Wikipedia:Reference desk/Archives/Science/2017 August 7

= August 7 =

Hearing aid battery tester.
I've always wondered how this little devil works. This link is to an amazon.com device that costs very little. What you do, you put a battery like 312 on the metal plate with the positive end down, then press it with you index finger and if the battery is full of charge, the other part, the display, will show a grid, a set of about 30 parallel bars. If they run all the way to the top, your hearing aid is fine. Otherwise it goes to the waste basket.

How does it work?

Thank you, --AboutFace 22 (talk) 01:53, 7 August 2017 (UTC)


 * If it is the usual kind of battery tester, it connects the two ends of the battery across a given resistance and measures the amount of current that flows. Looie496 (talk) 02:58, 7 August 2017 (UTC)

There is no circuit, unless it is through my body, besides my body is on an isolator, the floor. --AboutFace 22 (talk) 12:38, 7 August 2017 (UTC)
 * Well if there is no circuit then it cannot work. The picture is fairly low res, but AFAICT, and also based on the user comments, there seems to be a plate at the bottom and a clip to the side-up (in the direction shown in the picture). The bottom plate touches one terminal of the battery and the clip touches the other so there is a circuit in the device through these 2 terminals connecting to the 2 terminals on the battery. Your finger is mostly irrelevant, it's just need to apply pressure to ensure the battery makes good contact with the two terminals/contacts on the device. Nil Einne (talk) 14:20, 7 August 2017 (UTC)
 * This video with a Malaysian or Singaporean presenter [//www.youtube.com/watch?v=Re14xRaUc9Y] of a very similar device seems to confirm my suspicion. You can clearly see the clip, and also see it doesn't work until the battery connects to both the plate on the bottom and the clip on the side-up. Nil Einne (talk) 14:25, 7 August 2017 (UTC)
 * BTW, maybe in your version the clip is harder to see than the Amazon or video one. I suggest you look carefully and you will see there is another contact point. Nil Einne (talk) 16:37, 7 August 2017 (UTC)


 * Public service announcement: please recycle dead batteries. Don't throw them in the trash. Many batteries contain toxic substances, and in any case recycling allows their components to be reused. --47.138.161.183 (talk) 16:08, 7 August 2017 (UTC)

@Nil Einne, you are right. Now I begin to figure out how many batteries I've discarded because I never touched that little protrusion in my ignorance. That video shows exactly the device in question. --AboutFace 22 (talk) 19:48, 7 August 2017 (UTC)

How hard of a hit to the testes would be needed to temporarily incapacitate a gorilla?
What about a chimpanzee? Sagittarian Milky Way (talk) 04:41, 7 August 2017 (UTC)


 * Approximately 3 SMWs. 1 SMW is about what I feel like doing when I read one of these questions. Greglocock (talk) 05:07, 7 August 2017 (UTC)


 * Only 1? You're kinder than me..... Nil Einne (talk) 14:26, 7 August 2017 (UTC)


 * How do you know what 1 SMW is if your only information is that it's a third of that needed to incapacitate a gorilla? --129.215.47.59 (talk) 15:28, 7 August 2017 (UTC)


 * I did find a demonstration of the experiment: . I believe the force there is approximately equal to 1 SMW.  -- Jayron 32 16:34, 7 August 2017 (UTC)


 * Well that information is enough to know it's not enough. It's not necessary to know precisely how much it is. Nil Einne (talk) 16:35, 7 August 2017 (UTC)


