What is Time ?
" ... none of the parts of time has an abiding
existence, and that which does not abide can hardly have position.   It
would be better to say that such parts had a relative order, in virtue
of one being prior to another."
Aristotle, in Categories.

I am in process of writing a blog on this.   The purpose of the current  'Random Noise' blog is to discuss ideas about the nature of time.  My own theory of time embraces these notions:

Time is an artifact of human cognition, which is not quite the same as an artifact of perception.  We are not born with a notion of abstract time, it must be taught.  We grasp the notion of time only because it is a nice comfortable fit with our instinctive / intuitive grasp of matter, energy/food/fuel and  space.

We use up time, or save it.  We think we have too little or too much time.  But we journey only through space, we act in space, we observe relative locations and sequences in space, we look forwards or backwards in space.  But often the space to which we assign laws of physics is a mental space model that we have mis-labelled with the word 'time'.

If we try to think about the nature of time itself, our faculties are directed first to this mis-labelled artifact.  Of course we talk about time in terms of space.  Our entire linguistic notion of time is but an abstraction by the mind of some of the properties of space.

In fact, by adding in only one observable fact to the notion of time-as-space, time can be understood, in terms of physics, as not existing at all.  I don't know about quantum physics, but in Newtonian physics, the positions of objects moving in space can be described and calculated with no reference to time.

Your contributions to the discussion will be of great value to me.  If I am to publish such a daring theory, I do not dare overlook any perspective.

I'll leave it there, for discussion.

This topic is now blogged as:
A Theory of time, part 1, part 2