Dear Professor Greene, Having watched your documentary on Quantum Mechanics (most enjoyable) I have an idea (undoubtedly a distillation or misunderstanding of everything I've read on the subject so far): What if every possible outcome on the macro (human) scale is not played out in parallel universes but is actually played out simultaneously in this universe - an infinite number of parallel histories within this realm ? The observer can only see his own history as an infinite number of versions branch off into every possible direction. We accept that there is Spacetime - why not Metime ? (Me-time - where we/me are not the same person from moment to moment just as space is not the same space from moment to moment.)
This would (I think) explain the slit experiment whereby observation seems to fix the position of an otherwise locationally vague particle. It seems preposterous that just looking at something could set its position. I posit the following instead: By the time the observer sees the particle its position is already historic (the time the light takes to travel to the laboratory sensor) therefore the observer has not affected the position of the particle but 'chosen' the historic position from which to view the particle - the same observer (but in another history) would see the particle in a different place which would accord to an aggregate of probable quantum outcomes. Each observer (the same person, only different in different histories - in the same way as space is identified by its location in time) is unaware of the other as the histories take different branches. Would there be too many observers (every sentient being in the Universe) fixing the position of too many things ? Well this would give us some idea of the scale of infinity and the infinite number of outcomes that are needed to bring us the perfect picture of 'Now'. Entangled particles (large distances apart) are observed to spin in unison with each other - choosing the position of spin of one, therefore, does not need distance to be a factor in determining the position of spin of the other as it is the history that is being chosen (not the state of the particle) and history applies to the whole universe and not to close proximity. The effect of choosing history rather than position is, of course, instantaneous (infinitely faster than the speed of light) regardless of distance. Everything that can happen does happen at the sub-atomic scale... what if the same is so for the macro scale in this very universe, only that we are too close up to 'reality' (whatever that may be !) to see it ? Would a gigantic observer (a universe sized person, the same scale to us as we are to sub atomic particles) see us behaving in quantum ways and not as we see ourselves ? I apologise if I have missed something in your book, The Fabric of the Cosmos - I enjoyed this very much too. Kind regards Kevin ----- (England) PS, I gather you must get lots of fan mail. I promise not to write uninvited again. Please don't feel the need to write back but I would like to know if I've been of help.