Gamma Ray Anomaly Could Test String Theory 128
exploder writes "String theory is notorious for its lack of testable predictions. But if the MAGIC gamma-ray telescope team's interpretation is correct, then a delay in the arrival of higher-energy gamma rays could point to a breakdown of relativity theory. A type of 'quantum lensing effect' is postulated to cause the delay, which is approximately four minutes over a half-billion year journey." Ars's writeup is a little more fleshed-out than the Scientific American blog posting.
Layman Alert. (Score:2, Interesting)
But who am I to argue with quantum mechanics.
~Sticky
Re:Not specific to String Theory (Score:3, Interesting)
The neat thing about String Theory is that it is a coherent mathematical framework and a group of related models that unify the theories of several of the fundamental forces as they are currently understood. Essentially, it can't make predictions, because the if it does, in practice, the theories it unifies will have already made them. As of now, it is best understood as an "interpretation" in the sense that the Copenhagen or many-worlds interpretations are interpretations of quantum physics.
Note that individual string theories are falsifiable anyway. For example, there is a class of theories called the Super Symmetric String Theories that relies on the assumption of supersymmetry. If this assumption proves to be empirically false, the super symmetric theories will be abandoned.
If you're familiar with the methods of mathematical logic, an analogy can be useful. Some physicists have taken certain physical laws as axioms for something like a first-order logic. And many models (in the sense of model theory) have been created. Now the task is to figure out which models are representative of the physical world. This is kind of backwards from the scientific method, where a specific model (nature) is examined and attempts at an axiomatization of its working is attempted. But it is a logically sound technique, and as falsifiable as the axioms are.
Occam's Razor (Score:3, Interesting)
The gamma rays are due to infalling material. Flares are due to sudden large amounts of material falling in. As it falls in it gets hotter. The frequency of the emissions increases as the material heats, going from lower gamma rays to higher gamma rays. These are all accepted as fact. The hypothetical: The 4 minute delay is the time it took for the material to fall in far enough to raise the emission frequency by the observed amount.
Much simpler and neater. Even if I had the observed data and the data on the mass of the galaxy observed, I'm not capable of the relevant calculations, but the logic follows.
On the other hand, Willam of Ockam didn't have a razor -- he had a beard. Einstein trumped Newton with a more complex theory, so the parsimony beloved by scientists doesn't always hold. But in this case, I suspect it will.
String "theory" (Score:2, Interesting)
Re:Occam's Razor (Score:5, Interesting)
> birth corrected Newton's kinetic energy equation by emprical means (ie: dropped
> steel balls into clay and mesured the craters).
You're thinking of Emilie du Chatelet, paramour of Voltaire. I don't know how noble, but her family lived in a 30 room apartment overlooking Tuileries gardens in Paris. Certainly rich by birth, and married to a rich French military officer who conveniently left on a polar expedition.
And you're not quite correct about what she did; it was much better than that. The dropped ball and clay experiment was done by Willem 'sGravesande in the Netherlands, but he didn't have the theoretical background to understand what he had -- the craters got deeper with the square of the height (== energy). Liebniz had previously specified that energy should increase with the square of velocity, but that was somewhere between intuition, anti-Newtonian leanings (Newton got credit for calculus rather than he; Newton was pushing for mass times velocity, no square) and fortuitous guesswork. He didn't have the practical sense to develop a means to test it (or perhaps thought that beneath him). What du Chatelet did was put the two together and show the precise relationship between energy, mass and velocity that was supported by the data: E = mv^2.
Smiling Uncle Albert had it half written for him. What he plugged in was c for the Latin celeritas (rapidity), which he showed to have a limit of the speed of light, and that the E and m then equated completely and were thus interchangeable through it. Had she had the verification of Roemer's measurement of the speed of light to work with (said verification was just a few years old and not widely accepted yet) and had more time to work on it (she died from an infection after giving birth) she might have made progress towards that herself.
If she had done so, Poincare probably would have grasped the significance of his "theory of relativity" (Uncle A. never used that term until well after it became popularized, but Poincare used it explicitly in his own) and formulated the famous equation himself. He was, after all, right on the verge of it, and refused to talk about Ol' Al forever more because he failed to get all the way there first. It riled him no end, until the end of his days. Had he been younger and the age earlier, he might have challenged the young Bavarian Jew to a duel. A duel such as Francois-Marie Arouet threatened against a certain French nobleman, which resulted in his expulsion from France to England, where he learned of Newton and his work, which he brought back to France, along with his nom de plume, Voltaire. Or the duel (fencing match, actually) in which Jacques de Brun, the head of the King's bodyguards, was bested by a 16 year old girl named Emilie de Breteuil, as such was her family's name when they lived above Paris's Tuileries gardens.
If this was Connections, and I were James Burke, I'd be making a lot more money than what I'm getting for having written this. I am, however, every bit as pretty as Burke on camera, which is to say not at all.
Re:Not specific to String Theory (Score:4, Interesting)
Yeah, it's even possible to make a pretty reasonable model-independent argument that a variable speed of light must come out of any theory of quantum gravity. Lee Smolin makes a pretty simple model-independent argument that spacetime must be discrete in any theory of quantum gravity. The idea is that the Bekenstein bound [wikipedia.org] says there's a maximum amount of information that can be contained in any region of spacetime (e.g., a black hole has a certain entropy, which is proportional to the surface area of its event horizon). However, if spacetime was continuous, then you could store an infinite amount of energy in any volume of space. (Here [thymos.com] is a longer explanation.) Note that none of this requires any specific model such as string theory or loop quantum gravity. If spacetime is discrete, then there's a scale at which its discreteness occurs, and that corresponds to a certain minimum wavelength that a light wave can have. The propagation of light therefore has to be drastically modified as you approach that scale.