Customer Reviews

The Direction of Time (Library Reprint)

5 star:		(4)
4 star:		(1)
3 star:		(1)
2 star:		(1)
1 star:		(0)

 

 

If you didn't know, this book is hard. I am a first year engineering student, and I felt lost through most of it. I gather it was intended for full-fledged physicists, but I was intrigued to read it anyway because of a philosophical thread running through the work. But beware--get ready for some Immanuel Kant and Einstein in only the introduction. This book is as much about the physics of time as the philosophy concerning subjectivity of time. Even though I didn't understand a lot of the probability or almost any of the quantum mechanics math, I still got some pleasure out of some of the more bizzare conclusions of the book. Did you know that for an isolated system (one not interacting with any others), time can't be said to have any direction? Furthermore, time as we know it is just a statistic. Another interesting fact is that on the quantum mechanical level, there is no such thing as time! If these things intrigue you (and you know what a double Riemann sum is) go for this book. Otherwise, be very afraid...

It is a beautiful but exterememly difficult book. It covers the concept of time and direction of time from the beginning up to current thinking. Author, being one of the founding fathers of philosophical quantum theory first introduces a good understanding of Thermodaynamics and Statiastical Physics and defines the order of events to lead into statistical definition of arrow of time. A lot of difficult concepts from Classsical Statistical Physics, Probability Theory, Relativity and Mathematical Logic as well as a good understanding of Quantum Physics is assumed to be in the bag of the reader, after all this book is not a Popular Science book. Although the author claims that knowledge of derivations of the formulas used are not critical to understand this study yet time to time the language and logic becames exteremely difficult. This is a must read book in this subject, may be many times or time and time over after increasing the understanding in other subjects that only tools in this book.

I can't believe that everyone didn't rate this with 5 stars!

I had to write this because this was one of those really great books that changed my understanding of something that seems so basic, so obvious, time.

Well well worth the 5 bucks.

What Reichenbach doesn't say in this book is as important as what he does say. He takes an empirical approach to an investigation of time, which leaves out Husserl's "time consciousness." He examines from numerous standpoints (classical mechanics, quantum mechanics, statistical mechanics, etc.) the question of the direction of time. When leaving time conscioussness out of the mix, the question of the direction of time becomes very difficult.

Reichenbach's knowledge of physics plays well with his experience in the philosophy of probability to ensure that error in thinking is reduced. Overall, I think this a fine book worth any philosopher's time. If fundamental issues in physics are a concern for those in the field of physics, I also recommend this book.

I must caution the reader that this book contains mathematics necessary to the subject, so anyone without a knowledge of basic probability or knowledge of statistical mechanics would probably want to prepare themselves for this book. Rief's book on Statistical Mechanics should be more than adequate (but I am a partial Carnegie Mellon guy, so take your pick of thermo books w/ a statistical bent).

"The Direction of Time" is an important contribution on the nature of time, based on an advanced draft left by H. Heinchenbach after his death in 1953. The manuscript was published posthumously as a self-contained book, thanks to the care and attention of his wife, M. Heichenbach, who edited the manuscript for publication.

The book is divided into five chapters, namely: (1) introduction (basically, on the emotive significance of time); (2) the time order of mechanics; (3) the time direction of thermodynamics and microstatistics; (4) the time direction of macrostatistics; and (5) the time of quantum physics.

A final chapter for the book was planned by the author, summarizing a relation between subjective time (experienced by humans) and the objective time (as given by the formal analysis of physical time presented in the book). Unfortunately, the author died before being able to finish that final chapter. The editor was careful, however, to add an appendix outlining possible directions, based on a related paper by the author, published in 1953.

The book is basically a summary of the author's lifetime contributions to the problem of time, from the point of view of philosophy and physics. In particular, the author is very attentive to clarify as much as possible any philosophical inquiries with logical argumentation and to never loose sight of which mathematical models, based on known physics, can actually bring consistency to the discussion (with the exception of the first chapter, which is purely philosophical throughout).

The book is very clearly written, and any obscurities (there are some, in fact) are mainly due to the difficulty of the subject matter itself, not of his discourse. It is not, for that matter, a popularization book. Some prerequisites are necessary; in particular, with a good understanding of statistical mechanics, the reader will be able to get several insights (starting from chapter 3), based on original ideas and clever constructions, without which he/she would otherwise not be able to fully appreciate the richness and deepness of the arguments involved.

When I opened the book for the first time, I thought that the first chapter, given its title, would be too much subjective for my taste, but on the contrary, it was a nice summary of philosophical schools and inquires on the nature of time. I only found one thing regrettable: his critique of Bergson's "duration" and "intuition" concepts is based on a too literal interpretation -- revealing in fact a (common) misunderstanding. The best here is to read Deleuze's book "Bergsonism", which shows that Bergson's "intuition" concept is in fact a proposal of a method for knowledge, based on three distinct acts: 1 - the positioning and creation of problems (how to denounce false problems); 2 - the discovery of truthful differences of nature; and 3 - the apprehension of real time. Deleuze is usually confusing for me, but his reading of Bergson in particular is quite illuminating and serves here as an opposition to Reichenbach's brief critique.

