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NEIL DEGRASSE TYSON:
Once there was a world
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not so very different
from our own.
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There were occasional
natural catastrophes,
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massive volcanic eruptions
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and, every once in a while,
an asteroid would come
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barreling out of the blue
to do some damage.
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But for the first
billion years or so,
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it would've seemed
like a paradise.
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This is what we think
the planet Venus
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might have looked like when
our solar system was young.
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Then things started
to go horribly wrong.
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¶ ¶
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¶ ¶
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¶ ¶
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¶ ¶
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DEGRASSE TYSON:
The planet Venus,
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which once
may have seemed like a heaven,
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turned into a kind of hell.
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The difference between the two
can be a delicate balance,
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far more delicate
than you might imagine.
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Once things began to unravel,
there was no way back.
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This is what Venus,
our nearest planetary neighbor,
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looks like today.
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Venus's oceans are long gone.
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The surface is hotter
than a broiling oven,
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hot enough to melt lead.
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Why? You might think
it's because Venus
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is 30% closer to the Sun
than the Earth is,
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but that's not the reason.
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Venus is completely
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covered by clouds
of sulfuric acid that keep
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almost all the sunlight
from reaching the surface.
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That ought to make Venus
much colder than the Earth.
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So why is Venus scorching hot?
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It's because
the small amount of sunlight
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that trickles in through
the clouds to reach the surface
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can't get back out again.
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The flow of energy is blocked
by a dense atmosphere
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of carbon dioxide.
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That carbon dioxide gas--
or CO2 for short--
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acts like a smothering blanket
to keep the heat in.
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No one is burning coal
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or driving
big gas-guzzlers on Venus.
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Nature can destroy
an environment
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without any help
from intelligent life.
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Venus is in the grip
of a runaway greenhouse effect.
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Why does it look like
we're inside a bowl?
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It's due to the intense
atmospheric pressure.
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That's the wreck of Venera 13.
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In 1982, the scientists
and engineers
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of what was then
the Soviet Union
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successfully landed
this spacecraft on Venus.
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They managed
to keep it refrigerated
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for over two hours,
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so it could photograph
its surroundings...
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and transmit the images
back to Earth
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before the onboard electronics
were fried.
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Venus and Earth started out
with about the same amount
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of carbon, but the two worlds
were propelled
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along radically different paths,
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and carbon was the decisive
element in both stories.
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On Venus, it's almost all
in the form of gas--
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carbon dioxide--
in the atmosphere.
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Most of the carbon on Earth
has been stored for eons
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in solid vaults
of carbonate rock,
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like this one,
part of a chain that forms
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the celebrated
White Cliffs of Dover,
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right on the English Channel.
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What titan built
this wonder of the world?
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A creature a thousand times
smaller than a pinhead.
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Trillions of them.
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One-celled algae.
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Volcanoes supply carbon dioxide
to the atmosphere,
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and the oceans slowly absorb it.
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Working over the course
of millions of years,
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the microscopic algae harvested
the carbon dioxide
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and turned it
into these tiny shells.
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They accumulated
in thick deposits of chalk,
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or limestone,
on the ocean floor.
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Later, the restless Earth
pushed up the seafloor
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and carved out
these massive cliffs.
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Other marine creatures
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took in carbon dioxide
to build enormous coral reefs.
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And the oceans converted
dissolved CO2 into limestone
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even without any help from life.
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As a result, only a trace amount
was left as a gas
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in Earth's atmosphere.
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Not even three-hundredths
of one percent.
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Think of it--
fewer than three molecules
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out of every ten thousand.
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And yet, it makes
the critical difference
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between a barren wasteland
and a garden of life on Earth.
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With no CO2 at all,
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the Earth would be frozen.
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And with twice as many,
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we're still talking
about only six molecules
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out of ten thousand.
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Things would get
uncomfortably hot
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and cause us
some serious problems...
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but never as hot as Venus;
not even close.
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That planet lost
its ocean to space
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billions of years ago.
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Without an ocean,
it had no way to capture CO2
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from the atmosphere
and store it as a mineral.
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The CO2 from erupting volcanoes
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just continued to build up.
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Today, that atmosphere
is 90 times heavier than ours.
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Almost all of it is
heat-trapping carbon dioxide.
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That's why Venus is
such a ferocious inferno
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so hostile to life.
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The Earth,
in stunning contrast,
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is alive.
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It breathes...
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but very slowly.
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A single breath
takes a whole year.
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The forests contain
most of Earth's life,
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and most forests
are in the Northern Hemisphere.
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When spring comes to the north,
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the forests inhale
carbon dioxide from the air
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and grow,
turning the land green.
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The amount of CO2
in the atmosphere goes down.
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When fall comes and the plants
drop their leaves, they decay,
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exhaling the carbon dioxide
back into the atmosphere.
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The same thing happens
in the Southern Hemisphere
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at the opposite time
of the year.
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But the Southern Hemisphere
is mostly ocean.
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So it's the forests of the north
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that control the annual changes
in the global CO2.
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The Earth has been
breathing like this
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for tens of millions of years.
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But nobody noticed until 1958,
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when an oceanographer
named Charles David Keeling
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devised a way
to accurately measure
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the amount of carbon dioxide
in the atmosphere.
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Keeling discovered the Earth's
exquisite respiration.
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But he also discovered
something shocking--
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a rapid rise,
unprecedented in human history,
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in the overall level of CO2,
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one that has continued
ever since.
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It's a striking departure from
the CO2 levels that prevailed
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during the rise of agriculture
and civilization.
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In fact, the Earth has seen
nothing like it
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for three million years.
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How can we be so sure?
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The evidence is written
in water.
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DEGRASSE TYSON: The Earth keeps
a detailed diary
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written in the snows
of yesteryear.
