When was the acceleration due to gravity discovered

From the earliest times, gravity meant the tendency of most bodies to fall to earth. Aristotle was the first writer to attempt a quantitative description of falling motion: he wrote that an object fell at a constant speed, attained shortly after being released, and heavier things fell faster in proportion to their mass.

Galileo was the first to get it right. True, others had improved on Aristotle, but Galileo was the first to get the big picture. He also made the crucial observation that, if air resistance and buoyancy can be neglected, all bodies fall with the same acceleration , bodies of different weights dropped together reach the ground at the same time.

This was a revolutionary idea—as was his assertion that it should be checked by experiment rather than by the traditional method of trying to decipher what ancient authorities might have meant. Galileo also noted that if a ball rolls without interference on a smooth horizontal surface, and friction and air resistance can be neglected, it will move with constant speed in a fixed direction—in modern language, its velocity remains constant.

Using his terminology, then, natural horizontal motion is motion at constant velocity , and natural vertical motion is falling at constant acceleration. The crucial step was the realization that for a cannonball in flight, the horizontal and vertical motions can be analyzed independently.

The vertical drop of the cannonball at the end of successive seconds, the lengths of the vertical lines ci , df , eh are the same vertical distances fallen by something dropped from rest. If you drop a cannonball over a cliff it will fall 5 meters in the first second, if you fire it exactly horizontally at meters per second, it will still fall 5 meters below a horizontal line in the first second.

Meanwhile, its horizontal motion will be at a steady speed again neglecting air resistance , it will go meters in the first second, another meters in the next second, and so on. Vertically, it falls 5 meters in the first second, 20 meters total in two seconds, then 45 and so on.

He went on to work out the range for given muzzle velocity and any angle of firing, much to the gratification of his employer. Newton asked the question: what if we put the cannon on a really high imaginary, of course!

Knowing that the radius of the earth R is km, there is enough information in the above diagram to fix the value of v. The units for v are of course meters per second, on our diagram we show v as a distance, that traveled in the first second. This is in fact about right for a satellite in low earth orbit. It occurred to Newton one day possibly because of a falling apple that this familiar gravitational force we experience all the time here near the surface of the earth might extend outwards as far as the moon, and in fact might be the reason the moon is in a circular orbit.

Newton then boldly extrapolated from the earth, the apple and the moon to everything, asserting his Universal Law of Gravitation:.

Now suppose we are considering the gravitational attraction between two bodies as we always are , one of mass m 1 , one of mass m 2. If we think of m 1 as the earth, the force m 2 feels is proportional to m 2 , as argued above—so this must be true whatever m 1 is. And, since the situation is perfectly symmetrical, the force must also be proportional to m 1.

Putting all this together, the magnitude of the gravitational force between two bodies of masses m 1 and m 2 a distance r apart. It is important to realize that G cannot be measured by any astronomical observations. The harder the apple is thrown, the more horizontal distance it adopts and the farther it goes.

What Newton realized is that if the apple is thrown hard enough, it would go into orbit. It would continuously fall, but as it fell it would move horizontally, and it would keep going around the Earth.

Learn more about universal gravitation. He derived a mathematical equation to explain this force. He described a force in terms of four measurable quantities. The first one is the mass of an object.

The second variable is the mass of a second object. The third variable is the distance between these two objects. And finally, there is the force—the gravitational force that ensues. And this is the equation that Newton came up with. He said: force equals a constant—a capital G for the gravitational constant—times the first mass, times the second mass, divided by the distance squared. Consequently, there exists an attractive force of gravity between any two objects that is proportional to the product of their masses, divided by the distance between them squared.

Learn more about celestial and terrestrial mechanics. Newton used rather complicated mathematical reasoning and he demonstrated that stable orbits are possible only if there is a 1 over d2 kind of relationship. Though others had thought about it before him, Newton was the first to create a theory that applied to all objects, large and small, using mathematics that was ahead of its time.

Isaac Newton was born in England in As a young man he went to Trinity College in Cambridge, enrolling first as a student and eventually staying on as a fellow.

During this period he developed the first versions of his three laws of motion, including the law of gravity. During his career, he also made significant advances in the field of optics and the understanding of centrifugal force. He eventually became the first English scientist to be knighted for his work. A popular story says that Newton came up with the theory of gravity instantly, when an apple fell from a tree and hit him on the head. Actually, Newton saw an apple falling from a tree, and it got him to thinking about the mysterious force that pulls objects to the ground.

He compared the straight path of the apple to the curved path of a fired cannonball.