Forms of energy
We generally think of energy in terms of sources that are suitable for human use – the non-renewable fuels like coal, gas, oil and nuclear power, and renewable fuels like solar, wind, bioenergy and hydro. With the exception of nuclear energy, all these forms of energy can be traced back to the Sun which is the power generator for life on Earth. It is the energy from the Sun that drives the Earth’s climate by influencing winds, the patterns of rainfall and evaporation, and the heating of the oceans to produce climate-affecting water currents.
Radiation from the Sun is also absorbed by plants during photosynthesis and stored in carbon compounds that are formed from the combination of water taken from the soil, and carbon dioxide extracted from the atmosphere. This fundamental life process captures, in plant cells, energy that was formed by nuclear fusion in the Sun. Leaving the surface of the Sun, this radiant energy travelled through space at the speed of light for about 8.5 minutes before being absorbed by the plants on Earth. It is this energy that passes through the food chain from plants to animals and that powers our own bodies when we eat. Energy does not cycle like water and other elements and compounds, but passes through the biosphere to eventually leave in the form of heat.
Some of the ancient energy of the Sun has remained locked up in plants that became fossilised many millions of years ago. This highly concentrated energy, stored in coal, oil and natural gas, drives human industry. It is released, together with carbon dioxide, when fossil fuels are used, returning the long-stored carbon to a very different atmosphere and world from the one in which it was collected. Fossil fuels are intimately bound up in the history of the biosphere as well as our own history and way of life. The transition to a post-industrial society and a modern standard of living in the West can be attributed to the use of vast quantities of cheap fossil fuels. We now depend on these in almost every aspect of our daily lives, from our alarm clocks in the morning, to our travel to work, the lighting, heating, and cooling of buildings, and the production of the food we eat.