• On the relativity of rotation 

      Grøn, Øyvind (Nuovo cimento. B;(7), Journal article; Peer reviewed, 2010)
      The question whether rotational motion is relative according to the general theory of relativity is discussed. Einstein’s ambivalence concerning this question is pointed out. In the present article I defend Einstein’s way ...
    • The twin paradox and the principle of relativity 

      Grøn, Øyvind (Physica Scripta;87(3), Journal article; Peer reviewed, 2013-02-14)
      The twin paradox is intimately related to the principle of relativity. Two twins A and B meet, travel away from each other and meet again. From the point of view of A, B is the traveller. Thus, A predicts B to be younger ...