Marvels of the Aurora

One of the most vivid recollections of my early boyhood is that of seeing my father return hastily into the house one evening and call out to the family: ‘‘Come outside and look at the sky!’’ Ours was a country house situated on a commanding site, and as we all emerged from the doorway we were dumbfounded to see the heavens filled with pale flames which ran licking and quivering over the stars. Instantly there sprang into my terrified mind the recollection of an awful description of ‘‘the Day of Judgment’’ (the Dies Iræ), which I had heard with much perturbation of spirit in the Dutch Reformed church from the lips of a tall, dark-browed, dreadfully-in-earnest preacher of the old-fashioned type. My heart literally sank at sight of the spectacle, for it recalled the preacher’s very words; it was just as he had said it would be, and it needed the assured bearing of my elders finally to convince me that

That Day of Wrath, O dreadful day, When Heaven and Earth shall pass away, As David and the Sibyl say had not actually come upon us. And even the older members of the household were not untouched with misgivings when menacing spots of crimson appeared, breaking out now here, now there, in the shuddering sky. Toward the north the spectacle was appalling. A huge arch spanned an unnaturally dark segment resting on the horizon, and above this arch sprang up beams and streamers in a state of incessant agitation, sometimes shooting up to the zenith with a velocity that took one’s breath, and sometimes suddenly falling into long ranks, and marching, marching, marching, like an endless phalanx of fiery specters, and moving, as I remember, always from east to west. The absolute silence with which these mysterious evolutions were performed and the quavering reflections which were thrown upon the ground increased the awfulness of the exhibition. Occasionally enormous curtains of lambent flame rolled and unrolled with a majestic motion, or were shaken to and fro as if by a mighty, noiseless wind. At times, too, a sudden billowing rush would be made toward the zenith, and for a minute the sky overhead would glow so brightly that the stars seemed to have been consumed. The spectacle continued with varying intensity for hours.

This exhibition occurred in Central New York, a latitude in which the Aurora Borealis is seldom seen with so much splendor. I remember another similar one seen from the city of New York in November, 1882. On this last occasion some observers saw a great upright beam of light which majestically moved across the heavens, stalking like an apparition in the midst of the auroral pageant, of whose general movements it seemed to be independent, maintaining always its upright posture, and following a magnetic parallel from east to west. This mysterious beam was seen by no less than twenty-six observers in different parts of the country, and a comparison of their observations led to a curious calculation indicating that the apparition was about one hundred and thirty-three miles tall and moved at the speed of ten miles per second!

But, as everybody knows, it is in the Arctic regions that the Aurora, or the ‘‘Northern Lights, ‘‘ can best be seen. There, in the long polar night, when for months together the sun does not rise, the strange coruscations in the sky often afford a kind of spectral daylight in unison with the weird scenery of the world of ice. The pages in the narratives of Arctic exploration that are devoted to descriptions of the wonderful effects of the Northern Lights are second to none that man has ever penned in their fascination. The lights, as I have already intimated, display astonishing colors, particularly shades of red and green, as they flit from place to place in the sky. The discovery that the magnetic needle is affected by the Aurora, quivering and darting about in a state of extraordinary excitement when the lights are playing in the sky, only added to the mystery of the phenomenon until its electro-magnetic nature had been established. This became evident as soon as it was known that the focus of the displays was the magnetic pole; and when the far South was visited the Aurora Australis was found, having its center at the South Magnetic Pole. Then, if not before, it was clear that the earth was a great globular magnet, having its poles of opposite magnetism, and that the auroral lights, whatever their precise cause might be, were manifestations of the magnetic activity of our planet. After the invention of magnetic telegraphy it was found that whenever a great Aurora occurred the telegraph lines were interrupted in their operation, and the ocean cables ceased to work. Such a phenomenon is called a ‘‘magnetic storm.’’

