NARRATOR: Earth, the only
life-sustaining planet in our solar system. Yet, throughout its
history, our world has been a planetary
punching bag. Anything that crosses
the orbit of Earth could one day slam
into the Earth. NARRATOR: At this very moment,
violent celestial heavyweights roam the universe and
threaten to deal The earth a knockout blow. The power would be like
setting off the whole world's armament at one time. It would be like standing
next to Hiroshima, all over the world. Everything in us
would get ripped apart and your body would
fly off to infinity. NARRATOR: But some scientists
and former astronauts are not willing to go
down without a fight. They're racing to track
down these cosmic killers before they trigger Armageddon. [music playing] Earth shimmers like a sapphire
jewel in our solar system. We go about our days, unaware
that, in the far reaches of space, trouble could
be headed our way. BRITT: Our solar system is a
lot like an amusement park. The Earth and most
of the other objects carve predictable
paths around the sun. Normally, everything
is calm and smooth. But at times, things
get chaotic and violent. [music playing] Earth can be slammed
by space rocks, zapped by deadly space
weather, jolted, jostled, and threatened by
the objects, energy, and forces of the cosmos. NARRATOR: The Earth is on a
cosmic thrill ride, one that often involves extreme danger. ROBERT ROY BRITT: When
you're moving fast and on a predetermined path,
you hope nothing crosses it because there's
nothing you can do. Nicaraguan border
is right down along-- NARRATOR: Former astronaut Rusty
Schweickart knows firsthand how dangerous celestial
objects can be. In 1969, he piloted
the lunar module during the Apollo 9 mission. Now, Schweickart is ready
for more than a cruise through the cosmos. He's sounding alarms
about the dangers of one particular asteroid
named Apophis, which got too close for comfort in 2004. RUSSELL L. SCHWEICKART:
It immediately got everybody's attention
because the probability of impact was quite high. In fact, it was higher
than any impact probability that we had ever seen
up until that time. NARRATOR: And Schweickart has
a terrifying real-life example of just how damaging an impact
from an asteroid even smaller than Apophis could be. June 30, 1908, 7:15 AM. An object half the size
of a football field plunged down from space at
around 34,000 miles per hour and produced a stream
of fiery gas behind it. Within minutes, the fireball
entered our atmosphere and violently exploded above
Siberia's Tunguska Forest. [explosion] It became the largest
explosion on Earth in modern human history. The blast sparked heat waves
which torched 80 million trees in an area over half the
size of Rhode Island. Fortunately, no one died as a
direct result of the explosion because it was in a
thinly populated area. If that asteroid hit
just a few hours later, it would not have hit Siberia. It would have hit over Europe. And if that had exploded mid-air
over any of the major cities of Europe, a million people
would have died like that. NARRATOR: For the
last hundred years, the Tunguska explosion has
been shrouded in controversy. Today, many scientists agree
an asteroid caused the blast. Incredibly, it never
even impacted the ground. Rather, it exploded five miles
above Siberia's frozen ground. ROBERT ROY BRITT: A small,
stony asteroid can't survive the plunge through
Earth's atmosphere, and when it smacks into
the lower atmosphere doing about 50,000 miles an hour,
it's like an egg smashing onto concrete. [explosion] NARRATOR: The blast over Siberia
released energy equivalent to 15 megatons of TNT, 1,000
times greater than Hiroshima. If this were to happen
over a large city, it would annihilate it. [explosions] Scientists call these
trespassers Near-Earth Objects, or NEOs. They're asteroids
and comets which are leftovers from the
formation of the planets. Comets move in the Oort cloud
in the Kuiper Belt, which is beyond the planet Neptune. Asteroids travel in a band
between Jupiter and Mars, but their orbital trip
isn't always routine. ROBERT ROY BRITT: Most of the
asteroids orbit in a neat belt between Mars and Jupiter, and
we don't worry much about those. But when one gets away and all
that mass and energy is headed towards Earth, that's when the
astronomers start to worry. NARRATOR: Oftentimes,
these cosmic remnants get bumped out of
their orbit and head on a collision
course with Earth. Our planet's thick atmosphere
vaporizes the vast majority of them, but a larger object
can knock through our atmosphere and actually impact the ground. [explosion] NEIL DEGRASSE TYSON: If you
