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.
I was reading the article on friction in the section about negative coefficients of friction, where it discussed the force of friction decreasing with an increase in the normal force. However, shouldn't these mean that the force of friction is inversely porptional to the normal force? A negative coefficient of friction would mean the force of friction would be negative (which in terms of vectors would mean working in the same direction as the applied force), but it would still increase with an increase in the normal force. Am I wrong here? Thanks, --T H F S W (T·C·E)04:34, 8 January 2015 (UTC)[reply]
I agree with your interpretation. However, as far as I know, that doesn't exist in the real world, while what they described does. One example that comes to mind is ice skating, where the friction is reduced once the pressure builds in the area under the blade and melts the ice, so the skater is then gliding on water on ice. I'd call that a "negative change in the coefficient of friction". Of course, that's more of step function than a continuous case. StuRat (talk) 04:58, 8 January 2015 (UTC)[reply]
It is true that there is high pressure under a skate blade, which lowers the freezing/melting point, but it's a myth that this results in melting that makes skating possible. Artificial ice rinks are normally maintained at temperatures below the lowered freezing point. The truth is more complicated and involves other factors. --65.94.50.4 (talk) 05:09, 8 January 2015 (UTC)[reply]
Well, if it was due to friction that the ice melts, then you'd expect it to be very hard to get started moving on skates, since there's no frictional heating until after movement begins. Note that the pressure lowers the melting point, but the increase in pressure also heats the ice. As to the argument that water takes up less volume and therefore the pressure would decrease when it melts, this ignores the fact that the skater will simply sink down by a microscopic amount into the ice, to restore the pressure. StuRat (talk) 19:02, 8 January 2015 (UTC)[reply]
I agree that it's a misleading heading. I've put "negative" in quotes until someone comes up with a better way to express the concept. Dbfirs09:45, 8 January 2015 (UTC)[reply]
It may be misleading, but for better or worse a lot of scientific terminology is misleading to the uninitiated, no? That doesn't mean we get to change it on WP, we should be consistent with the literature. The authors of the cited paper say in the abstract "This leads to the emergence of an effectively negative coefficient of friction in the low-load regime." - I don't think it's our place to change the terminology that has been accepted in a Nature publication. It is unclear to me whether your solution of scare quotes is better than calling the section "effectively negative coefficient of friction" - any thoughts from the group? SemanticMantis (talk) 16:20, 8 January 2015 (UTC)[reply]
Sure, as a general practice, but I don't believe this specific case to be an error, and in general I would doubt our understanding before I would doubt the findings of Nature paper (sure, they occur, but much more rarely than errors in WP). SemanticMantis (talk) 20:09, 8 January 2015 (UTC)[reply]
Note that it is the coefficient of friction that is negative, not the force of friction. The coefficient relates the normal force to the frictional force, and is dimensionless. In this case, the coefficient is negative, because increasing normal force decreases friction (in at least one very special scenario) - read the abstract of the paper cited in our article here [1]. I actually think the article is fine how it was - it makes sense if you've read and understood everything up to that point. SemanticMantis (talk) 16:20, 8 January 2015 (UTC)[reply]
(ec) Note that a negative coefficient of friction invariable would lead to a negative frictional force:
Yes, what SM said. It's not as counter-intuitive as you would first think, because there is adhesion involved; there is a resistance to sliding even under zero normal load. The slip resistance is a constant (adhesion) plus a coefficient of friction times the normal force, and in this case that coefficient would be negative. But this is just decreasing the adhesion under increased vertical load; no one is saying that this could overcome the cohesion and start "pushing" in the same direction as the applied load. --Floquenbeam (talk) 17:02, 8 January 2015 (UTC)[reply]
Floquenbeam's explanation makes sense. But, there still can't be a fixed negative coefficient of friction, as that would indeed eventually lead to a frictional force, at high normal force ranges, which surpasses the adhesion force. So, the coefficient of friction must be variable, and only negative at certain low ranges of normal forces. StuRat (talk) 17:05, 8 January 2015 (UTC)[reply]
Yes, as SM already stated above, it's an "effectively negative coefficient of friction in the low-load regime." It's variable, and no one is saying it continues this behavior at higher loads. --Floquenbeam (talk) 19:07, 8 January 2015 (UTC)[reply]
I've changed the wording to an exact quote of the source, but left the scare quotes in the heading. Will this suffice? I've also moved the section to its proper place after the table of conventional positive values. Dbfirs19:41, 8 January 2015 (UTC)[reply]
Thanks, that's better. I personally don't like the scare quotes, because it seems to me the coefficient is literally negative under the specific regime studied. But I don't feel strongly enough about it to argue or change it :) SemanticMantis (talk) 20:06, 8 January 2015 (UTC)[reply]
If I'm not mistaken, it still opposes the applied force. The proportion of opposition gets smaller as more force is applied. I think a hydrofoil can be modeled as a negative coefficient of friction. Motion lifts it, drag is reduced, efficiency increases. It can be modelled other ways with more conventional positive coefficients but it's not as cool. --DHeyward (talk) 02:49, 9 January 2015 (UTC)[reply]
Snow Extrusion
Though the illustration might not demonstrate it very well, I'm interested in the natural phenomena of when snow forms an extended extrusion-like structure growing from behind of objects like trees or fences.
I assume it has something to do with wind, but how exactly does it work? 176.14.195.212 (talk) 12:36, 8 January 2015 (UTC)[reply]
This is a very interesting question, and it turns out to be very difficult to describe and understand all the things snow and wind can do! Here are some nice descriptions of how snow interacts with snow fences - [2][3]. I don't know of a specific term for the influence of trees/fences on snow, but Penitentes is a word for spire-like snow formations - these form from wind but also due to interactions with temperature and dew point. The general concept that would apply to snow/fence interactions is Aeolian_processes (sometimes spelt 'Eolian'). These processes can also cause pattern formation and have can have some degree of self organization. Behavior of snow due to wind is an active area of research, and there is a lot we still don't understand. Here is an example of a recent empirical paper on snow/wind dynamics [4], and here is a nice overview from the USGS[5]. There are also lots of simulation models and theoretical mathematical treatments, but those can get pretty heavy and might not be that useful for a general audience. An unrelated but interesting water 'extrusion' is ice spike. Both this and the photo you show (and the formation of snow flakes themselves]] are examples of dendritic growth.
If you have any more specific questions I might be able to find more suitable references. In the meantime, let's all enjoy these beautiful photos that we get searching /eolian snow pattern/: [6] or simpley /penitentes/ [7] :) SemanticMantis (talk) 16:06, 8 January 2015 (UTC)[reply]
Winter mountaineers in UK call this "rime ice" but we have an article on the same subject called Hard rime. On the hills, you can determine the prevailing wind direction (useful for avalanche prediction) because the ice grows into the wind. See Avalanche, the Basics - Part 2: Staying Safe; "Rime Ice is caused when super-cooled water vapour hits a freezing object (rocks, fence posts etc). Counter-intuitively, rime grows into the wind rather than away from it, so the direction it points is another handy indicator of recent wind direction" (just over halfway down the page). I rather like this picture. Alansplodge (talk) 16:32, 8 January 2015 (UTC)[reply]
Just what kind of person would be so easily impressed as to take such an interest in structures that arise out of snow anyway... Snowtalk11:22, 9 January 2015 (UTC)[reply]
The kind of people that try to avoid having your electricity supply or mobile phone cut off in Winter, or ensure cars going across bridges don't get impaled by falling icicles. Or any people who are generally interested in strange phenomena. Dmcq (talk) 12:00, 9 January 2015 (UTC)[reply]
I had considered that, but the problem is that it wouldn't necessarily have delineated that the sarcasm was self-effacing and I hoped that keeping my name at full scale would make that point more clearly. Oh well, just a reminder as to one of numerous reasons I don't attempt humour here as a general rule. :) Snowtalk02:47, 10 January 2015 (UTC)[reply]
Human only (or close) diseases.
According to their articles, both Smallpox (Variola Major) and Polio are found in nature only in Humans. (It apparently is possible to give smallpox to a primates, but no cases have been observed in the wild). Any idea where I could find a list of diseases that (like these) are more or less restricted to humans?Naraht (talk) 15:54, 8 January 2015 (UTC)[reply]
Would you include mental diseases ? I imagine many of those are human-only, as more complex brains are prone to more complex disorders. StuRat (talk) 16:55, 8 January 2015 (UTC)[reply]
That's a very good point, thanks! However, Malaria is on that list, and it definitely lives in mosquitoes as well as humans, though it doesn't give them the same symptoms. SemanticMantis (talk) 20:36, 8 January 2015 (UTC)[reply]
That's not necessarily true; you could eradicate it both in the human population and any other carrier populations (though unfortunately for members of that other species, the likely approach would be (and has at times historically been) to eradicate the carrier population itself. In any event, it's quite likely there's never truly been a human-specific pathogen; all infections to which humanity has been subject have arrived in the human population through zoonoses at some point or another, and there's no way of knowing with any degree of certainty that there's even so much as a single pathogen which entered the human ecological niche and then mutated into a form that has never since infected another member of any other species. Certainly there might have been cases where the only per-existant animal vector(s) disappeared to extinction, but these are surely a great rarity as well. Non-communicable diseases are of course another matter entirely, but I rather suspect Naraht was excluding them by principle. Snowtalk11:18, 9 January 2015 (UTC)[reply]
This is a difficult topic especially regarding viruses. There are closely related viruses that have different effects on hosts. SIV and HIV are closely related. AIDS is mostly human though. Rabies in bats is quite the different story for humans. The flu moves through swine, avian and human hosts that all contribute and affect each differently. I suspect the "human only" might be symptom related rather than antibody related and it would surprise me a bit to find a symptomless carrier in insects, birds or mammals that are simply unknown. --DHeyward (talk) 04:26, 10 January 2015 (UTC)[reply]
Beaver poo
Mice don't "hold it in" but rather urinate and defecate more or less constantly. Is this also true of larger rodents, such as beavers ? StuRat (talk) 17:25, 8 January 2015 (UTC)[reply]
According to [8], beaver droppings are found in the early morning at the water's edge. I don't know if that means they do it overnight and it's only found when the sun rises, or if they do the business at first light, but it implies they hold it in through daylight hours. Mogism (talk) 17:31, 8 January 2015 (UTC)[reply]
Are siblings the most genetically similar people to a person?
And if so... if one sibling is smart, and their sibling(s) is/are dumb, does that not demonstrate that the factors that determine smartness and dumbness are predominantly environmental and not genetic? 69.121.131.137 (talk) 22:32, 8 January 2015 (UTC)[reply]
As for the first question, apart from identical twins, the closest genetic relationship is that between two siblings or that between a parent and his/her child. A child has inherited 50% of its genome from each of its parents, so is 50% identical in its genome to either parent. Likewise you can calculate that two full siblings share on average 50% of their genome.
As for the second question, no, that does not logically follow, at least not from just a few cases. Children can inherit different genetic material from their parents, and so they need not share between them any of the genes which influence intelligence. In fact theoretically they need not share any genes. On average, they share 50% of their genes, but in individual cases it may be 60% or 45% or even 0% (though this would be exceedingly unlikely). - Lindert (talk) 22:45, 8 January 2015 (UTC)[reply]
(ec) Usually this is addressed with a twin study. Twins who are genetically identical are compared to those who share 50% of their genes, and the difference is considered. Of course, it might not be foolproof (what if the smart twin was sneaking in and takes tests for the dumb one, affecting how they are later treated, or if the teachers have a visually driven bias) but it's a pretty good way to look at it. Wnt (talk) 22:49, 8 January 2015 (UTC)[reply]
(ec) Siblings have 50% genetic overlap, the same as the overlap between a parent and child. That isn't enough to determine whether differences are due to environment or genes. However, identical twins have 100% genetic overlap, so the differences between them are much easier to interpret. The most powerful test of environment-versus-genes is to compare identical twins reared apart with identical twins reared together. It's hard to find good data, because the number of identical twins reared apart is quite small, but the data that exists is extremely useful. Looie496 (talk) 22:51, 8 January 2015 (UTC)[reply]
Because the exact proportion of "shared" genes in siblings can theoretically vary between 0% and 100% (though with an average of 50%) it is possible to have more "shared" genes with other people than with your sibling. (Note that these percentages refer to the genes that can vary between two people (i.e. your parents), and not to genes that you "must" have in order to be human rather than some other species). Your question about the factors determining intelligence is not yet resolved, though scientists are hard at work on it. Geneticists talk of the heritability of different traits. As you will see from our article on the heritability of IQ the best estimate of the heritability of intelligence seems to be about 50%. That is, about half of the variability of intelligence among the human population at large can be explained in terms of a genetic component. However, this figure refers to the population as a whole, and, because we don't know the proportion of genes you share with your sibling, we can't reach any conclusions about the relative impacts of nature and nurture in your particular case. RomanSpa (talk) 00:41, 9 January 2015 (UTC)[reply]
I saw my doppelganger at a train station a few years back. Looked nothing like my brother. Can't speak for the genes beneath the skin, but my resemblance was uncanny. InedibleHulk(talk) 00:48, January 9, 2015 (UTC)
Looie's answer is the correct one in general, but both male and female children bear their mother's mitochondrial DNA, so are slightly closer to each other and their mother than their father in that respect. There's also the question of the Y chromosome. Since the Y carries fewer genes than the X, again, children are closer to their mother, but two brothers, each carrying the same Y, are thereby closer to each other and their father than to a sister not carrying the identical Y. Ex chromosomes cross over, so the exes inherited by sisters are not necessarily identical, while the wyes carried by brothers are.μηδείς (talk) 01:33, 9 January 2015 (UTC)[reply]
Sisters do have identical X-chromosomes, since their father only has X-chromosome. Both sisters necessarily inherit all of the genetic material in their father's single X-chromosome (unless some genes could cross over between the father's X and Y). Of course the X-chromosomes they inherit from their mother could be quite different, but in that respect they are no different from two brothers either. - Lindert (talk) 09:59, 9 January 2015 (UTC)[reply]
One thing to clarify: First, let's ignore things that can alter the 50% from each parent (the things Medeis mentions, but also genetic disorders like XXY or XYY, etc), and focus on the simplified 50/50 model of genetic inheritance from each parent for alleles in nuclear DNA. Now, a parent is guaranteed to share 50% of your alleles (notgenes, let's be precise here :), and cannot share any more or less unless you get into edge cases. We don't know exactly which alleles are shared, in part due to recombination. In contrast, a sibling shares 50% as an expected value. So the situation is this - if you want a "safe bet" for most shared alleles, pick a parent, you'll never be far off from 50%. If you want to potentially maximize the shared alleles, pick a sibling, who will share more than 50% of alleles roughly half the time. As Lindert points out above, a sibling has the potential to share much more than 50% with you, but can also be lower, and this makes for some interesting differences, depending on our motive for finding a highly similar person. SemanticMantis (talk) 16:41, 9 January 2015 (UTC)[reply]
January 9
Trustworthy sources of Windows builds of open source software?
