but exactly because we hope that you are out

(05:27):
there listening with your kids and that inspires conversations. I'm
always really happy to hear when somebody writes it and says,
how was listening to your podcast with my eleven year
old and then we spent an hour talking about what's
inside a black hole or just on the way to school,
wondering about the nature of the universe. Our whole goal
here is to share our joy of our ignorance and
wondering about what's in the universe and helping you talk

(05:47):
to everybody in your life about it. Yes, so if
you're a kid listening to this podcast right now, we
want to thank you for listening. We're glad that you're here,
and I'm sure you have a lot of questions as
well as well as a lot of other kids. And
we have a whole box full of questions from kids,
that's right, So don't be shy to ask your parents
questions or to send your questions to us. We'd love
to tackle them. So to be on the podcast, we'll

(06:08):
be tackling kid questions about the universe. At least are
questions about kids or buy kids. These are the biggest
questions from the littlest people. These are questions about the
whole universe, about black holes, and about how things work,
you know, the kind of things that go through the

(06:29):
vines of an eight year old. And these are all
spontaneously generated, right like kids just sent this question in
with their parents, that's right. I don't know if the
parents put the kids up to it, or these are
actually child actors. I can't vouch for the veracity of these,
but they are good questions, and so I thought they'd
be fun to talk about on the podcast. Yes, so
long as you didn't go around soliciting little kids or
things on the internet, I think we're safe. No, I

(06:51):
try to stay as far away as I can from
the child acting industry down here in southern California. Yeah.
So we have all kinds of awesome questions here from
kids about black hole, about diamond cores, about the expanding universe,
and we have a whole bunch of him. So let's
dig into him. Daniel, what's our first question? Our first
question comes from Joey. He's seven years old. What are
the newest than the oldest black holes in the universe? Mmmm?

(07:16):
Appropriately A question about youngest and oldest something in the universe.
I wonder if there's a relationship there with like Grandpa
black holes and grandkid black holes. Yeah, like maybe the
younger black holes and more attitude, maybe they think they
had they know everything in the universe. I was thinking
the other direction, like maybe the little black holes look
up to the supermassive black holes and they're like, that's

(07:38):
gonna be me. One day. I'm gonna have my own
galaxy of stars swirling around me. I'm gonna devour millions
of stars and planets and potentially a civilizations and then
get bigger something. I'm gonna be huge and round. One day,
I'm gonna have a whole galaxy for bowling around me.
Just me. Yeah. So it's a great question because the

(07:58):
black holes weren't all made at this time. I guess
it's one thing that people may not know that black
holes are not all the same age. That's right, and
part of the reason is that we have several different
categories of black holes. We have different ways that black
holes could be made, so different processes that are capable
of creating this crazy density that you need to create

(08:20):
this craziest and most mysterious of universal objects. Yeah, so
there are black holes being born right now, and there
were maybe black holes that were made in the Big Bang.
So let's get into what we know, Daniel, What is
the youngest black hole that we know about? So we think,
as you say, that black holes are being made all
the time, right, because black holes come from collapsing stars,

(08:41):
at least one category do so. At the end of
the life of a star. We think that they collapse
and they form a black hole if they have enough mass,
and that should be happening basically all the time around
the universe. I mean, not like ten thousand every second
per cubic light year, but at a certain rate all
over the universe. So there should be a black hole
being made right now on another one right now, another
one right now. Every ten seconds, the black hole is born. Yeah,

(09:03):
it's like asking who is the youngest person on Earth.
It's a constantly changing answer because new babies are constantly
being born. But as you say, we can ask the question,
what is the youngest black hole that we have seen? Right?
And then there's another twist there, because you know, the
things that are further away from us are a little older.
So we're naturally going to have seen things that are younger,

(09:24):
that are closer to us, just because the light has
had a chance to reach us. Oh I see. So
there's kind of a delay between when something happens and
when we find out about it. So what we think
might be the youngest might not be the youngest. It's
just the youngest that we know about that the news
of which has gotten to us. Yeah, precisely. And so
the youngest black hole that we know about is about

(09:47):
twenty six thousand light years from Earth. It's called wt
B because astronomers are so creative with names, and we
think it's about a thousand years old. We think that
it was formed in a supernova that happened about a
thousand years ago. Supernova black hole. Now, not all stars
go supernova and become black holes, right, Like, there's lots

(10:07):
of stars that never become a black hole. Like, our
star is not going to become a black hole, that's right.
And our star won't even go supernova. And the whole
thing is determined just by how much stuff there is
in the original star. The more stuff there is, the
more likely that it's gonna have a supernova collapse. And
then only the heaviest of stars have enough mass to
create a black hole, because remember, to create a black hole,

(10:28):
you have to have gravity overcome all of the things
that are pushing back against gravity's pressure. Gravity is trying
to push everything into the smallest space possible because it's
just attracting mass to other mass. But things prevent that,
like our star is burning and shooting out radiation, which
prevents it from collapse. When that burning stops, then there
are other things that will prevent it from collapsing, like

(10:48):
just the atoms pushing against each other, or eventually just
like quantum mechanical effects. But if you have enough stuff,
you have a big enough scoop of original hydrogen serving,
then you can overcome that if you're above a minimum threshold.
So you're right, not every supernova becomes a black hole.
And so the youngest supernova and that that became a
black hole that we know about happened. We think a
thousand years ago, twenty six light years from Earth. Twenty

(11:11):
six thousand light years from twenty six thousands are light
years from Earth. What did I say? Twenty six thousand
miles light years? But hey, what's three years in magnitude
between friends? Yeah? It's right here, but really it must
have been then that it was maybe born twenty five
thousand light years or something like that years ago, Like
it can be a thousand years old, but then it's

(11:33):
twenty six thousand light years away, because it would take
twenty six thousand years for the light to get to us.
That's right. What we mean by that is the supernova
should have been visible here on Earth a thousand years ago, right,
And so a thousand years ago we should have seen
a supernova indicating the formation of the black hole. But
of course that would have happened twenty seven thousand years ago.

(11:53):
I guess, how do we know that it's there or
how do we know it's age? Like black holes are black,
so they're kind of hard to see in space. How
do we know it's there? And how do we know
how old it is? So these are tricky to identify. Right,
every time you see a supernova, you don't necessarily get
a black hole, and so you can't actually see these
black holes directly. You always have to infer it indirectly,
and so you see for example, in acretion disc forming,

(12:15):
but you don't see any object there at the core,
or perhaps you can measure the mass because there's something
else nearby, and you can measure the radios because things
are passing near it, and so you can tell what
the density of the object is. And it's denser than
a neutron star could be. And so, as we talked
about on a recent episode about black holes, we're never
a hundred sure about a black hole. Were always inferring

(12:36):
in the argument is usually something like this is denser
than a neutron star could be or anything we know,
therefore it must be a black hole. There's always a
bit of a leap there, like we don't know anything
other than a black hole that could be this small
and this dense, So therefore we think it's a black hole.
And that's sort of the argument we make when we
look at these nebula, right you sort of look at
it black spot in the in space and you see

(12:57):
things moving around it in an orbit, and so you
mustn't for that there's something like a black holder. But
I guess, how do you know it's a thousand years old?
Like how do you know when it happened? Like we
weren't looking a thousand years ago? That's right, But these
things have clouds, right, The supernova is an active process,
and so there's a big explosion and a lot of
the stuff gets thrown out to form this nebula and
some of it collapses into the black hole. But we

(13:19):
can watch the process of this nebula and it's going
to like create new planets and have all sorts of dynamics,
and so that's sort of a thing that we can
watch and we can look at and we can say, well,
this nebula looks like it's about a thousand years old,
because we think it looks like about a thousand years
worth of like gravitational reformation has happened. You can see
the wrinkles. You don't have to check the idea. You

(13:39):
can just guess by looking at it. You can measure
the velocity of things in the nebula by seeing the
red shift, and so you can sort of tell where
it is in this process of having exploded and then
reforming something. Sometimes you'll get like new planets forming around
the neutron star or the black hole at the core.
Well that's cool. So then that's the youngest black hole
we've ever seen, Like we haven't seen one in the

(14:01):
last thousand years, or we don't think one has come
into existence in the last thousand years. Isn't that weird?
Given how many stars there are in the galaxy and
in the universe. It is kind of weird. And there's
a couple of things going on there. One is that
there aren't that many supernova in our galaxy, Like there's
a lot of stars in our galaxy, and we expect
only like a few supernova per century because not many

(14:23):
stars actually end up turning into supernova. And one of
the weird things is that we haven't seen a supernova
in more than four hundred years, like the last supernova
in the Milky Way that we saw. We see lots
of them in other galaxies constantly, hundreds every year, but
the last one that we saw in our galaxy was
in sixteen o four. Kepler saw the last supernova any

(14:43):
human has ever observed in our galaxy. Whoa really, how
do you know we didn't miss it? Like in the
eighteen hundreds for everyone with everyone looking, was everyone looking diligently,
Like what if we kind of like one happened and
we were looking the other way, or you know, the
French Revolution was happening that the we were a little busy,
or World War two is happening, and so there are

(15:04):
other things we were attending to do. Yeah, there are.
There are a couple of candidates where we see in Nebula,
were like, Hm, this looks like it should have been
a supernova about a hundred years ago. We should have
seen it. Why didn't anybody notice it? There are a
couple of candidates, but even still is kind of weird
because we expect a few per century and we haven't
seen a single one in four hundred years. We're actually
gonna dig into that in a whole podcast episode about
the formation of supernov and why we haven't seen any

