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2009-01-05 08:41:27
By Professor Jim Al-Khalili
University of Surrey
Isaac Newton is, as most will agree, 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 700 years earlier.
For, without doubt, another great physicist, who is worthy of ranking up
alongside Newton, is a scientist born in AD 965 in what is now Iraq who went by
the name of al-Hassan Ibn al-Haytham.
Most people in the West will never have even heard of him.
As a physicist myself, I am quite in awe of this man's contribution to my
field, but I was fortunate enough to have recently been given the opportunity
to dig a little into his life and work through my recent filming of a
three-part BBC Four series on medieval Islamic scientists.
Modern methods
Popular accounts of the history of science typically suggest that no major
scientific advances took place in between the ancient Greeks and the European
Renaissance.
But just because Western Europe languished in the Dark Ages, does not mean
there was stagnation elsewhere. Indeed, the period between the 9th and 13th
Centuries marked the Golden Age of Arabic science.
Great advances were made in mathematics, astronomy, medicine, physics,
chemistry and philosophy. Among the many geniuses of that period 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 17th Century by Francis Bacon and Rene Descartes.
There is no doubt in my mind, however, that Ibn al-Haytham arrived there first.
In fact, with his emphasis on experimental data and reproducibility of results,
he is often referred to as the "world's first true scientist".
Understanding light
He was the first scientist to give a correct account of how we see objects.
He proved experimentally, for instance, that the so-called emission theory
(which stated that light from our eyes shines upon the objects we see), which
was believed by great thinkers such as Plato, Euclid and Ptolemy, was wrong and
established the modern idea that we see because light enters our eyes.
What he also did that no other scientist had tried before was to use
mathematics to describe and prove this process.
So he can be regarded as the very first theoretical physicist, too.
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 100km.
Enforced study
In common with many modern scholars, Ibn-al Haytham badly needed the time and
isolation to focus on writing his many treatises, including his great work on
optics.
An unwelcome opportunity was granted him, however, when he was imprisoned 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, 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-al
Haytham instead decided to feign madness as a way to escape punishment.
This promptly led to him being placed under house arrest, thereby granting him
10 years of seclusion in which to work.
Planetary motion
He was only released after the caliph's death. He returned to Iraq where he
composed a further 100 works on a range of subjects in physics and mathematics.
While travelling through the Middle East during my filming, I 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
Copernicus, Galileo, Kepler and Newton.
It is incredible that we are only now uncovering the debt that today's
physicists owe to an Arab who lived 1,000 years ago.
Professor Jim Al-Khalili presents Science and Islam on BBC Four at 2100GMT on
Monday 5, 12 & 19 January