Astronomy for Amateurs Part 17

We give two different drawings to represent these curious aspects of lunar topography. The first (Fig. 72) is taken in the neighborhood of the Apennines, and shows a long chain of mountains beneath which are three deep rings, Archimedes, Aristillus, and Autolycus: the second (Fig. 73) depicts the lunar ring of Flammarion,[14] whose outline is constructed of dismantled ramparts, and whose depths are sprinkled with little craters. The first of these two drawings was made in England by Nasmyth, the second in Germany by Krieger: they both give an exact idea of what one sees in the telescope with different modes of solar illumination.

In the Moon's always black and starry sky a majestic star that is not visible from the Earth, and exhibits this peculiarity that it is stationary in the Heavens, while all the others pa.s.s behind it, may constantly be admired, by day as well as by night; and it is also of considerable apparent magnitude. This...o...b.. some four times as large as the Moon in diameter, and thirteen to fourteen times more extensive in surface, is our Earth, which presents to the Moon a sequence of phases similar to those which our satellite presents to us, but in the inverse direction. At the moment of New Moon, the Sun fully illuminates the terrestrial hemisphere turned toward our satellite, and we get "Full Earth"; at the time of Full Moon, on the contrary, the non-illuminated hemisphere of the Earth is turned toward the satellite, and we get "New Earth": when the Moon shows us first quarter, the Earth is in last quarter, and so on. The drawing subjoined gives an idea of these aspects.

[Ill.u.s.tration: FIG. 73.--Flammarion's Lunar Ring.]

What a curious sight our globe must be during this long night of fourteen times twenty-four hours! Independent of its phases, which bring it from first quarter to full earth for the middle of the night, and from full earth to last quarter for sunrise, how interested we should be to see it thus stationary in the sky, and turning on itself in twenty-four hours.

[Ill.u.s.tration: FIG. 74.--Lunar landscape with the Earth in the sky.]

Yes, thanks to us, the inhabitants of the lunar hemisphere turned toward us are gratified by the sight of a splendid nocturnal torch, doubtless less white than our own despite the clouds with which the terrestrial globe is studded, and shaded in a tender tone of bluish emerald-green.

The royal orb of their long nights, the Earth, gives them moonlight of unparalleled beauty, and we may say without false modesty that our presence in the lunar sky must produce marvelous and absolutely fairy-like effects.

Maybe, they envy us our globe, a dazzling dwelling-place whose splendor radiates through s.p.a.ce; they see its greenish clarity varying with the extent of cloud that veils its seas and continents, and they observe its motion of rotation, by which all the countries of our planet are revealed in succession to its admirers.

We are talking of these pageants seen from the Moon, and of the inhabitants of our satellite as if they really existed. The sterile and desolate aspect of the lunar world, however, rather brings us to the conclusion that such inhabitants are non-existent, although we have no authorization for affirming this. That they have existed seems to me beyond doubt. The lunar volcanoes had a considerable activity, in an atmosphere that allowed the white volcanic ashes to be carried a long way by the winds, figuring round the craters the stellar rays that are still so striking. These cinders were spread over the soil, preserving all its asperities of outline, a little heaped up on the side to which they were impelled. The magnificent photographs recently made at the Paris Observatory by MM. Loewy and Puiseux are splendid evidence of these projections. In this era of planetary activity there were liquids and gases on the surface of the lunar globe, which appear subsequently to have been entirely absorbed. Now the teaching of our own planet is that Nature nowhere remains infertile, and that the production of Life is a law so general and so imperious that life develops at its own expense, sooner than abstain from developing. Accordingly, it is difficult to suppose that the lunar elements can have remained inactive, when only next door they exhibited such fecundity upon our globe. Yes, the Moon has been inhabited by beings doubtless very different from ourselves, and perhaps may still be, although this globe has run through the phases of its astral life more rapidly than our own, and the daughter is relatively older than the mother.

The duration of the life of the worlds appears to have been in proportion with their ma.s.ses. The Moon cooled and mineralized more quickly than the Earth. Jupiter is still fluid.

