"First let us ask: Whence comes all the motive power? What is the spring that drives all? We see the ocean rise and fall, the rivers flow, the wind, rain, hail, and snow beat on our windows, the trains and steamers come and go; we hear the rattling noise of carriages, the voices from the street; we feel, smell, and taste; and we think of all this. And all this movement, from the surging of the mighty ocean, to that subtle movement concerned in our thought, has but one common cause.
All this
energy emanates from one single center, one single source, the sun. The sun is the spring that drives all. The sun maintains all human life and supplies all human energy."
Nikola Tesla.
http://www.tfcbooks.com/tesla/1900-06-00.htm