Wikipedia:Reference desk/Archives/Science/2015 May 4

= May 4 =

Cosmic radiation on interplanetary voyages.
There is an article in yesterday's WSJ about experiments imitating radiation in deep space, meaning outside the earth protective magnetic field. Experiments are done on mice, of course. The title is: "Subtle Brain Damage a Likely Risk of Deep-Space Travel." I quote in part: "Six weeks later, they tested the irradiated mice and found the lab animals lacked normal curiosity , were less active, and become more easily confused, compared with control group, the researches said."

I won't say it is "subtle" to lose your curiosity and become easily confused. I think it is a damning result. Also "In 2013... radiation levels between Earth and Mars detected by the Mars Science Laboratory craft during its cruise to the red planet, ... and found that the exposure was equivalent of getting 'a whole body CT scan once every 5 to 6 days.'" Also it is my understanding that during that voyage and many others no solar flares in the direction of Mars took place thus creating what might be considered a default radiation level.

Also from memory, a travel to Mars would provide radiation exposure that will raise the cancer risk by 5%. But just quoted result appears to be even much stronger.

What is the solution? The article mentions some engineering solutions that must be found. They are not even on a drawing board now, perhaps the physics is such that those nebulous "solutions" will never be found. Also one has to look beyond the voyage. If it is an attempt to establish a colony, what are they going to do there? The radiation on the surface of Mars would not disappear. Every 5-6 days they will get their CT scan, right?

They must bring with them some heavy equipment, perhaps a good size bulldozer and an excavator to dig at least 30 feet underground to find protection from the cosmic rays. And how about walking around, doing explorations and geological surveys? Isn't the whole trip designed to find out everything about the geological history of the planet? --AboutFace 22 (talk) 00:19, 4 May 2015 (UTC)


 * Yea, there are so many reasons why a manned trip to Mars is just out of the question anytime soon. The radiation problem can be solved once we have faster ships, but that will require new technology, too.  So, I'm thinking many decades. StuRat (talk) 00:25, 4 May 2015 (UTC)

StuRat is an incorrigible optimist. :-) I would say we will never send humans to Mars, ever. --AboutFace 22 (talk) 00:42, 4 May 2015 (UTC)


 * You can browse the archive at NASA's Scientific and Technical Reports program. By searching for "manned spaceflight radiation", I found many publications - including publications on dosimetry and medical effects; effects of radiation on specific types of habitat construction materials; ... there are many questions to address.  This area of technology is highly specialized; there are problems relating to prediction of radiation intensity; related to construction of spacecraft and habitats for protection and durability; related to health effects on humans.  There is no single solution.  NASA's Science and Technology webpage - and their manned spaceflight website at http://spaceflight.nasa.gov - are great places to begin reading if you wish to inform yourself about the specifics of any particular solution that has been investigated.
 * If you are specifically interested in NASA's vision for a future manned space flight to Mars, they have an informational website outlining the proposal. To be clear: NASA is not presently working on a manned mission to Mars.  To quote the legalese, they are preparing enablement technologies, including the development of the Orion Spacecraft.  "NASA is developing the capabilities needed to send humans to an asteroid by 2025 and Mars in the 2030s – goals outlined in the bipartisan NASA Authorization Act of 2010 and in the U.S. National Space Policy, also issued in 2010."  This means that NASA presently does not have either a specific directive nor any specific contractor who is directly responsible for providing solutions to the problems that our OP has described.  There are open investigations which NASA is authorized to pursue, in order to enable future solutions.
 * Nimur (talk) 00:43, 4 May 2015 (UTC)


 * And WP:WHAAOE: Health threat from cosmic rays. PrimeHunter (talk) 00:50, 4 May 2015 (UTC)
 * For those Manned Mars Mission enthusiasts who are not regular subscribers to Orbital Debris Quarterly, you might also want to read the Spring 2015 issue released this week. Micrometeorite impacts on the Orion EFT-1 test flight were some 3x higher than predicted by numerical models: the spacecraft returned to Earth pockmarked by many more (and larger) micrometeorite craters than anticipated.  High-energy ionizing radiation is not the only hazard of the interplanetary environment: if we wish to safely send humans on interplanetary voyages, we must provide engineering solutions to all the difficulties of manned spaceflight.
 * Nimur (talk) 01:00, 4 May 2015 (UTC)