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Climate scientists
have drilled ice cores
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from the depths of glaciers
in Greenland and Antarctica.
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The ice layers have ancient air
trapped inside them.
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We can read the unbroken record
of Earth's atmosphere
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that extends back over
the last 800,000 years.
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In all that time,
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the amount of carbon dioxide
in the air never rose
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above three-hundredths
of one percent.
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That is, until the turn
of the 20th century.
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And it's been going up steadily
and rapidly ever since.
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It's now more than 40% higher
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than before
the Industrial Revolution.
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By burning coal, oil and gas,
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our civilization
is exhaling carbon dioxide
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much faster
than Earth can absorb it.
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So CO2 is building up
in the atmosphere.
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The planet is heating up.
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Every warm object radiates
a kind of light
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we can't see
with the naked eye--
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thermal infrared light.
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We all glow with invisible heat
radiation, even in the dark.
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This is what the Earth
looks like in the infrared.
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You're seeing the planet's
own body heat.
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Incoming light
from the Sun hits the surface.
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The Earth absorbs much
of that energy,
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which heats the planet up
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and makes the surface glow
in infrared light.
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But the carbon dioxide
in the atmosphere
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absorbs most of that outgoing
heat radiation,
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sending much of it
right back to the surface.
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This makes the planet
even warmer.
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That's all there is
to the greenhouse effect.
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It's basic physics,
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just bookkeeping
of the energy flow.
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There's nothing
controversial about it.
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If we didn't have any carbon
dioxide in our atmosphere,
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the Earth would just be
a great big snowball,
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and we wouldn't be here.
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So, a little greenhouse effect
is a good thing.
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But a big one can destabilize
the climate
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and wreck our way of life.
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All right... but how do we know
that we're the problem?
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Maybe the Earth itself is
causing the rise in CO2.
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Maybe it has nothing to do
with the coal and oil we burn.
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Maybe it's those
damn volcanoes.
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(deep rumbling)
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Every few years, Mount Etna,
in Sicily, blows its stack.
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Each big eruption sends millions
of tons of CO2
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into the atmosphere.
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Now, combine that
with the output
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of all the other volcanic
activity on the planet.
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Let's take the largest
scientific estimate--
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about 500 million tons
of volcanic CO2
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entering the atmosphere
ever year.
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Sounds like a lot, right?
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But that's not even two percent
of the 30 billion tons of CO2
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that our civilization
is cranking out every year.
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And, funny thing,
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the measured increase in CO2
in the atmosphere
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tallies with the known amount
we're dumping there
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by burning coal, oil and gas.
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Volcanic CO2 has
a distinct signature--
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it's slightly heavier
than the kind produced
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by burning fossil fuels.
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We can tell the difference
between the two
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when we examine them
at the atomic level.
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It's clear that
the increased CO2 in the air
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is not from volcanoes.
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What's more, the observed
warming is as much as predicted
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from the measured increase
in carbon dioxide.
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It's a pretty tight case.
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Our fingerprints
are all over this one.
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How much is 30 billion tons
of CO2 per year?
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If you compressed it
into solid form,
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it would occupy
about the same volume
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as the White Cliffs of Dover.
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And we're adding that much CO2
to the air every year,
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relentlessly, year after year.
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Unlucky for us,
the main waste product
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of our civilization
is not just any substance.
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It happens to be the chief
climate-regulating gas
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of our global thermostat,
year in, year out.
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Too bad CO2 is an invisible gas.
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Maybe if we could see it...
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(car engine starts)
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If our eyes were sensitive
to CO2--
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and perhaps there are
such beings in the cosmos--
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if we could see all
that carbon dioxide,
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then we would overcome
the denial
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and grasp the magnitude of
our impact on the atmosphere.
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But the evidence
that the world is getting warmer
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is all around us.
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For starters, let's just
check the thermometers.
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Weather stations
around the world
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have been keeping
reliable temperature records
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since the 1880s,
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and NASA has used the data
to compile a map
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tracking
the average temperatures
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around the world through time.
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Yellow means
warmer temperatures
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than the average,
for any region in the 1880s.
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Orange means hot.
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And red means hotter.
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The world is warmer than it was
in the 19th century.
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Back then, at the greatest fair
the world has ever seen,
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a forgotten genius demonstrated
the solution to this problem.
254
00:16:10,986 --> 00:16:12,420
Come with me.
255
00:16:17,476 --> 00:16:19,077
DEGRASSE TYSON:
Once there was a world
256
00:16:19,111 --> 00:16:21,929
that was not too hot
and not too cold.
257
00:16:21,981 --> 00:16:24,449
It was just right.
258
00:16:28,153 --> 00:16:32,056
Then there came a time
when the life it sustained
259
00:16:32,091 --> 00:16:36,427
began to notice
our lovely planet was changing.
260
00:16:36,462 --> 00:16:41,132
And it's not
as if we didn't see it coming.
261
00:16:44,937 --> 00:16:48,072
As far back as 1896,
262
00:16:48,107 --> 00:16:50,975
the Swedish scientist
Svante Arrhenius
263
00:16:51,010 --> 00:16:53,378
calculated
that doubling the amount
264
00:16:53,412 --> 00:16:57,181
of CO2 in the atmosphere
would melt the Arctic ice.
265
00:16:59,585 --> 00:17:03,121
In the 1930s, the American
physicist E.O. Hulburt,
266
00:17:03,155 --> 00:17:05,056
at the Naval
Research Laboratory,
267
00:17:05,090 --> 00:17:06,891
confirmed that result.
268
00:17:06,925 --> 00:17:09,827
So far, it was still
just theoretical.
