What is time? Merriam-Webster defines time as a nonspatial continuum that is measured in terms of events which succeed one another from past through present to future.
The Oxford Dictionary defines it as the indefinite continued progress of existence and events in the past, present and future regarded as a whole
The World English Dictionary defines it as the continuous passage of existence in which events pass from a state of potentiality in the future, through the present, to a state of finality in the past.
However time may be defined, the common element is motion. That conceptual entity we call “time” is moving or going somewhere, and typically from the past to the future, except in the World English Dictionary definition, with future to past. Time is a core concept of reality and, as such, is defined as a continuum. In each definition some form of the Latin continēre= “to hold together” is used, from which continued, continuous, and continuum are derived. Motion is always a core component of time, and each definition contains a motion-component, whether it is succeed, progress, or pass. Succeed comes from the Latin: sub=near; cedere=to go. Progress comes from Latin progressus, pp. of progradi: pro=forward; gradi= to go. Pass, the verb, means to move, proceed, or go. In essence, time’s definitions reveal it as a moving entity that holds existence or reality together.
Time is ultimately an abstract concept that is inferred to exist on the basis of our everyday experiences as events exist seemingly in a sequence from the past into the present, as the present-now becomes a past-present and a future-present becomes the present-now. Causality seems to be a major part of the process or flux of time. A match is struck and the flame follows. The held ball is released and falls. The procession from events viewed as causes to effects adds a certain scientific gravitas to time.
Is time a point or is it a flux? We have the clock definition for a point in time, the Now, and we see the second hand moving or the numbers changing on the digital timepiece, clock or watch. The Now seems to be the natural existential core over which minimal debate can be expected. The problem is that Now is not as obvious as we think. If it is in fact a point in time, then why do we see things move? We see a flag waving in the breeze, snow flakes falling, a ball thrown, various and sundry objects and creatures moving or changing. Time is not the mere summation of discrete points in time. When we look at a baseball travelling through the air, we see a flux of motion, not discrete locations of the baseball in temporal motion sequence. The human mind/brain in fact blurs some portion of the immediate past into the present moment of experiencing reality. The flux nature of time is embedded in our experience of it.
Most discussions of time include Einstein’s General and Special Relativity Theories. General Relativity is noted for Spacetime, the cosmic fabric consisting of time along with the three physical dimensions. Here, time receives a special validation in Einstein’s construct of the universe. Special Relativity fascinates people with time as being relative to motion relative to the speed of light. Time is not absolute as once enshrined in the preceding Newtonian scientific consensus. Time approaches zero as one approaches the speed of light, but mass also approaches infinity for the high-velocity traveler. Note that time comprises any scenario of a moving object, be it light itself or a super fast spaceship, as speed is the ratio of distance traveled per time interval. The interesting aspect of someone or something moving so fast to slow the passage of time is that the notion of a fixed stable time interval underlies the speed defined for this fast traveling. The current “exact speed of light” is listed as 186,282 miles per second in a vacuum. Whatever the scientific determination of distance traveled by light may be, there must be that time interval in the denominator for the distance numerator. As people entertain themselves with time slowing down for the space traveler as his/her earthbound friends and family experience normally progressing time, we are bound to the fundamental definition of speed or velocity dependent on a time interval.
Time in any discussion goes back to motion and change. Things move and change and time is inferred to exist to explain motion and change. The Arrow of Time has the progression of events from past to the present into the future. This constitutes the flow of time as normally experienced by people. I would clarify this concept of time “moving forward” as the causal chain or flux of events. Picture an object traveling and its motion is freeze-framed at points in time. Time 1 baseball moves to Time 2 position then to Time 3 position. The moving baseball is a causal flux and the past baseball leads to or causes the present and then the future baseball. In contrast to this causal-flux concept of time, I posit time-in-itself, such that all NOW’s slide into the past. What is now always becomes the past, and is thereby transformed into a “then” of the past. Simultaneously, a potential “Now” encased in the realm of future potentiality becomes Now. Physical reality possesses motion and change processes like links in a causal chain or flux that contains the infinite positions or states of an object or event in flux. Time-in-itself, core process of reality’s changing, means any given event originates as a potential event in the future, then “hatches” into the present reality or real event, potential having morphed into reality, and this present reality, a point in time, slides into the past, its past incarnation.
Given the paradox, of opposite flows, past to future and future to past, is there some resolution to solve it and make some coherent concept of time? Yes. If we conceive of NOW as perpetual, the one core constituent of experience, then this NOW is indeed moving into the future in harmony with the watch’s moving second hand or rapid flux of advancing numbers on a digital watch. Now is moving, therefore time is moving. BUT, what if time is not reduced to THE NOW? What if time is a process or dimension or basic component of reality or spacetime or existence? We have seen time is a process underlying motion and change. If we agree there is a past, present, and future, then what is the relationship or flux process among these three entities? As I stated, each present becomes a past event, and this requires a future potential event to replace the present event that slid into the past.
The unidirectional flow of time or Causal Flux is exemplified by entropy. In a closed thermodynamic system the Second Law of Thermodynamics has entropy increasing with the forward movement of time, from past to present to future. In a cup of hot water an ice cube is placed, and the discrete separation of hot water and cold ice morphs into warm water as the heat energy melts the ice and the ice’s coldness cools the surrounding water. A nail of pure iron becomes encrusted with rust, iron oxide or Fe2O3, whether by absorbing oxygen from the air or by water coming into contact with it. Definitions of entropy can be confusing, so I cite everyday examples. Time is theorized to exist as a principle underlying chemical and thermal processes or degradation. Yet another example, is a glass object, like a bottle, that shatters into pieces when falling onto the floor or hard nether surface, like brick or concrete or asphalt. The apparent “chaos” of glass fragments is chaos from order, so to speak. It is inconceivable to reverse “the flow of time” such that the chaotic array of glass fragments assemble to form a bottle.
My last example of science manifesting time is radioactive half-lives. A half-life is the amount of time it takes half a sample of a radioactive isotope to decay into another isotope. The carbon prevalent in nature is Carbon 12, the stable isotope consisting of 6 neutrons and 6 protons in the nucleus. There are also Carbon 13 and 14 isotopes. C-13 is about 1% of carbon, has 7 neutrons, and C-14 is exceedingly rare, about 1 part in a trillion of carbon on earth. Carbon-14 has a half-life of 5,730 ± 40 years—i.e., half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years. The phenomenon of radioactive half-lives seems to manifest the stable operation of time, as decay uniformly follows a schedule for half a sample to degrade from one isotope to another in a given time interval for that isotope. Here again, there is a process of change and has science designating some law of change and requiring time for it to occur. It’s a causal chain in the past-present-future framework discussed above.
In conclusion for this impromptu essay, Time is a real component of physical reality, non-spatial and immaterial. It’s a core dimension of the universe, underlying change and causation. Time is unique and indispensable, embedded in everyday experience and science’s conceptualization of the universe. The manifestations abound of change and motion, causal chains of event leading to event, and time emerges as the concept or continuum making these manifestations occur.
SOURCES: http://www.exactlywhatistime.com/definition-of-time/
https://www.merriam-webster.com/dictionary/time
https://en.wikipedia.org/wiki/Special_relativity
https://www.space.com/17661-theory-general-relativity.html
https://en.wikipedia.org/wiki/Entropy_(arrow_of_time)
http://mgaguru.com/mgtech/restore/rt106.htm
https://en.wikipedia.org/wiki/Carbon-14