Wikipedia:Reference desk/Archives/Science/2020 April 15

= 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. For the influenza A virus, the probability that a single virion entering a cell will successfully replicate is very low, but not zero. 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: . 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 &mdash; 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)
 * To add to the above, that "social distancing" won't eradicate a virus isn't a reason to not try other things. That's where vaccination comes in. Measles, for example, was so widespread that it would slip through the gaps of any attempted global quarantine, BUT a global vaccination program was actually fairly close to achieving global eradication. Most major developed countries had successfully eradicated measles within their borders before anti-vaxxers reduced herd immunity. Polio was similarly almost entirely eradicated, only present in a few third world countries, and even there, it was close to eradication. Anti-vaxxers have seen that change. That wouldn't work as well for things like diptheria or anthrax, which survive outside of humans in either environment or non-human reservoirs. For that, we need continual vaccination campaigns. --OuroborosCobra (talk) 14:08, 21 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.  -- Jayron 32 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.  -- Jayron 32 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.  -- Jayron 32 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.  -- Jayron 32 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.  -- Jayron 32 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 and  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/$\sqrt{ε_{0}μ_{0}}$ 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.   -- Jayron 32 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.  -- Jayron 32 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)
 * 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 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)
 * Drone, I'm confused, are you suggesting that a electricity with frequency = 0 is now not possible? 67.175.224.138 (talk) 01:25, 22 April 2020 (UTC).
 * Yea, thank you for posting on my wall, but that didn't answer my question there either. 67.175.224.138 (talk) 21:54, 22 April 2020 (UTC).