Earlier this week I was looking at the news. A group of researchers have achieved Quantum Entanglement in the largest object as yet observed, some billions of atoms. For those who have never heard of the term, quantum entanglement is basically a pair of objects which exist simultaneously, in which one cannot exist without reference to the other. In essence this started off with the Schrodinger's cat thought experiment where a dead cat and alive cat become quantum entangled so that the cat is both dead-and-alive at the same time. Clearly this is not an experiment that anyone has performed on a real cat, but many experiments have now been done which have produced pairs of particles (which can sometimes be separated by huge distances) which are entangled in this manner. Click here for an explanation of how particles can become entangled. Many people have speculated that quantum entanglement processes in the brain underpin consciousness, and some even go as far as saying that quantum entanglement allows us to construct reality.
In terms of Lost, it occured to me that the FST and the OT can be viewed as the single quantum-entangled state of two distinct objects. This explains the coincidences and the differences between them. In the FST the island does not exist; in the OT it does exist. (eg like the cat). Jack in the FST is the same Jack as the OT, but he has different experiences, and shows a different side. If this IS a parallel, and there is quantum entanglement going on, then the physics would tell us that what happens to one of the pair of particles can affect the other. In simple terms, if we measure the spin of one of the pair, that fixes the spin for the other one. One has the equal and opposite spin of the other. (however, as soon as we have stopped measuring, it randomises). This means that OT Jack can affect FS Jack and vice versa. WE may have seen this: FS Sayid was attempting to do the right thing and not kill Keamy at Omar's request. However, he became infected in the OT, and mercilessly gunned down Keamy. Linus finds resolution in the FS, and at the same time also finds resolution in the OT. I realise that the time appears to be out by 3 years, but there may be a good reason for that.
It would also explain what is happening with Jacob/MiB: they are two quantum-entangled entities. MiB cannot kill Jacob (& vice versa) without radically altering himself : this is not the same as commiting suicide, but it would mean that he cannot physically occupy the same state (i.e. place/time) as Jacob, and therefore the laws of physics prevents this (such an event would contravene the Pauli exclusion principle). The back story to Jacob/MiB could be that they arose in the past from some other manifestation of a 'split universe, where they were the different aspects of the same person. Note that a quantum entangled person like this would effectively be two people, but inextricably liked. In Lost terms, for example, it might be that one can be corporeal, the other not. When Ben killed Jacob, Jacob became non-corporeal; the body that MiB was in then became THE body for the entangled pair, MiB became the corporeal entity and Jacob becomes the ghost.
Resolution: Unknown; however, expect to see some very strange quantum weirdness in future episodes...