Dear Sir:

First, I must clarify that I am not an expert of Quantum Mechanics. However, I would try to answer your question, based on current theory. If you find my answer is inadequate, please ask the experts. According to the uncertain principle, xp ≥ h and Et > h , the accuracy of time (distance) would lead to inaccuracy of energy (momentum).
Details can be found in textbooks of quantum mechanics. Thank you.

Sincerely yours,

C. Y. Lo