October 30, 2018 • 32 mins
How we learned that something is tearing the Universe apart, and what it might mean.
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Episode Transcript
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Speaker 1 (00:05):
Some of the most amazing moments in science were totally unexpected.
You mean, like the discovery of microwave ovens or slinky
So I heard it was also discovered by accident. Yeah,
but I'm thinking about the times when you go out
there just to double check something, something you thought you
already understood, but you find an answer which makes no
sense and forced you to change how you'd see things. Yeah.
Like I heard one of the most fundamental things in
(00:27):
the universe was actually discovered this way by accident, and
it's totally amazing. It makes me wish that I had
been involved, and it makes us see the universe differently,
makes us see everything differently. Is it more impressive than
as slinky in a microwave? That's pretty hard to top,
but I think this one does. Hi, I'm RhE make cartoonists,
(00:58):
and I'm Daniel. I'm a article physicists, and this is
our podcast. Daniel and Jorgey explain the universe today on
the program. What is dark energy and why is it
everywhere in filling the universe? Is it powerful? Is it dangerous?
Is it dark after all? Will it stain your clothes?
(01:21):
And most important, why is it causing the universe to explode.
The universe is exploding, people, but don't get out of
your cars. It's going to take a while. Dark energy
is a mysterious topic. We went around and we asked people,
what do you know about dark energy? Um, is it
like empty space? I'm not sure. No, I have no
idea about it. It's like empty energy. Is dark energy
(01:44):
something with black holes? I don't know, but that's my speculation.
So most people really seem to have almost no idea
what dark energy is, which as a physicist, really surprised
me because it's one of the most dramatic and amazing
discoveries of the last thirty years. Yeah, it's but people
what it has seemed to have heard about it, right,
It sounded really familiar, but they didn't know what it was. Yeah,
(02:04):
some people thought it was dark matter. Some people maybe
thought it was something in black panther like. People really
didn't seem to have a good grip on what dark
energy is, which is amazing, not just because it was
a big discovery, but because it has huge consequences for
our lives. Yeah, it's a great name. I mean, I
think it's easy to see why people would confuse it
with dark matter, they're both dark and that's right. It
(02:26):
is a cool name, dark energy. It sounds so mysterious, though,
you're right. In the in like the HR meeting where
they decided what to call this weird physics thing, it
should have considered the fact that dark matter and dark
energy sounded like. I wonder if they do focus groups
when they do that kind of thing. Do you think
they thought, Hey, all those dark matter people get a
ton of grant money. If we call our stark energy,
we could also get some of that money. I'm sure.
(02:47):
I'm sure that was the number one concern in their minds. Yeah,
how will this play in my next grand proposal? Anyway?
Let's tell people what dark energy is and why it's
so important. Yeah, well, first of all, it's a huge,
huge deal, right, Like, it's not like an obscure thing
in physics. It's like a huge part of the universe.
That's right. Most of the energy and the universe is
(03:08):
actually taken up with dark energy, like sixties, right, that's right. Fully,
two thirds of all the energy in the universe is
devoted to this weird, mysterious force called dark energy, and
that's about all we know about it. Like when you
think of the universe and like atoms and protons and
electrons and rocks, asteroids, planets, all those suns, hamsters and
(03:31):
then the hamsters, yeah, hamsters, all that stuff out there
in the universe. Stars. That's not all there is to
it to the universe, right, A whole bunch of it
is dark energy, that's right. Yeah, most of the stuff
in the universe is not the kind of stuff that
we see around us, as you were saying, even stars
and planets and gas and dust, that all adds up
to a tiny little slipper like five turns out. And
(03:55):
this is the kind of stuff we've only learned recently.
Most of the universe is weird. Stuff we never even
thought about, we never even would have included in a
pie chart of the universe thirty years ago. Is the
biggest piece of the pie. It's this big kind of
mysterious energy that's out there, that's right. So imagine, for example,
you take like a cubic meter of space and you
(04:16):
ask what's in it. Well, on average, you average over
the whole universe that we can see, it has about
five or six hydrogen atoms worth of energy. And most
of that is not matter or or stuff that you're
familiar with. Most of it is dark energy, and another
big chunk of it is something called dark matter, which
we can talk about it in another episode. Yeah, and
(04:37):
and like dark energy is all around us, right, like
right now, two thirds of the room right now that
I'm in is filled with dark energy. That's right, most
of the energy in the universe and most of the
energy everywhere. And dark energy is not something that's out
there in space. You're exactly right. It's here, it's with you.
It's between your toes. It's getting refrigerator just other dark
matter between my toes. Let's be honest. I don't think
(05:00):
I want to know what he does, whether it's a
cosmic mystery physics or not. Yeah, let's not let's not
get into my toes on this. On this podcast, Daniel
Jorge explained the universe and Jorge's toes. That's right, that's
a winner right there. Um. But yeah, so it's a
huge deal. It's all around this and it's causing the
universe to explode. So that's that's kind of distressing. Yeah.
(05:23):
Not only is it turned out to be most of
the universe, it has huge consequences. Right. The universe is
exploding in every direction, and in some ways dark energy
is causing the universe to explode. Another way to think
about it is that dark energy is our description of
the fact that it is exploding. Like we saw the
universe is exploding. We named that dark energy. It's not
(05:45):
like there's two separate things where oh, here's dark energy,
we know that's the thing. Here's it's cause it's more
like dark energy is the description of the fact that
the universe is exploding and we don't really know why.
It's another name for the explosion of the universe. It's
a fancy tide or our lack of understanding the explosion
in the universe. It's like you don't understand something. You
have the pr version. We could have called it what
(06:07):
is going on with the universe? But dark energy sounds
better w two F energy your t F universe man, Yeah, exactly.
Well let's get into that. So how did how do
we find out about this dark energy that's all around
us and it's causing the universe to explode. Well, it's
one of my favorite stories in science because it's a
(06:29):
story where the answer was a surprise. You know, scientists
went into it asking one question and learning something totally
different about the universe. The question they started with was
what is the history of the universe and what is
the future of the universe? Like what's going to happen eventually? Yeah, exactly,
Like is this whole universe gonna keep going forever? Is
it going to compress into little dot? Do I have
(06:51):
time to like write that novel I've always been wanting
to write. You definitely have time to write that novel.
I have no excuse. Is it another young adult novel?
Because I have enough of those already. It's called dark
youth dark, um dark. So you've got vampires, you've got
where wolves have dark energy beings. Yeah. And so when physicists,
(07:14):
when physicists want to predict the future, where they typically
do is look into the past, try to understand what's
happened so far, and then extrapolate so to figure out
what the future of the universe was. They first looked
into the past and said, what's been going on so far,
and let's see what direction things are going in? Right, Like, um, uh, Like,
(07:34):
how am I doing financially? Do I have more money
now than I used to have money before? And that's
a that will sort of tell me, what might I
might expect in the future if I don't make ill
advised decisions. That's right. Yeah, if your net worth has
been rising, then you expected to keep going. What if
your bank account is dropping every single month, then you
can expect some sort of cataclysmic event in your near future.
And I need to record more podcasts to make more money.
