The concept of a creature with a "metabolic rate" rate to slow to detect seems like nonsense to me. Self sustained Chemical, thermal and electrical reactions are bounded by physical laws which are detectable. Even where liquid helium exists, maybe on Pluto, and it is so cold that our normal rules don't apply we should theoretically be able to send and observatory of a probe to observe.


On the other hand, this is the most interesting sentient theoretical "thing" I've heard of in a while. Boltzmann brain