Cosmos - Carl Sagan [28]
Modern popular astrology runs directly back to Claudius Ptolemaeus, whom we call Ptolemy, although he was unrelated to the kings of the same name. He worked in the Library of Alexandria in the second century. All that arcane business about planets ascendant in this or that solar or lunar “house” or the “Age of Aquarius” comes from Ptolemy, who codified the Babylonian astrological tradition. Here is a typical horoscope from Ptolemy’s time, written in Greek on papyrus, for a little girl born in the year 150: “The birth of Philoe. The 10th year of Antoninus Caesar the lord, Phamenoth 15 to 16, first hour of the night. Sun in Pisces, Jupiter and Mercury in Aries, Saturn in Cancer, Mars in Leo, Venus and the Moon in Aquarius, horoscopus Capricorn.” The method of enumerating the months and the years has changed much more over the intervening centuries than have the astrological niceties. A typical excerpt from Ptolemy’s astrological book, the Tetrabiblos, reads: “Saturn, if he is in the orient, makes his subjects in appearance dark-skinned, robust, black-haired, curly-haired, hairy-chested, with eyes of moderate size, of middling stature, and in temperament having an excess of the moist and cold.” Ptolemy believed not only that behavior patterns were influenced by the planets and the stars but also that questions of stature, complexion, national character and even congenital physical abnormalities were determined by the stars. On this point modern astrologers seem to have adopted a more cautious position.
But modern astrologers have forgotten about the precession of the equinoxes, which Ptolemy understood. They ignore atmospheric refraction, about which Ptolemy wrote. They pay almost no attention to all the moons and planets, asteroids and comets, quasars and pulsars, exploding galaxies, symbiotic stars, cataclysmic variables and X-ray sources that have been discovered since Ptolemy’s time. Astronomy is a science—the study of the universe as it is. Astrology is a pseudoscience—a claim, in the absence of good evidence, that the other planets affect our everyday lives. In Ptolemy’s time the distinction between astronomy and astrology was not clear. Today it is.
As an astronomer, Ptolemy named the stars, listed their brightness, gave good reasons for believing mat the Earth is a sphere, set down rules for predicting eclipses and, perhaps most important, tried to understand why planets exhibit that strange, wandering motion against the background of distant constellations. He developed a predictive model to understand planetary motions and decode the message in the skies. The study of the heavens brought Ptolemy a kind of ecstasy. “Mortal as I am,” he wrote, “I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the Earth …”
Ptolemy believed that the Earth was at the center of the universe; that the Sun, Moon, planets and stars went around the Earth. This is the most natural idea in the world. The Earth seems steady, solid, immobile,