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May 24

What's the best non-supernatural explanation for Lourdes and Fatima?

Or the appearance in Egypt which many Islamic people believed was a shining Mary on the church roof? How did 100,000 people not notice that the "Sun" started moving in the wrong azimuth? Good G-d, 14 year old me would notice that. Maybe it was a sundog (or a ball lightning)? Sagittarian Milky Way (talk) 00:18, 24 May 2014 (UTC)

The best non-supernatural explanation is human error. Observer bias is a well-documented effect. Humans can and do report seeing things that they are not actually seeing. This even applies to large groups of people. Nimur (talk) 00:38, 24 May 2014 (UTC)

Stripped of all of the layers of interpretation, the Our Lady of Fátima event consisted of:

1. Three children (aged 6, 8 and 9 years old) who were out herding sheep - who claimed to have seen something amazing.
2. A large crowd of people, desperate to see something amazing, who stood out in the midday sun through many hot summer days and more or less stared at the sun. A bunch of them said they saw something - but (according to our article) the witnesses gave widely varying descriptions of what they saw.

So - ignoring all of the other interpretation - the best guess from the facts is that the kids were bored, doing a boring job - so they made something up. The adults were staring into the sun - no surprise that they started seeing things. They couldn't agree on what they saw...so I don't think there is anything here that needs further explanation.

The Lourdes initial miracle was, again, a peasant girl with zero education who was gathering firewood with two younger kids (does this sound familiar?) and claimed that they saw something amazing. As people got more and more excited about this, their stories get progressively more detailed and amazing. Again, stripped of all of the layers of interpretation - the obvious conclusion is that the kids were bored and made something up. Anyone who has ever had kids will attest to their vivid imaginations and ability to fuse imagination and reality. Subsequent stories of cures for people visiting Lourdes and drinking the water, are likely a mix of placebo effect and confirmation bias...along with a healthy interest from the people who live there to "talk up" the stories and bring in more people willing to spend money in their two-bit town. Millions of people seek cures in Lourdes every year - it would be surprising indeed if there weren't a good number of miraculous recoveries.

There doesn't really seem to be any great scientific mystery to solve here. SteveBaker (talk) 00:46, 24 May 2014 (UTC)

Agree with responses above. OP may be interested in Shared_hallucination. Maybe if question volume stays low here I'll ask about the wow signal ;) SemanticMantis (talk) 01:09, 24 May 2014 (UTC)

Even rational, scientific people are susceptible to observer bias, and sometimes scientists draw irrational or unsupported conclusions. Sometimes, even scientists falsify or exaggerate claims. But because we have a method, it is easier to determine when we are wrong, so we can correct the records. We depend on hypothesis, controlled experiment, and repeatability. When experiments repeatedly contradict our hypothesis, we are responsible for retracting the claim. "Paranormal" enthusiasts fail to engage in this process, and that is why we consider them "wrong." The extremity of their claims is not actually the reason we consider them wrong! Scientists will make incredible claims if evidence and procedure supports the claim.

When you look at scientists who write about the Wow! signal - or, even when you read scientific commentary on SETI - the process is diligent. The claims are specific and logical. The claims do not depend on dubious eye-witness reports or single-case incidents. When paranormal enthusiasts write about the exact same topics, they draw conclusions that have little connection to actual observation. Nimur (talk) 14:34, 24 May 2014 (UTC)

Children are always making up stuff. See for example, the Cottingley Fairies. The bizarre and rather sad thing is that anyone believes them in the first place.--Shantavira| 08:05, 24 May 2014 (UTC)

To our modern eyes, they're obviously cardboard cutouts. But people will believe what they want to. Hence the shockingly large percentage of folks who don't believe we landed on the moon, despite the debunking of every issue the hoax-claimants have raised. ←Baseball Bugs carrots→ 20:43, 24 May 2014 (UTC)

To me the Cottingley Fairies seem like they might be an exercise of British humor analogous to Sir Bonar Neville-Kingdom (I actually started that little article, and it took me most of an hour to decide he was a hoax, since he seemed overall like an eloquent though uncharacteristically honest advocate of the mainstream of British politics where privacy issues are concerned) Wnt (talk) 23:46, 24 May 2014 (UTC)

No, the Cottingly Fairies article is about the true story of two little girls who got caught up in something that got completely out of hand and became a cause célèbre in Edwardian England. Not an exercise in British humour at all Richerman (talk) 00:04, 25 May 2014 (UTC)

To me it's more like the Salem witch trials, though rather less deadly. ←Baseball Bugs carrots→ 05:34, 25 May 2014 (UTC)

But the point is that kids do this stuff all the time. If you ever met a kid with an Imaginary friend, you'd understand how deep and rich these made-up fantasy ideas become - and how the child can actually come to believe that what they made up is actually true. The Cottingly Fairies are a great example of that.

If you want a scarey modern example, then read Wenatchee child abuse prosecutions - 43 adults in a small, unremarkable town in Washington state - accused of 30,000 child abuse incidents with 60 different kids and resulting three hundred sex-ring court cases...and seemingly all of it brought about by group hysteria, kicked off by children with vivid imaginations and goaded on by interviewers with an axe to grind. From one little girl making up a story - the entire thing spiralled out of control until hundreds of families were implicated in a town of only 32,000 people.

Looking at that case, who wouldn't say that the kids in the two incidents the OP linked to were anything other than that. You can imagine the kids making up the story - the proud parents telling everyone about it - the clergymen coming to interview them inadvertently giving them more ideas to work with (just like the child councillors did at Wenatchee). The town gets whipped into a frenzy of religious fervor - and then they all go stand out and stare at the sun for a while until they start to report seeing things.

If an entire town can believe that thousands of cases of child abuse were happening at the hands of friends, relatives and neighbors - why wouldn't you imagine that thousands of peasant farmers in a small portugese town wouldn't see the sun dance around the sky? SteveBaker (talk) 15:36, 25 May 2014 (UTC)

A similar notorious "witch hunt" was the McMartin preschool trial. ←Baseball Bugs carrots→ 18:06, 25 May 2014 (UTC)

Actually, I'm somewhat confused about what the OP is asking. At Lourdes a young girl reported seeing Our Lady of Lourdes and there were subsequently many reported miracles. Which part of that do you want an explanation for - the apparition or the miracles? At Fatima there was a reported Miracle of the Sun for which there are a number of scientific explanations given in the article. As for "the appearance in Egypt" with "a shining Mary on the church roof" what are we talking about - Our Lady of Assiut maybe? There's nothing about anything on the church roof in the article, although it is a very poor article. And what do you mean by "How did 100,000 people not notice that the "Sun" started moving in the wrong azimuth?" - which apparition does this refer to - Fatima? According to the article, there were between 30,000 and 100,000 people there. Some of them reported various different phenomena and some didn't see anything. Richerman (talk) 10:45, 25 May 2014 (UTC)

Miracle_of_the_Sun states not only wrong azimuth but also elevation. And what's up with the near instant drying? I've never heard of that before, that seems to be what should be reported, due to it's inexplicableness. Eh, De Marchi probably made that up ~1950. It must be okay to lie to save souls.

Holy crap, there's two Egypt Maries involving church roofs? (including the obvious fake, Our_Lady_of_Warraq). Our_Lady_of_Zeitoun is what I'm thinking of. Maybe it's a transparentish human construction lit with electricity. Did nobody bothered to go to the roof, or even look at the dang thing through magnification? Sagittarian Milky Way (talk) 22:04, 25 May 2014 (UTC)

You don't need an explanation for the phenomenon - the simplest explanation is that there was no phenomenon.

It doesn't matter how many highly expectant people (standing in the hot sun, staring fixedly at it) said that they saw weird stuff...what matters is the billion or so other people who happened to glance at the sun who didn't see anything unusual. The sun is the same sun everywhere - so if strange things were truly happening to it, it would have been FAR more widely noticed. The simplest explanation is usually the best.

If just a few people were dehydrated and heat-shocked to the point where they hallucinated - and more of them stared at the sun and saw after-images or whatever - and if they all reported it loudly enough as a miracle - then I'm pretty sure you'd get an "Emperor's New Clothes" effect where each individual who DIDN'T see anything felt that they were left out and therefore invented something that they claim to have seen. This snowballs until nearly everyone claims to have seen something. (This is called "Pluralistic ignorance"). The fact that they all claimed to see slightly different things strongly backs that hypothesis - the large crowd, mostly making up what they saw from their imaginations would be sure to produce wildly varying descriptions of the event.

SteveBaker (talk) 15:13, 25 May 2014 (UTC)

A science-loving atheist child could think of "people saw it in Russia or it didn't happen" a very religious child could think of that and say "God changed the see-er's senses - duh" The first one won't convince a single believer. Sagittarian Milky Way (talk) 22:04, 25 May 2014 (UTC)

I think that skeptics can be too quick to kill a strawman. For example, whatever the sun was up to at Fatima doesn't have to be the literal Sun throwing a tantrum out in space; it could be some atmospheric phenomenon. Whether you want to call it chance or prophecy, there are a wide range of neat-looking atmospheric phenomena that change how the Sun looks. Wnt (talk) 14:03, 26 May 2014 (UTC)

As a gross example, a solar eclipse is very vivid to those who've witnessed it, but the majority of the world's occupants are oblivious to it, unless they've been made aware of it. But if someone had never seen or heard of a solar eclipse, they might well be skeptical of such a report. ←Baseball Bugs carrots→ 14:18, 26 May 2014 (UTC)

The scientific community's past and present views on the observation that most animals, as a general rule, supposedly have the same number of heartbeats

I'm curious about the observation that most animals, as a general rule, supposedly have the same number of heartbeats. In the 1970s, did the scientific community generally accept this observation, or did it generally reject the theory? And today, does the scientific community generally accept this observation, or does it generally reject it? 02:14, 24 May 2014 (UTC)Ac05number1 (talk)

Could you point to a source promoting and expounding this theory? I've never heard of it. HiLo48 (talk) 02:29, 24 May 2014 (UTC)

Isaac Asimov made that observation (hardly a theory!) in one of his science essays for The Magazine of Fantasy and Science Fiction (which were collected in a series of books). —Tamfang (talk) 03:46, 24 May 2014 (UTC)

