Published on Explorable.com (https://explorable.com ) Indian Astronomy in the First Millennium So far, our look at ancient astronomy has concentrated very much upon Mesopotamia [1], European astronomy and the Islamic Golden Age. However, in any study of astronomy, it is impossible to ignore the work of the great Indian astronomers; their contribution to the science influenced Hellenic, Islamic [2] and European thought for centuries, with their work carried down the great Silk Road into Europe. Indian astronomy was heavily tied to their religious and spiritual outlook of the world, but it contained many accurate observations of phenomena. This acted as a catalyst for the growth of mathematics in the subcontinent, one of the greatest legacies passed on by India to the western world. Indian Astronomy, Astrology and the Vedas Rigveda Manuscript (Public Domain) The first records of sophisticated astronomy in India date back to at least 2000 BCE, where they are found in the Rigveda (c1700-1100 BCE), one of the primary and foremost texts of Hinduism. The ancient Indian astronomers used the stars and the planets to create astrological charts and read omens, devising sophisticated mathematical models and developing many interesting theories, many of which passed into the Islamic world and Europe. The Rigveda shows that the Indians divided the year into 360 days, and the year was subdivided into 12 months of 30 days. Every 5 years, two intercalary periods were added to bring the calendar back in line with the solar year, ensuring that years averaged 366 days. However, the Indian year still migrated four days in every five years, and Indian astronomers constantly tweaked and adjusted their calendars over the millennia. The text also shows that the Indians used four cardinal points for ensuring the correct orientation of altars. The Jyotisa Vedanga, the first Vedic text to mention astronomical data, records events going back as far as 4000 BCE, although many archaeoastronomers believe that this text may include observations from as early as 11 000 BCE. They point out that some of the records may have been copied from earlier manuscripts, but this is an area where more research is needed, as many of the references are unclear and couched in religious terminology.