The New York Times posted a great article this morning on astrology (via Jasper Palfree).  This has got me thinking again about the (im)possibility of astrology. Below are some of my thoughts on the stars, fate, gravity, Neptune, and my cat. Over the centuries the Earth has been precessing or wobbling as it orbits the sun.  This wobbling has changed the Earth's orientation with respect to the stars, causing a gradual realignment of the Zodiac signs.

> According to the report, Capricorn, which astrologers say begins its monthlong term in December, actually starts on Jan. 20, based on the actual position of the stars. Aquarius, meanwhile, would be bumped to February. And so on.

This has led to quite the outcry on Twitter amongst astrology followers:

>“My zodiac sign changed,” wrote one upset Twitter user on Friday morning. “Does that mean that I’m not anymore who I used to be?!?”

That comment highlights the main reason I have a serious problem with astrology. Everyday millions of people look to the stars and planets for guidance. These people trust astrologers to make critical life decision, throwing away reason, common sense, and their money. I am certain that many - perhaps most - astrologers are true believers and are sincere in their practice. I respect others beliefs and their right to have them, but my respect ends when those beliefs are used to inflict harm on others.

Astrology Fail

Astrologers are in damage control mode right now, pointing out that they have known about the Earth's tilt and account for it. One of the astrologers quoted in the NY Times article is Robert Brezsny. Brezsny claims: > “Astrology is a poetic language of the soul, not a scientific method,” he said, likening it to “a Neruda poem, Kandinsky paintings or a Nick Cave song.”

>“None of those things are rational or scientific,” he added.

Whenever the methods of astrologers are tested, they fall back on the standard defence that what they are doing is beyond the realm of science, and that scientist fail to understand the true methods behind astrology. The problem is that astrologers seem to be woefully ignorant of physics. Here is an excerpt from Brezsny's website:

> To reiterate: Western astrologers don't work with stars or constellations. Their focus is our solar system. They study the patterns of the planets and the moon as they pass through 12 zones defined by the relationship between the Earth and sun. Those zones have the same names as constellations because of a historical quirk, but they are unrelated to the constellations.

Is there any scientific basis for astrology?

No. This is the one area I agree with Brezsny. If the alignment of the planets and constellations can influence our personalities and fortunes, then there must be some force behind this influence. The only force we know of in nature that can have a significant influence on such cosmic scales is gravity.

All objects with mass exert a gravitational force on each other. We are attracted to the Earth, the Earth to the Sun, Mars to the Earth, my cat to me and so on. It does not matter what the object is made of, gravity acts in the same way. A kilogram of feathers and a kilogram of gold both exert the gravitational force.

Now take Neptune, one of the planets commonly used in astrological predictions. A quick calculation shows that the gravitational force that Neptune exerts on me is much smaller than the gravitational force I experience from my cat when she sits on my lap. At the moment of my birth, the doctors and nurses around exerted a far greater gravitational force on me than Neptune. But the mechanism behind astrology does not account for these and other important contributions.

cat vs. neptune

Clearly it is not gravity that is responsible for astrology. There must be some other force at play that does not depend on the distance and has a sharp influence on human psychological development at the exact moment a child leave its mother's womb. Such a force is certainly outside of the realm of science.

Is astrology testable?

Perhaps astrology is really driven by some mechanism that goes beyond science. Even if we don't understand the underlying mechanism there must be some test we can do. The reason one goes to an astrologer is to seek advice and predictions. This advice is testable--we should be able to measure the accuracy of these predictions over time.

A famous experiment took place in 1985 with the resulting study published in the journal Nature. The investigators worked with 30 expert astrologers to devise a test to see how well the astrologers could predict ones personality from their natal/birth chart. Each astrologer was given a natal chart along with three personality assessments: one assessment belonged to the person whose natal chart the astrologer possessed while the other two were from other individuals. The astrologers tried to match the natal chart to the correct profile. The astrologers succeeded one in three times at making the correct match--the same result as if they had randomly guessed. My cat could have done as good of a job matching the personality profiles as these expert astrologers. An excellent summary of the results can be found here.

The cat astrologer

Astrologers may argue that the test was biased or was unfair in someway. Even if this was so (I doubt it), there must exist a way to test the accuracy and validity of astrological predictions in a statistically significant way.

Can astrologers help people

Maybe. It is usually easier to see the problems in others as compared to problems we face in our own life. Talking to someone else can help us gain clarity and a new perspective on things. The benefit an astrologer brings is similar to that of a coach. But I bet in the majority of cases one would be better off seeking the advice of a professionally trained counsellor, advisor or mentor.

If astrology was real I would expect the help and advice given by an astrologer to be far superior to that of the average advisor. The astrologer, after all, should have extra insight into one's life path that a regular counsellor does not have access to. If I was a financial advisor with some knowledge, however imperfect, of the movement of financial markets, I would be able to make far more money than the regular investor. It is for this reason that insider trading is illegal. When it comes to advising people, there is no firm evidence that an astrologer possess the equivalent of insider knowledge of their future or life directions.

Save your money. Don't give it to someone who claims they can help you improve your life based on which house Neptune occupied at the moment of your birth.

For some more great info on debunking astrology, check out these videos by James Randi on Youtube here and here