Preface (selected portions)
We are immersed in a sea of light emanating from ordinary matter that is floating, as it were, on an ocean of dark matter. The dark matter itself floats on the dark energy of the particle vacuum that in turn is embedded within the scaffolding of space-time – which is shaped by the dark gravity effects from all matter and energy.
How did the profound beauty of our Earth, our Solar System, our Milky Way galaxy and indeed our universe unfold? Dark matter, dark energy, and dark gravity have made all the difference in how the universe has developed, and have been key to creating the overall environment that makes life possible.
I was motivated to write this book by the desire to make some of the most exciting recent developments in cosmology and by implication, particle physics, more accessible to the lay reader. Most have heard of the Big Bang, fewer about the inflationary Big Bang, and even fewer about the reacceleration of the universe’s expansion discovered a little over a decade ago. And increasingly, developments in cosmology and particle physics have become more intertwined. The understanding of gravity and space-time are key to cosmology and the relationship of gravity to the quantum world of particle physics world remains unsolved. Gravity, despite our common sense notion of it as appearing to be of significant strength, is incredibly weak compared to the other forces of electromagnetism and the nuclear forces.
We have only recently developed the ability to begin unlocking the secrets of dark matter, dark energy and dark gravity, thus providing a deeper insight into how a universe of this type is possible. It seems that because of dark matter, dark energy and dark (weak) gravity, our universe has the right attributes for the development of complex structure and the evolution of intelligent life that can engage in the quest to understand our world. These “dark” or more hidden attributes of the cosmos have very good outcomes.
In particular, the existence of dark matter makes it easier to form complex structures, including galaxies, stars and planets through gravitational collapse of denser regions of the universe. Planets are the most suitable abodes for the development of life. Dark energy acts to extend the lifetime of the universe by counteracting gravity and driving continued expansion of the universe. We currently expect our observed universe can continue for another trillion years at least and possibly much, much longer, although life as we understand it will be increasingly less probable after ten trillion years or so. Dark, or weak, gravity is critical. If gravity were much stronger, a universe with enormous scale such as ours could never form. It would have only a tiny microscopic existence and consequently a very short lifetime. What we want, in order to be here after a long multi-billion year evolutionary process, is weak gravity that persists over a long period of time. And this is what we see in our observations of the universe.
The text provides a summary of the latest astrophysical observational results and theoretical insights into what we know and what we hope to learn about dark matter, dark energy, and dark gravity. Dark matter, dark energy and dark gravity are essential to the existence of a universe with characteristics like ours. They have enabled a universe that is large, long-lived and can form complex structure, providing the opportunity for the formation and evolution of stars and galaxies, of carbon, nitrogen, oxygen, other heavy elements, of Earth-like planets and of life itself.
A fuller understanding of each of these “dark” but highly beneficial aspects of our universe is crucial as we seek to further uncover the nature of this universe, how it has evolved and how it will continue to evolve in the future.
I would like to thank Rich Brueckner for kindly agreeing to write the Foreword, and to thank also Henry Fong and Drs. Philip Bull, Peter Countryman, Ferhat Hatay, and James Simon for graciously providing
comments on the manuscript.