 * Out of curiosity, do you need an answer very very very very very very very quickly? If so, good luck. Hayttom (talk) 17:53, 7 August 2017 (UTC)
 * And for any needed repairs, there's always Gorilla glue. ←Baseball Bugs What's up, Doc? carrots→ 18:08, 7 August 2017 (UTC)
 * More like a prosthetic limb or three. Sagittarian Milky Way (talk) 18:24, 7 August 2017 (UTC)
 * "Ekʉa álulɔ ntile lé ebam" - a spear is never forged while a gorilla is screaming at you. Oddly, this is the only thing Google indexes for "self-defense against a gorilla", which suggests that many folks online have not taken this proverb to heart, or really aren't expecting gorilla warfare. Wnt (talk) 21:13, 7 August 2017 (UTC)
 * The incapacitation is supposed to happen via a severe pain reflex, but then wild animals will typically have more effective reflexes, so the gorilla may end up killing you in a strike that is triggered by that supposedly incapacitating pain reflex. Humans have bad reflexes and it is getting worse because children are not paying outside as frequently as they should. Many children today get broken bones due to falls, that's because by playing video games all they long they have not trained the reflexes they get when they are about to fall to prevent the fall or to break the fall. Count Iblis (talk) 19:28, 7 August 2017 (UTC)
 * Possibly useful context is that a gorilla's testes are slightly smaller than a human's whereas a chimpanzees, that source says, are three times larger.  It looks like Straight Dope struck out on this one, with nothing but guesses and humor. Wnt (talk) 21:19, 7 August 2017 (UTC)
 * Guesses and humor? No shit?  Wonder where I've seen that before?  If it's good enough for Uncle Cecil, it's good enough for us, I guess.  -- Jayron 32 22:32, 7 August 2017 (UTC)
 * Well, as many here have pointed out, it's really tough to find someone who got a Ph.D. to run a study, but is still dumb enough to kick a gorilla in the nuts. ;) Wnt (talk) 22:16, 8 August 2017 (UTC)

Pot with water, time to boil
If you are heating a pot with water and stir it with a spoon, would that change significantly how fast the water starts to boil/how heat is transferred? --Hofhof (talk) 12:36, 7 August 2017 (UTC)


 * This doesn't address your question (hopefully that will come later) but I think that a third option of putting a lid on the pot to reduce evaporation and leaving convection (the hot water should rise and the cold water should fall) to take care of the mixing would be the fastest (and most environmentally-friendly option). I'm looking for sources now but I expect to fail. --129.215.47.59 (talk) 12:47, 7 August 2017 (UTC) I've given up looking and this was the best I could find (it doesn't meet Wikipedia criteria for sources): it says there's 2.8% improvement for adding a lid but doesn't address stiring. --129.215.47.59 (talk) 13:09, 7 August 2017 (UTC)


 * There are multiple stages of boiling. If the water is still, you will see that the bottom of the pot will form bubbles first (assuming the pot is only heated at the bottom). That is because the water nearest the heat source is hotter and reaches boiling temperature first. Eventually, all the water will reach boiling temperature and the bubbles will form throughout the water. This is called a rolling boil. If you stir the water, you will keep moving the hottest water at the bottom with the cooler water on top (assuming you do a good job at stirring). So, you will delay the partial boil where the bottom forms bubbles, but the pot isn't entirely boiling. You will not significantly change the time to reach a full rolling boil. From a very technical and pointless point of view, you will be adding energy to the water by stirring, which will decrease the time to a rolling boil. But, it will not be significant. For example, you cannot make a pot of water boil just by stirring it extremely fast. Even with a power tool, you can't stir it fast enough to get it to boil. So, all you are really doing is keeping the pot mostly at the same temperature instead of hot on bottom and cold on top. 209.149.113.5 (talk) 12:49, 7 August 2017 (UTC)


 * Generally speaking you will slow boiling, because you will increase the rate of heat loss to the air. In fact if you have a weak enough heat source, vigorous stirring may be enough to prevent the liquid from boiling at all. Looie496 (talk) 13:35, 7 August 2017 (UTC)
 * Thompson's not pointless paper "An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction" of 1798 led Joule to propose this kinetic theory of heat: "wherever mechanical force is expended, an exact equivalent of heat is always obtained". Merely by stiring vigourously you may add heat to the water, and can eventually even boil it. If precautions are taken to eliminate loss of heat by conduction, convection and evaporation, the experiment can be done to measure the Mechanical equivalent of heat, exactly what Joule did in 1845, and still a valid result. Blooteuth (talk) 14:12, 7 August 2017 (UTC)


 * It is correct that moving warmer water to the top of the pot will increase the rate of heat loss to the air. In the same way, moving cooler water to the bottom of the pot will increase the rate of heat absorption by the water. 209.149.113.5 (talk) 17:20, 7 August 2017 (UTC)


 * The presence of a metal spoon itself may dissipate more heat out of the water, too, through heat transfer. — Paleo  Neonate  – 23:17, 8 August 2017 (UTC)


 * Stirring the pot will quicken the boil, as the water will touch the hot edges of the pot above what would be the static waterline, absorbing heat from a greater surface, and transporting it more quickly to the whole body of water. You can show this easily with two identical teapots only slightly full over a moderate flame. (Or do this twice, using a timer, if you only have one pot.) Let one sit on the flame, and swirl the water in the second one around so it sloshes against the superheated edges.  The swirled pot will boil much faster. μηδείς (talk) 22:18, 11 August 2017 (UTC)

