Wikipedia:Reference desk/Archives/Science/2017 December 26

= December 26 =

Are any indoor plants or domestic animals endangered?
Are any food plants endangered? I know game animals are where most species losses have been, right? 83.137.1.213 (talk) 01:31, 26 December 2017 (UTC)
 * There are some endangered breeds of domestic animals. 2602:304:B041:9A9:C0F2:20FE:D0F9:930B (talk) 01:39, 26 December 2017 (UTC)
 * Wow, they are like the dustbin of less-efficient meat and milk production, not even their occasional non-adorableness can keep them from having their embryos frozen? Thanks! 83.137.1.213 (talk) 16:47, 26 December 2017 (UTC)
 * CITES especially appendix II should have several examples. Rmhermen (talk) 17:41, 26 December 2017 (UTC)


 * The turnspit dog went extinct in fairly recent times because its specialization died out, and there were no preservation efforts because they used to be ubiquitous. 93.142.65.4 (talk) 18:09, 26 December 2017 (UTC)
 * That being a breed, is it theoretically possible to re-create it? ←Baseball Bugs What's up, Doc? carrots→ 00:47, 27 December 2017 (UTC)


 * Panama disease pushed the most widespread banana cultivar to economic extinction, and now threatens the current most popular variety, the Cavendish (which was developed indoors, in the glass houses of an English aristocrat - all credit to his gardener). See by way of contrast European Potato Failure. If the agricultural stock is too narrow, a blight can strike them all down. Carbon Caryatid (talk) 22:43, 26 December 2017 (UTC)

fish reproduction
how do sperm travels to eggs in water how do they see eggs to reach them?reason. — Preceding unsigned comment added by Basil mansuri (talk • contribs) 15:56, 26 December 2017 (UTC)
 * Wikipedia has an article titled fish reproduction that discusses the many different ways fish reproduce. It's a diverse topic.-- Jayron 32 15:59, 26 December 2017 (UTC)
 * They are chemically lured; see sperm chemotaxis. Klbrain (talk) 00:39, 28 December 2017 (UTC)
 * So they're ovum-seeking missiles? Sagittarian Milky Way (talk) 02:32, 28 December 2017 (UTC)

Troposphere
Does the atmosphere convection of lightning storm to give and assist Earth the electricity power for rotation and orbiting the Sun? SA 13 Bro (talk) 17:43, 26 December 2017 (UTC)
 * No. The causality is wrong, the scales are wrong.  Lightning is powerful, but it arises as a result of the movement of clouds (clouds which carry charge, leading to an electrical potential difference). The clouds were driven by air currents, caused by temperature and pressure differences as a result of the Sun heating the Earth's atmosphere. Rotation of large weather systems arises due to Coriolis forces from the Earth's rotation.
 * So it's the Earth that give rise to lightning, not the other way round.
 * Also the amounts of energy involved are vastly different. Lightning is powerful, but the Earth is far bigger. Lightning has no effect at that scale. Andy Dingley (talk) 17:50, 26 December 2017 (UTC)
 * Also they're just totally different things. Electromagnetism and gravity are two different forces, and as far as we know, neither influences the other. Gravity is only "produced" by the presence of mass-energy. To add a slight caveat, gravity can affect particles, including photons, which are the force carriers of the electromagnetic force. Indeed, this bending of light was an important early prediction of general relativity. However, when we say gravity affects them, we just mean they experience the same gravitational effect as anything else with equivalent mass-energy. Gravity doesn't produce an electromagnetic effect. Earth's rotation is not really a "force." It's just the consequence of conservation of angular momentum. Earth's rotation has slowed over time, so there's clearly nothing inputting noticeable amounts of energy to it. --47.157.122.192 (talk) 22:28, 26 December 2017 (UTC)
 * I agree and thank you very much to you'll for those acknowledgement. I am actually a astraphobia, and also a astronomer. I live in Singapore, a small island country of Geo-locate at SE Asia that is closest to the earth equator. While Singapore is a tropical rainforest climate nation, occur an thunderstorm weather are quite frequently, and I am quite hate of Lightning. <b style="color:red">S</b><b style="color:orange">A</b><b style="color:gold"> 1</b><b style="color:green">3</b><b style="color:blue"> B</b><b style="color:indigo">r</b><b style="color:violet">o</b> (talk) 01:42, 27 December 2017 (UTC)
 * Can I question that you are an astronomer? Someone who thinks that the Earth's orbiting of the Sun needs to be powered in 2017, that is not an astronomer. --Lgriot (talk) 15:11, 28 December 2017 (UTC)

