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The Challenge: Build accurate clocks

Mike and his watchHow was the portable clock made?

Making a portable clock or wrist watch, with no small springs, no battery and no precision tools ruled out making a mechanical clock, so we opted for a mini-sundial. To make sure that the sundial wristwatch was accurate, the gnomon had to point at the correct angle. This meant that the wristwatch had to be kept level using a plumb line or spirit level. The gnomon also had to face north so a compass was needed.

Roll up Mike Leahy's 'compact two-piece time-piece': a ridiculous contraption that looked like a miniature radar station. Amazingly, it worked, and even more incredible is the fact that during the sixteenth to eighteenth centuries people actually used to carry portable sundials around, complete with compasses — and they're still made in India! No doubt they looked a little smarter than the Rough Science creation though!

Web Links

The producers are not responsible for the content of external websites.

Building a sundial from the book on the Web "From Stargazers to Starships" by David P. Stern on the International Solar-Terrestrial Physics page on the NASA site
Links about sundials on The North American Sundial Society site
Sundials on the Internet - information about all aspects of sundials
All about sundials on Jack Aubertís webpage
Clepsydra from Reesís Clocks, Watches and Chronometers, 1819 on Gordon T. Uberís Home Page
How do Clocks Keep Time? on the Physical Science Lessons page on the Reach Out! Michigan website


Sundials, History, Theory and Practice by RRJ Rohr, Dover Publications 1996, ISBN 0 4862 9139 1

Making a Clock-Accurate Sundial Customized to Your Location (for the Northern Hemisphere) by Sam Muller, Naturegraph Publishers, 1997; ISBN: 0879612460

Time by A. Waugh, Headline 1999; ISBN: 0747221782 Longitude by Dava Sobel, Fourth Estate 1998 ; ISBN: 1857025717

The Illustrated Longitude by Dava Sobel Fourth Estate, 1999 ; ISBN 1841152331

Mapping Time by E. G. Richards, pub Oxford 1998, ISBN 0 19 286205 7

Sundials by Albert Waugh, pub Dover 1973, ISBN 0 486 22947 5 Sundials by Christopher St J. H. Daniel, pub Shire Album 1986, ISBN 0 85263 808 6