The cosmic microwave background sky mapped by NASA’s Wilkinson Microwave Anisotropy Probe, showing its polarization, represented by white bars. Future experiments might measure the polarization with enough sensitivity to prove the existence of gravitons, the quanta of gravity. WMAP SCIENCE TEAM/NASA
USING COSMOLOGY TO FIND QUANTUM GRAVITY
Via Nature News & Comment for 27 September 2013
Can a quantum of gravity ever be detected? Two physicists suggest that it can be seen in the traces left by the Gig Bang — using the entire Universe as a detector.
A paper posted on the arXiv preprint server on 20 September 
Lawrence Krauss, a cosmologist at Arizona State University in Tempe, and Frank Wilczek, a Nobel-prizewinning physicist at the Massachusetts Institute of Technology (MIT) in Cambridge
Can the existence of gravitons — and the quantum nature of gravity — be proved through some expected, but yet-to-be detected, features of the early Universe?
Read the report in Nature News & Comment for 27 September 2013.
Abstract of the Krauss & Wilczek Article
While many aspects of general relativity have been tested, and general principles of quantum dynamics demand its quantization, there is no direct evidence for that. It has been argued that development of detectors sensitive to individual gravitons is unlikely, and perhaps impossible. We argue here, however, that measurement of polarization of the Cosmic Microwave Background due to a long wavelength stochastic background of gravitational waves from Inflation in the Early Universe would firmly establish the quantization of gravity.
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