Lunar observation

“ Well, that is the sort of illumination which the lunar man will enjoy under these circumstances; all the features of his country will be brightly lighted up by the full earth. Of course, this earth-lighted side of the moon cannot be compared in brilliancy with the sun-lighted side, but the brightness will still be perceptible, so that when from the earth we look at the moon, we see this glow distributed all over the dark portion; that is, we observe the feebly lighted globe clasped in the brilliant arms of the crescent. ”

“ Many of the mountains of the moon are, foot for foot, as lofty as the highest mountains on the earth, while all of them, in proportion to the size of the moon's globe, are much larger than the earth's mountains. It is obvious, then, that the sunshine, as it creeps over these Alpine landscapes in the moon, casting the black shadows of the peaks and craters many miles across the plains, and capping the summits of lofty mountains with light, while the lower regions far around them are yet buried in night, must clearly reveal the character of the lunar surface. ”

“ Seated in silence and in solitude at a powerful telescope, abstracted from terrestrial influences, and gazing upon the revealed details of some strikingly characteristic region of the moon, it requires but a small effort of the imagination to suppose one’s self actually upon the lunar globe, viewing some distant landscape thereupon ”

“ And now for a time let us turn attention from the lunar sky to the scenery of the lunar landscape. Let us, in imagination, take our stand high upon the eastern side of the rampart of one of the great craters. Height, it must be remarked, is more essential on the moon to command extent of view than upon the earth, for on account of the comparative smallness of the lunar sphere the dip of the horizon is very rapid. ”

“ Now a lunar spectator watching the sun eclipsed by the earth, would see, during totality and at a coup d’œil, every point around our world upon which the sun is setting on one side and rising upon the other. To every part of the earth around what is then the margin, as seen from the moon, the sun is upon the horizon, shining through a great thickness of atmosphere, reddening it, and being reddened by it wherever the vaporous conditions conduce to that colouration. ”

“ The lunar night would be lit by our own earth, a gigantic moon, presenting a surface more than thirteen times as large as that which the full moon offers us, and hanging almost stationary in the heavens, while [pg 129] exhibiting all the effects of rapid rotation upon its own axis. Those appendages of the sun, which only the spectroscope or the fleeting total eclipse can reveal to us, the corona, the chromosphere, and the prominences, would there be constantly visible. ”

“ To understand what the lunar screen is doing for us, we may imagine ourselves at some station outside the earth, whence we should behold the moon’s shadow somewhat as in Fig. 29, where we must remember that since the lunar orbit is not a circle, but nearly an ellipse, the moon is at some times farther from the earth than at others. Here the extremity of its shadow is represented as just touching the surface of the globe, while it is evident that if the moon were at its greatest distance, its shadow might come to a point before reaching the earth at all. ”

“ We have only to recall the splendors of a night that is lighted by a full moon, and then to recollect that at new or old moon the earth is "full" as seen from our satellite, and that a full earth must give some fourteen times as much light as a full moon, in order to realize the brilliancy of an earth-lit night upon the moon. As the moon waxes to us, the earth wanes to the moon, and vice versa, and so the phenomenon of earth-shine on the lunar surface must be looked for before the first quarter and after the last quarter of the moon. ”

“ When we look at the moon through a telescope which magnifies 200 times, and survey its extensive plains, its lofty peaks, its circular ranges of mountains, throwing their deep shadows over the vales, its deep and rugged caverns, and all the other varieties which appear on the Lunar surface, we behold such objects in the same manner as if we were standing at a point 238,800 miles from the earth in the direction of the moon, or only twelve hundred miles from that orb, reckoning its distance to be 240,000 miles. ”

“ The little crystals of ice perform the same part with respect to the moon, when we see a lunar halo. Those between us and the moon, or within a certain distance from the line of sight to the moon, are, in reality, lit up by the moon's rays; but they send off those rays in such directions that we do not receive the light. Thus, all the space lying towards the moon, and for a certain distance all round, looks dark. ”

“ To an observer, however, upon the (to us) marginal regions of the lunar globe, it would appear only during a portion of the lunar day—being visible in fact only in that part of its small circular path which happened to lie above the observer’s horizon: in some regions only a portion of the terrestrial disc would make its brief appearance. From the lunar hemisphere beyond this marginal line the earth can never be seen at all.
The lunar spectator whose situation enabled him to view the earth would see it as a moon; and a glorious moon indeed it must be. ”

“ Although it is impossible for a habitant of this earth fully to realise existence upon the moon, it is yet possible, indeed almost inevitable, for a thoughtful telescopist—watching 158 the moon night after night, observing the sun rise upon a lunar scene, and noting the course of effects that follow till it sets—it is almost inevitable, we say, for such an observer to identify himself so far with the object of his scrutiny, as sometimes to become in thought a lunar being. ”

“ Now it is found that when at birth the Moon is increasing in light, that is, going towards the full, and above the horizon, or conversely, decreasing in light and below the horizon, the period from birth to inception is less than ten lunar months by a quantity determined by the Moon’s distance from the horizon. But when the Moon at birth is found to be decreasing and above the horizon, or increasing and below the horizon, the period of time from birth to inception is found to be more than ten lunar months by a quantity determined by the Moon’s distance from the horizon. ”

“ The age of the moon here is actually less than it was in the photograph that we last examined, yet, in consequence of libration, which has caused the moon, in effect, to roll a little to one side, the sunlight is farther advanced toward the east, and we see many features of the lunar world that before had not yet emerged from night. ”

