MadSci Network: Other |
There are three scientific ways to do this, both of which involve some astronomy. The easiest is to simply wait until the sun is due south (in the northern hemisphere), at which time it's high noon at your location. With a sundial, you can extend your solar time-telling, but it's hard to do by eye. At night, you can tell time using the "handle" of the Big Dipper as the hour hand on a clock - the direction it's pointing indicates the approximate time. This is not nearly as accurate as using the sun, though. Finally, if you have a telescope, you can look at Jupiter's largest moons. Each has a different orbit and, by noting their relative positions as one or more passes in front of or behind Jupiter, you can tell the time very precisely. Unfortunately, to do this, you need a telescope or good binoculars, a book with the orbital parameters of the moons, and a calculator. However, this method is so precise that it was used by Lewis and Clark and many others to determine the exact time and, from that, their longitude (i.e. distance east or west of the Prime Meridian in Greenwich, England). The best sources of information about telling time are Daniel Boorstein's book, The Discovers and another book called Longitude, by Dava Sobel. If you don't have access to the sun, the Big Dipper, or a telescope, your best bet is to ask a kind stranger who seems to be wearing a watch.
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