Wikipedia:Reference desk/Science

From Wikipedia, the free encyclopedia
Jump to: navigation, search

The Wikipedia Reference Desk covering the topic of science.

Welcome to the science reference desk.
Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

  • Provide a short header that gives the general topic of the question.
  • Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
  • Post your question to only one desk.
  • Don't post personal contact information – it will be removed. We'll answer here within a few days.
  • Note:
    • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
    • We don't answer requests for opinions, predictions or debate.
    • We don't do your homework for you, though we’ll help you past the stuck point.

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

  • The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
See also:
Help desk
Village pump
Help manual

December 5[edit]

What is the difference between these two glycines?[edit]

I saw these two illustrations in the article Glycine: and I don't understand what are the differences between these two structures. If it's the same molecule why they are different while using skeletal structure?

variant 1 of Glycine
Variant 2 Glycine (talk) 00:07, 5 December 2016 (UTC)

Zwitterion. TenOfAllTrades(talk) 01:08, 5 December 2016 (UTC)

Thank you. I know what is zwitterion but I'm not talking about the plus and minus signs that make it zwitterion. I am talking about the structure. It says that there are here TWO types of skeletal structure with different positions with different number of elements (H3N vs.NH2) (talk) 02:11, 5 December 2016 (UTC)

There's not a different number of elements. The H3N+ (or NH3+, if you want to more easily compare to NH2) is just the amine group protonated with a hydrogen. What had been a COOH is now a COO-, as it lost a hydrogen when it was deprotonated. The skeletal structure doesn't appear any different either. The second structure is merely rotated about 45 degrees clockwise from the first structure in space, but the connectivity is identical. It's as if you picked up the entire physical molecule, rotated it, and set it down. The central carbon is still SP2 hybridized. The only difference is, as TenOfAllTrades said, that the second structure is the zwitterion form. --OuroborosCobra (talk) 03:21, 5 December 2016 (UTC)
The neutral and zwitterionic forms are tautomers. The only difference is the location of one of the protons.
Your "variant 1" is the neutral form that is often quoted for simplicity, even though it actually won't occur at standard conditions: any pH high enough to deprotonate the –NH3+ group to –NH2 will also deprotonate the –COOH group to –COO. At biological pH, the amine is protonated and the carboxylic acid is deprotonated, giving your "variant 2". Double sharp (talk) 03:28, 5 December 2016 (UTC)
There is no chemical meaning for which side of the N the H are written ("H2" on the right of the N in variant 1 vs "H3" on the left of the N in variant 2). In both cases, and as always for condensed formula details, "adjacency implies connectivity". The bond from the implicit carbon of the CH2 group goes to the N specifically, so the nitrogen is obviously bonded to that carbon. The 2 or 3 H are written condensed and adjacent to the N, so they are bonded to it. The N has tetrahedral geometry regardless, so there is not an "H2" or "H3" group, nor are the set of N–H bonds all going in any one direction. DMacks (talk) 06:16, 5 December 2016 (UTC)

Reducing the waiting period to donate blood after male-male sex - practical impact?[edit]

Here in Australia, the rules state that a male cannot donate blood for a full 12 months after engaging in anal sex with another male. Many have argued that such a long period is unnecessary - it could be reduced to three months with no risk (feel free to disagree if I've somehow got the science wrong). The "window period" for modern HIV tests is never longer than that, as far as I am aware, and in many cases is shorter.

two questions:

1. Less important question: Would there be any safety risk to the blood supply in terms of avoiding HIV transmission, by reducing the exclusion period after male-male sex from twelve months to three?

2. This is my more important question: How much would such a move practically increase the donor pool? I would assume that the majority of men who have anal sex with men (I avoid the term "gay", as not all such men would identify with the title) would generally not do so on a one-off, or only once a year. Men who engage in this activity would, in general, I assume, tend to do so on a regular basis (i.e. significantly more frequently than once every three months). I know many answers here will be speculative, but I still believe it's a fair question: How many men are excluded by a one-year exclusion period, who would not be excluded by a three month exclusion period? How much of an impact would such a move have on donor numbers and blood stocks? Would it be significant at all? Or would it be trivial, making any rule change have little practical impact?

I don't think any of the answers to this question would potentially fall into the "medical advice" prohibition, as those who make the rules on these matters are at zero risk of taking advice from wikipedia! And the second question is not really a "medical" one in any case. Eliyohub (talk) 09:57, 5 December 2016 (UTC)

According to the UK's blood service, the 12-month window is to do with Hepatitis B rather than HIV - see the "Why a 12 months deferral?" section here. AndrewWTaylor (talk) 10:08, 5 December 2016 (UTC)
Hardly a reason - we've had vaccination against Hepatitis B available for many years now. Assuring a donor's vaccination is up to date, no need to defer them at all due to Hepatitis B - they're at near-zero risk. Besides, the reference you provided only says it takes up to 12 months to clear the virus. The window period to potential detection is far shorter, up to six weeks. In addition, if a person tests positive to Hepatitis B "surface antibodies", it indicates that not only are they free of the virus, they are immune (either due to vaccination, or recovery from past infection) Eliyohub (talk) 10:47, 5 December 2016 (UTC)
It's my impression that when these policies were first drawn up, it was surmised that there were other bloodborne diseases (like "non-A, non-B hepatitis", i.e. mostly hepatitis C) which were not understood, and there was some thinking that there were other unknown risks being addressed. Mixed, of course, with a certain amount of prejudice. There are some other curiosities that have emerged since like GB virus C that may justify a certain amount of ongoing paranoia, though one hopes that the number of diseases circulating undetected is falling. In general the blood banking system needs to think about both known and unknown threats - that said, there may well be different specific criteria to use that secure against them more effectively. Wnt (talk) 11:02, 5 December 2016 (UTC)

(EC) I found [1] which I think is the most recent review of the behavioural based donor deferral criteria in NZ. It mentions a 6 month deferral was considered but rejected based on what was felt was insufficient evidence that it wouldn't increase the risk. It also mentions other things like why more detailed sexual history (e.g. condom usage) was rejected (again insufficient evidence and what limited evidence there was caused concern as well as concern over whether such questions may be too invasive), why oral sex is included, etc. One thing it does mention is that the older 5 year period was at least partially due to concern over new TTIs. However it doesn't sound like the 12 month period was based on that.

I make no comment on the decisions and accuracy of the information contained in the report, except to note that it says the maximum window period is for hepatitis C which is 94 days. While it doesn't seem there's good evidence sexual activity is a strong risk for hepatitis C infections (except for certain co-occuring infections), since there is some limited evidence it may be the case that a conservative risk assessment would consider 3 months too short. The report does mention that in addition to the window period + margin of error for the test just in case, there is also concern over making the margin of error too short in case people don't remember correctly. Note it would seem easily possibly relying on people to remember if they've been properly (including all courses) remember if they've been vaccinated against Hepatitis B would raise similar concerns although I'm not sure if this arises since it doesn't seem Hepatitis B has the worst window period, e.g. Human T-lymphotropic virus 1 also has a longer window period.

Also the report makes it sound like in some countries (but not NZ anymore) there may be concern over a failure to remove a sample with a positive test result (quarantine failures/release errors). While improving systems to prevent this would be the primary goal, in the mean time reducing detected infections (by removing riskier individuals) may also be implemented to reduce the risk of TTIs, and this was evidently part of the reason for the old 5 year deferral.. Finally the report does mention 6 months was recommended by the blood service in Australia but rejected by the TGF. It is also was implemented in Japan and maybe elsewhere (I didn't look that well). I suspect you can probably find some info on why the TGA rejected the 6 month deferral. It also seems likely that if research in those countries where 6 months was adopted suggests it didn't result in an increase in TTIs, this would be then spread, as the report and other things I've read suggest this is what happened with 12 months.

Nil Einne (talk) 14:38, 5 December 2016 (UTC)

[2] is the TGA's decision rejecting the 6 month proposal. Nil Einne (talk) 14:45, 5 December 2016 (UTC)
That letter uses the jargon of "compliance" and describes some statistics -- what I *think* it means is that based on their statistics, the men are having sex more often than they recollect, and they are afraid that if men don't think they had sex in six months it will actually be less. (They admit that a shorter period "might" improve compliance, but say that isn't proven). Wnt (talk) 13:17, 6 December 2016 (UTC)
In the US, ever having had an active case of viral hepatitis permanently excludes one from donating blood. Part of the justification is that a small percentage of infections never clear but have a viral load that persists indefinitely at a low concentration. Of these, a small percentage have traces of a hepatitis virus (usually HBV) but no longer produce sufficient antigens or antibodies to be detectable during a standard blood screen. Dragons flight (talk) 14:06, 5 December 2016 (UTC)
I've just seen that we have an article on the subject, and also that the 12-month rule is being reviewed in the UK. AndrewWTaylor (talk) 14:22, 5 December 2016 (UTC)
From men who have sex with men, at least 2.9% of US men (age 15 to 44) had sexual activity with another man in the previous 12 months. [2.9% is the self-reported frequency, the authors believe that such activity is unreported due to perceived bias.] I don't think it is controversial to suggest that most people who have sex try to do so frequently, so much of that 2.9% are probably going to excluded by any choice of waiting period. I would guess that moving from a 12-month wait to a 3-month wait probably wouldn't increase the potential donor pool more than ~1%. Dragons flight (talk) 15:26, 5 December 2016 (UTC)
  • Cheeses, Murray and Joseph! I am HIV and Hep A, B, & C, negative, as well as negative for Syphilis, Gonnorhea, and Chlamydia. But I have still been told never to donate blood, given I have had three full transfusions. We do NOT give medical advice, please read WP:DISCLAIMER and then go elsewhere, like to a physician! μηδείς (talk) 04:33, 6 December 2016 (UTC)
None of the above is medical advice, μηδείς, It's a response to questions about medical regulations and the medical theories and knowledge surrounding them. There is no suggestion whatever that anybody either is or is not going to undergo or avoid any medical procedure as a result of it. {The poster formerly known as} (talk) 04:56, 6 December 2016 (UTC)
Thank you IP. μηδείς, sometimes you do go too far. I made it clear in my question that those who make actual decisions on these matters are at zero risk of taking advice from wikipedia. Presumably, you did not decide whether or not you would be allowed to give blood - the relevant medical regulator did! (Perhaps your case is an exception,ifs it involved question of your own health, not that of the recipient. But where a potential recipient's health may be at stake, as is the issue in the regulations I ask about, the decision is never left to the donor, or anyone liable to be influenced by the discussion taking place here). Eliyohub (talk) 12:42, 7 December 2016 (UTC)

Nil Einne, thanks for your answer. Two issues. One, re vaccination for Hepatitis C B, there is no need to rely on donors correctly remembering if they've been vaccinated - testing for "surface antibodies" will give this info as to immunity entirely accurately, as I mentioned in an earlier reply. I had such a test myself, for reasons unrelated to blood donation. My understanding is that such a test is no more expensive than a standard Hepatitis B test, and is in fact done by some clinics as a standard component of such tests.

Second, is there any info as to either a) What percentage of the male population have had sex with another man during the last 12 months, but not during the last 3 months, and b) did the cutting of the waiting period in Japan and any other jurisdictions which implemented it lead to any increase in donations? Eliyohub (talk) 13:12, 7 December 2016 (UTC)

I think your first comment is confusing Hep B and Hep C. There is no Hep C vaccine, and unlike Hep B, the typical antibody test for Hep C doesn't distinguish between an active infection and a previously recovered infection. Dragons flight (talk) 13:30, 7 December 2016 (UTC)
OH, you are correct, I meant Hep B! Struck out now and corrected. You are correct about Hep C, there is no vaccine, nor any simple test to distinguish between an active infection and a past one. Ergo, anyone who ever had Hep C is usually permanently excluded from donating. However, in my first comment near the very beginning of this question, I explicitly referred to Hep B. What I HAD intended to say this time was, as part of his response, Nil Einne mentioned the possibility that when it came to Hep B again, people might not correctly remember whether they've received the full course of vaccination, and I was replying that this is not a concern, it can be tested for. As I said, I agree with you that concern over Hep C is a different story, and a real issue, although as Nil Einne mentioned again, the degree to which it can be spread sexually is debatable. Eliyohub (talk) 14:05, 7 December 2016 (UTC)

Why are mitochondria called "mitochondria"?[edit]

I understand—from both the Wikipedia article and the Wiktionary article—that the word mitochondrion is constructed from the classical Greek for "thread" and "granule." My question is, why thread and granule rather than, say, potato and tennis racket?

