Astronomical unit from the transits of Venus
Medida de la unidad astronómica por los tránsitos de Venus
- Date
- 1761-1769 · confidence high
- Place
- Tahiti (Cook's expedition), French Polynesia
- Credited to
- International expeditions (Cook, Green, Chappe, Lalande)
- Field
- Cosmos & Earth
What was discovered
Following Halley's method, dozens of expeditions timed the transit of Venus from distant locations; Lalande obtained an Earth-Sun distance of about 153 million km. The first global scientific campaign.
The 'black drop effect' limited precision.
What it led to
- Absolute scale of the solar system
- International scientific cooperation
- Exploration of the Pacific (Cook)
Built on
Made possible
- Expedition timekeeping