General Lorenz transformation is not group

archipatelin

Thank you everybody for help!
I see. I thought intuitively (corse wrongly), that they frames are mutually in parallel relation. For special lorentz transformation (movement is on shared axis X), where is contracting just axis X and Y,Z are no changes, relation of parallel is true. But for general direct of valocity (general lorentz transformation) is occurs a contraction of each axis (X,Y,Z) in direct of velocity.Therefore cannot speak about parallel, and exist a appended rotating tranformation is needed.
Thus to understand the new.