A force sphere was a particularly dangerous phenomenon observed in the chute system of Metru Nui. When part of a chute was damaged, a portion of the magnetic force which held the liquid protodermis in place could fold in on itself and break off. This could travel through the chute, absorbing everything it passed and growing larger as a result. At a certain size, it would wreck the chute and then implode, destroying everything contained within it.
A chute consisted of protodermis with a magnetic energy sheath that keeps things moving fast through it. Sometimes, if there was a flaw in the chute construction, some of that energy snapped off and folded in on itself. It then traveled quickly through the chutes, and its magnetism drew things inside, such as tools or debris. The longer it existed, the stronger it became. When it got big enough and strong enough, it tore the chute apart, got buried under the wreckage, and imploded, destroying everything inside.
A force sphere moved through the chute network. Once it absorbed enough energy, it would implode, destroying anything that was inside of it.
If a flaw developed in a chute's construction, a portion of the magnetic energy could break off and fold in on itself, becoming a force sphere. It then flew through the chute, its intense pull drawing in tools, cargo, debris, and anything else floating in the chute. As it did so, the sphere grew bigger and bigger. Eventually, it tore the chute to pieces and then imploded.