exchemist

What is depicted in that drawing is not waves but a static field or potential.

Questions are fine. Nobody says don't ask questions, least of all Feynman. What he is saying is just don't expect nature to behave like classical mechanics, or to be easy to comprehend. Feynman's joke about going "somewhere else, where the rules are simpler, more aesthetically pleasing, more psychologically easy" (my emphasis) contains an important point. Nobody who has studied QM finds it easy to picture. The maths works, but the physical picture it conjures up is murky. At some level one has to accept that struggling to make a consistent physical picture of what is going on is not really possible. Anyway, to your original question, these entities are fuzzy so trying to apply classical electrostatics, when you can't define the distance of separation, is bound to have limitations.

Erm, this poster seems to be selling fake driving licence ID:

No, it would not follow they have structure. It just means they are fuzzy round the edges, like any quantum entity (uncertainty principle, again). There is no defined "size", just a matter of decreasing probability of interaction, the further from the classical path you get. (Look up "cross section"). The idea of these entities being pointlike particles with "an associated wave" is unhelpful. They are what they are and exhibit both wavelike and pointlike attributes according to circumstances. You need to think in terms of probabilities, not classical exact values. (For some purposes it can be easier to think of them as waves, which "collapse" to a point only when they interact - but that too can be misleading.) As Feynman said: "I'm naht gonna fake it, I'm naht gonna tell ya it's like a ball bearing on a spring, when it isn't."

Or bots. The list of “teaching staff” on the website has exclusively Spanish names. Probably someone has gone through the local phone book. Noteworthy too that the moment you click on anything you get a pop-up talking about money and offering a discount. That’s not what you see on any genuine university website.

OK in that case they must have enough extra energy to ionise positronium, then.

The contact number for this "university" is located in Tenerife, whereas its website implies it is in the United Kingdom. I think you may be pumping a scam.

Not at all. It leads us to think in terms of fields and waves. But another thing you need to bear in mind is that pair production in general does not lead to a pair that separates. They would be bound together by their mutual electrostatic attraction, cf. positronium: https://en.wikipedia.org/wiki/Positronium

You are not at liberty to decide for yourself that these entities behave as point particles during the interaction in question. If such an assumption leads to wrong outcomes then the assumption must be wrong, must it not? I am not a physicist but I know from quantum chemistry that the interaction between electrons in an atom and photons is not modelled in terms of point particles.

No. It is a quantum mechanical, wave particle entity, so it has some particle-like properties under some conditions and some wavelike properties under other conditions. You must know this, surely?

The photon isn't a pointlike particle.

Oops, sorry and sorry to @swansont - I must be getting senile. 😄

OK this sounds a bit confused. Ionisation of an atom requires an input of energy, because an electron has to be pulled out of the atom, against the electrostatic attraction of the positively charge nucleus. But what you seem to be concerned with the energy losses in the operation of fuels cells. That is another matter. It is to do with inefficiencies in the conversion of chemical potential energy into electricity. No conversion process is 100% efficient in practice. In fuel cells the theoretical output voltage cannot be obtained in practice due to some irreversible features of the process that occur when current is drawn. Irreversible processes involve entropy increase and that reduces thermodynamic efficiency. I don't know the ins and outs of fuel cell operation, though maybe someone else here does. For now the best I can so is give you a link that may give you an idea of the kinds of thing involved: https://www.fuelcellstore.com/blog-section/explanation-of-the-thermodynamics-behind-fuel-cell-and-electrolyzer-design

Your answer seems (a) irrelevant to the question asked and (b) does not seem to explain how the process you describe changes the wavelength, given that the light absorbed is the same wavelength as the light emitted unless certain other processes are also involved.

Sure, it might sometimes, but others on this forum have found instances where it is wrong or nonsensical. As @studiot says, it is language model. As such it is not well adapted for mathematical science. You asked if it is reliable, and the answer is evidently no it isn't.

No, north of the North Pole is not space. There is no north of the North Pole. The points of the compass relate to the surface of the Earth.

My understanding of the most popular model is that time itself only started at the big bang, i.e. there was no “before”.

Oh I don't know. I thought Martinique and la Réunion were pretty good when I visited. And my sister-in-law seems happy in New Caledonia, where she has lived for 30 years or more. But I have not lived in these places myself, admittedly.

You're a mug then, because it isn't. We've already had some threads discussing how unreliable it is for mathematical science.

What about Space X? Or Jeff Bezos's Bellend One? There is no bar to private companies getting into the business. The reason there are not more is the high cost and risk, which are easier for government to sustain than private companies, backed by commercial banks. And as it is NASA, ESA and the Russian and Chinese programmes compete to offer launches for satellites on a commercial basis, so not all their funding is from government by any means. But it's true that it is a freight rather than passenger business. There are obvious reasons for that. It's very expensive, the life support systems for people would add further cost. And what's the point? There's nowhere to go once you're up there.

To comment usefully on this we are going to need more than just pencil sketches, with no accompanying explanation. What is it that you have actually seen, and in what context? (I do hope it is not a YouTube video.)

And even that varies from ocean to ocean, hence all the markings on the Plimsoll Line on a ship's hull, showing the different limits to which it can be safely loaded:

The density of ice is lower than that of liquid water at the same temperature. Unlike most materials, ice expands upon freezing. Objects that are lower in density than the liquid in which they are immersed will tend to float in it. The reason it expands on freezing is because the molecules in the solid take up orientations that maximise the strength of hydrogen bonds between the molecules. This leads to a more "open" structure than in the liquid. The physics that governs whether and how an object floats is to do with the relative magnitude of the object's weight and the buoyancy force it experiences from the liquid. This is set out in what is known as Archimedes' Principle. There are details here: https://en.wikipedia.org/wiki/Archimedes'_principle

That may be a good strategy, as one of the issues not much discussed as yet is the need to rewire entire neighbourhoods to cope with the higher electricity demand, once most people have EVs. If people can generate at least a proportion themselves it could help a lot.

From what I have read, it is better to keep an old IC vehicle as long as you can, before trading it in for an EV, due to the large and unavoidable carbon footprint of manufacturing a new vehicle, of any type. But your next purchase, whenever it is necessary, should be an EV. The longer you can leave it , the greener the EV will be , since the renewable proportion of the electricity it consumes will grow as the years pass. Also the charging network will get better over time. I'm currently running a 19yr old petrol VW Golf, (the 1.4l one with both supercharger and turbocharger, which performs like a 2l but with much better fuel economy). It still works fine and does what I need it to do, so I intend to hang onto it for another year at least.