How tiny black holes might interact with the Sun, Earth, and living organisms

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Dead Planets Society is a podcast that explores imaginative scenarios involving cosmic phenomena—such as splitting the Moon or triggering a gravitational wave catastrophe—and examines them through the lens of physics. You can listen on Apple Podcasts, Spotify, or through our podcast page.

In the early universe, there might have been black holes smaller than atoms but with masses comparable to mountains. These hypothetical primordial black holes could address several significant questions in cosmology and provide intriguing topics for the Dead Planets Society to discuss.

In this episode, hosts Chelsea Whyte and Leah Crane are joined by black hole expert Allison Kirkpatrick from the University of Kansas. They investigate the effects of placing a primordial black hole inside various objects, including the Sun, Earth, and the human body. The results are more complex than one might expect.

For very small black holes, such as those smaller than atoms, their impact on stars or planets would be minimal—they might pass through or settle at the center, depending on their mass. However, if a black hole were slightly larger—say, with the mass of Earth but the size of a grape—it could have more dramatic effects. Such a black hole could significantly shorten the Sun’s lifespan or disrupt a planet from within.

On the positive side, black holes of this size might be used to influence cosmic structures through their gravitational effects. For instance, a tiny black hole near the Moon’s surface could potentially halt its gradual drift away from Earth.

For humans, staying several meters away from a small black hole would generally be safe, according to Kirkpatrick. However, as you get closer, its gravity could start to affect you, and getting too close could result in severe consequences. If a black hole were somehow placed inside the human body, the effects would be catastrophic.

Kirkpatrick emphasizes that placing a primordial black hole inside a human being is extremely dangerous and should not be attempted under any circumstances due to the severe harm it would cause. The American Medical Association has not provided any official comment on the potential effects of a black hole on the human body.