(15:26):
in the Milky Way pretty soon. But basically, we haven't
seen a lot of supernova in the Milky Way recently,
and you need a supernova to form these black holes,
all right, So then the answer is stay tuned. But
that is the youngest black hole we've seen. It's a
thousand years old, twenty six thousand light years from Earth,
and so what's the oldest black hole we know about?
The oldest black holes we know about are ones that
formed at the hearts of galaxies the very beginning of

(15:50):
the universe. Remember that after the Big Bang stuff flew
out and then gravity started doing its job and made
stars and galaxies, and that took about a billion years
for the universe to look familiar, you know, eight hundred million,
maybe a billion years before we had the first galaxies.
And the interesting thing is that we already have supermassive

(16:10):
black holes at the hearts of those galaxies. Now, those
galaxies are billions of years old, which means we can
only see them if they're very very far away, because
the light from those far away galaxies is just now
hitting Earth. So if you look deep out into space,
you're looking back in time and you're looking at the
very very early galaxies. And the crazy thing is at
the heart of those galaxies there are these very bright emissions,

(16:32):
these things we called quaisars, which are light from the
gas that's surrounding those huge black holes in the very
early universe. So we think that black holes were formed
at the heart of these early galaxies, you know, just
a few hundred million years after the Big Bang. M interesting,
so we can see these black holes because they're actually
really shiny, or at least what's around them is really shiny.

(16:54):
In fact, super shiny. Right, It's like it's brighter than
the whole galaxy that it's in. That's right. They are
crazy shiny. These things are called quasars, and when they
were first discovered, people didn't really understand. They didn't believe
them if there must be something wrong because you're looking
at something super distant and yet super bright, which means
that added source, it must be like riduculously bright. And
people thought that just must be wrong. What could power that.

(17:16):
Then they discover that, oh, it's the energy from these
black holes that's like squeezing and pushing on all this
gas around it that creates this very intense radiation. Again
not from the black hole, as you say, but from
the gas that's around it. And so you're saying that
we see these quasars, these super bright black holes in
galaxies that are really really far away, which means that

(17:37):
they're really really old, which puts their age at around
thirteen billion years old. We think the black hole is
thirteen billion years old. Yeah, we think the black hole
is thirteen billion years old. Now we haven't seen them recently, right,
we are looking at very outdated information. So we're looking
at a black hole which is fairly young, maybe a
few hundred million years, but thirteen billion years ago. So

(18:00):
now we're assuming that those black holes are still around
because we don't know of any mechanism for super massive
black holes to disappear. The only way a black hole
can shrink is through hawking radiation, but that happens very
very gradually for very large black holes, and these things
are probably still eating, so they're probably even bigger now
than we are seeing them from thirteen billion years ago. Well,

(18:21):
it's like getting a photograph of someone from the nineteen twenties,
and you know, assuming they're still alive, that would make
them really old, just because you have a photo of
them when they were young, but the photo is really old. Yeah, exactly.
So these things been around basically the entire history of
the universe, right, almost though almost by like what a
hundred thousand years you said, a few hundred million years

(18:44):
order between a podcast hook covers. That's right, exactly, So
those are pretty old. Thirteen billion years old is pretty old.
But there might be even older black holes, that's right.
We don't know, but it's possible that there were black
holes made before there was even matter, for the universe
cooled down so that the energy in the quantum fields

(19:04):
could even be described as like particles as you know,
like corks and electrons flying around when the universe is
still so crazy dense and intense that you couldn't even
describe things as particles. We think there might have been
black holes made in that state of matter, and those
we call primordial black holes. I see, because you don't
necessarily need matter to make a black hole, right, you

(19:25):
could also make one out of pure energy. That's right,
because general relativity treats matters just another form of energy,
and it's really energy density that curves space, and so
you can accomplish that with matter, of course, but you
could also accomplish that with energy. Like if you take
powerful enough lasers and overlap them, you can create a
black hole out of light. How about liquid niitrogen lightsabers?

(19:46):
What if you cross those beams? Can you cut a
black hole in half with a lightsaber? There's a physics
question I don't have the answer to. Only here, Yoda,
only after nine engineers of training. So least primordial black
holes would be the oldest black holes in the universe.
But we don't really know if they exist, right, We
definitely do not know if they exist. If they did exist,

(20:09):
we should be seeing them, because they should have been
created all sorts of different sizes, really large ones, really
small ones. It's nice to imagine that they might exist
because they might explain how supermassive black holes got so
massive so young, Like you might ask, how do you
get such a big black hole after only a few
hundred million years? While they could have been seeded by
primordial black holes, they could also explain what the dark

(20:31):
matter is. Maybe dark matter is just a bunch of
these primordial black holes floating around in the universe. But
if they were creating all sorts of different sizes, then
some of them should be just the right size to
live around fourteen billion years and then evaporate to disappear.
And when black holes evaporate, they're giving off their light.
It happens more rapidly. They get brighter and brighter as

