Water boils in a pot, and bubbles rise from the bottom. They grow, float up, and pop, and the water remains water. Something similar, physicists have found, can happen to space itself — if it contains dark energy (the mysterious force accelerating the expansion of the universe).

In such an eternally inflating universe, black holes are sometimes born. Not from dying stars, but directly from the void, like a vapor bubble in the bulk of a liquid. A new study refines this mechanism. The authors revisited an old idea according to which the birth of a hole is described by a special 'snapshot' of geometry — the so-called Nariai instanton. Previously, an important detail was missing: the calculations had no observer. When they added one, the required imaginary phase appeared in the formulas, and the process gained physical meaning.

Then comes more. The authors checked what happens to such a newborn hole. Earlier works predicted a strange 'anti-evaporation' scenario: the hole did not shrink but grew, feeding on the energy of expansion. The new analysis showed that this is an artifact of an unfortunate choice of initial state — with discontinuities at the horizon that should not exist in nature. If one takes a smooth state consistent with quantum birth, everything falls into place. The hole behaves like an ordinary one: it emits thermal radiation and loses mass.

Evaporation runs to completion. The hole disappears, and around it again is a smooth, empty, maximally disordered vacuum — the very one from which everything began. The full cycle turns out to be a kind of Boltzmann fluctuation: in a vast sea of equilibrium, a complex structure arises for a moment, only to melt away without a trace.