New Scientist magazine has a feature called "The last word", in which readers' questions are answered by other readers.

Recently one reader's question asked what point on earth was farthest from the nearest sea, meaning farthest from any inlet of the world ocean. Rivers don't count, just seas, connected to the world ocean and subject to tides of the whole sea, not just seiches.

A reply was published, calling this point the "continental pole of inaccessibility (CPI)", that said the question was raised in the 1960's when builders of submarine-mounted nuclear missiles wanted to tout an ability to target any point on land from a body of water accessible to the sub fleet.

The reply stated that the point is at 46°17'N, 86°40'E, in northwest China near the Russian border, and went on to say that the nearest arm of the sea was 2848 km away at Tianjin on the Yellow Sea. It stated further, that the sub proponents neglected to mention in promotional literature that as the rockets had barely enough range to cover this distance, that "to strike the pole [of inaccessibility] a large nuclear-powered submarine would practically have to visit Tianjin docks."

What's wrong with that reply to the reader's question?

Several points are wrong with the reply:

(1) If the location is accessible then it can't be a location of inaccessibility, but rather the location of least accessibility (from a body of water accessible to a sub fleet).

(2) The furthest distance from the nearest arm of a sea (connected to the world ocean) would require the location to be equidistant between two or more sea points, which the Tianjin dock area would only be one point.

(3) A submarine does not need be nuclear-powered to launch a  rocket. 

(4) The curvature of the Earth and other factors in calculating a rocket trajectory is different at each location and may not necessarily be from the same point as the sea point nearest to the location sought.  

Edited on May 15, 2008, 1:23 pm

Posted by Dej Mar on 2008-05-15 03:03:20