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July 22

Snake behaviour

I live in Hong Kong (regional context if it might be useful) in a village near the countryside. We've seen snakes outdoors before but this time it was different. We live on the first floor of the three-storey high house (G/F→1/F→2/F), and one night my mother was using the toilet when she felt something, and inside the toilet bowl was a snake. We immediately phoned police who brought a snake catcher, and they reported that it looked like a venomous one (just according to the shape of its head, species unknown). However, it went down the pipe in such a way that it could not be caught. We immediately boiled bucket loads of water and sent it down the pipe, and we kept pouring in hot water every night.

Two questions. 1) What was it doing in the toilet bowl? Other family members said that they had heard noises at night for more than a week but couldn't see the snake, and the noises were hissing and the toilet lid opening and closing. It is suspected that the snake thought my mother was the lid since it didn't attempt to bite her (it touched her with its back as it was turning upwards like a screw). Given the period of time it was lurking in the toilet, I assume it was laying eggs. Any other reasons? 2) Is it safe to use said toilet? Would the snake have died and its eggs made unviable? The Average Wikipedian (talk) 05:06, 22 July 2017 (UTC)

P.S. it climbed a whole storey up a vertical iron pipe to get to the toilet bowl, and it had to swim through the septic tank and all that. The Average Wikipedian (talk) 05:22, 22 July 2017 (UTC)

Snakes usually don't attempt to bite humans, unless they feel trapped, they would rather make a getaway from the much larger animal. You may have to put metal mesh across any air vent access to the the sewer at the bottom and top. Actual bites are not that common and make the news: https://www.google.com.hk/search?num=100&client=firefox-b&q=snake+in+toilet+bites+woman Snakes can bite guys too: https://www.google.com.hk/search?num=100&client=firefox-b&q=snake+in+toilet+bites+man Graeme Bartlett (talk) 09:09, 22 July 2017 (UTC)

But if you sat down on a toilet with a snake in it, would it feel trapped? In any case, I would consider the alternative hypothesis that the snake was living in the bathroom, but only on the last day it blundered into the toilet. I don't know how hard it is for an unspecified snake to get out of a toilet - I don't know how large it is, for example. For example, it could have made noises gliding on the toilet that made you think it was inside, or come up from a hole near the toilet where water might have rotted away some of the floor. Of course, since you saw it go down the pipe and say it was "turning upwards like a screw" before, I don't mean to suggest your hypothesis is wrong either; it's just hard, from this information, to say anything certain. I don't much trust the media commentary on this either, but BBC goes for your explanation [1] while Howstuffworks seems more favorable to my idea. [2] Slate points out that the balance of possibilities depends on how your plumbing is laid out. [3] Wnt (talk) 10:55, 22 July 2017 (UTC)

@Graeme Bartlett: Thanks for the reply. Not sure where the air vent accesses are though. @Wnt: There's no way it was living in the bathroom, literally no. There's no way in, not even the exhaust fan because we replaced it with a machine that completely seals it. It must have come up from the pipe. Also as mentioned noises of the toilet bowl cover were heard and it couldn't have made those outside the toilet bowl, which was left covered overnight. So it was probably living in the pipe for a week or even more. Question is what was it doing in there and has it gone away since. The Average Wikipedian (talk) 15:02, 22 July 2017 (UTC)

Snakes have to live somewhere. Some snakes make burrows and others doubtless shelter in convenient pre-existing cavities and holes. The snake may well have thought of the man-made pipe (which of course is mostly dry except for the water trap in the U-bend) as a convenient burrow, just as many cliff-dwelling birds treat buildings in cities as if they were natural cliffs. {The poster formerly known as 87.81.230.195} 94.12.80.244 (talk) 16:16, 22 July 2017 (UTC)

Snakes will seek shelter to escape heat, cold, or predators. Once in a narrow pipe, a snake can be unable to turn around, so may be forced to swim to the other end, which could be your toilet. One other possibility, in rural areas, is that the sewage just discharges, untreated, into a river, giving them easy access. I wouldn't expect that in Hong Kong, though.

I'm skeptical that your hot water cure will work. First, it might crack the toilet bowl. Second, it will rapidly cool to a temperature that won't bother the snake, after just a few feet mixing with the water in the S-bend, etc. You might try a chemical instead, such as bleach. That will have more staying power. But, it could also damage iron pipes. What are your pipes made of ? Another possibility is to use capsaicin, in the form of hot chilis, which apparently messes with their infrared sensors (assuming your type of snake has IR receptors): [4] StuRat (talk) 16:50, 22 July 2017 (UTC)

Don't imagine this will come as any comfort to the OP to point out that fatalities from snake bites in HK are extremely rare and death due to other causes over shadow them. After all, it is he and not me that has this issue. Pouring down boiling water will just give said creatures a hot bath. Poisons may not have much effect either (and anyway, in a little place like HK you will wreak the environment). However, a strong solution of ordinary household caustic soda may make them think twice about visiting your abode again. Also, have all the family become familiar with all the Venomous Land Snakes in Hong Kong and become aware that the best form of defence is to stay calm. As far as I know (with my limited knowledge) simply defecating on them will not cause them to become alarmed -but trying to kill them will. It is right to be wary of snakes, because although snakes don't strike without-out provocation, we don't see our own actions from a snakes point of view and thus might naïvely make the snake feel threatened. So, let the family know, that all they have to do is just step away. For extra reassurance, you can check this out with the AFCD in the link (above) I have given. Aspro (talk) 17:08, 22 July 2017 (UTC)

I'm imagining inserting a very large, nasty hook into a temporarily live mouse that is at the end of a sturdy fish line, tying off one end and flushing the rest down the toilet... who knew you could find a fishing snaking hole in the bathroom? This could be the beginning of a new sport... ;) Wnt (talk) 20:03, 22 July 2017 (UTC)

@StuRat: It was recommended by the snake catcher (at the time he was trying to draw it out so that it could be caught, but it went the other way i.e. down). We actually let out the cold water in the toilet before we poured the water in the following days, so it wouldn't have cooled down by much. Yes the pipes are made of iron which is why we aren't considering any chemicals that could react with it (definitely not acids). The toilet bowl hasn't cracked so far and it is pretty thick so I hope it will hold up to the hot water. We might try capsaicin, but again we don't know what exact snake it is so it might not work. I imagine however that the sheer volume of hot water should have at least deterred it, right? Sure we're fine without the toilet for a couple of days but we don't want to lose it forever. What do you think it was doing and do you think it has given up? @Aspro: We're perfectly calm and all that, our only concern is when it will be safe to use said toilet. Caustic soda sounds ok because it's alkaline, we might give that a think. We won't provoke the snake in any way (the hot water should cause discomfort but it's not like it can fight back, hopefully) and we're just leaving that toilet alone. Again, all we want is to have a safe toilet again :). @Wnt: Sounds good, but snakes don't chew so it will just kill itself, I guess? The Average Wikipedian (talk) 03:06, 23 July 2017 (UTC)

I was thinking that if the snake swallows the mouse, and the hook is in the mouse, then either the snake is on the hook or on the line... searching around I was having unusual difficulty finding fishermen with snakes on the line - Google didn't even report this one but DuckDuckGo did. I don't know if there are a bunch of censors running around or if it really is uncommon to get a snake on a fish line by accident, but as you see from the one video it definitely can be done - I'm not sure there though if the hook is in the fish or in the snake! Wnt (talk) 13:39, 23 July 2017 (UTC)

Bleach is also alkaline, but that's no guarantee that it won't corrode iron pipes. Sounds like the capsaicin might be safest. Cheapest way may be a big bottle of hot sauce, flushing some and leaving some in the toilet bowl. (Be sure to flush before using, maybe twice, as you don't want to be splashed by that.) As for the hot water, the iron pipes will also suck the heat right out of that in short order.

