Neutronium sword

[Admiral Valdemar]

This exact question was posted on ASVS by "erincss," who has an immense hard-on for nanotechnology. My comments were as follows:

Please explain how you would weild a sword with roughly the same mass as a small planet.

Lol, perhaps he should really mean a nanotech produced blade made from composite materials or a single crystal, neutronium? Hah, anyone who believes that stuff can be used in building ships in reality must also think that firing black holes at the enemy is somewhat efficient.

[Pu-239]

I don't think neutronium can be alloyed to make armor.

[Admiral Valdemar]

I don't think neutronium can be alloyed to make armor.

It can't, the stuff in SW is simply part of some pseudo-science armour that negates the whole mass thing unless it was a very tiny amount of neutronium that would negate any real advantage anyway.

This is not like working with steel or anything, it is just overly accepted in sci-fi because it's just about the strongest material you can get, is superfluid and totally non-reactive. It's a fallacy as bad as sparking bullets in movies.

[Alan Bolte]

Since the neutronium would immediately form itself into a sphere, it would make a spectacularly bad sword.

Crap! Does that mean we can't use it for armor?

You could use it as an alloying agent. Carbon atoms in steel are spherical inclusions in the matrix. But forming solid plates of fluid neutronium is ridiculous.

Could you really? Are you quite sure of this? Because that would be damn cool. I suppose if the spherical inclusions were made out of nuclear degenerate matter but coated in negatively charged particles you could keep it in the steel matrix...but could you do that? I know nothing.

[Admiral Valdemar]

Crap! Does that mean we can't use it for armor?

You could use it as an alloying agent. Carbon atoms in steel are spherical inclusions in the matrix. But forming solid plates of fluid neutronium is ridiculous.

Could you really? Are you quite sure of this? Because that would be damn cool. I suppose if the spherical inclusions were made out of nuclear degenerate matter but coated in negatively charged particles you could keep it in the steel matrix...but could you do that? I know nothing.

What would be the point though? It's excessively complicated, would require atomic precision and too much and your crew goes splat on the walls or at the very least it botches up any sensors.

It's simply impractical like building mechs. Sure, it could probably be done, but is it worth it?

[Darth Wong]

Crap! Does that mean we can't use it for armor?

You could use it as an alloying agent. Carbon atoms in steel are spherical inclusions in the matrix. But forming solid plates of fluid neutronium is ridiculous.

Could you really? Are you quite sure of this? Because that would be damn cool. I suppose if the spherical inclusions were made out of nuclear degenerate matter but coated in negatively charged particles you could keep it in the steel matrix...but could you do that? I know nothing.

Neutronium will beta-decay and become a huge-nucleus element. Even a small amount of such beta-decay would result in a positively charged, albeit massive nucleus with electrons in orbit.

Of course, the trick is to figure out how long this beta decay will take, or whether there's some way to slow it down. But it's certainly more feasible than making thick wall-plates out of pure neutronium.

[SyntaxVorlon]

A superthin string of forcefield held neutronium would be able to cut through anything, though it would take a very large and powerful field to keep ridged and thus it would probably be better to use a cutting laser.

[consequences]

So how heavy is your average planet anyway?

[ClaysGhost]

Neutronium will beta-decay and become a huge-nucleus element. Even a small amount of such beta-decay would result in a positively charged, albeit massive nucleus with electrons in orbit.

Surely it would produce a massive nucleus so far off the line of stability that it would make even ST's endless procession of transuranics look long-lived.

[Zoink]

How about a cosmic string whip?

[Admiral Valdemar]

Well one thing's for sure, no MBT today is going to have neutronium armour anytime soon.

[Keevan_Colton]

OK, let's do some math: let's say the sword is three feet long, three inches wide, and half an inch thick (averaged across its width). Its volume would be 54 cubic inches, or 884 cc (8.8E-4 cubic metres).

The nuclear density is roughly 2.8E17 kg/m^3, so if we assume this to be the density of neutronium, we're looking at about 250 billion tons.

