The idea of the outcome of an experiment depending on whether or not it is being observed is strange. I have never seen this happening in real live. Still in physics it is held that it does exist: the double slit experiment using very low-energy laser light (assuming that one photon passes the slits at the time), can show observer dependency. However, as the assumption here above already mentions, we have to, at a minimum, assume photons exist. Is this then a given? There appear to be many other assumptions underlying this kind of experiment. Also, for 'observing' usually a photon detector is used. What does that do to the assumed photon? Does the detector influence the experiment? Is there an interaction between the detector and the photon? Also, when exactly is the photon 'observed'? When it hits the screen? When it passes the detector? When the observation hits my retina? When I have processed the information in my brain? Also, who can be an observer? Another person, an animal, a computer, a stone, me? So, to me, there are too many assumptions and open questions... My question for this forum is: does anyone know of an obvious, simple, not-too-many assumptions based experiment that makes 'observer dependency' existence realistic?