269
00:17:12,131 --> 00:17:15,333
But then, the English engineer
Guy Callendar
270
00:17:15,367 --> 00:17:17,468
assembled the evidence to show
271
00:17:17,503 --> 00:17:20,738
that both the CO2 and
the average global temperature
272
00:17:20,773 --> 00:17:23,241
were actually increasing.
273
00:17:23,308 --> 00:17:27,612
Even now, man may be unwittingly
changing the world's climate
274
00:17:27,646 --> 00:17:29,914
through the waste products
of his civilization.
275
00:17:29,948 --> 00:17:31,916
Due to our release,
through factories
276
00:17:31,950 --> 00:17:34,619
and automobiles every year,
of more than
277
00:17:34,653 --> 00:17:36,904
six billion tons
of carbon dioxide,
278
00:17:36,955 --> 00:17:39,357
which helps air absorb heat
from the Sun,
279
00:17:39,391 --> 00:17:42,110
our atmosphere seems
to be getting warmer.
280
00:17:42,161 --> 00:17:43,995
This is bad?
281
00:17:44,029 --> 00:17:46,697
Well, it's been calculated,
a few degrees rise
282
00:17:46,732 --> 00:17:47,999
in the Earth's temperature
283
00:17:48,016 --> 00:17:50,802
would melt the polar ice caps.
284
00:17:55,841 --> 00:17:59,677
DEGRASSE TYSON: In 1960,
Carl Sagan's PhD thesis
285
00:17:59,711 --> 00:18:01,529
included the first calculation
286
00:18:01,580 --> 00:18:04,182
of the runaway
greenhouse effect on Venus.
287
00:18:04,216 --> 00:18:06,050
This was part
of a career-long interest
288
00:18:06,085 --> 00:18:09,187
in the atmospheres of
the planets, including our own.
289
00:18:09,221 --> 00:18:13,341
In the original Cosmos series,
in 1980, Carl Sagan warned...
290
00:18:13,392 --> 00:18:15,693
SAGAN: We are releasing vast
quantities of carbon dioxide,
291
00:18:15,760 --> 00:18:18,563
increasing
the greenhouse effect.
292
00:18:18,597 --> 00:18:20,298
It may not take much
293
00:18:20,332 --> 00:18:22,700
to destabilize
the Earth's climate,
294
00:18:22,767 --> 00:18:26,154
to convert this heaven,
our only home in the cosmos,
295
00:18:26,205 --> 00:18:28,206
into a kind of hell.
296
00:18:34,680 --> 00:18:36,881
Since Carl spoke those words,
297
00:18:36,915 --> 00:18:39,984
we've burdened the atmosphere
of our world with an additional
298
00:18:40,018 --> 00:18:44,489
400 billion tons
of carbon dioxide.
299
00:18:44,523 --> 00:18:46,390
If we don't change our ways,
300
00:18:46,425 --> 00:18:49,160
what will the planet be like
in our children's future?
301
00:18:49,194 --> 00:18:52,497
Based on scientific
projections,
302
00:18:52,531 --> 00:18:55,366
if we just keep
on doing business as usual,
303
00:18:55,400 --> 00:18:57,768
our kids are in
for a rough ride:
304
00:18:57,803 --> 00:19:00,905
Killer heat waves,
record droughts,
305
00:19:00,939 --> 00:19:04,742
rising sea levels,
mass extinction of species.
306
00:19:04,776 --> 00:19:07,245
We inherited a bountiful world
307
00:19:07,279 --> 00:19:10,414
made possible
by a relatively stable climate.
308
00:19:10,449 --> 00:19:12,783
Agriculture
and civilization flourished
309
00:19:12,818 --> 00:19:14,752
for thousands of years.
310
00:19:14,786 --> 00:19:20,992
And now, our carelessness and
greed put all of that at risk.
311
00:19:22,461 --> 00:19:24,629
Okay, so if we scientists
are so good
312
00:19:24,663 --> 00:19:27,632
at making these dire, long-term
predictions about the climate,
313
00:19:27,666 --> 00:19:30,535
how come we're so lousy
about predicting the weather?
314
00:19:30,569 --> 00:19:34,405
Besides, this year, we had
a colder winter in my town.
315
00:19:34,439 --> 00:19:36,374
For all us scientists know,
316
00:19:36,408 --> 00:19:38,276
we could be in
for global cooling.
317
00:19:38,310 --> 00:19:41,212
Here's the difference
between weather and climate:
318
00:19:41,246 --> 00:19:44,448
Weather is what the atmosphere
does in the short term--
319
00:19:44,483 --> 00:19:46,584
hour to hour, day to day.
320
00:19:46,618 --> 00:19:49,253
Weather is chaotic,
which means that even
321
00:19:49,288 --> 00:19:52,256
a microscopic disturbance can
lead to large-scale changes.
322
00:19:52,291 --> 00:19:55,126
That's why those ten-day
weather forecasts are useless.
323
00:19:55,160 --> 00:19:59,630
A butterfly flaps its wings
in Bali, and six weeks later,
324
00:19:59,665 --> 00:20:02,266
your outdoor wedding
in Maine is ruined.
325
00:20:02,301 --> 00:20:04,268
Climate is the long-term average
326
00:20:04,303 --> 00:20:06,470
of the weather,
over a number of years.
327
00:20:06,505 --> 00:20:09,106
It's shaped by global forces
that alter the energy balance
328
00:20:09,141 --> 00:20:12,176
in the atmosphere,
such as changes in the Sun,
329
00:20:12,211 --> 00:20:13,844
the tilt of the Earth's axis,
330
00:20:13,879 --> 00:20:16,647
the amount of sunlight
the Earth reflects back to space
331
00:20:16,682 --> 00:20:19,917
and the concentration
of greenhouse gases in the air.
332
00:20:19,952 --> 00:20:22,253
A change in any of them
affects the climate
333
00:20:22,287 --> 00:20:24,855
in ways
that are broadly predictable.