Heartbeat hypothesis is the article, but you will have to draw your own conclusions from it. Rate of living theory seems to be a related concept (Heartbeat theory even redirects to it). Sjö (talk) 08:47, 24 May 2014 (UTC)

Don't many flying birds have a much higher heartbeat rate than land animals? The Hummingbird, for example, has been measured as high as 1260 beats per minute. ←Baseball Bugs carrots→ 13:32, 24 May 2014 (UTC)

Well Hummingbirds don't live very long compared to a number of land animals, although our article does suggest their lifespan is high for their metabolism. Nil Einne (talk) 19:34, 24 May 2014 (UTC)

Regardless, it blows away the assumption raised by the OP. ←Baseball Bugs carrots→ 20:20, 24 May 2014 (UTC)

It can't be without regard to lifespan, since the assumption raised by the OP is not about heart rate, but actual total number of heartbeats over a lifetime. Small animals with higher heart rates and short life spans are according to the theory roughly equivalent to large animals with longer lifespans and lower heart rates in total number of heart beats/lifetime, - Nunh-huh 05:41, 25 May 2014 (UTC)

So hummingbirds have a 3 to 5 year lifespan (typically) - their beat rate slows dramatically at night so over (say) 4 years, their hearts beat 1.3 trillion times. For a human, averaged over day and night, we get about 60 beats per minute - so if we live for 70 years then we get about 2.2 trillion heartbeats. So it starts to look kinda approximately reasonable. But a typical mouse has a heartbeat about 10 times faster than a human - do mice live for 7 years? No...wild mice live about a year - and carefully looked after lab mice only two years - only very freaky genetically engineered lab mice live for 4 years - so we have a pretty big discrepancy at about 0.5 trillion beats. Elephants have hearts that beat about half the speed of humans - they don't live for 140 years, usually about the same as us - so they are about where the hummingbird is too. Perhaps we might argue that "wild" humans wouldn't live 70 years - maybe more like 40...which brings our number close to the Elephant and hummingbird - but still three times that of mice. Dogs have heart rates around twice that of humans...but they don't live 35 (or even 20) years - so they are also on the low side.

So this idea is very roughly right - it seems that most animals live for between maybe 0.3 and 3 trillion heartbeats...an order of magnitude of spread...Meh.

There are other similar metrics you come across - and they are always similarly approximate. One is that almost all animals with legs can jump about a foot up into the air from a standing jump. Clearly there are animals that do quite a bit better and others that do quite a bit worse...but it's a surprisingly close thing.

The point is that there are always going to be specialist animals that break the general rule.

SteveBaker (talk) 14:58, 25 May 2014 (UTC)

I think that there are a lot of related power laws of this type. For example, the smaller the animal, usually, the higher the pitch of its speech; the twitterings of a chimney swift are hard to follow at even quarter speed, where they sound like more of a human scale. There's also a question of whether subjective time is compressed like the sound waves, i.e. dog years. Larger animals tend to live longer. The problem with such laws is that they are only vague approximations; they don't arise as a predictable consequence of evolution, and yet... they remind us that however chaotic the probings of evolution through the space of all possibilities, it follows some sort of overall pattern. Wnt (talk) 14:11, 26 May 2014 (UTC)

(Steve misspelled billion.) Asimov's essay, that I mentioned above, remarked that the human count is about four times what's typical of other vertebrates. (He based his computation on the greatest recorded longevity for each species, not an average, but I imagine that makes little difference in the comparison.) I suspect that some simple life-extending metabolic trick was selected-for, after the invention of language made grandparents worth having beyond reproductive age. —Tamfang (talk) 01:00, 28 May 2014 (UTC)

Depression and memory loss

is depression is related with memory lost — Preceding unsigned comment added by 106.76.250.76 (talk) 05:41, 24 May 2014 (UTC)

Yes, it can be. See Major depressive disorder#Symptoms and signs. Red Act (talk) 06:14, 24 May 2014 (UTC)

Using liquid nitrogen as a source of nitrogen gas

I'm going to aliquot a reagent that I want to be stored under nitrogen gas (i.e. no oxygen). This lab has no equipment for this purpose so I'd like to assemble something makeshift. Normally we'd use a special container to slow down the evaporation of liquid nitrogen but I want the opposite. I don't suppose I can just pour liquid nitrogen into a glass Winchester bottle without it cracking but what if I cool the bottle to -150 C first? Another issue is that I want the liquid nitrogen to evaporate fairly quickly so I get a stream of nitrogen gas. Will this happen or would it be very slow? A metal bottle would be great but I don't we have one. I'll do this in a fume cabinet. — Preceding unsigned comment added by 78.148.110.113 (talk) 07:28, 24 May 2014 (UTC)

I've used small ordinary lab beakers to contain LN2 before, just poured it in slowly to minimise thermal shock. HOWEVER, thermal shock is going to be much more difficult to control in a big Winchester. Pre-cooling with dry ice or something would help, but I suggest extreme care, and would try to find a non-glass alternative. A metal container would be ideal for this, I'd think. Hight thermal conductivity and no risk of shrapnel. But ALWAYS run this past your department health and safety person and don't take random advice of people on the internet as gospel. Is there a chemistry department nearby? They'd be sure to have a argon purged Schlenk line set-up you might be able to use. Fgf10 (talk) 12:25, 24 May 2014 (UTC)

Likewise, I don't like the idea of a Winchester. One should design the experiment so that even if a Winchester (or other vessel) brakes, you don't have low viscosity liquid nitrogen freezing your toes off. However. The supplier of your liquid nitrogen will no doubt have a tech desk. They are manned by people who are often both knowledgeable and bored, so would love to spend time advising you -so ask them. It is in their companies interest to help, in order that they may sell you more liquid gas in the future. Liquid nitrogen isn't really dangerous but as Fgf10 advises don't take random advice of people on the internet as gospel. Your suppler wants to sell you more gas, to tell them your application and your budget (which sounds to me like $0). Failing that: Emigrate to China.--Aspro (talk) 14:51, 24 May 2014 (UTC)

...and also if it breaks. :-) StuRat (talk) 16:41, 24 May 2014 (UTC)

Well spotted. Funny; that if I reed some one else's rightings I can spot their faux par instantly. But knot when weeding my own diatribe. Keep it up - as I may - with your help and tuition, make it to third grade. :-( --Aspro (talk) 21:32, 24 May 2014 (UTC)

I agree that using glass to contain liquid nitrogen is crazy. I'd bring in a metal pot from home, if the lab didn't have one. That would be safer than using glass. (Although I'd avoid cast iron, as it's rather brittle, for a metal.) Pre-cooling the pot is a good idea, but I'd still expect to get more gas at the beginning, until the pot cools to the temp of liquid nitrogen. If it slows to too low of a rate, you could put it over a heat source. You also need to be careful that you can seal the nitrogen in, as too much released into the air will lower the oxygen content. Good ventilation of the area will also help to prevent this. StuRat (talk) 16:43, 24 May 2014 (UTC)

It's not crazy at all and can be done perfectly safe at small scales. It's even done in fancy drinks in clubs etc there days. Issue here is scaling up. Fgf10 (talk) 16:47, 24 May 2014 (UTC)

Agreed, it's the scale that makes it unsafe. Also, I suspect they add the liquid nitrogen to water or alcohol in those cases, so it's "coolth" is diluted before it hits the glass. StuRat (talk) 16:51, 24 May 2014 (UTC)

"I would like to handle a hazardous material, but I don't have the proper equipment." Have you asked your supervisor, and whoever is responsible for safety in your laboratory? Broadly speaking, I would strongly suggest not taking any of the advice here except Fgf10's guidance to talk to someone who knows what they're doing—someone who is familiar with this type of work and the associated hazards. Oh, and don't presume that the sash on a standard fume hood provides more than minimal protection from blast and shrapnel.

So to irritated the above. You should not have to ask here on Misplaced Pages but direct your concerns to your supervisor. If they say but everyone in this industry uses LN2 point that they have duty to educate you to do so likewise. I would agree that it is much more benign than liquid oxygen. With LN2 you can put a flask in the trunk and drive home to show the kids how to freeze bananas, flowers and things then shatter them.. but first you have to discover how not to freeze your toes off- because that can ruin your whole day--Aspro (talk) 22:26, 24 May 2014 (UTC).

(I'll note as an aside that most large liquid nitrogen tanks have fittings to dispense gas as well as liquid. If you have an appropriate regulator, that is the easiest and likely safest way to get gas to work with; our laboratory has used this approach for nitrogen purging of instruments when we haven't had house nitrogen on tap. Again, consult someone who knows what they're doing.) TenOfAllTrades(talk) 18:11, 24 May 2014 (UTC)

This is ridiculous. I've never seen people get special safety training to deal with small amounts of LN2 (<500 ml), and it really doesn't bite - even holding some drops in your hand usually won't cause injury because of the vapor barrier. Dropped on the floor it will skedaddle all the way to the far side and back causing no damage. I have never tried and wouldn't recommend dousing someone with it (I imagine that it could get stuck in clothing crevices and cause little burns) but I'd be stunned if they suffered any serious injury. The key thing is though that you should think Dewar, or at least a thermos - keeping it in something to make it evaporate faster is also nuts. You never have trouble with it taking too long to evaporate. With an open Dewar 4 inches or so wide with an inch of LN2 at the bottom, you'll see a clear layer of dry nitrogen gas falling continually around the edge, with the moisture of the air condensing more turbulently above it. So I imagine you could just take your chemical jar, put it below the lip level into that layer of pure N2, and since the nitrogen gas is so cold it should just pour right into your vial in no time. I assume you're not looking for 99.999% purity though!

