"it is certainly impossible to have knowledge of their influences." Early heliocentric models The Hellenistic Greek astronomer Seleucus of Seleucia, who advocated a heliocentric model in the 2nd century BC, wrote a work that was later translated into Arabic. A fragment of his work has survived only in Arabic translation, which was later referred to by the Persian philosopher Muhammad ibn Zakariya al-Razi (865–925). In the late ninth century, Ja'far ibn Muhammad Abu Ma'shar al-Balkhi (Albumasar) developed a planetary model which some have interpreted as a heliocentric model. This is due to his orbital revolutions of the planets being given as heliocentric revolutions rather than geocentric revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data was later recorded by al-Hashimi, Abū Rayhān al-Bīrūnī and al-Sijzi. In the early eleventh century, al-Biruni had met several Indian scholars who believed in a rotating earth. In his Indica, he discusses the theories on the Earth's rotation supported by Brahmagupta and other Indian astronomers, while in his Canon Masudicus, al-Biruni writes that Aryabhata's followers assigned the first movement from east to west to the Earth and a second movement from west to east to the fixed stars. Al-Biruni also wrote that al-Sijzi also believed the Earth was moving and invented an astrolabe called the "Zuraqi" based on this idea: In his Indica, al-Biruni briefly refers to his work on the refutation of heliocentrism, the Key of Astronomy, which is now lost: Early Hay'a program During this period, a distinctive Islamic system of astronomy flourished. It was Greek tradition to separate mathematical astronomy (as typified by Ptolemy) from philosophical cosmology (as typified by Aristotle). Muslim scholars developed a program of seeking a physically real configuration (hay'a) of the universe, that would be consistent with both mathematical and physical principles. Within the context of this hay'a tradition, Muslim astronomers began questioning technical details of the Ptolemaic system of astronomy. Some Muslim astronomers, however, most notably Abū Rayhān al-Bīrūnī and Nasīr al-Dīn al-Tūsī, discussed whether the Earth moved and considered how this might be consistent with astronomical computations and physical systems. Several other Muslim astronomers, most notably those following the Maragha school of astronomy, developed non-Ptolemaic planetary models within a geocentric context that were later adapted by the Copernican model in a heliocentric context. Between 1025 and 1028,