How Can We Tell The Distance To Stars?

How can we measure the distance to stars?

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Episode Transcript

Speaker 1 (00:07):
You know, Daniel, sometimes I think how far is everything
from us? Like how alone are we? We are nowhere
in the universe exactly, or maybe right on the edge
of the middle of nowhere. You mean, we're like in
the suburbs. That's right. You have to drive pretty far
to get somewhere excitings from where we are in the universe.
You know, if you look at into the night skuy,

(00:27):
it just looks black with little pinpoints, you know, Like,
how do we know how far away these things are? Yeah,
it's amazing. Some of these things we look at, the
nice guy are pretty close by, you know, planets, other
things are incredibly distant, you know, billions of light years away.
We are sitting on this little ball of rock floating
through space, and we are making these huge a statements

(00:48):
about the structure of the rest of the entire universe,
Like how could we possibly know all this? She's sitting
on this little tiny rock. Hi am Jorge, and I'm Daniel,

(01:16):
am my cartoonist. I'm a particle physicist. And this is
our podcast called Daniel and Jorge Explain the Universe, in
which we talk about all the things in the universe
and how we understand them. Or if we understand them.
Were actually most of the things that we don't understand
to be on the podcast, we're going to answer a
question from a listener. That's right. Listener Ryan Lynn wrote

(01:39):
in with a really interesting question. He said, how do
we know what we know? A lot of times in
science you hear about an amazing discovery or something science
has figured out. But this listener, Ryan always wondered, how
do they know that? How they figure that out? How
is it possible to know such crazy facts about the
universe given that we're stuck on this tiny rock in
one the will spot around the in the universe. Yeah,

(02:02):
and just for the record, we may or may not
have changed his name to protect his identity, and he
may or may not live at one two three Question Drive, Atlanta, Georgia,
And that's obviously made up. But yeah, if you have
any questions at listeners, please send them to us. You
can always write us at questions at Daniel and Jorge

(02:22):
dot com. So this is a very broad question, how
do we know what we know? But he had a
very specific example, right, He asked, how do we know
how far away the stars are? Yeah, which is a
great question because as you look up with the night sky.
A lot of the stars look similar, right, they're just
pinpoints in the sky. Yeah, And so you might ask, like,

(02:45):
how can you tell which ones are close by and
which ones are are far away? In fact, your eyes
sort of looks like they're all just painted on a
ceiling right to your eye, to your brain, they just
look like they're painted on a huge dome roof. Yeah,
And I think for many thousand and some years that's
what people thought. They thought they were looking up essentially
the ceiling of their living room, right, and that the

(03:06):
stars were painted on them. There's like a show and
it's very uh, you know, anthrocentric that suggests that there's
something created for us to experience, when in fact, of course,
it's a mostly cold, empty universe that ignores and ignores us.
I'd love to live in that house where your living
room is the size of the cosmos. Right. But that's
the thing. They had no idea how big it was, right.

(03:27):
They thought the sky was, you know, a few miles
or a a few hundred miles up there. They had no
concept at the scale of the thing they we're looking at,
you know. And that's the crux of the issue, is
that when you look up in the night sky, you
can't tell if something is really far away and huge
or really close by and not actually that big, right,
because like if you look out into a landscape, you
can see a mountain, and you sort of know how

(03:49):
big mountains are, so just kind of by the size
of how it looks, you can sort of guess how
far away it is, right, But a star is it's
like you don't even see it as a circle or
a ball or nothing. It's just like a pinpoint of light,
that's right. And that applies even for closer up stuff.
Like I was talking with my kids about this question yesterday,
and I told my daughter, you know that the sun

(04:10):
is much much bigger than the Earth, it just looks
small because it's far away, And she was surprised. She
didn't realize that the Sun was bigger than the Earth.
And of course we know now it's much much bigger
than the Earth. But in the sky it seems a
lot smaller than the Earth, which is huge right in
our perspective, But it only looks that way because it's
far away. And if you didn't know, like, well, how
big is it, then you would have no idea is

(04:32):
it enormous and far away or kind of small and
close up. Right. Yeah, so this is a good question,
and it's not an easy question, right, and it's taken
us a while to figure out how to tell how
far away stars are. But before we talk about how
scientists have done it, we thought we'd ask people on
the street if they hadn't in any ideas. Do people
know how the distance to far away stars is measured?

(04:53):
Or do they just take scientists at their word. Think
about it for a moment. You know, how would you
tell how far away a star is? Well, here's what
people around the U See Irvine campus had to say.
I have no idea how to tell that. No, I
don't know that at all. You use the telescope, I
don't know. Stressed out but sorry, um by some scientific

(05:18):
TV show something like that. Okay, yeah, I think so
I don't know, like who count we metch with that?
I don't know? Actually, okay, okay, So most people had
no idea how this is done, which I love, right,
And I could see in their faces when I asked
them they're all of a sudden they thought, what, wait,
that's a good question. I have no idea, not only

(05:39):
how you would how scientists do it, but how you
would even do it right? Most of the people reacted
that way. It's all familiar words. You know, how far
away something? Stars? Who know stars? But when you think
about it, like, it's really not that intuitive to know
how far away stars? Yeah, it's not that easy, though.
I love that some people had ideas, like one guy's like, well,
just watch scientific television shows and we'll tell you. Just

(06:01):
listen to a podcast. I mean, that's what scientists do, right,
you wanted the answer to question, just just turn on
science TV and listen for the answer. Then you write
it up in the paper. It's like a snake eating
its own tail. That's how all science has done. But
the point is that it's not an easy problem and
that most people don't know the answer. Yeah, maybe we

(06:23):
should start by talking about things that are close up,
Like how do we tell how far away things are? Well,
we have two eyes, right, So say, for example, Uh,
somebody's throwing a basketball at you. How do you know
how far away the basketball is? Well, one thing is
you know how big a basketball should be, So as
it gets bigger, you're imagining it's getting closer. But say
somebody throws something at you you've never seen before, you're

(06:45):
not familiar with. Right, has your brain know how far
away it is? The key is that you have two
eyeballs and not just one. Yeah, so you you your
brain looks at the difference between what your left eye
and your right eye are seeing. Right. Yeah, you have
to do this experiment. Hold out one finger in front
of your face and then look at it with your
left eye only and then your right eye only, and

(07:07):
you'll see it move right. You get two different images,
and you see a little bit different. You see a
little bit more of one side of the finger with
one eye and a little bit more of the other
side of the finger with the other eye. Right, so
you get its binocular vision right binocular meaning two eyes.
You get binocular vision, and your brain compares these two pictures.
And if these two pictures are really different, that means

(07:27):
the thing is pretty close, right, because you're looking at
the thing from very two very different angles. Um, only
if it's really close. But now move your finger as
far away as your arm will allow. Right. Please don't
chop off your finger and throw a bast room or
over driving. Then you do this as a mental exercise.

(07:48):
Please or pull over. Yeah, So now with your finger
further away, do the same thing where you look at
it only with one eye or the other, and you'll
you'll notice that the two images look more similar. And
as your finger gets further and further away, the two
images look more and more similar. Something that's really really
far away looks the same to both eyes, right, because
the distance between your eyes gets really small compared to

(08:11):
the distance to the object. Yeah, and it's more noticeable
if you switch eyes very quickly, right, Like, if you
go blink blink, blink, blink, blink, switch between eyes, you
can really see how things change the closer they are too,
that's right. It also kind of makes you look like
a crazy person. So if you're listening to this podcast
out in public, you know, maybe get a little privacy.
I'd love to imagine there's some some car pulled over

(08:32):
by this side of the road with a person blinking
back and forth, and somebody is now calling Homeland Security
saying because of somebody's suspicious behavior. Right, let's take a
quick break. So yeah, that's called parallel right, which is

(09:01):
is not a comic book villain. It's like an actually,
oh man, this should totally be a comic book villain
with like lots of sets of eyeballs or something. Parallax. Yeah,
that's um, that's called binocular vision, right end, or parallax.
And the idea there is that you see from different
angles if you have two views of it. So that
works for your eyeballs because they're spaced, um fairly, there

