::just for another reason, 'dark sucking' would play hell with various laws of conservation. where would all this sucked darkness go? a candle, for instance, would have to grow in length to store all the darkness it's sucking, and a light bulb would eventually collapse into a black (or white?) hole. but since these don't happen, you'd have to create a whole new set of theories about how darkness has negative volume/density (i.e., the more darkness something contains, the smaller it is, until the object reaches its maximal darkness capacity and disappears). --[[User_talk:Ludwigs2|<span style="color:darkblue;font-weight:bold">Ludwigs</span><span style="color:green;font-weight:bold">2</span>]] 23:18, 14 August 2010 (UTC)
::just for another reason, 'dark sucking' would play hell with various laws of conservation. where would all this sucked darkness go? a candle, for instance, would have to grow in length to store all the darkness it's sucking, and a light bulb would eventually collapse into a black (or white?) hole. but since these don't happen, you'd have to create a whole new set of theories about how darkness has negative volume/density (i.e., the more darkness something contains, the smaller it is, until the object reaches its maximal darkness capacity and disappears). --[[User_talk:Ludwigs2|<span style="color:darkblue;font-weight:bold">Ludwigs</span><span style="color:green;font-weight:bold">2</span>]] 23:18, 14 August 2010 (UTC)
:On [[printed circuit board]]s and [[Schematic diagram#Electrical and electronic industry|schematic diagrams]], incandescent bulbs (such as indicator lights) are abbreviated "DS", much as resistors are abbreviated "R", capacitors "C", inductors "L", and diodes "CR". ("L" is used as a symbol for inductance and "CR" stands for "crystal rectifier", but I don't know the origin of "DS". Is there a WP article on this?) I have always assumed that the phrase "dark sucker" was chosen to match the abbreviation. -- [[Special:Contributions/1.47.99.181|1.47.99.181]] ([[User talk:1.47.99.181|talk]]) 00:34, 15 August 2010 (UTC)
:::Apart from any comedy about light bulbs turning grey, see [[transactional interpretation]]. Light detectors emit "dark" as an advanced wave moving backward in time. [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 00:29, 15 August 2010 (UTC)
:::Apart from any comedy about light bulbs turning grey, see [[transactional interpretation]]. Light detectors emit "dark" as an advanced wave moving backward in time. [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 00:29, 15 August 2010 (UTC)
Revision as of 00:34, 15 August 2010
Welcome to the science section of the Wikipedia reference desk.
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.
What's the prospect of scientists creating enzymes that can treat prion diseases?
Based on what we know about prion diseases, what's the prospect that someday scientists will discover or engineer enzymes that can be used to safely break down amyloid plaques? --71.185.169.212 (talk) 01:50, 10 August 2010 (UTC)[reply]
I can't see any reason why it couldn't be done. They're just proteins and there are plenty of enzymes that break down proteins. I don't know enough about the subject to say how difficult it would, though. If scientists can find people with a genetic immunity that works by them producing a particular enzyme, then they might be able to track down the relevant gene, transplant it into a bacteria and then extract large amounts of the enzyme and administer it to patients, but no part of that process would be particularly easy. --Tango (talk) 03:10, 10 August 2010 (UTC)[reply]
Amyloid plaques consist of fragments of a larger protein, that build up outside of neurons. The key problems are those of drug delivery, as getting large molecules into the brain is extremely difficult, and selectivity: how to find a protein that digests amyloid plaques while leaving healthy proteins unaffected. I don't know for sure, but the amyloid plaques may be as much a symptom as a cause of the disease -- the breakdown of their parent protein may be the actual cause. Alzheimer's is also characterized by aggregation of an intracellular protein involved in maintaining the neuronal cytoskeleton, which would be even harder to target as it's intracellular. --Atemperman (talk) 05:25, 10 August 2010 (UTC)[reply]
Some care should be taken here with nomenclature. The prion proteinPrP forms the amyloid plaques that appear in the transmissible spongiform encephalopathies ('mad cow disease' in cattle, or Creutzfeldt-Jakob disease in humans) — but not all amyloid plaques are formed from prions. Indeed, when neurologists discuss amyloid plaques, the first thing that comes to mind is usually the amyloid beta peptide associated with Alzheimer's disease. (It is in this sense of the term that Atemperman's response above answers the question.) Amyloid beta does form amyloid plaques, but it is not believed to be a prion — amyloid just describes protein accumulations with a cross-beta structure and which exhibit certain histopathological features (like apple-green birefringence when stained with Congo red). It's also worth bearing in mind that PrP is not the only prion protein (several others have been identified in yeast, though PrP is so far the only known mammalian protein which can form a prion).
I'm going to assume that you're interested in the breakdown of PrP amyloid for the remainder of my response here. Developing a suitable protease requires meeting three major challenges. The first is that the protease even be able to digest PrP amyloid. This is a steep challenge all by itself; one of the hallmarks of PrP amyloid (and indeed, of most amyloids) is their resistance to protease digestion. PrP amyloid is resistant to detergent solubilization and even to exposure to proteinase K, which is able to digest normally-very-durable proteins like keratin (in hair). Nevertheless, there has been some work in this area; this paper describes some very aggressive enzymes secreted by thermophilic bacteria that might be able to do the job. (I'm not familiar with the literature in this area; that was just one of the first Google hits with the relevant keywords.)
The second challenge is one of specificity. Letting large amounts of an aggressive protease loose in human tissue is a recipe for disaster, unless it can be specifically targeted to PrP (ideally, just to misfolded PrP). The third challenge is delivery — Atemperman's response above describes the problem. TenOfAllTrades(talk) 18:51, 10 August 2010 (UTC)[reply]
They probably keep mum about this. But essentially, they wanted a new design (and may have needed more space or a different layout to realize the enhanced functionality). And from a technical point of view, reusing the structural elements of the frame as an antenna is exactly one of those very elegant ideas you fall in love with that unexpectedly turn around and bite you... --Stephan Schulz (talk) 13:37, 10 August 2010 (UTC)[reply]
Apple claims, and several independent tests have supported, [1] that the change improves reception in low-coverage areas -- provided that you don't hold the phone a certain way. My personal guess is that Apple's internal testing just didn't uncover the flaw: they've got an AT&T tower on their campus, so local testing isn't bothered. The phone that leaked in the field was enclosed in a case (which fixes the problem) -- so if that's typical, remote testing also wouldn't be bothered by the antenna placement issue. But that part is just guesswork. — Lomn13:41, 10 August 2010 (UTC)[reply]
Ironically, the new antenna was designed to improve the connection. My own personal experience has been that the iPhone 4 is indeed better than previous models as long as you don't hold it with the Death Grip. A Quest For Knowledge (talk) 13:47, 10 August 2010 (UTC)[reply]
In addition to the suggestions above, relocating the antenna to the outside of the case frees up room inside. This allows more internal space for additional hardware or a larger battery.--Zerozal (talk) 14:08, 10 August 2010 (UTC)[reply]
watch what they do after September 30th. I bet by then they'll have sold all the ones produced with revision 1, and be selling the revision 2: what is that change? Perhaps nothing more than a resinous coating... 92.230.233.247 (talk) 14:45, 10 August 2010 (UTC)[reply]
Agreed. He enunciates a little funny, and doesn't modulate much, but it's probably because he's trying to be easy to understand (he's not speaking conversationally). He's no voice actor but he does fine by academic standards. --Mr.98 (talk) 00:03, 11 August 2010 (UTC)[reply]
Cool research. Definitely a real person. A text-to-speech program wouldn't have gotten the rhythm of spoken language correct. For a particularly striking example, consider the phrase around 4:47: "The resulting mat # is consistent with the occlusions in the scene." The speaker puts a big pause at the "#" to let the listener focus in preparation for the coming big concept. There's no punctuation there; it takes intelligence to decide to put it in. Paul (Stansifer)03:55, 11 August 2010 (UTC)[reply]
yes! that must be it. thank you. the actual audio does sound computationally produced (as opposed to spoken as we hear it), because it is, but is a real person, because it is. 92.230.232.58 (talk) 11:29, 11 August 2010 (UTC)[reply]
Eh, I don't buy it. Sounds like a regular voice to me. Perhaps not one that you yourself hear around often, but around universities and science departments, it is not uncommon. --Mr.98 (talk) 13:02, 11 August 2010 (UTC)[reply]
According to the pickerel frog article, a pickerel frog is a type of leopard frog. (It doesn't say so explicitly, but it has a sentence that reads "All other leopard frogs ...".) Looie496 (talk) 22:43, 10 August 2010 (UTC)[reply]
Cycle helmets - do they reduce vision and impair hearing?
Hi all, thanks for reading.
A the title asks really, do cycle helmets impair peripheral vision and hearing, leading to greater likelihood of being involved in an accident?
I've been ot the CTC site ( http://www.ctc.org.uk/ ), and looked up some reports on helmet safety through google scholar, but they all seem to focus on injury patterns for helmet wearers and non wearers involved in accidents. I'm trying to find out if wearing a helmet actually does increase the likelihood of being involved in an accident.
Some facts/figures/reports would be great to back this up if you guys could.
This isn't homework, I'm having a robust conversation with a number of people on some forums, and its something I've been curious about for a while, but could never find the research to back-up my assertion that helmets do impair sensory perception, and in doing so, increase the likelihood of being involved in an accident.
These guys seem to manage OK. They're just the best in the world. The peloton of the Tour de France
Sorry, I know that's not an answer, but yours does seem to be a question based on rebellion and an unwillingness to change. HiLo48 (talk) 14:25, 10 August 2010 (UTC)[reply]
Look at this helmeted fellow. He would have to strain to see the helmet, and it's hard to believe it has any significant effect on his hearing. This is a bit like arguing that seatbelts are bad because they might trap you in a burning car. Perhaps true in a tiny minority of cases, but statistically marginal compared to the times they prevent serious injury. --Sean14:28, 10 August 2010 (UTC)[reply]
I bicycle a lot. Helmets are uncomfortable when it is 38C (100F) outside, but they do not seem to impair my hearing because they do not normally cover the ears. Normally they do not cover any of the sight range either (at least for my Schwinn helmet). --Chemicalinterest (talk) 14:32, 10 August 2010 (UTC)[reply]
There would be many factors to control for in any study. For example, maybe cyclist who where helmets are simply more careful (in general) than cyclists that don't, and so would be expected to have a lower rate of accidents. You would want to start by asking yourself how many cycle accidents are caused by ignorance of peripheral vision or hearing on the part of the cyclist (whether wearing a helmet or not). As a personal opinion, I don't buy the peripheral vision argument: a cyclist should always look over the shoulder to avoid the blind spot, and the blind spot is not affected in the slightest by wearing a helmet or not (it's way to the front of any helmet design). Physchim62(talk)14:42, 10 August 2010 (UTC)[reply]
Cheers all
@HiLo48 - You may have a point, and LOL at the Tour pic.
@Physchim62 - That was the main issue with the studies I did come across - the variables, particularly the ones that you mention, as well as issues of variable cycling competency, and the localities covered in various studies (obviously, road conditions, but also, localities with higher number of cyclists might record lower a lower than expected ratio of accidents because motorists the frequent that area are more familiar with sharing the road with cyclists etc).
I accept that my boldly proclaimed opinions on the subject elsewhere may have been entirely factually incorrect. Darn.
On the hearing front, I'd suggest that cyclists have more to be concerned about with the increasing numbers of virtually silent electric cars, than with helmets. HiLo48 (talk) 21:37, 10 August 2010 (UTC)[reply]
I would caution readers that the source linked above (a BBC story) doesn't quite jump to the same conclusions that the poster does in his text. The story only describes a study which noted that vehicles tend to pass closer (8.5 cm or about 3.3 inches; roughly 10% less total space) to cyclists wearing helmets than they do to cyclists without. The authors of the study speculate that drivers may assume a greater level of cycling competence, experience, and/or predictability on the part of the helmeted cyclists, and therefore those drivers may pass the cyclists more closely. The article does not indicate that helmeted cyclists are at greater overall risk, nor does it describe any research into this effect.
I just tried on my helmet, which I think is a pretty ordinary one, and noted that I can't see any part of it whatsoever while I am wearing it, even with my peripheral vision. Nor does it cover my ears. Looie496 (talk) 22:48, 10 August 2010 (UTC)[reply]
Some helmets come with sun visors, which normally can be snapped off. I think it's a good idea to snap them off — they do make it a bit hard to see forward when you're bent over for a descent, unless you hold your head in a tiring and unnatural position. The downside is that you lose the sun protection, but there's sunscreen and UV-protecting glasses for that. --Trovatore (talk) 22:51, 10 August 2010 (UTC)[reply]
There's some information about research into the benefits and drawbacks of helmets here. The evidence taken as a whole is certainly not clearly in favour of helmet-wearing and may be against. As a regular commuter cyclist I do not own and never wear one. AndrewWTaylor (talk) 18:07, 11 August 2010 (UTC)[reply]
I don't wear one when commuting either, but a person who rides at high speed or down steep hills without wearing a helmet is a suicidal maniac, in my humble opinion. If there is a significant chance of a Close Encounter of the Automotive Kind, I would also very much want to be wearing a helmet. Looie496 (talk) 00:24, 12 August 2010 (UTC)[reply]
If the car hits you in the head at a high relative speed, maybe the helmet doesn't help. I'm having trouble visualizing how that would happen, though. The more relevant scenario is: Car knocks you down, head hits the blacktop. --Trovatore (talk) 20:27, 12 August 2010 (UTC)[reply]
It's not going to make any difference at a reasonable speed, if a cager hits you there are other things to worry about. When downhill riding a full face and goggles is prudent and reasonable protection.
On the other hand I do wear mine while commuting. I had one incident a while ago where I sideswiped a wall at about 15 mph and given the damage to the helmet I'm glad I had it on, I did break my shoulder though. Also in London it's useful, it's all pretty slow speed but most cages don't leave room and it offers some protection from glancing blows.
Swings and roundabouts, an ex was knocked off by a van and if she'd had a helmet on may well have lost an eye...
The point about visibility or hearing restriction is pretty specious though, if one is riding defensively one should be looking round pretty frequently anyway.
Not going to make a difference because there are other things to worry about? That doesn't make any sense. Sure, the car could run over your chest and put a piece of rib through your heart, and in that case it won't make a difference whether your skull is broken. But in lots of other scenarios it might. --Trovatore (talk) 22:03, 12 August 2010 (UTC)[reply]
If I come off at 20-25mph because a car has hit me from behind I'm more likely to break my neck than get any value from a helmet. Similarly if a car clips me on the way past I'm going to fall into the vehicle rather than away from it, again it's more likely to break my back. Alternatively if I end up on the road in the wake of a car that's hit me, then the one immediately behind will hit me. That's on roads where the cars are doing between 50 and 70 mph.
At any kind of reasonable speed in traffic a helmet isn't going to make a significant amount of difference.
If I compare that to inside London, where the best I'm doing is about 15mph the cars generally aren't passing me so the threat is quite different, so a helmet can help.
Context and threat awareness are pretty significant. I'd say for about 60% of my commute I don't get any value from my helmet.
The reference above highlights that the evidence is inconclusive, some of the other discussion in CTC material highlights that the value is context dependent. Speed of cyclist and surrounding cages, both relative and absolute, varies the impact of the helmet, with little effect at high speeds.
The majority of work done in the UK focuses on urban accidents, so slow speed and the deaths are usually chest, pelvis or femur related.
I would add that yes, I am informing the interpretation by experience. In 35ish years of regular cycling; commuting, road racing and mountain biking, I don't recall anyone in a high speed hit by motor vehicle incident that hasn't had significant chest, back and arm injuries.
So first, I have to apologize that I hadn't really read your remarks completely before commenting. I do agree that if you get rear-ended by a car doing 70, you're quite likely dead regardless of helmet. But if you get sideswiped by a car doing 70, in my opinion you have a lot better chance with the helmet on. Yes, I agree you're likely to have significant injuries, but that's not the same thing as dead.
