This months puzzle corner is less about lateral thinking and more to do with a bit of pure maths, or, more specifically, geometry. In fact, the origin of the word geometry literally means the measurement of the Earth, and that's what this month's puzzle is all about.

Imagine if you ran a thin steel band tightly all the way round the earth. There are no gaps at all between the earth and the band and nothing, not even a sheet of paper, can be passed underneath it.

The circumference of the Earth is 40,000 kilometres and so the band is exactly that length. Now, imagine adding just 10 metres to the length of the band and see if you can work out how much of a gap would now be created in-between the band and the earth. Would it be enough for a fly to crawl under or something larger, like a mouse, a dog or maybe even a man? Can you guess, or, even better, can you work it out?

As usual there is a prize. For the first 10 correct answers, we've got a copy of the FESTO Dictionary of Electrical Drive Technology. E-mail andrew@controlinmotion.com and don't forget to include your address if you want the prize.