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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