Omar Khayyam · Mathematics

The Jalali Calendar: Measuring the Year

In 1079 Khayyam led the astronomers of the Isfahan observatory in reforming the Persian calendar for Sultan Malik-Shah. The resulting Jalali calendar, built on precise solar observation, was by many reckonings more accurate than the Gregorian calendar that Europe adopted five centuries later - measurement turned into civic science.

What you'll be able to recall

You learned that Khayyam directed the Isfahan observatory, measured the solar year with great precision, and helped design the Jalali calendar (1079) with an intercalation cycle so accurate that it rivalled or beat the later Gregorian calendar. Explain how astronomical measurement became civic science in his hands, an…

Leads to Muhammad ibn Musa al-Khwarizmi.

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