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, 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, 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]]. |