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Narrator: What safeguards our solar system...
is our star.
The sun provides a shield, stretching beyond the last
planet in its orbit: a force field that deflects these
"cosmic rays." But these
"solar winds" can be dangerous too,
especially during outbursts called coronal mass ejections.
Want a vision of earth gone
wrong? Just look at what solar storms do our
sister planet, Venus. They strip away lighter
elements in its upper atmosphere, hydrogen, oxygen
and the molecule they form: water.
What's left is a witch's brew of noxious
chemicals including thick sulfurous clouds.
How has Earth avoided the grim fate of Venus?
We can see the answer as the solar storm
approaches Earth.
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Our planet has a protective shield
all it's own-- A powerful magnetic field 
generated deep within its core.
In fact, that's just our first line of
defense. Much of the solar energy that gets through 
is reflected back to space by clouds, ice,
and snow. The energy that Earth absorbs
is just enough to power a remarkable planetary 
engine: the climate.
It's set in motion
by the unevenness of solar heating, due in part to the 
cycles of day and night, and the seasons that cause warm 
tropical winds to blow toward the poles and cold
polar air toward the equator.
Wind currents
drive surface ocean currents.
This computer simulation shows the
Gulf Stream winding its way along the coast of North America.
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This great ocean river carries enough heat energy
to power the industrial world a hundred times
over. It breaks down
in massive world pools that spread warm tropical 
waters over northern seas.
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Below the surface they mix
with cold deep currents that swirl around 
under sea ledges and mountains.
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Earth's climate engine has countless moving parts:
tides and terrain, cross winds and currents--
all working to equalize temperatures around
the globe.
