as an equatorium to calculate the lunar, solar and planetary longitudes, as well as predict eclipses. Jean Buridan (1300–58) was a French philosopher and priest. Although he was one of the most famous and influent philosophers of the late Middle Ages, his work today is not renowned by people other than philosophers and historians. One of his most significant contributions to science was the development of the theory of impetus, that explained the movement of projectiles and objects in free-fall. This theory gave way to the dynamics of Galileo Galilei and for Isaac Newton's famous principle of Inertia. Guy de Chauliac (1300-1368) was a French physician and surgeon who wrote the Chirurgia magna, a widely read publication throughout medieval Europe that became one of the standard textbooks for medical knowledge for the next three centuries. During the Black Death he clearly distinguished Bubonic Plague and Pneumonic Plague as separate diseases, that they were contagious from person to person, and offered advice such as quarantine to avoid their spread in the population. He also served as the personal physician for three successive popes of the Avignon Papacy. John Arderne (1307-1392) was an English physician and surgeon who invented his own anesthetic that combined hemlock, henbane, and opium. In his writings, he also described how to properly excise and remove the abscess caused by anal fistula. Nicole Oresme (c. 1323–82) was one of the most original thinkers of the 14th century. A theologian and bishop of Lisieux, he wrote influential treatises in both Latin and French on mathematics, physics, astronomy, and economics. In addition to these contributions, Oresme strongly opposed astrology and speculated about the possibility of a plurality of worlds. Giovanni Dondi dell'Orologio (c. 1330-1388) was a clockmaker from Padua, Italy who designed the astarium, an astronomical clock and planetarium that utilized the escapement mechanism that had been recently invented in Europe. He also attempted to describe the mechanics of the solar system with mathematical precision. Nicholas of Cusa (1401–1464) was a German philosopher, theologian, and astronomer who believed the Earth was not the center of the known universe, that celestial bodies were not perfect spheres, that their orbits were not entirely circular, and advanced the idea of relative velocity to explain the difference between theory and appearance of celestial objects. Regiomontanus (1436-1476), a German mathematician and astronomer whose works perhaps influenced the heliocentric model of the solar system established by