The sun's energy comes from nuclear fission
radioactive decay
intense heat
nuclear fusion

The formation of the planet uranus is estimated to have occurred approximately when?

Acivilization exists for several hundred yeaars, developing its own language. such a civilization probably has been: a. farming corn b. suffering from a lack of contact with the outside world. c. isolated by mountains or some other physical barriers. d. starving from lack of trade.

The process by which liquid water changes into water vapour is called what ?