Sagnac Effect on Equatorial Plane: MG-P Exp & GR Twist

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SUMMARY

The Sagnac effect occurs when two light beams are sent around the equator in opposite directions, as demonstrated by the Michelson-Gale-Pearson experiment. The Earth’s rotation causes the observer to detect the light beam traveling west before the one traveling east due to the rotation-induced space-time twist predicted by General Relativity (GR). Although frame dragging slightly reduces the Sagnac effect, this reduction is negligible. The measurable difference in time signals can be detected using atomic clocks, and the effect is significantly larger than any GR effects.

PREREQUISITES
  • Understanding of the Sagnac effect
  • Familiarity with General Relativity (GR)
  • Knowledge of light propagation and time measurement
  • Basic concepts of frame dragging
NEXT STEPS
  • Research the Michelson-Gale-Pearson experiment in detail
  • Study the implications of General Relativity on rotating frames
  • Explore the principles of frame dragging in GR
  • Investigate the use of atomic clocks in measuring relativistic effects
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Physicists, researchers in relativity, and anyone interested in the practical applications of the Sagnac effect and General Relativity in experimental physics.

davek
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If one were to send two light beams around the equator east and west, would the Sagnac effect occur? I know Michelson-Gale-Pearson measured it, but in their experiment the two beams would each travel both directions in separate rectangles, so I wonder if the effect would be weaker/stronger. How would it be affected by the earth-rotation-induced space-time twist predicted by GR?
 
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It does occur, and is easiest to understand if you think in terms of an Earth-centred non-rotating frame. Simply, the Earth rotates through some angle while the light is in transit so the observer will see the light sent to the west return to him before that sent to the east.

Frame dragging would slightly reduce the effect but the amount would be negligible.
 
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By the time light moved around the equator, the lab setup moved 62 meters relative to an inertial system. Sure, you get an effect from it. It is so large you could simply use atomic clocks to measure the time signals need. And it is orders of magnitude larger than any GR effects.
 

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