Some of the open source software I use is hosted at Sourceforge. I've stopped downloading Windows installers from SF since reports came out in 2013 that installers hosted there were bundled with extra/unwanted software. Are there trustworthy alternative sites for Windows builds of open source software, ones that don't bundle extra stuff in the installers?
Yes, that was a typo, and I fixed it. I'm now a little confused by the styling of "Ardipithecus ramidus" as "Ar. ramidus" - normally we only use the first letter of a genus name when describing the species, and the article for A. ramidus just says "A. ramidus" as I would expect. Our style guide Wikipedia:Manual_of_Style#Scientific_names is silent on the issue. Before I change these to single letter abbreviations for genera does anyone want to defend the abbreviations as they are currently used in this section? I can see the desire to avoid confusion with e.g. Australopithecus, but the two-letter genera still looks wrong to me... SemanticMantis (talk) 17:12, 9 January 2015 (UTC)[reply]
Ok I've found this style advice that says the two letter abbreviations are to be avoided but are tolerable in some publications to avoid ambiguity: [9], citing "Butcher’s Copy-editing" as the style guide. SemanticMantis (talk) 17:17, 9 January 2015 (UTC)[reply]
Thank you for clarifying the issue. In regards to the point you mentioned, I'm not a science student, whatever knowledge I acquired so far, is from Wikipedia. Personal point of view: I think "A." is used for the Australopithecus, well this is what I've come across so far in my readings. -- (Russell.mo (talk) 10:49, 10 January 2015 (UTC))[reply]
Resolved
Damages caused by too much staring at a screen (be it TV, computer or smartphone)
What could happen to my eyes, when we spend many hours starring at a screen? (I mean a modern TFT or LED backlight, not that old TVs.). Is this associated with any illnesses, poor vision or whatever? How can I know whether High-energy visible light is real or just a urban legend? How can I know if screens will cause another illness down the road? After all we didn't evolve starring at an illuminated screen. — Preceding unsigned comment added by Noopolo (talk • contribs) 18:25, 9 January 2015 (UTC)[reply]
At the very least, there's the problem of literally "staring" (not "starring") at a screen too much, be it TV or your computer screen, in that you might not blink enough, and your eyes might tend to get dry. ←Baseball BugsWhat's up, Doc?carrots→ 20:20, 9 January 2015 (UTC)[reply]
One problem is always having the same focal distance to the screen, which means you don't exercise the focusing muscles in your eyes and they atrophy. StuRat (talk) 22:31, 9 January 2015 (UTC)[reply]
That article is not at all relevant to the issue here, or the mechanism of atrophy you proposed. Vision therapy is for those who have per-existent conditions (such as motor disorders or those involving binocular coordination) not for people whose muscles "atrophied" because they weren't focusing at enough different varieties of distance, as you speculate. That's an absurd suggestion for many more reasons than I'm going to take the time to address here, but I will point out this much: the eyes are constantly in motion and constantly making minute changes to focus that we are not consciously aware of. As you stare at your monitor reading this message, your eyes are actually darting back and forth and focusing at/upon different points on the screen even when you are not willing them to. What we see and what we think we see are two very different things, as the visual cognition centers of the brain are applying many layers of filters to compose a perceptual image around that tiny little space that your eyes are focused on at any given time; the brain takes previously acquired optical information and uses color and shading ques and a huge array of assumptions to create the composite your conscious mind perceives as the field of vision you are experiencing -- but the truth is that, at any given instant, you are only "seeing" (in the sense of receiving visual information directly from that eye in that instant) a fraction of what you perceive yourself to be seeing, and the eyes themselves are almost never at rest to any significant degree (even when you have your eyelids closed).
Regardless, you're not going to find a source out there supporting your guess that any issues with vision that arise from starting at monitors too long proceeds from atrophy. Quite the opposite, in fact -- the eye strain involved comes from the manner of exertion, not the lack of it. Stu, please, we've been down this road a million times; please don't post outright speculation in responding to issues upon which you have no first-hand knowledge and no sources to back you up. Snowtalk05:38, 10 January 2015 (UTC)[reply]
Here's one source: [11]. Not a very good source, but it does show it's not just me making up stuff, as you seem to think. I heard this from multiple sources, so will try to track down some better ones. StuRat (talk) 05:54, 10 January 2015 (UTC)[reply]
That ref is not just a mediocre source, it's a three paragraph non-scientific fluff piece in a fad health e-mag recommending "eye yoga" that doesn't even discuss the physiology of the eye or even really relate to this topic. Even that description somehow doesn't do justice to how silly virtually every word in it is and how much it is working against you here in establishing that you aren't speculating wildly. As for convergence insufficiency, it is another example of a motor condition which has nothing to do with atrophy. Look, if you heard this from multiple sources I can only guess that it must be a piece of folk science making the rounds, because the physiology of the eye is not an area of trivial interest for me and I'm telling you that what you are suggesting is not consistent with the actual science. CVS is simply not caused by atrophy -- again, it's much closer to the opposite. Snowtalk11:16, 10 January 2015 (UTC)[reply]
Apparently, Medieval teenagers were also the demographic to stare at illuminations all day until they grew too old and blind. But at least they were reading. InedibleHulk(talk) 02:53, January 10, 2015 (UTC)
What's the problem of putting metal objects into a microwave oven?
I get that a sharp object will release sparks, but what would happen if I put a metal bowl with a metal top and water inside into the microwave? Would it get hot and heat the water, while blocking the microwaves that won't heat the water directly?--Noopolo (talk) 19:49, 9 January 2015 (UTC)[reply]
On rare occasions, you can also get the same arcing without metal. I managed to get it with a saltine with a jalapeno pepper and cheese on top. StuRat (talk) 22:27, 9 January 2015 (UTC)[reply]
I'd love to see an explanation for how certain nonmetallic objects cause arcing in the microwave oven. Salty brine seems to be one necessary ingredient. StuRat (talk) 05:01, 10 January 2015 (UTC)[reply]
If you cut a grape almost in half, so that the two halves are connected with a thin strip of skin and lay them with the cut faces uppermost in a microwave, you get quite impressive sparks. I'm sure there is some salt in a grape - but hardly very much. You can see it in a rare example of a YouTube video that isn't faked: https://www.youtube.com/watch?v=DrY0aC81wxI
The stuff that happens in a microwave is frequently hard to figure out - so unless the specific situation you're thinking about has been written about, I doubt we could come up with a definitive answer. SteveBaker (talk) 05:59, 10 January 2015 (UTC)[reply]
Yes, if you build a Faraday cage in a microwave, it will prevent EM radiation from entering. But water already does that and is a reason it heats. A microwave oven has numerous TE and TM modes of standing waves inside the cavity (the oven is much larger than half a wavelength). Low resistance metal forces the field to be zero and the field gradient can be large (causing arcs) and also causing electrical current in the metal. See TEM mode but only TE and TM modes are excited in the cavity. --DHeyward (talk) 05:57, 11 January 2015 (UTC)[reply]
They use muscles on their abdomen to flap the wings, and changing direction, I suppose, involves flapping one side harder than the other. Another possibility is wing warping. StuRat (talk) 01:21, 10 January 2015 (UTC)[reply]
The aerodynamics of butterfly flight has been the subject of multiple scientific studies - it is more complex than it might at first seem, and may involve different mechanisms for different phases of flight. This [12]Nature paper is unfortunately behind a paywall, but is well worth looking at if you can access it. AndyTheGrump (talk) 01:40, 10 January 2015 (UTC)[reply]
Thanks to all for your time and effort to provide an answer to my question. I just read the Nature article referenced by AndyTheGrump, through the link provided by Mikenorton. Andy, your comment "is more complex than it might at first seem" is a major understatement. I am left thoroughly amazed at the potential complexity of the techniques these small creatures can utilize while in flight - and all by virtue of instinct. I highly recommend using this link to all who have an interest in the mechanics of insect flight. Thanks again guys for this incredible eye-opener!75.171.82.75 (talk) 18:40, 10 January 2015 (UTC)[reply]
The method of pasteurizing grape juice to halt the fermentation has been attributed to a British physician and dentist, Thomas Bramwell Welch (1825–1903) in 1869. I am not happy with the wording and lack of a source. Wasn't pasteurization known before? Are there any specifics to that method? Isn't "has been attributed to" classic weasel wording that should be avoided? --92.202.13.41 (talk) 03:16, 10 January 2015 (UTC)[reply]
Reading the article you just linked to shows that "initially for milk of course" is quite incorrect; the process was for wine and beer -- "it would be many years before milk was pasteurized". --jpgordon::==( o )16:32, 10 January 2015 (UTC)[reply]
PG-1302-possibly a pair of black holes close to colliding
The news article I just read said these 2 black holes will probably collide in a million years. It also said the energy released at that time could be as much as 100 million supernovae, with spacetime warping effects. My questions are 1) Even allowing for the very great distance, billions of lightyears, could that released energy, a million years from now, still damage the life on Earth, assuming life on Earth then is similar to life on earth now? 2) Could the spacetime warping be large enough, even with the very great distance, so that in ordinary life,(not just when using sensitive scientific instruments) a human's senses could notice definite effects on spacetime, assuming humans exist then? thanks.2601:7:6580:5E3:9138:4390:6740:EBCC (talk) 03:41, 10 January 2015 (UTC)[reply]
There are masses of binary star systems in every galaxy and most even seem stable. Given the fact that "black holes" are very small stellar objects it seems near impossible that two such black holes will ever come into contact. They will always miss eachother and that way develope into one (exeptional) binary system. --Kharon (talk) 04:27, 10 January 2015 (UTC)[reply]
It's always an interesting calculation to identify the event horizon or Schwarzchild radius for objects with the mass of the sun or earth. "Small" isn't quite the right word when it physically warps space into itself. A black hole with the mass of the sun wouldn't be "smaller" but the rulers would be longer. --DHeyward (talk) 07:11, 10 January 2015 (UTC)[reply]
Back of an envelope calculation - 100 million supernovae at a distance of 3.5 billion light years is equivalent to one supernova at a distance of 350 thousand light years (inverse square law). That is about 3 times the diameter of our own galaxy. So it doesn't sound like we need to be worried about this. Gandalf61 (talk) 13:30, 10 January 2015 (UTC)[reply]
Chemicals used to enhance flavor in food?
No, I am not talking about complex chemicals called "spices". I am talking about monosodium glutamate and other flavor enhancers. I watched a documentary, and one part said that there are actually various flavor enhancers in food (i.e. citrate?). I do not remember the specifics, so can anyone list all the flavor enhancers that have been used in modern times to enhance the flavor of processed foods? 71.79.234.132 (talk) 05:20, 10 January 2015 (UTC)[reply]
No, it was not capsaicin or table salt. It was a chemical with a very scientific name and no common name. Capsaicin and table salt are not part of the list. 71.79.234.132 (talk) 05:34, 10 January 2015 (UTC)[reply]
I think the oceans are naturally warmer for New York than other countries at the same latitude. Compare swimming season for New York vs. Northern California, Europe, Japan at the same latitude. Pure anecdotal evidence so could be wrong. --DHeyward (talk) 08:41, 10 January 2015 (UTC)[reply]
The large-scale oceanic gyres are clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere, because of the differing sign of the Coriolis parameter. This means ocean currents in both hemispheres tend to be relatively warm off the east coasts of continents (e.g., New York) and relatively cold off the west coasts. Short Brigade Harvester Boris (talk) 18:56, 10 January 2015 (UTC)[reply]
Ah. Right. The NYC metropolitan area has an average January temperature right around 0 C. This puts it into the C Koeppen primary classification rather than the D classification that applies to most of the state, knocking it out of the Df "humid continental" range.
More complete response to OP: Keep in mind that the names for the Koeppen classifications are somewhat arbitrary and there's no agreed upon quantitative definition of "continental." Over the years there have been various indices proposed for continentality. A fairly well known one is the Conrad index. Using the Conrad index NYC (Central Park) has a continentality of 39. This compares to a value of 13 for London and (perhaps surprisingly) is not much below the value of 42 for Moscow. Short Brigade Harvester Boris (talk) 01:26, 11 January 2015 (UTC)[reply]
I was wondering if we had an article on re-enamel toothpaste, and also whether in general the consensus is that it works? I was surprised there's no Colgate Total + re-enamel for example? Despite the Triclosan controversy, the Triclosan ingredient is the reason I use colgate total products only (and I know about the cancer risk or whatever, and just take it as a given.) But I wonder why it is not combined in a re-enamel version? Do these things not work? Colgate does have re-enamel but not under its Total brand - despite the Total brand including lots of other sub-things, like a version for fresh breath, a version with whitening, and. All of these are popular: http://www.colgatetotal.com/toothpaste
but no re-enamel version. why not? Does that stuff not actually work / rebuild mineral into your teeth?
The active ingredient in such toothpastes is Amorphous calcium phosphate. Our article contains several references which indicate it does have some beneficial effect, although probably not as dramatic as the advertisments suggest. The first part of the question can only be answered by Colgate-Palmolive's marketing department, and I'm sure they keep their decision-making process highly confidential. See Brand management for our general article on the subject. Tevildo (talk) 09:43, 10 January 2015 (UTC)[reply]
But note that calcium and phosphate are already abundant in saliva and if you want more calcium phosphate, a good glass of milk will do the trick for non-vegans (it wasn't just old school dairy propaganda, milk really is pretty good for teeth, especially during development). Our (frankly kinda promotional-reading) amorphous calcium phosphate article seems to suggest it is the most ideal form of calcium phosphate and though I did not look into the ncbi articles it references in detail, I'm willing to buy that it might have some marginal advantages. But I will say that generally speaking the advantages of toothpaste are more in prevention than in repair. Tooth enamel will repair itself to an extent in healthy contexts, and fluoride is the real hero of toothpaste in this regard, so in this sense most all modern toothpastes are "re-enamel" toothpastes. I tend to be skeptical of any benefits from "amorphous" calcium phosphate being beyond (or even comparable to) to fluoride's. There's actually a journal specifically devoted to topics in this area, Cares Research and its website hosts abstracts for every article, and I couldn't find a single mention of calcium phosphate within it, though research found therein and elsewhere has deconstructed the efficacy of toothpaste from nearly every possible angle. Still, with enough persistence, one could probably find some relevant research therein. Snowtalk11:53, 10 January 2015 (UTC)[reply]
Guys, thank you. I found this incredibly helpful. As a non-expert, my impression had been that alternative toothpastes (Enamelon) figured out a way to remineralize teeth. It seemed to me that following this, it was incorporated into other products (this is Colgate's explicit offering, outside it's total brand: http://www.colgateprofessional.com/products/colgate-enamel-health/overview .) But what I didn't get is why it wouldn't ALSO include all the normal total stuff? Is it because they interfere with the remineralization process? Then why not brush with total first, for all its benefits, then rinse and use an enamelon-type product?
