Wikipedia:Reference desk/Archives/Science/2013 May 28

= May 28 =

What's New by Bob Park
Does anyone know what has happened to What's New by Bob Park? It used to come out weekly, but the last issue was nearly 3 months ago. Bubba73 You talkin' to me? 02:57, 28 May 2013 (UTC)


 * You could always email him and ask. Btw, this year's issues have been nothing like weekly.  Only 4 in the first 5 months.  --   Jack of Oz   [Talk]  08:29, 28 May 2013 (UTC)


 * I didn't want to bother him - he may be very sick or something. Bubba73 You talkin' to me? 14:11, 28 May 2013 (UTC)

Self-contamination possible? Trying to understand bathroom germ contamination and how it works
I obviously know that washing your hands thoroughly after going to the bathroom is extremely important in order to avoid gathering bacteria or other diseases from the bathroom itself and also to avoid spreading them onto whatever you touch. But can you self-contaminate? For example, if I were to live for a month entirely on my own, with no contact with any other humans, is it still important to thouroughly wash my hands each time I go to the bathroom? Basically what I am thinking is that the disease that may be on my hands from my bathroom, can only come from my own human waste, which was already inside my body, so if it existed in there, I was already contaminated by it, wasn't I, and it was benign to me since I wasn't sick, wasn't it? (I am not planning to spend a month away from humanity, and even if I did, I would still wash thoroughly out of habit, whatever your answers will be. So do not worry about my hygiene, this is just a thought experiment to help me understand how bathroom germs cause contamination). --Lgriot (talk) 14:18, 28 May 2013 (UTC)


 * You can self-contaminate, because your gut flora should not be allowed to live in your eyes, ears or throat. Your bacteria is kind of self-contained in different parts of the body. Washing hands avoid them spreading to other parts of the body. OsmanRF34 (talk) 14:29, 28 May 2013 (UTC)
 * Ok, I didn't know bacteria was successfully contained by the body within specific parts of itself, I thought that once it was inside, it could flow with the bloodstream and reach other parts. It makes sense now. thanks. --Lgriot (talk) 14:58, 28 May 2013 (UTC)
 * Flow in the blood steam?? You thought bacteria lived in our blood? Bacteria that manage to get into our blood are killed or we get very ill (see septicaemia). --89.241.227.119 (talk) 04:08, 1 June 2013 (UTC)
 * Humans only started washing hands to get rid of germs in what decade? The 1870's or thereafter? before that, and after that in much of the world, I expect that people only washed their hands if they could see or smell something on them that they did not want to include in their meal. Germ removal from hands post-toilet and pre-meal is a cultural custom and public health practice of 140 years duration or so for most in the world, though some cultures practiced ritual washing for religious reasons for thousands of years before that. It seems like a great idea, but many of my ancestors lived to ages of 80 or over before anyone ever suggested handwashing for germ removal. Handwashing improves health, but it does not prevent pathogens from being ingested in a world where we eat lots of fresh lettuce and fruit, since normal washing with water of produce is not that effective in removing pathogens which got on it from contaminated irrigation water or contaminated rinsewater at the packaging factory. Isn't it likely that one's own fecal bacteria are less of a health hazard than that of someone else, as in contaminated drinking water or contaminated produce? Edison (talk) 15:42, 28 May 2013 (UTC)
 * Certain cultures (Hindus, Sikhs) have long held the tradition of using one hand to feed yourself with and the other one to clean yourself with. --TammyMoet (talk) 19:11, 28 May 2013 (UTC)
 * Our lettuce and fruit has a myriad of bacteria on them, however, they shouldn't have any meaningful (i.e. that can make you sick) amount of e. coli. OsmanRF34 (talk) 18:45, 28 May 2013 (UTC)
 * One famous example of bacteria that are benign/helpful in the intestines, but cause disease in the mouth/stomach is E. coli. As far as I know, this suggests the answer to you last question is "no, not necessarily." SemanticMantis (talk) 15:45, 28 May 2013 (UTC)
 * So far as I know E. coli pathogenicity depends on the strain (and as I recall "strains" vary a lot, a substantial proportion of the total distance to Salmonella) not on self-contamination. However, pork tapeworm is a case that actually can become far nastier after a trip through the intestine. Wnt (talk) 17:02, 28 May 2013 (UTC)
 * My point was, if you have a potentially dangerous strain of E. coli in your gut (not causing any problems there), then self-contamination would definitely be a risk, and perhaps moreso than contamination from a different person who had no dangerous strains. SemanticMantis (talk) 19:05, 28 May 2013 (UTC)
 * Well, enteropathogenic Escherichia coli is, well, enteropathogenic, i.e. causing its damage in the gut itself. But it is true that the uropathogenic strains involve self-infection, which can be shown to occur in an ascending manner from the urethra going upwards.  Wnt (talk) 22:36, 28 May 2013 (UTC)
 * Ah, yes, thanks for the clarification! SemanticMantis (talk) 22:41, 28 May 2013 (UTC)