want to turn to the cosmos and look at the forces
that would have us dead, asteroids striking are
real, and they're bad. It's happened before. It will happen again. NARRATOR: 65 million
years ago, an asteroid the size of a small city
plummeted down from the sky. It exploded in the
Yucatan Peninsula near the present-day
Mexican village of Chicxulub with the force of 100
million megatons of TNT. NEIL DEGRASSE TYSON:
It hits the earth, casts, you know, billions
of tons of Earth's crust into the atmosphere, cloaking
Earth, blocking out sunlight, knocking out the base
of the food chain, and sending a wave of extinction
across the tree of life. NARRATOR: It is believed the
ferocious impact contributed to the mass extinction
of the dinosaur. NEIL DEGRASSE TYSON: We can
think of asteroids as being bad things, but were
it not for an asteroid, we wouldn't be here today. Our mammal ancestors were
running underfoot trying to avoid being hors
d'oeuvres for T-rex. T-rex gets taken out. Well, this opened up
an ecological niche that allowed our
mammal ancestors to evolve to something more
ambitious than a rodent. And out comes the primates,
and among the primates, we have people. NARRATOR: But ironically, the
very kind of cosmic boulder that paved the way
for humans to exist may one day wipe
us off the planet. [explosion] In 1998, Congress urged NASA
to detect all the near-Earth objects over a half mile
in diameter or more, and what they found
was unsettling-- over 850 NEOs in our vicinity. These asteroids are our closest
and most dangerous neighbors in the solar system. Donald Yeomans heads the
NEO program at NASA's Jet Propulsion Laboratory. He and his cosmic bounty hunters
search for potential killers lurking in our solar
system and put them on their most wanted list. DON YEOMANS: Finding
these near-Earth objects is somewhat akin to
tracking hurricanes. As you track it
day after day, you get a better idea of its orbit. You can predict
where it's going. You have a better idea
of how large it is, and if it should hit the Earth,
with what sort of velocity. NARRATOR: By using
telescopic technologies, NASA's Space Guard Survey
has detected over 90% of all NEOs deemed harmful. These frightening
objects could strike the Earth with
the energy greater than all the nuclear
weapons on our planet today. Such an impact could
trigger mass extinction. DON YEOMANS: You
wouldn't expect one to hit but every several
thousand or millions of years, but if one did hit, it could
wipe out a fair fraction of the population. So there are very
low-probability events but high-consequence events. [explosion] RUSSELL L. SCHWEICKART:
If they hit the Earth, they would have global effects. I mean, not only would you wipe
out a continent with really having shock waves,
but the ejecta would be thrown up in
the air and come down all around the planet. The atmosphere itself would
get to 1,000 degrees or so, and all the vegetation all over
the world where that happened would flash into flames. NARRATOR: Cataclysms could also
occur with smaller objects, so Congress now asks NASA
to locate all NEOs 500 feet in diameter, as wide
as the Roman Coliseum. An object that big could
decimate a metropolitan area or even a small state. And what worries
scientists most is not the asteroids they've
discovered, but the ones they have not yet found. DON YEOMANS: At any given time,
there's about two dozen objects for which we can't yet
rule out an Earth impact. NARRATOR: Former
astronaut Schweickart has taken the threat of
NEOs one step further. He's appeared before Congress
to request a special government agency be responsible
for protecting the public from space rocks. RUSSELL L. SCHWEICKART:
Today, we have the technology to stop near-Earth objects
from impacting the Earth for the rest of history. And we can literally
now begin to reshape the local solar system so
that our survival is enhanced. The question is, will we? Or will we go the
way of the dinosaurs? But Schweickart isn't
waiting for NASA or Congress to solve the problem. He has his own plans
to save the planet from the next asteroid impact. [explosion] NARRATOR: It's hard to believe
the Earth has survived over 4.5 billion years because
since its infancy, the planet has taken a beating. [explosion] Like a boxer, our world
is under constant assault from asteroids that enter
our orbit each year, but in the future, Earth
could be knocked out. Former Apollo 9 astronaut
Rusty Schweickart refuses to be
bullied by asteroids, and now he's ready
to defend Earth against these harmful rocks. RUSSELL L. SCHWEICKART: We've
