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April 14

Mechanism of hydrogen absorption by palladium

Why exactly is palladium so good at absorbing hydrogen? Nickel and platinum are in the same group, and they certainly are not. Double sharp (talk) 16:28, 14 April 2020 (UTC)

This is a rather old paper and highly technical, but may be a good start. This is a newer and more accessible synopsis article, which may be closer to helping answer the question; in summation there's something specific in the crystal lattice of the palladium metal that allows H2 to efficiently adsorb onto the palladium that metal atoms of different metallic radius or crystal shapes would not work as well. --Jayron32 19:53, 14 April 2020 (UTC)

That first ref notes that nickel does take up hydrogen, but that the amount is more limited for the bulk metal because of poor penetration below the surface. Might be some useful info to add to the nickel hydride article? Nickel is at least good enough for use in some hydrogenation catalysts, so please be careful with a blanket statement that nickel is not good at it. Doi:10.1016/j.ijhydene.2006.07.004 discusses use of nickel as a hydrogen-storage material. I found that last ref by google-scholar search for [adsorption of hydrogen onto nickel]. DMacks (talk) 23:45, 14 April 2020 (UTC)

Well, yes, what I meant was that Ni was certainly not as good as Pd at this. ;)

Hmm. Jayron32's comment about metallic radius and crystal structure prompted me to check other similar metals. Palladium has a metallic radius of 137 pm and has an fcc crystal structure; well, platinum is 138.5 pm and also fcc. But apparently platinum is not good at absorbing hydrogen, even under pressure. It looks like rhodium is the second-best platinum metal at doing this, but RhH_x is thermodynamically unstable. (Well, it is also fcc and 134 pm, so not far away.) So it must really be very sensitive to small changes. Double sharp (talk) 03:43, 15 April 2020 (UTC)

Anything relevant in a comparison of reduction potentials, thinking about forming an alloy with more M–H bonding than just an inclusion in the M structure? Doi:10.1039/B701402C is an experimental analysis of the structural changes of Pt (and Au) upon absorption of H2. DMacks (talk) 08:33, 15 April 2020 (UTC)

I just want to clarify that it isn't just the metallic radius and crystal lattice to the exclusion of all other possible factors which can explain palladium's properties here. There are probably dozens of properties relevant to our discussion (coordination number, electron affinity, electron configuration, reduction potential, atomic mass, spin-spin coupling, etc. etc. etc., along with many others I either can't think of or are too bored to list) each of which adds a non-trivial contribution to palladium's particular properties, causing it to hit that perfect sweet spot in terms of hydrogen adsorption. The fact that I found articles that highlighted those particular properties should in no way imply that the answer to the question was a simple as that, and that one could ignore everything else. --Jayron32 12:20, 15 April 2020 (UTC)

April 15

A single coronovirus

Many years ago while on a lecture for Infectious Diseases in the Medical School our professor said that there were only 4 infections which were able to cause the infectious agent to multiply and cause a clinical disease if only a single bacterium / parasite entered the body. Anthrax chiseled in my memory, but I forgot the other three. I wonder if the coronovirus can infect you via a single agent? Thanks, AboutFace 22 (talk) 01:01, 15 April 2020 (UTC)

While I do not know the answer, a better question may be what the probability is that a single SARS-COV-2 virion will lead to a detectable infection. It appears that at least for Baculovirus viruses, which infect butterflies, a single virion may lead to infection.^[1] For the influenza A virus, the probability that a single virion entering a cell will successfully replicate is very low, but not zero.^[2] Extrapolating from these cases, I think that it is likely that, likewise, this probability is non-zero for the various coronavirus species.  --Lambiam 08:25, 15 April 2020 (UTC)

Basic reproduction number (R₀) seems relevant. 107.15.157.44 (talk) 09:35, 15 April 2020 (UTC)

No - that refers to how many people are infected by a single case - nothing to do with how many virus particles entered the body.--Phil Holmes (talk) 11:35, 15 April 2020 (UTC)

I would be shocked if measles wasn't on that list; it is extremely infectious. However, I would urge caution in any kind of simple list like that; whether X germs will trigger a disease is not going to be the same number for all people at all times of their lives in all circumstances. Matt Deres (talk) 14:44, 15 April 2020 (UTC)

Measles might be able to infect with a single particle. The minimal amount of virus to establish an infection in a cell culture bereft of the body's immune system happens to also be the minimal amount to infect a living monkey. So while I don't know if every measles virion to leave a carrier's body is able to infect a cell, it probably only takes one to successfully infect to establish a stable infection. This was actually a surprise to me - I had assumed measles's extreme infectiousness was related only to the unusually high volume of viral particles spewed by patients, but I was wrong. It's both: [3]. Someguy1221 (talk) 13:27, 21 April 2020 (UTC)

In principle, it seems like any virus could potentially cause an infection from a single virion. It's not like they have to collaborate inside the body. It's just a question of whether the virion manages to find a cell to infect, and enough of its children do, and so on. As Lambiam says, the key question is how likely it is for this virus, and I really don't know the answer to that.

Another consideration is that an infection starting with a small number of virus particles takes more time to reach a high viral load, which may give the host's immune system more time to mount an adequate response. --Trovatore (talk) 19:47, 15 April 2020 (UTC)

I take it back — one of Lambiam's links above suggests that viruses do in fact collaborate inside the body, to fill out incomplete viral genomes. News to me. --Trovatore (talk) 21:14, 15 April 2020 (UTC)

It seems more clear in the context of bacterial infections and parasitic animals that some agents require a sort of critical mass in order for their immune suppressing secretions to be effective, and thus allow the infectious agent to reproduce. I wouldn't rule out that this could be true for a virus as well, but I've never heard of such a thing. Someguy1221 (talk) 13:30, 21 April 2020 (UTC)

Social distancing effect on other viruses

Does all this social distancing mean that other viruses will also be slower to spread such as common colds? 90.198.251.144 (talk) 14:19, 15 April 2020 (UTC)

This reference suggests that the answer is "yes". Which isn't surprising, given that methods of transmission (and prevention) are broadly similar. Washing your hands is a "good thing" for the prevention of many diseases. Matt Deres (talk) 14:46, 15 April 2020 (UTC)

The basic premises of germ theory would suggest that the answer is yes, as well, for almost any infection. Even if an infectious agent is truly airborne, the concentration of that agent will fall off as a factor of distance from someone infected (barring effects like wind), so even with an airborne infection, being 6 feet from other people vs 1 foot from other people will reduce infection rate. Same with bodily fluid transmissions, in so far as you are less likely to come into contact with blood from someone else if you are consciously staying 6 feet away from everyone. As for sexually transmitted diseases, I suppose that depends on whether individuals are likely to reduce their number of sexual partners while exercising social distancing, which I imagine will differ person to person and society to society. At a very basic level, social distancing is sort of a "quarantine lite," not quite as effective as a full on quarantine, but working on similar principles. --OuroborosCobra (talk) 19:09, 15 April 2020 (UTC)

Does this mean that in theory some viruses could be eradicated? Maybe the ones which weren’t that common to start with. 90.198.251.144 (talk) 09:45, 16 April 2020 (UTC)

Apart from samples kept in a few high-security research labs around the world, the viruses causing smallpox and rinderpest have been eradicated. See Eradication of infectious diseases.  --Lambiam 15:28, 16 April 2020 (UTC)

If you mean, could some diseases be eradicated accidentally, as a by-product of the social isolation, then I think it's a really long shot. It would have to be a disease that only has human reservoirs (i.e. doesn't exist in animal populations (so not influenza) or out in the environment (so not anthrax)), and it would have to resolve fairly quickly (so not HIV), not have asymptomatic carriers (so not typhoid), and already be rare enough (so not measles) to not slip through the cracks of populations who cannot or will not self-isolate. I've only listed a handful of examples, but each one could be expanded hugely. It's really unlikely that something would fall into all those categories simultaneously. We're not going to wake up one day and find out that diphtheria is just... gone. Matt Deres (talk) 14:24, 17 April 2020 (UTC)

Radio waves are not electromagnetic

In wikipedia articles on electromagnetic waves, Radio waves and Heinrich Rudolf Hertz it is stated or implied that Hertz has demonstrated that radio waves are electromagnetic. These articles are often accompanied by the diagram of the electromagnetic wave showing the magnetic and the electric component of the wave. Such a statement is not correct because Hertz has in fact detected his waves with the help of a loop of wire through electromagnetic induction, which means that he detected only the magnetic component of the wave. Thus Hertz had no means to detect the electric component. The authors of the wikipedia articles on the topics mentioned above need to refer the reader to the experiments (if any) that proved the existence of an electrical component in the radio wave.--2405:9800:BA00:3477:117:FE22:C3E0:C875 (talk) 20:13, 15 April 2020 (UTC)

Radio waves are absolutely electromagnetic, as are all parts of the electromagnetic spectrum. There is no functional physical distinction between phenomena such as light waves, radio waves, X-rays, gamma rays, etc. except that our human sense organs (eyes) are specifically tuned to react chemically to a specific narrow set of wavelengths in that spectrum. They are all electromagnetic waves. Uunderstanding that radio IS an electromagnetic wave really comes from Maxwell's equations, (which are probably more properly termed Heaviside's equations, but you know, we're stuck with existing nomenclature, see History of Maxwell's equations for more of the gory details) which establish the three-legged stool that is electricity, magnetism, and light as being all different manifestations of the same phenomenon. What Hertz did was to provide experimental verification of the relationship between what we now call "electromagnetic waves" (light more generally, including radio) and electromagnetism. Electricity and magnetism were already experimentally linked by Ørsted some decades before even Maxwell; Hertz therefore didn't also need to establish the connection between electricity and magnetism; by experimentally verifying Maxwell's connection between magnetism and light, he effectively united all three phenomena, and unlike your assertions, did not also need to establish the connection of magnetism to electricity. That was done at least 2 generations earlier. --Jayron32 20:32, 15 April 2020 (UTC)

