Home Technology Abraham Zacuto, the astronomer who predicted an eclipse and saved the life of Columbus December 26, 2021

Pedro Choker

Updated:12/26/2021 00:47h

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During the Middle Ages, religion permeated all aspects of society and the different communities learned to live together and share the same spaces. It was not an easy task, especially for the Jewish communities that alternated permissive moments with other intolerant and repressive ones.

This situation was not an obstacle for them to leave us an enormous cultural baggage. In some aljamas science, literature, drama, philosophy, theology experienced a real revolution.

In the Middle Ages, astronomers offered, as a general rule, a product based on astrological prediction, which was not an impediment for them to be used by some monarchs to make serious political decisions.

Portrait of Abraham Zacuto Spanish Foundation for Science and Technology, Eulogia Merle

In the middle of the 15th century, Abraham Zacuto (1452-1515) was born in Salamanca, a distinguished astronomer and mathematician who was called to revolutionize ocean navigation.

He belonged to a family of French exiles, his grandfather fled from the anti-Semitic laws dictated by the Frankish King Philip the Fair and in 1306, after crossing the Pyrenees, he settled on the Castilian plateau.

Abrahams father served as a rabbi on the banks of the Tormes, which allowed him to enjoy a privileged education and develop his scientific concerns. Around 1475 he published Composition Magna a complex work in which they appear astronomical tables, calculated for the Salamanca meridian, which corrected the errors of the Alphonsine Tables.

The interest of Jewish scientists in astronomy was due to the fact that it allowed them to accurately determine the time when the new moon appeared, which marked the beginning of the Sabbath and the beginning of the new year.

Zacuto was a strong defender of the role that astronomy played in the preservation of health, arguing that the signs of the zodiac influenced each of the parts of the body and that their knowledge helped physicists determine the prognosis of some diseases.

In 1492, with the expulsion of the Jews, Zacuto emigrated to Portugal, where King John II appointed him astronomer royal and court historian. His successor to the throne, Manuel I, asked him for advice on an expedition with which he planned to reach India bypassing the southern cone of the African continent.

Apparently the Hebrew gave a favorable opinion while emphasizing that the stars indicated that the success of the company depended on two brothers leading the expedition. It seems that this detail was decisive for Vasco de Gama, the senior captain of the Navy, was chosen, since he had a brother.

It is said that Zacuto prepared the maritime and astronomical calculations that made the expedition possible and that, in addition, he trained the crew in the use of an astrolabe of his creation and that allowed to determine the geographical latitude during navigation.

In 1496 he published a version of the Magna Composition under the title Perpetual Almanac which would enjoy enormous notoriety for more than a century.

The success of the maritime company under the Portuguese flag was not an obstacle so that, in 1497, in the context of a new anti-Semitic wave in Lusitanian lands, he had to emigrate to North Africa, from where he would travel to Damascus, the city that finally saw him. To die.

Christopher Columbus met Zacuto personally and used his maritime tables on the expedition to the Indies. In them the solar declination angle formed by the rays of the sun with the plane of the equator was collected that allowed to determine with enormous precision the position to the equator, without having to resort to the pole star.

During the last Columbian voyage in February 1504, the fleet was left to its own devices in Jamaica, where the natives refused to provide them with food. The Zacuto tables predicted a lunar eclipse for February 29. The admiral gathered the island chiefs and threatened to make the moon disappear if their needs were not met. Apparently the lunar eclipse scared the indigenous people so much that they not only respected the lives of the sailors, but also provided them with everything they asked for.

M. Jara

Pedro Gargantilla is an internist at the Hospital de El Escorial (Madrid) and the author of several popular books.

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