NARRATOR: Everything
that we know-- time, space, and matter-- are doomed-- Any life that depends on
sunlight will rapidly go extinct as there are fewer
sources of life-providing energy. NARRATOR: --whether by the
Armageddon of an inferno or in the grip of
an icy executioner-- The universe itself will
freeze to death and all life with it. [dramatic music] NARRATOR: --or even by an unseen
force from the depths of space. And literally every particle,
every atom, every structure in the universe would explode. [booms] NARRATOR: Beware. Here comes the
cosmic apocalypse. The year is 20 billion AD,
and there is something gravely wrong with the universe. Ever since its explosive
birth, the universe has been expanding,
growing ceaselessly into an infinite unknown. However, on this day
in the distant future, looking up at the sky,
galaxies from all directions have reversed course and are
speeding towards our own Milky Way. The catastrophic
implication is fatal-- the universe is collapsing,
and everything we know will cease to be. Life is doomed. When we look at
other galaxies, we'll see them coming in toward
us on a collision course. All of a sudden, we
see stars coming at us from all directions. ALEX: All the galaxies
will start colliding, and the stars within them
will get crunched together. The stars will collide. The planets will collide. The planets will get
swallowed by stars. MICHIO: All of a sudden,
temperatures begin to rise. All of a sudden,
the oceans boil. All of a sudden, the
mountains will melt. Oh, man. It's going to be chaos. It's going to be pandemonium. And the universe itself
begins to reach blistering temperatures. All intelligent life must
die because we'll all be incinerated. NARRATOR: The universe ends with
a bang in a cosmic fireball. This is the vision
of the apocalypse, according to a theory
known as the Big Crunch. What's happening with
the Big Crunch scenario is that all of the
matter in the universe and all of the energy, the
galaxies, the stars in them are all moving back
towards each other, and the universe is shrinking. Things are getting closer
and closer together. NARRATOR: Our universe right
now, on the other hand, is expanding. Each day there is
more and more space as galaxies get further
and further apart. The opposite happens
during a Big Crunch. The space between
things is shrinking. And that's rather like filling
up this hallway with people. When there are more and more
people, the space between them then is getting
smaller and smaller. They bump into each other. They're trying to dodge
out of each other's way. And so everything is heating
up and getting more and more energetic as more and
more things happen in this small space. Exactly the same thing would
happen in the Big Crunch scenario where various particles
that make everything up are bumping into each
other more frequently. The galaxies and the stars,
as they're getting closer to each other, start
distorting each other. And so the whole
thing's beginning to heat up, just like a
crowded room would heat up. The process continues with the
temperature of the universe getting higher and
higher to the point that the atoms themselves
begin to fall apart. NARRATOR: Finally,
our vast universe collapses into a
microscopic point. We'll end up with this
soup of matter which is made of fundamental
particles, which are milling around at high energy,
high temperature. NARRATOR: Life as we
know it has no escape. [booms] However, the universe
may not ultimately ignite into an
all-consuming hellfire. There are two basic paradigms
for the end of the world. First, the universe is
going to end in fire. [crowd screams] [fire crackles] That's the Christian
theory of Armageddon-- fire and brimstone
and the second coming. But the Norse also
had their legends. They had the legend of
Ragnarok, twilight of the gods, where there would be this
monstrous snowstorm that would engulf the entire universe. There would be this
great battle in heaven, and even Odin and even Thor and
all the great gods would slowly die one by one, and we would
all die in a great freeze when even the gods
themselves are frozen. NARRATOR: Whereas the Big
Crunch fits the Christian vision of the end of days, science also
has a different theory that it may instead all end in ice. Ultimately, it depends
on whether the momentum of the expansion of the universe
can overcome the collapsing attraction of gravity. Imagine that the moment of
contact between bat and ball is the initial explosion
of the Big Bang. CLIFFORD: Everything's
being thrown outward. And the issue is, will it
re-collapse upon itself or will it continue to expand? And those two
possibilities are very similar to what happens when
you launch a ball into the air. [thwacks] I launch it upwards, and
if gravity's strong enough compared to how much energy I
put into that initial launch, it will pull it back down. And that's like the universe
expanding out for a while and then crunching back in. NARRATOR: But the Big
Crunch doesn't have to be the end of everything. If the universe collapses,
what might subsequently follow is another Big Bang,
another expansion event. And that might expand for a
while and then re-collapse. So you can imagine the
possibility that actually the universe is just cyclic. And so it expands
and then contracts. NARRATOR: Each bounce
is another Big Bang. But what if there isn't
enough gravity to reign in the universe? CLIFFORD: I launch it
upwards with enough energy that it completely escapes. There's not enough
mass in the universe to make it re-collapse, and
so it continues to expand. NARRATOR: Eventually,
though this expansion ought to slow, shockingly, scientific
observations reveal something completely different. It's getting faster. MICHIO: The universe seems to
be careening out of control. This expansion is accelerating. It's kicking in once again. We are undergoing an
inflationary expansion. CLIFFORD: So the
universe we now know is expanding with this
extra acceleration that is beyond what you
would have thought was just due to the
initial explosion. [gloomy music] Not only does the
ball escape, but it's as though a little rocket
engine was on the ball, and it accelerates away
from the Earth even faster. This is a possibility that
was somewhat unexpected. NARRATOR: The volume of
space in the universe seems destined to
increase forever. What this means is that
distant galaxies are going to go zooming away from
us and will eventually become invisible because
they'll be too far away to see. NARRATOR: And without
seeing galaxies rushing away from each other,
future civilizations will lose all sense of history. They won't know that
there was ever a Big Bang. So you will think
that the only structure within the universe is
the Milky Way galaxy and that the rest of the
universe is effectively empty, devoid of stars. NARRATOR: Another
scientific theory proposes that this expansion
will balloon even faster. If this does happen, a
violent end awaits our cosmos. Suppose the amount of
repulsive energy increases with time per unit volume. It'll eventually
grow strong enough to cause clusters of
galaxies to get ripped apart, and then galaxies themselves
will get ripped apart. The stars will start flying
away from one another, no longer held
together by gravity. And then planetary systems
like our solar system will get ripped apart. And then stars and planets
will get ripped apart. And then humans will
get ripped apart. And then the very atoms
of which we are made will get ripped apart. That's called the
Big Rip, and it's a really scary possibility. But don't worry,
most of us don't think it's going to happen. NARRATOR: But even if
the rate of expansion never reaches this
tipping point, the future of our universe
still isn't promising. ALEX: Its temperature decreases. It's getting colder and
colder and darker and darker because the feeble
light emitted by stars is going into a
progressively larger volume. So the universe is going to get
really cold and really dark, basically a pretty gloomy place. The universe
itself we now believe will die in ice
rather than fire. We think the universe will
die in a great freeze, just like the Norse legends foretell,
rather than this Armageddon of a Big Crunch. NARRATOR: If the
universe continues on its present course, we're
destined for a cosmic Ice Age, where sunlight
itself goes extinct. [somber music] [whooshes] By the year 100 trillion
AD, the last remnants of human civilization
may be forced to settle here in this distant
dark corner of our galaxy. They'll be huddled around the
last burning star in the sky. But sadly, it too will soon die. Our Milky Way, so named
for its shimmering band of sparkling stars,
will be unrecognizable. Faint glowing embers
of dark stellar husks will be all that remain of
what was once a brilliant night vision. What happened to
all of the stars? How did we arrive at
such a dismal scenario? [gloomy music] Science decrees that as our
universe expands and ages, it will cool. Inevitably, the
future for life as we know it will grow
ever more hostile. MICHIO: We are headed for a
time when one day the universe itself will freeze to
death and all life with it. And that's a law. When we scientists look at
the evolution of the universe, some critics say, that's crazy. We can barely predict
tomorrow's headlines, and hear you are
predicting what's going to be happening billions
and billions of years from now. How do you do it? NARRATOR: Among the tools
available to scientists pondering the future
are the venerable laws of thermodynamics. The first law says that
total matter and energy are conserved. In other words, you can't
get something for nothing. There's no free lunch. So it turns out that the total
amount of matter and energy in a system can be neither
