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# Law of gravity

###### What is it ?

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 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 attracts bodies towards each other, but rather a curvature of space-time caused by the presence of mass or energy. When a massive body, such as 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.

###### Experiment with

## Law of gravity

A number of experiments to be conducted with a amsartphone are available to better understanbd the concept of gravity :

Estimation of the value of g using a smartphone acceleromter : https://www.fizziq.org/en/team/galileo

Analysis of the landing of a Space X rocket : https://www.fizziq.org/en/team/space-x

Ancre 1

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