Speaking of purity, the one odd trick LN2 has is that small amounts of oxygen in the air will liquefy and enter it when you let it sit out. If you let it all evaporate away, the last little bit will be pretty high in oxygen. You can just ruin a tissue specimen this way, and I imagine that if you had the wrong chemical something far more unpleasant could happen. I recommend that if you're dealing with genuinely dangerous or precious chemicals rather than just a "let's see if this works..." test, you go ahead and look for a professional solution for putting them under nitrogen. Wnt (talk) 21:50, 24 May 2014 (UTC)

? ridiculous. This is exactly why we suggest he puts the responsibility into the hands of his supervisor. A small amount of LN2 can increase the local oxygen levels in a confined space (read fume cupboard). The OP hasn’t said what else may be in the fume cupboard. We are not psychic, we just have to go by our experience of the realities of lab life. Nice if you work for NASA, where you have a whole fume cupboard to yourself but the OP appears to be asking the question from the point of view “ I've been thrown into the deep end -what do I do?”--Aspro (talk) 22:49, 24 May 2014 (UTC)

I certainly hope your fume cupboard is not a confined space. While liquid nitrogen can indeed accumulate liquid oxygen which can then evaporate, the evaporation of the liquid oxygen produces, well, oxygen. So long as the Dewar is not a primary source of air coming into the fume hood, it should not greatly change the overall oxygen level in the air in there. Wnt (talk) 23:30, 24 May 2014 (UTC)

There are special bottles for cryogenic stuff. It would take a long time to slowly cool down a heavy glass bottle. It's like cooling a superhot brick right from the oven to room temperature. Count Iblis (talk) 13:00, 25 May 2014 (UTC)

True, and even supposing that the evaporation rate weren't high enough (which I do not expect as a problem) then I'd prefer something more controlled like taking a metal rod and putting it into the Dewar, so that you could hold the top in your hand or otherwise heat it to control the rate. Wnt (talk) 22:22, 25 May 2014 (UTC)

TenOfAllTrades has the right idea. Unless you want to make your sample cold, there's no reason to have it in the same container with liquid nitrogen. What you want is an enclosed volume that can be purged out with dry nitrogen gas. You can use the boiloff from an LN2 dewar as a perfectly good source of purge gas. The purged volume could be any old container as long as it has a suitable inlet and outlet. --Amble (talk) 22:09, 26 May 2014 (UTC)

You should use a bottle of gaseous N2 at what ever purity level you require. These are easy to acquire. A supply from evaporating LN2 WILL contain O2 (I think the blueness in the vapor is a sign of such) and if mixed with organics can be dangerous. Also the temperature issue can easily cause cond3ensed water contamination. Juan Riley (talk) 22:18, 26 May 2014 (UTC)

Indeed, a bottle of warm dry nitrogen is a lot more professional, and withdrawing gas from a storage tank does make more sense if it is anywhere near your lab. I was going by the OP's "makeshift" idea because sometimes you just want to know if putting something under a mostly-nitrogen atmosphere helps it stay stable for longer. I should also say that reading there are some who are not as casual about LN2. I hadn't even thought about rings, and while I feel skeptical about the claim there that you can destroy "cubic centimeters" of flesh if the liquid nitrogen pours into a shoe, but then again I've never owned a pair of stormtrooper boots... so I may have been too quick to generalize. Still, the copious vapor production and ultra low viscosity do much to at least reduce the odds of trouble. Wnt (talk) 07:28, 28 May 2014 (UTC)

Alternative energy

Is this real or not? It sounds too good to be true to me. 24.215.188.243 (talk) 19:33, 24 May 2014 (UTC)

Yes, (see: Solar roadway) but there are many problems, not the least of which is cost see:http://science.howstuffworks.com/environmental/energy/solar-panel-highway2.htm Richerman (talk) 20:17, 24 May 2014 (UTC)

Things can be real without being practical. For example, humans have already built jetpacks, invisible ink, flying cars, square wheels, and cigarettes. The benefits of such inventions do not outweigh their numerous hazards and costs.

In this case, solar energy in the form of photovoltaic cells built into the roadway is so far from being useful that it's not even listed in the United States Department of Transportation's National Transportation Library section on solar energy. If you want to inform yourself about practical alternative energy solutions as they apply to highways in the United States, you might start by reading the program overviews at the Department of Transportation's research library.

You can also read about solar energy at the Department of Energy's website on science and innovation.

If you'd like a more tempered view on the subject of the OP's original link, here is a Washington Post article from a few days ago, reporting on the inventor whose video was linked above by our OP. Once you're past the attention-catching headline, the article actually outlines the more sobering realities about costs, maintenance, environmental effects, and the reasons why this inventor's funding was ... discontinued. It seems, however, that he had enough budget to hire a viral marketing firm to make a ludicrous video before his money dried up.

If we wanted to spend hours tearing apart this specific incarnation of solar roadways, our hardest challenge would be "where do we even start?" Just based on the Washington Post article, the crank scientist demonstrates his glass solar-panel roadway invention is "roadworthy" and sturdy by driving his tractor on it. Well, great... except that it is a tractor, designed with giant low-pressure tires to minimize ground pressure. Tractors can drive on soft ground and muddy surfaces too. Can the roadway withstand ordinary highway traffic? Probably not - but in classic fashion, our rogue inventor has concocted a ridiculous and flashy demonstration with no actual practical implication to distract us from actual analysis of the invention. There are dozens of other problems with this design that immediately come to my mind. But, I'll leave it to our other reference-desk regulars to take the rest of this "invention" apart piece-by-piece.

Nimur (talk) 20:12, 24 May 2014 (UTC)

I wonder how well they would survive if someone decided to take their traction engine or steamroller for a spin? Richerman (talk) 20:50, 24 May 2014 (UTC)

That's a rather biased view of not only the project, and also a poor summary of Washington Post article. It doesn't say why his funding was discontinued. The funding was from Phase I and II SBIR grants, which are for a finite amount of money and time, not ongoing contracts. The fact that they got a Phase II grant suggests the funding agency is interested in the project. Phase III requires getting private-sector funding. According to CNN, they've also done laboratory load and traction tests. Obviously there's still a lot of work to do, but just dismissing it out of hand and then needlessly insulting the inventor is inappropriate. Mr.Z-man 22:05, 24 May 2014 (UTC)

If you look on their FAQs here under "how much will you panels cost" it says "We are still in the midst of our Phase II contract with the Federal Highway Administration and we'll be analyzing our prototype costs near the end of our contract which ends in July, 2014". There is also an answer to the question of load bearing properties under "Can your Solar Roadways handle army tanks?" Richerman (talk) 22:45, 24 May 2014 (UTC)

As I'm sure you recall from previous discussions, I'm reasonably well-read on the subject of tank tracks! (I spent an intolerable period of my life in a former career, stressing out over land mines). For the uninitiated, tank tracks usually exert less ground pressure than an ordinary sports car. Low track pressure helps in off-road, soft terrain, and makes it harder for enemies to use a simplistic pressure fuse. But from the FAQ on the SolarRoads website, I can see that the inventor hasn't even correctly framed his answer in context! The total weight of the tank is completely irrelevant to its effect on the roadway. What matters is its ground pressure and the materials that contact the road surface. Nimur (talk) 23:20, 24 May 2014 (UTC)

Nope, I probably wouldn't have even read that, and if I had I wouldn't remember what was said by whom. But anyway they say under "How much weight can these panels support? Semi-trucks get pretty heavy!" - we decided to shoot for 250,000 pounds. Both 3D Finite Element Method analysis and actual load testing at civil engineering labs showed that our Solar Road Panels can handle that and more". Richerman (talk) 23:34, 24 May 2014 (UTC)

Here's an article worth reading: Pushing the Limits of Pavement, published by the DOT, from January. You can see how proper engineered road surface tests are performed. You might also want to read bridge weight limits and per-axle weight limits. The inventor isn't even using the right language to frame his responses about weight and loading! And this issue of material strength is just one minute aspect of the many problems of the total system design! Nimur (talk) 00:31, 25 May 2014 (UTC)

What I don't understand is where it says here "Brusaw said his initial target price is $10,000 for a 12 x 12 encapsulated solar panel. If it drops to $6900 during production, he said he could break even with asphalt". Are they just talking about the cost of manufacture? If so, how does that compare to the cost of asphalt which would be a few dollars for a chunk that size? The main cost with building an asphalt road is the preparation and construction, not the cost of the asphalt itself. Richerman (talk) 00:51, 25 May 2014 (UTC)

Ah, it seems they're talking about a 12 foot x 12 foot array of panels (I think) but even so, I didn't think asphalt was that expensive. Richerman (talk) 01:26, 25 May 2014 (UTC)

I think that solar roadways make a lot of sense... with the solar panels being above the roadway, of course. Roof and wall major highways, especially in well-populated areas, with large spans of panels and other materials where they don't make sense to keep in the noise and perhaps even process pollution somewhat, to keep them warmer and free of snow, and providing handy points for illumination at night while eliminating glare by day. But has anyone actually worked on something like this? Wnt (talk) 21:39, 24 May 2014 (UTC)

There's one problem with panels above the roadway. See the third paragraph of Truss bridge#Roadbed types for details. Plus, in places where you have rooves and walls on those highways, you're creating tunnels, and tunnels have their own hazards. Nyttend (talk) 03:24, 25 May 2014 (UTC)

Well, the size of the required tunnel does limit the amount of road that can be covered; still, however you cover a road, it has to be better to do that than to cover a big random patch of ground that otherwise could be a park or residential housing. As for tunnel fires, well, it's not really a tunnel. You could rig the side panels for quick release with the same low-melting bismuth alloy used in sprinkler systems, and as soon as the flames flashed up toward the roof, all the side panels slide down around the edges of the tunnel and land at either side of the road. Wnt (talk) 19:50, 25 May 2014 (UTC)

Oh good grief!

I'm sure we could fix the strength issues - that's really not the problem.

Each panel costs $10,000 now and is expected to drop to $5,000 - that's for a few square feet. What does a few square feet of asphalt cost? A typical 60 foot wide road costs $100 per linear foot (including the lighting, signage, etc)...so very roughly they cost $1.50 per square foot (). So this proposal increases the cost of road building by a factor of maybe a thousand.

Each year, the US spends around $150 billion on new road construction - around 1% of GDP...increase that by a factor of 1,000 and we're looking at a $150 TRILLION annual cost to build new roads with this stuff...and that's not considering the cost to gradually convert existing roads. The total annual income of all Americans put together is around () $15 trillion. So even if we spent every single penny we make on building new solar roads (and none whatever on food, housing, transportation or new iPhones!) - we'd only be able to build about 1/10th of our new roads this way and have no money whatever to upgrade existing roads.

