Two Worlds, One Sun
Project EarthDial with Bill Nye
Astrobiology Magazine had the opportunity to talk with Bill Nye, about the new EarthDial Project, a global endeavor to show sundials from around the world on one panel of updating web cams. In collaboration with the Planetary Society, those working around the world can see a dial particular to their local language, culture and sun position, all in one view. The instructions for participating in EarthDial, along with a collection point on the web to view other’s creative work, are provided on the Planetary Society’s project site.
The EarthDial project is the natural offspring of a project to use two similar sundials on Mars when soon after New Years, twin landing packages arrive on the red planet. Those two Mars sundials will not only tell solar position on another planet and demark interplanetary time. They also serve as color calibration targets to accompany those spectacular panoramic images that get beamed back to Earth for internet display. The idea came to fruition when both Mars Exploration Rovers, Spirit and Opportunity, needed to know the true colors of Mars’ pink sky and rusty soil. The resulting design seemed a perfect complement to teach about how a sundial simultaneously tells the time, location, and sun position on another planet. As Nye concludes: "Onwards to Mars".
Astrobiology Magazine (AM): Before we get into the Earth analog to your Mars Sundial project–called the EarthDial project, how are things looking with the two rovers getting ready to land? All very exciting?
Bill Nye (BN): All very exciting indeed. They have had many shake-down problems… er, uh challenges. The science and engineering teams have been conducting all kinds of tests and training exercises while these spacecraft are enroute. For more on this, try the Cornell science site.
|Various sundial designs have changed over time, but their principles of solar-tracking remain a constant.|
AM: For the EarthDial project, you and Woody Sullivan are collaborating with the Planetary Society to deploy sundial web cams across the globe, where local time is read in a progression around the world. Is this going to work a little like the Millennium parties on New Years, where one could see a 24 hour cycle of the 2000 New Year could be viewed in a global perspective?
BN: I suppose one could look at it that way. The difference is that this is continuous. It’s not a one-time event. We’re reckoning the passage of time world-wide. It is a non-stop global perspective. Log on anytime, and watch the shadows move.
Speaking of perspective, what is progressive, and what would be regressive or not-progressive? One of the fundamental ideas for each of us to mull over is that the establishment of a standard time for the whole world is pretty new historically. Humans have been using sundials for thousands and thousands of years. Clock time, time zones, and leap seconds are almost brand new notions.
AM: What does this perspective offer for understanding a sense of local time in different cultures, since the Earth dials can be customized with language differences and the subtleties of where they are in a time zone?
BN: One of the greatest discoveries in human history was the realization that we live on a big ball. That would be instead of a big table or on the back of an especially big turtle. With EarthDial cameras operating at different longitudes and different latitudes, one will be able to see not only the apparent motion of the Sun but also the shift in the angle and length of shadows world-wide with the change of seasons.
Having different artwork on each dial speaks of the regional culture and the commonality of people everywhere. Kangaroos may look different from giraffes and different from brown bears, but the people who observe and cherish these creatures are of just one species everywhere.
AM: The "Two Worlds, One Sun" motto seems very appropriate for comparing Mars and Earth, but do you consider the EarthDials to share any aspects of "One World, Many Times"?
|The first of many Earthdials along with a globe shown under illumination that both serves as its own sundial and illustrates how a moving shadow will reorient the shadow cast from a gnomon.|
Credit: NyeLabs/W. Sullivan/Planetary Society
BN: In order for the EarthDial project to be compelling or effective, we need to have cameras and dials operating in many time zones of the same planet. That would be our Earth. The EarthDial project could have been established any time in the last few years, since web cams became readily available. But now, we will be able to see solar time on another planet as well, namely Mars. Users will be able to compare the shape and speed of shadows of sundials on two different planets simultaneously. The shadows are all cast by the same star, our Sun. So, yes, the shadows on the two planets and the human-declared time zones along with the natural solar days on each planet have a great deal in common. It’s romantic.
Perhaps we should think of it as ‘Two Worlds Many Times’.
AM: The screensaver program, [seti@home], has a user in almost every country, which was also a project that Woody Sullivan was instrumental in launching. Their highest per capita usage is from Antarctica. Does an EarthDial in the South Pole, where half the year the sun never sets, and the other half the sun never rises–have any time on a dial that is measurable?
BN: In the Antarctic summer, the shadow will go around the gnomon like a clock, although it won’t be exactly like a clock. The shadow will go anti-clockwise, and it will take 24 hours to go around instead of the 12 that it takes on most clock and watch faces. In summer right now, it will very measurable indeed.
AM: The current Earth Dial is deployed in Seattle as a launch point. What is the history of how that beautiful dial on the web came to be made?
BN: Woody Sullivan and his family had me over to dinner a few months ago. We took a couple of large pieces of blank newsprint paper (butcher paper) and designed the dial. Bear in mind that Woody was one of the principal designers of the MarsDial, on which the EarthDial‘s design is based. We made a paper mockup on his dining room table.
I have always been charmed by the notion of a ping pong ball gnomon, because I love table tennis. And, the sport has a unique history in uniting people around the world. Ping pong balls are now all 40 millimeters in diameter everywhere. Also, I very much wanted the EarthDial to be 10 times the size of the MarsDial face. Ten times 80 mm is 80 centimeters world-wide. We took pictures of it and thought about ways to specify all the features it needed and no more. We wanted the specification to be as minimal as possible.
