Sir Isaac Newton (1642-1727) is said to have made his greatest contributions to original thought in science in 1665-6 while at his parents' home in Lincolnshire escaping the Great Plague (which had closed the universities), a period of which he wrote: 'I was in the prime of my age for invention'. It was at this fruitful time that he formulated calculus, hit upon the idea of gravity and did experiments which showed that white light was made up different coloured rays. Biographies and Autobiographies.