So I've studied physics at the university quite a bit and was a bit surprised when I couldn't answer this simple question a friend asked me. When something lands in water why are several ripples created? Like why is the resulting water wave made up of several peaks and valleys and not just one peak, valley or peak/valley pair? The only possible explanation I could come up with at the time was that an object does not cross the water surface instantaneously. It transfers energy to the water over some period of time and thus the water wave would have some spatial extension because of that. However I suspect that it's not the whole story.