1.NounThe known universe; the part of the universe that is not part of the dark sector; the segment of the universe that is explained by the known laws of physics, and whose components (particles) are predicted by it. The portion of the universe that is not dark matter nor dark energy.
The fraction of the universe that interacts with electromagnetism (ie. light).
2.NounThe fraction of the universe that interacts with electromagnetism (ie. light).