Mars landers create opportunity for Web-linked sundials around the world

November 20, 2003

Herbert Hoover reputedly wanted a car in every garage and a chicken in every pot. Woodruff Sullivan would settle for a sundial in every backyard.

Sullivan, a University of Washington astronomy professor, is teaming up with television personality Bill Nye, "the science guy," and The Planetary Society on EarthDial, a project to get schools, community organizations and individuals around the world to build their own sundials and display them on the Internet using 24-hour webcams.

Their hope is to have a broad sample of sundials from each time zone, illustrating the difference in shadows between the northern and southern hemispheres and the equator. The plan is to display the images together on a single Web site during the working life of two Mars landers, Spirit and Opportunity, that are scheduled to land on the red planet in January.

Both Spirit and Opportunity are equipped with sundials, referred to as Marsdials, that were largely designed and fabricated at the UW. They evolved from earlier Mars missions that were to land on Mars in 2002 but were postponed. In examining the plans for those missions, Nye noticed a small square and post that were to be used as a kind of test pattern to calibrate the spacecraft's color panoramic camera. He suggested that it could double as a sundial.

Now he and Sullivan, a sundial expert, have devised what they call the EarthDial project in which they are providing sundial construction plans that are adaptable for any place on Earth. Though each EarthDial will have room outside the main circle for individual touches and expressions of local culture, everything within that circle is expected to be relatively uniform so that they will be similar to each other and representative of the Marsdials.

"We'll have all the dials around the Earth and the two dials on Mars with the same general design," Sullivan said. "And they will have the same motto - 'Two Worlds, One Sun.'"

A big difference is that the motto, inscribed in English on the Marsdials, will be in the local language of each EarthDial built for the project. In addition, the Marsdials carry an inscription of "Mars 2004," while the EarthDials will be inscribed "Earth 2004," also in the local language.

The cost to individuals, schools and groups undertaking an EarthDial project is likely to be around $50 for building materials, plus the cost of acquiring and maintaining a webcam with around-the-clock Internet connection that refreshes the image regularly.

The EarthDials will be about 32 inches across, 10 times the size of the Marsdials. At any time, half of the EarthDials will be in darkness, Sullivan said, but displayed together on a Web page they will provide a unique look at the world.

"You'll get a palpable sense of what time is on this globe," he said. "As your eye sweeps across the screen, you'll see the shadow angles changing just like the hands on a clock in different time zones."

The project is being conducted in partnership with The Planetary Society, an organization that encourages exploration of the solar system and the search for extraterrestrial life. The society will host the EarthDial Web site throughout the Spirit and Opportunity missions on the Martian surface. Sullivan expects the project will prove to be a valuable education tool.

"Any teacher should be able to use this site for all kinds of interesting things having to do with timekeeping and with Earth as a planet," he said.
Those who want to build their own EarthDials can find further information and construction plans at

For more information, contact Sullivan at 206-543-7773 or; or Susan Lendroth at The Planetary Society, 626-793-5100 or

NOTE: High-resolution image available at

University of Washington

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