I'm trying to work my way through the nice, euphemistic, American(?) use of "bathroom" here to work our what User:Lgriot is really asking about. Is it urinating? Or defecating? Or both? I have seen it argued that for a healthy man who has recently bathed (i.e. within the last few hours), and wearing clean underwear, washing hands after urinating is fairly pointless. Unless he is a lousy shot or very clumsy when aiming for the toilet bowl, his hands won't be impacted in any negative way at all from handling his clean penis. In fact, before the act, his hands are likely to be dirtier than his penis, so the logical thing to do is to wash his hands before urinating in order to keep his penis clean. But defecating. That's different. It obviously depends on how much your hands get involved in cleaning up after the act. And if one uses a bidet, the hands may still never go near one's faeces. So, Answer =  It all depends. HiLo48 (talk) 04:34, 29 May 2013 (UTC)
 * Yes, Americans are quite secretive about the definition and use of the term "bathroom". Agree with much of your comment, except for the implication that getting urine on one's hands would contaminate them (as our article's lede indicates, it's typically sterile). -- Scray (talk) 04:41, 29 May 2013 (UTC)
 * Words HiLo doesn't regularly use = American. Funny, never heard other, smaller, vernaculars mentioned... Canadian perhaps? Shadowjams (talk) 03:46, 30 May 2013 (UTC)
 * Yes, that's true. So, if we're talking about a healthy, clean man simply urinating, washing hands afterwards could be seen as pointless. Now, being a fella, I'm not going to dare to attempt to comment on what the ladies should do. HiLo48 (talk) 04:47, 29 May 2013 (UTC)
 * Well, to answer explicitly, "going to the bathroom" in U.S. means urinating or defecating, but excludes things like nose-picking even though they may be done in the bathroom for privacy the same way (one hopes with hand-washing afterward) I can't tell you with absolute certainty, but I would suggest hand-washing after urination has something to do with .  There are times, like when omitting underwear with shorts in hot days of summer, when a last drop in the pants is just not presentable, and among the various options is to touch a hand to collect the last drop - however, honestly, the real reason is that many service employees can be fired for not hand-washing so they simply do it.  (I also wonder if some of this goes back to days when people claimed that toilet seats could spread gonorrhea, etc.) Wnt (talk) 06:02, 29 May 2013 (UTC)
 * I am not American, Scray, but yeah, I was assuming that both activities could lead to bacteria on your hands, somehow. Notice I said "could", not "would", and I guess it depends on well you handle the action. :-) --Lgriot (talk) 08:04, 29 May 2013 (UTC)

Life expectancy corrected for sleeping time
Humans in Western countries can expect to live till about age 80, but if you correct for the time spent sleeping, this only amounts to something like 50 years spent awake. Some animals like elephants also live quite long but they sleep a lot less than humans. So, I was wondering what mammal has the longest life expectancy if one corrects for the time spent sleeping (cold blooded animals with a slow metabolism can live for every long, let's not consider such cases). Count Iblis (talk) 17:12, 28 May 2013 (UTC)
 * Why discount sleeping and not, for example, standing stock still, or defacating? Is one activity more relevant than the others for life expectancy? If so, why? -- Scray (talk) 20:44, 28 May 2013 (UTC)


 * It could be more meaningful to have a list of long-lived creatures, including a column on average daily hours spent sleeping. Housecats seem to sleep a lot, yet they don't live very long. The creatures that live the longest are probably tortoises. That would be a good benchmark, if their daily average sleep time is known. ←Baseball Bugs What's up, Doc? carrots→ 21:01, 28 May 2013 (UTC)
 * Regarding tortoises, Count Iblis specifically asked about mammals and not reptiles though. --Modocc (talk) 22:00, 28 May 2013 (UTC)


