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Show Exploring he Lp Eartk U to Robert H.Moulton LJU g ... " V ) I iifs i z'---n " x x v y 1 HERB is a man in Chicago who I can measure one-flve-millionth 1 I of an Inch a distance amount- J I lng to one-fiftieth of the small- JuL 1 est distance revealed by a .JMMUMM 6j theoretically perfect micrc- IJfre5jTIKi scope. He can rule on a piece yW0JyMj of polished glass, one Inch bJ wide, 50,000 straight, parallel 4 lines, equally spaced. He has determined the length of the standard meter so accurately that his figures cannot be-subject be-subject to a fault exceeding more than one part in 2,000,000. He has measured the rate at which light travels with a possibility of error not more than one-fortieth of one per cent of the quantity measured and light flies 186,330 miles a second and, as a crowning achievement, he has' determined de-termined the rigidity of the earth. This man Is the first American to receive the Nobel prize in science and the only American who has ever received the Copley medal of the Royal Society of London. Despite achievements that are staggering in their significance, this man's name is little known outside of scientific circles. He is Albert Abraham MIchelson, Ph. D.( Sc. D.t LL.D., professor and head of the departs ment of physics at the University of Chicago. Professor Mlchelson's experiments to deter- r v i J it, i , . B h h? i V ' ' v H Jy "; ? If "Cr- ; ' BSJ 0 X ffl ii iji lifi i, . ""sS A AZZr JjS mine the rigidity of the earth are Intensely interesting. inter-esting. Science has long needed to know the physical properties of this globe. It Is Impossible Impossi-ble to learn this directly, as the deepest mines yet sunk penetrate less than two miles below the surface, a distanoe proportionately no greater than the thickness of the varnish on a two-foot globe. The Interior of the earth is believed to be intensely hot. This theory Is based on the fact that molten lava Is thrown forth by erupting volcanoes. Also, in descending a mine, there is a rise in temperature, amounting to 50 degrees per mile of descent If this rate of increase is constant, con-stant, the temperature at only 100 miles down' is-above is-above the melting point of all substances under-conditions under-conditions as they exist on the surface of the earth. However, despite the high temperature, the interior of the earth may be held in solid state by the tremendous pressure to which it Is subjected. Under the now accepted theory of the celestial mechanics, scientists assume that a heavenly body Is held in its course by the attractive force exerted by the other heavenly bodies on all sides of it. In this way Is determined the earth's course around the sun and the motion of the entire solar system through space. Assuming that the earth is not a solid mass, scientists have long struggled to discover how it resisted the attractive at-tractive forces exerted by other planets and stars whether as a viscous mass or as a perfectly elastic body. They have long known that the earth did' resist re-sist these forces in some degree. The ocean tides which sweep our shores twice dally are proof of this. It has long been known that the tides are caused by the attraction of the sun and the moon. If the earth offered no resistance to this attraction, the whole earth would respond quickly to it and there would be no tides. On the other hand, if the earth were a perfectly rigid body, it would resist this attraction completely; and the tides would reach their maximum height. The amount that the tides fall short of their theoretical maximum height would measure the degree of rigidity which the earth possesses. The next step was to determine the actual height of the tides. This long proved the stumbling stum-bling block. If shore lines were perfectly Btralght and the floor of the ocean perfectly level, the height of the tides could be measured directly; but crooked shore lines and shelving beaches resist re-sist the motion of the tides and make it impossible impos-sible to determine their height with the accuracy demanded by science. Sir George Darwin made elaborate experiments to determine the height of the tides, but was obliged to give up the problem in despair. Professor Pro-fessor Michelson solved this difficulty by laying two lengths of pipe, each five hundrri feet long, and measuring the rise and fall of the water in them. One length of pipe was laid north and south, and the other length east and west, in order to measur the tides In both directions. The pipes were buried six feot under ground to obtain a uniform temperature. At both ends of the pipes tees were inserted having glass windows for observatory purposes. The pipes were half filled with water; and the changes in the height of the water were obtained by measuring through a microscope the distance, between a poinr inserted just under the surface of the water and the image of the pointer reflected reflect-ed above the water The maximum;. tiiies in ttiose pipee did' no exceed ex-ceed one-thousandth of an inch; bate so perfect was the apparatus and so accurate trie readings by Professor Mtstoelson that1 all the variations in. the tides were 'accurately determined Tides are' complex things Their height varies witfr the i position and distance of both the aun an-J; the' moon and, therefore, is never the same two days in succession. Professor Mlishelson's experiments revesrfed 30 of these variations, whicii corresponded almost exactly with the variations obtained' theoretically by computing the variations in the attractive forces exerted' by the sun and tile mocn. The practical' correspondence of the actual height of the tides with the theoretical height proved that the earth through and through is as rigid as steer and that- it yields to ouirside forces as a perfectly elastic body and not as: a viscous mass. This experiment reveals the Imagination and1 the striking originality of Professor MIchelson. The first achievement to bring his name to the attention of the scientific worl'tf was his accurate determination of