Friday, June 30, 2006

No "Leap Second" Added Today

Add a second? Subtract a second? Just how important is "exact" time? The rotation of the earth is not only erratic but also has been slowing down since 1900, which makes an astronomical second longer than an atomic second, therefore adjustments are made by international agreement to keep the two clocks within 0.9 second of each other. June 30 is one of the days that has been favored for a change in our clock time to coordinate atomic and astronomical times. (December 31 is one of the other dates often used.) The Central Bureau of the International Earth Rotation Service at Paris, France, has been determining which days to select since 1972. As of July 1, 2005, a total of 22 leap seconds had been added. But not this year. No positive Leap Second will be introduced today. This information was found at the International Earth Rotation and Reference Systems Service web page.

We were started down this train of thought just browsing for fun in our Reference copy of Chase's Calendar of Events under today's date. Every day new trains depart.

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