To explain the data, some suggest that the physical word is both the processor and its output:
“The universe is not a program running somewhere else. It is a universal computer, and there is nothing outside it.” (Kelly, 2002)
Yet while computers process input to give output, most of the universe doesn’t (Piccinini, 2007), e.g. the sun inputs and outputs physical events not information. Computers input and output information but physical systems have physical input and output so the universe mostly doesn’t compute anything at all.
Also, that the physical world generates a program that generates the physical world is impossibly circular. A program is processing stored as information that is later read and executed, so the physical world cant be a program, what executes it, and the output all at once. In any virtual reality, the processor is always outside the world created. It is no more possible for the physical world to compute itself than it is possible for two hands to draw each other (Figure 1.3).
It is equally glib for physicists to talk of quantum processing occurring in our space and time:
“Imagine the quantum computation embedded in space and time. Each logic gate now sites at a point in space and time, and the wires represent physical paths along which the quantum bits flow from one point to another.” (Lloyd, 1999) p172.
To embed quantum processing in a fixed space and time contradicts relativity, which states that there is no fixed space or time. Conversely, if quantum processing creates a virtual physical world and its space and time, that processing can’t exist in the space-time that it created.
If our universe is virtual it must be finite because what is infinite can’t be computed, and indeed it is as it expanded from a fixed point. Equally all the laws of physics must be calculable which again they are. An abstract like pi can be infinite as long as it doesn’t represent a physical thing, which it doesn’t. This allows three hypotheses:
1. Calculable universe: That processing could calculate physical reality is accepted by most scientists based on the Church-Turing thesis that a finite program can simulate any specifiable output (Tegmark, 2007). It doesn’t imply determinism as not all definable mathematics is calculable, e.g. an infinite series. If our world is specifiable, even probabilistically, in theory a program could output it. The idea is not that the universe is a computer simulation but that it could be. That our world is a virtual reality could easily be falsified by a non-computable law of physics but none has ever been found. Indeed, our world has an algorithmic simplicity beyond all expectations:
“The enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious and there is no rational explanation for it.” (Wigner, 1960)
2. Calculating universe: Supporters of the idea that some sort of calculation creates physical events include main-stream physicists like Wheeler, whose “It from Bit” statement implies that processing (bit) somehow creates physical things (it). Now processing doesn’t just model the universe, it causes it (Piccinini, 2007).
3. Calculated universe: That processing actually does calculate physical reality is the final step. Now the physical world is just an output but few in physics support this “strong” view (Fredkin, 1990).
These statements cumulate, as each assumes the previous, so that which isn’t calculable can’t arise from some calculation, and that which can’t come from some calculation can’t be calculated reality. It is a slippery slope as a calculable physical reality that can be caused by some calculating could be calculated, i.e. virtual. And while the second option, that It does indeed come from Bit, sounds good, it is impossible for a physical world to compute itself. So logic reduces the three options above to two: either the physical world exists by itself alone and just happens to be very mathematically calculable, or it is in fact calculated and thus virtual. There is no middle ground.
Thus the quantum realism conjecture that physical reality is a processing output requires that processing to be quantum processing, which physics agrees cannot have a physical basis.