Gravitational acceleration

The acceleration of any object at the Earth's surface (g) is determined by the distance of the object from the center of the Earth radius (R), Newton's constant (G) and the mass of the Earth mass (m), given by the expression:

"g =  G * m/R^2" 

Using the radius of the R= 6 x 106 meters, m= 6 x 1024kg, this gives approximately 9.8m/s^2.

Also as an S-expression:

"(= g (* G (/ m (^ R 2))))" 

In formulae, typically has symbol g.