Читать книгу The New Astronomy - S. P. Langley - Страница 6

FIG. 26.—SPOT OF OCT. 13, 1876. (FROM ORIGINAL DRAWING BY S.P. LANGLEY.)

Figs. 22 and 24, for instance, are two sketches of a little spot, showing what, with low powers, gives the appearance I have called the honeycomb structure, but which we see here to be due to whirls which have disposed the filaments in these remarkable forms. The first was drawn at eleven in the forenoon of March 31, 1875, the second at three in the afternoon of the same day. The scale of the drawing is fifteen thousand miles to the inch, and the changes in this little spot in these few hours imply a cataclysm compared with which the disappearance of the American continent from the earth’s surface would be a trifle.

The very act of the solar whirlwind’s motion seemed to pass before my eyes in some of these sketches; for while drawing them as rapidly as possible, a new hole would be formed where there was none before, as if by a gigantic invisible auger boring downward.

FIG. 27.—PHOTOGRAPH OF EDGE OF SUN. (BY PERMISSION OF WARREN DE LA RUE, LONDON.)

M. Faye, the distinguished French astronomer, believes that, owing to the fact that different zones of the sun rotate faster than others, whirlwinds analogous to our terrestrial cyclones, but on a vaster scale, are set in motion, and suck down the cooled vapors of the solar surface into its interior, to be heated and returned again, thus establishing a circulation which keeps the surface from cooling down. He points out that we should not conclude that these whirlwinds are not acting everywhere, merely because our bird’s-eye view does not always show them. We see that the spinning action of a whirlpool in water becomes more marked as we go below the surface, which is comparatively undisturbed, and we often see one whirl break up into several minor ones, but all sucking downward and never upward. According to M. Faye, something very like this takes place on the sun, and in Fig.25 he gives this section to show what he believes to occur in the case of a spot which has “segmented,” or divided into two, like the one whose (imaginary) section is shown above it. This theory is to be considered in connection with such drawings as we have just shown, which are themselves, however, no way dependent on theory, but transcripts from Nature.

I do not here either espouse or oppose the “cyclonic” theory, but it is hardly possible for any one who has been an eyewitness of such things to refuse to regard some such disturbance as a real and efficient cause in such instances as this.

Fig.26, on nearly the same scale as the last, shows a spot which was seen on Oct. 13, 1876. It looked at first, in the telescope, like two spots without any connection; then, as vision improved and higher powers were employed, the two were seen to have a subtle bond of union, and each to be filled with the most curious foliage-forms, which I could only indicate in the few moments that the good definition lasted. The reader may be sure, I think, that there is no exaggeration of the curious shapes of the original; for I have been so anxious to avoid the overstatement of curvature that the error is more likely to be in the opposite direction.

We must conclude that the question as to the cyclonic hypothesis cannot yet be decided, though the probabilities from telescopic evidence at present seem to me on the whole in favor of M. Faye’s remarkable theory, which has the great additional attraction to the student that it unites and explains numerous other quite disconnected facts.

Turning now to the other solar features, let us once more consider the sun as a whole. Fig.27 is a photograph taken from a part of the sun near its edge. We notice on it, what we see on every careful delineation of the sun, that its general surface is not uniformly bright, but that it grows darker as we approach the edge, where it is marked by whiter mottlings called faculæ, “something in the sun brighter than the sun itself,” and looking in the enlarged view which we present of one of them (Fig.28), as if the surface of partly cooled metal in a caldron had been broken into fissures showing the brighter glow beneath. These “faculæ,” however, are really above the solar surface, not below it, and what we wish to direct particular attention to is that darkening toward the edge which makes them visible.

FIG. 28.—FACULA. (FROM A DRAWING BY CHACORNAC.)

This is very significant, but its full meaning may not at first be clear. It is owing to an atmosphere which surrounds the sun, as the air does the earth. When we look horizontally through our own air, as at sunrise and sunset, we gaze through greater thicknesses of it than when we turn our eyes to the zenith. So when we look at the edge of the sun, the line of sight passes through greater depths of this solar atmosphere, and it dims the light shining behind it more than at the centre, where it is thin.

This darkening toward the edge, then, means that the sun has an atmosphere which tempers its heat to us. Whatever the sun’s heat supply is within its globe, if this atmosphere grow thicker, the heat is more confined within, and our earth will grow colder; if the solar atmosphere grow thinner, the sun’s energy will be expended more rapidly, and our earth will grow hotter. This atmosphere, then, is in considerable part, at least, the subject of the action of the spots; this is what they are supposed to carry down or to spout up.

We shall return to the study of it again; but what I want to point out now is that the temperature of the earth, and even the existence of man upon it, depends very much upon this, at first sight, insignificant phenomenon. What, then, is the solar atmosphere? Is it a permanent thing? Not at all. It is more light and unsubstantial than our own air, and is being whirled about by solar winds as ours toss the dust of the streets. It is being sucked down within the body of the sun by some action we do not clearly understand, and returned to the surface by some counter effect which we comprehend no better; and upon this imperfectly understood exchange depends in some way our own safety.

There used to be recorded in medical books the case of a boy who, to represent Phœbus in a Roman mask, was gilded all over to produce the effect of the golden-rayed god, but who died in a few hours because, all the pores of the skin being closed by the gold-leaf, the natural circulation was arrested. We can count with the telescope millions of pores upon the sun’s surface, which are in some way connected with the interchange which has just been spoken of; and if this, his own natural circulation, were arrested or notably diminished, we should see his face grow cold, and know that our own health, with the life of all the human race, was waiting on his recovery.