In December of 1760, a British warship boldly left port on an unusual mission: a quest to measure the size of the solar system. The expedition was led by astronomer Charles Mason and his assistant, Jeremiah Dixon.
There was just one minor problem. Britain was at war with France, and within hours, the HMS Seahorse was attacked by a French ship and forced to return home with 11 dead. War or no war, though, the solar system was providing just a brief chance to measure its size, so the Seahorse sailed again a few weeks later.
The expedition's goal was to watch Venus move across the face of the Sun -- an event called a transit. Measuring the timing and path of the transit from different locations would allow scientists to calculate the distance from Earth to the Sun -- the basic ruler for measuring the entire solar system.
The project required measurements from far-flung spots around the globe. But with Britain and France at war, reaching these locations and getting home safely was dangerous.
A French expedition, for example, was beset by a British warship that ignored a letter of safe passage from the British Admiralty and destroyed two ships.
Mason and Dixon were more successful, though. They got good observations, and had a safe journey home. And their work earned them a new commission: surveying the border between Maryland and Pennsylvania -- the Mason-Dixon line.
More about wartime astronomy tomorrow.
Script by Damond Benningfield, Copyright 2008
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