A discussion of the likelihood or possibility of time travel elicits almost unending debate between its often highly-polarized and steadfast participants. There exist innumerable grounds on which one might approach the topic, each bringing with them yet another level of complexity accounting for earlier paradoxes whilst provoking the creation of many more. One such aspect of time travel and one that, often for the sake of complexity, we rarely consider is the likelihood or unlikelihood of there existing a ‘multiverse’. In this paper, I seek not to convince you of the existence or probability of time travel, for centuries of philosophers have waxed lyrical in an attempt to do just this, with the mere existence of this paper an indication that we still have much to learn. Rather, I intend to summarize and present an argument based around the plausibility of the multiverse’s existence. Essentially, that though the concept of actual time travel is highly controversial, the existence of many worlds when considering time travel provides a powerful argument on which to base a belief in time travel, and one that should not be disregarded due to complexity.
The term ‘multiverse’ is fairly broad in definition and as such appears frequently within articles that relate to time travel. However I, and many would agree, regard its appearance, for the most part, to be as a mere aside; often labeled as the ‘many-worlds’ interpretation, as in Hanley (1997), explained succinctly and never fully developed. When considering a multiverse in relation to time travel, we are essentially regarding two separate interpretations of time, which in the world of quantum mechanics encompasses worlds or universes (hence the multiverse moniker). These are known as branched worlds and parallel or separate worlds.
The branched worlds interpretation of the multiverse presents a particularly cumbersome construct of space-time and reality. It hinges around the idea that, when traveling back in time – such as Tim does to kill his grandfather in the familiar Grandfather Paradox – changing the past will form two branched universes or worlds. When considering the grandfather paradox, in one branched world Tim’s grandfather lives (this is the world he is traveling from) and in another branched world Tim’s grandfather dies (by killing him he has seemingly ‘created’ this world). Firstly, it appears that when considering time within a branched multiverse enacting changes in the past is not only possible but essential in the construction of time itself, and this is very true for both the branched and separate world interpretations as will be extrapolated further. However, when we consider a branched-multiverse, and, as Sider (1997) suggests, the concept of the multiverse as a whole, we must question the necessity for complexity when a simpler and similarly effective interpretation is available. With this in mind, an explanation of our separate worlds’ construct of time is necessary.
By viewing and considering time in the separate worlds’ interpretation of the multiverse, I believe we gain a simpler overall understanding of the complexities of time travel, particularly in relation to causality. This temporal interpretation suggests an infinite number of parallel worlds. We are currently experiencing just one but our time machine allows us to travel ‘back’ or ‘across’ time to another universe, in which the present is, in fact, our own past. This, at first, may appear to be the more complex of the pair but by considering the events of the Grandfather Paradox as a case-study for the parallel worlds model, many of the intricacies are exposed. Tim travels from his original universe (labeled A for instance) via his time machine to what he would consider the past (this is in fact the present of universe B, we will discuss the necessity of it being universe B’s present when considering the multiverse’s incorporation of Presentism) there he kills his grandfather. In universe B, Tim’s grandfather is killed and in universe A, Tim’s grandfather lives (and as such Tim can still exist, thus voiding the logical impossibility associated with the grandfather paradox in the standard single-world interpretation of time). The time machine is simply a device that allows transfer from one universe to another. When viewing time as an infinite series of separate-worlds we avoid the constant universal ‘creation’ associated with branching-worlds. Thus it is easier to track the path through time that, for instance, Tim has taken and, in turn, the causal relations between his actions and their consequences. This is not to say that we can completely disregard branching worlds from future considerations, I simply deem the parallel universes interpretation as providing a more plausible and hence less complex argument for the existence of a multiverse.
A concept of time travel in which there are parallel worlds paves the way for many original interpretations of the paradoxes related with time travel, particularly that of the aforementioned Grandfather Paradox. Deutsch and Lockwood (1994), relate the grandfather paradox, in the case of a multiverse, to the Autonomy Principle. Sider (1997) states the Autonomy Principle thus,
“If a person, C, is able to bring about some configuration of matter, M, then any other intrinsically similar person in physically possible circumstances C’ that are intrinsically similar to C is able to bring about configuration M, regardless of what goes on in the universe outside of circumstances C’”
Sider 1997, p142-143
When applied to the Grandfather Paradox, C relates to Tim and M is the action of killing his grandfather. If this is not possible, as most of the arguments for time travel claim, then this situation voids classical physics by hindering local possibility. In the case of a multiverse (which is based upon quantum physics) this problem cannot arise. Tim can change the past by killing his grandfather, as we have discussed above. This relationship provides a strong argument in support of the existence of a multiverse which, in turn, provides a simple and original interpretation of one of the more familiar problems that arises in the study of time travel.
An additional factor that supports the argument for there being infinite parallel universes and thus the existence of the multiverse is elucidated when considering time travel from the perspective of Presentism. Presentism basically states that only the present (that which we are experiencing now) actually exists. A particularly good analogy is given by Hanley (1997),
“The Presentist sees time as rather like a zipper. The present is represented by the location of the zipper head, the past is the closed-off seam behind the zipper head, and the future gapes open.”
