History Channel
Season 1 Episode.3
http://www.history.com/shows/the-universe
http://en.wikipedia.org/wiki/The_Universe_%28TV_series%29
http://www.youtube.com/watch?v=s4ss0j0aknM
EXCERPTS:
- DEEP THREATS TO OUR PLANET
APOPHIS, which got too close for comfort in 2004.
Tunguska Explosion @ Siberia
June 30th 1908, 7:15 am
An object, half the size of a football field,
plunged down from space at around 34,000 miles per hour.
violently exploded about Siberia's Tunguska forest.
It became the largest explosion on Earth in modern human history.
The blast sparked heatwaves which torched 80 million trees, area of the size of Rhodes island.
If that asteroid hit just few hours later,
it would not have hit Siberia,
it would have hit over Europe.
... million people would die like that. (clicking fingers)
...
The blast over Siberia released energy equivalent to 15 megatons of TNT,
a thousand times greater than Hiroshima.
Scientists call these trespassers Near Earth Objects, or NEOs.
They're asteroids and comets, which are leftovers from the formation of the planets.
Comets move in the Oort Cloud in the Kuiper Belt,
which is beyond the planet Neptune.
Asteroids travel in a band
between Jupiter and Mars.
[65 million years ago, an asteroid - size of small city, hit Yucatan Peninsula, present day Mexican village Chicxulub, and caused the extinction of dinosaurs and growth of mammals.]
In 1998 Congress urged NASA to detect all the Near Earth Objects over a half mile in diameter or more.
They found: Over 850 NEOs in our vicinity.
NASA's Space-guard Survey has detected over 90% of all NEOs deemed harmful.
... so Congress now asks NASA to locate all NEOs 500 feet in diameter.
It's hard to believe the Earth has survived over 4.5 billion years.
Apophis, is scheduled to pass dangerously close to our planet again,
on Friday, the 13th in April 2029.
Apophis has an over 99% chance of missing the Earth in 2029.
but if Apophis passes the Earth at a distance of exactly 18,893 miles,
it may pass through a GRAVITATIONAL KEYHOLE,
- a narrow region in space, a half mile wide -
if this happens, the Earth's gravity could upset Apophis,
and change its trajectory.
It could cause it to return, and hit Earth seven years later,
on April 13th 2036.
At the present time, Apophis has 1 in 45,000 chance of delivering a deadly blow in 2036.
But even these odds have scientists placing bets.
Apophis could impact any point along this "path of risk".
It begins in Western Siberia, cuts across and down the Pacific Ocean, near California,
then it traverses Central America and finished in Western Africa.
GAMMA-RAYS BURST
The potent radiation cooks the upper atmosphere,
Our ozone layer roasts,
Across the hemisphere, human beings burn to death from radiation a hundreds times the fatal dose.
The disappearing ozone layer causes increased temperatures around the world,
triggering cyclones, tsunamis and hurricanes.
Most life on the surfaces of land and water incinerates.
it could happen if a gamma-ray burst hit Earth from 100 light years away.
The gamma-ray burst is equivalent to
the brightness of million trillion suns.
For every 300 gamma-ray bursts that go off
only one is pointed in our direction,
and wo we only see 1 of those 300.
Even if a gamma-ray burst were to occur
not 100 but 1000 light years away,
the Earth could still face apocalyptic destruction.
Statistically this ghastly scenario has 1% chance
of happening once in the Earth's entire lifetime.
But even these odds aren't reassuring
if you're living on the planet at that very moment.
Gamma-Rays: They travel at the speed of light. 186,000 miles per second.
SUN
For over 4 billion years the Sun has been an ally,
warming and feeding our planet.
But in time our solar heater will become our enemy.
BIG RIP
Edwin Hubble first discovered that Universe is expanding back in the 1920s.
But it was not unitil 1998
when a crack team of scientists measured that this expansion
is moving like a runaway train.
_______________________________
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