Now that I've seen your references though, my impression is different. My impression is that Enamelon or other enamel-building categories didn't discover anything new. It's not a truly new category. It isn't something Colgate actually adopts or can use. Because it doesn't really work, it's just an invented fad. So, with this conclusion it makes perfect sense for Colgate to just add "enamel" to its list of benefits on normal Total products, without explicitly making an enamel-building version. (Which doesn't work or exist measurably better than its normal total properties.) At least, this is my impression today. Here is a cateogry of all toothpastes that are branded into this new fad: https://www.google.hu/search?q=enamel+building+toothpaste&tbm=isch in 2010 the wsj seemed skeptical: http://www.wsj.com/articles/SB10001424052748704141104575588374178767514 and they basically repeated what you've said above. In essence then, I think I fell for the idea that the popping up of that whole category (which is an area of the toothpastes section in every drug store) actually reflects something. It simply doesn't (in my current impression). Like if there were Night Time skin creams section with SPF 20+ factors. Sure. :)
Not at all, it's what we're here for. Toothpaste advertising is not a good example of objective scientific research - I saw a poster a few weeks ago that promised "Up to 100% less plaque!", which I think counts as "not even trying". Tevildo (talk) 17:03, 10 January 2015 (UTC)[reply]
As Telvido says, not a problem. I wouldn't go as far as to say that there haven't been developments in efficacy for toothpaste in recent times, by the way, but I think your skepticism about the branding is well-advised; for many consumer products relating to the body, diversification in the product field is as much or more the result of increased marketing efforts as genuine innovations in the products themselves -- a fact of which you are clearly aware. There's even a marketing term for the process by which competitors (or even a single company which own multiple brands) tend towards greater and greater differentiation in their branding and product claims, even if the product itself is identical, though I forget the term just now. I'm not willing to speculate that this is definitely the case with your re-enameling tooothpaste, but let's just say I'm not going to discourage you from the the belief either. Certainly the product line offerings raise the question that you point out: why not make a composite containing all of the elements that confer health benefits and other valuable properties (whitening and so forth); that's often the inconsistency a lot of companies have to just have to hope they won't be called on with regard to their massively diversified branding -- luckily the consumer is usually willing to meet them more than half way in suspending disbelief with regard to the "unique" properties of a particular variant of a product. Snowtalk20:49, 10 January 2015 (UTC)[reply]
Hard to tell for sure, but it looks to be steel reinforced concrete with decorating/insulating bricks (a concrete exterior doesn't look very "homey" or keep you very comfortable inside). StuRat (talk) 18:12, 10 January 2015 (UTC)[reply]
Somehow this distribution is pretty common in nature and society, and I suppose it's the most common (correct me if I am wrong). Besides this, what are some distributions that arise everywhere and why? (I suppose the normal dist. is the result of several binary options.) --Noopolo (talk) 20:49, 10 January 2015 (UTC)[reply]
I think the most common continuous distribution is indeed the Normal distribution, also known as the Gaussian distribution. However, the most common distribution encountered by most people in their daily lives is probably the Bernoulli distribution, because so many things either happen or don't with some probability. This is so common that most people don't even notice it, but every time they say something like "the car might crash" or "this cake might be delicious" or "the bus will probably be here in a moment" there's a Bernoulli distribution involved. Other discrete distributions evolve naturally out of the Bernoulli distribution, and these in turn lead naturally to consideration of their continuous equivalents. RomanSpa (talk) 21:59, 10 January 2015 (UTC)[reply]
Edibility/healthfulness of shellfish parts
What exactly are these shellfish parts? Are they safe/healthful to eat?
The soft, pasty part at the back of a cooked shrimp's head
The dark-colored, non-muscular part of a cooked mussel
The blister-like part of a limpet above its "foot"
In shellfish, the stuff is called tomalley when eaten as a food stuff. The tomalley of lobster is a common enough delicacy. Shrimp have a lot less of it, but it is of course just as edible. I'm not sure which part of the mussel you're asking after; perhaps the Byssus, also called the "beard", which is not edible. Not sure on the limpet. Never eaten those. --Jayron3201:56, 11 January 2015 (UTC)[reply]
I've not eaten limpets either. I've seen 2 YouTube videos in which limpets were collected, cooked, and eaten. In both cases, the presenters cut of the top part of the limpet bodies, consuming only the disc-like "feet". --96.227.60.16 (talk) 03:49, 11 January 2015 (UTC)[reply]
January 11
Can a goat really eat and digest a tin can?
Question as topic. I've found comments from goat owners online who say that they've never seen it happen for real. I know that goats, with their famously resilient stomachs, can and do eat things like newspaper, cardboard boxes, clothing and shoes without an apparent problem. I've even seen videos of them eating lit cigarettes without seeming to give the slightest damn. Anyone have a definitive answer? --Kurt Shaped Box (talk) 01:43, 11 January 2015 (UTC)[reply]
I doubt they could digest it. The greater question is whether they could pass it. Even humans can (and do) eat lots of undigestible stuff. If it is small enough, it will just show up in the stool later. --Jayron3201:57, 11 January 2015 (UTC)[reply]
I suspect they were just eating the labels off the tin cans, which might involve putting cans in their mouths as they work the labels loose with their tongues. StuRat (talk) 02:00, 11 January 2015 (UTC)[reply]
(EC) No,goats do not eat tin cans. It seems implausible that a typical tin can (actually tin coated steel) such as one I am looking at`which is about 3 inches in diameter by 4 3/8 inches high would pass through the esophagus of a goat, without killing the goat. It also seems implausible that it would pass through that esophagus if it were flattened. It also seems implausible that a goat's teeth could tear it into fragment small enough to swallow. A goat will certainly chew on a tin can, either to get the food residue on the inside or to eat the paper label on the outside, or to eat the glue..I recall an old published psych experiment, probably from the 1960s wherein goats were the subjects being conditioned, and the reward was the opportunity to chew on a length of chain, so they definitely are not averse to chewing on iron. Edison (talk) 02:10, 11 January 2015 (UTC)[reply]
Interesting question. A quick web search turns up some sources like Modern Farmer magazine that weigh against it ( [13] ). There's not really any general theory of biology that can honestly tell you a goat can't eat a tin can with any confidence; on all things goaty I'd trust a farmer's experience over a biologist's prediction any day.
The mention of goats chewing on a chain makes me wonder if there could be some "germ of truth" based on a sort of pica for them to obtain trace metals. I don't know if modern pet goats get too many vitamins/minerals or too good a diet to show some of that behavior. One thing that's clear, though, is that calling on YouTube for goat tin can gets lots of items that reflect the presence of the meme... yet no video of goats actually eating cans, or even chewing on them a bit. There's a curious example of one eating a page out of a book [14] which might reflect on the label eating behavior suggested above, but the video stops before we see whether it swallows or not. Wnt (talk) 00:40, 12 January 2015 (UTC)[reply]
Goats use their mouths to examine things in the same way that we use our hands, so people often think they are eating something when they are just investigating it. For example, they will pull clothes off a washing line to see what they are and check if they are worth eating, but then drop them and move on. What is surprising is that they will eat thorny bushes, brambles etc. without any problem, so they must have very tough mouths and guts. Richerman(talk)07:31, 12 January 2015 (UTC)[reply]
Yep. Just makes more sense for them. Hooves and horns are useful, but are about the clunkiest and least sensitive things any mammal has. With those crazy lips, they can eat the leaves from around the thorns so nimbly, you'd swear they were crazy. Just magicians, though. InedibleHulk(talk) 08:27, January 12, 2015 (UTC)
They have very nimble lips and can eat round thorns but I've also known then to eat brambles with no problem. According to this it's all down to their hard palate - and presumably a very leathery tongue. I suppose they chew them up well before swallowing. Richerman(talk)10:02, 12 January 2015 (UTC)[reply]
Is it true that the term, "global warming" was changed to, "climate change" as a euphemism to respond to arguments presented by conservative pundits who denied global warming existed simply because sometimes it got really cold outside? ScienceApe (talk) 02:09, 11 January 2015 (UTC)[reply]
Well, "global warming" isn't such a good term anyway, because the globe is only warming on average, with parts warming a lot, and other parts not at all, or even cooling a bit. Also, climate change includes things like changes in humidity, rain, and drought patterns, along with more numerous and more intense storms (hurricanes, tornadoes, cyclones, etc.). StuRat (talk) 02:41, 11 January 2015 (UTC)[reply]
The pundits and politicians who denied (and who continue deny) global warming based on the fact that "it sometimes still gets cold outside" aren't going to be satisfied anyway; a change in terminology isn't going to satisfy someone who makes a living from conflating "anecdote" and "data". One could argue that the terminology change is more useful (and perhaps more effective) in communicating the important or significant effects to the general public, however. "Climate change" – more extreme weather events like hurricanes, droughts, floods, etc. – is something that has a more conspicuous, tangible, visceral, and even economic impact than "global warming"—so what if it's a couple of degrees warmer? TenOfAllTrades(talk) 03:18, 11 January 2015 (UTC)[reply]
They don't mean the same thing. Global warming is an increase in the global average temperature, and climate change is a change of weather patterns. The former is one possible cause of the latter.
Google Ngram Viewer doesn't appear to support the claim that "climate change" has replaced "global warming" in more recent years. If that graph is to be believed, there was never a time when "global warming" was used much more than "climate change". Interestingly, the American English and British English trends are quite different from one another. -- BenRG (talk) 03:25, 11 January 2015 (UTC)[reply]
(edit conflict) Through the mid-2000s, "climate change" was essentially the European term for "global warming" as used in the U.S. Usage goes back and forth so that now "climate change" is seen a little more commonly in the U.S. than it was before. This happened in no really systematic way and there was never a conscious decision to replace "global warming" with "climate change." After all, the IPCC -- the Intergovernmental Panel on Climate Change -- was constituted way back in 1988. Short Brigade Harvester Boris (talk) 03:31, 11 January 2015 (UTC)[reply]
No. In the 1970's the term was "inadvertant climate modification" because they didn't know if it was warming or cooling. "Global warming" was coined in the 1970's in a paper that advocated that the climate change would be one of warming. In 1979 the Charney report was released and Charney adopted Broecker's usage. When referring to surface temperature change, Charney used "global warming." When discussing the many other changes that would be induced by increasing carbon dioxide, Charney used "climate change." Scientists maintain the distinction while clueless journalists (and Wikipedia articles) do not.[15]. --DHeyward (talk) 05:00, 11 January 2015 (UTC)[reply]
See Frank Luntz about him advising republicans to say climate change instead of global warming as a survey found it less worrying. So basically the opposite to the implication in the question. Both terms seem okay to me, people kow what they mean. Dmcq (talk) 10:43, 11 January 2015 (UTC)[reply]
"Climate change" is preferred by many climate scientists and atmospheric scientists, in part because many local regions could get cooler, or have more rain, or have less rain, or get warmer, etc. The local effects of CC are hard to predict, but several impacts will be more notable to people than simply "warmth." See also global weirding, and Effects_of_global_warming#Projected_impacts. Many of the most negative impacts of CC are not directly due to warmth, but warming is still indirectly responsible, e.g. speculation of the shutdown of some ocean conveyors would make the UK very cold, even though warming could be the cause. Same goes for more frequent storms and more frequent droughts, etc. SemanticMantis (talk) 16:12, 12 January 2015 (UTC)[reply]
What is the reason that the saturation (oxygen) rises after smoking?
Today someone showed me by the oxymeter that BEFORE he smoked he had 94% saturation, but AFTER he smoked it raised to 98%. What is the explanation for that? 213.57.31.194 (talk) 02:56, 11 January 2015 (UTC)[reply]
I don't know if it applies to smoking, but in general, carbon monoxide attached to hemoglobin can deceive oxygen saturation sensors. Jc3s5h (talk) 03:00, 11 January 2015 (UTC)[reply]
Indeed; see this paper: "... Pulse oximetry is unreliable in estimating O2Hb saturation in CO-exposed patients and should be interpreted with caution when used to estimate oxygen saturation in smokers." TenOfAllTrades(talk) 03:08, 11 January 2015 (UTC)[reply]
There are other factors as well including vascular and circulation changes from nicotine or changes in temperature (i.e. smoking outside). The pulse oxymeter is really not very useful except to correlate other clinical signs (i.e. congestion, labored breathing and low readings in a controlled setting like a hospital). 94% is relatively low number for awake and healthy patients but really a blood gas analysis and lung function test would be needed to show that it is abnormal. I've seen emergency pediatric doctors require the sleeping SpO2 to be above 90% before discharging asthmatic children but also at the same time, tell parents to throw their own pulse oxymeter away because the real signs are in behavior and type of breathing. They say the oxymeter should not be used to decide whether intervention is necessary and the number doesn't add any value. YMMV. --DHeyward (talk) 06:36, 11 January 2015 (UTC)[reply]
Attached with nails
Why do nails work? Is it solely friction? Push a pin into a pincushion, and you can pull it right out, but hammer a nail into a block of wood, and there's no way to pull it out without using the hammer or some other tool. Does the hammering process disrupt bits of wood that block the nail from being pulled? I understand why screws work (they bore thread-shaped holes in the wood, and the space between the threads provides significant resistance), but just as a stripped screw can easily be pulled, a nail "should" be easy to pull, but it's not. Nyttend (talk) 05:55, 11 January 2015 (UTC)[reply]
Framing nails also have a coating of glue that melts from friction of driving it and then binds it to the wood. I believe it also protects the nail from rust so they don't have to be galvinized. --DHeyward (talk) 06:39, 11 January 2015 (UTC)[reply]
For wood, Young's modulus and the bulk modulus are sufficiently high that when the wood is compressed by action of the intruding nail it applies a large compressive stress to the nail. The friction force that must be overcome if the nail is to be extracted is numerically equal to the coefficient of friction applicable to a wood/steel interface, multiplied by the normal force at work between the nail and the wood. The normal force is very large, thanks to the large compressive stress that exists between the wood and the nail. The coefficient of friction between wood and steel is also high. Consequently, to extract the nail a large force must be applied to overcome the force of friction that resists movement of the nail.
