[LEAPSECS] Looking-glass, through

Warner Losh imp at bsdimp.com
Fri Jan 14 11:13:15 EST 2011

On 01/13/2011 22:19, Tom Van Baak wrote:

>> It would appear that making adjustments every 10 days is not

>> often enough, at least in the US, viz:

>> http://www.nist.gov/pml/div688/grp50/NISTUTC.cfm

>> http://www.nist.gov/pml/div688/grp50/nistusno.cfm


>> Even if we abandon the leap second, we have issues at the nanosecond

>> level.


> This is what happens any time you have more than one clock

> and if you have bounds on frequency steering. You'll find that

> all of the UTC(k) clocks disagree at the nanosecond level and

> that they all wander around the mean paper clock, UTC. This

> also is normal and expected.

For large ensembles of clocks, you are pretty much guaranteed to have
this level of fussiness too, since you can never set the clock to the
frequency that you want. You can only ask it to set it to the frequency
you want. Clocks usually comply, mostly. There's always some tiny
error that gets through the process. It doesn't matter if that's a
Hydrogen Maser, a Cesium HP5071A or your wrist watch.

You don't notice the error either until it has had a chance to
accumulate. The errors in frequency are on the order of 1 in 1e14 or
so. Even these tiny errors accumulate to nanoseconds over days...


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