Friday, March 30, 2007

Light in the shadows

Science is under attack by the religious Right, the political Left, social constructivist philosophers, and certain environmentalists. I have addressed each of these assaults at various times in these Musings. For the moment, let's agree that the attacks, although worrisome in regard to science education and public support for science, have little influence on how science is practiced by scientists.

Science is not a body of knowledge. Science is a way of knowing that generates reliable -- although tentative and partial --knowledge of the world. Let me give one example from the history of science that suggests what science is all about.

Early in the 19th century, as part of a competition sponsored by the French Academy, Augustin-Jean Fresnel submitted an alternative to Newton's widely-accepted corpuscular theory of light. At issue was whether light consists of bulletlike particles (Newton) or waves such as you might see when you drop a stone into a pond (Fresnel). A judge of the competition, the mathematician Simeon-Denis Poisson, a champion of Newton, pointed out an implication of Fresnel's theory that even Fresnel was not aware of: When light falls on a disk, it will of course produce a circular shadow; Fresnel's wave theory predicts that under suitable circumstances there will be a bright spot at the center of the shadow, a conclusion Poisson thought absurd. The experiment was carefully performed. The shadow had a bright spot. Fresnel copped the prize.

No religious test here, no political agenda, no social construction. A bright spot or not? Put nature to the test. Fresnel's triumph led directly to Maxwell's electromagnetic theory of light and -- well, by application of the entire electromagnetic spectrum, to a goodly part of the technology that is enjoyed today by science-bashing TV evangelists, science-scolding political bloggers, and ivory-tower social constructivists who chatter on their cell phones even as they say science is all an arbitrary phantasmagoria of the human mind.