created nor destroyed. The matter and energy
can change forms, and they can turn
into one another, but the total remains the same. So for example, in this
rolled-up newspaper, there's a lot of energy
stored in the chemical bonds of the paper. But if I ignite the paper,
I can activate those bonds, and I can start breaking them. And that releases energy in
the form of light and heat, which you can see and feel. The total energy content
is still the same, but it's being dissipated
out into space. And a lot of particulate
matter goes off, as well, and smoke goes off. But if I were to
add up all the smoke and the particulate matter and
all the energy that's given off and everything total, I would
get exactly the same amount of mass and energy total
as I had to begin with. They simply changed forms. NARRATOR: If the total
amount of mass and energy remained constant, this seems to
imply the universe will always have energy and
should last forever. But the second law
of thermodynamics crushes this notion. The second law
of thermodynamics is the most curious of all. It says that total
amount of disorder, or entropy, always
increases in the universe. In other words, things rust. Things decay. Everything gets old and
eventually falls apart and rots. In some sense, the second law
is a death warrant, a death warrant for the universe. Second law says, all
things must pass. NARRATOR: The
ever-present supply of energy in the universe
inevitably becomes more dispersed, more
chaotic, and more unusable. Each star burning in the sky,
just like each brick head of this charcoal, must
one day face its fate. [fire crackles] This piece of
charcoal is fuel. It has a lot of
energy concentrated into this small,
little packet here. The energy goes from being
in the chemical bonds of the charcoal briquette
to being liberated in the form of heat and light. Now, a star does
a similar thing. It doesn't burn in
a chemical sense. Instead, in a star,
it's nuclear energy. The nuclei of atoms are
being forced together, fusing them, creating new
nuclei and, in the process, transforming some of that
matter, some of that mass, into the radiated energy
that we see and we feel. And the same process is going
on in all the active stars in the universe. Now, as this
charcoal is burning, the fuel is getting used up. And you can actually see that
it's turning into a gray color. It's turning into ashes. In a similar way, stars
use up their fuel. They fuse hydrogen into helium. And so, with time, there's
less and less hydrogen to fuse. And the ashes have
less energy content and thus are either harder to
burn or release less energy during the burning process. NARRATOR: This is the
eventual fate of our own sun. As it ages, it bloats and heats. ALEX: The Earth will
be fried to a crisp. Oceans will boil away. All plants and animals will die. Rocks will start to vaporizing
because the sun will be producing so much
light, so much energy. That'll be a pretty gruesome
death for the Earth. GREGORY: All through
the universe, stars that are like the sun are going to
be facing the same challenges that our own star will face. They're running out of fuel. They're swelling up. And they're causing problems
for the planets that orbit them. So it's not hard to imagine that
there are many locations where life has evolved and flourished
and is now being extinguished. NARRATOR: Just as each star
suffers the effects of entropy, so too will the rest
of the universe. But stars naturally increase
the entropy of the universe by giving off light and heat,
just like this fire of burning charcoal naturally increases
the entropy of the universe. Right now, we're kind of in
a steady period in the universe where stars are born,
live out their lives, die, give some of that gas
back to the next generation, then you have another
generation of stars. ALEX: But that rate
of star formation is gradually
decreasing with time. And as stars use up
their fuel and burn out, there aren't enough new stars
being formed to replace them. NEIL: But the moment we run
out of gas to make new stars, means for every dead star
in the roles, in the ranks, there's not a star
to replace it. And so that's a bad situation
to be in the day that happens. NARRATOR: So effectively,
galaxies, giant collections of stars, are growing
progressively dimmer with time on average. And eventually,
when the universe is something like 100
trillion years old, there will be essentially
no stars still shining. The universe will be
cold and dark, indeed. NEIL: Any life that
depends on sunlight will rapidly go extinct as
the universe continues to age as there are fewer,
fewer sources of life-providing
energy from a host star. NARRATOR: You might think the
most massive stars, the ones with the most fuel,
will last the longest. In reality, the more
fuel a star carries, the faster it burns through it. The final rays of sunlight
