Writing on Einstein’s view of physics (and thus on STR), Morrison suggests that STR is “afflicted by a most unfortunate misnomer”: Something can be defined relative to something else, without people being in any way involved. It is relative to something, but that something need not be a subject or a person. Importantly, a relative property need not be a subjective property (Power 2018). Relative is Neither Private Nor Subjective It does not matter, so long as we pick some frame from which to define motion and rest. Or, finding ourselves in complex motion relative to the Earth, we might choose the Earth because the maths is easier. For example, we might choose the frame in which we ourselves are at rest. The frame from which motion is defined can be a matter of convenience, and yet be no less special than any others. We can choose the frame from which things move and are at rest. That is, the frames we use to define speed and motion are arbitrary and conventional. There is nothing special about one frame’s set of values over another frame’s set. If, in frame A, the station moves (and the train rests), then this is as real a motion (or rest) as, in frame B, the station’s rest (or the train’s motion). No matter what is in either frame, the values for speed in В are as real values as different values in A. For example, according to A, the reference frame of the train, the train is at rest and has zero speed according to B, the reference frame of the station, the station is at rest and has zero speed.įurthermore, in modern physics, no individual frame is unique in defining motion or rest no frames are privileged.

In that case, it moves at a different velocity and has a different frame.īased on how frames define motion, what is in the frame is never in motion in that frame it is always at rest in that frame. However, one moves in the opposite direction to the other. For the platform, both move at the same speed. Instead of one train, say that two trains move through the station. This has significant consequences for thinking about values according to different frames.įor example, two things can have the same speed but different directions. As such, a reference frame is defined by speed and direction. Reference frames are coordinate systems for calculating values of spatial and temporal location and extent, with an origin defined by the frame. In physics, this relativity of speed and rest is defined according to reference frames. It also moves relative to anything at rest in the station, such as someone standing on the platform. The train moves relative to the station.It also moves relative to anything at rest in the train, such as the passenger and the cup. The station moves relative to the train.Both train and station are at rest to themselves-as is anything not moving relative to them.

Quartzcode use relative frame