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BRIAN COX: The natural world
is beautiful
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but complex.
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The skies dance with color.
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Yeah! Yes!
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Shapes of great geometrical beauty
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form and disappear.
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And the planet itself
is constantly transformed.
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But this seemingly infinite complexity
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is just a shadow of something deeper,
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the underlying laws of nature.
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The world we live in
is beautiful to look at
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but it's even more beautiful
to understand.
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Light is our window on the universe.
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By understanding how light
is emitted by the sun
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and how it interacts with the oceans,
atmosphere and life on our planet,
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we can explore worlds
beyond our solar system,
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and even search for the tell-tale
signatures of life amongst the stars.
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Night on our planet seems eerie,
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other, as if all the color
has drained away.
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But in a few places on Earth,
on just a handful of nights in the year,
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color bursts through.
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10,000 years ago,
at the end of the last ice age,
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the ice sheets melted
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and this part of Iceland rose up
and drove the coastline back.
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That left the Skoga River to tumble
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over the old sea cliffs
to form that, Skogafoss,
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one of Iceland's great waterfalls.
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When the sun, moon and Earth align,
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moonlight interacts with the spray
at the foot of the falls
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to form a moonbow.
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Light leaves the sun,
travels 93 million miles across space,
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and reflects off the surface of the moon
and enters the Earth's atmosphere,
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bounces in and out of water droplets
in the waterfall,
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enters my eye,
that sends a signal to my brain
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and I reconstruct the signal
into something beautiful.
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But the moonbow isn't just beautiful,
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it's physics.
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Understanding why something
is the color it is tells you something.
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It tells you about its structure,
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about the processes going on inside,
about its history even.
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And because light travels freely
across the universe,
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we can explore distant worlds
using light alone,
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and we can tell their stories, too.
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The reflected light from the moon
has its origin in our star, the sun.
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Stars illuminate the universe.
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They are the source of the light
that bathes the planets.
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But the processes by which light
is emitted by the stars
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can be explored here on Earth.
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On the 51st of August 2014,
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a vast chasm opened up
in central Iceland.
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At its peak, the Bardarbunga volcano
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spewed out 350 cubic meters
of molten rock every second,
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producing light so bright,
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it could be seen from space.
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And just like the sun,
lava glows because it's hot.
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Just look at that.
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It's many months since the eruption,
but it's steaming away back there.
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We're actually fortunate
that it erupted here.
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The helicopter pilot told me that
if it had erupted on the glacier,
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then we would have been plunged
into perpetual nuclear winter
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and civilization would
have been destroyed.
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That's not actually quite right
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but it would have
been significantly worse.
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The amount of ash that went up
into the atmosphere
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would have been really considerable.
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You get a sense of the power
and violence of the Earth.
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We're blissfully unaware of it usually.
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When it breaks through the surface
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you see what it can do.
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Today, the lava has cooled
into matte black rock
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but it's still giving off light.
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The thing is, everything is hot,
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everything has a temperature.
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But if it's cold, it just emits light
that we can't see.
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This camera can see it, though.
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It's called infrared light.
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You see there that this lava
is glowing brighter than the background,
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which means it's hotter.
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So, although we can't see it,
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everything shines.
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Light fills the universe.
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Radio waves are light.
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X-rays are light.
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Visible light is simply the part
of the spectrum we can see.
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Matter, like lava or you and me,
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is made up of electrically
charged particles.
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Here's one, moving along.
Say it's an electron.
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Temperature is a measure of how fast
those particles are moving around,
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how fast they're jiggling.
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So, in something hot,
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these particles are always
bouncing around and changing direction.
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Now, here's a fundamental law
of the universe.
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When a charged particle
changes direction,
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it emits a light particle
called a photon.
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Light can be thought of
as a stream of photons,
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particles whose energy
corresponds to their color.
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Cooler things, like solid black lava,
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emit lower energy photons,
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infrared light,
which our eyes can't detect.
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As things get hotter,
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they can radiate higher energy photons.
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At 7, 000 degrees Celsius,
molten la Va shines
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with mainly red light,
which our eyes can detect.
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The surface of the sun
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is 5,500 degrees Celsius,
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so it can also produce higher energy
green and blue photons
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alongside the red.
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The white light of the sun is made up
of all the colors of the rainbow
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and when it reaches the Earth,
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those individual colors are revealed.
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Photons from the sun rain down
and enter water droplets.
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They reflect off the rear face,
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out of the front again
and into your eye.
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But the blue photons,
the higher energy ones,
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behave differently to the green ones
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and the yellow ones and the red ones.
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They come out at a shallower angle,
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and that's why you get
the full spectrum of colors
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from the white light of the sun.
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And it's this light
that paints the Earth.
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The colors of our planet arise
because of the way photons from the sun
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interact with the matter
from which the Earth is made.
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From space, our planet is a blue world
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and that blue color arises
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because of the way light
interacts with water
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and the process is linked to one
of the planet's greatest migrations.
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Every spring,
Marine Biologist Oswaldo Vasquez
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heads out onto the high seas...
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(IN DISTINCT RADIO CHATTER)
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It's 11. 11 o'clock.
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In search of these waters'
most awe-inspiring seasonal visitors.
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(LAUGHS)
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Humpback whales.
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Every year, they make the longest
migration of any mammal on Earth,
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traveling up to 8,000 kilometers,
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from their feeding grounds
in the Northern Atlantic,
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to the striking blue waters
of the Silver Bank Marine Reserve.
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OSWALDO: This is the greatest nursery
of humpback whales in the world.
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85% of the North Atlantic population
comes here for breeding,
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mating and giving birth.
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So, from this place
depends the survival of this species.
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COX: The whales' life cycle
is intricately linked to the interaction
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between the light of the sun
and the water of the ocean.
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OSWALDO: In order to understand
their behavior, we need to go beneath,
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and to see with our own eyes
what is happening there.
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Not 'rust on surface, underwater.
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(OSWALDO SPEAKING)
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(IN DISTINCT)
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Yup, yup, yup.
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(OSWALDO SPEAKING)
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OSWALDO: Slow down, slow down.
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Slow down, slow down.
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OK.
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(WHALE some)
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COX: The reason humpbacks
come here to give birth
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is because the shallow waters around
Silver Bank are exceptionally warm.
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OSWALDO: Whales are warm-blood animals
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and when they give birth they have
a very skinny calf with no blubber.
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They need warm environment,
as they had inside mother.
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So, here in Silver Bank,
it's warm and it's protected,
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so it's suitable for giving birth.
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As photons of light rain down
onto the ocean,
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they strike water molecules,
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and some of this energy
goes into making them jiggle around,
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increasing their speed
and therefore their temperature.
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But it takes an awful lot of energy
to heat the oceans
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and so it's only here,
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exposed to the full glare
of the equatorial sun,
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that enough energy is absorbed
to raise the water temperature
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to a balmy 26 degrees,
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the perfect conditions for mothers
to raise their calves.
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(WHALE some)
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OSWALDO: The calves are really
very cute because they are like puppies
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but, underwater, it weighs one ton.
So, it's a big puppy. (CHUCKLES)
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But not all of the photons
that enter the water are absorbed.
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Some of them bounce
straight back out again
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and it's these photons
that reach our eyes
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and create the blue of the oceans.
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To understand why it's mainly
red photons that are absorbed
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rather than the blue ones,
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we need to take a closer look
at the structure of water.
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This is called Pingvellir.
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That's a rough pronunciation
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but in Icelandic
it means Parliament Valley
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because the Vikings use to meet here
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over 1,000 years ago
and had the world's first parliament.
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The thing is,
it's not actually a valley,
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in the sense
that it wasn't cut by a river
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or a glacier.
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It was actually formed by
the continents themselves
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splitting apart.
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So, that is the American
continental plate,
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and that is the Eurasian
continental plate.
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Now, if you just go about
a mile down the road,
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this place is flooded,
and you can dive in it.
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The rift is filled with glacial
melt water
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that seeps down from Iceland's
frozen interior.
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The sun's rays are much weaker here
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00:18:07,295 --> 00:18:10,344
but wherever sunlight hits
water molecules
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it always produces the same color.
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How's that feel?
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That's good.
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It's quite nice in here actually.
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I can't believe this water.
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You can see for miles.
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I've never seen anything like it.
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The reason for that purity
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is that the water's come 50 kilometers,
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sometimes going deep underground,
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and is filtered by these rocks.
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So it's some of the coldest,
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purest water you can imagine.
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It's really, really spectacular.
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Look at that. You can see forever.
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Descending deeper into the fissure,
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00:19:41,931 --> 00:19:44,855
the effects on the color
of my dry suit
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00:19:44,934 --> 00:19:47,858
hints at the process
by which the oceans
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acquire their distinctive blue.
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00:19:56,612 --> 00:19:58,706
Well, now we're down at about, uh...
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Well, 12 meters.
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And you see, down here
my beautiful red diving suit
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00:20:08,624 --> 00:20:11,423
is no longer quite as red as it was.
(CHUCKLES)
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In fact it's looking quite black.
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And the reason for that
is the structure
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00:20:18,300 --> 00:20:20,473
of water molecules themselves.
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A water molecule is an oxygen
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with two hydrogens attached,
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and when the light streams
into the water,
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the red light is just the right energy
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to start those molecules vibrating,
and they do.
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They start going like that,
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and like that, and even like that.
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So, all the energy
in the red light is taken
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making the water molecules
wobble and vibrate.
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00:20:55,296 --> 00:20:56,536
The blue light doesn't do that.
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00:20:57,590 --> 00:21:00,764
So, the blue light can scatter around
in the water
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00:21:00,843 --> 00:21:02,220
relatively unimpeded.
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00:21:03,596 --> 00:21:06,691
And that's why water is blue.
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00:21:08,476 --> 00:21:09,477
Cool, isn't it?
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00:21:19,153 --> 00:21:20,154
(WHALE some)
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00:21:20,237 --> 00:21:25,209
Vibrations inside the water molecules
themselves give the oceans their color.
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00:21:26,410 --> 00:21:31,132
The weaker bonds between water
molecules also absorb some light.
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00:21:32,333 --> 00:21:36,008
Together these processes
absorb so much energy
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00:21:36,086 --> 00:21:39,306
that there isn't a lot left
to increase the sea temperature,
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00:21:41,133 --> 00:21:44,103
which is why Humpbacks
must travel so far
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00:21:44,178 --> 00:21:46,601
to find water warm enough to give birth.
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00:21:57,399 --> 00:21:59,026
(DOLPHIN SQUEALING)
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00:22:06,033 --> 00:22:09,754
Because water is hard to heat up,
the temperature of the oceans
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00:22:09,829 --> 00:22:11,456
remains very stable,
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00:22:13,541 --> 00:22:16,920
creating the perfect conditions
for live to thrive.
