Abu Ibn Al-Haytham, also known as Alhazen in the west, was one of the greatest theoretical physicists during the middle ages. His works in optics, primarily, have established much of what we current study at the basic level. He was one of those great Islamic scholars, to whom, we are still indebted for much of our current scientific knowledge.
Following the collapse of the western Roman empire in the 5th century AD, the period of intellectual lethargy commonly (but wrongly) called the Dark Ages began in Europe. However, it was a golden time of development in the newly founded Islamic empire, under the protection of the Caliphate and the powerful military united by the messages of the Prophet. This gave rise to many great scientists, philosophers, authors, engineers and poets in the middle-east.
Al-Haytham was born in the 10th century AD in Basra, modern Iraq. The actual date of his birth is debated, but usually the figure 965 AD is accepted as the correct year. However, Al-Haytham spent most of his adult life in Egypt, where most of his work on optics, astronomy and mathematics was conducted.
It is said that the mad Caliph Al-Hakim had ordered Al-Haytham to somehow build a mechanism to control the waters of the Nile. Realizing his inability to do so, Al-Haytham feigned madness, and was put under house arrest. There, in solitude, he conducted most of his simple experiments, which established the basics of modern optics (much of which we now take for granted).
Al-Haytham has been called the first true scientist by Jim Al-Khalili, however we believe that's rather far-fetched, given the prowess displayed by the European and Indian practitioners of science before him. However, he definitely was a pioneer in the use of the scientific method.
Prior to Al-Haytham, people explained the mechanism of vision using two theories, both of which were incorrect. The first was the ancient Greek emission argument, which suggested that the eyes radiate invisible beams which scanned things around us. The second approach, called intromission, was championed by Aristotle. It claimed that physical matter or corpuscles of some kind, entered into the eyes from physical matter all around.
Al-Haytham, by experimenting in the dark, realized that both the emission and intromission theories were incorrect. Instead, he developed the notion of luminous,non-luminous and illuminated objects, which are now taught at the primary levels of our educational institutions. The luminous bodies, he concluded, emit light which is then reflected off the non-luminous bodies, and this reflected light is caught by the human eye, producing vision.
What we call the pinhole camera today was known as camera obscura back in the middle ages. Al-Haytham, by experimenting with pinhole cameras ans the inverted, real images of objects produced by them, hypothesized that the aperture in our eyes act like the hole in the pinhole camera, and there must be a screen of some sort inside the eye.
By repeating his experiments, he strengthened this hypothesis. This was the first truly scientific (although basic) description of the eye.
Al-Haytham was interested in studying the properties of light beams, and he was famous for using mechanical analogies to attempt to explain the properties of light. This is far from correct, though, but it established and emboldened the crucial corpuscular theory of light, which is still in use (alongside the wave-approach, in the wave-particle duality that we study).
Al-Haytham explained reflection and refraction using the analogies of moving balls and sticks. For example, his argument for the classical case of i = 0 degrees in refraction (i.e for perpendicular rays passing from one medium to the other) makes use of a falling stick. A stick, he relates, when falling perpendicularly on the earth, digs deep inside the soil. On the other hand, a stick falling obliquely would deflect.
This is far from the correct explanation, obviously, but we must keep in mind the technological limitation of his age, more than a thousand years ago.
Although Descartes is credited to have unified algebra and geometry by most of us, proto-analytical geometry was in use prior to him. And Al-Haytham is famous for his geometric method of adding the first 100 natural numbers. Thus, he verified,arithmetic progression can be related to geometry.
He also developed the earliest elliptical and hyperbolic geometries, as opposed to the planer Euclidean geometry that was in use back then.
In addition, Al-Haytham formulated the theorem (without proof) that every even perfect number can be expressed as 2^(n-1) * ( 2^n - 1 ), where the second term is prime. This might have been a case of accidental discovery though.
The scientific philosophy relies on the scientific method. This was something the ancient Greeks and Indians lacked, despite their brilliance. Prior to Bacon, Popper and Kuhn, there had been work on scientific philosophy, but nothing concrete was developed.
This notion is being challenged. As opposed to rationalism that was an integral part of the Aristotelian physics back in that period, Al-Haytham stressed the importance of empiricism. He was the first to have documented the process of changing his hypotheses based on experimental results, while simultaneously maintaining the internal logical consistency of his theories.
This is why Al-Haytham is hailed as the first theoretical physicist by many of us.
The phenomenon of the moon appearing bigger near the equator was first properly explained by Al-Haytham. Previously, the Ptolemic theory of astronomy explained this happening with the help of refraction. However, Al-Haytham was the first to challenge the use of refraction in this case.
This is a psychological phenomena, as known to us.
Al-Haytham wrote several treatises and books on optics and mathematics. Many of them are lost, but he had been referenced by the later Islamic scholars.
The official biography of Al-Haytham on Trinity College's website reads:
This shows us the importance of his works.
One of the moon's craters, Alhazen, is named after Al-Haytham (in the Latinised form of his name).
http://www.trincoll.edu/depts/phil/philo/phils/muslim/alhazen.html
http://news.bbc.co.uk/2/hi/science/nature/7810846.stm (Jim Al-Khalili's article on Al-Haytham)
http://www.geog.ucsb.edu/~jeff/115a/history/alhazen.html
Following the collapse of the western Roman empire in the 5th century AD, the period of intellectual lethargy commonly (but wrongly) called the Dark Ages began in Europe. However, it was a golden time of development in the newly founded Islamic empire, under the protection of the Caliphate and the powerful military united by the messages of the Prophet. This gave rise to many great scientists, philosophers, authors, engineers and poets in the middle-east.