“ But if we fail to perceive diversity of colour upon the lunar surface, we are in a very different position in regard to diversity of brightness or variable light-reflective power of different districts and details. This will be tolerably obvious to those casual observers who have remarked nothing more of the moon’s physiography than the resemblance to a somewhat lugubrious human countenance which the full moon exhibits, and which is due to the accidental disposition of certain large and small areas of surface material which have less of the light-reflecting property than other portions ”

“ This atmosphere of ours is the most influential element in beautifying our terrestrial scenery, and the absence of such an appendage from the moon is the great modifying cause that affects lunar scenery as compared with that of the earth. We are accustomed to the sun with its dazzling brightness—overpowering though it be—subdued and softened by our vaporous screen. ”

“ If the Moon were enveloped in an atmosphere similar to that which surrounds the Earth, the reflection and diffusion of light among the minute particles of watery vapour which permeate it would give rise to a gradual transition from light to darkness; the lunar surface would be visible when not illumined by the direct rays of the Sun, and before sunrise and after sunset, dawn and twilight would occur as upon the Earth. ”

“ The lunar influence is considered supreme in the hour of birth. Nay, with some the moon is potential even before birth. In Iceland it is said: "If a pregnant woman sit with her face turned towards the moon, her child will be a lunatic." [361] And this imagination obtains at home as well as abroad. We are told that "astrologers ascribe the most powerful influence to the moon on every person, both for success and health, according to her zodiacal and mundane position at birth, and her aspects to other planets. ”

“ In other words, if a race of beings resembling ourselves, or resembling any of our contemporaries in terrestrial life, ever existed upon the moon, they must long since have perished. That such beings may have existed, is possible, particularly if it be true, as generally believed, that the moon once had a comparatively dense atmosphere and water upon its surface, which have now, in the process of cooling of the lunar globe, been withdrawn into its interior. ”

“ The zodiacal light also, which in our English latitude and climate is but rarely seen and in more favourable 161 climes appears only when the sun itself is hidden beneath the horizon, would upon the moon be seen as a constant accompaniment to the luminary throughout his daily course across the lunar sky. The other planets would appear generally as they do to us on earth, but, never being lost in daylight, their courses among the stars could be traced with scarcely any interruption. ”

“ If a lunar atmosphere exist, which either by the substances of which it is composed, or by the vapours diffused through it, can exert a selective absorption upon the star’s light, this absorption would be indicated to us by the appearance in the spectrum of new dark lines immediately before the star is occulted by the moon. ”

“ Because we cannot now make out either habitations or habitants on the moon, it does not necessarily follow that the night will never come when, through some mightier medium than any ever yet constructed or conceived, we shall descry, beside mountains and valleys, also peopled plains and populous cities animating the fair features of this beautiful orb. One valuable auxiliary of the telescope, destined to play an important part in lunar discovery, must not be overlooked. ”

“ The moon seems, as a learned author has observed, in almost every respect to be a body similar to our earth, to have its surface diversified by hill and dale, mountains and vallies, rivers and lakes. With regard to a lunar atmosphere, the existence of which has long been a subject of much dispute, it is now generally admitted.122 The irregularity of the moon’s surface, arising from hills and vallies, renders her more capable of reflecting the sun’s rays to us. ”

“ And taking into account the whole effect of them, we may conclude that our view of the moon’s surface, instead of being confined to one half, is extended really to about four-sevenths of the whole area of the lunar globe. The remaining three-sevenths must for ever remain a terra incognita to the habitants of this earth, unless, indeed, from some catastrophe which it would be wild fancy to anticipate, a period of rotation should be given to the moon different from that which it at present possesses. ”

“ It would be seen to pass through its phases, just as does our satellite, once in a lunar day or a terrestrial month, and during that cycle of phases, since 29 of our days would be occupied by it, the axial rotation would bring all the 162 features of its surface configuration into view so many times in succession. But the greatest beauty of this noble moon would be seen during the lunar night, in considering which we shall again allude to it; for when it is full-moon to the earth it is new-earth to the moon. At lunar midnight this globe of ours is fully illuminated ”

“ Just as the growth and dwindling of plants became associated with the moon’s wax and wane, so changes of weather became associated with changes of the moon, while, by astrologer’s logic, it did not matter whether the moon’s change were real, at new and full, or imaginary, at the intermediate quarters. That educated people to whom exact weather records are accessible should still find satisfaction in the fanciful lunar rule, is an interesting case of intellectual survival. ”

“ The telescopic appearance of the Moon is very interesting and beautiful, especially if the orb is observed when waxing and waning. As no aqueous vapour or cloud obscures the lunar surface, all its details can be perceived with great clearness and distinctness. Indeed, the topography of the Moon is better known than that of the Earth, for the whole of its surface has been mapped and delineated with great accuracy and precision. The Moon is in no sense a duplicate of its primary, and no analogy exists between the Earth and her satellite. ”

“ Even during a partial eclipse, however, the observer may find considerable interest in watching the outline of the dark moon, as projected upon the bright background of the sun. It is frequently jagged or serrated, the projections indicating the existence, on the margin of the lunar globe, of lofty mountain ranges. ”

“ We have seen enough, we think, from our own observations during the last five and twenty years, to lead us to the conclusion that such distortion and projection is occasionally to be seen, and that therefore, contrary to the general belief of astronomers, a lunar atmosphere very probably exists, though it may be of greatly less weight and density than our own. ”