Timeline of astronomy Rectification of Planetary Theory", eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicus later also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. His rectification is later used in the Copernican model. Nicolaus Copernicus publishes "De revolutionibus orbium coelestium" containing his theory that Earth travels around the Sun. However, he complicates his theory by retaining Plato's perfect circular orbits of the planets. A brilliant
Against the Current: Essays in the History of Ideas Against the Current: Essays in the History of Ideas Against the Current: Essays in the History of Ideas (1979) is a collection of essays by 20th century philosopher and historian Isaiah Berlin. The collection was edited by Henry Hardy, and featured an introduction by Roger Hausheer. The book collects previously published essays in which Berlin discusses the thoughts of 20th century ideologic dissenters who were opposed to the prevailing wisdom of their time. A wide range of individuals are discussed including Machiavelli, Giambattista Vico, Montesquieu, Alexander Herzen, Georges Sorel, Verdi, and Moses Hess The collection represents Berlin's long-held interest in