On Tue, 28 Apr 1998, Chan Wei Lik wrote:

From:	Benjamin "Snowhare" Franz [SMTP:snowhare@xmission.xmission.com]

If you were to take a small piece of neutronium off the surface - it would
explode immediately without the gravity to keep it confined.

You forget, even the smallest sample you can scoop off a neutron star would 
be so dense, its gravity field would be enough to keep it condensed.

Ummm... No, it wouldn't. Gravity is *WEAK*.  Even the top few inches/feet
of a neutron star are degenerate matter - without the 'extra' squeeze of
stuff sitting on top of it in the gravity field of a star squeezed to the
size of a city, it can't become/stay neutronium. This layer gets thinner
as the mass of a neutron star goes up. It is only the fact the you are
piling a ridiculous amount of mass (1.4 solar masses) into a small space
that lets neutronium be stabilized by the gravity.

By the time you got the mass down to say 100,000 tons (around the mass of
a US aircraft carrier), the size is on the order of 1 millimeter and the
gravity is down to a mere 1,000 Gs. If you work the numbers you'll find
out the gravity is inversely proportional the the radius of the ball for a
constant density. A ball 1 meter in radius has a 1,000,000 G surface field
(which is *still* much too small to be stable - and masses around 1000
trillion tons).

About 50% of normal matter's mass is in the form of neutrons.

And when you go heavier than Uranium, there's much more neutrons than 
protons

Actually, well before that in the periodic table. But the 'about 50%'
remains true. Even for Uranium it is only up to around 62%. For hydrogen-1
it is 0%. But _overall_ - its around 50%. And I ignored the fact that
anti-neutrons _can_ react with protons explosively because they are in
fact both composite particle composed of up and down quarks.

They are kept stable (mostly) by the immense power of the strong nuclear 

force in atom's >nuclei.

It's the WEAK nuclear force. The strong force binds quarks inside nuclear 
particles.

No. The weak nuclear force is what causes 'beta decay' and is mediated by
W+, W- and Z0 particles (well, photons are technically in there too, but
that is in the realm of Electro-weak unification and we aren't going to
worry about it here). 

You are correct to say the strong nuclear force is what binds quarks
together into neutrons and protons, but that is only part of the story,
the _residual_ force between bound collections of quarks is what is
commonly called the strong nuclear force. 

The Strong nuclear force in its 'purest' form binds quarks together by
exchanges of virtual gluons. However, by exchanging virtual
quark-antiquark pairs (mesons) between protons and neutrons it *also*
binds the the neutrons and protons together into nuclei. 

The _Weak_ nuclear force mediates entirely different phenomena - the
decay of neutrons into protons, electons and anti-neutrinios (beta decay) 
and the transformation of a protons and electrons into neutrons (plus
neutrinos) (beta capture). It is important in the process of nuclear
fusion (specifically in the ppe- -> pn plus neutrino step), the formation
of neutron stars, and beta decay for certain radioactive elements. 

Boom. Big boom. *REALLY* *REALLY* big boom.

Quite.

Second off - even if you *do*, its density is so high that it will fall
*through* solid rock like it wasn't even there.

When is what happens in "Forge of God" by Greg Bear. The aliens drop a 
piece of neutronium and anti-neutronium into the Earth, they meet at the 
core and the resulting explosion shatters the planet.

Yes....but Greg Bear was playing fast and loose with the actual physics
involved, too. If you want hard neutron star physics, read Robert
Forward's 'Dragon's Egg' and 'Starquake' novels. Robert Forward is
actually a scientist specializing in gravitational physics, as well as a
damn fine science fiction writer. 

-- 
Benjamin Franz
"I think its time to quit talking about Neutronium. Ne?"