History Channel
Season. 1 Episode. 6
http://www.history.com/shows/the-universe
http://en.wikipedia.org/wiki/The_Universe_%28TV_series%29
http://www.youtube.com/watch?v=CrfJ56yZqeU
EXCERPTS:
"Without the magnetic field
Earth would be an airless waste devoid of life."
BELTS: Asteroid, Kuiper, Oort
"The objects that didn't become planets became refugees.
Asteroids, made of rock and iron, found asylum in the Asteroid Belt between Mars and Jupiter.
Comets, composed of ices dust and rock, sought shelter in the Kuiper Belt, just beyond the planet Neptune.
Others migrated to the Oort Cloud, over a trillion miles from Earth.
ORIGINS OF WATER
NASA's senior scientists, Michael Mumma.
says our planet's water came from space.
Comets, which are made up of frozen gases,
could have showered Earth with water.
'We know the Earth's oceans contain a mixture of normal water,
H2O, and heavy water HDO, which included deuterium,
a form of hydrogen that is twice as heavy as normal hydrogen.
BUILDING BLOCK OF LIFE
"Meteorites contain organic materials, including amino acids.
Photosynthesis, Cyanobacteria
"After 2 billion years of planetary and biological evolution,
the first plants and animals emerged from water onto land."
"The natural greenhouse effect is the absorption of infrared radiation
by our atmosphere, which warms our planet.
Without greenhouse gases, the Earth's surface would be up to 86 degrees F cooler.
But in the last 20 years there's been an increase in greenhouse gases,
especially carbon dioxide, produced by burning fossil fuels.
The increased heating is affecting agriculture, sea level, and weather.
In the past, carbon dioxide levels had spiked due to natural causes,
such as volcanic out-gassing.
However today's rises seem to be happening much more rapidly.
"The Earth's North and South Poles are known as the cryospheres,
regions blanketed with snow and ice.
They help regulate climate temperature and water levels around the globe.
The reason: ice and snow are white, they reflect sunlight and cool the planet.
By contrast, the open oceans absorb sunlight, which heats the globe.
However, as ice melts, it create more open water which sucks in more sunlight
and increasingly warms the planet.
At the South Pole the continent of Antarctica, holds 70% of the world's fresh water.
Humans could die out 500 million years from now
due to the brightening of the Sun
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