The most committed followers of super-string theory support the existence of ‘multiverses’. There would be 10500 ‘multiverses’, they say, if we take into account all the universes corresponding to all the possible varieties of Calabi-Yau, each one of them sailing in parallel branches.
In fact there could be even more, – if we take into account the multiverses that are totally disconnected, undetectable, unpredictable, pure creations of the mind, but which are necessary to guarantee the coherence of the supersymmetry defined by the mathematics of the super strings.
On the other hand, more conservative physicists consider that the theory of super-strings is not science but fairy tale. The theory of multiverses would come from the delirium of researchers who are so fond of the abstract power of mathematics that they consider it « real », whereas it is only an intellectual construction, and has no other reality than mental.
Plato already believed that mathematics has a form of reality, full of mystery. But he also believed that there were other, deeper mysteries beyond mathematics. As for the hypothesis of an infinity of parallel worlds, happily postulated by the physicists of the super-strings, he had also considered it by means of the metaphysical approach, and had clearly invalidated it:
« So that this world, in terms of uniqueness, may be similar to the Absolute Living, for this reason, it is neither two nor an infinite number of worlds that have been made by the Author, but it is on a unique basis, alone of its kind, that this world has come to be so, and that from now on it will be. »i
The alternative is simple: either there is only one universe (which Plato presents as « similar to the absolute Living Being »), or there is an almost infinite number of multiverses… What is the most likely hypothesis?
If there is an almost infinite number of universes, 99.9999…% of them (we must imagine here a sequence of millions of 9s, after the comma) are absurdly unstable, structurally deleterious – with the extremely rare exception of a handful of them.
And among this handful, infinitely rarer still those who would be able to generate the conditions for the emergence of human thought.
Now human thought has appeared. It therefore becomes a factor to be taken into account from the point of view of cosmological theory. Its very existence, and its extreme rarity on the scale of the large numbers of possible multiverses, are indicators of the exceptional nature (both statistical and conceptual) of the particular universe in which it has emerged.
Its existence and rarity have a cosmological significance. And this meaning inevitably interacts with the definition of the cosmos it seeks to conceive, – through the application of the Ockham principle and the anthropic principle.
Ockham’s principle states that it is futile to multiply beings without necessity. It is absurd to multiply them meaninglessly. A single universe with meaning and coherence (from the cosmological point of view) is preferable to a multiplication of non-viable, absurd and senseless universes (always from the cosmological point of view).
According to the anthropic principle, the mere fact of humanity’s existence requires us to affirm that the universe in which it was born is « special » and even « unique » (again from a cosmological point of view). Among the myriads of possible multiverses, which have no anthropic significance, the mere fact that the universe in which humanity exists implies an immeasurable cosmological chance, – if we just stick to the multiverses theory.
This « incommensurable » chance can be approximated. It can be measured by the hallucinating improbability of the « cosmological constant » essential for human life and thought to be possible.
Chance as it unfolds under the draconian constraints of cosmology can generally only produce ordinary (unstable or incapable of generating ‘human minds’) universes. However, this universe, ours, is not ordinary: it owes the very principle of its existence to the miraculously adequate precision of an infinitely hazardous cosmological constant to be implemented.
This universe is unique because it is special. Why so special? Because of the incredible and disconcerting improbability of the physical constants that govern its structure, and which are necessary for its existence.
These improbably « fine » constants, which physics detects and which mathematics theorizes, make possible the balance of cosmic forces, the existence of galactic clusters and life itself.
The cosmological constant, as deduced by observation and calculation, must be of a mind-blowing precision: a 0, followed by a comma, then 123 zeros, then a long series of numbers. The slightest variation in this sequence of figures would make the universe totally unstable, from the very first moments of the Big Bang, or would make it totally unfit for life.
Multiverses are, in theory, in almost infinite number. But only a very small number of multiverses are compatible with the anthropogenic principle.
The total improbability of the cosmological constants required by life implies that man had no chance of appearing in the infinity of possibly conceivable multiverses.
Yet humanity exists in this universe, and it is even possible to calculate approximately the minute probability of its existence.
The lower the probability, the lower the probability of validating the multiverses theory itself becomes.
As a result, the extreme probability of Plato’s thesis of the unique universe grows even greater.
This result gives us, probably, some nourishing food for thought…
i Plato,Timaeus, 31b