The Scientific Revolution

Nicolaus Copernicus was not an accomplished observational astronomer, but rather a mathematician who felt that Ptolemy's geocentric system (earth-centered universe) was too complicated and failed to accord with the observed motions of the heavenly bodies. In his work, "On the Revolutions of the Heavenly Spheres", Copernicus hoped that his heliocentric conception (sun-centered universe) would offer a simpler more accurate explanation. He argued that the universe consisted of eight spheres with the sun motionless at the center and the sphere of the fixed stars at res in the eighth place. The planets revolved around the sun in the order of Mercury. Venus, the earth, Mars, Jupiter, Saturn, and the moon revolving around the earth. Moreover, according to Copernicus, the movement of the sun and stars was really explained by the daily rotation of the earth on its axis and the journey of the earth around the sun each year. Copernicus, however, remained conservative and did not reject Aristotle's principle of the existence of heavenly spheres moving in circular orbits.

Andreas Vesalius was an anatomist and physician. He emphasized practical research as the principle avenue for understanding human anatomy. In his work, "On the Fabric of the Human Body", Vesalius deviated from traditional practice by personally dissecting a body to illustrate what he was discussing in his lectures. Vesalius's anatomical treatise presented a careful examination of the individual organs and general structure of the human body. Vesalius's hands-on approach enabled him to correct some of Galen's (a medieval anatomist) errors.

Johannes Kepler was a mathematician and astronomer and succeeded Tycho Brahe after his death. Using Brahe's detailed astronomical data, Kepler arrived at his three laws of planetary motion that confirmed Copernicus's heliocentric theory. Kepler published his first two laws of planetary motion in 1609. In his first law, he rejected Copernicus by showing that the orbits of the planets around the sun were elliptical not circular. In his second law, he demonstrated that the speed of a plant is greater when it is closer to the sun and decreases when it is farther away from the sun. This destroyed the Aristotelian tenet that planetary motion was unchanging and steady. Published in 1619, Kepler's third law established that planets with larger orbits revolve more slowly than planets with smaller orbits.

Galileo was the first European to make systematic observations of the heavens using a telescope. Through the use of his telescope, Galileo discovered mountains and craters on the moon, four moons revolving around Jupiter, the phases of Venus, and sunspots.Galileo's observations demolished the traditional cosmology that the universe seems to be composed of material substance similar to that of earth rather than perfect and unchanging substance. Galileo's revelations were published in his work, "The Starry Messenger" in 1610.

William Harvey's work, "On the Motion of the Heart and Blood", Harvey demonstrated that the heart and not the liver was the beginning point of the circulation of blood in the body, that the same blood flows in both veins and arteries, and most important, that the blood makes a complete curcuit as it passes through the body. Harvey's theory of the circulation of the blood laid the foundation for modern physiology.

In his previous work "The Starry Messenger", Galileo had revealed himself as a firm proponent of Copernicus's heliocentric system. The Roman Inquisition of the Catholic Church condemned Copernican-ism and ordered Galileo to reject the Copernican thesis. Galileo was told, however, that he could continue to discuss Copernican-ism as long as he maintained that it was not a fact but a mathematical supposition. As a response to his condemnation, Galileo published the "Dialogue on the Two Chief World Systems: Ptolemaic and Copernican". Galileo's work was written in Italian rather than Latin, making it more widely available to the public. The work to the form of a dialogue among Simplicio, a congenial but somewhat stupid supporter of Aristotle and Ptolemy; Sagredo, an open-minded laymen; and Salvati, a proponent of Copernicus's ideas. There is no question who wins the argument, and the "Dialogue" was quickly perceived as a defense of the Copernican system.

Margaret Cavendish was one of the most prominent female scientists of the seventeenth century. Cavendish was not a popularizer of science for women but a participant in the crucial scientific debates of her time. She wrote a number of works on scientific matters, including "Observations upon Experimental Philosophy" and "Grounds of Natural Philosophy". In her works, she did not hesitate to attack ehat she considered defects of the rationalist and empiricist approaches of scientific knowledge and was especially crucial of the growing belief that through science, humans would be masters of nature.

In his first book, "Principia", Newton defined the basic concepts of mechanics by elaborating the three laws of motion: every object continues in a state of rest or uniform motion in a straight line unless deflected by a force, the rate of change of motion of an object is proportional to the force acting on it, and to every action there is always an equal and opposite reaction. In book 3, Newton applied his theories of mechanics to problems of astronomy by demonstrating that these three laws of motion govern the planetary bodies as well as terrestrial objects. Integrated into his whole argument was the universal law of gravitation which explained why the planetary bodies did not go off in straight lines but continued in elliptical orbits. Newton's universal law of gravitation had enormous implications. Newton had demonstrated that one universal law, mathematical proved, could explain all motion in the universe. The secrets of the natural world could be known by human investigations. At the same time, the Newtonian synthesis created the concept of Newton's world machine in which it is believed that the universe was one huge, regulated, and uniform machine that operated according to natural laws in absolute time, space, and motion.

Francis Bacon, a lawyer and lord chancellor, rejected Copernicus and Kepler, and misunderstood Galileo.Bacon did not doubt humans' ability to know the natural world, but he believed that they had proceeded inorrectly. In his unfinished work, "The Great Instauration", Bacon's new foundation--a correct scientific method--was to be built on inductive principles from which logical conclusions could be deduced, he urged scientists to proceed from the particular to the general.

Rene Descartes proposed a different approach to scientific methodology than Francis Bacon. In his work, "Discourse on the Method", Descartes emphasized deduction and mathematical logic. He believed that one could start with self-evident truths and deduce more complex conclusions. His emphasis on deduction and mathematical order complemented Bacon's stress on experiment and induction.