"The Moon her monthly course had now begun,
And with increasing horns forsook the Sun;"
—Lucan's Pharsalia.
The semicircle then increases to an oval and by the time the moon is behind the earth with the earth between it and the sun, the oval has increased to a full circle. Each day the moon rises about 50 minutes later than on the preceding day and in the course of a month changes from a crescent—a quarter—a full shining face, to a quarter, a crescent and again a slender new moon. It has now traveled completely around the earth. Since the moon has always the same face toward the earth (if one will walk around a table with the eyes always toward the center, this journey will be well illustrated), it will be seen by us in all its phases before it completes a day and night, or, in other words, although the earth turns all sides to the sun in 24 hours, the moon must travel all the way around the earth, which takes almost 30 of our days, before it completes a day and night. This means a continuous stretch of 14¾ times 24 hours of daylight, which is about equal to 29 of our days, of daylight, followed by 14¾ times 24 hours of night, when the sun is below the horizon. It would be a strange experience to travel to this country where the day and night each last half a month.
If a journey to the weird, rough country of the moon were possible, one would experience even greater surprises than the length of the day and the night, for the sky, as seen from this airless sphere, would be strangely different from anything that we are accustomed to. Here the sun hangs like a big gold jewel edged with a tiny fringe of scarlet, the pearly petals of its delicate corona far outstretched against the star-filled sky. The brilliant ball of the earth, which would appear almost 13 times as large in area as the moon, rests immovable and ever present, its great globe turning completely around every 24 hours. Also, as the moon does to us, it would exhibit to an observer on the moon an interesting variety of phases, mammoth crescents, quarters and disks. Such a sky!—a huge white planet, a flower-like sun and multitudes of unwinking stars. And even more, for stretched from horizon to horizon of that black dome, even though the sun shines brightly, is the misty arch of the Milky Way glowing in a glory quite unknown to mortals on earth. All this would happen for the simple reason that the moon has no appreciable amount of atmosphere to diffuse the sun's rays, make the sky seem blue and render the stars invisible. This would also unveil many of the smaller stars that are not seen here without optical aid—and every star would "burn" but none would "twinkle." In the morning of that long lunar day of 354 hours, the yellow face of the sun would slowly push its gayly bedecked head above the black rim of the horizon unheralded by a dawn; neither would twilight trail behind it when it sank beyond our sight after the long day was done, for these phenomena are due entirely to the light-reflecting and refracting power of an atmosphere.
The absence of an atmosphere on the moon, or at least the presence of only a very rare one, is proved by the suddenness with which a star will disappear when the moon passes between the star and us. Also surface features would not otherwise stand forth with such clearness nor shadows be so sharp and inky-black. When the moon passes in front of the sun at the time of an eclipse, its outline shows perfectly sharp against the yellow disk, even showing, like jagged saw-teeth, the "mountains of eternal light" which tower near the southern pole. When Venus makes a transit across the sun its whole edge is illuminated instead of being merely sharply defined, for Venus is enclosed in a wrapping of atmosphere.
The spectroscope has proved that there is no water on the moon. If it is airless and waterless it consequently must be lifeless. But hold, a moment. Perhaps we go too fast with our this anti that and therefore, for here come reports from Pickering, one of our most tireless observers, who declares that there is a considerable amount of dampness still lodged in the deep cavities of the circular mountains, and that this dampness ascends in mists when the sun rises. These mists do not seem to float freely but cling to ridges and higher levels and later dissolve there. The outlines of these cavities are slightly blurred until the mist is banished.
THE GRAY LAND ON THE MOON
The curious gray areas which extend over two-fifths of the surface of the moon are the most conspicuous features to be seen with the unaided eye. These areas are comparatively smooth and level and invariably lower than the surrounding country.