(07:56):
That's right, that's right. And so in the physics world,
we went back to the very beginning of the universe
and said, okay, the universe started with a big bang, right,
and things blew up from there. And the question people
had in their minds was, you know, after the Big Bang,
things flying out from that huge explosion. The question was,
is there enough stuff in the universe for things to
(08:18):
slow down, for the gravity from that stuff to slow
things down, stop them, and then make them fall back in.
So that was one possibility people were considering that the
universe would stop, the expansion, would stop um and then
come back into a big crunch. So like the stuff
that flew out from the Big Bang, and now the
question is like, are they going to keep flying off
(08:39):
or maybe is there enough gravity pulling it all the
stuff together that it's gonna like slow down and then
pull back in, just kind of like how our solar
system forms. Yeah, exactly. Most of the stuff that we
know around us in the in the universe was formed
by gravity. Right, Gravity gathered together rocks and dust and
rubb and hamsters or whatever and coalesce it together. Right.
(09:03):
That's why the Earth is round because that's gravity's work,
tumbling everything towards a smooth surface. And that's how the
Sun is formed, its gravity compressing dust and gas until
it gets hot enough to burn. So gravity is is
very powerful force and and has a lot of time.
Um it's actually one of the weakest forces, but over
cosmic scales and all this time, it has enough power
to pull all this stuff together and compress it into objects.
(09:26):
So people thought, maybe that's going to happen with the
whole universe. Man, Like, maybe the whole universe is gonna
come back together and compress back into a tiny dot.
That would be pretty amazing, like a giant cloud. Does
we all just kind of come get pulled together and
we maybe come back down. That's one possible way that
the future the universe could end up. That's right. Yeah,
(09:48):
So option A was the big crunch. But people didn't know,
like is there enough stuff in the universe? Is there
enough gravity from that stuff to pull everything back together?
Because it could totally have been that the explore ocean
was more powerful essentially than the gravity, and the things
spread out forever. Oh, that could happen, like things that
are like a grenade out in space. It just blows
(10:09):
up so violently that gravity is too weak to pull
everything back together again. That's right, yeah, And that could
that could have been the fate of the universe. It
could be that the universe just keeps expanding, things spread
out and slow down like gravity. Gravity is still slowing
things down, but it doesn't have enough power to stop
it and have it fall back in. And so it
(10:30):
could be that just spreads out forever, getting cooler and
cooler and more distant until something we call the heat
death of the universe. That's when everything is the same temperature. Right,
So physicists were like, are we ever going to be cool?
That was a front question. We'll know in about to
find out if physicists are ever cool. So that's I mean,
(10:52):
that is a very significant question, right, Like we're we
live in this universe. We kind of want to know,
like where is this whole thing headed? Yeah, I wonder
if it's interesting to most people. To me, as a physicist,
I think it's one of the most interesting questions, Like
what is the future of this whole amazing, beautiful experiment
we're living in, you know, is it going to go
on forever? Is it going to tear uself apart? Is
(11:13):
it going to crunch together? Like? To me, that's a
really interesting question, Like do we live at the peak
of it? Or are we like in the after party,
you know what I mean? Like, or are we or
are our great grandchildren going to be like at the
peak of the universe? Yeah? I think I think that's
exactly right. And I think there's an issue of context there, right,
Like as humans, we are always striving to understand the
(11:33):
context of our existence. Why is this important? What's going on?
And one of those questions is like is Earth at
the center of the cosmos? Is Earth even important? And
another question is like that but in time? Right, like
are we living at an important time? What is the
future going to be? Like where do we fit in? Yeah?
Are people in a billion years going to look back
(11:54):
and say, man, I wish I'd lived when Daniel L. Jorge,
we're doing. They're awesome podcasts because those were the days,
many the good old days of the universe. Yeah, this
podcast is peak civilization, right, podcast is peak civilization. So
state tuned state that one. Let's take a quick break. Yeah.
(12:21):
So people were thinking about those two options, right, big
crunch or heat death of the universe. So option A
everything comes crashing back down. Option B things just gonna
float away, yeah, exactly. And so what they wanted to
do was look back in time because you can't actually
see the future, but it's not that hard in physics
to see the past, especially in astronomy. To see the past,
(12:43):
all you have to do is look out into space,
and everything you see in space happened in the past,
just because it takes light time to get here from there.
It's like back in the day when there was no
email or internet, you would get your news from mail letters, right,
And so the further away what did actually happened? At
(13:04):
some point the internet did not exist, Daniel, what what what?
It was all dark dark mail? Ye, dark mail. So yeah,
so like the further away you get a letter the
older that news was, yes, exactly. And some people think, oh,
that's a bummer. I think it's actually pretty cool because
it lets us look into the past, and so the
(13:24):
further out you look, the further in the back in
the past you can see. And the goal is to see,
like how fast is stuff moving away from us, you know,
the expansion of the universe. How fast is stuff moving
away from us now? And how fast was it moving
away from us earlier? So we could understand like, how
is this changing, what is the faith going to be?
Is its slowing down? How fast is it slowing down? Yeah, So,
(13:45):
because like if the fate of the universe was for
it to crunch down, then you would see things kind
of expanding slower now than before. Like before you think
this would be flying out, and now they would be
kind of slowing down, And so we could expect things
to crunch or if we measure things to be moving
at about the same now as as they were before,
(14:05):
then maybe the fate of the universe is just to
kind of keep floating off and getting cooler exactly. And
so that was the question. They were like, let's look
and see how things are changing. How much is it
slowing down? Is slowing down a lot, which means maybe
big crunch are slowing down just a little, which means
maybe heat death. That was the question they asked. But
it's actually fascinating how they did it because it's tricky, right.
(14:26):
In order to know how far back in the past
you're looking, you have to know how far away a
star is. And that's not easy to figure out, right,
because like, if you look at a star, it's um,
if it's dim, you don't know if it's just like
a weak star or a really far away star. It's
just a little point, right, it's hard to tell. You can't, like, um,
tell how far away it is just from how bright
(14:47):
that point is. That's right. You can't tell the difference
between a star that's very bright and far away and
very weak and close up. Um. We have some tricks,
but none of them are really good. Um. The early days,
UM people used to figure out how far away stars
were by seeing how they shifted as their Earth went
around the sun. Because if something was really close, then
you could see it sliding back and forth as the
(15:09):
Earth went around the Sun. That's called the parallax system.
It's like how you triangulate with your eyes, right, like
if yes, if something looks really different when you wink
one eye and you wink the other one, then it
must be pretty close. But if it doesn't change a
lot when you wink between eyes, then uh, it's far away. Yeah,
And so that's the original way people can figure out
how far stuff away is. And then it was like
(15:30):
in the nineteen twenties when Hubble figured out a new
way to look at stuff in the sky and he
found a particular kind of star called a seafid that
rotated and its brightness was connected to how fast it
was rotating, so you could figure out by measuring its
rotation how bright it is, which told you how far
away it was. So he was the first one to
be able to see things that were further away. And
(15:51):
he's actually the one who figured out not just that
the universe is expanding. Before that, people thought, oh, the
universe is just a bunch of stars hanging in space
ace And he figured out two amazing things. One is
the universe is expanding, and the other is that the
universe is more than just our galaxy. And what do
you mean more? He figured out that there were other galaxies.
