David Hill: The fault, dear people, is not in our stars but in astrology

I belong to the local Astronomical Society. I think I do, anyway. But at least twice a month, letters reach our post office box addressed to the Astrological Society.
That address is just a slip of the spell-checker. So far, nobody has written to us in the belief that we're a bunch of horoscope hustlers.

I'm glad of that. I know that for most people, astrology and horoscopes are just a light-hearted diversion. But I detest them.

I detest them because I resent the genuine science of astronomy being tainted by the nonsensical pseudo-science of astrology.

And because there are adults - and adulthood surely involves being responsible for your own behaviour and destiny - who really seem to believe that their actions can be explained or excused in terms of planetary positions at their birth.

Of course some astrological predictions come true.

Prophesying that you will meet a tall, dark/dank stranger, or that New Zealand cricket supporters will soon face a time of despair, hardly requires clairvoyant capabilities.

And, of course, our lives are affected by heavenly bodies. The sun grows our crops and our cancers. The moon drags seas around. Jupiter's gravitational pull stops lots of comets and asteroids from whacking us. When one of those comets does get through, it has a profound effect on terrestrial lives. Ask the dinosaurs.

But to claim that things were shaped by Saturn being in superior conjunction or the sun being in Pisces? I say again - nonsensical pseudo-science.

If you think I'm too harsh, try these points:

* Horoscopes are supposed to plot our fates according to planetary and stellar positions at our birth. So all horoscopes composed before 1846, when Neptune was identified, and 1930, when Pluto was located, must be faulty because they didn't factor in those planets. Indeed, since new stars and extra-solar planets are constantly being discovered, all horoscopes will always be incomplete and inaccurate.

* The distances of planets and stars also affect our lives, say some astrologers. But these distances are being continually refined. Up to the 1930s, the great Andromeda Galaxy was thought to be one million light years away. Now its distance is set at more than two million light years. Once again, horoscopes based on earlier information must be flawed.

* It's claimed that the light and gravity of heavenly bodies, known and unknown, influences our fates at birth. Certainly, starlight reaches us from immense distances. (Light from planets is reflected sunlight.) And we do feel the gravitational tug of every star and planet. But the lights in a hospital delivery room give millions of times more light than the stars in Sagittarius, and the bedside table has billions of times more gravitational effect. Maybe your real birth sign is Osram 200 watts, or Teak Veneer.

* The month of your birth and its associated zodiac sign is sometimes said to shape your character. If you're born in mid-June, you'll be a thoughtful, see-both-sides Gemini. Trouble is, as our solar system orbits through the Milky Way, the positions of background stars change. In a millennium, those born in mid-June won't be thoughtful. They'll be crabby Cancers.

So I regard astrology as infantile escapism that diminishes us as a thinking species. Yes, I repeat that to most people it's just light-hearted fun - like reality TV, which doesn't do the human race much good, either.

If people want a thrill from the heavens, I suggest they try astronomy. The proposed mission to Pluto, the astonishing space probes now on Mars and Saturn's moon Titan; the gamma ray bursts whose power exceeds half a galaxy; the evidence that our universe will expand for ever - that's where real excitement lies.

I await the angry astrological attacks. I'm sure they'll arrive soon. After all, the stars will have foretold that I was writing this.