Birth and life
Al-Haytham was born in the 10th century AD in Basra, modern Iraq. The actual date of his birth is debated, but usually the figure 965 AD is accepted as the correct year. However, Al-Haytham spent most of his adult life in Egypt, where most of his work on optics, astronomy and mathematics was conducted.
It is said that the mad Caliph Al-Hakim had ordered Al-Haytham to somehow build a mechanism to control the waters of the Nile. Realizing his inability to do so, Al-Haytham feigned madness, and was put under house arrest. There, in solitude, he conducted most of his simple experiments, which established the basics of modern optics (much of which we now take for granted).
Contributions to science
Al-Haytham has been called the first true scientist by Jim Al-Khalili, however we believe that's rather far-fetched, given the prowess displayed by the European and Indian practitioners of science before him. However, he definitely was a pioneer in the use of the scientific method.
1. Understanding the mechanism of sight
Prior to Al-Haytham, people explained the mechanism of vision using two theories, both of which were incorrect. The first was the ancient Greek emission argument, which suggested that the eyes radiate invisible beams which scanned things around us. The second approach, called intromission, was championed by Aristotle. It claimed that physical matter or corpuscles of some kind, entered into the eyes from physical matter all around.
Al-Haytham, by experimenting in the dark, realized that both the emission and intromission theories were incorrect. Instead, he developed the notion of luminous,non-luminous and illuminated objects, which are now taught at the primary levels of our educational institutions. The luminous bodies, he concluded, emit light which is then reflected off the non-luminous bodies, and this reflected light is caught by the human eye, producing vision.
2. The structure of the eye
What we call the pinhole camera today was known as camera obscura back in the middle ages. Al-Haytham, by experimenting with pinhole cameras ans the inverted, real images of objects produced by them, hypothesized that the aperture in our eyes act like the hole in the pinhole camera, and there must be a screen of some sort inside the eye.
By repeating his experiments, he strengthened this hypothesis. This was the first truly scientific (although basic) description of the eye.
3. An early explanation of refraction and reflection
Al-Haytham was interested in studying the properties of light beams, and he was famous for using mechanical analogies to attempt to explain the properties of light. This is far from correct, though, but it established and emboldened the crucial corpuscular theory of light, which is still in use (alongside the wave-approach, in the wave-particle duality that we study).
Al-Haytham explained reflection and refraction using the analogies of moving balls and sticks. For example, his argument for the classical case of i = 0 degrees in refraction (i.e for perpendicular rays passing from one medium to the other) makes use of a falling stick. A stick, he relates, when falling perpendicularly on the earth, digs deep inside the soil. On the other hand, a stick falling obliquely would deflect.
This is far from the correct explanation, obviously, but we must keep in mind the technological limitation of his age, more than a thousand years ago.
4. Contributions in mathematics
Although Descartes is credited to have unified algebra and geometry by most of us, proto-analytical geometry was in use prior to him. And Al-Haytham is famous for his geometric method of adding the first 100 natural numbers. Thus, he verified,arithmetic progression can be related to geometry.
He also developed the earliest elliptical and hyperbolic geometries, as opposed to the planer Euclidean geometry that was in use back then.
In addition, Al-Haytham formulated the theorem (without proof) that every even perfect number can be expressed as 2^(n-1) * ( 2^n - 1 ), where the second term is prime. This might have been a case of accidental discovery though.
5. Works on scientific philosophy
The scientific philosophy relies on the scientific method. This was something the ancient Greeks and Indians lacked, despite their brilliance. Prior to Bacon, Popper and Kuhn, there had been work on scientific philosophy, but nothing concrete was developed.
This notion is being challenged. As opposed to rationalism that was an integral part of the Aristotelian physics back in that period, Al-Haytham stressed the importance of empiricism. He was the first to have documented the process of changing his hypotheses based on experimental results, while simultaneously maintaining the internal logical consistency of his theories.
This is why Al-Haytham is hailed as the first theoretical physicist by many of us.
6. Experimental psychology
The phenomenon of the moon appearing bigger near the equator was first properly explained by Al-Haytham. Previously, the Ptolemic theory of astronomy explained this happening with the help of refraction. However, Al-Haytham was the first to challenge the use of refraction in this case.
This is a psychological phenomena, as known to us.
Legacy
Al-Haytham wrote several treatises and books on optics and mathematics. Many of them are lost, but he had been referenced by the later Islamic scholars.
The official biography of Al-Haytham on Trinity College's website reads:
"In his writing, one can see a clear development of the scientific methods as developed and applied by the Muslims and comprising the systematic observation of physical phenomena and their linking together into a scientific theory. This was a major breakthrough in scientific methodology, as distinct from guess and gesture, and placed scientific pursuits on a sound foundation comprising systematic relationship between observation, hypothesis and verification."
This shows us the importance of his works.
One of the moon's craters, Alhazen, is named after Al-Haytham (in the Latinised form of his name).
References
http://www.trincoll.edu/depts/phil/philo/phils/muslim/alhazen.html
http://news.bbc.co.uk/2/hi/science/nature/7810846.stm (Jim Al-Khalili's article on Al-Haytham)
http://www.geog.ucsb.edu/~jeff/115a/history/alhazen.html
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