Talk:Prime Meridian

So why did San Domingo vote against the siting of the Prime Meridian in Greenwich? Anybody know what their alternative was? Lisiate 01:23 24 Jul 2003 (UTC)

We need a public-domain map on this page, showing where this line is.

Last text version of Prime Meridian version: "The meridian (line of longitude) passing through Royal Greenwich Observatory, Greenwich, England is the prime meridian (longitude = 0 degrees).

The meridian was agreed upon in October 1884. At the behest of the President of the United States of America, 41 delegates from 25 nations met in Washington, DC, USA for the International Meridian Conference.

At the conference the following important principles were established:

1) It was desirable to adopt a single world meridian to replace the numerous ones already in existence. 2) The Meridian passing through the principal Transit Instrument at the Observatory at Greenwich was to be the 'initial meridian'. 3) That all longitude would be calculated both east and west from this meridian up to 180°. 4) All countries would adopt a universal day. 5) The universal day would be a Mean Solar Day, beginning at the mean midnight at Greenwich and counted on a 24-hour clock. 6) That nautical and astronomical days everywhere would begin at mean midnight. 7) All technical studies to regulate and extend the application of the decimal system to the division of time and space would be supported.

Resolution 2, fixing the meridian at Greenwich, was passed 22-1 (San Domingo voted against), France and Brazil abstained."

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The previous version declared that Rome meridian corresponds to 1° 30' 28" east of Greenwich, which is obviously nonsense. I have corrected it to 12° 27' 08.04", which is what I have in my sources, but I do not have any authoritative reference; if someone does and it contains some other value, please make a correction. --Mormegil 19:16, 11 Oct 2004 (UTC)

I've just thought of something. What if plate tectonics aren't entirely equal with every plate respective to every other.. wouldn't england move a bit, screwing up the prime meridian's placement??

You are correct. The prime meridian was defined to be where Airy's transit instrument was in 1884, but a different system is now used. Furthermore, the Royal Greenwich Observatory is now a museum, with no working instruments. The prime meridian is now defined relative to the International Terrestrial Reference System (http://www.iers.org/iers/products/itrs/), which uses extragalactic radio and visible sources to which the rotating Earth is referenced via Very Long Baseline Interferometry and other methods. In particular, it is defined to have no net rotation regarding horizontal tectonic motions over the whole earth. — Joe Kress 19:12, Mar 17, 2005 (UTC)

Changed Oslo to Kristiania. That was the name of the city when the local meridian was in use. Ulflarsen 18:42, 17 Mar 2005 (UTC)

I have copies from Norwegian maps (from U.S. Library of Congress) which say "Oslo meridian". As the stub at Kristiania says, that name applied from 1878-1924; as this article says, Greenwich was agreed on as the universal prime meridian in 1884. So it would only have been Kristiania for about a six-year period; most of the time when this was used, it would have been Oslo. BTW, I did find the coordinates and will add them too. Gene Nygaard 19:31, 17 Mar 2005 (UTC)

Well, okay, I caught myself--I should have known better. So it was "Christiania" rather than "Kristiania" from 1624 to 1878. Nonetheless, it is "Oslo" which I have seen on maps. I changed it to Oslo (Kristiania) and am not going to worry about the Chr- spelling, people should be able to figure that much out themselves. Gene Nygaard 19:41, 17 Mar 2005 (UTC)

Simply because the Greenwich meridian was adopted in 1884 does not mean that all local meridians suddenly ceased to exist. The Washington meridian itself was not repealed until 1912 (the borders of several western states were defined relative to it even after 1884). It was actually used for astronomical purposes until 1950 alongside the Greenwich meridian (see the American Ephemeris and Nautical Almanac). The Paris meridian has a very long history -- it was retained until 1911, and then Greenwich mean time was defined as Paris Mean Time retarded by 9 min 21 sec. Many small countries did not repeal their local meridians until much later, and some may still exist. Nepal used that of Katmandu until the 1990s and may still use it. — Joe Kress 02:42, Mar 18, 2005 (UTC)