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December 16

Why we shouldn't eat already dead animal instead of killing & eat them?

Question by Ram nareshji (talk) 02:53, 16 December 2014 (UTC) deleted as possible copyvio [1] given the lack of any reassurance from the editor that they are the original author. Nil Einne (talk) 13:29, 18 December 2014 (UTC)[reply]

One reason dead animals are not eaten is they may have died from a disease that could be transmitted to the person who eats meat from the carcass. Another reason is that since animals die of natural causes at unpredictable times, it would be difficult to butcher the carcass quickly enough to prevent decomposition.

But the biggest reason animals are killed rather than allowed to die of natural causes is that cattle are slaughtered before three years of age. If they were allowed to die of natural causes, they would have to be fed for several years, which would greatly increase the cost of beef. Jc3s5h (talk) 04:15, 16 December 2014 (UTC)[reply]

If found soon after death, it may become roadkill cuisine. Rmhermen (talk) 04:35, 16 December 2014 (UTC)[reply]

Mutton sometimes comes from sheep kept for wool production, which died of old age. StuRat (talk) 05:44, 16 December 2014 (UTC)[reply]

Have you got a source for that StuRat? Dying of old age implies no slaughter just waiting. Hmm, horrible. Richard Avery (talk) 07:52, 16 December 2014 (UTC)[reply]

This would be more common with subsistence farmers. Dairy animals would be another example. Basically they are kept alive for their primary use as long as possible, then used for meat after they die. StuRat (talk) 16:57, 16 December 2014 (UTC)[reply]

If you find a dead animal, it may also contain parasites. Some are obvious, like maggots, others may not be, like trichinosis, and may be potentially contagious. StuRat (talk) 05:48, 16 December 2014 (UTC)[reply]

As ever I wonder which planet you are from. The animal,before it was dead, also had the parasites. Including, quite possibly, maggots, which while they may not whet your appetite are edible. Greglocock (talk) 10:38, 16 December 2014 (UTC)[reply]

"Finding them dead" implies they weren't raised on a farm under controlled conditions, so are presumably more likely to have parasites. Maggots, however, normally are only found on dead tissue, although it is possible for the dead tissue to be on a live animal. But, after death the number of parasites quickly increases (although perhaps I should have called them "insect and microscopic scavengers", not parasites, in a dead animal). Also, existing parasites can rapidly increase in number, after death, due to the lack of immune of other responses from the host(s) (like chimps picking bugs off each other). StuRat (talk) 16:57, 16 December 2014 (UTC)[reply]

Tradition - religious tradition primarily - compels many people to make sure to not eat dead (deceased), improperly killed, severely sick or congenitally deficient animal. In Judaism, these fall under nevelah and treifah categories, see terefah. The original purpose of these commandments and rules may have been to ensure cleanness, both physical (hygiene) and spiritual (morality). Dr Dima (talk) 18:34, 16 December 2014 (UTC)[reply]

If I might sum up the above. The OP's fatherly advice was indeed a good dictum. And with all dictums there are exceptions. If a person is knowledgeable about how to judge the carcass as low risk and knows how to prepare and cook it safely. Then it could be eaten without suffering ill health. Outside that exception – then its better not to. Otherwise one could very well become ill or even end up as a cold stiff carcass oneself.--Aspro (talk) 02:52, 17 December 2014 (UTC)[reply]

Why does anxiety cause diarrhea or constipation?

Question deleted as probable copyvio by Ram nareshji as remarked below Nil Einne (talk) 15:06, 16 December 2014 (UTC)[reply]

Why are you copy-pasting questions from other websites into our reference desks? [2] AndyTheGrump (talk) 05:37, 16 December 2014 (UTC)[reply]

Heh, maybe someone is doing a sociological experiment to see whether our desk is better than theirs, or vice versa, by asking the same question both places and/or copy-pasting. If so, then let us oblige by answering the question, while also fouling up the experiment by knowing it is active, as it is a positive good to foil the schemes of those who hope to learn to predict us. But... if you go on PubMed and type anxiety and constipation, anxiety and diarrhea, you're in for a slog. At a quick look there's a lot of data about irritable bowel syndrome, where there's a definite comorbidity; the neuroendocrinology of the bowel itself is at issue: [3] But of course we all know the jocular phrases about needing a change of underwear after a scary situation, so it has to be a more general relationship. But I can't really dive into this right now... Wnt (talk) 06:20, 16 December 2014 (UTC)[reply]

The answer is in the parasympathetic nervous system. Vespine (talk) 22:18, 16 December 2014 (UTC)[reply]

Because anxiety causes the release of adrenaline, which speeds up the bodily processes, including the rate at which food is passed through the body [4][5]. I have often wondered whether diarrhea is just an unwanted side effect of the adrenaline rush, or whether it is a deliberate ploy by the body to evacuate the bowels quickly so you have less weight to carry and can run more quickly. However, I don't suppose there is any way to prove that one way or the other. If it is the latter then wearing underpants tends to defeat the object of that response. Richerman (talk) 09:19, 17 December 2014 (UTC)[reply]

For the record, irritable bowl syndrome (linked above) has three types, one with chronic diarrhea, one with constipation, and one that fluctuates between between periods of diarrhea and constipation. Typically, episodes occur over days or weeks, and alternate with periods of relief. There's no evidence adrenaline is the mediator of IBS, and treatment usually consists of ameliorating the symptoms with stool softener or anti-diarrheals, as the cause is unknown. (There is indeed co-morbidity with anxiety, which can be treated by benzodiazepines and other means.) Evacuation due to the fight-or-flight response is a one-time thing on a far smaller timescale, and does not involve constipation. μηδείς (talk) 22:12, 17 December 2014 (UTC)[reply]

Anxiety, which is a known factor in IBS, causes adrenaline to be released on a regular basis due to a perceived stressor - see: here. Richerman (talk) 10:55, 18 December 2014 (UTC)[reply]

Sound from laying your head on your hand

First off, I'm not looking for a medical diagnosis or advice. I don't think this is a problem and I think it's probably something everyone can experience.

When I lay on my side and put my head on my pillow, I often put my hand between my head and the pillow situated so that my ear is between my thumb and index finger. If my hand is completely relaxed, I don't hear anything other than ambient noise. If I flex my fingers even slightly, I hear a sort of white noise. It's very faint. Where is this noise coming from or what's causing it? If I'm not mistaken, muscles are making constant adjustments to the force it takes to perform a task. So would this be the result of that benign tremor? Dismas|^(talk) 06:32, 16 December 2014 (UTC)[reply]

It sounds like the seashell effect. ~~But have you been diagnosed with a benign tumor?~~ ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:12, 16 December 2014 (UTC)[reply]

Do ignore the diagnosis above, which is worth considerably less than what you paid for it. I experience the same thing, as do the authors of [6]. Wnt (talk) 11:27, 16 December 2014 (UTC)[reply]

What diagnosis? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:43, 16 December 2014 (UTC)[reply]

I'm not sure but I think i know the sound you are talking about, I always thought it was something to do with blood flow. The thing about your ear is that it is incredibly sensitive! It has been demonstrated that for you to detect a sound, air pressure has to deflect your ear drum by a distance LESS than the diameter of a hydrogen atom! Imagine that! So if you are lying in a very quiet environment, lying on your arm, I can sort of imagine that by flexing your fingers you are constricting the blood vessels slightly causing the blood to "rush" through the blood vessels making a very slight noise, possibly not even transmitting through the air, but through the material between your hand and you ear. Vespine (talk) 21:58, 16 December 2014 (UTC)[reply]

Citation needed for the "hydrogen atom" thing, please. --65.94.50.4 (talk) 02:09, 17 December 2014 (UTC)[reply]

I think Wnt is wondering why you suddenly mentioned a benign tumour which is very weird unless perhaps you misread Dismas mentioning a benign tremor as as a benign tumour. Nil Einne (talk) 14:34, 17 December 2014 (UTC)[reply]

For the record, the OP's experience is a perfectly normal human experience. See Seashell resonance and Occlusion effect for some related articles. --Jayron 32 15:34, 17 December 2014 (UTC)[reply]

Yikes! You're right. I need new glasses. Or maybe my brain wasn't expecting to see a term like "benign" next to "tremor". What exactly is a "benign tremor"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:25, 18 December 2014 (UTC)[reply]

Well if it helps, I actually made the same mistake and was nearly going to reply saying that perhaps Wnt missed the part where a benign tumour was mentioned until I noticed it wasn't. In my case I do definitely need new glass because my are scratched and falling apart (have an appointment with an optometrist early next year). But I don't think this was the cause, although I had read the bit about benign tumour already which may have influenced what I read. Nil Einne (talk) 19:45, 19 December 2014 (UTC) [reply]

Citations for the hydrogen atom thing. Vespine (talk) 00:08, 18 December 2014 (UTC)[reply]

@Dismas: It seems very likely that several things may be happening simultaneously here as other replies indicate, but the 'white noise' you possibly perceived when you flexed your fingers is real and originates in the myofibrils of your muscle fibres. "The sound produced by a muscle comes from the shortening of actomyosin filaments along the axis of the muscle. During contraction, the muscle shortens along its axis and expands across the axis, producing vibrations at the surface." [7] @ newscientist.com. A very technical reference [8] @ biomedical-engineering-online.com. However I am not certain that this is loud enough, or of such a frequency, as to be heard by ear. It's possible that the blood flow changes noted earlier by Vespine would drown it out. Link to a recording of muscle 'sound' here.
wp:WHAAOE! See Phonomyography. 220 of ^Borg 02:32, 20 December 2014 (UTC)[reply]

Thank you, everyone, for the great links and explanations! @Baseball Bugs: See benign tremor and simply tremor. Dismas|^(talk) 02:40, 20 December 2014 (UTC)[reply]

physics

summerfield model — Preceding unsigned comment added by 199.190.45.185 (talk) 07:56, 16 December 2014 (UTC)[reply]

What is your question? AndyTheGrump (talk) 07:59, 16 December 2014 (UTC)[reply]

Sommerfeld model? --Wrongfilter (talk) 08:24, 16 December 2014 (UTC)[reply]

Yes, five. Plasmic Physics (talk) 09:19, 16 December 2014 (UTC)[reply]

Good answer. I think you nailed it. Richard-of-Earth (talk) 20:05, 16 December 2014 (UTC)[reply]

Are you quite sure it's not four point nine repeating? μηδείς (talk) 06:58, 17 December 2014 (UTC)[reply]

It is four point nine repeating, but only on Wednesdays. Plasmic Physics (talk) 07:53, 17 December 2014 (UTC)[reply]

Mumps

1. Before the mumps vaccine, what percentage of the population had a bout of mumps in childhood? (Data for any country will do) 2. What percentage of people who have had actual mumps (not vaccination) gain lifelong immunity to the disease? Thanks. 184.147.124.158 (talk) 12:37, 16 December 2014 (UTC):[reply]

You can take your pick of which population population. The World Health Organization -Data and statistics has it all. Also, I don't think its certain (beyond all doubt) that naturally acquired Mumps gives truly life long immunity. It is certainly not the case with chickenpox and some other viruses where the individual used to have their immunity reinforced by coming into contact with the virus again and time again throughout life. Hence, adults are now getting some diseases at an age where serious complications can set in.--Aspro (talk) 22:39, 16 December 2014 (UTC)[reply]

"Natural infection was once thought to confer lifelong immunity, but we now know that reinfection can occur, although it tends to be milder and more atypical than in primary infection."[9] --Modocc (talk) 00:06, 17 December 2014 (UTC)[reply]

Thank you both for the links. How do I use them? I couldn't see mumps on the World Health page so I clicked on Immunization but it only talks about pertussis and measles. Can you tell me where you found the mumps Aspro? And Modocc, the data in that link is hard for me to parse. They seem to have picked out the same numbers of infected and non-infected people so I don't understand how to get the percentage who actually have immunity, can you explain? Thanks again. 184.147.124.158 (talk) 01:20, 17 December 2014 (UTC)[reply]

Whoops sorry. They will either refer to mumps as viral parotitis or epidemic parotiditis. --Aspro (talk) 03:02, 17 December 2014 (UTC)[reply]

The CDC states here that "Before the U.S. mumps vaccination program started in 1967, about 186,000 cases were reported each year." Since the US population then was around 190 million the percentage was approx. a tenth of one percent or one per thousand [per year. See below]. I'm not sure which study you are referring to, but the text I quoted is referenced to a study [10] that simply found evidence for recurrence by comparing 82 patients with possible recurrent mumps with an equal number of primary infected patients. That won't be much help though for estimating lifetime immunity for the various strains. --Modocc (talk) 03:11, 17 December 2014 (UTC)[reply]

Ditto. If the OP is referring to this paper then one will not be able to get the percentage as this was not what this study set out to discover.Both groups 1 & 2 of 82 individuals each showed symptomatic evidence of mumps so one must conclude that all where infected. The point was that the first group had low IgM. This suggest that they had previously had mumps before – as IgM is mainly involved in the first nouveau infection (don't quote me on all this, as these days I can't remember what I had for breakfast this morning). For subsequent infections IgM production is lower. Also, the cohort (group 4) of just 20 non-infected mumps-immune subjects was too small a sample from which to come up with a reliable figure. Without reading the full paper I can't even say how the immune cohort of 28 was selected (i.e., immune by inoculation or natural). I doubt if anyone has done such a study yet due to the cost. My advice is to just stay away from all kids – they are virus factories running at full production 24/7.--Aspro (talk) 04:06, 17 December 2014 (UTC)[reply]

I know things here in WP are meant to be referenced, and I have no reference to cite. But "approx. a tenth of one percent" is way off. When I was at school (in England, around 1960) every few years a wave of mumps (likewise chickenpox, measles) would sweep the school, infecting almost every pupil who had not already had it. It meant a few days in bed, with mild discomfort, but no lessons! And no "cases were reported". Maproom (talk) 09:01, 17 December 2014 (UTC)[reply]

The problem is that @Modocc: compared the number of people who had mumps each year with the total population, which doesn't tell you how many of that population had it over their lifetime. Back of the envelope approximations could be made from that figure and the average lifespan (i.e. multiply the number of cases per year by the average lifespan of a person, compare to the population), or comparing it to the birth rate (i.e. mumps cases per year / new people per year), but neither seems likely to be particularly accurate. MChesterMC (talk) 09:18, 17 December 2014 (UTC)[reply]

Whoops, I was half asleep (I still am) and missed the "in childhood' part of the question. Even if young children primarily got it and made up ten percent of the population (increasing the percent per year by a factor of ten), then for fifteen consecutive childhood years per person that adds up to only a childhood infection rate of only about fifteen percent. I don't know the reason why that is so low and only have guesses as to why. For instance, kids might have been asymptomatic or were only mildly sick and stayed home and did not see a doctor, such that these cases went unreported as Maproom suggested. Alternatively, again I am only guessing here, localized herd immunity perhaps created bottlenecks along major travel routes that may have hindered its spread. -Modocc (talk) 11:05, 17 December 2014 (UTC)[reply]

Thanks for the followups, much appreciated. Clearly this data is pretty hard to find. I will keep looking under the latin terms, if anyone does come up with the numbers please keep posting! 184.147.124.158 (talk) 11:55, 17 December 2014 (UTC)[reply]

Is it known which drug is with the longest half life

5.28.177.164 (talk) 12:53, 16 December 2014 (UTC)[reply]

"Half life"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:41, 16 December 2014 (UTC)[reply]

See biological half-life. The article lists some examples (Bedaquiline with 5.5 months, e.g.), but that's probably not the record-holder (also, see the metals) . All the "longest half life" items I googled in connection with drugs meant the longest within a certain group or sample of drugs, not of all known drugs. ---Sluzzelin talk 16:47, 16 December 2014 (UTC)[reply]

(edit conflict) Half-life is the standard way to analyze how a drug is metabolized and excreted in your body, since the measurable levels of the compound in your body will degrade in power law manner, you can calculate a drug's half-life. It's rudimentary stuff. I don't know the answer to the OP's question, but will direct him (and anyone who wants to read more) to the article on pharmacokinetics, which is the study of how the body processes a drug. Half-life is a very common measurement for a drug's presence in your body. --Jayron 32 16:49, 16 December 2014 (UTC)[reply]

Why wouldn't Mcdonald's French Fries rot?

I've seen some videos comparing Mcdonald's French Fries and home made ones. It seemed that Mcdonald's French Fries rot slower than homemade ones. Is it just because Mcdonald's French Fries has too much salt and too little water (in comparison the home made French Fries with large cross section[11] seems to rot faster than those with small cross section[12])? Or is it because Mcdonald's French Fries contains some artificial preservatives?--Bdog07 (talk) 13:32, 16 December 2014 (UTC)[reply]

Do you mean literally rotting, or simply becoming no longer tasty? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:42, 16 December 2014 (UTC)[reply]

(edit conflict) Salt is a perfectly good preservative. I have no idea what the methodology is behind those videos, but this is why you don't trust random youtube videos. There's far too many opportunities for someone to screw up the experiment, either unintentionally (for example, not salting the homemade fries to the same level as the McDonald's fries) or intentionally (because they have an axe to grind, see Super_Size_Me#Criticism_and_statistical_notes for how these things can go wrong). A random youtube video is NOT a controlled experiment, and should not be trusted one way or the other. I am not saying the people are lying, I am not saying the video is or isn't an actual experiment. What I am saying is there is no way to draw any meaningful conclusion from it because we can't trust the provenance or methodology or anything from it. So, we can't answer your question because we don't know if the videos are trustworthy, and as such, there's no need to explain why they are happening that way. You've started with the conclusion that the video maker has planted in your head, instead of starting with "can I trust the video one way or the other". If you can't answer THAT question to a satisfactory level, you can pretend you never saw it... because it means nothing. --Jayron 32 16:45, 16 December 2014 (UTC)[reply]

(edit conflict) They dry out before they can rot. The large surface area to mass ratio and water boiled off during frying combine to make this happen. If you were to keep them damp, then I suspect they would eventually rot. StuRat (talk) 16:46, 16 December 2014 (UTC)[reply]

I found McDonald’s Reveals 17 Foul Ingredients in Their French Fries, which if true, says that they use citric acid as a preservative amongst all the other stuff. Mmmm... Alansplodge (talk) 16:57, 17 December 2014 (UTC)[reply]

That site looks about as far from a reliable source on health matters as you can get. I think citric acid is pretty benign as food additives go - it's a major part of lemon juice, after all. AndrewWTaylor (talk) 17:23, 17 December 2014 (UTC)[reply]

Apologies, I was being lazy. Here is the ingredients list for the fries sold in the US (p.14): "FRENCH FRIES: Ingredients: Potatoes, Vegetable Oil (Canola Oil, Soybean Oil, Hydrogenated Soybean Oil, Natural Beef Flavor [Wheat and Milk Derivatives]*, Citric Acid [Preservative]), Dextrose, Sodium Acid Pyrophosphate (Maintain Color), Salt. Prepared in Vegetable Oil: Canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil with TBHQ and Citric Acid added to preserve freshness. Dimethylpolysiloxane added as an antifoaming agent. CONTAINS: WHEAT AND MILK. *Natural beef flavor contains hydrolyzed wheat and hydrolyzed milk as starting ingredients...".

Interestingly, McDonald's don't put any of that stuff in the fries that they sell in the UK: "Fries: Potatoes, Vegetable Oil (Sunflower, Rapeseed), Dextrose (only added at beginning of the potato season)." No idea why that is. Anyhow, perhaps the citric acid (harmless as it is) helps explain why their fries last longer. Alansplodge (talk) 22:18, 17 December 2014 (UTC)[reply]

Can you "see" a cell-phone probing for a network?

In the same way you can see a PC probing for a wlan?--Senteni (talk) 17:30, 16 December 2014 (UTC)[reply]

From a purist, physical scientific standpoint, "yes." Mobile telephones actively transmit radio frequency signals, and you could theoretically detect and decode such transmissions.

In a practical sense, "no," you can't buy the gear you need to break the encoding - or even to demodulate the radio signal in the most commonly used mobile telephone spectra.

With sufficient domain-specific expertise, and certain very expensive equipment, it is evidently possible - somebody is designing, building, and testing telephones! But those tend to be very large telecommunications companies who employ large numbers of highly-specialized engineers. There are many hobbyists who attempt to build their own cheaper "cellular"-band sniffer radios, and in principle this can be done - heck, when I was in graduate school we built UHF radio mixer-transceivers out of copper tape and single transistor amplifiers ... but to do this efficiently requires a lot of time, money, and experience. If you go down to your neighborhood HAM radio store, and dig around among the pretty high-end gear, you'll invariably find an abrupt "band-gap" in the available equipment right at the frequencies you might find interesting. A lot of times, you'll see this in the product marketing literature as a radio with "ultra-wide band (less cellular)." For example: The Alinco DJ-X30T wideband receiver covers 100 kHz to 1299.995 MHz (less cellular). But click around on the more expensive gear - no matter how much you spend, you can buy radio equipment in any band you want (less cellular). It's almost as if ... the Government forbids mere mortals from purchasing or using equipment that would interfere with common-use radio spectrum, ensuring that electronic surveillance isn't easy or cheap! In the U.S., you could probably get away with receiving signals passively, as long as you never transmitted... but in other countries, like the U.K., even a passive receiver may be illegal to operate.

Unlike IEEE 802.11 frequencies, mobile telephones operate in radio bands that are much more tightly regulated, which means that you cannot easily and cheaply buy electronic test equipment that receives or transmits in those bands. This is a good thing for the digital-radio-using public: it is just one of the many technical and administrative hurdles that prevent unauthorized hobbyist "eavesdroppers", "jammers," and other troublemakers from interfering with mobile digital radio.

Nimur (talk) 17:45, 16 December 2014 (UTC)[reply]

You can easily and cheaply hear the characteristic interference that mobile phones create in the reception of Longwave AM broadcasting such as BBC Radio 4 in the UK. Of course, you would need very different and much more expensive equipment to decode the signals. Dbfirs 21:38, 16 December 2014 (UTC)[reply]

This is an alternative link to Title 47 § 302a, for anyone having difficulty using Nimur's link. Tevildo (talk) 23:01, 16 December 2014 (UTC)[reply]

(Technically, you have linked to United States Code, Title 47; I linked to Code of Federal Regulations Part 47. These are parallel but distinct sets of laws and they serve different purposes; items in USC are codified statute law, while CFRs are federally-enforceable administrative regulations; CFRs tend to be a lot more specific but a lot less fun to read).

