- The universe appears to have a self-regulating
mechanism that prevents alien life-forms from invading other planets, a
leading scientist says today.
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- The theory put forward by James Annis,
an astrophysicist at the American government's Fermilab laboratory in Chicago,
may explain the Alien paradox posed by the Nobel Prize-winning physicist
Enrico Fermi in 1950.
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- Fermi pointed out that the Milky Way,
our Galaxy, is about 100,000 light years across. If aliens could explore
it at only a thousandth the speed of light (about 671,000 mph), they would
cover it in 100 million years.
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- As the Milky Way is about 10 billion
years old, this begged the question: where are the extra-terrestrials?
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- Prof Annis says today in New Scientist
that apocalyptic explosions, or gamma ray bursts, may destroy advanced
civilisations when they have just invented interstellar travel.
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- Gamma ray bursts are thought to be the
most powerful explosions in the universe, unleashing devastating amounts
of radiation in seconds, possibly when super-dense remnants of dead stars
or black holes collide.
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- The observed rate of gamma ray bursts
is about one a galaxy every few hundred million years. Prof Annis argues
that they were more common in the past, possibly sterilising galaxies every
few million years or so - a much shorter period than any plausible timescale
for the emergence of life capable of space travel.
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- "They just haven't had enough time
to get here yet," said Prof Annis. "The GRB model essentially
resets the available time for the rise of intelligent life to zero each
time a burst occurs."
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