Part IV
Cosmology
Cosmology seeks to answer the immodest question “What is the universe?”
(Freedman 2006). Cosmology entered the mainstream of physics only in the last
half of the twentieth century. This is due firstly to the existence of a viable theoretical structure in general relativity. Secondly, it is due to diverse observations of
distant galaxies and measurements of the cosmic microwave background radiation
that have confirmed the basic theoretical ideas and provided new questions. Observational cosmology has become diverse and sophisticated. It is an active part of science
and no longer largely speculative. There are many questions remaining, some very
deep, and most cosmologists would agree that the field is still in its infancy.
Our convention concerning the word “universe” should be noted here. For the
real-world universe, some authors capitalize U. For our theoretical or conceptual
universe, some authors use a small u. To avoid confusion, we will never capitalize
the “u” and hope we will be forgiven for appearing to demote the real world.
We will set up the Einstein field equations in Chap. 12 and study the way in
which they relate to the constituents of the universe. In Chap. 13, we will obtain the
cosmological metric based on general considerations of symmetry and show some of
its consequences. In Chap. 14, we will obtain the specific dynamical equations that
the cosmological metric obeys. In Chap. 15, the dynamical equations will be solved
for some interesting models, in particular the standard or LCDM model. Chapter 16
will be devoted to obtaining some of the important properties of the current universe.
Finally, in Chaps. 17–19 the earlier universe will be studied, including some of its
less well-understood properties and some basic unanswered questions.
Cosmology
Cosmology seeks to answer the immodest question “What is the universe?”
(Freedman 2006). Cosmology entered the mainstream of physics only in the last
half of the twentieth century. This is due firstly to the existence of a viable theoretical structure in general relativity. Secondly, it is due to diverse observations of
distant galaxies and measurements of the cosmic microwave background radiation
that have confirmed the basic theoretical ideas and provided new questions. Observational cosmology has become diverse and sophisticated. It is an active part of science
and no longer largely speculative. There are many questions remaining, some very
deep, and most cosmologists would agree that the field is still in its infancy.
Our convention concerning the word “universe” should be noted here. For the
real-world universe, some authors capitalize U. For our theoretical or conceptual
universe, some authors use a small u. To avoid confusion, we will never capitalize
the “u” and hope we will be forgiven for appearing to demote the real world.
We will set up the Einstein field equations in Chap. 12 and study the way in
which they relate to the constituents of the universe. In Chap. 13, we will obtain the
cosmological metric based on general considerations of symmetry and show some of
its consequences. In Chap. 14, we will obtain the specific dynamical equations that
the cosmological metric obeys. In Chap. 15, the dynamical equations will be solved
for some interesting models, in particular the standard or LCDM model. Chapter 16
will be devoted to obtaining some of the important properties of the current universe.
Finally, in Chaps. 17–19 the earlier universe will be studied, including some of its
less well-understood properties and some basic unanswered questions.