251
00:22:27,513 --> 00:22:32,895
Liquid water is the essential ingredient
for any life-supporting world.
252
00:22:36,814 --> 00:22:40,284
Oceans cover 70%
of the Earth's surface,
253
00:22:41,443 --> 00:22:45,118
their distinctive blue
broadcasting to the universe
254
00:22:45,197 --> 00:22:49,247
the message that Earth
is a possible home for life.
255
00:22:54,415 --> 00:22:57,419
And beyond the waves, on the land,
256
00:22:57,459 --> 00:23:00,429
we see life's other signature color,
257
00:23:00,462 --> 00:23:02,510
a blanket of green plants.
258
00:23:04,216 --> 00:23:08,016
As with all living things,
they depend on water to survive,
259
00:23:09,138 --> 00:23:11,561
and when the seasonal rains recede,
260
00:23:11,640 --> 00:23:15,895
the land reverts to the arid colors
of the naked earth.
261
00:23:28,198 --> 00:23:32,704
The intense African sun delivers
1,000 watts of solar power
262
00:23:32,786 --> 00:23:34,538
per square meter,
263
00:23:34,580 --> 00:23:37,504
baking the plains
of the Serengeti to dust.
264
00:23:42,838 --> 00:23:47,810
Scorched brown, barely a single blade
of green grass survives.
265
00:23:51,931 --> 00:23:56,983
For the Masai, the dry season
means months of hunger and hardship.
266
00:24:01,148 --> 00:24:04,072
Para Kapooni and his son and brother
267
00:24:04,151 --> 00:24:06,529
must say goodbye to their home valley
268
00:24:08,781 --> 00:24:11,284
and drive their cows across the plains
269
00:24:11,367 --> 00:24:15,372
in search of enough grass
and water to keep them alive
270
00:24:15,454 --> 00:24:16,922
until the rains return.
271
00:24:19,249 --> 00:24:21,377
(PARA KAPOONI
SPEAKING OWN LANGUAGE)
272
00:24:40,562 --> 00:24:41,609
(COWBELLS RINGING)
273
00:24:56,120 --> 00:24:58,214
At the end of their long journeys,
274
00:24:58,288 --> 00:25:00,916
Masai warriors from across
the Serengeti
275
00:25:01,208 --> 00:25:03,961
gather on the banks of Lake Masek.
276
00:25:04,837 --> 00:25:05,884
(KIDS CHATTERING)
277
00:25:08,007 --> 00:25:09,554
(PARA KAPOONI
SPEAKING OWN LANGUAGE)
278
00:25:37,494 --> 00:25:40,418
But survival on the plains
of the Serengeti
279
00:25:40,497 --> 00:25:45,219
forces Para Kapooni and his family
to spend the dry season apart
280
00:25:48,380 --> 00:25:52,886
because while he tends the cattle,
his wife, Nura Kapooni,
281
00:25:52,968 --> 00:25:55,938
must stay behind to look after
those too young
282
00:25:56,013 --> 00:25:57,936
or too old to make the trip,
283
00:25:59,558 --> 00:26:03,859
and eke out an existence
on the brown, lifeless plains.
284
00:26:06,940 --> 00:26:08,613
(NURA KAPOONI
SPEAKING OWN LANGUAGE)
285
00:26:30,172 --> 00:26:33,301
With the cows away,
the family must survive
286
00:26:33,342 --> 00:26:36,892
on their meager stores
of maize flour and water.
287
00:26:39,014 --> 00:26:40,391
(CRYING)
288
00:27:01,453 --> 00:27:03,080
(PARA KAPOONI
SPEAKING OWN LANGUAGE)
289
00:27:29,523 --> 00:27:31,196
(THUNDER RUMBLING)
290
00:27:32,734 --> 00:27:35,453
Now, after four long months apart,
291
00:27:36,613 --> 00:27:38,866
things are about to change.
292
00:27:48,458 --> 00:27:50,426
(NURA KAPOONI
SPEAKING OWN LANGUAGE)
293
00:28:08,562 --> 00:28:11,691
The coming of the rains
means the grass can grow again.
294
00:28:20,866 --> 00:28:24,040
Revived, new shoots emerge,
295
00:28:24,119 --> 00:28:27,623
packed with the green
pigment, chlorophyll,
296
00:28:31,460 --> 00:28:35,215
which allows plants to harvest
the sun's energy
297
00:28:40,552 --> 00:28:46,275
and the plains are transformed
from dusty brown to vibrant green.
298
00:28:51,355 --> 00:28:56,236
In just a few days,
the landscape is reborn.
299
00:29:16,004 --> 00:29:18,974
I suppose we think of green
as the color of life
300
00:29:19,049 --> 00:29:22,098
but actually it's the color
that life throws away,
301
00:29:22,177 --> 00:29:26,273
waste, green photons, reflected back
into our eyes.
302
00:29:26,348 --> 00:29:29,101
Plants absorb most of the rest
of the rainbow,
303
00:29:29,184 --> 00:29:31,528
the blue and red photons,
304
00:29:31,603 --> 00:29:34,402
and use their energy
to power photosynthesis.
305
00:29:37,818 --> 00:29:42,665
Photosynthesis is the process
by which plants harness light.
306
00:29:43,031 --> 00:29:45,910
They are the bridge
between nuclear reactions
307
00:29:45,993 --> 00:29:49,998
93 million miles away
and life on Earth.
