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Location: UFOUpDatesList.Com > 1999 > Jan > Jan 24

'Sorry, We'll Be Late'

From: Bob Young <YoungBob2@aol.com>
Date: Fri, 22 Jan 1999 23:01:23 EST
Fwd Date: Sun, 24 Jan 1999 00:07:40 -0500
Subject: 'Sorry, We'll Be Late'


Thought you'd be interested in this from New Scientist mag.

Clear skies,
Bob Young

--------------------------------------------------

From: New Scientist, 23 January 1999

Sorry, we'll be late

Robert Matthews


Gamma-ray bursts--incredibly powerful explosions that may be
caused by collisions between collapsed stars--could solve one of
the oldest riddles about extraterrestrial civilisations: why
haven't they reached Earth already? After studying the effects
of gamma-ray bursts on life, an astrophysicist has concluded
that aliens may have just started to explore their galaxies.

Enthusiasts for the existence of extraterrestrials have long
been haunted by a simple question supposedly posed by the Nobel
prizewinning physicist Enrico Fermi around 1950. Fermi pointed
out that the Galaxy is about 100 000 light years across. So even
if a spacefaring race could explore the Galaxy at only a
thousandth of the speed of light, it would take them just 100
million years to spread across the entire Galaxy. This is far
less than the Galaxy's age of about 10 billion years.

So if ETs exist in the Milky Way, where are they? Maybe they
don't share the human urge to explore. Or perhaps there's
another reason, says James Annis, an astrophysicist at Fermilab
near Chicago. He thinks cataclysmic gamma-ray bursts often
sterilise galaxies, wiping out life forms before they have
evolved sufficiently to leave their planet (Journal of the
British Interplanetary Society, vol 52, p 19). GRBs are thought
to be the most powerful explosions in the Universe, releasing as
much energy as a supernova in seconds. Many scientists think the
bursts occur when the remnants of dead stars such as neutron
stars or black holes collide.

Annis points out that each GRB unleashes devastating amounts of
radiation. "If one went off in the Galactic centre, we here
two-thirds of the way out on the Galactic disc would be exposed
over a few seconds to a wave of powerful gamma rays." He
believes this would be lethal to life on land.

The rate of GRBs is about one burst per galaxy every few hundred
million years. But Annis says theories of GRBs suggest the rate
was much higher in the past, with galaxies suffering one strike
every few million years--far shorter than any plausible time
scale for the emergence of intelligent life capable of space
travel. That, says Annis, may be the answer to Fermi's question.
"They just haven't had enough time to get here yet," he says.
"The GRB model essentially resets the available time for the
rise of intelligent life to zero each time a burst occurs."

Paul Davies, a visiting physicist at Imperial College, London,
says the basic idea for resolving the paradox makes sense. "Any
Galaxy-wide sterilising event would do," he says. However, he
adds that GRBs may be too brief: "If the drama is all over in
seconds, you only zap half a planet. The planet's mass shields
the shadowed side." Annis counters that GRBs are likely to have
many indirect effects, such as wrecking ozone layers that
protect planets from deadly levels of ultraviolet radiation.

Annis also highlights an intriguing implication of the theory:
the current rate of GRBs allows intelligent life to evolve for a
few hundred million years before being zapped, possibly giving
it enough time to reach the spacefaring stage. "It may be that
intelligent life has recently sprouted up at many places in the
Galaxy and that at least a few groups are busily engaged in
spreading."



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