When an object's distance from another object is changing it is in motion. Whether an object is moving or not depends on your point of view. For example, a man riding on a train is not moving in relation to the seat he is sitting on, but he is moving in relation to the buildings the bus passes. In order to detect motion you must compare it to something that is not moving. A reference point is a place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point.
Be careful what you compare a moving object too:
Be careful what you compare a moving object too:
- Sitting still while objects around you move
- Being at the same speed
- Sitting still on a moving object