A close up of the astrological clock in Piazza San Marco, Venice. 12 signs of the zodiac are depicted.iStockPhoto

Like many astronomers, I found myself (yet again) in an uncomfortable position last weekend. A stranger, upon learning I was an astronomer, said, "Oh, I'm a Gemini, what are you?" How many more times can I smile sweetly back, with a laugh, and say: "I'm not an astrologer, that's not what I do, I'm an astronomer."?

Look at the statistics and you'll see that there are more people now than ever before who read their star signs in the daily news. We live in a time that is more scientifically aware than any other period in history and yet people still believe the stars and planets can determine their fate.

Interestingly, astronomy and astrology share the same origins; in fact it's accurate to say that astrology came first. Ancient civilizations tried to find sense in the happenings in the sky and attribute them to their lives.

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We soon learned that perhaps there was no mystical force determining our future and the two subjects split into astronomy (the branch of physics that studies celestial bodies and the Universe as a whole) and astrology (a pseudoscience claiming divination by the positions of the planets, sun and moon).

Today though, astrology has turned into nothing more than a fairground act and astronomy has turned into a science having to point out the difference! And this is where I come in.

I thought it was interesting, as an (ahem) impartial writer that I highlight a couple of stumbling blocks supporting my belief that astrology really is a load of rubbish.

The zodiac is the band around the sky where the sun, moon and planets move through. The signs of the zodiac are the constellations of stars within this band. Both astronomers and astrologers agree on this bit.

But according to astrologers there are 12 signs of the zodiac. Wrong! There are 13 signs of the zodiac; Ophiuchus is the 'new' one yet for some curious reason I have never come across an Ophiuchian!

Taking the concept of the signs of the zodiac, I was born in July which means that when I was born the sun was in Cancer. Wrong again. Originally yes, the sun would have been in Cancer when the star/sun charts were produced about 2000 years ago. But in reality, the wobble of the Earth on its axis — which we call "precession" — has led to them being all out of sync.

In fact, when I was born, way back in July 1973, the Sun was in Gemini. News Flash: you're all reading the wrong star signs! All those astrology columns you've read that seemed spot-on were a fluke. Surprising eh?

The last point I want to throw out to the cyber world is the discovery of planets. Until 1781 there were only five planets known to affect us in the minds of astrologers: Mercury, Venus, Mars, Jupiter and Saturn.

In 1781, astronomer Sir William Herschel spotted an object moving in the sky and originally thought it was a comet but later realized its planetary nature. The object was the gas giant Uranus.

In 1846, another discovery was confirmed, the eighth planet in the solar system. This was an ingenious piece of work combining mathematics and observation. Astronomers noticed some peculiarities in the way Uranus moved through the sky and, after painstaking observation, concluded it must have been the gravitational tug from another object causing its curious motion. The position of the new planet was calculated from the movements of Uranus and subsequently identified telescopically. Neptune had been found.

The interesting thing here is that until the scientific discovery of the two new planets, astrologers had not once mentioned them. Following their discovery they found their way into astrological predictions. If they had a real impact on our lives, surely astrologers should have discovered them or at least known they were out there before astronomers?

Finally, don't even get me started on the nature of the magic/fairy dust that allows a planet to affect us here on Earth.

Science has shown us through measurement, observation and experimentation that there are four forces in the Universe: electromagnetism, strong interaction, weak interaction and gravitation. For reasons too detailed to go into in this article, none of them can impact humanity purely from the positions of the stars in the sky or how aligned the planets are.

If there is some mystical force (other than the fundamental four above) affecting our lives from the planets, then clearly distance is no object for this force as it doesn't matter if a planet or star is near or far.

How does it work, then, that we have found hundreds of exoplanets orbiting other stars? Or that there are over 200 billion stars in the Milky Way? Surely that 'force' would also be affecting us. Thankfully it doesn't, otherwise we would all be running round as complete loonies with all these 'influences' flying at us from all directions.

As you can tell, I'm not fond of astrology. It's all about telling people what they want to hear and we fragile humans' wanting something to believe in. After all, I've never once heard someone read out their predictions telling them that today is going to be a rubbish day; may as well just stay in bed.

Mark Thompson is a writer and astronomy presenter for the UK's BBC One Show. He also writes for his own website The People's Astronomer and you can follow him on Twitter: @PeoplesAstro.