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Isaac Israeli ben Joseph

Isaac Israeli ben Joseph 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 Israeli ben Joseph rather than just read about it. In short: Isaac Israeli ben Joseph or Yitzhak ben Yosef (often known as Isaac Israeli the Younger) was a Spanish-Jewish astronomer/astrologer who flourished at Toledo in the first half of the fourteenth century. He was a pupil of Asher ben Yehiel, at whose request (in 1310) he wrote the astronomical work Yesod Olam.

Isaac Israeli ben Joseph — main illustration
Isaac Israeli ben Joseph — illustration

Key takeaways

  • Isaac Israeli ben Joseph belongs to astronomy; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Isaac Israeli ben Joseph to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Isaac Israeli ben Joseph from memory before moving on to harder problems.

Reference excerpt

Isaac Israeli ben Joseph or Yitzhak ben Yosef (often known as Isaac Israeli the Younger) was a Spanish-Jewish astronomer/astrologer who flourished at Toledo in the first half of the fourteenth century. He was a pupil of Asher ben Yehiel, at whose request (in 1310) he wrote the astronomical work Yesod Olam. The book includes chapters on: geometry and trigonometry; the structure and position of the globe; the number and movements of celestial spheres; the time differences in days and nights in various parts of the Earth; the movements of sun and moon; solstices, neomeniæ, eclipses, and leap-years. It also contains astronomical tables (ephemeris) and a perpetual calendar. It also deals with the chronological systems of other nations and religions (iv, § 17), especially Christianity, and lists notable personages of the Biblical, Talmudic, and geonic periods, as per Sefer ha-Qabbalah of Abraham ibn Daud, in chronological order (iv, § 18). This last was included by Zacuto in his Sefer ha-Yuḥasin. The Yesod Olam was first published in Berlin by Jacob Shklower in 1777. A more complete edition, with a preface by David Cassel, was published by B. Goldberg and L. Rosenkranz (1848). Israeli's work was much studied in the Middle Ages. Isaac al-Hadib, Judah Bassan, and Elijah Mizrahi annotated it, and an anonymous author wrote a commentary on it (Neubauer, Cat. Bodl. Hebr. MSS. Nos. 2044, 746, 5). An abridgment was made in Arabic by the author's son Joseph Israeli ben Isaac, of which the Hebrew translation, Kitzur Yesod Olam is still extant (ib. No. 1319, 6). Israeli was also the author of two other astronomical works, Sha'ar ha-Shamayim and Sha'ar ha-Milu'im, both extant in manuscript (ib. No. 2046). Israeli apologizes for citing non-Jewish authors and claims that the ancient sages also possessed this knowledge before the destruction of the First Temple.

See also Hebrew astronomy

References

De Rossi, Dizionario, p. 130; Cassel, preface to Yesod 'Olam; Eliakim Carmoly, Itinéraires, p. 224; Steinschneider, Cat. Bodl. col. 1124; idem, Hebr. Uebers. p. 596; idem, Die Arabische Litteratur der Juden, § 121; Grätz, Gesch. vii. 249. This article incorporates text from a publication now in the public domain: Singer, Isidore; et al., eds. (1901–1906). "Israeli, Isaac ben Joseph (the Younger)". The Jewish Encyclopedia. New York: Funk & Wagnalls.

Illustrations

Isaac Israeli ben Joseph: Yesod Olam
Yesod Olam

Worked examples

Example 1 — a first encounter with Isaac Israeli ben Joseph

Start with the simplest possible case. Write down what Isaac Israeli ben Joseph 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 Israeli ben Joseph 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 Israeli ben Joseph 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 Israeli ben Joseph

In research
Isaac Israeli ben Joseph 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 Israeli ben Joseph 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 Israeli ben Joseph is common in secondary-school and first-year university syllabi. It links to neighbouring topics 14th-century Castilian Jews, 14th-century astrologers, 14th-century astronomers, so understanding it makes those chapters shorter.
In everyday life
Look for Isaac Israeli ben Joseph 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 Israeli ben Joseph in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Isaac Israeli ben Joseph means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Isaac Israeli ben Joseph out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Isaac Israeli ben Joseph in simple terms?

Isaac Israeli ben Joseph or Yitzhak ben Yosef (often known as Isaac Israeli the Younger) was a Spanish-Jewish astronomer/astrologer who flourished at Toledo in the first half of the fourteenth century. He was a pupil of Asher ben Yehiel, at whose request (in 1310) he wrote the astronomical work Yes…

Why does Isaac Israeli ben Joseph 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 Israeli ben Joseph?

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 Israeli ben Joseph.

Tags

  • 14th-century Castilian Jews
  • 14th-century astrologers
  • 14th-century astronomers
  • 14th-century deaths
  • Medieval Jewish astrologers
  • Medieval Jewish astronomers
  • Medieval Spanish astrologers
  • Medieval Spanish astronomers
  • People from Toledo, Spain

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