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Our sun...
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The heart of the solar system...
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The giver of light, heat,
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and, of course, life.
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But what does its future hold?
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Scientists are looking
to the stars to find out.
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Between these two stars is
what's gonna happen to our sun.
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Scientists today are almost
like modern-day prophets.
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They foresee
an apocalyptic future.
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Imagine the ball
is Andromeda galaxy
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on a head-on collision
with the Milky Way galaxy.
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The fate of the Earth
hangs in the balance.
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Wow! Look at this.
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The temperature of the surface
of the Earth
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will be enough to melt rock.
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Enough to melt the whole surface
of the Earth.
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This is the story of how our sun
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will transform the solar system
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it binds together...
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Before bringing it
to a spectacular end.
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Captions by vitac...
www.Vitac.Com
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captions paid for by
Discovery communications
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Peoria, Illinois,
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an average city
in midwest America,
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but it has one claim to fame
that's out of this world.
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In the middle of town,
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there's a 46-foot-wide mosaic
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of the Sun,
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the centerpiece
of a huge-scale model
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of our solar system
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created by local astronomer
Sheldon Schafer.
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And here we are at the Sun.
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And, boy, is it hot.
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It's about 10,000 degrees
here at the surface.
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And over a million Earths
could fit inside of the Sun.
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Peoria's solar system,
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99 million times
smaller than the real thing,
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accurately reveals
the relative sizes
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of our sun and its planets...
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Okay, we're all together?
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And the distances between them.
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My job title is curator
of the solar system.
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And we just went
33 million miles,
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until we got to this tiny
little two-inch Mercury.
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All right.
So, we're headed off to Venus.
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From Mercury,
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the inner planets
are strung along
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a picturesque riverside park,
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all the way to Mars.
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These planets
are relatively close together.
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The outer planets
are much further away,
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in some bizarre locations.
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Five miles
from the image of the Sun,
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above the local airport's
check-in desks,
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is five-foot-wide Jupiter...
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Well,
if you're gonna have a planet,
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you may as well have
the biggest one, right?
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So, it's fun to have Jupiter.
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Occasionally we have birds
that decorate,
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so we've had to clean it.
But not very often.
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While the children's section
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of a neighboring town's library
is home to saturn.
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Uranus is in princeville,
Illinois.
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From there, it's a 10-mile drive
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along route 91,
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or almost a billion miles
in cosmic terms,
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to the old railroad depot
in Wyoming, Illinois,
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and Neptune.
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And finally,
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in a furniture store
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40 Earth miles away
from the center of the Sun,
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in kewanee, Illinois,
is distant Pluto.
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Peoria's models
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are a perfect likeness
of the solar system today.
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But it won't always be this way.
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Scientists know that one day,
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the Sun
will fundamentally change,
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and transform the planets.
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Imagine fast-forwarding through
the next seven-billion years
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to watch the end
of the solar system.
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Dr. Eva Villaver
can predict this future...
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Because everything
that will happen to our sun
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is already happening
to countless other stars.
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Some, known as solar twins,
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are remarkably similar
to our own.
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We study solar twins
because they are very important
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to understand not only the Sun,
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but to tell us how the future
of our own solar system will be.
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In 2013,
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a solar twin called
corot sol 1 was discovered.
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Corot is over there, in
the constellation of monoceros.
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It's a star like the Sun,
and it has the same mass.
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Exactly the same mass.
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But astronomers found
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one particularly significant
difference...
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It had a lower concentration
of the element lithium,
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which helped them
to accurately calculate its age.
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It's a star
that is a little bit older
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than the Sun,
a few billion years older.
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And if we observe a star
that is older than our sun,
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we know what will happen
to the Sun.
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Eva and her team discovered
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that this older version
of our sun
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was giving out more radiation.
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So, it helped us
put the pieces together.
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As the Sun will get older,
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it will become brighter,
much brighter.
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Our sun's luminosity
is slowly increasing
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because of a change
deep inside the Sun,
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where two opposing forces
are in constant battle.
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Similar forces to those
that act on a hot-air balloon.
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00:07:08,128 --> 00:07:13,832
Pushing up and out is
the immense pressure of hot gas.
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In the Sun, this is created
by nuclear fusion.
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The Sun has been
burning hydrogen into helium
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for thousands
of millions of years now.
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This is like
the propane bottle here.
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It's generating heat
that warm up the air
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that keeps the balloon going.
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That's what happens in the Sun,
too.
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But pulling down
into the core of the Sun
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is an equally powerful force...
Gravity.
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The life of the Sun is nothing
but a battle against gravity.
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We have the gravitational force
trying to pull the star,
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crash the star together.
I mean like pushing it in.
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And then we have
the thermal pressure
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of the gas pushing outwards.
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So, the balance
between the two forces
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is what keeps the Sun stable.
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For 4.5-billion years,
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the two forces
have been in perfect balance.
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But as time passes,
this balance is shifting.
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As the Sun fuses hydrogen,
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it produces
around 600 million tons
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of helium every second,
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which is a denser gas.
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This change in density
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has a profound affect
on the nuclear reactions.
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As the core gets denser,
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hydrogen is burned
at a higher rate.
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It's like turning
the burners up.
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I mean,
we are increasing the energy
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that is coming out of the core
at that point.
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As a result,
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our sun is getting 10% brighter
every billion years.
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So the older it gets,
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the more it heats
up the solar system.
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And scientists know
that will one day
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have serious consequences.
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The Earth has oceans and clouds
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because it orbits a band
around the Sun
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called the habitable zone,
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which means it's just the right
temperature for liquid water.
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And that makes it the only
planet in the solar system
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where we know life can thrive.
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But as the Sun
becomes more powerful,
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the habitable zone will move.
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For a vision of the Earth
in two-billion years' time,
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astrobiologist
professor Lynn Rothschild
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believes we should
look to Venus.
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Venus is up in the sky, there.
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It's the brightest object
after the Sun and the moon.
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It's right near Jupiter
this morning.
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It's just an absolutely
spectacular day to see it.