Why was the helical structure of DNA such a big deal?
I can understand why now, with the knowledge of protein structures and how they might fit into the major or minor grooves and how DNA is compacted and unwound, knowledge of the helical structure of DNA is very important but back in the 50s was this as clear? Is the big deal just because it's digestible by the public like E=mc^2 and Dolly the Sheep? Was it seen as a big deal in the 50s or did it become a bigger deal in hindsight when later developments were seen to hinge on understanding the helix? What about discovery of the four main nucleotides themselves; isn't that worth an even bigger fuss? --129.215.47.59 (talk) 12:43, 7 August 2017 (UTC)


 * Understanding how cells store genetic information was/is the big deal. The DNA model has a double helix structure. Knowing this was a big step to understand it. This is the mainframe. Phoebus Levene's discovery bewtween 1909-1929 of the nucleotides was not enough to know how information gets processed. Nor was enough to isolate DNA for the first time as Friedrich Miescher did in 1869. There was a piece of the puzzle missing until Watson and Crick came along.--Hofhof (talk) 12:55, 7 August 2017 (UTC)


 * But why was the Watson/Crick part of the puzzle considered so big? I think they might be household names but I've no idea who discovered the nucleotides and I don't see the difference in significance. 129.215.47.59 (talk) 13:11, 7 August 2017 (UTC)


 * X-ray diffraction studies showed that DNA had a regular, repeating structure as early as 1937 - see William Astbury. In 1950 Erwin Chargaff discovered that the amounts of adenine and thymine in DNA were roughly the same, as were the amounts of cytosine and guanine - see Chargaff's rules. Rosalind Franklin concluded that the structure of DNA was a helix by January 1953 and in February 1953 Linus Pauling proposed an incorrect triple helix structure. But the "big deal" was Crick and Watson's announcement in April 1953 of a molecular structure which was consistent with all the known properties of DNA and also explained how the regular physical structure of DNA could still encode genetic information which varied from one individual and one species to another. Gandalf61 (talk) 13:20, 7 August 2017 (UTC)


 * (Edit conflict) See History of molecular biology. The important part of the discovery was not that DNA was a helix, but that it was doubled and made of paired bases. This meant that it could easily split in half and duplicate itself. This was a surprising discovery at the time - biologists guessed DNA played a role in inheritance thanks to the Hershey–Chase experiment, but they didn't know what its structure was (a common theory was triple-stranded DNA, but that didn't really work), and that meant they couldn't work out how genetics actually worked. Once it was clear that DNA had a simple structure and could copy itself easily, it became clear that it was the foundation of the genetic code. Our article on Watson and Crick's paper, Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid, has a little more information. Smurrayinchester 12:56, 7 August 2017 (UTC)


 * Oh right, thanks; that does seem like it explains the significance a lot better. I think my query can be considered resolved. Thanks again. 129.215.47.59 (talk) 13:14, 7 August 2017 (UTC)
 * As they said themselves in the paper (see Smurray's link): "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material". --69.159.60.147 (talk) 19:43, 7 August 2017 (UTC)
 * Nitpick: saying that DNA "copies itself" isn't quite correct. That's what DNA polymerase does. Now sure, the DNA in organisms contains the gene for DNA polymerase (actually several, in most organisms), but it has to go through the whole transcription process to produce the enzyme. RNA, on the other hand, can duplicate itself. Numerous ribozymes are found in cells, including the ribosome. The realization that ribozymes are essential to most cells gives a lot of evidence for the RNA world hypothesis, which asserts that life once used RNA as its genetic material. It eventually switched to DNA as the storage medium because DNA is more stable, but kept most of the RNA-based machinery, which is why life today still uses RNA as an intermediate in gene expression. Of course I'm not suggesting that the discovery of DNA's structure wasn't important; indeed, its structure explains why DNA is more stable. --47.138.161.183 (talk) 15:51, 7 August 2017 (UTC)


 * Excellent answers above; I would only re-emphasize that the discovery of an immediately graspable (and also reasonably accurate) icon helped make the discovery more widely publicized and understood. The concept of a threaded item serving as a model to create copies had been known and widely used for almost a century (see screw machine), so the double helix of DNA appealed to common sense. Consider the similar adoption of the quite incorrect, but easily graspable, Bohr model of the atom. A picture is worth 1,000 words, they say. Matt Deres (talk) 17:08, 8 August 2017 (UTC)

Feynman Lectures. Exercises. Exercise 10-3 JPG. Lecture 10
. .

