exchemist

Where does the methane come from?

No indeed. My question was far more basic, simply whether a static electric or magnetic field has mass as a consequence of its stored energy. I realise now that my question was at one level a bit stupid, since if a battery gains mass when charged (albeit to an unmeasurably small degree ), it means the energy in the chemical bonding goes up and gains mass - and the energy of that bonding is a sum of the electrostatic potential and kinetic energy of the electrons. So it seems to me now that a static field must indeed have an associated mass, even though this feels unintuitive when one thinks of the magnetic field of a solenoid for example. Also, from the other (very interesting) replies, it dawns on me that I should not find this idea of fields having mass unintuitive, since (as I understand it, very vaguely) fundamental particles are considered in QED to be excitations of a field. I probably need to let go of this rather 6th form idea of mass applying to things called "particles" of matter, as distinct from insubstantial things called "fields". You are psychic! I was just replying. (I was out most of yesterday.) There is some excellent food for thought in this thread and I'm glad I left it long enough for those replies to come in before responding.

Responding today to the thread in Speculations, it struck me I don't know how to treat the stored energy in a static EM field, according to E² = (mc²)² + p²c². Since, unlike the situation with EM radiation, there is no motion involved, I presume the second term does not apply. But does a static field gain rest mass, as its stored energy increases? Seems weird if true. I've a feeling I'm missing something here. Can anyone help?

Unfortunately this attempted explanation makes a common mistake. Matter is not converted to energy. What the equation says is that mass implies the presence of a type of energy, called rest energy. Both mass and energy are properties of physical systems. Neither is "stuff". You can't have a jug of energy, nor can you have a jug of mass. Any system comprised of matter that gains or loses energy will also gain or lose mass, according to the formula. So yes, your battery will gain or lose mass when charged and discharged. Note that both mass and energy are gained and lost together. They are not converted from one to the other. They go hand in hand. The formula is an incomplete, short, form of the full formula, which is E² = (mc²)² + p²c², where p is momentum (as measured from some frame of reference). So energy can be present due to momentum as well as due to rest mass. This accounts for the energy in radiation, which has no mass. If you have a nuclear reaction in which rest mass is lost, it just means some of the rest energy has been converted to energy in other forms, including energy in radiation and kinetic energy of particles. Just as when you discharge your battery, it too loses mass due to the release of electrical energy.

Well yes, to the extent that you swallow some of them and digest them. But that is going to be an infinitesimal proportion of your dietary intake.

Though it would presumably accelerate osteoporosis, eroding the gain.

Aha. Thanks very much. (I experienced 6 weeks of anosmia myself, without any apparent lung infection, with the plain vanilla original variant, back in March 2020).

That was deliberate on my part, once I had decided that generating a telephone number, via a series of ad-hoc, wild assumptions, would be too tedious and ultimately fairly meaningless. But do feel free to have a go........

That raises a question: the virus seems to work by binding to ACE2. I had thought ACE2 was most abundant in the lungs, rather than in the nose and throat. Yet Omicron typically gives a runny nose and sore throat, like other upper respiratory tract viruses. Do these also work via ACE2? If so why do they not also invade the lungs? Or do they work another way, and if so, does it suggest Omicron may also now be gaining entry by a different mechanism?

But you still have the same problem with an orbit around L2, as I understand it. There is a still a tendency for the object to drift either inward towards the Earth/Sun or outward away from them, i.e. to drift perpendicular to the plane of the object's orbit.

Relatively few, I should have thought. The only ways material can be incorporated in your cells are via respiration and metabolism, i.e. what you breathe in and out and what you eat and drink. Since nothing you eat and drink comes from your colleague we are really talking about breathing, specifically how many atoms from the CO2 and H2O you each exhale becomes incorporated in the other's cells. Since CO2 and water you breathe in does not become part of your cells to any significant extent, it would be the CO2 and H2O converted via photosynthesis to O2 and carbohydrate that you might subsequently breathe in or ingest. So if you want to minimise any exchange of atoms, get rid of all the office plants, and do not, on any account, eat any office-grown tomatoes. 😁 But as for numbers, it would be a difficult exercise to do, a huge range of assumptions would have to be made and the resulting telephone number would be essentially meaningless.

Well I suppose we should be grateful this is not promoting invermectin.......yet............🤪

Insofar as they control the behaviours in ADHD patients that lead them to suffer elevated risks of infection, yes. Otherwise, no. Or at least not according to my reading of these links. Specifically, there seems to be nothing here to suggest that a non-ADHD person would benefit from taking these medications.

