Energy needs and sources
The energy needs of the world are unending and ever increasing. We need energy for transport, industry, lighting, warmth, cooking etc. Without sufficient energy, the airplanes will stop flying, industry will grind to a halt, cities will be plunged into darkness -- in short -- the world as we know it will cease to exist.
There are many types of energy sources. Our ancestors used wood and other combustible material for burning in order to generate heat and light. Today we make use of fossil fuel and we harness solar, wind, water, chemical and nuclear energy for powering the many devices that we have invented.
Most of these energy sources are non-renewable, that is, they become depleted in time. An example is fossil fuel. Its supply is limited and it is a matter of time before it runs out. An example of a renewable energy source is wood. Trees can be grown but the process takes a long time.
The use of some of these energy sources causes pollution. The burning of wood and fossil fuel produces smoke and other gases. Harnessing energy from nuclear fission produces dangerous by-products that are difficult to manage. By contrast, hydroelectric power, solar energy and wind energy are examples of non-polluting energy sources.
As the population of the world keeps increasing, there is an urgent need to find and use more renewable and non-polluting energy sources.