Corpuscular Nature

R. Descartes first proposed, in 1636, that light consists of particles, and Isaac Newton (1642-1726) developed this into a full corpuscular theory: light is made of tiny, hard, elastic, and (crucially) MASSLESS particles called corpuscles, emitted by a source and travelling in straight lines through empty space in the absence of any external force. On striking a reflecting surface, Newton's corpuscles were imagined to undergo perfectly elastic collisions, automatically reproducing the law of reflection. Refraction was explained by proposing that the particles of a denser medium exert an additional ATTRACTIVE force on the corpuscles, pulling them (and accelerating them) towards the normal as they cross into that medium; different colours of light were attributed to corpuscles of different sizes. …