Pedro Nunes

Origins and early life

Pedro Nunes was born at Alcácer do Sal in 1502 and this fiche states plainly both what the evidence shows and what it does not: no baptismal or filiation record names a Jewish-born parent or grandparent, but three independent strands point to a New Christian family, one of those forcibly baptized in Portugal in 1497.

Work and career

The contemporary chronicler Damião de Góis calls him Português de Nação, the coded phrase of the period for a Portuguese of the Jewish nation; the Jewish astronomer Joseph Delmedigo, writing at Amsterdam in 1629, refers to him as a Jew; and, most tellingly, his grandsons Matias and Pedro Nunes were tried and imprisoned by the Coimbra Inquisition for secretly practising Judaism, which shows the family kept that identity across three generations.

Nunes himself lived and died a Catholic. He studied medicine and mathematics at Salamanca and Lisbon, and in 1529 was appointed royal cosmographer, later chief cosmographer of Portugal, at the height of the age of discovery, and professor of mathematics at Coimbra, where he taught the pilots of the India route and, among his students, Christopher Clavius, who reformed the calendar. His Tratado da Esfera and De arte atque ratione navigandi answered a practical scandal: ships steering a constant compass course were not sailing great circles, and no one could say what curve they described.

Nunes showed in 1537 that it is a spiral converging on the pole, the rhumb line or loxodrome, and gave navigation its mathematics; Mercator's projection of 1569 exists to draw those lines straight. He invented the nonius, a nest of concentric graduated circles for reading fractions of a degree on an astrolabe, which Vernier refined into the instrument used on every caliper since, still called nónio in Portuguese. He died at Coimbra on 11 August 1578.