Isaac Newton

Early Years

The great English scientist Isaac Newton was born in the little village of

Woolthorpe, not far from the old university town of Cambridge, on December

25, 1642. His father, a farmer, died before his son’s birth. Little Isaac

was left to the care of his mother, uncle and grandmother who sent him to

school.

In his early years young Isaac shone more as one who could make things

with his hands than a scholar. His neighbors watched him making various

things and tthought ho would probably become a well-known clock maker. There

was ground for thinking thus became he had already made a clock of a kind

which his neighbors had never heard of before. It worked by water. Besides

the water-clock, Isaac also made a sundial. His grandmother was never at a

loss to know the hour; for the water-clock could tell it in the house, and

the sundial outside. It is said that the sundial is still at Woolthorpe, on

a wall of the house where NNewton lived.

When he grew older, however, he took a considerable interest in

mathematics.

Though Isaac Newton never lost his manual skill his ability as a

mathematician and a physicist was the most important in his life. According

to Newton himself, his first pphysical experiment was carried out in 1658,

when he was sixteen years old. Wishing to find out the strength of the wind

during a storm, he jumped against and before the wind and by the length of

his jump he could judge the strength of the wind. Thus, even in his boyish

sports, he was searching out the secrets of nature and could find out

difficult things in simple ways. His brain was always busy observing

different phenomena of nature.

[pic] Earth mass

Not far from his grandmother’s home there was a windmill. When the

windmill was not working he examined the mechanism and when the windmill

worked he watched the process of its work. Then he made a model of the

windmill; every part of the mill and iits machinery was complete.

If Isaac was left to himself, he was either making something’s or studying

some book. At night he looked up at the stars, and wondered if they were

worlds like our own, and how great their distance from the earth was. There

were a lot of questions in his mind but nobody was able to answer them.

When Isaac was fourteen years old, his mother took her son from school to

help her on the farm at Woolthorpe, where she lived with three other

children – Isaac’s brother and two sisters. For more than two years he

worked on the farm and then his mother sent him back again to school to

prepare for the University.

On June 5, 1551, Newton entered the University of Cambridge where he

studied mathematics. Soon he became famous having made a number of

important contributions to mathematics by the time he was twenty-one.

When Newton was twenty-two years old he began studying the theory of

gravitation. In 1665, while on a visit in his negative village, he saw an

apple fall from a tree and began wondering what force made the apple fall.

Probably this was influenced by his knowledge of Galileo’s experiment from

the Tower of Pisa.

[pic] Moon

The Problem of Gravitation

We know that the moon makes a circle round the earth in about every twenty-

eight days. We know also that our earth and other planets move around the

sun. Does it not seem probable that the earth pulls the moon, and it moves

in its orbit under the influence of the earth’s gravitation? Perhaps also

the sun pulls the earth and the other planets.

It was over such possibilities that young Isaac Newton was thinking in the

solitude of his Lincolnshire home when tthe Great Plague raged in London and

he, along with other students, was sent home from Cambridge because of this

plague. In that quiet period of almost two years he finished considering

his discoveries which had perhaps the most far-reaching effect in the whole

history of science: the method of fluxions, decomposition of light and the

law of gravitation.

As a young man at Cambridge Newton had read with great interest the

writings of Galileo, he knew the geometry of Descartes, and he had already

partly worked out the methods of calculus, which he called the method of

fluxions. So when he began to think “of gravity extending to the orb of the

moon”, as he wrote, he immediately put this idea to the test of

calculation.

When Newton first began his calculations the available information of the

earth’s radius and of the moon’s distance were not accurate. The relative

distance between the various planets was not accurately known at the time.

Newton did not know whether he could treat the sun and the planets as

though they were points, concentrated at their respective centres through

which he could assume the forces acted so he put his calculations aside and

let the problem wait.

For some years he studied light, in which subject alone his work was

enough to place him in the first ranks among men of science.

Newton performed many experiments with light and found that white light

was made up of rays of different colors. He invented the reflecting

telescope, that was very small in diameter, but magnified objects to forty

diameters. Newton developed a mathematical method which is now known as the

Binomial Theorem and also differential and integral calculus.

In 1669 he was appointed professor and began lectures on mathematics and

optics at Cambridge.

Newton’s Theory of gravitation

Some years after Newton had begun to work on the problem of gravitation a

French observer made a new estimate of the earth’s radius, and reported his

results at meeting of the Royal Society. Newton then reviewed his old notes

and examined the information he had. He found that now he was nearer to the

solution of the problem than before, but he did not publish his results, he

was still not satisfied, because his theory was not completely worked out.

However, the time had come to publish his results on gravitation because

the problem was being discussed on all sides. An important work on

centrifugal force by a Dutch scientist Christian Huygens appeared in 1673.

The mathematical difficulties seemed insurmountable, so Huygens, together

with some Fellows of

the royal Society approached Newton on the subject. He

was asked what path a body would take if it were attracted by a mass with a

force acting inversely as the square of the distance. And Newton’s

immediate answer was, “an ellipse.”

Newton gathered together all his earlier calculations, and succeeded in

completing his whole theory. First he examined the general problem of the

attraction of one mass by another. He showed that a massive sphere attracts

another as if the whole mass were concentrated at tthe centre. This was a

result of great importance. It enabled Newton to treat the problems of the

sun, moon and earth like problems of geometry, for the masses of these

bodies could he treated as if concentrated at points. Thus he at last

justified the method of treatment which he had first adopted for the

problem of the earth and moon. The proof of his inverse square law was now

complete. He had demonstrated that the gravitational pull of the earth

extends as far as the mmoon and keeps it in its orbit. He demonstrated that

this pull is in accordance with the same law as that by which a stone falls

to the ground, namely gravity.

[pic] Newton

Newton then showed that the inverse square law represents not only

Kepler’s third law, but his first two laws as well. Thus he not only

combined the three results of Kepler, but the extended his own theory of

gravitation to the movements of the planets round the sun. the whole

machinery of the solar system was thus brought under the sway of one law,

which states that every particle attracts very other particle with a force

which changes inversely as the square of the distance between them. This

statement is part of Newton’s law of gravitation, which, together with all

his other theories, was given to the world in his great work Elements of

Natural Philosophy published in 1687.

It is interesting to mote that Newton did not want to publish his book. He

locked it in his desk aand decided to keep it there forever.

However, other scientists began to take interest in the subject of

gravitation. Astronomers, physicists and others talked about it at

conferences in London. Wren, the famous architect, offered a prize to any

scientists who could prove why the path of a planet must be an ellipse. But

nobody could solve the problem. Newton said he had already got the answer,

and promised to send his manuscript some time later. Halley received the

manuscript in the autumn of the same yyear but Newton’s great work, Elements

of Natural Philosophy, was published only in the middle of 1687. With this

book, a new period in the development of science began.

Newton’s law of inverse squares thus joined in one simple mathematical

statement the behavior of the planets as well as of bodies on this earth.

It was the first synthesis of physical knowledge. As such his contribution

to science is unique.