astronomy

Isaac ibn Sid

Isaac ibn Sid is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Isaac ibn Sid rather than just read about it. In short: Isaac ibn Sid was a Spanish-Jewish astronomer who flourished at the Toledo School of Translators in the second half of the thirteenth century. He is also known as Ibn Sa'id, Aben Çayd, Rabbi Zag, or Rabbi Çag.

Key takeaways

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Reference excerpt

Isaac ibn Sid was a Spanish-Jewish astronomer who flourished at the Toledo School of Translators in the second half of the thirteenth century. He is also known as Ibn Sa'id, Aben Çayd, Rabbi Zag, or Rabbi Çag.

Biography Isaac ibn Sid took a leading part in the compilation of the Alfonsine Tables with Yehuda ben Moshe. Isaac Israeli (ib.) states that he saw recorded in Isaac ibn Sid's own handwriting three observations of moon eclipses made by him at the order of Alfonso. In official documents (De Castro, "Bibliotheca," i. 184b) Isaac ibn Sid is termed by Alfonso "our learned Rabbi Çag." Zag de Sujurmenza was commissioned by the king to write Astrolabio redondo (spherical astrolabe), Astrolabio llano (flat astrolabe), Constelaciones (constellations) and Lámina Universal (an instrument that improved on the astrolabe). He translated the book Armellas de Ptolemy, and wrote about the Piedra de la sombra (stone of the shadow, or sundial), Relox de agua (clepsydra, or water clock) 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. He wrote a treatise on clockmaking for Alfonso, in which he described a cross-shaped main wheel similar to the construction of the noria. In 1277, Isaac translated from the Arabic a work on the quadrant. His name is connected with the invention of various instruments (De Castro, l.c. i. 144a, 156a, 157).

See also Toledo School of Translators Literature of Alfonso X Book of knowledge of astrology History of sundials Libros del saber de astronomía [The Books of the Wisdom of Astronomy by King Alfonso X, the Learned]

References

Heinrich Grätz, Gesch. vii. 115; Moritz Steinschneider, Hebr. Uebers. pp. 617 et seq. Jewish encyclopedia Rodriguez de Castro, Spanish Library This article incorporates text from a publication now in the public domain: Singer, Isidore; et al., eds. (1901–1906). "ISAAC IBN SID (ZAG; ÇAG)". The Jewish Encyclopedia. New York: Funk & Wagnalls. 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.

External links Langermann, Y. Tzvi (2007). "Ibn Sid: Isaac ibn Sid". In Thomas Hockey; et al. (eds.). The Biographical Encyclopedia of Astronomers. New York: Springer. p. 570. ISBN 978-0-387-31022-0. (PDF version) Los Libros de los relojes de Alfonso X el Sabio [Books 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 [Books of wisdom of astronomy of King Alfonso X the Wise] of Alfonso X el Sabio 13th century and various 13th-century astrolabes.)

Illustrations

Worked examples

Example 1 — a first encounter with Isaac ibn Sid

Start with the simplest possible case. Write down what Isaac ibn Sid claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Isaac ibn Sid before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Isaac ibn Sid ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Isaac ibn Sid

In research: Isaac ibn Sid appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Isaac ibn Sid in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Isaac ibn Sid is common in secondary-school and first-year university syllabi. It links to neighbouring topics 13th-century Castilian Jews, 13th-century astronomers, 13th-century translators, so understanding it makes those chapters shorter.
In everyday life: Look for Isaac ibn Sid outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Isaac ibn Sid in 20 minutes

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Frequently asked questions

What is Isaac ibn Sid in simple terms?

Why does Isaac ibn Sid matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Isaac ibn Sid?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Isaac ibn Sid.