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Venus and the Earth formed
out of the same materials.
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They're roughly the same size.
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The difference is that Venus
is closer to the Sun.
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It's no surprise
Venus is warmer than Earth.
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But strangely, Venus
is even hotter than Mercury
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despite being further
from the Sun.
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In 2006, the Venus express probe
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launched towards
our nearest planet
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to analyze
the venusian atmosphere
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in unprecedented detail.
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It found a vital clue
among the clouds
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to how Venus became so hot.
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Venus express allowed us to see
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that there was a lot
of deuterium,
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which is a heavy form
of hydrogen, left.
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And that's indicative
of the fact
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that there was once water here.
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It soon became clear
that in the past,
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Venus was a very different
world.
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So, here was this beautiful
water world
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not too dissimilar to, maybe,
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what the Earth is like today.
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There was liquid water
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and reasonable
atmospheric pressure
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and organic compounds.
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There's no reason that there
shouldn't have been life.
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The evidence suggests
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that Venus
was once in the habitable zone.
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But as the Sun grew brighter
three-billion years ago,
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it would have had a dramatic
effect on the planet's water.
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As the Sun
started to get hotter,
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the surface of Venus
started to get hotter,
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and therefore
the water turns into steam.
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And steam is a greenhouse gas,
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so that means it traps
the solar radiation.
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And therefore,
just like a greenhouse,
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it starts to get
hotter and hotter.
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It seems a runaway
greenhouse effect caused Venus
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to become the hottest planet
in the solar system.
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Mercury,
although closer to the Sun,
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has no atmosphere and no water.
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Earth has both.
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And as the brighter sun
evaporates our oceans,
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the affect is likely
to be far more intense
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than the man-made global warming
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00:13:06,343 --> 00:13:09,811
we see today.
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00:13:09,813 --> 00:13:12,013
Over the next two-billion years,
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temperatures on Earth
will rocket.
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Life here must adapt or die.
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Yellowstone national park
is a natural laboratory
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for Lynn to study how life can
survive in extreme conditions.
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The reason it's so great
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is that we have the whole range,
from the top predators...
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Things like wolves and bears
and so on,
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all the way down to the beavers
and the herbivores,
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and down to the very
tiny organisms,
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00:13:48,585 --> 00:13:51,152
and even some
incredible microbes.
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Life here is used
to dealing with extremes.
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But in about
a half-billion years' time,
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00:14:01,398 --> 00:14:04,566
these extremes will go
in the opposite direction,
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00:14:04,568 --> 00:14:08,870
as temperatures could climb by
up to 20 degrees in some places.
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00:14:13,577 --> 00:14:15,543
By then, life as we know it
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will have evolved
to be very different.
227
00:14:20,550 --> 00:14:23,184
But just as some of today's
animals have adapted
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00:14:23,186 --> 00:14:26,521
to survive harsh winters,
in the future,
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they may use similar strategies
to cope with scorching summers.
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00:14:31,294 --> 00:14:33,028
As the Sun gets hotter,
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00:14:33,030 --> 00:14:36,197
you could imagine the winter as
being the very pleasant season,
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00:14:36,199 --> 00:14:40,135
and the summers become
unbearably hot.
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00:14:40,137 --> 00:14:42,037
So, if you're thinking about
a bear
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00:14:42,039 --> 00:14:43,605
that lives in an area like this
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that would normally
hibernate in the winter,
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if you turn the thermostat
on the Earth high enough,
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it might be the reverse,
238
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so that now animals would be
hibernating in the summer
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00:14:53,283 --> 00:14:54,983
and be active in the winter.
240
00:14:54,985 --> 00:14:58,486
And grasses would be setting
seed now in the spring.
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00:14:58,488 --> 00:15:00,555
The seeds would be
what would carry the plant
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00:15:00,557 --> 00:15:02,323
through this harsh summer.
243
00:15:02,325 --> 00:15:05,393
And then, as the rain
started again in the Autumn,
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00:15:05,395 --> 00:15:06,561
they would germinate,
245
00:15:06,563 --> 00:15:09,364
and you would get the lush green
in the winter.
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00:15:14,304 --> 00:15:16,671
In less than
a billion years' time,
247
00:15:16,673 --> 00:15:20,842
the greenhouse effect
is expected to take off,
248
00:15:20,844 --> 00:15:23,044
sending temperatures soaring.
249
00:15:30,153 --> 00:15:32,087
As it gets hotter
and hotter on the land,
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00:15:32,089 --> 00:15:36,091
eventually even the winters will
be too hot for most organisms,
251
00:15:36,093 --> 00:15:39,461
certainly, to live.
252
00:15:39,463 --> 00:15:41,563
So, if you had a large animal
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like, say, a bison,
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that's also warm-blooded,
as it gets hotter and hotter,
255
00:15:46,503 --> 00:15:49,737
it won't be able to cool down,
and it will eventually die.
256
00:15:51,875 --> 00:15:53,241
And so, ultimately,
257
00:15:53,243 --> 00:15:56,511
large animals like that
will go extinct.
258
00:15:56,513 --> 00:15:59,214
In just over
a billion years from now,
259
00:15:59,216 --> 00:16:04,486
the land could be nothing but a
parched desert, devoid of life.
260
00:16:04,488 --> 00:16:07,655
The air is gonna
heat up much more quickly
261
00:16:07,657 --> 00:16:10,959
than water will,
and so I predict
262
00:16:10,961 --> 00:16:13,795
that, just like the ancestors
of whales and dolphins
263
00:16:13,797 --> 00:16:16,131
and so on moved
from the land to the water,
264
00:16:16,133 --> 00:16:20,602
so will the descendants of bison
if they want to survive.
265
00:16:20,604 --> 00:16:24,205
But models suggest
that in two-billion years' time,
266
00:16:24,207 --> 00:16:27,809
even the water will have gone.
267
00:16:27,811 --> 00:16:29,277
As it boils away,
268
00:16:29,279 --> 00:16:32,814
the Earth would increasingly
resemble Venus today.
