I came upon a very interesting article today: http://www.msnbc.msn.com/id/19875410/site/newsweek/ [Broken] I wanted to confirm what I read... this is the first time I ever heard of this kind of thing, and I was wondering if any of you have seen this before. It talks about a tweak of Young's double slit experiment. This is the main part. "If the blinds are closed so the detectors cannot see the slits, photons fly through both and form the stripes. Here's the twist: if the blinds open only after photons have passed the slits but before they reach the blinds, the stripes fail to form even though the photons have seemingly done what they must to form stripes—namely, fly through two slits, as they always do when unobserved. The act of observing alters what the photons did earlier, somehow changing things so they passed through one slit and not two."