The common popularization (which appears several times in this node) that the uncertainty principle is about "measurement affecting that which is being measured" is incomplete. In fact, the UP also applies when no measurement by anyone is happening. It is, for example, used to prove that electrons can't exist within an nucleus: if they did, their location would be so exactly fixed that their momentum, by virtue of the UP, would become extremely uncertain. Momentum is mass multiplied by velocity, and an electron's mass is so small that the velocity derived from the uncertainty is many times that needed to escape the atom core. QED.