Lost and found in transit
FOLLOW THE READER
MAREEBA, QLD COOKTOWN, on the Cape York peninsula of far north Queensland, will be the best place on earth to observe the solar eclipse on Wednesday.
Cooktown was arguably Australia’s first observatory. In 1770, when Lieutenant James Cook’s Endeavour was being repaired for six weeks in what became Cooktown harbour, an astronomical observation took place to pinpoint longitude — a division of the earth first suggested by Eratosthenes, who died in 194BC.
A transit of Venus occurred in 1769, just as it did in June this year. Cook’s first voyage was organised to observe that transit. Then the Endeavour set off to find Terra Australis Incognita.
And found it was, on April 19, 1770. Cook’s ship then travelled 4000km, charting the east coast before running aground on the Great Barrier Reef on June 11 at about 11pm. Luckily, Endeavour made it to the small harbour (Cooktown) where repairs could be made.
Through a telescope, Cook and Mr Green, the astronomer, were able to consult the universal clock suggested to mariners by Galileo Galilei. Mariners could not accurately plot longitude without a marine clock and many lives were lost and ships wrecked as a result.
The situation became so desperate that a huge prize of £20,000 was offered for the first accurate marine clock. Clockmaker John Harrison worked on his solution for more than 20 years.
The eclipse of one of Jupiter’s satellites on June 29, 1770, at 2.58:53am local time allowed Cook and Green to plot their longitude once the almanac for Greenwich had been read. Cook calculated their longitude at 214 degrees 42 minutes 30 seconds west of Greenwich and latitude 15 degrees 26 minutes south — a small margin of error in the 14,500km distance between what became Cooktown and London.
Cook and Green had observed a satellite to find longitude and so could be said to have made the first use in Australia of satellite navigation. Where would the modern traveller be without it? Send your 400-word contribution to our Follow the Reader column. Published columnists will receive a Lemnis Pharox Solar Kit. Ideal for outdoor adventures, this nifty device is both an energy-efficient portable light and a charger for devices such as phones and iPods. Charge via electricity before you leave or on the road with the included mini solar panel. $49.95. More: 1300 LEMNIS; lemnislighting.com.au.