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If we accept the conclusion that changes in the sun are one of the chief causes of changes in the weather, the next question is the cause of sun-spots and other solar disturbances. When my own investigations first led me to suspect that solar disturbances are somehow related to the planets, I scarcely dared entertain the idea. I frankly confess that I was afraid critics would make fun of me as one who seemed to revert to astrology. But the evidence cannot be neglected, and the men who have been convinced by it are not the kind to be easily swept off their feet. For example, Professor Schuster of Cambridge, England, an authority on mathematical correlations, concludes that there is less than one chance in four hundred thousand that certain coincidences could exist unless the planets really play a part in determining the time and intensity of sun-spots. Professor Ernest W. Brown of Yale, who has devoted a lifetime to studying the motions of the moon, came to a similar conclusion by quite different methods. Later, to be sure, he questioned his own results, but that was largely because Schuster criticized his methods. Dr. Arctowski, a leading Polish climatologist, has likewise found many evidences that the sun-spots have a periodicity corresponding to that of the various planets, while Dr. Bauer, head of the magnetic work of the Carnegie Institution of Washington, has come to a similar conclusion on the basis of electro-magnetic phenomena. Other authorities might also be cited, so that the list of those who have seriously entertained this view is impressive in numbers as well as in quality.

The gist of what all these men conclude is this: as the planets revolve

around the sun their distances from that body vary because of the eccentricity of their orbits. Their relative positions also vary, for sometimes several are on the same side of the sun and act together, while in other positions they tend to neutralize one another. A curve which combines the effects of all the planets from month to month and year to year shows a remarkably close resemblance to the sun-spot curve. The resemblance increases when allowance is made for other evidences of solar activity, such as magnetic effects, the faculæ, or bright clouds that dot the solar surface, and the red prominences that shoot out hundreds of thousands of miles from the sun's surface.

If the planets really affect the sun in any such way, the method by which they do so is of vital importance. Light, heat, gravitation, and electromagnetic energy seem the only possible agencies unless we appeal to some unknown form of radio-activity. Light and heat are almost universally believed to be out of the question. Professor E. W. Brown, whose work on the moon has been almost entirely a study of gravitation and tides, believes that a gravitational effect is equally impossible. Professor Schuster and Doctors Arctowski and Bauer are inclined to believe that whatever effect the planets produce upon the sun is electrical. My own work, as set forth for laymen in "Climatic Changes" and more technically in "Earth and Sun," seems to point in the same direction. It is now quite widely agreed that the sun sends out electrical emissions. It also seems probable that the outer part of the atmosphere of any body like the earth, that is, the part where the

atmospheric pressure is reduced almost to the vanishing-point,-is capable of an enormously high electrical potential, so that it may send out strong electrical emissions. In such circircumstances the outer shells of the atmospheres of the planets are presumably kept in a highly charged state by electrical emissions from the sun. If this is so, they in turn must send out similar emissions after their charge reaches a certain intensity. Part of these emissions must reach the sun and play their part in disturbing its electrical equilibrium. The degree to which any such disturbance will occur must vary according to the distances of the planets from the sun and their position with respect to the other planets. The energy sent by the planets to the sun must be of very small proportions, not nearly enough to supply even a minute fraction of the energy of sun-spots, faculæ, and other disturbances. In fact, the extreme minuteness of the electrical effects of the heavenly bodies, including the effect of solar electricity upon the earth, is the primary objection to the whole hypothesis here set forth. Nevertheless, the unsettling of the sun's atmosphere by even a small amount of energy from an outside source may act like a trigger to allow the sun's own internal energy to create electrified vortices and other disturbed areas.

Such in brief is the present form of the electrical hypothesis which connects planets, sun-spots, weather, sun-spots, weather, health, and happiness. Only the wildest visionary would claim that the hypothesis is proved. There is much to be said against it. Nevertheless, many important facts seem explicable in no other way that has yet been suggested.

