A new theoretical study asks whether a black hole can reverse the usual picture of mergers—spontaneously splitting into two smaller black holes. While standard black hole physics and observations of gravitational waves support merging, the study examines the counter-intuitive possibility of “fission” and what would be required for it to occur.
Across sources, the key obstacle is thermodynamics: black hole entropy relates to the area of the event horizon, and a simple split would tend to reduce total entropy, conflicting with the second law for isolated systems. One outlet describes this as a “thermodynamic dead end” for non-rotating black holes, because the entropy of one larger horizon outweighs the combined entropy of two smaller ones.
The same research argues that rotation changes the calculations. If a black hole spins extremely fast—near the maximum “extremal” limit—rotation energy could weaken the entropy barrier and make splitting possible in principle. However, the scenario requires such extreme conditions that it is unlikely in the observable universe, and—per the coverage—no such splitting has been observed.
