Timestream Physics 101 As physical entities, it is difficult for us humans to conceptualize the nature of the universe in the context of time. It is elementary to realize that physical reality exists in three dimensions. The first dimension is length, a straight line. The second dimension is width, those directions at a right angle to the first dimension. The second dimension encompasses all the lines and angles that may exist on an infinitely flat plane. Lastly, the third dimension is height, which exists at right angles to both length and width. The distinction between these dimensions is arbitrary, and dependent on the perspective and attitudes of the observer. What most humans and other forms of three-dimensional life fail to grasp is that time-based, or temporal, reality also extends in three dimensions. The fourth dimension is duration. The inertia of the Big Bang carries the physical mass of the universe in a single direction across the durational axis of time. If you were to imagine the temporal universe as a straight line extending from one point (the Big Bang) to another (the present moment), each point along the line contains the entire universe as it existed for an instant. However, this is only a fraction of what temporal reality really is.