A British expedition sailed to Tahiti just to watch a dot cross the sun

In 1769, Captain James Cook's first Pacific voyage carried a specific scientific mission: observe the transit of Venus from Tahiti as part of a worldwide effort to triangulate the exact distance from Earth to the Sun. The timing data gathered globally that year genuinely refined the astronomical unit — and the voyage's other result was the first detailed European charting of New Zealand and eastern Australia.

— James Cook, The Journals of Captain James Cook — First voyage, 1768–1771