THE SUN ON MARS.(The Talk of the Town)

Five years ago, at a meeting of Cornell University scientists to discuss the design of Mars probes for nasa, there was spirited debate, naturally, on the question of photometric calibration. What sort of apparatus would enable an unmanned spacecraft's cameras to adjust their color values to Mars' atmosphere? (The digital images radioed home by the Viking lander in 1976 were notoriously "over-pinked"; if you actually stood on Mars, you would see a landscape whose color resembled not cotton candy but butterscotch.) The consensus favored a post that would cast shadows across a "calibration target" of gray rings--and then Bill Nye piped up. Nye is a Cornell alumnus and a mechanical engineer whose hydraulic-pressure-resonance suppressor is used on the Boeing 747. But he is best known as the excitable, bow-tie-wearing, bubbling-beaker-holding host of the PBS show "Bill Nye the Science Guy," and he spoke now in his most irrepressible manner: "C'mon guys, it's got to be a sundial!"

As Nye recalled, speaking by telephone the other day from his office in Seattle, the other scientists said, "Bill, we've got a lot of clocks already, man--it's a space program. Space program." But Nye would not let the topic drop. Nye's father, Ned, was a quartermaster who spent most of the Second World War in Japanese prison camps. To stay sane, Ned Nye built sundials out of fence posts, using pebbles to establish the hour lines. Each day, he'd observe when the shadow was shortest and mark noon in the dust, then trace the migration of those marks over time--the analemma--to keep track of the earth's orbit, and thus the passing of seasons and years.

After the war, Ned Nye's compulsion grew to fill his expanded horizons. As a travelling salesman for General Electric in the Washington, D.C., area, he would settle into a booth at a Hot Shoppe restaurant, order a club sandwich and an iced coffee, and then ask the waitress, "Know of any sundials around here?" He started an ill-starred business in "sand-dials" (sundials for the beach); suggested repurposing the Washington Monument as a giant sundial; and in 1969 published his opus, "Sundials of Maryland and Virginia."

Similarly obsessed, Bill Nye finally persuaded his Cornell colleagues that sundials surrounded by gray rings would not only make photometric calibration possible but also mark the time, and "MarsDials" were built into the two Mars Exploration Rovers, the first of which, Spirit, will land on the Red Planet on January 3rd. Nye carried the day by pointing out that, because the Rovers would be roving about between Mars' ...