A date with Venus

There is something about the Transit of Venus that touches the imagination in ways that are not all to do with astronomy. The last Transit occurred in 2012, and if nobody who watched it will ever see another, the sight of that small black dot, making its almost imperceptible progress across the disc of the sun, offered, across the span of 243 years, an oddly moving connection with the scientists and sailors who quartered the globe and, sometimes, risked their lives in 1769 to attempt the first comprehensive observations of the event.

There is no shortage any more of ‘global events’ — a good, old fashioned footballing brawl between England and Colombia will stop the planet — but in the more localised world of the 18th century it was another matter. ‘In a globe parcelled up in parishes and towns, provinces and colonies, the Transit of Venus,’ Peter Moore writes in this bold and imaginative sweep of a book, was

a rare instance of people undertaking the simple action of pausing, looking and counting across dispersed space. As Cook and Green sat on their chairs in Fort Venus… Jeremiah Dixon was gazing upwards from Hammerfest Island in the Arctic Circle, and William Wales was peering through a telescope at Hudson’s Bay. In Newport, Rhode Island, Revd Ezra Stiles braced himself for the observation. Nearby in Cambridge, New England John Winthrop, professor of mathematics at Harvard, looked though smoked glass at the sun, as did Maskelyne at Greenwich London.

The prize for success was the mathematical data that might enable scientists to calculate the earth’s distance from the sun. The particular problem, in 1769, was that only the very beginning of the Transit would be visible from Britain or western Europe and that it should ideally be observed from somewhere in the South Seas.