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April 5

Biomedical engineering

Why are some parts of biomedical engineering such as biomedical materials, especially fields looking at the materials interaction with bacteria etc, classified as engineering at all? It seems more like biochemistry to me? What engineering principles are used? Clover345 (talk) 00:37, 5 April 2014 (UTC)

Adapting the physical world to suit a human purpose is "engineering." --DHeyward (talk) 11:41, 5 April 2014 (UTC)

Meaning of wine ageing.

I suspect this question has been asked before. Well, I still decided to give it a go. I am primarily interested in fortified wines like port, madeira and sherry. You go to a wine store and see the spread: regular port is between USD 7 and 20 and if it has been aged 10 years or so, the price will be about $30.00. If it is 20 years old you will pay around $50.00 and a 30 year wine will cost you a hundred dollars.

My question is: what is the meaning of wine ageing? What changes in the fortified wine when you keep it stored for many years. The alcohol content is obviously stays the same, then what is the difference? Is it something tangible that can be caught by scientific methods?

I am not really a wine drinker, so the whole thing is mystery to me. I am sure if given two goblets to compare I could not make out which is "better." I presume ageing is done to make the wine "better," correct? Again, better in what sense?

And why does it get better? Why does it not go in the opposite direction? How about wine that gets worse with time? — Preceding unsigned comment added by AboutFace 22 (talk • contribs) 01:38, 5 April 2014 (UTC)

Anecdotally I recall an acquaintance in a position to know (that person actually worked at the plant) told me about a famous Russian vodka made here in the USA, that they produce the liquor in a single production line but pour it in regular and premium bottles. The premium ones of course cost much more. I therefore wonder about the port wine also. As I said I do not drink but buy the stuff for someone who is of my age but does not drive and cannot easily get around.

What if they do not really age the wine but pour young port so to speak and stick an expensive label on it. This question bothers me.

Thanks, --AboutFace 22 (talk) 00:46, 5 April 2014 (UTC)

Have you read Aging of wine? Wine contains a lot of different chemical compounds that affect the flavor (we have a whole article on Wine chemistry). Aging allows time for reactions to occur that, in some wines, do improve the flavor. Fraud does occur, but it's taken pretty seriously. In Portugal, port production is regulated by the Instituto dos Vinhos do Douro e do Porto. Mr.Z-man 01:48, 5 April 2014 (UTC)

Chemical reactions in liquids take milliseconds, not years unless diffusion is involved then they may take minutes but it is hard to imagine any concentration gradients in a bottle of wine. --AboutFace 22 (talk) 13:43, 5 April 2014 (UTC)

Some reactions are quick, and some are slow (mainly organic reactions). If you examine bottles of expired (non-alcoholic) products, you will notice changes in color, consistency, odor, etc., which indicate chemical reactions which took years to complete. Of course, those are subjectively bad reactions, while the aging of wine is subjectively good. However, I do think there is some effect of people saying since it's more expensive, it must be better. See veblen good. StuRat (talk) 14:50, 5 April 2014 (UTC)

The speed of reactions can be dependent on the concentration of chemicals. While wine has a lot of chemicals in it, it's 95+% water and alcohol, most of the rest is acid and sugar. The organic compounds that create the flavor are less than 1%. Each indiviudal component may only be a few hundred ppm. Mr.Z-man 19:09, 5 April 2014 (UTC)

Something I didn't see specified above in Mr.Z-man's otherwise pertinent comments (although it's doubtless mentioned in some of the linked articles) is that such beverages are often aged mostly not in the bottles they're ultimately sold in, but in larger wooden vessels, sometimes ones that have previously been used for different beverages and or ones that have been so used for decades. The chemical reactions that can occur between the beverage being aged, the wood of the vessels, and the residue of previous beverages that have sunk into the wood can be very complex, and our taste buds are quite good at detecting the subtle effects of such changes. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:45, 7 April 2014 (UTC)

How many electromagnetic signals are in my room now?

Now that everyone has their very own broadcasting station with mobiles (cell phones to you Yanks), millions of signals that were not extant 25 years ago are moving thru the space in my room. Back one hundred years, there were no television or radio transmissions. But there still would have been signals from space.

Can you tell me, approx. how many

a. signals are moving thru my room now?

b. signals would there have been 30 years ago?

c. signals 100 years ago?

d. 4 billion years ago?

Is there a limit to the number of signals that can be overlapping in a given space?

Is there any credence we should give to the idea that too many such signals can be bad for one’s health? Myles325a (talk) 03:56, 5 April 2014 (UTC)

Sigh. Please don't be obnoxious, Medeis. Perfectly interesting question and correctly asked. Don't troll the questioner. Fgf10 (talk) 16:10, 5 April 2014 (UTC)
The following discussion has been closed. Please do not modify it.
Do you want answers from Yanks? Unsigned, insulting ones? — Preceding unsigned comment added by Medeis (talk • contribs) I don't know why Yanks should insult me, I certainly did not insult them - only pointing out that what we call mobile phones here (in Australia) they call cell phones. Did this have something to do with me not signing my name earlier? That was just an oversight, which I have amended now. Myles325a (talk) 03:56, 5 April 2014 (UTC)

I really think you're asking the wrong question here. The only answer would have to be an infinite number of electromagnetic waves are passing through your room, and always were passing through every point in space. What's really important is the frequency and power level of those waves. The usual threshold at which we would become concerned is when they start to heat things up. Cell phones are at a very low power level, so only the one next to your head could cause this. But if you happen to be right under some power lines, or next to a radio or TV station's broadcast antenna, or in the path of a 2 microwave transmission towers, then you might possibly get enough electromagnetic radiation to be of concern. StuRat (talk) 04:05, 5 April 2014 (UTC)

What exactly are you counting as an "electromagnetic signal"? An electromagnetic signal usually refers to electromagnetic radiation that's being varied in some intentional way in order to communicate information. But your question assumes that there were "signals from space" 100 years ago, even though 100 years ago there was nothing in space that was produced by humans that was intentionally varying electromagnetic radiation in order to communicate information. Are you counting (extremely weak) electromagnetic signals produced by whatever non-human civilizations there may be in the universe? Or are you counting electromagnetic radiation produced by natural processes, that isn't intentionally communicating information? And if you're counting electromagnetic radiation produced by natural processes, what counts as "one signal"? Each star in the visible universe produces electromagnetic radiation, for example, but other natural sources of electromagnetic radiation, such as the cosmic microwave background radiation, aren't so easily separated into a discrete, finite number of sources, unless you're counting individual photons. What lower limit, if any, are you using for how strong electromagnetic radiation needs to be in order to count toward the signal count? And what frequency range, if any, are you limiting your definition to? The answer to your question could be anything ranging from "zero" to "a practically infinite number", depending on how you define what "one electromagnetic signal" means. Red Act (talk) 05:56, 5 April 2014 (UTC)

It can be quantified by calculating the entropy of the electromagnetic background (thermal noise, mobile phone signals etc. etc.) per unit volume. The difference between this entropy and that of perfect white noise with k_B replaced by 1/Log(2)is the number of bits of information that one could in principle extract from the radiation (the contents of the mobile phone calls, some details about stars, the non-uniform microwave background giving away clues about the early universe etc. etc.) Count Iblis (talk) 15:01, 5 April 2014 (UTC)

a. and b.

The electromagnetic signals of interest need to be defined because there are more of them in your (unshielded) room that there is room for full-coverage receiving equipment. Consider just one broadcasting band 540-1610 kHz where in the Americas stations are allocated frequencies with 10 kHz spacing: that suggests 100 music programs can co-exist in the band without interference but in practice there are many more transmitted and your domestic receiver will pick up only a few satisfactorily. Wikipedia has an incomplete List of European medium wave transmitters.

c.

The OP and RedAct are is wrong about "back 100 years": in 1914 there were many radio transmissions. Hertz had demonstrated wave propagation through space (1873), both Popov and Marconi had built radio receivers (1895), voice transmission by radio had been demonstrated in Brazil (1900) and if you picked up a spark-gap wireless telegraph signal on 15 April 1912 it could have been the last one from RMS Titanic. A time traveller equipped with a modern sensitive radio receiver would hear dozens of signals, mostly in Morse code.

How was I wrong? I didn't assume there were no radio transmissions 100 years ago, just that there were no signals from space. 100 years ago well predates Sputnik or Vostok. Red Act (talk) 20:55, 5 April 2014 (UTC)

RedAct you wrote "nothing in space", not "signals from space". I accept now that you meant "no man-made signals were produced in space" not "no man-made signals penetrated into space" and have edited my post by striking accordingly. 84.209.89.214 (talk) 21:55, 5 April 2014 (UTC)

d.

4 billion years ago there were no man-made electromagnetic signals but the Cosmic background radiation remnant of the (presumed) Big Bang, modulated emissions from pulsars and occasional bursts from solar flares and planetary atmospheric discharges.

Overlapping electromagnetic signals

In a vacuum, air or any material with linear permeability any number of electromagnetic fields may overlapp since their vector component fields superimpose and do not interfere unless the peak magnetic field causes saturation or the peak electric field causes Electrical breakdown. The latter puts air into a hot plasma state.

Popular Culture: Contact (1997 film)

Relevant to the question, the opening scene of the movie is a three-minute computer-generated sequence, beginning with a view of Earth from high in the exosphere and listening in on numerous radio waves of modern programming emitting from the planet. The viewpoint then recedes, passing the Moon, Mars, and other features of the solar system, then to the Oort cloud, interstellar space, the Local Bubble, the Milky Way, other galaxies of the Local Group, and eventually into deep space. As this occurs, the radio signals start to drop out and reflect older programming, representing the distance these signals would have traveled at the speed of light, eventually becoming silent as the distance becomes much greater. 84.209.89.214 (talk) 16:26, 5 April 2014 (UTC)

Photos of meteor in dark flight

See this: http://www.universetoday.com/110963/norwegian-skydiver-almost-gets-hit-by-falling-meteor-and-captures-it-on-film/

If the rock is moving past at 300 km/hr, shouldn't its image be blurred? Bubba73 ^{You talkin' to me?} 03:03, 5 April 2014 (UTC)

Well, they might have been using a high speed camera to catch skydivers without making them into a blur. StuRat (talk) 04:13, 5 April 2014 (UTC)

If you watch the actual video, it goes past so fast that you barely see it, so I agree it was a high speed camera. And a website like that really should know the difference between a meteor (which it wasn't) and a meteoroid (which it maybe was).--Shantavira|^{feed me} 09:12, 5 April 2014 (UTC)

Were they sky diving in space? Dbfirs 15:49, 6 April 2014 (UTC)

I'm not buying it. The chance of being hit by a meteorite is very low. Of being hit while skydiving must be a million times lower. During the period the chute is actually open, less than that. (but I suppose many skydivers have cameras, so that doesn't divide any further) So we should look for other explanations. What I think we're seeing is that somehow a pebble was packed in on top of the chute last time and fell off when it was opened. In particular, this is why the 'meteor' is following a parabolic trajectory rather than a linear one. Otherwise, I think they should be searching the area for lifeforms, because I don't trust meteors that make course corrections. Wnt (talk) 12:20, 5 April 2014 (UTC)

They weren't hit and estimate it as around 5Kg which is considerably bigger than a pebble. I think one would notice packing that up with a chute! Dmcq (talk) 14:54, 5 April 2014 (UTC)

I don't believe it. I don't think that with a camera shooting bright sunlit sky with very fast settings (which should have a small aperature) you could tell the difference between a pebble next to the camera and a large stone ten times further away. As I recall the original article even said that the skydivers didn't notice the rock themselves; this image is all we have. It's true that even the original article (which seems to have come out first in English then in Norwegian a day later) was dated 4/3. But I think someone had April Fool's jollies out of this. Wnt (talk) 16:10, 5 April 2014 (UTC)

I believe there are more small meteors than you might think. Most just go by without anyone noticing. On a regular security camera, for example, such a small object would be a blur or would fall between frames entirely, so we'd never hear about it. Only when one falls near a high speed camera is anything worth mentioning captured. As far as it's apparent motion, remember that the camera is moving, too, and the spin of the object may cause some deflection from a straight path, as it does with a baseball. StuRat (talk) 15:04, 5 April 2014 (UTC)

Well, the Antarctic meteorites should give a number; I don't think of it as high overall. I need to balance the very unlikely chance of the real scenario against the far more likely chance of the hoax. If it can plausibly be a hoax, it is. It's the same principle as with crytozoology. Wnt (talk) 16:12, 5 April 2014 (UTC)

It would be great if they could find the rock. They should know approximately where it is. Bubba73 ^{You talkin' to me?} 16:21, 5 April 2014 (UTC)

Very approximately. And that film was a few years ago, so the hole it made may well have filled in by now. StuRat (talk) 18:14, 5 April 2014 (UTC)

Wnt, why do you reckon a skydiver is at "a million times" less risk of meeting a meteorite than someone not skydiving? —Tamfang (talk) 06:59, 6 April 2014 (UTC)

That's not quite what Wnt wrote. Skydivers seldom spend more than a millionth of their lifetime actually skydiving. I share Wnt's scepticism. Meteors are rare in the lower atmosphere, so we should look first for an explanation with higher probability. Dbfirs 12:20, 6 April 2014 (UTC)

Well, the chances of me being hit by one while saying grace at Sunday dinner would then be a million times less than for ordinary folk too. Are you sure you and Wnt thought this one out?

I think we are arguing at cross-purposes on the probabilities. Perhaps it's just a difference in the way we use the language? Dbfirs 21:58, 9 April 2014 (UTC)

Also, as most meteorites burn up, they would be rarer on the ground than in the lower atmosphere, but more common in the lower atmosphere than they are in the upper atmosphere and in space. What's your point? Myles325a (talk) 03:42, 9 April 2014 (UTC)

No meteorites burn up completely: they all (or at least the meteorite part) hit the ground, by definition. If this was a meteor that was going to burn up then wouldn't it be glowing from ram pressure? Dbfirs 21:58, 9 April 2014 (UTC)

btw, I believe there are two recorded cases of people being hit by a meteor in all of history, and one of a dog. So the chances are very low indeed. Myles325a (talk) 03:42, 9 April 2014 (UTC)

But the relevant question is what proportion of the outdoor filming with high speed cameras is done by skydivers. I bet that's considerably higher. StuRat (talk) 14:52, 6 April 2014 (UTC)

I believe that the proportion of filmed encounters with meteors correlates very closely with instances in which cameras were present in the vicinity. Myles325a (talk) 03:42, 9 April 2014 (UTC)

Are you claiming that meteorites can be detected only by high-speed cameras? Dbfirs 15:43, 6 April 2014 (UTC)

For small ones like this, yes, as it would either fall between frames or just be an unrecognizable blur on a normal speed camera. A larger object that leaves a trail behind it can be filmed with a normal camera, as in the recent one in Russia. But those are rare. StuRat (talk) 16:06, 6 April 2014 (UTC)

Back to the original question: the one website has a diagram that suggests that the frame interval is 1/30 sec. The blur seems to be far less than 1% of the travel distance between frames, which implies an exposure time of less than 1/3000 sec. The wide depth of focus suggests a tiny aperture setting. The lack of distortion implies an actual shutter (simply scanning the exposed pixels from the sensor element results in distortion for moving objects). In such a small commercial camera, this combination of attributes surprises me, but some camera fundi could comment. My expectation would be to see blurring unless the camera is truly exceptional. —Quondum 19:06, 6 April 2014 (UTC)

When taking pictures (or video) in broad daylight, shutter speeds on the order of 1/2000 of a second are nothing unusual. --Carnildo (talk) 02:53, 9 April 2014 (UTC)

• StuRat nearly has a valid objection, but ... no. I think that if someone had footage from a regular building security camera of a meteorite landing in the parking lot next to someone walking in, it would have hit the big time. Even more so if it landed in a lawn or garden plot and started a fire around it. I should also add that I went back and looked at the video, and it's just a few seconds from the moment the chute opens until the rock falls past - really, it seems like almost too short a time until we recall that the skydiver is rapidly decelerating once the chute opens and the rock retains its inertia. There's simply nothing unlikely about a pebble coming out like this, especially not this time of year. Sure, the guy ought to have gotten every last pebble out when he packed the chute, but parachutes are big, ground is full of stones, and he has other things he's worried about like whether he's folding it right so it will really open. I also encourage people to rethink any consideration of how the skydiver's motion could have distorted the rock's trajectory. We see the background sharp and crisp; he's not twisting within the duration of the exposure. The only question is whether his velocity relative to a distant meteor travelling at colossal speed is going to change by a visible proportion, creating a parabolic arc, within a single set of superimposed high-speed frames, and if so, whether it's going to change so that the meteor is going faster and faster toward the ground. I really don't think so! Come on, April Fools is over, this is busted. Wnt (talk) 20:13, 6 April 2014 (UTC)

Even if they caught it hitting the ground, I wouldn't expect a fireball from a rock this small, just a hole appearing in the lawn with some mud sprayed out. Of course, in that case, they could find it and dig it out, so that would make it more interesting than just the video alone. StuRat (talk) 20:39, 6 April 2014 (UTC)

For action shots in daylight I believe exposure times of about 1/1000 second per frame are quite usual. I believe the pixels are captured then shifted out serially out rather than there being any scanning of the pixels. Dmcq (talk) 20:27, 6 April 2014 (UTC)

I know that exposures of about that length are used in still cameras, but what about video cameras? The article says that that it was traveling 300 km/hour. That is 83 meters per second. With an exposure of 0.001 second, it would move 8cm during the exposure. It doesn't look like it is blurred that much to me, although the exposure could be much shorter than 0.001 seconds. Bubba73 ^{You talkin' to me?} 04:24, 9 April 2014 (UTC)

Filtered milk - contaminated after opening? Why filters and not irradiation?

