In 1761 and 1769 respectively, scientists were anxiously awaiting a pair of events that only occurs approximately every 100 years: two transits of Venus between the Sun and the Earth. By observing these transits from different locations all over the globe, they hoped to be able to calculate the distance from the Earth to the Sun.
The collaborative effort to collect data by scientists from many different countries was no easy task in the 18th century. The Seven Years’ War, for instance, split not only Europe into two but also affected the Americas and parts of Asia and Africa. However, not only political entanglements complicated things, but also the simple issue of traveling to faraway places like India, the American west coast, Siberia, or the South Sea was an arduous and dangerous feat. In any case, it became abundantly clear that global cooperation in scientific undertakings of such magnitude was absolutely essential for progress.
Hence there is a slew of interesting parts in here, for example, the story of Chappe d’Autoroche, who had survived an unbelievably strenuous journey to Siberia for the first transit, but died shortly after observing the second one in Baja California because he insisted on staying there for the sake of science despite a deadly outbreak of typhus, or the story of the unlucky Le Gentil who managed to miss both transits because of bad weather. The first voyage of James Cook to the South Sea was part of these observations as well, and really opened the door for science and scientists to be included in journeys of exploration and discovery.
The problem, however, is that most of these engaging stories are only touched on instead of discussed in-depth. Especially the second transit whose observation involved many more scentists and nations than the first one needed a more exhaustive treatment in my opinion. The book has only a little more than 300 pages, with many of them just notes, so length wouldn’t have been a problem either. Additionally, it could have used more science; it is pretty much a book about the problems of transnational cooperation and international travel in the 18th century, as well as a tale of adventure and hardships. Missing, however, are the facts about the astronomy and maths involved: How exactly would the observation of these transits help astronomers figure out the distance between the Sun and the Earth? This is not explained in a satisfactory way.
It is an impeccably researched book and I enjoyed reading it a lot, but it left me wanting. It is more of an introduction to the topic, one that is undoubtably entertaining, but any interested reader has to look elsewhere for a more comprehensive discussion.