Chasing Venus by Andrea Wulf

Subtitle: the race to measure the heavens
"Race" here is a relative term.  In 1716 Edmund Halley proposed a way to measure the solar system.  He figured out that the planet Venus would pass in front of the sun in 1761 and again in 1769.  By measuring the time and angle of the "transit of Venus" from multiple points on the planet, they could use mathematics to figure its distance from the sun and from that, the distance of all the other planets.  But this book is less about the math than it is the journeys. In 1761, Europe was at war, colonies were being won and lost, getting anywhere depended on ships and horse drawn carts and science had yet to become  SCIENCE.  It took years of gathering the support and finances necessary to make the needed astronomical observations.  They had to find ships that were kind of going in the right direction.  They fought weather and disease.  All the time knowing that to be accurate they had to do it again in 1769 for the math to work.  Hundreds of attempts were made in both years.  Only one man, Jean-Baptiste Chappe d'Auteroche, was able to view both transits and he died while finishing his notes.  Another Frenchman, Guillaume Le Gentile de la Galaisiere was gone so long chasing Venus that he was declared dead and all his belongings were sold.  Hundreds whose names you might recognize like James Cook (who went to Tahiti and had to buy back all the equipment that the natives took) and Charles Mason and Jeremiah Dixon (of Mason-Dixon line fame) were only marginally successful.  In the end, it was a grand world effort and it worked.  You have to wonder what they would think as the world hops on trains, cars and planes to watch a solar eclipse just to oh and ah and say we were there.  This book is not as engaging as her "Invention of Nature" but it is a pretty amazing thing to wrap your head around.