exchemist

What do you think would be the consequences for the relationship with Europe if it did? Can Europe afford to cut off China?

Nobody can know. But if China starts supplying weapons to Russia then it could snowball, certainly. Very important that the US finds a way to make it not worth China's while to try that.

My hovercraft is full of eels.

No, chirality refers to entities that cannot be superimposed on their mirror image. For example your right hand is a mirror image of your left and there is no way you can superimpose your right hand onto your left hand. The same is true of right hand and left hand helices. Spin polarisation is simply the (partial) alignment of the angular momentum vector with some external influence, e.g. a magnetic field. Chirality does not feature in that, since particles can and do flip from one orientation to another. If it were a matter of chirality, that would be impossible. Polarity refers to an asymmetrical distribution of a property giving rise to opposite "poles", in physics usually either electric or magnetic, as in a magnetic or electric dipole, or higher multipoles.

Polarity and polarisation are not the same, and neither is the same as chirality.

Maybe you can tell us how it is that somebody called Gareth Meredith wrote the paper at this link: https://www.academia.edu/24475326/The_Larmor_Phenomenon_around_Quasars_as_an_Extension_to_Hawking_Radiation From your comments on the other thread, I'm not to call you Gareth, apparently. 😁

Of course: cook it one day, leave it to cool overnight and reheat and eat the second day. Or cook and freeze in batches for later use. (I disagree about cottage pie though. I think it dries up too much and the mashed potato goes sludgy.)

Chirality is not the same as polarity at all. You have no idea what you are talking about, Reiku. You may be confusing it with polarization, viz. the way chiral systems can rotate the plane of plane-polarized light. But if you knew some physics you would not confuse the two.

No, Gareth, that's not right. Direction of spin determines the orientation of magnetic moment. It tells you nothing about any electric dipole. And compatibility of what with what?

That is a meaningless sentence, Gareth. Compatibility of what with what? And what does it mean to talk of spin being distributed as an observable? Spin is quantised: with an electron you can only measure one value (or two projections of that value in an external field, if one is present. You can't measure bits of spin here and there.

Yes maybe that's the best way to look at it.

OK that's what I thought. That seems to suggest there is no experiment one could ever devise that would be evidence of any property of these virtual particles. In that respect they are unlike, say, the Higgs boson, whose existence was predicted and then evidence was found.

I'm not sure what you man by no input or output. If you mean they have, even in principle, no measurable properties, then that seems to make my point. No measurable properties, even in principle => unreal, surely?

Evidence of them does appear in measurements, though. Almost all non-trivial observations in science are to some extent indirect. Even elusive things like neutrinos can be shown to be real by patient enough observation. But there is no known observation that can show the presence of a virtual particle, whether directly or indirectly. What experiment could be devised that could show whether virtual particles did or did not exist? I don't think anybody has ever tried to do that, and that's because physicists know it would be a futile exercise.

lectrons-spin-in-quantum-physics-after-all-heres-why/am And the electron has been observed to have a spherical charge distribution. This is at odds with the classical model divergence problem because it simultaneously assumed the charge was pointlike. https://www.sci.news/physics/spherical-electrons-06518.html I'll even demonstrate the mathematics of this singularity of the electron if anyone wishes. It's quite simple. And yet from simple assumptions came erroneous ideas that are no longer holding up, like they used to. If you set all constants to zero your expression also becomes zero.

I'm following this discussion as far as I can. There is an article by Strassler here that seems to me to say virtual particles are qualitatively different from real ones: https://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/. and perhaps should never have been given a label containing the word "particle".

Exactly.

I wonder if this may be about virtual photons as "force carriers" in magnetism. They do that, don't they, in QED? (I never learnt this stuff).

The figure derived from 2.5cm/secs is only (if my arithmetic is good) the increase in k.e. from a single absorption event, so yes, obviously to explore what happens in laser cooling is a lot more involved. But I was simply intrigued to see how significant the translational energy input is, compared to the energy of the photon, and what the effect on the temperature of a spectroscopic sample might be. I suppose since k.e. goes with the square of the speed, the kinetic energy transfer from the same amount of momentum to a lighter molecule, say hydrogen, would be somewhat greater.

