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The World's First Physicist

Jim al Khalili

Isaac Newton, as everyone knows, is the greatest physicist of all time. At the very least, he is the undisputed father of modern optics - or so we are told at school, where our textbooks abound with his famous experiments with lenses and prisms, his study of the nature of light and its reflection, and the refraction and decomposition of light into the colours of the rainbow.

Yet the truth is rather greyer; and I feel it important to point out that, certainly in the field of optics, Newton himself stood on the shoulders of a giant who lived seven hundred years earlier. For, without doubt, another great physicist, who is worthy of ranking up alongside Newton, is an Iraqi scientist born in 965 AD who went by the name of al-Hassan ibn al-Haytham. Most people in the West will never have even heard of him.

Isaac Newton, The British Library

As a physicist myself, I am quite in awe of this man's contribution to my field. As a science communicator and broadcaster I am also fortunate enough to have recently been given the opportunity to dig a little into his life and work. Although half my time is spent working as an academic within the Department of Physics at the University of Surrey, I am also honoured to hold the first Surrey chair in the public engagement in science. It is with this hat on that I have embarked on presenting a three-part BBC series on medieval Islamic scientists.

Popular accounts of the history of science typically show a timeline in which no major scientific advances seem to have taken place during the period between the ancient Greeks and the European Renaissance. In between, so we are told, Western Europe and, by extrapolation, the rest of the world, languished in the Dark Ages for a thousand years.

The story of this astonishing era remains largely untold outside academic circles despite being one in which Arabic scientific knowledge first built upon, and then far surpassed, that of the ancient Greeks. Advances were made in mathematics, astronomy, medicine, physics, chemistry, philosophy and just about every other scientific discipline. Among the many geniuses of that period - between the eighth and twelfth centuries - Ibn al-Haytham stands taller than all the others.

Ibn al-Haytham is regarded as the father of the modern scientific method. As commonly defined, this is the approach to investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge, based on the gathering of data through observation and measurement, followed by the formulation and testing of hypotheses to explain the data. This is how we do science today and is why I put my trust in the advances that have been made in science. But it is often still claimed that the modern scientific method was not established until the early seventeenth century by Francis Bacon and René Descartes. However, there is no doubt in my mind that Ibn al-Haytham arrived there first.

Ibn Al-Haytham

With his emphasis on experimental data and reproducibility of results, as exemplified his famous Book of Optics, Ibn al-Haytham made this insistence upon the primacy of the scientific method a central theme of his life's work. Indeed, his seven-volume classic ranks alongside Newton's Principia Mathematica in terms of importance in science, the consequence being that he is often referred to as the world's first true scientist.

He was the first scientist to give a correct account of how we see objects. He proved experimentally, for instance, that Aristotle's intromission theory of vision (which holds that light from an object enters our eyes) was correct, and that Plato, Euclid and Ptolemy's emission theory (which stated that light from our eyes shines upon the objects we see) was wrong. What he also did that no other scientist had tried before was to use mathematics (geometry) to describe and prove this process. So he can be regarded as the very first theoretical physicist! He is perhaps best known for his invention of the pinhole camera and should be credited with the discovery of the laws of refraction. He also carried out the first experiments on the dispersion of light into its constituent colours and studied shadows, rainbows and eclipses; and by observing the way sunlight diffracted through the atmosphere, he was able to work out a rather good estimate for the height of the atmosphere, which he found to be around 100 km.

In common with many modern scholars, Ibn-Haytham badly needed the time and isolation to focus on writing his many treatises, including his great Optics: an unwelcome opportunity was granted him, however, when he was placed under house arrest in Egypt between 1011 and 1021 having failed a task set him by a caliph in Cairo to help solve the problem of regulating the flooding of the Nile. While still in Basra, Ibn al-Haytham had claimed that the Nile's autumn flood waters could be held by a system of dykes and canals, and thereby preserved as reservoirs until the summer's droughts. But on arrival in Cairo he soon realised that his scheme was utterly impractical from an engineering perspective. Yet rather than admit his mistake to the dangerous and murderous Caliph, Ibn-Haytham instead decided to feign madness as a way to escape punishment. This promptly led to him being sectioned, to use a modern analogy, thereby accidentally granting him years of seclusion in which to work. He was only released after the caliph's death. He returned to Iraq where he composed a further one hundred works on a range of subjects in physics and mathematics.

While travelling through the Middle East during my filming I recently interviewed an expert in Alexandria who showed me recently discovered work by ibn al-Haytham on astronomy. It seems he had developed what is called celestial mechanics, explaining the orbits of the planets, which was to lead to the eventual work of Europeans like Kepler and Newton.

It is incredible that we are only now uncovering the debt that today's physicists owe to an Arab who lived one thousand years ago.

- Professor Jim Al-Khalili

Picture 1 - Newton by Eduardo Paolozzi, Flickr

Picture 2 - Ibn_haithem_Scientist by holy_zufikar, Flickr

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Introduction: 

You've heard of Isaac Newton, but have you heard of al-Hassan ibn al-Haytham?