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    Re: no leap second coming in December
    From: Frank Reed CT
    Date: 2004 Jul 29, 13:46 EDT
    George H wrote:
    "I know that delta-T has fluctuated significantly in the past, but this time
    there seems to have been a rather sudden increase in spin speed, by quite a
    large amount. What could be the cause of this rather dramatic change? "

    The recent changes in delta-t are not that dramatic. Here's some code I use for delta-t for the period 1750 to 2050 (gives a value for each decade year so for example DTtable(2) is 15 seconds for the year 1770):
    DTtable(0) = 12    '1750
    DTtable(1) = 14
    DTtable(2) = 15
    DTtable(3) = 16
    DTtable(4) = 16 
    DTtable(5) = 13.1  '1800
    DTtable(6) = 12
    DTtable(7) = 11.6
    DTtable(8) = 7.1
    DTtable(9) = 5.4
    DTtable(10) = 6.8  '1850
    DTtable(11) = 7.7
    DTtable(12) = 1.4
    DTtable(13) = -5.5
    DTtable(14) = -6
    DTtable(15) = -2.8 '1900
    DTtable(16) = 10.4
    DTtable(17) = 21.1
    DTtable(18) = 24.0
    DTtable(19) = 24.3
    DTtable(20) = 29.1 '1950
    DTtable(21) = 33.1
    DTtable(22) = 40.2
    DTtable(23) = 50.5
    DTtable(24) = 56.9
    DTtable(25) = 63.1 '2000
    DTtable(26) = 69
    DTtable(27) = 76
    DTtable(28) = 83
    DTtable(29) = 90
    DTtable(30) = 97   '2050
    DTtable(31) = 104

    Except for the speculative extrapolation for future t, this table is taken from Meeus' "Astronomical Algorithms". Note that there are changes in the 19th century that are quite large and that they are both positive and negative.

    Frank R
    [X] Mystic, Connecticut
    [ ] Chicago, Illinois
       
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