sethoflagos

Reasoning in the absence of supporting evidence is just wishful thinking.

Not explicitly.

Exactly. Can we now develop @exchemist's point and address whether the random quantum fluctuations of the vacuum state can perturb the momentum of a gas molecule?

I guess I can take a couple of negs here and there, but it would be nice to know the reason.

That's actually quite a big deal.

And thus the language of our noble ancestors lies dying in the no man's land of post-modernist chutzpah

Presumably this is consistent with a classical picture of momentum exchange in the interaction of a gas molecule and a photon. How about interaction with a random quantum fluctuation? Can the gas molecule 'leak' momentum into displacement of such 'virtual' particles? I'm really asking about phenomena distinct from the measurement problem. I can buy some fundamental uncertainty in the actual path taken. More, I'm trying to narrow it down from some kind of random walk to a spectrum of possible paths all of which are straight lines.

I've seen statements such as this kicking around for decades and always been troubled by a niggling doubt. I imagine that the phenomenon can be explained by normal electron scattering and tunnelling without invoking any deviation to conservation of momentum. But is that all there is to it? Is the momentum vector of a particle subject to variability due to, say, random quantum fluctuation in local field strength? This idea seems somewhat belied by the near point image my eyes can make of a distant star, but even so... My primary contextual interest is in the absolute deterministic nature of gas molecule trajectories between collisions - ie how 'straight' are their paths through free space.

Not here. Within the circles I move in, beer is the social brew of choice. Only to geordies who ask daft questions. More the chutzpah of those who believe their taste in tea is somehow superior to anybody else's. There is no universal 'perfect cuppa'. Just an individual's preference. The similarity of sugar cellars to salt cellars in many establishments has caused most of us to have conducted unplanned experiments with salty tea.

It does. Been recycling tepid tea that way for years.

It'd need a minute in the microwave otherwise you may as well be drinking bathwater.

Bless their little cotton socks! What do they miss out? The preheating the teapot bit, or the tea cosy to keep the heat in?

There's likely as much arsenic in the water you stew it in. See https://pubmed.ncbi.nlm.nih.gov/25526572/

Personally I take my tea strong, black and well stewed. The more astringent the better within reason. But it seems there are some folks who just can't get enough blandness into their lives. Salting tea sounds to me as doolally as decaf, but whatever floats your ⛵.

Do you imagine that 'billions' is an appropriate counting unit for, say, all the different possible permutations of the up to 40+ billion base pair sequences of DNA? (Try running 4^4^10 through your calculator to get an idea)

Ditto @Bufofrog. Could be something as simple as an unsuitable mattress. At least, that's my experience.

I mentioned it once in passing. It isn't a cornerstone of my argument. While grateful for your advice, I'm at a loss to see how it applies to the optical rectennas under discussion.

On reflection, I'm inclined to think that it's a bit of each. The salinity of the Hadean oceans would no doubt have reflected the mantle Na:K ratio which in turn is reflected in the Na:K estimated ratio of the solar system. So perhaps the similarity in current times isn't as much of a coincidence as I suggested in an earlier post. However, with the onset of plate techtonics in the mid-Archaean, the two following quotes, taken together indicate that both surface waters and their salt inventory are being continually recycled to and from the mantle: I guess the turnover time is at least oto 1 billion years so it's a very slow process and almost certainly not at equilibrium. But it is clear that there is some continuous limited exposure to mantle cation ratios that would act as a negative feedback loop tending to restore primitive values. Which leaves us with having to deal with why continental crust is so markedly different with a near unity Na:K mass ratio. Arguably so, but at constructive plate margins, there is no neighbouring granite for them to migrate to. Rather we have a fractionation process that might be roughly summarised as: 3 Peridotite => 1 Dunite + 2 (Gabbro + Basalt) Dunite is over 90% olivine, offers very limited hospitality to Na (maybe in some residual pyroxene) but as far as I can tell none to K. So most of the Na and all of the K plus the rest of the more volatile components creates a gabbro melt that ascends to fill the gap between the separating plates. At this point I wanted to give some indicative Na:K ratios for oceanic crust gabbro/basalt. Only to find lots of field data showing Na:K ratios up to 50+ for gabbro and 2 for basalt. The common understanding is that basalt is simply rapidly cooled gabbro. Clearly this is somewhat of a simplification. On the face of it, the fractionation process is not the unitary division I've just described, but some multistage fractionation process that preferentially shunts Na into the gabbro levels and K into the basalts. I'd be interested in your views on this. Anyway, it appears that we have the K concentrated in the upper basaltic levels of the oceanic crust, possibly in the form of a feldspathoid such as leucite, the Na evenly spread between the basalt and lower gabbro horizons within clinopyroxenes such as augite, and below the crust mantle boundary a zone of depleted cumulate dunite. At the other end of the conveyor hopefully the picture is a little clearer. As the old oceanic plate is subducted, it eventually reaches a region of high temperature, high pressure which (give or take a little controversy) is where it is converted to a highly metamorphosed rock type called eclogite, mainly comprising pyralspite garnet and a sodium rich clinopyroxene called omphacite. With the K being concentrated in the contact zone of the upper levels of the oceanic crust, and an incompatible mineral assemblage forming beneath it, the path for transport of the vast majority of it into the continental crust appears non-problematic. Na on the other hand has the option of joining with the K to progress upwards, or staying in situ within a compatible mineral assemblage. The nett result seems to be a roughly equal mass diffusion of sodium and potassium into the lower levels of continental crust. I basically have zilch documentary evidence to support the overall picture of this mass balance, but it makes some sort of sense to me and my researches haven't yet thrown up anything that cotradicts it significantly. Hope it helps. I'm not going to lose sleep over that 🙂