(09:24):
is space fairly wide. Right, It's kind of like a triangle, right,
Like if you draw a line between your eyes and
then another line from each of your eyes to the object,
you form a triangle, right, And that's how you it's
called triangulation for because then with the triangle, you can
tell how far away it is, that's right. And that's
why if you lose an eye or close an eye,
you don't have very good depth perception, right, because you

(09:46):
need both of those views to see how far away
things are. So people with one eye or people with
an eye Patriot ever, you know, they stumble more often
for this reason, and they have developed other techniques for
knowing how far away things are. So that also works
for the stars, right, and maybe you're thinking a whole
lot of second, the stars are super duper far away, right,
My eyes can't measure the distance to a mountain. How

(10:08):
can my eyes measure the distance to the stars? It
seems almost impossible. Well, what's happening when I look at
the stars with my naked eye? Like, why can't I
just resolve the use the same technique? Right? And the
reason is that the distance to the stars compared to
the distance between your eyes is almost infinite. Right, that
triangle you talked about a tiny little side which is

(10:30):
the distance between your eyes, and then you know the
other two sides that extend all the way to the stars.
It's like light years and light years and light years.
So basically those photons are parallel to each other, right,
And do you see the same image? Technically your eyes
see different images. It's just that maybe the difference is
so small your brain and your eyeball can't tell the

(10:52):
difference exactly. So in theory, if you had super duper vision,
then maybe you could use that information to tell the
distance to the stars. Or if your eyes were really
really far apart exactly, if your eyes are really far apart,
or you have really really good vision, those are two
ways to make this distance measurement measurement more possible. So
that's exactly what we do to make our eyes further apart.

(11:14):
We don't just look at the star up at the
night sky. We wait for the Earth to go around
the Sun, and we look at the star from both
sides of the Sun. So, you know, you look at
the star in in June and you're one side of
the Sun, and then the Earth goes around the Sun.
You look at the same star in December. Now you're
looking at the star from two astronomical units apart, right,

(11:37):
as if your eyeballs were two astronomical units apart, right
opposite sides of the Sun. So that's pretty good distance. Yeah,
it's like in December you open your right eye and
you look at the star, and in June you open
your left eye and you look at the star, and
you compare how those two images are different. That's right.
And I hope that you have things to do between
December and June other than just standing outside waiting for

(11:59):
six months to open and the other isn't that? I thought?
It depends on how devoted you are to science, you know,
like people, if you really care about this stuff. No,
that's exactly what it's like. And um, so you take
one piece of data in one part of the year,
and the other piece of dating the other part of
the year, and that's effectively like making your head you
know the size of the solar system, and so that's

(12:20):
a huge additional leverage Toto seeing things that are really
far away. I wonder if that's how they measured how
far the moon was, do you know what I mean?
Like maybe not waiting, waited until a whole half year,
but just kind of like looked at the moon, talk
to somebody who was a couple of miles away and
see what the what the difference between what he saw

(12:40):
and you saw That would tell you how far away
the moon is. Right, Well, there's a couple of things there.
One is them waiting part of the year won't help
you with the moon because the moon moves with the Earth, right,
we don't leave the moon behind. And the Moon is
actually so close up that you can do cool stuff
like bounce a laser off the moon or bounce radio
waves off the moon, and to measure the distance, that's
actually the best way to measure the distance to the moon.

