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Not just a second

??.three, two, one!? Revellers ringing in the New Year may not have noticed it, but their countdown to 2006 at midnight last Saturday was off by one full second.

india Updated: Jan 02, 2006 01:54 IST
PTI

“….three, two, one!” Revellers ringing in the New Year may not have noticed it, but their countdown to 2006 at midnight last Saturday was off by one full second. For at precisely 11:59:59 pm, global timekeepers added an extra ‘leap second’ to the world’s clocks — a move to keep what’s known as Coordinated Universal Time (UTC) aligned with the time determined by the Earth’s rotation. The planet’s spin has been slowing of late and the extra second was needed to reconcile this with the relentless tick of atomic clocks.

Man’s oldest clock is his own planet, taking 24 hours to spin once on its ‘axis’, give or take about .001 second per day. The trouble is, over time, the small discrepancy adds up to a huge deviation. Modern atomic clocks that determine International Atomic Time (TAI) aren’t linked to Earth’s rotation, and unless they’re adjusted, they would eventually move out of sync with day and night.

Curiously, the very act of synchronising UTC and TAI may now prompt scientists to redefine the current definition of UTC, which was adopted to minimise potential timing errors in celestial navigation. Satellite navigation depends on precise timing, underlining the importance of a uniform time scale for users. Thus leap seconds won’t affect the operation of the GPS, since it’s based on GPS Time that needn’t be adjusted to account for leap seconds. GPS provides you with UTC by transmitting the necessary data in its navigation message to allow your receiver to compute UTC from GPS Time. But users of the Russian GLONASS system will be at sea temporarily, till the system’s clocks are synchronised. This year’s New Year resolution: recast international agreements on time.

First Published: Jan 02, 2006 01:54 IST