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Last updated: Saturday, 14-Mar-2009 19:10:45 Central Daylight Time

November 16, 2001


Marker Explains Workings of UW-RF Sundial

Those wondering how to read the world's most accurate sundial, which graces the south face of the UW-River Falls Kleinpell Fine Arts Building, can learn from a free-standing plaque recently installed to explain the intricacies of its workings.

The sundial, measuring 30 x 60 feet and constructed of anodized aluminum, is the largest vertical-face sundial in North America. Because it is accurate to one minute on the hour at any given time of the year, it is also the most accurate sundial in the world. Most other sundials are accurate only to within 15 minutes.

The Swensen Sundial in named in honor of Dick Swensen, emeriti dean of the College of Arts and Sciences. Swensen was at UW-RF for 38 years, arriving in 1955 to teach in the chemistry department, then serving as dean from 1969 to 1988, and teaching again until his retirement in 1993.

Swensen saw a sundial on a castle in Heidelberg, Germany, while vacationing there with his family in 1970, and thought a sundial would be an ideal addition to the campus of UW-River Falls. He presented the idea upon his return, but there was no money available to fund the project.

In 1995, 25 years later and two years after Swensen¹s retirement, his dream was realized. UW-RF physics Professor John Shepherd, who has since retired from teaching, created the elegant design for the timepiece. It was constructed and installed with donations from alumni, and has been a source of fascination for students and visitors to the campus ever since.

Rather than numbers, the sundial has figure eight patterns, called analemmas, to tell the time. The shadow cast by the pointer, or gnomon, tracks the sun for about 10 hours each day

. Five lines run across the analemmas and correspond with special dates. The top lines are the winter solstice and the bottom are the summer solstice. The straight line between them corresponds with the vernal equinox, around March 21, when daylight and darkness are equal.

From the winter solstice starting Dec. 21 to summer solstice, starting June 21, the time is read on one side of the sundial. The rest of the year, the other side tells the time.

The University of Wisconsin-River Falls is located in western Wisconsin some 25 miles from downtown St. Paul, Minn. It is a Center of Excellence in Undergraduate Education in Chemistry and Physics.


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