(20:53):
they're about to disappear, so we should be able to
see them sort of like flashing out of existence. But
we've never seen that happen, and so it's sort of
hard to understand how you can have primordial black holes.
Maybe they feel out, you know, kind of silent. Maybe
they don't feel a lot with a bang. Is that
possible it's possible, but our current theory of black hole
evaporation suggests that when they evaporate they turn into photons

(21:16):
and also to other crazy particles, and we should definitely
be seeing those, like at the edges of the galaxy
or something. But we've been looking and we haven't seen
a single one. We've never seen a black hole evaporation,
and so that suggests that probably they're either just not
formed in the right sizes, like maybe their only form
really really small and really really big. That's possible, or
they just weren't made. But if they were made, then

(21:37):
they'd be essentially as old as the universe. They would
be made like less than a second after the Big Bang. Interesting,
But isn't it a theory that some of those super
massive black holes in the middle of galaxies maybe we're
made by primordial black holes. It could be, yeah, because
as we said, we don't understand how those black holes
got so big so fast. If you try to model

(21:57):
the formation of galaxies in the early universe, stars coming
together forming a black hole, cetera, you can't get black
holes that are like billions of solar masses so quickly.
So we just don't understand how that happened. And as
you say, one idea is maybe they got a jump
start because they were seeded by a really big primordial
black hole. So that's a possibility. So it sounds like
the oldest black holes in the universe are thirteen billion

(22:20):
years old at least at least it might be older.
All right, Well, thank you Joy for a great question.
I think that's your answer. The youngest and the oldest
black holes in the universe are both still older than
your parents apparently, but maybe billions of years or at
least a thousand years and maybe billions of years. That's right.
These black holes make your parents seem like children. All right,

(22:40):
Thank you, Joey. And so let's get into more questions
from kids. But first let's take a quick break. All right,
we are answering kids questions about the universe on today's episode,

(23:02):
and we have some pretty cool questions here, Daniel, or
any of these questions from your own kids. None of
these questions are from my kids. These are questions that
people didn't have the answers too, so they wanted me
to answer them. If my kids ask me questions, I
just answered them, or if I don't know the answer,
I try to look it up, but I don't send
them to the podcast. I see you're like a pinch
hit hitter for parents when it comes to physics questions. Yeah,

(23:25):
I try to be. I think that's a lot of fun.
I just love hearing the kinds of questions that other
kids are asking because it tells you something about how
they see the universe. And you know, I feel like
my brain is sort of like stuck in the modern
physics view of how things work, and I'm sure to
have all sorts of like misconceptions that have sort of
fallen into and been thinking about for twenty years. So

(23:46):
a kid's question can really stop you in your tracks
and ask you like, how do we know this? Or
why do we think about it this way? It's really refreshing, alright.
Our next question comes from Anthony, who has a question
about diamond core Daniel and horror. Hey, my name is Anthony.
I am eight years old, and why does fifty king

(24:07):
trying eat have a diamond core? Looking forward to hear
your answer, pleasing, thank you, Hey, thanks Anthony. What a
polite little young person. I know they said please and
thank you. Some of our listeners apparently are teaching their
kids manners in addition to science, can Anthony talk to
my kids please and run a little etiquette class? That's right,

(24:29):
and we will trae you some physics answers for some
manner's lessons. Now, this is an interesting question because, to
be honest, I didn't quite understand it. It almost sounded
like a Star Wars reference, like does this kind of
lightsaber model have a crystal core? It's a great question.
It's about an exo planet. This is the planet around
another star that we're trying to understand because you know,

(24:50):
we are looking at our own Solar system and wondering
are these the only kinds of planets you can have
or are there other weird kinds of planets out there.
As always, when we venture out from our little corner
of the universe, we expect to be shocked. We look
forward to seeing things that we couldn't have imagined. And
so this is a planet around another star, and we're
trying to understand what it's made out of it, you know,
like what it's like to walk on its surface. And

(25:13):
so there was a recent paper suggesting that maybe the
entire core of this planet could be one huge diamond,
and that's what Anthony is asking about WHOA. Yeah, because
we've seen now thousands and thousands of planets in other
solar systems, right like, we've detected them, we've even sort
of sort of have pictures of them. We can tell
what's in their atmosphere. Are we down to the point
where you can tell what's inside these planets out there

(25:35):
in space? We sort of can. And you know, we
have very limited information about each one of these things,
and so we're trying to do as much science as
we can with a very basic information. And here, for example,
we have like some knowledge about the mass of the
planet and then some knowledge of the radius of the planet,
and that lets you do really basic stuff like ask
what's the density of the planet. And if you know