discovered that there are these near-Earth objects
flying by us all the time, and we've gotten more
and more capability to modify our environment
to enhance our survival. NARRATOR: Schweickart
is particularly concerned about an asteroid
named 2004MN4, better known as Apophis. This pockmarked rock
approximately 750 feet in diameter swept
near Earth in 2004. Now it's scheduled to pass
dangerously close to our planet again, on Friday the
13 in April 2029. RUSSELL L. SCHWEICKART:
So in 2029, Apophis will come closer to
us than our own communications satellites orbiting the Earth. It will be so close that people
who are in the right place will be able to see
Apophis go by the Earth with your naked eye. You won't even have
to have binoculars. That's how close that
asteroid is going to come. NARRATOR: Apophis
has an over 99% chance of missing
the Earth in 2029, but if Apophis passes the Earth
at a distance of exactly 18,893 miles, it may pass through
a gravitational keyhole, a narrow region in
space a half mile wide. If this happens,
the Earth's gravity could upset Apophis and
change its trajectory. It could cause it to return
and hit earth seven years later on April 13, 2036. RUSSELL L. SCHWEICKART:
The gravitational effect of the Earth will cause it
to bend, cause the Apophis orbit to enlarge to
precisely the size which, seven years later,
it will come around and hit the Earth. NARRATOR: At the present time,
Apophis has a 1-in-45,000 chance of delivering
a deadly blow in 2036, but even these odds have
scientists placing bets. RUSSELL L. SCHWEICKART:
It's one thing to know that there is
maybe 1 chance in 45,000 that it's going
to hit the Earth. But what you'd like to know--
is there 1 chance in 100? Is there 1 chance in 10? Is-- can you-- is the
probability one that it's going to hit the Earth? NARRATOR: Schweickart believes
we must regard Apophis as we would any natural disaster. He's even mapped out where
Apophis might strike. RUSSELL L. SCHWEICKART: You
have the date of the impact, the time of the impact,
the orbital inclination, and you can make a map. And what that map shows is what
I have called a path of risk that goes all the way
across the planet. And I look at this, and I see
a high probability of impact, and I say, whoa. You know, where might it hit? NARRATOR: According
to Schweickart, Apophis could impact any
point along this path of risk. It begins in Western
Siberia, cuts across and down the Pacific Ocean,
near California. Then it traverses Central
America and finishes in Western Africa. Schweickart proposes
a chilling scenario of where Apophis might strike. The asteroid could land
in the Pacific Ocean, off the coast of California,
with the force of over 1 million megatons of TNT. Such an impact would
create a 5-mile-wide, 9,000-foot-deep
crater in the water, which would unleash tsunamis. Relentless 50-foot waves would
pound the coastline, resulting in unimaginable human loss. RUSSELL L. SCHWEICKART:
An asteroid that's 1,000 feet in diameter-- having a hit in the
ocean is not a good deal. Hundreds of billions
of dollars of damage from something like that. NARRATOR: Scientists
are presently working on technologies to
preempt such a cosmic strike. One idea involves
blowing up an asteroid, but some feel this could
compound the problem, sending several chunks of the asteroid
in our direction instead of just one. Consequently,
Schweickart's new mission is to change the orbit of
asteroids that could impact Earth. RUSSELL L. SCHWEICKART:
What you want to do is basically change the
asteroid's orbit very, very slightly. You change its velocity by
a 10/1000 of a mile per hour so that it will miss the
Earth instead of hitting it. NARRATOR: Rusty's colleagues
have drafted conceptual designs of spacecraft that could
deflect asteroids, particularly Apophis. One would tow harmful asteroids
away from Earth, but instead of lassoing the rock
like a bull in a rodeo, the tractor will
hover in front of it and use gravity as a tow line. RUSSELL L. SCHWEICKART: If you
park in front of an asteroid for a long enough period of time
and you stay close enough to it but not touching it, you're
going to increase its velocity. Or if you've parked behind
it while it's moving along, you're going to slow
it down very slightly. We can change the
orbit of an asteroid if we know about it far
enough ahead of time. NARRATOR: Although a space
probe has landed on an asteroid in the past, the
most challenging idea is launching
a manned mission. Once landing on the
rock, astronauts could mount a radio transponder
