The relativity of Simultaneity
• Simultaneity refers to the idea that different things can happen at the same time.
• Einstein's introduction of Special Relativity complicated this idea.
• The principle of simultaneity is that: Events that are simultaneous in one frame of reference will not be simultaneous in another frame of reference.
• This is explained through a thought experiment (Click here for a demonstration):
• A man at Point C, equidistant from Point A and Point B, observes a railroad
• The instant the man at Point D passes by Point C in a train moving at a relativistic speed \$v\$, Lightning strikes at Point A and Point B
• To the observer at Point C, the strikes will be simultaneous as he is equidistant from A and B
• Yet, by the time the light waves reach the observer on the train, the train has travelled \$vt\$ to Point D'.
• Thus the light waves from B take less time to reach the observer than light waves from A as the distance is shorter.
• Therefore, the person in the train would perceive that Lightning struck B before it struck A.
• Although there is a difference in the perception, Einstein states that both the observations are correct.
page revision: 1, last edited: 05 Mar 2011 13:13