Hello, This is my first ever post in an entirely science-dedicated forum. On another forum, another user and I theorised that the energy transfer in hydraulics from one point to another is instant. He initially posted about electricity being instant because electrons move at the same speed throughout a metal, and together we came up with this question: If I managed to make a pole one light-year long, and I pull on one end of this pole, would a friend standing at the other end of the pole experience this same movement instantly, or would there be a one-year delay? It's baffled me, and I was wondering if any of you wonderful people could shed some light on this question. Many thanks!