By Toutatis, the sky will not fall on our heads!

Asteroid time again - this time it's Toutatis, an old friend who drops by every four years or so.

The number of close approaches combined with its size - 4.5km long -  officially makes it a Potentially Hazardous Object but don't get too excited - current calculations put the chance of a collision within the next six hundred years as 'essentially zero' and it doesn't get much more likely after that either.

And in any case, 'close' is, of course, a relative term; astronomers start talking about 'proximity' when anything gets with a few million miles of Earth. Toutatis will actually be zipping by a comfortable 6.3 million miles away.

It's comforting, somehow, to know that Newtonian mechanics make some things, at least, predictable; there's quite enough uncertainly about already. To be honest, the chances of an asteroid wiping out civilization as we know it must be rather less than us bringing it about all by ourselves.

Though if the theory is right that human intelligence has been declining ever since we started practising agriculture and living in cities, the end will probably be less than spectacular, accompanied by the much-quoted whimper - or possibly the inane drivel of a world of radio show hosts.

Still, any flyby is a reason to raise a glass or two, so, tonight, we will be drinking a toast to Toutatis - a few days too early to put the wind up the Mayan prophecy lot but a good excuse for a party nonetheless.