To the different Planets the Heavens appear to turn round on different Axes.
120. If we could translate ourselves from Planet to Planet, we should still find that the Stars would appear of the same magnitudes, and at the same distances from each other, as they do to us here; because the width of the remotest Planet’s Orbit bears no sensible proportion to the distance of the Stars. But then, the Heavens would seem to revolve about very different Axes; and consequently, those quiescent Points which are our Poles in the Heavens would seem to revolve about other points, which, though apparently in motion to us on Earth would be at rest as seen from any other Planet. Thus, the Axis of Venus, which lies almost at right Angles to the Axis of the Earth, would have it’s motionless Poles in two opposite points of the Heavens lying almost in our Equinoctial, where the motion appears quickest because it is 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 with very different velocities on the same Axis, whose Poles are about 231⁄2 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 circumvolutions 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 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 was to go round the Earth in a day, he must travel upwards of 300,000 miles in a minute: but the Stars being at least 10,000 times as far as the Sun from us, those about the Equator must move 10,000 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 about the alternate returns of day and night.
Pl. II.
Objections against the Earth’s diurnal motion answered.
121. As to the common objections against the Earth’s motion on it’s Axis, they are all easily answered and set aside. That it may turn without being seen or felt to do so, has been already shewn, § [119]. But some are apt to imagine that if 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 again on the same place. A stone let fall from the top of a main-mast, if it meets with no obstacle, falls on the deck as near the foot of the mast when the ship sails as when it does not. And if an inverted bottle, full of liquor, be hung up to the cieling 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, this general answer may be made to them all, viz. ’tis 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 strictest 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 observed in the Heavens and shines upon us not by any inherent light of it’s own, but by reflecting the light of the Sun. If Moses had known this, and 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.
CHAP. IV.
The Phenomena of the Heavens as seen from different parts of the Earth.
We are kept to the Earth by gravity.
[PLATE II]. Fig. I.
Antipodes.
Axis of the World. It’s Poles. Fig. II.
122. We are kept to the Earth’s surface on all sides by the power of it’s central attraction; which, laying hold of all bodies according to their densities or quantities of matter without regard to their bulks, constitutes what we call their weight. And having the sky over our heads, go where we will, and our feet towards 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 beyond the opposite side of the Earth, would be up to the inhabitants on the opposite side. For, the inhabitants n, i, e, m, s, o, q, l stand with their feet toward the Earth’s centre C; and have the same figure of sky N, l, 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 middle of the island Sumatra. Each of these observers is surprised that his opposite or Antipode can stand with his head hanging downwards. But let either go to the other, and he will tell him that he stood as upright and firm on the place where he was as he now stands where he is. To all these observers the Sun, Moon, and Stars seem to turn round the points N and S as the Poles of the fixed Axis NCS; because the Earth does really turn round the mathematical line nCs as round an Axis of which n is the North Pole and s the South Pole. The Inhabitant U (Fig. II.) affirms that he is on the uppermost side of the Earth, and wonders how another at L can stand on the undermost side with his head hanging downwards. But U in the mean time forgets that in twelve hours time he will be carried half round with the Earth; and then be in the very situation that L now is, although as far from him as before. And yet, when U comes there, he will find no difference as to his manner of standing; only he will see the opposite half of the Heavens, and imagine the Heavens to have gone half round him.
How our Earth might have an upper and an under side.