The judge Al-Jisaboori reported: "I visited Abu Rayhaan Muhammad (Al-Bayrooni) when he was on his death-bed. He said to me: 'One day you asked me about such and such an issue.' I replied: 'Do you want me to explain it when you are in such a condition?' He replied: 'Tell me, is it not better that I depart this world with knowledge of this issue than die while ignorant of it?' I therefore explained the subject and he in turn taught me things that he had previously promised to explain. I had scarcely left him when I heard cries from his house announcing his passing away."

　　This episode sums up for us the personality of this great scientist, whose objective in this life was seeking knowledge. He was, in fact, an embodiment of the saying of the Prophet Muhammad : "Seeking (Islamic) knowledge is obligatory upon every Muslim."

　　Little wonder then that Al-Bayrooni contributed so much to the world of knowledge. We are told that a simple listing of his written works covered more than sixty pages. A well-known orientalist said of him: "Abu Rayhaan Muhammad Al-Bayrooni was called 'Al-Ustath' (lit. 'The master'). He was a Muslim physician, astronomer, mathematician, physicist, geographer and historian, and is perhaps the most prominent figure in the phalanx of those universally learned Muslim scholars who characterize the Golden Age of Islamic Science..." (Max Meyerhaff, Legacy of Islam, 332)

　　Al-Bayrooni was born in Khawaarizm (a part of modern Uzbekistan) in 362 A.H. He studied Islamic law and Arabic besides Persian, and delved into many different sources and branches of knowledge, contributing generously to all of them.

　　Being a true scientist, Al-Bayrooni was of the view that regardless of the subject being studied, one should:

　　(1) utilize every available related source, in its original form, (2) subject any externally obtained information to objective scrutiny, and (3) be empirical, i.e., investigate the subject through direct observation and experimentation. For this purpose our hero became one of the early polyglot scientists of Islam, having learnt Greek, Syriac and Sanskrit, besides Arabic and Persian. He used his knowledge of these languages very effectively to further his own knowledge, as well as that of mankind, in numerous fields of investigation. The contributions of Al-Bayrooni can be observed in astronomy, mathematics, geology, geography, physics and history.

　　In astronomy, Al-Bayrooni discovered seven distinct methods of finding the direction of the North and the South, and constructed mathematical techniques to determine the exact time of the commencement of the seasons. He also wrote about eclipses and the movement of the sun, as well as inventing certain instruments and tools to help astronomical studies.

　　In mathematics, Al-Bayrooni was a pioneer in the study of angles and trigonometry, which is in addition to his major contributions to geometry.

　　Al-Bayrooni also contributed generously to geology and geography through his studies on the determination of the circumference of the earth, geological eruptions and metallurgy, in addition to the measurement of longitudes and latitudes and methods of determining distances between relative locations. Cartography and ethnography also greatly benefited from Al-Bayrooni's genius.

　　As for history, we are told by Meyerhoff that: "His (i.e., Al-Bayrooni's) Chronology of Ancient Nations and Indian Studies are well known and widely available, due to him also contributing to the world of translation." In fact, through his meticulous geographical and historical investigations, he also contributed to the field of comparative religion.

　　In physics, he discovered the specific atomic weights of eighteen elements, compounds and mixtures, including many metals and stones.

　　What makes Al-Bayrooni of special interest to students of Islam and Islamic history is that he was an example of a true Muslim scientist whose Islamic guidance assisted his scientific investigations, and whose scientific discoveries strengthened his belief in his religion. In this regard, he once said: "My experience in the study of astronomy and geometry and my experiments in physics revealed to me that there must be a Great Planner of Unlimited Power. My discoveries in Astronomy showed that there are fantastic intricacies in the universe, which prove that there is a creative system and a meticulous control that cannot be explained through sheer physical and material causes."

　　Our hero lived in the company of many rulers, including Mahmood AI-Ghaznawi, who was the Muslim conqueror of the Indian Subcontinent, as well as his son Mas'ood but he never considered knowledge or its quest a means to fame, authority or material gains. We are told that when Al-Bayrooni finished his encyclopedic work entitled Al-Qanoon Al-Mas'oodi (lit. 'The Mas'oodi Canon'), Sultan Masood sent him three camel-loads of silver coins. Al-Bayrooni politely returned the royal gift saying: "I serve knowledge for the sake of knowledge, and not for money." With this mentality and dedication, and with these immense contributions in so many diverse fields, our hero truly earned the title of 'Al-Ustath', or the Master or Teacher par excellence, and his era was termed by some historians as 'The age of Al-Bayrooni.' He died in 440 A.H .