Gravity does not have a direct effect on friction, as friction is not affected by the force of gravity. However, gravity can indirectly influence friction by affecting the normal force. Normal force is the force exerted by a surface on an object in contact with it, perpendicular to the surface. Friction is a force that opposes the relative motion of two objects in contact, and its magnitude is proportional to the normal force.

Therefore, changes in the normal force can indirectly affect the magnitude of friction. For example, if an object is placed on an inclined surface, the normal force exerted on it will be smaller than if it were on a horizontal surface. This will cause the friction force to be smaller as well, making it easier to move the object up the incline.

In summary, while gravity does not have a direct effect on friction, it can indirectly influence friction by affecting the normal force, which in turn affects the magnitude of friction.