Wait a minute! But isn't science supposed to be based on observation? This very experiment has been observed, for crying out loud. So what does it mean? If you demonstrate something by scientific experimentation, therefore using observation, doesn't that mean you only demonstrate what happends when you look at something, rather than what that something is? Since the same experiment has been observed using eyes and it behaved differently when they use a finer tool, then it means the type of observer alters the result. Would things start behaving differently if an alien was to come on Earth? This is mind boggling.
Another YouTube video
Wikipedia on the double slit experiment
Cool java applet on wave interference