[LEAPSECS] Short notice for DST changes

Ian Batten igb at batten.eu.org
Tue Feb 25 02:10:38 EST 2014

On 24 Feb 2014, at 22:56, Rob Seaman <seaman at noao.edu> wrote:


> Rather, there have to be very close to 86,400 SI-seconds per day, because that how long a day is.

And this is why engineers and scientists make bad public policy, because of an unwillingness to make convenient but "unscientific" approximations.

All the arguments about rate comes down is what the definition of "very close" is. A day isn't 86400 SI seconds, nor is the average day 86400 SI seconds. Hence, whatever you do, there will need to be corrections made in some manner over a sufficient long time-scale. There are for practical purposes no applications outside astronomy where you need alignment of clocks to synodic days to a precision of more than a hour, or more: we know this, because many large population centres have their local noon an hour or more from mean solar noon, and very few population centres _do_ have their noon at local mean solar noon. Even places that do (for example, London) only have noon be "Sun at its zenth at 120000" on a few days a year, because mean solar time is not local apparent solar time on any given day. And for people who do need synodic time, the Internet can provide it.

[[ Clive and I, at least, frequent Another Place where railway ticketing is discussed. Whenever a proposal is made to remove, say, cash payment facilities, ludicrous scenarios are proposed about disabled orphans who communicate only in ancient Egyptian and have religious objections to payment in anything other than gold coins. Similarly, arguing that the civil time should be vetoed by some tiny pool of astronomical equipment is not going to convince anyone outside the astronomical community, and not even all of those. ]]

So there is a massive approximation in use already, and if we simply abandoned leap seconds and let civil time and synodic time drift at ~1s/18m, it would take hundreds of years for the error to build up to a level greater than current approximations. And the "what about people in 500 years?" argument is something to which most people's response will be "let them sort it out". I suspect that plans for 2014 made in 1514 have not proven to be durable.


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