How does life on earth depend on the sun?

In its natural state, solar energy is important to the earth because it warms the earth, makes plants grow, causes weather, causes water to evaporate and in turn rain, etc. The harnessing of solar energy as an alternate power source is important because it is less expensive and always available on clear days. Solar power will lesson our dependancy on other expendable resources. Solar power is a virtually pollutant free energy source.