Discovery that billions of planets in our galaxy may nurture life has spurred the search for extraterrestrial intelligence (SETI). If an epoch-shattering message were picked up by SETI, it likely will bring clues about religion in an advanced civilization. This would be of enormous value to us by suggesting what sort of religion can take a civilization beyond poverty, disease, strife, wars and pollution into a stable era of cosmic communication. Even greater than this is the exciting possibility of insight into a religion shared by millions of advanced civilizations.
It may seem unusual to discuss extraterrestrial religion in relation to SETI but bear in mind that there is a great deal of religious material broadcast electronically in our own civilization, including the pleas addressed by every politician for God to bless his own people and to deal severely with all others. It is therefore not unreasonable to anticipate that there will be religious content in the official material broadcast by an extraterrestrial civilization, although the crudities of terrestrial religions may be absent.
In fact the type of religious communication to be expected will depend on the cultural history of the civilization. When we calculate the probability of there being an extraterrestrial civilization near us, we learn that only civilizations with ages of hundreds of thousands to millions of years are close enough to communicate with each other. Therefore we will most likely hear from a civilization of great age that has overcome the destabilizing forces of competing religions and achieved an ecumenical spirituality. This spirituality will condition its response to other planetary systems.
Of course, in the absence of SETI detecting any messages, the investigation of an extraterrestrial religion is essentially a theoretical enterprise. It might even be called speculation. But I find this acceptable, because much that constitutes religion is indeed speculation. How can it be otherwise, since it deals with the ineffable and the intangible?
SETR (the Search for Extraterrestrial Religion) is an ongoing project to examine the various types of knowledge an advanced civilization will call on in reaching a transcendent vision of the universe.