 * There seems to be an implication that sleeping is wasted time. But it's vital to mental health and memory and is quite pleasant if properly done.  Googling sleep and life expectancy gives you lots of various sources and comments.  I do remember reading something along the lines of "is time spent sleeping wasted time" in a science blog recently, but it doesn't seem to have been notable enough to find easily.  I remember quite vividly an Italian Renaissance writer who in a sourcebook we used in my 400 level Renaissance and Reformation course advised his sons to sleep as little as possible, as time spent asleep was stolen from the total of one's life.  It may have been in The Civilization of the Italian Renaissance: A Sourcebook, but I haven't been able to find the quote. μηδείς (talk) 21:38, 28 May 2013 (UTC)
 * Sleeping helps you during your waking time, but if you're already counting waking time, adding sleeping time is double counting. You are not capable of conscious experience for (most of) your sleeping time, so counting it seems to make about as much sense as counting the time after you die. It's not wasted time, but counting it along with the time spent awake would be like counting the money you spent on your house along with your house itself when calculating your net worth, on the basis that the house wasn't a waste of money. Why do you say it is pleasant? How can something you're not conscious during be pleasant? — Preceding unsigned comment added by DanielLC (talk • contribs) 00:58, 29 May 2013
 * Whales can live over 200 years (see maximum life span) and I saw a documentary not long ago that they do sleep. But they probably still have a longer sleep corrected longevity than other mammals. But they would probably be awake for many years longer than other mammals. -Modocc (talk) 21:59, 28 May 2013 (UTC)
 * Are you saying there actually is a scientific concept of sleep-corrected longevity, Modocc? μηδείς (talk) 23:46, 28 May 2013 (UTC)
 * Its conceptually similar to the concepts of the longevity or service life of engines or light-bulbs, in this case, the longevity of accumulative wakefulness, in other words sleep-corrected longevity. Its obviously a derivative of longevity, and sufficiently well-defined that it can be empirically measured. -Modocc (talk) 01:56, 29 May 2013 (UTC)
 * As I suggested in my initial response above, I remain doubtful that sleep-corrected longevity is a concept supported by scientific consensus. Your comments underscore the impression that this is synthesis of concepts from appliances that have an "on"/"off" state that does not clearly apply to animals. -- Scray (talk) 02:16, 29 May 2013 (UTC)
 * Thanks for answering Modocc, but I do suspect that you are applying a concept from engineering that simply does not apply to biology. Being asleep is in no way being "off".  It is simply a different mode of being actively alive that applies to sentient organisms of a certain complexity. μηδείς (talk) 03:39, 29 May 2013 (UTC)
 * I didn't mean to suggest that being asleep was being off or not living though (see my explanation below for why I brought up machines). Its perfectly clear though that the OP was asking about the length of the time that we and animals spend awake however and that is a valid biological question with valid answers. I've revised my answer to avoid further objections though. Modocc (talk) 04:03, 29 May 2013 (UTC)
 * Googling the phrase "sleep corrected longevity" (ie put it quotes) returns precisely nothing. As does googling "sleep corrected life", and "sleep adjusted life".  Googling without quotes returns lots of sites, but they aren't talking about Modocc's or Count Iblis's concept.  They talk about things such as inadequate sleep can raise blood pressure and increase early death due to heart attacks, decreased attention and increased reaction time leading to more car accidents, and the like.  So it rather does look like this a concept invented by Modocc.  Even if valid, it would be very hard to measure as the amount of sleep you require depends on many factors.  For instance, if your days are spend doing heavy physical labour, you will need more sleep, and you will sleep better.  If your days are spent in learning new things requiring significant intellectual effort, you will need more sleep.  Most people whose jobs involve heavy physical labour don't actually live that long.  Those that are continually involved in intellectual stress, such as university professors involved in leading edge research tend to live longer than average.  Another factor:  My mother bred cocker spaniel dogs.  I have owned an Australian Cattle dog.  They sleep all day if you let them. Both are the same size.  Cocker spaniels have a reasonable amount of energy, but spend a lot of time sleeping.  Cattle dogs are a lot more active and sleep a lot less - about the same as humans.  Both breeds, when used as domestic pets, live about the same - 14 to 16 years.  Clearly other factors overide the duration of sleep when it comes to lifespan.  Sloths spend about 18 hours a day asleep, and even when they are awake are very inactive.  They live a maximum of 50 years in captivity if well looked after, compared with 50 to 90 years for similar sized and vastly more active apes.  Wickwack 124.178.175.45 (talk) 02:40, 29 May 2013 (UTC)
 * Forgive me, but I only read part of that [since the OP indicated below that I interpreted the question correctly]. The machines that I mentioned are simply an analogy and a demonstration that the semantics of the term longevity is broad and I am sorry guys if my initial explanation was not entirely clear on that particular point. Sleep labs actually do measure accumulative sleep debt and wakefulness and the OP simply asked about knowing the longest of other mammals' accumulative wakefulness (the longest total accumulative time a mammal is awake and not asleep, an empirical quantity), thus I obliged in order to incrementally increase the state of our collective knowledge (although the actual time a whale is aware does depend greatly on where it exists during its tail-wagging short life). That said, I revised my answer.  -Modocc (talk) 03:06, 29 May 2013 (UTC)


