Greeting Another New Year Without a Leap Second (Forwarded)

National Institute of Standards and Technology
Gaithersburg, Maryland

Media Contact:
Fred McGehan, (303) 497-3246,

December 19, 2003

Greeting Another New Year Without a Leap Second

Does it seem like the world is speeding up? That the pace of life is increasing?

If you feel that way, there's scientific evidence to prove your point. The world
has sped up over the last few years. Timekeepers at the National Institute of
Standards and Technology (NIST) note that they have not had to insert an extra
second (called a leap second) into their time scale for five years. Why? Because
the rate of the Earth's rotation has sped up since 1999.

From 1972 (when the world went to the current system of atomic timekeeping)
until 1999, 22 seconds were added to the world's time in order to keep atomic
time synchronized with Earth's time, as measured by the Earth's spin. Since
then, none, nada. Scientists are not sure why this is so, but they do offer some
thoughts.

Tom O'Brian, a physicist and chief of NIST's Time and Frequency Division in
Boulder, Colo., suggests changes in motion of the Earth's core, the effect of
ocean tides and weather, and changes in the shape of the Earth may all be
affecting the spin of Mother Earth. In general, he notes, the long-term trend
has been for the Earth's rotation to slow down, but not in the last five years.

O'Brian said most scientists expect the Earth to continue slowing down again in
the future. So maybe there is hope for those feeling particularly harried.

"The Earth's rotation rate has been the primary clock for nearly all of human
history," he says, adding that "only in the last 50 years have we had clocks
accurate enough to measure changes in the Earth's spin." NIST introduced the
world's first atomic clock in 1949.

For more information about leap seconds, see
http://tf.nist.gov/general/leaps.htm