Wikipedia:Reference desk/Archives/Science/2013 July 30

= July 30 =

Domesticated Hedgehog
Is there a scientific difference between a hedgehog and a domesticated hedgehog as there is between wolves and dogs or lions and cats? — Preceding unsigned comment added by 68.115.240.26 (talk) 01:49, 30 July 2013 (UTC)


 * Have a look at hedgehog, then domestication, then domesticated hedgehog. Those should cover the basics. Despite the name, my impression that the domesticated hedgehogs are not very domestic (i.e. less time under artificial selection, less derived traits), in comparison to the case of dogs derived from wild canines. SemanticMantis (talk) 03:48, 30 July 2013 (UTC)


 * As for your other examples, wolves and dogs now appear to be the same species, so that's a reasonable comparison, but lions and (house)cats are not the same species at all and cats certainly are not domesticated lions, but rather cats are domesticated African wildcats. StuRat (talk) 06:14, 30 July 2013 (UTC)
 * Wierdly enough though the dog and the wolf are (as of 1993) considered the same species and cats and the African wildcat are not even though dogs were domesticated much earlier. But I don't think that represents a higher amount of genetic change. And sorting out the genus and species of the smaller members of Felinae (like the wildcats) gets ugly.Naraht (talk) 13:33, 30 July 2013 (UTC)


 * I had never heard of a domesticated hedgehog until a few seconds ago. My only comment is that according to our article, it is a hybrid of two separate species and therefore different to any wild hedgehog. Is a mule different to a horse? Yes. Alansplodge (talk) 22:58, 30 July 2013 (UTC)

Feeling pain in a dream
I just woke up from a long nightmare. The last part of the dream was someone digging their hands into my chest, as if they were trying to murder me. The odd part was that I ran away from the person in my dream, but then I saw myself laying down where I was in real life right after, in my dream. The person was right there, which is when they dug their hands into my chest. An even more odd thing is that I felt the pain and woke up from it. I am very shaken and I don't think that I can get back to sleep which is understandable, considering I felt like I was being murdered. Has there been any reports of people feeling pain in their dreams? Please don't tell me that it can't happen, I felt the intense pain in my chest, in all of the correct spots. SL93 (talk) 08:38, 30 July 2013 (UTC)
 * When a person is in REM sleep brain activity is high and it will often interpret a physical stimulus and make it a part of a dream. This is such a common experience that it has become a film Cliché. Wikipedia has an article about Nightmare but the Ref. Desk will not interpret dreams. DreadRed (talk) 09:32, 30 July 2013 (UTC)
 * I wasn't asking for my dream to be interpreted. I have a habit of saying exactly what I want, rather than implying it. SL93 (talk) 09:34, 30 July 2013 (UTC)
 * You didn't help me. I know of lucid dreaming, but nothing that you linked mentions pain being involved. Someone even asked for a reliable source on the talk page for REM sleep. No wonder it isn't in the article. SL93 (talk) 09:37, 30 July 2013 (UTC)
 * Yes, there have been reports (other than yours) of people feeling pain in their dreams. It isn't common. Just search for pain+dreams in Google Scholar. You will then be in a position to update the REM sleep article.  Sean.hoyland  - talk 10:05, 30 July 2013 (UTC)
 * Thanks for the tip, but I have no interest in updating the article. SL93 (talk) 10:07, 30 July 2013 (UTC)

I feel pain in dreams fairly often. I was surprised a few years ago when I saw a thread on here about c-fiber nerves and people claiming that it is impossible to feel pain in dreams. I challenged it and nobody offered up a counter argument or any sources, and I haven't been able to find anything concrete one way or the other myself. But I assure you, when someone in a dream is cutting my fingers off or stabbing me, I feel it. 82.44.76.14 (talk) 10:31, 30 July 2013 (UTC)


 * I'll just note that this question has come up before. Looie496 (talk) 14:08, 30 July 2013 (UTC)

It appears than dreams can contain just about anything that real life can contain - including hearing, taste, feeling etc. Brains can be weird . Collect (talk) 15:57, 30 July 2013 (UTC)


 * The OP asked if there had been reports of people feeling pain in dreams. Certainly I have had dreams in which pain played a part, after surgery, when there was a sore back, when there was tonsilitis, when there was a belly ache. The dream incorporated and explained the pain in some way. The dreaming process sometimes explains away stimuli in such a way that you can just go on sleeping.  A Google book search will reveal countless books discussing pain in dreams, though many of them are "new age" self=help books or religious books. Freud, in "The interpretation of dreams" p190 mentions "headache dreams" and "toothache dreams." Edison (talk) 16:11, 30 July 2013 (UTC)


