Part 4
86. Every person who looks upon, and compares the Systems of Moons together, which belong to Jupiter and Saturn, must be amazed at the vast magnitude of these two Planets, and the noble attendance they have in respect of our little Earth: and can never bring himself to think, that an infinitely wise Creator should dispose of all his animals and vegetables here, leaving the other Planets bare and destitute of rational creatures. To suppose that he had any view to our Benefit, in creating these Moons and giving them their motions round Jupiter and Saturn; to imagine that he intended these vast Bodies for any advantage to us, when he well knew that they could never be seen but by a few Astronomers peeping through telescopes; and that he gave to the Planets regular returns of days and nights, and different seasons to all where they would be convenient; but of no manner of service to us, except only what immediately regards our own Planet the Earth; to imagine, I say, that he did all this on our account, would be charging him impiously with having done much in vain: and as absurd, as to imagine that he has created a little Sun and a Planetary System within the shell of our Earth, and intended them for our use. These considerations amount to little less than a positive proof that all the Planets are inhabited: for if they are not, why all this care in furnishing them with so many Moons, to supply those with light which are at the greater distances from the Sun? Do we not see, that the farther a Planet is from the Sun, the greater Apparatus it has for that purpose? save only Mars, which being but a small Planet, may have Moons too small to be seen by us. We know that the Earth goes round the Sun, and turns round it’s own Axis, to produce the vicissitudes of summer and winter by the former, and of day and night by the latter motion, for the benefit of its inhabitants. May we not then fairly conclude, by parity of reason, that the end and design of all the other Planets is the same? and is not this agreeable to that beautiful harmony which reigns over the Universe? Surely it is: and raises in us the most magnificent ideas of the SUPREME BEING, who is every where, and at all times present; displaying his power, wisdom, and goodness among all his creatures! and distributing happiness to innumerable ranks of various beings!
[Sidenote: Fig. II.
How the Sun appears to the different Planets.]
87. In Fig. 2d, we have a view of the proportional breadth of the Sun’s face or disc, as seen from the different Planets. The Sun is represented N^o 1, as seen from Mercury; N^o 2, as seen from Venus; N^o 3, as seen from the Earth; N^o 4, as seen from Mars; N^o 5, as seen from Jupiter; and N^o 6, as seen from Saturn.
[Sidenote: Fig. III.
Fig. IV.]
Let the circle _B_ be the Sun as seen from any Planet, at a given distance; to another Planet, at double that distance, the Sun will appear just of half that breadth, as _A_; which contains only one fourth part of the area or surface of _B_. For, all circles, as well as square surfaces, are to one another as the squares of their diameters. Thus, the square _A_ is just half as broad as the square _B_; and yet it is plain to sight, that _B_ contains four times as much surface as _A_. Hence, in round numbers, the Sun appears 7 times larger to Mercury than to us, 90 times larger to us than to Saturn, and 630 times as large to Mercury as to Saturn.
[Sidenote: Fig. V.
Proportional bulks and distances of the Planets.
PLATE I.]
88. In Fig. 5th, we have a view of the bulks of the Planets in proportion to each other, and to a supposed globe of two foot diameter for the Sun. The Earth is 27 times as big as Mercury, very little bigger than Venus, 5 times as big as Mars; but Jupiter is 1049 times as big as the Earth, Saturn 586 times as big, exclusive of his Ring; and the Sun is 877 thousand 650 times as big as the Earth. If the Planets in this Figure were set at their due distances from a Sun of two feet diameter, according to their proportional bulks, as in our System, Mercury would be 28 yards from the Sun’s center; Venus 51 yards 1 foot; the Earth 70 yards 2 feet; Mars 107 yards 2 feet; Jupiter 370 yards 2 feet; and Saturn 760 yards two feet. The Comet of the year 1680, at it’s greatest distance, 10 thousand 760 yards. In this proportion, the Moon’s distance from the center of the Earth would be only 7-1/2 inches.
[Sidenote: An idea of their distances.]
