01 Feb 2013 01:44:43
It is the things one has not done that one regrets, they say. A debatable proposition, but I now have one more regret to add to the list: that I did not make any effort to see the transit of Venus across the sun's face last year. There had been one eight years before, you see, and I was getting blase; and I had not fully appreciated that there would not be another one until 2117. So what, I thought. It's just a little dot, an astronomical phenomenon of small significance, and you couldn't even see it with the naked eye. Had I read this book when it came out in hardback a year before, I would have changed my tune: I'd have made a great deal of effort to see it, in honour of the scientists who had travelled to the most remote, far-flung and desolate parts of the globe to observe the transits of 1761 and 1769. The story of their various journeys bears retelling: we have it here.
In 1716, Edmond Halley published a paper in which he predicted, correctly, that the planet would appear, for a few hours on 6 June 1761, and then again eight years later, as a black dot moving across the face of the sun. As the phenomenon had only been observed once before, by Jeremiah Horrocks in 1639, let's just pause to give Halley some credit for this achievement in the first place. He urged the scientists of the next generation, or the next-but-one, to make sure that as many of them saw it from as many parts of the world as possible, and made the most accurate observations possible, and then combined their results. Because if they did, then we would finally be able to make a decent calculation of how far it was from the Earth to the sun; and thence make a start on working out the dimensions of the solar system. I do hope that everyone reading this agrees that it is much, much better to know these things than to be ignorant of them.
Travelling across the globe in the 18th century was not a walk in the park at the best of times; and having to make sure you got to a precise spot at a precise time – or rather, in time to build a functioning observatory which would be open for business at a precise time – was even more difficult. Pause before you curse your flight's delay, and reflect that you do not have to wait weeks for the winds to become favourable, or for the rivers to freeze (so you can sledge along them), or that you do not have to push your carriage from ditches, or that your wheels don't break, or that you don't get massacred by bandits. Now imagine that you are carrying an enormous amount of extremely expensive and irreplaceable scientific equipment, which is also very fragile. Every single piece has to get to its destination in perfect nick, or the months-long trip will have been utterly pointless. And your coach driver is drunk. And everyone's at war with everyone else. And there must be clear skies on the day.
So the story zips along. Of its 300 pages, 100 are notes, as well as complete lists of all the observers in 1761 and 1769. It is right that these are honoured. The rest is like an astonishing pre-Verne Around the World in Eighty Days. The science is grounded at the start of the book professionally enough to satisfy the reviewers of Nature and New Scientist; the rest is adventure story, against the clock.
We meet familiar faces: Captain Cook, freaking out when he discovers the Tahitians have stolen an essential quadrant; Charles Mason and Jeremiah Dixon on their first expedition together, trying to back out when attacked by a French warship and being told to go on Or Else; and overall, a thrilling, stirring tale, very well told, of global cooperation, and how the passion for Enlightenment triumphed against enormous odds. Let's hope it continues to do so.
