A Living Portrait of India
A Living Portrait of India |
India Heritage:Science:Physics |
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Light was an interesting phenomenon - and many theories were offered in explanation. Gautama, the author of Nyaya-sutra, states that rays of light from the eye came into contact with the object, similar to the light emanating from a lamp that settles on objects. This belief was based on a view that rays of light emanated from the eyes of felines. The Nyaya-Vaisesika system believed that in the manner of the light from a lamp circling out to illuminate the objects around, the tejas (light) from an eye spread in increasing circles to comprehend the objects around. The Mimamsaka school believed that vision too fans out in increasing circles, ending at the object. This was also regarded as the range of vision. They considered a flame to comprise of light particles (photons) in constant motion and forming a sort of radiation diffusing away from the wick. Cakrapani however felt that light rays move out in all directions much as sound waves do, the difference being that light travels faster. Modern physics accepts a combination of these two views, but with variations. Susruta (first century AD) accepted that the light arriving at the retina serves to both illuminate the eye and the world around, and thus becomes the faculty of vision. Reflection, as discussed by Varahamihira, was caused by light particles arriving on an object and then back-scattering (kiranavighattana, murcchana). Vatsyayana refers to this phenomenon as rasmiparavartana. This has been adapted to explain the casting of shadows, opacity etc. Refraction was understood to be caused by the ability of light to penetrate inter-atomic spaces of translucent or transparent materials. Uddyotakara drew a comparison with fluids moving through porous objects - tatra parispandah tiryaggamanam parisravah pata iti. Colour recognition was understood by the Nyaya-Vaisesikas as being caused by the nature of human eyes - eyes were made up chiefly by unseen tejas particles. Buddhists believed that the eye-balls were the physiological organs of sight and were able to see due to light beams emanating from an external source. They did not agree that the eyes were the source of light rays. Light was thus understood in a variety of ways. Colour and touch are perceptions - for instance, the sun's rays which can be seen by the eye and felt by the skin. Plus, touch cannot be manifested, while colour can - moonlight or light from a lamp can be seen but not felt. Conversely, touch is manifested while colour is not - for example, water being heated by sunlight. Also, both are unmanifest if the light rays are sourced from the eye.
SOURCES : The Cultural Heritage of India History of Science & Technology in India Concise Encyclopedia of Science and Technology Masters of the Millennium - 100 Indians who
shaped the century |
