- Imagine you are standing against a wall, a lit cigarette
gripped tightly between your teeth and a blindfold over your eyes. Then
imagine that a bullet fired directly at you ruffles through your hair,
a millimetre above your scalp, and imbeds itself in the wall.
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- A reprieve from imminent destruction can brighten anyone,s
day. But on Friday, 14 June 2002, the British population was more concerned
about Mick Jagger,s knighthood and the stock-market crash than savouring
each precious lungful of air. The fact that the "bullet" was
an asteroid the size of a football pitch and that it missed the earth by
75,000 miles, a whisker in the expanse of space, is no longer the point.
The point is that we dodged one bullet but remain in the path of a potential
galactic firing squad.
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- Hollywood movies such as Armageddon and Deep Impact relied
upon the skills of Bruce Willis and Robert Duvall to save the planet from
destruction by a big, dumb rock. In Armageddon, Willis, having landed on
the rock with his elite band of deep drillers, stayed on alone to ensure
the thermonuclear charge was placed at the correct depth, bravely blasting
himself into oblivion and the big, dumb rock into the path of some other
poor planet.
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- In Deep Impact, Duvall took his crew with him when they
agreed to fly into a fissure in their rock before detonating their charges
with the same result - Earth 1: Meteors 0.
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- In reality, the score should be roughly Meteors 650:
Earth 0 and this score only includes the big ones that have struck since
a lump of rock between five and ten miles in diameter wiped out the dinosaurs
65 million years ago. Their extinction was not, as Gary Larson the cartoonist
suggested, as a result of smoking. Scientists estimate that a "big
one" hits Earth once every 100,000 years. Really big ones, like the
sucker that took out the Tyrannosaurus Rex, are believed to be separated
out by tens of millions of years, but even small ones, such as the football
pitch that narrowly missed us a fortnight ago, would cause catastrophic
damage.
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- Had the meteorite landed on London on Friday the 14th,
it would have been travelling at more than 23,000 miles per hour, more
than 10 million people would have been killed and 3,000 square miles would
have been devastated. If it had landed in the Atlantic, a giant tidal wave
would have swamped the eastern seaboard of the United States.
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- The potential devastation of such an incident, coupled
with the relatively high frequency of occurrence, would make you suspect
that world governments would have the issue under control, that the flying
football field was being carefully tracked for months with thermonuclear
weapons locked on to its trajectory in the event that a direct collision
proved likely.
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- The fact that no-one noticed this one,s presence until
three days after it had zinged past is surely a cause for deep unease.
As Jon Giorgini, a senior engineer at NASA/Caltech Jet Propulsion Laboratory
in Pasadena explains, the number of people actively involved in tracking
asteroids worldwide is "about the same as a McDonald,s store: a couple
of dozen people, at most".
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- In April, Giorgini discovered a nightmare scenario with
which our descendants will have to deal. A giant asteroid, a kilometre
in diameter and named "1950 DA", appears to be on a collision
course with Earth. The good news is that the point of impact remains 878
years in the future. The bad news is that, should it strike, a large proportion
of the world,s population could perish. As Giorgini explains: "1950
DA would carry about 100,000 megatons of energy if it hit. It would make
a crater about ten to 15 miles across and devastate hundreds of thousands
of miles around it, kick up dust and steam into the atmosphere. Some of
it would even orbit the Earth for a while. It would be a global problem."
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- Asteroids or meteorites are the rubble discarded during
the creation of the solar system 4,560 million years ago. The planets were
born from the formation of trillions of lumps; the spare parts that now
compose our galaxy,s principal asteroid belt, lying between Mars and Jupiter,
were prevented from coalescing into a planet by the pull of Jupiter,s gravity.
Ever since, pieces of varying sizes have been knocked out of the main belt
and into the paths of other planets such as Earth.
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- The pounding of the Earth,s surface by meteorites has
dramatically shaped the planet,s history, with each giant twist in evolution
caused by what is known within the field as "near-Earth objects".
The "Great Dying" that wiped out 90 per cent of all living species
250 million years ago has been laid at their door, and mammals were given
a leg-up by a meteorite at the expense of reptiles 65 million years ago.
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- Even within the last 5,000 years, however, human history
has been altered by these killers from space. Forget the Chariots of the
Gods, the discredited theory that space aliens bequeathed our ancestors
with the knowledge to construct the pyramids. The only greeting they received
from the heavens was a fiery missile with an impact akin to the film Independence
Day. Evidence is emerging that the earliest human civilisations were devastated
by a meteor storm 4,000 years ago. A giant, two-mile-wide crater has been
discovered in southern Iraq, tying in with the discovery of impact points
as distant as Sweden and Argentina, all dated to around 2200BC. It was
into this post-apocalyptic world that the biblical patriarch Abraham was
born.
