April 24th, 2007

#371: Is neutronium a Bose-Einstein condensate?

Homey say what now?

Okay, here's some Wikipedia links for the physics challenged:

Bose-Einstein Condensate (BEC)

Think about it.

Not all naturally-occurring neutronium would be in a BEC, but if it is possible, then some neutron stars could eventually cool enough to form a BEC. It would take a very long time, of course. Since there have been supernovae since the beginning of the universe (minus a few million years) there should be some neutron stars which have cooled enough to reach the critical temperature. There could even be one within our galaxy; being a few millionths of a degree above zero Kelvin, it would be basically invisible. It would have to be in a relatively matter-free area of space, because a neutron star has immense gravity.

I can't even get a grip on the implications right now, but it seems to me that the entire star could be treated as a quantum object--which could be really interesting. Put an entire neutron star into superposition with one state some distance away; then collapse the wave function with a bias for the distant position, and guess what? You've (probably) teleported a stellar mass.

Now my head hurts.

* * *

Looking at the link for neutronium led me to the more generic entry on degenerate matter, which has some of its own interesting bits and pieces. Quark matter--wow, that should be really interesting stuff, assuming you could survive studying it. And if preons exist, what kind of density is required to achieve that?

The thing that really blows my mind about all this is that these states should be able to exist outside of a black hole. A black hole is infinitely dense and physics can't cope with what goes on inside of one. (As far as I know, anyway.) But stop short of a black hole, and what do you have? What happens if a neutron star gets cold? Does it collapse further into a quark star, and from there into a preon star? What is the maximum density of matter? Is there one?

I also have to wonder what happens when one passes the electron degeneracy limit--the point at which ordinary matter turns into neutronium. The proton and electron combine to form a neutron; it seems to me that there has to be some kind of an energy release from this interaction, but I can't put my finger on the exact mechanism.

When a star blows up, the event starts with an implosion--the star collapses--and some of the matter is converted into neutronium. (A supernova usually leaves a neutron star behind.) Does any of the energy of the explosion come from the conversion of normal matter into neutronium? If so, how much?

...This is the kind of stuff I think about when I'm trying to get to sleep. That's what I get for being a physics geek.

#372: More physics geekery

...in my (as yet unpublished) SF stories, there are weapons known as sub-nucleon weapons.

I forget where I got the idea from. Some long-established SF author wrote about them in a story, and I thought it was useful, so I took the idea and--in the words of Heinlein--filed off the serial numbers.

Some people in my past accused me of plagiarism when I did things like that. Well, you can't copyright the laws of physics, can you? Oh no, it was "plagiarism" for me to put a rotating habitat in a spacecraft and call it a "carousel". Instead of borrowing Clarke's term for it, I should have made up my own. Let me add here that the person responsible for these criticisms a) couldn't write his way out of a paper bag without adding several dangling participles, and; b) is a moron anyway.

My definition of "plagiarism" involves, y'know, copying someone's work without giving credit. For example, if I started a book with this line:

"The Go Big Red Fan was John Wesley Fenrick's, and when ventilating his system it throbbed and crept across the floor of his dorm room with a rhythmic chunka-chunka-chunk." (The first line, from memory, of Neal Stephenson's The Big U, a book I highly recommend.)

...that might be plagiarism. But I could have a character named John Wesley Fenrick, and he could have a fan he called the "Go Big Red Fan", and he could even be in college...all without plagiarizing Neal Stephenson. Now if I went on from that opening paragraph and rattled off 250 pages of The Big U and then signed my name to it, that would definitely be plagiarism.

Heinlein himself wrote a novel called Double Star. It was Prisoner of Zenda with the serial numbers filed off.

If you write a story in your own words, with your own characters--even if the events are identical to those in another story--it's not plagiarism. It's unimaginative, but it's not plagiarism.

For my purposes, then, I borrow all sorts of interesting concepts from all kinds of sources. Not just "subnucleon weapon" and "carousel" and other things. Why re-invent the wheel? But the important thing is, my stories are all my own--my characters, my situations, my words. The only time I ever copy text is when I want to directly quote someone, and then I attribute the quote.

So, subnucleon weapons:

The biggest bomb we can build right now is a weak force weapon--the atomic and hydrogen (ie fusion) bombs operate according to the weak interaction, which governs the atomic nucleus. The weak interaction is pretty powerful, as we've seen; finding a way to speed up nuclear decay has really done a lot for our ability to generate electricity and has even managed to put an end to total war, at least the way we used to fight them.

But really, it's not all that powerful. A couple of hundred megatons--I'm not sure what the theoretical upper limit is for a fusion bomb, but I can't believe it's unlimited. The biggest one ever set off was about 50 megatons, and that had been de-rated from 100 megatons. (The USSR did it in the 1950s.) But it seems to me that there has to be an upper limit to the power of fusion weapons.

Anyway, it got me to thinking about what there was that could be bigger? And it hit me: strong-force weapons, of course. The strong force is, by definition, the strongest of the four fundamental forces of nature (the other three being the weak force, of course; electromagnetism, and gravity. Before Maxwell it would have been "five", since Maxwell unified electricity and magnetism--and anyway it looks like electromagnetism and the weak force may be unifiable, too).

The strong force governs the interaction of quarks. It's mediated by gluons, and its effective radius is about the diameter of a proton. It takes a lot of energy to separate quarks against the strong force--so much, in fact, that if you stretch the bonds between quarks beyond the radius of a proton, the bonds "snap", and suddenly you find yourself with two particles. Energy becomes matter.

Particle physics has managed to generate a quark-gluon plasma (QGP) in particle accelerators. The QGP is a very interesting thing; it is an area of space which mimics conditions shortly after the Big Bang, at a time when things were still so hot that quarks couldn't form particles--there was too much energy around them, and the strong force bonds would be broken as quickly as they were formed.

Eventually, of course, the primordial QGP cooled enough for nucleons to form. The quarks locked themselves together and all the matter in the universe condensed from the QGP. It probably happened pretty quickly, too, once the critical temperature was passed.

So what about subnucleon weapons?

The point of any weapon more sophisticated than a bow and arrow is delivering energy. This is why the military uses depleted uranium for bullets and artillery shells--it packs the biggest wallop we can cram into a shell without excessive radioactivity. Guns are rated by their muzzle velocity and stopping power.

Bombs are no different. A bomb's primary focus is to deliver a certain amount of power to a target; lethality of the bomb is enhanced with a hard metal casing which fragments into shrapnel.

A nuclear bomb is just a bigger bomb. All the "work" of the bomb is done in thirty nanoseconds; the rest of the explosion is just the distribution of all that energy--and a nuclear warhead makes a lot of energy in a very short time.

But while nukes are great for space combat, they're a bit limited--miss someone by more than a couple of miles and the thing is wasted. Space is big and ships are tiny, so targeting becomes crucial.

If the reaction can be made hotter, more powerful, the effective radius of the device is increased. I thought, "what's better than weak-force weapons? How about strong force weapons?"

Why shouldn't it be possible? In 1920 I don't think anyone gave a moment's thought to the possibility of a nuclear bomb. But 25 years later we had designed, built, tested, and used two of the things in combat--and most of the R&D took place in the last 3 years of that time.

Imagine what it would be like. I figure that a fusion bomb would initiate the explosion, but after that I kind of get fuzzy on the details. Anyway, about thirty nanoseconds after the warhead is detonated, a small region of space temporarily reverts to Big Bang conditions. The heat in that area is intense, hotter than a supernova. All the mass of the warhead is converted into a QGP at millions or billions of degrees.

Anything inside the fireball is not just vaporized, but utterly disintegrated into quarks. The effective radius of the blast is huge; the infernal heat of the subnucleon reaction vaporizes objects that are too close. Gamma rays, x-rays, and cosmic rays will inundate anything nearby. (Photons are "fundamental" particles, so they can carry infrared radiation and light away from the reaction, right away.)

Farther out, there is still a danger from the EM of the reaction--but EM radiation is only part of the problem.

Once the QGP begins to cool, particles will condense from it--and they will be all kinds, all speeds, all directions. A howl of broad-band radiation will scream from the cooling fireball; things not vaporized and/or killed by the heat will be vaporized, killed, or damaged by the intense ionizing radiation--alphas, betas, protons, neutrons, and possibly some things we don't know about yet will boil out of the fireball like the furies from Pandora's box. The particulate radiation will be much more lethal that the electromagnetic; and particulate radiation is activating radiation, so anything exposed to it will itself become radioactive.

But even after all of this, the subnucleon weapon is not yet finished. Whatever is left of the weapon itself, vaporized, disintegrated, and re-condensed, will form a shock wave, moving very fast; it will cause yet more damage to whatever happens to be near enough. Structures which are not made to withstand the blast will be damaged or destroyed.

Such a weapon would have a yield measured in gigatons, and I expect that one could comfortably build a 100-gigaton weapon.

...but how? Duhh....

Well, I have some ideas. Build a big fusion bomb and contain the reaction in a magnetic "bottle" so the energy can't dissipate into the environment during the reaction. Make it big enough, and the "bottle" small enough, and the energy density will be high enough to form a QGP.

Not exactly a trivial exercise, mind you, but I don't see why it wouldn't work. But that's a brute-force method, and there may be better ones.

There might be a way to build a pair of fusion bombs at the ends of a magnetic waveguide. Set both bombs off at the same time and funnel their output into the waveguide--when the shock fronts collide, what happens? This is how we make QGP now, by colliding streams of particles. Might this work? (Maybe have a plutonium or uranium target in the middle, wrapped around some tritium. Use some of the fusion reaction's energy to vaporize and propel uranium atoms into this target.)

The main point is to concentrate a hell of a lot of energy on a very small region of space; do that, and you get a subnucleon reaction.

It's pretty much useless for power generation, though, IMHO.