exchemist

I had to look up what this is about. I assume you mean this: https://en.wikipedia.org/wiki/Optoelectric_nuclear_battery But there seem also to be non-luminescent nuclear battery devices that convert the energy of radiation directly to electric current: https://en.wikipedia.org/wiki/Betavoltaic_device These would not need to rely on a phosphor coating and a solar cell. I don't know how the efficiencies would compare. But since the mass of tritium would be proportional to the pressure in the tube, I'm sure you must be right that tripling the pressure would triple the power output, provided the energy conversion system was not saturated by it.

Oh, OK, that's a pity. But surely someone must give you feedback, or how do you know what needs attention? But if you have no feedback then, if I were you, I would choose a couple of topics where I know I am not very strong, and maybe a couple of topics that really interest me, where I can go further, perhaps beyond the course syllabus, out of interest. It's important to find things that interest you in school work, rather than just being a slave to the exam machine. It's one way to help decide you what to study at university.

Ask your teachers. They should know the topics on which you are strong and those on which you are weak. Also, with a mathematical subject like physics, it is worth getting some practice at solving problems. If you are like my son, you may understand the topics and know the equations but not be very good at answering problems involving unfamiliar scenarios, or requiring multiple steps. A bit of practice can give you more confidence. Avoid a scattergun approach. Decide on a small handful of things to work on and do those, until you feel you have made tangible progress. Good luck.

What you do is deploy what is known as critical thinking. This can include elements such as: - relying on a range of widely trusted sources for your information about the world, - cross-checking information from unknown or questionable sources against more reliable ones, - considering the likelihood of what is being claimed, compared to your previous information about the entities involved, - considering the quality of the evidence there is for what is claimed, - considering the motivation of the source: any known biases, agendas, affiliations, etc. This is not an exhaustive list, but it gives you an idea of how sensible people go about evaluating information they encounter. It is often worth taking the time to think for a bit about these issues before deciding what to information to accept. It is also a good idea to make a mental reservation about something new and surprising, in case it subsequently turns out to have been in error. Conspiracy theorists - as a rule- do not do any of this. They make improbable assertions, attributing malign motives and presuming illicit power of whoever their target happens to be. When you apply the above discipline to most conspiracy theories, you rapidly realise they are bunk. Just occasionally one of them may turn out to survive this scrutiny. Then, and only then, is the time to take it seriously.

I think this idea - that the sum of gravitational, mass energy and other energy in the cosmos equates to zero - has been around for quite a long time. I seem to recall reading about it over ten years ago. The thing I always struggle to keep in mind is that energy is not an entity, but merely a property of a physical system of some kind. So if you have no system, there can't be any energy. Presumably in this model the physical system of the cosmos came into existence - somehow or other - with a net zero of energy, which then became divided between -ve gravitational energy and +ve energy in radiation, rest mass of sub-atomic QM entities such as quarks, etc. I'm not sure that applying the laws of thermodynamics back to the first instants of the cosmos is valid, though. My understanding of QM is that energy is only conserved on average, due to quantum uncertainty - of which I can imagine there might have been a lot in the beginning. Then again, I'm not sure we can even assume that any of the laws of nature were in operation! But no doubt there are better qualified people than I on this forum to comment on all this.

I had to look up the Armstrong Limit, so I've learnt something as a result of your post. So thanks for that. 🙂 But this limit is, specifically, the pressure at which water, not any other liquid, boils at 37C, which is the temperature of the human body. The relevance of the Armstrong Limit is solely to do with the survival of human beings at high altitude without a pressure suit. It does not tell you anything about other fluids, or about boiling at other temperatures. Also, you get no energy from something boiling. You have to put energy in, in order to make it boil, because the Latent Heat of Vaporisation has to be supplied to enable the change of state to occur. What will happen when a liquid subjected to low pressure boils is that the liquid will become colder than the surroundings, as it extracts the necessary Latent Heat input from its environment. So I'm afraid this idea won't work. The First Law of Thermodynamics tells you "there is no free lunch".

Excellent! I see this company does this sort of thing in general. Good for them - makes a change to treat your customers, or potential customers, as if they can think. Respect!

Cities are attractive, especially to young people, because of the variety they offer and the social life. If you are not sure yet what you want to spend your life doing, the city offers you the chance to try one thing and change if you find something better. Also it offers you the chance to meet more people like yourself, or more people who are very different, if that's what you are looking for. And it offers a variety of entertainment. Rural life, all too often, has very few types of job available, very few like-minded people to socialise with, and nowhere to go for fun. QED. Of course when you are older and settled, rural life may have much to commend it. You may have a family and have stopped going out for socialising, you may value the peace and quiet, fresh air and walking, etc. In the UK we find the older people often want to move out of the city when they retire: as they slow down, they look for a gentler pace of life. Not me, though. I'm staying in London.

I'm not entirely sure I follow all this. But as a rule city housing is expensive because the land it stands on is expensive, due to its location - in the city. People want to live in cities, so demand is high and prices rise in response. What your question comes down to, it seems to me, is why it is that people want so much to live in cities. It is partly the variety of jobs available - many of them well-paid - and partly the amenities of cities, I guess: the bars, cafes and restaurants, the entertainment, the night life, the culture (theatres, concert halls, museums, art galleries) etc. Small town and rural life is often thought dull by comparison, especially to the young - who may also be looking for partners and therefore want to be where there are lots of similar aged people in the same position. People have tended to move to the cites for such reasons for centuries. (The story of Dick Whittington relates to a mayor of London from the c.14th, I gather.) There are many newspaper articles at the moment speculating whether the advent of the internet and the pandemic may have changed the attractiveness of cities, since desk workers have learned how to work effectively remotely. But it seems to me that most of the reasons I have listed will still apply, even post-pandemic.