(16:12):
That's right, before Hubble, we thought there is just our galaxy, Like,
imagine just a single galaxy floating in space. That's what
people thought the universe was. He saw these little smudges
up in the sky that people thought, oh, these should
just dust or clouds or something turns, and that he
proved by measuring the distance to them, that they were
way too far away to be part of our galaxy.
(16:34):
He proved that they were actually other galaxies, and that
those galaxies who were running away from us. It must
have been so mind blowing to be Hubble, you know,
to have this moment of realization, Uh, to understand this
huge context of our of our existence. Yeah, it must
be very humble to be Hubble. You know, I don't
(16:54):
know anything about Hubble, but a lot of these famous
physicists were not the nicest guys. So is that you
are their stories about Hubble. I don't know any of them,
but if I had to guess any random famous physicist
from history, they probably got there by not being the
nicest of a person. Yeah, humble. Anyway, Hubble was able
to see past our galaxy, but cosmically speaking, that's not
(17:17):
far enough to be able to tell because that's just
like the last you know, a little bit of the history.
Then it was in the nineties nineties, people developed a
powerful new technique that let them see much further, so
we could tell how far away things were that were
much much, much further, and that gave us a much
deeper view, further than like the nearest galaxy, yeah, really
far away galaxies. And that's a new kind of star
(17:39):
that we started to understand, called a type one, a supernova. Right,
they call him like the standard candles, right, exactly the
standard candles because they act the same way everywhere in
the universe. And so we can tell we know how
bright they are, so based on how dim they are
or how bright, we can tell how far away they are.
So it was in the nineties people figured this thing out, like, look,
(18:00):
we have a new standard candle that let's look much
deeper into the history of the universe and how we
can answer this question. We can figure out what is
the future of the universe, What is it going to be?
So most stars are you can't really tell, right, some
of them are dim, some of them are far away.
But there are this special type of star. It always
explodes the same way, so that if you see it
(18:21):
m really bright and must be closed, or if you
see it really dim, it must be far away, right,
that's right. And these are not just stars, as you said,
these are supernova, right, they're the end of stars. Right.
That's when stars collapse and implode, followed by huge, enormous
cosmic explosion. And that explosion is super bright, like a
single supernova can outshine the entire galaxy it's in, but
(18:43):
just for a few days. It's like crazily burning up
all of its fuel. It's like a flare. If you
set your house on fire, it's brighter than the whole neighborhood, right,
but not very long. So there were you know, people
figure this out, and then people um sort of split
into two teams. It was a team at Berkeley and
there was a team in Australia, and and they were
racing to discover to get as much data as possible
(19:03):
because supernova are not regular. It's not like you know
when it's going to happen. You have to just scan
the sky and hope to see one. Then it developed
special technology to look through all this telescope data and
try to find new stars that were appearing in the sky,
because that's what a supernova looks like, looks like a
bright new star that appears and then it fades over
a matter of days, and if you capture enough data
about it, then you can learn about its brightness and
(19:25):
figure out how far away it was. And so finally
one of them discovered, like, hey, we have a measurement
for how the universe is expanding, whether it's expanding faster
or slower than before. Yeah, it took a took a
couple of years for them to have enough data, and
it was a scramble and think, I think those people
must have been working twenty hour days in the seven
days a week. Yeah, everyone wanted to be the first
(19:47):
to say like, hey, here's that measurement exactly. Finally they
had this plot of how fast the universe is expanding
as a function of time. And what they discovered is
that the universe is not slowing down a lot or
slowing down a little. So it's not option A nor
option B. That's right. The universe went for secret options.
See secret Ope, you didn't even know it was on
(20:09):
the menu. And that's what we got for dinner, right.
And I love when the universe does that because it's like, oh,
you silly little humans, you have no idea what even
question you're asking? Right? You hadn't even thought about this answer.
That's right, and so secret options see is that the universe,
the expansion of the universe is not slowing down at all.
It's increasing. It's getting faster and faster, it's accelerating. So
the fate of the universe is not that it's going
(20:31):
to crunch down or just float away. Things are like
phraising away from each other, that's right, Faster and faster
every year. Something out there, we don't know what it is.
We can't explain it, we don't understand it at all.
Something out there is pushing all of these other galaxies
away from us, and it's doing it faster and faster
every year. Like if you you only need to know
a little bit of physics to know that accelerating an
(20:53):
entire galaxy hundreds of billions of stars, takes a huge
amount of energy. That's why we were talking earlier about
how two thirds of the energy in the universe, because
it's not a small feat to expand the whole universe
faster every year. Yeah, it's like these galaxies want to
get together because of gravity, either pulling on each other
to get closer, but something is actually pushing them apart.
(21:14):
That's right, and that's the thing we call dark energy.
So they discover this thing, total mind blow, like what
the universe is totally different from what we thought it was.
The fad of the universe is different from what we
possibly imagined. Then there's this second big question, which is
what is it? Right, we found it. We we know
that it's there, we see that it's happening, but we
don't understand it at all. We just observe it. Okay,
(21:36):
but before we get into that, let's take a quick break.
That's what dark energy is. It's like that thing that
is pushing all the galaxies apart. That's right, the totally unexplained,
(21:57):
ununderstood phenomena which is shredding the universe and causing it
to explode and changing its future. That's what dark energy is.
And most people walking in the street have no idea.
It's like the phenomenon of the universe expanding faster and faster.
That's dark energy. That's exactly right, like some kind of
like actual like energy like a photon or some kind
(22:17):
of like thing like we really don't know what it is.
All we know is that it's energy. That's all we know.
Um And we know that it's accelerating the universe. And
it fascinating thing is that it's not just pushing stuff
through space. Right. One way to imagine a galaxy moving
away from you is that it's moving through space away
from you, right, And that's what you imagine probably when
(22:38):
you think of the Big Bang. Everything comes out of
this tiny little ball and expands through space. But dark
energy is doing something else. It's also creating new space
between us and the other galaxies. It's not just pushing
things through space. It's making new empty space. It's not
pushing you and meet apart from each other. It's like
it's creating more uh room, more more land in between
(23:02):
in between us. That's right. It's making the four or
five even longer. Well you know what I mean, like
a like a tectonic plading now, like it comes up
and it creates land and it pushes things apart. That's
kind of what dark energy is doing out in space, Yes,
exactly right, creating new real estate in between you and me.
That's pushing me apart, further apart from you, that's right.
(23:24):
And it's hard to think about what it means new space.
What is that unless you think about space in a
different way spaces and just emptiness or nothingness. As we've
said on this podcast a few times, it's this dynamic
physical thing. And this is one reason we think it's
more than just emptiness, is that it can do this
thing that emptiness can't, which is create more of itself.
It's not nothing. It's like real estate, and there's more
(23:45):
of it being created. That's right. Location, location, location, you know,
it's the most important thing. Right And new space is
being created all the time, and that's what dark energy
is doing, is creating this new space. And we don't
have any explanation for it. You know, people think about
theories of what is dark energy? You could it be this?