(25:56):
what the density is, then you can ask questions like, well,
what could make a plant of that density? What materials
are consistent with that? So now we can't like go
and drill into the planet and say, oh, look, we
found diamond, but we can ask questions about what it
might be met out of based on what we do know.
Interesting and athink it was asking about a specific planet
that has been found out there, and he had a

(26:17):
name for it. It was fifty five something. Yeah, the
official name of the planet is fifty five can create E,
and so sometimes abbreviated fifty five C E can create E.
That does sound like a star trek name. It's a
planet that's orbiting the star. Fifty five can create A
and so can create E. Is you know, like one
of the things around can create A. I see there's

(26:40):
a B S D N A D. But we're talking
about the thing around that star. That's right. This is
the one that's most interesting, and it's kind of really
interesting history to it because it was first discovered in
two thousand four using the Wiggle method. The Wiggle method
says that a planet moving around a star should tug
on the star. It's not just that the stars pulling
on the planet. The planet is pulling on the star.

(27:03):
And so if you have a planet moving around the star,
you should see the star moving also, and you can
measure that by measuring the velocity of the star by
seeing how much it changes the light that's coming to
us from the star. So these doppler shifts, right, just
like like the Earth is making the Sun wiggle a
little tiny bit. And if you were you know, smart
knife and had pretty good tascos in another galaxy or

(27:24):
another planet, you could tell that we were here, And
so you can tell if there's a planet there because
it's pulling on the star, and you can tell something
about the mass of the planet because you can tell
how much it's pulling on the star, and you can
tell something about its period because you can tell, like
how when the star wiggles one way and the other way.
But this wiggle method doesn't tell you anything about the

(27:45):
size of the planet because you know, you don't know
if it's like a big fluffy pile of styrofoam or
a tiny little black hole. They would have the same
gravitational effect on the star, right, they would wiggle the
star in the same way. And so that was two
thousand four. All we knew about this thing was how
long it took to go around its Sun and how
massive it was. But then like seven years later, we

(28:07):
got better telescopes and we trained them on the star
and we were able to measure the size of this
planet by seeing it eclipsing its star. Like you know,
if you go out and you watching eclipse, you see
the Moon passing in front of the Sun and it
blocks it out it's very dramatic. This is very different
because the planet is much much smaller than the star,
and so it's sort of like watching a moth lock
in front of a light bulb from like thousands of

(28:28):
miles away and then measuring how much the light bulb
dims because of the moth And you can use that
to measure the size of the planet, because the larger
planet would dim the star more than a smaller planet. Right.
Or if you're like looking at the Moon at night,
for example, and a little fly between you and the Moon,
you would sort of see the light from the Moon,
you know, get a little bit dimmer. But it's just

(28:50):
a little tiny bit, just a little tiny bit. But
if you watch, you can see it. And you can
see it happened periodically also, which really helps. It's not
just like one blip and you say, oh, is that
noise or mistake in my data. If it happens periodically
regularly and it matches up with the velocity measurements you're
making of the star, that you can be pretty confident
that that's what you're seeing, So then you know the

(29:11):
size of the planet. Also from that, you can make
measurements of its density and you can know like something
about what it's made out of. So you can tell
the mass from the wiggle, and you can tell the
size from the shadow it makes in front of the
that star. And so we have a measure of its density,
and I'm guessing it must be pretty dense if we're
thinking it might be made out of diamond core. Yeah,
this thing is like nine times the massive the Earth,

(29:34):
but its diameter is only twice the Earth, right, and
so it's definitely denser than the Earth is by how
much like three or four times? Yeah, Well, the diameter
of twice the Earth means that is volume is eight
times the Earth, right, and it's got a massive nine
times the Earth, So it's actually only a little bit
denser than the Earth is. So it must be like
a rocky planet or something, but it's just a little

(29:56):
bit more dense than the Earth. And the Earth is
pretty dense, right, Like the Earth is a rock you
planet with lava and rock, right, it's not. We're not
made out of a coun candy exactly. But this planet
is very different from the Earth because it's so close
to its son and it has an eighteen hour orbit,
like it takes eighteen hours for a year to pass
on this planet, like it goes around its son every

(30:16):
eighteen hours. Every eighteen hours there's a birthday party. It's
spent basically all of your time shopping for presents, an
opening presence, half the time shopping the o they have
opening them, that's right, and eating cake. And that makes
the surface of this planet very, very hot, like three thousand,
nine hundred degrees fahrenheit or c that's hot. That's pretty hot.

