What is light composed of? Does the force that causes apples to fall to the ground extend beyond the Earth? These were problems that Newton raised during quarantine due to the Great Plague of London.
The great plague of London was the last outbreak of the Black Plague that a few centuries earlier had struck Europe. Between the years 1665 and 1666, the infection caused by the bacteria yersinia pestis, known as the black plague because the skin of the sick was covered with blackened blisters, claimed the lives of some 100,000 people in Britain. The quarantine prompted by the disease indirectly resulted in some of the most important advances in the history of physics and mathematics. The story took place in Woolsthorpe, about 100 kilometers from Cambridge where young Isaac Newton had been studying before going into quarantine for a period of almost two years. This was an invaluable time to concentrate on his scientific thinking.
The village of Woolsthorpe, located 150 kilometers from London, was a retreat for Isaac Newton’s family. During the quarantine fostered by the resurgence of the black plague that had claimed the lives of 200 million people in Europe between 1347 and 1353, this Cambridge student began to study the phenomena of light and gravitational force, among other big concerns.
“That time is known as the years of wonders because he focused on three topics of physics: optics, differential and integral calculus, and the laws of motion and gravitation,” says astronomer Luis Felipe Rodríguez, member of the Colegio Nacional (National College).
Rodríguez says it was during the lockdown that Newton realized that the spectrum of white light consisted of the overlapping of all the colors. A few years after the epidemic, Newton made use of a dark room and a ray of sunlight that struck the prism to achieve its decomposition and the definition of the concept of refraction of light.
Likewise, James Gleick, in his book Isaac Newton, tells the story that during quarantine, the physicist and mathematician realized that some equations never changed, such as the one used to draw the circumference of a circle, but that others changed over time. This critical observation was the basis for developing integral and differential calculus.
However, this discovery is also attributed to the German Gottfried Wilhelm von Leibniz, who worked independently. Today, it is recognized that both scientists unified and summarized concepts such as integrals and derivatives and who developed the symbolism and formal rules of calculus.
In case this weren’t enough, during quarantine Newton made progress on his experiments that allowed him to create the laws of inertia, acceleration, and interaction, which he had already been working on for a year before the epidemic. But, one of the best-known anecdotes about him, and to which the law of universal gravitation was owed was about a fruit.
It is common to mention the apple that supposedly fell on Newton’s head as what sparked his reflections on gravity. But, in January 2010, the Royal Society of London published the manuscript that tells the original story of how the physicist was inspired by that fruit to consider the type of force that attracted it to the ground and, simultaneously, to wonder why an object much larger like the Moon was not affected by the same phenomenon.
According to the Royal Society, the story revealed in William Stukeley’s biography The Life of Sir Isaac Newton (1752) was told thanks to the writer being a friend of Newton’s and had heard his reflections on this. The physicist claimed that the story of the apple that hit him in the head was true.
Newton acknowledged in a manuscript the reason for his advances during quarantine. “All this happened in the years of the plague. And, it was in those days that I was at the height of my powers for invention, and I was interested in mathematics and philosophy more than in any later era,” the book says.
The University of Cambridge reopened in 1667. After three months, Newton earned his degree, and when he turned thirty, he became the youngest member of the Royal Society.