RIDDLE OF THE UNIVERSE.

Wanganui Chronicle, Volume XLIX, Issue 12637, 26 October 1905, Page 7

RIDDLE OF THE UNIVERSE.

HOW THE SUN, MOON, AND STARS WERE FORMED.

Profesor G. H. Darwin delivered the second part of his presidential address to the British Association at Johannesburg last month. He began by dealing with the evolution of the community in the State or Commonwealth, and passed on to evolution throughout the external universe. He explained the theory, which he 'believed contained essential elements of truth, which points to the origin of the sun and planets from gradual accretions of meteoric stones, and referred in detail to the celebrated nebular hypothesis of Kant and Laplace, who traced 'the origin of the solar system to a nebula or cloud or ratified gas congregated round a central condensation whrich was ultimately to form the sun. Under the influence of rotation the nebula, which had come to assume the form of «, len6j became so flattened that a ring of matter detached itself, and each ring formed a subordinate 'nebula. But, said Professor Darwin, though the telescope seems to confirm the general oonreotJiess of Laplace's hypothesis, it is hardly too much to say that every stage presents to us some impossibility. He then Trent on to sketch tihe evolution of a rotating liquid planet like the earth, and dealt with the influence of tidal oscillations.

Let us consider* he said, the motion of the earth and moon Terolving dn company round the sun, on the supposition that the friction of the tideo in the earth n's the only effective cause of change. We are, an fact, to discuss a ■working model of the system analogous to those of which I have so often 6poken before; and it must suffice to eet forth the result in its main outline as referring only to the past. If we take the "day," regarding it as a period of varied length, to mean the time occupied by a single rotation of the earth on its axis; and the "month," likewise variable in absolute length, to mean the time occupied by the moon in a single revolution round the earth, the number of days in .the month expresses the speed of the.earth's rotation relatively to the speed of the moon's revolution. Now iin our retrospect both day and month are found continuously shortening; but as on the whole the month shortens much more quickly than the day. the number of days in the month also falls. We may, then, ask at onee —What is the initial stage to which the gradual transformation points? I say that, on following the argument to its end, the system may be traced back to a time when the day and the month were identical in length, and were both only about four or five of our present hours. The identity of day and month means that the moon was always opposite to the same ©ide of the earth ; thus at the beginning the earth always presented the same face to the moon, just as the moon now always shows the same face to. us. Moreover, when the month was only some four or .five of our present hours in length, tQie moon must have been only a few thousand miles from the earth's surface —a great contrast with tihe present distance of 240,000 miles. It might well be argued from tbis conclusion alone that the moon is separated from the earth more or less as a single portion of matter at a time immediately antecedent to the initial stage to which she has been traced. But there exists a yet more weighty argument favourable to this view, for it appears that the initial stage is one in wthich'the stability of tihe species of motion is tottering, so that the system presents the characteristic of a transitional form, which we have seen to denote a change of type or" species in a previous case. In discussing the transformations of a liquid planet we saw the tendency of the single mass to divide into two portions, and now we seem to reach a similar crisis from the opposite end, -when an retrospectr we trace back the system to two masses of unequal sizes in close 'proximity with one another. The argument almost .carries conviction with it, but I have necessarily been compelled to pass over various doubtful points. Our ideas are blank as to tihe time requisite for the evolution either according to Laplace's nebular hypothesis for the meteoritic theory. All we can asserjb is that they demand enormous intervals of time as estimated in years. If at every moment since the birth of the moon tidal friction 'had always been at work in euch a way as to produce the greatest possible effect, then we should find that 60,000,000 years would be consumed in this portion of evolutionary history. The true period must be much greater, and it does not seem unreason-, able to suppose that 500 to 1000 million years may nave elapsed since the birth of the moon. Such an estimate would not seem extravagant to geologists who have, in various ways, made exceedingly rough determinations of geological periods. As far as my knowledge goes I shoull say that pure geology points to some period intermediate 'between SO and 1000 millions of years, the upper limit toeing more doubtful than the lower. Thus far we do not find anything which renders the tidal theory of evolution untenable.