(30:38):
You don't need to lie your birthday candle. They're already
on fire, so I recommend a pool party. And that's
important to understand because when you're building models of these planets,
you have to understand like what state the materials that
you're putting into your model of the planet are. So
for example, they started off by assuming that this planet,
like Earth, has a lot of oxygen in it, Like
Earth is a lot of oxygen that doesn't have a

(31:00):
whole lot of carbon in it. And if you're going
to have a planet this size and with a lot
of oxygen in it, it should have a lot of
water on it. But it's sort of weird to have
all that water on the surface, like this planet would
be like ten water ten percent of the mass of
this planet would be watering to get the right size
and their identsity. But if you have that much water,
you're basically talking an ocean planet, but that much radiation

(31:22):
on the surface which split all the water and put
it in a supercritical state. So sort of a weird
idea to begin with. A right, it's not a good
assumption to think it's just like the Earth. Yeah, So
then what happened to convince them that maybe this planet
was different was that they learned something about the star.
They looked in more depth at what the star was
made out of, and they noticed that it had a
lot of carbon in it, a lot more carbon than

(31:44):
our star. For example, remember that these solar systems are
formed from leftover materials from other generations of solar systems,
So you have still mostly hydrogen, but like some of
them have more oxygen, some of them more carbon, some
of them have more of this, some of them have
more of that. This solar system seemed to have been
formed out of materials that were richer in carbon than

(32:04):
our solar system. So they think, Okay, that star has
a lot of carbon in it, Maybe the planet has
a lot of carbon also, maybe our assumption that this
planet was oxygen rich like the Earth was wrong. And
they said, well, what model could you build if you
started from carbon instead of from oxygen. I see, to
get the right sort of like size and mass, and
to make it sort of carbon ridge, you would have

(32:26):
to make the planet have a lot of carbon. Yeah,
so they said, well, maybe the planet is like one
third carbon, And then they started playing with models like
what would happen if you had a planet that was
one third carbon and this big right at this certain density.
They realized that would create an incredible pressure at its
core and that in some circumstances you would get an
enormous diamond, you know, like we're talking a diamond it's

(32:49):
like thousands of kilometers across because I guess you're assuming
all the carbon would sort default to the middle or
like it would push all the other stuff out as
it forms the diamond. And this incredible pressure, you know,
would essentially turn all of this carbon at the core
into a diamond. And obviously there would be impurities, right,
You'd have heavier metals like iron also, So wouldn't be

(33:09):
just like one pure perfect diamond, great triple A or anything,
but it would be like mostly diamond. Wow. And so
we're talking how big do you think this diamond is?
Like the size of Manhattan or the size of Australia.
How big do you think this diamond cores? You know,
this thing would be a third of the planet. So
it's huge. Yeah, I mean we're talking thousands of kilometers across. Wow,

(33:31):
Like bigger than the Moon, Bigger than much bigger, like
almost the size of Earth exactly. So what's kind of
ring would you need for a diamond bigger than the moon? Yeah,
so I guess if you like it, you better put
a rig on it, right exactly? There create a better
step up. All right, Well, thank you, Anthony. I that's

(33:52):
a great question, and I think that's the answer. We
think that this planet that's out there orbiting another star
has a lot of carbon in it. And if you
have that much carbon in a planet under that much
pressure inside it might form into a diamond. And so yes,
there might be a giant diamond inside of that planet.
That's right. But this, of course is all hypothetical. We

(34:12):
have a very few pieces of information. We're playing a
lot of games about what might be possible, and in
coming years we'll be able to image these planets and
see more about the light that's reflected from the surface
off of their stars and learning more about their atmospheres.
We'll get a lot more information about these planets, and
then we'll figure out what's out there, and probably what
we learned will be even more shocking than anything we hypothesized.

(34:34):
I guess the hard part would be mining this giant diamond, Like,
first of all, how do you like break it apart?
And the other part is how do you get it
out of the core of a giant planet? How do
you polish it right? You need to shine this thing
up if you're gonna sell it at market value. All right, well,
let's get into our last question from kids today, and
it's about the expanding the universe. But first let's take
another quick break. We are taking questions from kids today

(35:09):
and our last question comes from Addie, who is eight
years old. Hi, danieland my name is Abby and I
am eight years old. My question is, since the universe
is expanding faster than the speed of why can it
go back in time? Thank you? WHOA. This question just

(35:31):
blew my mind. Can the universe itself be traveling back
in time? That's crazy? But first, of all, I have
a question for you, Daniel, why do kids always identify
their age? Like, at what point do we as adults
stop saying how old we are? I think the point
where we stop remembering how old we are. I introduced
myself and I'm like, oh, I'm forty four. My kids
are like, no, you're forty six, dude. Yeah. Yeah, but

(35:56):
it's great to know. Thank you, Addie. This is a
great question. I think Audi is putting a couple of
ideas here together, right, Like we know, and we've talked
about the idea that the universe is expanding, and it's
expanding at its edges, or at least as far as
the furthest from us as you can faster than the
speed of light. And we've also talked about how like,
nothing can move this faster than the speed of light,