Well, here's from a recent Cochrane Review, PMID10796827: BACKGROUND: ... Head injury is by far the greatest risk posed to bicyclists, comprising one-third of emergency department visits, two-thirds of hospital admissions, and three-fourths of deaths. ... MAIN RESULTS: ... Helmets provide a 63%-88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. ... REVIEWER'S CONCLUSIONS: Helmets reduce bicycle-related head and facial injuries for bicyclists of all ages involved in all types of crashes including those involving motor vehicles.Looie496 (talk) 22:47, 12 August 2010 (UTC)[reply]
Original research - when I used to commute by bike into London, a car overtook me, pulled in and braked sharply. I was coasting downhill at the time, 10-15mph. My front wheel hit his rear bumper, I head-butted his hatchback resulting in a hemispherical dent in the car but no damage to head or helmet. Conclusion - I'm glad I was wearing one! Alansplodge (talk) 17:06, 13 August 2010 (UTC)[reply]
No the real wood has been sold as boards, two by fours, what have you. Like sawdust, these stirrers are just what falls to the ground during the cutting. 92.230.233.247 (talk) 17:59, 10 August 2010 (UTC)[reply]
I get where you're coming from, but those cuttings come from the original 'real' wood. So aren't the stirrers, by composition, exactly the same? Perhaps with a few impurities. Maybe I'm just not understanding you properly, I'm pretty slow today. Regards, --—Cyclonenim | Chat 18:08, 10 August 2010 (UTC)[reply]
I actually have to agree with Cyclonenim here. If the stirrers are made from a solid piece of scrap wood, they're still 'real' wood by any meaningful usage of the term. Particle board isn't comparable because that's a composite of particles of wood (sometimes not even that but other fibre) held together by a binder. In a similar way, someone may say a meat patty of some sort (burger, meatball, nugget etc) isn't 'real' meat but small pieces of meat which may be scrap and used for a stir fry or whatever is still 'real' meat. Note we have an article on Engineered wood, I'm pretty sure scrap wood of the form described by 92 doesn't fit in to it. In fact, very often people may use scrap wood from a building site or whatever to make things, no one is going to say that isn't 'real' wood. Nil Einne (talk) 19:14, 10 August 2010 (UTC)[reply]
Paint stirrers are solid wood, made by splitting a billet of pine or other soft wood parallel to the grain, since sawing them would waste about half the wood. High quality billets of wood are used, not pieces full of knots, since those would break. The wood needs to be of high quality, but the pieces could be short lengths, I suppose. I have never seen or heard of a paint stirrer made of any sort of composition of sawdust and glue. As for "free," their retail value in the US would be about 10 cents each, if you wanted to buy a bunch (like for a craft project, or for labels for garden plants, or whatever) and weren't buying any paint. Edison (talk) 14:57, 11 August 2010 (UTC)[reply]
Transforming a principal stress tensor to maximum shear stress tensor?
This is kinda science related and also software-related, but I reckon the people who are best to answer it are at this desk rather than the computing one. Are there any open source/freeware programs that do the same job as the FULL ChemSketch? Personally I can't afford to buy the program and I don't want to resort to illegality in getting it. Regards, --—Cyclonenim | Chat 17:09, 10 August 2010 (UTC)[reply]
I struggled with these at university and only got them the third time round. If you understand vectors, then that's a start as they are 1st order tensors (I'm going back a few decades here so others will I'm sure correct me if I'm wrong). Some physical things such as stress and strain need 9 'components' to fully describe them and for elasticity, which relates stress to strain, you need 81 components and that's a 4th order tensor. As the tensor article says, the stress tensor (2nd order) describes the relationship between two vectors (1st order tensors). I doubt that helps, as it's very difficult to describe this in laymen's terms, but good luck anyway. Mikenorton (talk)
Well, they are vectors in some sufficiently abstract sense. But that doesn't really say much — it just says you can add them and multiply them by scalars, and the normal obvious things happen.
The general question "what is a tensor?" is probably not going to have a really satisfying answer right now. You could say that it's a linear transformation from some power of a vector space to some power of a vector space, but I don't think that really gives the sort of intuition you're asking about.
Instead, I'd recommend studying some particular simple tensors, preferably of rank 2. The stress tensor is a good one — think of it as a rule that takes a little flat piece inside the object (which you can think of as a vector, with magnitude equal to the area of the piece and direction perpendicular to the piece), and returns a vector representing the force through that piece. Figure out why that's a linear transformation (hardly obvious!) and you've got a start.
A tensor, in the simplest possible terms, is a multidimensional matrix attached to a point in a multidimensional space, with the numerical entries in the matrix changing in specified ways when the coordinate system for the multidimensional space is altered. Looie496 (talk) 22:33, 10 August 2010 (UTC)[reply]
Those might be the simplest terms in some sense, but they're not the most illuminating ones. Better to emphasize coordinate-free formulations. --Trovatore (talk) 22:38, 10 August 2010 (UTC)[reply]
The tensors that show up in physics are usually either symmetric or antisymmetric. I don't know if "layman's terms" includes calculus, but both of these special classes of tensors are probably best thought of in calculus terms.
A symmetric rank-n tensor is what you get when you generalize nth derivatives to functions of more than one variable. The first derivative of a real-valued function of real variables is a vector (rank-1 tensor), called the gradient, whose components are (∂f/∂x, ∂f/∂y, ...). The second derivative is a matrix (rank-2 tensor) called the Hessian. It's a symmetric matrix because the order in which you take partial derivatives doesn't matter. In the case of a function of one variable, you get a one-component vector and a 1×1 matrix whose sole component is the usual first or second derivative. The most useful thing to know about symmetric real matrices is the spectral theorem, which says that you can always make the matrix diagonal by some orthonormal change of basis variables. Thus you can think of a symmetric rank-2 tensor as a set of perpendicular coordinate axes (the diagonalizing basis) with a number (the corresponding element on the diagonal) attached to each axis. These axes are sometimes called "principal axes". In terms of the original scalar function, what this means is that every smooth surface can be approximated locally to second order by an ellipsoid (just as it can be approximated locally to first order by a plane).
An antisymmetric rank-n tensor is a differential form, which is the thing that you write after an n-dimensional integral sign. For example, f(x,y) dx dy is a differential 2-form. In matrix form it would look like , assuming three dimensions with x and y the first two. It's antisymmetric because dx dy represents a little parallelogram in space (the "area element"); if you swap dx and dy the area element flips over, changing its sign, and if you make dx and dy the same vector it collapses to zero size. dx dy is more properly written , where is the wedge product, which is this case is the same as the 3D cross product. The number of independent components of an antisymmetric tensor is given by entries of Pascal's triangle. In three dimensions antisymmetric tensors of rank 0, 1, 2, 3 have 1, 3, 3, 1 components respectively, and they are scalars, vectors, pseudovectors, and pseudoscalars respectively. In four dimensions the tensors of ranks 0...4 have 1, 4, 6, 4, 1 components. The first two are scalar and vector and the last two are pseudovector and pseudoscalar. The middle one, in 3+1 spacetime dimensions, can be decomposed into a 3D vector and a 3D pseudovector. This is how the electromagnetic field tensor decomposes into electric and magnetic field vectors. There's more that could be said about antisymmetric tensors, but I'll leave it at that. -- BenRG (talk) 06:00, 11 August 2010 (UTC)[reply]
My impression from reading this, trying to understand, specifically this part:
All scalars are not tensors, although all tensors of rank 0 are scalars (see below).
All vectors are not tensors, although all tensors of rank 1 are vectors (see below).
...
was that an n-dimensional tensor is just a subset of n-dimensional matrices (the subset where a change of coordinates doesn't affect how the system works). I'm still working to get this myself. -Craig Pemberton08:12, 14 August 2010 (UTC)[reply]
Yeah I looked at that article and thought the same thing, especially since it would require a massive energy expenditure around any extraterrestrial body I can think of except perhaps Venus. Googlemeister (talk) 19:18, 10 August 2010 (UTC)[reply]
No, I don't think so. For Earth, where you get the rotation speed for free (or have to compensate for it), the difference is major. But for any other body, the rotation of the body is irrelevant - you're dropping in from outside the system, anyways, and, as long as the rotation is not relativistic, the other body simply behaves as a point mass. You can essentially chose any orbit you like. I would suspect that probes often chose a polar orbit, since that allows them to map the whole body over time. --Stephan Schulz (talk) 21:25, 10 August 2010 (UTC)[reply]
Plus, craft that we put in orbit about other bodies are either doing scientific/photographic missions or dropping off landers - and the lower the relative speed between surface and orbiter, the sharper the photos can be and the lower the re-entry speed of any lander. Using a retrograde orbit would pretty much guarantee worse results. SteveBaker (talk) 02:48, 11 August 2010 (UTC)[reply]
Corrected, it's a family of birds rather than an exact species. It'd be hard to pinpoint between the species within the family for they are specialised at different things. Regards, --—Cyclonenim | Chat 21:11, 10 August 2010 (UTC)[reply]
I would like our questioner to tell us what he or she thinks intelligence means, especially in birds. We have enough trouble agreeing on what it means for humans. When we try to apply the concept to totally different creatures it becomes very difficult to agree on what it means. HiLo48 (talk) 21:32, 10 August 2010 (UTC)[reply]
The smartest corvid would make for a dumb human. But at the same time, the smartest human would make for a dumb corvid. HiLo48 is right. Perhaps all you can say is that, amongst the various kinds of birds, the corvid's intelligence is most similar to human intelligence.91.104.151.200 (talk) 00:12, 11 August 2010 (UTC)[reply]
I remember a story from a few years ago in which a bird was able to form a hook out of a piece of wire then use it to retrieve some food at the bottom of a container, a behavior previously unobserved. I don't know what the species was, though. Hemoroid Agastordoff (talk) 17:00, 11 August 2010 (UTC)[reply]
Our article on this effect includes a short bit of discussion about individuals who previously recognised this effect. Would it be reasonable to say that Socrates observed this effect, since according to legend he was told that he was the wisest of all men because he knew that he wasn't wise? Nyttend (talk) 02:13, 11 August 2010 (UTC)[reply]
Why not? I don't see the difference, especially since the article includes those who remarked about the phenomenon before Dunning or Kruger were born. Nyttend (talk) 04:57, 11 August 2010 (UTC)[reply]
"according to legend" - nuff said. Note that if you are trying to add it to the article, you should be discussing it in the article talk page not here. Presuming other sources have made the connection you may be able mention that, it doesn't mean we can say with confidence Socrates observed the effect which is a quite different thing.
I would also note your statement doesn't really support the claim at all since you say "he was told that he was the wisest of all men because he knew that he wasn't wise" which would suggest someone else recognised this effect not Socrates. Whether Socrates even recognised the effect once told about it or whether he thought the person who said he was the wisest of all men because he knew that he wasn't wise was an idiot is not even clear from what you've described.
Notice the banding? Does anyone have any idea what might be causing that banding? It's not just a photographic artifact (though it may be not faithfully recreated by the camera); I took the picture because I noticed the banding with my eyes. At the bottom is obviously a cloud in front of the sun, but on the other half of the sun, there's nothing obvious to cause the interesting coloring. It was taken August 5th in southern Minnesota, if that makes a difference. Buddy431 (talk) 02:38, 11 August 2010 (UTC)[reply]
My guess is that the photograph was taken on a day when there were numerous layers of diffuse cloud and strata of humidity, perhaps enhanced by strata of pollutants. The photograph was taken when the sun was in such a position that it was observed through a number of these strata. As a result, the color of the sun was affected by the various strata in the atmosphere and so the sun shows distinct bands. It would be useful to take a few more photographs with the sun at the same elevation, both in the morning and in the evening. I wouldn't be surprised if the bands are only a rare observation. Dolphin(t)03:15, 11 August 2010 (UTC)[reply]
I don't think this is rare. I'm seeing lots of air pollution in that image, possibly smog or smoke from a wildfire of some kind. The temperature also appears to be above 30 C based on news reports in that region. Although there was a small fire in that area in the morning the photograph was taken, smog is a known problem during the summer, with local reports blaming gas-powered lawn mowers, in addition to wood fires, ATV's and cars. Viriditas (talk) 04:00, 11 August 2010 (UTC)[reply]
These small salamanders are found under slabs of rock within several feet of a stream. What are they? They are very common. Most of them have the stripes down the back. --Chemicalinterest (talk) 13:03, 11 August 2010 (UTC)[reply]
According to this document [6] from the New Jersey (I assume the NJ on your image is that) Department of Environmental Protection, etc. etc., there are 14 or 15 different species of salamander and several of them have stripes. There is a gallery of photos at the bottom of the document. Richard Avery (talk) 15:40, 11 August 2010 (UTC)[reply]
Lets say I'm voice chatting on my computer using skype or something. And I while we are chatting, I can hear my voice on the other person's computer. Would this "echo" be described as reverb? 148.168.127.10 (talk) 13:24, 11 August 2010 (UTC)[reply]
I don't think so. It's audio feedback, isn't it? The reverberation article seems to indicate it applies to echoes only. That is, I think feedback would be disqualified because it uses new sources of sound (the speakers) rather than a reflection of the original sound. Vimescarrot (talk) 13:59, 11 August 2010 (UTC)[reply]
There are two forms of echo in Telephony: Near-end echo has no delay and is desirable in a small amount as a Sidetone so the telephone does not seem "dead" to the user. Far-end echo is echo of one's own voice delayed; it is undesireable and may be caused electrically by a poorly balanced Telephone hybrid or by acoustic link between the far telephone speaker and microphone. The OP is hearing far-end echo. Cuddlyable3 (talk) 16:31, 11 August 2010 (UTC)[reply]
In my experience "reverb" is used to describe a reverb-y sound regardless of source. So, if the end result is a reverb type sound, then yes, I suspect people would call it reverb. Friday(talk)16:38, 11 August 2010 (UTC)[reply]
why do mockingbirds open their wings repeatedly while searching for bugs in the grass?--Horseluv10 13:27, 11 August 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)
I'm not sure that anyone knows the answer to that yet and I don't think it's really covered in Wikipedia which is a pity. There seem to be all sorts of theories e.g. it enhances their foraging by surprising the insects..somehow, anti-predator defense, territorial defense etc or maybe all of the above and more. Other mimids do it too. Sean.hoyland - talk14:01, 11 August 2010 (UTC)[reply]
Actually the opposite of shading has also been proposed as another explanation i.e. the exposure of bright white patchs during wing flashing illuminates prey. That theory is slightly ruined by several mockingbird species without white patchs flashing their wings while foraging... Sean.hoyland - talk10:06, 12 August 2010 (UTC)[reply]
Phage therapy
After reading phage therapy, including the obstacles section, I don't see a reason for why phage therapy is not licensed for medicinal use in Western countries like the U.S. and the U.K., especially given the ever-rising resistance against traditional antibiotics. Safety is a slight concern, though it's generally considered safe under supervision to look out for toxic shock. I'm guessing it has something to do with the practicality of having to develop very specific strains of phages. Is this uneconomical at present? Regards, --—Cyclonenim | Chat 15:03, 11 August 2010 (UTC)[reply]
Did you read the article you linked to? Phage therapy is not as well structured as it could be, but there are several points in it that explain why the therapy is not in wide use: The patient mounts an immune response against the phage, so you probably can use every phage only once. You have to know very specifically what kind of bacteria (or even mix of bacteria) has infected the patient, which is impractical as of now (that could change if sequencing costs keep dropping). Another point, which is not raised in the article I think, is that antibiotics are very cheap, and phages are not, at the moment. With multiresistance on the rise, the picture could change, but at the moment, phage therapy does not seem to have an advantage over antibiotics. --TheMaster17 (talk) 11:52, 12 August 2010 (UTC)[reply]
Thanks, I did read it but I only skimmed through it really. Even if you can only use each phage once in each patient, that doesn't seem like a massive reason not to use phage therapy. For example, certain rarer infections that people are only likely to get once could be treated by phage if not by antibiotics. Fair point regarding costs, I suspected it'd have something to do with that too. Regards, --—Cyclonenim | Chat 12:12, 12 August 2010 (UTC)[reply]
Since phage therapy is used in Russia successfully, there is no scientific reason why it can't be used. If you allowed some clever biology graduates to fill a few refrigerators with cultures and casually mix up non-sterile preparations, then they could probably run a therapy clinic as efficiently as a tattoo parlor. Of course, America has strict cultural taboos and draconian legal prohibitions against mixing the castes in this manner - people simply accept that tattoo artists can inject people's eyes with India Ink or slit their tongues in half, but allowing people to mix up their own phage preparations is absolutely unethical and must be greatly punished. Wnt (talk) 15:10, 14 August 2010 (UTC)[reply]
Mnemonic for functional groups in IUPAC nomenclature
Is there any mnemonic by which i can memorize the priority order for functional groups used while naming carbon compounds in IUPAC nomenclature?? harish (talk) 16:57, 11 August 2010 (UTC)[reply]
I don't know of one, but perhaps other people have come up with an idea for the more common ones at least! The full list is very long, and includes functional groups that most chemists will never have to deal with: on a practical, professional level, it's something you look up if you need it rather than keep in your head at all times. Physchim62(talk)17:13, 11 August 2010 (UTC)[reply]
carboxylic acids, sulphonic acids, acid anhydrides, esters , acid chlorides, amides, nitriles & isocyanides, aldehyde, ketone, alcohol, amino, C to C double bond, C to C triple bond, halogens=nitro=alkoxy=alkyl. I am just now in eleventh grade, so these few important groups will do. If there's some error in my order, please correct it too. thanks harish (talk) 12:21, 12 August 2010 (UTC)[reply]
(EC). There is a version on Google Books which I guess you've already found since it's the first Google result for 'Sexual Behavior in the Human female'. It isn't complete as the book appears to still be in copyright in the US where you live and likely other countries. Therefore the only place you're likely to find a complete non copyright violating copy online is on somewhere that sells ebooks (where you'll have to pay) but a quick search suggests it isn't available in such form. It should go without saying you won't receive any help here to violate copyrights. If you aren't desperate for an online copy, you could try a library Nil Einne (talk) 17:23, 11 August 2010 (UTC)[reply]
Well as I said above, I can't find evidence of any. Unfortunately there are still quite a lot of books which for a variety of reasons aren't available in legitimate ebook form Nil Einne (talk) 18:46, 11 August 2010 (UTC)[reply]
Buoyancy
I'm trying to calibrate my intuition about how buoyancy should work with a small amount of a fluid.
For example, consider the case of a large boat in a small lock (water transport). Archimedes' principle is that the boat needs to displace an amount of water equivalent to its weight in order to float. The boat can do that, but the lock is small enough that the amount of water remaining in it is going to weigh significantly less than the boat. Shouldn't the boat sink to the bottom, like a heavy weight overwhelming a light one on a balance beam? But then it seems like it would matter whether the lock is connected to a larger body of water, which would imply that when the door was closed off, the boat could suddenly sink - and that seems crazy.
So is there an intuitive explanation of why the amount of water surrounding the ship doesn't matter (if that's the case) which could be added to the article? This seems counter-intuitive given the pulley analogy used there. -- Beland (talk) 17:26, 11 August 2010 (UTC)[reply]
The quick-and-dirty thought experiment is easy: imagine the boat sailing up the canal and into the lock. While the lock's gates are open, the boat is floating in the entire volume of the river, so no problems. When the gates close, sealing the lock off from the rest of the river, it doesn't make any sort of intuitive sense for the boat to immediately sink, right?
The slightly longer explanation involves looking at the situation from an energy standpoint. Imagine a container that surrounds both boat and water, with the boat afloat. Now, think about what happens if you move the boat down into the water by a little bit. The layer of water that was sitting happily under the boat's hull gets pushed aside, and an equal volume of water (ignoring the very slight compressibility of water) gets pushed up to sit on the old 'surface'. Effectively, that layer of water has been lifted from under the boat up to the water's surface; doing that work takes energy. Now where would that energy come from? If the boat spontaneously sank when you closed the lock's gates, you'd be getting energy for free if the boat immediately sank and lifted up that water into the air. TenOfAllTrades(talk) 17:40, 11 August 2010 (UTC)[reply]
Taking a slightly different tack, the flaw in your scenario is that you're assuming a constant volume of water in the lock, and that's not correct. There may be a particular volume of water in the lock when it's closed and has no boat, but you don't put the boat in the lock in that state. Instead, the boat enters when the lock is open and part of the larger system. As Ten notes above, this is the boat floating in the whole river -- that works just fine. When the lock closes, though, the volume of water inside has already changed due to the boat, river, and everything else.
Of course, the problem I'm having with this is that the scenario of "too little water" seems unlikely. If there's not enough water in the closed lock to float the boat (and assuming that water level matches that of the river), then the boat is also too big for the river. Adding the boat's displacement to the lock makes the water level rise, not fall, and so the initial water amount isn't the limiting factor. Instead, it's merely whether or not the boat (a) floats at all and (b) floats in the depth of water available. — Lomn18:46, 11 August 2010 (UTC)[reply]
Assume that pressure is constant throughout the water. The pressure of water against the boat, and hence the nett upward force of buoyancy (see article), is the same whether the water volume is unbounded, i.e. in open sea, or bounded by lock walls that almost touch the boat. Cuddlyable3 (talk) 18:59, 11 August 2010 (UTC)[reply]
I think the OP's intuition is correct, it's just that the quantity of water that counts as "small" is not well-defined. Consider the extreme cases on both ends:
Lots of water (entire river) - boat floats. No problem, intuitively.
Extremely tiny quantity of water - say, a "puddle" that's only an inch deep. The boat will displace all that water under it, and raise the water level, but will hit the bottom before it has displaced enough water to counterbalance its weight. There is no way one inch of water will be able to float the boat (unless we consider an extremely tight fit between a boat and a canal with tall walls - then a tiny fluid-layer bearing would exist between the boat and the very closely-spaced walls of the canal).
In the intermediate cases, the boat must displace a volume of water such that the water-mass is equal to the boat-mass. But displacing water means moving water from under the boat to the sides of the boat. This can only work if the geometry of the water container (lock, river, etc.) is sufficient so that necessary water-volume can be moved to the side before the boat hits the bottom of the container (lock/river/lake/etc.) If the amount of water is very small, the boat does hit the bottom. The draft of a boat is the geometric parameter that defines this. Boats can not sail in (locks, rivers, canals) that are shallower than their own draft. Nimur (talk) 20:37, 11 August 2010 (UTC)[reply]
The scenario isn't clearly described. What do you mean by the amount of water remaining in the lock? Are you assuming that the water goes out of the lock after it has been displaced, perhaps by pouring over the gate? If so, then the boat will indeed sink to the bottom. If not, please clarify what you meant. Looie496 (talk) 00:16, 12 August 2010 (UTC)[reply]
The amount of water remaining in the lock is irrelevant, as is any open or closed connection between the lock and a larger body of water. All that matters is the notional weight of an amount of water that has the same volume as the submerged volume of the boat. As long as this is equal to the weight of the boat then the boat will float, even if it takes up more than half of the volume of the lock. If the boat floats in the river then it will float in the any lock that is long, wide and deep enough to accommodate it. Gandalf61 (talk) 14:41, 12 August 2010 (UTC)[reply]
I was thinking more in the opposite direction -- if the lock is closed, the boat can float in less depth than it would normally take, because the water it displaces, having nowhere to go, may raise the water level. I'm not certain this is relevant to the question, but then I didn't really understand the question very well. Looie496 (talk) 21:35, 12 August 2010 (UTC)[reply]
Yes, Looie496's intuition is correct. In a lock or other "container" that has a "boat-shaped" profile, the boat can still float even though it has "displaced" less water than its own weight. The critical weight is that of the "submerged volume" of the boat, not the actual amount of water physically displaced (i.e. moved). The normal statement of Archimedes Principle is not quite correct in this respect. The upthrust is actually equal to a weight of water equivalent to the submerged volume, regardless of the amount of water physically displaced. Archimedes was right, but he was measuring overflow when he thought of water "displaced". See the first note in the Buoyancy article. Dbfirs08:48, 13 August 2010 (UTC)[reply]
I'll just throw one more link to fluid bearing. It is possible to completely support the weight of an object using a very tiny quantity of fluid - but the parts must be almost perfectly identical in geometry. Nimur (talk) 16:43, 13 August 2010 (UTC)[reply]
I'd imagine that any gene creating a toxin with a significant effect on our bodies would have been eliminated from the gene pool. If it's a lethal toxin, everyone with it dies, and assuming this happens before they reach reproductive age (which it would, in all likelihood) then there would be no way to pass this gene on. Regards, --—Cyclonenim | Chat 17:50, 11 August 2010 (UTC)[reply]
Many toxins are produced within the body. Ammonia, for example. But a healthy human body has mechanisms for properly filtering them out again before they reach dangerous levels. APL (talk) 18:30, 11 August 2010 (UTC)[reply]
You're not talking about NDM-1, a recently-discovered gene-crossing enzyme that can cause bateria including those that infect humans to become antibiotic-resistant, by any chance? ~AH1(TCU)18:54, 11 August 2010 (UTC)[reply]
A gene that coded for a toxin directly wouldn't last long, since it would kill the host before they could pass it on. We have genes that produce enzymes that can produce toxins, though. For example, alcohol dehydrogenase will produce formaldehyde (which is very toxic) out of methanol. That is why methanol is dangerous. Methanol itself doesn't do much (it would get you drunk if you drank enough of it, but that's it), but it gets converted into something that does a lot of harm. (Alcohol dehydrogenase does a helpful job dealing with ethanol (drinking alcohol) and just tries to do the same thing with methanol, which turns out to be a bad idea.) --Tango (talk) 19:45, 11 August 2010 (UTC)[reply]
Several waste metabolic substances are poisonous if re-digested, such as undiluted urea. Does the immune system, in response to an pathogen, produce poisons at a sufficient level to subdue the pathogen, but not to seriously affect our own health. If so, can this process over-react and kill us? CS Miller (talk) 22:22, 11 August 2010 (UTC)[reply]
The immune system doesn't produce anything that is harmful to us. It produces antibodies but these are harmless to us, they merely seek out the pathogen. So no, it can't. Regards, --—Cyclonenim | Chat 22:29, 11 August 2010 (UTC)[reply]
I'd say "shouldn't" instead of "can't" and I'd cite Auto-immune disorder as my argument. The question is "can people have a gene", if there is such a thing as a gene that codes for toxin, I'd say it is possible, even if it is a disorder or mutation. If the question was "is it normal for a healthy person to have such a gene?" that's a different question. I think it's a little too simplistic to say "it would get selected out", why aren't ALL genetic disorders already "selected out" a long time ago? The subject is obviously a lot more complicated then some of the answers here suggest. Vespine (talk) 23:56, 11 August 2010 (UTC)[reply]
But auto-immune disorders are where your body attacks itself, it doesn't relate to pathogens. Your body can't ever poison itself when it tries to kill a pathogen. As for why all genetic disorders don't get selected out, that's very simple. The diseases which don't kill you or significantly prevent you mating can still be passed down. If a gene codes for a toxin (by definition something that causes harm and can eventually kill you) then the chances are that it will kill you before you reach reproductive age. Regards, --—Cyclonenim | Chat 00:04, 12 August 2010 (UTC)[reply]
I'm not sure I understand your 1st argument, how does your body "attack itself" if not almost precisely the same way it attacks a pathogen? I also don't believe your 2nd statement. Down syndrome is one of the most common genetic disorders, before modern medicine very few people with down syndrome would have lived long enough, or had the opportunity to procreate. Even today there would be very few people with down syndrome who become parents. I don't think toxin means it has to kill you, how about organisms that actually produce toxins? They have a gene that codes for it in their body right? What if you co-evolve a resistance to the toxin, isn't that what snakes do? Vespine (talk) 05:18, 12 August 2010 (UTC)[reply]
Well, your immune system can sort of kill you in response to an infection. See toxic shock syndrome. I say "sort of" because in TSS the infection is using its own toxin to trick your immune system into triggering global vasodilation so it can permeate all of your tissues. As for the original question, I don't think there's really much possibility of a meaningful answer. Too much of anything is bad for you. Tay sachs, phenylketonuria, while described as your body lacking something good, actually kill you through a buildup of compounds the body produces itself. Heck, too much water will kill you. Someguy1221 (talk) 05:34, 12 August 2010 (UTC)[reply]
@Vespine, when I say the body attacks itself, I mean it does so independently of any infection. Yes, sometimes, it attacks itself via the same mechanism it would a normal pathogen, but it is independant of such a pathogen's presence. The statement above my post is referring to 'when a pathogen is in our body, can we kill it off and have a detrimental effect on our bodies'. Strictly, the answer is no. There is no direct poisoning of our bodies through our own natural defenses. However, as Someguy just noted above me, toxic shock syndrome can occur, but that isn't directly a result of our own bodies. That's limited to where bacteria have toxins to trigger vasodilation. In response to your Down syndrome comment, I contest that anyone with Down syndrome would not have been able to live long enough to procreate. Down syndrome sufferers do not take any medication to prolong their lives. In fact, they have an average lifespan of around 50 years - which is more than long enough to procreate if they could. But they can't usually, and if they do it makes things more severe for the children. You assume that all diseases are simply passed down like other hereditary traits - it isn't true. Downs syndrome caused by a nondisjunction event where chromosomes fail to separate, so in that sense it's pretty much a random and rather unfortunate occurrence. Oh, did I also mention that pretty much all Downs syndrome males are infertile, and that women are often much less fertile than those without the disease? This is proof that it isn't a hereditary condition, because there wouldn't be anyone with it if it was! To address your last point, I don't really understand but I'll have a go, clearly if you develop a resistance to a toxin then that's great. You may have noticed though that we haven't. Snakes can still kill us, toxin-producing bacteria can kill us, deadly insects can... well, you get the point. We haven't "co-evole[d] a resistance" to any particular toxins other than the ones we have enzymes to digest. Seriously. Toxin infers that it's deadly or at least seriously harmful to chances of survival. Regards, --—Cyclonenim | Chat 08:09, 12 August 2010 (UTC)[reply]
Sorry, as an immunologist I have to completely disagree with Cyclonenim. First point: Where are the references for you bold claim that pathogens have nothing to do with autoimmunity? The true reasons for autoimmunity are not known, but one of the hypotheses that are discussed, at least for some forms of autoimmunity, is exactly the triggering by foreign antigens. These could just be "normal" allergens in the environment, but there's no reason why the defense against pathogens shouldn't be able to have the same effect (because pathogens bring a large pack of antigens with them). Next point: We are talking here about complex concepts. "Poisoning" and "Toxin" are not well defined. As someone else has pointed out, the dosis and entrance point of a substance are critical: Two molecules of a highly "toxic" bacterial protein won't kill me in my food, but if I drink some liters of pure water quickly, I will die. And what do you mean with "antibodies are harmless"? They are one of the deadliest mechanisms that our body has in its arsenal, because the adaptive immune system is constantly "evolving" to make them more and more effective. And only because we have intricate checks build into our immune system, this "weapon" does not harm most healthy humans. But in every person's blood, there are small amounts of autoreactive antibodies, because the control systems are leaky. So the exact same mechanism that destroys pathogens is constantly producing "toxic" substances. Another thing that goes into the same direction: Our macrophages use very toxic compounds, which they even store for later use, to kill other cells that they engulfed (for example reactive oxygen species and proteins that are capable to cut other proteins). In some cases, when the macrophage is unable to kill the intruder, the reaction gets "out of control" and even kills the macrophage and/or bystander cells (because both are not immune against reactive oxygen, for example).
And in addition, coming to the snake example, there are certainly snakes that are not immune to their own poison. They are only unaffected by their poison because the snake normally only produces and stores it in special organs, so it doesn't get a chance to get into the blood.
Coming back to the original question, I'd say that there's nothing in principle that could stop a gene producing a poison from working (look at all the poisonous pests around us). But as you specifically asked for people, it is unlikely that such a gene would "just show up" in a person. Humans have no use for poison, so there's no selection pressure in this direction. And complex traits as "poisonous" do not just spring into existence, they have to evolve step by step, and every step has to have a slight advantage over the previous one (or at least be neutral). --TheMaster17 (talk) 10:09, 12 August 2010 (UTC)[reply]
To summarize: "Can people have a gene that creates a toxin in our body? In other words is there genes that can make a toxin in our bodies?" Yes, we can and we do. Our immune system generates powerful weapons against microbes. One example is reactive oxygen species that are generated in neutrophils and macrophages. The gene encoding NADPH oxidase is responsible for the production of these molecules. --- Medical geneticist (talk) 12:24, 12 August 2010 (UTC)[reply]
Bacon crisps state 65g protein/100g
Dear Wikipedians, I was just at the store. There I browsed for some crisps/potatoe chips, and came upon a curious find: A Norwegian crisps company called Maarud sells "Bacongull" (Bacongold), and states 65g of proteins per 100g serve; 26.5g fat. Those 65g are normally carbohydrates, at least between 40-60 of them.
Is it true there are cases when getting cold water in a closed bottle out of a fridge would cause it to freeze suddenly when opening? If yes, then how can we explain this phenomenon?--Email4mobile (talk) 18:34, 11 August 2010 (UTC)[reply]
The trick here is that the fridge is too cold and is cooling the water to just below freezing, but the pressure in the bottle is stopping it from actually freezing. Release the pressure and ... bang, it freezes like magic about two seconds after you open the bottle. APL (talk) 18:59, 11 August 2010 (UTC)[reply]
(ec) Water freezes at a temperature below 0 °C under a pressure higher than 1 atm (0.10 MPa). Therefore liquid water in a bottle under pressure could freeze when the bottle is opened. Cuddlyable3 (talk) 19:08, 11 August 2010 (UTC)[reply]
I can find the pressurized bottle effect makes sense in some pressurized liquids, but not sure if water bottles are pressurized too since we expect vapor pressure to get lower as well by decreasing temperatures inside the fridge. --Email4mobile (talk) 19:30, 11 August 2010 (UTC)[reply]
Look at the phase diagram under Ice. The effect of even a 10000-fold change in pressure is only a 2-3 degrees C difference in the freezing point. Whatever the bottle is pressurized to, we're only looking at a fraction of a degree that the water would have to be within for the simple release of pressure to freeze it. You might heat it up by as much as that before you get it open. So I think it's far more likely that bubbles generated by moving the bottle, or contact with small irregularities, would nucleate freezing in the supercooled liquid. Wnt (talk) 15:22, 14 August 2010 (UTC)[reply]
A few years ago I had a habit of putting a 1 liter bottle of water in the freezer before going on my lunch break (1 hour). Upon returning, I retrieved the bottle and was able to observe the effects of supercooling by tapping the bottle with my fingertip. Hemoroid Agastordoff (talk) 16:43, 13 August 2010 (UTC)[reply]
My lab group just called this process whenever it occurred apoptosis but they're chemists (though they are branching out into the biology side), not cell biologists. Is autophagy a more accurate description? I don't see a description of these very visible bubbles in the apoptosis article.
