Pound-Rebka Experiment

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Pound-Rebka Experiment
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Experiment Background

• Experiment done in 1959 at Harvards Jefferson
  laboratory to test Gravitational Red-Shift of
  light predicted by Einsteins Theory of General
  Relativity

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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.

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Experiment Set Up

• 2 Light Sources- 1 on top of the 22.5 meter
  laboratory, 1 in the basement.

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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.

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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

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Equations Used in Experiment

• Difference in energy shifts from the 2 gamma ray
  emissions was predicted to be
• While it was measured as

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Results

• Basement emitted gamma ray of wavelength of 1
  measured on roof as having wavelength of
  1.000000000000002455
• Roof emitted gamma ray of wavelength 1 measured
  in basement as having wavelength of
  .99999999999999755

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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

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Bibliography

• Harvard Gravitational Red Shift Experiment.
  http//www.circlon-theory.com/HTML/poundRebka.html
  
• Equivalence Principle. http//en.wikipedia.org/w
  iki/Equivalence_principle
• Gravitational Red Shift. http//hyperphysics.phy
  -astr.gsu.edu/hbase/relativ/gratim.html