# Following time around the dial

Have you ever, as you sipped your tipple in your local hostelry, been momentarily disorientated by a clock, or at least what seems to be a clock, but one where the hands rotate in the reverse direction to the norm?

When you have recovered your aplomb, and ordered a glass of mineral water to ensure that things will get no worse, it may occur to you that there is nothing intrinsically wrong about this "fun" device. The numbers are arranged from 12 on top, to 3 where 9 is usually found, and so on anticlockwise around the face to 11, in the position conventionally occupied by 1. Such a clock can tell the time as well as any other, showing, say, 11.45 as a pattern that we usually recognise as 1.15.

The accepted convention can be traced to the daily movement of the sun. The very earliest clock was just the sun itself, its passage westward in the sky providing a convenient, albeit rough, approximation of the hour.

Then, more than 3,000 years ago, the Egyptians learnt to use a moving shadow as a measure of the time, an idea from which the sundial quickly evolved. And it so happens that, as the sun moves from east to west across the sky, the shadow on a sundial moves - "clockwise", as we now would call it - around the graduations on the dial. It seems reasonable to assume that the first clockmakers imported this familiar pattern when they learnt to measure and display the time by other means.

The interesting thing is that this clockwise sense has pervaded almost every area of life. The needle of a speedometer, for example, registers increasing speed by moving from left to right as it traverses the upper portion of the dial. The pointer on an anemometer dial does the same with increasing wind-speed; so, too, does that on the face of a temperature or fuel gauge, or indeed any device which employs a dial and pointer to indicate a value or a level of activity. The needles almost invariably indicate an increase by moving in a direction we have come to know as "clockwise".

And it is interesting to note that all these meters, including all our watches and our clocks, might well run "anti-clockwise" had the mechanical measurement of time originated in the southern hemisphere. In the Antipodes, although the sun rises in the east and sets in the west - the same as it does here - the shadow on a sundial, because of the northerly position of the sun, moves in an anti-clockwise sense around the dial.