Long Overlooked, This 11th-Century Astronomical Device Documents Scientific Exchange Among Muslims, Jews and Christians

The astrolabe features Hebrew and Latin inscriptions added by different owners over time

Gigante and Device
Art historian Federica Gigante examines the device at the Fondazione Museo Miniscalchi-Erizzo in Verona, Italy. Federica Candelato

When historian Federica Gigante glimpsed a rare artifact in the background of a photo on an Italian museum’s website, she immediately reached out to the institution. Soon, Gigante was studying the object up close, with sunlight illuminating its brass features. As she examined the device’s Arabic and Hebrew inscriptions, as well as its Western numerals, she thought she might be dreaming.

The item in question was a 1,000-year-old astrolabe, a tool designed by the ancients for celestial navigation, telling time and reading horoscopes. And its engravings told an unexpected tale.

“In the raking light, I realized that this wasn’t just an incredibly rare, ancient object but a powerful record of scientific exchange between Muslims, Jews and Christians over nearly a millennium,” Gigante, a researcher at the University of Cambridge in England, tells the New York Times’ Franz Lidz and Clara Vannucci.

Close up of Verona astrolabe
The Verona astrolabe is inscribed with Hebrew, Arabic and Western numerals. Federica Gigante

Staff at the Fondazione Museo Miniscalchi-Erizzo in Verona, which houses the astrolabe in its archaeological collection, had never studied the artifact in depth. Now, says Gigante in a statement, it’s “the single most important object in their collection.”

Astrolabes consist of several flat, distinctly carved components that are stacked and embedded in a disk called a mater, wrote Smithsonian magazine’s Laura Poppick in 2017. The device’s Greek name translates roughly to “star-taker”; experts estimate it was invented sometime between the second and fifth centuries, possibly during the life of Alexandrian mathematician and astronomer Ptolemy. As the statement notes, the astrolabe was “the world’s first smartphone, a portable computer which could be put to hundreds of uses.”

Scholars know that multiple groups in Europe and the Middle East used astrolabes during the ancient and medieval eras. But the Verona astrolabe—one of the oldest ever discovered—uniquely illustrates the tool’s far-reaching influence.

The astrolabe's "rete," pictured here, represents a map of the sky. Federica Gigante

During Gigante’s initial inspection, she was surprised to see odd scratches on the device. As she tells the Guardian’s Sam Jones, “They weren’t the scratches you’d expect from use.” In fact, they were deliberate markings, displaying this specific artifact’s rich history of cross-cultural exchange. Gigante published her findings in the journal Nuncius earlier this month.

“The Verona astrolabe underwent many modifications, additions and adaptations as it changed hands,” Gigante says in the statement. “At least three separate users felt the need to add translations and corrections to this object, two using Hebrew and one using a Western language.”

Astrolabe Full View
The astrolabe is composed of a circular frame and several inlaid plates. Federica Gigante

Based on the astrolabe’s engravings, Gigante—an expert on Islamic scientific instruments—concluded that it was likely made in the Iberian Peninsula’s Andalusian region in the 11th century. She theorizes the piece was created in Toledo, “at a time when it was a thriving center of coexistence and cultural exchange between Muslim, Jews and Christians,” the statement notes.

Featuring Muslim prayer lines and names, the astrolabe was originally intended to help practitioners of Islam perform their daily prayers. Two Jewish names inscribed in Arabic on the device—Ishaq and Yunus, or Isaac and Jonah—suggest the astrolabe once circulated within a Sephardi community in Spain. One of the device’s circular plates is marked for North African latitudes, meaning it may have been used in Morocco or Egypt. And somebody once scratched Western numeral translations all over the device. As Gigante writes in her paper, the result is a “palimpsest object,” showing layers of intervention over time.

The Verona astrolabe perfectly encapsulates both Gigante’s “passion for scientific instruments and her research into how Islamic artifacts, technology and decoration traveled into Europe,” writes the Guardian. She says historians were already aware of collaboration between Jewish, Christian and Muslim scientists in 11th-century Spain, but now, they can actually hold a product of this work in their hands.

“It’s not that this instrument tells us this for the first time,” Gigante tells the Guardian. “All this is known, but what I find extraordinary is that this is a very tangible, physical proof of that history.”

How to Calculate Time With an Islamic Astrolabe

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