Now suppose for a moment that this electrical hypothesis is correct. In that case there is nothing improbable in the supposition that other bodies in addition to the planets may cause disturbances in the sun's atmosphere. The question is merely one of distance. Are any stars or other bodies near enough to the solar system to have an appreciable effect on the sun's atmosphere? Was such the case in the past? Or will it be in the future? The answer to these questions is greatly influenced by some of the latest astronomical discoveries. For instance, a large portion of the stars are now known to be double. Instead of having no companions except bodies of vastly inferior size like the planets, at least a third of the stars are known to consist of two bodies of more or less equal size which revolve around a common center of gravity and are relatively close together. Sometimes the two bodies are of nearly equal brilliancy, but often one is faint or even dark, so that it can be detected only when it passes between the star and the earth. In view of the fact that many stars have not been fully investigated, while many others may have dark companions which cannot be detected, astronomers believe that at least half, and perhaps a still larger proportion of the stars, are double. If we are right in supposing that the atmospheres of the sun and the planets mutually excite one another, it stands to reason that the atmospheres of two great suns, or of a sun and a dark companion of approximately equal size, must excite one another vastly more. Hence the electrical emissions of double stars, and especially of stars where both parts are bright, must be far more effective than those of the

sun. If Jupiter, for example, were replaced by a body exactly like the sun, the combined electrical activity of the double star thus formed might be thousands of times as great as the present activity of the sun alone.

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Another important recent discovery has to do with the size of the stars. Formerly the sun was supposed to be a comparatively large body, but this is not the case. It is probably much smaller than the average star. The red star known as Betelgeuse has a diameter about two hundred and fifty times as great as that of the sun. If this huge star had its center at the present center of the sun, the star would extend not only to the earth, but approximately to Mars. If such a star were like the sun in temperature and in the degree of disturbance of its atmosphere, its electrical effect would be about sixty thousand times as great as that of the sun. If it were double, If it were double, its effect would increase indefinitely. Betelgeuse is by no means so hot as the sun and it is not known to be double, but other stars are enormously more potent. A double star which has recently been investigated has two parts which revolve around each other in only four days. One part is about twelve thousand and the other fifteen thousand times as bright as the sun. Since the two stars are close together, each must disturb the atmosphere of the other to an almost incredible extent. To suppose that the electrical emissions of such a double star are a million times as powerful as those of the sun may not be overstating the case.

The importance of these new discoveries will be realized when it is considered that the earth not only moves

around the sun, but that the whole solar system is rapidly moving through space, while all the stars and nebulæ are also moving. Inevitably the relation of the sun to other stars and nebulæ must continually change. Formerly it was believed that the distances between the stars are so great that despite the sun's rapid movement, there is only an almost infinitesimal chance that the sun and some other body will ever approach near enough to have much effect upon each other. But that was when only a gravitational effect was considered, and when we did not realize the vast size and highly disturbed condition of many of the stars. Gravitational effects depend upon the mass and distance of a body, while electrical effects depend upon size, temperature, degree of disturbance, as well as upon distance. If a star were twice as hot as the sun and had ten times the sun's diameter, its light-giving effect would be sixteen hundred times that of the sun. Hence the new discoveries mean that the distances at which the stars may be effective are far greater than was formerly supposed, and the chances that the sun will come near enough to some other body so that the solar atmosphere is much disturbed may be large enough to be important.

In order to discover how probable it is that anything of this sort may happen, Professor Schlesinger of the Yale Observatory and Professor Shapley of Harvard have helped me to compute the relative positions and importance of the stars nearest the sun for a period of seventy thousand years in the past and an equal time in the future.

Data are available for thirty-eight stars, but it must be borne in mind that

others which ought to have been included are omitted because their positions and motions have not yet been determined. Among those thirty-eight none that is specially brilliant or that is double has been at a minimum distance from the sun since about 24,000 years ago, nor will any be at a minimum distance for about 17,000 years in the future. On the other hand, between 24,000 and 49,000 years ago, that is, during the period presumably covered by the last advance of the ice, five important stars are known to have been at a minimum distance from the sun. All five, because of their magnitude as seen from the earth or because of being double, would be expected to have more effect upon the sun's atmosphere than any of the seven known stars which have been or will be at a minimum distance between 24,000 years ago and 17,000 years hence. From 17,000 to 34,000 years in the future, at least seven other stars will reach their minimum distance from the sun. Five of these, including Alpha Centauri, are double, and all seven are of such magnitudes that they would be expected to be more effective than any star arriving at its minimum distance from the sun between 24,000 years ago and 17,000 years in the future. Thus so far as the stars are known, there is nothing inconsistent with a glacial epoch from 25,000 to 40,000 years ago, an an interglacial epoch now, and another glacial epoch 20,000 or 30,000 years hence. I do not know whether these facts are important or not. They merely indicate that so far as our knowledge of the stars yet goes, there is nothing impossible in the supposition that they have something to do with changes of climate.

