Why does the rate of evaporation equal that of precipitation?

Answer 1

This is one of those odd circular situations where the definition is included in the observation. We scientists have to view the Earth, its gravitational well and atmosphere as a "closed system" to be able to handle the variables (among other considerations). A closed system assumes that nothing comes in or goes out (this obviously does not include things like meteorites, extraterrestrial probes, solar wind or the Hydrogen that escapes the gravitational well on a regular basis). Therefore, all water in the Earth's system has to stay here, and we have come up with observations like "what goes up must come down". Water molecules that evaporate go up, but they are too heavy to escape the gravitational attraction of the Earth by themselves so they must come down somewhere (Keep in mind that the higher it goes and the longer it stays up there, the less likely it comes down in the same place).

Answer 2

It is saturation.

^^That answer is WRONG!^^ DO NOT PUT THAT AS YER ANSWER!!

The answer is The Dew Point. *Thanks tew the wonderful Earth Science textbook :)*

Answer 3

it forms into clouds