British astronomers have given an answer as to why humanity has been unable to find traces of other, extraterrestrial, civilizations: what if they simply self-annihilated long before we started looking for them? Fortunately, even given such a scenario, traces of their destruction could still be observable.
. . . What if the extraterrestrial civilizations annihilated themselves long before we actually started attempting to find them?
Adam Stevens, Duncan Forgan and Jack O’Malley James used the Earth as a test case in order to categorize the potential scenarios for complete civilizational destruction, quantify the observable signatures that these scenarios might leave behind, and determine whether these would be observable with the current technology or technology which might be available in the near future. . . .
. . . The astronomers therefore analyzed various ways that humanity could destroy its own civilization, and the observational signatures these events may produce. . . .