Gravitational Field

Definition

The invisible influence a mass creates in the space around it — any other mass placed there feels a gravitational pull.

$g = \frac{GM}{r^2}$

Symbol: $g$ · Unit: N/kg (or m/s²)

Technical definition

A vector field g defined as gravitational force per unit mass: g = F/m. Near Earth's surface, g ≈ 9.81 N/kg (equivalently m/s²), directed toward Earth's center. More generally, g = GM/r².

Example

Earth's gravitational field at the surface is 9.81 N/kg — a 1 kg mass feels 9.81 N of force. On the Moon, the field is only 1.62 N/kg.

Common confusion

Gravitational field strength and gravitational acceleration are the same number with different units (N/kg vs m/s²) — two views of one thing. And the field exists whether or not a test mass is there to feel it.