I can guess that a mitochondrion's gross morphology may have stricken its discoverer(s) as particularly discrete and grain-like. I can also speculate that its strands of DNA may have stood out to the microscopically aided eye. But I know better than to trust my guesswork on a matter about which I am so far from expert.

Could someone please illuminate? And to clarify, although I do welcome guesses better educated than mine, what I'd really love is an authoritative explanation of what actually did inspire the namer, rather than merely what might plausibly have done so.—PaulTanenbaum (talk) 14:08, 5 December 2016 (UTC)

Read this. --Jayron32 14:13, 5 December 2016 (UTC)
(ec) See Carl Benda: 'Because of their tendency to form long chains, he coined the name mitochondria'. AndrewWTaylor (talk) 14:17, 5 December 2016 (UTC)
Wow, in a mere 5 minutes I got exactly what I'd requested. Thanks!—PaulTanenbaum (talk) 14:28, 5 December 2016 (UTC)

Is that claim proved scientifically?[edit]

I saw this video which is viral on Facebook and it claims that the way that people sit on the lavatory seat is not correct and not healthy and the correct way is like animals or as people used to do in the past (read the titles on the video). My question is if it's proved scientifically or it is nonsense? (talk) 15:43, 5 December 2016 (UTC)

There is some evidence that squatting reduces the amount of straining needed, but at the same time, it's also more difficult than sitting which seems to counteract the benefit. This study, for instance, actually finds squatting seems to increase stroke risk, and advises that at risk of stroke avoid it. Smurrayinchester 16:09, 5 December 2016 (UTC)

We have an article on this at Defecation postures, but it isn't a very good article.
There is also a video on this on youtube that I found to be hilarious.[3] Also see [4]
But enough of the silliness. What do the sources say?
  • "Conclusion: The results of the present study suggest that the greater the hip flexion achieved by squatting, the straighter the rectoanal canal will be, and accordingly, less strain will be required for defecation." --Influence of Body Position on Defecation in Humans (Full text here:[5])
  • "The patients were instructed to defecate using two types of toilet: an unraised, ground-level style (common in Iran), and a bowl with attached tank style (common in Western countries) ... Use of the Iranian-style toilet yielded a much wider anorectal angle, and a larger distance between the perineum and the horizontal plane of the pelvic floor than the European style. Bowel evacuation was also more complete using the Iranian-style toilet" --Impact of ethnic habits on defecographic measurements
  • "The magnitude of straining during habitual bowel emptying in a sitting posture is at least three-fold more than in a squatting posture and upon urge. The latter defecation posture is typical of latrine pit users in underdeveloped nations. The bowels of Western man are subjected to lifelong excessive pressures which result in protrusions of mucosa through the bowel wall at points of least resistance." --Etiology and pathogenesis of diverticulosis coli: a new approach.
  • "In conclusion, the present study confirmed that sensation of satisfactory bowel emptying in sitting defecation posture necessitates excessive expulsive effort compared to the squatting posture." --Comparison of Straining During Defecation in Three Positions: Results and Implications for Human Health (Full text here:[6])
  • "Cardio-vascular events at defecation are to a considerable degree the consequence of an unnatural (for a human being) seating defecation posture on a common toilet bowl or bed pan. The excessive straining expressed in intensively repeated Valsalva Maneuvers ... adversely affecting the cardio-vascular system is the causative factor of defecation syncope and death. The squatting defecation posture is associated with reduced amounts of straining and may prevent many of these tragic cases." --Cardio-vascular events at defecation: are they unavoidable?
  • "A considerable proportion of the population with normal bowel movement frequency has difficulty emptying their bowels, the principal cause of which is the obstructive nature of the recto-anal angle and its association with the sitting posture normally used in defecation. The only natural defecation posture for a human being is squatting. The alignment of the recto-anal angle associated with squatting permits smooth bowel elimination. This prevents excessive straining with the potential for resultant damage to the recto-anal region and, possibly, to the colon and other organs." --Primary constipation: an underlying mechanism.
  • "Our result clearly shows that modified commode squatting posture has the highest success rate for the treatment of chronic anal fissure." --Role of defecation postures on the outcome of chronic anal fissure
On the other hand, see the comment above mine for a study on blood pressure in hypertensives during squatting. Also, I can't help but wonder whether it makes a difference whether you squat with a toilet seat supporting your body, as seen in the squatty potty video above, or whether you support your weight with your legs/feet, as is don in Japan. --Guy Macon (talk) 18:16, 5 December 2016 (UTC)

Nice answers! thank you all (talk) 17:06, 7 December 2016 (UTC)

Arachidyl Alcohol[edit]

Arachidyl alcohol page isn't clear on this. Is this substance always derived from groundnut (peanut) oil? And if so, can it cause an allergic response in someone who has a peanut allergy? --TammyMoet (talk) 17:09, 5 December 2016 (UTC)

Regarding the second question: that would depend on whether or not the person was specifically allergic to this compound. The source of a pure compound makes no difference. It would only cause an allergic reaction in one of two cases: 1) if a person were specifically allergic to this compound or 2) if the compound was laced with impurities that the person WAS allergic to. This article lists the specific molecules that are known to trigger peanut allergies. Arachidyl alcohol is not listed there, they are mostly all proteins. --Jayron32 18:34, 5 December 2016 (UTC)
Thank you Jayron that's actually really useful. --TammyMoet (talk) 18:43, 5 December 2016 (UTC)
Well, there is a caveat that no compound you can buy is truly a pure compound; it can have exceedingly high purity, or then again, maybe not. A cold pressed peanut oil can contain allergens, according to that article. It is hard to imagine a purification scheme that concentrates the 1% arachidic acid present in peanut oil, then a chemical reduction to arachidyl alcohol, which leaves peanut allergens intact (these being low molecular weight proteins).[7] Nonetheless, they are water soluble and resistant to heat, so at least conceivably you could have a trace present but your scheme to extract the alcohol pulls them along and then they oil out and become concentrated at a key step... I'm not going to say impossible, and I doubt anyone can since the question is potentially open-ended for any conceivable synthesis approach. That said, the bulk of peanut oil, and the purest and cheapest stuff to use for this purpose, starts non-allergenic before you even begin trying to make or purify the alcohol. It's probably more likely some idiot drops a bag of peanut shells into the oil and they have to strain them out with cheesecloth than the allergens make it through purification. And Cupuaçu has something around six times more arachidic acid than peanut oil, and is "unlikely" to cause peanut allergy. :) Wnt (talk) 19:37, 8 December 2016 (UTC)
And, of course, if it's made from ethylene (as I described), then the whole allergy thing becomes a moot point. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 10:44, 9 December 2016 (UTC)
And regarding the first question, it's also one of the minor byproducts of the Fisher-Tropsch synthesis of liquid hydrocarbons (especially if the refinery is being run to maximize the production of diesel fuel). It can also be produced by Ziegler-Natta synthesis from ethylene, in which case it can be obtained in high purity. 2601:646:8E01:7E0B:99F8:B355:9D57:7021 (talk) 05:27, 6 December 2016 (UTC)

Fire safety[edit]

If the door's hot it's often said to tell the fire department where you are then seal cracks with wet towels. And breathe near the floor and through a wet towel if need be.

Would floating in a cool bathtub further increase the time before injury or death if the firemen take longer than average? Taking trash bag(s) of good air with you and only opening them to breathe? (exhale inside or outside the bag?) Holding your breath after you run out of air below a certain level of smokiness and hope they get there before you have to breathe again? What's the best breathing strategy? How smoky should the air become before holding your breath as long as you can becomes the best strategy? Sagittarian Milky Way (talk) 19:15, 5 December 2016 (UTC)

The bathtub? Probably not helpful. Most fire deaths are due to smoke inhalation. Trash bags? An interesting idea. I would favor exhaling into the room. You could try doing an experiment with ten bags (to account for the logistics of moving multiple bags of air around) and reporting how long the air lasted. Original research, of course, but I for one would be interested in the answer. How far could you crawl along a smoky hallway using one or two trashbags of air? If you wanted to prepare ahead of time you might consider getting the clothing and breathing gear that firefighters use. --Guy Macon (talk) 20:06, 5 December 2016 (UTC)
Definitely exhale INSIDE the trashbag, you only consume a fraction of the oxygen from the air in each breath. Air is about 20% oxygen, exhaled air is about 15% oxygen, you can inhale and exhale a bag of air several times before you deplete ALL the oxygen. Vespine (talk) 21:39, 5 December 2016 (UTC)
How hard is it to tell how close you are to depletion? The above seems risky, because the user may not realize that they are about to deplete all the oxygen and then start inhaling CO, which does not seem likely to have a good result. Also, we should clearly indicate that Wikipedia and its contributors disclaim any responsibility for the results of the proposed techniques described in this thread. Do not try these techniques at home! --03:17, 6 December 2016 (UTC) — Preceding unsigned comment added by (talk)
Smoke hood might be a useful article here (although, unfortunately, it doesn't go into much quantitative detail). Tevildo (talk) 22:12, 5 December 2016 (UTC)
With all the caveats of NOT TRYING THIS AT HOME! I think you would pass out before you die if you keep inhaling and exhaling into a bag, I don't think you could "keep" breathing into the bag until you die. Unless you stuck your head IN the bag which would definitely be a terrible idea. Vespine (talk) 03:43, 6 December 2016 (UTC)
Plastic garbage bags would melt if anywhere near heat, and catch fire if near flames. However, if you were in an area with smoke but no fire, that might work. I've myself thought if using a scuba tank in a bathtub. Hopefully that would allow you to survive, unless the building collapses (and even then, a bathtub full of water might offer some protection, say if it falls through the floor). StuRat (talk) 03:43, 6 December 2016 (UTC)
  • If I recall correctly, the CO2 percentage is the limiting factor, not oxygen depletion. So yes, you can stretch the time by exhaling back into the bag, but you cannot use all the oxygen. WWII-era submarines used a chemical (caustic soda?) to scavenge the CO2 and extend the time in emergencies, I think. Therefore, best practice is (probably) to inhale from the bag and hold the air in your lungs as long as possible with each breath to maximize oxygen extraction, then exhale into the room. Order-of-magnitude guess on time: taking a one-quart breath every 15 seconds, you get one minute per gallon, and a 30-gallon bag gives you half an hour. If you have N bags, after you have used the first bag, exhale the second bag into the first, and eventually you have N-1 bags of once-used air. You are now in trouble, but you can now use the once-used air, producing N-1 bags of twice-used air. If you are not rescued in time, you will lapse into unconsciousness, at some point. -Arch dude (talk) 01:58, 7 December 2016 (UTC)

Ginkgo fruit yield[edit]

How much fruit does a mature Ginkgo biloba produce in one season? Surtsicna (talk) 22:08, 5 December 2016 (UTC)

