exchemist

Sure, analysing the composition of a particular material would be one of the focused activities I was talking about.

I must say the link strikes me as a rather silly article. Nobody goes searching for new compounds for the hell of it. There is a reason and the the search is directed and narrowly focused, according to the objective. The number of permutations is practically endless, given the number of combinations of elements and the fact that many compounds, e.g. a lot of minerals, don't even have a fixed composition. So the quoted figure of 1% strikes me as pretty daft and arbitrary - just a number some journalist has pulled out of his arse, basically.

Plenty of explosives have a built-in oxidiser, apart from gunpowder. The issue with all these things is how to ensure you get a suitably controlled reaction that is triggered at the right point of the engine cycle rather than going off at the wrong moment or too fast. You don't want an actual explosion inside an engine. Nor do you want an unstable compound that might go off outside the engine. For a lot of applications you would probably better off getting motive power, or heat, another way. The great energy source you have in space is the sun.

OK, however I am not clear now what the relative proportions of Na and K would have been in the Earth's crust , or crust + mantle, before the oceans formed. Without that information it seems hard to determine whether the reason for the difference in concentration of today's seawater is due mainly to the original composition of the rocks or to the differential leaching that we have been discussing. By the way, the poster who asked the original question does not seem to have returned. Perhaps he is watching and chuckling to himself as we struggle with it.😁

No I’m not saying that. Your previous statement was different and made no sense. Neither “a line” nor “an area” are “values” unless specified, which you did not do. And you can’t add a linear measurement to a measured area. Both of these things are obvious.

No.

I'm not sure I follow this. Surely both Na and K prefer granite to peridotite, the latter being ultramafic (Mg/Fe), don't they?

This is excellent stuff, which I feel sure must be on the right track. The next question, in my rusty chemical mind, is why this should be so. I suspect something to do with the size of the "cages" in the crystal lattice formed by silica tetrahedra, in complex silicate minerals. I feel sure the difference must be to do with the difference in size of the cations in some way. Generally speaking large cations are more stable in structures with a counterion network that has larger interstices for them to occupy. It may be that Na+ "rattles around" in these structures, has less stability and can slowly diffuse out as they weather. As I recall, these minerals have silica tetrahedra that can be joined either at vertices or along edges, giving different sized holes. If I have time later I'll see whether I can find anything further along these lines to explain cation preferences in these minerals.

The latter point is what I too suspect, to do with ion sizes. But I’m not a mineralogist. We need to check what these abundance numbers mean. Do they include the oceans or not?

Yeah but the point is why would rainfall deplete Na more than K by a factor of 30, given that there are similar amounts - within a factor of 2 or so - in the Earth's crust to start with, and both form equally soluble cations, more or less.

Aha, that makes a difference, certainly! But there is a factor of 30 to account for.

Well those numbers are certainly different from the ones I had found. But even so, if you look further down in the article, at the graph for abundance in the upper crust, which is where the minerals in the sea would be leached from, the difference seems to be considerably less. Here's another source also suggesting levels of the two in the crust are comparable: https://pressbooks.lib.vt.edu/introearthscience/chapter/3-minerals/. Ah. Maybe I'll have a look into that later - I need to go and cook a kedgeree for supper.

Interesting question. I see the abundance of K in the earth's crust is similar to that of Na: http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/elabund.html . Both are of course alkali metals with many soluble salts. I have a feeling it may be to do with the stability of complex minerals containing K, e.g. aluminosilicates. Perhaps the greater ionic radius of K+ forms more energetically favourable lattices , or it is harder for the larger ion to migrate within minerals and eventually be leached out by water. But I confess I am guessing. I would be interested to know the reason. Perhaps someone more knowledgeable can comment.

Yes that's the thing. A photovoltaic device induces a non-equilibrium population of electrons and holes in a semiconductor from excitation by absorption of photons, which creates an electrical potential and can do electrical work as the population is restored to equilibrium. At the moment I can't see how this antenna produces a non-equilibrium situation.

