Precise test of general relativity from a cosmic cataclysm – Mirage News

Einstein’s general relativity (GR) is a beautiful theory, which explains how mass and energy interact with space-time, creating a phenomenon commonly known as gravity. GR has been tested and retested in various physical situations and over many different scales, and, postulating that the speed of light is constant, it always turned out to outstandingly predict the experimental results. Nevertheless, physicists suspect that GR is not the most fundamental theory, and that there might exist an underlying quantum mechanical description of gravity, referred to as quantum gravity (QG). Some QG theories consider that the speed of light might dependent on energy. This hypothetical phenomenon is called Lorentz invariance violation (LIV). Its effects are thought to be too tiny to be measured, unless they are accumulated over a very long time.
So how to achieve that? One solution is using signals from astronomical sources of gamma rays. Gamma-ray bursts (GRBs) are powerful and far-away cosmic explosions, which emit highly variable, extremely energetic signals. They are thus excellent laboratories for experimental tests of QG. The higher energy photons are expected to be more influenced by the QG effects, and there should be plenty of those; these travel billions of years before reaching Earth, which enhances the effect.
GRBs are detected on a daily basis with satellite-borne detectors, which observe large portions of the sky, but at lower energies than the ground-based telescopes like MAGIC. On January 14, 2019, the MAGIC telescope system detected the first GRB in the domain of teraelectronvolt energies (TeV, 1000 billion times more energetic than the visible light), hence recording the by far most energetic photons ever observed from such an object. Multiple analyses were performed to study the nature of this object and the very high energy radiation.

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