This occurs whenever the cell culture is about to die on the microscope slide after having been on the slide for too many hours, at room temperature, without the 5% carbon dioxide atmosphere. John Riemann Soong (talk) 19:45, 11 August 2010 (UTC)[reply]
(I notice that the images in each of these articles are either cartoony or not very vivid, so I want to include this photo in one of the articles, but I don't know which one is appropriate.) John Riemann Soong (talk) 20:45, 11 August 2010 (UTC)[reply]
Pardon me, but you seem to have been putting these types of photos up and asking extremely detailed questions regarding cell structure and function, the likes of which can probably only be answered by individuals with such highly specific training that you are unlikely to receive a good response on the ref desk. Good luck, though! DRosenbach(Talk | Contribs)20:47, 11 August 2010 (UTC)[reply]
Can you even tell which it would be from this photo? I was under the impression that either footage or a series of pictures over time is/are needed to determine which type of PCD is happening. Can't you tell which type is happening by observing what features degrade first? In autophagy, the nucleus should go towards the end. I also agree with DRosenbach above. These questions are pretty complicated and I'd take a guess that people at your University (in the biological and medical departments) may be better off answering your questions. Regards, --—Cyclonenim | Chat 21:29, 11 August 2010 (UTC)[reply]
Well I'm very familiar with the bubbling process. I've watched it happen like a million times. People identify very peculiar and specific insects I've never heard of all the time, so why not something as basic as a fundamental cellular process? Anyway, the nucleus takes a while to degrade -- the bubbles appear first -- before the cell blebs. Over time these bubbles can "take over" the cell. I'm not sure if apoptosis is triggering the hypothesised autophagy or vice versa. I think it this process is a consequence of nutrient or oxygen starvation.
Perhaps have a go at posting it at one of the WikiProjects first and see if someone can help you there. There's no rush :) I'd agree that it looks more like an autophagical process but it's hard to tell, as you mentioned, if it's being performed under the 'supervision' of a larger process. Regards, --—Cyclonenim | Chat 22:20, 11 August 2010 (UTC)[reply]
The best way to be sure would be to fix and immunostain the cells to look for specific markers for autophagosomes; microtubule-associated light chain 3 (LC3) associated with vesicle membranes is one of the popular markers in mammalian cells ([8]). Meanwhile, you can look for the activation of apoptosis machinery in the cells by staining for cleavedcaspase-3. It is apparent that there are some sort of perinuclear vesicles in those cells, but I would be hesitant to jump to conclusions about their identity. TenOfAllTrades(talk) 22:36, 11 August 2010 (UTC)[reply]
Burping in zero gravity
A while ago I needed to burp while lying down. I could not do it, I imagine because the bubble of burp-gas must be in contact with the upper sphincter of the stomach. In gravity this is no problem. But what do astronauts do in space? Google searching has not come up with any serious answer. Thanks. 92.15.14.45 (talk) 21:36, 11 August 2010 (UTC)[reply]
This article (towards the bottom) suggests that astronauts can burp in space, but since the gas isn't necessarily at the top of the stomach, it comes out as an unpleasant wet burp. anonymous649402:45, 13 August 2010 (UTC)[reply]
I asked a similar question here, but I figure this is more of a science question. The question is - if the water is pure when it is pumped into water supply system, can it get contaminated while it travels through piping (i.e. by something in the pipes, not foul play) ? ~~Xil (talk) 22:15, 11 August 2010 (UTC)[reply]
City water supplies are continually scoured by the flow of water so there is no opportunity for bacteria to establish a stationary colony in the pipe and contaminate the water flowing through. Where water lies stagnant in a pipe for a long period of time, such as in unoccupied houses, there is a risk of colonies of bacteria becoming established and contaminating the initial throughput of water when flow resumes.
The major risk of contamination of a city's water supply is contamination at the point of collection (such as a dam) or prior to collection if there are contaminants in the catchment area (such as a dead animal.) Dolphin(t)22:40, 11 August 2010 (UTC)[reply]
Older homes and some older municipal water systems may use lead solder and even segments of lead pipe. Water that is left standing for an extended period (several hours or overnight) may pick up a toxic level of lead.
Biological contamination is rare unless the pipes are damaged close to the end user and external organisms are able to contaminated the drinking water. (This is rare and rather difficult to do, as the water in the pipe is generally being forced out under pressure.) As well, in many municipal water systems water is treated with chlorine or chloramine; the latter compound in particular tends to persist for several days in the water, providing a residual disinfectant activity all the way out to the consumer's tap. TenOfAllTrades(talk) 22:56, 11 August 2010 (UTC)[reply]
Your note about lead reminded me - I read somewhere that piping for drinking water used to be made from copper to improve its quality, is any particular metal used or other material used for same purpose today ? Also asumtion here is that piping is old (not leaking old, but I figure pipes could be rusty, there could be some sediments or stuff growing on wals of pipes or something). Aside from being curious about water supply systems in general I am also concerned about water I am drinking, I found out that my city has two water sources. One is river water which is treated with aluminium sulphate, ozone and light dose of chlorine before it is pumped to consumers. However I live in another part of city which uses ground water taken from soils rich with iron and manganese. My issue here is that despite very good taste, I feel a light, but foul smell when drinking ~~Xil (talk) 08:37, 12 August 2010 (UTC)[reply]
Most of the piping in my own house (UK, about a century old, but repiped some time since the initial build) is copper, which was the default material in the UK at least until quite recently and is certainly still used for repairs. Plastics of some sort might be used in new buildings now, but primarily for cost rather than health reasons, copper being increasingly in demand for other purposes, and therefore increasingly expensive.
In the UK and, I think, most First-World countries, water supply companies are legally obliged to deliver drinkable water to customers, and are responsible for the pipework right up to the latter's property line - they would be heavily penalised if they failed to do so whether due to pipework contamination or for any other reason. Certainly water from different sources can differ in its trace elements as well as the treatments it has undergone to ensure it is potable, and this will be detectable in the taste and smell, which is partly why, for example, many breweries in the UK "Burtonise" their brewing water (or "liquor"), adding trace elements to make it more like the natural supply in Burton-on-Trent*. Different people find these different tastes and smells variably noticeable, innocuous or sometimes unpleasant, but unless something has gone wrong, they do not usually signify any health hazard. However, such factors are so variable from country to country that it is impossible to safely generalise for an unspecified locality.
(*As well as effecting the immediate taste to humans of the water component of the beer, the trace elements also influence the metabolism of the fermenting yeasts - but I digress.) 87.81.230.195 (talk) 12:14, 12 August 2010 (UTC)[reply]
In terms of sediment and stuff settling in the pipes, I don't think this is likely to be a significant problem due to the constant water flow. In Malaysia, when you get a water cut, you will find the water is dirty when it first starts flowing again. I'm not sure if this is from the pipes or the supply but I think it is the former as the water flowing again dislodges stuff that has settled and/or any oxides or whatever from the pipes Nil Einne (talk) 14:18, 12 August 2010 (UTC)[reply]
Yeah, they are legaly required to deliver clean water up to property line, however city's pipelines are known to be very old, so I'm not complitely sure that they can. Anyways, I don't feel any smell anymore and judging by what it smelled like I figure it could have been from water having stayed in pipes too long. Thank you for the answers ~~Xil (talk) 09:45, 14 August 2010 (UTC)[reply]
Antibiotic-resistant "super bug"
I just saw a story on the news about a "super bug" that's resistant to all known antibiotics and can spread this immunity to other bacteria. What research has been started to combat this before it causes the extinction of humanity? --70.134.48.188 (talk) 22:17, 11 August 2010 (UTC)[reply]
Firstly, don't listen to everything the news tells you. Yes, it's a fairly big blow for antibiotics but not absolutely condemning for all of humanity. Not just yet. What happens is that it prevents any antibiotic with β-lactam rings from working, but this protein that's causing all the havoc is only present in certain, limited Gram-negative bacteria (such as E. coli and others) so far. It could spread and become more common, but it hasn't yet. Other Gram-positive bacteria can still be treated, so contrary to popular opinion, it's not the end of antibiotics completely. There are currently no drugs in the pipeline (or at least pre-clinical stage pipelines) that are able to combat this obstacle, but that doesn't mean we're completely hopeless at finding another. One option, as I posted a question about above, could be to develop phages that actively hunt and kill off bacteria, but they are currently not approved for human, medicinal use. It is not the end of the world... yet. Regards, --—Cyclonenim | Chat 22:24, 11 August 2010 (UTC)[reply]
What "super bug" in particular ? In any case the bacteria evolve so they eventualy are resistant to older drugs, therefore new drugs need to be invented. This happens all the time, "super bug" is just media hype. One such "super bug" case was the recent swine flu pandemic. ~~Xil (talk) 22:34, 11 August 2010 (UTC)[reply]
What I meant was it does it have a name other than "super bug" ? If not it may very well have been a speculation that such "super bug" may emerge, not that it is currently infecting people (if it was and it wasn't contained we would see broader media coverage) ~~Xil (talk) 22:52, 11 August 2010 (UTC)[reply]
Let me clarify: it is not a super bug. It's a super plasmid. It accounts for resistance to any antibiotic that replies on beta-lactam rings (which is a lot of them) and is currently spreading around through various mechanisms I won't bother to go into. However, it's only relevant to specific bacteria called Gram-negative bacteria. Antibiotics that currently work on Gram-positive bacteria will still work (for now). We may even develop new ones for Gram-negative bacteria. The media is lying when it says it's the end of all known antibiotics. Regards, --—Cyclonenim | Chat 23:38, 11 August 2010 (UTC)[reply]
Another thing to bear in mind before writing off the human race is that the vast majority of bacteria (including those bearing exotic plasmids) are completely harmless to us. Bacteria that are either fatal or seriously harmful tend to evolve to be less nasty because if the host dies or becomes so sick that they go to bed and stay there, the bacteria have a much harder time spreading. From an evolutionary perspective, the optimum thing for the bacteria to do is to be massively infectious - yet produce as few symptoms as possible. Sure, when a new disease pops up, a good percentage of the population might die before that happens - but it's hard to imagine a scenario where that would take out more than a few percent of the worlds population. When you look at some of the worst pandemics in history - the 1918 flu pandemic, for example. Over the course of two years, one third of all people in the world were infected and 3% of the world's population died. There were absolutely no drugs that could to a thing to prevent it. The disease never was 'cured'. The pathogen simply evolved to be less obnoxious all by itself. Certainly a 3% death rate would be a monumental disaster - but (as you can tell from the 1918 event) the long term effects on humanity are minimal and the worst disease epidemic in history is barely even talked about, 90 years later. SteveBaker (talk) 03:34, 12 August 2010 (UTC)[reply]
Is that true? I'm unsure. I know it definitely applies to viruses, because they are, in a literal sense, parasites which invade our cells. If the cell dies (without it bursting), then they can't replicate and spread. Bacteria, however, aren't parasites. They invade our blood and tissues but they don't strictly interact with the cells, do they? Might be wrong. Regards, --—Cyclonenim | Chat 07:52, 12 August 2010 (UTC)[reply]
I don't think notion that disease cannot have long term effect on civilization is entirely true - the plague apparently did, though the death toll was higher than 3% ofcourse (still if people survived plague pandemic in age when health care was less developed, why wouldn't people survive now ?) ~~Xil (talk) 08:49, 12 August 2010 (UTC)[reply]
We do have examples, though, of basically entire civilizations being killed off by pandemics, e.g. the Native Americans, who under some estimates had 95% of their population killed by Old World viruses to which they lacked immunity. That's a pretty extreme scenario, but it's pretty hard to contemplate. Even 33% is a ridiculously high number, and would have massive effects on human civilization and society (as did the Black Plague on Europe). If you're willing to say that's OK because life will be different/better/go on, you might as well say that nuclear war is fine too, because those are the kinds of numbers we are talking about. --Mr.98 (talk) 12:51, 12 August 2010 (UTC)[reply]
Well, it's obviously not "fine" - but the point is that it's also not "the extinction of humanity" - which is what our OP is asking about. SteveBaker (talk) 14:10, 12 August 2010 (UTC)[reply]
Keep in mind, the bacteria still needs to be able to gain entry into the body to be harmful. We have many layers of innate resistance to microbes (see innate immune system), none of which are affected by bacterial acquisition of antibiotic resistance. According to BenRG's helpful reference above, many of the people who have been infected by these super-organisms were "infected by NDM-1 carrying bacteria while undergoing surgery under non fully-aseptic conditions." This means that the "super-bug" is largely responsible for nosocomial infections, certainly nothing like a "pandemic" that can somehow spread from person to person. It is another in a long example of antibiotic resistances that bacteria have evolved over the millenia. Where did we first get antibiotics from? mold. How long have bacteria and molds been fighting with each other? This is evolution in action and we are only recent players.
I'm not trying to downplay the devastating effect of antibiotic resistance on the way that medicine is practiced today, but you have to realize that the media is going to hype up this kind of thing to sell their product. This latest version of the "super-bug" is not going to cause the end of our species. --- Medical geneticist (talk) 12:40, 12 August 2010 (UTC)[reply]
An antibiotic-resistant "superbacteria" can cause a major pandemic with many casualties, but it will not drive humanity to extinction. Remember that we only have antibiotics since not much more than a hundred years ago: so people before it had to deal with illnesses having no antibiotics at all. A lot of people might die, but it's very far from extinction. --131.188.3.21 (talk) 23:49, 12 August 2010 (UTC)[reply]
NDM-1 isn't really "super", nor is it a "bug". It's an enzyme that gets into different types of bacteria and makes them immune to antibiotics, similarly to how disinfectants that kill 99.99% of bacteria and viruses leave the remaining 0.01% mutating into superbugs that over several cycles become completely resistant to antibiotics and disinfectants. It's not that the bacteria infected by this "superbug" become extra deadly, they just become much harder to kill. So if it found itself preferring a bacterium that has a high mortality rate in humans and quickly spreads in those bacteria, then we might have a problem. The real pandemics like the Black Death and the more recent 1918 flu pandemic were devastating, but the recent pandemics have been not that severe, although the melting of glaciers and permafrost in Arctic regions could release ancient viruses in the future. ~AH1(TCU)00:21, 13 August 2010 (UTC)[reply]
Bacteria have been living on Earth for about 4 billion years in all sorts of environments. Complex life forms have been around for a much shorter time and the environments they can live in is far more limited. Surely, then the massive use of anti-biotics is a stupid, self-defeating strategy as eventually you'll end up with superbugs that are only sensitive to drugs that are lethal to humans? Count Iblis (talk) 15:14, 13 August 2010 (UTC)[reply]
Probably, but it's good for saving lives in the meantime. There's no guarantee that bacteria will develop resistance because, like natural selection, you have to have the mutation occur first. If it doesn't happen, obviously you'll get no resistance. The reason resistance is currently so common is because a lot of our antibiotics only vary slightly. There are different classes, but within those classes the variation is limited, so there isn't much work needed to accidentally develop a resistance to a new antibiotic. Regards, --—Cyclonenim | Chat 21:15, 13 August 2010 (UTC)[reply]
The Soviet Union developed a reasonably effective alternative, phage therapy, which is banned in the U.S. because of political or economic inconvenience to the capitalist system. Hopefully, by the time the first 90% have died, people will reconsider their ethics. Wnt (talk) 14:59, 14 August 2010 (UTC)[reply]
August 12
Famous scientific hypothesis
I need to prepare for my science test a description of two famous hypothesis. Thus, I need your help to give me two science hypothesis (from any field), that is easy to understand and explain. Thanks! --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time!02:43, 12 August 2010 (UTC)[reply]
DO they need to be correlated (i.e., one versus the other, opposing theories)? If not, I suggest the quantum field theory and effective field theory (disclaimer: I'm an engineering graduate student ;). If so, how about the accepted Darwinian model of evolution versus the Lamarck model? You'll have to come up with the descriptions yourself ofcourse; if we did that it would be equivalent to doing your homework for you. 76.228.193.68 (talk) 03:04, 12 August 2010 (UTC)[reply]
But I think it's fairly well established that Mendel forged a significant amount of his data to fit with his hypothesis. It might have been true in the end, but that's not real research. DRosenbach(Talk | Contribs)15:02, 13 August 2010 (UTC)[reply]
The phlogiston hypothesis would be another good one that also proved to be wrong. --Anonymous, 03:20 UTC, August 12, 2010.
One rarely proves a hypothesis right. One only looks for disproof. The theory of natural selection, as noted above, is accepted as scientific fact, due to its lack of falsification and explanatory power. The Rhymesmith (talk) 03:27, 12 August 2010 (UTC)[reply]
Well, one very famous hypothesis which was tested and shown to be accurate was the experiment which proved the Gravitational lens prediction proposed by Einsteins' General Relativity. Arthur Stanley Eddington famously showed that the mass of the sun bent light so that objects behind the sun could be viewed during the Solar eclipse of May 29, 1919. It was a simple observation which confirmed an unusual hypothesis, that large objects could bend space-time, and thus cause light to appear to bend around them. --Jayron3205:44, 12 August 2010 (UTC)[reply]
In case the previous sentence was ambiguous, protons and neutrons are made of quarks, while electrons are not. The phrase "Atomic Theory" generally only refers to looking down to the level of atoms, and sometimes of the particles that make up atoms (protons, neutrons, and electrons). The "Standard Model" would be the "theory" that includes quarks. "Particle physics" would be a general term used to describe the physics of Elementary particles, including quarks. Obviously, these fields are not strictly defined, and there is a considerable amount of overlap. Buddy431 (talk) 03:58, 12 August 2010 (UTC)[reply]
Our articles don't seem to mention size. I assume that this is because the effective diameter depends on where the particles are, and what they are doing, and how we try to measure size. For most practical purposes, quarks and all of the particles mentioned by Astro above have zero size (i.e. they are all singularities in a general sense), so the comparison cannot be made. One could claim that they all have zero size. Perhaps, sometime in the future, when we find a way to measure distances less than a tenth of a millionth of a millionth of a millimetre, we might compare their effective sizes in some way, but, at present, we regard them all as point masses, charges, colours etc.