At my local supermarket there's the option of milk that's been filtered to keep it fresher for longer. To what extent do the milk-spoiling organisms come from the milk compared to being introduced when the bottle is opened and contents decanted?

Why don't they use gamma irradiation instead of filters? Also, wouldn't irradiation be preferable;e to UHT which alters the milk? --78.148.110.69 (talk) 13:00, 5 April 2014 (UTC)

Dairy products suffer from vitamin destruction and the creation of off-flavours when irradiated.[1]--Aspro (talk) 14:23, 5 April 2014 (UTC)

Let me just add a note that the IP of the person who asked the question geolocates to the UK. Looie496 (talk) 14:27, 5 April 2014 (UTC)

While I don't have a direct comment on the relative effects, it's worth remembering that there will often be at least a few days between packaging and opening the milk container. Even more if you often buy more than one bottle at a time but don't drink it that fast. And of course one advantage if this does work is you can do this to an even greater extent if it fits your lifestyle. And the stores themselves don't have to ensure their stock rotates so quickly.

And obviously the bacteria (including spores) in the milk are problematic otherwise your unopened refrigerated milk container wouldn't spoil within 2 - 3 weeks while your unopened unrefrigerated UHT milk container would last months or even years. (In case there's any confusion, although I can't find a ref which directly states this, while the UHT process does cause some changes which some find undesirable, the reason why it lasts longer is because of the much more effective sterilisation.)

In other words, if the filtering does work well, it would make the milk fresh for longer to some extent depending on the particular case. I don't know about your particular milk but [2] mentions a refrigerated shelf life of 60 to 90 days for an unopened container.

(Edit: Note that that source is from 2013 so I'm not sure if there will be anything on the market yet although it sounds like [3] this has been an active area of research recently. From what I can tell there is also some confusion because some extended shelf life milk which seems to generally anything which lasts more than 21 days or so milk just uses microfiltration and HTST pasteurisation, but others uses higher temperature treatements as well as microfiltration. Yet others just use high temperatures. And it varies whether the fat/cream is processed the same or subjected to UHT. There are also other possible steps like UV treatment. [4] (see also comments) [5] [6]. The journal source only used HTST and the other processes but achieves 60-90 days which I think may be partially why it's recent research. It sounds like in the UK microfiltration is the norm, but possibly also higher heat treatment. Our pasteurisation article also discusses the issues briefly. One thing the first (Dr. Gail Barnes) source mentions that's probably relevant although it may be obvious, you need to make sure you post processing such as packaging steps are good enough for your purposes, probably aseptic. So it may also be that your microfiltered milk has this done better too. And it also helps if you are careful with your input. And yes I recognise that this doesn't answer that well what appears to be your main question namely how much of a different this will make after you open the milk.)

As for when the container is opened, obviously if it's fresher from the beginning it may last longer. You shouldn't expect miracles since even UHT milk refrigerated before opening, carefully decanted and closed each time doesn't generally last more than 3 or 4 weeks at the extreme end from my personal experience so I don't see any reason to expect any of this to be better. (May be if you only ever open, decant and close in a laminar flow hood you can stretch it?)

Edit: I should clarify I only read the abstract and I'm not sure the research in the Journal of Dairy Science article was using unopened packaging. It's possible they weren't but were testing in conditions unlikely to be achieved in most real life ones, such as the laminar flow hood I earlier suggested. In other words, I'm pretty sure they were primarily thinking of an unopened packaging shelf life situation since as I suggested and I guess also StuRat below, it's generally difficult to prevent contamination after opening; and milk is a good culture media.

Edit2: Also there is some mention in Microfiltration#Dairy Processing and Milk#Microfiltration but it doesn't add much.

Nil Einne (talk) 14:48, 5 April 2014 (UTC)

The opening on the top of most milk containers is a problem, letting bacteria drop in whenever the cap is off. The air which rushes in to replace the lost milk will also contain bacteria. Milk bags can solve the second problem, as they are flexible and can be reduced in size to match the lower volume of milk. As far as not letting bacteria drop in from above, a system like some ketchup squeeze bottles use, where they open at the bottom, might work. Of course, ketchup is thicker, so avoiding spills would be trickier with milk. Another way to reduce spoilage is smaller containers, ideally single use. This can mean more packaging waste, though, so reusable glass bottles would be best for the environment and also eliminate leaching of plasticizers into the milk. StuRat (talk) 15:22, 5 April 2014 (UTC)

OMG, I had no idea that there was such a thing, as opposed to a "figure"-ative term. :) Wnt (talk) 16:14, 5 April 2014 (UTC)

Yes, for most Americans, the effort to get your hands on some milk bags will be a giant bust. StuRat (talk) 16:58, 5 April 2014 (UTC)

So, what you're saying is that we should go back to the milkman bringing pints of milk in reusable glass bottles to our doorstep. I can tell you from experience that the problem I had with this was that the bottles never seemed to completely lose the smell of stale milk, which put me off drinking the fresh milk. 86.146.28.229 (talk) 07:21, 6 April 2014 (UTC)

That's inadequate cleaning or perhaps the milk at the top had gone bad. They should avoid screw tops, as those are difficult to clean. A disposable cork might work better. I don't think the porch is an appropriate place to leave milk, as it gets warm there, especially if the sunlight hits it, and the labor cost of the delivery has to increase the price significantly. I'd still deliver it in stores, but in single-use glass containers, like a quart, pint or half-pint (depending on the family size). They can have a deposit on them to encourage people to recycle. StuRat (talk) 16:50, 6 April 2014 (UTC)

Well obviously it was improper cleaning, but my point is that when everyone actually used them (and they were cheap, because everyone used them: the delivery cost was no higher than the labour cost involved in delivering and setting bottles out in a supermarket, really) this was a problem. So I doubt it would be less of a problem for future implementations. And they weren't screw top: they were foil-top, to maximise hygiene and minimise costs. The bottles were returned by simply leaving them out to be collected when the next milk was delivered. The doorstep was considered an appropriate place to leave it for generations of people, since when people get up at a reasonable time in a temperate climate there is no issue: prior to that, the milkman came around with his horse and wagon, with a large vat of milk that released milk from a tap at the bottom (just like you said), and people took out their own containers to fill. You might think that it would in theory be unsuitable, but in practice for many years it actually was suitable, even if people round where you live don't do it. There were pint bottles, and rarely-used half-pint bottles, and third of a pint bottles to deliver to schools. People ordered however many pints they wanted (a quart bottle would surely cause problems, since it would be open for longer, and would also make the delivery and cleaning more complicated), and opened each sealed bottle as they used the last. But I could never switch back to communal, reusable glass bottles for milk, because my experience is that the industrial cleaning process doesn't completely eliminate the smell. 212.183.128.252 (talk) 08:19, 7 April 2014 (UTC)

How long ago was this ? They might have better cleaning methods now (UV lasers ?). StuRat (talk) 19:28, 7 April 2014 (UTC)

It was about 15 years ago, now. There were definitely better, more thorough cleaning methods available, even then, but the cost would quickly become prohibitive. 86.146.28.229 (talk) 12:16, 9 April 2014 (UTC)

Two million pints a day still delivered in glass bottles, though they are becoming rarer.[7] Dbfirs 22:15, 9 April 2014 (UTC)

Also note that many people have an irrational fear of irradiation, thinking that the food itself then becomes radioactive. This is rather ironic, since they don't worry about foods which are naturally radioactive, like bananas. StuRat (talk) 15:24, 5 April 2014 (UTC)

You are not allowed to sell irradiated milk in the UK.[8] Thincat (talk) 17:00, 5 April 2014 (UTC)

And why when the governmental Food Standards Agency says it is "a safe and effective way to kill bacteria in foods and extend its shelf life". It's because of lobby groups such as The Food Commission.[9] Thincat (talk) 17:15, 5 April 2014 (UTC)

And I see Long-life milk which is common in the EU, meets consumer resistance in the US. It seems irradiated milk in the US is ultraviolet treated,[10] not gamma radiation – I don't know if this is done in the UK (EU). Thincat (talk) 18:03, 5 April 2014 (UTC)

Hmm...the sentence "in the American market, consumers have been uneasy about consuming milk that is not delivered under refrigeration, and have been much more reluctant to buy it" in the UHT article not supported with a citation, so it should be treated with suspicion. Richerman (talk) 18:21, 5 April 2014 (UTC)

I'm not impressed by regulations against irradiation - I tend to think commercial interests like the idea of people throwing food away and buying more. But... irradiation isn't guaranteed to have no effect. Ionizing radiation can produce double-strand breaks in DNA to kill microbes, and it is true that many enzymes or mechanical agitation produce DNA with similar breaks. But there might be other molecules that radiation breaks in a place that few if any enzymes do. So I can't rule out the possibility of a harmful effect. Nonetheless, I wish we'd let people try more things experimentally, with labelling ... and also that we'd be faster to recognize when things like partially hydrogenated oil are not food and should not be labelled as such. Wnt (talk) 19:15, 5 April 2014 (UTC)

I wonder if there's any risk that irradiation could cause a mutation, say like the ones that causes mad-cow disease, by altering some proteins in the milk. StuRat (talk) 20:43, 5 April 2014 (UTC)

There's really no remotely plausible mechanism for that to occur.(+)H₃N-Protein\Chemist-CO₂(-) 02:10, 7 April 2014 (UTC)

Mad Cow disease? Now there is a thought! The protein has to get deformed by some agent initially. Expression of cellular isoform of prion protein on the surface of peripheral blood lymphocytes among women exposed to low doses of ionizing radiation. Still, I will never have to worry about contracting Mad Cows disease because I'm a helicopter. It is a sham that irradiation won't make milk radioactive, because if it did, it would be easier to see it glowing in the dark it when the fridge light has blown. It would also aid, my secret night-time food raids to the kitchen when everyone else is sleeping. We need (I need) genetically modified cows with some jellyfish genes, to create glow in the dark milk. Oh, and cheese cake. Err,.. Yes you scientists out there, concentrate on developing the cheesecake first.--Aspro (talk) 01:32, 6 April 2014 (UTC)

And if the milk is radioactive, you won't even need to warm it up ! StuRat (talk) 02:17, 6 April 2014 (UTC)

At first I was thinking this question would be unapproachable, but it appears that radiation exposure actually prolongs survival in mice exposed to prions [11]. Unfortunately I still don't see a way to get a good reliable stat on how frequently radiation induces prion disease because I assume it must be very rare; still, if the response to radiation protects against prions, it gives a whiff of plausibility that it could be a real consequence of radiation exposure. Still, this is nothing like evidence that irradiated food would have this happen to a meaningful probability. You really have to do the experiment directly. Wnt (talk) 21:03, 6 April 2014 (UTC)

Radiation can't cause mutations of nonliving material. If for instance you were to irradiate a steak, it could of course damage any residual DNA or RNA (that's sort of the point since it inactivates viral and bacterial contaminants). But since it's not part of a living organism anymore, it's not capable of replicating the damaged DNA, or expressing new proteins, so none of that can result in the production of mutant proteins. You could certainly cause some minor degradation of any proteins already present, but you're not going to magically change the sequence, besides people eat denatured protein all the time. Case in point, scrambled egg. The basic take home message here is that you can't "mutate" nonliving matter. That's genetics 101. (+)H₃N-Protein\Chemist-CO₂(-) 02:10, 7 April 2014 (UTC)

But my understanding of mad cow disease prions is that they are mutated proteins. The replication happens by other cells in the cow, or in a human once those prions are introduced there. So, one mutated prion gets in, and it can then be replicated to a dangerous level. Are you saying proteins can never be mutated directly ? StuRat (talk) 02:21, 7 April 2014 (UTC)

Prions are proteins that adopt alternate (or incorrect) folds and then propagate the misfolded form by trapping other unrelated proteins in the same incorrect tertiary structure. The idea being that the disease state is passed on structurally, trapping native proteins in alternate conformations. The initial misfolding event can be the result of a mutation, but the mutation itself can't be passed on to other proteins. A mutation is a change in sequence, so a mutant protein would literally have to have a different primary sequence. (+)H₃N-Protein\Chemist-CO₂(-) 02:31, 7 April 2014 (UTC)

Also, worth clarifying the terminology here: A mutant gene is a gene with a different nucleotide sequence, a mutant protein has a different amino acid sequence. A mutant gene can produce a mutant protein, or it could easily produce a wild-type protein depending on what specific change is made (See also: degenerate codon). The amino acid sequence itself can't replicate though, so one mutant protein can't make another copy of itself. (+)H₃N-Protein\Chemist-CO₂(-) 02:42, 7 April 2014 (UTC)

Sounds like a distinction without a difference to me. That is, you don't count a misfolded prion as being a mutation, but it can still be passed on to somebody who eats it and cause mad cow disease. So then, if radiation can cause a misfolded protein, that's a problem. StuRat (talk) 02:39, 7 April 2014 (UTC)

That's unfortunately, a completely baseless conclusion. Radiation could degrade a protein chemically, maybe even produce amyloid in an extreme case. But suggesting that radiation damage will produce infectious mutant prion proteins out of thin air is essentially invoking magic. Edit: Out of curiosity, where did you even get the idea that radiation causes prion diseases? (+)H₃N-Protein\Chemist-CO₂(-) 02:46, 7 April 2014 (UTC)

I didn't say that it could, I just asked if it's possible, as one example of a possible mutation. Another example would be in a surviving bacterium that might be mutated to be more harmful. StuRat (talk) 03:00, 7 April 2014 (UTC)

Also, some foods remain alive until irradiated, like onions or potatoes or grains which can sprout. I can easily imagine that some cells in the milk also remain alive. StuRat (talk) 13:49, 7 April 2014 (UTC)

Well, they wouldn't be alive anymore after being dosed with high levels of gamma radiation. So, there's still no mechanism for that to cause the overly specific mutations you've invoked above. Contrary to what happens in the comics, exposure to high levels of ionizing radiation tends to cause nonspecific and irreparable DNA damage resulting in either death (fast or slow) or sterility, neither are optimal conditions for passing on genetic material. It also doesn't actually turn you into a big green rage monster. In either case, irradiating food neither causes the food to remain radioactive, nor does it "mutate" the food in any genetic sense of the word. (+)H₃N-Protein\Chemist-CO₂(-) 13:16, 8 April 2014 (UTC)

Just like with antibiotics, the potential nutation danger would be in under-dosed foods. And while most mutations are either deadly or have no effect, a very few help the organism to survive. In the case of harmful bacteria, this could be bad news for us. StuRat (talk) 13:27, 8 April 2014 (UTC)

No, still not plausible. Bacteria can become resistant to the specific chemical mechanism of a particular antibiotic, it's all about the chemistry. Say a small molecule binds to a bacterial ion channel, then there's a strong selective pressure for an ion channel with a slightly different extracellular domain. The only way bacteria can respond to low level DNA damage is with so-called "DNA repair" proteins, allows them to repair minor damage induced by low level UV irradiation. Ionizing radiation is entirely different, if you irradiate a bacteria with gamma radiation you cause genome wide damage to its genetic material, there's no way to adapt to it because you're directly destroying the thing that would allow it to respond. IF you invoke incomplete irradiation, then maybe a few bacteria aren't exposed to the gamma radiation at all, but then there's no selective pressure. High dose ionizing radiation is a horrible way to introduce a stable mutation, chemical or UV methods work way better. For instance, directed evolution screens sometimes work this way. (+)H₃N-Protein\Chemist-CO₂(-) 14:25, 8 April 2014 (UTC)

Think what StuRat is trying to get across to you is that ionising radiation might 'flip' a non pathogenic prion into a pathogenic form. The people that suffered from Kuru (disease) ate the brains of their old folk, whom (one can reason) had more time on this earth to suffer from possible damage from natural radiation. OK, Prions, from all accounts, appear to be very resistant from ionizing radiation damage – yet millions of tax payers money (some of it yours) is currently being spent on building, running, analyzing - neutrino detectors. Events seldom happen. Yet statistically they do and get recorded. Likewise, the prion refolding 'must' happen for a reason – even if the originating spontaneous event happens very rarely. Even if God deems it so – he/she or it would leave evidence of a causative agent. Ok. Prions are small molecules, so gamma rays from Cobalt 60 might just whizz by. But industrial gamma source isotopes are not pure. They will emit more neutrons than your Moms Apple Pie has has calories. Do you know what a neutron can do? The other possibility, is a faulty DNA codon in the cow might create a pathogenic prion. However, that is a might also. So I can not fathom: how you can pontificate with certainty that Sturat's suppositions is is outside consideration. Scientist may be skeptics by nature but they are always ready to question their beliefs in the hope that they might have that Aha moment, which may lead them to sudden realization, new insights, inspiration, recognition, or (what we most of us all hanker towards) comprehension! They don't have a monkeys chance of getting a Noble if they leave higher education, confident in the knowledge that they now know everything. You may have a point but you need to state it.--Aspro (talk) 22:52, 8 April 2014 (UTC)

"Do you know what a neutron can do" To proteins? Yes, as a matter of fact seeing as how doing this to proteins is a major part of my own research. Neutrons interact weakly with light nuclei, they can on occasion "activate" certain transition metals, but that's very rare. One reason neutron scattering is so popular is that in contrast to synchrotron x-rays, neutrons are entirely chemically nondestructive. I'm actually extremely comfortable dismissing baseless pseudo-science, especially when people can't be bothered to even pretend there's a plausible mechanism for the thing they imagine science is doing to them. Is this the science desk, or should we just start calling it the ^ALTscience desk?(+)H₃N-Protein\Chemist-CO₂(-) 00:56, 9 April 2014 (UTC)

What's the thickness of the pleura membrane?