Also, besides James Clerk Maxwell, Hertz, and Oersted, you probably also want to look into the works of many other scientists to understand the many, many contributions to the field that led to our current understanding of electromagnetism and light. Oliver Heaviside, as noted above, provided us with our modern formulations of what we still call the Maxwell equations. Michael Faraday established the connection between magnetism and visible light, among many of his other contributions. André-Marie Ampère did additional experimentation based on Ørsted's earlier work. Charles-Augustin de Coulomb did some of the earliest work on connecting electricity and magnetism, noting the similar ways in which the two phenomena behaved, though he stopped short of recognizing them as physically connected in the way that later physicists did. Henry Cavendish also did some early work in the field that went into inspiring much of Maxwell's work. Joseph Larmor established the mathematical relationships between the motions of electrically charged particles and the emission of electromagnetic waves. There's probably dozens more you can read about at History of electromagnetic theory, those are just one's that I could think of off the top of my head. --Jayron32 20:44, 15 April 2020 (UTC)

Click here for Hertz's experiments that confirmed Maxwell's prediction that coupled electric and magnetic fields could travel through space as an EM ("electromagnetic wave"). This was not a single experiment but a range of experiments that confirmed the reflection, polarization, refraction, standing wave and speed properties of the EM. The OP's denial of the EM's nature that mainstream science has understood for more than a century as "incorrect" is arrogant and the title of the OP's non-question is merely provocative. DroneB (talk) 12:23, 16 April 2020 (UTC)

Sadly, this sort of thing is a problem with the persistent Great Man history version of science that scientific progress occurs through the herculean efforts of a select few great men, who perform singular feats of scientific discovery that the entirety of human understanding turns on. Instead, scientific advancement happens rather incrementally through the gradual and persistent effort of thousands and thousands of people working both independently and in collaboration, and who we give "credit" to is largely a function of public relations and marketing more than actual importance. I mean, as I noted above, look at Maxwell's equations. Don't get me wrong, Maxwell was super important, but not nearly as important as "Single-handedly invented the modern formulation of electromagnetism in 4 simple equations". There were dozens of people both before Maxwell and after Maxwell that put in a TON of work in developing that formulation, and while convenient, it does a massive disservice to the complexity of the process to do that. That's why people think they can do what the OP did: "I found a mistake in the work of so-and-so, so that MUST bring down the entirety of what all of science thinks". No, it doesn't. Because even if you did find that mistake, we weren't hanging our understanding on one person, or on one event or experiment. And guess what, even if you did find that mistake, someone already found it before you and fixed it. Arrogant is correct, but in many ways that arrogance is the fault of our historiography of science more than anything, and we're still dealing with this silly Great Man thinking today. --Jayron32 13:58, 16 April 2020 (UTC)

That was one of the main points of the TV series Connections, that everything we have invented built on previous things. Recently there was a show on PBS, I think it was, which exposed the fact that Leonardo DaVinci, who has almost a god-like reputation, had many entries in his notes which were copies of others' ideas. What DaVinci did in many cases was to improve upon those ideas. Kind of like guys such as Edison and Ford, whose main claim to fame was improving on things that often already existed in some form or another. And Edison, for example, didn't sit there all alone testing filaments until he found one that worked - he had a whole team working on it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:23, 16 April 2020 (UTC)

Such a good show. Everything James Burke has done is fantastic. Love all of his work. --Jayron32 14:35, 16 April 2020 (UTC)

The wisest of the philosophers was asked: "We admit that our predecessors were wiser than we. At the same time we criticize their comments, often rejecting them and claiming that the truth rests with us. How is this possible?" The wise philosopher responded: "Who sees further a dwarf or a giant? Surely a giant for his eyes are situated at a higher level than those of the dwarf. But if the dwarf is placed on the shoulders of the giant who sees further? ... So too we are dwarfs astride the shoulders of giants. We master their wisdom and move beyond it. Due to their wisdom we grow wise and are able to say all that we say, but not because we are greater than they. - Isaiah di Trani 1180 - 1250. Echoed by Isaac Newton in 1675: "If I have seen further it is by standing on the shoulders of Giants." DroneB (talk) 16:52, 16 April 2020 (UTC)

Sigh. Still not one of the above wikipedia editors is able to give a single reference to an experiment that detected the electric component of the so-called "electromagnetic" wave. So arrogant of me to ask a basic question required by the scientific method of investigation. Again, Hertz detected the waves with a loop of wire - that is through electromagnetic induction, so he detected only the magnetic component of the wave. And no one detected the electric component since then. This means that, as of today, radio waves are just magnetic waves. Which, incidentally, is what Stokes thought of Hughes' waves when he was called to investigate them 7 years before Hertz did his experiments. When you have the experimental evidence of the detection of the electric component of the "electromagnetic" wave, pls. let me know. Much appreciated. :)--Idnwiki (talk) 16:59, 16 April 2020 (UTC)

The unification of electricity and magnetism was first demonstrated by the experiments of Hans Christian Ørsted and shortly thereafter by André-Marie Ampère and Michael Faraday in the early 1800s. The work of James Clerk Maxwell established the geometric relationship between electric and magnetic waves that co-propagate orthogonally, and also established that these electromagnetic waves should be indistinguishable from light. Hertz's experiments established the connection between these co-propagating waves and light, specifically in the radio band, but radio is not a different phenomena than light (as shown by Oliver Lodge among many others), and Hertz's work was expanded on by the work of Jagadish Chandra Bose. Your question is nonsensical; asking how one would detect the "electrical component" as distinct from the "magnetic component" is like asking one to isolate the head of a coin from its tails. The two were inextricably linked via Maxwell et. al. and determined to be different manifestations of the same phenomenon, not individually isolatable phenomena. This was further demonstrated by the connections between special relativity and electromagnetism; which established that there is no reference frame that one can use to make consistent measurements of the electromagnetic force such that the "electric component" and "magnetic component" can be definitively isolated, and that really whether one observes the force as electrical or magnetic is really about which reference frame you choose to observe the phenomenon (see Lorentz force). You can see a pretty good explanation of this problem here or here. The ultimate point is; your question is nonsensical and by asking it you're showing a common misunderstanding of the nature of electromagnetism. We're trying to explain to you what that misunderstanding is, so you stop asking the nonsensical question. --Jayron32 17:21, 16 April 2020 (UTC)

In simple terms: changes in the magnetic field strength induce an electric component. The laws determining the precise relationship are given by Maxwell's equations. They have been confirmed experimentally with high precision. But every working dynamo is an experimental confirmation of the existence of this relationship. It works two ways: an electromotor is essentially a dynamo working in reverse. In modern high-speed electric trains and in many hybrid cars (e.g. Tesla), the motors become dynamos when the vehicle is reducing speed, allowing to save energy by storing the electricity generated in batteries. A "magnetic wave" implies a varying magnetic field strength – otherwise it would not be a (moving) wave. Therefore the electric component is an unavoidable companion.  --Lambiam 17:38, 16 April 2020 (UTC)

@Idnwiki You have been politely asked to stop posts at Talk:Electromagnetic_radiation such as [4] and [5] in which you demand to be given a proof just to satisfy you. However when you contend that there is no electric field in a radio wave the burden of proof is on you to explain how a microwave oven heats and why the ratio of the electromagnetic and electrostatic units of charge, 1/√ε₀μ₀ gives the speed of radio waves. DroneB (talk) 17:43, 16 April 2020 (UTC)

@Jayron32 In the reference frame in which the wave is produced, there are electric and magnetic fields that exist as such in and around the antenna and that can be detected through different methods and with different apparatus. What I get from you is only insults, attacks, not experimental proofs. It is nonsensical to know that the antenna had originally electric and magnetic fields and then say that in the wave produced these two become indistinguishable even if they are detected in the same reference frame as the transmitting antenna.--Idnwiki (talk) 17:48, 16 April 2020 (UTC)

@DroneB. Yes, I was asked that and so I did. And I was directed to ask further in this section. Still no meaninful answer, nothing new. All that you all 've been telling me I already know (and a little more than that). Now I am told by @Jayron32 that the electric and magnetic components of the "electromagnetic" wave are actually not distuishable any more. Thanks very much. Maybe you can explain then how the reception occurs in the receiving antenna. --Idnwiki (talk) 17:54, 16 April 2020 (UTC)

No one has insulted you. We've been trying to understand and to explain to you the misconceptions you seen to have that are leading you to the wrong conclusions. You've started by asking your question based on a premise that isn't a correct understanding. Simply put, we cannot answer your question as asked because it presumes certain things to be true that are not. I'm not sure what else we could do for you, you're trying to play "Gotcha" with 300 years of physics. That isn't how any of this works. You can either try to learn the physics (which will probably take quite a while is outside the scope of this desk) or you can accept that those thousands of scientists over those 350 years knew what they were doing. You've come up with some weird beliefs, and unless you are willing to dispossess yourself of those beliefs, and take learning physics with a dose of humility in deference to the people who did this work already, in not sure what else we can do. You aren't arguing with us, you're arguing with all of physics on this. --Jayron32 18:27, 16 April 2020 (UTC)

If you would like an experimental demonstration, try your microwave oven. Most would consider the radiation from it to be "radio waves," since it is roughly the sam portion of the spectrum as wifi and bluetooth. That it heats water is due to the electric component of the radio wave electromagnetic radiation. The electric field component of the radiation is what interacts with the electric dipole moment of a given molecule (say, water) to induce rotational molecular motion. You can do this experiment yourself. This can occur in molecules without unpaired electrons in any orbitals, and thus cannot be explained by any type of paramagnetic properties alone. --OuroborosCobra (talk) 18:51, 16 April 2020 (UTC)

The article Antenna (radio) is a good place to start. The electric and magnetic field components are distinguishable and you have not been told otherwise. They are orthogonal in the propagating EM wave. The polarization of an antenna refers to the orientation of the electric field (E-plane) of the radio wave with respect to the Earth's surface. Of the many Antenna types let's take the Yagi–Uda antenna that is a common sight on house rooves where analog TV is broadcast. The element rods have to be horizontal or vertical to match the plane of the electric field from the local transmitter. DroneB (talk) 19:07, 16 April 2020 (UTC)

I think the problem is that when the OP isn't asking a question about how an electromagnetic wave interacts with antennas. They are asserting the rather nonsensical position that no experiment has ever been done that shown that the interactions between radio waves and antennas showing the existence of electric component of the electromagnetic wave, and then demanding we produce an experiment that proves them wrong. I'm growing weary of arguing with someone who comes seeking affirmation rather than information. --Jayron32 19:59, 16 April 2020 (UTC)

