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| Paper: |
Israel's Quadrant: Weeping, Laughing, and the Measures of the Stars |
| Volume: |
441, The Inspiration of Astronomical Phenomena VI |
| Page: |
393 |
| Authors: |
Locci, A. A. |
| Abstract: |
In the Jewish culture of the Middle Ages, the astral bodies were
constantly given a special attention. They were deeply admired in
religious poetry, and studied and observed in scientific and technical
works. In an elegy of an anonymous poet of the 11th century,
which is usually read in the celebrations of the 9th day of
Ab, constellations and stars share the grief for the destruction of
the temple of Jerusalem. Like the Israel Tribes, all constellations
are said to weep; Pleiades and Orion are said to darken their face,
the Scales turn asymmetrical, the pan of death overrides the pan of
life; Scorpio is scared and trembles, Sagittarius turns his face back.
Jacob ben Machir ibn Tibbon, born in Marseille in 1236, was physician,
mathematician, and astronomer. He translated Euclides' Elements,
the Treatise of the Armillar Sphere by Qusta ibn Luqa, the Treatise on the Astrolabe by abu al-Kasim Ahmad ibn al Saffar, and
works of Ptolemy, Averroes, and Aristoteles. His most important work
is the short treatise Rova' Israel (“Israel's Quadrant”) which
he later translated in Latin with the help of Armengaud from
Blaise. In the first chapter, he discusses the Sun risings, the days
of the month, the place of the Sun in the sky, and the lunar
motion. In the second chapter, he discusses the relations between
sunrise and sunset, between moonrise and moonset, and between solar
year and lunar month. In the following chapters, he illustrates a
technical device which he had developed and which he designates
“Israel's Quadrant”. This instrument could be used both for the sky
and for the Earth, since it allowed to survey and measure the
elevation of the stars, the elevation of terrestrial reliefs, and
terrestrial horizontal distances. The quadrant is flat, and its area
is that of a quarter of a circumference. This instrument was very
versatile, it also allowed to calculate hours and time, and this
favoured its exceptional diffusion. Thus, its name, “quadrant”, was
transferred to the visible surface of the clock, notwithstanding the
fact that its shape is that of a complete circumference. |
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