Emphasis mine, from here [8]. That article doesn't clarify if that's a fresh or dry weight, but the cited source probably does. In my experience dry weight is what is usually reported in scientific contexts. Note also that wild types and cultivars not designed specifically for seed production will probably make less seeds, and they can take 20-30 years to mature, a fact stated earlier in the same article. SemanticMantis (talk) 22:19, 5 December 2016 (UTC)
Within 10 minutes! I had been searching for an hour. Thank you! Surtsicna (talk) 22:37, 5 December 2016 (UTC)
You're welcome! There are probably other estimates out there, this should be good enough for most casual usage. (It did take me several searches on Google Scholar. I think it was /Gingkgo seed production/ that worked, but part of it was being familiar enough with the literature to know that at least some estimate would certainly be there :) SemanticMantis (talk) 22:43, 5 December 2016 (UTC)
  • I am tempted to say "too much" but as a New Yorker, I would compare the yield to a non-cultivated Krabapple or cherry. No one would grow the plant for human consumption. μηδείς (talk) 04:19, 6 December 2016 (UTC)
  • @ Medeis, You are wrong, Read the article. Richard Avery (talk) 07:52, 6 December 2016 (UTC)
Non-Gingko meta discussion
You don't seem to properly understand what constitutes "personal attack", in the way that term is used on Wikipedia. And saying so is emphatically not a personal attack. See What is considered a personal attack? and perhaps ad hominem for more info. If you want to discuss further, take it to the talk page, as per your own previous good suggestions on similar matters. SemanticMantis (talk) 18:47, 6 December 2016 (UTC)
"You are wrong" is an ad hominem attack. ←Baseball Bugs What's up, Doc? carrots→ 19:01, 6 December 2016 (UTC)
No, you are wrong. What you said is incorrect. Your words, they are not right. Your understanding is flawed. You seem to be laboring under a misconception. Etc., etc. None of these are personal attacks or ad hominem remarks. None of them fit the description of anything on the ad hominem page. I am not critiquing you as a person, I am not using your character as grounds to disprove your assertions. Rather, I am addressing what you said. But I don't have any more time to volunteer toward educating you today, so I'm out, have a good one. SemanticMantis (talk) 19:26, 6 December 2016 (UTC)
"You are wrong" is a moral judgment on your target. ←Baseball Bugs What's up, Doc? carrots→ 19:30, 6 December 2016 (UTC)
Wow Bugs, you don't know what morality is either? Factual correctness is not a matter of morality. If you said 2+2=5, and I said "You are wrong", that is a statement of fact. I don't even know where to start untangling what is the source of your apparently deeply seated misunderstandings, so I won't. But let's just say, I genuinely look forward to the day when you take me or anyone to arbcom or ANI or whatever for a "personal attack" because you were told "You are wrong" :D SemanticMantis (talk) 18:03, 7 December 2016 (UTC)
No, "you have it wrong" is a statement of fact. "You are wrong" is a moral judgment. ←Baseball Bugs What's up, Doc? carrots→ 18:27, 7 December 2016 (UTC)
@ Medais, with the greatest respect for your wide and detailed knowledge I feel duty bound to graciously inform you that when you assert that "No one would grow the plant for human consumption" you are I fear somewhat mistaken. This error on your part is, possibly due to the fact that you seem not to have read the relevant article, to wit, Ginkgo biloba where it indicates that this tree is cultivated and harvested for it's slightly toxic nut widely in the Far East. Richard Avery (talk) 15:12, 6 December 2016 (UTC)
Perfect response to the hatted argument. Stated in the finest traditions of diplomacy. Debate in Parliament would benefit greatly from such an approach. Baseball Bugs, even you should now be satisfied! Eliyohub (talk) 13:28, 7 December 2016 (UTC)
Our article does not clearly state an essential fact, which is that the "fruit" of the gingko smells quite literally like dogshit. As a result most Americans don't like to have female gingko trees near their houses. Also the "nuts" are not valued enough here to make the trees worth cultivating. But they are highly valued in China, and the trees are extensively cultivated there. (FYI, an "@" has no effect if you don't spell an editor's name correctly.) Looie496 (talk) 15:15, 6 December 2016 (UTC)
Our article Ginkgo biloba does state that "smells like rancid butter or vomit", due to the butyric acid, which is the same reason Hershey's "chocolate" tastes/smells of vomit to some people. Perhaps there is someone out there who associates Gingko nuts with chocolate... My WP:OR is that the odor is only strong on the fresh pods, and the dried nuts are fine. SemanticMantis (talk) 18:53, 6 December 2016 (UTC)
AFAICT, those skilled in Cantonese cuisine can cook anything and make it taste good. Wnt (talk) 19:08, 6 December 2016 (UTC)
I'll happily admit defeat, as even dogs will eat their own feces. See μηδείς (talk) 04:22, 8 December 2016 (UTC)

December 6[edit]

School systems in America, England and Holland[edit]

<inappropriate solicitation removed>

Please do not solicit from this desk. It is inappropriate. Seek other means to get your surveys completed. Tobyc75 (talk) 18:09, 6 December 2016 (UTC)

Which school system is better: the Dutch, American or British one?[edit]

<inappropriate solicitation removed>

Please do not solicit from this desk. It is inappropriate. Seek other means to get your surveys completed. --Jayron32 17:07, 6 December 2016 (UTC)

The Singaporean one:

"Prof Sing Kong Lee, vice-president of Nanyang Technological University, which houses Singapore's National Institute of Education, said a key factor had been the standard of teaching. "Singapore invested heavily in a quality teaching force - to raise up the prestige and status of teaching and to attract the best graduates," said Prof Lee. The country recruits its teachers from the top 5% of graduates in a system that is highly centralized." Count Iblis (talk) 22:36, 6 December 2016 (UTC)

So, in essence, the answer to the OP's question is "No"? ←Baseball Bugs What's up, Doc? carrots→ 22:41, 6 December 2016 (UTC)
Not the OP's own system, apparently - or he would know that it is always the better of two, but the best of three or more. Wymspen (talk) 23:02, 6 December 2016 (UTC)
Unless each one is better than the other two. ←Baseball Bugs What's up, Doc? carrots→ 00:49, 7 December 2016 (UTC)
There's no "American" school system anyway. Shock Brigade Harvester Boris (talk) 01:21, 7 December 2016 (UTC)
Yes, American schools are operated at the state level, but there are also federal standards. ←Baseball Bugs What's up, Doc? carrots→ 10:02, 7 December 2016 (UTC)
No, there aren't. There are national or sort-of-national standards which have been developed by the states collectively without the participation of the Federal Government, such as the Common Core State Standards Initiative, but the Federal Government does not mandate any standards on their own, as noted here at, the U.S. Department of Education encourages states to develop their own standards, but has no say in what those standards are. To quote that webpage "Federal law requires that all states receiving Title I funds have high-quality standards. Federal law does not mandate a specific set of standards." (bold mine). --Jayron32 00:33, 8 December 2016 (UTC)
Yes, federal standards exist; see Title IX, for example, which despite being part of the Higher Education Amendments of 1972, applies to non-higher educational institutions as well. The Family Educational Rights and Privacy Act also imposes standards on schools at all levels. These standards apply only to schools accepting federal funding, but given the appearance of largesse from Washington and the consequent pressure on legislators to accept it, virtually all schools accept federal funding. Nyttend (talk) 05:41, 9 December 2016 (UTC)

When photons hit solar sails[edit]

Does the photons lose momentum? Could they hit infinitely many solar sails and move these without losing momentum? Doesn't this sound like energy for free? — Preceding unsigned comment added by Quotawk (talkcontribs) 19:04, 6 December 2016 (UTC)

One photon between two mirrors could, in principle, continue bouncing off each and pushing it in the opposite direction indefinitely. The combined momentum remains conserved. But where does the energy come from? Well, supposing a perfect mirror, the photon bounces off each object exactly the same way as it arrived... from the perspective of the mirror. That means that if the mirrors are moving away from each other, the photon, from the average perspective that sees them diverging, is coming back with a little less momentum each time. In other words, it is redder due to a Doppler shift. (The photon would actually be able to gain energy for a while if the mirrors were heading toward each other instead, but then again, it would be nothing unusual for them to hit each other and bounce - and whatever energy it gained would be lost due to the decreasing energy of the collision at the time they did hit each other, because it had slowed them a little first) Wnt (talk) 19:14, 6 December 2016 (UTC)
(edit conflict) You can read about this at Solar sail and radiation pressure. As explained at that second article, the photons do lose momentum; basically a photon's momentum is related to its frequency (p = h/c * ν), so when momentum is transferred to the sail, the light gets redder. --Jayron32 19:17, 6 December 2016 (UTC)
Yes. Note that the momentum of a photon is not constant in this regard, but depends on its energy, which is to say its frequency, which in turn (like momentum measurements of anything else) depends on what frame of reference it is viewed in. So in every frame it moves with the same speed but in frames where it is redder it has less momentum. Wnt (talk) 19:19, 6 December 2016 (UTC)
Right, whether we assume the reddening of the light is because, from the point of view of the accelerating sail, the light has become Doppler shifted to the red, or because of the DeBroglie relation, the photon loses momentum and this decreases in frequency (thus becoming redder) is the same concept viewed from two different perspectives. Either way, the laws of physics are happily obeyed. --Jayron32 19:23, 6 December 2016 (UTC)
OK, thanks for the answers.

December 7[edit]

Mountain gaps[edit]

According to its article, Virginia's Rockfish Gap in the southwest-northeast Blue Ridge is a wind gap. According to its article, a wind gap is essentially a dry water gap, a kind of mountain pass in which a river flows all the way through the mountain uninterrupted, thus producing a pass with no elevation change. All very nice.

If you drive U.S. Route 250 over the Rockfish Gap, as I do every week, you'll gain significant elevation in a short distance; less than a mile southeast of the 1903-foot col is a location below 1000 feet, the terrain drops rather fast to the northwest, and all in all the col is far higher than anything else around, except of course the ridge to the northeast and southwest. How can it be a wind gap when it's so far above everything else? Dry up a water gap, e.g. the James River Gorge near Glasgow, Virginia, and you get a canyon whose "summit" is essentially the same elevation as the ground at the base of the mountain (otherwise the river couldn't flow through; you'd get a pair of box canyons), not something where the nearest low ground is 900+ feet below the summit of the pass. Nyttend (talk) 04:03, 7 December 2016 (UTC)

One possibility is that geologic uplift, such as tectonic uplift, occurred after the gap was formed. StuRat (talk) 04:35, 7 December 2016 (UTC)
Yes see 3D Fold Evolution for some example of elevated wind gaps forming. Graeme Bartlett (talk) 06:37, 7 December 2016 (UTC)
This book has a description and some nice diagrams that seem to answer the OPs questions very nicely. --Jayron32 10:08, 7 December 2016 (UTC)

The whole point of a wind gap is that the water used to flow, creating a gap at the level of a valley, but when it stopped, the mountain began to be recreated by differences in erosion again. Note that the Appalachian Mountains aren't really the remnants of mountains in the naive sense that some of the height hasn't been worn down yet - rather, there are layers of rock embedded in anticlines and synclines that form a few weird little loops and a lot of long lines, and the differential erosion keeps them always present at a certain height, barring something like a river crossing them. Look at a satellite map and it should become clearer. Wnt (talk) 12:01, 7 December 2016 (UTC)

Alleghanian orogeny explains a bit more details about Wnt's statements. If one wanted to know more, they should research that topic. --Jayron32 13:02, 7 December 2016 (UTC)

Air pollution and what kind is the worst for your health[edit]

All things being equal, which is worst?

  • PM2.5
  • O3
  • NO2
  • SO2
  • CO

Many thanks.

Anna Frodesiak (talk) 05:16, 7 December 2016 (UTC)

PEL=permitted, REL=recommended, IDLH = immediate danger

substance PEL ppm REL ppm IDLH
O3 0.1 0.1 5
NO2 5 1 20
SO2 5 2 100
CO 50 35 1200

Looks like carbon monoxide is the "friendliest" poison gas. But as it has no odour, you may not notice. Graeme Bartlett (talk) 06:49, 7 December 2016 (UTC)

PM2.5 standards are about 100 to 1000 times lower in mass. So it suggests that is the worst, but I suspect it will be ozone that kills the quickest (50ppm in 0.5 hour). Graeme Bartlett (talk) 07:00, 7 December 2016 (UTC)

Thank you so, so much for taking the time on this one, Graeme. You have been really helpful. We have been getting a lot of PM2.5 over here -- in fact around the whole country. My very best wishes, and several people here reading this thank you also!!!! You're aces in my book. :) Anna Frodesiak (talk) 07:42, 7 December 2016 (UTC)
Yeah, China's air pollution sucks. [9] Dragons flight (talk) 08:04, 7 December 2016 (UTC)

For most of the world, particulate matter (e.g. PM2.5) is the most significant pollutant, accounting for 75-95% of air pollution related mortality. Most of the balance is associated with O3. For PM2.5 it is the effect of chronic exposure that is most important (leading to increased rates for stroke, heart disease, lung cancer, and other illnesses), while for O3 we tend to worry more about the effects of acute exposure (e.g. asthma and other breathing difficulties). NO2 and SO2 are almost never high enough to pose a significant direct mortality hazard, though people can become aware of them (e.g. reporting unpleasant / uncomfortable odors) at concentrations that are still well below the level that poses a direct mortality risk. By contrast, PM2.5 can significantly impact mortality risk even at levels that ordinary people don't perceive as unpleasant. As a result the health impacts of PM2.5 are often higher in many countries than local residents might expect. One should note that in addition to health impacts, there are also significant environmental impacts from many forms of air pollution (e.g. acid rain from SO2). Dragons flight (talk) 08:00, 7 December 2016 (UTC)

Emigrate to Finland before it is too late Count Iblis (talk) 08:22, 7 December 2016 (UTC)
I live in the Smoky Mountains. The air is nice and clean (except for the recent rash of forest fires). However, there is a huge problem with indoor air pollution from radon. My understanding (I haven't researched it) is that radon is a very nasty pollutant. (talk) 15:54, 7 December 2016 (UTC)
Maybe. As noted at Radon, it can be a serious risk factor for lung cancer; it is the second greatest linked cause of lung cancer after cigarette smoking. That being said, the only known group for whom Radon exposure is significant enough for risking lung cancer is Miners, who spend a long time underground in stale air that isn't often recycled at the surface. Back in the 1980s, there was a major Radon scare, as people began to worry about radon leaking into homes through basements and getting trapped in the house. As noted here however, few studies have found any significant risks from radon exposure in the home; it's possible if you a) lived in a basement with b) very poor ventilation, you COULD be at a higher risk of radon exposure; but most people live in homes that are "leaky" enough to avoid building up radon to dangerous levels. Which is not to say that there is no chance, but for most people, it shouldn't be a concern; except for people who run companies willing to charge you thousands of dollars to "seal" your foundation against radon getting in. They want you to be very scared. The science, (see source) is less sure. --Jayron32 18:26, 7 December 2016 (UTC)
Jayron's radon link is to a book on sexually transmitted diseases (see next section). Useful information can be found at [10] and [11]. (talk) 19:59, 7 December 2016 (UTC)
So corrected. --Jayron32 21:24, 7 December 2016 (UTC)

Thank you all very, very much!!! Anna Frodesiak (talk) 03:33, 9 December 2016 (UTC)

Sex with a Hepatitis C positive woman during her period[edit]

There is some controversy as to the degree to which Hepatitis C is sexually transmittable in bodily fluids other than blood. My question is, has anyone considered the issue of the risk involved to a man who has penile-vaginal sex with a Hepatitis C positive woman during her period, at a time when she is experiencing significant blood flow, such that her blood will inevitably get on his penis? I have no plans of having sex with such a woman, and to avoid "medical advice" problems, probably best if we can stick to linking to sourced answers which have looked at this question. (It would likely be of significant concern to the sex industry, where a significant portion of the prostitutes are IV drug users, and thus not infrequently get infected with Hepatitis C. On the other hand, many prostitutes either take a break during their period, are on the pill or implant and thus don't have a period, and/or universally insist on condom use. No, I am not involved whatsoever in the sex industry). Eliyohub (talk) 14:23, 7 December 2016 (UTC)

Some reading material: [12], [13], [14], [15]. --Jayron32 18:19, 7 December 2016 (UTC)

All other things equal is building fire a bigger or smaller risk at high altitude?[edit]

(moved to Science Desk)

Especially as high as La Paz/Lhasa a fire would more easily use up oxygen till you black out right? Woe to those who are lowlanders and unacclimated. Would low O2 balance things out though by making fires grow slower? Sagittarian Milky Way (talk) 19:40, 5 December 2016 (UTC)

This sounds like a science question to me, not a humanities question. I don't know the answer, but perhaps you should switch desks? Eliyohub (talk) 04:46, 6 December 2016 (UTC)
Note that breathing-wise, the lack of oxygen isn't the usual problem in a fire, it's the presence of toxic fumes. So, with that in mind, I suspect that the fire-retardant nature of thin air would make fires somewhat less dangerous at altitude. It would be interesting to find stats that support or counter this. StuRat (talk) 16:51, 6 December 2016 (UTC)
Think, the basics should be always kept in mind in answering this. The percentage of oxygen remains the same regardless of which floor one is on. The lowering of ambient pressure however, lowers the thermodynamic efficiency of combustion (think of it the other way around where the higher the compression ratio in an infernal combustion engine, the higher the efficiency). Also, the lowering of pressure, lowers the partial pressure between O2 and CO2 exchange in the lungs. So one may start panting to lower the blood CO2 only to inhale more toxic fumes. Modern furniture also tends to emit cyanide (which inhibits haemoglobin efficiency) therefore the nature of the fuel (in this hypothetical towering inferno) must be considered. There is nothing like an in vivo experiment to settle the matter – any volunteers?--Aspro (talk) 21:56, 7 December 2016 (UTC)
  • NFPA has a statistics on structure fires here [16]. Here [17] are all their pages that mention 'elevation'. You can contact their Fire Protection Research Foundation representative or statistics and data representative directly here [18]. SemanticMantis (talk) 22:04, 7 December 2016 (UTC)
Those reference appear to be concerned only with the hydrostatic pressure head of water not air. This form of liquid monoxide tends not to support combustion (although I am willing to be corrected, e.g. aluminium swarf fires).--Aspro (talk) 22:38, 7 December 2016 (UTC)
I think you are probably right, though I haven't checked every instance. While not related to O2 concentrations, water pressure, and the change due to elevation, is still an important factor in the eyes of the NFPA, and thus I thought it broadly relevant to OP's question of structure fire danger and elevation. P.S. OP: if you're interested in altitude/elevation effects on wildfire, let me know; there is tons of classic and ongoing research in that area, and I'd be happy to supply scholarly refs. SemanticMantis (talk) 23:32, 7 December 2016 (UTC)
I would be curious what elevation does to wildfires. What have people found? Sagittarian Milky Way (talk) 15:18, 8 December 2016 (UTC)
It would be difficult to judge, since vegetation and moisture levels are also different at altitude. So, you're comparing apples to oranges. StuRat (talk) 15:22, 8 December 2016 (UTC)

There is no one simple answer, and this is not something that we can wave our hands on and come up with something useful from first principles. I'd recommend starting here [19], where a mathematical modal of probabilistic fire risk is presented by some folks from the USFS. You'll have to read the whole paper to fully understand it, but Eq. 4 shows how elevation enters in to the model as spatially explicit variable.
Here [20] is another model specifically focused on risk assessment. It is free to read online if you register.
Here [21] is some work about using GIS data to calculate specific risks for specific areas.
Here [22] is a fairly readable case study for CO.
Mulivariate regressions and other fancy analyses show that elevation, slope, and aspect are all very important, as are the associated changes in plant cover. Fig 2. of the CO study lays out a schema for important variables, and Fig 1 of the first link shows how in OR the fire occurrence is related to elevation.
Fire will generally burn upslope, and generally risks will be higher in rain shadows of the region. I am not an expert in wildfire, but it is something I read a lot about. To my understanding, the most general effect of elevation on fire risk that is supported by data is the joint effect of Aspect_(geography) with elevation, with slope being a close third. With those three, within a certain region, you can make a pretty OK first pass fire risk map, assuming you also know how those affect the type of dominant plant cover and precipitation. Hope that helps, SemanticMantis (talk) 16:10, 8 December 2016 (UTC)

External temperature sensors on cars[edit]

I would like to know how these work and how they interface to the electronics systems on cars especcially Vauxhall Astra. When I look up temperature sensor on Wikipedia I get directed to thermometer. This is not a sensor but a combined sensor and display. Can someone create a new page for temperature sensor that is not a thermometer but is just a sensor like a thermistor??-- (talk) 23:23, 7 December 2016 (UTC)

Are you looking for something like List of temperature sensors? Looie496 (talk) 23:30, 7 December 2016 (UTC)
Sort of. But I think there should be a page on temp sensors not just a list. A sensor senses but does not 'measure'. A thermoMETER senses and displays as stated in its name (..METER). With sensors, other mechanisms/devices convert the physical sensor quantity to a reading of temperature. -- (talk) 00:00, 8 December 2016 (UTC)
Different sorts of temperature sensor and how they work and their applications would be the basis of the page. The list of sensors can be incorporated into that page. Searching temperature sensor should DEFINITELY NOT send users to the Themomoeter page! A theromoeter is NOT a sensor.-- (talk) 00:05, 8 December 2016 (UTC)
A thermistor seems the most probable. Email them and just ask,.. request a circuit diagram: >< If you think there should be a page on this subject you can create one yourself Wikipedia:Your first article. You can then assist us to improve Wikipedia.--Aspro (talk) 00:08, 8 December 2016 (UTC)
Yeah but as for WP, I think the article currently named List of temperature sensors should be renamed Temperature sensors and a lot more stuff added in to the page. How do I do that?-- (talk) 01:01, 8 December 2016 (UTC)
This would be considered a "move" I think. You could create a new article at temperature sensor (after deleting the redirect to "thermometer"), them paste in the "list of..." content, then delete "list of...". But while you can be WP:BOLD, for a move/rename like this, I think you should seek WP:CONSENSUS, at the talk page of "list of temperature sensors". SemanticMantis (talk) 17:14, 8 December 2016 (UTC)

December 8[edit]

Falling from a balloon[edit]

In the opening sequence to The World Is Not Enough, what altitude is the hot-air balloon at when it explodes? Would a fall from this altitude onto a sloped/domed concrete fiberglass roof, as depicted in the movie, be survivable? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 02:53, 8 December 2016 (UTC)

OK then, let me put it a different way: As depicted in the movie, how high (or I should rather say how low) are the approximate odds of survival? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 10:51, 8 December 2016 (UTC)
Wikipedia has an article and section Free fall#Surviving falls which may provide a starting place for your research. --Jayron32 11:34, 8 December 2016 (UTC)
Any place where I can find a table or graph of % chance of survival vs. altitude? Also, how does the slope of the surface affect the chance of survival? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 11:46, 8 December 2016 (UTC)
You can be killed in fall when you've got feet on the floor of your house. ←Baseball Bugs What's up, Doc? carrots→ 12:34, 8 December 2016 (UTC)
Just watched the relevant clip -- this shows that the altitude is about 60-80 m (definitely less than 100 m, as per the article), and the slope of the roof looks to be about 15-20 degrees -- what are the chances of survival in this case? (Assume the person rolls down the slope rather than just splatting straight down on the roof, as indeed is the case in the film.) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 13:14, 8 December 2016 (UTC)
This research paper has a section titled "Tolerance to impact acceleration" that lists some absolute limits; of course freak occurrences happen, but these values probably represent the expected maximum impact velocities for various landing configurations (feet first, head first, etc.) That would certainly help your research. --Jayron32 14:48, 8 December 2016 (UTC)
This study directly correlates height with lethality. --Jayron32 14:50, 8 December 2016 (UTC)
Thanks! So, possible but unlikely, right? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 01:10, 9 December 2016 (UTC)

Beech 18[edit]

What is the landing speed of the Beech 18? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:03, 8 December 2016 (UTC)

It is about 1.3 x stall_speed which is quite complicated to calculate. See also Without knowing exactly which Beech 18 model is hard to say but I would guess around 70-80 knots. I will ask an old-timer pilot I know and post again. (talk) 07:43, 8 December 2016 (UTC)
There is actually an internet-available flight manual for the Beech 18, circa 1948 [23]. I'll just quote exactly: "Gear, down... flaps, down, maximum speed 120 mph TIAS... Use small amount of power on approach. Approach speed is approximately 105 mph TIAS. Contact speed is approximately 80 mph TIAS." Someguy1221 (talk) 07:55, 8 December 2016 (UTC)
This account [24] says "just over 90 mph" approach speed which is 78 knots. (talk) 08:08, 8 December 2016 (UTC)
It also just hit me that there are many variants with different weights and engines, so presumably they could have different landing speeds. Someguy1221 (talk) 09:47, 8 December 2016 (UTC)
Thanks, all! So, about 80-90 mph, right? And question #2: If someone falls out of the plane as it touches down at that speed, is it possible for that person to survive? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 10:53, 8 December 2016 (UTC)
The frequent crashes of professional motorbike riders (in, for example, MotoGP) at similar or higher speeds without major injury suggest that it's certainly possible. They, however, are falling from a fairly low "altitude" (a "highside" crash might throw a rider perhaps 8 feet in the air - a broken collarbone, wrist or lower leg/ankle is likely in such a scenario: searching for such crashes on YouTube is likely to be productive) and are wearing protective leathers and gloves which allow them to slide rapidly on smooth tarmac without friction abrasion (to themselves). Portraying such an incident in a fictional work (which I'm guessing the OP is researching for) might need some careful details in the setup and description to retain verisimilitude. {The poster formerly known as} (talk) 12:02, 8 December 2016 (UTC)
Sure. With the right gear. [25] (talk) 11:55, 8 December 2016 (UTC)
I meant falling at the moment of touchdown (i.e. from just above ground level, as in the motorbike scenario), but without any special gear, like in this video -- would the secret agent get killed, or would he just break every bone in his body? (Also note that in the video I linked, the plane touches down at well above normal landing speed, as evidenced by the fact that it has its flaps up and that it bounces hard -- how would that affect the chances of survival?) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 12:32, 8 December 2016 (UTC)

African or European Beech 18? --Jayron32 15:23, 8 December 2016 (UTC)

Whichever one Kamal Khan has. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:17, 9 December 2016 (UTC)

Why defibrillator is not placed directly above the heart?[edit]

One might think that the manual external defibrillator's direct placement of paddles above the heart is more efficient than the currently used placement. Thanks.-- (talk) 09:49, 8 December 2016 (UTC)

There are different positions in which defibrillator pads can be placed, depending on several factors including the manufacturer's guidelines. It is in fact quite common for one of the pads to be placed over the cardiac apex. (NB I am qualified in advanced life support). — Preceding unsigned comment added by (talk) 10:39, 8 December 2016 (UTC)

  • (edit conflict) I have no medical qualifications whatsoever, but I think you imagine that the electrodes send the electricity forward to the heart, and hence it would make sense to place them as close to the heart as possible.
That is incorrect, because the electricity does not "know" it should go to the heart. Put another way: why are there two electrodes? The burst of electricity will flow from one to the other by multiple paths, and will "choose" preferentially the paths with the lowest resistance. Some paths go through the heart, others do not, and your job is to deliver the most of the electric burst to the heart.
If we make the assumption that a path's resistance is proportional to its length, if you place the two electrodes very close to each other, the path of least resistance will be very short compared to diving inside the body to reach the heart and back. If the electrodes are further apart, the detour is shorter, relatively speaking.
All the above is of course extremely simplified. First of all, electrical conductivity varies, probably by a huge factor, within the human body. Moreover, "resistance" should probably replaced by impendance because we are talking about a transient phenomenon. Finally, there might be medical reasons to target here rather than there that have little to do with the electricity. TigraanClick here to contact me 10:47, 8 December 2016 (UTC)
All things being equal, the bulk of the electricity will take the shortest path. And the skin can act as a barrier, such that electricity may be conducted along the sweat on the skin, instead of penetrating it. My Dad, who worked in medical electronics, had an invention idea of paddles with small tines that would penetrate the skin, similar to the tine test used for TB, to avoid this problem. Unfortunately, it hasn't caught on yet. StuRat (talk) 15:28, 8 December 2016 (UTC)

Sleeping positions[edit]

While lying in bed recently, I was wondering whether some sleeping positions are more preferred than others (e.g left side, right side, back, front)? Any statistics? In particular, I was reflecting on the fact that I generally prefer my left side over my right. Now this might just be habit, but I was wondering if there might be some advantage to sleeping on one side rather than the other. Since the heart and stomach are both somewhat to the left of center, maybe the left side improves circulation or reduces heart burn or something. I can't say I've ever really noticed a difference per se, but maybe I originally adopted the sleeping preference due to some small difference without really picking up on why. So, any stats on sleeping positions? Or perhaps physiological reasons why some positions might be better / more comfortable than others? Dragons flight (talk) 12:58, 8 December 2016 (UTC)

Read this. --Jayron32 13:03, 8 December 2016 (UTC)
I'd note that despite being a chest sleeper, I nearly always wake up either on my back or sideways. Perhaps subconsciously it's a natural way to get more oxygen (and give some space for occasional morning wood). In any case it's normal to change positions while sleeping. Just don't put your arms under the head or cheek as it will disrupt the bloodflow and nasty feelings will happen. Brandmeistertalk 13:58, 8 December 2016 (UTC)
Forgive me, but the first half of that linking sleeping positions to personality traits sounds like bad pseudoscience. Maybe the position statistics are correct, but I think I'd need a fairly large dose of peer review to be confident in anything presented with that introduction. Of course, even if accurate, it also doesn't address my right vs. left curiosity. Dragons flight (talk) 15:57, 8 December 2016 (UTC)
How about this one. --Jayron32 18:26, 8 December 2016 (UTC)
(EC). Does this help? Matt Deres (talk) 18:26, 8 December 2016 (UTC)
LOL, I have a few that aren't on any of these lists. There are two with one knee up - in one, the other foot rests against it forming a tetrahedron, and in the other the foot whose knee is up goes in front of the other leg with bent knee. Wnt (talk) 22:18, 8 December 2016 (UTC)

Star formation and Dark matter[edit]

It is said that dark matter can be affected by gravitational force. So during the formation of stars dark matter should also be accerted into them. So my question (doubt) is do stars contain dark matter?, if so why?, if they don't why?--G.Kiruthikan (talk) 14:31, 8 December 2016 (UTC)

The answer for any question you may have about dark matter is "we have no idea". Dark matter is a hypothetical explanation for a plethora of as-yet unexplained phenomena, dark matter has never been directly observed, its existence is likely, but only inferred from other observations, mostly that the observed velocities of distant objects is greater than would be expected from their measurable mass. The most common explanation is that the difference is caused by an undetectable mass which cannot otherwise be accounted for, which we call "dark matter". If we knew what it was, it wouldn't really be "dark matter" anymore, we'd just call it "matter" and describe it. Dark matter is name physicists use instead of unobtanium or some such, because that would sound silly, but otherwise, we don't know much about it, except what effects it has on the movement of large, distant objects (if it does exist and is indeed the cause of such phenomena). --Jayron32 14:40, 8 December 2016 (UTC)
As an addendum, just to show that physicists do have a bit of a sense of humor, competing theories of the source of dark matter go by names like Weakly interacting massive particles (WIMPs) and Massive compact halo object (MACHOs). --Jayron32 14:42, 8 December 2016 (UTC)
This is a good Q. If dark matter behaves the same way as ordinary mater, with respect to inertia and gravity, then wouldn't we expect a similar distribution ? But the proposed distribution of dark matter is more spread out, into large "halos" around galaxies. So, to me this suggests that dark matter may break the link between inertial mass and gravitational mass we see in ordinary matter. Specifically, it may have a higher inertial mass, making it move more slowly in response to the smaller gravitational pull it is subjected to. StuRat (talk) 15:38, 8 December 2016 (UTC)
Dark matter do "behaves the same way as ordinary mater, with respect to inertia and gravity" but because it is collisionless it spreads out in large halos. Ruslik_Zero 17:26, 8 December 2016 (UTC)
Right, even starting from similar initial distributions, you'd expect dark matter (of the WIMP variety) to have different final distributions, given it is basically a collisionless, frictionless, ideal gas, more or less. Someguy1221 (talk) 01:16, 9 December 2016 (UTC)
Here are a selection of research papers that discuss star formation and dark matter, they may provide some material of interest [26] [27] [28] [29]. SemanticMantis (talk) 17:10, 8 December 2016 (UTC)

Thank you for some great help. The thing that I can gather is that it has a different distribution. Someone please explain why it has a different distribution? And if it doesn't have any collisions there cannot be any charges (because it is the electrons that repel in collisions) or may be elactrons and protons (or charged particles like them) should lie in the same nucleus. Is my speculation theoretically right that dark matter may be electrons in the nucleus ? I think it may be right because nuclei like alpha can penetrate matter easily (Rutherford's gold sheet experiment). --G.Kiruthikan (talk) 10:15, 9 December 2016 (UTC)

You are right that dark matter particles have no electrical charge, or at least that is how they are usually modeled (no one has managed to detect one yet). Dark matter cannot be made of electrons and/or nuclear particles because even if the charges balanced, leaving it with a neutral charge, such a particle would still interact with electromagnetic fields. Also, alpha particles do not penetrate matter easily - they can in fact be stopped by a thick sheet of paper. In Rutherford's gold foil experiment, that foil was nanometers in thickness, and still managed to block a detectable number of alpha particles. The lack of interaction with ordinary matter would explain the different distribution of dark matter. Basically, there's nothing slowing it down. No collisions, no friction, no radiating energy by electromagnetism. They would in theory just go round and round the galaxy for billions of years quite happily. Someguy1221 (talk) 10:14, 9 December 2016 (UTC)
(admission: I don't know this well, caveat lector) Another issue is temperature: cold dark matter, for example, is apparently considered problematic because it ought to accrete into more dwarf galaxy objects then it does. There are dodges suggested there like fuzzy cold dark matter that is too light to exist in any one place much. Dark matter in general is used to postulate huge fuzzy spherical haloes in which galaxies are suspended, so the premise is that, mostly, it doesn't stay put in spiral arms let alone stars, and so even "cold" dark matter is really hot by our standards, like 5% the speed of light hot. Of course, the characteristics of the type of dark matter needed to make galaxies spin like record albums may not predict the characteristics of some other unknown type of dark matter... Wnt (talk) 12:17, 9 December 2016 (UTC)
OK boss. I accept that dark is now really dark indeed. I hope that we can 'light' it up some day. Things like no collisions, less interactions, lack of electro magnetism but with gravity, different distributions are parts of twilight for better understanding in future.--G.Kiruthikan (talk) 16:08, 9 December 2016 (UTC)

Are humans ever harmed by highways?[edit]

Other animals always die on the road as roadkill. Squirrels may run across the street, and then - BAM - a car strikes them. Are primitive human populations ever harmed by highways too? Maybe an advanced human population builds fancy roads and drives cars, while containing a group of primitive humans in a park. The group of primitive humans can't go anywhere and can't follow the migratory animals. If they do, then they have a high chance of getting hit by a car on the road. (talk) 17:33, 8 December 2016 (UTC)

I'm not sure about uncontacted peoples, but humans in modern urban USA are harmed by cars on highways all the time. In my current state of TX, we design things such that pedestrians have a very difficult and unsafe time. We killed two people with cars on Interstate 35 in Austin just this November [30] [31]. SemanticMantis (talk) 17:42, 8 December 2016 (UTC)
Have you heard of the Boulevard of Death? It averaged 2.5 dead pedestrians per mile per year in 1990. "The problem with Queens Boulevard is that everyone wants to get all the way across in one shot," said Mr. DePlasco. "We've been trying to teach people to be more patient, and cross half of it at a time.". It looks like a highway except usually 20+ intersections/mile and (in one part) 16 lanes, many elderly with canes, and not too far from Kowloon density (four subway tracks run under it or the neighborhood would be too dense to exist) Sagittarian Milky Way (talk) 21:20, 8 December 2016 (UTC)
Even the stupidest human is a lot smarter than the average squirrel. It's the difference between not knowing any better vs. not paying attention. ←Baseball Bugs What's up, Doc? carrots→ 17:51, 8 December 2016 (UTC)
It sounds like you're assuming that pedestrians are always at fault when they get killed by automobiles. That wold be a good example of victim blaming. Here in the USA, a pedestrian is killed about every two hours [32], and in my area, we are among the best in the nation at killing pedestrians with cars [33]. Maybe you're comfortable assuming that they were all "not paying attention", but I'm not. SemanticMantis (talk) 17:58, 8 December 2016 (UTC)
No, it could be the driver who wasn't paying attention. Or it could be both. ←Baseball Bugs What's up, Doc? carrots→ 18:00, 8 December 2016 (UTC)
Fairly sure the OP was referring to cars driven by humans, not squirrels. Nil Einne (talk) 15:15, 9 December 2016 (UTC)
In my experience, there is considerable overlap between the smartest squirrels and the stupidest humans.[ Citation Needed ] --Guy Macon (talk) 17:04, 9 December 2016 (UTC)
Could you specify what you mean by advanced and primitive humans? Those terms don't have any meaning in non-racist anthropology or sociology. I have to assume good faith that you're not a neo-Nazi, so I'm left perplexed by your terminology. Matt Deres (talk) 18:29, 8 December 2016 (UTC)
Primitive is still a common vernacular term. How is it derogatory?--Aspro (talk) 19:28, 8 December 2016 (UTC)
The difference between squirrels and "primitive humans" is that the humans, however "backward" their culture, very quickly learn from observation and from each other that highways are dangerous, just as children do in "advanced" cultures. Squirrels continue to scurry along roads in front of vehicles, apparently thinking that they can outrun them even when they observe squashed squirrel on the road. Dbfirs 21:33, 8 December 2016 (UTC)
I bet if some New York City pedestrians set spears and slew the oncoming beasts, they might make their roads as safe as roads in the jungle. :) (no, really, I don't know the statistics... feel like it could go either way though!) Wnt (talk) 22:22, 8 December 2016 (UTC)
You might want to look up road building in the Andaman Islands. -- zzuuzz (talk) 22:06, 8 December 2016 (UTC)

Comment There are several statements in this thread about the behaviour and cognition of squirrels, all of which totally unreferenced. This is a science reference desk - such statements should be supportable by RS. DrChrissy (talk) 22:39, 8 December 2016 (UTC)

Yes, apologies to all the red squirrels that I see squashed on the road. Perhaps they all deliberately committed suicide? Apologies to all readers for my WP:original research. Dbfirs 23:15, 8 December 2016 (UTC)
The premise is ludicrous that "an advanced human population builds fancy roads and drives cars, while containing a group of primitive humans in a park. The group of primitive humans can't go anywhere and can't follow the migratory animals. If they do, then they have a high chance of getting hit by a car on the road." No human is considered an animal. There are no "primitive humans". The question is nonsensical. Bus stop (talk) 23:26, 8 December 2016 (UTC)
The last time I looked at taxonomy, humans ARE considered to be animals. DrChrissy (talk) 23:39, 8 December 2016 (UTC)
We regard all humans differently than we regard all animals. There are no "primitive" humans. The word can be used figuratively only. Bus stop (talk) 23:46, 8 December 2016 (UTC)
Previously, you used the word "considered". I, and I suspect 99.99% of other biologists consider humans to be animals. Please note, I have not used the word "primitive". DrChrissy (talk) 23:55, 8 December 2016 (UTC)
Animals are forms of life. Humans are forms of life. Humans are animals. But humans are distinct from other forms of life and other animals. This could change. We can entertain ideas of forms of life elsewhere in the universe that we would have to regard as equal to ourselves in their humanness. But on the planet Earth we regard no other form of life as human except for humans. I know you didn't use the word primitive. And my response is not just based on the use of the word primitive. It is a word and it encapsulates my objection to the initial post. But the rest of the post implies a differentiation between one population and another: the highway builders on the one hand and those who are more primitive and follow migratory animals and might, in their particular stupidity, get hit by cars, on the other hand. This postulated scenario contradicts the actual relationship between humans and other forms of life on Earth. Bus stop (talk) 00:15, 9 December 2016 (UTC)
Thanks for this. I think we are in agreement that humans are animals. I will let others comment on other aspects of this thread. DrChrissy (talk) 00:46, 9 December 2016 (UTC)
Especially the ones with PhDs who dress fashionably and are connoisseurs of fine wine and especially the aficionados of current cultural entities and who have bank accounts containing enormous quantities of disposable income—they are really animals. Bus stop (talk) 01:42, 9 December 2016 (UTC)
The premise isn't that ludicrous. It could be a home for folks with Alzheimer disease, or a very good frat party. Wnt (talk) 12:21, 9 December 2016 (UTC)

Humans are harmed by highways (or roads as we Brits call them) in many ways other than being hit by cars. For example, living near a busy road exposes humans to pollution contributing to respiratory problems such as asthma. Living by a road can also be a source of noise pollution, which can in turn interfere with sleep and increase blood pressure. — Preceding unsigned comment added by (talk) 13:03, 9 December 2016 (UTC)

Only the section heading asks "Are humans ever harmed by highways?" The body of the text posits a question predicated on the notion that primitive humans, contained in a park, can't follow migratory animals without crossing highways. This is ludicrous firstly because there are no primitive humans. Secondly no humans are contained in a park. The question posits that some humans are not human. Now, it might be that some humans are not regarded as human, but that is highly problematical and the entire scenario of the question is completely asinine. Bus stop (talk) 13:37, 9 December 2016 (UTC)
That is a somewhat charitable description of The Village (2004 film), which is one of M. Night Shyamalan's better efforts. Wnt (talk) 13:42, 9 December 2016 (UTC)

Turing test considerations[edit]

In Turing test are there any problems with asking simple questions like "What's your hair color" or "Which person do you find attractive and why?" and/or more complex ethical/moral or judgemental open-ended questions? For instance, "in a disaster would you save the child or the dog in distress first and why?" Is it assumed that the machine can give false answers like "My hair color is black" or refuse to answer ("I don't know", "I don't want to tell", etc.)? As a side note, our article is a bit ambiguous. According to it, Turing asked "Can machines think?", so presumably the point of the test is not to determine whether one is chatting with a machine or not, but to determine its ability to think on its own. Brandmeistertalk 17:52, 8 December 2016 (UTC)

Near as I can tell, that's not quite it - it's to gauge whether the entity you're conversing with is distinguishable from a human, or not. ←Baseball Bugs What's up, Doc? carrots→ 17:57, 8 December 2016 (UTC)
The Turing test is not a set of questions, or even a style of questioning. It's a means by which to assess sentience; the idea being that sentience (and in general, other issues related to the Hard problem of consciousness) is not something which can be assessed except by other sentient beings. Just as Justice Potter Stewart once said of obscenity "I know it when I see it", the test for sentience is "Can another sentient being tell the difference". If a machine can interact with humans and those humans can't tell they are talking to a machine, the machine can (for all intents and purposes) be described as sentient. Philosophically, the Turing test is of the school of behaviorism, which holds that the only thing you can study about something is its behavior. If it isn't observable, it isn't testable. The Turing test sets out to qualitatively assess if a machine behaves sentient. If it does so behave, then we must say that it is. Also, the person who assesses the Turing test is not the person interacting with the machine. The assessor is a third-party evaluator: If I read a text conversation between, say, Jane and John, and I know that one is a machine, can I reliably pick out the machine from just the text of the conversations. The conversation is supposed to be structured as natural as possible, and not merely be a script of questions.--Jayron32 18:20, 8 December 2016 (UTC)
The Turing test can demonstrate that something appears to be sentient. But that does not logically lead to the conclusion that it actually is sentient. ←Baseball Bugs What's up, Doc? carrots→ 18:30, 8 December 2016 (UTC)
See Behaviorism and more to the point Experimental analysis of behavior. If you can't measure it, it doesn't exist. If it behaves as sentient as you are, then it is. --Jayron32 19:10, 8 December 2016 (UTC)
This is the kind of reasoning that ancient peoples used to conclude that natural phenomena are "alive". ←Baseball Bugs What's up, Doc? carrots→ 19:16, 8 December 2016 (UTC)
What is your alternate method of proving a phenomenon is happening if it cannot be observed or measured? If something exists, it can be measured. If it cannot be measured, it does not exist. What is your proof of sentience? --Jayron32 19:18, 8 December 2016 (UTC)
It's most likely the constant failure to rationalize a particular decision in a series of open-ended questions during conversation. If a machine repeatedly fails to offer either human or better-than-human solutions to moral and judgemental open-ended questions, then it's not sentient. If it does not, then it's sentient. Brandmeistertalk 19:41, 8 December 2016 (UTC)
Actually, the biggest problem right now is the AI-hard problem of natural language processing; which is mostly about deriving context clues from conversations based on assumed shared life experiences. Morality is still a set of rules, and machines can be made to learn the rules, or to develop their own morality from interactions with others (i.e. infer rules from observation, as most humans do). These issues are noted at the article I cited below. --Jayron32 20:11, 8 December 2016 (UTC)
Is there any similar test that, like the Turing test, tries to assess being sentient, but that's based on a non-behaviorist framework? Many cognitive scientist are not behaviorists, and would like to test it through different means.Llaanngg (talk) 18:37, 8 December 2016 (UTC)
There are things like the Hutter Prize which is based around the notion of AI-completeness and Natural language understanding, the idea being that data compression is a reasonable analogue for artificial intelligence. --Jayron32 19:17, 8 December 2016 (UTC)
I'm prone to apply the Turing test in unusual ways. Like, if you're in a room full of people who despise you but none of them says anything obviously hostile, they pass the Turing test for liking you, hence they like you. If someone reels off a line of pseudoscientific crap about his brilliant new perpetual motion machine and you can't see it's wrong, it passes the Turing test for physics, hence it's valid physics... :) Wnt (talk) 19:23, 8 December 2016 (UTC)
Yes, so if we are assessing sentience or are about "to gauge whether the entity you're conversing with is distinguishable from a human", then again what's wrong with asking open-ended questions that are germane to humans? Our article states that it's "a test... of a machine's ability to exhibit intelligent behaviour equivalent to, or indistinguishable from, that of a human". Since per article the evaluator "would judge natural language conversations", he/she might identify the machine answers as easily as the one who asks those open-ended moral or subjective human-centered questions. The evaluator may looks into machine's answers and figure out for himself/herself. Brandmeistertalk 19:23, 8 December 2016 (UTC)
You can ask anything and the computer is allowed to say anything. The way I interpret the test, you should try to determine whether or not you are talking to a normal, cooperative human. "Normal" for example means not insane or retarded, and "cooperative" for example means willing to give honest answers to questions humans wouldn't usually be unwilling to try to answer. For example, if you ask "Would you rather be sick or healthy?" then a human should probably be assumed to say healthy. If the answer is "Sick", "I don't know", "I don't want to tell", or something evasive like "That's an interesting question", "That's a silly question", "What do you think?", "Why do you want to know?" or "How about yourself?", then a computer will probably be judged to have failed the test, even though some humans would also give such responses. PrimeHunter (talk) 19:55, 8 December 2016 (UTC)
That's the kind of questions I was interested in. I thought that specifically human questions like the aforementioned "What's your hair color", "Which person do you find attractive and why?" and similar open-ended questions is a much simpler way to test the machine than complex scenario designed by Turing himself or others. Brandmeistertalk 22:24, 8 December 2016 (UTC)
What people perceive and what is real are not necessarily the same thing. I could argue that the little fortune-telling machine in that one episode of The Twilight Zone passes the Turing Test, because people are reacting to it as if it were a conscious being. They're thinking it is, doesn't make it so. ←Baseball Bugs What's up, Doc? carrots→ 22:49, 8 December 2016 (UTC)
You could argue it. You'd be wrong. But you could certainly make your mouth say those exact words. Saying words doesn't make them correct, you know. --Jayron32 01:30, 9 December 2016 (UTC)
What's your basis for arguing against the fortune-telling machine passing the Turing Test? ←Baseball Bugs What's up, Doc? carrots→ 03:04, 9 December 2016 (UTC)
Do you have a reliable source that shows the results of someone doing so? If you don't, there's a concept called the null hypothesis which basically says that unless you have actual positive results from an actual time someone did something, then it isn't valid to say a concept is confirmed. It's always the person proposing a statement like "a fortune telling machine would pass the Turing test" to provide the evidence that it is true. You cannot just make statements at random and then demand that the world prove you wrong... The burden of proof lies with the person who is making the positive assertion. --Jayron32 09:51, 9 December 2016 (UTC)
Are you aware of anything that has actually passed the Turing Test? ←Baseball Bugs What's up, Doc? carrots→ 11:51, 9 December 2016 (UTC)
No, I am not aware of one that has. Turing test#Predictions notes when people have guessed a computer WOULD pass it, but they have to keep nudging their estimates upwards. --Jayron32 13:34, 9 December 2016 (UTC)
Here are some Dilbert strips that reference the Turing Test idea.[34]Baseball Bugs What's up, Doc? carrots→ 03:25, 9 December 2016 (UTC)
  • I should note that my responses above to Bugs's misunderstanding of the Turing test are not meant in no way to imply that I am endorsing those answers as reality. That is, in the sense that I believe that the Turing test would be able to prove that computers could think in the way that humans can think. I was merely presenting information that already exists about what the Turing Test is and what it is based on (that's why it is so frustrating to be argued with, as though I had invented it, or that I could un-invent it by merely being convinced strenuously by those who disagree with it). I have not agreed with the Turing test (and in saying that, I am also not DISAGREEING with it); indeed my state of mind on the matter is open and I'm not really looking to be "convinced" to believe anything about it one way or the other; convincing me it is bullshit is useless, because I don't believe it to not be bullshit (and in saying that, I also don't believe it to be bullshit. I don't believe anything about it at all). Indeed my belief about its validity is unimportant, I am merely serving as a conduit to explain how it works. In the interest of providing information about other perspectives on artificial intelligence (and in providing this information, I am also not endorsing it anymore than I am endorsing what I have already presented about the other side), one should also read up on John Searle's Chinese room argument, which is perhaps the best known, and best articulated, refutation of the behaviorist approach by the Turing Test. @Llaanngg: asked above about such non-behaviorist responses to the Turing test, and that's a good place to start research on it. --Jayron32 15:21, 9 December 2016 (UTC)
How to tell if a computer is "sentient"? Pull out the plug! (talk) 16:34, 9 December 2016 (UTC)
The point in the Dilbert panels is to show a robot passing the Turing Test while the real humans fail it. ←Baseball Bugs What's up, Doc? carrots→ 17:11, 9 December 2016 (UTC)