308
00:29:53,250 --> 00:29:57,426
Energy released from nuclear
fusion reactions in the sun's core
309
00:29:57,504 --> 00:30:00,599
heats everything up
and shakes electrons around
310
00:30:00,966 --> 00:30:04,846
and those electrons will emit photons,
311
00:30:05,095 --> 00:30:07,564
which travel across space
for eight minutes,
312
00:30:07,639 --> 00:30:09,858
and then hit an electron
313
00:30:10,517 --> 00:30:12,190
in a chlorophyll molecule.
314
00:30:12,894 --> 00:30:16,239
But instead of that energy
being dissipated away as heat,
315
00:30:16,898 --> 00:30:18,741
chlorophyll is clever
316
00:30:18,817 --> 00:30:22,492
and ultimately the energy
imparted to that electron
317
00:30:22,571 --> 00:30:24,869
is used to do all sorts of clever things
318
00:30:24,948 --> 00:30:27,417
through an intricate piece
of machinery.
319
00:30:27,492 --> 00:30:31,122
Split water up,
force electrons on to carbon dioxide
320
00:30:31,204 --> 00:30:34,959
and ultimately build sugars,
which allows the plant to grow.
321
00:30:39,880 --> 00:30:41,928
COX: On the plains of the Serengeti,
322
00:30:42,007 --> 00:30:45,102
the intricate process of photosynthesis
323
00:30:45,177 --> 00:30:49,853
means Para Kapooni can begin
the long journey to rejoin his family.
324
00:30:52,517 --> 00:30:54,986
(NURA KAPOONI
SPEAKING OWN LANGUAGE)
325
00:31:01,193 --> 00:31:02,786
COX: After months apart,
326
00:31:02,861 --> 00:31:08,038
the greening of the Serengeti
transforms the harshest of environments
327
00:31:08,116 --> 00:31:11,290
into a place the Masai can call home.
328
00:31:15,540 --> 00:31:18,339
(NURA KAPOONI
SPEAKING OWN LANGUAGE)
329
00:31:41,733 --> 00:31:44,577
(PARA KAPOONI
SPEAKING OWN LANGUAGE)
330
00:32:13,140 --> 00:32:16,440
COX: Animals eat plants
that feed on sunlight.
331
00:32:22,399 --> 00:32:26,404
In this way, the sun's energy
powers the entire food chain.
332
00:32:32,117 --> 00:32:36,213
But photosynthesis does more
than provide life with energy.
333
00:32:39,458 --> 00:32:42,052
Around 2.5 billion years ago,
334
00:32:42,127 --> 00:32:47,429
it began to transform the composition
of the Earth's atmosphere itself
335
00:32:47,507 --> 00:32:51,728
by filling it with
the waste products, oxygen,
336
00:32:51,803 --> 00:32:55,603
the gas upon which
all complex life depends.
337
00:33:05,108 --> 00:33:09,784
Without air to breathe, there would be
no intelligent life on Earth.
338
00:33:15,994 --> 00:33:18,838
We rely absolutely on the oxygen
339
00:33:18,914 --> 00:33:22,043
that forms a fifth of the thin blue line
340
00:33:22,125 --> 00:33:24,048
that envelops our planet.
341
00:33:30,675 --> 00:33:32,928
And, perhaps paradoxically,
342
00:33:33,678 --> 00:33:37,899
why the sky is blue is best explained
in the dead of night.
343
00:33:51,071 --> 00:33:54,325
It's a beautiful, crisp autumn night
here in the south of England.
344
00:33:54,407 --> 00:33:57,832
Rolling hills illuminated by moonlight,
345
00:33:59,371 --> 00:34:03,501
which is the light from the sun
reflected off the surface of the moon.
346
00:34:06,211 --> 00:34:08,930
It's quite silent actually,
almost eerie.
347
00:34:09,005 --> 00:34:13,932
But out there, the Earth's shadow
is racing through space
348
00:34:14,010 --> 00:34:16,104
and actually is just beginning
349
00:34:16,179 --> 00:34:19,774
to cut off the top left-hand corner
of the moon.
350
00:34:23,520 --> 00:34:25,989
On a few nights every decade,
351
00:34:26,022 --> 00:34:29,196
the sun, moon and Earth line up
352
00:34:29,276 --> 00:34:32,576
to create one of the wonders
of the night sky,
353
00:34:32,654 --> 00:34:34,656
a total lunar eclipse.
354
00:34:37,534 --> 00:34:41,038
You get a real sense
of the celestial mechanics
355
00:34:41,121 --> 00:34:43,340
in action during an eclipse.
356
00:34:43,415 --> 00:34:46,464
The sun is somewhere
over there behind me,
357
00:34:46,501 --> 00:34:48,299
shining on our planet.
358
00:34:48,378 --> 00:34:52,383
And our planet is casting a shadow
through space,
359
00:34:52,465 --> 00:34:56,641
which falls on the surface
of our satellite, the moon.
360
00:35:01,349 --> 00:35:04,899
As the Earth moves
between the moon and the sun,
361
00:35:04,978 --> 00:35:08,653
it blocks light from falling directly
onto the lunar surface.
362
00:35:15,989 --> 00:35:19,539
Now, the moon is completely covered
by the Earth's shadow
363
00:35:20,368 --> 00:35:21,745
but it's not completely black.
364
00:35:22,370 --> 00:35:25,670
It's glowing a deep blood red.
