Sir Isaac Newton (December 25, 1642 - March 20, 1726/27) was an English physicist and mathematician who is widely recognised as one of the most influential scientists of all time and a key figure in the scientific revolution. His book Philosophiae Naturalis Principia Mathematica ( Mathematical Principles of Natural Philosophy ), first published in 1687, laid the foundations for classical mechanics. . Newton's Principia formulated the laws of motion and universal gravitation, which dominated scientists' view of the physical universe for the next three centuries. Newton built the first practical reflecting telescope and developed a theory of colour based on the observation that a prism decomposes white light into the many colours of the visible spectrum.
Sir Robert Stawell Ball FRS (July 1, 1840 - November 25, 1913) was an Irish astronomer who founded the screw theory. He was the son of naturalist Robert Ball and Amelia Gresley Hellicar. He was born in Dublin. Ball worked for Lord Rosse from 1865 to 1867. In 1867 he became Professor of Applied Mathematics at the Royal College of Science in Dublin. There he lectured on mechanics and published an elementary account of the science. In 1874 Ball was appointed Royal Astronomer of Ireland and Andrews Professor of Astronomy in the University of Dublin at Dunsink Observatory. In 1908 he published A Treatise on Spherical Astronomy, which is a textbook on astronomy starting from spherical trigonometry and the celestial sphere, considering atmospheric refraction and aberration of light, and introducing basic use of a generalised instrument.