Why explosion caused by the collision of a asteroids with a planet is compared with the Nuclear explosion ?
It depends upon size of the asteroid. It is compared with the nuclear explosion as on collision it creates such a pressure and heat that it can destroy the life on the earth by causing many undesirable changes in the environment,like it may produces a huges amount of dust ,smoke and chemicals that it can cover the whole earth and preventing the sun rays to reach the earth,and thus causing a ice age,also can give birth to many other problems. Similar things can happen when there will be such nuclear explosion on earth itself.
