The Beauties of Nature, and the Wonders of the World We Live In

by Sir John Lubbock

Who is there who has not watched them with admiration? "We first see her as an exquisite crescent of pale light in the western sky after sunset. Night after night she moves further and further to the east, until she becomes full, and rises about the same time that the Sun sets. From the time of full moon the disc of light begins to diminish, until the last quarter is reached. Then it is that the Moon is seen high in the heavens in the morning. As the days pass by, the crescent shape is again assumed. The crescent wanes thinner and thinner as the Moon draws closer to the Sun. Finally, she becomes lost in the overpowering light of the Sun, again to emerge as the new moon, and again to go through the same cycle of changes."[66]

But although she is so small the Moon is not only, next to the Sun, by far the most beautiful, but also for us the most important, of the heavenly bodies. Her attraction, aided by that of the Sun, causes the tides, which are of such essential service to navigation. They carry our vessels in and out of port, and, indeed, but for them many of our ports would themselves cease to exist, being silted up by the rivers running into them. The Moon is also of invaluable service to sailors by enabling them to determine where they are, and guiding them over the pathless waters.

The geography of the Moon, so far as concerns the side turned towards us, has been carefully mapped and studied, and may almost be said to be as well known as that of our own earth. The scenery is in a high degree weird and rugged; it is a great wilderness of extinct volcanoes, and, seen with even a very moderate telescope, is a most beautiful object. The mountains are of great size. Our loftiest mountain, Mount Everest, is generally stated as about 29,000 feet in height. The mountains of the Moon reach an altitude of over 42,000, but this reckons to the lowest depression, and it must be remembered that we reckon the height of mountains to the sea level only. Several of the craters on the Moon have a diameter of 40 or 50—one of them even as much as 78—miles. Many also have central cones, closely resembling those in our own volcanic regions. In some cases the craters are filled nearly to the brim with lava. The volcanoes seem, however, to be all extinct; and there is not a single case in which we have conclusive evidence of any change in a lunar mountain.

Fig. 50.—A group of Lunar Volcanoes.

The Moon, being so much smaller than the earth, cooled, of course, much more rapidly, and it is probable that these mountains are millions of years old—much older than many of our mountain chains. Yet no one can look at a map of the Moon without being struck with the very rugged character of its mountain scenery. This is mainly due to the absence of air and water. To these two mighty agencies, not merely "the cloud-capped towers, the gorgeous palaces, the solemn temples," but the very mountains themselves, are inevitable victims. Not merely storms and hurricanes, but every gentle shower, every fall of snow, tends to soften our scenery and lower the mountain peaks. These agencies are absent from the Moon, and the mountains stand to-day just as they were formed millions of years ago.

But though we find on our own globe (see, for instance, Fig. 21) volcanic regions closely resembling those of the Moon, there are other phenomena on the Moon's surface for which our earth presents as yet no explanation. From Tycho, for instance, a crater 17,000 feet high and 50 miles across, a number of rays or streaks diverge, which for hundreds, or in some cases two or three thousand, miles pass straight across plains, craters, and mountains. The true nature of these streaks is not yet understood.

THE SUN

The Sun is more than 400 times as distant as the Moon; a mighty glowing globe, infinitely hotter than any earthly fiery furnace, 300,000 times as heavy, and 1,000,000 times as large as the earth. Its diameter is 865,000 miles, and it revolves on its axis in between 25 and 26 days. Its distance is 92,500,000 miles. And yet it is only a star, and by no means one of the first magnitude.

The surface of the Sun is the seat of violent storms and tempests. From it gigantic flames, consisting mainly of hydrogen, flicker and leap. Professor Young describes one as being, when first observed, 40,000 miles high. Suddenly it became very brilliant, and in half an hour sprang up 40,000 more. For another hour it soared higher and higher, reaching finally an elevation of no less than 350,000 miles, after which it slowly faded away, and in a couple of hours had entirely disappeared. This was no doubt an exceptional case, but a height of 100,000 miles is not unusual, and the velocity frequently reaches 100 miles in a second.