213.57.121.149 (talk) 15:17, 5 April 2014 (UTC)

Your answer is going to vary considerably depending on just how refined a structure you are referring to regarding the pleural membrane, but assuming you are looking at just the visceral pleura, the thickness for a healthy individual is on the order of micrometers (in the ballpark of 30-80µm on average), though there are conditions (notably diffuse pleural thickening) which can increase the thickness by several millimeters. Snow (talk) 03:31, 6 April 2014 (UTC)

Yes, I'm looking for the pleural parietal too. I think there is a differnt of the thickness between the two. And if it's so thin how can it be he can hold whole the volume of the lungs. Thank you. — Preceding unsigned comment added by 194.114.146.227 (talk) 07:59, 6 April 2014 (UTC)

The parietal pleura is even thinner, at about 20µm. As to your second question, I assume by volume of the lungs you are inquiring as to how it contains the pressure of the volume of gas regularly inhaled. If so, the answer is that it does not, in itself, so much perform this function; air is conducted through still more internal structures, notably the bronchi, bronchioles, alveolar ducts, and the alveoli (where the bulk of gas exchange occurs) themselves, all of which is supported by a matrix of connective and vascular tissues. These tissues are more than sufficient, in most circumstances, to resist the pressure of the maximum volume of air. In fact, the function of the pleurae is less to resist internal pressure than it is to regulate it; the intrapleural space is filled with pleural fluid, which increases surface tension and keeps the visceral pleura in contact with the parietal pleura without friction between the two, such that, when the diaphragm contracts, increasing the volume of the thoracic cavity, the volume of the lungs is increased as well, drawing air into the bonchi, by way of the trachea. So in essence these structures are part of the mechanism which regulates volume (and thus pressure) in the lungs, and less so those which resist it. Snow (talk) 11:50, 7 April 2014 (UTC)

Airplane black box

Is there any reason why an airplane black box will "ping" for the specific time period of one month? Or is that just an arbitrary time frame established by the manufacturer of the box? Thanks. Joseph A. Spadaro (talk) 19:07, 5 April 2014 (UTC)

Battery life isn't infinite. However, this article suggest a push to extend the life to 90 days. As technology approves, the size, durability and lifespan of these devices will all optimize. Regulations must be in place to keep up with technology. Mingmingla (talk) 19:58, 5 April 2014 (UTC)

For me this reads like a requirement by a government agency and the manufacturer does exactly what he is obliged to do deliver 30 days of battery life. --Stone (talk) 20:36, 5 April 2014 (UTC)

More likely an international NON-government agency. HiLo48 (talk) 21:42, 5 April 2014 (UTC)

I've spent a good part of my career as an engineer in the provision of battery backup power (Unreakable Power Supplies - UPS) for critical computer systems, police telecommunications, hospitals, etc. The someone who can come up with a battery technology that never suffers unpredicted catastrophic failure upon discharge, offers a reliable discharge time (not forgetting that battery capacity is inherently proportional to temperature, as a battery is essentially a chemical system and all chemical reactions are temperature dependent), and offers a usuable capacity in a resonable size and weight, is a rich someone to whom the world will beat a path to their door. Nickel iron batteies come close when made at high cost. Super-capacitors have great promise. But this business of the black box battery being good for a known length of time is nonsense. 120.145.97.4 (talk) 00:30, 6 April 2014 (UTC)

My understanding is that one month is the GUARANTEED MINIMUM time that a black box will ping -- it might or might not ping for a longer time, but it WON'T stop before one month. 24.5.122.13 (talk) 03:07, 6 April 2014 (UTC)

Right, the 30 days are guaranteed, and there is a safety margin defined by some requirement. I know of a few parts were we have to built in a factor of 1.5 and for others 3 or even more for very dangerous systems. --Stone (talk) 08:45, 6 April 2014 (UTC)

Wikipedia has relevant information at Underwater locator beacon. This article points to a useful external link HERE, although this equipment is very modern and unlikely to be installed in Boeing 777 of the age of MH370. Dolphin (t) 11:00, 6 April 2014 (UTC)

Another question: Why aren't there two black boxes, one of which remains with the plane, and another of which is ejected? The one that is ejected (automatically) could be equipped not only with "pinging" ability but with a huge inflatable orange flotation device, which might aid in recovery. Bus stop (talk) 11:42, 6 April 2014 (UTC)

A proposal to this effect has been circulating in the US Congress for several years. This proposal has recently been re-introduced as a result of the search for MH370. See the information supplied by User:BBoniface about the SAFE Act - diff. Dolphin (t) 11:52, 6 April 2014 (UTC)

Given the chilly temperature at the bottom of the ocean, would that extend the batteries' life, or shorten it? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:18, 6 April 2014 (UTC)

It should slow the reaction extending the life, but on the other hand the maximum current would be reduced, so the useful life could be less. I hope 120 comments on that question. All the best, Rich Farmbrough, 14:19, 6 April 2014 (UTC).

As previously stated, battery discharge time goes down with any reduction in temperature. Mathematical formulae are available to predict the reduction for each type of battery, but I don't know just what battery technology is employed in the black boxes (actually, they are orange). However, googling "deep ocean temperature" throws up a multitude of websites that show that the temperature profile of deep oceans is not simple, and very deep areas may be quite warm. The area where MH370 is thought to have gone down is ~4 km deep and includes an area with underwater volcanoes. Discharge time is also affected by the service life of the battery in a complex way. Many rechargeable battery technologies increase in capacity over time before reducing near end of life.

If I were running the search operation, I would requisition a battery engineer from the manufacturer to review the service life of the particular unit, the performance of other batteries from the same batch, and the water temperatures at the assumed location, and make some sort of estimate of how long it's going to last. There's no such thing as a guarantee in the battery business, but if the design criteria is for a minimum of 30 days for some high percentage of units, then depending on all the factors a particular unit may last 2 or 3 times as long - or it may die today.

Another aspect that the search team should be aware of is that batteries recover somewhat when rested. This means that, depending on the battery technology and the design of the electronics, as the battery gets very weak, the electronics may skip pings. A simple way to exploit the full capacity of a battery is to parallel it with a super-capacitor. The capacitor accumulates energy as the near flat battery manages to dribble it out, and when the capacitor has accumulated enough, the electronics can turn on and send a ping. So, at first, pings are sent regularly at the design intervals. As the battery weakens, the interval between pings can get longer, and perhaps get to a stage where a few pings are sent then a long break before a few more pings, another long break, and so on... I have no idea of whether black boxes employ this technique, which is quite new.

120.145.70.125 (talk) 15:14, 6 April 2014 (UTC)

Thanks, all. Please see my new question below about black boxes (in the April 6 section, entitled "Airplane black box - another question"). Thanks. Joseph A. Spadaro (talk) 15:18, 6 April 2014 (UTC)

Manganese in Steel

I read at several points that the Spartans had superior steel weapons because their iron ore was contaminated with manganese. From my understanding at that point people used bog iron as mains source for iron. I can think of nearly no way how the manganese could come into the iron with the process used at that time. The good thing is that I also could not find a metallurgy or archeology article stating the claimed of manganese in steel in that time period, but it is stated in a good article of wikipedia so it must be true ;-). Is there anybody with a little advice for me?--Stone (talk) 20:35, 5 April 2014 (UTC)

Since bog iron is derived from groundwater, if the groundwater in question naturally contains manganese, so will the bog iron. 24.5.122.13 (talk) 03:01, 6 April 2014 (UTC)

And in fact, according to the article Pyrolusite, manganese is actually often found in bogs. 24.5.122.13 (talk) 06:32, 7 April 2014 (UTC)

A useful-looking source on manganese in bog iron, via a Google search: [12] AndyTheGrump (talk) 07:00, 7 April 2014 (UTC)

Lanthanide oxide crystal structures

Hello. I know that B-type lanthanide oxides can be formed for Pr-Gd (sometimes necessitating high T). According to the book I've got at hand, the B-type structure has three different sites, one of which is distorted capped octahedral, and two different face-capped trigonal prismatic sites. What differs between the two face-capped trigonal prismatic sites ? I can't seem to find any good illustrations of this structure online, so please point one out to me if you can ! Thanks. --2.100.5.77 (talk) 21:51, 5 April 2014 (UTC)

Illustrated at http://www.radiochemistry.org/periodictable/la_series/L12.html. I think this is it also [13] but you will have to register to use the Atom Work site. It looks to be capped at slightly different angles.

table of unit cell structure of Gd2O3 based on http://onlinelibrary.wiley.com/doi/10.1107/S0365110X58002012/pdf

No 	Site 	Atom 	Multi 	symmet 	x 	y 	z 	Occupancy
1 	O1 	O 	4 	m 	0.0259 	0 	0.6562 	1.0
2 	Gd1 	Gd 	4 	m 	0.1346 	0 	0.4900 	1.0
3 	Gd2 	Gd 	4 	m 	0.1899 	0 	0.1378 	1.0
4 	O2 	O 	4 	m 	0.2984 	0 	0.3738 	1.0
5 	O3 	O 	4 	m 	0.3250 	0 	0.0265 	1.0
6 	Gd3 	Gd 	4 	m 	0.4662 	0 	0.1879 	1.0
7 	O4 	O 	4 	m 	0.6289 	0 	0.2864 	1.0
8 	O5 	O 	2 	2/m 	0 	0 	0 	1.0 

The B-type is monoclinic prismatic C2/M. C-type is cubic. A type is P32/m. X-type is Im3m cubic, H-type is P6₃/mmc.[14] Graeme Bartlett (talk) 09:04, 7 April 2014 (UTC)

Awesome, I'll put that into crystalmaker. Cheers ! 2.100.5.77 (talk) 16:31, 8 April 2014 (UTC)

April 6

Diverticulitis questions

Okay, some of you know me, and I need help. I've got diverticulitis, the fever is down, the pain is almost gone now, and I'm on cipro and metro (generic flagyl). I had it once before, 3 years ago. I've read a lot and listened to my doctors, and I'm confused, frustrated and a little anxious. My preference would be a private conversation with anyone who's comfortable with the topic, but if there are no takers, I'll post a few questions. - Dank (push to talk) 02:43, 6 April 2014 (UTC)

Sorry Dank, but by policy we are prohibited from giving any form of medical advice or recommendations on the ref desks and on the project in general. The best we can do is to direct you to seek the assistance of a medical professional. Best of luck to you, though. Snow (talk) 02:54, 6 April 2014 (UTC)

• Yes, we can't really hold discussions or give advice. But searching google for diverticulitis support groups or forums finds many hits, like these. My from-experience advice, which I can give you, is that given the morbidity, especially with slipshod treatment, seek out aggressive specialist care. μηδείς (talk) 03:15, 6 April 2014 (UTC)
  • Thanks Medeis, I didn't know about those, that's very helpful. - Dank (push to talk) 03:33, 6 April 2014 (UTC)

information

Changes can be coaded as information — Preceding unsigned comment added by Gamts564 (talk • contribs) 03:14, 6 April 2014 (UTC)

I can't make out a question here, please clarify. StuRat (talk) 03:28, 6 April 2014 (UTC)

Uk DMAT

Does the UK have any DMAT teams? DMAT meaning disaster medical assistance team. A team of doctors and nurses, who work on call, to provide emergency care at scenes of incidents. What is it called in the UK? — Preceding unsigned comment added by 90.201.212.79 (talk) 10:46, 6 April 2014 (UTC)

I don't know if this is the same thing but there are MERITs, medical emergency response incident teams. These are small, 3 or 4 medics. All the best, Rich Farmbrough, 14:29, 6 April 2014 (UTC).

I'm not sure if it's exactly the sort of thing you're asking about, but in the East of England we have Magpas, which is a charity. AndrewWTaylor (talk) 09:07, 8 April 2014 (UTC)

USAR

Do urban search and rescue teams employ structural engineers? 90.201.212.79 (talk) 10:52, 6 April 2014 (UTC)

Yes -- see Urban Search and Rescue. 24.5.122.13 (talk) 01:19, 7 April 2014 (UTC)

Rectum

Is rectum part of anus? Link to my user page when you reply. HYH.124 (talk) 11:31, 6 April 2014 (UTC)

No, the anus is a sphincter muscle which closes the end of the digestive tract and facilitates controlled waste expulsion. The rectum is a cavity composed of smooth muscle tissue and attached at it lower margin to the anus. Its function is to consolidate faeces by means of peristalsis and moisture absorption. I'm sorry but I don't usually respond to orders from people I don't know who are asking me for information. Richard Avery (talk) 13:18, 6 April 2014 (UTC)

Here's a ping for you, User:HYH.124. Dismas|^(talk) 02:43, 7 April 2014 (UTC)

@Dismas: I saw... Isn't that too late? HYH.124 (talk) 11:46, 7 April 2014 (UTC)

Alfred Russell Wallace quote

On this site I read this, Even a replay of terrestrial evolution would almost certainly lead to substantially different end-products, a claim first put forcibly by [Alfred Russell] Wallace and echoed many times since. I'd like to find where Wallace said this, or one of the places he said it, so I can quote the original for an essay.

Thank you Adambrowne666 (talk) 12:28, 6 April 2014 (UTC)

PS I'm ashamed to say this is the first I've heard of Wallace - what a guy!

I think that, given a generic "plant", a rerun of evolution would lead to trees. Given a generic "bird", we would have ducks. (At least they would look like ducks and act like ducks though I'm not entirely sure they'd quack like ducks). Given any mammal, and ants for it to eat, we would eventually have anteaters. Given any animal at all, you'd soon have a worm. Basically, to continue this game, choose any nice popular term for a species that is paraphyletic, and we know that evolution can converge to it. Now whether evolution would converge at any distance further than we know it has converged, that is a harder one to guess, because we don't know how often a species would have taken up a niche and form but been unable because the incumbents were simply too good at it already.

