The Forgotten Geniuses Who Shaped Jewish and World History

Rabbi Avraham Zacuto: The Astronomer Behind the Age of Discovery

Long before GPS and Google Maps, Jewish wisdom helped explorers find their way. In 15th-century Castile, Rabbi Avraham Zacuto, a scholar, astronomer, and devout Jew, was shaping the course of global navigation. Though his name is not well-known today, his contributions to both Jewish scholarship and world history are profound.

Zacuto studied under Rabbi Yitzchak Aboab, a leading rabbi of Spanish Jewry, and became fluent in both Talmudic learning and Kabbalistic thought. Yet he didn’t stop there. He enrolled in the University of Salamanca to study astronomy and mathematics, explaining his motives with a quote from the Sages: “What wisdom is admired by the nations? The calculation of seasons and constellations.” He saw this knowledge as a gateway to deeper understanding of halachah (Jewish law) and Torah.

His astronomical skill was legendary. Zacuto identified a crater on the moon, which was later named the “Zagut (Zacut)” in his honor, making him the second Jew honored this way, after Gersonides (Ralbag). His expertise reached the highest levels of European leadership. Before sending Vasco da Gama on his historic voyage to India, King Manuel of Portugal privately consulted with Zacuto, who not only advised him but also supplied the navigational maps and copper astrolabe used for sea travel. Zacuto trained the navigators himself, enabling them to chart their paths by the stars.

But when Portugal ordered the forced conversion of its Jewish population, Zacuto left behind his career and his honors and refused to betray his faith. In 1523, he arrived in Jerusalem.

There, he wrote the monumental historical work “Sefer Yuchasin,” a foundational chronicle of Jewish history. Within its pages lies a rare document: an account of Rabbi Yitzchak of Acre’s journey from the Land of Israel to Spain in search of the origins of the Zohar.

Rabbi Zacuto passed away in Jerusalem. Rabbi Yosef ben Meir eulogized him as “a righteous man lost to his generation… we learned from him how to serve Hashem, whether through astronomy or Talmud.”

Rabbi Moshe Zacuto: The Kabbalist Who Rewrote the Siddur

The legacy of Rabbi Avraham Zacuto lived on through his great-grandson, Rabbi Moshe Zacuto, known by the acronym Ramaz, a towering Kabbalistic authority whose influence is felt every time Jews pray.

Born in the Sephardic community of Amsterdam, Rabbi Moshe studied under Rabbi Shaul Mortera and was well-versed in Latin and philosophy. But his soul yearned for deeper spiritual wisdom. After immersing himself in Kabbalah, he fasted for forty days to forget secular knowledge that, in his view, hindered his spiritual growth.

A disciple of Rabbi Binyamin Halevi, who studied under Rabbi Chaim Vital, the Ramaz was just three generations removed from the Arizal himself. In 1673, he became the chief rabbi of Mantua, Italy, where he founded a yeshivah and launched a Kabbalistic revival that would shape Jewish prayer for centuries.

Up until that point, the teachings of the Arizal were scattered, accessible only to a select few in Israel and Egypt. Rabbi Zacuto gathered, edited, and organized these writings, standardizing them and bringing them to European Jewry. He spearheaded a project of copyists and editors to transmit these texts with precision. More than that, he made them accessible by introducing mystical elements into the daily siddur (prayer book).

Thanks to his work, phrases like “LeShem Yichud,” “Ana B’Koach,” and “KeGavna” became standard parts of the siddur. Before him, these didn’t exist in most prayer books. Through careful discernment, he determined which customs to adopt and which to omit, leaving us with a siddur steeped in mystical resonance and spiritual clarity.

The Ramaz authored around 100 books, mostly on Kabbalah. He passed away in 1697 (16 Tishrei 5458) in Mantua. His burial place remained unknown until a recent discovery: a contractor renovating a construction warehouse in Mantua uncovered a Hebrew-inscribed gravestone, which experts confirmed to be that of Rabbi Moshe Zacuto, the man who gave shape and structure to Jewish prayer as we know it.

From royal courts to moon craters, and from Jerusalem to Italy, the Zacuto family left an indelible mark on both Jewish and global history.