Does a Cosmic Ray Gap Open the Door on New Physics?

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Science  22 Dec 1995:
Vol. 270, Issue 5244, pp. 1923-1924
DOI: 10.1126/science.270.5244.1923a


Physicists have long wondered what could hurl cosmic rays through space with energies millions of times higher than terrestrial particle accelerators can achieve. Now a clue may be emerging, from a gap that has appeared in the cosmic ray spectrum just below the highest energy events ever detected. In a separate report in this issue (p. 1977), a group of physicists propose that the gap marks the upper energy limit of an astronomical source of cosmic rays, such as violent processes in other galaxies. Cosmic rays above the gap, say these physicists, may be the offspring of a more exotic source: primordial defects in the fabric of spacetime.