LIGHT ON THE BEND

Dominion, Volume 13, Issue 81, 31 December 1919, Page 7

LIGHT ON THE BEND

NEWTON'S LAW MODIFIED

TIME AS THE " FOURTH DIMENSION "

The facts ascertained by the British astronomical expeditions to Brazil and Principe this year and the fascinating problems arising therefrom are lucidly discussed in the "Morning Post" of November 8. The actual fact established by the observers of tlio 1910 eclipse is simple enough. Onco upon a time wo believed that light was corpuscular matter, and, as such, would come under the law of gravitation. Then light camo to be known as an nether ray, and it was thought to be outside that law. Then it was suspected that light, though not "matter" in the usual sense of the term, was suseeotible to the law of gravitation. Now that is. to all intents and purposes, established. We have a series of photographs taken duriiijj ;_tjie~. 1919 eclipse showing the light raj's' of various stars being bent towards the sun by gravitation: and—here is the prompting to fascinating .speculations—the light rays are bent to doublo the extent that tho course of a cannon ball would be bent. History of tho Discovery. To see where this leads to, or may lead to. it is necessary to go back a little ill the history of physics. In 188(i two American scientists, Mitchelson and Morley, entered upon an ingenious series of experiments detect the difference in tho sliced of light travelling across tho nether stream and travelling with the aether strewn. Perhaps that phrase needs explanation. We know that the is travelling, as a whole, through tlio aether- Wo do not Ijnow in what direction/ nor at what speed. There seems a conspiracy of the Heavens to conceal that knowledge, for it has defied all inquiries. But we know ih does movo through the aether stream, and that Iho solar system in its relation in the aether stream may be compared to a boat moving along a flowing river. Now the American scientists proved that light travelling across that nether stream had the 'same speed as light travelling with that stream/ To translate that into earth ( . terms, it meant that a boat, with the fSamo power, should travel as quickly across a five-knot current in tho Thames as it would with that five-knot current. That, on tho face of it, seems absurd, but ns regards light and the nether current, it was a fact. Clearly «'e were here on the edge of some new principle, Unknown and perhaps Unknowable. ! How Quick is St, Paul's? A member of a Berlin Academy for Research, Einstein, seized on .that fact, and on .it based a hew 'mathematical theory which has never bfcen put into language yet, and is only recorded in terras of mathematics. So ono can only indicate its contention in general terms. It is. the theory of a "Fourth Dimension": Hint mutter has not only length, breadth, height, but also time. If wo snoke in the terms of the Fourth Dimension we would say in answer .to a tmestion of bow big St. Paul's Cathedral is: "Tt is so many feet long, so many feet bmad, so many feet high, and sn many miles nor se'eond ouic l --." To illustrate in another wa'v: The Fourth Dimension theory means that the size of a tiling depends, in part, on its rate of motion. i Some Consequences, , Now Finsloin'n theory involves certain consequences. Tt may be said to stand on them as on legs. Three of these- can be stated: Tim motion of Mercury's peri- 1 hrlion; the bending of light rays by gravitation to double the extent that matter travelling at an ordinary soeod is bent: the bending of the rays of the solar '■nectruin l\v gravitation. Conseouences Nos. 1 and 2 have been established as facts (No. 2 by these eclipse observation 1 :). Consequence-No. H has not been ostpliIHied: research so far lias negatived it. P.nt the verdict is nnt. anite conclusive vi>t in rcgiml to it. For the present tho Einstein theory of a Fourth Dimension has two good legs to stand upon. The Practical Aspept. Tf the Einstein theory is finally established we must, iti the realm of speculative thought, accept tho possibility of it six foot rule being sometimes Ihe same thing as a three font rule, of the straight line of. Euclid being not stmiehf, and. so on. But practically all this will nnt matter. Tt will not seriously affect any calculation within t'ie solar system. The straight line we draw (in imagination) from the earth to the sun ma.v not be straight at all; in terms of the Universe it may be part of a vast circle. But for all our earthly purposes it will be straight enough. Astronomers have always allowed for a margin of error. When it comes to one-hun-dredth of a second of an arc—or, (o put it popularly, to considering the size of a threepenny-bit 20(1 miles away—it is not worth while pursuing accuracy farther. Similarly, tho Newton law of gravitation need lose none of its earthly validity because in the dim distances of stellar snace we have detected a modification of its influence on matter travelling at the naco which light maintains. Our fastest railway expresses and flying machines will still be governed by the same old law. Even the planets in their eourses do not get up to a speed limit sufficient to modify their reaction to the law of gravitation—all except that very fast- fellow Mercury, who is slightly affected

But if the "Fourth Dimension" comes down to popular talk it will add a new terror to politics. Tf, under certain circumstances. a three-foot rule can become the same thing as a six-foot rule, then fourpence may really become ninepence.

PROFESSOR EINSTEIN. Dr. Albert Einstein, whoso astronomical discoveries described at the meeting of the Royal Society, is a Swiss Jew. forty-five years of age. He was for some time Professor in Mathematical Physics at the Polytechnic at Zurich, anil then Professor at Prague. Subsenueiitlv he was nominated a member of the Kaisar Wilhelm Academy for Research in Berlin. During..the war, as a man of liberal tendencies, he was one of the signatories of the protest against the German manifesto of the men of science who declared themselves in favour of Germany's part in tho war, and at the time of the armistice he signed an appeal in fivctir of the. German revolution. He is an ardent Zionist, and keenly interested in the proposed Hebrew University at Jerusalem, and has offered to co-operate in tho work there.