Changes
intro to left-side section
===The left side of the equation: the Einstein curvature tensor===
We will recall that the Einstein field equations can be written as a single tensor equation:
:<math> G_{\mu\nu} = 8\,\pi\,G\,T_{\mu\nu} </math>
The right side of the equation consists of some constants and the ''stress-energy tensor,'' described in significant detail in the [[#The right side of the equation: the stress-energy tensor|previous section]]. The right side of the equation is the "matter" side. All matter and energy in a region of space is described by the right side of the equation.
The left side of the equation, then, is the "space" side. Matter tells space how to curve, and space tells matter how to move. So the left side of the Einstein field equation must necessarily describe the curvature of spacetime in the presence of matter and energy.
====Some assumptions about the universe====
