star visible with the 36-inch Lick telescope. When the spectroscopic binaries are taken into account, however, it is estimated that 40 per cent., or even more, of the stars are double.20 Here, then, is a great field for the fission hypothesis. Stars, however, are certainly not incompressible liquids. With respect to the state of their interiors we know nothing at all, but as a mathematical model undoubtedly a compressible gas is much more acceptable than an incompressible liquid; but even a quiescent gas theory may be only a rough first approximation, notwithstanding the theory be mathematically complete, since a star is the most energetic thing we know anything about. The mathematical theory of the gas model, as might be expected, is much more difficult than the theory of the incompressible model21 and there is little that can be stated that does not rest largely upon conjecture. We are virtually thrown back upon the incompressible liquid for our intuitions. So far as we can depend upon this model, the observations of the binary stars are unfavorable to the fission theory. We have already seen that for this model the ratio of the masses can not exceed one third. But the observations of the binary stars do not harmonize with this ratio. If the fission theory is to apply to any stars at all it must be to the spectroscopic binaries, since Moulton22 has shown, and the same results were obtained later by Russell23 and by Jeans,24 that after fission has occurred the mutual tidal actions can never separate the two stars very far, so that if the visual binaries were ever formed by fission they were formed while the mass was still in the nebulous state; or perhaps better, the nebulous mass had two centers of condensation from the start, and the theory of fission is not applicable. Aitken gives a list of 32 spectroscopic binary stars25 for which the ratios of the masses were known in 1918. In this list there are but two stars for which the ratio is less than one third, and the average ratio for the entire 32 is .748. In the third list of spectroscopic binaries issued by the Lick Observatory26 which is complete to July 1, 1924, the ratios of the masses are given for 71 stars. There are only four stars in this list for which the ratio of the masses is less than one third, and the average ratio for the 71 stars is .746, which is practically identical with the average of Aitken's list. For 24 of these stars the ratio lies between .9 and 1.0, and for 14 it lies between .8 and .9. It is evident that an approximate equality between the masses is the rule. 66 It is a fair guess, therefore, that the fission theory does not account for the spectroscopic binaries. It is not applicable to the visual binaries, and it does not fit anywhere within the solar system. I can not, therefore, but differ from Jeans when he states:27 a double star must be supposed to be born as a result of cataclysmic motion," that is, by the process of fission; and agree with the opinion expressed by Moulton28 when he states that his results "are so uniformly contradictory to its implications as to bring it into serious question, if not to compel us to cease to consider it, even as a possibility." There is no doubt that from the mathematical point of view the theory of fission, as set forth by Poincaré and Darwin, is the most attractive portion of cosmogony. Like so much of his work, Poincaré's paper on the figures of equilibrium of rotating fluid masses is a masterpiece. Darwin's work is not characterized by mathematical brilliancy, but one can hardly read his memoirs on this subject without a feeling of the highest respect for his work. His patience and industry, his honesty and extreme modesty with respect to himself, his thoroughness in the examination of all details, command one's entire confidence, and make one feel that Darwin's attitude towards his problem is a model which should be emulated by all scientific workers who labor in regions in which definite conclusions can not be reached. One turns from this theory with a feeling of profound regret that the evidence seems to be fairly conclusive that, in the birth of the cosmic forms, nature has not followed this model. During the entire nineteenth century work in cosmogony was entirely in the hands of the mathematicians. Contraction and rotational instability were the central features. During the last two years of the century T. C. Chamberlin29 entered the field from the domain of geology. With him came a new set of ideas, and a somewhat new mode of treatment. We do not generally regard geology as a mathematical science, but, notwithstanding this, we can not deny that a competent geologist has a right to cosmogonical opinions. Indeed, a geologist has a closer and more intimate experience with one of the cosmic bodies than either an astronomer or a mathematician, and if he ventures to formulate an opinion in the difficult field of cosmogony the abstract worker 27 Problems of Cosmogony,'' 252. 28 Loc. cit., 133. See also p. 160. must listen to his ideas with respect. A pure geologist, however, would be in danger of running amuck in the china closet of dynamics, just as did the philosopher, Kant; and in associating himself with F. R. Moulton,30 Chamberlin formed a very happy combination of talents that gave promise of being fruitful. To-day no one would think of framing a hypothesis of the origin of the planets without considering very carefully its geological implications. The matter is no longer purely mathematical, nor purely astronomical. It is clearly a mathematicalastronomical-geological problem. The nebular hypothesis of Laplace had ignored everything outside of our own nebula. It asserted that, once upon a time, the earth, was an incandescent liquid mass slightly larger than at present, surrounded by an atmosphere which contained all the water which is at present in the ocean, and therefore 300 times as massive as it is at present. In addition to this it contained all the carbon dioxide which is at present locked up in coal and the sedimentary rocks. These conditions imply a climate, which, geologically speaking, became progressively cooler as the crust of the earth cooled, and the atmosphere was gradually relieved of its excess burden of water and carbon dioxide. Unfortunately, these relations can not be expressed in mathematical formulae; but they are very real for all that, and they must be checked up with the evidence of the rocks. In the introduction to "The Origin of the Earth," Chamberlin writes:31 But this theory of a simple decline from a fiery origin to a frigid end, from a thick blanket of warm air to a thin sheet of cold nitrogen, consonant with the current cosmogony as it was, logical under the premises postulated, pessimistically attractive in its gruesome forecast, already in possession of the stage, with a good prospect of holding it—this theory of a stupendous descensus none the less encountered some ugly facts as inquiry went on. It seemed to accord well enough with an ice age if the ice age came only in the later stages of the earth's history, but it was ill suited to explain an ice age in the earlier geological eras. Unfortunately for it, there began to appear signs of ice ages far back in time, and, besides, some of these had their seats much nearer the equator, and, in other respects, were even stranger than the latest great glaciation. The evidence of these later and stranger glaciations was at first quite naturally received with incredulity, but the proof grew steadily stronger with every new test, and the range of evidence was found wider and clearer as exploration advanced. 30 F. R. Moulton: "An attempt to test the nebular hypothesis by an appeal to the laws of dynamics,'' Astrophysical Jour. (1900). 31 Chamberlin, T. C., "The Origin of the Earth,” p. 4 (1916). While all this should have weakened, and did weaken, the fundamental concept of great warmth and a rich atmosphere in the earlier ages, while it should have roused skepticism as to the verity of the cosmogony on which it was based, and perhaps did so, still the old thermal concept and the old cosmogony continued to hamper all attempts at a radical revision of glacial theories. In the course of this,32 still further departures from the generalizations of the inherited view came to notice. Desiccation products were found to be scarcely less abundant and characteristic in the early strata than in the later, and no steady progress from humidity to aridity seemed to mark the progress of time; nor were there found any evidences of even an oscillatory progress from predominant humidity to predominant aridity. If the record favored any generalization it seemed to be that the severest and most prevalent period of aridity fell near the middle of the stratigraphic record. The implications of the nebular hypothesis are out of harmony with the history of the earth as revealed by the geological record. Moulton found them to be out of harmony also with the present dynamic of the solar system. For example, the present angular momentum of the solar system is less than 1/200 part of the angular momentum which the system must have had when the ring of Neptune was formed, notwithstanding that the elementary principles of dynamics require that the angular momentum of the system shall be constant; the axis of rotation of the sun is 5° out of its proper position; when the ring of Jupiter was formed one tenth of one per cent. of the mass received 96 per cent. of the moment of momentum; some of the satellites of Jupiter have forward motion, some have backward motion; similarly, with respect to the satellites of Saturn; one of the satellites of Mars has a shorter period of revolution than Mars' period of rotation; similarly, the period of the inner ring of Saturn is shorter than Saturn's period of rotation; the high eccentricities and inclinations of the orbits of Mercury and the asteroids are unexpected. There are other objections, but these are enough. It is abundantly evident that the nebular hypothesis of Laplace does not tell the true story of how our planetary system was formed: both astronomy and geology cry out against it and demand that a new story of its birth shall be told. The concept of rotational instability has been tried out in its various aspects during an entire century, and it has been found wanting. The planetesimal hypothesis 33 of Chamberlin and 82 Chamberlin, T. C., Op. cit., p. 7. 83 T. C. Chamberlin: "Fundamental Problems of Geology," Year Book No. 3 (1904) of the Carnegie Institution of Washington, p. 195–258, and subsequent issues. F. R. Moulton: "Evolution of the solar system,' Astrophysical Journal (1905). Moulton appeals to another principle, namely, dynamic encounter of the sun with another star. In the zoological world the lowest types of animals multiply by simple division, much as Darwin and Poincaré supposed a rotating liquid mass to do. But in the higher types of life two parents are required in the process of generation; and this is remotely analogous to the generation of the sun's family of planets. It is a bi-parental process.34 If I remember correctly, it was Lord Kelvin who likened the galaxy to a gas of which the molecules are stars. As in the kinetic theory of gases the collision of the molecules is a fundamental event, so in the dynamics of the galaxy the close approach of two stars is a fundamental event; the time scale in the two cases, of course, is very different. However improbable such an encounter may be for a given star and a given century, nevertheless in the course of time they are inevitable for all stars. If we take a sufficiently large survey of the galaxy we are compelled to face the question: What are the consequences of the close approach, but not collision, of two large, hot, highly active, gaseous masses which are moving on hyperbolic orbits with respect to their common center of gravity? There are many variable factors in such a situation, and quite likely a great variety of consequences may follow. The problem can be narrowed down somewhat by assuming that the sun had such an encounter some ten or twenty billion years ago, that at the time of the encounter it was in substantially its present condition, and that the distance of closest approach was neither too great nor too small for our purpose, which is, of course, the generation of our planetary system. The first obvious effect is that we have a tidal problem on our hands. On second thought, this tidal problem is complicated with a rotation of the sun about an unknown axis, and at an unknown rate. By the time that we have become adjusted to this idea, it has occurred to us that this is not a quiescent sun, sleek and complacent, but one with a fiery disposition, subject to explosions and great gusts of uncontrollable passion. I am sure that even such a redoubtable mathematician as Poincaré would have fled precipitately from such a problem, but Chamberlin fortunately is a geologist, accustomed to volcanoes and earthquakes; therefore he stood his ground and prepared to see what would happen. Quite naturally, what he tells us is not couched in mathematical terms, but with Moulton standing guard over the interests of matheChamberlin and Salisbury: "Geology," Vol. II (1906). F. R. Moulton: "Introduction to Astronomy'' (1906); also (1916). 34 Chamberlin, T. C., "Origin of the Earth," p. 102. matics and dynamics we may be sure that, judged from the point of view of present ideas, the picture presented is essentially correct and sound. If later research and study shows that this is not the correct story, the difficulties, I fancy, will not be perfectly obvious ones. The planetesimal hypothesis tells us that great tides were raised upon the sun, so that the shape of the sun ceased to be spherical and became somewhat prolate, its longest axis pointing towards the visiting star, but deflected slightly by rotation. The violent ascending and descending convective currents, which are always a normal part of the sun's activities, and which are responsible for or, at least, accompany, the great sun spots and prominences which make the study of the sun so interesting, were greatly stimulated by these vast tides, and were particularly violent in the direction towards and away from the passing star. What are now merely prominences that shoot up a quarter or a half a million miles, only to fall back upon the sun, were then intermittent streams of matter that left the sun with somewhat higher velocities so that some of it doubtless escaped from the sun's control altogether, some of it quickly fell back upon the sun, and some, slightly more than one tenth of one per cent. of the sun's mass, was deflected from its radial motion by the attraction of the visiting star and given an angular momentum about the sun in the same direction as the motion of the visiting star, thereby reducing the eccentricity of the star's orbit. After the star had passed on its way and the sun had returned to its lonely state, there existed a large amount of matter that had been torn from the sun moving about it in orbits that were in general highly eccentric, and in all of which the motion was forward. Much of this material consisted of free molecules, each of which moved in a Keplerian orbit until that orbit was changed by collision with other molecules; some of it was in large gaseous masses, which are called nuclei, whose gravitative power was sufficiently great to resist the gaseous tendency of expansion and dissipation, and thereby to preserve their identity; and some of it consisted of smaller gaseous masses which could not wholly resist expansion and dissipation, but large enough to delay the process until a certain amount of condensation from the gaseous state to a foggy or a liquid or a solid state had occurred. Thus, in a relatively short time there were large gaseous nuclei, small and smaller liquid masses, very small solid bodies, and free molecules, each pursuing its own path like a tiny planet about the sun-hence the term planetesimals. Owing to the high eccentricities of the orbits of these planetesimals there was a vast amount of crossing of paths, jostling and collisions. The larger masses gradually absorbed the smaller ones, and, in accordance with well-known principles in celestial mechanics, their orbits became fat and round, and the inclinations of their orbits to the plane of the passing star tended towards zero. In this manner the planets with their nearly circular orbits came into being. Large inclinations and eccentricities are to be expected only in small bodies for which the integration process was small, and it is only in the small bodies that they occur. There are no difficulties with angular momentum, as in the nebular hypothesis; and one can not say that the sun's axis of rotation is 5° out of place. That the axis of rotation of Saturn is 27° out of the perpendicular to its orbit and for the earth and Mars it is 24° out is a blow to the nebular hypothesis, but it causes no disturbance here. The axis of Uranus may be 90° from the perpendicular, and Neptune may rotate backwards without any one being surprised. The fact that there are a thousand asteroids between the orbits of Mars and Jupiter merely tells us that there was no dominant nucleus in this region from the beginning; and the zodiacal light suggests that the process of aggregation is not yet fully completed. That an eruption from the sun that produced the planetary nuclei also produced one or more smaller nuclei which were travelling at about the same speed seems not unlikely. If at the time of ejection such a system of nuclei were moving like a rigid system in rotation then, if they were not too far apart, they would continue to move as a dynamical unit and the smaller nuclei would move about the planetary nucleus as a system of satellites. Their direction of revolution would be the same as the direction of rotation of the planet and their orbits would lie in the plane of the planets' equator. This sub-hypothesis would account for the uniformity of motion of the larger satellites of the planets Jupiter, Saturn and Uranus. It would not, however, require that the plane of the planet's equator should coincide with the plane of the planet's orbit, nor that it should have any particular relation to the plane of its orbit. Observations on the planets themselves do not indicate that any relationship exists. Thus the inclination of Jupiter's equator is 3° and that of Saturn 27°, while the equators of the earth and Mars have sensibly the same inclination of 2312°. The inclinations of the planes of the orbits of the satellites of Uranus and Neptune are 98° and 145°, respectively; little is known about the planes of equators of the latter two planets. There is also a possibility that a satellite was cap tured during the interval of time in which the process of aggregation of the planetesimal material was going on, and this may account for the fact that Jupiter and Saturn have satellites whose motion is retrograde and whose orbits have a high inclination to the plane of the planet's equator. The high inclination of the plane of the moon's orbit to the plane of the earth's equator suggests that the moon, too, is a captured satellite. I can not, of course, enter into the wealth of details with which Chamberlin and Moulton support the argument for the planetesimal hypothesis. They will be found in Chamberlin's book "The Origin of the Earth," and a series of fifteen articles in the Journal of Geology, and in Moulton's "Introduction to Astronomy." To me the arguments are very persuasive, although they are, on the whole, qualitative and not quantitative. They appeal to one who loves nature rather than to one who loves merely mathematics. The planetesimal hypothesis is broad and elastic, capable of admitting much modification without losing its essential character. In this respect it contrasts sharply with the theory of a rotating fluid, incompressible mass, although it has yet to be proven that even this theory is precise after instability sets in. Jeans has attempted to set up a mathematical model35 for the planetesimal hypothesis by neglecting the sun's rotation and its violent internal activities, considering only the tidal actions of a quiescent gaseous mass moving in a hyperbolic orbit. But even this simplified problem is too difficult, and the orbital motion has to be eliminated. The results obtained for even this simplified model are valuable and interesting. The model is too inexact, however, to admit of any usable theorems, and in the present state of our mathematical development the naturalistic methods of Chamberlin, checked up mathematically in those places where the theorems of dynamics can be applied rigorously, give far the greater promise of progress. Certainty can not be reached by either method, for the naturalistic methods are not exact quantitatively, and mathematical models are not exact qualitatively. Our hope lies in a judicious combination of the two. As the matter stands at present, the planetesimal hypothesis of the origin of the planetary system has a clear field, since no other adequate hypothesis is in sight. THE THIRD PAN-PACIFIC SCIENCE CONGRESS AN announcement has recently been issued by the National Research Council of Japan concerning plans for the Third Pan-Pacific Science Congress to be held in Tokyo during the period from October 25 to November 18, 1926. It will be recalled that the first of this series of congresses was held in Honolulu in the summer of 1920 under the auspices of the Pan-Pacific Union. The second congress was held in Sydney and Melbourne, Australia, from August 13 to September 3, 1923, under the auspices of the Australian National Research Council. At the Australian congress the invitation was accepted from the Japanese delegation that the congress three years later be held in Japan under the auspices of the Japanese National Research · Council, and by action of the Australian Congress the plans for the congress in 1926 are to be in charge of the Japanese Research Council. At the Australian Congress action was also taken authorizing the formation of a committee to effect a permanent organization of scientific institutions of the various countries of the Pacific region. This organization committee is composed of representatives from Australia, Canada, Chile, France, Great Britain the Hawaiian Islands, Japan, the Netherlands, the Netherland East Indies, New Zealand, the Philippe Islands and the United States of America, the representative from Japan being the chairman of the committee. The purpose of this committee is to draft the constitution and methods of procedure for a permanent international scientific association in the Pacific region and to present this draft to the congress to be held in 1926. The committee has recently been organized. Dr. T. Wayland Vaughan, director of the Scripps Institution for Biological Research and vicechairman of the Committee on Pacific Investigations of the National Research Council, has been appointed the representative from the United States on this committee, and Dr. Herbert E. Gregory, director of the Bernice Pauahi Bishop Museum of Honolulu, and chairman of the Committee on Pacific Investigations, will represent Hawaii. The announcement recently issued by the Japanese Research Council states that: The main objects of the Third Pan-Pacific Science Congress, like those of the First Congress held in Honolulu, in 1920, or of the Second Congress held in Australia in 1923, are: (1) To initiate and promote cooperation in the study of scientific problems relating to the Pacific region, more particularly those affecting the prosperity and wellbeing of Pacific peoples, and (2) to strengthen the bonds of peace among Pacific peoples by means of promoting a feeling of brotherhood among the scientists and, through them, among the citizens in general of all the Pacific countries. As another means of realizing solidarity of feeling and action scientific programs have, for the most part, been arranged in the form of symposia upon selected subjects. Three have been tentatively selected for discussion at General Sessions and sixteen for discussion at Divisional Meetings, as given below, and cooperating scientific institutions are earnestly requested to make suggestions and give assistance in perfecting and carrying out the prograns. Some other subjects have been tentatively suggested for discussion at Sectional Meetings and these are also given below. It depends upon what contributions will actually be made, but it is quite possible that some of the subjects will have to be shifted from one of the groups to another, or cancelled or replaced by others. SYMPOSIAL SUBJECTS TENTATIVELY SELECTED FOR (1) Review of present knowledge of the physical and biological oceanography of the Pacific; tides and currents, temperature, salinity, hydrogen-ion concentration, abundance of plankton, duration of the swimming larval stages of organisms. (2) Meteorological and time service by radio-transmission in the Pacific region and causes which give rise to its disturbances. (3) Crustal movements and geotectonics in the Pacific region; earthquake, crust tides, variation of mean sealevel, etc. DIVISIONAL MEETINGS A. Division of Physical Sciences (1) Solar activity in relation to geophysical problems of the Pacific region. (2) Distribution of terrestrial magnetism in the Pacific region. (3) Meteorological study of the Pacific region; general circulation of atmosphere, cyclones, correlation of meteorological elements. (4) History of the strandline of the Pacific during Pleistocene and post-Pleistocene time. (5) Correlation of the Mesozoic formations of the Pacific region. (6) Metallogenetic epochs of the Pacific region. B. Division of Biological Sciences (1) Inter-relationship of the floras of Pacific regions as indicated by the distribution of certain groups of land and marine plants. (2) Flora and fauna of the islands of the Pacific, with special reference to the problems of endemism and migration. (3) Different plant successions as observed in various regions of the Pacific. |