Isaac Newton is generally regarded as one of the most original and influential theorist in the history of science. In addition to his invention of calculus and a new theory of light, Newton transformed the structure of physical science with his three laws of motion and the law of universal gravitation. As a foundation of the scientific revolution of the 17th century, Newton's work, when combined with the contributions of Copernicus, Kepler and Galileo, led to an entirely new perception of the universe.
Again, without expanding the details, there are several points in connection with Newton's life that are worthy of some initial note. Isaac Newton was born on Christmas Day (1642) in the village of Woolsthorpe in Lincolnshire, England. The same year Galileo died. Newton's father had died some three months before he was born. His mother remarries a wealthy, but elderly clergyman, and decides to leave Isaac behind in the care of his grandmother. Newton is just 3 years old. In 1653, some 8 years later, Isaac's mother returns following the death of her second husband, bringing with her three small children. However, within 2 years, Newton is again sent away to a grammar school in Grantham. The plan being that Newton would return at 17 to look after the farm, although fortunately for science, Newton was a total failure as a farmer.
Newton's childhood was far from happy and throughout his life he is often on the verge of emotional collapse. Occasionally, it will result in vindictive recriminations against those who Newton thinks have slighted him. In 1661, at the age of 19, Newton makes his way to Trinity College, Cambridge. In 1664, he is elected a scholar, guaranteeing him four years of financial support, but by another twist of fate, the plague has started to spread across Europe, and reaches Cambridge by 1665. The university has to close and Newton is forced home. However, in the next 18 months, Newton is to make a series of original contributions to science, which he himself called his `prime for invention`. In mathematics, Newton develops what he calls `fluxions', which is later to become better known as calculus, lays the foundations for his theory of light, and starts to tackle the problem of planetary motion, which will eventually lead to the publication of his most famous work `The Principia`.
In 1687, after publishing the Principia, Newton became more involved in public affairs and, in 1689; he is elected to represent Cambridge in Parliament. In 1696, Newton is appointed Warden and then Master of the Royal Mint. During these years in London, Newton acquires much success and power, and his position at the Royal Mint has assured him a comfortable social and economic status. In 1703, Newton is elected president of the Royal Society, a position he is to hold until his death. In 1704, Newton publishes his second major work `Opticks`. In 1705, he is knighted `Sir Isaac Newton`. Isaac Newton died in London on March 20, 1727.
What makes Newton so remarkable is that his work crosses so many boundaries, which were to separate into different disciplines. Today, we live in a world of specialization and it is rare indeed to find somebody with the ability to make such major contributions in more than one discipline.
Newton's most creative years in mathematics are to extend from 1664 to 1696. His interest in mathematics can be traced back to his undergraduate days at Cambridge. During the 2 years of the plague, he is to develop some of his fundamental ideas concerning analytic geometry, algebra, and calculus. Specifically, he is beginning to develop his theory on binomials and his method of fluxions. Newton's name for calculus is derived from a method for analyzing a continuously changing or flowing quantity, such as distance, area, or length. The essential elements of his work were recorded in a number of papers. However, the first `On Analysis`, was not to be published until 1711. Likewise, his work `The Method of Fluxions and Infinite Series` would not be published until 9 years after his death. Newton also wrote a number of other works, which were appended to his major works, such as `Opticks` in 1704 .
Newton's research into optics also begins during his formative years at Cambridge, however unlike his work on mathematics, it is published shortly after his election to the Royal Society, in 1671. During the period 1665-66, Newton performed a number of experiments on the composition of light. Inspired by the writings of Kepler and Descartes, Newton's discovers that visible, white light is composed of a finite number of primary colours. By experiment, Newton then goes on to demonstrate that a prism can separate white light into its constituent colours. In another experiment, Newton uses two prisms; the first splits a beam of white light into its coloured components and then passed each of these colours through a second prism. While the second prism causes further refraction of a coloured beam, no further separation of the beam is observed. From the results, Newton was to conclude that white light was a heterogeneous mixture of a spectrum of primary colours. His work `Opticks` first appeared in 1704. However, what is equally interesting is Newton's own statement that the purpose of Opticks was not to explain the nature of light by hypotheses, but to prove them by reason and experiments. Opticks comprises of three books, which cover the definitions, axioms, propositions, and theorems of light underpinned by experimental proof. This mixture of reasoning and careful observation is to become the model for experimental physics in the following centuries.
