Why does the rain fall?

Question: Why does the rain fall?
- Keywords:
  earth,
  rain,
  weather
Asked by mb to Claire, Liad, Ruth, Ryan, Mako on 15 Jun 2015. This question was also asked by pm.
- Ryan Cheale answered on 15 Jun 2015:
  
  Rain falls because as water condenses in clouds it becomes too heavy to sit up there then comes back down to earth
- Ruth Elderfield answered on 16 Jun 2015:
  
  The water on the ground warms up in the sunlight, which gives it lots of energy and because it has so much energy from the warmth the molecules in it spread apart and whizz around, so the water becomes a gas. The water vapour floats up into the sky, but the higher it gets in the sky the colder the surroundings are so the water vapour loses its energy and huddles back closer together forming a liquid again. This is heavier than the gases around it, so the water falls out of the sky as rain.

Question: Why does the rain fall?