Falling is movement due to gravity, but also has other uses not directly related to gravity.
Sensation
A sensation of falling occurs when the labyrinth or vestibular apparatus, a system of fluid-filled passages in the inner ear, detects motion. The same system also detects rotary motion. A similar sensation of falling can be induced when the eyes detect rapid apparent motion with respect to the environment. This system enables us to keep our balance by signalling when a physical correction is necessary.When a human is in free fall in an orbiting spacecraft, or in an aircraft in a steep dive, the sensation of falling is constant, and the sensation of there being an "up" and a "down" is missing or much attenuated. Some medical conditions, known as balance disorders, also induce the sensation of falling.
Accidents
Falling is a major cause of personal injury, especially for the elderly whose vision, nerve conduction and muscles are weaker, whose vestibular sense is diminished, whose
Source:
http://en.wikipedia.org/wiki/Falling