Why do objects in space continue moving indefinitely?

Objects in space continue moving indefinitely due to the absence of friction and other resistive forces.

In more detail, the principle that governs this phenomenon is Newton's First Law of Motion, also known as the Law of Inertia. This law states that an object at rest will stay at rest, and an object in motion will stay in motion, unless acted upon by an external force. On Earth, we're used to seeing things come to a stop because of forces such as friction or air resistance. However, in the vacuum of space, these forces are virtually non-existent.

When an object is launched into space and it escapes the gravitational pull of the Earth, it will continue to move in a straight line at a constant speed. This is because there are no significant forces to slow it down, change its direction, or speed it up. This is a direct application of Newton's First Law.

Gravity does play a role in space, but it doesn't stop objects from moving indefinitely. Instead, it changes their direction. For example, the Moon doesn't fall into the Earth because it's moving sideways fast enough that, despite being pulled towards the Earth, it keeps missing it. This perfectly illustrates the concept of an orbit, as further explored in our notes on satellites and orbits.

Understanding the different types of energy in physics can further elucidate why objects in space continue moving. Kinetic energy, in particular, is crucial in the context of objects moving in the vacuum of space.

In conclusion, the absence of friction and other resistive forces in space allows objects to move indefinitely, as per Newton's First Law of Motion. Gravity can change an object's direction, but it doesn't stop its motion.