Broadcasting but not receiving: density dependence considerations for SETI signals

TL;DR

This paper presents a quantitative model based on the Drake equation to analyze the conditions under which extraterrestrial civilizations might establish contact, considering factors like civilization density, communication range, and lifetime.

Contribution

It introduces a model that links civilization density and communication range to the probability of contact, highlighting scenarios where many civilizations exist but contact remains unlikely.

Findings

High civilization density does not guarantee contact due to limited communication range.

Short civilization lifetimes reduce the likelihood of contact.

Galaxies can be densely populated yet have no guaranteed communication links.

Abstract

This paper develops a detailed quantitative model which uses the Drake equation and an assumption of an average maximum radio broadcasting distance by an communicative civilization to derive a minimum civilization density for contact between two civilizations to be probable in a given volume of space under certain conditions, the amount of time it would take for a first contact, and whether reciprocal contact is possible. Results show that under certain assumptions, a galaxy can be teeming with civilizations yet not have a guarantee of communication between any of them given either short lifetimes or small maximum distances for communication.