[LEAPSECS] Reliability

[Rob Seaman]

Tony Finch wrote:


> Such as? I can't think of anything simple enough to count as common  

> sense

> which depends on the relation between UT1 and the various local times.



As with most issues discussed on this list, questions need to be  
framed properly before they can be addressed.

The key role that UTC plays in framing the "simple utilitarian  
inferences regarding the world around us" that I mentioned is as a  
prediction of UT1.  UT1 itself is only known retroactively.

Similarly, UTC (and GPS) provide access to TAI, which we have been  
informed time and again is some mystical perfect timescale unsuitable  
for use by mere humans.  (Or rather, it isn't UTC per se, but the  
various realizations of UTC that provide dual access to interval and  
Earth orientation timescales.)

Universally (to use that word metaphorically yet again), we do not use  
the "various local times" to compute or intuit global assertions about  
our world.  Which is to say, we may observe that the Sun is up or down  
at some particular moment, but to predict the behavior tomorrow we  
always tie into Universal Time in some fashion.

Currently access to UTC is automatically supplied (for both simple and  
complex utilitarian purposes) because it is built into the system of  
standard time zones.

The ITU proposal would sunder this.  Yes, we could cheat some of the  
purposes some of the time, and some other purposes all of the time,  
but most definitely not all of the purposes forever.

The real answer to "I can't think of" queries is to point out that  
these are explicit pleas to engage in a process of requirement  
discovery.  Neither God nor science reside in the gaps of our  
imagination.

Rob