269
00:16:37,187 --> 00:16:39,587
In less than
three-billion years' time,
270
00:16:39,589 --> 00:16:41,789
it's thought that that
the searing sun
271
00:16:41,791 --> 00:16:43,658
and a runaway greenhouse effect
272
00:16:43,660 --> 00:16:48,463
will have wiped out
virtually all life on Earth.
273
00:16:48,465 --> 00:16:53,601
But intelligent life
may just find a way out.
274
00:16:53,603 --> 00:16:55,803
We have something
that the other organisms
275
00:16:55,805 --> 00:16:58,840
out there don't have,
and that is we have technology.
276
00:16:58,842 --> 00:17:01,876
And we're gonna have the option
of going to other planets.
277
00:17:01,878 --> 00:17:03,878
As it gets too hot
for the Earth,
278
00:17:03,880 --> 00:17:05,713
Mars will start to warm up.
279
00:17:05,715 --> 00:17:09,517
And so that means that it's
just possible
280
00:17:09,519 --> 00:17:11,653
Mars will become a better place
for life.
281
00:17:11,655 --> 00:17:15,056
Who knows? I have great faith
in our descendants.
282
00:17:15,058 --> 00:17:16,491
By then, Mars is expected
283
00:17:16,493 --> 00:17:19,194
to be in the habitable zone,
284
00:17:19,196 --> 00:17:24,566
so it could provide a refuge,
but not forever.
285
00:17:24,568 --> 00:17:28,436
Because the next threat will be
the entire solar system...
286
00:17:34,077 --> 00:17:37,178
from 100-billion stars
racing towards us...
287
00:17:40,684 --> 00:17:42,817
the Andromeda galaxy.
288
00:17:46,323 --> 00:17:49,457
Scientists have long suspected
it will one day
289
00:17:49,459 --> 00:17:53,027
crash into our galaxy,
the Milky Way.
290
00:17:56,266 --> 00:18:02,170
But until recently, no one
had been able to say for sure.
291
00:18:08,296 --> 00:18:13,833
In 2012, Dr. Tony sohn
stepped up to the plate.
292
00:18:13,835 --> 00:18:15,301
He and his team set out
293
00:18:15,303 --> 00:18:18,471
to precisely measure
Andromeda's path,
294
00:18:18,473 --> 00:18:21,640
and discover
if it would be a near miss,
295
00:18:21,642 --> 00:18:23,409
a glancing blow,
296
00:18:23,411 --> 00:18:27,313
or a head-on hit
with our galaxy.
297
00:18:27,315 --> 00:18:28,681
To predict the outcome,
298
00:18:28,683 --> 00:18:32,618
he used a technique familiar
to baseball players.
299
00:18:32,620 --> 00:18:34,019
I found a thought experiment
300
00:18:34,021 --> 00:18:37,189
that can help explain how we
measure the motion of Andromeda.
301
00:18:37,191 --> 00:18:38,824
Imagine a game of baseball.
302
00:18:38,826 --> 00:18:41,360
The batter
is waiting for the ball,
303
00:18:41,362 --> 00:18:44,597
thrown by the pitcher.
304
00:18:44,599 --> 00:18:46,632
To work out
if the ball is on target,
305
00:18:46,634 --> 00:18:47,867
the batter needs to see
306
00:18:47,869 --> 00:18:51,003
whether it's drifting
to the side or not.
307
00:18:51,005 --> 00:18:54,106
So the instinctively
compare the motion of the ball
308
00:18:54,108 --> 00:18:55,941
against the background.
309
00:18:58,379 --> 00:19:00,846
Tony needed
to apply the same principle
310
00:19:00,848 --> 00:19:05,451
to discover if Andromeda
was heading towards us
311
00:19:05,453 --> 00:19:08,154
but in order to measure
the galaxy's motion,
312
00:19:08,156 --> 00:19:10,623
he had to find
fixed points behind Andromeda
313
00:19:10,625 --> 00:19:13,592
to compare it to...
314
00:19:13,594 --> 00:19:16,195
A daunting task.
315
00:19:16,197 --> 00:19:20,199
Most of the stars we see
in the sky are in our galaxy,
316
00:19:20,201 --> 00:19:24,837
so they cannot be used
as background objects.
317
00:19:24,839 --> 00:19:28,441
Instead, Tony had to
search for distant galaxies
318
00:19:28,443 --> 00:19:31,210
hundreds of millions
of light-years away.
319
00:19:31,212 --> 00:19:35,448
Only one telescope
was up to the task.
320
00:19:35,450 --> 00:19:37,616
We used the hubble space
telescope to do this project
321
00:19:37,618 --> 00:19:41,253
because we need
a very stable instrument,
322
00:19:41,255 --> 00:19:44,156
and we need to be above
the Earth's atmosphere
323
00:19:44,158 --> 00:19:47,326
to get very high resolution
of the image.
324
00:19:47,328 --> 00:19:51,163
With data from hubble,
Tony painstakingly tracked stars
325
00:19:51,165 --> 00:19:55,434
in Andromeda
against distant galaxies,
326
00:19:55,436 --> 00:19:59,171
just like a batter
tracks a ball.
327
00:19:59,173 --> 00:20:01,507
Imagine the ball
is Andromeda galaxy,
328
00:20:01,509 --> 00:20:05,010
and the fence behind that
are background galaxies.
329
00:20:05,012 --> 00:20:07,179
And what we did was we compared
330
00:20:07,181 --> 00:20:09,315
the position
of the Andromeda galaxy
331
00:20:09,317 --> 00:20:11,684
against the background galaxies
over time,
332
00:20:11,686 --> 00:20:14,954
and that's how we measure
the sideways motion.
333
00:20:14,956 --> 00:20:19,225
The results were conclusive.
334
00:20:19,227 --> 00:20:21,393
The sideways speed
of Andromeda we measured
335
00:20:21,395 --> 00:20:22,495
was effectively zero,
336
00:20:22,497 --> 00:20:24,930
so we can say with certainty
337
00:20:24,932 --> 00:20:27,166
that Andromeda is
on a head-on collision
338
00:20:27,168 --> 00:20:30,669
with the Milky Way galaxy.
