Why Sun is considered the Ultimate Source of Energy?

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Why Sun is considered the Ultimate Source of Energy?

The sun is the ultimate source of almost all kinds of energy on earth, either directly or indirectly. Fossil fuels (coal, oil and gas) are the transformed forms of plants (and animals) which once lived on the earth and grew capturing the energy of the sun. Biomass is a product of photosynthesis where the sun has the major role. Hydro-electricity depends upon the water cycle which again is dependent on solar radiation. Similarly, wind energy, tidal power, wave power all, in some way or other, and depend on the sun.

The sun is an extremely hot mass of gas, where continuous thermo-0nuclear reaction is taking place producing enormous quantities of heat and light. The sun radiates energy in the form of heat and light in all directions. Only a very small part of this energy is intercepted by our planet earth.

The radiations that reach the earth’s upper atmosphere are:

  1. Ultraviolet radiation,
  2. Visible radiation, and
  3. Infra-red radiation.

Ultraviolet radiation is harmful to the flora and fauna. But fortunately ozone layer on the top of our atmosphere (stratosphere) absorbs the major portion of ultraviolet radiation and a very small part of this radiation reaches the earth’s surface.

The major part of the solar radiation is occupied by visible light and heat wave, both of which contribute to our energy system.


The visible part of the solar radiation is continuously performing a very important service to the living world. This service is called photosynthesis. During this process the plant prepares its own primary food taking carbon dioxide from the air and water from the soul with the help of chlorophyll present in the leaves of green plants. Sunlight acts as the source of energy.

In this reaction carbon dioxide is absorbed from the atmosphere and assimilated into carbohydrates and free oxygen (obtained from breakdown of water) is released into the atmosphere.


The sun is often described as perpetual workers. We have seen that it performs photosynthesis. Also the thermal part of the solar radiation – the infra-red radiation causes evaporation from the oceans and other water bodies on the earth. The result is atmospheric water vapor, humidity, cloud, rain and snow which operate the water cycle. These are very important atmospheric phenomena without which life on earth would not survive.

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