As for why the snake keeps coming there, is it hot or dry outside ? If so, it may be seeking a cooler, moister environment. The moister part would be particularly important if it's a water snake. If it is, and there's a nearby pond that has dried up or been drained, that could cause it to seek water wherever it can find it. The rice paddy snake is one candidate. StuRat (talk) 15:07, 23 July 2017 (UTC)

This is assuming that snakes are sensitive to capsaicin. Birds are not. They don't chew the seeds and destroy them. Rather they spread them via their faeces. Snakes don't even eat chillies so probably capsicums haven’t evolved to be also a reptile irritant. Aspro (talk) 21:46, 23 July 2017 (UTC)

As per the link I provided previously, capsaicin messes with their IR sensors. Not all snakes have those, so it may only work on some. As to whether it irritates the rest, I don't know. But it's cheap enough to be worth a try. StuRat (talk) 21:52, 23 July 2017 (UTC)

This probably is a good time to mention that as per the Wikipedia general disclaimer, the Refdesk doesn't actually give advice, it only tries to provide information about questions. So we should not be telling you it is a good idea, best, or even OK to do anything in particular. So if you fill an apartment building's septic system with a mix of various harsh chemicals and capsaicin and suddenly there is an explosion and dozens of people are running out of their bathrooms pants down, covered in feces, with their flaps on fire, Wikipedia isn't going to pay for that. Please exercise your own judgment... Wnt (talk) 15:30, 23 July 2017 (UTC)

Somebody just has to write a screenplay with that scene included. {The poster formerly known as 87.81.230.195} 94.9.11.138 (talk) 16:26, 23 July 2017 (UTC)

Kraft Dinner + multivitamins = nutrition?

How long, and how well, can a person theoretically live on Kraft Dinner plus a daily multivitamin (as would have been my diet of choice when I was small, and pretty cheap too)? NeonMerlin 09:08, 22 July 2017 (UTC)

You will probably die from dehydration, the tablet may help avoid scurvy, but that takes weeks to develop. Graeme Bartlett (talk) 09:11, 22 July 2017 (UTC)

Okay, so how about KD, vitamins and milk? (I wouldn't drink much water when I was a kid, and in retrospect that may be why I couldn't pronounce K's properly. I had a speech pathologist give up on me after about a year. But insofar as I was hydrated, it was mostly by milk.) NeonMerlin 09:51, 22 July 2017 (UTC)

Adding milk will be a great help, as it provides many nutrients that are iffy from a pill. The main thing that seems to be missing from all 3 is fiber. Here's the nutrition info on Kraft Mac & Cheese: [5]. So, a lack of fiber may cause eventual digestive system problems. As for the other nutrients, the ratios are probably off (too many carbs can cause weight gain), and there may be many unknown nutrients in fruits and veggies you would miss, so adding something like broccoli and tomatoes to the mac and cheese would really help to balance everything out. StuRat (talk) 17:15, 22 July 2017 (UTC)

Chronic dehydration and pronunciation of K's

How well can a childhood speech impediment, where the K sound and G as in "good" are replaced by something described as "coughing", be explained by chronic dehydration? NeonMerlin 10:04, 22 July 2017 (UTC)

See Speech disorder and Speech sound disorders. In most cases their cause is unknown. Some known causes of speech impediments are "hearing loss, neurological disorders, brain injury, intellectual disability, drug abuse, physical impairments such as cleft lip and palate, and vocal abuse or misuse." Blooteuth (talk) 12:36, 22 July 2017 (UTC)

"Ross 128" signal

The signal that seemed to be coming from Ross 128 now seems most likely to have come from a geostationary satellite. Don't they have the orbital parameters for these things so they could quickly check to see if a satellite is a likely explanation for such a signal? Bubba73 ^{You talkin' to me?} 23:36, 22 July 2017 (UTC)

Sure, all the satellite locations are being tracked, along with lots of floating junk. But I suspect it was some type of reflection of the signal, so not coming straight from the satellite. Thus it couldn't be easily matched to a particular location. StuRat (talk) 00:42, 23 July 2017 (UTC)

To directly answer Bubba73's question, "Don't they have the orbital parameters for these things so they could quickly check...?" Well, yes, there are databases, but unless you define "quickly," ... I mean, they did check for satellites and found several plausible candidate interferers, and that search only took a few weeks. That was pretty quick.

Here is a broad overview of the science behind the Breakthrough Listen program.

To put it bluntly, it is not easy to compute whether any interference source might interfere with any specific instrument observation. Certain types of interference can be removed automatically, but even with the state of the art in hardware and software, a research scientist still must follow up manually to study the really interesting signals.

There exist thousands of databases, with thousands of different types of information - not only satellites and their orbits - but keep your mind open about all the other reasons why a very sensitive receiver might register a blip. A lightning strike in Indonesia - not to mention the background heat from Big Bang, and every Earthly WiFi router broadcasting cat photographs at 5.4 GHz - radiate more receivable radio signal in the C-band than a celestial source many light-years away. Whenever the Arecibo antenna, or the Green Bank Telescope - or any other large array involved in the SETI search - receives a signal, the involved scientists have a lot of work to subtract out the unwanted bits.

When the search encompasses such a broad range of possibilities, there is no single computer-system that contains every answer, immediately, in a format that is trivially incorporated.

Here is a preliminary report from Enriquez et al. on the event. They reference the Two Line Element source database, published by U.S. Strategic Command, available to the public at Space-Track (after a complicated registration process). That is not the only database of merit - but it's the most important one, because it's the one the researchers are using already.

Just to throw out some more examples: if we are concerning ourselves with objects in Earth orbit, I would also look at ORDEM from NASA's Orbital Debris Program Office. I doubt that there's a quick and easy way - today, anyway - to ingest that data into the Breakthrough Listen software; but until somebody does so - and a skilled scientist publishes peer-reviewed work explaining why it matters - we can't rule that stuff out; and we can't rule out any of the thousands of other plausible explanations for a signal. If we find something that matters, we will apply Occam's razor to rule out every other plausible explanation until the most likely answer is an extraterrestrial source - perhaps even one that indicates the existence of an intelligent civilization. That hasn't happened yet, and a lot of us think we aren't going to last long enough for it to ever happen. But, we try anyway.

Nimur (talk) 05:03, 23 July 2017 (UTC)

Resolved

Thank you for that in-depth answer. Bubba73 ^{You talkin' to me?} 16:05, 23 July 2017 (UTC)

July 23

Judgement of "healthy" and "sick"

If someone gets an infection and shows visible signs of illness, then it is obvious that the person is sick and requires treatment/cure. But having a pathogen is not so clear-cut. The pathogen may hide within the body and can manifest when the person's immune system weakens or when a person unconsciously spreads it to someone else. If a person catches a pathogen and the pathogen is strong enough or the immune system is weak enough, the person will get sick. But if the pathogen just hides in the body (chicken pox/shingles), then is this person sick or well? Also, what about chronic diseases? One may have an excessive amount of body fat and statistically would be more likely to have obesity-related diseases. But if that person eats many fruits and vegetables and does vigorous physical activity regularly and has no signs of chronic disease, then is that person healthy or is the increased risk for an illness enough to qualify as sickness? 50.4.236.254 (talk) 01:54, 23 July 2017 (UTC)

Your name is not Mary by any chance is it? 110.22.20.252 (talk) 06:04, 23 July 2017 (UTC)

We all carry many pathogens, some active and some dormant. I would use adjectives such as "infected" and "overweight" rather than "sick" or "ill" for such situations. Dbfirs 06:41, 23 July 2017 (UTC)

Check the origin of "sick" and it's reasonably clear that it means someone who has symptoms, i.e. has been "weakened" by whatever ails him.[6] ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:25, 23 July 2017 (UTC)

They'll probably have signs as well as symptoms. Richard Avery (talk) 07:58, 23 July 2017 (UTC)

An interesting article for this is Endogenous retrovirus; see also [7]. There are actually a handful of sequences that humans require to be healthy which are based on pathogens. Wnt (talk) 16:08, 23 July 2017 (UTC)

scores of thesis and books (i mean, serious books made by people teaching in university) have been written about this subject, with historic, ethnographic scope, and environmental so don't expect any straight answer. Social definition of the normal (including healthy/ill) change in place and time.

You know the sentence "it's not a bug, it's a feature"? Well, in biology/medecine you have the same thing happening. Sickle-cell disease is another example of the difficulty: it is either just a disease or an adaptation depending on whether malaria is controlled or endemic.

Gem fr (talk) 08:56, 25 July 2017 (UTC)

drilling and reaming

I'm trying fit a 1.5mm dowel pin into a piece of brass. My current plan is to:

1. Drill a 1.45mm undersized hole

2. Ream it to 1.5mm with a 1.5mm reamer

My question are:

Is the 1.45mm undersized hole really necessary? Or should I start with a 1.5mm hole right away?

