Here's a thought experiment that I would like you to comment on. Suppose you could construct two spaceships of exact design. I will call them spaceship A and B. Then let us also suppose you could construct a cable, or any tether device, sufficient enough in strength to be attached to the rear of both spaceships. Now, in this thought experiment, the two spaceship are attached by the tether and fly in opposite directions, reducing the slack of the tether until it is taunt. The speed of the spaceships will be sufficient to accomplish this within a reasonable amount of time, but not too forcefull as to break the tether. At some point, the spaceships will reach an equiliberium where the force of the thrusters is balanced with the tension in the cable between the ships so that the speed of each ship is 0, but the thrusters are still on. The distance between spaceship A and B should be at an optimum distance, say 3 or 5 or 10 light seconds apart for the next part of our experiment. After the equiliberium is reach and both ships are holding steady at a foward speed of 0, space ship A will release the tether and simultaneously send a beam of light to a receptor on the back of spaceship B. Spaceship B will recieve the beam of light in a detector 3 or 5 or 10 seconds later. This will be a way for spaceship B to know the precise moment spaceship A released the tether. Question: Will spaceship B immediately begin accellerating foward, having been released of the force holding it back (i.e spaceship A's release of the tether)? Will it remain at a speed of 0 for the 3 or 5 or 10 seconds it takes for that "information" to travel from spaceship A to spaceship B? If it remains under the force of the tether for a few seconds, what is holding it in place since it is now free of the tether? If it moves foward immediately, then how is that "information" transfered faster than the speed of light (i.e the light beam sent from spaceship A)?