Tentative nature of science

Tentative nature of science citing the LIGHT as an example.

Nature of Light.

 The earliest thoughts on its nature seem to have come from Indian seers and philosophers. In the sixth–fifth century  they described light rays as streams of high velocity atoms of tejas

(fire) and said that depending on the arrangement of the atoms, light can exhibit different characteristics.

The above ideas were only qualitative. The first quantitative theory was proposed by Euclid, the great mathematician, in third–second century BCE. In his book Optica Euclid noted that light rays travel in straight lines. Using geometry, he explained why distant objects appear smaller and nearby  objects appear bigger. He also described laws of reflection. Interestingly, he believed that vision is caused by the light rays emanating from the eye and falling on the objects seen. However, Aryabhatta pointed out in the fifth century CE that an object is seen when it is illuminated by light from an external source.

Reflection and refraction of light are the oldest phenomena known to us. Much of the discussion on the nature of light during renaissance centred around these phenomena. In the seventeenth century, Huygens proposed that light consists of waves. Later Newton proposed that light is composed of particles or corpuscles. Both of them were able to explain successfully the phenomena of reflection and refraction. However, when in the early years of the nineteenth century, interference of light was observed by Thomas Young, wave theory of light received a big boost because interference (and

later diffraction and polarisation of light) could be explained only if light propagated as waves. Wave theory was firmly established when Maxwell in the latter half of the 19th century showed theoretically that light must be electromagnetic wave. Almost a hundred years after Young’s experiment, Einstein revived the idea of Newton’s corpuscles to explain the photoelectric effect. He gave the name photons to the corpuscles of light. Science was at the threshold of a new idea. It was realised that light has dual nature. It behaves sometimes as waves and sometimes as particles. In phenomena like interference, diffraction, and polarisation, light behaves as waves, while in phenomena like photoelectric effect, pair production and Compton scattering light behaves as if consisting of particles. There the matter stands today. A future theory may provide a more satisfactory answer.