Heisenberg's uncertainty principle
Things that people do while observing things that change what is being observed are cases of the Observer effect. Some things that people do cause changes on the very small level of atoms and are cases of uncertainty or indeterminacy as first described by Heisenberg. The uncertainty principle shows that there is always a limit to how small we can make certain pairs of measurements such as position and speed or trajectory and momentum. The observer effect says that sometimes what people do in observing things, e.g., learning about an ant colony by digging it up with garden tools, can have big effects that change what they were trying to learn about.