To leap or not to leap
Chicago Tribune: Just before midnight chimes tonight on the world's official clock in Greenwich, England, and 2005 becomes 2006, one extra second will be added. This will mark the 23rd time a leap second has been added since international timekeepers decreed in 1972 that atomic clocks would be delinked from the planet's rotation.
Blame the necessity for these occasional leap seconds on Mother Earth. She adamantly refuses to rotate evenly and predictably with atomic clock time. That's due primarily to Earth's molten core and all the liquid sloshing around the surface. The moon's pull creates daily tidal action that brakes the Earth's spin in an uneven manner.
The International Earth Rotation and Reference Systems Service in 1972 became the coordinator of the two time scales -- the Earth's and atomic clocks. If the two deviate by more than nine-tenths of a second, the group calls for a one-second adjustment either on June 30 or Dec. 31. The previous adjustments have all been additions because the Earth's spin is slowing ever so imperceptibly. If Earth suddenly speeded up, however, the group could subtract a second. The last leap second was added at the end of 1998.
Long before atomic time-keeping, Earth provided the only clock anyone needed. Morning came when the sun rose and evening when the sun set. Earth's clock was sufficient for millenniums, even after humans developed other ways to measure time.
Fine tuning
All that changed when humans, with their insatiable lust for technological advances, invented atomic clocks. These clocks keep time by measuring the resonant frequency of atoms (cesium 133 is the standard) as they pass through a magnetic field. Atomic clocks measure time to the billionth of a second.
Although 22 leap seconds have been added to time without a hitch -- like, well, clockwork -- over the last 33 years, scientists will be watching with special care this New Year's Eve for the addition of the 23rd leap second. The modern world relies increasingly on global positioning and telecommunication systems high in the skies that are linked inextricably not to Earth time but to atomic time. Some experts worry that randomly adding a second here or there could be disruptive to the precision time they require. That risk, they fear, increases along with humankind's technological reliance.
But back here on terra firma, the concept of an extra second is less a technological worry and more a cosmic gift. For those keeping track in Chicago, your bonus 2005 second will come at 5:59:59 p.m. Central Standard Time, when it's midnight in Greenwich. This gives all of you one more blink of an eye to prepare for New Year's Eve festivities and the dawning of the new year. Spend it wisely.