The tiny spheroid that we call home hurtles through space as if there were no tomorrow. A thin surface crust covers a molten mass of which we know comparatively little. Surrounding the earth is a cocoon of atmosphere, which we understand rather better.

Recently we have learned that there may indeed be no tomorrow, since human-made changes are making an impact on the world's ecosystems that could bring to an end life as we have known it. This, in addition to the continuing possibility of a suicidal nuclear war, and the added threat of mass destruction posed by new technologies.

Earlier geological ages either predated or proceeded without significant interference from our ancestors. Respectful of nature in their own way, ‘primitive’ human beings often worshipped the sun and moon, making sacrifices to appease them or the gods of nature. The emergence of the great religions brought about change in this relationship, introducing the idea that man could, or even should, dominate nature. Confidence was even greater among some materialists. For example, the Soviet historian M. N. Pokrovsky declared in 1931: ‘It is easy to foresee that in future, when science and technique have attained to a perfection which we are as yet unable to visualise, nature will become soft wax in his [man's] hands which he will be able to cast into whatever form he chooses.’