Novelist Karl Schroeder has an intriguing possible answer to Fermi’s Paradox, i.e. the question “Where are all those aliens?”.
I’ve lately been trumpeting my revision of Clarke’s Law (which originally said ‘any sufficiently advanced technology is indistinguishable from magic’). My revision says that any sufficiently advanced technology is indistinguishable from Nature. […] Basically, either advanced alien civilizations don’t exist, or we can’t see them because they are indistinguishable from natural systems.
He proposes that an advanced civilization will inevitably reach a thermodynamic equilibrium with its surroundings. Since we try to detect alien civs via their waste products (heat, light, other radiation) we might not see them. Compelling idea.