His investigations into optics commenced in 1666 at the end of an annus mirabilis when, at home in Woolsthorpe, Lincolnshire due to the bubonic plague which was raging in Cambridge, he investigated gravity, calculus and the laws of motion. He determined to ‘try therewith the celebrated Phaenomena of Colour’. It had been thought previously that colour was created by the mixing of light and darkness. Newton noted, however, that the blended print on the white page of a book appears grey, not coloured, when viewed from a distance. His experiments in bending light through prisms led, eventually, to the revolutionary discovery of the existence in white light of a mixture of distinct coloured rays, distinguishable when refracted in a prism. In his first experiment he projected the light via a round hole in his shutters.