Monday, January 17, 2011

Astronomical BS

 A few years back, a friend and I got into an argument about astrology. She started telling me how much of a Gemini I am and how I very clearly match all the personality traits. As an experiment, I decided to screw with her and see how she reacted:  

Me: Actually, due to the precession of the equinoxes in the year I was born, I'm actually a Taurus. It's a very rare phenom. Most astrologists don't even know about it.  My birth year was the only time it's happened in the last 153 years.1

Her: Oh my God!  That's so amazing!  I've always thought you acted like a Taurus.  Now I know why!

She then proceeded telling me how much of a Taurus I am and how I very clearly match all the personality traits.   I've repeated this experiment several times with different people, always with similar results.  No matter what sign I give, cognitive dissonance sets in, then there's rationalization, then I'm told how much of a [fill in the blank] I am and how I very clearly match all the personality traits.

Apparently, my little experiment was coincidentally prescient.  In light of the latest astrological buzz, it turns out I actually am a Taurus.2  Unbeknownst to people who follow astrology, the zodiac calendar has been wrong for years.  In addition to the various dates being off, there's also a 13th astrological sign that was left out.  How many astrology-believing Americans just had their signs switched?

Despite the absence of evidence or even a plausible mechanism3, many Americans still believe the stars control our personalities.  According to Michael Shermer's Why People Believe Weird Things, a 1990 Gallup poll showed that 52% of Americans believe in astrology.  There's very little overlap between the zodiac calendar and the actual positions of constellations in the sky. For this reason, about 90% of people's zodiac signs changed. This means that

(3.0×108 Americans) · (0.52 believers per American) · (0.9 zodiac changes)
= 1.4×10
8 zodiac sign changes.

That's 140 million people and a whole lot of cognitive dissonance.  Thank you, Laurie for suggesting this one.

[1] At this point, I was basically making things up and throwing in ad-libed technical jargon.  The actual "precession of equinoxes" has nothing to do with astrology.
[2] But, no, this does not justify my astrologist friend's assertion.  As mentioned earlier, it doesn't matter what sign I give, astrologers will always say my personality matches.

[3]  And, no, the fact that the moon controls the tides does not constitute a mechanism.  Tidal forces are due to gravity, and as I show in How Many Licks?, the tidal force on you at birth due to the obstetrician is about 40 times larger than the largest tidal force of any heavenly body.

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