Isaac Israeli ben Joseph facts for kids
Isaac Israeli ben Joseph, also known as Isaac Israeli the Younger, was a smart Jewish scholar from Spain. He lived in the city of Toledo in the early 1300s. He was an expert in both astronomy (the study of stars and planets) and astrology (the belief that stars influence human events).
Contents
About Isaac Israeli
Isaac Israeli was a student of a famous scholar named Asher ben Yehiel. In 1310, Asher ben Yehiel asked Isaac to write a special book about astronomy. This book became known as Yesod Olam. It was considered one of the best books on astronomy written in Hebrew literature.
The Book Yesod Olam
Yesod Olam means "Foundation of the World." This important book covered many topics about space and our planet.
What Yesod Olam Teaches
The book explained different ideas, including:
- Geometry and trigonometry: These are branches of mathematics that deal with shapes, sizes, and angles.
- The structure of Earth: How our planet is shaped and where it is in space.
- Celestial spheres: The number and movements of the imaginary spheres that ancient people believed carried the stars and planets.
- Time differences: How days and nights change in length in different parts of the Earth.
- Movements of the Sun and Moon: How these celestial bodies move across the sky.
- Special events: Like solstices (the longest and shortest days of the year) and eclipses (when one celestial body blocks the light from another).
- Hebrew calendar: How to figure out leap years in the Jewish calendar.
Calendars and History
Yesod Olam also included useful tools for telling time. It had ephemeris (tables that show where planets and stars will be at certain times) and a perpetual calendar (a calendar that works for any year).
Isaac Israeli also wrote about the calendar systems used by other nations and religions, especially Christianity. He listed important people from the Biblical, Talmudic, and geonic times in order. This list was based on another famous book called Sefer ha-Qabbalah.
The Yesod Olam was first printed in Berlin in 1777. A more complete version was published later in 1848. Many scholars in the Middle Ages studied Isaac Israeli's work. Some scholars, like Isaac al-Hadib and Elijah Mizrahi, even wrote notes about it.
Isaac Israeli's son, Joseph Israeli ben Isaac, made a shorter version of the book in Arabic. A Hebrew translation of this shorter version, called Kitzur Yesod Olam, still exists today.
Other Works
Isaac Israeli also wrote two other books about astronomy. They were called Sha'ar ha-Shamayim (meaning "Gate of the Heavens") and Sha'ar ha-Milu'im (meaning "Gate of the Completions"). Both of these books are still available as old handwritten copies.
See also
- Hebrew astronomy
