Dear Tom,
For every 100 miles east or west of Chicago what is the difference in the time of sunset?
Tom Crawford
Dear Tom,
At Chicago’s 42 (degrees) N latitude the EarthM-9s surface is rotating at a speed of about 770 m.p.h. which equates to an approximate speed of 13 miles a minute. Therefore sunset (or sunrise) differs by one minute for every 13 miles of travel east or west of the city. The difference in time for a city 100 miles from Chicago would be a bit more than 7.5 minutes. The U.S. Naval Observatory computes the nationM-9s official sunrise/sunset times. Chicago’s times are based on a location near the Stevenson Expressway and Western Ave., a point close to the city’s population weighted center. Given the vast expanse of the metropolitan area, sunrise/sunset times differ by several minutes from locations west of the Fox Valley to the far eastern suburbs in northwest Indiana.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