365
00:35:29,461 --> 00:35:31,634
At the height of the eclipse,
366
00:35:31,713 --> 00:35:34,091
the only photons reaching the moon
367
00:35:34,174 --> 00:35:36,973
have passed through
the atmosphere of our planet.
368
00:35:39,846 --> 00:35:46,149
It's red because of the way that light
interacts with the Earth's atmosphere.
369
00:35:46,227 --> 00:35:50,858
Imagine that rain of photons passing
through the atmosphere from the sun,
370
00:35:50,940 --> 00:35:53,193
all the colors of the rainbow.
371
00:35:53,276 --> 00:35:57,156
Well, the blue photons,
the higher energy photons,
372
00:35:57,238 --> 00:36:00,959
have a higher probability
of bouncing off the molecules
373
00:36:01,034 --> 00:36:02,502
in the Earth's atmosphere.
374
00:36:02,577 --> 00:36:04,045
So they scatter around.
375
00:36:06,539 --> 00:36:09,793
That just leaves the lower energy
red photons,
376
00:36:09,876 --> 00:36:13,221
have a much lower probability
of bouncing around,
377
00:36:13,296 --> 00:36:16,220
and therefore can pass
through the Earth's atmosphere
378
00:36:16,299 --> 00:36:18,051
relatively unscathed.
379
00:36:18,134 --> 00:36:23,015
So they're the ones that make it
onto the moon's surface
380
00:36:23,098 --> 00:36:25,271
and reflect back into my eye.
381
00:36:25,350 --> 00:36:27,603
And that's why, in a lunar eclipse,
382
00:36:27,686 --> 00:36:29,859
you get a blood-red moon.
383
00:36:41,116 --> 00:36:42,288
And by day,
384
00:36:42,409 --> 00:36:47,882
the blue photons the atmosphere scatters
are what paint the skies blue.
385
00:36:51,501 --> 00:36:54,095
So, when you look up to the sky
on a summer's day
386
00:36:54,170 --> 00:36:55,922
and see that deep blue,
387
00:36:56,005 --> 00:36:59,305
what you're actually seeing
is blue photons
388
00:36:59,342 --> 00:37:02,642
scattering around off the molecules
in the atmosphere.
389
00:37:09,310 --> 00:37:15,033
Red, green, blue.
The primary colors of our planet.
390
00:37:16,109 --> 00:37:18,487
The Earth is painted by the photons
391
00:37:18,570 --> 00:37:21,494
that rain down
from the surface of the sun.
392
00:37:23,491 --> 00:37:25,164
But for us to see them,
393
00:37:25,243 --> 00:37:28,964
those photons
must take one final journey.
394
00:37:43,845 --> 00:37:45,597
(SALMA SPEAKING BENGALI)
395
00:37:54,272 --> 00:37:57,572
COX: Salma lives
with her seven-year-old son, Magidal,
396
00:37:57,650 --> 00:38:00,529
on the banks of the Gorai River
in Bangladesh.
397
00:38:06,034 --> 00:38:08,753
(SALMA SPEAKING BENGALI)
398
00:38:19,714 --> 00:38:22,263
COX: This is a vibrant place
to grow up.
399
00:38:23,676 --> 00:38:28,147
But unlike the other children,
Magidal can't experience it.
400
00:38:32,644 --> 00:38:34,442
(SALMA SPEAKING BENGALI)
401
00:38:50,870 --> 00:38:54,465
COX: For us to see,
photons must travel into our eyes.
402
00:38:55,375 --> 00:38:58,424
But Magidal was born
with severe cataracts.
403
00:39:00,046 --> 00:39:02,925
The lenses of his eyes are so clouded,
404
00:39:03,007 --> 00:39:05,886
he's been effectively blind
since birth.
405
00:39:09,389 --> 00:39:11,517
(FATHER SPEAKING BENGALI)
406
00:39:27,907 --> 00:39:31,628
COX: But today, Magidal's life
is about to change.
407
00:39:39,377 --> 00:39:43,302
His family are making the eight-hour
journey to the capital, Dhaka,
408
00:39:51,139 --> 00:39:54,860
because this afternoon,
Magidal will undergo surgery
409
00:39:54,934 --> 00:39:57,028
designed to restore his sight.
410
00:40:04,777 --> 00:40:07,781
(DOCTOR SPEAKING BENGALI)
411
00:40:15,580 --> 00:40:17,378
COX: If the surgery is successful,
412
00:40:17,916 --> 00:40:21,261
replacing his faulty lenses
with artificial ones
413
00:40:21,336 --> 00:40:24,931
will allow light to travel directly
into Magidal's eyes.
414
00:40:37,185 --> 00:40:38,357
It's at the back of the eye
415
00:40:38,436 --> 00:40:41,531
that photons collide
with cells in the retina
416
00:40:41,606 --> 00:40:44,701
sensitive to red, green and blue light,
417
00:40:47,153 --> 00:40:51,408
and trigger the nerve impulses
that allow us to see in color.
418
00:41:06,130 --> 00:41:07,757
(BICYCLE BELL RINGING)
419
00:41:11,219 --> 00:41:13,313
(SALMA SPEAKING BENGALI)
420
00:41:22,313 --> 00:41:23,690
(DOCTOR SPEAKING BENGALI)
421
00:41:41,165 --> 00:41:42,963
COX: For the first time in his life,
422
00:41:43,835 --> 00:41:47,760
photons are able
to enter Magidal's eyes unimpeded.
