The Hindu civilization, which emerged in the third millennium BC, has had a long history in the march of humanity. The Hindus invented most likely the nine numerals and made contribution to trigonometry, as they used half chord and a table of sinuses. They also knew medicine, mathematics and astronomy[
then what caused their decline ?
This was the civilization of India before Islam blatant ignorance, degrading idolatry, and social injustice that has never been witnessed in any nation in history. For more information see Al-Biruni's Tahqiq ma lil-Hind min Maqulah Maqbulah fil-`Aql aw Mardhulah (Reviewing What's Reasonably Accepted or Rejected in India's Culture), which stated and harshly criticized these aspects.
Abul Hasan Nadwi, head of Nadwat-ul-Ulama in India, gives an account of the civilization of India in the sixth century AD. He says that the authors of the India's history agreed that the lowest religious, moral and social aspects in India started in the early sixth century AD. After Nadwi had portrayed their corrupted faith, he said the most heinous class system emerged in India in a crueler, more class discriminating and more dishonoring manner that had never been witnessed by any nation in history.
The Brahmin Civilization
Three centuries before the Christ, the Brahmin civilization flourished in India, where a civil and political law was developed and agreed upon nationwide until it became an official law and a religious reference ...more