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Is space-time a prism?

26 Jan 2016, 04:01 UTC
Is space-time a prism?
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Tl;dr: A new paper demonstrates that quantum gravity can split light into spectral colors. Gravitational rainbows are almost certainly undetectable on cosmological scales, but the idea might become useful for Earth-based experiments.Einstein’s theory of general relativity still stands apart from the other known forces by its refusal to be quantized. Progress in finding a theory of quantum gravity has stalled because of the complete lack of data – a challenging situation that physicists have never encountered before. The main problem in measuring quantum gravitational effects is the weakness of gravity. Estimates show that testing its quantum effects would require detectors the size of planet Jupiter or particle accelerators the size of the Milky-way. Thus, experiments to guide theory development are unfeasible. Or so we’ve been told. But gravity is not a weak force – its strength depends on the masses between which it acts. (Indeed, that is the very reason gravity is so difficult to quantize.) Saying that gravity is weak makes sense only when referring to a specific mass, like that of the proton for example. We can then compare the strength of gravity to the strength of the other interactions, demonstrating its relative weakness – a puzzling fact ...

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