 * "List of long-living organisms" may be of interest.—Wavelength (talk) 22:02, 28 May 2013 (UTC)
 * Dolphins and probably whales and number of other marine mammals and many birds sleep one half of the brain at a time. I don't know if we should multiply by half the time while half the brain is asleep. Just shows how difficult a straightforward question like this can be. Dmcq (talk) 14:47, 29 May 2013 (UTC)

The rational for this question is what Modocc mentioned. Suppose that we could make fundamental changes to our biology. If you had the choice between a new body that will last for 400 years but you need to sleep 16 hours a day or you could choose one with a lifespan of only 250 years but you then only need to sleep 8 hours a day ,then what would you choose? Count Iblis (talk) 15:58, 29 May 2013 (UTC)

Best Hook Orientation
I recently got into a very intense debate over which is the best hook orientation to use when hanging a part. Here are the two different methods. I would like to know which one is the best way, but more importantly how to tell which one is the best way? (NOTE: We are only disagreeing about the lower hook in the pictures)

Method A (Wrong Method) http://i40.tinypic.com/2qu6azd.jpg

Method B (Correct Method) http://i42.tinypic.com/2u4pun7.jpg

192.43.65.245 (talk) 21:53, 28 May 2013 (UTC)


 * The "wrong" is not ideal on either hook, the "correct" has better force distribution on both hooks. As for how you can tell: you can spend a lot of time learning about statics and structural loads. Alternatively, you can probably see intuitively that the "wrong" picture has more force acting to "unhook" the hooks, that is, to straighten them out. Another rubric: a hook like that should not have any appreciable angle to its chain while loaded. Compare all the angles between hooks and chains, and you will see that the "correct" picture has angles closer to 180. You want the force directed mainly to the chain, and only slightly into the hook. I should also note that this reasoning assumes that it requires less force to bend the hook than it would to break the chain. If you buy this sort of thing at a hardware store, it should list the safe working load, and sometime will have a picture showing how the hook is loaded to get that number. SemanticMantis (talk) 22:09, 28 May 2013 (UTC)


 * For the purposes of this question, please ignore the angle between the hook and the chain. They should be straight, but the model does not show this.  The discussion we are having is over the direction the hook is facing. 204.54.36.245 (talk) 22:17, 28 May 2013 (UTC)
 * For that kind of setup (small holes in plates), the way the hook faces absolutely affects the angle with the chain. Even disregarding that aspect, I think the "correct" picture is better, but I'm also interested to hear what others have to say. SemanticMantis (talk) 22:37, 28 May 2013 (UTC)


 * Well, my comment is that if you look at the chains (not those in the diagram but real lifting tackle), you will see that they are designed to have the hooks facing out from the center of gravity. This helps to avoid the load being taken on the bill of the hook. The load ought to be taken on the saddle – which is the strongest part of the hook. Finally, if the hooks face the load, then, if and when, the load touches down and the chains go slack – the ruddy hooks can fall out! Same goes for attaching them properly in the first place when the chains are still slack.--Aspro (talk) 23:24, 28 May 2013 (UTC)
 * Absolutely! If you are operating the crane by yourself or with a dogger, neither of you should have to hold the hooks in place while the load is taken up, it's a sure-fire way to get a finger pinched or worse. 122.108.189.192 (talk) 05:01, 29 May 2013 (UTC)