If we kept to current expenditure and just switched to solar panel roadways, we'd take 1000 years to make just the new roads we need for this year alone!

But hey - we'd earn/save a ton of money from the electricity we'd make - right? The video said that if every road, footpath and sport field were converted to this technology overnight, it would generate three times the present energy needs of the USA. Present energy costs equal about 5% of GDP () - so three times that is only 15% of GDP that these roadways would earn...and we need 10 times GDP just to build new roads. (It's actually a lot worse than that because with all that free energy, the cost of energy would plummet - so we wouldn't earn much by doing it).

Furthermore - these panels make energy during the day. How would we store it all during the night? That's an altogether non-trivial problem.

This is a ridiculously stupid idea. Solar panels are a great idea - but you've got to keep the cost-per-square foot down as low as possible - and making them super-strong and integrating lights, LED's power distribution, pressure sensors and god-knows-what-else into them is stupid. If you really wanted to do this to generate all of the electricity the US needs (rather than three times as much) - then use a strip of the median of every road that's about a third the width of the road and cover it with regular solar panels - their math says that's enough. The energy generated would be at least as good (probably better because that strong, bumpy glass probably isn't that transparent - and you could orient them toward the prevailing sun direction). Conventional panels cost $6 per square foot, not $1000 - so instead of it costing us 1000 times what normal road construction costs, it would add about $2 to the $1.50 it currently costs to build a square foot of road...that would double our road building cost - and if we're going to gradually upgrade existing roads, we should probably spend more than that...but it would still be only a few percent of GDP - and free energy for everyone would save about 5% of GDP - so it would be a reasonable investment.

Of course then you have to ask why we're building them next to roads when we have all of that boring desert out there in New Mexico that we could cover with solar panels.

Sorry - but this is an utterly batshit-crazy idea.

SteveBaker (talk) 14:15, 25 May 2014 (UTC)

Steve, the touted figure of $6,900 was for one of their original 12'x12' panels, not for one of their more recent smaller hexagonal panels. $6,900 for a 12'x12' panel is about $48 per square foot, not the $1000 per square foot that you came up with. I'm not concluding that the panels would be cost effective; I'm just saying that their cost shouldn't be overestimated by a factor of 20. Red Act (talk) 15:46, 26 May 2014 (UTC)

Yet another reason why it's crazy is the difficulty in keeping the panels clean. Rubber from tires continually coats our roads, you can even see the dark tread marks on a white concrete road. And, being horizontal, they accumulate dust, sand, etc. That could be removed by regular street sweeping, but removing the rubber would require scrubbing the roads.

If we forget about solar panels, though, glass roads makes more sense than you might think. It's made from sand, which is in ample supply around the world, unlike petroleum, which is an ingredient in asphalt. And glass can be made quite strong, and to have a zero coefficient of thermal expansion, which would keep it from cracking due to temperature changes, as concrete does. I'd use glass bricks, like cobblestones (technically, setts), so they can be replaced as needed, rather than having to patch a road, which doesn't last long, or repave the whole thing. And water can't trickle into glass, freeze, expand, and crack it, as it does with concrete or regular bricks. Asphalt could be used between the glass bricks. The usually problem with asphalt is that it wears away quickly, so the road develops troughs where wheels roll, but the glass would prevent that. Another problem with asphalt is that it breaks away at the edge, so some type of glass edging bricks could be used there, maybe with a silicone rubber seal between them. The surface of the glass could be coated with sand, to increase friction. StuRat (talk) 18:59, 25 May 2014 (UTC)

Sometimes an 'obvious' benefit is less so on deeper investigation. One issue with making more durable road surfaces is that you don't want them to wear peoples tires out unduly either. Here in Texas, the summer temperatures get hot enough to soften 'conventional' asphalt - so they use a harder mix than most places. This results in higher tire wear and tires here wear out about 5% faster than elsewhere. Grip is another issue - and how the grip varies with moisture levels is of great concern.

Current tire design is based around current road surfaces - and vice-versa - they have co-evolved. Tires might have to change radically if some other road surface were to become commonplace. But then you get into Path dependence - where even if someone invents MiracleSurface-3000 (tm) that costs half what asphalt does, is good for the environment and never wears out, if it requires that you use MiracleTires-3000 (tm) that are half the price of regular tires and last ten times as long - it'll never happen. You can't replace the road surface until everyone has the new tires - and you can't use the new tires until all of the roads are resurfaced. That's a problem you can never escape with a system as large as the road network. Every change has to be small and evolutionary. Revolutionary solutions have to be 100% backwards and forwards compatible at every stage - which is a tough engineering challenge. SteveBaker (talk) 13:57, 26 May 2014 (UTC)

You raise a good point about other factors of significance to consider. Another example is the road noise levels – some asphalt road surfaces are substantially quieter than others, and glass is not a great material in this regard. I expect that solving the economics and engineering problems of solar panels and road surfaces separately (even if that means putting panels on top of all buildings) will be better than trying to find some joint solution for a long time to come. Once we no longer have roof area that can be repurposed, this would change, but until then ... —Quondum 16:51, 26 May 2014 (UTC)

Hopefully using asphalt between the glass bricks would absorb the vibrations and make the total system quieter. And I agree that solar panels on roofs makes more sense, since there will be less of an issue with them getting dirty or covered with debris there, and hopefully the power can be used right in that building, eliminating the need to distribute it over large distances. StuRat (talk) 18:07, 27 May 2014 (UTC)

BTW, Solar roadway is a dead redirect. - ¡Ouch! ( / _{more pain}) 14:47, 27 May 2014 (UTC)

Cyclophosphamide

Hello, could somebody help me define the pharmacodynamic and pharmacotherapeutic group of cyclophosphamide? I didn't find much about such classification in English literature but have to include it in my presentation of cyclophosphamide. For example, the PD group of Ibuprofen is inhibitor of cox1 and cox2 and the PT group is NSAID. Another example: Indapamide - PD: inhibitor of Na/Cl symporter, PT: thiazide-like diuretics. I thought the PD group might be alkylating agent or nitrogen mustard and the PT group cytostatic drugs (chemotherapeutics) and immunosupressive drugs... I'm really confused, any help and explanation would be appreciated. — Preceding unsigned comment added by Atacamadesert12 (talk • contribs) 22:50, 24 May 2014 (UTC)

Try here - where it says it's an alkylating agent of the nitrogen mustard type. It says here it is an alkylating agent with cytotoxic and immunosuppressive properties. Richerman (talk) 23:23, 24 May 2014 (UTC)

Based on our Cyclophosphamide article, I would say that the PT group is nitrogen mustard alkylating agent, and the PD group is alkylating antineoplastic agent. Looie496 (talk) 23:27, 24 May 2014 (UTC)

Per the Davis Drug Guide for Nurses, cyclophosphamide is PT: anti-neoplastic immunosuppressant and PD: alkylating agent, nitrogen mustard. Epolk (talk) 04:30, 28 May 2014 (UTC)

May 25

Which is good AC or Fan for our health?

Zonex shrestha (talk) 04:32, 25 May 2014 (UTC)

Define "healthier". ←Baseball Bugs carrots→ 05:33, 25 May 2014 (UTC)

Is this about the idea that electric fans can kill you in your sleep? If so, please see Fan death about that urban legend. Sjö (talk) 08:07, 25 May 2014 (UTC)

A good AC system will filter out the air pollution. A fan will actally increase the amount of dust particles in the air. Count Iblis (talk) 12:48, 25 May 2014 (UTC)

People generally sleep better when the ambient temperature is more comfortable - and getting good sleep is well known to be important to good health. So, in some climates, there is likely to be an important health benefit. Fans are less obviously good - they mostly help A/C to work effectively - but Sleep#Insomnia points out that white noise (such as produced by a noisy fan) is believed to help with insomnia. SteveBaker (talk) 13:34, 25 May 2014 (UTC)

Note that this depends significantly on climate, house design etc. A fan can make a big difference to the comfort level in somewhere like Malaysia where it's hot and humid but rarely gets hot enough that a fan will make it worse. AC helps more obviously but many can't afford the cost to run one all the time and will be able to comfortably sleep (at night at least) with a fan but often not so much without one. Definitely during a power cut I usually found it harder to get to sleep in Kuala Lumpur and I rarely used AC. (Of course some people have to do without either.) Having the windows open usually help a bit but not so much, probably for various reasons like house design and the presence of mosquito netting on windows.

Here in Auckland, most of the time if it's too hot, opening the windows is enough. Occasionally during the very hot days of summer it's still a bit hot. In those cases a fan often helps (and I generally find sufficient). A fan is also a great help if you're exercising in doors during the colder nights and don't want to open the windows either for the benefit of others in the house/room or for you when you stop. Few people would suggest you ever really need AC here for a residential building. It may be slightly nice to have, but really the main reason why people have one is because they want the heat pump functionality. And a big percentage of our heating uses electricity and combined with the generally considered mild climate, a heat pump makes a lot of sense if you do need heating.

So while a fan doesn't affect the indoor climate like the way AC does, it shouldn't be thought of as primarily something which helps AC to work.

Nil Einne (talk) 17:26, 25 May 2014 (UTC)

Certainly a fan is not pure "white noise", especially certain emplacements that make substantial low frequency, allegedly subsonic sounds; and white noise is a very poor substitute for the sounds of crickets and countless other small creatures which, by right, should be the performers of the nightly tune. But in my opinion even urban noises of people and passing cars are more relieving than the incessant, obtrusive, meaningless noise of these devices. Wnt (talk) 05:45, 26 May 2014 (UTC)

I've known folks who like those types of random sounds you're describing, and I've known some who hate the whoosh of a fan or air conditioner and require absolute silence. I find that a constant sound such as a fan is relaxing (as long as it's not too loud). Everyone's needs are different. ←Baseball Bugs carrots→ 10:55, 26 May 2014 (UTC)

Some arguments for fans:

1) They use less energy, so the cumulative effects of energy use, like global warming from burning fossil fuels to generate that electricity, are reduced with fans. This can protect human health by slowing the spread of malaria into (currently) cooler climates, etc.