Actually the particles have a de Broglie wavelength which defines their size. Calling them "singularities" seems sort of pointless (they're not black holes, you can't fall in, and you can never measure them as points, but as fuzzy clouds of probability that affect their collisions and interactions) But to measure the de Broglie wavelength of a quark, you need to have one to measure its mass ... and having one is the problem (see free quark). Wnt (talk) 14:53, 14 August 2010 (UTC)[reply]
No. It's speculated that hydrogen might do that at extremely high pressures and extremely low temperatures, but it has never been observed. I believe all known superconductors are solids. Dragons flight (talk) 07:01, 12 August 2010 (UTC)[reply]
Is it possible to build a gun like this ? The drop is tightly fit in the breech. When the firing pin hits and drop is exploded the ball rushes out and do the usual gun thing ? Jon Ascton (talk)05:07, 12 August 2010 (UTC)[reply]
I'm not sure that Prince Ruperts Drops explode with all that much force. Its a rather spectacular splash of glass, but the "explosion" is many orders of magnitude smaller than any combustable material or high explosive. It doesn't really explode as much as crack very fast. It may generate enough force to make the ball dribble out of the barrel of your gun, but little more. --Jayron3205:35, 12 August 2010 (UTC)[reply]
When something implodes, fragments can still fly outwards -- the ones that happen to pass through the center without hitting other fragments, or as a result of fragments colliding elastically. But it is true that they'll tend to lose kinetic energy as they come together, of course. --Anonymous, 17:52 UTC, August 12, 2010.
Do viscous substances have more Surface tension than non viscous substances?? How does Lyophilic colloids have less surface tension than the solvent??Rohitbastian (talk) 06:03, 12 August 2010 (UTC)[reply]
Viscosity and surface tension are unrelated to each other. Water has a relatively high surface tension, and a relatively low viscosity, for example. And lots of mixtures have lower surface tension than the pure solvents they are based on. See Surfactant for more. --Jayron3206:33, 12 August 2010 (UTC)[reply]
Erectile dysfunction drugs
Did the makers of Cialis and Levitra copy and modify the chemical structure of Viagra or did espionage occur? It seems like they came out right after Viagra did. It would be understandable if they came out years later, but I believe they came out within a short period of time after Viagra (but I may be wrong). Would it be really possible to find or make a similar medication within such a period of time if they didn't copy it? —Preceding unsigned comment added by 76.169.33.234 (talk) 06:09, 12 August 2010 (UTC)[reply]
While Sildenafil (Viagra) and Vardenafil (Levitra) share some similar chemical structure, Tadalafil (Cialis) appears to be quite different. The first of these, Viagra, was not originally marketed for use in fixing erectile dysfunction, rather as a hypertension medication. The erection was basically a side effect which ended up becoming the actual intended use. Both Cialis and Levitra were developed, at least in part, by GSK, so that explains some of their connection. The general class of drugs is discussed at PDE5 inhibitor. --Jayron3206:30, 12 August 2010 (UTC)[reply]
I actually worked at an Eli Lilly site when Cialis appeared, and hadn't known the GSK connection until now. (Checking Jayron32's answer, I found that it was discovered by an SK/ICOS joint venture, but developed & marketed by an ICOS/Lilly one.) Apparent coincidences like this are partly explained by the very long times it takes to develop newly discovered "candidate molecules" all the way to market (assuming they make it - only around 1 in 10 do): up to 10 years (and a cost of around half a billion US$) is typical. A Company might be able to speed up the process a little by devoting more resources to a given candidate, and might be inclined to do that if a competitor is known to be in the works, so as not to concede more market advantage that they have to by allowing more of a head start: thus the release dates can converge. 87.81.230.195 (talk) 11:46, 12 August 2010 (UTC)[reply]
BTW if you read the obvious articles, which Jayron32 has helpfully linked above, you'll find Sildenafil i.e. Viagra received FDA approval in March 1998 and the other two in August and November 2003 or over 5 years later. I'm not sure whether you consider that 'short period of time' or 'years later' but I would say it isn't an unresonable length of time just for fairly normal development, particularly since the drugs were already in development even if not for the specific purpose and as 87 has mentioned a company may devote more resources if they see it as important or likely to be a success. Nil Einne (talk)
PROGESTERONE
Progesterone:-
would the use of progestrone, used in the form of an transdermal cream, have an effect on a person who has high colesterole? —Preceding unsigned comment added by Gilpill (talk • contribs) 08:56, 12 August 2010 (UTC)[reply]
Could you clarify the question? Are you asking whether progesterone has its normal effects even if the person has high cholesterol? Or if progesterone affects cholesterol levels? Or if the specific transdermal application has specifically different effects related to cholesterol? As a starting point, Bioidentical hormone replacement therapy#Lack of evidence for claims suggests that--at least in the cases considered there--route/form of administration of progesterone does not have an effect consistent with altered cholesterol levels. DMacks (talk) 13:12, 12 August 2010 (UTC)[reply]
Or was it Miroslav Smotlacha who is a famed Czech mycologist who died at age 86 back in 2007? According to his obituary, his entire family are mushroom experts - so it could have been any of half a dozen people with the same surname. SteveBaker (talk) 14:05, 12 August 2010 (UTC)[reply]
It would appear that Miroslav Smotlacha is František Smotlacha's son. The dates the species were described, and that the author abbreviation is "Smotl.", not "Smotl.f" / "Smotl.p", would suggest the article about Smotlacha-the-person-whose-author-abbreviation-is-Smotl. should be about Miroslav Smotlacha. I am indeed mistaken.--Shirt58 (talk) 06:11, 14 August 2010 (UTC)[reply]
how can that possibly be true???
It says 1.5 million facebook users die every year!! How can that possibly be true??? That can't be just a coincidence, but what could possibly explain this, it just doesn't make sense! Is it just a lie?! Or how is it true!!! 84.153.200.162 (talk) 14:54, 12 August 2010 (UTC)[reply]
The world death rate is something like 8 deaths per thousand people per year. Facebook has something like half a billion active users. Thus if Facebook users are as likely to die as anyone else, we would expect about four million to die every year. So if your figure is accurate, then Facebook users are in fact much less likely to die than people on average – as we would expect, given its target demographic. Algebraist15:01, 12 August 2010 (UTC)[reply]
Given that average life-expectancy is around 70 years, then 500million / 70 year = 7 million/year. This of course assumes that facebook's user demographics is about the same as the average person, which probably is not accurate. CS Miller (talk) 16:48, 12 August 2010 (UTC)[reply]
Except, as I'm sure we're all aware, it's not that simple. I'd suggest that Facebook has a lot more users in the 16-40 years old range than elderly 70 year olds. If 1.5 million Facebook users die every year, I'm sure a lot of those will be unfortunate accidents. Regards, --—Cyclonenim | Chat 21:05, 12 August 2010 (UTC)[reply]
When Facebook first started, the largest group of users was likely young adults in post-secondary education such as college or university. Currently the fastest-growing demographic group on Facebook is women over 55. ~AH1(TCU)00:09, 13 August 2010 (UTC)[reply]
How much does an aluminium soda can tab weigh?
(This is an offshoot of a question on the misc ref desk - but I'm hoping someone with an accurate laboratory scale can get me a better answer).
How much does the ring-pull 'tab' on a typical soda can weigh?
For clarification... are you referring to the old style that completely comes off the can or the new style that stays on the can, but you can remove if you bend it back and forth a lot? If it is the old style, that will be hard to answer. If I can locate a can, I can do the new type. Everyone around here appears to use bottles now. -- kainaw™15:20, 12 August 2010 (UTC)[reply]
The newer kind that you have to bend back and forth to remove...to a very rough precision (I guess tabs from different manufacturers are a bit different)...+/-20% should be fine. Thanks! SteveBaker (talk) 15:29, 12 August 2010 (UTC)[reply]
I thought this would be trivial to do, but there are no cans here. Our vending machines only have bottles and the convenience store across the street only has bottles. If nobody answers, I will do my best to remember to bring in a few tabs tomorrow and weigh them on one of the drug scales which go to 1/1000th gram. -- kainaw™16:49, 12 August 2010 (UTC)[reply]
As a completely random aside primarily arising because it's something I've been looking at recently. You can get cheap high precision scales from China/HK eBay sellers, something like US$6.00 shipped for a 100g/0.01g or US$8.50 shipped for a 300g/0.01g scale isn't uncommon. I wouldn't use these for serious work but from what I've read the precision is usually fairly good, i.e. they will give about the same value for the same weight and neither where you put the mass nor the temperature (within reason) have a significant effect. However the accuracy on these scales is likely to be far more questionable and there is a possibility they may drift over time (I read one person saying their one did). They can usually be calibrated and you can buy cheap calibration weights but of course the accuracy of cheap calibration weights is also questionable. However if you do have access to a accurate high precision scale, you could test them or for that matter make your own calibration weight to hopefully give you a resonably accurate high precision scale (you can also test it with various masses after calibration). I've seen some people use coins but I'm dubious that will give you an accurate enough calibration or test weight. Of course the precision is useful if that's all you need, I think some people use them for balancing RC helicopter rotors blades. There are also 0.001g ones but they're a fair bit more, like US$15.00, and while I haven't looked in to them much, I do wonder whether that precision is worthwhile on something so cheap. Nil Einne (talk) 18:34, 12 August 2010 (UTC)[reply]
I get 0.300 grams. I wouldn't be surprised if that can swing at least a few milligrams up or down depending on precisely where the tab tears when it is removed from the can. (I don't know what the distribution is; I only conducted one measurement.) TenOfAllTrades(talk) 18:22, 12 August 2010 (UTC)[reply]
It is usually stated in his biographies and obitiaries as "unspecified". When someone dies peacefully in their bed at age 95, there isn't generally any cause of death listed. "Natural causes" or "Old age" is the best you're going to get. Of course, something very specific did kill him - heart failure or something - but nobody is gonna being doing an autopsy to find out. SteveBaker (talk) 19:21, 12 August 2010 (UTC)[reply]
He had suffered a stroke on September 7, 2003, and died two days later. (Goodchild, Edward Teller, The Real Dr. Stranglove, 394.) At age 95 he suffered from a whole host of old-age related maladies. I think "old age" or "natural causes" is probably whatever his certificate said; they probably did not bother doing an autopsy. I've added the basic info to the article.--Mr.98 (talk) 00:00, 13 August 2010 (UTC)[reply]
Panic, mass hysteria, paranoia. Plus the ordinary run of the mill mistakes in the justice system that allows innocent people to be executed to this very day.
It seems likely to me that there were at least a few people around who thought they were witches and could cast spells. After all, there are people today who think that, in this far more rational age. But of course the great majority who were burnt were completely innocent. Looie496 (talk) 21:25, 12 August 2010 (UTC)[reply]
And, let's be clear, unless those people who thought they were witches were actually poisoning people or animals, they were also completely innocent. You can't be guilty of actually casting evil magic spells that cause your neighbour's cows to dry up. 82.24.248.137 (talk) 00:09, 13 August 2010 (UTC)[reply]
Magic is usually defined as "Powers outside of nature", but as soon as someone discovers how to do something, it's automatically part of nature. So by that definition magic can never exist - because as soon as it's discovered, it's no longer magic. But, if we change the definition to "Unexplained phenomena" then magic did (and does) exist, because there were (and are) lots of unexplained things. In the search for explanations for the unexplained (especially the tragically unexplained) people accused those that were different. Ariel. (talk) 21:24, 12 August 2010 (UTC)[reply]
I take issue with your comparisons, Dr Dima. From a Jewish perspective, while technology is reproducible and morally neutral, magic is not. You mustn't pray, "Oh Awesome Computer, please send my email!!" Rather, you click on the button, and whether you're an old lady who executes cats in her basement after torturing them or an upstanding member of the community, the computer will send your email. But cauldrons of potion require incantations and the like, beseeching the (non-existent) power of magic. If one is worthy, one's virgin in the volcano is accepted and the magical request may be granted. Thus, magic and technology are examples of two distinct and non-overlapping magisteria. DRosenbach(Talk | Contribs)15:14, 13 August 2010 (UTC)[reply]
In the Old Testament there is an explicit instruction that women who are witches or sorceresses are to be put to death. It is found in Exodus 22:18. Different versions of the Bible translate this instruction in different ways, but the central message is the same – a woman is to be put to death if she might be a person who practices magic.
Thou shalt not suffer a witch to live (King James Version)
Put to death any woman who practices magic (Good News Version – makes one wonder what the Bad News Version would say!)
You shall not permit a sorceress to live (Revised Standard Version)
There is no similar instruction regarding the execution of men - only women! And there is no opportunity for tolerance or a lesser punishment such as counselling or even a curfew – death is the only acceptable outcome!
In past centuries, prior to the broadcast of science and education, people relied heavily on ancient scriptures to guide them in their daily lives. As a result, all manner of injustice and foolishness pervaded human communities that practised loyalty to these ancient scriptures. The murder of women, and particularly old women, out of fear of witchcraft and sorcery is merely one of the injustices that persisted for thousands of years as a result of the unquestioning loyalty to ancient scriptures. Dolphin(t)03:46, 13 August 2010 (UTC)[reply]
It's 22:17 not 18. And your rant about women is wrong because you forgot about Deuteronomy 18:10 which uses the male version of the female word used in Exodus. The rest of your rant has nothing to do with scriptures and everything to do with people who simply wanted to, due to fear of "other", or "strange", scriptures were just an excuse. Just look at Africa today where such executions are still carried out and have nothing to do with scripture. Ariel. (talk) 06:09, 13 August 2010 (UTC)[reply]
I did not forget about Deuteronomy 18:10 because I know nothing about it. However, the nineteen persons (or groups of persons) responsible for the nineteen translations listed at Ex 22:18 might have forgotten about it, but I doubt it because to translate the Bible, and have it published, one must be an expert. In those nineteen translations no masculine word, or male version of a female word is used. The female word sorceress is used many times, but the male equivalent sorcerer is not used in any of the nineteen translations (except in the expression female sorcerer.) I concede that the gender-neutral word witch is used in two of the translations, and the word witchcraft once, but no unambiguously male word appears. I agree that many executions of alleged-witches would have been because people just didn't like the person and were motivated to murder that person, but the existence of Exodus 22:18 provided many of the murderers with re-assurance and justification that what they were doing was not only legitimate but an explicit commandment from holy scripture. Dolphin(t)07:39, 13 August 2010 (UTC)[reply]
See the Copenhagen interpretation. When the First Man looked up into the sky, the stars coalesced from formless chaos. Is that not magic? But be wary of pursuing the paranormal - you may find that you harm all you encounter, and lose the capacity of meaningful choice, and that your "talent" is nothing but a disease, and a crime, and an abomination, and an art of the damned. Look to Diocletianic Persecution for a remedy. Wnt (talk) 14:42, 14 August 2010 (UTC)[reply]
You might have to buy the glass shakers separately (supermarkets usually sell in plastic, but I've seen pretty good ones at a 'restaurant supply store' that is open to the public.) RJFJR (talk) 21:12, 12 August 2010 (UTC)[reply]
I was watching this episode of House, and they did an experiment where they where able to see what a person was thinking by reading brain waves while look at pictures so the computer knows what triggers what in the brain. Is this actually possible? 99.114.94.169 (talk) 20:31, 12 August 2010 (UTC)[reply]
To a very limited extent, yes. You can see what areas of the brain are being used at any given time with various forms of functional neuroimaging (read that article and the articles it links to for details). While that isn't enough to work out what someone is thinking from scratch, you can compare it to previous scans of the same person and find a match and know that they are probably having the same kind of thoughts (eg. you show them a bunch of pictures and see what parts of their brain are active when they consider the picture and then show them one of the pictures again at random and you can work out which one it is by comparing the brain scans). While there are general areas of the brain that do the same thing is everyone, there is enough variation that you do generally need to establish a "baseline" using scans of that particular person's brain before you can use new scans to determine anything substantial about their thoughts. Also, the best you can do is work out what kind of thinking they are doing (for example, thinking about something they enjoy, thinking about moving their body, thinking about hearing something, etc.). You can't work out specific thoughts. --Tango (talk) 21:07, 12 August 2010 (UTC)[reply]
If our article's description of the episode is correct, the things they do (mapping the thoughts of an unconscious person) go vastly beyond anything that is currently possible. Current technology is at the level of things like trying to read brain waves well enough to let a person to use them to move a lever back and forth. Looie496 (talk) 22:35, 12 August 2010 (UTC)[reply]
If I recall the episode correctly, they show the patient a huge number of reference images, and have the computer create a sort of database of what this patient's brain looked like when they were looking at each of the images. Only after hours of that did they start trying to reverse the process. They don't dwell on it, but I got the impression they were relying on the computer running some sort of algorithm, possibly like facial recognition software, making up the new image out of combinations of basic features from the huge database of images. Do I mean eigenfaces? It was the sort of thing that seemed probably not possible with current technology, but plausible in the not-distant future. (In fact, the characters in the episode are all a bit surprised it works) But I'm no expert. 82.24.248.137 (talk) 00:04, 13 August 2010 (UTC)[reply]
Worst. Episode. Ever. I'm afraid my criteria for 'seems plausible in the not-distant future' is that I can imagine the mechanism by which it would work, using merely more-advanced versions of technology we currently possess. It seems probably not possible with current imaging, although with enough care and a large enough database of examples for that individual, I wouldn't be wildly surprised by a much vaguer result being achievable. The sort of result that might let you tell whether they were thinking of a round thing or a tall thing, a dark thing or a light thing, a single shape or many shapes. 86.164.66.83 (talk) 22:23, 13 August 2010 (UTC)[reply]
It's definitely quite impossible right now. I'm skeptical that the approach suggested in House would actually work - it presumes a lot of things about the brain that we simply do not know to be true. SteveBaker (talk) 02:23, 13 August 2010 (UTC)[reply]
I think it might work in principle, but current functional imaging techniques don't come close to the spatial resolution or signal-to-noise ratio that would be needed. Correlation-based reconstruction is pretty robust -- it can work well even if you don't have any idea what the activity patterns actually mean. Looie496 (talk) 03:07, 13 August 2010 (UTC)[reply]
I don't know the episode of House in particular (don't watch it) but from what's been discussed so far some may be interested to know various companies are developing fMRI lie detector tests. These have even been (controversially) used in Indian court cases www.policyinnovations .org/ideas/briefings/data/000172 (black listed site) Nil Einne (talk) 17:35, 13 August 2010 (UTC)[reply]
Ca2+ It coordinates well with lewis bases such as crown ethers. In a similar way, it can bind to various sorts of structures during a reaction to allow one part of a molecule to serve as a template for another. For example, residual calcium ions from one step were critical in stabilizing a structure by two hydroxyls and an ether cause a subsequent reaction to proceed a certain way. (doi:10.1002/1521-3773(20010105)40:1<191::AID-ANIE191>3.0.CO;2-C) DMacks (talk) 23:41, 12 August 2010 (UTC)[reply]
Supra-ventricular tachycardia is caused by a group of cells on top of the ventricle going haywire nad is not the same as fibrilation.--JyzzCannon (talk) 23:02, 14 August 2010 (UTC)[reply]
Who's good with chemical nomenclature?
