Wikipedia:Reference desk/Archives/Science/2020 May 17

= May 17 =

neutrino speeds and the speed of hypothetical axion
I think I understand the that the reason for neutrinos going so near lightspeed is that they are created in somewhat energetic nuclear reactions while also being very low mass, and then not slwing down by being neutral in charge. But axions are theorized to be cold dark matter, so they are slowExactly why sre they slow? And they are slow relative to the galaxy they orbit?Rich (talk) 00:16, 17 May 2020 (UTC)
 * It has to do with the creation mechanisms for these particles in the early universe. Neutrinos decoupled from a state of thermal equilibrium and cooled only through the expansion of the Universe. Due to their small mass they had velocities (more precisely, velocity dispersion) close to the speed of light at the time relevant for structure formation, i.e. they were "hot". I don't understand the details for axions, but I refer to the articles Axion and Misalignment mechanism, which indicate that an interaction robbed axions of their kinetic energy making them "cold"  early on. --Wrongfilter (talk) 12:10, 17 May 2020 (UTC)
 * I gather you're getting at hot dark matter versus cold dark matter models. Noting this for other readers; there are also warm dark matter models. --47.146.63.87 (talk) 20:17, 17 May 2020 (UTC)
 * I'm not contradicting anything you stated, just filling in details: neutrinos have an incredibly tiny mass, long thought to be zero, so it doesn't take much to get them to high velocities, and they only interact through gravity and the weak interaction so they're basically unimpeded by "ordinary matter" or photons and hence there's nothing to slow them down. A fascinating thing is that in contrast, neutrons, though they have no net electric charge, do interact electromagnetically and have a magnetic moment, which I think means they still can scatter off charged particles and lose energy that way. Someone please correct me if I'm wrong. --47.146.63.87 (talk) 20:17, 17 May 2020 (UTC)
 * They probably can, but there are no free neutrons (a free neutrons decays after 8 or 9 minutes). Axions (presumably, if they exist, blabla) have much smaller masses than neutrinos, which is probably what prompted the question in the first place. --Wrongfilter (talk) 20:50, 17 May 2020 (UTC)
 * Yes that was at least part of what prompted it. So how fast are neutrinos that emerge from a nuclear reactor or from the Sun? They aren’t usually primordial, unless they just happened to pass thru at the right time, right? Do they also travel closse to light speed?Rich (talk) 05:57, 21 May 2020 (UTC)
 * The energy E is $$E = \frac{m}{\sqrt{1-v^2}}$$ where m is the rest mass and v is the speed in c = 1 units. The masses of the neutrinos are not precisely known, but there should be one with a mass of the order of 1 eV. Neutrinos from the Sun have a typical energy of 0.4 MeV. You can then solve for the speed by putting $$v=1-\epsilon$$, this yields $$E \approx \frac{m}{\sqrt{2\epsilon}}$$, therefore $$\epsilon\approx \frac{m^2}{2 E^2}$$. Multiplying by the speed of light yields that the speed of the typical solar neutrino is 9 micrometers per second slower than the speed of light, after traveling from the Sun the neutrinos will lag about 5 millimetres behind massless particles. Count Iblis (talk) 09:39, 21 May 2020 (UTC)

wow that’s neat. thanks!Rich (talk) 11:56, 21 May 2020 (UTC)

vaccine research
Our President is on TV saying he expects a covid-19 vaccine by the end of the year, and at least some people seem to take this seriously. Some vaccines like Ebola have in fact been developed pretty fast. Some older ones like polio may have taken longer, but they didn't have modern biotech then. But, there is no HIV vaccine even today, other than pre-exposure prophylaxis that has to be taken frequently.

Is there some reason to expect covid-19 vaccines to be easier to develop than HIV vaccines? I think I've heard HIV might be unusually difficult, but I don't know specifics. Thanks. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 01:24, 17 May 2020 (UTC)


