In search of a definition of 'time'

Nothing is forever. Not even the Nationalist government, or the drydocks problem. The process of change is inexorable, and it affects everything. It affects living things. Individuals age and species evolve. It affects society, urban landscapes, historical monuments, power structures, technology, societal mores, natural landscapes, geography, the shape of continents.

Everything is changing in the universe. Stars come into existence through the contraction of huge clouds of gas, burn themselves out, and eventually either explode or expand into red giants, before contracting into a white dwarf, a neutron star, or a black hole. Our dear old sun will eventually run out of hydrogen, which for another 4 and a half billion years will be undergoing nuclear fusion, turning into helium and providing all that vast amount of energy being produced right now. It will then expand into a red giant, engulfing the inner planets including our own earth, before contracting into a white dwarf the size of our planet, and starting a long, long cooling off process that will last till the end of time.

What was that? The end of time? Is time going to end then? Maybe. I'll be coming to this later. But what, actually, is this concept that we call time?

At a practical level, it's easy enough to explain a unit of time, but only in terms of the concept itself - a day is the amount of time that it takes the earth to rotate once upon its axis. So we're nowhere near giving an explanation of the concept that way. We're just splitting it up into arbitrary slices.

The sensation we feel, of time proceeding from the past into the future, may be the result of our remembering what has occurred in the past. If we didn't have any memory at all, and were only aware of the present instant, I don't think we would have the concept of time at all in our minds. So, for living entities, or rather, entities that are aware and have some form of memory, time would be their subjective experience of being conscious. Like waiting for a bus for an hour. Or holding one's breath underwater for a minute. Before we were born, i.e. before we became aware, for 13 billion years or so, time did not exist at all for us. Neither, in fact, did time have any meaning for us when we were babies - it was just a matter of fulfilling basic natural needs, feeding, breathing, feeling comfortable, defecating. It was only when we became toddlers, when we started to have thoughts, rationalise, process ideas, that time started to 'hang' on our hands. When we are unconscious, say during an operation, time ceases to exist and literally jumps from the moment consciousness dissolves into general anaesthesia to the next subjective moment when we regain consciousness.

So, is time a meaningful concept only in relation to conscious beings? Does time mean anything at all as far as inanimate matter is concerned? Or empty space? Consider the moon, which as far as we know is entirely inanimate. It still takes one year to orbit the sun once, and about 28 days to spin once on its own axis. A block of ice of given mass at given conditions of temperature and pressure takes a specific, precise amount of time to melt completely. Light from the sun reaches the earth in 8 minutes. Any process one may think of takes place in a specific amount of time. But, and here we start to home in on the crux of the matter, something must be happening. And that something, whatever it is, involves the transformation of energy from one form into another, the progression from an unstable state into a more stable state.

The sun is burning itself into a much more stable white dwarf state. An accelerating car is apparently reversing this trend - approaching a more unstable state - but the overall level of stability of the car/fuel package becomes more stable, the high energy content of the petrol having been turned to heat and dissipated as kinetic energy (the fast moving car) which will soon slow down to a halt through friction. You end up with heat energy, inert water vapour and carbon dioxide (instead of high octane petrol), and a stationary car. All the available energy is used up, and nothing else happens, unless we apply more energy to the vehicle through an external force or if we fill it up with yet more fuel.

Musing on the matter the past few days, when I decided to explore the matter of the meaning of the concept of time, the more I thought about it, it seemed to me that time is intimately tied to the expenditure of energy. Any system of measuring time involves something happening, and for anything to happen there must be transformation of energy. To test this idea, I imagined a situation where there was no expenditure of energy at all, where nothing was happening at all. Objects are not moving relative to each other - all atoms are at a standstill, at absolute zero temperature. All stars have burned themselves out, and dissipated all their heat. There is therefore no electromagnetic radiation at all. Absolutely no movement, no flow of energy. Nothing is happening at all! At such a stage, time would be really at a standstill. It wouldn't have any meaning anymore.

I wonder if such a stage will ever be reached. Let's consider our solar system again, very very very far in the future, with our white dwarf sun having cooled to a black dwarf, at absolute zero temperature. Will the outer planets, Jupiter, Saturn, etc, also at absolute zero temperature, still be orbiting it? Maybe tidal forces will lock them all into the same frozen position, so that all objects within the whole system wouldn't be moving at all relative to each other. If we go even further into the future, maybe the whole galaxy, or groups of galaxies, will be motionless relative to each other, and there will be no exchange of energy whatsoever. Nothing will be happening, and the concept of time will be utterly meaningless.

Maybe that's the final destiny of the universe. Time came into being, as an integral part of the universe, when the Big Bang unleashed all that unimaginable amount energy, with the consequent formation of matter, the stars and everything that's been happening since then, as the universe winds itself down to a state of overall uniformity of energy level.

So, based on the above considerations, I am proposing a definition of time that may seem a bit bizarre, but is entirely the result of my own thoughts on the subject: time is the flow of energy from a state of instability to equilibrium.

Maybe, hopefully, I will in future arrive at a better definition. An entire winter of long training runs is beckoning, so there will be ample opportunity for further introspection. For the time being, I'm more than happy with the result, which I had once thought to be an impossible task to achieve.