How can shadows be used...
Shadows provide a way of measuring time. The length of shadows and their orientation changes with the sun's position in the sky. In the morning and evening when the sun is very low near the horizon, the shadows are much longer compared to midday, when the sun is overhead.
Shadows also vary according to season: in winter, when the sun is low in the sky, shadows are much longer than in summer.
The main use of shadows is in time keeping. Countless civilisations have used sundials to measure time. Sundials work because the position of a shadow changes over time due to the sun's movement. However, now replaced by clocks and wrist watches, sundials in the modern world are mostly for display.
>An example of a sundial used by an ancient civilisation, located in Beijing's Forbidden City
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>This is a satellite image of a sundial in Herten, Germany. Can you tell the time? Each one of the horizontal lines represents the months. |
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For more information on sundials, see below:
http://en.wikipedia.org/wiki/Sundial
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