One Hundred Years of Relativity

Einstein’s Paper on the General Theory of Relativity was published in November 1915. Musings by Josef Eisinger, a physicist and Einstein scholar whose recent book, Einstein on the Road, is based on Einstein’s personal diaries. A second book, Einstein at Home, is based the recollections of the Einstein family’s housekeeper in Berlin and will appear in May 2016. (Both books are published by Prometheus Books.)

This morning I read that by comparing the vibrational frequency of a chemical bond of methane located in a distant galaxy, with that of methane here on Earth, we now know that in the past seven billion years, the proton to electron mass ratio has remained unchanged to within at least one part in ten billion. While this experimental result failed to ease my mind significantly with regard to the stability of our world, it does illustrate the deep understanding we now have of our universe. I even felt a little pleased for having made minuscule contributions of my own to the magnificent edifice of present-day physics. Its foundations were, of course, laid well before Einstein’s theory of general relativity, but his theory did open up vast new vistas that have revealed to us the origin and evolution of the universe we inhabit – surely one of humanity’s grandest intellectual achievements.

Albert EinsteinIt is exactly one hundred years ago that Einstein published the general theory of relativity – ten years after his annus mirabilis when he, arguably, laid the foundations of quantum physics. In its broadest terms, the general theory established the intimate connection between space, time, and matter. This inseparable relationship has been verified in innumerable experiments and has no practical consequences under normal conditions; it modifies Newton’s well-established laws of motion only under very extreme conditions, say, at speeds approaching the speed of light. That is why Einstein was so astonished by the enormous fuss created six years later, when an astronomical observation – the deflection of light by the sun’s gravity – confirmed a prediction of his theory. He maintained that unlike the theory of Copernicus which demoted our planet from its central role in the solar system, his (Einstein’s) theory did not affect anyone’s philosophy or world view. And indeed, in 1915, when Einstein’s eight-page paper, “On the General Theory of Relativity” appeared in the Proceedings of the Prussian Academy, not many people paid attention to it, and among physicists, there were not a few skeptics.

Einstein’s article on the general theory of relativity was just one of seven articles he published in 1915. Among them was one entitled “My Opinion on the War” in which he defended his pacifist position, even as nationalistic fervor was sweeping Germany.

Surprisingly for that time, Einstein presented his new theory to the general public, even before it was quite finished, first in a newspaper article, and soon after that in a popular lecture in Berlin’s Treptow Observatory in June 1915. Nor was that an isolated event, for he gave popular lectures on many other occasions and also wrote a hugely successful popular book about relativity. To be sure, having to explain your work to lay audiences is an excellent way to clarify your own ideas, but Einstein also saw it as a scientist’s responsibility toward society. He once said: “all those people should be ashamed of themselves, who have no more intellectual appreciation of science, than the cow has of the botany of the grass it blissfully eats.”

That Einstein was able to complete his theory under the conditions prevailing in 1915 Berlin is evidence of his extraordinary power of concentration. The Great War was in its second, bloody year, bread was rationed, and Einstein’s personal life was in a shambles. His marriage to Mileva had broken up the year before and she had returned to Zurich, their previous domicile, with their two sons. Since then, Einstein had been engaged in a bitter exchange of letters with Mileva, even while anxiously trying to retain a close relationship with his sons, now five and eleven. He had moved to an apartment not far from that of his cousin and good friend Elsa, and lived there like a bachelor.

Eventually, a divorce agreement with Mileva was negotiated, and when it became final in 1919, Einstein married Elsa. In November of the same year, Sir Arthur Eddington announced at a well-publicized meeting of the Royal Society in London, that his astronomical expeditions had measured the deflection of starlight by the gravitational field of the sun and that the result confirmed the general theory of relativity. Einstein became a worldwide celebrity overnight and his life was changed forever.

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