A new 2025 analysis models how a tiny primordial black hole passing through a person would affect the body—and why the worst effects are limited by size and speed.
Primordial black holes are often portrayed as cosmic monsters, but when you zoom in on the physics, the story becomes oddly more restrained—and scientifically more interesting.
A keyphrase behind the hype is “primordial black hole. ” and Misryoum takes a careful look at what a research team concluded in 2025: a very small primordial black hole—born in the universe’s earliest moments. if they exist—could cause serious effects. yet not in the movie-style way people might imagine.
First. the background: primordial black holes (PBHs) are hypothetical objects that could have formed in the first fractions of a second after the Big Bang. when conditions of extreme density and pressure might have allowed small regions of matter to collapse into black holes.. Unlike most black holes we know from stellar collapse or black-hole mergers. PBHs—if they exist—could span a wide range of masses. including extremely tiny ones.. That smallness matters because quantum effects imply that the tiniest black holes gradually evaporate via Hawking radiation.. For the mass scale discussed in the Misryoum review. the PBH would be small enough to be startling. but not so small that it would already have vanished since the early universe.
So what happens when one rips through something as complex as Earth—or a human?. The crucial idea is that gravity does not act uniformly.. A black hole’s gravitational pull is intense, but only over very short distances.. As the PBH moves, the strength of its influence changes rapidly with distance from its path.. Even if the black hole’s mass is enormous by everyday standards. its effective “grabbing radius” is tiny because it’s a minuscule object.. In other words. a PBH can be gravitationally dramatic while still interacting with only a very small fraction of the matter it passes.
Misryoum notes that for an asteroid-mass PBH. Earth-scale effects are more about a fast-moving gravitational disturbance than about tearing the planet apart.. A PBH passing straight through Earth would zip through in under a minute. exciting a brief shock wave as the surrounding material is pulled and then overwhelmed by the rapid passage.. Earlier work cited in the piece compared the resulting seismic signature to something around a modest earthquake magnitude—enough to be detectable. not enough to be planet-ending.
The 2025 paper then focuses on the human-body scenario.. Here, the analysis is conceptually similar—gravity plus motion—but the stakes shift from planetary geology to biological tissue.. The researchers calculated the energy deposition by treating the PBH’s passage like a fast. localized projectile interaction. using established physical analogies from impact physics.. Their conclusion: “significant” injury would require a PBH of just above roughly one hundred billion metric tons—about the same mass range already being discussed for Earth passages.
Why does that not translate into instant destruction?. Misryoum’s interpretation centers on two constraints: time and scale.. The PBH would cross a human body in roughly a microsecond—about the blink-and-you-miss-it timescale in biological reality.. Even if the gravitational field changes sharply along the path. the tissue doesn’t have time to be uniformly destabilized before the object is gone.. The second constraint is the length scale of interaction.. Because the PBH is tiny and extremely fast. it would likely couple most strongly to a small number of atoms along its track. leaving only a submicroscopic “tunnel” effect rather than a wide channel of devastation.
The study also considers tidal forces, which are the gravitational differences across distance that can strain structures.. In the human case. the extremely brief traversal means the tidal damage remains limited even for a passage through sensitive regions such as the brain.. The modeling suggests that to reach a truly tissue-damaging level. a PBH would need to be far more massive—about a hundred times larger than the threshold for “significant” injury discussed in the paper.. That doesn’t make the scenario pleasant; it just makes it more physically specific.
There’s also a probability reality check—one that Misryoum thinks is central to how these ideas land with non-specialists.. PBHs are not confirmed. and even the speculative scenario where they constitute a fraction of dark matter comes with huge uncertainty.. Using the kind of dark-matter abundance assumptions employed in the research discussed here. the expected rate of a PBH hitting a human is effectively “never” on human timescales.. Earth, being bigger, is the more likely target—but even then, the numbers land on billion-year timescales.
For everyday life. Misryoum suggests putting this in perspective: while the primordial-black-hole scenario is a fascinating exercise in extreme physics. real risk comes from more immediate. measurable hazards—traffic. climate impacts. and the mundane slips that turn into injuries.. Still. the value of work like this is not that it predicts a catastrophe tomorrow; it’s that it converts sci-fi dread into calculable boundaries. tightening what we know about how gravity behaves at unusual scales.
And if PBHs do exist. studies like this also hint at where future efforts might look—not for “collisions” as dramatic events. but for subtle signatures in astrophysical data.. In a universe full of unknowns. sometimes the best progress is learning exactly how bad the worst case could be. and how quickly nature’s own constraints narrow the possibilities.