# Gravity

Gravity is a basic concept of modern physics.

## Newtonian gravity

Newtonian gravity belongs to the classical theory of gravity. Newtonian theory of gravity believes that there is mutual attraction between two masses. This kind of gravitation is also called universal gravitation. The interaction between gravity is expressed by the following formula.

$F=G{\frac {Mm}{r^{2}}}$ ## Relativistic gravity

Relativity theory of gravity is a theory that deals with gravity in a geometric way. Study the strength of gravitational interaction through the change of space-time structure. In general relativity, when a mass appears in space-time, it will cause the space-time to bend, thereby producing gravitational interaction.

## Measurement of gravitational constant

The measurement of the gravitational constant is a process requiring very high accuracy. Need to combine the most advanced science and technology to complete. Due to the rapid development of science and technology, especially the development of materials science, the accuracy of the gravitational constant has been improved. Nevertheless, the accuracy of the gravitational constant is still very low compared to other physical constants, such as electronic charge and Planck's constant.

## Changing gravitational constant

Because the gravitational constants measured by different laboratories vary greatly at different times, and the accuracy is not high, there are many theories that the gravitational constants may be constantly changing.