In contrast to the ecosphere, the technosphere is composed of objects and materials that reflect a rapid and relentless process of change and variation. In less than a century, transport has progressed from the horse-drawn carriage, through the Model T Ford, to the present array of annually modified cars and aircraft. In a not much longer period, writing instruments have evolved from the quill pen to the typewriter and now the word processor. Synthetic organic chemistry began innocuously enough about 150 years ago with the laboratory production of a common natural substance-urea-but soon departed from this imitative approach to produce a huge array of organic compounds never found in nature and, for that reason, often incompatible with the chemistry of life. Nylon, for example, unlike a natural polymer such as cellulose, is not biodegradable-that is, there is no enzyme in any known living organismthat can break it down. As a result, when it is discarded into the ecosphere, nylon, like plastics generally, persists. Thus oceanographers now find in theircollecting nets bits of orange, blue, and white nylon and larger pieces jammedin the digestive tracts of dead turtles-the residue of nylon marine cordage. In the technosphere, nylon is a useful new commodity; in the ecosphere, nylon, untested by evolution, is a harmful intruder.