We observe that our universe uses
a reversible computation, yet our
brains only appear to use irreversible computation. It seems important to ask why. Is it possible for SAS’s to live in a universe that is directly associated
with an irreversible computation?
If so then why are we special?
Computer science seems to be
centered around the concept of “assignment”. For example, computer memory undergoes
state changes in the form of assignments to memory locations. A Turing machine uses assignment
operations each time a 1 or 0 is written on the tape. Assignment involves lost information
because it simply overwrites the previous value with a new value. It is fundamentally
I have been wondering whether we
can get a better understanding of reversible computation by distinguishing
between movement of information and assignment of information. The analogy of the Turing machine
would be that we need to cut up the tape with scissors – we are only allowed
to move bits of tape around, rather than reassign values on the tape. This leads quickly to the view
of particles that move around,
rather than the idea of a particle that is stored in space (= memory)
that moves as the result of “assignments to
So rather than think of a small
piece of space having an attribute of what particle is in it, we should think
of a particle as having an attribute of where it is in space. The latter view makes space seem
rather incidental – rather than thinking of particles as being embedded in
space. I wonder to what
extent physicists distinguish between these two views.
I guess the distinction evaporates
in string theory, where there is nothing but (higher dimensional)
space-time. There is
nothing to assign to because the information is present in the topology of
space itself. Movement of
information is more like a ripple on a pond.
The Turing machine seems to lack a
direct relevance to our universe.
However, can’t a Turing
machine emulate a reversible computation?