What, exactly, is time? Consider its characteristics as we recognize them. Time can be measured. But when we measure time, we do so with an object that changes in a predictable and regular way through a series of cycles: A swinging pendulum, a vibrating crystal, or an atom going through repeating quantum fluctuations. We then define a period of time, such as a second, as a certain number of these repetitions of motion.
In defining time this way, we observe that time always seems to “move” in one direction. We call it the arrow of time. We continually press forward in time, from the past, into the present, and toward the future. We define the past as a period of time that has occurred already. We define the future as a period of time that has not revealed itself to us yet.
It is difficult, if not impossible, to define time precisely because the words we use to define it are words that are associated with its meaning and characteristics: Past, future, present, yet, occurrence, flowing, happened, etc. You can’t define the word “flow” for example without an assumption of time. That time flows is assumed in its definition and is part of the definition.
Time is also defined as the fourth dimension. In our everyday world there are three spatial dimensions, up and down, back and forth, in and out, representing height, width, and depth. Time is a dimension that represents a changing state or position within these three spatial dimensions. In order to get from point A to point B in space, a certain amount of time must pass. We know we have moved from A to B on our way to C because we remember A; we can observe B, and we have no memory of C, thus the arrow of time. It depends upon our memories and perceptions.
But does time actually exist apart from our ability to perceive it? Did the universe really “begin” in a gigantic explosion called the Big Bang 13.7 billion years ago and then proceed to evolve into our present universe that we observe today? Or could it be that what we call the past still exists “today”? Could it be that the future is here “already” but we, for some reason, just can’t observe it “yet”?
Consider the arrow of time again. Time always moves forward. Or does it? Maybe it doesn’t “move” at all. What would happen, for example, if the flow of time suddenly came to a halt? What would we observe?
Well, to start, time can’t come to a halt, by definition, because our definition of time is that it is always a progression, from the past to the future. And how long would time be halted for? If time is stopped, by what measure would determine how long that state would exist? And even so, we would not notice a thing, because if time has stopped, then all our thought processes would also stop in time and with time. So whenever time started again, our thoughts would continue from that precise moment.
But what if time moved backward? Surely we would notice that, right? Well, probably not. Our thought processes, including our memories, are connected to the time frame in which they occur, so if time moves backwards, all our brain functions, thought processes, and memory accumulation would also move backward. That means we would remember the future and have no recollection of the past. The future and past would take on reverse roles. So if we remember the future but because time is going backward, we are heading into the past, our perception of events would be precisely the same as what they are now. Again, we would not notice.
What if time sped up or slowed down? Again, our thought processes, the events taking place in our brain on an atomic level, would speed up and slow down as well. So we still would not notice. The speed with which time flows and its direction will always appear the same. Our perception of time will always be that time moves forward and always at the same rate (unless you are watching a pot come to a boil).
So what does that say about what time really is? Well, what if time actually didn’t flow at all? What if time, like space, is simply a fabric within the 11-dimensions of the multiverse? What if time is simply another dimension of space but one which we perceive differently? One postulate of M-theory is that, at the moment of the Big Bang, time and space were equivalent, which helps explain the inflationary period of the universe. What if it still is but we, our minds, simply perceive it in another form?
Consider a large throw rug composed of concentric rings of yarn. Imagine each strand of yarn is an entire universe and the rug itself is part of the multiverse. All the spatial dimensions are compressed into the thickness of the strand of yarn. The time dimension is its length. But the full length of the yarn is there all the time. It doesn’t flow or move; it’s just there. At some point along the length of the strand of yarn is the Big Bang. Another point along the strand is what we call the present time.
You might imagine us as moving from the Big Bang to the present along the strand of yarn. But what if that is not the case at all. Maybe the entire time continuum has been there all along. What if it is only our perception that is moving along the strand from place to place, but maybe not even in a regular direction or at a constant speed? Maybe our place in time is determined by random quantum fluctuations? I’ve already discussed the notion that our perception of time would not change regardless of what direction time flowed, how fast it flowed, or even if it stopped. So what difference does it make whether or not time is always flowing forward at a constant speed? It would all look the same to us anyway.
But, you might ask, why do we all agree that this moment is the present? Why is it the present for everyone? What is so special about this moment in time that we can call it the present?
Perhaps this moment is only the present to me. Maybe you are at a totally different point along the time continuum strand of yarn. It still would not matter to what I perceive, or what you perceive. I would be perceiving you as you are (or will be or have been) at the precise point that my perception is located along the strand. Remember, it is a strand of time that contains every moment at all locations simultaneously. So if I am perceiving events at Point A and if you exist in time at that point, I will perceive you doing what you will be doing at Point A, even though your own perception might actually be at Point B. In addition, I will perceive you as perceiving me at Point A, even though, again, you are actually at Point B in your time. In fact, maybe everybody has there own unique place of perception along the time continuum. To everyone, it’s as if everyone else is at the same juncture in time. It’s all a matter of personal perception.
Yes, I know this discussion is highly esoteric, but it would explain a lot in terms of metaphysics, and even real physics if it were true. There would be no more wondering about time paradoxes. There would be no more wondering about a creation event. The universe was not created; it has always existed and the entirety of its time continua have existed with it. Time doesn't flow or move at all, only our perception of it.
Of course, such a scenario might bring up many more questions. Does the strand of yarn representing time branch out or is it a single strand? M-theory seems to suggest a branching thread of yarn. Is there a mathematical formula for the rate at which we perceive time to pass? And, if we extend the metaphor of the throw rug, one might ask, how was the rug created?