On Fri, 12 Jan 2007 09:03:29 -0800, chornedsnorkack wrote:
John Schilling kirjutas:
On 10 Jan 2007 14:50:25 -0800, "bbbl67" wrote:

Now, I know the interior of a neutron star has been described as a
fluid. But I find it hard to believe that something so dense that its
neutrons are touching could be a fluid. Can the neutrons slip past one
another, somehow?

In order for a thing to *not* be a fluid, something has to hold each
particle in a particular spot, and that something has to be the strongest
force at work in the system. In ordinary solid materials, a particular
arrangement of the electromagnetic force does this just fine.

In a neutron star, you've got A: neutrons, which are B: compressed to
such a density that gravity overwhelmes electromagnetism. If even
electromagnetism applied, which it doesn't because neutrons are
electrically neutral.

But you also have something that counteracts the gravity and stops the
neutrons from being compressed to decreasing volume and black hole.
Neutrons must repel each other.

And this means that the best way to minimize the repulsion is occupying
specific positions in space in a well-packed framework. Which would be
solid. Any change of shape would increase the mutual repulsions
somewhere.

That's not a bad thought. A bunch of well lubricated ball bearings
being packed into a sphere just barely big enough to fit them will
pack into a rigid formation.

However, this gets into the difference between a "solid" and a "liquid".
A liquid like water is nearly incompressible because the molecules are
packed in almost as much as possible--but there's enough random motion
to keep them "jiggling" and thus able to easily slide past each other.

Similarly, a neutron star might theoretically compress into a rigid
"solid", but with any sort of temperature the neutrons will "jiggle"
enough to be a fluid.

Isaac Kuo