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September 23

Biology - Genus: Hepatocystis - conflict - Who described it?

Article Hepatocystis mentioned 'Miller 1908' was the first to describe the genus. According to Taxonomicon the genus Hepatozoon was described by Miller 1908, not Hepatocystis. Unfortunately I can't verify the information in Taxonomicon from a second source. Who could verify it and - if necessary - edit the article? -- from de.wikipedia.org Temdor (talk) 00:33, 23 September 2013 (UTC)

What does the letter V of ECG stand for?

In ECG there is 12 leads, every one of them called V. In example V1 and V2 and V3 and so on... so, what does the letter V stand for? Thank you 95.35.220.182 (talk) 08:43, 23 September 2013 (UTC)

I always assumed it was for "Voltage" as these are points at which electric potential difference (voltage) is measured. This is just an assumption though. -- Q Chris (talk) 08:57, 23 September 2013 (UTC)

The 6 "V" leads are the precordial or "chest leads" (the other leads go on the arms or legs), and they get numbered from 1 to 6 as they are placed across the chest from right to left. I'm not certain why the chest leads are designated with "V", but perhaps it's from "ventrum", the Latin for chest. Actually, the "V" does stand for voltage: The use of chest leads was first described in 1932: Wolferth CC, Wood FC. The electrocardiographic diagnosis of coronary occlusion by the use of chest leads. Am J Med Sci 1932;183:30-35, and the positions were standardized in 1938: Barnes AR, Pardee HEB, White PD. et al. Standardization of precordial leads. Am Heart J 1938;15:235-239. It's in this latter paper that we can find that the "V" stands for voltage. - Nunh-huh 09:45, 23 September 2013 (UTC)

Thank you a lot for the help! 95.35.220.182 (talk) 10:45, 23 September 2013 (UTC)

article of CC

I'm looking for the article for the question what does the letters CC of measurement stand for? I mean about 1CC of medicine for example. 95.35.220.182 (talk) 11:34, 23 September 2013 (UTC)

cubic centimeter. -- Staecker (talk) 11:37, 23 September 2013 (UTC)

Yes, and it is equivalent to 1 ml. 1 table spoon is roughly 14.8 cc. Dauto (talk) 13:52, 23 September 2013 (UTC)

In the metric system, a tablespoon as a measure is generally considered exactly 15 ml, by definition, just as a teaspoon is considered 5 ml. I assume the weird stuff where tablespoons and teaspoons are considered non-integer numbers of ml are due to some conversion from american units of measure? 86.164.30.45 (talk) 20:46, 23 September 2013 (UTC)

Ah, I see from our article that the US considers a tablespoon to be 1/2 fl oz, which is then converted to 14.8 ml. So a standard US tablespoon measure is very slightly smaller than a standard metric tablespoon measure. Still, if you're going to say 'roughly', why not give a round integer? 86.164.30.45 (talk) 20:50, 23 September 2013 (UTC)

I guess I'm not that rough? :-)

Garden Spider doing a spot of trawling?

So i'm in Britain and i've got some Zantedeschia aethiopica (Calla Lillies) sitting outside in a pot inside a washing up bowl. This washing up bowl has a few inches of water in and has many what i assume to be Mosquito larvae swimming round the water inside.

I have noticed that there is what i believe to be a rather large European Garden spider sitting on the water with its mouth submerged (and mouth-pincers(?) moving) and it seems to be slowly moving around the bowl.

What i'm wondering is, is it hunting and also is this usual behaviour? I've also noticed a small clump of soil attached to one of its rear legs and was wondering if it is possible for it to use its web to trawl like a fishing vessel?

I've considered the possibility that it is stuck but it seems to be rather happy on the water surface tension and looks large enough to pull itself out. (Cesdeva (talk) 12:04, 23 September 2013 (UTC))

Depends on the size of the spider, but Raft spiders are semi-aquatic and may exhibit such behaviour. (I don't want to look...) --TammyMoet (talk) 13:32, 23 September 2013 (UTC)

I think you're right. After re-observing, the Spider does look more like it resembles those species within Dolomedes. Now to find out which one... (Cesdeva (talk) 13:53, 23 September 2013 (UTC))

Dehumidifiers >100% efficient have a COP > 1 as heaters.

I read on a forum comment that dehumidifiers have a secondary effect of warming the room, and the amount of heat added to the air is more than 100% of the energy consumed (COP > 1). The reason given was that the latent energy from the water vapour is also emitted into the room. The system was likened to a giant heat pump where the dehumidifier takes the place of the compression side and the sun on the oceans as the evaporator?

Is this correct? If so what percentage extra heating would you get, is it significant or marginal? -- Q Chris (talk) 12:08, 23 September 2013 (UTC)

Note as our article mentions (Heat pump#Efficiency), the word 'efficiency' is generally avoided when talking about such things as efficiency is generally taken to a have a specific thermodynamic definition, instead the Coefficient of performance is normally discussed. Nil Einne (talk) 13:04, 23 September 2013 (UTC)

Noted, I have corrected the question -- Q Chris (talk) 13:31, 23 September 2013 (UTC)

It will generate more heat than the electricity it consumes (by a very tiny amount) only until the room is as dry as it can make it be. At that point, it'll be no more than 100% efficient. You might argue that you can put some water in the room to evaporate and replenish the humidity - but that evaporation would cool the room by exactly as much as the humidifier is more than 100% efficient...so the net benefit in terms of heating drops to zero. SteveBaker (talk) 14:15, 23 September 2013 (UTC)

• At a practical level, the most common way of dehumidifying air is to use an air conditioner, which causes water vapor to condense on the chilling elements. Air conditioners obviously don't warm a room -- rather the dehumidifying effect shows up as a reduction in cooling efficacy. Looie496 (talk) 14:37, 23 September 2013 (UTC)

  But they do heat the outside. If you kept the condenser of the AC unit inside the room with you, and then just drained the water outside, you'd have a dehumidifier that heated the room rather than cooled it. --Jayron32 14:47, 23 September 2013 (UTC)

To actually answer the question asked this (possibly unreliable bloggy) page [1] say they achieved a COP of 1.52, ie 52% increase. This [2] more scientific investigation achieved latent COPs up to about 0.38, ie a 38% improvement, depending on the exact setup. I extracted this data from the graphs at the end of the paper. Latent COP represents only the latent heat of condensation, 1.0 has to be added to this to get the total COP assuming all the power going into the dehumidifier unit ends up as heat in hte room. SpinningSpark 17:37, 23 September 2013 (UTC)

Microwave attacks?

When I was at grammar school in the '60', there was a girl in my class with a birth deformity, which impaired her walking. She was the daughter of diplomats who had been located in Moscow, prior to her birth. There was talk at the time that the Russians were bombarding diplomatic staff with microwaves. Was this ever proved, and have there been instances since of people being damaged by microwave or other forms of electromagnetic or focused radiation? — Preceding unsigned comment added by 31.25.4.14 (talk) 13:20, 23 September 2013 (UTC)

People have certainly been killed accidentally by microwaves, but it's unlikely that they would cause birth defects. Generally speaking it takes ionizing radiation to do that -- microwave photons don't have enough energy to break apart a DNA molecule. Looie496 (talk) 14:32, 23 September 2013 (UTC)

Articles such as this one suggest that the microwave bombardment of the embassy building was done from the late 1950's all the way into the early 1970's. The girl you knew must have been between 11 years old and 17 years (because she was "at grammar school") and you say it was "in the 1960's" - which means that she was conceived sometime between 1943 (17 years old in 1960) and 1958 (11 years old in 1969). We know (eg from this) that the radiation started around 1956 or 57. So if you knew her in your first year at grammar school and it was the late 1960's - then it's just about numerically possible that she was irradiated before birth. Mostly, that seems to have caused cancers in the embassy staff at some unreasonably high rates. The daughter of Franz Misch (who was born in 1968) seems to have suffered mental defects - which might be attributable to the microwave bombardment - and if it was indeed the cause of that - then other deformities are certainly possible.

It would help to know what year you were born (because this girl was in your class - and therefore, presumably, within a year or so of your age) - that would tell us whether she was conceived before all of the microwave business started - which would efficiently disprove your theory.

Obviously there is no possible way to prove it. Children are born with deformities all the time - and microwave bombardment isn't often the cause - so even if she was there during the worst of the attacks, the microwaves might still have had no effect on her.

SteveBaker (talk) 14:35, 23 September 2013 (UTC)

Hmmmm - further down this article, it says: "It turned out that the Soviets had been bombarding us with microwaves, beginning in about 1964 or 1965." - which would totally bust this theory since the girl would have had to be at least 5 years old when the attack started. However, the first reference I found said: "Two retired US Secret service agents who accompanied then Vice-President Richard Nixon to Moscow in 1959 said in 1976 that the embassy was bombarded with such heavy radiation that one radiation detection device was damaged". That report seems a bit suspect to me - I mean, what kind of radiation detector would be damaged in that way? Also, if they had detectors installed in 1959, then you'd presume that the bombardment must have gone on for a while before the attack was noticed and the detectors had to be installed. Then this says that "Washington had known what was going on since the 1960's" - which doesn't fit with a destroyed radiation detector in 1959. Then this says that "US officials noticed that the Soviets had begun directing microwaves at the embassy in 1962, perhaps starting as early as 1953"...so that also confirms that the radiation detector couldn't have been destroyed in 1959 - but throws this new curve ball in by saying it might have started MUCH earlier.

So I guess the start date is a bit "fuzzy". SteveBaker (talk) 15:00, 23 September 2013 (UTC)

And more...this suggests that the microwave bombardment was actually a kind of power source for their system of hidden microphones in the embassy...interesting! SteveBaker (talk) 15:22, 23 September 2013 (UTC)

Indeed sources say it was Steve. See Thing (listening device) (unless that's where you got your spybusters source?) -∇-220 of ^Borg 17:10, 23 September 2013 (UTC)

• Who'da thunk the Soviets were such evil bastards? In any case, Looie496's got it right. Microwaves cause heating, not mutations. The Soviets might as well have been pricking voodoo dolls. μηδείς (talk) 15:36, 23 September 2013 (UTC)

In 1971 the Australian magazine Electronics Today published a full technical explanation, with diagrams and a photo, of the Soviet seal microwave eavsdropping system. Based on the operating principle (passive detection & re-radistion) and the distances involved, only around a few watts from the microwave source are required. Nobody would be hurt by that. 120.145.70.130 (talk) 15:43, 23 September 2013 (UTC)

Could that be in the public domain by now? Though the sources for the on-line explanations are probably the same as ETIs'. -√- 220 of ^Borg 17:10, 23 September 2013 (UTC)

See "Kvikk case" and "Radium Girls" and "SCOJ 2005 No.1977" and "Vatican Radio lawsuit".

—Wavelength (talk) 16:49, 23 September 2013 (UTC)

A more directly relevant article is the Great Seal bug. SpinningSpark 17:08, 23 September 2013 (UTC)

There are a large number of publications on PubMed about microwaves (and terahertz radiation, which was not considered a separate category until recently) and DNA. However, there has not been any finding of teratogenesis in experiments. [3] The caveat there, however, is that experiments with broad-band emissions may not cover the field, because there have been specific, frequency-specific interactions observed in terahertz, to the extent that they are under study for things like identifying pathogenic bacteria in environmental samples. The idea encounters considerable skepticism because these photons do not carry the energy to physically break chemical bonds in DNA - they would have to work by vibrating the strands somehow and shaking loose interacting proteins, etc. But I am not convinced such a thing does not occur. Wnt (talk) 18:33, 23 September 2013 (UTC)

Of course, it is also possible that her mother suffered mutation due to increased cosmic ray radiation during repeated air travel. Wnt (talk) 18:34, 23 September 2013 (UTC)

It might also be the father. The Kvikk case suggests that damage to the father's sperm can cause club-foot - which is exactly the kind of thing that our OP could have seen in this girl. SteveBaker (talk) 19:11, 23 September 2013 (UTC)

You're absolutely right -- sorry, "mother" was a stupid thing to say. Actually, fathers are if anything more prone to mutations in specific genes as the result of aging and background radiation, whereas mothers are a bit more prone to pick up large-scale chromosomal aberrations. Wnt (talk) 04:16, 24 September 2013 (UTC)

So if "The Thing" (aka "The Great Seal Bug") was being illuminated at 330MHz - that's only just barely into the microwave part of the spectrum (normally defined as 300Mhz to 300GHz)...it's going to behave more like low frequency radio wave. It's hard to imagine how that could hurt anyone. For sure, the one documented case of birth defects in embassy staff's children could have been a completely unrelated fluke. But what about the increased cases of cancer?

