Did IBN SINA Observe The Transit of Venus 1032 AD?

Abstract

The Persian polymath Ab ū AīIbn Sīnā (980-1037 AD), known to early Western sources as Avicenna, records in one of his works, Compendium of the Almagest that ‘I say that I saw Venus as a spot on the surface of the sun’. The date and place of the observation are not given. This statement has been quoted subsequently by some Muslim astronomers, for example, by Na ī r al-D ī n alu (1201–1274 AD). A transit of Venus indeed took place in Ibn Sina ’s time, on 24 May 1032 AD (Julian). Did Ibn S ī n ā see this transit or did he merely see a nspot? The question was addressed by Bernard Goldstein in 969 who concluded that “this transit may not have been visible where he lived”. The conclusion was based on the input provided to him y Brian Marsden who in turn used mathematical tables prepared by Jean Meeus in 1958 and gave sets of limiting terrestrial latitudes and longitudes from where the Contact I and II could be just observable. We have re-examined the question employing Espenak’s Transit predictions as also Jubier’s. The astronomical circumstances of the transit episode and the specific commentary on the monumental work Kit ā b al Shif āof Ibn S īnā show that he could indeed have obtained a glimpse of the transit of Venus just before sunset from the place – Isfahan or Hamadan. That is also the best time to view with one’s naked eyes, should ground conditions permit. In other words, when Ibn S ī n ā said he saw Venus on the surface of the Sun, he meant it. We consider also if Ibn S ī n ā’ s observation could be that of a sunspot. Although the sunspot possibility can not be dismissed altogether, it does not emerge as a cogent proposition. His statement that every conjunction does not result in a transit can come rom an actual observation only. Ibn S ī n ā ’s claim perhaps fills an important gap in the history of astronomy for the period 1030 AD onwards and bears testimony to his observational acumen and computational precision