A few days later, I made that EarthDial in my basement using a handsome piece of plywood. As I write, it’s enroute back from Reno, Nevada where the National Science Teachers’ Association (NSTA) western regional meeting was held last week. I’ll set it back up as soon as it gets home. It’s minimal. It is designed to give teachers and other web site visitors an ideal of what might be involved. I used a lot of varnish, and stainless steel fittings. We’ll see how it lasts. I’m glad you think it’s beautiful. Wait until we all see what really creative people around the world come up with.
AM: What are the plans looking like for internet display of the Mars Dials as the sun sweeps across its face after landing? That has a number of subtle differences, not the least of which is it will neither be stationary, nor aligned to a pole, nor precisely known for landing target until it actually gets there–correct?
|The new Pancam design has a camera bar that contains Pancam and Navcam (navigation camera) heads. A "visor" changes the elevation of the cameras so the rover can look up or down.|
Credit: Cornell University
BN: Whenever Steve Squyres and his team of scientists feel there is time and telemetry available, we’ll point the panoramic cameras (pancams) at the radiometric calibration targets (MarsDials), and observe the motion of the shadows– the apparent motion of the Sun. In just a few moments, we’ll compute the local solar time on Mars and create patterns of hour lines, solstice curves, and equinox lines that web visitors back on Earth can simultaneously compare with the apparent motion of the many EarthDial shadows back on Earth. Since we will very quickly know the positions and orientations of the rovers, it won’t take but a moment to complete the trigonometric calculations to produce hour lines etc. on-line.
What once took quite a few minutes to compute only 30 years ago can now be computed in a few microseconds.
|Mars Sundial and color test calibration target for the Mars PanCam, the panoramic camera. Click image for larger view.|
AM: Woody Sullivan told us that the Mars Cameras will know their orientation by looking for the sun in the sky, just like how the Mars Dials will look in part to the cameras to identify their own locations. In a way, is this an interesting throwback to the ancient ways of finding direction with a modern implementation in one of the most alien environments imaginable?
BN: If you know the time of year, you can tell where south is on Earth or on Mars by observing the shadow. At high noon, the shadow is the shortest. In the Northern Hemisphere’s winter, that shadow points due north. In the Southern Hemisphere’s winter, that shadow points due south. In summer, spring, and autumn, you need to know your latitude. You may refer to it as a throwback, but the verity of that notion has not changed in billions of years. It’s about as reliable as they come.
AM: There is a NASA story about the color correction on the first Viking image of the martian surface that came down. There were theories that the atmosphere was just dense enough to have a slightly bluish daylight sky, so they overcompensated the color adjustments and all the newspapers sent out a blue sky, red soil picture. After a few days getting oriented and calibrated, the true sky color turned out not be bluish, but more orange and pink. But the burnt-orange soil and blue sky was already distributed around the world, and difficult to follow-up with in print as more images came down. Do you think this is a remarkable endorsement of the color calibration spectrum offered to the cameras on the Mars dials?
BN: If by "endorsement" you mean "need," yes we need the color patches and the shadow cast on gray rings of different values (each of different degrees of darkness). The photometric calibration targets take up over 1 percent of the solar panel area that might otherwise be available. They add weight to the spacecraft. They add the potential for a catastrophic failure in vibration. Metal plates bouncing around in the payload areas would be a disaster. They take up room, when the spacecraft is folded for launch and cruise. We would not have put them there, if we thought we could do better without them. I guess that’s an endorsement for including calibration targets to get accurate colors in our pictures. As a bonus, they’ll reckon the passage of time.
AM: The planetary society logo is a tall sailing ship that morphs into the voyager spacecraft. Do you have any thoughts on that as a metaphor for the Mars dials, something like a compass morphing into a clock that eventually becomes a key to getting the first color pictures back?
BN: To me, almost all analog dial instruments are elegant and wonderful. Compasses and clocks both use traditionally round faces. But more importantly, they both are used for navigation. They both are needed to find one’s way around. They do different jobs however, so I’m not crazy about morphing compasses into clocks. Like airspeed indicators and artificial horizons on an aircraft’s instrument panel, they are connected but different. Clocks, compasses, and these MarsDials are all beautiful navigational instruments. With no mishaps, the images they help produce will be beautiful.
Onward, to Mars.
Collaborators on the Mars Sundial project include:
* Bill Nye, a 1977 Cornell engineering graduate, Rhodes Class of ’56 Professor and host of the PBS show, "Bill Nye the Science Guy", and the upcoming "Eyes of Nye" television shows
* Steven Squyres, Cornell professor of astronomy and principal investigator for the Athena suite of science instruments carried by the rovers;
* Jim Bell, Cornell assistant professor of astronomy and lead researcher for the high-resolution stereo Pancams carried by both rovers;
* Woodruff "Woody" Sullivan, sundial enthusiast and professor of astronomy at the University of Washington;
* Tyler Nordgren, Cornell Ph.D. ’97, an artist and astronomer at the University of Redlands in California;
* Jon Lomberg, an artist and creative consultant to the Mauna Kea Center for Astronomy Education, University of Hawaii at Hilo;
* Louis Friedman, executive director of the Planetary Society.