Frame dragging and absolute rotation

In summary, according to the author, there is no absolute reference point in regards to rotating reference frames, meaning that rotational frame dragging is a result of each rotating body trying to coerce its surrounding space-time field that its rotating reference frame is the correct one. Mach's principle is not satisfied by GR, meaning that the centrifugal force is not always determined by a body rotating in reference to the matter around it.
  • #1
nottay
9
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I'm trying to wrap my head around how rotational frame dragging affects the centrifugal force of a massive, rotating body and was hoping someone could explain this concept to me better. If I am confused on any of the points below please let me know.

It is my understanding that there is no such thing as an absolute reference point even in terms of rotating reference frames in GR and rotational frame dragging is the result of each rotating body trying to coerce its surrounding space-time field that its rotating reference frame is the correct one. Absolute rotation is a result of all the matter in the universe influencing their space-time and defining what bodies are rotating and how much.

My question is, if there is a massive body rotating at high speeds with no other mass close by, will it eventually (thru frame dragging) re-orient the space-time field around it in such a way that it will no longer be rotating from its point of view and experience no centrifugal force?

I've created a thought experiment which will hopefully make my question clearer:

Lets say the entire universe is comprised of only three masses and space-time. The first mass is very massive, comprising 95% of all the matter in the universe but is not very dense and doesn't collapse under the effect of its own gravity. The second mass has very low mass and located far enough away from the first mass that any gravitational attraction to the first mass is canceled out by the cosmological constant in such a way that these two masses always remain the same distance from each other and do not rotate relative to their space-time field or each other. The third mass makes up the other 4.99% of the universe and collides with the first mass off-center at high speed and is absorbed into the mass by the impact causing the combined mass to rotate relative to the space-time field. An observer on the second mass with a very powerful telescope sees the impact and notes that the rotation of the body is causing it to bulge about its axis of rotation due to the centrifugal force of its rotation. So as time passes the observer watches as the rotating body drags the space-time field around it through rotational frame dragging. My question is whether the frame dragging would eventually cause the entire "universe" to rotate with the body therefore eliminating the centrifugal force in such a way that the observer on the second mass would eventually see the bulge disappear and the first mass be transformed back into a perfect sphere by gravity?

I really hope this makes sense :)
 
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  • #2
nottay said:
It is my understanding that there is no such thing as an absolute reference point even in terms of rotating reference frames in GR [...]
That's not actually true. You can detect whether you're rotating by referring to a gyroscope, for instance.
 
  • #3
I know rotation can be detected by a number of different tests but doesn't relativity imply that there shouldn't be such a thing as absolute rotation if all frames of reference are equal? I'm referring to Mach's principle and the idea that a rotating body experiences centrifugal force due to the inertia of the rest of the matter in the universe as implied in his quote:

"You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move?"
 
  • #4
nottay said:
I know rotation can be detected by a number of different tests but doesn't relativity imply that there shouldn't be such a thing as absolute rotation if all frames of reference are equal? I'm referring to Mach's principle and the idea that a rotating body experiences centrifugal force due to the inertia of the rest of the matter in the universe as implied in his quote:

"You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move?"

GR doesn't satisfy Mach's principle. Who is the quote from?
 
  • #5
The quote is from Ernst Mach. So if the centrifugal force isn't caused by a body rotating in reference to the matter around it then what determines the absolute rotation? I find it hard to believe that there is simply a preferred reference point when it comes to rotation.
 
  • #6
Frame dragging may be caused by the time lag of EM propagation, mighten it?. When a charged particle "moves", even rotates, the EM fields that any particular point feels will be different from that it would feel if it weren't rotating or moving. That brings about non-locality.

The Kramers–Kronig relations are one place where that non-locality is identified. The Jackson textbook on EM has a very nice introduction and explanation.
 

1. What is frame dragging and absolute rotation?

Frame dragging and absolute rotation are concepts in general relativity that describe how the rotation of a massive object, such as a planet or star, can affect the surrounding spacetime. This means that the rotation of an object causes the space and time around it to be dragged along with it, creating a twisting effect.

2. How does frame dragging and absolute rotation affect objects in space?

Frame dragging and absolute rotation can affect the orbits of objects in space, causing them to precess (rotate) in a different direction than they would without the effect. This can also have an impact on the accuracy of satellite navigation systems, as they rely on precise measurements of time and space.

3. Are there any observable effects of frame dragging and absolute rotation?

Yes, there have been several observations that support the existence of frame dragging and absolute rotation. One of the most well-known examples is the Lense-Thirring effect, where the rotation of a massive object causes the orbit of a smaller object to precess. This effect has been observed in Earth's orbit around the Sun and in the orbits of some binary star systems.

4. Can frame dragging and absolute rotation be tested or measured?

Yes, there are experiments and tests that have been conducted to measure the effects of frame dragging and absolute rotation. One notable experiment is the Gravity Probe B mission, which used gyroscopes to measure the rotation of Earth's spacetime caused by its mass and rotation. This experiment confirmed the predictions of general relativity regarding frame dragging.

5. How does frame dragging and absolute rotation relate to Einstein's theory of general relativity?

Frame dragging and absolute rotation are consequences of Einstein's theory of general relativity, which describes the relationship between gravity and spacetime. The theory predicts that the presence of mass and energy can cause distortions in spacetime, and this includes the effect of frame dragging and absolute rotation.

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