to track its whereabouts. You could just use
a robotic mission to go to an asteroid
and land, grab a sample, and bring it back. That's not that difficult. What
you gain by a manned mission is they can react to interesting
areas on the asteroid's surface. They could go here,
there, or there, and they wouldn't have to
rely on remote navigation. Nicaraguan border-- NARRATOR: Schweickart
insists we should remain on high alert regarding
asteroid Apophis, and his cause
hasn't gone unheard. Now the United Nations plans
to draft a treaty which will include who will be
responsible for deflecting killer asteroids. RUSSELL L. SCHWEICKART:
That would be a real crime, if we are so irresponsible,
knowing that this is going to happen, that we continue
to do nothing about it. NARRATOR: But asteroids
and comets are not the only deep space threats. Earth has had its ups,
and Earth has had its downs. We never know what's going
to be around the next corner, and a lot of it is bad. NARRATOR: In far-off
galaxies, galactic invaders are at work, itching to end life
on the planet as we know it. Three times daily, a strange
flash pulsates across our sky. It's hundreds of times more
powerful than the world's total nuclear armament,
but it's not man-made, and if one happens
close enough to earth, it could end life on our planet. Most Earthlings are unaware of
the potential hazards in space, but the list is
long and growing. Imagine this. Within our own
galaxy, the Milky Way, a massive star explodes,
sending a lethal burst of energy rocketing toward our planet. This is a gamma ray burst,
the biggest explosion to rock the universe
since the Big Bang. In the cities and
countryside below, there's no Warning of
what's about to happen. And then it strikes. [explosion] It would be equivalent
to standing one mile away from Hiroshima any
place on the Earth. NARRATOR: The potent radiation
cooks the upper atmosphere. Our ozone layer roasts. Across the hemisphere,
human beings burn to death from radiation
100 times the fatal dose. The disappearing ozone layer
causes increased temperatures around the world, triggering
cyclones, tsunamis, and hurricanes. Most life on the surfaces of
land and water incinerates. This may seem like
science fiction, but it could happen if a
gamma ray burst hit Earth from 100 light years away. Gamma ray bursts are
the brightest explosions in the universe. Because they're so far away
and yet still so brilliant, they must involve an
enormous amount of power, as much energy as the sun will
emit in its entire 10 billion year lifetime. NARRATOR: As a young student,
Stan Woosley always liked experiments that go boom. Now, the work of
this astrophysicist is more than child's play. He's one of the galactic
detectives trying to uncover the mysteries
behind gamma ray bursts. We know there are many
planets and many stars throughout the
cosmos, so there may have been countless
civilizations that were destroyed by gamma ray bursts. NARRATOR: These peculiar
beams of radiation were first spotted in the 1960s. At first, most astronomers
believed these gamma ray bursts must exist in our own
galaxy, the Milky Way, because they're so bright. There were reasons for that. One was that if they
were outside the galaxy, the energy was
almost unbelievable. NARRATOR: But at the time, even
the most powerful telescopes couldn't determine
their location and distance because the bursts
lasted for a few seconds, then disappeared. But then astronomers wondered,
what about their afterglow? Cosmic explosions
typically leave behind some luminous residue
that sometimes lasts for days or weeks. In the late 1990s, satellites
used upgraded optics and X-ray detectors to finally capture
a gamma ray burst's afterglow. STAN WOOSLEY: It became clear
that gamma ray bursts actually were cosmological, coming from
very far outside of our galaxy from millions and billions
of light years away. And that meant their energy
had to truly be astronomical. RENE ONG: To get some idea
of how incredibly bright a gamma ray burst is, we
could represent the brightness of our sun by this
relatively dim LED, and we could represent the
brightness of the gamma ray burst by the very, very intense
search light that's behind me. Isn't that incredibly bright? Unfortunately, with
this comparison, the search light is not
nearly bright enough to represent fully
the gamma ray burst. And in fact, we would need
100 billion such search lights to have an adequate comparison. The gamma ray burst is
equivalent to the brightness of a million trillion suns. NARRATOR: These massive
bursts could decimate Earth, but what causes them? STAN WOOSLEY: We are quite