left in the universe will come from stars
known as red dwarfs. These miniature stars, 10 times
less massive than our own sun, burn thousands of
degrees cooler. Red dwarf stars and much
more miserly with their fuel consumption. And so even though they have
less fuel to begin with, they last much, much longer
than our sun will last. NARRATOR: A typical red dwarf
can live for as long as 14 trillion years. That's 1,000 times longer
than the current age of our universe. Eventually, though, even
these stingy little suns will begin to die off. So when our Milky Way galaxy
is tens of trillions of years old and there's only a
few red dwarfs remaining, you might imagine that any
surviving civilizations will realize that the end
is nigh, and they will start crowding around
these few sources of energy, trying to scrape
out an existence. NARRATOR: Red dwarfs
could be oases of life in the vast,
inhospitable desert of the universe. But for planet to receive
as much heat and energy from its red dwarf host, as
our Earth does from the sun, it would need to orbit so
closely that one full year would last just six Earth days. The sky would be much
more sort of whitish red than our blue skies here
on Earth because the red dwarf puts out so little blue light. You wouldn't be able to have
the kind of nice blue skies that we have here now. NARRATOR: However, nothing
left in the universe would be hotter or brighter. So there will be a time in
our galaxy when there's just a few red dwarfs still glowing
and maybe just, then, three and two and one
as they blink out. And gosh, when there's one
red dwarf left and suppose I'm on the planet circling
it, I'll think, man oh man, what a lonely place
the universe is. What a depressing
future it holds. NARRATOR: What happens after
the last red dwarf blinks out of existence? [energetic music] Life in the 21st
century on Earth thrives within a universe
that has existed for about 14 billion years since the
spark of the Big Bang. But that's no time at all in
the grand scheme of the cosmos. If the universe is
comparable to a human lifespan, we are still in the
infancy of the universe. NARRATOR: Getting a grasp of the
time that has already elapsed and the time span still to
come can boggle the mind. To gain a perspective
of the vast time scales of the universe, let's
compress the roughly 14 billion year history of the universe
into one normal calendar year. But we'll call this
a cosmic calendar. So the Big Bang occurred
on New Year's, January 1st. On that scale, our
Milky Way galaxy formed near the end of January. And our solar system formed
around the beginning of August or so, about 2/3 of the
way through the year. Life formed some time
a little bit later in, August but humans formed
less than a day ago. So on December 31st some
time, humans finally arose. NARRATOR: We can also
look into the future on the same cosmic
calendar timescale. ALEX: Near the end of
January of this coming year, our Earth will become
quite inhospitable. By around May or so,
our sun will have died. But there are some other
stars, the low mass stars, which will live for much,
much longer, up to 10,000 of these cosmic years. NARRATOR: That's 10,000 times
longer than the entire history of the universe before these
final longest living red dwarf stars die off. But then what happens? When we talk about the
extremely distant future, we're talking about immense
spans of time, time measured in quadrillions of years
and septillions of years. And it becomes so
overwhelming that we need to evolve another concept
to really deal with it. So we came up with the idea
of cosmological decades. A cosmological
decade, each decade is 10 times longer than all
the time that happened prior to the start of the decade. And one way to
think about this is like a staircase, not
an ordinary staircase like this one, but one in which
each step is 10 times higher than the step before. So you can imagine
the staircase going up and up and up to higher and
higher cosmological decades. Right now, we're living in
the 10th cosmological decade. NARRATOR: On this scale,
the 10th cosmological decade is 10 times longer than
the previous nine decades combined that have passed
since the Big Bang. GREGORY: The hallmark of
the 10th cosmological decade is the fact that stars are
burning brightly in the night sky and also that the planets
are beginning to develop life and intelligence
on their surfaces. Another interesting hallmark
of the 10th cosmological decade is the beginning of the
acceleration of the expansion of the universe. NARRATOR: As our cosmological
decade continues, all of the other galaxies
disappear from view, and stars begin to die off
without being replaced. GREGORY: During the
latter part of this era, there will always be
about 50 stars shining in the galaxy at any one time. And that would be the last sort
of gasp of the kind of world, the kind of planets,