I keep thinking about what Nimur said. It is very interesting. Reading between the lines, perhaps, I think the top NASA men understand that human exploration of deep space is a pipe dream but who would dare saying that? Millions of dollars of funding are at stake, thousands of jobs, a dream of generations! So, the legalese comes to the rescue. They are working on “enabling technology.” Very clever. You can work on “enabling” for two hundred years. --AboutFace 22 (talk) 15:16, 5 May 2015 (UTC)
 * What's your basis for saying it's a pipe dream? You said the same thing above but gave no support for it whatsoever. --Trovatore (talk) 15:13, 6 May 2015 (UTC)

Secondary effects of learning a second language
The obvious benefit of learning a second (or further) language is the ability to communicate with more people than any single language allows. However, I sometimes hear people argue that learning an additional language also has less obvious benefits. Things I've seen suggested include improving memory recall, improving verbal ability in one's native language, improving creativity, improved multi-tasking, etc. Have such secondary benefits (i.e. effects not directly related to the utility of the second language) been reliably documented in scientific literature? Secondly, other than the simple fact that the time spent learning a language might have been spent elsewhere, are there any hidden costs associated with learning a second (or further) language. For example, if you train your brain to learn many languages is it then harder to learn unrelated skills (like calculus)? My guess is that training language skills probably has no impact on math and other non-verbal skills, but I would be curious to know if this has ever been tested. Dragons flight (talk) 01:33, 4 May 2015 (UTC)
 * This is an advocacy site so obviously biased and likely to be selective in what they selected, but the studies are probably still useful to look at . It doesn't specifically mention math but some of the tests may include math. does mention math and links to some studies, although "impact on math" appears to largely means "on average score better in standardised tests" (although admitedly it's not like there's some other excellent measurement, unless you want to look at performance later in life). You'd probably want to explore how they tried to account for confounding factors.  also has some links relating to maths. There may also be some useful links in Cognitive advantages of bilingualism Nil Einne (talk) 02:33, 4 May 2015 (UTC)


 * I can tell you that formal study of French, then to a lesser extent German, Greek and Latin, but mostly French, greatly improved my vocabulary, spelling, grammatical understanding and compositional ability in English. I finally understood English sequence of tenses and the subjunctive in English after taking French. Beforehand I could use those faculties tacitly, but I didn't understand what I was doing or why.


 * You cannot understand a concept unless you have multiple examples, and until you learn at least one other language's grammar explicitly (my knowledge of Rusyn and Spanish was not taught in school) most grammatical concepts are very hard to understand in any concrete way.


 * As for improving other entirely non-language related skills? It may be the case, but I can't say I have experienced it.  There's also this great recent piece from the Guardian on the Homer Simpson Effect.


 * μηδείς (talk) 02:56, 4 May 2015 (UTC)


 * Would my directional skills improve if I learned Guugu Yimithirr language on location by natives? Native speakers are said to intuitively pick out any cardinal direction instantly, even blindfolded and spinned around in a cellar. I have known people who could not see certain variations in colour to save their lives until they learned the language that had that nuance.Star Lord  -   星王 (talk) 14:23, 4 May 2015 (UTC)


 * Your skills might improve, but more as a result of learning those specific concepts, rather than learning the entire language itself. For instance, many tribal languages have extremely limited vocabulary relating to numbers, some having systems with one, two, many or one, two, three, many as their only basic number terms.  (They can still say something like, the same as one hand to mean five.  And five, finger and fist all come from the same PIE root.)  Such people could be taught calculus after years of instruction by using coinages or words borrowed from, say, English.  But they wouldn't necessarily need or have to have any other fluency in English just to do math. μηδείς (talk) 19:09, 4 May 2015 (UTC)


 * As you say, μηδείς, I would only need to learn those specific concepts, probably exactly in the way they learn them as children. This may involve me having to be childlike, and for the natives to see me as such. Bit of a hurdle at my age. Still, if it worked, it would be one example of a secondary effect. Star Lord -   星王 (talk) 20:02, 4 May 2015 (UTC)
 * If the reports are correct that none-natives so far have never been able to point out any cardinal direction blindfolded in a cellar better than a foursided dice, then any improvement at all would seem to me to be the same as aquiring a totally new skill. Star Lord -   星王 (talk) 23:03, 4 May 2015 (UTC)


