Mars has been studied in much detail and, of all the planets, has excited the most popular interest. Conditions are such that markings, mysterious at this distance, and colorful details, may be studied with comparative ease. The other planets that have been studied are too far away, too close to the sun, or are obscured by too cloudy atmospheres to permit detailed observations. The great planet Jupiter forms a magnificent picture, his broad face striped by colored bands which occasionally vary. This planet may be seen to turn completely around in 9 hours and 50 minutes, while four of its moons revolve about it in close attendance. Saturn is even more superbly magnificent than Jupiter, for the great, flat, shining ring which encircles this planet is the wonder of the whole solar system.
Because the planets are so much closer than the stars, they may be seen to change their places against the background of the constellations. An almanac will tell which of these worlds are visible in the evening during the different months and where they may be found. Since they lie nearly in the same plane as the orbit of the earth, they are always found within the boundaries of a pathway 16 degrees wide. This pathway circles the sky and is marked by the sun in the daytime and the moon at night. All the planets except Mars, Venus and Mercury travel nearly in the middle of this path which in ancient times was named the zodiac.
The constellations which lie along the pathway of the sun, moon and planets are called the constellations of the zodiac. The following are the Latin names of the signs of the twelve parts of the zodiac, with their English equivalents:
| Spring: | Aries, the Ram ♈︎ |
Summer: | Cancer, the Crab ♋︎ |
| Autumn: | Libra, the Scales ♎︎ |
Winter: | Capricornus, the Goat ♑︎ |
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