Pop quiz: States of matter

[unixronin]

OK, folks, let's test your scientific knowledge.

[Poll #1278483]

Most grade school science classes still teach that there are three states of matter — solid, liquid, and gas.  But there are several others.

• If you heat and compress any substance beyond its thermodynamic critical point, the result is a supercritical fluid that behaves in many respects like a liquid and like a gas simultaneously.  If you drink decaf coffee, it's likely it was decaffeinated using supercritical carbon dioxide.
• If you pump sufficient energy into any substance possessing atomic structure, its electrons become dissociated from the atomic nuclei, forming a plasma, a highly energetic cloud of free electrons and nuclei.  Plasmas behave like gases in most respects, but have several useful additional properties.  Fluorescent lights (including CFLs) and neon tubes employ plasmas, as do the various experimental fusion reactors that rely on magnetic confinement.
• Compress any normal atomic matter enough, and its atomic structure collapses.  This gets us into a whole class of states of matter known collectively as degenerate matter.  The most common form of degenerate matter is probably the electron-degerate matter believed to compose white dwarf stars, while the best known is what used to be called neutronium, now more correctly termed neutron-degenerate matter.  Weirder, possibly speculative members of the family include strange matter, quark matter (aka QCD matter), and possibly preon matter.
• As several people have reminded me, if you cool a substance sufficiently, slowing its atomic motion until the atoms are essentially at rest, their position becomes uncertain due to Heisenberg's uncertainty principle, and the wave functions of the atoms spread out accordingly. If you can cool therm enough that their wave functions overlap, you get a Bose-Einstein condensate — a cloud of atoms all in exactly the same quantum state, acting as though they were one giant atom.  (However, the atoms you start with have to be bosons.)

So if you answered "Six or more", you're correct.  Probably.  As far as we know.  For now.  And remember, this isn't an exhaustive list.

Comments

[unixronin.livejournal.com]

And of course - there's the mysterious 'dark matter' that composes over 95% of the universe.

Though so far, nobody seems to be able to quite agree either on exactly what it is, or how much of it there is — and for that matter, at present even our arguments for its existence at all are based entirely on inferential evidence. We have observations that don't fit classical theories, so we infer that something else is there, but we don't really know what it is.

[cipherpunk.livejournal.com]

The dark matter skeptics, such as myself, find unusual parallels between dark matter and luminiferous ether. In the case of the ether, we concluded it existed, that it must exist, because the alternative was that our understanding of physics was totally bogus.

Then along came Einstein, who showed us that Newtonian physics was totally bogus.

It's still quite possible the same will happen with dark matter. I'm not persuaded by arguments from necessity. The universe is not required to refrain from upending our theories. :)

[unixronin.livejournal.com]

Neither am I.

First, there was dark matter. Then, the CDM theorists had to invent dark energy because they couldn't explain everything with dark matter. And then there's the Bullet Nebula, which was at first trumpeted as proof of dark matter, but then the CDM theorists realized they actually couldn't explain it even using both dark matter and dark energy, so at least one CDM group decided it was necessary to invent a fifth basic force whose properties are completely undefined except that it makes the calculations on the Bullet Nebula work (i.e, match the observations).


"Would you like epicycles with that?"

[smandal.livejournal.com]

I'd like to see the paper for that makes this claim.

AFAIK, the cold dark matter model is completely consistent with the Bullet Cluster; dark energy ("Lambda" in "Lambda-CDM") is not relevant here, as its effect is negligible on such a small scale.

WMAP observations of the cosmic microwave background are concordant with the dark matter fraction given by lensing, mass-to-light measurements and rotation curves, as well as the dark energy fraction inferred by the acceleration of supernovae.

MOND is ruled out because it is not consistent with tests of general relativity, which come up null. TeVeS is still alive, but only (IMHO) tendentiously. Much of the motivation is gone since the Bullet Cluster observation, as the whole point was to make baryons create the same gravitational effects that are conventionally explained by CDM and Lambda. Well, lensing by the Bullet Cluster shows there is a lot more mass that behaves just like CDM with the baryons trailing far behind in the shockwave from the collision.

[ithildae.livejournal.com]

The ironic thing is that epicycles actually work. If you think of them as coefficients of a Fourier series with circles as the orthogonal basis vectors, it all works. The only real problem is that you need an infinite sequence of coefficients. (How many digits do you really need for calculations? In Tycho's day they used about fourteen.)