A brief(er) history of time: Part one

Time; the fourth dimension, inexplicably linked with space and dynamic in nature. According to Einstein and backed up by decades of empirical research, time is a variable phenomenon. This seems contrary to common belief as we often represent time as a pillar of stability, marching inevitably forwards and unwaveringly ticking away. This ‘inevitability’ of time has lead to the attachment of negative connotations, including themes of death and the ‘running out of’ time itself. As our society tends towards briefer periods of meaningful interaction and longer periods of unpleasant activities (work, commuting, queuing) it seems as though attitudes towards time are most favourable when it is ‘running fast’, thus minimising mental stress and anguish (reducing the perceived waiting/unproductive period). To this effect, time has been described as ‘the fire in which we burn’; a finite (at least in terms of human lifecycles) feature of our universe that is personified into some sort of omnipotent adversary. It is my intent, through the medium of a two-part article, to firstly present a condensed and brief history of the physical representations of time followed by the current understanding of this phenomenon and how it relates to everyday experience.

Humankind has been fascinated by time ever since the dawn of consciousness and self-directed thought. Exemplified and measured initially through the patterns and cycles exhibited by nature, time was quickly utilised as both a tool and a catalyst for philosophical thought. Time is the canvas upon which causes and effects occur. Without it, there would be no history, no future, only unconnected moments blended into one almighty chronometric experience. In a timeless universe and provided the intelligent observer was also given the gift of immortality, they would similarly experience both the birth and death of the universe in an instant; non-locality would be universal (time to travel between points would be instantaneous as there would be no reference against which to measure its passing). In short, the agent would be a god. But of course, this is not the case. We tend to think about time in the infintesimally short periods that correspond to the duration of the average human lifespan – 70 to 80 years. Ironically, the thing that we most wish would ‘hurry-up’ is only hastening our own non-existence (in the form of death).

Time fascinated early civilisations (and undoubtedly the groups of nomadic hunter gatherers that preceded them). They constructed vast, complicated monuments and invested much time and effort creating increasingly complex tools to measure the passage of time. Our ancestors realised that in order to measure time, the most important component needed is an objective, regular cycle. Naturally occurring examples of this were plentiful; seasonal changes in foliage signaled the changing of climate and food availability, and tracking the sun and other astronomical bodies in the sky could be used to measure the period of day and night. Water-powered clocks were perhaps the first timepieces that were independent of astronomical intervention (eg the sundial and yardstick). These devices worked by harnessing the regularity of flowing water. Quite complex additions to the basic flow such as gears, weights and threaded screws allowed a constant source of energy (water flow) to power timing components of the clock (filling up containers, raising pointers, turning wheels and gears). Quite quickly, the need for increasingly accurate devices to quantify time acted as a momentum for technological development in this area. Galileo (and Huygens) are credited with creating the first of such devices; a timepiece powered by the harmonic motion of a mass connected to a central pivot point via string. This improvement introduced more accurate timepieces, however they still lacked practicality. Like the water clocks before them, pendulums were bulky, unreliable over long time periods and required stability in order to function. These issues, coupled with a desperate need to improve the accuracy of marine navigation spurred John Harrison on to create the first purely mechanical and portable clock. The problem of nautical accuracy stemmed in part from the lack of a reliable method of keeping time. With an accurate timepiece and heading (provided by the compass) navigators could keep better track of the vessel and utilise the method of longitude/latitude to plot complex courses through the oceans. Designed specifically for the rugged conditions aboard a sailing vessel, Harrison’s device offered unparalleled accuracy on long voyages and a solution to the problem. Unfortunately, Harrison battled for the remainder of his life to claim the prize offered by the British government for creating such a timepiece.

Of course, modern timepieces have advanced rapidly. The next ‘great’ advancement was the wristwatch, or more specifically, the digital wristwatch. Quartz crystal displays the useful property of piezoelectricity. When placed within an electric field (attached to a power source) the crystal will change shape. By sculpting the crystal’s shape into that of a tuning fork, it can be made to resonate at a specific frequency, which in turn, allows for these cycles to keep track of time. In effect, the regularity of the quartz bending and flexing (through electric stimulation) can be specified by shaping the material in a specific way and can be electronically ‘tallied’ and modulated to the base unit of seconds (and, in turn, minutes, hours etc). Even further improvements to the measure of time were introduced with the atomic clock. This method of time-keeping, in a very general sense, works similarly to the oscillating quartz crystal, however the crystal is replaced with radiation. Most commonly, caesium gas is used as the oscillator, and excited by beaming microwaves into the apparatus. The universal ‘second’ is thus defined as the number of cycles of radiation emitted by a caesium atom when progressing through two levels of the ground energy state. Basically, the point I am trying to illustrate here is that the measurement of time becomes increasingly accurate as the underlying complexity increases. The concept of a ‘second’ has improved from a simple definition (time taken to fill a holding capsule – water clocks) to one involving cycles of radiation as an atom is excited (9 192 631 770 cycles : 1 second). Therefore, with an increase in the inherent complexity of the underlying measurement unit (the second) and the regularity of the cyclic period, we see a direct relationship to overall accuracy of both the device and practical applications that make use of time.

But what does it all mean? What is the point of pushing the development of timepieces towards increasing accuracy? As in Harrison’s time, navigation relies heavily on the use of accurate time keeping. GPS works by establishing communication between orbiting satellites (at least 3) and the ground receiver unit. A timestamped signal and orbital information are transmitted from each satellite (an atomic clock is installed on each orbiter) to the ground. The receiver calculates the delay between transmission and interception, then uses the process of trilateration to determine the object’s ground position on a sphere (centred around the satellite). By combining three of more satellite sphere, the exact location can be pinpointed (at the intersection of each sphere).

Thanks for reading my brief introduction to the history of time measurement. The next part of this article will explore more philosophy-orientated subject matter, and use the knowledge of how we measure time to discuss how we think about time and place ourselves within its boundaries.