Is the reaming step necessary? Would a 1.5mm drilled hole still be able to achieve an interference fit with a 1.5mm dowel pin?

Should I use HSS or carbide for drilling and reaming brass? Covfefe beans (talk) 05:36, 23 July 2017 (UTC)

Looking at the reamers, some are advertised for hand tool use, and some for machine tool use. What's the difference? The machine tool ones are significantly cheaper.

Would I still able to jerry rig a machine tool one for hand tool use? I'm only making ten holes with hand tools for hobby usage, so I can't really justify paying 5 times the price for the hand tool ones. Covfefe beans (talk) 05:41, 23 July 2017 (UTC)

Since you haven't specified what the use is, it is impossible to answer your main question, but a 1.5 drill will produce an oversize hole. As to machine reamers as opposed to hand ones, I suspect but do not know that the hand reamer will have a more progressive lead-in taper. At that size yes you will probably get away with a machine reamer. If it is too difficult to get houing then grind some more taper on it. Greglocock (talk) 10:21, 23 July 2017 (UTC)

I'm trying to mount a 15mm long 1.5mm diameter dowel pin coaxially on a 60 tooth brass gear, and using said dowel pin to drive another rotary mechanism. The gear is 5mm wide, and the hole is through all, so the dowel pin will sit 5mm deep into the gear. Ideally it will be an interference fit so that I won't have bother with glues and stuff. Covfefe beans (talk) 11:34, 23 July 2017 (UTC)

Is there a reason you choose not to use Tap and die tools to cut threads on the pins and holes so they can be simply screwed together?

A possible tool for your plan is a Dremel power drill with stand. If you begin with a slightly undersized hole, you may

• Chamfer the edges of pins and holes for easier insertion.
• Noting that the Thermal expansion coefficient of pure Brass is 19 x 10^-6 K^-1, freezing a pin may allow it to be pressed into a warm undersized hole.
• A last resort is to split the end of a pin with a very fine saw so that it can compress to fit the hole. To keep a strong fit you could use Cyanoacrylate or Epoxy adhesive. Blooteuth (talk) 16:26, 23 July 2017 (UTC)

Dowel pins are case-hardened steel, so a die won't even scratch it. You'd need a CNC gear grinder to get a thread on there.

Though you do bring up a good point. I could go with a M1 or M2 tapped hole, and put a threaded rod or some sort of a headless screw in there. I actually never considered that approach. Covfefe beans (talk) 02:06, 24 July 2017 (UTC)

• Use your experience to judge the best method. Gain some experience by just trying it, with the accessible tools you have.

There's more than one way to do this, the best is often simply that which works, given what you have.

A 1.5mm reamer is brittle as anything (and expensive) and must be used in some sort of jig - a vertical drill press or tapping machine, turned by hand but held accurately vertical. Holding it by hand is (IM-clumsy-E) just a way of snapping such thin, brittle reamers. If you must, use a pin vice rather than a (heavier) tap wrench.

I would suggest finding some books on clockmaking, or even watchmaking (1950s ones are best, as representing a level of technology that's easily accessible by a hobbyist today, 60 years on). They'll discuss plenty of ways to put an axle into a wheel, attach it firmly, then true it afterwards. This seems a far more achievable goal than trying to make a perfect hole, then have a pin fit into it perfectly, by the Power of Optimism.

Another approach to achieving impossible standards is to find a reason why it's not needed. Redesign the mechanism such that it's less critical for perfect alignment. Using a larger pin, or a pin with a larger mounting boss, or a flat-face flange against the face of the disc, could all be useful approaches. Andy Dingley (talk) 20:40, 23 July 2017 (UTC)

A rollpin is a better choice than a dowel. I think you'll find clock makers often used tapered pins for this job. The reamer for a tapered hole will probably cost more than a cylindrical one. It is possible to make your own finishing reamers, called D-bits in our workshop. basically take a steel rod, turn it to the desired shape, and then grind half of it away. Then harden it and you have a single flute reamer. It is accurate but not much use for anything other than final sizing. Greglocock (talk) 20:48, 23 July 2017 (UTC)

North Korea fissile material

Where does North Korea currently get its fissile material? According to North Korea and weapons of mass destruction, it could be at the 5MWe reactor at Yongbyon or at the spent fuel reprocessing facilities (also part of Yongbyon?). The same article says that NK has 6 to 10 plutonium warheads or 13 to 30 nuclear equivalents for plutonium and uranium stockpiles.

Where does NK produce fissile material? Have the North Koreans ever built a nuclear warhead? If so, where? --RoyGoldsmith (talk) 21:38, 23 July 2017 (UTC)

"Have the North Koreans ever built a nuclear warhead? If so, where?" They've built at least 5. One was around 10-30 kT TNT equivalent. Yongbyon is the most likely assembly facility. it is a moot point as to whether any of these devices were physically small enough to be a warhead. Greglocock (talk)

@Greglocock: Do you have any sources? As near as I can tell, your statement about (1) five warheads with one 10-30 kT and (2) Yongbyon being the most likely factory isn't mentioned in the article. If we have reliable sources, we ought to modify it.

Also, where does NK produce fissile material in 2017? I'm talking about centrifuges and all that. Not the assembly of a warhead (however small) using the fissile material. Again, the article doesn't say that it's all done at Yongbyon. Do we have any sources? --RoyGoldsmith (talk) 10:59, 24 July 2017 (UTC)

I don't know about the production sites, but we have an article about warhead tests: List_of_nuclear_weapons_tests_of_North_Korea. The sources for that article may help you find more. --Lgriot (talk) 15:04, 24 July 2017 (UTC)

Idle googling suggests http://www.aljazeera.com/news/2017/05/north-korea-testing-nuclear-weapons-170504072226461.html as a good place to start, but first of all you have to skip the many existing wiki articles on NK nukes. Greglocock (talk) 20:07, 24 July 2017 (UTC)

July 24

Meteoritic vugs

This image's description refers to the off-color section at far left as a "vug", and our vug article discusses the subject in terrestrial rocks, but not in meteor(ite)s such as the pictured object. How would a vug form in this context? I can find references to the subject ([8] [9], etc.) plus the results of Google thinking that I made a typo for bug, but nothing answering my question. Nyttend (talk) 00:59, 24 July 2017 (UTC)

The image description says ''Note the "vug" inclusion on the middle left of the slice', not 'far left'. :) --CiaPan (talk) 05:42, 24 July 2017 (UTC)

Our articles on this are at Iron meteorite and the yellow mineral would be troilite. From http://www.sciencedirect.com/science/article/pii/S0016703767800279 it appears that when molten, the iron sulfide would be all dissolved with the other liquid metal. Then iron/nickel solidified, leaving a concentrated lower melting point liquid that crystallized troilite ( and other minerals) when it cooled more. I wouln't call what's in the pic a vug. Graeme Bartlett (talk) 13:01, 24 July 2017 (UTC)

Widmanstätten patterns resemble lines in a typical 60 degree pattern. The sample in the picture looks more like a bad forgery then a real meteorite to me. Obviously allot of money can be made with little effort on selfmade samples like that. --Kharon (talk) 05:58, 25 July 2017 (UTC)

Comet tail fitting in a suitcase

According to this page, among other comet-related articles and sources I've read, the amount of material in a comet's tail would fit into a suitcase. Is this correct, and if so, how does it compare in density to inteplanetary/interstellar space in general? Also, if this thought experiment could be actually carried out, what would the packed comet tail look and feel like-- dust, packed sand, heavy stone, or something else? 2602:306:321B:5970:997C:317E:34C0:891 (talk) 01:04, 24 July 2017 (UTC)

I suspect that the comet's tail is far more dense than dust in an average nebula, etc., as those are far larger than the comet's tail width, so a much lower density will block or reflect as much light. From our article: "a nebular cloud the size of the Earth would have a total mass of only a few kilograms."StuRat (talk) 03:37, 24 July 2017 (UTC)

vacuum also has some examples and digits relative to outer space Gem fr (talk) 09:09, 25 July 2017 (UTC)

