What Happens If a Small Black Hole Passes Through the Human Body According to a New Physics Study
A new physics study has tackled a question that sounds like pure science fiction but is grounded firmly in real theoretical science: what would actually happen if a small black hole passed straight through the human body? While the odds of such an event are astronomically low, the research offers valuable insight into black holes, dark matter, and the limits of human biology when exposed to extreme cosmic forces.
The study was conducted by Professor Robert J. Scherrer, a physicist who explored the effects of a specific type of black hole known as a primordial black hole. His work was published in the International Journal of Modern Physics D in 2025 and aims to understand whether such an encounter would be harmless, dangerous, or fatal—and what that might tell scientists about the universe itself.
Understanding Primordial Black Holes
Primordial black holes are not the same as the massive black holes formed when stars collapse or the supermassive ones found at the centers of galaxies. These black holes are hypothetical objects thought to have formed in the earliest moments of the universe, possibly within the first second after the Big Bang.
During that brief and chaotic period, matter in the universe may not have been evenly distributed. Extremely dense pockets could have collapsed under their own gravity, forming black holes of vastly different sizes. According to theoretical models, primordial black holes could range in mass from far lighter than everyday objects to heavier than the Sun by thousands of times.
One of the most intriguing reasons scientists are interested in primordial black holes is their potential connection to dark matter, the invisible substance that makes up most of the universe’s mass. If primordial black holes exist in large enough numbers, they could account for some—or even all—of this mysterious material.
Why Study Their Effects on Humans?
At first glance, studying how a black hole might affect the human body seems like an odd choice. However, Scherrer’s work builds on a logical scientific approach. If certain types of dark matter objects were common enough and dangerous enough, we might expect to see evidence of their effects over human history.
In earlier research, Scherrer and collaborators examined macroscopic dark matter objects, often referred to as MACROs. These hypothetical objects would be large, dense, and destructive if they passed through living tissue. Since no unexplained deaths or injuries consistent with such events have been recorded, scientists can use that absence to set limits on how common or massive these objects can be.
Scherrer realized similar calculations could be applied to primordial black holes. By determining the minimum mass required for a black hole to seriously injure or kill a human, researchers can narrow down which types of primordial black holes could plausibly exist as dark matter.
Two Main Ways a Black Hole Could Cause Damage
The study focuses on two specific physical effects that would occur if a primordial black hole passed through a human body at high speed.
The first effect involves supersonic shock waves. A primordial black hole moving through the body would almost certainly travel faster than the speed of sound in human tissue. When any object moves supersonically, it generates a shock wave—a powerful, cone-shaped disturbance that violently displaces material in its path. In the human body, this would mean the destruction of cells and tissues along the black hole’s trajectory, similar in some ways to the damage caused by a high-velocity bullet.
The second effect comes from tidal gravitational forces. Gravity weakens with distance, so the side of a cell closer to the black hole would experience a stronger pull than the side farther away. This difference creates stretching forces that can literally tear cells apart. The study highlights that brain cells are especially vulnerable to this kind of damage due to their delicate structure.
How Massive Does a Black Hole Need to Be to Be Dangerous?
One of the most important findings of the study is that size matters enormously. Not all primordial black holes would be dangerous to humans.
Scherrer calculated that a primordial black hole would need to have a mass comparable to that of a small asteroid or larger to cause serious injury or death. At this scale, the combined effects of shock waves and tidal forces would be strong enough to destroy critical tissues, potentially leading to fatal outcomes.
Smaller primordial black holes, on the other hand, could theoretically pass through the human body without causing noticeable harm. Their gravitational influence would simply be too weak to significantly disturb cells or tissues.
Interestingly, the study found that shock waves are generally more important than tidal forces when it comes to causing injury. This means the damage would be more like a localized, violent disruption rather than a slow stretching effect.
Should Anyone Actually Be Worried?
Despite the dramatic nature of the scenario, the answer is a clear no. Even if primordial black holes exist, their estimated number density in the universe is extraordinarily low. The chance of one passing through a human body during a lifetime—or even over the entire history of humanity—is essentially zero.
The study is not meant as a warning about a hidden cosmic danger. Instead, it uses the human body as a useful reference point to explore the physical consequences of extreme gravitational phenomena.
Why This Research Still Matters
While the idea of a black hole passing through a person grabs attention, the real value of the study lies in its contribution to fundamental physics. By establishing how massive a primordial black hole would need to be to cause harm, scientists can rule out certain mass ranges when considering primordial black holes as dark matter candidates.
If dark matter were made primarily of black holes massive enough to be deadly, we would expect to see evidence of such encounters. Since we do not, those possibilities become less likely. This helps researchers narrow their focus and refine models of what dark matter could be.
A Brief Look at Black Holes and Gravity
Black holes are regions of space where gravity is so strong that nothing—not even light—can escape once it crosses a boundary called the event horizon. Despite their fearsome reputation, black holes do not act like cosmic vacuum cleaners. Their gravitational pull depends on mass, just like any other object.
A small black hole passing through the Earth would not swallow the planet. In fact, unless it were extremely massive, its effects would be subtle and localized. This study highlights that principle clearly by showing how even something as extreme as a black hole can be harmless if it is small enough.
Science Fiction Meets Real Physics
The question explored in this research has appeared in science fiction for decades, often portrayed as instantly fatal or catastrophically destructive. What makes this study interesting is that it replaces speculation with careful calculations. The results show that reality is far more nuanced—and in many cases, far less dramatic—than fiction suggests.
Final Thoughts
This research offers a fascinating glimpse into how scientists explore the universe using creative but rigorous questions. By asking what would happen if a primordial black hole passed through the human body, physicists gain valuable insights into black holes, dark matter, and the limits of known physics.
While the scenario itself is incredibly unlikely, the knowledge gained from studying it helps move science one step closer to understanding the hidden structure of the cosmos.
Research Paper:
https://doi.org/10.1142/S0218271825410032
