A field has a magnitude and a direction at every point in space. The Earth's gravitational field is 9.8 m/s² pointing toward the center of the Earth.

Gravitational field:   g

=

F m

where F is the force of gravity.

Near the Earth's surface, the field is uniform. The strength of a field is reflected by the density of field lines - a uniform field has equally-spaced field lines.

Further from the Earth, the field is non-uniform and radial. The field lines separate as they get further from the Earth, reflecting the fact that g decreases with distance. At any point, the field-line pattern shows the direction of the gravitational force that would be experienced by a mass placed at that point.