Nature of Light
However, there are aspects of Newton's work in Opticks, which goes beyond experimental science. During the 17th century, it was widely believed that the underlying nature of light could best be described as a wave , a position well articulated by the likes of Robert Hooke and Christiaan Huygens. While Newton's position is to evolve over time, Newton believes the basic nature of light can best be described as being particle-like. His view is initially based on his experimental observations that light, unlike sound, travels in straight lines because its casts a sharp shadow. Newton believes this property can best be described if light is composed of discrete particles moving in straight lines. Another aspect that Newton considered, and was to become a basis of his dispute with Hooke, was the perception that a wave needed a medium through which to travel, i.e. sound travels through air, a wave travels through water. As such, a light-wave would require an all-pervasive medium to support its propagation, which was both rigid yet so ethereal that it could not be detected. Possibly for these reasons, and others, Newton was to reject the basic wave models of Hooke and Huygens. Newton's work Opticks was to become a milestone in the development of science, but perhaps the most provocative part of the work is the section known as the 'Queries' at the end of the book. It is here that Newton outlines his opinions on the nature of light, matter and the forces of nature.
This is Newton's great work in the area of mechanics and the dynamics of moving objects that evolved over a period of some 20 years, which in itself highlights the complexity of his eventual achievement. The actual truth about Newton's inspiration on gravity coming from an apple falling on his head is possibly more poetic than true. What is known is that Newton's first ideas concerning gravity begin while he is in Woolsthorpe during the years of the plague. Early manuscripts suggest that Newton did not initially consider the Moon as having any attractive force that bound it to the Earth; rather he was focusing on the issue of centrifugal force that would cause the Moon to spin away from the Earth. At this time, Newton simply balanced the Moon's centrifugal force against some, as yet unknown, equal and opposite mechanical constraint. His concept of `action at a distance` has not yet been considered, nor is he aware of Kepler's hypothesis of planetary motion. Newton's initial assumption is that the Moon's orbit is circular and its centrifugal force is proportional to the square of its velocity and inversely proportional to the radius of its orbit. This is derived from Kepler's work that the square of a planet's orbital period is proportional to the cube of its mean distance from the sun. He then tries to test the inverse square relation against empirical data, by comparing the centrifugal force against the acceleration of a falling object on Earth. However, while not recanting the details, his data on the Moon and Earth are not exact and he is to abandon the problem.
In 1679-1680, Newton has exchanged letters with Robert Hooke, who was the president of the Royal Society prior to Newton. Hooke outlined his hypothesis, in 1674, in his work entitled `Attempt to Prove the Motion of the Earth`. Hooke's proposal assumed that the planetary orbits resulted from a tangential motion and some attractive force acting towards the central body within the orbit. Later, Hooke outlines that this attractive force would reduce as a square of distance. It is clear that Hooke's work provides Newton with a valuable in-sight that changes his perception of the problem. Unfortunately, Hooke is later to seek acknowledgement of his contribution to Newton's work to which the temperamental Newton takes offence. While there is obviously some basis to Hooke's claim, it is clear that Hooke never came close to matching Newton's mathematical in-sights that were to eventually lead to Newton's most famous work, the `Principia`, published in 1687.
The Laws of Motion
The Principia is divided into 3 books. Book-1 begins with eight definitions and three axioms, which are to become known as Newton's laws of motion:
- Every body continues in its state of rest or uniform motion
in a straight line, unless acted on by a force.
- The acceleration of an object is directly proportional to the
force acting on the object, is in the direction of the force and
is inversely proportional to the mass of the object.
- To every action there is an equal and opposite reaction.
Book-3 is subtitled `The System of the World` in which Newton goes on to apply his laws of motion to planetary bodies. Central to this work is Newton's Law of Universal Gravitation that states:
The force between any two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them, i.e. F = G Mm/R2.
This law holds that all matter is mutually attracted with a force `F` that is proportional to the product of their masses `Mm` and inversely proportional to the square of distance `R2` between them with `G` being a constant that depends on the units used for mass and distance. Newton then uses the concept of gravitational attraction to explain the motion of the planets and their moons, the precession of equinoxes, the action of the tides, and the motion of comets. And so, the Newtonian universe is born, uniting heaven and earth within a single set of laws. These insights into the workings of the universe are to create a new worldview that extends beyond science in way that was possibly not understood by the establishment at the time. The implication of Newton's work was that the universe worked in accordance to a set of consistent laws of physics rather than constantly varying due to divine intervention. In this respect, Newton's work, in combination with that of Copernicus is to change both science and philosophy, as defined by Aristotle and the accepted theology of the Church. This new worldview will stand essentially unchallenged until the beginning of the 20th century.
