Customer Reviews

Exhilarating and irritating - By: Nigel Seel, 05 Dec 2005
Michael Lockwood's book is both exhilarating & irritating.

Chapter 1 introduces the ideas of tensed & 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 expressedin mathematical language, with its clear semantics & rules of inference, rather than ordinary language discussion.

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

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

Things get murky againin 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 topicsin 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 & energy eigenstate superposition as the driver of time-varying quantum probabilities. We are then brought to the Measurement Problem, the EPR paper & the various interpretations of QM. This is all pretty brisk, & 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 & loop quantum gravity - the two main unification thrustsin current physics.

Chapter 17 suddenly goes offin an new direction, focusing on the neurological & 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 endsin 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 & current frontier thinkingin fundamental physics, where it is first-rate. The chapters which deal specifically with philosophical issues probably appeal to a different audience: they seem irritating & 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 & 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 degreein maths or a science subject to really engage with this book.