[LEAPSECS] Schedule for success

M. Warner Losh imp at bsdimp.com
Mon Dec 22 13:43:03 EST 2008

In message: <F0158734-CA0B-4CD1-BB0E-6B0AD31A1EB7 at noao.edu>
Rob Seaman <seaman at noao.edu> writes:

: Tony Finch wrote:


: > On Mon, 22 Dec 2008, Rob Seaman wrote:

: >>

: >> No. We have been using mean solar time formally since the 19th

: >> century, and informally since we woke each morning to light shining

: >> through

: >> the entrance of the cave.

: >

: > Apparent solar time is not mean solar time. Remember that for a lot of

: > history we used rubber hours that varied according to the time between

: > sunrise and sunset. Mean solar time cannot be established without

: > reasonably accurate clocks.


: Either you haven't read this message yet:


: http://six.pairlist.net/pipermail/leapsecs/2008-December/000714.html


: or I've yet again failed to make my point.


: Mother Earth "establishes" mean solar time simply by spinning on its

: axis and orbiting the sun. Apparent solar time is a mere happenstance

: of angles. Rates matter more than offsets.

But the second is no longer defined in terms of solar time, so why
does this really matter? UTC isn't the same as local time for most of
the planet. We already do time zones, and we already accept an hour
or two of difference between our local time and the sun's time. Why
then the slavish need to keep UTC corresponding to the time at what is
at best an arbitrary meridian? The second no longer measures earth


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