The quest to pin down the fundamental constants of nature usually results in increased precision over time, but knowledge of the Newtonian constant of gravitation (G), known among physicists as Big G, has not improved much in recent years because different measurement methods continue to disagree.
Now, Terry Quinn and his colleagues at the International Bureau of Weights and Measures in Paris have added to the uncertainty by finding a value for G of 6.67545 × 10−11 m3 kg−1 s−2. This is significantly larger than several other measurements from the past decade, but is in agreement with a 2001 result by the same group using a similar but independent experimental set-up.
The researchers used a torsion balance (pictured), in which a thin metal strip changes orientation in response to test masses. The authors say that they do not know why their apparatus gives a different result from other approaches.
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A startling value for gravitation. Nature 501, 139 (2013). https://doi.org/10.1038/501139c
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DOI: https://doi.org/10.1038/501139c
