Some suggest that the physical world 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)
But while computers process input to give output, most of the universe doesn’t compute anything at all (Piccinini, 2007). For example, the sun inputs and outputs physical events not information.
In addition, that the physical world causes processing that causes the physical world is impossibly circular. When a program runs to generate an output, the output is apart from the processing as a cause that causes itself is an infinite circular act that can neither stop nor change. In contrast, our universe is changing and it will one day stop because it began. Every process that our computers run is always apart from its output, so the physical world can’t be both the process and what it outputs. The physical world can no more compute itself than two hands can draw each other (Figure 1.3).
It is equally glib for physicists to talk of quantum processing occurring in our spacetime:
“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 doesn’t allow a fixed space or time. If quantum processing creates a virtual physical world and its space and time, that processing can’t exist in the space-time it created.
If our universe is virtual, it must be finite because what is infinite can’t be computed, and indeed it is. Equally all the laws of physics must be calculable, which again they are. An abstract like π can be infinite as long as it doesn’t represent a physical thing, which it doesn’t. So the universe could be:
- Calculable: Most scientists accept that processing could calculate physical reality based on the Church-Turing thesis, that a finite program can simulate any specifiable output (Tegmark, 2007). This is not 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 it could be a virtual reality would 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)
- Calculating: That some sort of calculation creates physical events is supported by many academics, including 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).
- Calculated: That processing actually does calculate physical reality is the final step, but few in physics support this “strong” view, that the physical world is just an output (Fredkin, 1990).
These statements cumulate, as each assumes the previous, so that which isn’t calculable can’t arise from any calculation, and that which can’t come from any calculation can’t be a calculated output. It is a slippery slope, as a calculable reality that can be caused by some calculating could be calculated, i.e. virtual. But while the second option, that It does indeed come from Bit, sounds good, it is impossible for a physical world to compute itself. Logic reduces the above options to two: either the physical world exists by itself alone and just happens to be mathematically calculable, or it is in fact calculated and thus a virtual output. The physical world is either processor or output and there is no valid middle ground.
Quantum realism concludes that physical reality is generated by non-physical quantum processing.