The
standard acceleration due to gravity (or
standard acceleration of free fall), sometimes abbreviated as
standard gravity, usually denoted by or , is the nominal
gravitational acceleration of an object in a vacuum near the surface of the Earth. It is
defined by standard as , which is exactly (about , or ). This value was established by the 3rd
CGPM (1901, CR 70) and used to define the standard
weight of an object as the product of its mass and this nominal acceleration. The acceleration of a body near the surface of the Earth is due to the combined effects of
gravity and
centrifugal acceleration from rotation of the Earth (but which is small enough to be neglected for most purposes); the total (the apparent gravity) is about 0.5 percent greater at the poles than at the equator.