89. To assist the imagination in conceiving an idea of the vast distances of the Sun, Planets, and Stars, let us suppose, that a body projected from the Sun should continue to fly with the swiftness of a cannon ball; _i. e._ 480 miles every hour; this body would reach the Orbit of Mercury, in 7 years 221 days; of Venus, in 14 years 8 days; of the Earth, in 19 years 91 days; of Mars, in 29 years 85 days; of Jupiter, in 100 years 280 days; of Saturn, in 184 years 240 days; to the Comet of 1680, at it’s greatest distance from the Sun, in 2660 years; and to the nearest fixed Stars in about 7 million 600 thousand years.
[Sidenote: Why the Planets appear bigger and less at different times.]
90. As the Earth is not the center of the Orbits in which the Planets move, they come nearer to it and go farther from it and at different times; on which account they appear bigger and less by turns. Hence, the apparent magnitudes of the Planets are not always a certain rule to know them by.
[Sidenote: Fig. I.]
91. Under Fig. 3, are the names and characters of the twelve Signs of the Zodiac, which the Reader should be perfectly well acquainted with; so as to know the characters without seeing the names. Every Sign contains 30 degrees, as in the Circle bounding the Solar System; to which the characters of the Signs are set in their proper places.
[Sidenote: The Comets.]
92. The COMETS are solid opaque bodies, with long transparent trains or tails, issuing from that side which is turned away from the Sun. They move about the Sun, in very excentric ellipses; and are of a much greater density than the Earth; for some of them are heated in every Period to such a degree, as would vitrify or dissipate any substance known to us. Sir ISAAC NEWTON computed the heat of the Comet which appeared in the year 1680, when nearest the Sun, to be 2000 times hotter than red-hot iron, and that being thus heated, it must retain it’s heat until it comes round again, although it’s Period should be more than twenty thousand years; and it is computed to be only 575. The method of computing the heat of bodies, keeping at any known distance from the Sun, so far as their heat depends on the force of the Sun’s rays, is very easy; and shall be explained in the eighth Chapter.
[Sidenote: PLATE I.
Fig. I.
They prove that the Orbits of the Planets are not solid.
The Periods only of three are known.
They prove the Stars to be at immense distances.]
93. Part of the Paths of three Comets are delineated in the Scheme of the Solar System, and the years marked in which they made their appearance. It is believed, that there are at least 21 Comets belonging to our System, moving in all sorts of directions: and all those which have been observed, have moved through the ethereal Regions and the Orbits of the Planets without suffering the least sensible resistance in their motions; which plainly proves that the Planets do not move in solid Orbs. Of all the Comets, the Periods of the above-mentioned three only are known with any degree of certainty. The first of these Comets appeared in the years 1531, 1607, and 1682; and is expected to appear again in the year 1758, and every 75th year afterwards. The second of them appeared in 1532 and 1661, and may be expected to return in 1789 and every 129th year afterwards. The third, having last appeared in 1680, and it’s Period being no less than 575 years, cannot return until the year 2225. This Comet, at it’s greatest distance, is about 11 thousand two hundred millions of miles from the Sun; and at it’s least distance from the Sun’s center, which is 490,000 miles, is within less than a third part of the Sun’s semi-diameter from his surface. In that part of it’s Orbit which is nearest the Sun, it flies with the amazing swiftness of 880,000 miles in an hour; and the Sun, as seen from it, appears an hundred degrees in breadth; consequently, 40 thousand times as large as he appears to us. The astonishing length that this Comet runs out into empty Space, suggests to our minds an idea of the vast distance between the Sun and the nearest fixed Stars; of whose Attractions all the Comets must keep clear, to return periodically, and go round the Sun; and it shews us also, that the nearest Stars, which are probably those that seem the largest, are as big as our Sun, and of the same nature with him; otherwise, they could not appear so large and bright to us as they do at such an immense distance.
[Sidenote: Inferences drawn from the above phenomena.]
