Hello everybody, my apologies if this is a stupid question. Under the sound (specifically vibrations and waves) unit in my textbook, it briefly mentions nodes. However, it merely describes it as a "centre point [that] always stays at the equilibrium and never vibrates." My question is: what is the significance of mentioning these nodal points? (Please don't take this the wrong way, I'm all for extra tidbits of info, but I'm curious as to why the textbook bothers to mention this phenomena.) Thanks for all your help!