" … It was dark. There were no dead stars, no rogue planets. Matter itself had long evaporated, burned up by proton decay, leaving nothing but a thin smoke of neutrinos drifting out at lightspeed. But even now there was something rather than nothing. The creatures of this age drifted like clouds, immense, slow, coded in immense wispy atoms. Free energy was dwindling to zero, time stretching to infinity. It took these cloud-beings longer to complete a single thought than it once took species to rise and fall on Earth... "

― Stephen Baxter , Manifold: Origin