In the "extension" to the standard model of particle physics, formulated by Alan Kostelecky of Indiana University and colleagues, light could perform an entirely new trick. Its polarization might change as it shines through empty space, dependent on its frequency and the distance traveled. Overall, Kostelecky says, this is the best test of special relativity violations in any system to date, and improved imaging of distant galaxies will only sharpen it.
The standard model extension suggests places for high-energy particle-physics experiments to look as well. Measurements of the muon's magnetic moment at Brookhaven National Laboratory could spot an effect, as could experiments at the Fermi National Accelerator Laboratory on kaons and D mesons--two exotic, short-lived particles. Fermilab researchers are currently poring over data obtained from the Kaons at the Tevatron (KTeV) and the FOCUS (FOtoproduction of Charm: Upgraded Spectrometer) experiments on kaon and D-meson decay. A violation could show up as a variation in certain decay parameters on a 24-hour cycle, says Bruce Winstein of the University of Chicago. Winstein reports that researchers have gone through half the KTeV data so far, with another year and a half of number crunching to go, and no anomalies have cropped up yet. "It's probably not there at all," he says. But "it's important to look for things you don't expect to see."
An array of atomic clocks set to board the International Space Station within the decade or fly off into space on satellites will offer additional high-accuracy tests. Their measurements won't supersede those of Earth-based tests, says Kostelecky. Rather, he explains, because the clocks will fly and rotate faster, and in a different plane, than they would on Earth, they will give experimenters access to a wider spectrum of potential violations. "It's like a spacetime roller coaster ride," he remarks. --JR Minkel
