Bender

So QM cannot explain magnetism after all. My example of the deflecting beam was poorly worded. I was referring to the mechanical deformation of a structure. My point is: I can explain the working of EM devices perfectly without QM, just like I can explain the motion of a thrown ball or a rainbow without QM. Every scientific model has elements that just have to be accepted, even QM.

Does QM explain why an electron has a charge or a magnetic moment? What about the deflection of a beam? Do I need QM to understand that? After all, all mechanical forces are basically QM effects.

Doubling the depth is probably going to more than double the required length, since evaporation will only be effective at the surface.

Did you just imply that children sacrificed their own children? Probably. Definitely off topic here

To be honest, based on other posts I've seen from you, I assumed you did not mean it the way I interpreted it. However the notion exists among many religious people and annoys me enough to make my point anyway. I disagree that a couple of stories is going to matter much. Plenty of stories get written all the time, and plenty get forgotten. Most contain some morality element, but I would suggest morality comes first and the story is but a means to convey the message. Genesis eg is of dubious worth. I tried reading it once, but didn't get very far. It is boring and very poorly written by todays literary standards. The moral message is also highly questionable: "obey me blindly and without thought, or I will punish you and all your posterity horribly."

It took taking a step back from religion to think maybe women are equal to men. Even buddhism is far from perfect in this regard, depending on the flavour. The notion that religious myths are required for morality is arrogant, ignorant, and slightly offensive.

Any relevant formula I can throw at you is going to produce very wild guesses at best. The air in between the soil particles will probably be saturated quite quickly, and natural convection will take a long time to evacuate a significant amount of water. You could do a test with a small amount of soil and see how deep under the surface the soil has dried. I assume that under that dept, there will be hardly any change in humidity at all. You could at the very least make an energy estimate. How much water do you need to evaporate, and what is the maximum power you can put into heating. At the very least, that should give you a lower boundary for the total length. But for any reliable estimates, I would advice a test with one heap of soil which you can mix every day and track the humidity. Alternatively, if there are existing facilities nearby: visit and copy/extrapolate.

Torsion. Eg two geodesics (locally) describing (part of) a double helix. If that is possible, a bowl of water in between those geodesics could have a flat surface, even though its orientation with respect to the distant stars is changing.

Can some timelike geodesics "twist" with respect to others?

Isn't it just a matter of how easy an addition would be combined with the effect on fitness? There is eg a wide variety in the number of legs in centipedes, sometimes even between individuals of the same species. This can be explained because the mechanism repeating the body sections could easily skip one or add another, without much effect on fitness. For a mamal, however, an extra limb has no straightforward attaching point and is almost exclusively ballast. An extra rib on the other hand has obvious positions to occur, and hardly any effect, so the genes linger on with little reason to increase or decrease in spread.

To rephrase the question: can one portion of spacetime rotate with respect to another? Frame dragging to me seems to suggest the answer is yes, but I'm not familiar enough to be sure.

I don't think so. The equality sign in a "proper" equation has specific meaning. It eg shouldn't matter if you switch right and left (= is commutative ). This property is violated by both the chemical reaction and the computer language assignment.

1) it is not because you found a meaningless example that the ratio is meaningless in general. I could divide the length of my shoe laces by the time I brush my teeth, but that does not make length over time a meaningless ratio. 2) if someone is controlling a load with an actuator, the ratio of stationary energy consumption could be useful to determine whether it is cost effective to install a break instead of using the actuator to keep the load stationary. I admit that the power over torque ratio is probably more useful, and most likely not constant enough to be used at all. However, it is not because I cannot give a convincing example off the top of my head, that it can never have a meaning.

But for a moving lever, the ratio is the number of radians turned; not exactly meaningless. Radians is an interesting cause of screw-ups in dimensional analysis. The confusion with rotations has lead to countless errors.

So it is more a discussion about different uses of the = sign? I guess in chemistry, it can be used for a transition, and in programming it can be used as assignment. In my experience, chemists are less strict/pedantic about their notation than physicists or mathematicians. But I don't know whether that is general. I see no reason to lecture others for how they use symbols. Not necessarily. It can be useful as a dimensionless number in a specific case. Engineers regularly use similar numbers to describe the general behaviour of a system, especially in fluid dynamics. Also: changing the units in such a way that it stays dimensionless, does not change the value. List of examples I've also made my own to describe the stability behaviour of a generalised solenoid actuator.

If they are using the metric system, they will be using s, not sec. Anyway the equation is dimensionally consistent, because the conversion factor has dimensions. To return to the previous example, it occured to me that all chemical reactions are usually written with arrows. Eg Wikipedia a has dimensions. Its value changes according to its units. Also: dimensional analysis does not guarantee a result which makes sense.

It would work better with an arrow where the = sign is.

Perhaps I'll change my answer to this. It isn't an actual equation, because it doesn't behave like one. You can't use it to substitute H2O in another equation eg. That would make no sense at all.

Your term HCl is actually: 1 H + 1 Cl + 0 O + (energy of one molecule of HCl; for specific circumstances)

That equation is really four equations in one, a bit like how a complex equation is two in one (real and imaginary). In this case the four equations each are consistent in their own dimension: - number of H atoms - number of O atoms - number of Cl atoms - energy

And I thought my scriblings are untidy...

You have my sympathy. There is little that gets me as upset as such idiocy. They won't be persuaded because they couldn't live with themselves for taking such risks with there children. They will find reasons to dismiss any argument, however convincing, because emotionally they cannot afford being wrong. It is hard, if not impossible, to battle such delusions once the stakes are too high.

I agree, but I think DNA testing would be able to distinguish the original and new populations. There would be some genetic drift and new mutations (possibly in the junk DNA). I guess a criterion for hierarchy could be that one population would produce fertile offspring with the ancestor, while the other wouldn't. I admit pretty worthless, as it is impossible to test. As you say, there could only be hierarchy in very specific cases.

It depends on what you like. Both are primarily management functions. If you like research or actual engineering, neither are a good option. I think at the University you have more freedom, but are further away from actual applications. You'll be writing a lot of proposals and papers. If you like teaching, that's usually also part of the job. In a company, valorisation is more important, and you are closer to the application. There is more focus on people management since the managed group is more diverse and less intrinsically motivated. There is more potential for a higher income, if you are good, but less competitive for actually getting a position. These are of course general statements, with exceptions. First question you need to ask yourself is: do you like the academic world and are prepared to work in the publish or perish atmosphere?

It is possible to track mutations through populations. The number of mutations unique to one group compared to another gives an indication for the amount of generations the groups were separated. As has been repeatedly pointed out, both groups will have mutations, and there is little point trying to nominate one as the ancestor of the other. One group can appear more similar to the ancestor for various reasons, but that doesn't mean a thing. In short: there is no test to identify hierarchical relations, because there is no hierarchy between coexisting (sub)species.