Rabbi Zag de Sujurmenza was a Jewish convert of 13th-century Spain who helped King

Alfonso X of Castile Alfonso X (also known as the Wise, es, el Sabio; 23 November 1221 – 4 April 1284) was King of Castile, León and Galicia from 30 May 1252 until his death in 1284. During the election of 1257, a dissident faction chose him to be king of Germ ...

with his scientific works. Zag de Sujurmenza was commissioned by the king to write ''Astrolabio redondo'' (spherical

astrolabe An astrolabe ( grc, ἀστρολάβος ; ar, ٱلأَسْطُرلاب ; persian, ستاره‌یاب ) is an ancient astronomical instrument that was a handheld model of the universe. Its various functions also make it an elaborate inclin ...

), ''Astrolabio llano'' (flat astrolabe), Constelaciones (constellations) and ''Lámina Universal'' (an instrument that improved on the astrolabe); he also translated the book ''Armellas de

Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...

'', and wrote about the ''Piedra de la sombra'' (stone of the shadow, or sundial), ''Relox de agua'' (clepsydra, or

water clock A water clock or clepsydra (; ; ) is a timepiece by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the amount is then measured. Water clocks are one of the oldest time-m ...

) ''Argente vivo o azogue'' (quicksilver or mercury) and ''Candela'' (candle clock). Of his works, the most important are those of the "round astrolabe" and the "flat astrolabe". In the first, the author rises to profound scientific considerations that reveal the vast knowledge he possessed in sciences. It has been said that with this book, Zag Sujurmenza reformed the character of the science of astronomy and contributed to its advancement, without losing sight of the studies of Arab scholars, following in their footsteps and correcting their errors. Other works of Zag de Sujurmenza, if less extensive, are not without merit.

External links

Los Libros de los relojes de Alfonso X el Sabio
ooks of the Clocks of Alfonso the Wise
"Las ciencias exactas y físico-naturales", by Julio Samsó
("The court of Spain in the 13th century", "scientific works of Alfonso X: translations and original works"...)
Los Astrolabios y los Nocturlabios: Los primeros utensilios portátiles para medir la posición y el tiempo.
(images from Libros del saber de astronomía ooks of wisdom of astronomy of King Alfonso X the Wiseof Alfonso X el Sabio 13th century and various 13th-century astrolabes.)

References

*Rodriguez de Castro, Spanish Library The content of this article incorporates material of Volume 70 of the Enciclopedia universal ilustrada europeo-americana ( Espasa) with copyright before 1932, which is in the public domain. {{authority control Converts to Roman Catholicism from Judaism Spanish Jews Spanish Roman Catholics Spanish translators 13th-century translators 13th-century astronomers Medieval Spanish astronomers Medieval Jewish astronomers

See also

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References