Definition for Quantum tunnelling
From Biology Forums Dictionary
Quantum tunnelling is the name given to the mechanism by which small particles can overcome energy barriers. For example, an electron in a low energy level can occasionally "tunnel" through an energy barrier to a higher energy level. The effect arises because the absolute energy of an object is never precisely known because of the uncertainty principle. The uncertainty, in absolute terms, is very small, but for quantum particles, the relative uncertainty can be significant and occasionally allows a particle to "jump over" an energy barrier.
