Robert M. Wald

A remarkably good book, certainly the best pop physics book I've read in the GR field, and perhaps ever.

In most respects the author was far more careful than most to hedge his speculations, to clarify some of the more exotic points, and to refrain from wild-eyed speculation.

Having said that, I still found some areas disappointing --- can I truly be the only person on earth who understands this stuff?
* The discussion of black hole thermodynamics did not give us the claim about the entropy representing the number of ways the black hole could form, thank god, but seemed unaware of how the thermodynamics could be seen as an extension of Plancks 1895 work, and thus treated black hole entropy as something strange, not "real" entropy.
* There was no discussion of the interior of black holes, or anything to do with black holes as absolute elsewhere. Thus we get statements that are simply wrong, like creation of a black hole violates conservation laws like baryon number conservation.
* The discussion of Penrose energy extraction with its strange statements about negative energy based on "space-like" time made absolutely no sense to me.… (más)