Tuesday, December 25, 2007
Mortals! Rejoice at so great an ornament to the human race!
The title of this post is a translation of a Latin inscription on Sir Isaac Newton's tomb. This is the fourth year that we at 3QD celebrate the auspicious 25th day of December as Newton's Day, an idea that we coincidentally came to independently on the same day as Richard Dawkins proposed it. (Newton was born 365 years ago today.) Each year I have given some small snippet about Newton's life (previous years' posts here, here, and here in chronological order) and this year I'll present a simple experiment that changed our understanding of the nature of light. Even though Newton had done the experiment in 1666, he did not publish it as part of his first major bit of scientific writing until 1672. In fact, just as in a more fair world (with a more fair academy in Oslo!) Einstein should have won four Nobels for the work he published as a 26 year-old in 1905 (the photoelectric effect, Brownian motion, special relativity, and the derivation of the law of the equivalence of mass and energy, E=mc2, from the equations of special relativity), Newton's achievements of the summer of 1666 (which caused Murray Gell-Mann to joke about that annus mirabilis that Sir Isaac could have written quite a "What I did on my summer vacation" essay!) were no less astounding: the law of gravitation, the laws of motion, the work on optics, and the invention of the calculus!
In addition, Newton refined Galileo's notion of scientific method to the point where it is basically indistinguishable from a modern statement of it by a scientist today. He writes in the Opticks:
As in mathematics, so in natural philosophy, the investigation of difficult things by the method of analysis, ought ever to precede the method of composition. This analysis consists in making experiments and observations, and in drawing general conclusions from them by induction and admitting of no objections against the conclusions, but such as are taken from experiments, or other certain truths. For hypotheses are not to be regarded in experimental philosophy. And although the arguing from experiments and observations by induction be no demonstration of general conclusions; yet it is the best way of arguing which the nature of things admits of, and may be looked upon as so much the stronger, by how much the induction is more general. And if` no exception occur from phenomena, the conclusion may be pronounced generally. But if` at any time afterwards any exception shall occur from experiments, it may then begin to be pronounced with such exceptions as occur. By this way of analysis we may proceed from compounds to ingredients, and from motions to the forces producing them; and in general, from effects to their causes, and from particular causes to more general ones, till the argument ends in the most general. This is the method of analysis: And the synthesis consists in assuming the causes discovered, and established as principles, and by them explaining the phenomena proceeding from them, and proving the explanations.
Now just look at the elegant simplicity of this beautiful experiment that Newton performed with just two prisms and a convex lens. This is from a University of California, Riverside, physics webpage:
Newton's first work as Lucasian Professor was on optics. Every scientist since Aristotle had believed light to be a simple entity, but Newton, through his experience when building telescopes, believed otherwise: it is often found that the observed images have colored rings around them (in fact, he devised the reflecting telescope to minimize this effect). His crucial experiment showing that white light is composite consisted in taking beam of white light and passing it through a prism; the result is a wide beam displaying a spectrum of colors. If this wide beam is made to pass through a second prism, the output is again a narrow beam of white light. If, however, only one color is allowed to pass (using a screen), the beam after the second prism has this one color again. Newton concluded that white light is really a mixture of many different types of colored rays, and that these colored rays are not composed of more basic entities.
So, once again, Happy Newton's Day to all!
Posted by S. Abbas Raza at 12:00 AM | Permalink