Dava Sobel article on sundials new and old in the January Smithsonian Magazine
Dava Sobel, author of Longitude, Galileo's Daughter, and The Planets,
has an article in the January, 2007 issue of Smithsonian Magazine on
sundials titled "The Shadow Knows" online here:
http://www.smithsonianmagazine.com/issues/2007/january/sundial.php
Check the print edition for more images of historical sundials, many of
which are true works of art. And the sidebar discusses the invention of
the first sundial that can tell time just about any place on Earth.