Would it be possible to develop a substance, consisting only
of neutrons ? What could be the use of it ?
You would use neutronium to construct the hull of a planet-killer.
What would hold it together? Without electrons to form bonds with other atoms I think the whole thing would just fly apart.
In a neutron star its gravity doing the work of keeping things all smushed up. Given that the neutrons in a neutron star are incredibly dense I don’t think you’d want to use any anyway. IIRC a tablespoon of neutron star material weighs about as much as Mt. Everest.
I figure, theoretically, a starship hull laminated with a
nucleus-sized thickness of neutronium would keep out
neutrinos…for whatever advantage that would bring.
Unless I’m mistaken, neutronium is only stable under very high gravitational pressure. You couldn’t plate anything with it, because when you remove it from the consitions of a neutron star, it ceases to be neutronium fast.
Furthermore, even if you could take it out and play with it, you wouldn’t be able to form it into any shape other than a sphere. What prevents one piece of matter from going through another is the repulsion between the valence electrons. Neutronium doesn’t have any valence electrons, it’s a jam-packed mass of neutrons, and vastly more dense than conventional matter. The rest of your starship (or whatever) would be an irrelevent thin fog compared to the neutronium; it would be like trying to support a lead block with tissue paper. The neutronium would collapse under its own gravitational mass into a sphere, completely ignoring anything in its way.
Now, if you could store small spheres of neutronium somehow, and then hurl them at high speed, it would make one hell of a weapon. No armor is going to stop that.
What force would make a mass of neutrons fly apart?
Not electromagnetic - no charge.
Not gravity - that only attracts.
And I thought that the strong and weak forces were also attractive forces. But I’m admitting my ignorance.
I guess if there was nothing to hold it together, then just brownian motion would cause it to “evaporate” fairly quickly. Maybe quickly enough to be considered flying apart.
I must be missing something because…
I don’t know what would make it fly apart either. I think that the opposite would be the sticking part, here. The strong nuclear force would hold the physical neutrons together.
On the other hand, I see a problem of making any conventional spacecraft out of neutronium. As I recall, a teaspoon of neutronium would be closer to the combined mass of the solar system, then the mass of a mountain.
With this much mass combined in such a small space, anything around it would experience noticable time distorting effects, not to mention crushing any other material (supporting steel, people on board a ship) that got close to it.
I could be horribly mistaken, of course, hopefully an expert will come along and clear this up a bit.
-Lixi
I may be admitting my own ignorance here too but here’s my guess…
In a Neutron Star all of the electrons have been crammed into the nucleus of the atom due to gravity (which is what is keeping everything together).
Minus gravity the electrons would, I think, pop back into their orbits (for lack of a better word) and the whole thing would fly apart due to repulsion from the electrons.
I’d imagine if you could somehow magically cancel the gravitational effect in a neutron star you’d probably get the mother of all explosions (except for the Big Bang itself).
Just a guess though…hopefully Ring or Chronos or a few others who know more will come around to correct us.
As I understand it, the electrons of whatever material became neutron matter (usually hydrogen) are NOT in any way compressed into the nucleus. Instead, the process of creating the NM expels both electrons and protons into the surroundings, leaving the neutrons behind.
Though the gravitational collapse of the remains of a post-novaed star is the natural way to make neutronium (don’t confuse this with black hole formation, BTW), the idea that the strong nuclear force could bind together de-charged nucleii formed by some other method sounds at least possible.
In the core of a collapsing star, the pressure of the several solar masses of material crashing down smashes the electrons into the nucleus. You still need an anti-neutrino to form neutrons, but (mumble mumble… it’s been too long since I studied the details) they must be available. The electrons, protons and antineutrinos form neutrons.
A free neutron left to itself will spontaneously decay into an electron, proton and anti-neutrino on average in about 11 minutes. I have no idea if a chunk of neutronium would be stable against this spontaneous decay or not. I have often wondered what the lower mass limit must be to prevent this. I know someone who studies condensed matter. I’ll ask her when I see her at Thanksgiving.
Where to start…
Gravity is superfluous for creating neutronium. You only need extremely high pressure. Gravity is a convenient source of the pressure, but in principle another source could be used.
One doesn’t need anti-neutrinos to form neutrons. Compressing a proton and electron together will give you a neutron and a neutrino. (Just use anti-matter algebra on the equation.)
The strong force can be either attractive and repulsive, depending on the distances involved. The strong force holds nuclei together, but also breaks up unstable ones. A lump of neutronium is like one (huge) atom of element zero (assuming there are no protons in the lump). This atom will sponateously decay very, very quickly and emit a lot of radiation. As Whack-a-Mole mentioned, explosion would be a better word.
If by some magic you could keep your neutronium from decaying, it still not be an effective shield against neutrinos (or anti-neutrinos). I don’t remember the cross sections involved, but you would need a very thick layer to have much hope. Of course, why would you want to stop neutrinos anyway?
Spacetime distortion would not be a big problem; you have to get to black-hole densities for that to become a major issue. But you would notice a definite gravitational attraction to your neutronium plating. (And, yes, I know that that attraction is actually a spacetime distortion.)
Just have to pipe in on the neutron stars question.
Two things:
First: there are some neutrons formed by the collapse of electrons into the nucleus. Those of you who said so were correct.
Second: A neutron star does have some protons and electrons in it. You can treat the problem thermodynamically and show that the protons can only account for a small percentage of the mass of the star.
A helpful thread:
One other thing to note about neutronium: it’s superfluid. That means that there is no friction between the particles composing it. Or to put it another way, it has less structural integrity than air.
So much for the neutronium spaceship hulls…
Near a supernova, the neutrino flux from the initial burst can give a lethal dose of radiation absorption (like, form an AU away or so). That would make useful shielding on a starship.
Neutron decay is Beta decay and it’s caused by the Weak Force.
Neutron -> electron + proton + neutrino
The absorption of an electron by a proton is called beta capture.
Proton + electron -> neutron + neutrino
One thing it took me awhile to figure out was how a neutron star or a black hole could form without violating the Pauli Exclusion Principle.
A degenerate neutron or electron gas has many very weird properties.