Extremely potent cosmic rays—high-speed atomic fragments that pack asmuch energy as a bullet—reach Earth from quasars billions oflight-years away. That perplexes cosmologists, whose calculationssuggest the rays should collide with the bits of microwave radiationthat fill the universe and be destroyed long before they arrive. Someresearchers consider the conundrum so strange that it can be solvedonly by trashing Einstein's theory of relativity. But Richard Lieu, anastrophysicist at the University of Alabama in Huntsville, says thetheory is fine, once you understand how to combine it with quantumtheory.
Lieu invokes the example of clocks and moving trains to explain theflaw in current thinking. According to Einstein, a clock on a movingtrain appears to be ticking more slowly than normal from theperspective of a stationary observer on the platform. Furthermore, anyerror in timekeeping measured by the moving clock would be magnified;at 99.5 percent the speed of light, a clock running a second behindwould appear 10 seconds slower than it actually is to the unmovingobserver. In this interpretation, the cosmic rays are moving so swiftlythat quantum jitters—the smallest possible units of time—appear toexpand into large chunks of temporal uncertainty that obscure the exactspeed or energy of the cosmic rays.
If it is impossible to measure the speed of the cosmic rays,Lieu argues, we cannot predict how they will interact with themicrowave radiation. In fact, that fundamental uncertainty could offeran escape so they do not interact at all. "If so, then the cosmic rayscan coast through the microwave background," he says. The persistenceof the cosmic rays is not an attack on Einstein, therefore, but anothertribute to the subtlety of his ideas.