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265 A network of tightly beamed communications channels might connect he advanced technologies of our Galaxy, suggested Bracewell. The prob- ability that we would come within the beams of such transmissions is very small. If technologically advanced aliens do not wish to allow others to une in, it is unlikely that we will intercept their messages.”° Human searchers hope that other civilizations will choose a signaling method that does not mimic nature. The Ohio State University search strategy even assumed that a civilization transmitting at the hydrogen line requency would offset their transmission in just the right way to remove all motions with respect to the center of the Galaxy.*! Such best-case assumptions are driven by the limitations of our technologies. Even if signals are above our detection threshold, we might not realize hat they were messages. “At this very moment,” Sagan imagined, “the messages from another civilization may be wafting across space, driven by unimaginably advanced devices, there for us to detect them—if only we knew how.... Perhaps the messages are already here, present in some everyday experience that we have not made the right mental effort to rec- ognize.” Drake admitted that we might receive an information-bearing message and never realize it.” We may fail to detect the signal of another civilization because we don’t know the code. It might appear to us as static; as a civilization becomes more efficient, Minsky warned, transmissions look more and more like noise. A few years of technology development can make the new signals incomprehensible to the senders of the old signals.” We may not have qualified scientifically for entering the galactic com- munications network, Bracewell proposed, because we still have not dis- covered the next thing that awaits downstream for us in physics. It may be that communication hinges on this next discovery.** We could be in a tem- poral hiatus between older, more advanced civilizations that have moved too far beyond us to be detectable, and newer civilizations that have not yet developed technologies for which we can search. Drowned out Some believe that certain species of whales share an ancient culture, communicated through long, elaborate songs like the oral histories of ancient human bards. Once, those songs might have reached throughout the world ocean, interconnecting the species. That communications web may have been suppressed by the noises of human technology: thou- sands of chugging engines and whining propellers, filling the liquid medium with random, unintelligent noise. Weakly transmitting civilizations—perhaps including ours—may be drowned out by the Galaxy’s electromagnetic turmoil. Even if They Will Be Detectable