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- Great collisions between humanity and lumps of space
rock have occurred ever since. Meteorite showers are thought to have occurred
in ninth-century France and 12th-century New Zealand. In the 15th century
a meteorite is believed to have killed more than 10,000 people in China.
In 1908, a meteor half the size of the flying football pitch destroyed
800 square miles of forest in Siberia.
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- The citing of celestial bodies as harbingers of bad times
began with the Egyptians. Shakespeare, in Julius Caesar, wrote: "When
beggars die, there are no comets seen/The heavens themselves blaze forth
the death of princes." It was only in France during the 18th century,
when a scientific committee was formed to dispel the idea, that the facts
about rocks falling to Earth were established.
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- The odds on any individual being wiped out in an asteroid
attack are actually ridiculously long. Two scientists in America, Clark
Chapman and David Morrison, have computed there was probably the same likelihood
of this happening as dying in a plane crash. Other scientists, such as
Britain,s Duncan Steel, believe the odds are slightly higher. Their calculations
are based on balancing the great infrequency of an asteroid impact against
the huge potential destructiveness if one should occur. Steel, an expert
on near-Earth objects at Salford University, argued in an essay in Prospect
magazine that if the government spent money on tackling the issue it would
have a better balance of cost versus benefit than any other public spending
project. "We have seen what happens to a planet in the firing line.
In 1994, 20 comet fragments slammed into Jupiter, causing damage over an
area much greater than that of Earth. We don,t have to get a bloody nose
ourselves before we realise that it will hurt," Steel wrote.
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- So who is actually looking out for these giant fists
of rock? The answer, as Jon Giorgini explained, is not that many. Until
the late 1980s asteroids that sailed a little too close to Earth were discovered
by chance in the course of a variety of other astronomical tasks. Today,
the Lincoln Laboratory Near-Earth Asteroid Research Project based in New
Mexico dedicates its time to tracking space rubble. Its main concern is
larger asteroids and the most recent near-miss, codenamed 2002MN, was discovered
by chance. NASA, meanwhile, also concentrates on the larger asteroids.
"NASA has a goal of discovering orbits for all the near-Earth objects
with diameters larger than one kilometre. Asteroids of this size could
potentially destroy civilisation as we know it," says Thomas Morgan,
a scientist at NASA,s headquarters in Washington. NASA is spending tens
of millions of dollars each year on a series of satellites designed to
track asteroids and comets. But such is the blizzard of material hurtling
towards the Earth that scientists around the globe discover on average
one asteroid per night that is approaching our planet.
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- It seems we will all have to take our chances with the
smaller meteors, but what about 1950 DA, that huge hunk of rock speeding
towards us at 23,000 miles per hour with a docking date scheduled for 2880AD?
Or, worse, the other ones we don,t yet know about? Will we one day have
to send the great, great, great, great, great-grandson or daughter of Bruce
Willis and Robert Duvall into space to do deadly battle with a monstrosity
the size of Glasgow City Centre and the IQ of a table top?
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- Perhaps, but given enough time, there are other less
violent options. "In hundreds of years, it,s hard to imagine what
ways we,ll have to deal with it," says Giorgini, the rock,s proud
discoverer. "It,s sort of like guys 900 years ago trying to plan the
interstate highway system. It would probably be more sensible to leave
it to future generations.
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- "If you have centuries of warning like this, you
can just change the way it absorbs and reflects light and heat. Sunlight
shines on it and heats one side, and it rotates around to the back and
the heat radiates off into space and pushes on it like a weak rocket. Over
centuries, that,s enough to push it out of the way. If you have hundreds
of years of warning, you could spread chalk or charcoal over the surface,
which would change the way it reflects light and its velocity, or you could
send a solar sail - a big sheet of mylar-like plastic - and shrink-wrap
it. The sunlight over centuries would push it away."
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- If the lead-time shrank to a matter of weeks or months,
then it would be time to dust down the nuclear missiles, according to Steel,
who explains that the targeting would have to be perfect in order to push
the meteor off-course rather than shattering it into a number of rocks
all heading for Earth.
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- A discovery only a few days before impact would be of
little use. Professor Jim Emerson of Queen Mary, University of London -
the leader of the Vista project, which is building a giant telescope in
the Chilean Andes in order to track near-Earth objects - explains his position:
"Then it might be better not to know. If I,m going to have a heart
attack next week, I,d rather not be warned about it." If the warning
did come, there would be just enough time to slip on a blindfold and light
up a fag. This time the firing squad would be unlikely to miss.
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- First published 6-28-02 http://www.thescotsman.co.uk/s2.cfm?id=699152002
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