Sunday, August 26, 2007

Does Anybody Really Know What Time it Is?

"Does anybody really know what time it is? Does anybody really care?" So sang the rock group Chicago back in 1970, in their hit song from their first album, Chicago Transit Authority. People have been asking that question for centuries, and have devised all kinds of devices for providing the answer. In Denver's Cranmer Park, there is a more modern version of one such device that dates back to antiquity. A giant sundial stands there to mark the hours as the earth makes its daily rotation in relation to the Sun.

The sundial in Cranmer Park, Denver. Click photo to enlarge.

This is not the original sundial in this park. This is one placed in 1966 to replace the first one, which was placed in 1941. The stone is tilted to the plane of earth's equator, and the shadow producing rod points pretty much at Polaris, the North Star. According to the instructions engraved in stone behind it (enlarge picture below to read), you can make adjustments from solar time to standard time by using the diagram on the instructions. They appear to have been engraved for the 1941 dial.

As you can see from the time indicated, I was at the park at noon solar time, and that is very close without any adjustments, as my watch indicated 1:02 PM, but that is Daylight Savings Time, which adds one hour to standard time. Standard time is the average for the time zone, and the Mountain Time Zone's average is at the 105 degree meridian west of Greenwich, which the instructions tell us is at Navajo Street in Denver. Therefore standard time in the Mile High City is just about solar time. Since time zones are drawn for convenience, and not necessarily true to solar time, Denver is closer to the Central Time Zone than the Pacific. If one heads east on I-70, you enter the Central zone at the second county in Kansas, just past the town of Goodland, KS. That is about 200 miles away. To reach the Pacific Time Zone, you have to traverse two-thirds of Colorado and all of Utah to the west, entering Pacific time in the state of Nevada.

Instruction chart from the original 1941 sundial. Click to enlarge.

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