It sounds like something a phony theorist might posit to explain the Bermuda triangle, but scientists now believe that thousands of mini black holes pass through the Earth on a daily basis, according to Physorg.com.
The bad news is that these mini black holes really do seem capable of gobbling up Earth's matter as they pass through. The good news is that they are so small that the time it would take for a mini black hole to swallow the entire Earth would be many orders of magnitude longer than the age of the universe.
In other words, though they sound frightening, they actually pose a very minimal threat to the planet. They're fascinating nonetheless, and the physics of how they might work is just beginning to be understood.
Mini black holes are a bit different than the astrophysical black holes people are more familiar with. Unlike astrophysical black holes, which are formed by the collapse of massive stars, mini black holes are believed to have formed during the Big Bang (they are also sometimes called primordial black holes for this reason). They're also much smaller. An astrophysical black hole has a minimum mass of 1030 kg, but the mass of mini black holes range from the tiny Planck mass to trillions of kilograms or more.
Because scientists have yet to detect one in nature, mini black holes remain theoretical entities. But a paper recently published by researchers Aaron P. VanDevender and J. Pace VanDevender has posited a new theory about how detection might be possible.
The VanDevenders calculate that the properties of some mini black holes make them capable of gravitationally binding and capturing matter as they pass by. In other words, while some of the matter that encounters a mini black hole will get gobbled up, some matter may also get caught in the black hole's orbit. Though the mini black hole itself is undetectable, that orbiting matter might produce emissions that could be detected with current technology.
Furthermore, because mini black holes are strong candidates for what composes the universe's dark matter, the VanDevenders estimate that about 40 million kg of mini black holes could pass through the Earth every year (assuming that dark matter is evenly distributed throughout the galaxy). That means that there would be about 400 mini black holes with the right properties to gravitationally bind matter that could be detectable each year. Those aren't great odds for detection, but they are odds that are potentially manageable.
Of course, before they got too excited about their findings, the VanDevenders also wanted to calculate what kind of danger these mini black holes might pose to the Earth. Luckily, it turns out that mini black holes of any size would not absorb large amounts of matter very quickly. For instance, a black hole with a mass of 1 kg, it would take 1033 years to swallow the Earth. By comparison, the universe is about 13.7 x 109 years old, so the black holes would take longer than the age of the universe to consume the planet.