Ice Stories
Exploratorium Home

Clockwise



MCMURDO STATION, ANTARCTICA– (By Ron Hipschman) Why do the hands on clocks go “clockwise?” Seems like a circular definition, but if you looked closely at sundials in the northern hemisphere, you’d notice that the shadow of the sun moves around the sundial in a “clockwise” direction. This was adopted by clock-makers and became the standard we know today.

In the southern hemisphere, the sun’s shadow moves around the dial in the opposite direction, so if clocks had been invented there, our watches would move the other way.



Get the Flash Player to see this player.




Tags: , , , , , ,

2 Responses »

  1. O K , what does it do at the equator…I hate to ask a dumb question…but I don’t know

  2. David,

    Not a dumb question at all. In fact it’s very interesting. Since the sun is below the equator for half the year (Sept 21 to March 21) the shadow on a dial at the equator will be cast to the north and the dial goes clockwise. The other half of the year (March 21 to Sept 21) the sun is north of the equator and the shadow is cast on the south side of the dial. During this part of the year the shadow moves counter clockwise. On the equinoxes (March and Sept 21) when the sun is exactly ON the equator, the shadow moves from west to east, straight across the dial neither clockwise or counter clockwise.

    Ron