We apprehend a three dimensional world in time, and in time it has been since its beginning. From the moment at which the infinitely massive, infinitely dense, concentrated singularity explosively began its expansion outwards, creating space as we know it, the universe had a direction. This asymmetry, this basic directionality in the universe, is called Time
Time is change and change in time is irreversible. Time itself is irreversible, unrepeatable, and whether or not it exists outside of consciousness ,(footnote here regarding theories that time does not exist outside of the subjective consciousness)this principle of irreversibility is what time is. It has one fundamental property: direction. It is even misleading to say that time has a direction, in fact time is direction, and everything that inhabits it, the totality of the three dimensional world, can be described in term s of it.
The measurement of time, and its utilization in human communities throughout the world, in other words, the utilitarian concept of time in common practice, is both different and similar to the existence of time in the sense discussed above, as a universe principle. In the prior sense, time is a dimension, and its effect, that of directionality in terms of itself, is detectable throughout the universe. In our human experience, directionality in time is a fundamental irreversible constant present in every aspect of our experience, and this informs time’s utilitarian applications and our measurement practices regarding it. Commonplace linguistic and practical usage of time referents belie a deeper truth: expandable and compressible spacial dimensions – when describing an object like a planet or a peanut – exist in the medium of time. In the English language, in fact, objects are described as being “in” time, and the use of this preposition, and the inherent inside/outside dualism that it implies places objects within time as as if spacial entities, their developments, and space itself, exist in suspension, floating in a moving river of time, to borrow a common traditional metaphor. In any case, spacial entities, their developments, and space is commonly referred to in terms of time, and it seems as if it must be, as if time with its property of irreversibility, provides a ground on which the figures of spacial articulation, that is three-dimensional objects, interact. Yet a paradox lurks within this idea, for it is the expansion of space itself, outward from its beginning with a big bang, that creates the directionality, the endless change, that gives a future and a past to the universe, and thus creates time, which is this property of movement itself.
So then, looking past the immediate perception of time and thus sidestepping the entire question of whether the perception of time is an artifact of our conscious mind itself, a function of the memories we store as biochemicals in our brains, it is clear that if one adopts a cosmological model of universal expansion – at least for the present development of the universe- than one also accepts that the universe has a shape and a direction. Put another way, it is possible to assume a certain consistency between cosmological scales and human scales of time perception In common practice, given a consistent linearity between time as perceived in our own life experiences, and time as perceived in the earth’s fossil record, for example. In short, the action of time seems consistent across many (foot note ref QED Fenneyman) if not all frames of reference. Such an idea relates our sensation of time not inconsistently to the directionality of the universe as a whole, as implied by spacial expansion in one direction since the big bang.
At least one currently popular cosmological model seems to agree with this (citation). The universe, it seems, and space itself, is expanding, and always has been, since the beginning. Before the big bang time did not exist, and neither did anything else. Judging by recent estimates (citation and footnote) of how much mass exists in the universe, some theories indicate that it should, in fact, continue to expand forever. In such a model reversibility, or repeatability, could not exist on any scale. Such a universe of three, four, or more dimensions exists as a great puddle of change spilling forth from an initial point and such universal, infinite expansion of everything in an outward vector implies direction, at least, from an earlier more inward point. On the other hand, as such an expansion is not an expansion into anything, how can it be said to exist? If reality expands into, as it were, itself, than how can we trace its progress , and would the expansion itself be consistent or variable?
The answer comes along with that energy which itself makes it possible for us to know that such expansion exists. That energy is light. Light emitted by stars represents a broadband, high energy radiation. When it is shifted into the red from the perspective of an observer, this means that the object is travelling away from the observer. Fundamentally, this is very close to the audio phenomena of Doppler Shift, in which, for example, an ambulance approaching an observer at high speed, passing the observer and then continuing to speed away into the distance is heard to emit a siren which, from the standpoint of a stationary observer first rises in frequency (perceived as pitch) and then falls as the ambulance approaches and then passes the observer, respectively. This effect occurs from the standpoint of an observer because the sound waves emitted by a moving object are first compressed in the direction of motion with respect to the listener and then elongated as the sound producing source recedes into the distance. Since higher frequencies are perceived as higher pitches, the spacial compression of the wavelength emitted by the sound producing object (the siren in the example above) results in a higher frequency as perceived by the stationary observing listener, though the sound emitted by the siren itself (or any sound producing body in motion) remains consistent.
In terms of light higher frequencies correspond to the blue end of the visible spectrum and lower to the perceived red end, therefore objects in recession with respect to an observer appear to be redish in color, while those in motion towards an observer would appear blueish. Since, according to recent astronomical observations, all other galaxies appear to be redshifted with respect to our vantage point in the Milky Way, one can deduce that in fact these redshifted structures are moving away from us. All apparent large scale structures moving apart from one another seems a credible argument for universal expansion, for spacial expaqnsion. This becomes more complicated, however, if one considers the question of what the universe, what space itself, is expanding into.
