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August 5

Surface-to-surface missile

Recent news[1] got me thinking: has there been cases of surface-to-surface missiles or rockets launched at a ground target that managed to accidentally hit an airborne aircraft? Mũeller (talk) 04:47, 5 August 2017 (UTC)

Yes. Especially mobile man carried versions meant to hit enemy tanks are at opportunity also used to shoot down helicopters. --Kharon (talk) 05:05, 5 August 2017 (UTC)

I appreciate English is not your first language but I think you should make sure you understand key words like wiktionary:accidentally before you try and answer questions like this. Nil Einne (talk) 05:22, 5 August 2017 (UTC)

No accidentally accidental collisions. --Kharon (talk) 06:00, 5 August 2017 (UTC)

What does that mean? It's not even a proper English sentence. Akld guy (talk) 06:42, 5 August 2017 (UTC)

Note that User:Kharon changed the word after I drew attention to it. Deceitful. I have restored the erroneous word and struck it out. Akld guy (talk) 09:16, 5 August 2017 (UTC)

Let's not be too hard on him, guys. He's just trying to help; his intentions are good. His response might not answer my question but is still very much appreciated. Mũeller (talk) 07:56, 5 August 2017 (UTC)

(EC) As Akld guy said your reply is unclear. Are you saying there have never been any accidental hits of an airborne target from a surface-to-surface missile or rockets? If so, what's your evidence? This seems to be the sort of thing really difficult to rule out. While an aircraft being hit is often a big deal, even just a helicopter, still there have been a lot of conflicts and countries sometimes prefer to keep details under wraps especially in friendly fire cases to save face etc. And even more so if we go to the pre-internet age, and consider non catastrophic damage, it this could have happened without it being widely known. Nowadays you can also include drones (I'm thinking the more commercial ones than the military ones) to further complicate the situation. Note that accidental doesn't have to mean almost random. For example, in a confused combat situation, it would seem possibly for an aircraft and a careless person targeting ground targets to be both involved leading to the potential for such an accident. I mean the Taiwanese managed to hit a fishing vessel AFAICT, probably without targeting it [2]. Nil Einne (talk) 08:08, 5 August 2017 (UTC)

The guided versions are actually not that common. Mostused ground to ground missiles are unguided ballistic versions, the socalled Rocket artillery or multiple launch rocket system (MLRS). Then there are the person carried versions. And then the motorized versions. Apart from the ballistic versions these missiles are mainly aimed to fight armored vehicles and thus have a very limited range. Newer BGM-71 TOW for example have a range of only 4,5 km. Airplanes typically fly much higher - especially the big ones. Additionally these and the ballistic ones are rather slow, compared to anti-air missiles. So the chances are very limited even if these missiles would be used constantly everywhere, which they are not. The only theoretically threat for planes would be the ballistic ones, because they go quite high when shot on long distances. But their use is also rather limited in wartimes. Our Atmosphere is simply a to big space for accidental collisions. Even Airplanes almost never collide with other airplanes, nomatter they all fly near eachother day and night in rather narrow "sky streets" between the few airport. --Kharon (talk) 09:13, 5 August 2017 (UTC)

Who said anything about guided? Or aeroplanes? You yourself seemed to already agreed that helicopters in flight are airborne aircraft and no has disagreed with you on the point. In fact as I pointed out drones (in flight), even the more commercial like ones, would also generally be considered so. So I'm not sure why you're suddenly restricting the question to aeroplanes. The only point of contention was you original talked about intentional targeting (of helicopters) when I pointed out the OP specifically asked about an accidental hit so intentional/opportunistic hits are not counted. You then suggested (I think), it had never happened but asked what evidence you have for this. I pointed out this seems to be something which would be very difficult to actually prove conclusively didn't happen. If by your own agreement helicopters are airborne aircrafts that can be intentionally hit by surface to surface missiles and rockets, then it seems plausible this could also happen accidentally in the chaos and confusion of wartime. And that it may not have been widely reported, especially if it was minor enough that the aircraft survived (or it was unmanned) and the side who owned the aircraft would perhaps prefer it not to be widely known even more so if it was a friendly fire incident so the side who hit it also feel the same and even more so in the pre-internet and information revolution age so even if it was reported in some local paper, there's a far greater chance no one noticed and picked it up because of how unusual it is. Note also that almost never is not never. The OP did not ask if it was common, simply if it ever happened. A single incident would mean 'no accidental collisions' would not be true. P.S. I should go back to the fishing ship case. Yes that was a 2D instead of 3D situation. But it was also a, from what I've read, completely accidental firing in a non combat something which in itself rarely happens. Which IMO further highlights why we should be very careful about assuming hitting something unintentionally never happens. Nil Einne (talk) 11:50, 5 August 2017 (UTC)

Anyhow, The Rocket Propelled Grenade by Gordon L. Rottman says: "...hundreds of helicopters [were] damaged or destroyed by RPGs in Vietnam..." but that threat only came to widespread attention after the Battle of Mogadishu (1993), when two Sikorsky UH-60 Black Hawk helicopters were shot down by shoulder-launched unguided RPGs. Alansplodge (talk) 14:25, 5 August 2017 (UTC)

Our List of accidents and incidents involving the Lockheed C-130 Hercules says: "April 7, 1979 : C-130H 116 of the Libyan Arab Air Force was shot down by an RPG-7 round during take-off from Entebbe, Uganda, which was subsequently captured by Tanzanian troops during the capture of Kampala". However, all of the above were probably intentional, but who knows? Alansplodge (talk) 14:34, 5 August 2017 (UTC)

