 In order to more precisely analyze our expanding universe, modern cosmologists place a grid over the three-dimensional sphere. We treat the distance between two galaxies, r, as a constant. Then we set the grid's scale factor, a, equal to one at the present time, and vary it to account for changes in distance over time instead of changing r. Now consider a cube enclosing a volume of space containing some number of galaxies. With our scale factor approach, the amount of matter inside the volume remains the same as the volume increases or decreases. But the matter density goes down when the scale factor increases, and it goes up when the scale factor decreases. Taking with Newton's model and incorporating the cosmic scale factor, we can rewrite the Friedman equation. We see that the scale factor a is the only variable. In other words, the history of the universe comes down to the history of the scale factor. And the history of the scale factor depends completely on the contents of the universe and how that content affects the space it exists in.