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And to make it personal, it invites
the user to say how far he or she is from the point of impact in order
to reveal the probable injuries to their bodies, clothes, house and
neighbourhood. And so, to start things rolling, I dropped a three
mile-wide iron asteroid on Edinburgh at 160,000 mph.
Edinburgh didn't do so well. It
suffered an explosion equivalent to 300 million megatons of TNT. A
fireball 120 miles across rose over the city. There was an impact crater
107 miles wide and more three quarters of a mile deep. Eighteen hundred
cubic miles of soil and rock were vaporised. There was an earthquake of
10.3 on the Richter scale, greater than any in recorded history.
In London 300 miles away, where I had
placed myself, the effects were less severe. Windows shattered. The city
was covered by ejected debris 16 feet thick. All but the best-designed
buildings partially collapsed. Peoples' clothing, grass, and deciduous
trees caught fire. Walls, factory chimneys, and monuments collapsed.
So much for accident, but what of
malice? Charles Pellegrino and George Zebrowski, in their 1995 novel The
Killing Star, suggested that humanity might be deliberately
destroyed by a horrible weapon called a ``relativistic bomb.''
Their reasoning was unpleasantly
simple. No other intelligent civilisations have been found in space, a
mysterious absence that has been called the Great Silence. So where is
everyone? The explanation might be that they are hiding themselves for
fear of one among them, a violently paranoid civilisation, intolerant of
the existence of any other save its own.
These murderous creatures, like the
fastest gunmen in the Wild West, would assume that all other inhabitants
of the Galaxy would behave as ruthlessly as themselves if only they
became sufficiently powerful.
They would therefore wish to destroy
any possible rivals as soon as they emerged. Their most probable weapon
would be a relativistic bomb, a projectile that strikes its target
planet at close to the speed of light. At this velocity, the kinetic
energy released would be so frightful that no life whatever would
survive. Of all human artifacts, perhaps only the Pyramids would be left
standing.
Unfortunately, while we slowly build
up data on all the rocks in the Solar System that might strike us at
tens of thousands of miles per hour and do us partial damage, there is
no way whatever to assess the chances of one that might hit us hundreds
of millions of miles per hour.
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