For a pin cushion, Young's modulus and the bulk modulus are many orders of magnitude smaller than they are for wood. Consequently, compressive sress in the pin cushion's filling is almost zero and normal force is almost zero. I suspect the coefficient of friction between the cotton filling and steel is also less than for wood and steel.
If the nail is driven into a pre-drilled hole, the wood surrounding the hole does not need to be compressed as much as when the nail is driven without the aid of a hole. Consequently the wood is not compressed as much, the normal force is less, and the friction force is less, allowing the nail to be extracted with less force. Dolphin(t)10:23, 11 January 2015 (UTC)[reply]
Another point here is that in most structures where nails are used, the forces applied to the structure are generally at right angles to the long axis of the nail. Imagine, for example, hammering a nail into a wall and hanging a picture on it. So the forces applied to the nail aren't pulling it out of the hole so much as deforming the nail - or forcing it to break through the wood along it's entire length. When overloaded, what generally happens is that the nail bends - and then pulls out relatively easily because some of the force is now directed along the length of the nail rather than at right angles to it. When nails are required to resist a pull at 90 degrees to the surface of the wood, they are generally hammered in at an angle for precisely that reason. SteveBaker (talk) 16:23, 11 January 2015 (UTC)[reply]
Agree with the above, that it's more about the material than the fastener here. Try pushing a nail into a pincushion, and you will be able to easily pull it out (but it will likely leave a large hole behind). If you could manage to drive a pin into wood, it would also be quite difficult to extract. The thinness of the pin would make it nearly impossible to drive it into wood without it bending, though. Perhaps a high speed, like from a tornado, would make this possible. StuRat (talk) 04:18, 12 January 2015 (UTC)[reply]
With any slender body, including a pin, that is to be driven into a solid material such as wood, the failure mechanism is going to be failure as a column - see Column#Equilibrium, instability, and loads. See also Buckling#Columns. If an attempt is made to drive a pin into timber with a single blow, or a small number of blows, the pin will inevitably fail as a column before it is fully inserted. Even at high speed from a gun or a tornado the pin would buckle as a column before it was inserted very far. That is why nails are usually hammered into place with a number of blows rather than one giant blow, and the nail is supported laterally until it is firmly established in the timber. Dolphin(t)05:06, 12 January 2015 (UTC)[reply]
I seem to recall a piece of straw stuck into a tree by a tornado. At those speeds materials behave differently, as there isn't time for the buckling to occur. Similarly, if you watch a bullet shot through a rubber sheet using high speed photography, the rubber doesn't stretch, but fractures as if it was glass. StuRat (talk) 05:20, 12 January 2015 (UTC)[reply]
But others have proposed explanations for seeing the same result, and possibly also have actual experimental evidence contradicting MB's tests: [17]. DMacks (talk) 05:32, 12 January 2015 (UTC)[reply]
Yea, I've never been impressed by MythBusters. They often conclude, incorrectly, that since they couldn't do X, then X can't be done. StuRat (talk) 05:36, 12 January 2015 (UTC)[reply]
Body weight and g-force tolerance
Is it possible to get any meaningful calculation of how many G's would you theoretically tolerate based on your weight? Specifically, considering persons whose body mass index is lower than normal, for instance 58 kg for a 179-cm tall man (for 10 G, for example, this yields 580 kg, which is similar to Manuel Uribe). Brandmeistertalk09:23, 11 January 2015 (UTC)[reply]
Our article, High-G training, links to several sources, including a NASA tech note that suggests astronaut-grade test-pilots can withstand 9g for 60 seconds while performing complicated tasks. In my experience flying the Citabria, most mortals start getting queasy or puking around a peak acceleration of +2g for just a fraction of a second - say, during the recovery from a spin - so although they will live through higher accelerations, they probably won't "tolerate" it. Here's a few videos from inside the cockpit and an external view of a Super Dec doing the same. Here's a tutorial video in a 7GCBC with a visible accelerometer on the panel. Quantitatively, the g-load a NASA test pilot would endure is some 5x greater than the peak accelerations experienced during these maneuvers. Nimur (talk) 09:49, 11 January 2015 (UTC)[reply]
Usually, queasiness/nausea (and stall/spin) is negative G-force with the feeling of falling. But I think the question is variations regarding body type and/or medical factors. I don't have the paper anymore but at one time, the air force studied whether their flight standards were based on anything more than a recruiting poster (i.e. 6' foot, 180 lbs, lean and physically fit). I think what they found was that shorter, slightly overweight, high blood pressure and near-sighted performed better at high-G. 5'6", 180 lbs, high blood pressure with glasses outperformed their "ideal" in stress tests. Some of the best videos are when pilots lose consciousness in the simulator. If you didn't know any better, it looks like the sim is producing a stress that the pilot is fighting. Then they go limp and it's clear all the stress is induced by the pilot to stay conscious through G-LOC.[18]This one has more funky chicken spasms. They go limp at the same G they were straining against. --DHeyward (talk) 10:32, 11 January 2015 (UTC)[reply]
This sort of question earns big bucks for highly trained geologists and tax attorneys! I think the best we can do is point you to our article, which you've already found, and to the references section it contains. In particular, the United States frequently reclassifies the taxable status of speculative reserves of minerals and energy... so the answer will constantly be changing. Nimur (talk) 17:16, 11 January 2015 (UTC)[reply]
January 12
Poly oxalate
I have heard that Poly oxalate is applied after placing the foam spray in a structure, I want to know what properties does this chemical has? and how is this applied.120.28.45.234 (talk) 05:38, 12 January 2015 (UTC)Garry from Philippines.[reply]
different units used in blood pressure measurement
My doctor measured my blood pressure and told me the result was 18. As he is French and I am English, that meant nothing.Could someone please tell me what that is in pounds,shillings and pence and whether he had reason to be anxious. I am 66, Thank you. — Preceding unsigned comment added by 109.12.62.210 (talk) 12:17, 12 January 2015 (UTC)[reply]
My first reaction was to comment that you are unlikely to read this reply, but perhaps it depends on where the pressure was measured and in what units. The usual units are millimetres of mercury, but perhaps French doctors use different units (centibars? but 18 would be a bit high). Alternatively, perhaps the measurement was for systolic pressure measured in the pulmonary artery or right ventricle, then 18 might be normal, but this measurement is an invasive procedure done in a hospital. Dbfirs12:31, 12 January 2015 (UTC)[reply]
The following discussion has been closed. Please do not modify it.
Oh yes, I should have checked that. You should have been told two figures. I assume that the 18 is systolic, and equivalent to 135 mm Hg which would be classed as Prehypertension in the USA or just on the high side of normal in the UK (but not serious). We can't give medical advice, of course, so you should go back to your doctor if you are worried. Dbfirs12:50, 12 January 2015 (UTC)[reply]
I'm hiding ("hatting") this paragraph because it makes an unwarranted assumption with dangerous medical implications if the assumption is wrong. RomanSpa (talk) 13:12, 12 January 2015 (UTC)[reply]
In France blood pressure is measured in kiloPascals, while in the UK blood pressure is measured in "millimetres of mercury", which is almost exactly the same as another unit called the torr. There are technical differences in the way these different units are defined, and you can read about them here, here and here, but the main thing you need to know is simply the conversion factor, which is 7.5. That is, when your doctor said the result was "18" he meant "18 kPa", so to convert this into the measure you are used to you just multiply by 7.5. So 18kPa = (18 times 7.5)mmHg = 135mmHg. So his "18" is your "135".
As you know, Wikipedia is not able to give medical advice, but you will see from our article on blood pressure that doctors usually provide two measures of blood pressure, "systolic" and "diastolic". You can compare your reading with a standard table here, and should clarify with him whether your result was for systolic or diastolic blood pressure. In any case of illness or uncertainty, you should always contact your doctor. RomanSpa (talk) 12:56, 12 January 2015 (UTC)[reply]
One worrisome thing in this question is that you didn't ask the doctor. If you aren't even comfortable asking him what units your BP reading is in, and whether that's the diastolic or systolic reading, then I doubt if you are asking him any questions at all. Many studies have shown that such a lack of communication with your doctor is quite bad for your medical outcome. In the US, we even have a series of PSAs encouraging patients to ask their doctors questions. StuRat (talk) 16:01, 12 January 2015 (UTC)[reply]
Thank you to the kind people who answered my question. With regard to asking a doctor questions - there speaks someone who is used to just one language and one system. I have been in France over 2 decades and speak such good French I even write poems in it. Of course I asked questions but, in all honesty, the doctor did not know the answers. He only knows his own system. (To add to the confusion, 18 might have been one word or 10 and 8, which is how the French say 18. So he might have been quoting me one number or two. The latter result would have converted me from hyper to hypo.) This has happened before when, presented with printouts of blood tests or even Xrays taken abroad, the doctor has refused to look at them and insisted all be done again because, in reality, he did not understand them. You might remember that if ever you need the services of any professional not trained in US. — Preceding unsigned comment added by 109.12.62.210 (talk) 09:55, 13 January 2015 (UTC)[reply]
Well, the doctor certainly knew the answer to whether he was saying one number or two, so you should have at least asked that. It's possible he didn't know the units he was using, but a quick look at the readout on the sphygmomanometer should answer that Q. StuRat (talk) 15:00, 13 January 2015 (UTC)[reply]
Why do electric guitars have tunable bridges but acoustic guitar fixed ones
I'm not sure if this is the right forum for this, but I wonder why electric guitars have tunable bridges but acoustic guitars have fixed bridges and saddles. The tunable bridge allows the length of individual strings to be changed. I know that some acoustic guitars have compensated saddles, which come with different lengths set from the factory, but this is just a set and forget.
Also am I right in thinking that even for an electric guitar this won't ever change as long as the strings are uniform in thickness and weight along the length? -- ????
The general consensus here is that tunable bridges have too much mass for an acoustic and kill the tone. Also, tunable bridges have moving parts and, because an acoustic works by resonance through the body of the guitar, the moving parts will tend to vibrate against each other and rattle. This doesn't matter with an electric guitar as they have pickups that convert the vibrations of the strings directly above them into an electrical signal, but not vibrations from elsewhere in the guitar body. Richerman(talk)14:25, 12 January 2015 (UTC)[reply]
That makes sense. The weight at the saddle is dead weight at the point where the string needs to vibrate the resonator. The moving parts bit also makes sense. In electric guitars the bridge can be fixed solid to avoid vibration, as the string is the only thing that needs to vibrate -- Q Chris (talk) 16:26, 12 January 2015 (UTC)[reply]
TTL IC L293D
I was playing with the TTL IC L293D when something interesting happends.
Indeed. Looking at the TI datasheet (page 7), the enable inputs have an internal pull-up resistor, so they need to be connected to ground to disable the output. With no connection, they'll be high and the output will be active. Tevildo (talk) 21:19, 12 January 2015 (UTC)[reply]
genetics
thx. I know it is basic, but I seem to have missed this lecture.72.183.121.78 (talk) 22:46, 12 January 2015 (UTC)
my question is about the transcription of chromosomes in humans. for example, are all genes on both the maternal chromosome 1 and the paternal chromosome 1 transcribed? Or is either the maternal or paternal chromosome 1 shut down and only the other completely transcribed? or is there partial transcription of both? how does this happen? thx much.72.183.121.78 (talk) 16:32, 12 January 2015 (UTC)[reply]
The nature of recessive genes tells us that both parent's chromosomes can be used. Once the two haploids come together to make a diploid of genetic material, there is just "the two chromosomes" with zero differentiation between which one came from which parent (with the exception of a male offspring's Y obviously coming from the father). DMacks (talk) 17:25, 12 January 2015 (UTC)[reply]
You get half your genes from each parent (not counting mitochondrial genes, which come exclusively from the mother). So, there is a 50% chance you will inherit a gene from that parent, and a 50% chance you won't get that gene from that parent (although you might still get the same gene from the other parent). However, not all genes you inherit are activated. Many remain dormant. In some cases, you must inherit 2 copies of a gene (one from each parent) for it to be activated (or fully activate, at least). For example, the gene that causes sickle cell anemia is only a serious problem when 2 copies are present. Also, mutations can occur, in which case the gene you inherit isn't quite the same as the original in the parent. StuRat (talk) 17:51, 12 January 2015 (UTC)[reply]
Remember, the gene is just the location of the information, the allele is the version or type of information that is carried. For a certain gene X, every human has that gene, insofar as we all have some information in that location of our DNA. However, many of us will have different alleles at that location. It is very common to confuse the two concepts, but we should be clear about the distinction on the reference desk. SemanticMantis (talk) 19:57, 12 January 2015 (UTC)[reply]
Our article says "locus" is the name of the location. As I understand it, the "gene" would then be something like "eye color", and the "allele" something like "blue eyes". StuRat (talk) 20:07, 12 January 2015 (UTC)[reply]
The difference is that a locus can be any region, e.g. a gene, a sequence, a portion of a chromosome, etc. Many people prefer to not use the word 'gene' at all, and instead use locus and allele for the separate concepts. This helps to avoid the nonsense of using 'gene' to mean both the region and the information stored at that region (which is what our askers and respondents usually do here on the ref desk). Still, the definition we use for 'gene' in our article makes it clear that it is ultimately a location or region:
“
"a locatable region of genomic sequence, corresponding to a unit of inheritance
”
(emphasis mine) The gene is not the "what" of inheritance, it is the "where." I just think we should make it a habit to use the right words for concepts on the ref desk, instead of perpetuating a common-but-incorrect usage. But your example is basically right (though there are many genes that control eye color) - everyone has genes for eye color, you get one allele from each parent. This also illustrates why it is technically incorrect to say "I got this gene from my father" - you would still have genes for eye color no matter who your father was, but a different father can lead to different alleles. I may seem picky here, but this is basic stuff, and is usually stressed in any intro bio course that covers DNA and inheritance. SemanticMantis (talk) 20:49, 12 January 2015 (UTC)[reply]
To quibble slightly, you can be missing genes. For example, a woman is simply missing SRY, has no place to put it, like anything on the Y chromosome. It's also possible that someone is missing both copies of some nonessential gene through deletion mutations, though far less likely. Where this gets tricky is that a fair number of characteristics, even common ones, are caused by null mutations in which the gene is functionally disrupted; it's as if it isn't even there, for many practical uses. But since often there is no actual deletion, just a frameshift mutation or a particularly bad point mutation, disrupted enhancer element, etc., the gene still recombines, so it's not really right to say that someone is "missing the gene"; just that what they have isn't active or effective. Wnt (talk) 02:56, 13 January 2015 (UTC)[reply]
@Wnt: Thanks for the clarification. I was pretty sure truly missing genes were possible as a rare event, but I didn't know the right names. Basically I've noticed that ~95% of the uses of "gene" on ref desk should really be "allele", and decided to start my own mini awareness campaign. I can tolerate the sloppy/incorrect usage on TV or in the bar, but I think we should hold ourselves to a higher standard here ;) SemanticMantis (talk) 15:39, 13 January 2015 (UTC)[reply]
Effective Lifetime of Hydrogen Peroxide Solution
If I have a sink filled with 10 gallons of a 4% hydrogen peroxide solution how long will it last? How would I calculate it? The temperature should be "cold" tap water. This would be indoors, but there would probably be some light. I basically want to figure how long it can be used to effectively kill yeast on produce before needing to mix a new batch. Thank you. Any other additional information that you think I should be aware of would be greatly appreciated. David Bradley I (talk) 20:09, 12 January 2015 (UTC)[reply]
I believe nucleation sites are critical to the formation of oxygen bubbles from hydrogen peroxide, meaning it there are many nucleation sites it won't last nearly as long. Note that washing food with it will "use it up", as well.
