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Scientists Tried To Break Einstein's Speed of Light Rule (sciencedaily.com) 72

Posted by BeauHD from the search-continues dept.
Scientists are putting Einstein's claim that the speed of light is constant to the test. While researchers found no evidence that light's speed changes with energy, this null result dramatically tightens the constraints on quantum-gravity theories that predict even the tiniest violations. ScienceDaily reports: 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. [...] 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 Merce 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.

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.
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Scientists Tried To Break Einstein's Speed of Light Rule

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  • If the hypothesis was true, then high speed particles would smear (like a fuzzy comet) over a long distance. How to observe and measure it is not clear.

  • That's not how you get clicks. (Score:4, Insightful)

    by Petersko ( 564140 ) on Saturday January 10, 2026 @07:34AM (#65914530)

    "New test might break physics - scientists are terrified!" Thumbnail should have a picture of somebody not quoted. Neil Tyson is traditional. Negative result can be in small print at the end, or optionally omitted entirely.

    Do you even edit, bro?

  • Scientists continue to test their beliefs ... (Score:5, Insightful)

    by Alain Williams ( 2972 ) <addw@phcomp.co.uk> on Saturday January 10, 2026 @08:08AM (#65914548) Homepage

    this is what makes it science and distinguishes it from religion.

    Long may scientists continue to try to show their beliefs wrong.

    • this is what makes it science and distinguishes it from religion.

      Long may scientists continue to try to show their beliefs wrong.

      Even we have our foibles, like string theory, which has religion-like qualities. Otherwise yes, always try to get closer to truth.

      • "Science progresses one funeral at a time"

        https://en.wikipedia.org/wiki/... [wikipedia.org]

        So it's mostly true.

      • Re: (Score:3)

        by HiThere ( 15173 )

        If it's an alternate explanation that's consistent with the data, then it counts as part of science. Then scientists need to look for special cases where the alternate explanations disagree. (You can't depend on Occam's razor.)

        • You can't always depend on Occam's Razor, but you should keep it handy and prepare to wield it.

          A theory that explains the data only as well as the established one, but is more complicated and has plausibility issues, is nice and warrants consideration. But you would need a pretty good reason to jump if you were deciding to devote a few years to it.

          • Re: (Score:2)

            by HiThere ( 15173 )

            I agree completely. One should always *prefer* to use Occam's Razor. But that's a matter of engineering or efficiency, not of truth. NASA gets along quite well by almost always ignoring Einstein's theories, and preferring those of Newton. (But not when they're using GPS.)

            If a new theory is more complex and only explains the existing data as well as the accepted (simpler) one, then one needs to look for the cases where they predict different things for science, but for engineering the current theory may

            • I agree completely. One should always *prefer* to use Occam's Razor. But that's a matter of engineering or efficiency, not of truth. NASA gets along quite well by almost always ignoring Einstein's theories, and preferring those of Newton. (But not when they're using GPS.)

              Deep space navigation also requires taking relativity into account. They use Parameterized Post-Newtonian (PPN) which adds relativity terms to Newtonian calculations for the level of precision required (easier than doing a full solution). PPN works when gravity fields are weak and speeds slow.

        • If it's an alternate explanation that's consistent with the data, then it counts as part of science. Then scientists need to look for special cases where the alternate explanations disagree. (You can't depend on Occam's razor.)

          And in String theory, you can just create some more dimensions. String is the just so story of "science, where we must accept things without proof.

          How do we falsify string theory?

          • Re: (Score:3)

            by HiThere ( 15173 )

            If you can't falsify it, then *MAYBE* it's correct. Of course, being correct doesn't imply that it has any useful meaning.

  • .. in order to limit the computatonal power needed by the simulator.

    • Re: (Score:3, Insightful)

      by sinij ( 911942 )
      Speed of light is a maximum rate of conversion between space and time while still preserving causality.

    • Nah it's just to prevent edge cases.

      Like how in Snowrunner when your trailer tries to inhabit the same space as your vehicle, it does a Bethesda-esque bounce around and HEAD FOR THE STARS maneuver... That wouldn't happen if they would place a sensible limit on velocity.

  • I don't understand how energy could possibly matter when it is itself a relative quantity. A photon emitted with the same energy a billion years ago could ultimately be absorbed as either a gamma or radio wave.

    If you want to preserve quantum mumbo jumbo over all of that time having a leaky theory in which you can cheat via gravity doesn't make much sense.

    • If you want to preserve quantum mumbo jumbo over all of that time having a leaky theory in which you can cheat via gravity doesn't make much sense.

      Imagine you have two perfectly calibrated light sources.

      A photon from each arrives at the same time interval with the same energy from the same direction such that a detector is unable to discern any difference when switching between either source.

      One of the photon sources is down the hall, the other 14 billion light years away.

