Subj : Re: 'Leap Second' to Be Added on New Year's Eve This Year To : All From : Imvalid@somewear.com Date : Sat Dec 31 2016 15:57:00 From: "James Wilkinson Sword" Subject: Re: 'Leap Second' to Be Added on New Year's Eve This Year On Thu, 22 Dec 2016 13:43:58 -0000, Mr. Man-wai Chang wrote: > 'Leap Second' to Be Added on New Year's Eve This Year > > Full story: > > Revelers will get to celebrate New Year's Eve for a tiny bit longer > than usual this year. > > A "leap second" will be added to the world's official clocks on Dec. 3= 1 > at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC= ), > which corresponds to 6:59:59 p.m. EST; the clocks will read 23:59:60 > before ticking over to midnight. The goal is to keep two different > timescales in sync with each other. > > The units of time had long been defined based on Earth's rotation > relative to distant celestial bodies. But that changed with the > invention of atomic clocks in the mid-20th century; scientists then > decided to base the second on the natural vibrations of the cesium ato= m. > [How to Build the Most Accurate Atomic Clocks (Video)] > > These two timescales don't match up exactly, however. Measurements sho= w > that, because the moon's gravitational pull and other factors are > gradually slowing Earth's spin, the rotation-based scale loses between= > 1.5 and 2 milliseconds per day compared to atomic time =E2=80=94 meani= ng the two > diverge by a full second every 500 to 750 days. > > Leap seconds are a way to make up for this difference. Since 1972, the= > International Earth Rotation and Reference Systems Service (IERS) =E2=80= =94 the > organization that keeps track of time for the world =E2=80=94 has adde= d 26 leap > seconds to atomic clocks, with the last such insertion coming on June > 30, 2015. > > The aim is to keep the two timescales within 0.9 seconds of each oth= er. > > "We can easily change the time of an atomic clock, but it is not > possible to alter the Earth's rotational speed to match the atomic > clocks," officials with the U.S. Naval Observatory (USNO), which > maintains the Department of Defense's master clock, noted =E2=80=94 wr= yly, it > would seem =E2=80=94 in a statement today (July 6). > > While Earth's rotation rate is slowing, the effect is quite subtle. > > "Confusion sometimes arises over the misconception that the occasional= > insertion of leap seconds every few years indicates that the Earth > should stop rotating within a few millennia," USNO officials wrote. > "This is because some [people] mistake leap seconds to be a measure of= > the rate at which the Earth is slowing. The 1-second increments are, > however, indications of the accumulated difference in time between the= > two systems." > > When leap seconds are added, they are always inserted on June 30 or De= c. > 31 of a particular year. In 1972, IERS officials called for a leap > second to be inserted on both dates. I wish they'd turn their attentions to not turning the clocks back and f= orth all the fucking time! -- = I was doing some remolishments to my house the other day and accidentall= y defurbished it. --- ViaMAIL!/WC v2.00 * Origin: ViaMAIL! - Lightning Fast Mailer for Wildcat! (1:261/20) .