I think I have read much more than what you wrote in your wikipedia article on Antenna (radio), including the references. And the arguments of "300 years" and of the "many scientists" and of "arguing with all of physics on this" (plus the virulent answers of some of you) do not scare me neither convince me. You should know that people are not discouraged by these methods of intimidation. Many people thought that airplanes cannot fly, in the phlogiston and many other nonsense in their times. Yagi antenna and any receiving antenna works through electromagnetic induction - a current is induced in the antenna by the magnetic component of the radio wave. The only plausible experimental proof of the existence of the electric component (which IS the thing I've been asking for from the beginning) seems to be microwaves/water system. I'll look into it, thanks. But the way some of you choose to treat someone posing a legitimate scientific question is disgusting and shameful. You know who you are.--Idnwiki (talk) 20:15, 16 April 2020 (UTC)

Well, you are what you've described, for one. --OuroborosCobra (talk) 20:29, 16 April 2020 (UTC)

I don't think it good form for me to box an exchange in which I have taken part and there have been excellent references in most of the responses here. However if an uninvolved editor decides to box this whole discussion that arose not from a question, more like an insubstantial complaint, that will put a tidy end to the matter. DroneB (talk) 21:17, 16 April 2020 (UTC)

Just for the record: wikipedia editors state that radio waves are electromagnetic. They show the electromagnetic wave having electric and magnetic components. Then someone (me) asks for proof that the electric component of the wave has been detected and for adding reference to such proof in articles. The wikipedia editors do not give any such proof but instead call the question "nonsensical", "arrogant" and "provocative", implying that the person asking the question needs to study more, although the issue raised is legitimate from the point of view of the rules of scientific method of investigation.Typical.--Idnwiki (talk) 04:20, 17 April 2020 (UTC)

@Idnwiki: Then the proper trick were I know that electromagnetic radiation has an electric and a magnetic component. Please show me an experiment which detects the electrical component. That would have spared the irritation from people thinking you wanted to revise hundreds of years of physics. Tgeorgescu (talk) 04:52, 17 April 2020 (UTC)

Yes, such a genuine request would have brought helpful replies. Here are practical tests of the electric component of an EM wave.

• Go to where a TV is receiving a VHF or UHF broadcast with a Yagi antenna. Rotate the antenna on its axis 90 degrees to move the dipole rods from the signal E-plane to the signal H-plane. Explain why this particular antenna stops working even though it is oriented the same as other antennas in other areas that do work well.
• Satisfy yourself by experiment that a Faraday shield blocks radio waves but does not block a magnetic field.
• Attempt to feed more rf power into a waveguide than the electrical breakdown in air limit calculation[6] allows.

It's not too late to study how the rate of change of D, the electric displacement field is a source of the magnetic field just as actual current is. DroneB (talk) 12:44, 17 April 2020 (UTC)

Just to add a quick link to Yagi–Uda antenna (despite how common they are/were and simple design, they aren't often called by this formal name in lay language), Faraday shield (easy to build), and waveguide. DMacks (talk) 15:10, 17 April 2020 (UTC)

Separate question
So a moving electrical current creates a magnetic field. Is it possible to distinguish a magnetic field that originated from AC electricity and DC electricity? 67.175.224.138 (talk) 12:51, 18 April 2020 (UTC).

Yes because an AC (Alternating Current) flow creates an alternating magnetic field that in turn induces an alternating voltage in a conductor such as a wire or a coil, which can be measured. (This is how a Transformer works.) A DC (Direct Current) flow just creates a steady magnetic field, like a bar magnet. DroneB (talk) 13:30, 18 April 2020 (UTC)

And since DC electricity is a type of AC electricity, DC electricity is actually AC electricity with a frequency = 0. So when they're both create a magnetic field, does that bar magnet have something = 0? 67.175.224.138 (talk) 00:26, 19 April 2020 (UTC).

"DC electricity is a type of AC electricity"??? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:45, 19 April 2020 (UTC)

Right, only when the frequency is 0. 67.175.224.138 (talk) 01:59, 19 April 2020 (UTC).

Wrong, "zero frequency AC" is an Oxymoron because "zero frequency" means not alternating and steady. Here is further reading about Magnetism. DroneB (talk) 12:03, 20 April 2020 (UTC)

How is this comment replying to me and not Bugs? When the frequency of AC electricity becomes 0, then it is now DC electricity, by definition. So what becomes 0 in bar magnets? 67.175.224.138 (talk) 17:23, 20 April 2020 (UTC).

@IP User 67.175.224.138 my indent and language are clear in rejecting your claim. Your "separate question" was answered. (You may ask about the mathematical variable Frequency that can have negative, complex or zero value by submitting a properly framed request for references.) However this thread can not be prolonged into a debate to investigate what ideas you have about permanent magnets or Magnetism. DroneB (talk) 11:50, 21 April 2020 (UTC)

April 16

Aviation / ADS-B / which parameters are sent?

Hi! I believe, I heard in 2015, that todays airplanes transmit their intended flight level via radio frequencies, that everybody could "hear" and then decode. E. g.: The plane is at 30000ft and the pilot configures the flight computer to 20000ft and then the plane sends to the ground "<time stamp> <airline specific parameter id> <value>". Is it true? I cant find that in Automatic dependent surveillance – broadcast. Is it used now for quality assurance, so that pilots, who are too far off, win a flower pot, so that they can see how beautiful the world can be? Thx. Bye. --Homer Landskirty (talk) 14:39, 16 April 2020 (UTC)

ADSB (Automatic dependent surveillance – broadcast) sends a periodic message that provides actual position, velocity and time but, at present not pilot intent. DroneB (talk) 17:58, 16 April 2020 (UTC)

hmmm... ohoh... and ACARS? or was it fake news? they said FlightRadar24.com saw it, too... and that every airline uses its own id and scaling (e.g.: 0 meant 100ft for D-AIPX)... --Homer Landskirty (talk) 18:23, 16 April 2020 (UTC)

A few things have changed with respect to ADSB since 2015 - especially in the United States. Most prominently, the very-heavily-advertised January 1 2020 deadline has long passed; and nearly all aircraft in the United States National Airspace System now require operational ADS-B equipment when flying in "most controlled airspace". Those who need to know these things... should already know these things; and if they didn't get the memo yet, ... somebody with authority has almost surely found them by now.

Here's a few highlights from FAA's website:

• Automatic Dependent Surveillance-Broadcast (ADS-B) - a general overview
• Equip ADS-B - information for aircraft owners and operators
• Information on ADS-B Capabilities
  • ADS-B In and ADS-B Out, including TIS-B, FIS-B, ADS-R, and related technologies
  • Resources, including easy links to the relevant regulations, TSOs, and technical papers; and statements of policy

Like many aspects of aerospace engineering, the technical details of the technology that we lump together as "ADS-B" can become quite complicated. So it's really important to think about formulating your question more specifically. Are you looking for engineering resources? Legal or regulatory guidance? Information for pilots? Information for mechanics? Information for aircraft owners? Information for aeronautical or engineering students? Information for HAM-radio enthusiasts? Information for people (pilots, operators, ...) who are not in the United States? ... There are a lot of different communities who have stake in this kind of thing - and while it's very thoroughly documented, it can be hard to navigate - so let us know if we can point you to a more appropriate source.

And if you're just looking to waste time while hanging around indoors, may I recommend that you take advantage of all this free-time to start memorizing the FARs in preparation for some future day when you might want to accomplish a checkride? I guarantee that no matter how much free time you have, there are enough FARs to fill them...

Nimur (talk) 18:24, 16 April 2020 (UTC)

actually i look for proof, that it is not my delusion, when i say, that those engineers at my university r insane... my psychiatrists always say, that i am insane, although they never even spoke with those engineers (one even told me that a professor warned him, not to be too radical, because radicals just hurt, if they get to much... he always intrigued and lied IMO...)... i mean: if they talk about engineers in general, then one example should be reason enough, to reconsider the diagnosis/medication they gave me... --Homer Landskirty (talk) 18:55, 16 April 2020 (UTC)

there r the findings of flightradar24: [7]... looks like they received the config of the autopilot... right? --Homer Landskirty (talk) 18:41, 16 April 2020 (UTC)

April 17

tele video on camera phone

for shooting video on camera phone, can the rear tele camera be used? reviews only discuss video on the main camera. this is on phones with a designated tele camera, like the Realme 6 Pro. thanks! --RM — Preceding unsigned comment added by 14.194.233.88 (talk) 22:04, 16 April 2020 (UTC)

Most reviews on phones I read discuss both front and rear cameras. Certainly both can be used for video. --OuroborosCobra (talk) 02:00, 17 April 2020 (UTC)

I believe that our questioner is asking if phones with multiple cameras on the rear are able to take video from all of them. For instance, the specifications for the aforementioned Realme 6 indicate that is has four rear facing cameras:

64 MP, f/1.8, 26mm (wide), 1/1.72", 0.8µm, PDAF

8 MP, f/2.3, 13mm (ultrawide), 1/4.0", 1.12µm

2 MP, f/2.4, 22mm (macro), 1/5.0", 1.75µm

2 MP B/W, f/2.4, (depth)

but does not indicate which can record video, saying only:

2160@30fps, 1080p@30/60/120fps, gyro-EIS

-- ToE 13:31, 17 April 2020 (UTC)

I don't know why this is on the science desk. But I can say that my Huawei P30 can record video from any of the 3 rear cameras. While multiple rear cameras are starting to get more common, I would be surprised if here is any phone that is flawed enough that it cannot record video from any normal rear camera. (Specialist cameras like depth ones may be more complicated although they are probably sometimes used for video, as opposed to recording video.) I would suggest a more careful look at the review would probably reveal if it can record using all rear cameras at least if it's a decent review. E.g. if screenshots show the option on the camera app when recording video, or if review discusses how each camera performs at video. The review may also have samples of video from the different camera. Nil Einne (talk) 22:58, 17 April 2020 (UTC)

As I claimed see e.g. this review for the Realme 6 [8] which does discuss video of both the ultrawide and wide cameras. To be fair it also strongly implies the macro camera cannot be used for video, but that's sort of a specialist camera even if it can be used directly for photos, so this isn't that surprising. Note that this review also demonstrates the point I was trying to make. The video quality can vary quite a bit depending on the camera used. So any decent review should look at the different cameras. (Although it does look like the review failed to look at video for the front camera. An interesting omission in this time of lockdowns in many places including India.) Nil Einne (talk) 23:04, 17 April 2020 (UTC)

thanks! --RM

Whitcomb rule for cars?

