I'm Sagittarian. Unless I'm not...

As an employee of a reasonably-professional accommodation provider, I am required to work the occasional breakfast shift. As if the horror of getting up at 4:30am isn't enough, the powers that be insist that we broadcast mindless drivel on the restaurant's television.

Now I don't know anyone that's going to claim that Channel Seven's Sunrise program even vaguely resembles quality programming, but last Sunday's episode was something special. Not half an hour after broadcasting this attempt at balanced journalism the Sunrise crew were throwing to their resident astrologer for the daily horoscopes.

As was explained in the aforementioned video, astrology is the pseudoscience that claims that the positions of the stars and planets can be analysed in order to provide information about human personalities, behaviours and the workings of society in general. In the West this tradition manifests itself most frequently in the form of horoscopes which can be found in trashy magazines and newspapers everywhere. These lovely snippets of "information" claim to provide predictions about the future, based solely on the reader's date of birth.
According to astrologers a person's zodiac sign is determined by the position of the sun relative to the background stars on the date of their birth and that person will have certain character traits determined by their particular zodiac sign. For example, between November 23 and December 22 the sun is said to appear in the constellation of Sagittarius and therefore, with my birthday falling on the 25th of November, I am said to be a Sagittarius. According to Astrology.com.au Sagittarians are extremely confident, prone to bouts of good fortune, are known for their contagious enthusiasm and so on.

But there are some major problems with this theory. Firstly, in order to believe what astrologers tell us, we must convince ourselves that the position of the sun at a particular date, relative to the background stars, can actually affect an individual's personality. Exactly how it does this is a mystery but Astrology.com.au offers this helpful explanation;

"...our luminescent sun apparently moves month by month throughout the year, transceiving the energy of those different constellational signs and thereby transmitting the celestial radiations to our Earth".

Ok, so that makes perfect sense. The sun somehow grabs some sort of mystical personality-building energy from constellations that are millions of kilometres away (the closest star in the Sagittarius constellation is Ross 154 and is located 91,577,915,000,000 kilometres from the sun) and beams it down to earth. Sounds very scientific to me.

Secondly, even if it's true that the position of the sun at the time of my birth imbues me with certain character traits, astrologers would have us believe such traits are common to all Sagittarians. That is, everyone born between November 23 and December 22 is supposed to share a set of common character traits. I find it rather difficult to believe that everyone born between these dates is confident, lucky and enthusiastic as I supposedly am.

Even if we believe all of that, there is still one major hurdle to overcome. When the Babylonians first drafted the Zodiac around 2,500 years ago, the sun was in the constellation of Sagittarius between November 23 and December 22. However, thanks to the efforts of Greek fellows like Aristarchus of Samos, Hipparchus of Rhodes and Ptolemy we now know of the phenomenon known as "axial precession".

While you may know that the Earth spins while in it's orbit around the Sun, you might not know that it spins off-centre. While we are taught to think of the Earth as spinning around a vertical axis, this axis is actually tilted by 23 degrees. In addition to causing the different seasons that we experience on Earth, the tilt of the Earth's rotational axis has a secondary effect. As this short clip demonstrates, by having an axis that is a certain amount away from the vertical, the axis of rotation actually moves over a period of time. This results in a gradual change in our observable "star field".
Imagine you are lying in the dentist's chair at the end of a check-up, focused on a spot on the ceiling. Imagine too that you can't move your eyes at all and that you are forced to look straight ahead. As the dentist changes the angle of the chair to bring you into an upright position, your eyes, unable to look around, will trace a straight line from the ceiling down the wall. Axial precession is kind of like that - as the angle of the Earth's rotational axis changes, so what we can see from our vantage point on the Earth changes.

So, what does this have to do with astrology and the Babylonians? Well, as I mentioned, the signs of the Zodiac were first assigned around 2,500 years ago. Since that time axial precession has changed the apparent location of the background stars. So, the Sun, which once appeared to be in the constellation of Sagittarius on the 25th of November now appears to be in the constellation of Scorpio. Therefore I am no longer "a Sagittarius", instead I am "a Scorpio".
In order to be a Sagittarius now I would need to be born between December 18th and January 19th.

Well that's all pretty clear cut isn't it? Astrology is a pseudoscience that makes claims above and beyond its station without considering the workings of relevant celestial phenomena.
But two days after watching Sunrise at work I stumbled upon a book at my local shopping centre that I couldn't resist flicking through. It was "What Your Birthday Reveals About You" by Phyllis Vega and it claimed to provide "astonishingly accurate revelations about your future, your secrets and your strengths" based, you guessed it, on the individual's zodiac sign. I flicked sceptically to November 25 and read through some of my alleged character traits;

• Those born on November 25 are inclined to live "intense lives of crusading ideals"

• Although I "give the impression of being a bit of a loner", I'm "actually searching for meaningful ways to connect with other people"

• I could "satisfy my creative muse...as a writer, journalist, publisher, artist, musician or actor"

• I am "a natural athlete with a genuine love of the outdoors".
  

I could go on. Scarily, all of these suggestions are quite true and as I read on, more and more of the statements seemed to be accurate. I faced a brief internal struggle - "I know astrology is bogus, but how are these predictions so accurate?"
And then it occured to me. If astrology is an accurate and consistent scientific pursuit then surely these predictions are based on some immutable, objective truth that is directly related to my date of birth. Consequently, if I was to go to another source of birthday-based wisdom, I would find similar, if not exactly the same results. So, does Astrology.com.au say the same things as Phyllis Vega about those of us born on November 25?

Life of crusading ideals? Not mentioned. Loner with intent to communicate at a higher level? Not in so many words. Suited for a creative career like journalism? Not quite. Naturally sporty? Doesn't come up.
However, I am apparently blessed with a colourful imagination and a rare tolerance for others. Are either of these mentioned in Ms. Vega's book? I think you know the answer to that...