TV phosphorescence
I have an old CRT TV whose screen emits phosphorescent light (it will shine very faintly after all the light in the room has been turned off, provided it has been beforehand left on for some time)even though it hasn't been plugged in in years. Should I be worried that it's emitting ionizing radiation? The Wikipedia article on phosphorescence isn't clear on this. 93.142.65.4 (talk) 18:18, 26 December 2017 (UTC)
 * No. Ruslik_ Zero 19:21, 26 December 2017 (UTC)
 * ...For our very young readers, this discussion pertains to old-fashioned cathode ray tube displays and televisions, and not to new technology including LCDs, OLEDs, DLPs, projectors, ...
 * Well, that's a succinct answer, but hardly well-referenced!
 * From the FDA, here are some facts: Yes, cathode ray tubes emit ionizing radiation; but from consumer televisions, that radiation is rarely hazardous.
 * Strictly from a scientific perspective, a cathode ray tube absolutely emits ionizing radiation, both in the form of leaked electrons from the gun that leak through the enclosure, or directly through the glass and coating; and also in the form of secondary radiation of (mostly) X-ray photons - braking radiation - emitted each time an electron bombards the screen. For a correctly-functioning television set, both effects should be small.  "Afterglow" after you turn the unit off is phosphorescence - those photons are in the visible light spectrum and are the least harmful type of radiation your unit emits.  The nasty stuff - electrons and x-rays - are only emitted when the unit is energized ("when it's on"); the electrons typically won't travel more than a few inches through normal room air; the X-rays are pretty weak and should be below harmful levels.
 * Whether you should be concerned - in other words, whether those effects have any meaningful health consequences - depends on how well you trust government regulators. The FDA regulates television sets by setting performance standards for televisions built after 1970.  The regulations set safe standards for maximum allowable radiation, but they specifically do not use the important legal phrase "as low as reasonably possible," which has special meaning in the context of radiological health, see e.g. the glossary at the NRC.
 * If you still have a CRT, you might also be concerned about chemical health hazards - it's extremely likely that organic and inorganic materials like lead, mercury, arsenic, and phosphor are present. CRTs are hazardous demading waste in the USA.  Those chemical hazards are more likely to cause health hazard than the ionizing radiation from the television.  Once again, the levels of those hazardous materials should be "very low" and are regulated by various consumer agencies; but whether you should be concerned is at your own discretion.
 * Realistically, more people are harmed by acute electrocution (by playing with wiring or disassembling a TV); or by electrical fires consequent to such hazards. You should be more worried about frayed wiring than about radiation.  For example, here's an ancient 1975 study published by CDC, in which chronic exposure to CRT radiation was surveyed in the same context as chronic exposure to airborne dust: exposures "were not toxic..." based on medical evidence.  But in fairness, when comparing acute events to chronic low-dosage exposures, statistics and studies can be biased...
 * Nimur (talk) 19:31, 26 December 2017 (UTC)
 * I see, thanks. The afterglow is what I was interested in - most other stuff doesn't apply since the TV is unplugged and I have no interest in using or disassembling it. Re: chemical hazards - I keep a little jar of mercury on my desk and play with it occasionally. People aren't too happy about that either... :) 93.142.65.4 (talk) 20:05, 26 December 2017 (UTC)
 * Don't play with liquid mercury. Here is information from the CDC: ToxFAQs: Mercury.  The cancer is among the least of your worries; you should inform yourself, and concern yourself, with the near-certain probability of CNS damage and renal failure.  Do you think chemotherapy is unpleasant?  Read about chronic dependency on dialysis.  What you can expect..., from the website of the Mayo Clinic.
 * For the love of humanity, respect your kidneys. They, or the gigantic machine that replaces them, are literally the only things that can take the piss out of you.
 * Nimur (talk) 22:51, 26 December 2017 (UTC)
 * My impression of erethism is that traditionally it involved very significant exposures to mercury. Thanks to the profound legal precedent banning trade unions in the Danbury Hatters' case, people were working in small confined areas with large amounts of mercury vapor routinely right up until 1941, when the practice was ended not out of consideration for workers, who were merely raw material, but because some compound, mercury fulminate I'd guess, was needed to make explosives.  Consider the number of strange ritualistic things that still go on in the U.S. to this day -- people who intentionally take liquid mercury in capsules, or sprinkle it around for some sort of "luck" (bad luck, I'd wager).  Now there are people who are hypersensitive, perhaps even people with vulnerable kidneys, but my thought is that occasional playing with mercury in a well ventilated area by someone who is knowledgeable enough that he ought to know better and cleans up afterward probably isn't too bad, though of course no doctor is going to recommend it. Wnt (talk) 14:23, 27 December 2017 (UTC)
 * Play with mercury? If you have amalgam filling in your teeth your getting 24/7 mercury exposure. Far more than the exposure one gets from the occasional fascination of getting little globules to agglomerate, just like in the Terminator film. But photon activated luminance of the phosphor screen is no problem Aspro (talk) 22:37, 26 December 2017 (UTC)
 * Only if they leak. ←Baseball Bugs What's up, Doc? carrots→ 02:48, 28 December 2017 (UTC)


