New Year hangs by second

Scientists are delaying the start of 2006 by the first “leap second” in seven years, a timing tweak meant to make up for changes in the Earth’s rotation.

The adjustment will be carried out by sticking an extra second into atomic clocks worldwide at the stroke of midnight Coordinated Universal Time, the widely adopted international standard, according to the U.S. National Institute of Standards and Technology.

“Enjoy New Year’s Eve a second longer,” the institute said in an explanatory notice. “You can toot your horn an extra second this year.”

A leap second is added to keep uniform timekeeping within 0.9 second of the Earth’s rotational time, which can speed up or slow down because of many factors, including ocean tides. The first leap second was added on June 30, 1972, according to NIST, an arm of the U.S. Commerce Department.

Since 1999 until recently, the two time standards have been in close enough synch to escape any need to add a leap second, NIST said.

Although it is possible to have a negative leap second - that is, a second deducted from Coordinated Universal Time - so far all have been add-ons, reflecting the Earth’s general slowing trend due to tidal braking.

Deciding when to introduce a leap second is the responsibility of the International Earth Rotation and Reference Systems Service, a standards-setting body. Under an international pact, the preference for leap seconds is Dec. 31 or June 30.

Precise time measurements are needed for high-speed communications systems among other modern technologies, Reuters reports.

V.Y.