Sundials: From Ithaca to Mars

Sundials often go unnoticed, but they can be found everywhere on Cornell’s campus. The Joseph N. Pew Sundial has been an icon of the Engineering Quad for over three decades. It was designed by Cornell President Emeritus Dale Corson and Prof. Emeritus Richard Phelam. The Pew sundial is very accurate, being able to provide correct time with only a 30-second margin of error. The sundial underwent repairs in 2006 but it is now fully operational. Another Cornell icon, the Sheldon Sundial, is not often recognized as a sundial because of its plain, decorative appearance. It was installed in 1910 at the southern entrance to Goldwin Smith Hall, surrounded by a semi-circular seat of marble. It was given to the University by the late Charles Lacy Sheldon in memory of his sons, Franklin Lacy Sheldon 1892 and Charles Lacy Sheldon Jr. 1901. The sundial is mounted upon a stone table at the center of this monument.

Cornell sundials are not limited to the Ithaca campus or even to this planet. Cornell-affiliated sundials can be found on the Spirit and Opportunity rovers on Mars. The sundials originally had a different purpose that involved cameras taking pictures of the Martian surface. In order to take images and convert them into scientific information, the cameras needed to be calibrated.

Prof. Steve Squyres ’81, astronomy, was one of the scientists working on the rover. He and his team, which included famous alumnus Bill Nye ’77, developed a calibration target to include on the rover which would allow the cameras to be calibrated. Squyres said that once he showed Nye the calibration target, Nye said only one thing: “dude, that’s a sundial!”

“Bill also made the point that by using the calibration target as a sundial it would provide a wonderful opportunity to explain some really fundamental aspects of astronomy to people following the mission. Everyone knows sundials,” said Squyres. “Bill is passionate about sundials. He was really the driving force behind this.”

As a result, Squyres and his team transformed the calibration target into a sundial. Because the rovers moved around on the Martian surface, engraving permanent sundial markings on the calibration target would be unfavorable. Instead, the scientists electronically superimposed sundial markings so that the target could tell time accurately regardless of its position. This would allow scientists to orient the markings depending on the position of the rover, thus making it much easier to tell time. The sundial on Mars allows scientists to examine the passage of time and how the sun moves throughout the Martian sky.

Bill Nye’s ’77 Solar Clock

The Bill Nye Solar Noon Clock atop Rhodes Hall was dedicated earlier this semester as a gift from The Science Guy himself. The clock not only serves as a method of telling legal time, but it also illustrates the point at which the sun is highest in the sky, otherwise known as solar noon. Prof. Michel Louge, mechanical and aerospace engineering, led a group of five undergraduate students in designing the controller inside the clock. This controller uses GPS technology to allow light in at the precise moment of solar noon.

Avraham Aisenberg ’09, an electrical engineering student in the development team, described how the solar clock works. Both the clock and the controller inside operate with GPS technology. Signals from GPS satellites tell the scientists the time and date down to the millisecond. By converting this information into a code, the scientists can look up the specific time of day that solar noon will occur. Three minutes and thirty seconds before solar noon, the valves begin to open and allow light in. The same amount of time is spent closing the valves after solar noon in order to provide an effect of the sun rising and setting on the face of the clock.

The Clocktower

McGraw Tower is a common symbol of Cornell. The tower’s defining feature lies on the inside: 21 bells, which provide daily concerts for Cornellians on central campus. This makes it one of the largest musical instruments of its kind in the world. The tower originally held the library’s stacks, but currently holds the chimes, a small museum, a practice room, and the 1875 Seth Thomas clock with a 14-foot pendulum. If one were to climb the 161 steps to the top of the tower, they would be able to see the clockworks and pendulum, although the clock itself is now run by a computer. The chimes, however, are still fully operated by the chimesmasters. When the bells and tower underwent restoration in 1999, the clockworks were linked to a global positioning system in order to promote precision and accuracy. Because of this, all four sides of the clock are identical and correct, up to the second. It is also a tradition for the clock to change its appearance a few times a year in honor of noteworthy campus events, such as turning green in anticipation of Dragon Day or donning the appearance of a jack-o-lantern for Halloween.