sethoflagos

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?

You're effectively claiming the ability to extract useful work from a system at thermal equilibrium. Not sure there's anywhere to go from here.

Just to emphasise this crucial point, consider the major introgression of 'alien' DNA the ancestors of some of us experienced in the not too distant past. Yet the vast majority of our genome has been swept clean of neanderthal alleles (the so-called neanderthal deserts). This example is far from the picture of small random mutations slowly accumulating over time. And yet the end result is just what Darwin would have predicted. We retained useful alleles, particularly those helpful to climate adaptation and immune responses, and lost those those that didn't sit well with the core sapiens 'team' of genes. It undoubtedly influenced the speed of evolution, but the fundamental principle of evolution by natural selection remained unchallenged. As we're in the Speculations section, I might add that I'm inclined to the view that evolution by natural selection is an inevitable process driven by differential efficiencies in the utilisation of energy flow through a system. The detailed mechanics of genetics then becomes more of a consequential effect than a prime.cause.

He wouldn't be. Just faster than the light heading 'in his direction' was receding from the event horizon.

Does the light need to be travelling in the outward direction? If the infalling observer is falling faster than the wavefronts are receding, he catches up with them doesn't he?

The detailed mechanics of aerial design are way beyond my pay grade, but you seem to be making two distinctions here that I would be wary of: Until it is. Can you say this when the received phonons are indistinguishable from the sea of thermal phonons flooding the lattice of the receiving aerial? Cooling is thermodynamically difficult. I'd be reluctant to use the word in place of "not getting quite as warm as you might otherwise expect". Revisiting Kirchoff's Law briefly, there are some useful bits of information to be had from Electromagnetic Reciprocity. This caught my eye:

The bottom line here is Kirchoff's Law of Thermal Radiation which is often expressed as: If this were not true then there could be spontaneous nett heat flow from a cool body to a hotter one which simply doesn't happen. However, the proviso 'in thermal equilibrium' is key since 'arbitrary bodies' can have widely different emissivities at different wavelengths corresponding to different equilibrium temperatures. This is where the misunderstandings arise. Taking an arbitrary example quote from https://en.wikipedia.org/wiki/Emissivity Here the absorptivity is with reference to thermal equilibrium radiation at the surface temperature of the sun, whereas the emissivity is with reference to local thermal equilibrium in the vicinity of the collectors. The collectors are NOT in thermal equilibrium with the surface of the sun. Without the temperature difference, there would be no loophole to exploit. Okay so far. But note that emission by the antennae is NOT independent of the temperature of the antennae, The receiver does not reradiate incident solar radiation because it is not at the same equilibrium temperature. Therefore there is an asymmetry between absorption and emission that can be exploited. But refer to the relevant paragraph in https://en.wikipedia.org/wiki/Optical_rectenna The proposal neglects to consider the equivalence of absorptivity and emissivity at thermal equilibrium. So it falls foul of Kirchoff's Law, and by logical extension, the 2nd Law of Thermodynamics.

As I understand it, the theorical maximum efficiency from a 2nd Law point of view is 1 minus the temperature ratio of absorber over emitter. This yields something like 85% for solar spectrum conversion. Trying to convert near ambient spectrum IR would yield zilch I suspect as the antenna would be emitting about as much as it absorbed.

Imagine the current generated is used to charge a battery. Losses are generated by the required electrode overpotentials and internal Ohmic resistance of the cell resulting in radiation of waste heat to the environment. An overall picture of the thermodynamics can be found here. Closely related is Thermodynamic bounds on Work Extraction from Photocells and Photosynthesis which connected a lot of loose strings for me at least. Attached. Well worth a read imho. Photocells and Photosyntesis.pdf

Given that current generation PAC-2/3 interception missiles can top Mach 4, their speed deficit against say Avangard and Starry Sky-2 hypersonic glide vehicles is perhaps less of a challenge than keeping track of these highly manoeuvrable devices as they actively evade defence systems. That they achieve their impressive success rates via direct kinetic impact (rather than nearby fragmentation) I find quite staggering. Perhaps the real test will come with the future deployment of the BrahMos II Russian/Indian scram jet powered hypersonic cruise missile which will be capable of Mach 8-ish.

