Newton was 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 mathematics 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 unified picture 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, not round.
Isaac 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.
The 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 change
The 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.
When 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.
Isaac 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.
Isaac 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.
Three Laws and Rockets
Issac Newton's Three Laws as appiled to rocketry.
Sir Isaac Newton was an English
scientist (1642 - 1727) who invented the reflecting telescope in 1668.
Newton always considered himself
a natural philosopher, and the central strand of his scientific development
consisted of his speculations on the nature of physical reality, speculations
that led him away from the reigning mechanical philosophy and to a major
modification of it that asserted the existence of forces acting at a distance.
Newton, Sir Isaac (1642-1727), mathematician
and physicist, one of the foremost scientific intellects of all time.
Ye Shoulders of Giants
His contribution to establishing
science and the scientific method as providing the best description of
the material world, and the awe in which he was held by his contemporaries,
were neatly encapsulated early in the eighteenth century by the poet Alexander
Pope, with his famous couplet Nature and Nature's laws lay hid in night:
God said, Let Newton be! and all was light.
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