Why do clock's hands always rotate clockwise?


Long before we have watches, people have always tell time by Sun Dials. Mechanical watches did not become generally available until early 20-century. The designers of these watches natually make the hands of their watch to emulate the movement of the shadow of a sun dial.

Plant a 8-ft long post on the ground. This pole is called the "gnomon" of the Sundial. Stand in front of it facing North. Watch the shadow cast by the Sun on the ground. It looks like this.

The Sun is on the Southern part of the sky. It casts a shadow of the post on the ground to the North of the pole. Mark the end point of the shadow as the hour goes by. As the time passes, the Sun moves from East to West in the sky. The end point, on the other hand, moves from west to east. The shadow of the pole, which looks like a line, rotates around the pole in the clockwise direction.

Is it any wonder that when the watchmakers began to make watches to compete with sun dials they make the hands of their clocks rotating clockwise as well? Just like the Sun Dial!

NASA has a webpage showing this fact as well as a lot of additional details. bri


Sun Dial Page