the velocity of right, accomplished accom-plished also after overcoming tremendous expert-mental expert-mental difficulties. Light Is the fastest thing in nature; it represents the absolute limit of speed. After four years of work and study, Professor Michelson announced that light travels with a velocity of 186,330 miles per second. The maximum maxi-mum error in this figure does not exceed one-fortieth one-fortieth of one per cent On the subject of spectrum analysis, Professor Michetson has devoted many of the best years of his life. Spectrum analyses are obtained by means of the spectroscope. Every substance when heated emits a characteristic light. By means of the spectroscope this light is analyzed and the elements giving off the light are thereby revealed. The spectroscope has enabled scientists sci-entists to determine the elements in far distant stars. It has made possible tremendously important impor-tant discoveries concerning the nature of atoms, the minute particles of which all matter is composed. com-posed. The difficulties of spectrum analysis will be realized when it Is learned that a single atom of sodium emits 800,000.000,000 vibrations per second sec-ond of two slightly different kinds of light. Professor Pro-fessor Michelson was engaged in spectrum analysis very long before he improved the spectroscope, spec-troscope, calling the improved type an echelon spectroscope. This wonderful machine divides light into its various constituents and makes possible pos-sible their separate analysis. The echelon spectroscope uses a glass grating a piece of hishly polished glass on which is ruled from 15.000 to 50,000 straight equally-spaced lines to the inch. To make these gratings- Professor Pro-fessor Michelson invented a ruling engine that is the most accurately constructed mechanical device de-vice in the world. It is operated in a room the temperature of which Is kept constant to within one-hundredth of a degree. To assist in analyzing the lines of the spectrum into their fundamental constituents. Professor Michelson invented the "harmonic ana.lyzpr," a machine as complicated and as delicate as the linotype machine. By its use an assistant can in a few minutes make calculations that would take a skilled computer weeks to accomplish. Scientists have long endeavored to determine the absolute motion of the earth through space. It is known that the earth swings around t.k,e sun " and that the entire solarsypiom is moving toward! the constellation Hercules at the raicof 12: mile per seeond, or 400,000,000 Exiles pw; year. However, How-ever, as scientists have tot yet been able to-measure to-measure the motion of Hercalee, tlisy still do not know the absolute motion o-f the 'sarth. In 18801 Professor Mfchelson attacked the problem' of determining de-termining the motion of tt earth 1 with reference to the ether, the all-pervatiing maditun that fills, interstellar space. All of us have notice J - that. wheTt- walking-through walking-through the rain, althougri It is actually failing vertically, it seems to be ialling t an angle, the' degree of this apparent deflectioii-depending upon' the speed with which wiy have moved? Looking out the window of a fasumovin train, scientists have noticed a similar deflection In trie angle of the light coming to the aarth from sume far distant dis-tant star. As the. medium that" carries the light between heavenly bodib3 is the- ether, scientists, argue that the deflection Is doe to the relative-motion relative-motion of the earth through the ei-fter. Professor Michelson eventually overcsime the-tremendous the-tremendous experimental dif.Icultlas In connection connec-tion with this problem; but no motion- of the earth with respect to the ether w&s found: This result came as a profound s.trpri& to tne entire scientific world.' In order to solve tfils proOlem Professor Michelson Mich-elson Invented a most marvelous Instrument, which he called the "Interferonreter."" This Instrument In-strument is B0 times more powerful than an absolutely ab-solutely perfect microscope woulif be. The microscope's micro-scope's power is limited by the length of a light wave: and the smallest distance- it can reveal 13 one-half a wave length, or one hundred-thousandths of an inch. Ry wClHzln the properties of light in another manner-, the Interferometer can reveal distances equlvaent to one five-millionth of an inch. The microscope has been of Immense value both in scientific work and fn practical life; and the invention of the Interferometer, an instrument in-strument 50 times more powerful, is in Itself an achievement that shonid' -win' for Professor Michelson Mich-elson undying fame. He nsed this Instrument to aid Mm In measuring measur-ing the standard meter, the foundation of the metric system, In terms of infinite exactitude and in a manner that will make this unit perpetual. The original meter length is carefully preserved at Paris: but scientists have long worried over the possibility of Its destruction. In 1893 an International In-ternational commission on weights and measures nsked Professor Mlchetaon to devise pome method by which the meter length could be accurately reproduced. The ioM?r is theoretically one forty-millionth forty-millionth of the earth's circumference; but this definition is. not accurate enough for scientific purposes. Professor Michelson announced the length of the meler In terms of radmfum light wavfts, with a maximum error of one part in two milTfon. This definition will always enable scientists sci-entists to reproduce the meter accurately, as long as the earth exists. These are the most striking achievements of America's greatest scientist. Any one of them Is sufficient to perpetuate a man's name In the annals of science. The result of Professor Michel-son's Michel-son's experiments with reference to the motion of the earth has raised questions that it will take science many years to answer satisfactorily; and his determination of the rigidity of the earth has made possible further and more wonderful, progress in the sphere of celestial mechanics. |