•Density – amount of something/volume it’s contained in•As the universe expands, the matter density goes down. •The universe was radiation (light) dominated for the first 72,000 years of its life. It then became matter dominated until space expanded enough in the coming years to cause the universe to become dominated by dark energy.•Critical Density – the total energy density, of all forms combined, that must be present in the universe if the universe is flat.•Universe Density = total density/critical densityoIf the universe density is > 1, the curvature of space is spherical and the universe is closed.oIf the universe density is <1, the curvature of space is hyperbolic and the universe is open.oIf the universe density is = 1, the curvature of space is flat and the universe is flat.•We have tried to examine the density of the universe through light rays, seeing they remain parallel over large distances (flat), diverge (open), or converge (closed).
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