The Nature of Time
This topic is going to wend between time and consciousness, which are (as we will see) deeply interconnected subjects. It's a nasty chicken-vs-egg sort of problem, so we'll just arbitrarily start with time and then explore until we uncover the deep circular nature of the subject.
Time is problematic in many ways: philosophically chief amongst them, although there are other difficulties involved in the entire notion of time which I'll gloss over for the purposes of this essay. The issues are numerous, and include (but are hardly limited to) such issues as time travel paradoxes, physics problems, entropy, and so forth. A major outstanding question in physics involves the so-called "arrow of time." According to the currently accepted models of physics, there is no particular reason why time should "flow forward" as we perceive it to do. Relativity allows all manner of time-related phenomena, and in a general sense, suggests that all temporal states of the universe exist simultaneously in a four-dimensional space. Quantum mechanics is modeled on processes that are fully reversible in time; that is to say, the equations are solvable and produce valid results for both positive and negative deltas in time.
Even classical Newtonian mechanics shows no bias for time moving in a particular direction; the sign of delta-t can be positive or negative freely, allowing us to both predict future outcomes of mechanical processes as well as reverse-engineer prior states of a system, provided we know enough about its current state and its workings. This is fundamentally at the heart of most of the outstanding research in physics, and in particular in cosmology; when studying distant objects such as galaxies millions (or billions) of light-years away, we rely on the reversible nature of temporal equations to allow us to draw conclusions about the processes that govern the universe as well as its past (and future) states.
So why is it that we seem to only experience time moving forwards?
The root of this question is, of course, "experience." What we perceive does not, in any meaningful sense, capture the full reality of what exists. If all states of the universe exist simultaneously, either in relativistic 4D space, or in quantum superpositioning of some form, then why do we only "feel" that time moves forwards? Why can't we rewind time and perceive the past, or accelerate it and perceive the future? Why do we have these notions of "now" and "past" and "future" to begin with?
It is my contention that the essence of consciousness is a crucial component in understanding the phenomenon of our perception of time; this may seem at turns either deeply profound or almost nonsensically tautological, depending on how you think about it.
So, let's consider the nature of consciousness.
Consciousness is, for lack of a better descriptive metaphor, a form of feedback loop. As events progress, they affect our perceptions, which feed into our mental model of reality, which in turn leads us to act out and cause further events. Even if we conduct a brief thought experiment involving a hypothetical being which can consciously observe but not influence the universe, this principle holds; such a being would affect its own state simply by making an observation. This is deeply intertwined with the nature of quantum mechanics, although the full extent of that particular exploration deserves an essay all its own.
In a nutshell, consciousness is all about constantly updating a mental model of reality based on perceived inputs from that reality. We can distort the inputs (as in blindness, deafness, and so on) and thereby distort the mental model; or we can distort the mental model and thereby distort the entire process of consciousness itself (as in psychosis). This observation stems from the processes we use to model AI, which follow a fundamentally identical pattern.
To expand, our mental model can be thought of as a continuous refinement of "snapshots" of reality. As perceptions are received, the model is adjusted correspondingly. Whether this is genuinely continuous in a mathematical sense, or instead discrete, is up for debate - but, fortunately, that is largely irrelevant. The important factor is that the model is progressively updated as perceptions occur.
Therefore, at time T, our mental model consists of the mapping of our perceptions at time T combined with the data we have accumulated at all times up until T-epsilon, where epsilon is any arbitrarily small value. This data is filtered through the same mental model in a process that both reflects the current state of the model, and mutates that state; thereby we can understand, reflect, and interpret, while drawing on past experiences, and also learn by adapting our mental model to accommodate new information.
The Arrow of Consciousness
This raises an important question: can we model consciousness as a process analogous to classical mechanical processes, i.e. can we describe it in a way where time is reversible?
This is a tricky question. On the one hand, we can "rewind" to any previous state by subtracting out any perceptions received between the current state and the prior one, and reversing any mutations of the mental model correspondingly. We can also "accelerate" by providing perceptions that do not correspond to the current mental model state, i.e. come from future times. In a sense, then, consciousness is fully reversible from an outside perspective. Given sufficient information, we can simulate traveling through time in both directions.
The problem is that this is a fundamentally destructive process, because of the feedback nature of consciousness. To move backwards, we must eliminate information and undo mutation of the mental model. To move forwards, we must provide additional information and mutate the model at all steps between the initial and target time snapshots.