(36:17):
but if it does, it would mean it would sort
of go back in time or break the rules of time. Yeah,
these are two really fun ideas, and I love hearing
kids put these ideas together and your first you're like, no,
that's crazy, and you know, hold on a second, Maybe
that's a good point. Maybe he's right, maybe going back right,
it's not just kids I'm like, yeah, yeah, what's the
answer here is the edge of the universe going back
in time. It's a great question, and you know, he's

(36:40):
right that the universe is expanding faster than the speed
of light. But there's some important subtleties there, right, like
what is happening. It's not that things are flying out
through the universe and that they're traveling relative to each
other faster than the speed of light. You know, like
no object is looking at another object and saying your

(37:00):
velocity is greater than the speed of light. However, that
doesn't mean that distances can't increase faster than the speed
of light. Right, It all depends on sort of who's
asking the question. It's like, nobody is moving faster than
the speed of light, but things are. The space itself
is growing faster than the speed of light overall. That's right,
because new space is being created between galaxies, new spaces

(37:24):
being created, and there's no limit to how fast space
can be created. And you might ask, like a hold
on a second, who's creating new space and how does
it work? And surely there's somebody in charge of it
and there's limits, right, we don't know. The answer is
to any of those questions. We just see that space
is expanding. This is what we call dark energy, and
so we know that something out there is capable of

(37:45):
expanding the universe itself, of stretching space or making new space,
and that's happening everywhere Isotropically, the whole universe is expanding,
but it only happens a little bit over a short distance.
So between me and you, for example, wherever you are
in the Earth Earth, space is expanding a very very
tiny bit every year, but you know, the Earth holds
us together. Between us and the Sun, space is expanding

(38:07):
a little bit more every year, but the Sun holds
us together. But between us and other galaxies, there's a
lot of space there. So all the new little bits
of space add up and it becomes pretty significant. And
across the whole universe is huge amounts of space. So
you're add up all of those expansions and you actually
do get speeds that exceed the speed of light. It's
kind of like maybe for audi here it's almost like

(38:29):
you can't run faster than the speed of light in
your house, but your house is sort of growing a
little bit. So you stand on one end of the
house and you look at the other end of the house,
at the on the other side, you would see it
sort of growing faster than like could move. That's exactly right,
And so we can measure the distances to things we
see that those velocities do seem to add up to

(38:50):
be greater than the speed of light. But you know,
if you looked at any one thing and you asked,
how fast is this one thing moving relative to me,
you would never measure a velocity greater than the speed
of light, because remember, you can't measure velocity relative to space.
Space doesn't have like a reference frame. There's no absolute
frame there. You can only measure velocities relative to an object.
All right, So then the universe is expanding faster than

(39:13):
light can travel, but nothing is actually moving faster than light.
And so the other idea they put together is this
idea that going faster than light somehow breaks time or
makes you go backwards in time. Yeah, that's a really
fun conclusion, and it's sort of meant to tell you
that you can't go faster than the speed of light.
You know, we have these ideas of how the universe works,
of how information can propagate, and how there's a maximum

(39:36):
speed of information, that no information can move faster than
the speed of light. No object, and no information, no particle,
no wave can ripple faster than the speed of light.
And what happens if you ask, like, well, what happens
if an object does move faster than the speed of light, Well,
then you get a paradox, You get contradictions. You get
things like, well, if it could move fast in the
speed of light, that would be equivalent to it moving

(39:58):
backwards in time, which we know to be impossible. And
so it's sort of just like another way of saying
that you can't move fast in the speed of light.
Sometimes people interpret this saying like, oh, if you want
to go backwards in time, all you gotta do is
go fast in the speed of light. But it's sort
of like saying no, that's impossible, right, like Superman and Superman.
But I guess maybe I'm wondering if it's maybe a
little bit of a circular argument, Like you're sort of

(40:19):
assuming you can't go it faster than the speed of light,
and then you say, but if you can, then it
would break the rules. It's almost like you make an
assumption and then you say, if you break the assumption,
then it doesn't work. Yeah, absolutely, And you're right, And
we don't understand this limit at all. You know, we
observe this limit. We say the speed of light is constant.
It doesn't depend on who is sending the message or

(40:40):
their velocity. It's always the same speed. And if you
start from that, then you get to consequences like you
can't move faster than the speed of light, and all
sorts of things about how time varies, all of special
relativity is based on that one observation. We don't know
why that thing is true, but everything flows from that
thing that the speed of light is constant for all observers,
and so that's what limits you to going faster than

(41:02):
the speed of light. And so you're right. If we
observe the scenario in which that wasn't true anymore, then
maybe you would, you know, change all these other rules,
or maybe that's wrong and we just don't understand. So
if you see somebody going fast in the speed of
light or going backwards in time, that suggests that the
speed of light is not constant for all observers. Interesting,
I see. It's like from what we can see about
the universe, we came up with the speed limit of

(41:25):
the universe, and then breaking that speed limit suddenly breaks
everything we know about time and everything else. But it is,
I guess, technically possible that you could would like go
faster than light. It's technically possible in the sense that,
you know, we've never observed it, and everything we have
observed suggests that it is impossible. But you know, that's
just physics. These are theories. We make an observation here,
we infer about the universe. From it, we draw conclusions.