423
00:41:54,220 --> 00:41:56,097
For the first time in his life,
424
00:41:57,265 --> 00:41:58,391
he can see.
425
00:42:02,311 --> 00:42:03,528
(SPEAKING BENGALI)
426
00:42:47,440 --> 00:42:50,535
COX: Our eyes reveal to us
the colors of the Earth.
427
00:42:55,490 --> 00:42:59,290
The first step towards
understanding their meaning.
428
00:43:05,333 --> 00:43:08,678
The blue that signals
the presence of liquid water.
429
00:43:11,464 --> 00:43:16,595
The green that marks out our planet
as a home for complex life.
430
00:43:18,930 --> 00:43:23,276
And, in this most distant image
of the Earth ever taken,
431
00:43:23,351 --> 00:43:28,403
from six billion kilometers away
by the Voyager spacecraft.
432
00:43:28,481 --> 00:43:30,984
The sunlight bouncing off our atmosphere
433
00:43:31,067 --> 00:43:34,196
reveals our planet as a pale blue dot,
434
00:43:34,946 --> 00:43:37,699
hanging in the void of space.
435
00:43:40,243 --> 00:43:44,214
And even from this distance,
anyone who happened to be looking
436
00:43:44,288 --> 00:43:48,964
could tell our planet
contained the ingredients for life.
437
00:43:50,253 --> 00:43:53,257
Because in the most
delicate color signals,
438
00:43:53,339 --> 00:43:57,640
we have measured with precision
what the universe is made of.
439
00:44:03,141 --> 00:44:08,648
And those signals can be glimpsed
at the very edge of our own atmosphere.
440
00:44:23,911 --> 00:44:26,460
BECKY. What are we drawing?
OCEANIA: A sun dragon!
441
00:44:26,706 --> 00:44:29,926
- What's a sun dragon?
- It's just like a sun,
442
00:44:31,794 --> 00:44:35,424
and it's got smoke
coming out of its mouth
443
00:44:37,133 --> 00:44:40,433
'cause it's starting to make fire
on the world.
444
00:44:40,511 --> 00:44:41,683
(ROARS)
445
00:44:43,389 --> 00:44:46,814
Now, let's just do the fire.
446
00:44:48,102 --> 00:44:49,822
BECKI: We need to get ready
to go, don't we?
447
00:44:51,189 --> 00:44:52,190
Push!
448
00:44:52,273 --> 00:44:54,446
COX: For seven years,
the Nation family
449
00:44:54,525 --> 00:44:57,028
have been consumed by an obsession,
450
00:44:59,614 --> 00:45:02,663
ready to drop everything
at a moment's notice
451
00:45:02,700 --> 00:45:05,579
in pursuit of a light show
like no other.
452
00:45:09,081 --> 00:45:11,925
I'm an aurora chaser!
453
00:45:16,255 --> 00:45:18,849
COX: They've left their home
on the Sussex coast
454
00:45:18,925 --> 00:45:21,553
for the cold climes
of northern Norway...
455
00:45:22,678 --> 00:45:24,646
73, 98, 97.
456
00:45:25,723 --> 00:45:27,691
69, 98, 100.
457
00:45:28,684 --> 00:45:29,924
COX: Spending their weekends
458
00:45:29,977 --> 00:45:33,481
chasing one of the planet's
most extraordinary phenomena,
459
00:45:34,190 --> 00:45:37,694
the Northern Lights, Aurora Borealis.
460
00:45:40,821 --> 00:45:44,075
It's an addiction,
it's an absolute full-blown addiction.
461
00:45:44,158 --> 00:45:46,502
It's a buzz
and it's a rush of adrenaline
462
00:45:46,994 --> 00:45:48,962
and it's a holding of your breath and...
463
00:45:49,038 --> 00:45:50,915
(IN HALES) Wow.
464
00:45:53,125 --> 00:45:55,423
COX: The aurora
was once thought to be caused
465
00:45:55,503 --> 00:45:57,881
by dragons fighting in the sky.
466
00:46:00,132 --> 00:46:04,979
But today, we know its ethereal light
is created by charged particles
467
00:46:05,054 --> 00:46:06,931
known as the solar wind
468
00:46:07,014 --> 00:46:09,893
interacting with the gases
of the upper atmosphere.
469
00:46:14,855 --> 00:46:16,903
BECKI: Well, our eldest,
Aurora, she's 11.
470
00:46:16,941 --> 00:46:18,864
She's fascinated by,
471
00:46:18,901 --> 00:46:21,825
"Why do those different gases
make those different colors?"
472
00:46:21,904 --> 00:46:23,406
She's quite fascinated by them.
473
00:46:23,739 --> 00:46:26,288
Oshey, she likes the pink
'cause she likes pink.
474
00:46:26,367 --> 00:46:28,415
It's her favorite color,
so pink's cool.
475
00:46:28,494 --> 00:46:31,043
Anything else, just wake me up
if it goes pink.
476
00:46:31,122 --> 00:46:34,547
And Lyrica is quite a fact box
on everything.
477
00:46:34,625 --> 00:46:36,969
She can explain to you
what causes an aurora,
478
00:46:37,044 --> 00:46:38,421
where it comes from,
479
00:46:38,462 --> 00:46:41,841
the technical names and, you know,
what the magnetic field does,
480
00:46:41,924 --> 00:46:45,144
and how it stops the solar wind
from harming us.
481
00:46:49,974 --> 00:46:51,942
COX: But the aurora is elusive.
