exchemist

Quora is a lousy reference source to rely on, and adopting such a snooty tone won't win you any friends, but I now agree you were right about the principle of this - and I was was initially wrong. So I've learnt something. However the notion that neolithic people actually floated megaliths in mercury is still outlandish, for the reasons given in this thread.

Oh, my commiserations. Hope it goes well and they get it all out. I dimly remember a derivation of Archimedes' principle at school, based on calculating the upthrust, from pressure at a point at given depth, due to a column of liquid above, multiplied by the area in cross-section, parallel to the surface, of the object to be floated. This gives you a force equal to the weight of fluid occupied by the object. So I think all you need is a column of fluid of sufficient depth to make a "hole" that it big enough. It's the hole that does it, rather than the fluid that would be in it.

According to my reading, it seems the torsion pendulum was used to detect the thrust allegedly produced from this RF resonant cavity thingie. I recall that torsion pendulums have been used in determinations of big G, so are known to be capable of responding to very small forces. So now it makes sense - even if the physics doesn't........

I initially thought this, but I now think it is wrong. One has to consider carefully what "displace" means in this context. It means the object to be floated has to occupy a volume below the surface of the fluid which, if it were filled with the fluid, would have a weight equal to its own weight. It does not mean you have to have that volume of fluid present initially and then physically move it out of the way. The upthrust required to float the object results from the pressure exerted at depth. So it results from the height of the column of fluid exerting the pressure, integrated over the dimensions of the object. (Hg has a density of 13.6, by the way - a number familiar to anyone who has worked with manometers 😉.)

What is a "low thrust torsion pendulum"? Torsion pendulum I understand, but "thrust"?

Yes I think you are right. So long as the mercury rises up the side of the stone enough that the volume occupied by the stone below the surface is that which, if filled with mercury, would be equal to its mass, then it will start to float.

Sorry, I meant 60 cubic metres, i.e. 60, 000 litres.

Yes, cinnabar has been used for thousands of years as a pigment. What evidence is there of mercury metal being produced, at the scale of hundreds of litres, by the people that built megalithic monuments? That's crap - as in fact one of the respondents in that Quora thread quickly points out. Floating indeed requires displacing an equivalent mass of the object. So a 20t megalith needs >20t of Hg to float it. It is true that the density of , say, sandstone, is about 2.5 whereas that of Hg is 13.6, so Hg can float a volume of sandstone about 6 times its volume. But for a 20t stone that is still more than 3000litres of Hg. And your 800t stone will need about 60t of Hg to make it float.

I hope you are not imagining that Neolithic people had access to hundreds of litres of liquid mercury. That would be quite mad.

Very sound advice.

Could be helpful. Ammonia, being alkaline, might promote the hydrolysis reaction. But I notice that these "use and care" guidelines include a section on dealing with stains from dyes, which advise the user to, er, consult the use and care guidelines. So that's effing helpful, isn't it?🙄

Yes it seems to be the same as malachite green. (The name apparently comes from the colour- it’s an aniline dye: nothing to do with actual malachite, which is copper carbonate). You may find a bleach will add chlorine across one of the double bonds and break up the conjugated system responsible for the colour. I also see that this stuff can hydrolyse to a compound containing an alcohol group that does not have the colour. Alkaline hydrolysis in the presence of cationic surfactants seems to be one route. You might try oven cleaner. But do just one spot first in case it makes matters worse. Or it may just fade with time and routine cleaning.

No. E=mc² is just a special case of the full formula: E² = (mc²)² + p²c², p being momentum and m the rest mass, repeat rest mass. In the case of objects at rest relative to the observer that reduces to E=mc², as p is zero in such cases. In the case of light, that is obviously untrue. As photons have zero rest mass, you get E=pc. De Broglie's relation tells you that p=h/λ, so E= hc/λ , but since c=νλ, i.e. c/λ=ν, then voila, E=hν, Planck's relation.

If he doesn't, we may have to resort to the Telegraph.

That doesn't make a lot of sense. E=mc² returns a result of zero for a massless entity like a photon. You need the full formula including momentum, which for a massless entity reduces to E=pc, which in turn, via de Broglie's relation, gives you Planck's formula E=hν. More fundamentally, "light is energy" is just wrong. Energy is one of many properties of light. You seem to have watched too much Star Trek.😀

Bagasse is already used to provide power to run the sugar mill, with excess sold to the electricity grid. https://en.wikipedia.org/wiki/Bagasse.

If our poster is being consistent, he or she won't even see your response! (I'd have thought that posting on a discussion forum, with the express intent of not reading or reacting to responses, defeats the goal of the forum and should probably be treated as spamming. But perhaps I'm being harsh.)

It could be a uric acid crystal. Here's a picture I found of some on the internet: To me, your picture does not look biological, but more likely chemical. But I am prejudiced, of course.😀

Can you provide a source for these reports you speak of? I've never heard of this before.

Oh I don't know that scam. I must look out for it. But people are naïve. Several quite educated people I know think these Brita water filters must be good because you see a few black particles in the water reservoir at the top. In fact that's just a bit of the activated carbon filtration material that has escaped: they really work mainly by ion exchange but use carbon to trap chlorine etc. (I use one because it makes better tea, with less insoluble tannin deposit in the cups and teapot).

This all sounds a bit hysterical. We most certainly are not "assaulted by thousands of deadly chemicals" every day. If we were, we would be, er, dead. Yet life expectancy continues to rise in the developed world. That would not be happening if what you claim were true. So it's obvious there is no "chronic onslaught" on our bodies- or not one our bodies are not coping with, for the most part. There are some artificial substances around, e.g. endocrine disruptors, where there seems to be a case for reducing our levels of exposure, and there have of course been some scandals in the past. We learn more every day, but it is quite wrong to talk in such apocalyptic terms. No. If you want to know more about ageing, I suggest reading a bit about telomeres: https://en.wikipedia.org/wiki/Telomere#Association_with_aging Forget "toxins". That is mostly health woo for the gullible.

There can be, obviously, and these cause what we call "poisoning". But by and large these are specific agents, not generally encountered in normal life by most people.

It seems to me the whole idea of "toxins" building up in the body is a bit bogus. It's a term used almost exclusively by people trying to peddle health gimmicks, and not by health professionals, so far as I can see. There are a few real toxins, I suppose, such as lead or mercury, that can be picked up from some polluted foods or environments, and you can get poisoned by substances such as alcohol or drugs, but these aside I don't think it's in general a very helpful idea. Your liver converts most substances capable of causing damage into forms that can be excreted normally via the kidneys or bowel. Drink plenty and eat healthily and let those excretion systems handle it.

I understand it could shed light (haha) on dark matter. If it's confirmed and has the right mass, or something, ........................

Yes we all suffer, Ducky. I do most earnestly say unto thee: "Get thee gone, thou facetious timewaster".😁