 * "OUR President"? This is a global encyclopaedia. My country doesn't have a President. Anyway, I suspect there is a bigger effort being put into finding a vaccine this time around than has ever happened before. And despite the repeated hate talk about the country, Chinese authorities made public the details of its genome from their own research quite early in the piece.That increases the odds considerably. HiLo48 (talk) 01:38, 17 May 2020 (UTC)
 * If you ask him I'm sure he'd attest to being everybody's president ;). More seriously I'd expect the HIV genome is sequenced also.  It's been around for decades so I'm wondering what's different. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 01:43, 17 May 2020 (UTC)
 * I'm sure the original poster meant his or her own country's president, and just forgot to mention which country. No big deal. --76.71.5.208 (talk) 05:02, 17 May 2020 (UTC)
 * Sadly, English lacks a clusivity marker that some other languages have, which would have reduced the confusion that led to HiLo48's expressions of offense to being included in the "we" which the OP did not intend to do. -- Jayron 32 13:16, 18 May 2020 (UTC)
 * It's possible Trump wants the public to think he'll have a vaccine soon by year's end, in order to get more votes. ←Baseball Bugs What's up, Doc? carrots→ 01:45, 17 May 2020 (UTC)
 * By Novemeber it will be pretty clear how vaccines are coming, and also how well the human sacrifice reopening plan has worked out. Trump most of all seems to want the virus to just go away so we can get back to whatever.  So he tends to be optimistic about anything that might make that happen.  We'll see if the current thing works.  The last few didn't, but I suppose it's important to keep trying.  2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 05:09, 17 May 2020 (UTC)