the kind of environments that are familiar to us. NARRATOR: As we move through the
succeeding cosmological decades and after the last star dies,
we enter a new alien age. So up here, we're in
the cosmological decade 20 through 30. And if we look out
at the night sky, it's absolutely, utterly,
completely black. But if we're able to
look in light that's far too red for the
human eye to see, then we would actually see
that the sky is speckled with dead stars. [gloomy music] This is the Degenerate Era. NARRATOR: In the Degenerate
Era, the most massive dead stars have collapsed
into black holes. But punctuating the
total blackness of space, the leftover ashes
of once bright stars are still ebbing energy. These ashes are
called a white dwarf. Now, they're really weird
because you've got something like half the mass of our
sun, roughly 160,000 times the mass of our Earth
compressed into a volume just the size of the Earth. So it's very dense stuff. It's weird ashes,
that's for sure. So it'll be like the
dying ember after a fire. It'll be generating no
new energy of its own through nuclear fusion. NARRATOR: But as the dying
embers of a white dwarf cool, they still emit many
megawatts of power. GREGORY: But that is
vastly, billions, trillions of times less energy than the
sun is producing right now. [alarm blares] And so if we think we
have an energy crisis now, the energy crisis in
the Degenerate Era will be far more severe
and far more profound. [dramatic music] NARRATOR: Even so,
the energy emanating from these ancient star
remnants is still greater than that consumed today
by all human civilization. GREGORY: If we were to
imagine that somehow a human civilization were to
persist into the Degenerate Era, they might be
tapping the energy that's emerging from the white dwarf. NARRATOR: However,
humans wouldn't be able to establish an
energy-gathering outpost on its surface, such as an
oil rig anchored to the ocean floor. Surface gravity is
incredibly strong. You would basically
be crushed if you tried to stand on the
surface of a white dwarf. NARRATOR: To survive,
future civilizations would need to establish
an orbiting colony. GREGORY: They would probably
tap that energy that's coming from the white dwarf by
having some sort of absorbing panels that are also in
orbit around the white dwarf. So the energy that's
emanating up from below would be captured
and trapped and used. Still, light in this
white dwarf orbiting future would have to be
generated artificially. GREGORY: There's no
stars shining in the sky. There's no moonlight. There's no sunlight. You're simply orbiting
gigantic dead black mass. NARRATOR: Unfortunately,
dead black masses will make up the
bulk of galaxies during the Degenerate Era. GREGORY: So as we go
into the Degenerate Era, we'll have roughly 100 billion
dead stars orbiting each other in a giant elliptical
configuration. Occasionally, they'll
interact with one another, and one will get flung
out of the galaxy, causing the galaxy to lose mass. The galaxy, in a sense, will
evaporate slowly with time as these things are flung out. NARRATOR: White dwarfs and
remaining galactic material fall prey to black holes. ALEX: So gradually,
with time, what will happen is the galaxy will
have fewer and fewer objects in it, and a greater and
greater fraction of them will be black holes. NARRATOR: And whatever
isn't seized by the millions of black holes roaming the
universe begins to decay with old age. And this is another example
of the general process by which the total amount of randomness
increases in the universe. The second law of thermodynamics
is once again at work. [birds chirp] And all the
structures, all the stars are basically
evaporating into nothing. So by about cosmological decade
40, most of the stuff that's been built-- the planets and the
stars-- are all gone. And the Degenerate Era, which
is stretched for huge amounts of time, is coming to an end. NARRATOR: With nothing
left in their way, black holes stand poised
to rule the universe. [gloomy music] This may be the grim
future of the cosmos. The planets decay and dissolve. Dark galactic remnants scatter
across a bloated universe. And even light is just
a faint, distant memory. As we continue through the
vast stretches of time measured in cosmological decades,
massive black holes survive as the only recognizable
features of our once brilliant night sky. GREGORY: We're up to
about cosmological decade 60 something. And when you look
out at the night sky, it's incredibly cold. It's incredibly black. And there's only the faintest
crackle of radio waves and gravitational
radiation echoing through the empty skies. This is the black hole era. NARRATOR: The continuous
expansion of the universe has taken its toll. The unimaginable cold saps
energy and constricts movement. Time itself seems
to lose meaning. In the midst of
the Black Hole Era, even the Degenerate Era looks