334
00:20:24,890 --> 00:20:26,824
My friend'd's meandering
335
00:20:26,858 --> 00:20:28,960
represents
the short-term fluctuations--
336
00:20:28,994 --> 00:20:31,596
that's weather.
337
00:20:31,630 --> 00:20:33,164
It's almost impossible
to predict
338
00:20:33,198 --> 00:20:34,999
what'll attract
his interest next,
339
00:20:35,033 --> 00:20:38,102
but not hard to know what the
range of his meandering will be,
340
00:20:38,136 --> 00:20:40,871
because I'm holding him
on a leash.
341
00:20:42,574 --> 00:20:45,042
We can't
observe climate directly--
342
00:20:45,077 --> 00:20:46,877
all we see is the weather--
343
00:20:46,912 --> 00:20:48,879
but the average weather,
over the course of years,
344
00:20:48,914 --> 00:20:50,548
reveals a pattern.
345
00:20:50,582 --> 00:20:52,984
I represent
that long-term trend,
346
00:20:53,018 --> 00:20:55,152
which is climate.
347
00:20:55,187 --> 00:20:59,056
Keep your eye on the man,
not the dog.
348
00:21:01,727 --> 00:21:04,028
Weather is hard to predict,
like my friend here,
349
00:21:04,062 --> 00:21:06,631
but climate is predictable.
350
00:21:06,665 --> 00:21:09,700
Climate has changed many times
in the long history of the Earth
351
00:21:09,735 --> 00:21:12,370
but always in response
to a global force.
352
00:21:12,404 --> 00:21:15,706
The strongest force driving
climate change right now
353
00:21:15,741 --> 00:21:18,709
is the increasing CO2 from
the burning of fossil fuels,
354
00:21:18,744 --> 00:21:21,045
which is trapping more heat
from the Sun.
355
00:21:21,079 --> 00:21:23,881
All that additional energy
has to go somewhere.
356
00:21:23,915 --> 00:21:25,716
Some of it warms the air.
357
00:21:25,751 --> 00:21:27,818
Most of it ends up
in the oceans.
358
00:21:27,853 --> 00:21:32,089
All over the world,
the oceans are getting warmer.
359
00:21:32,124 --> 00:21:34,525
It's most obvious
in the Arctic Ocean
360
00:21:34,559 --> 00:21:37,428
and the lands that surround it.
361
00:21:40,032 --> 00:21:43,000
Okay, so we're losing
the summer sea ice
362
00:21:43,035 --> 00:21:46,604
in a place
where hardly anyone ever goes.
363
00:21:46,638 --> 00:21:50,241
What do I care if there's
no ice around the North Pole?
364
00:21:59,384 --> 00:22:02,353
Ice is the brightest
natural surface on the Earth,
365
00:22:02,387 --> 00:22:05,289
and open ocean water
is the darkest.
366
00:22:05,324 --> 00:22:08,893
Ice reflects incoming sunlight
back to space.
367
00:22:08,927 --> 00:22:10,961
Water absorbs sunlight
368
00:22:10,996 --> 00:22:14,298
and gets warmer,
which melts even more ice,
369
00:22:14,333 --> 00:22:17,568
which exposes
still more ocean surface
370
00:22:17,602 --> 00:22:19,570
to absorb even more sunlight.
371
00:22:19,604 --> 00:22:23,040
This is what we call
a positive feedback loop.
372
00:22:23,075 --> 00:22:26,811
It's one of many natural
mechanisms that magnify
373
00:22:26,845 --> 00:22:29,947
any warming caused
by CO2 alone.
374
00:22:29,981 --> 00:22:32,216
We're at Drew Point, Alaska,
375
00:22:32,250 --> 00:22:37,154
on the edge of the Arctic Ocean.
376
00:22:44,780 --> 00:22:48,649
DEGRASSE TYSON:
When I was born, the shoreline
was a mile farther out,
377
00:22:48,683 --> 00:22:52,686
and it was breaking off at a
rate of about 20 feet per year.
378
00:22:52,721 --> 00:22:54,688
Now...
379
00:22:54,723 --> 00:22:58,859
it's being eaten away
at about 50 feet per year.
380
00:22:58,894 --> 00:23:00,861
The Arctic Ocean is warming
381
00:23:00,896 --> 00:23:03,230
and at an increasing rate.
382
00:23:03,265 --> 00:23:06,333
So it's ice-free
during more of the year.
383
00:23:06,368 --> 00:23:08,335
That leaves the shore here
384
00:23:08,370 --> 00:23:10,871
more exposed to erosion
from storms,
385
00:23:10,906 --> 00:23:13,207
which are also getting
more powerful,
386
00:23:13,241 --> 00:23:16,410
another effect
of climate change.
387
00:23:16,445 --> 00:23:19,413
The northern reaches of Alaska,
Siberia and Canada
388
00:23:19,448 --> 00:23:21,282
are mostly permafrost,
389
00:23:21,316 --> 00:23:24,718
ground that has been frozen
year-round for millennia.
390
00:23:24,753 --> 00:23:26,554
It contains lots
of organic matter,
391
00:23:26,588 --> 00:23:29,290
old leaves and roots
from plants
392
00:23:29,324 --> 00:23:32,460
that grew thousands
of years ago.
393
00:23:32,494 --> 00:23:34,462
Because the Arctic regions
are warming faster
394
00:23:34,496 --> 00:23:36,397
than anywhere else on Earth,
395
00:23:36,431 --> 00:23:38,466
the permafrost is thawing
396
00:23:38,500 --> 00:23:41,469
and its contents are rotting,
397
00:23:41,503 --> 00:23:44,138
just like when you unplug
the freezer.
398
00:23:47,008 --> 00:23:50,411
The thawing permafrost
is releasing carbon dioxide
399
00:23:50,445 --> 00:23:53,981
and methane, an even more
potent greenhouse gas,
400
00:23:54,015 --> 00:23:55,749
into the atmosphere.
401
00:23:55,784 --> 00:23:58,152
This is making things
even warmer,
402
00:23:58,186 --> 00:24:01,822
another example of a positive
feedback mechanism.
403
00:24:01,857 --> 00:24:04,592
The world's permafrost stores
enough carbon
404
00:24:04,626 --> 00:24:08,162
to more than double the CO2
in the atmosphere.
405
00:24:08,196 --> 00:24:09,497
At the rate we're going,
406
00:24:09,531 --> 00:24:11,098
global warming
could release most of it
407
00:24:11,133 --> 00:24:12,833
by the end of the century.
408
00:24:12,868 --> 00:24:16,270
We might be tipping the climate
past a point of no return
409
00:24:16,304 --> 00:24:18,906
into an unpredictable slide.
410
00:24:18,940 --> 00:24:21,742
Okay, the air, the water
411
00:24:21,776 --> 00:24:24,078
and the land
are all getting warmer,
412
00:24:24,112 --> 00:24:26,914
so global warming
is really happening.
413
00:24:26,948 --> 00:24:29,083
But maybe it's not our fault.
414
00:24:29,117 --> 00:24:31,152
Maybe it's just nature.
415
00:24:31,186 --> 00:24:33,220
Maybe it's the Sun.
416
00:24:34,689 --> 00:24:37,525
No, it's not the Sun.
417
00:24:39,794 --> 00:24:43,097
We've been monitoring the Sun
very closely for decades,
418
00:24:43,131 --> 00:24:47,835
and the solar energy output
hasn't changed.
419
00:24:47,869 --> 00:24:50,671
What's more, the Earth
is warming more at night
420
00:24:50,705 --> 00:24:52,840
than in daytime,
421
00:24:52,874 --> 00:24:55,676
and more in winter
than in summer.
422
00:24:55,710 --> 00:24:59,113
That's exactly what we expect
from greenhouse warming,
423
00:24:59,147 --> 00:25:01,382
but the opposite of what
increased solar output
424
00:25:01,416 --> 00:25:03,417
would cause.
425
00:25:05,854 --> 00:25:08,556
It's now clear beyond
any reasonable doubt
426
00:25:08,590 --> 00:25:11,292
that we are changing
the climate.
427
00:25:11,326 --> 00:25:13,294
The Sun isn't the problem.
428
00:25:13,328 --> 00:25:15,129
But it is the solution,
429
00:25:15,163 --> 00:25:17,331
and we've known this
for a long time,
430
00:25:17,365 --> 00:25:21,001
much longer
than you might think.
431
00:25:24,539 --> 00:25:28,075
Paris, September 1878.
432
00:25:28,109 --> 00:25:32,446
The Eiffel Tower won't be built
for years to come.
433
00:25:39,054 --> 00:25:41,855
Witness one
of the most glorious spectacles
434
00:25:41,890 --> 00:25:44,892
the world has ever seen.
435
00:25:44,926 --> 00:25:48,162
The magnificent head
of the Statue of Liberty
436
00:25:48,196 --> 00:25:50,731
has just been completed.
437
00:25:56,271 --> 00:25:59,506
Thousands of exhibitors
from around the planet
438
00:25:59,541 --> 00:26:01,742
covered 66 acres of Paris
439
00:26:01,776 --> 00:26:04,044
with their inventions
and goods.
440
00:26:04,079 --> 00:26:07,047
Edison's first public
demonstration of the lightbulb
441
00:26:07,082 --> 00:26:09,717
will not take place
for another year.
442
00:26:09,751 --> 00:26:12,620
There's no such thing
as electrical appliances.
443
00:26:12,654 --> 00:26:15,623
People don't flick switches
and press buttons.
444
00:26:15,657 --> 00:26:19,260
It's a hand-cranked,
horse-drawn world.
445
00:26:26,468 --> 00:26:29,103
That's the guy we came to see,
446
00:26:29,137 --> 00:26:31,939
the one
with the crazy moustache.
447
00:26:31,973 --> 00:26:34,975
He's a math teacher
named Augustin Mouchot.
448
00:26:35,010 --> 00:26:37,444
Remember, it's 1878.
449
00:26:37,479 --> 00:26:40,914
This is a world
lit mostly by gaslight.
450
00:26:40,949 --> 00:26:43,317
The automobile
is still years away.
451
00:26:43,351 --> 00:26:47,121
But Mouchot, here,
is dazzling the crowd
452
00:26:47,155 --> 00:26:49,089
with his solar power
concentrator.
453
00:26:51,159 --> 00:26:54,428
The Sun belongs to all of us!
454
00:26:54,462 --> 00:26:58,632
Even though it is 150 million
kilometers away from us,
455
00:26:58,667 --> 00:27:00,801
feel its awesome power!
456
00:27:00,835 --> 00:27:04,805
My invention concentrates
the free energy of the Sun
457
00:27:04,839 --> 00:27:07,808
and converts it
into mechanical motion.
458
00:27:07,842 --> 00:27:10,444
It can power any kind
of machine.
459
00:27:10,478 --> 00:27:14,815
It can produce electricity
or run a printing press
460
00:27:14,849 --> 00:27:17,117
or make ice
on a hot day.
461
00:27:20,221 --> 00:27:21,789
Et voilà!
462
00:27:21,823 --> 00:27:23,324
(spectators gasp, chatter)
463
00:27:31,966 --> 00:27:32,916
(chuckles)
464
00:27:32,967 --> 00:27:33,934
Think of it,
465
00:27:33,968 --> 00:27:36,370
sunlight converted into ice.
