Wednesday, September 3, 2014

The precariousness of scientific theories

It is better to keep a certain skepticism about scientific theories,. Not only because these theories are always simple approximations tuned by further advances, as in the case of Newtonian gravitation and Einstein’s general relativity, quoted in a previous article. It may also be the case that a scientific theory, after decades, centuries or even millennia of total domination, turns out to be simply wrong. This has happened many times in all the sciences, as will be seen with a sample of a few selected cases.
·         In astronomy, Aristotle’s theory of quintessence, arguing that the heavenly bodies are not made of the same stuff as the Earth, was the standard theory for nearly two thousand years.
·         In mathematics, the problem of squaring the circle with ruler and compass wasted efforts for centuries until it was shown to have no solution. Although amateurs keep trying, at least professionals no longer have to waste their time with the alleged demonstration they regularly receive.
·         In chemistry, the phlogiston theory, which dominated for nearly a century, tried to solve the problem of combustion assuming that a burning body loses a part of its substance (the mysterious phlogiston). The real process turned out to be precisely the opposite. Rather than losing phlogiston, burning bodies absorb oxygen, as Lavoisier showed in the late eighteenth century.
·         In physics, for almost half a century in the late nineteenth century, no one doubted the existence of the ether, a mysterious substance with strange properties, which should provide support for the movement of electromagnetic waves. In the early twentieth century it was concluded that the ether does not exist.
·        In biology, in the middle twentieth century, everyone was convinced that the compound eyes of insects gave rise to a mosaic of many repeated nearly identical images. This belief affected even the movies, where science fiction film The Fly (1958) shows a spectacular image of the vision of a man with a fly's head, according to that theory. Today we believe that insects see just like we do, because their brain integrates the various images into one, as ours does with both our eyes.
·         In medicine, which sometimes seems more an art than a science, these things have happened much more often. 50 years ago, assertions as the following were usual:
o    White fish is much healthier than blue fish.
o   Seed oil is healthier than olive oil.
o   It is better to refrain from drinking wine altogether.
Today, as we know, doctors say exactly the opposite.
Will future scientists conclude that some of the theories we are so proud of were as wrong as the previous examples? This may happen specially with some physical theories that still lack an experimental confirmation, decades after they were proposed:
·         The Big Bang inflationary theory.
·         String theory and the derived M theory.
·         The multiverse theories: at least six different incompatible theories.

The same post in Spanish
 Manuel Alfonseca

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