Isaac Newton

Isaac Newton's early life

Isaac Newton, Sir Isaac Newton in full, was born on 25th December 1642 (old calendar) in the village of Woolsthorpe in Lincolnshire, England. His father, a farmer also called Isaac Newton, had died a few months prior to his birth, so he was left only with his mother, Hannah Ayscough. Around two years after her first husband died, Newton's mother married again, this time to a wealthy older man, minister Barnabas Smith.

Barnabas Smith took Hannah Ayscough to the neighbouring village, Grantham, but left young Isaac Newton behind. He lived with his grandmother until Barnabas Smith died in 1653. From Newton's diaries, we are aware that he did not appreciate his stepfather. These diaries were possible, though, because he learnt to read and write from his mother and grandmother.

Once Barnabas Smith had passed away, Newton's mother went back for her son together with three new children, Newton's stepsiblings. Newton was sent to a grammar school in Grantham and was set to manage the considerable estate his mother now owned upon his return, two years later. However, he was not very good at this, getting constantly distracted. Thus, he was sent back to grammar school to prepare for university. He entered Trinity College in 1661.

Isaac Newton's education

As we just mentioned, Newton started his education at home, learning to read and write from his mother and grandmother. He then attended grammar school and prepared for university there in Grantham. Eventually, he entered Trinity College in Cambridge in 1661.

Cambridge had been undergoing deep changes since the time when Newton was born up until he joined. Previously, the college had been under the control of the Anglican Catholic Church. However, due to the political turmoil from 1642 to 1660, the church lost its grip on Cambridge. This allowed for the emergence of the Royal Society of London in 1660, among other changes in the intellectual world of the time.

At Trinity College, Newton started by studying the classics, such as Aristotle. He soon discovered more modern philosophers and mathematicians like Descartes, who in contraposition to Aristotle, saw matter as built from smaller particles in motion and who thought that all natural phenomena derived from their mechanical interaction.

Newton started to write his scientific ideas down under a set of notes called Quaestiones Quaedam Philosophicae. From there he started to delve into physics and mathematical concepts, fields which propelled his scientific career forward.

In April of 1655, Newton received his bachelor's degree. His most early productive years were the following ones when he had to interrupt his studies at Trinity College during the plague (1665-1667). After years of further research and the development of his Principia, Newton became warden, and eventually master, of The Royal Mint. Eventually, he also became President of The Royal Society.

Death of Isaac Newton

During his final years, Isaac Newton published new editions of his previous works. He continued to lead The Royal Mint and The Royal Society until his death. He died at age 84 on 20 March 1727. Multiple posthumous works were published after his death.

Inventions by Isaac Newton

Isaac Newton made contributions to multiple fields, but we will go over his most well-known ones in this section.

Newton's contributions to classical mechanics

Newton is possibly most well-known for his contributions to classical mechanics. His three laws of motion are still studied in all schools and are essential to understanding contemporary physics and mechanics, in particular the behaviour of objects in motion.

Newton enunciated his three laws of motion in his book "Philosophiæ Naturalis Principia Mathematica", published in 1687:

In addition to his laws of motion, Newton also developed the law of universal gravitation, which describes the force of gravity between any two objects in the universe. This law states that the force of gravity is proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them (\(F_g = \frac{GM}{r^2}\)).

Newton's contributions to optics

Isaac Newton also made significant contributions to the field of optics. His experiments with light and prisms led him to discover that white light is composed of a spectrum of colours, which can be separated by a prism.

Newton's work on optics culminated in the publication of his book "Opticks" in 1704, in which he presented his theory of light and colour. He proposed that light is composed of particles, rather than waves as many scientists of his time believed. This theory was later challenged by the wave theory of light, but it laid the groundwork for the development of quantum mechanics in the 20th century.

Newton also discovered the phenomenon of colour mixing, which occurs when two different colours of light are combined to create a third colour. He also developed the first reflecting telescope, known as the Newtonian telescope, which uses a curved mirror to reflect light instead of a lens.

Newton's contributions to calculus

Newton's main contribution to calculus is that he invented this mathematical discipline. At the time there was a great controversy about this, as Gottfried Leibniz also developed calculus in parallel and only a little later than Newton. The two scientists got caught up in a feud about their role in the invention of calculus and the significance of their contributions until Leibniz's death.

Despite the disagreements around calculus, Newton continued his work in the field. He developed calculus to aid him in the calculation of the rate of change of the speed of a falling object.

He coined the idea that derivatives and integrals are opposite mathematical operations. Derivatives are currently used to:

• Find the rate of change of a quantity (crucial to Newton's development of calculus)
• Find the approximate value of a function.
• Find the equation of the tangent to a curve at a given point.
• Find the maxima, minima and points of inflexion of a curve.
• Determine if an equation is increasing or decreasing between two points.

Integrals, on the other hand, are widely used in mathematics to find:

• The average value of a curve
• The area between two curves
• The area under a curve

And in physics to find:

• The centre of gravity and the centre of mass
• The mass and moment of inertia and satellites
• The velocity and trajectory of a satellite
• Thrust

On top of that, Newton's method enabled the calculation of maximums and minimums of functions. This method has been developed further throughout the years and is no longer applied as Newton first designed it, but Newton provided the seed for this very useful tool in calculus.

Isaac Newton and the Apple Tree

Isaac Newton and the apple tree is a famous historical anecdote that is often used to illustrate Newton's discovery of the law of universal gravitation. According to the story, Newton was sitting under an apple tree in his garden when an apple fell and struck him on the head. This event led him to ponder the nature of gravity and inspired him to conduct further experiments and observations.

Fig. 3. Newton and the apples that sparked his interest in gravity.

While the story is likely embellished, there is some truth to it. Newton did write about the concept of gravity and the motion of objects in his book "Philosophiæ Naturalis Principia Mathematica". This book is widely regarded as one of the most important works in the history of science, as it introduced the concept of gravitational force and laid the foundation for modern physics.

Regardless of the accuracy of the story, the image of Newton sitting under an apple tree has become an enduring symbol of scientific discovery and innovation.

Isaac Newton: Facts

Here are some curious facts about Newton:

1. Isaac Newton was an avid alchemist but kept his interest secret. He spent much of his life trying to find the philosopher's stone, which was believed to turn base metals into gold.
2. He invented calculus, a branch of mathematics that is used to solve problems in physics, engineering, and economics. He did so almost a decade before Leibniz, although the latter is the one associated with this invention.
3. Newton was knighted by Queen Anne in 1705, becoming Sir Isaac Newton.
4. Newton was a deeply religious man and wrote extensively about theology and the Bible.
5. He suffered from several nervous breakdowns throughout his life. He already showed signs of emotional turmoil in his early diaries, and he struggled severely with criticism.
6. Newton had bitter rivalries with several scientists of his time. He clashed with Robert Hooke, who accused Newton of stealing from his work. He also fought with Gottfried Leibniz over who had invented calculus first, and who had contributed the most to this new branch of science. Newton accused Leibniz of stealing from his ideas, but Leibniz could prove that he had developed some of the most basic foundations of calculus independently. Finally, Newton also had strong disagreements with astronomer John Flamsteed. Some of Flamsteed's observations on comets provided helpful insights for Newton's law of gravitation. However, Flamsteed felt that Newton had not credited him properly; in fact, Newton removed all citations of Flamsteed's work in his second edition of the Principia.