A philosophical digression perhaps worth noting is that the existence of evolutionary convergence tends to refute those who say that the universe is without purposeful design. Because the so many immediately recognizable archetypes exist, which evolution has come to by multiple paths, it seems more accurate to say that they were already "intended" by the laws of logic and physics long "before" the first example lived and breathed. See Theory of Forms. Wnt (talk) 20:40, 6 April 2014 (UTC)

Using a google search I can't find any quote by him along those lines. The nearest I can find is here where he says "In order to produce a world that should be so precisely adapted in every detail for the orderly development of organic life culminating in man, such a vast and complex universe as that which we know exists around us, may have been absolutely required." Some of his publications are given in our article Alfred Russel Wallace but he was very prolific and it says there were at least 750 publications in total. Richerman (talk) 09:58, 7 April 2014 (UTC)

Purely negative evidence, but one of the major themes of Stephen Jay Gould's Wonderful Life is precisely the contingency (non-replay-ability) of the history of evolution, and the book contains no reference to such a statement by Wallace. I find it hard to believe that, if Wallace had ("forcibly") expressed such a view, Gould, who was quite familiar with Wallace's writings, would have omitted any mention of it. There's a contact link on the home page of David Darling's site; perhaps you should ask him for a reference. Deor (talk) 13:50, 7 April 2014 (UTC)

Yes, good point, Deor, and thanks for the contact link - thanks, all, for the leads. Adambrowne666 (talk) 21:43, 7 April 2014 (UTC)

need info (oxygen content of water)

Hello I never had chemistry in school but want to know something. If you released oxygen gas in a water solution would it stay suspended for any length of time say one hour and how could you measure the percent of that content? Thanks a paying donor. — Preceding unsigned comment added by 74.130.204.252 (talk) 15:15, 6 April 2014 (UTC)

Oxygen does not suspend in water, it dissolves. If you bubble oxygen through water, some of it will dissolve. If you can keep the bubbles inside the water long enough, eventually all of it will dissolve. There are a variety of ways of measuring the oxygen content of water. For example, people who own aquariums can buy a "dissolved oxygen meter" that uses an electrochemical probe. Looie496 (talk) 15:38, 6 April 2014 (UTC)

There is however a limit to how much oxygen can be dissolved in water, depending on the temperature, salinity, etc. As for air bubbles, they will eventually either rise to the surface and pop or dissolve into the water. Smaller bubbles are more likely to stay underwater long enough to dissolve. Agitation, as by wave action, both has the potential to add new bubbles and keep existing bubbles underwater longer, allowing them more time to dissolve. Thus agitated water is likely to contain more dissolved oxygen than stagnant water. The action of microbes and macroscopic life forms also matters, as plants can add oxygen to the water (and remove carbon dioxide) while animals do the reverse. StuRat (talk) 16:44, 6 April 2014 (UTC)

The actual amount of oxygen that can be dissolved is governed by Henry's law. The Lake Nyos tragedy was a direct result of this law.--Jasper Deng (talk) 07:53, 10 April 2014 (UTC)

Airplane black box - another question

I know virtually nothing about how an airplane black box works. If a suicidal or rogue pilot wanted to sabotage (or at least impede) an airplane's search and recovery efforts by causing "harm" to the black box, would that be possible? Is there any way that a pilot (or any person) can disable, disengage, tamper with, or "shut off" the black box? Or is this notion impossible for some reason? Thanks. Joseph A. Spadaro (talk) 15:17, 6 April 2014 (UTC)

Yes, of course, but I believe that to do it while the plane is flying would take tools capable of cutting through metal. On the ground it would be pretty easy. Looie496 (talk) 15:23, 6 April 2014 (UTC)

As a practical matter, no. The flight recorder and cockpit voice recorder are located in a crash-resistant shell at the tail of an aircraft, inaccessible to anyone onboard during flight. But "any" way? Sure. Shoot them with a gun, or smash up the cockpit so that the instruments they operate from are non-functional, or set the tail of the airplane on fire, or, or, or. It's not "impossible", but it's a scenario of last resort.

There's also not much reason. Other than the deep-water "ping", the recorders don't do anything to assist in a SAR effort. Assuming a hijacker does something like fly to the secret Nazi moonbase in Antarctica and lands there, the recorders can't be found unless the whole aircraft is found. — Lomn 15:25, 6 April 2014 (UTC)

Huh? Isn't that a "chicken or egg" scenario? You said that "the recorders can't be found unless the whole aircraft is found". But, isn't the finding of the recorder itself (via its pings) an event that (sometimes) leads to the finding of the aircraft? Can't it work both ways (which is found first, leading to which is found second)? Joseph A. Spadaro (talk) 15:31, 6 April 2014 (UTC)

The weak ping makes them not much use in finding the airplane very quickly. You have to be almost on top of it to find it anyway. So, it's really only of use during a long recovery process, not for tracking a hijacked airplane while in flight. StuRat (talk) 15:34, 6 April 2014 (UTC)

Thanks. I am not talking about finding a hijacked plane in mid-flight. My original question is only referring to finding a plane that has crashed (or perhaps, just landed, without a crash). Thanks. Joseph A. Spadaro (talk) 15:37, 6 April 2014 (UTC)

OK, in that case the still likely need to spot the wreckage to know where to look to get close enough to detect the ping. The black box isn't designed to help them find the crash site, but rather to find the black box and retrieve it's flight info after they've found the crash site. StuRat (talk) 16:03, 6 April 2014 (UTC)

Some links you may find useful that are to do with Search and rescue, Black box (transportation), Cockpit voice recorder, Flight data recorder and Distress radiobeacon. CambridgeBayWeather (talk) 16:24, 6 April 2014 (UTC)

Note that the "pinger" only works underwater. It's just a sound that it generates so it can be picked up by a hydrophone/Towed pinger locator. The ELT is a separate piece of equipment. Mr.Z-man 16:34, 6 April 2014 (UTC)

So, if an airplane crashes on land, there is no "pinging"? Joseph A. Spadaro (talk) 22:39, 6 April 2014 (UTC)

Correct. If it crashes on land, they can just search through the wreckage manually, and it's generally constrained to a small area. If it crashes in water, it could break apart before it sinks and disperse over a wide area, so trying to find 2 little boxes with remote-controlled submersibles is more difficult. Mr.Z-man 02:36, 7 April 2014 (UTC)

No, not correct. Just different equipment. The black box will start sonar pings after it comes in contact with salt water. The ELT (which is required on all aircraft, unlike a black box) will emit a radio beacon after a crash. It can also be turned on manually or a voice broadcast on the ELT frequency. The impact force will set it off. In water, however, the radio waves will not be detectable. The ELT's used to operate at 121.5 MHz and 243 MHz but now I believe commercial aircraft have a variety of frequencies for satellite as well as terrestrial location. A crash on land of sufficient force would set off the ELT automatically and if it survives the fire, crash and battery life, will allow rescuers to locate it. I do not know if the black box also has an ELT transmitter. --DHeyward (talk) 06:21, 7 April 2014 (UTC)

But the ELT is a radio transmitter, not a pinger. Using the same terminology for significantly different things is what causes this confusion in the first place. Mr.Z-man 14:43, 7 April 2014 (UTC)

It was obvious that the question wasn't about sonar pings when it was stated as a crash on land. There are other types of "pings" so it's incorrect to say that a "ping" is only about underwater sonar pings. In fact, you can open a terminal window on your computer and type "ping localhost" to get a computer ping. See this about MHL satellite pings [15] --DHeyward (talk) 22:24, 7 April 2014 (UTC)

I have to admit that with the statement the plane "purposefully" avoided Indonesian airspace in order to fly to a location in the South Indian Ocean, I'm beginning to hum Bond music. How hard is it to build an ad hoc private aircraft carrier capable of landing a jet plane anyway? (And throwing the box overboard...) Wnt (talk) 20:44, 6 April 2014 (UTC)

The longest Supercarrier class built is 333 m long. Laden Boeing 777's usually land on 6 to 10 000 foot runways that don't roll up and down with the waves or have an immediately adjacent Conning tower. 84.209.89.214 (talk) 00:04, 7 April 2014 (UTC)

It can land on a 6 foot runway ? Awesome ! :-) StuRat (talk) 02:33, 7 April 2014 (UTC)

If you're coming in at 160 knots while the carrier is going at 159, you can. However, that argument is invalid; why should anyone with that kind of carrier steal a plane? 217.255.182.173 (talk) 06:13, 7 April 2014 (UTC)

... and even more unlikely that the rogue carrier would find an ocean current of that sort of speed, even with a steady opposing headwind. Dbfirs 06:59, 7 April 2014 (UTC)

Actually I was thinking of something more like nailing together a few hundred meters of wooden planks, having the plane try to land on it and brake as much as possible before rolling off the end, in order that it could "ditch" without ??? being ripped apart. Then towing the intact plane somewhere. But true, a rocket powered supercarrier standing up on hydrofoils looks a lot more bad-ass carrying the plane back to your secret underwater volcano base. Wnt (talk) 12:58, 7 April 2014 (UTC)

So... I'm not the only one to think about a James-Bond-esque supervillain with a high-speed carrier?

There might actually be 3 different designs:

• Hydrofoil (tried and tested, but a bit on the slow side)
• Hovercraft (another proven approach, but a maintenance nightmare — but hey, if you have 100s of minions, go ahead, use them)
• Cavitating high-speed hull (don't even know what it's called). Basically the hull forms a bubble, and doesn't touch the water any more, which reduces drag to that of a plane.

And then there's the ekranoplan (it's a redirect, but there's a photo in the artickle article) which is even faster. Not a carrier, but a plane/ship hybrid. IP has a point: Why steal a passenger plane if you have one of these? - ¡Ouch! (^{hurt me} / _{more pain}) 07:16, 8 April 2014 (UTC)

I demand to be acknowledged as Emperor Penguin and to be paid a ransom in unmarked sardines in return for releasing the hostages unharmed from my undetectable floating Pykrete aerodrome somewhere in Antarctica defended by my helmeted stormtroopers massed at "Deception" island volcano base. Yours insanely Mr. P. 84.209.89.214 (talk) 12:49, 8 April 2014 (UTC)

In Australia, our military has the Over The Horizon Radar (Jindalee OTHR), which would have detected such fanciful devices. The aircraft track is well within the Jindalee detection range. Hopefully. 120.145.70.125 (talk) 10:34, 8 April 2014 (UTC)

Could you refresh my memory why it didn't track the plane then? Wnt (talk) 22:13, 8 April 2014 (UTC)

It jolly well should have. I was attempting humour. The Jindalee OTHR is a notorious example of the Australian military establishment's penchant for buying special customised hardware, at enormous cost, that doesn't work very well. Jindalee cost about $1.8 billion and seems to be a near useless white elephant. Another example is submarines. They bought a fleet of one-of-a-kind subs that are such that only one or 2 can put to sea at any given time due to major breakdowns. Here's the big picture: USA annual defence budget - about $480 billion. Australian annual defence budget - about $110 billion. From that you would expect the Australian defence force to be about a tad less than one quarter of the US defence force in size. US military personel - 1,200,000. Australian military personel - 61,000 (ratio 20:1). US navy vessels - 289; Australian navy vessels 51. US aircraft 4250; Australian aircraft 275 (ratio 15:1). US ICBM's 450. Australian ICBM's - none. It's disgusting. I'm not objecting to our military being tiny compared to the US military. We are a much smaller country population and GDP wise. What I'm objecting to is the very low bang per buck due to waste & incompetence. 120.145.70.125 (talk) 02:39, 9 April 2014 (UTC)

Australia's defence budget is 23% of the US defence budget? What is your source for that? Dolphin (t) 13:05, 9 April 2014 (UTC)

Announcements on Australian news media + http://useconomy.about.com/od/usfederalbudget/p/military_budget.htm, Wikipedia articles and other online sources. Note that I have excluded data for the US Coast Guard, for which there is no direct equivalent in Australia, but similar functions are performed by other services, and the accounting for the War in Afganistan - both counties allocate additional funds for that. I've also excluded the US National Guard, which has no counterpart in Australia, which is perhaps a little unfair to Australia, as some functions are performed by the Australian military. The big picture is reasonably correct though: Australia has a huge defence expenditure but little to show for it. It's a disgrace. 121.221.33.67 (talk) 15:33, 9 April 2014 (UTC)

A more important figure would be, what percentage of the total budget is devoted to military, in US vs. Australia? ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:58, 9 April 2014 (UTC)

In terms of the necessary taxation causing a contraction of the ecomony, yes. That is a separate issue. But a good measure of economic impact is the military $spend per head of population. USA (318 million people) - its about $1500 per head. For Australia, it's about $4200 per head. I'm more concerned with the waste & incompetence. $4k of my taxes is ok by me if there was something comensurate to show for it - eg submarine availability 80% instead of 15%, an OTHR radar that worked, navy ships that didn't catch fire & be written off due to poor maintenance etc etc... 120.145.12.236 (talk) 17:12, 9 April 2014 (UTC)

Note that high military spending isn't always bad for the economy, because it can put unemployed people back to work, and thus improve the productivity of the nation. During the military buildup before and during WW2 in the US, for example, the economy dramatically improved, ending the Great Depression there. However, if instead of relying on your own defense industry, you buy everything from abroad, then that's another story. StuRat (talk) 17:34, 9 April 2014 (UTC)

@121.221, I'm not sure that you're reading the figures correctly. The Australian Minister for Defence says: "In the 2013-14 Budget, the Government has provided $113.1 billion (including $1.4 billion for Operations) to Defence over the Forward Estimates (my emphasis), with the Budget growing from $25.3 billion in 2013-14 to $30.7 billion in 2016-17. This compares to $103.2 billion (including $1.9 billion for operations) in the 2012-13 Budget Forward Estimates."[16] So the annual budget for this year seems to be AUD 25.3 billion. See also the table produced by the Stockholm International Peace Research Institute shown in our List of countries by military expenditures article, viz: United States USD 682.0 billion and Australia USD 26.2 billion. Our List of countries by military expenditures per capita article only has 2009 figures, but puts Australia in 12th position at USD 893 for each taxpayer, compared to the USD 2,141 that the average American had to find. And if it makes you feel any better, spending lots of money on military technology that doesn't work or turns out to be not needed seems to be quite common; see British Aerospace Nimrod AEW3 or Long Endurance Multi-intelligence Vehicle. Alansplodge (talk) 19:27, 9 April 2014 (UTC)

No brain

I remember reading somewhere about a not too recent medical case regarding an intellectually normal adult person that congenitally lacked most of the brain. If I remember correctly he/she only had the brainstem and all the rest was replaced by water. Has anyone heard of it? --151.41.135.57 (talk) 15:53, 6 April 2014 (UTC)

Hydrocephalus is the name of the condition, specifically hydrocephalus ex vacuo. The remarkable case I heard of is where the person had essentially normal intelligence, which means the parts of their brain they did have were apparently rewired to take on the functions of the missing parts. StuRat (talk) 15:56, 6 April 2014 (UTC)

Come on now, we have some leeway on the Ref Desks, but this is beyond the usual level of unsourced/uninformed (and in this case, frankly silly) speculation that sometimes takes roots here. I'd like to use the old chestnut "this isn't brain science" but that's clearly not the case here. Nevertheless, try to appreciate how easily debunked these stories are with the application of the most basic assumptions we can make in neuroscience and appreciate the sentiment one would usually be trying to put across with that idiom. "The parts of their brain they did have were apparently rewired to take on the functions of the missing parts."? We're not talking about one of the temporal lobes taking over function for the other after the latter is damaged or removed; these are vastly different structures with different functions, form and composition. One can no more think without a cerebrum than one could breath without a brainstem and they are not suited to adapting to cover one-another. This is grade-school level brain science. Snow (talk) 22:44, 7 April 2014 (UTC)

I made no comment on which parts were absent in this case, and therefore which parts took over their function. StuRat (talk) 23:53, 7 April 2014 (UTC)

No, but without that specification it certainly seems as if you are validating the scenario forwarded by the OP as realistic, and he does specify the presence of only a brainstem. And if you weren't speaking to that particular scenario, then the response doesn't say much, since clearly people are capable of losing some brain tissue from any number of regions while maintaining normal intelligence. But your wording does suggest to me that you were speaking to that or a similarly extreme (and impossible) scenario. Regardless, the Ref Desks are not the place for forwarding speculation based on apocryphal tales; we're meant to be assisting those with questions in finding and contextualizing established answers to their questions, ideally backed by solid sources or at least content from within the project, not pure conjecture based on an old wive's tale. As I said, we get some latitude with regard to WP:V, owing to our unique function within the project, but that doesn't mean we can throw the principle out the window altogether. There's a bit too much of that here at times and it's a liability to these pages since, A) it's likely undermine trust in our responses, collectively, and B) it might start to cause some to question if we are operating in a manner that is consistent with broader wikipedia policy and priorities. In short, we may not have to go through the formality of sourcing every claim we make in answering a question as we would in an article, but we do need to be at least reasonably certain we could provide a reliable source if it came down to it, that those sources would be trusted sources in an article context, and that the claims themselves pass basic empirical rigour. Snow (talk) 00:54, 8 April 2014 (UTC)

I provided the relevant link to a Wikipedia article, along with the specific variation the OP described. From there they can find all the sources they need. StuRat (talk) 00:57, 8 April 2014 (UTC)

It's not the mention of that condition or that wikilink that I found inappropriate to this locale, but rather your following statements. Given that he mentioned water, it was reasonable to point him to that information, no doubt; that is a medical condition with firm sourcing. The following speculation (not at all consistent with any medical science), however, is not appropriate as it cannot be verified and the scenario you presented is likely to cause the OP, and possibly others reading it, to think there is some possibility that the story he heard is plausible, which it is not - not even vaguely. This type of extraordinary claim should not be so much as mentioned here as an empirical possibility without verification, which is certainly not found in the article linked to. Snow (talk) 01:16, 8 April 2014 (UTC)

This paper might interest you[17] Sean.hoyland - talk 16:17, 6 April 2014 (UTC)

• I've encountered this question literally dozens of times, over a span of 25 years. Rather than write out a long answer here, I've placed it on my personal web site so that in future I can just give a pointer to it -- see http://weskaggs.net/?p=2311. Our article on John Lorber is also relevant. Looie496 (talk) 16:26, 6 April 2014 (UTC)

Well you might like to check out this lady, who was a neighbour of mine in Barnsley and I can tell you she was one sharp cookie! --TammyMoet (talk) 18:08, 6 April 2014 (UTC)

Unfortunately that case never seems to have been published -- and web pages, as we Wikipedians all know, can't be treated as reliable sources. Looie496 (talk) 21:08, 6 April 2014 (UTC)

http://www.thepsychologist.org.uk/archive/archive_home.cfm/volumeID_16-editionID_96-ArticleID_583-getfile_getPDF/thepsychologist%5C0703mdia.pdf --TammyMoet (talk) 09:40, 7 April 2014 (UTC)

