The Twin Paradox and the Nature of Physical Reality

The role of the observer is essential in determining the reality as well as making measurements of the state of a physical situation. This observation becomes important in elaborating a long-standing paradox of physics known as the Twin Paradox of the Special Theory of Relativity (STR). Einstein showed that the time interval between two events determined by a moving observer is greater than that determined by a stationary observer. The effect is known as time dilation. However, it leads to the paradox that a twin brother returning from a space trip is younger than his twin sister who had stayed home. The resolution of the paradox is assisted by introducing a new requirement of physics called the “reality test.” This states that whatever an observer measures must be real. It also reveals that discrepancies in time measurements can be attributed to the change of state the traveling twin undergoes as he changes velocity over the journey.