Could it be that. One idea that physicists like is
to think about the energy of this empty space, like
(24:06):
maybe space itself has energy. Maybe space can never really
be empty. You know, it's full of the Higgs field,
and it's full of virtual particles, and it's full of
all this little quantum frothing bubblinus. Right Like by its
very nature is just like this has a bubbly personality.
That's right. Space is friendly. It wants to have more
(24:26):
of itself. It's social and so one idea is maybe
dark energy is this energy of empty space. Problem is,
if you sit down to do the calculations, you say,
all right, well, let's calculate how much energy there is
an empty space, and compared to what we see, you
come up with a number that's way off, like not
a little bit off off by ten to the sixty
and let's ten with sixty zeros beyond its error. It's
(24:47):
a pretty big mistake. So the other fascinating thing is
that it hasn't been doing it forever. It turned on
about five billion years ago and started this acceleration. And
again we don't know why. We don't know what turns
it on. We know what we turn it off. You
know what is dark energy? Like you know long walks
on the beach. I don't know. We don't know very
much about it. It wasn't always there from the beginning
(25:09):
of the Big Bang. It's just some somehow five billion
years ago it started pushing things more actively. Yeah, these days,
the most modern picture of cosmology, I think, considers the
Big Bang and dark energy to be sort of connected. Like,
imagine a huge expansion of the universe in the very
first few moments that we called the Big Bang or
these days we call that inflation. And then that stopped
(25:29):
and things just sort of floated through space for a while,
and then five billion years ago it started again. So
one sense you could think of dark energy is like
phase two of the Big Bang. The Big Bang continued,
you know, but just when you thought it was safe
to get into space, here comes the dark energy, Here
comes the Bigger Bang. Yeah, both of them are expansions
of space. We think they're probably related, but we don't
(25:52):
really know how or why you cannot do the same thing.
But who knows why would take a nap for five
billion years? That's right, I'm sorry what you do and
the time are we getting build for that time? Yeah, exactly.
And there are big consequences for the fact that it's
not just pushing things through space but actually creating new space. Yeah,
because we started a podcast asking like what's going to
(26:13):
happen to the universe at the end, and so it
has you say, it has big consequences for like what's
going to happen to the universe. Yeah, because it's creating
new space, which means it's effectively evading the speed limit
of the universe, the speed of light. Right, nothing in
the universe can move through space faster than the speed
of light. All right, that's a hard and fast limit.
(26:34):
And so these galaxies can't move through space away from
us faster than the speed of light. But there's no
limit on how fast you can create new space, the
new spaces being created between us and these other galaxies
faster than light can go through it. It's like if
I was trying to get to you done at Irvine U,
(26:54):
and I can only go seventy miles per hour in
the highway. You know, nominally you'd be lucky to do that.
Let's say it's like two am and have your private
Let's say I was using the carpool lane, all right,
and uh but yeah, but like let's say that a
new land was being created between you and me faster
than seventy miles per hour, I would never get to you.
(27:15):
That's right. If they're just laying new road and you're
faster than you're driving through it, you'll never get down
to Irvine, exactly right. And that's the situation. Those photons
that are leaving those galaxies now will never reach us
because the space in between us is growing faster and
the photons go through it right at some point they'll
stop reaching us, right like um like, we'll see them,
and then suddenly they'll blink out of existence. Exactly things
(27:39):
that used to be in our observable universe, things that
we see now because light has had a chance to
get through the universe to us, will no longer be
observable because dark energy is pushing them out of this
sphere of the observable universe. All the stuff we can
see because light has had a chance to get to us.
So galaxies in the sky are disappearing right now, right now,
(28:00):
quick rush outside of Things that are on the edge
of our observable universe are disappearing because dark energy is
pushing them beyond the bounds of things we can see.
So the nice guy is getting darker and darker. So
like if you hit the fast forward button on a
camera point and at the sky, you would see like
stars just snuff out, just like yeah, you would see
(28:20):
galaxies snuff out of their clusters of stars. And so
in that scenario, all these galaxies snuff out of the sky,
right they get pushed out beyond our observable horizon and
they disappear, And then we're left with the single galaxy
in the universe, just like people before Hubble thought, right then,
and imagine astronomers in the future, right after all these
(28:41):
galaxies are pushed out, They're gonna think we're the only
there's only one galaxy in the entire universe. Yeah, because
they would be the only thing they could see. Right,
It's amazing to imagine, how to to try to think
about how could they learn about the universe if all
they could see was their galaxy? How could they even
possibly know? Right? They would have no how big it
actually is. Yeah, they would have no idea what's beyond
(29:03):
their observa universe. And that's really humbling because it reminds
you of how little we know. Right, we're, after all,
fourteen billion years into the history of the universe. There
could be fascinating clues about the way the universe works
and what it's made out of that have already been
pushed beyond our sky that we cannot see and we
will never see. Right, So what's lost in the night sky? Well,
(29:26):
we have no idea, right there kinds of galaxies? Who
knows that we can't see anymore? Yeah, exactly, And continue
even further, and remember, dark energy is not just out
there in space. It's here, it's with me, it's with you.
It's literally pushing me and you apart right now. The
reason we don't see it is because we have bonds
that are holding us together, right like their dark energy
(29:47):
is trying to create new space between the molecules in
my hand, But the molecules are bound together tightly enough
to resist that. But if dark energy continues, it might
eventually shred the Milky Way, right, take our own galaxy
and tossed the stars out into space. Eventually we might
just be a solar system floating in the inky blackness
of space, seeing nothing. Right, that's one potential future, thinking
(30:09):
that we're the only star in the entire creation, the
entire universe. That's right, that's right, that's one real possibility. Now, again,
we don't know what dark energy is gonna do. We
don't know if it's strong enough to do that. We
don't know if it's gonna stop. We don't know if
something else is going to happen. We really have no idea.
But it's it's amazing to me that it's only this
knowledge is only twenty years old, twenty years ago before
(30:31):
we discover the stuff we didn't know that the universe
was accelerating, and we didn't know that most of the
universe was this thing called dark energy. Like, think about
how recent that discovery is. That to me is inspiring
because it makes me hope that we have more mind
blowing discoveries ahead, you know, more of these moments of
like what the universe is totally different from what I imagined.
(30:52):
That's what I live for in physics. Well, you know,
this is when it give me. Think. This past weekend,
I was camping with my kids and my family and
it was a beautiful night. You could see all the stars.
And I pointed out to my daughter, was like, look
at all the stars. And I was pointing out some
(31:13):
of the constellations and stuff, and she's like wow. And
I talked pointed out the Big Dipper and she's like,
that's the Big Dipper. And she proceeded to tell me
this whole complicated story about the Big Dipper that she
read in this book she had at school that she's
read like a million times, but for the first time
she had actually seen the stars, She had actually seen
(31:33):
the Big Dipper. What a fun moment for her. Yeah,
to make to make these things real yeah, yeah, and
so yeah, so I think that's a big lesson. You know,
go out there, look at the stars before they go away.
And this is not abstract. I mean, this is our
universe we're actually talking about. And you can go along
and live your life and worry about traffic and paying
the next bill in your own financial big bang. But
(31:54):
these things are our context, right, This is the universe
we live in that we're definitely trying to discover before
it blow was itself up. It's changing all the time,
so go out there and experience it. Absolutely. If you
still have a question after listening to all these explanations,
(32:14):
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.
