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Updated: Jul 6, 2026

Method to Measure Tone of Axial and Proximal Muscle
Published on: December 14, 2011
Test of the equivalence principle using a rotating torsion balance
S Schlamminger1, K-Y Choi, T A Wagner
1Center for Experimental Nuclear Physics and Astrophysics, University of Washington, Seattle, Washington 98195, USA.
Abstract:
We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Deltaa(N),(Be-Ti)=(0.6+/-3.1)x10(-15) m/s2 improves limits on equivalence-principle violations with ranges from 1 m to infinity by an order of magnitude. The Eötvös parameter is eta(Earth,Be-Ti)=(0.3+/-1.8)x10(-13). By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding eta(DM,Be-Ti)=(-4+/-7)x10(-5). Space-fixed differential accelerations in any direction are limited to less than 8.8x10(-15) m/s2 with 95% confidence.
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