| A | B |
|---|
| Big Bang | Theory that all matter started as a single point in space and then exploded to its current position. |
| Closed Universe | It is a universe that is finite and has no edge like a sphere, it has enough mass to stop expansion and close in on itself, this occurs when the mass of the universe is above the critical density. |
| Cosmic Microwave Background | The remnant of the energy that created the entire universe and is constant in all directions. |
| Cosmological Principle | Constructed on the ideas that the universe is largely homogenous and isotropic. |
| Cosmology | The study of the structure and evolution of the entire universe. |
| Critical Density | Is the mass inside of the universe that is needed to slow the expanding universe to marginally bound. |
| Critical Universe | A universe with no curvature, where the density is equal to the critical density and rides the line between a universe that can recollapses or expand forever. |
| Olbers’s Paradox | Idea that if the universe is homogenous and isotropic than the night sky should be as bright as the sun. |
| Open Universe | When the density of the universe is much less than the critical mass then, a universe without enough gravity to stop the universe from growing. |
