Say you have two people holding either end of a very long (several light seconds), taut string. The first person gives the string a pull (supposing he is able to pull a string of that mass), and the second person holds the other end (whilst watching the first person through a powerful telescope). Does the second person feel the pull before, at the same time or after he sees the first person pulling?
Nothing is supposed to travel faster than light, so what happens to the string to allow the force to be transmitted slower than it?