It would *REALLY* help if our OP could tell us his/her age so we can narrow down the likely range of dates over which this girl would have been exposed to this radiation in the womb. SteveBaker (talk) 19:02, 23 September 2013 (UTC)

Our article may be wrong about the frequency. The source Steve found earlier [4], which seems quite knowledgeable, disputes the assesment of the antenna as a quarter-wave and says it is more likely a half-wave monopole. They, and other sources, put the frequency of operation at 1.1 GHz. Quarter-wave monopoles do not work very well without a ground plane to create an image and this was absent here. It is significant in this respect that later American versions of this device used a quarter-wave dipole. Also, the cavity shown on the diagram (0.775" dia) seems much too small to resonate at 330 MHz. SpinningSpark 19:52, 23 September 2013 (UTC)

A retrospective cohort study of embassy personnel found no adverse health effects of the radiation. A 2012 review of this study (http://www.ehjournal.net/content/11/1/85) concludes: "The conclusions of the original report are supported. Contrary conclusions given in some other reports are due to misinterpretation of the results."

Seems that "an opinion piece, not an intended to be a balanced presentation of the literature" by John Goldsmith got more attention than the mentioned study. Ssscienccce (talk) 11:41, 24 September 2013 (UTC)

There are a couple things I want to contribute. In the 50s & 60s perhaps, the American Embassy in Moscow was driving a station wagon around Moscow streets. It was large and the body was made out of wood. It certainly stood out of other (Russian) cars. The KGB puzzled for a while until they figured out what was going on. The car had hidden microwave detectors inside. They were mapping the Soviet Defense Industry. Radiation of every kind was a hot topic those days.

Aside from microwave there might be another potential source of birth defects in Moscow. They still have so called Kurchatov's Institute where Igor Kurchatov and Alexander Sakharov made the atomic and hydrogen bombs. There was a malfunction there in the 50s resulting in radiation contamination of a large district in Moscow. I don't know how far Kurchatov's Institute is from the American Embassy but can find out.

- Alex174.52.14.15 (talk) 01:28, 25 September 2013 (UTC)

Your replies are engrossing. The girl would have been born between 1951-1953. And I think she had a club foot. So your replies are suggestive but not conclusive. Thanks.31.25.4.14 (talk) 09:24, 27 September 2013 (UTC)

...and that's the best you can possibly get. A "conclusive" determination is impossible because that condition happens "naturally" to about one in a thousand children. So even if you knew for 100% certain that she was exposed to some hypothetical kind of radiation that is known to cause club foot in 99% of those exposed, then there was still a chance that she was one of the lucky 1% who was not affected by the radiation - but on of the unlucky 0.1% who got the condition "naturally".

But I think the issue here is that microwaves are not known to cause this problem - and the rash of club-footed children in the Kvikk case is of uncertain cause. So while there is reasonable grounds to suspect that her condition could be blamed on the Russians, it's far from certain that this is anything other than a random birth defect.

Consider the theory that someone posted above. The father was on the embassy staff during one of the busiest times in history for a US diplomat - and therefore probably spent a lot of time flying back and forth across the Atlantic in high altitude airplanes. He'd be getting repeated doses of X-rays to the testicles. One transatlantic flight gets you a dose of 0.07 mSv. Compare that to 0.02 mSv (a chest X-ray on a modern machine) or 0.18 mSv (the maximum that a Nuclear power worker is allowed to incur in an entire year).

SteveBaker (talk) 15:10, 27 September 2013 (UTC)

Surgical treatments for Tibialis (Anterior) Tendinitis?

How could Surgery help to solve such a problem? interesting, Thanks. Ben-Natan (talk) 16:34, 23 September 2013 (UTC)

? Ben-Natan (talk) 19:17, 25 September 2013 (UTC)

Donate my personal data to science

I know I can donate my body to science when I die, but I'd also like to donate my personal data, from my DNA to my Gmail and Facebook archives, so that even my weaknesses and failures will ultimately contribute something to society. Is there a way to do this? I have Asperger Syndrome and other reasons to suspect I may be of interest as a case study. NeonMerlin 17:47, 23 September 2013 (UTC)

What scientists are currently doing that research? Is there a presumed religious freedom to have that information destroyed as a funerary right, many ancient religions believed belongings had to follow to the world of the dead. — Preceding unsigned comment added by CensoredScribe (talk • contribs) 19:15, 23 September 2013 (UTC)

And why do you need to wait until you die to do it? Data is easy enough to copy - and if some kind of research did need it, there would be much greater worth if they could come back and ask you questions about it. I guess the key question here is whether Asperger researchers are lacking data of this sort. I rather suspect that they aren't - or we aspies (yes, me too!) would be being asked for it...and I see no sign of that happening. Anyway - there is a list of Asperger research groups here - I suggest you try to contact them to see how you can help. SteveBaker (talk) 20:47, 23 September 2013 (UTC)

Your Gmail and Facebook archives are not your personal data. The people you corresponded with presumably assumed the conversation would be kept private, since they never gave you permission to disclose it. Donating the data to science would violate their right to privacy. --128.112.25.104 (talk) 20:42, 23 September 2013 (UTC)

In American law you own the copyright to letters you send, but not the letters you receive. For example, one can publish one's own collected letters, but can reproduce letters from others in that collection only with permission. μηδείς (talk) 21:02, 23 September 2013 (UTC)

No need to donate, it's already being used. Count Iblis (talk) 00:16, 24 September 2013 (UTC)

Omg! "Your Data: If You Have Nothing to Hide, You Have Nothing to Fear". Sounds familiar! :-/ -ʊ-220 of ^Borg

Count Iblis's website link is a joke/satire website. The correct link to the NSA's website is https://www.nsa.gov and their statement on the recent issue, available online, largely seeks to correct several mischaracterizations of their activity. Nimur (talk) 09:02, 24 September 2013 (UTC)

And what makes you think that the NSA is telling the truth, and the whole truth? I understand that their activities imply keeping things under wraps. (although I don't believe they go through most communications, and I worry more about private companies accessing my data than governmental agencies which could subpoena it anyway). OsmanRF34 (talk) 14:07, 24 September 2013 (UTC)

Because all activities conducted by the National Security Agency are directly accountable to its administrator, and to the Executive and to Congress; not to mention the United States Supreme Court; and after extensively reading about the involved issues - from other sources I trust, including the Senate committee and House committee, and statements provided directly from our Executive, I have decided for myself that I have high confidence that our form of government is able to adequately provide checks and balances, even in situations when confidential material cannot be disclosed to the entire public. I respect that other people may disagree with that position. I also believe that most other people have not chosen to inform themselves about these issues in great depth. Nimur (talk) 14:28, 24 September 2013 (UTC)

Yeah, that's what they want you to believe. I suppose any descent conspiracy theory will dismiss your evidence, but yes, it seems compelling to me. As said above, I worry more about private companies trying to get hold of my data (maybe to improve their credit ratings, or vet my employability?). And I wonder how could I have the same privacy through email that I have through letters (specially considering that the other side would also need some form of encryption, which many are unwilling or unable to implement).OsmanRF34 (talk) 14:49, 24 September 2013 (UTC)

But is NeonMerlin even in the US or US citizens? They didn't say so in their post and their user page is unclear to me although referring to themselves as a university student seems something less likely for someone from the US to say. The statement you linked to mostly talks about protetions for US citizens and those living in the US. It's great that you living in the US as a US citizen can trust the NSA to protect your rights given the checks and balances, but this may be cold comfort to someone who is not in the US nor a US citizen, who may still have legitimate questions over where this leaves them even if they are not particularly hostile to the US or engaged in any extreme activities, particularly considering there is strong evidence that being a close ally may not be enough to protect you (which isn't particularly surprising). Really the only thing going for NeonMerlin is that despite some ridiculious figures banded around, whatever they do, and with no disrespect, it's likely to be so insignificant that it will never get any specific attention (not so much because the US wants to protect their rights but because the cost would be astronomical). Nil Einne (talk) 15:56, 24 September 2013 (UTC)

Too bad this xkcd came out after this discussion "Privacy Opinions"--220 of ^Borg 09:13, 2 October 2013 (UTC)

Do cats despise potential energy?

Why do cats do things like this? I've known many cat owners and many have reported similar things. My own cats do this as well. A small item like a pen will be sitting on a table minding its own business when a cat will come along to knock it off the table for what seems like no reason. I've even seen one of my cats get up onto a shelf with what appeared to be the sole purpose of knocking each and every item off the shelf. Is there a scientific reason for this? Dismas|^(talk) 20:24, 23 September 2013 (UTC)

I don't think their goal is to knock the items down. Exploring an item involves batting it around, and if it's on a shelf, this results in it falling off the shelf. I'd expect similar behavior from a baby. Both also might put the item in question in their mouth to explore it. An adult human might pick the item up, turn it around, then put it back where it was, but cats and babies lack the coordination/fingers to do this.

In the case of the shelf, though, they might want the junk off the shelf so they can sleep there. I've found many cats like high spots, for the better view. They also know they won't be stepped on there. StuRat (talk) 20:47, 23 September 2013 (UTC)

I am fairly certain the appropriate concept here is not entropy, but evil. You don't find dogs doing this stuff. μηδείς (talk) 20:57, 23 September 2013 (UTC)

True, but dogs in turn tear things to pieces. At least for cats that knock things off high places, some things are salvageable. Plasmic Physics (talk) 21:44, 23 September 2013 (UTC)

Tearing things to pieces is a stage with some puppies, and not usual in most dogs. Don't all cats engage in the knocking things down behavior? μηδείς (talk) 02:20, 24 September 2013 (UTC)

Indeed. I have 5 dogs currently and only one of them finds quite a bit of enjoyment in chewing up rawhides. Three of them nibble on them occasionally. And the last has no interest, though it might have something to do with his advanced age. I have 7 cats as well and I have observed most of them knocking things off tables (mostly pens). Dismas|^(talk) 06:50, 24 September 2013 (UTC)

My cat has never done any knocking things off of anywhere, nor has it jumped onto any furniture that we didn't teach it to, ever. Plasmic Physics (talk) 10:01, 24 September 2013 (UTC)

"Ever." As far as you know. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:52, 24 September 2013 (UTC)

Do what, Dismas? Can you provide a link that doesn't require us to log in to imgur? Astronaut (talk) 15:26, 24 September 2013 (UTC)

Bah! Sorry, Astronaut. Thought I grabbed the universal link. I've changed the link to one that doesn't require login. Apologies, Dismas|^(talk) 16:23, 24 September 2013 (UTC)

I love the concept of cats despising potential energy. Dogs with big tails, in particular Labs, seem to have the same characteristic, though they try to pretend it's accidental. --jpgordon^{::==( o )} 16:42, 25 September 2013 (UTC)

Why does the USA use odd tenths of a Mhz for FM radio?

I noticed that while the United States has radio stations like 99.1, 104.3 and 107.7, in Indonesia and Greece, the same FM band uses stations like 102.6. When was it determined that the USA should use odd tenths and is there any particular reason why? (I flipped a coin in determining whether to post this here or the Entertainment refdesk)Naraht (talk) 23:48, 23 September 2013 (UTC)

It seems to have been an arbitrary choice, as explained here by the FCC. See also FM broadcasting in the United States, based on the lowest frequency a station could use and the bandwidth of each possible channel. Other countries just made a different arbitrary choice or had a different starting frequency With old radios having analog tuning there was no problem going from Europe to the US, but some modern digital radios don't work equally well with both frequency assignment systems. See [5]. Edison (talk) 00:22, 24 September 2013 (UTC)

Of course the FCC site says that the bottom end of the broadcast spectrum is 88.1 and Wikipedia says that there are two stations broadcasting on 87.9, sigh...Naraht (talk)

Years ago I heard that the FCC uses the odd decimals to make everyone have a "point something". So it would be 97.1 instead of 97. I don't know if that is correct. Bubba73 ^{You talkin' to me?} 02:34, 24 September 2013 (UTC)

The FM broadcast band in the US is 88 MHz to 108 MHz and the channel spacing is 200 kHz. As mentioned already, these are arbitrary choices, but given these numbers, it is a simple mathematical consequence that the centre frequencies are an odd decimal. Stations which have overlapping coverage areas, however, are separated by at least 400 kHz. In the UK the radio environment is quite different: there are a lot of stations in an overcrowded space and several nationwide stations broadcasting from multiple sites. Two transmitters with overlapping areas are sometimes spaced at 300 kHz, especially when they are carrying the same nationwide programme.[6] Obviously, one or the other of them must then be on an even decimal centre frequency. The situation in Greece (see List of radio stations in Greece) seems best to be described as anarchy with the regulation system having semi-broken down. I don't know anything about Indonesia but I would guess the reasons for the mix are similar either to UK or Greece or both. [7] says that the Indonesian FM band starts at 87.5 MHz which would naturally lead to even decimal centre frequencies at 200 kHz spacing. List of radio stations in Jakarta, for instance, shows a lot (but by no means all) of stations on even decimals. SpinningSpark 14:46, 24 September 2013 (UTC)

The job of allocating frequncies for broadcast stations is actually quite complicated - more so for AM, where the ground wave may travell 2000 km or more, and there is no "capture effect" (FM receivers have capture effect - a strong signal will render a weak signal on the same frequency inaudible. With AM, the weak station will be audible at low volume), but even for FM it is quite complicated. Here's the basics: 1) stations serving a given city should have widely spaced frequencies to make selection and tuning easy. But not too far apart, or the stations near the edges of the band will be upset as they won't capture listeners tuning between stations. We have some community stations near the top of the band - around 107 to 108 MHz. Hardly anyone knows they are there as all the big name commercial stations are around 94 to 96 MHz. 2) Due to how radios work, downconverting the signal to 10.7 MHz for amplification, two stations separated by 10.7 MHz will together interfere with all other stations in the area. This is due to what is known as cross-modulation in the input circuitry of recievers. 3) Stations that are a multiple of an analog TV channel vision frequency, TV sound frequency, or a multiple of the TV vision/sound separation are at a dissadvantage (in USA and other countries that used NTSC, multiples of 4.5 MHz, making FM channels 90.0, 94.5 MHz, 99.0 MHz, 103.5 MHz bad choices, in standard PAL countries, multiples of 5.5 MHz, ie FM channel 93.5 MHz, 99.0 MHz, 104.5 MHz bad choices, in Britain with unstandard PAL, multiples of 6.5 MHz, making FM channels 91.0 MHz, 97.5 MHz, 104.0 MHz bad choices.) In theory, these issues would not apply if everyone had well designed receivers. An the demise of analog TV has changed things. However, the allocation rules were determined years ago and allow for some people having very cheap poorly performing radios. — Preceding unsigned comment added by 1.122.206.159 (talk) 03:53, 25 September 2013 (UTC)

Actually the superheterodyne technique of an oscillator running at 10.7 MHz higher than the tuning station makes cheap high quality radios compared to AM. --DHeyward (talk) 04:06, 27 September 2013 (UTC)

Well, no, because the superheterodyne technique is used for AM radios as well, with the oscillator running 455 kHz (some radios differ slightly, American car radios made up to the 1950's used a 262 kHz oscillator offset, many radios prior to the 1930's used a 175 kHz offset.) The percieved high quality of FM comes from the wide bandwidth more easy to provide on VHF frequencies. However the same bandwidth and quality is possible with AM. The frequencies used for AM are more subject to interference though. 121.215.63.7 (talk) 10:34, 27 September 2013 (UTC)

September 24

Could polar bears move to mainland Norway and survive there?

