THE LAST SOLAR NEWS.
NOTHING is more curious than to note the tendency of physical science to dissipate the popular notion of solidity as a measure of strength. In fact, modern physics seem to bring us back to the most attenuated forms of matter as the real reservoirs of force,—forms so attenuated as to bear a close analogy to that most tenuous of all forms of life, mind itself, in which so many new dispositions and economies of force originate. The new number of the Cornhill Magazine has a very interesting paper, probably from the pen of a distinguished English astronomer of almost boundless literary activity, on the new solar theory of an American astronomer, to which ho adds a confirmatory suggestion of his own as to the source of the solar spots. The theory itself is due to Professor Young, of Dartmouth College, Hanover, U.S., and accounts for certain phenomena visible in the solar atmosphere on the hypothesis that the sun is really a bubble whose interior consists of gases,— hydrogen and others chiefly metallic,—at temperatures so high as to be hardly conceivable by us ; which gases are condensed into metallic clouds and molten rain in the regions furthest from the cen- tral heat, while the explosions which send forth what are known as the "red prominences " are in that case due to the rushing of the compressed gases of the centre through these metallic rains and banks of metallic cloud. The curious observation which most powerfully suggested this theory of Dr. Young's is thus recorded by the writer in the new Cornhill: "He was observing the edge of the sun in October, 1871, having his- telescope (armed with a powerful spectroscope) directed upon a long, low-lying band of solar clouds. We say low-lying, but in point of (act the upper side of the cloud-layer was fully fifty thousand miles above the sun's surface, the lower side being not less than twenty thousand miles above that surface. The cloud-layer was about 400,000 miles in length. Professor Young was called away from his telescopic work for half-an-hour at a somewhat interesting epoch, for he had noticed that a bright rounded cloud was rapidly forming beneath the larger and quieter cloud-layer. In less than half-an-hour he returned, however ; and then, to his amazement, he found that the great cloud had been literally scattered into fragments by an explosion from beneath. The small rounded cloud had changed in shape, as if the explosion had taken place through it, and all that remained of the large cloud was a stream of ascending fragments, averaging about three thousand miles in length and about three hundred in breadth. Professor Young watched the ascent of these fragments (each of which, be it noted, had a surface largely exceeding that of the British Isles), and he found that before vanishing (as by cooling) they reached a height of about 210,000 miles. Moreover, he timed their ascent, and from his time- measurements the present writer was able to demonstrate the surprise- ing fact that the outrushing matter by which the great cloud had been rent to shreds, must have crossed the sun's surface at a rate of at least five hundred miles per second!"
Now, as the writer in the Cornhill remarks, there can be no violent explosive force which is not due to some kind of previous repression. The force with which gunpowder explodes is partly due to the repressive force of the chemical affinity which previously compressed into a very small space elements that, when liberated from each other's attraction, at once occupy a very large space ; and partly to the artificial compression under which, in the barrels of guns and all similar instruments, the liberation takes place ; and in the case of the sun, the containing shell, through which jets of glowing hydrogen and other gases constantly burst, may be, according to Professor Young, a cloud-band of liquefied gas which descends on the sun in the shape of a torrent of metallic and other rains :— " The eruptions which are all the time occurring on the sun's sur- face," says Professor Young, " almost compel the supposition that there is a crust of some kind which restrains the imprisoned gases and through which they force their way with great violence. This crust may con- sist of amore or less continuous sheet of rain, not of water, of course, but of materials whose vapours are shown by means of the spectroscope to exist in the solar atmosphere, and whose condensation and combine- tions are supposed to furnish the solar heat. The continuous outflow of the solar heat is equivalent to the supply that would be developed by the condensation from steam to water of a layer about five feet thick over the whole surface of the sun per minute. As this tremendous rain descends, the velocity of the falling drops would be retarded by the resistance of the denser gases underneath, the drops would coalesce until continuous sheets would be formed, and the sheets would unite and form a sort of bottomless ocean resting upon the compressed vapours beneath, and pierced by innumerable ascending jets and bubbles. It would have nearly a constant depth in thickness, because it would re- evaporate at the bottom nearly as fast as it would grow by the descending rains above, though probably the thickness of this sheet would con- tinually increase at some slow rate, and its whole diameter diminish. In other words, the sun, according to this view, is a gigantic bubble whose walls are gradually thickening and its diameter diminishing at a rate determined by its loss of heat. It differs, however, from ordinary bubbles in the fact that its skin is constantly penetrated by blasts and jets from within."
