exchemist

If you can’t do maths it will be crap. You can get away without much maths in a number of sciences, but in physics it is indispensable. Sorry. But I see you and I discussed this 3 years ago, in a thread now in the Trash Can, and that moderation told you not to bring it up again. So this one is probably heading the same way, I would think.

Yes that explanation makes no sense. I did find this, which does seem to make sense: https://www.canopyclimate.com/post/the-best-portable-heat-pump-and-one-type-to-avoid According to this, the mode of operation is to draw ambient air from the room, rejecting the captured heat back into the room and exhausting the cold air thereby created to the exterior. As the writer says, the problem is the expelled air has to be replaced by air from within the house, so you must draw outside air in somewhere, which will be cold, if not as cold as the air the pump exhausts. And in the process it will create a cold draught, which subjectively may make the occupants of the room feel cold, too. Sounds pretty crappy to me, if not actually a scam. 2 hose job must be far better, I feel sure. But no doubt it will dehumidify the air, which may make it feel less chilly, I suppose.

This is not new. Lala (someone of Parsee descent whose parents anglicised the family name to Laland) is a prof at St. Andrews and a prominent exponent of the “extended evolutionary synthesis”. Details here:https://en.wikipedia.org/wiki/Extended_evolutionary_synthesis Nothing about this implies “control” by populations of organisms over how they evolve, in any conscious sense. However it does propose that environmental factors can affect evolution through means other than simple natural selection. For example, I was fascinated to read some years go of research suggesting that at times of environmental stress, organisms may reduce the normal corrective mechanisms that correct the errors in genetic material that lead to mutations. It’s as if they go off to the casino and spin the wheel, to see what novelties they can create, some of which might be helpful. Not everyone buys into the extended synthesis, but it has been for some time a live hypothesis in conventional evolutionary theory.

I don’t think so. To me, resonance implies it is the natural frequency of the pipe, not a forced oscillation. I might do a bit more reading about it tomorrow (right nowI’m suffering from a bad cold and have little mental energy in the evenings🙂).

Hmm, I see. But it must be hard to tune them so they have identical resonant frequency. Or do they have some ingenious way round that?

Yes I think that’s right. What I don’t follow yet, not having read it up, is how this phase shift thingie gets detected and converted to a mass flow readout. Some explanations show a pair of tubes in parallel. Not sure what that does.

You’re not the only one: the diagram in the OP refers to a “twist angel” [sic]. 😁

This is interesting. I had vaguely heard of Coriolis flow meters from my time in the oil industry, but never looked into the principle of operation. So thanks for posting this query. I have learnt something. I think I've got it. It's the inertia of the flowing fluid inside the tube. The arrows show what takes place during the "upward" phase of oscillation of the tube. Fluid entering from the left resists being made to flow slightly upward due to its inertia, creating a downward force on that part of the tube. Conversely, the fluid leaving, back to the left again, has by now been made to flow slightly upward and therefore resists being made to flow horizontally once more, creating an upward force on that part of the tube. So, seen end-on from the right, the tube will have a slight twist as shown. When the tube is in the "downward" phase of its oscillation, the converse happens. When it is in the centre, there is no twist. So, again as seen end-on from the right, there will be a rocking or twisting motion superimposed on the up-down oscillation. In effect, on the side the fluid leaves, the phase is slightly advanced relative to the oscillation with no flow, while on the side the fluid enters the phase is slightly retarded. The downstream side leads the upstream side. The magnitude of the force will depend on the rate of flow of mass, because when it flows faster more mass has to be made to change direction in unit time, i.e. the rate of change of momentum, d(mv)/dt is greater. d(mv)/dt = ma = F. And then of course there a load of fancy stuff about detecting this distortion of the resonant frequency via phase shift etc.

According to this: https://en.wikipedia.org/wiki/2024_US_air_base_drone_incursions_in_the_United_Kingdom the UK incidents took place over 4 days in late November. I’m not aware it is still going on, at least, I don’t see anything in the news.

Ah, racemases. I didn’t know about those. So there are biological ways to convert one stereoisomer into another. That answers my question.

That was certainly how it seemed to me. We are nowhere close to creating organisms from scratch. But my real interest is in whether a hypothetical bacterium or virus employing molecules of opposite chirality to that present in terrestrial life could interact effectively with it. My understanding is that the wrong chirality in, say, sugars renders them useless because they can't be metabolised by organisms.

How would this work? Surely these bacteria would be unable to utilise biochemical molecules from normal organisms, because they would have the wrong handedness?

Where do you get this balls? Odeon comes from the Greek word for roofed theatre, while nickelodeon was originally the name given to small local cinemas in the US where one could gain admission cheaply, e.g. for a nickel. What evidence do you have of George Bush, of all people, doing rituals in the woods?

Fair enough, but this guy is at GCSE level. No point in blowing up his brain with all that 😄

It means the particle behaves like a tiny bar magnet, with a North and South pole. Like a magnetised compass needle, it will tend to line up with any external magnetic field. Conversely, if you can get a lot of these particles, in practice electrons, to line up in a block of material, that will make the bulk material magnetic - which is what happens in a permanent magnet. You have a lot of atoms each with an electron that can be made to line up in the same direction, adding their effects together to make a stronger field. So permanent magnets are magnetic because - or mostly because - of the “spin” of electrons.