94. The extreme heat, the dense atmosphere, the gross vapours, the chaotic state of the Comets, seem at first sight to indicate them altogether unfit for the purposes of animal life, and a most miserable habitation for rational beings: and therefore [17]some are of opinion that they are so many hells for tormenting the damned with perpetual vicissitudes of heat and cold. But, when we consider, on the other hand, the infinite power and goodness of the Deity; the latter inclining, and the former enabling him to make creatures suited to all states and circumstances; that matter exists only for the sake of intelligence; and that wherever we find it, we always find it pregnant with life, or necessarily subservient thereto; the numberless species, the astonishing diversity of animals in earth, air, water, and even on other animals; every blade of grass, every tender leaf, every natural fluid, swarming with life; and every one of these enjoying such gratifications as the nature and state of each requires: when we reflect moreover that some centuries ago, till experience undeceived us, a great part of the Earth was judged uninhabitable; the Torrid Zone by reason of excessive heat, and the two Frigid Zones because of their intollerable cold; it seems highly probable, that such numerous and large masses of durable matter as the Comets are, however unlike they be to our Earth, are not destitute of beings capable of contemplating with wonder, and acknowledging with gratitude the wisdom, symmetry, and beauty of the Creation; which is more plainly to be observed in their extensive Tour through the Heavens, than in our more confined Circuit. If farther conjecture is permitted, may we not suppose them instrumental in recruiting the expended fuel of the Sun; and supplying the exhausted moisture of the Planets? However difficult it may be, circumstanced as we are, to find out their particular destination, this is an undoubted truth, that wherever the Deity exerts his power, there he also manifests his wisdom and goodness.
[Sidenote: This System very ancient, and demonstrable.]
95. THE SOLAR SYSTEM here described is not a late invention; for it was known and taught by the wise _Samian_ philosopher PYTHAGORAS, and others among the ancients; but in latter times was lost, ’till the 15th century, when it was again restored by the famous _Polish_ philosopher NICHOLAUS COPERNICUS, who was born at _Thorn_ in the year 1473. In this, he was followed by the greatest mathematicians and philosophers that have since lived; as KEPLER, GALILEO, DESCARTES, GASSENDUS, and Sir ISAAC NEWTON; the last of whom has established this System on such an everlasting foundation of mathematical and physical demonstration, as can never be shaken: and none who understand him can hesitate about it.
[Sidenote: The Ptolemean System absurd.]
96. In the _Ptolemean System_ the Earth was supposed to be fixed in the Center of the Universe; and that the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn moved round the Earth: above the Planets, this Hypothesis placed the Firmament of Stars, and then the two Crystalline Spheres; all which were included in and received motion from the _Primum Mobile_, which constantly revolved about the Earth in 24 hours, from East to West. But as this rude Scheme was found incapable to stand the test of art and observation, it was soon rejected by all true philosophers; notwithstanding the opposition and violence of blind and zealous bigots.
[Sidenote: The Tychonic System, partly true and partly false.]
97. The _Tychonic System_ succeeded the _Ptolemean_, but was never so generally received. In this the Earth was supposed to stand still in the Center of the Universe or Firmament of Stars, and the Sun to revolve about it every 24 hours; the Planets, Mercury, Venus, Mars, Jupiter, and Saturn, going round the Sun in the times already mentioned. But some of TYCHO’s disciples supposed the Earth to have a diurnal motion round it’s Axis, and the Sun with all the above Planets to go round the Earth in a year; the Planets moving round the Sun in the foresaid times. This hypothesis, being partly true and partly false, was embraced by few; and soon gave way to the only true and rational System, restored by COPERNICUS and demonstrated by Sir ISAAC NEWTON.
98. To bring the foregoing particulars at once in view, with several others which follow, concerning the Periods, Distances, Bulks, _&c._ of the Planets, the following Table is inserted.
A TABLE
Of the PERIODS, REVOLUTIONS, MAGNITUDES, &c. of the PLANETS.
