Preface
Four truly profound questions have always permeated science and served as its
basis: what is matter, what is the universe, what is life, and what is thought. The
twentieth century has been extraordinary in that three of these have been at least
partially answered. The answers in brief and broad outline are: matter is made of
quarks and leptons and the quantum gauge fields that hold them together; the
universe is an isotropic and homogeneous expanding curved spacetime that is
dominated on the cosmological scale by gravity; life is a mechanism whereby the
molecular polymer deoxyribonucleic acid (DNA) makes more DNA from its
environment.
We have not been so successful concerning the nature of thought; indeed some
people are of the opinion that almost no real progress has been made. One rather
entertaining view is that thought is an illusion and we do not really think at all. That
is to say we merely think that we think. Perhaps it is good that there remains such a
field with so much to be explored in our future mental adventures.
While the nature of matter and life are part of the undergraduate curriculum in
physics and biology, the nature of the universe is often left for a graduate course on
general relativity, and cosmology is often treated only briefly at the end of the
course. Some universities offer an undergraduate course on cosmology not based on
general relativity, but of course this is no substitute for a more complete treatment.
There is no good reason that general relativity and cosmology should not be studied
by undergraduates as well as beginning graduate students. This book is thus
directed primarily at beginning graduate students but also at advanced and confident
undergraduate students. The mathematics needed is only a short step beyond vector
and matrix analysis, the physical concepts are simpler than those of quantum
mechanics, and the subjects have become very mainstream. Such topics as black
holes, dark matter, the shape of the universe, the big bang, the primordial fireball,
and the ultimate fate of the universe can be appreciated and understood by almost
anyone with an undergraduate physics background. Some of the appendices should
help undergraduates and others with gaps in their background.
vii
Four truly profound questions have always permeated science and served as its
basis: what is matter, what is the universe, what is life, and what is thought. The
twentieth century has been extraordinary in that three of these have been at least
partially answered. The answers in brief and broad outline are: matter is made of
quarks and leptons and the quantum gauge fields that hold them together; the
universe is an isotropic and homogeneous expanding curved spacetime that is
dominated on the cosmological scale by gravity; life is a mechanism whereby the
molecular polymer deoxyribonucleic acid (DNA) makes more DNA from its
environment.
We have not been so successful concerning the nature of thought; indeed some
people are of the opinion that almost no real progress has been made. One rather
entertaining view is that thought is an illusion and we do not really think at all. That
is to say we merely think that we think. Perhaps it is good that there remains such a
field with so much to be explored in our future mental adventures.
While the nature of matter and life are part of the undergraduate curriculum in
physics and biology, the nature of the universe is often left for a graduate course on
general relativity, and cosmology is often treated only briefly at the end of the
course. Some universities offer an undergraduate course on cosmology not based on
general relativity, but of course this is no substitute for a more complete treatment.
There is no good reason that general relativity and cosmology should not be studied
by undergraduates as well as beginning graduate students. This book is thus
directed primarily at beginning graduate students but also at advanced and confident
undergraduate students. The mathematics needed is only a short step beyond vector
and matrix analysis, the physical concepts are simpler than those of quantum
mechanics, and the subjects have become very mainstream. Such topics as black
holes, dark matter, the shape of the universe, the big bang, the primordial fireball,
and the ultimate fate of the universe can be appreciated and understood by almost
anyone with an undergraduate physics background. Some of the appendices should
help undergraduates and others with gaps in their background.
vii