As we cant predict when a really big asteroid will arrive is there really any point in worryng about it? NASA thinks there is. It estimates that there are between 1,000 and 4,000 asteroids at last 1 kilometre 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 4,000 chance of being around when its happens. A small risk,maybe but much bigger the risk of dying in an air crash,which is one in 20,000. NASA aims to set up six new telescopes and psend 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. One expert recently proposed inventing a new nuclear bomb 10,000 times as powerful nuclear bomb,10,000 times as powerful as anything we have at the moment. He did not explain how.