First of all, the precession of the earth's axis through its 26,000 year cycle means that there is a distinct 'wobble'. Those stars in constellations rising with the sun in its ecliptic are not the same stars that rose with the sun when the zodiacal signs were first identified in antiquity. The period December 21 to January 21 is known as 'Capricorn'. In 200 BCE, on my birthday, January 5th, the sun did indeed rise in the house of Capricorn. However, it now rises in Saggitarius. The whole zodiac is out of whack due to the precession of the earth's axis. All those people who read their horoscopes thinking that they are in fact Capricorns, are wrong. They are more likely to be Saggitarians.
It is true that heavenly bodies influence events on earth. The moon's gravity creates tides in our oceans, and the sun has the effect of creating seasons in places north or south of the earth's equator. Surely the planets and distant stars will also affect the earth and the life that lives on it. Indeed, humans are over 98% water: how can we not be affected? However, much of astrology seems to be based on the moment of a person's birth, and not on the moment of his or her conception. At the time of conception, perhaps the influence of heavenly bodies could pre-determine or shape a person's personality. The problem here is that the time of a person's birth is largely not a question of nature, but rather is subject to cultural imperatives, like diet, exercise, state of mind, stresses to mind and body. One simply cannot parse the cultural variables away from the positions of the stars at the time of a person's birth.
Third, astrology is a field which seems to present predictions that either are not proven or are unproveable. For example, I might read a horoscope in a newspaper and find that on this day, the numbers 8, 10, and 14 are somehow lucky for me. This is using inductive reasoning: because of the position of the stars (data), we can make a prediction for future events. However, we tend not to see deductive reasoning in the field of astrology. The readership is never surveyed to see whether those that are born under that particular sign found the numbers 8, 10, and 14 to be lucky on that day. If in fact this prediction were true, then a certain number of people who fall into that category should have found those numbers lucky. However, to my knowledge, astrological hypotheses are not put through these types of scientific tests. Followers seem to rely on 'belief' and 'faith' that these predictions are true, and so astrology would more easily be placed into the category of 'religion' than 'science'.
However, since Copernicus and Galileo, our knowledge of the universe and our physical place in it has been growing exponentially. Perhaps one day, through the use of powerful satellite-based telescopes and supercomputers, we might be able to link the effect of stars on human personalities. One might have to work out a series of times of conception, and collect data on personality traits among those who were born at a cerain instant in time. Once done, one might then test such predictions against new data to see whether the hypotheses stand up. A body of predictions linked to empirical data might then be compiled, and predictions applied to people who are born at times in the future when the heavenly bodies are positioned in similar ways. At that point, 'astrology' might pass into the realm of science.
