能的来源(Sources of Energy)

　　nearly all energy comes from the sun, either in a roundabout① way or straight from it, in the form of heat rays and light rays. the light from the moon, too, comes from the sun. the moon can be said to be like a large mirror which throws back the sun's light to the earth.

　　electrical energy comes from the sun in a roundabout way, e.g.②, it can come from the power of water falling down a mountainside③. the water fell there as rain, and we know that rain is made by the sun's heat evaporating the water on the earth's surface. this water vapour rises, condenses④ on cooling, and falls as rain.the light and heat energy from coal also comes from the sun in a roundabout way. coal was made by the rocks pressing on trees and plants which died millions of years ago. those trees and plants grew with the aid of sunlight, from which they made carbohydrates⑤, in this way changing the sun's energy into chemical energy. when we burn coal, some of this energy is set free.

　　energy which we use to drive car engines comes from petrol⑥,which also was made with the aid of the sun in a roundabout way. plants, and animals which ate the plants, died millions of years ago, and the parts of them that were left were pressed under the rocks in the 301earth. these parts left from dead animals and plants made petroleum⑦,from which petrol and oil are now obtained.

　　thus we can say that the is the place where nearly all energy comes from, and that without the sun's heat and light, there could be no life on earth.