The interest excited by the Aurora in scientific circles was greatly stimulated when, in the last half of the nineteenth century, it was discovered that it is a phenomenon intimately associated with disturbances on the sun. The ancient ‘‘Zurich Chronicles, ‘‘ extending from the year 1000 to the year 1800, in which both sun-spots visible to the naked eye and great displays of the auroral lights were recorded, first set Rudolf Wolf on the track of this discovery. The first notable proof of the suspected connection was furnished with dramatic emphasis by an occurrence which happened on September 1, 1859. Near noon on that day two intensely brilliant points suddenly broke out in a group of sun-spots which were under observation by Mr R. C. Carrington at his observatory at Redhill, England. The points remained visible for not more than five minutes, during which interval they moved thirty-five thousand miles across the solar disk. Mr R. Hodgson happened to see the same phenomenon at his observatory at Highgate, and thus all possibility of deception was removed. But neither of the startled observers could have anticipated what was to follow, and, indeed, it was an occurrence which has never been precisely duplicated. I quote the eloquent account given by Miss Clerke in her History of Astronomy During the Nineteenth Century.

This unique phenomenon seemed as if specially designed to accentuate the inference of a sympathetic relation between the earth and the sun. From August 28 to September 4, 1859, a magnetic storm of unparalleled intensity, extent, and duration was in progress over the entire globe. Telegraphic communication was everywhere interrupted -- except, indeed, that it was in some cases found practicable to work the lines without batteries by the agency of the earth-currents alone; sparks issued from the wires; gorgeous auroras draped the skies in solemn crimson over both hemispheres, and even in the tropics; the magnetic needle lost all trace of continuity in its movements and darted to and fro as if stricken with inexplicable panic. The coincidence was even closer. At the very instant of the solar outburst witnessed by Carrington and Hodgson the photographic apparatus at Kew registered a marked disturbance of all the three magnetic elements; while shortly after the ensuing midnight the electric agitation culminated, thrilling the whole earth with subtle vibrations, and lighting up the atmosphere from pole to pole with coruscating splendors which perhaps dimly recall the times when our ancient planet itself shone as a star.

If this amazing occurrence stood alone, and as I have already said it has never been exactly duplicated, doubt might be felt concerning some of the inferences drawn from it; but in varying forms it has been repeated many times, so that now hardly anyone questions the reality of the assumed connection between solar outbursts and magnetic storms accompanied by auroral displays on the earth. It is true that the late Lord Kelvin raised difficulties in the way of the hypothesis of a direct magnetic action of the sun upon the earth, because it seemed to him that an inadmissible quantity of energy was demanded to account for such action. But no calculation like that which he made is final, since all calculations depend upon the validity of the data; and no authority is unshakable in science, because no man can possess omniscience. It was Lord Kelvin who, but a few years before the thing was actually accomplished, declared that aerial navigation was an impracticable dream, and demonstrated its impracticability by calculation. However the connection may be brought about, it is as certain as evidence can make it that solar outbursts are coincident with terrestial magnetic disturbances, and coincident in such a way as to make the inference of a causal connection irresistible. The sun is only a little more than a hundred times its own diameter away from the earth. Why, then, with the subtle connection between them afforded by the ether which conveys to us the blinding solar light and the life-sustaining solar heat, should it be so difficult to believe that the sun’s enormous electric energies find a way to us also? No doubt the impulse coming from the sun acts upon the earth after the manner of a touch upon a trigger, releasing energies which are already stored up in our planet.

But besides the evidence afforded by such occurrences as have been related of an intimate connection between solar outbreaks and terrestial magnetic flurries, attended by magnificent auroral displays, there is another line of proof pointing in the same direction. Thus, it is known that the sun-spot period, as remarked in a preceding chapter, coincides in a most remarkable manner with the periodic fluctuations in the magnetic state of the earth. This coincidence runs into the most astonishing details. For instance, when the sun-spot period shortens, the auroral period shortens to precisely the same extent; as the short sun-spot periods usually bring the most intense outbreaks of solar activity, so the corresponding short auroral periods are attended by the most violent magnetic storms; a secular period of about two hundred and twenty-two years affecting sun-spots is said to have its auroral duplicate; a shorter period of fifty-five and a half years, which some observers believe that they have discovered appears also to be common to the two phenomena; and yet another ‘‘superposed’’ period of about thirty-five years, which some investigators aver exists, affects sun-spots and aurora alike. In short, the coincidences are so numerous and significant that one would have to throw the doctrine of probability to the winds in order to be able to reject the conclusion to which they so plainly lead.