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    Re: Leap seconds
    From: Gary LaPook
    Date: 2009 Jan 4, 03:06 -0800

    You should also read this paper:
    
    http://www.ucolick.org/~sla/leapsecs/dutc.html
    
    gl
    
    On Jan 2, 11:07�pm,  wrote:
    > Geoffrey, last week you wrote:
    > "Is there any reasonable and accurate account available of the UK's current
    > argument within the working group of the ITU, in which the UK rejects the
    > abolition of leap seconds?"
    >
    > I haven't been able to find anything like that, but there is a detailed 
    argument against the abrupt and unconsidered abolition of leap seconds 
    here:http://www.ucolick.org/~sla/leapsecs/
    >
    > Lots of useful details, some nice graphs on the "figures and tables" page. 
    Some of the information is out-of-date, but it's still good reading.
    >
    > One thing struck me while reading on that site (not something that he 
    directly points out). The real risk from keeping leap seconds might not be 
    ordinary leap seconds but the possibility, which might still happen, of a 
    negative leap second. It's very easy to imagine computer systems which would 
    do this incorrectly. Even without that risk, I still think it makes good 
    sense to drop leap seconds due to the smaller risk from programming positive 
    leap seconds.
    >
    > If you read comments from "ordinary people" (and I saw you posted at The 
    Times site so I would guess you read some of those), you may notice that 
    people are easily worked up by the thought of arbitrary changes to their time 
    systems. This can get out of hand if the reasons for the changes are not 
    explained carefully and in clear terms. I was reminded of an exchange between 
    two prisoners in the gulag in Solzhenitsyn's "One Day in the Life of Ivan 
    Denisovich." One character says, "Since then it's been decreed that the sun 
    is highest at one o'clock." The other wonders, "Who decreed that?" And the 
    first answers, "The Soviet government." It's supposed to be a wry comment on 
    the absurdity of the Communist government: who but the Soviets would think to 
    order the Sun to change its time?! What they're talking about is Soviet (and 
    now Russian) "decree time" which sets clocks about one time zone ahead 
    year-round (with Summer Time additional). There's nothing necessarily wrong 
    with it, and it's not an example of a government gone mad. But time is 
    something that everyone thinks they understand. For example, 'noon: that's 
    when the Sun's straight overhead,' right? :-) Everybody "knows" that, and if 
    governments or scientific bodies try to change it, they must be corrupt. As I 
    say, that's the big risk in not explaining this correctly.
    >
    > I think the important point that needs to be made in communication with the 
    public is that we gave up "sun time" long ago. In fact, I would say we've 
    given it up three times. First, in the late 18th century (and not until 1834 
    in the Nautical Almanac), when we abandoned local apparent time for local 
    mean time. Clocks replaced the Sun, but on average they still agreed within 
    20 minutes. Second, in the late 19th century, zone time replaced local mean 
    time. That added up to an hour of difference but usually less than thirty 
    minutes. And most recently, in the early and mid 20th century, "Summer Time" 
    or DST added another hour of difference. In other words, today, we keep time 
    by the Sun only in the most general sense; it should be daylight in 
    mid-latitudes when the clock says "noon". Dropping leap seconds will not 
    change that. Your post on The Times site was right on the mark: if we can 
    deal with "Summer Time," then we can deal with the abolition of leap seconds.
    >
    > -FER
    > PS: while looking for some further thoughts on Soviet "decree time", my 
    googling led me to a post regarding the time of launch of some satellites for 
    the Russian Glonass system, and the poster asked whether that time was 
    Russian decree time or not. Small world that this is, the poster was NavList 
    member Richard Langley.
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