My teacher was talking about this today. He said and warned the class before he told about the experiment, "I'm not even going to try and pretend to understand what's going on here" But he told us about the experiment which goes a little like this. There's a light source that shines light through two slits. When the light goes through the paper, it behaves as a wave and diffracts as it passes through the slits onto the wall. In another case, if there's a counter, which counts exactly how many photons go through the slits, they exhibit particle-like properties. As a result, the light does not diffract. All of this simply because of an observation. This experiment seems to suggest philosophical implications. This leads me to another question. What if you have a counter counting the photons passing through, but you do not observe the counter. Does it still exibit particle properties? What if one person observes the counter, while another does not? Can someone tell me more about this, or at least give me something to read about it? I know this has something to do with quantum mechanics and how quantum computers will work some day.