339
00:20:30,671 --> 00:20:32,338
Tony's team confirmed
340
00:20:32,340 --> 00:20:34,273
that over 100-billion stars
341
00:20:34,275 --> 00:20:38,210
are on course
for a strike at 2,000 times
342
00:20:38,212 --> 00:20:40,246
the speed of a fast ball.
343
00:20:43,851 --> 00:20:45,518
But since it's so far away,
344
00:20:45,520 --> 00:20:47,386
the galaxies won't collide
345
00:20:47,388 --> 00:20:50,322
until nearly four-billion years
from now.
346
00:20:54,195 --> 00:20:57,196
Tony's precise measurements
allow him to predict
347
00:20:57,198 --> 00:21:00,032
how this clash of the titans
will look.
348
00:21:02,169 --> 00:21:07,540
To anyone on Earth,
it would be a spectacular sight.
349
00:21:07,542 --> 00:21:09,041
We'll see the Andromeda galaxy
350
00:21:09,043 --> 00:21:10,576
getting bigger
and bigger in the sky.
351
00:21:10,578 --> 00:21:14,380
And then eventually, in about
four-billion years from now,
352
00:21:14,382 --> 00:21:17,082
we'll see the collision
of the two galaxies.
353
00:21:23,424 --> 00:21:24,823
On impact,
354
00:21:24,825 --> 00:21:28,327
clouds of dust will be
crushed together,
355
00:21:28,329 --> 00:21:31,163
with sensational results.
356
00:21:33,534 --> 00:21:36,101
What we'll see is a lot
of stars getting formed.
357
00:21:36,103 --> 00:21:38,003
And this will look
something like
358
00:21:38,005 --> 00:21:40,639
stellar fireworks in the sky.
359
00:21:47,682 --> 00:21:49,648
Tony can even calculate the odds
360
00:21:49,650 --> 00:21:51,016
that our solar system
361
00:21:51,018 --> 00:21:53,752
will crash into one
of Andromeda's billions of stars
362
00:21:53,754 --> 00:21:56,488
during the collision.
363
00:21:58,459 --> 00:22:01,694
Surprisingly,
the prognosis is good.
364
00:22:01,696 --> 00:22:04,296
Galaxies
are essentially empty space.
365
00:22:04,298 --> 00:22:07,967
So the chances of stars
colliding with another star
366
00:22:07,969 --> 00:22:09,301
is very slim,
367
00:22:09,303 --> 00:22:12,037
because the distance
between the stars is vast.
368
00:22:12,039 --> 00:22:13,606
So when the collision happens,
369
00:22:13,608 --> 00:22:16,175
the solar system will pass
through an empty space
370
00:22:16,177 --> 00:22:18,243
between the stars.
371
00:22:22,083 --> 00:22:25,250
After passing
like ghosts in the night,
372
00:22:25,252 --> 00:22:28,887
the irresistible pull of gravity
will draw them back together
373
00:22:28,889 --> 00:22:31,423
over the next two-billion years
374
00:22:31,425 --> 00:22:36,862
to finally settle as a new
supergalaxy nicknamed milkomeda.
375
00:22:41,869 --> 00:22:45,537
Our galaxy will no longer exist.
376
00:22:45,539 --> 00:22:49,675
Yet calculations suggest
the solar system will survive.
377
00:22:51,946 --> 00:22:54,146
It will merge into
one big galaxy,
378
00:22:54,148 --> 00:22:56,749
and it will look like
a giant ball in the sky.
379
00:22:59,253 --> 00:23:02,187
Sadly, it's unlikely
anyone will be on Earth
380
00:23:02,189 --> 00:23:05,357
to witness this colossal
galactic collision.
381
00:23:09,930 --> 00:23:13,065
But there's a slim chance
an extreme form of life
382
00:23:13,067 --> 00:23:17,803
could be clinging on
as the two galaxies meet
383
00:23:17,805 --> 00:23:21,206
despite the searing heat
from the aging sun.
384
00:23:26,313 --> 00:23:29,815
In yellowstone, professor
Lynn Rothschild has found
385
00:23:29,817 --> 00:23:32,818
evidence of what
those last remaining Earthlings
386
00:23:32,820 --> 00:23:34,853
might be like.
387
00:23:34,855 --> 00:23:37,022
This area of yellowstone
388
00:23:37,024 --> 00:23:39,825
is extremely acidic,
and it's also hot.
389
00:23:39,827 --> 00:23:41,460
You can see the steam rising.
390
00:23:41,462 --> 00:23:45,097
So, in other words, it's sort
of like boiling battery acid.
391
00:23:45,099 --> 00:23:47,666
Very few living things
can actually live
392
00:23:47,668 --> 00:23:49,501
at this high temperature,
393
00:23:49,503 --> 00:23:50,969
but there are a couple
of organisms
394
00:23:50,971 --> 00:23:52,805
that are very well-adapted
for it.
395
00:23:52,807 --> 00:23:57,109
You can see the beautiful colors
behind me.
396
00:23:57,111 --> 00:23:59,411
The kaleidoscope colors
397
00:23:59,413 --> 00:24:01,080
of yellowstone's Springs
398
00:24:01,082 --> 00:24:03,649
are caused
by heat-loving microbes.
399
00:24:10,558 --> 00:24:13,125
We can pretty much
use these as a thermometer.
400
00:24:13,127 --> 00:24:15,728
Anything that is green means
401
00:24:15,730 --> 00:24:18,063
that it's got chlorophyll,
just like plants.
402
00:24:18,065 --> 00:24:19,965
And once they get
to a temperature
403
00:24:19,967 --> 00:24:22,835
above about 73 degrees or so,
404
00:24:22,837 --> 00:24:24,570
their chlorophyll breaks down.
405
00:24:24,572 --> 00:24:27,339
And so when you start
getting warmer than that,
406
00:24:27,341 --> 00:24:29,842
you start to move
into other sorts of organisms.
