CLUB . . . If you see us, it's too late !

It's 100 years and a day since some sort of heavenly object struck Tunguska in Siberia. Luckily in Siberia it only caused massive damage to a trees and swamps and only caused a few human casualties.

Scientists tell us that if a similar object were to explode over London all life would be extinguished out to the M25 causing millions of deaths. Luckily cities like London and Birmingham take up only a tiny percentage of the Earths surface area, much of which is ocean or uninhabited so the chances of receiving a direct hit are very low.

Nevertheless scientists seem to be consistently revising their estimates of how often the Earth is struck by meteors, asteroids or comets and their revisions mainly seem to be downward. We can expect a tunguska style impact once every 3,000 years although some scientists claim it may be even more common than that.

Also around 100 years ago there was a much less widely reported but similar impact over the Amazon rainforest in Brazil and as recently as 2002 American military satellites detected a 12 kiloton explosion. in the upper atmosphere which they say was some sort of heavenly objected exploding in our atmosphere.

A space probe is currently under construction to be sent out to rendevous with a large 270M wide chunk of rock in 2029 as it passes close to the Earth, close enough to be seen with the naked eye. The probe will monitor the position of the asteroid closely because scientists have calculated that if it passes through a particular area of space 100Km across it will then hit the Earth on it's next orbit in 2036. We know that the asteroid will pass close to this crucial position and scientists are worried that Earth bound observations will not be accurate enough to tell us definitely whether it is on a collision course or not. Were it to hit us in 2036 all life as we know it would immediately end.

The BBC has a very interesting article here http://news.bbc.co.uk/1/hi/sci/tech/7470283.stm