At the turn of the twentieth century, when the science of radioactivity was still young, Bertram Boltwood was considered to be the United States' foremost authority. This was a reputation he had earned, along with Great Britain's Ernest Rutherford, by advancing the experiments of Henri Becquerel, Marie Curie, and Pierre Curie. Among his accomplishments was the proof of a radioactive series (the transformation of one radioactive element into another) that led eventually to a reliable method for determining the age of Earth.

Boltwood came from an academic family: his grandfather had helped found Amherst College in Massachusetts, and his cousin was the poet Ralph Waldo Emerson (1803-1882). Though his father died when Bertram was only two, his mother continued her husband's legacy of education. He entered the chemistry department of Yale University in 1889, graduating at the top of his class three years later. After spending two years in...