Reflections on Eye Rays
As a young child I used to puzzle about how the world worked. It seemed to me that objects fell to earth very quickly – I remember wondering whether this was instantaneous or not – though my vocabulary would have been more basic! I also thought about how I could see things and hence how eyes worked – I presumed that this was through some kind of rays that came from my eyes. Little did I know that I was in good company in this thought – Plato had the same theory in the 4th Century BCE.
Of course we were both mistaken. The alternative theory, that light comes from the objects (reflected or emitted) to our eyes was advocated by Aristotle only about 40 years after Plato. The two models were debated for many centuries, until Ibn al-Haytham, in the 11th Century CE firmly established the merits of Aristotle’s view in his seven volume ‘Book of Optics’.
What marks al-Haytham out as an outstanding scientist and philosopher was not just this theory; it was his method. Born in Basra, in modern day Iraq, Ibn al-Haytham had access to translations of works by Greek, Syriac (an ancient dialect of Aramaic) and Persian thinkers; the library in Basra had over 15,000 books at the time. However, rather than purely distilling the thoughts of these earlier writers, al-Haytham set out to test the theories by experimentation and observation. This was a huge step forward from the prevailing approach of studying received wisdom. Indeed, he wrote:
“If learning the truth is the scientist’s goal … then he must make himself the enemy of all that he reads”
Many of al-Haytham’s books found their way to Toledo where they were translated into Latin, then the common language for academics in Europe. Centuries later, scientists including Kepler and Da Vinci were influenced by his methods.
A few years ago, searching for an interesting activity for the afternoon for my wife and me and my visiting parents, we stumbled across the Sultans of Science exhibition which was then being shown at the Petrosains (‘Petroscience’) centre underneath the Petronas Towers in Kuala Lumpur.
This excellent exhibition has toured the world and showcases the mathematical, scientific and technological achievements of Islamic people, primarily from the period 800 – 1500CE. The interactive exhibits really are fascinating, including wonders such as Al-Zahrawi’s tools for eye and bone surgery (surely both were eye-watering in the anesthesia-free 10th Century CE), and Al-Jazari’s 12th Century CE Water Clock. And here was Al-Haytham again – some of the most popular exhibits were his pinhole camera and his prisms with which he showed rainbow of colours making up white light.
Moving to the Eastern Hemisphere, it remarkable how many different cultures produced individuals who made fundamental scientific discoveries.
Around the end of the 1st Century CE in China, Zhang Heng was studying astronomy and other sciences. As well as inventing a sophisticated seismometer to detect earthquakes, he studied the light of the moon. He realised that the moon does not emit its own light like the sun; instead it reflects the light of the sun. Throughout his life, he produced 32 scientific works, including a complete star map of the sky.
In India, about 400 years later Aryabhata, was a 5th Century mathematician, astronomer, astrologer and physicist. At the age of only 23, he wrote Aryabhatiya, which was a summary of mathematics of his time. Like Zhang Heng, he also studied the moon, planets and the sun, and independently came to the conclusion that the moon reflected the light of the sun.
Remarkably, Aryabhata developed a heliocentric model of the solar system, a thousand years before Galileo. At the time the view was that our planet earth is ‘Achala’ (immovable); Aryabhata’s theory was that the ‘earth is round and rotates on its own axis’. He explained that the appearance of the sun moving from east to west is a false perception caused by relative motion ; ‘When a person travels in a boat, the trees on the shore appear to move in the opposite direction’. He also gave a scientific explanation for solar and lunar eclipses clarifying that the “eclipses were not because of Rahhu and/or Ketu or some other rakshasa (demon)”. The way that Aryabhata reasoned against the prevailing religious views has a close parallel with Galileo’s own conflicts with the church over a thousand years later, over the same issue. However, given that Aryabhata lived a scientifically productive life past the age of 70, it seems that the environment in Patna (now capital of Bihar state in India) was more liberal than that in early 17th Century Europe!
Heedless of creed
Whilst researching this piece, I found that the religion of the scientist was almost never mentioned, except when the scientist was a Muslim – in which case their name was usually prefixed by ‘the Muslim scientist’ or the ‘Islamic mathematician’. This was the case for articles written both by Muslims and by other authors. Perhaps this reflects a kind of (well meant) religious positive discrimination.
Exhibitions like ‘Sultans of Science’ are certainly needed to redress the imbalance of over-concentration on ‘western’ scientists – and it certainly was a well-designed and interesting exhibition. However I think we do a disservice by thinking of the development of science in cultural or religious silos. This culturally categorized view may have contributed to a widespread lack of awareness of how science has evolved, often independently, in almost all of the world’s civilisations.
Far better to take a balanced, culturally-blind, planet-wide view of the incredible achievements of all the world’s brilliant scientists, regardless of creed.
Here at the Global Scientist we will endeavor to do just that.
Scientists of Ancient India : http://www.nios.ac.in/media/documents/SecICHCour/English/CH.15.pdf