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    Re: clock synchronization
    From: Robin Birch
    Date: 2004 Feb 5, 08:57 +0000
    As far as I know it was established by Greenwich Observatory for their own use, then became a standard for the country which was then adopted worldwide in preference to other national observatory's standard as at the time Britain was the predominant maritime nation.

    Rather than Greenwich adopt it from or for a local observatory, it was the observatory at Greenwich that set it and every one else adopted it. Originally they indicated 12:00 by dropping a signal ball on a post on the roof (it's still there and I believe they still do this). This was visible from most of the anchorages in the Thames until you got to Tower Bridge and so ships could set their clocks to 12:00.

    If you get a chance go and visit Greenwich. Both the observatory and the maritime museum are very well worth the visit.



    Inactive hide details for Patrick Stanistreet <be708@LAFN.ORG>Patrick Stanistreet <be708@LAFN.ORG>

            Patrick Stanistreet <be708@LAFN.ORG>
            Sent by: Navigation Mailing List <NAVIGATION-L@LISTSERV.WEBKAHUNA.COM>

            05/02/2004 04:08
            Please respond to Navigation Mailing List

    Subject: clock synchronization

    Based upon a rather hasty bit of research concerning how it
    was possible to synchronize clocks in different parts
    of the world it seems that galileo, cassini and others
    that I cannot credit due to ignorance came up with the
    idea of creating an astronomical clock based on the
    eclipses of jupiters moons. By creating accurate
    tables of the times of the eclipses it was possible
    to set clocks to both local time and greenwich time
    to perhaps a few seconds at locations quite distant
    from each other. Although not a feasible method
    for ships on the ocean, they could at least compare
    their clocks in ports that had observatories monitoring
    jupiters moons.

    The next question is say at greenwich, how was it decided
    to set the local time to a particular clock time say 12:00
    noon to the second? Was it a convention or was their some
    method useful to any nearby observatory?
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