123. Babylonian Discovery of the Planets
The Babylonians, together with the Egyptians, were also the first astronomers. The Egyptians turned their interest to the sun and the year, and devised the earliest accurate solar calendar. The Babylonians lagged behind in this respect, adhering to a cumbersome lunar-solar calendar. But they acquired more information as to other heavenly phenomena: the phases of the moon, eclipses, the courses of the planets. They devised the zodiac and learned to half predict eclipses. It is true that their interest in these realms was not scientific in the modern sense, but sacerdotal and magical. An eclipse was a misfortune, an expected eclipse that did not “come off,” a cause for rejoicing. Yet this superstitious interest did lead the Babylonians to genuine astronomical discoveries.
Among these was the observation that five luminaries besides the sun and moon move regularly across the heavens, visible to the naked eye and independent of the host of fixed stars: the planets that we call Mercury, Venus, Mars, Jupiter, and Saturn. This impressive fact must have significance, they felt, and from anthropocentric reasons they found the significance in the influence of these bodies on the fortunes of men. This was the beginning of astrology, which charlatans and dupes still practise among ourselves, but which in its youth represented one of the triumphs of civilized knowledge. The planets were identified with gods by the Babylonians, at any rate named after gods.
It is even probable that the ancient priest-astronomer-magicians were driven to distinguish the full set of observable planets by their desire to attain the full number seven. It is not an obvious thing by any means that the all-illuminating sun should be set on a par with moving stars that at times are no more conspicuous than some fixed ones. No people unaffected by the Babylonian precedent has ever hit upon the strange device of reckoning sun and moon as stars. Then, too, Mercury is perceptible with difficulty, on account of its proximity to the sun. It is said that great astronomers of a few centuries ago sometimes never in their lives saw this innermost of the planets with naked eye, at least in northern latitudes. It seems possible therefore that its Babylonian discovery may have been hastened by an eagerness to attain the perfect seven for the number of the traveling bodies.