Even the Earth finds it hard to be on time

THIS morning will stretch longer by a second. A leap second.
Nanjing Night Net

International timekeepers are adding a second to the clock at midnight universal time Saturday, June 30, going into July 1. That is 10am. Universal time will be 11.59.59 and then the unusual reading of 11.59.60 before it hits midnight.

A combination of factors, including the Earth slowing down a bit from the tidal pull of the moon, and an atomic clock that is a hair too fast, means that periodically timekeepers have to synchronise the official atomic clocks, said Daniel Gambis, the head of the Earth Orientation Service in Paris, which co-ordinates leap seconds.

The time it takes the Earth to rotate on its axis – the definition of a day – is now about two milliseconds longer than it was 100 years ago, said Geoff Chester, a spokesman at the US Naval Observatory, keeper of the official US atomic clocks. That’s each day, so it adds up to nearly three-quarters of a second a year.

Timekeepers add that leap second to keep the sun at its highest at noon, at least during standard time. This is the first leap second since January 2009 and the 25th overall. Mr Gambis said the next one probably would not be needed until 2015 or 2016.

There should be no noticeable effect or inconvenience on computers or any other technology that requires precise timekeeping because they adjusted for these leap seconds, Mr Gambis said.

Earlier this year, official timekeepers discussed whether to eliminate the practice of adding leap seconds. They decided they needed more time to think about the issue.

So for now, Mr Chester said, ”you get an extra second – don’t waste it.”


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