Next message: Frank Reed: "Lunars: Did anyone visit the "sadlerium"?"
In 1908, shortly after the death of the famous classical physicist Lord
Kelvin (William Thomson), "The Observatory" published a note on a little game
involving longitude by lunar distance observations which Kelvin had proposed for
a math competition at Cambridge in 1874. The challenge he proposed was:
" Describe the method of 'lunars' for finding longitude at sea, explaining
the use of each of the observations to be made, and the character of the
tabular data required. Why is this method rarely used in modern navigation?
Show how a castaway in the N. hemisphere could, on any clear night, with no
other instrumental appliances than a piece of small cord, determine his
latitude approximately, and on moonlight nights, with favourable stars, his
longitude, if he has a Nautical Almanac. Estimate limits of error for each
determination."
Which was followed by an early version of an old joke:
" One of the other examiners remembers that on this unusual type of
question coming before the board, the following solution was suggested: --Hang up
the Nautical Almanac by the cord, determine the time of its swing as a
pendulum, and hence find the force of gravity; and then find the latitude from the
formula connecting it with gravity."
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
