P. Z. Myers notes the silliness that anti-science types get involved in, especially when they attempt to make scientists look bad over something complex enough that it just can’t be worked out — leap years!
The two most amusing explanations for why we have leap years that I’ve heard came from creationists:
- Those scientists can’t even measure the length of the year accurately! They have to keep fudging their numbers every few years to make everything add up, so why should I trust them?
- We have leap years because the earth is slowing down in its orbit, which proves that the earth can’t be old — a million years ago the earth would have been whirling around the sun so fast it would have flown out of orbit!
Phil Plait at the misnamed (for this post) Bad Astronomy explains in glorious mathematical detail how leap year calculations work, and why we need wait around for more than three millennia to lobby for another calendar correction. Phil is really a remarkable story teller, for an astronomer:
We have two basic units of time: the day and the year. Of all the everyday measurements we use, these are the only two based on concrete physical events: the time it takes for the Earth to spin once on its axis, and the time it takes to go around the Sun. Every other unit of time we use (second, hour, week, month) is rather arbitrary. Convenient, but they are not based on independent, non-arbitrary events.
It takes roughly 365 days for the Earth to orbit the Sun once. If it were exactly 365 days, we’d be all set! Our calendars would be the same every year, and there’d be no worries.
But that’s not the way things are. There are not an exactly even number of days in a year; there are about 365.25 days in a year. That means every year, our calendar is off by about a quarter of a day, an extra 6 or so hours just sitting there, left over. After four years, then, the yearly calendar is off by roughly one day:
4 years at 365 (calendar) days/year = 1460 days, but4 years at 365.25 (physical) days/year = 1461 days.
These are mysteries that beg for explanations in social studies classes. For example, the differences in George Washington’s birth date, as recorded in the year he was born, and as listed today, are due to England’s and the English-speaking world’s late adoption of the Gregorian Calendar, switching from the Julian (England made the switch in 1752, about a half century after almost everyone else in the west, 170 years after Pope Gregory XIII proposed it).
If nothing else, social studies should be good for providing cocktail party trivia, shouldn’t it? And it won’t really matter to you unless one is a scientist launching rockets at a distant planet, or a churchman trying to fix the date of Easter, or a farmer trying to be certain the planting calendar is accurate to the season, or a commodities futures trader trying to figure out when agricultural goods come to market, or a mortgage banker working to make sure mortgages are calculated correctly for the next 30 years and that notices go out to homeowners as required by law, or a homeowner checking up on your mortgage bank, or an average investor checking up on your commodities futures traders and REIT investment advisor, or just a kid interested in the minutiae of how science really affects us in our every day lives.
Now we wonder: In comments, will some creationist bring up the old canard about Harold Hill and NASA’s calculations being off by the one day Joshua stopped the sun?