Water cycle or hydrologic cycle is a cycle of condensation and evaporation. It controls the distribution system of water on the earth. A process in which water changes in to gasses form from its liquid form is known as evaporation. A process in which gas changes in to liquid form is called condensation.

The water cycle supplied water filtration naturally. It was discovered by Norwegian-American meteorologist, Jacob Aall Bonnevie Bjerknes in 1957. He was born on Nov 2, 1897 in Sweden. He worked at the University of Leipzig in Germany.