The Labyrinth of Time: Introducing the Universe [Hardcover]

Michael Lockwood's book is both exhilarating and irritating.

Chapter 1 introduces the ideas of tensed and tenseless time: this distinction contrasts the common sense view that time flows from an under-defined future through the instantaneous present to a fixed past, vs. the classical physics view that `now' is simply an index into a pre-existing space-time block universe, where there is no flow of time as such. This chapter may put off the casual reader, as it includes much conceptual hand-wringing on the meaning of words. It is a reminder of why science uses precise models expressed in mathematical language, with its clear semantics and rules of inference, rather than ordinary language discussion.

Chapters 2-7 are far better. A conceptually clear explanation of special and general relativity, with a discussion of time travel (closed timelike curves) and mechanisms such as wormholes for accomplishing it.

Chapter 8 changes gear as Lockwood introduces the Hamiltonian approach to classical mechanics, and phase spaces. Chapters 9 and 10 form an extended discussion about the role of entropy in time asymmetry, placed in a historical context. Again interesting and clear.

Things get murky again in chapters 11-13. These purport to be a discussion about why we remember the past, but not the future, but the discussion is shapeless, visiting a number of topics in a meandering fashion.

Chapter 14 brings us to Quantum Mechanics. As is the fashion these days, we are taken briskly through the `old quantum mechanics' to Hilbert spaces and energy eigenstate superposition as the driver of time-varying quantum probabilities. We are then brought to the Measurement Problem, the EPR paper and the various interpretations of QM. This is all pretty brisk, and the reader really needs to have had prior exposure to the Hilbert space formulation of QM to follow what is going on here. Lockwood, like David Deutsche, is a supporter of the `many worlds' interpretation of QM - he prefers a variant model comprising an `actuality' dimension. In chapter 15 he explains why this model (space-time-actuality) can resolve time travel paradoxes. Chapter 16 is a clear conceptual discussion of string/M-theory and loop quantum gravity - the two main unification thrusts in current physics.

Chapter 17 suddenly goes off in an new direction, focusing on the neurological and philosophical basis of our psychological construct of the present moment. This is an extended period - Lockwood thinks about a second - called `the specious present'. The chapter ends in an obscure philosophical debate on `the temporal mode of presentation'. And that's it, the book ends.

Read this book for the explanations of relativity, quantum mechanics and current frontier thinking in fundamental physics, where it is first-rate. The chapters which deal specifically with philosophical issues probably appeal to a different audience: they seem irritating and nit-picking to this reviewer - why not translate the discussions into formal models where they can be analysed properly?

Finally, a number of issues are not well analysed or resolved, such as the nature of causality, the subjective view of time flowing and the reasons why we don't remember the future. Surely these are not purely philosophical issues, disconnected from our best physical theories? The lack of a concluding chapter is also a serious omission. Finally, you would need a degree in maths or a science subject to really engage with this book.

This book provides a great overview of the more interesting parts of modern physics, with some emphasis on time and the philosophy of time.
It is less clearly focused on time than the cover suggests. If you want a deep and narrow focus on time, Huw Price's book Time's Arrow is more appropriate and provocative.
Labyrinth of Time explains many things better than other physics books do.
For instance, the standard description of the twin paradox suggests that acceleration is responsible for the differences in how each twin ages. Lockwood refutes that with a nifty diagram of a cylindrical space-time where unaccelerated twins age differently on world-lines of different lengths.
The book provides good explanations of why the alleged paradoxes of time travel aren't sufficient to imply that time travel is impossible.
Lockwood does a relatively good job of arguing in favor of the Everett (many world) interpretation of quantum mechanics, but that section requires enough experience with the subject that many laymen will have trouble following it.
The speculations he reports about how time might mean before the Planck time are really strange.

As I picked up this book I was reminded of the old story of how at around 1900 the world's understanding of physics was considered 'all knowed up.' To be sure, there were a few constants to be evaluated to a few more decimals. Then came 1905 and an obscure physicist published a paper that turned everything upside down. His name was Einstein. Among the things that was turned upside down was our understanding of time. It appears that the fundamental nature of time is very far fron what common sense would lead us to believe.

This book has the simple intent of changing the way that we look at time. It discusses the latest theories to in a non-mathematical approach intended for the non-scientist. The concepts he discusses are at the leading edge of presently understood cosmology. Perhaps understood is to strong a word, believed.

Surprising to me is that the author has taught philosophy at Oxford for many years. As such he is willing to talk about things like time travel that the more doctrinaire physicists don't mention. Note that non-mathematical does not necessarily mean simple. These are not elementary concepts. Good Reading!

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