Death of the Dinosaurs
65 million years ago, dinosaurs suddenly became extinct, together with a large number of other species. But why did it happen?
Many scientists believe that the cause was a large asteroid crashing into the Earth, According to this theory, the asteroid threw huge amounts of dust and water vapour into the atmosphere, blocking out the light of the sun, the vegetation died off, and the dinosaurs starved to death.
Evidence for the theory came in 1992 when scientists inMexico uncovered an underground crater 175 kilometers wide which turned out to be exactly 65 years old. The crater was probably caused by an asteroid 10 km in diameter hitting the Earth at thousands of miles an hour, with the force of 70 million one megaton bombs.
According to David Raup of the University of Chicago, this was just one of many such cases. He says that asteroids have caused more than half of species extinctions since life of Earth began 600 million years ago. If he is right, it seems likely that Homo sapiens will end its days in the same way.
NASA to the Rescue
As we can’t predict when a really big asteroid will arrive, is there really any point in worrying about it ? NASA thinks there is, It Estimates that there are between 1,000 and 4,000 asteroids at least 1 kilometer in diameter which regularly cross Earth’s orbit, if such an asteroid hits the Earth once every 300,000 years, this gives the average person roughly a one in 4000 chance of being around when it happens, A small risk, may be, but much bigger than the risk of dying in an air crash, which is one is 20,000.
NASA aims to set up new telescope and spend the next 25 years working out which large asteroids are likely to arrive within the next century or two. The idea is that once they’ve identified an asteroid heading straight for us, they can move it out of the way by hitting it with powerful nuclear bombs.
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