Do you mean the uncertainty principle or the observer effect? From Wikipedia: https://en.wikipedia.org/wiki/Uncertainty_principle https://en.wikipedia.org/wik

Do you mean the uncertainty principle or the observer effect? From Wikipedia: https://en.wikipedia.org/wiki/Uncertainty_principle https://en.wikipedia.org/wiki/Uncertainty_principle > In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which the values for certain pairs of physical quantities of a particle ... can be predicted from initial conditions. > Historically, the uncertainty principle has been confused with a related effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the system, that is, without changing something in a system. The former just means that the more precisely we know the location, the less precisely we can predict the momentum given the initial information of the system. It has nothing to do with "disturbing the atoms"; as Wikipedia explains it's a property of wave-like systems. https://en.wikipedia.org/wiki/Observer_effect_(physics) https://en.wikipedia.org/wiki/Observer_effect_(physics) On the other hand, the observer effect simply says that measurements involve active processes and those can effect the system. But it has nothing to do with velocity or position per se, just the fact that measurements can have effects.