Nimur (talk) 02:18, 17 December 2014 (UTC)[reply]

Ah, sorry. I can't get your link to work at all, so I guessed what it referred to based on the URL. The precise text of the legislation is probably irrelevant here. Tevildo (talk) 09:23, 17 December 2014 (UTC)[reply]

Yes. The point is that cellular radio equipment is not easy to legally purchase, because it is tightly regulated. Anybody who legitimately needs to know more will know where to look. Nimur (talk) 15:49, 17 December 2014 (UTC)[reply]

I'm unconvinced it's as difficult to buy equipment capable of receiving those signals as you suggest. Various sources like [13] [14] [15] [16] [17] [18] [19] [20] suggest you can probably at least detect (which seemed to be what the OP referred to), if not even decode (I'm actually a bit surprised by this, I didn't quite expect the RTL-SDR to be good enough for that level) a number of mobile phone network signals using a simple RTL-SDR. I don't want to comment much on the legal issues but I'm fairly sure owning a DVB-T stick with the RT2832U chipset would be legal in much of Europe including the UK where DVB-T is common. And definitely these are easily available on places like Ebay and Amazon for under US$20 or less, including from local sellers. I'm not totally sure if these are legal in the US since DVB-T isn't used there but since as was mentioned, the legal restrictions on devices only capable of receiving are generally far less stringent it wouldn't surprise me if they were and they can definitely be purchased from sellers in the US. Of course, just because it's legal to own and use the device for its intended purpose doesn't mean it is to use the device for other purposes, particularly monitoring frequencies associated with mobile phone networks [21]. But the point remains, legally buying and owning equipment capable of at least detecting the signals probably isn't as difficult as you suggest even if actually doing it could theoretically get you in to trouble. BTW, as also highlighted a previous time this came up another option which isn't that cheap but also isn't super expensive is a USRP (the sited figure was around ~$1200) combined with an appropriate daughterboard like [22] (specifically advertised as being suitable for such purposes). I have no idea however how easy this is to buy in the US but the seller has existed for a while now without any apparent major problems despite some confusion last time. (Of course my early point stands that just because you can own it doesn't mean you can use it for the purpose without theoretically getting in to trouble and if you're actually transmitting rather than receiving, it may be more than theoretical. Then again, transmission was never mentioned by the OP.) Nil Einne (talk) 17:57, 18 December 2014 (UTC)[reply]

The first problem you will run into is interference. Cell phones trying to make a connection use the same radio frequencies as are used for communication. So unless you are out in the wilderness or inside a faraday cage you are going to have a hard time picking out the signal you want. If you are isolated I imagine you would be able to 'see' the signal with radio receiver that can tune to the required frequency and an oscilloscope to display the signal. You won't be able to decode the signal with that kind of setup, but you should be able to tell if the cell phone is transmitting. If you want to decode the data, then Software Defined Radio [23] is the rat hole you need to crawl into. — Preceding unsigned comment added by 50.43.56.168 (talk) 09:18, 17 December 2014 (UTC)[reply]

December 17

Mystery fruit (?) in hay bale

Here's a good, old-fashioned species ID question for everyone. I am a farm dweller (southeastern United States), and I have been coming across these things in bales of hay from time to time. They are what appear to be very tiny fruit, the largest being maybe 7 or 8 mm in diameter. They don't look ripe to me, but not knowing what they are, I guess that would be a hard call to make. They are yellow (obviously) and full of seeds (hence, fruit). I was brave enough to taste one, and decided I didn't like the taste; decidedly pepper-like, but quite bitter. The skin, though, has a slightly irregular, almost citrus-like texture. Any ideas? Evan ^{(talk|contribs)} 05:08, 17 December 2014 (UTC)[reply]

Horsenettle, Solanum carolinense --Digrpat (talk) 06:41, 17 December 2014 (UTC)[reply]

Yes indeed. I won't be giving it another taste then, in that case! Glad I spit. Thanks for the reply. Evan ^{(talk|contribs)} 06:52, 17 December 2014 (UTC)[reply]

Is that hay for horses ? If so, I'd be a bit concerned that they may get sick if they eat too many of those. StuRat (talk) 06:57, 17 December 2014 (UTC)[reply]

Yeah, I've been picking the fruit out before feeding the horses on the off-chance it was bad. I'll start being even more careful, and maybe have a chat with my new hay provider; never seen these in hay from anyone else. Evan ^{(talk|contribs)} 07:00, 17 December 2014 (UTC)[reply]

OK, but don't be too hard on him, it's apparently a bitch to get rid of that weed. I'll mark this Q resolved. StuRat (talk) 07:09, 17 December 2014 (UTC)[reply]

Resolved

Gap in teeth

Some people have a very prominent gap between their front teeth. Here is a photo of an example: Michael Strahan: Why I Never Closed the Gap in My Teeth. Is there a name for that (other than simply "gap")? Also, what causes this? Thanks. Joseph A. Spadaro (talk) 05:17, 17 December 2014 (UTC)[reply]

Diastema. Evan ^{(talk|contribs)} 05:19, 17 December 2014 (UTC)[reply]

Thanks! Never heard that term before. Thank you. Joseph A. Spadaro (talk) 18:12, 17 December 2014 (UTC)[reply]

Regarding what causes a it, there are physiologically important diestemata (plural) in animal dentition that serve to both prevent food impaction and to aid in occlusion. Animal dentitions are super strange from a human-focused perspective because there are gaps and missing teeth and all sorts of wacky things that exist quite normally that, if found in the human dentition, would appear quite odd.

But back to human diastemata -- a midline diastema, as exemplified by Michael Strahan, is sometimes caused by an overly large incisive papilla (I'd steer you toward Google images for this, rather than the Wiki article because the latter is very misleading: the photo is from a terrible angle, exhibits terrible shadowing and the palate manifests a torus palatinus which can easily be mistaken for the focus of the photo as used by the article). Also, if the incisive papilla happens to be positioned a little more anteriorly than normal, the central incisors (which are the two large front teeth) may not be able to erupt into proper position, thus forming a midline diastema.

Back to animals, for a second -- I did come across something very interesting recently while reading about the rhinarium, or mammal wet nose. Apparently the groove on the rhinarium, the philtrum, is embryologically similar to the groove primates (and humans) have under their nose, even if they do not possess a wet nose (i.e. haplorhines). There's much debate about how to classify the various prosimians based on some of the variations that exist with these structures (see here) and, apparently, the presence of the rhinarium and its philtrum creates a gap between the roots of the maxillary central incisors (see second paragraph here). As a dentist for humans, I can confirm that there is a gap between the roots of maxillary central incisors for humans, even when there is no gap between the crowns (and so, no diasthema) because the two maxillary bones fuse at the midline suture. I have not seen clinical or radiographic information related to what is meant when the aforementioned citation refers to a gap between the central incisor roots in strepsirrhini, so I can't know for sure the comparative anatomy. But in humans, the incisive papilla is the exit of the nasopalatine nerve from the nasopalatine canal and if the nerve would exit more anteriorly, I can see it being very much in the way of the two central incisors being close together. DRosenbach ^{(Talk | Contribs)} 01:55, 18 December 2014 (UTC)[reply]

Thanks, all. Joseph A. Spadaro (talk) 17:00, 19 December 2014 (UTC)[reply]

Missing teeth (technical terms)

Inspired by the previous question: Is there a technical name for adult teeth that are missing because they never developed? For example, suppose a person simply doesn't have cuspids and never did, is there a technical name for such missing teeth (or perhaps a name for a medical condition associated with having fewer teeth than normal)? Dragons flight (talk) 05:33, 17 December 2014 (UTC)[reply]

Hypodontia gives several terms to related this condition. Also "aplastic" can be used to describe any missing organ.--Digrpat (talk) 06:02, 17 December 2014 (UTC)[reply]

This is anecdote, but the lack of cuspids is rare. The lack of wisdom teeth is most common, and the human jaw is one of our rapidly evolving body parts. I mention this from my having had impacted molars extracted. μηδείς (talk) 06:54, 17 December 2014 (UTC)[reply]

Thanks. That's exactly what I was looking for. Dragons flight (talk) 02:54, 18 December 2014 (UTC)[reply]

Heat engine problem

Hi, I'm working on a homework question and basically I feel like I've gotten the whole thing but I'd really appreciate someone else to helping me check because I'm not sure if I did it right.

It's a heat engine problem, going from A to B to C Volumes and pressures are as follows A = 7x10^4 Pa, 2.5*10^-2 m^3 B = 3x10^5 Pa, 2.5*10^-2 m^3 C = 3x10^5 Pa, 7.5*10^-2 m^3

I got that the engine has a power output of 57.5 J by finding the area inside the points (just using 1/2 b*h) and an efficiency of 12% by finding the total heat added by Q=dU+Work from A=>B and B=>, but I'm just not sure if I'm doing it right. Can anyone please help me confirm with their steps?

166.137.252.91 (talk) 05:41, 17 December 2014 (UTC)[reply]

I think we're missing some information here. From A to B the pressure goes up and then from B to C the volume goes up. In both steps energy is being added to the gas. But we don't know what kind of gas it is, its mass or its specific heat.50.43.56.168 (talk) 08:28, 17 December 2014 (UTC)[reply]

I think I'm supposed to assume it's an ideal gas, and the temperature at A is 290K. 67.247.2.127 (talk) 02:45, 18 December 2014 (UTC)[reply]

Your first statement is incorrect. Joules is not a power output. J/s is power and is expressed in Watts (alternatively as horespower). --DHeyward (talk) 06:55, 18 December 2014 (UTC)[reply]

What's the centre of mass of the Local Group of galaxies?

What do the galaxies in the Local Group orbit around?Whereismylunch (talk) 07:51, 17 December 2014 (UTC)[reply]

According to our Local Group article: "Its gravitational center is located somewhere between the Milky Way and the Andromeda galaxies" (although the center of mass and gravity aren't technically the same, they may be close enough for you purposes). However, I don't think it's correct to say that everything in the Local Group orbits about that point, since the way that distance is critical in determining gravitational attraction ensures that each galaxy is far more affected by those galaxies near it than by those far away. So, in effect, each galaxy will orbit about a different center of gravity, as viewed from it's perspective.

To compare with magnetism, we might say that all compasses on Earth should point toward magnetic north, but local variations in the magnetic field, or nearby magnets, can easily change the direction the compass points. It's not that those things are more powerful than the Earth's magnetic north pole, they are just closer. StuRat (talk) 07:58, 17 December 2014 (UTC)[reply]

But what's at the gravitational centre? — Preceding unsigned comment added by 199.119.235.178 (talk) 08:58, 17 December 2014 (UTC)[reply]

Nothing. --Jayron 32 11:21, 17 December 2014 (UTC)[reply]

Or, more accurately, the gravitational center is never going to be made of anything, since it's a point, an abstract construct rather than a physical body. To be clear, something might be occupying the space that roughly corresponds to that point, but it needn't be a significant body contributing any particular amount of gravitational force. Snow talk 12:54, 17 December 2014 (UTC)[reply]

Wikipedia also has an article Centers of gravity in non-uniform fields which may be a bit technical, but does provide some explanation of the concept. --Jayron 32 13:51, 17 December 2014 (UTC)[reply]

I was about to link to the same article which explains that the concept is not really clearly defined for clusters of galaxies, but I think our "Local Group" article probably refers to roughly where the CofG would be if (suddenly and inexplicably) a uniform gravitational force suddenly appeared (from the edge of the universe? or the Great Attractor, or Dark flow?) and acted on the whole cluster. It is more usual to call this "point" the centre of mass. The theoretical point about which the galaxies seem to be revolving (on average, see StuRat's comment above) is not necessarily the same point, but might be somewhere near the centre of mass. Dbfirs 13:11, 18 December 2014 (UTC)[reply]

How accurate is reentry?

The recent test flight of the Orion spacecraft ended with a splashdown in the Pacific Ocean where is was picked up by the USS Anchorage. How far was the ship from the point where the spacecraft touched down? What was the predicted impact point and/or area? Once the retro rockets have been fired, does the spacecraft have any further control of where it lands? — Preceding unsigned comment added by 50.43.56.168 (talk) 08:13, 17 December 2014 (UTC)[reply]

Well, to give you some idea. The Mars Science Laboratory only went to our nearest planet and yet it missed point zero by 5½ miles. Better luck next time eh.--Aspro (talk) 09:00, 17 December 2014 (UTC)[reply]

The distances involved in a re-entry procedure are significantly shorter than those of an interplanetary trajectory, such that, under many conditions, a given error in trajectory at the outset results in a larger divergence (in terms of absolute distance between resulting arrival points) for the latter, relative to the former. Snow talk 12:34, 17 December 2014 (UTC)[reply]

It was 1.5 miles, not 5.5 miles. --Bowlhover (talk) 18:56, 17 December 2014 (UTC)[reply]

Which, considering a trip of 675 million kilometers and the necessity for incredibly accurate timing (in that each planet is in motion in its own orbit) is pretty impressive in it's own right. Sure, close is often not good enough in astronautics, which is why most missions now include a handful of opportunities for course corrections. Still, if I launched something 675 kilometers via mechanical means and managed to land it within 1.5 millimeters of my (swiftly moving) target, I dare say it would be regarded as the single most impressive thing I'd ever do. Snow talk 20:23, 17 December 2014 (UTC)[reply]

One of the points about splashing down in the ocean is one can ensure there aren't people anywhere near! So hopefully they were some distance away, especially as it was a test flight. Dmcq (talk) 11:33, 17 December 2014 (UTC)[reply]

To the question in the OP's heading, the answer would seem to be "not necessarily very accurate". The charts at Splashdown#Locations include "miss distances", which indicate rather variable results (though the entry for the Orion test does not include a miss distance). Deor (talk) 12:46, 17 December 2014 (UTC)[reply]

But they can be. @50.43.56.168: The closest to calculated landing point appears to be "Apollo 16 on April 27, 1972 at 0°43′S 156°13′W by USS Ticonderoga (CVS-14)" only missed by 0.55 km[24] (≈0.34 mile)! Though Aurora 7 on May 24, 1962 missed by 400 km (≈250 miles). As for control of landing point after the retros fire? Yes I believe they can control it,(see cached NASA source below) but the main concern would be to maintain the correct re-entry 'attitude', or the craft may either skip out of the atmosphere or burn up and 'land' as cinders. Where it lands would be a pretty low priority, so long as it's in one piece on water.

