Liquid Spacetime

Seems like if it were a fluid, then the viscosity might vary from place to place with difference local conditions.

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It seems like this theory will be put to the test as we get a better handle on experimentally verifying frame dragging. Frame dragging at different distances should provide a good idea of the viscosity at various points, to see if it behaves substantially as a fluid and how consistent the viscosity is at various places with similar conditions.

I think we should call it Lumeniferous Aether!

Seems to me that if spacetime really did behave like a superfluid, frame-dragging would behave very differently - if it occurred at all.

Liquid helium is a superfluid. A circulating current (fluid, not electrical) in a container of stationary liquid helium will circulate forever without coupling to adjacent regions where there is no current. An axially-rotating cylinder placed into stationary liquid helium will not couple to the fluid at all - the fluid remains stationary. This is not how spacetime behaves around a spinning mass; rather, spacetime is dragged along with it, the amount of drag varying with distance from the mass and the amount of mass present. It is the rotation being coupled to spacetime. Frame-dragging speaks more of spacetime having a 'viscosity' rather than its behaving like a superfluid.

Superfluid ⁴He will couple with the rotation of the walls of the container, by forming a vortex, but only if the angular velocity of that rotation exceeds minimum threshold as the superfluid is restricted to only quantized rotation... if the container doubles that critical angular velocity, a second vortex will form.

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For superfluid ⁴He (I'm not sure about superfluid ³He) a portion of the fluid has superfluid properties below the λ line, increasing as temperature approaches absolute zero. Only at absolute zero would 100% be superfluid. Since we never get all the way to zero, there will always be some helium in the mix that lacks superfluid properties. As such the behavior will never be purely that of only HeII phase, and always retain some properties of a normal liquid. Perhaps that is what they had in mind..... still seems like they are suggesting quantized frame dragging rates.

Cool. Citation? I want to read more about this.

Here are a couple:

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Rotons

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Experiment contradicts theory

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Around minute 20 in this video you can see a demonstration, though it lacks an obvious vortex. It is notable that initially the paddle wheel does not turn, and when it does begin to turn it does so at a constant rate.