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    Re: no leap second coming in December
    From: Richard B. Langley
    Date: 2004 Jul 27, 12:58 -0300

    See  and the PDF file
    The length of the astronomical day varies because of several different
    phenomena including tidal friction and the exchange of angular momentum
    between the Earth's core, mantle, and atmosphere. During the past 100 years or
    so, the length of day based on the Earth's rotation has almost always been
    longer than a day containing exactly 86,400 seconds (the UTC day). The shorter
    UTC day requires the periodic insertion of leap seconds, the last one at the
    end of December 1998. Over the past few years, the Earth's average rate of
    rotation has increased slightly and consequently the need for an additional
    leap second has not yet been announced.
    -- Richard Langley
    On Tue, 27 Jul 2004, George Huxtable wrote:
    >On 24 July Paul Hirose wrote-
    >>A few days ago the IERS announced there would be no leap second at the
    >>end of this year. We will have a record-setting run of six
    >>consecutive years with no leap second. The previous longest break was
    >>1986 and 1987.
    >>At present UT1 is .46 second behind UTC. The offset is predicted to be
    >>.49 second at the end of the year, and .52 second in mid-2005.
    >Does this imply, then, that delta-T, the difference between universal time
    >and ephemeris time, has remained "stuck" at a constant, or nearly-constant
    >value, over that period of six years? If so, what vaue has it stuck at?
    >And if so, does anyone understand the geophysical causes that have resulted
    >in the slowing of the Earth's rotation, which has been so consistent over
    >the last 80 years or so, to suddenly switch off, 6 years ago?
    >Or have I misunderstood something completely?
    >contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    >01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    >Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
     Richard B. Langley                            E-mail: lang@unb.ca
     Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
     Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
     University of New Brunswick                   Fax:      +1 506 453-4943
     Fredericton, N.B., Canada  E3B 5A3
         Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/

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