like the first sliver of time after the Big Bang. NARRATOR: Does life have a
chance in this environment? GREGORY: Humans won't
exist at that time because protons won't exist. But it's possible to imagine
some kind of entity which is living in an
extraordinarily slow rate. NARRATOR: If it
lives slowly enough, perhaps strange
life could emerge. A thought would take
trillions of years. It may take a
trillion years for you to decide what to have for lunch
because everything is so slow. Everything is near
absolute zero. [water splashes] [bird chirps] NARRATOR: The creeping time
scale of the Black Hole Era can be compared to the
growth of vegetation. From a human perspective
involving minutes, hours, and days, plant life
can seem frozen in time. GREGORY: Absolutely nothing
seems to be happening. It appears to be completely
dead, completely static. [clock ticks] But if we speed up the clock,
then we see the activity. The plant grows. The plant moves its leaves and
responds to where the sun is. The plant is
continuously in motion. It's continuously doing things. But that whole
scale of existence is on a time frame that's longer
than what our experience is used to dealing with. [somber music] NARRATOR: The real action
in the Black Hole Era occurs when two
black holes meet. [dramatic music] Although invisible
to human eyes, a collision between
these two beasts sends a shudder
through space time. This event can be imagined in a
sheet of perfectly still, calm water. GREGORY: It's a bit
like suddenly dropping a gigantic rock [splashes] into
that calm water, sending out a huge series of ripples. And you have a lot of action
for a little bit of time, but then that dissipates. The ripples die away. And you're back to that smooth,
glass-like sheet of water. NARRATOR: But even for these
kings of the Black Hole Era, time is running out. And you might think,
oh, they'll last forever. But even they don't last forever
because they evaporate very, very slowly with time. NARRATOR: Black holes
in today's universe grow larger as they gobble
up surrounding matter. But eventually,
far in the future, there will be so little material
to swallow that the evaporation rate will start dominating over
the rate at which they swallow material from
their surroundings. So the evaporation rate proceeds
more quickly when the universe is very, very old. NARRATOR: An
evaporating black hole does not go out with a whimper
like the planets do when they die, but, rather, with a bang. [booms] That's because it behaves
counterintuitively as it runs out of fuel. GREGORY: There's basically two
strategies that you can adopt. One is to sort of ease
up on the gas pedal and try to conserve your
energy and basically try to roll into the next
gas station on fumes. The other strategy is to
become impatient and floor the accelerator and try to
drive to the gas station as fast as you can in hopes
of getting to the gas station before your gas runs out. And the black holes
are definitely taking the second route. NARRATOR: Unlike a car, when
a black hole finally runs out of fuel, it explodes. [booms] And then in the last
second of the black hole, when you're releasing megatons
and megatons' worth of TNT equivalent, a huge variety of
particles that haven't been seen for many cosmological
decades comes spewing into existence and kind
of flicker away in a last fireworks-like burst after
the black hole is gone. So after about a
googol years or so and the most
supermassive black holes have evaporated away,
what you've got left is a vast universe that is
really almost entirely empty. NARRATOR: Next, the universe
enters the Dark Era. Now we're out beyond
cosmological decade 100. We're in the middle
of the Dark Era. In the Dark Era,
everything that we have now that is familiar to us is gone. You know that expression,
"Angels fear to tread?" That's the Dark Era. The Dark Era you never want
to go to because everything has crumbled, not just the sands
and monuments, the man's folly, but even the atoms themselves
have begun to crumble. Even black holes are not
possible in the Dark Era. NARRATOR: If the universe
continues to expand forever, it may be that only a cosmic
mush of random particles remains. But a few surprises may yet
rise out of these ashes. If, in the distant future,
chaos does rule over order, our once glowing
hot universe will descend into a chilling
galactic Ice Age. [wind whistles] But it may still harbor
some potential, at least according to quantum theory,
which examines physics at its most primal level. CLIFFORD: In quantum
physics, even the vacuum of space, that
thing that we think of as being empty with nothing
in it, is not actually empty. Quantum physics
allows for everything to happen with some probability. [upbeat music] NARRATOR: In other
words, the universe is playing a risky
game of chance, and quantum theory
seeks to explain the behavior of particles
