🚀 go-pugleaf

Dave Barlow (db@decuk.uvo.dec.com) wrote:
> 
> Ever heard of the problem of Helium-4 rotation in the superfluid state. 
> If you have a rotating container with He4 in it, cool it below the super-fluid
> critical temperature then all the fluid stops rotating or all of it rotates.
> This is independant of frame of reference, the container still rotates.
> If you stop rotating th econtainer there is, scant, evidence that the He4
> is rotating. The question is with respect to what is at rest, rotating to ?
> It is thought that this is a case of an Einstein-Bose Quantum Fluid.
> 
> It indicates that the He4 is stationary, rotating wrt the "Fixed Stars". 

My understanding of this was that, when you have liquid helium
in a small "bucket", and it's below that critical temperature,
when you rotate the bucket, the helium remains still *at first*
but then suddenly starts rotating, all of it, instantly. It
doesn't accelerate; one moment none of it's moving, the next,
all of it is. If you like, it starts off stationary relative to
the (stationary) bucket, even when the bucket starts moving,
then ends up stationary relative to the (rotating) bucket. the
fixed stars don't come into it.

John Gribbin's book, "In Search of Schrodinger's Cat" describes
this.

Pete

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Pete Ford                     >>>>>>> Ford@ens.ascom.ch <<<<<<<
South Wales, UK
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"Cry Hammock! and let sleep the dogs of war."