The Birmingham age-herald., 1921-07-04
E|NSTE|N ID MAKE
 ANOTHER TRY ID
 PROVE HIS THEORY
Experiment Will Be Held Un- der Auspices of University of Chicago-PIace to Be
 Chosen Later
By Associated Press

By Associated Press Chicago July 3.-The Einstein theory of relatvity is to be sub jected to a new practical test by Prof. Albert A. Nicholson of the University of Chicago, whose dis coveries led to it's formulation. The forthcoming experiment Is expected either to lend substantial support to the theory or to disprove it.
 Professor Nicholson, who is now lecturing at the University of Paris is expected back about July 1 and the test Is planned within the next year. It will be conducted under the auspices of the University of Chicago, either in this city or in some mountainous country. The experiment has been under taken at the request of Dr. Ludwick Sllberstein of the Eastman Research. laboratories at Rochester, N. Y., who has worked out it's terms. It is said that Prof. Albert Einstein on his re- cent visit to the United States ex. pressed his belief in the efficacy of the experiment.
 Just what 1t is planned to do to determine whether Einstein's theory holds or not was explained here to- day by Prof. Robert A. Millikan, col. league of Professor Nicholson in tho department of physics of the Univer. sity of Chicago. Divesting the sub. ject of technical details, Professor Millikan said:
 Suggested 20 Years Ago
 This is. as matter of fact, ar experiment suggested by Professor Nicholson 20 years ago as one way of testing whether or not it Is pos sible to detect a motion of the earth with respect to the medium which carries light.
 All efforts thus far made to de- tect by means of light effects the motion of any material body with respect to the ether have. failed. But all preceding attempts have been made with the idea of trying to measure the linear motion through space of point to the earth with respect to the ether surrounding that point, and the results thus far obtained have been wholly negative.
 Tn other words, the observed ef- fleets have been precisely those to be expected if there is no relative mo- tion of the earth with respect to the ether at all. To illustrate, if an observer were himself immersed in a great sphere of rotating water and were to send sound signals simul- taneously forward in the direction in which he Is moving and also back ward, and if these sound signals were reflected by mirrors placed at equal distances ahead and behind him. the echoes would obviously cein., back at exactly the same instant, provided there were no relative mo. tion between himself and the water In other words, he could not detect by such an experiment the movement of himself or the water unless he were moving more rapidly or more slowly than the water, in which case he would be able to detect and to measure his relative motion with re- spect to the water by the difference in the time of return of the echo from the forward mirror and the back mirror.
 Experiments Up to Date
 Now the results of all expert ments of this sort up to date in which we have sent light signals for ward and back have been to show no difference in the time of return Of the light echo to the observer. From this the conclusion has been drawn that the ether. if it exists at al, moves with the earth so as to make 1t impossible to detect any relativa motion.
 Now Dr. Silberstein has asked Professor Nicholson to take up again the projected experiment because he has computed that if the general theory of relativity Is correct. there | should be a difference in the time l of return to the source of signals sent in opposite directions around the pole in the manner indicated.
 "A little computation shows that 1t should be just as satisfactory to send beam around a circuit of known area in the latitude of Chl- | Chicago as Is the latitude of the pole
 The Difference
 '"The difference between this ex- pertinent and it's predecessor lies in the fact that this utllizes the chang ing speed which the earth's rotation imposes upon points of different dis tances from the earths pole, while the former was quite independent of this fact.
 Professor Nicholson has there fore agreed In view of the immense interest which there is now in reia- tivity to take up again this experi. ment. which has acquired added in- terest because of the fact that Dr. Silberstein's analysis of the theory of relativity requires that there be a positive measurable effect when the experiment is performed in this way
 If the predicted amount of this effect is exactly checked experi- mentally. Einstein's theory of rel ativity will receive support. If on the other hand as In the preceding experiment. there should be found to be no observable difference 'n the time required for the light ,o go in opposite directions around tn. circuit, or If the observed difference does not check numerically with tn computed, then the Einstein theory will have been disproved."
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