Exoplanet Transits as the Foundation of an Interstellar Communications Network

TL;DR

This paper proposes that exoplanet transits can serve as a low-energy, reliable method for interstellar communication, enabling a connected network of civilizations within the Galactic Habitable Zone through cumulative transit observations.

Contribution

It introduces a novel interstellar communication method based on exoplanet transits and demonstrates, via simulations, that such a network can become fully connected over time within the Galactic Habitable Zone.

Findings

The network is likely to be cumulative, ensuring future connectivity.

Simulations show the network can connect all civilizations within ~100,000 years.

Paths between civilizations are shorter than the size of the Galactic Habitable Zone.

Abstract

Two fundamental problems for extraterrestrial intelligences (ETIs) attempting to establish interstellar communication are timing and energy consumption. Humanity's study of exoplanets via their transit across the host star highlights a means of solving both problems. An ETI 'A' can communicate with ETI 'B' if B is observing transiting planets in A's star system, either by building structures to produce artificial transits observable by B, or by emitting signals at B during transit, at significantly lower energy consumption than typical electromagnetic transmission schemes. This can produce a network of interconnected civilisations, establishing contact via observing each other's transits. Assuming that civilisations reside in a Galactic Habitable Zone (GHZ), I conduct Monte Carlo Realisation simulations of the establishment and growth of this network, and analyse its properties in the context of graph theory. I find that at any instant, only a few civilisations are correctly aligned to communicate via transits. However, we should expect the true network to be cumulative, where a "handshake" connection at any time guarantees connection in the future via e.g. electromagnetic signals. In all our simulations, the cumulative network connects all civilisations together in a complete network. If civilisations share knowledge of their network connections, the network can be fully complete on timescales of order a hundred thousand years. Once established, this network can connect any two civilisations either directly, or via intermediate civilisations, with a path much less than the dimensions of the GHZ.