Since the early 1950s, a general societal perception likely to have been experienced by everyone is that we are in the midst of a knowledge explosion in science. The result of the perceived knowledge explosion is the rendering of the impression that scientific knowledge is temporary and unreliable. This image of unreliability leads, in turn, to teaching methods that emphasize how science is done at the expense of scientific knowledge. The science education literature reveals that many scientists and educators assume that this creates problems for education by causing existing knowledge to go out of date. For example, Glass (1970) stated:
It can now be affirmed unequivocally that the amount of scientific knowledge available at the end of one's life will be about 100 times what it was when he was born. In rapidly advancing fields of biology, for example, textbooks are scarcely written and printed before they are sadly out of date. (p. 39)
The notion of fields of inquiry rapidly advancing has led to the term "scientific revolution" often being used to describe scientific change. The implication is that new knowledge is exchanged for old and that past learning is seemingly wasted.
Even more startling is the assumption that, therefore, scientific knowledge is not dependable.
If there is one thing that the history of science proves, it is that all theories turn out to be more or less "wrong" in the end. (Burbules & Linn, 1991, p. 232) Because of this perceived unreliability, knowledge is no longer valued as an important part of science; it is seen as merely the "product" or "conclusion" of science and its value is diminished. This has led, in turn, to approaches that aim to teach scientific methods or problem solving skills, rather than scientific knowledge (Gibbs & Lawson, 1992). Van der Steen & Sloep (1993) assert that: