Alfred Wegener gave the continental drift theory. On the basis of his theory, the world was a solitary compressed protocontinent at the beginning, which afterward got drifted away into distinct continents as seen today. He named this protocontinent as Pangaea that means all the lands. In order to support this theory, he further stated that a land bridge once prevailed between Africa and Brazil, and thus, one can witness identical fossilized animals and plants in the two parts of the planet.
A nuclear reaction<span> in which two or more atomic nuclei come very close and then collide at a very high speed and join to form a new type of atomic nucleus. Hope this helps :) </span>
