exchemist

How do you print a permanent magnet?

While there are electrolytic reduction processes for CO2: https://en.wikipedia.org/wiki/Electrochemical_reduction_of_carbon_dioxide. none of them seem to yield oxygen.

Yes I suppose that must be it. I was thinking of anaerobic bacteria that use alternative chemistry as fuel, like sulphate reducing or iron reducing bacteria.

From what I have just quickly read, these seem to have independently evolved, from mitochondria, several times in different species. So an example of convergent evolution, enabling their possessors to adapt to anoxic environments. What remains unclear to me is what the energy source is for their respiration. The flow charts I have seen seem to show pyruvate as the input, presumably from glycolysis. So that suggests glycolysis as usual, followed by some alternative to the Krebs cycle that does not require oxygen. Maybe someone can explain how this works. They don’t seem to be sulphate-reducing or anything like that.

OK. I suppose if there were a full stop after “human”, and if “believes” were rewritten as “beliefs”, it could be rendered partly intelligible, though the bit about faith and believes [sic] still doesn't seem to make a lot of sense in the context of the rest. Can you paraphrase it for my benefit, or get AI to do so?

Extremely interesting, thanks for posting this. It seems this may shed some light on very early evolutionary processes by which other organelles may have arisen, by being first endosymbionts and then getting integrated into the cell. I know next to nothing about this but I presume a key feature of the change would be the progressive migration of at least parts of the genetic coding needed for replication, from the endosymbiont to the nucleus of the host cell. I think I have read this is thought to have happened with mitochondria, which still retain some of their own DNA, separate from the cell nucleus. I see this work says that the template for some of the proteins the former endosymbiont needs is now in the cell nucleus, but a label is attached to them which gets them picked up by the "nitroplast". Perhaps investigation of this will help us understand how eukaryotes acquired other organelles in the long distant past.

Yes I think you have got it. I admit I don’t know how this is presented to students in the US today. My experience with Imperial units dates from schooldays in the UK in the early 1970s, when we transitioned from Imperial to metric. I remember how awful it was, compared to the simplicity of metric, and specifically, the version of metric that later came to be known as Systeme International (SI) units.

You are muddling metric and old-fashioned Imperial units. g in old units is 32ft/sec squared. g is 9.8 m/sec squared in modern SI units. If you multiply lb by g in old units you get the force in something called poundals, defined as the force needed to give a 1lb mass an acceleration of 1ft/sec squared. So there are 32 poundals in 1 lb-force. A pressure given in units of lb/sq in is implicitly in units of lb-force, not lb mass. lb-force is a force unit already, so no need to multiply by g. It’s a nightmare. If you really want to do your head in, read this: https://en.wikipedia.org/wiki/Poundal

There is a unit of force called “lb force”, which is the force exerted by the weight, at the Earth’s surface, of a mass of 1lb. So lb x g is what it really means. One of the advantages of metric SI units, now used just about everywhere except the USA, is to avoid the potential confusion of this kind of thing. You would then have mass in kg, force in N and g in m/sec squared and less risk of confusing mass with force.

Can you restate that in coherent sentences please? At present this is incomprehensible. Perhaps if you can split it into several sentences, with one idea per sentence, it might help.

Recommend paying attention to the physics of waves. This will help you a lot with visualising what goes in quantum systems. Also matrices and complex numbers in mathematics, for later.

What groups are these that American scientists were finding themselves in, in 2009, that would prevent them replying with honesty to an anonymous survey? I cannot envisage how that would work.

Why would an atheist, in the USA in 2009, have felt the need for courage to respond honestly, in an anonymous survey?

But you could easily do studies in liberal democracies where no such persecution or social expectation applies. This would be true of anywhere in N America, W Europe or Japan. There is this Pew study, conducted in the USA for example: https://www.pewresearch.org/religion/2009/11/05/scientists-and-belief/ What this does not seem to correct for is any correlation between religious belief and level of educational attainment. It may be also that more educated people tend to be less religious, regardless of subject studied.

What does it mean to “harvest” a direction? You must mean harvesting energy, surely? If this is a quantum system in its ground state, you cannot extract energy from it without breaking up the system. You have a form of zero point motion. You can’t extract energy from that. But if you have not yet learned any quantum theory you may find this hard to understand. All I can suggest is to read a bit, e.g. this link: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hosc4.html Don’t be scared by the maths, just read the text.