Going to start proof reading and cleaning up the Glimepiride article, and have noticed two different sources stating the following IUPAC names. I can't distinguish between the two, so could someone who's good with naming large molecules have a look? Here are the two options:
I'm not quite in a mental state to confidently name a molecule quite that nightmarish, but do bear in mind that with molecules of that level of complexity you can very easily have more than one completely equivalent, and hence completely correct, name. If the sources are decent they may both be correct. ~ mazcatalk23:09, 12 August 2010 (UTC)[reply]
The second name is missing a whole chunk in the middle, as you can see from the three opening brackets without closing brackets. The first name agrees with the name on ChemSpider (apart from the minor point of "phenethyl" vs. "phenylethyl"). Physchim62(talk)07:30, 13 August 2010 (UTC)[reply]
August 13
Why expend effort finding pulsars?
According to this article, there are 262 000 computers running a program to locate pulsars in space. Is it worth the additional energy expenditure to know that there's a spinning star somewhere far away? We can't benefit from the information. We can't harness it in any way. If you're going to use energy in this way, wouldn't it be better to use it on something that can actually be used in the 21st century, like folding@home? ----SeansPotato Business01:15, 13 August 2010 (UTC)[reply]
Probably the best answer would be a justification of theoretical astrophysics by some prestigious scientist. On the Method of Theoretical Physics. Are astrophysics, or high-energy physics, or other branches of theoretical physics useless? Probably, at this point in the development of our species and civilization, we are well past the regime where we can say that there is a practical engineering application to many of the remaining unsolved questions in physics. But we don't know for sure. And even if there is no practical purpose, there is still interest in finding answers to difficult questions; so there are still scientists working out on the far fringes of physics. Nimur (talk) 01:30, 13 August 2010 (UTC)[reply]
Pulsars can be used to measure the motion of distant systems because their super-regular 'pulses' slowly change frequency due to relativity. Also, pulsars are known to be neutron stars - and those can be used as 'standard candles' (see Cosmic distance ladder for details) which allows you to measure their distances. I'm sure there are a bunch of other clever things that can be figured out from their properties. SteveBaker (talk) 01:55, 13 August 2010 (UTC)[reply]
As for the power consumption: The thing is that this program is running on the computers of private individuals when they aren't being used for something else...they run this program instead of running a screen-saver. There is a small amount of extra power consumed when they are running the program versus idling - perhaps 50 Watts. But that number of 262,000 computers is not the number that are running 24 hours a day - that's the number of people who've logged onto the site and signed up their computers to use the site. It's perfectly possible that only a small fraction of those are running the program at any given moment. This makes it really hard to estimate the amount of power they are consuming. But if (let's say) a quarter of them are running the program at any given time - and each one is consuming 50 Watts extra because of that - that's about 3 MegaWatts - about the same amount of power that a railroad locomotive produces. It's not all that outrageous if the result is useful. To put it in context, the power consumption of the entire world is about 15 TWatts - so this expenditure represents about one five millionth of humankind's power consumption. If we're looking to save energy, there are much better places to cut. SteveBaker (talk) 02:15, 13 August 2010 (UTC)[reply]
If we were to assume, for the sake of argument, that the information generated by Einstein@Home is completely and totally valueless to humanity in any objective sense, the question could generalized to, "Is it worth the additional energy expenditure for people to have hobbies and interests?" Sometimes, we just do science to satisfy curiosity. (Occasionally, that sort of bluy-sky curiosity-driven basic research does lead to important results, however.) For a project like this one, some people (some thousands of people, really) have decided that one of the ways they wish to spend their entertainment budget is on helping to map out features of our Universe. Their hardware cost is already sunk, and they figure that the marginal additional energy cost is, to them, a reasonable price of admission. Is that 'better' or 'worse' than using free time to play chess (with or without a computer...) or FarmVille? TenOfAllTrades(talk) 14:04, 14 August 2010 (UTC)[reply]
Would bloodletting be an effective treatment for hypertension? Don't worry--Im not looking for medical advice ( and I certainly wouldn't try to exsanguinate myself, since I don't even have hypertension), it just occurred to me. —Preceding unsigned comment added by 99.183.166.165 (talk) 03:00, 13 August 2010 (UTC)[reply]
There are two major problems with this approach. The first is that the body is actually rather good at compensating for a loss of blood. Our article on hypovolemia discusses some of the physiological responses which occur in response to blood loss; blood pressure tends to be maintained through constriction of blood vessels and the migration of water from tissues into blood plasma. Remarkably, the body can handle the acute loss of up to about 15% of its blood (roughly 750 mL) before it starts losing the ability to regulate blood pressure. After that, the combination of constricted blood vessels with elevated heart rate actually leads to an increased diastolic blood pressure. It takes the loss of about a third of one's blood (about 1500 mL) before you start seeing consistent declines in blood pressure — and then you're in a really bad way otherwise.
The second major issue is the chronic anemia that would result from the regular removal of so much blood. While the body can make up lost liquid (plasma) volume rather quickly, generating new red blood cells takes a bit more time. TenOfAllTrades(talk) 03:21, 13 August 2010 (UTC)[reply]
Bloodletting, however, has some positive effects on the renal system of a diabetic -- I asked about it in a lecture at Columbia University last October and the professor agreed with my assessment. That being said, there is this one benefit overpowered by many, many disadvantages unrelated to the way in which bloodletting can be beneficial, and since we can't isolate the benefit from the harm, bloodletting is not done in civilized medicine. DRosenbach(Talk | Contribs)15:18, 13 August 2010 (UTC)[reply]
What would and does happen is that you would, first of all, suffer the effects of the Lupus or Leukemia. AIDS does not in itself primarily cause illness, it is a Deficiency in one's Immune system leading to a Syndrome of signs and symptoms caused by other diseases that one consequently catches, hence its acronymic name. (The Acquired part distinguishes it from an inherited genetic deficiency, also possible, since one acquires it from infection by the HIV virus.) Hence, the Lupus or Leukemia may well (though not certainly) be the consequence of having AIDS, and in addition one is quite likely to already have caught, or develop in the future, other illnesses as well. As the already-linked Comorbidity article describes, it's perfectly possible to suffer from two or more diseases simultaneously; the resulting signs and symptoms will depend on the particular diseases involved and may interact in unusual and/or unpredictable ways. 87.81.230.195 (talk) 12:41, 14 August 2010 (UTC)[reply]
I found a report about a man who had HIV, HBV, HCV, and lupus.[9] According to this, HIV generally protects against activation of lupus to some degree. But this person received interferon-alpha treatment - apparently good for HCV, bad for lupus. It's also interesting to note that HIV and lupus may have a lot more in common than you'd imagine - according to one idea [10] lupus may involve the response to a retrovirus already present in the human genome that can be set off by other viral infections! I suppose if we didn't have the technology to fight it, HIV would be part of the human genome also someday. Wnt (talk) 14:18, 14 August 2010 (UTC)[reply]
I wouldn't describe gravity as a pseudo force because this description is normally used for fictitious forces in Euclidean space, and gravity is certainly a real force in Newtonian terms. In General relativity, gravity is not a force at all, of course, just a consequence of the curvature of space, but this is a non-Euclidean space (in fact a Pseudo-Riemannian manifold combining space and time). Dbfirs07:33, 13 August 2010 (UTC)[reply]
... an article which says that gravity is not really considered as a fictitious force within the meaning of the article. Dbfirs07:43, 14 August 2010 (UTC)[reply]
Fictitious forces depend on the chosen frame of reference and in some reference frames they disappear altogether. First-order (local) gravitational effects disappear in a free-falling frame of reference. However, second-order (tidal) effects cannot be eliminated, so gravity does not fit the definition of a fictitious force. Gandalf61 (talk) 10:22, 13 August 2010 (UTC)[reply]
I am certainly happy to be corrected on this, but isn't the whole point of GR that what Newton called the gravitational force (e.g. the G) is actually just the path of least resistance in spacetime, because mass warps spacetime? That is, there is no "force of gravity," there is just a warping of spacetime by mass, and following the subsequent curves. Yes? No? This is, I am fairly sure, what I was taught, though I am sure it is an abstraction. It seems like we are perhaps getting hung up on the "force" terminology in strange ways. --Mr.98 (talk) 14:24, 13 August 2010 (UTC)[reply]
Let's be clear: the idea that there are "four fundamental interactions" is one effort to explain the universe in the most simplified terms possible. The grand unified theory (which does not yet exist) will hypothetically unite all forces into one fundamental force interaction (or something). At present, we have "four" (or "three", because of the electroweak unification at high energy). So we basically can say that there are four (or three) fundamental ways that the universe "behaves". Gravity (with its mind-bending and space-bending behavior) is one of those ways. The other forces behaviors (strong nuclear, weak-nuclear, & electromagnetic interactions) do not behave in the same way - they do not warp the geometry of space-time to actuate their matter/energy interactions. Note that most descriptions call these four properties of the universe "fundamental interactions" and not "fundamental forces" - they are not really "forces." They are abstract generalizations of the ways that matter and energy come together to change their distributions. For normal, reasonable, human-sized scales of size, time, energy, and so on, these interactions look like forces - that is, they follow a Newtonian relation between position, velocity, acceleration, and the gradient of a potential energy field. Nimur (talk) 17:02, 13 August 2010 (UTC)[reply]
I asked this question before (at Talk:Graviton) and received an interesting reply: that other forces also can be modeled as warping of spacetime in higher dimensions. But still don't really understand it. Though it appeals to my uneducated understanding of the topic, Fictitious force#Gravity as a fictitious force is actually an unsourced section - the "reference" is just more unsourced content. Always look for the sources for anything in Wikipedia before you put too much faith in it. Wnt (talk) 14:02, 14 August 2010 (UTC)[reply]
There are definitely efforts to describe other forces in a general-relativity framework (modeling them as tensors and so on); and there are parallel efforts to develop a quantum gravity theory. So far, the best of those efforts still have trouble consistently and accurately describing the behaviors of the universe, (in other words, describing the strong-nuclear force as a space-warping leaves some mathematical inconsistencies unresolved, or fails to match some experimental observation, etc). This is why mainstream physicists still consider there to be four fundamental types of interactions (or, three, depending how you want to count the electro-weak interaction). It is not widely agreed whether it is even possible to have a "grand unified theory". But there are definitely good efforts toward the goal, which is to describe all four fundamental interactions as different "versions" of the same behavior, using a single mathematical framework to describe all of them. Nimur (talk) 18:36, 14 August 2010 (UTC)[reply]
The Standard Model forces are all gauge forces, meaning that they are derived from a symmetry principle (gauge symmetry) that's analogous to background independence in general relativity. They do look a lot like general relativity applied to extra dimensions. In this thread, which I've been linking a lot recently, I talk about twisting circles at each point of spacetime. That's a geometric description of a U(1) gauge theory. If you replace the circles with spheres, you get an SU(2) gauge theory. So the idea of unifying gravity with the Standard Model by unifying the Standard Model gauge symmetries with the local symmetries of spacetime is an obvious one. For some reason, it has been incredibly difficult to get it to work. But it's always lurking in the background of discussions of quantum gravity. -- BenRG (talk) 21:26, 14 August 2010 (UTC)[reply]
Sieve Map
I was reading up on urban planning and the services (such as water, medical etc) requirements involved and I came across the term "sieve maps" listed as a tool to enable analysis of services requirement, without any further explaination of what they are. I have carried out wikipedia and google searches for this term but nothing jumps out. Any ideas? Thanks 150.49.180.199 (talk) 05:09, 13 August 2010 (UTC) Mark[reply]
In what context? Both are words that have a wide variety of related meanings - when you're talking about a range of frequencies available for transmitting data, the two can be roughly equivalent - but in other circumstances they can mean very different things indeed. Could you clarify? ~ mazcatalk14:07, 13 August 2010 (UTC)[reply]
"Bandwidth" specifically refers to a measurement of the amount of spectrum that a signal occupies. Most commonly (i.e., for simple signals), "bandwidth" refers to the "3-dB bandwidth", i.e. the span of frequencies that the signal falls to to 50% of its peak power. In more specialized contexts, "bandwidth" can refer to other numerical measures of a signal. (This is especially true of complicated signals that do not have nice, peak-like spectra). "Spectrum" usually refers to the frequency spectrum, which is the representation of a signal in the Fourier domain (or frequency domain). These terms can often be used loosely and interchangeably, so if there is not much clarification provided, you should assume that these terms are referring to the vague concept of the frequency-representation of a signal. Nimur (talk) 16:56, 13 August 2010 (UTC)[reply]
Quantum mechanics and predicting the future.
Let's suppose you knew everything about the current state of the universe. Would the stochastic nature of quantum mechanics still render you unable to predict the future? Or is the future state of the wavefunctions deterministically dependent on its current state in this sense?--Alphador (talk) 09:17, 13 August 2010 (UTC)[reply]
Well one huge problem is you cannot "know everything about the current state of the universe" – there is a fundamental principle called the uncertainty principle that limits the detail to which you can "know" the state of the system. Physchim62(talk)09:48, 13 August 2010 (UTC)[reply]
"Knowing everything" in this case means knowing the wave function. And yes, if you know the full wave function of the world at the present time you can predict (via Schrödinger's equation or the like) the wave function at any future time. The results of any particular measurement will of course be stochastic, with probabilities dependent on the wave function and subject to the uncertainty principle for non-commuting observables. --Wrongfilter (talk) —Preceding undated comment added 10:07, 13 August 2010 (UTC).[reply]
I've heard about the schrödinger equation, but I only have a rudimentary understanding of it. Could you give me an example of how you could use the schrödinger equation to predict the future state of the wavefunction?--Alphador (talk) 11:05, 13 August 2010 (UTC)[reply]
Well, it is a differential equation like so many others in physics. The equation itself tells you the rules of the game, i.e. in what state will the system be in a moment when it is in such and such a state right now. Schroedinger's equation contains the Hamiltonian operator which defines the system that you're looking at, how it interacts with the outside world and so forth. To solve any differential equation you need to specify initial conditions, that would be the state (the wave function!) now (or at any given point in time). The solution will then tell you what state the system will be in at any other time in the future (or in the past). --Wrongfilter (talk) 13:41, 13 August 2010 (UTC)[reply]
(ec)This is one of the Big Questions, isn't it, that people come to rather different positions on.
My understanding is that the wavefunction is presumed to evolve in a deterministic way (otherwise, where would the new information come from?), so if like some updated Laplace's demon you could have a complete knowledge of the wavefunction now, and could somehow iterate that forward, then you would have a complete knowledge of the wavefunction at a particular time in the future.
However, you would then have the question of interpreting what that wavefunction meant. Specifically, according to decoherence, it is suggested that that evolved wavefunction is likely to evolve into an almost perfect product of factor wavefunctions for a number of essentially disjoint non-interacting separate distinct "histories" -- the multiple universes in many worlds interpretation language.
