The Sun's Journey Through Space
Having gained some idea of the nature of the electrical hypothesis of
solar disturbances and of the possible effect of other bodies upon the
sun's atmosphere, let us now compare the astronomical data with those of
geology. Let us take up five chief points for which the geologist
demands an explanation, and which any hypothesis must meet if it is to
be permanently accepted. These are (1) the irregular intervals at which
separated sometimes by hundreds of thousands of years; (3) the length of
glacial periods and epochs; (4) the occurrence of glacial stages and
historic pulsations in the form of small climatic waves superposed upon
the larger waves of glacial epochs; (5) the occurrence of climatic
conditions much milder than those of today, not only in the middle
portion of the great geological eras, but even in some of the recent
inter-glacial epochs.
1. The irregular duration of the interval from one glacial epoch to
another corresponds with the irregular distribution of the stars. If
glaciation is indirectly due to stellar influences, the epochs might
fall close together, or might be far apart. If the average interval were
ten million years, one interval might be thirty million or more and the
next only one or two hundred thousand. According to Schuchert, the known
periods of glacial or semi-glacial climate have been approximately as
follows:
LIST OF GLACIAL PERIODS
1. Archeozoic.
(1/4 of geological time or perhaps much more)
No known glacial periods.
2. Proterozoic.
(1/4 of geological time)
a. Oldest known glacial period near base of Proterozoic in
Canada. Evidence widely distributed.
b. Indian glacial period; time unknown.
c. African glacial period; time unknown.
d. Glaciation near end of Proterozoic in Australia, Norway,
and China.
3. Paleozoic.
(1/4 of geological time)
a. Late Ordovician(?). Local in Arctic Norway.
b. Silurian. Local in Alaska.
c. Early Devonian. Local in South Africa.
d. Early Permian. World-wide and very severe.
4. Mesozoic and Cenozoic.
(1/4 of geological time)
a-b. None definitely determined during Mesozoic, although
there appears to have been periods of cooling (a) in the
late Triassic, and (b) in the late Cretacic, with at least
local glaciation in early Eocene.
c. Severe glacial period during Pleistocene.
This table suggests an interesting inquiry. During the last few decades
there has been great interest in ancient glaciation and geologists have
carefully examined rocks of all ages for signs of glacial deposits. In
spite of the large parts of the earth which are covered with deposits
belonging to the Mesozoic and Cenozoic, which form the last quarter of
geological time, the only signs of actual glaciation are those of the
great Pleistocene period and a few local occurrences at the end of the
Mesozoic or beginning of the Cenozoic. Late in the Triassic and early in
the Jurassic, the climate appears to have been rigorous, although no
tillites have been found to demonstrate glaciation. In the preceding
quarter, that is, the Paleozoic, the Permian glaciation was more severe
than that of the Pleistocene, and the Devonian than that of the Eocene,
while the Ordovician evidences of low temperature are stronger than
those at the end of the Triassic. In view of the fact that rocks of
Paleozoic age cover much smaller areas than do those of later age, the
three Paleozoic glaciations seem to indicate a relative frequency of
glaciation. Going back to the Proterozoic, it is astonishing to find
that evidence of two highly developed glacial periods, and possibly
four, has been discovered. Since the Indian and the African glaciations
of Proterozoic times are as yet undated, we cannot be sure that they are
not of the same date as the others. Nevertheless, even two is a
surprising number, for not only are most Proterozoic rocks so
metamorphosed that possible evidences of glacial origin are destroyed,
but rocks of that age occupy far smaller areas than either those of
Paleozoic or, still more, Mesozoic and Cenozoic age. Thus the record of
the last three-quarters of geological time suggests that if rocks of all
ages were as abundant and as easily studied as those of the later
periods, the frequency of glacial periods would be found to increase as
one goes backward toward the beginnings of the earth's history. This is
interesting, for Jeans holds that the chances that the stars would
approach one another were probably greater in the past than at present.
This conclusion is based on the assumption that our universe is like the
spiral nebulae in which the orbits of the various members are nearly
circular during the younger stages. Jeans considers it certain that in
such cases the orbits will gradually become larger and more elliptical
because of the attraction of one body for another. Thus as time goes on
the stars will be more widely distributed and the chances of approach
will diminish. If this is correct, the agreement between astronomical
theory and geological conclusions suggests that the two are at least not
in opposition.
The first quarter of geological time as well as the last three must be
considered in this connection. During the Archeozoic, no evidence of
glaciation has yet been discovered. This suggests that the geological
facts disprove the astronomical theory. But our knowledge of early
geological times is extremely limited, so limited that lack of evidence
of glaciation in the Archeozoic may have no significance. Archeozoic
rocks have been studied minutely over a very small percentage of the
earth's land surface. Moreover, they are highly metamorphosed so that,
even if glacial tills existed, it would be hard to recognize them.
Third, according to both the nebular and the planetesimal hypotheses, it
seems possible that during the earliest stages of geological history the
earth's interior was somewhat warmer than now, and the surface may have
been warmed more than at present by conduction, by lava flows, and by
the fall of meteorites. If the earth during the Archeozoic period
emitted enough heat to raise its surface temperature a few degrees, the
heat would not prevent the development of low forms of life but might
effectively prevent all glaciation. This does not mean that it would
prevent changes of climate, but merely changes so extreme that their
record would be preserved by means of ice. It will be most interesting
to see whether future investigations in geology and astronomy indicate
either a semi-uniform distribution of glacial periods throughout the
past, or a more or less regular decrease in frequency from early times
down to the present.
2. The Pleistocene glacial period was divided into at least four epochs,
while in the Permian at least one inter-glacial epoch seems certain, and
in some places the alternation between glacial and non-glacial beds
suggests no less than nine. In the other glaciations the evidence is not
yet clear. The question of periodicity is so important that it
overthrows most glacial hypotheses. Indeed, had their authors known the
facts as established in recent years, most of the hypotheses would never
have been advanced. The carbon dioxide hypothesis is the only one which
was framed with geologically rapid climatic alternations in mind. It
certainly explains the facts of periodicity better than does any of its
predecessors, but even so it does not account for the intimate way in
which variations of all degrees from those of the weather up to glacial
epochs seem to grade into one another.
According to our stellar hypothesis, occasional groups of glacial epochs
would be expected to occur close together and to form long glacial
periods. This is because many of the stars belong to groups or clusters
in which the stars move in parallel paths. A good example is the cluster
in the Hyades, where Boss has studied thirty-nine stars with special
care.[120] The stars are grouped about a center about 130 light years
from the sun. The stars themselves are scattered over an area about
thirty light years in diameter. They average about the same distance
apart as do those near the sun, but toward the center of the group they
are somewhat closer together. The whole thirty-nine sweep forward in
essentially parallel paths. Boss estimates that 800,000 years ago the
cluster was only half as far from the sun as at present, but probably
that was as near as it has been during recent geological times. All of
the thirty-nine stars of this cluster, as Moulton[121] puts it, "are
much greater in light-giving power than the sun. The luminosities of
even the five smallest are from five to ten times that of the sun, while
the largest are one hundred times greater in light-giving power than our
own luminary. Their masses are probably much greater than that of the
sun." If the sun were to pass through such a cluster, first one star and
then another might come so near as to cause a profound disturbance in
the sun's atmosphere.
3. Another important point upon which a glacial hypothesis may come to
grief is the length of the periods or rather of the epochs which compose
the periods. During the last or Pleistocene glacial period the evidence
in America and Europe indicates that the inter-glacial epochs varied in
length and that the later ones were shorter than the earlier. Chamberlin
and Salisbury, from a comparison of various authorities, estimate that
the intervals from one glacial epoch to another form a declining series,
which may be roughly expressed as follows: 16-8-4-2-1, where unity is
the interval from the climax of the late Wisconsin, or last glacial
epoch, to the present. Most authorities estimate the culmination of the
late Wisconsin glaciation as twenty or thirty thousand years ago. Penck
estimates the length of the last inter-glacial period as 60,000 years
and the preceding one as 240,000.[122] R. T. Chamberlin, as already
stated, finds that the consensus of opinion is that inter-glacial epochs
have averaged five times as long as glacial epochs. The actual duration
of the various glaciations probably did not vary in so great a ratio as
did the intervals from one glaciation to another. The main point,
however, is the irregularity of the various periods.
The relation of the stellar electrical hypothesis to the length of
glacial epochs may be estimated from column C, in Table 5. There we see
that the distances at which a star might possibly disturb the sun enough
to cause glaciation range all the way from 120 billion miles in the case
of a small star like the sun, to 3200 billion in the case of Betelgeuse,
while for double stars the figure may rise a hundred times higher. From
this we can calculate how long it would take a star to pass from a point
where its influence would first amount to a quarter of the assumed
maximum to a similar point on the other side of the sun. In making these
calculations we will assume that the relative rate at which the star and
the sun approach each other is about twenty-two miles per second, or 700
million miles per year, which is the average rate of motion of all the
known stars. According to the distances in Table 5 this gives a range
from about 500 years up to about 10,000, which might rise to a million
in the case of double stars. Of course the time might be relatively
short if the sun and a rapidly moving star were approaching one another
almost directly, or extremely long if the sun and the star were moving
in almost the same direction and at somewhat similar rates,--a condition
more common than the other. Here, as in so many other cases, the
essential point is that the figures which we thus obtain seem to be of
the right order of magnitude.
4. Post-glacial climatic stages are so well known that in Europe they
have definite names. Their sequence has already been discussed in
Chapter XII. Fossils found in the peat bogs of Denmark and Scandinavia,
for example, prove that since the final disappearance of the continental
ice cap at the close of the Wisconsin there has been at least one period
when the climate of Europe was distinctly milder than now. Directly
overlying the sheets of glacial drift laid down by the ice there is a
flora corresponding to that of the present tundras. Next come remains of
a forest vegetation dominated by birches and poplars, showing that the
climate was growing a little warmer. Third, there follow evidences of a
still more favorable climate in the form of a forest dominated by pines;
fourth, one where oak predominates; and fifth, a flora similar to that
of the Black Forest of Germany, indicating that in Scandinavia the
temperature was then decidedly higher than today. This fifth flora has
retreated southward once more, having been driven back to its present
latitude by a slight recurrence of a cool stormy climate.[123] In
central Asia evidence of post-glacial stages is found not only in five
distinct moraines but in a corresponding series of elevated strands
surrounding salt lakes and of river terraces in non-glaciated arid
regions.[124]
In historic as well as prehistoric times, as we have already seen, there
have been climatic fluctuations. For instance, the twelfth or thirteenth
century B. C. appears to have been almost as mild as now, as does the
seventh century B. C. On the other hand about 1000 B. C., at the time of
Christ, and in the fourteenth century there were times of relative
severity. Thus it appears that both on a large and on a small scale
pulsations of climate are the rule. Any hypothesis of climatic changes
must satisfy the periods of these pulsations. These conditions furnish a
problem which makes difficulty for almost all hypotheses of climatic
change. According to the present hypothesis, earth movements such as are
discussed in Chapter XII may cooeperate with two astronomical factors.
One is the constant change in the positions of the stars, a change which
we have already called kaleidoscopic, and the other is the fact that a
large proportion of the stars are double or multiple. When one star in a
group approaches the sun closely enough to cause a great solar
disturbance, numerous others may approach or recede and have a minor
effect. Thus, whenever the sun is near groups of stars we should expect
that the earth would show many minor climatic pulsations and stages
which might or might not be connected with glaciation. The historic
pulsations shown in the curve of tree growth in California, Fig. 4, are
the sort of changes that would be expected if movements of the stars
have an effect on the solar atmosphere.
