Part 1, which begins our examination of the question 'what is time?' can be viewed here.
Part 2 Some travels through time can be viewed  here.
A proposed discussion of Foucault's pendulum has been postponed to a later part of this blog series.

A Theory of Time

Interlude

What follows is a sample from many notes I have written for my language studies about how human language encodes notions of time. It is not a theory of cosmology. It is not quantum theory. These  deductions are mostly based on observable phenomena. There is some philosophical speculation.
Please note where I submit, speculate or suggest.  At these points I am in conflict with established theories, so please do not mistake my suggestions for any established fact - especially if you are studying for school or college.

... we postulate that bodies uninfluenced by forces move in such a way that equal distances spell equal times...
Sir Isaac Newton
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A Brief Note on Time in language:

The notion of time is embedded in a vast slice of every human language. Verbs have tenses for past, present and future events. Suffixes such as -ing, -tion, -ize, -ate, -en, -ify, -al generally denote processes. Processes are conventially described as changes over or during a time period, but, I suggest, they may as well be labelled as chains of causality.  There are words, proper nouns, which amount to a personification of time: March, Sunday, etc. There are locations in time: before, after, now, next, etc. In language we have a choice between the paradigms of time as noun, time as preposition and time as verb. An analysis of how language encodes time would fill a book. A very large book.
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Wish-fulfilment:

I believe that we are not born with a notion of time. Small children grasp the concept 'wish' long before they learn to read clocks. The child's wish-concept says 'I am hungry. If I wish hard enough for food, I will get fed.' The adult's wish-concept says 'I am hungry. If I just wish for food, I'll starve.'  As children grow they learn that wish-fulfillment requires making an effort. If the toy won't come to the child, then the child must go to the toy.

A child soon learns that a personal change of location requires effort. In later life, this grasp of the facts of nature helps in the learning of the concepts of power and energy. A change of physical states equates to a change in energy states.  When we strain to hear something, we are literally straining our smallest muscles: the  tensor timpani and the stapedius. A tighter eardrum is more sensitive to sound than a more relaxed one.  We talk also of eye strain.  We become aware that mere observation requires the expenditure of energy.
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The Word as an Arbitrary Sign.

Many words for time can also be used for space. Before can mean in front of. After can mean behind. Next applies equally and indifferently to space and time. 'The next town after that' can mean next in space along a path, or next in time along a journey. Every journey requires the expenditure of effort in some way proportional to the length of the journey.

It is but a small step from this to the concept of a human life as a journey. Having once formulated the journey concept, the question must be asked: 'a journey through, across or along what?'  I suggest that abstracting from the notion of life, with its beginning and end as a journey, it is but a small step to imagine any connected sequence of events as a journey.  And so, a chain of causality becomes a journey. 

Since our ancestors could not journey through the air or the ground to any meaningful extent, they formulated the notion that a causal journey cannot be through the three dimensions of space.  Moreover, we have always been aware of a force pinning us to the ground.  I speculate that our ancestors, being aware of a sort of wishing that made them walk, would have discovered that however much they might wish it, they could travel neither forwards nor backwards in the journey through life.  I speculate that this led, in all languages, to the labelled intuition of a force restricting us to travel in only one direction through life.  Absent the power to abstract the sophisticated notion of inertia, the only option is to label and intuit a dimensional entity - time.

In whatever natural human language, I suggest, there is no linguistic model of time in three dimensions like space.  When the human brain abstracts a lesser concept from a greater, or vice versa, it creates a need for a word to label it.  But the label for a newly grasped concept can be entirely arbitrary, and the label is no proof of the reality of any concept.  Just check out all words for describing the metaphysical - ghost, pixie, elf etc.
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The sufficient and Necessary Components of Intuitive Time.

I hold the view that time, as a space-like entity is an artifact of human cognition, which is not quite the same as an artifact of perception. I propose that the linguistic categories: space, change, energy and inertia are sufficient and necessary to the formulation of the linguistic category 'time'. I use the term 'inertia' here to mean 'resistance, reaction or opposition to any kind of change', a resistance which must be opposed by application of some kind of force. I shall try to show that 'time' is an intuitive grasp of the concept of 'inertia'- that the same mental 'inertia' categories - the 'inertia' processes of cognition - create the illusion that time is a reality.
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Order and Sequence in the Brain's Neural Structures

Ordering of stored information in the mind appears to be based on the notion that any two things may be mutually categorised in terms of a single attribute, provided only that at least one of the two has some quantity of that attribute. The relationship is an ordering relation based on comparison. It is reasonable to assume that somewhere in the brain is a neural structure which stores data such as the size sequence: mouse < cat < dog < elephant. This is object-memory. If event-memory is viewed as a sequential LIFO (Last In First Out) stack, then events will be stored in a LIFO sequence.

Suppose now that the brain's linguistic-category invention, or labelling system is applied to this LIFO stack. Surely space metaphors will be applied: the brain determines categorisation similarities between the separations and sequences of objects in space and applies those as associative links to the LIFO stack. The space-labels: approaching, leaving, near, far, etc. will be adapted to the contents and comparisons in the LIFO stack. New labels are required for these LIFO categories, together with a supercategory label.

In a very real sense, any property of a LIFO stack is an emergent property of the way the LIFO stack works. If event memory can be shown to operate on a hard-wired LIFO principal, then any intuitive reality, such as sequence in time, derived from LIFO operation can be shown to be an artifact of the LIFO stack's operation. Immanuel Kant saw that the mind could not function as a container that simply receives data. Something has to give order to the incoming data. Images of external objects have to be kept in the sequence in which they were received.

Conclusion: This LIFO ordering, I suggest, together with the application of an A resembles B labelling system,  causes the mind's intuition of time.

Footnote: I shall take on board all comments and try to address them in the next part of this discussion.
Continued in part 4