**Al-Hasan Ibn al-Haytham (c. 965–c. 1040 CE)**
**Biography:**
Al-Hasan Ibn al-Haytham, known in the Western world as Alhazen, was an influential Arab mathematician, astronomer, and physicist. Born in Basra, in present-day Iraq, Ibn al-Haytham later moved to Cairo, Egypt, where he lived most of his life. He made significant contributions to the principles of optics and visual perception, and his works laid the groundwork for modern scientific methods. He was a pioneer in the scientific method, emphasizing experimentation and empirical evidence.
Ibn al-Haytham’s most renowned work is the "Book of Optics" (Kitab al-Manazir), which profoundly influenced both Islamic and European science. His contributions extended beyond optics, impacting mathematics, astronomy, and engineering.
**Major Contributions and Discoveries:**
1. **Optics:**
- **Book of Optics (Kitab al-Manazir):** In this comprehensive seven-volume treatise, Ibn al-Haytham systematically studied light and vision. He challenged the Greek theories of vision proposed by Euclid and Ptolemy, which suggested that vision resulted from rays emitted by the eyes. Instead, Ibn al-Haytham correctly posited that vision occurs when light rays enter the eyes from external sources.
- **Camera Obscura:** Ibn al-Haytham’s work with the camera obscura, a darkened room with a small hole or lens through which light enters to form an image on the opposite wall, was instrumental in understanding the behavior of light and the principles of image formation. This concept is foundational in the development of photography.
2. **Scientific Method:**
- **Empirical Evidence and Experimentation:** Ibn al-Haytham is considered one of the first scientists to use the scientific method rigorously. He emphasized the importance of experimentation and observation in developing and verifying scientific theories. His approach laid the groundwork for modern scientific inquiry.
3. **Mathematics and Geometry:**
- **Geometrical Optics:** Ibn al-Haytham applied mathematical principles to his study of optics, using geometry to explain the behavior of light. His work included detailed studies of reflection, refraction, and the properties of lenses and mirrors.
- **Algebra and Number Theory:** While primarily known for his contributions to optics, Ibn al-Haytham also worked on problems in algebra and number theory, contributing to the mathematical knowledge of his time.
4. **Astronomy:**
- **Celestial Models:** Ibn al-Haytham developed models to explain the apparent motion of celestial bodies. He critiqued and built upon the work of Ptolemy, contributing to the understanding of planetary motion and astronomy.
5. **Engineering:**
- **Hydraulics and Civil Engineering:** Ibn al-Haytham wrote on various topics related to engineering, including the behavior of water and the principles of hydrostatics. His insights were applied in the design and construction of various hydraulic structures.
Ibn al-Haytham's groundbreaking work in optics and his methodical approach to scientific investigation have left an indelible mark on the history of science. His pioneering use of experimentation to validate theories set a standard for future scientific endeavors and earned him a prominent place among the great scientists of the medieval Islamic world and beyond.
