Classical Science: Telling Time with the Sun

Time to run outside in the sun!

For a simple animation of how shadows vary with time and position of the sun, click here. The animation here shows you how to estimate the size of a very large object (like the Statue of Liberty or T Rex) by comparing shadows.

When Isaac Newton was a boy, he was interested in studying the patterns of how shadows moved. He eventually constructed many sundials around his house and could tell the time just by looking at the placement of shadows.

For a good background on telling the time by the sun, and a print-out template for one to make yourself, click on this NASA site. You'll have to determine your latitude before you can use the sundial accurately so that you can factor in the tilt of the earth and its curvature. There are many beautiful sundial pictures at Wikipedia.

Another device an ancient Roman could use was an horologium ex aqua, or water clock - that displayed the month and hour on a column of water. For more on how ancient Romans kept time, check here.

If you're wondering how a person in the Middle Ages might have been able to tell the time at night, they could have used a Star Clock that uses the pointers of the Big Dipper.

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