Leap Second To Make Tuesday Year's Longest Day
Tuesday will be a day longer by one second than other days of the year. The extra 'leap second' is being inserted to compensate for slowing of Earth's rotation.
NASA explained that Earth's rotation is slowing due to various factors, some predictable and some unpredictable. While the length of a day as accounted by the Coordinated Universal Time is 86,400 seconds, Earth today takes around 86,400.002 seconds to complete one rotation. The length of actual day has been longer than the UTC day since the 1820s. The UTC is based on transitions of Caesium atom.
"Earth's rotation is gradually slowing down a bit, so leap seconds are a way to account for that," said Daniel MacMillan of NASA's Goddard Space Flight Center.
Earth's slowing is a result of the gravitational tug of war between Earth, Sun and the Moon but other factors including atmospheric and climatic conditions can affect rotation, NASA said.
Though a millisecond is not much time to lose every day, it adds up over the year, throwing the UTC off by as much as a second. Given that Earth's slowing is set to continue and leap second additions more frequent, suggestions have been mooted to do away with them as leap seconds cannot always be accounted before insertion.
"In the short term, leap seconds are not as predictable as everyone would like. The modeling of the Earth predicts that more and more leap seconds will be called for in the long-term, but we can't say that one will be needed every year," said Chopo Ma, a member of the directing board of the International Earth Rotation and Reference Systems Service, which inserts the leap second.