As in the VW beetle (originally Hitler's "Strength Through Joy" car), the Porsche series derived from it and the VW camper van, all of which use flat 4 or flat 6 "boxer" engines. As the cylinders are more exposed, these can also make air cooling practical, simplifying the design. Which reminds me of a story from my time in the Lubricants division of Shell UK, at the end of the 70s. Some fellow lodged a quality complaint that the Shell engine oil he had bought had gone solid in the sump and ruined his engine. We analysed a sample of the strange jellylike material from his engine and found traces of what seemed to be the oxidation products of ethylene glycol. Further enquires revealed that as winter was coming on, he had decided it was time to put antifreeze in the engine. He had opened the only filler cap he could see and poured it in........ We also, at that time, made a special product for British Rail, called Rotella HST, for the Paxman Valenta engines in the High Seed Train. These were prone to leak traces of coolant into the oil system. From memory this product had some sort of boosted antioxidancy, to resist the autocatalytic effect of glycol oxidation products in the oil. But I digress.

Actually I was wrong on one point: seems kerosene is used for rocket fuel. So no doubt they could collect a kerosene fraction from this pyrolysis process and use it. But it's not very environmentally friendly, as the other fractions are carbon-rich fuels. I'm not sure we want to burn our waste plastic if we can help it.

Thanks, um, Kevin. These are nothing to do with Space X, I notice. The NASA one seems to be a kind of artificial photosynthesis, but they don't explain what they aim to react with the CO2. If they want to make methane, they need hydrogen from somewhere. Is this water? Doesn't seem to be specified. All very unclear. The National Geographic report is about capture of atmospheric CO2 (which I have read is being done at pilot plant scale in Iceland) and reacting that with hydrogen from electrolysis. So it requires a lot of electricity - just as producing hydrogen itself does. For rocket fuel I can't see this has much advantage over simply producing hydrogen, which is a well established rocket fuel already. As for Musk's claim, again I struggle to see the point if all it involves is reacting CO2 with a hydrogen source to produce a hydrocarbon fuel. When you burn it, you will get the CO2 back again. So what is the advantage over simply generating hydrogen and burning that? Re plastic waste, there is a pyrolysis method for producing a mixture of light, medium and heavy hydrocarbons, rather analogous to the products of fractional distillation of crude oil. No doubt some of these fractions could potentially be used as rocket fuel, but since methane, propane, gasoline, diesel etc., are not used for rocket fuel today, I suspect the products of this process would not be first choice for rocket engineers.

Um, Kevin, Elon (Musk) is a person. Perhaps you mean Space X is on its way to using CO2 for rocket fuel. However all I can find on this is some throwaway comment on social media from Musk. Do you have information about a concrete proposal from Space X to do this? How do they plan to do it?

Getting an engine to do work is extraneous to the problem in mechanics that the OP was trying to resolve. But never mind, it's solved now anyway.

You can treat an "ideal" flywheel, crank and piston assembly as a closed system, for the purpose of understanding why there are no intrinsic energy losses in the motion. All the other stuff, while obviously true of real engines, is extraneous to the problem.

Yes, that's it exactly. For an isolated mass, you would need to do work on it from outside in some way, to accelerate it. But for the piston in an engine, it just exchanges kinetic energy with the flywheel and crank, twice per revolution of the engine.

If you read my post about this you will see I say the (kinetic) energy of the piston goes into the flywheel (and in some cases other pistons) and then comes back to the piston on its return stroke. Just as in @mistermack's sprung mass example, the kinetic energy goes into potential energy in compressing or stretching the spring and then comes back to kinetic energy again. But the total energy of the system stays constant, if there is no friction or other source of loss. That's what the crank does: transforms linear kinetic energy into rotational energy and back again. Think of a single cylinder engine. Every power stroke, the piston gives a kick to the flywheel, which is then able to move the piston back on the exhaust, induction and compression strokes, slowing down all the while, until it is given another kick by the next power stroke. The flywheel is the kinetic energy store and its speed changes throughout the cycle as it gains energy from, and loses energy to, the piston. When the piston decelerates, it does work on the crankshaft and flywheel, and then the crankshaft and flywheel do work on it to accelerate it again. No net energy loss need occur.

You can judge that for yourself I think, by what they say about such things. If you talk to a Methodist, or an Anglican, or Episcopalian, or a Scottish Presbyterian (I don't know about Presbyterians elsewhere), or a Lutheran or a Catholic, i.e. major recognised denominations with a body of theology and some form of authority structure, you won't find them taking literally all these bloodthirsty stories in the Old Testament.

The caricature of Christian belief and the association of it with US right wing politics. Don't get me wrong: both the caricature and the association seem to have a fair amount of validity in a US context, sad to say. Elsewhere however it would not be seen as a very thoughtful critique of Christian belief, that's all.

This is all very American.

OK, you will know better than I, I'm sure. I suppose what you are saying is that there is something about pure mathematics that corresponds to the physical world and this is not necessarily what one might expect. I shall have to think about that.