In reply to Sharp:
> If you put two ropes together (that aren't designed as twins) then they'll not stretch as much and therefore wont absorb as much energy
if they don't absorb the energy of the fall, they break! And it's already been established that non-compromised ropes don't break.
The energy of the fall comes from the potential energy released by the mass of the climber descending under the influence of gravity. For a given climber falling a given distance, the energy is the same. (It's true that skinnier ropes stretch more, so the total distance the climber descends will be greater, but the stretch should be relatively insignificant cf the fall distance, so you can effectively ignore its contribution to the energy of the fall. Although it is catered for in the classic fall arrest equation.)
The reason that less stretch is a bad thing is that the fall is arrested over a shorter distance and over less time. That's what makes the peak force higher, not some hand-wavy idea that the ropes absorb less energy. The energy is there to be absorbed: it's
how the rope absorbs it that makes the difference.
> increasing the load on your gear and increasing the chance it'll rip.
Also increasing the load on the climber, increasing the risk they will be injured by the fall arrest itself. On routes with bolts for pro, this is arguably a more serious risk than the gear failing.
[I should perhaps explain that a pet hate of mine is the incorrect use of terms like "force" and "energy", which have specific meanings in discussions about physics. At least when people use "energy" in the context of crystal healing or whatever, you know that they're talking b*ll*cks from the outset so it doesn't really make any difference if they misuse a technical term. Stick "quantum" in there as well if you need further proof that they're selling expensive snake oil…]