Needless to say, it would be rather difficult for you to swing this thing around. Worse yet, it would form a sphere of roughly 6 cm radius. At its surface, the gravitational acceleration would be nearly half a million G's. Even 10 metres away, its gravitational acceleration would be more than 15 G's.

And people think an Iconian structure sitting on a planet's surface could have thick walls of pure neutronium

You do have to admit it would make for a great novelty when playing with marbles.....

As for a sword...great mass is not really what you need....a sharp blade is far more useful than a heavy one, save for blocking....where the mass is more important.

[Darth Wong]

Neutronium will beta-decay and become a huge-nucleus element. Even a small amount of such beta-decay would result in a positively charged, albeit massive nucleus with electrons in orbit.

Surely it would produce a massive nucleus so far off the line of stability that it would make even ST's endless procession of transuranics look long-lived.

Actually, transuranics are short-lived because the coulomb repulsion of all the protons is large in relation to the nuclear binding force. In this case, there would be very few protons. The trick is to retard the beta decay process which turns neutrons into protons (while shooting off an electron), assuming it progresses quickly (not that we know how quickly it will progress).

[Durandal]

Neutronium will beta-decay and become a huge-nucleus element. Even a small amount of such beta-decay would result in a positively charged, albeit massive nucleus with electrons in orbit.

Surely it would produce a massive nucleus so far off the line of stability that it would make even ST's endless procession of transuranics look long-lived.

Actually, transuranics are short-lived because the coulomb repulsion of all the protons is large in relation to the nuclear binding force. In this case, there would be very few protons. The trick is to retard the beta decay process which turns neutrons into protons (while shooting off an electron), assuming it progresses quickly (not that we know how quickly it will progress).

Outside the confines of massive gravity, wouldn't you expect the nucleus to undergo fission due to the huge amounts of potential energy it has?

[Darth Wong]

Outside the confines of massive gravity, wouldn't you expect the nucleus to undergo fission due to the huge amounts of potential energy it has?

Yes, that's the beta decay I was talking about. I don't see why it would split in half; it seems more likely that it would throw out little bits at a time via beta decay. But of course, there's not much in the way of research on this subject AFAIK.

[Durandal]

Outside the confines of massive gravity, wouldn't you expect the nucleus to undergo fission due to the huge amounts of potential energy it has?

Yes, that's the beta decay I was talking about. I don't see why it would split in half; it seems more likely that it would throw out little bits at a time via beta decay. But of course, there's not much in the way of research on this subject AFAIK.

I guess it'd be helpful to know exactly what neutronium's atomic mass would be. If we assume a really high number, it's likely that it would fission to produce two unstable nuclei, which would then fission on their own or decay into more stable nuclei.

I'd expect the fission to occur more rapidly, however. The lifetime of a neutron is roughly 900 s, which is a very long time in comparison the speed with which fission in such a high potential energy state would take place. It'd be interesting to think about the possible relativistic consequences on the nucleus due to the large potential energy state. Would the nucleus experience time dilation as per general relativity?

[Admiral Valdemar]

Outside the confines of massive gravity, wouldn't you expect the nucleus to undergo fission due to the huge amounts of potential energy it has?

Yes, that's the beta decay I was talking about. I don't see why it would split in half; it seems more likely that it would throw out little bits at a time via beta decay. But of course, there's not much in the way of research on this subject AFAIK.

I guess it'd be helpful to know exactly what neutronium's atomic mass would be. If we assume a really high number, it's likely that it would fission to produce two unstable nuclei, which would then fission on their own or decay into more stable nuclei.

I'd expect the fission to occur more rapidly, however. The lifetime of a neutron is roughly 900 s, which is a very long time in comparison the speed with which fission in such a high potential energy state would take place. It'd be interesting to think about the possible relativistic consequences on the nucleus due to the large potential energy state. Would the nucleus experience time dilation as per general relativity?

IIRC, there have been instances when neutrons have formed molecules of some description in the lab, a French science team found this out last year I believe when neutrons were used to basically create Element 0 which consisted of nothing more than 4 neutrons tied together for a few nanoseconds.

I'll see if I can find the articles on it, but it might help us with some basic properties of neutronium which will decay as stated unless it is kept in significant quantities.

