Changes

The '''Universe''' is defined as the summation of all particles and energy that exist and the [[space-time]] in which all events occur. Based on observations of the portion of the universe that is [[observable universe|observable]], physicists attempt to describe the whole of space-time, including all [[matter]] and [[energy]] and events which occur, as a single system corresponding to a mathematical model.

The '''Universe''' is defined as the summation of all particles and energy that exist and the [[space-time]] in which all events occur. Based on observations of the portion of the universe that is [[observable universe|observable]], physicists attempt to describe the whole of space-time, including all [[matter]] and [[energy]] and events which occur, as a single system corresponding to a mathematical model.