2) Indoor air is not always good quality. Especially in a new home, outgassing from all the building materials can be problematic, as can household chemicals used for cleaning, etc. Then there might be a smoker in the house, and cooking without a proper exhaust fan can pollute the air, too. Fans placed in windows provide for better ventilation than A/C.

3) A/C units can create their own health concerns. My window A/C units smell like mildew when I first turn them on. With central air, there's Legionairre's disease to worry about.

I use both, myself. I use fans when the outdoor air is cool, dry, and unpolluted, and A/C otherwise. StuRat (talk) 19:28, 25 May 2014 (UTC)

Using air conditioning to deal with polluted air sounds like a futile spiral to me. If the air is really that polluted, a person should either flee or be willing to take part in the fate of the Earth.

A basic step in dealing with hot weather is to acclimate to it as much as possible, to be comfortable inside and out. But what mystifies me about air conditioning is that it seems to "addict" a room beyond that - take a room that is air conditioned, leave the thing off for an hour, and it seems intolerable compared to any neighboring room that never had one of them running. The obvious explanation would be humidity, but they visibly dehumidify the air, often with constant dripping water outside. So what's the reason? Wnt (talk) 04:56, 26 May 2014 (UTC)

Most of the population of China lives in areas where the air has particulate matter pollution at levels that the US EPA would consider unhealthy on more than 100 days a year. Central air with filters can appreciably improve indoor air quality and reduce the incidence of pollution related disease for these people. As long as the filters are present, even running a central air system in "fan-only" can help to clean the air without necessarily having to use cooling or heating functions. Dragons flight (talk) 05:22, 26 May 2014 (UTC)

Trillions of plastic fragments in Arctic ice

Re , given that most plastics are as inert as possible by design, what are the potential risks to ocean life from plastics? What are the likely risks? I remember from sophomore biology lab that rayon is a decent scaffolding for plant life in fresh water. How long will it take for solar ultraviolet to break these fragments down to indistinguishable ocean water components in the Arctic? 180.173.84.34 (talk) 12:32, 25 May 2014 (UTC)

Plastics are chemically inert - but not physically inert. For example, the plastic mesh used in fishing nets can get wrapped around the head of some fish or marine mammal - and precisely because it's so chemically inert, stays there until the animal grows to maturity and is slowly and painfully choked by it. Some animals see bits of plastic as food and eat it - since it doesn't break down in their guts, it can get lodged there and prevent other food from being eaten...the animal starves to death. Our article Plastic particle water pollution describes consequences from the spill of small particles of "inert" plastics.

Perhaps there are a few minor benefits to a few, specific local lifeforms - but note that those lifeforms got on just fine without the plastic - so the benefits are likely to be minimal. Even if some specie does benefit from it, it'll boom in population and unbalance the local ecology - probably to the severe detriment of other species in the area.

Solar ultraviolet is not very strong in the Arctic regions - and in any case, the UV is filtered by the water and/or ice - so only plastic that's floating at or near the surface would be affected. Some plastics are not much affected by UV light. It's hard to say how long it would take for each of the myriad types of plastic to break down - but places like the three, known "Garbage patches" in oceans across the world suggest that even near the equator, this stuff has a very long half-life.

Our Great Pacific garbage patch article (and others linked from it) discuss in detail the harm caused by plastics in the ocean - and the mechanisms by which it may (or may not) be naturally removed. It's a deeply depressing read!

SteveBaker (talk) 13:29, 25 May 2014 (UTC)

What polymer is formed from phthalic acid and ethylene glycol?

Zonex shrestha (talk) 13:00, 25 May 2014 (UTC)

A Google search for "phthalic acid and ethylene glycol" will give you the answer in the very first link. (Since this has the appearance of a homework question, I am not going to supply it.) Looie496 (talk) 15:50, 25 May 2014 (UTC)

Fan housing

I have box fans I use as window fans. Since the fan housing is square, I've created a circular "mask" to go outside the area swept by the blades, to prevent back-flow of air in the corners. Is my assumption that the ideal mask should contain a hole exactly the size of the area swept by the blades correct, or should it be larger or smaller ? (It's not in the same plane as the blades, so there's no risk of them hitting the mask.) StuRat (talk) 18:28, 25 May 2014 (UTC)

This seems like a complex problem in turbulent flow dynamics. I can picture anything from air backflowing as you suggest to air being entrained and actually adding to the flow in the area. Can you do an ad hoc test where you take a paper mask, cut holes in it, hang tissue paper in the holes, see which ones are really passing air backward? Wnt (talk) 19:44, 25 May 2014 (UTC)

I thought of that, and I could fairly easily determine the direction of airflow at each point, but it occurred to me that I might end up with more total airflow if I constrain it to blow through a smaller hole at high speed, rather than a larger hole at low speed, even without any back-flow. StuRat (talk) 20:18, 25 May 2014 (UTC)

It's true that any solution would be iterative, since changing the overall shape of the mask could change the airflow in any given test hole. I'm at least hoping it ought to converge, though. Wnt (talk) 22:11, 25 May 2014 (UTC)

Yep, and I may very well try that approach out tonight. Just wanted to see if anyone had any insight before I went the trial-and-error route. StuRat (talk) 03:31, 26 May 2014 (UTC)

• I'd re-ask this at the math desk and see if you can open the frame and put triangular styrofoam blocks in the corners. That might be better for the problem User:Wnt mentioned. Sounds like something rom a Clancy novel. μηδείς (talk) 20:06, 25 May 2014 (UTC)

• This is a fluid dynamics problem, which falls squarely into the realm of applied science. StuRat (talk) 20:15, 25 May 2014 (UTC)

The presence or absence of backflow is going to be significantly influenced by the nature of the space you are blowing air into. If the room in question is mostly sealed, you can expect the excess pressure created by the fan to result in a lot of backflow at those corners, but if there are other natural exits (such as vents, open windows, or other large air leaks), then I wouldn't expect to see much backflow and you might even see some entrainment. To get the best possible air flow you need to keep in mind both how the air enters and how it exits. Dragons flight (talk) 04:05, 26 May 2014 (UTC)

Coincidentally - I have the exact same problem right now! My wife runs a couple of laser cutters in a spare room - these machines generate quite a lot of wood smoke - which is sucked out and vented through a chimney in the roof - but a small amount of smoke inevitably leaks out into the room. We have a dual-fan, window-mounted device for that reason - but yesterday I did some upgrades to make the laser cutters quite a bit faster and when they are both running at full speed, enough smoke particles build up in the air in sufficient quantity to set off the smoke detector in the adjoining room! (The are incredibly sensitive - they go off when you can neither see nor smell the smoke).

Increasing the flow rate out of the window would be a very good thing - and a huge box fan seems like it would have a higher flow rate than the smaller window fans. But just like our OP, I need to make a mask so that on windy days, the air isn't blown back into the room around the edges of the fan.

My best guess is that the hole should be a little smaller than the fan blades because there will presumably be Wingtip vortices that would pull outside air back in again...so my first guess is to make a hole that's maybe a half inch smaller than the diameter of the fan. (Another consideration is that it's much easier to change my mind and make the hole bigger later on than it is to make it smaller!)

At any rate, I'm very interested in the results...so perhaps StuRat would care to get in touch via my email (it's on my User: page) - and we can collaborate on the research and report back. SteveBaker (talk) 13:27, 26 May 2014 (UTC)

For one thing, I suggest you put box fans in all windows where they will fit, with an equal number pointing in and out, although I'd avoid windows which are much wider than the fan. In your case, I'd blow air into the adjacent room from outside, and blow it out of the room where the smoke is generated. Try not to have an intake fan on the same side of the house as an exhaust fan, so it won't suck the bad air back in. In addition to the mask, you also have to worry about the gaps around the fan housing. I find just jamming something flexible in there, like my curtains, is one way to seal it fairly well. Oh, and remove any feet on the box fans that they add for stability, as those introduce gaps. Also, you can put the fan in the window sideways, if the controls keep it from fitting properly upright. Close the window on the fan tightly. The mask should be on the intake side of the fan, as it will tend to be sucked towards it, that way. I also am using a mask a bit smaller than the area swept by the blades, for the reasons you mentioned. I used a flexible material, similar to linoleum, but I think something a bit stiffer might have worked better. StuRat (talk) 04:49, 27 May 2014 (UTC)

Hmmm - the "pro/con" lists in Ducted fan is educational. SteveBaker (talk) 13:36, 26 May 2014 (UTC)

Reverse tomography for 3D "printing"

There's been a lot of good discussion of the issues with 3D printing here recently, so I'll ask: why don't the devices doing this take a tomographic approach? There's a minor precedent with the gamma knife, and the idea of simply reversing the data collected from tomography seems straightforward enough. Just have a rotating ring with lots of individual emitters, which software programs to focus microwaves at various points within the sample. Wherever the tightly packed powder filling the target container gets hot enough, it sinters together and solidifies. Potentially you could do multiple passes, allowing heat to dissipate from some regions you don't want to solidify after you've sintered others in place. Excess powder in cavities would be poured out from small holes left in the finished product. I think you might even be able to do it by having gamma sources around a ring and irradiating a metal powder that would resist microwave heating, shouldn't you? The result would not have a visible pixel structure. Wnt (talk) 20:01, 25 May 2014 (UTC)

I believe that those medical scanners cost around a million dollars each, and that's a bit pricey, even by 3D printing standards. StuRat (talk) 20:23, 25 May 2014 (UTC)

That's the medical racket - nothing in medicine has sane pricing; the modalities for recovery are held for ransom. True, I don't picture a very free market emerging in radioactive sources emerging in any case, but at least there isn't as much upward pressure on the price. Wnt (talk) 22:09, 25 May 2014 (UTC)

I don't think it's medical inflation only. Those medical scanners have big moving parts that can be controlled with great precision, something like astronomical telescopes which rotate as the Earth does, to keep a steady aim at the same spot in the sky. Such devices are expensive. StuRat (talk) 03:29, 26 May 2014 (UTC)

The difficulties are things like:

1. These machines have to be large enough to scan an entire human. Most hobby-level 3D printers have around 6"x6"x6" build volumes - we'd need 24"x24"x80".
2. They have to be reasonably fast. Sick people don't want to spend an hour in those scarey, claustrophobic, noisy conditions - and a typical 3D printer takes an hour just to make a 2"x2"x2" cube.
3. They have to move considerable weight. The print head of a 3D printer weighs less than half a pound - the "business end" of most body scanners is so heavy that it's easier to move the patient and the bed they lie on than it is to move the scanner.
4. They have to be approved by the FDA with all of the animal and human trials processes.
5. It has to be possible to keep them clean and sterile
6. The patient has to be protected from the machine itself (liquid helium, the radiation source or the big magnets)
7. Sales volumes are small - so R&D costs have to be shared between a few thousand machines rather than tens or hundreds of thousands.

