In the first part of this article, I outlined a possible definition of time and (keeping in touch with the article’s title) offered a brief historical account of time measurement. This outline demonstrated humanity’s changing perception of the nature of time, and how an increase in the accuracy with which it is measured can affect not only our understanding of this phenomenon, but also how we perceive reality. In this article I will begin with the very latest physical theory explaining the potential nature of time, followed by a discussion on several interesting observations concerning the fluctuations that seem to characterise humanity’s chronological experience. Finally, I hope to promote a hypothesis (even though it may simply be stating the blatantly obvious) that the flow and experience of time is uniquely variable, in that the concept of ‘absolute time’ is as dead as the ‘ether’ or absolute reference point of early 19th century physics.

Classical physics dominated the concept of time up until the beginning of the 20th century. In this respect, time (in the same vein as motion) as having an ‘absolute’  reference point. That is, time was constant and consistent across the universe and for all observers, regardless of velocity or local gravitational effects. Of course, Einstein turned all this on its head with his theories of general and special relativity. Time dilation was a new and exciting concept in the physical measure of this phenomenon. Both the speed of the observer (special relativity) and the presence of a gravitational field (general relativity) were predicted to have an effect on the passage of time. The main point to consider in combination with these predictions is that by the very nature of the theory, relativity insists that all events are relative, or change with perspective, in respect to some external observer.

Consider two clocks (A and B), separated by distance x. According to special relativity, if clock B is accelerated to a very high speed (at least 30,000km/s for the effects to become detectable), time dilation effects will come into play. In effect, relative to clock A (which is running on ‘normal’ Earth time), clock B will be seen to run slower. An observer travelling with clock B would not notice these effects – time would continue to pass normally within their frame of reference. It is only upon return and the clocks are directly compared that the inaccuracy becomes apparent. Empirically, this effect is well established, and offers an explanation as to why muons (extremely short-lived particles) are able to make it to the Earth’s surface before decaying. Cosmic rays slam into the Earth’s atmosphere at high speed, producing sufficient energy when they collide with molecules for the generation of muons and neutrinos. These muons, which normally decay after a distance of 0.6km (if stationary/moving slowly), are travelling so fast that time dilation effects act to slow down the radiological emission process. Thus, these particles survive much longer (penetrating some 700m underground) than normal.

General relativity also predicts an effect on our perceptions of time. Objects with large mass produce gravitational fields, which in turn, are predicted to influence time by slowing down its perceived effects in proportion to the observer’s proximity to the field. Clock A is on the Earth’s surface, while Clock B is attached to an orbiting satellite. As Clock B is further from the centre of the Earth, the gravitational field at a lower potential, that is, it is weaker and exerts less of an effect. Consequently, the elapsed time at B (relative to Clock A) will be shorter (ie, Clock B is running faster). Again, this effect has been tested empirically, with clocks on board GPS satellites forced to undergo regular adjustments to keep them in line with Earth-bound instrumentation (thus enabling accuracy in pinpointing locations). Interestingly, the effects of both types of dilation are additive; the stronger effect wins out, resulting in either a net gain or loss of time. Objects moving fast within a gravitational field should then experience both a slowing down and speeding up of time relative to an external observer (this was in fact recorded in an experiment involving atomic clocks on board commercial airliners).

Frustratingly, the physical basis for such dilation seems to be enmeshed with the complicated mathematics and technical jargon. Why exactly does this dilation occurs? Descriptions of the phenomenon seem to lack any real insight into this question, and instead proffer statements to the effect of ‘this is simply what relativity predicts’. It is an important question to ask, I think, as philosophically, the question of ‘why’ is just as important as the empirical ‘how’, and should follow as a natural consequence. By probing the meta-physical aspects of time we can aim to better understand how it can influence the human sensory experience and adapt this new-found knowledge to practical applications.

