Newton was born on the 25th December 1642 and died in 1727. He was born
In Woolsthorpe in Lincolnshire. His father was a farmer but he died
Three months before Newton was born. His mother remarried and Newton
spent his childhood with his grandmother. At school he showed great
skill in making model kites, sundials and windmills. In 1665 when he was
18 he went to study mathematics at Cambridge University. He continued
his studies at home when the University closed because of the plague.
The Reflecting Telescope
Because Newton was working with light in 1668 he made the first
reflecting telescope. The light was collected and reflected from a
curved mirror instead of being refracted through a lens. It was far
superior from the refracting telescopes at that time because it
reflected all the light in the same way. It did not produce colour
fringing or blurring which occurred in the early refracting telescopes.
The Nature of Light
Newton discovered the nature of light when he darkened his room and
"made a small hole in my shuts to let in a convenient quantity of the
sun's light." He passed this beam of sunlight through a prism. When the
light came out of the prism is was not white but was of seven different
colours: Red, Orange, Yellow, Green, Blue, Indigo and Violet. The
spreading into rays was called DISPERSION by Newton and he called the
different coloured rays the SPECTRUM. He learnt that when the light rays
were passed again through a prism the rays turned back into white light.
If only one ray was passed through the prism it would come out the same
colour as it went in. Newton concluded that white light was made up of
seven different coloured rays. The rays were dispersed through the prism
because the rays were reflected at different angles.
Newton wondered whether the different colours of the spectrum travelled
at different speeds. He wrote to Flamstead to ask if when he observed an
eclipse whether the colour changed all at once of at different times.
Flamstead wrote back to him to say that the colours changed all at once.
Newton invented the Calculus branch of mathematics around 1669. He did
not publish his ideas until around 1704, 35 years later. This branch of
mathematics is divided into two parts:
Differential Calculus deals with the rates things change at. When a car
moves off from a halt the distance changes slowly at first. When the
speed increases the distance changes quicker. As shown in the graph
What really happens is shown below:
The car accelerates quickly at first. The acceleration drops as the car
changes gear. The acceleration is zero when the car reaches a cruising
speed. Differential Calculus is used to calculate the orbits of planets
and satellites very exactly.
Integral calculus is used for measuring quantities by dividing them into
many small parts. An example is the area of a circle. The circle is
divided into sectors. As the number of sectors increases the size of the
sectors get smaller. The sectors are arranged into a rectangle:
As the sectors shrink to almost nothing, the shape is almost a
rectangle. The height of the rectangle is almost equal to R (Radius) and
the width is ?C (Circumference), as the circumference is spread between
the bottom and top of the rectangle. The area of the rectangle is R x ?C
. As C=2pR the area of the rectangle is R x ? 2pR or pR2.
The books Newton wrote
Newton's most famous book was called "Philosphe Naturalis Principia
Mathematica" It was published in 1678 and was known as "Principia". The
book contains all his laws of motion and theories of tides and
gravitation. He also wrote another book, "Optiks", which was published
in 1704 and describes the Calculus and other mathematics. It also
describes his theory of light.
Motion and Gravity
In 1670 Newton worked more on chemistry and alchemy than on optics and
mathematics. It is said that Newton wondered why objects fell to earth
when he was sitting in a garden and saw an apple drop in front of him.
This is still believed by some people although many people think it is
untrue. Newton thought back to the subject which he was thinking about
in 1665-66. This was "Why things move as they do." He made three laws of
First Law of Motion
A body continues in a state of rest or to move with a steady velocity in
a straight line if it is not acted upon by forces.
If a ball is kicked in outer space it will continue to move at the same
speed as no forces act upon it, such as friction and air resistance.
If a ball is kicked on earth it will slowly come to halt on the ground
as friction, air resistance and gravity have acted upon it.
Second Law of Motion
When a force acts on body it produces an acceleration which is
proportional to the magnitude of the force.
If a ball is kicked its acceleration is related to the power of the kick
and the mass of the ball. The ball also moves in the direction of the
force. Therefore a small, light ball travels faster than a big, heavy