Here is the article in question. They used the analogy of the wobbling head of a spinning top. Am I to then believe that the top is also warping space and time on a minute scale? Is this something we can theoretically measure?
Related questions, if I may (I just read a similar article on Space.com):
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What is the vector quantity of the frame dragging on an orbiting object? If the object is orbiting in the same direction as the spin of the object it is orbiting, is it a) pulled forward in it’s orbit, b) backward, c) some perpendicular direction?
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(similar to the OP) On what scale does frame dragging operate? Is the orbit of a galaxy orbiting a galaxy cluster deflected to some degree by the frame dragging of the cluster as a whole?
I though this was going to be about low riders! :smack:
I’ll try to answer since no one else has jumped in yet. I hope someone who knows more than I do will give a more authoritative answer.
First of all, in General Relativity all mass-energy (moving or not) warps spacetime. Rotating objects, like your top (or squeegee’s galaxy cluster), warp spacetime differently from stationary ones. This difference is what’s being detected by the experiment whose results you linked to. IIRC, this spacetime distortion acts like you’d expect if space were a slightly viscous fluid: inertial reference frames near the rotating body are dragged along in the direction of rotation (so near the Earth, inertial frames are dragged eastwards). This is very difficult to measure even for something the size of the Earth, though, so for a top the frame-dragging is probably about (wild guess here) 30 orders of magnitude too small to measure. It only becomes nontrivial for very dense rotating bodies, like rapidly spinning neutron stars and black holes (Kerr black holes).
GR is one of a large class of similar theories of gravity, and some of these predict different amounts of frame dragging than others do, so having a quantitative measurement is useful for ruling out some of these theories. Earlier observations of this effect were all of astrophysical objects, for which it is hard to get independent measurements of mass, rotation speed, and other important numbers to get a quantitative result.
One problem with measurements taken near the Earth (like this one) is that the results will necessarily be to “lowest order.” GR, though it’s a nonlinear theory, can be linearized in a weak gravitational field. The higher-order terms are always drowned out by the lowest nonzero-order term, so you can’t use these measurements to learn much about the nonlinear behavior of the theory. I don’t know of any quantitative measurements of higher-order terms in the weak-field expansion; have any been made?