Some Further Historical Perspective
It is possibly less well-known that Newton held some surprising views given that he is often described as the founder of modern science, requiring both rationalism and experimental verification. However, there is another aspect of Newton's work that involves research into theology and historical biblical scriptures, plus a significant interest in alchemy, which alludes to the fact that Newton's worldview was more complex than implied above. It has been estimated from Newton's manuscripts, which would have amounted to about 20 books, that his interest in these subjects was not just idle curiosity. From our own perspective, we are trying to ascertain how the spread of worldviews, which exist today, has evolved. It has also been stated that over time, the real truth about key events or people in history gets lost and we are left with only a shadow of the truth. Therefore, we should not be bias in what we accept as facts about our heroes, and what is but extrapolation and assumption.
We know that before his death, Newton refused the sacrament. This act would not have been taken lightly in the 18th century. We also know that Newton was raised in the Protestant faith and that when, in 1667, he was made a Fellow of Trinity College, he was required to accept the 39 Articles of the Church of England, which align to the doctrine of the Trinity. However, possibly more significant, he was required to take a vow of celibacy and to promise to take holy orders within 7 years of his graduation. However, by 1673, he has begun a life-long study of the textual history of the Bible, which leads him to conclude that the doctrine of the Trinity is a heretical error introduced in the 4th century. Unable to accept the beliefs of the Church of England, he is forced to go to the Secretary of State to seek dispensation from taking holy orders, as required by the statutes of his vow to Trinity College. This is granted, and the statutes altered for Newton's benefit in perpetuity, so that future Lucasian professor need not take holy orders. Although it is not clear on what grounds he argues for his exemption, it is almost certainly based on his disagreement with the Church's position on the Trinity.
While not wishing to get embroiled in too much detail of this aspect of Newton's life, it is known that Newton was not only a passionate theist, but also a firm believer in the Bible and its power of prophecy. Newton's view of God, being both omnipotent and omniscient, is that God not only created the world, but knows its eventual fate. There is much circumstantial evidence that Newton believed in these prophecies and that they could reveal the `history of things to come`. However, it was believed that these prophecies were described in a symbolic and metaphorical language that required knowledgeable interpretation. It was this challenge that was to occupy Newton for the rest of his life. In later editions of his scientific works he expresses a strong sense of God's providential role in nature; however, the full extent of Newton's unorthodox views was only recognized in the last century through the re-examination of his private manuscripts.
Alchemy and Chemistry
As indicated, Newton left a mass of manuscripts on the subjects of alchemy and chemistry. These manuscripts reflect Newton's search for clues he hoped were hidden in the obscurity of ancient alchemy and mysticism. In part, it is believed he was seeking an understanding of the nature and structure of all matter that he believed God had created. In his work `Queries`, which was appended to `Opticks` and in a subsequent essay `On the Nature of Acids`, published in 1710, Newton outlines an incomplete theory of chemical forces, but carefully conceals his research of alchemy, which only became known after his death.
The General Scholium
This work was added to the Principia, in 1713. While it is one of his most famous texts, it is probably also one of the least understood. For obvious reasons, it is felt that Newton deliberately hid some of his more controversial ideas within others that initially appear conventional. However, subsequent access to Newton's private manuscripts has helped scholars decipher elements of the oblique language used in the General Scholium to reference the much less guarded wording of his private writings. With these insights, it appears that Newton not only challenges the natural philosophy of Descartes, but also embeds a subversive attack on the doctrine of the Trinity, which he believed to be a corruption of Christianity. However, the General Scholium, also appeals for a inductive approach to both natural philosophy and religion. In his hidden manifesto of natural philosophy and theology, Newton reveals his commitments to the dual reformation of philosophy and theology. One conclusion drawn of Newton's research into theology, prophecy, and history, is that it is a quest for the unity between knowledge and belief. As such, it is assumed that Newton was trying to reconcile his understanding of the `laws of nature` with his belief in the `laws of God`. So in reality, like many key figures of the Renaissance, Newton was possibly a man stranded between two different worldviews of the universe.