is the Porsche 911 GT1 designed according to Whitcomb rule? is it of any value at these speeds? thanks! --RM

The Whitcomb area rule, also called the transonic area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.75 and 1.2 (575 to 920 mph, 926 to 1482 kph), see Area rule. A Porsche 911 GT3 manages at most "only" 193 mph (311 km/h) and the GT1 is slower, so No and No. DroneB (talk) 01:18, 17 April 2020 (UTC)

Quiz question. One GT3 can manage Mach 0.25. How much can four GT3s manage?  --Lambiam 08:18, 17 April 2020 (UTC)

Quiz answer: by exchanging fuel they can send one car twice as far. Cars #1..4 set off in parallel. When cars #1 & #3 consume 50% fuel they stop and instantly (this part is magic) give their remaining fuel to cars #2 and #4 respectively. When cars #2 and #4 again have 50% fuel, car #2 stops and (magic again) gives its remaining fuel to car #4. Car #4 now has full fuel tank again and completes the trip. DroneB (talk) 15:39, 17 April 2020 (UTC)

Car #1 is driving on the roof of car #2, car #3 on the roof of car #2, and car #4 on the roof of car #3. Net result is car #4 much greater than Mach 0.25 in the frame of an observer outside the car-stack. Sadly even if we do this as plain vector addion, neglecting all aerodynamic, acceleration-distance, and wobbly-stack concerns, we can only get up to Mach 13.25, as the next Mach 0.25 increment is missing. DMacks (talk) 15:56, 17 April 2020 (UTC)

At User:DroneB's request, I have small'ed my US-centric ancient pop-culture humor. DMacks (talk) 02:24, 20 April 2020 (UTC)

Ooh! Ooh! ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:51, 20 April 2020 (UTC)

Dare I say, the speed and aerodynamics of four cars driving near each other at high velocity are governed by difficult nonlinear equations? 16:14, 17 April 2020 (UTC)

The hell they do. DMacks (talk) 16:20, 17 April 2020 (UTC)

We have a Whitcomb area rule article. DMacks (talk) 14:51, 17 April 2020 (UTC)

thanks! --RM

What is the color of iron(II) selenate???

I'm don't sure that iron(II) selenate will have green colored (penta- and hepta- hydrate). So what is color of this compound??? (Sorry if you don't understand, because my English is not good).--Ccv2020 (talk) 09:55, 17 April 2020 (UTC)

It appears to be a compound without nearly any commercial application; indeed I can't find anything more than confirmation that it is possible to make it. There is not even an MSDS for it [9] which is a dead giveaway that you literally can't buy it anywhere, which will put a crimp on finding pictures of it to check out the color. As such, it is super rare to find anything about it online; the Wikipedia article iron(II) selenate has only one non-print reference, but even that is a scan of a 1918 paper describing its synthesis. I can't find anything at all about it more recently than a few random papers that mention it from the mid 1990s. Your question may not be easily answerable from available information. --Jayron32 12:40, 17 April 2020 (UTC)

Could one estimate it computationally through ligand field theory? Yanping Nora Soong (talk) 14:59, 17 April 2020 (UTC)

Could one? Maybe. Has one? Probably not. --Jayron32 15:02, 17 April 2020 (UTC)

Tutton in the 1918 paper mentioned describes the mother liquor as green but the crystal were very hard to obtain, decomposing quickly with heat and air and he never seems to actually state the color of the crystal itself but notes the red and brown opaque contamination as they decompose. Green is most likely. Having worked on similar crystals, modern inert atmosphere techniques and vacuum systems as well as ice baths would seem to make the synthesis much simpler today but his story of waiting for a record cold snap in a severe winter to run the successful double salt reactions makes for an amusing story. Rmhermen (talk) 04:53, 18 April 2020 (UTC)

I agree green makes sense. Selenate probably adds little too the color, and iron (II) compounds are often a pale green in color.--Jayron32 18:00, 18 April 2020 (UTC)

Why do some scientists keep calling the Warburg effect and aerobic fermentation "inefficient"?

I've been a little confused by these two articles. We're covering these topics in grad school and almost all my lecturers take it as a given that aerobic glycolysis promotes accumulation of biomass (e.g. anabolism) rather than oxidation of carbon-carbon bonds to carbon dioxide (i.e. catabolism). I'm aware there are many nuances, including apoptosis and particular molecular targets or mediators, but overall, this seems like such an obvious driving force. Why do some scientists keep calling aerobic fermentation "inefficient"? Oxidative phosphorylation efficiently produces ATP, but it does not efficiently produce fatty acids to expand the lipid bilayer or new amino acids. Much of our assigned readings and reviews argue that in fact aerobic glycolysis is very efficient at incorporating biomass, just not that efficient at conserving ATP in times of starvation, emphasizing parallels between the "well-fed state" and the "starvation state" at both the systemic and cellular levels. Yanping Nora Soong (talk) 09:57, 17 April 2020 (UTC)

I think they're just alluding to the fact that aerobic respiration releases much more energy per molecule of substrate. At least for most animals I believe fatty acids and amino acids are obtained from the diet if possible; anabolic pathways are mainly used to convert one type into another as needed. De novo synthesis is done mainly to store excess nutrients or when needed in the fasting state, and essential nutrients can't be synthesized de novo at all. Not sure exactly how that goes in other organisms. I mean, I think you're right that calling it "inefficient" is probably an oversimplification. It sounds like people calling it that are thinking in terms of whole multicellular organisms rather than the cellular level.

Side note, but at least for most mammals, anabolism is linked to the well-fed state by insulin. When you're well-fed, high insulin levels promote uptake of nutrients and tissue repair and growth. --47.146.63.87 (talk) 22:54, 17 April 2020 (UTC)

Yes, but for T-cells, yeast and cancer cells alike, who are rapidly proliferating, glucose is a much faster way of obtaining biomass than capture of fatty acids AFAIK. Yanping Nora Soong (talk) 11:34, 20 April 2020 (UTC)

Yes, they're explicitly talking about the inefficient production of ATP per molecule of glucose. Honestly it strikes me as weird to talk about fermentation as being a better route toward biomass accumulation, since this necessarily ignores its last step, which leaves that carbon trapped in a toxic byproduct. And this can't explain the preference for fermentation when carbon is not a limiting factor to growth. But in that case, fermentation still has the advantage of being significantly faster in terms of atp production per unit biomass per unit time. That is, even though respiration generates 16 times the usable energy per glucose, fermentation is so much faster that it can overcome that. Though even that can't fully explain the preference. It's pretty complicated, not fully understood, and numerous models are still being debated. I'd point you to [10] What is generally agreed on is that when a cell is uptaking glucose very quickly, the use of fermentation leads to faster accumulation of biomass, though does not require that fermentation is even the pathway through which the biomass is being accumulated. Someguy1221 (talk) 13:41, 18 April 2020 (UTC)

Proliferating T-cells show Warburg effect-like metabolism ... indeed, any proliferating cell. Does the sheer amount carbon of glucose end up in pyruvate? What about the pentose phosphate pathway? Yanping Nora Soong (talk) 11:34, 20 April 2020 (UTC)

Depends on the cell of course, but most of it leaves as lactate, with glutamine instead being used as a source of carbon for making new molecules. [11]. A lot of microbes also prefer this arrangement. Someguy1221 (talk) 13:12, 21 April 2020 (UTC)

Scientific evidence of possibility of lab theories (Coronavirus)

Is there any scientific basis currently in the politicians claims that the SARS-COV2 could have been accidentally released from a lab? 90.198.251.144 (talk) 11:33, 17 April 2020 (UTC)

It depends on the politicians. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:06, 17 April 2020 (UTC)

No. it is a bullshit conspiracy theory. You should pay it no mind, and become highly suspicious of anyone who claims such nonsense as credible.[12]. In the U.S., the main sources of the "theory" seem to be 1) Fox News 2) the New York Post (basically the print arm of Fox News) and 3) The Trump Administration, who started making public statements about it after Fox News began floating the idea (this is a standard pattern for statements by the Trump administration). In China, a similar theory is that it was created by the U.S. and released in China as a sort of bioweapon.[13]. Both of these are bullshit theories. Nearly all actual reliable sources make it clear two things 1) we don't know much about it at all, and making definitive statements are hard and 2) what we do know seems to lean towards a zoonotic origin, likely a market in Wuhan. See [14] for example. This is probably the best non-press summary about the current understanding. Scientists who are studying the disease most intently have a pretty clear consensus this is of natural origin. The "Made in a lab" bullshit is only coming from news organizations with sketchy reputations and non-scientific government officials with axes to grind. --Jayron32 12:53, 17 April 2020 (UTC)

It is not helpful to conflate "Made in a lab" conspiracy theories with the "naturally occurring virus accidentally released by lab which was studying it" question asked here. For the latter, see Misinformation related to the 2019–20 coronavirus pandemic#Accidental leakage. -- ToE 13:44, 17 April 2020 (UTC)

It's still a bullshit conspiracy theory. You'll note that you linked to the "misinformation" article. --Jayron32 15:01, 17 April 2020 (UTC)

I think it is incorrect to call it a "conspiracy theory" if the theory involves no conspiracies – except for the authorities not coming clean about it, which however is a ubiquitous phenomenon with people in power. Also, it is not impossible; the lab in question studies coronaviruses obtained from wildlife. Accidents happen, and the lab is situated close to the market. However, there is not a thread of non-circumstantial evidence, and specific allegations brought forward that seemingly support the theory appear, on closer inspection, to be made up or in any case incorrect. There is even no certainty that the wet market (or its close surroundings) were the source; it can have been a highly focal but secondary source.  --Lambiam 17:57, 17 April 2020 (UTC)

I agree, it's not a conspiracy theory. However, it's then a bit strange that the accidentally released virus happens to be such a massive problem for us now. If a lab collected coronaviruses from nature for study, then how did they end up with such a problematic virus for us? So, if it really happened this way, then the lab would likely have done experiments like e.g. mixing SARS with other viruses to see if a virus that is more infectious to humans than SARS could arise in nature. Count Iblis (talk) 19:37, 17 April 2020 (UTC)

