ABSTRACT
Among the nine planets in the solar system, Earth is the only one which is known to support life. All the materials we use are taken from the Earth and it supplies us with everything we eat and drink. It receives energy from the Sun, which drives its climates and biological systems, but materially it is self-contained, apart from the dust particles and occasional meteorites that reach it from space (ADAMS, 1977, pp. 35-36). These may amount to 10000 tonnes a year, but most are vaporized by the heat of friction as they enter the upper atmosphere and we see them as ‘shooting stars’. At the most fundamental level, the Earth is our environment.