One rather simple way to test it would be to put a sample in a bottle and shake it. If it foams up (many tiny bubbles), it's still good. If it reacts like normal water (few, large bubbles), replace it. After doing this test several times you can get an idea for how long it tends to last, under your conditions. StuRat (talk) 20:15, 12 January 2015 (UTC)[reply]
Thanks for the tip. Is there a way of estimating how long it should last? I only need it to work for a couple hours. Also, I'll ask another question in another section which is related. David Bradley I (talk) 20:19, 12 January 2015 (UTC)[reply]
I don't think you could get a good estimate without testing it under your conditions. For example, if you wash produce with lots of surface area, it won't last as long. Under some conditions, I don't think it would last 2 hours.
BTW, in case you don't already know, you should wear gloves and safety glasses when using it. It will hurt a bit on any cuts or hangnails on your hands, and really hurt if it splashes in your eyes. StuRat (talk) 20:21, 12 January 2015 (UTC)[reply]
Maybe I'll buy a cheap bottle of medical hydrogen peroxide and do some tests at home to see how long it lasts. Maybe that would be a good way of estimating how much we'll need. David Bradley I (talk) 20:46, 12 January 2015 (UTC)[reply]
Have you considered not putting it in a tub, but just pouring it over the produce ? If you keep it in a dark, sealed container, between uses, it will last longer. However, soaking in a tub will get more of it into contact with the produce (the hidden folds, etc.). What kind of produce is it, anyway ? StuRat (talk) 20:34, 12 January 2015 (UTC)[reply]
I think for our setup we couldn't just pour it over. I'm not sure how long the produce should soak in a 4% solution, but I was thinking 10 minutes. Is that too long? It might be possible to cover the sink to keep it fairly dark, but it wouldn't be sealed. David Bradley I (talk) 20:36, 12 January 2015 (UTC)[reply]
I think 10 mins is good. You might consider portable containers, where you can seal each batch of produce in and let it soak in hydrogen peroxide, then discard it when done. Ideally you should be able to cram the container full of produce, and invert it or shake it so it all gets wet. StuRat (talk) 20:38, 12 January 2015 (UTC)[reply]
We're basically talking about a couple hundred of pounds of produce over a period of two hours. The intent is to reuse the solution as much as possible. If we had to discard the solution after each soak then it wouldn't be an economical way of getting rid of the yeast. David Bradley I (talk) 20:55, 12 January 2015 (UTC)[reply]
I was thinking you could pack it in tightly, to limit the amount of solution used. You probably can't pack it in as tightly in an unsealed container, since some produce will float. You need the lid to push it down into the solution. StuRat (talk) 21:03, 12 January 2015 (UTC)[reply]
Also, if you can "recharge" the solution with a higher concentration of hydrogen peroxide, rather than discarding it, that might be less expensive. There's the cost of the water, but more importantly the remaining potency of the stale batch can be reused then, and you only need to add enough H2O2 to bring it back up to 4%. StuRat (talk) 21:21, 12 January 2015 (UTC)[reply]
Yes, this is ideal, but I have no idea how to figure out if a solution is 4% after I mix it and it decays. If it is too strong then it might bleach the produce, harm the sink, pipes or workers. If it is too weak then it wouldn't be effective. Acetic acid might be a better solution if only for the fact that I can use litmus paper to test it at various times. It is difficult to find out which substances are effective at killing yeast, while being safe for food and workers. Washing with a food-safe artificial fungicide for the yeast would be fine. We just can't use such ingredients in the product itself. David Bradley I (talk) 18:27, 13 January 2015 (UTC)[reply]
Erm, given your phrasing and the scale you're talking about here and the question below, it comes across to me as that you're running some kind of commercial operation. If this is the case, I very much doubt you should be seeking advice about your production process from random strangers on the internet. If this is the case, I would strongly advise you to check the relevant legislation. Waste management for starters, if you're talking about hydrogen peroxide. If my assumption is wrong, please ignore! Fgf10 (talk) 22:43, 12 January 2015 (UTC)[reply]
That's the great thing about hydrogen peroxide, it breaks down into just water and oxygen, so no toxic waste barrels needed. StuRat (talk) 23:37, 12 January 2015 (UTC)[reply]
What are the most economical ways of removing or killing yeast on the surface of produce?
I've been looking into using a hydrogen peroxide soak, but perhaps someone else knows a better way of doing it. I'm basically trying to prevent fermentation, but I can't use any unnatural preservatives in the final product so I'm trying to get rid of the yeast on the produce prior to it being processsed. I'm unaware of any natural preservatives that would prevent fermentation. Thank you. David Bradley I (talk) 20:23, 12 January 2015 (UTC)[reply]
The other method that comes to mind is a UV light, but you would need to rotate the produce so all sides are exposed, and it wouldn't get into hidden folds. With that in mind, your hydrogen peroxide method sounds better, to me. I am of course assuming that cooking or using ionizing radiation (like gamma rays or X-rays) are both out. (The radiation method is inexpensive only on a large scale, and many people won't buy food treated with it.) StuRat (talk) 20:27, 12 January 2015 (UTC)[reply]
Cooking is out, but if hot tap water could kill the yeast then that might be an option. I know it also grows better in a more acidic environment. Does that mean a basic environment could kill it? It might just inhibit growth which wouldn't work at all, but if it could kill yeast then I'm sure there is an economical and safe way of turning large quantifies of water into a mild base. David Bradley I (talk) 20:33, 12 January 2015 (UTC)[reply]
I think that would work, but the people I work for say the labor cost on that would be too high. I've read that sulfur dioxide kills yeast, but I think it might not be legal to wash produce with a solution of it. Potassium sorbate works, but we aren't allowed to use that preservative. David Bradley I (talk) 20:43, 12 January 2015 (UTC)[reply]
That wouldn't be economical either, as you'd need breathing masks for your employees and/or a sealed system with an exhaust fan. StuRat (talk) 20:49, 12 January 2015 (UTC)[reply]
Oh, and don't forget the value of pre-washing it, as that will remove much of the yeast mechanically. The rest will be easier to kill with hydrogen peroxide or some other method. And if it's some type of produce where you can just discard the outer layers, like an onion, even better. StuRat (talk) 20:40, 12 January 2015 (UTC)[reply]
David Bradley I, here's a reference: [19] is a detailed discussion of how to sanitize produce. It's published by the US government. A number of different solutions are discussed, including hydrogen peroxide (which is apparently one of the least used commercially, which might be why it's hard to find a source that answers your earlier question about how long it lasts.). Scroll down for a chart comparing the various methods and below that for references to the original studies.Taknaran (talk) 21:20, 12 January 2015 (UTC)[reply]
Non-organically is fine for the cleaning process. "Natural" preservatives may be okay for the final product. I just haven't found any acceptable ones yet. I have actually looked at that link. Most of the methods aren't approved, don't work well, or don't have much info with regards to killing yeast. One of the reasons I went with hydrogen peroxide was because it was my understanding that Lactobacillus acidophilus killed yeast with hydrogen peroxide. I did notice, in that link, that the waxy coating may actually trap the pathogens in it. Would hydrogen peroxide be able to remove it then? Or is this all in vain? David Bradley I (talk) 18:38, 13 January 2015 (UTC)[reply]
The way that sulfur dioxide is used to kill yeast is to use a solution of potassium metabisulfite. Home winemakers and brewers use it to sterilize their equipment before use. You would need an extraction system of some sort to draw away the sulfur dioxide that's produced but that would probably be the case with most sterilizing agents. I think the main question would be whether any sulfite would be left on the produce after the washing process. There is some information about the use of sulfites here. Richerman(talk)22:36, 12 January 2015 (UTC)[reply]
Actually that will probably make the problem worse. Yeast grows better in a more acidic environment. Killing it with a wash is most probable with a basic environment. David Bradley I (talk) 18:39, 13 January 2015 (UTC)[reply]
Can dogs survive in the wild?
I'm trying to convince my idiot friend that evolution is true, and dogs proves it. I tell him to look at all the different kinds of dogs there are, and since these animals were made by humans via artificial selection, that proves that evolution is a fact. But he's dumb, and says that god made them all. So I want to counter that by saying that god couldn't have possible made them because dogs can't survive without humans taking care of them. I'm fairly certain that dogs, even large ones like Great Danes and what not can't survive in the woods without humans taking care of them, but I just want to make sure. Keep in mind, I'm not talking about animals like the dingo which used to be domesticated, but evolved to revert back to their feral state. 69.121.131.137 (talk) 03:09, 13 January 2015 (UTC)[reply]
Unfortunately, they can survive on their own. Many third world cities (without dog catchers) have large stray dog populations. StuRat (talk) 03:30, 13 January 2015 (UTC)[reply]
For a casual proof of evolution, you might point out that the human spine causes all sorts of problems because, in evolutionary terms, we very recently began walking upright, and the spine design has not yet caught up. Specifically, I'd say the spinal chord should not be inside the spine, which leads to pinched nerves. Instead there should be a tough, rubbery cartilage there, and the spinal chord should be more like a notochord. Unfortunately, there's no evolutionary path to lead there, since a spinal chord half inside and half outside the spine is worst of all. If God designed us, he would have presumably done a better job of it. StuRat (talk) 03:34, 13 January 2015 (UTC)[reply]
It isn't worth arguing with someone who doesn't think that human selective breeding is responsible for various breeds of dogs or of livestock. That is agreed even by most creationists. Whether dogs can survive in the wild, as mentioned, depends on the breed. Some can survive in the wild. The original poster is trying the impossible, which is to persuade someone whose mind is made up. It is fortunate that the characterizations made by the OP apply off-wiki, because calling another editor "dumb" or an "idiot" on Wikipedia would be personal attacks. I suggest that the OP, first, tone down his or her rhetoric about someone who isn't here, and, second, stop wasting time trying to reason to someone who isn't listening to reason. Also, creating an account has advantages. Robert McClenon (talk) 03:38, 13 January 2015 (UTC)[reply]
StuRat meant to say they have large populations of stray dogs, not populations of large stray dogs. And no, evil breeds, like the chihuahua, and monsters like the Great Dane cannot survive as such breeds in the wild. Only those dogs that maintain a form close to what God made (the Dingo, the German Shepherd) can survive without human sinfulness. μηδείς (talk) 03:41, 13 January 2015 (UTC)[reply]
It's not going to work. You can show them all the scientific evidence there is. Denialists by the very definition, choose to disregard all evidence that opposes their personal views. If you truly want your friend to seriously consider the viability surrendering their willful ignorance, you'll have to debate the matter on their field of choice - you'll have to make a well thought-out theologically based argument. As an aside, it will be much more difficult to persuade them while you're insulting them, directly or by implication.
Dogs have a good chance of surviving in the wild, since their instinctive ability to hunt and scavenge is genetically hardwired into them. I'm afraid you haven't quite got that one right. Plasmic Physics (talk) 03:46, 13 January 2015 (UTC)[reply]
Your friend is only an "idiot" if he thinks that dog breeds have always been around and is in denial of artificial selection. But even if he knows what artificial selection is, "God" (i.e. natural biological processes) made those breeds. And either way, it doesn't prove anything about evolution. ←Baseball BugsWhat's up, Doc?carrots→ 03:50, 13 January 2015 (UTC)[reply]
I think you're barking up the wrong tree (pun intended) here. If God created all the different breeds of dog, then surely there shouldn't be any more new breeds being recognised? Well guess what: on 1st January, the American Kennel Club recognised 4 new breeds of dog. Did God just wave his hand and say "I guess I'll just create a new dog breed"? Or did some breeders develop a breed over many years? You need to get in touch with the AKC and investigate the history of the new dog breeds, find who their (human) originators are, and get a statement from them. Your friend is not dumb for his blind faith in Creationism, he is dumb because he is wilfully ignorant of real life. --TammyMoet (talk) 09:57, 13 January 2015 (UTC)[reply]
I'm with the above answers but I'll leave an additional note that whatever your friend may have said, I think you'll find creationists more commonly claim that artificial breedingdoesn't produce new species, the claimed microevolution vs macroevolution distinction [20], (all wrong in many ways, as explained in our articiles), and that artificial breeding is simply "destroying information" [21] so it isn't surprising if some dogs would have poor survival were it not for humans. To be clear, these are poor arguments with many holes, I mean creationists come up with silly things like the alleged perfection of the banana (which I think even the inventor acknowledges was a dumb argument), but the point is you aren't likely to get anywhere by arguing whether or not dogs can survive in the wild (which isn't to say you'd get anywhere by pointing our more substanial flaws). Nil Einne (talk) 11:22, 13 January 2015 (UTC)[reply]
BTW, I would add even if your friend wants to suggest all the different dog breeds were made by god, their likely argument in response to any of your claims that they can't survive in the wild would simply be that that's how god created them intentionally because they were intended to be companions to humans, and they weren't intended to survive in the wild, similar to the banana argument, or many other things like that. Of course, as mentioned by others, it seems difficult to sustain the idea that all breeds were created by god, since we're creating new ones, so ultimately it seems likely your friend will have to accept that some breeds were basically created by humans, even if they're then likely to fall back on to other arguments like those I highlighted. (You can also get in to arguments about why god created dogs breeds primarily intended to attack other animals or even humans, when god didn't want any of that but that's not an argument unique to dogs. And in any case, it's likely creationists will suggest that these dog breeds were only created by god after the downfall of Eden or he created them because he knew it was going to happen even if he didn't want to or even simply they weren't like that before Eden despite having the teeth, build etc suited to that purpose and it's not god's fault it all changed after Eden despite him designing them in such a way they seemed well suited to change when humans broke Eden [22].) Nil Einne (talk) 17:22, 13 January 2015 (UTC)[reply]
To begin with, artificial selection isn't really quite the same thing as natural selection after all. The problem is that the human breeder eagerly picks out genes of large effect that have many pleiotropic consequences, which won't actually be used for evolution in the wild. (This effect is stronger in a lab setting, e.g. mutating fruit flies with radiation, where huge deletions of the genome may be brought about that practically never happen in normal evolution; some of the confusion over this ties into the "hopeful monster" concept) The result is that the human-made breeds tend to be more sickly in ways that a slow, sane pace of natural selection wouldn't have caused. Now to be sure the dogs, if released to the wild, should still survive; eventually they will ditch the worst large-effect mutations and, if they still need the trait the breeder selected for, find small effect mutations that affect it more precisely.