466
00:27:36,372 --> 00:27:39,206
You see, my friends,
what wonders we can work
467
00:27:39,240 --> 00:27:42,376
if we harness
the bounteous energy of the Sun.
468
00:27:42,410 --> 00:27:46,180
The world will someday
run out of coal,
469
00:27:46,214 --> 00:27:50,384
but the magnificent Sun
will always be there for us.
470
00:28:04,899 --> 00:28:07,368
Mouchot took home the gold medal
from the fair.
471
00:28:07,402 --> 00:28:09,203
But the price of coal tumbled,
472
00:28:09,237 --> 00:28:12,706
becoming so cheap that there was
no interest in solar energy.
473
00:28:12,741 --> 00:28:15,476
Besides,
no one understood, back then,
474
00:28:15,510 --> 00:28:18,212
what the true cost was
of burning fossil fuel.
475
00:28:18,246 --> 00:28:21,382
Mouchot's research funding
was cut off.
476
00:28:21,416 --> 00:28:25,819
35 years later, in the early
years of the 20th century,
477
00:28:25,821 --> 00:28:28,489
another door opened
to an alternative future.
478
00:28:28,523 --> 00:28:32,526
It happened in Egypt,
on the banks of the Nile.
479
00:28:39,467 --> 00:28:42,436
DEGRASSE TYSON:
Memo to future time travelers:
480
00:28:42,470 --> 00:28:44,772
this would be
an excellent entry point
481
00:28:44,806 --> 00:28:47,875
for averting climate change.
482
00:28:47,909 --> 00:28:50,878
Egypt, 1913.
483
00:28:50,912 --> 00:28:53,981
That's Frank Shuman
of Philadelphia.
484
00:28:55,750 --> 00:28:58,051
He's only had
three years of schooling,
485
00:28:58,086 --> 00:29:03,056
but his genius for innovation
more than makes up for that.
486
00:29:03,091 --> 00:29:07,127
Before he was 30, Shuman
had invented safety glass.
487
00:29:07,162 --> 00:29:11,965
Its use in automobiles and
skylights saved countless lives
488
00:29:12,000 --> 00:29:14,301
and made him a very rich man,
489
00:29:14,335 --> 00:29:18,238
rich enough
to pursue his real passion,
490
00:29:18,273 --> 00:29:20,474
solar energy.
491
00:29:20,508 --> 00:29:22,743
Shuman led the team
that designed and built
492
00:29:22,777 --> 00:29:25,979
an array
of solar energy concentrators.
493
00:29:26,014 --> 00:29:29,466
It could power a steam engine.
494
00:29:29,517 --> 00:29:32,653
Shuman is hoping
to use the Sun's power
495
00:29:32,687 --> 00:29:34,188
to irrigate the desert
496
00:29:34,289 --> 00:29:36,089
and turn it green.
497
00:29:36,124 --> 00:29:37,724
The official inauguration
498
00:29:37,759 --> 00:29:40,727
of Shuman's solar power plant,
in 1913,
499
00:29:40,762 --> 00:29:42,429
was a dazzling success.
500
00:29:45,800 --> 00:29:49,503
He had invented a practical way
to tap the Sun's energy
501
00:29:49,537 --> 00:29:52,139
on an industrial scale,
502
00:29:52,173 --> 00:29:55,976
making solar energy
even cheaper than coal.
503
00:29:57,946 --> 00:30:00,414
The British
and German governments
504
00:30:00,448 --> 00:30:02,416
both offered Shuman
generous funding
505
00:30:02,450 --> 00:30:04,318
to develop his invention.
506
00:30:04,352 --> 00:30:07,354
It was the ideal source
of abundant power
507
00:30:07,388 --> 00:30:09,356
in tropical regions,
508
00:30:09,390 --> 00:30:13,193
where imported coal
was prohibitively expensive.
509
00:30:13,228 --> 00:30:16,964
But Shuman was dreaming
even bigger.
510
00:30:16,998 --> 00:30:19,366
In a letter
to Scientific American,
511
00:30:19,400 --> 00:30:22,202
he calculated
that his solar power plants,
512
00:30:22,237 --> 00:30:24,538
if deployed in an area
of the Sahara Desert
513
00:30:24,572 --> 00:30:28,609
only 150 miles on a side,
could supply as much power
514
00:30:28,643 --> 00:30:31,778
as consumed by all
the industries of the world.
515
00:30:31,813 --> 00:30:33,780
But it was not to be.
516
00:30:33,815 --> 00:30:36,884
The market for a liquid
fossil fuel, petroleum,
517
00:30:36,918 --> 00:30:38,719
was exploding for shipping,
518
00:30:38,753 --> 00:30:41,355
home heating,
and cars and trucks.
519
00:30:41,389 --> 00:30:44,024
Oil was abundant,
cheaper even than coal,
520
00:30:44,058 --> 00:30:48,028
and much easier to get
out of the ground and process.
521
00:30:48,062 --> 00:30:52,533
It took 100 men a week
to fuel a ship with coal,
522
00:30:52,567 --> 00:30:55,052
but with oil,
one man could do the job
523
00:30:55,103 --> 00:30:56,737
in a single day.
524
00:30:56,771 --> 00:31:00,574
A year after Shuman's
triumph in the desert,
525
00:31:00,608 --> 00:31:02,709
World War I broke out.
526
00:31:02,744 --> 00:31:07,180
His solar collectors
were recycled into weapons.
527
00:31:07,215 --> 00:31:11,184
Frank Shuman's dream
of a solar-powered civilization
528
00:31:11,219 --> 00:31:13,820
would have to wait
another century
529
00:31:13,855 --> 00:31:16,456
before it was reborn.
530
00:31:18,693 --> 00:31:21,094
There's another inexhaustible
source of clean energy
531
00:31:21,129 --> 00:31:23,130
for the world.
