Sir Isaac Newton | The Language of the Natural World
“Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion.”
― Isaac Newton
The two men walked out the door and into the garden. The weather was warm, with the sun falling over the horizon, almost blinding them as it set. They talked and strolled to an apple tree and sitting beneath it, sipped their tea as they watched the tall grass move against the wind. One of the men turned to his friend and spoke.
“You know, I was just in the same situation not long ago, when the notion of gravitation came into my mind.
“I’m sure it weighed on you heavily,” said the man with a chuckle.
The other man merely smiled and looked out across the field in deep contemplation.
“It was occasion’d by the fall of an apple,” he said finally. “And I wondered to myself, why should that apple always descend perpendicularly to the ground…?”
Early Life
Isaac Newton was born on January 4, 1643, in Woolsthorpe, Lincolnshire, England. He was the only son of a wealthy farmer, also named Isaac Newton, and a mother named Hannah. His father died months before he was born, leaving his mother to raise him. When he was three years old, she remarried and moved away, leaving him in the care of his maternal grandmother. According to many historians, Newton resented his mother and stepfather for this, referencing it many times later in his life via journal entries and in conversations with close friends.
To deal with the dejection and abandonment of his mother, the young Newton spent his spare time reading and tinkering with mechanical toys, taking them apart and then reassembling them again and again. When he turned 12, he was sent to the King’s School in Grantham, where he would stay until the age of 17. Due to his upbringing, Newton had several learning and behavioral issues early in his academic career. Despite this, he showed promise, with many of his teachers and the schoolmaster recognizing his potential and encouraging him to continue his studies. While at King’s school, he learned Latin and Ancient Greek – two staples for English boarding schools at the time. For Newton, this created the foundation for his deep interest in mathematics as it relates to the natural world. Even early in life, Newton had a deep religious faith and throughout his academic career, there was never a time when he divorced his discoveries in natural philosophy from his views on faith and God. One could not exist without the other, and as he learned more about mathematics, natural philosophy, and complexities that required an intentional creator, he found his faith validated all the more. His time at King’s School encouraged his burgeoning interest in the “why” of things around him and served as the catalyst for discovering the “how” through testing and experimentation.
Adherence to, and redefinition of, Natural Philosophy
Before we continue, I want to clarify that the term and title of “scientist” is almost exclusively a 19th-century invention. Before the creation of the word in 1833, those who studied the natural world and how it worked operated within the realm of what was called natural philosophy. Before Newton, the modern delineation of sciences such as physics, chemistry, and biology had not yet been formed. As a result, the category of natural philosophy comprised many different areas of study, from the research of heavenly bodies to the nature of matter and the human psyche. Natural philosophers saw the natural world as an overt machine that was governed by rules set within space and time. The field was vast, as were the number of practitioners who worked to discover the “why” and “how” of the natural world. Newton, who had shown a penchant for mathematics, naturally entered into this field when he joined Trinity College, Cambridge at the age of 18.
At Cambridge, Newton was fully able to explore his interest in why different elements interact, and how those interactions helped answer the larger question he posed regarding the nature of the universe. At that time, the ideas and theories of Aristotle governed the foundations of natural philosophy. Aristotelian traditions concentrated on the nature of objects and on causation rather than mathematic discipline. Though Newton immersed himself in this philosophy, he joined many of those who came before him by rejecting this approach, believing instead that new mathematical, conceptual, and experimental methods were required to gain a true understanding of space, time, light, and motion.
For Newton, this took the form of his first written piece in 1664, titled “Certain Philosophical Questions”, where he revealed his new understanding of nature as influenced by Rene Descartes. Descartes was a seminal figure in the Enlightenment and Scientific Revolution, joining other prominent leaders in natural philosophy to push against older practices. Descartes's writings made a lasting impact on Newton and served as a “true north” for much of his early arguments against Aristotelian tradition.
As Newton delved more and more into the mathematics behind some of Descartes's philosophy, he began to question the scope of some conclusions. Through further study, he determined that Cartesians – self-described followers of Descartes – did not go deep enough into the mathematics that governed the natural world. As a result, Newton eventually came to reject much of Cartesiasim, instead centering on natural absolutes that would serve as the foundation for his theories. Specifically, “Newton began to formulate a distinction that would remain salient throughout his long intellectual career, contending that a philosopher must distinguish between a conclusion or claim about some feature of nature that is derived from experimental or observational evidence, and a conclusion or claim that is a mere “hypothesis”, a kind of speculation about nature that is not, or not yet anyway, so derived. Newton’s much later proclamation in the second edition of the Principia (1713), “Hypotheses non fingo”, or “I feign no hypotheses”, would infuriate his critics just as much as it would prod his followers into making the pronouncement a central component of a newly emerging Newtonian method.”
Descartes believed that mathematical and mechanical principles were a mere foundation of all natural science, while Newton believed that mathematical models – such as the study of motion – were tools for specifically explaining the behavior of the natural world and that through said mathematics, he could prove it.
The Slope of a Curve & the Preliminary Discovery of Calculus
In 1669, Newton wrote, On the Analysis by Infinite series, where he began exploring the problem of tangents, which involves finding the slope of a curve at a particular point. To solve this problem, he developed a “method of fluxions," which involved calculating the rate of change of a curve over time. Translated in today’s terms, Newton stated that the fundamental problems of the infinitesimal calculus were: (1) given a fluent (or function), to find its fluxion (or derivative); and, (2) given a fluxion or function, to find a corresponding fluent or indefinite integral).
