The Oxford Dictionary defines time as 'the indefinite continued progress of existence and events in the past, present, and future regarded as a whole'. With this the definition leaves open a lot of the really interesting questions, or does it include additional possibilities?
It does name a number of features such as past, present and future, as some sort of categories. Further it list progress implying change or even improvement. This is attributed two further elements continued and indefinite. The first one hinting at ongoing change and the later one ads a never ending property which is sort of in itself an timely attribute.
However to come to the questions, interesting are the aspects of linearity, the arrow of time, the multitude, singular or plural and of course the conception.
In todays everyday life, time has become so immersed and integrated it is generally regarded as something a natural as breathing (Glennie & Thrift, 2009, Shaping the Day). Usually perceived as an additional sense, a timesense?, but at least a natural fact. However, this is fiercely debated and often opposed by scholars. Nowadays aspects of time are everywhere everything is on time, timepieces rule every single step we take in the city and we surround us with timepieces (to make the clear distinction between clocks, watches and timepieces) where ever we are. Most household kitchens will nowadays spot about five different fix installed units telling the time of day, plus some gadgets telling the time temporal or are mobile. Of course there is more, navigation, communication, computers all really on hyper accurate timepieces, without which nothing would work.
This sort of clocktime (Glennie & Thrift, 2009, Shaping the Day) is however, not very old.
Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium atoms. SI defines the second as 9,192,631,770 cycles of that radiation which corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom. This has developed from the discovery by Galileo that a pendulum swings regularly regardless of the distance it covers. There were however timepieces long before this, sundials and water clocks, but they were less reliable and uniformed.
Since Galileo's discover around 1600 the concept of the clock developed and gained increasing significance in everyday life particularly in social life, as an regulator of practices. This nowadays manifests in the time disciplinary enforcing institutions such as schools or workplaces, but also leisure activities and entertainment.
Image taken from Wikipedia / The Creation of Adam, ca 1511, by Michelangelo Buonarroti (1475–1564)
In terms of rituals and religious practices time has played an important role for a much longer time. This has obviously defined the cultural conception of time. The linear understanding of time can be traced in Christianity with the ideas of the Beginning, God's creation of Adam and Eve and the End as the Second Coming of Christ or the last Judgement. A one way, linear procession dominates the scenes and leaves a lasting impression in the collective memory.
Image taken from Wikipedia / The Last Judgement. The Louvre. Date not known, but the work was engraved in 1615. It was probably painted in the last decades of the Valois dynasty (1560–89), by Jean Cousin the Younger, also called Jehan Cousin Le Jeune (lived c. 1522–1595).
In other cultures and religions however the conception of time is different. Cyclical in Budhism and for example in the Egyptian culture. The Greeks used two concepts for time, a formal objective Chronos and a expressive subjective time, Kairos, as an opportunity as gap or timeout.
In the culture of the Hopi Indians, natives in the south west of the Americas, the concept of time does not cover the same three tenses present, past and future. Instead the Hopi's use only two times (Whorf), an objective time and a subjective time (the terms might be confusing but the anthropology research reaches back in time where these terms might have had slightly different coinings). Those are manifested (object) and manifesting (subject). Objective elements are all the things accessible to the sense, being physical. What we call future would be in the real of the subject, the desire or the mental. The Hopi culture also relates time to space in the sense that distance is part of the manifested as a duration. As a result simultaneity does not exist. something far away can not have the same time since the 'distance' lies in between. (Tuan 1977, p.120) Spatially very interesting here is how the two concepts meet in the distance, far away merges with the dream.
Image taken from Space and Place by Yi-Fe Tuan 1977 / Page 121, Figure 15. Hopi space time: subjective and objective realms. The objective realm is the horizontal space within the cardinal grid, but at the distant edges it merges with the subjective realm as represented by the vertical axis.
Science has occupied the debate and dominated the conception of times as linear for the best part since Galileo's pendulum. Only in the 20st century, the discussions on the topic, covered in various disciplines has taken on a different perspective. Where Newton strongly argued for an objective time, a single and true time concept, Einstein developed with the relativity theory an alternative concept, allocating time a subjective role, with time passing at different speeds for different observers. This is the development in physics, but simultaneously the conception of time was reexamined by philosophers, especially the french league with Bourdieux, Lefebvre (Rhythmanalysis), Serra, DeCerteaux and others. Here the debate between objective and subjective time continued with the phenomenologists entering the debate. However, as Elias points out in his Time: an Essay, both view in their base found on the concept that time is something given, a fixe instance, measurable. In this context the third concept of social time was developed. As Elias describes it (Elias 1992): 'To perceive time requires focusing-units (humans) capable of forming a mental picture in which event A, B and C follow one after another, are present together and yet, at the same time, are seen clearly as not having happened together; is a synthesis only humans are capable of and learned and developed over generations. Knowledge of time'.
In the current debate most philosophers would agree with a concept of time that is non linear and the concept of multiple times is accepted as a social aspect.
In exact science however, the linear singular clocktime continues to dominate everything. The discussions as well as the projects and work undertaken. This lead to the increasing exclusion of temporal aspect due to the arising problems with the integration of linear time that doesn't fit with the complex systemic concepts any longer.
This could be about to change with the recent envelopment in spatial research and the focus on mobility and location data. Aspects of temporality all of a sudden move into the prime light. This of course goes hand in hand with a shift in development and availability of specialised and capable technology.
There have, in visualisation terms, interesting approaches developed. The time geography dominated by Thorsten Hagerstrand is one example (actually this one goes beyond a mere visualisation), but also the time distance based distortion maps or animated visuals. Also the aspect of comparison between two instances is used quite often. Usually the same object is shown at two different stages to visualise the change that took place between the two points in time. Implying the Newtonian time aspects apply.
How aspects of the modern discussion on the term time apply to science in the field of geography and particularly spacial analysis is still blurred, even though we increasingly see promising approaches emerge.
Image taken from datavisualisation.ch / Ebb & Flow of Book Characters by Jeff Clark working with adapted StreamGraph code to work with arbitrary text documents.