I have found answers to the first two questions png. Don't understand last question. There is the retarding force in opposite direction to the velocity. So magnitude of the velocity must decrease. Then the satellite must deorbit and go to an elliptical spiral orbit (If the retarding push were single, then the apogee would be at this point.). At this moment we do not know that the atmosphere is exponential, so I suppose that density = const. Why does Feynman think that the satellite will remain in a circular orbit (his last sentence in brackets)? Username160611000000 (talk) 13:50, 7 August 2017 (UTC)


 * Because the total drag experienced per orbit is very small, it is possible to use a quasi-steady state approximation and model the satellite as following a series of circular orbits whose radius is very slowly decreasing over time. As you probably know, a circular orbit with a smaller radius must also have a faster velocity.  In effect, deorbiting the satellite due to drag actually causes it to gain velocity from the Earth's gravity well.   Dragons flight (talk) 15:10, 7 August 2017 (UTC)


 * Hm... We don't know the formula for potential energy in non-constant gravitational field at the moment of Lect. 10. So I think I will use my formula for v(R) : $$v(R) = \sqrt{g(R)\cdot R} = \sqrt{\tfrac{GM}{R}}$$, -- and formula $$a = \tfrac{v^2}{R} $$ for constant a. Quick calculations shows that velocity increases even faster then it should according to the v(R) formula.Username160611000000 (talk) 06:40, 8 August 2017 (UTC)


 * Using formula $$a = \tfrac{v^2}{R} $$ with $$a=\text{const}$$, we get $$\tfrac{r_2}{r_1}=(\tfrac{v_2^*}{v_1})^2$$, where  $$v_2^* = v_1 + a_\text{ret}\text{d}t$$ . Using formulae (speed of a circular satellite orbit vs. height) $$v_1 = \sqrt{\tfrac{GM}{r_1}}$$,  $$v_2 = \sqrt{\tfrac{GM}{r_2}} $$ : $$\tfrac{r_2}{r_1}=(\tfrac{v_1}{v_2})^2$$  ∴ $$\tfrac{v_2}{v_1}=\tfrac{v_1}{v_2^*}$$, which is only possible if $$v_2 = v_2^* = v_1$$. But such reasoning  seems alogical. First , this implyies r1=r2, which is not the case. Second, can't accept that in one formula the acceleration is const, but is not in the another. — Preceding unsigned comment added by Username160611000000 (talk • contribs) 06:40, 8 August 2017 (UTC)


 * When a satellite is at the low point (perigee) of its orbit, it is moving fastest, and the air density is greatest. For both reasons, the air friction is greatest at this point.  So I think that the satellite, experiencing the most drag directly backward at the low point in its orbit, ought to end up in a lower circular orbit.  This is not, however, a detailed simulation....  The not very convincing looking source  found in a web search for sites that agree with me, agrees with me.  The more refined source  is ... well, not quite so easy to make sense of, and doesn't actually model the effect of air drag within an orbit, but talks about orbits losing circularity from it.  If this is less than convincing, well, I should indeed have another hack at it. ;) Wnt (talk) 22:05, 8 August 2017 (UTC)
 * For an elliptical orbit the speed at perigee is greater than necessary for a circular orbit with a radius rperigee, and at apogee the speed is less than necessary for a circular orbit with radius rapogee. E.g. for Table 9–2 adjusting length unit ≡ 12 800 km and time unit ≡ 2.3•103 sec so that GM = 1 (length unit)3(time unit)-2, we find that vp = 1.63 speed units = 9.099 •103 m/sec ; va = 0.797 speed units = 4.449 •103 m/sec. $$\tfrac{v_\text{p}}{v_\text{a}}=\tfrac{r_\text{a}}{r_\text{p}}$$ . vcirc,p=7.894•103 m/sec, vcirc,a=5.521•103 m/sec. Username160611000000 (talk) 12:01, 9 August 2017 (UTC)
 * Using formula for potential energy $$P_1 = -\tfrac{GMm}{r_1}$$, I found that falling from r1 to r2 would release energy $$GMm(\tfrac{1}{r_2} - \tfrac{1}{r_1})$$. But the satellite kinetic energy increase = $$0.5m({v_2}^2 - {v_1}^2) = 0.5m(\tfrac{GM}{r_2} - \tfrac{GM}{r_1}) = 0.5GMm(\tfrac{1}{r_2} - \tfrac{1}{r_1})$$. Thus the energy output at a falling is twice as large as the required for circular orbits. Excess energy can be consumed to supply particles with speed, if the circular orbits  hypothesis is correct, which is still unproved . Username160611000000 (talk) 04:49, 10 August 2017 (UTC)


