Scientific Predictions
I've never envied the weatherman. After all, if you say it's going to be sunny and it's sunny, ho-hum. But if it rains, look out! Living on (or up to) one's predictions makes for a truly uncertain existence, even when those interpretations of future possibilities are based on what seems to be sound evidence. I've made a few earthquake predictions over the past 20 years, and none of them panned out. Fortunately for me, I never publicized them. A distinguished research group at the University of Colorado went public with an earthquake prediction for Adak Island in the Aleutians last year. The prediction, based on solid geophysical data, was that a major earthquake would occur near Adak before the end of October 1985. When it didn't materialize, the scientists gracefully admitted that it had been a "failed prediction." But six months later, on May 7, 1986, a magnitude 7.7 earthquake did occur at precisely the location they had predicted. That's pretty good for a field in which there are no absolutes.
The sciences are littered with failed predictions, yet are punctuated with equally many good ones that have pointed us toward a better understanding of the universe. Only recently we have been reminded of Edmund Halley's predicted 76-year return of "the" comet.
The existence of the planet Neptune was predicted by Urbain Leverrier from calculations of perturbations in the orbit of Uranus. The helical structure of the DNA molecule was discovered because of predictions made by Nobel laureates Linus Pauling and Lawrence Bragg. Newton and his followers thought that light was composed of particles. In a way, they were almost right, as Einstein demonstrated centuries later. The route to that demonstration began in the 19th century when astronomers discovered that the planet Mercury (closest to the sun) didn't quite follow the rules. It swung its slightly lopsided orbit around the sun a little too fast, seemingly breaking the principles that Newton had set down. Einstein's equations of relativity accounted for that by introducing the idea that space was warped by the introduction of a massive gravitational body such as the sun.
Closely related to this notion, Einstein predicted that gravitation also bent the travel paths of light almost as if the light was made up of particles as Newton had proposed. A few years after Einstein published the final version of his theory of relativity in 1916, the opportunity arose for scientists to check it out. On May 29, 1919, a total eclipse of the sun occurred over the south Atlantic.
English astronomers, led by Sir Arthur Eddington, set up camp on the Island of Principe, off the coast of West Africa. They would photograph the sun during the period of totality. The reasoning was that, if the gravitational field of the sun actually did bend light rays, the stars seen around the sun during the eclipse would be observed slightly displaced from their catalogued positions. Einstein's theory predicted that they would be offset by 1.7 seconds of arc. The photographs obtained by the observers showed five stars, each displaced by 1.61 seconds of arc--well within the experimental error limits.
Scientific predictions will always be chancy--as the University of Colorado group can testify. There are probably as many scientists who would argue that we are headed into another ice age as there are those who say that the ice caps are melting and the coastal cities will be flooded in another 20,000 years. The important point is that predictions often give an aim and a purpose to scientific investigations, and that's what it's all about.
