Podcaster: Fraser Cain and Dr Pamela Gay
Title: Astronomy Cast Ep. 319: The Zodiac
Organization: Astronomy Cast – http://www.astronomycast.com
Link : This episode has been streamed live on http://www.youtube.com/watch?v=nd_DYgU9k-c
Description: Although the Zodiac is best known for astrology nonsense, it has a purpose in astronomy too. The constellations of the Zodiac define the plane of the ecliptic: the region where the Sun, Moon and planets appear to travel through the sky. What are the constellations of the Zodiac, and how do astronomers use them as way points?
Bio: Fraser Cain is the publisher of Universe Today and Dr. Pamela Gay is a professor at Southern Illinois University-Edwardsville. They team up to do Astronomy Cast, a weekly facts-based journey through the cosmos.
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365 Days of Astronomy
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I’m afraid you’ve fallen into a common pitfall when critiquing astrology. Let me say from the start I do not believe in astrology as a valid system of analyzing or predicting human behavior. However, as an amateur historian of Medieval Natural Philosophy, I have studied some of its tenants and principals from an academic point of view.
The terminology used in astrology is ‘sign of the zodiac’, not ‘constellation of the zodiac’. These are two very different things. Trained astrologers are well aware of the procession of the equinoxes and that the signs of the zodiac don’t align with the constellations through which the ecliptic passes. The signs of the zodiac are simply a method of depicting ecliptic longitude. Stating with the First Point of Aries the first thirty degrees circling westward are labeled Aries 0 – 30. For example, the twelfth degree of Gemini would be ecliptic longitude 72 degrees and the second degree of Sagittarius corresponds to ecliptic longitude 242 degrees. This method originated in antiquity and was used in scientific literature into the 19th century.
There are lots of things that can be critiqued about astrology, but their historically-based method of utilizing the signs of the zodiac is not one of them.