 * On the occasions I have felt pain in my dreams it was always because of some real stimulus outside of my dream, such as thinking my leg is in a bear trap to wake up and find I am in a twisted position and it has fallen asleep, or feeling that my mouth is full of ashes and my teeth are falling out to wake up and find I am gagging because I have been mouth-breathing and my mouth is entirely dried out. This seems to be the brain rationalizing the real stimulus into the dream.  But I cannot say I have ever felt a pain in a dream without some external reason.  The exception seems to be sex dreams, which can be very pleasantly authentic feeling without any real external stimulus. μηδείς (talk) 16:21, 30 July 2013 (UTC)


 * Original research: I've personally had at least four dreams involving physical pain: on one occasion, I dreamed that I was shot to death right through the heart by a crooked cop; on another, that my mouth and throat were stuffed full of sharp plastic shards (this was when I was down with strep throat and bacterial sinusitis on top of that); on the third occasion, that I was bayonetted to death (also right through the heart) by a Red Army soldier (of the four, this was the dream I remember best -- in that dream, I was a White Army squad leader during the Russian Civil War, and me and my squad had just ambushed a Red Army column but bit off more than we could chew, so we all died fighting); and on the final occasion, I dreamed that I was shot in the chest by a gangster, but survived and had enough strength to strangle my attacker. So yeah, it can totally happen -- and also, you CAN dream that you were killed without actually dying (contrary to a popular misconception). 24.23.196.85 (talk) 02:44, 31 July 2013 (UTC)
 * So Nightmare on Elm Street was wrong? :( SL93 (talk) 04:22, 31 July 2013 (UTC)
 * Well, the difference here is, I don't have casual sex with every Tina, Dolly and Helen that I meet (unlike the characters in that movie), which means I'm safe on that end. 24.23.196.85 (talk) 08:40, 31 July 2013 (UTC)


 * So the possibility exists that you suffered real chest pains which were then incorporated into you nightmare. For chest pains, you would want to consult a doctor, but these are possibly dreamt chest pains.  I'm not sure what the medical guidelines are for reporting those.  Also, your sleeping position could possibly cause cramps in the chest muscles, which your brain interpreted as the heart.  But, do you get chest pains during the day ?  If so, you should definitely see a doctor. StuRat (talk) 09:05, 31 July 2013 (UTC)
 * No, I don't get chest pains during the day. And I normally sleep facedown, if this matters.  Or were you replying to SL93? 24.23.196.85 (talk) 00:30, 1 August 2013 (UTC)


 * This is pure OR, but in one of my lucid dreams, I decided to test the hypothesis (often assumed to be true in cartoons for children) that you can't feel a pinch in a dream. I pinched myself and definitely felt the pain--it felt very similar to a pinch in real life.  --Bowlhover (talk) 22:14, 31 July 2013 (UTC)


 * Lucid dreams are fun. One example is where you become lucid whilst in a painful situation, and then decide that since you're dreaming, you may as well will the situation to become painless, continue to mold the dream into anything you can imagine. However, the tricky part is remembering that you are dreaming. It is all too easy to forget, and slip right back into a non-lucid dream. It takes practice to avoid either waking up from a lucid dream, or retaining lucidity. You have to remain in perfect equilibrium, concentrating to remain relaxed and aware in a balanced manner. Occasionally, it is possible to regain lucidity within the same dream. Once in a lucid dream, I changed the taste of an apple to that of a blueberry. Another time, I wanted to fly, so I did. Halfway through my flight, I lost lucidity for a moment, and fell to the ground from ~50 m up. I got the wind knocked out of me, but was otherwise just fine. Strange, I thought that it would be a bit more painful than that. Plasmic Physics (talk) 01:01, 1 August 2013 (UTC)


 * I would love to see some sources here, but I'm not sure where to begin because I can't think of how to do the experiment. I know, for example, that to me sleep and pain are so incompatible that when I had the gout I would avoid moving/"awakening" my legs for an hour after awakening to maintain sleep paralysis, preventing any sensation of the quite severe pain from the attack, but I haven't found any commentary about that (pity, because it ties into hypnosis for pain relief and perhaps more serious issues...) Wnt (talk) 04:53, 1 August 2013 (UTC)

Deaths Cap in homeopathy and well poisoning
I have read that death's cap is responsible for most mushroom poisonings; including the deaths of a few roman emperors; which makes me wonder how often it was used in medieval well poisonings. I know that is a rather sensational subject from hundreds of years ago and the numbers were inflated for propaganda purposes; but there were at least some recorded instances. I recently tried adding an article I found on PubMed Central about the use of Amanita phalloides homeopathically to treat B-cell chronic lymphocytic leukemia. I'm aware that a single study needs to be repeated; which is why I'm not contesting the removal. Now I don't believe in water memory; but what is the difference between homeopathy and diluting something in water; wouldn't diluting poison with water allow for smaller amounts of it to be consumed? They do say that the poison is in the dosage. I'm also confused as to whether alternative medicine journals are legitimate primary medical sources when they are from the NIH or other government health organizations. Here is the link; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3151460/. Thanks for answering these questions. — Preceding unsigned comment added by CensoredScribe (talk • contribs) 19:04, 30 July 2013 (UTC)


 * Homeopathy is tricky. The homeopaths have their own special backdoor into the medical racket, allowing them to dispense "treatment" and "medicine" according to their own peculiar standards.  In practice, there are two different kinds of homeopathy encountered: one uses astronomically high dilutions to sell tap water to unsuspecting customers, given sometimes even by mainstream physicians who have applied medical ethics (i.e. profit) to determine that the act of patients giving them money for bogus medicine will make them feel better.  The other, more interesting variety, uses absolute minimum homeopathic dilutions to deliver genuinely therapeutic treatments - the catch being that they are not medically evaluated and they have the potential to harm as readily as heal.  For example Zicam causing loss of smell,, and others.  In this case, the amanitin is diluted by "D4" (1:10000) and 5-40 drops are given.  Sometimes homeopathy includes a hidden dilution factor (a drop flicked into a bottle of sugar pills) but it is not guaranteed and I don't think we should count on it here.  So there is possibility of a beneficial effect, but the utmost skepticism is required! Wnt (talk) 20:14, 30 July 2013 (UTC)


 * Right, be careful about identifying homeopathy with homeopathic dilution. Homeopathic dilution is the aspect of homeopathy that probably gets the most attention, but it isn't the whole discipline, just one practice.  Homeopathy is an entire framework of (mostly if not entirely bogus) theory and (possibly occasionally effective and/or dangerous) practice. --Trovatore (talk) 20:23, 30 July 2013 (UTC)

Symbol/syntax for denoting an (intentional) error?
Hi, in the Orders of magnitude (speed) article, I wanted to highlight the fact that the speed measured in the Faster-than-light neutrino anomaly is "incorrect". Is there a symbol or syntax I could use to denote an intentionally incorrect value or item (in science)? I thought I could use italic for the values, or maybe an asterisk or something similar, but I frankly have no idea. Thanks in advance. --CesarFelipe (talk) 21:44, 30 July 2013 (UTC)


 * Won't [sic] do? Or a footnote? - Nunh-huh 21:47, 30 July 2013 (UTC)
 * Just asterisk/footnote or other text annotation would be good. It's a disproven or contradicted statement, not a typo that would merit "sic". DMacks (talk) 22:00, 30 July 2013 (UTC)

MPN / CFU relationship
Hi Guys,

Is there a direct relationship or conversion factor for comparing fecal coliform results by enzyme reaction reported as MPN and results by membrane filtration reported as CFU? Thanks! — Preceding unsigned comment added by 148.66.156.178 (talk) 22:02, 30 July 2013 (UTC)
 * No simple conversion seems possible but models have been proposed to compare results of the two methods. Also results may depend on circumstances, for example a Korean study found MPN for e. coli larger than CFU, except in winter. On the other hand, enterococci were lower in MPN than in CFU.
 * Maybe this helps: "Modeling the relationship between most probable number (MPN) and colony-forming unit (CFU) estimates of fecal coliform concentration." Gronewold AD, Wolpert RL. pdf download. Ssscienccce (talk) 10:51, 31 July 2013 (UTC)

Thanks, that helps a bunch! I didn't think they directly related but it seems they are at least roughly comparable as my results are either near zero or in the 20-30k range. — Preceding unsigned comment added by 148.66.156.178 (talk) 00:26, 2 August 2013 (UTC)