Dear Tom,
Mrs. Kelley, my son’s third-grade teacher at Fox Ridge School in St. Charles, asked: Why do we have leap year?
Jeff Sharko, St. Charles
Dear Jeff,
We want the seasons to jibe with the calendar. At Chicago, for example, February is always late winter. Because the seasons are determined by the Earth’s annual revolution around the sun, we have to adjust our calendars so that, on any given day, the Earth occupies the same position in space, relative to the sun, as it did on that date one year earlier. Astronomer Dan Joyce tells us, “One year (the time it takes the Earth to revolve once around the sun) is equal not to 365 exact days but something closer to 365 and a quarter days, which is made up by adding a day every four years, most conveniently at the end of the shortest month.” That extra day, Feb. 29, gives a year with 366 days: leap year.
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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.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
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