G. Rajasekaran

Isaac Newton

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Beginning

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Isaac Newton was born in Woolsthorpe in England in the year 1642 which was the year when Galileo died. His mother Hannah Ayscough thought that he will not live for long since he was a premature baby. His father died before he was born. His mother remarried Barnabas Smith. They left Newton under the care of his grandmother Margery Ayscough.

 

Since he was forsaken by his mother in this way and had not seen his father, he was affected throughout his life. He hated Barnabas. Later in 1662, he has written in his diary that he had threatened his mother and Barnabas that he will burn them along with their house.

 

Even when he was young, signs of his future greatness appeared. He was very much interested in mechanical models and architecture. He spent much time in making clocks, sundials and small machines that use mice for their operation.

 

In his fifth year, he entered the schools in Skillington and then in Stoke. But he was regarded as a backward student, not attentive in the class room and lazy. Although he was interested in learning, he could not pay attention to the school lessons.

 

When he was ten, Barnabas Smith died. His mother Hanna became the owner of all the properties left by Barnabas. Newton and his grandmother started living with Hanna.

 

Since Newton's school education did not proceed well, Hanna made him leave the school and appointed him to manage her lands and other properties.

But Newton did not like this type of work, nor did he know how to do it well. So, Hanna's brother William admitted Newton in school again.

 

Newton stayed with John Stokes who was the Headmaster of the school. He progressed well in the school. It is said that a bully in the school hit him on the head so hard that Newton's brain was activated and induced his interest in learning!

 

He prepared well for joining University and joined the Trinity College in Cambridge University.

 

College

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In the Trinity College, he cleaned up the rooms of teachers and served food for them. He continued his education through the money earned this way. But in 1664, he was selected as a scholar and thereafter he did not need to work for educational expenses.

 

In 1665, because of bubonic plague, the University was closed. Newton returned to Woolsthorpe and spent the next 18 months there.

 

Beginning of research

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In Woolsthorpe, he was involved in mechanics and mathematics. He has called the year 1665 as "annus mirabilis" (the miraculous year). For, it is in this year that he discovered many things.

 

The famous "apple incident" took place at this time. The apple that fell on his head when he was sleeping under an apple tree, inspired him to discover gravitation. Newton himself has written about it.

 

He wrote  "I was in the right age for discoveries. From that time I was interested in Mathematics and Philosophy."

 

After returning to Cambridge, he read Philosophy from Aristotle and Descartes and Science from Thomas Hobbes and Robert Boyle. He was attracted by the Astronomy of Copernicus and Galileo and Kepler's Optics.

 

As for his Mathematics before his coming to Cambridge, nothing much is known. At Cambridge, his first teacher was Benjamin Pulleyn. After that, it was the famous mathematician who was one of the founders of the Royal Society, Isaac Barrow. He taught Newton Elements of Euclid. After that, Newton learnt Algebra from William Oughtred and François Vitet. Most importantly, he studied the geometry of Descartes.

 

Now Newton started his experiments on refraction and dispersion of light.

 

An important event in the University affected his future very much. That was the appointment of Isaac Barrow as the Lucasian Professor of Mathematics. in the year 1669, Barrow left his professorship to devote himself to Theology. He knew of Newton's great mathematical abilities and recommended him for the Lucasian Professorship.

 

Lucasian Professor

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Soon after he became Lucasian Professor, Newton became involved in Optics research. Through many experiments he discovered that white light is composed of many colours and that a prism separates the different colours.

 

He did many experiments to prove that light is made of particles. Robert Hooke and other scientists opposed that idea and argued that light is a wave.

 

Hooke challenged Newton to prove his ideas on light. Newton's response was to withdraw from this argument! He refused to publish his book "Optiks" until Hooke died in 1703.

 

He found good progress in Mathematics research, but he did not share them with the other scientists. Newton created Calculus before 1666.

But a big battle started with the supporters of the German mathematician and philosopher Gottfried Wilhelm Leibnitz about the priority in the discovery of calculus.

 

Leibnitz published his discovery only after another 10 years. Both Newton and Leibnitz discovered the same calculus, but Leibniz published it before Newton. Newton's supporters said that Leibnitz saw Newton's papers.

 

Who discovered calculus first? Newton or Leibnitz? This fight lasted until 1716 when Leibnitz died.

 

It is now accepted that Newton and Leibnitz discovered calculus independently and hence this fight is an unnecessary one.

 

Later Newton was involved in another fight; it was about the colours of light. Because of these fights he went through mental illness in 1678.

 

We now come to the most important discoveries of Newton.

 

Laws of motion and law of gravitation

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Galileo and Kepler who came before Newton had discovered many things in Astronomy.