• Specifically the landing point from Splashdown#Locations was 23.6°N 116.4°W, 275 miles west of Baja California. However the Exploration Flight Test 1 page says "23.61°N 114.46°W" 640 miles (1,030 km) SSE of San Diego. 'Miss' distance unspecified as Deor noted.
• I can't find out "How far was the ship from the point where the spacecraft touched down?" however "The target landing accuracy of an Orion capsule using automatic bank angle control of downrange and crossrange, when subject to the full range of atmospheric, aerodynamic, navigation, control, and mass properties dispersions, is within 10 km (5.4 nmi)".[25] a google cache of http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110013203.pdf, which appears to be unavailable at that URL

Those 'miss distances' may not be correct! Use with care. The actual HTML version, here, of the source for the Apollo 16 says "3.0 n mi from the target point" (5.56 km; 3.45 miles) not 0.55 km/0.34 miles! That may be a slip of the decimal point. The big 400 km Aurora 7 miss however is supported by the reference on page 225, [26] (PDF 8.162 MB), though the URL has changed.--220 of ^Borg 08:16, 20 December 2014 (UTC)[reply]

Lioness hunting tactics

I read yesterday in a Simon & Schuster mammal field guide from about 1985 that lionesses tend to kill their prey with a single blow to the back, breaking the spinal cord. I'm not naive enough to simply ask how could it be that striking with a paw leaves the prey with fatal damage but no damage to the lioness' paw, but I was just intrigued at everything that needs to go into such a technique. It seems obvious to me that lionesses do not consider their options like a person would, but of all the possibilities and all the alternatives, I find it fascinating that the lioness would consider this means of execution over, say, chomping on the trachea. I see Youtube videos on lionesses attacking buffalo and they seem to try to bit into the ventral neck, but the buffalo resists. What sort of force is required to tear out a trachea, and why would a lioness find that difficult? Is it really more efficient to snap a spinal cord? Thoughts and insights are welcome. Thanks! DRosenbach ^{(Talk | Contribs)} 17:18, 17 December 2014 (UTC)[reply]

The way the lioness kills her prey is directly related to how she approaches it. The typical approach would be to stalk and then attack from behind - this makes the back of the neck the clearest and easiest target for a killing blow. Going for the throat would require a frontal approach which could lose the element of surprise, as well as leaving the lioness open for a counter-attack from the prey's hooves, horns, etc.

There is a lioness-eye-view video of a hunt and kill available here:This is what hunting looks like from a lioness' point of view. (Don't watch it if you may be disturbed by seeing an animal get killed.) The narrator notes that a lioness "will generally sneak up to the prey, as close as possible, and then make a sprint for it." That sneak attack pretty much demands going for the back of the neck rather than the throat. - Eron^Talk 18:13, 17 December 2014 (UTC)[reply]

Yep, also going for the throat puts a lion in easy kicking/stomping range of a quadruped. But all of this is massive simplification. Does the field manual mention the technique is to jump on a zebra, overshoot, flip over, almost get trampled then run away? Because that happens a lot too :) Finally a serious spinal injury at the neck makes a mammal stop, nearly instantly - even if it's not dead it's not moving. But I wouldn't want to be around a wildebeest with its trachea recently ripped out. It will still be deadly for an important minute or so, and you lose all that tasty and nutritious blood. SemanticMantis (talk) 18:20, 17 December 2014 (UTC)[reply]

Here's a few refs - an old paper [27], and a newer ref [28]. The first (paywalled) link has a table with data on kill rates - males killed a bit more than females, immature and old prey made up the majority of kills, but "prime" healthy prey made up the plurality. Humorously, the latter is on a Lion King fan site, but it does have additional citations, and mentions the importance of cooperative hunting and scavenging. It reports (and you can also see in videos) that often several lions will jump on a prey at once, attacking various parts simultaneously. The point being that kills made by a solitary female are probably a rather small part of a lion's average weekly diet. SemanticMantis (talk) 18:33, 17 December 2014 (UTC)[reply]

Lions often hunt together, but as for pouncing on the prey together, that's only needed for large prey. StuRat (talk) 18:44, 17 December 2014 (UTC)[reply]

Buffalo made up over 60% of lion kills in this study [29]- though they do mention that smaller prey are probably underrepresented in their study, because the lions might finish eating before the observers could find the body. SemanticMantis (talk) 18:51, 17 December 2014 (UTC)[reply]

And for more throat-based killing, check out Cheetahs, they seem to be generally less effective at killing - this paper [30]] says

“

Cheetah spend several minutes killing prey. Five minutes is common, but 15-25 minutes was not rare, even with small impala fawns.

Some prey revive from strangulation killing attempts and have to be “strangled” two to three more times before death occured.

”

SemanticMantis (talk) 18:51, 17 December 2014 (UTC)[reply]

Many years ago I read a research paper on Lions' killing methods.(Sorry, can't find it now) They found that most prey were killed by a bite that forced the canines between the vertebrae, rather than crushing the vertebrae. Using high-speed photography and post mortem dissections, they found that lions have some rapid response muscle fibres in their jaw muscles, that can very quickly do a series of test bites until the canine teeth find the softer area between the vertebrae. An amazing bit of evolution!! 122.108.177.30 (talk) 03:44, 18 December 2014 (UTC)[reply]

Bugging the outdoors with spiderweb-like antennas

I ran across an interesting story at [31], in which three planes flew close overhead and fine spiderweb-like fibers were then seen sticking to the landscape. I am for now discounting the site's explanation of "geoengineering" entirely, but assuming the truth of their published lab analysis that indicates the presence of aluminum (1020 mg/kg), barium (34.1 mg/kg), and strontium (70.8 mg/kg). These are small but perhaps not negligible amounts, up to 0.1% aluminum in the sample as collected.

To be clear, I have found a fairly persuasive "debunk" of the story at [32]. If we assume that the witnesses were wrong about the association with the planes and the fall of the webs immediately afterward, or if it's just a remarkable coincidence, the webs are explained; if they were contaminated with soil the aluminum is explained; I'm not so sure about the rarer barium and strontium. The test was consistent with spider silk, which would be more impressive if they hadn't first identified it as wheat flour and bacitracin; suffice it to say that some non-metallic matrix containing peptide has to be the major constituent of whatever these fibers are.

But to be contrary, just because the fibers look natural doesn't rule out another explanation, since they might intentionally be camouflaged. My question is whether this data could be explained with some known form of antenna that could be sprayed through a nozzle as a plane flies overhead, land as an intact radio-reflective surface, and then have a signal bounced off it to measure changes to it, i.e. vibrations caused by the speech of nearby persons? (as a wild guess, probably wrong because it also contains titanium, see [33]). Alas, I'm not familiar with this literature. How thick would such a metal fiber actually have to be to be used this way? And is this metal composition actually practical to include in some sort of polymer "spider silk" that can be sprayed from a plane?

I'd also welcome any other possible explanations. Wnt (talk) 21:51, 17 December 2014 (UTC)[reply]

So much of this is such utter nonsense I'm not sure where to start. I don't even believe that a plane flying at 5000-8000 feet could distribute "spider web like fibers" to the ground in anything like a reliable fashion. This is also one of the major problems with chem trails, there is an absolutely immense volume of air to travel through from a mile up and there are all sorts of wind currents and turbulence to get through, to suggest that a spider silk would just gently fall all the way to the ground from where it was dropped by a plane a mile up is ridiculous. Also, known form of antenna and radio reflective surface are mutually exclusive concepts. I suppose you are talking about something like a Laser microphone but that already exists and would be a far simpler way to "bug" someone without the need to spread square miles of high tech spider silk antennas randomly around the country side. Vespine (talk) 23:58, 17 December 2014 (UTC)[reply]

Well, the non conspiratorial explanation is ballooning (spider) - which can reach the jet stream and return safely to the ground. Therefore, it should not be impossible to drop it from the height of a plane, though getting around the difference in velocity would indeed be an interesting technical problem. (for example, you can picture a flexible boom that wiggles back and forth, regularly reaching near zero airspeed) As for chem trails, so far as I know this is simply jet fuel that contains up to 0.3% sulfur;^[34] it is said to delay global warming by 6 months, kills 1000-4000 people every year, but hey, it makes the jet fuel 1.6 to 7 cents cheaper a gallon. Officially not a conspiracy, just business as usual, with a side spin of "good for the environment". (And where else did people think the chemtrails would be coming from, if not the fuel tank?) The presumed purpose of the scheme would not be to place a specific bug in a known location, but to place many bugs in multiple locations that are hard to identify as such, so that the conversations of a large number of people are simultaneously screened for bits of interest while being as easy to deny as possible. Wnt (talk) 00:36, 18 December 2014 (UTC)[reply]

I came across something that sounds vaguely similar. Google "Huntsville weather anomaly". Here's one site: http://valleywx.com/2013/06/04/mystery-blob-over-west-huntsville/ — Preceding unsigned comment added by 50.43.56.168 (talk) 01:35, 18 December 2014 (UTC)[reply]

Well for one, I wasn't saying that spider webs 'couldn't be dropped from a plane and land somewhere, my point was that it would not land anywhere near where it was dropped, to the point where it would be practically futile. Notice how low a crop duster flies to spray a field, that's not done from a mile up for precisely the same reason, the amount of spray that would actually reach the ground at the target location would be negligible. Similarly if you dropped cobwebs from a mile up, I propose it would be very difficult if not impossible to say with any level of confidence where those cobwebs would land. If it's purely a 'non targeted' attack and they don't care where it lands, and I'm assuming it's supposed to be covert since no one knows about it, then why wouldn't they just fly the mission at night when no one would notice? I suppose the conspirators were just too stupid to think of that? Or is it because they control all the media and so they don't care if a few people notice? I'm guessing this thread has already been tagged and will be deleted soon and me and you will disappear without a trace? Also, pollution from ships kills about 60,000 people a year, compared to 4000 a year from planes, so I guess the conspiracy should really be "chem wakes" not "chem trails"? And lastly, coal fired power plants kill hundreds of thousands globally with their pollution, what conspiracy is that? chem power plant? Vespine (talk) 02:40, 18 December 2014 (UTC)[reply]

This is an interesting argument. How well can the path of the dropped material be predicted, given extensive modelling of local weather? Wnt (talk) 13:39, 18 December 2014 (UTC)[reply]

What kind of answer do you expect? "Well enough"? The question is too vague. IF there was actually some practical requirement for the military to drop spider web like material from a plane flying a mile high, I doubt there is any challenge there that could not be overcome, given enough research and resources. I just don't think the practical need exists and there would be far easier and more efficient ways of achieving a similar result for less cost and effort. Vespine (talk) 23:02, 18 December 2014 (UTC)[reply]

The aerodynamic coefficient (I just made that up) will make a huge difference. Iron cannon balls will have a fairly predictable trajectory. Threads of spider silk, not so much.

Another point is that antennae must have some precisely controlled placement of the antenna elements, not the random distribution you'd get from a spider web tossed from a mile up. A fractal antenna could potentially be disguised as a natural object though, since fractals are common in nature. StuRat (talk) 18:20, 20 December 2014 (UTC)[reply]

December 18

Hydrochloric acid and methylbenzene

Why is hydrochloric acid acidic in everything except methylbenzene? I am really confused about this as my textbooks do not include anything of the sort and I have been told that this would appear in my exam. Please help. Thanks! pcfan500 (talk) 06:28, 18 December 2014 (UTC)[reply]

You'll probably want to review the concepts about what makes things "acidic" - see Brønsted–Lowry acid–base theory and Lewis acids and bases for an overview of the two big ones. In short, a compounds is an acid because it donates a proton (accepts an electron pair). Hydrochloric acid is a strong acid because the chloride doesn't hold on to the proton very well ... at least in water. Other solvents (like the aforementioned methylbenzene) don't do as good of job stabilizing the separated state, so the proton and the chloride want to stick together. I'm not sure why methylbenzene is being highlighted specifically - I'd expect other similar solvents (ethylbenzene, for example) to also behave similarly, sot it's not really the case that hydrochloric acid is acidic in "everything" but methylbenzene. -- 141.39.226.228 (talk) 08:45, 18 December 2014 (UTC)[reply]

why is time known as the fourth dimension?

why is time known as the fourth dimension? 94.98.4.75 (talk) 09:37, 18 December 2014 (UTC)[reply]

I've added a heading to this question. It's known as the fourth dimension because it is one in a physical sense, i.e. subject to the rules of physics in a very similar sense. Of course you can also see the sense in which it!s a dimension: just consider cases where we remove a dimension and use it for time instead, like a flipbook of animation . There are two dimensions shown at a time and the third dimension gets shown over time. 91.120.14.30 (talk) 11:23, 18 December 2014 (UTC)[reply]

To fully describe where an object can be found, you need 4 dimensions, with the 4th being time. Consider trying to describe the location of something which no longer exists, like the Lighthouse of Alexandria. You can go there now, but you won't find much. StuRat (talk) 11:37, 18 December 2014 (UTC)[reply]

You might (or might not) be interested in the technicalities given in articles such as Spacetime and Minkowski space. Dbfirs 12:37, 18 December 2014 (UTC)[reply]

(edit conflict) Geometry "works" with any numbers of dimensions. You know how there are all sorts of "math" you can do with shapes and lines and such? Calculating area, length, volumes, velocity, etc.? Well, the "rules" that allow you to make those calculations are not restricted to any number of dimensions. For example, you can establish a line in two dimensions by defining two sets of points, say point A = [0,0] and point B = [1,2]. You can then set up equations in either cartesian coordinates or vector coordinates to define the line that goes through those points. Well, you can do the same in 3 dimensions by defining the points in 3D space as A = [0,0,0] and B = [1,2,3] or some such, and then can write an equation to define that line. Now, the deal is, even though you can't picture a line in any more than three dimensions, the rules for writing the equation of a line still apply in any number of dimensions. You just do the algorithms and define the line. I can define a line in 4 dimensional space simply by saying A = [0,0,0,0] and B = [1,2,3,4], and the rules for writing the equation for THAT line (which has no reasonable PICTURE, but never mind that) are the same rules as writing lines in less dimensions. I can have any arbitrary number of dimensions, and the math for describing an object called a "line" in those number of dimensions is the same as it is in 2D, 3D, or whatever. So that brings us back to why even bother to treat time as a dimension like space dimensions: that is, we have the three spacial dimensions (up-down, left-right, forward-backward) and add time as a fourth number into that set. The reason why has to do with Einstein's theory of special relativity. What special relativity shows (among other things) is that you can vary how you move through time. Just as you can move through space at various rates, it turns out that time passes at different rates depending on certain conditions, such as the mass and velocity of an object relative to nearby objects (the effect of mass on time passage is actually covered by general relativity, not special, but whatever). Now, it turns out that because the rate of passage of time for an object is variable just as it's movement through space is variable, in order to completely describe the motion of an object, one needs to consider not only how it's position is changing, but also how it's timescale is changing with respect to other objects. In order to do that, you treat time like a dimension, and do your calculations in 4D rather than 3D; but the rules for doing so (as noted above) still apply. One last thing about time, however, is that the time "dimension" doesn't behave like the other "dimensions": it has it's own set of rules which is different than the others; however as long as you take those rules into account, you can still do math with it to predict the behavior of objects (and that's what physics is: the science of being able to predict the behavior of objects in motion). The specific set of dimensions (which includes the three spatial dimensions and the one time dimension) we use to do these calculations is called Minkowski space, named after the mathematician who worked out the math of such a system. The last question someone might ask is why do we have to do all that. The answer is because it is necessary to explain observable phenomena where normal 3D "Cartesian/Euclidian" space cannot, for example experimentally verifiable phenomena like time dilation, or the invariance of the speed of light. I know this was a little TL;DR but I hope it is clear enough to help one understand the entire point of treating time like a dimension. --Jayron 32 12:39, 18 December 2014 (UTC)[reply]

Your "TL" discussion makes sense. The way I like to "picture" the time dimension is to think of the state of the universe (or some portion of it) at a series of points in time - as with the flip-book discussed earlier. So the fourth point in that [x,y,x,t] coordinate system can be pictured as what that [x,y,z] system looks like as "t" changes. Beyond that, of course, it gets tricky trying to picture. But in math, as you say, you can have any number of dimensions and the equations still work, albeit getting more and more complicated with added dimensions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:52, 18 December 2014 (UTC)[reply]

Actually imaginary time is the fourth dimension. The distance in relativity calculations seems to be determined by x² + y² + z² - t². Wnt (talk) 14:34, 18 December 2014 (UTC)[reply]

Not really. Normal, everyday time is the fourth dimension. Imaginary time is used only for very specialized calculations, such as to eliminate the singularity (division by infinity) at the Big Bang or in black holes. --Jayron 32 15:17, 18 December 2014 (UTC)[reply]

I'd say that normal everyday time is a fourth dimension. It's definitely the most common choice in any non-technical context. As you discuss above, there are lots of other choices for what dimension we might call the fourth (or fifth, sixth etc.) especially if one is delving into theoretical physics (e.g. string theory) or certain mathematical structures (e.g. octonians)SemanticMantis (talk)

Yes, "the" in this case refers to "the fourth dimension used in Minkowski space for relativity purposes". Imaginary time as a fourth dimension only has limited utility in understanding a few physical phenomena. --Jayron 32 15:58, 18 December 2014 (UTC)[reply]

My understanding of the "spacetime interval" (see Spacetime) is that we can treat time as a fourth dimension for calculating a distance if we treat c as the conversion factor between our measurements, and recognize that when measuring time we are measuring multiples of i. Wnt (talk) 19:14, 18 December 2014 (UTC)[reply]

I think the consensus nowadays is that treating time as an imaginary spatial coordinate is a cute mathematical trick, but probably too cute, because it seems more meaningful than it is. I believe there's a note on it in Gravity by Misner, Thorne, and Wheeler, a book we should probably have an article on if we don't already. --Trovatore (talk) 21:05, 18 December 2014 (UTC)[reply]

Per Trovatore, it's a matter of perspective. Because of the sign conventions of working in Special Relativity, the "time" dimension has the opposite sign of the spatial dimensions. Mathematically, this means that some of the terms have a value of i attached to them. The math is identical if you attach the i to each of the three spatial dimensions, and leave time in the real number set; or if you attach i to the time dimension and leave the three spatial dimensions in the real numbers. Conventionally, we tend to leave the i in the time dimension because it makes the math a bit easier (in the sense that we have one imaginary number and three real numbers), but time itself is a real number. The use of imaginary time only comes in, if I am not mistaken, in unusual situations where the standard sign convention [-,+,+,+] for [t,x,y,z] produces physically paradoxical results (such as singularities). At least, that's my understanding. --Jayron 32 21:18, 18 December 2014 (UTC)[reply]

And we do have an article on the book. It's called Gravitation. Not Gravity. --Jayron 32 21:21, 18 December 2014 (UTC)[reply]

Well, what I'm thinking is that if you use a two or three dimensional coordinate system, you can say that within that coordinate system, every two points has a defined distance between them. That distance doesn't change unless you look at it from a frame where the whole coordinate system is changed. But in a system of "four dimensions" with real time, the distance between any two points is not constant, but depends on the frame of reference of whoever is looking at it. So to say time is the fourth dimension in that case is sort of meaningless. I mean, you can make the color of the object the fourth dimension, if you're willing to have a coordinate system that you can't calculate distance in. But use time * i as the fourth dimension and you do have a real distance that is Lorentz invariant. Wnt (talk) 21:25, 18 December 2014 (UTC)[reply]

Here's a less coordinate-dependent way of phrasing things. It requires you to know a little differential geometry. The point is that the metric tensor has three positive eigenvalues and one negative one. This is just a fact; it's not based on which arbitrary coordinate system you choose.

The x₄=ict trick is sort of an attempt to obscure this fact, or if not actually an attempt, risks obscuring it. --Trovatore (talk) 21:29, 18 December 2014 (UTC)[reply]

Alright, I'll admit it... I'm in the fog here. I'm afraid I'm missing how spacetime coordinates have four eigenvalues in the first place. Wnt (talk) 00:22, 19 December 2014 (UTC)[reply]

Because there are four dimensions to move in: up-down, left-right, forward-backward, and past-future. --Jayron 32 01:32, 19 December 2014 (UTC)[reply]

Wnt and Jayron, I think you're both confusing imaginary time (as mentioned, for example, in A Brief History of Time) with the old (now disfavored) convention of using a pure imaginary value for the t coordinate instead of a flipped sign in the metric. They are different. "Imaginary time" is kind of the opposite of what you're thinking: it starts with a mixed-sign metric with all coordinates including t real-valued, and then considers (unphysical) imaginary values of t to make the metric effectively Euclidean. -- BenRG (talk) 19:30, 19 December 2014 (UTC)[reply]

Changes in Mammalian Milk composition - Biochemistry question

I understand that a cattle's food, environment, and artificial hormone shots can change the composition of it's Breast Milk. Any professional name for this phenomenon? I need it to efficiently search for some literature in this subject. Thx. Ben-Natan (talk) 13:10, 18 December 2014 (UTC)[reply]

One source suggests "biochemical alterations" in breast milk after heating. I'd think the preferred term in that case is denaturation. Though, it's certainly not what you're looking for. Let me see if I can find a better term. 71.79.234.132 (talk) 14:46, 18 December 2014 (UTC)[reply]

I just searched google scholar for /diet nutrition effect cow milk/ - These articles were near the top of the list [35] [36] [37]. From skimming the abstracts, it does not seem that there is a single term to cover all the food/environment/hormone effects on cow's milk. The term "ruminal biohydrogenation" and "Conjugated linoleic acid" are used quite a bit, and the keywords used by the articles should help further searchers, e.g. "mammary metabolism", "fatty acid desaturation" "milk fatty acids." The first linked ref above should be especially useful, as it is an Annual Reviews article, which are usually an expert summary of a broad field of research and give lots of references. SemanticMantis (talk) 15:33, 18 December 2014 (UTC)[reply]

circuit analysis

How do I solve the first order differential equation for an LR circuit WITHOUT using Laplace transforms ie from first principles? — Preceding unsigned comment added by 109.152.195.34 (talk) 13:46, 18 December 2014 (UTC)[reply]

The canonical solution for a linear first-order ordinary differential equation is a solution using the separation of variables method. In the case of an L-R circuit, you'd have a first-order equation in current with respect to time, parameterized by the inductance and resistance.

When I write out every step, this procedure takes longer than simply applying the Laplace transform by inspection, so in practice, mathematically-inclined people tend to memorize the solution of a simple circuit (instead of explicitly re-solving it). You must simply recognize the standard form, understand the relationship between the relevant variables, and recall the standard-form solution.

Nimur (talk) 15:27, 18 December 2014 (UTC)[reply]

How do the enzymes and nutrients in breast milk survive body temperature?

This source suggests that heating breast milk can denature some enzymes and nutrients. I haven't read the full article yet, so I can't tell what temperature they set the breast milk at. But human body temperature is 37 degrees Celsius. Can't the breast milk's enzymes survive when exposed to some heat but not too much heat? Would it be better for women to take stored breast milk from the refrigerator and heat it up with their own body temperature? Or would they have to acquire a wet nurse? 71.79.234.132 (talk) 14:57, 18 December 2014 (UTC)[reply]

Self-evidently those proteins do not degrade at body temperature; they are made at body temperature, stored at body temperature, and consumed at body temperature. --Jayron 32 15:14, 18 December 2014 (UTC)[reply]

Obviously this can't be a problem. We (and all other mammals) have evolved to do this without any refrigeration or whatever. Also, any degradation due to a brief period at body temperature would happen in the baby's mouth, throat and stomach anyway. Clearly the problems with heating milk (any milk, actually) happens at much higher temperatures. Efforts to (for example) sterilize milk might well suffer from this problem. SteveBaker (talk) 15:44, 18 December 2014 (UTC)[reply]

The temperature required to denature the proteins in breast milk would be roughly the same as required to cook an egg. The change in going from raw egg to cooked egg is mostly the process of protein denaturation.

Different proteins denature at different temperatures. In fact, a common experimental technique to measure the stability of the protein is to look at the circular dichroism of a protein as a function of temperature. (See also Protein_folding#Circular_dichroism). For most proteins you see a sigmoidal transition from "folded" spectra to "unfolded" spectra, with a characteristic transition point at a defined temperature. This temperature is called the "melting temperature" of the protein, and varies from one protein to another. Some are very unstable, and will unfold at or around room temperature (mostly proteins from psychrophiles). Some are stable at room temperature (25 C) or body temperature (37 C) but will unfold at 45 C or so. Different proteins unfold at different points, all the way up to 95+ C, where it becomes hard to measure. (There are proteins which don't unfold even under boiling conditions - mostly these are from thermophiles, but there are some mutants of proteins from mesophiles which have very high melting temperatures.) - So the answer to the original question is that there's a large swath of temperatures between 37 C and 100 C, and there are some proteins which are stable at 37 C but which will unfold at 45 C or 55 C or 65 C or 75 C, etc. And the temperature at which the unfolding/denaturation happens for one protein is not indicative of what will happen for other proteins.-- 141.39.226.228 (talk) 10:40, 19 December 2014 (UTC)[reply]

Resistance of electrically conductive paint.

I've been looking at these electrically conductive paints:

  http://www.solianiemc.com/assets/Specifiche/Conductive-Paint-Specification.pdf

...and trying to find out how much resistance I'd get if I painted strips of varying widths.

It quotes the resistance in units of ohms/sq - I have no idea what 'sq' means...square meter? square millimeter? Then the values are 0,3 (which I suspect is 0.3 in one of those places in the world where they use '.' and ',' in the opposite sense to the more common US/UK useage).

Anyway, if I use a layer of the stuff of the recommended thickness to paint a 'wire' that's N mm wide and some much longer length - what kind of resistance would I measure per mm of length for various values of N? (This seems like it might be a variant of: http://xkcd.com/356/ ...in which case, I apologize in advance!)

TIA SteveBaker (talk) 15:35, 18 December 2014 (UTC)[reply]

“

The reason for the name "ohms per square" is that a square sheet with sheet resistance 10 ohm/square has an actual resistance of 10 ohm, regardless of the size of the square.

”

- from Sheet_resistance#Units I don't know how to compare the resistance of an Nx1cm strip to a Nx1m strip, but this seems to say rather clearly (if counter-intuitively) that the resistance of a NxN square is equal to the resistance of a (2N)x(2N) square. It's unclear to me if the resistance would be different for a (2N)x(2N) square compared to a (N)x(4N) rectangle (but I'd guess they would be different). If you figure it out let us know :) SemanticMantis (talk) 15:47, 18 December 2014 (UTC)[reply]

Oh...that's strongly counterintuitive! So a square that's a mile by a mile has the same resistance as a 1" x 1" square?! I guess that as the distance increases, so do the number of parallel paths that the electrons can travel though...so the two numbers cancel out and the resistance stays the same. Weird!

So if the resistance of an NxN square is always the same - then I could mentally chop my 1cm wide strip of paint into 1cm squares that are in series and say that an N cm long by 1cm wire has N times the resistance of a 1cm x 1cm strip...which is just the ohms/sq number?

Which would mean that the ohms per meter of a strip of this stuff is inversely proportional to the width...which seems entirely reasonable.

Resistance = ohms/sq * length / width ?

If someone could confirm my intuition on this one, we can call it "answered". (And thanks to User:SemanticMantis for a great & fast reply).

SteveBaker (talk) 16:40, 18 December 2014 (UTC)[reply]

Upon further reflection, the geometry is probably more important than the area. So a circle of any area will also have the same resistance, but it will be different than the square resistance. And once the proportions of a rectangle are fixed, they should have the same resistance independent of area as well, I think... SemanticMantis (talk) 18:54, 18 December 2014 (UTC)[reply]

Sounds right. Read the second paragraph of the section linked by SemanticMantis. It says you just multiply the square resistance by the aspect ratio to get the resistance for a rectangle. Proving the exact result for painted traces with corners or other bends would be tricky, but I suspect that total length over width is still a good approximation. 12.195.117.49 (talk) 19:25, 18 December 2014 (UTC)[reply]

Specifically, SteveBaker, resistance is proportional to the length and inversely proportional to the cross section. With paint, the cross section is, for all intensive purposes, the same as the width, and by definition for a square, the length and width are the same. μηδείς (talk) 01:33, 19 December 2014 (UTC)[reply]

Ah...yeah - that makes sense. ...BTW: the phrase is: "all intents and purposes"...not "all intensive purposes".

Thanks everyone...I think I have everything I need. SteveBaker (talk) 04:17, 19 December 2014 (UTC)[reply]

Cloning by chance

This is a topic I've read about before, but I recently came across it in a graphic novel, so I'm interested in recalling the specifics: Given the size of the human genome, what are the chances of an individual being born with DNA identical to that of another individual? The story in question posits an interplanetary population of 100+ trillion humans, and one of the characters claims that "three people are born with my DNA every day," which seems impossibly high. Like I said, I know I've read about this idea in scientific literature before; just not sure what keywords to use or where to start looking. Evan ^{(talk|contribs)} 18:57, 18 December 2014 (UTC)[reply]

The human genome is about 3 Gigabases. So, there is around 4 to the power 3,000,000,000 possible combinations. Not, all of them are, of course, actually possible but this rough estimate still holds. So, the claim that "three people are born with my DNA every day" is false if the population is around 100 trillion. Ruslik_Zero 20:06, 18 December 2014 (UTC)[reply]

That's theoretically true - but some of those possibilities would imply that the mother gives birth to a tree or a duck or a elephant. Totally random DNA isn't likely to arise in a population. An oft-quoted number is that 99.9% of my DNA is identical to yours (or to any other human) - so taking that rough number says that only 3,000,000 base pairs are really likely to vary between people. Still, that's 4^3,000,000 - let's say 10^1,000,000 to pick a nice round number. Given that there are only around 10⁸⁰ atoms in the visible universe - it's still SPECTACULARLY unlikely that two people would ever have the same exact DNA by chance reshuffling of A's, G's, C's and T's.

However, we have to consider that the man and woman (who love each other *very* much and make some babies) each only have 23 pairs of chromosomes - their child doesn't get a random selection of A's, G's, C's and T's from each parent - it gets entire chromosomes. So for any given pair of humans, there are only 2²³ possible chromosomally unique children that they can have...about 8 million. If those children were to in-breed, so no new chromosomes appear then their children would still only have some combination of their grandma & grandpa's DNA. So if our 100 trillion humans were all descended from Adam and Eve, there would only be 8 million unique human chromosome combinations - and there would indeed be a bunch of people with the same DNA. However, copying errors, mutations and the fact that it's been a hell of a long time since our most recent common ancestors guarantees that there is considerably more variation than that.

I don't buy the story's claim...but it's not so simple to dismiss it as that. SteveBaker (talk) 20:55, 18 December 2014 (UTC)[reply]

Note chromosomal crossover in meiosis is essentially a required event for proper gamete production (it can be omitted, but only with a significantly greater chance of abnormalities as I recall). This means that there are vastly. vastly more than 2²³ outcomes. Wnt (talk) 21:18, 18 December 2014 (UTC)[reply]

Depends on how you're defining "the same". A DNA database will try to claim an absurdly low probability, but will only look at as many markers as are needed to reach that -- and there is a risk that in a particular small ethnic group the different markers will not truly be independent, but will be more likely each to go a certain way. This risk seems to be very low, but it is not zero - consider the trivial case where a person turns out to be the identical twin of someone who was secretly swapped at birth, which however soap opera unlikely is not astronomically unlikely. However, the ways in which this can happen are fewer the more markers are examined. The identical twin will always come out the same, but fellow 100% Tasmanian aborigines will eventually be distinguished, assuming any known method of reproduction.

I still have in the back of my mind a nagging doubt whether it could ever happen that humans clone themselves naturally, if a diploid egg or sperm were to provide all the genetic material to the exclusion of the other gamete. Such embryos normally die, but that observation only holds up until a counterexample can be found. But with the number of large-scale genetic tests on the general population this is rapidly fading from absurdly unlikely to genuinely ruled out. Wnt (talk) 21:14, 18 December 2014 (UTC)[reply]

How much would it cost get tested for every genetic risk factor known to man?

How many are there (including the minor ones like propensity for male pattern baldness)? Hundreds? Thousands? Where would one go? Would that be an unusual request there? I guess they could give you the list of risky genes that can take effect before 30 (hundreds?). You'd take it home, cross out the ones that'd be unoverlookable by your age (bubble boy syndrome, complete immunity to chickenpox..) and only get tested for genes that could bother you before testing gets cheaper. How much would that cost? I don't think I'd actually do it though, I'd wait till it's cheaper and understanding of genetics isn't so piecemeal. Well, if it's tens of dollars (yeah right) I'd consider it but I'm curious how much I'd have to have to not mind spending the money. Also, how much is it to find out just the known genes for cancer? breast(40s) — colon, skinny male breast (!) is my parental history of cancer. I guess a single disease is cheaper to test for than many. (grandpa died from cigarette cancer at 56 before we could find out whether he would've died from regular cancer, other grandpa died a year after being well enough to make baby the original way, increasing the chances that it was cancer, but he might've smoked) Sagittarian Milky Way (talk) 22:23, 18 December 2014 (UTC)[reply]

That's not a question that is easy to answer, as there are many genetic risk factors about which we know, but which we don't know (i.e. we know they are inheritable, but we don't know which combinations of genes cause them). If you thrown in a research program to identify them all (or even just a few of them), the sky is the limit. On the other hand, if the genetic factors are well understood, testing all of them should not be impossibly expensive - a quality whole genome sequence cost Steve Jobs US$100000, and prices have come down significantly. I think the analysis of the genome should be highly automatable, at least in principle. --Stephan Schulz (talk) 22:55, 18 December 2014 (UTC)[reply]

Your question implies there is a test for every genetic risk factor known to man, but not every gene or set of genes that causes a disease that runs in a family has been identified. This is about the third time since halloween that we've had this question, you might want to serach the archives for lengthy previous answers. μηδείς (talk) 01:18, 19 December 2014 (UTC)[reply]
- Thanks Medeis, but what search terms should I use? I can't seem to find one, much less two after Halloween. Sagittarian Milky Way (talk) 15:00, 19 December 2014 (UTC)[reply]

You may want to look into 23andMe and in particular their pre November 22, 2013 test kits (probably available at elevated prices on eBay). Ariel. (talk) 08:13, 19 December 2014 (UTC)[reply]

It would probably cost you your life. When you add up the X-ray exposure, exposure to radioactive tracers, exposure to chemicals, tissue damage due to biopsies, blood drawn for hundreds of tests, etc., the net result is a pretty large insult to the body. Looie496 (talk) 15:37, 19 December 2014 (UTC)[reply]

He meant "genetic" and I have fixed the title to reflect that. μηδείς (talk) 19:24, 19 December 2014 (UTC)[reply]

- I think you're describing getting tested for every "disease with a non- nurture component known to man". Clearly no one is going to want a piece of their lung (much less every organ) pulled out of their body and many other invasive tests in their 20s with no evidence of malfunction. And I actually imagined "every blood test known to man, including thousands of toxins" as a child, pictured hundreds of vials of blood and thought the image amusing.

- If you could get a full genome without too much somatic expense then you should easily be able to get enough DNA for fewer genes. Sagittarian Milky Way (talk) 16:40, 19 December 2014 (UTC)[reply]

See $1,000 genome. Even so, be skeptical, because medicine is a racket. The 23andMe action corresponded with other efforts to have it declared "unethical" to get genetic testing done without getting certain common specific genetic tests done, starting with the infamous BRCA1. However, shortly after that decision the Supreme Court ruled against a broad class of gene patents, creating some hope again. Even so.... I think that one way or another, someone will step forward to demand a huge amount of protection money before the average person is allowed to find out about his genome, because that's how medicine works. Wnt (talk) 21:46, 19 December 2014 (UTC)[reply]

In your hair

After seeing a shampoo advert, I was wondering, what does caffeine do to your hair? Would the same results occur if you used tea, coffee or a high caffeine drink e.g. Monster or Red Bull? What would be the effects of each of those? Also why do some people pour beer or another alcoholic drink in their hair? 5.69.204.149 (talk) 23:34, 18 December 2014 (UTC)[reply]

Beer is supposed to give hair body. You can google beer shampoo for that answer. What caffeine does is wash out and run down the drain. μηδείς (talk) 01:23, 19 December 2014 (UTC)[reply]

Its just bogus marketing. There is no benifit in caffeine on your hair. They just play men to belive "activating" will prevent the loss of hair at advanced age but since this is a natural process caused by hormones "activation" will likely even speed up that natural process. --Kharon (talk) 11:58, 19 December 2014 (UTC)[reply]

Caffeine may not do much to your hair, but it can be absorbed through the skin [38]. There are products like caffeinated soap [39] that purport to deliver the drug through the skin. So if there's a lot of caffeine in shampoo, absorption through the scalp may deliver similar effects to taking caffeine orally. SemanticMantis (talk) 18:02, 19 December 2014 (UTC)[reply]

Anything that would deliver a clinically measurable dose of caffeine through the skin would have a lethal dose of caffeine per mouthful. Given how often people consume soap and shampoo, there'd be a flurry of deaths and an episode of Inside Edition with Bill O'Reilly exposing the danger. μηδείς (talk) 19:22, 19 December 2014 (UTC)[reply]

December 19

Did anyone ever make a weird mathematical treatment of physics with extra dimensions of time?

Where every possible spacetime really exists, more than that universes just like ours except one electron was on the other side of the electron cloud at 10^61 Planck times exist (if you even looked at it at the wrong time (slightly before 10^61), you couldn't distinguish the universes anyway, even in theory, it's almost not even a different universe). Of course people make weird unfalsifiable, Occam's Law-violating or even debunked physics theories all the time, a theory existing doesn't mean that it deserves serious thought. Sagittarian Milky Way (talk) 00:30, 19 December 2014 (UTC)[reply]

Imaginary time. μηδείς (talk) 01:21, 19 December 2014 (UTC)[reply]

OK...the title here is a question - the answer to which is "Yes...several versions of String theory suggest multiple time dimensions." The rest is not. But to comment on what you have to say:

Certainly if the Many worlds interpretation of quantum theory turns out to be true, then many universes are seemingly (or actually) completely identical. There is no problem with that - if a quantum-mechanical event causes a universe to split into two parallel paths, then one of them can go on to have another event that perfectly undoes the first one - and now you have a pair of parallel universes that are utterly identical. This causes no specific problems - if the hypothesis is true, then there would be vastly more universes than there are atoms in our universe - there would be no shortage of them and no 'cost' to creating new ones. We could even imagine that there are an infinite number of them.

Isn't the many worlds universe be more like an "exploding cone-time" where the Big Bang is a point, BB+1 Planck time is x wide, the third Planck time is x*x wide, the fourth Planck time is x*x*x wide and so on? That is not usually what two dimensions means. In 2-D time with perpendicular axes the Big Bang would be a line at the left edge and universes that won't split from ours for trillions of years would start already separated. Sagittarian Milky Way (talk) 18:11, 19 December 2014 (UTC)[reply]

The many worlds hypothesis may very well be unfalsifiable. We define "the universe" as "all of spacetime and everything that exists therein, including all planets, stars, galaxies, the contents of intergalactic space, the smallest subatomic particles, and all matter and energy." So anything we could detect or measure about these "parallel universes" would make them be a part of our universe. So by the very definition of the word "universe", anything that happens in a different one in undetectable. For this reason, the many worlds hypothesis must seemingly be unfalsifiable. That doesn't mean that it's "false" - it just means that we may never be able to prove or disprove it.
Occam's Razor isn't a "law" - it's not even a hypothesis - and it's not always true. It's just a handy guide that you can employ when there are many possible explanations for something and you want to pick the most likely one. So, if I can't find my TV remote, it might have fallen behind the sofa cushion, or it might be that a team of crack commandoes from North Korea may have broken into my home and removed the remote just to be really REALLY sure that I can never watch "The Interview". In terms of the science, I may not be able to decide which of those hypotheses are true right now...but Occam's razor suggests that I should probably do the experiment of looking behind the sofa cushion BEFORE I contact Homeland Security. It should be called "Occam's Very Rough Rule of Thumb" or something.

I hardly gave any thought whatsoever while writing those two words, if I knew that wasn't a common name for the idea then I wouldn't bothered to Google Occam. I knew it wasn't utterly unable to be wrong. Sagittarian Milky Way (talk) 18:11, 19 December 2014 (UTC)[reply]

A "theory" (the scientific term, meaning something that's proven and widely accepted) does deserve serious thought. Most useful hypotheses (thing that we think are good explanations, but are not yet proven) are sometimes worthy of serious thought - and sometimes not. Many Worlds is a pretty good hypothesis that could certainly explain bizarre stuff like Schrödinger's cat - and is taken seriously by many reputable physicists. So I think it does deserve serious thought, even though it's not proven, may never be proven, and may very well be unfalsifiable.

But physics "theories" (in quotation marks) go all the way to "the sun is made of iron" and Time Cube. Even if no one with a degree in a relevant field takes it seriously (note that I didn't say that's the case) it might be easy enough to add the terms needed to make Einstein's theory 3+2 dimensional (I haven't studied the equations, I can't tell) but have little enough physics sense to take it seriously. Sagittarian Milky Way (talk) 18:11, 19 December 2014 (UTC)[reply]

Is it possible that stored memory could be misinterpreted as another time dimension?165.212.189.187 (talk) 16:43, 19 December 2014 (UTC)[reply]

No. --Jayron 32 18:37, 19 December 2014 (UTC)[reply]

One recent proponent is Itzhak Bars who had an article in New Scientist some years ago. We have an article Multiple time dimensions. I remember reading a discussion of likelihood of multiple time dimensions in a popular science book (i.e. if there are Compact dimensions are they spacelike or timelike or both) a while ago, possibly The Road to Reality by Roger Penrose? JMiall ₰ 10:59, 20 December 2014 (UTC)[reply]

Is the heart's valves made of cartilage?

I read the articles here and eventually I don't understand if yes or not149.78.45.16 (talk) 02:53, 19 December 2014 (UTC)[reply]

No. See cartilage and heart.--Shantavira|^{feed me} 12:03, 19 December 2014 (UTC)[reply]

Is it true that any tendon has two sides - one connected to muscle and the other to the bone or cartilage?

Is it true that any tendon has two sides - one connected to muscle and the other to the bone or cartilage? another sentence that I think about is that always tendon needs to be connected to the muscle or the bone. not? 149.78.45.16 (talk) 02:58, 19 December 2014 (UTC)[reply]

Wikipedia has an article titled Tendon which may be able to help you learn more about tendons. --Jayron 32 03:56, 19 December 2014 (UTC)[reply]

There may be special cases (Patellar tendon), but the answer to your initial question is generally 'yes', as is stated in the first sentence in the lede of the article that Jayron32 linked to. --NorwegianBlue^talk 23:38, 19 December 2014 (UTC)[reply]

how many people with gonorhea eventually go on to develop prostatitis?

close trolling by blocked sock

The following discussion has been closed. Please do not modify it.

Or maybe a better question to ask is, how common is acute prostatitis, and of those with it, how many test positive for gonorrhea? — Preceding unsigned comment added by 199.119.235.174 (talk • contribs)

What's taking so long?Whereismylunch (talk) 4:20 pm, Today (UTC−5)

Assuming it is not developing prostatitis you are in a hurry for, you can google "gonorrhea percentage prostatitis". μηδείς (talk) 21:26, 19 December 2014 (UTC)[reply]

Hard to find an answer, compared to when I looked many weeks ago percentage of oropharyngeal cancer patients positive for hpv.Whereismylunch (talk) 22:27, 19 December 2014 (UTC)[reply]

According to UpToDate [40],

The pathogens associated with acute prostatitis reflect the spectrum of organisms causing cystitis, urethritis, and deeper genital tract infections (such as epididymitis). Gram-negative infections, especially with Enterobacteriaceae (typically E. coli or Proteus species), are the most common. In retrospective studies of men with acute bacterial prostatitis, such pathogens have been identified in positive urine cultures at the following frequencies:

E. coli – 58 to 88 percent
Proteus species – 3 to 6 percent
Other Enterobacteriaceae (Klebsiella, Enterobacter, and Serratia species) – 3 to 11 percent
Pseudomonas aeruginosa – 3 to 7 percent

Sexually active men may have sexually transmitted urogenital infections, which also acutely involve the prostate, in which case Neisseria gonorrhoeae and Chlamydia trachomatis are important pathogens. --NorwegianBlue^talk 23:29, 19 December 2014 (UTC)[reply]

At what frequency has gonorrhoeae been identified in positive urine cultures?Whereismylunch (talk) 01:19, 20 December 2014 (UTC)[reply]

I figured this was a troll when I saw he edited in a signature over the unsigned IP address, and he has been indeffed. μηδείς (talk) 03:35, 20 December 2014 (UTC)[reply]

HIV testing

I know about the window period for HIV testing, but (and I'm asking this question without much scientific knowledge so bear with my ignorance) is there a particular point at which testing will pick up HIV?

Am I right in thinking that HIV tests will test positive after seroconversion occurs? Is seroconversion the same as acute HIV infection (early HIV symptoms)? After the acute HIV infection, is the patient seroconverted and the HIV detectable?

What about during the acute HIV infection?36.224.250.37 (talk) 18:20, 19 December 2014 (UTC)[reply]

Seroconversion. μηδείς (talk) 21:17, 19 December 2014 (UTC)[reply]

"Seroconversion" occurs when the infected person produces antibodies against HIV antigens in sufficient amounts to be detected. Tests that detect the HIV virus itself will usually be positive a few days before seroconversion. There are tests that detect HIV proteins and tests that detect HIV nucleic acids. See Diagnosis of HIV/AIDS for details. According to that article, nucleic acid testing (NAT) appears to be preferred in the EU for blood donor screening (somewhat unclear in the article). I doubt that that is generally true, although it may be true in some EU countries (I know that it's true in Denmark). The EU blood directive [41] does not mandate the use of NAT testing for HIV. In Norway (which is not technically part of the EU, but which through the EEA agreement is more faithful to EU regulations than most EU countries), combined tests (that detect both HIV proteins and antibodies against HIV) are used in blood donor screening. --NorwegianBlue^talk 23:03, 19 December 2014 (UTC)[reply]

What is the nature of the relationship between seroconversion and the acute HIV infection? Does seroconversion occur while a patient is having primary HIV symptoms (if any)?36.226.148.49 (talk) 04:33, 20 December 2014 (UTC)[reply]

The HIV/AIDS article gives the symptoms of the initial acute phase of the infection. Have you understood the seroconversion article? μηδείς (talk) 05:58, 20 December 2014 (UTC)[reply]

Relative concentration of Chitinase in various fruits

Chitinase#Presence in food says:

Bananas, chestnuts, kiwis, avocados, papaya, and tomatoes, for example, all contain significant levels of chitinase.

