Does a Computer have an Arrow of Time?

TL;DR

This paper critically examines the proposed link between thermodynamic and psychological arrows of time, arguing that computational processes are compatible with both increasing and decreasing entropy, challenging prior claims of their necessary alignment.

Contribution

It demonstrates that computational processes can occur in universes with decreasing entropy, challenging previous arguments linking thermodynamic and psychological arrows of time.

Findings

Computational processes are possible in entropy decreasing universes.

The supposed necessity of arrow alignment is challenged.

Alternative explanations for arrow alignment are discussed.

Abstract

In [Sch05a], it is argued that Boltzmann's intuition, that the psychological arrow of time is necessarily aligned with the thermodynamic arrow, is correct. Schulman gives an explicit physical mechanism for this connection, based on the brain being representable as a computer, together with certain thermodynamic properties of computational processes. [Haw94] presents similar, if briefer, arguments. The purpose of this paper is to critically examine the support for the link between thermodynamics and an arrow of time for computers. The principal arguments put forward by Schulman and Hawking will be shown to fail. It will be shown that any computational process that can take place in an entropy increasing universe, can equally take place in an entropy decreasing universe. This conclusion does not automatically imply a psychological arrow can run counter to the thermodynamic arrow. Some alternative possible explana- tions for the alignment of the two arrows will be briefly discussed.