Unaccounted source of systematic errors in measurements of the Newtonian   gravitational constant G
  Many precision measurements of G have produced a spread of results incompatible with measurement errors. Clearly an unknown source of systematic errors is at work. It is proposed here that most of the discrepancies derive from subtle deviations from Hooke's law, caused by avalanches of entangled dislocations. The idea is supported by deviations from linearity reported by experimenters measuring G, similar to what observed, on a larger scale, in low-frequency spring oscillators. Some mitigating experimental apparatus modifications are suggested. 
Riccardo DeSalvo
cond-mat.mtrl-sci