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The experiment compares gamma-ray emission and resonant absorption at different heights in Earth's field, using the Mössbauer effect to resolve the small gravitational redshift. Its weak-field result is the frequency shift $\Delta \nu /\nu =-gH/c^2$ for an upward ray over height $H$. Any metric theory with the corresponding static lapse predicts this leading effect; the test alone does not distinguish general relativity from the weak-field prediction of Nordstrom theory of gravitation.