B
bonepile
Guest
I have had trouble understanding how an absolute frame of reference CANNOT exist for some time now. I figured that a lot of people who can explain this to me probably visit this message board, so here goes:<br /><br />The "Twin Paradox" usually is explained where one "twin" accelerates away from the other "twin", and then accelerates back. I realize that acceleration has implications in motion through the space-time continuum, so allow me to present an alternate example that does not deal with acceleration.<br /><br />Let's say we have three probes in deep space: probes X, Y, and Z. X and Y are touching, and Z is moving towards them at near c velocity. X and Y each have an atomic clock, which they synchronize. Then, X and Y move apart from each other along the line shared with Z. After some time, X and Y both stop.<br /><br />At this point, X and Y's clocks are still synchronized, right?<br /><br />Now X and Y are both broadcasting their time into space. Z has a receiver and can take into account the Doplar affect of the transmissions from X and Y and all that. As Z flies by X (the first probe), it synchronizes its own internal clock to the value of X's broadcast.<br /><br />Then, as Z flies by Y, it compares Y's broadcast time with its own internal clock.<br /><br />Which clock is ahead, Z's or Y's?<br /><br />Remember, velocity terms like "c" and "stop" are all relative. From Earth's perspective, it could just as well be X and Y that are moving at near c velocity.