Part 16 (1/2)

----------------------------------------------------------------------- 11 .37 .41 8.0 +65000 -1.8 1.2 27.50 0.429000 12 .31 .32 10.2 +34000 0.5 3.0 5.25 0.051300 13 .16 .16 20.4 -24000 7.9 8.9 0.023 0.000055 14 .18 .23 14.2 +69000 6.3 8.1 0.048 0.000238 15 .19 .... .... ...... .... 10.4 0.0057 ........

----------------------------------------------------------------------- 16 .41 .76 4.3 +20000 6.2 10.7 0.0044 0.000238 17 .19 .22 14.8 -20000 8.2 9.9 0.009 0.000041 18 .34 .... .... ...... .... 14.7 0.00011 ........

19 .19 .... .... ...... .... 9.9 0.009 ........

20 .76 1.03 3.2 -28000 -0.5 4.6 1.20 0.117500 ----------------------------------------------------------------------- 21 .17 .22 14.8 -598000 4.0 5.8 0.40 0.001815 22 .18 .19 17.1 -36000 5.6 7.1 0.12 0.000412 23 .18 .... .... ...... .... 9.7 0.011 ........

24 .19 .... .... ...... .... 7.1 0.12 ........

25 .17 .17 19.2 +21000 5.7 7.1 0.12 0.000329 ----------------------------------------------------------------------- 26 .22 .... .... ...... .... 10.8 0.004 ........

27 .53 .70 4.7 +10000 9.1 13.3 0.0025 0.000114 28 .19 .... .... ...... .... 5.7 0.44 ........

29 .29 .... .... ...... .... 11.1 0.0030 ........

30 .20 .23 14.2 -49000 4.5 6.3 0.25 0.001238 ----------------------------------------------------------------------- 31 .21 .51 6.4 +117000 -0.7 2.8 6.30 0.153600 32 .30 .38 8.6 +19000 5.1 8.0 0.053 0.000715 33 .25 .26 12.6 -11000 6.6 8.6 0.030 0.000189 34 .28 .31 10.5 +17000 4.6 7.0 0.13 0.001230 35 .26 .... .... ....... .... 11.3 0.0025 ........

----------------------------------------------------------------------- 36 .29 .29 11.2 -3000 7.1 9.4 0.014 0.000111 37 .17 .... .... ....... .... 9.9 0.009 ........

38 .22 .22 14.8 -7000 8.2 9.9 0.009 0.000041 -----------------------------------------------------------------------

On the basis of column 14 and of the movements and distances of the stars as given in the other columns Fig. 10 has been prepared. This gives an estimate of the approximate electrical energy received by the sun from the nearest stars for 70,000 years before and after the present. It is based on the twenty-six stars for which complete data are available in Table 6. The inclusion of the other twelve would not alter the form of the curve, for even the largest of them would not change any part by more than about half of 1 per cent, if as much. Nor would the curve be visibly altered by the omission of all except four of the twenty-six stars actually used. The four that are important, and their relative luminosity when nearest the sun, are Sirius 429,000, Altair 153,000, Alpha Centauri 117,500, and Procyon 51,300. The figure for the next star is only 4970, while for this star combined with the other twenty-one that are unimportant it is only 24,850.

Figure 10 is not carried more than 70,000 years into the past or into the future because the stars near the sun at more remote times are not included among the thirty-eight having the largest known parallaxes.

That is, they have either moved away or are not yet near enough to be included. Indeed, as Dr. Schlesinger strongly emphasizes, there may be swiftly moving, bright or gigantic stars which are now quite far away, but whose inclusion would alter Fig. 10 even within the limits of the 140,000 years there shown. It is almost certain, however, that the most that these would do would be to raise, but not obliterate, the minima on either side of the main maximum.

[Ill.u.s.tration: _Fig. 10. Climatic changes of 140,000 years as inferred from the stars._]

In preparing Fig. 10 it has been necessary to make allowance for double stars. Pa.s.sing by the twenty-two unimportant stars, it appears that the companion of Sirius is eight or ten magnitudes smaller than that star, while the companions of Procyon and Altair are five or more magnitudes smaller than their bright comrades. This means that the luminosity of the faint components is at most only 1 per cent of that of their bright companions and in the case of Sirius not a hundredth of 1 per cent.

Hence their inclusion would have no visible effect on Fig. 10. In Alpha Centauri, on the other hand, the two components are of almost the same magnitude. For this reason the effective radiation of that star as given in column 14 is doubled in Fig. 10, while for another reason it is raised still more. The other reason is that if our inferences as to the electrical effect of the sun on the earth and of the planets on the sun are correct, double stars, as we have seen, must be much more effective electrically than single stars. By the same reasoning two bright stars close together must excite one another much more than a bright star and a very faint one, even if the distances in both cases are the same. So, too, other things being equal, a triple star must be more excited electrically than a double star. Hence in preparing Fig. 10 all double stars receive double weight and each part of Alpha Centauri receives an additional 50 per cent because both parts are bright and because they have a third companion to help in exciting them.