482
00:46:53,060 --> 00:46:56,064
To see it, conditions
have to be just right.
483
00:47:00,526 --> 00:47:01,926
BECKI: Shall we go build a snowman?
484
00:47:02,820 --> 00:47:07,451
COX: Clear, dark skies must combine
with strong solar winds.
485
00:47:14,373 --> 00:47:15,966
(CHATTERING)
486
00:47:16,625 --> 00:47:18,093
Mum, aren't you going to burn it?
487
00:47:29,388 --> 00:47:32,107
COX: All the family can do is wait.
488
00:47:55,873 --> 00:47:57,500
Ooh! Ooh, ooh, ooh!
489
00:47:58,501 --> 00:48:00,048
I can see some uprights there.
490
00:48:02,713 --> 00:48:04,340
Oh, wow!
491
00:48:14,100 --> 00:48:16,819
BECKI: Oh, yeah!
MR NATION: Here we go, look at it!
492
00:48:18,604 --> 00:48:21,824
BECKI: Beautiful! Look at it!
493
00:48:24,276 --> 00:48:26,074
Look how bright that is up there, look!
494
00:48:35,579 --> 00:48:38,048
Yeah! Yes! (LAUGHS)
495
00:48:38,958 --> 00:48:40,801
Now, that's what I'm talking about!
496
00:48:42,920 --> 00:48:45,799
Look! (GASPS) Ooh!
497
00:48:48,008 --> 00:48:49,168
Look! Look! Look! Look! Look!
498
00:48:49,677 --> 00:48:53,307
Corona, corona! Look at it!
499
00:48:53,514 --> 00:48:55,767
MR NATION: Look at the reds at the top!
500
00:48:56,100 --> 00:48:58,068
BECKI: Stunning! MR NATION: Wow!
501
00:49:02,648 --> 00:49:05,071
Oh! Oh! Oh! Oh, look at that!
502
00:49:07,987 --> 00:49:10,536
And on the left, on the left,
look there's some pink as well...
503
00:49:10,614 --> 00:49:12,287
BECKI: Yay! (INDISTINCT)
504
00:49:15,786 --> 00:49:18,380
COX: But the aurora
isn't simply beautiful.
505
00:49:19,165 --> 00:49:20,587
It contains information.
506
00:49:26,589 --> 00:49:29,843
As charged particles strike gas atoms,
507
00:49:29,925 --> 00:49:32,223
a photon of light is released.
508
00:49:35,514 --> 00:49:39,485
And because the atoms of every element
have a unique structure,
509
00:49:40,019 --> 00:49:43,489
each one gives off a photon
of a unique color.
510
00:49:47,359 --> 00:49:52,456
The green comes from oxygen atoms,
pink from nitrogen.
511
00:50:01,624 --> 00:50:02,625
BECKY. Yes:!
512
00:50:06,170 --> 00:50:08,719
COX: The colors
dancing across the sky
513
00:50:08,797 --> 00:50:11,516
reveal the composition
of our atmosphere.
514
00:50:14,637 --> 00:50:19,313
And it's these fingerprints
encoded in photons of light
515
00:50:19,391 --> 00:50:22,144
that have shown us the entire universe.
516
00:51:17,074 --> 00:51:18,872
In the last few 100 years,
517
00:51:19,159 --> 00:51:23,539
astronomers have gazed out
from the edges of our home world
518
00:51:26,041 --> 00:51:28,669
and dreamt of a universe beyond.
519
00:51:36,885 --> 00:51:41,106
In the shadow of the Eiger,
that is the Sphinx,
520
00:51:41,140 --> 00:51:46,067
and, despite appearances, isn't
the lair of some alpine super villain.
521
00:51:46,145 --> 00:51:47,772
It's an observatory.
522
00:51:47,855 --> 00:51:49,607
It was built in 1937,
523
00:51:49,690 --> 00:51:51,863
and since then,
astronomers have been coming here
524
00:51:51,900 --> 00:51:54,995
from all over the world
to look at the night sky.
525
00:52:04,538 --> 00:52:09,544
And by decoding messages hidden
in the light reaching our telescopes,
526
00:52:10,127 --> 00:52:13,347
we've discovered the true nature
of the cosmos.
527
00:52:19,011 --> 00:52:21,105
That's an aurora in a box.
528
00:52:21,180 --> 00:52:24,775
It's a tube full of hydrogen gas
that's heated up.
529
00:52:25,100 --> 00:52:28,525
And what you're seeing
in that pinky-red color
530
00:52:29,104 --> 00:52:33,610
are the fundamental laws of nature
themselves in action.
531
00:52:34,318 --> 00:52:37,117
See, they tell you that a single proton,
532
00:52:37,571 --> 00:52:41,621
which is a nucleus of hydrogen,
and a single electron
533
00:52:41,700 --> 00:52:44,169
can only behave in certain ways.
534
00:52:44,244 --> 00:52:48,590
The electrons can only go
in certain places around the proton.
535
00:52:48,666 --> 00:52:52,762
So, when you heat them up,
they can only jump high up.
536
00:52:54,213 --> 00:52:55,510
And then when they cool down,
537
00:52:55,589 --> 00:52:58,559
they can only fall back
in a specific way,
538
00:52:58,634 --> 00:53:03,481
releasing light of a particular energy
which equals a particular color.
539
00:53:03,806 --> 00:53:06,559
And those laws
don't just apply here on Earth,
540
00:53:06,642 --> 00:53:09,020
they apply everywhere
across the universe.