Hmm, whether this intrinsic angular momentum also represents energy or not is a bit of a moot point, since you can't stop the spin, i.e. you could never get any such energy out of the particle. These particles certainly do have energy associated with their mass, according to E=mc², but I don't think it's a good idea to think they have a kind of kinetic energy due to their "spin". Anyway, for GCSE, all you need to know is you can put a maximum of 2 electrons into each atomic orbital, which is allowed so long as one has spin "up" and the other has spin "down".

OK. Like a lot of things in quantum theory this is not like the behaviour we are used to at the scale of everyday life, so it may take a few iterations to understand it.

Yup, h is Planck's constant. The symbol h with a line across, known as "h bar", is h/2π. This quantity appears in a lot of places in QM maths, so it was thought worth giving it its own symbol to simplify algebraic expressions. When it comes to elementary particles they have angular momentum, just as a spinning top or wheel has. This is often referred to as "spin", but it's not really like a little ball spinning on its axis. For one thing this "spin" is intrinsic to the particle. An electron has a spin of 1/2 spin units*, always. You can't stop it spinning or make it spin faster. The spin value it has is fundamental to its identity as an electron, just as much as its -ve electric charge is, or its mass. This so-called spin is a way of saying they have a set amount of angular momentum. That is important because angular momentum is a conserved property, like linear momentum or energy. So in particle interactions, one rule is the total angular momentum of the system, before and after, has to be the same. That has certain consequences in physics. However, because these elementary particles don't behave like little balls, one can't talk of a speed of rotation or anything like that. They have have a set amount of intrinsic angular momentum and that's that. * I had better add a bit here so I don't get my balls shot off by the real physicists on the forum - always a risk here😁. You don't need really to know this. "Spin units" is just my lazy shorthand for saying the spin quantum number, s, of electrons is 1/2. The actual magnitude of the angular momentum is given by the angular momentum formula √(s(s+1)). h/2π, which for s=1/2 gives you √3/2. h bar. However the projection of the angular momentum vector along any specified axis is a bit less, 1/2. h bar, basically because of the way Heisenberg's Uncertainty Principle works for angular momentum (There's always a bit of angular momentum left over, that points in an indeterminate direction and which can't be pinned down). So particles like electrons are known as "spin 1/2" particles. The formula you are asking about is the magnitude of this projection - which is what matters in practice, in the lab and so forth.

There is also, I suppose, a nice point as to whether in black body processes one is right to say the atoms do the emitting or absorbing. The black body “oscillators” are systems comprising collections of atoms and it is those systems that do it rather the individual component atoms. In your steel bar, absorbing an IR photon, no single atom absorbs it, surely? I imagine it will initially excite the conduction band electrons and this will get converted into a lattice vibration, won’t it?

Continuing the guitar theme, time for a bit more Bach: Prelude from 1st Cello Suite played on the guitar by the lovely and talented Julia Lange: What I like about this performance is that, unlike some guitar performers of this piece on YouTube (there are quite a few) she doesn't try to make it all about herself by messing about with the tempo and inserting dynamic contrasts all the time, as if it were a Romantic piece. It's Baroque. She allows Bach's pulse (always very strong) to carry it forward and lets his cascades of notes do the expressive work, with just a little inflexion here and there to stress key moments. Very classy interpretation, I thought. And she looks as if she in a sort of calm and peaceful ecstasy throughout, which is rather delightful.

Ah, so you refer to atoms in bulk rather than individually, then, radiating or absorbing as a black body. Fair enough.

Not sure I follow that last bit. Surely atoms do only gain or lose energy in discrete amounts, don’t they? But knowing you, you have some subtlety in mind: can you elucidate?

You (and Tetrode) are describing the emission of a photon by an atom and its subsequent absorption by another - obviously at a different location. That is not what entanglement is. To produce entanglement one needs a process that results in a pair (or more) of QM entities together, such that they are correlated: their quantum state can only be described for the combined system and not for the individual entities. You do not have that when an atom emits or absorbs a photon. You have misinterpreted what Tetrode was talking about. I think you have also misunderstood what the Cramer & Mead paper is about. It proposes a mechanism for wave function collapse in the course of an interaction. That has nothing specifically to do with entanglement either. It is completely general to all QM interactions, whether the participating entities are entangled or not. (By the way, it looks to me as if it assumes an interpretation of QM in which the wave function is a physical thing, rather than a description of information about the system. As such it would appear to be at odds with some other interpretations of QM, such as the Copenhagen or the Relational interpretations. But I don't profess to be expert on that subject.)

There is nothing about entanglement here. It sounds like an idea for how light might transfer energy as discrete quanta - something they were wrestling with at the time, after Einstein's work on the photo-electric effect.

But that makes no sense as an explanation. Tetrode didn't use the word "electron" in the passage you quoted. He said "atom". Why would the translator explain the possible meaning of a word Tetrode didn't use? (An atom is not an electrically charged particle, of course - not that electric charge has any bearing on entanglement.)