Some of the most amazing moments in science were totally unexpected.
You mean, like the discovery of microwave ovens or slinky
So I heard it was also discovered by accident. Yeah,
but I'm thinking about the times when you go out
there just to double check something, something you thought you
already understood, but you find an answer which makes no
sense and forced you to change how you'd see things. Yeah.
Like I heard one of the most fundamental things in
(00:27):
the universe was actually discovered this way by accident, and
it's totally amazing. It makes me wish that I had
been involved, and it makes us see the universe differently,
makes us see everything differently. Is it more impressive than
as slinky in a microwave? That's pretty hard to top,
but I think this one does. Hi, I'm RhE make cartoonists,
(00:58):
and I'm Daniel. I'm a article physicists, and this is
our podcast. Daniel and Jorgey explain the universe today on
the program. What is dark energy and why is it
everywhere in filling the universe? Is it powerful? Is it dangerous?
Is it dark after all? Will it stain your clothes?
(01:21):
And most important, why is it causing the universe to explode.
The universe is exploding, people, but don't get out of
your cars. It's going to take a while. Dark energy
is a mysterious topic. We went around and we asked people,
what do you know about dark energy? Um, is it
like empty space? I'm not sure. No, I have no
idea about it. It's like empty energy. Is dark energy
(01:44):
something with black holes? I don't know, but that's my speculation.
So most people really seem to have almost no idea
what dark energy is, which as a physicist, really surprised
me because it's one of the most dramatic and amazing
discoveries of the last thirty years. Yeah, it's but people
what it has seemed to have heard about it, right,
It sounded really familiar, but they didn't know what it was. Yeah,
(02:04):
some people thought it was dark matter. Some people maybe
thought it was something in black panther like. People really
didn't seem to have a good grip on what dark
energy is, which is amazing, not just because it was
a big discovery, but because it has huge consequences for
our lives. Yeah, it's a great name. I mean, I
think it's easy to see why people would confuse it
with dark matter, they're both dark and that's right. It
(02:26):
is a cool name, dark energy. It sounds so mysterious, though,
you're right. In the in like the HR meeting where
they decided what to call this weird physics thing, it
should have considered the fact that dark matter and dark
energy sounded like. I wonder if they do focus groups
when they do that kind of thing. Do you think
they thought, Hey, all those dark matter people get a
ton of grant money. If we call our stark energy,
we could also get some of that money. I'm sure.
(02:47):
I'm sure that was the number one concern in their minds. Yeah,
how will this play in my next grand proposal? Anyway?
Let's tell people what dark energy is and why it's
so important. Yeah, well, first of all, it's a huge,
huge deal, right, Like, it's not like an obscure thing
in physics. It's like a huge part of the universe.
That's right. Most of the energy and the universe is
(03:08):
actually taken up with dark energy, like sixties, right, that's right. Fully,
two thirds of all the energy in the universe is
devoted to this weird, mysterious force called dark energy, and
that's about all we know about it. Like when you
think of the universe and like atoms and protons and
electrons and rocks, asteroids, planets, all those suns, hamsters and
(03:31):
then the hamsters, yeah, hamsters, all that stuff out there
in the universe. Stars. That's not all there is to
it to the universe, right, A whole bunch of it
is dark energy, that's right. Yeah, most of the stuff
in the universe is not the kind of stuff that
we see around us, as you were saying, even stars
and planets and gas and dust, that all adds up
to a tiny little slipper like five turns out. And
(03:55):
this is the kind of stuff we've only learned recently.
Most of the universe is weird. Stuff we never even
thought about, we never even would have included in a
pie chart of the universe thirty years ago. Is the
biggest piece of the pie. It's this big kind of
mysterious energy that's out there, that's right. So imagine, for example,
you take like a cubic meter of space and you
(04:16):
ask what's in it. Well, on average, you average over
the whole universe that we can see, it has about
five or six hydrogen atoms worth of energy. And most
of that is not matter or or stuff that you're
familiar with. Most of it is dark energy, and another
big chunk of it is something called dark matter, which
we can talk about it in another episode. Yeah, and
(04:37):
and like dark energy is all around us, right, like
right now, two thirds of the room right now that
I'm in is filled with dark energy. That's right, most
of the energy in the universe and most of the
energy everywhere. And dark energy is not something that's out
there in space. You're exactly right. It's here, it's with you.
It's between your toes. It's getting refrigerator just other dark
matter between my toes. Let's be honest. I don't think
(05:00):
I want to know what he does, whether it's a
cosmic mystery physics or not. Yeah, let's not let's not
get into my toes on this. On this podcast, Daniel
Jorge explained the universe and Jorge's toes. That's right, that's
a winner right there. Um. But yeah, so it's a
huge deal. It's all around this and it's causing the
universe to explode. So that's that's kind of distressing. Yeah.
(05:23):
Not only is it turned out to be most of
the universe, it has huge consequences. Right. The universe is
exploding in every direction, and in some ways dark energy
is causing the universe to explode. Another way to think
about it is that dark energy is our description of
the fact that it is exploding. Like we saw the
universe is exploding. We named that dark energy. It's not
(05:45):
like there's two separate things where oh, here's dark energy,
we know that's the thing. Here's it's cause it's more
like dark energy is the description of the fact that
the universe is exploding and we don't really know why.
It's another name for the explosion of the universe. It's
a fancy tide or our lack of understanding the explosion
in the universe. It's like you don't understand something. You
have the pr version. We could have called it what
(06:07):
is going on with the universe? But dark energy sounds
better w two F energy your t F universe man, Yeah, exactly.
Well let's get into that. So how did how do
we find out about this dark energy that's all around
us and it's causing the universe to explode. Well, it's
one of my favorite stories in science because it's a
(06:29):
story where the answer was a surprise. You know, scientists
went into it asking one question and learning something totally
different about the universe. The question they started with was
what is the history of the universe and what is
the future of the universe? Like what's going to happen eventually? Yeah, exactly,
Like is this whole universe gonna keep going forever? Is
it going to compress into little dot? Do I have
(06:51):
time to like write that novel I've always been wanting
to write. You definitely have time to write that novel.
I have no excuse. Is it another young adult novel?
Because I have enough of those already. It's called dark
youth dark, um dark. So you've got vampires, you've got
where wolves have dark energy beings. Yeah. And so when physicists,
(07:14):
when physicists want to predict the future, where they typically
do is look into the past, try to understand what's
happened so far, and then extrapolate so to figure out
what the future of the universe was. They first looked
into the past and said, what's been going on so far,
and let's see what direction things are going in? Right, Like, um, uh, Like,
(07:34):
how am I doing financially? Do I have more money
now than I used to have money before? And that's
a that will sort of tell me, what might I
might expect in the future if I don't make ill
advised decisions. That's right. Yeah, if your net worth has
been rising, then you expected to keep going. What if
your bank account is dropping every single month, then you
can expect some sort of cataclysmic event in your near future.
And I need to record more podcasts to make more money.
