Why did James Cook travel to Tahiti in 1768?

In 1768, the Royal Society and the British Admiralty organized an expedition to Tahiti with two primary objectives:1

• Scientific Observation: The primary mission was to transport scientists to Tahiti to observe the transit of the planet Venus across the Sun, which occurred on June 3, 1769. Accurate timing of this event was crucial for 18th-century astronomers to calculate the distance between Earth and the Sun, known as the astronomical unit.12
• Geographical Exploration: Once the astronomical observations were complete, James Cook was ordered to search for the hypothesized southern continent, often referred to as Terra Australis, which philosophers of the time believed must exist to balance the landmasses of the Northern Hemisphere.31

This voyage, conducted aboard the HMS Endeavour, marked the beginning of Cook's significant contributions to the exploration of the Pacific, which included surveying New Zealand and the eastern coast of Australia.14