407
00:24:29,844 --> 00:24:32,544
Organisms that,
for example, eat iron,
408
00:24:32,546 --> 00:24:35,848
and then you see
these beautiful orange colors.
409
00:24:35,850 --> 00:24:38,717
Once all the water
on Earth has turned to steam,
410
00:24:38,719 --> 00:24:41,019
it's possible
that heat-loving microbes
411
00:24:41,021 --> 00:24:46,959
could continue to live
in the clouds.
412
00:24:46,961 --> 00:24:48,861
We know some
of the earliest organisms
413
00:24:48,863 --> 00:24:50,596
on the Earth were thermophiles,
414
00:24:50,598 --> 00:24:52,564
organisms that lived
at high temperature.
415
00:24:52,566 --> 00:24:53,799
And so at some point,
416
00:24:53,801 --> 00:24:55,400
it may be organisms like this
417
00:24:55,402 --> 00:24:57,269
that once again
inherit the Earth.
418
00:25:00,341 --> 00:25:03,375
The microbes
will have their day,
419
00:25:03,377 --> 00:25:06,678
but their reign
will inevitably be cut short.
420
00:25:10,184 --> 00:25:13,552
Because when the Sun
is twice the age it is now,
421
00:25:13,554 --> 00:25:18,624
astronomers foresee a turbulent
new phase written in the stars.
422
00:25:27,082 --> 00:25:28,047
On a clear night,
423
00:25:28,049 --> 00:25:29,849
many of the stars you can see
424
00:25:29,851 --> 00:25:33,986
with your naked eye today
are going through a phase.
425
00:25:33,988 --> 00:25:37,957
You can tell which ones
they are because of their color.
426
00:25:37,959 --> 00:25:40,893
They're known as red giants.
427
00:25:43,731 --> 00:25:45,598
It's very easy
to see red giant stars,
428
00:25:45,600 --> 00:25:46,966
because they are very bright.
429
00:25:46,968 --> 00:25:48,901
They are giant
and they are bright.
430
00:25:48,903 --> 00:25:52,105
So, they are everywhere
in the sky.
431
00:25:52,107 --> 00:25:54,340
Some red giants are so large
432
00:25:54,342 --> 00:26:00,179
you could fit our own sun inside
them millions of times over.
433
00:26:00,181 --> 00:26:01,881
Yet astronomers are confident
434
00:26:01,883 --> 00:26:06,786
our sun will one day
grow to become one itself.
435
00:26:06,788 --> 00:26:10,256
So these stars are a glimpse
of our future.
436
00:26:13,595 --> 00:26:15,795
If we study stars
that grow in size,
437
00:26:15,797 --> 00:26:18,264
we can tell the fate
of the planetary systems
438
00:26:18,266 --> 00:26:19,799
that are orbiting them.
439
00:26:19,801 --> 00:26:21,767
Stars like that
give us already clues
440
00:26:21,769 --> 00:26:25,905
about what will be the future
fate of our own solar system.
441
00:26:30,145 --> 00:26:33,045
The transformation
of our sun into a red giant
442
00:26:33,047 --> 00:26:35,047
will begin deep below
its surface,
443
00:26:35,049 --> 00:26:37,216
where all the heat is generated.
444
00:26:41,689 --> 00:26:42,989
The burning core
445
00:26:42,991 --> 00:26:46,826
is the only place hot enough
for hydrogen to fuse.
446
00:26:46,828 --> 00:26:49,162
And yet it makes up less than 2%
447
00:26:49,164 --> 00:26:51,130
of the Sun's total volume.
448
00:26:53,168 --> 00:26:55,501
For the next five-billion years,
449
00:26:55,503 --> 00:26:58,571
it's thought
the core will be stable.
450
00:26:58,573 --> 00:27:04,310
Finally balanced between two
phenomenal opposing forces...
451
00:27:04,312 --> 00:27:08,447
The crushing pull of gravity
452
00:27:08,449 --> 00:27:12,318
and the explosive push
of nuclear heated gas.
453
00:27:15,623 --> 00:27:17,089
But like a hot-air balloon,
454
00:27:17,091 --> 00:27:19,659
the core will eventually
run out of fuel.
455
00:27:21,963 --> 00:27:25,264
Just as gravity
pulls the spent balloon down,
456
00:27:25,266 --> 00:27:29,035
in the Sun, gravity
would pull on the core.
457
00:27:31,839 --> 00:27:33,606
When the balance is broken
458
00:27:33,608 --> 00:27:36,242
because the hydrogen
runs out in the core,
459
00:27:36,244 --> 00:27:38,110
the dominant force
will be gravity.
460
00:27:38,112 --> 00:27:41,480
It will try to squish the core.
461
00:27:41,482 --> 00:27:44,317
But the Sun
will be far from spent.
462
00:27:44,319 --> 00:27:46,352
As gravity crushes the core,
463
00:27:46,354 --> 00:27:50,690
it will trigger a transformation
in the rest of the Sun.
464
00:27:50,692 --> 00:27:52,258
For the first time,
465
00:27:52,260 --> 00:27:57,530
the hydrogen gas surrounding
the core will begin to fuse,
466
00:27:57,532 --> 00:28:00,399
giving the Sun access
to far more fuel
467
00:28:00,401 --> 00:28:03,102
than it's already burned.
468
00:28:03,104 --> 00:28:05,538
We run out already
of one bottle of propane,
469
00:28:05,540 --> 00:28:07,607
but we have three more.
470
00:28:07,609 --> 00:28:11,177
So, it's like the Sun.
471
00:28:15,250 --> 00:28:18,985
The burning shell of
hydrogen releases so much heat
472
00:28:18,987 --> 00:28:22,288
that gravity is overwhelmed,
473
00:28:22,290 --> 00:28:26,092
tipping the balance
in favor of rapid expansion.
474
00:28:26,094 --> 00:28:28,494
Gravity's not winning
the battle.
475
00:28:28,496 --> 00:28:32,164
So, the star expands
as a red giant.
476
00:28:36,638 --> 00:28:40,172
Astronomers predict that
in about five-billion years,
477
00:28:40,174 --> 00:28:42,742
the Sun will start
to grow into a vast,
478
00:28:42,744 --> 00:28:47,780
seething ball of fire...
479
00:28:47,782 --> 00:28:51,384
A red giant,
480
00:28:51,386 --> 00:28:55,354
sending temperatures soaring
across the solar system.
481
00:28:58,192 --> 00:29:00,693
The inner planets
will become far too hot
482
00:29:00,695 --> 00:29:03,362
to support any kind of life.
483
00:29:03,364 --> 00:29:05,865
But the distant outer planets
484
00:29:05,867 --> 00:29:08,334
will bask
in the warm glow of the Sun
485
00:29:08,336 --> 00:29:10,403
for the first time.
486
00:29:13,341 --> 00:29:18,711
The habitable zone, where
life can exist, will sweep out.
487
00:29:23,151 --> 00:29:25,351
In Peoria's solar system model,
488
00:29:25,353 --> 00:29:26,986
it would have meant
the habitable zone
489
00:29:26,988 --> 00:29:30,022
would leave town and head
for the outskirts.
490
00:29:34,696 --> 00:29:38,664
Here at the airport is Jupiter.
491
00:29:44,472 --> 00:29:49,141
When the Sun grows, Jupiter
will come in from the cold.
492
00:29:52,046 --> 00:29:53,946
And although life as we know it
493
00:29:53,948 --> 00:29:56,882
could never survive
on gassy Jupiter,
494
00:29:56,884 --> 00:30:01,654
the solar system's biggest
planet has several icy moons.
495
00:30:03,791 --> 00:30:07,660
These are likely to melt
and become cosmic watering holes
496
00:30:07,662 --> 00:30:13,132
for any refugees fleeing
the parched inner solar system.
497
00:30:13,134 --> 00:30:17,536
Astronomers have speculated
that Jupiter could change color.
498
00:30:21,042 --> 00:30:23,109
As clouds of ammonia vaporize,
499
00:30:23,111 --> 00:30:26,412
it might turn
into a deep shade of blue.
500
00:30:31,786 --> 00:30:35,121
After Jupiter, astronomers
expect the habitable zone
501
00:30:35,123 --> 00:30:37,289
to move swiftly towards saturn.
502
00:30:41,596 --> 00:30:44,430
If saturn
still has its icy rings by then,
503
00:30:44,432 --> 00:30:47,199
they're forecast
to vaporize and disappear.
504
00:30:54,142 --> 00:30:56,542
But like Jupiter,
saturn's icy moons
505
00:30:56,544 --> 00:30:59,745
could melt and be
safe havens for life.
506
00:31:08,289 --> 00:31:10,790
Then models
predict the habitable zone
507
00:31:10,792 --> 00:31:13,526
will sweep out
faster and faster,
508
00:31:13,528 --> 00:31:18,464
past the solar system's most
distant planets and their moons.
509
00:31:18,466 --> 00:31:20,499
First, uranus.
510
00:31:26,874 --> 00:31:29,041
Then deep-blue Neptune.
511
00:31:31,779 --> 00:31:35,281
Astronomers think they, too,
will be transformed.
512
00:31:35,283 --> 00:31:39,852
But exactly how they'll look in
the future is still a mystery.
513
00:31:42,957 --> 00:31:47,426
Eventually, the habitable zone
is forecast to pass beyond
514
00:31:47,428 --> 00:31:50,129
all the planets and their moons.
515
00:31:52,400 --> 00:31:55,167
Although Neptune's
the final planet,
516
00:31:55,169 --> 00:31:59,705
the solar system
doesn't finish there.
517
00:32:05,916 --> 00:32:08,049
In July 2015,
518
00:32:08,051 --> 00:32:12,554
the New Horizons mission finally
revealed Pluto's secrets.
519
00:32:18,996 --> 00:32:22,998
The first clear images ever
captured of the dwarf planet
520
00:32:23,000 --> 00:32:26,902
revealed some startling terrain.
521
00:32:26,904 --> 00:32:31,139
Strange troughs, cliffs,
522
00:32:31,141 --> 00:32:32,974
and even dunes.
523
00:32:36,647 --> 00:32:40,148
After a 12-billion-year-long
winter,
524
00:32:40,150 --> 00:32:41,316
the expanding sun
525
00:32:41,318 --> 00:32:44,052
may bring spring to Pluto.
526
00:32:49,293 --> 00:32:53,728
But while the red giant
nurtures Pluto,
527
00:32:53,730 --> 00:32:55,230
it poses a grave threat
528
00:32:55,232 --> 00:32:58,400
to the planets
of the inner solar system.
529
00:32:58,402 --> 00:33:01,002
They face total annihilation.
530
00:33:07,144 --> 00:33:09,711
Studying the night sky,
531
00:33:09,713 --> 00:33:12,547
Dr. Eva Villaver
uncovered grisly evidence
532
00:33:12,549 --> 00:33:17,752
of what red giants can do
to their inner planets.
533
00:33:17,754 --> 00:33:19,621
A search for distant worlds
534
00:33:19,623 --> 00:33:22,290
had led to the constellation
of perseus,
535
00:33:22,292 --> 00:33:26,461
where a star called bd+48 740
536
00:33:26,463 --> 00:33:31,266
caught her attention
for two reasons.
537
00:33:31,268 --> 00:33:34,703
There we have a star,
a red giant,
538
00:33:34,705 --> 00:33:36,171
that was very peculiar,
539
00:33:36,173 --> 00:33:39,975
because the star itself has
a very high content in lithium,
540
00:33:39,977 --> 00:33:42,644
and that's very unusual
for these type of stars.
541
00:33:42,646 --> 00:33:46,414
So, that was one of the pieces
of the puzzle.
542
00:33:46,416 --> 00:33:50,151
And the other one was that it
has a Jupiter-like planet
543
00:33:50,153 --> 00:33:55,156
orbiting the star that has
an orbit that is very unusual.