convinced that the common gamma ray burst comes from the
death of a massive star at least 10 times
the mass of the sun, and such stars are
quite rare, by the way. NARRATOR: Woosley masterminded
a groundbreaking model of how gamma ray
bursts may be created. When an extremely
massive star dies, it collapses into a black hole. Black holes are created when a
collection of matter collapses to such a high density that
light itself cannot escape. But Woosley proposes
that some of the star resists getting sucked into
the center of the black hole. As a result, a high-speed
spinning disk of matter forms around it. Within seconds, jets
of plasma shoot out from its rotational poles. These beams of energy
unleash dangerous gamma rays into space. RENE ONG: If you
can imagine just trying to squeeze a fruit
or some kind of sphere of some object into
a very small space, things are going to squirt out. And in this case, the
squeezing is done very rapidly and you're talking about
a huge amount of mass. NARRATOR: At the same time the
gamma ray bursts are ejected, the collapsing star explodes or
goes supernova to the extreme. STAN WOOSLEY: One of the
reasons gamma ray bursts are so incredibly bright is that
they take an enormous amount of power, and then they focus
that power into a very small portion of the sky. For every 300 gamma
ray bursts that go off, only one is pointed
in our direction, and so we only see
one of those 300. NARRATOR: Even if a gamma ray
burst were to occur not 100 but 1,000 light years
away, the Earth could still face apocalyptic destruction. STAN WOOSLEY: If a gamma ray
burst happened within 1,000 light years of
the Earth, then it would be approximately 500
times brighter than the sun and emitting gamma rays. The energy delivered to the
Earth's upper atmosphere would be like 100,000 megatons
of nuclear explosions. The ozone would be depleted. We'd have acid
rain, but we'd also have flash burns,
incineration of vegetation, perhaps something
resembling nuclear winter. So there could be a global
extinction of many species. Now, the far side of the
Earth would be a special place to be because gamma rays
don't go through the Earth. And if you were
on the other side, you wouldn't get flash burned. But the effects of
depleting the ozone and changing the composition
of the atmosphere would eventually come
to the other side, and there, the
effects are unknown. NARRATOR: Statistically,
this ghastly scenario has a 1% chance of happening
once in the Earth's entire lifetime, but even
these odds aren't reassuring if you're living on the
planet at that very moment. If you're caught in the
beam, that's a bad day for you. If one of these
happens in your galaxy and that beam is coming
your way, go hide in a cave because this is very
high-energy radiation. It's the kind of energy that
will decompose your molecules, and you just don't want to be
around when that's happening. NARRATOR: There
currently are no defense measures to shield us
from gamma ray bursts if they happen close to Earth. They travel at the
speed of light, 186,000 miles per second. By the time we detect them,
they will have already struck our planet. STAN WOOSLEY: Gamma ray
bursts could pose a hazard to the Earth or to
anything living that came within their bore site. But as we've seen,
they're very infrequent, and there are other
things in the heavens and on the Earth that
are much more dangerous. NARRATOR: Cataclysms
routinely erupt in some corner of the universe,
and one day, something will snuff out Earth. ROBERT ROY BRITT: Most of the
time, our ride around the sun is gentle and uneventful,
like this Ferris wheel. And as long as nothing
gets in our way, we can go on like this
for millions of years. But sooner or later, we know
that this smooth ride will come to an end. We just don't know when. NARRATOR: Sadly, our planet's
ultimate demise will probably come from the very thing
that provides us life. Earth maintains a cozy lifestyle
being third rock from the sun. For over 4 billion
years, the sun has been an ally, warming
and feeding our planet. But in time, our solar
heater will become our enemy. The sun and the Earth
have a unique relationship to each other. The Earth has a
particular temperature. It's a particular size. It has life on it and
oceans, and those things depend on the sun. The sun is at the root of the
existence of life on the Earth, and the sun will be at the
root of its demise as well. NARRATOR: Earth's
relationship with the sun will become dysfunctional when
our solar mother really turns up the heat. GIBOR BASRI: The sun gets hotter
