Principle of locality

In physics, the principle of locality states that an object is only directly influenced by its immediate surroundings. A physical theory is said to be a local theory if it is consistent with the principle of locality. An alternative to the earlier concept of instantaneous "action at a distance", locality evolved as a property of the field theories of classical physics. The concept of locality is that, for an action at one point to have an influence at another point, something in the space between the points, such as a field, must mediate the action. To exert an influence, something, such as a wave or particle, must travel through the space between the two points, to carry the influence.