This page says a swimming pool (at the density of water) rather than a suitcase, but that's still a pretty small volume. We can make a guesstimate as follows. The JPL text says that the coma can be "tens of thousands of kilometers across" and the tail "can reach 150 million kilometers in length". So let's assume a tail with a length of 10^8 km and a cross section of 10^5 km^2, so a total volume of 10^13 km^3. Outer space says that the average density of matter in interplanetary space is 10^6 particles per m^3 and most of this consists of hydrogen and helium atoms. That gives a density of about 10^15 atoms per km^3, or about 10^-11 kg per km^3. Multiply by a factor of 100 to account for the higher density in the comet's tail, and we get 10^-9 x 10^13 = 10^4 kg of matter in the comet's tail. So that's bigger than a suitcase but smaller than a swimming pool. Gandalf61 (talk) 09:54, 25 July 2017 (UTC)

Pipe wrench

What kind of pipe wrench can exert the greatest amount of torque on smooth stainless steel pipe -- an ordinary pipe wrench, a strap wrench or a chain wrench? (Note: it doesn't matter whether or not it will leave marks on the pipe -- what matters is maximum torque and nothing else.) 2601:646:8E01:7E0B:A51C:A8E5:DDE4:3E35 (talk) 06:13, 24 July 2017 (UTC)

The longest one - assuming none of them slip. Torque and grip are different things. 196.213.35.146 (talk) 08:08, 24 July 2017 (UTC)

It depends on the diameter, the grade of stainless, and the quality of the wrench.

A chain wrench in particular won't work well on a small diameter pipe. The links are individually rigid, so they provide few contact points around the pipe. Achieved torque owing to grip is dependent on contact area, even though friction in most theoretical models isn't (and that whole independent model fails if the friction arises due to an applied clamping force rather than weight). There are some techniques for chain wrenches that allow multiple turn, helical wraps, to get round this problem (a flexible bike roller chain can be used instead of a rigid block chain, but they are easily broken too).

Some stainless pipe has quite a hard surface - a Stillson type pipe wrench with worn jaws may be unable to grip at all, as the pipe surface is too hard to allow the teeth to dig in and engage.

On the whole, you might find (surprisingly) that a strap wrench gives the best grip on the surface of smooth stainless pipe. Although you need a strap wrench designed to withstand such a force, not just a rubber strap to open kitchen jars with. Multiple turns of (natural fibre) rope can be useful too, despite looking archaic.

Also check the assumption that surface damage is acceptable. That pipe is expensively stainless (thus hard to work with for a reason). Damage pits can be a focus for corrosion, for stress risers and for dirt accumulation - all reasons against why stainless might have first been used. Andy Dingley (talk) 08:22, 24 July 2017 (UTC)

Well, let me rephrase: which type of wrench (out of the 3 types listed above) offers the best grip on smooth stainless pipe of medium diameter (say, 1-1/4 inch)? And yes, surface damage is acceptable within reasonable limits (visible scratches and marring is OK, a mangled pipe obviously isn't). 2601:646:8E01:7E0B:A51C:A8E5:DDE4:3E35 (talk) 09:13, 24 July 2017 (UTC)

Hard to say without trying the specific tools and pipe concerned. But don't rule out a good strap wrench, with a strong nylon strap and a steel head to fit a ratchet handle. Andy Dingley (talk) 11:02, 24 July 2017 (UTC)

By design/physics chain wrenches can apply the most torque since they have the most grip but for that they need to fit the pipe well. Pipe wrenches are the next best sollution and they are better suited for different sizes thus they are commonly used by professionals. --Kharon (talk) 05:43, 25 July 2017 (UTC)

Color of wet rocks

Rocks display characteristic colours. Many types of rock display distinct and attractive colours. When a rock surface is damp or wet the color usually becomes significantly deeper and more intense. What aspect of reflection of light from the surface of rock explains the increasing intensity of color when the surface is damp or wet? Dolphin (t) 12:58, 24 July 2017 (UTC)

Chatoyance might be a useful term, although from woodworking, not geology. Highly figured wood, such as birdseye maple isn't at its best unless given an oiled finish, or even just wiped with water in the workshop.

The explanation for this is to do with specular vs diffuse reflection, and reflection vs. transmission overall. A raw pebble, even if polished smooth, is still rough at the optical scale. So it acts to give diffuse reflection of any illumination. It looks matt and greyish. Coating it would a smooth-surface (such as a clear liquid under surface tension) is akin to finely polishing it. It now loses the diffuse reflection in favour of a specular reflection. This is also less strong as a surface reflection (its albedo might actually decrease) and the reflection is now from deeper within the rock, influenced by its colours. Andy Dingley (talk) 14:22, 24 July 2017 (UTC)

I actually asked myself the very same thing, some rainy day.

first, "deeper and more intense" actually means more contrasted. Most solids are, really are, darker when wet. Water absorb light that would had been reflected/scattered.

second, color has examples of how intensity alter color perception

third, most objects are covered by all sort of material of any size, from molecules and microbes to dust and dirt. Water (or oil) will somewhat clean the solid, turning the color disturbance of these thing into just a loss of light.

fourth, same as @Andy Dingley:: a thin liquid pellicle reduce surface color effects (those effects that peak in Structural coloration )

But i am still wondering

Gem fr (talk) 10:12, 25 July 2017 (UTC)

Medical printer

While looking for something else, I ran across an eBay listing for a KELLER MEDICAL PRINTER/PULSE OXIMETER/ VITAL SIGNS MONITOR. I understand the idea of something that monitors vital signs, and I've had pulse oximeters applied to me plenty of times, but what's a medical printer? Developing a specific kind of printer just for medical purposes seems a bit of a waste, since computer printers can print stuff of any subject, and printers for lots of different paper sizes and types already exist. Nyttend backup (talk) 13:31, 24 July 2017 (UTC)

As far I can tell from the pictures, it's either one inter connected device being sold. It's possible the vital signs monitor is seperatable from the pulse oximeter, but I'm not sure how likely this is to be done, especially with a second-hand device. It looks like it's possible the printer component is also separatable, but it's only likely to be used together with the device, unless I guess you have a working device of some sort and just need to replace the printer and it's compatible. The printer component is surely either for real time printing of vital signs as commonly seen on older TV shows and movies or like with this device [10], or for printing stored records e.g. as with this device [11] or both. Even for store records, the reason why you may want the ability to print the records where the machine is and not have to risk relying on a network connection to some other external printer where you'll collect the results seem obvious. By the same token many check out machines either have a built in printer, or are directly connected to one, rather than sending the receipts to be printed in some other location. Nowadays they often are networked so the receipts are generally retrivable and printable in some other location and this may be done for various reasons (and the data will often also be used by the company in various ways too), but it doesn't take away the benefit from having the directly connected printer. Nil Einne (talk) 14:24, 24 July 2017 (UTC)

The question, though, is "what is a medical printer"? A search for "medical grade printer" gets a lot of hits; they seem mostly but not all to be thermal; many but not all of them still have parallel ports. What makes a printer "medical grade"? --jpgordon^{𝄢𝄆 𝄐𝄇} 14:30, 24 July 2017 (UTC)

But nothing was said about medical grade printer until now. The OP did ask about a medical printer but, only provided one single example. I did personally think there probably was such a thing as a medical grade printer, since it struck me as the sort of thing that would likely be needed given the requirements (many mentioned here) including supporting whatever required standards and also having appropriate certifications but since the only thing here at the time was am ambigious question, it's not something I bothered to research more than demonstrated above. If anyone the question about a medical grade printer had been asked, I either would have researched it or let someone else answer it but this question only came after I responded. Nil Einne (talk) 16:25, 25 July 2017 (UTC)

Agreed. Also, a medical printer should be more reliable. Certain printer technologies are too unreliable to be used in a situation where lives could depend on it. For example, the page feed mechanism used in many printers is prone to failure by pulling in more than one sheet at a time, pulling a sheet in off-center, etc., thus causing a jam. The system used on adding machines, where there's one continuous roll of paper fed through a pair of rubber rollers, is much more reliable, and should be used here: [12]. Time is also critical, and the printer shouldn't need to be turned on and given time to warm up, clean the print heads, etc., before it can be used. And finally, it should be possible to sterilize the printer, so all the parts should come apart for cleaning. StuRat (talk) 14:34, 24 July 2017 (UTC)

Does anyone have any real informed answers, rather than guesses? --jpgordon^{𝄢𝄆 𝄐𝄇} 14:47, 24 July 2017 (UTC)

The path to truth can be a gradual one, the goal gradually coming clearer in the distance; the odd part is, so long as you are walking it, you have not arrived. In any case, I would guess that if "medical printer" is a phrase with a meaning, the ISO standards would mention it, and searching medical printer ISO I get a variety of promising hints; the top one [13] says that "Our ISO 9001:2008 and ISO 13485:2003 certifications and FDA Registration serve as a testament to our knowledge and understanding of the critical guidelines that are required by the industry." Now, I tend to have more knowledge of relatively inconsequential things like science than the better-paying and more stable field of bureaucratese, so I'll let someone else try to take this from here. Keep walking... Wnt (talk) 15:32, 24 July 2017 (UTC)

Note that both ISO 9001 and ISO 13485 are Quality management systems standards. The later one specifically for medical devices. The former is general purpose, there was a time when everyone was touting their ISO 9001 compliance. Incidentally, I don't know if this applies to medical devices but there was a time when it came to ISO 9001 as per my earlier comment while you probably wanted a manufacturer/designer who was ISO 9001 compliant/certified, you probably did not want one who made a big deal over their ISO 9001 compliance/certification. They are arguably important, but you should understand what they are and what they actually mean. Nil Einne (talk) 17:09, 25 July 2017 (UTC)

• Keller Crescent Printing made specialized printer equipment and paper, such as label printers for pill bottles and things like that: [14]. I think they no longer exist anymore, it looks like they were bought out in 2007,[15] and many of their plants have since closed down.[16] What this specific device printed labels for, I'm not sure, but it was some specialized printer that output a label. (maybe a readout of the vital signs the machine measures in order to put it on a chart?) --Jayron32 15:37, 24 July 2017 (UTC)
• I think the item is just being improperly parsed. It's not (medical printer)/(pulse oximeter)/(vital signs monitor), it's a medical item including a printer, a pulse oximeter, and a VS monitor. That is, "medical" really only modifies the latter two portions of the description and a printer is just a printer (which in this case is attached to a medical device). Sort of a purple people eater problem. Matt Deres (talk) 16:10, 24 July 2017 (UTC)

  Right, which explains why there are many many printers on the market sold explicitly as "medical printers". I think Wnt's suggestion is correct; "medical printer" is associated with conformance with particular ISO standards for medical devices and also for medial record keeping. --jpgordon^{𝄢𝄆 𝄐𝄇} 16:30, 24 July 2017 (UTC)

Well medical grade printers obviously exist, I don't think anyone denies that. But the specific eBay item being sold seems to be as Matt Deres described or I described. The attached printer is most likely designed to only print out information. There's a fair chance it's not designed to print out images, which is what many devices sold specifically as medical printers seem to be for, amongst other things. It would seem likely the attached device is a medical grade printer but a highly specialised one. The standards it may have to meet may be different from a more general medical printer. As I said above, it's possible it's detachable and usable with other devices but this probably isn't that likely to be done in practice and in any case this would only be with similar devices. Nil Einne (talk) 16:31, 25 July 2017 (UTC)

To give an example of what I mean see this device [17]. Yes it's a medical printer but for a specific purpose. What requirements, standards and certification it has to met, I'm lazy to research but while some of them may be the same, there's a fair chance some of them are different from [18] this device to give another random example. Nil Einne (talk) 16:39, 25 July 2017 (UTC)

All the flailing around here has to do with philosophy. I mean, is a "medical printer" an intersection of two words, or whatever is called by that phrase. Is it defined as any printer used for medical purposes (like the one on your desk if you use it to print out a report from the hospital)? But most often I think it means a printer that can safely be sold and used for medical work without the local shamans and cartel enforcers turning up to cause accidents for the merchant. People need medicine and therefore there are many, many rackets that must be paid; hence the regulatory definition. But it should be noted that this definition may vary country to country, county to county, howevermuch globalists try to make their "international standards" sound like laws of nature. Perhaps a printer is only "medical" if it cannot print unflattering things about Kim Jong Il (not that I'm a North Korean lawyer). If an armed gang of nihilists broke into your hospital and said you could only print medical records from the printers you'd scribbled red with permanent markers then those would be "medical printers" in your parlance within a day or so. And if violence is truth, then a medical printer is not defined by what it is, but where and when it is also, and even that may only be a best guess with a margin of safety; so long as the Inspector smiles it is a medical printer, and if He frowns, watch out! Wnt (talk) 10:26, 26 July 2017 (UTC)

Our medical grade printers come from Sony. They are dye-sub, which is more resistant to splashes than ink. They connect directly to most medical equipment. They also produce laminated printouts if necessary. They dye used is also marked medical grade. It is resistant to bacteria and mold. The same with the paper - medical grade. 209.149.113.5 (talk) 16:53, 24 July 2017 (UTC)

Strength of non-drug related addictions

How strong are non-drug related addictions? Which on is the stronger? Porn, sex, gambling, adrenaline thrill seeking, sport, internet? How do they compare to drug addictions?--Clipname (talk) 23:39, 24 July 2017 (UTC)

You may find Addiction interesting. I don't know how you would define "stronger". The impact could vary by individual. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:58, 24 July 2017 (UTC)

Behavioral addiction could be characterized as less severe than chemical addictions, in that stopping isn't as likely to cause severe physical symptoms, like delirium tremens. Also, many chemical addictions, like alcoholism or smoking, are also behavioral addictions. StuRat (talk) 00:26, 25 July 2017 (UTC)

Revealingly addiction is often connected to behavíor or consumption, just because someone regards it unhealthy, often with rather far-fetched arguments. So obviously it is disputed when and even if at all behavior and/or use of "soft drugs" can be regarded an addiction. Only on hard drugs everyone agrees that these are addictive, because hard drug withdrawal is well known to make most addicted do anything aka go crazy for a new dose. Since that is clearly only true for the real "hard drugs" it seems wrong to categorize anything else addictive. Else where to draw the line? Are all women "addicted" to chocolate? Are all children addicted to sweets? --Kharon (talk) 05:26, 25 July 2017 (UTC)

Demonstrably all addiction strengths vary by the person. For instance I had (or perhaps have) a nice little medically induced Endone habit, which I could kick after a week (several times). Cheese, on the other hand... Greglocock (talk) 05:04, 25 July 2017 (UTC)

@Kharon:I personally define me as addicted to (among other), water, food, and air (oxygen); to my kids, too (and their mother, even more so) ; and pretty much so to chocolate, cheese, and video games (which i can stop wherever i want, as any addicted person will tell you of its addictive habbit). I definitely get crazy when i am hungry (the very same stimulus what would make me laugh after lunch, could fly me into rage before lunch; i know for sure that most human are the same in this regard, some proverbs and some habits, like the habit to treat serious business just after or during dinner, testify). And try lack of air, you bet you will "go crazy for a new dose". These drugs removal is just impossible, you'll die if you try. I guess "kids removal" won't kill a mother outright, but i strongly advise against for the health of the children, the mother, and the person trying the feat (since the mother is likely to get crazy enough to kill if she can). etc. Gem fr (talk) 13:40, 25 July 2017 (UTC)

Porn, sex, gambling, adrenaline thrill seeking, sport and internet are drug-related, in some way. Or, rather, drug related addictions tap on pleasure and pain chemical systems of our body, and they have no reason to be stronger per se. What drugs are, for sure, is: easier, less time consuming, and not as limited in strength. I mean, to enjoy sensation similar to neurobiological effects of physical exercise aka "runner's high" (for instance), you need either hour-long and physically taxing exercise (and the pleasure will be limited), or a shot of some drug in a matter of seconds, with no exercise, and you can get the dose equivalent you would get by running 1000km or 1 Million km if you want (which you cannot get by running!) .

So, why would morphine be more addictive than an equianalgesic dose of enkephalin or beta-endorphin, produced by the body, all binding to the μ-opioid receptor so that in effect the body is mainly unable to make a difference between them?

Then again, the main difference is in doses, and it makes sense to expect a stronger addiction to stronger doses, doesn't it?

Gem fr (talk) 13:39, 25 July 2017 (UTC)

Or short Reward system. I have to disagree with Gem fr regarding the doses. Contrary nature even adapts by making frequent usage less rewarding, even when the dosage is risen. Up to states when addicted dont get their "kick" or reward anymore, like eating something you really dont like - but the hunger is gone. You will never feel pain from not getting chocolate or sweets anymore but you will from hard drugs. So hard it will define you completely. Much more even then any grade of hunger or thirst. All these other things you mentioned will not absolutely define you. Thats how i compare them (as not addictive). --Kharon (talk) 22:52, 25 July 2017 (UTC)

I don't think we disagree. equianalgesic mention the effect of chronic use and tolerance as something to take in consideration (among other factors), as it change effects. Hunger is not a pain, it is ... hunger. Same thing for thirst or love. Even though we usually describe these feeling as being sometime "painful", they use specific biologic systems (see those article), not the pain warning system and hence don't mess with it, as hard drugs do. I am pretty sure chocolate and sweets don't tap on the pain system, either, that's why stopping them shouldn't be painful. Gem fr (talk) 10:30, 26 July 2017 (UTC)

Anorexia can be like a non-drug addiction, and for a significant percent of those afflicted with it, it can be fatal. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:10, 25 July 2017 (UTC)

July 25

Ant-covered food

I sometimes leave food on the table for too long before eating it. The dish would get crawled by ants by the time I come. In that case to avoid wasting the food, I would blow wind to scare them away. For the last few remaining ones that stay too long, I either remove them using a tissue or blow violently to fling them out. So, are there any changes in the food, and are they significant enough to even think about it? Because this has happened several times, I want to make sure it's ok, although I suppose it is. Thank you in advance! 123.16.110.210 (talk) 07:08, 25 July 2017 (UTC)

Ants are relatively clean insects, by observation. They don't regurgitate spit onto the food in-situ to dissolve it, as they seem to prefer cutting it up and taking it back to the nest. BUT. They walk over the place before they walk on your food. I don't think you are taking an enormous risk, although I'm sure the scaredy cats will try to tell you otherwise. Your biggest problem is likely to be crunchy ant surprise, a dish often accompanied by nasty bites to the inside of the mouth. Greglocock (talk) 08:01, 25 July 2017 (UTC)

The risk from their feet is not as much as you might think. They groom themselves with their antiseptic saliva very regularly. (It's neat to watch. They're like tiny cats.) Straight Dope:Are Ants Disease Carriers.

ApLundell (talk) 14:28, 25 July 2017 (UTC)

Ants are not, AFAIK, disease vectors.

Now my 2 cents: obviously my own hands, dishware and even the food left on the table itself are already covered in invisible matter (microbes and the like) no better than anything ants may bring with them (I wouldn't say the same for flies or rodents). so, I personally don't care about ants, as opposed to flies or rodents.

BTW ants taste like a kind of crunchy bit of vinegar (because of formic acid) ; you may find it pleasant ... or not. So if some ants remains, well, i remove them with care or not depending on whether the acid would spoil the dish taste or not (did you ever tried honey with ants? i did; that's not awful, but i have rather honey without not; but not for health reason, anyway.

Gem fr (talk) 12:05, 25 July 2017 (UTC)

Some people regard ants as a delicacy.--Shantavira|^{feed me} 12:07, 25 July 2017 (UTC)

Note that while the ants may not have MADE the food unfit to eat, they may serve as an indicator that it is. That is, it normally would take some time for a scout to happen upon the food, then bring all his cronies there to the feast. During that time bacteria are growing in it. So, if it's a type of food which tends to develop toxins when it rots, like meat, being covered with ants may serve as an indicator that you should avoid eating it, or at the very least cut off the exposed parts. StuRat (talk) 15:33, 25 July 2017 (UTC)

Clearly you have never encountered ants in this situation. They have very effective communication systems based on pheromones. Ants will seek out food and cover it in minutes, and the idea that you may have put food down and then rely on ants to inidicate its safety is stretching it a bit. Richard Avery (talk) 07:50, 26 July 2017 (UTC)

Wow! I really don't expect to be replied so quickly and by so many people like this. So I suppose there is no need to concern about the situation more than other risks, as I have expected. Thanks everyone! 123.16.104.104 (talk) 03:30, 26 July 2017 (UTC)

Personally, I think my fellow refdeskers have gone too speculative here, not sourcing a single thing before telling you that your activity is more or less safe. (And in so doing, also forgotten that we are not supposed to answer questions which impact even vaguely upon medical/health advice, no matter how trivial the matter and how confident they are in the answer). So I'm put in the awkward position of choosing between doing what we were all meant to do (not say anything) or giving you a word of caution you need to consider. Not all ants are equal, some are toxic and many will sting or bite if threatened. I wonder if those commenting above momentarily forgot about such things... And the last place you want a reaction to a sting is in the the oral cavity.

Now, if your question is whether you can expect longterm health effects from having eaten a few ants in the past, then I would say you have reason to feel in the clear; because of the very slight mass of the ants, any long-term repercussions are unlikely in the extreme, and more acute problems (toxic shock, allergic response to ingestion or sting) would have been known to you at the time, of course. That said, I wouldn't make a habit of this, especially if you are not particularly familiar with your local species. As we all know, ants have been consumed as a treat in some locales for a long time...but by people who know the local species and which make for good eating. I would no more recommend eating a species of insect you aren't deeply familiar with than I would recommend that you eat a wild mushroom you didn't recognize. Lastly, it's worth noting that ants do sometimes carry parasites, some of which are known to be transferable to larger fauna that eat the ant. No known cases of zoonotic transfer to humans (that I've ever heard of, anyway) but food for thought if you are going to go munching on novel species. Snow ^{let's rap} 08:51, 26 July 2017 (UTC)

(For some reason my IP has changed. 123.16.104.104 (talk) 03:34, 26 July 2017 (UTC))

Does sport oxydate us?

Doing more sport implies higher general oxygen consume? Is that bad?

"Oxidation" is not exactly the right word, but Yes. Aerobic_exercise does increase oxygen consumption. That's not bad. In most situations it's good for you. ApLundell (talk) 14:24, 25 July 2017 (UTC)

Oxidative stress does cause damage, and exercise will tend to increase that. However, we seem to have a defect in our genetic "design" that regular exercise is required to make our bodies function properly (not really a defect, but rather an adaptation to an environment where starvation was a huge threat). If we can figure out the method hibernating animals use to avoid that, then we can skip the exercise, but, for now, doing so causes muscular atrophy and other problems, so we need to exercise. StuRat (talk) 15:22, 25 July 2017 (UTC)

(edit conflict) Oxidation is one of those unfortunately-chosen words from back in the mists of time that frequently leads modern students of science astray (see etymological fallacy). Oxidation has very little to do with the element oxygen, excepting that oxygen is itself a decent oxidizing agent. Oxidative stress in the body is not due to atmospheric oxygen and our normal breathing; rather it is due to the presence of free radicals in the body which can convert normal oxygen to a reactive oxygen species. Increased oxygen in the body due to sports/exercise really has nothing to do with it, as increased ground state triplet oxygen doesn't do much of anything in that regard. --Jayron32 15:28, 25 July 2017 (UTC)

I disagree with most of your post, and particularly your last sentence. See [19]. StuRat (talk) 15:40, 25 July 2017 (UTC)

So corrected. Thank you for that! --Jayron32 15:43, 25 July 2017 (UTC)

You're quite welcome ! (And notice I didn't feel the need to insult you, I just said I disagree, and provided my proof. Please do the same.) StuRat (talk) 15:48, 25 July 2017 (UTC)

I disagreed, too, but couldn't provide ref so i stayed quiet; now, Oxidative stress, free radical, reactive oxygen species and triplet oxygen remains useful regarding the question, don't they? Gem fr (talk) 15:53, 25 July 2017 (UTC)

I've never stated that they were not. --Jayron32 16:11, 25 July 2017 (UTC)

bad for what?

Apnea is obviously a situation where higher general oxygen consumption will kill you faster, so you try to lower oxygen use. And while the lung can get you as much oxygen from the air as you need, the blood may have trouble transporting it, hence the use of Hemopoietic growth factor for doping in sport to get higher VO2 max.

In between those two extremes, well, humans evolved in an oxygen-rich environment and adapted to it. The level of oxygen in the body is controlled so as to remain where it belongs (Homeostasis, Homeostasis#Blood_partial_pressure_of_oxygen_and_carbon_dioxide, Homeostasis#Blood_oxygen_content), whether you use lot of it (high exercise level) or few (sleeping). Even, if need be, your level of activity will adapt to oxygen availability (somewhat).

Gem fr (talk) 15:48, 25 July 2017 (UTC)

Open circuit power draw of an SMPS

I have a mobile phone charger without any sort of LED to say that it's connected to the mains supply. How much power is it using when nothing is connected to it? It is one with a USB port at the other side.

Of course, I don't expect anyone to provide an exact figure without further details, but I'll add that it is about two years old. Are there easy ways that I could find an exact figure?--Leon (talk) 15:24, 25 July 2017 (UTC)

• Well, the question seems to have been asked (and kind of answered) at [20] already. Not sure if that answers your question (the order of magnitude is about 1W, but there is some large spread). Tigraan^{Click here to contact me} 15:36, 25 July 2017 (UTC)

Standby power suggests for a modern charger the answer should be 0.5W or less if it's sold in the EU or California. Nil Einne (talk) 16:11, 25 July 2017 (UTC)

According to No load power there is theoretically a star system. I say theoretically because I don't think I've ever actually seen it used even with Samsung or LG phones/charges but I must admit I've never looked that closely. Nil Einne (talk) 16:14, 25 July 2017 (UTC)

I'm a little dubious about the No load power article. The only reference is a dead link that does not appear in wayback.

The line "The no-load power contribution to a country’s household energy demands is thought to be considerable" seems particularly suspect to me. Considerable? A few phone chargers and power-strips with nothing connected to them? ApLundell (talk) 17:21, 25 July 2017 (UTC)

I agree it's not very good. But I just noticed it mentions an EU code of conduct. Sure enough a quick search finds [21] [22] which suggests to me it probably should be either 0.150W or 0.075W for any signatory. I don't actually know who are signatories although it's possible all of these participants are [23]. One of the things not well discussed in either article that I noticed is there has been a fairly big drop in wasted no load power since everyone moved away from simple linear power supplies to using switch moded power suppliess although the primary reason for that was IIRC because of the price of ironcopper. Nil Einne (talk) 18:54, 25 July 2017 (UTC)

This one has an oscillator and a shutdown circuit, which disables the oscillator over the Opto-isolator device when the output voltage is reached.

Actually this [24] is very long but seems to be implying the Minimum energy performance standard in Australia and NZ did contribute to the demise of linear power supplies there. I'm sure I've read before that the primary reason for the switch from linear to switch mode power supplies was the price of copper (and possibly iron) but I'm having trouble finding it again although [25] does mention the price of copper albeit for PSUs for control systems and seems to suggest at low currents linear power supplies are still cheaper. In any case, it may be both energy savings and the price of copper (and iron?) were factors. And maybe not just price rises but reduced costs for the components needed for SMPS. Nil Einne (talk) 19:23, 25 July 2017 (UTC)

Also the EPA restricts maximum power consumption on stand-by devices. --Hans Haase (有问题吗) 20:50, 25 July 2017 (UTC)

If you're interested in this sort of thing you might consider buying a Kill A Watt to measure the power drawn by various devices. It's not usually sensitive enough to measure standby power but still is fun (well, at least for us nerdy types) and useful. Shock Brigade Harvester Boris (talk) 23:43, 25 July 2017 (UTC)

Birds eating fried potatoes

Why do many bird species found in urban areas like fried potatoes so much? I've seen gulls attack people for French fries, and I've encountered a family of ravens who love tater tots (even preferring them over peanuts). It doesn't seem like any food they'd find in the wild would be similar in appearance, texture, or nutritional value, so why do birds go for this sort of human food? 2602:306:321B:5970:A883:9889:9D93:BBC1 (talk) 21:03, 25 July 2017 (UTC)

Maybe it tastes good to them. And keep in mind that some birds (crows, for example) will eat pretty much anything. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:05, 25 July 2017 (UTC)

(OP here) That's true, gulls will eat anything! But in my experience, at least, they and ravens seem to really like fried potato products, and I"m wondering why they seem to especially like these.2602:306:321B:5970:9560:D613:AD37:85EC (talk) 21:12, 25 July 2017 (UTC)

Why fat is a bird's best friend. Alansplodge (talk) 21:16, 25 July 2017 (UTC)

Fried potatoes provide very high nutrition. Theres oil or fat from frying, providing long time energy and much carbohydrates for the quick power and other ingredients, see Potato#Nutrition. Cooking or frying makes the ingredients more efficient for nutrition. Such food is still more powerful. Already to fat to fly? --Hans Haase (有问题吗) 21:26, 25 July 2017 (UTC)

Maybe it does also have something to do with the shape of the food they "normally" eat and how their ingestive anatomy, physiology and behavior had evolved before the advent of McDonald's ... Worms and other longish invertebrates might indeed seem "similar in appearance" too. A New Scientist article, "Birds prefer to eat at outdoor cafes with slow plate-clearing", writes "The shape of the food is important too, with Eurasian jackdaws partial to long French fries and herring gulls diving for hot dogs". This observation, among many others, was made by Paul Haemig, an animal ecologist who studied birds and their fast-food behavior, for example in "Ecology and phylogeny of birds foraging at outdoor restaurants in Sweden". ---Sluzzelin talk 21:37, 25 July 2017 (UTC)

(OP here) Interesting link, thanks! 01:25, 26 July 2017 (UTC)

Note that the shape of the food being long and skinny may not just be a preference, but may be all they can swallow. While birds of prey are able to rip food apart with their talons, some other birds may not be able to. So, that leaves food that can be swallowed whole. StuRat (talk) 03:27, 26 July 2017 (UTC)

What is the implication for bird feeding enthusiasts? I buy cracked corn, shuck sunflower seeds and make sugar syrup for the hummingbirds. Is there anything wrong with it? Thanks, - --AboutFace 22 (talk) 22:23, 25 July 2017 (UTC)

You will probably be shocked but since you asked so very specific: Infact its the crushing, the crunchiness, that reminds us of eating insects and Birds love to eat insects like nothing else, just as we loved eating insects like nothing else some multiple thousand years ago. Hope you will still enjoy your bag of "pure crunch" chips. --Kharon (talk) 23:13, 25 July 2017 (UTC)

P.S.:If you are freeminded, maybe even give insects (or spiders) a try , since they are said to be very healthy food ontop of being crunchy (and even free for everyone who manages to grab em) :D --Kharon (talk) 23:26, 25 July 2017 (UTC)

And don't forget Crunchy Frog. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:32, 25 July 2017 (UTC)

I don't quite understand what you guys mean. Where am I going to get the insects, worms and frogs? I don't mind spending money on them though. I am not sure my birds will be interested, quail for instance. They mostly eat cracked corn spread on the ground. --AboutFace 22 (talk) 23:59, 25 July 2017 (UTC)

No wonder you never find any. Unfortunately you are far to slow to compete with them birds in finding and eating insects. So sneakily follow them, remember the place and try your luck later on, when them birds check the other spot!! --Kharon (talk) 00:57, 26 July 2017 (UTC)

The mention of both ravens and jackdaws made me wonder about crows. Well, if crows like French fries, it appears they like fish better! [26] They'll settle for wet French fries though [27] ... and there are more of them just eating them however they can scrounge them from the trash. Wnt (talk) 01:00, 26 July 2017 (UTC)

(OP here) I have seen crows dipping bread in a puddle; maybe that's how they figured out fishing. As an aside, herons fish with bread but I'm pretty sure they don't eat it. 2602:306:321B:5970:AC9C:C42E:DAFD:280A (talk) 01:25, 26 July 2017 (UTC)

Crows (or raven) seem a special breed of birds. Astonishing near human like intelligent a recent study [28] found out. Not clear if they are intelligent enough to transcend from their nature but obviously smart enough to make choices that imply some real meditation. --Kharon (talk) 07:23, 26 July 2017 (UTC)

Animal population control

I am aware that controlling the deer population may involve introducing natural predators (wolves, humans) or introducing birth control. Does are injected a contraceptive vaccine to prevent fawns from being born. I am just wondering if it's possible to use the same kind of contraception on the human population to prevent most females of childbearing age from reproducing, especially those in their early twenties as they tend to be highly fertile. Deer and humans are both mammals. Can they use the same contraception? 50.4.236.254 (talk) 23:19, 25 July 2017 (UTC)

In addition to the eugenics aspect of that idea for humans, where did you see that female deer are injected with anything? There are millions of those creatures running around, and they can be very elusive. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:22, 25 July 2017 (UTC)

Sub-cutaneously injected contraceptives for humans do exist and have been in use for several decades. In the UK they are colloquially known as "the jag." Of course, they are usually only administered with the consent of the recipient.

Contra Bug's incredulity, Wildlife contraceptives are also in widespread use, not least for deer species.{The poster formerly known as 87.81.230.195} 90.212.201.233 (talk) 23:44, 25 July 2017 (UTC)

I was aware they were being used in relatively small, confined areas. Trying to impact the entire species would be well nigh impossible. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:48, 25 July 2017 (UTC)

I would think fitting does with virtual reality devices and wifi, and bombarding them with WP:SEALIONING by IP users with prison-library internet access would cause mass cervine extinction within a fortnight. μηδείς (talk) 00:43, 26 July 2017 (UTC)

Eugenics never really goes far out of fashion. [29] Wnt (talk) 01:02, 26 July 2017 (UTC)

See also compulsory sterilization. In India in 1976, there was a programme of vasectomy for men and tubal ligation for women, officially in return for various cash or property incentives but many were actually forced by the police. Needless to say, the government lost power at the next election; see The Emergency (India). Alansplodge (talk) 11:07, 26 July 2017 (UTC)

July 26

Feynman Lectures. Exercises. Exercise 9-16 JPG. Lecture 9

. .

First there is a problem with question b). To find e.g. x(t₄) , we need v(t₃ + 0.5Δt). To find v(t₃ + 0.5Δt) we need a(t₃). To find a(t₃) we need v(t₃). But we are asked to calculate steps with time interval Δt. Even with interval 0.5Δt the errors appear xlspng.

Second, there are two functions that are similar with Excel graph x(t) : $f_{1}(t)=-e^{-t}$ and $f_{2}(t)=-{\tfrac {1}{t}}$. From different m and k , I see that when k=1 & m=2 max. x increases to 2 units , when k = 2 & m = 1 max. x decreases to 0.5 units. So equation must look like x = (m/k) f(t).

By means of guessing, from eq. ${\tfrac {d^{2}}{dt^{2}}}x=-{\tfrac {k}{m}}{\tfrac {d}{dt}}x$, it seems that $x=e^{-{\tfrac {k}{m}}t}$ satisfies. Username160611000000 (talk) 10:17, 26 July 2017 (UTC)

• It seems when I take double interval and arithmetical mean , I get increasing accuracy twice (during double time)  : xls png . But it is not enough I think, as acceleration is changing with same rapidity as speed, and we maybe have to count this someway (maybe analogous formula 0.5at² for distance) Username160611000000 (talk) 14:50, 26 July 2017 (UTC)

The numerical methods that Feynman is illustrating in section 9-6 and 9-7 are the Euler method and the midpoint method. For an interval of size h the local error in the Euler method is order O(h²) whereas the local error in the midpoint method is O(h³). Gandalf61 (talk) 15:54, 26 July 2017 (UTC)

Where does this drop of water push down with a million-g force?

Fun article at phys.org about Buller drops (Reginald Buller) that launch fungal spores. They show an artificial system in which one drop of water joins with another and launches it into the air. The energy comes from surface tension. However -- there also has to be conservation of momentum, action and reaction. They say that the force on the drop is actually "a million g's". Yet it looks like only a tiny part of the drop touches the substrate. It's as if there is a truss inside the thing that would put a skyscraper to shame, and I can't even tell where it presses down. Wnt (talk) 11:08, 26 July 2017 (UTC)

The force is small. g is an acceleration. When you divide a small thing (force) by a tiny thing (mass) the result (acceleration) can still be high.

One of my favourite books is Pennycuick, C.J. (1992). Newton Rules Biology. Oxford University Press. ISBN 0198540213. It covers lots of this sort of thing about the fundamental and unavoidable scaling laws: why elephants can't jump (big things can't have legs strong enough), why fleas are so bad at jumping (when you're that light, jumping becomes so easy in comparison that fleas aren't actually that special) and why bees can't fly (at their scale the air is viscous enough to allow them to swim). Andy Dingley (talk) 11:27, 26 July 2017 (UTC)

I should have been more careful in my wording; yes, the force is a million g's times the mass of the drop. But that still implies that the drop can become, in a sense, one million times heavier than it normally is, yet it still does not wet or even deform to fit against the substrate! I suppose I am guilty of a scaling error in not appreciating that the force required to move a given volume drops per the square of scale, and I also don't know how small these drops really are. But it seems surprising that water drops could be so solid that they do not visibly react to the force. Also, I still don't actually know even which drop presses down. Wnt (talk) 12:53, 26 July 2017 (UTC)

Don't think about pressing down, it's done by pulling.

The spores are flat sided. That's energetically a poor shape for a surface (considering surface tension). Place a small drop alongside and lower than it, and the drop merges to the liquid layer covering the spore. The small radius sphere, and the constrained flat surface, are replaced by an energetically favoured larger radius. The attached drop CoG is pulled upwards by this shrinking surface. The overall effect is like one of those permanent magnet railguns (Youtube will have videos) where a magnet is accelerated by having others hit it from behind. By Newton there has to be a reaction force, but that's the spore pushing downwards, not the drop. Andy Dingley (talk) 14:20, 26 July 2017 (UTC)

Does quickly removing a plaster/band-aid/waxing strip result in quantifiably less pain than doing it more cautiously?

Does quickly removing a plaster/band-aid/waxing strip result in quantifiably less pain than doing it more cautiously? --129.215.47.59 (talk) 11:26, 26 July 2017 (UTC)

• No-one seems to agree with a single, simple reason, but there are plenty of contenders.

Anticipation (waiting to do it is worse than doing it), duration and mostly speed - there's a limit on how much pain you can notice per second. If you exceed that, you don't feel it as any worse than you would by doing it slowly, but it's certainly over more quickly. Andy Dingley (talk) 11:30, 26 July 2017 (UTC)

• What does your own experience tell you? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:30, 26 July 2017 (UTC)

• To answer this question, it is important to know that the only accepted way of quantifying pain is by a subjective scale, for example, "On a scale of 1 to 10, with 10 being the worst pain you can imagine, how would you rate this?" There is no objective tool available for measuring pain levels. So the question basically comes down to whether people say the pain is less; and the answer is yes, most people do. Looie496 (talk) 13:40, 26 July 2017 (UTC)

There are a number of Pain scales for self-reporting. The Wikipedia article about Pain notes that fMRI brain scanning has been used to measure pain, giving good correlations with self-reported pain. Blooteuth (talk) 14:22, 26 July 2017 (UTC)

On my own tedious/hate/pain scale ripping ecg patches off is less annoying than tearing them off slowly. The most important thing is shaving before they are applied. Greglocock (talk) 14:37, 26 July 2017 (UTC)

Unidentified seashore life (San Diego)

I saw this odd pink seaweed and these tiny shells on a kelp float at the beach yesterday. I haven't gotten a response on iNaturalist; does anyone here know what they are? 2602:306:321B:5970:D9:F312:FC8A:C37C (talk) 13:50, 26 July 2017 (UTC)

I'm not 100% certain, but I think the tiny shells are a type of Spirorbis worm. Even less certain about the "pink seaweed", but I suspect it's actually a piece of a coral colony, perhaps Leptogorgia chilensis? ---Sluzzelin talk

Novice magnifier question

I've noticed that the more powerful a magnifier glass the smaller the lens is and the closer to the subject the lens has to be. Is there any way to overcome this? I need a free standing 10x strength magnifier similar to this but with a wider field of view and increased distance from the subject from 5cm tall to 15cm tall. Basically imagine the picture I linked but scaled three times bigger. I can't seem to find anything available with these specs. Is it impossible?

Hopefully a better answer is on the way but I think it might be possible with more than one lens. Loupes for medical professionals allow higher magnification and at an increase focal distance than any single lense I could find and I think it's enabled by the use of compound lenses. I'll be interested in the answers to your question also. --129.215.47.59 (talk) 16:36, 26 July 2017 (UTC)