That's not a peer-reviewed source, and in any case the conclusions there are pretty conservative. I have no doubt that hydrocephaly can tell us important things about brain plasticity. But there is no acceptable evidence from it that you can have normal intelligence with only a tiny sliver of a brain. Looie496 (talk) 13:29, 7 April 2014 (UTC)

• I think you're thinking of anencephaly. Extreme degeneration from hydrocephalus might work too, but that shouldn't take effect until after a brain has formed. Wnt (talk) 20:50, 6 April 2014 (UTC)

I've never seen a claim of normal intelligence, or anything resembling it, in anencaphaly. Almost certainly the question relates to the hydrocephaly stuff, which has been permeating the internet for decades. Looie496 (talk) 21:08, 6 April 2014 (UTC)

D'oh! true, I missed the part about the normal intelligence :) . Could be microcephaly, which can display normal intelligence, but I suppose anencephaly by definition ought not to (though there are some genetic causes that can be associated with either). Wnt (talk) 22:49, 6 April 2014 (UTC)

Stephen King's Thinner mentions just such a case, but as a background detail [18].--Auric talk 03:26, 7 April 2014 (UTC)

Good link - trace it back a few steps and you arrive at John Lorber's non peer reviewed book "Is Your Brain Really Necessary?" But the issue is, it's not peer reviewed and our article suggests he might not have read the scans right. Which I should mention reminds me of the famous Terri Schiavo case - when forum participants would look at the brain scan on the right, half would say that "all her brain is gone but a few bits", and the other half would say that there's still a thick layer of cortex and even if there's a real difference in density within that, that doesn't prove it's genuinely gone. I'm not actually an expert in reading brain scans but I'll confess some affinity for the latter position. Wnt (talk) 11:34, 7 April 2014 (UTC)

I suspect that a part of the misinterpretation here is that if you (as an untrained lay-person) look at a photograph of a brain scan - a simple 2D cross-section through the skull - there are at least three very serious ways in which you might misinterpret what you see:

1. Suppose, hypothetically, you see a scan where a region about half the diameter of the brain-case is full of water. A naive first guess is "OMG! That person has lost 50% of his/her brain!"...but that's not true. The volume of a sphere is proportional to the cube of the radius - so it's not 50% that's missing, it's only 12.5%. Someone with "half a brain" is going to be in a lot more trouble than a person with 88% of a brain. I'm guessing most people would have no trouble believing that someone with 88% of their brain intact could be quite intelligent.
2. The person who did the scan probably took numerous cross-sections of the brain. Only one of those 'slices' is presented in the photograph that you are being "wowed" with. Ask yourself: Of all of those slices, which one gets published? Well, it's likely to be the most dramatic one. So if (again, hypothetically), someone had a flattened ellipsoidal void in their brain, we'd be seeing pictures of the largest cross-section through it...it's perfectly possible that the brain appears completely intact in the scans just a half inch higher or lower. By assuming this is a roughly spherical void, you might be grossly over-estimating the lost volume.
3. The part of the brain that's missing may not be a part that's particularly to do with intelligence. Certainly the limbic system and the cerebellum are generally not considered to be areas responsible for what we'd consider to be "intelligence". On the other hand, a loss of large chunk of cerebrum would be pretty catastrophic.

Taken together, it's easy to imagine seeing an exceedingly alarming brain cross-section and have only a few percent of the brain matter actually being missing - and that could easily come from areas unrelated to intelligence. So perhaps, this kind of thing isn't so surprising after all.

SteveBaker (talk) 20:53, 7 April 2014 (UTC)

A TV news program, probably 60 Minutes on CBS, ran a story years ago about a high school girl whose brain had been affected by hydrocephalus such that only a half-inch or so of brain tissue was visible in CT scan, next to the skull, but she was very average in her grades. Her gait was affected slightly. Edison (talk) 01:02, 8 April 2014 (UTC)

As a first approximation say a brain is a sphere four and a half inches in diameter, with volume about 90 cubic inches. If she still has a half inch around the outside that gives sphere of 3 and half inches diameter missing. So she would have (4.5^3-3.5^3)/4.5^3 of the brain remaining which is just over half of it. People can get by with half a brain. Plus the pressure probably enlarged her head a bit so that could easily be a bad underestimate. Dmcq (talk) 12:43, 8 April 2014 (UTC)

Krubera Cave

I was reading several of the articles of the various cave systems in the world. How do scientists measure the depth of the caves (e.g. Krubera Cave)? 99.250.118.116 (talk) 18:14, 6 April 2014 (UTC)

The Wikipedia article about the Krubera Cave in Georgia notes that it is the deepest-known cave in the world and has been explored to a record 2,197 ± 20 metres. The sea floor topography near Arabika has been revealed by a digital bathymetric map that combines depth soundings and high-resolution marine gravity data. The data used to make bathymetric maps typically comes from an echosounder (sonar) mounted beneath or over the side of a boat, "pinging" a beam of sound downward at the seafloor. The amount of time it takes for the sound or light to travel through the water, bounce off the seafloor, and return to the sounder informs the equipment of the distance to the seafloor. 84.209.89.214 (talk) 23:34, 6 April 2014 (UTC)

Barometric altimeter + depth gauge for the wet bits most likely. --catslash (talk) 00:15, 7 April 2014 (UTC)

Any cave that is explored generally has a cave survey made, but I have no idea how surveying methods work underwater. shoy (reactions) 12:16, 8 April 2014 (UTC)

Medical prostration

According to the "Signs and symptoms" section of Marburg virus disease, patients in the disease's early virus phase experience prostration; the article links to our Prostration article, but that covers "the placement of the body in a reverentially or submissively prone position as a gesture". What's actually meant? Prostration has a hatnote saying to read Hyperthermia for "heat prostration", but I'm not sure whether that's meant, whether they mean that the patient is unable to be in any position except lying down, or something else. Nyttend (talk) 18:40, 6 April 2014 (UTC)

The word "prostration" in general means lying in a spread-out position.[19] ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:21, 6 April 2014 (UTC)

See Definition 2 here. As a medical term, it means "exhaustion". Heat prostration is an exact synonym of "heat exhaustion", which is when you become so hot, you can no longer effectively move around, or even support your own weight. --Jayron32 19:43, 6 April 2014 (UTC)

April 7

Induction lamp cooking

As far as I know a powerful enough oscillating magnetic field can light up a lamp. Does it mean that you can make a light bulb glow by putting it on the induction cooking stove? 91.77.167.192 (talk) 08:38, 7 April 2014 (UTC)

Those induction cookers need a big thick slab of metal to induce currents in. A light bulb filament is not enough. If you irradiated it with millimeter wave or other microwaves, perhaps you could light it. Graeme Bartlett (talk) 09:06, 7 April 2014 (UTC)

Centimeter wavelengths will certainly light up an incandescent light bulb as generations of schoolboys and numerous You Tube videos can attest. --2A01:E34:EF5E:4640:9D8E:1D42:1F74:5600 (talk) 13:33, 7 April 2014 (UTC)

And what if you attach a light bulb to this “thick slab of metal”, will it light up? I'm just curious if it is possible to get something glowing with a cooker of this type.91.77.167.192 (talk) 13:25, 7 April 2014 (UTC)

I don't suggest you do the experiment, but I would think it more likely to melt. What you want is an Induction lamp.--Shantavira|^{feed me} 14:01, 7 April 2014 (UTC)

Could a machine assemble molecules on demand just starting with the atoms?

That would be easier than synthesizing compounds. If you wanted gasoline (C8H18) or cocaine (C17H21NO4), this hypothetical machine would just pick the right atoms and start putting them together. Or maybe, could a machine generate random molecules from a set of atoms? Maybe putting them under pressure, or pass an electrical current through them and see what gets out of the process. — Preceding unsigned comment added by 88.14.192.119 (talk) 17:58, 7 April 2014 (UTC)

How do you put them together fast enough? 12 grams of carbon contains 602,000,000,000,000,000,000,000 atoms. Even if a machine could grab and use a million carbon (and equivalent number of hydrogen) atoms per second, that would still take 602,000,000,000,000,000 seconds to make just 16 grams of methane (CH4). That's a bit more than 19,000,000,000 years. The earth has only existed for 4,500,000,000 years. --Jayron32 18:15, 7 April 2014 (UTC)

(ec, same idea, other numbers) I think you underestimate the number of molecules that make up a useful amount of gasoline. A molecule of octane weights 114 u. Thus a mol of gasoline weights 114 g. That's 6.022×10²³ molecules - in other words, one litre has about 3.6×10²⁴ molecules. If your machine makes a million molecules per second, it would have made about 0.01 litres in the time since the beginning of the universe. A big advantage of chemical reactions is that they happen in a massively parallel manner, thus yielding macroscopic amounts of product in realistic time frames. --Stephan Schulz (talk) 18:21, 7 April 2014 (UTC)

Hmmmm, isn't your body made out of such machines? Count Iblis (talk) 18:42, 7 April 2014 (UTC)

No, it isn't. You can not program yourself to excrete gasoline or cocaine out of your nose. You (that is, any human) can not even produce all the amino acids the body needs to maintain its structure and function; some of them are essential amino acids, meaning you've got to get them from outside (as food) and can not manufacture them internally (although some other organisms can). There are organisms that can produce hydrocarbons suitable as fuel for internal combustion engines; but there are no "universal" organisms that can produce any chemical compound you want on demand. --Dr Dima (talk) 19:17, 7 April 2014 (UTC)

That is the intent of Molecular assemblers - an idea to make very, very tiny robots that are capable of assembling things atom by atom. The way such devices would overcome Jayron's objection is by self-replicating themselves - making enough of them to do the needed work in a reasonable amount of time - then disassembling each other again when the work is done. It's not entirely clear whether such things are possible, given the laws of physics as we know them...but the idea is not without merit.

HOWEVER, this won't get you free gasoline. The amount of energy a machine such as this would require to make gasoline would be many, many times more than the energy you'd get back by burning the gasoline subsequently. The general problem is that you need to apply significant amounts of force to (for example) dismantle a CO2 molecule into carbon and oxgen atoms - and yet more energy to force them back together into the form you wanted.

Anyway - check out the Molecular assembler article - it pretty much explains all of this. SteveBaker (talk) 19:12, 7 April 2014 (UTC)

• They're called refineries, chemical plants, plants, bacteria, yeast, etc. The notion of mechanically assembling molecules, rather than chemically assembling them, strikes me as about as practical as training llamas to become brick-layers. μηδείς (talk) 21:03, 7 April 2014 (UTC)

Are we going out of fertilizer ingredients, in the same way we are going out of oils?

They are the six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); eight micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel (Ni). I dont mean locally on the soil of a concrete location, but globally. — Preceding unsigned comment added by 88.14.192.119 (talk) 18:06, 7 April 2014 (UTC)

Peak phosphorus, Peak copper -- Finlay McWalterᚠTalk 18:09, 7 April 2014 (UTC)

(edit conflict) See Peak phosphorus. This is considered, in some circles, to be a greater problem than Peak Oil, and a major looming catastrophe, specifically because of the need of phosphorus in fertilizers. --Jayron32 18:11, 7 April 2014 (UTC)

Note that only chemical fertilizers are in danger of running out. There's no shortage of manure (especially around elections), and, if night soil is included, we have quite a dollop of that. StuRat (talk) 18:22, 7 April 2014 (UTC)

Au contraire, the problem is there isn't enough bullshit in the world, even accounting for politicians, to cover all the fertilizing needs we have. --Jayron32 18:24, 7 April 2014 (UTC)

If 100% is collected and reused, and no-till farming is employed, along with other methods to prevent soil run-off, then I'd expect very little chemical fertilizer would be needed. StuRat (talk) 18:35, 7 April 2014 (UTC)

(if 100% is reused, then we have no harvest! ;) Our yield of e.g. corn is approaching ten times the historical values [20]. Some of the increase is due to pesticides, breeding, and other methods. But without cheap, concentrated chemical fertilizers, corn yields would be back in the ~20 bushels an acre across the USA cornbelt. And that would drive up the cost of the many food products using corn and it's derivatives. Sure, you can compost everything and do low-input agriculture in your backyard, but that doesn't change the fact the the majority of the agricultural industry in the USA is based off of cheap and widely-accessible processed fertilizers. It is true that agronomically, we know how to do better, and grow with less energy and inputs. But what matters is what the large agribusinesses actually do. SemanticMantis (talk) 18:53, 7 April 2014 (UTC)

You'd need to set up a system to collect sewage from sewage processing plants and move it to farms. We'd also need to stop flushing old meds, etc. A dual sewage system could be set up, with things like meds going to a septic tank, instead. StuRat (talk) 19:06, 7 April 2014 (UTC)

• Um, phosphorus isn't destroyed. If run-off into the oceans is a problem, then the oceans are also the solution--recovery from salt pans and, as the price increases, use of nuclear energy to extract trace elements from the ocean. It's simply silly to assert we are running out. It's just becoming more expensive to procure. μηδείς (talk) 20:58, 7 April 2014 (UTC)

I would disagree with that. Recycle before it goes into the sea would help prevent algae blooms that cut off light to the sea-floor, which cause the seabed plants to die off, which in-turn removes a vital food source for the local coastal sea-life which in turn means we reduce the amount sustainable seafood that we enjoy. This is a growing problem around the world and some sizeable lakes too are now dead. The sea is too large a volume for the concentration of Phosphorus to increase above 13mg/kg to point were it becomes economic to recover it.--Aspro (talk) 21:55, 7 April 2014 (UTC)

I didn't say anything about not recycling or preventing run-off, which will also become increasingly economically urgent. The problem is the question as posed is a typical "what if all the farmland gets used for parking lots?!?!" question that ignores market forces. As phosphorus or farming land or any commodity gets more scarce its value increase, and more money is invested into procuring phosphorus or land values increase, and people sell their sprawling lots and move into efficient high rises high-rises. You are making the same mistake. At some point if phosphorus becomes rare its price will increase and people will invest in new ways to concentrate it and it will be economical to recover it at 13mg/liter.

Hmmm, 160E6 metric tonnes/ yr currently produced = 1.6E11 kg, divided by the 13 mg/kg seawater = 1.2E16 kg of seawater to process. The Nile discharges 2830 m³/s, x365.25x24x60x60x1E6 = 8.9E16 kg/s. So if you desalinate a substantial river of water to meet the needs of dry surface areas, in theory you should get enough potassium phosphorus left over to do the fertilization. If you can separate it somehow. It takes a lot of energy, but so does any solution to the vast deserts predicted to arise from global climate change. Wnt (talk) 23:08, 7 April 2014 (UTC)

When did we switch to potassium? There's no shortage of potassium. I'm assuming you just mistyped. --Trovatore (talk) 23:36, 7 April 2014 (UTC)

Burn seaweed in a steam engine (Algae fuel) then process the ashes. Jim.henderson (talk) 23:43, 7 April 2014 (UTC)

This brings back the old proposal to build a canal to flood the depression in the African dessert from the Med Sea. You could then let it dry out to get your phosphorus, but you'd also have to remove the salt. StuRat (talk) 23:44, 7 April 2014 (UTC)

Ah - Qattara Depression Project. Wnt (talk) 00:30, 8 April 2014 (UTC)

Yep, that's the name. Thanks. StuRat (talk) 08:44, 9 April 2014 (UTC)

Or process brine left over as water evaporates to a low level behind the proposed Red Sea Dam. Since the Red Sea is of fairly recent origin, it's hard for me to feel too bad about destroying a major ecosystem, if the energy goes a substantial way toward ending global warming and provides irrigation for the entire region. Besides, I have a crank notion about it as a prophesied solution to the Israel-Palestine conflict. :) Wnt (talk) 00:18, 8 April 2014 (UTC)

(Un-indent) What is all this idle talk about extracting phosphorus from seawater, flooding the Sahara, damming the Red Sea, etc., when a much more cost-effective solution has already been devised -- that being to precipitate phosphates out of municipal sewage (at the sewage treatment plant) with, e.g., calcium hydroxide? 24.5.122.13 (talk) 05:13, 8 April 2014 (UTC)

I think people are assuming that first we manage to use up all the cheap phosphorus, then we say oh no, what are we going to use, when it's already washed out to sea. Which, given our track record, seems not unrealistic. :( Besides, I was thinking of this as a byproduct only - the purpose of the Red Sea Dam is electrical power, and if taken to a perhaps unrealistic extreme, creation of new lands irrigated by water desalinated with that abundant power. Wnt (talk) 19:11, 8 April 2014 (UTC)

As Wnt correctly stated (I assume it was Wnt, even though the comment appears to be unsigned), the price of phosphorus will begin to rise LONG before all the apatite is mined out, and THAT will make large-scale recovery of phosphorus from sewage the next major source of the stuff even BEFORE the apatite runs out -- and THAT, in turn, will preclude your scenario of all the readily available phosphorus "washing out to sea". 24.5.122.13 (talk) 05:59, 9 April 2014 (UTC)

I don't see the unsigned comment, but ... while biology may not know theory, economics is outright hostile to logic. The system that gives us Bitcoins and housing bubbles may or may not react sanely to a shortage of phosphorus. Wnt (talk) 11:42, 9 April 2014 (UTC)

24.5.122.13 (talk) 01:07, 10 April 2014 (UTC)

Economics is exceedingly and brutally logical. It's people that aren't. The market makes very logical and unemotional corrections. People don't like it and try to manipulate it to "soften" the reality. Left on it's own, the market will correct for overpopulation. It's people that object to the outcome. (people manipulate the other way, too, like subsidizing fuel from corn/food). --DHeyward (talk) 02:46, 10 April 2014 (UTC)

Considering that the "market correction" for overpopulation involves millions of people dying, by starvation, war, disease, etc., I can understand why some might object. (It's even possible that it could lead to the extinction of the human race, via nuclear or biological warfare.) StuRat (talk) 03:03, 10 April 2014 (UTC)

LCD TVs that are not black?