Direct eye contact

As you know, some shy or otherwise modest people avoid prolonged direct eye contact. Does it really has to do with human evolution where our simian and more distant ancestors perceived staring as a sign of aggression and/or intention to attack (as observed in some modern mammals)? That said, does the ultimate cause lie in evolution and not in shyness or other personal traits? Thanks. 212.180.235.46 (talk) 08:59, 5 August 2017 (UTC)

Simply, a predator with good eyesight will always keep his prey in focus, when it sneaks up or waits for it and ofcourse also in the assult or hunt. Thus all higher lifeforms instinctively judge staring at them as danger or threat. Shy people simply instinctively signal the opposite intend to everyone by avoiding eye contact. --Kharon (talk) 09:30, 5 August 2017 (UTC)

methink you should had rather provided shyness and Eye contact (i couldn't believe this one exists, but it does!) for reference, as suits the ref desk Gem fr (talk) 11:27, 5 August 2017 (UTC)

An early stage of training in Scientology requires the student to confront a coacher eye-to-eye for two hours without blinking despite whatever the coach may do to "bullbait" (distract) him. The church says this is useful. Blooteuth (talk) 14:43, 5 August 2017 (UTC)

You can't literally "not blink" for anything close to that time. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:49, 5 August 2017 (UTC)

Yes, but Scientology promises perfect vision. You can throw away your eyeglasses, you won't need them. I guess you can throw away your eyelids too. ;) Wnt (talk) 16:04, 5 August 2017 (UTC)

But first you have to throw away your brain. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:19, 5 August 2017 (UTC)

The Man Who Stared for 41 Minutes. Blooteuth (talk) 17:40, 5 August 2017 (UTC)

There are also cultural variations. I spent part of my childhood in Hong Kong and Singapore, in whose local (predominantly Chinese) cultures (so I later read, and as is suggested in Section 6.2 of Gem fr's first and 5 of his second linked references above) looking directly into another's eyes is usual only in situations of intimacy or dominance/hostility. Having internalised this, as well as being somewhat shy by nature, I am in Western culture often perceived as "shifty" because I do not make eye contact as often as the local norm. (Possibly as a side effect, I also rarely notice or remember others' eye colour.) {The poster formerly known as 87.81.230.195} 90.202.208.125 (talk) 20:36, 5 August 2017 (UTC)

August 6

How to determine electric and magnetic susceptibility

What are the methods to measure electric susceptibility (or polarizbility) and magnetic susceptibility of a given material experimentally? — Preceding unsigned comment added by Sayan19ghosh99 (talk • contribs) 05:23, 6 August 2017 (UTC)

See Electric susceptibility and this learning package. One might measure by constructing a capacitor with the test material as dielectric.

See Magnetic susceptibility which mentions experimental methods to determine susceptibility that include the Gouy balance and Evans (or Johnson-Matthey) balance. Blooteuth (talk) 14:27, 6 August 2017 (UTC)

Mounting Hole Diameter for M1.5 spring pin

I have a M1.5 spring pin and I'm trying to determine the correct hole diameter for it. So far I found this chart[3], which is for imperial sizes roll pins. I just need a similar chart but for metric sizes. Mũeller (talk) 06:06, 6 August 2017 (UTC)

Lokking at the imperial chart it looks as though the pins are sized for the quoted diameter, ie in your case 1.50mm. here's atable, it says 1.50 to 1.60 https://technifast.co.uk/recommended-hole-sizes Greglocock (talk) 06:21, 6 August 2017 (UTC)

Thanks! Mũeller (talk) 09:09, 6 August 2017 (UTC)

Resolved

Flowers' identification help

• 
  1
• 
  2
• 
  3
• 
  4
• 
  5
• 
  6

All these pictures of flowers were taken at the Fitzroy Gardens Conservatory (apart from 6, which was outside in the gardens). Can anyone here help identify them please? --SuperJew (talk) 13:08, 6 August 2017 (UTC)

For convenience I should note the conservatory is in Melbourne near the southern extreme of the Australian mainland. I haven't made many attempts to identify flowers, so I should start by pointing at plant identification, which has some resources listed at the end; this guide to 50 most common families may also be useful; searching the web for australia flower identification turns up more specifically useful resources like [4] [5] (an image database, more for confirmation I would think). The government of Australia claims to have resources [6], but ends up pointing you at a selection of copyrighted "CD keys" written for archaic operating systems... with many other hits also, it looks like beating off the ads to find the usable resources is the tough part.

I would encourage people to try to explain how to do good plant identification with limited data we see in a case like this, and to upgrade the plant identification article to match. Wnt (talk) 15:08, 6 August 2017 (UTC)

"The government of Australia claims to have resources [7]" is a duplicate of the previous link. I don't think this was intentional since none of the links there point to anything to do with CD keys. Nil Einne (talk) 15:43, 6 August 2017 (UTC)

The fact that the conservatory is in Melbourne doesn't necessarily mean the plants are local, and the fact that they are in a conservatory means that the local weather isn't a factor either. --SuperJew (talk) 16:47, 6 August 2017 (UTC)

It looks to me like 1 could be some form of Aeonium, perhaps Aeonium arboreum. Definitely it looks like some kind of succulent. (P.S. If this right, I worked it out partially based on a Google reverse image search. It looked familiar but I didn't know what it was, but it looked distinctive enough it seemed worth giving it a shot. I tried the same thing on 4 but didn't see anything that hopeful although didn't look that carefully.) Nil Einne (talk) 17:20, 6 August 2017 (UTC)

@Nil Einne: That does look very promising (and reinforces my theory that they don't have to be local flowers). A Google reverse image search is a great idea! Thanks --SuperJew (talk) 17:31, 6 August 2017 (UTC)

I agree there's a reasonable chance they're not local since it doesn't seem to be the focus of the gardens or the conservatory (unlike say the Royal Botanic Gardens, Cranbourne). That said, I wouldn't say it's useless information to know it's in Melbourne, especially since we are talking about Australia and our article suggests they're state and city owned. I have a strong feeling given those circumstances, it's unlikely they're going to intentionally display anything that's a noxious weed (or whatever terms they use for problem invasive species) in Melbourne/Victoria unless they have a very good reason. And actually a quick search finds [8] which supports my suspicion. Nil Einne (talk) 14:48, 7 August 2017 (UTC)

I'm wondering maybe 2&3 are Impatiens walleriana?

