Al Biruni (973-1048) lived during the golden age of Islam. He was a polymath, a philosopher , a scientist etc. He quite accurately calculated the circumference of the earth. He wrote widely on topics including Hindus (their religion, philosophy etc.). Ibn Sina ,Avicenna(980-1037) and several other scholars were his contemporaries.
Here is a link to BBC radio 4 a program called “In Our Times.”