Just running with Weinreich's quip about the difference between a language and a dialect (https://en.wikipedia.org/wiki/A_language_is_a_dialect_with_an_army_and_navy).

AFAIK they never controlled a Navy, so I guess so.

We call it 'the universe' We call it 'space'. The pressure is <10-6 Pascals which is a near-perfect vacuum by earthly standards Mott-Gurney shrapnel distributions apply to this sort of 'big bang' The uniform shrapnel distribution we see on the larger scale is more suggestive of free gas expansion. ie there wasn't any shell casing involved. Photons emitted from a uniform shrapnel distribution? Do you think photons emitted by the shrapnel can only travel in the same direction as the shrapnel?

You can recycle all of it back into 'useful energy' in principle if you have a handy heat sink at absolute zero and lots of time to realise near-reversible thermodynamic processes. Trouble is the 'ifs'. They tend to cost a lot of capital. y

To emphasise this point, the Kelvin was redefined in May 2019 as: ... though perhaps the wikipedia article should clarify that it's strictly one degree of freedom of thermal energy change rather than the total change.

Except for your tardis.

You miss my point entirely. A precambrian rabbit would predate anything we believe remotely capable of giving birth to the first rabbit by half a billion years. 'Our history' as we understand it supports a pretty clear picture of the growth of the tree of life supported by millions of well-documented data points with not one single notable exception. If subterfuge and misidentification etc. could be ruled out, we are left having to explain the existence of a genuinely identified item not of its rightful time. For those seeking evidence of time travel, anachronistic artefacts like precambrian rabbits (or 1st Dynasty Tricorders etc) are precisely the sort of hard evidence they would be looking for.

To paraphrase JBS Haldane (albeit in a slightly different context)

I'm not sure you fully appreciate: a) how impossible your question is to answer in the absence of any information regarding the amount and composition of what you are attempting to mix. b) how technically deep the answer you seek may be even given full disclosure of what you are attempting to do. I've attached an open access brief summary paper 'A General Review of the Current Development of Mechanically Agitated Vessels': Jaszczur & Mlynarczykowska, Processes, Aug. 2020 to give you an idea of the basics. It runs to 39 pages and references no less than 309 sources. (downloadable from https://www.mdpi.com/2227-9717/8/8/982) This is not a topic you can at all usefully summarise in a single forum post. The answers you seek will be in there somewhere, though not necessarily in an easily digested form. However, if you can narrow down the scope of your OP, one or other of us should be able to help clarify. processes-08-00982-v2.pdf

As a postscript for those who are interested in how deep the rabbits have dug this particular burrow. Replacing the Latin alphabet with a phonemic alternate more suited to the English language is not a new idea. The best known is perhaps the Shavian alphabet produced under the bequest of the playwright George Bernard Shaw. According to https://en.wikipedia.org/wiki/Shavian_alphabet 48 letters might sound a lot for an alphabet, but Shavian doesn't use capitalisations, so it's actually shorter than our standard orthography. Being phonemic, @studiot and I would use different spellings for 'bath': bib-are-thigh vs bib-ah-thigh for example. Another difference may be that I don't have a 'strut' vowel in my dialect so I would spell 'up' not as up-peep (which sounds somewhat illegal anyway), but as wool-peep. It would actually make for a very concise orthography. Standard written English is significantly more concise than most languages, but Shavian would further trim the character count of most texts by about 30% due mainly to the elimination of digraphs and clusters like 'ough' and 'ght'.

A nod's as good as a wink to a blind man 🤐

Thanks, @MigL. Matter of picking the correct wording in the main. Is the end of time a singularity? Have to sleep on that one. That and would we see a step change in CMBR intensity when it comes around for the second time? Do you mind if I ignore everything after 'but'? It's late and the rest is way off the point I was trying to make.