Perhaps 4 is Hydrangea macrophylla, like in this pic?

Maybe 5 is a form of Fuchsia, perhaps Fuchsia boliviana or something similar? --SuperJew (talk) 18:13, 6 August 2017 (UTC)

No. 6 could be a variety of clivia. Richard Avery (talk) 07:41, 7 August 2017 (UTC)

2 & 3 are a variety of Impatiens hawkeri ("New Guinea impatiens"), I think. William Avery (talk) 11:49, 7 August 2017 (UTC)

Weight loss depression

Is depression a common occurrence in people who lose a lot of weight very quickly? Weisqusestion (talk) 14:05, 6 August 2017 (UTC)

“ Reduced nutrition can cause weight loss. The more hyperstimulated the body becomes, the more weight we can lose. These are just a few examples of how increased stress and anxiety can cause weight loss. ” — Jim Folk, Marilyn Folk, BScN., http://www.anxietycentre.com/anxiety-symptoms/weight-loss.shtml

50.4.236.254 (talk) 16:31, 6 August 2017 (UTC)

Lack of sleep can cause more calories to burn during the waking hours. Hence weight loss. Selective serotonin reuptake inhibitors, which are used to treat depression, may cause weight loss in older adults, but that's kind of speculative. Selective serotonin reuptake inhibitors (SSRIs) may produce side effects, including insomnia, nervousness, restlessness, and diarrhea. Nervousness and restlessness may produce more physical agitations, and hence, more fuel is burned. Diarrhea may cause malabsorption of nutrients. Depression is also heavily associated with bulimia.

Source: Jae Allen, http://www.livestrong.com/article/330360-why-does-depression-cause-you-to-lose-weight-even-though-you-eat-a-lot/

50.4.236.254 (talk) 16:46, 6 August 2017 (UTC)

The above sources suggest that the symptoms of depression may induce weight loss. It is possible that intentional weight loss may induce depression, as shown here. Source: http://abcnews.go.com/Health/w_DietAndFitnessNews/diets-depression-learn-mice/story?id=12357575 50.4.236.254 (talk) 16:58, 6 August 2017 (UTC)

Understanding temperature

The definition of temperature is

${\frac {1}{T}}={\frac {\partial S}{\partial U}}$

So in order to calculate $T$, one must express $S$ in terms of $U$.

The definition of entropy is

$S=-k\sum _{i=1}^{\Omega }p_{i}\ln p_{i}$

and the definition of internal energy is

$U=\sum _{i=1}^{\Omega }p_{i}E_{i}$.

But it should be clear that it is not necessarily possible to express $S$ in terms of $U$.

For example, suppose $\Omega =3,E_{1}=\epsilon ,E_{2}=2\epsilon ,E_{3}=3\epsilon$.

Then

$\{p_{1}={\frac {1}{3}},p_{2}={\frac {1}{3}},p_{3}={\frac {1}{3}}\}$ and $\{p_{1}={\frac {1}{4}},p_{2}={\frac {1}{2}},p_{3}={\frac {1}{4}}\}$

give the same value for $U$, but different values for $S$. So how can you define temperature? PeterPresent (talk) 14:58, 6 August 2017 (UTC)

Not an expert, but by my quick reckoning both of your examples have U = 2e. The first has evenly split energy states and entropy -k ln (1/3), while the second has -k ln (1/sqrt(8)). The second has less entropy because we have a good guess that a particle will be in the second energy state. Now of course S/U doesn't mean much by itself; we want the derivative of S/U, which means we have to look at how energy can increase. Which means that we need to look at how much S changes when energy is increased. And you're at kind of a funny point in that regard, like halfway to a negative temperature, in the sense that with one system you've defined three energy states and put the lower one as less likely than a higher state. So if we change 1/4 1/2 1/4 to say 1/4 3/8 3/8 the entropy drops from 1.03 k to 0.24 k, i.e. the entropy drops as energy is added increases to 1.08 k -- sorry, that isn't a suitable example after all -- ... at least if it is added this particular way. I'm not sure how you decide in what ratio of ways the energy is added. We'll need someone better at physics to go on from here... Wnt (talk) 15:29, 6 August 2017 (UTC)

Temperature is only well defined in thermal equilibrium, which means that you can only consider probability distributions that maximize S. Here you are free to impose constraints that prevent a global maximum from being reached, but you then have to specify these constraints (e.g. take a gas in a container of a fixed volume, the outside is a vacuum, if the volume were not fixed then the maximum entropy would be reached in the limit of an infinite volume). Now, in this case you have 3 probabilities, the sum of the probabilities is equal to 1, the internal energy provides another constraint, so there is one degree of freedom left. You should then fix this by either maximizing S or this is going to be fixed due to some other constraint the system is subject to. You then have a well defined S as a function of U, so the temperature is then well defined. Count Iblis (talk) 15:34, 6 August 2017 (UTC)

The formula for entropy expressed through $p_{i}$ pre-supposes that those probabilities $p_{i}=\exp(-E_{i}/T)/Z$ i.e. they obey Gibbs distribution ($Z$ is canonical partition function). Only in this case the (inverse) temperature can also be expressed as the first derivative from the entropy by the total energy. Ruslik_Zero 19:29, 6 August 2017 (UTC)

It makes sense that, given equal energies, entropy would reach a maximum as @Count Iblis: says. And as @Ruslik0: says, we expect to see a Gibbs distribution of energy states under normal circumstances. But are these things compatible, and can we derive the formula from the assumption? I suppose if we have a p_i, p_i+1, p_i+2 and we assume that the energy differences between them are equal, then converting x particles from p_i and p_i+2 to p_i+1 will involve no change in entropy. The total entropy from those three states only will be proportional to (p_i - x) ln (p_i - x) + (p_i+2 - x) ln (p_i+2 - x) + (p_i+1 + 2x) ln (p_i+1 + 2x). We want to minimize that negative number to maximize total entropy (-k multiplied by it). The derivative d/dx, for the limit of small x, should be - ln(p_i) - ln(p_i+2) + 2 ln (p_i+1) - p_i (1/p_i) - p_i+2 (1/p_i+2) + 2 p_i+1 (1/p_i+1) At least at a hasty consideration, I think the second terms of each derivative product cancel out in the end. Now we want an extremum of entropy, so this derivative should be 0, i.e. ln(p_i + ln(p_i+2) = 2 ln (p_i+1); taking e to the each we get p_ip_i+2 = p_i+1². This indicates an exponential relationship, at least, among the populations of energy levels, though it would take (at least) some normalization to get to the Gibbs distribution. Wnt (talk) 14:19, 7 August 2017 (UTC)

You can derive it quite easily using Lagrange multipliers. At the maximum the partial derivative of the entropy w.r.t. p_i should be a linear combination (independent of the index i) of the partial derivatives w.r.t. the constraint functions. The sum of the probabilities is one constraint function as this must equal 1 and the partial derivative if this function w.r.t. p_i equals 1. The expectation value of the energy is the sum over p_i e_i is another constraint function, the partial derivative w.r.t. p_i equals e_i. So, you then find that the logarithm of the probability is a linear function of the energy,so we're led to the Gibbs distribution. Count Iblis (talk) 19:37, 7 August 2017 (UTC)

What would happen if you brought a horse to a big pressurized lunar dome?

Would it learn the way to move from A to B with least energy or most speed? Would that gait involve jumping? How fast could it go? Sagittarian Milky Way (talk) 18:22, 6 August 2017 (UTC)

What have you found on Google so far? ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:55, 6 August 2017 (UTC)

Somehow I doubt that there're any experimental results floating around (no pun intended, probably) regarding horses on the Mun... Whoop whoop pull up ^{Bitching Betty | Averted crashes} 07:37, 7 August 2017 (UTC)

[9] Sagittarian Milky Way (talk) 19:06, 6 August 2017 (UTC)

I strongly suspect that the only way we'd ever find out would be to actually take it there – from the literature and and lectures I've read/attended in the area of possible Crewed Mars missions, we're still uncertain as to how humans will best perambulate in Mars' gravity (very roughly twice that of the Moon's). One possibility might be a mentally broken, catatonic horse. It might also depend on whether the horse was taken as an adult or raised from embryo/early infancy on the Moon: Arthur C Clarke once suggested that a canary hatched in a zero-gravity space station would easily adapt to flight there, but I don't think he had any experimental data. {The poster formerly known as 87.81.230.195} 90.202.208.125 (talk) 20:51, 6 August 2017 (UTC)

Language peeve: twice that of the Moon's what? that in this phrase means 'the gravity'; and I don't think it's normal English to say "the gravity of the Moon's" in the same way as "a friend of Alice's". Or – since Moon's is parallel in form to Mars's – maybe it's twice [the something else] of the Moon's [gravity]? —Tamfang (talk) 05:37, 7 August 2017 (UTC)

Some thoughts:

1) We do know that horses are capable of adapting their gait to different situations. For example, they learn to move more slowly when wading through water, or to step higher when walking through thick mud or heavy snow.

2) So, it's reasonable to assume they would also adapt their gait to less gravity.

3) However, bouncing higher into the air with each step might be scary, causing them to use less force to take smaller steps. This would be especially true if they fall over, say by rotating when airborne, when using full force.

4) They may eventually learn to use full force again safely. Or, their muscles may atrophy from less use. Perhaps something in-between is the most likely outcome. StuRat (talk) 19:49, 7 August 2017 (UTC)

Wireless telephone in 1922

Sinclair Lewis mentions wireless telephones in his novel Babbitt, published 1922. What does he mean by that? The wireless telephone article redirects to cordless telephone, but these telephones were not invented until the 60s. Extract:

"Though he no longer spoke of mechanical engineering and though he was reticent about his opinion of his instructors, he seemed no more reconciled to college, and his chief interest was his wireless telephone set. "

--Hofhof (talk) 20:56, 6 August 2017 (UTC)

The device is closer to the mobile radio telephone of the 1950s and 1960s. These were VHF voice radios, about 150MHz and FM modulation, which could be used from within a moving car. They were also simple enough to operate, with simple crystal-controlled channel selectors, to not require "tuning" and thus a separate operator. They connected to a regional base station and operator who was able to patch them into the national telephone network. Andy Dingley (talk) 21:03, 6 August 2017 (UTC)

Wireless telephones existed by the 1910s. Here's a 1916 song about the subject.[10] ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:44, 6 August 2017 (UTC)

And here's a 1914 photo of one (not quite a "mobile" phone):[11] — 2606:A000:4C0C:E200:4890:FAC5:8AED:1CC9 (talk) 23:09, 6 August 2017 (UTC)

In that era, telephones was a word used for what we now call headphones, at least in Britain. See the testimony of Harold Bride, wireless operator of the Titanic, when he gave evidence at the American inquiry into the sinking. The relevant testimony is here and you need to scroll up about one screen page from the bottom. Akld guy (talk) 00:31, 7 August 2017 (UTC)

And again, here, again about one page up from the bottom. Akld guy (talk) 01:16, 7 August 2017 (UTC)

@Baseball_Bugs, after I listened to the song you've posted, I said: "This guy is a genius. He provided an answer, an incredible historical reference and an entertainment. I would like to get the lyrics, though. Can you do it? Thanks, - --AboutFace 22 (talk) 12:36, 7 August 2017 (UTC)

We have an article: Hello, Hawaii, How Are You?. The wireless telephone in question is (presumably) this. AndrewWTaylor (talk) 13:21, 7 August 2017 (UTC)

Resolved

With kudos and thanks to Baseball Bugs for his pertinent, well referenced response from the world of entertainment. Blooteuth (talk) 14:41, 7 August 2017 (UTC)

• Remember that at the time "wireless" was a synonym for "radio", but most radio signals were Morse code, so the term "telephone" was needed to specify that the radio was sending and receiving voice, not Morse code. The name of the firm "Cable & Wireless" dates from that era. -Arch dude (talk) 04:21, 9 August 2017 (UTC)

August 7

Hearing aid battery tester.

I've always wondered how this little devil works[12]. 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 [13] 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: [14]. I believe the force there is approximately equal to 1 SMW. --Jayron32 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 [15] 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. --Jayron32 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. —PaleoNeonate – 23:17, 8 August 2017 (UTC)

Why was the helical structure of DNA such a big deal?

Resolved

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#History of DNA biochemistry. 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

. .

...

10-3. An earth satellite of mass 10 kg and average cross-sectional area 0.5 m² is moving in a circular orbit at 200 km altitude where the molecular mean free paths are many meters and the air density is about 1.6 x 10 ^-10 kg m^-3. Under the crude assumption that the molecular impacts with the satellite are effectively inelastic (but that the molecules do not literally stick to the satellite but drop away from it at low relative velocity), calculate the retarding force that the satellite would experience due to air friction. How should such a frictional force vary with velocity? Would the satellite's speed decrease as a result of the net force on it? (Check the speed of a circular satellite orbit vs. height.)

—  R. B. Leighton , Feynman Lectures on Physics. Exercises

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 formula (speed of a circular satellite orbit vs. height) $v_{1}={\sqrt {\tfrac {GM}{r_{1}}}}$:
$v_{2}={\sqrt {\tfrac {GM}{r_{2}}}}={\sqrt {\tfrac {GM}{r_{1}({\tfrac {v_{2}^{*}}{v_{1}}})^{2}}}}=v_{1}{\tfrac {v_{1}}{v_{2}^{*}}}$
or
${\tfrac {v_{2}}{v_{1}}}={\tfrac {v_{1}}{v_{2}^{*}}}$,
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 [16] found in a web search for sites that agree with me, agrees with me. The more refined source [17] 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 r_perigee, and at apogee the speed is less than necessary for a circular orbit with radius r_apogee. 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 v_perigee = 1.63 speed units = 9.099 •10³ m/sec ; v_apogee = 0.797 speed units = 4.449 •10³ m/sec.
v_circular,p=7.894•10³ m/sec, v_circular,a=5.521•10³ m/sec.Username160611000000 (talk) 08:56, 9 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. --Jayron32 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 [18] 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 [19] 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 [20] 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. --Jayron32 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. --Jayron32 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 [21]. It may be a Pectinophora gossypiella, a type of bollworm, per this, but that doesn't look like a great fit either. --Jayron32 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.--Jayron32 01:53, 8 August 2017 (UTC)

The article Microbiota is where you want to start your research.--Jayron32 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. --Jayron32 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. [22] 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. —PaleoNeonate – 03:57, 9 August 2017 (UTC)

August 8

Escalators changing directions

One day the escalator is going up and the next day down. Why? Anna Frodesiak (talk) 02:13, 8 August 2017 (UTC)

Because somebody flipped the switch that reversed it's direction.--Jayron32 02:23, 8 August 2017 (UTC)

Excellent answer, Jayron32. :) Now, why did they flip that switch? Anna Frodesiak (talk) 02:32, 8 August 2017 (UTC)

In response to the Q, "Why did the Titanic sink ?", Jayron's answer would no doubt be "Because it was full of water." :-) StuRat (talk) 03:36, 9 August 2017 (UTC)

It's possible that they adjust the direction to match traffic flow. So, for example, if they have 3 escalators, they may have 2 going up and one down when people are coming into the building, and the reverse when they are leaving. Unlike changing the directions on roads, this operation should be fairly simple. Just put up a barrier blocking people from getting on, wait until everyone is off, then flip the switch and remove the barrier. StuRat (talk) 02:41, 8 August 2017 (UTC)

They might do this at large sports venues, for example. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:51, 8 August 2017 (UTC)

Yes, it's a standard thing to do at locations like that, and similarly in public transit stations where some escalators will run one way in the morning peak and the other way in the evening. (Details will depend on the traffic at the specific location, of course.) With the ones that I've seen, there may be a small sign telling staff what time each day to change it, next to the up/down switch (which is key-operated, by the way). But Anna says this isn't the case she's asking about. --69.159.60.147 (talk) 05:16, 8 August 2017 (UTC)

I'm not sure that's it. I see in lots of malls, a pair of escalators switching up to down and down to up. These are quiet malls with no traffic-flow reason to do this. Could this be about the gears and evening out wear from continuous single direction usage? Or is it psychological to shake up and wake up the people, or make them flow in a different direction when they disembark, like to make them see now products? Anna Frodesiak (talk) 02:58, 8 August 2017 (UTC)

They also switch up directions so that the escalators wear evenly. .--B8-tome (talk) 02:52, 8 August 2017 (UTC)

Edit conflict. I just guessed what you wrote! See above. Are you sure though? Thanks. :) Anna Frodesiak (talk) 02:58, 8 August 2017 (UTC)

If you want to be sure, you'll have to ask the building management people. --69.159.60.147 (talk) 05:16, 8 August 2017 (UTC)

Many modern escalators have sensors to detect people getting on. If no-one uses them for a while, they shut down, and re-activate in the useful direction when the next person gets on. --Stephan Schulz (talk) 12:41, 8 August 2017 (UTC)

Assuming that's true, it sounds like trouble waiting to happen. And what does it do if two people get on opposite ends at the same moment? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:08, 9 August 2017 (UTC)

There is no such thing as two events happening "at the same moment" for a control computer. One or the other will win. If it goes your way, you grin apologetically at the other person. If not, you glare at them while you wait or use the stairs, which are usually next to the escalator. --Stephan Schulz (talk) 04:45, 9 August 2017 (UTC)

Neuroscience question

Is it possible to remove consciousness (like the feeling of under anaesthetic), but keep your body alive and functioning normally in everyday life? I.e. is it possible to turn a person into a meat machine? Why does consciousness even exist? If materialism is correct there shouldn't be any consciousness. It would reduce a lot of suffering in this world if people can do this, unless dualism/idealism is correct. Money is tight (talk) 05:31, 8 August 2017 (UTC)

Vital body functions can remain alive when the patient is in coma, yes. Of course that is not the same as functioning usefully. Unconsciousness, coma, brain death and autonomic nervous system may be useful. As for the part about materialism and machines, it is indeed expected that neuroscience may eventually explain consciousness. Parts of consciousness are being understood but a lot remains to be discovered. You appear to infer that the source of consciousness would be a hypothetical soul or the like. We can invent such explanatory devices, symbols and concepts for things that are unknown. We also do this as part of science, but more rationally. Some hypothesize that the impression of self-consciousness is an illusion. Also see hard problem of consciousness, existence of God and problem of evil. —PaleoNeonate – 06:38, 8 August 2017 (UTC)

Maybe it is possible. If an evil scientist had selectively removed consciousness from half of the human race but left them functioning exactly as usual in all other respects (including stating that they were actually conscious when asked) then how could you tell ? See philosophical zombie. The materialist response is that a philosophical zombie is a logical or physical contradiction - like a three-sided square or dry water. Gandalf61 (talk) 08:24, 8 August 2017 (UTC)

An Induced coma by barbiturates such as Pentobarbital and Thiopental can be maintained (e.g. for brain surgery, 7-14 days with monitoring by an anaesthesiologist) with some risks which are noted here as: Myocardial depression, Increased in venous capacitance, Impaired gastrointestinal motility, Increased hepatic microsomal activity, Possible allergic reaction and Impaired immune response. Blooteuth (talk) 10:05, 8 August 2017 (UTC)

Why focus strictly on materialism? That is a subset of desire, which is one of the four noble truths. 209.149.113.5 (talk) 15:02, 8 August 2017 (UTC)

You may be confusing ontological materialism with economic materialism. Gandalf61 (talk) 15:15, 8 August 2017 (UTC)

Materialism and consciousness are friends. People who formulated materialism had consciousness. --AboutFace 22 (talk) 16:04, 8 August 2017 (UTC)

That's only trivially true. They also had pancreases and eyebrows and mothers, but that doesn't mean that knowing that leads us to a deeper understanding of materialism. Post hoc ergo propter hoc and all that jazz. --Jayron32 16:11, 8 August 2017 (UTC)

There is no problem of understanding materialism. There is a problem of understanding idealism and religions. I subscribe to the quantum theory of consciousness[23]. --AboutFace 22 (talk) 16:41, 8 August 2017 (UTC)

Which is no less based on a pure-faith belief than any other religion, except it uses sciencey words so it makes the athiests feel better. --Jayron32 18:38, 8 August 2017 (UTC)

I wouldn't say that athiesm requires justification, or that quantum mind is pure faith, but it is pseudoscience (or at least, a far fetched hypothesis for now). —PaleoNeonate – 20:22, 8 August 2017 (UTC)

Or just give up on materialism and accept that there only exist a mathematical multiverse. This is a set of all algorithms, one of these algorithms will be me at precisely this moment when I'm writing exactly this part of this sentence. Another algorithm is me a few seconds later writing this part of the next sentence. And yet another algorithm is Jayron32 writing to AboutFace 22 that what he says is no better than any other religion. Note here that the algorithms contain all the information about what the person (or some other entity) is aware of, it doesn't imply the existence of an external world, it encodes the external world indirectly as that's contained in whatever the person is aware of. Count Iblis (talk) 20:18, 8 August 2017 (UTC)

See Zombie#Haitian_tradition. This holds that it is possible, by use of a psychoactive substance, to disable their decision making processes, rendering them highly susceptible to suggestion. Not medically verified to be true, though, perhaps because voodoo priests/priestesses tend to be highly secretive about their methods. (This tradition also holds that zombies rise from the dead, but perhaps they were just in a coma from the substances ingested.) StuRat (talk) 04:16, 9 August 2017 (UTC)

Cooling a CCFL bulb without straining the glass

I want to make a floodlight from salvaged CCFL lamps. Despite their name, they do generate heat and I'm going to be using them in high-density so I need to cool them (their efficiency drops off beyond about 30 °C) and I'd like to do it passively if possible (mostly because of the noise). The way I'm considering doing this is affixing the glass tubes to an aluminium panel (thickness not determined), possibly using thermal adhesive or possibly a cheaper adhesive. My concern is that with cooling on one side of the glass tube, it could lead to stress and fracturing which would destroy the tube. Is that a valid concern? --145.255.246.78 (talk) 06:23, 8 August 2017 (UTC)

Yes it's a valid concern. Consider immersing the lamps in a transparent oil. Blooteuth (talk) 09:43, 8 August 2017 (UTC)

I am not an expert, but perhaps immersing high voltage devices in oil could give rise to some safety or reliability concerns ? Gandalf61 (talk) 10:13, 8 August 2017 (UTC)

Oil immersion is commonplace for high voltage transformers and contact breakers. Blooteuth (talk) 11:45, 8 August 2017 (UTC)

Indeed. But the fact that some high voltage devices are designed to be immersed in oil does not give me confidence that taking some other high voltage device that is not designed for this and immersing it in oil is either safe or sensible. Gandalf61 (talk) 12:28, 8 August 2017 (UTC)

Oil is a poor coolant for this task. In large devices, it circulates and the heat transfer is by convection. Here you need something that's useful by conduction. There are such thermal tapes available, they're now widely used for mounting COG (Chip On Glass) LEDs onto aluminium heatsinks. They're also slightly flexible, to avoid straining the glass. Andy Dingley (talk) 14:47, 8 August 2017 (UTC)

^^ That is the answer, I think, but I'm rooting for one of those misting devices they use for produce at Wal-Mart. You would try to make sure the ends are sealed up and then you have a flooded floodlight dripping gentle shining warm ?high voltage? rain. Would look really cool... Wnt (talk) 18:32, 8 August 2017 (UTC)

Glass is a thermic isolator. Aluminium alloys have a typical Thermal conductivity (W·m⁻¹·K⁻¹) of over 100. Glass has a typical thermal conductivity of 0.5 - 2! Thus you can not use glass as part of a heat "bridge" or cooling "chain". It does not matter much if you cool the glass with aluminium, copper or graphene. Its like putting a stretch of plastic between 2 copper cable ends and then ask if the electric current would improve if you would use gold contacts on the plastic ends. --Kharon (talk) 11:30, 8 August 2017 (UTC)

The glass is non-negotiable since the body I want to cool is made of glass. Attaching it to an aluminium sheet with some heatsink attached would maintain a temperature gradient. One option is glass and aluminium and the other is glass and air. The aluminium would greatly increase the surface area in contact with air. 129.215.47.59 (talk) 14:48, 8 August 2017 (UTC)

The quoted thermal conductivity of glass is 0.8 to 0.93 W·m⁻¹·K⁻¹ This diagram shows it relative to other materials. Blooteuth (talk) 12:08, 8 August 2017 (UTC)

The best way to keep the tubes cool would be to allow natural convection between them. What orientation will you have them in? Dbfirs 12:53, 8 August 2017 (UTC)

They will be arranged all in parallel. I made this useless animation to try to compare active versus passive approaches. Since I want these floodlights to illuminate my dumb YouTube videos (in progress), I don't really want the noise of the fans. I'm planning on having 50-70 in parallel, representing about 200-300 W of heat yet I need to keep them below 60 °C maximum (40 °C would be better) 129.215.47.59 (talk) 14:48, 8 August 2017 (UTC)

Will they be horizontal or vertical ? I would expect convection to work better if they were vertical, provided there is a sufficient air gap between each tube, it's neighbors and the housings.

As for fans, they can be made to be silent, provided they are large and slow moving. I have large box fans hooked up to a dimmer switch so I can reduce the speed and hence noise down to a whisper. StuRat (talk) 02:53, 9 August 2017 (UTC)

Lard diet

I've been reading about "no carb" diets and I was wondering how long could a human survive eating nothing but lard? — Preceding unsigned comment added by 190.117.188.223 (talk) 09:40, 8 August 2017 (UTC)

As long as it takes for one of these diseases to kill you. It's probably somewhat variable based on your particular biology, but you'll die of one of those. --Jayron32 10:51, 8 August 2017 (UTC)

Are you sure of that? I can't help wondering if Kwashiorkor or some effect of protein deficiency will kill you first, especially for a child. And what about Mineral deficiency? This may depend on your precise water and lard, but what about a sodium or potassium deficiency? P.S. I'm assuming that this isn't excluding drinking water since I suspect you'll probably quickly die of dehydration if you only eat even unrendered lard and don't drink anything. Nil Einne (talk) 15:53, 8 August 2017 (UTC)

That'd work too. There's lots of ways to day of malnutrition. --Jayron32 15:58, 8 August 2017 (UTC)

Or even ways to die of malnutrition tomorrow ; -) Aspro (talk) 18:21, 8 August 2017 (UTC)

Pronounce "day" the Aussie way and it works. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:45, 8 August 2017 (UTC)

I believe that you would die of Hyponatremia before any of the other conditions mentioned gets you. Under the right conditions, [24] severe, life-threatening hyponatremia can occur in a matter of hours.[25] Too-rapid restoration of normal sodium levels may also cause trouble.[26] --Guy Macon (talk)

Wouldn't the hyponatremia be due to a sodium deficiency arising from insufficient dietary intake? Assuming as I said above they had a sufficient but not excessive water intake and weren't trying to run a marathon or something. Yes it may not normally be the sole cause, but it seems to me it would be in this case. Nil Einne (talk) 04:16, 9 August 2017 (UTC)

You'll survive longer on blubber. Count Iblis (talk) 20:25, 8 August 2017 (UTC)

Ventricular fibrillation by palpation

Not a medical request, just curiosity Is it possible to detect ventricular fibrillation by chest palpation instead of electrocardiogram? Would the palpating person sense quivering instead of beating? 212.180.235.46 (talk) 17:10, 8 August 2017 (UTC)

Some people arrive at the hospital with a chief complaint that indicates they are feeling the effects of arterial fibrillation. Descriptions I've heard are skipping a beat, hearing a thud, or just chest pain. Ventricular fibrillation is different. With ventricular fibrillation, the heart pumps little to no blood. Cardiac arrest and unconsciousness follows very quickly. Therefore, I seriously doubt the person will be able to say what they felt. Of note, there will be no transfer of short-term memory to long-term memory. So, they will have no memory of the few minutes before losing consciousness. Therefore, they will not be able to describe what they felt. 209.149.113.5 (talk) 17:39, 8 August 2017 (UTC)

[1] you mean atrial fibrillation, not arterial. [2] the questioner seems to be asking if a second person (that is, the examiner, rather than the person with ventricular fibrillation him or her- self) could detect ventricular fibrillation. A person with would be pulseless, but this is usuallly determined by palpating an artery rather than the heart per se. And there are other pulseless rhythms (pulseless electrical activity). Generally, if someone is in ventricular fibrillation, the examiner will be more interested in hooking them up to a monitor/defibrillator than in practicing their palpation skills. - Nunh-huh 18:05, 8 August 2017 (UTC)

August 9

timing belt idler wheels

I have a bunch of timing belt idler wheels that I want to mount onto a plate[27]. The ball bearings inside these have a inner diameter of 5mm. What's the "proper" way of mounting them?

If I use a screw to mount them (like the left side of [28]), then the screw will improperly contact the side of the wheel, and the wheel will grind against the plate.

I tried putting a 5mm diameter dowel pin inside the wheel and mounting the dowel pin instead (right half of [29]). But the problem is that dowel pins are always oversized, so the mere act of the putting in the dowel pin has managed to destroy the bearings. Mũeller (talk) 05:15, 9 August 2017 (UTC)

I think the idea of the screw, or a bolt, is the right way to go. You need two flat washers whose outer diameter is no greater than the outer diameter of the inner race. Place one washer between the idler and the plate, and the other under the head of the bolt. When you tighten up the bolt, the inner race will be placed under compression and will not turn, leaving only the outer race to turn around it. You need good quality washers to avoid uneven compression and deforming of the inner race. Akld guy (talk) 06:20, 9 August 2017 (UTC)

Thanks. I'm having a hard time finding the right washers. ID is 5mm, and the outer diameter of the inner race is only 6.3mm. The smallest M5 washer I can find is 8mm. Mũeller (talk) 07:49, 9 August 2017 (UTC)

Here's the cheapest nastiest solution. http://www.unitedfasteners.com.au/media/images/product/product_tmp/large/UN0104_2861351072354.JPG I suspect you will encounter problems with the the bolt working loose in the plate, really you should be supporting both ends of the bolt. You may get away with it depending on the usage profile. Greglocock (talk) 08:14, 9 August 2017 (UTC)

If I bolt it on without using washers as spacers then the wheel won't turn at all. Mũeller (talk) 09:27, 9 August 2017 (UTC)

The proper way would be an Axle with grooves for retaining rings at the right positions. If you want to fixate your belt wheel precisely you fix one ball bearing form both without any space for it to move. The other beraring will then only be secured with enough free space so it can run free but not fall off. If precise fixation is not that important you use an Axle with 2 groves and 2 rings that fixates both bearings with enough free space to run properly. You can manage something identical with a screw (put in from the opposite side of your plate, a fitting washer on the side of your bearing to get away from the plate and two nuts where one fixates you first bearing (you will have to get one of them out of your wheel and after reassembling the last nut should be a selfsecuring version at the end of the wheel so it has a tiny space to run free. --Kharon (talk) 10:26, 9 August 2017 (UTC)

(edit conflict) Those dimensions suggest the use of a ring instead of a machined washer. Try a shop that repairs small electric motors to see whether they have rings of the suitable size. Another approach would be to get a shop to machine a circular groove around the hole in the plate to provide clearance for the outer race, leaving just a small ring around the hole. It's a precision job, needs to be cut only a mm or two deep, and is probably the best solution because it removes the need for a washer or ring which introduce tolerance uncertainties. Akld guy (talk) 10:31, 9 August 2017 (UTC)

Hang on, your photo had 'standoff' inners on the ball bearings' or am I imagining things (I'm not i just checked)? If not, then yes, you need spacers. Vague badly defined questions get vague answers. Sad but true. Kharon is talking nonsense. Greglocock (talk) 10:35, 9 August 2017 (UTC)

@Greglocock Well i assume you are a professional (from your page discription). Guess here where i live (Germany) we do construction differently or i wrote it down to complicated. Have a look at the german wiki [30] a glimps on some drawings if you like. Couldnt find any english wiki articles. Because of the many differend bearings, applications and requirements for all possible constructions for all possible tasks the professional approach for bearings ofcourse is much more complicated and sophisticated. --Kharon (talk) 10:57, 9 August 2017 (UTC)

Yes I am a mechanical engineer. Your post is nonsense in English. Don't blub, i couldn't write a whole sentence in German, never mind using the right technical terminology. Greglocock (talk) 11:14, 9 August 2017 (UTC)

Blindness to important information because of deluge of irrelevant emails

Is there any research suggesting that someone whose received emails are <90% irrelevant to them are liable to start missing information? It happens to me and I'd like to make the suggestion that my college start providing more mailing lists so that people that are meant to be receiving the e-mails do and I and everyone else don't. I imagine that the cost of wasted person-hours is considerable. --129.215.47.59 (talk) 11:22, 9 August 2017 (UTC)