The meaning of "quark matter" is twofold: 1) It refers to compound states known as "subquarks" (the most fundamental constituents of matter), with quarks consisting of nuclear matter or "nucleons" (the constituents of the nucleus), and 2) compound states of quarks that consist of roughly equal numbers of up, down, and strange quarks, and which may be absolutely stable. Recently, both types of quark matter have become very intriguing subjects in physics and astronomy since the recently discovered Higgs boson, which may be taken as a composite object (possibly, a bound state of subquark-antisubquark pairs). Additionally, many recently observed compact stars have been considered "strange stars" (stars consisting of quark matter). In this book, these subjects in physics and astronomy are discussed without requiring readers to comprehend mathematical details. This book consists of three chapters: Chapter One: "Quark Matter and Strange Stars", Chapter Two: "Composites of Subquarks as Quark Matter", and Chapter Three: "Dark Energy, Dark Matter, and Strange Stars". Their contents include the following: In Chapter One, quark matter and strange stars are discussed in detail. In Chapter Two, the unified subquark model of all fundamental particles (quarks, leptons, and gauge and Higgs bosons) and forces (strong, electromagnetic, weak, and gravitational forces) is discussed in detail. In Chapter Three, pregeometry, in which the general theory of relativity for gravity can be derived as an approximate theory at long distances, is briefly reviewed. Furthermore, special and general theories of "inconstancy" in pregeometry in which fundamental physical constants may vary are introduced. Finally, possible solutions to the most puzzling problem in current cosmology of dark energy and dark matter in the universe are presented. Between Chapters One and Two, pictures of Dr. Abdus Salam added, as Dr. Salam was one of the founders of subquark models. Also, between Chapters Two and Three, pictures of Dr. Andrei Sakharov are added, as Dr. Sakharov was the founder of pregeometry.

Prior to the 1920s it was generally thought, with a few exceptions, that our galaxy, the Milky Way, was the entire universe. Based on the work of Henrietta Leavitt with Cepheid variables, astronomer Edwin Hubble was able to determine that others had to lie outside our own. This books looks at 60 of those that possess some unusual qualities that make them of particular interest, from supermassive black holes and colliding galaxies to powerful radio sources.

In the years since its publication in 1988, Stephen Hawking's A Brief History Of Time has established itself as a landmark volume in scientific writing.  It has become an international publishing phenomenon, translated into forty languages and selling over nine million copies.  The book was on the cutting edge of what was then known about the nature of the universe, but since that time there have been extraordinary advances in the technology of macrocosmic worlds.  These observations have confirmed many of Professor Hawkin's theoretical predictions in the first edition of his book, including the recent discoveries of the Cosmic Background Explorer satellite (COBE), which probed back in time to within 300,000 years of the fabric of space-time that he had projected.

Eager to bring to his original text the new knowledge revealed by these many observations, as well as his recent research, for this expanded edition Professor Hawking has prepared a new introduction to the book, written an entirely new chapter on the fascinating subject of wormholes and time travel, and updated the original chapters.

In addition, to heighten understanding of complex concepts that readers may have found difficult to grasp despite the clarity and wit of Professor Hawking's writing, this edition is enhanced throughout with more than 240 full-color illustrations, including satellite images, photographs made made possible by spectacular technological advance such as the Hubble Space Telescope, and computer generated images of three and four-dimensional realities.  Detailed captions clarify these illustrations, enable readers to experience the vastness of intergalactic space, the nature of black holes, and the microcosmic world of particle physics in which matters and antimatter collide.

A classic work that now brings to the reader the latest understanding of cosmology, A Brief History Of Time is the story of the ongoing search for t he tantalizing secrets at the heart of time and space.

Prior to the 1920s it was generally thought, with a few exceptions, that our galaxy, the Milky Way, was the entire Universe. Based on the work of Henrietta Leavitt with Cepheid variables, astronomer Edwin Hubble was able to determine that the Andromeda Galaxy and others had to lie outside our own. Moreover, based on the work of Vesto Slipher, involving the redshifts of these galaxies, Hubble was able to determine that the Universe was not static, as had been previously thought, but expanding. The number of galaxies has also been expanding, with estimates varying from 100 billion to 2 trillion. While every galaxy in the Universe is interesting just by its very fact of being, the author has selected 60 of those that possess some unusual qualities that make them of some particular interest. These galaxies have complex evolutionary histories, with some having supermassive black holes at their core, others are powerful radio sources, a very few are relatively nearby and even visible to the naked eye, whereas the light from one recent discovery has been travelling for the past 13.4 billion years to show us its infancy, and from a time when the Universe was in its infancy. And in spite of the vastness of the Universe, some galaxies are colliding with others, embraced in a graceful gravitational dance. Indeed, as the Andromeda Galaxy is heading towards us, a similar fate awaits our Milky Way. When looking at a modern image of a galaxy, one is in awe at the shear wondrous nature of such a magnificent creation, with its boundless secrets that it is keeping from us, its endless possibilities for harboring alien civilizations, and we remain left with the ultimate knowledge that we are connected to its glory.