How might Isaac Newton's Principia be seen as the final link in the chain of astronomical development? How did Newton build upon the achievements of his predecessors?
Newton is quoted as saying, "if I have seen farther than others, it is because I was standing on the shoulders of giants," by way of thanking his predecessors for the contributions to science which made his Principia possible. Indeed, Newton's work represents the finale in a long chain of theory and discovery that evolved throughout the Scientific Revolution. The beginnings of progress had come in the sixteenth century. Nicolas Copernicus suggested that perhaps the ancient concept of the Earth's position in the universe was flawed. Giordano Bruno went one step further to claim that the universe itself was far different than the ancients and the Church perceived, and that it stretched out infinitely. Next, Johannes Kepler reduced the motions of the planets to intelligible mathematical rules. Galileo developed the system of earthly mechanics that he hinted might be applied to the heavens. Newton's work was the culmination of this chain of science, inspired by the ideas of these men and the methods and tools developed by them and others of his predecessors. The Principia linked the last two remaining pieces of the puzzle--Galileo's physics and Kepler's astronomy--and emerged with the "grand design" so many before him had sought. The design seemed not to have been established by any planning or simple geography, but rather by the interaction of the forces of nature, principally gravitation, on an enormous scale.
The progress of logic and knowledge of the physical world during the Scientific Revolution was constantly at odds with the oppositional force of religion and mysticism. How were average Europeans, and the scientists themselves, affected by the dilemma created by these forces?
In the lives of the impoverished masses, stability was of the utmost importance. Maintenance of one's job, one's family life, and one's quality of living were the utmost goals of the commoner, and these goals informed the common reaction to the suggestion that the principles upon which everyday life was thought to be based were no longer valid. In the face of the instability and change threatened by advancement of science, common Europeans often turned to the Church for guidance. The Church had been the most stable feature of the previous millennium, defining the phenomena of the often hard to understand natural world, and in essence telling the common churchgoer what to believe. The combination of the influence of the Church and the traditions which had been passed down for hundreds of years produced an attitude of mysticism that seemed to answer all of the difficult questions of everyday life. Events in the natural world occurred not because of the interaction of mechanical forces but because of the influence of the positioning of the planets. This was a convenient and well-ingrained belief system.
In fact, this belief system was so ingrained that even scientists themselves often fell prey to it. The most illustrative case is that of Johannes Kepler, who was convinced that the universe had to be arranged according to some grand scheme, and that the teachings of astrology were largely correct. In keeping with these ancient beliefs, Kepler searched for a simple geometric model of the universe, largely ignoring the evidence to the contrary. Kepler's was a common dilemma faced by the thinkers of the sixteenth and seventeenth centuries. The ancient traditions exercised a strong pull on many scientists, who often allowed the supposed authorities of the past, or even simply the spirit of the past, to cloud their judgment and limit the progress made by their work.
How did the scientific view regarding authority change during the Scientific Revolution?
During the Middle Ages, science was undertaken more often in the library than in the laboratory. Even Nicolas Copernicus was content to synthesize the ideas and records of others rather than to directly collect and test his own data. Similarly, other fields of science were dominated by study of the classics. However, during the later sixteenth century, attitudes toward additional authority were changing. Men were no longer content to rely on ancient authority for the truth. Instead, they sought to do their own experimentation and observation. Nowhere was this more true than in the Royal Society. The society instituted the method of scientific inquiry most unfavorable to the persistence of dogmatism: laboratory experimentation. To quote past authority was useless, and frowned upon. The crest of the Royal Society bears the motto Nullius in verba ('On the word of no man'). This motto expresses the demand for tangible evidence, for repeatable experimentation, which created the spirit of science, as we know it today.