[LEAPSECS] Cost: getting rid of GMT & discontinuing leap seconds

Brian Garrett mgy1912 at cox.net
Mon Oct 25 14:17:17 EDT 2010

From: "Rob Seaman" <seaman at noao.edu>
Sent: Monday, October 25, 2010 7:53 AM
To: "Leap Second Discussion List" <leapsecs at leapsecond.com>
Subject: Re: [LEAPSECS] Cost: getting rid of GMT & discontinuing leap

> On Oct 25, 2010, at 12:01 AM, Brian Garrett wrote:


>> More accurately, civil timekeeping is sorta kinda like mean solar time.

>> For now.


> See numerous (perhaps beyond count) threads from the archives.


> One more time. The entire reason that the ITU-R scheme can be

> contemplated is that the SI "second" (what should have been called the

> "essen") was mistakenly sized "sorta kinda like" the Babylonian second

> (1/60 of 1/60 of 1/24 of a day). Sure the ITU-R can cheat for a while for

> some purposes, but this is only because for that period for those purposes

> an "SI day" (a non-existent unit) is close enough to resemble the actual

> mean solar day (a unit predating mathematics). Interval time shouldn't

> even be represented with sexagesimals (a way of expressing angles).


> Etc and so forth.


>> There's no reason that couldn't change. If legislators were somehow to

>> be convinced that TAI or GPS time were the way to go, then that's what

>> they'd impose and that's what _hoi polloi_ would use.


> Legislators can attempt to impose all sorts of things. Over the long

> term, the true underlying natural "requirements" (in the engineering

> sense) will reveal themselves.


Over the VERY long term, yes. Over a human lifespan no.

> Another name for "hoi polloi" is "citizens" or "customers".


>> Indeed, I can totally imagine how that could happen, especially since

>> they already think imposing an offset of 216000 seconds for seven months

>> out of the year is a good idea.


> Confuses periodic and secular effects. Apparent solar time is a red

> herring. Mean solar time is simply the natural sidereal period of the

> Earth adjusted for one day "lost" each year lapping the Sun.


> Have no idea what the number 216000 seconds (2.5 days) is supposed to

> mean.

I should have said 3600 seconds. One hour. The amount of a DST offset.


>> Anybody who uses UTC professionally and does not live in a place where

>> UTC is the local zone time has already divorced themselves from local

>> mean solar time. So has any location that uses summer/daylight saving

>> time.


> UTC is the zero point for the entire standard zone civil timekeeping

> system. It is one unified whole. It is the existence of an underlying

> common timescale that permits separate time zones and variations like

> daylight saving time to function.


> Rob


Which could still work if a monotonic time scale like TAI were legislated.


> _______________________________________________

> LEAPSECS mailing list

> LEAPSECS at leapsecond.com

> http://six.pairlist.net/mailman/listinfo/leapsecs


More information about the LEAPSECS mailing list