From Bear Island it's only 400 km to the Norwegian mainland, polar bears are able to swim that distance. So, occasionaly polar bears could arrive in mainland Norway. But could polar bears survive on the mainland? Once on the mainland, the bears may not not need to hybernate, so they wouldn't need to find large amounts of food to build up enough fat reserves for that. They could perhaps supplement their diet with edible thrash they can find at landfills. Count Iblis (talk) 01:22, 24 September 2013 (UTC)

Is your question whether bears eat trash? μηδείς (talk) 02:21, 24 September 2013 (UTC)

This is speculation on my part, but brown bears and polar bears can interbreed. If just one or a few polar bears arrive at Norway, I assume that if they survive and breed, they will be introgressed into the population. Wnt (talk) 04:12, 24 September 2013 (UTC)

My New-Word-of-the-Day: Introgression, --220 of ^Borg 06:22, 24 September 2013 (UTC)

Sure they could. See Churchill, Manitoba where the bears survive uite well. They may eat the garbage but it's not their preferred food. CambridgeBayWeather (talk) 12:21, 24 September 2013 (UTC)

400 km is a huge distance to swim, even for a polar bear. Why would they choose to swim 400 km south when their immediate problem is the lack of sea ice on which to hunt? After all, they don't know that Norway is there, let alone that it might possibly have some tasty rubbish to eat. SpinningSpark 12:46, 24 September 2013 (UTC)

Some [polar bears (GPS tracked) indeed manage to swim those distance], although it's rare. I know that some polar bears reached Island, but above an iceberg. 15:26, 24 September 2013 (UTC)

But if they made it to the equator, would that turn them into cartesian bears? - ¡Ouch! (^{hurt me} / _{more pain}) 09:06, 25 September 2013 (UTC)

Spherical bears, more likely. ;-) 24.23.196.85 (talk) 22:11, 26 September 2013 (UTC)

Like these? - ¡Ouch! (^{hurt me} / _{more pain}) 12:28, 27 September 2013 (UTC)

Psychotherapy - Control Freak

What is the cure for a control freak? — Preceding unsigned comment added by 31.25.4.14 (talk) 09:03, 24 September 2013 (UTC)

There are a number of things wrong with this question. First, we don't provide medical advice, so can't "cure" anything. Second, there is no clinical definition of "Control Freak". Third, perhaps most importantly, there are, in general, no "cures" for mental issues in the same way that there are cures for the flu, and, really, only a trained psychologist/psychiatrist (like the one diagnosing) should provide anything related to alleviating the issue (as far as possible).Phoenixia1177 (talk) 10:13, 24 September 2013 (UTC)

Most "cures for the flu" don't do that either. It's a virus. Your body's own abilities and time are the main factors in getting rid of it.HiLo48 (talk) 10:22, 24 September 2013 (UTC)

I'm aware of that, but I think it works as an analogy; the point being that the concepts of what "cure" means in the context of the flu compared to ptsd are very different things.Phoenixia1177 (talk) 10:59, 24 September 2013 (UTC)

We have an article on Control freak but I don't think it will help you chill out and stop worrying :) Dmcq (talk) 10:17, 24 September 2013 (UTC)

OP thank you. Perhaps you are being a bit over-literal. I will rephrase. Control freak behaviour, perhaps as a result of psychological/environmental damage, or innate personality, perhaps a personality disorder (not something I suffer from, except in being on the receiving end) are destructive behaviours, to self or others - I wished to know in the context of psychiatry if there is a known method of correcting the personality/behaviour to "normal" (a bit like removing a phobia as one example). So that at the end of treatment, the person is a happy, cheerful, relaxed, fun to be with person instead of control obsessed. — Preceding unsigned comment added by 31.25.4.14 (talk) 11:41, 24 September 2013 (UTC)

Wanting to "fix" someone else's supposed problems in order to benefit yourself, sounds like its own version of "control freak". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:50, 24 September 2013 (UTC)

WP:AGF BBB. SteveBaker (talk) 13:24, 24 September 2013 (UTC)

I don't assume any bad faith. I merely point out that the OP should consider who he's really trying to benefit. I'd have thought that was an obvious issue: "I don't like the way you behave, and I don't feel like changing in order to accommodate you, so you need to change instead, to accommodate me." ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:15, 24 September 2013 (UTC)

Being a control freak is a personality trait - and unlike "fixing" a phobia, you have a hard time changing someone's core personality - and you might not like what they turn into when you do! If what you're asking is how to manage a control freak at work or at some social grouping, the usual trick is to swamp them with a mindless number of small details to micro-manage. They generally end up either learning to delegate or being so busy that they don't have time to bother you anymore. If the control freak is a spouse - then marriage counciling can do wonders. SteveBaker (talk) 13:24, 24 September 2013 (UTC)

My inner control freak obliges me to point out that you mean "counselling" (with one L, if you insist)AndrewWTaylor (talk) 13:28, 24 September 2013 (UTC)

Cognitive behavioural therapy has had some success with OCD, which is a form of control freakery. --TammyMoet (talk) 20:20, 24 September 2013 (UTC)

Interesting replies. Thankyou. Actually I was thinking of the problem in general. In UK at the moment we are inundated with a plethora of fiddling rules, which I suppose originate in some control freaks mind in a position of power. The end results are people being forced to follow rules, even when the result is disastrous, for one example a child died in a pond three foot deep because the community cops were told not to enter the water as they weren't trained in the procedure. And there have been other deaths in similar circumstances. Like psychopaths, the control freak is rarely inconvenienced by their characteristic but it can damage others. So I wasn't thinking of a particular person. But Steve Bakers reply made me think of one. I knew a perfectionist who appears to have been subjected to severe trauma, and now she is a control freak. That is she no longer observes normal social boundaries, but just dives in everywhere she wants with her meddling. As you suggest, although perhaps I have noticed the method by which a control freak is made, the process of undoing the damage is likely to be enormously difficult.31.25.4.14 (talk) 09:39, 27 September 2013 (UTC)

My food gives me a warm, glowing feeling...

...but perhaps that's because it's radioactive, containing isotopes like K⁴⁰ and C¹⁴.

So, my questions:

1) Does consuming these radioactive isotopes contribute to aging ?

2) Are they significant mutagens and carcinogens ?

3) Has anyone tried to remove the radioactive isotopes ? For example, if you could remove the radioactive potassium from fertilizers we use to produce food, that should significantly reduce the radioactivity of that food. I'm guessing that this can't be done in a cost effective manner, but just how costly would it be ? (I'm thinking of another aisle in the grocery store next to organic foods, with "low radiation foods", which would sell at a premium price.) StuRat (talk) 12:59, 24 September 2013 (UTC)

They are not significant mutagens, or carcinogens. They are not just in the fertilisers, they are in the very air we breathe, and in the ground, naturally occurring. Removing them would require isotope enrichment which should increase the price of products by several thousand percent. Plasmic Physics (talk) 13:07, 24 September 2013 (UTC)

According to Isotope_separation#Commercial_materials, only three elements have been isotopically separated for commercial materials, and K is not one of them. K^40 is sometimes separated to use as a radioactive tracer to study nutrient cycling, so you could probably look up prices from a scientific supply company. Short answer: I agree with Plasmic: fertilizing with depleted K would be insanely expensive, and have dubious benefit. SemanticMantis (talk) 13:12, 24 September 2013 (UTC)

Yes, but there might be a market for it nonetheless, as there is for organic foods. A "several thousand percent" increase in price might be acceptable to some well-to-do customers. StuRat (talk) 13:18, 24 September 2013 (UTC)

⁴⁰K and ¹⁴C are long-lived with low enough decay energies that they don't really do any significant harm to you. Given that you probably already have the average equilibrium amount of these isotopes in your body (K through homeostasis, C because it's a very common element and you'll be hard-pressed to find anything without it), abruptly stopping your intake isn't really going to do any non-negligible change to your daily radiation dose.

Particularly radiophobic well-to-do customers might be worried enough to consider foods supposedly with limited amounts of them; but if so, I would advise they reevalute their radiation priorities, since your average exposure from the air (mostly Rn) is on average four times as large as your average exposure from food! Double sharp (talk) 14:13, 24 September 2013 (UTC)

One very important unresolved issue is whether or not small radiation doses are bad for you. It might actually be good. The answer is not known for sure. read Radiation hormesis.Dauto (talk) 14:26, 24 September 2013 (UTC)

Or simply it's something we can deal with. Since we are constantly exposed to it, otherwise we would all be dead. OsmanRF34 (talk) 15:29, 24 September 2013 (UTC)

Just a ball-park analysis of price: Regular Glucose-D is available as a food additive and priced at $500/metric ton. Glucose-D labelled with C¹³ is manufacture and sold for medical applications (Carbon MRI specifically), and is priced in the range of $175-1700/gram (guessing that the 6 varieties offered are for how many C atoms in the Glucose molecule are substituted with C¹³). That is a price ratio of ~1,000,000.

Of course, there are several obvious caveats to this analysis (relative abundance of isotopes; refining for C¹³ vs removing C¹⁴; different processes for separation; meeting the medical vs food industry standards; economy of scale etc) but all in all I think the "several thousand percent" estimate would be unduly optimistic. Abecedare (talk) 15:21, 24 September 2013 (UTC)

That million-to-one price estimate is probably about right for something as simple as glucose - but making a carrot with no C¹⁴ in it would likely be a few orders of magnitude harder - and making a steak without C¹⁴ in it would probably cost more than putting a man on the moon. SteveBaker (talk) 15:37, 24 September 2013 (UTC)

I didn't say the food would have to be completely free of radioactive isotopes, but just at a measurably reduced level, which should be far cheaper. StuRat (talk) 11:18, 27 September 2013 (UTC)

Far in the future, someone will dig up the remains of the eccentric billionaire on a C¹⁴-free diet and get very misleading results from the carbon dating. Katie R (talk) 15:55, 24 September 2013 (UTC)

Actually, I don't think the precise quantity of C¹⁴ matters, as long as there is a sufficient amount. That's because the absolute amount of C¹⁴ isn't how age is determined, but rather the ratio of C¹⁴ to it's decay products. StuRat (talk) 11:20, 27 September 2013 (UTC)

• To address the first two questions: It's unclear whether low-level environmental radioactivity contributes to cancer, because (a) that radioactivity is present everywhere and impossible to get rid of, and (b) many cancers have unknown causes. On the other hand, it's very unlikely that it contributes to aging. Aging seems to be mainly a combination of genetically programmed changes over time, accumulation of protein byproducts in tissue, and gradual shortening of telomeres in the DNA. None of those would be affected by very-low-level radiation. Looie496 (talk) 17:49, 24 September 2013 (UTC)

• I thought an accumulation of genetic damage also causes aging. StuRat (talk) 11:18, 27 September 2013 (UTC)

Why produce metallic technetium?