(07:56):
That's right, that's right. And so in the physics world,
we went back to the very beginning of the universe
and said, okay, the universe started with a big bang, right,
and things blew up from there. And the question people
had in their minds was, you know, after the Big Bang,
things flying out from that huge explosion. The question was,
is there enough stuff in the universe for things to
(08:18):
slow down, for the gravity from that stuff to slow
things down, stop them, and then make them fall back in.
So that was one possibility people were considering that the
universe would stop, the expansion, would stop um and then
come back into a big crunch. So like the stuff
that flew out from the Big Bang, and now the
question is like, are they going to keep flying off
(08:39):
or maybe is there enough gravity pulling it all the
stuff together that it's gonna like slow down and then
pull back in, just kind of like how our solar
system forms. Yeah, exactly. Most of the stuff that we
know around us in the in the universe was formed
by gravity. Right, Gravity gathered together rocks and dust and
rubb and hamsters or whatever and coalesce it together. Right.
(09:03):
That's why the Earth is round because that's gravity's work,
tumbling everything towards a smooth surface. And that's how the
Sun is formed, its gravity compressing dust and gas until
it gets hot enough to burn. So gravity is is
very powerful force and and has a lot of time.
Um it's actually one of the weakest forces, but over
cosmic scales and all this time, it has enough power
to pull all this stuff together and compress it into objects.
(09:26):
So people thought, maybe that's going to happen with the
whole universe. Man, Like, maybe the whole universe is gonna
come back together and compress back into a tiny dot.
That would be pretty amazing, like a giant cloud. Does
we all just kind of come get pulled together and
we maybe come back down. That's one possible way that
the future the universe could end up. That's right. Yeah,
(09:48):
So option A was the big crunch. But people didn't know,
like is there enough stuff in the universe? Is there
enough gravity from that stuff to pull everything back together?
Because it could totally have been that the explore ocean
was more powerful essentially than the gravity, and the things
spread out forever. Oh, that could happen, like things that
are like a grenade out in space. It just blows
(10:09):
up so violently that gravity is too weak to pull
everything back together again. That's right, yeah, And that could
that could have been the fate of the universe. It
could be that the universe just keeps expanding, things spread
out and slow down like gravity. Gravity is still slowing
things down, but it doesn't have enough power to stop
it and have it fall back in. And so it
(10:30):
could be that just spreads out forever, getting cooler and
cooler and more distant until something we call the heat
death of the universe. That's when everything is the same temperature. Right,
So physicists were like, are we ever going to be cool?
That was a front question. We'll know in about to
find out if physicists are ever cool. So that's I mean,
(10:52):
that is a very significant question, right, Like we're we
live in this universe. We kind of want to know,
like where is this whole thing headed? Yeah, I wonder
if it's interesting to most people. To me, as a physicist,
I think it's one of the most interesting questions, Like
what is the future of this whole amazing, beautiful experiment
we're living in, you know, is it going to go
on forever? Is it going to tear uself apart? Is
(11:13):
it going to crunch together? Like? To me, that's a
really interesting question, Like do we live at the peak
of it? Or are we like in the after party,
you know what I mean? Like, or are we or
are our great grandchildren going to be like at the
peak of the universe? Yeah? I think I think that's
exactly right. And I think there's an issue of context there, right,
Like as humans, we are always striving to understand the
(11:33):
context of our existence. Why is this important? What's going on?
And one of those questions is like is Earth at
the center of the cosmos? Is Earth even important? And
another question is like that but in time? Right, like
are we living at an important time? What is the
future going to be? Like where do we fit in? Yeah?
Are people in a billion years going to look back
(11:54):
and say, man, I wish I'd lived when Daniel L. Jorge,
we're doing. They're awesome podcasts because those were the days,
many the good old days of the universe. Yeah, this
podcast is peak civilization, right, podcast is peak civilization. So
state tuned state that one. Let's take a quick break. Yeah.
(12:21):
So people were thinking about those two options, right, big
crunch or heat death of the universe. So option A
everything comes crashing back down. Option B things just gonna
float away, yeah, exactly. And so what they wanted to
do was look back in time because you can't actually
see the future, but it's not that hard in physics
to see the past, especially in astronomy. To see the past,
(12:43):
all you have to do is look out into space,
and everything you see in space happened in the past,
just because it takes light time to get here from there.
It's like back in the day when there was no
email or internet, you would get your news from mail letters, right,
And so the further away what did actually happened? At
(13:04):
some point the internet did not exist, Daniel, what what what?
It was all dark dark mail? Ye, dark mail. So yeah,
so like the further away you get a letter the
older that news was, yes, exactly. And some people think, oh,
that's a bummer. I think it's actually pretty cool because
it lets us look into the past, and so the
(13:24):
further out you look, the further in the back in
the past you can see. And the goal is to see,
like how fast is stuff moving away from us, you know,
the expansion of the universe. How fast is stuff moving
away from us now? And how fast was it moving
away from us earlier? So we could understand like, how
is this changing, what is the faith going to be?
Is its slowing down? How fast is it slowing down? Yeah, So,
(13:45):
because like if the fate of the universe was for
it to crunch down, then you would see things kind
of expanding slower now than before. Like before you think
this would be flying out, and now they would be
kind of slowing down, And so we could expect things
to crunch or if we measure things to be moving
at about the same now as as they were before,
(14:05):
then maybe the fate of the universe is just to
kind of keep floating off and getting cooler exactly. And
so that was the question. They were like, let's look
and see how things are changing. How much is it
slowing down? Is slowing down a lot, which means maybe
big crunch are slowing down just a little, which means
maybe heat death. That was the question they asked. But
it's actually fascinating how they did it because it's tricky, right.
(14:26):
In order to know how far back in the past
you're looking, you have to know how far away a
star is. And that's not easy to figure out, right,
because like, if you look at a star, it's um,
if it's dim, you don't know if it's just like
a weak star or a really far away star. It's
just a little point, right, it's hard to tell. You can't, like, um,
tell how far away it is just from how bright
(14:47):
that point is. That's right. You can't tell the difference
between a star that's very bright and far away and
very weak and close up. Um. We have some tricks,
but none of them are really good. Um. The early days,
UM people used to figure out how far away stars
were by seeing how they shifted as their Earth went
around the sun. Because if something was really close, then
you could see it sliding back and forth as the
(15:09):
Earth went around the Sun. That's called the parallax system.
It's like how you triangulate with your eyes, right, like
if yes, if something looks really different when you wink
one eye and you wink the other one, then it
must be pretty close. But if it doesn't change a
lot when you wink between eyes, then uh, it's far away. Yeah,
And so that's the original way people can figure out
how far stuff away is. And then it was like
(15:30):
in the nineteen twenties when Hubble figured out a new
way to look at stuff in the sky and he
found a particular kind of star called a seafid that
rotated and its brightness was connected to how fast it
was rotating, so you could figure out by measuring its
rotation how bright it is, which told you how far
away it was. So he was the first one to
be able to see things that were further away. And
(15:51):
he's actually the one who figured out not just that
the universe is expanding. Before that, people thought, oh, the
universe is just a bunch of stars hanging in space
ace And he figured out two amazing things. One is
the universe is expanding, and the other is that the
universe is more than just our galaxy. And what do
you mean more? He figured out that there were other galaxies.