Among the thirty-eight stars which are now near the earth, Alpha Centauri is the most interesting. This is partly because it is the nearest known star. It is also because Alpha Centauri is a brilliant, double star in which each part is about as bright as our sun, while a third and fainter star revolves around the other two at a considerable distance.

The two main parts of the star go around each other in about eighty-one years; their orbits are so eccentric that when the two suns are nearest together, they are about half as far apart as when they are most distant. According to our hypothesis, the disturbances in the atmospheres of the two stars, and hence their effect upon other stars, ought to increase when the two parts are approaching each other and diminish when the stars are moving apart. The records of sun-spots are fairly complete as far back as about 1750. They show that during the last two periods when the two parts of Alpha Centauri were approaching one another, and also since about 1915, when the two parts have again been approaching, the activity of the sun has been decidedly greater than during the corresponding periods when the parts of Alpha Centauri are moving away from each other. The main sun-spot cycle, which perhaps owes its periodicity to the combined effect of the planets, especially Jupiter and Saturn, is as pronounced as ever, but the maxima are much higher than usual, and the minima do not sink to the customary low level. In other words, the present cycles of sun-spots show the conditions that would be expected if Alpha Centauri were one of several factors in setting the dates of greater or less activity. Of course this may

be a mere coincidence, but it is a coincidence that is worth examining.

In view of all the evidence, it seems not unreasonable at least to entertain, but by no means accept, the tentative hypothesis that our fate is written in the stars. As the sun and its little satellites fly swiftly through illimitable space they may be bound on a great adventure. During one geological era they are far from all stars or approach only those that are of small size and slight activity. Those may be the times when the sun's atmosphere is relatively undisturbed, and the earth enjoys a long period of mild and monotonous climate. The same species of plants and animals may persist almost unchanged for millions of years. Next the solar system reaches a region where many large, bright stars are comparatively close together, and where many are double, multiple, or variable. As the sun shoots forward in its smooth flight, it comes under the influence of first one star and then another. During such periods, perchance, a glacial epoch ensues on the earth, then another, and a third; and these together form a glacial period like that which was potent in the evolution of early man. Each star which passes near the sun may possibly create not only one main disturbance, but innumerable minor ones, due to its own fluctuations and to the varying positions of its companions and satellites. Thus in such a period the climate of the earth may be subject to constant changes. If that were the case, evolution would presumably proceed rapidly.

Even in our own day the varying positions of the sun, the earth, and the other planets, and possibly

of the parts of Alpha Centauri, and perhaps of other bodies, may have some connection with storms, floods, droughts, and famines. They may compel the settlers in a region like western Kansas to abandon their farms because the crops are a failure; they may help to cause millions of other farmers to be unable to pay the interest on their mortgages, and may unsettle finance and business for virtually every one. Perhaps they ought at least to share with the Democrats the responsibility for the troubles of the farmers who had to leave western Kansas in the early nineties because of the prolonged drought. But perhaps, on the other hand, it is just as far from the truth to bring the heavenly bodies into the matter as it was for the farmers who drove back across Illinois to adorn the sides of their wagons with signs reading: "I'm going back to my relations. Damn Cleveland's administration!"

The thoughtful reader of this article is almost sure to say that it is highly speculative. Such is undoubtedly the case. It must not be forgotten, however, that every advance in science must be preceded by a great deal of speculation. Only by following out all sorts of clues can we ultimately find which one leads upward to the truth. The mere possibility of such relationships as are here suggested ought to stimulate the most searching investigation. The point of the whole matter is that modern research seems to suggest that what was formerly held to be utterly impossible may be within the bounds of possibility. The stars in their courses may really have fought against Sisera. The new astrology may not be wholly a dream.

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