= Nordtvedt effect
{c}
{title2=$m_G/m_I=1+\eta_N E_G/(mc^2)$}
{wiki}
A violation of the <strong equivalence principle> can make the gravitational-to-inertial mass ratio depend on a body's negative gravitational self-energy $E_G$. Bodies with different self-binding fractions would then fall differently in the same external field, even after composition-dependent weak-equivalence effects are removed. For the Earth and Moon this produces a polarization of the lunar orbit toward the Sun, measurable by lunar laser ranging. <General relativity> predicts $\eta_N=0$.
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