The cosmic silence is sort of mysterious. We’ve seen no plausible signs at all of radio signals or other methods of communication that we can recognize emanating from an extraterrestrial origin.

I suspect it’s because we’re both early to the party (likely one of the first tech civilizations) and because technological civilizations will tend not to last very long. Also, I suspect those that do persist will recognize that there is substantial existential risk in advertising their presence.

Still, the silence is bothersome. It hints that we’re alone, or that we won’t last long. Global climate change seems to be confirming that latter hypothesis.