Science: Englished Light

A billiard or pool player or a bowler better than most people can get an understanding of an important physical observation, reported last week by Sir Chandrasekhara Venkata Raman, great Indian physicist. Sir Chandrasekhara was scientifically succinct in his announcement. Very few details reached Europe or the Americas. But, according to what he has done in the past and according to the corroborative work of other students, this, simply, is what he said.

Light is a stream of particles, which may be called quanta or photons. Each particle twirls as it moves away from its source.

The twirling of light particles is a new realization in physics. What makes the fact quickly acceptable to other physicists is that Sir Chandrasekhara says he has proved it true. Although he learned all his science in India and has done all his scientific work there, Occidental scientists know his results well. Light has not been his sole research. He has worked out a mechanical theory of bowed strings and violin tone, and a theory of musical instruments. Seven years ago he made a brief visit to California Institute of Technology at Pasadena, rendezvous of Nobel Prize winners. Word from his Chair of Physics at Calcutta University is scientific dogma. Last autumn he received a Nobel Prize (TIME, Nov. 24).

A game of pool or billiards or bowling-in-the-alley provides a simple illustration of what this great Indian and his colleagues are saying in the exact phrases of science. Pool is somewhat the best of the three illustrations.

On the pool table lie 15 round balls. They are closely packed into an equal-sided triangle, five balls to a side. The pack of balls represents any form of matter you please—a crystal of iron, a tum-bler of water, a flask of gas. The balls are atoms or molecules. They are all wobbling very, very fast, and in every direction. You cannot tell which ball is where at any instant. But you, pretending to be a mathematical physicist like Professor Einstein or Professor Raman, can calculate the average place of the average ball at any instant. That is almost as satisfactory as to know where each is all the time. And that is what scientists mean when they say that nothing is, which seems to be. The thing they look at becomes something new while they look at it.

A few years ago Professor Arthur Holly Compton of the University of Chicago aimed some x-rays at a crystal, that is, a conglomerate of pool balls. If the x-rays were waves, as had been the general conception, the waves would have wriggled between the atoms without displacing them and without being changed by them. It would have been as though a bucket of water had been swished across the pool table baize.

But, in Professor Compton’s experiments, the x-rays bounced off the collection of atoms which were the crystal. They rebounded in a peculiar way. The more glancing their blow at the crystal, the longer the x-rays became. That indicated that x-rays were pellets moving with stupendous rapidity. They were like a swift flow of cue balls glancing off the triangle of balls. For his experiments Professor Compton won a 1927 Nobel Prize.

Professor Raman demonstrated exactly the same phenomena with liquids and light rays. In liquids molecules are more mobile than in solids. They dance more actively and through a wider range than in a solid. In a solid they waltz, in a liquid foxtrot. Light rays and x-rays are closely akin. Both are electromagnetic phenomena.* Showing, in a way that other physicists could duplicate his work, that light behaves like a stream of particles won Professor Raman his belated Nobel Prize.

In both Professor Raman’s and Professor Compton’s experiments the quanta of x-ray and the quanta of light, that is, the cue balls of this homely pool illustration, were calculated as darting straight ahead with no movement except forward. What if the particles of radiation were twirling on their own axes as they dashed forward? What if they were not perfect, perfectly balanced spheres? That is, what if they were tumbling onward? What if they swelled and shrank, if they pulsated? What if they zigzagged?

Professor Raman tried to find out by studying the effect of light rays on gases. In gases the molecules of the gaseous matter are comparatively far apart, and they dash with a mad helter-skelter. Nonethe-less light taps them, and caroms off. And that is where Professor Raman made his find. He measured the average strength with which each molecule (pool ball) was whirling. He measured the amount of his light’s (cue ball’s) bounce. And he came to the conclusion that each quanta of light was twirling. In technical language each particle had angular momentum. That means, in the parlance of the pool game, that each pellet of light was englished. And just as the pool player knows just where to jab his cue ball, and with just how much strength, in order to place a ball just where he wants it, Professor Raman could figure the reverse. By knowing where his balls were moving, their spin-ning energy, the carom of the light, he could calculate how much force the light had before it struck.

The practical value of this discovery lies in the fertile future. It may someday explain why the sun turns a tomato red, a face tan; why an ape is not a man.

In all this a moral was painted last week for lazy young boys. Professor Chandrasekhara Venkata Raman was only 16 when he earned his Bachelor of Arts degree, and his Master of Arts degree when only 19. Now he is but 42, with half a lifetime ahead of him for more accom-plishments.

*The known electromagnetic spectrum: cosmic rays (shortest, most penetrating), gamma rays, x-rays, soft x-rays, ultraviolet light, visible light (violet, blue, green, yellow, orange-red, dark-red), infrared, heat, short electric waves, radio waves (longest).