According to the electro-stellar hypothesis, Alpha Centauri is more important climatically than any other star in the heavens not only because it is triple and bright, but because it is the nearest of all stars, and moves fairly rapidly. Sirius and Procyon move slowly in respect to the sun, only about eleven and eight kilometers per second respectively, and their distances at minimum are fairly large, that is, 8 and 10.2 light years. Hence their effect on the sun changes slowly.

Altair moves faster, about twenty-six kilometers per second, and its minimum distance is 6.4 light years, so that its effect changes fairly rapidly. Alpha Centauri moves about twenty-four kilometers per second, and its minimum distance is only 3.2 light years. Hence its effect changes very rapidly, the change in its apparent luminosity as seen from the sun amounting at maximum to about 30 per cent in 10,000 years against 14 per cent for Altair, 4 for Sirius, and 2 for Procyon. The vast majority of the stars change so much more slowly than even Procyon that their effect is almost uniform. All the stars at a distance of more than perhaps twenty or thirty light years may be regarded as sending to the sun a practically unchanging amount of radiation. It is the bright stars within this limit which are important, and their importance increases with their proximity, their speed of motion, and the brightness and number of their companions. Hence Alpha Centauri causes the main maximum in Fig. 10, while Sirius, Altair, and Procyon combine to cause a general rise of the curve from the past to the future.

Let us now interpret Fig. 10 geologically. The low position of the curve fifty to seventy thousand years ago suggests a mild inter-glacial climate distinctly less severe than that of the present. Geologists say that such was the case. The curve suggests a glacial epoch culminating about 28,000 years ago. The best authorities put the climax of the last glacial epoch between twenty-five and thirty thousand years ago. The curve shows an amelioration of climate since that time, although it suggests that there is still considerable severity. The retreat of the ice from North America and Europe, and its persistence in Greenland and Antarctica agree with this. And the curve indicates that the change of climate is still persisting, a conclusion in harmony with the evidence as to historic changes.

If Alpha Centauri is really so important, the effect of its variations, provided it has any, ought perhaps to be evident in the sun. The activity of the star's atmosphere presumably varies, for the orbits of the two components have an eccentricity of 0.51. Hence during their period of revolution, 81.2 years, the distance between them ranges from 1,100,000,000 to 3,300,000,000 miles. They were at a minimum distance in 1388, 1459, 1550, 1631, 1713, 1794, 1875, and will be again in 1956. In Fig. 11, showing sunspot variations, it is noticeable that the years 1794 and 1875 come just at the ends of periods of unusual solar activity, as indicated by the heavy horizontal line. A similar period of great activity seems to have begun about 1914. If its duration equals the average of its two predecessors, it will end about 1950. Back in the fourteenth century a period of excessive solar activity, which has already been described, culminated from 1370 to 1385, or just before the two parts of Alpha Centauri were at a minimum distance. Thus in three and perhaps four cases the sun has been unusually active during a time when the two parts of the star were most rapidly approaching each other and when their atmospheres were presumably most disturbed and their electrical emanations strongest.

[Ill.u.s.tration: _Fig. 11. Sunspot curve showing cycles, 1750 to 1920._

_Note._ The asterisks indicate two absolute minima of sunspots in 1810 and 1913, and the middle years (1780 and 1854) of two periods when the sunspot maxima never fell below 95. If Alpha Centauri has an effect on the sun's atmosphere, the end of another such period would be expected not far from 1957.]

The fact that Alpha Centauri, the star which would be expected most strongly to influence the sun, and hence the earth, was nearest the sun at the climax of the last glacial epoch, and that today the solar atmosphere is most active when the star is presumably most disturbed may be of no significance. It is given for what it is worth. Its importance lies not in the fact that it proves anything but that no contradiction is found when we test the electro-stellar hypothesis by facts which were not thought of when the hypothesis was framed. A vast amount of astronomical work is still needed before the matter can be brought to any definite conclusion. In case the hypothesis stands firm, it may be possible to use the stars as a help in determining the exact chronology of the later part of geological times. If the hypothesis is disproved, it will merely leave the question of solar variations where it is today.

It will not influence the main conclusions of this book as to the causes and nature of climatic changes. Its value lies in the fact that it calls attention to new lines of research.

FOOTNOTES:

[Footnote 120: Lewis Boss: Convergent of a Moving Cl.u.s.ter in Taurus; Astronom. Jour., Vol. 26, No. 4, 1908, pp. 31-36.]

[Footnote 121: F. R. Moulton: in Introduction to Astronomy, 1916.]

[Footnote 122: A. Penck: Die Alpen im Eiszeitalter, Leipzig, 1909.]