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Digital Clock Without Electricity or Moving Parts
NerdMachine writes "Throw away those slide rules and embrace the digital age. The Digital Sundial is a 10 year old invention on display in Sundial Park (Genk, Belgium), Deutsches Museum (Munich Germany), Kölnisches Stadtmuseum (Cologne, Germany), and Martha's Vineyard, USA. You need to pivot it to adjust daylight savings time. If you can't visit one of these, Digital Sundials International can sell you one for US$12,000+, or you can buy a pocket version for under US$100 for that special nerd in your life."
I read an article in an old Scientific American about an especially simple sundial: mount a globe of the Earth outside, orienting it to be exactly parallel to the real Earth. That means pointing the north pole of the globe at the North Star, and rotating it so that your current meridian of longitude runs across the top. This will put your current location exactly at the top of the globe.
The cool thing is that sunlight will now fall on the globe in exactly the way it falls on the Earth (during the day, that is). You can see the day-night terminator and it will be the same as the terminator on the actual Earth. You can see which polar regions are getting 24 hour sunlight or night. You can tell whether it is day or night anywhere on Earth, and even estimate what time it is there.
It sounded pretty cool although I never bothered to try to set one up. You'd need some kind of waterproof globe that wouldn't fade in the sunlight. Probably there are some like this on public display somewhere.