...the list goes on. Sure, you can find cheap solutions to some parts of this - but engineering with ALL of those constraints isn't cheap.

The one thing that ISN'T hard to deal with is precision! FMRI machines only manage a precision of about 2mm, I know that the table that moves the patient through various other kinds of scanner only moves in either 1mm or 3mm increments - so we might expect them to have only about 1mm precision elsewhere. Most 3D printers, CNC routers and laser cutters built by hobbyists are easily capable of sub-millimeter precision.

The intersection of precision, size, speed, cost and weight is what causes the biggest issues for body scanners - you can move something small with great precision - but something large and heavy is much harder. Moving something very slowly and with great precision is also not difficult - but doing it rapidly is much harder. SteveBaker (talk) 12:46, 26 May 2014 (UTC)

Right, just like measuring mass within a gram isn't hard for a kitchen scale, but would be a serious challenge for a truck scale. StuRat (talk) 12:56, 26 May 2014 (UTC)

Yep - my point exactly. SteveBaker (talk) 13:03, 26 May 2014 (UTC)

The devil is in the details with these kinds of machine. Heating up powder is tough because most powders conduct heat - so getting one "voxel" (a 3D pixel) hot enough to melt it will make the adjacent voxels fairly hot too. When you zap a bunch of voxels that are near to each other - but not touching, the heat contained in the volume has to be conducted away somehow.

• If the material conducts heat poorly, then the voxels that you melted will stay liquid for a long time - and then unmelted powder nearby can float around and move in the parts of the object that you melted.
• If the material conducts heat well, then areas that you didn't want to melt that are adjacent to areas that you did want to melt will get hot enough to melt in turn - and the finished object won't have the precise shape that you wanted.

With plastic extrusion machines, getting the temperature just right is the biggest problem. It has to be high enough to allow the plastic to be extruded through a very thin nozzle - and high enough to allow new layers to fuse with the layer below - yet not so high that the object will slump into a puddle or that the new layer will completely melt the layer beneath - and slowly enough that the thermal expansion of the material doesn't cause warping. Computer-controlled fans are one answer to this - cooling the material after it's been extruded. This is hard enough when the material is placed only where you need it and you can apply cooling airflow. In the machine you have in mind - it would be virtually impossible to control that.

The other problem is that this machine is going to be spectacularly dangerous. Spewing focussed microwaves in all directions is not nice! It's just not the kind of thing that a bunch of enthusiasts can easily build...the spectacular decrease in the price of 3D printers (they used to cost $35,000 - the "Peachy" printer was Kickstarted for under $100!) is because amateurs can easily tinker with them. SteveBaker (talk) 13:03, 26 May 2014 (UTC)

Professional athletes

When professional athletes stop training in between seasons, do they stop training completely or do they maintain some light activity? — Preceding unsigned comment added by Clover345 (talk • contribs) 21:38, 25 May 2014 (UTC)

They'll typically exercise but at a lower impact allowing their bodies to get the necessary repairs. Note that when they exercise normally, they will increase the intensity of that to the point where it becomes unsustainable on the long run. They then suddenly power back causing their fitness levels to greatly overshoot the level they would be able to attain when sticking to a constant exercise routine. This is damaging to the body on the long run, so they need to give their bodies some rest for the next season. But what is rest and low impact exercise for athletes would still be extremely heavy exercise for most normal people. Count Iblis (talk) 22:56, 25 May 2014 (UTC)

May 26

Example of a distributed parameter system

Can someone give me an example of the equation for a distributed element model? For example, for a circuit with an inductor, ${\displaystyle V=L{\frac {dI}{dt}}}$ is the ODE for the lumped parameter system. Can someone give me an example of a distributed parameter system? 203.45.159.248 (talk) 02:23, 26 May 2014 (UTC)

Sure: the telegrapher's equations provide differential equations to define the voltage at each point in the signal path. You can do the same thing for the derivation of the radar equation, but that equation is conventionally simplified to solve for power received at a fixed location.

The key concept is that your lumped-element equation is an ordinary differential equation in one variable (time). When we model a distributed system, we must use a partial differential equation with variables for time and position. The telegrapher's equation is of course simplified to one position-parameter: distance along the transmission line. In full three-dimensional representation - like a full-form RADAR scatter solution - we need three position variables x,y,z; and before long, we are actually solving the general form of the wave equation, as expressed by Maxwell's equations, with electromagnetic parameters specified for every point in the model-space. Nimur (talk) 03:50, 26 May 2014 (UTC)

OK. Thanks for your answer. I see the full telegrapher's equations under "Lossy transmission line" on the article. I am interested to know the three-dimensional equation, and how that reduces to Maxwell's equations. Also, are L, R, G, and C functions of position and time too? 203.45.159.248 (talk) 06:25, 26 May 2014 (UTC)

Those parameters might vary with position. That will make the solution more difficult - at a certain point, an analytic solution is impractical, and we would use a numerical method to solve.

For three dimensions, we have many options. I would solve the nonhomogeneous form of Maxwell's equations, where the nonhomogeneous term is a field function describing the resistance and inductance (in terms of permittivity and permissivity). I would solve this using the staggered cell method, which is pretty stable but slow. A friend of mine works for a small company and writes commercial software to solve this equation by the Galerkin method. A few other options include solution by Fourier transform or solution by multiresolution methods. All of these fall under the giant umbrella of finite element analysis, but they are simply techniques to deal with the many many terms in these equations.

Unless your simulation environment is mostly empty, a closed-form analytic solution is probably impractical. Nimur (talk) 15:19, 26 May 2014 (UTC)

Also, at the reference section in our article lists several of the standard textbooks on this topic. Nimur (talk) 17:07, 26 May 2014 (UTC)

What can be taken to heal mouth ulcer?

Zonex shrestha (talk) 04:42, 26 May 2014 (UTC)

We have an article on mouth ulcer which explains there are different kinds. If your interest is academic you might want to narrow down your question. If you're looking for treatment for your mouth ulcer, people here can't readily diagnose which kind you have, and there are some people who are dogged about preventing people from even trying. Wnt (talk) 04:59, 26 May 2014 (UTC)

Zonex, the majority of your questions can be answered by googling or searching wikipedia. Try those first and come back if you have questions that weren't answered by your searches. Justin15w (talk) 15:11, 26 May 2014 (UTC)

Banana worms

I often hear of stories of people seeing worms or parasites in bananas but yet I've never seen one and can't even find a picture on the web. Are there really works which live inside bananas or is it just a figure of people's anxieties about parasites? — Preceding unsigned comment added by 82.40.46.182 (talk) 15:09, 26 May 2014 (UTC)

There are a few that attack the roots, and we even have some pictures. Please see List of banana and plantain diseases#Nematodes, parasitic. Not sure whether any get to the fruit.--Shantavira| 15:26, 26 May 2014 (UTC)

Our article on banana has a section on pests. Most of the pests that affect the fruit are fungi. Nimur (talk) 15:31, 26 May 2014 (UTC)

Fruit fly larva are "worms". And, as you know, "Fruit flies like a banana, but time flies like an arrow". StuRat (talk) 15:35, 26 May 2014 (UTC)

I believe the OP is referencing a fairly recent urban legend making the rounds that the little smutzy bits at the end of each banana (i.e. the little chunks that usually stay in the peel or you otherwise pick off and throw in the trash) are parasites or discrete living things of some sort. Complete nonsense. There's a bit of background here. They're slightly fibrous and a bit squishy, but harmless. Matt Deres (talk) 01:32, 27 May 2014 (UTC)

May 27

Synthesising milk in bioreactors?

Could milk be made in bioreactors using engineered bacteria to make the proteins? --78.148.110.113 (talk) 02:36, 27 May 2014 (UTC)

Probably, but why ? Are you hoping to make it more cheaply than from actual cows ? Are you hoping to make it healthier ? If so, removing the fat from cow's milk or using one of the many substitutes, like almond milk, soy milk, and rice milk, might be a better option. StuRat (talk) 04:28, 27 May 2014 (UTC)

Cosmic Microwave Background radiation

According to Fred Hoyle c.s.,

“It has been known for many years that the energy density of the microwave background is almost exactly equal to the energy released in the conversion of hydrogen to helium in the visible baryonic matter in the universe Thus the energy released in the production of this He through the conversion H → He is 4.5 × 10 erg/cm, which if thermalized gives a radiation field of 2.78 K.”*

According to present measurements the temperature of the CMB is 2.72548 K.

My question is

1. Does the temperature difference –Hoyle’s 2.78 K versus 2.72 K – invalidate Hoyle’s statement that the CMB may originate in the H → He conversion?
2. How is radiation is thermalized?
3. How does the baryon-to-photon ratio determine the temperature of the CMB? Has this ratio been set to produce the desired temperature or is it measured –and, if so, how?