      The detector now engages some sort of wakefield accelerator in its detection circuit that boosts the absorption energy of detected photons. Now it is able to discern the difference

      • Re: (Score:2)

        by PPH ( 736903 )

        wakefield accelerator

        I don't understand how such a device would affect photons. A wakefield accelerator accelerates plasmas. Not photons.

        • I don't understand how such a device would affect photons. A wakefield accelerator accelerates plasmas. Not photons.

          The modality isn't important. The idea is for accelerated particles to absorb photons and the detector to record the event.

      • Better to use a light source... a million watt light and a 1,000 watt light... is there a difference in speed in a vacuum?

        • Better to use a light source... a million watt light and a 1,000 watt light... is there a difference in speed in a vacuum?

          If you have a brighter light you just have more photons. The energy of each photon is what TFA thought could have had an impact rather than the number of photons.

    • Re: (Score:2)

      by gweihir ( 88907 )

      If you want to preserve quantum mumbo jumbo over all of that time having a leaky theory in which you can cheat via gravity doesn't make much sense.

      Indeed, it does not. And that is why the predictions they are making are pure nonsense. Their theory is not even mathematically sound. How do they expect it to be sound for physical reality?

  • and you shine a light towards the event horizon? Where does it go? Doesn't gravity stop it?

    • It would follow the local curvature of space. Near a black hole space is extremely curved, so "outward" is actually a spiral. Inside the event horizon, that spiral can only get tighter, it cannot spiral outward. So the question is sort of ill-posed.

      • Are you the outside observer or the inside observer?

        Extremely curved?
        For the inside observer, time passes normally at the event horizon... the outside observer witnesses time slow down the closer he gets to the EH. And, with no information escaping the black hole, we'll never know what happens when you pass the EH... and the fact that it's so gravitationally dense that nothing escapes it, means that the starship you made it there in gets crushed to a single atom and added to the mass of the thing.
        So, no ra

        • That's what math is for. Note that the crushing doesn't happen right at the event horizon. That's the point at which you cease being able to influence outside causality in any way. But depending on the properties of the black hole, the tidal forces may not tear your ship apart until later. Or far earlier.

          • Well, right... and, I know about that stuff. I'm not going to get into spaghettification and all that exotic stuff on here (some fun reading and contemplating there, for sure).
            Honestly, we don't know what happens (in the real teacup and car crash world) as we get closer to the EH.
            Things get weird when looking at black holes... time slows (outside observer POV) approaching one, nothing (including information, in theory) escapes (the images of Sagittarius are the accretion disk (or, should it be disc) (this

            • In my very limited understanding, the "wormhole in the black hole" idea has a few problems. First, that model was a non-spinning one. Second, it's a bridge to another universe, not another location in this one. And third, if there's an event horizon it's useless anyway. More like two universes sharing a black hole than anything traversable.

              There are mathematical solutions for traversable wormholes but it's not clear if they exist in reality.

              • Keep in mind, this is all theoretical... there's no way to know anything about 'our little buddies' (the black holes) until we launch a human a thousand light years into space.

                • Sort of but not entirely. It doesn't matter how close you get, all you can learn is what you see. Which means, it's really just a matter of resolution. With enough time and money we can create a virtual telescope the size of Earth's orbit and see things very well.

                  • Virtual telescope? You mean like a group of a dozen Hubble's across a specific region of sky/space and we stitch the results together?
                    That could work, from a distance... but the fun bit would be having a thing fall into a BH with a solid clock on the outside (that the 'scopes can see)... we know the appearance of the thing (sacrificial satellite?) and the 'scopes get video as it gets closer to the EH. We'd see who's theory is right.
                    Of course, that isn't a weekend-long project... we'd have to do a launch o

    • Re: (Score:2)

      by gweihir ( 88907 )

      Not at all. But at some time before the light gets there, the black hole explodes.

      • How do you know if you're not right by it? On Terra/Earth Prime, by the time we know it explodes, it'd be over a thousand years since it happened.

    • Re: (Score:2)

      by PPH ( 736903 )

      Look behind you. There's somebody shining a light on the back of your head.

  • They are making an elementary mistake: Expecting Quantum-Gravity to respect all the other things they think are true but that are missing Quantum-Gravity for an actually complete theory. In actual reality, Quantum-Gravity could invalidate any number of things, including universality of physical laws. We cannot know until we do.

  • I'm not a physicist, but I think what we call 'the speed of light' is actually the speed of cause and effect.

    Maybe there is only one speed in the universe. When things are moving slower, it's because they are made up of sub atomic particles that are bouncing back in forth inside some sort of containment field and therefore moving in a zig zag as the larger object seems to move in a straight line. That's why time contraction seems to happen, as the object moves faster, the zigging and zagging has to go fur

  • Thank you, Slashdot! (Score:1)

    by Anonymous Coward
    No real addition to the subject matter, but these conversations are fascinating, and that's why I come to /.. Thanks, guys!
  • Comedian: What if you are traveling at the speed of light, and turn on the headlights

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