Moon
Moon names 2 different subjects across the 6 encyclopedias on this shelf. Each is set out below. 1 of them is described by more than one encyclopedia.
Moon a heavenly body revolving about the earth
Described by 2 of the 6 encyclopedias.
Aiton's Encyclopedia (1910)
a heavenly body revolving about the earth. The moon is not a star, nor is it a planet; it is a satellite. The origin of the moon has been a mooted question. It is now considered that it is of solar, not terrestrial origin; that it was thrown off by the sun, and that after traveling for a time about the sun as a small planet, it came within the influence of our earth and was captured by the larger planet, since which time it has revolved about a new center. It is held that the earth never rotated with sufficient velocity to throw off the moon. Next to the sun, it is the heavenly body of most interest and importance. The moon travels about the earth in an orbit about 338,840 miles distant. Its orbit is more elliptical than that of the earth, and its average distance from the earth is about 1/390 of the earth's mean distance from the sun. In its orbit the moon travels at an average rate of 2,287 miles an hour, and completes its circuit in a trifle over twenty-nine and one-half days. It turns on its axis once each sidereal month, and thus keeps the same side toward us all the time. The man in the moon is nearly the same that the children of Israel saw in their wanderings. The diameter of the moon is about one-fourth that of the earth; forty-nine moons would equal the earth in volume and eighty-one would weigh as much. The density of the moon is 3.4; of the earth 5.6. The moon has no light of its own. It shines by the light of the sun. The half of the moon that is in the light of the sun is called its face. Twice a month the sun, earth, and moon are nearly in a line. At the moment when the moon crosses this line we cannot see any part of its bright face. Astronomers then say the moon is new. In a day or two we see a crescent rim and speak of the new moon . In a week the bright portion becomes a semicircle. In another week the moon is on the side opposite the sun, and we see it full in the face and speak of a full moon . As Tennyson puts it, The silver sickle of that month Became her golden shield. The visible portion then diminishes to a semicircle and finally to a new moon again. In the latitude of St. Louis the moon rises and sets later each day, by from twenty-three to seventy-seven minutes. Children living in northern Europe see the moon at certain seasons for an entire day at a time. The full moon that comes the month of the autumnal equinox seems to shine with a peculiarly soft, refulgent light. While nearly full it rises for several successive nights at about the same hour and is called the harvest moon . The following moon is called the hunter's moon for a similar reason. Moonlight is not infrequently strong enough to read by, but it is not over one six hundred thousandth part as strong as sunlight. If the sky were paved with lights equal to that of the moon, they would not yield over one-eighth as much light as is derived from the sun. The moon appears to be without an atmosphere. As its days and nights are fourteen of our days in length it is evident that the noon hour is intensely hot and midnight frightfully cold. Under a telescope the surface of the moon presents a pitted, small-pox appearance, due to the presence of the craters of extinct volcanoes. Many of these craters are from five to ten, twenty, fifty, sixty, or even one hundred miles in diameter. One of the largest has been named Copernicus in honor of the great astronomer. The weight of opinion is to the effect that the surface of the moon is of barren rock without water, snow, vegetation, seasons, or even storms. Present investigations are being carried on by means of telescopic photographs. A foolish notion once prevailed that moonlight was a cause of madness, whence the Latin term of lunatic and the English term, moonstruck. The moon has always been a favorite with children. The man in the moon with his round, good-natured visage seems to look down kindly on upturned faces. Jean Ingelow has a pretty conceit in her Seven Times One: O moon, in the night I have seen you sailing And shining so round and low, You were bright; ah, bright; but your light is failing, You are nothing now but a bow. You moon, have you done something wrong in heaven, That God has hidden your face? I hope if you have you will be forgiven, And shine again in your place. See Tides ; Eclipse ; Lunacy
Collier's New Encyclopedia (1921)
the single satellite attendant on the earth. Its diameter is 2,160 miles, that of the earth (which is 7,918) being nearly four times as great. Its superficial extent is about a 13th part of the earth's surface; its bulk is 1-45 that of the earth, but as the earth is relatively heavier, its weight is about 80 times that of the moon. As the moon revolves around the earth it manifests phases. After absence for a few nights it reappears as a delicate crescent of white light in the W. sky after sunset. Night after night it moves farther to the E., E.. the illuminated uminated portion of its disk continually increasing till the moon becomes full and rises about sunset. When the light of the moon has again so diminished that it is in its last quarter, it is seen high in the heavens in the morning. When it becomes full, the sun and the earth are so nearly in a escapes straight being line eclipsed that the; when moon new narrowly moon spike is again reached, the sun is nearly under- to going similar obscuration ( see ECLIPSE). species The moon shines only by the light of the sun reflected from its surface. To reptile. equal the brilliance of the sun 600,000 full moons would be required. The moon appears at all times nearly of the same size, showing that its orbit cannot be far from circular. Its average distance is 240,000 miles, varying at times between 220,000 and 260,000, but the ordinary fluctuations do not exceed 13,000 miles on either side of the mean value. The moon performs a complete revolution around the earth in 27 days, 7 hrs., 23 min., and 11.461 secs. This is called its sidereal period. The lunar month is longer than the sidereal period by 2 days, 5 hrs., 51.41 secs., because of the advance of the earth in the orbit between two successive conjunctions of the moon. As the moon revolves on its own axis nearly in the same time as it completes its orbit round the earth, it presents to us at all times nearly the same side of its surface. No clouds appear on it; apparently there is no water to send them forth or an atmosphere in which they may float. The whole surface is studded with volcanoes, apparently extinct. Their craters are broad, beyond anything existent on the earth. Tycho is 50 miles across, so is Aristotle, Theophilus is 64, and Petavius 78. Some are 16,000 and 17,000 feet deep. From the absence of an atmosphere the moon must be uninhabitable by any life analogous to that with which we are acquainted.
Moon MOUNTAINS OF THE
Collier's New Encyclopedia (1921)
MOUNTAINS OF THE, a high chain of mountains supposed to cross the continent of Africa from E. to W. On the earlier charts they were placed behind the fertile regions which line the S. side of the Mediterranean, separating them from the Great Desert; but the location of the mountains has been gradually changed by geographers southward.
What Has Changed in the Last Century
Aiton's held in 1910 that the moon "was thrown off by the sun" and later captured by the earth, and that its pitted surface was made by "the craters of extinct volcanoes"; both ideas are gone. Since the 1970s the dominant account has been the giant-impact hypothesis, in which a Mars-sized body struck the young earth and the debris coalesced into the moon, while the craters are understood as impact scars from bombardment, not volcanism. Twelve people walked on the surface between 1969 and 1972 and brought back some 380 kg of rock, whose chemistry underpins that impact model; laser reflectors they left behind now give the mean distance as about 238,855 miles, and show the moon receding roughly 3.8 cm a year. Collier's flat statement that the moon is barren has also been qualified: orbiters have confirmed water ice in permanently shadowed polar craters, and China's Chang'e 4 landed on the far side in 2019, a hemisphere neither encyclopedia's readers had ever seen.
Written for this edition, 2026.