“…Simon Morley, a man who understands Time.” Prof Andy S….

The word “time” is the most commonly used noun in the English language. Time is something we treat as fundamental. We live our lives regulated by it, and we endure what seems to be its ceaseless, unstoppable advance. But what is time — the thing, the noun, the article? Surely we know this. It must be obvious. Time is so intrinsic to our existence, and so ubiquitous in our lives, that understanding it cannot be difficult.

Except that it has been difficult.

Aristotle tied time to change, and did not settle what either owed the other. Newton distinguished the measures we make from an absolute time that, on his account, flows of itself, independently of anything external. Einstein replaced that picture with space-time, in which the rate recorded by a clock depends on path and place, without thereby saying what, if anything, time is beyond the structure used to describe motion. Hawking, opening A Brief History of Time, set the nature of time aside as unsettled, and wrote instead about its role in cosmology. The positions differ. What they share is that the nature of time was left open. It is still widely called a mystery.

That is a strange state of affairs for a word everyone uses.

This site exists because that gap is not only a gap in technical physics. It is a gap in how the question has often been approached. Two ordinary academic habits have been easier to set aside than to keep; firstly what do we see, what is the emprical evidence, and secondly ‘define your terms’, i.e. what does the word mean.

The first is to look at what is actually seen. Clocks move. Materials decay. Objects change place. Faces age. What is in front of us, in every case, is change. An investigation that begins by assuming an invisible thing called time, and then asks how that thing flows, has skipped the evidence it already has.

The second is to define the terms. “Time” is not used in one way. It is used for the measure on a clock, for the order of events, for a stretch of experience, for a parameter in an equation, and for a supposed entity that passes whether or not anything else is happening. Arguments can slide from one of these to another without noticing. A word that cannot keep a single meaning cannot support a single conclusion about what exists.

Those two habits — look at what is seen, and say what the word is doing — are the method of this site. It asks whether the work done by the word can be done by change, and by the ways we compare change, without assuming an additional flowing substance. That question is not treated as already closed. A reader can accept the observations and reject the conclusion. The pages say which is which.

They are written for a reader who is not a specialist, and checked against the sources a specialist would expect. No equation is required to follow the argument. No appeal to mystery is accepted as a conclusion.

The path is short. First, what is seen: change, including the change in us, and why time is a poor candidate for its cause. Then two uses of the word, offered as this argument’s way of keeping those uses apart. Then space and motion, and what the familiar term space-time is doing. Then what follows if the frameworks are only scoring change — the arrow, persistence, period, duration. Then the mathematical t, and the step by which a label was treated as a thing. A close states the conditional claim. A last page says what difference it would make, and what difference it would not. What is left open is stated where it arises, not only at the end.

” ‘What is Time?’ takes the excellent approach of ruthlessly and logically, analysing and decoding, our dictionary definitions of Time.”

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