(16:12):
That's right, before Hubble, we thought there is just our galaxy, Like,
imagine just a single galaxy floating in space. That's what
people thought the universe was. He saw these little smudges
up in the sky that people thought, oh, these should
just dust or clouds or something turns, and that he
proved by measuring the distance to them, that they were
way too far away to be part of our galaxy.
(16:34):
He proved that they were actually other galaxies, and that
those galaxies who were running away from us. It must
have been so mind blowing to be Hubble, you know,
to have this moment of realization, Uh, to understand this
huge context of our of our existence. Yeah, it must
be very humble to be Hubble. You know, I don't
(16:54):
know anything about Hubble, but a lot of these famous
physicists were not the nicest guys. So is that you
are their stories about Hubble. I don't know any of them,
but if I had to guess any random famous physicist
from history, they probably got there by not being the
nicest of a person. Yeah, humble. Anyway, Hubble was able
to see past our galaxy, but cosmically speaking, that's not
(17:17):
far enough to be able to tell because that's just
like the last you know, a little bit of the history.
Then it was in the nineties nineties, people developed a
powerful new technique that let them see much further, so
we could tell how far away things were that were
much much, much further, and that gave us a much
deeper view, further than like the nearest galaxy, yeah, really
far away galaxies. And that's a new kind of star
(17:39):
that we started to understand, called a type one, a supernova. Right,
they call him like the standard candles, right, exactly the
standard candles because they act the same way everywhere in
the universe. And so we can tell we know how
bright they are, so based on how dim they are
or how bright, we can tell how far away they are.
So it was in the nineties people figured this thing out, like, look,
(18:00):
we have a new standard candle that let's look much
deeper into the history of the universe and how we
can answer this question. We can figure out what is
the future of the universe, What is it going to be?
So most stars are you can't really tell, right, some
of them are dim, some of them are far away.
But there are this special type of star. It always
explodes the same way, so that if you see it
(18:21):
m really bright and must be closed, or if you
see it really dim, it must be far away, right,
that's right. And these are not just stars, as you said,
these are supernova, right, they're the end of stars. Right.
That's when stars collapse and implode, followed by huge, enormous
cosmic explosion. And that explosion is super bright, like a
single supernova can outshine the entire galaxy it's in, but
(18:43):
just for a few days. It's like crazily burning up
all of its fuel. It's like a flare. If you
set your house on fire, it's brighter than the whole neighborhood, right,
but not very long. So there were you know, people
figure this out, and then people um sort of split
into two teams. It was a team at Berkeley and
there was a team in Australia, and and they were
racing to discover to get as much data as possible
(19:03):
because supernova are not regular. It's not like you know
when it's going to happen. You have to just scan
the sky and hope to see one. Then it developed
special technology to look through all this telescope data and
try to find new stars that were appearing in the sky,
because that's what a supernova looks like, looks like a
bright new star that appears and then it fades over
a matter of days, and if you capture enough data
about it, then you can learn about its brightness and
(19:25):
figure out how far away it was. And so finally
one of them discovered, like, hey, we have a measurement
for how the universe is expanding, whether it's expanding faster
or slower than before. Yeah, it took a took a
couple of years for them to have enough data, and
it was a scramble and think, I think those people
must have been working twenty hour days in the seven
days a week. Yeah, everyone wanted to be the first
(19:47):
to say like, hey, here's that measurement exactly. Finally they
had this plot of how fast the universe is expanding
as a function of time. And what they discovered is
that the universe is not slowing down a lot or
slowing down a little. So it's not option A nor
option B. That's right. The universe went for secret options.
See secret Ope, you didn't even know it was on
(20:09):
the menu. And that's what we got for dinner, right.
And I love when the universe does that because it's like, oh,
you silly little humans, you have no idea what even
question you're asking? Right? You hadn't even thought about this answer.
That's right, and so secret options see is that the universe,
the expansion of the universe is not slowing down at all.
It's increasing. It's getting faster and faster, it's accelerating. So
the fate of the universe is not that it's going
(20:31):
to crunch down or just float away. Things are like
phraising away from each other, that's right, Faster and faster
every year. Something out there, we don't know what it is.
We can't explain it, we don't understand it at all.
Something out there is pushing all of these other galaxies
away from us, and it's doing it faster and faster
every year. Like if you you only need to know
a little bit of physics to know that accelerating an
(20:53):
entire galaxy hundreds of billions of stars, takes a huge
amount of energy. That's why we were talking earlier about
how two thirds of the energy in the universe, because
it's not a small feat to expand the whole universe
faster every year. Yeah, it's like these galaxies want to
get together because of gravity, either pulling on each other
to get closer, but something is actually pushing them apart.
(21:14):
That's right, and that's the thing we call dark energy.
So they discover this thing, total mind blow, like what
the universe is totally different from what we thought it was.
The fad of the universe is different from what we
possibly imagined. Then there's this second big question, which is
what is it? Right, we found it. We we know
that it's there, we see that it's happening, but we
don't understand it at all. We just observe it. Okay,
(21:36):
but before we get into that, let's take a quick break.
That's what dark energy is. It's like that thing that
is pushing all the galaxies apart. That's right, the totally unexplained,
(21:57):
ununderstood phenomena which is shredding the universe and causing it
to explode and changing its future. That's what dark energy is.
And most people walking in the street have no idea.
It's like the phenomenon of the universe expanding faster and faster.
That's dark energy. That's exactly right, like some kind of
like actual like energy like a photon or some kind
(22:17):
of like thing like we really don't know what it is.
All we know is that it's energy. That's all we know.
Um And we know that it's accelerating the universe. And
it fascinating thing is that it's not just pushing stuff
through space. Right. One way to imagine a galaxy moving
away from you is that it's moving through space away
from you, right, And that's what you imagine probably when
(22:38):
you think of the Big Bang. Everything comes out of
this tiny little ball and expands through space. But dark
energy is doing something else. It's also creating new space
between us and the other galaxies. It's not just pushing
things through space. It's making new empty space. It's not
pushing you and meet apart from each other. It's like
it's creating more uh room, more more land in between
(23:02):
in between us. That's right. It's making the four or
five even longer. Well you know what I mean, like
a like a tectonic plading now, like it comes up
and it creates land and it pushes things apart. That's
kind of what dark energy is doing out in space, Yes,
exactly right, creating new real estate in between you and me.
That's pushing me apart, further apart from you, that's right.
(23:24):
And it's hard to think about what it means new space.
What is that unless you think about space in a
different way spaces and just emptiness or nothingness. As we've
said on this podcast a few times, it's this dynamic
physical thing. And this is one reason we think it's
more than just emptiness, is that it can do this
thing that emptiness can't, which is create more of itself.
It's not nothing. It's like real estate, and there's more
(23:45):
of it being created. That's right. Location, location, location, you know,
it's the most important thing. Right And new space is
being created all the time, and that's what dark energy
is doing, is creating this new space. And we don't
have any explanation for it. You know, people think about
theories of what is dark energy? You could it be this?
Could it be that. One idea that physicists like is
to think about the energy of this empty space, like
(24:06):
maybe space itself has energy. Maybe space can never really
be empty. You know, it's full of the Higgs field,
and it's full of virtual particles, and it's full of
all this little quantum frothing bubblinus. Right Like by its
very nature is just like this has a bubbly personality.
