The Tropical and Sidereal Zodiac

Despite all the recent activity on the Internet regarding "wrong Zodiac signs" the debate over sidereal versus tropical astrology is actually quite old. It is in fact largely a "east versus west" difference in methodology - European astrologers generally use the tropical system, in which the sign Aries begins on the Vernal Equinox, while Vedic astrologers in India use the sidereal system, in which the signs are determined in reference to the actual location in the sky of the specific constellations.

Here's what started off the latest round of posts and comments:

According to Parke Kunkle, a board member of the Minnesota Planetarium Society, cool or not, it's written in the stars. Star signs were created some 2,000 years ago by tracking where the sun was in the sky each month. However, the moon's gravitational pull has slowly moved the Earth in its axis, creating about a one-month bump in the stars' alignment, reports the Minnesota Star Tribune. Now, during what we think as the month of Pisces, the sun is actually in the sign of Aries.

The new dates would therefore be:

Capricorn: Jan. 20-Feb. 16
Aquarius: Feb. 16-March 11
Pisces: March 11-April 18
Aries: April 18-May 13
Taurus: May 13-June 21
Gemini: June 21-July 20
Cancer: July 20-Aug. 10
Leo: Aug. 10-Sept. 16
Virgo: Sept. 16-Oct. 30
Libra: Oct. 30-Nov. 23
Scorpio: Nov. 23-Dec. 17
Sagittarius: Dec. 17-Jan. 20

All that really happened here is that Kunkle discovered the sidereal Zodiac - the one that's been used in India for many centuries - and presented it as some sort of new revelation. As a matter of fact, if a Vedic astrologer did your chart and you were born at the beginning of May, your Sun sign would indeed come out as Aries rather than Taurus. My Sun is still in Taurus in my Vedic chart, but only because I was born on May 18th at the very end of the sign.

So does this mean Western mystics and magicians should change the dates for the signs? It could be argued, of course, that charts done using the two systems are both accurate but give insight into different factors of personality or destiny. It seems to me, though, that it might be possible to use science to answer this question. To do this, we need to have some idea of how astrology influences personality. We know that there is no scientific evidence for "energy waves" or "gravitational fields" related to astrological influences. So what else might be a possible explanation?

My working hypothesis about astrology is that it is an organic system that evolved over time to explain the influence of natural cycles on the various areas of life that are said to be ruled by particular planets. Modern astrology has moved away from the more predictive Medieval model and in the direction of personality typing. From this standpoint, the clock analogy is fairly obvious. Nobody argues, for example, that human hormonal cycles seems to follow a pattern in which the cycle length is approximately one lunar orbit. It is the significance of longer cycles that is more controversial.

Recent research has found evidence that the solar cycle is important as well - it turns out that the season in which mice are born seems to have some influence on health and personality.

This study, conducted on mice, showed that mice born in the winter showed a "consistent slowing" of their daytime activity. They were also more susceptible to symptoms that we might call "Seasonal Affective Disorder."

Whether or not this can be applied to humans remains to be seen, but it's wiorth noting that the two signs most associated with winter months, Capricorn and Aquarius, are ruled by Saturn under the system that was in use prior to the recent discovery of the outer planets. These "winter traits" certainly sound Saturnine to me. And since the effect is seasonal, this would support the tropical rather than the sidereal model of the signs.

"What is particularly striking about our results is the fact that the imprinting affects both the animal's behavior and the cycling of the neurons in the master biological clock in their brains," said Ciarleglio. This is one of the core principles of astrology: That the position of the planets at the time of your birth (which might be called the "season" of your birth) can actually result in changes in your brain physiology which impact lifelong behavior.

The explanation for this in humans could prove positively prosaic. Depending on the season in which we are born, the first year of our lives will progress differently. Children born in the spring will likely spend much more time outdoors in their early months, for example, while those born in the winter will have to wait until the weather improves. Is it much of a stretch to view astrology as a proto-scientific distillation of how our reactions to those conditions can shape our personalities?

So far research has not been done on birth time, which would relate to the Ascendant, so it's unclear whether or not there is any normal scientific basis to the claims of astrology in that area. But if such research does return positive results, the conclusion that our astrological personalities are largely described by Sun Sign, Moon Sign, and Ascendant starts to look feasible. This model suggests that the time of the year is what we should be looking at for Sun Sign, not where the Sun is in reference to any particular section of the night sky. If you were born in the spring, you were born in the spring - plain and simple.

Testing this hypothesis would be relatively easy - with a large sample we should expect to see greater conformation of personality types to astrological signs in parts of the world where the climate changes the most between summer and winter. Scientists could also compare people who are born in the southern versus the northern hemisphere, where the seasons are reversed. The problem with getting this sort of research done has nothing to do with testing methodologies and everything to do with the fact that anyone looking to perform it is going to encounter all sorts of problems securing funding in our current academic environment.

So my advice to anyone who is wondering about this would be to leave your tropical Zodiac sign as is, unless of course you want to visit a Vedic astrologer and see what they come up with for your entire chart.