[Darth Wong]

I'd expect the fission to occur more rapidly, however. The lifetime of a neutron is roughly 900 s, which is a very long time in comparison the speed with which fission in such a high potential energy state would take place.

Would their inclusion in a nucleus affect this half-life? After all, the neutrons in many normal-element nuclei can remain stable for billions of years.

[Durandal]

I'd expect the fission to occur more rapidly, however. The lifetime of a neutron is roughly 900 s, which is a very long time in comparison the speed with which fission in such a high potential energy state would take place.

Would their inclusion in a nucleus affect this half-life? After all, the neutrons in many normal-element nuclei can remain stable for billions of years.

Not sure, I'll have to look in my physics book again to see whether that's the lifetime of a free neutron or not (you're probably right though ... the neutrons uranium don't go off decaying after 15 minutes). It doesn't really affect the point though. If their inclusion in a nucleus turns them into stable particles, then the fission will be the mechanism of the nucleus' breakdown.

If the strong force is clinching them together, though, I don't know how likely it is that beta decay would occur. If it does, I doubt the electron would have enough kinetic energy to escape the massive potential well anyway. The emitted neutrino might, though. Perhaps the emitted electrons (if any) would begin orbiting the nucleus, which would certainly make for an interesting nucleus.

[ClaysGhost]

Actually, transuranics are short-lived because the coulomb repulsion of all the protons is large in relation to the nuclear binding force. In this case, there would be very few protons. The trick is to retard the beta decay process which turns neutrons into protons (while shooting off an electron), assuming it progresses quickly (not that we know how quickly it will progress).

The most stable elements have roughly equal number of protons and neutrons, and even unstable elements are clustered around this line of stability. Di-neutronium (n+n) cannot survive, deuterium (n+p) does.

Would their inclusion in a nucleus affect this half-life? After all, the neutrons in many normal-element nuclei can remain stable for billions of years.

Yes, indeed. Strongly bound neutrons are very stable (that lifetime is correct for a free neutron).

I'll see if I can find the articles on it

New Scientist did one. As I understand it, the result is open to interpretation. The original team are following it up with a dedicated experiment (the original was something of a chance discovery, if I remember right).

[Admiral Valdemar]

Clay: Yeah that's the one, I forget the name of the element, but they are still testing to see if it really was a major breakthrough. Looks interesting all the same, neutrons have no reason to group up in fours like that.

[ClaysGhost]

Clay: Yeah that's the one, I forget the name of the element, but they are still testing to see if it really was a major breakthrough. Looks interesting all the same, neutrons have no reason to group up in fours like that.

They called it a tetraneutron, I think.

[Admiral Valdemar]

Clay: Yeah that's the one, I forget the name of the element, but they are still testing to see if it really was a major breakthrough. Looks interesting all the same, neutrons have no reason to group up in fours like that.

They called it a tetraneutron, I think.

Hmm, yep, that's what I thought too, was going to say tetrads but that's something entirely different.

[phongn]

Clay: Yeah that's the one, I forget the name of the element, but they are still testing to see if it really was a major breakthrough. Looks interesting all the same, neutrons have no reason to group up in fours like that.

They called it a tetraneutron, I think.

Hmm, yep, that's what I thought too, was going to say tetrads but that's something entirely different.

Quite

::beats AV with some chromatin::

[Durandal]

Actually, transuranics are short-lived because the coulomb repulsion of all the protons is large in relation to the nuclear binding force. In this case, there would be very few protons. The trick is to retard the beta decay process which turns neutrons into protons (while shooting off an electron), assuming it progresses quickly (not that we know how quickly it will progress).

The most stable elements have roughly equal number of protons and neutrons, and even unstable elements are clustered around this line of stability. Di-neutronium (n+n) cannot survive, deuterium (n+p) does.

What exactly causes this instability? Neutrons and protons have roughly the same mass, so there's not much of a potential energy difference between di-neutronium and deuterium, and from my understanding, the strong force affects all particles with the same amount of force within a certain radius, so they're no more tightly bound than one another. Also, there is no Coloumb repulsion in either, so what causes the nucleus to decay?