in a universe where anything is possible. It's as if the universe were
a card dealer, continuously shuffling a deck containing
the very building blocks of our reality. So if you have a bunch of
particles in a quantum field theory, what happens is
they're going to just rearrange themselves over and over and
over again in what looks to us like a random set
of fluctuations. [gloomy music] NARRATOR: Quantum theory
can't predict the result of a particle shuffle, but
it can reveal the probability of each outcome. SEAN: If you have something
that happens forever, an infinite number of times,
even very, very unlikely things will eventually happen. NARRATOR: Ordinarily when
shuffling a deck of cards, the result is a random sequence. Likewise, particles,
churning on a quantum level, don't usually create
anything orderly. However, with enough time, any
kind of quantum fluctuation can form, even one
that seems impossible. SEAN: If you're in a universe
that lasts forever, if you have a car dealer that is shuffling
cards forever and ever, even unlikely events like
that will occasionally happen. [uplifting music] NARRATOR: One of these
unique and improbable random fluctuations can change
the fabric of space itself. Empty space is kind of
like water in the sense that it can appear
in different phases. It could be hot and be vapor. It could be solid,
like an ice cube. Or it could be liquid. The space around us right now
is in a certain physical state. But a phase
transition can happen where that physical state
changes into something else. NARRATOR: The wrong kind
of random fluctuation can induce a devastating
phase transition. The way that would occur
is that some region of space, some point, would witness
the formation of a bubble. And that bubble would
spread throughout the space around it, just like this ink
would spread through the glass. NARRATOR: Just as the
ink changes the nature of the water, so could a
phase transition transform the nature of the cosmos. SEAN: The laws of physics
would be different in the wake of this bubble passing. The masses of different
particles would change. The charge of different
particles would change. All of chemistry as we know it
would be completely different after this phase
transition occurred. What that means is
that suddenly there are new ways to arrange all the
particles that we're made of. And it's sort of like
everything in the universe becomes an atomic bomb. It would just rearrange
itself, releasing energy, and literally every particle,
every atom, every structure in the universe would explode. [rumbling] So no complicated structure
can possibly survive that sort of transition. What would be left is
just a mess, nothing but a gas of particles bumping
randomly into each other. NARRATOR: But a random
quantum fluctuation can also spark a bubble of hope. Some theoretical
physicists suggest that some of these
quantum fluctuations actually can give rise to almost
detached portions of space, dimensions that
sort of branch off from ours into a new universe. [dramatic music] NARRATOR: Perhaps a
quantum fluctuation sparked the Big Bang and gave
rise to our own universe. So you can imagine that
a universe like ours, even though it's 10
billion light years across, is actually a baby universe
that arose by pinching off from some much bigger universe. NARRATOR: We can picture
the birth of a baby universe with this bottle, representing
an old dying chaotic universe. My breath is like
quantum fluctuations, creating new universes
that look like bubbles. And each one of those bubbles
is a separate universe all of its own. There is the possibility that
there are other universes out there, perhaps budded
off from our universe, and they may have
their own fate, either eternal expansion
or ultimate re-collapse. NARRATOR: If other
universes exist, then perhaps future
civilizations may not face an
irrevocable death sentence. So I would suspect that
trillions, quadrillions of years from now, when the
universe gets really cold and the universe is near death,
intelligent beings will be so powerful then that they
may be tempted to assemble enough energy at one point to
open up bubbles, little soap bubbles, gateways
to another universe where it's a lot of warmer, and
they can start all over again. NARRATOR: Whether or not
our descendants muster the technology to
leave this universe, there's no avoiding the
fact that, like all things, it will come to an end. While science wrestles with
questions of how the universe will die, humanity is left to do
the same with how it will live. ALEX: Our lives are important. I'm important.
You're important. Your loved ones are important. Your friends are important. And we need to make the
most of our existence during the fleeting
time that we have here. This is your life. This is my life. We make the most
of it, regardless of the fate of the universe.
