Energy

Abstract

In the vastness of the universe the sun is as insignificant as a grain of sand in the desert. Yet, from the human point of view the amount of energy emitted each year by the sun for the last 5000 million years is unimaginably large. Most of the sun’s radiation is lost in the infinite depths of the universe but an extremely small fraction of it is received by the earth, a small sphere, 150 million kilometres away in space. Some 40 per cent of the solar radiation that reaches the earth’s atmosphere is reflected by clouds, by dust in the air or by the sea and land surfaces, and sent back into space. The absorption of the remaining 60 per cent is exactly sufficient to keep the world average temperature within the narrow range required for the development of life and the sun has thus been the very reliable source of energy for all the creatures that ever existed on our planet. It is therefore not surprising that the sun-cult was the basis of many primitive religions and that the sun-god was believed to be the almighty being who gave life to this earth.