 * See COVID-19 vaccine and HIV vaccine. Most humans can beat the COVID-19 virus on their own and build immunity (unknown for how long). A vaccine may only have to trigger this existing defense system. The COVID-19 pandemic causes many resources to be used, and some projects to bypass normal safety standards. COVID-19 vaccine currently says "By May, 159 vaccine candidates were in development". Some are bypassing animal trials, and it's considered to deliberately expose volunteers to the virus to measure vaccine efficiency faster. PrimeHunter (talk) 02:26, 17 May 2020 (UTC)
 * A news story I watched earlier tonight referred to the process "deliberately expos[ing] volunteers to the virus to measure vaccine efficiency" as human challenge trials. I think Wikipedia should have an article on that, or if there is an appropriate existing article, that phrase should redirect to it. --76.71.5.208 (talk) 05:02, 17 May 2020 (UTC)
 * We have variolation which is sort of related. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 05:11, 17 May 2020 (UTC)
 * Though variolation involves intentional infection (with a low initial viral load -- see 2 questions above) in order to generate immunity, these proposed human challenge trials would involve intentional infection in order to test for immunity. -- ToE 15:11, 17 May 2020 (UTC)
 * We have the section COVID-19 vaccine, though it's not really an appropriate target for a redirect from your red link. A more general article on the history and ethics of challenge studies in general would be welcome. -- ToE 15:11, 17 May 2020 (UTC)
 * Small consolation to the 85,000+ Americans who weren't able to beat it. ←Baseball Bugs What's up, Doc? carrots→ 02:54, 17 May 2020 (UTC)
 * As seen in the articles that PH linked to, there are specific challenges to HIV vaccine development that should not be ascribed, without reasonable basis, to any other vaccine development. HIV is unique in a number of ways that make it challenging to develop a vaccine. Among these is that classical vaccine development often intentionally mimics the ways the body develops natural immunity to an infection, but HIV has less than a handful of case where human immune responses actually beat it and developed immunity. That's not true of COVID19. HIV antigens also don't seem to be stable in non-live virus, which makes it hard to use killed virus as a vaccine. HIV has a high mutation rate, and specifically, a high rate of mutation to allow it not only to evade the immune system, but to attack and kill the immune system. Its infection target is the very system that a vaccine uses to provide immunity, the immune system. COVID19 certainly has a wide range if effects, but its main target is the lungs, not the immune system. Honestly, HIV is fairly unique in its difficulty to develop a vaccine, almost everything else out there is much, much easier to develop vaccines against. --OuroborosCobra (talk) 20:53, 17 May 2020 (UTC)
 * Ok but for example don’t flu vaccines not always work that well for the year they’re designed for, and don’t they take quite a while to make? And common cold vaccine has been a big challenge too. So i’m not sure optimism is called for.Rich (talk) 06:04, 18 May 2020 (UTC)
 * Influenza vaccines don't always work that well for the year (actually influenza season) they're designed for mostly because they're based on predicting months in advance, from the the previous seasons, what strains of flu will be common. Such predictions aren't always successful especially when new strains emerge as happened with the 2009 H1N1 pandemic. As for "don't they take quite a while to make", it depends what you mean by "quite a while". The recommendations for the "2020 southern hemisphere influenza season" which is ongoing were published on 27 September 2019 [//www.who.int/influenza/vaccines/virus/recommendations/2020_south/en/]. I don't know about other countries, but in NZ these vaccines started to be come available in late March, and vaccination is now in full swing. The recommendations for the "2020 - 2021 northern hemisphere influenza season" were published on 28 February [//www.who.int/influenza/vaccines/virus/recommendations/2020-21_north/en/]. I assume it's intended to be available in September or maybe October of this year [//www.cdc.gov/mmwr/volumes/69/wr/mm6907a1.htm]. In other words, it takes about 6 months for mass production of the vaccine [//www.who.int/csr/disease/swineflu/notes/h1n1_vaccine_20090806/en/] [//www.cdc.gov/flu/prevent/vaccine-selection.htm].  To be clear, although often the strains don't change much from year to year (see Historical annual reformulations of the influenza vaccine), even when they do the extra time is not that great. For example, with the aforementioned 2009 pandemic where the virus was first described in April 2009, the 2010 Southern hemisphere vaccine recommendations (i.e. to be released in ~March 2010) [//www.who.int/influenza/vaccines/vaccinerecommendations1/en/] included "A/California/7/2009 (H1N1)-like virus" i.e. the Pandemic H1N1/09 virus. In addition, because the virus obviously missed the 2009-2010 Northern hemisphere vaccine from February [//www.who.int/influenza/vaccines/vaccinerecommendations1/en/index1.html], special vaccines were made which began to become available in November 2009, see 2009 swine flu pandemic vaccine.  Of course this is after there has already been a lengthy process of research and development such that we have a decent understanding of how to develop and produce influenza vaccines.  Note also a vaccine for the "common cold" is actually a fairly non specific thing. As mentioned in our article, there are number of different virus strains that could be responsible. While Rhinoviruses are the most common, even then we're talking about a number of different types. So developing a vaccine against the common cold point blank is not a simple ask. It's true that we don't have a vaccine against any of the possible viruses involved, the challenges are often similar (large number of rapidly mutating strains), but at the same time there may also be specific challenges depending precisely what virus you're thinking of. [//scopeblog.stanford.edu/2019/09/16/scientists-close-in-on-a-cure-for-the-common-cold/]  In terms of SARS-2-CoV, there's still a fair amount we don't know about it. And I'm not really suggesting optimism, I'm not sure if OuroborosCobra really was either. But if we are going to contrast and compare to different examples, we should understand how these may be different or similar. Definitely as OuroborosCobra said, HIV has enough differences that there's perhaps only a little we should take away from it about probability of success, and challenges that may be faced.  Nil Einne (talk) 07:57, 18 May 2020 (UTC)
 * Exactly. The only optimism I mean to suggest is that we should not look to the challenge and lack of success with HIV vaccine research as something to compare with vaccine development of anything else, be it SARS-CoV-2, Ebola, Zika, etc. HIV has some extraordinary (and I mean that in the literally sense, as in "extra and beyond the ordinary") properties and challenges that are not an issue for any other virus that I am aware of. As you say, we don't yet know enough about this coronavirus to say for sure how easily it will be to vaccinate against, but given the 100+ promising vaccines currently in development, I'd say our chances are more towards either a truly effective vaccine, or possibly something more like influenza and a need to regularly re-vaccinate. I also always hate the description of the influenza vaccine as "not working well." It works great. As you said, the issue is in predicting the strain, but when the strain is predicted right, it gives near 100% protection. Even when they get the strain a bit wrong, the flu vaccine greatly reduces the severity of the flu. We have a problem in the US, at least, of not enough people getting vaccinated every year. If we did, we would have a lot fewer flu related deaths than we do now, because the flu vaccine is highly effective. --OuroborosCobra (talk) 13:46, 18 May 2020 (UTC)
 * Thanks, that’s important information that I didn’t know.Rich (talk) 15:40, 18 May 2020 (UTC)
 * My own suspicion is that we get something by the autumn but it's not great. The one in development in Oxford has been tested on monkeys, and it looks like it reduces symptoms but they still get it and can still spread it. I think it's very possible that governments are going to wince and says "we'll take that" unless side effects they can be blamed for are showing up. If the government has pre-ordered doses, they'll probably give them to key workers and the vulnerable; even a small reduction in cases and spread would be a lot right now, it's obvious we're heading for a great depression otherwise. For comparison, the sorta-worked RV 144 HIV vaccine trial reduced cases by 31% (caveat about small sample sizes). That wasn't good enough for governments to go with it when it's such a rare disease as HIV that can usually be prevented by dirt-cheap condoms (the vaccine regime required six separate inoculations over a six-month period; governments were looking for a 50% reduction to buy it) but for a coronavirus that spreads fast 31% would be a big development. 16:38, 21 May 2020 (UTC)

