Tiny black holes from cosmic collisions express
Cosmic rays, particles with monstrous energy, race through the darkness of intergalactic space. In a head-on collision, their force can crush into a black hole the size of an atom. It’s not dangerous: like a drop on a hot skillet, such a hole instantly evaporates, flying apart into a stream of neutrinos — ghostly particles that even lead cannot stop. This process was described by Stephen Hawking.
Astronomers have already analyzed neutrinos from the galaxy TXS 0506+056. It turned out: if black holes are born, it’s only at energies where the very fabric of spacetime behaves strangely. Future telescopes will go further. The intrigue in this detective story: when evaporating, such holes emit an equal number of neutrinos of all flavors — an anomaly that can be recognized amid the noise. And if extra dimensions exist, some neutrinos might dive in and return, producing mysterious flashes in the void. That would be a hint at hidden realities where gravitational waves wander.
Original abstract
as written by the authors arXiv:2510.11879
Cosmic ray collisions at high center of mass energy could enable graviton and black hole production as expected in theories of low-scale quantum gravity, such as extra-dimensions, many species, or some versions of string theory. Here we propose three novel phenomenological tests of these theories. We first consider the collision of cosmic rays with ambient protons, electrons and photons in Active Galactic Nuclei (AGN), finding that high-energy neutrino data from the blazar TXS 0506+056 places a constraint on the fundamental scale of gravity of $$M_f \gtrsim 0.3$$ TeV, and future high-energy neutrino data could raise this bound to $$M_f \gtrsim 200$$ TeV. We then point out that collisions of pairs of cosmic rays could occur at a sizable rate in AGN where the accelerated cosmic rays are not collimated, or on supermassive black hole binaries. This consideration could potentially let us test unprecedented large fundamental scales of $$M_f \gtrsim 2$$ PeV. We further compute the corresponding thermal neutrino emission arising from the Hawking evaporation of black holes produced in cosmic ray collisions, finding a spectrum that clearly differs from that expected in meson decays. Finally, we speculate with an scenario which would produce high-energy neutrino and gamma-ray emission from regions in the sky where no multi-wavelength counterparts would be expected, via graviton propagation from a different brane, which then decays in our Universe.
A micro black hole with the mass of a mosquito would vanish in $10^{-27}$ seconds, releasing the energy of a ton of TNT, but safely: almost all of it would go into neutrinos, which would fly right through you unnoticed.
The idea of particles leaking into other dimensions is reminiscent of the series 'Fringe,' where parallel universes exchanged inexplicable signals.