| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 109-110 |
|
Courtesy of 
|
Ben Solomon:
Judah ben Solomon ha‐Kohen
Y. Tzvi Langermann
Born Toledo, (Spain),
circa 1215
Died probably (Italy),
after 1274
Judah ben
Solomon was born and educated in Toledo, where the Jewish community, despite
a century and a half of Christian rule, maintained a tradition of Arabic learning
in science and philosophy. At the age of 18, he entered into correspondence
with some savants at the court of Frederick II. Apparently as a result of
these exchanges, Judah immigrated to Italy. There he translated into Hebrew
his major work, an encyclopedia called Midrash ha‐ḥokhmah (The study of wisdom),
which he had earlier compiled in Arabic.
The astronomical section of Midrash ha‐ḥokhmah is a combination of the
theories of Ptolemy
and Biṭrūjī. For
matters of timekeeping, mathematical geography, and solar and lunar theory,
Judah relies upon Ptolemy. However, when moving on to planetary theory, he
abandons Ptolemy in favor of Biṭrūjī. Judah preferred
Biṭrūjī for
theological reasons. In the latter's system, in which the motions of the planetary
orbs were all powered by a mechanical link to the swiftly moving outermost
orb, the connection between God and the Universe was patently clear: God set
in motion the outermost orb, with the daily revolution, and this energized
the entire cosmos.
Biṭrūjī
was not the only Andalusian astronomer whose work influenced Midrash ha‐ḥokhmah. Jābir
ibn Aflaḥ, Ṣāʿid al‐Andalusī, and an otherwise unknown
Jewish astronomer by the name of David ben Naḥmias
are also cited. Judah knew as well the discussion of the “moon illusion” in
Ibn al‐Haytham's commentary to the Almagest.
To the
extent that there are original investigations in Midrash ha‐ḥokhmah, they are motivated by
theology or mysticism. Thus, for example, Judah noticed that Ptolemy's value
for the ratio in volume between the Sun and the Moon, 6644.5, is an approximation
(Almagest V.16; cf. ibid., V.14). The exact value, which
Judah asserts to be 6,300, is obtained not by observation, but by an operation
upon the alphanumerical values of the two letters of the Hebrew alphabet that
are said to stand for the Sun and the Moon.
Selected References
Langermann, Y.
Tzvi (2000). “Some Remarks on Judah ben
Solomon ha‐Cohen and His Encyclopedia, Midrash ha‐Ḥokhmah.” In The Medieval Hebrew Encyclopedias
of Science and Philosophy, edited by Steven Harvey, pp. 371–389.
Dordrecht: Kluwer Academic Publishers.