because it's burning hydrogen into helium. Four hydrogen atoms
become one helium atom. Now, that means there are
fewer particles bouncing around inside the sun, and
that process basically means that the sun has to
get hotter and brighter to hold itself up. NARRATOR: As the sun's
core gets hotter, its outer parts will swell
in size and turn red. GIBOR BASRI: If
you have a bonfire, you have all this wood there. You build it up. And at some point,
enough logs get burnt and the thing collapses, and you
get this huge burst of sparks and it gets much brighter. In a sense, it's like that
because the sun is right now burning hydrogen into
helium, and the helium is the ash of that, if you like. And then, as the sun
collapses enough, the ash relights, and the
helium burns into carbon. And that's when
things get really hot. NARRATOR: At this point, the
sun will expand into a red giant and incinerate most
complex life on Earth. GIBOR BASRI: When the
sun becomes a red giant, it will grow to
30 times its size. So the surface of
the sun will actually be out beyond the
orbit of Mercury. The luminosity of the sun will
go up by, like, 1,000 times, and that's going to make the
Earth so hot that the outer crust-- the rocks, the
solid part of the Earth-- will melt. The
whole planet would be a glowing ball of lava. ROBERT CALDWELL: The sun
will fry the inner planets, and even though the sun
will become red and cooler, the Earth will be much
hotter, just leave the Earth a burned cinder, like
a charcoal briquette. So that would be bad
for life on Earth. NARRATOR: And the Earth's
hellish fate isn't over. As a red giant, the sun
will fluctuate in size before collapsing
into a white dwarf. GIBOR BASRI: The
sun that was huge suddenly becomes the sun that's
very small and extremely dense. It's only about the
size of the Earth, sitting down there at the center
of our solar system, very much fainter than it used to be. And then everything cools
off, and then that object is no longer generating
energy, either, so it begins to cool as well. So the final fate
of the solar system will be to cool off and freeze. NARRATOR: Humans will
probably have relocated to another planet or become
extinct before the sun turns Earth into a snowball. However, the sun may dry
up our world much sooner. GIBOR BASRI: If the
sun doesn't get us at the time of the
red giant phase, it may well get us earlier by
just becoming bright enough to cause the oceans
to evaporate. Water is an essential
component for all life itself. If the Earth actually
loses all its water, then that's another reason
why life might disappear from the Earth, and it would
again be the sun's fault. NARRATOR: There may
be ways for Earth to win a stay of execution. GIBOR BASRI: So as
the sun is swelling, it also begins to lose mass
much more rapidly than it's losing it now. And of course, if it's
getting less massive, it has less of a
hold on the Earth. The Earth will move further
out into a larger orbit. And so it's kind of a
race between the growing sun and the growing heat
from the sun and the Earth actually moving a little bit
away from that fire that's getting too hot. NARRATOR: If our
planet somehow manages to avoid getting fried
or frozen by the sun, its future remains
increasingly bleak. ROBERT ROY BRITT: This place is
full of adventure, rides that put your stomach up
into your throat, things that collide, scary stuff. It's a lot like riding around
the sun on planet Earth. But when Earth gets
smacked or when things start to come apart,
the ride can really be over. ROBERT CALDWELL:
I don't know what that means, for the universe
to end, because I like time. I live in it, so it's hard
to imagine time ending. NARRATOR: Today,
scientists contemplate our inevitable fate. In the distant future, the
Earth and the entire universe may face the ultimate
cosmic monster. No one suspects that Earth's
most lethal enemy lurks amongst the stars,
but in the future, and without prior warning,
a cosmic grim reaper will unleash the
ultimate Armageddon. The dark villain will
stretch apart the universe. Galaxies themselves
will split apart. Stars and planets
will tear to shreds. The ultimate apocalyptic event
is being called the Big Rip, and when it begins,
it won't stop until every atom and nuclei
in the universe are mincemeat. ROBERT CALDWELL: The Big Rip-- it really is the
end of the universe. It's not like we're the last
ones at the party and wondering what's going on and we
can go do something else. It's really like you've
turned off all the lights and the universe just ends. NARRATOR: Innovative physicists