+--------+------------+-------------+--------+--------+-------------+ |Sun and |Annual | Diurnal |Diameter| Mean |Mean distance| |Planets.|period | rotation | in |diam. as|from the Sun | | |round | on it’s |English |seen fr.| in English | | |the Sun. | Axis. |miles. |the Sun.| miles. | +--------+------------+-------------+--------+--------+-------------+ |Sun | ---- |25d. 6h. | 763000 | ---- | ---- | |Mercury | 87^d 23^h|Unknown. | 2600 | 20ʺ | 32,000,000 | |Venus | 224^d 17^h|24d. 8h. | 7906 | 30ʺ | 59,000,000 | |Earth | 365^d 6^h| 1d. 0h. | 7970 | 21ʺ | 81,000,000 | |Moon | 365^d 6^h|29d. 12-3/4h.| 2180 | 6ʺ | 81,000,000 | |Mars | 686^d 23^h|24h. 40m. | 4444 | 11ʺ | 123,000,000 | |Jupiter | 4332^d 12^h| 9h. 56m. | 81000 | 37ʺ | 424,000,000 | |Saturn |10759^d 7^h|Unknown. | 67000 | 16ʺ | 777,000,000 | +--------+------------+-------------+--------+--------+-------------+
+--------+------------+--------+---------+---------+---------+----------+ |Sun and |Excentricity| Axis |Orbit |Place of |Place of |Proportion| |Planets.| of it’s |inclined|inclined |it’s |it’s |of | | | Orbit |to |to |Aphelion.|Ascending|Diameters.| | |in miles. |Orbit. |Ecliptic.| |Node. | | +--------+------------+--------+---------+---------+---------+----------+ |Sun | ---- | 8° 0ʹ| ---- | ---- | ---- | 10000 | |Mercury | 6,720,000 | Unkn. | 6° 54ʹ |♐ 13° 8ʹ|♉ 14° 43ʹ| 34-1/10 | |Venus | 413,000 | 75° 0ʹ| 3° 20ʹ |♒ 4° 20ʹ|♊ 13° 59ʹ| 103-1/2 | |Earth | 1,377,000 | 23° 29ʹ| 0° 0ʹ |♑ 8° 1ʹ| ---- | 104-1/2 | |Moon | 13,000 | 2° 10ʹ| 5° 8ʹ | ---- |Variable.| 28-1/2 | |Mars |11,439,000 | 0° 0ʹ| 1° 52ʹ |♍ 0° 32ʹ|♉ 17° 17ʹ| 58-1/6 | |Jupiter |20,352,000 | 0° 0ʹ| 1° 20ʹ |♎ 9° 10ʹ|♋ 7° 29ʹ|1061-2/3 | |Saturn |42,735,000 | Unkn. | 2° 30ʹ |♐ 27° 50ʹ|♋ 21° 13ʹ| 878-1/9 | +--------+------------+--------+---------+---------+---------+----------+
+--------+----------+--------+----------+----------+--------+-------+--------+ |Sun and |Proportion|Prop. of|Proportion|Proportion|Propor. |Hourly |Hourly | |Planets.|of |Gravity |of | of |quantity|motion |motion | | |Bulk. |on the |Density. |Light |of |in it’s|of it’s | | | |surface.| |& Heat. |Matter. |Orbit. |Equator.| +--------+----------+--------+----------+----------+--------+-------+--------+ |Sun |877650 |24 |25-1/2 |45000 |227500 | ---- |3818 | |Mercury |1/27 |Unkn. |Unkn. |6-1/2 |Unkn. |95000 |Unkn. | |Venus |1 |Unkn. |Unkn. |1-3/4 |Unkn. |69000 |43 | |Earth |1 |1 |100 |1 |1 |58000 |1042 | |Moon |1/50 |34/100 |123-1/2 |1 ± |1/40 | 2290 |9-1/2 | |Mars |1/5 |Unkn. |Unkn. |3/7 |Unkn. |47000 |556 | |Jupiter | 1049 |2 |19 |1/28 |220 |25000 |25920 | |Saturn |586 |1-1/2 |15 |1/90 |94 |18000 |Unkn. | +--------+----------+--------+----------+----------+--------+-------+--------+
+--------+------------------+------------------------+-------------+ |Sun and | Square miles in |Cubic miles in solidity.|Would fall to| |Planets.| surface. | | the Sun in| | | | | | | | | | | +--------+------------------+------------------------+-------------+ |Sun | 1,828,911,000,000|232,577,115,137,000,000 | days h. | |Mercury | 21,236,800| 9,195,534,500 | 15 13 | |Venus | 691,361,300| 258,507,832,200 | 39 17 | |Earth | 199,852,860| 265,404,598,080 | 14 10 | |Moon | 14,898,750| 5,408,246,000 | 64 10 | |Mars | 62,038,240| 45,969,335,840 | 121 0 | |Jupiter | 20,603,970,000| 278,153,595,000,000 | 290 0 | |Saturn | 14,102,562,000| 155,128,182,000,000 | 767 0 | | | | | If the | | | | | projectile | | | | | force was | | | | | destroyed. | +--------+------------------+------------------------+-------------+ If the Moon’s projectile force was destroyed, she would fall to the Earth in 4 days 21 hours.
