"The thing that hath been, it is that which shall be, and the thing which is done, is that which shall be done," says the writer of Ecclesiastes, enigmatically. But then he goes on to make more sense: "And there is no new thing under the sun." This wise statement by Solomon - for it was he, tradition has it, who was the author of this pessimistic tome - is of particular relevance at present. This, as every body knows, is Energy Week, and "there is no new thing under the sun" might almost be an enunciation of the principle of the conservation of energy.
Now energy conservation in this context has little to do with the good behaviour, like turning down the central heating, that the organisers of Energy Week are keen to inculcate. It concerns the indestructible nature of energy itself - the strange fact that energy can neither be created nor destroyed, but merely changes form. When energy of a certain kind - be it mechanical, electrical, or thermal - seems to have been totally consumed in one place, an equivalent amount of energy, albeit in some different guise, appears elsewhere.
This chameleon-like nature is well illustrated by tracing the vast amounts of energy that stream towards our planet from the sun. In its most obvious form, solar energy is evident as light and radiant heat. But wind, too, is a manifestation of energy and exists because air moves across the world propelled by differences in atmospheric pressure, these in turn arising because some parts of the planet have absorbed the sun's heat more efficiently than others; wind, therefore, is ultimately a form of solar energy. And taking the conversion process a step further, wave energy comes from the action of the wind - so wave power, too, is a form of solar energy.
The conservation of energy is not obvious, because, in any conversion process, such as that from electrical energy into light, some of the energy is wasted; it is not lost, but is converted into a form from which it cannot usefully be recovered, dissipated throughout the environment, usually in the form of heat.
Energy irretrievably gone from us in this way is reflected in the scientific term entropy. Since energy is continually being converted from one form to another, and since there is some wastage at each conversion, the entropy of the universe is continually increasing; it is a vast and ever-increasing reservoir of used and useless energy - a huge imaginary cesspool into which all the frenzied activity of the world is irresistibly and finally drawn.