Now as to your argument, presumably your friend recognizes that there are breeds of dogs that exist now that never existed in the past; yet he says God created them. That means that he recognizes that something created by God doesn't have to date back to Noah's ark; God is allowed to have a plan for something to appear. Now if that is so, then you and he are arguing over very little, because no scientist will argue that something will evolve unless it is physically possible and indeed is a pretty good solution to the ecological problems of its niche. In religious terms, unless God planned it. Wnt (talk) 14:49, 13 January 2015 (UTC)[reply]
I don't think your argument about dogs is a good one. Evolution requires three things: One is that living things inherit characteristics from their parents - another is that natural selection favors plants and animals that are better able to reproduce than others, the third thing is that the process of inheritance makes mistakes (albeit rather rarely). The situation with dogs shows that dogs inherit characteristics from their parents - a poodle plus another poodle results in a whole lot of poodles. But it doesn't demonstrate that dogs that are better suited to their environment reproduce better - to the contrary. It's unlikely that a highly specialized pedigree dog will have fewer defects than a 'mutt'. Inbreeding has caused all sorts of defects to develop in pedigree dogs - and the very "best" of them are far more likely to have a hard time reproducing than a dog that's some random mix of many breeds. Also, the "selection" process isn't "natural selection" - it's clearly human intervention...which is almost like an "intelligent designer" at work.
So what you need is a much better example. There are two examples that I think are compelling - but they both take a bit of investigation. If your friend is simply dismissive of your ideas, then you're unlikely to get him/her to sit still long enough to be convinced.
Peppered moth evolution is a classic. These moths were colored white with little black speckles to match the lichen and tree bark in rural England. Up until around 1811, there had been no examples of these moths in any other patterns. But gradually, butterfly collectors noticed an increasing number of black peppered moths showing up. It turns out that the smoke and pollution from industry in the areas where the moths lived was coating the trees with dark soot. Within a decade or two, almost all of the moths were black...then, when the Clean Air laws were passed and the amount of smoke in the air decreased spectacularly, the black moths became rarer and rarer until today, you can't find a single one. Clearly the moths were evolving to be better camoflaged against the trees - and then evolved back again when lighter colors worked better.
The Recurrent laryngeal nerve in mammals - and especially in the giraffe is a fascinating demonstration. It seems that the vocal chords (the larynx) evolved from a greatly distorted gill from each side of some primordial fish. The nerves going to each of the two gills on that original fish had to bypass the arteries going to the heart - the right one went over the artery, the left one, under...and modern fish of all species are just like that. No big deal if you're a fish. But as the two gills moved closer together over millions of years of evolution - one nerve was forced to loop past the heart. So in a giraffe (or a human, or almost any other animal) - the nerves controlling the right side of the larynx go directly from brain, down the neck for a short distance to the larynx...but the left side nerve goes from the brain, all the way down to the heart, around that artery, then all the way back UP the neck to the larynx. In humans, this is no big deal - but in a giraffe, it means that one nerve is about 15 feet longer than the other. Since electrical signals from the brain have to travel 15 feet further to get to the left of the larynx than to the right, this makes it almost impossible for the poor giraffe to coordinate the muscles in the larynx. This is why giraffes are almost the only mammals that don't make vocalizations. Now, your friend needs to explain why god decided that all animals have to have this nerve looped around that artery...it makes no sense whatever. If "God" designed the giraffe, he was not the "intelligent designer" but rather the "bloody stupid idiotic designer". Sure, you might argue, he may have decided that giraffes don't need to make a noise - but then why bother having a larynx - let alone bothering to connect up a nerve in such a totally crazy way? Why would ALL air-breathing animals from dinosaurs, to humans and giraffes have such an unbelievably stupid design? Any rational design would have both nerves going the short way to the larynx...and if they did, then the spectacular song of the male giraffe during gentle courtship of his mate would grace the plains of Africa as testimony to God's Greatness...but no. If hard-pressed, a giraffe can make a sound that's been described as a cross between a bleat and a cough. God did not make the giraffe...it's just not credible...it evolved from a fish - and when you look at the evidence with an open mind, there is really no other conclusion.
These are great examples...there are many, many more. Why do some people have lactose intolerance? Why do some people inherit sickle cell anemia? Why do bacteria develop immunity to drugs in hospitals? Why do rats in New York have genetic immunity to Warfarin? Why do rabbits in Australia have genetic immunity to mixamatosis? All of these things are clear demonstrations of evolution happening on human timescales. There are several long-running experiments where bacteria are forced to evolve by changing their living conditions - and they change over time, in exactly the way that evolution predicts.
It's actually very hard to imagine how evolution might NOT occur. If the shape and nature of an animal or plant derives from it's DNA (which is hard to deny) - and if DNA is replicated from parent to offspring (also, hard to deny) - and there are occasional errors in that copying process (again, hard to deny) - then occasionally, a small variation will occur in a plant or animal. If that variation makes it reproduce a little more efficiently than the others of it's species, then its genes will (inevitably) be copied into more of the next generation than the original genes - and gradually, more an more of the members of that species will carry that gene. Eventually, every plant or animal in that species will have the new and improved gene. Evolution has happened. Do that enough times and you get human beings from fish.
We can even see evolution happening in systems that are not biological in nature. If a song or a TV show or a movie becomes successful through some clever innovation, other makers will tend to copy that idea. Making a movie is expensive - and going with some crazy new idea is dangerous - so most of the time, they make variations on what worked before. Movies that embody themes that fit the times make more money than those that don't - and that allows their makers to make more of them. Hence you get huge waves of movie genres (cowboy films, film noire, disaster movies, etc) that come and go as the environment favors one or the other. All of the essentials of evolution are there...movies that 'work' tend to produce 'offspring' that are broadly similar. Movies that do well in the box-office earn more money and therefore inspire more copy-cats. Movies that do badly are dropped and produce no copy-cats. Over time, movies adapt to fit the viewer preferences. You can see the same things happening in a huge range of fields. Whenever there is copying with variations and pressure for things to do well or do badly, for reasons that the makers don't really understand - then evolution occurs. Why is it that almost all cars come in silver or black - but almost none in purple? I'm pretty sure it's evolution.
If you absolutely MUST stick with the dog thing. Point to the Labradoodle. A Labradoodle is a cross between a labrador and a poodle. There are breeders all around the world that 'make' labradoodles by crossing parent dogs of those two breeds. But, you can also take two labradoodle and mate them - and you get another labradoodle. Clearly, god didn't make the labradoodle. There was no 'labradoodle' breed before 1955...although presumably an occasional accidental mating of a labradore and a poodle would have happened, we didn't have a 'breed' of these animals that you can point to and say "Oh - look! A labradoodle". At this point, your friend either has to admit that god didn't design the labradoodle - we humans can make a labradoodle where there was no labradoodle before. We can do it anytime we want. Labradoodles are a stable, well-recognized breed. Of course your friend is at liberty to claim that labradoodles aren't a "real" breed...so they don't count. But then we have to look at other kinds of dog that he does claim are breeds that were made by god. Maybe God made the Labrador? Sadly, no. We know that all labradors are descended from two very specific dogs...and, remarkably, we even know their names! "Avon" and "Ned". These dogs (which were known to be good gun dogs - but which were definitely not "labradors") were given by the Earl of Malmesbury to assist the Duke of Buccleuch's breeding program in the 1880s. Before that, there were no Labradors...so we know for sure that labradors are "the work of man" - just like labradoodles. If you go through all of the Wikipedia pages for various dog breeds, you'll find some (like the Labradoodle and the Labrador) who's origins are very well known and documented - and others (like the poodle) where we know only that the first known examples were around on some particular date.
So I suppose that your friend (if a rational, thinking person) would be forced to admit that Labradoodles were definitely NOT created by God, and more surprisingly, neither were Labradors. Of course (s)he may cling to the view that poodles are a divine creation...but at least one is forced to segment the world of dogs into the originally-created-by-God set - and the set that were created by man. Now you have to ask whether some of the dogs in the "made by god" set really belong in the "made by humans" pile? In the end, the only thing we really can deduce from human history is that the wolf was not created by man...but most dog breeds were.
Sadly, this doesn't get you any closer to an argument about evolution. It does demonstrate that mankind is capable of producing new kinds of dogs - which I suppose breaks the doctrine that 100% of all species were made by God in the Garden of Eden. There were no labradoodles in Eden. SteveBaker (talk) 17:19, 13 January 2015 (UTC)[reply]
The dangers of messing with labradoodles.
Actually, if you cross a Lab and a Poodle you will get a Labradoodle. But if you cross a Labradoodle and a Labradoodle you can get everything from a Lab to a Poodle to a Dabraloodle to a Poobradaddle, to a Cobrababble, to an Oprahbubble, to an Oobracadoobra. From there it's just one small misstep to a Scooby Doo or a Deborah Messing. See dihybrid cross. μηδείς (talk) 19:00, 13 January 2015 (UTC)[reply]
My wife and I went to a breeder with the idea to get one for a pet, they said that they used labradoodles to parent their puppies. This is confirmed in Labradoodle#Types. (In the end, we decided that labradoodles are not such great animals after all). SteveBaker (talk) 19:45, 13 January 2015 (UTC)[reply]
Yes, if he's paying close attention, culling (i.e., selling) the less true-to-form puppies, and only breeding the ones with traits he wants, he'll eventually start getting mostly passable labradoodles. But they won't breed true unless it turns out that all the desirable and defining traits are homozygous. μηδείς (talk) 20:10, 13 January 2015 (UTC)[reply]
SInce people have been breeding labradoodles for close to 60 years, and aggressively so for 20 years - at maybe 2 to 3 years per generation, they're likely to have eliminated almost all risk of throwbacks. But they certainly don't yet have the complete uniformity of more established breeds - and already they're getting the inevitable genetic diseases starting to pop up. However, the original point remains - we have labradoodles, they (mostly) breed true - and god didn't create them in the Garden of Eden. Either humans created this breed or we have no free will. Pick either one! QED. SteveBaker (talk) 20:25, 13 January 2015 (UTC)[reply]
We're really getting into philosophy more than science here. A pointier version of this argument came up in the U.S. a year or so ago when Richard Mourdock was lambasted for saying that pregnancies following rape were part of God's plan.[23] Now I'm normally all for roasting a Republican, but this struck me as unfair, because the alternative position is to single out the kid in the class who was produced by a rape, point your finger at him and say "you are not part of God's plan". We should think a bit more about what God's plan actually means first! I think a good analogy is with the putatively endless set of contigency plans come up with by military organizations like the U.S. Army. One kind of assumes that if Belgium ever decides to invade Virginia Beach, they have a plan for it. My understanding is that theologians try to accept both that there is a divine plan for everything, even after all the weird events that have happened in history, and that there is free will, which makes for some creative logic, but so long as they believe God is omniscient and all-powerful it is nothing they can't handle. The bottom line though is that there should be no litmus test for religion set up at a security counter at the classroom door - everyone is capable of learning what evolution predicts in terms of what we measure by natural means, regardless of what they think the theology behind it is; they should be able to recognize it is practically useful without having to believe any religious assertion that our lives are unplanned, random, meaningless, or insignificant. Wnt (talk) 18:27, 13 January 2015 (UTC)[reply]
The problem being that if you accept that all things that happen are a part of god's plan then you wave goodbye to free will because you're saying that the rapist didn't have a free choice to rape or not - he was merely being constrained to follow god's plan in the creation of this child whom you're claiming is indeed a part of the plan. That's a logical possibility, obviously - but the absence of free will is definitely contrary to most religious thinking - and would cause severe upset in society if it were true. If the rapist is able to make a totally free choice - then one of those options has to be to veer away from any "plan" - and now you're forced to point to the kid in class and tell him that he's not a part of the plan. Neither of those options are particularly appealing!
