Isaac Newton

Isaac Newton is widely regarded as one of the most influential scientists in history. Born in 1643 (modern calendar) in England, Newton made groundbreaking contributions to mathematics, physics, and astronomy during his lifetime. His most famous work, the Philosophiæ Naturalis Principia Mathematica, laid out the laws of motion and gravity that are still used by scientists today. In addition to his scientific work, Newton also served as a member of Parliament and as Master of the Royal Mint. He is just one of many examples of how scientists before modern times would contribute to several fields, and not specialise as much as we do now.

Isaac Newton Isaac Newton

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Table of contents

    Isaac Newton, Portrait of Isaac Newton, StudySmarterFig. 1. Portrait of Sir Isaac Newton. Source: Wikimedia Commons.

    Born25 December 1642/ 4 January 1643
    Died20 March 1727
    Known for
    • Newton's Laws of Motion
    • Gravity
    • White light colour composition/light dispersion
    • Calculus
    Famous works
    • Philosophiæ Naturalis Principia Mathematica (1678)
    • Opticks (1704)
    • Warden and Master of the Mint (1696-1699; 1699-1727)
    • President of the Royal Society (1703-1727)
    • Fellow of the Royal Society (1672)
    • Knight Bachelor (1705)
    Table 1. Isaac Newton biography - summary

    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.

    The Royal Society of London is an unaffiliated scientific institution of the UK, committed to championing eminence in scientific knowledge and expertise, for the betterment of mankind.

    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.

    As the master of The Royal Mint, Newton was known for pursuing counterfeiters.

    The Royal Mint is the company in charge of producing coins for the UK.

    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:

    Newton's first law of motion states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity unless acted upon by an external force.

    His second law of motion states that the force acting on an object is equal to its mass times its acceleration (\(\vec{F} = m \cdot \vec{a}\)).

    Isaac Newton, Force and acceleration graph, StudySmarterFig. 2. Force is proportional to acceleration.

    His third law of motion states that for every action, there is an equal and opposite reaction.

    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 observed that the speed of falling objects increased every second, but that there was no explanation for that. Thus, he started to work on calculus, which is the branch of mathematics that focuses on the rate of change.

    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:

    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.

    Newton's method is a root-finding algorithm that allows the calculation of ever more accurate approximations to the zeroes (or roots) of a real-valued function (i.e. to the points at which \(f(x) = 0\)).

    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.

    Isaac Newton, Illustration of Isaac Newton sitting under an apple tree while an apple is falling on him, StudySmarterFig. 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.


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    Frequently Asked Questions about Isaac Newton

    What is Isaac Newton most famous for?

    Isaac Newton is most famous for:

    • inventing calculus,
    • developing the three laws of motion, 
    • developing the theory of gravity
    • developing a new theory of light and colour, and 
    • inventing the first reflecting telescope.

    Did an apple really fall on Isaac Newton’s head?    

    There is no evidence to support the claim that an apple actually fell on Newton's head, although it seems that it was apples falling to the ground that made him wonder about the phenomenon of gravity.

    What did Isaac Newton discover?

    Isaac Newton discovered the three laws of motion, calculus and some of the principles of light and colour.

    When was Isaac Newton born?

    Isaac Newton was born 25 December 1642 according to the old calendar, or 4 January 1643 according to the new calendar.

    What was Isaac Newton's IQ?

    It is estimated that Isaac Newton's IQ was between 190 and 200.

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