You would therefore be able to predict these different, effectively disjoint, outcomes; and even assign them probability-like weights; but not say which one your own future consciousness will associate with.
That at any rate seems to be a thumbnail sketch of one answer that some people seem to find acceptable.
But I suspect it depends on quite another set of cans of worms -- for example, with reference to what is your wavefunction of the universe defined? What absolute scales or place or time? They surely don't exist. How can such a wavefunction have any information content? Information implies the reality of counter-factual states from which the current state can be distinguished. But how can states that are by definition counter-factual have any reality? etc, etc.
To do physics, we essentially have to make approximations -- separating the "system of interest" from the "background", and then assuming the background is homogenous, uninteresting, unimportant -- an external scale through which we can define place, time, or any other variable of the system of interest. And of course most of the time this works brilliantly. But I suspect that it becomes a serious problem, if we want to start talking about a "wavefunction of the universe", which properly would have to absorb all of that background into itself - leaving what to define the wavefunction against? Such questions may even become significant, even if we do not go to such lengths. For example, I suspect we regularly make a change in the system/background approximation when we introduce a "measuring apparatus", and that is why that appears to produce a distinct break in determinism.
So: decoherence gives one answer to your question, but the terms in which you ask it perhaps in themselves open up deeper questions.
Science is not interested in your opinion. It is interested in clearly defined theories that explain empirical results. --Tango (talk) 00:12, 14 August 2010 (UTC)[reply]
Even if you did know everything about the curent state, determinism is not proven so it would be near-impossible to predict anything with 100% certainty and accuracy. ~AH1(TCU)14:47, 13 August 2010 (UTC)[reply]
You don't need to invoke quantum mechanics to prove the impossibility of this. Even in a perfect 'clockwork universe' where you somehow had perfect knowledge of the initial state of things - there are two major problems with predicting the future:
(As we discussed a few days ago) How are you going to store the perfect knowledge of the current state of the universe? You can't build a computer big enough to do it because your computer is a part of the universe and in order to do a perfect prediction, it has to factor in it's own influence on the universe. Every bit of memory in the computer needs at least a bit of memory to describe its own state. In fact, no computing device can have perfect knowledge of even its own state as well as having knowledge about anything beyond that.
Consider the time it would take to run these calculations. The physical processes used in the computer would have to run faster than the real universe or else your "prediction" would arrive considerably later than the events they were predicting. Again, to produce a perfect prediction, the computer would have to predict it's own answer before the answer would become available because the nature of the answer includes the effect of giving that answer on the progress of the universe.
So the answer is a clear "No". However, having said that, we most certainly can make some predictions of the future - but they must definitely either be imperfect (like weather forecasting) or very limited in scope (like predicting that the sun will rise at such-and-such time tomorrow morning). Quantum mechanics isn't a necessary consideration here - it merely makes perfect future prediction more impossible than just straightforwardly impossible. Chaos theory also imposes sharp limitations on our ability to predictions.
I occasionally find frogs with two yellowish stripes running down their backs. It mentions them in the grass frog article, but does not give any specific species. All I have to give for pictures is these twoblurry pictures to give. Can anyone identify them? I do not see anything in Frogs in New Jersey or in the NJ.gov index of frogs and toads in New Jersey. Thank you. --Chemicalinterest (talk) 12:36, 13 August 2010 (UTC)[reply]
If you want to talk about 'capacity' that's a rather difficult question IMHO. I wonder whether you could teach a chimpanzee or orang utan or gorilla to be good swimmers with enough effort. This [11] claims orang utans and gorillas can't because of their centre of gravity is in their necks and sternums, but as with the person writing, I'm sceptical whether that's the whole story. These two refs have various discussions of swimming chimpanzees, the general conclusion I draw from that is it's likely to be possible [12][13] and a chimp may even be able to outswim an olympic swimmer. Note that if you can't teach an animal to swim, it may as much as anything be because the animal lacks the learning capacity or intelligence necessary for you to be able to teach it. It's also likely to be difficult to prove whether or not you can teach whatever animal how to swim without significant effort, which would likely have to start at learning to teach the animal effectively. In other words, the best answer may be most primates may have it, but we'll probably never really know. Nil Einne (talk) 17:17, 13 August 2010 (UTC)[reply]
Long-distance swimming says that a few humans are capable of swimming 100km without a break - over 800 people have completed 30+km swims across open ocean and there are many Marathon swimming competitions in which hundreds of people are able cover 5 to 10km distances in open water. Ironman Triathalon events involve 3 to 4km swims (along with biking and running) and are fairly commonplace events that most moderately fit humans could train to complete. Almost all of us can comfortably swim a hundred meters. Can anyone name one other primate that can come even close to doing that? No? Me either. I conclude that we are likely to be by far the best adapted primate for this kind of thing. We have long limbs - we are mostly hairless (we don't get water-logged) - we have our center of gravity in the right place and we have vast amounts of stamina for covering long distances. SteveBaker (talk) 00:28, 14 August 2010 (UTC)[reply]
How large a factor is behaviour, though? Humans can only swim several kilometres following extensive and specialised training and only do so with the motivation of challenging themselves and proving their abilities. I can't see a wild primate attempting such a thing. They might well be capable of it if they did train for it and actually attempted it. --Tango (talk) 00:38, 14 August 2010 (UTC)[reply]
You don't need particularly specialized training. You just need to learn how to swim, and then get in really good shape. It's true that swimming is a skill sport, but you don't need that much skill to swim 4000m — just basic competence plus good physical condition and a willingness to grind it out. --Trovatore (talk) 06:46, 14 August 2010 (UTC)[reply]
In addition, swimming for so long is as much about endurance as anything. I've seen it suggested humans are one of the primates with the best endurance/stamina so we can run marathons or more importantly chase prey over very long distances and stuff like that. I'm not offering any opinion on the validity of this claim but if it is true, it may be one of the reasons why we can swim for such long distances. But you could just as well say we are the primates best adapted for having sex that lasts several hours or for jumping up and down in one spot for hours. Nil Einne (talk) 06:39, 14 August 2010 (UTC)[reply]
Test on toes
What is the name of the test or sign whereby the doctor holds one toe and pushes it up or down while the patient's eyes are closed. The patient then advises whether it was moved up or down. Kittybrewster ☎15:55, 13 August 2010 (UTC)[reply]
You need to think what the purpose of the car is. Reliability wise Honda are very reliable, well made cars (at least the ones we get in the Uk). It really depends on the use though - there will be a number of bests - small-car, the best 4x4, the best people carrier, the best pick-up and so on. That said any 'best' is really just a matter of opinion, but I would recommend using something like Parkers Guide (or whatever the US equivalent is - assuming US based on Chevvy/mustang). ny156uk (talk) 16:39, 13 August 2010 (UTC)[reply]
This question has been removed, per the medical advice guidelines.
We cannot offer medical advice. Please see the medical disclaimer. Contact an appropriate medical professional. We have articles about the various drugs so you can learn about them and maybe find links to more information about them. DMacks (talk) 16:27, 13 August 2010 (UTC)[reply]
This is about as clear a violation of our medical-advice guidelines as ever. You need to consult with your doctor to discuss any effects of any medication the doctor has prescribed to you. Your doctor can help you decide the right course of action. Nimur (talk) 16:49, 13 August 2010 (UTC)[reply]
How do people find the wavefunction of an elementary particle? Often in quantum mechanics problems you are simply told what it is, I would like to know how people determine the wavefunction.--Alphador (talk) 22:03, 13 August 2010 (UTC)[reply]
Wavefunctions are linear combinations of the eigenfunctions that solve Schrodinger's equation. Solving the latter in any particular case requires specifying the Hamiltonian operator, which includes a generic part related to kinetic energy and specific part related to how the particle(s) potential energy can be expected to change as a function of position and/or time. In most cases, the potential part is specified by the solver in terms of the fundamental forces involved (e.g. electromagnetism) and the details of the larger environment within which the particle is being studied. Once the potential field is specified, finding the eigenfunctions is an exercise in solving partial differential equations (i.e. pure math). Exact solutions generally only exist for fairly simple systems, so often the eigenfunctions are found either via numerical approximation or by approximating complex systems in terms of simpler systems that are analytically solvable. Finding a precise wavefunction to match the system's state is then a problem of finding the precise linear combination of eigenfunctions that match some specified initial conditions, i.e. a boundary value problem. Dragons flight (talk) 22:33, 13 August 2010 (UTC)[reply]
It is impossible to measure the wavefunction experimentally, as it is not an observable quantity. Some functionals of the wavefunction have a physical meaning of observable quantities (energy, momentum, angular momentum, etc. in a given system of reference), those can be measured; but not the wavefunction itself. For example, if you consider a wavefunction in coordinate representation, absolute value squared of the wavefunction at a given point correspond to the probability density of finding the particle there, and the phase of the wavefunction does not correspond to anything observable. Probability is not an observable quantity, either (indeed, in any single trial an outcome is either 0 or 1; the probability is only determined in many trials). However, if you can prepare many identical systems, and perform many identical trials, this may -- at least theoretically -- allow you to map the probabilities of finding an electron at different locations. This gives you the amplitude of the wavefunction of that state, in coordinate representation, with a desired precision. --Dr Dima (talk) 10:24, 14 August 2010 (UTC)[reply]
Short answer: You will know the wavefunction of a system after you have measured a complete set of commuting observables of the system. The state of the system will then have collapsed in the simultaneous eigenstates of the observables determined by the measured eigenvalues of all the observables. Count Iblis (talk) 14:46, 14 August 2010 (UTC)[reply]
August 14
Will scars ever be possible to remove/are they possible to remove?
Not seeking medical advice, and already looked up the wikipedia article on scars but it seems outdated. I was captivated by this story on the Extra-Cellular Matrix and how it helped regrow a man's finger with-out scar tissue.
Removed the OP's details about their scars. Sorry, I know you didn't mean to ask for medical advice, but we cannot comment on your specific case, and I don't want strangers on the Internet giving you false information and speculation about your scars when only a medical professional's word is accurate.--el Aprel (facta-facienda) 18:28, 14 August 2010 (UTC)[reply]
Per our article on scars, the American Association of Dermatology notes that no scar can be completely removed, though many can be considerably reduced. We cannot say whether or not perfect removal will someday be possible. — Lomn02:02, 14 August 2010 (UTC)[reply]
How long can someone live who is on medication on average that has HIV that has developed into AIDS? The AIDS talks about how long if you ARE NOT getting treatment, but how long if you are? Also, are people who have HIV that has advanced to AIDS usually in the hospital? —Preceding unsigned comment added by 76.169.33.234 (talk) 05:16, 14 August 2010 (UTC)[reply]
Have you looked at our article on AIDS? It says there that 'HAART is thought to increase survival time by between 4 and 12 years'. HAART is the treatment you are talking about. I can't answer your second question, I'm afraid.--HarmoniousMembrane (talk) 09:58, 14 August 2010 (UTC)[reply]
I think I recall the article saying the average survival length is about 10 years. However people who have AIDS generally don't die from it, rather they die from pneumonia or brain inflammation or cancer etc. ~AH1(TCU)22:53, 14 August 2010 (UTC)[reply]
A simple internet search should find things like Norman Borlaug#Dwarfing, [14] & [15] which should mostly answer your question. I'm doubtful this merits a seperate article so I've redirected it to wheat which also already contains some info on dwarfing, feel free to add more with references as appropriate Nil Einne (talk) 06:29, 14 August 2010 (UTC)[reply]
Bruegal's The Harvesters shows that wheat used to be nearly as tall as people. Some typical wheat I saw growing in a field in the UK recently was somewhat over a foot high. In past decades I recall seeing wheat about half this height, but have not seen any of that in recent years. Presumably modern wheat is dwarf wheat. 92.28.251.219 (talk) 12:34, 14 August 2010 (UTC)[reply]
Phase Diagram Topology
A typical phase diagram. The dotted green line shows the behaviour of substances like water (the minority) which expand on freezing.
Is there a finite set of phase diagramtopologies? Are there any invariant properties of all phase diagrams? For example, are there any substances completely missing basic phases? Do they ever demonstrate fundamentally different phase layouts? -Craig Pemberton07:57, 14 August 2010 (UTC)[reply]
There are certainly substances that break down chemically when heated and that prevents the existence of a liquid and/or vapor phase. I'm not sure if that is the kind of thing that you had in mind though. Dragons flight (talk) 08:18, 14 August 2010 (UTC)[reply]
Helium has a unique phase diagram, in that there is no triple point and two liquid phases. Many susbtances display a variety of solid phases and there's no consistent pattern between these. But the generic phase diagram shown in the figure works for the vast majority of substances. Physchim62(talk)08:39, 14 August 2010 (UTC)[reply]
Looking at the phase diagram for Helium, it seems like you could achieve the same topology by drawing lines into the area of negative temperature and pressure. It's like Helium's triple point has fallen off the chart. Are there other exceptions of this nature? Are there other kinds of exceptions? 24.206.78.155 (talk) 09:08, 14 August 2010 (UTC)[reply]
Helium is also unique in having two distinct liquid phases, which is what "causes" the triple point to "fall off the chart" (not that negative pressure has any understood physical meaning, but to take your topological analogy). Physchim62(talk)18:29, 14 August 2010 (UTC)[reply]
There are general patterns of adjacency. In almost all cases (i.e., I can think of a few but only very few exceptions), at a given temperature, decreasing pressure goes from solid (possibly through several different ones) to liquid to gas, assuming each of those states exists at that T. Likewise, at a given pressure, increasing temperature goes from solid(s) to liquid to gas, assuming each exists there. That's just like saying "a solid melts when you cross its melting-point temperature" and similar general ideas of phase transitions. Well, except water and a few others whose volume-change at freezing is reversed. And some things likely have both a meta-stable solid (or maybe technically "glass"?) phase with low melting point and a highly crystalline solid phase with a high melting point. DMacks (talk) 09:15, 14 August 2010 (UTC)[reply]
What other exceptions are you thinking of? I am also wondering if the line of sublimation always begins exactly at the origin of the diagram. -Craig Pemberton09:42, 14 August 2010 (UTC)[reply]
Assuming the lines are drawn as equilibrium lines (as is conventional for phase diagrams), then no, the line of sublimation does not always begin absolutely at the origin. To draw it like that is really just laziness, but it does also indicate that, for most substances, we have very little idea o phase transitions at very low temperatures and very low pressures. Physchim62(talk)18:20, 14 August 2010 (UTC)[reply]
Phase diagram for water
I'm sure the set of possible phase diagrams is finite, but it may be pretty large. Consider for example the full phase diagram of water, as illustrated in this image. Looie496 (talk) 18:14, 14 August 2010 (UTC)[reply]
If you're going to include all solid phases, then I would say that the number of topologies is countably infinite (as is the number of possible chemical substances). If you limit yourself to pure substances and lump all crystalline phases together as "solid", then I believe that there are only a few known types of phase diagrams, and plenty of theory to explain why. Physchim62(talk)18:29, 14 August 2010 (UTC)[reply]
isn't science a religion?
Let's take one simple thing - the paradox. Obviously, scientists strongly believe that the actual, physical Universe cannot evince any paradox. Any "paradox" is in the mind of the weak, inept understander, who must change his mind about what he had thought about the Universe.
But why do they believe this? They have a definition of the paradox, but believe strongly, I would say religiously, that the Universe can contain none. Granted it is a negative religious belief, different from believing in the existence of something. But isn't the belief of science in the non-existence of paradox just as religiously strong? 84.153.210.148 (talk) 09:45, 14 August 2010 (UTC)[reply]
The difference between science and religion is that the latter requires some sort of faith in something untenable, whereas the former requires evidence. I'm sure some philosopher will correct me, but that's always how I've defined the distinction. Regards, --—Cyclonenim | Chat 10:48, 14 August 2010 (UTC)[reply]
Yes, science is built on a constantly growing base of evidence, knowledge and information. For most religions, the evidence is fixed and unchanging, and unlikely to be acceptable to modern science. HiLo48 (talk) 11:02, 14 August 2010 (UTC)[reply]
neither of you addressed my specific point: scientists' views of paradox in the Universe. Namely, they take it on faith that there can be none, and any theory that would show one must be (ipso facto) flawed. How is this faith in the absence of paradox not religious? 84.153.210.148 (talk) 12:45, 14 August 2010 (UTC)[reply]
VanBurenen asks a good question. If unambiguous and repeatable experimental evidence of a "paradox" (whatever you mean by that term) is produced then science has to accept the reality of that evidence. Scientists then look for a new or extended theory that can accommodate and explain the new experimental evidence without contradicting other known facts. The results of relativity and quantum mechanics, were, at one time, regarded as "paradoxical" because they did not fit into the previously accepted theories of classical physics. "Paradoxes" such as the ultraviolet catastrophe, the photoelectric effect and the Michelson–Morley experiment were triggers for the development of new scientific theories. All science is based on the assumption that the physical world obeys consistent laws, but I don't think that is the same as "faith in the absence of paradox". Gandalf61 (talk) 13:10, 14 August 2010 (UTC)[reply]
Well, let's break this into two pieces:
1. Does science have preconceived notions? (Is the lack of paradoxes in nature just an assumption?)
2. Does having preconceived notions make something a religion?
As for #1 — obviously yes. The paradox example might not be a good one because arguably that is just a question of logic. But in any case there are many others. There are lots of deep-seated philosophical views that scientists have that they don't question and don't have any evidence for other than it makes sense. These are best seen in retrospect, when we look at scientists in the past, who make gigantic assumptions that we now think look quite odd, even though they were very smart people. Scientists are, of course, human, and it is very hard to see the philosophical assumptions that underlie one's whole life and profession, much less one's general society. A key point, though, is that the really brilliant and cherished scientists are the ones who can pull the rug out of such assumptions. Einstein is an icon because he was able to point, in a very specific way, at major assumptions about the nature of "time" and "space" and "measurement" that were being taken for granted by other scientists of his day, and show how they were not only wrong, but that with a more philosophically grounded approach, one actually ended up with a totally different physical theory, one that proved to resolve a number of problems with the previous theory. That's one of the nice things about science — it actually values (in the long run, anyway) being shown where its assumptions are trash.