That's right. Space is friendly. It wants to have more
(24:26):
of itself. It's social and so one idea is maybe
dark energy is this energy of empty space. Problem is,
if you sit down to do the calculations, you say,
all right, well, let's calculate how much energy there is
an empty space, and compared to what we see, you
come up with a number that's way off, like not
a little bit off off by ten to the sixty
and let's ten with sixty zeros beyond its error. It's
(24:47):
a pretty big mistake. So the other fascinating thing is
that it hasn't been doing it forever. It turned on
about five billion years ago and started this acceleration. And
again we don't know why. We don't know what turns
it on. We know what we turn it off. You
know what is dark energy? Like you know long walks
on the beach. I don't know. We don't know very
much about it. It wasn't always there from the beginning
(25:09):
of the Big Bang. It's just some somehow five billion
years ago it started pushing things more actively. Yeah, these days,
the most modern picture of cosmology, I think, considers the
Big Bang and dark energy to be sort of connected. Like,
imagine a huge expansion of the universe in the very
first few moments that we called the Big Bang or
these days we call that inflation. And then that stopped
(25:29):
and things just sort of floated through space for a while,
and then five billion years ago it started again. So
one sense you could think of dark energy is like
phase two of the Big Bang. The Big Bang continued,
you know, but just when you thought it was safe
to get into space, here comes the dark energy, Here
comes the Bigger Bang. Yeah, both of them are expansions
of space. We think they're probably related, but we don't
(25:52):
really know how or why you cannot do the same thing.
But who knows why would take a nap for five
billion years? That's right, I'm sorry what you do and
the time are we getting build for that time? Yeah, exactly.
And there are big consequences for the fact that it's
not just pushing things through space but actually creating new space. Yeah,
because we started a podcast asking like what's going to
(26:13):
happen to the universe at the end, and so it
has you say, it has big consequences for like what's
going to happen to the universe. Yeah, because it's creating
new space, which means it's effectively evading the speed limit
of the universe, the speed of light. Right, nothing in
the universe can move through space faster than the speed
of light. All right, that's a hard and fast limit.
(26:34):
And so these galaxies can't move through space away from
us faster than the speed of light. But there's no
limit on how fast you can create new space, the
new spaces being created between us and these other galaxies
faster than light can go through it. It's like if
I was trying to get to you done at Irvine U,
(26:54):
and I can only go seventy miles per hour in
the highway. You know, nominally you'd be lucky to do that.
Let's say it's like two am and have your private
Let's say I was using the carpool lane, all right,
and uh but yeah, but like let's say that a
new land was being created between you and me faster
than seventy miles per hour, I would never get to you.
(27:15):
That's right. If they're just laying new road and you're
faster than you're driving through it, you'll never get down
to Irvine, exactly right. And that's the situation. Those photons
that are leaving those galaxies now will never reach us
because the space in between us is growing faster and
the photons go through it right at some point they'll
stop reaching us, right like um like, we'll see them,
and then suddenly they'll blink out of existence. Exactly things
(27:39):
that used to be in our observable universe, things that
we see now because light has had a chance to
get through the universe to us, will no longer be
observable because dark energy is pushing them out of this
sphere of the observable universe. All the stuff we can
see because light has had a chance to get to us.
So galaxies in the sky are disappearing right now, right now,
(28:00):
quick rush outside of Things that are on the edge
of our observable universe are disappearing because dark energy is
pushing them beyond the bounds of things we can see.
So the nice guy is getting darker and darker. So
like if you hit the fast forward button on a
camera point and at the sky, you would see like
stars just snuff out, just like yeah, you would see
(28:20):
galaxies snuff out of their clusters of stars. And so
in that scenario, all these galaxies snuff out of the sky,
right they get pushed out beyond our observable horizon and
they disappear, And then we're left with the single galaxy
in the universe, just like people before Hubble thought, right then,
and imagine astronomers in the future, right after all these
(28:41):
galaxies are pushed out, They're gonna think we're the only
there's only one galaxy in the entire universe. Yeah, because
they would be the only thing they could see. Right,
It's amazing to imagine, how to to try to think
about how could they learn about the universe if all
they could see was their galaxy? How could they even
possibly know? Right? They would have no how big it
actually is. Yeah, they would have no idea what's beyond
(29:03):
their observa universe. And that's really humbling because it reminds
you of how little we know. Right, we're, after all,
fourteen billion years into the history of the universe. There
could be fascinating clues about the way the universe works
and what it's made out of that have already been
pushed beyond our sky that we cannot see and we
will never see. Right, So what's lost in the night sky? Well,
(29:26):
we have no idea, right there kinds of galaxies? Who
knows that we can't see anymore? Yeah, exactly, And continue
even further, and remember, dark energy is not just out
there in space. It's here, it's with me, it's with you.
It's literally pushing me and you apart right now. The
reason we don't see it is because we have bonds
that are holding us together, right like their dark energy
(29:47):
is trying to create new space between the molecules in
my hand, But the molecules are bound together tightly enough
to resist that. But if dark energy continues, it might
eventually shred the Milky Way, right, take our own galaxy
and tossed the stars out into space. Eventually we might
just be a solar system floating in the inky blackness
of space, seeing nothing. Right, that's one potential future, thinking
(30:09):
that we're the only star in the entire creation, the
entire universe. That's right, that's right, that's one real possibility. Now, again,
we don't know what dark energy is gonna do. We
don't know if it's strong enough to do that. We
don't know if it's gonna stop. We don't know if
something else is going to happen. We really have no idea.
But it's it's amazing to me that it's only this
knowledge is only twenty years old, twenty years ago before
(30:31):
we discover the stuff we didn't know that the universe
was accelerating, and we didn't know that most of the
universe was this thing called dark energy. Like, think about
how recent that discovery is. That to me is inspiring
because it makes me hope that we have more mind
blowing discoveries ahead, you know, more of these moments of
like what the universe is totally different from what I imagined.
(30:52):
That's what I live for in physics. Well, you know,
this is when it give me. Think. This past weekend,
I was camping with my kids and my family and
it was a beautiful night. You could see all the stars.
And I pointed out to my daughter, was like, look
at all the stars. And I was pointing out some
(31:13):
of the constellations and stuff, and she's like wow. And
I talked pointed out the Big Dipper and she's like,
that's the Big Dipper. And she proceeded to tell me
this whole complicated story about the Big Dipper that she
read in this book she had at school that she's
read like a million times, but for the first time
she had actually seen the stars, She had actually seen
(31:33):
the Big Dipper. What a fun moment for her. Yeah,
to make to make these things real yeah, yeah, and
so yeah, so I think that's a big lesson. You know,
go out there, look at the stars before they go away.
And this is not abstract. I mean, this is our
universe we're actually talking about. And you can go along
and live your life and worry about traffic and paying
the next bill in your own financial big bang. But
(31:54):
these things are our context, right, This is the universe
we live in that we're definitely trying to discover before
it blow was itself up. It's changing all the time,
so go out there and experience it. Absolutely. If you
still have a question after listening to all these explanations,
(32:14):
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.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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