Just a problem I thought about the other day. It’s just curiosity to know the answer, I’m not a physics expert (my first post also). Let’s imagine we could build a straight bar or something similar which is 1 light-day length (or any other huge length) made from any solid material (ie: fiber optics, cast iron, etc). For simplicity imagine the bar to be in empty space and let’s make the bar so one could grab one end and begin pulling it with some acceleration for some time (just imagine you have the means for doing it), so the bar will begin moving (in theory). The other end is still in empty space. Since nothing can travel faster than light, would the other end of the bar remain motionless for a day waiting for the energy that begins pulling it (going at light speed, the energy signal will arrive one day later), and consequently the bar would probably just break at some point (remember one end is moving because I’m pulling it)? Is this due to mass inertia? (Is mass inertia due to speed of light constraints over mass?) If the previous reasoning is wrong, would the bar move all at the same time? If so, how the other end of the bar received the energy so fast to begin moving? Thanks for your time.