Guerrero Review Tightens Light-Speed Variation Limits by 10-Fold Across 65 Measurements
Updated
Updated · The Brighter Side of News · May 25
Guerrero Review Tightens Light-Speed Variation Limits by 10-Fold Across 65 Measurements
1 articles · Updated · The Brighter Side of News · May 25
A new Physical Review D review combined 65 astrophysical measurements to constrain 25 Lorentz-violation coefficients, finding no evidence that photons of different energies travel at different speeds.
The team recast pulsar, active-galaxy and gamma-ray-burst timing data into the Standard Model Extension, added instrumental and systematic uncertainties, and standardized results as two-sided 95% confidence limits.
GRB 221009A delivered the strongest single-event bound—more than 10 times tighter than earlier constraints—but the authors stressed that only many sources across the sky can separate source effects from new physics.
Across the coefficient set, limits improved by roughly an order of magnitude, narrowing where quantum-gravity-related departures from Lorentz invariance could still hide.
The review says roughly a dozen more strong measurements could sharpen sensitivity to some coefficients by another 5 orders of magnitude, raising the stakes for future data from the Cherenkov Telescope Array Observatory.
We test cosmic laws with light, gravity, and neutrinos. Which will be first to reveal physics beyond Einstein?
Einstein's theory holds up again, but what happens to physics if we finally find a crack in its foundation?
If the speed of light is constant, why do other cosmic particles hint at traveling at different speeds?
2025 Breakthrough: Tenfold Tighter Limits on Lorentz Invariance Violation from Astrophysical Gamma-Ray Observations
Overview
In 2025, the Mercè Guerrero review published in Physical Review D set a new standard for testing Lorentz invariance, the principle that the speed of light is constant for all observers. Motivated by quantum gravity theories that suggest the speed of light might vary with photon energy, researchers analyzed photons from distant cosmic sources, especially very-high-energy gamma rays. By studying the arrival times of these photons over vast distances, the review found no evidence of variation in light speed, improving previous limits on Lorentz invariance violation. This work significantly narrows the possibilities for new physics beyond Einstein’s theory.