Stable neutral black holes produced by cosmic rays would pass through Earth without being gravitationally captured
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verdict confidence 0.85 · credence 0.95
This claim describes a point of rare agreement in the debate over hypothetical stable black holes from particle collisions. A cosmic ray striking a stationary nucleus in Earth's atmosphere delivers an enormous forward momentum, so any black hole produced would move at nearly the speed of light, vastly faster than Earth's escape velocity of about 11 kilometers per second. If such a hole were electrically neutral, it would interact with matter only through gravitationally driven accretion, whose cross-section is far too small for Earth's bulk to slow it appreciably. It would therefore traverse the planet and continue into space rather than being captured. Both sides of the safety debate accept this. Giddings and Mangano, authors of the principal safety analysis, computed the stopping power of Earth-density matter across a wide range of TeV-scale gravity scenarios and concluded that neutral cosmic-ray-produced black holes cannot be efficiently slowed in Earth or in other planets and ordinary stars; critics of the safety case cite the same result, since it is precisely why Earth's survival under eons of cosmic-ray bombardment does not by itself rule out danger from stable neutral black holes made in a collider, where head-on collisions can yield slow-moving products. That acknowledged gap is what motivated the alternative bound from the survival of white dwarfs and neutron stars, which are dense enough to stop even relativistic holes. A minor qualification: a vanishingly small fraction of production events could yield a hole slow enough to be trapped, but the rate is far too low to matter over Earth's lifetime, so the claim holds as a statement about the cosmic-ray population as a whole.
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