541
00:53:09,144 --> 00:53:12,774
So, anywhere that you see
glowing hydrogen gas,
542
00:53:12,856 --> 00:53:16,702
let's say, in a nebula
heated up by young stars,
543
00:53:16,777 --> 00:53:19,747
then you'll see that specific color.
544
00:53:26,120 --> 00:53:28,839
Vast clouds of glowing hydrogen
545
00:53:28,914 --> 00:53:32,464
create some of the most
spectacular sights in the cosmos,
546
00:53:36,130 --> 00:53:39,930
their pink hue revealing
the identity of the gas
547
00:53:40,008 --> 00:53:41,510
from which they're made.
548
00:53:53,939 --> 00:53:58,991
And what's true for nebulae
is true for everything in the universe.
549
00:54:02,156 --> 00:54:04,158
By analyzing the light from the stars,
550
00:54:04,450 --> 00:54:07,954
we know that they're not
just twinkling lights in the sky.
551
00:54:08,036 --> 00:54:12,086
They are other suns made out
of the same stuff as ours,
552
00:54:12,166 --> 00:54:15,466
and if there are other suns,
then there must be other planets,
553
00:54:15,544 --> 00:54:17,672
maybe even other Earths.
554
00:54:33,312 --> 00:54:36,612
By understanding the origin
of the colors of our world,
555
00:54:38,692 --> 00:54:40,410
the blue of its oceans,
556
00:54:43,197 --> 00:54:44,744
the green of its life
557
00:54:48,118 --> 00:54:50,917
and the colors
dancing in its atmosphere,
558
00:54:53,290 --> 00:54:57,796
we've uncovered the color signature
of a life-supporting planet.
559
00:55:02,549 --> 00:55:06,224
And because we understand
the signature of our own world,
560
00:55:07,054 --> 00:55:11,184
we can look for worlds like ours
elsewhere in the cosmos.
561
00:55:18,440 --> 00:55:21,284
But here's what I think
is the most wonderful thought of all.
562
00:55:21,401 --> 00:55:22,698
When you look out
563
00:55:22,778 --> 00:55:26,248
to those distant star systems
and planets,
564
00:55:26,323 --> 00:55:27,996
you're connected to them, see?
565
00:55:28,242 --> 00:55:32,964
An electron somewhere out there
radiated a photon
566
00:55:34,706 --> 00:55:38,176
which hit an electron in your eye.
567
00:55:39,169 --> 00:55:42,389
Alien photons
crossing light years of space
568
00:55:42,464 --> 00:55:44,216
entering your retina,
569
00:55:44,299 --> 00:55:47,098
and carrying stories of distant worlds.
570
00:55:53,475 --> 00:55:57,025
In the constellation of Pegasus,
around a sun-like star,
571
00:55:57,104 --> 00:55:58,981
there's a planet called Osiris.
572
00:55:59,273 --> 00:56:03,904
It's way closer to its parent star
than Mercury is to our sun
573
00:56:03,986 --> 00:56:07,991
but it's a massive gas giant,
a hot Jupiter.
574
00:56:08,073 --> 00:56:11,953
And by measuring the light
that shines through its atmosphere,
575
00:56:12,035 --> 00:56:16,290
we've found that the atmosphere's
full of hydrogen and methane
576
00:56:16,373 --> 00:56:17,716
and water.
577
00:56:20,210 --> 00:56:23,965
And just 24 light years away,
in the constellation of Scorpius,
578
00:56:24,047 --> 00:56:26,425
there's a small rocky world,
579
00:56:26,508 --> 00:56:29,227
one of the most
Earth-like worlds we know.
580
00:56:29,303 --> 00:56:32,182
It orbits around a red dwarf star,
581
00:56:32,264 --> 00:56:35,268
which is one of three stars
in the system.
582
00:56:36,226 --> 00:56:39,321
A planet with three suns in the sky.
583
00:56:43,692 --> 00:56:48,493
In the last 20 years, we've found
hundreds of planets around distant suns.
584
00:56:49,323 --> 00:56:51,701
We've begun to analyze
their atmospheres
585
00:56:51,742 --> 00:56:54,621
and search for life-giving water.
586
00:57:02,794 --> 00:57:05,047
Science is about gathering data,
587
00:57:05,297 --> 00:57:08,676
information about the natural world,
and trying to understand it.
588
00:57:09,092 --> 00:57:11,470
When put like that, it seems a bit dry.
589
00:57:12,179 --> 00:57:16,104
But when that information
carries stories of alien worlds
590
00:57:16,183 --> 00:57:19,403
around distant suns
hundreds of light years away,
591
00:57:19,478 --> 00:57:21,480
that's a whole different thing.
592
00:57:21,563 --> 00:57:25,409
Astronomy turns data into dreams,
593
00:57:25,484 --> 00:57:28,363
dreams of worlds of ice and snow,
594
00:57:28,445 --> 00:57:32,200
dreams of worlds
with hemispheres in perpetual day
595
00:57:32,282 --> 00:57:34,000
and permanent night.
596
00:57:34,117 --> 00:57:37,337
Dreams of worlds with moons
and moonbows,
597
00:57:37,412 --> 00:57:41,337
and perhaps, just perhaps,
alien astronomers,
598
00:57:41,875 --> 00:57:46,756
observing the light passing through
the atmosphere of our blue world,
599
00:57:47,381 --> 00:57:48,598
and dreaming of us.
48759
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