Earth
Earth 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.
Earth the name applied to the third planet in order from the sun
Described by 2 of the 6 encyclopedias.
Collier's New Encyclopedia (1921)
the name applied to the third planet in order from the sun. Ta the eye it appears as if the earth was in the center of the universe, the sun and the stars revolving round it. The phenomena are much better accounted for by supposing the apparent revolution of the celestial vault to be produced by an actual rotation of the earth on its axis in about 24 hours, producing day and night. In possessing a satellite (the moon) the earth resembles various other planets, except that they have more attendant bodies than one. In fact, the earth is a planet, and, like other planets, its figure is not far from spherical, as is proved by its having been sailed round. Magellan led the way, having circumnavigated a great part of the globe between 1519 and 1521, being killed in the Philippine Islands in the last-named year. Sebastian del Cano, one of his officers, completed the enterprise. terprise. Sir Francis Drake returned alive from a similar enterprise successfully carried out between 1577 and 1579 or 1580. The sight of the masts of a vessel appearing before the hull comes in sight is a proof that at least that portion of the world visible to us is a curve. Moreover, in an eclipse of the moon the shadow of the earth obscuring the face of the luminary is found to be circular, and there are other arguments in the same direction. Only in a broad sense can the earth be described as spherical; it is really an oblate spheroid- i. e. i. e., the distance between the two poles is less than that between two extremities of a diameter drawn through the equator. This form may have been produced by the rotation of a partially fluid sphere. According to Bessel, the greater or equatorial diameter is 7,925.604 miles, the lesser or polar one 7,899.114 miles; the difference of diameter, or polar compression, is 26.471 miles, and the proportion of the equatorial to the polar diameter as 299.15 to 298.15. The dimensions given by Sir R. Airy slightly differ from these. The force of gravity at the poles is to that at the equator very nearly as 180 to 179. It is not of uniform density, the French mathematician, Clairvault, assuming it to consist of ellipsoidal strata increasing in density as they approached the earth's center, and, taking it for granted also that the attractive force might be calculated on the law of liquids, proved that the amount of gravity at the poles to that at the equator is as 180 to 179, and that the earth's polar axis was to its equatorial one as 299 to 300, which almost exactly agrees with the result of observation. Clairvault believed the mean density of the earth, taken as a whole, to be about twice that of the parts near the surface. Henry Cavendish, Dr. Reich, and Francis Baily considered the density of the earth to be 5.67, and Sir R. Airy believed it 6.565, that of water being 1. The number of cubic miles in the earth is about 259,800,000,000, each cubic mile containing 147,200,000,000 cubic feet. The surface of the land is to that of the water on the earth in the proportion of one to three. The land is unequally distributed, most of it being in the N. hemisphere. The universal opinion of geologists is that the earth is of immeasurable antiquity. The old view that our planet is but a few thousand years old now exists only among the uninformed. It is not yet proved that astronomical changes have ever taken place since the first establishment of the solar system seriously to modify the state of things existing on the earth. The action of the earth on magnetic substances is like that of a magnet, and it has two poles different from the ordinary poles.
Aiton's Encyclopedia (1910)
the planet third in order from the sun. Mercury and Venus are nearer the sun. The general shape of the earth is spherical. Whenever the earth's shadow falls on the moon it has a circular outline. The curvature of the earth's surface is such that, if three stakes in a line be driven half a mile apart, so that the tops of the first and third are on a water level with the top of the second, it will be found, on sighting across, that a straight line from the top of the first stake to the top of the third cuts about eight inches below the top of the second stake. In other words the surface of a lake curves about eight inches per mile. Scientists have actually made numerous measurements-a score or more-of considerable portions of a meridian, that is to say, a north and south line. One measurement extended from Hammerfest, in the north of Norway, to the mouth of the Danube; another from the Himalayas to the Southern point of Hindustan. From these measurements it has been found that a degree of a meridian is 3,000 feet longer in Sweden than in southern India; in other words, that the earth is flattened at the poles. Various computations agree so well that it is believed the following dimensions of the earth are correct, to within a fifth of a mile. Equatorial diameter 7,926.614 miles. Polar diameter 7,899.742 miles. Difference 26.872 miles. Average diameter 7,920 miles. Equatorial circumference 24,912 miles. Area of surface 196,971,984 sq. miles. Weight in pounds including atmosphere 6,666,225,819,600,000,000,000 The earth has three motions and possibly four: 1. It rotates on its axis once in each twenty-four hours. The rotary speed of the earth's surface varies from zero at the poles to one thousand miles an hour on the equator. 2. It revolves about the sun in an elliptical orbit once in each year, flying at a rate of about 66,600 miles an hour in its travels. This orbit is fairly regular, yet it is thought that the earth wobbles on its axis a trifle, and is jolted out of its path 4,000 miles or so. 3. It follows the sun in its travels at an estimated rate of 150,000,000 miles a year. 4. Very possibly the universe may be changing its position in space. The density of the earth's crust is about three times that of water. The average density of the earth is 5.5 times that of water, from which it is argued that the interior is about eight or nine times as dense as water. Inasmuch as pressure tends to solidify, and heat tends to liquefy, it is not known whether the interior is solid or fluid; but it is pretty well agreed that the interior is dense and intensely hot. See Geography ; Equator ; Altitude ; Latitude ; Longitude ; Season
Earth originally, in the opinion of the ancient chemists
Collier's New Encyclopedia (1921)
originally, in the opinion of the ancient chemists, or alchemists, one of the four elements, of which all material things in the world were held to be composed, the others being fire, air, and water. Not even one of the four is really a simple substance. Later, a name given to various substances, opaque, insipid to the taste, incombustible, and, when dry, friable, i, e., easily separated into particles. Five divisions of them were recognized: (a) Boles, (b) Clays, (c) Marls, (d) Ochers, and (e) Tripolis. Under these categories were ranked the oxides of the cerium, aluminium, beryllium, metals zirconium, yttrium, erbium, thorium, etc. These oxides are insoluble in water, and are all very rare except aluminum. They are difficult to separate from each other, occurring together in rare minerals, and hence the number of metals belonging to this class is not known.
What Has Changed in the Last Century
The measurements have held up remarkably well: Aiton's 1910 equatorial diameter of 7,926.6 miles is within a mile of the satellite-derived figure used today, and Cavendish's density of about 5.5 times water (Collier's quotes 5.67, and Airy's too-high 6.565) is close to the modern 5.51. What has changed is everything about the inside and the history. Where Collier's could only say the earth is "of immeasurable antiquity," radiometric dating of meteorite lead by Clair Patterson in 1956 fixed the age at about 4.55 billion years; the layered interior of crust, mantle, liquid outer core and solid inner core was worked out from earthquake waves over the same period; and from the 1960s plate tectonics established that the continents move, at a few centimetres a year. Collier's remark that no astronomical change has been proved to "modify the state of things existing on the earth" was overtaken by Milankovitch's work on how slow shifts in the orbit and tilt pace the ice ages, and by the 1980 case for an asteroid impact at the end of the Cretaceous. Neither writer could have seen the planet whole: that waited for Apollo 8's Earthrise photograph in 1968.
Written for this edition, 2026.