532
00:31:24,799 --> 00:31:27,868
The winds themselves
are solar powered,
533
00:31:27,902 --> 00:31:32,305
because our star drives
the winds and the waves.
534
00:31:32,307 --> 00:31:34,041
Unlike solar collectors,
535
00:31:34,075 --> 00:31:37,210
wind farms take up
very little land,
536
00:31:37,245 --> 00:31:39,513
and none at all, if offshore,
537
00:31:39,547 --> 00:31:42,549
where the winds are strongest.
538
00:31:42,584 --> 00:31:45,419
If we could tap even
one percent of their power,
539
00:31:45,453 --> 00:31:49,590
we'd have enough energy
to run our civilization.
540
00:32:03,671 --> 00:32:06,974
And more solar energy
falls on Earth in one hour
541
00:32:07,008 --> 00:32:09,610
than all the energy
our civilization consumes
542
00:32:09,644 --> 00:32:11,478
in an entire year.
543
00:32:11,512 --> 00:32:13,280
If we could harness
a tiny fraction
544
00:32:13,314 --> 00:32:15,415
of the available
solar and wind power,
545
00:32:15,450 --> 00:32:18,585
we could supply
all our energy needs forever,
546
00:32:18,620 --> 00:32:21,822
and without adding
any carbon to the atmosphere.
547
00:32:31,499 --> 00:32:33,634
It's not too late.
548
00:32:33,668 --> 00:32:35,736
There's a future
worth fighting for.
549
00:32:35,770 --> 00:32:37,404
How do I know?
550
00:32:37,406 --> 00:32:40,774
Every one of us comes
from a long line of survivors.
551
00:32:40,808 --> 00:32:44,411
Our species is nothing
if not adaptive.
552
00:32:44,445 --> 00:32:46,947
It was only because
our ancestors learned
553
00:32:46,981 --> 00:32:50,083
to think long-term,
and act accordingly,
554
00:32:50,118 --> 00:32:51,752
that we're here at all.
555
00:32:51,786 --> 00:32:53,854
We've had our backs
to the wall before,
556
00:32:53,888 --> 00:32:56,990
and we came through
to scale new heights.
557
00:32:57,025 --> 00:33:00,527
In fact, the most mythic
human accomplishments of all
558
00:33:00,529 --> 00:33:03,296
came out of our darkest hour.
559
00:33:10,955 --> 00:33:12,622
DEGRASSE TYSON:
Once there was a world
560
00:33:12,657 --> 00:33:17,127
rigged with 60,000
hair-triggered nuclear weapons.
561
00:33:17,161 --> 00:33:18,762
The combatants were
562
00:33:18,796 --> 00:33:21,431
the two most powerful
countries on Earth,
563
00:33:21,466 --> 00:33:23,600
and they were locked
in a deadly embrace,
564
00:33:23,634 --> 00:33:26,203
each vowing that
they would rather see
565
00:33:26,237 --> 00:33:28,105
everything we love destroyed
566
00:33:28,139 --> 00:33:30,674
than submit
to the will of the other.
567
00:33:31,370 --> 00:33:33,337
When I was three years old,
568
00:33:33,372 --> 00:33:35,890
the largest man-made
explosion of all time
569
00:33:35,941 --> 00:33:39,377
was detonated
by the Soviet Union.
570
00:33:42,279 --> 00:33:45,415
That terror has subsided,
to be replaced by new fears.
571
00:33:45,449 --> 00:33:48,184
The danger that the 2,000
largest cities on Earth
572
00:33:48,186 --> 00:33:51,220
would be reduced to rubble
in the space of an afternoon
573
00:33:51,255 --> 00:33:54,223
is no longer one of them.
574
00:33:54,291 --> 00:33:56,893
The nuclear rivalry
between the United States
575
00:33:56,927 --> 00:33:57,927
and the Soviet Union
576
00:33:57,962 --> 00:34:02,231
had another by-product.
577
00:34:02,266 --> 00:34:05,335
The Apollo missions to the Moon
were an extension
578
00:34:05,337 --> 00:34:09,072
of the arms race
that raged between them.
579
00:34:09,106 --> 00:34:11,174
Sending people
to orbit the Earth
580
00:34:11,208 --> 00:34:14,243
or go to the Moon
requires big, reliable,
581
00:34:14,245 --> 00:34:17,647
powerful rockets--
precisely the same technology
582
00:34:17,681 --> 00:34:20,416
you need to carry
a nuclear warhead
583
00:34:20,451 --> 00:34:21,985
halfway around the planet
584
00:34:22,019 --> 00:34:26,155
to destroy your enemy's
largest cities.
585
00:34:27,959 --> 00:34:29,760
PRESIDENT KENNEDY:
I believe that this nation
586
00:34:29,795 --> 00:34:32,963
should commit itself
to achieving the goal,
587
00:34:32,998 --> 00:34:36,801
before this decade is out,
of landing a man on the Moon
588
00:34:36,835 --> 00:34:40,237
and returning him safely
to the Earth.
589
00:34:40,272 --> 00:34:43,007
DEGRASSE TYSON:
President Kennedy's 1961 speech
590
00:34:43,041 --> 00:34:45,342
electrified the nation,
591
00:34:45,377 --> 00:34:48,746
and it contained much
that was remarkably prophetic--
592
00:34:48,780 --> 00:34:51,248
but not a word about
a scientific objective
593
00:34:51,283 --> 00:34:53,250
for going to the Moon.
594
00:34:53,285 --> 00:34:55,519
No questions
about the Moon's origin
595
00:34:55,537 --> 00:34:58,656
or the hope of bringing back
samples to analyze.
