The intellectual success of Islam's Golden Age has affected the world greatly today. The knowledge of the empire could be seen mostly through the advances in medicine and science. The works of Al-Zahrawi and Ibn Sina became standard medical texts for centuries in Europe. The most famous doctor of the Golden Age was possibly Al-Razi, who wrote about 200 books on medicine. Arabic numerals and the idea of zero made algebra possible for the world. Mathematician Al-Khwarizmi wrote an algebra textbook that was used for centuries. Ibn- al-Haytham, is known as the first "scientist" and conducted experiments that inspired the scientific method.