"Naturally occurring virus accidentally released by lab which was studying it" would be easy to prove if that had happened. Scientific research, including at labs like that in Wuhan, is well documented. Early in working with a virus like this, they would have sequenced its genome (which, in fact, the Chinese did do early on in the outbreak, as there was no genome before the outbreak). That would be a very early step used then to classify any other results they made while studying this viral strain in comparison to other coronaviruses, such as SARS-CoV-1 and MERS. So... where's the documentation? All of the documentation out of Wuhan studying coronaviruses have different genomes than SARS-CoV-2, different enough that it clearly isn't a release from their lab. In my own lab, I could tell you the genome of the strains of infectious bacteria that I work with. I don't just know that I work with Staphylococcus aureus, but I know down to monoclonal strains, such as S. aureus Newman D2C NCTC 10833 or USA-300 strain of MRSA, etc. If the SARS-CoV-2 strain wasn't in their laboratory, they can't have accidentally released it. However, we HAVE found almost identical strains of coronavirus in bats and pangolins, which is why we think they are the likely zoonotic vector (most recently I have seen pangolins to bats to humans). There is a lot of piling evidence for the zoonotic vector, and zero evidence for an accidental lab release. It is still a conspiracy theory, as in order for it to be true, there would have to be a well organized conspiracy to suppress the evidence of a lab release. --OuroborosCobra (talk) 19:44, 17 April 2020 (UTC)

This. --Jayron32 20:09, 17 April 2020 (UTC)

Trump says it's plausible because "that bat wasn't in that area". Count Iblis (talk) 23:47, 17 April 2020 (UTC)

That is a really phenomenal example of an either-or fallacy. Someguy1221 (talk) 13:51, 18 April 2020 (UTC)

Conveniently ignoring the fact that bats fly and pangolins (also involved and the more likely final animal-to-human vector in this case) get moved around by people as part of the food and "traditional medicines" trades. {The poster formerly known as 87.81.230.195} 90.203.117.240 (talk) 03:30, 18 April 2020 (UTC)

If anyone is interested in shaping how our articles cover or don't cover this, they may want to participate in Talk:2019–20 coronavirus pandemic#Leaked from lab, in particular Talk:2019–20 coronavirus pandemic#Break. Nil Einne (talk) 11:39, 18 April 2020 (UTC) 02:55, 19 April 2020 (UTC)

Could presession (rosette-shaped orbits) be explained by gyroscopic effects, due to the orbiting body's spin?

Could presession (rosette-shaped orbits) be explained by gyroscopic effects, due to the orbiting body's spin?

Gyroscopic effects make it harder to change the direction of motion of a spinning object. Correct me if I'm wrong, but I believe this effect would affect the motion of a rotating body that's in an elipse-like orbit, more, when it's furthest from the object that it orbits, where gravity is much weaker, causing the far end of the eliptical orbit to be wider, thus causing presession.

What makes me think of this is the recent news report of confirmation of pressession of a star in an excentric orbit around our galaxy's supermassive black-hole. https://www.abc.net.au/news/2020-04-17/chile-astronomers-discover-star-dancing-einstein-theory/12158154

Secondarily, I'd like to know if it might also be because there's more drag closer to the black-hole due to electromagnetic forces or more dense dust-clouds.

I'm aware of possible relativity-based causes, of presession, however the exact mechanism by which this would cause presession has not been well explained in anything I've read thus-far. MathewMunro (talk) 14:18, 17 April 2020 (UTC)

I don't think so. As long as its mass can be considered equivalent to a mass concentrated in the orbiting body's centre of gravity – which is true if its diameter is small compared to its distance at periapsis from the host body – Newton’s laws govern the orbit (if the local spacetime geometry is flat). Gravity is the only force acting on the point mass.  --Lambiam 15:08, 17 April 2020 (UTC)

Lambian, do you believe that the orbit of a rapidly spinning object will be exactly the same as that of one that doesn't spin? I thought that the additional angular momentum of the rotation of a body around its axis would exert forces on its centre of gravity when it is in a gravitational field. Intuitively, if you try to turn an object like a rapidly spinning bicycle wheel, you notice that there are resistive forces that are not present when the wheel isn't rotating. MathewMunro (talk) 21:39, 17 April 2020 (UTC)

Gyroscopic effects make it harder to change the direction of the spin axis of a rapidly spinning object, but have no effect on the motion of the centre of mass. The spin frequency of an orbiting body can affect the apsidal precession (by creating a gravitational quadrupole moment as the object deforms and by relativistic frame dragging), but that's a very small effect and has nothing to do with gyroscopic effects. Read apsidal precession. Note that the general relativistic part of the apsidal precession in that article is not related to frame dragging. PiusImpavidus (talk) 09:15, 18 April 2020 (UTC)

"Gyroscopic effects make it harder to change the direction of the spin axis of a rapidly spinning object, but have no effect on the motion of the centre of mass." Thanks PiusImpavidus (and Lambian) for clearing up that misconception of mine. MathewMunro (talk) 20:58, 18 April 2020 (UTC)

"as the object deforms" - do you mean essentially tidal effects causing an exchange of angular momentum between the orbiting object and the body it orbits? MathewMunro (talk) 19:09, 18 April 2020 (UTC)

Not really. On the one hand there's tidal deformation of the planet orbiting a star (or a star orbiting a supermassive black hole). The tidal forces don't depend on the spin of the object, but the resulting deformation does. On the other hand there's the equatorial bulge of a spinning body. For symmetry reasons it must work both ways, but usually we can ignore the equatorial bulge of the secondary. With these deformations the body is no longer spherically symmetric and equivalent to a point mass, so apsidal precession will result. PiusImpavidus (talk) 09:58, 19 April 2020 (UTC)

Regarding the equatorial bulge of the central body due to spin, if an equatorial bulge were distributed equally on both sides of the line between the centres of mass of both objects, I don't think it would cause a deviation from elliptical motion. However, if the orbital plane & the central body's axis of rotation were oriented such that the equatorial bulge is sometimes off-centre, it would cause a deviation from elliptical motion, however such a bulge is not necessarily going to be offset by the same amount each time like a tidal-bulge is, so it wouldn't cause consistent apsidal precession. MathewMunro (talk) 13:07, 19 April 2020 (UTC)

Consider a spinning planet with its spin axis perpendicular to its orbital plane. The equatorial bulge moves mass from the poles to the equator. Some of this mass ends up at the terminator, sunset or sunrise. This is at the same distance from the star as the poles, so it doesn't affect gravity. Some of it ends up at the places where it's noon or midnight. This moves the mass towards the star or away from it, in the same way as tidal bulges do. The mass moving to the noon side cause a larger increase in gravity than the decrease coming from the mass going to the midnight side, and the effect is stronger when the planet is closer to the star. The effect does not rely on a misalignment between the axes of the ellipsoid of the planet and the line connecting the planet to the star. Redistributing the mass from a point at the centre of the planet to a spherically symmetric shell around it does not have this effect, as most of the surface area of the shell is further away from the star than the centre is, which exactly compensates for the larger increase in gravity for the parts that get closer to the star. PiusImpavidus (talk) 10:31, 20 April 2020 (UTC)

Thanks again PiusImpavidus. What would be the effect of equitorial bulge in the secondary on its orbit? I'm guessing that it would accelerate near the periapsis more than a non-rotating body would, which I'm guessing would swing it wide (negative aspidal presession), and increase eccentricity (although of course, other effects may dominate, and probably do, as most talk seems to be of positive rather than negative aspidal presession).

I'm also guessing that a body in an eliptical orbit, even a non-rotating one, would experience a torque for reasons similar to the ones you describe above (due to the side that is closer to the primary being pulled more strongly than the other side, and the net force being mis-aligned with the centre of mass of the secondary other than when it's travelling perpendicularly to the primary, at the apsis). I'm guessing that in the case of positive aspidal presession, due to asymmetry, there would be a net torque in one direction, I'm guessing it's in the counter-orbital spin direction. Your thoughts? MathewMunro (talk) 11:50, 21 April 2020 (UTC)

Also, since scientists are able to calculate the theoretical effect of spacetime curvature on the orbit very precisely (see Two-body problem in general relativity), the observed precession is adequately described by the theory (but perhaps not by anything you've read).  --Lambiam 15:20, 17 April 2020 (UTC)

Does the OP mean Apsidal precession, Axial precession, or Nodal precession? --Jayron32 15:14, 17 April 2020 (UTC)

The recently observed precession using the Very Large Telescope is reportedly apsidal.^[15]  --Lambiam 15:20, 17 April 2020 (UTC)

The star in question, S2, is at periapsis still 18 billion kilometres away from the black hole. For comparison, that is four times the distance of Neptune from the Sun. It is not plausible that dust clouds have a significant (observable) effect. If they did, causing the orbiting body to lose kinetic energy, the effect would not be precession but inward spiraling.  --Lambiam 15:30, 17 April 2020 (UTC)

Lambian, you wrote that "the effect [of gas-drag] would not be precession but inward spiraling", but might it be counterbalanced by a phenomenon known as "tidal despinning and orbital expansion", as described in this article: https://www.planetary.org/blogs/guest-blogs/2016/1017-rapidly-rotating-regular-satellites-and-tides.html (written by an orbital dynamicist and Associate Professor of Physics). "our own Moon is thought to have been mostly formed at a distance of ~3 Earth radii... Tides are then invoked to move it to its current position at ~60 Earth radii." MathewMunro (talk) 21:28, 17 April 2020 (UTC)

Lambian, there may be much more gas in the vicinity of the galactic centre than you think, even extending out to the range of S2's orbit. Refer to: https://www.mpg.de/8777573/gas-cloud-galactic-centre and https://www.sciencealert.com/strange-objects-have-been-found-orbiting-our-galaxy-s-supermassive-black-hole

The first article shows a picture of the massive gas clouds G1 & G2 whose orbit took them across the path of S2. The second article mentions that in passing close to the galactic centre, they shed outer layers of gas. It also refers to four other similar gas clouds, and suggests that binary star orbits may be destabilised by proximity to the supermassive black-hole, resulting in relatively frequent creation of gas clouds.

Another factor that might be relevant is solar-wind density being greater closer to the galactic centre. MathewMunro (talk) 00:57, 18 April 2020 (UTC)

Tidal locking is caused by a drag-like effect within the rotating body. It has nothing to do with drag caused by the interstellar medium. 93.136.29.149 (talk) 20:20, 18 April 2020 (UTC)

93.136.29.149, S2 would not be in tidal lock with the supermassive black hole. Tidal acceleration (or retardation) likely affects its orbit though. Tidal acceleration would speed-up an object in an eliptical orbit more at the periapsis than at the apoapsis, and if it's in a prograde orbit, that would cause retrograde apsidal presession (however S2 was observed to exhibit prograde apsidal presession), as well as making the orbit larger and more excentric, whereas a retrograde orbit, would have the opposite effect.

