Cosmology is a study of the history of the universe from a perspective of physics.
To address these questions, cosmology uses the physics of the very small. The pressure that drives the expansion of the early universe can only be understood from a perspective of particle physics. By combining nuclear physics models with measurements of isotopic populations, one can ascertain the conditions of the early universe. Both are written at an appropriate level. There also exists a CD counterpart to Hawking's book by the same title.