Solution to the Mystery of Ultra-energetic cosmic rays
The cosmic microwave radiation has an effect ONLY upon charged particles. Hence, these unusually energetic cosmic ray particles must be neutral, in fact, they must be neutrons. This bypasses the limit completely.
Of course, the erroneous objection is made that the life expectancy of a neutron is only 18 minutes, so the neutrons must have decayed long ago. This is seen to be specious when the time dilation is taken into consideration. In the rest frame of such a neutron, it has only been flying for a fraction of a second, so it has not yet had time to decay.
David F Mayer