[ntp:questions] Leap second to be introduced in June

William Unruh unruh at invalid.ca
Mon Jan 26 17:11:44 UTC 2015

On 2015-01-26, William Unruh <unruh at invalid.ca> wrote:
> On 2015-01-26, Jochen Bern <Jochen.Bern at LINworks.de> wrote:
>> On 01/23/2015 08:03 PM, schmidt.rich at gmail.com wrote:
>>> The US will soon be considering a means for dissemination of delta T via NTP
>> Does that read "there's *several* teams working on NTPv5 and not
>> communicating with each other right now" ... ?
>>> The ITU has just met in Geneva and discussed the future of leap seconds.
>>> The US is in favor of dropping them, the Brits are in favor of keeping
>>> the tradition of leap seconds, [...]
>> Leap seconds are an artefact of a) rotation of Earth (which is ever
>> slowing down because of mechanisms that nothing short of pointing a
>> giant disintegrator ray at the Moon can stop, on top of the uncertainty
>> reflected in the unpredictability of current leap seconds), b) the
>> precision we have achieved in measuring - supposedly immutable -
>> physical time, and c) a desire to have time represented in a way that
>> alludes to the traditional "apparent position of the Sun right where I
>> stand (on the surface of the Earth)" notion. You can quantize and/or
>> distribute "leap seconds" in a different way, but you can NOT "drop
>> them" short of kissing one of these three basics goodbye.
> No. It arises from the fact that the second is defined according to a
> physical principle ( the frequency of oscillation of a cesium atom in a
> certain transition) and the rotation of the earth. It used to be defined
> by the rotation of the earth (which was the best clock available) 86400
> seconds in a mean solar day. But as you say, defined in terms of the
> oscillations of that transition, the length of the day can vary-- both
> because of the moon and because of things like earthquakes and global
> warming. Were we to define the mean solar day as 86400 sec, then it
> would always be 86400 sec. But theory says that that would make the
> behaviour of may other systems much more difficult to describe. 
>> (If you read through the comments ITU received along with the votes when
>> they put up the poll, you will notice that a great many "abolish leap
>> seconds" voters proposed schemes that actually do *not* *abolish* the
>> concept of leaps but merely distribute the corrections differently, from
>> infinitesimal leaps to the exceedingly rare leap minute.)
>> Regards,
>> 								J. Bern

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