Time is.

Time has two aspects. First, the arrow of time, it's direction. Second, the rate of flow or passage, the time dilation factor.

'Time' is what we percieve when something that travells at infinite speed (light in a vacuum) is 'slowed' to a finite speed. At infinite speed there is no causality at finite speed there is.

Why does light when unrestricted travel at infinite speed? We know that photons do not experience time. Therefore, in a sense they can be thought of as travelling at infinite speed. However, to travel at infinite speed implies a lack of causality which in turn implies no arrow or perhaps a double ended arrow to time. So, light to travel at infinite speed can only do so outside of time as we know it. Therefore, the concept of 'speed' becomes meaningless when talking about infinite speed.

The origins of Time.

Having established that Time has two aspects, the arrow and time dilation factor. Where do they come from? Obviously they are artefacts of the Universe. What does the Universe contain? Mass/energy, gravity and space-time.

We understand from GR that local time dilates near to a massive object due to it's gravity. (Local time as opposed to non-local time.) Therefore, one of the ingredients of time is gravity. Gravity slows light and gives it a finite speed.

We could measure the speed of light in the vacuum anywhere in the Universe and it would be the same. We can therefore use c as a clock. I would suggest the Universes master clock. What is light? Light (to the best of my knowledge) is the purest form of energy. A clock in an accelerated time frame runs faster. Obvious you might think but what does that actually mean. For that time frame to accelerate implies an input of energy. Therefore the other ingredient of time is energy.

Energy unrestricted would dissipate over maximum distance in zero time. But, under those circumstances both distance and time become meaningless concepts. Gravity introduces the concept of 'Time'. It introduces an arrow of time and the relationship between energy and gravity introduces a time dilation factor. Energy makes the clock run faster, gravity slows it down.

E=mc

^{2} If we re-arrange this we get c

^{2}=E/m. If c can be used as a reference clock, which it can, then c represents the time dilation factor. In other words the time dilation factor (Td) is equal to energy divided by mass. Td=E/m. Which is what I have arrived at above.

Time is created by gravitational braking of the instantaneous dissipation of energy. For time to 'flow' energy must be consumed. No consumption of energy, no flow of time. Therefore, the arrow of time is entropy. All miner arrows are aspects of that.

Time within the Universe is both local and universal depending upon Td=E/m both locally and universally. Only if the energy/mass ratio of the Universe remains constant can Td remain constant. The energy/mass ratio does not remain constant. At this epoch mass is being converted into energy. That implies that time is speeding up (contracting) in relation to the past.

Time and gravity are so closely interwoven that it is impossible to talk about one without the other. It is therefore suggested that this post should be read in conjunction with

http://www.thenakedscientists.com/forum/index.php?topic=43495.0_{With apologies. When talking about time it is inevitable that certain words will be used in a confusing manner . For instance talking about the 'rate of flow' of time or 'passage of time' or 'speed of passage or flow' is technically incorrect but necessary due to the inadequacies of language.}