When Black Holes Turn Inside Out ✎ express
A black hole is a cosmic pocket into which everything, even light, falls. But the pioneering work of John Wheeler, Stephen Hawking, and Roger Penrose showed: sometimes, due to the colossal spacetime curvature, the pocket turns inside out. Then the black hole becomes a white hole — a cosmic fountain spewing out matter and light.
Scientists have simulated such a burst: a hot blob where there are more light particles and electrons than heavy protons. As it expands, it cools, and its radiation stretches into a spectrum — like a rainbow. The energy of this release is comparable to decades of sunshine, and it can be seen halfway across the universe.
If, in the infancy of the expanding universe, microscopic black holes with the mass of the Moon were born, today they could be exploding as white holes. Calculations say: there are enough of these events to be noticed. The most surprising thing is that these bursts last milliseconds but are billions of times brighter than ordinary stars.
A gamma-ray burst from a Moon-mass black hole would be billions of times brighter than a star, but would last only milliseconds.