If some versions of string theory are correct, then high-energy cosmic rays could create black holes when they collide with molecules in the Earth's atmosphere.
Theodore Tomaras, a physicist at the University of Crete in Heraklion, Greece, and his Russian collaborators hypothesize that these miniature black holes could explain certain anomalous observations made by cosmic-ray detectors in the Bolivian Andes and on a mountain in Tajikistan.
In 2003 an international team of researches from Russia and Japan found out that the mysterious observation from mountain-top cosmic ray experiments can be explained with conventional physics.
The signal observed in the lower detector was similar to an ordinary interaction occurred at low altitude above the chamber, thus providing a natural solution: passing of a cascade of particles through a gap between the upper blocks.
So-called "exotic signal" observed so far in cosmic ray experiments using a traditional X-ray emulsion chamber detector can be consistently explained within the framework of standard physics.