Al-Hassan bin Al-Haytham (Alhazen)
He was one of the distinguished scholars of the first half of the eleventh century AD.
He was born in the year 354 of the Hijra, around 965 AD, and he was the first to live in Basra, Iraq.
His life began in the eras of Islamic civilization from the scientific point of view, and it was one of the brightest eras in the history of science, the whole world, only books of philosophy, medicine, engineering, and mathematical sciences were transferred from the Greek language to the Arabic language.
And Islamic scholars had begun to explain and comment on it, and the stage of creativity and innovation had also begun, and scholars of medicine, philosophy, chemistry and science had appeared.
He began to study everything that his hand fell upon from what was available from the books of the predecessors, in the field of scientific, mathematical and applied studies, he studied the origins of Euclid’s geometry and the conics of Abu Lunius and the articles of the natural scientist Archimedes in the centers of the weights of bodies and burnt mirrors, and what Euclid and Ptolemy wrote in the science of light, then he went beyond this to the study of astronomy Relying on the book Almagest of Ptolemy and others and the writings of Western scholars.
And among his writings in the first stage of philosophers and logicians, and among them is directed towards it a special direction from his book The Geometric and Numerical assets, which he described himself saying: A book in which I collected the Geometric and Numerical assets from the book of Euclid and others, in which the fundamentals were diversified and proved by sensitive and logical proofs.
Alhazen 's writings indicate his intellectual independence and lack of commitment to what preceded him.
His writings during that period take on a local nature, such as his article on the extraction of the azimuth of the qiblah, and his article, which is an applied scientific survey of engineering, such as extracting between two countries in distance from the point of view of engineering matters.
Among his books on engineering arts, his book on the science of surveying, in which he dealt with many issues, including an issue now known as the area of the sphere, and the determination of the area of the sphere, and they used to express it by squaring the sphere.
Thinking about building a dam in southern Egypt
Al-Hakim bi-Amr Allah the Fatimid was informed of the words of al-Hasan ibn al-Haytham:
If I were in Egypt, I would do something in the Nile that would bring benefit in every state, whether it be an increase or a decrease, it has been informed me that it descends from the place of the world in Egypt.
Al-Hakim wanted to benefit from what Ibn al-Haytham had said regarding the Nile, so he provided him money and gifts, and made it pleasing to him to come to Egypt.
And Al-Hasan Ibn Al-Haytham responds to Al-Hakim's invitation. He travels to Cairo and before he reaches it, he finds Al-Hakim, by God's command, who has gone out with a group of his scholars to receive him in a village near one of its gates.
The ruler was eager to complete that project, so the conditions of the flood at that time changed, causing many tragedies and difficulties that afflicted the country, such as high prices, famines, and epidemics.
Ibn al-Haytham began his journey at the head of a delegation of craftsmen, workers and builders, and the mission was equipped with all the tools, materials and equipment it needed.
And the journey took its way south to the shore of the Nile, and when he reached the waterfall south of Aswan in Upper Egypt, he was aware of his condition, and he did not find the high place from which the Nile descended at its borders, and on which he relied to determine his idea.
He began to think and increase his thinking and reconsider his calculations, and finally decided that he could not implement the project.
Ibn al-Haytham realized that he had made a mistake in his assessment and regretted a lot for his haste and for relying on the narrators instead of relying on realistic observations and personal experiences.
His correction of the theory of vision and his achievements in the science of light
Ibn al-Haytham found the Greek theory in the way things are seen, that seeing things takes place by the exit of a ray from the eye to the body that it sees, and thus seeing things takes place.
Ibn al-Haytham's theory accounts for a fact that the Greek's couldn't easily explain: why it gets dark sometimes.
From this view, Ibn al-Haytham established his theory of vision and the properties of light when it is reflected, refracted or transmitted in transparent bodies.
as Ibn al-Haytham, explained how human vision works and that paved the way for glasses for corrective purposes.
His theory was the basis on which modern light science was based.
The facts of the science of light before Ibn al-Haytham had no link that binds them, nor a system that unites them, even the first and simple foundation of light being an existence in itself, and that it is the influencing that creates vision and sensation with it.
This idea, which is now considered one of the axioms and basics of the science of light, was not recognized for its validity before Ibn Al-Haytham
Ibn al-Haytham was the pioneer of the science of light in the early 11th century, just as Newton was the pioneer of mechanics in the 17th century.
Al-Hassan bin Al-Haytham did other researches in the science of nature, such as his treatise on the phenomena of twilight, the colors of the spectrum, the aura, the shadow, the eclipse, and the eclipse, and he created a mirror that was much superior to the mirrors of the Greeks.
He has a lot of researches in the field of mathematics, and he used his unique mathematical ability in his experiments and tests, and he demonstrated many of the laws of nature.
He also gave the first clear description and correct analysis of the camera obscura and pinhole camera.
He also wrote other books on astronomy, medicine, anatomy, especially the eye, and other things that had a far-reaching impact on the books and research of Europeans.
Ibin Al-Haytham solved problems involving congruences using what is now called Wilson's theorem.
Ibin Al-Haytham was also described as the "First World" for his innovation of the scientific method, and his pioneering work in the field of visual cognition is an introduction to natural psychology and experimental psychology.
Opinions of Western scholars in benefiting froM him
And the famous French scientist Viardo admitted that natural science had grown to take its information in light, especially what was related to it, including the refraction of light in the atmosphere, from the books of Ibn al-Haytham says: {The greatness of Islamic innovation is evident to us in optics of Ibn al-Haytham}
It is well established that Ibn Al-Haytham’s book the optics, which contains 7 volumes, is considered one of the largest books in fulfillment of light research and the highest in value. In presenting scientific material, it is based on the latest methods that are superior to some of them in light research, the anatomy of the eye, the anatomy of the eye, and how images are formed on the retina.
