Um Erro Com Um Seculo
  The "rigid bodies" must be in Relativity the "deformable bodies" where the longitudinal waves propagate with the maximun speed $c$. In 1909, Born studied the "relativistic underformable body" but made the mistake of calling it "rigid". The "rigid body" one can find in all Relativity books is, in fact, Born's "undeformable body" of 1909. This error was at the origin of a lot of difficulties and paradoxes not yet clarifed in any relativity book. The "relativistic elastic laws for rigid bodies in one dimension" were discovered by Mc Crea, in 1952, and by A.Brotas, in 1968. The generalization of these laws for 2 and 3 dimensions resolve all those paradoxes. We propose the introdution of these laws in the elementary courses of Relativity. 
Antonio Brotas