In other words, if a conscious being were to have its "mind" rewound, it would not be able to tell. To rewind consciousness we must remove information from the universe, lest any remaining dregs of that information influence the agent's perceptions, and thereby bring down the entire house of cards. This is tantamount to rewinding the entire state of the universe. If one's mind were rewound without rewinding all of time simultaneously, there would be an instant disconnect between perceptions and the mental model, and the mind itself would rebel; in a word, this would cause instant insanity and possibly even the self-termination of consciousness altogether.
By the same token, we cannot accelerate a mind without accelerating all of reality at the same time. A mind is shaped by its continual perceptions and refinements of its internal model of reality; to maintain integrity of the mind during an acceleration, we must maintain the integrity both of the perceptions over time as well as their mutative effects on the mental model itself.
Therefore, consciousness is indeed independent of time - but not in a sense that is practically useful to the conscious agent itself. One would have to literally transcend the existence of the universe to meaningfully affect the temporal state of a conscious mind, or risk destroying it altogether.
So in a sense, when considering a single self-contained conscious agent, we cannot usefully travel through time independently of the state of the remainder of the universe. In relativistic terms, consciousness is directly bound to individual positions along the temporal axis. That is, there is a one-to-one correspondence between snapshots of our mental model and snapshots of all reality. We cannot, even in principle, experience a moment which we are not physically bound to.
Revisiting the Arrow
In practical terms, this has interesting implications. Suppose time were to flow backwards for a while, then resume its normal course of forward travel. As conscious beings, we would never know; all of reality would rewind, and with it so would our mental states. Once forward progress resumed again, we would continue as if nothing had happened. We would not be able to "be aware" that time had rewound, because our own mental model would rewind with it. Consequently, time could arbitrarily move forwards and backwards whenever it pleased, and we would have no means to detect it whatsoever, even in principle.
The same reasoning applies to acceleration. If time were to flow forwards more rapidly for a period, we would not be able to notice; our mental models are, fundamentally, bound to our physical perceptions of reality, and therefore if time moved more quickly, our mental models would simply move more quickly right along with it.
Perhaps most interestingly, this applies to negative, positive, and zero time movement. That is to say, if time stopped for a while, we'd have no way to notice, because our mental models would cease to be updated during the pause.
Therefore, it is entirely possible that time moves all over the place and in many directions; we would never know.
So why, then, do we perceive time to move forwards?
Simply put, this is because it's the only way we can perceive anything at all. To perceive and understand that perception is to update our mental models; but this requires advancing both our minds and our physical states in lockstep. Rewinding makes no difference, pausing makes no difference, and acceleration makes no difference. The only thing that produces an effect on our minds is forward progress, and it will do so at a constant ratio to the forward progress of time in a universal sense.
The Chicken and the Egg
Consciousness, then, is a result of the flow of time in a forward direction. Without this flow, the process of consciousness does not update, and therefore nothing happens within the mind. With accelerated or reversed flow, consciousness changes states to match physicality; it can't detect anything but forward movement.
But wait! The flow of time is a result of consciousness! If we were not aware, we would not care if time moved forwards or backwards at all. We would have no way to determine if time did anything, ever. All states of the universe could coexist physically along a fourth spatial dimension, with no problems whatsoever. We could move randomly between those positions in temporal space without issue, but we would never know it happened, because at each slice of physical space, our consciousness would by necessity be accelerated or rewound into the corresponding mental model state.
Therefore, time could be a shuffled deck of cards for all we know. 1994 could just as easily have occurred before the formation of the Earth as vice versa. From our perspective as conscious agents, this is immaterial; as the state of the universe changes, so must the state of our minds accordingly, and thus the "real" sequence of events is forever impossible to ascertain. All we can do is perceive the physical consequences of time moving in a single direction, and since our ratio of consciousness-elapsed-time to real-elapsed-time is locked to one, we effectively always perceive time moving at a single rate. (Don't drag me into debates about how "today felt really long" here; that's a fundamentally emotional epiphenomenon which is interesting in its own right, but not worth examining here.)
The best I can summarize this is that consciousness and time are fundamentally linked, much like electricity and magnetism. I think they are not so much distinct concepts as orthogonal aspects of the same single entity. The weave is tight here, and the significance - I suspect - is profoundly deep.
The consequences I cannot pretend to plumb in so short a space, or with so little sleep to draw upon.