 

Galileo used his observations through the telescope to infer that planets did not go around the Earth and that all the planets including the Earth go around the Sun. He declared this Heliocentric theory clearly and loudly.

 

A heavy object and a light object falling down from a height will fall on the Earth at the same time. Galileo proved this by experiment. He discovered many more things about the motion of bodies.

 

Kepler used Tycho Brahe's observational data on planetary motion to deduce the correct laws of this motion.

 

Kepler's famous three laws are:

 

1. Earth and all the other planets go around the Sun, but not in circular orbits. They follow elliptic paths, with Sun at one of the foci.

 

2.If we draw a straight line connecting the planet with the Sun, this straight line will cross the same area per unit of time; that is, the areal velocity is constant.

 

3.The period of revolution of each planet around the Sun is proportional to the 3/2 power of the length of the semimajor axis of its elliptic orbit.

 

The supreme creations of Newton are two: first, laws of motion of all material bodies, second, the law of gravitation.

 

Newton's laws of motion:

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Newton's law of gravitation:

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Newton created a new mathematics called Calculus, which enabled the precise calculation of velocity and acceleration. As we already mentioned, Leibnitz also independently discovered Calculus. This is a great discovery. Through this only, mathematics, physics and engineering made great progress.

 

Using his Laws of Motion and Law of Gravitation,Newton proved Kepler's laws of planetary orbits. Thus it was established that it is Sun's gravitational attraction that holds the planets in elliptic orbits and also is responsible for the other two laws of Kepler.

 

Through his work, Newton proved that all material bodies - whether they are on the Earth, or in the heavens - obey the same Laws of Science.

He showed that the human brain is capable of understanding all this through mathematics. It is this fact that led to the advance of Physics and in fact all of Science.

 

We now say a little about how Newton discovered his laws.

 

Kepler's three laws described the planetary orbits completely, but he could not explain why the planets go around the Sun. He thought that the planets and the Sun are connected by a magnetic force since magnetism was the only force known at that time. It was left to Newton to introduce the new force, gravitation.

 

Newton began to search for the reason for the elliptic orbits of the planets. From Kepler's third law, he deduced the inverse square law of gravitation, namely, the force is inversely proportional to the distance.

 

According to this inverse square law, the accelerations of the falling apple and the Moon must be in the ratio                            For, the Moon is 60 times further away as compared to the apple. This is actually correct. But in Newton's time, Earth's radius had not been measured accurately. Hence Newton could not complete the calculation successfully.

 

In the year 1684, Robert Hooke, Edmund Halley (of the Halley comet fame) and Christopher Wren (who was the architect of the St Paul Cathedral) were involved in a debate on the connection between the inverse square law and planetary orbits. It is this debate that was responsible for the birth of the famous book Principia of Newton.

 

Hooke claimed that he can prove the elliptic orbits of the planets from inverse square law, but he also said he is not going to publish this now.

Halley conveyed this to Newton and asked him what will be the planet's orbit if the force law is inverse square. Newton answered immediately that it will be an elliptic orbit. He also said that he had proved this four years ago, but lost the paper containing the proof.

 

At Halley's request, Newton spent the next three months in reconstructing the proof. He then worked with renewed energy on all his discoveries.

Some days, he even forgot to take food!

 

Newton wrote up all his discoveries in three volumes of Principia. Halley was immensely happy and called it a magnificent and unique achievement.

Also, Halley spent his money to publish Principia.

 

Earlier, Galileo had discovered that bodies were attracted towards the Centre of the Earth. Newton proved this from his law of gravitation. He also proved that the Moon's orbit around the Earth is due to gravitation and the rise and fall of the tides in the oceans of the Earth is also due to gravitation. Principia contains many more discoveries.

 

Newton was appointed as the Head of the Royal Mint at the beginning of the eighteenth century. He became the President of the Royal Society. In the year 1905, Queen Anne bestowed knighthood on Newton.

 

In March 1727 Newton died and he was buried in Westminster Abbey.

 

Since during his whole lifetime, Newton was involved in fights with Hooke and Leibnitz, he was regarded as a haughty man by most people. But in his last days, this is what he said about himself: " I do not know how I appeared to the world, but to me I appear to be a boy playing in the seashore. Sometimes I felt happy when I saw a stone with regular shape or a beautiful sea-shell. But the great ocean of Truth lies unfathomable in front of me."

 

Following are the beautiful words of Newton's friend,the poet Alexander Pope :

        Nature and its Laws lay hidden in darkness.   

         God said: "Let Newton be."          

         Everything came to Light.  

 

Reference

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God created the integers, by Stephen Hawking, Running Press, Philadelphia and London, 2005.