The progress of optics brings us already very close to this neighboring province. 'Tis a pity we can not get a little nearer!

A telescopic magnification of 2,000 puts the Moon at 384,000/2000 or 192 kilometers (some 120 miles) from our eye. Practically we can obtain no more, either from the most powerful instruments, or from photographic enlargements. Sometimes, exceptionally, enlargements of 3,000 can be used. This = 384000/3000 or 128 kilometers (some 80 miles). Undoubtedly, this is an admirable result, which does the greatest honor to human intelligence. But it is still too far to enable us to determine anything in regard to lunar life.

Any one who likes to be impressed by grand and magnificent sights may turn even a modest field-gla.s.s upon our luminous satellite, at about first quarter, when the relief of its surface, illuminated obliquely by the Sun, is at its greatest value. If you examine our neighbor world at this period, for choice at the hour of sunset, you will be astonished at its brilliancy and beauty. Its outlines, its laces, and embroideries, give the image of a jewel of shining silver, translucent, fluid, palpitating in the ether. Nothing could be more beautiful, nothing purer, and more celestial, than this lunar globe floating in the silence of s.p.a.ce, and sending back to us as in some fairy dream the solar illumination that floods it. But yesterday I received the same impression, watching a great ring half standing out, and following the progress of the Sun as it mounted the lunar horizon to touch these silvered peaks. And I reflected that it is indeed inconceivable that 999,999/1,000,000 of the inhabitants of our planet should pa.s.s their lives without ever having attended to this pageant, nor to any of those others which the divine Urania scatters so profusely beneath the wondering gaze of the observers of the Heavens.

CHAPTER X

THE ECLIPSES

Among all the celestial phenomena at which it may be our lot to a.s.sist during our contemplation of the universe, one of the most magnificent and imposing is undoubtedly that which we are now going to consider.

The hirsute comets, and shooting stars with their graceful flight, captivate us with a mysterious and sometimes fantastic attraction. We gladly allow our thoughts, mute questioners of the mysteries of the firmament, to rest upon the brilliant, golden trail they leave behind them. These unknown travelers bring a message from eternity; they tell us the tale of their distant journeys. Children of s.p.a.ce, their ethereal beauty speaks of the immensity of the universe.

The eclipses, on the other hand, are phenomena that touch us more nearly, and take place in our vicinity.

In treating of them, we remain between the Earth and the Moon, in our little province, and witness the picturesque effects of the combined movements of our satellite around us.

Have you ever seen a total eclipse of the Sun?

The sky is absolutely clear: no fraction of cloud shadows the solar rays. The azure vault of the firmament crowns the Earth with a dome of dazzling light. The fires of the orb of day shed their beneficent influence generally upon the world.

Yet, see! The radiance diminishes. The luminous disk of the Sun is gradually corroded. Another disk, as black as ink, creeps in front of it, and little by little invades it entirely. The atmosphere takes on a wan, sepulchral hue; astonished nature is hushed in profound silence; an immense veil of sadness spreads over the world. Night comes on suddenly, and the stars shine out in the Heavens. It seems as though by some mysterious cataclysm the Sun had disappeared forever. But this tribulation is soon over. The divine orb is not extinct. A flaming jet emerges from the shadow, announcing his return, and when he reappears we see that he has lost nothing in splendor or beauty. He is still the radiant Apollo, King of Day, watching over the life of the planetary worlds.

This sudden night, darkening the Heavens in the midst of a fine day, can not fail to produce a vivid impression upon the spectators of the superb phenomenon.

The eclipse lasts only for a few moments, but long enough to make a deep impression upon our minds, and indeed to inspire anxious spirits with terror and agitation--even at this epoch, when we know that there is nothing supernatural or formidable about it.

In former days, Humanity would have trembled, in uneasy consternation.

Was it a judgment from Heaven? Must it not be the work of some invisible hand throwing the somber veil of night over the celestial torch?

