“In any case, only one thing seems certain: if we really live in a simulation, it doesn't run on Windows.”  
Seth Lloyd 

Recently the universe has been compared to a huge computer, albeit in different ways and with more or less radical implications. If in the 700th and 800th centuries the metaphor of the universe as a great mechanism was valid, a clockwork mechanism, describable in terms of deterministic mechanics, today the dominant metaphor is that of a gigantic information manipulation system 

This comparison is declined in different ways ranging from the metaphor of the hologram, to the actual identification of the world with a computer, up to the more radical thesis which claims that our universe is nothing more than a gigantic simulation (in the literal sense) , simulation of which we ourselves would be part. 


The first suggestion comes from the study of black holes. Proven by Hawking that black holes are not that black after all since they evaporate, albeit very slowly, it remains to be understood what happens to the information they contain, given that quantum physics does not contemplate the loss of information. Losing information, in fact, means compromising the deterministic character of the universe: how can I go back from the present to the previous (or future) states of the universe if I am missing pieces? 

The solution seems to lie in the fact that all the information contained in the black hole is actually deposited as a thin film around the black hole itself (around the event horizon, to be precise) as if it were a hologram, and therefore it is not lost.  

By extension, the theory hypothesizes that all objects in the universe and the universe itself are surrounded by a two-dimensional layer of bits that contain all the information relating to the object they surround which is therefore nothing more than the hologrammatic projection of that layer. In this case we live not really in a computer, but in a hologram and we are holograms ourselves 

Among the most convinced supporters of this approach are Leonard Susskind and Gerard 't Hooft (the latter Nobel Prize for Physics in 1999), not exactly two naive people. 


According to other physicists and information theorists - such as Seth Lloyd or Fotini Markopoulo Kalamara - the universe is nothing more than a gigantic quantum computer, in the literal and non-metaphorical sense of the term.  

The universe in fact consists of a material substrate that can embody any information. Atoms and all subatomic particles can have two states (up and down, spin to the right or left), and this is enough to make them possible carriers of information: to be such, in fact, it is enough to have the possibility of being able to embody two physical states (0 and 1, open current and closed current, ...). There is no doubt about the fact that the universe is quantum, which immeasurably amplifies its computational capabilities.  

In this panorama, physical laws constitute the software that simultaneously runs on and modifies the hardware. The constants of the universe (speed of light, Planck's constant...) are instead the parameters that regulate everything. 


But probably the most radical and surprising position is that expressed by Nick Bostrom in the so-called “simulation topic” 

The topic of the simulation is articulated in three hypotheses 

  1. Human civilizations become extinct before reaching a technological development that allows them to implement computer simulations of their precursors. 
  2. Civilizations (or a large part of them) that reach this technological stage, for whatever reason, do not wish to create simulations of worlds and their inhabitants. This is either because of the ethical problems that such simulations entail, or simply because of the cost in terms of computational space and memory that they imply, or simply because they are not interested. 
  3. With a very high degree of probability we live in a simulation created by beings other than us.

If 1 and 2 are not true it is in fact very likely that we are the inhabitants of a gigantic simulation; in other words, it is easy for civilizations that have reached full technological maturity to be interested in creating enormous simulations, for example of their ancestors. The inhabitants of the simulations could in turn reach full technological maturity and also develop simulations with sentient beings. In this scenario the number of simulations would exceed the number of real universes, with a consequent increase in the probability that we are nothing but a simulation (maybe of a simulation) 

And, in turn, we may soon reach the level of technological development that will allow us to create other simulations, in a dizzying recursive regress. 

We thank for the contribution PAOLO RICCARDO FELICIOLI