That's a great question! The
That's a great question! The answer is steeped in history and myth but unfortunately is beyond the scope of this format. We suggest that you ask your local public library to locate resources detailing the history of Western astrology. Try searching for information about Empedocles, Aristotle, and other Greek philosophers who studied the four elements (some added a fifth element, Aether), and Ptolemy, who is said to have linked them to zodiac signs. (His work called Almagest might give some clues.) Also check ancient Mesopotamian, Babylonian, and Hellenistic astrology/astronomy. You might also be interested in comparing this to Indian astrology, as well as to the five elements of Chinese astrology (earth, fire, water, metal, and wood) and their associated planets.