Not only are fully a third of all the visible stars double, as we have
already seen, but at least a tenth of these are known to be triple or
multiple. In many of the double stars the two bodies are close together
and revolve so rapidly that whatever periodicity they might create in
the sun's atmosphere would be very short. In the triplets, however, the
third star is ordinarily at least ten times as far from the other two as
they are from each other, and its period of rotation sometimes runs into
hundreds or thousands of years. An actual multiple star in the
constellation Polaris will serve as an example. The main star is
believed by Jeans to consist of two parts which are almost in contact
and whirl around each other with extraordinary speed in four days. If
this is true they must keep each other's atmospheres in a state of
intense commotion. Much farther away a third star revolves around this
pair in twelve years. At a much greater distance a fourth star revolves
around the common center of gravity of itself and the other three in a
period which may be 20,000 years. Still more complicated cases probably
exist. Suppose such a system were to traverse a path where it would
exert a perceptible influence on the sun for thirty or forty thousand
years. The varying movements of its members would produce an intricate
series of cycles which might show all sorts of major and minor
variations in length and intensity. Thus the varied and irregular stages
of glaciation and the pulsations of historic times might be accounted
for on the hypothesis of the proximity of the sun to a multiple star, as
well as on that of the less pronounced approach and recession of a
number of stars. In addition to all this, an almost infinitely complex
series of climatic changes of long and short duration might arise if the
sun passed through a nebula.
5. We have seen in Chapter VIII that the contrast between the somewhat
severe climate of the present and the generally mild climate of the past
is one of the great geological problems. The glacial period is not a
thing of the distant past. Geologists generally recognize that it is
still with us. Greenland and Antarctica are both shrouded in ice sheets
in latitudes where fossil floras prove that at other periods the climate
was as mild as in England or even New Zealand. The present glaciated
regions, be it noted, are on the polar borders of the world's two most
stormy oceanic areas, just where ice would be expected to last longest
according to the solar cyclonic hypothesis. In contrast with the
semi-glacial conditions of the present, the last inter-glacial epoch was
so mild that not only men but elephants and hippopotamuses flourished in
central Europe, while at earlier times in the middle of long eras, such
as the Paleozoic and Mesozoic, corals, cycads, and tree ferns flourished
within the Arctic circle.
If the electro-stellar hypothesis of solar disturbances proves well
founded, it may explain these peculiarities. Periods of mild climate
would represent a return of the sun and the earth to their normal
conditions of quiet. At such times the atmosphere of the sun is assumed
to be little disturbed by sunspots, faculae, prominences, and other
allied evidences of movements; and the rice-grain structure is perhaps
the most prominent of the solar markings. The earth at such times is
supposed to be correspondingly free from cyclonic storms. Its winds are
then largely of the purely planetary type, such as trade winds and
westerlies. Its rainfall also is largely planetary rather than cyclonic.
It falls in places such as the heat equator where the air rises under
the influence of heat, or on the windward slopes of mountains, or in
regions where warm winds blow from the ocean over cold lands.
According to the electro-stellar hypothesis, the conditions which
prevailed during hundreds of millions of years of mild climate mean
merely that the solar system was then in parts of the heavens where
stars--especially double stars--were rare or small, and electrical
disturbances correspondingly weak. Today, on the other hand, the sun is
fairly near a number of stars, many of which are large doubles. Hence it
is supposed to be disturbed, although not so much as at the height of
the last glacial epoch.
After the preceding parts of this book had been written, the assistance
of Dr. Schlesinger made it possible to test the electro-stellar
hypothesis by comparing actual astronomical dates with the dates of
climatic or solar phenomena. In order to make this possible, Dr.
