• PROJECTS
  • Advocacy and Education
  • Extrasolar Planets
  • Innovative Technologies
  • International Mission Participation
  • Mars Exploration
  • Near Earth Objects
  • Search for Extraterrestrial Life
  • Past Projects
• THE PLANETARY REPORT
• PLANETARY RADIO
• BLOG
• SOCIETY UPDATES

browse projects: Apophis Mission Design Competition Asteroid Impact Mapping System Catalog of Exoplanets Drive a Mars Rover Extrasolar Planets Transit Search International Lunar Decade LIFE Experiment: Phobos Mars Climate Sounder Team Website Messages from Earth Observing Earth Pioneer Anomaly Planetary Microphones S.O.S: Save Our Science! SETI Optical Telescope SETI Radio Searches SETI@home Shoemaker NEO Grants Solar Sailing Space Advocacy Space Information Stardust@home Target Earth Visions of Mars

browse space topics: 2001 Mars Odyssey Asteroids and Comets Cassini-Huygens Chandra X-Ray Observatory Chandrayaan-1 Chang'e 1 Compare the Planets Dawn Deep Impact Earth Extrasolar Planets Genesis Hayabusa (MUSES-C) Hubble Space Telescope Jupiter Kaguya (SELENE) Lunar Reconnaissance Orbiter (LRO) Mars Mars Exploration Rovers Mars Express Mars Global Surveyor Mars Reconnaissance Orbiter Mars Science Laboratory Mercury MESSENGER Moon Near Earth Objects Neptune New Horizons New Horizons Digital Time Capsule Past Missions Phoenix Planetary Analogs Planetary Exploration Timelines Planetfest 2008 Pluto and Charon Pluto Top Ten Postcards from Venus Private Missions Rosetta Saturn Search for Extraterrestrial Intelligence SMART-1 SOHO Space Imaging Spitzer Space Telescope Stardust Trans-Neptunian Objects Ulysses Uranus Venus Venus Express Voyager Weekly Planetary Radio Trivia Contest

Projects: EarthDials

Basic Facts

The EarthDial Project is a worldwide network of sundials to show the passage of time the old-fashioned way by tracking the motion of the Sun across the sky. The EarthDials are designed 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 bear the common motto “Two Worlds One Sun” because it’s the same Sun that moves across the skies of Earth and Mars.

The EarthDial Project is a partnership between The Planetary Society; Bill Nye, the Science Guy; and Woody Sullivan, a professor of astronomy at the University of Washington.

Each EarthDial is constructed to a common specification.  Each EarthDial is a circle 80 centimeters (32 inches) in diameter, 10 times the size of the MarsDials. Within each circle are hour markings allowing the time of day to be read, as well as the exact location of the EarthDial on Earth.  Outside the circle, each EarthDial is unique, with individual touches and expressions of local culture.  Written around the circle is the motto “Two Worlds One Sun,” in the local language of the EarthDial host. 

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.  EarthDials must be located where they can sit in sunlight for most of the day.  A popular location that provides both daylight and a relatively secure location for a Webcam is the flat roof of a school building or home.  Click here for detailed instructions on how to build your EarthDial.