As readers may have noticed, I am a moon watcher. Eclipses of either the sun or the moon had been a sort of passion throughout my life, ever since my late father woke me up at 3 o’clock in the morning on Saturday, December 19, 1964 for a total eclipse of the moon. I was just 9 years old and bought my first small telescope the next year from saved pocket money.
When living in the Middle East, moon watching became even more important for me as I tried to understand the Muslim calendar, in patricular the beginning and end of the holy month of Ramadan.
There was one remarkable occasion, on March 29, 2006, when a partial eclipse of the sun occurred in Kuwait. I had manufactured a simple camera obscura from a cardboard box which produced an image of the sun, already partially covered by the moon, on the tiled floor in the entrance hall of Kuwait University’s FOD. I showed the image to my friend, the former Dean of the Faculty, who was surprised as the light was not dimmed in the slightest way by the moon.
On June 6, 2012, a rare Venus transit occurred very early in the morning, which was best to be seen on the disc of the midnight sun in the Arctic. So, I was in Tromsø and I was well-prepared to observe it with the aid of my cardboard box. In the woods close to the building where I lived I looked for a proper place but I had forgotten one important tool: a white piece of paper for projecting an image of the disc of the sun through the little hole in the cardboard box. I realized that the forest floor wasn’t suitable for that. So, I did not see the transit and, honestly, I doubt whether I ever would have been able to see it with this primitive camera obscura.
The 2012 Venus transit was the second of a pair of transits which occur eight years apart (so the previous one was in 2004). The next pair will be in December 2117 and December 2125. While Johannes Kepler was the first to correctly predict a transit in 1631 (which wasn’t visible from his location), it was Jeremiah Horrocks who, after carefully studying Kepler’s tables, made the first recorded observation of a Venus transit on December 4, 1639 (Greg).
Persian polymath Abu ’Ali Ibn Sina (980-1037 CE), or Avicenna as known in the West, had claimed that he had actually observed a Venus transit without giving a date. During his lifetime, only one happened, on May 24, 1032 (Julian).
The most comprehensive study on Avicenna’s claim had been published by RC Kapoor in 2013, its manuscript (received by the Indian Journal of History of Science on September 10, 2012) most probably being inspired by the very 2012 transit. Kapoor first refers to Bernard R. Goldstein’s study in which Avicenna’s claim was discussed who had identified the latter’s quote in a commentary on Ptolemy’s Amagest that Venus, at least sometimes below the sun, had appeared as “a mole on the face of the sun.”
Kapoor also mentions S.M.H. Hadavi (1986) who had found a similar claim in Avicenna’s Al-Isharat wa’l-Tanbihat. It is very much worth reading Kapoor’s meticulous arguments as regards the circumstances of the 1032 transit, its particular possible visibility at sunset in central Iran, Avicenna’s whereabouts in that particular year, i.e. Isfahan or Hamadan, and whether he even was possibly mistaken by just sun spots on the surface of the sun. According to Kapoor, it is extremely unlikely that Avicenna actually noticed the planet by chance. Rather, the possible observation must have been well-prepared in the days before and known astronomical tables, zijes.
Pouria Nazemi, with whom Kapoor had communicated when writing his report, had found another mention of the Venus transit by Avicenna. He had published a respective paper in the defunct Nojum – The Astronomy Magazine of Iran in 2003/2004. Nazemi found the respective short quote in Kitab al-Shifa’, Avicenna’s “Book of Healing”. It is his major philosophical work (and not about Medicine, as Kapoor erroneously claims; that is his celebrated Qanun fi at-Tibb).
In the old days people believed the spheres of Mercury and Venus were located beneath the sphere of the Sun, but then some other people assumed that the two spheres were over the Sun, because they never saw the two planets covering the Sun. But their argument is not convincing, since it is possible that the path of these planets lie beneath the Sun, but is not located in the same plane that passes through our eyes and the center of the Sun. In that event, the two planets will not cover the Sun, and that is (is like the situation that) occurs most of the times when the Sun and the Moon are in conjunction. I say that I have seen Venus as a spot on the Sund’s face. (Emphasis added.)Nazemi P. Historical Observations of Venus Transits in Iran. Nojum 2003/2004.
Kapoor quotes from a personal communication with Nazemi, and his quote slightly differs from the above. He suggests that Avicenna’s deduction can only come from direct observation and that “the venue [of this observation] might be way up north-west of Isfahan, possibly near Hamadan.”
I have witnesses a sun spot maximum around 1980 and could easily identify, with the naked eye, spots on the sun’s face. Of course only at sunrise or its set. It was certainly similar as the above real transit of Venus as captured by Tamas Ladanyi.
Would it not be highly likely that Avicenna, occupied with a deeper understanding of Ptolemy’s very complicated heliocentric world view while finishing the astronomical part of his major philosophical work, has mistaken a sun spot with a Venus transit? Of which he did not even know that it was going to happen during his lifetime.
The most striking argument against Avicenna’s claim is that the Venus transit occurred so late in his life. After all, as far as we know Kitab al-Shifa’ was completed already around 1020 and published in Arabic (by making copies in handwriting) in 1027. That he repeated his claim in one of his last works, al-Isharat wa’l-Tanbihat, does not solve the problem.
So, it must be concluded that Avicenna has most probably not witnessed the Venus transit of 1032, which might even be more tragic as he had forecast a Venus transit but has not even known that it would occur during the last years of his life.
12 September 2022 @ 8:40 am.
Last modified September 12, 2022.