Furthermore, if everything that happens is a part of the plan - then god's plan boils down to the universe slavishly following the laws of physics - and if that happens then you don't need the existence of a god to explain things that happen because the laws of physics do a perfectly fine job of doing that. Then the existence of god boils down to a gross violation of Occams Razor...which is fine if you like that kind of thing...but is what ultimately leads me to scrap the entire silly idea. SteveBaker (talk) 20:03, 13 January 2015 (UTC)[reply]
Well, ever see a Choose Your Own Adventure book? You have many choices to make, yet every one brings you to some page written by the author of the book. I'm not saying that's way it is - there's a huge variety of philosophy possible here - but this illustrates how things can be neither random nor predetermined, and besides, if mankind is created in the Creator's image, it's always in our creative works that we'll find the most useful metaphors for understanding. Nobody is denying that, so far as we can observe, the laws of physics seem to be valid. But they always proceed from some starting point. Is it really Occam's Razor-able that that starting point was some simple set of starting conditions "at" the Big Bang, even though it seems like the complexity of the events in the universe expands without limit the closer you look back toward it, and we know nothing about it? Even though we then turn around and use the anthropic principle - itself more or less a form of creationism! - to say that somehow the "right" starting conditions were picked? What if the starting conditions aren't set at infinity in an uncaring way for the random development of interesting life someday, but right here, right now, by some God who actually sees and cares about us? It's all very mysterious, but beware of taking some (atheistic) religious assumption, dressing it up in sciencey garb and hiding it in the part of the theory of the cosmos that we don't actually know anything about. Wnt (talk) 20:24, 13 January 2015 (UTC)[reply]
Well, yes - let's take your analogy of the 'choose your own adventure' book. You're trying to tell the kid in the classroom that he's a part of the plan - but it's inconceivable that any other path than the rape of his mother would result in him being there. In order to be who he is on that day with that specific birthday, it pretty much had to be the free will of the rapist that caused him to be there, on that day, with that eye and hair color and that birthday with a mother who was 15 years old when he was born, etc, etc. There just aren't too many other routes through the 'choose your own adventure' book that would lead to that. 99.999999% of the other ways that free will could have directed us through the book would result in him not existing. Let's face it, a free-will decision by Attilla the Hun would have resulted in a large fraction of the population of the world not existing...and Og-the-caveman could have picked a different wife and NONE of us would exist. So this is a REALLY large book - and hardly any of the pages have you or I on them.
So what you have to imagine is that this one particular path through the book included this kid - but that there were many other paths ("plans of God") that would have resulted in him never existing...yet you're still going to tell him that he's a part of god's plan...although technically, you're saying "You're a part of plan number 153920423 of 1032534070734095738087230498 plans that god made but which didn't play out." Taken to a very reasonable extreme, the location of the pencil on my desk right now is also a part of God's Plan - and my putting it there as an act of free will was just a page in this adventure book-style plan that included me deciding to put the pencil someplace else - 1/100th of a millimeter to the left, or to toss it in the trash, eat it...whatever. This means that this plan book, ultimately resembles the "many worlds hypothesis" - where every possible bifurcation of reality at the quantum level results in another whole section of the "choose your own adventure" book. That's fine - but again, we've arrived at a place where the laws of physics suffice to explain all of this - and your belief in god once again rests on denying free will, or denying Occam's Razor. That's a very slippery path because then I have to ask why you'd choose this particular unlikely (but possible) denial of the razor rather than the near infinity of others...such as that SpongeBob SquarePants actually created the universe. SteveBaker (talk) 20:52, 13 January 2015 (UTC)[reply]
I can't really say that idea is right (it is chosen more as a counterexample, after all) but when one considers the total number of 'plans' that could exist, not merely in infinity, but in an infinity of cosmoi, it doesn't matter how many numbered plans exist; each is still a truly unique inspiration. But bear in mind two things -- first, that since the laws of physics are time-reversible, each moment can have multiple pasts as well as multiple futures; and also, that they are nondeterministic, which means that it is possible that our fate might be nudged this way and that rather than proceeding along a random vector. I think it is worth considering that our consciousness might exist with at least two dimensions of time - one in which the normal laws of physics operate, and one reflecting the progressive work by which God steadily revises and perfects the universe. In keeping with accounts that "every tear will be wiped away", perhaps people pass into parallel worlds, keeping the virtues that they have attained by resisting evil, yet seeing all that evil pass from mind, and indeed, never even having been real at all, in some sense. So while I mentioned one fixed 'initial condition' in the present above, actually I mean that there may be multiple initial conditions, with the time between them interpolated to fit using non-deterministic physics, so that it is possible for the author of the universe, with our input, to steadily revise the entire plot - past, present, and future - within his own dimension of time rather than the time frame that flows within the context of the story.
Now we've really gotten far off the point with this, but for this question: it's possible that God had in mind the form of a certain kind of poodle from a previous revision of the cosmos, or from some Eden (next door to "the" number line, and the place where the six regular polytopes that can exist in four dimensions might be found) or from some other sort of plan. It might not be without significance; it might not be random; we know it's not truly all our choice because we can't just breed up anything at all. And the same is true of the species we share the planet with. Of course, it will be so much easier to see if ever mankind were to visualize a foreign planet with its own kind of life, because I have little doubt that that world will have its own trees, which we may even be tempted to give familiar names, and its own fish, and countless other organisms we recognize, as well of course as a few residents of Eden who have not yet been spotted on Earth (but give our biologists time...) Wnt (talk) 22:18, 13 January 2015 (UTC)[reply]
What is the difference between analgesic and sedation?
Briefly, analgesics are intended for use as painkillers. Sedatives are to reduce anxiety, irritability - generally to calm the user. In many cases, analgesics are also sedatives and vice-versa - so there is considerable overlap. A mild sedative might not directly act to reduce pain, but may reduce the anxiety and stress caused by the pain and thereby make it more bearable. SteveBaker (talk) 16:04, 13 January 2015 (UTC)[reply]
Professional laptops
Why do many gamers and professionals, such as graphics designers or engineers, seem to use big, bulky, heavy laptops in this day of thin and portable devices? 194.66.246.5 (talk) 14:43, 13 January 2015 (UTC)[reply]
There's really no substitute for a large screen, which allows you to see details you just can't make out on a tiny screen, even at the same resolution. Similarly, a full-sized keyboard allows for faster entry than a compact keyboard. And what are the advantages of being small ? It won't fit in your pocket, in any case, so then it's just a question of whether the weight fatigues you as you carry it. Most people can carry several pounds indefinitely without becoming fatigued. StuRat (talk) 14:48, 13 January 2015 (UTC)[reply]
Some of the laptops I see people using don't look portable though. It looks silly for example opening it up in a coffee shop due to its size. 194.66.246.5 (talk) 15:03, 13 January 2015 (UTC)[reply]
Well, obviously they are portable, if they were carried into a coffee shop. The more general question for any device is "How small is too small ?". Traditionally, technology limited how small we could make things, but now we are getting to the point where the technology allows us to make something that is so small as to be unusable for other reasons. Larger cell phones (especially flip phones), for example, allow a microphone by the mouth and a speaker by the ear, which makes for much better communication. Here the upper limit is probably that it needs to fit in a pocket, but there's not much point in making it much smaller. You also want to be able to hit all the buttons by hand, not have to use a stylus, and with a full QWERTY keyboard there are a lot of buttons, so the space adds up. And people want a longer battery life for any device, which requires bigger batteries. StuRat (talk) 15:21, 13 January 2015 (UTC)[reply]
I don't know exactly what models you're thinking of, but people doing graphics-intensive work are surely going to want a large display. They may also want more options for what can be attached or inserted, such as an Ethernet connection, USB, and a Blu-ray disc. Jc3s5h (talk) 14:51, 13 January 2015 (UTC)[reply]
In some respects, yes. Certainly you can pack twice as much into a laptop twice the size. But eventually we will hit a point where you can pack more than enough memory, storage space, battery etc., into as small of a space as you would want. Then we hit those ergonomics limits. There are some possible workarounds, like a roll-up keyboard and screen, to make it more portable without being unusably small. StuRat (talk) 15:31, 13 January 2015 (UTC)[reply]
I'm one of those people - I write C++ realtime 3D graphics code for a living (I'm currently doing "augmented reality" stuff). I don't often haul any of my laptops around with me (I have 4 of them!) - but when I do, it's because I need the power of a decent computer - otherwise I'd use a tablet or even just my phone with a folding bluetooth keyboard. Those little folding keyboards are surprisingly comfortable to type on. So the need for a really good laptop is a combination of wanting a full-performance GPU, a good sized screen with really good back-lighting, a high-horsepower CPU and a ton of memory + disk space. The super-thin computers tend to have poorer everything.
It would be different if I was some kind of executive who needs to be able to do email and display powerpoints in airport lounges...and not much else. When you need your laptop to compile a million lines of C++ code - or to debug subtle graphics glitches - you really need something with some 'oomph'. All of that horsepower also makes the laptop consume a ton of energy - so you need chunkier batteries and active cooling - all of which adds considerably to the weight and thickness. The large screen and decent backlight makes that even worse. But since I'm only using it when I absolutely need that much power (and when I absolutely can't do it at home or in my office) - then that's the best option.
In addition to my big Dell laptop, I do actually have an HP "Chromebook" - which essentially runs a browser and nothing else, has very little local storage and doesn't even have a hard drive, and an old "netbook" - which I like because it's physically tiny - but which has been supplanted by the Chromebook. The battery life on the chromebook is incredible and it's very lightweight. That's great for taking on vacation and leaving in the car for occasional use. It's better than a phone or tablet - but useless as a general purpose computer. My big-assed Dell laptop is good for heavy-duty work - but I wouldn't want to lug it around with me everywhere. My day job bought me an Apple laptop - it's like a piece of jewelry - pretty to look at, pleasant to the touch, fancy magnetic power cord (why?!) - but falls between the Dell laptop and the Chromebook for all practical purposes. When I need horsepower, it's inadequate, when I just need to surf the web, it's over-kill. There never seems to be a time when I actually need it. So it collects dust until I need to test something on it (and 99% of the time when I do the battery in that super-sexxy Apple mouse needs to be replaced!).
So for me, it's a matter of picking the right tool for the job. Most of the time, I use a deskside computer with three large monitors and a really good ergonomic keyboard. My one less-than-ergonomic peripheral is my MINI Cooper-shaped mouse (it has brake lights that light up when you stop moving the mouse!)...it's actually much more sensitive than most mice and I love the subtle detents in the scroll wheel.
As a counterpoint, I did all the computations an simulations for my PhD. dissertation on a tiny 13" Powerbook laptop. As you know, actual computational complexity isn't always closely related to the complexity of the work. So, while that computer would have choked up a bit on large compile jobs, it was more than enough for my scientific computing needs at the time. The take-home point for the OP is that people have different use cases, and for the foreseeable future computational power will trade off with weight and battery life. Also not all users act rationally, and I suspect many area coffee shop workers like to show off their big, heavy, high powered laptops, even if another machine could suffice :) SemanticMantis (talk) 16:09, 13 January 2015 (UTC)[reply]
What about engineers? Don't they often require both portability and high powered computers? Since they use specialist software but also travel a lot to make presentations etc. So do they have a portable laptop and a high power one? 194.66.246.5 (talk) 16:20, 13 January 2015 (UTC)[reply]
Engineers are a very diverse group, so I don't think we can talk about all of them at once. Some do a lot of presentations, some never do. Some engineers need computational power, some don't. For example, my brother in law uses a normal modern (thin-ish, light-ish) 15" Dell laptop for his job as an on-site industrial engineer - he runs in-house software but has never mentioned performance issues. But a mechanical engineer using finite element methods to model complex material deformation via partial differential equations might need more computational power. That's the point I was trying to make above - in the modern era, even rather sophisticated modeling and computation can sometimes be relatively computationally inexpensive. Even a very sleek and small modern Macbook Air can do computations in minutes that would have taken days on older desktops. So don't confuse "complicated, hard to understand work" with "work that requires very high performance computers by modern standards"
Going the other way, it's really computationally hard to factor large numbers into primes, but conceptually it's very easy. On the other hand, the fast fourier transform requires a lot of mathematical background to understand, but runs very quickly and is used in many engineering applications. SemanticMantis (talk) 16:37, 13 January 2015 (UTC)[reply]
I typically run 3 or 4 solvers in parallel (they are single threaded) on my vehicle dynamics simulations, but I have found the actual speed of execution of a given job is only vaguely related to the headline numbers of a given computer, things like drive I/O speeds are often as important. I use a laptop for most of my data crunching because I occasionally need to use it in cars and meetings. For a given thread it is slightly faster than my engineering workstation, but that can handle 8 threads at a time, the laptop only 4, and it has much more storage. Greglocock (talk) 19:53, 13 January 2015 (UTC)[reply]
I'm not sure exactly which laptops you don't think are "portable". Even the big ones are really not that heavy. Unless you have physical challenges or are planning on going hiking with it, I'm not sure what the problem is. Cowboy up.
I did get a smaller laptop for my last trip to Europe; it is more convenient to carry than my older 17'' model (which however is much nicer to look at pictures on). So sure, there's a tradeoff, but it's not really "portability". They're all portable. --Trovatore (talk) 16:45, 13 January 2015 (UTC)[reply]
There is certainly no "one-size-fits-all" rule here.
These days, presentations are often uploaded to the Internet - so when I turn up at some customer's site to do a presentation, I just tell them the URL and have them bring it up on their conference room display screen. So the need to use a computer of any kind is kinda limited. If I'm concerned that my host might not have an internet-connected TV, I also carry a "chromecast" gizmo - which is no bigger than a memory stick and can be plugged into any TV with an HDMI port...I can use my phone to instruct it to grab video off the Internet and display it. Using a laptop to do this is definitely overkill.
However, if I'm called upon to do a demo of some piece of software, something that can't be done with video, still images and text - then I'll very often have to figure out how to connect my laptop to whatever in-house video system is present - and this is *ALWAYS* a nightmare!
Mostly, my computer usage splits into stuff that's on the web (for which my phone or tablet (plus bluetooth keyboard) may just barely suffice - but the HP Chromebook is perfect) and stuff that's heavy programming/documenting work. For the latter, I get massive productivity benefits from having multiple high-resolution screens, so a desktop computer is the only answer. My large laptop is only useful for those super-rare circumstances where I have a lot of heavy work to do, yet somehow can't be at my desk either at home or in the office...and even then, I increasingly remote-login to a server someplace to do heavy computational stuff.
I used to one of the people with a power laptop to manage complex scientific codes. However, my code outgrew what any laptop can offer, so now I either run on uber workstations (16 cores, 256 GB of RAM) or on computer clusters. As a result of that transition, I now do most work via remote login, so I no longer need a big laptop. Hence, a light-weight laptop plus a fast internet connection is now fine. It really is about the use cases and how much power you need with you to do your work. Some people want (or need) very powerful laptops and other people have found ways to get things done with less and hence may opt for light-weight, less powerful configurations. Dragons flight (talk) 19:49, 13 January 2015 (UTC)[reply]
For me, the nicest thing about large laptops is precisely that they're large. The keyboard is easier to type on; the display is easier to view. Whether that's worth the extra weight depends on how heavily you're using it, and how far you're planning to walk.
