Hi. Firstly, can a particle every be found within the potential barrier? I've used the search function to look for an answer for this question, but I didn't really get anything conclusive. However, from what I gather, since there is a probability associated with it being 'found'(meaning it is observed at that position) within the barrier, if the experiment is conducted many times, there will be some cases where the particle is found in the classically forbidden region. Now what happens if I force a measurement of the particle's momentum and hence its kinetic energy? I accept that its impossible for the particle to have both a definite momentum and position at the same time, but that doesn't stop me from forcing a measurement, just that I'll obtain a different results every time since its associated with a huge uncertainty. So within the barrier the particle seems to have negative KE, but when a measurement of velocity is forced upon it, it will definitely have a positive KE(since you cannot have complex velocity). Where did the extra energy come from? Is it simply the act of observing it that disturbed its energy and made it seem to have more total energy than before?