This view of the sun's composition would account for its exceeding tenuity,—its density is, in spite of the enormous attraction of gravity due to its huge mass, hardly more than that of water, —and the Cornhill writer shows that this view is in some respects curiously-confirmed by the phenomena of the solar spots, which appear to be large openings, accompanied with signs of great agi- tation,— cyclones, in fact,—in the superficial regions of the sun, and these, he suggests, are due to showers of meteoric stones falling in the wake of some comet which goes very near the sun, and which, •when encountering, and being checked by their collision with, the sun's atmosphere, have no longer sufficient velocity to carry them on in their orbit, and therefore fall into the sun, breaking through -its bands of metallic cloud. For the grounds which suggest both Professor Young's explanation of the constitution of the sun, and the writer's theory of the possible cause of the spots, we must refer to the paper itself, which is as interesting as a noveL All we wish to call attention to here is the curious tenuity which physical science is more and more disposed to assign to the most powerful causes and conditions of physical change to be found in the universe. It is here suggested that the sun,—and if our sun, then in all proba- bility almost all the fixed stars, which are known to be constituted in ways closely similar to our sun,—are mere great envelopes of gas, bubbles of hydrogen and metallic vapour, of which molten metal is the most solid, and burning hydrogen probably the most rarified constituent ; while the bodies which occasion the most violent changes in these central suns are the comets, whose extreme tenuity is so great that the earth is supposed more than once to have encountered one in her path without our knowing • it. It is strange to conceive of the fields of space as sown with countless " bubbles " of this kind,—which " bubbles," as far as science can tell us anything, are the magazines of all the forces with which man has any acquaintance. Nay, it is the very intensity of the forces which they contain which causes them to assume the character of bubbles. Heat, which appears to be,—not perhaps the primitive force in these suns, but at all events the characteristic form of forces (for scientific men are still divided as to whether it is possible to refer back the heat given out by a sun to any other antecedent form of force such as the rush of meteoric bodies under the influence of gravity into the centre of attraction), tends so powerfully to drive all material atoms apart, that condensation is only possible as heat diminishes,—which is saying, in other words, that solidity is due to the loss of the most characteristic form of force, and that high attenuation is the necessary result of its greatest intensity. Indeed, Mr. Proctor has suggested that in the planetary world the same rule may be true. He regards Jupiter, which is a mass immensely greater than that of our earth, as being so much leas dense because the central fire has not yet fully shrunk within a solid crust, so that in Jupiter, on Mr. Proctor's theory, there is a combination of the function of sun with that of planet. Nor is he indisposed to extend the same theory, though more on grounds of mere analogy, to the large and distant planets of Saturn and Uranus. Now, if this is a true view, the relatively slight density of the major planets is due to the more violent forces which are still working in them, while the high density of the earth and Mars must be traced to the more rapid or more nearly completed process of the radiation of their heat. Anyhow, the great solar reservoirs of vital forces are relatively vastly less ' substantial ' than the earth we live on ; it is bubbles that govern the movements of all habitable planets ; while solid worlds are fostered by the light and heat these bubbles give, and are swung through space by these irresistible conglomerates of gas and vapour.
Nor is it only in relation to what we commonly call ' matter' that physical science seems to magnify more and more that which seems to us utterly unsubstantial. The undulatory hypothesis of light assumes a medium which is not appreciable by the senses at
all, which has neither inertia, nor of course, weight, and yet which is described by Professor Jevons as something truly ada- mantine—indefinitely closer in texture, and more elastic than steel. Abything leis solid hi the common sense of the term, —i.e., less adapted to resist motion,—than this assumed ether, it is impossible to imagine ; yet any condition more essential to us as the vehicle of all the forces by which out life is constituted, cannot be conceived; nor in the scientific sense, can anything more adamantine be imagined. Moreover, the myriad bubbles' which contain all the stored forces of the universe could not apparently feed even one poor planet with the blessings of their fiery rain, but for this invisible and imperceptible 'somewhat' whose vibrations convey light and heat. That which to us is the next thing to nothingness, which we know only by inference and hypothesis, is, according to the most trustworthy judgment of science, the durable foundation out of which all life is built. Force generated in a bubble, and committed to the care of an agency which no sense can recognise, but which reason declares to be nearer the ideal adamant than anything which sense can perceive, is the pith and marrow of the whole visible- universe, till at length it appears to issue in human thought, which is as inapprehensible to sense, and as much beyond the region of weights and scales as the imagined ether- itself. To say that the mysteries of science are little short of those of faith, is to express with exceedingly little force the paradoxes to which science leads us. That bubbles should be the fountains of solidity, and that the infinite spaces of the universe should be firmly and closely welded together by what to our senses is pure emptiness, is a conception so bewildering, that we may well admit, as involving even a less shock to our experience, the paradoxical assertion that the weak things of the world are intended to confound the mighty, and the things which are not, to bring to nought the things which are.
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