Solar System, the planets and comets which circle round the sun; also called planetary system. No change of much magnitude can take place in the elements of the planets without having effect on the earth and its inhabitants, on account of the mutual attractions of the planets for each other; in fact, they appear as members of one family, bound together by common ties, which could not be ruptured in the case of one individual without communicating a general shock to the others. The various members of the solar system, and their motions, are noticed under PLANETS, COMET, SUN, MOON, SATELLITES, METEORS, GRAVITATION, CENTRE, PRECESSION, ECLIPSE, &c., so that it only remains here to tabulate the more interesting numerical facts connected with them.
| Name. | Diameter in Miles. | Density, Earth's being = 1. | Mass, Sun's being = 1. | Distance from Sun in Millions of Miles. | Period of Revolution, in Days. | Velocity in Orbit—Miles per Hour. | Velocity of Rotation at Equator—Miles per Hour. | Force of Gravity on Surface (Earth = 1). |
|---|---|---|---|---|---|---|---|---|
| Mercury..... | 3,008 | 1.26 | 0.055 | 36 | 88 | 107,012 | 392 | 0.47 |
| Venus..... | 7,480 | 0.92 | 0.815 | 66 | 225 | 78,284 | 1,006 | 0.87 |
| Earth..... | 7,926 | 1.00 | 1.00 | 92 | 365 | 66,579 | 1,040 | 1.00 |
| Mars..... | 4,999 | 0.45 | 0.107 | 141 | 687 | 53,938 | 638 | 0.28 |
| Jupiter..... | 88,439 | 0.23 | 3.178 | 483 | 4,332 | 29,203 | 28,001 | 2.55 |
| Saturn..... | 75,036 | 0.11 | 0.302 | 886 | 10,759 | 21,560 | 22,476 | 1.15 |
| Uranus..... | 30,875 | 0.25 | 0.046 | 1783 | 30,687 | 15,202 | 10,210 | 0.85 |
| Neptune..... | 37,205 | 0.17 | 0.055 | 2794 | 60,127 | 12,156 | ? | 0.80 |
| Sun..... | 866,200 | 0.25 | 1.00 | .. | .. | .. | 6,567 | 23.71 |
| Moon..... | 2,160 | 0.63 | 0.00123 | .. | .. | 2,273 | 10 | 0.15 |