History Presentation: The Works of Al-Khwarizmi (780 AD - 850 AD)

     Today, I will talk about the works of Al-Khwarizmi. Al-Khwarizmi was the mathematician who gave us the word algebra and introduced the idea of zero to the Western world. He was also a geographer and astronomer. He measured the length of one degree of the meridian of the earth. He also studied the stars. He dedicated a book of tables describing the movements of the sun, the moon, and the planets to the caliph who is the sovereign of the Islamic Empire.

     He gave us the word algebra and introduced the idea of zero to the Western world. He wrote book called Al-jabr wa-al-muqabala which menas "Completing and Balancing." In medieval Europe, the word algebra came to have wider meaning than just completing equations. Algebra helped people solve problems connected with the complex Muslim laws of inheritance. In a book called Addition and Subtraction by the Method of Calculation of the Hindus, he introduce the idea of zero to the Western world. He used a dot to indicate a column with no beads, and called the dot sunya, which means empty. When the idea was adopted by the Arabs, they usedthe symbol "0" instead of a dot and called it sifr. This gave us our word cipher. Two hundred and fifty years later, the idea of sifr reached Italy, where it was called zenero, which became "zero" in English. The idea of zero as a symbol came before zero as a number. Zero, as a number, answers the question "How many?" It is, however, a strange number.

     Al-Khwarizmi did not limit his interests to mathematics. He wrote a book on geography called The Book of the Form of the Earth. The book contains lists of longitudes and latitudes for various cities, mountains, seas, islands, and rivers. He grouped places according to the amount of daylight on the longest day of the year. Some of his information came from Ptolemy's Geography, but al-Khwarizmi's book is more than just a translation of the earlier work. His world map is more accurate than Ptolemy's, particularly in areas that had been converted to the Muslim religion.

     Al-Khwarizmi also studied the stars. Caliph al-Ma'mun appointed him to the post of court astronomer. By way of thanks, al-Khwarizmi dedicated a book of tables describing the movements of the sun, the moon, and the planets to the caliph. The tables could be used for predicting eclipses of the moon and the sun. Some of the information came from records mad in Baghdad, but al-Khwarizmi also drew on Hindu wisdom and on Ptolemy's tables. He used commentaries that had been made four centuries earlier by Theon and Hypatia of Alexandria.

     Al-Khwarizmi was mathematician, geographer, and astronomer. He gave us the word algebra and introduced the idea of zero to the Western world. He measured the length of one degree of the meridian of the earth. He also studied the stars. He dedicated a book of tables describing the movements of the sun, the moon, and the planets to the caliph who is the sovereign of the Islamic Empire.

Bibliography: Margaret J. Anderson and Karen F. Stephenson Scientists of The Ancient World, Enslow Publishers, 1999