Book review: The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, by Brian Greene.
This book has a lot of overlap with Tegmark’s Our Mathematical Universe
Greene uses less provocative language than Tegmark, but makes up for that by suggesting 5 more multiverses than Tegmark (3 of which depend on string theory for credibility, and 2 that Tegmark probably wouldn’t label as multiverses).
I thought about making some snide remarks about string theory being less real than the other multiverses. Then I noticed that what Greene calls the ultimate multiverse (all possible universes) implies that string theory universes (or at least computable approximations) are real regardless of whether we live in one.
Like Tegmark, Greene convinces me that inflation which lasts for infinite time implies infinite space and infinite copies of earth, but fails to convince me that he has a strong reason for assuming infinite time.
The main text is mostly easy to read. Don’t overlook the more technical notes at the end – the one proposing an experiment that would distinguish the Many Worlds interpretation of quantum mechanics from the Copenhagen interpretation is one of the best parts of the book.