Wind is the oldest source of energy in the world. It was only till the last century that the ships were moved with the help of sails. In a way man used wind to move from one place to another. It served as energy for communication. As no such carriages could be made that could move on land with wind it was easier to travel on seas and rivers than on land. But wind was again the first source of energy after horses and bullocks to draw water from the wells and to grind wheat etc. wind mills were common in a number of countries.

Wood was available in abundance throughout the world .It replaced wind as a source of energy as wind could be used only in the areas it was fast. Wood supplied direct heat. The heat changed water into steam. This steam became a very important source of energy. For a long time mills, machines, boats, steamers, ships required either man power or steam power. The problem with wood was that it required great space. Thus it could not be stacked on ships. The discovery of coal solved the problem. As the black gold, as it was called, gave more heat and required lesser space to stock steam ships became common. Transport became speedier. It was just a matter of time to use it in locomotives, steamers and mills and factories.

Being heavy coal could be and is still used either in railways or in factories where it can be easily stocked. It also gave us thermal power stations where electricity is generated through propellers moved by steam generated through the heat of coal. Thus coal became and is still the greatest source of energy. It gave us steam power to run locomotives and machines directly. It also gave us electricity, most probably, the last source of energy.

But on one hand the stocks of coal are limited, on the other it could not be used on land transport system. The hunger of man for new resources led him to oil that is found below earth and in the sea bed. In India it was first available in Assam. But today Bombay high is the biggest reservoir of oil in the country. Most of the requirements of the developed countries are supplied by Arab Countries that are now known as the petro dollar countries. Petrol being the lightest source of energy made flights and air communication possible. Oil has a hundred uses. But its largest quality is supplied for generating electricity and allowing the aero planes cross the speed barrier of sound.

In New England in the USA the state has totally banned nuclear power stations. A large number of nuclear power stations have been closed in the world after leakage in the Chernobyl plant in the former USSR. The scientists are turning to new sources of energy like bio-gas, sea waves, wind and solar energy. Sun is a permanent source of energy if we can procure from it and stock heat and energy according to our needs. The last source of energy may become the last of course but a perennial source. A very large number of households in Japan and Israel depend on solar energy generated by them. They have even started supplying electricity to the national grid. In India too, many business houses have manufactured sun lamps. A firm in Madras supplies huge Kitchen stoves that work as efficiently as the gas one. As silicon that is found in abundance is the base of solar energy plant a day may come when solar energy replaces all other sources. It may only be supplemented with sea and wind. The ecological problem too will be solved for ever- Nature coming to the aid of man.