3.4 The Endeavour mission’s scientific objectives

Transit of Venus

You could say the heavens brought the Endeavour to the Pacific. A key aim of the Endeavour’s voyage was to go to Tahiti to record the 1769 transit of Venus. This is a rare event where the planet Venus passes between the earth and the sun. They wanted to measure how long it took Venus to move across the sun, which would help them work out the distance between the earth and the sun. Separate expeditions were planned across the globe, including Europe, North America and the Pacific. Unfortunately the observations at Tahiti were disappointing, as they were affected by disturbances in the earth’s atmosphere, including solar winds.

Transit ready

The Endeavour carried the most advanced astronomical tools. The Royal Society supplied Cook and astronomer Charles Green with telescopes. Daniel Solander, the ship’s naturalist, took his own.

‘Dr. Solander observed as well as Mr. Green and myself, and we differ’d from one another in observing the times of the Contacts [phases of the transit] much more than could be expected. Mr Greens Telescope and mine were of the same Magnifying power but that of Dr [Solander] was greater than ours.’

^{James Cook, 3 June 1769}

Under canvas

The Endeavour crew erected a tent at Tahiti to house the ‘astronomical clock’ they had brought with them. Look at the photograph above of this special clock, also called an Orrery. The clock showed the positions of the sun, moon, stars and planets, including Venus.

‘[The clock] was set up in the middle of one end of a large tent, in a frame of wood made for the purpose at Greenwich ... The pendulum was adjusted exactly to the same length as it had been at Greenwich.’

^{Charles Green and James Cook, 1771}

Technology has advanced and knowledge has changed. You can use the internet to research many things which Cook and his Endeavour crew could not.