CHAPTER 3

The Great Plague of 1665 was a tremendous human tragedy, yet a fortuitous boon to science. The bubonic plague had ravaged Great Britain in several episodes from the time of the Black Death in 1348 until 1665, when the Great Plague became one of the worst epidemics to afflict London during those centuries. There was no known cure at that time for bubonic plague, and to avoid the illness, people migrated to other habitats to avoid contracting the dreaded disease. In 1665 Cambridge University closed to disperse students and faculty to remote regions of Great Britain. One of these Cambridge University students was Isaac Newton, who returned to his widowed mother’s home in Lincolnshire to sit out the Great Plague. It was during these eighteen months that this young college student had time to reflect and to formulate laws of force and motion that would revolutionize scientific knowledge in the seventeenth century, and lay the foundations for modern science.

Newton’s scientific "breakthrough" occurred when he made a connection between two phenomena that no one had ever previously connected. His creative insights led him to find a connection for the first time between the motion of the Moon around the Earth and the falling motion of an apple from a tree. He hypothesized that some mysterious property of the Earth caused the motions of both the apple falling to the ground and the moon orbiting the Earth. His brilliance was that he recognized that the motions of both the apple and the Moon were falling motions directed toward the Earth. This mysterious property was attributed to gravity, an ever-acting force of attraction innate to all objects. The greater the mass of an object, the greater its ability to attract other objects. Newton’s revolutionary laws were published in The Principia some 20 years after his brief leave from Cambridge University due to the bubonic plague. Newton’s Laws of Motion and his Law of Universal Gravitation have dominated the physical sciences since 1686, for more than 300 years.

Newton’s ingenuity was his hypothesis that an attractive force called gravity caused both the apple to fall to the ground and the Moon to orbit the Earth. What is a force? What kind of motion does a force cause? How can a force of attraction cause orbital motion?

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