a long time
A: It would be impossible for the air to hold that much water.
Because rain is evaporated oceans and sea water
Salt is not evaporated with water.
Evaporated water mostly come from bodies of water.
Rain would decrease if the oceans died because there wouldn't be enough water to evaporate into clouds.
The atmosphere doesn't have the capacity to hold all that water. If the water in the oceans all evaporated, the air would be so saturated with water that it would fall back down,a phenomenon known as rain.
Known as the water cycle, basically, water is evaporated off the oceans and form clouds. The clouds drop rain on the land, and the rain water flows downwards and into rivers, and returns to the ocean. The water cycle then continues.
The reverse process is condensation, formation of a liquid.
Clouds are formed by water vapour evaporated off the oceans by the sun and wind. Not all clouds produce rain, as the droplets in some clouds may not be heavy enough to drop to earth.
Oceans are kept full by the constant drainage (via rivers, streams, etc.) and precipitation of water into them, causing an equilibrium between what is evaporated and what is coming in. Since Earth is virtually a closed system (no water generally leaves earth or comes to Earth), the amount of water on Earth remains a constant, and whatever is evaporated condenses eventually and precipitates over land or the oceans in the form of rain, snow, hail, etc., and (after melting, if frozen) flows back to the oceans.
Rivers get their water from the rain, and rain is fresh because it is in effect distilled. Evaporated water that re-condenses as rain has left impurities or salts behind, when it evaporated.
rain
Because in the water cycle, when water is evaporated, it accumulates in clouds and eventually falls back to Earth in the form of rain. If it didn't rain, Earth's water would evaporate, and eventually, the Earth would be dry.