Here's why:
* Motion is always relative: There is no absolute motion. We can only describe an object's motion in comparison to something else.
* Frame of reference: A frame of reference is a set of axes (like x, y, and z) that we use to define position, velocity, and acceleration.
* Relative motion: When we say an object is moving, we are actually describing its motion relative to a chosen frame of reference.
For example:
* A person walking on a train is moving relative to the train.
* The train is moving relative to the Earth.
* The Earth is moving relative to the Sun.
The concept of relative motion is essential in understanding how objects move in the universe and is fundamental to physics and astronomy.