 * Using numerical methods I found that the trajectory is an ellipse and the speed does oscillate (for clarity ρ is set 1.6•10-8) xlspng1 . Without retarding acceleration : png2. You can see that the oscillations without retarding acceleration are in range < 1 m/sec (not very accurate initial conditions ). Username160611000000 (talk) 16:47, 10 August 2017 (UTC)

Can biomass be sold in bulk to thermoelectric plants?
I have mainly interest on the situation in the UK, but knowing about other countries is OK too. So, if someone has biomass (like paper, or a farmer with tonnes of dung) in excess, as residual stuff, would a thermoelectric plant buy it, in the same way that other commodities are traded? Can such a plant operate with different types of inflammable biomass? That is, can you throw paper, dung, sawdust or chipped wood? Does this make financially and ecologically sense? --B8-tome (talk) 17:44, 7 August 2017 (UTC)


 * One big difference is water content. Dry biomass, like sawdust, can be burnt to release energy (although it's so flammable it can be an explosion risk).  That wouldn't work with wet biomass, like dung (you could dry it first, but that would use more energy than you get from it or create a big stink if you spread it out in the sunlight).  Allowing it to decompose to generate heat and methane, which you would collect and/or burn, would be a better option there.  Farmers might do better to use manure as fertilizer, though, unless there's a concern over spreading disease that way (either to humans of other animals).


 * Note that a steam turbine is one technology that's remarkably flexible as to the fuel. You can use nuclear energy, geothermal energy, or any flammable material to make the steam from water, then extract energy from it.  However, you would need a different mechanism to store, load, and burn the fuel, say with sawdust versus methane. StuRat (talk) 18:07, 7 August 2017 (UTC)


 * Often, biomass fuel is singly-sourced to a specific industry or even specific source within that industry for a regular supply chain, see for example, Bagasse, one of the more common biofuels, which is used at the site of production as a fuel source. -- Jayron 32 18:45, 7 August 2017 (UTC)


 * Oh, and I should mention that using biomass for fuel is considered to be carbon-neutral and renewable energy, as it's assumed that those materials would decompose and release carbon dioxide and methane on their own, but doing so in a way where we collect energy from them during the process doesn't release any more, unlike when we burn fossil fuels. StuRat (talk)


 * A typical thermoelectric plant is setup to handle a specific fuel in terms of its storage, loading, and the handling of any residual waste. It is often not too difficult to retrofit a plant that runs on one fuel to run on another fuel, e.g. converting a coal plant to run on natural gas is common.  However, the typical plant is unlikely to want to accept an occasional pile of random waste.  The won't be set up to handle it, and won't want the extra hassle.  The exception may be plants designed to burn municipal waste.  In some areas, most residential and commercial trash is sent to incinerators rather than landfills.  Those incinerators can be setup to generate electricity (though usually only a small fraction of a country's needs) and are likely to have the flexibility to accept a wide range of materials.  Dragons flight (talk) 19:40, 7 August 2017 (UTC)


 * Miscanthus x giganteus is a biofuel/bio-engergy crop subject to much recent interest and research. You can harvest the dried crop, and run it through a pelletizer to make pellet fuel. Since Miscanthus can be grown in a carbon-negative manner, burning this fuel results in no net increase in atmospheric CO2. Put simply, you can grow grass as a carbon sink, then burn it for heat/energy, and still sequester more carbon in the soil than you've released in to the air. See here for a freely accessible research article detailing the carbon dynamics of Miscanthus in central IL. There really is tons of research on this, see also here  for another good set of references and context. There is considerable interest in the UK and EU for developing this type of market. I don't know much about actual extant power plants in the UK but in principle they can be adapted to burn pellet fuels. See here  for some information on EU power generation via pelletized biofuel. SemanticMantis (talk) 21:24, 7 August 2017 (UTC)


