Unveiling the Shocking Truth: What Happens When a Tiny Black Hole Strikes?

In 1974, author Larry Niven imagined a chilling question: could a tiny black hole kill someone? While most would quickly say yes—given its intense gravity and destructive potential—the real scientific answer is more complex.

First off, it’s clear that large black holes can be deadly. But what about smaller ones? A black hole the size of a hydrogen atom is too tiny to even notice. This brings us to a vital question: at what size does a black hole become dangerous? That’s what a recent study on arXiv investigates.

The study focuses on primordial black holes, which are theoretical remnants from the early universe. These black holes could range from the mass of an atom to several times that of Earth. Though we haven’t spotted any primordial black holes directly, scientists know that certain sizes aren’t possible. For instance, any black hole smaller than about 10¹² kg would have evaporated by now due to Hawking radiation.

On the other end, black holes larger than 10²⁰ kg would bend light from stars in our Milky Way, and since we haven’t seen this effect, it’s likely they’re rare, if they exist at all.

Some theories propose that primordial black holes might be linked to dark matter. If that’s true, their masses would likely fall between 10¹³ and 10¹⁹ kg—roughly comparable to asteroids.

The study digs into two main effects that a primordial black hole might have: tidal forces and shock waves.

Tidal forces occur because gravity gets stronger as you get closer to a mass. If a small black hole passes near you, it could exert a force that differentiates across your body. Depending on where it passes, the outcome could vary. For instance, if it travels through your limb, you might feel slight damage, similar to a needle. But passing through your head would be far worse, potentially damaging sensitive brain cells with even a slight gravitational difference.

However, shock waves created by a black hole could pose an even greater risk. As it moves through your body, it generates waves that can physically harm tissues and transfer heat. For a shockwave equivalent to that of a 22-caliber bullet, a black hole would need a mass of around 1.4 x 10¹⁴ kg—definitely feasible within the primordial black hole range.

So, yes, a primordial black hole could indeed be lethal. But don’t worry! Even if such black holes exist, the chances of encountering one in your lifetime are astronomically low—less than one in 10 trillion.

This information highlights how the universe’s mysteries can spark both intrigue and fear. But while the science is fascinating, the likelihood of a tiny black hole causing harm remains a thrilling but distant thought.