Ancient Black Holes Could Burst into White Holes express
Some black holes are remnants from the Big Bang. Usually they fade via a slow radiation leak — predicted by Stephen Hawking. But a quantum switch could invert them into white holes, explosively releasing all energy like popcorn kernels that suddenly pop.
A new study calculates this switch’s likelihood, factoring in the warping of space and cosmic expansion. The pop rate peaks only when a black hole’s lifetime matches the universe’s age — exactly timed, like popcorn in hot oil. Astronomers tested whether these pops cause mysterious fast radio bursts — brief, intense blips from deep space. Match? Barely: only in a sliver of cases, with very light black holes or those vanishing before the flip.
So the cosmic popper rarely delivers. Observations from gravitational waves to gamma rays dismiss white holes as the prime burst culprit. Yet here’s the twist: a black hole primed to pop would be tinier than an atom but as heavy as a mountain. The takeaway? It sharpens the hunt for these improbable cosmic flashes.
Original abstract
as written by the authors arXiv:2603.22516
We calculate the present-day and cosmological volumetric rate of primordial black hole (PBH) quantum tunneling events to white holes, incorporating the competition between Hawking evaporation and tunneling, cosmological depletion, realistic mass-dependent abundance constraints, extended mass functions, and the alternative memory-burden scenario. The burst rate is maximized along a narrow ridge in the mass--tunneling-parameter plane where the effective PBH lifetime is comparable to the age of the Universe. Within the canonical Planck-star range of tunneling timescales, FRB-level rates arise only in two highly restricted regions: a low-mass window near the evaporation boundary, and a narrow sequential window where evaporation precedes tunneling; broadening the PBH mass function does not qualitatively alter this conclusion. We further assess observational constraints from FRB repetition statistics, radio spectral properties, prompt and diffuse gamma-ray limits, host-galaxy demographics, and gravitational-wave signatures. All current observations are consistent with a subdominant white-hole contribution to the FRB population but strongly disfavor a dominant origin. The rate calculation does not generically support FRB-level event densities, and any viable FRB interpretation requires narrow, fine-tuned, and strongly assumption-dependent corners of parameter space.
An ancient black hole could be smaller than an atom yet weigh as much as a mountain.
In the sci-fi comedy Red Dwarf, a white hole makes time flow backwards.