We'll have detected the existence of, but probably not yet made contact with, an extraterrestrial civilization.

The article also suggested that information-bearing physical artifacts might be a more likely first form of contact with an extraterrestrial civilization than radio signals.

The hailing component was designed to be easily decoded by an extraterrestrial civilization, which was confirmed by a double-blind experiment.

Some theories suggest that an extraterrestrial civilization could be advanced enough to dispense with biology, living instead inside of advanced computers.

In contrast to the belief that an extraterrestrial civilization would want to establish an empire, irkovi proposes that an extraterrestrial civilization would maintain equilibrium rather than expand outward.