[LEAPSECS] Time-of-day

[Rob Seaman]

Poul-Henning Kamp wrote:


> Clocks do simulating anything, there is nothing for them to simulate.


Aside:  A nice example of the system engineering process.   You are rejecting the assertion of a requirement.  Note that we aren't led into back alleys of fretting about one particular solution versus another.  Rather we can debate the requirement by itself.

To continue the debate:

Balderdash!  Of course clocks simulate some external process.  You argue this yourself:

	"The goal of all metrology, is to use fundamental concepts that allows measurements to be reliably reproduced anywhere, any time, independently."

You are asserting that clocks should in the future simulate other "fundamental concepts", that's all.  Does your wristwatch actually function using those concepts?  No - it simulates them.  We don't differ on the question of "simulation", we differ about what is required to be simulated.

You are attempting to assert that no requirement exists to tie the zero point or rate of UTC to macroscopically visible shared phenomena:


> Seconds have been liberated from their earthly toil, and there is absolutely no reason to confuse them with earth rotatation angle anymore:


And yet the ITU isn't seeking this liberation.  They are tied very closely to mimicking a mean solar time scale.  I am merely asserting that their limp proposal is not nearly close enough.  You are asserting it is.  This is very different than claiming the freedom to "liberate" the clocks entirely.  The ITU proposal is not - cannot be - to mistune length-of-day by even as little as one part in one hundred-thousand.  The ITU proposal is not - cannot be - to shift the phase by a jump of even minutes, let alone hours.  Mistune from what?  From the synodic day.

Those limitations on the ITU proposal are the result of underlying system requirements.  In particular of a requirement that "day" means "synodic day".  There is an additional requirement that clocks simulate a cadence corresponding to the SI-second.  These are two separate requirements and any proposed solutions have to engage in trade-offs of one sort or another.

The ITU are the ones confusing SI-seconds with synodic days.  They represent two different clocks.  


> Ever since Harrisson we have been able to keep time without telescopes.


Er - no.  Chronometers were set via Greenwich observations prior to setting sail.

Rob