When an observer in a rocket, or even in a stationary room, sees light hitting a rear wall and a forward wall at the same time, he is not actually seeing the light hit the walls at the same time; he is actually seeing the reflected light from each wall arriving at his position at the same time. There are two events: the light hitting the walls (event A), and the reflected light arriving at his eyes (event B). If the observer claims that he sees the light hit the walls, then he’s claiming that event B is event A, and he is thus an idiot.
According to Einstein, and common sense as well, if lightning strikes either end of a moving train simultaneously, then the light from each strike will converge on an observer at the center of the train at two different times, i.e. non-simultaneously. Logically, the converse must also be true: if a bolt struck the center of the moving train, light from the bolt would strike the ends of the train non-simultaneously. From this we can conclude the following: if our observer at the center of the moving train shines a light toward the front and rear of the cabin at the same time, then each light beam will strike its respective wall at a different time, i.e. non-simultaneously…which would be in agreement with an outside observer who is stationary with respect to the train. The light will reflect from each wall and converge on the observer at the center of the cabin at the same time, and he will erroneously conclude that the light hit both walls simultaneously. The observer on the rocket and the outside observer disagree on the timing of the light hitting the walls. The observer on the rocket says it hit simultaneously, the outside observer says non-simultaneously. But the outside observer is correct, since the rocket’s observer is basing his conclusion on an erroneous perception. As I have shown, there is in fact no actual, physical difference as to when the light hit each wall; the thought experiment put forth by Einstein himself shows this, but he and his followers have failed to realize it. The relativist is not justified in concluding that simultaneity is relative, since it is only relative in the mistaken perception of the moving observer.
Can't quite agree. The observer at the center of the cabin is not "erroneous" from the perspective of his own frame of reference; ditto the cabin observer shouldn't say the outside observer is erroneous either. They are both correct within their respective frames; provide them with the proper math tools and they can correct for the different points of view caused by the moving frame and thereby understand what is causing the difference in perception.
ReplyDelete"...there is in fact no actual, physical difference as to when the light hit each wall;" But there is. Once the light leaves the source and enters "spacetime", it enters what is basically a resting frame with respect to the train. Within that frame it travels at its constant light speed. Now the rear of the car is moving within that spacetime "frame" towards the source and will therefore be struck first by the light beam. Similarly the front of the car is moving away from the source and will require a bit longer for the light beam to hit it.
The situation reverses when the beam of light is reflected and comes back to the observer and, consequently, he concludes that they struck at the same time. Therefore, simultaneity is not a matter of "mistaken" perception, it's a matter of comparing observations made from different frames of reference.