Physicists have demonstrated with unprecedented accuracy that the speed of light remains constant.
In 1887, a landmark physics experiment was carried out by American researchers Michelson and Morley. They attempted to detect Earth’s motion through space by comparing the speed of light along Earth’s path of travel with the speed of light measured at a right angle to that path.
Their inability to find any difference became one of the most influential null results in science. This outcome helped inspire Einstein to propose that the speed of light is constant, which ultimately led to his development of special relativity.
According to this theory, the laws of physics remain identical for all observers, regardless of their relative motion — a principle known as Lorentz invariance.
As physics advanced, quantum theory emerged and placed Lorentz invariance at the foundation of its major frameworks, especially quantum field theory and the Standard Model of Particle Physics. The Standard Model has become the most rigorously tested scientific theory to date and has been confirmed with extraordinary accuracy.
So why doubt Lorentz invariance after 115 years of uninterrupted success?
Einstein’s Other Theory and a Deep Incompatibility
The reasoning once again leads back to Albert Einstein. This time, to his theory of general relativity, which explains gravity as a distortion of spacetime geometry. General relativity has also passed many stringent tests, proving remarkably accurate in a wide range of situations, from regions of very weak gravity to environments with extremely strong gravitational fields.
The problem lies in the fundamental incompatibility between the probability wave functions of quantum field theory with their movement through curved geometry, and at the same time, their modifications of spacetime curvature. Most attempts to reconcile the two theories into a common framework of quantum gravity have resulted in the need to break Lorentz invariance, albeit only slightly.
Thus, Michelson and Morley’s quest continues today, aided by modern laboratory experiments carried out with vastly improved technology.
Astrophysical Tests at Extreme Distances
One prediction of several Lorentz-Invariance-Violating quantum gravity theories is a dependence of the speed of light on photon energy. Any deviation from a constant speed of light must be extremely small to remain compatible with current constraints, but may become detectable at the very highest photon energies, known as very-high-energy gamma rays.
A team of researchers led by former UAB student Mercè Guerrero and current IEEC PhD student at the UAB Anna Campoy-Ordaz, with the participation of Robertus Potting from the University of Algarve and Markus Gaug, lecturer at the Department of Physics of the UAB and also assigned to the IEEC, has now tested Lorentz invariance to unprecedented precision with the help of astrophysics.
This is possible because tiny differences in the group velocity of photons may accumulate into measurable arrival-time delays on Earth if the photons were emitted simultaneously from a source located at a very large distance.
The team combined a collection of existing bounds from astrophysical measurements of very-high-energy gamma rays using a new statistical method to test a series of Lorentz-invariance-violating parameters, currently favored by theoreticians, of the Standard Model Extension (SME).
The researchers hoped to prove Einstein wrong but, like so many others before them, did not succeed. Nevertheless, the new bounds improve upon previous limits by an order of magnitude.
In the meantime, the quest to experimentally test the predictions of quantum gravity theories continues, with next-generation instruments just around the corner—such as the Cherenkov Telescope Array Observatory—designed to greatly improve performance on the detection of very-high-energy gamma rays from distant sources.
Reference: “Bounding anisotropic Lorentz invariance violation from measurements of the effective energy scale of quantum gravity” by Merce Guerrero, Anna Campoy-Ordaz, Robertus Potting and Markus Gaug, 4 November 2025, Physical Review D.
DOI: 10.1103/k3xg-wkrc
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5 Comments
Conflicts between quantum theory and general relativity have inspired the possibility of slight violations detectable only at extreme energies or cosmic distances.
WHY? WHY? WHY?
Contemporary physics are sure they are right when working with a system they believe is wrong – they are gonna have a hard time getting out of their rut. The key difference between TVT and traditional physics (e.g., Newtonian mechanics, relativity, quantum mechanics) lies in its perspective on describing the universe. TVT emphasizes the ideal fluid properties and topological structure of space, rather than focusing solely on the direct interactions of particles and forces. This perspective offers a new paradigm for understanding the structure of the universe. Its core predictions (e.g., cosmic-scale vortex networks) have been confirmed across multiple disciplines. For example:
Topological structures, such as vortices, are prevalent in nature and science across a wide range of length scales, ranging from macroscopic cosmic strings (1), mesoscale liquid crystals (2, 3) and ferromagnets (4), nanoscale ferroelectrics and superconductor/superfluid Bose-Einstein condensate states (5, 6), down to the atomic nucleus (7).
——Excerpted from https://www.science.org/doi/10.1126/sciadv.adu6223.
Complexity does not necessarily mean that there is no logical and architectural framework to follow. Mathematics is the language and tool that reveals the motion of spacetime, rather than the motion itself. Although the physical form of spacetime vortices is extremely simple, their interaction patterns are highly complex, and we must develop more and richer mathematical languages to describe and understand them.
The development of the Topological Vortex Theory (TVT) reflects a progression from concrete physical phenomena to abstract mathematical modeling and, ultimately, to interdisciplinary unification. Its core innovation lies in forging the continuous spacetime geometry of general relativity with the discrete interactions of quantum field theory within the same topological dynamical system.
——Excerpted from https://scitechdaily.com/microscope-spacecrafts-most-precise-test-of-key-component-of-the-theory-of-general-relativity/#comment-909171.
Besides measuring the speed of light in seconds, a fairly rattle-ee-trap notion, it also specifies the flaws in human numbering – which strangely reifies numbers. All so we don’t have to imagine a new system of measure.
If the physical world resolves with light and our numbers have to be altered to account it, perhaps thinking what is assumed to be constant, should be zero and relationships account from it.
But of course, numbers are the animal-brain, earth bound tether we’re likely going to stay with.
Mathematics is the language and tool that reveals the motion of spacetime, rather than the motion itself. Although the physical form of spacetime vortices is extremely simple, their interaction patterns are highly complex, and we must develop more and richer mathematical languages to describe and understand them. The development of the Topological Vortex Theory (TVT) reflects a progression from concrete physical phenomena to abstract mathematical modeling and, ultimately, to interdisciplinary unification. Its core innovation lies in forging the continuous spacetime geometry of general relativity with the discrete interactions of quantum field theory within the same topological dynamical system.
——Excerpted from https://scitechdaily.com/microscope-spacecrafts-most-precise-test-of-key-component-of-the-theory-of-general-relativity/#comment-909171.
Mathematics is the language and tool that reveals the motion of spacetime, rather than the motion itself. Although the physical form of spacetime vortices is extremely simple, their interaction patterns are highly complex, and we must develop more and richer mathematical languages to describe and understand them. The development of the Topological Vortex Theory (TVT) reflects a progression from concrete physical phenomena to abstract mathematical modeling and, ultimately, to interdisciplinary unification. Its core innovation lies in forging the continuous spacetime geometry of general relativity with the discrete interactions of quantum field theory within the same topological dynamical system.
——Excerpted from https://scitechdaily.com/microscope-spacecrafts-most-precise-test-of-key-component-of-the-theory-of-general-relativity/#comment-909171.