Question from a Non physicist: COnsidering the most famous Quantum experiment, the double slit exp., I am wondering what the current thinking is on the "observer" in such that senario. As in, the electron beam chooses a slit if-and-only-if an "observer is there to observe it go through a slit. My fisrt question (as I'm sure everyone's first question) is, what is an observer? Is it just an eyeball connected to a bundle of nerve and brain tissue? A person makes an observation which is important in QT, but a person is surely just an organized collectionof atoms. Philosophically, what is it that connects an observer to the quantum world? I wanted to aske physicist, not philosophers. As I said in another thread, I recently read Kaku's Physics of the Impossible, which mentions this sort of conundrum. In his usual hyperbolci style Kaku saidsome quantum physicists think that there must be a "consciousness" pervading the univese to observe quantum events.