Changes

'''Lines of longitude''' or '''meridians''' are imaginary lines that run north and south across the earth.  They are used to measure east-west location, relative to a "prime meridian" which by definition is 0&deg;.  While in the past many meridians have been used, since 1884 the Greenwich Meridian has become the universal standard.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> Longitude is an ''angular'' measurement and is given in degrees, minutes, and seconds, represented by the symbols &deg;, ', and " respectively.

'''Lines of longitude''' or '''meridians''' are imaginary lines that run north and south across the earth.  They are used to measure east-west location, relative to a "prime meridian" which by definition is 0&deg;.  While in the past many meridians have been used, since 1884 the Greenwich Meridian has become the universal standard.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>

 

Longitude is an ''angular'' measurement and is given in degrees, minutes, and seconds, represented by the symbols &deg;, ', and " respectively. The longitude of the NOAA weather station in New Brunswick, New Jersey, for example, is 74°26'W;<ref>[http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwDI~StnSrch~StnID~20018874 NCDC / Climate-Radar Data Inventories]</ref> that is to say, seventy-four degrees, twenty-six minutes West of the Greenwich meridian.

 

At the Equator, the circumference of the Earth is about 25,000 miles; so one degree of longitude is about 25000 / 360 = 69.4 miles, and one minute is 69.4/60 = 1.15 miles. Originally, a ''nautical mile'' was intended to be one minute of longitude at the equator. (The nautical mile is now ''defined'' to be exactly 1852 meters, so a minute of longitude is actually 1.0018 nautical miles). A second of longitude is only about a hundred feet; before GPS, it was difficult to measure longitude to an accuracy of a second.

Although lines of longitude may be imaginary, they are very important to navigators; [[Lewis Carroll]] joked about this in his long nonsense poem [[The Hunting of the Snark]]:

Although lines of longitude may be imaginary, they are very important to navigators; [[Lewis Carroll]] joked about this in his long nonsense poem [[The Hunting of the Snark]]: