In some cases NEOs hit the Earth. Most of these meteors explode harmlessly in the upper atmosphere. But some NEOs are dangerous. We try to find out when one is going to hit Earth using impact prediction. On 30 June 1908, a meteorite of around 45 metres in diameter exploded over the basin of the Podkamennaya Tunguska River. It released an energy of 10–15 megatons of TNT and destroyed roughly 2,000 square kilometres of forest. 