It's hard to know what the effect of interstellar medium would have higher average momentum in an outward direction due to sling-shot effects, imparting a net positive kinetic energy and gravitational potential energy to S2, or it may generally cause drag, and more so nearer the periapsis. It clumps and its density varies in a non-systematic way.

Accretion-disk radiation-pressure, would also be greater closer to the black-hole, by a factor greater than the square of the distance between the bodies, because the radiation is not only spreading-out in an inverse-squared way, but also being reduced in intensity as it climbs against gravity. It would also be offset from the black-hole's centre of mass to the approaching side of the accretion disk (presuming it's rotating as most are thought to), due to red or blue-shifting, which would contribute to apsidal presession, consistently.

And there's an inverse r to the sixth power involved in the tidal formulas. So these things may combine in a way that causes apsidal presession without noticable orbital expansion or contraction.

Without knowing the magnitude of all these things, I think it's jumping to conclusions to say that the apsidal presession of S2 proves General Relativity as the mass-media tends to. MathewMunro (talk) 10:57, 20 April 2020 (UTC)

I think we can safely say that electromagnetic effects are negligible. The accretion disk of the supermassive black hole in our Galaxy isn't particularly bright. PiusImpavidus (talk) 09:58, 19 April 2020 (UTC)

I don't know. The radiation pressure article says: "had the effects of the sun's radiation pressure on the spacecraft of the Viking program been ignored, the spacecraft would have missed Mars' orbit by about 15,000 km". Sagitarius A* has been described as "very bright" in radio frequencies. How does it compare to the sun for typical total electromagnetic energy output? MathewMunro (talk) 14:14, 19 April 2020 (UTC)

When I take the mass of the Viking probes and divide it by surface area pointing towards the Sun, I get about 200 kg/m². When I do this for star S2, I get about 5E11 kg/m². Radiation pressure acts on the surface turned towards the radiation source, gravity acts on the mass. So the effect of radiation pressure on the Viking probes, compared to gravity, was about 2.5 billion times stronger than on a star like S2 under the same circumstances. Add to this that Sgr A* is a particularly strong source of gravity (a few million times stronger than the sun). Sgr A* is a strong radio source, but there's little energy and momentum in radio waves. It's also a significant X-ray source, but that's relative: the entire Galaxy is quite dim in X-rays. In optical, you can't even see Sgr A* in images where you can see S2. PiusImpavidus (talk) 10:31, 20 April 2020 (UTC)

Thanks PiusImpavidus, nice. I wonder if the huge mass of Sgr A* would also make tides (and possibly even its own equatorial bulge) relatively less significant in a similar way? And is the mass of the accretion disk likely to be significant? MathewMunro (talk) 11:05, 20 April 2020 (UTC)

If you take a look through this user's contributions, they've come here before to push their pet physics "theory" that totally demolishes relativity. They appear to be here to just ask questions, not to learn. --47.146.63.87 (talk) 22:15, 17 April 2020 (UTC)

47.146.63.87 I deleted your irrelevant and rude contribution once already, as it was not worthy of a reply. Please kindly desist your disruptive editing. MathewMunro (talk) 01:03, 18 April 2020 (UTC)

April 18

Is sidereal month constant?

According to what I see here: "the time interval between two consecutive identical phases of the moon, for example, the time between consecutive new moons. The duration of the synodic month is not constant; the average length is 29.530588 mean solar days, and deviations range up to 13 hours". Is the duration of the synodic month is not constant because the the duration of the sidereal month isn't constant too, or the synodic month is the only one that isn't constant (while the the sidereal is)?

What's the reason for deviation of up to 13 hours in the synodic month?

What's the reason for deviation of up to 13 hours in the synodic month? and where I can find tables for this deviation in details with example of 12 months comparison? It's really interesting to see current examples. Thank you ThePupil (talk) 02:17, 18 April 2020 (UTC)

The sidereal month (also defined on the same site as your link in your previous query) varies with the time of year, because it's measured in relation to the background stars as seen from Earth, which drift around a full 360° over the course of one year (i.e. one orbit of the Earth around the Sun).

If the Earth's orbit around the Sun were circular, this drift would be constant, so the Sidereal month would be (close to) constant. However, the Earth's orbit is actually elliptical: the Earth is closest to the Sun in January and furthest away six months later, so it is moving fastest in January and slowest in July. Consequently the rate of drift of the background stars also varies, and in January (for example), the Moon has to travel a bit further to regain the same position with respect to them.

This is the main reason for the deviations, but there are other longer term variations in both the Moon's orbit around the Earth (see also Lunar theory) and the Earth's around the Sun, which also contribute small amounts.

In my experience, astronomers calculate the deviations using complex formulae when they need to rather than looking them up in tables, but its some decades since I was much involved in this stuff, so I don't know what current references might exist. {The poster formerly known as 87.81.230.195} 90.203.117.240 (talk) 03:20, 18 April 2020 (UTC)

charged particles emit virtual photons at each other? What wavelength/energy?

What kind of function of charge amounts and separation distance is it? Is an integer number of half wavelengths equal to the separation? Also what kind of wavelength/energy would be the photons between quarks inside of a proton?Rich (talk) 07:21, 18 April 2020 (UTC)

The interaction between quarks is mediated by gluons, not photons.  --Lambiam 08:12, 18 April 2020 (UTC)

They're charged particles - there will be an electrical interaction, even if it's not the dominant one. Someguy1221 (talk) 13:52, 18 April 2020 (UTC)

Elaboration: quarks have electric charge as well as color charge (associated with the strong interaction). They interact with each other electromagnetically, but when they are very close to each other, the strong force is much more powerful. --47.146.63.87 (talk) 22:36, 19 April 2020 (UTC)

Nothing is emitted. What is going on here is that a model that describes the true physical situation where the particles couple to photons cannot be treated exactly. We then consider a simplified model where the interaction between the particles and photons is zero, and we then perform an expansion around this zero interaction strength to get to a series expansion in powers of the interaction strength. what then happens is that the terms in this series expansion can be represented diagrammatically (Feynman diagrams) that look like physical processes where photons are emitted and absorbed. But these are not real physical processes. In these computations the so-called virtual photons can have energies and momenta that are not consistent with zero mass, they can have any mass, even an imaginary mass, because you have to integrate over the energies and momenta independently. Count Iblis (talk) 23:23, 18 April 2020 (UTC)

thanks!Rich (talk) 01:07, 19 April 2020 (UTC)

You might also find this helpful, again from Prof. Matt Strassler, written for a general audience. --47.146.63.87 (talk) 22:36, 19 April 2020 (UTC)

April 19

The definition of evolution in relation to humans

Evolution is simply whenever the genetic makeup of a particular population changes as a result of reproduction and, of course, the older generations gradually passing away, correct? The same also applies to human evolution, correct? As in, if a particular human group has its smart members reproduce much more than its not-so-smart members, then this group's genetic makeup is going to change over the generations (and it would also "help" with this that the older generations are gradually going to pass away) and thus this group is going to evolve to become smarter on average, correct? This would be an example of human evolution in action, correct?

All of this seems so obvious but I just want to make sure about all of this considering that I get the impression that some people even nowadays are oblivious as to the fact that humans are not immune from evolution even nowadays and that depending on which members of society reproduce more, humans even nowadays are capable of evolving in all sorts of different ways--whether becoming smarter, becoming duller, becoming thinner, becoming fatter, becoming stronger, becoming weaker, becoming taller, becoming shorter, becoming more liberal, becoming more conservative, et cetera. Of course, at least some of these factors could also be influenced by the environment, but nevertheless my point here is that even nowadays the genetic makeup of a particular human group/population could change through reproduction. thus causing this specific human group/population to evolve in some way. Futurist110 (talk) 06:58, 19 April 2020 (UTC)

See sickle cell trait and lactase persistence for examples of evolution in action in human populations in relatively recent times (last 10,000 years or so). Mikenorton (talk) 08:39, 19 April 2020 (UTC)

Yep, and another, much more controversial hypothesis is that Ashkenazi Jews evolved a higher average IQ over the last 1,200 years or so. If you'll take a look at this article, a 2005 paper actually proposed this as a hypothesis--as in, that there was selection for intelligence among Ashkenazi Jews during the Middle Ages and that smarter Ashkenazi Jews consistently out-reproduced duller Ashkenazi Jews for centuries during this time--thus causing the Ashkenazi Jewish average IQ to increase by ten or more IQ points from 800 AD to, say, 1800 AD or so. Futurist110 (talk) 18:32, 19 April 2020 (UTC)

Isolation of population groups is a factor in evolution. You can observe this in group traits and also in languages. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:47, 19 April 2020 (UTC)

Much of the change in the genetic make-up of Homo sapiens is due to random genetic drift, which is as often detrimental as it is beneficial, the separate minute changes being too small to result in an appreciable selective advantage. Natural selection operates as well, but its "natural" (often cruel) ways are nowadays often mitigated by medical intervention. Featuring a prediction of the long-term evolution of humankind used to be a staple item in pop-science magazines. Usually focussing on the phenotype, they described a future of hairless eggheads with formidable domes to accommodate their phenomenally large brains. For now, a breeding couple's being more educated tends to give more moderately sized litters, so I do not expect being smart to give much advantage until everyone can enjoy a good education. (Frankly speaking, I don't expect it will confer much of an advantage then either.) It only becomes really interesting if we have speciation, like the split into the Eloi and the Morlocks from The Time Machine. In other science fiction stories, space-faring humans have been depicted as having evolved to adapt to the weightless environment. If at some time genetic engineering applied to human embryos becomes socially acceptable (as it is in Brave New World), all bets are off.  --Lambiam 16:49, 19 April 2020 (UTC)

Human intelligence is a hugely polygenic trait which is also massively influenced by environment (nature versus nurture). You seem to be implying "smart parents have smart children", which is not really accurate. --47.146.63.87 (talk) 22:53, 19 April 2020 (UTC)

