The Surya Siddhanta (; ) is a Sanskrit treatise in Indian astronomy dated to 505 CE, in fourteen chapters. The Surya Siddhanta describes rules to calculate the motions of various planets and the moon relative to various constellations, diameters of various planets, and calculates the orbits of various astronomical bodies. The text is known from a palm-leaf manuscript, and several newer manuscripts. It was composed or revised c. 800 CE from an earlier text also called the Surya Siddhanta. The Surya Siddhanta text is composed of verses made up of two lines, each broken into two halves, or pãds, of eight syllables each. As described by al-Biruni, the 11th-century Persian scholar and polymath, a text named the Surya Siddhanta was written by Lātadeva, a student of Aryabhatta I. The second verse of the first chapter of the Surya Siddhanta attributes the words to an emissary of the solar deity of Hindu mythology, Surya, as recounted to an asura called Maya at the end of Satya Yuga, the first golden age from Hindu texts, around two million years ago. The text asserts, according to Markanday and Srivatsava, that the earth is of a spherical shape. The text is known for some of earliest known discussion of sexagesimal fractions and trigonometric functions. The Surya Siddhanta is one of several astronomy-related Hindu texts. It represents a functional system that made reasonably accurate predictions. The text was influential on the solar year computations of the luni-solar Hindu calendar. The text was translated into Arabic and was influential in medieval Islamic geography. The Surya Siddhanta has the largest number of commentators among all the astronomical texts written in India. It includes information about the orbital parameters of the planets, such as the number of revolutions per Mahayuga, the longitudinal changes of the orbits, and also includes supporting evidence and calculation methods. Textual history In a work called the Pañca-siddhāntikā composed in the sixth century by Varāhamihira, five astronomical treatises are named and summarised: Paulīśa-siddhānta, Romaka-siddhānta, Vasiṣṭha-siddhānta, Sūrya-siddhānta, and Paitāmaha-siddhānta. Most scholars place the surviving version of the text variously from the 4th-century to 5th-century CE, although it is dated to about the 6th-century BCE by Markandaya and Srivastava. According to John Bowman, the version of the text existed between 350 and 400 CE wherein it referenced sexagesimal fractions and trigonometric functions, but the text was a living document and revised through about the 10th-century. One