Nick Lomb, Transit of Venus: 1631 to the present (NewSouth Publishing, 2011)Every so often, the planet Venus does something remarkable. Its orbit brings it to a point directly between the Sun and the Earth, where it appears to us as a black dot moving across the bright disc of the Sun. This transit of Venus is rare, occurring in pairs eight years apart and then not for more than a hundred years; it has fascinated astronomers for centuries.
Seeing last week's transit of Venus was an exciting and humbling experience. More than just an interesting celestial phenomenon, it was an almost tangible link to astronomers of the past. Astronomers such as Jeremiah Horrocks, who was the first person to see a transit of Venus, in 1639; or poor Guillaume le Gentil, whose attempts to observe in 1761 and 1769 kept him away from home for more than nine years and only met with failure; Captain James Cook, who used the 1769 expedition to observe the transit in Tahiti as a base for exploration and discovery; or the Australian astronomers who used a Janssen apparatus to make a photoheliograph of the 1874 transit.
Astronomers such as Kepler, Halley and Isaac Newton—who all helped to predict and identify the dates of Venus transits—never saw the phenomenon themselves. Unfortunately, if you missed the one on June 6th this year, you probably won't get to see the next one, which is due in December 2117.