In Physical, the cone of light is the fundamental object of the General relativity. It finds its origin in the relation past-future. It is this object which creates the distinction between a last event and an event Futur. That is to say an event e_0 made conspicuous, all the other events of the Espace-temps are divided into three categories: the last absolute and the future absolute of e_0 on the one hand, these events occurring inside cone represented on the diagram, and the elsewhere on the other hand which is consititué other events. The events located in elsewhere of e_0 are known as causalement disconnected from e_0 and cannot thus influence it.

Time interval

Another event, that we will name e_i (letter I for interior ), located inside the cone of e_0 is separated from this last by an interval known as of the type time ( \ Delta s_ {I} negative).

Interval of space

Let us see what occurs outside this cone. Let us consider a third event e_a now ( has for elsewhere ). That Ci will then be separated from e_0 by an interval known as of the type spaces ( \ Delta s_ {I} being then positive).

Interval of light

For all the other event located on the surface even of the cone of light, their interval of space time with e_0 is cancelled. And this because they are located at the border between the interior and elsewhere (consequently, \ Delta s_ {I} is null). These intervals are called intervals of the type light . To explain why, consider a fourth event, e_s ( S for surface), which, him, would be located on the surface of the cone of light of e_0. The space distance which separates these two event, is then the distance which the Lumière would cross during the temporal distance which separates them.

See too

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