Does anyone have an idea how and why the Tc shown in the picture in the article might have been produced? (Especially why, since the applications section of the Tc article doesn't mention any use of metallic Tc.) Double sharp (talk) 14:23, 24 September 2013 (UTC)

The obvious explanation is because non-metallic Technetium doesn't exist. When it comes to elements in the vast majority of cases "take it or leave it" is the only choice you have about the form it takes - metals are metalic, non-metals are non-metallic and so on. Some elements have a few different crystal structures e.g. carbon where you do have a choice, but they are the exceptions to the rule. Roger (Dodger67) (talk) 14:50, 24 September 2013 (UTC)

I meant why make Tc the element, not Tc compounds. Double sharp (talk) 14:55, 24 September 2013 (UTC)

The answer, of course, is the same as the answer George Mallory gave when asked why he wanted to climb Everest, at least in spirit. The answer Mallory gave, famously, was "Because it's there". The reason to create metallic technetium is because one CAN create it, and people who don't understand the fundemental human need to do things just to prove one can do them would never understand such reasoning anyways, but acceptable or not, that is the most likely reason why: it serves no greater purpose or reason than that it was possible to do so and someone wanted to do it. --Jayron32 16:56, 24 September 2013 (UTC)

Apparently one reason for producing metallic technetium in bulk is because in that form waste technetium can be processed in a nuclear reactor by neutron capture into stable ruthenium.[8] Presumably such processing of a compound or mixture would produce other undesirable isotopes as well. SpinningSpark 17:05, 24 September 2013 (UTC)

Thanks. Double sharp (talk) 09:58, 25 September 2013 (UTC)

Besides, the hard part is the creation of the elemement, not the chemical processing of the element into a metallic form which can be easily done by standard chemical procedures. So... Why not? Dauto (talk) 17:58, 24 September 2013 (UTC)

It's not that hard to create it, according to the paper I linked U235 yields 6% Tc99 in fission products. Sellafield, according to our technetium article, managed to dump 900 kg of Technetium into the Irish Sea between 1995 and 1999. Producing a couple of small pills of metal out of all that waste does not seem to be such a big deal. SpinningSpark 18:33, 24 September 2013 (UTC)

Is there a mechanism to 'turn off' feelings?

For example, if you are hungry and are confronted by a dangerous situation, would you brain 'turn off' the hunger and activate the being afraid, or at least cautious, feeling? OsmanRF34 (talk) 15:12, 24 September 2013 (UTC)

See Fight-or-flight response, which notes the suppression of various body functions during high stress situations, such as digestion and sexual response. --Jayron32 16:52, 24 September 2013 (UTC)

(EC) Jayron beat me to the link. You also might be interested in the differences between feeling and sensation and emotion and perception. SemanticMantis (talk) 16:57, 24 September 2013 (UTC)

Depression and various psychiatric conditions can supress many urges and "feelings" and various drugs also have such effects. Roger (Dodger67) (talk) 06:59, 25 September 2013 (UTC)

Need some help here!

Last night I left an answer here to the smart insects question and index a photo, but apparently did something wrong in lightroom because the exif info have my real email… can somebody more advance than me fix that? I have read some articles showing how to change all kind of stuff but now I don’t remember and don’t have time so I’ll appreciate that very much… Thanks

https://en.wikipedia.org/wiki/File:Avipa-asesina-LR-.jpg

Iskánder Vigoa Pérez (talk) 15:16, 24 September 2013 (UTC)

I can't see how to edit that page at all. Odd! Suggest you contact a Commons Administrator to delete the page, then re-load it without your e-mail. It appears that that info is added in the camera? You may have to change a setting there too so it isn't added. ExifTool may be applicable here. -©-220 of ^Borg 16:22, 24 September 2013 (UTC)

I can't help here, but thanks for that cool photo! SemanticMantis (talk) 16:22, 24 September 2013 (UTC)

The metadata is embedded in the file so it cannot be removed by editing the page. You need to upload a new version of the file with the metadata removed (or with only the metadata you want to be seen). You can then ask for an administrator on Commons to revdelete the old versions so it can't be seen in the history. Administrators on Wikipedia cannot do this as Commons is a separate project and you have uploaded to Commons, not to Wikipedia. SpinningSpark 16:43, 24 September 2013 (UTC)

I will assist Iskánder and upload a corrected version in case nobody gets to this in the next hour or so. Nimur (talk) 16:53, 24 September 2013 (UTC)

Oh man… I thought it would be easier… that’s very odd, I don’t remember have input my mail in the d90, I don’t even know how to do it — Preceding unsigned comment added by Iskander HFC (talk • contribs) 16:59, 24 September 2013 (UTC)

It's a great photo! Can I ask where geographically was this photo taken? I'd like to try to identify the tarantula hawk species in the image, but I need to know the location for that. Thanks in advance! --Dr Dima (talk) 17:05, 24 September 2013 (UTC)

Above at the insect question [9], Iskander says he's in Cuba. That should be enough of alocation to help ID, unless there are tarantula hawks endemic to different specific valleys or something. SemanticMantis (talk) 18:09, 24 September 2013 (UTC)

Your email was added by PhotoShop when you used it to edit the image -- at some point you set up PhotoShop to use a generic copyright statement that includes your email address. You should be able to remove it by editing the image again with PhotoShop and changing the copyright metadata -- however the version with the email address would still remain in the file history until a Commons admin deletes it. Looie496 (talk) 18:12, 24 September 2013 (UTC)

You can remove the metadata without any application, at least you can in Windows 7. Right click on the file icon on your computer, click on properties, click the details tab, click "Remove Properties and Personal Information". SpinningSpark 18:27, 24 September 2013 (UTC)

Nimur, I watched your notifications, thank you very much, but I’m very short in time, I do renders and only come here to refresh in the inter-times… here you can learn some very interesting things

Thanks all for the answers… the personal data like name and location really doesn’t bother m e, it’s just the email, but if it means too much trouble to cut it out, I’ll be fine, and will take more care next time

Iskánder Vigoa Pérez (talk) 01:03, 25 September 2013 (UTC)

Feminism and Science

Okay, so I'm supposed to be writing a paper on feminism and science, and have to read up as many articles on the topic as I possibly can. What I need is pointers. Can someone recommend good articles written on the topic? (Articles are preferred since going through an entire book is harder with a month's deadline.) I've already collected some essays that anyone can find after googling things like "feminism and science" or "feminism versus science". The reason for posting this here is that some of you might know relatively unknown (or not so obvious) titles or authors. Bonus points if they're pro-science (I'm taking a pro-science stance), and also if they write intelligible English and not the jargon-filled garbage that humanities students are prone to using. 202.153.41.162 (talk) 18:06, 24 September 2013 (UTC)

I'm a bit confused - "feminism versus science" and "pro-science stance" makes it sound like you're framing feminism and science as opposite each other. There are certainly a lot of feminist scientists and pushes to get more women into STEM fields. Parts of the skeptic community heavily push feminist ideals and a pro-science viewpoint. Katie R (talk) 18:36, 24 September 2013 (UTC)

@Katie: I am framing them opposite each other. I don't see where your confusion lies. 202.153.41.162 (talk) 18:53, 24 September 2013 (UTC)

What does "feminism vs. science" mean? That's like saying "abolition vs. mathematics". ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:14, 24 September 2013 (UTC)

[ec]I don't have anything to contribute, but I am curious about how this turns out because it seems like you are comparing apples to pencils here. If we had a better idea of what you were looking for, perhaps we could help a little better. Feminism isn't the opposite of science; it's the opposite of not-feminism. Science is the opposite of unsubstantiated guessing. Mingmingla (talk) 19:15, 24 September 2013 (UTC)

To be more specific, my paper talks about feminists' accusations of how science is a male dominated field, and scientific reasoning is a masculine "tool of oppression" as opposed to feminine intuition. I want articles that talk about how a feminist approach to science might look like, whether it's a reasonable enterprise, or, if not, why. Also whether it's the fault of science in particular that we have more male scientists, or the fault of the society and its constructs. 202.153.41.162 (talk) 19:19, 24 September 2013 (UTC)

Blaming science for how some male scientists might treat female scientists is like blaming the game of baseball when a pitcher throws a spitball. The "fault" is not in science, it's cultural - as in upbringing and old established societal norms, as indicated in the last part of your statement. That's your proper focus for this subject. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:27, 24 September 2013 (UTC)

• (ec) Obvious intersections are sociobiology and evolutionary psychology. Feminists who are of a want to deny innate differences between the sexes are going to challenge claims that women are designed as nurturers by biology. μηδείς (talk) 19:21, 24 September 2013 (UTC)

Women_in_Science,_Technology,_Engineering,_and_Mathematics_(United_States) would be a good starting point. Skimming it, it seems to cover a lot of the arguments about why women are underrepresented in the fields and approaches for addressing the imbalance. It looks well-referenced, so it should provide quite a few sources for you. Katie R (talk) 19:25, 24 September 2013 (UTC)

Women in computing is one area that interests me. My feeling is that having some women around improves the social aspect and makes teams work better. However even though, umm don't hit me for being non pc here, even though women practically got an automatic pass through in our job screening if they were anyway good enough (we didn't say that!) we still couldn't find the number we wanted because so few go in for computing. The situation used to be much better in the past. Dmcq (talk) 21:02, 24 September 2013 (UTC)

• The "masculine tool of oppression" notion isn't a criticism of a certain type of science, it is an attack on the notion of any objective science--objectivity being one of those masculinist ideas. You might profit from a look at Stephen Hicks' Explaining Postmodernism (just found the book is available for free as a pdf from the author) which is one of the standard college texts on the subject. It gives you a wider context in which to look at such "feminist" attacks. (I'd prefer to call them post-modern feminist, since they have little to do with Friedan or de Beauvoir. μηδείς (talk) 21:27, 24 September 2013 (UTC)

Are you talking about postmodernism-vs-science with a focus on feminism? If so, are you looking for books, internet, or journal resources? It's a topic I used to have an interest in (the broader one), I know I have some material still around at home, if this fits the bill, I can dig some up.Phoenixia1177 (talk) 03:41, 25 September 2013 (UTC)

@Phoenix: That would be much appreciated, thanks! Yes, something along those lines surely. I'm very to new the arts (I've recently shifted from a science background) , so my ideas are still very half-baked. I need to do a lot of reading! (= 202.153.41.162 (talk) 06:08, 25 September 2013 (UTC

• Go to newscientist.com and input your search terms there, "Women in science" and "science and feminism" come up with plenty of hits but you will need to find someone with a subscription to access some of the full articles. Richerman (talk) 22:02, 25 September 2013 (UTC)

There is no such thing as a feminist opinion of science, or a scientific opinion of feminism. Among feminists, you'll find every imaginable opinion about science. Plenty of people think science is fascinating, awe-inspiring, and gives humanity unlimited potential to make the world a better place. I'm one of those people, and though I'm not a feminist activist, most people would consider me a feminist sympathizer. On the other hand, you have radical feminists like Sandra Harding who called Newton's Principia a rape manual and thought E=mc^2 was a sexed equation. For more information, see Science Wars. I also highly recommend Higher Superstition: The Academic Left and Its Quarrels with Science by Gross & Levitt, which has been recommended before on these reference desks. It's a condemnation of postmodernism and its willingness to play fast and loose with the facts. It also has a section dedicated to feminism. Keep in mind, however, that this book was written 20 years ago. Since then, the humanities have become much more epistemologically conservative, and consequently more sane. --Bowlhover (talk) 05:45, 26 September 2013 (UTC)

Since most feminist critiques of science are based on postmodern thought, you might find Sokal_affair a useful link. OldTimeNESter (talk) 14:58, 26 September 2013 (UTC)

I should think that actual science (versus a random bunch of misogynostic scientists) would rather support feminism, in that it has no use for social conventions, tradition, etc., which are all forces that oppose feminism. For example, if we include economics under science, having a larger pool of skilled workers, by training and then employing women, clearly has the potential to help the economy. And the scientific method would have us test out new things, like career women who never marry, to determine if this is a workable model, rather than just judging them as being bad. StuRat (talk) 11:13, 27 September 2013 (UTC)

See also Lawrence Summers#Differences between the sexes. Duoduoduo (talk) 13:28, 27 September 2013 (UTC)

You may be interested in ecofeminism, where I see the same shift that Bowlhover has described. Recent ecofeminist theory tends to critical realism rather than social constructionism. Like social ecology generally it has no quarrel with science as a method of enquiry but is critical of the way that science is mobilised for military purposes, agribusiness and other questionable pursuits. Itsmejudith (talk) 07:38, 28 September 2013 (UTC)

Shear force

In the following example, why is the parallel axis theorem used to calculate the second moments of area of the 4 parts of the beam sticking out? Clover345 (talk) 19:29, 24 September 2013 (UTC) http://academic.cuesta.edu/jjones/Engr52/homework/6-29.pdf

Because you need I of the whole beam. Incidentally that answer is a fail, even by my scrappy standards. Random equations that come up with the right answer is not acceptable.Greglocock (talk) 01:10, 25 September 2013 (UTC)

September 25

Controlled Release Medications

I have have certain medications like controlled release melatonin which seem to work mechanically, having an agent that slows there dissolution in the digestive tract. I am curious is this is the sole or typical type of controlled release medicine? Do some CR medicines have a different chemical formulation that changes or slows release or clearing in the bloodstream? I am particularly curious about Zolpidem CR. I don't find any explanation in our article or at the Sanofi website. Thanks. μηδείς (talk) 01:26, 25 September 2013 (UTC)

To clarify, I know from having taken oral morphine after a major abdominal surgery that it is not the morphine itself, but the metabolites that have the most effect. So I wonder if that is the case with controlled release substances--are they designed to take advantage of that phenomenon. μηδείς (talk) 03:57, 25 September 2013 (UTC)

We have a controlled release/time release technology pair of articles. The main methods (by concept, not ordered by popularity or usefulness in certain contexts) are gradually removing a coating to expose the active ingredient, gradually leaching the active ingredient out of a matrix or containment, or chemically cleaving the active ingredient from an inactive-complex precursor. DMacks (talk) 04:07, 25 September 2013 (UTC)

We answered an similar, but unrelated question, a few days ago. The answer can be found in the field of pharmacokinetics. The rate at which a drug enters the blood stream is a matter of a combination of factors, some of it due to the chemistry of the drug compound itself and its natural rate of absorption, and some of it is because of the way the pill is prepared to control how fast the drug is released from the pill, a process called liberation. The so-called "inactive" ingredients (those without pharmacological activity) are actually quite important here; these ingredients are called excipients and they have a lot to do with how the drug is liberated and absorbed. --Jayron32 04:55, 25 September 2013 (UTC)

Okay, so you have both confirmed for me what I expected, there are many means of doing controlled release pills, and it may indeed be a more complicated chemical process than just a physically hard to dissolve tablet, which was the case I ran into when I inadvertently got time release melatonin (anyone who knows how melatonin works would know how silly a product that is) which I had to spend minutes chewing out of their gummy substrate.

So, my specific question is, which of these methods of action applies to Zolpidem CR? Our article doesn't say that they have different formulae or that one is the metabolite of the othert. I couldn't find anything in the Sanofi literature either. So I am curious, can someone find out which of the mentioned mechanisms delays the release of the drug? μηδείς (talk) 05:26, 25 September 2013 (UTC)

PS, to save confusion, I got a BA in Bio as one of my majors as an undergrad, and tested out of Chem 101-102 at an ivy league via my scores in AP chem. So feel free to talk to me about this as a big kid. It help finding the specific info which I am really looking for. Thanks μηδείς (talk) 05:38, 25 September 2013 (UTC)

Zolpidem CR uses hypromellose (hydroxypropyl methylcellulose) for extended release, I think, judging by the difference in ingredients between CR and regular form. Here is some info on the mechanism: http://www.colorcon.com/literature/marketing/mr/Extended%20Release/METHOCEL/English/PTEarticle.pdf Ssscienccce (talk) 05:42, 25 September 2013 (UTC)

Excellent, thanks. μηδείς (talk) 18:50, 25 September 2013 (UTC)

Resolved

Also note that some medications do have slow-acting and fast-acting forms, such as insulin. Our article seems rather deficient on this aspect, so try here, instead, and particularly note the graph at the end: [10]. StuRat (talk) 11:00, 27 September 2013 (UTC)

Sensation in throat

we don't give medical advice
The following discussion has been closed. Please do not modify it.
Whenever I lean my neck and head down, craning my neck I think it's called, while still standing up, I get a tingling feeling in my throat, as if a bubble is passing through it. It almost feels as if my neck is being fractured, but it isn't painful. What is this sensation called and what exactly is going on here anatomically? Bennett Chronister (talk) 05:41, 25 September 2013 (UTC) Sorry - but it is against guidelines to provide medical advice. Please see Wikipedia:Reference desk/Guidelines/Medical advice. Zain Ebrahim (talk) 09:29, 25 September 2013 (UTC) A clarification: I wasn't asking for medical advice. This isn't bringing me pain or injury or anything. I'm just interested, in an academic way, in what this phenomenon is, since I don't think I've ever read about it. Bennett Chronister (talk) 15:10, 25 September 2013 (UTC) Most likely you're compressing a nerve -- that's the usual cause of a tingling sensation when the body is put into a strained posture. Looie496 (talk) 15:33, 25 September 2013 (UTC) It doesn't mater whether the OP feels pain or not, we cannot suggest a cause for his condition. μηδείς (talk) 20:42, 25 September 2013 (UTC) Resurrecting Henny Youngman... Patient: "It hurts when I do this." Doctor: "Then don't do that." ←Baseball Bugs What's up, Doc? carrots→ 21:06, 25 September 2013 (UTC) "Condition"? I thought this was something that happened normally in everybody's body when they stood like that. My question is like asking, "What goes on when I hiccup"? Surely you wouldn't close a hiccup question down.right? Bennett Chronister (talk) 02:30, 26 September 2013 (UTC) The OP has been told we don't do medical advice and no serious answers have been given--feel free to answer with refs outside the hat. μηδείς (talk) 02:44, 26 September 2013 (UTC)

Courting behavior when males ram into each other head first

Is there a scientific term for such a behavior (described in the subject line)? Specifically the rams of bighorn sheep. I was wanting to see a list of other animals that also behaved similarly, but the action doesn't seem to have its own article or category. Rgrds. --64.85.215.13 (talk) 09:05, 25 September 2013 (UTC)

Rutting. Also practised by some breeds of deer and goat (and some humans). --TammyMoet (talk) 09:06, 25 September 2013 (UTC)

I saw that article (Rut (mammalian reproduction)), but figured that ramming was something that was done during the rutting season. So I was hoping there was something on that one specific behavior. --64.85.215.13 (talk) 09:16, 25 September 2013 (UTC)

It is neither courting nor rutting. It's called butting, or locking horns. I also found a nice obsolete word in the OED: to nurt: to push or butt with the horns.--Shantavira|^{feed me} 12:16, 25 September 2013 (UTC)

However, it should be noted that many animals will do a one-sided head-butt at other times, as well, as a means of attack or defense. Thus the comic image of a person bending over when a goat "nurts" them from behind. StuRat (talk) 10:49, 27 September 2013 (UTC)

Mummification

In this distressing case (another link), what exactly does it mean to say that the boy's body was 'mummified', and what could have caused it to happen (as opposed to simply decomposing)? Our article doesn't seem to cover this - it seems to imply that mummification happens as a result of deliberate action or fairly extreme and unusual conditions. AndrewWTaylor (talk) 12:52, 25 September 2013 (UTC)

The body dries out, and the absence of moisture prevents or stops decomposition. The child died in december, in low temperature (near freezing) the decomposition would be slow and with a dry, cold atmosphere and constant draft (open window perhaps) the body could have dried completely. Low bodyweight, absence of food in the digestive system and severe dehydration before death would make it more likely, I assume. Ssscienccce (talk) 13:52, 25 September 2013 (UTC)

<OR here> Based on the first link, it sounds like the word “mummified” was used by the detective constable who discovered the corpse. It is possible he simply misspoke. Based on the description of the smell in the house, it is likely that the body was indeed decomposing. Zain Ebrahim (talk) 14:13, 25 September 2013 (UTC)

(e/c)Yes, mummification is a deliberate preservation of the body, whereas mummify (hence mummified) is used more loosely and can mean "of tissues or organs: to dry or shrivel up." (OED again).--Shantavira|^{feed me} 14:19, 25 September 2013 (UTC)

As I understand it, the smell was coming from rotting food inside the house. They entered the house in september 2011, the boy died in december 2009.

The weather conditions may have contributed as well, see Winter of 2009–10 in Great Britain and Ireland. Very cold air outside would result in very low humidity inside the house. Ssscienccce (talk) 14:41, 25 September 2013 (UTC)

Effect of direction of impact on traumatic brain injury

I heard from a friend that a car crash in which your car is hit from the side is far more likely to kill you then if you were hit from the front. Basically, his explanation was that if the brain experiences sideways acceleration and bounces from left to right instead of from front to back, the middle part of the brain separating the two hemispheres (I believe it's called the Corpus callosum?) is a weak spot and is more likely to tear or suffer damage and you end up with a much worse injury. Is this actually true? If so, would that mean if you were about to drive into a wall, looking away before impact would increase your chance of brain injury?--182.55.86.32 (talk) 14:17, 25 September 2013 (UTC)

If I understand it correctly, PMID 715906 supports the claim that a sideways head acceleration is more damaging than a front-to-back acceleration. However, there are many other factors that come into play when comparing a sideways car crash with a head-on collision. Looie496 (talk) 15:26, 25 September 2013 (UTC)

...the most obvious being that in a head-on collision, you have a nice soft bumper and lots of crumple-zones in front of you to absorb the energy of the collision. Some cars absorb energy by pushing the engine down and behind (which absorbs lots of energy because it's heavy!). In a side impact, there is almost nothing between you and the oncoming vehicle and even with clever design, the car can only crumple in an inch or two before it hits you. Another problem is that your seat back and belt stop you from moving forwards and backwards in a frontal impact - but there is much less there to stop you from sliding sideways in a side impact. Your lap belt will hold your hips in place - but your upper body is hardly restrained at all. A frontal impact in one of the nastiest death-traps ever built - a VW microbus (the last of which is mercifully rolling off the production line in December!) is very often fatal - which is largely because there is nothing between you and the front of the vehicle and it originally had only lap belts. That's a good analogy for a side impact in a modern car. Another issue is that when a car is hit from the front or back, it can usually roll backwards or forwards to retain some kinetic energy and suffer a smaller impact...but the tires on your car strongly resist being pushed sideways in a side impact. Some newer cars now have side-impact airbags to help this situation a bit - but even so, it's not a good way to get into an accident. SteveBaker (talk) 18:04, 25 September 2013 (UTC)

I disagree on your tire argument. While low-speed impacts won't cause a car to move sideways, a high-speed impact will, and there it's just like a frontal or rear impact with the brakes on, in either case the car skids. Also, rolling forwards or backwards (if the brakes are not engaged), can get you into more trouble, with additional impacts, etc., so isn't really a good thing. And, finally, having your car start to move in the opposite direction it was headed only increases the rapid acceleration/deceleration injuries. StuRat (talk) 10:41, 27 September 2013 (UTC)

Schizophrenia rat experiments

You know how some research experiments on Schizophrenia use rats? In order to simulate Schizophrenia in rats, it is known that scientists make an environment that is hopelessly inaccessible for the rat. This presumes that rats have some sort of desire going on. The thing is, how do scientists measure desire in rats? Is it possible that the rat may ever grow tired of the object so that the object will not be desirable at all? Also, how do scientists get access to illegal drugs like PCP in order to perform research on rats and thus simulate schizophrenia? 164.107.103.177 (talk) 15:36, 25 September 2013 (UTC)

As far as I can tell you are describing the paradigm called learned helplessness, but that's considered a model of depression, not a model of schizophrenia. Usually the motivation is to escape from something bad, not to gain access to something good. There are no widely accepted animal models of schizophrenia, but our article will give you an overview of the ideas that have been batted around. And finally, in the USA scientists can get access of controlled substances by getting a license from the FDA, although the process is often difficult. Looie496 (talk) 15:51, 25 September 2013 (UTC)

For more on your final question, see Controlled Substances Act, which governs research access to drugs that are not legally available to the public (at least in the USA, there are similar laws and governing bodies in Europe and elsewhere). Basically, the scientists and the producers of such drugs go through a lot of paperwork and government oversight, involving the Food and Drug Administration, and potentially other agencies. SemanticMantis (talk) 15:54, 25 September 2013 (UTC)

Our article on the economic concept of a Giffen_good mentions an experiment where rats were given water mixed with quinine (which is not tasty to rats). The citation in the article is the 3rd footnote. From memory, the cited book discusses the properties of rat utility functions and how to conceptualize and measure a rat's desire for different things. OldTimeNESter (talk) 15:15, 26 September 2013 (UTC)

Ah, I forgot to address that part of the question. Basically scientists measure desire by the amount of work that an animal is willing to do to obtain something, or the way that it trades off with some other type of reward or (as in the example you mention) punishment. The Behaviorists did a huge amount of work using that approach, generating reams and reams of literature. Looie496 (talk) 15:46, 26 September 2013 (UTC)

aragonite

why are most shells made of calcium carbonate instead of aragonite? — Preceding unsigned comment added by 149.152.20.214 (talk) 15:58, 25 September 2013 (UTC)

Our article on aragonite says that your premise is false, and that most shells are made of a combination of aragonite and calcite. Looie496 (talk) 16:07, 25 September 2013 (UTC)

The presence or absence of magnesium in sea water plays an important role in determining whether aragonite or calcite will be the prevalent form of calcium carbonate present. The levels of magnesium have changed over geologic periods and there were periods in Earth's past when aragonite was the prevalent form. see Aragonite sea and Calcite sea. Dauto (talk) 00:04, 26 September 2013 (UTC)

I seem to have it backwards in my previous post. We are actually living in aragonite sea period currently, so my answer now seems inconsistent. I'm not sure. Dauto (talk) 00:09, 26 September 2013 (UTC)

Turns out your premiss is incorrect and most modern shells include substantial amounts of aragonite which IS a form of calcium carbonate! Dauto (talk) 00:14, 26 September 2013 (UTC)

I'm not sure his premise is wrong, as the calcite article states: "Calcite is often the primary constituent of the shells of marine organisms". Calcite is the more stable form of calcium carbonate, but ultimately the type of crystal will depend on the specific circumstances I suppose. And in old fossils, aragonite originally present will have turned into calcite. Ssscienccce (talk) 07:57, 26 September 2013 (UTC)

Nautical twilight

How many kilometers above you is the daylight when it's nautical dawn at sea level? — Preceding unsigned comment added by 12.196.0.56 (talk) 18:14, 25 September 2013 (UTC)

For starters, Nautical dawn is when the "Sun is 12 degrees below the horizon in the morning" according to Dawn#Nautical_dawn. The earth is roughly 152,098,232 km from the sun, and the Earth's radius is roughly 6,371 km. So you should be able to do some geometry from there to get your general answer. Depending on the accuracy you want, you could take seasonal and latitudinal considerations into account. SemanticMantis (talk) 18:26, 25 September 2013 (UTC)

Why the distance from the sun? Maybe I misinterpret the question, but wouldn't it simply be r*(sec(12°)-1) (about 143 km)? Ssscienccce (talk) 19:15, 25 September 2013 (UTC)

I pictured an ant on a basketball, and a flashlight. It seemed to me that moving the flashlight closer to the basketball would change how high the ant would have to go to see the flashlight, starting from a dark portion of the basketball (i.e. the 12° dark position). But maybe I'm missing something too :) SemanticMantis (talk) 20:17, 25 September 2013 (UTC)

You're missing the fact that the sun is so freaking far away that you can consider it to be at infinite so its actual distance doesn't matter.

Ah...but to know that that is a valid simplification, you need to know how far away the sun actually is!  ;-) --Stephan Schulz (talk) 23:56, 25 September 2013 (UTC)

Yes, it's all about how accurate you want/need the model to be ;) SemanticMantis (talk) 00:57, 26 September 2013 (UTC)

Bestiality and interspecies mating

Did bestiality evolve from the consequences of interspecies mating? In humans, I am not sure if there is a benefit from interspecies mating, because the offspring may neither be viable nor fertile; therefore, the reproduction - as costly as it is - is futile. How did cultural notions of bestiality evolve? 164.107.214.74 (talk) 22:01, 25 September 2013 (UTC)

You might be interested in our article zoophilia, and concepts like ring species and hybrid species. For what it's worth, my opinion is that the answer to your first question is "no." SemanticMantis (talk) 22:34, 25 September 2013 (UTC)

Zoophilia is sufficiently rare that it can be attributed to simply being an abnormality. Just as people often have physical abnormalities which don't increase their chances of reproductive success, they can also have such behavioral abnormalites. StuRat (talk) 10:04, 27 September 2013 (UTC)

I doubt zoophilia has anything to do with wanting to reproduce. Although it reminds me of this quote from Tom Lehrer about his friend "Hen3ry": "He majored in animal husbandry... until they caught him at it one day." ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:49, 27 September 2013 (UTC)

Yes, it's most likely a consequence of the domestication of animals and the increased free time available in modern civilization. Production of offspring requires genetic compatibility, none of which any known animal species has. Not even apes. The closest one can get is Feral children. --Auric talk 22:45, 27 September 2013 (UTC)

September 26

Field interaction from photons or other electromagnetic radiation

If an sub-atomic particle like an electron moves through space it will interact with electrostatic and magnetic forces. Now if a photon or other electromagnetic entity moves through space, will it interact with any other force at all? (besides nuclear cores or gravity) Ie, would it be possible to detect or make a readout of vector direction of a photon source without significantly disturb the photon? Electron9 (talk) 01:01, 26 September 2013 (UTC)

Yes, a photon can interact with another photon, see Two-photon physics. The measurement of a photon properties is subject to the same fundamental constraints as any other measurement in quantum mechanics. --Dr Dima (talk) 01:11, 26 September 2013 (UTC)

Does it have to be the same wavelength photon? or amplitude? or even with the same vector/speed direction? Anyway my thinking was to find out the vector direction of photons before entering an object and then compare that with the photons that exit the same object. If possible.. Electron9 (talk) 01:22, 26 September 2013 (UTC)

No, it doesn't have to be the same wavelength. Regarding photons entering and exiting an object, you may want to read Borrmann effect and Mossbauer effect. --Dr Dima (talk) 06:14, 26 September 2013 (UTC) Regarding the momentum vector of the photon before and after, a local measurement of a photon momentum will change its momentum (or, equivalently, destroy the original photon and create a new one), so it is unclear what you would achieve in this case. If you were trying to use an act of Stimulated emission to amplify the photon population in your measurement (having created the population inversion in the medium beforehand), then indeed you may end up with "identical copies" of the original photon, and subsequently measure their distribution of momentum. --Dr Dima (talk) 06:40, 26 September 2013 (UTC)

The easiest way to detect photons is by using electrons. Dauto (talk) 04:20, 26 September 2013 (UTC)

How big is the blue stars in diameters

I was wondering how big is the blue main sequence stars. Because I am ignorant of radius, I dislike the radius usage and rather use diameter instead This shows how can blue main sequence stars O and B have luminosity of 30,000 and 1000 times. I was wondering is blue main sequence stars with planets around can have a substantial atmosphere if they were the diameter of Earth or twice the Earth diameter, or size of Mars. said Blue main sequence stars have luminosity of 2000 for B3 and 1400000 for O3 main sequence stars. When they use the radius of the size of that star, I am confused about the diameter. --69.233.252.198 (talk) 04:40, 26 September 2013 (UTC)

Have you looked at radius and diameter? The diameter is just two times the radius. --Bowlhover (talk) 05:46, 26 September 2013 (UTC)

Can life harbor of planets around white main sequence stars, or yellow-white main sequence stars

Because my college professor told me try to harbor life on planets around white (A) main sequence stars are quite difficult because their time of main sequence only last 1 billion year at the most, so when a planet around A main sequence stars can they have life harboring around the planets, or only simple bacteria can exist if at all? Can yellowish white (F) main sequence harbor intelligence life around their planets if the main sequence only last 3 billion years. I am not sure if F (yellow-white) main sequence star's planets can reach dinosaurs, something like reptiles if the main sequence lasts about 5 billion years. My astronomy professor told me life develop on celestial body needs to take a long time, in just few million years Main sequence is not going to receive any life forms around any planets. To get a intelligence life around celestial bodies to the parent star needs to take billions of years 4 Ga at least.--69.233.252.198 (talk) 04:49, 26 September 2013 (UTC)

Life, probably yes. Bacteria are a form of life, and as far as we know, bacteria came into being essentially as soon as the Earth had cooled enough to have liquid water. Complex life and intelligence are a lot harder - we work from a sample of one, and there seems to be a lot of randomness in the process. No-one knows if intelligence is inevitable or even likely. Maybe without the Chicxulub asteroid, we'd be dominated by stupid T-rexes. Or maybe Jurassic Park had it right and 64800000 BCE the first Velociraptor would have landed on the moon ("It's a small step for a man-eating monster, but a large jump for dinosaurierhood"). --Stephan Schulz (talk) 05:54, 26 September 2013 (UTC)

"What's a man?" "I don't know... man-eating just sounded cool!" MChesterMC (talk) 08:50, 26 September 2013 (UTC)

It's hard to know - but our Sun is 4.57 billion years old - Earth was formed 4.54 billion years ago and life appeared here about 3.5 billion years ago. So it took about a billion years between star/planet formation and first life. So even a star with just a billion years to live has enough time to form planets and jump-start life.

The problem is that we don't really know why life waited around so long before getting going. It's possible that it took that long for the bombardment by big space rocks to slow down enough - or for a stable atmosphere to form - or for the overall temperature to get low enough. There are many possibilities. That being the case, it's plausible that in some other solar system, the orbital dynamics of various gas giants could clear out all of the big rocks much sooner - or that the primordial composition of the future life-bearing planet could allow it to cool off much faster.

Because we still don't have solid knowledge of how life started on earth, it's also possible that the panspermia hypothesis is true and life arrived in the form of complete, working bacteria from some other source. That being the case, we'd have bacteria from the very moment the planet was suitable for them to take hold.

The limiting factor on higher life forms is the rate of evolution. Here on earth, it took at least a billion years for photosynthesis to evolve - which meant that there was no free oxygen in the atmosphere - and that prevented more complex life forms from appearing. Then another two billion years before we started having things that are recognisably plants and animals. On the plus side, it only took half a billion years to get from simple multicellular life to humans.

So what I think would be fair to say is that your college professor is correct if we assume that things around this hypothetical star proceeded like they did here. But: We can make alternative assumptions (such as that panspermia is correct) and that in this hypothetical world, then by chance, they'd have had multicellular, photosynthesizing life deposited onto the surface of an already reasonable planet after (say) a half billion years. That's not entirely unreasonable. If that were the case, then intelligent life and space-faring civilizations could easily evolve before the star died.

SteveBaker (talk) 14:11, 26 September 2013 (UTC)

The late heavy bombardment only ended about 3.8 billion years ago, and may have completely remelted the previously solid surface of the Earth. We have (some, but quite strong) evidence for complex communities of (unicellular) life 3.5 billion years ago. Indeed, some scientists argue that carbon isotope ratios in much older mineral samples (4.25 billion years old) already indicate life back then. It is in no way certain that life did not arise earlier than 3.5 billion years ago, and it may, indeed, have arisen multiple times, being extinguished or reduced to minimal levels again by the late heavy bombardment or similar events. --Stephan Schulz (talk) 14:36, 26 September 2013 (UTC)

Yes - which kinda emphasizes my final point. If you presume that the same sequence of events happens around some other star - then it's reasonable to come to the conclusion that 1 billion years isn't enough to come up with more than primitive single-celled life. The real question at the heart of this is whether life could start sooner and/or develop faster in solar systems where the initial conditions were different. If you read Late_heavy_bombardment#Possible_causes, you'll see that it's very possible for those dangerous rocks to stay put - or to be swept up by some super-Jupiter in a closer orbit to this alternate-Earth. In such a scenario, life could easily have started a half billion years sooner. The next issue is the question of why it took so long for photosynthesis to evolve - which seems to have been the major impediment to intelligent multicellular life. Why that took so long is an interesting question - especially following the discovery of an independently-evolved photosynthetic system in the Oriental hornet - which can't have taken more than a few million years to evolve. SteveBaker (talk) 18:41, 26 September 2013 (UTC)

It's a sample size of one - impossible to know for sure. At a wild guess I would be more skeptical about the redder stars; I'm not so sure life can get started without some hard UV to blast apart and reform polymers over and over again. But there are lots of ideas in the literature (clays, black smokers, all sorts of crazy things) which would disagree with my impression. Wnt (talk) 18:34, 26 September 2013 (UTC)

Yes - it is hard to know for sure. But those red stars could still get life started by panspermia...which is definitely getting increasing respectability in the scientific world as years go by. SteveBaker (talk) 18:41, 26 September 2013 (UTC)

Life may have evolved 3.5 billion years ago, or even earlier. But it was only simple single celled organisms. It took 3 billion years and the evolution of sexual reproduction to occur to allow the evolution of multicellularity in the Cambrian Explosion, which happened only .5 billion years ago. μηδείς (talk) 18:42, 26 September 2013 (UTC)

Of course, the development history of life on another planet may be totally different from the history of Earth. Without the separation of the Moon or late heavy bombardment, life on Earth might have started much earlier - pretty much as soon as the surface had cooled enough. Once life had a foothold on Earth, it had numerous setbacks - extinction event lists at least 15. I can certainly imagine advanced multicelluar organisms evolving in much less than a billion years under ideal conditions; and equally I can imagine multicelluar organisms never getting off to a good start even after many billions of years. Astronaut (talk) 18:53, 26 September 2013 (UTC)

The extinction events only removed the top predators and macrofauna, and can as easily be credited for opening up opportunities for diversity as be blamed for removing the dinosaurs and trilobites. Without the moon's separation there would be no tides, vital for life that cannot live in stagnant water. The delay of that event and the late bombardment hardly effects the overall scheme of 3 Billion years from origin to multicellularity. Most planets with life probably harbor nothing more complex than bacteria. μηδείς (talk) 00:56, 27 September 2013 (UTC)

Without the Moon's separation there would be tides (note first sentence), though with only about 1/3 the maximum range they have now – people commonly forget that the Sun also has a significant tidal influence on the Earth. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:33, 27 September 2013 (UTC)

It depends what you define "life" as. Non-carbon based life might have a better chance in some circumstances.--Auric talk 20:29, 26 September 2013 (UTC)

Everett branch convergence

In the many-worlds interpretation of quantum physics, does anything prevent Everett branches from reconverging (by leading to the same future by different chains of events) at the same rate as they diverge? NeonMerlin 09:19, 26 September 2013 (UTC)

Surely separate branches can never produce exactly the same future because their futures have different pasts. If event A happens in branch 1 but not in branch 2, then all the descendants of branch 1 will have future states in which event A happened, whereas all the descendants of branch 2 will have future states in which event A did not happen. Gandalf61 (talk) 11:41, 26 September 2013 (UTC)

That does't really follow. In the long run the past is no more certain than the future, you only see the current evidence. Dmcq (talk) 11:55, 26 September 2013 (UTC)

Because some branches can gather in a circle or just assemble back in time , it is possible to reconnect .Thanks Water Nosfim — Preceding unsigned comment added by 81.218.91.170 (talk) 13:10, 26 September 2013 (UTC)

We know very little indeed about what the implications of many-worlds truly is. Heck, we don't know whether it's true - or complete bunkum - and there are reasons to believe that it's an unfalsifiable hypothesis anyway. So whether different parallel universes could ever recombine is anyone's guess. Any effort to give you an answer to your question should therefore be ignored!

That said, Gandalf61's answer is clearly incorrect because if two universes are precisely identical - then any past memories would also have to be precisely identical because if they differed then whatever systems stored that past history would have to identical too. There would be no conceivable test to determine whether two universes with wildly different pasts - but no differences whatever in the present that resulted from that, actually had different pasts.

God only knows where User:81.218.91.170 came up with that answer - but I guarantee there are no reliable sources to back it up.

Bottom line: We definitely don't know the answer to your question. We probably can't ever know the answer. It may well be logically impossible for there even to be an answer. SteveBaker (talk) 13:47, 26 September 2013 (UTC)

Steve - maybe I didn't explain myself very clearly above, but I think we are in agreement. Different Everett branches have different pasts so they cannot recombine in some mysterious way to produce a hybrid future state. In the Everett interpretation of Schrodinger's cat, there is a "cat dead" branch and a "cat alive" branch, and their descendants must remain separate. The two branches cannot recombine into a "cat both dead and alive" branch. Gandalf61 (talk) 14:16, 26 September 2013 (UTC)

But if you threw the box, cat and all, into a black hole, surely the resulting universe in both cases would be on a "that information is unknown" branch? MChesterMC (talk) 08:14, 27 September 2013 (UTC)

Different branches do recombine all the time, this is a trivial consequence of unitary time evolution. The entire multiverse in fact does not evolve in time at all, H|psi> = 0. Time doesn't exist at the multiverse level. Count Iblis (talk) 13:55, 26 September 2013 (UTC)

the word "branch" is really a bit misleading, as it suggests that quantum history has a tree structure. What really happens in the multi-world interpretation is that the probability wave function spreads out over a huge-dimensional state space. There are an infinite number of possible history-paths, including an infinite number that diverge and then come together again. Looie496 (talk) 15:41, 26 September 2013 (UTC)

I'm out of my field here, but my impression is that CPT invariance means that there should be multiple pasts for a given moment of time just as there are multiple futures, provided that there are multiple futures for particles of any charge or parity. However, we live in a gradient of entropy with less in the past than in the future, so does that mean there are fewer pasts than futures? Or are there as many pasts, just more 'orderly' on average? Hmmm. In any case, the trivial case of this is the double-slit experiment - there are two worlds, one with the particle going through the one slit, one the other, but we find ourselves in a world where we're looking at a dot and there is no way to tell which was our past. Wnt (talk) 18:29, 26 September 2013 (UTC)

The entropy increases, but this does not mean that the number of future states increases. Unitary time evolution implies that this number stays exactly the same. So, how can entropy increase? Thing is that if you were to define the entropy as logarithm of the number of states an isolated system really can be fund in then that entropy would stay constant. The entropy one uses in thermodynamics is defined in a different way, it is proportional to the logarithm of the number of microstates that have the same macroscopic properties as the given system has.

Consider the following example. If you do a free expansion experiment with an ideal gas that initially fills half of a totally isolated container, then the entropy will increase by N k Log(2), because the number of states each of the N molecules can be in will have doubled. But if you look more carefully, then you see that the number of states the molecules can really be in must be the same as you started out with, because each initial states evolves determinstically according to the Schrodinger equation to a final state, the transform from initial to final state is unitary, which then implies that the number of states actually stays the same.

But what matters for thermodynamic entropy is that the gas when it has expanded has certain macroscopic properties (e.g. in this case it has a larger volume) and given those macroscopic properties there are then a larger number of microstates that are compatible with it, than in case of the initial state (with a smaller volume). But most of those microstates are not states the gas can be found in, clearly almost none of them will evolve back to the initial state under time reversal, while any of the states the gas really can be in would evolve back to the initial volume under time reversal (note that this is thought experiment where we assume perfect isolation). Count Iblis (talk) 20:54, 26 September 2013 (UTC)

Colour variations on displays

Do all screens whether a tv, pc monitor, laptop or tablet have varying colours even on the same model? For example, would all screens of a particular make and model have the same sorts of colour hues or would they differ slightly? Clover345 (talk) 11:13, 26 September 2013 (UTC)

How accurately can you measure (or perceive) color and brightness? All that matters to the manufacturer is that the color accuracy and consistency are as good as its customers need. You can buy scientific-grade equipment, if you're willing to pay a premium; otherwise your products will fall along the spectrum, ranging from "professional consumer" to "bargain basement." Start by reading colorimetry. Nimur (talk) 12:04, 26 September 2013 (UTC)

Colours do vary, even in sets of same make and model. Variation comes primarily from user adjustment and the display technology (CRT, LCD, etc). All due respect to Nimur, but whether a set is a cheapie or an expensive professional item has little or nothing to do with it, providing the set is not defective or maladjusted. There are six basic aspects of colour reproduction in television:-

• Choice of primary colour filters in TV cameras (not applicable perhaps to this question)
• The colour accuracy of photographic film when movies or film-based programmes are televised (not applicable perhaps to this question, however if comparing one receiver with another some time later, may trick you)
• Accuracy of gamma in the televion station cameras
• The choice of primary colour phosphors or pigments in the reciver
• Adjustment of signal strength of each primary colour circuit in the reciever
• Accuracy of gamma in the reciever.

The television industry industry very early in the days of colour television standardised the primary colour filters used in cameras. You can asume variation here is neglible. Standardisation of primary colours is assisted by the fact that although there are a vast number of TV and monitor manufacturers, thaere are only a few manufacturers of the actuall displays in the World, which they sell to the various set makers, along with other critical parts.

The television industry very early in the days of colour television standardised the colour phosphor primary colurs for use in receivers. You could neglect variation here too, however Japan standardised on a slightly different red than Europe and USA. So reception with a Japanese receiver in USA or Europe will be slightly inaccurate. It is unlikely that you would notice it, however I recall comparing a Philips receiver with a Sanyyo TV some years ago and side by side you can see a difference when a full red test signal is used.

The pigments used in LCD and plasma displays are not as accurate as CRT displays, but they are getting very good.

The colour accuracy depends on the adjustment of the TV set ("colour" control and/or "tint control" user controls, and internal controls accessible to technicians. This variation can be significant. Some people never adjust their sets properly. Some shops intentionally missadjust TV sets as a sales technique, as some customers like to say "I'll buy that one, I like it's nice colours."

"Gamma" is the term for the correspondence between the electrical signal and the colour intensity over the range from black to maximum light output. The relationship is not linear. Gamma accuracy can vary depending on the display technology - CRT, LCD, plasma, and on how well teh user adjusts the brightness and contrast controls. — Preceding unsigned comment added by 1.122.206.159 (talk) 13:25, 26 September 2013 (UTC)

The way I was interpreting the question was with regard to the variation you see by feeding identical inputs to multiple units within a single product-model - amongst products that are built from ostensibly identical parts. For example, an LCD panel's backlight brightness is specified in nits; but if you build a hundred units, the actual brightness follows something like a bell-curve. There is absolutely a correspondence between price you pay (as an end consumer) and the product vendor's ability to tightly control the statistical distribution of part quality. Now that we live in a mostly-digital-video-signal, mostly-solid-state technology ecosystem, it is arguable that even cheap products are "good enough..." for users who don't notice minute details. The color and illumination variance is lower in this type of technology, compared to, say, phosphor screens (as Steve mentions below); and analog imperfections are avoided for most of the signal path, right up to the point where you're emitting or collecting photons. Ultimately, though, the degree you can tolerate imperfection depends on how accurately you can actually detect variation. Graphics professionals (like Steve) and image processing scientists (like myself and my colleagues) pay lots of attention to minutia that most people won't even notice; but our efforts manifest, perhaps somewhat ambiguously, as "better overall products." As I recall, somebody famously called our color accuracy "26% better" a few years ago, a stunningly quantitative figure. Nimur (talk) 13:52, 26 September 2013 (UTC)

The TV we have in our living room has a menu option marked "STORE MODE" - which makes the picture much brighter and more vibrant (too much more, I would argue) as well as disabling the controls on the side of the TV. There is a pop-up there that says that using this mode may shorten the life of your TV and consume more electricity! So judging color quality by what you see in the store is at best of dubious value! SteveBaker (talk) 18:06, 26 September 2013 (UTC)

Back in the era of CRT monitors, it was extremely common for the colors to drift over time due to screen burn, miscalibration of the analog parts and just general age. My personal experience has been that modern LCD panels do not seem to exhibit these problems - but our article Screen burn-in has a section on plasma, LCD and OLED displays that suggests that they are also prone to this phenomenon. Using a screen saver should alleviate the issues of certain common patterns being "burned" into the display - but a general overall degradation of brightness and color performance must still occur. So if our article is to be believed (and it does have some pertinent references) - then the answer to your question is "they differ" - but only after the displays have been in use for some large amount of time and with differing degrees of usage. However, I work in computer graphics where it is important to have color consistency between the displays used by (for example) different artists working on 3D models for the same game. Back in the era of CRT's, we'd have little devices that you stuck on the bottom right corner of the display's screen that adjusted the analog signals from the computer to achieve a stable color balance as the CRT aged - and between different CRT's being used by different people. Since we switched over to LCD displays, we haven't had to do that. But perhaps with OLED's becoming popular, we'll have to revisit that decision! SteveBaker (talk) 13:33, 26 September 2013 (UTC)

Steve, we still use those on LCD displays. Unless you are using specific, expensive monitors, color replication is still a problem. Even on a single brand of monitor, you get variation that is enough to warrant it.217.158.236.14 (talk) 14:08, 26 September 2013 (UTC)

• I'd just like to add that all of this is sort of a moot point, because the color that a viewer perceives on a monitor is strongly dependent on the lighting of the room where the viewer sits. Our brains are designed to minimize our awareness of that fact, but it is true nevertheless. So attempting to precisely control monitor properties is a waste of effort unless you can also precisely control the viewer's environment. If that is not possible, then the only way to get consistent perceptions is to calibrate each monitor individually and use it in a place with consistent illumination. Looie496 (talk) 15:36, 26 September 2013 (UTC)

And you need specially calibrated light-bulbs; and you need matte-gray walls painted with calibrated paint; and you need a government certification for every combination of room wall and lightbulb.... Nimur (talk) 17:30, 26 September 2013 (UTC)

Don't forget the monitor hood lined with black velvet. (some of them costing more than what I would spend on a monitor). Ssscienccce (talk) 03:05, 27 September 2013 (UTC)

Yet another factor (at least with LED screens) is the vertical angle between you and the screen, e.g. colour and contrast will both vary depending on whether you sit or stand.--Shantavira|^{feed me} 16:13, 26 September 2013 (UTC)

Tools like the "LaCie blue-eye" has the ability to monitor ambient room light - and that's plenty good enough for what we do. The objective for us is not to have perfect color - because we know that our end-users are using who-knows-what displays and calibrations. The idea is that all of our artists see the same thing - so that they aren't continually correcting and re-correcting the color of each other's work to make it look good with whatever they are building themselves. Doubtless LCD's do have color differences - both between manufacturers and between screens made by the same manufacturer - but the differences are tiny compared to old-school CRT's. SteveBaker (talk) 18:06, 26 September 2013 (UTC)

A Sony leaflet for their Full HD widescreen medical monitors writes: "every LCD panel used in the LMD-2450MD is precisely color calibrated at the factory, providing consistent characteristics. The colorimetry of an LCD display, by nature, can exhibit inaccurate color characteristics and gamma curves, which can make precise color matching between multiple monitors a challenge." So yes, even within the same lot, batch or model, there can be color variations. Ssscienccce (talk) 03:05, 27 September 2013 (UTC)

When dental veneers go wrong...

When someone has veneers done - but they end up with a set of teeth that looks like Barney the dinosaur's choppers or that they're wearing a mouthguard. What exactly is it that's gone wrong to cause that? I presume that they didn't go into it expecting their teeth to look like that afterwards... --Kurt Shaped Box (talk) 18:48, 26 September 2013 (UTC)

Our resident dentist can answer this question :) .Count Iblis (talk) 20:37, 26 September 2013 (UTC)

searching of arm anatomy illustration

I'm looking for an arm anatomy illustration a long time... But it's very important for me that it will be the same same to the real thing as much is possible... (I even agree to pay money for that, particular if it's on 3D format). Until now I've saw only some things that are not real, it says that they does not reflect the real things. My target is to know well the names of the veins of the arm, from the start to the end. thank you. 95.35.246.240 (talk) 21:17, 26 September 2013 (UTC)

http://teleflexhandbook.com/chapter-13-right-heart-cath-from-the-arm has a couple of pictures that might give you most of what you want. Looie496 (talk) 00:26, 27 September 2013 (UTC)

Keep in mind that there is considerable variability in the venous anatomy of the upper extremities (more than in the legs). The number of venous branches and their respective lengths show great inter-individual differences in the arm, so it's unlikely that an illustration will match someone's arm exactly. A Nigerian study noted 10 types of venous patterns (link), the abstract of another study mentioned four patterns. One example is the Median cubital vein between the cephalic and basilic veins in the H-shaped pattern, present in 70% of population, while 30% has the M-pattern, with five segments, the cephalic and basilic veins and the intermediate cephalic, intermediate basilic and intermediate antebrachial veins. 3-D views that you can turn and zoom in can be found at several sites (for example anatomyexpert or healthline). Ssscienccce (talk) 01:26, 27 September 2013 (UTC)

September 27

SF - Some kind of anatomic pathology?

