Ibn al-Haytham

Hello! My name is Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham, but many people in the West later came to know me as Alhazen. I was born in a bustling city called Basra, in what is now Iraq, around the year 965. Growing up, I was filled with endless questions about everything I saw. I would gaze at the night sky and wonder about the stars, or watch the river and think about its immense power. I wasn't satisfied with simply accepting what others told me was true; I had a deep desire to discover the answers for myself. This curiosity led me to read every book I could get my hands on, studying subjects like mathematics, medicine, and the sciences. My passion for learning eventually led me to a position working for the government, but my mind was never still. It was always buzzing with bigger ideas and more profound questions about the nature of the world around me.

My reputation as a skilled problem-solver grew, and my name became well-known. Around the year 1010, I received an important invitation to come to Cairo, Egypt. It was from the powerful ruler, Caliph al-Hakim. He had a very serious problem that needed a clever solution. The mighty Nile River flooded every year, but its timing was unpredictable, causing great difficulty and damage for the farmers who depended on the land. The Caliph asked me to find a way to control the river's floods. I accepted the challenge and traveled all along the river, carefully studying its path and its incredible force. After a thorough investigation, I came to a difficult conclusion. With the tools and technology we had in those days, building a dam large and strong enough to control the Nile was simply impossible. I had to report my failure to the Caliph. To protect myself from his anger, I pretended to be unwell. This led to me being placed under house arrest, where I remained for about ten years until the Caliph’s death in 1021.

You might think being confined to my house for a decade would be a terrible punishment, but for me, it turned into the most productive and important time of my entire life. I finally had what every thinker dreams of: endless, uninterrupted quiet time to study, ponder, and conduct experiments. My thoughts focused on one of my biggest questions: how do we see? For centuries, brilliant scholars had believed that we see because our eyes send out invisible rays, like tiny flashlights, that hit objects. But I thought that didn't make any sense. If that were true, why can't we see in a completely dark room? To find the answer, I decided to test it with an experiment. I sealed a room to make it completely dark, then made a single tiny hole in one wall. I watched as light from the sunny world outside streamed through that tiny hole in a perfectly straight line. It projected an image of the outside world onto the opposite wall, but the image was upside-down. This device was a 'camera obscura,' which means 'dark room' in Latin. My experiment proved my idea was right! We see because light enters our eyes, not because our eyes send out rays.

I was so thrilled by my discoveries about light and vision that I knew I had to write everything down. I carefully recorded every single experiment, step by step, and wrote down every conclusion I reached based on my observations. Around the year 1027, I completed my most important work, a huge, seven-volume collection called the Book of Optics. In Arabic, its name is Kitāb al-Manāẓir. In this book, I explained everything I had learned: how light travels in straight lines, how it reflects off mirrors, how it bends when it passes through water, and how our eyes work just like the camera obscura. Most importantly, I described a new way of learning about the world. First, you must ask a question. Then, you make an educated guess, which we call a hypothesis. Finally, you must test that guess with experiments, repeating them to make sure your results are correct. Today, you know this process as the scientific method. It was a revolutionary way of thinking, based on physical proof instead of just accepting old beliefs.

After I was finally freed from house arrest in 1021, I spent the rest of my years living in Cairo, where I earned a living by teaching and writing about the many subjects I loved. I lived to be about 75 years old. My ideas did not stay locked away in Egypt. Hundreds of years after I wrote my Book of Optics, scholars translated it into Latin, and it was read by scientists and thinkers all across Europe. My work on light and vision even influenced famous minds like Leonardo da Vinci and Isaac Newton. Because of my focus on testing ideas with experiments, I am often called the 'father of modern optics' and one of the world's first true scientists. I am so happy that my curiosity helped to light up the world with a new way of seeing and understanding our universe.