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bodies are governed by the same set of natural laws, by demonstrating
the consistency between Kepler's laws of planetary motion and his
theory of gravitation, thus removing the last doubts about heliocentrism
and advancing the Scientific Revolution.

French mathematician Joseph-Louis Lagrange often said that
Newton was the greatest genius who ever lived. English poet Alexander
Pope was moved by Newton's accomplishments to write the famous

epitaph:
Nature and nature's laws lay hid in night;
God said "Let Newton be" and all was light.

Newton was born in the same year that Galileo died. Galileo
performed a number of careful experiments on the motions of bodies.
Galileo studied accelerated motion by dropping bodies and by rolling

balls down inclined planes. Eventually, he became convinced that a ball on
a perfectly frictionless horizontal plane would persist forever in its motion
at constant speed. The revolutionary idea proved most fruitful in
developing the understanding of motion.Newton accepted Galileo's

conclusions and formulated this idea as his first law of motion.
From the original Latin of Newton's Principia:“Lex I: Corpus omne
perseverare in statu suo quiescendi vel movendi uniformiter in directum,

nisi quatenus a viribus impressis cogitur statum illum mutare. ”
Translated to English, this reads:“ Law I: Every body persists in its
state of being at rest or of moving uniformly straight forward, except

insofar as it is compelled to change its state by force impressed.
There are many ways in which this great principle can be enunciated.
Another up-to-date statement is the following:

There are such frames of reference in which bodies conserve
state of rest or uniform motion if force doesn’t act on these
bodies or resulting force is zero.
In the Newton's first law of motion there appears an important

property of matter known as inertia — property of matter by which it
remains in its state of rest or uniform motion in straight line, unless that
state is changed by external force.(Inertia comes from the Latin word,

iners, meaning idle, or lazy). Really, every body doesn't want to change
its state of rest or uniform motion.
When an automobile is suddenly stopped, the passengers obey
Newton's first law and continue in motion with constant velocity until

some external force changes their state of motion. Newton's first law is
often called the inertia law. All matter has inertia. The concept of mass

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