Books: Parallel Worlds, by Michio Kaku

The universe is weirder than you think. I got this perception from "Parallel Worlds", written by Michio Kaku, a professor of theoretical physics at the City University of New York (first published 2005).

The topic of the book (amazon.com) is the idea that our universe isn`t alone and unique. There could be many more universes or so-called parallel worlds. "Maybe our universe is just a bubble in an ocean, with new bubbles forming all the time" muses Kaku.

This is very speculative, of course, nobody can prove that. But there are indeed some logical and somewhat plausible arguments for the existence of parallel universes. Kaku points to the fact that life as we know it needs a lot of benign conditions, otherwise we wouldn´t exist. For instance we need just the right amount of sunlight and just the right amount of gravity (which holds just the right amount of atmosphere without crushing us). If our moon would be smaller or farther away, the course of the earth would be less stable, causing catastrophic climate changes. If the basic physical forces which keep the particles of the atoms together (the so-called weak and the strong force) would be a bit different, then the particles wouldn`t glue together and there would be no atoms and no molecules, therefore no matter. Is it just luck, that our universe is in a Goldilocks-zone where everything suits to our existence?

No, says Kaku. There could be a huge number of universes which don´t have the right conditions and are without life. These universes might have just fogs of electrons without suns and planets, thanks to different physical forces. The beneficial conditions which shape our universe could be the result of the "law of averages".  "If there is a large stock of clothing, you`re not surprised to find a suit that fits" explains the author using a quote from the astronomer Martin Rees from Cambridge Univerity.

Another rationale for the multiple universe theory delivers the quantum theory, which claims that the movements of electrons and others particles of atoms are random and not predictable (Heisenberg`s uncertainty principle) and electrons act both as a particle and as a wave.  "Once we introduce the possibility of applying the quantum principle to the universe, we are forced to consider parallel universes".  For instance the existence of parallel universes could explain Schrödinger`s famous example, that a cat could be either dead or alive, depending on the spectator (wikipedia). Maybe there is one universe where the feline is alive and another where the animal is dead, offers Kaku.

And he goes further. He claims that there could be so-called wormholes which allow traveling to the parallel worlds. These connections could be black holes, because their extreme gravity shapes the law of physics. Some of these black holes could be shaped like a ring and rotate around a centre (an idea from the physicist Roy Kerr from New Zealand). These black holes could rotate very fast and produce intense centrifugal force pushing outwards. These forces could cancel the inward force (extreme gravity) which would otherwise crush the traveller.

Albeit of all these speculative ideas the book is based on serious scientific theories. Kaku, who is an acclaimed physicist by himself, builds his arguments on theories and mathematical models developed in the last century by physicists & mathematicians like Einstein, Hawking, Heisenberg, Schrödinger, Dirac, Born, Gödel and a lot of others.

The author has the gift to explain sometimes bizarre considerations in a lively and narrative style. Kaku´s "Parallel Worlds" is therefore an open door into cutting edge physics, maybe a wormhole buy itself.