Energy enables us to work or play. It is also essential to the machinery. A pair of scissors, an axe or a plough, are useless until someone has the energy to use them. A water wheel will not revolve, unless there is falling water to drive it. A railway-locomotive will never move out of the station, unless there is coal to burn and make steam, or oil to burn to drive its diesel engines. And great factories full of machinery will produce nothing, unless there is electricity or steam or some form of energy to drive the machinery. Therefore the people of the modern world must never stop looking for sources of energy.

In the old days, and in many parts of Africa, Europe, America and Asia, until recently, men and animals were the main sources of energy. In ancient Egypt, men built the pyramids and temples. Today in Nigeria, they till the soil, build the places of the Emirs, and their own homes, push and carry loads, reap and harvest the crops. And so it will continue for many years to come. Anyone who chinks that man power is of no importance as a source of energy, and that modern science is like a magician who with a wave of his hand; can relieve us of the duty of hard work, is very foolish. Machines can only relieve us of some work and they will not work by themselves. We can not put down our tools, and leave the machines to do work for us. There must be energy to drive the machines.

Water and wind were among the first alternatives to man-power which were discovered. The man who first hoisted a sail and allowed the wind to carry his boat along, saved his oarsmen from many weary hours of work. The man who erected the first wind mill saved many men and women from pounding corn. The people who had no need to grind corn because of the inventions of the windniill and the water-wheel, were able to do other work, to add to the wealth of the family or tribe. In the same way, the discovery of new sources of energy in the eighteenth, nineteenth, and twentieth centuries, has released more manpower, so that the world has become richer.

Coal and oil are sources of energy. When burnt, they produce heat, which. may be used to drive engines and these engines will drive the machines. This illustrates an important fact. There are many forms of energy, including chemical energy, heat, light, electricity and mechanical energy:. We can only drive machines by mechanical energy, but all other forms may be changed into mechanical energy or into one another. Energy is always changing from one form to another until at last it all becomes waste heat which leaks away into the atmosphere and can never be used again.