exchemist

Exactly. It's the state of preservation that is remarkable. From what I understand, it shows that the embryos of this species of dinosaur were folded up inside the egg in just the same way as modern birds. Which is interesting, but perhaps what one might have expected rather than not.

Yes, it is my understanding that the Casimir effect can be accounted for in terms of London (dispersion) forces between the plates. However I recall reading that the dispersion forces model is actually equivalent to the vacuum fluctuation model. I do not know any QED however, so I'm in no position to understand how this equivalence may arise. The common feature would seem to be the concept of random fluctuations, in the one case arising in the vacuum and in the other arising in the charge distribution of the electrons of the plates. If anyone here can shed more light on this I'd be interested.

Reflection certainly implies the matter in question must interact, i.e. be polarisable by, EM radiation. If it can be polarised by it, there will be some wavelength at which it will absorb and emit, won't there? And, if it reflects, wouldn't we observe reflected radiation.

I'm a bit lost. Surely if S is a surface area, then dF/dS is a pressure function rather than an energy, isn't it?

Expiry date won't make a difference, since neither oxidation nor bacterial action are likely to cause any more dangerous species to be formed when the item is burnt. But burning anything in an open hearth generates smoke - fine particulates, part-pyrolysed organic compounds etc - which tend to be damaging to the lungs and potentially carcinogenic. Here's a short article on the subject: https://www.barbecue-smoker-recipes.com/barbecue-smoke-dangers.html which mentions some of the chemical species that are troublesome. Of the particulates, it is the "PM 2.5" that are considered the most injurious to health. But if it's only a bit and you don't breathe the smoke then I doubt there is much to worry about.

Because when a QM entity is confined by a potential barrier, the wave function penetrates the barrier to some extent. The barrier can be thought of as "damping" the wave function progressively to zero. The lower the barrier, the further the wave function penetrates. If the barrier is also sufficiently thin, the wave function may not be damped to zero by the time it reaches the far side. In such a case, that represents a finite probability of detecting the QM entity outside the confining potential barrier.

Yes in the USA (and the EU) it seems 10ppb is the current maximun for drinking water: https://www.epa.gov/dwreginfo/drinking-water-arsenic-rule-history One of the problems in modern life is that our ability to detect chemical species is now so great that we can scare ourselves by finding trace levels of all sorts of things everywhere. Even if there is "no safe level", that does not mean you run a significant risk at very low levels. It just means nobody has found a level at which they can confidently claim there is zero risk. Life is not risk-free. By the way, if you drink bottled water you may still find it has arsenic: https://southernscientificireland.com/arsenic-in-bottled-water/ But I confess I do not much like the sound of 500ppb. Anything over 50ppb would seem to be a bad idea.

Yep.

The spin angular momentum is an intrinsic property with a fixed value. Orbital angular momentum is not. I'm not a relativity expert but I would not have thought that linear relative motion would affect the observed angular momentum.

From what I can see the main risk is via ingestion. If you live in the developed world, I doubt any approved water supply would have enough that taking showers or baths would be likely to do you any harm, and the amount left behind on dry dishes would be pretty minimal I should have thought. But what level of As are you talking about?

So you say. But that is exactly what a malware spammer would say too, isn't it? Why would I believe you, when I have no idea who you are? As several others have now also said, post relevant text directly here if you want to discuss something. Apart form the malware question It is bad form, and a bit lazy, to send readers off-site, without providing at least the gist of the issue in your own words here, first.

There is not much point people here reciting basic information that is widely available on-line. Suggest reading, say, the Wiki article and then asking any questions you have arising from that. But I must say this is a very odd question for someone who teaches astronomy to be asking.

No one is going to click on an unknown link with potential malware. If you want a response, I suggest you copy and paste the relevant sections into a post on this forum.

Yes indeed. An atom is of the order of 0.1 nanometres in radius. A water molecule is about 0.3nm across. So in a cubic nanometre, which is 10⁻⁹ of a cubic micron, there are about 3 molecules on a side, i.e. 30 molecules in the cube. (So that checks out with my arithmetic above, phew!)

The key to questions like this one is Avogadro's Number, which is the number of carbon atoms in 12g of carbon, or, say, the number of molecules in 18g of water. This number is roughly 6 x 10²³, (6 followed by 23 zeros, if you write it out longhand). One can use this to work through your aerosol droplet example. 18g of water has a volume of 18cm³ (because the density of water is 1 in these units). There are a million (10⁶) cm³ in a cubic metre, so this becomes 1.8 x 10⁻⁵ m³. Let's pretend your aerosol droplet is a cube rather than pear-shaped, as the error in doing this is not great and it makes the calculation simpler. A cube with a side of 10μ has a volume of (10⁻⁶)³ = 10⁻¹⁸ m³. So it will contain 10⁻¹⁸/1.8 x 10⁻⁵ ~ 5.5 x 10⁻¹⁴ of Avogadro's number of molecules, so the number of molecules will be 5.5 x 10⁻¹⁴ x 6 x 10²³ which is about 3.3 x 10¹⁰. This is 33 billion molecules. That's if I have not made any blunders in my arithmetic (which is easy to do with all these powers of ten, admittedly). Each molecule of water has 3 atoms in it: 2 of hydrogen and 1 of oxygen. So the number of atoms would be of the order of 100 billion. I'm not sure where your 1.3 million comes from but it looks far too small to to me. You can do similar exercises for other small volumes of other materials, but you need to know the molecular weight (molar mass) of the material and its density.

I was always taught the best thing is to clear it off the ground before anything melts - which seems to be what you have been doing.

Something odd about the linked article. It claims half a gallon of fluid can gather in the head: "SANS is not a problem on Earth, where gravity pulls fluids down into the body each time a person gets out of bed. In space, the lack of gravity prevents this daily unloading process, allowing more than half a gallon of body fluids to gather in the head and apply pressure to the eyeball." What can this mean? There is no way that any significant extra volume of fluid can get into someone's head, given the rigidity of the skull, surely?

Barely. With deuterium you can see some differences from regular hydrogen but that's because the mass is doubled. This affects things like some spectroscopic properties and reaction rates a bit. With heavier elements to a first approximation they don't differ.

Hmm, I'm afraid this doesn't seem to mean very much. "All cause is relative to infinite effect"? Eh? And what is an "infinite cause", when it's at home? This sort of guff reminds me of Chopraesque woo. Whatever it is you are asserting, it seems unmoored in evidence and nothing to do with science.

He's right about the breeder blanket, according to the link I included in my post of 10th Dec. This is proposed, in the DEMO reactor, to run at 300-500C, be cooled by helium and thus provide the heat for steam-raising. So whatever it is made of it must be able to convert the energy of most of the neutrons to heat. It will have some Li in it, for breeding more tritium. ITER has a blanket, though it won't breed and won't generate power: https://www.iter.org/mach/Blanket

Really? It seemed to be the opposite: you have not seen China and yet you do believe it exists. But OK, if seeing is not believing, I'm not sure how that can be applied to the discussion in this thread. The singularity that can be extrapolated from the Big Bang theory is only a conjecture anyway, based on physics that we have reason to think may not have applied in that regime. It is not supported by any evidence. So seeing does not come into it. And nor does believing.

So what, though? The subtleties of nature are not anything like determining the existence of a country. If you had been a Newtonian physicist, you would have used logic and evidence to "determine" that the kinetic energy of a moving body is 1/2 mv². And you would, a couple of centuries later, have been shown that that was not the case. If you had been J J Thomson, at the turn of the c.20th, you would have used logic and evidence to "determine" that the atom had a structure like that of a plum pudding - only to find out a decade or so later, that that was entirely misconceived. Science has been burnt often enough in history by such changes in understanding that it avoids speaking of truth or reality where a theory is concerned, but only of models that predict the behaviour of nature. These models aim, in that limited sense, to represent physical reality, but they are potentially imperfect, not definitive and always subject to change in the light of new evidence. So it's not really at all like whether a country exists or not.

There may be some misunderstanding here. @studiot is talking about the UK, where I am also located. So the US FDA is not relevant. Here, we have a National Health Service. If someone were to suffer an anaphylactic reaction, after going home from a vaccination, any medical treatment they received would come from the NHS, who would rapidly ascertain that the patient had just had a Covid vaccination. So there is no doubt that the NHS, having administered tens of millions of vaccinations, would know by now if such events were significant. We do know, from the campaign, about various rare side effects of the different vaccines. Everyone has been on the lookout for them and has been reporting them. There is no way that a serious and dramatic effect like anaphylaxis would somehow have been missed.

There seems to be evidence that choosing a booster different from your previous shots widens your scope of protection. Omicron seems to be crowding out delta in the UK, at great speed. What I'm not clear about is whether this means delta will die out. I suppose that if omicron confers immunity against delta that would be expected: omicron would tend to get to a person first and then they would be less likely to catch delta later. But if omicron does not confer significant immunity against delta, I don't see why omicron's presence would stop delta proliferating as well. Maybe someone more knowledgeable can comment.

Does common sense also tell you to ignore all the evidence that contradicts your hypothesis, as you seem intent on doing? And how does your BA in Engineering help you account for why, if, as you suggest, Pangaea is the remnant of a moon, it is only the outer shell that is splattered on the surface of the Earth? Why would an outer shell detach and be preserved, and what happened to all the rock inside? Or do you perhaps think this moon was hollow? Lastly, why pose a question on a science forum, when you are convinced you already know the answer and are not prepared to consider any objections to your hypothesis?