Events are Invariant

An event is something that happens at a particular place at a particular time time. It is an invariant aspect of reality, completely independent of who may or may not observe it.

Conceptually, an event corresponds to a point in spacetime. It is uniquely defined by telling where and when it occurs. More specifically, an observer quantifies his frame of reference by defining an appropriate coordinate system. One of the most common coordinate systems used is the rectangular Cartesian coordinate system where an event is defined by specifying its coordinates x, y, z, t.

In one reference frame the event may have the coordinates x, y, z, t and in a second frame it may have a different set of coordinates x' ,y' ,z', t'. Although the coordinates of an event may be different for different observers, the event itself is independent of the observer. In 4-D space this is equivalent to the statement that the coordinates of a point may depend on the coordinate system but the point itself is independent of any coordinate system.

ModPhy1/Unit1/SpecialRelativity/InvariantView/