Since the mass of the sun is known, the total amount of the Qieat generated in it, in ■whatever mode it was formed, can be estimated with a considerable amount of precision. The heat received at the earth from the sun can also be measured with some accuracy, and hence it is a mere matter of calculation to determine how much heat the eun sends out in a year. The total heat which cam have been generated in the sun divided by the annual output gives a quotient of about 20,000,000. Hence it seemed to be imperatively necessary that the whole history of the 6olar system should be comprised within Borne 20,000.000 yoairs. This argument, which is due to Helmboltz, appeared to be absolutely crushing, and for the last 40 years the physicists have been accustomed to tell the geologists that they must moderate their claims. But for myself I have always believed that the geologists were more nearly correct than the physicists, notwithstanding the fact that appearances were so strongly against them.

Radium is perhaps millions of times mow powerful than dynamite. Thus it =i 6 estimated than an ounce of radium would contain enough power to raise 10.000 tons a mile above the earth's surface. Another way of starting the same estimate is:—The energy needed to tow a ship of 12,000 tons a distance of 6000 eea miles at 15 knots is contained in 22 oz. of radium. The Saxon probably bums 5000 or 6000 tons of coal on a, voyage of approximately the same length. Other lines of argument tend in 'the same direction. Now we know that the earth contains radio-active materials, and it is 6afe to assume that it forms in some degree a sample of the materials of the solar system; hence it is almost certain that the sun is radioactive 'also. This branch of science is a.s yet but in its infancy,- but we already sve how unsafe it ds to dogmatise on the potentialities of matter. It appears, then, that the physical argument is not susceptible of >a greater degree of certainty than that of geologists, and the scale of geological time remains in greaib measure unknown. I have now ended my discussion of the solar system, and must pass on to the wider fields of the stellar universe.

A celestial photograph looks at first 'like a dark sheet of paper splashed with whitewash, but further examination Allows thaib there ds method in the ar-r-angeinenlt of the white spots. Thus there ds -order of some sort in the heavens, and, altGiough no reason can be assigned for the observed arrangement in any particular case, yet it is possible to obtain general ideas as to the succes-

sion of events in stellar evolution. Besides the stars there are numerous (.'breaks, wisps and agglomerations of nebulosity, whose light we know to emanate from gas. Spots of in tenser light are observed in lees brilliant regions ; clusters of stars aro sometimes embedded in nebulosity, while in other ca^es each individual star of a cluster stands out clear by iteelf. These and other observations force on us the conviction that the wispy clouds represent the earliest stage or development, the more condensed nebula© a later stage, and the stars themselves the last stage. This view is in agreement with the nebular hypotheieis of Laplace, and we may fairly conjecture that chains and lines of stars represent pre-existing streaks of nebulosity.

Wo have seen that it is possible to ■ trace the solar system back to ft primiI tive riebu'a with some uegree of confidence, and that there Ls reason to believe ihat the stars in general have ori- , ginated in the same manner. But such (primitive nebulae stand in as much j need of explanation a6 their stellar off- ; spring. Thus, even if vvo grant the exact truth of these theories, the advance | towards an explanation of the universe [ remains miserably slight. Man is but a' I microscopic being relatively to astrono- | mical space, and he lives on a puny ' planet circling round <a stair of inferior j rank. Does it not, then, seem ns futile jto imagine that he can discover the origin and tendency of the universe as to expect a housefly to instruct us as to the theory of the motions of the planets? . And yet, a« 'ong as he shall last, he i will pursue his search, and wil1 no doubt 1 discover many wonderful things which > aro still bidden. We may indeed be | amazed at al 1 that man has been able ■ to find out; hut th© immeasurable mag--1 nitude of the undiscovered will through- | out all time remain to humble his pride, i Our children's children will etill be gaz- | ing and marvelling at the starry heav- ! ens, but the riddle will never be read.