Astrology question

I was watching a show from the Discovery Science channel the other night and they said that, due to astrologers basing their predictions on the old Julian calendar instead of the Gregorian calendar that we use today, nobody was actually born under the sign they think they were; it’s actually shifted by a whole sign. So if you’ve spent your whole life thinking you’re a Scorpio, you’re actually a Virgo (or whatever, I don’t know the order of the signs.)

I’m asking for clarification because I was only mostly paying attention. Is my basic understanding of what they said correct, and where can I read more about this?

I’ll be completely honest: I’d love to have one more reason to ROFL at people who believe astrology and this, if true, is a whopper. It’s the best one I’ve ever heard.

I think you’re after precession of equinoxes rather than Julian vs. Gregorian calendar. May I recommend two websites for you? -
Phil Plait - Misconceptions about Precession of Equinoxes
Phil Plait - Overall misconceptions about Astrology

Between the two sites, he pretty much covers every argument the astrologers have managed to come up with.

I don’t think the calander shift is the culprit (it might have something to do with it, I could be wrong), but rather precession, the wobbling of the Earth’s axis. Astrology doesn’t exactly use the constellations themselves, but rather 12 equal “houses” that no longer correspond to the constellations due to precession. They didn’t precisely correspond to the constellations before, either, because they were equal and the consellations aren’t; the sun is actually in Virgo for something like 40 days and Aries for something like 7. In an older thread somebody linked to a neat website that told you what your actual Zodiac sign should be accounting for precession and the size of the constellation, but it looks like it may have gotten lost in the move.

ETA: or, what the Bad Astronomer said. :slight_smile:

I think this is it, from Yeticus Rex in a previous thread. Scroll down a bit.

This is correct. It is one (among the least of them) problem I have with astrology. Clearly it isn’t the influence of the stars determining your fate, if the stars you were actually “born under” aren’t the ones used to determine your horoscope.

I will also add that in modern context, a constellation is a rather arbitrarily defined patch of sky, not just the stars that define the namesake “sign” (the “big dipper” stars of Ursa Major for example). That is properly known as an asterism.