It is important in the understanding of simultaneity and simultaneous to completely understand time and to build a central or primary rule or principle on which time is based. Time is the rudiment of existence, time is said to have begun of the big bang some what fourteen billion years ago. Time is said to be the thing that stops things happening all at once. Presently we refer to time as a measurement, the movement of the hands of a clock or the present use of Caesium clocks and it is said that the integral of the frequency is time, 9,192,631,770 hertz being equal to one second of time measurement. In ordinary terms , time is the mechanism that allows us to synchronise our everyday lives, synchronised in respect relative to the inertial accelerating reference frame of the gravitational constant of the Earth and relative velocity, but not simultaneous relative to other reference frames according to relativity. However it is important we do not overlook the mind experience and the observation of time, all observers must agree on the observation of time to be equal.

In thought let us imagine a spaceship that was going to make a journey from the Earth to the Moon. On Earth Sam holds in his hand the modern technology of a camcorder, onboard the spaceship Sarah also holds an identical camcorder, finally on the Moon , Sid also holds an identical camcorder.

Sarah starts the engines on the spaceship and starts her journey from t=0 .

All three observers Sam, Sarah and Sid all synchronise their recording start on the camcorders, starting to fill the internal storage with observed data in synchronisation with the light and time.

**It is not important we need to consider a forth observer or the speed of the journey or a time on a clock recording the journey. **

Sarah arrives at the Moon to pick up Sid to return Sid to Earth, where Sarah , Sid and Sam compare the observation of the recordings.

All observers agree they have recorded the exact equal amount of data, all observers agree that they experienced the same amount of time in either location or in motion. All observers agree the observation was simultaneous.

In this example we are defining time -** ''Time is the synchronisation of observation'**

Therefore I propose a rudiment principle that is self evidently true.

**Principle - All observers of time must agree that the observation of time is synchronous and constant.**

**Relative maths. **

If we imagine a single Photon travelling from A → B and a single Photon travelling a parallel journey from B → A over a length of space-time X, we can calculate the net difference of time between the two photons journey times to reveal 0 net difference in time.

L=X

A_{t}=(+ve=c)

B_{t}=(-ve=c)

A_{t} - B_{t} = 0_{t} net difference.

**Relativistic diagram**

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