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The formation of black holes is often associated with massive stars collapsing under their own gravity. However, new research suggests the chaotic conditions of the early universe may have enabled the creation of primordial black holes (PBHs) long before stars existed. These PBHs, theorized to account for elusive dark matter, remain undetected despite decades of speculation.
A study co-led 
by Clarence Oxford
Los Angeles CA (SPX) Dec 03, 2024
The formation of black holes is often associated with massive stars collapsing under their own gravity. However, new research suggests the chaotic conditions of the early universe may have enabled the creation of primordial black holes (PBHs) long before stars existed. These PBHs, theorized to account for elusive dark matter, remain undetected despite decades of speculation.
A study co-led by the University at Buffalo proposes novel methods to identify PBHs. Researchers suggest their signatures could be found in massive hollow celestial bodies or microscopic tunnels in materials on Earth, such as rocks, metals, or glass.
The findings, published in Physics of the Dark Universe and available online, hypothesize that a PBH could hollow out the core of a planet or leave tunnels in solid materials as it passes through. "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 Dejan Stojkovic, PhD, professor of physics at UB.
The study explored the mechanics of PBHs consuming planetary cores and examined whether the remaining hollow structures could withstand their own weight. Researchers also calculated the probability of PBHs passing through objects on Earth.
Hollow planetoids and the search for small PBHs
PBHs, formed during the rapid expansion after the Big Bang, would be far less massive than stellar black holes but immensely dense, compressing the mass of a mountain into the size of an atom. Theoretical models suggest a PBH trapped in a planet with a liquid core could absorb the core and escape, leaving behind a hollow shell.These hollow objects, no larger than one-tenth of Earth's radius, could be identified by their unusually low density. "If the object's density is too low for its size, that's a good indication it's hollow," said Stojkovic. Such objects could potentially be detected through telescope observations of their orbits.
PBH tunnels in everyday materials
For objects without liquid cores, PBHs might create straight microscopic tunnels. A PBH with a mass of 10 grams, for instance, could leave a tunnel 0.1 microns wide. These tunnels, preserved in ancient materials, could provide evidence of PBHs."You'd have better odds searching for existing tunnels in very old materials, from buildings that are hundreds of years old to rocks that are billions of years old," explained co-author De-Chang Dai, PhD, from National Dong Hwa University and Case Western Reserve University. However, the probability of a PBH passing through a billion-year-old rock was calculated to be a mere 0.000001.
Despite these odds, Stojkovic emphasized the minimal cost of such searches compared to their potential scientific impact. "We have to think outside of the box because what has been done to find primordial black holes previously hasn't worked," he said.
New frameworks for cosmic mysteries
The study underscores the need for innovative approaches to tackle unresolved scientific problems, such as the nature of dark matter. "The smartest people on the planet have been working on these problems for 80 years and have not solved them yet," Stojkovic said. He advocates for fresh theoretical frameworks to advance the field.As scientists continue to seek evidence of PBHs, this research highlights the importance of exploring unconventional avenues, from studying planetary anomalies to investigating the oldest materials on Earth.
Research Report:Searching for small primordial black holes in planets, asteroids and here on Earth
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