Flamsteed AS Prof Jim Al Khalili Medieval Arabic Astronomy

Flamsteed Astronomy Society

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[Pics: Mike Dryland]

“Medieval Arabic Astronomy — Filling the gap between Ptolemy and Copernicus”

a talk by Prof Jim Al Khalili — April 4, 2011

Jim considered the greatest physicists in history, spanning 2000 years, to be: Archimedes (3rd C. BC); Ibn al-Haytham (11th C. AD); and Isaac Newton (17th C. AD). Al-Haytham made immense contributions to the study of optics and astronomy, and was one of the first philosophers seriously to question the work of Ptolemy. In his Almagest (itself the Arabic title), Ptolemy had given the world the geocentric theory. Arabic scholars, including Al-Haytham, were wedded to this theory, but Al-Haytham was highly critical of Ptolemy’s mathematical models of the solar system and devised far more sophisticated models of his own.

Nicolaus Copernicus was the Polish genius who is credited with being the first to propound the heliocentric model. But was he the first? Actually…No!

Aristarchus of Samos first promoted this idea in the 3rd C. BC – but nobody believed him!

Then Indian astronomers also proposed this theory, followed by the arabic astronomer, al-Sijzi (945-1020).

Copernicus was thought courageous in promoting the heliocentric theory, but he certainly used a lot of guesswork — there was no observational proof for the heliocentric theory! But it is clear that Islamic thinking and mathematics helped him significantly in his deliberations. Copernicus frequently refers to the work of Al-Battani and there is no doubt he used al-Tusi’s theories and maths about circles. In 1259 al-Tusi persuaded Hulagu Khan to construct the great observatory at Maragha east of Tehran. Maragha lends its name to the Maragha Revolution, a major reappraisal of Ptolemy’s work. Rather than seeing Copernicus as the ‘first’, it may be much more correct to see him as the last of the Maragha School.

Eventually Galileo was supreme; his application of the telescope to astronomy enabled the heliocentric theory to be proved beyond doubt.

Finally, Jim returned to the Islamist mathematician, Ibn al-Haytham (965 – 1039), who can be regarded as the first person to define the “Scientific Method”.

This was a fascinating and stimulating lecture by Prof Jim Al-Khalili, delivered to an attentive, and almost full, house and provided the opportunity for some pertinent questions from the audience during the Q & A session that followed.