(13:02):
And what they've discovered actually is that the Moon is
getting further and further every every year. We're losing the moon,
like the Moon is orbiting the Earth. But what orbit
grows very gradually? Yeah, when when are we going to
lose the moon? Let's see what time is it now?
You know, um, it's gonna be a long time. We're
gonna have the Moon around for a while. You don't
have to worry about it. And if you bought real

(13:23):
estate on the Moon, you're fine. But I think by
a centimeter of years is the number. I remember. The
distance from the Earth to the Moon is growing. That's
not nothing. That's not nothing. But also the astronauts put
mirrors on the Moon when they landed there so that
we can shine lasers at those mirrors and do cool
tests stuff like a global selfie. That's exactly right. Yeah,

(13:45):
And so so we're saying, if you want to get
better measurements of UM using this parallax system, you either
need to have your eyes further apart and when you
do that is so the June and December, or you
need better eyes. So, of course we don't just use
my eyeballs or Jorges eyeballs or my students eyeballs. We
use telescopes and telescopes out in space that can tell
the difference between really really small images, right, that can

(14:08):
look really really far away and measure very precisely where
these stars are at different times of the year. Yeah,
I just think it's amazing that you can see something
so far away. You know, like here on Earth, you're
used to far away things looking blurry or faded or faint.
But just the idea that you know, millions trillions of
light years away, you know, a photon left the star,

(14:31):
traveled throughout the entire cosmos and then arrived into your eyeball,
right when you're looking at the night sky. That's one
of my favorite things of the night sky is that
it's the world's greatest view. It's the universe is greatest view.
You know, you are seeing across billions of light years
of space. It's it's amazing to me. I totally agree
that those photons traveled unimpeded for so long and then

(14:52):
finally just get absorbed by your eyeball and then you
just a little a glance away, you know. Okay, So
then what are other ways? How do we tell how
are weight things are beyond a few thousand light years? Well,
that's really the best method we have, is this parallax method.
And so science has been working on that really hard,
and it's actually cool because our ability to do this
is improving pretty rapidly. It used to be we could

(15:14):
only see things to like maybe a thousand of thousand
light years away, and then we've got better telescopes and
navigate they see things pretty reliably up to several thousand
light years, And now that we have even better telescopes,
we're seeing some things up to like ten fifteen thousand
light years away. So as we get better and better telescopes,
we're gonna get better and better measurements of this than
Parallax is really the crux. That's the way that we

(15:36):
really believe that it gives us the most reliable estimates
of distance, so everything is built on that. Beyond that,
when things are further away, then there's you know, fuzziness,
there's questions and people out there might get a little
skeptical and how do we know some of these things?
But essentially what you need to do is what we
talked about earlier, is find something that's a reference point.

(15:57):
Find something where you know how bright it is, so
you can tell like a mountain, like, you know how
big amountain typically is. Yeah exactly. Um, yeah, So if
you if somebody was, for example, standing on a mountain
and shining a really bright light, and you knew how
bright that light was at the source, then you could
measure how dim it is where you are, and you

(16:17):
could tell the distance, right, because the brightness falls like
one over the distance squared, because the photons go out
in every direction, and the surface area of a sphere
around the star goes like radius squared, and so the
same amount of light is spread over more and more areas.
You just get fewer of those photons the further away
you are, even if with no atmosphere, no air between you,

(16:39):
that's right, things just spread out. And so, as you said,
we get just a little stream of those photons. Most
of the photons from stars are going somewhere else, right,
something somewhere else in the universe, and eyeball, we hope
is picking up one of those photons. So we're only
seeing a tiny little slice of the photons that come
from that star. So, as we were saying, if you
want to know how far aways something is, you have

(17:00):
to know how bright it was originally, how bright it
is at the source, and then compare that to the
brightness you're measuring on Earth. That's pretty tricky because the
universe is filled with weird stuff that we don't understand, right,
and so it's sort of chicken and egg, Right, you
want to know how far away is that stuff? When
what is it? Well, you don't know either one. You're
you're sort of in a in a pinch. It just
looks like little dots. It just looks like little dots.

