Why should there be only one universe?

We once thought the Earth was the only planet, the Sun the only star and the Milky Way the only galaxy. But none of this is unique, as science progresses. So why aren’t there multiple universes, too?

This question is asked by science journalist Anas Heckenberg multiverse, a thin but in-depth handbook of the Pocket Series new world. “Physical theories regularly raise the possibility that our universe is in fact not alone,” she writes. Five of these theories are discussed. With clear language and sense of humor.

It’s a good thing that these theories are all on the fringes of science and that they originate from all kinds of different corners of physics: from the Big Bang to string theory.

The chapter on the theory of the so-called many-worlds interpretation of the American physicist Hugh Everett is particularly interesting. This theory stems from quantum mechanics, the tiny particle physics from which everything is built. According to Everett, each time a selection is made, new universes appear: one for each possible outcome. “Here the multiverse is all the different paths you could have taken, and they are all there, but you (or rather: this version of you) are only fully exploring one,” Heckenberg wrote. These different outcomes do not occur at the human scale, but at the small particle scale.

The book ends with the pros and cons. None of the theories have been proven yet. But this happens more often in physics: something is invented, like a black hole, and its existence is proven decades later. Only, “most multiverse theories suggest that these additional facts, if any, are beyond the reach of our scientific tools,” Heckenberg wrote. If physicists never find it, will they have to spend time in it? Yes, ‘even if it’s just a thought exercise […]. “