544
00:33:55,158 --> 00:33:57,592
Eva thought
the two strange features
545
00:33:57,594 --> 00:34:00,128
must be somehow connected.
546
00:34:00,130 --> 00:34:01,629
Something had happened
547
00:34:01,631 --> 00:34:05,400
that had affected both
the planet and the star itself.
548
00:34:09,206 --> 00:34:12,007
In around 5.5-billion years,
549
00:34:12,009 --> 00:34:15,944
our own sun will enter this
extraordinary phase of its life.
550
00:34:18,915 --> 00:34:22,617
Evidence suggests its surface
will reach out towards Mercury,
551
00:34:22,619 --> 00:34:24,686
Venus, and Earth,
552
00:34:24,688 --> 00:34:28,990
threatening
their very existence.
553
00:34:28,992 --> 00:34:31,393
Local astronomer Sheldon Schafer
554
00:34:31,395 --> 00:34:35,196
is leading his weekly
interplanetary bicycle tour,
555
00:34:35,198 --> 00:34:39,801
with the Sun's surface
hot on his heels.
556
00:34:39,803 --> 00:34:41,669
And here we are,
approaching Mercury.
557
00:34:45,909 --> 00:34:49,677
You can see it's easily a stunt
double for the Earth's moon.
558
00:34:49,679 --> 00:34:52,480
It's a heavily cratered world
without an atmosphere.
559
00:34:52,482 --> 00:34:56,051
Hot in the Sun
and cold in the darkness.
560
00:34:56,053 --> 00:35:00,388
But the solar system's smallest
planet will get hotter still.
561
00:35:00,390 --> 00:35:02,190
Off to Venus.
562
00:35:02,192 --> 00:35:05,460
Because astronomers predict
that less than a billion years
563
00:35:05,462 --> 00:35:08,263
into the red giant phase,
564
00:35:08,265 --> 00:35:11,032
the Sun's surface
will reach Mercury.
565
00:35:13,503 --> 00:35:15,303
After more than 10-billion years
566
00:35:15,305 --> 00:35:17,038
of relative calm,
567
00:35:17,040 --> 00:35:21,242
the solar system
will lose a planet.
568
00:35:27,484 --> 00:35:32,720
And the Sun
will continue to expand,
569
00:35:32,722 --> 00:35:35,256
growing ever closer to Venus.
570
00:35:39,796 --> 00:35:45,066
The next planet is Earth.
571
00:35:47,370 --> 00:35:49,971
By the time
the Sun engulfs Venus,
572
00:35:49,973 --> 00:35:53,942
the Earth's oceans are expected
to have boiled away.
573
00:35:56,613 --> 00:36:01,549
The ultimate fate of our world
appears to be on a knife's edge.
574
00:36:10,026 --> 00:36:12,727
For a vision of those final days
on Earth,
575
00:36:12,729 --> 00:36:16,197
Dr. Eva Villaver
has come to a unique facility
576
00:36:16,199 --> 00:36:19,234
in odeillo, France...
577
00:36:19,236 --> 00:36:22,337
The world's largest
solar furnace.
578
00:36:25,142 --> 00:36:27,442
As the Sun becomes a red giant,
579
00:36:27,444 --> 00:36:31,079
we will have a red star
occupying most of the sky.
580
00:36:31,081 --> 00:36:35,416
And the energy that
every single inch of the Earth
581
00:36:35,418 --> 00:36:37,018
will receive will increase.
582
00:36:37,020 --> 00:36:41,523
I hear that this is exactly
what these mirrors are doing.
583
00:36:41,525 --> 00:36:45,426
Around 10,000 mirrors
focus the Sun's rays
584
00:36:45,428 --> 00:36:48,763
like a giant magnifying glass,
585
00:36:48,765 --> 00:36:51,466
which allows them
to replicate the conditions
586
00:36:51,468 --> 00:36:57,272
the Earth will face when the Sun
becomes a red giant.
587
00:37:04,804 --> 00:37:07,571
Dr. Eva Villaver
is calculating the temperature
588
00:37:07,573 --> 00:37:10,408
of the Earth's surface
when the Sun's radiation
589
00:37:10,410 --> 00:37:14,078
will be nearly 3,000 times
more intense than today.
590
00:37:19,252 --> 00:37:21,118
So, to simulate our future,
591
00:37:21,120 --> 00:37:26,891
the solar furnace has magnified
the Sun's power by 3,000 times.
592
00:37:28,961 --> 00:37:32,329
We are focusing
the light of the Sun in a beam
593
00:37:32,331 --> 00:37:34,965
and trying to see what will be
the effect on a rock,
594
00:37:34,967 --> 00:37:37,902
because the Earth is a rock
floating around the Sun.
595
00:37:46,379 --> 00:37:48,245
Wow! Look at this.
596
00:37:54,253 --> 00:37:55,986
There it goes.
597
00:38:01,227 --> 00:38:03,160
The temperature
of the surface of the Earth
598
00:38:03,162 --> 00:38:08,132
at that point will be
of the order of 1,400 degrees...
599
00:38:08,134 --> 00:38:09,633
Enough to melt rock,
600
00:38:09,635 --> 00:38:12,036
enough to melt the whole surface
of the Earth.
601
00:38:16,976 --> 00:38:18,776
It's thought
the planet will be covered
602
00:38:18,778 --> 00:38:21,412
in a vast ocean of molten lava.
603
00:38:23,950 --> 00:38:26,484
But even after
the Earth's surface is melted,
604
00:38:26,486 --> 00:38:29,053
the heat is expected
to increase further
605
00:38:29,055 --> 00:38:32,323
as the planet is engulfed.
606
00:38:32,325 --> 00:38:34,692
The maximum intensity
of the solar furnace
607
00:38:34,694 --> 00:38:38,762
is 16,000 times
the Sun's power today.
608
00:38:41,267 --> 00:38:42,900
Still only a fraction
609
00:38:42,902 --> 00:38:48,305
of what the Earth would
encounter inside the red giant.
