Frame Dragging

[KALSTER]

To quote Wiki:

Albert Einstein's theory of general relativity predicts that rotating bodies drag spacetime around themselves in a phenomenon referred to as frame-dragging. The rotational frame-dragging effect was first derived from the theory of general relativity in 1918 by the Austrian physicists Joseph Lense and Hans Thirring, and is also known as the Lense-Thirring effect.[1][2][3] Lense and Thirring predicted that the rotation of an object would alter space and time, dragging a nearby object out of position compared to the predictions of Newtonian physics. The predicted effect is incredibly small — about one part in a few trillion. In order to detect it, it is necessary to look at a very massive object, or build an instrument that is incredibly sensitive. More generally, the subject of field effects caused by moving matter is known as gravitomagnetism.

Different forms of:

Rotational frame-dragging (the Lense-Thirring effect) appears in the general principle of relativity and similar theories in the vicinity of rotating massive objects. 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. It is now the best-known effect, partly thanks to the Gravity Probe B experiment.

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).[4]

Static mass increase is a third effect noted by Einstein in the same paper.[5] The effect is an increase in inertia of a body when other masses are placed nearby. While not strictly a frame dragging effect (the term frame dragging is not used by Einstein), it is demonstrated by Einstein to derive from the same equation of general relativity. Again, a tiny effect difficult to confirm experimentally.

Ok, so my question is whether this effect occurs on a planetary surface as well? What about underground? There is a Gravity Probe experiment underway which involves the launching of satellites into orbit in order to measure the tiny effect with the use of gyroscopes, but this will only measure the effect in near space and not on the surface or underground.

[Tormod]

As is stated above, it happens with all objects and thus also on a planetary surface, but the effect is so small that it's almost impossible to detect.

[KALSTER]

Originally Posted by Tormod

As is stated above, it happens with all objects and thus also on a planetary surface, but the effect is so small that it's almost impossible to detect.

Thanks, but what I was wondering was how the effect changes in strength as you move through the atmospheer and onto the surface? You see, I always thought that the measured effect would lessen as you come closer to the surface, because you would be entering the frame of the earth. But then if that were the case, that would mean that the frame of the earth is isolated from the surrounding space to some degree, no?

[KALSTER]

No takers?

[sanctus]

Why should it lessen? It is the frame of earth which is draggened along no?

[KALSTER]

Originally Posted by sanctus

Why should it lessen? It is the frame of earth which is draggened along no?

Yes, I am asking about the measured effect lessening. As you move further out into space the measured effect would become larger. In other words whether the frames of the earth on the surface and an arbitrarily chosen second frame would become more isolated from each other as the second frame moves away from the earth.

[modest]

Originally Posted by KALSTER

Yes, I am asking about the measured effect lessening. As you move further out into space the measured effect would become larger. In other words whether the frames of the earth on the surface and an arbitrarily chosen second frame would become more isolated from each other as the second frame moves away from the earth.

The closer you are to the angular momentum of the mass dragging the frame the greater the effect. In other words, the effect diminishes with distance from earth's surface. Also, yes - frame dragging persists in a rigid mass. A neutrino (or some other particle) that passes through the earth would do so faster (by a ridiculously small amount) if it passes through the side with positive velocity relative to the neutrino's movement. This would be a very hard thing to calculate - beyond my ability.

-modest

[KALSTER]

Thanks. I was just wondering, supposing an ether in some form did exist, if the frame-dragging effect might influence Michelson–Morley type experiments in such a way as to give results that would appear to confirm the absence of it. Some modern ether theories do not think of the hypothetical ether as being comprised of some type of conventional particle anyway. Does the presence of an ether in all its proposed varieties necessarily contradict relativity?

I have always in my mind sort of linked the geometric nature of the space-time fabric to some form of aether. I mean what exactly is bent in the presence of matter to have the phenomenon of gravity as a result? And when carrying the 2D idea of bent space (you know, the stretched cloth with a marble in the centre) over to a 3D scenario has in my mind led to an analogy of stretched rubber with the varying degrees of local tension (and maybe even a form of density) corresponding to the strength and direction of the local force of gravity.

I am trying to think at what exactly space-time is. When you start from a point, you can go in three main directions (3D) with any direction possible as a combination of these three. Time is nothing other than a way to measure relative movement. So if I am not mistaken, the 4D space-time geometric equation () incorporates time to be able to provide a convenient and accurate mathematical basis from which to work when describing movement in space-time. So from this utilitarian perspective on space-time as more of an accurate mathematical model, at least in my mind, no paradox need result from some kind of aether theory. So while it might make predictions, I think of relativity theory more in terms of a mathematical model that describes phenomena, observed and experimentally verified, but that it does not neccesarily describe the precise nature of the space-time fabric. The same goes for QM in my mind. It does (maybe by accident) quantifiably describe the sub-atomic world, but that it does not neccesarily mean that it exactly describes the exact nature space-time. Am I way off-base here?

[KALSTER]

Sorry

[modest]

Originally Posted by KALSTER

Thanks. I was just wondering, supposing an ether in some form did exist, if the frame-dragging effect might influence Michelson–Morley type experiments in such a way as to give results that would appear to confirm the absence of it.

No, the effect is too small by many orders of magnitude.

Originally Posted by KALSTER

Some modern ether theories do not think of the hypothetical ether as being comprised of some type of conventional particle anyway. Does the presence of an ether in all its proposed varieties necessarily contradict relativity?

Relativity does not exactly make æther an impossibility. What it does is take the property of motion (or time) from it. If æther is going to have any interaction that is measurable then it cannot be bound to a particular reference frame. Which means the historical quality æther had (that of being a mechanical medium for light propagation) it cannot have.

Originally Posted by KALSTER

So while it might make predictions, I think of relativity theory more in terms of a mathematical model that describes phenomena, observed and experimentally verified, but that it does not neccesarily describe the precise nature of the space-time fabric. The same goes for QM in my mind. It does (maybe by accident) quantifiably describe the sub-atomic world, but that it does not neccesarily mean that it exactly describes the exact nature space-time. Am I way off-base here?

I think it would be a mistake to think the fields in general relativity or quantum mechanics need a luminiferous-like æther to exist. The geometry of spactime is not what is normally though of as an æther.

That said, Einstein himself did not rule out the possibility:
Ether and the Theory of Relativity

-modest