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Rating: 
Summary: Not Sure I understood what I read.
Review: I look out in the vast heavens and often wonder what is the size of the universe. I have pondered the questions of, where did it all begin? Where does it end? Can anything change the course of the universe? Lawrence Krauss may have the key to unlock these mysteries with this book.Krauss, who is the Chairman of Physics at Case Western Reserve University, explains in great detail that the old idea the missing mass of space is nothing more than the space itself. Krauss has written a highly convincing book. Krauss shows that is given enough black space, a gravitational pull will occur and therefore cause the universe to alter its position. While I am a little more than a novice in this area I found the reading fascinating and hard to put down. What captured my attention was Krauss's quantum fluctuations of empty space and how it can create a, as he calls it, a nonzero energy. Grab a copy of this book and you can read his explanation of this phenomenon. Overall this book was very good, although tailored to specific reader genre.
Rating: 
Summary: Worth the effort.
Review: I understand the negative reviews. This book is dense with information and is most appropriate for the lay reader who really wants to get some idea of where professional cosmology is today, and how it got there. Reading it just once, quickly, like a cheap novel, is not going to be good enough. You need to read it at least twice before it will start to really click (unless you have more background than I do!). I remember reading a book about Feyman (the Nobel prize-winning physicist) in which he related that, when he was a kid, he would read a heavy-duty science book until he couldn't understand it anymore. Then he would put it aside. The next day, he would pick it up again, start reading and, lo and behold! the foggy became clear and he could get a little further. He would repeat this process until he had finished the book. Sometimes, if you want to know, you just have to make that kind of effort. This book rewards the effort. It is excellent, but it's not a cheap date and you aren't going to get very far in a single encounter. Unless, again, you have a good background in this area already. Buy it. Live with it for a week. It will pay off. You will be fascinated. Do it now.
Rating:
Summary: Qunitessential modern science?
Review: I was fortunate this autumn to have lots of train journeys round the south of England, and this book was a fascinating and thought provoking companion. Less mathematical than some other recent treatments (Bernstein's Introduction to Cosmology, or Peacock's Cosmological Physics), it nevertheless covers what sems to be a transition in cosmology from a theoretical set of models to a practical observational subject. The reviewer who thinks that scientists in this area simply demonstrate ignorance presumably didn't get past the dust jacket since the book is full of empirical discoveries which still require adequate theoretical coverage. If there is one weakness it is the near absence of treatment of string theories, which are held, in some quarters to provide the only adequate descriptions of quantum gravity - but also seem to 'explain' so much else that their correspondence to our actual universe is still highly moot. (Also the mathematics seems to be so abstruse as to make it intrinsically uncertain!) One final point, I had not read Krauss's earlier work and was worried that I would be reading an update to a 10 year old work which must have been seriously left behind by the discoveries of the 90s, but, impressively, the work reads seamlessly and I could not tell what (if any) came from the original work, and what was new.
Rating: 
Summary: Too dense for the lay reader
Review: I've read many books on physics, and several written by Krauss. But this book is entirely too dense for the lay reader. Worst yet, Krauss seems to have lost his magical touch for keeping the reader's interest. Unless you're a professional (or student) of quantum physics, this book will bore you.
Rating:
Summary: It's about the missing mass in the universe
Review: Krauss takes his title, "Quintessence" from ancient concepts about space, and makes the point that some of our concepts have come full circle (though not in ways envisioned by their first proponents). The subject is the "missing mass" of the universe. The universe, of course, is exactly what it is - so there isn't really any "missing mass." What's meant by that phrase is that we know there is more mass in the universe than what we see, and the question is, what is this hidden material? That might seem like a narrow subject for such a long book, but missing mass, it turns out, has implications for just about everything, from quantum mechanics to the broadest theories of formation of the universe. For me, the book started off slow. The first chapter is mostly about ancient notions of the universe, with discussions about Aristotle's aether, and things like that. This chapter is basically a very short history of science, from earliest concepts through Einstein's development of the theory of relativity, and the demise of the aether. With the theory of relativity, physics viewed empty space as just that - empty. The idea of a uniform background of invisible stuff (particles, aether, etc.) lay pretty much discarded. Then we had the beginnings of the modern science of cosmology and the discovery of the cosmic microwave background (CMB), which has been confirmed as the closest-to-theoretical blackbody radiation source ever discovered. The CMB is one of the pillars of evidence for the expanding universe and the Big Bang theory of cosmology, and Krauss does a nice job of following the historical and logical sequence of discoveries in its development. Within the Big Bang theory, the amount of matter in the universe has broad implications for how the universe will continue to evolve, so any "missing mass" is very important. Krauss covers these topics in a relatively brief but nicely done chapter on the Big Bang and large-scale structure in the universe. One of the things I like best about this book is the extra bit of detail Krauss offers that is often over looked in other books. The sort of details that help the reader better understand the specifics and particulars that real science is made of. The subjects in this book range from the very large (theories of the evolution of the cosmos) to the very small (concepts and ideas in quantum physics). For example, there is an early introduction to the concept of virtual particles and the resolution they bring to many different and important calculations in physics. One of the most important of these is the philosophical problem of action at a distance, which virtual particles solve nicely by providing a mechanism for transferring force from one particle to another. Chapter