The Einstein Theory -- By: L. Franklin Gruber
BSac 79:313 (Jan 1922) p. 85
The Einstein Theory1
When the war clouds were lifted from Central Europe the scientific world outside of Germany was startled by the daring researches which a lone German scholar of Jewish descent had brought to completion during those days of darkness. That Newtonian gravitation should be declared to be only a first approximation to the truth, that even light should be said to be deflected in passing through a so-called gravitational field and that this deflection should be twice as much as could be accounted for by Newton’s laws if light really came under the power of gravitation, came to English men of science like a shock. A test of so bold a theory must therefore be made. Two astronomical expeditions, in charge of some of England’s foremost astronomers, were accordingly sent out to make observations during the total eclipse of the sun, May 29, 1919, to see whether rays of light from a star are deflected in passing near the sun, and if so whether the amount of deflection corresponds to that predicted by Dr. Einstein. And to their astonishment their observations confirmed Einstein’s prediction: theory was found to be matched by scientific fact. Light was found to be deflected by the sun, and the amount of deflection averaged approximately 1.7 seconds of arc for rays passing the limb of the sun, or twice the amount that might be due to Newtonian gravitation.
But this is only one of the applications of the theory itself. To discuss that adequately would manifestly not
BSac 79:313 (Jan 1922) p. 86
be possible within the limits of this brief article. All we expect to do is to call attention to the theory and to the works in which the more intelligible elements of the same are set forth. A few of the more interesting points may, however, be given.
Dr. Einstein first calls attention to the fact that all motion is relative, and that we can know of uniform motion of one body only with reference to another body, either at rest or also in motion. This is illustrated on looking out of a uniformly moving train and in the case of the motions of the earth, in both of which cases we are apt to regard ourselves as at rest. Hence it is found that general laws of nature should hold for a body in uniform motion the same as for a body at rest. This is the fundamental principle of the Special Theory of Relativity.
One of the most startling points—and this has been confirmed by experiment—is this, that the velocity of light is unaffected by the velocity of its source, always retaining its standard of 186,000 miles a second. But this fact is so in conflict with the law of the addition of velocities in mechanics that...
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