OK everybody, here鈥檚 the plan.
As soon as dawn breaks in your part of the world, we need you to start
running east, towards the Sun. Or take the car if you feel so inclined. The more
mass you move, the better鈥攖ake the dog along too. If you live on an
eastern coast, get the boat out, or better still, hire a 747.
Now, keep going as fast as you can until the Sun reaches its zenith in
whatever part of the world you find yourself. Then go home. The closer you live
to the latitude where the Sun is directly overhead at midday, the more helpful
your effort will be. If you live anywhere that has permafrost, well . . . thanks
for turning out, but you needn鈥檛 have bothered. Everybody else, same again
tomorrow, please. In fact, keep on doing this until we tell you to stop.
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Why this bizarre request? To save the Earth, oddly enough. By now, everyone
must have picked up an inkling of the doomsday asteroid鈥攐r
comet鈥攖hat is lurking out there. It depends on who you talk to, but the
risk to interested parties here on Earth (us) seems to range from 鈥渁 slight
possibility of a nick鈥� to 鈥渁 dead-cert wipeout situation鈥�.
We鈥檙e not talking about the lunatic fringe here, who frequently claim that
something the size of Botswana is due to hit your locality at lunchtime next
Saturday. No, we鈥檙e talking about your respectable scientist here, who is simply
flagging up the theoretical risk, you understand, but at the same time subtly
implying that anyone who gets flattened in the initial impact can regard
themselves as lucky.
But to risk posing a simplistic question, shouldn鈥檛 we be doing something
about this? At the moment, we just seem to be looking. The next time we have a
near miss (and we鈥檝e already had one or two) we can no doubt expect the
President of the US to go on network TV and explain how the world owes its
thanks to the country鈥檚 firm resolve and technical know-how. Likewise, in
Westminster, the Prime Minister will stand up to make a brief statement in the
House of Commons that will dwell largely on the fact that, had the opposition
been in power, we might not have got off so lightly. But then what?
Agreed, my plan to set up a longitudinal Mexican wave that peaks at the point
on Earth closest to the Sun may not be perfect鈥攂ut hey, I鈥檓 just trying to
get the debate going here. We鈥檒l assume that we get about 10 weeks鈥� notice that
an asteroid or whatever is set on collision course.
In order to dodge the blow, we need to speed up, or maybe slow down, the
Earth as it orbits around the Sun. Since the angular momentum of the Earth
around the Sun is conserved, if we redistribute some mass a little closer to the
Sun, the Earth should speed up a bit in its orbit to compensate. The spinning
ice-skater demonstrates the principle, although in this case we are considering
the angular momentum of the Earth about the Sun, not about its own axis.
Alternatively, we could all move westwards away from the Sun to slow down. Let鈥檚
leave the details to the guys with the big telescopes.
Up until now, mind you, we鈥檝e been leaving it all up to Jupiter鈥攁nd the
Sun, which is the root cause of all the trouble anyway. Jupiter is 鈥渨here it鈥檚
at鈥�, gravitationally speaking. This gives it the ability to suck up cosmic grit
like it鈥檚 going out of fashion, and that is just what it has been doing for
quite a while, with only the occasional careless lapse. But for how much longer
can we rely on such philanthropy?
Some of the probabilities quoted for a significant impact are surprisingly
high, such as 鈥渁 few per cent鈥� over the next 100 years. If you want a more
detailed analysis, you can look up The Spaceguard Survey, published in
1992 by NASA鈥檚 Ames Space Science Division. But even a rough estimate is enough
to tell you that your chances of being killed by this sort of thing in 1997
alone are reckoned to be greater, from what the Ames scientists seem to be
claiming, than your chances of being involved in an accident next time you fly
off on your summer holiday. Scary, eh?
So we鈥檇 better start thinking, though maybe we shouldn鈥檛 take the
Mexican-wave plan too seriously, especially when you can still fit the entire
population of Earth into Hong Kong if everyone breathes in. More significantly,
the total mass of humanity represents less than 1 billionth of one per cent of
the mass of the planet.
Nah. A better idea would be to vaporise the Moon with ray guns. Now you would
really be shifting some angular momentum with that plan . . .