ABSTRACT
It was previously pointed out that ‘motion’ in relativity theory is defined in a more general sense than it is in classical physics. I will now elaborate on this somewhat further. With the classical approach, when we talk about space and time, we refer to absolute coordinates of measure. The classical ‘motion’ then refers to changes of spatial measures with respect to a time measure. For example, the x1-component of the velocity of a particle of matter is called cm/sec, where δt denotes the same change of time measure to all observers. Thus,
is the ‘rate of change’ of the spatial measure in the x1 direction with respect to the time change δt.
