An experimantal study is possible provided that; 1) nature is invariant under space-time translations. (so that it is possible to reproduce the results) 2) nature is invariant under Lorentz's group. (and this establishes a possible causal connection between parts of experimental setup) If you agree with me (I hope) on the above, can I say that Poincare' invariance is the reason why we are able to do experiments? If yes, does this reduces experimental physics to theoretical physics? But then, what makes theoretical physics possible? Please note that these are not philosophical questions, so don't be philosophical about them.