Isaac Newton (Edexcel A-Level History): Revision Notes
Isaac Newton
Isaac Newton (1643–1727) is recognised as one of the most influential scientists in history. His groundbreaking work on mathematics, physics, and astronomy transformed our understanding of the natural world and laid the foundations for modern science during the Age of Reason.
Newton's early life and education
Newton was born in Lincolnshire in 1643. He enrolled at Trinity College, Cambridge in 1661, where he would spend most of his academic career. In 1669, at just 26 years old, he was appointed Lucasian Professor of Mathematics at Trinity College, a prestigious position he held until 1696.
Key dates in Newton's early career:
- 1643: Born in Lincolnshire
- 1661: Enrolled at Trinity College, Cambridge
- 1665-1666: Developed theory of gravity (apple falling legend)
- 1666: Performed prism experiments discovering the spectrum
- 1669: Appointed Lucasian Professor of Mathematics (age 26)
During the 1660s, Newton conducted intensive research that would form the basis of his most important discoveries. According to legend, he conceived his theory of gravity after observing an apple fall from a tree in 1665 or 1666. In 1666, he performed his famous prism experiments, discovering that white light could be separated into a spectrum of colours.
Building on earlier thinkers
Newton openly acknowledged his debt to earlier scientists, famously stating: "If I have seen further, it is by standing upon the shoulders of giants." His work built directly on the achievements of previous thinkers who had begun the Scientific Revolution.
René Descartes (1596–1650)
Descartes was a French mathematician, scientist and philosopher who continued Galileo's approach of combining mathematics with natural philosophy. He took great interest in astronomy and came close to publishing a work called The World in 1653, which would have provided further mathematical explanations for events in the universe. However, fearing condemnation by the Inquisition (like Galileo before him), Descartes withdrew the work from publication.
Christiaan Huygens (1629–95)
Huygens is viewed by historians as a direct forerunner to Newton. He wrote about optics, pendulums, and the rings of Saturn, but his most significant contribution was his work on motion and gravity. During the 1650s and 1660s, his research on motion led him to propose a formula remarkably similar to what later became known as Newton's second law of motion. Huygens published this work in 1673, fourteen years before Newton's Principia Mathematica.
Newton's career and public roles
Newton's career extended beyond scientific research into public service and administration.
Academic positions
- 1669: Appointed Lucasian Chair of Mathematics at Trinity College, Cambridge
- 1672: Elected to the Royal Society (Britain's leading scientific organisation)
- 1703: Elected President of the Royal Society, re-elected annually until his death in 1727
Political roles
- 1689: Elected Member of Parliament for Cambridge in the Convention Parliament (a parliament assembled without formal monarchical authority, which offered the throne to William and Mary during the Glorious Revolution)
- 1701: Elected MP for Cambridge for a second time
Newton's election to Parliament in 1689 resulted from his resistance to King James II's attempt to transform the universities into Catholic institutions.
Administrative roles
- 1696: Appointed Warden of the Royal Mint (the organisation with sole authority to manufacture coins in England) and moved to London
- 1699: Promoted to Master of the Mint
These positions gave Newton significant influence beyond the scientific community and demonstrated the respect he commanded in public life.
The Principia Mathematica (1687)
Newton's most celebrated work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), was published in 1687. This book is considered one of the most important works in the history of science.
Major achievements in the Principia
The Principia Mathematica made several groundbreaking contributions to human understanding of the universe:
Proving Kepler's laws mathematically: Newton demonstrated that Johannes Kepler's laws of planetary motion could be proven through mathematical calculation, not just observation.
Challenging Aristotle's physics: Newton questioned the long-accepted view, first proposed by Aristotle, that physics on Earth worked differently from physics in the rest of the universe. Newton showed that the same physical laws applied everywhere.
Explaining centrifugal force: Newton adequately explained centrifugal force (the apparent force that acts on an object moving in a circular pattern, causing it to move away from the centre of its path).
Developing acoustics theory: He developed a theory of acoustics (the study of sound), showing that sound varied depending on the density of the medium through which it passed.
Establishing universal gravitation: Most significantly, Newton established that the force propelling planets in orbit around the Sun is the same force that keeps people and objects on the ground on Earth—gravity. This was revolutionary because it unified celestial and terrestrial physics.
Newton's three laws of motion
Newton proposed three fundamental laws of motion that remain central to physics today:
Newton's First Law of Motion
Every object will remain in a uniform straight line or at rest unless an external force compels it to change direction.
This is sometimes called the law of inertia—objects maintain their state of motion unless something acts upon them.
Newton's Second Law of Motion
The external force on an object is equal to the mass of the object multiplied by its rate of acceleration.
This can be expressed as:
where is force, is mass, and is acceleration.
This law explains why heavier objects require more force to move them at the same speed as lighter objects.
Newton's Third Law of Motion
For every force (action) in nature, there is an equal and opposite force (reaction).
When you push against a wall, the wall pushes back against you with equal force.