• From: Further astrophysical quantities expected in a quasi-steady state Universe Hoyle, F; Burbidge, G; Narlikar, J.V.; Astron. Astrophys. 289, 729-739 (1994), Ch. 4.1, http://adsabs.harvard.edu/abs/1994A%26A...289..729H

Antonquery (talk) 03:06, 27 May 2014 (UTC)

Woah, dense questions! I'd love to tackle all of them, but let's start with the easiest: how is radiation thermalized? We can throw some handwaving around about poynting vectors and energy density... if you spend any reasonable time with those equations, somebody (either you or your intellectual superior) will eventually derive a relation between radiation temperature and energy density. But I couldn't remember exactly how that worked out... so I pulled out Pacholczyk's Radio Astrophysics, which has an appendix working the math out. In broad brush strokes, we start out from the plane wave solution to Maxwell's equations, in empty space. From this, we write the intensity of the radiation in terms of its field amplitude. Apply the Poynting theorem (Pacholzyk spells this "Pointing") to relate intensity to flux. Then some gorey math to transform the beam to equivalent Stokes parameters (just a different coordinate frame to completely define an arbitrarily-polarized wave)... literally four pages of heavy mathematics later, and we can write this as a Planck function - which you obviously already know is nearly the blackbody radiation equation..., and presto, we have a effective temperature directly derived from an energy density. Just putting a bunch of joules in a box means that there's a corresponding temperature, no matter how you arrange that energy. (Of course, that energy is, in this case, arranged as oscillation of electric and magnetic fields). My textbook then cites Chandrasekhar, Radiative Transfer (1950), as its reference... and that's probably the direct path to the original source of this particular unit of knowledge (as discovered by our species). So, there you have it: electromagnetic radiation is thermalized because it inherently has a radiation temperature. Nimur (talk) 05:51, 27 May 2014 (UTC)

... It seems that your Question 3 is answered by Hoyle's reference to his own 1968 lecture, which is available on JSTOR or from the publisher. (On closer inspection, it's the transcript of his award lecture). If I can get access tomorrow or later this week, I'll read through it and report back. I don't think we can answer Question 1 until we know how he arrives at the 2.78 K number, which he calls "fortuitous." I think your answer hinges on whether that value is intended to be very accurate, (i.e. no handwaving). Nimur (talk) 06:27, 27 May 2014 (UTC)

Fascinating lecture. It can be accessed at no cost if you create a JSTOR account.

A few more comments: there is no mention of "baryon to photon ratio." The Hydrogen-Helium conversion rate appears to be a direct observation, made consistent with known nuclear chemistry.

Based on the number of significant figures, and based on Hoyle's collection of several disparate sources of radiation lumped together by "approximately" equal temperatures, I doubt he would have worried too much about accuracy to a few hundredths of a Kelvin. You can read his paper to make up your own mind; but he lists several sources that are equal in order of magnitude, and calls this an unlikely coincidence.

Whether his thesis has merit is a different issue altogether; but I don't think a 2.72 K measuresd, vs. 2.78 K predicted, effective temperature in itself is sufficient to invalidate his theory. Nimur (talk) 07:14, 27 May 2014 (UTC)

Nimur, the thermalization problem is how you get from H → He fusion in stars to a near-perfect 2.7 K blackbody filling all of space, not how energy is related to temperature.

I'm not well informed on this, so take what I say with a grain of salt, but re question 2, the paper attributes the thermalization to scattering by dust, "much of it in the form of iron needles". Re question 1, it also mentions a prediction of 2.68 K for the blackbody temperature, a full 0.1 K away from 2.78 K, so it's plausible that with more tweaking they could get 2.73 K. Re question 3, I don't know if the baryon-photon ratio is related to the CMB temperature but it is related to the anisotropy of the temperature via acoustic oscillations. Measuring the ratio and setting it to produce the desired (observed) result are the same thing, so the answer to that part is both. In addition to the temperature anisotropy, I think the ratio is independently constrained by big bang nucleosynthesis and by direct measurements of the baryonic matter and CMBR photon density in the present-day universe, but you could take any of those to be the measurement and the others to be tests of a prediction based on the measured value. There isn't really any difference.

Ned Wright's page on steady-state cosmology may be a useful source of references, and it also explains the reasons that no one takes Hoyle et al seriously any more. Wright mentions "carbon and iron whiskers" as the agents of thermalization. -- BenRG (talk) 08:34, 27 May 2014 (UTC)

Some of the fusion energy to convert H to He is also "wasted" on energy in relic neutrinos (aka Cosmic neutrino background) which will account for some of the missing energy too. Also don't expect that the average density of He or H in the universe is accurately known. Graeme Bartlett (talk) 11:09, 27 May 2014 (UTC)

Gull knows how to turn on tap/faucet to get water?

See this video, found today after randomly browsing gull vids. Is this something that we already knew that they were known to do? Never seen or read about anything like it myself. --Kurt Shaped Box (talk) 07:16, 27 May 2014 (UTC)

I'm no "expert" on gulls, pigeons and chickens. But I have spent a lot of time watching them, just as a consequence of laziness. They certainly do have sharp eyesight and long-term memory, so I don't doubt this bird's motive was drinking.

But without knowing the backstory, exact shape or flavour of the tap, s/he may have been merely pecking at it, until something more interesting suddenly came along, for unknown reason. If I just happened to wander through the end of a rainbow, and instinctively caught the bright, loud leprechaun to get rich, I'll still have no idea why that (allegedly) happens.

We're not so different, mammals and birds. One huge similarity is how we prioritize water on a warm day. But priorities aren't always goals. It'd be nice to see some time-lapse birds around taps, and get to the bottom of this. InedibleHulk (talk) 07:42, May 27, 2014 (UTC)

If chickadees can figure out how to open milk bottles, then why do you suppose a seagull would be any less capable of figuring things out? 24.5.122.13 (talk) 08:24, 27 May 2014 (UTC)

I dunno, maybe I'm wrong, but biting a hole in something to get at what's inside (which gulls do all the time too!) doesn't seem to me anyway, to be as much of a leap of intellect as switching something on. Seems to be more of an abstract thought... --Kurt Shaped Box (talk) 18:47, 27 May 2014 (UTC)

light bulb air conditioning savings?

Suppose you replace 10 85-watt incandescent bulbs that are on for 10 hours per day with LED bulbs that use 9.5 watts. Is that going to make a noticeable difference in the electricity used for air conditioning, or is it negligible? (I'd say that 10 US cents per day is not quite negligible.) Bubba73 07:31, 27 May 2014 (UTC)

This is a common question on Reference Desk. You might like to search the archives.

The answer is, it depends. Let's say its mid summer where I live. The diurnal mean ambient temperature is about 28 C. That will make me run the aircon on cooling all day long. To need 10 x 85 watt bulbs, you'd own a mansion with 10 rooms and be very wasteful. Let's be more realistic - my house has 1 kitchen, 1 laundry, 1 living room, 2 bedrooms, 2 studies/offices, and 3 toilet/bathrooms. Total 9 rooms. Each room except the kitchen and living has ONE 42 watt bulb, kitchen and living rooms each have 2 x 42 watt bulbs. On an average day all rooms except bedrooms, bathrooms & laundry has lights on 12 hours per day. Bedroom, bathrooms and laudry average less than one hour per day 0.5 hour per day - lets forget them.

So I have 5 x 42 W x 12 / 1000 = 2.5 kilowatthours per day consumption. The central aichon is rated at 9 kilowatt cooling and just manages to cope with the worst of summer. It's 40 years old and has a Coefficient Of Performance (ratio of cooling to consumption) of 2.2 (typical for its type). So if it has to shift out 2.5 extra kilowatt hours due to the lights, it will draw an extra 1.12 kilowatt hours. So the true cost of lighting to me is 2.5 + 1.14 ie 3.6 kilowatt hours per day.

Now if I replace all bulbs with LEDS, I'll save approx 3 kilowatthours per day, worth about 48 cents at the rate my power company charges.

Now, let's say its winter. Where I live, mid winter diurnal mean is about 16 C, and that means I run the aircon on heating mode all day. So the 2.5 kilowatthour draw of the lights ease the laod on the aircon, causing it to draw less. In heating mode its COP is only about 1.9, so the DECREASE in aircon draw (due to less heat required) is about 1.3 kilowatt hours. So my true cost of lighting with bulbs in winter is about 2.5 - 1.3 = 1.2 kilowatthours per day. If I replace all bulbs with LEDS, the true lighting cost is now reduced by about 17 cents.

Lets say I replace the aircon with the latest type with invertor unloading and economy cycling. I might get a COP of about 3, only a small improvement but I would save about 70 kilowatt hours per day, worth about $10 per day. It happens my total energy bill (lights, aircon, water heating, cooking, appliances, etc) is about $16 to $18 per day.

The moral of the story is that while more efficent LED lighting will save energy, who in their right mind cares? You and I would do better by carefully looking at what really pulls the power. When I replace the hot water system (they last about 10 years), I'll go for the heat pump tupes now available - that will save dollars per day, not cents.

Note that I have a somewhat large house, and work as a consulting engineer from home, so my power bill is quite large. Most would have a pwer bill much lower.

Floda124.182.50.125 (talk) 08:07, 27 May 2014 (UTC)

(ec)Total power used by incandescent lights = 8.5 kWh/day

Total power used by LED lights = 0.95 kWh/day

How efficient is the AC?

According to http://energy.gov/energysaver/articles/room-air-conditioners a reasonable Seasonal energy efficiency ratio (SEER) for modern room air conditioner is 10. EER is the BTU/h rating of the AC divided by the power consumption in kWh.

We need to convert between BTU and kW so that we use the same units for heat in and heat out. According to British thermal unit 1000 BTU/h is approximately 293.071 W.

The incandescent bulbs are therefor adding 8500/293.071 ≈ 29 BTU of heat to the room per day.

An AC with a SEER of 10 will consume 2.9 kWh to remove that much heat from the room per day.

The 950Wh/day from the LED lights converts to 950/293.071 ≈ 3.24 BTU

An AC with a SEER of 10 will consume 0.324 kWh to remove that much heat from the room per day.

So the total electricity saving (all other things being equal of course) by switching from incandescent to LED lighting is:

Incandescent lights - LED lights: 8.5 - 0.95 = 7.550 kWh

AC power saved 2900 - 324 = 2.576 kWh

Total daily electricity saved 7.550 + 2.576 = 10.126 kWh, a significant saving in anyone's currency! Roger (Dodger67) (talk) 08:20, 27 May 2014 (UTC)

Why mess about with BTU's? The heat put out by incandescents is, in SI, measured in watts. You can stay in watts for the whole time - much simpler. The heat shifted by an aircon is measured in kilowatts, the electrical power input is also measured in kilowatts. That's why the aircon industry uses the term COP (coefficient of performance), which is the ratio of heat shifted (in kilowat hours) to the electrical input (in kilowatt hours). Typical older domestic aircons have a COP of about 2.2 to 2.5. It can be improved by invertor techonolgy and other modern tricks. It would be even better if they had not banned freon.