I've just caught up with this discussion and I agree about the apparent Maxwell's Demonish nature of the explanation on Wiki. The problem I have with it is just as you say, that the arriving photons are not in phase so there won't be any coordinated flow of electrons induced. All you will get is an increase in their thermal, i.e. uncoordinated) kinetic energy. The diode aspect of the device would seem to have to work at the level of individual photon-induced excitations. I am reminded of the "Brownian Ratchet": https://en.wikipedia.org/wiki/Brownian_ratchet But I would be most interested if someone can point out what I am missing.

That is being kind. This is Quantum Woo. Belongs in Religion rather than Physics, at best. Is Deepak Chopra involved? 🤪

We've been through the black hole thing. I pointed out there is no inconsistency in what Hawking said. But you've ignored it, being the aggressive and slightly mad idiot you clearly are. Enough of this tomfoolery.

Eh? Research is done all the time on transient phenomena. If there is doubt about the results, someone can repeat it to confirm it. In science, what happens is that the researchers write up the experimental procedure and their findings in great detail, precisely so that it can be reviewed and challenged by suitably qualified people in the field, and so that other researchers can try to replicate it. Here is a history of the first entanglement experiments: https://scitechdaily.com/first-experimental-proof-that-quantum-entanglement-is-real/ You will see from this that entanglement experiments have been done from as early as the 1970s.

What I am still not sure about is the lattice vibration thing, i.e. phonons. The article I read mentioned absorption in the far IR, which shades off into the microwave region. I presume that in a large crystal there will be a huge range of states, the longer wavelength ones having a pretty low excitation energy. But whether microwaves can excite these seems a bit hazy so I’m guessing a bit. Regarding rotation, molecules in liquids can of course rotate, but each rotation will get interrupted by banging into neighbours so you end up with an incoherent mess of absorptions from all kinds of dipole-induced excitation that can’t really be said to due to any specific degree of freedom. What I am fairly sure of, though, is that the classical stretching and bending modes of covalent bonds need photons of IR frequency to stimulate them.

Yep, I don't use it much for defrosting, except things like soup where you get it started and then tip into a pan to heat through. Interestingly I once bought some frozen quails stuffed with foie gras at Picard, the frozen food chain in France. These they recommended you cook in a pan from frozen! By the time the outside is golden and the quail is cooked, the foie gras in the centre is nicely defrosted, without getting too hot and all melting out! They were in fact delicious. Also bought some frozen Burgundy snails, to be cooked in the oven on the same principle. Only the French............. Getting them back from France before they defrosted was the challenge. Possible if bought at Calais with a cool box and you jump on the shuttle. Not feasible now that we go on the ferry from St Malo (8hr crossing).

I'd like to experiment with an ice cube. As that is only frozen water, in theory it should only absorb a few very low-lying lattice vibrational excitations. But I imagine once it starts to melt it will go a lot faster.

I've been looking into this a bit today. It seems that in the liquid phase, pure rotations of water are quenched by the transient weak intermolecular bonding, but a broad band of microwave absorption is still present due to the breaking and forming of these weak bonds. Also it is not just water that absorbs, since other polar molecules can also be affected by the radiation. I imagine this is important in defrosting food, since molecules in ice itself will not be able to absorb, as they are bound in fixed positions. However, there may be lattice vibrations that are low-lying enough to be excited. So it's actually quite complicated, apparently. I have found, the hard way, that some crockery can heat up very rapidly in the microwave oven, to the point of cracking the glaze, whereas other (white) crockery stays cold. I suspect some of the dyes in coloured glazes may absorb, or something.

I think it will be rotation. You would need IR to excite stretching and bending vibrational modes, surely?

No I have never heard this ballocks. But then I bought my first microwave oven decades after leaving university, so I would have been fairly impervious to such myths.

OK thanks for running up the Jolly Roger. Now we know what we are dealing with. Once again the Galileo Gambit proves to be an accurate litmus test. If we ever have a thread on QAnon, we'll look forward to your contribution with great interest 😄.