Newton, Isaac

English scientist and mathematician

Born: Woolsthorpe, Lincolnshire, December 25, 1642

Died: London, March 20, 1727
"If I have seen far, it it because I have stood upon the shoulders of giants." - Isaac Newton

Newton



Newton was born prematurely in the year that Galileo died. He showed no signs of unusual brightness until well into his teens. His uncle urged him to attend college in Cambridge and he graduated in 1665. By this time, Newton had already worked out the binomial theorem in mathematics and was developing what was later to become calculus.

When the great plague struck London in 1666, Newton retired to his mothers farm to avoid the danger. While there he watched an apple fall to the ground from a tree, and wondered if the force that caused the apple to fall was the same force that held the moon in its place. Newton theorized that the rate of fall was proportional to the gravitational force, and that this force decreased according to the square of the distance from the center of the earth. Strangely, Newton put aside the problem of gravitation, and only returned to it fifteen years later.

Meanwhile, the writings of Kepler on optics, had interested Newton and he experimented with prisms. Newton was able to show that the colours of the rainbow, red, orange, yellow, green, blue and violet, combined to make white light. He proved this by passing the rainbow colors through a second prism, producing white light again.

The prism experiments made Newton famous and in 1669, at the age of twenty-seven, Newton was made a professor of mathematics at Cambridge. At that time, the refracting telescopes in use were reaching the limits of their usefulness. Light passing through the lenses cast coloured shadows, blurring the detail of heavenly bodies, a phenomenon known as "chromatic aberration". Newton then invented the relecting telescope that concentrated light by reflection in a parabolic mirror, eliminating chromatic aberration. The prism work of Newton was later to result in the invention of the spectrograph by Kirchhoff.

In 1684, a friend asked Newton how he thought the planets moved. "In ellipses." said Newton at once. "How do you know?" the frend replied. "Why, because I have calculated it." Newton thus returned to his study of gravity. He published a book entitled Philosophae Naturalis Principia Mathematica in which he formulated his famous three laws of motion. Namely, without an outside force, a body will remain at rest, force equals mass times acceleration, and, for every action there is an equal and opposite reaction.

From these three laws, Newton was able to deduce the manner in which the gravitational force between the earth and the moon could be calculated. The equation is a famous one: F = Gm1m2/dē, where m1 and m2 are the masses of the earth and moon, d the distance between their centers, G the gravitational constant and F the force of the gravitational attraction between them.

In 1703 Newton was elected president of the Royal Society for the rest of his life, and he was knighted by Queen Anne in 1705.

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