+---------+--------------++---------+--------------+ |Jupiter’s|Periods round || Saturn’s|Periods round | | Moons. | Jupiter. || Moons. | Saturn. | |---------+--------------||---------+--------------+ | N^o | D. H. M. || N^o | D. H. M. | |---------+--------------||---------+--------------+ | 1 | 1 18 36 || 1 | 1 21 19 | | 2 | 3 13 15 || 2 | 2 17 40 | | 3 | 7 3 59 || 3 | 4 12 25 | | 4 | 16 18 30 || 4 | 15 22 41 | +---------+--------------+| 5 | 79 7 48 | +---------+--------------+
CHAP. III.
_The_ COPERNICAN SYSTEM _demonstrated to be true_.
[Sidenote: Of matter and motion.]
99. Matter is of itself inactive, and indifferent to motion or rest. A body at rest can never put itself in motion; a body in motion can never stop nor move slower of itself. Hence, when we see a body in motion we conclude some other substance must have given it that motion; when we see a body fall from motion to rest we conclude some other body or cause stopt it.
100. All motion is naturally rectilineal. A bullet thrown by the hand, or discharged from a cannon would continue to move in the same direction it received at first, if no other power diverted its course. Therefore, when we see a body moving in a curve of whatever kind, we conclude it must be acted upon by two powers at least: one to put it in motion, and another drawing it off from the rectilineal course which it would otherwise have continued to move in.
[Sidenote: Gravity demonstrable.]
101. The power by which bodies fall towards the Earth is called _Gravity_ or _Attraction_. By this power in the Earth it is, that all bodies, on whatever side, fall in lines perpendicular to it’s surface. On opposite parts of the Earth bodies fall in opposite directions, all towards the centre where the force of gravity is as it were accumulated. By this power constantly acting on bodies near the Earth they are kept from leaving it altogether; and those on its surface are kept thereto on all sides, so that they cannot fall from it. Bodies thrown with any obliquity are drawn by this power from a straight line into a curve, until they fall to the Ground: the greater the force by which they are thrown, the greater is the distance they are carried before they fall. If we suppose a body carried several miles above the Earth, and there projected in an horizontal direction, with so great a velocity that it would move more than a semidiameter of the Earth, in the time it would take to fall to the Earth by gravity; in that case, if there were no resisting medium in the way, the body would not fall to the Earth at all; but continue to circulate round the Earth, keeping always the same path, and returning to the point from whence it was projected, with the same velocity as at first.
[Sidenote: Projectile force demonstrable.]
102. We find the Moon moves round the Earth in an Orbit nearly circular. The Moon therefore must be acted on by two powers or forces; one which would cause her to move in a right line, another bending her motion from that line into a curve. This attractive power must be seated in the Earth; for there is no other body within the Moon’s Orbit to draw her. The attractive power of the Earth therefore extends to the Moon; and, in combination with her projectile force, causes her to move round the Earth in the same manner as the circulating body above supposed.
[Sidenote: The Sun and Planets attract each other.]
103. The Moons of Jupiter and Saturn are observed to move round their primary Planets: therefore there is such a power as gravity in these Planets. All the Planets move round the Sun, and respect it for their centre of motion: therefore the Sun must be endowed with attracting force, as well as the Earth and Planets. The like may be proved of the Comets. So that all the bodies or matter in the Solar System are possessed of this power; and perhaps so is all matter whatsoever.
104. As the Sun attracts the Planets with their Satellites, and the Earth the Moon, so the Planets and Satellites re-attract the Sun, and the Moon the Earth: action and re-action being always equal. This is also confirmed by observation; for the Moon raises tides in the ocean, the Satellites and Planets disturb one another’s motions.
105. Every particle of matter being possessed of an attracting power, the effect of the whole must be in proportion to the number of attracting particles: that is, to the quantity of matter in the body. This is demonstrated from experiments on pendulums: for, if they are of equal lengths, whatever their weights be, they always vibrate in equal times. Now, if one be double the weight of another, the force of gravity or attraction must be double to make it oscillate with the same celerity: if one is thrice the weight or quantity of matter of another, it requires thrice the force of gravity to make it move with the same celerity. Hence it is certain, that the power of gravity is always proportional to the quantity of matter in bodies, whatever their bulks or figures are.