Powers of the weak

"Why is it that, in such a vast cosmos, with hundreds of billions of stars in this galaxy alone, and no doubt billions of Earth-like planets orbiting them, we have found no evident of intelligent alien life? No evidence that alien have ever visited Earth (other than discredited UFO mythology), no detectable signals...? The stories in this anthology offer intriguing explanations for this enigma, looking seriously or comically at solutions..."--P.[4] of cover.