596
00:34:58,690 --> 00:35:01,525
No, the Apollo missions
were conceived
597
00:35:01,543 --> 00:35:03,928
as a demonstration
of the superior power
598
00:35:03,962 --> 00:35:06,964
and precision
of our strategic missiles.
599
00:35:06,998 --> 00:35:09,300
But a funny thing
happened to us
600
00:35:09,334 --> 00:35:12,536
on our way to the Moon.
601
00:35:12,571 --> 00:35:14,839
We looked homeward...
602
00:35:14,873 --> 00:35:18,076
and discovered another world--
our own.
603
00:35:18,350 --> 00:35:21,652
For the first time,
we inhabitants of Earth
604
00:35:21,687 --> 00:35:25,123
could step back
and see it as it really is--
605
00:35:25,213 --> 00:35:27,781
one world, indivisible,
606
00:35:27,815 --> 00:35:30,884
and kind of small
in the cosmic context.
607
00:35:32,235 --> 00:35:35,170
Whatever the reason we first
mustered the enormous resources
608
00:35:35,204 --> 00:35:37,606
required
for the Apollo program,
609
00:35:37,640 --> 00:35:40,442
however mired it was
in Cold War nationalism
610
00:35:40,476 --> 00:35:42,511
and the instruments of death,
611
00:35:42,545 --> 00:35:45,514
the inescapable recognition
of the unity
612
00:35:45,548 --> 00:35:47,516
and fragility of the Earth
613
00:35:47,550 --> 00:35:50,052
is its clear
and luminous dividend,
614
00:35:50,086 --> 00:35:52,521
the unexpected gift of Apollo.
615
00:35:52,555 --> 00:35:55,724
A project conceived
in deadly competition
616
00:35:55,758 --> 00:35:59,061
made us recognize
our community.
617
00:36:09,539 --> 00:36:13,208
What titan built
this wonder of the world?
618
00:36:14,411 --> 00:36:17,413
It was the Ifugao people
of the Philippines,
619
00:36:17,447 --> 00:36:20,682
working with not much more
than their hands.
620
00:36:20,717 --> 00:36:25,354
About 10,000 years ago,
our ancestors all over the world
621
00:36:25,388 --> 00:36:28,924
took advantage of another form
of climate change,
622
00:36:28,932 --> 00:36:33,169
the gentler climate of the
intermission in the ice age--
623
00:36:33,236 --> 00:36:36,739
they invented agriculture.
624
00:36:36,774 --> 00:36:38,908
They gave up
the ceaseless wandering,
625
00:36:38,942 --> 00:36:42,211
hunting and gathering
that had been their way of life
626
00:36:42,246 --> 00:36:44,147
for a million years or so,
627
00:36:44,248 --> 00:36:47,850
to settle down and produce food.
628
00:36:47,885 --> 00:36:50,353
They found a way to harvest
629
00:36:50,387 --> 00:36:53,556
ten to a hundred times
more solar energy
630
00:36:53,590 --> 00:36:58,361
than the environment naturally
provided for their ancestors.
631
00:36:58,395 --> 00:37:01,898
People all over the world
made the difficult transition
632
00:37:01,932 --> 00:37:05,201
from nomadic cultures
to agricultural ones
633
00:37:05,235 --> 00:37:08,438
that used solar energy
more efficiently.
634
00:37:08,472 --> 00:37:12,074
It gave rise to civilization.
635
00:37:12,109 --> 00:37:15,645
We stand on the shoulders
of those who did the hard work
636
00:37:15,662 --> 00:37:19,248
that such a fundamental
transformation required.
637
00:37:19,283 --> 00:37:22,652
Now... it's our turn.
638
00:37:27,524 --> 00:37:30,092
Once there was a world...
639
00:37:34,932 --> 00:37:38,835
If life ever existed on Venus,
it would have had no chance
640
00:37:38,869 --> 00:37:42,472
to avert the hellish destiny
of this world.
641
00:37:44,107 --> 00:37:47,743
This runaway greenhouse effect
was unstoppable.
642
00:37:47,778 --> 00:37:50,780
(thunder crashing)
643
00:37:57,280 --> 00:37:59,014
Once...
644
00:37:59,048 --> 00:38:01,250
there was a world...
645
00:38:02,653 --> 00:38:04,787
...ours.
646
00:38:04,821 --> 00:38:07,456
And that world is now.
647
00:38:07,491 --> 00:38:09,959
There are no scientific
or technological obstacles
648
00:38:09,993 --> 00:38:11,827
to protecting our world
649
00:38:11,862 --> 00:38:15,297
and the precious life
that it supports.
650
00:38:15,332 --> 00:38:17,199
It all depends...
651
00:38:17,234 --> 00:38:20,186
on what we truly value...
652
00:38:20,237 --> 00:38:23,873
and if we can summon
the will to act.
653
00:38:40,590 --> 00:38:43,259
¶ ¶
654
00:39:09,753 --> 00:39:11,921
PRESIDENT KENNEDY:
But why, some say, the Moon?
655
00:39:11,955 --> 00:39:15,091
Why choose this as our goal?
656
00:39:15,125 --> 00:39:17,226
And they may well ask,
657
00:39:17,260 --> 00:39:19,729
why climb the highest mountain?
658
00:39:19,763 --> 00:39:22,998
We choose
to go to the Moon...
659
00:39:23,033 --> 00:39:25,101
we choose to go to the Moon...
660
00:39:25,135 --> 00:39:27,503
(applause, cheering)
661
00:39:31,775 --> 00:39:34,310
...we choose to go to the Moon
in this decade
662
00:39:34,344 --> 00:39:36,178
and do the other things,
663
00:39:36,213 --> 00:39:39,849
not because they are easy,
but because they are hard.
664
00:39:47,357 --> 00:39:39,849
Captioned by
Media Access Group at WGBH
access.wgbh.org