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

William Unruh unruh at invalid.ca
Mon Jan 26 16:53:49 UTC 2015


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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