**4. Simultaneity is not relative**

A similar problem affects textbook examples attempting to prove that *simultaneity* is somehow dependent on motion of an observer [6]. Either two events occurred at the same time t, or they occurred at two different times. For example, two light waves or sound waves of fixed speed, produced at the same instant, arrive at an observer at different times if the observer is in motion and shifts from the midpoint. This is due to different distances for each wave to reach him. This does not mean that the waves were themselves produced at different times, but that they traveled different distances to reach him. The stationary observer directly at the midpoint between the two sources would of course conclude correctly that the waves were produced simultaneously. A moving observer must adjust the distance to the source origins by the amount he shifted from the midpoint during the wave travel time, to know whether they were simultaneously produced.