Robert Caldwell and Marc Kamionkowski proposed
the notion of the Big Rip, a grim hypothesis about
the final fate of the universe. MARC KAMIONKOWSKI: We used to
think that the universe, which is currently
expanding, could reach a point of maximum expansion. The Big Rip is the idea that
the expansion will not only continue and accelerate but rip
everything apart as it does so. NARRATOR: Caldwell
and Kamionkowski calculated that the universe
is expanding at an alarming and increasing pace, and that
something is sucking everything outward, like a vacuum. Acting like a
galactic vice squad, these young scientists
hunt for the cosmic killer. They believe a mysterious
phenomenon called dark energy may be the culprit. ROBERT CALDWELL: Figuring
out what dark energy is is probably the number-one
goal of cosmologists today. Dark energy is dark,
so you can't see it. We can feel what it is. We feel it through its effects
on the gravitational behavior of the universe. There could be some dark energy
in this room, under the chair. It's only when you look at
its properties on really big, cosmological length
scales billions of light years across that you start to
see the cumulative effects of the dark energy. It causes things to be pushed
farther away from each other and contributes to the
expansion of the universe in a quickening pace. NARRATOR: Edwin Hubble, whom
the Hubble Telescope is named after, first discovered the
universe is expanding back in the 1920s, but
it wasn't until 1998 when a crack team of scientists
measured that this expansion is moving like a runaway train. ROBERT CALDWELL: A nice analogy
is to imagine that the universe are three-dimensional spaces
like the surface of a rubber balloon that I'm blowing up. OK, I'm going to blow up the
balloon as a demonstration of the effects of the
expansion of the universe. As the balloon
gets bigger, that's a depiction of the
expansion of galaxies. MARC KAMIONKOWSKI:
There's a galaxy. Another one. ROBERT CALDWELL:
Where's our galaxy? We live there. OK, that's our home. As the universe expands,
every other galaxy gets farther away from us. In ordinary expansion, each
galaxy stays the same size. But if you have
super-accelerated expansion, then the galaxies themselves
can each expand, which is sort of what's happened here. If I could blow it up fast
enough to depict the Big Rip, then the balloon would explode. That's like space time
not being able to take it and coming to an end. So instead, we'll just
pop a hole in the balloon. [pop] That's the Big Rip. NARRATOR: According to
Caldwell and Kamionkowski, the universe has no hope
of surviving the Big Rip. They've even come
up with a countdown to this apocalyptic event. ROBERT CALDWELL: The Big Rip
kind of rolls up its sleeves and progressively takes apart
the universe layer by layer, working from the outside in,
going from the largest scales to the smallest scales. A billion years to pull apart
clusters of galaxies, then hundreds of millions of years to
pull apart galaxies themselves, and then down to the
size of a solar system, we're talking hundreds
of thousands of years. And then, to tear
apart the Earth itself would take less than an hour. It's kind of interesting to
think about what that would look like. If I'm in my protective
capsule watching things happen, I would see this
wall of darkness that starts coming towards us. I would no longer at that
point be able to see any stars. The Earth, layer by layer, will
be peeled off and ejected away. MARC KAMIONKOWSKI:
Everything in us, the molecules that
hold us together, would get ripped apart. And every atom that makes
up your body would get-- would get-- would fly off to
infinity in a very short period of time. NARRATOR: Fortunately, mankind
doesn't need to lose sleep over the Big Rip. Caldwell and Kamionkowsi
estimate that it will climax 50 billion years from now,
when the universe is over three times its current age. MARC KAMIONKOWSKI:
What's really fun for us is to try to figure out
whether this is actually what's going to happen, to
paint the science fiction scenario of what might happen
and to think what might happen to us. NARRATOR: Deep space
threats are real. Some could harm us tomorrow,
others in the far future. But one thing is certain. Something will terminate
Earth, and probably the entire universe,
once and for all. It's only a matter of time. ROBERT CALDWELL: It's
useful to sometimes think about how fragile our
life is here on Earth, that maybe we aren't going
to be here for eternity. Maybe there's a hope,
but the way it looks, the universe just
ends, and that's it.
