How does a ring laser detect Earth's rotation?

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    Laser Ring Rotation
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Discussion Overview

The discussion revolves around the functioning of a ring laser in detecting Earth's rotation. Participants explore the principles behind ring lasers, particularly in relation to the Sagnac effect, and how these principles apply when the laser is stationary on the Earth's surface.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how a ring laser can detect Earth's rotation when it is not positioned perpendicularly to the rotation, suggesting that the laser path would need to encompass the entire Earth.
  • Another participant references the Sagnac effect as a relevant concept, linking it to the operation of ring lasers.
  • A participant questions the necessity of the laser path going around the Earth, arguing that a rotating frame can still exhibit rotation effects even when off-axis.
  • One participant acknowledges understanding the detection of rotation around the center of the area enclosed by the ring laser but struggles to comprehend how it detects rotation in other configurations.
  • A later reply introduces the Coriolis effect as a related concept that may help clarify the situation.

Areas of Agreement / Disagreement

The discussion features multiple competing views regarding the mechanics of how a ring laser detects Earth's rotation, with no consensus reached on the necessity of the laser path's orientation or configuration.

Contextual Notes

Participants express varying levels of understanding regarding the principles involved, indicating potential limitations in their grasp of the underlying physics, particularly concerning the Sagnac effect and the Coriolis effect.

journierman
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This is my first time posting here so I hope I am in the right place. So I have read about some scientists who have built a ring laser that is sensitive enought to detec the Earth's rotation. I can get how a ring laser can detect the rotation of a missile say if the laser path is perpendicular to the direction of the missile travel. I can not seem to get my head around how a ring laser could detect the rotation of the Earth if its sitting on the surface of the Earth and the beam path is not perpendicular to the Earth rotation. It seems like to me for a ring laser to detect the Earth rotation the laser path would have to go around the whole earth. Can anybody help me understand this?
 
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Why would it have to go around the Earth? If you take a rotating frame and move it off axis, it's still rotating by the same amount.
 
Sorry I am dense. So I understand how it detects rotation when you rotate the ring laser around the center of the area it encloses. I do not understand how it could detect rotation any other way. Does this help?
 
Do you know the Coriolis effect? It's essentially that really.
 

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