* Newton's First Law of Motion (Inertia): This law states that an object at rest stays at rest, and an object in motion stays in motion at a constant speed and direction *unless acted upon by a net force*.

* Friction is a Force: In the real world, objects often slow down due to forces like friction (air resistance, ground friction). These forces oppose the motion of the object. However, if there are truly no forces acting on an object, it will continue moving at a constant speed and in the same direction forever.

Example: Imagine a spaceship in the vast emptiness of space, far away from any gravitational influence. If it's moving, and nothing is pushing or pulling on it, it will keep moving at the same speed and in the same direction forever.