# Gravity

###### What is it ?

Gravity is a force that pulls each massive body towards each other. It is responsible for the fall of objects towards the ground and the elliptical trajectory of celestial bodies around their star.

Gravity was theorized by English astronomer and physicist Isaac Newton in the 17th century. Newton relies on the work of Galileo who observed that all objects fall to the ground at the same speed, regardless of their mass. Newton had the intuition that this was due to a universal gravitational force exerted by the Earth. Newton also formulated the laws of mechanics which describe the movement of bodies under the influence of gravity. According to these laws, the gravitational force between two bodies is proportional to their mass and the distance between them, and it always acts along a line that connects the centers of mass of the two bodies. Later, German physicist Albert Einstein developed the theory of general relativity, which provides a more accurate description of gravity by taking into account the effects of the speed of light and the curvature of spacetime. According to this theory, gravity is the result of the curvature of spacetime caused by the mass and energy of bodies. "

"Kinetic energy is the energy that a moving object possesses. It is directly related to its speed and mass, and can be calculated using the following formula:

Kinetic energy = 1/2 * mass * velocity^2

The heavier an object is and the faster it moves, the more kinetic energy it has.

An example of kinetic energy is the movement of a soccer ball kicked by a player. When the ball is kicked, it acquires kinetic energy due to the force exerted by the player's foot, which gives it high speed. The higher the speed of the ball, the more kinetic energy it has.

"The Law of Gravitation is a physical law that describes the gravitational attraction between two bodies. It states that all bodies in the universe are attracted to each other with a force proportional to their mass and inversely proportional to the square of the distance between them.

The law of gravity was discovered by English scientist Isaac Newton in the 17th century. He also developed the mathematical formula that describes it:

F=G*(m1*m2)/d²

where F is the gravitational force (in newtons), G is the gravitational constant (6.67 × 10^-11 N.m²/kg²), m1 and m2 are the masses of the two bodies (in kg) and d is the distance between them (in meters).

An example of this law is the gravitational attraction between the Earth and the Moon. The gravitational force between these two bodies can be calculated using the above formula. If the mass of the Earth is 5.97 × 10^24 kg and that of the Moon is 7.35 × 10^22 kg, and if the average distance between these two bodies is 3.84 × 10^8 meters, then the gravitational force acting between them is:

F = 6.67 × 10^-11 * (5.97 × 10^24 * 7.35 × 10^22) / (3.84 × 10^8)² = 1.23 × 10^20 N

According to Albert Einstein's theory of general relativity, gravitation is not a force that pulls bodies together, but rather a curvature of spacetime caused by the presence of mass or d 'energy. When a massive body, like a planet or a star, is present in the universe, it "digs" a kind of ""hole"" in space-time due to its mass. The other bodies which are near this hole, like satellites or objects in free fall, are attracted towards it by following the curve of space-time. This is what creates the gravitation effect.

Einstein developed an equation to describe this curvature of spacetime, known as the equation of general relativity. This equation predicts with great precision many phenomena observed in the universe, such as the deflection of light by the Sun and the precession of the perihelions of the planets of the solar system. The theory of general relativity is one of the most important and successful theories in modern physics.

###### Experiments using FizziQ

Compute the value of gravity g with your smartphone : https://www.fizziq.org/en/team/galileo