Evidence of primordial black holes may be right here on Earth

Primordial black holes are enigmatic remnants from the universe’s infancy that hold the key to unlocking some of the biggest secrets in space.

These small yet powerful black holes, along with elusive dark matter, remain among the most perplexing mysteries in astrophysics. Though theorized for decades, they have yet to be directly observed.

Primordial black holes and dark matter

Conventionally, when we speak of black hole formation, we visualize a massive dying star collapsing onto itself.

Nevertheless, the early universe’s turbulent environment might have allowed many minuscule black holes to form, even before the birth of the first stars.

These black holes from the universe’s dawn, known as primordial black holes (PBHs), might form mysterious dark matter, which makes up 85% of the total mass in the universe.

In a game-changing approach, new research proposes that we scale our search both up and down to uncover these elusive entities.

This radical proposal suggests that signs of these primeval black holes could range from the enormously vast, such as empty planetary bodies, to the fantastically small, such as microscopic passageways in everyday materials on Earth.

Hollow primordial black holes

The researchers imagine a captivating scenario where a trapped primordial black hole inside a large celestial object, such as an asteroid or a planet, would consume its liquid core, leaving it hollow.

In a different scenario, a fleeting primordial black hole might leave behind straight tunnels large enough to be visible under a microscope, if it passes through a solid material, including substances present on Earth.

“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,” explained Dejan Stojkovic, PhD, professor of physics in the UB College of Arts and Sciences and the study’s co-author.

Taking a new approach to this cosmic detective work, the researchers emphasize that conventional methods have failed in the quest to discover primordial black holes, sparking the need for innovative thinking.

Clues in the universe

The experts proceeded to estimate how large a hollow celestial body could be without caving in on itself and the likelihood of a primordial black hole passing through an Earthly object.

The comforting conclusion was that such an occurrence would not be fatal to humans.

“Because of these long odds, we have focused on solid marks that have existed for thousands, millions or even billions of years,” said study co-author De-Chang Dai, PhD, of National Dong Hwa University and Case Western Reserve University.

Trapped primordial black holes

In the cosmos’s infancy, dense zones in the rapidly expanding universe could have collapsed and formed PBHs.

While PBHs would have much less mass than stellar black holes born from dying stars, they would still be intensely concentrated.

A PBH might become trapped within a planet, moon, or asteroid during or after its formation and absorb the liquid core of the object, leaving nothing but a hollow shell.

What happens next? The PBH might escape the object if it’s hit by an asteroid. If the object survives, it could be a hollow celestial body, detectable via telescopes.

By studying an object’s orbit, scientists can deduce its mass and density.

“If the object has a liquid central core, then a captured PBH can absorb the liquid core, whose density is higher than the density of the outer solid layer,” said Stojkovic.

Everyday items as black hole detectors

On a smaller scale, PBHs might pass through objects without a liquid core, leaving behind a straight tunnel. Everyday items could, therefore, act as black hole detectors.

The odds of a PBH passing through a human are minuscule. Even if it did, one probably wouldn’t notice.

Due to its small tension, a PBH would not tear apart human tissue. Furthermore, it moves so fast that it cannot release much of its kinetic energy during a collision.

Unresolved mysteries of the cosmos

Theoretical studies like these are vital as they challenge existing notions and open up new possibilities in the quest to decipher universal truths.

The unresolved mysteries of the cosmos, like dark matter, continue to baffle us, thereby motivating us to explore new frameworks beyond the century-old theories of quantum mechanics and general relativity.

“The smartest people on the planet have been working on these problems for 80 years and have not solved them yet,” stated Stojkovic. “We don’t need a straightforward extension of the existing models. We probably need a completely new framework altogether,” he added.

In the grand scheme of things, we’ve only just scratched the surface of the universe’s mysteries.

These potentially hollow celestial bodies and microscopic tunnels in everyday objects could be the breadcrumbs leading us to the holy grail of astrophysical discovery – primordial black holes.

The research was supported by the National Science Foundation and National Science and Technology Council (Taiwan).

The full study was published in the journal Physics of the Dark Universe.

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