Scientists tried to break Einstein’s speed of light rule

Science News from research organizations Scientists tried to break Einstein’s speed of light rule Einstein’s speed-of-light rule just survived its toughest cosmic stress test yet. Date: January 8, 2026 Source: Universitat Autonoma de Barcelona Summary: Einstein’s claim that the speed of light is constant has survived more than a century of scrutiny—but scientists are still daring to test it. Some theories of quantum gravity suggest light might behave slightly differently at extreme energies. By tracking ultra-powerful gamma rays from distant cosmic sources, researchers searched for tiny timing differences that could reveal new physics. They found none, but their results tighten the limits by a huge margin. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY More than a century after a famous “failed” experiment helped inspire Einstein’s theory of relativity, scientists are still pushing its limits. Credit: AI/ScienceDaily.com In 1887, a landmark experiment reshaped our understanding of the universe. American physicists Albert Michelson and Edward Morley attempted to detect Earth's motion through space by comparing how fast light traveled along different directions. Their experiment found no difference at all. This unexpected null result became one of the most influential outcomes in scientific history. It led Albert Einstein to propose that the speed of light is constant, a cornerstone idea behind his theory of special relativity. Special relativity rests on the principle that the laws of physics remain the same for all observers, regardless of how they are moving relative to one another. This idea is known as Lorentz invariance. Over time, Lorentz invariance became a foundational assumption in modern physics, especially within quantum theory. Why Question a Principle That Works So Well Quantum theory evolved with Lorentz invariance at its core. This is especially true for quantum field theory and the Standard Model of Particle Physics, which is the most thoroughly tested scientific theory ever created and has passed experimental checks with extraordinary precision. Given this track record, it may seem strange to question Lorentz invariance after more than a century of success. The motivation comes from another of Einstein's breakthroughs. His theory of general relativity explains gravity as a bending of spacetime itself. Like special relativity, it has been confirmed with remarkable accuracy across many environments, from weak gravitational fields to extreme cosmic conditions.

The Clash Between Quantum Theory and Gravity Despite their individual successes, quantum theory and general relativity do not fit together smoothly. Quantum physics describes reality using probability wave functions, while general relativity describes how matter and energy shape the geometry of spacetime. These two approaches struggle to coexist when particles move through curved spacetime while also influencing that curvature. Efforts to combine the two theories into a single framework known as quantum gravity often run into the same obstacle. Many proposed solutions require small violations of Lorentz invariance. These violations would be extremely subtle but could offer clues about new physics beyond current theories.

Testing Einstein With Light From the Cosmos One prediction shared by several Lorentz-invariance-violating quantum gravity models is that the speed of light may depend slightly on a photon's energy. Any such effect would have to be tiny to match existing experimental limits. However, it could become detectable at the highest photon energies, specifically in very-high-energy gamma rays. A research team led by former UAB student Mercè Guerrero and current IEEC PhD student at the UAB Anna Campoy-Ordaz set out to test this idea using astrophysical observations.

The team also included Robertus Potting from the University of Algarve and Markus Gaug, a lecturer in the Department of Physics at the UAB who is also affiliated with the IEEC. Their approach relies on the vast distances light travels across the universe. If photons of different energies are emitted at the same time from a distant source, even minuscule differences in their speeds could build up into measurable delays by the time they reach Earth. Sharper Limits on New Physics Using a new statistical technique, the researchers combined existing measurements of very-high-energy gamma rays to examine several Lorentz-invariance-violating parameters favored by theorists within the Standard Model Extension (SME). The goal was ambitious. They hoped to find evidence that Einstein's assumptions might break down under extreme conditions. Once again, Einstein's predictions held firm. The study did not detect any violation of Lorentz invariance. Even so, the results are significant. The new analysis improves previous limits by an order of magnitude, sharply narrowing where new physics could be hiding. The search is far from over. Next-generation observatories such as the Cherenkov Telescope Array Observatory are being designed to detect very-high-energy gamma rays with far greater sensitivity. These instruments will allow scientists to continue testing the deepest foundations of physics and to keep pushing Einstein's ideas to their limits. RELATED TOPICS Space & Time Space Exploration Space Telescopes Black Holes NASA Matter & Energy Physics Albert Einstein Quantum Physics Materials Science RELATED TERMS Quantum computer Introduction to quantum mechanics Physics Quantum entanglement Dark energy Scientific method Quantum number Quantum dot Story Source: Materials provided by Universitat Autonoma de Barcelona. Note: Content may be edited for style and length. Journal Reference: Merce Guerrero, Anna Campoy-Ordaz, Robertus Potting, Markus Gaug. Bounding anisotropic Lorentz invariance violation from measurements of the effective energy scale of quantum gravity. Physical Review D, 2025; 112 (10) DOI: 10.1103/k3xg-wkrc Cite This Page: MLA APA Chicago Universitat Autonoma de Barcelona. "Scientists tried to break Einstein’s speed of light rule." ScienceDaily. ScienceDaily, 8 January 2026. . Universitat Autonoma de Barcelona. (2026, January 8). Scientists tried to break Einstein’s speed of light rule. ScienceDaily. Retrieved January 8, 2026 from www.sciencedaily.com/releases/2026/01/260107225544.htm Universitat Autonoma de Barcelona. "Scientists tried to break Einstein’s speed of light rule." ScienceDaily. www.sciencedaily.com/releases/2026/01/260107225544.htm (accessed January 8, 2026). Explore More from ScienceDaily RELATED STORIES The Squid Galaxy's Neutrino Game Just Leveled Up May 8, 2025 — In space, energetic neutrinos are usually paired with energetic gamma rays. Galaxy NGC 1068, however, emits strong neutrinos and weak gamma rays, which presents a puzzle for scientists to solve. A ... Einstein's Equations Collide With the Mysteries of the Universe Nov. 11, 2024 — Why is the expansion of our Universe accelerating? Twenty-five years after its discovery, this phenomenon remains one of the greatest scientific mysteries. Solving it involves testing the fundamental ...

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