Physicist Explains: What Happens If a Tiny Black Hole 'Hits' a Human?

The Astonishing Impact of a Micro Black Hole on a Human Body

Imagine a cosmic encounter that sounds like pure science fiction: a tiny black hole passing through a human. While the concept might conjure images of instant annihilation, the reality, as explored by physicist Robert Scherrer of Vanderbilt University, is far more nuanced and, in some ways, less terrifying than one might initially believe.

Unveiling the Science of Stellar Remnants

Black holes, those enigmatic celestial bodies with gravity so intense that nothing, not even light, can escape, are typically associated with the cataclysmic deaths of massive stars. However, the universe might harbor a different class of these gravitational titans: primordial black holes. These hypothetical entities, theorized to have formed in the chaotic aftermath of the Big Bang due to extreme density fluctuations, are considered one of the leading candidates for dark matter—the invisible scaffolding that holds galaxies together and accounts for the universe's observable gravitational anomalies. NASA's cosmic pie chart of the universe – 5% ordinary matter, 27% dark matter, and a whopping 68% dark energy – highlights the profound mystery of what constitutes the vast majority of existence.

Primordial Black Holes: Rare but Possible Candidates

While the idea of primordial black holes as dark matter is intriguing, their existence is not definitively proven. The conditions required for their formation were incredibly rare, even within the turbulent early cosmos. If they do exist, their contribution to the universe's dark matter is likely minuscule. Nevertheless, their mere possibility ignites profound questions, spurring physicists like Scherrer to explore their potential interactions with matter as we know it.

When Gravitational Giants Collide with Flesh and Bone

Scherrer's research, rekindled by recent gravitational wave detections from merging black holes and new imaging breakthroughs, delved into a thought experiment that haunted his imagination since reading a 1970s sci-fi tale: what happens when a black hole passes *through* a person? His calculations reveal a surprising outcome. A black hole weighing a staggering 100 billion tons, if it were to “plow” through a human, might inflict less damage than a simple .22 caliber bullet. The true agent of destruction in such a scenario? Not the black hole itself, but the explosive shockwave it generates.

The Science of Spaghettification vs. Shockwaves

To inflict significant damage, a primordial black hole would need a minimum mass of approximately 140 quadrillion grams, or about 140 billion metric tons – a mass roughly seven times that of the asteroid Toutatis. At this immense density, the black hole would be infinitesimally small, possessing a Schwarzschild diameter of a mere 0.4 picometers. For perspective, a hydrogen atom is about 106 picometers wide! Such a minuscule object, traveling at around 200 kilometers per second, would likely zip through human tissue with minimal interaction. However, this speed far surpasses the speed of sound. The resulting supersonic boom, trailing the black hole, would tear flesh apart with a force comparable to a bullet's shockwave.

Tidal Forces: The Ultimate Stretcher

Beyond shockwaves, black holes exert a gravitational pull that, when applied unevenly, creates tidal forces. These forces stretch and tear objects apart in a phenomenon ominously known as “spaghettification.” This occurs because the part of an object closer to the black hole is pulled more strongly than the part farther away. However, for a human body, the atomic and molecular bonds holding our tissues together are, at these scales, stronger than the tidal forces of smaller black holes. You're not spontaneously disassembling on Earth, a planet weighing an unfathomable 6 sextillion metric tons, for a reason!

The Threshold for Devastation

For tidal forces to truly wreak havoc, a primordial black hole would need a mass of at least 7 quintillion grams, or 7 trillion metric tons – roughly the mass of the asteroid Iрида. Only at this minimal threshold would the black hole's gravity be potent enough to transmute a human into cosmic spaghetti. Otherwise, the aforementioned supersonic shockwave would likely deliver the fatal blow. Happily, for all us earthlings, the rarity of these theoretical black holes means the probability of such an encounter with a human is astronomically low, estimated at once in a quintillion years – a timeframe vastly exceeding the current age of our universe (13.8 billion years).