exchemist

My son graduated from there this summer. What took you to St. Andrews?

I hardly drink Scotch these days but one of my favourites is Bowmore: an Islay malt, peaty enough to remind me of climbing the munros, but not in-your-face phenolic like Laphroaig.

Er yes, probably. One suspects they banned you because they felt you were not talking good science.

Reset? What do you mean by that?

Do you really think posting this adds to your credibility?

I'm not a cosmologist but I should have thought the temperature of the black body radiation from the Surface of Last Scattering could be worked out from the CMBR and the degree of cosmological redshift since then.

Also Norway. I recall being given a bottle by a group of Norwegian shipping line customers to whom I gave a tour of our oil blending plant when I was production manager there. The problem for me was that possession of alcohol on a refinery site was a matter of instant dismissal. They should never have been allowed in with it. I decided not to make a scene, accepted the gift courteously and - and got it off site pronto in my car when I drove home. This was what the Norwegian called Linie (pronounced like "linear") Aquavit, meaning it has gone round the world by ship to mature, crossing the equator, i.e. the line. So that's why a shipping line would give it as a gift. But I think this is a lot closer to vodka than to whisky (or even whiskey). Certainly the taste was, um, not that great.

Yes that's very familiar, but the interesting thing to a chemist is the deep connection between refractive index and the absorption and emission of EM radiation, through the polarisability of the medium and how close the light frequency is to an absorption band. For instance my understanding is that the reason why blue light is bent more than red in glass is because there is an absorption in the UV, so blue light experiences more refraction than red, as it is closer to the resonant frequency at which real absorption will occur. From this point of view it is a bit unsatisfactory to stick entirely to a classical picture, as absorption is quintessentially a quantum phenomenon. I suppose one could envisage a fleeting pseudo-absorption followed by almost instant stimulated pseudo-emission. That would avoid the scattering issue that would arise if true absorption were to occur, as then spontaneous emission in random directions would be expected, as @KJW points out. So one would picture photons progressing at c, but in stop-start fashion, through the medium. In the trampoline analogy, you put your foot down and the surface gives, preventing forward motion, but then it rebounds, giving your input energy back and sending you on your way after a brief delay. (I realise such analogies can't be pushed too far, but it is handy to be able explain the phenomenon is a way that gives non-experts some idea of the process.)

Yes this expresses how I like to think of it. I have sometimes used the analogy of running on a trampoline, whereby you put energy into undulation of the surface, lending it energy and getting it back a bit later, but the net effect being that it makes it slower to run. This type of wave-based explanation accounts for the reduced phase velocity. However, while it avoids claiming there is actual absorption and re-emission (and thus the scattering problem), what I struggle with is how to show this is consistent with the speed of photons under these conditions still being c. I am aware that (again in wave terms) the group velocity and the signal velocity will differ from the phase velocity in a polarisable medium, but I have yet to see any source claim that either of these corresponds to the velocity of the photons, or that either of these velocities remains equal to c within the medium. How would you describe how it is that photons still travel at c in a polarisable medium, in spite of all this going on?

OK. Pity you didn't have some baking powder to hand.

Yes that sounds plausible. @Externet seems to be worried about oil starvation if the sump level drops enough to lose suction. However if the resting oil level is as it should be, it seems unlikely that this is an issue. I have no feel for the volume of oil in the galleries of a machine like this, but I note the sump pan is quite small compared to the size of the 3 cylinders and the substantial-looking crankcase. I suppose the +ve crankcase (and sump) pressure may be a consequence of a small amount of blow-by past the piston rings.

I confess I had never even heard the term jaggery until now - but I've looked it up. It is possible that if a dye has been used, the colour may change with pH. I can't remember if we have discussed this, but does the green turn back to brown at high pH? Or could there be 2 dyes, one red and one green, giving brown at neutral-high pH, but the red one becomes colourless at low pH, leaving just the green? Phenolphthalein does that, for instance. But I realise I may be overthinking this..........

Also, the BBC doesn’t rely on regulation by the US government, nor does it need any business deals approved by the US authorities. So they don’t need Trump’s approval the way US news media do. Therefore, if they have a solid legal defence they can call his bluff.

Surely you know the oil suction tube must be successfully picking up the oil, because if it were not, the oil level would not go down when the machine is running. As for why the oil immediately runs down and fills the pan when the filler cap is removed, that suggests maybe that there is some +ve pressure in the system that is released when the filler cap is removed and this pressure for some reason inhibits the oil from returning to the sump. Is there an escape of air when you remove it? But if that is happening it is hard to know whether is by design or indicative of a fault without knowing more about the compressor design. The oil is clearly going somewhere inside the machine and eventually returns when it stops, so it is not being lost. That suggests to me it may be normal. The handbook ought to say something about the oil level, when to measure it and so on, which could give a clue. The sort of guy who might know is @sethoflagos , who seems to have oil industry engineering experience.

☹️🔫

......nor even the shpelling mishtake......😁

Many thanks for the explanation - and for taking the time to fix it so promptly at such a busy time of year. But a bit disturbing that a little forum like this should be the target of a DOS attack. What could be the motive, I wonder? Disgruntled obsessive, computer-literate crank, perhaps? Or does some shadowy organisation take exception to political views expressed here? Seems hard to credit. On the site functionality side, the move appears to have actually restored a couple of functions I had lost, so no complaints there.

Delighted to see service is now resumed after the flood of bots. I notice that the restored system once more allows me to use the Edit and Report functions from my laptop, a feature that had become disabled for some reason recently, though I could still use it from my tablet, oddly. Is the site using the same host and the same version of the software, or has either of these now changed in response to the incident? Happy Christmas, all.🌲

Yeah, it will be a "framework" for sure. 😁

Actually, I and others went to considerable lengths to identify exactly where, in the operating cycle of that machine, the input work was required , even though we also told you that we knew in advance, just from the laws of thermodynamics, it would not produce any net energy gain. And of course we were right.

Individual atoms don’t carry information about their previous environment.

Nice enough picture but what is the discussion topic?

E=mc2 is not about converting mass into energy.

I’m not opening that file. You need to present its contents here.

This rings a bell. I think you may have mentioned it before. Maybe it was in the context of @Prajna ’s machine with magnets, the one he tried to make before AI drove him bonkers.