according to special relativity theory, any object that has relative velocity also has lorenz- contraction L' = L0 *sqrt (1-(v/c^2)) it sounds odd that this is only kind of length contraction known to exist. why there are no other kind of length expansions or contractions, or are them impossible to exist for some reason that comes from relativity- or particle physics theories? -For example If someone would tell you that he has observed an object in space with his telescope that has isotropical length expansion, could you make good argument against his claim? i put here some arguments against that i have found: 1 according to lights spectral lines, supernovas and other events, all laws of nature seems to be same everywhere in observed space 2 In particle physics experiments, no length expansions or contractions have been ever observed 3 if some object would have length expansion, at least it cant move or emit light at superluminal speed - that is not possible according to special relativity theory. 4 Does particle that have isotropic length expansion or contraction have more or less momentum or energy than normal particle? IF SO, where has the particle got its momentum from? What kind of force can have influence to to make the particle have isotropic length expansion or contraction?