exchemist

No and yes, respectively. First, no we can't explain, because the order* in nature just is, as far as science is concerned. And then yes, we can explain why we can't explain, because science does not pretend to be able to answer every question it is possible to dream up. Science limits itself to theories (that is to say, models) of nature that can be tested by observation. That requirement imposes limits on what science can model. In fact the refusal of science to dream up answers to questions that can't be validated by observation is what gives it its reliability and explanatory power. This is in contrast to some other systems of thought, such as metaphysics, that indulge in unverifiable theories. * This order is sometimes called referred to as the "laws" of nature, though actually these "laws" are merely man-made descriptions of the order, as we perceive it.

No, we do not define liquids by the quantity that we have. You can characterise water, or petrol, say, perfectly well without any reference to the quantity you are talking about. The same is true for other things, e.g. sheep. The definition of sheep does not require any information about the number of them that someone may have. Quantity or volume information is generally not intrinsic to an entity.

One a point of detail it is untrue that something must have mass to interact with something else. Something can be a field for example, as with photons. But more fundamentally, you seem to assume one can identify one piece of nothing as distinct from another piece, such that one can speak of one portion of nothing "replacing" other nothing. But that's rather silly, isn't it?

Indeed, but worth a look, in view of the numbers reporting long Covid.

There do seem to be some indications it may help long Covid: https://3ca26cd7-266e-4609-b25f-6f3d1497c4cf.filesusr.com/ugd/8bd4fe_a338597f76bf4279a851a7a4cb0e0a74.pdf But indeed studies on long Covid have not had much time to report, as yet.

I agree with @chenbeierthat you need to learn at school. There is not a lot of point in just starting practical work if you don't really understand what you are doing. Having said that, it is fun to do simple things at home to supplement what you learn at school. Learning about acids and bases is a good starting point, with immediate application domestically. (Even little things like when you wash out a bowl that has had red fruit in it, the colour changes from red to purple, if you live in a hard water area, or how baking powder, or oven cleaner, works.). A bit of electrochemistry can also be fun. You can make a battery from copper and zinc rods and a lemon, or a potato. With a low voltage DC electricity supply, e.g. from a train set, you can electrolyse various solutions and see what you get. I would also recommend that you read up a bit about the types of chemical bonding before you start anything. You need to understand the difference between ionic and covalent bonding, and between molecules and giant structures, before you can get vary far. And you ought to have a good look at the Periodic Table and see where the various chemical elements that you come across appear and what sort of properties they have.

Yes but out of 23, only 3 have gone to hospital with it. My 93 year old father got Covid at his nursing home after being vaccinated, too. But he had no fever, was just rather breathless for a week (no oxygen needed) and lost his appetite, and then made a full recovery. UK experience with the Delta variant is that the vaccines are effective at preventing serious disease, provided you have had both shots. This finding seems to be based on the rates of hospital admission since the Delta variant started to spread. Collecting data on whether vaccines prevent a person testing +ve is harder to obtain. I have not seen any numbers on that. The people in nursing homes are very fragile and their immune systems are weak. It is not surprising that they can catch the virus after being vaccinated. What matters is how ill they get. The vaccines do seem to help, considerably, with this.

If you had a South pole facing inward all the way round, then there would be no reason for a force to be produced that was not purely radial. So there would be no rotation.

It would generate energy, yes, but very little. What this device would do is displace a volume of water equal to the area of the pipe x the tidal range, once every 12hrs, so it would be a sort of very slow pump. To extract energy from the tides, you are far better off to use a place where a natural restriction, say the entrance to a bay, causes a significant tidal current and then use a turbine of some kind. That way, you exploit the tidal displacement of an entire bay's worth of water volume every cycle.

It seems to me a lot of this is old gnus.

OK, I see what you are saying, but if that were a valid explanation for the cosmological red shift, then presumably GR would be false and would predict results contrary to observation in other respects. Is that the case? Or can you somehow preserve GR AND this idea at the same time?

Re your last line, I think you may be confusing motion through space with expansion of the metric.

As far as I'm aware, we don't have a theory for that. As quarks are the most elementary unit of matter we know of, I doubt that we have anything on which to base any speculations as to whether or not they might be decomposable into something "more" fundamental. Though I'd be interested if any physicists have anything to add on that.

People theorise about "quark matter", I think, viz. a form of degenerate matter in which neutrons lose their identity and one has just quarks. But I know nothing about this. I gather we don't know enough about the strong force to model it very well.

You mean, what would we see if the laws of physics were not what they are? Surely that would depend on what they were instead, wouldn't it?

Energy is a property of a physical system of some sort. It is not "stuff": you can't have a jug of energy. So it becomes pretty hard to see how a singularity can have energy. It would have to be a system, and that would prevent it being a singularity.

I have not altered the meaning of what you wrote in any way. Whereas your cutting the part of my sentence which actually already addresses the point you go on to make, does alter its meaning.

Do you really think nobody would notice this "resource consumption" and take steps to limit it?

My actual sentence, part of which you have snipped out of the whole, thereby altering its meaning, was : " If the foetus has the normal complement of chromosomes and the mother has no problems in the pregnancy, it would seem there are no issues for the child, once it is born. " Down's syndrome involves an extra copy of all or part of chromosome 21.

All these issues seem to relate either to chromosomal abnormalities or to the process of pregnancy itself. If the foetus has the normal complement of chromosomes and the mother has no problems in the pregnancy, it would seem there are no issues for the child, once it is born.

Well yes, sure, if it is literally zero, but equally one can say density has no physical meaning if one has a zero-sized lump of material. What I suppose I mean is it that has physical meaning if instead one considers, let us say, an arbitrarily small volume of space close to the nucleus. What I'm rather more interested in, though, as I don't have the physics to know the answer to this, and I hope you might, is whether one can legitimately speak of an s-electron passing through the nucleus. I am not sure whether any of the interactions operating in the nucleus would prohibit this. Do you know?

I'm not sure I agree. It seems to me that the concentration of a dissolved chemical substance, or the strength of a magnetic field - or indeed the density of a material - has a physical meaning, regardless of what volume one considers.

Yes, I've got Roslin's book. What you say is trivially true, if your 0.001th percentile does indeed generate waste exponentially. But that nicely illustrates how naive (a polite way of saying "wrong") it is to model just about anything on the basis of a pure exponential - a point Roslin makes repeatedly. Nothing works like that. In the case of resource consumption, it is obvious that as a resource becomes more scarce, it becomes more costly and the incentive to substitute it with something else - or to stop the activity entirely- grows. So very quickly you get a departure from exponential behaviour. In the case of fossil fuel consumption, we do not see anything like exponential growth. We are still seeing growth, true, but it is linear or plateauing. So please put aside these exponential extrapolations. They almost invariably give wrong predictions. Just about their only use is to show people what would happen if nothing were done to prevent a runaway exponential.

Isn't that just tantamount to saying that a sphere of zero radius contains zero volume, so the chance of the electron being there is zero, the non-zero probability density function notwithstanding?

Bitcoin is just the latest IT fad, followed by a handful of nerdy and greedy people. It already looks doomed, because of its absurd energy consumption, cf. the recent reverse ferret by Elon Musk (now that he has made a tidy profit, no doubt). If Bitcoin doesn't fix this, it will get shut down. By governments. Human society has lots of ways of preventing runaway exponentials. Population growth is another. All the indications are it will stabilise, because as people get more prosperous they delay having children and want to focus more attention on a small number of them. More and more countries are now worrying about ageing or even falling populations, China included. Climate change and pollution are far more pressing concerns than bloody bitcoin*. * Once memorably described by Warren Buffet as "rat poison, squared".