The theory of universal gravitation
Newton's theory of gravitation had a profound impact on understanding the universe, particularly planetary orbits. His insight fundamentally changed how scientists understood celestial mechanics.
Kepler versus Newton on planetary motion
Understanding the difference:
Kepler's view: Planets move in orbit because something pushes them from behind, propelling them forward along their paths.
Newton's view: Planets are pulled towards the Sun by gravity. The natural path of a planet (which would be a straight line if undisturbed by any force) becomes a circular orbit because the Sun's gravitational pull provides just enough force to curve the planet's path without pulling it directly into the Sun.
This same principle applies to the relationship between the Earth and the Moon—the Moon orbits Earth because Earth's gravity pulls it into a curved path rather than allowing it to travel in a straight line.
The impact of Newton's theories
Completing the Scientific Revolution
Despite his achievements, Newton recognised that his success depended on earlier thinkers who had begun the Scientific Revolution. His work represents the final stage of a long process of theory and discovery that had evolved for over a century.
The Principia Mathematica represents an important break from the medieval mindset. Historians have concluded that Newton completed the 'mathematisation' of natural philosophy because, unlike earlier thinkers, he succeeded in making all his calculations work consistently, leaving no mysteries or unexplained grey areas.
Making science accessible
Initially, Newton's works were not accessible to many people, partly because they were published in Latin (the traditional language of scholarship) and partly because the mathematics was extremely complex. However, later interpreters such as Voltaire provided simpler versions of Newton's work for ordinary people, helping to spread his ideas throughout society.
The acceptance of mathematical natural philosophy
Historian John Henry explains Newton's significance: before Copernicus and other Renaissance mathematicians raised the status of mathematics, natural philosophy and mathematics were essentially separate and distinct fields. Newton's book title, Mathematical Principles of Natural Philosophy, would have been almost unthinkable in earlier periods. By the final decades of the seventeenth century, however, the idea that there could be mathematical principles of natural philosophy had become accepted. Although Newton's book met some fierce criticism, nobody questioned the fundamental validity of applying mathematics to understand nature.
Newton and magic
Despite his reputation as a deeply rational and mathematical thinker, Newton, like Kepler before him, still believed in hidden knowledge and supernatural forces. This aspect of Newton's thought reveals the complex intellectual context of the period, when scientific rationalism coexisted with mystical beliefs.
Magical explanations for gravity
In early drafts of the Principia Mathematica, Newton speculated that gravity might result from some kind of magical force. He claimed that followers of the Ancient Greek philosopher Pythagoras had a basic understanding of gravity and knew that planets circle the Sun. As evidence, Newton pointed to Pythagorean symbolism showing the sun-god Apollo playing a seven-stringed lyre.
Newton appeared obsessed with the numerological significance of the number seven. In his presentations to the Royal Society on the colours of the light spectrum, he made comparisons with the seven musical notes of the octave. This belief in cosmic harmonies followed Kepler's belief in a harmonious universe where God had created six planets to fit a perfect geometric plan.
Alchemy and occult forces
Newton, like several contemporaries in the Royal Society, was an alchemist (someone who attempts to transform common substances such as base metals into gold or create potions to cure diseases). He believed that different particles could be attracted to each other across empty space, and his confidence in the power of light and gravity stemmed from a genuine belief that supernatural or occult forces were responsible.
Even Robert Boyle (1627–91), one of the most respected members of the Royal Society, practised alchemy. His approach to natural philosophy was based on alchemical principles, showing that these beliefs were widespread even among leading scientists.
Biblical prophecy
Newton's study of the Bible was as dedicated as his scientific work. He was particularly concerned with prophecies he believed could be found in the books of Daniel and Revelation. He wrestled with their meanings from a young age and remained mystified by them throughout his life. In later years, he wrote down many supposed hidden messages he had discovered (most remained unpublished), including speculation about when the world would end.
The contradiction in Newton's thought
The coexistence of rigorous mathematical reasoning and mystical beliefs in Newton's work highlights an important aspect of the intellectual context during this period. The Age of Reason and the Scientific Revolution did not immediately eliminate older ways of thinking about the world. Instead, new rational approaches existed alongside traditional beliefs in magic, alchemy, and divine mysteries.
This contradiction shows that the transition from medieval to modern scientific thinking was gradual and complex. Even the greatest scientific minds of the period combined revolutionary rational insights with continued belief in supernatural forces.
Key Points to Remember:
- Isaac Newton (1643–1727) was one of history's most influential scientists, whose work on mathematics, physics and astronomy transformed understanding of the natural world
- His masterwork, Principia Mathematica (1687), established the three laws of motion and the theory of universal gravitation, showing that the same physical laws apply on Earth and in the heavens
- Newton built on earlier thinkers including Descartes and Huygens, acknowledging: "If I have seen further, it is by standing upon the shoulders of giants"
- He completed the 'mathematisation' of natural philosophy, proving theories with consistent mathematical calculations and leaving no unexplained mysteries
- Despite his rational reputation, Newton believed in alchemy, magic and biblical prophecy, showing that the Scientific Revolution coexisted with traditional mystical beliefs