The force of gravity is what keeps objects on Earth grounded and prevents them from floating away. It is a force of attraction between any two objects with mass. The more massive an object is, the stronger its gravitational force. On Earth, this force is what keeps us from floating off into space and also determines the weight of an object.
Mass is a measure of the amount of matter in an object, while weight is a measure of the force of gravity acting on an object. Mass is measured in kilograms (kg) while weight is measured in Newtons (N). On Earth, an object's mass and weight are directly proportional, but on other planets with different gravitational forces, the weight of an object may change while its mass remains the same.
The gravitational force between two objects decreases as the distance between them increases. This is known as the inverse-square law, which states that the force of gravity is inversely proportional to the square of the distance between two objects. This means that as the distance between two objects doubles, the gravitational force between them decreases by a factor of four.
Gravity affects the motion of objects by causing them to accelerate towards the center of the Earth. This acceleration is known as the acceleration due to gravity and is approximately 9.8 meters per second squared (m/s²) on Earth. This means that objects will fall towards the ground at a rate of 9.8 m/s², regardless of their mass.
Newton's law of universal gravitation states that every object in the universe is attracted to every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Einstein's theory of general relativity, on the other hand, explains gravity as the curvature of spacetime caused by the presence of mass and energy. It is a more comprehensive theory that accounts for the effects of gravity on a larger scale, such as the motion of planets and galaxies.