As Cougar says, experiments have verified that only the creation of an *opportunity* to measure/observer a certain event is enough to see the whacky world of the Heisenberg Uncertainty Principle in action. i.e., the idea that an observer is needed to "collapse the wave function" has been demonstrated to be bunk. Weirdness happens whether or not we are actually in the act of illuminating our sample with other electrons or photons. And even when we are, the magnitude of the effects is usually many times larger than those imposed by the energy/momentum transfer from the "illuminating" particles.

And "Schroedinger's Cat" was put forward as a poke in the eye at some of the early interpretations of quantum mechanics - it was never intended to be taken literally and it does not apply at all to the real world. Cats are macroscopic objects composed of zillions of quantum particles, far more than is necessary to produce completely incoherent "noise" that totally swamps the weirdness effects of individual quanta (such as the HUP). Unfortunately, the punchline was lost amongst some popularizers of science.