Why is the speed of waves in a medium fixed? I'm trying to conceptualize this, but I can't. I imagine a long piece of chain on the ground, of course made up on individual links. If I yanked on the first link by lifting it up, it wouldn't in act a force on the second link until it made tense contact with it. But If i yanked up the first link incredibly fast (ex: 100,000 mph) shouldn't the first link very quickly (that is in time) force the second link up , which in turn forces the third link up that much faster. Can anyone help me understand?