In the ending of Revelations, when Ezio finds Altair and the Apple, looking at the PoE, he decides to leave it where it is and he mentions aloud Desmond. The latter gets in touch with Ezio through some sort of atavistic wireless phone, and just for a moment, the two meet. Here, what the hell has happened?
How can Ezio in the past see Desmond?
We already had a taste of this phenomenon, we had it exactly in the ending of ACII when Minerva barely appoints Desmond’s name in front of an extremely confused Ezio, who is told to shut up and be a medium for an unknown receiver. We labeled the thing as determinism, or rather Minerva appoints Desmond knowing his existence in the same manner for which if we drop a glass from our hands, we know that, reaching the floor, it will smash in a thousand pieces. In substance, she appoints Desmond, she determines his existence in a remote future, she doesn’t know how he is, neither who he is, she only knows that he will be called Desmond and thus a link between Minerva’s past and Mr. Miles’s present is formed, namely we find a connection between the knowledge of Minerva and the presence of Desmond. But this line of argument stands only if we contextualize all the events in a linear and consequential succession, meaning that the deposition of Minerva was the first to happen, and only afterwards Desmond was able to see the thing via the Animus. But what if the order of the timing was reversed? How is it possible?
In my memory still houses a residue of remembrance of a documentary about time travelling. the experts in it were saying (on a completely theoretical way) that if it ever was possible to do, first the means to accomplish it had to be created, but above all, that before the creation of those means it was impossible to go back. I mean: assuming that the means has the form of a portal, at the very moment it is created and activated, it becomes the possible limit of time travel. That is, creating the portal and letting it project into the future, for example, of one week, a connection between the portal of a week ago and the current one would be created, allowing the potential time traveler to get back. If he wanted to go back of a week plus one day, he wouldn’t be able to, for the simple fact that on that date, the portal didn’t exist, so there wouldn’t be "the other exit of the tunnel." Same thing for a journey into the future resulting in the destruction of the medium. In essence, until the means exists, the opportunity of travelling also exists.
This theory is a reference to the speculations of Frank Tipler.
After this, what’s inside the universe of AC that reflects what is written above?
You will notice that the Pieces Of Eden meet all the requirements. Technological objects, but very old, that thanks to their robustness were able to cross ages from a very remote time up to the present. Think about the PoE’s as suspended in an eternal present, that incorporate pieces of information and continually bestow them independently from the time in which they are observed. The theory of relativity applied to the PoE’s instead of the light. Try to see the whole picture: the Piece of Eden projects himself in the future, creating a connection between its existence in the past and its existence in the present. The connection allows then a transfer, in our case of information, from the future to the past and backwards. It would be explained why Minerva knows about Desmond. The latter wonders about the fact that Minerva knows his name, but having to rely on the vision of Tipler, it finds its own logic. In AC: Brotherhood Desmond touches the Apple and the voice of Juno says that his DNA communed with the P.O.E. (“communes” has a double meaning: to ~ with the [nature] to ~ with [person].) So if we take for valid the argument made so far, the perpetual connection between the Apple of the Past and the Apple of the Future made possible the backward transfer of Desmond’s genetic information up to the moment in which Ezio hands the Apple to Minerva who touches it, as if she were reading its contents, and from there starts with her speech to the future.
In simple terms Minerva in ACII talks to Desmond, but referring to the Desmond of AC: Brotherhood. Desmond, in ACII, finds himself during a connection, unaware of the fact that in the future he’ll touch the Piece of Eden. By the point of view of Minerva, that event has already happened and through the gesture of Desmond, she goes back to him and communicates with him. The deterministic idea then falls in favor of this, much closer to the current conception of things in the plot of AC. If in fact we couple the time paradox theory with the now confirmed TWCB ability to perceive time in a higher way than men, it is not surprising. At this point, however, a legitimate question arises: Desmond touches the Apple in the Colosseum, the one in possession of Ezio, which we know to be distinct from the one of Altair. How is it then that Desmond appears in the one buried in Masyaf? Subject 16, in his voice messages inside the Glyphs, used to refer to the PoE as once belonging to a whole. What seen in Revelations confirms the existence of an interconnection between the objects, which then creates a system. The time travel of a single Piece must be then seen in collective terms, with a system of objects connected to each other, projecting into the future and transferring themselves and between themselves the information they have stored during the flow of time.