Suppose there are three space ships in a line, A, B and C each at rest wrt each other. Ship A is 100 million km from ship C and ship B is roughly in the middle, 60 million km from ship A. There is a really long fibre optic cable coiled up in ship A, which we'll say is 300 million km long. We use a forth ship to feed one end of the cable through ship B, and then attach it to ship C. So there is 100 million km of cable between ship A and ship C, which passes through ship B and 200 million km of cable left on ship A. Ship A sends a light pulse through the cable. Assuming 300,000 km/s for c, and that the light pulse would travel at c in the cable, it would take 1,000 seconds for the light pulse to travel the length of the cable and reach ship C and approximately 866.6 seconds for it be detected by ship B, as there is 260 million km of cable between ship B and ship A. Ship A also sends a light beam directly to ship B at the same time it sends the pulse through the cable (Same time from ship A’s frame.) So ship B would detect the light beam after 200 seconds and would then detect the light pulse in the cable 666.6 seconds later. Ok so far I hope. Ship C, where the other end of the cable is attached, now instantly accelerates away to a constant velocity of 0.75c, pulling the cable with it from ship A. Just at the point where there is exactly 60 million km of cable left between ship A and ship B (the exact distance between them.) ship A sends a final light pulse through the cable just before it is pulled loose. Also at the same time it sends a light beam to ship B. (Same time from ship A’s frame.) As ship A and ship B are still at rest wrt each other, the light beam still takes 200 seconds to reach ship B. However, as the light pulse is travelling in the cable, and the cable is now travelling at 0.75c wrt to ship A and ship B, does that mean that the light pulse is closing the gap at a rate of 1.75c wrt to ship B and thus wouldn’t the light pulse arrive at ship B before the light beam? If so, then ship A has sent information to ship B quicker than the speed of light? Obviously that can’t be so, but I can’t figure out why.