Abraham bar Hiyya facts for kids

Abraham bar Ḥiyya ha-Nasi (born around 1070 – died 1136 or 1145) was a very important Jewish mathematician, astronomer, and philosopher from Barcelona, Spain. He is also known as Abraham Savasorda.

He played a key role in bringing Islamic science to Christian Europe. He translated many scientific books from Arabic into Latin. He was probably the first person to introduce Arabic algebra to Europe.

Abraham bar Ḥiyya also wrote his own books on mathematics, astronomy, Jewish philosophy, and land surveying. His most famous book is Ḥibbur ha-Meshiḥah ve-ha-Tishboret. This book was about geometry and algebra. It included the first known complete way to solve a quadratic equation (like x² - ax + b = c). This work later influenced famous mathematicians like Leonardo Fibonacci.

About His Life

Abraham bar Ḥiyya came from an important family. He held a high position in the royal court, working as a kind of "chief of police" and having the title of "governor" or "prince." People believe he got this title in the court of Saragossa-Lerida.

He was highly respected for his knowledge of astronomy. He even had discussions with learned priests, showing them how accurate the Hebrew calendar was. Some scholars think he was a student of Rabbi Moshe haDarshan and a teacher of Abraham Ibn Ezra.

He wrote about the shape of the Earth, the elements, and how the planets move. He also wrote about astrology, trigonometry, and music. He spent some time in Narbonne, where he wrote for the Jews of Provence. He sometimes complained that they didn't know enough about mathematics.

His Important Works

Abraham bar Ḥiyya was a major figure in a movement that helped share knowledge between the Arabic scientific world and the Christian world. He did this through his own writings and his translations.

His book Yesode ha-Tebunah u-Migdal ha-Emunah (meaning "The Foundations of Understanding and the Tower of Faith") was the first attempt in Europe to combine Ancient Greek and Arabic mathematics. This book talked about how different parts of math, like number theory, geometry, and optics, are connected.

His most famous work is Ḥibbur ha-Meshiḥah ve-ha-Tishboret (meaning "Treatise on Measurement and Calculation"). This book was translated into Latin in 1145. It became a key text for later mathematicians, including Leonardo Fibonacci, who used it as a base for his own work on geometry.

Abraham bar Ḥiyya also wrote religious books. These included Hegyon ha-Nefesh ("Contemplation of the Soul") about repentance, and Megillat ha-Megalleh ("Scroll of the Revealer") about the future of the Jewish people. Even these religious books included scientific ideas and astrological thoughts. He used astrology to predict that the Messiah would appear in the year 1358 CE.

A very important thing about Abraham bar Ḥiyya is that he wrote all his works in Hebrew. Before him, Jewish scientific books were often written in Judaeo-Arabic. By writing in Hebrew, he helped make Hebrew a language for science.

Other Notable Books

• "Form of the Earth" (Hebrew: צורת הארץ): This book was about how the heavens and Earth were formed. Parts of it were translated into Latin and French.
• "Calculation of the Courses of the Stars" (Hebrew: חשבון מהלכות הכוכבים): This was a follow-up to "Form of the Earth," focusing on how stars move.
• "Tables" or "Tables of the Prince" (Hebrew: לוחות or לוחות הנשיא): These were important astronomical tables.
• "Book of Intercalation" (Hebrew: ספר העבור): This is the oldest known Hebrew book that explains how to calculate the Hebrew calendar.
• "Meditation of the Soul" (Hebrew: הגיון הנפש): This was an ethical book about living a good life based on reason and religion.
• "Scroll of the Revealer" (Hebrew: מגלת המגלה): This book used astrology to explain Jewish history and predict the coming of the Messiah.

Translations He Helped With

Abraham bar Ḥiyya worked with other scholars to translate scientific books from Arabic into Latin. One of his most famous collaborations was with Plato of Tivoli. Together, they translated Ptolemy's Tetrabiblos in 1138 in Barcelona.

Some of the translations he was involved in include:

• De Horarum Electionibus, a work by Ali ben Aḥmad al-Imrani.
• Capitula Centiloquium, which contained astrological sayings.
• A commentary on the Centiloquium by Aḥmad ibn Yusuf.
• De Astrolabio by Rudolph de Bruges.
• Liber Augmenti et Diminutionis, a book on mathematics.

Abraham bar Ḥiyya said that he wrote his own books in Hebrew because his Jewish friends in France didn't have access to scientific works in Arabic. He wanted to help spread knowledge among Hebrew readers, even if his own scientific terms were not always perfect.

His Philosophy

Abraham bar Ḥiyya was a pioneer in Jewish philosophy. He believed in the importance of repentance and living a pure life. He also thought that non-Jewish philosophers, even without knowing the Torah, could discover important truths about the world.

He believed that people should try to live a life devoted to God. He taught that the human soul is like it's "imprisoned" in the body and that our animal desires can pull us away from spiritual goals. However, he also said that truly religious people don't need to do extreme fasting or other harsh practices, only what the law requires.

He also believed in astrology, thinking that the stars could influence events.

Mathematics

Bar Ḥiyya's theorem in a copy of the Talmud.

Abraham bar Ḥiyya's book Ḥibbur ha-meshīḥah ve-ha-tishboret was the first place in the Western world where quadratic equations were fully explained.

He also proved a formula for the area of a circle using a special geometric method. The formula is: Area = Circumference × (Radius / 2). This means if you know the distance around a circle and its radius, you can find its area.

See Also

In Spanish: Abraham Bar Hiyya para niños

• Golden age of Jewish culture in the Iberian Peninsula