Many cosmologists suggest (citation) that the cosmos is not, in fact, expanding into anything, but that space itself is expanding. Stretching, as it were, out into all dimensions. However, since space is more or less nothing, how do we map it in order to understand its direction of expansion. Further, how can we know the shape of the universe?
Space is mapped by the energy that it contains, whether this energy is contained in three- dimensional objects or whether it exists as fields of radiation. Light, or electromagnetic radiation in general, can function as an indicator to map out the shape and development of the cosmos. Radiation, including light, interacts with objects, including our telescopes and other instruments, and offers us a way to theorize about the age, size, direction of motion, or behavior in general;, of cosmological bodies. We look to the galaxies furthest from us, receding, from our perspective on earth, at a rate close to the speed of light, as an indicator of the furthest cusp of spacetime, and the edge of the expanding universe.
Here light emerges again, but this time its function is as a limit. As is well known in popular and professional publications (citation) the speed of light sets certain limitations on the realm of human experience. According to the theory of Special Relativity (citation) frames of reference in motion relative to one another account for the difference in the energies and information perceived by an observing system at rest relative to its own coordinate system and those emitted by a system moving relative to the observers coordinate system (whether or not that system is moving or at rest relative to their own coordinate frame. Further, as a moving system increases in velocity relative to an observer at rest relative to its own coordinate system, the moving system would be seen to elongate in space and become more massive. In addition, it would be observed that a clock present in such a moving system approaching the speed of light in relation to one at rest within a coordinate system would tick slower and slower as the velocity approaches the speed of light. From the standpoint of an observer within the moving system, however, all would progress as usual (or so goes the theory), such an observer would not perceive a change in size, mass, and the clock would tock as before, even Stephen, and the moving system could continue to try to accelerate towards the speed of light.
The problem is that this seems to suggest that in fact the speed of light cannot be exceeded. If, upon approach to it objects mass, and size increase towards infinity and time moves infinitely slower, than the situation becomes similar to trying to cross the threshold of a door by taking a step one half the distance of each previous step. Forgiving for a moment the limit of one’s foot size, which would impose itself on the situation rather quickly, one can see how the situation quickly explodes into an infinity of fractions and the doorway would remain forever unreachable. To try to port this metaphor into our experience of objects moving relative to one another and relative to the speed of light is fairly logical since we have information about objects at a distance do to the radiation, the light that they emit. A system moving faster than itself is not possible, and one moving faster than all energy emitted by it would certainly be invisible, not to say bizarre. Movement exists in relation to a coordinate system perceived to be at rest, or a system at rest relative to its own coordinate system, however if the universe itself is expanding as indicated by the directionality of the time dimension, it is difficult to say that stasis exists objectively anywhere.
Further, if the systems of perception, that is, the systems for receiving information are limited by lightspeed for their reception of radiation-energy than it would be logical that to exceed that would be impossible while inside of such a frame of reference. It also seems impossible to adopt another frame of reference, in practice. Any attempts to break out of this one by crossing the lightspeed limit result in the distortions discussed above, or so goes the theory. Thus, it seems that the speed of light sets a limit on the nature of reality in general. It is interesting to consider, however, if this is true across several orders of magnitude.
This introduces a number of problematic situations. First of all, the galaxies furthest from us, those mentioned above whose light we might hope to use to indicate the furthest visible cusp of the expanding universe, in fact seem to be moving away from us at a rate faster than the speed of light! Further, going the other direction along orders of magnitude, very small particles are sometimes annihilated within atomic reactions in which a particle is said to interact with an anti-particle of the same type (citation). In such reactions it has been argued that in fact what happens is that time is moving backwards as these energies are in motion close to light speed.
With regard to the first situation, that of the galactic recession at super light speed, it is possible to consider that the rate of expansion of space itself is in fact faster than the speed the light from the galaxies is traveling towards us. Thus the velocity of spacial expansion is faster than the velocity of light in space. If the spacial expansion can be utilized to explain the directionality of time, than it could be said that the velocity of time is greater than the velocity of light, and that does not, on the surface seem to make sense.
One partial solution to the problem, however, is to consider the coordinate system from which we are viewing these galaxies from. We too, are in motion, and seeing as the light reaching us from these furthest receding galaxies (as seen by the Hubble Deep Field telescope, citation etc) takes a considerable amount of time to reach us, along with the distortions enacted up on by the gravitational fields of massive objects around which light bends along with space itself, which, according to further relativistic theory, is the cause of gravitation (citation). This introduces still more fascinating problems such as how it is possible that the galaxies furthest from us appear to us to recede from us at a value greater than than of the speed of light. Is this due to some change in the value for the speed of light at the edges of the universe? Or could such a phenomena be caused by our observational position with regard to the universe as a whole?
Space and time, though often conceptually separated in commonplace experience, are tightly united physically and cosmically. Is space itself moving, expanding, faster than the speed of light? Since the Hubble constant is a spacial constant but not a temporal one, could it be said that galaxies expanding along with universe itself could exceed the speed of light? Does this mean that the speed of light might itself be slower than the “speed of time”, which in this case the rate of universal expansion itself?