Why did James Cook sail to the South Sea?

James Cook travelled to the South Sea, in the Pacific Ocean, three times on assignments from the British Government. It was the first voyage (1768-1771) that made him famous. With his ship 'Endeavour' he brought scientists to Tahiti, who wanted to observe the passage of the planet Venus in front of the sun. This was supposed to be helpful in calculating the distance between the Earth and the sun. Map makers had always assumed that there was a continent in the south, but James Cook discovered it. On April 28,1770, he set foot upon the eastern coast of Australia and took possession of the continent as his land.