Why did Al-Biruni developed interest in …

Al-Biruni arrived in Ghazni as a hostage, but gradually developed a liking for the city, where he spent the rest of his life until his death at the age of 70. It was in Ghazni that Al-Biruni developed an interest in India. 

 This was not unusual. Sanskrit works on astronomy, mathematics and medicine had been translated into Arabic from the eighth century onwards. When the Punjab became a part of the Ghaznavid empire, contacts with the local population helped create an environment of mutual trust and understanding. Al-Biruni spent years in the company of Brahmana priests and scholars, learning Sanskrit, and studying religious and philosophical texts. While his itinerary is not clear, it is likely that he travelled widely in the Punjab and parts of northern India. Travel literature was already an accepted part of Arabic literature by the time he wrote. This literature dealt with lands as far apart as the Sahara desert in the west to the River Volga in the north. So, while few people in India would have read Al-Biruni before 1500, many others outside India may have done so.