(17:21):
But we found a few things that we can use
for reference points. But maybe let's take a break and
we can dig into that in a moment. Okay, So
what are the other ways we can tell how far

(17:42):
away stars are? So one of the ways is with
these really weird kind of stars that are variable stars
that don't shine the same amount of brightness all the time.
And the reason is that, well, there's some really complicated
astrophysics that's beyond me, frankly. But the thing that's important
to know these stars, which are called sapid's um, they pulsate,

(18:02):
and the rate at which they pulsate is very closely
connected to their brightness. So if you can measure how
fast they are pulsating, you can know their brightness. It's
got this internal layer that stores and releases energy so
that the whole star expands and contracts, and that's what
makes it pulsate, kind of like a lighthouse. Yeah, just

(18:22):
like a lighthouse exactly. Um, it's just like a lighthouse.
So these things are like lighthouses out there in in
our galaxy and in other galaxies. And people figured out
by using parallax that the ones that are pretty close
up that there's a relationship between how bright they are
and how fast they pulsate. And that's really cool because
then there are ones that are really far away where

(18:44):
we can't use parallax to tell how far away they are,
but we can tell how fast they are pulsating. Right,
that's not hard to measure. You just watch it and
you see blink on and off. You can then say,
you know how bright it is at the source. You
know how bright it is at the source, and you
know how bright it is here on Earth. Then you
can do some simple math to figure out how far

(19:04):
away it must be. Like it's telling you using Morse
code how bright it is, right, Like it's like I'm
really right, I'm really dim yeah, and so and that's
the key. These things are called standard candles, and they're
just ways to know how bright something is at the
source without knowing how far away it is, right, that's
the key. You have to have some other way of
knowing how bright they are. And so these were discovered,

(19:27):
you know, almost a hundred years ago, and it was
Hubble himself, Edwin Hubble, who used these and found them,
a bunch of them that were surprisingly far away. He
looked up in the night sky, and back then people
thought the whole universe was just the Milky Way Galaxy.
That was it. You know, there was just a bunch
of stars and we are galaxy and nothing else right
like there was it was all concentrated around us. Yeah,

(19:49):
they thought that was the whole universe. And you know,
even that was mind blowing to people. Right If if
all you thought was, oh, it's just just the Earth
and a few other planets and everything else is sort
of painted on the living room of the sky, then
it's mind blowing to think, what, there's a whole galaxy
of zillions of stars, right. So people were just are
slowly accepting that. And then Hubble he looked to try

(20:09):
to measure these these syfids and see how far away
they were, and he got some really weird results. He
got results that suggested that these things were crazy far away,
far away than any star anybody has seen before, and
so we thought, well, maybe these things are not just
like weird nebula or weird other stars. Maybe there are
other galaxies. And that must have been a mind blowing

(20:30):
moment for him, Right, Wow, It's like, it's not just
us in our living room, there's other houses around us, exactly, exactly.
And that's what I love about this question is figuring
out how far away the stars is, gives us a
three D map of the universe, right, tells us where
everything is, what is the structure where we living, Like,
are we in the suburbs? Are we in the exciting

(20:52):
downtown hip area of the universe? Right? So it's so important,
and it's exactly what's led to these moments of realization
where you discover or that the universe is totally different
from the way you thought it was. I hope to
I hope to have one of those moments myself in
my science career. It's it's let us map the universe
and where we are in exactly. That's a big exactly,
that's a huge deal. And that really was the birth

(21:14):
of modern cosmology. You know, knowing there were other galaxies
and wondering how many are there and how did this
all come together? And you know, and obviously if there
are other galaxies, then maybe we're not the most important
one or at the center of anything or all those
questions were created just at that moment when we discovered
that there were other galaxies. Okay, so that's a really

(21:37):
cool trick is find an astronomical object that somehow tells
you how bright it is, not by how bright it is,
but through some other information. Yeah, exactly, and so you
have to really know the astrophysics of it. And the
cepheids were calibrated by comparing to the parallax scale, So
parallax works up to you know, maybe ten tho light years,

(21:57):
and in that sphere there are some of these stars,
these variable stars. Once you know that, then you can
look at the ones even further out using this technique
exactly exactly. An astronomers call this the cosmic distance ladder.
Because there's a bunch of different techniques that use for
things at different distances, and then you try to overlap
them and stitch them together. There's no one technique that
will work for everything really close up stuff. You've got

