section_path: Other contributions/Astronomy and astrology
section_name: Astronomy and astrology
paragraph_text: Astronomy and astrology
  
  Avicenna wrote an attack on astrology titled Missive on the Champions of the Rule of the Stars (رسالة في ابطال احكم النجوم) in which he cited passages from the Quran to dispute the power of astrology to foretell the future. He believed that each classical planet had some influence on the Earth but argued against current astrological practices.
  
  Avicenna's astronomical writings had some influence on later writers, although in general his work could be considered less developed than that of ibn al-Haytham or al-Biruni. One important feature of his writing is that he considers mathematical astronomy a separate discipline from astrology. He criticized Aristotle's view of the stars receiving their light from the Sun, stating that the stars are self-luminous, and believed that the planets are also self-luminous. He claimed to have observed the transit of Venus. This is possible as there was a transit on 24 May 1032, but ibn Sina did not give the date of his observation and modern scholars have questioned whether he could have observed the transit from his location at that time; he may have mistaken a sunspot for Venus. He used his transit observation to help establish that Venus was, at least sometimes, below the Sun in the geocentric model, i.e. the sphere of Venus comes before the sphere of the Sun when moving out from the Earth.
  
  He also wrote the Summary of the Almagest based on Ptolemy's Almagest with an appended treatise "to bring that which is stated in the Almagest and what is understood from Natural Science into conformity". For example, ibn Sina considers the motion of the solar apsis, which Ptolemy had taken to be fixed.