My father had a question for me last week. One of his customers had told him that LCD TVs would fit much more nicely to their home design if they were white when powered off instead of black. My father asked me if this is possible. I didn't have any idea, as electronics design is not my profession, it's computer software. I know at least that some monochrome LCDs are light gray when powered off, and the lit crystals are black, but is this kind of thing at all possible on a full-colour LCD? JIP | Talk 18:17, 7 April 2014 (UTC)

I suggest the TV be placed in a cabinet and the doors closed when not in use. (Eventually, I hope the cost of displays will come down and reliability will go up to the point where we can use them as lights, always on, displaying an all-while panel or whichever background we prefer.) StuRat (talk) 18:29, 7 April 2014 (UTC)

One problem I foresee is that if the error correction is not spot on for every frame, one will notice lots of bright speckles on the picture. Whereas now, when a few pixels at a time are randomly going dark here and there for each and every frame, they are not perceived by the eye. I seem to remember the luminous signal on analogue TV is negative going, for the reason that the radio static is less noticeable when there is a good signal to noise ratio. When the S/N ratio diminishes towards no broadcast signal at all, even the cosmic background radiation can be seen as a mass of speckles often referred to as snow.--Aspro (talk) 22:57, 7 April 2014 (UTC)

Permit a sceptic to doubt that Aspro's TV is capable of displaying cosmic background radiation. 84.209.89.214 (talk) 12:12, 8 April 2014 (UTC)

Oh. It is always wise to be a sceptic (especially if the inland revenue says you owe more tax than the 1% pay in ten years) - so count yourself permited. Here is a link (obviously, if the Big Bang theory gets proved wrong – you can demise it) : The CMB is so bright at millimetre-wavelengths that if you de-tune an old analogue TV to show the snow-like static, a few percent of the signal your TV is picking up will have come from the start of the Universe.. Not a lot of people know that.--Aspro (talk) 23:40, 8 April 2014 (UTC)

And Wikipedia turns out to have a section on the disadvantage of positive modulation (luminance) that I was referring to. 405-line_television_system#Susceptibility_to_impulse_interference.--Aspro (talk) 00:02, 9 April 2014 (UTC)

Analogue TV's receive at metre and decimetre (VHF and UHF) but not millimetre wavelengths and their no-signal display of electrical noise is dominated by front-end Johnson–Nyquist noise i.e. thermal noise in the input stage transistor. The quoted claim that Cosmic noise forms "a few percent of the signal your TV is picking up" lacks any quantitative values of power or criteria for why CMB is purportedly visible. Does the random speckle display on Aspro's TV look noticeably different when it is moved from a tent to a metal shielded room? Is Aspro in the habit of lecturing to awed visitors that his TV is a viewport to the start of the Universe? And there's no argument about the visibility of impulse interference. 405-line monochrome TV receivers often had an "Interference limiter" control, actually a peak video level clipper or inverter, that had to be carefully adjusted somewhere between white crushing or having white spots bloom on the screen when cars drove by. 84.209.89.214 (talk) 14:17, 9 April 2014 (UTC)

I don't believe that this is easy. Current TVs display white by turning on a backlight, and making the LCD clear so the white backlight can shine through. (roughly speaking) So, unpowered, they're going to be, if not black, then at least dark.

Purely reflective screens can be light-colored when they're powered off. (Think of a digital watch, or a calculator.) But I don't think those would make a very good TV. (Which you want to glow in the dark.) APL (talk) 15:28, 8 April 2014 (UTC)

From what I understood from what my father's customer wanted, they wanted the screen to be white without any sort of electricity or light output required. It would be practically the inverse of current full-colour LCD technology - instead of having the pixels dark and grow lighter when powered up, they would be light and grow darker when powered up. I understand that this means that when viewed with no outside light source, such as in a darkened room, the whole TV would be pretty much invisible, regardless of what it was showing. I just want to know that even if we accept this, is this kind of thing at all possible, in full colour? JIP | Talk 18:10, 8 April 2014 (UTC)

3-color reflective LCD display

I think HP used to make some color graphing calculators with that sort of display, but I'm having trouble finding a reference so it may have been a different brand. Obviously the update time and pixel density were nowhere near what you need for a TV, but the basic principle has been implemented. Katie R (talk) 11:52, 9 April 2014 (UTC)

Ahh, here it is. Casio's "three-color" display did black red green and blue. It's a looong way from a TV display, but no one has had a reason to develop that technology. Katie R (talk) 11:57, 9 April 2014 (UTC)

Ah, I had almost forgot about those Casio colour graphics calculators. I used to own a couple of models myself, and I think I still have one. From what I can recall, they accomplished the four-colour reflective LCD with two monochrome LCDs laid on top of each other, with different colours. This leads to a new question: Both Casio and Texas Instruments have now developed graphing calculators with 65536-colour displays. Does anyone know if these LCDs also utilise this reflective technology, or are they backlit the same way as LCD TVs and monitors? JIP | Talk 18:23, 9 April 2014 (UTC)

I have a coworker that just purchased a new TI one. It's a backlit display, and it seems a bit lower quality than the average modern smartphone screen, but incredible compared to the older calculators. Of course, the battery doesn't last for months like the old ones did. Katie R (talk) 19:45, 9 April 2014 (UTC)

It's certainly possible to make color displays that are reflective instead of backlit. Pixel Qi makes some that will replace the screens on certain laptops, so you could certainly watch a movie on them if you wanted. It'll never get the brilliant colors of a backlit TV on a purely reflective screen though, it's always going to look a bit muted. (But maybe you'd get used to it. Even a glossy magazine cover looks dull and lifeless if you hold it up next to your TV, but they look great on the newsstand next to the other magazines.) APL (talk) 14:15, 9 April 2014 (UTC)

Hmmm, how's electronic paper doing? (I think it still has problems, and even in concept might not be well suited for TV use) Wnt (talk) 19:08, 8 April 2014 (UTC)

Is it true that the Pacific Ocean makes the west coast of North America warmer?

My friend told me he wants to move to Vancouver because it's warmer there, and he insists that it's warm because the Pacific Ocean makes the climate warmer there. Is this true? ScienceApe (talk) 19:04, 7 April 2014 (UTC)

Yes, similar to how the Gulf Stream in the Atlantic makes Western Europe warmer. The water can be warmer near Vancouver, Seattle, etc, than in Los Angeles. Of course, that warm water also brings lots of rain, and global warming may eventually change the ocean currents. StuRat (talk) 19:11, 7 April 2014 (UTC)

It is Alaska_Current. Ruslik_Zero 19:12, 7 April 2014 (UTC)

Thanks, StuRat (talk) 08:46, 9 April 2014 (UTC)

More moderate; both less cold and less hot; see Oceanic climate Jim.henderson (talk) 19:13, 7 April 2014 (UTC)

See http://cliffmass.blogspot.com/2012/06/why-are-coastal-water-temperatures.html for a pic showing unusual cooler water temps hugging the coast. StuRat (talk) 19:16, 7 April 2014 (UTC)

(ec)Warmer than where? Large bodies of water have, in general, a mediating influence on peak temperatures, both high and low. So Seattle is warmer in January than e.g. Bismarck, North Dakota. On the other hand, Bismarck is warmer than Seattle in Juli. Also see continental climate vs. oceanic climate. --Stephan Schulz (talk) 19:17, 7 April 2014 (UTC)

Note that water behaves like land if it freezes solid, but remains mostly liquid near Vancouver year-round. And where the currents go the other way, as in Maine or Korea, it's not particularly warm in winter. StuRat (talk) 19:19, 7 April 2014 (UTC)

Even in Maine, costal areas are a lot warmer in winter than North Dakota. Similarly, South Korea is warmer in winter than North Dakota. North Korea has a continental climate, with winter temperatures influenced by weather systems coming out of Siberia. But still, its winter is not colder than North Dakota's. --Stephan Schulz (talk) 21:46, 7 April 2014 (UTC)

Still, if one wants a Canadian city with a mild climate, with little snow, then Vancouver is a better choice than Newfoundland: [21]. StuRat (talk) 00:28, 8 April 2014 (UTC)

Well, St. John's, Newfoundland and Labrador is about 150 miles further north than Vancouver, so that may have a bit to do with it as well. --Jayron32 01:49, 8 April 2014 (UTC)

• "The Pacific Ocean makes the west coast of North America warmer" is only true down to the latitude of Seattle or so. Farther south the ocean has a cooling effect. In San Diego, for example, it is usually very pleasant if you are within a couple of miles of the ocean, but rapidly gets blazing hot if you go a little farther inland. Looie496 (talk) 01:57, 8 April 2014 (UTC)

If all you care about is the annual average temperature, then the Pacific ocean doesn't have a large effect. Along the Pacific coast, annual average temperatures run from about 1 C below to 2 C above what you would expect based solely on latitude and elevation. That said, the ocean has a very strongly moderating effect on seasonal and weather variation. The difference between winter and summer along the Pacific coast is only 10 C or less, while 20-30 C ranges are typical for most of the US. Similarly, there is much less variation is weather. The Pacific Coast isn't much warmer on average, but it is more predictable, and one can avoid both extreme heat and cold. Dragons flight (talk) 19:42, 8 April 2014 (UTC)

Like others here, I too suspect Science Ape's friend is referring to the low temperatures (winters) being warmer on the Pacific Coast. This map of the US, for example, shows the average annual extreme minimum temperatures 1976 - 2005. I found it in our article on hardiness zone. ---Sluzzelin talk 09:07, 9 April 2014 (UTC)

Interesting. I wonder why the Pacific coast has such a wide band which is warmed by the sea, while in Maine it's such a narrow band. Is this due to the prevailing wind direction ? StuRat (talk) 09:55, 9 April 2014 (UTC)

Yes - see Westerlies. Wnt (talk) 18:24, 9 April 2014 (UTC)

Inflatable hot tub mystery.

We have an inflatable hot-tub. It's construction is more or less identical to a kiddies paddling pool - three stacked inflatable rings with an inflatable "floor", each with it's own air valve. The "floor" valve is underwater, the other three are on the outside of the tub. The thing is made of some kind of very heavy duty vinyl and is about 5' in diameter and two feet deep and contains around 250 gallons of water at around 38 degC (100F). There is a separate heater/water pump and a gizmo to blow air into the water via a channel around the inside of the bottommost ring..but I don't think that's relevant here. We've been using it off and on for about 6 months - and it's never been completely emptied or deflated in all that time.

The other day, we had occasion to empty the water and deflate all of the air chambers. I was surprised to find that the "floor" had about two gallons of water sloshing around INSIDE the sealed air bladders.

I'm totally mystified as to how the water got in there! The floor is under considerable pressure (2 feet of water resting on it) - so if there were some kind of a leak, you'd expect it to deflate in short order - and it didn't seem to be deflated to any noticable degree. The air must be at about the same pressure as the water when the tub is full. It's conceivable that the air we put into the floor part at the outset was really humid - but even if all of the water vapor condensed out of that air...there was FAR too much water in there to be accounted for in that way.

It's not exactly important that I know the answer - but it's been bothering the heck out of me for the past week...and I can't explain it!

There is a picture of the hot tub here:

 http://www.ebay.com/itm/like/350868160135?lpid=82

...ours has an outer protective cloth cover in bright blue and an inflatable "lid" that covers it when not in use - but that's the thing I'm talking about here.

SteveBaker (talk) 19:31, 7 April 2014 (UTC)

I'd say an equal volume of air leaked out as the water that leaked in, so the total volume remains the same. The water likely leaked in at the valve, the air might have also leaked out there, but too slowly to notice the bubbles, or perhaps there's a pinhole leak elsewhere. The water pressure might go up instantly when you first sit in the tub, just enough for a few drops of water to drip in each time.

It might actually make more sense to fill the bottom with water than air, as that should make it more stable in the wind. It would also make it heavier, but if you don't plan to move it until you drain it, then that's OK. StuRat (talk) 20:06, 7 April 2014 (UTC)

My problem with that idea is that when you step into the tub, the weight of your foot on the floor must increase the pressure of the air inside above that of the water on top of it...so I could believe in a bubble being expelled through a tiny hole each time - but the water would have to force it's way in through a positive pressure gradient. It's not like the floor is a rigid container either - it's flexible/stretchable plastic - and you'd think that the tension it adds would keep the air pressure consistently higher than the water pressure. SteveBaker (talk) 20:29, 7 April 2014 (UTC)

In that case, maybe when you get out, the lowered pressure in the air bladder sucks in some water to replace the gas bubbles which escaped when you got in (escaped from the air bladder, not from you, as those gas bubbles aren't relevant here). StuRat (talk) 00:25, 8 April 2014 (UTC)

• Get a copy of the owner's manual or contact the manufacturer. They will likely have something to say about the issue. μηδείς (talk) 20:52, 7 April 2014 (UTC)

I think a pinhole leak/defect is always possible; it's also conceivable that water could permeate the polymer directly. (Trying to calculate that, based on the exact polymer and plasticizer compositions, would be a decent test of the Refdesk). Wnt (talk) 22:54, 7 April 2014 (UTC)

Even if there is just a bit of vapor permeability (whether directly through the polymer layer, or through the valves) there will be tendency for liquid water to accumulate on the bottom of the bladder. The liquid in the hot tub (and the polymer layer in contact with it) is likely to often (or always) be at a temperature higher than the ground under the tub. Warm vapor that enters through the top side of the bladder cools and condenses when it reaches the bottom, forming a pool of liquid water...that will just keep growing, for however many months the tub remains in use. TenOfAllTrades(talk) 14:02, 8 April 2014 (UTC)

Did you inflate it yourself? Is it possible someone deliberately put water in to anchor it before inflation? -- Q Chris (talk) 14:52, 8 April 2014 (UTC)

I'm going to guess that the floor has one of those valves that is in-only unless you squeeze it a certain way.

If so, and if the water pressure was higher than the floor's air pressure (or became so thanks to temperature changes, or momentary changes in the weight people put on it.) water could flow into the floor without an actual "leak", but air would not be able to flow back out, per its design.

Ok, it's not a perfect theory, and it requires that the cap on the valve is not water-tight, but it could be close. APL (talk) 15:11, 8 April 2014 (UTC)

April 8

3D Printing using soil

Are there any useful building materials in soil? Like if one day in the future they have such advanced 3D printers that you can just take some soil from your back yard, dump it into the machine, and it's able to build something useful out of it. ScienceApe (talk) 13:06, 8 April 2014 (UTC)

Depending on what type of soil you have, perhaps:

1) Clay: Can be fired to make ceramics.

2) Sand: Can be melted to form glass.

In both cases, you can't use current 3D printing techniques to make objects directly out of those materials, but you might be able to use a mold or form you create using 3D printing to make an object out of clay or sand. StuRat (talk) 13:13, 8 April 2014 (UTC)

Yes, there are useful building materials in soil. You don't need to use a 3D printer. Mudcrete is often used in road construction, while Rammed earth has been used for building for many millennia. As you will see from the top of the page, though, we are unable to provide predictions or speculation about future technological developments. RomanSpa (talk) 13:25, 8 April 2014 (UTC)

Soil has been used as a building material for thousands of years. It is literally the first building material. Besides clay, ceramics, and glass noted above, there's other building materials made essentially out of dirt: brick, adobe, mudbrick, sod, Cob, and dozens more which I am tired of searching for. --Jayron32 14:24, 8 April 2014 (UTC)

If you're imagining a sci-fi "matter converter" where random unsorted matter is dumped in one end and it's automatically sorted, purified, chemically altered, and used for manufacturing, then we're a long way off.

However, if you're looking for just crudely converting available matter into stuff, you might be interested in this Solar Sinter project, or even more basic, but probably more useful, this open-source brick press from the Global Village Construction Set.

APL (talk) 15:04, 8 April 2014 (UTC)

What about stuff like silicon to make electronics? ScienceApe (talk) 15:39, 8 April 2014 (UTC)

Silicon certainly exists in (some) soil. But purifying it would be an ordeal. It's not impossible that in some sci-fi future the silicon is somehow separated for use making chips on demand. That's way in the future though. I don't think anyone even has a good idea how that would work. If we're talking future sci-fi tech, Carbon nanotubes might also be used to make electronics. There's plenty of carbon in most soil.

To be honest, most dirt is probably best used for growing stuff in. Either the old fashioned way, or in some sci-fi way. APL (talk) 16:07, 8 April 2014 (UTC)

That reminds me of another use for dirt, you can put it in a form (perhaps made with a 3D printer) and grow a fungus inside the form to hold it all together, then seal it in with a vinyl covering, to make a cushion. StuRat (talk) 17:10, 8 April 2014 (UTC)

A common ingredient in quartz sand is silicon dioxide, so you can purify silicon from that. StuRat (talk) 17:07, 8 April 2014 (UTC)

Much of the Earth's crust is feldspar, which contains aluminum, silicon, and oxygen. If we had unlimited cheap power, we could make aluminum conductors and structural components, silicon semiconductors, hard corundum pieces out of it. Wnt (talk) 22:10, 8 April 2014 (UTC)

I'd think circuit boards would be first. Layers of circuit traces, via holes and insulators. A 4 layer PCB would be an awesome 3D printer application for multiple element printers. You would then solder the ICs to it. That would be a huge prototyping breakthrough. --DHeyward (talk) 03:02, 10 April 2014 (UTC)

Antibiotic resistance arguments applied to vaccines

If it is recommended that usage of antibiotics be limited to discourage antibiotic resistance, why does it not then follow that vaccine usage be limited to discourage vaccine resistance? (Note: I am not a supporter of the anti-vaccination movement, but I have heard this argument against vaccines advanced by some anti-vaccination partisans and would like to hear a counterargument.) —SeekingAnswers (reply) 13:55, 8 April 2014 (UTC)

Vaccines are far more specific than antibiotics. A typical antibiotic acts against a broad range of bacteria, but a typical vaccine only acts against one very specific type of virus. In fact often the biggest challenge in developing a vaccine to is get it to work against all the different strains of a particular kind of virus. The consequence is that resistance to one type of vaccine does not cause problems in dealing with any type of virus except the specific one that that vaccine is designed for. Looie496 (talk) 14:12, 8 April 2014 (UTC)

Also, it should be noted that antibiotics act as vaccines for the bacteria they kill. That is, the general idea behind antibiotic resistance is that bacteria are exposed to an agent designed to harm them, and they adapt so the agent isn't harmful anymore. Which is almost exactly what a vaccine does for you. In the first case, you're training bacteria to not be harmed by the antibiotics, and in the second case, you're training yourself to not be harmed by viruses. Furthermore, in science we don't base our understanding of the world by incomplete analogy. We base it by actual data. Antibiotic resistance is an observed phenomenon, and is happening. For most diseases we vaccinate against, we aren't finding any such evidence of that happening. I say most, because there are SOME diseases which show resistance to vaccinations: [22] but as that reference makes clear, most of those are the exception and not the rule. --Jayron32 14:19, 8 April 2014 (UTC)

Sorry, but "antibiotics act as vaccines for the bacteria they kill" is at best misleading. Vaccines work by activating the body's immune system; antibiotics work by attacking bacteria directly. Vaccine resistance is possible, but the only way for a virus to develop resistance is for it to get better at overcoming the immune response, and there is strong evolutionary pressure in that direction even without any vaccine being present. Looie496 (talk) 14:48, 8 April 2014 (UTC)

No, vaccines cause the host organism (you) to develop resistance by exposing them to the harmful agent. You know, like antibiotics cause the host organism (bacteria) to develop resistance by exposing them to the harmful agent. The exposure to an agent which causes resistance to that agent is in common to both how vaccines prevent disease in you, and how antibiotic-resistance works in bacteria. --Jayron32 15:00, 8 April 2014 (UTC)

This sounds like you're thinking of a collection or colony of infecting bacteria as a superorganism or similar. Exposure to antibiotics over time can lead to a colony of resistant bacteria, but any individual either resist, or dies from the antibiotic, right from the start. Over time, only resistant individuals are left. This is rather different than engaging the human immune system. (At least that's the common mode of action... Do you have a ref for acquired resistance to antibiotics within an individual bacterium over time?) SemanticMantis (talk) 16:15, 8 April 2014 (UTC)

That's exactly correct. --Jayron32 16:37, 8 April 2014 (UTC)

Well, vaccines do change over time - for example, influenza vaccine is different every year, and the virus keeps evolving, in part to get around current natural immunity and in part to avoid the vaccines. With many other viruses it's not so much of a problem - for example, smallpox and cowpox parted ways a long time ago, so I doubt smallpox will come up with a way to avoid cowpox-based immunity any time soon (not without help anyway). Then there's HIV, which evolves so damn fast it avoids even the natural immune system, and so far vaccine makers are still struggling. Wnt (talk) 16:35, 8 April 2014 (UTC)

I take your point that influenza quickly evolves, and we make new vaccines every year. But I'm not sure that's "resistance," because the virus is merely scrambling the features that identify it to our immune system, and it would do that just as much even without vaccines, right? Sure, it's a bit of a red queen hypothesis situation, but I don't agree with the semantics of saying "flu resists last year's vaccine." -- It's simply that last year's vaccine loses its effectiveness as the virus mutates on. SemanticMantis (talk) 21:19, 8 April 2014 (UTC)

p.s. (Do we have a WP:TELEOLOGY warning? No? I'm pretty sure you'd agree that the flu has no goal or end in mind ;)

Well, when H5N1 came out, I remember reading stories that it was spreading quickly due to not being affected by existing vaccines. I don't think it's as dramatic an effect as antibiotic resistance simply because we don't give it time to add up - every year the vaccine can be made differently, while the drug remains the same. Wnt (talk) 11:38, 9 April 2014 (UTC)

Viruses don't evolve with natural selection the way other living organisms do. Influenza is a classic virus as it moves from species to species picking up pieces as it goes. Influenza moves between pigs, birds and humans. It's survival is mixing different elements of each and is horizontal gene transfer. Whether a particular strain has more human effects or not is not particularly relevant to its survival. Viruses like small pox and polio generally affect only humans so there is no development or adaptation. Because of that, small pox has largely been eradicated. The biggest threat is when a virus picks up a gene sequence that gives it a route to humans. --DHeyward (talk) 03:54, 10 April 2014 (UTC)

A key distinction between the two is that vaccines don't directly act upon viruses, they act upon the host's immune system, which does all the real "work" in fending off disease. That is why it "doesn't follow." Think about your analogy from the other direction too: there is no analogue to herd immunity in the case of antibiotics and bacteria, because an antibiotic doesn't spread itself from host to host by its own action. SemanticMantis (talk) 22:02, 8 April 2014 (UTC)

Exactly the opposite. Vaccination promotes the survival of humans resistant to viruses. Antibiotics promotes the survival of bacteria resistant to antibiotics. It is probably true that more rare/severe viruses become higher value targets but only because the more common ones are eradicated. --DHeyward (talk) 00:57, 9 April 2014 (UTC)

About a birds name

I have seen a bird in towns in eastern side of India in West Bengal.the birds are big in size have copper coloured wings and rest of the body is black.But unfortunately I dont know the name of this bird.Please tell me the name of this bird and its habits.Please mention if there is any Wikipedia article about this bird.Another type of bird that has come to my notice is even smaller than a sparrow but I am startled and amazed by its colour.There is a greenish lustre or blueish green lustre.It appears as if the bird's feathers act as a diffraction grating.It has very thin carved beak which I think can prominent feature.Please identify this bird and give its name and corresponding Wikipedia article.Pleasemention the habits of these birds and where you have seen them.117.194.229.124 (talk) 14:01, 8 April 2014 (UTC)

It sounds like a member of the Starling or Myna family, many of which are known for their iridescent feathers as you describe. --Jayron32 14:09, 8 April 2014 (UTC)

I see the picture of Starlig but it doesnt match the second type of bird I queried about.Please dont forget to mention about the first bird.117.194.229.124 (talk) 14:14, 8 April 2014 (UTC)

A straightforward Google search finds the Greater Coucal. Looie496 (talk) 14:17, 8 April 2014 (UTC)

There are hundreds of different species of birds in the starling family. Your second type of bird could be any number of them, including the Common Starling, which also has a number of subspecies. Don't just look at one picture in the first article you find. Search through pictures of different kinds of starlings and see if you find any matches. --Jayron32 14:21, 8 April 2014 (UTC)

Searching Google for Greater Coucal I got resuls inn image section purplecoloured sunbird and luckily it was the second type type of bird I asked about.The first type of bird is Greater Coucal. Actually in our locality there is overcrowding of crows a menace with some sparrows so it is a delight to see these wonderful birds.Thanks for your kind help.117.194.229.124 (talk) 14:53, 8 April 2014 (UTC)

Let me just add a pointer to our Purple Sunbird article. Looie496 (talk) 16:05, 8 April 2014 (UTC)

Chemical analysis

Suppose a person stumbles upon a substance and he wants to know the chemical composition of the substance.The substance can be quite complex mixture of organic and inorganic compounds.How will the chemist know about what are the compounds present and in what proportion.How this used to be accomplished when there was no NMR spectra or computers available and how is it done nowadays.Isthis type of analysis required in forensic studies and where else this type of analysis required. Can natural substances like fruit skin,fruit juice and products like soaps perfumes creams ointments can be analysed to dtermine composition and what knowledge and expertise and what level of nhemistry knowledge is required to do this.117.194.229.124 (talk) 14:11, 8 April 2014 (UTC)

The first thing the person would have to do is some form of separation techniques to get the mixture into its component substances. A common method is to combine a separation technique with an analytical technique to then identify the substances as soon as they are separated. Analytical systems like GC-MS or LC-MS (for gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry respectively) are commonly used for that exact purpose. You can also do your separation techniques prior to doing your analysis work; for example using Ion-exchange chromatography and then isolating each product and doing analysis individually. This is commonly done for techniques that don't "marry" well to a gas chromatograph, such as Infrared spectroscopy or Nuclear Magnetic Resonance. --Jayron32 14:35, 8 April 2014 (UTC)

The methods you mentioned require computers or electronics but without these using these gadgets how can the work be done as was the case in 19th century or early 20th century.Or was such analysis was impossible at that time.117.194.229.124 (talk) 14:58, 8 April 2014 (UTC)

Basic chromatography techniques such as thin-layer chromatography and paper chromatography and ion-exchange chromatography could be used to separate mixtures without the use of electronics at all. Prior to the use of electronic methods of analysis, the only methods of chemical analysis were called wet chemistry methods, and basically involved a series of chemical tests to elucidate the structure of unknown compounds. For just a few examples, there's the Baeyer's test, universal indicator, the Van Slyke test, Seliwanoff's test, the iodoform test. --Jayron32 15:07, 8 April 2014 (UTC)

If all matter outside the solar system ceased to exist?

To put the question somewhat more specifically than the header title above puts it, what would be the effects on the solar system if all matter outside a radius of, say, 50 astronomical units from the sun (that is, from approximately outside the Kuiper Belt) spontaneously ceased to exist? This is the only counterfactual; in all else, the laws of physics remain the same. Also to clarify, this is a one-time event; matter that after this event passes across the 50 AU boundary does not cease to exist. (A clarification edit: by "matter", I mean objects with rest mass, so electromagnetic radiation, for instance, would continue to exist outside the boundary.) I'll mention several specific phenomenon, with related questions, in particular.

First, how quickly would scientists realize that this disappearance of matter had occurred, and what pieces of evidence would this conclusion rely upon?

Second, I suspect that without the gravitational effects exerted by matter outside the solar system to counterbalance the gravitational pull of the sun, objects (including planets such as our Earth) would begin to fall toward the sun. Is this supposition correct? And if it is correct, how fast would the fall be (that is, how long from this event before the Earth is swallowed by the sun)?

Third, what would the ultimate fate of the solar system be, given this event? I assume it would be some kind of thermodynamic heat death, but how long would the process take? Would the remaining matter from within the solar system all become packed together forever from gravitational effects, or would some or all of the matter disperse, getting forever further away?

I'd also be interested in hearing about whatever other effects people here can think of.

—SeekingAnswers (reply) 15:18, 8 April 2014 (UTC)

First, 7 hours after the event the Fixed stars disappear from the night sky. It takes about 24 hours for the phenomenon to be confirmed by all earth-bound telescopes but by the 2nd day there are videos on YouTube and TV "expert" commentators explaining whether the End of the World is nigh. A Stock market crash ensues.

Second, the nett pull of the rest of the Universe on our solar system is virtually zero which is why we don't accelerate madly in any particular direction. Gravitational force of the Sun remains the dominant factor keeping the planets in their present orbits unchanged.

Third, if you can explain why the solar system (Address: Local Interstellar Cloud, Local Bubble, Orion–Cygnus Arm, Milky Way) was specially preserved through this singularly destructive event, you probably have the basis for a Belief system that gives a comforting answer to any remaining questions. 84.209.89.214 (talk) 15:46, 8 April 2014 (UTC)

Good and basically comprehensive answer, 84. But I am not so sure there wouldn't be a huge number of people concluding that it was not the rest of the universe that had been destroyed, but we sinners who had been snatched into the void. μηδείς (talk) 16:26, 8 April 2014 (UTC)

Regarding the fixed stars disappearing after 7 hours: In my original question, when I mentioned "matter", I was specifically referring to objects with rest mass. So fixed stars wouldn't disappear from our view after 7 hours, since photons from beyond 50 AU that were emitted before the stars ceased to exist would continue to stream toward us. So fixed stars disappearing that quickly couldn't be what tips everyone off that something has happened.

And on the third part, still, what would happen eventually in the end? Would everything be drawn together or disperse?

Also, if I'm understanding your answer, basically, other than human panic, there would be no real negative effects on Earth?

—SeekingAnswers (reply) 16:50, 8 April 2014 (UTC)

IP 84 has already answered your answer correctly, regardless of your further qualification. You seem to know that the light doesn't disappear if the light doesn't disappear, so your question would seem to be resolved. μηδείς (talk) 20:51, 8 April 2014 (UTC)

cosmic rays would greatly decrease, possibly leading to a decrease in cancer, though the health risk or benefit of low level radiation is unclear; see hormesis. We would also be freer to send out interstellar spacecraft, apart from one small problem. Interest in the Pioneer and Voyager spacecraft would suddenly explode as people became curious if their impact with or passage through the "barrier" could be detected. I think most of us would assume the barrier was some sort of alien quarantine or embargo, or a failure in an existing system meant to simulate an unpopulated universe. Wnt (talk) 16:41, 8 April 2014 (UTC)

Seems like Mach's principle would be relevant. Katie R (talk) 16:51, 8 April 2014 (UTC)

If light and other EM radiation kept coming in from the former stars, it would take 4.3 years for the nearest stars to go dark. So, we would know something serious was going on then. I'm not sure if we would detect anything before that, such as the lack of dust clouds just outside the border, or the lack of gravitational perturbation on Kuiper belt objects from nearby stars (this would result in fewer comets, eventually, but this could take thousands of years to become noticeable). The solar system no longer orbiting the galactic center wouldn't be noticeable, as the gravity from the galactic core was exactly counterbalanced by our orbit. StuRat (talk) 17:21, 8 April 2014 (UTC)

For one thing, the Voyager spacecraft would both stop communicating at the same time. Eris and Sedna would disappear from telescope images. --Bowlhover (talk) 18:57, 8 April 2014 (UTC)

As other people already pointed out, there wouldn't be any noticeable perturbation in planetary orbits. But there would be an interesting effect when the last light of a given star reaches us: There is a lot of electromagnetic radiation within a star that is normally prevented from escaping quickly by the matter (plasma) of the star. And that would then escape at once, so for the last few seconds before becoming invisible, a star would become a lot brighter (for a timespan of its diameter divided by the speed of light, so e.g. 0.65 seconds for Proxima Centauri and 8 seconds for Sirius A).

And a similar thing must happen with the gravitational field of stars, which should relax and dissipate as gravitational radiation (someone will think of Birkhoff's theorem (relativity): A star is often approximately spherically symmetric, and a spherically symmetric metric is static and thus non-radiating according to General Relativity, but General Relativity isn't really compatible with things suddenly disappearing; and neither is Maxwell's electromagnetism). So gravitational wave detectors will finally detect something a few years after the event.

Icek (talk) 19:28, 8 April 2014 (UTC)

If we're going with the premise that the light remains but not the matter, note that it takes something like 10,000 to 170,000 years for gamma rays to escape the Sun as visible light. So in that second the star would get something like a trillion times brighter, all in hard radiation. Alpha Centauri starts at magnitude 1.3, so it would come out at something like 3 orders of magnitude brighter than the sun, in X-rays. Not a nice surprise. :) But then again, how much of the lifespan of the gamma rays inside the Sun is counted as "associated with" matter enough that it would be disappeared with the matter, and how much as "free"? (I don't think you can frame the premise meaningfully really??) Wnt (talk) 20:12, 8 April 2014 (UTC)

If you ask the question of what happens if a charge (like an electron or proton in the star) disappears from the viewpoint of Maxwell's equation, you run into a contradiction: Assuming a spherical charge distribution, and the charge becoming less with time, the $\mathbf {E}$ field changes according to

$\nabla \cdot \mathbf {E} ={\frac {\rho }{\varepsilon _{0}}}$

Then everywhere tangential magnetic fields should be created according to

$\nabla \times \mathbf {B} =\mu _{0}\left(\mathbf {J} +\varepsilon _{0}{\frac {\partial \mathbf {E} }{\partial t}}\right)$

where $\mathbf {J}$ is zero (no current).