 * I have heard that different language families have different sorts of orientation systems, but I cannot from personal experience comment here. If the matter is as you say, then perhaps it's a phenomenon like perfect pitch, which some people achieve on their own, and others develop because they have been intensively trained in music since a young age.  The original question above was whether learning any other languages aids in general cognitive skills.  I can confirm that formally learning languages closer and further from your own greatly increases your understanding of your own language and language related skills.  Wider claims would require proof in my opinion.  This website has some good quotes:
 * "Those who know nothing of foreign languages know nothing of their own." ‒Johann Wolfgang von Goethe
 * "You can never understand one language until you understand at least two." ‒Geoffrey Willans
 * "To have another language is to possess a second soul." ‒Charlemagne
 * "A man who knows two languages is worth two men." ‒French Proverb (I have heard this attributed to Frederick the Great.)
 * "Americans who travel abroad for the first time are often shocked to discover that, despite all the progress that has been made in the last 30 years, many foreign people still speak in foreign languages." ‒Dave Barry
 * μηδείς (talk) 01:32, 5 May 2015 (UTC)

my skin exudes smelly substance
trigger warning: this question will make your stomach turn, so don't read it unless you can deal with a disgusting topic.

disclaimer: I am NOT describing a health problem, infection, disease or anything abnormal, and I am NOT asking for a diagnosis. I fully believe the substance I am describing is a perfectly normal thing, like ear wax or mucus and I just want to know what it is called.

There is a liquidy substance that my certain areas of my skin seems to give off if I don't bathe for about 24 hours or more. I usually find in crevice type areas, like in the "leg pit" areas around my crotch (but not on the genitals themselves), or like behind my ears. This liquid is pretty smelly and gross. I can only compare it to the scent of swiss cheese and artificially flavored salt-and-vinegar potato chips. It's not sweat, it's more greasy and slippery than sweat, and I know what my sweat smells like, and it doesn't smell like that. So what is it? Why is it so smelly?

Sorry for the gross question.--Captain Breakfast (talk) 01:46, 4 May 2015 (UTC)
 * Sounds like a variation on "toe jam". ←Baseball Bugs What's up, Doc? carrots→ 01:50, 4 May 2015 (UTC)


 * Basically sweat which is has evaporated and left the non-water parts behind. There's a lot of smelly stuff in sweat.  See Body odor for a more general description as well.  -- Jayron 32 01:55, 4 May 2015 (UTC)


 * Interesting and possible. I just figured because the sweat on my torso (armpit and chest, etc) smells NOTHING like this vile substance, that it was something different.--Captain Breakfast (talk) 02:03, 4 May 2015 (UTC)


 * Sounds like sebum. Are you by any chance obese ?  I've noticed that deep in the skin folds of the obese there seem to be anaerobic bacteria that grow in the sweat and sebum, giving off a rather pungent odor.  This warm, damp, dark environment is ideal for those bacteria.  This doesn't seem to occur in normal weight people, because oxygen gets to all portions of their skin, killing off those bacteria.  (Normal bacteria still grow on them, of course, but they have a different, more familiar odor.) StuRat (talk) 05:00, 4 May 2015 (UTC)


 * Sebum was my first thought; if damp, I believe it's attractive to some bacteria. Like StuRat I also notice a distinctive and generally unpleasant smell that is characteristic of fat people (quite distinct from the smells of different ethnicities, genders, menstruation and "good honest sweat"). RomanSpa (talk) 09:52, 4 May 2015 (UTC)


 * Also, if you're not obese, maybe you just don't shift position often, as most people do, to get air to all parts of their skin. (It's a rather subconscious process, you just feel uncomfortable and move a bit.) StuRat (talk) 02:08, 5 May 2015 (UTC)


 * Thanks that's what it is! I googled "sebum smell" and it sounds like other people described it the same way I did. I'm not terribly fat but the not shifting position part rang true because I only notice the smell when I spend long periods of time working/studying/sleeping without moving much.  So, so nasty.  thanks for the info.--Captain Breakfast (talk) 18:28, 5 May 2015 (UTC)


 * OK, just try to get air into the folds in your skin and wash those areas a bit more often. StuRat (talk) 18:38, 5 May 2015 (UTC)


 * Medical advice. You are banned. ;-) --Captain Breakfast (talk) 05:14, 6 May 2015 (UTC)


 * There's some kind of smelly substance in the piercings in my earlobe (I have two permanent rings in each lobe), even if I clean the area with Alcohol, it still smells on my fingers if I rub the area or put other earrings in. I always figured it was dead skin fluffing off. Raquel Baranow (talk) 18:52, 5 May 2015 (UTC)
 * Just googled and found it is Sebum causing the smell, lots of articles about it. Raquel Baranow (talk) 18:56, 5 May 2015 (UTC)