Well I must say that video seemed to make perfect sense to me, as a total non-expert in this area. Sabine's key point seemed to be that there is a vacuum energy inherent in GR that is just a constant of nature, arising purely from GR in a self-contained way, with no connection at all to the energy of vacuum fluctuations in QFT. Is that controversial?

No I don't think so. See the Wiki article: https://en.wikipedia.org/wiki/Time_crystal and especially this passage: Time crystals do not violate the laws of thermodynamics: energy in the overall system is conserved, such a crystal does not spontaneously convert thermal energy into mechanical work, and it cannot serve as a perpetual store of work. But it may change perpetually in a fixed pattern in time for as long as the system can be maintained. They possess "motion without energy"[16]—their apparent motion does not represent conventional kinetic energy.[17] I'll admit I know nothing about time crystals apart from what I have just quickly read, but it looks to me as if these things exhibit motion in their ground state. The definition of a ground state is it is the lowest energy state allowed for the system. From that it follows that energy cannot be extracted from the system (unless you break the system up, I guess, which would be a one-off exercise). You have much the same thing with the zero point energy in a harmonic oscillator, or, to give a real example, in the vibrational ground state of a diatomic molecule. There is still residual motion, even at absolute zero (hence "zero point"), but none of it can be extracted as energy.

No, this is wrong. You need to understand the difference between excitation and ionisation. Photons are often absorbed without having enough energy to eject an electron. They just move it to a higher, but still bound, energy state. This creates an excited state of the atom or molecule that has absorbed the photon. The whole of spectroscopy involves processes of this kind.

I wonder, though, whether this question may be about something else, viz. the "elasticity" of the current-carrying electrons in the circuit. For instance is the voltage is at its maximum value at one end, what will be the phase of the voltage 10 metres along the wire. Will that also be at the max, or is there a phase lag due to the compressibility of the current carriers?

Hard to know where to start with this gibberish. Almost everything you say is wrong, almost as if intentionally so. Just to take one point, there is no photoionisation in the retina of the eye. Photons are absorbed by proteins called opsins, which thereby enter an excited state and change from one isomer to another (cis ->trans). The isomerised version then undergoes a chemical reaction with other molecules to start a cascade of biochemistry, resulting in a nerve signal. This is not photoionisation.

There is apparently a meaning relating to an Ancient Greek theory of sight, in addition to the more, er, Sid James sense of the word.......

OK, I'm trying to follow this in the context of a permanent magnet. I'm not finding the motor analogy very helpful (sorry, my background is chemistry rather than engineering). I'm aware that ferromagnetism arises due to aligned, unpaired electron intrinsic "spin" and orbital angular momentum. So I presume the "current" you refer to in this case would comprise the "spinning" (not really but let's call it that) and orbital motion of the electrons. Is that right? But it seems to me this aligned angular momentum does not lead to an overall E field external to a bar magnet, which can interact with a nail some distance away. Or does it? If, as you say, the energy in the magnet that changes, when the nail is brought close to it, comes from the E field, what change do we get at the atomic level? Are we saying the quantum states of the unpaired electrons drop slightly in electrostatic energy, e.g. their mean distance from the nucleus reduces fractionally, or something like that? As you will see, I am trying to get a physics tutorial on this from @Mordred, who is I gather a professional physicist (respect). It looks to me so far (i.e. pending what I may be about to learn) that I may have been a bit too cavalier in strict physics terms in claiming the work done by, and on, your magnets comes from what I have been calling "the magnetic field". We are now into a discussion of the E field and the B field and where exactly the extra energy due to magnetisation resides in a permanent magnet. I think though that, in terms intelligible to a non-physicist, we can still say it is the extra energy in the fields due to their magnetised condition that rises and falls as work is done. But let's see what brother Mordred comes back with. I just hope I have enough grey cells left, at approaching 70, to take in a change in my mental picture of how this all works. 😀

OK, but what gives rise to the E field in this case and what form does it take?

I don’t think that matters. But let’s say it has been brought up from infinity (a concept physicists seem to like), held in place on the table and then released. Work is done against friction as the nail moves towards the magnet. What provides the energy?

If a nail is attracted towards a permanent magnet, doing work against friction, where does the energy come from?