Saturday, January 15, 2011

Think losing your zodiac is bad? Try your birthday

There's been a lot of fuss lately about the Minnesota Planetarium Society's recent re-alignment of the zodiac, which added a new sign to the group and threw almost everything we thought we knew about our star signs out the window.

But moving your birthday to a new zodiac sign —even one with such a tongue-twisting name as Ophiuchus— really isn't so bad.

In 1582, Pope Gregory XIII decreed that ten days be removed from the calendar to make it more accurately reflect changes in the seasons. Thus, the day after Thursday, October 4, became Friday, October 15, 1582.

And so, if you were unlucky to have been born within the second week of October, you were suddenly out of a birthday.

Pope Gregory's decision was disconcerting, but necessary: it addressed a very small error in the calendar being used throughout Europe since the time of Julius Caesar.

Among other things, the so-called Julian calendar was off by eleven minutes in a year. A very small amount, to be sure, but it added up over the centuries until the discrepancy became a matter of days.

And so we continue to use this "reformed" system, which is still known today as theGregorian calendar.

Disconcerting but necessary change

To be fair to the ancients, it's not that they weren't able to measure time accurately. It's just that the heavens don't like being bound to our mortal conventions.

Regardless of whether you're an astronomer or an astrologer, the fact is that whatever measuring system you use —be it a calendar or a zodiac— has to be regularly updated to account for changes in the seemingly regular movements of heavenly bodies.

Minnesota Planetarium Society board member Parke Kunkle rightly pointed out that the Earth's precession or "wobble" around its axis, caused partly by the Moon's gravitational pull, makes the years grow longer over time. 

This, in turn, changed the appearance of the constellations in the sky ever-so-slightly over thousands of years. By now, the difference is so great that the ancient Babylonian zodiac needed to be adjusted to account for the discrepancy.

Sounds familiar? This is essentially the same reason why there were so few birthday parties that fine autumn in 1582.

And astrologers are well aware of this fact.

"We've known about this for ages. The constellations don't suggest what's coming up, it's the planets! The constellations are (just) a measuring device," popular astrologer Susan Miller told ABC News in an interview.

"In ancient days there were, like, 50 constellations. Then they finally got together and agreed on 18. Then they narrowed it down (even further)," Miller added.

There's more to astrology than you think

The problem, according to astrologers, is that popular culture has painted an overly simplified view of their craft.

"Those so-called horoscope columns in the newspapers were designed as a publicity stunt to increase circulation. As a result, most people think that all there is to astrology is to know about your 'sign'. (That is) absolutely untrue. Sun-sign columns are most emphatically not real astrology. I denounce them at every turn," said professional astrologer Bob Marks on his website.

In the same website entry, Marks addresses the perceived inaccuracy of astrology due to precession:

"There are TWO zodiacs, the tropical and the sidereal. The vast majority of astrologers use the tropical. In that zodiac, the signs have not changed. (Also,) constellations do not really exist at all. Astrologers know this. Constellations are used as place markers, nothing more," he explains.

"The Zodiac, the twelve divisions of the sky made up of the horoscope signs, and the Zodiac, the band of constellations in the sky, are two different things. This is how a lot of skeptics of astrology trick people to convince themselves and others that there's nothing to astrology. But in reality, we're talking about two different things," elaborated professional astrologer and author Matthew Currie in an interview with

Whatever you may think about astrology, it's a very rigorous discipline.

Tough time for science

Scientists don't have it any easier, though.

The International System of Units (SI) measures time in multiples of a second, which has a pre-defined duration based on atomic movement. This means there should be 31,556,952 seconds in a Gregorian year.

That's assuming that the planets move with the same precise regularity as the atoms that they're made of. But they don't, and here's where precession rears its ugly head once again.

To keep time measurements in step with the longer years brought about by precession, scientists have agreed to introduce a "leap second" every now and then.

The first leap seconds were added to the calendar on June 30 and December 31, 1972. Since then, a total of 22 leap seconds have been added, the last one in 2008.

No matter what calendar or zodiac we end up using, such minute adjustments will help make sure that the movements of the heavens match up with our earthly measurements. 

It's certainly a much smaller price to pay than losing your birthday.

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