How Does Frame Dragging Affect Light Speed Observations?

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Discussion Overview

The discussion revolves around the effects of frame dragging on light speed observations, particularly in the context of the Lense–Thirring effect. Participants explore theoretical implications, observational differences between various observers, and the nature of coordinate charts in general relativity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant cites the Lense–Thirring effect, suggesting that light traveling in the direction of a rotating object appears to move faster than light traveling against it, as observed by a distant observer.
  • Another participant argues that the change in light's observed speed is due to space being dragged around the rotating object, while locally, the speed of light remains constant.
  • A question is raised about the meaning of "wrt itself," with clarification that the velocity of light with respect to itself is undefined, as one cannot have a frame of reference moving with a beam of light.
  • There is a discussion about the meaning of a "coordinate chart," with a participant stating that general relativity does not utilize global frames of reference, and that a coordinate chart refers to a set of coordinates labeling events in a region of spacetime.

Areas of Agreement / Disagreement

Participants express differing views on the implications of frame dragging on light speed observations and the interpretation of coordinate charts, indicating that multiple competing views remain without consensus.

Contextual Notes

Limitations include potential misunderstandings of the relationship between light speed and reference frames, as well as the implications of general relativity on the concept of coordinate charts.

narrator
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From http://en.wikipedia.org/wiki/Frame-dragging" :

"Under the Lense–Thirring effect, the frame of reference in which a clock ticks the fastest is one which is rotating around the object as viewed by a distant observer. This also means that light traveling in the direction of rotation of the object will move around the object faster than light moving against the rotation as seen by a distant observer."

Is this a speed change to light wrt itself? Is the observation of the "distant observer" different to an observer sitting on the object?

Side question: Is the location of the object, the observer and the traveling light what is meant when people talk about a "coordinate chart"?
 
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The change is due to space itself bing dragged around the rotating object. This drag would affect the time it takes for light to travel past the object because space itself is being altered. Locally the speed of light is the same.
 
narrator said:
Is this a speed change to light wrt itself?
Not sure what you mean by "wrt itself." The velocity of a physical object with respect to itself is always zero. You can't have a frame of reference moving with a beam of light, so the velocity of light with respect to itself isn't zero, it's just undefined.

narrator said:
Side question: Is the location of the object, the observer and the traveling light what is meant when people talk about a "coordinate chart"?
No, GR doesn't have global frames of reference like that. A coordinate chart means a set of coordinates that label every event in a certain region of spacetime.
 
Thanks folks.. understandable and makes sense :)
 

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