I've recently had this thought experiment, and wanted to share it. My HS physics teacher had talked about "perfect" strings that had no mass, does not stretch, and is completely flexible when describing physics experiments. Using such a hypothetical string means it does not interfere with the experiment. It has no mass to alter momentum, does not stretch under stress and smoothly wraps around pulleys. In this thought experiment I adopted this. Take a length of material that, much like the perfect string, has no mass and does not bend under stress. Balance or suspend it across a fulcrum, so that it appears like a see saw or teeter-totter. Like so. Code (Text): ____________ ^ If its initial position is perfectly horizontal, and someone pushes down on one end , the other end rises up, correct? The answer, of course, is yes. However the question I have been asking myself is, how much time passes before the other end rises up? As the material does not bend and has no mass for momentum be an issue, as near as I can determine myself, it rises up simultaneously as the opposite end is pushed down, or t=0. Now, extend the length of the material to a light second (299,792,458 m). Again, push down on one of the ends and simultaneously send a photon/s down the length. The time for the photon/s to reach the opposite end (assuming vaccuum) is t=1 sec, while the time for the opposite end to rise remains the same, t=0. I cannot see how the time for the opposite end to move is anything but t=0 regardless of its length, or by how much force is applied. t=0. If an observer was stationed at each end, they each would be aware when the opposite end was moved prior to the photon/s arriving. Simple, yet seems profound and yet almost not true. feedback?