But that's not quite possible in a spherically symmetric problem.

The only more fundamental theory is quantum field theory, and I guess renormalization won't be possible anymore if you just take out all the massive particles at a particular point in time.

Icek (talk) 21:08, 9 April 2014 (UTC)

Could I get an answer on the third part of the original question: in this hypothetical universe, in which the only the only matter remaining is that in the solar system, which of the various theories about the ultimate fate of the universe would likely be correct? —SeekingAnswers (reply) 19:07, 9 April 2014 (UTC)

The solar system doesn't have enough mass to collapse to anything denser than a white dwarf. And in the long run, as we seem to be in a universe with accelerating expansion and the cosmic background radiation's temperature becomes lower and lower, everything would cool and evaporate.

By the way, the mass density equivalent of the cosmic background radiation is about 4.64*10^-31 kg/m³, or about half an electron mass per cubic meter. So within 4.3*10⁶⁰ m³ of otherwise empty intergalactic space there is about one solar system's mass of about 2*10³⁰ kg. It's only a ball with a bit less than 11000 light years radius. Icek (talk) 21:08, 9 April 2014 (UTC)

Minor point: the x-ray burst from alpha Centauri wouldn't be a surprise at all. Because of this. - ¡Ouch! (^{hurt me} / _{more pain}) 06:26, 10 April 2014 (UTC)

Is the technic of the suction cup - base on surface tension?

I've read our article about, but it's not clear for my question. 5.28.177.131 (talk) 18:58, 8 April 2014 (UTC)

No, a suction cup works on the principle of differential pressure. There's lower pressure inside, higher pressure outside, so the difference in pressure keeps it pressed against whatever it is sticking to. --Jayron32 19:01, 8 April 2014 (UTC)

What Jayron32 said. When the suction cup is not stuck on something (i.e. when it's like most other objects you interact with) it's surrounded by air, so the atmospheric pressure we experience here on earth kind of balances out. When you remove all of the air from one side, however, the only pressure is what's pushing down on it from the other side. The strength of the suction is basically a measure of how easily air can sneak back in. This is also why suction cups can't work in space, where there is no atmospheric pressure. --— Rhododendrites ^talk |  20:44, 8 April 2014 (UTC)

Perhaps that air not sneaking back in quickly is what this Q is about, as that is the interesting part, at least to me. There's obviously a pressure differential, yet the vacuum doesn't immediately suck the air back in along the edges. Adhesion of the suction cup material to the material on which it's mounted gets the credit there, I believe. StuRat (talk) 00:52, 9 April 2014 (UTC)

There is definitely something going on that we haven't explained yet, but I don't think we need to invoke adhesion or any other chemical or electrostatic forces. I think it's all to do with the elasticity of the cup. Imagine the situation with a rigid vessel, like the Magdeburg hemispheres. It's obvious what's happening there, because somebody used a vacuum pump to suck out the air. Now imagine that the copper hemispheres are replaced with rubber ones. You don't need a vacuum pump any more: you just squash the two hemispheres together, expelling the air, and then let them expand by their own elasticity. They could have called them the "Magdeburg sink plungers". The suction cup works like that, only with one hemisphere replaced by a flat surface. A suction cup is its own vacuum pump, using its elasticity to expand a sealed volume against atmospheric pressure. Thus it causes the atmosphere to exert a force on it, and that force pushes the rubber against the wall to create the seal (and incidentally, to create the friction that stops it from sliding down the wall). --Heron (talk) 18:30, 9 April 2014 (UTC)

Well, the grease was needed in the hemisphere case, and water helps to keep a suction cup stuck, so I believe those liquids are an important part of the equation, with adhesion serving to plug the gaps with those fluids. StuRat (talk) 23:11, 9 April 2014 (UTC)

April 9

Chemical Test

How is a chemical test developed and/or discovered.Please explain with an example.117.194.234.95 (talk) 03:22, 9 April 2014 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. StuRat (talk) 04:51, 9 April 2014 (UTC)

I am not a student of school college university.I asked you question that has nothing to do with homework.I disapprove prejudiced notions.I dont think it will be a good thing to go to school/college in thirties.I soloicit your answer to my query and not these malicious conjenctures.117.194.249.163 (talk) 13:32, 9 April 2014 (UTC)

What chemical test did you have in mind? Wikipedia has an article titled Chemical test that discusses many wet chemistry chemical tests. There's a long list of them. If you read articles on any one of them, it may discuss how that test came to be. --Jayron32 14:14, 9 April 2014 (UTC)

I think the OP is thinking about a "chemical test" like the pH paper that you find so often in Chemistry labs. In that case, we may have to look up the history of the pH paper. But it all depends on whatever "chemical test" you're talking about. 140.254.227.100 (talk) 22:02, 9 April 2014 (UTC)

Skin cream gun control study

Hello, maybe you've heard of the study in which participants had to assess the results of a (fake) study about the efficacy of either skin cream or g*n c*ntr*l laws (with exactly same numbers), which purportedly showed that peoples' math reasoning ability declined when the math problem in question had to do with a politicized issue. I'm interested in the (fake) problem itself:

	rash got better	rash got worse
patients who used the cream	223	75
patients who didn't use the cream	107	21

After that the participants had to "indicate whether the experiment shows that using the new cream is likely to make the skin condition better or worse." It says on the internet that it's not enough to compare the numbers, one has to do the ratios. But what ratios? I see two ways of going about solving this:

• Of those who used the cream, 223/(223+75)=75% got better, vs 107/(107+21)=84% of those who didn't => ergo, cream sucks
• Of those whose rash got better, 223/(223+107)=68% used the cream, vs 75/(75+21)=78% of those, whose rash got worse =>cream still sucks

Which way is the correct one and why? (If I'm ever recruited for a similar study:) And is it incidental that in this example they devised, the conclusion is the same either way or is it mathematically inevitable?

Asmrulz (talk) 05:37, 9 April 2014 (UTC)

I'm not an expert, but it seems to me that the 1st method is correct. The 2nd group is your control group, you are comparing the effectiveness of the treatment vs the control group, which can be "no treatment" as in this case, or can be the current best available treatment (especially where withholding treatment all together would be unethical). So yes, put simply with the treatment 75% got better, without it 84% got better, so the treatment actually performed WORSE then no treatment at all. Vespine (talk) 06:02, 9 April 2014 (UTC)

You can only use the second method if you extrapolate the numbers ("normalize"?) to make the population sizes equal. The first group has 298, the second only 128. Multiply the second row by 2.328 and you get 249 and 49. That makes it clearer that using the cream has no particular effect. In fact, it appears that letting the body's own immune system handle it seems to be better than using the cream. But as to whether it "sucks" or not, you would have to do some kind of statistical analysis to see whether the 249 and the 223 are statistically different across the given population. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:25, 9 April 2014 (UTC)

Why the asterisks on "gun control" ? Is it considered an obscene term in your part of the world ? StuRat (talk) 08:33, 9 April 2014 (UTC)

It's from the Jargon file of hacker slang which I read long ago (link) It's funnier this way :) Asmrulz (talk) 10:16, 9 April 2014 (UTC)

The first method where one comparess the ratios of improvement in two unrelated populations is a rational test of the cream. The second method conflates the ratio of interest with the ratio of test and control populations, which is arbitrary, and cannot justify its conclusion. In this data the cream demonstrated less improvement 75% than whatever else (unspecified) other people did that improved 84% of them. The cream really sucks but the lesson here will not be welcomed by g*n r*ghts l*bby*sts with kn**-j*rk th*nk*ng st*ck *n 1791. 84.209.89.214 (talk) 13:08, 9 April 2014 (UTC)

• I agree with others that the first method is the correct one. But let me just add a note that the differences are not actually statistically significant (p = 0.0574 using Fisher's exact test, calculated using this tool, so the conclusion in a published paper would be that the data don't establish that the cream has any effect. Looie496 (talk) 14:02, 9 April 2014 (UTC)

Thanks to all of you for your answers. Asmrulz (talk) 14:43, 9 April 2014 (UTC)

Heat and magnetic fields.

As I understand it, heat destroys magnetism. So why then, does the magnetic field of the earth survive when the core of our planet which is hot enough to create a molten core? — Preceding unsigned comment added by 86.6.96.72 (talk) 09:59, 9 April 2014 (UTC)

Your understanding is wrong. --DHeyward (talk) 10:12, 9 April 2014 (UTC)

Explain?

Heat can stop a magnet being magnetic, this is true. Read the following to understand why we have a magnetic field around the Earth. http://en.wikipedia.org/wiki/Earth's_magnetic_field#Physical_origin 217.158.236.14 (talk) 11:29, 9 April 2014 (UTC)

A Magnetic field is produced by electric charges in motion i.e. Electric current. The way that works was explained by Maxwell in his elegant set of differential equations which hold true at all temperatures that we experience. 84.209.89.214 (talk) 12:09, 9 April 2014 (UTC)

Just to clarify, I am aware of the above and I am not debating it, however it is also true that ferromagnets can lose magnetic properties when heated to above the Curie temperature.217.158.236.14 (talk) 12:23, 9 April 2014 (UTC)

Yes, but that isn't because "heat destroys magnetism". It's because heat alters the crystal structure of the iron so it no longer has ferromagnetism. Different ideas. --Jayron32 12:31, 9 April 2014 (UTC)

Agreed, which is why I said "Heat can stop a magnet being magnetic", and not "destroys magnetism". — Preceding unsigned comment added by 217.158.236.14 (talk) 13:14, 9 April 2014 (UTC)

• To add detail to the answers above: ultimately magnetism arises from the movement of large numbers of electric charges in a synchronized way. In a ferromagnet (an ordinary solid iron magnet), the synchrony comes from the fact that large numbers of atoms are frozen into alignment with each other. If you heat a ferromagnet to near the melting point, the atoms lose their alignment and the magnetic field disappears. But the Earth is not a ferromagnet. Its magnetic field arises from electric currents flowing coherently through the magma on a vastly larger scale. The reason why that happens, incidentally, is not very well understood -- but clearly it does happen. Looie496 (talk) 13:52, 9 April 2014 (UTC)

Vast energies are stored in the Earth's magnetic field and evidence in the Geologic record that it has periodically reversed polarity is evidence that it is part of a resonant system. As yet no simple global model of Earth's resonant modes, that may be linked with resonances in other bodies, has emerged because the short time span of collected data is plagued by Heteroscedasticity of local anomalies. 84.209.89.214 (talk) 16:02, 9 April 2014 (UTC)

(Hey, you seem to be giving some good responses/refs here recently... or at least I think so, but it's hard to keep track of IPs... any chance we can convince you to register? It is less anonymous and more pseudonymous than signing with an IP, but it may actually increase your privacy too :) SemanticMantis (talk) 22:58, 9 April 2014 (UTC)

I'm pretty sure the editor behind the IP has had multiple accounts and are technically WP:block evading. People are just turning a blind eye because they aren't harping on about its/it's and other grammar and spelling issues. However registering another account is still probably not a good idea, instead requesting an unblock under one of their blocked accounts, preferably the main one. Nil Einne (talk) 05:01, 10 April 2014 (UTC)

Many factors establish the earth's magnetic field. It's not constant and rotation and heat affect it. If you want an extreme case, look at the sun. It has no iron core. It's created by heat and rotation. It flips N/S polarity every 11 years and often has a weak quadropole during maximum sunspot activity. The resultant magnetic field is very strong at sunspot minima. The earth has a different mechanism, but it's not correct to simply associate heat with the destruction of the magnetic field. There are solid magnetic properties as well as rotating, conducting fluids. See Dynamo theory to see how the Earth's magnetic field is created and changes. A ferromagnetic solid may reflect the magnetic field imprinted on it, but it's not necessarily the force that is responsible for the magnetic field. --DHeyward (talk) 05:42, 10 April 2014 (UTC)

Institutional dependence

Hi there. I am interested in a phenomenon whereas an individual who spends many years in a restrictive environment, e.g. prison, becomes dependent on the institution and develops unhealthy reactions sabotaging normal release process for instance. I am also interested if the phenomenon like this has ever been coded, if there is a corresponding ICD-9 or ICD-10 code describing it. Thank you --AboutFace 22 (talk) 20:01, 9 April 2014 (UTC)

Stockholm syndrome came to my mind. Brandmeister^talk 20:07, 9 April 2014 (UTC)

Oh lordy! I just was about to get back and add that in my understanding the phenomenon I am looking for or the code thereof is NOT the same as Stockholm syndrome. It should be distinct from it. Thanks.--AboutFace 22 (talk) 20:10, 9 April 2014 (UTC)

I think Learned_helplessness is relevant, since it describes the effect that a punitive environment has on individual volition. OldTimeNESter (talk) 20:17, 9 April 2014 (UTC)

So, you are asking about individuals who become institutionalised? 86.146.28.229 (talk) 21:21, 9 April 2014 (UTC)

Quadruple axels and beyond

What actually prevents a figure skater from making quadruple or even quintuple axels and similar feats? And what capabilities should (s)he theoretically have to perform them and similar stuff? Is it just a muscular force of legs during the jump-off, adequate jump height giving more time and a good sense of balance? --93.174.25.12 (talk) 20:04, 9 April 2014 (UTC)

The article on Jumping mentions the force-velocity ratio for muscles, which establishes the biomechanical limits on jumping height. OldTimeNESter (talk) 20:29, 9 April 2014 (UTC)

Basically you have to do it "just right", or you'll be either over or under rotated and will land with the skate blade not pointing in the right direction, and will probably fall. You also have to keep your center of gravity "just so", or you'll land at the wrong angle... and will probably fall. The more spins you have in a given jump, the harder it is to do. But it will happen eventually. The double axel was once considered tough to do. And lots of skaters fall on triple axels. As the commentators said at the Olympics recently, "It's really hard!" But someone will eventually succeed in doing the quad axel (4 1/2 times around) and that will set the bar higher. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:54, 9 April 2014 (UTC)

Maybe we'll see it done some day. But there are limits to the torque a skater can apply to himself, as well as (perhaps softer) limits to the ability to control. I'm confident there's some n for which humanity will never see an n-tuple axel, but what that n is is probably best investigated by watching competitions and waiting, rather than trying to model it from first principles. In other words, I think the answer to your last question is "yes"; it's "just" those three things that would have to improve. Maybe replace "sense of balance" with kinesthetic intelligence. SemanticMantis (talk)

It probably varies per-person, given the above comments. But the basic thing is that you must have enough angular velocity to complete those axels in the time you remain in the air. A quantitative analysis would require the maximum impulse the skater could deliver using the muscles in question, and how quickly (so the time for spinning can be calculated). The axis of rotation should be close to vertical for balance purposes, you do not want any torque components other than the vertical component to deal with (torque is a pseudovector).--Jasper Deng (talk) 07:48, 10 April 2014 (UTC)

Nature of carbon atom

Why do carbon atom form bonds tetrahedral in shape? Why do two carbon atoms not form a quadruple bond? 117.242.108.105 (talk) 05:53, 10 April 2014 (UTC)

Only diamonds are tetrahedral, I believe. Graphite is hexagonal and in sheets. The 3 double bonds are actually shared with 6 carbon atoms. Bond order and quantum mechanics are the reason why quadruple bonds aren't common. Basically, the higher the order the less stable so mixtures with lots of carbon will reform into lower order bonds. Acetylene has a triple bond and the amount of energy released when the bond is broken is tremendous. It would be difficult or impossible to have a carbon substance with quadruple bonds, and the diatomic distance associated with it, without it reducing to paired covalent bonds at farther spacings and less potential energy. --DHeyward (talk) 06:40, 10 April 2014 (UTC)

Deep water pressure

Why Titanic and other deep water debris is not crushed flat by water pressure?--93.174.25.12 (talk) 07:34, 10 April 2014 (UTC)

It is because the pressure is basically uniform over the entire surface of the object, including the part on the seabed (yes, the part on the seabed gets more force because that force must be the sum of the debris weight in addition to the water weight, but that extra force has always been there regardless of whether there was water), so the forces could only ever act to compress the object. It would be natural to think the metal panels have compressed already, so they will compress no further.--Jasper Deng (talk) 07:43, 10 April 2014 (UTC)

(edit conflict)Because the water is on the inside as well as the outside. The solid pieces of steel are strong enough to withstand very high pressure, though they will compress very slightly so that they have internal stress to match the external pressure. Dbfirs 07:46, 10 April 2014 (UTC)

For clarity, my comment applies to solid objects, not hollow objects which have no internal stress.--Jasper Deng (talk) 08:26, 10 April 2014 (UTC)

Pretty lakes

Why are supposedly "polluted" lakes always so full off vegetation? It seems to me that unnatural chemicals would stop plants from growing!