Looking towards the sky: Cairo, the year 1000

Ahmed Al-Moslemany
Tuesday 14 Jan 2020

In 1000 AD, Egyptian scientist Ibn Yunus Al-Misry laid the groundwork for much of our knowledge about astronomy and mathematics

The renowned scientist Galileo used to fawn over those in power for the sake of their patronage of scientific research. The scientists of the Renaissance would dedicate their discoveries to those who sponsored them. This was embarrassing to scientists. So, Galileo decided to resort to a sole authority whom he would be fawn over for the sake of financing all his researches.

In the seventeenth century, Cosimo II de' Medici became the Grand Duke of Tuscany, Italy. The de' Medici family’s emblem was five balls. Galileo named the four moons revolving around Jupiter as the ‘Medician Stars’, in honour of the future patron Cosimo II de' Medici and his three brothers. Galileo said: "Behold, therefore, four stars reserved for your illustrious name... which... make their journeys and orbits with a marvellous speed around the star of Jupiter... like children of the same family... Indeed, it appears the Maker of the Stars himself, by clear arguments, admonished me to call these new planets by the illustrious name of Your Highness before all others."  Cosimo II appointed Galileo the court's official philosopher and mathematician for a large salary. Thus, the eminent scientist was able to spend on his research without the need to be honey tongued to noblemen and people of wealth.

I was one of those amazed by the crowd around an original copy of Galileo's book at the hall of the Spanish Royal Academy of Sciences. I was with Dr. Ahmed Zuwail in Madrid along with Ambassador Yasser Mourad. Dr. Zuwail gave us a general idea about the book.

Galileo was a great scientist and his scientific contributions were astounding and immortal. However, one of the contributions attributed to him is not correct. A number of science historians attribute to him the invention of the clock pendulum, but most likely this invention was taken by Galileo from an Egyptian scientist, Ibn Yunus Al-Misry.

In 1000 AD, Europe was outside history and Cairo was the world’s science capital. Ibn Yunus Al-Misry was the director of biggest observatory of space studies; Al-Muqattam Observatory.

The outstanding Egyptian scientist Ibn Yunus Al-Misry was born in Sedfa, in Assiut governorate. His father was an eminent historian and was known for his literary salon. In this salon, Ibn Yunus met with the greatest Arab poet, Abu-Tayyeb Al-Mutanabbi, who told his father that his son would be a great astronomer.

Ibn Yunus lived in the Fatimid era, and the Fatimid Caliphs sponsored his works. He produced a number of important books, but his book “Al-Zij Al-Kabir”, which comprises 81 chapters, was his magnum opus.

Al-Zij is a Persian word that means tabulating parameters used for astronomical calculations. The famous Al-Zij, at the time, was Al-Zij Al-Mumtahan authored by Yahya Ibn Abi Mansur, which was released in Baghdad two hundred years before Ibn Yunus’ book. Ibn Yunus displayed, corrected and completed all the previous astronomical mathematical tables in addition to his own original contribution.

In acknowledging Ibn Yunus’ excellence over all those who preceded and were contemporaneous to him, Gustave Le Bon wrote: “Ibn Yunus wrote his famous Al-Zij Al-Kabir Al-Hakimi in Cairo and he erased from memory every previous Zij in the world.” So, Ibn Yunus’ theories in astronomy and mathematics became the most important in centuries.

Science historians have said that Ibn Yunus was the first to reach solutions to some equations in astronomy by using trigonometry. The way he facilitated mathematical calculations contributed to paving the way for the emergence of logarithms. He also succeeded in observing the solar and lunar eclipses in Cairo in 978 AD and his calculations were accurate and very close to the modern scientific level.

There is a big controversy regarding the clock pendulum and science historians in the West have been divided between those who acknowledge Ibn Yunus’ precedence in inventing it and those who deny this and ascribe it to the West.

The British historian David King held the view that Arabs did not come to know this invention except through Europeans. The French historians Jean-Étienne Montucla in his book History of Mathematics and Pierre Laplace in his book Summary of the History of Astronomy also support the theory that Europe invented the pendulum and that Ibn Yunus was not its progenitor.

However, other science historians have said that Ibn Yunus preceded Galileo and the West. The British scientist Thomas Young backed this opinion in his book Lectures in Natural Philosophy and Mechanical Arts, where he says, “Ibn Yunus used in 1000 AD the pendulum’s vibrations to measure time.” The American science historian David Eugene Smith shared the same opinion and asserted in his book The History of Mathematics that the idea of “the pendulum, which was attributed to Galileo, was hinted at by Ibn Yunus in Cairo.”

The historian Alexander von Humboldt in his book Cosmos said that “using the pendulum to measure time goes back to the great astronomer Ibn Yunus in Egypt.”

British historian Edward Bernard, who was an Oxford professor, preceded all the aforementioned in 1684, he said: “Ibn Yunus preceded us and used the clock pendulum in Cairo centuries ago.”

To a great extent, the Egyptian scientist Ibn Yunus contributed more than 200 Arabic words in astronomy until nowadays.

Unfortunately, Ibn Yunus begat an unworthy son who sold his father’s works by the pound. Consequently, much was lost. However, what did survive placed Ibn Yunus at the top of the field of knowledge for several centuries.

The son of Assiut was capable of amazing Al-Mutanabbi and the world.

“Perhaps Ibn Yunus was the greatest Muslim astronomer,” said George Sarton.

It is a pity that what remains of Ibn Yunus is a small street in Al-Waili neighbourhood in Cairo. No foundation, no forum, no award in his name… Not a building, academy or complex named after him.

Ibn Yunus suffered injustice twice: when his son sold his works by the pound, and when he fell victim to the Egyptian cultural institutions’ forgetfulness and neglect.

Today, when I remember standing in long line amid the European scientific elite crowding to see Galileo’s book in Madrid, and when I see the non-existence of an Egyptian scientist who surpassed Galileo in theory and application, I find grievous injustice has befallen our country and our history and it is high time to correct it.


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