 * The OP states: “even though it hasn't been plugged in in years” thus the only ionizing radiation is that of the glass itself. One can assume that the CRT was made after atmospheric atomic  tests started. In making glass, a certain amount of air enters the mix. So post 1945 the glass  will be a little bit more radio-active than glass before that date (OK before some wise guy jumps in, I am not including green radio-active uranium glass) .  If the OP has a tub of say 'low sodium salt' in order to reduce his daily dietary sodium intake – the potassium salt substitute will be more radio-active than the glass envelope of the CRT, as  potassium is radio-active. See also: Low-background steel. So relax !  Astronauts on the International Space Station receive  twice the allowable  dose of a  a ground based nuclear worker and the only health effects so far observed is the early onset of eye cataracts,.  Although having said that, these astronauts  do seem prone to develop  an early onset of belief  in extraterrestrial intelligence.  Can see their point on  this, for after watching Fox News,  I find it hard to believe that there is any intelligent life 'here' on planet Earth. Aspro (talk) 22:18, 26 December 2017 (UTC)
 * ...That is a terrible answer completely devoid of scientific references. Do you have any evidence or sources for any of the claims you have made?  "The only health effects...?"  The numerous health effects of space flight - including, in specific, cancer caused by radiation during spaceflight - are heavily studied: the effects are very severe, and were cited by Charles Bolden as essentially the most serious reason we have not continued extensions of manned space flight beyond Earth orbit.  When the last NASA Administrator says that keeping astronauts safe from health effects of space flight is more troublesome than getting funding for space flight, that carries a little more weight than an unsourced internet comment.
 * Here is more from the Human Research Roadmap program at Johnson Space Center: Radiation Risks, including acute CNS problems, degenerative tissue disease, and probable death.
 * Sorry to burst some popular-science bubbles, but the scientific consensus is that humans aren't going to travel into deep space unless we can afford some heavy metal shielding.
 * Nimur (talk) 22:40, 26 December 2017 (UTC)


 * You're concatenating. In the low Earth obit of  the ISS the big danger is from from high energy protons  and gamma.   Not only  are high energy protons not good news but the shell of the ISS is of aluminium. Interaction with such light elements  can convert HEP 's to  equally harmful Bremsstrahlung radiation. That is why the ISS refuge have a thick layer  (some two inches thick)  of a high hydrogen density polythene  like plastic.   Hydrogen absorbs most of these .  Also, if the ISS crew is forewarned of a really bad  solar storm, the astronauts  quickly place in their  refuge,  extra hydrogen-rich  material.   HEP 's don't travel at the speed of light but they are travailing at millions of miles per hour, which gives the astronauts (or if they are Russian - Cosmonauts) just about ½ hour to prepare.   25 years from now we may not  need heavy metal shielding. A craft surrounded  with an electrostatic charge could deflect the worst of the sub-atomic particles because they have 'charge'.  This research has been going on for many a year, so if you want references – Google Scholar is your friend.  The Chinese may get to Mars first, as they discovered America long before Columbus so why shouldn't they get to Mars first?  Oh ! can  I hear your bubble now going  pop. Aspro (talk) 00:41, 27 December 2017 (UTC)
 * . Nimur (talk) 00:49, 27 December 2017 (UTC)


