Hi- I recently read Brian Greene's Fabric of the Cosmos which led me to think of an interesting concept that I would appreciate further explanation on. On page 456 Greene describes how in the multiverse view, if you traveled back to the past, you would have gone back to a past in a parallel universe and so any changes you would make in the parallel past would not affect the universe in which you came from. Another theory he explained is that the past is unalterable and that any actions you take in the past, happened originally and so you were just fulfilling your "destiny" or rather committing the same actions that you had already done in the past, even if it was before your birth, etc. These two ideas made me wonder: For example, in the double slit experiment, when an unobserved photon passes through, it appears in a wave pattern, however when it is observed, the probability wave collapses and it becomes a point particle. I am curious as to if this explanation can also work for both theories of time travel. Since there are many parallel universes in the multiverse that we are not physically conscious of, could this be the "wave," similar to the photon? Likewise by going into the past, which would be "unchangeable" would this probability wave shrink, leaving us as the point particle so to speak, which would mean this past that we were conscious of could only have one outcome that we couldn't change. I'm sorry if this is confusing, but I've done my best to describe this idea, jumbled as it may be. I appreciate your time in trying to explain if the combination of these ideas has already been thought of, if they're totally crazy or wrong, or just any comments or concerns in general. Thanks!