A 1974 science fiction story sparked curiosity about whether a tiny black hole could be lethal. The scientific answer is more intriguing than initially thought.
While a large enough black hole would undoubtedly pose a significant threat, even a small one with the mass of a single hydrogen atom is too weak to notice. Instead, researchers focus on the critical mass at which a black hole becomes deadly.
Primordial black holes, theoretically formed in the Universe’s earliest moments, have masses ranging from atomic to several Earth masses. However, their existence is constrained by observations: any smaller than 1012 kg would evaporate due to Hawking radiation, while those larger than 1020 kg would cause gravitational lensing effects that haven’t been detected.
The study investigates two effects: tidal forces and shock waves. Tidal forces become stronger as a black hole approaches, but the force differential might not be fatal even if it passes through vital organs like the head or midsection. However, if the black hole enters the body via the head, tidal forces could tear apart brain cells.
Shockwaves generated by a black hole entering the body are more hazardous. To create an energy similar to that of a 22-caliber bullet, the black hole would need only a mass of 1.4 x 10^14 kg, within the range of possible primordial black holes.
While this possibility is gruesome, it’s unlikely to occur in reality due to the rarity of asteroid-mass primordial black holes. The chances of encountering one in their lifetime are less than one in 10 trillion.
Source: https://www.sciencealert.com/study-reveals-what-would-happen-if-you-were-struck-by-a-tiny-black-hole