Although comets are no longer regarded with superstitious awe as in old times, mystery still clings to them. Astronomers can tell what path a comet is travelling upon, and say whence it has come and whither it will go, can even in many cases predict the periodic returns of a comet, can analyse the substance of these strange wanderers, and have recently discovered a singular bond of relationship between comets and those other strange visitants from the celestial depths, the shooting stars. But astronomy has hitherto proved unable to determine the origin of comets, the part they perform in the economy of the universe, their real structure, the causes of the marvellous changes of shape which they undergo as they approach the sun, rush round him, and then retreat. As Sir John Herschel has remarked: 'No one, hitherto, has been able to assign any single point in which we should be a bit better or worse off, materially speaking, if there were no such thing as a comet. Persons, even thinking persons, have busied themselves with conjectures; such as that they may serve for fuel for the sun (into which, however, they never fall), or that they may cause warm summers, which is a mere fancy, or that they may give rise to epidemics, or potato-blights, and so forth.' And though, as he justly says, 'this is all wild talking,' yet it will probably continue until astronomers have been able to master the problems respecting comets which hitherto have foiled their best efforts. The unexplained has ever been and will ever be marvellous to the general mind. Just as unexplored regions of the earth have been tenanted in imagination by
anthropophagi and men whose heads
Do grow beneath their shoulders,
so do wondrous possibilities exist in the unknown and the ill-understood phenomena of nature.
In old times, when the appearance and movements of comets were supposed to be altogether uncontrolled by physical laws, it was natural that comets should be regarded as signs from heaven, tokens of Divine wrath towards some, and of the interposition of Divine providence in favour of others. As Seneca well remarked: 'There is no man so dull, so obtuse, so turned to earthly things, who does not direct all the powers of his mind towards things Divine when some novel phenomenon appears in the heavens. While all follows its usual course up yonder, familiarity robs the spectacle of its grandeur. For so is man made. However wonderful may be what he sees day after day, he looks on it with indifference; while matters of very little importance attract and interest him if they depart from the accustomed order. The host of heavenly constellations beneath the vault of heaven, whose beauty they adorn, attract no attention; but if any unusual appearance be noticed among them, at once all eyes are turned heavenwards. The sun is only looked on with interest when he is undergoing eclipse. Men observe the moon only under like conditions.... So thoroughly is it a part of our nature to admire the new rather than the great. The same is true of comets. When one of these fiery bodies of unusual form appears, every one is eager to know what it means; men forget other objects to inquire about the new arrival; they know not whether to wonder or to tremble; for many spread fear on all sides, drawing from the phenomenon most grave prognostics.'
There is no direct reference to comets in the Bible, either in the Old Testament or the New. It is possible that some of the signs from heaven recorded in the Bible pages were either comets or meteors, and that even where in some places an angel or messenger from God is said to have appeared and delivered a message, what really happened was that some remarkable phenomenon in the heavens was interpreted in a particular manner by the priests, and the interpretation afterwards described as the message of an angel. The image of the 'flaming sword which turned every way' may have been derived from a comet; but we can form no safe conclusion about this, any more than we can upon the question whether the 'horror of great darkness' which fell upon Abraham (Genesis xv. 12) when the sun was going down, was caused by an eclipse;[38] or whether the going back of the shadow upon the dial of Ahaz was caused by a mock sun. The star seen by the wise men from the east may have been a comet, since the word translated 'star' signifies any bright object seen in the heavens, and is in fact the same word which Homer, in a passage frequently referred to, uses to signify either a comet or a meteor. The way in which it appeared to go before them, when (directed by Herod, be it noticed) they went to Bethlehem, almost due south of Jerusalem, would correspond to a meridian culmination low down—for the star had manifestly not been visible in the earlier evening, since we are told that they rejoiced when they saw the star again. It was probably a comet travelling southwards; and, as the wise men had travelled from the east, it had very likely been first seen in the west as an evening star, wherefore its course was retrograde—that is, supposing it was a comet.[39] It may possibly have been an apparition of Halley's comet, following a course somewhat similar to that which it followed in the year 1835, when the perihelion passage was made on November 15, and the comet running southwards disappeared from northern astronomers, though in January it was 'received' by Sir J. Herschel, to use his own expression, 'in the southern hemisphere.' There was an apparition of Halley's comet in the year 66, or seventy years after the Nativity; and the period of the comet varies, according to the perturbing influences affecting the comet's motion, from sixty-nine to eighty years.
