[LEAPSECS] Leap smear

[Ian Batten]

On 19 Sep 2011, at 1446, Rob Seaman wrote:


> 

> If you don't believe that civil time is time-of-day where "day" means "synodic day", then assert an alternate definition for what the word day means.  Then we can debate the two alternatives head-to-head independent of the complexity of how different deployed solutions will address the requirements.


Clive's man on the Clapham Omnibus probably realises that timezones are a fiction, and are a discrete approximation to a continuous function (although he won't describe it like that).  He might have a dim memory from school of being told about towns having their own time and standardisation coming with the railways.   He'll be aware that sundials usually don't agree with his watch, and that when he crosses the channel the sun doesn't suddenly step in the sky.  It might even have occurred to him that one reason the evenings are longer in Cornwall is that you're well to the west of London. Certainly, explaining those things is not difficult.  In America, or mainland Europe, where you can drive your car across a timezone boundary whilst looking out of the window, he'll be even more aware that they're an approximation.

Even if he doesn't know these things, English law's well-known "reasonable man" would not find it hard to understand that his watch ticking the same time in Norwich as in Penzance is a convenient way to make sure that he can turn the radio on in time for The Archers, but that the sun rises and sets at different times within that time zone.

Therefore, he'll be able to understand that he's already accepting up to two hours' disconnect --- one for the width of the time zone, one for daylight saving --- between civil time and solar time.  And he might even realise that his holiday home in Brittany (4' 20"W, UTC+2 in summer) is an even more dramatic example. 

So he's going to be pretty resistant to the idea that a few seconds a decade matters in the slightest.    Civil time is what his watch says.  He already knows civil time isn't solar time.  So shouting that there's a risk that civil time is going to unhitch from solar time by around a minute a century and the sky is going to fall isn't going to frighten him.

ian