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EarthDials

The EarthDial Project was a partnership between The Planetary Society; Bill Nye, the Science Guy; and Woody Sullivan, a professor of astronomy at the University of Washington, designed to capture interest in the motion of the Sun across the skies of Earth and Mars. EarthDials were an international network of Webcam-equipped sundials. All EarthDials shared a basic design that was intended to remind us of the MarsDials aboard NASA's Spirit and Opportunity rovers that arrived at Mars in January 2004. The MarsDials and the EarthDials bore the common motto "Two Worlds One Sun" because it's the same Sun that moves across the skies of Earth and Mars. But every EarthDial was unique to its location on the planet Earth.

That's because the Sun's apparent motion is different for observers on different parts of Earth. The path that the Sun traces -- and consequently the lines and curves on the faces of the EarthDials -- were very different from Scandinavia to Seattle to South Africa. By observing the motion of sundial shadows around the world at the same time, an observer can get insight into the nature of planetary motion and our place in the solar system. And while the EarthDials were made to a common pattern, each one was decorated in the language and cultural motifs of its host.

Although the Earthdial project is now over, you can still download instructions on how to build your own Earthdial for your own location and learn about the motion of the Sun across your sky as you watch the continued adventures of Spirit and Opportunity.