Pleiades - singular or plural?
Is Pleiades singular or plural? They are individual stars, but it is a cluster. Bubba73 You talkin' to me? 02:19, 4 May 2015 (UTC)
 * According to Merriam and/or Webster, plural. Our article treats it as plural, twice, at Pleiades, and never as singular. &#8213; Mandruss  &#9742;  02:21, 4 May 2015 (UTC)
 * One wikt:Pleiad, two or more wikt:Pleiades. However, the plural form gets used as a singular often enough when describing the cluster as a whole.  In fact, the first sentence in our article Pleiades treats it as singular: it boils down to "The Pleiades is an open star cluster".  I find enough examples of this usage in authoritative sources to say that it's well established and there's nothing wrong with it.  --Amble (talk) 04:40, 4 May 2015 (UTC)
 * That's a WP:ENGVAR issue: Some varieties of English treat a grouping as a singular unit when treated together. See Synesis.  -- Jayron 32 08:52, 4 May 2015 (UTC)
 * No, Jayron, I don't think so. I find plenty of examples from American authors in ApJ (example: "If the Pleiades is normal in some sense", ), HubbleSite, just as for British authors in MNRAS (example: "The Pleiades is ~125 Myr old", ).  I see no evidence at all that usage differs appreciably in different countries.  --Amble (talk) 16:30, 4 May 2015 (UTC)
 * But the usage is perfectly appropriate. It may not be country specific, but the representing of a group as a singular is common enough usage, and not wrong.  The difference is whether your dialect favors notional or formal agreement.  See the article I linked. FWIW, ngrams favors "the Pleiades are..." over "the Pleiades is" but not by enough to make a difference, essentially the two usages are interchangeable.  There were even some years when the ..."is"... construction is favored.  -- Jayron 32 16:37, 4 May 2015 (UTC)
 * Any ngram evidence is dubious considering forms such as this from our article: "The earliest known depiction of the Pleiades is ...". &#8213; Mandruss  &#9742;  16:40, 4 May 2015 (UTC)
 * Which would be balanced by forms such as "...Depictions of the Pleiades are..." I'd expect such uses to cancel out somewhat.  -- Jayron 32 16:54, 4 May 2015 (UTC)
 * Of course it's not wrong. That's why I said that this usage is well established and there's nothing wrong with it.  Still not seeing any evidence of any correlation with dialect.  To the contrary, using Pleiades as singular vs. plural appears to cut across dialects.  --Amble (talk) 19:58, 4 May 2015 (UTC)

If disease is beneficial to putting the population in check, then why do people want to minimize disease or delay death?
Why do people want to prevent disease even though "pathogenic" microorganisms are just trying to compete for survival? 140.254.70.33 (talk) 13:00, 4 May 2015 (UTC)


 * The obvious answer is that humans care more about the lives, happiness, and success of humans than we do about pathogens. If you were dying of a curable disease, would you somehow worry that the cure might kill off some bacteria?  Dragons flight (talk) 13:30, 4 May 2015 (UTC)


 * You seem to be asking a related but different question in the header from the question itself. If you want the question in the header answered, always repeat it in some form in the question proper, otherwise there's a good chance it will be missed and it's very confusing anyway. Nil Einne (talk) 13:51, 4 May 2015 (UTC)


 * There's not just one viewpoint, there are many. So it's not that useful to talk about what "people want." You'll get different answers from the Population_Connection organization, various sects of Buddhism, even scientists have a lot to say about |the role of infectious diseases in biological conservation. You might also be interested in reading up on the background of carrying capacity and human overpopulation. Whether the role of disease is beneficial is really more of a debate than a science question, and we shouldn't do that here. SemanticMantis (talk) 14:20, 4 May 2015 (UTC)


 * Per Marcel Duchamp's epitaph, death is for other people. The same person can one hand hope and pray for one billion strangers to die in horrible agony somewhere out of sight for Earth's general health, yet not wish that upon his mother, kid or casual acquaintance. Those people do good things for us, unlike pathogens and humans from across the globe. They're no use to us dead, even if they go peacefully.


 * Pathogens are free to compete. If we stopped preventing them from winning, there'd be no competition. No competition means no benefits or detriments for anyone. We'd all be equally bored to death, without a reason to persevere. InedibleHulk (talk) 14:22, 4 May 2015 (UTC)


 * Your question is not totally clear, but indeed medicine has treated (no pun intended) the issue of antibiotic overuse (see Antibiotic misuse). Sometimes it's better not to try to fight all bacteria that we can. I'd say that bacteria keep our immunological system in check. --Llaanngg (talk) 17:34, 4 May 2015 (UTC)


 * For a fictional treatment of the question in the title (as opposed to the one in the text), you might be interested in the original Star Trek episode The Mark of Gideon.


