# What is gravity? Concept of gravity on the solar system

### What is Gravity?

Gravity is a force of attraction. The exact reason why it pulls all things is yet to be ascertained by scientists.

Gravity is defined a natural force that pulls (or attracts) a body towards the center of the earth. It is also defined as a force that pulls a physical body with a lesser mass to another body with a greater mass. You may think of gravity as a magnet that pulls together anything that has mass.

Mass is defined as the quantity or amount of matter a body has.

The earth is governed by the force of gravity and that’s why everything present on it, including humans, plants, animals and even air is always drawn towards it. To overcome gravity, one will need some form of force greater than gravity in order to pull oneself away from the earth.

As an instance, the earth as we know is spherical in shape and held in space. Also, all humans live on a constantly rotating earth (and not inside the earth). Since we live on a spherical earth held in space, how come humans are yet to fall off the constantly rotating earth?

Well, the answer is gravity. Even if we attempt to jump off the earth into space, the force of gravity present on earth will still pull us down. In fact, in order to leave the earth; there has to be a force stronger that gravity; which must be applied to whatever is attempting to leave the earth. For this reason: 'whenever one jumps, a certain amount of force must be applied by that person. However, gravity still return the person back to earth because the applied force had been exhausted.

Planes and jets leave the earth and remain in the atmosphere simply because a certain amount of force is constantly applied to it; and this force is always stronger than gravity throughout its flight.

Also, gravity holds the air we breathe towards earth. As one moves away from the earth, the air becomes thinner until it vanishes. This is why astronauts wear oxygen mask whenever they are in space.

### Gravity on earth and moon

It is important to understand that gravity is not even (the same) all round the surface of the earth. It is slighter stronger on earth surfaces with a greater mass underground than those with lesser masses.

The gravity on earth has also got some impact on its satellites. Think of a satellite as either a machine or moon or planet that revolves around a larger body.

The earth has got one natural satellite (that's the moon) and many artificial satellites. Interestingly, the earth is also a satellite to the sun. This is true because it revolves round the sun.

The earth's natural satellite (moon) constantly revolves around the earth because the earth draws it closer to itself via the force of gravity. Even the moon has its own force of gravity. In short, everything in the universe have got gravity acting on them and that is why they are all held in space. This will include all the planets, the moon, sun, stars and other components of the solar system.

The larger the size of an object, the greater its force of gravity. Gravity is therefore affected by the size and closeness of objects.

Since the earth is larger than the moon, it will have a greater gravitational force than the moon. We will be attracted more to the earth than we would on the moon if we were astronauts on the moon. This implies that we will weigh differently on both places. For this reason, our weight will also vary on the various planets (because they are of different sizes). This is shown in the diagram below:

Weight depends on the degree at which the gravity on earth or moon or another planet pulls an object while the mass of any object or body will always remain the same (constant) since it is the amount or quantity of matter in the body.

### Gravity on the solar system

We can escape earth’s gravitation pull by travelling far away from the earth into space. Since the space is somewhat empty and has no gravity, we will end up floating in it because nothing attracts (pull) us in space. For this reason, astronauts will float in space as a result of a condition termed weightlessness. In simple terms, weightlessness results from a lack of gravity.

It is not compulsory that the force of gravity must pull everything into contacting themselves. It can also bring objects close to one another and not necessarily into contact. For instance the moon, sun, stars and other planets of the solar system does not make contact with the earth; rather, they have varying proximity to it as a result of gravity.

Please read on the planets of the solar system and their characteristics here

Other planets have their moons and they revolve around them. This is also a result of gravity that exists between these planets and their respective moons.

The scientists Sir Isaac Newton and Albert Einstein have been credited for their insight and explanations on gravity.

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