Homer does not, to the best of my recollection, refer anywhere directly to comets. Pope, indeed, who made very free with Homer's references to the heavenly bodies,[40] introduces a comet—and a red one, too!—into the simile of the heavenly portent in Book IV.:—
As the red comet from Saturnius sent
To fright the nations with a dire portent
(A fatal sign to armies in the plain,
Or trembling sailors on the wintry main),
With sweeping glories glides along in air,
And shakes the sparkles from its blazing hair:
Between two armies thus, in open sight,
Shot the bright goddess in a trail of light.
But Homer says nothing of this comet. If Homer had introduced a comet, we may be sure it would not have shaken sparkles from its blazing tail. Homer said simply that 'Pallas rushed from the peaks of heaven, like the bright star sent by the son of crafty-counselled Kronus (as a sign either to sailors, or the broad array of the nations), from which many sparks proceed.' Strangely enough, Pingré and Lalande, the former noted for his researches into ancient comets, the latter a skilful astronomer, agree in considering that Homer really referred to a comet, and they even regard this comet as an apparition of the comet of 1680. They cite in support of this opinion the portent which followed the prayer of Anchises, 'Æneid,' Book II. 692, etc.: 'Scarce had the old man ceased from praying, when a peal of thunder was heard on the left, and a star, gliding from the heavens amid the darkness, rushed through space followed by a long train of light; we saw the star,' says Æneas, 'suspended for a moment above the roof, brighten our home with its fires, then, tracing out a brilliant course, disappear in the forests of Ida; then a long train of flame illuminated us, and the place around reeked with the smell of sulphur. Overcome by these startling portents, my father arose, invoked the gods, and worshipped the holy star.' It is impossible to recognise here the description of a comet. The noise, the trail of light, the visible motion, the smell of sulphur, all correspond with the fall of a meteorite close by; and doubtless Virgil simply introduced into the narrative the circumstances of some such phenomenon which had been witnessed in his own time. To base on such a point the theory that the comet of 1680 was visible at the time of the fall of Troy, the date of which is unknown, is venturesome in the extreme. True, the period calculated for the comet of 1680, when Pingré and Lalande agreed in this unhappy guess, was 575 years; and if we multiply this period by five we obtain 2875 years, taking 1680 from which leaves 1195 years B.C., near enough to the supposed date of the capture of Troy. Unfortunately, Encke (the eminent astronomer to whom we owe that determination of the sun's distance which for nearly half a century held its place in our books, but has within the last twenty years been replaced by a distance three millions of miles less) went over afresh the calculations of the motions of that famous comet, and found that, instead of 575 years, the most probable period is about 8814 years. The difference amounts only to 8239 years; but even this small difference rather impairs the theory of Lalande and Pingré.[41]
Three hundred and seventy-one years before the Christian era, a comet appeared which Aristotle (who was a boy at the time) has described. Diodorus Siculus writes thus respecting it: 'In the first year of the 102d Olympiad, Alcisthenes being Archon of Athens, several prodigies announced the approaching humiliation of the Lacedæmonians; a blazing torch of extraordinary size, which was compared to a flaming beam, was seen during several nights.' Guillemin, from whose interesting work on Comets I have translated the above passage, remarks that this same comet was regarded by the ancients as having not merely presaged but produced the earthquakes which caused the towns of Helice and Bura to be submerged. This was clearly in the thoughts of Seneca when he said of this comet that as soon as it appeared it brought about the submergence of Bura and Helice.