The paper explores the theoretical biological effects of a primordial black hole (PBH) with a tiny mass (around 10^15 grams) passing through a human body. While such an event is improbable, the authors calculate the gravitational forces exerted by the PBH as it traverses different tissues. They find that these forces, though exceeding Earth's gravity by many orders of magnitude for a brief period, are unlikely to cause significant macroscopic damage due to the extremely short interaction time. However, the study suggests potential disruptions at the cellular level, specifically stretching of DNA molecules, which might lead to mutations or other biological consequences. The overall conclusion is that while mechanically disruptive effects are likely minimal, biological impacts from the induced strains warrant further investigation.
The preprint titled "Gravitational Effects of a Small Primordial Black Hole Passing Through a Human Body" explores the hypothetical scenario of a primordial black hole (PBH), specifically one with a minuscule mass comparable to a small asteroid (around 10^17 kg), traversing a human body. The authors meticulously analyze the potential biological consequences of such an encounter, focusing predominantly on the gravitational influence of this relatively low-mass black hole.
Contrary to popular depictions of black holes violently consuming all matter in their vicinity, the study emphasizes that the primary interaction with the human body would not be accretion, or the sucking in of matter. Instead, the dominant effect would stem from the tidal forces exerted by the PBH's gravitational field. These tidal forces, arising from the difference in gravitational pull across the dimensions of the human body, would be the primary mechanism of interaction.
The paper details a comprehensive calculation of these tidal forces, considering the varying densities and distributions of tissues within the human body. It meticulously considers the relative motion between the PBH and the body, assuming a range of plausible velocities for such an object. Furthermore, the analysis investigates the temporal evolution of these forces as the PBH approaches, passes through, and recedes from the body.
The authors quantify the magnitude of these tidal forces and compare them to the known mechanical strengths and tolerances of various biological tissues. They discuss the potential for cellular deformation, tissue disruption, and even potential nerve stimulation that could arise from these forces. However, the analysis concludes that, for a PBH of the specified mass and at realistic encounter velocities, the induced tidal forces are likely to be significantly smaller than the forces experienced by the human body during routine activities or even minor impacts. Consequently, the paper suggests that, while detectable in principle, the biological effects of such a transit would likely be negligible and potentially even imperceptible.
The authors underscore the importance of distinguishing these subtle gravitational effects from the more dramatic consequences associated with larger black holes, where accretion and energy release would be the dominant processes. This nuanced perspective provides a valuable contribution to the understanding of the potential interaction between hypothetical primordial black holes and biological systems, highlighting that not all black hole encounters would necessarily be catastrophic.
Summary of Comments ( 59 )
https://news.ycombinator.com/item?id=43102425
Several Hacker News commenters expressed skepticism about the practicality of detecting the effects described in the paper, especially given the rarity of primordial black holes and the subtle nature of the gravitational influence. Some questioned the assumptions made in the calculations, like the density and velocity of the black holes. Others pointed out that other everyday gravitational forces, like those from nearby objects or even the moon, would likely dwarf the effect of a tiny black hole passing through the body. A few commenters engaged in humorous speculation about potential (and unlikely) biological impacts, while others debated the overall significance of the research. Several users also discussed the plausibility of primordial black holes as dark matter candidates.
The Hacker News post titled "Gravitational Effects of Small Primordial Black Hole Passing Through Human Body" (https://news.ycombinator.com/item?id=43102425) has a modest number of comments, sparking a discussion around the plausibility and effects of such an event.
Several commenters focus on the extremely low probability of this event actually occurring. One commenter points out the vastness of space and the tiny size of a human, making a collision incredibly unlikely. Another echoes this sentiment, emphasizing the rarity of primordial black holes themselves, combined with the low chances of intersection with a human.
The discussion then delves into the potential consequences if such an improbable event were to occur. One commenter, referencing the paper's calculations, highlights that a small primordial black hole (PBH) passing through the body would likely cause negligible damage, contrary to what might be assumed. They explain that the gravitational force exerted would be incredibly localized and brief, leading to a minor displacement of tissues rather than any catastrophic damage. This comment sparks a small thread discussing the inverse square law and how the rapid transit of the PBH minimizes its overall effect.
Another commenter questions the assumption of a straight trajectory through the body. They propose that the PBH might interact with the Earth's gravitational field, potentially leading to a more complex path, like an orbit. This raises further questions about the duration and overall effect of the PBH's interaction with a human in such a scenario, which goes unanswered in the thread.
One commenter injects a touch of humor by wondering if such a transit would be detectable as a sudden, unexplained weight loss.
Finally, a commenter circles back to the probability aspect, highlighting the greater risks posed by everyday occurrences compared to the astronomically low chances of a PBH encounter. They mention that worrying about such an event is akin to worrying about being struck by lightning while simultaneously winning the lottery – a colorful analogy emphasizing the extreme improbability.
In essence, the comments section explores the implications of the paper's findings with a mix of scientific curiosity and healthy skepticism, acknowledging the extremely low probability of the event while exploring the theoretical consequences. The discussion remains grounded in the paper's focus on small PBHs and their relatively minor impact on the human body, should such an improbable encounter occur.