Where can I find the relative concentration of Chitinase in these and other fruits? -- ToE 20:08, 19 December 2014 (UTC)[reply]

I don't know, but this pdf would be a decent ref for that sentence if you care to add it [42]. SemanticMantis (talk) 20:35, 19 December 2014 (UTC)[reply]

If you are interested in chitinases as food allergens, this web search may be of interest. --NorwegianBlue^talk 23:14, 19 December 2014 (UTC)[reply]

Thanks so far. The food-allergens.de page says: "almost 50% of these allergic [latex alergy] patients also show hypersensitivity to some plant foods, especially chestnut, banana, and avocado, but also to kiwi, papaya, tomato and others." I don't know if that is because the former three have a greater concentration than the latter, or because they have different forms of Chitinase, which I understand describes a group of enzymes.

The allergen.org site gives specific allergens, such as Mus a 2 from banana, a "Class 1 chitinase", and Ziz m 1 from Chinese-date, a "Class III chitinase", but it doesn't seem to give the typical concentrations in the food source and doesn't explain the difference between the chitinase classes. -- ToE 12:33, 20 December 2014 (UTC)[reply]

December 20

Tiny islands

Google Maps (I have no real data to back this up) makes it look as if there are many mountains in the sea of which just the top is above sea level. So if the sea level would go up a little, say 300 ft, many of them would disappear, where if it would go down a little, again 300 ft, a lot less new islands would appear. Is that true, and if so how come? Erosion perhaps? Joepnl (talk) 00:04, 20 December 2014 (UTC)[reply]

Yes, there are lots of different types of islands. Some are newly created by undersea volcanic activity, others are the remains of eroded rock, and yet others are mountaintops from before the last post-glacial rise in sea level. See New islands and Sea level#Changes through geologic time for a few details. I'm sure some experts here can add further to this reply. Dbfirs 00:14, 20 December 2014 (UTC)[reply]

Other relevant articles include seamount and guyot.--Jayron 32 00:56, 20 December 2014 (UTC)[reply]

(edit conflict) When a new volcanic island forms, a thin ring of coral forms around the edges. The volcano becomes extinct (often cause the crust leaves the hotspot of the mantle that caused the volcano behind), the mountain erodes and/or subsides, leaving behind a coral reef on top of a submerged mountain. The corals cannot live where it's too dark (tens of feet or meters, it's one of those, I don't remember) and will die if they're not wet. But no problem, if they die from depth new ones build their exoskeletons on top of the dead ones until they reach the tide level and can't grow up anymore, so they are always right below the sea level if they've been there enough millennia. 100,000 years ago the sea level was 20 feet higher than now in one of the hottest periods in millions of years (though I think this would happen (if not double) if we burn the carbon till 2100 or something and then wait for the ice to stop melting (centuries), so not especially hot by 2014 standards), the highest sea level in at least 400,000 years and maybe millions (I don't remember), 100 Kyr is short enough that the coral reefs killed by the low sea level of the last ice age have not have time to be eroded away yet and are still there as islands. Sagittarian Milky Way (talk) 01:27, 20 December 2014 (UTC)[reply]

Also, it is often in the nature of land to be barely above sea level (wave and freak 5000 year hurricane created islands like Coney Island and the more well known [Atlantic City]] island, river deltas, river islands, coastal wetlands.. Those don't look like mountains on Google Earth, though. Sagittarian Milky Way (talk) 01:38, 20 December 2014 (UTC)[reply]

If the surface of the Earth were randomly bumpy, the greatest number of islands would exist when the sea covered half its surface (for a proof of this, ask at the math desk). If the sea level sank, so that more than half of the surface was land, more of the random islands would become part of the mainland. If the sea level rose so that more than half the random surface was covered with water, more islands would sink below the surface.

The Earth has two great differences: the ocean covers 71 percent of it, and its surface is far from random. So the question is an empirical one which I cant answer. But see Zealandia and Kerguelen Plateau for interesting reading. μηδείς (talk) 04:18, 20 December 2014 (UTC)[reply]

If Venus were terraformed and given an ocean would probably have to be made of comets) Earth would likely have almost 50% more land by percentage and many more islands (Venus has only two continents). If Mars was terraformed it would likely be only 33% water in one ocean and have few islands. Go figure. Sagittarian Milky Way (talk) 16:29, 20 December 2014 (UTC)[reply]

You seem to be assuming arbitrary water levels? Wnt (talk) 17:38, 20 December 2014 (UTC)[reply]

Were blacksmiths losing their hearing?

I'm not sure whether I'm in the right section of RD, my question is rather between history, trade and medicine. Traditional blacksmiths of the past were being exposed to constant metallic noise during their life, but did that make any impact on their hearing? Were they losing their hearing during their life? Do blacksmiths use any protection for their ears today?--Lüboslóv Yęzýkin (talk) 08:47, 20 December 2014 (UTC)[reply]

In the introduction to An Inevitable Consequence: The story of industrial deafness (if you google that title you will find an online PDF copy) Dick Bowlder writes "There are references going back over several hundred years to the fact that some noisy occupations - in particular those involving the hammering of metal - will cause permanent deafness or tinnitus. Tinsmiths in the middle ages had “ringing in the ears”. But the first authoritative reference was in 1831 when Dr Fosbroke, writing in The Lancet, states that "Blacksmith's deafness is a consequence of employment.” And yes, blacksmiths today use hearing protection [43][44] Richerman (talk) 11:13, 20 December 2014 (UTC)[reply]

See Google Books for Fosbroke's original article, and here for Bowdler's paper. Fosbroke cites Daniel Sennert (in Latin) for his own historical reference on the subject. Tevildo (talk) 11:17, 20 December 2014 (UTC)[reply]

Is not keeping bread in a fridge really a good piece of advice?

It is commonly stated (including in the WP article: Staling) that keeping bread in a fridge makes it go stale (or more precisely: speeds up the staling process).

This contradicts my own experience: I keep my bread in a fridge at between 0 and 5 Celsius. I keep it in the fridge to stop it going mouldy (or more precisely: to slow down the going mouldy process) and I have not experienced my bread going stale, (even if I keep it long enough to start going mouldy even in the fridge).

Some possibilities:

it depends on the type of bread (though the advice I constantly come across does not refer to particular types of bread),
the staling referred to is not something that bothers me.

I have come across one person checking for themselves [45] , but they used white baguette loaves from a local bakery, which is probably not the most commonly consumed type of bread (in the UK, and many other countries, at least).

The type of bread I am referring to as not seeming to go stale in the fridge is cheap supermarket own-brand, medium sliced, wholemeal, in a plastic bag with no holes, bought in the UK. Ingredients: Wholemeal Wheat Flour, Water, Yeast, Salt, Spirit Vinegar, Emulsifier (Mono- and Di- Acetyltartaric Esters of Mono- and Di-Glycerides of Fatty Acids, Sodium Stearoyl-2-Lactylate), Soya Flour, Rapeseed Oil, Preservative (Calcium Propionate), Palm Fat, Flour Treatment Agent (Ascorbic Acid).

I notice that some of these ingredients are mentioned as anti-staling agents in the Staling article.

Why does this issue matter? People might be wasting bread because they believe the advice about not keeping bread in a fridge, and thereby having it go mouldy. (Advice is often given that bread can be frozen instead, and not go stale or mouldy, but this is less convenient and so less likely to be done.)

Note that this is not a question about why refrigerating bread makes it go stale (I have found copious information about that), but whether it is really true and a significant effect for all types of bread, and therefore whether saying not to put bread in the fridge, without further qualification, is a good piece of general advice. FrankSier (talk) 12:58, 20 December 2014 (UTC)[reply]

I'm from the UK and my family doesn't keep bread in the fridge - not because of anything we've been told, but simply because we have a bread bin, and the fridge has other things in it which need to be kept in there. We do, however, keep bread in the freezer, then bring it out when we need it (thawing it out first, of course), and that has never affected the bread in any way. I think this idea of bread going stale when put in the fridge comes from people putting sandwiches in the fridge (sometimes half eaten), so, being exposed to the air, they will go stale (whether they are in the fridge or not). Putting cling-film over them helps to preserve the bread, in my experience. KägeTorä - (^影_虎) (Chin Wag) 17:52, 20 December 2014 (UTC)[reply]

@FrankSier: The Staling page is not well referenced, having only one footnote to a ten year old book, though the first rather technical external link is downloadable for free. It does say bread "... stales most rapidly at temperatures just above freezing" Perhaps the chemical composition of bread has changed in the last ten years, and this is no longer accurate? Then again, a quick Google turned up heaps of sites saying that bread does indeed go stale faster if stored in a fridge! By up to six times! [46]

It certainly appears that the prevailing advice is to store bread at 'room' temperature. (or freeze it)
Comment on mold. Totally personal OR, avoid touching the bread with your hands and you will get far less mold. You might want to try it, get a piece and put your thumb on it, then leave it to 'moulder'. There is a very high likelihood that you will get a thumb shaped patch of green.
More OR, there are many types of bread and I have found that some types, IIRC unsliced wholegrain are more resistant to going stale (and to mould) Though often the mould gets the bread before the 'stale' (especially in humid summer weather as here in Australia. Ǝ 220 of ^Borg 18:03, 20 December 2014 (UTC)[reply]

A to D s

What sort of A/D s are used in GHz sampling rate digital scopes ?--86.169.152.43 (talk) 13:31, 20 December 2014 (UTC)[reply]

Could fat tissue be a beneficial cancer?

Naybe the ancestral version of the fat cell was a more harmful cell, and it evolved to be more beneficial? Thanks.2601:7:6580:5E3:7CBD:D2E0:7058:C21D (talk) 18:00, 20 December 2014 (UTC)[reply]

Could slow-growing cases of prostate cancer be beneficial in some cases?

Note:i'm not asking about if a gene that causes or predisposes to prostate cancer also has beneficial effects. I mean does the cancer it self help in some way, for example, like kicking in increased ability of sperm to impregnate.I suspect a counterargument will be that it occurs at advanced age that we haven't until the last few thousand years survived to, so we haven't had time to evolve to make it serve a purpose. But it could have been triggered at a younger age back when we lived less long. thanks.Rich (talk) 18:23, 20 December 2014 (UTC)[reply]

@@ Line 594: / Line 594: @@
 to be more beneficial? Thanks.[[Special:Contributions/2601:7:6580:5E3:7CBD:D2E0:7058:C21D|2601:7:6580:5E3:7CBD:D2E0:7058:C21D]] ([[User talk:2601:7:6580:5E3:7CBD:D2E0:7058:C21D|talk]]) 18:00, 20 December 2014 (UTC)
-== Could slow-growing of prostate cancer be beneficial in some cases? ==
+== Could slow-growing cases of prostate cancer be beneficial in some cases? ==
-Note:i'm not asking about if a gene that causes or predisposes to prostate cancer also has beneficial effects. I mean does the cancer it self help in some way, for example, like kicking in increased ability of sperm to impregnate.I suspect a counterargument will be that it occurs at advanced age that wehaven't until the last few thousand years survived to, so we haven't had time to evolve to make it serve a purpose. But it could have been triggered at a younger age back when we lived less long. thanks.[[User:Richard L. Peterson|Rich]] ([[User talk:Richard L. Peterson|talk]]) 18:23, 20 December 2014 (UTC)
+Note:i'm not asking about if a gene that causes or predisposes to prostate cancer also has beneficial effects. I mean does the cancer it self help in some way, for example, like kicking in increased ability of sperm to impregnate.I suspect a counterargument will be that it occurs at advanced age that we haven't until the last few thousand years survived to, so we haven't had time to evolve to make it serve a purpose. But it could have been triggered at a younger age back when we lived less long. thanks.[[User:Richard L. Peterson|Rich]] ([[User talk:Richard L. Peterson|talk]]) 18:23, 20 December 2014 (UTC)