Had not the Earth strayed off her appointed path, and were we not all to be deprived eternally of the light of our good Sun? Was some monstrous dragon perhaps preparing to devour the orb of day?

The fable of the dragon devouring the Sun or Moon during the eclipses is universal in Asia as in Africa, and still finds acceptance under more than one lat.i.tude. But our readers already know that we may identify the terrible celestial dragon with our gentle friend the Moon, who would not be greatly flattered by the comparison.

We saw in the preceding lesson that the Moon revolves round us, describing an almost circular orbit that she travels over in about a month. In consequence of this motion, the nocturnal orb is sometimes between the Sun and the Earth, sometimes behind us, sometimes at a right angle in relation to the Sun and the Earth. Now, the eclipses of the Sun occur invariably at the time of New Moon, when our satellite pa.s.ses between the Sun and ourselves, and the eclipses of the Moon, at the moment of Full Moon, when the latter is opposite to the Sun, and behind us.

This fact soon enabled the astronomers of antiquity to discover the causes to which eclipses are due.

The Moon, pa.s.sing at the beginning of its revolution between the Sun and the Earth, may conceal a greater or lesser portion of the orb of day. In this case there is an eclipse of the Sun. On the other hand, when it is on the other side of the Earth in relation to the Sun, at the moment of Full Moon, our planet may intercept the solar rays, and prevent them from reaching our satellite. The Moon is plunged into _the shadow of the Earth_, and is then eclipsed. Such is the very simple explanation of the phenomenon. But why is there not an eclipse of the Sun at each New Moon, and an eclipse of the Moon at each Full Moon?

If the Moon revolved round us in the same plane as the Earth round the Sun, it would eclipse the Sun at each New Moon, and would be itself eclipsed in our shadow at each Full Moon. But the plane of the lunar orbit dips a little upon the plane of the terrestrial orbit, and the eclipses can only be produced when the New Moon or the Full Moon occur at the line of intersection of these two planes, _i.e._, when the Sun, the Moon, and the Earth are upon the same straight line. In the majority of cases, instead of interposing itself directly in front of the sovereign of our system, our satellite pa.s.ses a little above or a little below him, just as its pa.s.sage behind us is nearly always effected a little above or below the cone of shadow that accompanies our planet, opposite the Sun.

When the Moon intervenes directly in front of the Sun, she arrests the light of the radiant orb, and conceals a greater or less portion of the solar disk. The eclipse is partial if the Moon covers only a portion of the Sun; total if she covers it entirely; annular, if the solar disk is visible all round the lunar disk, as appears when the Moon, in her elliptical orbit, is beyond medium distance, toward the apogee.

On the other hand, when the Moon arrives immediately within the cone of shadow that the Earth projects behind it, it is her turn to be eclipsed.

She no longer receives the rays of the Sun, and this deprivation is the more marked in that she owes all her brilliancy to the light of the orb of day. The Moon's obscurity is complete if she is entirely plunged into the cone of shadow. In this case, the eclipse is total. But if a portion of her disk emerges from the cone, that part remains illuminated while the light of the other dies out. In that case there is a partial eclipse, and the rounded form of the Earth's shadow can be seen projected upon our satellite, a celestial witness to the spherical nature of our globe.

Under certain conditions, then, the Moon can deprive us of the luminous rays of the Sun, by concealing the orb of day, and in other cases is herself effaced in crossing our shadow. Despite the fables, fears, and anxieties it has engendered, this phenomenon is perfectly natural: the Moon is only playing hide-and-seek with us--a very harmless amus.e.m.e.nt, as regards the safety of our planet.

But as we said just now, these phenomena formerly had the power of terrifying ignorant mortals, either when the orb of light and life seemed on the verge of extinction, or when the beautiful Phoebus was covered with a veil of c.r.a.pe and woe, or took on a deep coppery hue.

It would take a volume to describe all the notable events which have been influenced by eclipses, sometimes for good, more often with disastrous consequences. The recital of these tragic stories would not be devoid of interest; it would ill.u.s.trate the possibilities of ignorance and superst.i.tion, and the power man gains from intellectual culture and scientific study.

