Picture yourself sitting sideways in a train looking out of the window. You can not get up from your seat and the train is moving at a constant speed. The window is 1 metre high and its width may vary from 1 to 1000 millimetres. Notice that this width is measured in the direction (dimension) parallel to the one the train is moving in. What do you see?
Regardless of the width of the window, the light reflected by the passing landscape will reach your eyes; you will see the same no matter how wide or narrow the window. Still, the wider, the better you will be able to comprehend what you are seeing. This is because with a wider window every detail will be visible for a longer period of time than with a narrower one.
The above is an analogon. Instead of sitting in a train, we are "being" and "moving forward" in time. Instead of a window, we have "awareness", which is in fact the perception of events in time, including ourselves and our own thoughts. Note that a dead unaware object would be analogous to a person sitting in the train without a window in front of one.
Like the window has a width in the direction the train is moving in, awareness has "extendedness" in time. Since the window is moving, the time interval of awareness is shifting forward in time. Like the window may vary in width, the time interval — let us call it "Time Window" — may vary. And the longer it is, the better we are able to comprehend what we perceive and experience.
Time Windows of different entities are centred. Otherwise we would not perceive each other.
We can likely extend our Time Window a little by concentrating to understand or solve something. And when unconscious or in a dreamless sleep it shrinks to almost nothing.
The size of our Time Window is probably below or in the order of our threshold of perception, which is on average somewhat below 100 milliseconds. It may even be related to this threshold. In this respect it should be mentioned that this threshold has been found to correlate with intelligence test scores; Arthur Jensen reports on this research in his book The g factor.
The correlation of perceptual threshold with I.Q. however is negative, so that low thresholds go with high I.Q., which shows that this threshold itself is not the Time Window. At this moment (2024) I am not certain at all if the Time Window, if it exists, has size in time as such. I am considering it may have size in a spatial dimension, like the fourth dimension, also but misleadingly called "imaginary time" and having the √-1 metre for a unit. My best current guess is that the Time Window is what I call "awareness" or (in its outward expression) "creativity", being the synergy of conscientiousness, intelligence, and associative horizon. If true, this trait would then have a physical measurement in (imaginary) metres.
More precisely, I imagine the working mechanism behind all this to be something like the following: The brain receives input from the senses, resulting in brain activity that, thus triggered, mirrors the outside world in the form of patterns of neuronal activity. But the brain also mirrors itself while mirroring the world, and this embeddedness may be what constitutes awareness. I picture that the embedded imaging of the world brings forth, as an "extra" or emergent phenomenon, an extendedness in a spatial dimension perpendicular to the usual three, and this perpendicular extendedness then provides a perspective on the world that allows aware perception. I would even suggest that the thus emerged extendedness actually creates that dimension, and therefore creates time in case it is the (imaginary) time dimension. Moreover, the thus resulting aware perception and (time) dimension give rise to existence itself, for nothing exists without aware perception/verification, and nothing exists without time. The existence of the universe starts with the emergence of awareness, and anything "before" it is hypothetical and speculative.
An interesting question is whether awareness as meant above is localized and restricted to its emanating brain, or is part of a single global or universal awareness, as some suggest. Given that, in my understanding, awareness requires a compact brain infrastructure with sufficient conduction speed for the needed patterns of activity to arise within a few tenths of a second, I do not see how a global or universal awareness could emerge. The infrastructure is not there, and the distances are too great. For similar reasons, the notion of awareness being possessed by every little piece of dead matter must be rejected. Nevertheless I believe that phenomena like extrasensory contact between different units of awareness, as well as clairvoyance, precognition, psychokinesis, and morphic resonance, can not be entirely excluded, seeing the nature of spacetime, not to mention quantum physics. There may be theoretical possibilities for such extrasensory or psychic phenomena, but the practical proof of them is heretofore lacking. I also doubt that the assumption of the existence of such phenomena is necessary to explain any observation. On the other hand, the assumption of extrasensory contact or coordinating resonance between units of awareness might be required to explain why we are all living in the same objective world, and not in different private subjective worlds of our own.