Apollo machete[edit]

Why did the designers of the Apollo command module suppose that the astronauts might need a machete? I'm not aware of any jungles on the moon (or at their landing in the ocean). SpinningSpark 21:11, 8 December 2016 (UTC)

When you splash down back on Earth you might need to cut parachute cords and whatnot. (talk) 21:28, 8 December 2016 (UTC)
They were going to the Moon which stays within +/-28 point something degrees declination (sky equivalent of latitude from equator). So that an emergency landing in an unplanned place might be in Earth's tropics is not far fetched. This may have been a consideration. Sagittarian Milky Way (talk) 21:40, 8 December 2016 (UTC)
According to every website I can find, these machetes were meant for jungle use, in case that's where the module landed. And the design allowed them to double as a prying tool if that was needed for whatever reason. However, I haven't been able to find any official documentation for why NASA commissioned these knives, so I'm not entirely sure where these sites got their information. The Smithsonian Institute apparently gives lectures on "space knives", but I haven't found a video or transcript available online. Someguy1221 (talk) 21:46, 8 December 2016 (UTC)
I'm not sure if it is good for prying. I read "Although the machete has yet to be needed on a mission, it has proved to be a very useful item during the training exercises. The blade is of high-quality stainless steel, but is brittle and will break if used for prying. A more desirable material for the blade should be considered for further development."[35] Bus stop (talk) 02:06, 9 December 2016 (UTC)
The claim is that the prying would be done with the ricasso, rather than inserting the point into something and then putting pressure on the handle. That should minimize the chance of breaking. But the geometry then would only make it possible to pry things by the corner... If they were already giving astronauts a 17 machete, presumably they also could have given them a proper prying tool if they thought it was necessary. Someguy1221 (talk) 02:51, 9 December 2016 (UTC)
Considering the Apollo astronauts were trained in jungle survival, it makes sense to give them tools for surviving in such an environment. WegianWarrior (talk) 21:50, 8 December 2016 (UTC)
Nothing to add except I found this picture of the full "Survival Kit #1" mentioned in the first link. Alansplodge (talk) 22:31, 8 December 2016 (UTC)
Bingo! "The survival kit is designed to provide a 48-hour postlanding (water or land) survival capability for three crewmen between 40 degrees North and South latitudes". From Apollo 11 Lunar Landing Mission Press Kit (page 135). Alansplodge (talk) 22:39, 8 December 2016 (UTC)
Slightly related, you might find TP-82 interesting. Vespine (talk) 23:27, 8 December 2016 (UTC)
So if it came to a fight, cosmonauts would beat astronauts! SpinningSpark 00:17, 9 December 2016 (UTC)
And they could use the knives if they got into a fight with aliens on the Moon. Bubba73 You talkin' to me? 01:41, 9 December 2016 (UTC)
They were for survival if they had to make an emergency landing away from the landing zones. See this. Bubba73 You talkin' to me? 23:36, 8 December 2016 (UTC)

Today, the main webpage at published a set of historical images of John Glenn... usually, like most pilots, he looked pretty sharp with those aviator sunglasses and closely cut hair - but there were also a few photos that you might not have seen before, showing him and his fellow astronauts looking pretty scruffy:
  • The Original Mercury Seven During Survival Training, at Stead Air Force Base (now Reno Stead Airport, home of the Air Races). "Portions of their clothing have been fashioned from parachute material, and all have grown beards from their time in the wilderness." We've all been there!
  • Survival Training: "Some of NASA's sixteen astronauts participate in tropic survival training from June 3, through June 6, 1963, at Albrook Air Force Base, Canal Zone"
One thing to remember is that spaceships (and jet airplanes, for that matter) fly very fast. In a slow airplane, you can get miles beyond the edge of human civilization in just a few seconds. If you have to bail, you may bail into a place where there are no roads, no lights, no help. In a jet, you might be tens of miles from help after flying for just a few seconds.
In a spaceship, you can easily end up a few hundred miles off course. You might end up in a different time and climate zone than your rescuers. NASA prepared astronauts to survive.
Here's NASA Tech Note TN D-6737: Apollo Experience Report - Crew Provisions and Equipment Subsystem (1972). Page 30 describes the infamous machete. Although the machete has yet to be needed on a mission, it has proved to be a very useful item during the training exercises.
If you should ever find yourself a few miles from help, you might wish you had a machete among your equipment. It's a generally useful tool. At the very least, you can use it to shave.
When you travel in space, you've gotta be prepared to land in sand or snow, oceans or deserts or forests or mountains or foreign lands... Earth is a strange and mysterious place!
Nimur (talk) 23:46, 8 December 2016 (UTC)
Scott Carpenter in Mercury-Atlas 7 overshot the landing site by 250 miles. Bubba73 You talkin' to me? 00:14, 9 December 2016 (UTC)
Considering the Earth's circumference is 25,000 miles, and he's basically aiming an unnavigable hunk of metal at it from a few hundred miles above the earth and coming within about 1% of his target. That's pretty freaking good, if you ask me... --Jayron32 01:26, 9 December 2016 (UTC)

December 9[edit]

How many levels of carbons are there in isoleucine?[edit]

I watched this video where the woman explains (16:20) that the Leucine has carbon alpha, beta, gamma and delta 1(D1) & delta 2 (D2). She jumped on the description of the levels of carbons of ISOleucine. Can I say that it has 4 levels of carbons in the following order: carbon alpha, beta, carbon gamma 1 (G1), carbon gamma 2 (G2) and carbon delta? (we never count the carbons of basic amino acid structure i.e carboxylic group, we start to count carbons from the alpha carbons) (talk) 04:06, 9 December 2016 (UTC)

Sure, that's a reasonable description of isoleucine following the pattern of the given leucene example. DMacks (talk) 06:01, 9 December 2016 (UTC)
Yes. I should say though that it is rare for people to keep track of gamma and delta carbons in this way: instead, the main chain is simply numbered per IUPAC and side chains are described simply as methyl groups. On the other hand, I should mention that an alpha carbon is not limited to amino acids or the context of biochemistry, as it is of very great importance to organic chemistry. For example, acetone is (very) mildly acidic because the alpha carbons (on either end) can potentially release a proton and become double bonded to the central carbon leaving a negative charge on the oxygen (an enolate), and this conjugate base is then a potent nucleophile and could serve as a donor in an aldol condensation or many other reactions.
I should add that her approach on the delta carbons seems old-fashioned, as does the old usage of the term "imino acid" I noticed while flipping forward at 13:24 - see [36] where I was given a correction on that point. But I haven't watched any substantial portion overall. Wnt (talk) 13:54, 9 December 2016 (UTC)
Indeed, I have to agree with Wnt's assessment here on the use of Greek letters as a means of identifying carbons. In actual practice, it is rare to use any convention beyond its usefulness. Yes, one COULD assign Greek letters to every carbon in a molecule, but I have rarely (if every) encountered anyone using a letter passed beta, never mind delta. There just isn't any useful reason to do so. If you need to indicate carbons at other places in the chain, there's a perfectly useful system (the IUPAC systematic name) to do so. You'll notice that the Wikipedia article is titled alpha and beta carbon; it's just weird among chemists to get much beyond that. --Jayron32 15:29, 9 December 2016 (UTC)
Thank you all, I learnt from you a lot of information - you are really amazing with your knowledge and also patient to explain to dummies like me. Thank you again! (talk) 16:59, 9 December 2016 (UTC)
@Jayron32, BTW you wrote that if I need to indicate carbons at other places in the chain, there's a perfectly useful system. It's very interesting for me to what is this way. I entered the link that you put and I didn't found myself there because it's a huge page. May you focus me please? (talk) 16:59, 9 December 2016 (UTC)
Sure. The IUPAC rules work thusly 1) Identify the longest chain of carbons, use the alkane of that length as the base chain. 2) Number that chain from one end, such that the substituent groups (i.e. branches and heteroatoms not on the main chain) have the lowest possible numbers 3) Number and name the substituents as prefixes and suffixes on the base alkane. Under IUPAC rules, leucine is "2-Amino-4-methylpentanoic acid" The longest chain is five carbons. That's pentane Since the carboxylic acid is there (pentanoic acid), that's on the end, so that is carbon "1" in our chain. Numbering the other 5 going out from there there's an NH3 group on carbon 2 and a CH3 group on carbon 4. Most of the biological amino acids are "2-amino carboxylic acids" under IUPAC rules; alanine is 2-Aminopropanoic acid (a three carbon chain is propane), cysteine is like 2-amino-3-mercaptopropanoic acid, etc. --Jayron32 20:59, 9 December 2016 (UTC)
Our main article on this naming process is IUPAC nomenclature of organic chemistry. It walks through the process Jayron32 notes, of finding the parent (longest chain), identifying the various substituents and other functional groups, and then stringing the words together to describe which groups are where on the parent. DMacks (talk) 21:04, 9 December 2016 (UTC)
FYI, I already linked that. He read it and got lost in the TLDR nature of the article. That's why I simplified it. --Jayron32 21:12, 9 December 2016 (UTC)
Also, I should note, that the connection between IUPAC and the alpha/beta system is not consistent. For the alpha/beta system, the carbon that is part of the carboxyl group is not considered part of the carbon chain, so one calls the next carbon over the alpha. For IUPAC, that means that in amino acids, alpha is always carbon 2. However, in something like an alcohol (like say 1-Pentanol) the alpha carbon is the one attached to the hydroxy group, so in that case alpha = 1. Thus, if you did a lithium aluminum hydride reduction of your leucine and turned the carboxyl group into a hydroxy group, like this, you'd go from "alpha-amino-carboxylic acid" to a "beta-amino-alcohol". That sounds like the amino moved. But with the IUPAC system, you'd go from a "2-amino-carboxylic acid" to a "2-amino-alcohol". Much simpler and more consistent. --Jayron32 21:12, 9 December 2016 (UTC)
To paraphrase my engineering friends, "the great thing about systematic methods is that there are so many systems to choose from". DMacks (talk) 21:19, 9 December 2016 (UTC)
Thank you. btw, regarding to methionine according to the method of this woman, can we say that the carbon of methyl group which is attached to the sulfur- is delta carbon or it's correct to say that since it's attached to the sulfur then the counting of the carbons is stopped? (talk) 01:11, 10 December 2016 (UTC)
The later letters in the alphabet do linger on in some old names, most famously, "gamma-hydroxybutyrate" (GHB, an undesirable variant of alcohol that had a brief fad popularity as a party drug and subsequently was vilified and highly prohibited as a so-called rape drug) Wnt (talk) 17:02, 9 December 2016 (UTC)
up through gamma/delta or so, maybe one or two more, are still commonly used in some areas for lactones (to describe the ringsize or reaction that forms it, not to name the whole molecule). And gamma is also used when discussing deprotonation of enones and related structures (for example doi:10.1002/ejoc.200500145). DMacks (talk) 20:28, 9 December 2016 (UTC)
Yeah, there's a few. But not many. They're the exception rather than the rule. --Jayron32 20:59, 9 December 2016 (UTC)

Predicting solar eclipses[edit]

When was the first solar eclipse predicted reliably? Google found me some potential answers, e.g. [37] and Eclipse of Thales. But now I'm left wondering: when was it first possible to predict the specific minutes of the eclipse, whether minutes of totality or minutes of partiality, for a specific location? Who first achieved this, and where in the world? Nyttend (talk) 05:43, 9 December 2016 (UTC)

Solar eclipse of May 3, 1715. Count Iblis (talk) 06:08, 9 December 2016 (UTC)
See also here. Count Iblis (talk) 06:13, 9 December 2016 (UTC)
(ec)Our article mentions Edmund Halley, but his fairly accurate prediction was apparenty preceded by that of William Whiston. According to this Guardian article:

Flamsteed's lunar tables were later used by William Whiston and, corrected with Newtonian theory, used to produce another predictive eclipse map, also published by Senex in March 1715. Whiston’s text was more technical than Halley’s and his map less immediately appealing to “The Inquisitive” he called on to help observe, but he seems to have got there first (and twice).

Halley's first map (Low-res)
Whiston's map (3mb)
Halley's second map, corrected and with prediction for the next eclipse (6mb)
How accurate Flamsteed's tables, Whiston's map or Halley's second map were, I do not know.
ps. Actually, looking at Whiston's map, he says So that the Middle of the General Eclipse in common or apparent Time will be 50' 56″ after nine in the Morning, differing from Dr Halley's Computation near 9 min. So maybe the Grauniad is wrong and Halley did get there first?
pps. Have updated our article on the Solar eclipse of May 3, 1715 to mention Whiston.
ppps. A better source for the Halley/Whiston predictions here
pppps. As to the first good prediction of length of totality, that may be for the next eclipse in May 22, 1724. Halley notes in his map: The Curious are desired to Observe it, and especially the duration of the Total Darkness, with all the care they can; for therby the Situation and dimensions of the Shadow will be nicely determin'd; and by means thereof, we may be enabled to Predict the like Appearances for the future, to a greater degree of certainty than can be pretended to at present, for want of such Observations. --Hillbillyholiday talk 07:27, 9 December 2016 (UTC)
After further research I found that Philippe de La Hire invented an eclipse calculator in 1704, with which (according to this less-than convincing site) he may have predicted the May 1706 eclipse to within 1' 30″. I can't find any other source that confirms this, but it seems that reasonably accurate predictions were possible by then. Apparently Jean Le Fèvre was better than La Hire at predicting eclipses (link), but I can't find any solid proof of this either. Also here is a pdf with predictive maps by Symon van de Moolen (nl) (1705) and Andreas van Luchtenburg (nl) (1706). The first known predictive eclipse map is Erhard Weigel's 1654 map, which was 100km off (Celestial Shadows: Eclipses, Transits, and Occultations a good overview of the subject). Perhaps an article on Eclipse prediction is in order using some material already here?
The historical improvements in measuring lunar longitude relate to the potential accuracy of predictions: In 1474 Regiomontanus was 1.3° off, twice as good as Ptolemy, but by c.1630 Horrocks had reached 12', a 6.5x improvement on Regiomontanus. By 1702 Newton got to within 7', by 1753 Mayer had 1.5', and by 1787 Mason had 6″, a 15x improvement on Mayer giving an error in the shadow-path axis of roughly 5km on the ground. --Hillbillyholiday talk 12:13, 9 December 2016 (UTC)
It would appear that solar eclipse prediction is not yet entirely exact, at least in terms of time of day predictions for 2500 years ago - ancient documents indicated times that are off from about 7 hours from what was expected based on tidal slowing of the Earth's rotation, due presumably to changes since the end of the last major glaciation... just saw this news story [38] citing [39] Wnt (talk) 20:24, 9 December 2016 (UTC)
Erm, sorry, I mean from what is expected; I meant that the current predictions of past eclipses turn out to be wrong by seven hours as indicated by checking ancient documents. Wnt (talk) 21:03, 9 December 2016 (UTC)
You can also consider the most dominant perturbations of the lunar orbit due to Jupiter which would have been impossible to take into account without using classical mechanics developed by Newton (the influence of the Sun is much larger but this was effectively taken into account by empirical formulas). Jupiter causes a perturbation of the position of Moon during one orbit of the order of 1 km. This means that the shadow of the Moon on the Earth will shift by a distance of the order of a kilometer due to Jupiter. Count Iblis (talk) 20:39, 9 December 2016 (UTC)
Long term predictions of of the movements of ANY bodies in the solar system are impossible. It is an n-body problem, and for the number of moving parts in the solar system, it can't be done. After several thousands of years, you're going to become progressively further and further afield of your predictions even if you could take into account all of the various effects. --Jayron32 20:47, 9 December 2016 (UTC)

What do speculation of raw materials?[edit]

What was Brenda wearing?[edit]

People ask medical questions here, and these can be answered under limited circumstances. My goal is to improve the inadequate article Hospital gown, though I haven't had a lot of luck. This would represent a case where someone is wearing something different from a hospital gown (maybe) which, given a proper source, would be useful information to add to the article. There are situations where a hospital gown would be necessary, and others where it wouldn't or one would wear something different. I feel this idea is something useful for the article. In the case of Brenda, a character on Beverly Hills, 90210 (played by Shannen Doherty who had breast cancer for real years later) there was a breast cancer scare which required a biopsy. I did some research on what someone would wear for a biopsy, and while every source indicated one would wear a hospital gown (though they didn't necessarily say how the breast is uncovered for the biopsy), Brenda was covered by a sheet and we could see her head and shoulders, but nothing covering her shoulders, as if she was in bed with a guy.— Vchimpanzee • talk • contributions • 17:39, 9 December 2016 (UTC)

Even if you found out what someone normally would wear for a biopsy, adding such info to the article would be "original research". Also, how does having bare shoulders in a hospital bed equate to having a bed-partner? ←Baseball Bugs What's up, Doc? carrots→ 17:45, 9 December 2016 (UTC)
It doesn't. I was just making the point that it happened all the time on that show. I was trying to find actual sources that would improve the article. I thought maybe someone could point me in the right direction because I'm not having much luck.— Vchimpanzee • talk • contributions • 17:55, 9 December 2016 (UTC)
You would need to find a source that explains why she was depicted bare-shouldered instead of wearing a hospital gown. That could be a challenge. ←Baseball Bugs What's up, Doc? carrots→ 17:59, 9 December 2016 (UTC)
I guess what I'm looking for is a source that explains why the show would have depicted her not wearing a gown, based on the reality of what might actually be done. I was hoping to find someone who might speculate rather than give a specific answer, but would know of a source which might lead to the information I need for the article. — Vchimpanzee • talk • contributions • 18:25, 9 December 2016 (UTC)
A nursing textbook might work for improving the Wikipedia article. I had been looking at online journals and not finding much. I go to several libraries at colleges that have nursing programs.— Vchimpanzee • talk • contributions • 18:56, 9 December 2016 (UTC)
Again, trying to add something about what you think she "should have been" wearing amounts to original research and probably won't be allowed. And keep in mind that the show is fictional, so there's no reason to expect it to conform to some sort of real-world routine. ←Baseball Bugs What's up, Doc? carrots→ 19:43, 9 December 2016 (UTC)
I can't really picture complaining about any inaccuracy that left more of her exposed to the viewer, and it is definitely not important enough to mention in an article about hospital gowns in general. You're pushing relevance just to include it in an article about that episode of the TV series, if we have one (and I wouldn't be surprised...) Wnt (talk) 20:27, 9 December 2016 (UTC)
I think everyone is interpreting my question backwards. This isn't about Brenda, but whether it represents reality, and only reality would be relevant to the article. I'll follow up if I get answers, but I think everyone is too focused on Wikipedia here. If I got the answer about Brenda, I might be able to use that to find the relevant information for Wikipedia later.— Vchimpanzee • talk • contributions • 20:33, 9 December 2016 (UTC)
I'm still failing to see how knowing what specific garment ANYONE would wear for a biopsy (even if we COULD find a reliable source) is something that belongs in an encyclopedia article. Just because it's true, and EVEN if it is verifiable, doesn't mean we should write it. What are you trying to do with this information (if we can find it for you). --Jayron32 20:44, 9 December 2016 (UTC)
I'm not sure at this point. It sounds like my theory on how to improve the article is not being accepted.— Vchimpanzee • talk • contributions • 20:53, 9 December 2016 (UTC)
I'm sure that a misplaced sense of modesty does kill a few cancer patients each year, so if we could provide some reassurance that a breast biopsy does not mean having fifty medical students standing around taking selfies and Vine videos with your bare bosoms there is a small but non-zero chance it could save a life. So I won't say useless, exactly. But without a source beyond a TV episode, obviously we're not getting there. Wnt (talk) 21:00, 9 December 2016 (UTC)
See, it's not the TV episode that's the source. I was hoping to find a web site or possibly someone who knew something here, which would lead to a real source and something concrete for the article. I think Wnt is getting there.— Vchimpanzee • talk • contributions • 21:02, 9 December 2016 (UTC)

I think people are being too hard on this question. If there are indeed different types of hospital gowns worn for specific procedures, that would definitely be relevant to the Wikipedia article on the subject. Someguy1221 (talk) 21:47, 9 December 2016 (UTC)

Men taking a pregnancy test[edit]

I read that if a man takes a pregnancy test and it tests positive (meaning pregnant) that the man very likely has early stages of testicular cancer. Is this well substantiated among medical science communities? (talk) 01:10, 10 December 2016 (UTC)

[40]. --Jayron32 01:36, 10 December 2016 (UTC)
In your link jayron it says "Primary pulmonary choriocarcinoma is an extremely rare tumor in men, with 13 cases reported in the literature." Does this mean that men using urine pregnancy tests can only test for this specific condition? there have only been 13 reported cases? (talk) 01:41, 10 December 2016 (UTC)
I don't know what it means. --Jayron32 01:46, 10 December 2016 (UTC)

The positive result on the pregnancy test is caused by expression of human chorionic gonadotropin by some cancers of testicular origins, and this is frequently the hormone that pregnancy tests are reactive to. There is more than one type of testicular cancer, and the one that most commonly produces this hormone only does so in about half of cases ("mixed germ cell tumor"). Some types of testicular cancer appear to never produce this hormone. There are also several varieties of this hormone - a given pregnancy test may be sensitive to one, several, or none. HCG does have some predictive power in staging and prognosis of testicular cancer [41]. Someguy1221 (talk) 01:51, 10 December 2016 (UTC)

In what way teachers in academy used to draw the signs of skeletal structures?[edit]

Many of the molecules in biochemistry (bio-molecules) have special signs such as: dashed lines, bold-wedged lines, solid lines, wavy lines, dotted lines or arrows - all of them about the 3D directions or the condition of the bindings. Anyway my question is if in academy teachers used to draw it (while drawing and explaining on blackboard) in way that we see on books & wikipedia illustrations (see here example of isoleucine with bold-line and wavy line) or there is another practical way to denote these things/symbols? (personally I didn't find it that easy to draw those signs when I have to draw man molecules, it takes a lot of time to deal with it and I suspect that normally teachers also don't do that, but maybe I'm mistaken)

L-Isoleucin - L-Isoleucine.svg (talk) 01:36, 10 December 2016 (UTC)

I (as a high school chemistry teacher) do, as does every instructor at every level I have ever known. You could also look at the Journal of Chemical Education, the primary peer-reviewed journal for chemistry education, which also uses it extensively. --Jayron32 01:38, 10 December 2016 (UTC)
So when you use whiteboard do you draw these lines as the are drawn in the book? (what did you tell me to check in the link? I found that it's a name of printed journal, it's not handwriting if I'm not mistaken) (talk) 02:23, 10 December 2016 (UTC)