Presence On Earth of Non-Identical Particles
  We speculate on some novel consequences possibly associated with a change of elementary particle constants with time. These concern the question as to whether particles reaching the earth from distant parts of the universe reflect their properties at their point of origin and so can be different from local particles. Assuming that such particles would be present in very high energy cosmic rays, we estimate their density on the earth by two different methods, finding on this hypothesis a density of roughly $10^{-28}-10^{-29}$. Various possibilities for detection are discussed, including the formation of unusual nuclear isotopes. 
L. Stodolsky