The Most Amazing Scientist Ever”The godfather Of many inventions”
Alhacen, Alhazen, or Ibn al-Haytham, the real name is Abo Aly al-Hasan ebn el-Hasan ebn el-Haytham1 (Basra, 965 – Cairo, 1039).
He was an Arab mathematician, philosopher, and physicist in medieval times.
An early proponent of the experimental scientific method, but also one of the leading theoretical physicists to use mathematics, he is renowned for his pioneering work in the field of physiological optics and optics. Some, for these reasons, describe him as the first true scientist.
Alhazen was born in 965 in Basra (present-day Iraq), where he received an education. However, he completed this education in the city of Baghdad.
|Ibn al-Haytham Basra|
At the time, Basra was under the control of the dynasty of Buwayhids who ruled Persia.
That’s why sometimes he is referred to as al-Basri.
Although, while some people don’t accept this version, most people agree that he died in Cairo, Egypt in 1039.
Alhazen began his scientific career in his native city of Basra.
However, he was summoned by the Caliph Hakim, who wanted to control the Nile floods that struck Egypt every year.
After leading an expedition in the desert to trace the source of the famous river, Alhazen realized that this project was impossible.
Back in Cairo, he feared that the Caliph, who was furious at his failure, would seek revenge, and so decided to feign madness.
The Caliph confined him to house arrest.
Alhazen took advantage of this enforced leisure to write several books on various subjects such as astronomy, medicine, mathematics, the scientific method, and optics.
The exact number of his writings are not known with certainty, but there is talk of a number between 80 and 200.
Many of these works, in fact, have survived to this day.
Some of them, those on cosmology and his treatises on optics, in particular, survived only through their Latin translation.
After the death of Caliph Hakim in 1021, Alhazen stopped faking his madness and was able to leave his residence.
He therefore took the opportunity to take a few trips, including visiting Al-Andalus (Spain nowadays). He died in 1039.
Most of his research involved geometric and physiological optics.
He was one of the first physicists to study light, one of the first engineers, and one of the first astronomers.
Contrary to popular belief, he was the first to explain why the sun and moon appear larger when close to the horizon (it was long believed that it was Ptolemy). He also established that moonlight comes from sun.
It was he who contradicted Ptolemy in the fact that the eye would emit light. According to him, if the eye was designed that way we could see at night. He understood that the object scattered the sunlight and then entered the eye. He was also the first to show the anatomy of the eye with a diagram.
|the eye with a diagram|
As this diagram is not innovative compared to the anatomical knowledge of Galen, doubt remains as to whether it was copied from an ancient Greek manuscript or if it comes from a contemporary dissection.
He also outlined a theory of judgment and object recognition.
He notes that it recognizes only the objects that we know, and the image of an object persists for some time after he closed his eyes. The recognition is based on memory and is not a mere feeling related to judgment, because we do not recognize objects that are unknown to us.
He also studied the mechanics of movement and said that an object in motion continues to move as long as no force interferes.
The principle of inertia is enunciated by Galileo and will be later formulated rigorously by Isaac Newton.
In astronomy, he attempted to measure the height of the atmosphere and found the phenomenon of twilight (light at sunrise and sunset without seeing the sun).
This is due to the refraction phenomenon; sun rays should not exceed an angle of 19 ° in the atmosphere.
He also spoke of the attraction of the masses, and it believed that he knew of gravitational acceleration.
Alhazen wrote several books on optics. In his Book of Optics, a book on optical physics that he wrote over a period of six years (1015-1021), it scientifically proves Aristotle’s theory of intromission of how light enters the eye.
It proves that all objects reflect light in all directions, but it is when a ray collides at 90 ° with the eye that it will reflect a beam.
The image, Alhazen stated, formed on the lens.
In the same field, he said that the eye could perceive the shape, color, transparency and the movement of objects.
It also proved that the eye sees two images, even if one sees only through demonstration, and not by the logic and beauty of reasoning. This book was translated into Latin in 1270.
According to him, the refraction of light is caused by a slowdown or acceleration of light in its movement.
In a denser medium light travels more slowly, as Alhazen discovered.
There is also a relationship between the angle of incidence and the angle of refraction, but this ratio is constant only when it is the same material that refracts the ray.
He performed all of his work in a dark room, which is how he discovered and then explained the power of the magnifying lens.
In the fifth book devoted to his Catadioptric Optical Treaty is a discussion on the issue known today under the name of the “billiard problem”.
The problem can be summarized as “finding the point on the edge of a circular “billiard” table at which a cue ball at a given point must be aimed in order to carom once off the edge of the table and strike another ball at a second given point“(Wikipedia). Alhazen was able to find it with conic sections, but it does not prove it with a mathematical algebraic reasoning.
Leonardo da Vinci designed a system to build a mechanical solution to the problem of Alhazen.
Several scientists have tried to solve this problem, such as Christian Huygens.
But it was only in 1997 that Peter M. Neumann, a professor at Oxford, has shown that the solution uses an equation of the fourth degree.