As for #2 — I don't think so. What makes religion "religion" is not that there are some things which are not regularly questioned, that there are preconceived notions. Religions are a bit more complicated than that, a bit deeper than that. They are not just "things you don't question." (It is not a "religion" that I, say, am clueless or possibly wrong about what happens to the trash that I put out on the curb. It is not a "religion" that I think it looks better when I comb my hair than when I don't.)
Now, whether science has "religious" qualities (like faith, dogma, etc.) is an entirely valid question, but this isn't really the approach that will get you any good answers on that front, I don't think. In any case, my personal opinion is that while pointing to similarities between science and religion is a useful enterprise — it gets those of us who are so smug about our supposed greater connection to truth to come down a notch or two and admit that indeed, human knowledge is flawed — it does obscure some pretty important differences between scientific practices and religious practices, between scientific knowledge and religious knowledge. There is some overlap, to be sure, especially historically — but the really important aspects about both science and religious lie elsewhere, in my opinion. --Mr.98 (talk) 13:10, 14 August 2010 (UTC)[reply]
Another example could be found in the development of quantum mechanics, which defied all sort of regular logical precepts. In QM, things often happen without a reason; information can simply not exist sometimes where you would expect it to; time is a pretty complicated thing; things can sometimes be two things at once, etc. The fact that many of these discoveries violated all conventional, macroscopic logic, certainly did make them hard sells. But in the long run these kinds of "weird", "illogical" explanations actually worked out better than the "classical, logical" approach. Does the fact that people believed that the universe acted consistently causally, or that all information was theoretically knowable, make physics before QM a religion? Does the fact that they believe the opposite now make it a religion? It's the wrong question to ask, in the end. --Mr.98 (talk) 13:20, 14 August 2010 (UTC)[reply]
There are lots of things that scientists "take on faith", as you say. Most basically, that observations and experimentation can lead to accurate descriptions of the universe. If this were not true, then there would be no point in doing science (or theology, or pretty much any intellectual activity). Why should this be described as religious? Just because a belief is "religiously strong" doesn't mean it is a religious belief. I believe about as strongly as possible that Barack Obama is president of the USA, but that's not a religious belief. Staecker (talk) 13:16, 14 August 2010 (UTC)[reply]
The problem is in the definition of the word "paradox". It is by definition something that cannot be - something which is simultaneously both true and not true. The word implies something that cannot possibly be. If the word "paradox" meant "something difficult which can still be the truth" then we'd just have to invent a new word to mean "something self-contradictory that cannot be".
So this is not a case of scientists not being prepared to accept the possibility of there being actual, real world paradoxes - it's that when someone thinks they have found a paradox, we know that cannot (by the very definition of that word) be the case - so we have to look to see whether they are using the word incorrectly to describe something which can really be accepted as possible - or whether there was something they didn't understand that means that this wasn't really a paradox at all - or whether the laws of physics or some part of mathematics are making something seem paradoxical because those laws are incorrect in some way.
The latter situation is very interesting to science because it leads us to find errors in our laws - which is always an exciting and interesting thing! So when Gödel found a way to make a mathematical statement akin to the English phrase "This sentence is false." - this seeming paradox lead him to discover Gödel's incompleteness theorems that proves that there are statements in mathematics that cannot be proven to be either true or false (they aren't paradoxes though - they are things we can't discover the truth of - not things that are both true and false at the same time).
Accepting that something is a paradox is a typical religious reaction to a flaw in their belief system (eg: "Can God create an object so heavy that he cannot lift it?") - which is to try to bury the consequences and say "This is something mankind was not meant to know" or some similar bullshit. (Check out Omnipotence_paradox#Proposed_answers for some of the pathetic efforts to resolve this issue.)
A scientist has to find an explanation to discover why this is not, in fact, a paradox. So we might say "Well, the assumption that there exists a being that has absolutely no limits whatever is undoubtedly a paradox. So there must (by definition) be something wrong with our assumptions here. Either there is no such being - or the being is truly limited in what he can lift or in the maximum weight of object that he can create - or he lacks "free will" and that actively prevents him from choosing to create unliftable things - or to choose to lift things he previously created as unliftable"...and so on. A scientist might then go on to try to investigate which of those things is true (and in this case fail because there is an unfalsifiable hypothesis here).
But we are forced to deduce that either there is no God or God has at least one fundamental limitation that he cannot breach. Religions will accept neither of these possibilities - so they are forced into fluffy B.S answers like "accepting a paradox", which is about as reasonable as "Proving a falsehood" or saying that 1=0. You can't truly "accept a paradox" because the very meaning of the term is that this is something that cannot be accepted.
No. One can indeed "accept a paradox" (it's not beyond the capability of the brain to simultaneousy treat contradictory propositions as true). People quite routinely do. The result is normally some form of cognitive dissonance. The Rhymesmith (talk) 23:51, 14 August 2010 (UTC)[reply]
There is a small difference: Science is the belief in the exstence of an (as of yet unknown) objective truth that you can then try to find using sound strategies (Occam's Razor and taking falsifiability of theories serious etc. etc.), while religion is based on the acceptance of dogmas that are most likely false. Count Iblis (talk) 14:38, 14 August 2010 (UTC)[reply]
This has already been well responded to, but let me add one more thing, in response to: Obviously, scientists strongly believe that the actual, physical Universe cannot evince any paradox. It's not obvious to me that one can say anything about scientists in general. I am friends with some scientists who believe all kinds of wacky things. And there are plenty of scientists who are also very religious--in the "spiritual" or "mystical" sense. There's no reason why a scientist can't believe the universe is fundamentally paradoxical at some level. Scientists are people. Their lives involve more than just doing science. Pfly (talk) 16:26, 14 August 2010 (UTC)[reply]
I just want to add that I am truly tired of this continuous science/religion squabble. I know a lot of scientists and a lot of religious people, and it's clear to me that thoughtful people in both camps are all very interested in understanding the true nature of the world. They are interested in different aspects, of course - scientists are focused on the material world, while theologians are much more interested in the characterization of human existence - but for the most part they are complementary rather than opposed. This entire squabble is the result of zealots on both sides of the fence who are worried that the other side is trying to uproot their ontology. yeeee.... --Ludwigs223:07, 14 August 2010 (UTC)[reply]
Darksucker Theory
Hello Everyone. A few years ago, I remembered reading in the New Scientist 'Last Word' section a reply (I think for a question about why light bulbs turn grey over time), that light bulbs do not emitt light, but suck dark. It sounded very fishy, but I forgot about it. Recently, however, I was thinking about it again, and wanted to know the full theory. I did a google search and found this, which explains the full theory. To be honest, it seems to be phrased as a joke; but I was wondering what exactly means it is BS. I thought of two reasons:
1.Dark cannot travel faster than light, as it would violate casuality per Relativity
2.Light has been shown to be Photons/EM waves, depending on curcumstances, not some Field that is revealed when dark is removed.
Any more reasons why this theory cannot be true? (I know it probably isn't, but I would like some concrete reasons). Thanks for any answers. And incidentally, it was startling, when I put 'Darksucker' into the search bar, to be returned with 'Do you mean 'dicksucker'!--HarmoniousMembrane (talk) 09:52, 14 August 2010 (UTC)[reply]
first of all - maybe you were signed in, and Google knows you all too well? Second, you can see even just a few photons with your naked eye, and we have machines that can emit photons (particles of light) one by one, so obviously "sucking dark" is a joke. The punchline is, that's why when an incandescent lightbulb "goes out" you can see the filament turns black (or even releases smoke): it's sucked all the dark it can. 84.153.210.148 (talk) 10:13, 14 August 2010 (UTC)[reply]
Yes, that's a good point, about devices that can produce photons one at a time. I can remember Feynman mentioning them during one of his online lectures: what are they callled? And I wouldn't have been surprised if google did it, but I was talking about the wikipedia search bar!--HarmoniousMembrane (talk) 10:39, 14 August 2010 (UTC)[reply]
The New Scientist's 'Last Word' page is a question and answer section much like this Ref desk, and sometimes deliberately includes joke answers if the joke is good enough, although the assuption is that readers will not really be taken in by it. Much humour can be extracted from treating abstract concepts, and absences or deficiencies of actual entities, like dark (absence of light) or cold (relative deficiency of heat), as entities in their own right (there's a special word for this, which I've momentarily forgotten - anyone?). Terry Pratchett often deploys this tactic, and has argued that (at least on the Discworld, where light is slowed to near-sonic speeds by the intense magical field) dark must be faster than light, because it has to be able to see the light coming and get out of the way in time. 87.81.230.195 (talk) 12:16, 14 August 2010 (UTC)[reply]
As I understand it there are no evidence against a theory where photons are a hole in a field of darknes analogous to electron hole in a semiconductor but as long as it does not explain more observations than the theory that a photon is a elementary particle it fails Occam's razor.
--Gr8xoz (talk) 14:46, 14 August 2010 (UTC)[reply]
Just for the record, "dark", being the absence of light, travels at the speed of light. If a star twenty light-years away suddenly stopped shining, we would see the light "go out" twenty years later, give or take. When a light bulb is turned on, the "dark" would travel away from the light rather than be sucked into it. ~AH1(TCU)22:45, 14 August 2010 (UTC)[reply]
just for another reason, 'dark sucking' would play hell with various laws of conservation. where would all this sucked darkness go? a candle, for instance, would have to grow in length to store all the darkness it's sucking, and a light bulb would eventually collapse into a black (or white?) hole. but since these don't happen, you'd have to create a whole new set of theories about how darkness has negative volume/density (i.e., the more darkness something contains, the smaller it is, until the object reaches its maximal darkness capacity and disappears). --Ludwigs223:18, 14 August 2010 (UTC)[reply]
On printed circuit boards and schematic diagrams, incandescent bulbs (such as indicator lights) are abbreviated "DS", much as resistors are abbreviated "R", capacitors "C", inductors "L", and diodes "CR". ("L" is used as a symbol for inductance and "CR" stands for "crystal rectifier", but I don't know the origin of "DS". Is there a WP article on this?) I have always assumed that the phrase "dark sucker" was chosen to match the abbreviation. -- 1.47.99.181 (talk) 00:34, 15 August 2010 (UTC)[reply]
Not this year, because IIT Madras is full for its M.Tech. courses! You really need to ask the IIT itself if you want to know how they treat candidacies: note that they might change requirements from year to year, so don't rely on the 2010 rules being valid for 2011. Physchim62(talk)18:44, 14 August 2010 (UTC)[reply]
Old student directories would be of little use unless you are a recent graduate, since people move. You might see their parents address and get the current address from them if it hasn't been too many years since the directory was issued. Some old college directories are for sale from time to time on Ebay. Classmates.com exists to connect you with old high school or college classmates who wish to be contacted. Facebook has "groups" of alumni from many colleges and highschools, without the high subscription fees Classmates demands. Some colleges have alumni internet sites where you can email classmates who have also joined. Some schools demand you pay to join the alumni association. It is possible to use internet people finder services, which (possibly for a fee) will find just about anyone, but your old classmates might see you as a stalker if it is clear you spent a lot of time and money tracking them down. If the old classmates have websites, like for business, or Facebook pages, it seems natural enough to drop them a friendly note. Edison (talk) 20:04, 14 August 2010 (UTC)[reply]
Looking for old classmates has become a tricky area on the Internet. There are some sites that purport to help with this task but which are more spam sites than real directories. As for the old school helping, privacy requirements will often get in the way of this, but the old school may be wiling to pass your details on to others so that they may contact you. HiLo48 (talk) 23:08, 14 August 2010 (UTC)[reply]
If an icebreaker hit the iceberg that sank the Titanic...
Icebreakers are designed to break through sea ice -- which is relatively soft -- up to a given thickness. They aren't designed to hit massive icebergs of the sort that calve from glaciers. Looie496 (talk) 18:03, 14 August 2010 (UTC)[reply]
The titanic would have survived the iceberg had it hit it head on - it was the sidewise hit and extended damage down the side of the hull that did it in. An icebreaker would likely suffer the same fate, though it might be a little more resistant. Icebreakers are designed to use their bow weight to crack ice, not to bash through it like a chisel, so I doubt they are extensively reinforced down their sides. --Ludwigs223:24, 14 August 2010 (UTC)[reply]
This is a photo of the iceberg that the Titanic most likely hit.
It depends a lot on how the hit occurred. The Titanic iceberg was described (and photographed) as a "large" iceberg. "Large" (in this context) is actually a technical term used by the International Ice Patrol for a berg roughly 45–75 metres high (above water) and 120–200 metres wide. Since icebergs only have 10% if their total height above water - we could estimate the total volume of this one as about a million cubic meters - hence weighing in at about a million tonnes.
A modern icebreaker (let's pick the USCGC Healy as an example) weighs just 16,000 tonnes. Running into an iceberg weighing 60 times more than the ship is a lot like hitting an immovable object. The worst-case energy released by a 16,000 tonne vessel moving at (let's say) the top speed of the Healy (30kph - roughly 8meters/sec) and coming to a dead stop would be considerable: mv2 is 16x106kg x 82 ms-1 is 109J - which is an ungodly amount. Enough energy to completely melt a ton of steel for example! More than enough to make a considerable mess of an icebreaker. The difficult question is what fraction of that energy would be transferred to the iceberg and what fraction to the ship - but it's pretty clear that the worst-case impact would not be survivable.
However, the impact with the Titanic was a glancing blow. The Healy has most of her heaviest plating at the bow and stern and within one meter of the waterline - and she has a double hull and stiffer internal ribbing in those areas. The hole in the Titanic's hull was more than a meter below sea level - so that thicker steel closer to the waterline wouldn't help the icebreaker much. The Titanic has steel plates between an inch and an inch and a half thick - but it was of a type of steel that became brittle in those cold ocean temperatures. The Healy uses a special type of steel that doesn't suffer from that problem - but it's nothing like as thick that far below the waterline.
CONCLUSION: As you can tell - this isn't a simple call. The double-hull design of a modern icebreaker would certainly help a lot - but I'm personally skeptical that it would be enough. A head-on impact produces a lot of energy - but on the strongest part of the ship - a Titanic-like impact happens on parts of the icebreaker that aren't specially reinforced - but the double-hull might be enough to save her from sinking. Perhaps the biggest saving grace is that the radar and satellite links available to modern ships of all kinds should allow them to completely avoid iceberg impacts in the first place - and that's probably the best answer here.
The derivation of the terms might be somewhat independent. Aether just comes from the greek word for 'upper air': the philosophical use is obvious, since they were looking for something that bound everything together; the chemistry use may merely have been a reference to the fact that these compounds have comparatively low boiling points and thus are more likely to be gaseous - compare with 'ester' which refers to fatty-type substances. --Ludwigs223:36, 14 August 2010 (UTC)[reply]
because the effect would likely be short-lived, the crash after debilitating, and the risk of death unacceptably high. --Ludwigs223:27, 14 August 2010 (UTC)[reply]
Needing to run for your life or fighting hand to hand are very rare occurrences, things that never happen to the vast percentage of people in the world throughout their entire lives. Worse still, in cases where running/fighting is necessary, you probably don't have time to stand around sticking needles into yourself. Hence, carrying a shot of adrenaline around with you for that specific purpose would be kinda stupid. (Although people with certain medical conditions do actually do that - in the form of EpiPens, Anapens and Twinjects.) It's also worth mentioning that in Fight-or-flight response situations, your body produces adrenaline quite naturally - and probably in a carefully controlled optimum amount, so injecting yourself with more of the stuff is almost certainly unnecessary - and quite likely to be counter-productive. Your body does a whole bunch of other things during 'fight or flight' that make the naturally occurring adrenaline more effective. Using the stuff routinely would also be kinda stupid - it has a bunch of not-so-great side-effects and using it too often would put the body under a lot of additional stress. SteveBaker (talk) 23:36, 14 August 2010 (UTC)[reply]
![[5]](https://en.wikipedia.org/wiki/File:Flag_of_East_Germany_with_cut_out_emblem.svg){kind=link}
We cannot offer medical advice. Please see the medical disclaimer. Contact an appropriate medical professional. We have articles about the various drugs so you can learn about them and maybe find links to more information about them. DMacks (talk) 16:27, 13 August 2010 (UTC)
