2.4: Planets and the Zodiac
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Not all stars keep fixed positions on the sphere of the heavens. Even early sky-watchers noted that a few moved about: the ancient Greeks called them “planets", which translates to wanderers. The names we use today came from the Romans, who named them after their chief gods --- Mercury, Venus, Mars, Jupiter and Saturn. Mercury and Venus are always close to the Sun and can only be seen shortly after sunset or before sunrise: Mercury is so close that most of the year it cannot be seen at all, because the bright sky drowns out its light. Venus is brighter than any other star (with appropriate conditions and looking right at it, you can see it even in the daytime) and Jupiter takes second place.