- Hollywood's latest disaster movie fixation,
the Earth threatened by the impact of giant comets or asteroids, could
be dangerously out of date according to scientists in the US.
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- They believe life on Earth is more likely
to be wiped out by an impact with a cosmic cloud.
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- The predictions by Gary Zank, from the
Bartol Research Institute at the University of Delaware, have been presented
to the American Geophysical Union's spring meeting in Boston, Massachusetts.
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- His research shows that if the Solar
System hits even a small gas cloud in space, the "bubble" surrounding
it which protects life on our planet could burst.
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- "The protective solar wind would
be extinguished, and cosmic radiation might lead to gene mutations,"
he said.
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- "Hydrogen would bombard the Earth,
producing increased cloud cover, leading perhaps to global warming, or
extreme amounts of precipitation and ice ages."
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- He based his prediction on computer simulations
of what might happen to the "cocoon" created by the solar wind,
charged particles flowing out from the sun.
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- "We're surrounded by hot gas. As
our sun moves through extremely `empty' or low-density interstellar space,
the solar wind produces a protective bubble, the heliosphere around our
Solar System, which allows life to flourish on Earth.
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- "Unfortunately, we could bump into
a small cloud at any time, and we probably won't see it coming. Without
the heliosphere, neutral hydrogen would interact with our atmosphere, possibly
producing catastrophic climate changes, while our exposure to deadly cosmic
radiation in the form of very high-energy cosmic rays would increase.
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- "We won't know that our heliosphere
is collapsing until we see highly elevated levels of neutral hydrogen and
cosmic rays," said Professor Zank.
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- Although there is no need to panic right
now, our descendants in 50,000 years should be alarmed.
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- Pushed by galactic wind, a particularly
troublesome cloud zone located in a star-forming region near the Aquila
Rift, about 815 light years away, is "clearly headed our way"
according to Professor Zank.
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- He is also warning that small knots of
gas called the "Local Fluff" could be encountered far sooner.
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- Mankind has been lucky so far, Professor
Zank believes, as over the past five million years "we've had incredibly
smooth sailing" because the sun has been coasting through calm interstellar
waters that are virtually empty, containing on average less than one atom
per cubic inch of space.
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- Although the solar system is in a region
of space containing between three and four atoms per cubic inch, the weather
in space could change because the universe is "full of clouds".
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