Just to make this clear from the start, I am a Scorpio, and Scorpios don't believe in astrology. I am also a math guy, by the way, and math guys don't believe in Scorpios. Is there any truth in astrological signs? I do a little experiment here on mathematicians to test this.
Recently, I was invited to join a LinkedIn group where this question showed up: "Do you believe in astrology?" There were hundreds of responses. When I last check, the number was 487. I admit that I have not read all of them, but I did read a bunch of the responses. May of them were of the form "astrology is science, but..." Here are some of the "buts".
1. There is a dearth of competent astrologers. Most of them are quacks out to scam you.
2. Astrology has not been systemized.
3. The data was revised many years ago, causing it to be flawed today.
4. There is so much to learn, that few become competent. One estimate was one in a thousand.
5. It is science, but one requires intuition to practice it.
Wow. I'm pretty sure these folks were not in my junior high science class. If they were, I don't think they passed. It would appear that their definition of science is that it has lots of math, involves planets and stuff, and makes predictions. By that definition, the movie 2001 A Space Odyssey was science. The fact that the prediction of what was to happen in 2001 did not come true is obviously irrelevant.
What sign was Hal born under?
What is Science?
Let me clarify. I am not asking about weird science, just regular science. Everybody knows that Weird Science is a movie with Kelly LeBrock. While there may be some science involved with why LeBrock is so gorgeous, I am asking about the more general topic of Science that encompasses stuff beyond my hormones.
That which science cannot improve upon
I think that perhaps the people who commented in the LinkedIn thread have a little different take than I on what an idea has to do in order to be welcomed into the club of science. Maybe I am wrong, but here is my take on the initiation rites.
First, a postulant postulate must be a clearly stated idea that can lead to predictions about what is likely to happen in the future. If the idea has not been systemized, too complicated to ever learn, or requires intuitin to work, then sorry, it's not science.
The second step to initiation is to put the idea to the test. A set of circumstances must be laid out, the idea must be used to create a prediction, and that prediction must come to pass, at the very least, that prediction must come to pass with better than chance likelihood.
A couple of things really help if the idea is to join the inner circle that includes the Pythagorean Theorem, the electron, and my latest approach to making a killing on the stock market. If the idea is replicated by various people, that helps a bunch. If researchers disprove an idea, it's OK to discount a few researchers as being incompetent ninnies, but if 999 out of 1,000 are deemed incompetent, then you should probably read my blog post about cranks.
The in crowd of scientificalish ideas
Another good way to get into the inner circle is to have members in the inner circle vouch for you. If the proposed scientifical idea is consistent with all the other ideas in the inner circle, then it's got a shot. Let's say that you have a marvelous idea that you want to get into the club, and it involves the invocation of of some force from zillions of light years away that has a profound effect on your future, but only takes effect at the moment you were born. I'm thinking that might not fly.
Testing the idea
I came up with a test of astrology, or at least of one aspect of astrology, the idea that your birth sign has some influence over your personality. If there is indeed any validity to this horoscope idea, then you would expect that people of one glamorous and specialized profession would have a tendency to fall into one of the signs of the zodiac.
Inserting math-os-sterone into certain zodiac signs
So... what glamorous and specialized professions can we come up with? I dunno... let's try mathematicians? We all know that all mathematicians are logical, stoic, without humor, and incredibly good looking. My mere existence is proof of this.
Mathematicians are fuzzy and lovable creatures
I consulted a few websites to determine which sign of the zodiac is more likely to give birth to mathematicians. Virgo seems to fit the best.
"the Virgoan preciseness, refinement, fastidious love of cleanliness, hygiene and good order, conventionality and aristocratic attitude of reserve. They are usually observant, shrewd, critically inclined, judicious, patient, practical supporters of the status quo, and tend toward conservatism in all departments of life. On the surface they are emotionally cold, and sometimes this goes deeper, for their habit of suppressing their natural kindness may in the end cause it to atrophy, with the result that they shrink from committing themselves to friendship, make few relationships, and those they do make they are careful to keep superficial."
These agree substantially with the attributes of a Virgo espoused in "The Round Art of Astrology" by A. T. Mann. I quote from page 11: "work, perfectionism, health and hygiene, diet, secondary education, analysis, prudence". The words that I typed in bold are the ones that seem to me to be consistent with the idea of mathematician.
Since the first three places I looked seem to all point toward Virgo as the preferred sign for mathematicians, I will go with that as the initial hypothesis: Mathematicians are disproportionately represented under the sign Virgo.
Now we need some data with which to test our hypothesis. I used the MacTutor History of Mathematics Archive to find my data. I figure that if a mathematician from the early 1800's made it into their list of biographies, they must be legitimately considered a mathematician. I chose the period of time from 1800 to 1840, and recorded the birthdates of all 189 mathematicians where the birthdate was known.
First, the most important question. How many were born on my birthday? Unfortunately only one.
Here is the distribution of mathematicians among the various astrological signs. I have identified the mathematicians according to both the tropical and sidereal signs , just in case one of them is correct and the other not.
We see that Virgo is entirely unremarkable among the signs, regardless of whether we are looking at tropical or sidereal zodiac. Further, it is tough to see that there are any signs that favor mathematicians.
One would have though that this was a slam dunk. Mathematicians, of any professions, have earned a strong stereotype. There is nothing in this data that suggests that the astrological sign could be of any use in predicting this.
Spoiler alert - this book was not written by believers in astrology
My research is original, but not unique. In the book The Gemini Syndrome, Culver and Ianna report a list of 60 professions (including mathematician) that are not correlated with astrological sign. They also list 35 physical characteristics, and 26 personality traits that are not correlated with astrological sign.
It's really more complicated than this
I realize that there are likely to be some naysayers. In particular, "real" astrologers generally look down their noses on a simplistic horoscope that relies strictly on the 12 signs of the zodiac. A "real" astrologer needs the exact time and location of birth to make an accurate assessment. To cast a "real" horoscope, a "real" astrologer must look at not only the position of the planets at the birth of the subject, but also the position of the planets.
Culver and Ianna reported on studies that went further, to look for correlation of some characteristic with combinations astrological sign with another aspect. They found nothing. So, clearly, you need to know the position of Mercury (12 possibilities), Venus (12), Mars (12), Jupiter (12), Neptune (12), and the Moon (12). That would give us 35,831,808 different astrological signs, each with its own destiny. It's a good thing that we have the internet, because delivering a newspaper with space for everyone's horoscope would be just too hard.
I had a blog post about a related topic, by the way: Finding the Right Model. It says that if you are given enough variables to work with, you can model anything to as much accuracy as you wish.
But I got a question for you, Mr. or Ms. Astrologer Person. If there are almost 36 million different combinations, and looking at one or two of the variables by themselves is not fruitful, how did anyone ever figger out what personality traits and physical characteristics and fates went with which type?
 Tropical and sidereal? Why are there two? It is a little known fact that the zodiac has shifted about 26 days since the time that Ptolemy codified the rules of astrological signs. Your Capricorn was not your great-great-great-great grandfather’s Capricorn. The tropical zodiac is the one in common use today..