The second chapter was quite surprising as well, as I thought that I would learn nothing new about the concept of time from the point of view of classical mechanics. I was wrong. Making time order distinct from time direction was quite revealing. It is a very strong principle to always have in the back of one's mind. Chapter 3 gradually constructs the hypothesis of branch structure based on the statistical isotropy of the universe as the origin of time direction. This is something to take serious note as well. I have previously seen arguments linking time and the increase of entropy, but Reichenbach's shows how this notion is not as straightforward as basic statistical mechanics indicates, and further assumptions seem to be necessary. Finally, I have found Chapter 4 the most obscure part of the book, and further thinking and re-reading are necessary.

As the book was written in the 50's, there is of course some outdated information. The idea of relating entropy to information has evolved significantly from the time the book was written, specially with respect to quantum computation and information. The same concerns the material on the last part of chapter 5, which, for instance, still addresses Dirac's hole theory interpretation. A treatment of time in modern quantum field theory is, understandably enough, missing. However, the book is, for its most part, still valid and an excellent source for investigation on this never-ending puzzling subject. It certainly does not present a final theory of time, but offers an excellent outline of several lines of thought, reveals some intriguing possibilities and summarizes the foundations of the subject.

In some parts of the book, I have found myself surprised by some subtle conclusion based on gradually complex argumentation which nevertheless were founded on very simple concepts. Overall, I highly recommend the book for those seriously interested in the nature of time, and who are eager to spend good -- time -- thinking over the matter. Being a Dover publication, the price is quite accessible and it is, of course, a classic for your bookshelf.

H.Reichenbach is undoubtly one of the most remarkable scientists that the world has ever witnessed. The interested mind is to be very strongly urged to read the book 'The direction of time' by him. Time is an essential concept to every physics student, as without it nature would be meaningless, and therefore the study of nature would be an empty pursuit. Whenever we wish to understand why we are in the 'world', say rather than in the planet MARS we have to understand thoroughly what actually happenned in the past, beginning from The Big Bang, that is, from the beginning of time. The book gives us a clear understanding into this inquiry ('TIME') developing both classical and quantum mechanical content of the concept of time starting from the first principles. The book carefully clarifies many confusing conceptions about time. For instance, the author clearly explains the contradictions lying in the famous Zeno's paradox which attemts to prove that time does not exist, in such a way that the physics student is now much more confident with such essential concepts as displacement and velocity. Also in the book, another essential concept of statistical physics ENTROPY is developed in a very systematic way and through this concept the direction of time is decisively established. Moreover, the issue of DETERMINACY or INDETERMINACY , an issue which is simply ignored in the text books or mentioned briefly in a few sentences as if it is self-evident and therefore does not need further elaboration, is discussed in depth, so both theoretical and experimental physicists have now a strong ground in arguing their proposals. I, as a physicist of 18 years of university lecturing experience, strongly recommend it to every single physics student or actually every single mind (student or not) who cares about the future, and who needs a decisive explanation (justification) for their potential steps to save (before being too late) our home THE WORLD WHICH WE NOW LIVE IN, only home only home and only home for us and for our childeren including of course our organic bodies, the animals and the plants. The direction of time and equally of The ENTROPY are the key concepts to understand what technology actually is, and to understand why it is inevitable to face more and more polluted environment as technology advances.

I think it was a good thing that Reichenbach never published the book: if only his wife had not found the manuscript and published it posthumously. Upon reading the second chapter I was astounded at how dismissive he was about identity and persistence. He makes a controversial presumption about identity without any arguments for why he presumes such identity and without giving anything close to identity criteria. He then glosses over the problem of identity through time, whether endurantist or perdurantist or whatever. And he claims to be a philosopher! These are such important issues in the philosophy of time, in philosopher in general. That said, this is not so much a book about the philosophy of time as it is about the philosophical foundation of statistical mechanics: whether statistical mechanics is a good explanation for the second law of thermodynamics or not. And this is where Reichenbach fails. Instead of dealing with the philosophy of statistical mechanics, per se, he wants to validate its worth by giving it a sound mathematical basis using probability. That is not philosophy at all. But the worst is his seemingly ad hoc explanation for why the universe is moving from a low entropy state to a high entropy state by dealing with the symmetry problems in statistical mechanics, that is, the symmetry of Newtonian physics and the statistical postulate with respect to time. He posits a branching system, which has been updated by Paul Davies in "The Physics of Time Asymmetry". Reichenbach's branching system is just absurd! He gives two arguments to buoy up his branching system: i) an idea of a causal chain that creates a net, which is open and ii) a probability lattice. Now I realize that he comes up with very sound math to prove the soundness of his probability lattice, but correct math does not a universe make. The probability lattice, while requiring a suspension of disbelief to analogize it to his branching system qua explanation of why the universe came from a low entropy state towards a higher one and why there "seem" to be entropic subsystems (e.g. a fully formed ice cube melting in a glass of water), is predicated on Reichenbach's belief that the arrow of time is explained by the phenomena of cause and effect as a open chain that creates a net. For him, a cause is an interaction and an interaction creates a subsystem which branches off of the overall trajectory of the entropy of the universe. I have no idea what this means. Why is cause an interaction and what is an interaction exactly? Does cause and effect have to be the working of occult powers? What causes interactions? Can interactions be caused, since by definition they are causes? None of this makes any sense despite his valiant and tedious efforts to back up his theories with a mathematical foundation. But, this is philosophy, not theoretical mathematics. And all his theories, or more accurately, his equations, seem to make statistical mechanics more complex and fantastical than needed or wanted. There is no elegance here. There is, however, a hodgepodge of equation after equation for ever more complex and incoherent theory after theory, without any rigorous analysis or argumentation from a philosophical standpoint.