Who the hell is going to run 10 x 85 watt globes unless they are very rich and wastefull dudes? An 85 watt glode will overheat in a standard light fitting anyway.

Floda 124.182.50.125 (talk) 08:36, 27 May 2014 (UTC)

It would indeed have been easier to work only in SI units but the sources I found used BTU, so I had to do the conversion. I chose to answer the OPs question as asked and not to create a totally different scenario. Roger (Dodger67) (talk) 09:09, 27 May 2014 (UTC)

Thanks all. My kitchen has nine can lights, plus two other lights in a fixture. These would be 65 watts each if they were incandescent. The house my father is in has a lot of 85-watt PAR 38 incandescent bulbs all over the house. I think there are at least 10 in the kitchen/dining/living area - probably a few more. My air conditioner is SEER 10 but the ones there are newer and should be more efficient. But from the figures above, it looks like the a/c savings are about 1/3 as much as the savings of LED over incandescent, when a/c is needed, which is about 250 days/year here. Bubba73 16:38, 27 May 2014 (UTC)

When I ran the numbers for my house, it paid off nicely to switch from incandescent to CFL bulbs, but the additional step to LEDs did not make economic sense, because the energy savings relative to CFLs is minimal, and the purchase price is on the order of 20 times more for LEDs than CFLs here. There's also an oddity in CFL pricing here that 60 watt equivalent (13 watt actual) CFLs cost half as much as 40, 75, or 100 watt equivalent bulb purchases, and anything bigger than 100 watt equivalent is prohibitively expensive. I therefore purchased 7 floor lamps, at < $20 each, which accept 5 bulbs each, and I put the cheaper 60 watt equivalent bulbs in each socket, for 300 watts equivalent, and 65 watts actual, per lamp. I also retrofit a lamp which only had 3 sockets with a couple socket splitters, so I can put 5 bulbs in there, too. So, I can light every room this way now, and only have to pay 50 cents when I replace a 60 watt equivalent CFL, which is rarely, in any case.

I also have a 300 watt halogen floor lamp, but I've concluded that I should only use it during winter, and in the room where I am located, as it's rather like running a lamp and an electric space heater at once. (This can actually be beneficial form of zone heating, in winter.)

As for recessed "can lights", I used to have those, but concluded that they were absurdly inefficient, in that they only light a small spot directly underneath them. So, I can see why you might need so many of those to light a room. A light fixture in the middle of the ceiling is far more efficient. To verify this for yourself, I suggest you turn on the 9 can lights in your kitchen alone, and then the 2 fixture lights alone. I'd bet you get as much light or more from the 2 fixture lights.

One last comment on lighting is that you need light-colored walls. Dark wood paneling has the ability to absorb as much light as you shine on it, and still keep the room dark. StuRat (talk) 17:24, 27 May 2014 (UTC)

We have all light-colored walls, except for the dining room.

I don't like CFLs because they take so long to come on and get dimmer as they get older. I'm not taking out working CFLs to put in LEDs, though. And sometimes they start buzzing. And some CFLs last a long time (I've got some that are 11 years old) and some don't. I put CFLs in the kitchen when we remodeled it in November 2012 and already three of them have died (one today).

In the kitchen, seven of the cans are on one switch and two are on another switch. The two in the fixture are 40-watt equivalent each. Seven cans are much brighter than those two.

BTW (to all), I knew about the direct electricity savings. I was asking about additional air conditioning savings. I had googled and found it discussed in some places, but didn't find any figures, or even estimates. Bubba73 18:35, 27 May 2014 (UTC)

I, like just about everyone else, have found that CFL's don't last long - around 4 to 12 months (varies depending on brand), which is not as good as incandescents. That makes them uneconomic. So I've given up using them, except in bathrooms. They are good in bathrooms because of their slow warm up. If I get up for a pee in the middle of the night, I'm not blinded by the sudden large amount of light you get from other types. I used to fit 25 watt incandescents in bathrooms/toilets, but sometimes you need a good light. I tried LED lighting in my home office, but the colour is not as good as incandescents. 60.230.250.114 (talk) 00:46, 28 May 2014 (UTC)

CFLs last for years for me. You can't use them where heat is an issue, like in those "cans", or where they will constantly be turned on and off, like when connected to a motion sensor. And you need special CFLs for dimmer switches or "instant on" ones where that is important.

As far as an estimate, I'd say just doubling the direct electricity savings, in summer, is a rough way to estimate your total savings. That is, the electricity wasted as heat requires roughly the same amount of electricity to remove that heat from the room. Some factors would push that up, like A/C not being 100% efficient, while other factor keep the costs down, like using more efficient methods of cooling, such as fans in windows or heat pumps, or not needing to get the temperature all the way back down at night. Also, the excess heat from incandescents is a slight benefit in winter, when it reduces your heating bill a bit. StuRat (talk) 03:35, 28 May 2014 (UTC)

Zone heating/area heating

Do we have an article ? Are these known under another name ? (They both mean that areas of a building can be heated independently, as with space heaters, to allow more heat where needed and less elsewhere.) StuRat (talk) 18:01, 27 May 2014 (UTC)

See Zone valve and Damper (flow)#Automated zone dampers. Red Act (talk) 21:12, 27 May 2014 (UTC)

Why are fruits classified as living things?

Apples are given the species name of Malus Domestica. But I don't think fruits in general should have species names, because they should not be considered living things in the firs place.. Fruits are ovaries of plants. And an ovary of a human would not be a living thing. So why are fruits classified as living things? Ac05number1 (talk) 07:58, 27 May 2014 (UTC)

That's the name of the tree, not the fruit. The wording in the apple article is admittedly a bit confusing: "The apple is the pomaceous fruit of the apple tree, Malus domestica..." -- BenRG (talk) 08:42, 27 May 2014 (UTC)

..And in any case, you eat fruit and vergetables when they are fresh. That means when they are alive. Plants are not animals. Animal metabolism goes at a fast rate, generating considerable heat. When you cut off blood flow to animal parts, death occurs quickly. But plant material depends on the flow of sap, which is an extremely slow process. Plant metabolism gnerates negligible heat, however the minute oxygen/CO2 exchange of fresh fruit and vegetables can be measured. When you cut off the flow of sap to a plant part, it keeps on living. Floda 124.182.50.125 (talk) 08:47, 27 May 2014 (UTC)

• There are major problems with coming up with a concise, complete, and self-evident definition of "life". Whether something is defined as "living" really depends on how you carefully define your terms, and there's not a lot of agreement on this. Life#Definitions covers some of the multitude of problems with the definitions. Just be aware that even the experts don't have wide agreement on what life is. --Jayron32 17:10, 27 May 2014 (UTC)

Fruits are not ovaries, they are the product of male X female reproduction (pollen and blossoms, to put it simply). Also, it's important to keep in mind that flora and fauna could not care less how humans classify them. They just go on doing their thing as they always have. ←Baseball Bugs carrots→ 19:14, 27 May 2014 (UTC)

Um, you're going to have to inform every botanist and plant scientist in the world that fruit are not ovaries. From the Misplaced Pages article titled fruit, in the opening sentence,: "In botany, a fruit is a part of a flowering plant that derives from specific tissues of the flower, one or more ovaries, and in some cases accessory tissues" (bold mine) and later in the same article, the "Fruit development" describes, in some detail, the changes that occur in the ovary as it develops into the fruit. --Jayron32 21:10, 27 May 2014 (UTC)

The OP compared this type of "ovary" with a human ovary. From what you're saying, that is not a valid comparison. ←Baseball Bugs carrots→ 22:47, 27 May 2014 (UTC)

You said "Fruits are not ovaries." But they are. If you didn't mean that, you shouldn't have said that. --Jayron32 01:36, 28 May 2014 (UTC)

Yes, you're right, as per Ovary (botany). So when the OP said, "Fruits are ovaries of plants. And an ovary of a human would not be a living thing," he was almost literally mixing apples and oranges. ←Baseball Bugs carrots→ 02:25, 28 May 2014 (UTC)

So, you've established that humans are not plants. I'm pretty sure we all figured that out already. --Jayron32 02:41, 28 May 2014 (UTC)

Are you sure the OP has figured that out already? ←Baseball Bugs carrots→ 10:05, 28 May 2014 (UTC)

So, eating an apple in a random place - say Paradise - would be oral sex? --Cookatoo.ergo.ZooM (talk) 21:23, 27 May 2014 (UTC)

Masturbation/ejaculation and hormone levels.

Does masturbation or ejaculation increase hormone levels in men? Thanks in advance. --Thomas W. Richardson (talk) 19:15, 27 May 2014 (UTC)

Yes, in particular the hormones oxytocin and prolactin, according to the Orgasm article. Red Act (talk) 19:37, 27 May 2014 (UTC)

I imagine any effect on androgen production would be more pertinent to the intention behind the OP's question. Evan  01:46, 28 May 2014 (UTC)

May 28

X:A ratio

The X:A ratio articles defines the X:A ratio as the ratio "between the X chromosome and the number of sets of autosomes in an organism."

But an X chromosome is not a number. Does the article mean "number of X chromosomes"? But an organism has either one or two X chromosomes... 65.92.7.8 (talk) 01:45, 28 May 2014 (UTC)

Fruit flies can have three... 24.5.122.13 (talk) 02:02, 28 May 2014 (UTC)

Yes, the article means "...number of...", so I just now clarified the article. And although it's uncommon, humans can also have more than two X chromosomes; see Aneuploidy#Types. Red Act (talk) 02:20, 28 May 2014 (UTC)

Okay, thanks. 65.92.7.8 (talk) 03:06, 28 May 2014 (UTC)

Radiation exposure

How do I go from roentgens to Sieverts? Thanks in advance! 24.5.122.13 (talk) 07:34, 28 May 2014 (UTC)

One sievert equals 100 rem. per the Sieverts article you linked. it also states it here. Richard-of-Earth (talk) 08:44, 28 May 2014 (UTC)

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