He distributed “On Analysis…” within his inner circle who, over time, shared the work with others. This publication was highly regarded and seen as a seminal work within the field of mathematics as a way of solving problems related to rates of change and the accumulation of infinitesimal quantities. Newton also began working on a method for calculating areas under curves. This work led to the development of integral calculus, which involves finding the accumulation of infinitesimal quantities. In summary, Newton systematically discovered the way to determine quantities as rates of change, and in doing so, created calculus.
Optics and Particles
Around the time that Newton was becoming aware of calculus, he was also pursuing the study of light. Influenced again by Descartes's assertions about the nature and quality of light, Newton began conducting experiments with prisms. From 1667-1672 he investigated the refraction of light, discovering the light spectrum, and as a result, concluded that light existed as a series of particles rather than waves, as stated by Newton:
“These things being so, it can be no longer disputed, whether there be colors in the dark, nor whether they be the qualities of the objects we see, no nor perhaps, whether Light be a Body. For, since Colours are the qualities of Light, having its Rays for their entire and immediate subject, how can we think those Rays qualities also, unless one quality may be the subject of and sustain another; which in effect is to call it substance. We should not know Bodies for substances, were it not for their sensible qualities, and the Principal of those being now found due to something else, we have as good reason to believe that to be a substance also.”
In this, he surmises that since rays of light have colors as features, colors should be regarded as qualities or properties of the rays; but doing so requires us to think of the rays as bearers of qualities. Stay with me here folks. He concludes by saying that light is a stream of particles (or corpuscles), and not waves because waves are a component of something else (such as waves on a lake), whereas particles are unique and distinctive. According to this theory, these particles move in straight lines until they are reflected or refracted by a surface. This theory challenged the prevailing view at the time, which held that light was made up of waves.
The idea that light was composed of particles was, at the time, a revolutionary idea wrought with controversy, which Newton utterly detested. His distaste for debate was often described as defensiveness by his colleagues, who would encourage him to debate his ideas in order to help said ideas gain more prominence. For Newton, his frustration with those that would argue against his ideas may have been based on a belief that his opponents simply didn’t get it. This presumption by Newton was not based on arrogance on his part, but rather a genuine annoyance that he had to stop his work to argue the reality of his work.
Principia
From 1679-1687, Newton returned to his study of celestial mechanics. His depth of work and immersion into it is best illustrated by a true story of an encounter he had with Sir Edmond Halley at Cambridge in 1684. Halley had heard that the Royal Society – of which Newton was a part – was studying how to make approximations of planetary objects and their movement – Kepler Laws – and understand why the objects moved in the way they did.
“Halley asked Newton the following question: what kind of curve would a planet describe in its orbit around the Sun if it were acted upon by an attractive force that was inversely proportional to the square of its distance from the Sun? Newton immediately replied that the curve would be an ellipse (rather than, say, a circle). Halley was amazed that Newton had the answer at the ready.”
The reason Newton had the answer ready is that he was working actively working on one of the most influential books in the history of natural philosophy and science, the Principia. Published in 1687, the book was a “quantitative description of the motions of visible bodies” and contains Newton’s three laws of motion.
that a body remains in its state of rest unless it is compelled to change that state by a force impressed on it;
that the change of motion (the change of velocity times the mass of the body) is proportional to the force impressed;
that to every action there is an equal and opposite reaction.
Newton's law of universal gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This law was based on both empirical evidence and mathematical reasoning. Using mathematical reasoning, he proved that the force that kept the moon in orbit around the Earth was the same force that kept the planets in orbit around the Sun. Newton used his previous discovery of calculus to solve problems related to gravitational attraction. He calculated the gravitational force between two masses and then extended his calculations to the larger masses.
The publication of Principia immediately elevated Newton as the leader in natural philosophy. Newtonians began to spring up around Great Britain and the rest of the world. Using the mechanics described by Newton, mankind was now able to understand the “why” and “how” of motion in nature, using definable equations.
Impact
Sir Isaac Newton continued his work as well as other roles right up until his death in 1727 at the age of 84. Per usual, it is difficult to summarize all of what he did, what he got right and wrong, and his work in other mediums – such as alchemy – in 15 minutes. I fully expect Jon to ask me about such things during our discussion, and as always, I invite you, our amazing audience, to submit your questions and join in.
Jon once told me that becoming fluent in German meant that he could understand that part of Europe in a genuine way. To converse with someone in their language enabled him to connect with them in a way that simple translation could not. I cannot help but think of Newton’s discoveries as a language with which he directly communicated with creation itself. He once said, “We know is a drop, what we do not know is an ocean.” His interest in both the why and how of the natural world provoked his pursuit of what he could define, to help him understand what he could not define.
The study of mathematics and understanding nature as it relates to space and time is literally seeking to understand the nature of everything. In the Age of Enlightenment, Newton is classified as not contributing to existing philosophy but rather creating his own. Though he coined the phrase, “I have stood on the shoulders of giants,”, he was able to pull from Descartes and other great thinkers’ views on the natural world, and derive his own path. He paved the way for a better understanding of the world around us using mathematical languages that allowed a fluent conversation between us and the fabric of life. In this, Newton did not simply change the world. He opened a dialogue that fueled our better understanding of nature, and as a result, each other.