I was reading today that it's more or less certain that all of the US flags that were left on the moon by the Apollo landing crews will have been bleached white by the sun. (Evidently the flags were a last-minute addition to the mission and were bought at a local branch of Sears without consideration of dye stability in intense sunlight!)...I find this kinda ironic...but that's another matter.
Anyway - this made me wonder. Most of the astronauts brought photos of their families or dead friends, etc to leave on the moon as a perpetual memorial to them. It seems likely to me that those too may have been bleached white.
How do the materials in photographs from the 1960's and 70's survive in that kind of intense UV light? At least a couple of the photos seem to be color pictures...and I know that color photos I have from the 1960's have faded quite a bit - despite being kept mostly in the dark. It doesn't look like the pictures were in any way special...like not special dyes used to make them or anything.
Did all of those treasured pictures wind up as white cardboard squares?
I'd think yes, they would be bleached white if left exposed to the Sun. But perhaps they buried them under a layer of Moon dust, or even if not intentionally done, the dust generated when the lander took off might have coated them with a thick enough layer to block UV. StuRat (talk) 15:34, 13 January 2015 (UTC)[reply]
Ignoring launch events "It would take 1,000 years for a layer of moon dust about a millimeter (0.04 inches) thick to accumulate" [24]. I'm not sure how much the launch would have generated, but unless that was enough by itself the natural dusting process wouldn't provide enough protection. SemanticMantis (talk) 15:50, 13 January 2015 (UTC)[reply]
Have you done any research on the insolation of the moon across the spectrum? It might be useful to be able to express irradiation on the moon in terms of how much more or less light hits the surface at each wavelength, compared to the Earth. The other thing would be to narrow down what type of printing technology was likely to have been used. E.g. a polaroid may well fade much more quickly than a Kodachrome print. Also they may have put them in protective sleeves, as mentioned at Photograph#Polyester_enclosures. The article mentions atmospheric protection, but also "Polyester contains a benzene ring that absorbs UV light" (https://en.wikipedia.org/wiki/Sun_protective_clothing) For Earth-bound photos, much of the degradation is due to reactions with the atmosphere (e.g. humidity), in addition to light. Obviously the moon has less humidity fluctuation so that might help to counteract any increase in UV exposure. SemanticMantis (talk) 15:50, 13 January 2015 (UTC)[reply]
It's not really an "image format" in the sense of "JPEG" or something. It's a monochrome raster image (such as would be transmitted to a TV set back in the days of black and white analog television) - but for some reason they scaned the images vertically instead of horizontally. So the horizontal resolution of the images are 512 lines but the vertical resolution is determined only by the quality of the recording and playback equipment - but probably less than 512 "pixels" per scanline because that explains why they'd use vertical scanning to improve the overall resolution of non-square images. The amplitude of the wiggles in the grooves of the record are the brightness of the image. It's about as simple as it could possibly be, given the (essentially analog) standards of the day. They even included a stylus with the record to allow the disk to be read more easily. Color images are encoded with three consecutive images in red, green and blue. SteveBaker (talk) 19:17, 13 January 2015 (UTC)[reply]
Dumb questions? Science at school never explained certain stuff to me.
1) Why do we count seconds and minutes up 60. Why not have 100 seconds in a minute. And 100 minutes in an hour. It would make time math so much more simple. 2400 minutes in a day.
2) And also, why do helicopters keep their relative position whilst hovering. Since the earth is spinning, shouldn't the ground be moving underneath it. Likewise, what if you were travelling in a plane at the speed of earths rotation. Shouldn't this enable you to hover and remain in once place.
3) And also, what if I was travelling 1mph below the speed of sound and a threw myself forward 2 mph. Would that cause a sonic boom, would I be technically travelling faster than the speed of sound. Again likewise, isn't that cute, sexy cabin stewardess pushing that trolley up the aisle moving faster than the plane she's travelling on. Wow. — Preceding unsigned comment added by 82.19.76.217 (talk) 17:26, 13 January 2015 (UTC)[reply]
1) The base 60 system is left over, I believe, from Babylonian times. They wanted a number that's divisible by a lot of integers, and 60 is divisible by every integer up to 6, while 100 isn't even divisible by 3. This was before fractions or decimals were much used, so they liked keeping things as integers, whenever possible. So, if you had 6 people taking shifts using pedals to drive a pottery wheel, each would have a 10 minute shift, nice and easy. During the French Revolution, they tried to introduce metric time, but it was just too different.
2) The helicopter and plane all move by displacing air, so their base speed is that of the air, and then they either add or subtract from that speed. See air speed and ground speed, which can vary dramatically, say if the plane is in a jet stream. The air moves with the Earth, ignoring wind, because the same forces which started the Earth spinning also did the same thing to the atmosphere, and friction with the ground ensures that the atmosphere moves more or less at the same speed as the rest of the Earth.
3) A sonic boom is caused by the relative velocity of two objects, not the absolute speed (if there is such a thing). So, you won't create a sonic boom on the plane, but I suppose if you were crazy enough to have an open window at that speed and yelled as you ran down the aisle, you might indeed create a very minor sonic boom to observers on the ground. Of course, you won't make nearly as much noise as jet engines, so they likely won't even hear it. StuRat (talk) 18:41, 13 January 2015 (UTC)[reply]
It is probably based on the Egyptian calendar actually since a year was 360 days (plus 5 extra days). Months were always 30 days and weeks were 10 days. I would think the helicopter question is mostly a matter of inertia. When a helicopter takes off it retains its inertia that it had while grounded. It moves by changes its inertia relative to the planet. Otherwise its natural state should be to move in the same direction as the planet (i.e. hover). Taking off doesn't reset its inertia to zero and cause the planet to rotate away from it.David Bradley I (talk) 19:06, 13 January 2015 (UTC)[reply]
We have 60 seconds to a minute, 60 minutes to an hour, and 24 hours to a day because we inherit these measures from older civilisations. Many, in particular the Babylonian civilisation, divided things into 60 because it is a particularly easy number to divide into smaller parts. Thus, 60/2 is 30, 60/3 is 20, 60/4 is 15, 60/5 is 12, and 60/6 is 10. Also, 60/12 is 5. 60 is the smallest number that when divided by 2, 3, 4, 5, 6, 10 and 12 gives a whole number answer. This is very useful if you don't have a calculator to help with your arithmetic. We have 24 hours in a day because originally the day and the night were each divided into 12 hours (24=12+12). 12 also has lots of divisors (2, 3, 4, 6, 12), and so is again a helpful number when you're doing arithmetic without a calculator, particularly when you're doing business that has to be equally split between 2, 3 or 4 people.
So our measures for time are really the result of people in history choosing numbers that made it easy for them to do their sums. If we were going to design a new time measurement system today, we might well choose something different. RomanSpa (talk) 18:55, 13 January 2015 (UTC)[reply]
(ec)
Why 60's? The Egyptians liked to use numbers that are effectively in base 60 - and from then we get 60 minutes in an hour, 60 seconds in a minute, 60 degrees in an equilateral triangle and so forth. 60 is actually a nice number to choose because it divides evenly by 2,3,4,5,6,10,12,15,20 and 30. 100 isn't so nice: 2,4,5,10,20,25 and 50.
The air more or less follows the rotation of the earth because of friction between it and the ground - helicopters remain stationary compared to the air (not really the ground).
Yes, if you could do that outside the airplane, that would cause a sonic boom. Yes, you would be travelling faster than sound. However, the speed of sound is (just like the helicopter) measured relative to the speed of the air. So inside the plane, the air is moving at the same speed as you are and the speed of the trolley is only a couple of mph faster than the air...so the speed of sound isn't broken. If you put the cart on the wing of a plane that's flying 1mph below the speed of sound and pushed it forwards at 2mph - it would break the sound barrier...boom...etc.
DF has the correct answer and refs below. But perhaps you got confused with the doppler effect? Interestingly enough the common illustrations like those used in our article are vaguely similar to the illustrations for sonic booms. SemanticMantis (talk) 19:59, 13 January 2015 (UTC)[reply]
Hmmm....I don't see how. The sonic boom has to travel from A to B (eg from a Concorde airliner to a car window down on the ground that shatters from the sonic boom)...the intervening air can't "know" how fast the car is moving - either the energy is transmitted or it isn't - and when that energy arrives at the observer, it still needs to be dissipated by shattering the window. If what you say were true then aircraft travelling at supersonic speeds would be suffering sonic booms from buildings on the ground...and how would the air near to the buildings 'know' to transmit the energy up to an aircraft that may or may not be above them? I think you must be incorrect.
No, a sonic boom occurs when an object is traveling through a medium (e.g. air) faster than the speed of sound in the medium. The only things that matter are the relative velocity of the object to the media and the local speed of sound. Observers don't enter into it. Either a shockwave forms, or it doesn't. It doesn't matter if someone is there to hear it. Dragons flight (talk) 19:54, 13 January 2015 (UTC)[reply]
The air more or less follows the rotation of the earth because of friction between it and the ground .. Actually I do not believe that is correct. Sturat AND stevebaker both said this, I'm a little surprised.. Is this a common misconception or are they just over simplifying things? This makes it sound like the earth is or was spinning faster than the atmosphere, or that the atmosphere somehow "lags" behind the earth for some reason. The fact is, the atmosphere has mass, just like the earth. The earth is rotating freely, there is no extra force keeping the earth spinning that has to somehow transfer to the atmosphere. In the earth's rotational frame of reference, the atmosphere is perfectly stationary, just like the water, just like a ball you put on a flat surface and just like us. I do not believe friction plays any part in it. Vespine (talk) 22:00, 13 January 2015 (UTC)[reply]
Babylonian mathematics
The use of base 60 is not Egyptian. The Egyptians used a non-place-value system of numerals, similar to Roman numerals, as did many ancient peoples. The Babylonians did use the sexagesimal system, which was a place-value system. It had great computational power, as do Arabic numerals, but its use required memorizing an extremely large addition table and an extremely large multiplication table. It, like base-ten Arabic numerals, did allow fractional computation to any desired amount of accuracy, by just computing the multiplication or division to the required number of sexagesimal (or decimal) places. In classical antiquity Babylonian arithmetic was used for astronomy and astrology, and not for other purposes, because it was difficult (but precise). Why the Babylonians used base 60, rather than base 10 or base 20, is a historical mystery. Robert McClenon (talk) 21:24, 13 January 2015 (UTC)[reply]
Helicopter question
The helicopter obeys Newton's first law of motion "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force". If that wasn't the case if you jumped off the ground at the equator the Earth would move under you at 465 meters/second and you would end up a long way from where you started. So because you are already moving at a velocity of 465 meters/second when you jump, and there is no "external force" to slow you down, you carry on at the same velocity as the Earth and land in the same spot. But don't worry, you're not dumb. It took a genius like Isaac Newton to work all this out. Richerman(talk)22:00, 13 January 2015 (UTC)[reply]
Well, once you ignore Newton's laws, anything could happen, but there's no reason to assume he'd hover above the ground pushing air out of the way at orbital speed, why not have him fly off to space in a slowly expanding spiral, staying above the launch point, and moving upward at his original launch velocity? μηδείς (talk) 22:54, 13 January 2015 (UTC)[reply]
Is it safe to add lactobacillus acidophilus to gazpacho and would it prevent or slow fermentation?
I guess this all comes down to how well it could compete against yeast and would the sugars available in gazpacho (mostly tomatoes) be adequate for feeding it? An ancillary question is how active is lactobacillus acidophilus in producing gases? The main problem with the fermentation is the gas produced and so it would make little sense to replace one gas-producing organism with another. — Preceding unsigned comment added by David Bradley I (talk • contribs) 18:48, 13 January 2015 (UTC)[reply]
How much Phytoestrogens, on average, we have on 100g of cocked soybeans?
This source says 40mg per 1/2 cup of soy beans, 165mg per 3.5 oz of roasted soy beans [25]. It appears to be a fairly reliable source but it does not itself cite sources, so better-cited sources will still be helpful. SemanticMantis (talk) 22:16, 13 January 2015 (UTC)[reply]
Female ejaculate
So I read over here that female ejaculate is actually just urine. However from what I read from other people and what I've seen in pornos, it looks more clear than normal urine and doesn't have the same offensive odor. I also heard that when it dries up it leaves behind a whitish residue as opposed to a yellow residue. My question is, is female ejaculate safe to consume unlike normal urine? Mind you, this is not a medical question, I'm just curious. 69.121.131.137 (talk) 22:51, 13 January 2015 (UTC)[reply]
How do household appliance water tanks work?
I've had a few small humidifiers and they have all had a similar water delivery system. A removable water tank with a sealable opening (used to refill the tank with water from a faucet) and an opening at the bottom to allow the water to empty from the tank into the humidifier itself. It appears that the opening at the bottom has a spring such that when the spring is compressed, water will exit and when the spring is unaltered, the water tank is sealed closed. Somehow, the humidifier must be able to let in an appropriate amount of water from the tank into the humidifier via this spring opening. However, if it lets in too much water, the humidifier will leak, and too little water will interfere with humidifying a room. I've never seen any apparatus or anything that appears to somehow press the water tanks spring in some sort of regulated fashion.
While I know this description is not perfect, I'm wondering if it is enough for anyone to explain or find references that explain how the humidifier is able to let in the appropriate amount of water into the tank, especially given the absence of any noticeable mechanism on the humidifier that performs this job. — Preceding unsigned comment added by 68.10.236.226 (talk) 22:55, 13 January 2015 (UTC)[reply]
Lorentz Contraction at near light and faster than light speeds
I am having some trouble visualizing this concept, so I will start my question with an example. For the sake of clarity, the descriptions I provide throughout this question will contain, perhaps, more detail than necessary. Let's say there are only two objects in the universe: the Earth, and a spaceship beside the Earth traveling in a line perpendicular to the radius. Let's also say for the moment that there is no warping of spacetime due to the Earth's gravity.
For relativistic speeds, the ship would need to be traveling at, say 0.925c. 1) At this speed, Lorentz Contraction dictates that Earth would contract along the y-axis and appear more like a watermelon lying on its side, correct? 2) Is this because traveling closer to c means that more horizontal beams of light (from the Earth to the ship, along the x-axis) hit your eye than normal? 3) Wouldn't this also make the squashed Earth appear brighter since the eye is receiving more light-per-second than normal?
This is all I am writing for now, though I do have more questions. To those who respond, please be sure to sign your replies. Thanks, Loonybin0 (talk) 23:02, 13 January 2015 (UTC)[reply]
Resolved
