The Extraordinary Life Of Rabbi Avraham Zacuto, Rabbi, Astronomer, Astrologer, Mathematician, and Historian

By: Nosson Wiggins

Born in Castile, Spain in 1452, Rabbi Avraham (ben Shmuel) Zacuto studied under the preeminent Spanish Rosh Yeshiva Rabbi Yitzchak Abuhav (author of Menoras HaMaor). He also attended the prominent University of Salamanca, which was established more than two centuries prior, in 1218, by King Alfonso IX. (From that time until the end of the 16th century, the University of Salamanca was one of the leading universities in Europe along with the Sorbonne in Paris, Bologna, and Oxford.) In the University of Salamanca, Rabbi Zacuto studied a number of sciences including astronomy.

The Astronomer

In 1473, at the age of twenty-one, Rabbi Avraham Zacuto composed his famed solar declination tables titled “Almanach Perpetuum Coelestium Montium” (The Perpetual Almanac of the Heavenly Bodies). These tables, which were originally written in Hebrew under the titled HaChibbur HaGadol, were immediately translated into Spanish, Latin, and Arabic and were used by the Spanish explorers of the 15th century to navigate their positions at sea. Rabbi Zacuto forged a relationship with Christopher Columbus and gave him a copy of his tables prior to his famed expedition across the Atlantic.

Rabbi Zacuto’s renown as an astronomer earned him the position of Professor of Astronomy at the University of Salamanca, and later at Saragossa. Despite his prominence and prestige among monarchs and influential academics, when the Jews were expelled from Spain in 1492, Rabbi Zacuto and his family were forced to flee their homeland.

Initially, Rabbi Zacuto settled in Portugal where he was appointed Royal Astronomer in the court of King Joao II. There, he advised another great explorer, Vasco da Gama, before his voyage to India in 1497.

In Portugal, Rabbi Zacuto perfected his model of a copper astrolabe, a tool that measured the altitude of celestial bodies throughout the day and night. This model was designed to be used on ships, and together with his solar tables, enabled captains to accurately calculate their positions while navigating at sea.

The Historian: Sefer Yechusin

In 1497, Portugal expelled its Jews, sending Rabbi Zacuto and his family once again into exile. This time, they crossed the Mediterranean and after twice being captured by pirates finally reached the shores of northern Africa and settled in Tunisia. During these years, Rabbi Zacuto completed his Sefer Yechusin, an important work on Jewish history. In the introduction, he argues for the importance of having a basic knowledge of time and place of the Sages of the Mishnah and Talmud. Although, as the author submits, Sefer Yechusin was written during a difficult period of exile (and therefore contains errors), it is nonetheless considered an important work on Jewish history and the lives of the Tannaim and Amoraim.

It is believed that Rabbi Zacuto died in Jerusalem in 1515, but other reports indicate his final home was the Jewish community in Damascus and his death occurred in 1520. Like other giants of the Jewish faith, Rabbi Zacuto desired to be buried as close to Jerusalem as possible and made his final pilgrimage to the Holy City during a Passover gathering. n

Nosson Wiggins (@jewishhistorysheimhagedolim) is the author of two books on the subject of Jewish history, “The Tannaim & Amoraim” and “The Rishonim” (Judaica Press). He researches Jewish History at the Klau Library, HUC-JIR in his hometown of Cincinnati and leads tours of Klau’s Rare Book Room. He is a passionate enthusiast of Jewish history and when he’s not in the hospital working as a nurse, he can be found researching and writing posts for his Substack, “Jewish History—Sheim Hagedolim.”