North Magnetic Pole rapidly shifting
Is this article true? What would the implications be for the economy? EllenCT (talk) 04:56, 17 May 2020 (UTC)
 * Is it true that the NMP has been moving? Well, many scientists have been tracking this movement for years.
 * Is it true that the cause is as described in the article? It's the best explanation we currently have: you can read the abstract of the original scientific paper here for free, or read the whole thing for a modest fee, and decide for yourself.
 * What are the implications for "the economy" (whose?)? In the short term, there'll surely be more economic activity in the sectors concerned with global navigation, as maps and systems will continue to need adjustments and amendments. Longer term, changes in the details of how the Earth's magnetic field shields higher latitudes from geomagnetic storms may mean more (or less) damage to electrical systems, mains electricity grids, communications, navigation systems, satellite hardware, pipelines and doubtless other things. As an economics student, you are better placed to research and opine on such matters than I.
 * No doubt others have more knowledge in these fields and can add further details. {The poster formerly known as 87.81.230.195} 90.197.24.23 (talk) 06:37, 17 May 2020 (UTC)


 * The paper on which this pop-science article is based appeared in Nature Geoscience ("Recent north magnetic pole acceleration towards Siberia caused by flux lobe elongation"). It is behind a paywall and I did not read it, but "lobes of negative magnetic flux" as mentioned in the abstract are not "massive blobs", nor do I expect the paper to describe these lobes as "writhing" and "duking it out" to each other. In the abstract, the authors ascribe the faster motion (about 2 mm/s compared to an earlier 0.5 mm/s) to "elongation of the Canadian lobe, probably caused by an alteration in the pattern of core flow between 1970 and 1999". As a result, magnetic north is now very close to true north. There is no indication that the global magnetic field has weakened, only that its orientation has changed. I see nothing that looks like it might have implications for economic activity. --Lambiam 08:07, 17 May 2020 (UTC)
 * One implication is that in the UK, compass navigation is much easier because magnetic variation is insignificant in most parts of our island, here in London it's only 1° and decreasing. Hooray! Alansplodge (talk) 11:22, 17 May 2020 (UTC)
 * And, also in the UK, our national broadcaster has seen fit to publish a nice animation showing that this is nothing new.  Bazza (talk) 16:22, 17 May 2020 (UTC)
 * Although (according to the BBC animation) it's moved more in the last 30 years than in the preceding 150 years. Alansplodge (talk) 12:16, 18 May 2020 (UTC)

Pleurisy and dancing
Why was Anna Pavlova told that she could not dance ever again if treated surgically for pleurisy? The article on pleurisy is silent on this subject.--Jasper Deng (talk) 18:32, 17 May 2020 (UTC)
 * I'm thinking there's a lot of legend wrapped around Pavlova's demise, in particular the "refused an operation" part. Victor Dandré's account indicates nothing of the sort. --jpgordon&#x1d122;&#x1d106; &#x1D110;&#x1d107; 05:02, 18 May 2020 (UTC)
 * The account linked by is persuasive. However, assuming for the moment that the "refusal" story were true, the Pleurisy article suggests that the principal (only?) long-term surgical treatment for the condition is Pleurodesis. This would necessarily mean that the functionality of the Pleural cavity would be eliminated, which in turn would surely compromise the patient's peak lung function such that they would thereafter be unable to perform vigorous physical activity, such as dancing. {The poster formerly known as 87.81.230.195} 90.197.24.23 (talk) 07:53, 18 May 2020 (UTC)
 * "Researchers investigating the demands of classical ballet have concluded that classical ballet is a high-intensity intermittent form of exercise. This form of exercise requires a good aerobic foundation..."  Alansplodge (talk) 15:07, 19 May 2020 (UTC)
 * "...compared to the 61 common sports, only professional [American] football is more physically demanding than ballet".  Alansplodge (talk) 15:07, 19 May 2020 (UTC)


 * The other pertinent view is related to how many times do we hear about individuals who achieve something that doctors said was impossible. There remains the not unreasonable possibility that doctors are not infallible. Richard Avery (talk) 07:24, 20 May 2020 (UTC)