[LEAPSECS] Following an open source process

[Tom Van Baak]

> - the civil day is the synodic day


Rob, please define "is". Surely you don't mean equality, in a
mathematical sense. What really is meant by this statement?

You bring this topic up a lot. But everyone knows civil time is
now only grossly associated with anything solar; it doesn't match
at the second level, not even the minute level, though usually near
an hour or two, the equivalent of hundreds or thousands of miles.

Local civil time used to be determine by the astronomer-guy in
your local village. Now it's not. Get over it.


> - the unit of time is the SI-second


Agreed.


> - a non-UT timescale should be called something other than "UTx"


This sounds more like a preference than an absolute requirement,
but I agree it's a good preference, so leave it on the table.

I notice some model have dates to models; like JD2000. Would it
help so use that for UT as well, like UT1972 or UT2020? Or make
things worse.


> And we have options to debate such as:

>

> - preserving the current time scale to permit an orderly transition

>

> - immediately lengthening the leap second schedule to the 2-3 years that appears possible without loosening the DUT1 

> constraint

>

> - building a plan to prudently increase DUT1 in stages to permit lengthening the schedule to 10 years or beyond


Any progress with relaxing decades-old outdated requirements on
DUT1 would be a good thing. Astronomers have UT and no one is
touching that. Presumably you use UT in your automated systems.
The world of precision timing has TAI and its clones and no one is
touching that. Civil time switched from its UT-base in the 60's.

It seems most of the problem we're running into is keeping DUT1
within some magical bounds. If you read the old papers it was
navigators and their sextants they were worried about. First they
wanted 0.1 second tolerance. Then, what, 0.5? 0.7? 0.9? No one
worried about astronomers; they already had UT-sub-n for their
work. It was the sailors that was the problem back then.

Personally I don't see a problem if DUT1 is allowed to grow to a
much larger value. Seconds, many seconds, even minutes. But
probably keep it under an hour.

The beauty is that the change is not sudden. It is certain that
any systems within the astronomical community that have some
sort of DUT1 dependency have different accuracy thresholds.
And thus any glitches that go undetected will occur sporadically
over the next decade or century, not all at once.


> However, pretending the entire world can ignore the synodic day is not an option.


Please define "ignore".

/tvb