Anatomy of a rope What makes some ropes stretchy and others not so much? History 1935->Nylon is invented and changes the game. much more dynamic (and therefore safe) than the previously used natural fibers its a part of why the ropes are so stretchy. 1953->the game itself gets reinvented when Eldrid drops the Kernmantle the method of using a strong interior core to support weight while having a resilient sheath around it made ropes much easier. https://www.teufelberger.com/en/products-services/safety-and-rescue-ropes/application-specific-menu-safety-and-rescue-ropes/technology/rope-constructions.html The strands of the core rub against each other and turn the climber's energy from their fall into thermal energy. The purpose of the sheath is to protect the core and to make it easier to handle the rope (prevent twisting and other funky stuff)