Your belief in purpose is not a scientific belief, so you won't get much help from asking about purpose in a science thread. What is the "purpose" of a shark? Or a mosquito? It makes little sense, scientifically, to ask such a question. There is no "evolutionary intention". Evolution favours traits that permit reproduction, and traits that do that will depend on the environment the organism is in. And that's about it, really. Religion may consider Mankind has a purpose, but this is not an idea that is supported by science. Not quite. Evolution preferentially selects features that give reproductive advantage. That is the driver of evolutionary change.

You must be joking. You look like a spammer to me.

Perhaps if you could explain a bit about the route that you have seen described as "associatively dissociative, we could suggest an alternative description that does not seem so self-contradictory. I tried googling this term in relation to fuel cells and could not find it. The closest thing I found was something about dissociative adsorption of oxygen.

Something in that. I recall reading an article about the psychology of conspiracy theorists which said it was a general mindset rather than a fixation on one topic. Believers in one thus tend to go in for many. It may the same with cold fusion: people who just want conventional science to be wrong, for reasons of their own, or who want there to be an easy source of energy - and they latch onto cold fusion. But it seems to be quite a little cottage industry, with groups all over the place, conferences, and even this "E-CAT" bloke Andrea Rossi (who I think may have actually done time for fraud) who has claimed for years to have a machine that exploits "LENR", and somehow dodges ever having to pony up and show the world it works. https://en.wikipedia.org/wiki/Andrea_Rossi_(entrepreneur)

What the article does not touch on is that cold fusion has spawned a "zombie science" that continues to this day. If you google LENR (for low energy nuclear reaction), you will get pages of references to groups, self-published papers and even conferences that continue to tend the flame of Fleischmann and Pons, in the hope of limitless cheap energy. It seems impossible to kill this off - and I suppose we should not worry too much. Time will eventually do that if, as seems certain, there is nothing in the idea. But I find myself wondering if it was always like this with dead ends in science, or whether the internet somehow artificially prolongs the life of dud ideas nowadays. P.S. I enjoyed the mixed metaphor about the exploding or, rather, not exploding, goose. 😊

You mean, neither claims to heal physical ailments, I presume. Yes, I think that's right. Or is that not what you mean?

I think a distinction can be drawn between religion and pseudoscience. Astrology and crystal healing are pseudoscience, in that they make claims about observable physical phenomena, based on theories for which there is no evidence and which conflict with science. Attacking pseudoscience is fair enough, I would say, for anyone with a scientific education. Religion, at least in its more reasonable manifestations, is something different from pseudoscience. It is mainly a guide for living one's life, inspired by stories and ideas that don't make testable physical claims. However one can certainly dismiss these ideas and stories, and anyone in a liberal democracy is free to do that. Your objection seems to be that figures who rely on the support of the wider public tend to refrain from ridiculing religion. That's a pragmatic choice they make, so as not to alienate believers. It is not forced on them. In fact, the same applies to pseudoscience, in that a politician who ridicules crystal-healing, or homeopathy, risks losing the crystal healers' vote or the homeopath vote. (I recall the elder Bush made the error of saying how much he disliked broccoli, causing consternation in his campaign that he had lost the broccoli farmers' vote!) So I don't really see that "fairness" comes into it.

Haven't we just had an economic crash, bigger than anything in the last 300 years? That seems to be what the papers have been telling us.

Thanks for the link to the paper, which satisfies my curiosity. Agree we should not pursue the topic of H bonds further here, interesting though I find it.

Yes, I agree, I don't think I would expect bore width to affect pitch. As I understand it, that will be a function of tube length, as you say. What the article I linked seems to say is that width affects the degree to which various harmonics are excited, which alters the character of the tone rather than its pitch.

Bloody hell, a gas radio! And it's not April 1st any more, either. I'll have to look that up!

There is an informative, though very long, article here about the physics of organ pipes that may be relevant: https://www.academia.edu/24411933/The_Physics_of_Organ_Pipes Buried in this is a bit about the effect of width of the pipe. It seems that a wide pipe is effective at resonating for the lower harmonics only, while a narrower one allows higher harmonics to resonate more and thus sounds brighter. So yes, a softer or mellower tone will be produced by a wider bore, but it may sound rather dull.

Most of the (electric) fridges I've seen have a water drain to remove condensation from the cold panel (evaporator). This is typically connected to an exterior evaporating trough at the back, warmed by the heat exchanger (condenser) that rejects the heat. It's not a lot of moisture, obviously, but there is a little. And there is certainly warmth. Perhaps it could be primarily an effect of warmth, combined with the natural damp in the walls, or something. P.S. On the subject of gas fridges, I remember someone's girlfriend being conned into thinking that, for caravans, one could have a gas television.😊

That table seems to agree with my understanding of the strength of H bonds, i.e. up to ~ 10kcal/mol or so. Did you ever find the organic chemistry example you were talking about, of a much stronger one?

Do you understand the principle of resonance structures, e.g. in benzene? Here is how it works: Now try to apply something similar to the structure you have been given. Can you do that?

That's interesting and I fully admit I am pretty rusty on a lot of this stuff. I had in mind as typical H bond strengths of the order of 5-10kcal/mol (showing my age). Can you give examples of much stronger ones?