|Education : Physics|
Gravity is the name given to the force of attraction between any two masses.
The key idea is that any substance with mass will exert its own attraction on other matter, even if this is negligible, and this is gravity.
The earth is truly massive, and its gravity pulls you towards it, hence you stay on your feet. The moon is less massive and its gravity is much less - you can jump higher.
Key point: the greater the mass, the greater its gravity. This makes sense: all the planets orbit the Sun because it has by far the greatest mass.
Questions about gravity: