Outlines of Creation

by Elisha Noyce

FIG. 6. PLANETS SEEN IN QUADRATURE.

The third planet from the sun is the Earth, distant about 95,000,000 miles, with a diameter of 7925 miles, so that the most lofty mountains (five miles high) bear about the same proportion to it as would an elevation one-fourteenth of an inch in height to a ball of ten feet in diameter; therefore, with all its valleys and high hills, the surface of the earth is smoother in proportion to its bulk than the rind of an orange. The earth is not a perfect sphere, but has a slightly flattened form, as though it had been compressed at the poles. The diameter at the poles is the smallest, and is 7899 miles, while that at the equator (its greatest) is 7925 miles, being a difference of twenty-six miles; but this is so small, when compared with the size of the earth, that if an exact model of it were made, four inches in diameter, it would require the most accurate measurement to determine that it was not a perfect sphere.

FIG. 7.

The form of the earth has been demonstrated by accurate experiments and calculations, but there are many things we may observe, convincing us of its rotundity; one of the most evident of these is the fact that as a ship at sea goes from the land, the hull first disappears, then the lower sails, and lastly the tops, while a ship approaching the shore shows first the topsails, and lastly the hull; see fig. 7, where A shows a ship on the horizon, B hull-down, C out of sight. In the same way, the tops of distant mountains are seen at sea long before the lower lands. Another proof is drawn from the fact, that ships have been sailed quite round the earth; by steering as nearly as possible in one direction, they have arrived at the place from which they started. A third proof of the earth's rotundity is found in the form of its shadow, when the moon is eclipsed by it; this shadow, as thrown by the earth upon the moon, is circular, in whatever position the earth may be, and a sphere is the only solid form which can in all positions cast a circular shadow.

The earth turns upon its axis every 23 hours, 56 minutes, and 4 seconds, which constitutes a day, and makes one revolution round the sun in every 365¼ days, which make up a year; but the earth's axis is not at a right angle to an imaginary line drawn from the earth to the sun, but at an angle of 23 deg. 28 min. to it, as shown at fig. 8, where the line from n to s is the earth's axis of rotation, the dotted line leading to s is the sun's direction, and e q is the equator.

FIG. 8.

The earth travels through space at a rate of more than a million-and-a-half miles per day, besides the distance which each object upon it is carried in its diurnal rotation (24,000 miles). At first thought it would seem impossible that such a rapid motion should not be felt; but as the air and clouds, and every object belonging to the earth, moves with it, and this motion is perfectly smooth, it can only be perceived by looking at objects independent of the earth. If sailing on the water, when it is quite smooth and the land not very near, the ship seems to be stationary and the objects on shore appear to pass along in an opposite direction to that in which the ship is going. It is the same with the earth; the sun, which appears to move, is stationary, while the earth is going round it; and the result is, while the earth turns round on its axis the whole firmament appears to move, we lose sight of those stars which are to the westward, which are then said to "set," while those to the eastward, constantly coming into sight, are said to "rise," the whole appearing to pass from east to west, while in reality the earth's surface is passing from west to east. At the equator, or that part of the earth which lies midway between the poles, the sun and stars appear to rise and set perpendicularly to the horizon and at equal times above and below it, it is therefore 12 hours day and 12 hours night; in places not situated on the equator, they do not rise and set perpendicularly to the horizon, but form portions of circles at greater or less altitudes in the heavens, and the nearer the observer is to either of the poles, the smaller the circle, and the more of it is seen; so that, at the poles, any star situated exactly overhead does not appear to move at all. This place is called the north pole of the heavens, and the nearest star to it is called the "polestar," which neither rises nor sets, and, as it always keeps the same position, serves as a guide to mariners. All this is the effect of the diurnal motion of the earth, its annual motion not affecting the position of the stars, they being at such an immense distance that the circle which the earth forms in passing round the sun—although nearly 200,000,000 miles across—is as a mere point in proportion. But not so with the sun: as before stated, at the equator it is twelve hours above the horizon and the same time below it; now, as we approach towards the poles, it forms at each rotation an arc above the horizon, lower and lower, until at the poles its daily rising and setting is lost altogether, and there would never be daylight there, provided that the earth was only subject to the diurnal motion (fig. 9); but as the earth turns upon an oblique axis, the north and south poles share the blessing of daylight between them, so that through one-half of the earth's orbit the north pole is towards the sun, as shown in the figure, and the south pole during the other half. There is therefore at the poles but one day and one night in the year—the day being summer and the night winter. In less northern climates, as England, this exists to a much smaller extent; for half the year the sun is longer above than below the horizon, constituting our summer, the other half of the year the sun is longer below the horizon than above it, and this is winter. Hence, in each case, midway between, the sun is twelve hours above and twelve below the horizon, which occurs in spring and autumn, being called the "equinoxes" (equal nights); the vernal or spring equinox takes place on the 21st of March, the autumnal on the 21st of September. The times just between these, when the sun is the longest and shortest time below the horizon, are called the summer and winter solstices, and occur on the 21st of December and the 21st of June.