What is Linear Frame Dragging in General Relativity?

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Discussion Overview

The discussion centers on the concept of linear frame dragging in the context of general relativity, exploring its theoretical implications, terminology, and experimental challenges. Participants examine its relationship to other effects such as rotational frame dragging and the geodetic effect, as well as its connection to Mach's principle.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants question the terminology of "linear frame dragging," suggesting it may not be widely accepted or could be a misinterpretation from sources like Wikipedia.
  • One participant describes linear frame dragging as an effect where a test mass near an accelerating massive object experiences a slight acceleration in the same direction, implying a uniform acceleration of the universe, consistent with Mach's principle.
  • Another participant notes the difficulty of measuring linear frame dragging compared to rotational frame dragging, emphasizing its small magnitude relative to ordinary gravitational acceleration.
  • There is a request for a physical explanation of frame dragging, with a specific inquiry about its derivation from the Kerr metric and its relation to the Einstein stress-energy tensor.
  • Participants express curiosity about the relationship between frame dragging and the geodetic effect, noting a lack of clarity in existing literature.
  • A reference to Brian Greene's work suggests that the concept of rotational frame dragging follows the equivalence principle, indicating a connection between acceleration and gravitational effects.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the terminology and theoretical underpinnings of linear frame dragging, with no consensus on its acceptance or clarity in its relationship to other effects.

Contextual Notes

There are limitations in the discussion regarding the definitions of terms used, the assumptions underlying the effects described, and the unresolved nature of the relationships between frame dragging and other relativistic effects.

tiny-tim
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"Linear frame dragging"?

wikipedia at http://en.wikipedia.org/wiki/Frame_Dragging#Frame_dragging_effects says:
Linear frame dragging is the similarly inevitable result of the general principle of relativity, applied to linear momentum. Although it arguably has equal theoretical legitimacy to the "rotational" effect, the difficulty of obtaining an experimental verification of the effect means that it receives much less discussion and is often omitted from articles on frame-dragging (but see Einstein, 1921)

(Naty1 has drawn attention to this to this in a Library comment.)

What is this referring to?

Is it a generally accepted terminology, or is it just wikipedia's wishful thinking? :confused:
 
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Linear frame-dragging is the effect that if a test mass is near to an accelerating massive object, its frame of reference is slightly accelerated in the same direction, giving the impression that the rest of the universe is accelerating slightly in the opposite direction. This is consistent with the Mach's principle idea that if the whole universe were accelerating uniformly in the same direction, local reference frames would also accelerate with it, making the acceleration unobservable.

This linear frame-dragging effect is of course tiny in comparison with the ordinary gravitational acceleration and is even more difficult to measure than rotational frame-dragging.

I don't know where the terminology came from; I've heard it before, but I've also heard this effect being referred to as "inertia induction" (by Dennis Sciama, in his fascinating paper "On the Origin of Inertia").
 


If anyone knows a physical explanation for frame dragging, I'd sure be interested. Wiki derives the ffect from the Kerr metric: does the interaction arise from a specific piece of the Einstein stress energy tensor??

Also, how is frame dragging related to the geodetic effect; Wikipedia has a cross reference with frame dragging, but the relationship isn't clear..

http://en.wikipedia.org/wiki/Geodetic_effect
 


When I read a few pages about rotational frame dragging in Fabric of The Cosmos by Brian Greene, I see I wrote myself a note:

"seems to follow the equivalence principle of acceleration and "g", but here via
v = w(r)" ...not too far fetched...

Brian Greene says :
...just as a massive objects warps space and time so a rotating object drags space and time around it...(it) implies, for example, an asteroid freely falling toward a rapdily rotating neutron star or black hole will get caught up in a whirlpool of spinning space and be whipped around as it journeys downward."
 

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