![Figure 1](wep.png)
Figure 1: Selected tests of the weak equivalence principle, showing bounds on
, which measures
fractional difference in acceleration of different materials or bodies. The free-fall and Eöt-Wash
experiments were originally performed to search for a fifth force (green region, representing many
experiments). The blue band shows evolving bounds on
for gravitating bodies from lunar laser
ranging (LLR).
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![η](article30x.gif)