 * .@ User:Nimur. For citations you may like to read this , then  let me ask you . After fifth grade who needs to be held by the hand any more? Don't look to me because I won't ! It spoils  the demanding child and encourages  him to be intellectually  lazy. Aspro (talk) 02:02, 27 December 2017 (UTC)
 * If you're not interesting in giving people references, don't post here at all. This is not the "tell people things I know desk". This is the reference desk.  If you find it patronizing when people ask you for references, you're free to never come by here again.  You will not be missed.-- Jayron <b style="color:#090">32</b> 00:41, 28 December 2017 (UTC)
 * Also, this is the English Wikipedia. We expect a high standard of English spelling, because there are people reading this whose first language is not English and we need to set a good example. You have a long history of glaring spelling mistakes (travailing instead of traveling, above). If you cannot write acceptable English or think it's funny to throw in the odd misspelling, it's better that you don't contribute here. Akld guy (talk) 20:06, 28 December 2017 (UTC)


 * A study in the early 1980's found that office CRT terminals did indeed emit ionizing radiation. ALmost all of it came from radon in the dust that was electrostatically attracted to the front of the CRT, from the air in the office. This dust is of course present even after the CRT is turned off, until someone finally wipes it off. -Arch dude (talk) 17:17, 29 December 2017 (UTC)
 * I googled for ad found this . -Arch dude (talk) 17:20, 29 December 2017 (UTC)

tanked hot water heaters
As I understand it, hot water heaters (the tank types) have one water pipe that supplies water to the tank, and one pipe that exits the tank to supply the house. I'm trying to understand if the heated water is somehow contained strictly within the tank while no hot water supply valves are open inside the house or if heated water ends up expanding into either the supply or exit pipes. If heated water is prevented from extending into either pipe, I'd like to learn about how that is achieved.

Answers, recommended wiki pages, or other references appreciated. (I have tried to google this, my google search results speak to stuff like how long water stays hot inside of a tank and removing air from plumbing lines.) 128.229.4.2 (talk) 19:00, 26 December 2017 (UTC)


 * Start with Hot water tank, and also the references linked there such as . RudolfRed (talk) 18:38, 26 December 2017 (UTC)


 * There should also be a vented overflow pipe, which usually runs vertically out through the ceiling and through the roof. In particularly hot weather, or if the system is misadjusted or malfunctioning, hot water or even steam can be seen flowing out of the pipe and onto the roof. This site describes how it works, with a diagram. Akld guy (talk) 22:43, 26 December 2017 (UTC)


 * How about Code Requirements on Thermal Expansion Control in Domestic Service Water Heating Systems from the West Virginia Department of Health and Human Resources.
 * Summary: In older open systems with no check valve between the house and the city water supply, expansion in the water heater would cause some reverse flow backwards from the house toward the city supply to relieve the pressure increase, but modern closed or non-return systems include check-valves which prevent such backflow, necessitating the installation of an expansion tank on the water heater's inlet line. "All national cross-connection codes, including the Uniform Plumbing Code (1991 edition), now carry requirements for the provision of an approved thermal expansion control device."  That paper does not address houses with their own water well pump, but such systems already include an expansion tank to smooth the pressure and limit pump cycling. -- ToE 22:47, 26 December 2017 (UTC)  Since practices may vary by region, note that the questioner's IP geolocates to Virginia, USA. -- ToE 23:57, 26 December 2017 (UTC)
 * Just FYI, expansion tanks are not required everywhere. Modern water heaters have a pressure relief valve.  Specific climates may dictate exactly what is required in each locale.  --DHeyward (talk) 04:34, 28 December 2017 (UTC)


 * Thanks all. This ref did a pretty good job of answering my questions.128.229.4.2 (talk) 13:33, 27 December 2017 (UTC)