New Study Claims There Is One Past and Two Futures
Why does time tend to move forward rather than backwards, or in both directions simultaneously? A new study from a trio of physicists in Canada and the U.K. proposes a solution to the "asymmetry of time": that the laws of the Universe cause one past to branch off into two futures.
Many different large-scale phenomena of our universe display an asymmetry of time. Asymmetry of time, in simplest terms, means that if one played a recording of a phenomena backwards, it would cease to be logical or physically possible. However, on the microscopic level, scientists have generally come to the consensus that physical processes follow time-symmetric laws. Physicists call this problem the "arrow of time" problem, and have been attempting to explain for many years why certain macroscopic phenomena seem to operate according to "an arrow of time that points in the same direction everywhere at all times." Trying to reconcile these phenomena with time-symmetric laws often leads to a "past hypothesis," or the assertion that "the initial condition with which the Universe came into existence must have been very special."
But the idea of "specialness" is not an easy one to swallow in science, so this new study proposes that there were no special initial conditions, but rather that the fundamental laws of the universe lead to a system in which it only seems that time movies in one particular direction as a result of our frame of reference. The universe tends to begin with a low-complexity structure in which the distribution of particles is mostly uniform and then forms larger structures that increase in complexity. According to the authors, this is happening in both directions of time, with our position determining which path we perceive to be our "future."
From the paper: "Each solution can be viewed as having a single past and two distinct futures emerging from it. Any internal observer must be in one half of the solution and will only be aware of the records of one branch and deduce a unique past and future direction from inspection of the available records."
[Credit: Daily Galaxy]
In this diagram, we would "start" in the middle, in a low-complexity past that evolves into the higher complexity future shown at the left and right. The symmetry of time is reflected in the similarity between the left and right boxes, and the arrow of time displayed in the diagram is, in the words of the authors, "purely conventional," but time could really move in either direction. The observer would perceive time to move in a particular direction depending on which half of the mass in the center he or she was located (so if he or she was on the left half, then he or she would experience the future in the left box, and same for the right side). In other words, one past branches off into two futures, and one's position in the past determines which future he or she experiences.
The physicists' calculations lead them to conclude that there were no special initial conditions, but rather that time only moves in one particular direction in the mind of the observer: "Our results are a proof of principle: all the solutions of a time-symmetric dynamical law suited to approximate our Universe have a strongly time-asymmetric behavior for internal observers... We conclude that the origin of time's arrow is not necessarily to be sought in initial conditions but rather in the structure of the law which governs the Universe."