Schlesinger and his assistants have prepared Table 6, giving the
position, magnitude, and motions of the thirty-eight nearest stars, and
especially the date at which each was nearest the sun. In column 10
where the dates are given, a minus sign indicates the past and a plus
sign the future. Dr. Shapley has kindly added column 12, giving the
absolute magnitudes of the stars, that of the sun being 4.8, and column
13, showing their luminosity or absolute radiation, that of the sun
being unity. Finally, column 14 shows the effective radiation received
by the sun from each star when the star is at a minimum distance. Unity
in this case is the effect of a star like the sun at a distance of one
light year.
It is well known that radiation of all kinds, including light, heat, and
electrical emissions, varies in direct proportion to the exposed
surface, that is, as the square of the radius of a sphere, and inversely
as the square of the distance. From black bodies, as we have seen, the
total radiation varies as the fourth power of the absolute temperature.
It is not certain that either light or electrical emissions from
incandescent bodies vary in quite this same proportion, nor is it yet
certain whether luminous and electrical emissions vary exactly together.
Nevertheless they are closely related. Since the light coming from each
star is accurately measured, while no information is available as to
electrical emissions, we have followed Dr. Shapley's suggestion and used
the luminosity of the stars as the best available measure of total
radiation. This is presumably an approximate measure of electrical
activity, provided some allowance be made for disturbances by outside
bodies such as companion stars. Hence the inclusion of column 14.
TABLE 6
THIRTY-EIGHT STARS HAVING LARGEST KNOWN PARALLAXES
Star
Code
1 Groombr. 34
2 ++[Greek: e] Cassiop.
3
4 ++[Greek: k] Tucanae
5 [Greek: t] Ceti
6 [Greek: d]2 Eridani
7 ++[Greek: e] Eridani
8 ++40(0)^2 Eridani
9 Cordoba Z. 243
10 Weisse 592
11 ++[Greek: a] Can. Maj. (Sirius)
12 ++[Greek: a] Can. Min. (Procyon)
13 ++Fedorenko 1457-8
14 Groombr. 1618
15 Weisse 234
16 Lalande 21185
17 Lalande 21258
18
19 Lalande 25372
20 ++[Greek: a] Centauri
21 ++[Greek: x] Bootes
22 ++Lalande 27173
23 Weisse 1259
24 Lacaille 7194
25 ++[Greek: b] 416
26 Argel -0.17415-6
27 Barnard's star
28 ++70p Ophiuchi
29 ++[Greek: S] 2398
30 [Greek: s] Draconis
31 ++[Greek: a] Aquilae (Altair)
32 ++61 Cygni
33 Lacaille 8760
34 [Greek: e] Indi
35 ++Krueger 60
36 Lacaille 9352
37 Lalande 46650
38 C. G. A. 32416
(++ Double star.)
(1) (2) (3) (4) (5) (6)
Right Declination Visual Spectrum Proper Radial
Star Ascension [Greek: d] Mag. m Motion Velocity
code [Greek: a] 1900 km. per
1900 sec.
------------------------------------------------------------------
1 0^h 12^m.7 +43 deg.27' 8.1 Ma 2".89 + 3
2 43 .0 +57 17 3.6 F8 1 .24 + 10
3 43 .9 +4 55 12.3 F0 3 .01 .....
4 1 12 .4 -69 24 5.0 F8 .39 + 12
5 39 .4 -16 28 3.6 K0 1 .92 - 16
------------------------------------------------------------------
6 3 15 .9 -43 27 4.3 G5 3 .16 + 87
7 28 .2 - 9 48 3.8 K0 .97 + 16
8 4 10 .7 - 7 49 4.5 G5 4 .08 - 42
9 5 7 .7 -44 59 9.2 K2 8 .75 +242
10 26 .4 - 3 42 8.8 K2 2 .22 .....