Herodotus records that the Scythians, having some grievance against Cyaxarus, King of the Medes, revenged themselves by serving up the limbs of one of his children, whom they had murdered, at a banquet as rare game. The scoundrels who committed this atrocious crime took refuge at the Court of the King of Lydia, who was ill judged enough to protect them. War was accordingly declared between the Medes and Lydians, but a total eclipse of the Sun occurring just when the battle was imminent, had the happy effect of disarming the combatants, who prudently retired each to their own country. This eclipse, which seems to have occurred on May 28, 584 B.C., had been predicted by Thales. The French painter Rochegrosse has painted a striking picture of the scene (Fig. 75).

In the year 413 B.C. the Athenian General Nicias prepared to return to Greece after an expedition to Sicily. But, terrified by an eclipse of the Moon, and fearing the malign influence of the phenomenon, he put off his departure, and lost the chance of retreat. This superst.i.tion cost him his life. The Greek army was destroyed, and this event marks the commencement of the decadence of Athens.

In 331 B.C. an eclipse of the Moon disorganized the troops of Alexander, near Arbela, and the great Macedonian Captain had need of all his address to rea.s.sure his panic-stricken soldiers.

Agathocles, King of Syracuse, blocked by the Carthaginians in the port of this city, had the good fortune to escape, but was disturbed on the second day of his flight by the arrival of a total eclipse of the Sun which alarmed his companions. "What are you afraid of?" said he, spreading his cloak in front of the Sun. "Are you alarmed at a shadow?"

(This eclipse seems to be that of August 15, 309, rather than that of March 2, 310.)

[Ill.u.s.tration: FIG. 75.--Battle between the Medes and Lydians arrested by an Eclipse of the Sun.]

On June 29, 1033, an epoch at which the approaching end of the world struck terror into all hearts, an annular eclipse of the Sun occurring about midday frustrated the designs of a band of conspirators who intended to strangle the Pope at the altar. This Pope was Benedict IX, a youth of less than twenty, whose conduct is said to have been anything but exemplary. The a.s.sa.s.sins, terrified at the darkening of the Sun, dared not touch the Pontiff, and he reigned till 1044.[15]

On March 1, 1504, a lunar eclipse saved the life of Christopher Columbus. He was threatened with death by starvation in Jamaica, where the contumacious savages refused to give him provisions. Forewarned of the arrival of this eclipse by the astronomical almanacs, he threatened to deprive the Caribs of the light of the Moon--and kept his word. The eclipse had hardly begun when the terrified Indians flung themselves at his feet, and brought him all that he required.

In all times and among all people we find traces of popular superst.i.tions connected with eclipses. Here, the abnormal absence of the Moon's light is regarded as a sign of divine anger: the humble penitents betake themselves to prayer to ward off the divine anger. There, the cruelty of the dread dragon is to be averted: he must be chased away by cries and threats, and the sky is bombarded with shots to deliver the victim from his monstrous oppressor.

In France the announcement of a solar eclipse for August 21, 1560, so greatly disturbed our ancestors' peace of mind as to make them idiotic.

Preparations were made for a.s.sisting at an alarming phenomenon that threatened Humanity with deadly consequences! The unhappy eclipse had been preceded by a mult.i.tude of ill omens! Some expected a great revolution in the provinces and in Rome, others predicted a new universal deluge, or, on the other hand, the conflagration of the world; the most optimistic thought the air would be contaminated. To preserve themselves from so many dangers, and in accordance with the physicians'

orders, numbers of frightened people shut themselves up in tightly closed and perfumed cellars, where they awaited the decrees of Fate. The approach of the phenomenon increased the panic, and it is said that one village _cure_, being unable to hear the confessions of all his flock, who wanted to discharge their souls of sin before taking flight for a better world, was fain to tell them "there was no hurry, because the eclipse had been put off a fortnight on account of the number of penitents"!

[Ill.u.s.tration: FIG. 76.--Eclipse of the Moon at Laos (February 27, 1877).]