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Posted 19 August 2007

About Time

by Frikkie de Bruyn

Time is a dimension we all thought we knew what it was, until we were asked to describe it.

Time has always fascinated man and yet it is so slightly understood. Everything we do or experience takes place at a specific time and at a point in space. It is many things to different people but attempts to describe it fail and this is where the problem begins. We use language to describe and communicate and language is always limiting whether a scientist describes a scientific problem or when a person describes his personal experiences. Our language contains time-laden words, such as ‘event’, ‘succession’ and our consciousness is bound up in time. We ‘experience’ time but can we be sure it exists, out there, independent of us? This question is of great importance in science where one of the central issues is the question of objectivity.

Time is experienced in two fundamental ways. It seems to flow like a river, the seconds, days and years passing relentlessly. Our perception of time is also characterised by a succession of moments with a clear distinction between past, present and future. We have knowledge about the past but never of the future. The past and future are connected to what is described as the ‘now’. This experience of time is also connected to the idea of flow, but the observer is positioned at a static instant and each moment is marked off as time past.

Closely related to these perceptions of time are the more general ideas of linear and cyclical time. Time appears to be cyclical most of the time. It is like a giant ruler, stretching back into the past marked in scale of years, decades and centuries and it stretches away into the future. This idea of time arises essentially from the Judeo-Christian tradition, characterised by the creation when time began and is distinguished by unique events. Modern cosmology makes use of this perception of time, the big bang, when everything, including time began. Such a view of time is ‘progressive’ or cumulative.

Time is also perceived as cyclic and not necessarily progressive. This perception of time is based on the various cycles occurring in nature, days, seasons, and years. Time becomes therefore the element within which natural events occur, summer gives way to autumn, to winter, to spring in never ending cycles. Cyclic time is associated with pre-literate

society where time and the language used were more organic and quite unlike western languages. Language cannot be avoided when something is to be described, but the limitations of language can be made explicit. Therefore, a ‘natural’ view of time will be closely associated with its system of description. The perception of time in such societies were determined by the spacing of activities; the time it takes to walk to the nearest town, how long it takes to boil water, etc. Personal and social lives were dominated by the hours of daylight and night and the seasons and religious festivals.

The introduction of the clock and subsequently the watch changed our lives and was of great importance for science. It brought with it a new awareness of time. Our minds process information from clocks and ‘interpret’ that information as ‘being time’. Importantly the language to describe time also changed. One of the great revolutions in our perception of time was Einstein’s relativity theory. The Newtonian perception of time as separate and independent, ticking away irrespective of human activities, was replaced by the ‘personalised’ relative interpretation of time. Every person had his own time. Even watches and clocks slow down in areas of strong gravitational pull. As we approach velocities close to the speed of light, time slows down and we now know that time comes to an end in a black hole.

Time is a measure of the separation of events in space and is clearly connected to change. Such a relativistic view of time is closely related to Einstein’s relativity theory, which is a causal theory. An object, such as a star, is seen as a process with the birth of the star as the beginning and its death as the end of the process. The rate of change is then interpreted as a quantity that applies to the ‘now’ and must not be confused with the ‘flow’ of time referred to above. In physics the change of time as things change, that is the ‘flow’ of time is not a property of changes but of time itself. In short, time does not exist in the sense of objects and changes. It is a human invention that provides a mental tool to measure change and change means events separated in space.

The use of time to measure distances and changes in astronomy and cosmology illustrated the circumstantial development of our perception of time. It was nonsensical to describe galactic and cosmological distances and changes in our limited language. The astronomer refers to distances as parsecs (3.26 ly) and light years, the distance it takes light (travelling at 300 000 km/s in a vacuum) to travel in one year. Recent developments

in science indicate that the smallest unit in time is the Planck time of 10-43 seconds (the time it takes a photon to cross the Planck length of 10-33 cm. Any attempt to divide the Planck length (and Planck time) in half results in a doubling of that distance and time. This is interpreted by some scientists as indicating that time and possibly space consist of small units which cannot be further divided. The concept of time is closely related to space, the spatial separation of objects and change such as the change of seasons and days and nights. Time has simply no existence outside this context.

Frikkie de Bruyn

Books used in research for this article

- Davies, P. About Time. Einstein’s Unfinished Revolution. Penguin Books. U.K. 1995
- Green Brian. The Fabric of the Cosmos. Space, Time and the Texture of Reality. Allan Lane, U.K. 2004.
- Hawking, S. W. A Brief History of Time. Bantam, New York, 1988
- Thorne, K.S. Black Holes and Time Warps. Norton, New York. 1994
- Palle Yourgrau. A World Without Time. The Forgotten Legacy of Godel and Einstein.    

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