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noctial, where the motion appears quickest; tecause it is seemingly performed in the greatest circle. And the very poles which are at rest to us, have the quickest motion of all as seen from Venus. To Mars and Jupiter, the heavens appear to turn round
different velocities on the same axis, whose poles are about 23į degrees from ours.
Were we on Jupiter, we should be at first amazed at the rapid motion of the heavens; the Sun and stars going round in 9 hours 56 minutes. Could we go from thence to Venus, we should be as much surprised at the slowness of the heavenly motions; the Sun going but once round in 584 hours, and the stars in 540. And could we go from Venus to the Moon, we should see the heavens turn round with a yet slower motion; the Sun in 708 hours, the stars in 655. As it is impossible these various circumvo. lutions in such different times, and on such different axes, can be real, so it is unreasonable to suppose the heavens to revolve about our Earth, more than it does about any other planet. When we reflect on the vast distance of the fixed stars, to which 162,000,000 of miles, the diameter of the Earth's orbit, is but a point, we are filled with amazement at the immensity of their distance. But if we try to frame an idea of the extreme rapidity with which the stars must move, if they move round the Earth in 24 hours, the thought becomes so much too big for our imagination, that we can no more conceive it than we do infinity or eternity. If the Sun were to go round the Earth in 24 hours, he must travel upward of 300,000 miles in a minute : but the stars being at least 400,000 times as far from the Sun as the Sun is from us, those about the equator must move 400,000 times as quick. And all this to serve no other purpose than what can be as fully and much more simply obtained by the Earth's turning round eastward, as on an axis, every 24 hours; causing thereby an apparent
diurnal motion of the Sun westward, and bringing
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121. As to the common objections against the objecEarth's motion on its axis, they are all easily an- against *. swered, and set aside. That it may turn without be. Earth's rii ing seen or felt by us to do so, has been already tion anshewn, § 119. But some are apt to imagine that if swered. the Earth turns eastward (as it certainly does, if it turns at all) a ball fired perpendicularly upward in the air must fall considerably westward of the place it was projected from. This objection, which at first seems to have some weight, will be found to have none at all, when we consider that the gun and ball partake of the Earth's motion; and therefore the ball being carried forward with the air as quick as the Earth and air turn, must fall down on the same place. A stone let fall from the top of a main-mast, if it meet with no obstacle, falls on the deck as near the foot of the mast when the ship sails as when it does not. If an inverted bottle full of liquor, be hung up to the ceiling of the cabin, and a small hole be made in the cork to let the liquor drop through on the floor, the drops will fall just as far forward on the floor when the ship sails as when it is at rest. And gnats or flies can as easily dance among one another in a moving cabin, as in a fixed chamber. As for those scripture-expressions which seem to contradict the Earth's motion, the following reply may be made to them all: It is plain, from many instances, that the Scriptures were never intended to instruct us in philosophy or astronomy; and therefore, on those subjects, expressions are not always to be taken in the literal sense; but for the most part as accommodated to the common apprehensions of mankind. Men of sense in all ages, when not treating of the sciences purposely, have followed this method : and it would be in vain to follow any other in addressing ourselves to the vulgar, or bulk of any
community. Moses calls the Moon a GREAT LUMINARY (as it is in the Hebrew) as well as the Sun: but the Moon is known to be an opaque body, and the smallest that astronomers have observ. ed in the heavens; and that it shines upon us, not by any inherent light of its own, but by reflecting the light of the Sun. Moses might know this; but had he told the Israelites so, they would have stared at him; and considered him rather as a madman, than as a person commissioned by the Almighty to be their leader.
The Phenomena of the Heavens as seen from different
Parts of the Earth.
kept to the 122.
E are kept to the Earth's surface, on Earth by
all sides, by the power of its central gravity. attraction; which laying hold of all bodies accord
ing to their densities or quantities of matter, with. out regard to their buiks, constitutes what we call their weight. And having the sky over our heads, go where we will, and our feet toward the centre of the Earth; we call it up over our heads, and down under our feet: although the same right line which is down to us, if continued through and be.
yond the opposite side of the Earth, would be up to Plate II. the inhabitants on the opposite side. For, the inFig. 1.
habitants n, i, e, m, 4, 0, 9. I stand with their feet toward the Earth's centre C; and have the same figure of sky N, I, E, M, S, O, Q, L, over their heads. Therefore, the point S is as directly upward to the inhabitant s on the south pole, as N is to the inhabitant n on the north pole : so is E to the inhabitant e supposed to be on the north end of Peru; and Q to the opposite inhabitant q on the mid
dle of the island Sumatra. Each of these observers podes.
is surprised that his opposite or antipode can stand with his head hanging downward. But let either
go to the other, and he will tell him that he stood as Plate II.
123. When we see a globe hung up in a room, How our we cannot help imagining it to have an upper and an Earth under side, and immediately form a like idea of the might Earth; from whence we conclude, that it is as im- upper possible for people to stand on the under side of the and an Earth, as for pebbles to lie on the under side of a side. common globe, which instantly fall down from it to the ground; and well they may, because the attraction of the Earth being greater than the attraction of the globe, pulls them away. Just so would it be with our Earth, if it were fixed near a globe much bigger than itself, such as Jupiter : for then, it would really have an upper and an under side with respect to that large globe; which, by its attraction, would pull away every thing from the side of the Earth next to it; and only those bodies on its surface, at the opposite side, could remain upon it. But there is no larger globe near enough our Earth to overcome its
Plate II. central attraction; and therefore it has no such thing
as an upper and an under side; for all bodies on or near its surface, even to the Moon, gravitate toward its centre.
124. Let any man imagine the Earth, and every thing but himself, to be taken away, and he left alone in the midst of indefinite space; he could then have no idea of up or down; and were his pockets full of gold, he might take the pieces one by one, and throw them away on all sides of him, without any danger of losing them; for the attraction of his body would bring them all back by the ways they went, and he would be down to every one of them. But then, if a sun, or any other large body, were created and placed in any part of space, several millions of miles from him, he would be attracted toward it, and could not save himself from falling down to it.
125. The Earth's bulk is but a point, as that at C, compared to the heavens; and therefore every inhabitant upon it, let him be where he will, as at n, e, m, s, &c. sees half of the heavens. The inha. bitant n, on the north pole of the Earth, constantly sees the hemisphere E NQ; and having the north pole N of the heavens just over his head, his hori.
zon coincides with the celestial equator EC Q. Half of Therefore all the stars in the northern hemisphere the hea: EN Q, between the equator and north pole, appear ble to an to turn round the line NC, moving parallel to the inhabitant horizon. The equatorial stars keep in the horizon, part of the and all those in the southern hemisphere ESQ are Earth. invisible. The like phenomena are seen by the ob
server s on the south pole, with respect to the hemi. sphere E SQ; and to him the opposite hemisphere is always invisible. Hence, under either pole, only