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

[Brian Garrett]

--------------------------------------------------
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 
seconds


> 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.


Brian


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