(22:20):
parallax for stuff that's a little further away. You got
these these variable stars, the cfids, and then after that
you have to use GPS. After that you just watch
a science TV show that you have to do everything. Um,
the problem is that cefids are just stars, and so
they're bright, but they're not that bright and you want
to see something like in another galaxy or really really

(22:42):
far away galaxies. You can't resolve individual stars in super
duper far away galaxies, so that has a limit to Yeah,
so then they needed something super crazy bright to serve
as a standard candle for the rest of the universe
because these stars, even though they blink, they get lost
in the light from the rest of the galaxy they're in. Yeah, exactly,

(23:04):
they're not particularly bright kind of stars, and so that's
why the end of the cosmic distance Ladder is dominated
by supernova. Supernova is when a star goes boom, right
when it's time to check out. It's had all of
its fun and it's decided we're done with all this
fusion stuff. Let's just blow it on one last big party.
It collapses basically right like it runs out of fuel

(23:26):
and then it just yeah, and we did a whole
fun podcast episode on house stars and their lives um
which you should go out and listen to you're interested
in that kind of detail. But the critical thing is
that one kind of star ends in a very particular way,
and it's called a type one a supernova, and the
supernova are extraordinarily bright. The thing you have to understand
is that the stars like using up all of its

(23:48):
fuel in a very short amount of time, and so
it's extremely bright, and a single supernova can be brighter
than the entire galaxy that it's in. So that's how
we can see it. I mean, if you look at
the night sky, you can see these these little fuzzy
things that are the other galaxies, but you can't really
resolve any particular star in it right. Well, for the
close up ones you can, like for Andromeda, which is

(24:10):
whe of the nearest galaxies, you can see the shape
of it, you can see individual stars, but you're right.
For the furthest ones, they're just little smudges and you
can't resolve individual stars except when one of them goes boom,
and then you can see it and it's brighter than
the hundred billion stars combined. Right. That's it's incredible to
me how bright these supernov are. And you don't want
to be close to any of these things, right, any

(24:31):
Anybody near these things gets instantly sterilized. So we would
see it as a like a little dot in the
inside of a galaxy which is flash like it will
just yeah, And in the night sky you see it
as maybe a new star. Right. There could be like
a little smudge there you never noticed from a really
far away galaxy, and all of a sudden, there's a
bright star there. And you can look back in history

(24:52):
and see the record where ancient people's saw these things
in the night sky. Right, we have a history of
supernov explosions that goes back more than a thou and
years because like Chinese astronomers are noticed, hey, on this date,
a new star appeared in this guy and the only
lasted for three weeks and then it was gone. Boy,
that was weird. And the trick is that these supernova
are always the same, right, It's not like do you

(25:14):
have small supernovas and big supernovas. It's like, if you're
gonna have a supernova, it's always this bright. Well, there
are a lot of different kinds of supernova. But this
one kind, called Type one A always has the same
sort of curve, this light curve when we talk about
how bright it gets and then it hits a peak
brightness and then dims away, and the whole process last days.
But it always has the same shape and always has

(25:37):
the same peak brightness. Now, for those of you who
know a lot about this, there are some technical details
and in the variation of the peak brightness, but that
can get calibrated away, and we can talk about that
another time. But the basic version of the story is
that they always have the same peak brightness because it's
always the same kind of process. It's always the same
size star with the same amount of fuel in it.

(25:58):
It's not like every star those supernova. It's like only
once with a particular size and stuff, and it will
collapse at some point right in a very particular way.
That's exactly right. There's lots of different kinds of supernova,
but one kind which comes from binary star systems, in
which one of them is a white dwarf that leads
to Type one A supernova, and which just happens to

(26:19):
be very regular, and it happens to be very little
variation between the brightness of different type one A supernova.
And this is something people realized, you know, like twenty
thirty years ago, but it took some work. You know,
people are constantly out there looking for new ways to
find distance metrics, new ways to figure out how far
away things are. And people we're working on Type one

(26:41):
A supernova and other people working on this kind of thing.
So people work on the other kind of thing. People
today right now are working on new ways to measure
distances because we always want to know more precise information.
So behind the scenes, grad students were slogging away, can
we figure out how far away type and supernova are?
Can we calibrate they're they're like her, so that they
all look the same. And then about in the late nineties,

(27:04):
people figured out how to do it, and the technology
became possible and they started collecting this information, right, and
so all of a sudden, a whole new window into
the universe. We could tell how far away things that
are super far away we're because the supernova are so bright. Right,
But it's sort of interesting because it came from kind
of a random occurrence in the universe, right, Like people
just cataloging and observing supernova just for the sake of science.