610
00:38:48,307 --> 00:38:50,841
The rock would be stripped away,
611
00:38:50,843 --> 00:38:53,611
leaving just
the planet's iron core.
612
00:39:01,687 --> 00:39:02,853
Wow! Look at this.
613
00:39:02,855 --> 00:39:08,092
Just sun radiation.
614
00:39:08,094 --> 00:39:13,464
That's iron being melted
by the radiation of the Sun.
615
00:39:13,466 --> 00:39:18,836
This is how the last
moments of our world would be.
616
00:39:18,838 --> 00:39:21,372
So, everything,
the whole material of the Earth,
617
00:39:21,374 --> 00:39:23,274
will melt, all the way
down to the core.
618
00:39:23,276 --> 00:39:25,209
Even the iron core will melt.
619
00:39:25,211 --> 00:39:27,177
And the whole material
of the Earth
620
00:39:27,179 --> 00:39:29,046
would be part of the material
of the Sun.
621
00:39:29,048 --> 00:39:31,882
Everything
would be mixed together.
622
00:39:31,884 --> 00:39:34,485
According
to the latest calculations,
623
00:39:34,487 --> 00:39:36,854
the world will end in fire.
624
00:39:41,227 --> 00:39:45,529
But our solar system's
story is not quite over yet,
625
00:39:45,531 --> 00:39:48,599
because the final phase
of the Sun's life
626
00:39:48,601 --> 00:39:53,637
will be the most
spectacular of all.
627
00:39:53,639 --> 00:39:54,738
There's seven sisters.
628
00:39:54,740 --> 00:39:56,173
Like an upside down "l."
629
00:39:56,175 --> 00:39:58,008
Nick, you wanted
to see the Andromeda?
630
00:39:58,010 --> 00:39:59,843
It's really cool.
631
00:39:59,845 --> 00:40:01,445
Wow.
632
00:40:01,447 --> 00:40:04,214
In Peoria, every Saturday night,
633
00:40:04,216 --> 00:40:07,985
the astronomy society meets
by the northmoor observatory
634
00:40:07,987 --> 00:40:10,187
at the edge of town.
635
00:40:10,189 --> 00:40:13,390
Between these two stars
is the remnant
636
00:40:13,392 --> 00:40:17,361
of what's gonna happen
to our sun.
637
00:40:17,363 --> 00:40:19,029
So, we're gonna move
the telescope.
638
00:40:19,031 --> 00:40:21,899
And, Brian, do you want
to move the dome?
639
00:40:21,901 --> 00:40:24,935
Tonight, Sheldon
is searching for a distant,
640
00:40:24,937 --> 00:40:27,938
dying star...
641
00:40:27,940 --> 00:40:30,007
The ring nebula.
642
00:40:32,411 --> 00:40:34,945
Okay. That's good, Brian.
643
00:40:34,947 --> 00:40:38,682
Ha!
I think it's there.
644
00:40:38,684 --> 00:40:42,052
Okay. So, come on over
and take a look.
645
00:40:42,054 --> 00:40:43,520
Look through the eyepiece.
646
00:40:43,522 --> 00:40:44,989
And you should see
a lot of stars.
647
00:40:44,991 --> 00:40:47,057
And then right in the middle, do
you see that little smoke ring?
648
00:40:47,059 --> 00:40:48,592
Yes.
649
00:40:48,594 --> 00:40:51,161
- It's just barely there, right?
- Yeah.
650
00:40:51,163 --> 00:40:51,895
Wow.
651
00:40:51,897 --> 00:40:52,830
And, so, this is a star
652
00:40:52,832 --> 00:40:56,500
that, after the red giant stage,
653
00:40:56,502 --> 00:40:58,636
it puffs off shells of itself.
654
00:40:58,638 --> 00:41:01,605
It expels most
of its matter into, like,
655
00:41:01,607 --> 00:41:04,441
bubbles of gas.
656
00:41:04,443 --> 00:41:07,878
The planetary nebulae
produced by dying stars
657
00:41:07,880 --> 00:41:10,914
are some of the most
spectacular celestial objects
658
00:41:10,916 --> 00:41:13,617
in the night sky.
659
00:41:13,619 --> 00:41:18,722
When our sun dies,
it too could make a nebula.
660
00:41:18,724 --> 00:41:22,359
Astronomers have calculated that
up to half of the Sun's mass
661
00:41:22,361 --> 00:41:27,197
could be thrown off
into space as gas and dust.
662
00:41:27,199 --> 00:41:32,836
Including much of the material
that came from the Earth.
663
00:41:32,838 --> 00:41:36,040
The vaporized remains
of half the solar system
664
00:41:36,042 --> 00:41:39,877
would glow brilliantly
for around 10,000 years.
665
00:41:44,150 --> 00:41:46,517
Then, as it spreads into space,
666
00:41:46,519 --> 00:41:50,988
the light would slowly fade...
667
00:41:50,990 --> 00:41:53,590
And our solar system will end.
668
00:41:59,832 --> 00:42:02,933
But in a sense,
it's just a new beginning.
669
00:42:06,505 --> 00:42:09,006
The materials
that make up our bodies
670
00:42:09,008 --> 00:42:14,645
may well ultimately get spit out
into the cosmos
671
00:42:14,647 --> 00:42:15,779
and be the raw materials
672
00:42:15,781 --> 00:42:19,817
for another generation
of stars, planets,
673
00:42:19,819 --> 00:42:21,585
and maybe even life forms.
674
00:42:24,957 --> 00:42:28,158
We're all famously
made of star stuff.
675
00:42:30,596 --> 00:42:34,631
And one day,
we may return to a star...
676
00:42:34,633 --> 00:42:39,436
Our sun.
677
00:42:39,438 --> 00:42:45,209
But then, in an extraordinary
process of cosmic rebirth,
678
00:42:45,211 --> 00:42:48,312
the Sun would return our atoms
679
00:42:48,314 --> 00:42:51,815
to interstellar space
680
00:42:51,817 --> 00:42:55,886
to form new worlds,
681
00:42:55,888 --> 00:42:59,256
and perhaps new life.53073
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