Based on relativity’s notion of a non-absolute framework of time, and incorporating the predictions of time dilation, it seems plausible that time could be reducible to a particulate origin. The field of quantum physics has already made great headway in proposing that all matter acts in a wave-particle duality; in the form of waves, photons and matter travel along all possible routes between two points, with the crests and troughs interfering with, or reinforcing, each other. Similar to the double slit experiment (light and dark interference pattern), only the path that is reinforced remains and the wave collapses (quantum de-coherence) into a particle that we can directly observe and measure. This approach is know as the ‘sum over histories’ hypothesis, proposed by Richard Feynman (which also opens up the possibility of ‘many worlds’; alternative universes that branch off at each event in time).

In respect to time, perhaps its re-imagining as a particle could explain the effects on gravity and velocity, in the form of dilation. One attempt is the envisaged ‘Chronon’, a quantised form of time which disrupts the commonly held interpretation of a continuous experience. This theory is supported via the natural unit of Planck Time, some 5.39121 x 10ˆ-44 seconds. Beyond this limit, time is thought to be indistinguishable and the notion of separate events undefinable. Of course, we are taking a leap of faith here in assuming that time is a separate, definable entity. Perhaps the reality is entirely different.

Modern philosophy seems to fall over when attempting to interpret the implications of theoretical physics. Perhaps the subject matter is becoming increasingly complex, requiring dedicated study in order to grasp even the simplest concepts. Whatever the reason, the work of philosophers has moved away from the pursuits of science and towards topics such as language. What science needs is an army of evaluators, ready to test their theories with practical concerns in mind. Time has not escaped this fate either. Scientists seem content, even ‘trigger happy’ in their usage of the anthropic principle in explaining the etiology of their theories and any practical inquiry as to why things are the way they are. Basically, any question of why evokes a response along the lines of ‘well, if it were any different, conditions of the universe would not be sufficient for the evolutions of intelligent beings such as ourselves, who are capable of asking the very question of why!’. Personally, this approach does make sense, but seems to have the distinct features of a ‘cop-out’ and circularity; alot of the underlying reasoning is missing which prohibits deeper inquiry. It also allows theologians to promote arguments for the existence of a creator; ‘god created the universe in such a way as to ensure our existence’.

What has this got to do with time? Well, put simply, the anthropicists propose that  if time were to flow in a direction contrary to that which is experienced, the laws of science would not hold, thus excluding the possibility of our existence as well as violating the principles of CPT symmetry (C=particle/antiparticle replacement, P=taking the mirror image and T=the direction of time). Even Stephen Hawking weighs in on the debate, and in his Brief History of Time, proposes the CPT model in combination with the second law of thermodynamics (entropy, or disorder, always increases). The arrow of time, thus, must correspond to and align with the directions of these cosmological tendencies (universe inflates, which is the same direction as increasing entropy, which is the same as psychological perceptions of time).

So, after millenia of study in the topic of chronology, we seem to be a long way off from a concrete definition and explanation of time. With the introduction of relativity, some insights into the nature of time have been extracted, however philosophers still have a long way to go before practical implications are expounded from the very latest theories (Quantum Physics, String Theory etc). Indeed, some scientists believe that if a grand unified theory is to be discovered, we need to further refine our definitions of time and work backwards towards the very instant of the big bang (under which it is proposed that all causality breaks down).

Biologically, is time perceived equally among not only humans but also other species (animals)? Are days where time seems to ‘stand still’ sharing some common feature that could support the notion of time as a definable physical property of the universe (eg the Chronon particle)? On such days are we passing through a region of warped spacetime (thus a collective, shared experience) or do we carry an internal psychological timepiece that ticks to its own tock, regardless of how others are experiencing it? When we die is the final moment stretched to a relative infinity (relative to the deceased) as neurons loose their potential to carry signals (ala falling into a black hole, the perception of time slows to an imperceptible halt) or does the blackness take us in an instant? Maybe time will never fully be understood, but it is an intriguing topic that warrants further discussion, and judging by the surplus of questions, not in any hurry to reveal its mysteries anytime soon.