Scientific methods will ever end

Frontal attack on the scientific method

Many multiverses

The idea of ​​a multiverse is based on a mystery: Why are the values ​​of natural constants such as the fine structure constant, which describes the strength of the electromagnetic interaction, or the cosmological constant, which is related to the accelerated expansion of the universe, precisely within that very narrow range, in where life can develop? According to the multiverse theory, there are billions of unobservable parallel universes in which all possible values ​​of these constants occur. So there has to be a life-friendly universe like ours somewhere, improbable as that may be.

Many physicists believe that the multiverse is unbeatable in explaining many other wondrous coincidences. For example, the low value of the cosmological constant - which is 120 orders of magnitude smaller than the value predicted by quantum field theory - is difficult to understand.

Last year, Carroll, as a representative of the multiverse and many worlds hypothesis, dismissed Popper's criterion of falsifiability as a "clumsy instrument". Instead, he names two other conditions: A scientific theory should be "clear" and "empirical". Carroll understands "clear" to mean that the theory "makes precise and unambiguous statements about the nature of reality". With the second prerequisite - empirical - he follows the common definition that the success or failure of a theory can be judged according to whether it agrees with the previous data.

Inaccessible areas can have a "drastic effect" on our cosmic backyard, says Carroll, and that would explain why the cosmological constant is so small in the regions of space that we can observe. In the context of the multiverse theory, however, this explanation could always be given, regardless of what astronomers measure. Because not only should all conceivable combinations of cosmological parameters occur somewhere, the theory also contains many variables that can be adjusted. Other theories, such as unimodular gravity - a modified form of general relativity - can also explain why the cosmological constant is small.

Physicists also developed verifiable variants of the multiverse theory: Leonard Susskind's version could be falsified, for example, if one could prove a negative curvature of space in the universe. However, this finding would say nothing about the many other variants. Ultimately, the idea of ​​a multiverse is based on string theory, which has not yet been confirmed, and on speculative mechanisms that enable different physics in different parallel universes. Therefore, in our opinion, this hypothesis is not robust, let alone verifiable.

In the many-worlds interpretation of quantum mechanics, proposed by physicist Hugh Everett, quantum mechanical probabilities also affect the macroscopic world. According to Everett, each of Schrödinger's famous cats would be realized in its own universe: the dead and the living, that is, those that were poisoned in their locked boxes or not - depending on whether radioactive decay took place or not. Even if we make a decision - even if it's just that we now go to the left and not to the right - an alternative universe pops up from the quantum vacuum every time, in which we choose the other option, i.e. go to the right.