1. Pound-Rebka Experiment

2. Experiment Background
Experiment done in 1959 at Harvard’s Jefferson laboratory to test Gravitational Red-Shift of light predicted by Einstein’s Theory of General Relativity

3. Background Information
Principle of Equivalence states that the force of a gravitational field is equivalent to the acceleration of a given reference system.
From the Principle of Equivalence we can also conclude that any frequency shift in light produced by acceleration can also be produced by the appropriate gravitational field. This is like a relativistic Doppler shift.

4. Experiment Set Up
2 Light Sources- 1 on top of the 22.5 meter laboratory, 1 in the basement.

5. Experiment Set Up
Hypothesized that the Gamma Rays emitted from basement would have a gravitational red shift and Gamma Rays emitted from the roof would have a gravitational blue shift.
Prepared the Gamma Ray detectors out of a combination of Iron and Cobalt heated to a high temperature to increase its sensitivity and resolution to red shift.

6. Equations Used in Experiment
By using equations for gravitational potential energy and the relativistic energy expression, the gain in energy of a photon which falls a distance h is :

7. Equations Used in Experiment
Difference in energy shifts from the 2 gamma ray emissions was predicted to be:
While it was measured as:

8. Results
Basement emitted gamma ray of wavelength of 1 measured on roof as having wavelength of
Roof emitted gamma ray of wavelength 1 measured in basement as having wavelength of

9. Implications
The measured energy difference and gravitational shift was within the error margin of the predicted value by General Relativity
Experiment claimed as Proof of General Relativity

10. Bibliography
“Harvard Gravitational Red Shift Experiment.”
“Equivalence Principle.”
“Gravitational Red Shift.”