Illustration showing small primordial black holes. However, in reality, these tiny black holes would struggle to form the accretion disks that make them visible in the image. Primordial black holes are ancient enigmas that originated in the universe’s early moments. Unlike regular black holes formed from collapsing stars, these emerged when ultra-dense regions of space crumpled under their own gravitational pull. These cosmic remnants come in various sizes, ranging from as heavy as a mountain compressed into a space no larger than an atom to those with less mass but significant gravitational influence. Scientists have long speculated that these peculiar entities could account for dark matter, the unseen substance constituting most of the universe’s mass. Despite the potential, direct observations of primordial black holes are lacking. New theories suggest that these elusive black holes might leave traces in more familiar settings like planets, asteroids, or even deep within Earth. Researchers Dejan Stojkovic, PhD, from the University at Buffalo and De-Chang Dai, PhD, from National Dong Hwa University put forth two concepts aiming to shed light on these ancient objects. Their study, published in Physics of the Dark Universe, delves into how primordial black holes might interact with other celestial bodies. One theory explores what happens when a primordial black hole becomes ensnared within a planet or asteroid with a liquid core, gradually corroding its interior over time. The resulting structure would be a hollow shell supported solely by its outer layer—an equilibrium that could hold if the body remains relatively small. According to their models, these peculiar celestial bodies wouldn’t exceed a tenth of Earth’s size. Detection of these hollow objects could involve studying their orbital characteristics, as insufficient density relative to size may indicate hollowness. The other concept examines solid objects lacking molten cores. If a primordial black hole cuts through one of these, it might leave a narrow tunnel in its wake, lasting for billions of years. The researchers propose monitoring large metal slabs or ancient rocks for the sudden appearance of these microscopic tunnels. While the chance of a primordial black hole passing through a boulder over its billion-year lifespan is extremely minute, the search cost is nominal compared to the potential discovery. The research also evaluates the stability of hollow planetoids formed by primordial black holes, discerning that objects larger than a tenth of Earth’s size would likely collapse. As a result, primordial black holes may exhibit a preference for interacting with smaller celestial bodies like minor planets and asteroids.
The journey of Primordial Black Holes (PBHs) through Earth or other materials would go unnoticed through direct experience. Their immense speed and density prevent them from releasing significant energy during such interactions. For instance, human tissue would not be torn apart by a PBH due to its rapid movement, which does not allow molecular structures to react in time.
Explaining this phenomenon, Stojkovic compares it to the difference between throwing a rock at a window, causing it to shatter, and shooting a bullet, which simply leaves a hole. This insight has implications beyond just detecting PBHs. If dark matter indeed consists of PBHs, their interactions could hold the key to unraveling one of the most enduring mysteries in physics.
Stojkovic stresses the importance of exploring unconventional approaches in such investigations, as existing models of physics have yet to crack the enigma of dark matter despite being over a century old. He advocates for a fresh framework rather than a mere extension of current models.
While the chances of directly observing a PBH are slim, the potential rewards are immense. These studies offer new avenues to delve into the unseen forces that shape our universe, highlighting the significance of innovative thinking in scientific breakthroughs.
(Credit for the image: Physics of the Dark Universe)
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