Nasir al-Din al-Tusi: The Astronomer Copernicus Copied
Nasir al-Din al-Tusi developed a mathematical device in 1247 CE that Copernicus used, without attribution, in his heliocentric model three centuries later. The evidence is in the manuscripts: identical diagrams in both, with the Arabic original predating the Latin by 300 years.
Who He Was
Muhammad ibn Muhammad ibn al-Hasan al-Tusi (1201–1274 CE), known as Nasir al-Din al-Tusi, was a Persian polymath, mathematician, astronomer, philosopher, and theologian. He directed the Maragheh Observatory in Iran, one of the greatest scientific institutions of the medieval world.
What He Did
The Tusi Couple: Al-Tusi developed a mathematical device (now called the Tusi Couple) that produces linear motion from two circular motions. He introduced it in his 1247 work Tadhkira fi Ilm al-Hay'a (Memoir on the Science of Astronomy). It was designed to solve a mathematical problem in Ptolemaic astronomy that had not been resolved for over a thousand years.
Correcting Ptolemy: Al-Tusi and other Islamic astronomers at the Maragheh school (including Ibn al-Shatir) systematically identified and corrected the mathematical problems in Ptolemy's Almagest. Their work redefined the field.
Mathematics: Al-Tusi's Treatise on the Quadrilateral was the first work to treat trigonometry as an independent mathematical discipline rather than a branch of astronomy.
The Copernicus Problem
Nicolaus Copernicus published his heliocentric model in De Revolutionibus in 1543 CE, an event described as one of the most important in the history of science. What is less discussed is that his model uses the Tusi Couple and other mathematical devices developed by Islamic astronomers, in diagrams that are virtually identical to the Arabic originals.
The historian of science Noel Swerdlow demonstrated in 1973 that Copernicus's lunar model was derived directly from Ibn al-Shatir's model, which itself built on al-Tusi's work. George Saliba's research further documented the specific mathematical derivations.
The diagrams in Copernicus's manuscript are identical to al-Tusi's, not similar, not parallel, but identical. Al-Tusi's work predates Copernicus by 300 years. Copernicus gave no attribution.
How Copernicus accessed al-Tusi's work remains an open question, the most likely route is through Byzantine manuscripts or through the translation networks of 15th-century Europe. What is not open is the priority.
What This Means
The Copernican revolution (the event that displaced the Earth from the centre of the universe and initiated the scientific revolution) was built on mathematical foundations developed by Muslim astronomers working in 13th-century Persia. The revolution belongs to Islamic astronomy as much as to Copernicus.
Common Misconceptions
"Copernicus developed his heliocentric model independently." The mathematical frameworks he used (including the Tusi Couple) were developed by Islamic astronomers 300 years earlier. Identical diagrams appear in both sources. The academic case for derivation rather than independent invention is well-established.
"This is just Islamic triumphalism." The research is by mainstream Western historians of science (Noel Swerdlow, George Saliba) published in peer-reviewed academic journals.
Scholar References
- Nasir al-Din al-Tusi, Tadhkira fi Ilm al-Hay'a (1247 CE)
- Noel Swerdlow, 1973: on the derivation of Copernicus's lunar model from Ibn al-Shatir
- George Saliba, Islamic Science and the Making of the European Renaissance (2007)