Sam: Welcome to the Sound of Science on WNIJ. I’m Sam from NIU STEM Outreach.
Christine: And I’m Christine from NIU Outdoor Adventures – and I’m going rock climbing!
Sam: So what’s the science behind that – other than gravity?
Christine: It’s about the life-saving engineering that keeps you from falling: the carabiner attached to the top, the belay device the safety person at the bottom uses, and the rope in between.
Sam: Let’s start with the carabiner at the top. How does that giant metal clip keep a climber safe?
Christine: When you first set up a climbing route outdoors, you need to find anchor points at the top. These are things that simply will not move except through extreme circumstances. Things like big trees and boulders. Ideally, we want three of these anchor points to help distribute the force. It’s a lot easier for a tree to withstand 300 newtons of your weight than 900, especially if the climber takes a big fall.
Sam: And the belay device - that’s the metal tube with teeth the person at the bottom threads the rope through, right?
Christine: Yeah. In top rope climbing, the person at the bottom -- known as the belayer -- keeps the climber from falling in case they slip. The belayer strings the climbing rope through their belay device and a carabiner attached to their harness. The rope goes down into it, and back up.
Sam: like a “U” shape.
Christine: Right. And that U shape has only one bend of the rope. That allows the rope to move freely. To lock the rope in place, the belayer pulls down rope to create another bend.
Sam: Like a sideways “S” shape.
Christine: And if the climber falls, the S basically pinches itself. The belayer doesn’t use their strength to grasp the rope, they just pull the rope down and let physics do most of the work.
Sam: Last one – the rope. What’s special about it?
Christine: Climbing rope is dynamic. That means it’s like a spring. It will stretch as you fall, decreasing the force by increasing the time. A regular rope without stretch would just stop you all of a sudden, and the force could even break your back.
Sam: Learn how to climb safely, and have a ton of fun, by joining Outdoor Adventures on one of their many trips. This is The Sound of Science on WNIJ.
Christine: Where you learn something new every day.