Anthony Grafton in American Scientist:
The 16th-century astronomer and mathematician Georg Joachim Rheticus confronts 21st-century readers with an enigma. A humanist steeped in Latin and Greek, Rheticus proclaimed himself a lover of the classics. In 1541, when he offered a lecture course on astronomy at the University of Wittenberg, he described Ptolemy’s second-century handbook of astronomy, the Almagest, as “by far the most beautiful among works of human hands.” Rheticus had used equally flattering language to describe Ptolemy in 1540 in the book for which he is chiefly remembered—his Narratio Prima, in which he offered the European public its first detailed report on the heliocentric planetary theory of Copernicus, which he enthusiastically espoused. Even in this manifesto he praised Ptolemy—whose geocentric astronomy Copernicus rejected—as “the divine parent of astronomy.” Indeed, Rheticus noted that Copernicus had set out his own work in imitation of Ptolemy’s.
For all his love of traditional scholarly pursuits, Rheticus was a thoroughly modern, unbookish figure. He loved to travel, preferred direct observation of the skies to reading old texts about them and eagerly collaborated with the printers who were transforming the fabric of learned life. In his later years, he rejected all of Greek planetary theory, including the work of Ptolemy, in favor of what he called an “astronomy without hypotheses.” Moreover, in his second career, as a medical man, he rejected the ancient theories of Galen and accepted the radical new iatrochemistry—alchemical medicine—of Paracelsus. Which, one wonders, was the true Rheticus—the humanist who wrote eloquent Latin or the innovator who chose modern theories over ancient ones even when doing so made his personal situation risky?
In The First Copernican, Dennis Danielson brings learning, admiration and precise scholarship to the task of writing the first popular biography of this puzzling figure.