(27:27):
Suddenly they realized that this gives us a tool for
mapping the universe exactly. And that's what astronomy is all about.
It is like, let's figure out how to use the
idiosyncrasies of the universe to give ourselves clues, right, And
so yeah, it's just luck, right, I mean, I mean
it's luck. What is it revealing that we underneed the
surface exactly? That is that is pure science right there.

(27:49):
It's like, let's nail down facts about the universe by
things that accidentally reveals to us. I mean, everything the
universe tells us is an accident, right, nobody's purposely sending
us information. We're just a sit unless we're living in
a simulation, in which case everything is on purpose. Um. Yeah,
So Type one A supernova stand out really really far.

(28:10):
The best distance measurements we have come from type one
A supernova. So this sort of three step louder there.
There's the parallax for close up stuff, the cepids for
medium range stuff, and then the type one A supernova
for super far away stuff. And you know they overlap,
which allows us to calibrate. And it's built one on
top of the other, right, like what we know from
supernovas is built on what we know from these blinking stars,

(28:34):
which is built on what we know about from parallax,
which is built on our eyeballs. That's right, exactly, it's
built on our listeners eyeballs. And now we actually have
a new way to measure distance, which is really cool,
which has only been possible recently, and that's um from
gravitational waves. Gravitational waves are these ripples in space time

(28:58):
that we can measure by seeing how these observatories shrink
and expand by my new distances as the gravitational wave passes.
And just like with type one A supernova or with cepheids,
we know something about the strength of the gravitational wave
based on what it looks like here, based on not

(29:19):
on its brightness, but like on how fast it's wiggling,
because because gravitational waves wiggle right there waves of space,
so something about how they're wiggling gives you a clue
as to how bright, how intense they were at the source.
And then we can by measuring how the intense they
are here, we can tell how far away things were.
So this is a whole new handle. We only recently
added to our cosmic distance ladder. You sound pretty excited

(29:43):
about gravitational waves. Um, I am, I am. It's a
it's a heavy topic. Um, but it's sort of cool.
I guess just taking a step back just to think
that we went from like a two D v of
the universe just looking at these things that we thought
we're painting on the ceiling, to this now really sort
of incredibly rich and deep three D conception of the

(30:07):
entire cosmics. Right, It's absolutely incredible, and it's more than
three D. Actually, it's actually kind of like four D
because when we look out into space, we don't just
look at it where things are. We look at where
things used to be, right, so we see things in
sort of these spheres, like the things that are nearby
are recent, things that are far away are old. And
so we're not just looking out at where we are

(30:29):
in the universe like a three D map. We're looking
at these shells that get further and further back in time,
and so this allows us to see what the universe
used to be like, so absolutely gives us a sense
for the structure the universe, but also gives us a
sense for how that structure is changing, and why you
cannot get more rich information about the formation of the
universe in our context and why we're here and all

(30:51):
that crazy important stuff. Then understanding how the universe came
to be the way it is, right, all that just
from looking up. That's right. So next time you're looking
at the night sky, wonder is there more information there
that I'm seeing? If they're more information than even scientists know. Bobile,
future scientists laugh at us for missing what's going to

(31:11):
be in those futures science shows what's going to be
on a future science podcast. All right, thank you very
much for listening, and thank you to Ryan for sending
this question. Thanks for listening, See you next time. If
you still have a question after listening to all these explanations,

(31:33):
please drop us a line. We'd love to hear from you.
You can find us at Facebook, Twitter, and Instagram at
Daniel and Jorge that's one word, or email us at
Feedback at Daniel and Jorge dot com.