------------------------------------------------------------------
11 6 40 .7 -16 35 -1.6 A0 1 .32 - 8
12 7 34 .1 + 5 29 0.5 F5 1 .24 - 4
13 9 7 .6 +53 7 7.9 Ma 1 .68 + 10
14 10 5 .3 +49 58 6.8 K5p 1 .45 - 30
15 14 .2 +20 22 9.0 ... .49 .....
------------------------------------------------------------------
16 57 .9 +36 38 7.6 Mb 4 .78 - 87
17 11 0 .5 +44 2 8.5 K5 4 .52 + 65
18 12 .0 -57 2 12.0 ... 2 .69 .....
19 13 40 .7 +15 26 8.5 K5 2 .30 .....
20 14 32 .8 -60 25 0.2 G 3 .68 + 22
------------------------------------------------------------------
21 14 46 .8 +19 31 4.6 K5p .17 + 4
22 51 .6 -20 58 5.8 Kp 1 .96 + 20
23 16 41 .4 +33 41 8.4 ... .37 .....
24 17 11 .5 -46 32 5.7 K .97 .....
25 12 .1 -34 53 5.9 K5 1 .19 - 4
------------------------------------------------------------------
26 37 .0 +68 26 9.1 K 1 .33 .....
27 52 .9 + 4 25 9.7 Mb 10 .30 - 80
28 18 0 .4 + 2 31 4.3 K 1 .13 .....
29 41 .7 +59 29 8.8 K 2 .31 .....
30 19 32 .5 +69 29 4.8 G5 1 .84 + 26
------------------------------------------------------------------
31 45 .9 + 8 36 1.2 A5 .66 - 33
32 21 2 .4 +38 15 5.6 K5 5 .20 - 64
33 11 .4 -39 15 6.6 G 3 .53 + 13
34 55 .7 -57 12 4.8 K5 4 .70 - 39
35 22 24 .4 +57 12 9.2 ... .87 .....
------------------------------------------------------------------
36 59 .4 -36 26 7.1 K 6 .90 + 12
37 23 44 .0 + 1 52 8.7 Ma 1 .39 .....
38 59 .5 -37 51 8.2 G 6 .05 + 26
(7) (9) (11) (13) (14)
Present Minimum Magnitude Luminosity Effective
Parallax Distance at Min. Dist. radiation
[Greek: p] Light Yrs. at
minimum
(8) (10) (12) distance
Star Maximum Time of Absolute from sun
Code Parallax Minimum Magnitude
Distance
-----------------------------------------------------------------------
1 ".28 ".28 11.6 -4000 8.1 10.3 0.0063 0.000051
2 .18 .19 17.1 -47000 3.5 4.9 0.91 0.003110
3 .24 .... .... ...... .... 14.2 0.00017 ........
4 .16 .23 14.2 -264000 4.2 6.0 0.33 0.001610
5 .32 .37 8.8 +46000 3.3 6.1 0.30 0.003840
-----------------------------------------------------------------------
6 .16 .22 14.8 -33000 3.6 5.3 0.63 0.002960
7 .31 .46 7.1 -106000 3.0 6.3 0.25 0.004970
8 .21 .23 14.2 +19000 4.3 6.1 0.30 0.001470
9 .32 .68 4.8 -10000 7.6 11.7 0.0017 0.000074
10 .17 .... .... ...... .... 9.9 0.009 ........
-----------------------------------------------------------------------
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.
from the stars.]
In preparing Fig. 10 it has been necessary to make allowance for double
stars. Passing 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.
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 Cluster 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.]
[Footnote 123: R. D. Salisbury: Physical Geography of the Pleistocene,
in Outlines of Geologic History, by Willis and Salisbury, 1910, pp.
273-274.]
[Footnote 124: Davis, Pumpelly, and Huntington: Explorations in
Turkestan, Carnegie Inst. of Wash., No. 26, 1905.
In North America the stages have been the subject of intensive studies
on the part of Taylor, Leverett, Goldthwait, and many others.]
More
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