The Gravitational Field

We can represent the force of gravitational attraction as a field. A field is a graphical representation of the strength of a force and the direction in which the force is felt.

Figure 1. A Uniform field

In a local region on the surface of the Earth the gravitational field is essentially uniform. We can see this because the number of field lines per unit are does not change. If the force was stronger in a particular region, the number of field lines in that region would increase. The lines of force act downwards toward the centre of the Earth but on this scale the gravitational field is uniform as shown in figure 1.

Figure 2. Gravitational field on a larger scale.

On a larger scale, the gravitational field varies in direction and magnitude. The direction of the field lines is perpendicular to the surface of the Earth. As the height above the surface of the Earth increases the magnitude of the force decreases as is shown by the increasing separation of the field lines.

Figure 3. The Earth’s gravitational field as a whole.

Considering the Earth as whole, (Figure 3), the gravitational field is directed toward the centre of the Earth. On opposite sides of the Earth the gravitational field has an opposite magnitude.