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Links of Interest

1410 - Prague Clock

The Old Town Hall of Prague consists of five different clocks, the oldest dating from 1410.  The dial shows unequal hours as well as regular hours.  Through animations, the details of the clock's working are described, showing how the clock accommodates the irregular length of daylight throughout the year.  An engineering marvel and astronomical delight. Don’t miss the Excel spreadsheet at the bottom of the page.




Oldest astronomical calculator?  Read about the discovery of the Antikythera over one hundred years ago.  Only recently has its purpose been revealed through x-ray analysis and digital analysis.  This website points to a number of research sites and published articles such as "Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism" and "Calendars with Olympiad display and eclipse prediction on the Antikythera Mechanism".



Atmospheric Effects

Why is the sky blue?  Well, yes, because of Rayleigh scattering of ligh.  But the result of a blue sky is the red sunrise or red sunset.  This website provides easy to read scientific literature that tells of light's action in the open air and backs up words with wonder photos of these phenomenon of rainbows, arcs, sundogs, and sun pillars.  The site and links are worth browsing.



The Sundial Mail Archive

Want to know what's the latest topic in sundials?  What are some of the questions asked about sundials?  You can join Dan Roth's Sundial Mailing List but here you'll find the Sundial Mail Archives.  Follow sundial topics and see what the experts say.  Interesting historical items are uncovered and new dialing techniques discussed.  Enjoy it all.



Two Worlds - One Sun

The Mars Exploration Rover carried the first interplanetary sundial that primarily served as a panoramic camera color and intensity calibration target. The dial inscription in part read "People launched this spacecraft from Earth in our year 2003. It arrived on Mars in 2004. We built its instruments to study the Martian environment and to look for signs of life. We used this post and these patterns to adjust our cameras and as a sundial to reckon the passage of time. The drawings and words represent the people of Earth. We sent this craft in peace to learn about Mars' past and about our future. To those who visit here, we wish a safe journey and the joy of discovery." The sundial design team included Bill Nye (the Science Guy), Steven Squyres, James Bell, Woodruff (“Woody”) Sullivan, Tyler Nordgren , Jon Lomberg and Louis Friedman.  This inspired the idea to make a simple copy of this Mars dial, a gnomonic dial, that could be built by dialists and students all around the earth.  The motto was “Two Worlds, One Sun.”  At one time the sun never set on these dials.


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