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Title: About Time: Einstein's Unfinished Revolution
ISBN: 0684818221
Author:
Paul Davies
Publicate Date: 1996-04-09
Publish: 1996-04-09
List Price: $15.00
Average Customer Rating: 4.0
Format: Paperback
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Amazon Lowest New Price: $3.25
Amazon Lowest Used Price: $0.01
Amazon Merchant Price: $10.20
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| Customer Review: |
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1: About Time
I liked this book. When I read the first pages, I thought that I had chosen the wrong book, but afterwards everything changed. Here you can find a light and clear review of many aspects of time.
It is not perfect, and some times it is not clear what the author means with "time reversal", etc, even if he tries to explain it several times. The theory about the proximity of Doomsday is also quite weak.
In spite of this, you find a clear view of time as it is currently known by science. I have not found many new ideas, but in general they are well structured and consolidates what you have read separately in many other books. Apart from that, it has good rhythm, and it is easy to read and understand.
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2: Entertaining, informative and very well written.
This, as the title states, is a book about time; all the possible aspects of time, from that of the Greek philosophers, through Newton's idea of time, to Einstein's relativistic view of time and beyond. The book is a blend of philosophy, physics and physiology, but heaviest on the physics aspects of time. Everyone thinks that they know what time is, but on closer examination it is not so clear what time actually is. Is it an illusion or just the interval between events? Does it flow, or is it only perceived to do so? Does time always run forward, or can it run backwards? What is imaginary time, or quantum time? Did time start at the instant of the big bang? What does time look like in a black hole? How does the brain perceive time?
To the ancient Greeks time was a mystery, to Newton time was absolute and to Einstein it is relative to the observer. All these are subjects (and much more) that are discussed in the book; discussed in a very literate and highly entertaining manner. This is not, however, a physics text, although much of it is concerned with the physics of time. There are no equations and only the results of relativity theory, quantum mechanics and cosmology are discussed, not the details. Nonetheless, it brings time to life (to use the sort of analogy that is discussed in the book) in a way that the details of a physics text cannot. I highly recommend this book to students and to anyone who wants their perception of the most basic aspect of consciousness challenged. Read this book and you will never perceive time in quite the same way again.
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3: Everything is reversible?
This over-simplistic physics account which holds that universal time and entropy are reversible and that Poincare's recurrence theorem disproves the 2nd law of entropy increase in isolated systems (and Boltzman's statistical mechanics) ignores the fact that physics equations are idealizations and that mathematical equations are tautoligies that do not define direction or cause. These arguments generally ignore real world effects such as friction, noise, chaos (e.g. the 'many body' problem for gravity) and non-linear effects and correlations etc.
For instance the wikipedia description of Poincare's recurrence theorem points out that environmental noise and chaos alone can break the idealization. In addition chaos can cause entropy increase in both time directions (e.g. P. Cipriani). Various authors (with articles on the net) have pointed out that for non-adiabatic processes, 'the natural evolution of entropy is towards larger values because the natural state of matter is at a positive temperature' (M. Campisi), and only in adiabatic classical mechanics are energy and entropy both conserved and time reversible (e.g. Silverberg and Widom). In addition 'One of the basic postulates of the classical statistical physics is an assumption that the particle's interaction range is considered to be small compared with the system size. If this condition does not hold the internal and free energies, entropy etc are no more additive physical quantities... the Boltzman relationship between the entropy and the statistical weight is not any longer valid. The non-extensive systems are common in physics- gravitational forces, Coulomb forces in globally charged systems, wave-particle interactions, magnets with dipolar interactions etc.' (Apostolov et al, April, 2007).
Essentially all of Davies' book is concerned with the idealizations and so most of the paradoxes he describes are not real and he has not updated the debate since Boltzman from the early 20th century. His analysis of the 'twin paradox' from Einstein's early relativity of the same era is also dated (even though his book is a century later!). This paradox about the twins each measuring each other's clocks with telescopes appearing slower to the other when one takes a fast spaceship into space and yet one returning younger is readily dismissed by Davies as the effect of the traveller's acceleration, is in fact not fully accepted. For instance S. Kak's recent article succinctly describes the actual situation:
"There exist many different 'resolutions' to the paradox [which] are not in consonance with each other. The slowing down of all clocks and processes - including atomic vibrations - on the travelling twin cannot be laid on the periods of accleration and turning around during the journey, since they can, in principle, be made as small as one desires... Einstein's own 'resolution' in 1918 (13 years after Davies says he reolved it!) which was an attempt to counter the criticism related to the paradox until that time, used the gravitational time dilation of the theory of general relativity to explain the asymmetrical time dilation of the travelling twin. This explanation is generally considered wrong and is different from the other 'resolutions...In this article we present a new principle for the identification of inertial frames in a matter-filled universe [assumed away in the other idealizations!] that allows us to easily resolve the twins paradox. The principle implies that the identification of a frame as being inertial depends on whether the universe has spatial isotropy with respect to it. This is equivalent to determining the motion of objects against the background of distant stars."
One might describe this solution as 'Machian', whose central principle was that a particle's mass was determined by all of the other particles in the universe. There has been some evolution of this (Mach's general) theory which has gained some popularity and some authors have shown how it can be adapted to conform to any gravitational theory including Einstein's relativity. There are also some good books on this subject for sale on Amazon.
So once again when one does away with the idealizations and enters some reality into the models one can resolve many of the so-called paradoxes.
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4: Will CERN 2007 render this book obsolete?
After eight years in the waiting the CERN Hadron collider is set to resume testing in 2007. In so doing it will -- according to noted physicist Ed Witten -- have an opportunity to test some of the more gross predictions of cosmic string theory and in so doing perhaps re write notions of space and time itself.
That being said, Professor Davies book is up to his usually high standards of scholarship and communication in discussing that most pivtol of topics: time.
From recounting speculations of ancient philosophers such as Augustine to telling the modern story of how we are better understanding time to his own speculations, Davies does a wonderful job of briefly recounting the material and making it accessible to the layman.
Well worth reading, but definately keep your eyes peeled for events at CERN.
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5: Ok, But Not the Best
About Time discusses twentieth century developments in theoretical physics and their impact on our notion of time. Davies is a well known and prolific Australian science writer. I offer the following thoughts for potential readers.
Aimed at the general reader the book does not require a detailed knowledge of physics or mathematics. In light of the counter intuitive nature of modern theoretical physics, however, the uninitiated reader may require a little effort to get the gist of this intriguing but esoteric topic. Given the broad scope of material addressed in the text the time spent on each issue is relatively limited.
I concur with previous reviewers that the book is generally quite readable - Davies' technique of using a hypothetical skeptic as a means to highlight certain issues may strike some as awkward (that was my impression). From an overall stylistic perspective, however, Davies has improved significantly from his earlier efforts and become a solid writer.
The author does a nice job of discussing relativity and some of its implications. For instance, his handling of the twins paradox is among the best I have come across. I agree with Davies that there is solid empirical evidence to support time dilation - his transition from this to a tenseless view of time, however, seems premature - or at least insufficiently argued. Indeed, many of Davies assumptions regarding the nature of time, though interesting, will likely not be convincing to those who do not hold his narrow verificationist view of knowledge.
I found the latter part of the book that discusses highly speculative issues such as time travel to be of limited value. At this point much of the thought in this area, though wonderful to ponder, is largely unstructured and untestable - more science fiction than science. Probably the two biggest challenges facing About Time, however, is it dating (a lot has happened in the interim) and the increased competition in this genre of writing.
Overall, it is not a bad book. There are, however, better options available to readers interested in this subject matter - Greene, Singh and Ferris are authors worth looking at.
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