Every October, Christopher Columbus returns not only as history but as controversy. The voyages associated with his name transformed the world, but their legacy is inseparable from conquest, coercion and the destruction that followed European expansion. 

Yet the same Iberian age also produced a quieter and far less controversial revolution: advances in astronomy, mathematics, cartography, instruments and practical navigation that made sustained oceanic voyaging possible. Its protagonists included scholars, translators, mapmakers, instrument makers and pilots whose names are far less familiar than those of the captains who commanded the ships.

Among them, one figure deserves particular remembrance on Columbus Day: Abraham Zacuto, a Jewish astronomer born in Salamanca around 1452. Zacuto belonged to the same Iberian world as Columbus, but experienced its monarchies very differently. In 1492, Columbus sailed west under the patronage of Ferdinand and Isabella. That same year, the Catholic monarchs ordered the Jews of their realms to convert or leave. Zacuto left Castile and continued his work in Portugal. The celebrated maritime discoveries and the expulsion of Iberian Jewry were therefore not distinct historical worlds; they unfolded under the same rulers, at the same moment, within the same culture of ambition, knowledge and power.

Zacuto stands out within that larger scientific story. He was a rabbi, astronomer, mathematician and historian whose astronomical work helped give oceanic navigation a new degree of precision and practicality. His contribution belongs not at the margins of the Age of Exploration but within the scientific infrastructure that made long-distance navigation increasingly systematic.

Around 1478, Zacuto completed his great Hebrew astronomical work, “Ha-Hibbur ha-Gadol,” the “Great Composition.” Working within a long scientific conversation that included Greek, Islamic, Jewish and Christian astronomy, he refined and organized astronomical calculations in forms of exceptional practical value.

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