Anyone of you guys heard about a pathology shortly named "SF" ? (Common in runners), Can someone tell me it's actual name? thanks. Ben-Natan (talk) 00:00, 27 September 2013 (UTC)

I'm betting stress fracture. Looie496 (talk) 00:18, 27 September 2013 (UTC)

Agree. I've added it to the SF disambiguation page.--Shantavira|^{feed me} 09:32, 27 September 2013 (UTC)

...and it's been reverted. Oh, well...--Shantavira|^{feed me} 16:12, 27 September 2013 (UTC)

Google search failed to find ANY cases where people had used the abbreviation "SF" in conjunction with running except in the context of San Francisco and Science Fiction. So, yeah - I support that revert - I don't think it belonged in the dab page for SF. SteveBaker (talk) 19:10, 27 September 2013 (UTC)

You probably used the wrong search terms. I got many relevant hits mentioning runners and stress fracture in which "SF" is abbreviation for the latter. Here're some snippets from the hits:

• "Medial tibial stress syndrome (MTSS) and tibial stress fracture (SF) are common lower leg disorders in runners." [11]
• "We assessed CDR in female runners (> or = 20 km/wk) with a recent stress fracture (SF) and with no stress fracture history (NSF)." [12]
• "Anyone who's experienced a stress fracture, please comment. Is the pain from a SF constant or only when it's bearing weight?" [13]
• "Subjects consisted of 10 females with a history of at least one lower extremity stress fracture (SF) .... All subjects were between ages 18-35 and ran between 30-80 miles per week." [14]

--98.114.146.6 (talk) 02:01, 28 September 2013 (UTC)

Waterfall fish kill ?

Do dead fish accumulate at the bottom of waterfalls, having died when they hit rocks at the bottom ? If not, why not ? StuRat (talk) 11:41, 27 September 2013 (UTC)

I'm interested to know why you think fish allow themselves to be carried over waterfalls in any but insignificant numbers. There are other issues to consider. The size of the fish, the depth of the splash pool, the volume of the flow, the speed of the flow, for example. The question is a little vague, but if we take it at face value I suspect the flow of water, local predators and natural decay prevents any accumulation. Richard Avery (talk) 14:01, 27 September 2013 (UTC)

I should think that waterfalls high enough to kill fish would be sufficiently rare that they wouldn't have developed an evolutionary response, that is, an avoidance strategy. Indeed, going over short waterfalls would be in the interest of the species, allowing it to spread to new areas. And can a fish tell how high a waterfall is, from the top side ? Maybe, if they can detect the low frequency sounds generated when the water hits, hundreds of feet below ? StuRat (talk) 14:50, 27 September 2013 (UTC)

I would expect that fish do get carried over waterfalls every so often, but really nothing except rock can accumulate there, because it is constantly scoured by a blast of water. Looie496 (talk) 14:57, 27 September 2013 (UTC)

I don't think that's true, there are often eddies there holding floating objects right against/behind the falls. StuRat (talk) 15:29, 27 September 2013 (UTC)

You mean a recirculating stopper or hole, which can pin a kayak full of buoyancy to the riverbed for a considerable length of time. An eddy (in whitewater terms) is an area of placid water formed at the side of the main current. Alansplodge (talk) 21:59, 27 September 2013 (UTC)

Sometimes, a little research can be helpful. Bielle (talk) 15:44, 27 September 2013 (UTC)

Interesting. Apparently the falls pose more of a danger to ducks and such. Wouldn't you think they'd just fly away when they went over the top ? StuRat (talk) 17:28, 27 September 2013 (UTC)

I've often see birds hanging around waterfalls. They probably help in collecting whatever edible debris might go over. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:39, 27 September 2013 (UTC)

Algebra

How does n=e/(1+e) become e=n/(1-n). If you rearrange it just becomes n(1+e) = e. am I missing a rule of algebra here? Clover345 (talk) 12:02, 27 September 2013 (UTC)

$n={\frac {e}{1+e}}$

$\Rightarrow n(1+e)=e$

$\Rightarrow n+ne=e$

$\Rightarrow e-ne=n$

$\Rightarrow e(1-n)=n$

$\Rightarrow e={\frac {n}{1-n}}$

Gandalf61 (talk) 12:09, 27 September 2013 (UTC)

And don't forget:

Algebra = Desk_Math

$\Rightarrow$ Algebra <> Desk_Science

StuRat (talk) 12:56, 27 September 2013 (UTC)

Way to get Oils or Oil remnants of the hair?

If regular shampoo's doesn't help, how do you think you would take off (In a generally safe way), oils out of your hair? (Oils that might have got there by oily shampoos or other ways). Thanks. Ben-Natan (talk) 16:47, 27 September 2013 (UTC)

A detergent is what you need. Detergents for hand washing dishes are often strong, yet not too toxic, since they are for cleaning out greasy pots, but also must be safe to touch your hands. Of course, a shampoo designed for oily hair will also have some detergent in it. As always, be careful not to get either in your eyes. Heat will also help, so turn the water temperature up as high as you can stand it. And, after you remove the (presumably dirty) oil, you may want to replace it with clean oil, which is what hair conditioner does. The only exception is if your scalp produces so much oil that your hair will soon be oily again, in any case. StuRat (talk) 17:13, 27 September 2013 (UTC)

Wash, rinse. Repeat. and Repeat. --208.185.21.102 (talk) 17:55, 27 September 2013 (UTC)

A Google search suggests that clarifying shampoos are specially formulated to remove a buildup of product residues and/or oils from hair, where ordinary shampoos may fail to do so. - Karenjc (talk) 18:24, 27 September 2013 (UTC)

Touching a touchscreen

If you were to put a human standing on the top of a huge capacitive touchscreen (the human won't be touching anything else, but has the option of stepping on an isolating material or touching the screen with his skin), could the human activate the touchscreen?̉ OsmanRF34 (talk) 17:37, 27 September 2013 (UTC)

Capacitive sensing does not sound dependent on the user being grounded or having any other specific electrical properties beyond making contact. Could you explain the reason you suspect the person in your scenario would not be able to activate it? DMacks (talk) 17:44, 27 September 2013 (UTC)

I thought that in this scenario the human would acquire the same charge as the capacitive touchscreen, and the touchscreen won't be able to register any contrast. OsmanRF34 (talk) 17:56, 27 September 2013 (UTC)

You're thinking DC. But an AC current can continuously flow to an object (such as the human body) which doesn't appear to be a part of a closed circuit, due to self-capacitance. See also body capacitance. Red Act (talk) 20:45, 27 September 2013 (UTC)

Why are the babies in need of sleep more than adults?

Why are the babies in need of sleep more than adults (almost twice as adults)? 95.35.246.240 (talk) 19:58, 27 September 2013 (UTC)

We don't understand why humans (or other animals) need sleep - so it's unlikely that there is solid information about why babies need more of it. Our article on sleep says: "Children need more sleep per day in order to develop and function properly" - which doesn't really tell us much.

IMHO, it's evolutionary - if babies didn't give their parents enough time to recover from 6 hours of solid screaming and fussing - they'd never make it past 6 months! SteveBaker (talk) 20:13, 27 September 2013 (UTC)

An interesting fact, and probably an important clue, is that babies spend a much larger fraction of their sleep in the REM (dreaming) state than adults do. Looie496 (talk) 22:15, 27 September 2013 (UTC)

We need sleep because we get sleepy. Babies probably get more sleepy than adults, therefore they sleep more. OsmanRF34 (talk) 22:39, 27 September 2013 (UTC)

Seriously, it is as Steve says, nobody knows exactly. But we know something about sleep: all species do it (=> it has to be pretty old, in evolutionary terms), in one form or the other. Although not all sleep the same. :Other species need more sleep than us. Some bats need 20 hours, elephants 3-4, giraffes need just 2 hours. If you deprive a rat of sleep, it will die in 2 weeks (=> it is biologically necessary).

Human babies need to sleep a lot for proper development. Growth hormones are secreted by the pituitary gland at a much faster rate while babies sleep. However, other baby mammals, like baby dolphins and baby orcas, don't seem to sleep at all, (=> evolution found other ways of making it work). OsmanRF34 (talk) 23:08, 27 September 2013 (UTC)

One valuable clue of the importance of sleep is what happens as a consequence of lack of sleep, as with fatal familial insomnia. Those suffering from that disorder are literally unable to sleep - and it's a death sentence. They eventually suffer dementia and finally they die. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:21, 28 September 2013 (UTC)

It seems to me that this is fundamentally a game theoretical issue. Suppose you start with two identical systems that compete with each other and they also need to repair themselves. Initially they function in a uniform way, they go about their business and do the repairs they need to do to themselves at a constant rate. But then one system can outperform the other by working at a faster rate that on the long run is unsustainable and then having a downtime later to do extra repairs. As a bonus those repairs can be perfomed more efficiently during the downtime. Count Iblis (talk) 01:47, 28 September 2013 (UTC)

How does a laser cut glass?

It seems counterintuitive that a laser could cut something that is clear. How is this possible? Specifically, laser cut sapphire glass. --208.185.21.102 (talk) 21:27, 27 September 2013 (UTC)

Are you looking for a technical or a non-technical answer? This absolutely is counter-intuitive; commodity laser cutters can't do it (reliably). Our article describes several distinct physical mechanisms that allow a laser to cut a material. In the case of glass, the procedure is difficult and dangerous; a powerful laser is shined onto a surface that's simultaneously specular and transparent... it takes a lot of engineering to make sure the laser energy gets absorbed, and not wasted, or reflected back into the laser, or accidentally reflected to somewhere else undesirable. Nimur (talk) 21:47, 27 September 2013 (UTC)

Was that the technical or non-technical answer? It seems you didn't answer the question at all except to say, "With difficulty man! It's hard!! In fact commodity lasers can't do it. It takes a lot of engineering." I guess "with a lot of engineering" counts as a nontechnical answer for how does a laser cut glass! :) 178.48.114.143 (talk) 23:07, 27 September 2013 (UTC)

My response wasn't really meant as an answer... it was just a request for clarification. Shall we deep dive into optical physics and evanescent waves now, or should we wait for Steve Baker (who has operated his own laser cutter nearly 24/7 for the last year!) to bring a more pragmatic hands-on style explanation? I have a sort of suspicion that his lasersaur does not cut sapphire glass, but I'd be curious to hear his input. Nimur (talk) 23:15, 27 September 2013 (UTC)

If Steve Baker has operated his own laser cutter nearly 24/7 for the last year, 1) he's probably the world's least qualified person to answer this question 2) give up man, just give up already... 178.48.114.143 (talk) 23:29, 27 September 2013 (UTC)

I've been working with laser optics for over a decade, for many different purposes, ranging from laser cutting to optical probes of chemical species, materials and surface properties; and Steve's one of the reference-desk's best and most well-respected contributors; but if you're unhappy with the quality of our free information and would like me to "give up," perhaps you can find better information by purchasing a textbook on laser physics. My class used an unpublished textbook, and its course webpage is not currently available; but you can purchase Laser Materials Processing at Amazon for the low price of just $350. Nimur (talk) 00:56, 28 September 2013 (UTC)

It's just a joke, Nimur. If Steve's been running a laser non-stop for a year, he's not making very much progress (unless he's trying to break into Fort Knox). Clarityfiend (talk) 01:23, 28 September 2013 (UTC)

Steve's running a small business manufacturing miniature laser-cut figures, and operates out of his living room (or so it appears). His laser cutter, according to his website and his comments, has been highly utilized. He'll probably be happy to discuss it in more detail. Nimur (talk) 01:36, 28 September 2013 (UTC)

I'm far from an expert on lasers, but I presume that at least one consideration is that sapphire glass is only transparent in the wavelength range of about .15-5.5 µm, so it's opaque to the light from lasers outside of that range. There exist commercially available lasers with wavelengths up to 699 µm; see here. Red Act (talk) 21:59, 27 September 2013 (UTC)

Mould growth from artificially increased humidity

Can putting water in a bowl on a radiator, to moisturise a room, contribute to mould growth? Clover345 (talk) 00:46, 28 September 2013 (UTC)

No, because putting water in a bowl on a radiator isn't an effective way to moisturise a room. What you need to do is to poor that water on one or more towels and put these wet towels on the radiator. Count Iblis (talk) 01:38, 28 September 2013 (UTC)