What are action-at-a-distance forces?

Action-at-a-distance forces are defined as forces that can exert influence between objects without needing to be in physical contact with them. Examples of such forces include gravitational force and electromagnetic force, both of which can affect the behavior of objects over distances. For instance, the Earth's gravity pulls objects toward its center, even when there is significant space between the object and the planet. Similarly, magnetism can attract or repel objects without the need for direct contact.

This phenomenon contrasts with contact forces, which only operate when there is physical interaction between objects, such as friction or tension. Understanding action-at-a-distance forces is crucial in physics, as they describe interactions that take place across non-physical barriers, allowing for a broader understanding of how forces operate in the universe, particularly in fields like astrophysics and electromagnetism.