# What is gravity on earth surface, theory and its concept

Once in everyone’s life, u might have come across a moment when u would have stared at the sky and thought about the outer space. u might have thought about the force which holds u down to earth.

Besides, u might have thought why can’t u fly like a bird and so on. If u are getting my point I am actually trying to draw your attention towards my today’s topic and that is what is gravity.

If u are a science student and looking for the meaning of what is gravity then my topic will definitely be going to help u today.

So let’s start the journey to find out the topic gravitational force.

## what is gravity?

All the matter that exists and visible to us is known as an object. On the other hand invisible matter inside the object like atom, neutron, proton, electrons are separate forms of particles represents the molecular structure.

besides, when these particles gather collectively form a mass. This mass has some weight that can be measured in units like gram, milligram, kg, etc. Gravity is the only cause for objects to stay stable and seems to stick towards the earth’s surface.

without gravity, things may be seemed floating above the earth’s surface. This can be easily compared with the moon where gravity seems lower and 1/10th of the gravity of earth. In addition to this, Astronauts feel zero gravity at space when they leave the earth’s surface.

### The gravity of Outer space

Above all in the solar system where the planets and sun maintain a balanced form of attraction are simply awesome.

How do the planets rotate to the sun on a fixed path in an orbit is interesting.

In addition to this, how does the sun manage all of the planet to make it happen is a subject of invention and experiment.

Not only invention but also the imagination of natural phenomena where it comes from is quite interesting for scientists till now.

Many scientists and physicists gave many theories on gravity satisfactorily so far.

However, to understand the phenomena in true sense is vast and out of human ability.

In fact, the exact theory behind gravity and it’s existence could solve the mystery we all want to know.

And that is how the universe comes to its existence. scientists have been searching and experimenting with all the facts they achieve year by year.

However, some of the scientists tried and also gave some close theory describing the phenomena of gravity scientifically.

But in a true sense, nobody till now close to finding the real cause behind the gravity when black holes have come to the picture.

However, this theory is on the progress mode and soon we will have the real meaning behind gravity.

## Let’s see some of the concepts of Gravity according to philosophers, physicists, and scientists.

There has been an evolution in experiment and development in every generation for deriving the meaning of earth’s gravity. However, it has also be seen that every concept has its own specific belief. Which is later found contradict by other scholars in their later experiment.

It is also interesting to know that while one invention takes place the other starts rising in order to complete the lack of the previous one. In this way, the process has been continuing till now.

Let’s study theories of gravity according to the Ancient world.

#### Theory of Archimedes on gravity.

According to Archimedes if two objects possess the same mass but their center of gravity is established differently.

Then the masses taken together has a center of gravity at the middle of the line joining between the center of masses of the two object.

He also discovers the center of gravity of the triangle for the first time using this concept of gravity.

Concept of Aristotle and polymath Nicolas about gravity.

Ancient scholars hoping to describe the universe in their own ability and knowledge. They said the universe came up with its own expectations and natural phenomena for why things fall below the ground.

The Greek philosopher Aristotle maintained that objects have a natural inclination to move toward the center of the earth, which he considered to be the middle of the Earth.

Besides, he believed that higher mass objects have more gravity and more inclination towards the earth.

The Polish polymath Nicolas Copernicus comprehended the paths of the planets in the solar system. According to him the sun in the middle of the solar system attract the planets with certain force to balance the solar system. All indicate the force of gravity and make much more sense.

#### Aryabhata and bramgupta on gravitational force.

Both these scholars in ancient India described their point of view on earth’s gravity. According to Aryabata whenever an object is thrown upward in the outward direction it falls back. He indicated the Force which pulls back on earth’s surface is due to the rotation of the earth. Bramagupta in ancient India used the term gurutvaakarshan for the first time for gravity.

#### Galileo Galilei views on gravity.

According to Aristotle the higher weight object have a higher gravitational force of attraction. That means when u consider the two objects with different mass always the higher mass has considerably more gravitational force.

But Galileo contemporary to Aristotle proved it wrong when he did his experiment. In his experiment, he dropped a ball from the tower of Pisa to discover the acceleration of gravitational force. Subsequently, he did another experiment of the ball fall from an inclination.inorder to determine the differences between above the experiments.

However in both the experiment he found that the acceleration force is the same for both the object. In addition to this, he discovers that the ball either higher weight or lower weights are only affected by the air resistance.

Due to the air resistance the acceleration of force changes. Besides, he gave hint for the first time that the lower weight masses posses less gravitational force on air. As a result, they fall slowly in the ground as compared to higher weight objects.

After these concepts, the later physicist had their own path of discovery expanding the facts already found.

### Introduction of modern physics

#### Newton’s discovery on earth gravity.

according to Newton law of gravitation states that every object in this universe attracts each other with a particular force of attraction which directly proportional to the product of their masses and inversely proportional to the square of the distance between the center of their masses.