(41:47):
If those conclusions are wrong, then either our inference was
wrong or the observations we made were wrong, And hey,
that would be awesome because that would be you know,
a childlike dream to overthrow something so basic. Is like
the fact that the speed of light is the same
as measured by everybody. But you know, it's something it's
experiments we've been doing for more than a hundred years,
and we've seen it very concretely and very stable for

(42:09):
a long time. So we're pretty confident in this observation
that the speed of light is always the same no
matter who measures it, and the implication of that that
it means that you can't go faster than the speed
of light is also pretty solid, so I think it's
pretty air tight. But yeah, we have made mistakes before, right,
And so where there's this idea that going faster than
the speed of light would make time go backwards somehow, Well,

(42:30):
it comes from the idea that time is sort of fungible,
that like the order of events that happen depends on
your speed. Like if you're watching two things happen, like
Alice eats a pie and then Bob eats a pie,
and you're sitting there with them and you're watching, maybe
you think Alice finishes first. But if I'm going at
really high speed, I can find some scenario in which

(42:51):
I see the order of events happening differently. Right, So,
like Alice finishing before Bob is not like a universal truth.
It depends on who's asking and how fast they're going.
And so this idea that you know you can change
the order of events depends on your velocity tells you
that you can sort of play with time, and that
the velocity and time are connected. But it's not necessarily

(43:13):
the case that if you are going faster than the
speed flight. Let's say it was possible that some out
time would flow backwards or like your clocks would certainly
start going the other way, or you know, you would
travel to a different time. And that's sort of so
far kind of not really establishing the math. Well, what
the math suggests is that if you go faster than
the speed of light, then you can invert the order

(43:35):
of things that you otherwise shouldn't be able to, Like
you can switch who wins the pie eating contest, Alice
or Bob by going faster or slower, going in some
direction because those things aren't like caustically connected, doesn't really
matter which one happens first. But if you go faster
than the speed of light, then you might see weird
things like Alice arrives in the pie eating contest before
she leaves her house. You know, you can switch the

(43:56):
order of things so they're like reversed in time. So
in that sense, you're sort of like going backwards. You
would maybe experience things backwards, is what you're saying, which
is sort of like and if the whole universe is
going backwards, and it's sort of like you're going back
in time, is what you're saying. And we have a
whole interesting episode about this theoretical particle called a tachion,
which in principle moves faster than the speed of light.

(44:18):
But you know, if it exists, it would break all
sorts of special relativity, but has really weird properties, like
you see it as if it's leaving, even if it's arriving,
because the later light arrives first, because it's moving faster
than light. I see. So if this particle is really
would be very tacky. It would be breaking everything in
the universe, and that's just not cool. That's right. You'd

(44:39):
invited your birthday party and it would look like it's
leaving your birthday party, and you're like, hey man, yeah,
hey man. All right. Well it's a great question from Audi,
is if the universe expanding faster than light, can I
go back in time? And the answer is kind of
yes and no, Like, yes, the universe is expanding faster
than light, but for you to sort of break the
laws of time, you kind of have to travel faster

(45:01):
than light, which is not what the universe is doing.
The universe is expanding faster than light, but it's not
traveling faster than light. That's right. Nothing is moving faster
than light relative to any other thing, and so that
doesn't break the laws of special relativity. Well, things are
growing in distance from one edge of the universe to
the other. It's faster than light, but nothing's actually you
could say, is traveling through that space faster than than light? Yeah,

(45:23):
that's right, all right. Well those were three awesome questions
from kids. Thank you kids for sending in your questions,
and thank you parents for encouraging your kids to think
about the universe and ask the deep questions, because it's
those kids that we hope are going to one day
figure out the answers to these questions. They're not so
entrenched in today's ideas about how the universe work, and
they might have crazy new ideas about how to use

(45:46):
lightsabers to cut open black holes and solve the mysteries
of quantum gravity. I don't think we need to think
the parents, Daniel. Everyone knows it's a thankless job you
don't really get. But thank you to all of our listeners,
young and old for having question us about the universe.
I've been curious for wandering about this amazing and mysterious
cosmos that we live in. And if you have questions,

(46:07):
please feel free to send them to us. We hope
you enjoyed that. Thanks for listening, See you next time.
Thanks for listening, and remember that Daniel and Jorge explained.
The Universe is a production of I heart Radio. For
more podcast for my heart Radio, visit the i heart

(46:30):
Radio app, Apple Podcasts, or wherever you listen to your
favorite shows. Ye