There’s an adage coined by [Ian Betteridge] that any headline ending in a question mark can be answered by the word “No”. However, Lorentz invariance – the theory that the same rules of physics apply in the same way in all frames of reference, and an essential component of special relativity – has been questioned for some time by researchers trying to unify general relativity and quantum field theory into a theory of quantum gravity. Many theories of quantum gravity break Lorentz invariance by giving photons with different energy levels very slightly different speeds of light – a prediction which now looks less likely since researchers recently analyzed gamma ray data from pulsed astronomical sources, and found no evidence of speed variation (open-access paper).
The researchers specifically looked for the invariance violations predicted by the Standard-Model Extension (SME), an effective field theory that unifies special relativity with the Standard Model. The variations in light speed which it predicts are too small to measure directly, so instead, the researchers analyzed gamma ray flare data collected from pulsars, active galactic nuclei, and gamma-ray bursts (only sources that emitted gamma rays in simultaneous pulses could be used). Over such great distances as these photons had traveled, even slight differences in speed between photons with different energy levels should have added up to a detectable delay between photons, but none was found.
This work doesn’t disprove the SME, but it does place stricter bounds on the Lorentz invariance violations it allows, about one and a half orders of magnitude stricter than those previously found. This study also provides a method for new experimental data to be more easily integrated into the SME. Fair warning to anyone reading the paper: the authors call their work “straightforward,” from which we can only conclude that the word takes on a new meaning after a few years studying mathematics.
If you want to catch up on relativity and Lorentz invariance, check out this quick refresher, or this somewhat mind-bending explanation. For an amateur, it’s easier to prove general relativity than special relativity.
Top image: Crab Pulsar, one of the gamma ray sources analysed. (Credit: J. Hester et al., NASA/HST/ASU/J)
Even worse news for sci-fi fans
https://hackaday.com/2026/01/15/is-the-theory-of-special-relativity-wrong/
If only the article provided a convenient link to the article, otherwise the article is very difficult to find.
TBH the null vector kind of is like this.
For a moment I thought it was time travel, then I was horrified to realize (yet again) that we indeed are in year 2026!
“Many theories of quantum gravity break Lorentz invariance by giving photons with different energy levels very slightly different speeds of light – a prediction which now looks less likely”
Sounds like it’s not Special Relativity that is wrong, but the theories of quantum gravity.
“The researchers specifically looked for the invariance violations predicted by the Standard-Model Extension (SME), an effective field theory that unifies special relativity with the Standard Model.”
Something’s off here. The Standard Model is already a (specially) relativistic theory; the whole anti-particle setup comes from Dirac’s work doing precisely that.
Yep, that quote isn’t accurate. The SME is all about adding small amounts of violation of Lorentz invariance (i.e. speed of light is universal max speed, all directions are the same etc) to the standard model, i.e. it adds small changes that break special relativity.
Who told you that Lorenz invariance have anything to do with speed of light? It is only about speed of information carrier used for observation. It is about how observer will percieve things in another frame if he will use f.e. EM waves to observe what happening in it. If you will use sound to observe, you will have speed of sound in the exactly same Lorenz formulas instead of speed of light. If you will use carrier pigeons for observations, then you have speed of pigeon as c in formulas. That simple.
In math, it might make sense to think of the Lorentz Invariant as a rule that can be generalized for different propagation speeds but in physics it is c = speed of light, in every case.
A good way to think of the special relativity formulas is that every particle is moving the same speed, but some things are moving in more a timeward direction and others in more a spaceward direction. Light itself moves only in space and not in time. I, personally, move mostly in time and not in space. If this was true then the Lorentz transform would be just the pythagorean theorem. Which it is!!
That single speed is c. It isn’t the speed of sound.
Read your first sentence again. It must be a slow news day.
They may be using the wrong yardstick here. Photons appear to travel at whatever c is in the local medium, and there are “mechanisms” for this particle to shed kinetic energy when that medium changes to a more restrictive regime than a vacuum – Cherenkov radiation. So variations in the speed, not so much, as variations in the energy levels of the photons.
I, personally, have always wondered what happens when the opposite is the case… when transitioning to a vacuum.
In the practical case of Special Relativity, we don’t get emitted photons going at the source’s relativistic speeds plus c – a Newtonian notion – which is where time itself comes into play, along with some other quirky things related to the nature of spacetime. So a relativistic object emitting photons would have kind of a “bow shock” of photons traveling at local c at all energy levels, DC to daylight.
In some respects, ST:TNG got the whole “photonic boom” thing right for object approaching relativistic velocities…. in my opinion.
Isn’t SR a theory for flat space-time and inevitably “wrong” in the real world? Add accelerations and gravitation and it doesn’t work, thus GR?