The \^G Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. I. Background and Justification

TL;DR

This paper advocates for infrared searches for extraterrestrial civilizations with large energy supplies, discussing philosophical issues, the complementarity of artifact-based and communication SETI, and the implications of galaxy colonization timescales.

Contribution

It extends Hart's galaxy-spanning life argument to energy supplies, analyzes colonization timescales, and highlights the potential of infrared surveys like WISE for detecting large alien civilizations.

Findings

Galaxy colonization timescale is less than 1 billion years.

Large energy supplies are plausible due to exponential growth and overcoming resource limitations.

Infrared surveys like WISE are promising for detecting extraterrestrial civilizations.

Abstract

We motivate the \^G infrared search for extraterrestrial civilizations with large energy supplies. We discuss some philosophical difficulties of SETI, and how communication SETI circumvents them. We review "Dysonian SETI", the search for artifacts of alien civilizations, and find that it is highly complementary to traditional communication SETI; the two together might succeed where either one, alone, has not. We discuss the argument of Hart (1975) that spacefaring life in the Milky Way should be either galaxy-spanning or non-existent, and examine a portion of his argument that we dub the "monocultural fallacy". We discuss some rebuttals to Hart that invoke sustainability and predict long Galaxy colonization timescales. We find that the maximum Galaxy colonization timescale is actually much shorter than previous work has found ($< 10^9$ yr), and that many "sustainability" counter-arguments to Hart's thesis suffer from the monocultural fallacy. We extend Hart's argument to alien energy supplies, and argue that detectably large energy supplies can plausibly be expected to exist because life has potential for exponential growth until checked by resource or other limitations, and intelligence implies the ability to overcome such limitations. As such, if Hart's thesis is correct then searches for large alien civilizations in other galaxies may be fruitful; if it is incorrect, then searches for civilizations within the Milky Way are more likely to succeed than Hart argued. We review some past Dysonian SETI efforts, and discuss the promise of new mid-infrared surveys, such as that of WISE.