This all has an air of Reiku/Graviphoton/Gareth Meredith...... and all stations to Cardiff......about it.

OK I've had a go at this, taking gas phase sodium atoms as an example, since I see that has been used in laser cooling experiments. My arithmetic may need checking but if it's right it goes like this: Take gas phase sodium atoms, absorbing at the D line. Wavelength of D line, λ = 590nm Momentum, p = h/λ (de Broglie) => p ~ 6.6 x 10⁻³⁴/5.9 x 10⁻7 ~ 10⁻²⁷ kg-m/sec = Δmv for a sodium atom absorbing a D line photon. ------------------------------ Mass of a sodium atom is 23g/mol, i.e. 0.023/6 x 10⁻²³ ~ 4 x 10⁻²⁶ kg. So for the absorbing atom, Δv = 10⁻²⁷/4 x 10⁻²⁶ = 2.5 x 10⁻² m/sec. Hence the increase in translational k.e. will be: 1/2 . 4 x 10⁻²⁶ . ( 2.5 x 10⁻²)² = 0.5 . 4 x 10⁻²⁶ . 6.25 x 10⁻⁴ = 1.25 x 10⁻²⁹ J ---------------------------- Translational k.e. = 3/2 . kT. So ΔT due to extra momentum = 2/3 . ΔE/k = 2/3 . 1.25 x 10⁻²⁹/1.4 x 10⁻²³ ~ 6 x 10⁻⁷ Deg. This is a “temperature” increase, for each atom that absorbs a photon, of under a millionth of a degree. Expressing that in terms of the energy of the photon, that energy will be hν = pc = 10⁻²⁷ . 3 x 10⁸ = 3 x 10⁻¹⁹ J. So the proportion of its energy that contributes to thermal k.e. is 2.4 x 10⁻¹⁰ , so almost infinitesimal. Now I understand why this is never mentioned in spectroscopy.

Of course. That's what I meant when I referred to collisional relaxation. What I have been trying to get at is whether radiation can directly stimulate the translational degrees of freedom. I think the answer is no, save for this issue of momentum transfer when a photon is absorbed by another form of excitation, which @swansontput me onto. (By the way, this whole area of relaxation from excited states, esp. the mechanisms for the redistribution of thermal energy among the available degrees of freedom, is something that seems to me to be quite complex and often rather glossed over, in particular how electronic excitation comes to be redistributed into vibration, rotation and translation.)

Sure, but that's just the redirected blue wavelength photons. I don't think the effect can be much because this is never discussed in spectroscopy. In principle what you are saying is that the absorbed photon has to do two things: excite a transition to an excited state AND contribute to an increase in translational k.e. But we ought to be able to calculate the k.e. increase from the momentum, shouldn't we? For the photon E=pc = hν.

Do you think Rayleigh scattering can produce a significant heating effect, then?

I have a memory of a sci-fi short story I read as teenager in the 1960s, in which, after a spacecraft crashes on an alien world, 4 members of the crew regain consciousness to find their bodies, apart from the brain and spinal cord, have been consumed by a sort of protoplasmic organism. The organism however supports and hosts the brain and spinal cord, as it is useful to its existence to have a directing mind. All four are in one blob and are able to communicate telepathically within the blob. The blob is shape-shifting and can take on forms instructed by the brains it hosts. So they can "make" arms, for example, by a process of mind control. The 4 crew members argue, fight and two eventually are killed, while the remaining two separate and try to reconstruct their human forms. I don't remember the author but I think the title was "Four In One". I've searched the internet for this without success. Does anybody recognise this story from my description and, if so, can you provide any more details about it? Update: I've found it: Damon Knight, 1953. There is even a pdf of the story: https://epdf.tips/four-in-one.html So now the question is different: does anyone else but me know this story? It's one that made quite an impression on me at the time, so that I still remember it, more than half a century later.