Time holds a unique place in science and the human consciousness. However, defining or describing what it is extremely difficult. Some define it only in the abstract saying that is an invention of the human consciousness that gives us a sense of order, a before and after so to speak. However many physicists define it in terms of the physical properties of a space-time dimension.
Yet, the observable properties of time are something that most of us can agree upon.
One of the most persistent is that it is not directly perceived as matter or space but as an irreversible physical, chemical, and biological change in physical space.
This indicates a unit of time may only be a non-physical measure of when in relation to other events an irreversible physical, chemical, and biological change in physical space take place similar to how a unit of length is the non physical measure of the ordering of a position of an object in space. This is because similar to time, length is not perceived to have the physical properties of matter or space but as only as measurement of where in relation to a previous event an object is located.
However, as mentioned earlier many physicists view time in terms of the physical properties of a space-time dimension. For example, a physical curvature in space-time is viewed by many physicists to be causality of the force of gravity.
Therefore, assuming the physicality of time or a space-time dimension appears to contradict the fact that as mentioned earlier most of us do not perceived time as having the physical properties of matter or space.
Additionally our perception of irreversibly of time or that it always moves in one direction forward also appears to contradict the concept of time or a space-time dimension has physical properties because it is possible to physically reverse the position of an object in space. For example, one can move an object to a different position, reverse the process and move it back to its original position three-dimensional space whereas one cannot in a space-time dimension because as mentioned earlier observations tell us one only move forward in it.
Therefore, defining it in terms of its physical properties does not appear to be consistent with the observation that time is irreversible.
However, these same observations, as mentioned earlier suggest that time may be only a measure of the sequential ordering of the casualty of events because one cannot reverse the causality of an event without creating a new event thereby making it consistent with the perception of its irreversibility. This would be true in both our physical and mathematical perceptions of time.
This also defines the reason events always move forward in time because the act of reversing an event would be the next event in that sequence which must occur at a future time.
Therefore, defining time only in terms of a measure of the sequential ordering of the causality of an event would seem to provide an unambiguous definition of time that is more consistent with both physical and mathematical observations than defining it in terms of the physical properties of a dimension.
However, it would also free physicists from the constraints imposed by defining time in terms of its physical properties and allow them to consider the possibility the laws of nature are a result the existence of four *spatial* dimensions instead of four dimensional space-time as we have done in the article “Why four spatial dimensions?”
Copyright Jeffrey O’Callaghan 2007