It’s the name he gave to the astrolabe, itself derived from the Greek word for “star finder”, (as borrowed by Game of Thrones, though for a wholly different purpose).
This device was significantly improved and refined by Levi ben Gershon (1288 – 1344), Gersonides or “RaLBag” as we know him from his work on Jewish philosophy. The moon’s crater “Rabbi Levi” is named after him for his notable contributions to astronomy.
These included his observations of solar and lunar eclipses, his conclusion that the planets were ten billion times more distant than previously thought, and his refutations of aspects of Ptolemy’s geocentric planetary model, foreshadowing by three centuries the work of Copernicus and Galileo on the solar system as we know it.
R. Levi’s accomplishments would have been impossible without an astrolabe. There’s a superb example in the British Museum of this instrument from his time, complete with Hebrew inscriptions as shown. In 2010 it was discussed by the museum’s then director Neil MacGregor in the BBC’s landmark series A History of the World in 100 Objects.
This fascinating gadget, a unique marriage of Greek science with Gothic art and one of the most sophisticated inventions of the Middle Ages, was essentially an image of the mediaeval universe that you could hold in your hand or even put in your (outsize) pocket.
A gleaming assemblage of interlocking brasswork, it was used for observations and calculations based on the position of the sun or the stars, in disciplines as diverse as astronomy, astrology, cosmology, mathematics, navigation, surveying, the calendar, and timekeeping.
Anticipating the versatility of our technologies by a thousand years, it soon became a must-have object for the affluent, often wrought in silver or gold, sometimes studded with precious stones, making it sought after by kings, courtiers and nobles, the Rolex and Patek Philippe of its day.
The Hebrew names of the Zodiac appearing on both astrolabe faces remind us that pre-eminence in astrology often gave Jews the same access to the royal courts of Europe as did the practice of medicine. It became de rigueur for monarchs and aristocrats to seek Jewish predictions (though with predictably mixed results) of important dates and outcomes for their marriages, wars, and alliances.
Jewish communities, always hoping and praying for the Messianic coming, were not immune, so that astrological calculations of its date inevitably led to disillusionment. (Abraham b. Hiyya, for example, forecast 1358 as the year of redemption).
No wonder Maimonides (1138 – 1204), the pre-eminent Jewish scholar of his time, was uncompromising in his opposition. Writing to the Marseilles community in 1194, he denounced astrology as bordering on idolatry, “a disease, not a science, a tree in whose shadow all kinds of delusion thrive, and which must be uprooted, giving way to the Tree of Knowledge, the Tree of Life”.
Maimonides’ warnings notwithstanding, even the great Abraham Zacuto of Salamanca, (1452 – 1515), the rabbi whom John II of Portugal appointed Royal Astronomer after fleeing Spain in 1492, allowed himself to predict, and be disappointed by, 1503 as the Messianic year. However, that’s not why we remember him, or why a further moon crater carries his name.
It was Zacuto’s updated copper maritime astrolabe together with his detailed astronomical tables that helped Columbus reach the New World, and Vasco da Gama to discover the sea-route to India six years later.
He received no thanks for his part in those epoch-making events. Barely had he instructed da Gama and his captains in the use of his inventions for their departure in July 1497, before he had to make a further escape when Manuel I gave his Jews the option of baptism or death. Small wonder that he came to speculate about the date of his long-suffering people’s redemption.
Yet his accomplishments were to help change the world for ever, much like those of Albert Einstein and the scores of eminent scientists who fled Nazi Jew-hate almost half a millennium later. Nothing new under the sun, then.
Eli Abt writes on the Jewish arts