Sodium is relatively happy in some mafic minerals, particularly clinopyroxenes. I suspect potassium simply won't fit in that lattice. In a feldspar environment, the alkali metal hole is clearly big enough for potassium and maybe this gives a little more stability to the potassium version under most surface conditions. However relative weathering rates show a high pH and temperature sensitivity so perhaps there are multiple mechanisms at play.

@swansont's reference is dominated by the composition of the earth's mantle. This is indeed the ultimate source of sodium and potassium at the earth's surface, and the sodium:potassium ratio is strikingly similar to the marine ratio. However, I think this is coincidental. Except for odd cases such as a notable ocean bed exposure off the Cape Verde islands, surface waters and upper mantle rocks are not significantly in contact. Rather, there are a number of fractionation processes in the vicinity of the crust-mantle boundary that enrich the alkali metal content and deplete the mafic materials (Mg, Fe predominantly), starting with emplacement of basalt/gabbro at constructive plate margins and culminating with the granitisation of the base of the continental crust at destructive plate margins. Even this is quite a simplification as there are a number of other processes involved most of which are not fully understood, so I tend to take a first order engineering approximation of the mantle injecting granite into the continental crust. It's easier on my head and the overall mass balance still works. The concentration factors of 30 for sodium and 600-ish for potassium reflect their relative preferences for a granitic environment over a peridotite environment.

If this helps, the primary route for transport of sodium and potassium into the earth's crust from the mantle is via emplacement of granitic intrusions which occurs in roughly equal weight proportion. From https://en.wikipedia.org/wiki/Granite Chemical weathering of rock minerals follow the Goldich Dissolution Series This indicates that the potassium rich minerals (orthoclase, muscovite, biotite) are relatively resistant in comparison to sodium rich minerals (sodic plagioclase, some amphiboles and clinopyroxenes). By logical extension, sodium is over-represented in sea water and evaporites, whereas potassium is over-represented in detrital sands and sandstones.

Reckon so. I've seen somewhere that albite (sodium feldspar) weathers at 10 times the rate of orthoclase (potassium feldspar).

Excellent link! Cherry-picking one particularly apt paragraph:

We're pretty much aligned here, and I too am pushing the limits of my understanding of EM field behaviour. I was hoping that @swansont or someone else with expertise in this field would have picked up on my previous post and confirmed or otherwise the mental picture I have of this. But in the absence of such... I think it reasonable to picture the thermal energy of a metallic antenna as being largely contained in the motion of a 'gas' of the unbound electrons. If you can persuade a significant excess of these to move in a coordinated way in a particular direction then that yields an electrical current distinct from the thermal motion. However, I suspect that this requires the incoming radiation to be both directional and/or phase-coordinated. Thermal radiation from the sun satisfies the directionality requirement and I presume the higher frequency part of the spectrum may have sufficient 'kick' to push a few electrons across the junction gap of a diode which might explain the measurable current reported in that scenario. But ambient thermal radiation is omnidirectional and the individual photons are much weaker. Trying to extract energy from this scenario just sounds a little too Maxwell's Demonish for comfort. May be this picture is all wrong, but it at least tends towards consistency with the Kirchoff's Law/2nd Law objections I raised earlier.

I'm getting a picture here of transmitted photons perturbing the EM field of an antenna aligned with the source somewhat analogously to a steady trade wind generating oceanic waves. And just as the energy of oceanic waves can be harvested by an appropriate machine, the waves in the field of the antenna induce an alternating pd across the terminals of the antenna which can in turn be harvested. Is this analogy a useful one?