Schwarzchild radius over the body's radius.
A method of verifying this effect uses the interference between the oscillations of two cesium atoms fired across a gap and shot with a laser. In the low-field limit, this effect's strength is equal to one minus g h over c-squared; a full treatment shows its strength as the length scale goes to infinity is a factor of negative one, plus one over the square root of one minus the (*) Schwarzchild radius over the body's radius. Walter Adams confirmed this effect by looking at spectral lines of Sirius B. A mylar bag full of helium was used to cut down on scattering in an experiment testing for this phenomenon in which two Mossbauer-active samples of iron-57 were placed on the roof and in the basement of the Jefferson Laboratory at Harvard by Pound and Rebka. For 10 points, name this phenomenon predicted by general relativity in which a large mass changes the frequency of electromagnetic radiation travelling near it.
A method of verifying this effect uses the interference between the oscillations of two cesium atoms fired across a gap and shot with a laser.
gravitational redshift [prompt on partial answer; also accept gravitational time dilation; prompt on partial answer in all cases]