Leap second away
31 December 2005
by Carina
Lee
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Most people have heard of the term 'leap year', but perhaps not so many are familiar with the term 'leap second'. In fact, leap seconds have nothing to do with leap years. At the end of this year, a leap second will be added to the Coordinated Universal Time at 23:59:59. Atomic clocks will read 23:59:60 UTC before changing to all zeros. It is the first time in seven years this has occured. This second will be the 23rd leap second to be inserted since its 1972 introduction. A leap second is defined as a second that is measured by an atomic clock, compensating the inaccuracies of the Earth's rotation. An atomic clock works by measuring the way atoms vibrate and atomic time was adopted as the primary reference for all scientific timing in 1972. The leap second is usually calculated as 1/86400 of an average solar day. As the Earth rotates it wobbles on its axis, therefore one second is added onto a chosen day to make up for the second lost. Scientists in time-keeping laboratories monitor the rotation of the Earth. When the majority of laboratories around the world agree that the Earth's rotation has slowed by a second, a leap second is added to Greenwich Mean Time (GMT) at midnight. There can be both positive and negative leap seconds, and there are factors affecting the solar day, such as the tidal acceleration of the Moon. |
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