To have half as much potential energy, the rock climbers would need to be halfway down the cliff.

Here's why:

* Potential energy is the energy an object possesses due to its position relative to a reference point.

* Gravitational potential energy is specifically related to an object's height above the ground. The formula is: PE = mgh

* PE = Potential Energy

* m = mass

* g = acceleration due to gravity (constant)

* h = height

Since the mass (m) and gravity (g) remain constant, the potential energy is directly proportional to the height (h). If you reduce the height by half, you reduce the potential energy by half.