born in 1642 in a manor house in Lincolnshire, England.
His father had died two months before his birth. When Isaac was
three his mother remarried, and Isaac remained with his grandmother.
He was not interested in the family farm, so he was sent to Cambridge
University to study.
Isaac was born just a short time after the death of Galileo,
one of the greatest scientists of all time. Galileo had proved
that the planets
revolve around the sun, not the earth as people thought at the time.
Isaac Newton was very interested in the discoveries of Galileo and
others. Isaac thought the universe worked like a machine and that
a few simple laws governed it. Like Galileo, he realized that
was the way to explain and prove those laws. Isaac Newton was one
of the world’s great scientists because he took his ideas,
and the ideas of earlier scientists, and combined them into a
of how the universe works.
Isaac Newton explained the workings of the universe through mathematics.
He formulated laws of motion and gravitation. These laws are math formulas
that explain how objects move when a force acts on them. Isaac published
his most famous book, Principia, in 1687 while he was a mathematics
professor at Trinity College, Cambridge. In the Principia, Isaac explained
three basic laws that govern the way objects move. He then described
his idea, or theory, about gravity. Gravity is the force that causes
things to fall down. If a pencil falls off a desk, it will land on
the floor, not the ceiling. In his book Isaac also used his laws to
show that the planets revolve around the suns in orbits that are oval,
Newton used three laws to explain the way objects move. They
are often call Newton’s Laws. The First Law states that
an object that is not being pushed or pulled by some force will
stay still, or will keep moving in a straight line at a steady
speed. It is easy to understand that a bike will not move unless
something pushes or pulls it. It is harder to understand that
an object will continue to move without help. Think of the bike
again. If someone is riding a bike and jumps off before the bike
is stopped what happens? The bike continues on until it falls
over. The tendency of an object to remain still, or keep moving
in a straight line at a steady speed is called inertia.
Second Law explains how a force acts on an object. An object
accelerates in the direction the force is moving it. If someone
gets on a bike and pushes the pedals forward the bike will begin
to move. If someone gives the bike a push from behind, the bike
will speed up. If the rider pushes back on the pedals the bike
will slow down. If the rider turns the handlebars, the bike will
Third Law states that if an object is pushed or pulled, it will
push or pull equally in the opposite direction. If someone lifts
a heavy box, they use force to push it up. The box is heavy because
it is producing an equal force downward on the lifter’s
arms. The weight is transferred through the lifter’s legs
to the floor. The floor presses upward with an equal force. If
the floor pushed back with less force, the person lifting the
box would fall through the floor. If it pushed back with more
force the lifter would fly into the air.
most people think of Isaac Newton, they think of him sitting
under an apple tree observing an apple fall to the ground. When
he saw the apple fall, Newton began to think about a specific
kind of motion—gravity. Newton understood that gravity
was the force of attraction between two objects. He also understood
that an object with more matter –mass- exerted the greater
force, or pulled smaller object toward it. That meant that the
large mass of the earth pulled objects toward it. That is why
the apple fell down instead of up, and why people don’t
float in the air.
Newton thought about gravity and the apple. He thought that maybe
gravity was not just limited to the earth and the objects on
it. What if gravity extended to the moon and beyond? Isaac calculated
the force needed to keep the moon moving around the earth. Then
he compared it with the force the made the apple fall downward.
After allowing for the fact that the moon is much farther from
the earth, and has a much greater mass, he discovered that the
forces were the same. The moon in held in an orbit around earth
by the pull of earth’s gravity.
Newton’s calculations changed the way people understood the
universe. No one had been able to explain why the planets stayed
in their orbits. What held them up? Less that 50 years before Isaac
Newton was born it was thought that the planets were held in place
by an invisible shield. Isaac proved that they were held in place
by the sun’s gravity. He also showed that the force of gravity
was affected by distance and by mass. He was not the first to understand
that the orbit of a planet was not circular, but more elongated,
like an oval. What he did was to explain how it worked.