Let’s say we have a spaceship traveling through space at uniform velocity. The pilot, Vincent, is standing in the middle of the cabin. He has a digital clock beside him, as well as a switch. The switch is connected by wire to a light bulb at the front of the cabin, and a light bulb at the rear of the cabin, so that, when the switch is thrown, both light bulbs light up. Each light bulb is connected to a clock right beside it. These clocks detect and record the exact moment when the pulse comes through the wire and activates the bulb. These clocks were synchronized with Vincent’s by putting them right beside Vincent’s clock and set to the time of Vincent’s clock. The two clocks were then instantaneously teleported to their respective positions beside the light bulbs at the front and rear of the cabin. Or they were walked to their positions by Vincent, or whatever. Any way you can imagine that the clocks would get to their positions without getting out of synch with Vincent’s due to motion. We are absolutely certain that when I look at the rear or forward clock, I can be sure that Vincent’s clock is showing the same time.
Okay. Vincent throws his switch, carefully noting the time as he does so. What will happen? First, due to the forward motion of the ship, the light bulb at the rear of the cabin will light up, its clock will stamp the time, and the light from the bulb will head back toward Vincent at the center of the cabin. Seconds later, due to the forward motion of the ship, the light bulb at the front of the cabin will light up, its clock will stamp the time, and the light from the bulb will head back toward Vincent at the center of the cabin. Because the light from the rear has further to travel due to the forward motion of the ship, and the light from the front has less distance to travel, the lights each reach Vincent at the same time. He concludes that the pulse from his switch reached both walls at the same time, triggering their lights. (This is incontrovertible; Einstein would agree: if he claims that when two lightning bolts hit the front and rear of the train simultaneously from the vantage point of an outside observer, but will be perceived as non-simultaneous to an observer in the rocket, then he must agree that the reverse would hold true: that non-simultaneous strikes would be perceived as simultaneous by the rocket’s observer, which is exactly the situation I have described above.
Since Vincent sees the lights at the same time, he believes that when he compares the two clocks at the front and rear of the cabin, they will both contain the same time stamp. He performs this comparison. Astonishingly, the time stamps are not identical. The clock at the rear has an earlier time stamp than the clock at the front. How can this be? he wonders.
Let us further say there is an observer, Nancy, standing alongside the rocket’s path. There is a v-shaped mirror in directly in front of her, which will allow her to see both lights without turning her head. When the light bulbs go off, she sees the rear bulb go off first, and the front bulb go off second, agreeing with the judgment of Vincent’s clocks.
Clearly, Vincent’s perception of the simultaneity of the bulbs going off was in error. He cannot argue with his clocks; despite his perception, the bulbs did not go off simultaneously. He must agree with Nancy. Yet special relativity would have us accept Vincent’s perception as accurate, and believe that a discrepancy exists between Nancy and Vincent: Vincent says the lights went off simultaneously, Nancy says they didn’t. Therefore simultaneity is relative.
You cannot claim that I am misunderstanding relativity here. My illustration is in perfect agreement with the two main illustrations put forth by Einstein and proponents of relativity: namely, the thought experiment where the observer shines a light from the middle of the train, or spaceship, or whatever vehicle you choose to use; and the thought experiment where lightning strikes the front and rear of the train, spaceship, etc.
The proponent of relativity will probably say there is one thing wrong with my thought experiment: the clocks have not been properly synchronized. Once Vincent’s clocks are positioned at the front and rear of the cabin, we must send light signals back and forth between them, to adjust them properly. But I utterly reject this second phase of synchronization. This synchronization merely adjusts for the error that exists. It is merely a way of getting the clocks out of synch again, and into agreement with relativity’s conclusions. The error exists; you can’t “sweep it under the rug” by “synchronizing the clocks with light. To do so is to merely adjust the clocks so that the error seems to go away. I’m right and you’re wrong, yet you’re trying to tell me I’m wrong because I haven’t adjusted for your error. That’s ridiculous! I don’t care if you’ve got Albert Einstein and the supposedly greatest minds of the past hundred years of physics behind you, if you’re wrong, you’re wrong, I don’t care who you are. Was Galileo wrong about heliocentrism just because the Church said he was? If the whole of the scientific church says someone is wrong, does that mean they truly are? At 4:45, if I want to leave work, and I set the clock forward to 5:00 and leave, I can’t then pretend, without being in error, that I didn’t leave fifteen minutes early. No matter that I set the clock forward to 5:00, the fact remains that I left work fifteen minutes early. My boss will claim that I left work fifteen minutes early, and will want to dock me fifteen minutes’ pay; shall I attempt to wriggle out of this by claiming that there is an actual, physical difference between my 5:00 and his, merely because I moved the clock forward?o:p>
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