 * As for how scientists view the question in the title, here we have multiple cases:


 * 1) Wild animals. Here the population is controlled by predation, disease, starvation, etc., and disease is a "healthy" part of the wild environment.  Of course, there may be exceptions where a disease gets out of control in the wild, threatening to cause extinctions.


 * 2) Domesticated animals. Here we handle the population control ourselves, by neutering, culling, or just keeping males and females apart, so we don't need disease to do that for us.  Thus disease is unwanted, although the measures to control it, like widespread use of antibiotics, may be worse that the disease.


 * 3) Humans. Same as above for the developed world, although there do still seem to be populations of humans which don't manage to control their own population growth.  Here, it's quite inevitable that something will limit the population, whether war, disease, starvation, etc.  In that scenario, disease doesn't seem any worse than the alternatives, except that it tends to spread into populations of humans which are able to control their population, without infectious disease. StuRat (talk) 17:57, 4 May 2015 (UTC)


 * I know of a local ruler in Nigeria fifty years ago who had it down for modern medicine as it meant there were more people and the land was going to get overpopulated. I believe the population has doubled since then and I can see he had a point. There are too many people and we're destroying too much, but nobody is going to willingly die of a horrible disease because of that! Also it does seem as though people cut down on the birth rate eventually which is good, it is just a pity we couldn't have done both in parallel. Dmcq (talk) 20:07, 4 May 2015 (UTC)


 * Most residents of Earth do not yet accept the promise of rebirth after death. Count Iblis (talk) 20:41, 4 May 2015 (UTC)


 * Given current trends in all developing countries except subSharan Africa and some Middle Eastern populations towards limiting family size, the UN and other authorities have been projecting a world population maximum of around 10 Billion in 2050 and a decrease thereafter. Economically, a large population is good, since it has greater division of labor and economies of number and scale.  Hysteria about overpopulation belongs to the age of the Pet Rock or perhaps coal mines before the invention of railroads. μηδείς (talk) 00:56, 6 May 2015 (UTC)


 * There are plenty of reasons to worry about overpopulation. There's the depletion of non-renewable resources, pollution (including global climate change), increased spread of disease in densely populated areas, etc.  Couple this with the uncontrolled population growth being in places with few resources, and you will get wars over those scarce resources. StuRat (talk) 12:13, 7 May 2015 (UTC)


 * Well, yes, but one of those many reasons doesn't seem to be that it's going to happen. It should also be quite clear that "overpopulation" is a buzzword that assumes a negative in the world itself.  Once you use it, you've conceded the argument.  I'd suggest people look at Russia, which has been shrinking in population.  Are they doing better off?  Using the term the 'dangers' of 'underpopulation' would be the same sort of question begging. μηδείς (talk) 22:36, 7 May 2015 (UTC)


 * There are dangers to underpopulation, but they are completely different. Not being able to defend your nation is one risk.  Eventually a lack of genetic diversity becomes a concern, but that's down around thousands of individuals or less, not billions.  As for Russia, yes, I believe their per capita income has gone up, although this was reversed when oil prices dropped and stiff Ukraine sanctions kicked in. StuRat (talk) 01:08, 9 May 2015 (UTC)

How to start up a coal power plant
In electricity related news discussions, sometime people quote that coal power plant needs 24 - 36 hours to start up from cold. Why it is so long? How do they cold start the entire power plant? 118.137.194.159 (talk) 14:46, 4 May 2015 (UTC)
 * Read This. -- Jayron 32 14:50, 4 May 2015 (UTC)

Satiety and appetite
If one individual were to accomplish satiety with one bowl of food, but still looks forward to having a large, juicy apple for dessert, would he or she be able to finish the apple? If not, how many large, juicy apples does one have to eat to feel satiated and have no appetite to eat anymore? Is the subjective uncomfortable distention of the stomach enough to reduce appetite in a normal individual? 140.254.70.33 (talk) 15:35, 4 May 2015 (UTC)


 * When an individual achieves satiety s/he does not look forward to anything else. The high class Romans got by this puking up – so that they could gorge more. But that was more of a social thing.--Aspro (talk) 16:00, 4 May 2015 (UTC)


 * Satiety is not the same thing as appetite. An individual may feel full, but he may be eager to munch on dessert. 140.254.70.33 (talk) 16:20, 4 May 2015 (UTC)


 * Appetite has some info. SemanticMantis (talk) 17:03, 4 May 2015 (UTC)


 * How full the stomach is is only one of many factors that limits appetite. How much each individual relies on that will vary greatly. StuRat (talk) 18:01, 4 May 2015 (UTC)