OxBlog

Tuesday, June 08, 2004

# Posted 4:11 AM by Patrick Belton  

OXBLOG REVERSES ITS ADVICE: Save your eyesight, watch BBC! You can watch the transit of Venus safely on the BBC's SunCam. In 1761 and 1769, the transit of Venus proved crucial in calculating the astronomical unit - the mean distance between Earth and the sun - as roughly 150 million kilometres. This methodology was urged on astronomers by the Astronomer Royal, Edmund Halley, before his death (the distance had already been approximated at 140 million kilometres by Jean Richer and Giovanni Cassini in 1672, using the parallax of Mars.)

The Economist has an amusing tale of the transit quests of 1761, which motivated Cook's first voyage of discovery and an expedition to Sumatra by the later-famous British explorers Mason and Dixon - and, on the French side of a cross-channel scientific rivalry which predated the twentieth century's space race by two hundred years, the pathetic tale of the excessively-surnamed Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisiere. Later, in 1874, that year's transit impelled the first (and badly functioning) motion camera. (There's also a great deal more history here.)
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