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.   
      
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