# Comment on 'The aestivation hypothesis for resolving Fermi's paradox'

## TL;DR

This paper critiques the aestivation hypothesis for Fermi's paradox by arguing that civilizations can dispose of entropy more efficiently using local reservoirs, challenging the idea that waiting for a cold universe is necessary.

## Contribution

The authors construct a concrete model demonstrating that entropy disposal is possible without waiting for low cosmic background temperatures, countering the original hypothesis.

## Key findings

- Entropy can be transferred to local reservoirs at any time.
- Waiting for a low-temperature universe does not improve entropy disposal.
- The original hypothesis's assumption about entropy disposal is incorrect.

## Abstract

In their article [arXiv:1705.03394], 'That is not dead which can eternal lie: the aestivation hypothesis for resolving Fermi's paradox', Sandberg et al. try to explain the Fermi paradox (we see no aliens) by claiming that Landauer's principle implies that a civilization can in principle perform far more (${\sim} 10^{30}$ times more) irreversible logical operations (e.g., error-correcting bit erasures) if it conserves its resources until the distant future when the cosmic background temperature is very low. So perhaps aliens are out there, but quietly waiting. Sandberg et al. implicitly assume, however, that computer-generated entropy can only be disposed of by transferring it to the cosmological background. In fact, while this assumption may apply in the distant future, our universe today contains vast reservoirs and other physical systems in non-maximal entropy states, and computer-generated entropy can be transferred to them at the adiabatic conversion rate of one bit of negentropy to erase one bit of error. This can be done at any time, and is not improved by waiting for a low cosmic background temperature. Thus aliens need not wait to be active. As Sandberg et al. do not provide a concrete model of the effect they assert, we construct one and show where their informal argument goes wrong.