Descartes and the hyperbolic quest

Historical Significance: Rene Descartes (1596-1650) was a French philosopher, mathematician, and scientist. He s often called the father of modern western philosophy: much of subsequent Western philosophy is a response to his writings,which are studied closely to this day. He was the founder of algebra, Cartesian geometry and calculus. Descartes also made contributions to optics. He showed by using geometric construction and the law of refraction (also known as Descartes' law or more commonly Snell's law) that the angular radius of a rainbow is 42 degrees (i.e., the angle subtended at the eye by the edge of the rainbow and the ray passing from the sun through the rainbow's centre is 42?). He also independently discovered the law of reflection, and his essay on optics was the first published mention of this law. This book explores his endeavours to design and make a machine to automatically grind aspheric lenses to correct for spherical aberration so as to improve the resolution of telescopes. The books contains much information on the ancient craft of spectacle lens making and the development of machines to make better lenses than was possible by hand grinding. Descartes essay Dioptrique 1637 is known as his greatest contribution to optics, as it is the first publication of the Law of Refraction. See Descartes theory of light and refraction by M A Smith (1987) Cat no 2281 in the Hewett Collection