Max von Laue

“ What is unsatisfactory for some in this way of conclusion, is the fact that it only gives a reason for its recognition, but not a cause; it doesn't follow the causal relation of reality. Before we attempt to fill this gap, we still want to emphasize that such a deviation of the line of reasoning from the causal interconnection is nothing unusual in physics. On the contrary, its value for science (especially as regards the most general natural laws) rests on the fact, that it relieves us from the effort, to follow the often less vivid causal-connections of nature in all details. ”

“ The consequence will be, that the previous shape of the body doesn't correspond to an equilibrium state, on the contrary, we must apply external forces to maintain its shape. If the force is missing, as it is assumed in the discussion about the Lorentz contraction, then the shape must vary. ”

“ That this conclusion wasn't drawn before the relativity theory, was only due to the fact that this reference system was previously materialized as "aether". But relativity theory has banished the idea of a corporeal aether.
Now we come back to the body, which at first rests in system , but afterwards it obtains a motion against . Its shape is the result of the equilibrium existing between the forces acting from atom to atom (this word is used in the widest sense, thus with the inclusion of electrons or similar things) . If we set the body in motion with invariable shape, i.e. ”