I tend to believe that the ability to score high on intelligence tests is not 100% an environmental matter, but that there is also a genetic component. I expect that children of very smart parents are, on average, at least a bit smarter than children of very not-smart parents. For evolution to work over very long periods, event slight heritable advantages suffice.  --Lambiam 00:37, 20 April 2020 (UTC)

There is also regression toward the mean to consider. This should also apply to IQ. So, on average, the children of extremely smart parents should be a bit duller than these parents themselves are. I've heard that regression occurs towards the family mean, but when we don't know what the family mean is, we should use the racial mean or ethnic mean instead assuming largely endogamous mating within this specific racial or ethnic group. For the children of mixed-race couples, of course, the regression should be towards the midway point between the means of the races of these children's parents. Futurist110 (talk) 00:57, 20 April 2020 (UTC)

Eugenics had been considered a legitimate scientific subject, but has become a taboo subject for scientists (for the obvious reason). There is, however, something known as New eugenics. 2606:A000:1126:28D:38A7:2D25:F9F0:4858 (talk) 19:05, 19 April 2020 (UTC)

I am actually personally a huge fan of (non-coercive) "new eugenics" just so long as everyone actually manages to have access to this technology--if necessary, through state/government subsidies for those people who cannot afford to use such technology out of their own pockets/checkbooks. Futurist110 (talk) 20:45, 19 April 2020 (UTC)

Do you consider elective abortion to be "non-coercive"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:43, 19 April 2020 (UTC)

Yes, I do. Why? Futurist110 (talk) 00:47, 20 April 2020 (UTC)

Yes, biological evolution is just change over time in a population. Unless a species goes extinct, it's always evolving. There are lots of widespread misconceptions about evolution, often because it's not taught very well, and also in some cases due to misinformation spread by creationists. A lot of people wrongly conceptualize evolution as a process that has some kind of "final result" it's trying to achieve. And because we humans tend to think rather highly of ourselves, many assume humans are the "pinnacle" of evolution and humans are "done evolving"; this can be seen in the outmoded idea of a "great chain of being", which is often still implicitly popularized by the common visual metaphor of a linear progression of human ancestors leading up to modern humans. I like this Rationalwiki page which explores some of these misconceptions. --47.146.63.87 (talk) 22:53, 19 April 2020 (UTC)

I haven't looked at that RationalWiki page specifically and thus won't comment on it, but it's quite interesting how RationalWiki is attempting to smear anyone (such as Richard Haier, Noah Carl, Bo Winegard, and Nathan Cofnas) who argues in favor of an evolutionary explanation to observed human group differences on various important traits (such as intelligence)--or who is at least open to this possibility. RationalWiki denounces such views as "racist pseudoscience" yet it's fairly clear that with different selection pressures, different groups of humans could have indeed evolved differently on various important traits--including within relatively short time periods (such as centuries, in the possible case of Ashkenazi Jews) if the selection pressures on these traits were sufficiently strong. The SPLC is also guilty of being a bit too eager to dismiss such hypotheses (and, of course, to label such hypotheses "racist pseudoscience" or whatever--as if it's actually going to be the end of the world if these hypotheses will actually be proven to be true/correct!), in my honest opinion. In comparison to RationalWiki and the SPLC, people such as Steve Sailer really do appear to be voices, beacons, and paragons of reason in regards to this specific issue. Seriously. Futurist110 (talk) 00:50, 20 April 2020 (UTC)

Nah, the denunciation makes perfect sense. The type of people you're referring to aren't being flagged as racists for having controversial hypotheses - they're being flagged as racists for using uncertain science to argue for racist policies, and/or palling around with nazis (at least when the flagging is being done by those who have actually looked into the issue). The "I'm being persecuted for believing in SCIENCE" line is often a deflection from the real issue. Now, there is definitely a fear of stigmatization and knee-jerk reactions in this field, but that's due to how freaking many of the people publishing in it really are demonstrably racist.

Also, best to avoid ever saying you support eugenics. Simply because of who uses the term, it will for the foreseeable future be assumed to mean, "the coercive or forceful use of government power to prevent reproduction by individuals subjectively considered by those in power to be undesirable, usually on the basis of race, religion or national origin, but ostensibly in the interest of improving the average human condition." For comparison, even the most hardcore supporter of the death penalty would do well not to say something like, "let's do the holocaust, but for criminals."

I, for one, support the availability of genetic counseling and family planning, including voluntary abortion, provided on an individual level by one's own healthcare providers. I think parents should have the freedom to make decisions on the basis of genetics and the best science if so desired. I would never in a million years call this eugenics, because that word is used for racist ideas. Though if someone's idea of family planning is encouraging latinos not to procreate, it's not the word that's the problem. Someguy1221 (talk) 06:20, 20 April 2020 (UTC)

This is why there's a distinction between "positive eugenics" and "negative eugenics". I obviously support the former but not the latter. If terminology is a problem, though, then how about someone comes up with some better terminology for this? For instance, "population genetic improvement" or something even better? Personally, I like the term "positive eugenics", but if there's a better term for this, by all means, please present it!

As for advocating for racist policies, exactly which racist policies did people such as Richard Haier, Noah Carl, Bo Winegard, and Nathan Cofnas actually advocate? The only "racist policy" that I can think of in regards to Bo Winegard is that he apparently supports policies to slow down the rate of racial and ethnic demographic change in the US--or at the very least views the support of such policies (such as immigration restrictionism of some sort) as being a perfectly legitimate political position. (I deduced this information from looking at his Twitter feed.) Which other racist policies are any of these people advocating? By all means, please do tell!

As for palling around with undesirable people, this appears to be a guilt by association fallacy. The fact that someone pals around with, say, Communists does not in itself actually make this person a Communist. By this logic, maybe we should criticize, say, W. Kamau Bell for making conscious efforts to interact with the alt-right for his TV show, eh? Futurist110 (talk) 22:05, 20 April 2020 (UTC)

A new phase of human evolution may have started about 10,000 years ago due to invention of agriculture and the changes in the diet. Human remains from just after this transition show evidence of malnutrition due to eating one-sided diets. The original diet was a primarily whole food plant-based type supplemented by small amounts of meat and fish. So, we got all our protein from the plant-based sources and the small amounts of meat and fish made up for the compounds like vitamin B12 that are absent in the plant-based foods. After the invention of agriculture, we could get all our calories from more refined carbs and fats which are depleted n nutrients, particularly protein. We then had to get our protein from animal products, so we needed to eat much more meat and dairy. This was also necessary due to the lack of minerals like zinc and calcium from the new refined agricultural products.

Lactose intolerance which was the norm before agriculture, vanished in Northern Europe around this time. The driving force behind this was the high mortality of malnourished children due to diarrhea. If children could drink more milk, they would have a better chance to survive.

Polar bears are a good example of this, see here:

"But they are descended from terrestrial bears that, before colonising the frozen Arctic, ate a very different diet. “Their ancestors will have eaten healthy food like tubers and berries, and all of a sudden there they were eating almost exclusively fat and blubber from seals,” says Rasmus Nielsen of the University of California at Berkeley. “So the fast-food experiment has already been done by nature.”

To find out how the first polar bears coped with this dramatic shift in diet, Nielsen and his colleagues sequenced the genomes of 89 polar bears and 10 brown bears, their closest relative. Out of 20,000 genes, they found 20 gene variants that were most distinct in polar bears, and which evolution has evidently favoured."

The list of genes was dominated by metabolism, heart function and coat colour. “Usually, the genes that evolve most radically in species are immune and defence genes,” says Nielsen. “What’s surprising was the focus on cardiovascular function.”

Of the top 20 genes, nine relate to heart function or development in humans. One variant that scored especially highly was the APOB gene. This makes Apolipoprotein B (ApoB), the protein component of “bad cholesterol”, otherwise known as low-density lipoprotein (LDL). ApoB normally removes artery-clogging LDL from the bloodstream, dumping it out of harm’s way in fat cells or elsewhere." Count Iblis (talk) 01:43, 20 April 2020 (UTC)

I'd say you're right that nothing stops evolving, but it would be a mistake to assume that the existence of a selective pressure implies the population is evolving in the direction of that pressure. Not only are we often considering complicated and poorly understood genetic phenomena that are strongly influenced by environment (and that includes the behavior of other humans), we're talking about a population under many simultaneous pressures. It is my impression that "humans stopped evolving" is mostly an inaccurate executive summary of the vast selective pressures that have been minimized by modern medicine and other technology. Someguy1221 (talk) 06:26, 20 April 2020 (UTC)

I think the 47's point about creationists and misunderstandings of evolution is also important here. Some creationists like to spread nonsense like we've observed microevolution, but no macroevolution which they then argue doesn't exist which leads to the mistaken belief that evolution must mean radical changes. And outside of humans, there is also a lot of similar confusion, e.g. the belief that living fossils 'stopped evolving'. (When you combine the 2, you get a lot of weird confusion as the 47 sort of mentioned. E.g. questions over why monkeys or other primates "stopped evolving" or didn't evolve into humans.) Nil Einne (talk) 06:59, 20 April 2020 (UTC)

Virus Movie #2

Virology

• @Alansplodge:, @Lambian:, @Graeme Bartlett:, @DroneB:, @Graham Beards:
  

• I have re-recorded the video on the basis of your critique. I would appreciate if you can take 6 minutes time to view and add a brief evaluation. Thank you for your review.
• --Cookatoo.ergo.ZooM (talk) 17:37, 19 April 2020 (UTC)

after watching, it is now much less cluttered. Though you could popup some text when you mention a technical term, so that people know how the word is spelled. As regards accuracy I don't think is is quite correct to say that chains of amino acids polymerise into proteins. I should probably listen again to the exact wording, but amino acids polymerise into proteins (which are chains of amino acids). PS I am more into the chemistry side of Wikipedia. Graeme Bartlett (talk) 00:40, 21 April 2020 (UTC)

Car air conditioning

Does the A/C in a 2017 Subaru Crosstrek draw in air from outside of the car? 67.253.78.55 (talk) 20:09, 19 April 2020 (UTC)

On page 250 of your owner's manual, the 'Air inlet selection' section explains that "On" position recirculates cabin air and "Off" draws outside air. 2606:A000:1126:28D:38A7:2D25:F9F0:4858 (talk) 20:28, 19 April 2020 (UTC)

High consequence infectious diseases (HCID) definition

According to the UK government, Covid 19 is not a "High Consequence Infectious Diseases" [[16]].

