Key Words

• average density of matter

• Big Bang

• closed universe

• combined average mass density

• compression

• cosmic background radiation

• cosmic microwave background

• cosmic light horizon

• cosmic singularity

• cosmological constant

• cosmological principle

• cosmological redshift

• cosmology

• critical density

• dark energy

• dark energy density parameter

• dark-energy-dominated universe

• density parameter

• era of recombination

• flat space