[LEAPSECS] UTC Redefinition Advanced
Jonathan E. Hardis
jhardis at tcs.wap.org
Sat Oct 23 00:05:49 EDT 2010
On Oct 22, 2010, at 11:14 PM, Rob Seaman wrote:
> ... Clocks appear in numerous places in the workflow. It is no
> simple feat to coordinate all these clocks with vintages ranging
> over the last quarter century. GPS? Phones? Web apps?
> Data start at a mountaintop telescope, but flow downhill to archives
> and pipelines and virtual observatory portals. Redefining UTC will
> put a permanent kink in scientific and historical timescales, as
> when performing the frequent chore of combining data from different
> epochs - or from different telescopes. Astronomers assemble light
> curves from observations taken worldwide (and in space - wanna
> estimate the cost of a space certified interface box). These
> systems have to interoperate, something that is automatically
> provided by UTC's current definition as an approximation to mean
> solar time.
> What about space missions in progress? What about preserving a
> coherent data set from decade-long synoptic surveys? Telescopes
> aren't just the cartoon illustration of Palomar, what about radio
> interferometers, gravity wave detectors, neutrino telescopes buried
> beneath Antarctic ice? The increasingly common networks of robotic
> telescopes pursuing common investigations? ...
Now comes the moment of self-appraisal.
How many of these systems CURRENTLY properly handle leap seconds? How
many of these cell phones and space systems and digital devices
"buried beneath Antarctic ice" CURRENTLY are built to a specification
that a minute can contain either 59, 60, or 61 seconds? Or that when
a leap second occurs, it occurs at midnight only in the UTC+0 time
zone? (4:00 PM in the afternoon in California)
Leap seconds have been around since 1972 (IIRC). Notwithstanding
those in denial on this mailing list that the ones before the COMPETES
Act somehow didn't count, we have had, since 1972, an explosion of
digital infrastructure that is designed and built without regard to
leap seconds. Minutes contain 60 seconds ... period.
If you're going to get angry, don't get angry that some at the ITU
don't share your sense of esthetics. Get angry that we live in a
world full of badly designed digital stuff. That's both the true
problem and the solution. Work towards the day when any digital
system that must be certified must meet a specification of being able
to deal with leap seconds. Work towards the day when all OSes handle
them gracefully, and in a uniform fashion. Work towards the day when
being able to handle leap seconds is the norm, rather than the
exception. At that point ... after most everything around you now has
made it into the landfill ... your kids or grandkids will be in a much
better position to continue the practice.
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