Without question, the greatest name in physics during the Arab/Islamic Empire was Ibn al-Hay-tham, born in the city of Basra, Iraq, in 965 A.D. By the time he died in 1030, he had made major contributions to optics, astronomy and mathematics, some of which would not be improved upon for six centuries.
Ibn al-Haytham's main field of interest and the one to which he made his greatest contributions, was the branch of physics we call optics. Striking parallels exist between his work and that of the seventeenth century English physicist, Isaac Newton, one of the greatest scientists of all time.
One of Newton's major accomplishments was his famous Law of Universal Gravitation. The most significant aspect of this theory is that it considers gravitation to be universal; that is, the same laws apply in the heavens and throughout the universe as apply on earth. This contradicts the idea held from the time of Aristotle (384-322 B.C.) that there is a difference between the laws governing events on earth and those pertaining to celestial bodies. Newton realized that the force that causes an apple to fall from a tree is the same force that holds the moon and all the planets in their orbits and, indeed, is the same as that which governs the motion of the stars themselves.
If this idea were considered new in the seventeenth century, it was certainly new in the eleventh. Yet some of Ibn al-Haytham's experiments showed that he, too, believed that extraterrestial phenomena obeyed the same laws as do earthly ones.
Ibn al-Haytham evolved his theories of optics through the study of light rays, and his investigations revealed a number of important properties:

that light travels in a straight line; that every point of a luminous object radiates light in every direction; and that light weakens as it travels from its source. He studied these characteristics of light from a variety of light sources, i.e. self~mitting (the sun, fires and various lamps), and reflecting (the moon and reflecting bodies on earth).

This seemingly trivial experiment is in fact an early example of what is known as the "scientific method." Ibn al-Haytham designed an experiment to test a hypothesis, namely, that light travels in anamely, that light travels in a

  straight line. His experiment was arranged to avoid the possibility of the experimenter's bias affecting the conclusions. Today, it seems obvious that light travels in straight lines, yet there was a time when intelligent men thought it obvious that the sun travels around the earth. The most advanced and sophisticated theory in modern physics, the Theory of Relativity, is derived from a refutation of ideas that are based on our everyday experience. Performing experiments to test and verify theories is at the heart of all modern scientific methods.

Ibn al-Haytham's experiments have even greater significance. By using the sun, the moon, lamps, fires and a variety of other light sources in his experiments, he was saying that light is light, regardless of its source. In this sense, he anticipated the universal laws of seventeenth century scientists.
We have described only the simplest of Ibn alHaytham's experiments on the properties of light rays, but there are many others that were considerably more sophisticated. Ibn al-Haytham foresaw the works of later scientists not only in his use of experimentation but in the use of instrumentation:

devices to help make measurements, the key to all modern science. He designed and constructed a variety of instruments, pipes, sheets, cylinders, rulers and plane, concave and convex mirrors in order to conduct his tests.

In addition to his studies of reflection, he also studied refraction, a phenomenon in which light rays bend when travelling from one medium to another, such as from air to water. The effect causes an object to appear to be in a location other than where it actually is,making him the first scientist to test a property of refraction that seems so obvious today. He demonstrated that a ray of light arriving perpendicular to the air-water boundary was not bent at all and showed that this was true for light passing through not just two, but several media. Clear parallels exist between his work and that of Isaac Newton six centuries later: both men studied the effects of light passing through glass, and both realized that the accepted ideas of their day were wrong.
It is difficult to appreciate the degree of intellect required by both these men to overcome the


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