 * Waste-to-energy may also lead you to interesting places for your research. -- Jayron 32 22:31, 7 August 2017 (UTC)
 * Decades ago I saw an abandoned waste-burning power generating pilot project. It had a conveyor belt which fed municipal waste into a furnace, where it was burned along with natural gas to heat a boiler to generate a small amount of power for a utility. The idea was to reduce the need for landfill while producing power. I don't recall that they addressed the issue of environmental pollution from burning random plastic and other waste items. The project was abandoned because it required too much labor to chisel impurities off the grate (think clinker fro a coal furnace, but worse.) At the time it did not seem to my naive view to be an insuperable problem, but the utility would have rejected "free" biomass since it had handling and cleaning problems which made it more expensive to use than traditional fuels. In the 1970's the US government developed the "MIUS" or modular integrated utility system, which would be a neighborhood-scale utility plant which would burn the trash to generate power, while using the energy to purify the sewage, and return the purified water for household use, while providing heating and cooling. It seems to have failed the failed the "NIMBY" (not in my backyard) test since people feared the fumes it would emit. Edison (talk) 02:49, 8 August 2017 (UTC)


 * At the other end of the spectrum, Switzerland completely banned the use of landfills for normal waste as of 2000. All municipal waste is either recycled or incinerated.  The incinerators generate about 2% of Switzerland's electricity.   Dragons flight (talk) 11:04, 8 August 2017 (UTC)


 * Cement plants are notorious for taking almost any kind of organic waste and using it in incinerators; our article gives them credit for producing more toxins than ordinary incinerators, and mentions issues with them burning BSE cows. The Sicilian Mafia is described in that article as having a dominant interest in cement plants, since everything from hazardous waste to Jimmy Hoffa can end up in them.  If you search "cement plants" biomass you'll get all sorts of hits like this.  Just watch out for folks who make you an offer you can't refuse... Wnt (talk) 22:11, 8 August 2017 (UTC)


 * He may never be found, but at least his article can be: Jimmy Hoffa. :-) StuRat (talk) 01:16, 9 August 2017 (UTC)

How much heat does a CCFL output?
Can someone help determine the amount of heating power that applies to a CCFL as used in LCD displays? Those I've tested consume 0.4 A at 12 V (4.8 W) and that includes the energy lost by the inverter. If the inverter is 80% efficient then 3.8 W are passed on to the lamp which I guess produces X amount of light and Y amount of heat. I don't think the length is important to know; only the percentage that goes to light (or heat) --145.255.246.78 (talk) 20:52, 7 August 2017 (UTC)
 * Warning: I asked a similar question about light vs heat efficiency of a bulb here before. Everyone refused to answer because the consensus was that all energy becomes heat so the bulb outputs only heat and light is just a side effect. 2600:1004:B108:9BD0:F9E8:F75:A476:CF30 (talk) 22:09, 7 August 2017 (UTC)


 * I'm specifically interested in the heat experienced by the bulb itself, not its environment, so photons that leave the bulb don't count much towards the heating of the bulb. --145.255.246.78 (talk) 05:26, 8 August 2017 (UTC)


 * This article Seems to lead where you're looking, and it has footnotes to other places to help your research. -- Jayron 32 22:30, 7 August 2017 (UTC)
 * Could you determine the heat current going to the bulb as opposed to the light current?Edison (talk) 02:28, 8 August 2017 (UTC)


 * Thanks but I'm interested in CCFLs (from LCD monitors) not CFLs. 145.255.246.78 (talk) 05:29, 8 August 2017 (UTC)


 * Related to your question, we have an infrared camera. I thought it would be interesting to see how average LCD monitors look. They should show up warm because they produce heat. They don't. They are dark purple - barely different that the blue background heat indicating room temperature. I looked at my phone. It has and OLED display, not LCD. I can see the processor as a red square in a purple rectangle. Then, I thought to look at the back of the monitor to see if it is any different. It is blue, not purple. So, less heat. Maybe a little purplish on the top. The power bricks are getting redder though. I figure that if I had a high quality camera, I could tell you the exact temperature of the monitors. All I can see is blue to white colors. 209.149.113.5 (talk) 14:48, 8 August 2017 (UTC)


 * Were you looking at a desktop or laptop monitor. In most cases, the light is coming from one of the edges (in laptops, usually the bottom and in desktops, usually both the top and the bottom). The heat will therefore be concentrated at the very top or the very bottom with nothing in the middle of the monitor. In some cases, the CCFLs are arranged evenly spaced at the back but I've only seen this once in about 10 desktop monitors. How long was the monitor on for? My desktop LCD gets nice and warm over the course of a couple of hours use, although some of that will be from the electronics for processing the display and the power supply for it and the CCFLs. CCFLs which I left connected to power on the bench also get warm/hot. 129.215.47.59 (talk) 18:01, 8 August 2017 (UTC)


 * We have desktop monitors. They are always on. They don't get warm to the touch at all even though the hospital is kept relatively cool. There are many models. I see a Dell, an HP, and a Gateway from where I'm sitting right now. 209.149.113.5 (talk) 18:20, 8 August 2017 (UTC)


 * While I don't think the CCFLs in most computer monitors gets that warm, it's worth remembering most computer monitors in the past few years (maybe since 2012 or so) will have LED back lights not CCFLs. So if they're recent, unless you're sure the monitors being looked at were CCFL they're probably not. Nil Einne (talk) 19:38, 8 August 2017 (UTC)


 * P.S. I believe CCFLs are or at least were on monitors requiring a wide colour gamut until very recently. I assume these may be used in some hospital settings but the above monitors sound like they're probably just normal desktop monitors provided with computers sold for offices etc. Nil Einne (talk) 04:23, 9 August 2017 (UTC)

Mystery caterpillars (San Diego)
What is this pink caterpillar, and what's it doing on a clump of seaweed on a sandy beach? (Assuming it is a caterpillar; if not, what is it?). I also found a similar looking yellow one on a sidewalk a few weeks ago. What species are these? 169.228.146.121 (talk) 22:50, 7 August 2017 (UTC)
 * It may be, but probably not, a Microphotus angustus per . It may be a Pectinophora gossypiella, a type of bollworm, per this, but that doesn't look like  a great fit either.  -- Jayron 32 15:57, 8 August 2017 (UTC)

Do scientists know what type of bugs are required to colonize the body for healthy living?
Keeping clean may sound like a good idea, but hyper-cleanliness may mean that the wrong type of microorganisms get on the body. Playing in mud is probably not practical and disgusting, and drinking toilet water is a good way to die by dysentery. So, is there a middle ground to get the RIGHT type of bugs for healthy living, or are some individuals doomed no matter what? 50.4.236.254 (talk) 22:51, 7 August 2017 (UTC)
 * Technically, everyone is doomed. ←Baseball Bugs What's up, Doc? carrots→ 01:32, 8 August 2017 (UTC)
 * Everyone has to die of something.-- Jayron 32 01:53, 8 August 2017 (UTC)
 * That's not very skeptical of you. Aging may be defeated, and then it's possible that advanced intelligences will figure out a way to overcome the heat death of the universe. PeterPresent (talk) 12:56, 11 August 2017 (UTC)
 * The article Microbiota is where you want to start your research.-- Jayron 32</b> 01:53, 8 August 2017 (UTC)


 * While it has never been done with healthy humans, scientists have created "axenic" plants and small animals (e.g. mice) which have no bacteria present at all. Maintaining that condition is naturally challenging, but the plants and animals generally mature normally and usually have only mild side effects or other limitations.  For animals, the most important beneficial role for bacteria is often in digestion where they can break down food in the gut prior to absorption into the body.  The lack of such microbes may limit the ability to digest some foods.  Dragons flight (talk) 11:14, 8 August 2017 (UTC)
 * I remember reading about some studies that show children who grow up in natural environment, including much more exposure to "dirt" develop far less allergies than children which grow up in a "clean" enviroment. Here one study finds Amish children have a 10% chance to develope asthma and allergies while Hutterite children have a risk over 20% for asthma and 30% for allergies.
 * However id say its not entirely clear, because modern, or as you call them, hyper-clean families for shure have way more unnatural to questionable chemicals and even real poisons around them, compared to amish families, from food contained in plastic to Urinal deodorizer block, if its the dirt that helps or the chemicals that harm. Likely even both. --Kharon (talk) 11:17, 8 August 2017 (UTC)


 * It is also important to note that, by population of cells, you're about 1/2 bacteria. (that article debunks an inaccuracy that your body is 90% bacteria.  However, it does confirm that the ration is about 1:1 bacterial:human cells in your body).  Obviously, most of those bacteria aren't actively killing you, and many have developed a symbiotic relatioship with humans, for instance many of your gut bacteria produce vitamins you need to survive, among other functions.  -- Jayron <b style="color:#090">32</b> 14:06, 8 August 2017 (UTC)


 * You may be interested in reading about probiotics, the human microbiome, and gut flora. SemanticMantis (talk) 15:09, 8 August 2017 (UTC)


 * See here: "In summary, the characterization of the metabolic phenotype of the Hadza during the rainy season, when their diet is primarily based on plant foods, allowed us to make a step toward deciphering the intricate host-microbe relationships that regulate human biology and have contributed to our evolutionary history. In parallel to the peculiar features of their microbiota and microbiome, the Hadza fecal metabolome showed a unique enrichment in metabolite classes that may have an impact on human health. Our findings lend support to the notion that the enteric ecosystem co-evolved in the ancient selective environments of our presiding forager legacy, thus complementing human physiology in present day hunter-gatherers. In addition to the abundance of hexoses (simple sugars), that seems to be indicative of a diet rich in microbiota-accessible carbohydrates (MAC)3, the high presence of sphingolipids and glycerophospholipids, together with low levels of amino acids, suggests a robustly healthy gut metabolic profile that is specifically poor in factors known to trigger or contribute to the typical inflammation-based Western diseases. The high-MAC diet, as that of the Hadza and other traditionally living humans, may then be uniquely permissive of a diverse community of gut microbiota that also demonstrates a functional specificity aligned with preserving local and systemic health and mitigating disease risks52." Count Iblis (talk) 15:49, 8 August 2017 (UTC)


 * Note that mental health, and therefore mental state, is influenced by those gut bacteria.  Would you be you without gut bacteria?  Just as we have come to accept that we are not just one kind of cell, but cells in symbiotic relationships with mitochondrial endosymbionts, it may be that we should define ourselves not as humans, but as a colony of symbiotic species working together.  Even if one seems to dominate more than Russia in the old Soviet Union. Wnt (talk) 18:36, 8 August 2017 (UTC)


 * As far as a healthy middle ground, here are some suggestions:


 * 1) Eat healthy foods, many of which are prebiotic (nutrition), meaning they are food for good microbes in your digestive tract.


 * 2) Avoid anti-bacterial soap/detergent, such as those containing triclosan.


 * 3) If you have occasion to use diapers or urinary incontinence pads, make sure they aren't treated with anti-bacterial agents.


 * 4) Eat and drink probiotics. There's yogurt with active (live) yogurt cultures, and fermented foods, like sauerkraut and, if you're a bit braver, kimchi.  Drink kefir, or milk with acidophilus added.


 * 5) Avoid using alcohol or hydrogen peroxide on your skin.


 * You will be happy to know that a fecal transplant isn't recommended for everyone, only those with a severe digestive problems. StuRat (talk)


 * The above borders medical advice yet includes beliefs. Please take with a grain of salt.  — Paleo  Neonate  – 03:57, 9 August 2017 (UTC)


 * And stop taking showers, while not yet rigorously proven to benefit the microbiome, there isn't any medical evidence that taking showers is good for anything at all. Put differently, the reason why most of us take regular showers is because we find it comfortable to do so, and many of us believe it's good for our health, but there isn't a shred of evidence that it is actually doing anything good for us. Count Iblis (talk) 18:11, 11 August 2017 (UTC)


 * A few of us don't like smelling like moldy onions and week old diapers, so there's that... -- Jayron <b style="color:#090">32</b> 18:15, 11 August 2017 (UTC)


 * Yes, but it wasn't that long ago that people used to take a bath once a week. In the army they have a lot of experience with what is really necessary for staying healthy, e.g. proper sanitation is necessary; the army manual contains a lot of instructions on how to safely discard of waste when out in the wilderness. Taking daily showers is not essential, you actually want to conserve water as much as possible. When the army deployed in Afghanistan in remote outposts it was quite difficult to get in in the heads of young people who were used to taking showers multiple times a day in hot weather, that simply washing with a wet towel once day is more than good enough. The real problem here is that many of them believe that they'll come down with some horrible disease if they don't take regular showers. Count Iblis (talk) 18:47, 11 August 2017 (UTC)


 * Yes, we would need to keep the psychological aspects in mind when recommending an end to bathing. If they end up with no friends, significant other, or job as a result of their odor, that can't be good for their mental health, and is likely to cause stresses on their physical health, too.  So, in our society, bathing regularly is an important aspect of total health. StuRat (talk) 22:02, 11 August 2017 (UTC)