three was one of the most interesting for me, and marks the beginning of the real meat of the book. It describes how astronomers weigh the universe. At first, this can seem either trivial or impossible, depending on your expectations. On one hand, it seems that all you need do is count stars (not literally, of course, but by measuring an average density and multiplying by total volume) multiply by some sort of average stellar weight, and there you have it. On the other hand, closer examination begins to show cracks in that method. What about dim stars? Gas? Dust? Planets? How much mass do they contribute? Krauss does an excellent job of pointing out these difficulties, and showing how, one by one, scientists refined their estimates by including more and more candidates for matter in the universe. It was a monumental task, and Krauss does a nice job of illustrating for the informed layman the incredible intricacies that had to be included in the methods and calculations that went into calculating the amount of barionic matter in the universe. Next, Krauss shows how you can use Newtonian mechanics to predict the amount of mass within a given radius by measuring how fast objects outside the radius orbit the center. He begins with an example showing the average orbital velocity of the planets as a function of the distance from the sun. He uses this example to predict the solar mass, and to also illustrate how much (how little, actually) other material besides the planets there is in the solar system. I find this aspect of science fascinating; how, with some careful observations of lights in the sky, we can infer the amount of mass resulting from countless unseen specs of dust orbiting the sun in an unimaginably large volume of space. The orbital velocities for planets in the solar system fall off rapidly with increasing distance from the sun. But when we apply these techniques to galaxies, we see something different: the orbital velocities fall off as if there was an invisible halo of mass around them. Taking the best estimates for matter in a typical galaxy, and measuring the velocities of stars orbiting various galaxies, scientists found that the amount of matter they thought was there is a small percentage of the amount that is inferred by the measured orbital velocities. This is the origin of the central problem of Krauss' book: the missing mass of the universe. We know it's there, but what is it? What is it made of? If current estimates are correct, it is the dominant source of mass in the universe. Most of the rest of the book looks at the central question of what the missing matter - called dark matter - is made of. Along the way Krauss examines possible candidates from neutrinos and WIMPS to vacuum energy. As I said, this is a nicely written book, and one that wraps a whole lot of information on the universe together. If you enjoy amateur cosmology (like I do) I think you'll want to read it.
Rating:
Summary: Can be read by the layperson
Review: The bottom line is Lawrence Krauss has been able to give us a glimpse of an open, fascinating problem in physics which is far from being solved: the existence and essence of dark matter. The book can be read by the layperson but is also useful for scientists, non-specialists in cosmology. Pedro G. Ferreira, Oxford A complete review is availabele in CERN Courier, June 2000
Rating:
Summary: a cogent look at a fascinating, if difficult topic
Review: The only conclusion I could draw from this dreary tome is that physicists have no clue what the univere is made of or what it's future will be. The author leads the reader up one rosy path after another to lead only to "...on the other hand..." After reading this book, I feel we are truely primatives cogitating on the shore of space making up myths. (Or could it be the author.) The six point font doesn't help either. If you have trouble going to sleep at night, this is the book for you; an instant cure for insomnia!
Rating:
Summary: A Moderately Bright Description of Dark Matter
Review: Will the universe expand forever, begin to contract at some time in
the future, or get to a balanced state? The answer depends on the
amount of mass it contains. To explain the behavior of galaxies
unaccountable by the mass of visible matter, the idea of "dark
matter" was proposed in the 1980s. The title of the book
"Quintessence" means "The Fifth Essence." The
latter was the title of the first edition of this book published in
1989. In ancient philosophy, it meant the heavenly material that was
supposed not only to form stars but also to pervade all things, and is
used here to represent dark matter and vacuum energy in the
universe. Lawrence Krauss starts the story by an intriguing brief
review of the earliest notions of cosmologies and gives an updated and
much detailed account of the dark matter problem for lay readers. The
account covers both theoretical and experimental studies including
those to be done in the near future. Some chapters might be hard for
bedside reading even for scientists, because the author often lays one
reason upon the other for an explanation. However, thorough reading of
this book would be rewarding if you like to wonder about the mysteries
of the universe and scientists' efforts to resolve them. The book
contains some irritating misprints. For example, "decrease"
should read "increase" at one place, and "charge"
should read "change" at another.
Rating:
Summary: A Moderately Bright Description of Dark Matter
Review: Will the universe expand forever, begin to contract at some time in
the future, or get to a balanced state? The answer depends on the
amount of mass it contains. To explain the behavior of galaxies
unaccountable by the mass of visible matter, the idea of "dark
matter" was proposed in the 1980s. The title of the book
"Quintessence" means "The Fifth Essence." The
latter was the title of the first edition of this book published in
1989. In ancient philosophy, it meant the heavenly material that was
supposed not only to form stars but also to pervade all things, and is
used here to represent dark matter and vacuum energy in the
universe. Lawrence Krauss starts the story by an intriguing brief
review of the earliest notions of cosmologies and gives an updated and
much detailed account of the dark matter problem for lay readers. The
account covers both theoretical and experimental studies including
those to be done in the near future. Some chapters might be hard for
bedside reading even for scientists, because the author often lays one
reason upon the other for an explanation. However, thorough reading of
this book would be rewarding if you like to wonder about the mysteries
of the universe and scientists' efforts to resolve them. The book
contains some irritating misprints. For example, "decrease"
should read "increase" at one place, and "charge"
should read "change" at another.
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