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

In summary, the Sagnac effect does occur when two light beams are sent east and west around the equator. This effect is easiest to understand in an Earth-centred non-rotating frame, where the Earth's rotation causes the light to travel different distances. The effect is slightly reduced by frame dragging, but is still significant enough to be measured using atomic clocks. It is also much larger than any effects predicted by general relativity.
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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.
 

1. What is the Sagnac effect on the equatorial plane?

The Sagnac effect refers to the phenomenon where a rotating object experiences a change in the time it takes for light to travel in opposite directions along its circumference. This effect is most commonly observed in devices such as gyroscopes and interferometers.

2. How is the Sagnac effect observed in the MG-P experiment?

The MG-P experiment is a variation of the classic Sagnac experiment, where a light beam is split and travels in opposite directions along a circular path. The difference in the time it takes for the light to return to its starting point is measured and can be used to calculate the rotational velocity of the device.

3. What is the significance of the Sagnac effect on the equatorial plane in the context of general relativity?

In general relativity, the Sagnac effect on the equatorial plane plays a crucial role in understanding the effects of rotation on space and time. It is used to explain the phenomenon of frame dragging, where the rotation of a massive object causes a distortion in the surrounding space-time.

4. How does the Sagnac effect on the equatorial plane differ from the Sagnac effect on other planes?

The Sagnac effect on the equatorial plane is unique because it occurs on a plane that is perpendicular to the axis of rotation. This results in a different pattern of interference fringes compared to the Sagnac effect on other planes, where the fringes are parallel to the axis of rotation.

5. What are the practical applications of the Sagnac effect on the equatorial plane?

The Sagnac effect on the equatorial plane has various applications in fields such as navigation, geodesy, and astronomy. It is used in the development of sensitive rotation sensors and gyroscopes, which are essential in spacecraft navigation and other technological devices. It also has implications in the study of gravitational waves and the rotation of celestial bodies.

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