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A null test of General Relativity: Long term comparison of H-masers and Cs-fountains



Neil Ashby, Thomas E. Parker, Bijunath Patla


The fractional frequency comparison of clocks based on different atoms: hydrogen and cesium, is used to test one of the main postulates of general relativity to an accuracy five times better than previous tests. We compare the long-term fractional frequency variation of four hydrogen masers that are part of an ensemble of clocks comprising the National Institute of Standards and Technology(NIST), Boulder, timescale with the fractional frequencies of primary frequency standards operated by leading metrology laboratories in the United States, France, Germany, and Italy for a period extending more than 14 years. The measure of the assumed variation of the non gravitational interaction---within the atoms of H and Cs---over time as the earth orbits the sun, has been constrained to $\{Δ}\β=2.2 \times 10^{-7}$ with an uncertainty of $2.8\× 10^{-7}$. For any metric theory of gravity $\{Δ}\β=0$.
Science Magazine


atomic clock frequency comparisons, local position invariance, tests of general relativity


Ashby, N. , Parker, T. and Patla, B. (2018), A null test of General Relativity: Long term comparison of H-masers and Cs-fountains, Science Magazine, [online], (Accessed June 21, 2024)


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Created August 1, 2018, Updated February 21, 2019