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There are better books on cosmology and better books on quantum parallel worlds...
am 24. Mai 2017
and there may even be better books on the mathematical multiverse.
I bought this book because I was looking for more info about Everett's many-worlds-interpretation. When I read the table of contents of Tegmark's book, I thought that freshening up my limited knowledge on cosmology couldn't hurt. Well, it did hurt at least little bit: The writing style is so casual that you easily miss many of the interesting connections between measurements and theory. For example, dark matter and dark energy are postulated to explain the movement of stars and the expansion of the universe, respectively. Tegmark mentions both concepts in the book, but their meaning or motivation is much less clear there. Since this was only one of the many instances where I felt that the book is far behind other books on cosmology (e.g. "Kosmologie fuer kluge Koepfe"), I was quite disappointed by Part I of the book. An exception was maybe the chapter on inflation, but probably only because these facts were really new to me.
Part II, dealing with quantum theory, was the reason I bought this book. It did not live up to my expectations. In fact, after reading these chapters, the quantum multiverse hypothesis is now even less clear than it was before reading the book. And this owes, again, to Tegmark's casual writing style. He writes:
"[...] suggested that Everett postulated [...] parallel universes and that our Universe would split into parallel universes whenever you made an observation. Indeed, even today, many of my physics colleagues still think that this is what Everett assumed."
He then goes on about the importance of checking the original sources, or misquotations in science before, just one page later, he writes:
"[...] Everett realized that even though there's still only one wavefunction and one quantum reality [...] this is in practice as if our Universe has split into two parallel universes! At the end of the experiment, there will be two different versions of you, each subjectively feeling just as real as the other, but completely unaware of each other's existence."
Such simplifications make clear how the prevailing misinterpretations come about. He later even contradicts the last sentence in the quote by showing that the two "parallel universes" can in principle interact (because decoherence is not complete).
So we are left with Part III, where he explains his mathematical universe hypothesis, his idea that the universe is a mathematical structure (and that actually all (finite?/computable?) mathematical structures correspond to parallel universes). I can only say that I found his argumentation rather weak, and that the book would have benefitted a lot if this (and the other parts) were structured a bit more like logical arguments. (Suppose P1 and P2 is true, then it follows P3, and from observation follows P4, so in conclusion we have C.) Rather, he gives lengthy explanations of the obvious and jumps over the more difficult parts trusting that the reader will just believe it. Also the other concepts he touches in the book (strong self-sampling assumption, doomsday argument, sleeping beauty problem, etc.) would benefit a lot from adding a few formulas for the mathematically inclined (in the appendix, say). I have no reason to believe the strong self-sampling assumption unless I saw some explanation (say, from a Bayesian perspective). In conclusion, although this part of the book was interesting and new to me, I was not convinced because of the weak writing.
Tegmark's writing style is as egocentric as it is casual. He does present the basic ideas of cosmology and quantum theory including the microwave background, expansion of our universe, wavefunction collapse, decoherence, etc. and he explains how we came up with these hypotheses. But doing so, he never fails to emphasize his own contribution to the respective field (or other things he did, like programming a 3D version of tetris). This culminates in the last chapter where he spends only 40 pages to write about existential risks, the future of physics, the future of our universe, the future of humanity, etc. -- 40 pages that cannot contain much more than name dropping, given the scope he devoted to them. While this is perfectly fine for an autobiography, I felt it was a bit out of place for a pop-sci book. Admittedly, the subtitle of the book reads "MY quest for the ultimate nature of reality", so it may very well be that the book was intended as an autobiography.