THE STRUCTURE OF LIGHT
THE study of Physics or Natural Philosophy is the most funda- mental of all the natural sciences, and the others are dependant on it for the basic data of quantity and quality from which they themselves are elaborated. It is easy to realize, therefore, the all-importance of the most exact knowledge, and the greatest possible degree of correlation in its several branches, for on the unity and stability of physical conceptions so much else stands or falls. For example the physical aspects of chemistry are becoming more and more important, and the chemists' most striking recent advances have been made in this direction.
It would seem that the tremendousness of the issues has called forth a particular type of mind to cope with them, for the history of physical research appears as one of the most brilliant constellations in the scientific heavens. Genius is unlimited in the scope of its attention, but the particular breadth of vision and courage in speculathan of these minds calls for especial admiration. One may single out the history of investigations on light, truly one of the most exacting of subjects, owing to the great -difficulties under which the work has to be done. Light travels at the rate of 186,000 miles per second, and traverses distance in space so great that even centuries are spent on the journey : it is not surprising that such properties should continually tantalize the scientist with the question "What manner of thing is this ? "
The nature of light is a key concept which has long been sought. The first hypothesis of any importance was the brilliant one of Sir Isaac Newton who formulated the "Corpuscular Theory," which was to the effect that light was composed of extremely minute bodies, or corpuscles, which emanated from lucent obje;ts, and which were accompanied
by waves in the ether set up by their own vibrations. It ii extraordinary how this thesis foreshadowed the most modern
conception, which has been made possible by the correlation of light with electrical phenomena. This theory held the field till the genius of Thomas Young was directed to the question, and his discoveries of" interference" and certain other optical properties resulted in the birth of the Wave Theory of Light. The intrinsie difference between the two is that in the former the distribution of energy through space is supposed to be scattered or discontinuous, while the latter demands that it should be a continuous or homogeneous disturbance of the ether.
The next contribution of first magnitude was the magnificent work of Clerk Maxwell in 1865, when he elaborated his Electro- Magnetic Theory, and stated that light waves were the same as waves of electric force, only differing in being much shorter. Hertz, the father of wireless, confirmed this Work experiment- ally, and thus the wave idea was placed ona still sounder basis. There are several objections, however, to the entire validity of the theory, such as certain effects obtained by means of X-rays, which could not be brought into line. Sir J. J. Thomson has now produced a new and startling idea, which, if it stands the test of extensive experiment—as it would seem to have a good chance of doing—will revolutionize the whole science by correlating the _corpuscular and wave theories, which were thought to be mutually incompatable.
It follows on the Quantum Theory, which is broadly to the effect that energy is discontinuous, and is thrown out in finite units of extremely small size ; and it conceives of light quanta being lines of electric force, which are freed from attachment to a molecule, and form a closed curve. Such a ring would set up waves in the ether of the type postulated by Clerk Maxwell, while it would be in effect a corpuscle at the same time.
This arresting Contribution of Sir J. J. Thomson will cer- tainly stimulate much research, which should be fruitful whether it be confirmatory or not ; and if it prove true it will mean that once again a leap has been made to transport us to a new country full of novel possibilities and tempting vistas. It is hard for a layman to appreciate the importance of this hypothesis, or indeed its very meaning, but the author has done his best to make it easy, and has succeeded in no small degree. He has sketched its outlines in the first Fison Memorial Lecture, which has just been published in the small brochure mentioned above, and it is a model of clarity, concise- ness and simplicity.
The Fison Memorial Committee, who inaugurated this annual Lecture as a mark of recognition to the late Alfred H. Fison, of Guy's Hospital, have earned the gratitude of those who were privileged to know this fine man and physicist, and they are to be thoroughly congratulated on the auspicious start which has been made.
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