The government website, and every other site I can find discussing or defining this only gives a qualatative definition:

• acute infectious disease
• typically has a high case-fatality rate
• may not have effective prophylaxis or treatment
• often difficult to recognise and detect rapidly
• ability to spread in the community and within healthcare settings
• requires an enhanced individual, population and system response to ensure it is managed effectively, efficiently and safely

Does anyone know (or know where to find) the quantitative definition of a HCID? (In particular, what fatality rate counts as "a high case-fatality rate"?) Iapetus (talk) 20:49, 19 April 2020 (UTC)

Googling the subject, it kind of seems like a judgment call. For example, Ebola virus disease has a high death rate, so presumably it would qualify. The UK originally labeled COVID-19 as HCID because they didn't know what the death rate was. It turns out to be relatively low, at least compared with Ebola. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:41, 19 April 2020 (UTC)

That's what I assumed was the reasoning, given that most of the listed examples seemed to be "any contact with an infected person and you will probably die" types of diseases. But it would be nice to have a harder definition - especially as I've seen people making various assumptions about the reason for the downgrade that either border on conspiracy theories ("the government is trying to cover up that it didn't take this seriously") or are out-right conspiracy theories ("Covid 19 isn't dangerous, the government is just using it as an excuse to impose a lockdown, for reasons").

April 20

Electric vehicles

If cars, buses, motorcycles become electric then will it affect the fossil fuel industry? -- 42.110.196.234

It depends on what gets burned to produce the electric power those vehicles will charge their batteries with. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:25, 20 April 2020 (UTC)

I was wondering about that. Given that large power stations are far more efficient at extracting energy than a small car or bus engine, could it be that, even if the power stations providing the electricity for those vehicles used the same petrol as the vehicles, we would need a lot less? But there is some loss when the electricity is transported into the battery, so it could cancel out, or be worse. Has anyone seen some calculation? --Lgriot (talk) 11:13, 20 April 2020 (UTC)

Yes, it will affect the fossil fuel industry. That's the whole point (in addition to reduced local emission of pollutants). Motorcycles and cars mostly run on oil-derived fuel (in particular petrol). Buses are more variable; around here they use compressed biogas, compressed natural gas, hydrogen fuel cells (they don't say how the hydrogen was made), electricity via batteries or overhead wires (they don't say where they buy the electricity) and sometimes still diesel. In any case, most road vehicles use oil-derived fuel, but fossil fuel power stations mostly use natural gas or (rapidly disappearing in Europe) coal, so at the very least there will be a shift away from oil. And a large fraction of our electricity, expected to increase, doesn't come from fossil fuels: hydropower, nuclear, solar, wind, ...

Given the efficiency of batteries and (to lesser extend) transport losses, battery-electric cars combined with oil burning power stations could very well give higher oil consumption than petrol powered cars (but don't forget the losses from converting crude oil to petrol). But that's irrelevant as there are (practically) no oil-fired power stations. The trick is to charge battery-electric vehicles when there's such a supply of wind or solar power that the price of electricity drops to zero (or less), which guarantees that they indeed charge from clean electricity. Of course, owners of solar panels or wind farms won't make a lot of money that way... PiusImpavidus (talk) 12:01, 20 April 2020 (UTC)

I think LNG is a good bet for fossil fuel future, it's cheaper than driving on both petrol and diesel and suitable for existing engines. A taxi company in my city started out with Priuses but when it decided to go bargain busting it swapped them all for petrol cars converted to LNG. Plenty of city buses use it too, although I think the majority are still diesel (and none are electric). 89.172.105.177 (talk) 00:39, 21 April 2020 (UTC)

Note that oil at least has many important uses beyond use as fuel (e.g. as a raw ingredient of plastics). So even a total switch to non-fossil fuel power sources wouldn't eliminate the oil extraction and refining industries. Iapetus (talk) 09:42, 21 April 2020 (UTC)

Renewable electricity overtakes fossil fuels in UK for first time (October 2019). Alansplodge (talk) 12:38, 21 April 2020 (UTC)

Penetration by particles

How exactly do beta and gamma particles penetrate human body? Do they slip through some microstructures or actually perforate, leaving microscopic holes like bullets on a larger scale? Thanks. 212.180.235.46 (talk) 11:11, 20 April 2020 (UTC)

They pass right through our atoms. PiusImpavidus (talk) 12:02, 20 April 2020 (UTC)

As shown by Ernest Rutherford in the famous experiment with metal foil. Under his direction Hans Geiger and Ernest Marsden fired alpha particles at various metal foils. The previous model of material was that mass was evenly distributed through space, so when they observed high-angle backscatter for a minority of the particles, this demonstrated that matter was instead concentrated in atomic nucleii. When Geiger reported back about the backscattered alpha particles, Rutherford said "It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. " Mikenorton (talk) 13:38, 20 April 2020 (UTC)

So, to elaborate on this, the mental image of microstructures that particles can slip through is wrong. Think of marbles (representing the nuclei of the atoms of molecules) floating in space, practicing social distancing, where the recommended inter-marble distance is something like a half kilometre. Now you shoot at random into that largely empty space. Chances are that your bullet goes a long way before it hits a marble. Maybe it emerges at the other end without having hit anything. The molecular social distancing is the result of the van der Waals force, operating on the molecules substances are made up from. The same force keeps your feet from sinking into the floor as you stand: the molecules of your feet and those of the floor repel each other when approaching each other at a very short distance.  --Lambiam 15:59, 20 April 2020 (UTC)

The beta rays will disturb the electrons as they pass, perhaps ionising the atoms, or causing molecules to become excited, or to vibrate more. As suggested above, to actually make a hole you would actually have to hit or move a nucleus of an atom. For gamma rays, the photons do not punch a cylindrical hole, and only have an effect once they hit something and are absorbed and or scattered. You can expect disruption where they hit. Graeme Bartlett (talk) 00:34, 21 April 2020 (UTC)

Alpha particles colliding with nuclei can cause atoms to get displaced. It has been suggested that one can also search for dark matter this way by searching for tracks of atoms displaced by collisions with dark matter in certain minerals at some depth, see here. Count Iblis (talk) 03:31, 21 April 2020 (UTC)

Predatory Journals

Hi, while writing a draft on a Medical policy and saving it. I got a message saying some of citations might be “Predatory Journals”. I would like to know more about this particularly, wether any of my sources cited are in Blacklisted category. Where do I find more information on this? Regards Santoshdts (talk) 15:32, 20 April 2020 (UTC)

See WP:VANPRED. Mikenorton (talk) 15:43, 20 April 2020 (UTC)

What animal is this?

Is that a hippo? Or a warthog? It's from Central Africa (Gabon or neighboring territories), this is certain. Thank you! --Edelseider (talk) 16:21, 20 April 2020 (UTC)

Yes, it is a hippopotamus skull, as you can confirm here by comparing the two. In your picture, the top and bottom are not correctly aligned; the upper jaw is rotated clockwise (as viewed from looking over the top of it) relative to the lower jaw. --Jayron32 17:53, 20 April 2020 (UTC)

@Jayron32: Ah, okay, thank you very much! --Edelseider (talk) 20:18, 20 April 2020 (UTC)

What is this metal object?

I was walking in a forested area in south-east England and I found this metal disc thing embedded in the ground.

What is it?

Something used in forestry or agriculture? Thank you. --Polegåarden (talk) 21:24, 20 April 2020 (UTC)

• 
  Unknown object
• 
  Unknown object

I have no idea, but the second photo clearly doesn't seem to be the same object. What's up with that? --76.71.6.31 (talk) 23:45, 20 April 2020 (UTC)

I think they are the same. The first object isn't lying on the ground. It's sitting on top of the axle/post/metal rod(?) it's attached to. The second pic is a side-on view. But I have no idea what it is. HiLo48 (talk) 00:25, 21 April 2020 (UTC)

I agree that the in the first photo the disk may not be lying on the ground, although we were told that the thing is "embedded in the ground". But it is clearly circular and has a circular recess in the top, and a screw or bolt protruding at least 1/2 inch or 1 cm. The object in the second photo has four straight sides, no circular recess, and no protruding screw. So...? --76.71.6.31 (talk) 03:15, 21 April 2020 (UTC)

The second image is from directly side-on. We can't see anything about the top or the bottom surfaces, such as if there is a depression, or if there is a bolt in the depression that is not taller than the depression. Several of the other items visible on the ground in the two images match each other. Because I'm going stir-crazy from travel restrictions and needed a break from work-at-home, I annotated four such details (go to File:Unknown_object_in_rural_area.jpg and File:Unknown object in rural area 2.jpg in two adjacent windows, hover your mouse over each to see identified regions). DMacks (talk) 04:10, 21 April 2020 (UTC)

I think it is a feeding station for gamebirds. Greglocock (talk) 00:29, 21 April 2020 (UTC)

That would have been my guess based on shape (or a mounting on which a feeder is bolted), but it seems too low (squirrels and other ground creatures could get up to it). DMacks (talk) 04:10, 21 April 2020 (UTC)

Thank you for your replies. Yes, the two photos are of the same thing. I've heard that it might be part of an old pheasent feeding station with some part missing. --Polegåarden (talk) 06:26, 21 April 2020 (UTC)

Something like this perhaps?. Alansplodge (talk) 12:34, 21 April 2020 (UTC)

Flu Vaccine Effectiveness

I've heard that all the flu vaccine does is decrease the time you have it, that does not stop you from getting it. Is this true? Pealarther (talk) 22:56, 20 April 2020 (UTC)

See Influenza vaccine. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:44, 20 April 2020 (UTC)

April 21

What is this common insect (Sweden)?

I have recently been observing a lot of these insects in my apartment in Linköping, Sweden:

• http://privat.rejbrand.se/insekt.jpg
• http://privat.rejbrand.se/insekt2.jpg
• http://privat.rejbrand.se/insekt3.jpg
• http://privat.rejbrand.se/insekt4.jpg
• http://privat.rejbrand.se/insekt5.jpg

The animal's body length is about one centimetre (0.4 inches). What kind of insect is it? --Andreas Rejbrand (talk) 10:26, 21 April 2020 (UTC)

A non-biting midge (Chironomidae)? Mikenorton (talk) 11:05, 21 April 2020 (UTC)

Agree, probably a male with those fluffy antennae, so not likely to bite. Richard Avery (talk) 13:28, 21 April 2020 (UTC)