To find black holes we usually have to look thousands of light-years away. But a new study suggests we could find evidence of them right here on Earth, as tiny tunnels they’ve carved out in rocks or old buildings.
Unlike regular black holes, which are born from the collapse of massive stars, primordial black holes are hypothetical objects created soon after the Big Bang. Models suggest that they’d be tiny – cramming the mass of an asteroid into the space of an atom – and should still be whizzing around the cosmos to this day. Invisible and only interacting with matter via gravity, they’re a candidate for dark matter.
For the new study, physicists at the University at Buffalo and National Dong Hwa University have calculated what a tiny, fast-moving black hole would do when it encounters a solid object, like a planet. They found that a primordial black hole with a mass of 1019 kg would bore right through a planet, leaving a tunnel just 100 nanometers wide.
That’s roughly the mass of 324 Bamberga, the 16th-largest asteroid in the main belt. It’s about 22 times bigger than the rock that killed the dinosaurs, but it wouldn’t cause that level of destruction – the black hole would be moving much faster and packs its mass into an area far smaller, so it hits like a bullet not a bomb.
“If a projectile is moving through a medium faster than the speed of sound, the medium’s molecular structure doesn't have time to respond,” said Dejan Stojkovic, co-author of the study. “Throw a rock through a window, it's likely going to shatter. Shoot a window with a gun, it’s likely to just leave a hole.”
And these holes could be just the smoking gun (pun intended) we need. Though tiny, these tunnels are big enough to be seen with a microscope, meaning we could scan rocks that are billions of years old, or even buildings a few hundred years old, for signs of perfectly straight, microscopic wormholes through solid materials.
Unfortunately, there’s a catch of course: the odds are fairly slim. The team calculated that the probability of a primordial black hole passing through any given billion-year-old boulder would be just 0.000001%. Still, it’s a simple enough test that it might be worth running anyway.
“The chances of finding these signatures are small, but searching for them would not require much resources and the potential payoff, the first evidence of a primordial black hole, would be immense,” said Stojkovic.
But what if something isn’t solid all the way through? The team also modeled what a primordial black hole would do to a planet with a liquid core. In those cases, it’s likely to get stuck in the center, where it would slurp up the liquid materials and hollow out the planet.
The black hole could linger at the center of planets like this, or even stars according to previous research, and we might never know. But an impact with another object could jostle the black hole loose, leaving behind a hollow shell.
If the planet was less than one-10th the size of Earth, and had just the right composition, the researchers calculated that the hollow shell could support itself. Any bigger than that, however, and it would collapse.
The team says this is another potential way to hunt for evidence of primordial black holes. If a minor planet or small moon is detected with a far lower density than should be expected, that could indicate it’s hollow.
It might be a long shot, but it’s at least a unique way to go about looking for potential signs of primordial black holes. It’s not too surprising that this is from the same researcher who outlined where and how we might be able to detect wormholes in space.
The research was published in the journal Physics of the Dark Universe.
Source: University at Buffalo
