Firstly, I have a confession.  Although I have never believed that astrology is anything other than nonsense,occasionally, for a while in the 1970s and early 1980s I would produce astrological charts for people!  I did this from a few books I bought on astrology, like Linda Goodman's Sun Signs.  I plotted all the positions of the "celestial bodies" accurately, based on the books, and then just pulled random phrases from the various books not always corresponding to the birth sign.  The few people for whom I did this thought I was incredibly accurate.  But in reality, you could see them taking phrases and making them fit in their minds. 

Something that really worries me is that about a third of American adults used to believe that astrology is scientific; this figure has increased in 2014 to nearly half!  It is even worse among millennials where more than half believe it is at least somewhat scientific.  From the way the question was phrased, they are not just confusing astrology with astronomy, either.  Astrology and scientific are two words that should never be in the same sentence without the word "not" in between them.  Sorry guys; you are wrong.  Astrology is unmitigated nonsense without a thread of scientific data to back it up.  Saying "but we don't understand everything" or "it's been around for so long there must be some truth in it" is not a reason.  There is no evidence to back it up, in fact there is no evidence for any of the mystical or psychic garbage that is propagated. 

Yes; it's true.  In the past, up to, say, the seventeenth century, many famous scientists also made astrological forecasts.  They had to make enough money to eat after all.  But we have come a long way since then.  We can now say, with certainty, that astrology holds absolutely no place in the modern world.  Now; astrologers would have you believe that the heavenly bodies exert some sort of mystical force.  Presumably, this force be must independent of distance; after all, some planets are much further from us than others, and the stars in the constellations are at all sorts of varying distances.  Remember; the stars in a constellation may look like they are close to each other, but this is just an alignment; the distances vary enormously.

Now, a really telling point.  The Earth's axis "wobbles" producing a precession that cycles over a period of 25,800 years.  Over the two thousand years or so since the first basics of astrology were set down, the Earth's axis has precessed to the point where all the positions of the signs have moved over by about a month, or one whole sign.  You may think you are a Capricorn, but really you are Sagittarian!  Remember also that in about 10,000 years, you will also find that the pole star has become Vega, and the zodiac will have changed out of all recognition.  In ancient astrology, only the planets out to Saturn were known.  Uranus, Neptune, the minor planets like Eris, Pluto and Sedna; all were unknown.  So how does that reconcile with the accuracy of past predictions? 

In an interesting experiment, James Randi gave about 100 people a reading ostensibly based on their time, place and date of birth.  About 80% said it described them perfectly.  Very interesting!  However, each was given an identical reading.  So; it really is all a load of nonsense. 

I have linked here to a website that does a splendid job of debunking this crap.  It is quite a long piece on Phil Plait's Bad Astronomy page, but really thorough.   If you "believe" in astrology, I dare you to read it.  On the other hand,
if you "believe" in astrology, rational thought will not sway you. 

Pseudo-Scientific Nonsense