The Heisenberg Uncertainty Principle
If there's one thing we humans do well, it's meddle. Our meddlesome ways are no superficial pastime -- our influence can be found as deep as the atoms and molecules around us, at the tiniest level of quantum mechanics.
German theoretical physicist Werner Heisenberg, on the heels of his formulation of matrix mechanics (his early breakthrough work in the development of quantum mechanics), proposed this very thing in 1927; it is impossible to determine a particle's exact location and exact momentum because we affect that particle's momentum. This is the Heisenberg uncertainty principle in quantum theory. And although it's unintentional and unpredictable, it's unavoidable (at least as far as we know today).