The above definition is also represented by the formula.

F =Gm1*m3/r2

Here u can learn it by heart or u can understand it by doing deep analysis. So let’s do an analysis to understand the concept of Newton’s law of gravity.

According to Sir Isacc Newton: in this universe whatever we see has a shape, size and exists in the form of particles. these particles in whole represent a mass or u can say posses some weight. This mass or weight has a tendency to attract another mass with a certain calculated amount of Force.

This force is nothing but the Gravitational force or force of gravity. Gravitational force varies masses to masses. That means whenever u put two different masses in this formula F = Gm1*m2/r2 each time u get a result accounting to your input.

In this formula, m1 represents the wight of one particular object and m2 represents the weight of another object. Again if u go through the formula and definition a word has come “the center of masses”. That means in this universe whatever object exists has a center inside it.

Now a question arises where is the position of this center reside. However to find out the position of the center we do have some experiments to find out. It can be easily understood by seeing the below image.

in the image arrow mark indicating the center of gravity. It is the point where gravity tends to its best effect. When u think about the mass this point is taken as a reference when the center is considered. So the distance between two masses indicates length between the center of gravity between two masses.

#### Explore more on distance

Furthermore, from the definition, it is revealed that the Gravitational force is inversely proportional to the square of its distance. What does it mean? Here it means that when distance increase the gravitation force decreases and vice verse.
The force F and G is gravitational constant directly proportional. G is constant has a fixed value depending upon the geographic location on earth.

#### Henrey Cavendish experiment

English scientist Henrey Cavendish was the first man who experiments the theory of Newton in 1797-98. The experiment was to draw the gravitational force between two masses to see the output. After the experiment, they came to a conclusion to decide the actual value of gravitational constant “G” stated in Newton’s gravitational formula.

Image source – Google | image by https://commons.m.wikimedia.org/

In his experiment, he used two balls one had lower mass or weight than the other ball. As per newton’s law, the masses attract each other. so here you can see the balls goes down with the higher masses, indicating lower masses attract higher masses.

He used a 6 feet long wooden road placed horizontally to the surface of the earth. This wooden road was suspended by a wire, the rode is attached with two-sphere each side. Each sphere having a weighing weight of 0.73 kg and a 2-inch diameter radius each. besides, another two balls having a weight of 158kg each suspended over the horizontal road with a separate suspension system.

Theses balls are placed in such a way that the distance between the small ball and the big one is maintained by 9 inches on either side. This experiment was done to see the gravitational effect of balls with different masses, how it attracts with each other.

#### Observation of the experiment

With observation passes it has been seen that the two balls at the end of the rode change their initial position. This indicates that the two big balls attract the smaller one with a certain amount of force.

This force ultimately affects the horizontal rode and it moves to change its position in order to maintain the balance. As horizontal rode change its position it created a certain angle to its initial position. When this angle measured it gave the output of the twisting force applied on the balls.

eventually, how much gravitational force of the earth was applied on the pair of the ball was found by weighing the ball. Later on, arriving conclusion from this experiment and from Newton’s law of gravitation the specific gravity of the earth was calculated.

#### General relativity Theory

General relativity theory is also known as Einstein’s General relativity theory. Which gives an overview of the relation between space and time. The concept has been established by Albert Einstein in 1915.

The fundamental of general relativity is that space and time are two major aspects of spacetime. Spacetime is a curved establishing relation to the curvature between gravity, matter, energy, as well as momentum. The connections between those forces are displayed from the Einstein field equations.

This theory can be understood by a good illustration to make a correlation between gravity, momentum, matter.

#### Illustration for better understanding

A good illustration is that two individuals, one in an elevator sitting around the surface of the planet, and another in an elevator in outer space accelerating at 9.8 m/s2, will each observe the identical behavior of an item they fall in their hands.

The thing will accelerate into the ground in 9.8 m/s2 in either instance, which makes it impossible to differentiate whether they are at rest in a specific field or accelerating upwards at the same specific gravity g. There are lots of kinds of this equivalence principle.

#### Effect of Centrifugal force

The Sun is seen as this sort of valley in spacetime, and among the other things in the valley would be your Earth. The Earth doesn’t roll straight towards the Sun since it’s moving overly quickly. The power pulling on the Earth towards the sun is around the same as another force. This second drive is known as the centrifugal force.

The centrifugal force is present since the Earth moves around the sun sidewise. Since the Earth has a centripetal force act towards the center of the sun. This can be seen in space between the moon and earth. Their relation can also be compared to find centrifugal force acts of the earth on the moon and vice versa to find centripetal force.

#### The outcome of relativity theory

Relativity theory states that the law of physics remains the same for all observers who are not in motion. In addition to this, it also gives the concept of speed of light in a vacuum which is independent of the observer whether it is moving or remain still. This concept later give the introduction of special relativity theory on gravity and established a new concept for space and time.