Hanley 1997, p.200
This view of the construction of time does not allow for time travel in the conventional single world manner since there is no future or past to which one may travel. However, when considering time as being an infinite construction of parallel universes we not only provide an argument for time travel in the Presentist perspective, we strengthen our argument for the existence of a multiverse. For a Presentist only the ‘present’ is in actual existence, however in each of the infinite alternate universes there is another ‘present’ just as real as the one we are experiencing in our own universe. This other ‘present’, though it exists and streams along in the same manner and space-time as our own, it need not do so at the same period as our own. If in our universe A it is 2005; in universe B it may well be 1905; 2105 in universe C and so on for any other time we care to mention. Abbruzzese (2001) provides a methodological explanation that accounts for Presentist time travel,
“For every time, t, there exists a universe, w, such that the present time in w is t”
Abbruzzese 2001, p.36
Thus it may be clear that, when viewing time from the perspective of a Presentist, a multiverse allows for time travel. Presentist time travel, however, also provides an argument for the existence of parallel universes and thus a multiverse. If we view time as being an infinite series of parallel universes, mapping causal relations is made significantly simpler since we can eliminate the need for ‘backwards’ causation. From our own perspective we might tie our shoelaces together now, travel via our time machine to the past and promptly fall over (from a single world perspective and that of our own this would be an example of backwards causation). However, in a reality where there exist infinite separate universes connected in a Presentist’s perspective of space-time, the action of tying ones shoelaces together and falling over would occur in their natural and consecutive causal arrangement.
This is a particularly simple and powerful concept to grasp and is certainly in opposition to the general belief that by incorporating a multiversal construct of space-time we impose unmanageable complexity.
Of course, as with every model that attempts to explain the plausibility of time travel, there are a number of limitations. These challenges have been put forward, in particular, by Abbruzzese (2001) in contrast to the Presentist’s multiversal time travel concept. Whilst most arguments in opposition to the concept of a multiverse focus on the complexity of the model (when there are a number of other models that can account for similar problems) rather than pointing out actual issues with the reasoning, the proposals put forward by Abbruzzese are particularly pertinent and do challenge our understanding of the multiverse. The first stems directly from our previous argument in support of a parallel world construction of time. It concerns whether or not we can consider time travel, particularly by our Presentism method as being actual time travel,
“The time traveler who journeys to 1001 is not traveling back to 1001 at all, as the traditional conception of time travel would seem to require; rather, it is more precise to think of his traveling across to 1001”
Abbruzzese 2001, p.37
By eliminating backwards causation, have we in turn eliminated actual time travel? In my opinion, this is not the case. We may well travel ‘across’ time but surely this universe (which up until our arrival is the same in every respect to our own) could be considered a ‘present’ version of our past? It appears that, rather than directly questioning the existence of a multiverse, this argument questions our definition of what time travel exactly encompasses.
Abbruzzese concedes that, although this travel may indeed be peculiar from the perspective of space-time (backwards causation never arises) this is not enough to disqualify the interpretation of parallel universes as being a plausible construct for time travel.
The second limitation concerns identity and its relation to a construct of infinite worlds. We might, as Deutsch (1997) suggests, travel to another universe to meet ourselves, or to kill our grandfather. As our model of the multiverse suggests, we are fully capable of performing these actions, they will simply occur in a universe that dictates their occurrence, but is this person who they appear to be? Abbruzzese (2001) suggests that this is not the case, claiming that “exact similarity, as the metaphysicians tell us, falls short of identity.” (Abbruzzese 2001, p.37). It is at this point that philosophers in support of a multiverse model of time travel, such as Deutsch (1997), question our understanding of the concept of identity. If the multiverse is to provide an adequate model for time travel, which he and I believe it does, then our current understanding of identity and time needs work. In contrast, the skeptics of the many-worlds interpretation of time travel would claim that it is the theory which should change.
I believe the primary strength of a multiversal construct of space-time is its unique interpretations of time travel. A multiverse, regardless of whether it be comprised of branched or parallel worlds, is one of the few concepts which, when dealing with time travel, allows for change in the ‘past’ and can accommodate time travel even when viewed from the Presentism perspective. Many, such as Sider and Abbruzzese consider the idea of a multiverse as adding needless complexity to an already hugely intricate concept and this, I would concede, is true to a certain degree, as we have seen in the consideration of identity. But such complexity need not spell the entire disregard for a truly unique interpretation of time travel as we so often see in the philosophical works devoted to time travel. Thus, I claim that though arguing the plausibility of a multiverse may involve the consideration of unusual and complex theory, it is by doing so that we gain a truly unique interpretation of space-time, one which can provide remarkably original explanations to the concepts of time travel.
yeah we've got a fair bit of drokz... Can't help myself when it comes to akira, tailz n drokz... Let u know soon when good to catch up... speack soon.. JEN xxx
thanx.. Will b on next night terror recordings compilation out soon... AAAAAHHHHHH!!!! less then 2 weeks to go until utter madness!!! u know what time ur playin @ yet?
2 more new tracks.. one by jen Original minds commit original crimes. And anti-establishmenTERRORist by both of us... hope u enjoy... let us know what time ur playin @ nightbreed hopefully not early u diserve a descent time...
