Wednesday, April 27, 2011

Wordy Wenesday: Sundials

The Sun's apparent motion from east to west across the sky causes objects on Earth to cast shadows. The changing position of the shadow cast by an object during the day indicates a change in time. The sundial is one of the oldest, if not the oldest, known device for the measurement of time. It is made of an object called a gnomon, ( Greek for "the one that knows") which casts a shadow on a scaled surface. The shadow of the gnomon falls on different points on the scale, telling you what time it is.

The scale of a sundial is designed so that the differences in the direction of shadows during the day indicate time. In the morning, shadows are long and point toward the west. As the day progresses, shadows shorten. At noon, when the Sun is at its highest point in the sky, shadows are shortest. In the afternoon, shadows are longer again and in the opposite direction, toward the east.

For more interesting facts about sundials check out this website.

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