For a moment, suppose the truth of Everett’s Many-Worlds interpretation of the collapse of the wave function: every possible interaction occurs, in some branching of the universe. This cascade of parallel universes is normally considered to move only into the future, like the branches of a tree. We can’t predict the future, because quantum randomness mangles our estimates with each particle interaction. Yet, we think of the past as somehow finalized.
When quantum weirdness blips an electron into sight, the traditional physicists say that the electron’s wave function collapsed. The electron was ‘smeared out’ in space, until we looked at it. The many-worlds view is of many possible futures stemming from each uncertain moment.
I am a fan of many-worlds, especially because that interpretation suggests the possibility of time travel. Though, it wouldn’t really be time travel — you would blip out of existence on this end, and be gone. There is also a parallel universe where you happen to appear at your chosen time, but this parallel is just as valid as an elephant appearing then, or a rowboat. They all happen. Would your present consciousness perceive travel to that time? I don’t know what consciousness is.
Yet, many-worlds as it is usually presented does not consider that, for the particular future we observe in the next moment, there are just as many various pasts which converge upon that same moment’s state. Like rivulets forming streams down to a river, these disparate pasts merge into now. Which past was real? Many-worlds must admit all these pasts as parallel. Just like parallel futures.
So, the branching and crossing of past and future paths is not a tree, it is tapestry. Many worlds lead to this moment, and many scatter from this moment. As far as our present consciousness can perceive, the threads of tapestry grow hazy in both directions, like a fog.
If we could see the width of that tapestry, all the parallel presents, the majority of particles in the majority of universes would follow normal physical laws, while some small fragment of some of those worlds would see quantum tunneling at that moment. Does that mean those ‘majority’ cosmos are more real? Are there more copies of you, experiencing those parallels? If each world occurs, there is a cosmos for each path you choose to take — there are worlds where, by quantum coincidence, you choose to be a saint or a serial killer. Are those people really you, when the vast majority of worlds have you turn out much like you are?
This is a question of the supra-real — what mostly happens, across the thick of parallel times? And, another question about the supra-real: if time travel is possible, do the world-paths with time travelers become more abundant? Suddenly, a local majority of parallel universes contain you, with your memories of the future, far in the past. Would that mean you really had traveled back? Would the consciousness on this side of time perceive continuity? Whole swaths of parallel universes, far removed from our local strands in time’s tapestry, would be populated by time travelers. Galactic empires, forged by future selves who went back to the earliest fusing and cooling, may be more numerous than our traveler-less timeline. Is that what the universe is for?