[MereInterest]

At some point, they could be. The heaviest of elements are formed in the "r-process" [1]. We're not really sure where it happens (either core-collapse supernova or neutron star mergers, but that is a different topic altogether), but we know in general what is happening in it.

The r-process starts with something fairly stable and relatively light, like iron. Then you start throwing phenomenal amounts of neutrons at it. Outside of a nucleus, neutrons are unstable, and decay to protons in about 15 minute, so this can only happen if something is producing lots and lots of neutrons, all at once. Anyways, the iron catching those neutrons, becoming heavier and heavier.

Eventually, the nucleus becomes heavy enough that beta decay, in which a neutron inside the nucleus changes into a proton, starts happening at the same rate as neutron capture. At this point, it is a competition. In the table of isotopes [2], neutron capture moves to the right, and beta decay moves diagonally up and to the left. Between the two, the nuclei get heavier and heavier, with more and more protons and neutrons. The general path is known [3], zig-zagging through the isotopes, becoming more and more unstable.

The process stops when the source of neutrons runs out. At that point, everything beta-decays back to stability. Everything is finished, and the heavy elements of the universe have been produced.

There is a theorized "island of stability" [4]. We have enough protons, but not enough neutrons. Remember how the r-process adds one neutron at a time? Well, if the island of stability is as stable as predicted (half-lives of a few hours are typically predicted), then we might be able to produce those isotopes by careful selection of the input nuclei. Nature is limited to what exists in stellar environments, and can't choose. So (and here I'm stepping out of my area of expertise), since this selection wouldn't happen in nature, it is entirely possible that we are creating conditions that haven't existed in large quantities elsewhere.

[1] https://en.wikipedia.org/wiki/R-process [2] http://cdn.iopscience.com/images/0034-4885/76/5/056301/Full/... [3] http://www.onafarawayday.com/Radiogenic/Ch1/Ch1-2_files/imag... [4] https://en.wikipedia.org/wiki/Island_of_stability

[grkvlt]

I have always wondered about whether there might be some kind of similar 'island of stability' with strange particles. Since particles come in three flavours, the normal kind, then ones made of strange/charm quarks and then top/bottom quarks, you could feasibly make 'strange atoms' with the strange equivalents of protons, neutrons and electrons. The same could even be done for top/bottom atoms. As far as I know, though, the half-lives of these strange family particles are too short to let them hang around for long enough. However, if we collect enough together to make e.g. strange-carbon or strange-uranium, maybe the fact that they are bound together as an atomic structure would stabilise them? It's really hard to find anything out about this, as most discussions of strange matter are about things like replacing the electron in a hydrogen atom with a muon, not replacing every particle in a larger atom with its strange counterpart...

[MereInterest]

The problem there is one of energy scales. Whenever a system decays, it goes from a state of higher energy to a state of lower energy. In order for something to be stable, there must be no decays that can possibly happen. That is, the system must already be at the lowest energy possible.

For example, the neutron decays to a proton, because a proton+electron system has less energy than a neutron. Bind the neutron with a proton, forming deuterium, and suddenly it is stable. The neutron is unstable by only a free MeV, and so the binding to a proton can stabilize it.

All matter is made of up and down quarks. The next lightest quark, the strange quark, is about 100 MeV. It order to stabilize it, there would need to be some binding effect that would bind a strange quark 100 MeV more strongly than an up or down quark. That would be the only way to make the strange quark system be the most stable.

And here we run into the problem that, of the four fundamental forces, none of strong enough and specific enough to the strange quark to do so. The strong nuclear force, which stabilizes the neutron, is the strongest, and only provides that few MeV of binding, not the 100 or so that would be necessary.

[grkvlt]

Thanks for this explanation - it makes more sense now! I still think 'Strange Atoms' would be a great handwavium type plot device in an SF novel ;)

[MereInterest]

You are welcome, and I completely agree that they would work well in a fictional setting. The most obvious use would be as a compact storage of energy. If you had one strange quark replacing a down quark in a Carbon-12 atom, it would have an energy density of about 660,900,000 MJ/kg. For reference, this is about a factor of 8 more than Uranium-235, and a factor of 14 million more than gasoline.

Getting at that energy after it is stored would require a bit more handwavium, since you don't want it to destabilize (read: catastrophically explode) on common use. I could imagine using a gamma-ray laser (same principle as regular laser, but they don't currently exist) to destabilize the strange carbon.